Note: This page contains sample records for the topic exponential population growth from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: August 15, 2014.
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

Modeling Exponential Growth  

NSDL National Science Digital Library

This lesson plan from ATEEC will help students learn the concept of exponential growth, as well as interpret and apply exponential relationships. It is intended for environmental science or biology classes. The activity sheet includes a list of materials and resources needed as well as a description of the lesson. This resource is free to download from ATEEC; users must create a free login to access.

Willey, Babe

2013-07-09

3

Universality in stochastic exponential growth.  

PubMed

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

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

2014-07-11

4

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

5

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

6

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

7

Lesson 29: Exponential Growth and Decay  

NSDL National Science Digital Library

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

2011-01-01

8

Estimation after subset selection from exponential populations  

Microsoft Academic Search

Let ?1 ??k be k independent exponential populations with means ?1 ? ?krespectively. Let Y1, ?,Yk denote the sample means based on n independent observations from each population. For selecting a nonempty subset containing the best population (the one associated with the largest ?i ) we consider the rule of Gupta which selects ?i. if and only if where 0

S. Jeyaratnam; S. Panchapakesan

1986-01-01

9

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

10

Analysis of the Stochastic Super-Exponential Growth Model  

NASA Astrophysics Data System (ADS)

Empirical data suggests that the human population has grown super-exponentially for the past 2000 years. The super-exponential growth is the property of dynamical systems exhibiting endogenous nonlinear positive feedback. Based on the wide range of empirical evidence on global and local scale, we assume a strong correlation between the dynamics of population growth and the human technological innovations. A mathematical model have been devised to describe the dynamics of super-exponentially growing population with stochastic fluctuations. These fluctuations can be of environmental origin or can arise from the inherent fluctuations within the demographics. The noise has been assumed to act on the growth rate multiplicatively and is assumed to be Gaussian white noise à la Stratonovich. An analysis of the stochastic super-exponential growth model is presented. The exact analytical formulae for the conditional probability density of the population size and the first and second moments of population size are presented. We have also calculated the probability density of the population's lifetime, and the higher moments of the population size, as well as the population's prospective lifetime. Interpretations and various applications of the results are discussed.

Avila, P.; Rekker, A.

2011-11-01

11

Isotonic Rules for Selecting Good Truncated Exponential Populations.  

National Technical Information Service (NTIS)

The problem of selecting truncated exponential populations better than a control under an ordering prior is studied. Based on some prior information, it is reasonable to set lower bounds for the concerned parameters. Through this consideration, an isotoni...

T. Liang

1985-01-01

12

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

1984-01-01

13

Exponential order statistic models of software reliability growth  

NASA Technical Reports Server (NTRS)

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

Miller, D. R.

1985-01-01

14

Exponential order statistic models of software reliability growth  

NASA Technical Reports Server (NTRS)

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

Miller, D. R.

1986-01-01

15

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

16

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

2012-08-01

17

Initiating Exponential Growth in NEA Exploration with NEA Science Missions  

NASA Astrophysics Data System (ADS)

Development of asteroid and cometary resources, interplanetary human settlements, and protection against impact threats (including long period comets) will all involve large-scale activities in the inner solar system. Each of these activities require answers to specific scientific questions - some of which can be addressed by future Near Earth Asteroid (NEA) sample return missions, as will be identified at this workshop. This paper addresses the question of how to initiate the exponential growth required to create these large-scale activities, and the role of near-term NEA sample return missions in triggering this growth. It is now recognized that NEA science will play a central role in future human activities in the inner solar system. In addition to the technical issues, how the NEA missions are conducted will also affect how quickly these activities are initiated. Historically, interplanetary missions have been conducted with the assumption that only governments and government/contractor teams could accomplish these complex tasks. Recently, the Discovery Mission model has established new roles for the Principle Investigator and contractor teams. Currently there are proposals for data purchase arrangements and other mechanisms to further separate the roles of purchasers and providers. This paper will examine these proposals in the context of NEA science, development, and exploration. The paper will report on a project currently underway to identify cross-cultural solutions to maximize science return within resource constraints while initiating exponential growth in exploration and development of NEAs.

Dahlstrom, Eric L.

2000-01-01

18

Population growth (annual %)  

NSDL National Science Digital Library

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

Bank, World

19

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

PubMed

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

Cartes-Velásquez, Ricardo Andrés

2013-01-01

20

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

21

World Population Growth  

NSDL National Science Digital Library

Using Maple, Mathmatica, or MatLab, learner should be able to study the historical data on human population growth, and to compare the "natural" and "coalition" differential equation models as possible descriptions of the growth pattern.

Smith, David; Moore, Lawrence

2001-01-22

22

Classical and Bayes-P Subset Selection Procedures for Double Exponential Populations.  

National Technical Information Service (NTIS)

The exact distribution of the sample mean from a double exponential(Laplace) model is derived. A classical subset selection procedure based on the sample mean for selecting the population associated with the largest location parameter of k double exponent...

S. S. Gupta Y. Liao

1990-01-01

23

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

24

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

25

Population growth and development.  

PubMed

Development is a complex process that has no universal laws to guide it. However, there is widespread agreement that population growth is a crucial factor in the process of social and economic development. Population growth is not always in itself detrimental to development, especially in some developed countries where there are economies of scale and sufficient human and physical capital for new investments. Developing countries face an environment that is less favorable for economic growth than did the developed countries of the past. The major problem lies in the extended time lag between population increases on the 1 hand and technological advances and adaptations on the other hand. In populations that are not equipped to make the necessary technological and infrastructural changes, even moderate population growth can arrest the development process. The transfer or adaptation of new technologies requires time, money, and other structural changes. Moreover, rapid population growth reduces the proportion of household savings, making less money available for per capita investment in both physical and human capital. At the family level, less time and money are available for child development. At the societal level, it becomes more difficult to finance the physical and human investments necessary for sustained economic growth. Under the best conditions, a developing Asian country can expect to achieve better economic performance in the longterm if the population has moderate growth, doubling over a 50-year period. While a slower rate of growth can accelerate development, it introduces a host of new social problems such as providing security to the elderly. PMID:12315484

Gajanayake, I

1986-12-01

26

Global population growth.  

PubMed

The global population passed 5 billion in 1987. In the year 2000 the world's population will be more than 6 billion, increasing by 90-100 million each year. About 95% of future demographic growth will take place in developing countries. The number of school age children is projected to increase from 940 million in 1980 to 1280 million by the year 2000. Under current labor force growth projections in developing countries, around 1.6 billion new jobs will have to be created between 1980 and 2025, with nearly 1 billion of them in Asia. Population often increases at a more rapid rate than agricultural growth. Food production per capita has declined in 70 developing countries. Much of the projected population increase will take place in environmentally fragile regions of the developing world. Population pressures contribute to deforestation, desertification, and scarcity of clean water. The United Nations Population Fund has estimated that in Asia over 43% of women not using family planning would like to postpone, space, or limit their childbearing. Over half of the world's couples of reproductive age are now using contraception. Family planning to postpone the first birth and to eliminate late child bearing would reduce both child loss and maternal illness and death. Both infant and maternal mortality are greater with higher order births. Reducing average family size is an effective way of reducing infant and maternal mortality. The World Bank has given high priority to population assistance, with large programs in Bangladesh, Egypt, India, Indonesia, the Philippines, and Thailand. Population assistance provided by the Australian International Development Assistance Bureau totaled about $4.5 million during 1989-90 and is expected to be about $8 million during 1991-92. Australia should increase the proportion of its development assistance budget devoted to population, and family planning programs should increase to around $26 million in line with other major donors. PMID:12179437

Langmore, J

1992-07-01

27

Analysis of highbush blueberry ( Vaccinium corymbosum L.) fruit growth with exponential mixed models  

Microsoft Academic Search

Blueberry fruit growth commonly exhibits a double-sigmoid pattern. The goal of this work was to characterize and compare fruit growth of cultivars differing in ripening time using exponential non-linear mixed models. Mixed-effects five-parameter exponential (Gompertz I and II; logistic; monomolecular) models were fitted to fruit diameter data from 2 years and three cultivars grown in the field in a cool

Carlos Godoy; Gloria Monterubbianesi; Jorge Tognetti

2008-01-01

28

Population Growth in Planaria Dugesia tigrina (Gerard)  

PubMed Central

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

Davison, John

1973-01-01

29

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

PubMed Central

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

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

2007-01-01

30

Connections Between von Foerster Coalition Growth Model and Tsallis q-Exponential  

NASA Astrophysics Data System (ADS)

The paper will show the direct connections between q-Malthusian growth model, i.e. the classical exponential growth model generalized in Tsallis statistics, and the coalition growth model introduced by von Foerster in 1960. As it will turn out, the equations that have been taken into account when the coalition model was introduced, are closely related to the equations that describe the non-extensive generalization of entropy.

Strza?ka, D.

2009-01-01

31

Scientometric studies on chemistry I: The exponential growth of chemical substances, 1800–1995  

Microsoft Academic Search

The number of chemical substances is considered as a cumulative measure of the cognitive growth of preparative chemistry.\\u000a During the past 200 years there is approximately exponential growth without saturation. Separate analysis of organic and inorganic\\u000a chemistry suggests at least a two-phase model either. Detailed discussion of the results (considering also the growth of chemists,\\u000a chemical papers, patents, and chemical

J. Schummer

1997-01-01

32

The extracellular proteome of Rhizobium etli CE3 in exponential and stationary growth phase  

PubMed Central

Background The extracellular proteome or secretome of symbiotic bacteria like Rhizobium etli is presumed to be a key element of their infection strategy and survival. Rhizobia infect the roots of leguminous plants and establish a mutually beneficial symbiosis. To find out the possible role of secreted proteins we analyzed the extracellular proteome of R. etli CE3 in the exponential and stationary growth phases in minimal medium, supplemented with succinate-ammonium. Results The extracellular proteins were obtained by phenol extraction and identified by LC-ESI MS/MS. We identified 192 and 191 proteins for the exponential and stationary phases respectively. Using the software Signal P, we predicted signal peptides for 12.95% and 35.60% of the proteins identified in the exponential and stationary phases, respectively, which could therefore be secreted by the Sec pathway. For the exponential growth phase, we found in abundance proteins like the ribosomal proteins, toxins and proteins belonging to the group "defence mechanisms". For the stationary growth phase, we found that the most abundant proteins were those with unknown function, and in many of these we identified characteristic domains of proteases and peptidases. Conclusions Our study provided the first dataset of the secretome of R. etli and its modifications, which may lead to novel insights into the adaptive response of different stages of growth. In addition, we found a high number of proteins with unknown function; these proteins could be analyzed in future research to elucidate their role in the extracellular proteome of R. etli.

2010-01-01

33

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.

34

The mechanism of double-exponential growth in hyper-inflation  

NASA Astrophysics Data System (ADS)

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

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

2002-05-01

35

Entire solutions with exponential growth for an elliptic system modelling phase separation  

NASA Astrophysics Data System (ADS)

We prove the existence of entire solutions with exponential growth for the semilinear elliptic system \\begin{equation*} \\left\\{\\begin{array}{@{}ll@{}} -\\Delta u = -u v^2 \\quad& in~{R}^N,\\\\ -\\Delta v= -u^2 v \\quad&in~{R}^N, \\\\ u,v>0, \\end{array}\\right. \\end{equation*} for every N ? 2. Our construction is based on an approximation procedure, whose convergence is ensured by suitable Almgren-type monotonicity formulae. The construction of the resulting solutions is extended to systems with k components, for every k > 2 in this case, the proof is much more involved and is achieved by approximation of solutions with exponential growth by means of solutions with algebraic growth of increasing degree, translating the limit \\begin{equation*}\\lim_{d \\to +\\infty} \\Im\\left[\\left(1+\\frac{z}{d}\\right)^{d}\\right] = \\rme^x \\sin y \\end{equation*} in the present setting.

Soave, Nicola; Zilio, Alessandro

2014-02-01

36

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

37

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

38

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

39

Limited Population Growth  

NSDL National Science Digital Library

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

Moore, Lawrence; Smith, David

2001-01-22

40

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

41

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

PubMed

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

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

2007-05-01

42

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

43

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

44

Water and world population growth  

Microsoft Academic Search

Freshwater is renewable but finite. Over the next 50 years, world population growth will reduce the renewable water supply per capita by approximately one third. By 2025, an estimated 3 billion people—38 percent of the projected global population—will live in countries classified as water-stressed. In many regions, numerous signs that water use is not sustainable are already in evidence in

Sandra L. Postel

2000-01-01

45

Population Growth: Family Planning Programs.  

ERIC Educational Resources Information Center

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

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

46

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

47

Population growth and foreign policy.  

PubMed

Australian foreign policy is examined in light of the population issue and its relationships to its developing Asian neighbors. Rapid population growth has been a 20th-century phenomenon. In the ESCAP region, almost all governments are anxious to reduce growth rates and welcome international assistance for population programs. The motivation of these governments seems to be both political and economic. Asian countries do not share the view expressed at Bucharest by Latin American and African representatives that high population growth rates are not a problem. Results of national family planning programs in 16 developing Asian countries are assessed. Major fertility decline has only occurred so far in the most prosperous of these countries. Future fertility trends are hard to predict. Present inadequate knowledge of the determinants of human fertility and limited knowledge regarding fertility limitation techniques hamper progress in population reduction. Australia has aided these countries in demographic training and data collection. For both economic and humanitarian reasons, this aid should be extended to program implementation. PMID:12309219

Flood, P J

1978-04-01

48

Human Population: Fundamentals of Growth and Change.  

ERIC Educational Resources Information Center

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

Stauffer, Cheryl Lynn, Ed.

49

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

50

Hyperproduction of Poly-?-Hydroxybutyrate during Exponential Growth of Azotobacter vinelandii UWD  

PubMed Central

The transformation of Azotobacter vinelandii UW with A. vinelandii 113 DNA resulted in the formation of rifampin-resistant colonies, 13% of which also inherited a previously unrecognized mutation in the respiratory NADH oxidase. These transformants produced colonies with a white-sectored phenotype after prolonged incubation. Cells from these sectors were separated and purified by streaking and were named UWD. The dense white phenotype was due to the production of a large amount of poly-?-hydroxybutyrate during the exponential growth of strain UWD. The polymer accounted for 65 or 75% of the cell dry weight after 24 h of incubation of cultures containing glucose and either ammonium acetate or N2, respectively, as the nitrogen source. Under the same conditions, strain UW cells contained 22 to 25% poly-?-hydroxybutyrate, but O2-limited growth was required for these optimal production values. Polymer production was not dependent on O2 limitation in strain UWD, but the efficiency of conversion of glucose to poly-?-hydroxybutyrate was enhanced in O2-limited cultures. Conversion efficiencies were >0.25 and 0.33 mg of poly-?-hydroxybutyrate per mg of glucose consumed under vigorous- and low-aeration conditions, respectively, compared with an efficiency of 0.05 achieved by strain UW. Strain UWD, therefore, appeared to from poly-?-hydroxybutyrate under novel conditions, which may be useful in designing new methods for the industrial production of biodegradable plastics. Images

Page, William J.; Knosp, Olga

1989-01-01

51

[Population growth and the environment].  

PubMed

The impact of population growth on the enviornment has been extensively researched; it consists of the depletion of resources (agricultural land absorbed by urban expansion, loss of soils, desertification, loss of biodiversity, less availability of minerals, dwindling of petroleum reserves) and the degradation of natural resources (air and water pollution). For politicians, journalists, and environmentalists, population growth is identified as the principal villain, which is a unidirectional and negative opinion. Demography is supposed to examine the negative and positive effects of the environment-population relationship; however, it is postulated that there has not been much produced in the last 2 centuries in this area. Examination of the research literature does not indicate any view that transcends the Malthusian vision, although a few empirical studies exist (Hogan, 1989). Durham (1979) identified the replacement of subsistence agriculture by export-oriented agriculture as the key factor in overpopulation in El Salvador and Honduras that led to migrations and international conflicts. Tudela (1987) related a similar process in the Mexican state of Tabasco, where a period of malnutrition was accompanied by the expansion of export agriculture and nutritional improvements emanated only from recapturing subsistence agriculture. Fearnside (1986) researched the dynamics of the occupation and destruction of Amazonia. However, Kahn and Simon went further and denied the existence of real environmental problems: population is the ultimate resource, and the more minds, the more good ideas and solutions for any problem. However, in all these cases of pure or modified Malthusianism the relation of population/resources is reduced to a unidimensional relationship; and fertility, mortality, migration, marriage, and age structure receive little attention. A prime candidate for the attention of population specialists should be migration and patterns of settlement and their relationships to the physical environment, aspects of the depletion and degradation of resources as well as socially useful alterations. PMID:12286258

Hogan, D J

1991-01-01

52

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

ERIC Educational Resources Information Center

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

Castillo-Garsow, Carlos

2010-01-01

53

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 flares in the impulsive phase are complex in general, which is expected given the complexities of the flare environment in the magnetic field dominant corona. With the GOES (Geostationary Operational Environmental Satellite) observations, we however find that there are a subset of flares, whose impulsive phases are dominated by a period of exponential growth of the emission measure. The flares occurring from January 1999 to December 2002 are analyzed, and the results from the observations made with both GOES 8 and 10 satellites are compared to estimate the instrumental uncertainties. The frequency distribution of the mean temperature during this exponential growth phase has a normal distribution. Most flares within the 1? range of this temperature distribution belong to the GOES class B or C with the frequency distribution of the peak flux of the GOES low-energy channel following a log-normal distribution. The frequency distribution of the growth rate, and the duration of the exponential growth phase also follow a log-normal distribution with the duration covering a 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 flux. We also find 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 flares are discussed at the end.

Han, F. R.; Liu, S. M.

2012-11-01

54

Lesson 30: Exponential Functions  

NSDL National Science Digital Library

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

2011-01-01

55

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

Microsoft Academic Search

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

Mark A. Richards; Gary A. Shaw

2003-01-01

56

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

57

[Activation of the expression of the microcin C51 operon upon glucose starvation of cells at the exponential growth phase].  

PubMed

It was earlier shown that expression of the microcin C51 operon in Escherichia coli cells is activated upon decelerated growth of cells during their transition to the stationary growth phase and depends on the sigmaS subunit of RNA polymerase. Using a single-copy construct containing the cloned promoter region of the microcin C51 operon and a promoterless lac operon (P(mcc)-lac), it was shown that the promoter of the microcin operon was also induced by stress caused by the transition of cells at the exponential growth phase into the medium without glucose as a sole carbon source. Activation of P(mcc)-lac expression upon severe glucose starvation occurred in rpoS+ and rpoS- strains. In cells carrying the rpoD800 mutation that renders the sigma70 subunit of RNA polymerase temperature-sensitive, an activation of P(mcc)-lac expression was observed at nonpermissive temperature, in contrast to its complete inhibition in E. coli cells at the phase of delayed growth. Other stressors-nitrogen starvation, high temperatures, osmotic shock, tetracycline and chloramphenicol-did not activate P(mcc)-lac expression in cells at the exponential growth phase. PMID:15771250

Veselovski?, A M; Metlitskaia, A Z; Lipasova, V A; Bass, I A; Khmel', I A

2005-01-01

58

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

59

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

2013-04-01

60

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

61

Population Bulletin. World Population Projections: Alternative Paths to Zero Growth.  

