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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

Modelling population growth vialaguerre-type exponentials  

Microsoft Academic Search

We use the Laguerre-type exponentials, i.e., eigenfunctions of the Laguerre-type derivatives, in order to construct new models for population growth. Relevant modifications of the classical exponential, logistic, and Volterra-Lotka models are investigated.

S. De Andreis; P. E. Ricci

2005-01-01

3

Populations with quadratic exponential growth  

Microsoft Academic Search

Stable population models, based on fertility and mortality rates that do not change over time, are too unrealistic and inflexible to capture the dynamics of many observed populations. Dynamic models, which allow vital rates to change over time, are needed to systematically analyze such populations.Here we examine dynamic—hyperstable—models with increasing or decreasing vital rates, providing the first detailed analysis of

Young J. Kim; Robert Schoen

1996-01-01

4

Interpolation solution in generalized stochastic exponential population growth model  

Microsoft Academic Search

In this paper, first we consider model of exponential population growth, then we assume that the growth rate at time t is not completely definite and it depends on some random environment effects. For this case the stochastic exponential population growth model is introduced. Also we assume that the growth rate at time t depends on many different random environment

M. Khodabin; K. Maleknejad; M. Rostami; M. Nouri

5

A Stochastic Super-Exponential Growth Model for Population Dynamics  

NASA Astrophysics Data System (ADS)

A super-exponential growth model with environmental noise has been studied analytically. Super-exponential growth rate is a property of dynamical systems exhibiting endogenous nonlinear positive feedback, i.e., of self-reinforcing systems. Environmental noise acts on the growth rate multiplicatively and is assumed to be Gaussian white noise in the Stratonovich interpretation. An analysis of the stochastic super-exponential growth model with derivations of exact analytical formulae for the conditional probability density and the mean value of the population abundance are presented. Interpretations and various applications of the results are discussed.

Avila, P.; Rekker, A.

2010-11-01

6

Impulsive exponential stabilization of discrete population growth models with time delays  

Microsoft Academic Search

The purpose of this paper is to investigate the impulsive exponential stabilization for the positive equilibrium points of a class of discrete population growth models with time delays. By using Lyapunov functionals, some new exponential stability criteria are given. It is shown that impulses can indeed make unstable equilibrium points exponentially stable, and when the impulses are employed to stabilize

Yu Zhang; Jitao Sun

2010-01-01

7

Exponential Population Growth and Doubling Times: Are They Dead or Merely Quiescent?  

Microsoft Academic Search

Exponential Growth” and “Doubling Times”: Use of these popular population buzzwords of the last half of the twentieth century was fully justified by the growth rates of that period. However, those growth rates have now all but disappeared and so have the underlying reasons that those buzzwords made sense. Misuse of such expressions today costs credibility. Though the world's population

John R. Bermingham

2003-01-01

8

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

Microsoft Academic Search

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

O. Arino; E. Sánchez; G. F. Webb

1997-01-01

9

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

ERIC Educational Resources Information Center

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

McDonald, Michael A.; And Others

1996-01-01

10

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

ERIC Educational Resources Information Center

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

McDonald, Michael A.; And Others

1996-01-01

11

Noise in Exponential Growth  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

12

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

13

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

Microsoft Academic Search

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

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

2007-01-01

14

Supercritical branching processes and the role of fluctuations under exponential population growth  

Microsoft Academic Search

We study some exact properties of supercritical branching processes. A proper rescaling of the relevant variable allows us to determine the distribution of population sizes after a number of generations have elapsed. Both time-continuous and discrete processes are analysed and compared. The obtained results are of relevance for the growth of populations that are not resource limited (a typical situation

Susanna C. Manrubia; Mar??a Arribas; Ester Lázaro

2003-01-01

15

A PRECALCULUS PROJECT ON EXPONENTIAL POPULATION GROWTH AND LINEAR FOOD PRODUCTION  

Microsoft Academic Search

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

Michael A. McDonald; Emily Puckette; Charles Vuono

1996-01-01

16

Fitness Distributions in Exponentially Growing Asexual Populations  

Microsoft Academic Search

We explore a mean-field model for the evolution of exponentially growing populations of mutating replicators. Motivated by recent in vitro experiments devised to analyze phenotypic properties of bacterial and viral populations subjected to serial population transfers, we allow our in silico individuals to undergo unrestricted growth before applying bottleneck events. Different dynamical regimes of our model can be mapped to

Susanna C. Manrubia; Ester Lázaro; Juan Pérez-Mercader; Cristina Escarmís; Esteban Domingo

2003-01-01

17

Balanced Exponential Growth of Operator Semigroups  

Microsoft Academic Search

AC0-semigroupS(t),t?0, on a Banach spaceX(weakly, strongly, uniformly) approachesbalanced (or asynchronous) exponential growthif there exists somes?R such that[formula]exists (in the weak, strong, uniform operator topology) andPis not the 0 operator. In this paper, the strong and uniform approach to balanced exponential growth is characterized and applicable sufficient conditions are derived. The results will be applied to models for age-size-structured population dynamics

Horst R Thieme

1998-01-01

18

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

19

Fitness Distributions in Exponentially Growing Asexual Populations  

NASA Astrophysics Data System (ADS)

We explore a mean-field model for the evolution of exponentially growing populations of mutating replicators. Motivated by recent in vitro experiments devised to analyze phenotypic properties of bacterial and viral populations subjected to serial population transfers, we allow our in silico individuals to undergo unrestricted growth before applying bottleneck events. Different dynamical regimes of our model can be mapped to different experimental situations. Numerical and analytical results for fitness distributions calculated at the statistically stationary states of the dynamics compare favorably with available experimental data. Our model and results provide a common framework to better understand populations evolving under different selection pressures.

Manrubia, Susanna C.; Lázaro, Ester; Pérez-Mercader, Juan; Escarmís, Cristina; Domingo, Esteban

2003-05-01

20

Explanation of Stretched Exponential Growth Behavior.  

National Technical Information Service (NTIS)

We show that the photoinduced defect population growth of an optically thick film may have stretched exponential time dependence if the defect does not decay nor diffuse within the time scale of the experiment. After the formulation of this simple model, ...

K. Kim A. Epstein

1995-01-01

21

Asynchronous exponential growth in an age structured population of proliferating and quiescent cells  

Microsoft Academic Search

A model of a proliferating cell population is analyzed. The model distinguishes individual cells by cell age, which corresponds to phase of the cell cycle. The model also distinguishes individual cells by proliferating or quiescent status. The model allows cells to transit between these two states at any age, that is, any phase of the cell cycle. The model also

Janet Dyson; Rosanna Villella-Bressan; G. F. Webb

2002-01-01

22

On Exponential Growth and Mathematical Purity: A Reply to Bartlett  

Microsoft Academic Search

Though Bartlett has offered several constructive criticisms of the mathematical formulations that were included in my paper, Exponential Population Growth and Doubling Times, not one of them undermines either of the two basic points made in my paper—that exponential population growth is no longer being projected for any nation in the world and, this being so, writers and speakers addressing

John R. Bermingham

2003-01-01

23

Simulating Population Growth.  

ERIC Educational Resources Information Center

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

Byington, Scott

1997-01-01

24

Exponential Growth Bias and Household Finance  

Microsoft Academic Search

Exponential growth bias is the pervasive tendency to linearize exponential functions when assessing them intuitively. We show that exponential growth bias can explain two stylized facts in household finance: the tendency to underestimate an interest rate given other loan terms, and the tendency to underestimate a future value given other investment terms. Bias matters empirically: More-biased households borrow more, save

VICTOR STANGO; JONATHAN ZINMAN

2009-01-01

25

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 earthâs 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

26

Uniform Growth in Groups of Exponential Growth  

Microsoft Academic Search

This is an exposition of examples and classes of finitely-generated groups which have uniform exponential growth. The main examples are non-Abelian free groups, semi-direct products of free Abelian groups with automorphisms having an eigenvalue of modulus distinct from 1, and Golod–Shafarevich infinite finitely-generated p-groups. The classes include groups which virtually have non-Abelian free quotients, nonelementary hyperbolic groups, appropriate free products

Pierre De La Harpe

2002-01-01

27

Estimating Population Size with Exponential Failure  

Microsoft Academic Search

We are given J observations obtained by truncated sampling of a population of N items which fail independently according to the exponential distribution, where both N and the scale parameter of the exponential are unknown. Estimates of N are developed, and compared. These are conditional and unconditional maximum likelihood estimates, and a class of Bayes modal estimates. On the basis

Saul Blumenthal; Richard Marcus

1975-01-01

28

Guelph Physics Tutorials: Exponential Growth and Decay  

NSDL National Science Digital Library

This website offers a tutorial on exponential growth and decay. The tutorial includes an introduction to exponential growth and decay, example problems, and a series of self-paced questions. This is part of series of tutorials on physics and mathematics used in physics classes.

2008-07-26

29

Avoiding exponential parameter growth in fuzzy systems  

Microsoft Academic Search

For standard fuzzy systems where the input membership functions are defined on a grid on the input space, and all possible combinations of rules are used, there is an exponential growth in the number of parameters of the fuzzy system as the number of input dimensions increases. This “curse of dimensionality” effect leads to problems with design of fuzzy controllers

M. K. Giiven; Kevin M. Passino

2001-01-01

30

Exponential Growth of Nonlinear Ballooning Instability  

SciTech Connect

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

Zhu, P.; Hegna, C. C.; Sovinec, C. R. [Center for Plasma Theory and Computation, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)

2009-06-12

31

Polynomial versus Exponential Growth in Repetition-Free Binary Words  

Microsoft Academic Search

It is known that the number of overlap-free binary words of length n grows poly- nomially, while the number of cubefree binary words grows exponentially. We show that the dividing line between polynomial and exponential growth is 73. More precisely, there are only polynomially many binary words of length n that avoid 73-powers, but there are exponentially many binary words

Juhani Karhumaki; Jeffrey Shallit

2003-01-01

32

Polynomial versus exponential growth in repetition-free binary words  

Microsoft Academic Search

It is known that the number of overlap-free binary words of length n grows polynomially, while the number of cubefree binary words grows exponentially. We show that the dividing line between polynomial and exponential growth is 73. More precisely, there are only polynomially many binary words of length n that avoid 73-powers, but there are exponentially many binary words of

Juhani Karhumäki; Jeffrey Shallit

2004-01-01

33

Teaching Exponential Growth and Decay: Examples from Medicine  

Microsoft Academic Search

A treatment of exponential growth and decay is sketched which does not require a previous course in calculus. Rate of change is introduced by considering compound interest and is determined graphically by using semilog paper. Examples of exponential growth and decay are given which will interest premedical students. These include bacterial growth, sterilization, survival in certain chronic diseases, clearance, and

Russell K. Hobbie

1973-01-01

34

Noise suppresses or expresses exponential growth  

Microsoft Academic Search

In this paper we will show that noise can make a given system whose solutions grow exponentially become a new system whose solutions will grow at most polynomially. On the other hand, we will also show that noise can make a given system whose solutions are bounded become a new system whose solutions will grow exponentially. In other words, we

Feiqi Deng; Qi Luo; Xuerong Mao; Sulin Pang

2008-01-01

35

Population Growth in Planaria  

Microsoft Academic Search

Planaria reproduce by transverse fission. Isolated worms increase in number exponentially, while social animals at the same density are inhibited in terms of numerical increase, but over a 25 day period undergo a larger in- crease in mass. Isolated posterior fission products reproduce faster than isolated anterior fission products. Regulation of population growth is independent of density over a 16-fold

JOHN DAVISON

36

101 Ways to Teach About Exponential Growth and Its Consequences.  

ERIC Educational Resources Information Center

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

Allen, Rodney F., Ed.

37

Population growth and economic growth.  

PubMed

This discussion of the issues relating to the problem posed by population explosion in the developing countries and economic growth in the contemporary world covers the following: predictions of economic and social trends; the Malthusian theory of population; the classical or stationary theory of population; the medical triage model; ecological disaster; the Global 2000 study; the limits to growth; critiques of the Limits to Growth model; nonrenewable resources; food and agriculture; population explosion and stabilization; space and ocean colonization; and the limits perspective. The Limits to Growth model, a general equilibrium anti-growth model, is the gloomiest economic model ever constructed. None of the doomsday models, the Malthusian theory, the classical stationary state, the neo-Malthusian medical triage model, the Global 2000 study, are so far reaching in their consequences. The course of events that followed the publication of the "Limits to Growth" in 1972 in the form of 2 oil shocks, food shock, pollution shock, and price shock seemed to bear out formally the gloomy predictions of the thesis with a remarkable speed. The 12 years of economic experience and the knowledge of resource trends postulate that even if the economic pressures visualized by the model are at work they are neither far reaching nor so drastic. Appropriate action can solve them. There are several limitations to the Limits to Growth model. The central theme of the model, which is overshoot and collapse, is unlikely to be the course of events. The model is too aggregative to be realistic. It exaggerates the ecological disaster arising out of the exponential growth of population and industry. The gross underestimation of renewable resources is a basic flaw of the model. The most critical weakness of the model is its gross underestimation of the historical trend of technological progress and the technological possiblities within industry and agriculture. The model does correctly emphasize the exponential growth of population as the source of several complications for economic growth and human welfare. Stabilization of population by reducing fertility is conducive for improving the quality of population and also advances the longterm management of the population growth and work force utilization. The perspective of longterm economic management involves populatio n planning, control of environmental pollution, conservation of scarce resources, exploration of resources, realization of technological possibilities in agriculture and industry and in farm and factory, and achievement of economic growth and its equitable distribution. PMID:12314595

Narayana, D L

38

A Learning Cycle on Exponential Growth and the Energy Crises.  

ERIC Educational Resources Information Center

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

Dykstra, D. I., Jr.

1982-01-01

39

Multipliers and singular integrals on exponential growth groups  

Microsoft Academic Search

We propose a simple version of Calderón–Zygmund theory, which is applicable to spaces with exponential volume growth, and then show that important specific operators can be treated within this framework.

Waldemar Hebisch; Tim Steger

2003-01-01

40

Stability of Parameter Estimates in the Split Population Exponential Distribution.  

ERIC Educational Resources Information Center

|The split-population exponential design suggested by Maltz and McCleary to predict parolee recidivism (TM 502 998) was applied to discharged psychiatric inpatients. Parameter estimates changed systematically as greater and greater observation time was allowed in the computation, thus limiting extrapolability. (Author/GDC)|

Miley, Alan D.

1978-01-01

41

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

42

The Ramsey model with logistic population growth  

Microsoft Academic Search

In standard economic growth theory it is assumed that labor force follows exponential growth, a not realistic assumption. As described in Maynard Smith (1974), the growth of natural populations is more accurately depicted by a logistic growth law. In this paper we analyze how the Ramsey growth model is affected by logistic growth of population, comparing it with the classic

Juan Gabriel Brida; Elvio Accinelli

2007-01-01

43

Capacity Expansion for Random Exponential Demand Growth with Lead Times  

Microsoft Academic Search

The combination of demand uncertainty and a lead time for adding capacity creates the risk of capacity shortage during the lead time. We formulate a model of capacity expansion for uncertain exponential demand growth and deterministic expansion lead times when there is an obligation to provide a specified level of service. The service level, defined in terms of the ratio

Sarah M. Ryan

2004-01-01

44

Bayesian D-optimal designs for the exponential growth model  

Microsoft Academic Search

Bayesian optimal designs for nonlinear regression models are of some interest and importance in the statistical literature. Numerical methods for their construction are well-established, but very few analytical studies have been reported. In this paper, we consider an exponential growth model used extensively in the modelling of simple organisms, and examine the explicit form of the Bayesian D-optimal designs. In

Saurabh Mukhopadhyay; Linda M. Haines

1995-01-01

45

Noise-driven unlimited population growth  

Microsoft Academic Search

Demographic noise causes unlimited population growth in a broad class of models which, without noise, would predict a stable finite population. We study this effect on the example of a stochastic birth-death model which includes immigration, binary reproduction, and death. The unlimited population growth proceeds as an exponentially slow decay of a metastable probability distribution (MPD) of the population. We

Baruch Meerson; Pavel V. Sasorov

2008-01-01

46

Staphylococcal Enterotoxin Synthesis During the Exponential, Transitional, and Stationary Growth Phases  

PubMed Central

Small inocula (1 to 10 colony-forming units per ml of broth) of Staphylococcus aureus strains S-6, S-6R, and FRI-100 were employed to study growth and enterotoxin synthesis in 4% protein hydrolysate powder broths. For each strain, the exponential growth phase ended once the population approached 109 to 2 × 109 colony-forming units per ml. By that time, the concentrations of enterotoxins A and B reached the minimal level (1 to 2 ?g/ml) at which the single gel diffusion tube method becomes applicable. By microslides and reverse passive hemagglutination, enterotoxins A and B were found to be synthesized during the exponential growth phase, but at different exponential rates.

Czop, Joyce K.; Bergdoll, Merlin S.

1974-01-01

47

POPULATION GENETICS OF NEUTRAL MUTATIONS IN EXPONENTIALLY GROWING CANCER CELL POPULATIONS  

PubMed Central

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

DURRETT, RICK

2013-01-01

48

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…

Gordon, Sheldon P.

2009-01-01

49

An elevation of the molar growth yield of Zymomonas mobilis during aerobic exponential growth  

Microsoft Academic Search

Elevated values of molar growth yield (Yx\\/s = 14–26 g mol–1) were obtained during exponential growth (? > 0.4 h–1) of Zymomonas mobilis ATCC 29191 by using reduced concentrations of glucose (6.25–100 mM) and increased oxygen supply (E\\u000a h > 300 mV) in the growth medium, as compared to the Yx\\/s of anaerobic exponential growth (8–10 g mol–1). Aerobically grown

Ramona Krú?e

1997-01-01

50

Exponential growth combined with exponential decline explains lifetime performance evolution in individual and human species.  

PubMed

The physiological parameters characterizing human capacities (the ability to move, reproduce or perform tasks) evolve with ageing: performance is limited at birth, increases to a maximum and then decreases back to zero at the day of death. Physical and intellectual skills follow such a pattern. Here, we investigate the development of sport and chess performances during the lifetime at two different scales: the individual athletes' careers and the world record by age class in 25 Olympic sports events and in grandmaster chess players. For all data sets, a biphasic development of growth and decline is described by a simple model that accounts for 91.7% of the variance at the individual level and 98.5% of the variance at the species one. The age of performance peak is computed at 26.1 years old for the events studied (26.0 years old for track and field, 21.0 years old for swimming and 31.4 years old for chess). The two processes (growth and decline) are exponential and start at age zero. Both were previously demonstrated to happen in other human and non-human biological functions that evolve with age. They occur at the individual and species levels with a similar pattern, suggesting a scale invariance property. PMID:21695422

Berthelot, Geoffroy; Len, Stéphane; Hellard, Philippe; Tafflet, Muriel; Guillaume, Marion; Vollmer, Jean-Claude; Gager, Bruno; Quinquis, Laurent; Marc, Andy; Toussaint, Jean-François

2011-06-22

51

World population growth—a general model  

Microsoft Academic Search

National populations currently fall into two categories, those in or closely approaching a stationary “K” phase, those still in an “r” phase of exponential growth. Throughout human history the “K” phase, in which populations match their available resource bases, has generally predominated. The exploitive “r” phase has intermittently occurred, and has then normally featured some revolutionary improvement in extractive capacity,

A. S. Boughey

1974-01-01

52

Analyzing population growth curves  

Microsoft Academic Search

Assessing animal population growth curves is an essential feature of field studies in ecology and wildlife management. We used five models to assess population growth rates with a number of sets of population growth rate data. A 'generalized' logistic curve provides a better model than do four other popular models. Use of difference equations for fitting was checked by a

L. L. Eberhardt; J. M. Breiwick; D. P. Demaster

2008-01-01

53

The kinetics of cellular recovery in exponential and plateau growth phase human glioma cells following {gamma}-irradiation  

SciTech Connect

In this study the kinetics of recovery following irradiation was examined in a human glioma cell line. Specific objectives were: to determine whether recovery is mono- or biexponential in nature; to determine if recovery half-times are different in exponential and plateau growth phase cells; to compare recovery half-times as a function of dose or recovery levels; and finally, to compare the kinetics of sublethal damage recovery and potentially lethal damage recovery in plateau growth phase cells. U-87MG cells were irradiated in exponential and plateau growth phases and then subjected to incubation at 37{degrees}C for various periods of time following or between doses prior to assaying for survival. Survival recovery curves were fit to a sum of exponential terms. Potentially lethal damage recovery was monoexponential in both exponential and plateau growth phase cells and occurred at the same rate when isorecovery values were compared. Recovery half-times increased in an exponential manner within the observed dose range. Recovery between doses of radiation (sublethal damage recovery) proceeded at a slower rate than recovery following a single dose of radiation (potentially lethal damage recovery). This study suggests that potentially lethal damage recovery is a saturated process and that the recovery half-time may increase in a linear-quadratic exponential function of dose similar to the absolute recovery level. In addition, if iso-recovery levels are compared, the recovery half-time is similar in rapidly and slowly proliferating cell populations. 42 refs., 6 figs., 3 tabs.

Heller, D.P. [Ottawa Regional Cancer Centre, Ontario (Canada)]|[Carleton Univ., Ontario (Canada); Raaphorst, G.P. [Ottawa Regional Cancer Centre, Ontario (Canada)

1994-09-30

54

Exponential growth by cross-catalytic cleavage of deoxyribozymogens  

Microsoft Academic Search

We have designed an autocatalytic cycle based on the highly efficient 10-23 RNA-cleaving deoxyribozyme that is capable of exponential amplification of catalysis. In this system, complementary 10-23 variants were inactivated by circularization, creating deoxyribozymogens. Upon linearization, the enzymes can act on their complements, creating a cascade in which linearized species accumulate exponentially. Seeding the system with a pool of linear

Matthew Levy; Andrew D. Ellington

2003-01-01

55

World Population Growth  

NSDL National Science Digital Library

The purpose of this module is to study the historical data on human population growth, and to compare the "natural" and "coalition" differential equation models as possible descriptions of the growth pattern.

Smith, David; Moore, Lang

2000-09-22

56

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

57

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

58

Population growth with randomly distributed jumps  

Microsoft Academic Search

.  ?The growth of populations with continuous deterministic and random jump components is treated. Three special models in which\\u000a random jumps occur at the time of events of a Poisson process and admit formal explicit solutions are considered: A)?Logistic\\u000a growth with random disasters having exponentially distributed amplitudes; B)?Logistic growth with random disasters causing\\u000a the removal of a uniformly distributed fraction of

Floyd B. Hanson; Henry C. Tuckwell

1997-01-01

59

Exponential Codimension Growth of PI Algebras: An Exact Estimate  

Microsoft Academic Search

LetAbe an associative PI-algebra over a fieldFof characteristic zero. By studying the exponential behavior of the sequence of codimensions {cn(A)} ofA, we prove thatInv(A)=limn??cn(A)always exists and is an integer. We also give an explicit way for computing such integer: letBbe a finite dimensionalZ2-graded algebra whose Grassmann envelopeG(B) satisfies the same identities ofA; thenInv(A)=Inv(G(B))=dimC(0)+dimC(1)whereC(0)+C(1)is a suitableZ2-graded semisimple subalgebra ofB.

A Giambruno; M Zaicev

1999-01-01

60

Improvement in Estimating the Population Mean Using Exponential Estimator in Simple Random Sampling  

Microsoft Academic Search

This study proposes some exponential ratio-type estimators for estimating the population mean of the variable under study, using known values of certain population parameter(s). Under simple random sampling without replacement (SRSWOR) scheme, mean square error (MSE) equations of all proposed estimators are obtained and compared with each other. The theoretical results are supported by a numerical illustration.

Rajesh Singh; Pankaj Chauhan; Nirmala Sawan; Florentin Smarandache

61

Molecular basis for the explanation of the exponential growth of polyelectrolyte multilayers  

Microsoft Academic Search

The structure of poly(L-lysine) (PLL)\\/hyaluronan (HA) polyelectrolyte multilayers formed by electrostatic self-assembly is studied by using confocal laser scanning microscopy, quartz crystal microbalance, and optical waveguide lightmode spectroscopy. These films exhibit an exponential growth regime where the thickness increases exponentially with the number of deposited layers, leading to micrometer thick films. Previously such a growth regime was suggested to result

C. Picart; J. Mutterer; L. Richert; Y. Luo; G. D. Prestwich; P. Schaaf; J.-C. Voegel; P. Lavalle

2002-01-01

62

Reformulation of the Solow economic growth model whit the Richards population growth law  

Microsoft Academic Search

In standard economic growth theory it is usually assumed that labor force follows exponential growth. That is not a realistic assumption. In this paper we introduce a generalized logistic equation (Richards law) that describes more accurately population growth. Then we analyze the neoclassical Solow model with growth of population following the Richards law, and compares it with the classical model

Elvio Accinelli; Juan Gabriel Brida

2005-01-01

63

Population Growth and Periodic Instability of the International System  

Microsoft Academic Search

From the perspective developed in this paper, it can be argued that exponential population growth resulted in the exponential decrease of the life-span of consecutive stable periods during the life-span of the European international system (1480-1945). However, it becomes evident as well that population growth as such is not a sufficient condition to generate a punctuated equilibrium dynamic in the

Ingo Piepers

2006-01-01

64

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, in this lesson students work in small groups to design experiments that will determine how environmental factors affect yeast population growth.

Engineering K-Ph.d. Program

65

[Study population theories and control population growth].  

PubMed

The development of population theory in China from Confucius and Mencius to the present day is considered. The author stresses the need to understand population statistics in order to develop population theory. The relationship between population growth and economic development is examined, and the need to control population growth is stressed. PMID:12178290

Wu, F

1980-03-01

66

Evolution of linkage disequilibrium of the founders in exponentially growing populations  

Microsoft Academic Search

Evolution of linkage disequilibrium of the founders in exponentially growing populations was studied using a time-inhomogeneous Itô process model. The model is an extension of the diffusion approximation of the Wright–Fisher model. As a measure of linkage disequilibrium, the squared standard linkage deviation, which is defined by a ratio of the moments, was considered. A system of ordinary differential equations

Shuhei Mano

2007-01-01

67

Exact likelihood inference for two exponential populations under joint Type-II censoring  

Microsoft Academic Search

Comparative lifetime experiments are of paramount importance when the object of a study is to ascertain the relative merits of two competing products in regard to the duration of their service life. In this paper, we discuss exact inference for two exponential populations when Type-II censoring is implemented on the two samples in a combined manner. We obtain the conditional

N. Balakrishnan; Abbas Rasouli

2008-01-01

68

An improved exponential estimator of finite population mean in simple random sampling using an auxiliary attribute  

Microsoft Academic Search

In this paper, we propose an exponential ratio type estimator of the finite population mean when auxiliary information is qualitative in nature. Under simple random sampling without replacement scheme, the expressions for the bias and the mean square error of the proposed estimator have been obtained, up to first order of approximation. To show that our proposed estimator is more

Lovleen Kumar Grover; Parmdeep Kaur

2011-01-01

69

Exponential vs Algebraic Growth and Transition Prediction in Boundary Layer Flow  

Microsoft Academic Search

For applications regarding transition prediction, wing design andcontrol of boundary layers, the fundamental understanding of disturbancegrowth in the flat-plate boundary layer is an important issue. In thepresent work we investigate the energy growth of eigenmodes andnon-modal optimal disturbances. We present a set of linear governingequations for the parabolic evolution of wavelike disturbances validboth for the exponential and algebraic growth scenario.