ERIC Educational Resources Information Center

This report is an adaptation of selected parts of a book on world population projections by Tomas Frejka. An explanation of the demographic terms that form a foundation for these projections is included, as well as discussions of the growth potentials for 24 nations throughout the world. Frejka's projections for a nongrowing population have been…

Peck, Jennifer Marks

1974-01-01

62

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

USGS Publications Warehouse

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

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

2006-01-01

63

Population growth and development planning in Africa.  

PubMed

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

1980-12-01

64

Growth in Experimental Populations of Tilapia Mossambica.  

National Technical Information Service (NTIS)

Two populations of Tilapia mossambica were raised in tanks and their growth (weight and length) recorded for a period of 36 months. The relationship between number and weight is graphed, but was drastically disturbed by accidental mortalities at month 21....

R. P. Silliman

1970-01-01

65

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

66

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

67

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

ERIC Educational Resources Information Center

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

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

2008-01-01

68

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

NASA Astrophysics Data System (ADS)

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 of hyperbolicity in chaotic domains which coincides with that given by the Lyapunov characteristic number. Here the MEGNO is applied to a rather simple model, the 3D perturbed quartic oscillator, in order to visualize the structure of its phase space and obtain a quite clear picture of its resonance structure. Examples of application to multi-dimensional canonical maps are also included.

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

2003-08-01

69

The Oenococcus oeni clpX homologue is a heat shock gene preferentially expressed in exponential growth phase.  

PubMed

Using degenerated primers from conserved regions of previously studied clpX gene products, we cloned the clpX gene of the malolactic bacterium Oenococcus oeni. The clpX gene was sequenced, and the deduced protein of 413 amino acids (predicted molecular mass of 45,650 Da) was highly similar to previously analyzed clpX gene products from other organisms. An open reading frame located upstream of the clpX gene was identified as the tig gene by similarity of its predicted product to other bacterial trigger factors. ClpX was purified by using a maltose binding protein fusion system and was shown to possess an ATPase activity. Northern analyses indicated the presence of two independent 1.6-kb monocistronic clpX and tig mRNAs and also showed an increase in clpX mRNA amount after a temperature shift from 30 to 42 degrees C. The clpX transcript is abundant in the early exponential growth phase and progressively declines to undetectable levels in the stationary phase. Thus, unlike hsp18, the gene encoding one of the major small heat shock proteins of Oenococcus oeni, clpX expression is related to the exponential growth phase and requires de novo protein synthesis. Primer extension analysis identified the 5' end of clpX mRNA which is located 408 nucleotides upstream of a putative AUA start codon. The putative transcription start site allowed identification of a predicted promoter sequence with a high similarity to the consensus sequence found in the housekeeping gene promoter of gram-positive bacteria as well as Escherichia coli. PMID:10542163

Jobin, M P; Garmyn, D; Diviès, C; Guzzo, J

1999-11-01

70

The Oenococcus oeni clpX Homologue Is a Heat Shock Gene Preferentially Expressed in Exponential Growth Phase  

PubMed Central

Using degenerated primers from conserved regions of previously studied clpX gene products, we cloned the clpX gene of the malolactic bacterium Oenococcus oeni. The clpX gene was sequenced, and the deduced protein of 413 amino acids (predicted molecular mass of 45,650 Da) was highly similar to previously analyzed clpX gene products from other organisms. An open reading frame located upstream of the clpX gene was identified as the tig gene by similarity of its predicted product to other bacterial trigger factors. ClpX was purified by using a maltose binding protein fusion system and was shown to possess an ATPase activity. Northern analyses indicated the presence of two independent 1.6-kb monocistronic clpX and tig mRNAs and also showed an increase in clpX mRNA amount after a temperature shift from 30 to 42°C. The clpX transcript is abundant in the early exponential growth phase and progressively declines to undetectable levels in the stationary phase. Thus, unlike hsp18, the gene encoding one of the major small heat shock proteins of Oenococcus oeni, clpX expression is related to the exponential growth phase and requires de novo protein synthesis. Primer extension analysis identified the 5? end of clpX mRNA which is located 408 nucleotides upstream of a putative AUA start codon. The putative transcription start site allowed identification of a predicted promoter sequence with a high similarity to the consensus sequence found in the housekeeping gene promoter of gram-positive bacteria as well as Escherichia coli.

Jobin, Michel-Philippe; Garmyn, Dominique; Divies, Charles; Guzzo, Jean

1999-01-01

71

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

72

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

PubMed

Fermenting cells growing exponentially on rich (YPAD) medium underwent a transition to a slow-growing state as glucose levels declined and their metabolism shifted to respiration. During exponential growth, Fe import and cell-growth rates were matched, affording an approximately invariant cellular Fe concentration. During the transition period, the high-affinity Fe import rate declined slower than the cell-growth rate declined, causing Fe to accumulate, initially as Fe(III) oxyhydroxide nanoparticles but eventually as mitochondrial and vacuolar Fe. Once the cells had reached slow-growth mode, Fe import and cell-growth rates were again matched, and the cellular Fe concentration was again approximately invariant. Fermenting cells grown on minimal medium (MM) grew more slowly during the exponential phase and underwent a transition to a true stationary state as glucose levels declined. The Fe concentration of MM cells that just entered the stationary state was similar to that of YPAD cells, but MM cells continued to accumulate Fe in the stationary state. Fe initially accumulated as nanoparticles and high-spin Fe(II) species, but vacuolar Fe(III) also eventually accumulated. Surprisingly, Fe-packed 5-day-old MM cells suffered no more reactive oxygen species (ROS) damage than younger cells, suggesting that the Fe concentration alone does not accurately predict the extent of ROS damage. The mode and rate of growth at the time of harvesting dramatically affected cellular Fe content. A mathematical model of Fe metabolism in a growing cell was developed. The model included the import of Fe via a regulated high-affinity pathway and an unregulated low-affinity pathway. The import of Fe from the cytosol to vacuoles and mitochondria and nanoparticle formation were also included. The model captured essential trafficking behavior, demonstrating that cells regulate Fe import in accordance with their overall growth rate and that they misregulate Fe import when nanoparticles accumulate. The lack of regulation of Fe in yeast is perhaps unique compared to the tight regulation of other cellular metabolites. This phenomenon likely derives from the unique chemistry associated with Fe nanoparticle formation. PMID:24344915

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

2013-12-31

73

On the theory of global population growth  

NASA Astrophysics Data System (ADS)

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

Kapitza, Sergei P.

2010-12-01

74

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

75

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

76

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

ERIC Educational Resources Information Center

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

Kent, Mary Mederios

77

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

2005-12-01

78

Differential Dependence of Levansucrase and ?-Amylase Secretion on SecA (Div) during the Exponential Phase of Growth of Bacillus subtilis  

Microsoft Academic Search

SecA, the translocation ATPase of the preprotein translocase, accounts for 0.25% of the total protein in a degU32(Hy) Bacillus subtilis strain in logarithmic phase. The SecA level remained constant irrespective of the demand for exoprotein production but dropped about 12-fold during the late stationary phase. Modulation of the level of functional SecA during the exponential phase of growth affected differently

Laurence Leloup; Arnold J. M. Driessen; Roland Freudl; Régis Chambert; Marie-Françoise Petit-Glatron

1999-01-01

79

Effect of Growth Rate on the Production of ?-Galactosidase from Escherichia Coli in Bacillus Subtilis Using Glucose-Limited Exponentially Fedbatch Cultures  

Microsoft Academic Search

The effect of specific growth rate (?) on the production of ?-galactosidase from Escherichia coli in Bacillus subtilis was assessed using glucose-limited exponentially fedbatch cultures (EFBC). A B subtilis strain carrying a chromosomal copy of the lacZ gene under the control of the subtilisin (aprE) regulatory region was used in this study. This strain also carries the hpr2 and degU32(Hy)

Alfredo Mart??nez; Octavio T Ram??rez; Fernando Valle

1998-01-01

80

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

81

Population Growth and Poverty in the Developing World.  

ERIC Educational Resources Information Center

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

Birdsall, Nancy

1980-01-01

82

Population Growth Problem in Developing Countries: Coordinated Assistance Essential.  

National Technical Information Service (NTIS)

Rapid population growth in developing countries impedes efforts to improve the quality of life. Many governmental, international, and private and voluntary organizations provide population assistance to an ever-increasing number of countries. Cumulative a...

1978-01-01

83

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

NASA Astrophysics Data System (ADS)

The solution chemistry during the initial (slow increase of dissolved iron and sulfate) and main stage (rapid increase of dissolved iron and sulfate) of pyrite leaching by Acidithiobacillus ferrooxidans ( Af) at a starting pH of 2.05 shows significant differences. During the initial stage, ferrous iron (Fe 2+) is the dominant iron species in solution and the molar ratio of produced sulfate (SO 42-) and total iron (Fe tot) is 1.1, thus does not reflect the stoichiometry of pyrite (FeS 2). During the main stage, ferric iron (Fe 3+) is the dominant iron species in solution and the SO 42-:Fe tot ratio is with 1.9, close to the stoichiometry of FeS 2. Another difference between initial and main stage is an initial trend to slightly higher pH values followed by a drop during the main stage to pH 1.84. These observations raise the question if there are different modes of bioleaching of pyrite, and if there are, what those modes imply in terms of leaching mechanisms. Different oxygen and sulfur isotope trends of sulfate during the initial and main stages of pyrite oxidation confirm that there are two pyrite bioleaching modes. The biochemical reactions during initial stage are best explained by the net reaction FeS 2 + 3O 2 ? Fe 2+ + SO 42- + SO 2(g). The degassing of sulfur dioxide (SO 2) acts as sink for sulfur depleted in 34S compared to pyrite, and is the cause of the SO 42-:Fe tot ratio of 1.1 and the near constant pH. During the exponential phase, pyrite sulfur is almost quantitatively converted to sulfate, according to the net reaction FeS 2 + 15/4O 2 + 1/2H 2O ? Fe 3+ + 2SO 42- + H +. We hypothesize that the transition between the modes of bioleaching of pyrite is due to the impact of the accumulation of ferrous iron, which induces changes in the metabolic activity of Af and may act as an inhibitor for the oxidation of sulfur species. This transition defines a fundamental change in the growth strategy of Af. A mode, where bacteria gain energy by oxidation of elemental sulfur to sulfite but show little growth is switched into a mode, where bacteria gain a smaller amount of energy by the oxidation of ferrous iron, but induce much faster pyrite leaching rates due to the production of ferric iron.

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

2008-06-01

84

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

85

Population Growth and a Sustainable Environment.  

ERIC Educational Resources Information Center

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

Mortimore, Michael; Tiffen, Mary

1994-01-01

86

U.S. Population Growth: Prospects and Policy.  

ERIC Educational Resources Information Center

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

McFalls, Joseph A., Jr.; And Others

1984-01-01

87

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

88

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

89

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

Microsoft Academic Search

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

Alfred E. Hartemink

2007-01-01

90

Introduction of Trojan sex chromosomes to boost population growth  

Microsoft Academic Search

Conservation programs that deal with small or declining populations often aim at a rapid increase of population size to above-critical levels in order to avoid the negative effects of demographic stochasticity and genetic problems like inbreeding depression, fixation of deleterious alleles, or a general loss of genetic variability and hence of evolutionary potential. In some situations, population growth is determined

Samuel Cotton; Claus Wedekind

2007-01-01

91

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

92

Activation of the expression of the microcin c51 operon upon glucose starvation of cells at the exponential growth phase  

Microsoft Academic Search

It was earlier shown that expression of the microcin C51 operon in Escherichia coli cells is activated upon decelerated growth of cells during their transition to the stationary growth phase and depends on the sS subunit of RNA polymerase. Using a single-copy construct containing the cloned promoter region of the microcin C51 operon and a promoterless lac operon ( Pmcc-lac

A. M. Veselovskii; A. Z. Metlitskaya; V. A. Lipasova; I. A. Bass; I. A. Khmel

2005-01-01

93

Activation of the expression of the microcin C51 operon upon glucose starvation of cells at the exponential growth phase  

Microsoft Academic Search

It was earlier shown that expression of the microcin C51 operon in Escherichia coli cells is activated upon decelerated growth of cells during their transition to the stationary growth phase and depends on the sS subunit of RNA polymerase. Using a single-copy construct containing the cloned promoter region of the microcin C51 operon and a promoterless lac operon (Pmcc-lac), it

A. M. Veselovskii; A. Z. Metlitskaya; V. A. Lipasova; I. A. Bass; I. A. Khmel

2005-01-01

94

Heat and pulsed electric field resistance of pigmented and non-pigmented enterotoxigenic strains of Staphylococcus aureus in exponential and stationary phase of growth.  

PubMed

The survival of four enterotoxigenic strains of Staphylococcus aureus (with different pigment content) to heat and to pulsed electric fields (PEF) treatments, and the increase in resistance to both processing stresses associated with entrance into stationary phase was examined. Survival curves to heat (58 degrees C) and to PEF (26 kV/cm) of cells in the stationary and in the exponential phase of growth were obtained. Whereas a wide variation in resistance to heat treatments was detected amongst the four strains, with decimal reduction time values at 58 degrees C (D(58 degrees C)) ranging from 0.93 to 0.20 min, the resistance to PEF was very similar. The occurrence of a higher tolerance to heat in stationary phase was coincident with a higher content in carotenoid pigmentation in S. aureus colonies. However, cells of the most heat resistant (pigmented) and the most heat sensitive (non-pigmented) strains in the mid-exponential phase of growth showed similar resistance to heat and to PEF. Therefore the increase in thermotolerance upon entrance into stationary phase of growth was more marked for the pigmented strains. Recovery in anaerobic conditions particularly enhanced survival to heat treatments in a non-pigmented strain. Strain CECT 4630, which possess a deficient sigma B activity, showed low heat resistance, low pigmentation, and reduced increase in thermotolerance in stationary phase. These results indicate that the magnitude of the development of a higher heat resistance in S. aureus in stationary phase is positively related to the carotenoid content of the strain. The development of tolerance to pulsed electric field was less relevant and not linked to the carotenoid content. PMID:17804103

Cebrián, G; Sagarzazu, N; Pagán, R; Condón, S; Mañas, P

2007-09-30

95

[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

96

Diet Quality Limits Summer Growth of Field Vole Populations  

PubMed Central

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

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

2014-01-01

97

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

Microsoft Academic Search

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

Paul C. Cheshire; Stefano Magrini

2006-01-01

98

Lesson 33: Applications of Exponential Functions  

NSDL National Science Digital Library

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

2011-01-01

99

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

100

Growth and size structure in a baltic Mytilus edulis population  

Microsoft Academic Search

Since Mytilus edulis L. has very few predators and competitors for space, it has become a biomass dominant in the Baltic proper covering hard substrates from the water surface to more than 30 m depth. In order to investigate the factors controlling size and production in a Baltic M. edulis population, growth was studied by the analysis of annual growth

N. Kautsky

1982-01-01

101

The role of fertility and population in economic growth  

Microsoft Academic Search

Two recently improved sets of cross-country panel data are combined in order to re-examine the effects of population growth and fertility on economic growth. Using a 107 country panel data set covering 1960-85, we find that high birth rates appear to reduce economic growth through investment effects and possibly through “capital dilution”, although classic resource dilution is not evident in

James A. Brander; Steve Dowrick

1994-01-01

102

Population growth. Its magnitude and implications for development.  

PubMed

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

Birdsall, N

1984-09-01

103

Double-Exponential LR Circuit.  

National Technical Information Service (NTIS)

Simple LR and RC circuits are familiar to generations of physics students as examples of single-exponential growth and decay in the relevant voltages, currents, and charges. An element of novelty can be introduced by connecting two (instead of one) LR coi...

C. E. Mungan

2005-01-01

104

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

105

Population growth and the development of a central place system  

NASA Astrophysics Data System (ADS)

This paper describes the spatial and functional evolution of a central place system as market conditions change with population growth. Utilizing a partial equilibrium optimization model, we examine the spatial response of two economic sectors to increases in market populations resulting from natural increase and migration. Response in both sectors is conditioned by threshold demand, with factor prices also affecting one of the sectors. As the central place system evolves it exhibits spatial and functional characteristics that are initially consistent with a Löschian landscape, then a Christallerian landscape at higher populations, while at even larger populations Krugman’s landscape emerges.

Cromley, Robert G.; Hanink, Dean M.

2008-12-01

106

TOPICAL PROBLEMS: The phenomenological theory of world population growth  

NASA Astrophysics Data System (ADS)

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

Kapitza, Sergei P.

1996-01-01

107

A model of northern pintail productivity and population growth rate  

USGS Publications Warehouse

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

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

1998-01-01

108

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

109

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

NASA Astrophysics Data System (ADS)

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

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

2008-09-01

110

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

111

Population growth and technological change in a global warming model  

Microsoft Academic Search

Global warming (GW) is now recognized as a significant threat to sustainable development on an international scale. After providing some introductory background material, we introduce a benchmark dynamic game within which to study the GW problem. The model allows for population growth and is subsequently generalized to allow for changes in technology. In each case, a benchmark “Business as Usual”

Prajit K. Dutta; Roy Radner

2006-01-01

112

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

113

The Economic Base of Recent Population Growth in Nonmetropolitan Settings.  

ERIC Educational Resources Information Center

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

Long, Larry; DeAre, Diana

114

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

115

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

Microsoft Academic Search

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

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

2010-01-01

116

Demographic modeling of transient amplifying cell population growth.  

PubMed

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

Nakaoka, Shinji; Inaba, Hisashi

2014-04-01

117

An Exceptional Exponential Function  

ERIC Educational Resources Information Center

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

Curgus, Branko

2006-01-01

118

A Multivariate Exponential Distribution  

Microsoft Academic Search

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 serves to indicate conditions under which the distribution is appropriate. Two of these derivations are based on “shock models,” and one is based on the requirement

Albert W. Marshall; Ingram Olkin

1967-01-01

119

Growth curves for ostriches (Struthio camelus) in a Brazilian population.  

PubMed

The objective of this study was to fit growth curves using nonlinear and linear functions to describe the growth of ostriches in a Brazilian population. The data set consisted of 112 animals with BW measurements from hatching to 383 d of age. Two nonlinear growth functions (Gompertz and logistic) and a third-order polynomial function were applied. The parameters for the models were estimated using the least-squares method and Gauss-Newton algorithm. The goodness-of-fit of the models was assessed using R(2) and the Akaike information criterion. The R(2) calculated for the logistic growth model was 0.945 for hens and 0.928 for cockerels and for the Gompertz growth model, 0.938 for hens and 0.924 for cockerels. The third-order polynomial fit gave R(2) of 0.938 for hens and 0.924 for cockerels. Among the Akaike information criterion calculations, the logistic growth model presented the lowest values in this study, both for hens and for cockerels. Nonlinear models are more appropriate for describing the sigmoid nature of ostrich growth. PMID:23243259

Ramos, S B; Caetano, S L; Savegnago, R P; Nunes, B N; Ramos, A A; Munari, D P

2013-01-01

120

Deer Population  

NSDL National Science Digital Library

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

School, Maryland V.

121

The alternative sigma factor SigB of Corynebacterium glutamicum modulates global gene expression during transition from exponential growth to stationary phase  

PubMed Central

Background Corynebacterium glutamicum is a gram-positive soil bacterium widely used for the industrial production of amino acids. There is great interest in the examination of the molecular mechanism of transcription control. One of these control mechanisms are sigma factors. C. glutamicum ATCC 13032 has seven putative sigma factor-encoding genes, including sigA and sigB. The sigA gene encodes the essential primary sigma factor of C. glutamicum and is responsible for promoter recognition of house-keeping genes. The sigB gene codes for the non-essential sigma factor SigB that has a proposed role in stress reponse. Results The sigB gene expression was highest at transition between exponential growth and stationary phase, when the amount of sigA mRNA was already decreasing. Genome-wide transcription profiles of the wild-type and the sigB mutant were recorded by comparative DNA microarray hybridizations. The data indicated that the mRNA levels of 111 genes are significantly changed in the sigB-proficient strain during the transition phase, whereas the expression profile of the sigB-deficient strain showed only minor changes (26 genes). The genes that are higher expressed during transition phase only in the sigB-proficient strain mainly belong to the functional categories amino acid metabolism, carbon metabolism, stress defense, membrane processes, and phosphorus metabolism. The transcription start points of six of these genes were determined and the deduced promoter sequences turned out to be indistinguishable from that of the consensus promoter recognized by SigA. Real-time reverse transcription PCR assays revealed that the expression profiles of these genes during growth were similar to that of the sigB gene itself. In the sigB mutant, however, the transcription profiles resembled that of the sigA gene encoding the house-keeping sigma factor. Conclusion During transition phase, the sigB gene showed an enhanced expression, while simultaneously the sigA mRNA decreased in abundance. This might cause a replacement of SigA by SigB at the RNA polymerase core enzyme and in turn results in increased expression of genes relevant for the transition and the stationary phase, either to cope with nutrient limitation or with the accompanying oxidative stress. The increased expression of genes encoding anti-oxidative or protection functions also prepares the cell for upcoming limitations and environmental stresses.

Larisch, Christof; Nakunst, Diana; Huser, Andrea T; Tauch, Andreas; Kalinowski, Jorn

2007-01-01

122

[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

123

Population growth and the changing ecosystem in Mindanao.  

PubMed

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

Magdalena, F V

1996-04-01

124

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

PubMed

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

Moreland, R S

1982-01-01

125

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

NASA Astrophysics Data System (ADS)

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

Lambert, Guillaume; Kussell, Edo

2013-03-01

126

Exponential Graphing Using Technology  

NSDL National Science Digital Library

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

Gaynr, Cheryl

2012-07-27

127

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

128

Localization and Extinction of Bacterial Populations under Inhomogeneous Growth Conditions  

PubMed Central

The transition from localized to systemic spreading of bacteria, viruses, and other agents is a fundamental problem that spans medicine, ecology, biology, and agriculture science. We have conducted experiments and simulations in a simple one-dimensional system to determine the spreading of bacterial populations that occurs for an inhomogeneous environment under the influence of external convection. Our system consists of a long channel with growth inhibited by uniform ultraviolet (UV) illumination except in a small “oasis”, which is shielded from the UV light. To mimic blood flow or other flow past a localized infection, the oasis is moved with a constant velocity through the UV-illuminated “desert”. The experiments are modeled with a convective reaction-diffusion equation. In both the experiment and model, localized or extinct populations are found to develop, depending on conditions, from an initially localized population. The model also yields states where the population grows everywhere. Further, the model reveals that the transitions between localized, extended, and extinct states are continuous and nonhysteretic. However, it does not capture the oscillations of the localized population that are observed in the experiment.

Lin, Anna L.; Mann, Bernward A.; Torres-Oviedo, Gelsy; Lincoln, Bryan; Kas, Josef; Swinney, Harry L.

2004-01-01

129

An Unusual Exponential Graph  

NASA Astrophysics Data System (ADS)

This paper is an addition to the series of papers on the exponential function begun by Albert Bartlett.1 In particular, we ask how the graph of the exponential function y =e-t/? would appear if y were plotted versus ln t rather than the normal practice of plotting ln y versus t. In answering this question, we find a new way to interpret the mean life (or time constant) ? using such a linear-log graph.

Syed, M. Qasim; Lovatt, Ian

2014-05-01

130

Interspecific synchrony of seabird population growth rate and breeding success  

PubMed Central

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

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

2013-01-01

131

Interspecific synchrony of seabird population growth rate and breeding success.  

PubMed

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

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

2013-07-01

132

Modelling population growth with delayed nonlocal reaction in 2-dimensions.  

PubMed

In this paper, we consider the population growth of a single species living in a two-dimensional spatial domain. New reaction-difusion equation models with delayed nonlocal reaction are developed in two-dimensional bounded domains combining diferent boundary conditions. The important feature of the models is the reflection of the joint efect of the difusion dynamics and the nonlocal maturation delayed efect. We consider and ana- lyze numerical solutions of the mature population dynamics with some wellknown birth functions. In particular, we observe and study the occurrences of asymptotically stable steady state solutions and periodic waves for the two-dimensional problems with nonlocal delayed reaction. We also investigate numerically the efects of various parameters on the period, the peak and the shape of the periodic wave as well as the shape of the asymptotically stable steady state solution. PMID:20369915

Liang, Dong; Wu, Jianhong; Zhang, Fan

2005-01-01

133

Social policy and population growth in South-East Asia.  

PubMed

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

You Poh Seng Rao, B; Shantakumar, G

1974-01-01

134

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).

135

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

ERIC Educational Resources Information Center

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

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

136

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

PubMed

The US decision since the 1960s to link foreign policy with family planning and population control is noteworthy for its intention to change the demographic structure of foreign countries and the magnitude of the initiative. The current population ideologies are part of the legacy of 19th century views on science, morality, and political economy. Strong constraints were placed on US foreign policy since World War II, particularly due to presumptions about the role of developing countries in Cold War ideology. Domestic debates revolved around issues of feminism, birth control, abortion, and family political issues. Since the 1960s, environmental degradation and resource depletion were an added global dimension of US population issues. Between 1935 and 1958 birth control movements evolved from the ideologies of utopian socialists, Malthusians, women's rights activists, civil libertarians, and advocates of sexual freedom. There was a shift from acceptance of birth control to questions about the role of national government in supporting distribution of birth control. Immediately postwar the debates over birth control were outside political circles. The concept of family planning as a middle class family issue shifted the focus from freeing women from the burdens of housework to making women more efficient housewives. Family planning could not be taken as a national policy concern without justification as a major issue, a link to national security, belief in the success of intervention, and a justifiable means of inclusion in public policy. US government involvement began with agricultural education, technological assistance, and economic development that would satisfy the world's growing population. Cold War politics forced population growth as an issue to be considered within the realm of foreign policy and diplomacy. US government sponsored family planning was enthusiastic during 1967-74 but restrained during the 1980s. The 1990s has been an era of redefinition of the issues and increased divisiveness among environmentalists, feminists, and population control advocates. The current justification of US population program assistance is based on concern for the health of women and children. Future changes will be dependent on ideology, theology, and political philosophy. PMID:12346346

Sharpless, J

1995-01-01

137

WEIGHTED EXPONENTIAL INEQUALITIES  

Microsoft Academic Search

Necessary and sucient conditions on weight pairs are found for the validity of a class of weighted exponential inequalities involving certain classical operators. Among the operators considered are the Hardy averaging operator and its variants in one and two dimensions, as well as the Laplace transform. Discrete analogues yield characterizations of weighted forms of Carleman's inequality.

H. P. HEINIG; R. KERMAN; M. KRBEC

138

The turbulent exponential jet  

Microsoft Academic Search

A new, self-similar, turbulent jet flow is postulated in which the global vorticity (O mega) is a constant following any vortex. In contrast, conventional self-similar flows all exhibit Omega inversely proportional to the vortex age. In order for the newly postulated flow to exist, the nozzle exit speed must increase exponentially with time. It is shown that this circumstance may

Robert Breidenthal

1986-01-01

139

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

PubMed Central

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

Attwood, Stephen W.; Upatham, E. Suchart

2013-01-01

140

Phase space interpretation of exponential Fermi acceleration  

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

141

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

PubMed

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

Pimentel, D

1991-01-01

142

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

PubMed

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

Khalatbari, P

1986-07-01

143

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

Microsoft Academic Search

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

Oded Galor; David N. Weil

1998-01-01

144

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

Microsoft Academic Search

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

Oded Galor; David N. Weill

2000-01-01

145

Bivariate Exponential Distributions  

Microsoft Academic Search

A bivariate distribution is not determined by the knowledge of the margins. Two bivariate distributions with exponential margins are analyzed and another is briefly mentioned.In the first distribution (2.1) the conditional expectation of one variable decreases to zero with increasing values of the other one. The coefficient of correlation is never positive and lies in the interval –.40???0, and the

E. J. Gumbel

1960-01-01

146

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.

147

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

148

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 ...

149

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

ERIC Educational Resources Information Center

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

Carter, Ashley J. R.

1999-01-01

150

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

151

Turbulent Mixing in Exponential Transverse Jets.  

National Technical Information Service (NTIS)

The effects of acceleration on vortex growth and molecular mixing have been systematically explored for the first time in a transverse array of exponentially increasing jets. The issue is the influence of a new kind of forcing which imposes on a vortex a ...

R. E. Breidenthal

1990-01-01

152

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

153

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

154

A New Exponential Gravity  

NASA Astrophysics Data System (ADS)

We propose a new exponential f(R) gravity model with f(R) = (R - ?c) e ?(c/R)n and n > 3, ? >= 1, c > 0 to explain late-time acceleration of the universe. At the high curvature region, the model behaves like the ? CDM model. In the asymptotic future, it reaches a stable de-Sitter spacetime. It is a cosmologically viable model and can evade the local gravity constraints easily. This model shares many features with other f(R) dark energy models like Hu-Sawicki model and Exponential gravity model. In it the dark energy equation of state is of an oscillating form and can cross phantom divide line ?de = -1. In particular, in the parameter range 3 < n <= 4, ? ~ 1, the model is most distinguishable from other models. For instance, when n = 4, ? = 1, the dark energy equation of state will cross -1 in the earlier future and has a stronger oscillating form than the other models, the dark energy density in asymptotical future is smaller than the one in the high curvature region. This new model can evade the local gravity tests easily when n > 3 and ? > 1.

Xu, Qiang; Chen, Bin

2014-01-01

155

Exponentially Accelerating Jet in Crossflow  

Microsoft Academic Search

Effects of exponential acceleration on penetration and mixing characteristics of a jet in crossèow have been investigated experimentallyinawatermodel. To imposean exponential acceleration on the èow, both the injection speed and the nozzle width of the jet increased exponentially in the downstream direction of the crossèow. An acceleration parameter ® is deé ned as the ratio of the revolution time of

Adnan Eroglu; Robert E. Breidenthal

1998-01-01

156

Effects of Growth Phase and Temperature on ? (B) Activity within a Listeria monocytogenes Population: Evidence for RsbV-Independent Activation of ? (B) at Refrigeration Temperatures.  

PubMed

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

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

2013-01-01

157

Population Growth in the United States and Mexico. Geography Curriculum Project.  

ERIC Educational Resources Information Center

The self-study unit for intermediate grades treats population growth in the United States and Mexico. The major objectives are to improve skills in using graphics and to teach about population growth. The teaching method used is the Forced Inferential Response Mode (FIRM). The students are presented with data through maps, graphs, tables,…

Dale, John R.; Rice, Marion J.

158

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

Microsoft Academic Search

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

Oded Galor; David N. Weil

2000-01-01

159

Sedimentary iron inputs stimulate seagrass ( Posidonia oceanica) population growth in carbonate sediments  

Microsoft Academic Search

The relationship between sedimentary Fe inputs and net seagrass population growth across a range of Posidonia oceanica meadows growing in carbonate Mediterranean sediments (Balearic Islands, Spain; SE Iberian Peninsula, Spain; Limassol, Cyprus; Sounion, Greece) was examined using comparative analysis. Sedimentary Fe inputs were measured using benthic sediment traps and the net population growth of P. oceanica meadows was assessed using

Núria Marbà; Carlos M. Duarte; Marianne Holmer; Maria Ll. Calleja; Elvira Álvarez; Elena Díaz-Almela; Neus Garcias-Bonet

2008-01-01

160

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

161

Comparison of Native and Introduced Flathead Catfish Populations in Alabama and Georgia: Growth, Mortality, and Management  

Microsoft Academic Search

We compared growth of flathead catfish Pylodictis olivaris from two native populations in Alabama (Coosa and Tallapoosa rivers) and two introduced populations in Georgia (Ocmulgee and Satilla rivers). We also compared mortality rates and potential outcomes of various management regimes (minimum length limits [MLLs]) among the populations. Total length–log10(age) regression slopes for introduced fish were higher than those for native

Peter C. Sakaris; Elise R. Irwin; Jeffrey C. Jolley; Donald Harrison

2006-01-01

162

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

163

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

ERIC Educational Resources Information Center

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

Pelletti, John C.

164

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

165

Energy use, population and growth, 1800–1970  

Microsoft Academic Search

In this paper, the role of energy use is incorporated into unified growth theory. The paper presents some interesting evidence\\u000a about the evolution of energy in the transition from stagnation to growth, and it subsequently develops a growth model where\\u000a the observed increase in conversion efficiency in the coal energy sector is explicitly modelled and calibrated to existing\\u000a data over

Maria Fröling

2011-01-01

166

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

167

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

ERIC Educational Resources Information Center

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

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

168

MathHelp Notebook on Exponential Functions  

NSDL National Science Digital Library

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

Mathhelp; London, University C.

169

Population Ecology: Experiments with Protistans  

NSDL National Science Digital Library

In Part A, "Investigations in Population Ecology" students identify five different protistans, estimate the number of protistans in a culture, dilute stock cultures to achieve specific concentrations of protistans, set up and carry out a competition or predator-prey experiment of their design using one or more of the protistans available. In Part B, "Basic Population Ecology" students use mathematical models to describe exponential and logistic growth in populations of organisms and to analyze, graph, and interpret data.

Zimmerman, Melvin

2010-02-16

170

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

171

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

PubMed

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

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

2014-01-01

172

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

PubMed Central

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

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

2014-01-01

173

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

174

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

175

Molecular-Level Variation Affects Population Growth in a Butterfly Metapopulation  

PubMed Central

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

Saccheri, Ilik

2006-01-01

176

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

177

An Intergenerational Model of Population Growth, (301.32012-R278).  

National Technical Information Service (NTIS)

The authors first outline a general model of optimum population growth. In order to discuss explicitly various economic aspects of population they use in the analysis a simple case. The plan of the paper is as follows. In Section II they set up the basic ...

A. Razin U. Ben-Zion

1973-01-01

178

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

Microsoft Academic Search

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

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

2007-01-01

179

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

Microsoft Academic Search

BackgroundMatrix models are widely used to study the dynamics and demography of populations. An important but overlooked issue is how the number of individuals sampled influences estimates of the population growth rate (?) calculated with matrix models. Even unbiased estimates of vital rates do not ensure unbiased estimates of ?–Jensen's Inequality implies that even when the estimates of the vital

Ian J. Fiske; Emilio M. Bruna; Benjamin M. Bolker; Mark Rees

2008-01-01

180

Population Growth and Economic Development: Lessons from Selected Asian Countries. Policy Development Studies, Number 10.  

ERIC Educational Resources Information Center

The major findings of a research project on the relationship between population growth and economic development are summarized in this monograph. The study compares recent demographic and economic trends in Japan, Korea, Thailand, and Indonesia to worldwide experience as described by an econometric model of population and development. The study…

Mason, Andrew; And Others

181

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

ERIC Educational Resources Information Center

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

Population Reference Bureau, Inc., Washington, DC.

182

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

Microsoft Academic Search

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

A. Blanc; J. Attia

1992-01-01

183

The environment and population growth: decade for action  

SciTech Connect

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

Not Available

1992-05-01

184

Population growth of Mexican free-tailed bats ( Tadarida brasiliensis mexicana ) predates human agricultural activity  

Microsoft Academic Search

Background  Human activities, such as agriculture, hunting, and habitat modification, exert a significant effect on native species. Although\\u000a many species have suffered population declines, increased population fragmentation, or even extinction in connection with\\u000a these human impacts, others seem to have benefitted from human modification of their habitat. Here we examine whether population\\u000a growth in an insectivorous bat (Tadarida brasiliensis mexicana) can

Amy L Russell; Murray P Cox; Veronica A Brown; Gary F McCracken

2011-01-01

185

Sedimentary iron inputs stimulate seagrass ( Posidonia oceanica) population growth in carbonate sediments  

NASA Astrophysics Data System (ADS)

The relationship between sedimentary Fe inputs and net seagrass population growth across a range of Posidonia oceanica meadows growing in carbonate Mediterranean sediments (Balearic Islands, Spain; SE Iberian Peninsula, Spain; Limassol, Cyprus; Sounion, Greece) was examined using comparative analysis. Sedimentary Fe inputs were measured using benthic sediment traps and the net population growth of P. oceanica meadows was assessed using direct census of tagged plants. The meadows examined ranged from meadows undergoing a severe decline to expanding meadows (specific net population growth, from -0.14 yr -1 to 0.05 yr -1). Similarly, Fe inputs to the meadows ranged almost an order of magnitude across meadows (8.6-69.1 mg Fe m -2 d -1). There was a significant, positive relationship between sedimentary iron inputs and seagrass net population growth, accounting for 36% of the variability in population growth across meadows. The relationship obtained suggested that seagrass meadows receiving Fe inputs below 43 mg Fe m -2 d -1 are vulnerable and in risk of decline, confirming the pivotal role of Fe in the control of growth and the stability of seagrass meadows in carbonate sediments.