Ori Levin; Dan S. Henningson

2003-01-01

70

Connecting Population Growth and Biological Evolution  

NSDL National Science Digital Library

This activity will allow students to develop a model of the mathematical nature of population growth. The investigation provides an excellent opportunity for consideration of the population growth of plant and animal species and the resultant stresses that contribute to natural selection. Students will discover that populations grow or decline through the combined effects of births and deaths and through emigration and immigration into specific areas, increase through linear or exponential growth, with effects on resource use and on environmental pollution, and reach limits to growth. They will realize that carrying capacity is limited and although living organisms have the capacity to produce populations of arbitrarily large size, environments and resources are finite and this fundamental tension has profound effects on the interactions between organisms. This site has a list of materials and all other information required to complete this activity.

71

Modeling the growth of individuals in crowded plant populations  

Microsoft Academic Search

Aims We present an improved model for the growth of individuals in plant populations experiencing competition. Methods Individuals grow sigmoidally according to the Birch model, which is similar to the more commonly used Richards model, but has the ad- vantage that initial plant growth is always exponential. The individual plant growth models are coupled so that there is a maximum

Christian Damgaard; Jacob Weiner

2008-01-01

72

Why do rotifer populations present a typical sigmoid growth curve?  

Microsoft Academic Search

To determine the underlying processes to population growth in the rotifer Brachionus plicatilis, we conducted an experiment using 1.5 ml cultures for 70 days. All individuals were transferred daily to culture media containing algae, and the number of individuals, clutch sizes and number of deaths were counted. The population dynamics showed a typical sigmoid curve. The population density increased exponentially

Tatsuki Yoshinaga; Atsushi Hagiwara; Katsumi Tsukamoto

2001-01-01

73

Population growth in random media  

Microsoft Academic Search

In this second part of a two-part presentation, we continue with the model introduced in Part I. In this part, the initial configuration has one particle at each site to the left of 0 and no particle elsewhere. The expected number of particles observed at a site moving at speed t? has an exponential growth rate (speed-t growth rate) that

A. Greven; F. den Hollander

1991-01-01

74

Laws of population growth  

PubMed Central

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

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

2008-01-01

75

Exponential growth of fingering instabilities of spreading films under horizontal thermal gradients  

Microsoft Academic Search

A thin liquid ribbon deposited on a wettable surface and subjected to a horizontal thermal gradient develops periodic fingers towards the cold region. We present an observation of the exponential growth regime, expected at early times, but not accessible in other driven fingering patterns induced by gravitational flows, spinning drops, or vertical thermal gradients. We have monitored the wavelength ?

J. B. Brzoska; F. Brochard-Wyart; F. Rondelez

1992-01-01

76

[Poverty and population growth].  

PubMed

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

1983-07-01

77

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

Microsoft Academic Search

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

Mirjam Ebersbach; Wilma C. M. Resing

2008-01-01

78

Noise-driven unlimited population growth  

NASA Astrophysics Data System (ADS)

Demographic noise causes unlimited population growth in a broad class of models which, without noise, would predict a stable finite population. We study this effect on the example of a stochastic birth-death model which includes immigration, binary reproduction, and death. The unlimited population growth proceeds as an exponentially slow decay of a metastable probability distribution (MPD) of the population. We develop a systematic WKB theory, complemented by the van Kampen system size expansion, for the MPD and for the decay time. Important signatures of the MPD are a power-law tail (such that all the distribution moments, except the zeroth one, diverge) and the presence in the solution of two different WKB modes.

Meerson, Baruch; Sasorov, Pavel V.

2008-12-01

79

Transition of Linear to Exponential Hole Growth Modes in Thin Free Standing Films.  

NASA Astrophysics Data System (ADS)

Transition of Linear to Exponential Hole Growth Modes in Thin Free Standing Films. J.H. Xavier1, J. Sokolov1, M.H. Rafailovich1, Y.Pu1, T. Petersen2 1 Department of Materials Science and Engineering, SUNY at Stony Brook. Stony Brook, N.Y. 11794 2 Princeton University, Princeton, N J 08544. Abstract: We have measured the rate of hole growth in free standing polystyrene films 800Å to 1?micron-meter thick and of molecular weights (MW) 65K to 2M . We have observed a transition from linear to exponential growth of the hole at a temperature which depends on MW and thickness. For thin films of 800Å, we observed at 100°C a linear growth mode nearly independent of MW. For micron thick films at temperatures above 130°C, exponential growth was observed, consistent with the results of Debregeas et al (ref.1). At intermediate temperatures and thicknesses, a crossover transition was observed. Relevant physical models will be discussed. Reference: [1] G. Debregeas, P. Martin and F. Brochard-Wyart. Phys.Rev.Lett.75, 3886 (1995).

Xavier, Jean-Harry; Sokolov, Jonathan; Rafailovich, Miriam; Pu, Yuxie; Petersen, Tom

2002-03-01

80

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

81

Exponential-Phase Glycogen Recycling Is Essential for Growth of Mycobacterium smegmatis  

PubMed Central

Bacterial glycogen is a polyglucose storage compound that is thought to prolong viability during stationary phase. However, a specific role for glycogen has not been determined. We have characterized SMEG53, a temperature-sensitive mutant of Mycobacterium smegmatis that contains a mutation in glgE, encoding a putative glucanase. This mutation causes exponentially growing SMEG53 cells to stop growing at 42°C in response to high levels of glycogen accumulation. The mutation in glgE is also associated with an altered growth rate and colony morphology at permissive temperatures; the severity of these phenotypes correlates with the amount of glycogen accumulated by the mutant. Suppression of the temperature-sensitive phenotype, via a decrease in glycogen accumulation, is mediated by growth in certain media or multicopy expression of garA. The function of GarA is unknown, but the presence of a forkhead-associated domain suggests that this protein is a member of a serine-threonine kinase signal transduction pathway. Our results suggest that in M. smegmatis glycogen is continuously synthesized and then degraded by GlgE throughout exponential growth. In turn, this constant recycling of glycogen controls the downstream availability of carbon and energy. Thus, in addition to its conventional storage role, glycogen may also serve as a carbon capacitor for glycolysis during the exponential growth of M. smegmatis.

Belanger, Aimee E.; Hatfull, Graham F.

1999-01-01

82

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

83

Global Compactness Properties of Semilinear Elliptic Equations with Critical Exponential Growth  

Microsoft Academic Search

Sequences of positive solutions to semilinear elliptic equations of critical exponential growth in the plane either are precompact in the Sobolev H1-topology or concentrate at isolated points of the domain. For energies allowing at most single-point blow-up, we establish a universal blow-up pattern near the concentration point and uniquely characterize the blow-up energy in terms of a geometric limiting problem.

M Adimurthi; Michael Struwe

2000-01-01

84

The Exponential Function--Part VIII  

ERIC Educational Resources Information Center

|Presents part eight of a continuing series on the exponential function in which, given the current population of the Earth and assuming a constant growth rate of 1.9 percent backward looks at world population are made. (SL)|

Bartlett, Albert A.

1978-01-01

85

Population Growth: Crisis and Challenge.  

ERIC Educational Resources Information Center

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

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

86

Growth rate control of adherent bacterial populations.  

PubMed Central

We report a novel in vitro method which, through application of appropriate nutrient limitations, enables growth rate control of adherent bacterial populations. Exponentially growing cells are collected by pressure filtration onto cellulose acetate membranes. Following inversion into the bases of modified fermentors, membranes and bacteria are perfused with fresh medium. Newly formed and loosely attached cells are eluted with spent medium. Steady-state conditions (dependent upon the medium flow rate) at which the adherent bacterial biomass is constant and proportional to the limiting nutrient concentrations are rapidly achieved, and within limits, the growth rate is proportional to the medium flow rate. Scanning electron microscopic studies showed that such populations consist of individual cells embedded within an extracellular polymer matrix. Images

Gilbert, P; Allison, D G; Evans, D J; Handley, P S; Brown, M R

1989-01-01

87

Population growth and environmental degradation in Malawi.  

PubMed

Malawi has been ranked by the World Bank as one of the poorest countries in Africa. Malawi's only resources are its people and fertile soil, which comprises about 55% of land area. Environmental degradation and population growth conditions in Malawi were used to illustrate the model of environmental degradation linked to population pressure on land resources and government development strategies that favored large-scale agricultural farms. The result has been deforestation, overgrazing, overuse of land for subsistence, and increased population density. The argument was that population growth in some developing countries has been so rapid that environmental collapse is the result. The theoretical framework linking population growth, environment, and resources emphasized processes: 1) the precursor stage of underlying causes; 2) the problem phase with potential ecological and economic decline; and 3) consequences (environmental decline, reduction in food production systems, and reduction in standard of living). The precursors were identified as an agrarian society, lack of a population policy, and emphasis on large families. The problems were rapid population growth and immigration from Mozambique, which led to increased demand for trees for fuel and consequent deforestation, increased demand for arable land and consequent landlessness, increased investment in livestock and consequent overgrazing, and continued population momentum which was a financial burden to government and resulted in increased labor competition. The ecological consequences were soil erosion, degradation of vegetation, and water supply contamination and decline. Eventually, famines will occur and lead to disease, migration, deserted villages, urbanization, unemployment, ethnic conflicts, and political unrest. Population was estimated at 8.75 million in 1990, with exponential growth expected. Completed family size was 6.6 children per woman. Even replacement fertility would mean growth for 50 more years. Population density was 85 persons per sq. km and 300 persons per sq. km on arable land in the Southern Region. 26% of land area could be cultivated to accommodate future population growth; most of this land would be in the Southern Region with higher population density. Delicate marginal lands had been cultivated with resultant mineral leaching, hard panning, and soil erosion. Shifting cultivation patterns have been replaced due to population pressure. Small landholders produced 80% of agricultural products in the past, but landlessness and commercial farming are growing concerns. PMID:12288851

Kalipeni, E

1992-01-01

88

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

NASA Astrophysics Data System (ADS)

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

Maitra, Arijit; Dill, Ken

2013-03-01

89

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

NASA Astrophysics Data System (ADS)

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

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

2000-07-01

90

Estimation of population growth or decline in genetically monitored populations.  

PubMed Central

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.

Beaumont, Mark A

2003-01-01

91

Patterns in the effects of infectious diseases on population growth  

Microsoft Academic Search

An infectious disease may reduce or even stop the exponential growth of a population. We consider two very simple models for microparasitic and macroparasitic diseases, respectively, and study how the effect depends on a contact parameter K. The results are presented as bifurcation diagrams involving several threshold values of ?. The precise form of the bifurcation diagram depends critically on

O. Diekmann; M. Kretzschmar

1991-01-01

92

A mutation in rpoS enhances biofilm formation in Escherichia coli during exponential phase of growth  

Microsoft Academic Search

Biofilm formation in Escherichia coli is a process that involves slow growth and stress conditions where several molecular signals and growth phase regulated genes are involved. Here we show that rpoS mutant strains (defective in the stress regulator ?S) exhibit an increased production of biofilm, especially in the exponential phase of growth. Our results indicate that rpoS mutants produce an

F. Paola Corona-Izquierdo; Jorge Membrillo-Hernández

2002-01-01

93

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

94

Limited Population Growth  

NSDL National Science Digital Library

This module models population as a function of time in a setting where there is a maximum population M that the environment will support. More specifically, to see that we can develop a graphical model from assumptions about the rate of change -- without any knowledge of an algebraic form for the model function.

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

2000-09-22

95

Population growth and natural resource scarcity: long-run development under seemingly unfavourable conditions  

Microsoft Academic Search

The paper develops a model with non-exponential population growth, nonrenewable natural resources, and endogenous knowledge creation to analyse substitution between primary inputs and an essential use of resources in the innovation sectors, which is generally considered as most unfavourable for growth. We show that population growth and poor input substitution are not detrimental but even needed to obtain sustainable consumption.

Lucas Bretschger

2008-01-01

96

Staphylococcus aureus Aconitase Inactivation Unexpectedly Inhibits Post-Exponential-Phase Growth and Enhances Stationary-Phase Survival  

Microsoft Academic Search

Staphylococcus aureus preferentially catabolizes glucose, generating pyruvate, which is subsequently oxidized to acetate under aerobic growth conditions. Catabolite repression of the tricarboxylic acid (TCA) cycle results in the accumulation of acetate. TCA cycle derepression coincides with exit from the exponential growth phase, the onset of acetate catabolism, and the maximal expression of secreted virulence factors. These data suggest that carbon

Greg A. Somerville; Michael S. Chaussee; Carrie I. Morgan; J. Ross Fitzgerald; David W. Dorward; Lawrence J. Reitzer; James M. Musser

2002-01-01

97

Solar Flares with an Exponential Growth of the Emission Measure in the Impulsive Phase Derived from X-ray Observations  

NASA Astrophysics Data System (ADS)

The light curves of solar ?ares in the impulsive phase are complex in general, indicating that multiple physical processes are involved in. With the GOES (Geostationary Operational Environmental Satellite) observations, we ?nd that there are a subset of ?ares, whose impulsive phases are dominated by a period of exponential growth of the emission measure. The ?ares occurred from January 1999 to December 2002 are analyzed, and the results from the observations made with both GOES 8 and GEOS 10 satellites are compared to estimate the instrumental uncertainties. Their mean temperatures during this exponential growth phase have a normal distribution. Most ?ares within the 1? range of this temperature distribution belong to the GOES class B or C, with the peak ?uxes at the GOES low-energy channel following a log-normal distribution. The growth rate and duration of the exponential growth phase also follow a log- normal distribution, in which the duration is distributed in the range from half a minute to about half an hour. As expected, the growth time is correlated with the decay time of the soft X-ray ?ux. We also ?nd that the growth rate of the emission measure is strongly anti-correlated with the duration of the exponential growth phase, and the mean temperature increases slightly with the increase of the growth rate. The implications of these results on the study of energy release in solar ?ares are discussed in the end.

Han, Fei-ran; Liu, Si-ming

2013-07-01

98

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

99

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

100

[Population ethics and growth].  

PubMed

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

Boim, D

101

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

102

The Outlook for Population Growth  

PubMed Central

Projections of population size, growth rates and age distribution, although extending to distant horizons, shape policies today for the economy, environment, and government programs such as public pensions and health care. The projections can lead to costly policy adjustments which in turn can cause political and economic turmoil. The United Nations projects global population to grow from about 7 billion today to 9.3 billion in 2050 and 10.1 billion in 2100 while the Old Age Dependency Ratio doubles by 2050 and triples by 2100. How are such population projections made, and how certain can we be about the trends they foresee?

Lee, Ronald

2011-01-01

103

The outlook for population growth.  

PubMed

Projections of population size, growth rates, and age distribution, although extending to distant horizons, shape policies today for the economy, environment, and government programs such as public pensions and health care. The projections can lead to costly policy adjustments, which in turn can cause political and economic turmoil. The United Nations projects global population to grow from about 7 billion today to 9.3 billion in 2050 and 10.1 billion in 2100, while the Old Age Dependency Ratio doubles by 2050 and triples by 2100. How are such population projections made, and how certain can we be about the trends they foresee? PMID:21798936

Lee, Ronald

2011-07-29

104

Conflict, Distribution and Population Growth  

Microsoft Academic Search

This paper studies an optimal foraging model where distributive conflicts among foragers emerge from population growth. It investigates distributive rules set to resolve the conflicts. Efficient distributive rules are the ones associated with the most efficient productive decisions. Unequal societies, where the ruling class or King maximizes the surplus, engender the choice of more efficient productive combinations and to a

Joáo Ricardo Faria; Andre Rossi De Oliveira

2003-01-01

105

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…

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

106

Nutrition, Development, and Population Growth  

ERIC Educational Resources Information Center

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

Berg, Alan

1973-01-01

107

Phase space structure of multi-dimensional systems by means of the mean exponential growth factor of nearby orbits  

Microsoft Academic Search

In this paper we deal with an alternative technique to study global dynamics in Hamiltonian systems, the mean exponential growth factor of nearby orbits (MEGNO), that proves to be efficient to investigate both regular and stochastic components of phase space. It provides a clear picture of resonance structures, location of stable and unstable periodic orbits as well as a measure

P. M. Cincotta; C. M. Giordano; C. Simó

2003-01-01

108

Maximum Likelihood Estimation of Population Growth Rates Based on the Coalescent  

Microsoft Academic Search

We describe a method for co-estimating 4Nem (four times the product of effective population size and neutral mutation rate) and population growth rate from sequence samples using Metropolis-Hastings sampling. Population growth (or decline) is assumed to be exponential. The estimates of growth rate are biased upwards, especially when 4Nem is low; there is also a slight upwards bias in the

Mary K. Kuhner; Jon Yamato; Joseph Felsenstein

1998-01-01

109

Population Growth and National Population Policy of India  

NASA Astrophysics Data System (ADS)

The population growth in India may overtake China by the year 2030. The National Population Policy of India targets population stabilization in India by the year 2045. The present paper carries out objective analysis of the population growth in India in terms of change in specific growth. At the present rate of specific growth rate decline, the population by the end of the century will be 2.49 billion. For the population to achieve zero growth by the year 2045, a decline in specific growth rate will have to be achieved at the rate of 0.000428 per year.

Thukral, A. K.; Singh, B. P.

2008-01-01

110

Gene Genealogy and Properties of Test Statistics of Neutrality Under Population Growth  

Microsoft Academic Search

We consider the Wright-Fisher model with exponential population growth and investigate effects of pop- ulation growth on the shape of genealogy and the distributions of several test statistics of neutrality. In the limiting case as the population grows rapidly, the rapid-growth-limit genealogy is characterized. We obtained approximate expressions for expectations and variances of test statistics in the rapid-growth-limit genealogy and

Akinori Sano; Hidenori Tachida

2005-01-01

111

Exponential Energy Decay for Damped Klein-Gordon Equation with Nonlinearities of Arbitrary Growth  

Microsoft Academic Search

We derive a uniform exponential decay of the total energy for the nonlinear Klein-Gordon equation with a damping around spatial infinity in the whole space or in the exterior of a star shaped obstacle.

Lassaad Aloui; Slim Ibrahim; Kenji Nakanishi

2010-01-01

112

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

113

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

PubMed Central

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

Rosenberg, Eugene; Katarski, Mary; Gottlieb, Peter

1967-01-01

114

Fatigue crack propagation model for plain concrete – An analogy with population growth  

Microsoft Academic Search

In this work, an analytical model is proposed for fatigue crack propagation in plain concrete based on population growth exponential law and in conjunction with principles of dimensional analysis and self-similarity. This model takes into account parameters such as loading history, fracture toughness, crack length, loading ratio and structural size. The predicted results are compared with experimental crack growth data

Sonalisa Ray; J. M. Chandra Kishen

2010-01-01

115

Exponential-Phase Glycogen Recycling Is Essential for Growth of Mycobacterium smegmatis  

Microsoft Academic Search

Bacterial glycogen is a polyglucose storage compound that is thought to prolong viability during stationary phase. However, a specific role for glycogen has not been determined. We have characterized SMEG53, a temperature-sensitive mutant of Mycobacterium smegmatis that contains a mutation in glgE, encoding a putative glucanase. This mutation causes exponentially growing SMEG53 cells to stop growing at 42°C in response

AIMEE E. BELANGER; GRAHAM F. HATFULL

1999-01-01

116

Population growth and air quality in California  

Microsoft Academic Search

Demographers are often interested in the environmental impacts of population growth. I examine the impact of growth specifically\\u000a on air quality in California. In recent decades, California has suffered from notoriously polluted air and has experienced\\u000a rapid population growth. Despite the population .growth, air quality actually has improved since the early 1980s due to aggressive\\u000a regulatory efforts. Using data for

James C. Cramer

1998-01-01

117

Modelling urban - rural population growth in China  

Microsoft Academic Search

The population of China is still growing despite a dramatic decline in fertility in the past two decades. There are marked urban - rural differentials in fertility and, as a result, the pace of urbanization has significant effects on population growth. In this research an attempt is made to model urban - rural population growth in China. A demoeconomic model

J Shen; N A Spence

1996-01-01

118

Cosmic history of viable exponential gravity: equation of state oscillations and growth index from inflation to dark energy era  

NASA Astrophysics Data System (ADS)

A generic feature of viable F(R) gravity is investigated: it is demonstrated that during the matter dominated era the large frequency oscillations of the effective dark energy may influence the behavior of higher derivatives of the Hubble parameter with the risk to produce some singular unphysical solutions at high redshift. This behavior is explicitly analyzed for realistic F(R) models, in particular, exponential gravity and a power form model. To stabilize such oscillations, we consider the additional modification of the models via a correction term which does not destroy the viability properties. A detailed analysis on the future evolution of the universe and the evolution history of the growth index of the matter density perturbations are performed. Furthermore, we explore two applications of exponential gravity to the inflationary scenario. We show how it is possible to obtain different numbers of e-folds during the early-time acceleration by making different choices of the model parameters in the presence of ultrarelativistic matter, which destabilizes inflation and eventually leads to the exit from the inflationary stage. We execute the numerical analysis of inflation in two viable exponential gravity models. It is proved that at the end of the inflation, the effective energy density and curvature of the universe decrease and thus a unified description between inflation and the ?CDM-like dark energy dominated era can be realized.

Bamba, Kazuharu; Lopez-Revelles, Antonio; Myrzakulov, R.; Odintsov, S. D.; Sebastiani, L.

2013-01-01

119

The General Growth Logistics of Cell Populations  

Microsoft Academic Search

An increment model based on thermodynamics lays bare that the cell size distributions of archaea, prokaryotes and eukaryotes\\u000a are optimized and belong to the same universal class. Yet, when a cell absorbs mass or signals are processed, these conditions\\u000a are disturbed. Relaxation re-installs ideal growth conditions via an exponential process with a rate that slows down with\\u000a the cell size.

H. G. Kilian; D. Bartkowiak; D. Kaufmann; R. Kemkemer

2008-01-01

120

AI2 does not function as a quorum sensing molecule in Campylobacter jejuni during exponential growth in vitro  

Microsoft Academic Search

Background  \\u000a Campylobacter jejunicontains a homologue of theluxSgene shown to be responsible for the production of the signalling molecule autoinducer-2 (AI-2) inVibrio harveyiandVibrio cholerae. The aim of this study was to determine whether AI-2 acted as a diffusible quorum sensing signal controllingC. jejunigene expression when it is produced at high levels during mid exponential growth phase.\\u000a \\u000a \\u000a \\u000a \\u000a Results  AI-2 activity was produced by

Kathryn Holmes; Tim J Tavender; Klaus Winzer; Jerry M Wells; Kim R Hardie

2009-01-01

121

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.

Godfray, H Charles J; Rees, Mark

2002-01-01

122

Population Growth, Economic Growth, and Future Requirements for Public Assistance.  

National Technical Information Service (NTIS)

The purpose of the study is twofold: First, to assess the probable need for public assistance over the next three decades; second, to examine how this need will differ under different rates of population growth and of economic growth.

D. Greenberg

1973-01-01

123

THE NEOCLASSICAL MODEL OF SOLOW AND SWAN WITH LOGISTIC POPULATION GROWTH  

Microsoft Academic Search

This paper is an attempt at studying the neoclassical Solow-Swan model within a framework where the change over time of the labor-force is given by the logistic population model. In the canonical Solow-Swan model, the growth rate of population is constant, yielding an exponential behavior of population size over time, which is clearly unrealistic and unsustainable in the very long-run.

MASSIMILIANO FERRARA; LUCA GUERRINI

124

Cell population heterogeneity during growth of Bacillus subtilis  

PubMed Central

We have discovered that cells of Bacillus subtilis at the mid-exponential phase of growth are a mixed population of two strikingly different cell types. One type is single swimming cells (or cell doublets) in which the transcription factor for motility, ?D, is active (?D ON). The other type is long chains of sessile cells in which ?D is inactive (?D OFF). The population is strongly biased toward ?D-ON cells by the action of a novel regulatory protein called SwrA. SwrA stimulates the transcription of a large operon (the flagellum/chemotaxis operon), which includes the genes for ?D and an activator of ?D-directed gene expression, SwrB. Cell population heterogeneity could enable B. subtilis to exploit its present location through the production of sessile cells as well as to explore new environmental niches through the generation of nomadic cells.

Kearns, Daniel B.; Losick, Richard

2005-01-01

125

AI-2 does not function as a quorum sensing molecule in Campylobacter jejuni during exponential growth in vitro  

PubMed Central

Background Campylobacter jejuni contains a homologue of the luxS gene shown to be responsible for the production of the signalling molecule autoinducer-2 (AI-2) in Vibrio harveyi and Vibrio cholerae. The aim of this study was to determine whether AI-2 acted as a diffusible quorum sensing signal controlling C. jejuni gene expression when it is produced at high levels during mid exponential growth phase. Results AI-2 activity was produced by the parental strain NCTC 11168 when grown in rich Mueller-Hinton broth (MHB) as expected, but interestingly was not present in defined Modified Eagles Medium (MEM-?). Consistent with previous studies, the luxS mutant showed comparable growth rates to the parental strain and exhibited decreased motility halos in both MEM-? and MHB. Microarray analysis of genes differentially expressed in wild type and luxS mutant strains showed that many effects on mRNA transcript abundance were dependent on the growth medium and linked to metabolic functions including methionine metabolism. Addition of exogenously produced AI-2 to the wild type and the luxS mutant, growing exponentially in either MHB or MEM-? did not induce any transcriptional changes as analysed by microarray. Conclusion Taken together these results led us to conclude that there is no evidence for the role of AI-2 in cell-to-cell communication in C. jejuni strain NCTC 11168 under the growth conditions used, and that the effects of the luxS mutation on the transcriptome are related to the consequential loss of function in the activated methyl cycle.

2009-01-01

126

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

127

The end of world population growth  

Microsoft Academic Search

There has been enormous concern about the consequences of human population growth for the environment and for social and economic development. But this growth is likely to come to an end in the foreseeable future. Improving on earlier methods of probabilistic forecasting, here we show that there is around an 85 per cent chance that the world's population will stop

Wolfgang Lutz; Warren Sanderson; Sergei Scherbov

2001-01-01

128

Longer Life and Population Growth  

Microsoft Academic Search

Enthusiasm about the prospect of large increases in human life expectancy is often dampened by fears that lower mortality will increase population size, hence population pressure. A simple mathematical model of life-cycle stretching demonstrates that if increased longevity is accompanied by later childbearing, a trend that is already underway, future declines in mortality will not increase population size. Copyright 1999

Joshua R. Goldstein; Wilhelm Schlag

1999-01-01

129

Population aging and endogenous economic growth.  

PubMed

We investigate the consequences of population aging for long-run economic growth perspectives. Our framework incorporates endogenous growth models and semi-endogenous growth models as special cases. We show that (1) increases in longevity have a positive impact on per capita output growth, (2) decreases in fertility have a negative impact on per capita output growth, (3) the positive longevity effect dominates the negative fertility effect in case of the endogenous growth framework, and (4) population aging fosters long-run growth in the endogenous growth framework, while its effect depends on the relative change between fertility and mortality in the semi-endogenous growth framework.Electronic supplementary material The online version of this article (doi:10.1007/s00148-012-0441-9) contains supplementary material, which is available to authorized users. PMID:23576847

Prettner, Klaus

2012-09-15

130

On Population Growth Near Protected Areas  

PubMed Central

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

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

2009-01-01

131

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

Microsoft Academic Search

We continue the previous article's discussion of bounds, for preva- lent dieomorphisms of smooth compact manifolds, on the growth of the num- ber of periodic points and the decay of their hyperbolicity as a function of their periodn. In that article we reduced the main results to a problem, for certain families of dieomorphisms, of bounding the measure of parameter

VADIM Y. U. KALOSHIN; BRIAN R. HUNT

2007-01-01

132

A perspective on population growth in India.  

PubMed

Population growth is heralded as a major problem of India; it will determine to a large extent the living conditions of people for decades to come. This paper analyzes the interrelated issues of population growth stabilization, the magnitude of necessary efforts to provide basic essentials to the growing population, and the impact upon the environment. Estimates of population projections are presented, based on the optimistic but probable assumption that India could reach reproductive level fertility in the period 2000-05. If sustained thereafter, the country's population would stabilize around the year 2100 at 1420 million people. In the mean time, the absolute increase of population in the next 2-3 decades will be greater than at present. The effect of population growth on cities and the living conditions of the city dwellers is reviewed and it is pointed out that it is in developing countries where population growth is the primary force producing large urban centers. Population growth presents problems with respect to employment opportunities. The predicted flood of manpower cannot be totally absorbed by the organized sector; it is argued that the agricultural sector is the only one which can help the country during this period of high population growth. To support this large and rising population, India will need to rapidly increase its average crop yields 2-3 times the present level for a modest improvement process. The expected population growth will also have consequences on environmental deterioration and water supply contamination. Finally, progress on human development lines has been taking place in India, but achievements to date are uneven. It is stressed that a national concerted effort is required to achieve such goals. PMID:12179091

Singh, H

133

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

134

Philopatry and Population Growth of Red Kites, Milvus milvus, in Wales  

Microsoft Academic Search

Between 1946 and 1993, the number of territorial red kites, which form an isolated relict population in mid-Wales, has increased from 7 pairs to 113 pairs. Population growth has been approximately exponential at a mean rate of 5% per year. Breeding success was generally poor, but improved from an average of 0.53 young per pair in 1946-1960 to 0.71 young

I. Newton; P. E. Davis; D. Moss

1994-01-01

135

Cell wall mannoproteins during the population growth phases in Saccharomyces cerevisiae  

Microsoft Academic Search

Mannoproteins from cell walls of Saccharomyces cerevisiae synthesized at successive stages of the population growth cycle have been solubilized with Zymolyase and subsequently analyzed. The major change along the population cycle concerned a large size mannoprotein material; the size of the newly-synthesized molecules varied from 120,000–500,000 (mean of about 200,000) at early exponential phase to 250,000–350,000 (mean of about 300,000)

E. Valentín; E. Herrero; H. Rico; F. Miragall; R. Sentandreu

1987-01-01

136

Population Growth and Economic and Social Development.  

ERIC Educational Resources Information Center

All evidence shows that fast population growth slows development in the developing countries. It is the combination of social development and family planning that is so powerful in reducing fertility. Governments must act now. (RM)

Clausen, A. W.

1985-01-01

137

Population priorities: the challenge of continued rapid population growth  

PubMed Central

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

Turner, Adair

2009-01-01

138

Generalized Verhulst Laws for Population Growth  

Microsoft Academic Search

The growth or decay of population of a single species interacting with a large number of other species (or environment) according to the Volterra-Lotka model is investigated. When the environment is initially very close to its equilibrium level, the growth of a single species follows a generalized Verhulst law, containing hereditary effects. The derivation, modeled on statistical mechanical theories of

Robert Zwanzig

1973-01-01

139

Stochastic population growth in spatially heterogeneous environments.  

PubMed

Classical ecological theory predicts that environmental stochasticity increases extinction risk by reducing the average per-capita growth rate of populations. For sedentary populations in a spatially homogeneous yet temporally variable environment, a simple model of population growth is a stochastic differential equation dZ(t) = ?Z(t)dt + ?Z(t)dW(t), t ? 0, where the conditional law of Z(t+?t)-Z(t) given Z(t) = z has mean and variance approximately z ??t and z²?²?t when the time increment ?t is small. The long-term stochastic growth rate lim(t??) t?¹ log Z(t) for such a population equals ? ? ?²/2 . Most populations, however, experience spatial as well as temporal variability. To understand the interactive effects of environmental stochasticity, spatial heterogeneity, and dispersal on population growth, we study an analogous model X(t) = (X¹(t) , . . . , X(n)(t)), t ? 0, for the population abundances in n patches: the conditional law of X(t+?t) given X(t) = x is such that the conditional mean of X(i)(t+?t) ? X(i)(t) is approximately [x(i)?(i) + ?(j) (x(j) D(ji) ? x(i) D(i j) )]?t where ?(i) is the per capita growth rate in the ith patch and D(ij) is the dispersal rate from the ith patch to the jth patch, and the conditional covariance of X(i)(t+?t)? X(i)(t) and X(j)(t+?t) ? X(j)(t) is approximately x(i)x(j)?(ij)?t for some covariance matrix ? = (?(ij)). We show for such a spatially extended population that if S(t) = X¹(t)+· · ·+ X(n)(t) denotes the total population abundance, then Y(t) = X(t)/S(t), the vector of patch proportions, converges in law to a random vector Y(?) as t ? ?, and the stochastic growth rate lim(t??) t?¹ log S(t) equals the space-time average per-capita growth rate ?(i)?(i)E[Y(i)(?)] experienced by the population minus half of the space-time average temporal variation E[?(i,j) ?(i j)Y(i)(?) Y(j)(?)] experienced by the population. Using this characterization of the stochastic growth rate, we derive an explicit expression for the stochastic growth rate for populations living in two patches, determine which choices of the dispersal matrix D produce the maximal stochastic growth rate for a freely dispersing population, derive an analytic approximation of the stochastic growth rate for dispersal limited populations, and use group theoretic techniques to approximate the stochastic growth rate for populations living in multi-scale landscapes (e.g. insects on plants in meadows on islands). Our results provide fundamental insights into "ideal free" movement in the face of uncertainty, the persistence of coupled sink populations, the evolution of dispersal rates, and the single large or several small (SLOSS) debate in conservation biology. For example, our analysis implies that even in the absence of density-dependent feedbacks, ideal-free dispersers occupy multiple patches in spatially heterogeneous environments provided environmental fluctuations are sufficiently strong and sufficiently weakly correlated across space. In contrast, for diffusively dispersing populations living in similar environments, intermediate dispersal rates maximize their stochastic growth rate. PMID:22427143

Evans, Steven N; Ralph, Peter L; Schreiber, Sebastian J; Sen, Arnab

2012-03-18

140

Delay eect in models of population growth  

Microsoft Academic Search

First, we systematize earlier results on the global stability of the model ? x + µx = f(x(· )) of population growth. Second, we investigate the eect of delay on the asymptotic behavior when the nonlinearity f is a unimodal function. Our results can be applied to several population models (7, 9-13) because the function f does not need to

Dang Vu Giang; Yongwimon Lenbury; Thomas I. Seidman

141

Nepal's rapid population growth still a concern.  

PubMed

The Nepal representative of the Economic and Social Commission for Asia and the Pacific (ESCAP) noted at the 194 ESCAP Commission meeting in Beijing that rapid population growth was still a problem: 2.1% per year. The annual average income growth rate was only 3.5% and poverty was widespread. The combination of poverty and rapid population growth were contributing to environmental damage. Sustainable solutions were needed for dealing with all three aforementioned issues. A high priority was already attached to population control programs, because population growth was linked to raising the standard of living and solving environmental problems. Women need to be placed in prominent positions in development efforts and given equality with men. Nepal representatives did attend the preparatory meeting on April 22, 1994, to the International Conference on Population and Development (ICPD) to be held in Cairo in September. The Preparatory Committee will be developing a report for the Conference. Solutions to population issues were seen as instrumental to achieving poverty alleviation and high economic growth. PMID:12288618

1994-05-01

142

Growth of mammalian cells on substrates coated with cellular microexudates. I. Effect on cell growth at low population densities  

PubMed Central

Mammalian and avian cells cultured on glass or plastic substrates produce microexudates of cellular macromolecules which remain bound to the substrate when the cells are detached. The gross macromolecular composition of microexudates from a range of diploid, heteroploid, and virus-transformed cells was determined with cells labeled with radioisotopes. Significant differences in the amounts of cellular glycoproteins, proteins, and RNA present in microexudates were found between different cell types and between cells of the same type at different stages of growth. Inoculation of cells onto substrates "coated" with microexudates altered their growth behavior. Microexudates from exponentially growing subconfluent homotypic and heterotypic cell populations enhanced the growth of mouse and chick embryo cells seeded at very low densities, but similar microexudates had no effect on the proliferation of cells seeded at higher densities. The enhanced growth of low-density cell populations seeded on microexudates was compared with the growth enhancement produced by feeder cell layers and conditioned medium.

1975-01-01

143

Exponential Probabilities  

NSDL National Science Digital Library

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

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

2009-01-21

144

Demographic heterogeneity, cohort selection, and population growth.  

PubMed

Demographic heterogeneity--variation among individuals in survival and reproduction--is ubiquitous in natural populations. Structured population models address heterogeneity due to age, size, or major developmental stages. However, other important sources of demographic heterogeneity, such as genetic variation, spatial heterogeneity in the environment, maternal effects, and differential exposure to stressors, are often not easily measured and hence are modeled as stochasticity. Recent research has elucidated the role of demographic heterogeneity in changing the magnitude of demographic stochasticity in small populations. Here we demonstrate a previously unrecognized effect: heterogeneous survival in long-lived species can increase the long-term growth rate in populations of any size. We illustrate this result using simple models in which each individual's annual survival rate is independent of age but survival may differ among individuals within a cohort. Similar models, but with nonoverlapping generations, have been extensively studied by demographers, who showed that, because the more "frail" individuals are more likely to die at a young age, the average survival rate of the cohort increases with age. Within ecology and evolution, this phenomenon of "cohort selection" is increasingly appreciated as a confounding factor in studies of senescence. We show that, when placed in a population model with overlapping generations, this heterogeneity also causes the asymptotic population growth rate lambda to increase, relative to a homogeneous population with the same mean survival rate at birth. The increase occurs because, even integrating over all the cohorts in the population, the population becomes increasingly dominated by the more robust individuals. The growth rate increases monotonically with the variance in survival rates, and the effect can be substantial, easily doubling the growth rate of slow-growing populations. Correlations between parent and offspring phenotype change the magnitude of the increase in lambda, but the increase occurs even for negative parent-offspring correlations. The effect of heterogeneity in reproductive rate on lambda is quite different: growth rate increases with reproductive heterogeneity for positive parent-offspring correlation but decreases for negative parent-offspring correlation. These effects of demographic heterogeneity on lambda have important implications for population dynamics, population viability analysis, and evolution. PMID:22073789

Kendall, Bruce E; Fox, Gordon A; Fujiwara, Masami; Nogeire, Theresa M

2011-10-01

145

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

PubMed Central

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

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

2012-01-01

146

Managed growth and optimum population: Irreconcilable concepts  

Microsoft Academic Search

“Managed growth” is a politically popular rallying point which offends no faction by insisting upon nonnegotiable limits. Subscribers to this philosophy focus upon short-run accommodations to growth which apparently mitigate its physical consequences. “Managed growthers” react to longterm numerical projections with rejection, if not outright hostility. They may be more amenable to quality-of-life rationales for population limitation evolving from the

B. Meredith Burke

1996-01-01

147

Keynes on population and economic growth.  

PubMed

This article discusses the evolution of Keynes's thinking on population based on an unpublished paper from 1914, "Is the Problem of Population a Pressing and Important One Now?" The paper is reported to have 39 pages, but in fact there are many missing page numbers. Keynes's "Essays in Biography" (1933) follows the basic structure and much of the verbal detail of the first 16 pages of "Population." Chapter 2 of the "Economic Consequences of the Peace" discusses the key ideas of "Population." The passages in "Population" and Chapter 2 were probably the sources of a fierce controversy in 1923-24 between Keynes and W.H. Beveridge over Keynes' neo-Malthusianism. "Population" was the basis for the three themes that were central to Keynes's writing on population. Keynes's framework shifted from a global perspective in "Population" to a progressively narrower focus in the 1930s on England and Wales. Keynes was stronger in his advocacy of birth control in "Population" compared to later writings. Keynes was concerned about the quality of population but disagreed on the methods of achieving this. Keynes argued that 75% of the world was not subject to Malthusian dynamics, and the other 25% had developed technology to relieve population pressure. "Population" sketches out the rudiments of the welfare implications of the great divide between North and South population growth rates. Keynes assumes that overpopulation in the South will be compensated for by the international market without consideration of income deficits. Keynes argues against pronatalism. The 1933 essay shows Keynes shift away from Malthus as population expert to Malthus as political economist. By 1937, Keynes had recanted and was very aware of the uncertainty of the economy. The author believes that it is unfortunate that this 1913-14 manuscript remains unknown and, if known, misunderstood. PMID:12293644

Toye, J

1997-01-01

148

Future trends in world population growth.  

PubMed

Because world population growth is marked by differing trends in the more developed and developing regions, the successful solution of future social and demographic problems will depend, in all likelihood, on whether population growth is considered in isolation or as a problem which is inextricably interwoven with other leading features of social and economic development.Both total population growth and changing age structure produce new economic and social problems, and within both the more developed and the developing regions, there are sub-areas in various stages of development. First, together with the total estimated increase in working-age population, there will be substantial differences in age structure. Although the proportion of world population of dependent age is expected to go down, up to 1980its level will be higher than in 1960, owingto an upward tendency in developing regions, where the "heavy youth dependency" is so extraordinarily high that even in 1980 there will be about ten children to every old person, and at the end of the century, more than seven. It is estimated that in the more developed regions there will be twenty-five to every one-hundred old persons in 1980, and twenty-two in the year 2000. This shows that heavy old-age dependency will have arisen in these regions. Second, the dependency ratio will probably grow, moreover, as a consequence of the degree of economic activity and variation. Although there will bea decrease in the proportion of dependent children, these will still constitute over one-half of the dependents in all areas. These forecasts seem to indicate that the changing structure of dependency and the increase in its total volume may be expected to create problems, particularly in the developing regions. Third, working life tends to become longer as a result of declining mortality, and this, combined with rising labor-force replacement levels, will result in an increased total labor supply.While such an expansion of world population obviously emphasizes the quantitative aspect of population problems, structural and qualitative aspects seem to be of equal importance. But these aspects are largely overshadowed by the growth problem, for growing numbers of people have more and more needs: the inflow of people into schools, into the labor market, and into towns and cities will be apparently unprecedented.In recent years circumstances have not favored the development of conditions needed for rapid change in reproductive behavior in the developing regions. The mobilization of resources and the adaption of different types of society in view of the future growth of total population-with emphasis on the less-developed regions-will be one of the most important challenges to mankind's ability to meet its own needs.The main value of the calculations of various characteristics of future population growth discussed in this paper is to show "in the light of contemporary information" future trends and some relationships of world population of world population growth to economic and social development. PMID:21318666

Vavra, Z

1967-06-01

149

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.

Lopez Fidalgo, J.; Ortiz Rodriguez, I.M.

2010-01-01

150

Closed form solutions to a generalization of the Solow growth model  

Microsoft Academic Search

The Solow growth model assumes that labor force grows exponentially. This is not a realistic assumption because, exponential growth implies that population increases to infinity as time tends to infinity. In this paper we propose replacing the exponential population growth with a simple and more realistic equation - the Von Bertalanffy model. This model utilizes three hypotheses about human population

Erick José Limas Maldonado; Juan Gabriel Brida

2005-01-01

151

Closed form solutions to a generalization of the Solow growth model  

Microsoft Academic Search

The Solow growth model assumes that labor force grows exponentially. This is not a realistic assumption because, exponential growth implies that population increases to in…nity as time tends to in…nity. In this paper we propose replacing the exponential population growth with a simple and more realistic equation - the Von Bertalany model. This model utilizes three hypotheses about human population

Juan Gabriel; Bridaand Erick; José Limas Maldonadoy

152

Optimal age of retirement and population growth  

Microsoft Academic Search

.   The purpose of this paper is to study intergenerational optimal resources sharing when the social planer can choose the retirement\\u000a age in addition to consumptions and investment. We use the extension of the Diamond analysis by Hu [1979] that incorporates\\u000a endogenous retirement age. We found that the optimal retirement age is an increasing function of the population growth rate

Bertrand Crettez; Patricia Le Maitre

2002-01-01

153

A role for the umuDC gene products of Escherichia coli in increasing resistance to DNA damage in stationary phase by inhibiting the transition to exponential growth.  

PubMed

The umuDC gene products, whose expression is induced by DNA-damaging treatments, have been extensively characterized for their role in SOS mutagenesis. We have recently presented evidence that supports a role for the umuDC gene products in the regulation of growth after DNA damage in exponentially growing cells, analogous to a prokaryotic DNA damage checkpoint. Our further characterization of the growth inhibition at 30 degrees C associated with constitutive expression of the umuDC gene products from a multicopy plasmid has shown that the umuDC gene products specifically inhibit the transition from stationary phase to exponential growth at the restrictive temperature of 30 degrees C and that this is correlated with a rapid inhibition of DNA synthesis. These observations led to the finding that physiologically relevant levels of the umuDC gene products, expressed from a single, SOS-regulated chromosomal copy of the operon, modulate the transition to rapid growth in E. coli cells that have experienced DNA damage while in stationary phase. This activity of the umuDC gene products is correlated with an increase in survival after UV irradiation. In a distinction from SOS mutagenesis, uncleaved UmuD together with UmuC is responsible for this activity. The umuDC-dependent increase in resistance in UV-irradiated stationary-phase cells appears to involve, at least in part, counteracting a Fis-dependent activity and thereby regulating the transition to rapid growth in cells that have experienced DNA damage. Thus, the umuDC gene products appear to increase DNA damage tolerance at least partially by regulating growth after DNA damage in both exponentially growing and stationary-phase cells. PMID:10648540

Murli, S; Opperman, T; Smith, B T; Walker, G C

2000-02-01

154

Toxicity of Polychlorinated Biphenyls to 'Euglena gracilis': Cell Population Growth, Carbon Fixation, Chlorophyll Level, Oxygen Consumption, and Protein and Nucleic Acid Synthesis.  

National Technical Information Service (NTIS)

Populations of Euglena gracilis in exponential growth under light were exposed to 2.5, 5.0, 7.5, and 10 ppm of Aroclor 1221. With Aroclor 1242, no inhibition of growth was observed with up to 100 ppm exposure. Cell cultures exposed to 4.4 ppm of Aroclor 1...

W. G. Ewald J. E. French M. A. Champ

1976-01-01

155

LebensraumParadoxically, Population Growth May Eventually End Wars  

Microsoft Academic Search

Population growth may progressively reduce one of the motives for making war. Namely, population growth threatens shortages of resources, and especially land. Impending shortages cause a search for ways to mitigate the shortages. The discoveries eventually produce greater availability of resources than if population growth and pressure on resources had never occurred. The argument runs as follows: (1) Rhetoric about

Julian L. Simon

1989-01-01

156

Population growth, demographic change, and cultural landscapes.  

PubMed

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

Woodgate, G; Sage, C

1994-01-01

157

Population of Exponentially Distributed Individual Lifespans Cannot Lead to Gompertzian or to Weibull (with Increasing Mortality Rate) Dynamics.  

National Technical Information Service (NTIS)

It is well documented in the biological literature, that many species throughout the animal kingdom, exhibit Gompertizian or Weibull-like population level survival distributions. Many researches have long assumed, believed, or other wise postulated that a...

F. Guess M. Witten

1986-01-01

158

Migration, urban population growth and regional disparity in China  

Microsoft Academic Search

The main objective of this paper is to study the determinants of city population growth in China during the 1990s', as well as the determinants of migrations towards cities, which constitutes the main source of urban population growth in this period. A second objective is to identify regional differences in the urban growth and migrations, that is, whether urban growth

Mary-Françoise Renard; Nong ZHU

2007-01-01

159

Growth patterns of Italian local chicken populations.  

PubMed

Predictions of growth are important factors that contribute to the profitability of an operation in poultry production. Modern commercial hybrids have a higher body growth in comparison with the local purebreds. However a niche market for meat and egg poultry production needs to be established using local purebreds to promote biodiversity. The aim of this study was to model the growth response of male and female chickens belonging to 5 local Italian populations: a commercial slow-growing hybrid (Berlanda, B), the Padovana pure breed [2 plumage varieties: silver, argentata (PA) and chamois, camosciata (PC)], and their crosses PC×B and PC×PA. A total of 398 one-day-old birds were reared until 180 d of age under indoor conditions. The linear and 3 nonlinear models (logistic, Gompertz, and Richards) were compared to study the growth patterns of these chicken populations. Significant (P < 0.01) differences were observed among the genotypes for several curve parameters. In males, PC×B showed the lowest age at inflection point, B showed the highest age and BW, whereas PA showed the highest age and the lowest weight. In females, the age at the inflection point did not differ among the groups; B showed the highest weight. All the nonlinear models gave a good fit of male and female data with R(2) ranging from 0.992 and 0.999, but the logistic equation had higher value of root mean square error than the Gompertz and the Richards values. Based on residual sum of squares for both sexes, the Richards model was better (P < 0.05) than the logistic but not superior to the Gompertz. The logistic equation showed an overestimation of initial BW for all the groups and sex. For Italian local chicken populations, the Richards model requires a measure of BW recorded at 90 d or after to obtain a good fit of the asymptotic weight. However, the Gompertz model has the advantage that it requires one less parameter than the Richards model. PMID:23873574

Rizzi, C; Contiero, B; Cassandro, M

2013-08-01

160

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

PubMed

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

Zhu, J

1995-01-01

161

Nonlinear stochastic modeling of aphid population growth.  

PubMed

This paper develops a stochastic population size model for the black-margined pecan aphid. Prajneshu [Prajneshu, A nonlinear statistical model for aphid population growth. J. Indian Soc. Agric. Statist. 51 (1998), p. 73] proposes a novel nonlinear deterministic model for aphid abundance. The per capita death rate in his model is proportional to the cumulative population size, and the solution is a symmetric analytical function. This paper fits Prajneshu's deterministic model to data. An analogous stochastic model, in which both the current and the cumulative aphid counts are state variables, is then proposed. The bivariate solution of the model, with parameter values suggested by the data, is obtained by solving a large system of Kolmogorov equations. Differential equations are derived for the first and second order cumulants, and moment closure approximations are obtained for the means and variances by solving the set of only five equations. These approximations, which are simple for ecologists to calculate, are shown to give accurate predictions of the two endpoints of applied interest, namely (1) the peak aphid count and (2) the final cumulative aphid count. PMID:16183082

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

2005-09-23

162

Enhancerless Cytomegalovirus Is Capable of Establishing a Low-Level Maintenance Infection in Severely Immunodeficient Host Tissues but Fails in Exponential Growth?  

PubMed Central

Major immediate-early transcriptional enhancers are genetic control elements that act, through docking with host transcription factors, as a decisive regulatory unit for efficient initiation of the productive virus cycle. Animal models are required for studying the function of enhancers paradigmatically in host organs. Here, we have sought to quantitatively assess the establishment, maintenance, and level of in vivo growth of enhancerless mutants of murine cytomegalovirus in comparison with those of an enhancer-bearing counterpart in models of the immunocompromised or immunologically immature host. Evidence is presented showing that enhancerless viruses are capable of forming restricted foci of infection but fail to grow exponentially.

Podlech, Jurgen; Pintea, Rares; Kropp, Kai A.; Fink, Annette; Lemmermann, Niels A. W.; Erlach, Katja C.; Isern, Elena; Angulo, Ana; Ghazal, Peter; Reddehase, Matthias J.

2010-01-01

163

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.

Sibly, Richard M; Hone, Jim

2002-01-01

164

Population growth rate as a basis for ecological risk assessment of toxic chemicals.  

PubMed Central

Assessing the ecological risks of toxic chemicals is most often based on individual-level responses such as survival, reproduction or growth. Such an approach raises the following questions with regard to translating these measured effects into likely impacts on natural populations. (i) To what extent do individual-level variables underestimate or overestimate population-level responses? (ii) How do toxicant-caused changes in individual-level variables translate into changes in population dynamics for species with different life cycles? (iii) To what extent are these relationships complicated by population-density effects? These issues go to the heart of the ecological relevance of ecotoxicology and we have addressed them using the population growth rate as an integrating concept. Our analysis indicates that although the most sensitive individual-level variables are likely to be equally or more sensitive to increasing concentrations of toxic chemicals than population growth rate, they are difficult to identify a priori and, even if they could be identified, integrating impacts on key life-cycle variables via population growth rate analysis is nevertheless a more robust approach for assessing the ecological risks of chemicals. Populations living under density-dependent control may respond differently to toxic chemicals than exponentially growing populations, and greater care needs to be given to incorporating realistic density conditions (either experimentally or by simulation) into ecotoxicological test designs. It is impractical to expect full life-table studies, which record changes in survival, fecundity and development at defined intervals through the life cycle of organisms under specified conditions, for all relevant species, so we argue that population growth rate analysis should be used to provide guidance for a more pragmatic and ecologically sound approach to ecological risk assessment.

Forbes, Valery E; Calow, Peter

2002-01-01

165

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

PubMed

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

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

2010-07-16

166

Population growth, changing agricultural practices, and environmental degradation in Zaire  

Microsoft Academic Search

This paper examines linkages between the demographic changes taking place in Zaire, particularly overall population growth\\u000a and rapid urbanization, changes in agricultural practices, and related environmental degradation. Pressures to feed Zaire's\\u000a rapidly increasing urban population, which fall on a rural population that has been growing relatively slowly in recent years,\\u000a as well as population growth and increased population density in

David Shapiro

1995-01-01

167

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

NASA Astrophysics Data System (ADS)

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

Celestin, Sebastien; Pasko, Victor P.

2011-03-01

168

A new piezoelectric response model for population growth of bacteria  

Microsoft Academic Search

A piezoelectric response model on the population growth of microorganism is proposed. This model is based on a novel population growth model, which has a more obvious ecological meaning and the fact that the series piezoelectric quartz crystal (SPQC) sensor responses to conductivity changes of the medium during the growth of the microorganism. From the response model four parameters can

Lili Bao; Huwei Tan; Le Deng; Wanzhi Wei

1998-01-01

169

Cell Population Dynamics Modulate the Rates of Tissue Growth Processes  

Microsoft Academic Search

The development and testing of a discrete model describing the dynamic process of tissue growth in three-dimensional scaffolds is presented. The model considers populations of cells that execute persistent random walks on the computational grid, collide, and proliferate until they reach confluence. To isolate the effect of population dynamics on tissue growth, the model assumes that nutrient and growth factor

Gang Cheng; Belgacem B. Youssef; Pauline Markenscoff; Kyriacos Zygourakis

2006-01-01

170

Volatility and Growth in Populations of Rural Associations  

ERIC Educational Resources Information Center

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

Wollebaek, Dag

2010-01-01

171

Volatility and Growth in Populations of Rural Associations  

ERIC Educational Resources Information Center

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

Wollebaek, Dag

2010-01-01

172

Brazilian population 1982: growth, migration, race, religion.  