Marbà, Núria; Duarte, Carlos M.; Holmer, Marianne; Calleja, Maria Ll.; Álvarez, Elvira; Díaz-Almela, Elena; Garcias-Bonet, Neus

2008-02-01

186

Genetic Parameter Estimation in Seedstock Swine Population for Growth Performances  

PubMed Central

The objective of this study was to estimate genetic parameters that are to be used for across-herd genetic evaluations of seed stock pigs at GGP level. Performance data with pedigree information collected from swine breeder farms in Korea were provided by Korea Animal Improvement Association (AIAK). Performance data were composed of final body weights at test days and ultrasound measures of back fat thickness (BF), rib eye area (EMA) and retail cut percentage (RCP). Breeds of swine tested were Landrace, Yorkshire and Duroc. Days to 90 kg body weight (DAYS90) were estimated with linear function of age and ADG calculated from body weights at test days. Ultrasound measures were taken with A-mode ultrasound scanners by trained technicians. Number of performance records after censoring outliers and keeping records pigs only born from year 2000 were of 78,068 Duroc pigs, 101,821 Landrace pigs and 281,421 Yorkshire pigs. Models included contemporary groups defined by the same herd and the same seasons of births of the same year, which was regarded as fixed along with the effect of sex for all traits and body weight at test day as a linear covariate for ultrasound measures. REML estimation was processed with REMLF90 program. Heritability estimates were 0.40, 0.32, 0.21 0.39 for DAYS90, ADG, BF, EMA, RCP, respectively for Duroc population. Respective heritability estimates for Landrace population were 0.43, 0.41, 0.22, and 0.43 and for Yorkshire population were 0.36, 0.38, 0.22, and 0.42. Genetic correlation coefficients of DAYS90 with BF, EMA, or RCP were estimated to be 0.00 to 0.09, ?0.15 to ?0.25, 0.22 to 0.28, respectively for three breeds populations. Genetic correlation coefficients estimated between BF and EMA was ?0.33 to ?0.39. Genetic correlation coefficient estimated between BF and RCP was high and negative (?0.78 to ?0.85) but the environmental correlation coefficients between these two traits was medium and negative (near ?0.35), which describes a highly correlated genetic response to selection on one or the other of these traits. Genetic Trends of all three breeds tend to be towards bigger EMA or greater RCP and shorter DAYS90 especially from generations born after year 2000.

Choi, Jae Gwan; Cho, Chung Il; Choi, Im Soo; Lee, Seung Soo; Choi, Tae Jeong; Cho, Kwang Hyun; Park, Byoung Ho; Choy, Yun Ho

2013-01-01

187

Exponential approximations in optimal design  

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

188

Improved Techniques for Fast Exponentiation  

Microsoft Academic Search

We present improvements to algorithms for efficient exponentiation. The fractional window technique is a generalization of the sliding window and window NAF approach; it can be used to improve performance in devices\\u000a with limited storage. Window NAF splitting is an efficient technique for exponentiation with precomputation for fixed bases in groups where inversion is easy (e.g.\\u000a elliptic curves).

Bodo Möller; Fachbereich Informatik

189

Recent explosive human population growth has resulted in an excess of rare genetic variants.  

PubMed

Human populations have experienced recent explosive growth, expanding by at least three orders of magnitude over the past 400 generations. This departure from equilibrium skews patterns of genetic variation and distorts basic principles of population genetics. We characterized the empirical signatures of explosive growth on the site frequency spectrum and found that the discrepancy in rare variant abundance across demographic modeling studies is mostly due to differences in sample size. Rapid recent growth increases the load of rare variants and is likely to play a role in the individual genetic burden of complex disease risk. Hence, the extreme recent human population growth needs to be taken into consideration in studying the genetics of complex diseases and traits. PMID:22582263

Keinan, Alon; Clark, Andrew G

2012-05-11

190

Exponential stability, exponential expansiveness, and exponential dichotomy of evolution equations on the half-line  

Microsoft Academic Search

LetU=(U(t, s))t=s=O be an evolution family on the half-line of bounded linear operators on a Banach spaceX. We introduce operatorsGO,GX andIX on certain spaces ofX-valued continuous functions connected with the integral equation\\u000a$$u(t) = U(t,s)u(s) + \\\\int_s^t {U(t,\\\\xi )f(\\\\xi )d\\\\xi }$$\\u000a, and we characterize exponential stability, exponential expansiveness and exponential dichotomy ofU by properties ofGO,GX andIX, respectively. This extends

Nguyen Van Minh; Frank Räbiger; Roland Schnaubelt

1998-01-01

191

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

NASA Astrophysics Data System (ADS)

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 cancer cells in the Webb-Gyllenberg model. The drug is assumed to kill all cell types, each at a specific rate. Considering the total cell population growth in the presence of the drug, the behavior and the size of proliferating and quiescence subpopulations, as well as the related transition rates have been investigated.

Shojania Feizabadi, Mitra

2006-03-01

192

Influence of plant population and nitrogen-fertilizer at various levels on growth and growth efficiency of maize.  

PubMed

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 800,000?plants ha?¹ corresponding to spacings of 75 × 25, 60 × 25, and 50 × 25?cm) and 4 doses of N (100, 140, 180, and 220?kg?ha?¹) were the treatment variables. Results revealed that plant growth, light interception (LI), yield attributes, and grain yield varied significantly due to the variations in population density and N-rates. Crop growth rate (CGR) was the highest with the population of 80,000?ha?¹ receiving 220?kg?N?ha?¹, while relative growth rate (RGR) showed an opposite trend of CGR. Light absorption was maximum when most of densely populated plant received the highest amount of N (220?kg?N?ha?¹). Response of soil-plant-analysis development (SPAD) value as well as N-content to N-rates was found significant. Plant height was the maximum at the lowest plant density with the highest amount of N. Plants that received 180?kg?N?ha?¹ with 80,000?plants?ha?¹ had larger foliage, greater SPAD value, and higher amount of grains cob?¹ that contributed to the maximum yield (5.03?t?ha?¹) and the maximum harvest index (HI) compared to the plants in other treatments. PMID:24163615

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

2013-01-01

193

Effect of stage-specific vital rates on population growth rates and effective population sizes in an endangered iteroparous plant.  

PubMed

Effective population size (N(e)) determines the strength of genetic drift and can influence the level of genetic diversity a population can maintain. Assessing how changes in demographic rates associated with environmental variables and management actions affect N(e) thus can be crucial to the conservation of endangered species. Calculation of N(e) through demographic models makes it possible to use elasticity analyses to study this issue. The elasticity of N(e) to a given vital rate is the proportional change in N(e) associated with a proportional increase in that vital rate. In addition, demographic models can be used to study N(e) and population growth rate (?) simultaneously. Simultaneous examination is important because some vital rates differ diametrically in their associations with ? and N(e). For example, in some cases increasing these vital rates increases ? and decreases N(e). We used elasticity analysis to study the effect of stage-specific survival and flowering rates on N(e), annual effective population size (N(a)), and ? in seven populations of the endangered plant Austrian dragonhead (Dracocephalum austriacum). In populations with ? ? 1, the elasticities of N(e) and N(a) were similar to those of ?. Survival rates of adults were associated with greater elasticities than survival rates of juveniles, flowering rates, or fecundity. In populations with ? < 1, N(e) and N(a) exhibited greater elasticities to juvenile than to adult vital rates. These patterns are similar to those observed in other species with similar life histories. We did not observe contrasting effects of any vital rate on ? and N(e); thus, management actions that increase the ? of populations of Austrian dragonhead will not increase genetic drift. Our results show that elasticity analyses of N(e) and N(a) can complement elasticity analysis of ?. Moreover, such analyses do not require more data than standard matrix models of population dynamics. PMID:22268810

Andrello, Marco; Nicolè, Florence; Till-Bottraud, Irène; Gaggiotti, Oscar E

2012-04-01

194

Population growth and the enclosure movement in Ankole, Uganda.  

PubMed

There is a rush for people to fence their land in West and East Ankole, Uganda, and fenced fields now represent close to 15% of the total land area and 30% of the area that is used for grazing. Since fencing is allowed only after a person is in possession of a valid land title, the acceptance of this innovation means the acceptance of noncustomary tenurial arrangements in the area. This paper contends that the primary drive of the fencing movement is insecurity about land. This insecurity is the outcome of the rapid increase of both the human and livestock population of the area. Discussion covers the land and the people, contemporary land tenure systems, the enclosure movement, land pressure, and the rise of modern pastoralism. The 2 districts of West and East Ankole comprise a total land area of 16,182 km; roughly 1000 km of this is classified as forest and game reserve. In general a typical landholding of an individual in West Ankole is about 2 hectares and is roughly equally divided between perennial and annual crops. Land in Ankole is either privately held or is vested in the Public Land Commission. Privately held land falls into 2 major categories: land can be surveyed, registered, and then granted as either freehold or leasehold. Freehold land in Ankole is of 3 main types: grants or freehold land can be made out to each of the religious sects in the area; grants of freehold land can be made to individuals out of what is commonly referred to as "Mailo" land; privately held land under lease from the Uganda Public Land Commission, or prior to independence from the British Crown. The bulk of Ankole land is held under what is commonly referred to as customary tenure. Under this arrangement, all the land is vested in the Uganda Public Land Commission, which acts as an umbrella under whose protection land is freely used as the customs of the Banyankore stipulate. Over the past decade, Ankole has experienced a marked increase in its human population. The population increased from 530,000 in 1959 to more than 1 million in 1974. Migration as well as natural increase has been a significant factor. The rapid increase of population in Ankole has resulted in considerable densities in several localities. Due to increases both in the human and livestock populations, incidents of land pressure in the area have become quite common. Several people feel insecure about land. Individuals who have ample land around them are fencing it since this is the way that fields can go fallow and pasturage ensured. In most instances fencing is being carried out on land where signs of effective ownership do not exist. There is also a realization that through segregated grazing that better quality animals can be obtained. PMID:12265055

Muwonge, J W

1978-01-01

195

[It is imperative to control population growth in a planned way].  

PubMed

To facilitate modernization and prosperity of the Chinese nation, it is important that population growth be curbed in a planned way so as to correspond to the development of the national economy, and to stabilize the population at about 1.2 billion people by the year 2000. The 1-child policy should be strongly advocated. Currently, young people under 21 years old constitute 50% of the total population; 20 million of them are expected to get married and bear children each year before the end of this century, contributing to a high birth rate if allowed to remain unchecked. The 1-child policy is the best method for reducing birth rate and ensuring zero population growth in the year 2000. Because of strong leadership by authorities over family planning, the rate of natural population growth in this country has been lowered at a fairly rapid pace from 23.4/1000 in 1971 to the current 12/1000. Population growth rate in many provinces and municipalities is continually declining, and the masses have raised their consciousness of practicing family planning. Evidence has strongly indicated that broad masses of people have indeed fully understood the close relationship between childbirth, the realization of the 4 modernizations, and happy life for many generations to come. Because of the volume of work involved in enforcing family planning policies, authorities at all levels should strengthen their leadership and place high priority on family planning and population growth control. Emphasis should also be given on various methods to vigorously publicize the relations between family planning and the realization of the 4 modernizations, to publicize the country's goals and measures to control population growth, to continuously eliminate the decadent concept of the superiority of the male child, and to publicize the benefits of a 1-child family. Particular attention should also be given to 800 million people living in rural areas. PMID:12263994

1980-02-15

196

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

197

Urban population growth: implications for India and South Asia.  

PubMed

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

Murickan, J

1974-01-01

198

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

199

Growth of deleterious mutant genes in a large population.  

PubMed

Formulae for the arrival probability and first arrival time for a single mutant gene to reach a certain number have been obtained by using a continuous branching process. If the mean of the progeny number of heterozygotes is less than one the arrival probability increases with increasing variance of the progeny distribution whereas if the mean is greater than one the contrary is true. Since most human populations are growing at fairly high rates, the result indicates that the probability for a single mutation to grow to a large number is quite high. Numerical computations show that the mean first arrival time decreases with increasing variance of the progeny distribution of the mutant carriers. The results have been applied to investigate the case of the acheiropodia gene in Brazil. The hypothesis that all acheiropodia genes in Brazil were derived from a single mutation seems to be tenable. PMID:952486

Li, W H

1976-05-01

200

A MULTI-PATCH MALARIA MODEL WITH LOGISTIC GROWTH POPULATIONS.  

PubMed

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

Gao, Daozhou; Ruan, Shigui

2012-01-01

201

Regional viewpoints on population growth: perspectives of the genocide issue.  

PubMed

Genocide implies an effort by the white races to reduce the number of or eliminate the colored races. In Africa the belief that family planning is a way of advocating genocide combines with the problem of lack of real experts in the field of family planning and of disproportionate allocation of funds to this area without regard to the goals of overall development. Additionally, some methods of fertility control are recommended by foreign "experts" which may be culturally unacceptable. In spite of these problems population programs are advancing in Africa. In order to be more readily acceptable, however, they will have to be considered within the global context of overall development, and they will have to be carried out largely by national personnel with international aid and international personnel remaining in the background. PMID:4788253

Sai, F T

1973-01-01

202

The ocean blues. Navigating the course of population growth.  

PubMed

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

Sarkar, D

1996-01-01

203

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

PubMed

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

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

2014-06-01

204

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

205

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

PubMed Central

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

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

2013-01-01

206

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

PubMed

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

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

2011-08-01

207

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

208

Neutral genomic regions refine models of recent rapid human population growth  

PubMed Central

Human populations have experienced dramatic growth since the Neolithic revolution. Recent studies that sequenced a very large number of individuals observed an extreme excess of rare variants and provided clear evidence of recent rapid growth in effective population size, although estimates have varied greatly among studies. All these studies were based on protein-coding genes, in which variants are also impacted by natural selection. In this study, we introduce targeted sequencing data for studying recent human history with minimal confounding by natural selection. We sequenced loci far from genes that meet a wide array of additional criteria such that mutations in these loci are putatively neutral. As population structure also skews allele frequencies, we sequenced 500 individuals of relatively homogeneous ancestry by first analyzing the population structure of 9,716 European Americans. We used very high coverage sequencing to reliably call rare variants and fit an extensive array of models of recent European demographic history to the site frequency spectrum. The best-fit model estimates ?3.4% growth per generation during the last ?140 generations, resulting in a population size increase of two orders of magnitude. This model fits the data very well, largely due to our observation that assumptions of more ancient demography can impact estimates of recent growth. This observation and results also shed light on the discrepancy in demographic estimates among recent studies.

Gazave, Elodie; Ma, Li; Chang, Diana; Coventry, Alex; Gao, Feng; Muzny, Donna; Boerwinkle, Eric; Gibbs, Richard A.; Sing, Charles F.; Clark, Andrew G.; Keinan, Alon

2014-01-01

209

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

210

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

PubMed Central

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

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

2013-01-01

211

Detecting population growth, selection and inherited fertility from haplotypic data in humans.  

PubMed Central

The frequency of a rare mutant allele and the level of allelic association between this allele and one or several closely linked markers are frequently measured in genetic epidemiology. Both quantities are related to the time elapsed since the appearance of the mutation in the population and the intrinsic growth rate of the mutation (which may be different from the average population growth rate). Here, we develop a method that uses these two kinds of genetic data to perform a joint estimation of the age of the mutation and the minimum growth rate that is compatible with its present frequency. In absence of demographic data, it provides a useful estimate of population growth rate. When such data are available, contrasts among estimates from several loci allow demographic processes, affecting all loci similarly, to be distinguished from selection, affecting loci differently. Testing these estimates on populations for which data are available for several disorders shows good congruence with demographic data in some cases whereas in others higher growth rates are obtained, which may be the result of selection or hidden demographic processes.

Austerlitz, Frederic; Kalaydjieva, Luba; Heyer, Evelyne

2003-01-01

212

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

PubMed Central

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

2014-01-01

213

Existence of limit cycles in the Solow model with delayed-logistic population growth.  

PubMed

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

Bianca, Carlo; Guerrini, Luca

2014-01-01

214

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

Microsoft Academic Search

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

Christopher R. Webster; Michael A. Jenkins

2008-01-01

215

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

USGS Publications Warehouse

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

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

2006-01-01

216

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

217

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

218

On the Exponentiated Weibull Distribution  

Microsoft Academic Search

The important extension of the Weibull family—the exponentiated Weibull distribution—is reviewed with various new statistical measures. An explicit expression for the mode is derived and a comparison between the authors'and Mudholkar and Hutson's results are tabulated for various values of the parameters of the distribution. A general formula for the mean residual life function is obtained.

Manal M. Nassar; Fathy H. Eissa

2003-01-01

219

Quantum properties of exponential states  

SciTech Connect

The use of Renyi entropy as an uncertainty measure alternative to variance leads to the study of states with quantum fluctuations below the levels established by Gaussian states, which are the position-momentum minimum uncertainty states according to variance. We examine the quantum properties of states with exponential wave functions, which combine reduced fluctuations with practical feasibility.

Luis, Alfredo [Departamento de Optica, Facultad de Ciencias Fisicas, Universidad Complutense, 28040 Madrid (Spain)

2007-05-15

220

Analysis of rounded exponential data  

Microsoft Academic Search

The problem of inference based on a rounded random sample from the exponential distribution is treated. The main results are given by an explicit expression for the maximum-likelihood estimator, a confidence interval with a guaranteed level of confidence, and a conjugate class of distributions for Bayesian analysis. These results are exemplified on two concrete examples. The large and increasing body

Gunnar Taraldsen

2011-01-01

221

Exponential Finite-Difference Technique  

NASA Technical Reports Server (NTRS)

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

Handschuh, Robert F.

1989-01-01

222

Linear or Exponential Number Lines  

ERIC Educational Resources Information Center

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

Stafford, Pat

2011-01-01

223

Conjugate Priors for Exponential Families  

Microsoft Academic Search

Let $X$ be a random vector distributed according to an exponential family with natural parameter $\\\\theta \\\\in \\\\Theta$. We characterize conjugate prior measures on $\\\\Theta$ through the property of linear posterior expectation of the mean parameter of $X : E\\\\{E(X|\\\\theta)|X = x\\\\} = ax + b$. We also delineate which hyperparameters permit such conjugate priors to be proper.

Persi Diaconis; Donald Ylvisaker

1979-01-01

224

Population versus Customized Fetal Growth Norms and Adverse Outcomes in an Intrapartum Cohort  

PubMed Central

Objective To compare population versus customized fetal growth norms in identifying neonates at risk for adverse outcomes (APO) associated with small for gestational age (SGA). Study Design Secondary analysis of an intrapartum fetal pulse oximetry trial in nulliparous women at term. Birthweight percentiles were calculated using ethnicity- & gender-specific population norms and customized norms (Gardosi). Results 508 (9.9%) and 584 (11.3%) neonates were SGA by population (SGApop) and customized (SGAcust) norms. SGApop infants were significantly associated with a composite adverse neonatal outcome, neonatal intensive care admission, low fetal oxygen saturation and reduced risk of cesarean delivery; while both SGApop and SGAcust were associated with a 5-minute Apgar score < 4. The ability of customized and population birthweight percentiles in predicting APO was poor (12 out of 14 APOs had AUC <0.6). Conclusion In this intrapartum cohort, neither customized nor normalized-population norms adequately identify neonates at risk of APO related to SGA.

Costantine, Maged M.; Lai, Yinglei; Bloom, Steven L.; Spong, Catherine Y.; Varner, Michael W.; Rouse, Dwight J.; Ramin, Susan M.; Caritis, Steve N.; Peaceman, Alan M.; Sorokin, Yoram; Sciscione, Anthony; Mercer, Brian M.; Thorp, John M.; Malone, Fergal D.; Harper, Margaret; Iams, Jay D.

2013-01-01

225

Analytic Modeling with Matrix Exponential Distributions  

Microsoft Academic Search

In this paper, we review matrix exponential distributions and Linear Algebra Queueing Theory. The ma- trix exponential distribution is very powerful and has useful properties that allow it to be used in the construction of gen- eral analytic models. We show how common distributions can be represented exactly as matrix exponential distribu- tions. We also show how matrix exponential distributions

K. Mitchell; A. van de Liefvoort

1995-01-01

226

Simple quasi-exponential slope generator  

NASA Technical Reports Server (NTRS)

Circuitry for digitally generating an exponentially decaying wave function permits discrete values to be sampled from the exponential waveform for comparison with a binary number of specified accuracy. This exponential-decay generator employs a simple binary counter to count in the sequence of exponential decay.