PubMed

The rate of population increase dropped to less than 2.5% annually in Brazil between 1970-80, but 26 million more people were born. The 1980 census also provides details of continuing urbanization, settlement of the farthest frontiers, and changes in racial composition. The direct cause of the drop in population increase was a drop of about 15% in the fertility rate that had been projected for the decade. Brazil's rate of population increase declined impressively despite the fact that the country continued to make progress in reducing mortality. The greatest improvement occurred between 1930-60. The mortality rate averaged 20.9/1000 between 1940-50 but dropped to 14.2/1000 between 1950-60. Even though the crude death rate dropped 28% in the 1970-80 decade and each child born in 1980 can expect to live 6.5 years longer than a child born in 1970, the life expectancy of 62 years compares with Colombia and El Salvador, which are much poorer countries. In Brazil as a whole the crude birthrate in the 15-19 age group was 66/1000 in 1980. It was 46/1000 in 1970, an increase of nearly 50%. In urban areas the rate increased from 37/1000 to 57/1000 and in the countryside from 59/1000 to 89/1000. The crude birthrate went down slightly in Brazil from 1970-80 from 34 to 32/1000. The total fertility rate (TFR) dropped in the same period from 4.9ll to 3.983. The question that arises is whether fertility rates will increase, with women in the youngest age group continuing to have more children during their reproductive years. Internal migration plays a major role in the distribution of the population. Between 1970-80 there were changes in the migration pattern from the previous decade. All the rapidly growing areas, defined as the frontier, have high fertility rates, but much of their growth results from migration. Between 1960-70 and 1970-80 the most rapidly growing areas of the frontier changed. Few are aware of the extent to which Brazil is becoming a country of large cities. The top 10 of the 30 largest cities in the country all have more than 1 million inhabitants. Another manifestation of urbanization within states is the overall loss of population in the rural areas while most of the capital cities grew quite rapidly. Brazil is a multiracial society based on the native Amerindians, Europeans, Middle Easterners, the decendants of African slaves, and Orientals. A substantial portion of the population is racially mixed and cannot be placed within any of these categories. In the 1980 census the racial categories were the ones used in prevouse censuses: white, black, yellow, and "parda" (mixed). Brazil's population is predominantly white, but nearly 45% is racially mixed or black. Orientals are less than 1%. In regard to religion, the clearest trend is an increase in Protestants. PMID:12338986

Sanders, T G

1982-01-01

173

The H-NS-like protein StpA represses the RpoS (sigma 38) regulon during exponential growth of Salmonella Typhimurium.  

PubMed

StpA is a paralogue of the nucleoid-associated protein H-NS that is conserved in a range of enteric bacteria and had no known function in Salmonella Typhimurium. We show that 5% of the Salmonella genome is regulated by StpA, which contrasts with the situation in Escherichia coli where deletion of stpA only had minor effects on gene expression. The StpA-dependent genes of S. Typhimurium are a specific subset of the H-NS regulon that are predominantly under the positive control of sigma(38) (RpoS), CRP-cAMP and PhoP. Regulation by StpA varied with growth phase; StpA controlled sigma(38) levels at mid-exponential phase by preventing inappropriate activation of sigma(38) during rapid bacterial growth. In contrast, StpA only activated the CRP-cAMP regulon during late exponential phase. ChIP-chip analysis revealed that StpA binds to PhoP-dependent genes but not to most genes of the CRP-cAMP and sigma(38) regulons. In fact, StpA indirectly regulates sigma(38)-dependent genes by enhancing sigma(38) turnover by repressing the anti-adaptor protein rssC. We discovered that StpA is essential for the dynamic regulation of sigma(38) in response to increased glucose levels. Our findings identify StpA as a novel growth phase-specific regulator that plays an important physiological role by linking sigma(38) levels to nutrient availability. PMID:19843227

Lucchini, Sacha; McDermott, Paul; Thompson, Arthur; Hinton, Jay C D

2009-10-19

174

Analogue Simulation in the Teaching of Population Ecology  

ERIC Educational Resources Information Center

|Described is the use of analogue computer modules in simulating population ecology. Computer modules demonstrating exponential growth and predator-prey interactions are described and diagramed. (SL)|

Summers, M. K.; Summers, J. M.

1976-01-01

175

Section 39 (Population and Development) Title: Rapid Population Growth and Development in Ghana  

Microsoft Academic Search

Ghana's Demographic and Health Surveys 1988 and 1993, and Ghana's 1984 Population Census report were used to examine the effect of rapid population growth on 4 key sectors in Ghana. The population issue in Ghana concerns the high rate of growth and not the number of people. The rapidly increasing expenditure on education is associated with sharp increases in the

Eric Adjei Boadu

176

Prediction of fatigue crack growth and residual life using an exponential model: Part II (mode-I overload induced retardation)  

Microsoft Academic Search

Almost all load bearing components usually experience variable amplitude loading (VAL) rather than constant amplitude loading (CAL) during their service lives. A single overload cycle introduced in a con- stant amplitude fatigue loading retards fatigue crack growth and increases residual fatigue life. Although many models have been proposed on this subject, but life prediction under these complex situations is still

J. R. Mohanty; B. B. Verm; P. K. Ray

2008-01-01

177

Growth and Composition of Branching Populations.  

National Technical Information Service (NTIS)

Single type general branching populations developing by individuals reproducing according to i.i.d. point processes on the positive reals, interpreted as the individuals' ages, are discussed. Such a population can be measured or counted as those born, tho...

P. Jagers O. Nerman

1983-01-01

178

Menaquinone synthesis is critical for maintaining mycobacterial viability during exponential growth and recovery from non-replicating persistence.  

PubMed

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

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

2009-02-11

179

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

180

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

PubMed

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

Ngendakumana, M

1988-04-01

181

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

182

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.

Saether, Bernt-Erik; Engen, Steinar

2002-01-01

183

[The most rapid population growth in world history].  

PubMed

This is a study of recent global population growth by continent. Sections are included on continents with low growth rates, variations in demographic transition, death rates, immigration, and estimates for the year 2000. Charts provide comparative growth data by continent for the years 1960-1980 and data on birth and death rates for selected areas. PMID:12341463

Stempell, D

1987-01-01

184

A Multivariate Exponential Distribution.  

National Technical Information Service (NTIS)

A number of multivariate exponential distributions are known, but they have not been obtained by methods that shed light on their applicability. This paper presents some meaningful derivations of a multivariate exponential distribution that serve to indic...

A. W. Marshall I. Olkin

1966-01-01

185

The growth and prospects of population sociology in China.  

PubMed

Population sociology is an immature science in China. Several issues are important to consider as population sociology develops. 1) Research subjects need to be specified more rigorously. 2) More indepth discussion needs to take place on a system of research. 3) Population sociology needs to be explained in terms of the relationship to socialism and the contribution to population policies. The future of population sociology within population science is secure because the Party's session in 1978 adopted guidelines to promote the development of science and culture, and because it is necessary to the understanding of population problems in the socialist modernization. Population sociology plays a major role with population economics in policy formation. A large number of scholars have invested effort in the dicipline. One of the basic characteristics of population sociology is the ability to view population and social development dynamically. Research covers population problems related to social problems, and vice versa. It is distinct from other sciences, particularly in research scope. It studies the effects of social elements and population development on one another, which delineates the incompatibility between population growth and social development. China's population sociology did not begin until 1978, even though worldwide the discipline was founded early in the century and grew rapidly during World War II. China's population growth is a hindrance to social and economic development, and more indepth studies are needed to analyze the conflicts between population and modern Chinese society and economy, and to assess how best to slow the population growth. There have been 4 basic views on the study of population sociology. The 1st view is that endorsed by Soviet scholars and emphasizes sociolgical principles which affect population growth. This position is population sociology as a brance of sociology rather than as an independent science. The 2nd view pertains to the explanations of the individual aspects of the relationships between population problems and societal ones. The author considers this view superficial. The 3rd view explains the relationships between development and social phenomena and conditions. The impact of social conditions on population development is explored, and the nature of the status and role of population in social life, particularly socialization. This view lacks a description of the research system. The 4th view reflects the effects of population and social development on one another, which is the preferred view. PMID:12316992

Li, M

1989-01-01

186

Development of tolerogenic dendritic cells and regulatory T cells favors exponential bacterial growth and survival during early respiratory tularemia  

PubMed Central

Tularemia is a vector-borne zoonosis caused by Ft, a Gram-negative, facultative intracellular bacterium. Ft exists in two clinically relevant forms, the European biovar B (holarctica), which produces acute, although mild, self-limiting infections, and the more virulent United States biovar A (tularensis), which is often associated with pneumonic tularemia and more severe disease. In a mouse model of tularemia, respiratory infection with the virulence-attenuated Type B (LVS) or highly virulent Type A (SchuS4) strain engenders peribronchiolar and perivascular inflammation. Paradoxically, despite an intense neutrophilic infiltrate and high bacterial burden, Th1-type proinflammatory cytokines (e.g., TNF, IL-1?, IL-6, and IL-12) are absent within the first ?72 h of pulmonary infection. It has been suggested that the bacterium has the capacity to actively suppress or block NF-?B signaling, thus causing an initial delay in up-regulation of inflammatory mediators. However, our previously published findings and those presented herein contradict this paradigm and instead, strongly support an alternative hypothesis. Rather than blocking NF-?B, Ft actually triggers TLR2-dependent NF-?B signaling, resulting in the development and activation of tDCs and the release of anti-inflammatory cytokines (e.g., IL-10 and TGF-?). In turn, these cytokines stimulate development and proliferation of Tregs that may restrain Th1-type proinflammatory cytokine release early during tularemic infection. The highly regulated and overall anti-inflammatory milieu established in the lung is permissive for unfettered growth and survival of Ft. The capacity of Ft to evoke such a response represents an important immune-evasive strategy.

Periasamy, Sivakumar; Singh, Anju; Sahay, Bikash; Rahman, Tabassum; Feustel, Paul J.; Pham, Giang H.; Gosselin, Edmund J.; Sellati, Timothy J.

2011-01-01

187

Bounded Population Growth: A Curve Fitting Lesson.  

ERIC Educational Resources Information Center

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

Mathews, John H.

1992-01-01

188

Toxicity of polychlorinated biphenyls (PCBs) to Euglena gracilis: Cell population growth, carbon fixation, chlorophyll level, oxygen consumption, and protein and nucleic acid synthesis  

Microsoft Academic Search

Summary Populations ofEuglena gracilis in exponential growth under light were exposed to 2.5, 5.0, 7.5, and 10 ppm of Aroclor 1221. The ID50\\/48 of Aroclor 1221 was estimated to be 4.4 ppm, while Aroclor 1232 tested at 20, 35, 50, and 100 ppm resulted in an ID50\\/48 of 55 ppm. With Aroclor 1242, no inhibiton of growth was observed with

William G. Ewald; John E. French; Michael A. Champ

1976-01-01

189

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

PubMed

Africa, currently one of the least densely populated continents, is growing so rapidly that its population will comprise some 1.5 billion inhabitants around 2020, and Africans will be more numerous than the population of the developed world. Attitudes about Africa's population size vary widely; many educated Africans believe that low density is a greater disadvantage than overpopulation, but most specialists believe the population of the developing world, and of Africa especially, to be too large, the prospects of significant voluntary reduction are dim. The rate of population growth has thus attracted attention as a factor amenable to modification. Africa's demographic transition remains largely in the future. Its case is unique because of the rate of demographic growth and because the phase of rapid growth will apparently continue far longer in Africa than in any other continent. The widening gap between population growth rates and rates of economic development in Africa inspires great pessimism about the future wellbeing of the population. Population officials urge that demographic growth be slowed in order to reduce pressure on economic and ecological resources and to gain time for social and economic development. But despite the consensus of international organizations, such as the UN Fund for Population, on the desirability of slowing population growth to encourage and permit economic growth, there has actually been relatively little progress since the time of Malthus in understanding the relationship between population, development, and the environment. Some recent works suggest that demographic growth has benefits as well as disadvantages, and the net impact on development is uncertain. Demographic pressure is in this view a far more potent force for innovation than is usually recognized. Population is not just an exogenous variable in development, but it is at the heart of the process. There can be no true integration of population into development until the value of human resources everywhere is reaffirmed. The recognition by international organizations that per capita income or other economic indicators alone are not adequate measures of progress is a favorable sign. The failure of structural adjustment programs to attain their stated goals and the new resolve to lessen their effects on the most vulnerable population sectors are also promising. New orientations toward development in which human resources are given greater prominence may be as ideologically inspired as those they replaced, but they have the merit of greater neutrality concerning the content and form of development and they do not accept the process of development in the West as their sole reference. PMID:12317452

Loriaux, M

1991-12-01

190

Studies on comparative population growth of some species of the rotifer Lecane (Rotifera).  

PubMed

We compared the population growth patterns of 5 species of the rotifer genus Lecane [(L. quadridentata (Ehrenberg, 1830), L. comuta (Muller, 1786), L. papuana (Murray, 1913), L. unguitata (Fadeev, 1925) and L. pyriformis (Daday, 1905)] ranging in adult average body size from 30 to 140 microm. All species were cultured under laboratory conditions for 25-30 days using the green alga Scenedesmus acutus as the exclusive diet, at a density of 1.0 x 10(6) cells ml(-1) at 24 degrees C. Regardless of the species, lecanids reached their peak population densities after 4 weeks. Peak population densities ranged from 15 to 320 ind. ml(-1), depending on body size. There was an inverse curvilinear relation between body lengths and peak population abundances (densities) of the Lecane species. Egg ratios (eggs per female) for the tested species were < 0.6 during the exponential phase but declined to 0.1 (or lower) as the population density increased. The rates of population increase for the lecanids were in general lower(0.10 to 0.21 day (-1)) than other well-studied rotifer species including members of Brachionidae. PMID:22315832

Serrania-Soto, C R; Sarma, S S S; Nandini, S

2011-07-01

191

Quantitative Modeling of Growth and Dispersal in Population Models.  

National Technical Information Service (NTIS)

This document discusses techniques for the estimation of nonlinearities and state-dependent coefficients in parabolic partial differential equations. Applications to density-dependent population dispersal and nonlinear growth/predation models are presente...

H. T. Banks K. A. Murphy

1986-01-01

192

Temperature alters the relative abundance and population growth ...  

Treesearch

Title: Temperature alters the relative abundance and population growth rates of species ... Description: Temperature has strong effects on metabolic processes ... interactions, providing multiple pathways for temperature to affect the system.

193

Density-dependent population growth in a reintroduced population of North Island saddlebacks  

Microsoft Academic Search

Summary 1. Reintroductions provide a good opportunity to study density-dependent population growth, as populations can be studied at a range of densities and the change in density is not confounded with environmental conditions. An understanding of density depend- ence is also necessary to predict dynamics of reintroduced populations under different management regimens, and assess the extent to which they can

DOUG P. ARMSTRONG; R. SCOTT DAVIDSON; JOHN K. PERROTT; JON ROYGARD; LEN BUCHANAN

2005-01-01

194

Impact of Demographic Distribution and Population Growth Rate on Haplotypic Diversity Linked to a Disease Gene and Their Consequences for the Estimation of Recombination Rate: Example of a French  

Microsoft Academic Search

A disease gene introduced into a rapidly growing population by a single individual remains in strong linkage disequilibrium with the surrounding molecular markers. Mapping strategies taking advantage of this phenomenon allow increased mapping resolution as compared to pedigree analysis. Demographic models underlying these strategies usually assume the population exponential growth approximated by Pois- son distribution of the number of children

Frédéric Austerlitz; Evelyne Heyer

195

Family Altruism with Renewable Resource and Population Growth  

Microsoft Academic Search

In an overlapping-generations model with non-constant population growth, households own a natural renewable resource and have a family-altruism resource bequest motive. The natural resource can be either extracted and sold to firms, or bequeathed to children to increase their adult disposable income. Numerical applications show how family altruism interplays with population growth to shape the whole economy. The role of

THIERRY BRÉCHET; STÉPHANE LAMBRECHT

2009-01-01

196

Population growth overshooting and trade in developing countries  

Microsoft Academic Search

This paper examines a developing economy using a family-optimization model in which the number of children is a normal good.\\u000a Trade liberalization generates two effects: the income effect that increases population growth and the gender wage effect\\u000a that, in the short run, increases, but, in the long run, decreases population growth. With higher income, families invest\\u000a more in capital if

Ulla Lehmijoki; Tapio Palokangas

2009-01-01

197

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

198

Population Ecology Issues in Tumor Growth  

Microsoft Academic Search

Mathematical models developed from population ecology are applied to tumor-host interactions and demonstrate the importance of increased efficiency in substrate absorption as a mechanism enabling tumor cells to (a) proliferate despite inefficient energy production and (b) compete successfully for resources with the numerically superior host cells. As with many biological invasions observed in nature, success of the invaders can be

Robert A. Gatenby

1991-01-01

199

Giving Exponential Functions a Fair Shake  

ERIC Educational Resources Information Center

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

Wanko, Jeffrey J.

2005-01-01

200

Giving Exponential Functions a Fair Shake  

ERIC Educational Resources Information Center

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

Wanko, Jeffrey J.

2005-01-01

201

Effects of cell motility and chemotaxis on microbial population growth.  

PubMed Central

A mathematical model is developed to elucidate the effects of biophysical transport processes (nutrient diffusion, cell motility, and chemotaxis) along with biochemical reaction processes (cell growth and death, nutrient uptake) upon steady-state bacterial population growth in a finite one-dimensional region. The particular situation considered is that of growth limitation by a nutrient diffusing from an adjacent phase not accessible to the bacteria. It is demonstrated that the cell motility and chemotaxis properties can have great influence on steady-state population size. In fact, motility effects can be as significant as growth kinetic effects, in a manner analogous to diffusion- and reaction-limited regimes in chemically reacting systems. In particular, the following conclusions can be drawn from our analysis for bacterial populations growing at steady-state in a confined, unmixed region: (a) Random motility may lead to decreased population density; (b) chemotaxis can allow increased population density if the chemotactic response is large enough; (c) a species with superior motility properties can outgrow a species with superior growth kinetic properties; (d) motility effects become greater as the size of the confined growth region increases; and (e) motility effects are diminished by significant mass-transfer limitation of the nutrient from the adjacent source phase. The relationships of these results for populations to previous conclusions for individual cells is discussed, and implications for microbial competition are suggested.

Lauffenburger, D; Aris, R; Keller, K

1982-01-01

202

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

203

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

PubMed Central

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

Lazarus, L R; Travers, A A

1993-01-01

204

Capital accumulation, endogenous population growth, and Easterlin cycles  

Microsoft Academic Search

In this paper we attempt to explain the occurrence of population cycles in industrialised economies where the birth rate depends on the difference between the actual and the expected consumption rate. This model of an endogenously growing population brings together Easterlin's idea of an adapting aspiration level with the neoclassical optimal growth paradigm. It is shown that in this highly

Gustav Feichtinger; Engelbert J. Dockner

1990-01-01

205

Thermal constraints to population growth of bacterial-feeding nematodes  

Microsoft Academic Search

Bacterial-feeding nematodes are important participants in decomposition pathways and nutrient cycles in soils. The contribution of each species to component processes depends upon the physiology of individuals and the dynamics of populations. Having determined the effects of temperature on metabolic rates of several species of bacterial-feeding nematodes, we now present the effects of temperature on population growth rates and relate

R. C. Venette; H. Ferris

1997-01-01

206

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

ERIC Educational Resources Information Center

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

Mumford, Steven

1981-01-01

207

UPDATE OF GROWTH PERCENTILES FOR CHILDREN OF AN IRANIAN POPULATION  

Microsoft Academic Search

Growth percentiles require periodic revision because of the changes in the ethnic mix of the population as well as socioeconomic and environmental conditions. This paper describes the new reference percentile curves for weight, height, and head circumference in an Iranian population between birth and 6 years of age. Methods - Fifteen-hundred and forty children (808 boys and 732 girls) were

Shams Vazirian

2003-01-01

208

Food-dependent individual growth and population dynamics in fishes  

Microsoft Academic Search

It is long since well established that growth and development in fish individuals are heavily dependent on food intake. Yet, this dependence of individual development on food levels has only to a limited extent been taken into consideration when studying fish population and community processes. Using the modelling framework of physiologically structured population models and empirical data for a number

L. Persson; Roos de A. M

2006-01-01

209

Rapid Population Growth and Human Carrying Capacity: Two Perspectives.  

National Technical Information Service (NTIS)

The paper is one in a special series of World Bank Staff Working Papers on population change and development. The papers cover a range of topics, including the effects of population growth and change on economic development, the determinants of fertility ...

D. J. Mahar R. Muscat J. W. Kirchner G. Ledec R. J. A. Goodland

1985-01-01

210

A Role for M-Matrices in Modelling Population Growth  

ERIC Educational Resources Information Center

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

James, Glyn; Rumchev, Ventsi

2006-01-01

211

Regulatory Design Governing Progression of Population Growth Phases in Bacteria  

PubMed Central

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

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

2012-01-01

212

Put an end to population growth and improve productivity.  

PubMed

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

Chung, U W

213

Modelling individual growth and competition in plant populations: growth curves of Chenopodium album at two densities  

Microsoft Academic Search

Summary 1 We modelled the growth in estimated biomass of individuals in experimental popu- lations of Chenopodium album grown at two densities and measured sequentially nine times over 128 days. Competition is modelled by coupling individual growth equations and, within the population, the growth rate of a plant at any point in time is a function of its size to

Christian Damgaard; Jacob Weiner; Hisae Nagashima

2002-01-01

214

The Distribution of the Kolmogorov-Smirnov, Cramer-von Mises, and Anderson-Darling Test Statistics for Exponential Populations with Estimated Parameters  

Microsoft Academic Search

This article presents a derivation of the distribution of the Kolmogorov–Smirnov, Cramer–von Mises, and Anderson–Darling test statistics in the case of exponential sampling when the parameters are unknown and estimated from sample data for small sample sizes via maximum likelihood.

Diane L. Evans; John H. Drew; Lawrence M. Leemis

2008-01-01

215

Male turnover reduces population growth: an enclosure experiment on voles.  

PubMed

Turnover of individuals is assumed to cause disruptions of social organization, followed by reduced reproduction and survival. We tested how male turnover (removal of resident males and their replacement by unfamiliar males) affected population performance in experimental root vole (Microtus oeconomus) populations. The treatment simulated predation of adult males, with the subsequent replacement by immigrants, and provided insight into the interaction between extrinsic (i.e., predation) and intrinsic (i.e., social organization) factors. We showed that recruitment and female survival dramatically declined and that reproduction commenced slightly later in treatment populations compared with control populations. The treatment nearly halved the population growth rate. We suspect that recruitment failed due to infanticidal immigrating males. Reduced female survival was particularly apparent in treatment populations in which females exhibited a high degree of spatial overlap. Our experimental results show how males may significantly shape population dynamics and suggest how predation and social factors interact mechanistically. PMID:16634299

Andreassen, Harry P; Gundersen, Gry

2006-01-01

216

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

217

Age-structured cell population model to study the influence of growth factors on cell cycle dynamics.  

PubMed

Cell proliferation is controlled by many complex regulatory networks. Our purpose is to analyse, through mathematical modeling, the effects of growth factors on the dynamics of the division cycle in cell populations. Our work is based on an age-structured PDE model of the cell division cycle within a population of cells in a common tissue. Cell proliferation is at its first stages exponential and is thus characterised by its growth exponent, the first eigenvalue of the linear system we consider here, a growth exponent that we will explicitly evaluate from biological data. Moreover, this study relies on recent and innovative imaging data (fluorescence microscopy) that make us able to experimentally determine the parameters of the model and to validate numerical results. This model has allowed us to study the degree of simultaneity of phase transitions within a proliferating cell population and to analyse the role of an increased growth factor concentration in this process. This study thus aims at helping biologists to elicit the impact of growth factor concentration on cell cycle regulation, at making more precise the dynamics of key mechanisms controlling the division cycle in proliferating cell populations, and eventually at establishing theoretical bases for optimised combined anticancer treatments. PMID:23311359

Billy, Frédérique; Clairambault, Jean; Delaunay, Franck; Feillet, Céline; Robert, Natalia

2013-02-01

218

The effects of nonmetropolitan population growth on resource management  

Microsoft Academic Search

Studies of nonmetropolitan growth have neglected the effect of changes in the nature of new residents and land?holding size on individual resource management. This study of management of a resource?at?risk shows that deleterious resource management does not follow automatically in the wake of population growth. There is no difference in likelihood of new and long?standing residents to manage resources, although

Louise Fortmann; Lynn Huntsinger

1989-01-01

219

A stochastic computer model for simulating population growth  

Microsoft Academic Search

Summary  A model is described for investigating the interactions of age-specific birth and death rates, age distribution and density-governing\\u000a factors determining the growth form of single-species populations. It employs Monte Carlo techniques to simulate the births\\u000a and deaths of individuals while density-governing factors are represented by simple algebraic equations relating survival\\u000a and fecundity to population density. In all respects the model’s

Frank J. Sonleitner

1977-01-01

220

Seasonal growth rate and population dynamics of a freshwater sponge  

Microsoft Academic Search

Five sites of various water depths on four transects were sampled on a seasonal basis to determine Ephydatia fluviatilis population dynamics. The temporal occurrence of life cycle events was influenced by factors (e.g. water temperature) that varied with water depth. The shallow-water (1.5 m deep) portion of the population. Sexual reproduction occurred in the spring. Seasonal growth rates were determined

Russell B. Raderl; Robert N. Winget

1985-01-01

221

Population growth capacities and regulatory factors in monospecific cultures of the cladocerans Moina micrura and Diaphanosoma excisum and the copepod Thermocyclops decipiens from Côte d’Ivoire (West Africa)  

Microsoft Academic Search

The cladocerans Moina micrura and Diaphanosoma excisum and the copepod Thermocyclops decipiens were studied in microcosms (0.8 m3) under semi-controlled experimental conditions at 25–29 °C for 32 days, by daily sampling after an initial monospecific inoculation. For each species, the time series began with an exponential population growth phase. M. micrura showed a higher daily population growth rate (mean = 1.19)

Marc Pagano; Lucien Saint-Jean; Robert Arfi; Marc Bouvy; Helguilé Shep

2000-01-01

222

The population growth consequences of variation in individual heterozygosity.  

PubMed

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

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

2011-05-18

223

Population growth, resources and health: Challenges for public health professionals  

Microsoft Academic Search

Summary Current global developments as regards demographic growth and resource utilization represent one issue most difficult to tackle, in terms of (general and health) policy as well as in human terms. In the 1960s–1970s, the debate was active and led, among other things to an expansion of technical cooperation programs aiming at fertility reduction. The 1974 World Population Conference in

Jean Martin

1995-01-01

224

Matrix analysis of interregional population growth and distribution  

Microsoft Academic Search

Among available operational methods for analyzing and forecasting population growth and change, one may broadly distinguish between those models which are concerned only with total births, deaths and migration from those which focus on the behavior of cohorts disaggregated by age and sex. The former class of models typically are referred to as components-of-change models; the latter have been defined

Andrei Rogers

1967-01-01

225

Is There Hidden Potential for Rural Population Growth in Sweden?  

ERIC Educational Resources Information Center

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

Niedomysl, Thomas; Amcoff, Jan

2011-01-01

226

AN ASSESSMENT OF BIRD HABITAT QUALITY USING POPULATION GROWTH RATES  

Microsoft Academic Search

Survival and reproduction directly affect population growth rate (l), making l a fundamental parameter for assessing habitat quality. We used field data, literature review, and a computer simulation to predict annual productivity and l 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

Melinda G. Knutson; Randy K. Hines; Larkin A. Powell; Mary A. Friberg; Gerald J. Niemi

2006-01-01

227

The Educational Effects of Rapid Rural Population Growth.  

ERIC Educational Resources Information Center

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

Ross, Peggy J.; Green, Bernal L.