Anderson, T. O.; Hurd, W. J.

1969-01-01

227

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

PubMed

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

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

2007-06-01

228

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

Microsoft Academic Search

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

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

2001-01-01

229

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

Microsoft Academic Search

An investigation was made of factors controlling algal succession in a small, oligotrophic lake during summer stratification. Weekly measurements were made of growth rate, sedimentation rate, and population density for each of the dominant phytoplankton species. Weekly diel measurements were made of zooplankton grazing rates using ¹⁴C labeled algae. Cyclotella michiganiana was the dominant algae through the end of June

Crumpton

1980-01-01

230

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...

231

Demography and population growth of Asplanchna girodi (Rotifera) as a function of prey (Anuraeopsis fissa) density  

Microsoft Academic Search

Laboratory studies on population growth and life table demography of Asplanchna girodi were conducted at 25±1 °c using Anuraeopsis fissa as prey at four (250, 500, 1000 and 2000 ind ml-1) densities. A prey density of 100 ind ml-1 per predator per day did not support A. girodi, while at the highest prey concentration, A. girodi reached a peak of

H. J. Dumont; S. S. S. Sarma

1995-01-01

232

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

233

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

234

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

PubMed

Theoretical and empirical issues are explored as related to the extent to which population growth, particularly population redistribution through internal migration, may influence land use patterns and the deterioration of natural resources. Conceptual approaches are presented including a model of the relationships among population growth, migration, and the rural environment. Population growth has direct effects on increased demand for fuelwood and food and land fragmentation. Indirect effects exist through the demand for food which puts pressure on land extensification and intensification which affects soil quality and out migration which affect deforestation and desertification. The prevailing natural resource endowments affect the extent to which extensification of intensification of agriculture takes place in a given time period, the forms in which it occurs, and whether demographic factors play a significant role. Current trends are described for population growth and redistribution, agricultural expansion, and deforestation, desertification, and soil erosion in low-income counties. Data are for 1990 in Asia (23), Latin American (23), and Africa (39) for 85 countries with a population 1 million. Also described are cross-country relationships and the implications. In Africa population growth rates have not changed substantially and the pressure on resources is significant, while dramatic declines have occurred in east and southeast Asia, in Latin America, population growth has changed considerably. Consequences of socioeconomic development are declines in the % of gross domestic product from agriculture and the agricultural labor force. Only Thailand, Nepal, Indonesia, and North Korea out of 23 Asian countries had increases in the % of total land used for agriculture and this resulted in deforestation. Levels were already high in 1965, with 8 countries having 20% of land in agricultural use and 4 countries having 15% in agricultural use. In Bangladesh and Indian 50% of land is used for agriculture. Latin American has lower levels of agricultural land use; Bolivia and Paraguay increased land use by 100%, Nicaragua, Bolivia, and Paraguay by 50%, and 8 others by 20-50%. Africa has a small amount of agricultural land, with only 10 countries having 15% in agriculture. Irrigation and fertilization patterns are also described. Scattergrams are used to express the relationship between deforestation and increase agricultural land. The policy implications are specifically identified, and in general better data within countries and micro data (household surveys) are needed on resource depletion; national accounts need to include an appropriate computation for this. PMID:12158965

Bilsborrow, R E

1992-01-01

235

Growth and competitive effects of Centaurea stoebe populations in response to simulated nitrogen deposition.  

PubMed

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

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

2012-01-01

236

Relative tibia long bone growth in the Libben and Bt-5 prehistoric skeletal populations.  

PubMed

Patterns of tibia long bone growth were examined for the Libben Late Woodland and Bt-5 Late Archaic hunter-gatherer skeletal groups. Subadults included in the analyses ranged in age from birth to 10 years. The primary goals were to identify potential differences in relative tibia growth and evaluate the extent to which such differences were concordant with demographic and epidemiological characteristics of the two groups. Methods used were designed to minimize the shortcomings of unknown age and sex of the skeleton, small sample sizes, and population differences in adult size attained. Results showed that Bt-5 preadolescent growth performance and health status in general were superior to those of the Libben group. Modifications in the rate and timing of Libben tibia growth occurred early and were primarily restricted to the weaning period. It is suggested that high levels of infectious disease experienced in the first years of life at Libben played a substantial role in the etiology of early long bone growth retardation, a greater prevalence of iron deficiency anemia in the childhood years, and elevated levels of subadult morbidity and mortality compared to Bt-5. Paleodemographic, paleoepidemiological, and modern comparative population data that support these inferences are discussed. No evidence of chronic malnutrition owing to dietary inadequacy was observed for either group. Alternatively, higher population density and greater degree of sedentism alone may have been responsible for elevated disease loads at Libben compared to low levels that were observed for the seasonally mobile semisedentary Bt-5 hunter-gatherers. PMID:4061614

Mensforth, R P

1985-10-01

237

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

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

238

Modelling for prediction of global deforestation based on the growth of human population  

NASA Astrophysics Data System (ADS)

Deforestation due to ever-increasing activities of the growing human population has been an issue of major concern for the global environment. It has been especially serious in the last several decades in the developing countries. A population-deforestation model has been developed by the authors to relate the population density with the cumulative forest loss, which is defined and computed as the total forest loss until 1990 since prior to human civilisation. NOAA-AVHRR-based land cover map and the FAO forest statistics have been used for 1990 land cover. A simulated land cover map, based on climatic data, is used for computing the natural land cover before the human impacts. With the 1990 land cover map as base and using the projected population growth, predictions are then made for deforestation until 2025 and 2050 in both spatial and statistical forms.

Pahari, Krishna; Murai, Shunji

239

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

240

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

241

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

PubMed Central

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

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

2010-01-01

242

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

PubMed

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

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

2000-03-01

243

Population growth of soybean aphid, Aphis glycines, under varying levels of predator exclusion.  

PubMed

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

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

2010-01-01

244

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

PubMed Central

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

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

2011-01-01

245

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

PubMed Central

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

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

2013-01-01

246

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

PubMed

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

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

2010-03-01

247

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

PubMed Central

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

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

2010-01-01

248

Comparative population growth of Ceriodaphnia dubia and Daphnia pulex (Cladocera) exposed to zinc toxicity.  

PubMed

Population growth of two cladocerans (Ceriodaphnia dubia and Daphnia pulex) exposed to 4 different concentrations of ZnCl(2) (0.125, 0.25, 0.5 and 1.0 mg L(-1), plus controls) at one algal food (Scenedesmus acutus) density (0.5 X 10(6) cells mL(-1)) was quantified for 30 days. Population densities of C. dubia and D. pulex decreased with increasing concentration of Zn in the medium. At a concentration of 1 mg L(-1) of ZnCl(2), both C. dubia and D. pulex did not reproduce and died within a week. The peak population densities of C. dubia ranged from 0.2 to 6.0 ind. mL(-1), depending on the Zn level in the medium, whereas this range was lower for D. pulex (0.2 to 4.1 ind. mL(-1)). The peak population density was inversely related to the Zn concentration. The rate of population increase (r) varied from -0.12 to +0.14 and -0.02 to +0.23 per day for C. dubia and D. pulex, respectively, depending on the Zn level in the medium. Statistically, both the peak population density and the r were significantly affected by the heavy metal concentration in the medium. Multiple comparison tests showed that the rate of population increase (r) of D. pulex in the lowest ZnCl(2) level (0.125 mg L(-1)) was significantly higher than controls. However, under similar conditions, the r of C. dubia was significantly lower than controls. With a further increase in Zn level, the growth rates of both the cladoceran species were significantly reduced as compared to controls. The results are discussed in relation to published data on the toxicity of zinc to freshwater zooplankton. PMID:20390839

Sanchez-Ortiz, Jonathan Raul; Sarma, S S S; Nandini, S

2010-01-01

249

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

PubMed Central

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

1992-01-01

250

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

SciTech Connect

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

Lyashenko, O.I.

1995-12-10

251

F-LE Exponential Functions  

NSDL National Science Digital Library

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

252

Exponential Formulae and Effective Operations  

NASA Technical Reports Server (NTRS)

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

Mielnik, Bogdan; Fernandez, David J. C.

1996-01-01

253

Differences in population growth of rotifers and cladocerans raised on algal diets supplemented with yeast  

Microsoft Academic Search

We studied the population growth of two rotifer (Brachionus calyciflorus and Brachionus rubens) and two cladoceran (Ceriodaphnia dubia and Moina macrocopa) species fed three diets (Chlorella vulgaris (Ch), Scenedesmus acutus (Sc) and yeast (Saccharomyces cerevisiae) (Y) in seven combinations (alone or mixed in equal proportions (on dry weight basis): Ch+Sc, Ch+Y, Sc+Y and Ch+Sc+Y). In general, the cladocerans were more

Fabiola Peña-Aguado; S. Nandini; S. S. S. Sarma

2005-01-01

254

POPULATION GROWTH OF EUCHLANIS DILATATA (ROTIFERA): COMBINED EFFECTS OF METHYL PARATHION AND FOOD (CHLORELLA VULGARIS)  

Microsoft Academic Search

In the present work, the combined impact of four concentrations (0, 0.0625, 0.125, and 0.25 mg\\/L) of methyl parathion and three densities (0.5 × 10, 1.0 × 10, and 2.0 × 10 cells\\/mL) of the green alga Chlorella vulgaris on the population growth of Euchlanis dilatata was studied. In general, regardless of the food level, an increase in the concentration

S. S.S. Sarma; S. Nandini; José L. Gama-Flores; M. A. Fernandez-Araiza

2001-01-01

255

Population growth of some genera of cladocerans (Cladocera) in relation to algal food ( Chlorella vulgaris ) levels  

Microsoft Academic Search

We studied the patterns of population growth of 7 cladoceran species (Alona rectangula, Ceriodaphnia dubia, Daphnia laevis, Diaphanosoma brachyurum, Moina macrocopa, Scapholeberis kingi and Simocephalus vetulus) using 6 algal densities, viz. 0.05×106, 0.1×106, 0.2×106, 0.4×106, 0.8×106 and 1.6×106 cells ml-1, of Chlorella vulgaris for 18 – 30 days. In terms of carbon content these algal concentrations corresponded to 0.29, 0.58,

S. Nandini; S. S. S. Sarma

2003-01-01

256

Heterogeneous population growth, parental effects and genotype–environment interactions of a marine oligochaete  

Microsoft Academic Search

Cultures of asexually reproducing populations of the oligochaete Paranaislitoralis (Müller) collected from six different patches (3 to 50?m apart) on an intertidal mud flat in Flax Pond, New York, on two\\u000a occasions, June and October 1993, showed significant differences among lines in life span, number of offspring produced, and\\u000a in finite rate of increase (?). Although growth rates were significantly

P. Nilsson; J. P. Kurdziel; J. S. Levinton

1997-01-01

257

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

Microsoft Academic Search

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

R. Pradel

258

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

PubMed Central

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

Picard, Nicolas; Liang, Jingjing

2014-01-01

259

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

PubMed

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

Picard, Nicolas; Liang, Jingjing

2014-01-01

260

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

USGS Publications Warehouse

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

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

2000-01-01

261

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

PubMed Central

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

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

2006-01-01

262

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

PubMed

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

Shaw, R P

1992-02-01

263

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

PubMed

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

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

2007-01-01

264

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

USGS Publications Warehouse

The relative importance of genetic, demographic, environmental, and catastrophic processes that maintain population bottlenecks has received little consideration. We evaluate the role of these factors in maintaining the Puerto Rican Parrot (Amazona vittata) in a prolonged bottleneck from 1973 through 2000 despite intensive conservation efforts. We first conduct a risk analysis, then examine evidence for the importance of specific processes maintaining the bottleneck using the multiple competing hypotheses approach, and finally integrate these results through a sensitivity analysis of a demographic model using life-stage simulation analysis (LSA) to determine the relative importance of genetic, demographic, environmental, and catastrophic processes on population growth. Annual population growth has been slow and variable (1.0 6 5.2 parrots per year, or an average k?1.05 6 0.19) from 16 parrots (1973) to a high of 40-42 birds (1997-1998). A risk analysis based on population prediction intervals (PPI) indicates great risk and large uncertainty, with a range of 22?83 birds in the 90% PPI only five years into the future. Four primary factors (reduced hatching success due to inbreeding, failure of adults to nest, nest failure due to nongenetic causes, and reduced survival of adults and juveniles) were responsible for maintaining the bottleneck. Egghatchability rates were low (70.6% per egg and 76.8% per pair), and hatchability increased after mate changes, suggesting inbreeding effects. Only an average of 34% of the population nested annually, which was well below the percentage of adults that should have reached an age of first breeding (41-56%). This chronic failure to nest appears to have been caused primarily by environmental and/or behavioral factors, and not by nest-site scarcity or a skewed sex ratio. Nest failure rates from nongenetic causes (i.e., predation, parasitism, and wet cavities) were low (29%) due to active management (protecting nests and fostering captive young into wild nests), diminishing the importance of nest failure as a limiting factor. Annual survival has been periodically reduced by catastrophes (hurricanes), which have greatly constrained population growth, but survival rates were high under non-catastrophic conditions. Although the importance of factors maintaining the Puerto Rican Parrot bottleneck varied throughout the 30-year period of study, we determined their long-term influence using LSA simulations to correlate variation in demographic rates with variation in population growth (k). The bottleneck appears to have been maintained primarily by periodic catastrophes (hurricanes) that reduced adult survival, and secondarily by environmental and/or behavioral factors that resulted in a failure of many adults to nest. The influence of inbreeding through reduced hatching success played a much less significant role, even when additional effects of inbreeding on the production and mortality of young were incorporated into the LSA. Management actions needed to speed recovery include (1) continued nest guarding to minimize the effects of nest failure due to nongenetic causes; (2) creating a second population at another location on the island --a process that was recently initiated--to reduce the chance that hurricane strikes will cause extinction; and (3) determining the causes of the low percentage of breeders in the population and ameliorating them, which would have a large impact on population growth.

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

2008-01-01

265

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

PubMed Central

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

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

2008-01-01

266

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

NASA Astrophysics Data System (ADS)

Urban growth and sprawl have drastically altered the ecosystems and ecosystem services. Urban areas are an increasingly important component of the global environment, yet they remain one of the most challenging areas for conducting research. Remote sensing based information is one of the most important resources to support urban planning and administration in megacities. It is possible to provide the up-to-date information regarding the extent, growth, and physical characteristics of urban land. Remote sensing provides spatially consistent image information that covers broad areas with both high spatial resolution and high temporal frequency. Therefore, remote sensing is an important tool for providing information on urban land-cover characteristics and their changes over time at various spatial and temporal scales. Urban land-use and land-cover changes are linked to socio-economic activities. Urbanization includes both the physical growth of a city and the movement of people to urban areas. As a consequence, it is essential to combine remote sensing derived parameters with socio-economic parameter to analyze the spatial-temporal changes and interaction of both factors. The aim of the research was to use1-km2 grid cells to investigate the spatial and temporal dynamics of urban growth in the world mega cities. The research was conducted in the 50 global cities using Landsat ETM/TM remote sensing imagery from 1985 - 2011, and time series population census data (1-km2 resolution gridded population census data of Japan and 2.5 arc-minute resolutions Gridded Population of the World). First, maximum likelihood classification (MLC) method were used to produce land cover maps by using Landsat images. Then intersect the land cover maps with 1-km2 grid cell maps to represents the proportion of each land cover category within each 1-km2 grid cell. Finally, we combined the proportional land cover maps with gridded population census data on 1-km2 resolution grid cells to investigate the spatial relationships between the changes of land-cover classes and changes of population density. A case study in Tokyo, Japan and Beijing, China were provided. The results showed that the urban area decreased in the metropolitan inner core as the city center experienced depopulation in Tokyo. Spatial correlation analysis showed a strong positive correlation between urban expansion and population density change and that urban expansion was strongly negatively correlated with cropland change both in Tokyo and Beijing. Time series of land-cover maps of the Tokyo in 1987, 2001, and 2011. Urban B. refers to the urban/built-up class. The black lines indicate the major railway and metro lines. Five broad land-cover categories;

Bagan, H.; Yamagata, Y.

2012-12-01

267

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

268

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

PubMed

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

Rhein, E

1994-08-25

269

[The impact of population growth on Tamba Kosi, a Himalayan valley in Nepal].  

PubMed

Two several-month-long stays in the isolated Tamba Kosi valley in Nepal in 1983 and 1986 allowed an assessment of the importance of changes in rural societies. In about 50 years, the oldest inhabitants of some villages have seen the number of houses quadruple. In the absence of reliable statistical data, the inhabitants say that the Tamba Kosi valley population has doubled in the last 25 years. This population growth exacerbates the multiethnic fight for good land (i.e., ground of modest slope, hot, and humid). Many people have emigrated, which has somewhat eased problems relative to population growth. Soil degradation, which is becoming more and more acute, drives the inhabitants to cut down trees and clear the land for cultivation of new plots. These new plots are running up against steep slopes and high altitude. Most families have barely two hectares, which must suffice to feed 5-6 people on average. This fuels intensification of agricultural production, resulting in low efficacy. Livestock mutilate forests with their hooves and teeth. The marked increase in the variety of livestock accelerates this destruction. Three types of building materials are used in this high valley: thatch, shingles (fir tree), and bamboo matting. The disappearance of wild grasses used to make thatch roofs and people moving to higher and higher altitudes resulted in use of shingles to make roofs. Buildings made of shingles, which demanded changes in construction techniques, changed the conception of homes. They became the preferred building type, which increased the demand for fir trees and deforestation. This lead to a demand for roofing material made of bamboo matting and another change in construction techniques. The retreat of the forest and disappearance of the most wanted plant species are the most spectacular impacts of population growth. This environmental degradation exacerbates erosion at all bioclimatic altitudes. PMID:12319796

Verliat, S

1994-01-01

270

Integrating physiological and biomechanical drivers of population growth over environmental gradients on coral reefs.  