228

POPULATION AGEING, HUMAN CAPITAL ACCUMULATION AND ECONOMIC GROWTH IN CHINA  

Microsoft Academic Search

This paper uses a Computable General Equilibrium model to explore the macroeconomic impact of growth in the human capital stock for a given ageing profile of the population in China, during the first half of this century. It examines whether the projected reduction in the total dependency ratio for the period 2000 to the 2030s can be exploited for energetic

Xiujian Peng

2005-01-01

229

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

ERIC Educational Resources Information Center

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

Daley, Michael; Hillier, Douglas

1981-01-01

230

Political instability, gender discrimination, and population growth in developing countries  

Microsoft Academic Search

This paper introduces gender discrimination and population growth into a model of political economy. The government keeps up the military for the sake of political instability in the country. It is shown that if the risk of internal conflicts is high, then the government needs a bigger military and a larger supply of young men for it. The government is

Ulla Lehmijoki; Tapio Palokangas

2006-01-01

231

Political Instability, Gender Discrimination, and Population Growth in Developing Countries  

Microsoft Academic Search

This paper introduces gender discrimination and population growth into a model of political economy. It is assumed that households are family dynasties and the government keeps up the army for the case of political instability in the country. It is shown that there are eco- nomic limits to conscription from young men. Therefore, to ensure the su-cient supply of the

Ulla Lehmijoki; Tapio Palokangas

2004-01-01

232

Family altruism with a renewable resource and population growth  

Microsoft Academic Search

We develop an overlapping-generation model `a la Diamond with a non-constant population growth in which households privately own a natural renewable resource and have a family- altruism resource bequest motive. The natural resource can be either extracted and sold to the producing ?rms as a production factor, or bequeathed to the offspring to increase his adult disposable income. With a

Thierry BRECHET; Stéphane LAMBRECHT

2006-01-01

233

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

234

Spatial scaling of avian population dynamics: population abundance, growth rate, and variability.  

PubMed

Synchrony in population fluctuations has been identified as an important component of population dynamics. In a previous study, we determined that local-scale (<15-km) spatial synchrony of bird populations in New England was correlated with synchronous fluctuations in lepidopteran larvae abundance and with the North Atlantic Oscillation. Here we address five questions that extend the scope of our earlier study using North American Breeding Bird Survey data. First, do bird populations in eastern North America exhibit spatial synchrony in abundances at scales beyond those we have documented previously? Second, does spatial synchrony depend on what population metric is analyzed (e.g., abundance, growth rate, or variability)? Third, is there geographic concordance in where species exhibit synchrony? Fourth, for those species that exhibit significant geographic concordance, are there landscape and habitat variables that contribute to the observed patterns? Fifth, is spatial synchrony affected by a species' life history traits? Significant spatial synchrony was common and its magnitude was dependent on the population metric analyzed. Twenty-four of 29 species examined exhibited significant synchrony in population abundance: mean local autocorrelation (rho)= 0.15; mean spatial extent (mean distance where rho=0) = 420.7 km. Five of the 29 species exhibited significant synchrony in annual population growth rate (mean local autocorrelation = 0.06, mean distance = 457.8 km). Ten of the 29 species exhibited significant synchrony in population abundance variability (mean local autocorrelation = 0.49, mean distance = 413.8 km). Analyses of landscape structure indicated that habitat variables were infrequent contributors to spatial synchrony. Likewise, we detected no effects of life history traits on synchrony in population abundance or growth rate. However, short-distance migrants exhibited more spatially extensive synchrony in population variability than either year-round residents or long-distance migrants. The dissimilarity of the spatial extent of synchrony across species suggests that most populations are not regulated at similar spatial scales. The spatial scale of the population synchrony patterns we describe is likely larger than the actual scale of population regulation, and in turn, the scale of population regulation is undoubtedly larger than the scale of individual ecological requirements. PMID:18027754

Jones, Jason; Doran, Patrick J; Holmes, Richard T

2007-10-01

235

The slowdown in population growth: causes and consequences.  

PubMed

U.S. population trends are projected using data from the Bureau of the Census. The focus is on the economic consequences of these trends. The authors conclude that the economic impact will be relatively slight up to the year 2000. "After 2000, the changes to the economic outlook will be more significant. The aging of the population will accelerate and the pace of economic growth is likely to slow even further. More resources will be devoted to caring for the elderly, while public and private pension systems will need to draw down savings to provide for the retirement of the baby-boom generation." PMID:12342613

Willmann, H; Hoyt, S

1989-01-01

236

Effect of growth conditions on flow-induced inhibition of population growth of a red-tide dinoflagellate  

Microsoft Academic Search

The population growth of some dinoflagellates is known to be reduced by exposure to fluid flow. The red-tide dinoflagellate Lingulodinium polyedrum was used to examine the effect of growth conditions on flow-induced inhibition of population growth. Three factors were tested: time of exposure relative to the light : dark (LD) cycle, illumination level, and culture growth phase (early vs. late

Andrew R. Juhl; Vivianna Velazquez; Michael I. Latz

2000-01-01

237

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

PubMed

This work uses Keynesian principles and an analysis of the Colombian population in the 1970s to argue that the Colombian policy of slowing population growth, which was adopted with the aim of improving the general welfare of the population, has had shortterm negative effects on effective demand and thus on the level of employment and welfare. These negative effects were caused by the inflexibility of income distribution, which prevented expansion of the internal market, complicated by the stagnant condition of the external sector and the budget deficit. The results of the Colombian case study demonstrate how the deceleration of population growth beginning in the 1960s had a significant impact on the levels of consumption and savings and on the patterns of consumption, leading to low levels of investment and little dynamism. Although the current Colombian economic recession is aggravated by contextual factors such as the world economic recession, the high cost of capital, the industrial recession, and declining food production among others, at the core of the crisis are longer term structural determinants such as the decline in the rate of population growth and the highly unequal distribution of income and wealth, which have contributed to a shrinking of the internal market for some types of goods. Given the unlikelihood of renewed rapid population growth, the Keynesian model suggests that the only alternative for increasing aggregate demand is state intervention through public spending and investment and reorientation of the financial system to achieve a dynamic redistribution of income. Based on these findings and on proposals of other analysts, a stragegy for revitalization is proposed which would imply a gradual income redistribution to allow increased consumption of mass produced goods by the low income groups. Direct consumption subsidies would be avoided because of their inflationary and import-expanding tendencies; rather, incentives and support would be provided to 3 productive sectors: traditional agriculture, small factories producing mass consumption goods, and construction of low income housing. The strategy would promote economic growth and expansion without further deterioration of income distribution, employment, and price stability. A simulation study demonstrated the advantages of such a strategy in relation to alternative strategies. PMID:12266019

Banguero, H

1983-05-01

238

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

PubMed

This philosophical review of 2 arguments about responsibility for and solutions to environmental degradation concludes that both sides are correct: the ultimate and the proximal causes. Ultimate causes of pollution are defined as the technology responsible for a given type of pollution, such as burning fossil fuel; proximate causes are defined as situation-specific factors confounding the problem, such as population density or rate of growth. Commoner and others argue that developed countries with low or negative population growth rates are responsible for 80% of world pollution, primarily in polluting technologies such as automobiles, power generation, plastics, pesticides, toxic wastes, garbage, warfaring, and nuclear weapons wastes. Distortionary policies also contribute; examples are agricultural trade protection, land mismanagement, urban bias in expenditures, and institutional rigidity., Poor nations are responsible for very little pollution because poverty allows little waste or expenditures for polluting, synthetic technologies. The proximal causes of pollution include numbers and rate of growth of populations responsible for the pollution. Since change in the ultimate cause of pollution remains out of reach, altering the numbers of polluters can make a difference. Predictions are made for proportions of the world's total waste production, assuming current 1.6 tons/capita for developed countries and 0.17 tons/capita for developing countries. If developing countries grow at current rates and become more wealthy, they will be emitting half the world's waste by 2025. ON the other hand, unsustainable population growth goes along with inadequate investment in human capital: education, health, employment, infrastructure. The solution is to improve farming technologies in the 117 non-self-sufficient countries, fund development in the most unsustainable enclaves of growing countries, break institutionalized socio-political rigidity in these enclaves, and focus on educating and empowering women in these enclaves. Women are in charge of birth spacing and all aspects of management of energy, food, water and the local environment, more so than men, in most countries. PMID:12284190

Shaw, R P

1989-01-01

239

Population growth impairment of aliphatic alcohols to Tetrahymena  

Microsoft Academic Search

The toxicity of a series of 120 aliphatic alcohols was evaluated using the Tetrahymena pyriformis population growth impairment assay. For tertiary propargylic alcohols; primary, secondary, and tertiary homopropargylic alcohols; allylic alcohols; and saturated alcohols, a statistically robust structure-activity model was developed for toxicity data [log (IGC(50) (-1))] using the 1-octanol\\/water partition coefficient (log K(ow)) as the lone descriptor [log (IGC(50))(-1)

T. Wayne Schultz; Julie Seward-Nagel; Karen A. Foster; Vera A. Tucker

2004-01-01

240

Growth rate determination of heterogeneous microbial population in swine manure  

Microsoft Academic Search

The effect of manure concentration on the growth of the heterogeneous microbial population under batch condition was studied.\\u000a Four manure concentrations were used in the study. The dehydrogenase activity was used as a measure of the active biomass\\u000a in the manure. The chemical oxygen demand test was used to measure the change in organic material caused by biological activities.\\u000a The

A. E. Ghaly; R. Kok; J. M. Ingrahm

1989-01-01

241

Ecology of Increasing Diseases: Population Growth and Environmental Degradation  

Microsoft Academic Search

The World Health Organization (WHO) and other organizations report that the prevalence of human diseases during the past decade\\u000a is rapidly increasing. Population growth and the pollution of water, air, and soil are contributing to the increasing number\\u000a of human diseases worldwide. Currently an estimated 40% of world deaths are due to environmental degradation. The ecology\\u000a of increasing diseases has

D. Pimentel; S. Cooperstein; H. Randell; D. Filiberto; S. Sorrentino; B. Kaye; C. Nicklin; J. Yagi; J. Brian; J. O’Hern; A. Habas; C. Weinstein

2007-01-01

242

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

Microsoft Academic Search

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

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

1999-01-01

243

Body size, ration level, and population growth in Asplanchna  

Microsoft Academic Search

1.)The daily ration required to maintain a population growth rate, rm, of zero (threshold ration) increased with increasing Asplanchna body mass. This relationship is described by the equation T=0.342 W0.797 where T=threshold ration (µg day-1 dry mass) and W=Asplanchna body mass (µg adult-1 dry mass).2.)The threshold ration of large campanulate morphs of A. silvestrii was 3.7 times greater than that

Richard S. Stemberger; John J. Gilbert

1984-01-01

244

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

PubMed

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

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

245

Exponentially Enhanced Quantum Metrology  

Microsoft Academic Search

We show that when a suitable entanglement-generating unitary operator depending on a parameter is applied on N qubits in parallel, a precision of the order of 2{sup -N} in estimating the parameter may be achieved. This exponentially improves the precision achievable in classical and in quantum nonentangling strategies.

S. M. Roy; Samuel L. Braunstein

2008-01-01

246

Exponentially Enhanced Quantum Metrology  

Microsoft Academic Search

We show that when a suitable entanglement-generating unitary operator depending on a parameter is applied on N qubits in parallel, a precision of the order of 2-N in estimating the parameter may be achieved. This exponentially improves the precision achievable in classical and in quantum nonentangling strategies.

S. M. Roy; Samuel L. Braunstein

2008-01-01

247

Exponentially Enhanced Quantum Metrology  

SciTech Connect

We show that when a suitable entanglement-generating unitary operator depending on a parameter is applied on N qubits in parallel, a precision of the order of 2{sup -N} in estimating the parameter may be achieved. This exponentially improves the precision achievable in classical and in quantum nonentangling strategies.

Roy, S. M. [Computer Science, University of York, York YO 10 5DD (United Kingdom); School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110067 (India); Braunstein, Samuel L. [Computer Science, University of York, York YO 10 5DD (United Kingdom)

2008-06-06

248

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

249

Evolutionary determinants of population differences in population growth rate × habitat temperature interactions in Chironomus riparius.  

PubMed

Little is known about intraspecific variation in fitness performance in response to thermal stress among natural populations and how this relates to evolutionary aspects of species ecology. In this study, population growth rate (PGR; a composite fitness measure) varied among five natural Chironomus riparius populations sampled across a climatic gradient when subjected to three temperature treatments reflecting the typical range of summer habitat temperatures (20, 24 and 28 °C). The variation could be explained by a complex model including effects of genetic drift, genetic diversity and adaptation to average temperature during the warmest month, in addition to experimental temperature. All populations suffered a decrease in PGR from 20 to 28 °C and ?PGR was significantly correlated with the respective average habitat temperature in the warmest month-populations from warmer areas showing lower ?PGR. This implies that long-term exposure to higher temperatures in the warmest month (the key reproductive period for C. riparius) is likely to be a key selective force influencing fitness at higher temperatures. A comparison of phenotypic divergence and neutral genetic differentiation revealed that one phenotypic trait--the number of fertile egg masses per female--appeared to be under positive selection in some populations. Our findings support a role for response to temperature selection along a climatic gradient and suggest population history is a key determinant of intraspecific fitness variation. We stress the importance of integrating different types of data (climatic, experimental, genetic) in order to understand the effects of global climate change on biodiversity. PMID:23124273

Nemec, Sabrina; Patel, Simit; Nowak, Carsten; Pfenninger, Markus

2012-11-03

250

Interspecific synchrony of seabird population growth rate and breeding success.  

PubMed

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

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

2013-05-30

251

Regional viewpoints on population growth: the debate in Africa.  

PubMed

Because Africa is a relatively empty continent, population growth has become a critical issue in only a few districts, such as some in Rwanda, Kenya, Malawi, Ghana, and Nigeria. It is difficult for Africa's citizens to realize that both present and future Africans will have a better life if Africa fills up slightly more slowly than it has in the past or at present. Military strength is equated with mere numbers of soldiers. Tribes within the countries and countries themselves grow fearful when they see that proportionately they are decreasing. Political difficulties are compounded by personal ones and there are deep psychologic impediments to family limitation. Children are greatly enjoyed, fertility and potency are commonly not distinguished, the capacity to bear children is highly regarded by both sexes, sons and daughters are security in old age, and many children do die. Traditional family planning methods are common in many tribes, but there is much resistence to the modern methods that attempt to replace them. African universities have been slow in seeing the advantages of a slower rate of population growth. The recent bloodshed in Rwanda was at least partly due to the pressure of people on the land. It is remarkable that the case for a rational population policy has progressed as far as it has in so many African states in view of so many arguments against it. PMID:4788251

King, M H

1973-01-01

252

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

253

Exponentially Enhanced Quantum Metrology  

Microsoft Academic Search

We show that when a suitable entanglement generating unitary operator\\u000adepending on a parameter is applied on N qubits in parallel, and an appropriate\\u000aobservable is measured, a precision of order 2 raised to the power (-N) in\\u000aestimating the parameter may be achieved. This exponentially improves the\\u000aprecision achievable in classical and in quantum non-entangling parallel\\u000astrategies. We propose

S. M. Roy; Samuel L. Braunstein

2008-01-01

254

Population growth of Yellowstone grizzly bears: Uncertainty and future monitoring  

USGS Publications Warehouse

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

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

2007-01-01

255

A restricted cell population propagates glioblastoma growth following chemotherapy  

PubMed Central

Glioblastoma multiforme (GBM) is the most common primary malignant brain tumor, with a median survival of about one year1. This poor prognosis is due to therapeutic resistance and tumor recurrence following surgical removal. Precisely how recurrence occurs is unknown. Using a genetically-engineered mouse model of glioma, we identify a subset of endogenous tumor cells that are the source of new tumor cells after the drug, temozolomide (TMZ), is administered to transiently arrest tumor growth. A Nestin-?TK-IRES-GFP (Nes-?TK-GFP) transgene that labels quiescent subventricular zone adult neural stem cells also labels a subset of endogenous glioma tumor cells. Upon arrest of tumor cell proliferation with TMZ, pulse-chase experiments demonstrate a tumor re-growth cell hierarchy originating with the Nes-?TK-GFP transgene subpopulation. Ablation of the GFP+ cells with chronic ganciclovir administration significantly arrested tumor growth and combined TMZ-ganciclovir treatment impeded tumor development. These data indicate the existence of a relatively quiescent subset of endogenous glioma cells that are responsible for sustaining long-term tumor growth through the production of transient populations of highly proliferative cells.

Chen, Jian; Li, Yanjiao; Yu, Tzong-Shiue; McKay, Renee M.; Burns, Dennis K.; Kernie, Steven G.; Parada, Luis F.

2012-01-01

256

The Solow model in discrete time and decreasing population growth rate  

Microsoft Academic Search

This paper reformulates the neoclassical Solow-Swan model of economic growth in discrete time by introducing a generic population growth law that verifies the following properties: 1) population is strictly increasing and bounded 2) the rate of growth of population is decreasing to zero as time tends to infinity. We show that in the long run the capital per worker of

Juan Gabriel Brida

2008-01-01

257

Determinism, noise, and spurious estimations in a generalised model of population growth  

Microsoft Academic Search

We study a generalised model of population growth in which the state variable is population growth rate instead of population size. Stochastic parametric perturbations, modelling phenotypic variability, lead to a Langevin system with two sources of multiplicative noise. The stationary probability distributions have two characteristic power-law scales. Numerical simulations show that noise suppresses the explosion of the growth rate which

Harold P. de Vladar; Ido Pen

2007-01-01

258

The linkage between relative population growth and purchasing power parity: Empirical evidence from selected countries  

Microsoft Academic Search

Relative population growth affects relative prices through the so-called Balassa- Samuelson (BS) effect and that in turn impacts PPP. This paper empirically investigates the relationship between PPP exchange rate and relative population growth in a panel of 80 selected countries in the world. Following the BS hypothesis this paper argues that relative population growth affects nominal wages that impact price

Ruhul Salim; AFM Hassan

259

[The metropolitan area of Guadalajara. The population growth transition].  

PubMed

The Guadalajara metropolitan area, containing approximately three million inhabitants in the municipios of Guadalajara, Zapopan, Tlaquepaque, Tonala, and El Salto, has high rates of population growth due to in-migration, natural increase, and annexation of localities. The average annual rate of growth declined from 6.8% in the 1950s to 2.6% in the 1980s. Despite the decline, which can be considered an indicator of transition, the increase in absolute numbers resulting from a 2.6% rate of growth amounts to 78,000 new inhabitants each year. A change has occurred in recent decades in the migratory patterns and urban spatial distribution of Western Mexico. In-migration to the Guadalajara metropolitan zone has slowed in both absolute and relative terms. Growth of smaller and intermediate sized cities is now more rapid than is that of the metropolitan zone. Surveys in Guadalajara indicate that the proportion of in-migrants from urban areas has increased substantially. Despite the slowing pace of growth, the Guadalajara metropolitan area faces serious problems of housing, land use, transport, and urban infrastructure and services in general. Because of rapid growth and the preponderance of young people among the migrants, the problems are likely to persist for some time. Population projections suggest that 66,000 new jobs will be needed during 1990-95 and 57,000 during 1995-2000, assuming no significant increases in the proportion of women who work. An average of 2500 hectares of land will be needed every five years, nearly equivalent to the total area of the city in 1940. The number of daily trips on urban transit is projected to increase from 6 million at present to 7 million in 2005. The daily load of solid waste is expected to increase from 4000 to 5000 tons in 2005. The economic structure of the city is also changing. Commerce and small and medium-sized manufacturing enterprises have lost their primacy and large national and transnational manufacturing and commercial enterprises have gained ascendancy. The urban development plans for the Guadalajara region were essentially created in the 1970s and do not adequately reflect economic and demographic changes. PMID:12158059

Arroyo Alejandre, J

1994-01-01

260

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

261

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

2012-12-20

262

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.

Polanski, A; Kimmel, M

2003-01-01

263

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).

264

q-exponential distribution in urban agglomeration  

NASA Astrophysics Data System (ADS)

Usually, the studies of distributions of city populations have been reduced to power laws. In such analyses, a common practice is to consider cities with more than one hundred thousand inhabitants. Here, we argue that the distribution of cities for all ranges of populations can be well described by using a q-exponential distribution. This function, which reproduces the Zipf-Mandelbrot law, is related to the generalized nonextensive statistical mechanics and satisfies an anomalous decay equation.

Malacarne, L. C.; Mendes, R. S.; Lenzi, E. K.

2002-01-01

265

The evolutionary demography of ecological change: linking trait variation and population growth.  

PubMed

Population dynamics and evolutionary change are linked by the fundamental biological processes of birth and death. This means that population growth may correlate with the strength of selection, whereas evolutionary change can leave an ecological signature. We decompose population growth in an age-structured population into contributions from variation in a quantitative trait. We report that the distribution of body sizes within a population of Soay sheep can markedly influence population dynamics, accounting for up to one-fifth of observed population growth. Our results suggest that there is substantial opportunity for evolutionary dynamics to leave an ecological signature and visa versa. PMID:17363672

Pelletier, Fanie; Clutton-Brock, Tim; Pemberton, Josephine; Tuljapurkar, Shripad; Coulson, Tim

2007-03-16

266

Formulating variable carrying capacity by exploring a resource dynamics-based feedback mechanism underlying the population growth models  

Microsoft Academic Search

Most of the population growth models comprise the concept of carrying capacity presume that a stable population would have a saturation level characteristic. This indicates that the population growth models have a common implicit feature of resource-limited growth, which contributes at a later stage of population growth by forming a numerical upper bound on the population size. However, a general

Hsin-i Wu; Amit Chakraborty; Bai-Lian Li; Charles M. Kenerley

2009-01-01

267

Population Growth Rate And Carrying Capacity For Springtails Folsomia Candida Exposed To Ivermectin  

Microsoft Academic Search

Forecasting the effects of stressors on the dynamics of natural populations requires assessment of the joint effects of a stressor and population density on the population response. The effects can be depicted as a contour map in which the population response, here assessed by population growth rate, varies with stress and density in the same way that the height of

Helen L. Noël; Steve P. Hopkin; Thomas H. Hutchinson; Tim D. Williams; Richard M. Sibly

2006-01-01

268

Population dynamics of the whitebacked planthopper, Sogatella furcifera (Hemiptera: Delphacidae) with special reference to the relationship between its population growth and the growth stage of rice plants  

Microsoft Academic Search

A population census was conducted to describe the effects of the growth stage of rice on the population dynamics ofS. furcifera, in particular, on immigration, seasonal abundance, population growth rate, and wing-form expression. The number of immigrants\\u000a was highest on rice plants 17 to 30 days after transplanting (DAT), which suggested that immigrants prefer to settle or remain\\u000a more on

Masaya Matsumura

1996-01-01

269

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

270

Whither the global population problem  

Microsoft Academic Search

Growth of the human population has been underway for thousands of years and was never a problem until recently. It is now expanding exponentially, and today global population stands at nearly 6 billion with 97 million being added each year. Currently, overpopulation has led to serious social and environmental problems such as poverty, overcrowded slums, crime, terrorism, pollution of air

Roy O. Greep

1998-01-01

271

Grassland ecology and population growth: striking a balance.  

PubMed

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

Hou, D; Duan, C; Zhang, D

2000-06-01

272

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

273

Population growth "neutralizes" India's efforts to improve quality of life.  

PubMed

With one of the world's oldest family welfare programs, direct interventions, and policy initiatives, India has managed to reduce its crude birth rate from 41.7/1000 in 1951-61 to 27.4/1000 today; the crude death rate and infant mortality rate have also fallen. However, despite these successes, efforts to improve the quality of life in India have been neutralized by population growth. Policies are therefore now targeted to the employment-oriented development of the rural infrastructure. The resulting interventions have led to a reduction in both rural and urban poverty. An holistic approach is being applied to poverty alleviation, including institutional reforms, capacity building, and asset creation through sustainable productive economic processes and the involvement of communities and nongovernmental organizations in family welfare initiatives, with emphasis upon population and health and special focus upon vulnerable sections. The problems of infants and the elderly must be addressed. A community needs assessment has been underway since April 1996 in the attempt to achieve decentralized participatory planning at the service provider's level. PMID:12294106

274

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

ERIC Educational Resources Information Center

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

Williams, James D.

275

Has population growth restricted improvements in food availability per head, 1970-95?  

Microsoft Academic Search

Using data from the Food and Agricultural Organization and some other sources, it was estimated that rapid population growth in countries with an initial average calorie availability of below 2800 per head inhibited improvements in food production and availability per head during the 1980s and early 1990s. There were statistically significant negative effects of population growth on the growth in

ØYSTEIN KRAVDAL

2001-01-01

276

Induced population growth and induced technological progress: Their interaction in the accelerating stage  

Microsoft Academic Search

A simple model of Malthusian population growth combined with population?induced technological progress generates accelerating growth. The model may be relevant for a first stage of growth in which natural resource limitations can be overcome through technological progress; it is not applicable to a later stage in which resource constraints are more resistant. Parameter values are roughly inferred from historical experience.

Ronald Demos Lee

1988-01-01

277

Population growth and agriculture in poor countries: A review of theoretical issues and empirical evidence  

Microsoft Academic Search

The paper contributes a critical survey of the very extensive literature dealing with various aspects of the economic and institutional responses of agriculture to population growth in poor countries, encompassing a discussion of the main underlying theoretical issues. Such responses are evaluated in the framework of the general population-development debate.The main conclusion is that, although population growth induces adjustments in

Nadia Cuffaro

1997-01-01

278

The hydrocarbon era, world population growth and oil use -- a continuing geological challenge  

Microsoft Academic Search

The world's use of oil, the relationship of world population growth to this use, and what the energy situation might be in the future is a challenge to the geologist. The earth's population doubled between 1930 and 1975 and a comparison of world petroleum use and population growth show similar upward curves. Of the annual fossil fuel resources used in

Townes

1993-01-01

279

THE SOURCES OF REGIONAL ELDERLY POPULATION GROWTH: MIGRATION AND AGING-IN-PLACE  

Microsoft Academic Search

A region's elderly population has two sources of growth: net migration and the net aging-in-place of its resident population. This paper outlines a method for identifying the projected relative contribution of these two sources of elderly population growth over time, and illustrates it with data for the states of Arizona, California, Florida, Illinois, and New York. The sources of elderly

Andrei Rogers; Jennifer Woodward

1988-01-01

280

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

Microsoft Academic Search

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

Barry Sinervo

1990-01-01

281

Growth and Control of Population in China: The Urban-Rural Contrast  

Microsoft Academic Search

China's population is large and its annual growth significant. Since the mid-1950s, the Chinese government has made four attempts to curb the growth and hopes to limit the total population to 1.2 billion by the year 2000. Thus it has established a policy of limiting families to one child each. These efforts of population control have been successful in cities

Mei-Ling Hsu

1985-01-01

282

The petroleum exponential (again)  

NASA Astrophysics Data System (ADS)

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

Bell, Peter M.

283

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 ...

284

Density-dependent growth as a key mechanism in the regulation of fish populations: evidence from among-population comparisons.  

PubMed Central

It is generally assumed that fish populations are regulated primarily in the juvenile (pre-recruit) phase of the life cycle, although density dependence in growth and reproductive parameters within the recruited phase has been widely reported. Here we present evidence to suggest that density-dependent growth in the recruited phase is a key process in the regulation of many fish populations. We analyse 16 fish populations with long-term records of size-at-age and biomass data, and detect significant density-dependent growth in nine. Among-population comparisons show a close, inverse relationship between the estimated decline in asymptotic length per unit biomass density, and the long-term average biomass density of populations. A simple population model demonstrates that regulation by density-dependent growth alone is sufficient to generate the observed relationship. Density-dependent growth should be accounted for in fisheries' assessments, and the empirical relationship established here can provide indicative estimates of the density-dependent growth parameter where population-specific data are lacking.

Lorenzen, Kai; Enberg, Katja

2002-01-01

285

Exponential metric fields  

NASA Astrophysics Data System (ADS)

The Laser Interferometer Space Antenna (LISA) mission will use advanced technologies to achieve its science goals: the direct detection of gravitational waves, the observation of signals from compact (small and dense) stars as they spiral into black holes, the study of the role of massive black holes in galaxy evolution, the search for gravitational wave emission from the early Universe. The gravitational red-shift, the advance of the perihelion of Mercury, deflection of light and the time delay of radar signals are the classical tests in the first order of General Relativity (GR). However, LISA can possibly test Einstein's theories in the second order and perhaps, it will show some particular feature of non-linearity of gravitational interaction. In the present work we are seeking a method to construct theoretical templates that limit in the first order the tensorial structure of some metric fields, thus the non-linear terms are given by exponential functions of gravitational strength. The Newtonian limit obtained here, in the first order, is equivalent to GR.