PubMed

Coral reefs exhibit marked spatial and temporal variability, and coral reef organisms exhibit trade-offs in functional traits that influence demographic performance under different combinations of abiotic environmental conditions. In many systems, trait trade-offs are modelled using an energy and/or nutrient allocation framework. However, on coral reefs, differences in biomechanical vulnerability have major demographic implications, and indeed are believed to play an essential role in mediating species coexistence because highly competitive growth forms are vulnerable to physical dislodgment events that occur with high frequency (e.g. annual summer storms). Therefore, an integrated energy allocation and biomechanics framework is required to understand the effect of physical environmental gradients on species' demographic performance. However, on coral reefs, as in most ecosystems, the effects of environmental conditions on organisms are measured in different currencies (e.g. lipid accumulation, survival and number of gametes), and thus the relative contributions of these effects to overall capacity for population growth are not readily apparent. A comprehensive assessment of links between the environment and the organism, including those mediated by biomechanical processes, must convert environmental effects on individual-level performance (e.g. survival, growth and reproduction) into a common currency that is relevant to the capacity to contribute to population growth. We outline such an approach by considering the population-level performance of scleractinian reef corals over a hydrodynamic gradient, with a focus on the integrating the biomechanical determinants of size-dependent coral colony dislodgment as a function of flow, with the effects of flow on photosynthetic energy acquisition and respiration. PMID:22357590

Madin, Joshua S; Hoogenboom, Mia O; Connolly, Sean R

2012-03-15

271

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

PubMed Central

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

Nicole, Florence; Jacquemyn, Hans; Tuljapurkar, Shripad

2013-01-01

272

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

PubMed Central

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

Worku, Alemayehu

2009-01-01

273

Genetic correlations among growth, feed, and carcass traits of broiler sire and dam populations.  

PubMed

Genetic correlations based on sire variance and covariance components were estimated for broiler traits. Data were collected from various selected and control strains of sire and dam populations during five generations of selection. Results of analyses of variance for each of the strains within generations and populations were pooled across strains and generations. Correlations between body and carcass weights were all above .8. Weight gain (WG) had similar correlations with these traits with the exception of body weight at 28 days (.57 in site and .69 in dam populations). Body and carcass weights and WG had high correlations with feed consumption (FC) (greater than .7); however, values for feed efficiency (FE) varied: -.58, -.23 for 28-day body weight; -.17, .16 for 42-day body weight; .25, .43 for WG; and .53 in the dam population for carcass weight. Correlations of body and carcass weights and WG with abdominal fat weight (AFW) and percentage (AFP) were generally small to moderate with values being about half as large for AFP as for AFW. Feed consumption and FE were negatively correlated (-.51, -.22) in both populations. In the dam population, FC was positively correlated with AFW and AFP (.42, .55) but FE was negatively correlated with these traits (-.41, -.70). Abdominal fat weight and AFP were highly correlated (.99, .97). Values tended to be similar not only for these populations but also for this and other studies. Simultaneous genetic improvement of growth rate, FE and carcass leanness is feasible in broilers. Selection for WG, FE, and AFP should be effective. PMID:1876548

Wang, L Z; McMillan, I; Chambers, J R

1991-04-01

274

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

PubMed

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

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

2007-01-01

275

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

PubMed Central

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

Haase, Dagmar; Kabisch, Nadja; Haase, Annegret

2013-01-01

276

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

PubMed

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

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

2011-12-01

277

Population Growth and Development in the Chesapeake Bay Watershed to the Year 2020: The Report of the 2020 Panel to the Chesapeake Executive Council.  

National Technical Information Service (NTIS)

Analyzes the environmental effects of population growth upon the Bay and recommends a series of actions to concentrate development in suitable areas, protect sensitive areas, direct growth to existing population centers in rural areas and protect resource...

1988-01-01

278

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

NASA Astrophysics Data System (ADS)

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

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

2010-03-01

279

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

Microsoft Academic Search

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

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

2001-01-01

280

Life-history evolution and density-dependent growth in experimental populations of yeast.  

PubMed

We studied the evolution of the correlation between growth rate r and yield K in experimental lineages of the yeast Saccharomyces cerevisiae. First, we isolated a single clone every approximately 250 generations from each of eight populations selected in a glucose-limited medium for 5000 generations at approximately 6.6 population doublings per day (20 clones per line × 8 lines) and measured its growth rate and yield in a new, galactose-limited medium (with ?1.3 doubling per day). For most lines, r on galactose increased throughout the 5000 generations of selection on glucose whereas K on galactose declined. Next, we selected these 160 glucose-adapted clones in the galactose environment for approximately 120 generations and measured changes in r and K in galactose. In general, growth rate increased and yield declined, and clones that initially grew slowly on galactose improved more than did faster clones. We found a negative correlation between r and K among clones both within each line and across all clones. We provide evidence that this relationship is not heritable and is a negative environmental correlation rather than a genetic trade-off. PMID:23206137

Jasmin, Jean-Nicolas; Zeyl, Clifford

2012-12-01

281

Field Study Comparing Growth and Viability of a Population of Phototrophic Bacteria  

PubMed Central

The growth and viability of an anoxygenic, phototrophic bacterial community in the hypolimnion of Zaca Lake, Calif., were compared throughout the summer. The community is dominated by a single species, “Thiopedia rosea,” that inhabits the entire hypolimnion (6 to 8 m) for approximately 11 months. Suboptimal conditions in the hypolimnion (extremely low light intensity, high or low H2S levels) result in zero or extremely low growth rates (doubling times > 1 month) for most of the population, most of the time, yet cells remain viable and capable of high specific growth rates (doubling times of 1 to 10 days) when placed under favorable conditions (higher light intensities and temperatures). We first conclude that phototrophic bacterial populations in situ may frequently exist in a viable yet nongrowing state. Second, the viability of cells is likely to be reduced with depth owing to higher concentrations of potentially toxic chemicals and to changes in the physiological state associated with the prolonged periods of darkness commonly found at the bottom of bacterial plates.

Folt, Carol L.; Wevers, Mary Jo; Yoder-Williams, Michael P.; Howmiller, Richard P.

1989-01-01

282

Mutational identification of fibroblast growth factor receptor 1 and fibroblast growth factor receptor 2 genes in craniosynostosis in Indian population  

PubMed Central

OBJECTIVE: The Objective of this study was to identify the association of mutation of fibroblast growth factor receptor 1 (FGFR1), FGFR2 genes with syndromic as well as non-syndromic craniosynostosis in Indian population. MATERIALS AND METHODS: Retrospective analysis of our records from January 2008 to December 2012 was done. A total of 41 cases satisfying the inclusion criteria and 51 controls were taken for the study. A total volume of 3 ml blood from the patient as well as parents was taken. Deoxyribonucleic acid extracted using phenol chloroform extraction method followed by polymerase chain reaction-restriction fragment length polymorphism method. RESULTS: There were 33 (80.4%) non-syndromic cases of craniosynostosis while 8 (19.5%) were syndromic. Out of these 8 syndromic cases, 4 were Apert syndrome, 3 were Crouzon syndrome and 1 Pfeiffer syndrome. Phenotypically the most common non-syndromic craniosynostosis was scaphocephaly (19, 57.7%) followed by plagiocephaly in (14, 42.3%). FGFR1 mutation (Pro252Arg) was seen in 1 (2.4%) case of non-syndromic craniosynostosis while no association was noted either with FGFR1 or with FGFR2 mutation in syndromic cases. None of the control group showed any mutation. CONCLUSION: Our study proposed that FGFR1, FGFR2 mutation, which confers predisposition to craniosynostosis does not exist in Indian population when compared to the western world.

Pandey, Rajeev Kumar; Bajpai, Minu; Ali, Abid; Gayan, Sukanya; Singh, Amit

2013-01-01

283

Effect of Intraspecific Density on Life History Traits and Population Growth Rate of 'Neanthes arenaceodentata' (Polychaeta: Nereidae) in the Laboratory.  

National Technical Information Service (NTIS)

The effects of intraspecific density on life history traits and population dynamics of the nereid polychaete Neanthes arenaceodentata Moore were assessed in a laboratory experiment. Survival, growth, and fecundity were measured for one generation of worms...

C. E. Pesch R. N. Zajac R. BB. Whitlatch M. A. Balboni

1987-01-01

284

In the national interest: the PCSD puts population growth back on the agenda.  

PubMed

In 1972, President Nixon launched the Rockefeller Commission on Population Growth and the American Future. The US population has grown by more than 50 million people since 1972. In 1995, a report by the President's Council on Sustainable Development (PCSD) states that failure on the part of the US to stabilize its population will jeopardize any effort to achieve sustainable development. As a follow-up to the Earth Summit, President Clinton established the PCSD in 1993 to identify ways to encourage sustainable development in the US. The Council has 25 members representing government, business, and public interest organizations and has 8 critical issues task forces, including Energy, Transportation, Sustainable Community, Education and Outreach, Natural Resources, Eco Efficiency and Sustainable Agriculture. Timothy Wirth, Under Secretary of State for Global Affairs, spearheaded efforts to create a task force on the twin issues of population and consumption. The Population and Consumption Task Force, which began its official discussions in the spring of 1994, aimed to solicit public comment on critical population-related issues. These meetings sought both general public and expert participation on subjects such as teen pregnancy, resource use, and economic indicators. Among these recommendations are improving access to family planning services for all Americans; focusing on special efforts to reduce teen pregnancy and childbearing; improving external factors such as poverty and a lack of economic opportunities for girls and women; and reducing immigration to the US. A combination of actions are needed, including a tax shift from labor and earnings to natural resource use; development of environmentally sound technologies; and public understanding of the importance of sustainable life style and consumption choices. Individual and community action is crucial since the current Congress is unlikely to adopt policies to promote sustainable development without significant public pressure. PMID:12320284

Dixon, B

1995-01-01

285

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

286

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

PubMed

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

Cruz-Rivera, Erica; Vasilieva, Olga

2013-02-01

287

Regression and inhibition of sarcoma growth by interference with a radiosensitive T-cell population.  

PubMed

BALB/c mice were inoculated subcutaneously with 10(6) cells from either of two syngeneic sarcomas 1315 and 1425. 6--8 days later, the mice were randomized into groups which were left untreated or given 400 rads of whole body irradiation. Irradiation significantly retarded the growth of both sarcomas, and complete regressions were seen of approximately equal to 30% of the small, established 1315 tumors. The anti-tumor effect of irradiation was abolished if the irradiated mice were inoculated with a T-cell-enriched (but not with a T-cell deprived) suspension of syngeneic spleen cells, suggesting that the irradiation inhibited tumor growth by affecting a radiosensitive population of host suppressor T cells. PMID:308987

Hellström, K E; Hellström, I; Kant, J A; Tamerius, J D

1978-09-01

288

Regression and inhibition of sarcoma growth by interference with a radiosensitive T-cell population  

PubMed Central

BALB/c mice were inoculated subcutaneously with 10(6) cells from either of two syngeneic sarcomas 1315 and 1425. 6--8 days later, the mice were randomized into groups which were left untreated or given 400 rads of whole body irradiation. Irradiation significantly retarded the growth of both sarcomas, and complete regressions were seen of approximately equal to 30% of the small, established 1315 tumors. The anti-tumor effect of irradiation was abolished if the irradiated mice were inoculated with a T-cell-enriched (but not with a T-cell deprived) suspension of syngeneic spleen cells, suggesting that the irradiation inhibited tumor growth by affecting a radiosensitive population of host suppressor T cells.

1978-01-01

289

[A model of world population growth as an experiment in systematic research].  

PubMed

A mathematical model was developed for the estimation of global population growth, and the estimates were compared with those of the UN and covered the stretch of 4.4 million years B.C. to the years 2175 and 2500 A.D. The estimates were also broken down into human, geological, and technological historical periods. The model showed that human population would stabilize at the level of 14 billion around 2500 A.D. and 13 billion around 2200 A.D., in accordance with UN projections. It also revealed the history of human population growth through the following stages (UN figures are listed in parentheses): 100,000, about 1.6 million years ago; 5 (1-5) million, 35,000 B.C.; 21 (10-15) million, 7000 B.C.; 46 (47) million, 2000 B.C.; 93 (100-230) million, at the time of Christ; 185 (275-345) million, 1000 A.D.; 366 (450-540) million, 1500 A.D.; 887 (907) million, 1800 A.D.; 1158 (1170) million, 1850 A.D.; 1656 (1650-1710) million, 1900 A.D.; 2812 (2515) million, 1950 A.D.; 5253 (5328) million, 1990 A.D.; 6265 (6261) million, 2000 A.D.; 10,487 (10,019) million, 2050 A.D.; 12,034 (11,186) million, 2100 A.D.; 12,648 (11,543) million, 2150 A.D.; 12,946 (11,600) million, 2200 A.D.; and 13,536 million, 2500 A.D. The model advanced the investigation of phenomena by studying the interactions between economical, technological, social, cultural, and biological processes. The analysis showed that humanity has reached a critical phase in its growth and that development in each period depended on external, not internal, factors. This permits the formulation of the principle of demographic imperative (distinct from the Malthusian principle), which states that resources determine the speed and extent of the growth of population. PMID:12293734

Kapitsa, S

1997-01-01

290

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

PubMed

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

Patterson, J G; Shrestha, N R

1988-01-01

291

Effects of salinity on growth and survival in five Artemia franciscana (Anostraca: Artemiidae) populations from Mexico Pacific Coast.  

PubMed

Salinity is an important factor influencing growth and survival of aquatic organisms such as Artemia, a valuable aquaculture species. This study evaluated the effects of salinity on A. franciscana populations from different water bodies in Mexico's Pacific Coast. With this purpose, five autochthonous bisexual Artemia populations were tested to assess their survival and growth values against salinities of 40, 60, 80, 100 and 120 g/l, under laboratory conditions (25 +/- 2 degrees C; pH 8-10; constant light and aeration). The organisms were fed with 100 mL of rice bran and 2L of Tetraselmis suecica (500 000 cel/ml). The culture experiments were made in 200L plastic tanks, and survival and growth final values were obtained after 21 culture days. Survival and growth curves were determined by a regression analysis (R2). The significant differences between salinities were determined by ANOVA test (p < 0.05). The best survival and growth rates were found at salinities of 100-120 g/l. When the Mexican Artemia populations were cultivated at 40 g/l of salinity, 100% mortality was observed in the juvenile stage. This study determined that survival and growth values of A. franciscana populations increased with salinity. The five A. franciscana populations presented significant differences in their survival rate under various salinity regimes. The studied populations experienced high mortality at salinities under 60 g/l and over 200 g/l, and especially during the metanauplius stage. The present study confirms that growth rates in Mexican A. franciscana populations from Pacific Coast habitats are not inversely proportional to salinity. These A. franciscana populations should be cultured at 100-120 g/l of salinity to obtain better survival and growth rates. This data is useful to improve culture systems in aquaculture biomass production systems. PMID:21513197

Castro-Mejía, Jorge; Castro-Barrera, Talía; Hernández-Hernández, Luis Héctor; Arredondo-Figueroa, José Luis; Castro-Mejía, Germán; de Lara-Andrade, Ramón

2011-03-01

292

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

PubMed

This summarizes population trends in the U.S.S.R. since the early 19 00's. On August 9, 1973, the population topped 250 million, almost precisely double that of Russia at the time of the 1st general census in 1897. Since 1922 it had increased by more than 84%. Russia has suffered more population loss in wars than any other country in modern times. The First World War, the Civil War, and the Second World War took a toll of more than 30 million, more than 20 million during the Second World War alone. The extent of these loses can be judged from the following: between 1897 and 1913 the population of Russia increased at the rate of 1.55% per annum or 34.6 million; if this had continued the population would have been at least 182.8 million by the end of 1922. As it was, the population was 136.1 million by 1922 and the hypothetical 182.8 million was not reached until 1952. More than 4/5 of today's population have been born since the October Revolution. Only 43 million were born before the revolution and only 7.5 were born in the last century. The economic base has grown much more rapidly than the population. For the period 1940-1972 the population increased 1.27 times, national income 9.51 times, fixed assets, 8.76 times, industrial production, 13.65 times, agricultural output, 2.14 times, and capital investment 14.52 times. The birthrate has been falling since World War 1 but total population growth has increased steadily. Birthrates have declined from 45.5/1000 in 1913 to 17.8/1000 in 1972 and a slight upturn is seen. It is expected that the birthrate will continue to increase slightly, then stabilize. Much of the population increase has come from significantly reduced mortality rates. 1st and 2nd children now account for 71% of all births. Family allowances, child care, free health care, and other social benefits encourage births while high employment levels for women, a shortage of men in the marriageable age ranges, and late marriages tend to depress the birthrate. The shortage of men is directly the result of the losses during World War 2. Employment opportunities have changed dramatically. The country has gone from a primarily agricultural nation to one in which 80% of the people are working class wage or salary earners. The current problem is closing the urban-rural gap and equalizing population density. 3/5 of the people are town-dwellers. To fight declining population in the villages and in the areas of Siberia and the Far East, new towns and new industrial and cultural centers are being established such as Bratsk, Ust-Ilim, Norilsk, and others. PMID:12307196

Simchera, V

1974-01-01

293

EXPONENTIAL GALAXY DISKS FROM STELLAR SCATTERING  

SciTech Connect

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

Elmegreen, Bruce G. [IBM Research Division, T.J. Watson Research Center, 1101 Kitchawan Road, Yorktown Heights, NY 10598 (United States)] [IBM Research Division, T.J. Watson Research Center, 1101 Kitchawan Road, Yorktown Heights, NY 10598 (United States); Struck, Curtis, E-mail: bge@watson.ibm.com, E-mail: curt@iastate.edu [Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States)] [Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States)

2013-10-01

294

Theory, computation, and application of exponential splines  

NASA Technical Reports Server (NTRS)

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

Mccartin, B. J.

1981-01-01

295

Exponential Galaxy Disks from Stellar Scattering  

NASA Astrophysics Data System (ADS)

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

Elmegreen, Bruce G.; Struck, Curtis

2013-10-01

296

Exponential Galaxy Disks from Stellar Scattering  

NASA Astrophysics Data System (ADS)

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

Elmegreen, Bruce; Struck, C.

2014-01-01

297

Population structure, growth and reproduction of introduced Pacific mullet, Mugil so-iuy, in the Black Sea  

Microsoft Academic Search

Population structure (age and sex composition), growth and reproduction of Pacific mullet (Mugil so-iuy) were determined from specimens collected on the eastern Turkish Black Sea coast during May–August 1995. The species has been introduced to Black Sea recently and the age composition of the newly established population varied between 1 and 6, with age group 4 dominant. Total length and

?brahim Okumu?; Nadir Ba?çinar

1997-01-01

298

Exponential ground impedance models and their interpretation  

NASA Technical Reports Server (NTRS)

The authors compare the results of Donato's exponentially varying ground model, Attenborough's exponentially varying ground model and the rigid backed thin layer model. They show that these models produce similar results for slow variations. For rapid variations the results are quite different, but the basic theory used is only correct for the thin layer model. These results suggest that the exponentially varying models are not necessary for fitting ground impedance data.

Raspet, Richard; Sprague, Mark

1990-01-01

299

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

NASA Astrophysics Data System (ADS)

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

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

1994-03-01

300

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

NASA Astrophysics Data System (ADS)

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

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

301

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

PubMed

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

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

2005-05-01

302

Mesoherbivores reduce net growth and induce chemical resistance in natural seaweed populations.  

PubMed

Herbivory on marine macroalgae (seaweeds) in temperate areas is often dominated by relatively small gastropods and crustaceans (mesoherbivores). The effects of these herbivores on the performance of adult seaweeds have so far been almost exclusively investigated under artificial laboratory conditions. Furthermore, several recent laboratory studies with mesoherbivores indicate that inducible chemical resistance may be as common in seaweeds as in vascular plants. However, in order to further explore and test the possible ecological significance of induced chemical resistance in temperate seaweeds, data are needed that address this issue in natural populations. We investigated the effect of grazing by littorinid herbivorous snails (Littorina spp.) on the individual net growth of the brown seaweed Ascophyllum nodosum in natural field populations. Furthermore, the capacity for induced resistance in the seaweeds was assessed by removing herbivores and assaying for relaxation of defences. We found that ambient densities of gastropod herbivores significantly reduced net growth by 45% in natural field populations of A. nodosum. Seaweeds previously exposed to grazing in the field were less consumed by gastropod herbivores in feeding bioassays. Furthermore, the concentration of phlorotannins (polyphenolics), which have been shown to deter gastropod herbivores, was higher in the seaweeds that were exposed to gastropod herbivores in the field. This field study corroborates earlier laboratory experiments and demonstrates that it is important to make sure that the lack of experimental field data on marine mesoherbivory does not lead to rash conclusions about the lack of significant effects of these herbivores on seaweed performance. The results strongly suggest that gastropods exert a significant selection pressure on the evolution of defensive traits in the seaweeds, and that brown seaweeds can respond to attacks by natural densities of these herbivores through increased chemical resistance to further grazing. PMID:17225156

Toth, Gunilla B; Karlsson, Malin; Pavia, Henrik

2007-05-01

303

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

PubMed Central

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

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

2013-01-01

304

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

NASA Astrophysics Data System (ADS)

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

Griffiths, Roberta J.

1981-01-01

305

Population dynamics of Gluconacetobacter diazotrophicus in sugarcane cultivars and its effect on plant growth.  

PubMed

Different experiments have estimated that the contribution of biological nitrogen fixation (BNF) is largely variable among sugarcane cultivars. Which bacteria are the most important in sugarcane-associated BNF is unknown. However, Gluconacetobacter diazotrophicus has been suggested as a strong candidate responsible for the BNF observed. In the present study, bacteria-free micropropagated plantlets of five sugarcane cultivars were inoculated with three G. diazotrophicus strains belonging to different genotypes. Bacterial colonization was monitored under different nitrogen fertilization levels and at different stages of plant growth. Analysis of the population dynamics of G. diazotrophicus strains in the different sugarcane varieties showed that the bacterial populations decreased drastically in relation to plant age, regardless of the nitrogen fertilization level, bacterial genotype or sugarcane cultivars. However, the persistence of the three strains was significantly longer in some cultivars (e.g., MEX 57-473) than in others (e.g., MY 55-14). In addition, some strains (e.g., PAl 5(T)) persisted for longer periods in higher numbers than other strains (e.g., PAl 3) inside plants of all the cultivars tested. Indeed, the study showed that the inoculation of G. diazotrophicus may be beneficial for sugarcane plant growth, but this response is dependent both on the G. diazotrophicus genotype and the sugarcane variety. The most positive response to inoculation was observed with the combination of strain PAl 5(T) and the variety MEX 57-473. Although the positive effect on sugarcane growth apparently occurred by mechanisms other than nitrogen fixation, the results show the importance of the sugarcane variety for the persistence of the plant-bacteria interaction, and it could explain the different rates of BNF estimated among sugarcane cultivars. PMID:14722690

Muñoz-Rojas, J; Caballero-Mellado, J

2003-11-01

306

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

USGS Publications Warehouse

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

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

2011-01-01

307

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

PubMed

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

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

2011-09-01

308

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

PubMed

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

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

2012-09-01

309

Effects of tag loss on direct estimates of population growth rate  

USGS Publications Warehouse

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

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

2005-01-01

310

Submarine slopes with an exponential curvature  

Microsoft Academic Search

The curvature of submarine slopes is a little used source of information on transport processes and sediment composition. In a survey of modern submarine slopes selected from all over the world, about 15% are characterized by very regular profiles with sharp shelfbreaks and concave-upward curvature. An exponential function describes this morphology very well. These exponential profiles are from three very

Erwin W. Adams; Wolfgang Schlager; Evert Wattel

1998-01-01

311

Discontinuous exponential stabilization of chained form systems  

Microsoft Academic Search

In this paper a novel approach to exponential stabilization of chained form system is proposed. Provided that the control law ful0lls mild assumptions, it is shown that a Brunovsky-like change of coordinates depending on the control transforms any chained form system into a system having a linearly bounded nonlinear part. Using linear tools, it is possible to exponentially stabilize a

Nicolas Marchand; Mazen Alamir

2003-01-01

312

Exponential Tethers for Accelerated Space Elevator Deployment  

Microsoft Academic Search

An exponential space elevator is a space elevator with a tether cross-section that varies exponentially with altitude. With such an elevator it is possible to reel in tether material at one end of the elevator while reeling out at the other end, without changing the overall taper prole. I show how to use this property to build up or clone

Blaise Gassendy

313

Discrete Quantum Walks Hit Exponentially Faster  

Microsoft Academic Search

This paper addresses the question: what processes take polynomial time on a quantum computer that require exponential time classically? We show that the hitting time of the discrete time quantum walk on the n-bit hypercube from one corner to its opposite is polynomial in n. This gives the first exponential quantum-classical gap in the hitting time of discrete quantum walks.

Julia Kempe

2005-01-01

314

Method for nonlinear exponential regression analysis  

NASA Technical Reports Server (NTRS)

Two computer programs developed according to two general types of exponential models for conducting nonlinear exponential regression analysis are described. Least squares procedure is used in which the nonlinear problem is linearized by expanding in a Taylor series. Program is written in FORTRAN 5 for the Univac 1108 computer.

Junkin, B. G.

1972-01-01

315

Natural Exponential Families with Quadratic Variance Functions  

Microsoft Academic Search

The normal, Poisson, gamma, binomial, and negative binomial distributions are univariate natural exponential families with quadratic variance functions (the variance is at most a quadratic function of the mean). Only one other such family exists. Much theory is unified for these six natural exponential families by appeal to their quadratic variance property, including infinite divisibility, cumulants, orthogonal polynomials, large deviations,

Carl N. Morris

1982-01-01

316

Exponential approximations to compacted sediment porosity profiles  

Microsoft Academic Search

Sediment compaction and corresponding porosity variations can be modeled by a simple exponential with depth. The porosity solution is derived analytically as a complicated function of pore water pressure, but the underlying form is shown to approximate an exponential except near the surface where the behavior is linear. Even though the analytical simplifications ignore some of the detailed effects of

David B. Bahr; Eric W. H. Hutton; James P. M. Syvitski; Lincoln F. Pratson

2001-01-01

317

The matrix exponential in transient structural analysis  

NASA Technical Reports Server (NTRS)

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

Minnetyan, Levon

1987-01-01

318

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

PubMed

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

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

2014-06-01

319

Rearranging the Exponential Wall for Large N-Body Systems  

NASA Astrophysics Data System (ADS)

The general quantum mechanical N-body problem is widely believed to be NP complete, a complexity class for which no polynomial time algorithm has been found. The resources required for an exact solution are thought to scale exponentially with N, doubling for every particle added. With current numerical resources, this problem ``hits a wall'' around N=10 (within a factor of 2). We have formulated a perturbation method for bosons which uses symmetry to rearrange this exponential wall by shifting the work from numerical effort for a single N to analytic work valid for all N. This series is invariant under the N! operations of the symmetric group SN, allowing group theory and graphical techniques to be used to solve the problem exactly and analytically at each order for an arbitrary interaction and for arbitrary N, i.e. the problem scales as N^0 at each order. The current work investigates the growth of complexity as a function of order by enumerating the graphs that correspond to the basis tensors at each order. The exponential complexity reappears in an exponential wall that scales with the order of the series. Thus, exact analytical calculations are possible for very large systems through low order.

Dunn, Martin; Watson, Deborah

2010-03-01

320

Finessing the Exponential Scaling with N Problem for Manybody Systems  

NASA Astrophysics Data System (ADS)

The resources required for an exact solution of the general quantum mechanical N-body problem are widely believed to scale exponentially with N, typically doubling for every particle added. With current numerical resources, this problem ``hits a wall'' around N=10 (within a factor of 2). We have formulated a perturbation method for the general N-boson problem that uses symmetry to rearrange this exponential wall so the problem scales as N^0. This is achieved by using a perturbation expansion that is invariant under the N! operations of the symmetric group SN, allowing group theory and graphical techniques to be used to solve the problem exactly and analytically at each order for arbitrary interactions and for arbitrary N, i.e. the problem scales as N^0 at each order. This approach also shifts the work from numerical effort for a single N to analytic work valid for all N. The exponential complexity reappears in an exponential wall that scales with the order of the series. We have investigated the growth of complexity as a function of order by enumerating the graphs that correspond to the basis tensors at each order. This formulation opens up the possibility of exact analytical calculations for very large N systems through low order.

Watson, Deborah; Dunn, Martin

2011-06-01

321

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

PubMed

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

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

2011-06-01

322

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

PubMed Central

Purpose The purpose of this study was to determine whether genetic variants in the insulin-like growth factor-1 (IGF-1) gene were associated with high myopia in the Chinese population. Methods A case-control association study of 421 unrelated Chinese patients with high myopia and 401 control subjects matched in ethnicity and gender was undertaken. Genomic DNA was prepared from peripheral blood. All individuals were genotyped for 7 tag single nucleotide polymorphisms (tSNPs) across the IGF-1 gene region. Genotypic distribution was tested for Hardy–Weinberg equilibrium. The genotype and allele frequencies were evaluated using the ?2 tests. Bonferroni corrections for multiple comparisons were performed. Results The polymorphism of rs12423791 showed positive association with extreme myopia (pallel=0.006 and pallel1 recessive model=0.004, respectively) after Bonferroni correction for multiple testing and the haplotype GC of rs5742629-rs12423791 was also associated with extreme myopia (p=0.033) after 50,000 permutations for multiple comparisons. Conclusions The polymorphism of rs12423791 in IGF-1 may be associated with extreme myopia in the Chinese population and should be investigated further.

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

2012-01-01

323

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

NASA Technical Reports Server (NTRS)

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

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

2008-01-01

324

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

PubMed

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

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

2013-05-01

325

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

SciTech Connect

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 assessment is then made of how these energy demands might be met, capitalizing as much as possible on the indigenous energy resources for each of the ten major regions of the world: North America, Latin America, Europe OECD, Former Soviet Union and Central and Eastern Europe, China, Pacific OECD, East Asia, South Asia, Africa, and the Middle East. Consideration is also given to the potential need to limit carbon emissions because of global warming concerns. The study highlights the crucial nature of energy efficiency improvements and the need to utilize all energy sources, if the world is to find a sustainable future with an improved standard of living for the developing world.

Sheffield, J.

1998-01-01

326

Effect of plant growth on dehydration rates and microbial populations in sewage biosolids.  

PubMed

The high water content of sewage biosolids makes them expensive to transport. Two experiments were done to see if it was practical to use transpiration by plants as a low cost method to dehydrate biosolids. (i) To assess biosolids as a growth-medium for plants, maize, beans, pumpkin, forage oats and an annual ryegrass were grown in pots of fresh biosolids. Plant growth varied between species and potassium deficiency was found to be a limiting factor for barley. Roots were slow to penetrate anoxic biosolids in the bottom of the pots. (ii) Dehydration rates were measured in 30 litre boxes of biosolids from two different sources. Boxes were planted with maize or beans, or kept fallow. Despite the high (73-83%) initial water content of the biosolids, plants were susceptible to wilting on warm days which suggested that a significant proportion of the water in biosolids is not freely available to plants. Shrinkage caused a major reduction in biosolids volume in both experiments. When change in volume of the biosolids residue was accounted for, there was a 56% average water loss in planted treatments and 34% water loss in the fallow treatment. This indicates that planting may have some potential as a technique to accelerate dehydration of biosolids. Water contents were not reduced sufficiently to influence biosolids microbial populations. PMID:16797975

Crush, J R; Sarathchandra, U; Donnison, A

2006-12-01

327

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

SciTech Connect

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

Crumpton, W.G.

1980-01-01

328

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

PubMed

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

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

2014-06-01

329

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

PubMed

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

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

2013-01-01

330

Involvement of Fibroblast Growth Factor Receptor Genes in Benign Prostate Hyperplasia in a Korean Population  

PubMed Central

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

Park, Hae Jeong; Kim, Su Kang; Kim, Jong Woo

2013-01-01

331

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

NASA Technical Reports Server (NTRS)

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

Noever, David A.

1990-01-01

332

Superdiffusion driven by exponentially decaying memory  

NASA Astrophysics Data System (ADS)

A superdiffusive random walk model with exponentially decaying memory is reported. This seems to be a self-contradictory statement, since it is well known that random walks with exponentially decaying temporal correlations can be approximated arbitrarily well by Markov processes and that central limit theorems prohibit superdiffusion for Markovian walks with finite variance of step sizes. The solution to the apparent paradox is that the model is genuinely non-Markovian, due to a time-dependent decay constant associated with the exponential behavior.

Alves, G. A.; de Araújo, J. M.; Cressoni, J. C.; da Silva, L. R.; da Silva, M. A. A.; Viswanathan, G. M.

2014-04-01

333

Exponential Stability of Stochastic Differential Delay Equations  

Microsoft Academic Search

: In this paper we study both pth moment and almost sure exponential stability of thestochastic differential delay equation dx(t)=f(t;x(t);x(t\\\\Gamma?))dt+g(t;x(t);x(t\\\\Gamma?))dw(t). Introducethe corresponding stochastic differential equation (without delay) dx(t)=f(t;x(t);x(t))dt+g(t;x(t);x(t))dw(t) and assume it is exponentially stable which is guaranteed by the existenceof the Lyapunov function. We shall show that the original stochastic differential delay equationremains exponentially...

Xuerong Mao; Anita Shah

1994-01-01

334

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

PubMed

Overfishing of sharks is a global concern, with increasing numbers of species threatened by overfishing. For many sharks, both catch rates and underwater visual surveys have been criticized as indices of abundance. In this context, estimation of population trends using individual demographic rates provides an important alternative means of assessing population status. However, such estimates involve uncertainties that must be appropriately characterized to credibly and effectively inform conservation efforts and management. Incorporating uncertainties into population assessment is especially important when key demographic rates are obtained via indirect methods, as is often the case for mortality rates of marine organisms subject to fishing. Here, focusing on two reef shark species on the Great Barrier Reef, Australia, we estimated natural and total mortality rates using several indirect methods, and determined the population growth rates resulting from each. We used bootstrapping to quantify the uncertainty associated with each estimate, and to evaluate the extent of agreement between estimates. Multiple models produced highly concordant natural and total mortality rates, and associated population growth rates, once the uncertainties associated with the individual estimates were taken into account. Consensus estimates of natural and total population growth across multiple models support the hypothesis that these species are declining rapidly due to fishing, in contrast to conclusions previously drawn from catch rate trends. Moreover, quantitative projections of abundance differences on fished versus unfished reefs, based on the population growth rate estimates, are comparable to those found in previous studies using underwater visual surveys. These findings appear to justify management actions to substantially reduce the fishing mortality of reef sharks. They also highlight the potential utility of rigorously characterizing uncertainty, and applying multiple assessment methods, to obtain robust estimates of population trends in species threatened by overfishing. PMID:21966402

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

2011-01-01

335

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

Microsoft Academic Search

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

Mark E. Seamans; R. J. Gutiérrez

2007-01-01

336

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

PubMed Central

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

Lopez-Collado, Jose; Isabel Lopez-Arroyo, J.; Robles-Garcia, Pedro L.; Marquez-Santos, Magdalena

2013-01-01

337

Profit Maximization Models for Exponential Decay Processes.  

National Technical Information Service (NTIS)

A number of real world processes can be modelled as exponential decay processes. Examples are: machine replacement, oil well extraction, advertising goodwill, repair and cleaning activities, etc. In this paper we analyze a series of discounted or undiscou...

S. P. Sethi G. L. Thompson V. Udayabhanu

1980-01-01

338

A note on exponential absolute stability.  

NASA Technical Reports Server (NTRS)

A new sufficient condition is formulated for the Lur'e type nonlinear continuous system to be exponentially absolutely stable. The condition relaxes the assumptions on the nonlinear characteristic by modifying the requirements on the linear part of the system.

Siljak, D. D.; Sun, C. K.

1972-01-01

339

Population mixture model for nonlinear telomere dynamics  

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

340

A Survey of Fast Exponentiation Methods  

Microsoft Academic Search

Public-key cryptographic systems often involve raising elements of some group (e.g. GF(2n), Z\\/NZ, or elliptic curves) to large powers. An important question is how fast this exponentiation can be done, which often determines whether a given system is practical. The best method for exponentiation depends strongly on the group being used, the hardware the system is implemented on, and whether

Daniel M. Gordon

1998-01-01

341

Exponential stabilization of nonholonomic chained systems  

Microsoft Academic Search

This paper presents a feedback control scheme for the stabilization of two-input, driftless, chained nonholonomic systems, also called chained form. These systems are controllable but not asymptotically stabilizable by a smooth static-state feedback control law. In addition, exponential stability cannot be obtained with a smooth, time-varying feedback control law. Here, global, asymptotical stability with exponential convergence is achieved about any

O. J. Sordalen; O. Egeland

1995-01-01

342

[Contraception as an instrument against population growth: expert discussions and the public sphere in 1960s West Germany].  

PubMed

Theoretically, the introduction of the contraceptive pill in the 1960s created new possibilities to control population growth on a global scale. Several of those involved in developing the pill belonged to the transnational population control movement. In the Federal Republic, demographic and medical experts in the 1960s debated the advantages and dangers of the new contraceptive, and they argued about whether it could be of benefit in West Germany and/or in developing countries. The paper examines the contemporary debate about the pill and the role it was awarded in the effort to solve what was considered a global population problem. PMID:21469390

Silies, Eva-Maria

2010-09-01

343

Genetic and Environmental Factors Influencing the Placental Growth Factor (PGF) Variation in Two Populations  

PubMed Central

Placental Growth Factor (PGF) is a key molecule in angiogenesis. Several studies have revealed an important role of PGF primarily in pathological conditions (e.g.: ischaemia, tumour formation, cardiovascular diseases and inflammatory processes) suggesting its use as a potential therapeutic agent. However, to date, no information is available regarding the genetics of PGF variability. Furthermore, even though the effect of environmental factors (e.g.: cigarette smoking) on angiogenesis has been explored, no data on the influence of these factors on PGF levels have been reported so far. Here we have first investigated PGF variability in two cohorts focusing on non-genetic risk factors: a study sample from two isolated villages in the Cilento region, South Italy (N?=?871) and a replication sample from the general Danish population (N?=?1,812). A significant difference in PGF mean levels was found between the two cohorts. However, in both samples, we observed a strong correlation of PGF levels with ageing and sex, men displaying PGF levels significantly higher than women. Interestingly, smoking was also found to influence the trait in the two populations, although differently. We have then focused on genetic risk factors. The association between five single nucleotide polymorphisms (SNPs) located in the PGF gene and the plasma levels of the protein was investigated. Two polymorphisms (rs11850328 and rs2268614) were associated with the PGF plasma levels in the Cilento sample and these associations were strongly replicated in the Danish sample. These results, for the first time, support the hypothesis of the presence of genetic and environmental factors influencing PGF plasma variability.