Dos Santos, Wytler Cordeiro

2011-01-01

286

OPINION: Safe exponential manufacturing  

NASA Astrophysics Data System (ADS)

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

Phoenix, Chris; Drexler, Eric

2004-08-01

287

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

PubMed

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

2011-06-29

288

Population age structure and rhizome growth of Cymodocea nodosa in the Ria Formosa (southern Portugal)  

Microsoft Academic Search

The population age structure and derived population dynamics (recruitment, growth and mortality), rhizome growth and flowering effort of Cymodocea nodosa in the Ria Formosa (south of Portugal) were examined using reconstruction techniques. The horizontal rhizome elongation rates were low (13.8–30.7 cm year-1), which is consistent with the low population growth rate (-2.35 to 0.29 year-1). The vertical elongation rate was proportional to the

A. H. Cunha; C. M. Duarte

2005-01-01

289

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 ...

290

Extrapolating Growth Reductions in Fish to Changes in Population Extinction Risks: Copper and Chinook Salmon  

Microsoft Academic Search

Fish commonly respond to stress, including stress from chemical exposures, with reduced growth. However, the relevance to wild populations of subtle and sometimes transitory growth reductions may not be obvious. At low-level, sustained exposures, Cu is one substance that commonly causes reduced growth but little mortality in laboratory toxicity tests with fish. To explore the relevance of growth reductions under

Christopher A. Mebane; David L. Arthaud

2010-01-01

291

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

Microsoft Academic Search

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

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

2001-01-01

292

The role of density-dependent individual growth in the persistence of freshwater salmonid populations  

Microsoft Academic Search

Theoretical and empirical models of populations dynamics have paid little attention to the implications of density-dependent\\u000a individual growth on the persistence and regulation of small freshwater salmonid populations. We have therefore designed a\\u000a study aimed at testing our hypothesis that density-dependent individual growth is a process that enhances population recovery\\u000a and reduces extinction risk in salmonid populations in a variable

Simone Vincenzi; Alain J. Crivelli; Dusan Jesensek; Giulio A. De Leo

2008-01-01

293

Climate, food, density and wildlife population growth rate.  

PubMed

1. The aim of this study was to derive and evaluate a priori models of the relationship between annual instantaneous population growth rate (r) and climate. These were derived from the numerical response of annual r and food, and the effect of climate on a parameter in the numerical response. The goodness of fit of a range of such deductive models to data on annual r of Soay sheep and red deer were evaluated using information-theoretic (AICc-based) analyses. 2. The analysis for sheep annual r showed negative effects of abundance and negative effects of the interaction of abundance and climate, measured as March rainfall (and winter NAO) in the best fitting models. The analysis for deer annual r showed a negative effect of deer abundance and a positive effect of climate measured as March rainfall (but a negative effect of winter NAO), but no interaction of abundance and climate in the best fitting models. 3. There was most support in the analysis of sheep dynamics for the ratio numerical response and the assumption that parameter J (equilibrium food per animal) was influenced by climate. In the analysis of deer dynamics there was most support for the numerical responses assuming effects of food and density (Ivlev and density, food and density, and additive responses) and slightly less support for the ratio numerical response. The evaluation of such models would be aided by the collection of and incorporation of food data into the analyses. PMID:17302843

Hone, Jim; Clutton-Brock, Tim H

2007-03-01

294

Extreme natural hazards: population growth, globalization and environmental change.  

PubMed

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 10,000 people. A calamity with a million casualties is just a matter of time. This situation is mainly a consequence of increased vulnerability. Climate change may also be affecting the frequency of extreme weather events as well as the vulnerability of coastal areas due to sea-level rise. Disastrous outcomes can only increase unless better ways are found to mitigate the effects through improved forecasting and warning, together with more community preparedness and resilience. There are particular difficulties with extreme events, which can affect several countries, while the largest events can have global consequences. The hazards of supervolcanic eruptions and asteroid impacts could cause global disaster with threats to civilization and deaths of billions of people. Although these are very rare events, they will happen and require consideration. More frequent and smaller events in the wrong place at the wrong time could have very large human, environmental and economic effects. A sustained effort is needed to identify places at risk and take steps to apply science before the events occur. PMID:16844639

Huppert, Herbert E; Sparks, R Stephen J

2006-08-15

295

Density-dependent growth as a key mechanism in the regulation of fish populations: evidence from among-population comparisons  

Microsoft Academic Search

It is generally assumed that ® sh populations are regulated primarily in the juvenile (pre-recruit) phase of the life cycle, although density dependence in growth and reproductive parameters within the recruited phase has been widely reported. Here we present evidence to suggest that density-dependent growth in the recruited phase is a key process in the regulation of many ® sh

Kai Lorenzen; Katja Enberg

2002-01-01

296

Is the Astronomical Literature Still Expanding Exponentially?  

NASA Astrophysics Data System (ADS)

Have the recent reductions in funding for astronomy resulted in a significant decrease in the exponential growth of our astronomical publications? I studied the growth of five American and European journals (A&A, AJ, ApJ, MNRAS, and PASP) that publish papers on a broad range of astronomical topics. For each, I counted the numbers of normalized pages and papers published at 10 intervals in 1960-1996. The average numbers of pages showed an exponential increase of 11% per year before the mid-1970s and 6% per year thereafter. The average number of papers increased exponentially by 9% before the mid-1970s and by 4% per year thereafter. The difference between these two sets of numbers is caused by an increase in average paper lengths from six normalized pages in 1960 to a constant 12 pages per paper during the last decade. Thus, the average paper lengths have asymptotically reached a constant value. However, there is no sign of a leveling off in the growth of our literature. The number of different authors also increased steadily. Over the past 36 years there have been few systematic shifts from one journal to another, implying that few authors have changed their habitual choices of journals. The numbers of papers in the three American journals has been directly proportional to the numbers of AAS members at 0.41 papers per year per member during the past 36 years. Therefore, the growth in our numbers of papers is entirely due to the growth in the numbers of astronomers, and the additional growth in pages is due to the growth in paper lengths.

Abt, Helmut A.

1998-02-01

297

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.

Liao, David

298

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

299

Markov processes and exponential families  

Microsoft Academic Search

We study Markov processes the distribution of which stays for some interval of time in a given exponential family of distributions with one parameter. We show that the generator of such a process can be canonically associated to the generator of a Markov process on , having the same stability property with respect to a natural exponential family of distributions

Bernard Ycart

1992-01-01

300

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.

301

Eco-evolutionary dynamics: fluctuations in population growth rate reduce effective population size in chinook salmon.  

PubMed

We empirically assess the relationship between population growth rate (lambda, a parameter central to ecology) and effective population size (N(e), a key parameter in evolutionary biology). Recent theoretical and numerical studies indicate that in semelparous species with variable age at maturity (such as Pacific salmon, many monocarpic plants, and various other species), differences in mean reproductive success among individuals reproducing in different years leads to variation in lambda, and this in turn can reduce N(e). However, this phenomenon has received little empirical evaluation. We examined time series of abundance data for 56 populations of chinook salmon (Onchorhynchus tshawytscha) from the northwestern United States and compared N(e) (calculated from demographic data) with the total number of spawners each generation (NT). Important results include: (1) The mean multigenerational ratio N(e)/N(T) was 0.64 (median = 0.67), indicating that annual variation in lambda reduces effective population size in chinook salmon by an average of approximately 35%. These reductions are independent of, and in addition to, factors that reduce N(e) within individual cohorts (uneven sex ratio and greater-than-random variance in reproductive success). (2) The coefficient of variation of lambda was the most important factor associated with reductions in N(e), explaining up to two-thirds of the variance in N(e)/N(T). (3) Within individual generations, N(e) was lower when there was a negative correlation between annual N(i) and lambda, i.e., when relatively few breeders produced relatively high numbers of offspring. Our results thus highlight an important and little-studied eco-evolutionary trade-off: density-dependent compensation has generally favorable ecological consequences (promoting stability and long-term viability) but incurs an evolutionary cost (reducing N(e) because a few individuals make a disproportionate genetic contribution). (4) For chinook salmon, N(eH) (an estimator based on the harmonic mean number of breeders per year) is generally a good proxy for true N(e) and requires much less data to calculate. PMID:20426347

Waples, Robin S; Jensen, David W; McClure, Michelle

2010-03-01

302

Habitat heterogeneity affects population growth in goshawk Accipiter gentilis  

Microsoft Academic Search

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

Oliver Kruger; Jan Lindstrom

2001-01-01

303

Asymmetries in population growth regulated by intraspecific competition: Empirical studies and model tests  

Microsoft Academic Search

The linearity assumption in the logistic model of population growth is violated for nearly all organisms. Two simple models, the ?-logistic and the ?-Ricker, are shown to account for asymmetric patterns of population growth for 27 species of Drosophila and for a variety of other organisms, where the data were derived from the literature. These models are developed so as

Mark J. Pomerantz; William R. Thomas; Michael E. Gilpin

1980-01-01

304

How does population growth contribute to rising energy consumption in America?  

Microsoft Academic Search

The contribution of American population growth to rising energy consumption is analyzed for the period 1947–91. Energy consumption is disaggregated into electricity and nonelectricity consumption, and by end-use sectors: residential and commercial, industrial, and transportation. Population growth has been relatively unimportant as a contributor to yearly fluctuations in energy consumption. However, whereas energy changes induced by nonpopulation factors are erratic,

Allan Mazur

1994-01-01

305

Effects of Population Growth on the Economic Development of Developing Countries  

Microsoft Academic Search

The existing state of knowledge does not warrant any clear-cut generalization as to the effect of population growth on economic development in today's less developed areas. Some theoretical analyses argue that high population growth creates pressures on limited natural resources, reduces private and public capital formation, and diverts additions to capital resources to maintaining rather than increasing the stock of

Richard A. Easterlin

1967-01-01

306

Population Growth and Environmental Impact: Ideology and Academic Discourse in Israel  

Microsoft Academic Search

This article addresses the discourse of Israeli academics, policy makers, and environmental activists regarding the environmental implications of population growth in Israel. While there are compelling reasons that population growth should be a prominent topic for local environmental research and discussion, it is rarely considered in environmental campaigns or in the academic literature. I attribute this to the embeddedness of

Daniel E. Orenstein

2004-01-01

307

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

PubMed

Hatchling Sceloporus occidentalis from northern populations (central Oregon) grow more slowly than hatchlings from southern populations (southern California) in nature. In this study, I determine whether this difference in growth rate results from differences in thermal environment and/or in thermoregulatory behavior. To determine the degree to which the thermal environment affects growth rate among populations, I reared hatchings from the northern and southern populations in a cycling thermal regime in one of three experimental treatments differing in access to radiant heat (6, 9, or 12 h radiant heat; remainder of 24 h at 15°C). I also measured the body temperature that each individual voluntarily selected over the course of the daily activity cycle. Growth rate varied positively with duration of access to radiant heat. Within the three treatments, individual growth rate was positively correlated with body temperature. Moreover, the difference in growth rate between the northern and southern populations was due in part to differences in behavior - individuals from northern populations selected lower body temperatures. I found that significant variation in body temperature was associated with family membership, suggesting that thermal physiology has a genetic basis. Moreover, growth rate was correlated with body temperature among families in each population suggesting a genetic correlation underlies the phenotypic correlations. Thus, genetically based variation in thermal physiology contributes to differences in growth rate among individuals within a population as well as to differences among populations. PMID:22160116

Sinervo, B

1990-06-01

308

Exponential analysis in physical phenomena  

NASA Astrophysics Data System (ADS)

Many physical phenomena are described by first-order differential equations whose solution is an exponential decay. Determining the time constants and amplitudes of exponential decays from the experimental data is a common task in semiconductor physics (deep level transient spectroscopy), biophysics (fluorescence decay analysis), nuclear physics and chemistry (radioactive decays, nuclear magnetic resonance), chemistry and electrochemistry (reaction kinetics) and medical imaging. This review article discusses the fundamental mathematical limitations of exponential analysis, outlines the critical aspects of acquisition of exponential transients for subsequent analysis, and gives a comprehensive overview of numerical algorithms used in exponential analysis. In the first part of the article the resolution of exponential analysis as a function of noise in input decays is discussed. It is shown that two exponential decays can be resolved in a transient only if the ratio of their time constants is greater than the resolution limit, which can be explicitly calculated from the signal-to-noise ratio in the transient. Although the signal-to-noise ratio is generally limited by the sensitivity of the equipment, it is shown that digitalization of the decays may be a major source of noise. The requirements for type of analog-to-digital converter, number of digitized data points and duration of digitized transients, which must be met to obtain the theoretical resolution limit and to improve stability of the exponential analysis, are formulated. The second part of the review article gives an overview and comparison of major numerical techniques of exponential analysis, such as the nonlinear least squares fit, the Prony method, the method of modulating functions, the method of moments, the Laplace-Padé approximation, the Tikhonov regularization method, the Gardner transformation, the method of maximum entropy and others.

Istratov, Andrei A.; Vyvenko, Oleg F.

1999-02-01

309

Natural Increase: A New Source of Population Growth in Emerging Hispanic Destinations in the United States  

Microsoft Academic Search

Updated US Census Bureau estimates and race\\/ethnic-specific birth and death data for the post-2000 period are used to highlight the increasing role of natural increase as an engine of population growth in emerging Hispanic destinations. Newly emerging Hispanic growth areas are distinguished from established and high-growth areas from the 1990s. The findings document that recent Hispanic population gains have been

Kenneth M. Johnson; Daniel T. Lichter

2008-01-01

310

Population Growth, Migration and Urbanisation. Environmental Consequences in Kathmandu Valley, Nepal  

Microsoft Academic Search

Population growth is an important factor for local environment change. More importantly, the consumption level and the technology\\u000a assume to play a vital role in the overall environmental change. Ehrlich and Ehrlich (1990) argue that population growth causes\\u000a a disproportionate negative impact on the environment. Commoner et al (1971) in their study conclude that though population\\u000a plays role in environmental

Pushkar K. Pradhan

311

Transitional dynamics in the Solow-Swan growth model with AK technology and logistic population change  

Microsoft Academic Search

This paper offers an alternative way, based on the logistic population growth hypothesis, to yield transitional dynamics in the standard AK model with exogenous savings rate. Within this framework, we show that the dynamics of the capital stock per person and its growth rate can be non-monotonic over time. Moreover, even in the presence of negative growth, the capital stock

Alberto BUCCI; Luca GUERRINI

2008-01-01

312

Regional Growth in Central Europe. Long-term Effects of Population and Traffic Structure  

Microsoft Academic Search

In a simple growth model we explore the current and future growth effects of the regional population structure. Regional GDP growth in 227 regions within six countries in central Europe is explored as how they depend on the young and old dependency ratio. The young dependency ratio (YDR) is defined as ratio of the less than 20 years old and

Wolfgang Polasek; Helmut Berrer

2005-01-01

313

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

314

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

315

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

316

Influence of bacterial type and density on population growth of bacterial-feeding nematodes  

Microsoft Academic Search

The contribution of bacterial-feeding nematodes to litter decomposition and nutrient mineralization depends, in part, on the abundance of particular nematode species. Population dynamics will be constrained by edaphic factors, food availability and food quality. We report the population growth rates for six nematode species as affected by different bacterial isolates and by changes in food supply. Populations of Caenorhabditis elegans

R. C. Venette; H. Ferris

1998-01-01

317

Relationships between the Individual Growth Rate and the Population Spatial Structure and Dynamics in Rodents  

Microsoft Academic Search

The effects of the population density on individual animal growth, development, and reproduction has been extensively studied and reported in detail [1]. However, the existing explanations of these phenomena are incomplete and often inconsistent. The population dynamics of small rodents (especially at northern latitudes) exhibits large-amplitude oscillations called population cycles [2]. Their emergence is often attributed to the operation of

K. V. Maklakov; F. V. Kryazhimskii

2002-01-01

318

Cougar predation and population growth of sympatric mule deer and white-tailed deer  

Microsoft Academic Search

Mule deer (Odocoileus hemionus) populations throughout the west appear to be declining, whereas white- tailed deer (Odocoileus virginianus) populations are increasing. We compared abundance, number of fetuses per female (maternity rate), recruitment, and cause-specific adult ( ?1 year old) mortality rate for sympatric mule deer and white- tailed deer in south-central British Columbia to assess population growth for each species.

Hugh S. Robinson; Robert B. Wielgus; John C. Gwilliam

2002-01-01

319

Dynamics of single-species population growth: stability or chaos  

SciTech Connect

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

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

1981-01-01

320

The Poisson and Exponential Models  

ERIC Educational Resources Information Center

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

Richards, Winston A.

1978-01-01

321

Exponential stability of interconnected systems  

Microsoft Academic Search

Sufficient conditions are given for exponential stability in the large of the equilibrium of systems of interconnected components taken from a class of nonlinear time-varying multi-terminal components.

W. Thompson

1970-01-01

322

A Photometer for Measuring Population Growth in Yeast.  

ERIC Educational Resources Information Center

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

Tatina, Robert; Hartley, Tamela; Thomas, Danita

1999-01-01

323

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

PubMed Central

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

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

2012-01-01

324

Exponential function of chymotrypsin action.  

PubMed

Enzyme kinetics are usually described by the hyperbolic Michaelis-Menten equation, but they can also be described by the following exponential function: -dS/dt = Vm [1 - exp (-S/Km)]. The time-dependent decrease of the substrate (-dS/dt) is an exponential function of maximal velocity (Vm), the Michaelis constant (Km) and the actual substrate value (S). This exponential function is based on the assumption that the association of the substrate-enzyme complex is a concentration-dependent process, whereas the transformation of the substrate-enzyme complex is time-dependent. It can be shown that this exponential function is a more general solution of which the hyperbolic Michaelis-Menten equation is a special derivative under the conditions of low substrate (S) and high constant (Km) values. If the association process is time-dependent, the decline in substrate values will show a more concave curve. However, exponential functions in general are more concave than hyperbolic functions. Probably, therefore, the enzyme action of chymotrypsin could be described more appropriately by the present exponential function than by the conventional hyperbolic function. PMID:6714197

Keller, F; Koeppe, P; Emde, C

1984-01-01

325

Population Growth of Yellowstone Grizzly Bears: Uncertainty and Future Monitoring  

Microsoft Academic Search

Grizzly bears (Ursus arctos) in the Greater Yellowstone Ecosystem of the US Rocky Mountains have recently increased in numbers, but remain vulnerable due to isolation from other populations and predicted reductions in favored food resources. Harris et al. (2006) projected how this population might fare in the future under alternative survival rates, and in doing so estimated the rate of

Richard B. Harris; Gary C. White; Charles C. Schwartz; Mark A. Haroldson

2007-01-01

326

Anticipatory Reproduction and Population Growth in Seed Predators  

Microsoft Academic Search

Mast seeding, the intermittent, synchronous production of large seed crops by a population of plants, is a well-known example of resource pulses that create lagged responses in successive trophic levels of ecological communities. These lags arise because seed predators are thought capable of increasing reproduction and population size only after the resource pulse is available for consumption. The resulting satiation

Stan Boutin; Lucas A. Wauters; Andrew G. McAdam; Murray M. Humphries; Guido Tosi; André A. Dhondt

2006-01-01

327

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.

328

Population Growth Inflates the Per-Individual Number of Deleterious Mutations and Reduces Their Mean Effect  

PubMed Central

This study addresses the question of how purifying selection operates during recent rapid population growth such as has been experienced by human populations. This is not a straightforward problem because the human population is not at equilibrium: population genetics predicts that, on the one hand, the efficacy of natural selection increases as population size increases, eliminating ever more weakly deleterious variants; on the other hand, a larger number of deleterious mutations will be introduced into the population and will be more likely to increase in their number of copies as the population grows. To understand how patterns of human genetic variation have been shaped by the interaction of natural selection and population growth, we examined the trajectories of mutations with varying selection coefficients, using computer simulations. We observed that while population growth dramatically increases the number of deleterious segregating sites in the population, it only mildly increases the number carried by each individual. Our simulations also show an increased efficacy of natural selection, reflected in a higher fraction of deleterious mutations eliminated at each generation and a more efficient elimination of the most deleterious ones. As a consequence, while each individual carries a larger number of deleterious alleles than expected in the absence of growth, the average selection coefficient of each segregating allele is less deleterious. Combined, our results suggest that the genetic risk of complex diseases in growing populations might be distributed across a larger number of more weakly deleterious rare variants.

Gazave, Elodie; Chang, Diana; Clark, Andrew G.; Keinan, Alon

2013-01-01

329

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

Microsoft Academic Search

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

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

2010-01-01

330

DIFFERENCES IN TOWNSEND'S CHIPMUNK POPULATIONS BETWEEN SECOND AND OLD-GROWTH FORESTS IN WESTERN OREGON  

Microsoft Academic Search

Because Townsend's chipmunks (Tomias townsendii) may be important in maintaining natural ecosystem processes in forests in the central Oregon Cascade Range, we compared their population char- acteristics in young second-growth and old-growth forests. We live-trapped Townsend's chipmunks in 5 young (30-60 yr old) second-growth and 5 old-growth (>400 yr old) Douglas-fir (Pseudotsuga menziesii) stands during spring and autumn 1987-90 in

DANIEL K. ROSENBERG; ROBERT G. ANTHONY

331

Evaluating the Impact of Population Bottlenecks in Experimental Evolution  

Microsoft Academic Search

Experimental evolution involves severe, periodic reductions in population size when fresh media are inoculated during serial transfer. These bottlenecks affect the dynamics of evolution, reducing the probabil- ity that a beneficial mutation will reach fixation. We quantify the impact of these bottlenecks on the evolutionary dynamics, for populations that grow exponentially between transfers and for populations in which growth is

Lindi M. Wahl; Philip J. Gerrish; Ivan Saika-Voivod

2002-01-01

332

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

PubMed Central

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.

Johnson, Christopher N.; Brook, Barry W.

2011-01-01

333

Introduced Brassica nigra populations exhibit greater growth and herbivore resistance but less tolerance than native populations in the native range.  

PubMed

Rapid post-introduction evolution has been found in many invasive plant species, and includes changes in defence (resistance and tolerance) and competitive ability traits. Here, we explored the post-introduction evolution of a trade-off between resistance to and tolerance of herbivory, which has received little attention. In a common garden experiment in a native range, nine invasive and 16 native populations of Brassica nigra were compared for growth and defence traits. Invasive populations had higher resistance to, but lower tolerance of, herbivore damage than native populations. Invasive populations survived better and produced more seeds than native ones when released from herbivores; but fitness was equivalent between the regions under ambient herbivory. The invasive populations grew taller, and produced more biomass and lighter seeds than natives, irrespective of insecticide treatment. In addition to supporting the idea of post-introduction rapid evolution of plant traits, our results also contribute to an emerging pattern of both increasing resistance and growth in invasive populations, contrary to the predictions of earlier theories of resistance-growth trade-offs. PMID:21410474

Oduor, Ayub M O; Lankau, Richard A; Strauss, Sharon Y; Gómez, José M

2011-03-15

334

Exponential growth and atmospheric carbon dioxide  

Microsoft Academic Search

The adequacy of assumptions required to project atmospheric COâ concentrations in time frames of practical importance is reviewed. Relevant issues concern the form assumed for future fossil fuel release, carbon cycle approximations, and the implications of revisions in fossil fuel patterns required to maintain atmospheric COâ levels below a chosen threshold. In general, we find that with a judiciously selected

John A. Laurmann; Ralph M. Rotty

1983-01-01

335

Minimal varieties of algebras of exponential growth  

Microsoft Academic Search

The exponent of a variety of algebras over a field of characteristic zero has been recently proved to be an integer. Through this scale we can now classify all minimal varieties of given exponent and of finite basic rank. As a consequence, we describe the corresponding T-ideals of the free algebra and we compute the asymptotics of the related codimension

A. Giambruno; M. Zaicev

2003-01-01

336

Exponential growth and future of artificial organs.  

PubMed

One hundred thousand (100,000) people are living--thanks to Artificial Kidneys. We need more emphasis on Home Dialysis. The immediate future will bring us: WAK (Wearable Artificial Kidney) FAK (Filtrating Artificial Kidney) PAK (Peritoneal Artificial Kidney) HAK (Hemoperfusion Artificial Kidney). Intra-aortic balloon pumps and transapical left ventricular bypass may offer patients now dying from heart failure, a possibility to either recover or be maintained until an artificial heart is available. Our aim is to create an Artificial Heart to totally replace the irreparably sick human heart. We have obtained survival times up to more than six months after total replacement of the natural heart in calves. Dr. Steve Jacobsen's Artificial Arm is activated by electromyographic signals that are derived from the shoulder muscles. The Artificial Eye makes use of direct stimulation of the visual cortex of the brain by arrays of electrodes situated against the visual cortex. For the Artificial Ear, we stimulate the fibers of the eighth nerve by threading platinum wires up into the cochlea. Deaf volunteers can hear rhythm, loudness and some pitch. PMID:616276

Kolff, W J

1977-08-01

337

Attached Growth of Sphaerotilus and Mixed Populations in a Continuous-flow Apparatus1  

PubMed Central

The effects of NH4Cl concentration, organic nitrogen compounds, glucose concentration, dissolved oxygen concentration, and flow rate on the attached growth of pure cultures of Sphaerotilus natans and of a mixed population in a continuous-flow apparatus are described. Low concentrations of NH4Cl and oxygen, and high flow rates resulted in attached populations that were dominated by Sphaerotilus. The conditions that allowed maximal attached growth in pure culture did not correspond to the conditions that promoted attached growth of Sphaerotilus in a mixed population. Images Fig. 1-5 Fig. 6-8 Fig. 9-10 Fig. 11-12 Fig. 13-16

Dias, F. F.; Dondero, Norman C.; Finstein, M. S.

1968-01-01

338

Dynamics of fisheries that affect the population growth rate coefficient  

NASA Astrophysics Data System (ADS)

Conventional surplus production models indicate that destruction of fish populations by overfishing is difficult, if not impossible, but catastrophic declines in abundance of exploited populations are common. Surplus production models also do not predict large continuing fluctuations in yield, but large fluctuations in yield are common. Conventional surplus production models assume that fisheries do not impact the population's capacity to increase, but changes in age structure or a decrease in age-specific fecundity resulting from fishing can decrease the coefficient of increase. A surplus production model is developed in which fishing reduces the capacity of a population to increase; the model is applied to describe the fluctuations observed in yield of lake herring ( Coregonus artedii) from the upper Great Lakes. The fisheries of the Great Lakes were decimated by the combined effects of heavy fishing and a changing environment. For some species, yield increased to high levels and then the fisheries collapsed; for other species, yield and effort fluctuated greatly.

Jensen, A. L.

1984-03-01

339

Modeling synchronous growth of bacterial populations in phased cultivation  

Microsoft Academic Search

The phasing technique is a method for synchronizing cell populations in a bioreactor. Periodic changes of substrate supply\\u000a and depletion can provoke a cell cycle phasing of originally stochastic scattered proliferation patterns. Synchronized cell\\u000a populations characterized by changes in DNA content distribution can be monitored by flow cytometry. Thus, studies of the\\u000a dynamics of single cells in specific cell cycle

Stephan Noack; Wolfgang Klöden; Thomas Bley

2008-01-01

340

Religio-cultural issues in population growth in Nigeria.  

PubMed

The author examines the impact of religion and religious beliefs on fertility, family size, and contraception acceptance in Nigeria. After a brief discussion of the effects of Nigeria's high fertility on its infrastructure and the standard of living of its population, the belief systems of tribal religions, Islam, and Christianity concerning sexuality and fertility are explored. Difficulties in formulating population policies that are acceptable to these religious groups and that will lower fertility are also described. PMID:12343739

Ejizu, C I

1990-01-01

341

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

PubMed

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

2002-09-29

342

Differential Effects of Growth and Loss Processes in Controlling Natural Phytoplankton Populations.  

National Technical Information Service (NTIS)

An investigation was made of factors controlling algal succession in a small, oligotrophic lake during summer stratification. Weekly measurements were made of growth rate, sedimentation rate, and population density for each of the dominant phytoplankton s...

W. G. Crumpton

1980-01-01

343

Valiant's Model: From Exponential Sums to Exponential Products  

Microsoft Academic Search

Abstract We study the power of big products for computing multivariate polynomials in a Valiant-like framework. More precisely, we define a new class V?P, as the set of families of polynomials that are exponential products of easily computable polynomials. We investigate the consequences of the hypothesis that these big products are themselves easily computable. For instance, this hypothesis would imply

Pascal Koiran; Sylvain Perifel

2006-01-01

344

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.

345

[Population growth and perceptions: an integrated population policy, some initial questions].  

PubMed

A review of the population factor in the African region around the great lakes of Victoria and Tanganyika is presented. The emphasis is on the level of awareness among the governments concerned of the relevance of the population factor to their development plans and the relationship between such awareness and traditional pro-natalist values in the formation of population policies. Particular attention is given to Burundi and Rwanda. PMID:12314354

Thibon, C

346

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

347

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

Microsoft Academic Search

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

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

2007-01-01

348

Population growth responses of Tetrahymena shanghaiensis in exposure to rare earth elements  

Microsoft Academic Search

This article presents the population growth responses of Tetrahymena shanghaiensis s1 in exposure to rare earth elements (REEs). Both the light REEs (La, Sm) and the heavy REEs (Y, Gd) were investigated with\\u000a 24- and 96-hr population growth assays to evaluate their aquatic toxicity. Four end points, cell count, frequency of neutral\\u000a red (NR) uptake, total protein, and nucleic acid

Yongxing Wang; Min Zhang; Xiaorong Wang

2000-01-01

349

Studies on the growth and encystment of Polytomella agilis  

Microsoft Academic Search

Summary Changes in cell population density, cell protein and cell carbohydrate levels of the flagellatePolytomella agilis during growth in batch cultures on a complex medium at 25° C, 18° C and 9° C were examined. At 25° C, cell protein and carbohydrate levels fell markedly during exponential population growth. At 18° C, cell protein values remained fairly constant, while cell

Phillip Sheeler; Marvin Cantor; Joseph Moore

1970-01-01

350

Impact of Population Growth on Food Supplies and Environment  

Microsoft Academic Search

As the world population continues to grow geometrically, great pressure is being placed on arable land, water, energy, and biological resources to provide an adequate supply of food while maintaining the integrity of our ecosystem. According to the World Bank and the United Nations, from 1 to 2 billion humans are now malnourished, indicating a combination of insufficient food, low

David Pimentel; Xuewen Huang; Ana Cordova; Marcia Pimentel

1997-01-01

351

Calculating the Financial Impact of Population Growth on Education.  

ERIC Educational Resources Information Center

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

Cline, Daniel H.

352

Global Water Resources: Vulnerability from Climate Change and Population Growth  

Microsoft Academic Search

The future adequacy of freshwater resources is difficult to assess, owing to a complex and rapidly changing geography of water supply and use. Numerical experiments combining climate model outputs, water budgets, and socioeconomic information along digitized river networks demonstrate that (i) a large proportion of the world's population is currently experiencing water stress and (ii) rising water demands greatly outweigh

Charles J. Vörösmarty; Pamela Green; Joseph Salisbury; Richard B. Lammers

2000-01-01

353

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

Microsoft Academic Search

About one?quarter million people daily are added to the 5.3 billion that already exist on earth. This rapidly growing population is increasing the pressures on the global environment, threatening its ability to supply itself with adequate amounts of food, water, and fuel and with a quality environment. The growing use of fossil fuels, deforestation, and other human activities is increasing

David Pimentel

1991-01-01

354

SOUTH AFRICA'S NATURAL RESOURCES AS RELATING TO POPULATION GROWTH  

Microsoft Academic Search

Natural resources include everything physically available to mankind. Man will never exhaust these, the limiting factor being determined by what can be exploited economically at any particular time. For this part of a natural resource the term ‘reserves’ is used.There is a complex interaction between population and natural resources. In any country the use of resources is related to the

N. Stutterheim

1978-01-01

355

Population growth dynamics of the rotifer Brachionus plicatilis cultured in non-limiting food condition  

Microsoft Academic Search

Population growth parameters in batch culture of Brachionus plicatilis under a continuous supply of freeze-dried microalgae powder have been determined. Two B. plicatilis strains (L- and S-types) and four microalgae species (Nannochloropsis oculata, Nannochloropsis gaditana, Nannochloris oculata and Tetraselmis suecica) have been tested, establishing the dynamics of growth at different daily food rations. Cultures showed a short lag phase, an

M. Yúfera; N. Navarro

1995-01-01

356

Numerical solution of population balance equations for nucleation, growth and aggregation processes  

Microsoft Academic Search

This article focuses on the derivation of numerical schemes for solving population balance models (PBMs) with simultaneous nucleation, growth and aggregation processes. Two numerical methods are proposed for this purpose. The first method combines a method of characteristics (MOC) for growth process with a finite volume scheme (FVS) for aggregation process. For handling nucleation terms, a cell of nuclei size

Shamsul Qamar; Gerald Warnecke

2007-01-01

357

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

358

Population growth and physiological characteristics of microalgae in a miniaturized bioreactor during space flight  

Microsoft Academic Search

A strain of microalgae (Anabaena siamensis) had been cultured in a miniaturized bioreactor during a retrievable satellite flight for 15days. By means of remote sensing equipment installed in the satellite, we gained the growth curve of microalgae population in space every day in real time. The curve indicated that the growth of microalgae in space was slower than the control

Gaohong Wang; Haofeng Chen; Genbao Li; Lanzhou Chen; Dunhai Li; Chunxiang Hu; Kun Chen; Yongding Liu

2006-01-01

359

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

Microsoft Academic Search

The Biomass Production Chamber at John F. Kennedy Space Center is a closed plant growth chamber facility that can be used to monitor the level of biogenic emissions from large populations of plants throughout their entire growth cycle. The head space atmosphere of a 26-day-old lettuce (Lactuca sativa cv. Waldmann's Green) stand was repeatedly sampled and emissions identified and quantified

Jennifer H. Batten; Gary W. Stutte; Raymond M. Wheeler

1995-01-01

360

Vulnerability of Korean water resources to climate change and population growth  

Microsoft Academic Search

Freshwater availability is affected by changes in climate and growth. We assessed the freshwater vulnerability for five major Korean river basins for 2015 and 2030. We used a regional climate model based on the IPCC SRES A2 scenario, US Geological Survey's Precipitation Rainfall Simulation Model, and population and industrial growth scenarios for impact assessment. The model simulation results suggest increasing

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

2007-01-01

361

Population changes in a growth center region with reference to the Israeli Negev  

Microsoft Academic Search

The aim of this paper is to present a scheme of relative population changes in a geographic-termed growth center region, with reference to a real problem of development as implemented in the Israeli Negev arid zone. The growth process described in the scheme leads to dynamic steady-states which indicate stable structure and stable relationships between the components of the regional

E. Stern; M. Sonis

1981-01-01

362

GROWTH OF VARROA DESTRUCTOR (ACARI: VARROIDAE) POPULATIONS IN RUSSIAN HONEY BEE (HYMENOPTERA: APIDAE) COLONIES  

Technology Transfer Automated Retrieval System (TEKTRAN)

The growth rate (r) of Varroa destructor populations in Russian and Italian honey bee (Apis mellifera L.) colonies was monitored from 2001 to 2003 in Baton Rouge, Louisiana. Over this period, our results consistently showed lower mite growth in the Russian than in the Italian colonies. In 2001, ins...

363

The enduring and vanishing American Indian: American Indian population growth and intermarriage in 1990  

Microsoft Academic Search

The American Indian and Alaskan Native population has grown rapidly since 1950 because of changes in the racial classification of persons with mixed Indian and non?Indian descent. These changes have challenged once common expectations that the Indian population was likely to shrink over time through assimilation. However, in regions of the United States where the recent growth of the Indian

Karl Eschbach

1995-01-01

364

Potential for rural--urban population balance. [Evaluation of potential for employment growth  

Microsoft Academic Search

Pressure is building for a national policy on population distribution, with emphasis on stopping the involuntary migrations caused by a lack of employment opportunities and establishing an adequate work force to support employment growth. This study focuses on the rural-urban population balance and the relationship of job opportunities and labor force in the rural areas. Demographic figures used to trace

W. M. Musser; F. C. White

1977-01-01

365

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

366

Population Growth and Sprawl on the Pine Ridge Indian Reservation, South Dakota  

Microsoft Academic Search

The most important impact on global land cover is human use and development. With the recent population growth occurring on the reservations in South Dakota, especially Pine Ridge Indian Reservation, the towns and agricultural areas of the reservation are undergoing a change. Although urban sprawl certainly is not a consideration on the reservations, the population explosion currently underway has seen

R. L. Campbell

2006-01-01

367

Modeling stem cell population growth: incorporating parameters for quiescence, differentiation and apoptosis  

Microsoft Academic Search

The use of stem cells in cell-mediated therapies or cell transplantation applications will require a controlled, scalable system for expansion of the cells and for control of cellular differentiation. Modeling stem cell population growth is one step towards developing such a system. Stem cell populations are heterogeneous and include cells which are non-mitotic. In particular, stem cells may be quiescent

B. M. Deasy; R. J. JankowskiiP; T. R. Payne; J. S. Greenberger; J. Huard

2002-01-01

368

Models and model selection uncertainty in estimating growth rates of endangered freshwater mussel populations  

Microsoft Academic Search

Appropriate inference of population status for endangered species is extremely important. Using a single model for estimating population growth rates is typically inadequate for assessing endangered species because inferences based on only one ''best'' model ignore model uncertainty. In this study, the endangered dromedary pearlymussel (Dromus dro- mas) in the Clinch and Powell rivers of eastern Tennessee, USA, was used

Yan Jiao; Richard Neves; Jess Jones

2008-01-01

369

The Ecological Determinants of Population Growth in a Drosophila Culture. I. Fecundity of Adult Flies  

Microsoft Academic Search

The common coactions between plant and animal populations can readily be studied in the normal Drosophila melanogaster culture, and from this laboratory model it may be possible to obtain some indication of the significant variables affecting the growth of similar populations in nature. This model may also be used to test the validity of the assumption inherent in the various

Forbes W. Robertson; James H. Sang

1944-01-01

370

Aids and population growth in sub-Saharan Africa: Assessing the sensitivity of projections  

Microsoft Academic Search

Despite different models to project the course of the AIDS pandemic and a scarcity of data to provide standard input parameters for those models, a limited consensus emerges from distinct sets of population projections. In sub-Saharan Africa, population growth rates are projected to remain positive in spite of the pandemic over the next few decades. To investigate this conclusion, alternative

Patrick Heuveline

1997-01-01

371

Modeling oyster growth rate by coupling oyster population and hydrodynamic models for Apalachicola Bay, Florida, USA  

Microsoft Academic Search

The eastern oyster (Crassostrea virginica) plays an important role both ecologically and economically in Apalachicola Bay, Florida. Oyster population features such as population size, age structure, spawning, growth, and reproduction are closely related to bay salinity, which is often affected by freshwater flows from the Apalachicola River. Existing modeling approaches have used statistical models to examine the effects of changing

Hongqing Wang; Wenrui Huang; Mark A. Harwell; Lee Edmiston; Elijah Johnson; Ping Hsieh; Katherine Milla; John Christensen; Jessica Stewart; Xiaohai Liu

2008-01-01

372

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...

373

CHARACTERISATION OF A KABYLIAN POPULATION OF RABBITS IN ALGERIA: BIRTH TO WEANING GROWTH PERFORMANCE  

Microsoft Academic Search

The aim of this study was to characterize the growth of rabbits of a local Algerian population (Kabylian) from birth to weaning at 28 days. A total of 216 litters from 82 females of the local population were regularly weighed between birth and weaning (28 d) in the experimental rabbitry of the Tizi-Ouzou University (100 km east of Algiers). The

374

Dynamical Feedbacks between Population Growth and Sociopolitical Instability in Agrarian States  

Microsoft Academic Search

Most preindustrial states experienced recurrent waves of political collapse and internal warfare. One possible explanation of this pattern, the demographic-structural theory, suggests that population growth leads to state instability and breakdown, which in turn causes population decline. Mathematical models incorporating this mechanism predict sustained oscillations in demographic and political dynamics. Here I test these theoretical predictions with time-series data on

Peter Turchin

375

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

Microsoft Academic Search

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

Elizabeth W. Moen

1984-01-01

376

On the Distinction Between Lag and Delay in Population Growth  

Microsoft Academic Search

The analysis and results presented in this paper provide conclusive evidence to distinguish between the delay effect and the\\u000a lag as two biologically distinct phenomena. It therefore dispels the incorrect notion that delay effects represented by delay\\u000a differential equations are the biological reason behind the lag phase in microorganism growth. The resulting consequence so\\u000a far is that the only other

Peter Vadasz; Alisa S. Vadasz

2010-01-01

377

[Population growth and factors associated with underdevelopment in Africa].  

PubMed

Factors associated with Africa's lack of progress in achieving socioeconomic development are explored. The author suggests that the solution does not lie in tackling the population problem, but in resolving the structural factors causing underdevelopment, such as the export of wealth, the burden of debt, and the unfavorable balance of payments. The need to replace inappropriate models of development based on Western experience with African models is also suggested. PMID:12346965

Ngondo A Pitshandenge, S

1993-10-01

378

ATTRACTING DYNAMICS OF EXPONENTIAL MAPS  

Microsoft Academic Search

We give a complete classiflcation of hyperbolic components in the space of iterated exponential maps z7! ‚ exp(z) , and we describe a preferred parametrization of those components. More precisely, we associate to every hyperbolic component of period n a flnite symbolic sequence of length n¡ 1 , we show that every such sequence is realized by a hyperbolic component,

Dierk Schleicher

2000-01-01

379

Countries with Rapid Population Growth and Resource Constraints: Issues of Food, Agriculture, and Development  

Microsoft Academic Search

Recent long-term demographic projections suggest a fast deceleration of global population growth and the eventual peaking of world population later in this century at about 9.2 billion, roughly 50 percent above the present level. Some low-income and food-insecure countries, however, have projected populations in 2050 that are multiples of present ones. In some of these countries agriculture must play a

Nikos Alexandratos

2005-01-01

380

When can environmental variability benefit population growth? Counterintuitive effects of nonlinearities in vital rates.  

PubMed

Using models for unstructured populations, we investigate the effect of environmental variability on population growth when the environment affects vital rates through nonlinear functions. We focus here especially on interannual variation in food resources availability, for which sigmoid functions are relevant. Considering first unregulated populations in stochastic environments, we show that classic sigmoid annual growth rates cannot lead to positive effects of increased environmental variability on population growth. This is true even when the temporal average of food availability is low, and Jensen's inequality predicts an increased arithmetic mean of the annual growth rate. The result is due to the log-concavity of many sigmoid (and other accelerating) functions, as convexity of the logarithm of the annual growth rate is needed for positive effects of variability to appear. Then, separating the effects of a food availability variable on reproduction and survival rates, we show that populations with less sensitive survival rate to food are more likely to benefit from food variability-as opposed to populations that have survival rates accelerating with food availability, which is rather counterintuitive given Jensen's inequality. Again, this is explained by log-convexity properties of nonlinear functions. We further extend these results to regulated populations, in which similar positive effects of food variability can affect average population size. Positive variability effects seem however more likely to occur in regulated populations. Finally, we extend our results to stage-structured populations. We connect to the previous work showing positive effects of environmental variability with matrix models, and show that these effects are well captured by simpler unstructured models. PMID:23906589

Barraquand, Frédéric; Yoccoz, Nigel G

2013-07-29

381

Understanding the growth of massive galaxies via stellar populations  

NASA Astrophysics Data System (ADS)

The formation and evolution of massive galaxies represent one of the most intriguing open problems in astrophysics. Their underlying stellar populations encode valuable information about their past history. Detailed spectroscopic observations allow us to constrain the star formation histories, revealing a complicated mixture of a strong, early formation process, followed by passive evolution in the cores, along with an extended assembly of the outer regions via minor mergers. In this contributed talk, some recent results are presented from the analysis of samples of massive galaxies both at z ~ 0 and moderate redshift.

Ferreras, Ignacio

2013-07-01

382

Global water resources: vulnerability from climate change and population growth.  

PubMed

The future adequacy of freshwater resources is difficult to assess, owing to a complex and rapidly changing geography of water supply and use. Numerical experiments combining climate model outputs, water budgets, and socioeconomic information along digitized river networks demonstrate that (i) a large proportion of the world's population is currently experiencing water stress and (ii) rising water demands greatly outweigh greenhouse warming in defining the state of global water systems to 2025. Consideration of direct human impacts on global water supply remains a poorly articulated but potentially important facet of the larger global change question. PMID:10894773

Vörösmarty, C J; Green, P; Salisbury, J; Lammers, R B

2000-07-14

383

Global Water Resources: Vulnerability from Climate Change and Population Growth  

NASA Astrophysics Data System (ADS)

The future adequacy of freshwater resources is difficult to assess, owing to a complex and rapidly changing geography of water supply and use. Numerical experiments combining climate model outputs, water budgets, and socioeconomic information along digitized river networks demonstrate that (i) a large proportion of the world's population is currently experiencing water stress and (ii) rising water demands greatly outweigh greenhouse warming in defining the state of global water systems to 2025. Consideration of direct human impacts on global water supply remains a poorly articulated but potentially important facet of the larger global change question.

Vörösmarty, Charles J.; Green, Pamela; Salisbury, Joseph; Lammers, Richard B.

2000-07-01

384

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

PubMed Central

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

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

2013-01-01

385

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

USGS Publications Warehouse

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

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

2011-01-01

386

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

387

Population and Scenarios: Worlds to win?  

Microsoft Academic Search

Demographic developments have played an important role in the structure\\u000aand functioning of the Earth's system. The exponential population growth\\u000aof the last century has led to high pressures on the environmental\\u000asystem, with the issue of hunger as representative of harmful effects. \\u000aDespite the fact that the population growth is currently negative in some\\u000aof the world's regions, the

Hilderink HBM

2007-01-01

388

Population and Scenarios: Worlds to Win?  

Microsoft Academic Search

Abstract Demographic,developments,have played an important role in the structure and functioning of the Earth’s system. The exponential population growth of the last century has led to high pressures on the environmental system, with the issue of hunger as representativ e of harmful effects. Despite the fact that the population growth is currently negative in some of the world’s regions, the

H. B. M. Hilderink

2004-01-01

389

Combining a total cell population growth and cell population dynamics in the presence of anti-cancer agents  

Microsoft Academic Search

A two-compartment Webb-Gyllenberg model describes the population dynamics of proliferating and quiescent cancer cells. Combination of the total cell growth curve and the two-compartment model yields an analytical solution for the behavior of proliferating subpopulation and the net transition rate between proliferating and quiescent cells as a function of time. This work presents a qualitative model for drug interaction with

Mitra Shojania Feizabadi

2006-01-01

390

The impact of disease on the survival and population growth rate of the Tasmanian devil.  

PubMed

1. We investigated the impact of a recently emerged disease, Devil Facial Tumour Disease (DFTD), on the survival and population growth rate of a population of Tasmanian devils, Sarcophilus harrisii, on the Freycinet Peninsula in eastern Tasmania. 2. Cormack-Jolly-Seber and multistate mark-recapture models were employed to investigate the impact of DFTD on age- and sex-specific apparent survival and transition rates. Disease impact on population growth rate was investigated using reverse-time mark-recapture models. 3. The arrival of DFTD triggered an immediate and steady decline in apparent survival rates of adults and subadults, the rate of which was predicted well by the increase in disease prevalence in the population over time. 4. Transitions from healthy to diseased state increased with disease prevalence suggesting that the force of infection in the population is increasing and that the epidemic is not subsiding. 5. The arrival of DFTD coincided with a marked, ongoing decline in the population growth rate of the previously stable population, which to date has not been offset by population compensatory responses. PMID:17714271

Lachish, Shelly; Jones, Menna; McCallum, Hamish

2007-09-01

391

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.

GAO, DAOZHOU; RUAN, SHIGUI

2013-01-01

392

Potential population growth and harmful effects on humans from bed bug populations exposed to different feeding regimes.  

PubMed

Effects of host availability and feeding period on bed bugs, Cimex lectularius (L.) (Hemiptera: Cimicidae), were measured. Population growth and the potential harmful effect of bed bug populations on human hosts were modelled. Bloodmeal sizes were affected by both feeding length and frequency, with >2-fold difference between insects fed daily or weekly. Blood consumption increased >2-fold between bed bugs fed occasionally and often, and 1.5-fold between occasional and daily feeding. Bed bugs fed more often than once a week, potentially every 2-4 days. Egg production was associated with nutrition, being strongly correlated with blood consumption in the previous week. Bed bug populations can grow under different feeding regimes and are hard to control with <80% mortality. Bed bugs can survive and grow even in locations with a limited blood supply, where bed bug persistence may be important for the continual spread of populations. Persistence in non-traditional locations and a potential association with human pathogens increase the health risks of bed bugs. Potential blood loss as a result of a bed bug can have serious consequences because uncontrolled populations can reach harmful levels in 3-8 months. The reproduction potential of bed bug populations suggests serious consequences to human health and the need for efficacious control measures. PMID:23046478

Pereira, R M; Taylor, A S; Lehnert, M P; Koehler, P G

2012-10-10

393

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

394

Population growth and economic development: two new U.S. perspectives.  

PubMed

This report compares the research paths of economic development reports by the US National Academy of Sciences (NAS) and the American Assembly of Columbia University. The NAS group, made up principally of economists and demographers, refrained from recommending population reduction targets, in contrast to the stronger terms of its 1971 report. A 1965 report by the Assembly spoke of population as a serious negative influence for economic development, political stability, and world peace, while the new report speaks of negative socioeconomic effects, and of the limiting of a person's right to control family size. The NAS agenda was established before the US delegation to the UN population conference in Mexico City retreated from declaring population growth to be a necessarily negative influencer of socioeconomic progress. The Assembly took the position that possible benefits of population growth would be far outweighed by factors such as resource depletion and women's health. The NAS maintained that growth might provide incentives for institutional adjustments (market development, investment in education) and control of growth should not be considered a substitute for such interventions. Both reports agree that control of fertility is a human right, but the NAS report examined the question of the acceptable degree of compulsion to be used to encourage couples. The Assembly objected to limiting access to family planning by defunding abortion programs oversease. Differences exist between the 2 reports in questins such as the negative impact of 1950's population growth, the synergistic effect of growth on many areas of human activity, the extent to which welfare of future generations is considered relevant today, and the adequacy of pure economic analysis in assessing need. Much study of population/development linkages is still required. PMID:2878823

Wulf, D; Klitsch, M

395

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

396

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

397

Getting the timing right: antler growth phenology and sexual selection in a wild red deer population.  

PubMed

There has been growing interest in the determinants of the annual timing of biological phenomena, or phenology, in wild populations, but research on vertebrate taxa has primarily focused on the phenology of reproduction. We present here analyses of the phenology of the annual growth of a secondary sexual characteristic, antlers in red deer (Cervus elaphus) males. The long-term individual-based data from a wild population of red deer on the Isle of Rum, Scotland allow us to consider ecological factors influencing variation in the phenology of growth of antlers, and the implications of variation in antler growth phenology with respect to the phenotype of antler grown (antler mass) and annual breeding success. The phenology of antler growth was influenced by local environmental conditions: higher population density delayed both the start date (during spring) and the relative end date (in late summer) of antler growth, and warmer temperatures in the September and April prior to growth advanced start and end dates, respectively. Furthermore, there was variation between individuals in this phenotypic plasticity of start date, although not in that of end date of growth. The phenology of antler growth impacted on the morphology of antlers grown, with individuals who started and ended growth earliest having the heaviest antlers. The timing of antler growth phenology was associated with breeding success in the following mating season, independently of the mass of antlers grown: an earlier start of antler growth was associated with siring a higher number of the calves born the following spring. Our results suggest that the phenology of traits that are not directly correlated with offspring survival may also regularly show correlations with fitness. PMID:20480184

Clements, Michelle N; Clutton-Brock, Tim H; Albon, Steve D; Pemberton, Josephine M; Kruuk, Loeske E B

2010-05-18

398

[A brief discussion on the effect of religion and feudal superstitions on China's population growth].  

PubMed

According to Marxism, population development is subject to the determination of production means under certain social and historical conditions, but it is also influenced by ideology, religions, and other factors. China is a country with numerous religions and traditional superstitions. Their impact on China's population growth cannot be underestimated. All religions and feudal superstitions have a role in the increase of the population, and they oppose birth control and abortion. Similarly, traditional feudal concepts of having more children for good fortune, ancestral worship, and filial piety also encouraged early marriage and having more children, and they have contributed to population growth. On the contrary, "individualism" practiced by Buddhist monks and nuns, the "sacred war" believed by Islamic people, and the offering of human sacrifices by many primitive religions, and the murdering of baby twins have served to reduce the population. Most of the religions and feudal superstitions are in favor of increasing the population. The popularity of Buddhism in the past was caused by an oversupply of the labor force. Many farmers became Buddhist monks as a way to earn a living. Since liberation, unhealthy religions and feudal superstitions have been prohibited but their everlasting infulence upon the people cannot be ignored. Uncontrolled population growth is harmful to the nation's economy and improvement of people's livelihood. In family planning work, attention should also be given to the prevention of interference from religions and feudal superstitions in people's ideology. PMID:12159370

Chen, G

1983-05-29

399

Sex, population dynamics and resting egg production in rotifers  

Microsoft Academic Search

The interaction between sexual reproduction and population growth in the rotifer Brachionus plicatilis was examined using exponential and logistic growth models. A computer simulation was used to explore the effects of the frequency\\u000a of sex and the proportion of a female's daughters reproducing sexually on population growth rate and resting egg production.\\u000a Within the parameters of the simulation, the proportion

Terry W. Snell

1987-01-01

400

Height-growth response to climatic changes differs among populations of Douglas-fir: a novel analysis of historic data.  

PubMed

Projected climate change will affect existing forests, as substantial changes are predicted to occur during their life spans. Species that have ample intraspecific genetic differentiation, such as Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), are expected to display population-specific growth responses to climate change. Using a mixed-effects modeling approach, we describe three-year height (HT) growth response to changes in climate of interior Douglas-fir populations. We incorporate climate information at the population level, yielding a model that is specific to both species and population. We use data from provenance tests from previous studies that comprised 236 populations from Idaho, Montana, and eastern Washington, USA. The most sensitive indicator of climate was the mean temperature of the coldest month. Population maximum HT and HT growth response to changes in climate were dependent on seed source climate. All populations had optimum HT growth when transferred to climates with warmer winters; those originating in sites with the warmest winters were taller across sites and had highest HT growth at transfer distances closest to zero; those from colder climates were shortest and had optimum HT growth when transferred the farthest. Although this differential response damped the height growth differences among populations, cold-climate populations still achieved their maximum growth at lower temperatures than warm-climate populations. The results highlight the relevance of understanding climate change impacts at the population level, particularly in a species with ample genetic variation among populations. PMID:22471081

Leites, Laura P; Robinson, Andrew P; Rehfeldt, Gerald E; Marshall, John D; Crookston, Nicholas L

2012-01-01

401

Growth, Natural Mortality, and Predicted Response to Fishing for Largemouth Bass and Smallmouth Bass Populations in North America  

Microsoft Academic Search

Growth, natural mortality, latitude, elevation, average air temperature, and degreedays exceeding 10°C were summarized for 698 populations of largemouth bass Micropterus salmoides and 409 populations of smallmouth bass M. dolomieu in North America and used in simulations to determine the effects of fishing on populations of varying productivity. Length at age and von Bertalanffy growth equation parameters varied greatly among

Raymond C. P. Beamesderfer; John A. North

1995-01-01

402

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

403

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

404

Richards growth model and viability indicators for populations subject to interventions.  

PubMed

In this work we study the problem of modeling identification of a population employing a discrete dynamic model based on the Richards growth model. The population is subjected to interventions due to consumption, such as hunting or farming animals. The model identification allows us to estimate the probability or the average time for a population number to reach a certain level. The parameter inference for these models are obtained with the use of the likelihood profile technique as developed in this paper. The identification method here developed can be applied to evaluate the productivity of animal husbandry or to evaluate the risk of extinction of autochthon populations. It is applied to data of the Brazilian beef cattle herd population, and the the population number to reach a certain goal level is investigated. PMID:21152780

Loibel, Selene; Andrade, Marinho G; do Val, João B R; de Freitas, Alfredo R

2010-12-01

405

When Did the Human Population Size Start Increasing?  

Microsoft Academic Search

We analyze the frequency spectra of all available human nuclear sequence data sets by using a model of constant population size followed by exponential growth. Parameters of growth (more extreme than or) comparable to what has been suggested from mtDNA data can be rejected for 6 out of the 10 largest data sets. When the data are separated into African

Jeffrey D. Wall; Molly Przeworski

2000-01-01

406

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

407

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

NASA Astrophysics Data System (ADS)

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

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

2010-09-01

408

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

409

The role of transient dynamics in stochastic population growth for nine perennial plants.  

PubMed

Most populations exist in variable environments. Two sets of theory have been developed to address this variability. Stochastic dynamics focus on variation in population growth rates based on random differences in vital rates such as growth, survival, and reproduction. Transient dynamics focus on short-term, deterministic responses to changes in the stage distribution of individuals. These processes are related: demographic variation shifts stage structures, producing transient responses, which then contribute to the overall variability of population growth rate. The relative contributions of vital rates vs. transient responses to stochastic dynamics, and the implications for transient analyses, are unclear. This study explores the role of transient responses in stochastic dynamics of nine perennial plant species. Across the species, transient responses contributed more on average to variability in annual population growth rates than did variation in vital rates alone. Transient potential of an average matrix was indicative of the contribution of transient dynamics, although these metrics varied greatly across years. Transient responses were often in the opposite direction as demographic variation, suggesting that transient dynamics may at times have a buffering effect on populations. Overall, transient dynamics had an important role in modulating environmental variation, with implications for both processes in understanding stochastic dynamics. PMID:24015512

Ellis, Martha M; Crone, Elizabeth E

2013-08-01

410

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

411

Economic development and population growth: an inverted-U shaped curve?  

Microsoft Academic Search

There has been a large debate on the relations between demography and economic development. Our paper discusses the possibility that there exists an inverted-U curve, similar in shape to Kuznets’s curve, between the growth rate of population and the growth rate of the per-capita GDP. The cross-country empirical analysis, carried out on over 90 countries in the period 1980-2010, seems

Valli Vittorio; Saccone Donatella

2011-01-01

412

A mixed model for investigating a population of asymptotic growth curves using restricted B -splines  

Microsoft Academic Search

We introduce a new method for modeling a population of growth curves with B-splines, adapting the usual regression spline basis to ensure a horizontal upper asymptote in all fitted curves. The new\\u000a method is easily implemented in standard statistical software. We motivate and illustrate our method using data on the growth\\u000a of Brown Kiwi (Apteryx mantelli) in the North Island

Geoffrey Jones; Joyce Leung; Hugh Robertson

2009-01-01

413

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

Microsoft Academic Search

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

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

2007-01-01

414

Marine Growth and Morphometrics for Three Populations of Atlantic Salmon from Eastern Maine, USA  

Microsoft Academic Search

Significant differences in growth and prespawning body morphology were detected among three stocks of Atlantic salmon reared in a common marine environment. Smolts originating from river-specific broodstock of the Machias, East Machias, and Dennys populations were reared at two marine net-pen facilities for 25 months. Significant differences in stock-specific growth were observed among two stocks at both sites, suggesting a

Timothy F. Sheehan; John F. Kocik; Steven X. Cadrin; Christopher M. Legault; Ernest Atkinson; David Bengtson

2005-01-01

415

Growth strategy of heterotrophic bacterial population along successional sequence on spoil of brown coal colliery substrate  

Microsoft Academic Search

The bacterial population of brown coal colliery spoil (Sokolov coal mining district, Czechia) was characterized by measuring\\u000a viable bacterial biomass, the culturable to total cell ratio (C:T), colony-forming curve (CFC) analysis and species and\\/or\\u000a biotype diversity. Bacterial representatives that differed in colony-forming growth (fast and\\/or slow growers) were used for\\u000a growth-strategy investigation of heterotrophic bacteria. Spoil substrates from the surface

V. Krišt?fek; D. Elhottová; A. Chro?áková; I. Dostálková; T. Picek; J. Kal?ík

2005-01-01

416

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

Microsoft Academic Search

The pest potential of stored product mites depends on the reproduction rate that is affected by the environmental conditions.\\u000a In this study we investigated the effect of temperature, ranging from 5 to 35°C, on the population growth of three important\\u000a mite species, Acarus siro, Tyrophagus putrescentiae and Auleroglyphus ovatus at 85% r.h. Starting with 10 individuals the population increase of

Gamila Aspaly; Vaclav Stejskal; Stano Pekár; Jan Hubert

2007-01-01

417

Trans-Theta Logistics: A New Family of Population Growth Sigmoid Functions  

Microsoft Academic Search

Sigmoid functions have been applied in many areas to model self limited population growth. The most popular functions; General\\u000a Logistic (GL), General von Bertalanffy (GV), and Gompertz (G), comprise a family of functions called Theta Logistic ($$ \\\\Uptheta $$\\u000a L). Previously, we introduced a simple model of tumor cell population dynamics which provided a unifying foundation for these\\u000a functions. In

F. Kozusko; M. Bourdeau

418

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

Microsoft Academic Search

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

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

2006-01-01

419

Connecting phenological predictions with population growth rates for mountain pine beetle, an outbreak insect  

Microsoft Academic Search

It is expected that a significant impact of global warming will be disruption of phenology as environmental cues become disassociated\\u000a from their selective impacts. However there are few, if any, models directly connecting phenology with population growth rates.\\u000a In this paper we discuss connecting a distributional model describing mountain pine beetle phenology with a model of population\\u000a success measured using

James A. Powell; Barbara J. Bentz

2009-01-01

420

Population growth rate and energy consumption correlations: Implications for the future  

Microsoft Academic Search

The fertility rate for women and the related population growth rate, for numerous developing (transitional) countries, show a downward trend with increasing annual per capita energy use. On the assumption that such historic trends will continue, estimates are made for some simple cases of the energy demands required to stabilize the world`s population in the period 2,100 to 2,150. An

1998-01-01

421

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

422

Population and economic growth: a cointegration analysis of lesser developed countries.  

PubMed

The authors examine the temporal relationship between population growth and economic growth in Nepal, India, Ghana, Sri Lanka, Bolivia, Philippines, Guatemala, Syria, Peru, Thailand, Chile, Argentina, and Mexico, conducting Granger-causality tests in the context of error correction models when cointegration is present. Their goal is to provide additional time series econometric evidence on the short-run and long-run time series behavior of population growth and the growth of real per capita gross domestic product for a sample of low to middle income developing countries. Cointegration was found in only 3 of the 13 countries examined. Even though 10 countries in this study exhibited no properties of cointegration, researchers conducting time series studies of the relationship between population growth and economic growth using differenced data should nonetheless evaluate the possible long-term relationship. Capturing the short- and long-run behaviors of the respective time series may give the researcher a more robust test of Granger-causality. PMID:12348722

Payne, J E; Ewing, B T

1997-11-01

423

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

424

[A preliminary inquiry into the interrelationship between population growth and economic development in Hong Kong].  

PubMed

Hong Kong includes Hong Kong Island, Kowloon, New Territory, and more than 230 islands. During World War ii, the population of Hong Kong decreased sharply, and the total number decreased to less than 600,000. Since the war ended in 1945, the population of Hong Kong has been increasing rapidly at an annual rate of 20%. By the end of 1981, its total population had increased to 5.2 million, including 1.25 million newly arrived immigrants. The average age is 24.8. People above the age 65 constitute only 6% of the total population. This shows that there is a sufficient supply of labor for local economic development. Because of continued economic growth, there has been a constant demand for more labor. Low wages provide an excellent condition for high-speed industrial development. An improved quality of professional workers and management personnel also contributes much to Hong Kong's industrial modernization. Because of high employment among the labor population, the general population earns income and spends a great deal, and this has created a rather active economy. General population growth trends include: 1) continued population growth will bring the total population to 6.3 million by the end of 1981, and the housing problem will become more serious; 2) a stable decline in the natural population growth rate will gradually change the population pattern to a low birth, low death, and low natural growth situation; and 3) improvements in science and technology, health care, and living conditions will reduce the death rate, and the average age will lengthen, and with the increase in old people, the demand for social welfare will also increase; and 4) there will be a shortage in experienced labor (professional technicians and high management personnel) in the 1980s. Facing the new situation, Hong Kong's economic structure needs reform, moving from a labor intensive enterprise to a capital-technological intensive enterprise. The market will be expanded and Hong Kong will earn more profit in China's mode rnization process. PMID:12266136

Zhang, Z S

1982-05-29

425

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

426

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...

427

Stochastic simulation of growth curves of Acidithiobacillus ferrooxidans  

Microsoft Academic Search

To reveal the low growth rate of Acidithiobacillus ferrooxidans, a stochastic growth model was proposed to analyze growth curves of these bacteria in a batch culture. An algorithm was applied\\u000a to simulate the bacteria population during lag and exponential phase. The results show that the model moderately fits the\\u000a experimental data. Further, the mean growth constant (K) of growth curves

Yu Yang; Hong Peng; Guan-zhou Qiu; Jian-she Liu; Yue-hua Hu

2006-01-01

428

Population Growth and Development of the Psocid Lepinotus reticulatus at Constant Temperatures and Relative Humidities  

Microsoft Academic Search

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 by using methylene blue, chalk powder, and ßuorescent powder to differentiate nymphal stages during development. We found that marking psocids by using methylene blue increased mortality and took twice as

G. P. Opit; J. E. Throne

2008-01-01

429

Survival, Population Density, Growth, and Movement of the Wild Brown Trout in Crystal Creek  

Microsoft Academic Search

A portion of the data accumulated in a 4-year study of the trout of Crystal Creek, New York State, is reported. An annual population inventory of the same 13 sample sections of the stream each September for 4 years provided information on survival, density of fish, growth, movement, and other factors. The percentage survival of the young brown trout of

Howard A. Schuck

1945-01-01

430

Growth of the human lens in the Indian adult population: Preliminary observations  

PubMed Central

Context: The eye lens grows throughout life by the addition of new cells inside the surrounding capsule. How this growth affects the properties of the lens is essential for understanding disorders such as cataract and presbyopia. Aims: To examine growth of the human lens in the Indian population and compare this with the growth in Western populations by measuring in vitro dimensions together with wet and dry weights. Settings and Design: The study was conducted at the research wing of a tertiary eye care center in South India and the study design was prospective. Materials and Methods: Lenses were removed from eye bank eyes and their dimensions measured with a digital caliper. They were then carefully blotted dry and weighed before being placed in 5% buffered formalin. After 1 week fixation, the lenses were dried at 80 °C until constant weight was achieved. The constant weight was noted as the dry weight of the lens. Statistical Analysis Used: Lens parameters were analyzed as a function of age using linear and logarithmic regression methods. Results: Data were obtained for 251 lenses, aged 16–93 years, within a median postmortem time of 22 h. Both wet and dry weights increased linearly at 1.24 and 0.44 mg/year, respectively, throughout adult life. The dimensions also increased continuously throughout this time. Conclusions: Over the age range examined, lens growth in the Indian population is very similar to that in Western populations.

Mohamed, Ashik; Sangwan, Virender S; Augusteyn, Robert C

2012-01-01

431

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

ERIC Educational Resources Information Center

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

Wallace, Robert L.

2005-01-01

432

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

Microsoft Academic Search

Few data exist on potential toxic effects that pollutants may have on zooplankton fed microalgae exposed to pesticides. For that reason, microalgal cultures were exposed to different concentrations of the triazine herbicide terbutryn, and used as exclusive food source to Brachionus sp. females, with the aim to evaluate potential deleterious effects upon population growth, survival, reproduction and feeding of the

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

2007-01-01

433

Geographic origin of Pinus sylvestris populations influences the effects of air pollution on flowering and growth  

Microsoft Academic Search

Flowering and height growth of 20 Scots pine (Pinus sylvestris L.) populations from 10 countries were analyzed at two replicated provenance sites established in 1984 in western Poland. One site was 2 km from a phosphate fertilizer factory that emits SO2 and fluorides, and the other 12 km to the southeast in an area free of acute air pollution levels

J. Oleksyn; W. Chalupka; M. G. Tjoelker; P. B. Reich

1992-01-01

434

The effects of aging and population growth on health care costs  

Microsoft Academic Search

Aging and population growth both contribute importantly to the rise in health care costs. However, the percentage contribution of these factors declined between 1970 and 1990, and we expect a continued decline through 2005. Data indicate that the relative costs of treating patients age sixty-five and over grew more rapidly than did the costs of treating other patients. Sensitivity analyses

Daniel N. Mendelson; William B. Schwartz

1993-01-01

435

Urban public pension, replacement rates and population growth rate in China  

Microsoft Academic Search

This paper uses an overlapping generations model to investigate the urban public pension in China. It examines the effects of the replacement rates and population growth rate on the capital–labor ratio, pension benefits, consumption and utility, and finds the optimal replacement rate. It is shown that raising the individual account benefit replacement rate only induces the increase in the individual

Zaigui Yang

2009-01-01

436

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

ERIC Educational Resources Information Center

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

Jacobsen, Judith E.

437

EFFECTS OF CADMIUM ON THE POPULATION GROWTH OF A BENTHIC INVERTEBRATE AEOLOSOMA HEADLEYI (OLIGOCHAETA)  

EPA Science Inventory

A chronic toxicity test using population growth of an aquatic oligochaete, Aeolosoma headleyi, was evaluated for usefulness in determining the hazard of chronic exposures to cadmium. Tests were conducted in artificial hard water (180 mg/L hardness) and dechlorinated tap water (60...

438

Age-patterns of famine-related mortality increase: implications for long-term population growth  

Microsoft Academic Search

In this paper, we reaffirm Watkins and Menken's (1985) conclusion that there is 'little likelihood that famines will be a major determinant of population growth in the future, any more than ... in the past'. We find that age and sex-specific patterns of famine mortality change that have markedly different proportional change in group-specifi c mortality can nevertheless lead to

Jane Menken; Cameron Campbell

439

Effect of the epizoic rotifer Brachionus rubens on the population growth of three cladoceran species  

Microsoft Academic Search

Using population densities and growth rates as criteria, we studied interactions between the epizoic rotifer Brachionus rubens and each of three cladoceran species differing in size and reproductive rates — Daphnia carinata, Moina macrocopa and Ceriodaphnia rigaudi. In all mixed — species experiments, B. rubens existed in both the epizoic mode, attached to the cladoceran host, and in the free-swimming

Nandini Iyer; T. Ramakrishna Rao

1993-01-01

440

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

441

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

ERIC Educational Resources Information Center

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

Garkovich, Lorraine

442

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

Microsoft Academic Search

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

Rodolfo E. Mendoza

1998-01-01

443

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

ERIC Educational Resources Information Center

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

Simon, Julian L.; Pilarski, Adam M.

1979-01-01

444

Native and Introduced Populations of Smallmouth Bass Differ in Concordance between Climate and Somatic Growth  

Microsoft Academic Search

We characterized the association between climate and somatic growth in 125 North American populations of smallmouth bass Micropterus dolomieu. Using multivariate techniques (i.e., principal components and Procrustes analyses), we found an overall significant concordance between eight climate variables (cloud cover, frost frequency, precipitation, mean air temperature, minimum air temperature, maximum air temperature, mean summer air temperature, and growing degree-days above

Erin S. Dunlop; Brian J. Shuter

2006-01-01

445

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

446

The Effects of Biological Control Agents on Population Growth and Spread of Melaleuca quinquenervia  

Microsoft Academic Search

The main goal of this study was to evaluate the effectiveness of two biological control agents in reducing population growth and spread of the invasive tree Melaleuca quinquenervia, a subtropical tree native to Australia, and invasive in Florida, Puerto Rico, and the Bahamas. While in Florida two insects Oxyops vitiosa (weevil), and Boreioglycaspis melaleucae (psyllid) have been established as biocontrol

Lucero Sevillano Garcia Mayeya

2010-01-01

447

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

Microsoft Academic Search

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

Islam M. Faisal; Saila Parveen

2004-01-01

448

Population Growth and Natural Resource Scarcity: Long run development under seemingly unfavourable conditions  

Microsoft Academic Search

The paper considers an economy which is constrained by natural resource use and driven by knowledge accumulation. Resources are essential inputs in all the sectors. It is shown that population growth and poor input substitution are not detrimental but, on the contrary, even necessary for obtaining a sustainable consumption level. We find a new type of Hartwick rule defining the

Lucas Bretschger

2010-01-01

449

Impacts of population growth, economic development, and technical change on global food production and consumption  

Microsoft Academic Search

Over the next decades mankind will demand more food from fewer land and water resources. This study quantifies the food production impacts of four alternative development scenarios from the Millennium Ecosystem Assessment and the Special Report on Emission Scenarios. Partially and jointly considered are land and water supply impacts from population growth, and technical change, as well as forest and

Uwe A. Schneider; Petr Havlík; Erwin Schmid; Hugo Valin; Aline Mosnier; Michael Obersteiner; Hannes Böttcher; Rastislav Skalský; Juraj Balkovi?; Timm Sauer; Steffen Fritz

2011-01-01

450

Effects of Population Growth and Climate Variability on Sustainable Groundwater in Mali, West Africa  

Microsoft Academic Search

Groundwater is increasingly relied on as a source of potable water in developing countries, but factors such as population growth, development, and climate variability, pose potential challenges for ongoing sustainable supply. The effect of these factors on the groundwater system was considered in four scenarios using a numerical model to represent the Bani area of Mali, West Africa. By 2040,

Alexandra Lutz; James M. Thomas; Mamadou Keita

2010-01-01

451

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

Microsoft Academic Search

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

Daniele Menniti; Alessandro Burgio; Nadia Scordino

2007-01-01

452

Population Growth, Technical Progress, Intergenerational Equity and the Investment of Resource Rents  

Microsoft Academic Search

We establish that if rents from exhaustible resources are invested in reproducible capital and if the population growth rates equal the rate of capital augmenting technical change, then for general neoclassical production functions, per capita consumption remains constant. We establish our new result in one and two sector models. Stability and the role of the elasticity of substitution are investigated

John Hartwick

1977-01-01

453

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

Microsoft Academic Search

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

John G. Patterson; Nanda R. Shrestha

1988-01-01

454

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

455

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

2013-07-13

456

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.

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

2012-01-01

457

Population growth, agricultural intensification, induced innovation and natural resource sustainability: An application of neoclassical growth theory  

Microsoft Academic Search

Using a simple neoclassical type growth model including both man-made and natural capital as inputs to production, the theoretical basis for a U-shaped relationship between agricultural intensification and farm household investment in renewable resource capital is established. As development of technology, infrastructure, or markets increase the relative return to investment in man-made capital over natural capital, resource depletion occurs as

John L. Pender

1998-01-01

458

Estimating individual contributions to population growth: evolutionary fitness in ecological time  

PubMed Central

Ecological and evolutionary change is generated by variation in individual performance. Biologists have consequently long been interested in decomposing change measured at the population level into contributions from individuals, the traits they express and the alleles they carry. We present a novel method of estimating individual contributions to population growth and changes in distributions of quantitative traits and alleles. An individual's contribution to population growth is an individual's realized annual fitness. We demonstrate how the quantities we develop can be used to address a range of empirical questions, and provide an application to a detailed dataset of Soay sheep. The approach provides results that are consistent with those obtained using lifetime estimates of individual performance, yet is substantially more powerful as it allows lifetime performance to be decomposed into annual survival and fecundity contributions.

Coulson, T; Benton, T.G; Lundberg, P; Dall, S.R.X; Kendall, B.E; Gaillard, J.-M

2005-01-01

459

Estimating individual contributions to population growth: evolutionary fitness in ecological time.  

PubMed

Ecological and evolutionary change is generated by variation in individual performance. Biologists have consequently long been interested in decomposing change measured at the population level into contributions from individuals, the traits they express and the alleles they carry. We present a novel method of estimating individual contributions to population growth and changes in distributions of quantitative traits and alleles. An individual's contribution to population growth is an individual's realized annual fitness. We demonstrate how the quantities we develop can be used to address a range of empirical questions, and provide an application to a detailed dataset of Soay sheep. The approach provides results that are consistent with those obtained using lifetime estimates of individual performance, yet is substantially more powerful as it allows lifetime performance to be decomposed into annual survival and fecundity contributions. PMID:16537125

Coulson, T; Benton, T G; Lundberg, P; Dall, S R X; Kendall, B E; Gaillard, J-M

2006-03-01

460

Observational constraints on exponential gravity  

SciTech Connect

We study the observational constraints on the exponential gravity model of f(R)=-{beta}R{sub s}(1-e{sup -R/R}{sub s}). We use the latest observational data including Supernova Cosmology Project Union2 compilation, Two-Degree Field Galaxy Redshift Survey, Sloan Digital Sky Survey Data Release 7, and Seven-Year Wilkinson Microwave Anisotropy Probe in our analysis. From these observations, we obtain a lower bound on the model parameter {beta} at 1.27 (95% C.L.) but no appreciable upper bound. The constraint on the present matter density parameter is 0.245<{Omega}{sub m}{sup 0}<0.311 (95% C.L.). We also find out the best-fit value of model parameters on several cases.

Yang, Louis; Lee, Chung-Chi; Luo, Ling-Wei; Geng, Chao-Qiang [Department of Physics, National Tsing Hua University, Hsinchu 300, Taiwan (China)

2010-11-15

461

Population growth and physiological characteristics of microalgae in a miniaturized bioreactor during space flight  

NASA Astrophysics Data System (ADS)

A strain of microalgae ( Anabaena siamensis) had been cultured in a miniaturized bioreactor during a retrievable satellite flight for 15 days. By means of remote sensing equipment installed in the satellite, we gained the growth curve of microalgae population in space every day in real time. The curve indicated that the growth of microalgae in space was slower than the control on ground. Inoculation of the retrieved microalgae culture showed that the growth rate was distinctively higher than ground control. But after several generations, both cultures indicated similar growth rates. Those data showed that algae can adapt to space environment easily which may be valuable for designing more complex bioreactor and controlled ecological life support system in future experiment.

Wang, Gaohong; Chen, Haofeng; Li, Genbao; Chen, Lanzhou; Li, Dunhai; Hu, Chunxiang; Chen, Kun; Liu, Yongding

2006-03-01

462

Size bimodality in plant populations: an alternative hypothesis  

SciTech Connect

Symmetric competition among seedlings in a spatially random population was simulated using the exponential growth function. In these simulations each plant was randomly assigned values for m/sub 0/ (initial seed mass), r (exponential growth rate), and germination time chosen from normal distributions. The growth rate reduction factor resulting from neighbors within each plant's zone of resource depletion was calculated as the inverse of the number of plants within the zone. This reduction factor was multiplied by the randomly assigned exponential growth rate to determine the actual exponential growth rate for each plant. Bimodality produced by this model is a consequence of the discontinuous distribution of exponential growth rates resulting from a Poisson distribution of the number of neighbors. This simple model based on symmetric competition in a spatially random population provides an alternative mechanism for the appearance of bimodality. The model may explain why increasing plant density in experiments with regularly spaced plants produces results that conflict with patterns found in experiments with a random spatial pattern. 10 references, 2 figures.

Huston, M.

1986-02-01

463

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

PubMed Central

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

Slatkin, M; Bertorelle, G

2001-01-01

464

Modeling spatial population dynamics of stem cell lineage in tissue growth  

PubMed Central

Understanding the dynamics of cell population allows insight into the control mechanism of the growth and development of mammalian tissues. It is well known that the proliferation and differentiation among stem cells (SCs), intermediate progenitor cells (IPCs), and fully differentiated cells (FDCs) are under different activation and inhibition controls. Secreted factors in negative feedback loops have already been identified as major elements in regulating the numbers of different cell types and in maintaining the equilibrium of cell populations. We have developed a novel spatial dynamic model of cells. We can characterize not only overall cell population dynamics, but also details of temporal-spatial relationship of individual cells within a tissue. In our model, the shape, growth, and division of each cell are modeled using a realistic geometric model. Furthermore, the inhibited growth rate, proliferation and differentiation probabilities of individual cells are modeled through feedback loops controlled by secreted factors of neighboring cells within a proper diffusion radius. With specific proliferation and differentiation probabilities, the actual division type that each cell will take is chosen by a Monte Carlo sampling process. With simulations we found that with proper strengths of inhibitions to growth and stem cell divisions, the whole tissue is capable of achieving a homeostatic size control. We discuss our findings on control mechanisms of the stability of the tissue development. Our model can be applied to study broad issues on tissue development and pattern formation in stem cell and cancer research.

Cao, Youfang; Liang, Claire; Naveed, Hammad; Li, Yingzi; Chen, Meng; Nie, Qing

2013-01-01

465

Modeling spatial population dynamics of stem cell lineage in tissue growth.  

PubMed

Understanding the dynamics of cell population allows insight into the control mechanism of the growth and development of mammalian tissues. It is well known that the proliferation and differentiation among stem cells (SCs), intermediate progenitor cells (IPCs), and fully differentiated cells (FDCs) are under different activation and inhibition controls. Secreted factors in negative feedback loops have already been identified as major elements in regulating the numbers of different cell types and in maintaining the equilibrium of cell populations. We have developed a novel spatial dynamic model of cells. We can characterize not only overall cell population dynamics, but also details of temporal-spatial relationship of individual cells within a tissue. In our model, the shape, growth, and division of each cell are modeled using a realistic geometric model. Furthermore, the inhibited growth rate, proliferation and differentiation probabilities of individual cells are modeled through feedback loops controlled by secreted factors of neighboring cells within a proper diffusion radius. With specific proliferation and differentiation probabilities, the actual division type that each cell will take is chosen by a Monte Carlo sampling process. With simulations we found that with proper strengths of inhibitions to growth and stem cell divisions, the whole tissue is capable of achieving a homeostatic size control. We discuss our findings on control mechanisms of the stability of the tissue development. Our model can be applied to study broad issues on tissue development and pattern formation in stem cell and cancer research. PMID:23367175

Cao, Youfang; Liang, Claire; Naveed, Hammad; Li, Yingzi; Chen, Meng; Nie, Qing

2012-01-01

466

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

PubMed

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