Sorice, Rossella; Ruggiero, Daniela; Nutile, Teresa; Aversano, Mario; Husemoen, Lotte; Linneberg, Allan; Bourgain, Catherine; Leutenegger, Anne-Louise; Ciullo, Marina

2012-01-01

344

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

NASA Astrophysics Data System (ADS)

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

Prisniakov, Vladimir

2002-01-01

345

Growth of captive leatherback turtles, Dermochelys coriacea, with inferences on growth in the wild: Implications for population decline and recovery  

Microsoft Academic Search

Leatherback turtles (Dermochelys coriacea) are endangered, and declining population trends suggest that they are vulnerable to becoming extinct in the Pacific Ocean. Population recovery depends on strong conservation measures (e.g., nest protection, reduction of bycatch, and foraging habitat preservation) and on how fast leatherbacks grow and reach maturity, making the latter of grave concern. The research reported here marks the

T. Todd Jones; Mervin D. Hastings; Brian L. Bostrom; Daniel Pauly; David R. Jones

2011-01-01

346

Energetics of growth and reproduction in a high-tidal population of the clam Ruditapes decussatus from Urdaibai Estuary (Basque Country, N. Spain)  

Microsoft Academic Search

Energetics of growth and reproduction were studied in a high-tidal population of the clam Ruditapes decussatus living in the Mundaka Estuary in the Biosphere Reserve of Urdaibai (Basque Country, North Spain). The study included an analysis of growth rings on the shells to establish the growth curve as well as seasonal patterns of growth and body condition, and estimates of

M. B. Urrutia; I. Ibarrola; J. I. P. Iglesias; E. Navarro

1999-01-01

347

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

NASA Astrophysics Data System (ADS)

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

Nentwig, W.

348

Effects of differential growth and mortality in the seasonal succession of phytoplankton populations in Lawrence Lake, Michigan  

Microsoft Academic Search

An investigation was made of factors controlling algal succession in a small, oligotrophic lake during summer stratification. Phytoplankton population densities, growth rates, sedimentation losses, and mortality due to zooplankton grazing were measured weekly. Cyclotella michiganiana was the dominant alga through the end of June, at which time Cyclotella comensis began to increase, becoming the dominant by August. In August, high

W. G. Crumpton; R. G. Wetzel

1982-01-01

349

Identification of quantitative trait loci for plant height, lodging, and maturity in a soybean population segregating for growth habit  

Microsoft Academic Search

The use of molecular markers to identify quantitative trait loci (QTLs) has the potential to enhance the efficiency of trait selection in plant breeding. The purpose of the present study was to identify additional QTLs for plant height, lodging, and maturity in a soybean, Glycine max (L.) Merr., population segregating for growth habit. In this study, 153 restriction fragment length

S. H. Lee; M. A. Bailey; M. A. R. Mian; E. R. Shipe; D. A. Ashley; W. A. Parrott; R. S. Hussey; H. R. Boerma

1996-01-01

350

Population dynamics of the sea urchin Strongylocentrotus purpuratus in a Central California kelp forest: recruitment, mortality, growth, and diet  

Microsoft Academic Search

The population dynamics of Strongylocentrotus purpuratus inhabiting dense mats of geniculate coralline algae in a shallow central California Macrocystis pyrifera forest was examined. Sea otters had occupied the area for over two decades. Sea urchin density and size distribution were sampled during 1984–1986 to determine recruitment and mortality patterns. Growth rates were obtained from tetracycline-labeled individuals and changes in sizefrequency

M. C. Kenner

1992-01-01

351

Strain localisation and population changes during fault system growth within the Inner Moray Firth, Northern North Sea  

Microsoft Academic Search

The evolution of fault populations is established for an area within the Late Jurassic Inner Moray Firth sub-basin of the North Sea. Sedimentation rates outstripped fault displacement rates resulting in the blanketing of fault scarps and the preservation of fault displacement histories. Displacement backstripping is used to establish the growth history of the fault system.Fault system evolution is characterised by

J. J. Walsh; C. Childs; J. Imber; T. Manzocchi; J. Watterson; P. A. R. Nell

2003-01-01

352

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

PubMed Central

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

Fuller, Amy C.; Harhay, Michael O.

2011-01-01

353

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

PubMed

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

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

1989-03-01

354

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

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

355

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

PubMed

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

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

2004-07-01

356

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

USGS Publications Warehouse

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

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

2009-01-01

357

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

USGS Publications Warehouse

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

Obedzinski, M.; Letcher, B. H.

2004-01-01

358

Decoherence and Exponential Law: A Solvable Model  

NASA Technical Reports Server (NTRS)

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

Pascazio, Saverio; Namiki, Mikio

1996-01-01

359

Lower Urinary Connective Tissue Growth Factor Levels and Incident CKD Stage 3 in the General Population  

PubMed Central

Background Connective tissue growth factor (CTGF) is involved in the development and progression of kidney diseases including diabetic nephropathy and kidney fibrosis, but may also play a role in mesangial repair following injury. It is unknown whether, in the general population, urinary CTGF levels are associated with reduction of estimated glomerular filtration rate (eGFR) to less than 60 ml/min/1.73m2 (ie, development of chronic kidney disease [CKD] stage 3). Study Design Nested case-control. Setting & Participants 100 cases of incident CKD stage 3 and 100 age-and sex-matched controls in the Framingham Heart Study (FHS); 141 cases and 135 age-, sexand race-matched controls in the Atherosclerosis Risk in Communities (ARIC) Study. Controls had eGFR ?60 ml/min/1.73m2 at follow-up in both studies. Predictors Urinary CTGF concentrations. Outcomes Incident CKD stage 3, defined as eGFR <60 ml/min/1.73m2. Measurements Stored urine samples from Framingham Heart Study and ARIC were measured for CTGF. Covariates were obtained from Framingham Heart Study and ARIC participant examinations. Results In Framingham Heart Study, the median baseline urinary CTGF concentration was lower among cases (1.35 ng/mL) than controls (2.35 ng/mL; paired t-test P<0.0001). The multivariable-adjusted OR for incident CKD stage 3 was 0.33 (95% confidence interval [CI] 0.17–0.64; P<0.001) per 1-standard deviation increase in log urinary CTGF after adjustment for CKD risk factors, baseline eGFR and baseline log urinary albumin-creatinine ratio, with similar results among participants without diabetes (n=184). Results were not materially different when urinary CTGF was indexed to urinary creatinine (multivariable-adjusted OR, 0.34; 95% CI, 0.21–0.56; P<0.001). A similar, but non-significant, trend of risk of incident CKD stage 3 with lower baseline urinary CTGF concentration was observed in an independent case-control study conducted in the ARIC Study, with the strongest results observed among participants free of diabetes. This inverse relationship was robust in meta-analysis of both the overall and diabetes-free groups. Limitations Observational study; causality cannot be inferred. Conclusions Lower urinary CTGF concentrations precede the onset of CKD stage 3 in the general population. Further work is required to fully characterize how CTGF influences risk of CKD.

Seaghdha, Conall M. O'; Hwang, Shih-Jen; Bhavsar, Nrupen A.; Kottgen, Anna; Coresh, Josef; Astor, Brad C.; Fox, Caroline S.

2011-01-01

360

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

PubMed Central

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

Muschiol, Daniel; Schroeder, Fabian; Traunspurger, Walter

2009-01-01

361

Rodent malaria-resistant strains of the mosquito, Anopheles gambiae, have slower population growth than -susceptible strains  

PubMed Central

Background Trade-offs between anti-parasite defence mechanisms and other life history traits limit the evolution of host resistance to parasites and have important implications for understanding diseases such as malaria. Mosquitoes have not evolved complete resistance to malaria parasites and one hypothesis is that anti-malaria defence mechanisms are costly. Results We used matrix population models to compare the population growth rates among lines of Anopheles gambiae that had been selected for resistance or high susceptibility to the rodent malaria parasite, Plasmodium yoelii nigeriensis. The population growth rate of the resistant line was significantly lower than that of the highly susceptible and the unselected control lines, regardless of whether mosquitoes were infected with Plasmodium or not. The lower population growth of malaria-resistant mosquitoes was caused by reduced post blood-feeding survival of females and poor egg hatching. Conclusion With respect to eradicating malaria, the strategy of releasing Plasmodium-resistant Anopheles mosquitoes is unlikely to be successful if the costs of Plasmodium-resistance in the field are as great as the ones measured in this study. High densities of malaria-resistant mosquitoes would have to be maintained by continuous release from captive breeding facilities.

Voordouw, Maarten J; Anholt, Bradley R; Taylor, Pam J; Hurd, Hilary

2009-01-01

362

Growth, population structure, and reproduction of western pond turtles (Actinemys marmorata) on the central coast of California  

USGS Publications Warehouse

We studied the population structure and growth of western pond turtles (Actinemys marmorata) at Vandenberg Air Force Base along the coast of central California in April 1995 and June 1996. We captured 179 individuals (115 males, 27 females) from 7 ponds during 26 days of trapping. Many turtles were adult-sized, but based on scute annuli, 74% were < 10 years of age, including many 2- to 3-year-olds. This population structure likely was due to a relatively fast growth rate, especially compared with closely related aquatic turtles in eastern North America. Mean clutch size was 5.2, but 66.7% of females were gravid, and 1 female produced 2 clutches. These reproductive data are similar to those reported for other populations in the southern portion of the species' range. Females reached reproductive maturity as early as 4 years of age. The relatively mild temperatures of California's Mediterranean climate, especially when compared to the seasonal extremes in more continental and northern regions of North America, may explain the different growth rates and population characteristics of freshwater turtles from these 2 regions of North America. ?? 2008 Chelonian Research Foundation.

Germano, D. J.; Rathbun, G. B.

2008-01-01

363

Higher order decompositions of ordered operator exponentials  

NASA Astrophysics Data System (ADS)

We present a decomposition scheme based on Lie-Trotter-Suzuki product formulae to approximate an ordered operator exponential with a product of ordinary operator exponentials. We show, using a counterexample, that Lie-Trotter-Suzuki approximations may be of a lower order than expected when applied to problems that have singularities or discontinuous derivatives of appropriate order. To address this problem, we present a set of criteria that is sufficient for the validity of these approximations, prove convergence and provide upper bounds on the approximation error. This work may shed light on why related product formulae fail to be as accurate as expected when applied to Coulomb potentials.

Wiebe, Nathan; Berry, Dominic; Høyer, Peter; Sanders, Barry C.

2010-01-01

364

A method for nonlinear exponential regression analysis  

NASA Technical Reports Server (NTRS)

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

Junkin, B. G.

1971-01-01

365

Estimation of microbial growth using population measurements subject to a detection limit  

Microsoft Academic Search

In this paper we develop a maximum likelihood estimation procedure for determining the mean and variance in microbial population size from microbial population measurements subject to a detection limit. Existing estimation methods generally set non-detectable measurements equal to the detection limit and are highly biased. Because changes in the mean and variance in the microbial population size are typical in

P. R. Shorten; A. B. Pleasants; T. K. Soboleva

2006-01-01

366

Rapid population growth and its impact on residential land use in Ghana: The case of Madina-Adenta in the Accra metropolitan area  

Microsoft Academic Search

Rapid population growth rates coupled with low levels of economic development in developing countries have created among others immense obstacles to the provision of adequate housing to the majority of residents. Population growth rates are growing faster than the provision of new housing and housing infrastructure. This has resulted in intensive usage of the existing stock of housing and deterioration

Louis Awanyo

1992-01-01

367

Session 1 C 2 - Environment and Development II: Sustainable Development Population Growth, Food Production and the Environmental Resource Base in Poor Countries  

Microsoft Academic Search

The paper outlines the theoretical issues and empirical evidence concerning the relationship between population growth and food production in poor countries. The linkages between population pressure on land and land degradation (as an environmental constraint to food output growth) are then discussed through: (i) a survey of case studies and (ii) a statistical analysis using data from the Global Assessment

Nadia Cuffaro; Frank Heins

1998-01-01

368

Clonal Variation in Growth Plasticity within a Bosmina longirostris Population: The Potential for Resistance to Toxic Cyanobacteria  

PubMed Central

Many aquatic organisms respond phenotypically, through morphological, behavioral, and physiological plasticity, to environmental changes. The small-size cladoceran Bosminalongirostris, a dominant zooplankter in eutrophic waters, displayed reduced growth rates in response to the presence of a toxic cyanobacterium, Microcystisaeruginosa, in their diets. The magnitude of growth reduction differed among 15 clones recently isolated from a single population. A significant interaction between clone and food type indicated a genetic basis for the difference in growth plasticity. The variation in phenotypic plasticity was visualized by plotting reaction norms with two diets. The resistance of each clone to dietary cyanobacteria was measured as the relative change in growth rates on the “poor” diet compared with the “good” diet. The enhanced resistance to M. aeruginosa in B. longirostris was derived from both the reduced slope of reaction norms and the increased mean growth rates with two diets. The large clonal variation within a B. longirostris population may contribute to local adaptation to toxic cyanobacteria and influence ecosystem function via clonal succession.

Jiang, Xiaodong; Li, Qingmei; Liang, Huishuang; Zhao, Shiye; Zhang, Lihua; Zhao, Yunlong; Chen, Liqiao; Yang, Wei; Xiang, Xingyu

2013-01-01

369

Effect of growth conditions and substratum composition on the persistence of coliforms in mixed-population biofilms.  

PubMed Central

Laboratory reactors operated under oligotrophic conditions were used to evaluate the importance of initial growth rate and substratum composition on the long-term persistence of coliforms in mixed-population biofilms. The inoculum growth rate had a dramatic effect on the ability of coliforms to remain on surfaces. The most slowly grown coliforms (mu = 0.05/h) survived at the highest cell concentration. Antibody staining revealed that Klebsiella pneumoniae existed primarily as discrete microcolonies on the surface. Both coliforms and heterotrophic plate count bacteria were supported in larger numbers on a reactive substratum, mild steel, than on polycarbonate.

Camper, A K; Jones, W L; Hayes, J T

1996-01-01

370

A pooling procedure for the exponential distribution  

Microsoft Academic Search

If two censored samples come from the same exponential distribution, it is advantageous to pool the two samples for estimating the scale parameter. In practice, when there are two censored samples available and it is uncertain whether these two samples come from the same distribution, the question of whether to pool these two samples is usually determined via a preliminary

Paul Chiou

1995-01-01

371

On two stage shrinkage testimation for exponential  

Microsoft Academic Search

Let ? be the mean of an exponential distribution for which prior knowledge is available in the form of a value ?o. A two stage testimator T(m), already proposed in the literature, is given as follows. If the hypothesis Ho : ? = ?o is accepted by the UMPU test based on the first random sample of n1 observations, where

D. V. Gokhale

1989-01-01

372

Car Loans - Real World Exponential Equation  

NSDL National Science Digital Library

This activity has been modified from Real World Learning Objects, Internet-based Activities for Higher Education. The need to access an online calculator has been removed. Students are asked to price a car, determine an acceptable monthly payment and then using the formula calculate the number of months needed to pay off the loan. This requires solving an exponential equation using logarithms.

2011-01-01

373

Exponential and Uniform Ergodicity of Markov Processes  

Microsoft Academic Search

General characterizations of geometric convergence for Markov chains in discrete time on a general state space have been developed recently in considerable detail. Here we develop a similar theory for $\\\\varphi$-irreducible continuous time processes and consider the following types of criteria for geometric convergence: 1. the existence of exponentially bounded hitting times on one and then all suitably \\

D. Down; S. P. Meyn; R. L. Tweedie

1995-01-01

374

Tracking People with Twists and Exponential Maps  

Microsoft Academic Search

This paper demonstrates a new visual motion estimation technique that is able to recover high degree-of-freedom articulated human body configurations in complex video sequences. We introduce the use of a novel mathematical technique, the product of exponential maps and twist motions, and its integration into a differential motion estimation. This results in solving simple linear systems, and enables us to

Christoph Bregler; Jitendra Malik

1998-01-01

375

On a Class of Tests of Exponentiality  

Microsoft Academic Search

The class of statistics T, = (? i=1, Xi\\/n)\\/ , where ? > 0 and ? 1, have been considered in the literature for testing exponentiality versus omnibus alternatives. These tests have a twosided rejection region. It is shown here that tests based on these statistics are not consistent for certain alternatives. However, it is shown that one-sided tests based

S. C. S. Lee; Charles Locke; John D. Spurrier

1980-01-01

376

Target-setting problem with exponential utility  

Microsoft Academic Search

A classic target-setting problem with a two-piece linear outcome function is extended to include an exponential utility function over outcomes and a normal distribution over uncertain inputs. An expression for the optimal target is derived that facilitates the decision and sensitivity analyses

R. Krzysztofowicz

1990-01-01

377

Diagrammatic exponentiation for products of Wilson lines  

SciTech Connect

We provide a recursive diagrammatic prescription for the exponentiation of gauge theory amplitudes involving products of Wilson lines and loops. This construction generalizes the concept of webs, originally developed for eikonal form factors and cross sections with two eikonal lines, to general soft functions in QCD and related gauge theories. Our coordinate space arguments apply to arbitrary paths for the lines.

Mitov, Alexander; Sterman, George; Sung, Ilmo [C.N. Yang Institute for Theoretical Physics, Stony Brook University, Stony Brook, New York 11794-3840 (United States)

2010-11-01

378

Quantum Random Walks Hit Exponentially Faster  

Microsoft Academic Search

We show that the hitting time of the discrete time quantum random walk on the n-bit hypercube from one corner to its opposite is polynomial in n. This gives the first exponential quantum-classical gap in the hitting time of discrete quantum random walks. We provide the framework for quantum hitting time and give two alternative definitions to set the ground

Julia Kempe

2002-01-01

379

Computing integrals involving the matrix exponential  

Microsoft Academic Search

A new algorithm for computing integrals involving the matrix exponential is given. The method employs diagonal Padé approximation with scaling and squaring. Rigorous truncation error bounds are given and incorporated in a Fortran subroutine. The computational aspects of this program are discussed and compared with existing techniques.

C. Van Loan

1978-01-01

380

Optimal Properties of Exponentially Weighted Forecasts  

Microsoft Academic Search

The exponentially weighted average can be interpreted as the expected value of a time series made up of two kinds of random components: one lasting a single time period (transitory) and the other lasting through all subsequent periods (permanent). Such a time series may, therefore, be regarded as a random walk with “noise” superimposed. It is also shown that, for

John F. Muth

1960-01-01

381

Exponential lower bounds for the pigeonhole principle  

Microsoft Academic Search

In this paper we prove an exponential lower bound on the size of bounded-depth Frege proofs for the pigeon- hole principle (PHP). We also obtain an ~(log log rz)- depth lower bound for any polynomial-sized Frege proof of the pigeonhole principle. Our theorem nearly com- pletes the search for the exact complexity of the PHP, as Sam Buss has constructed

Paul Beame; Russell Impagliazzo; Jan Krají?ek; Toniann Pitassi; Pavel Pudlák; Alan R. Woods

1992-01-01

382

Efficient Elliptic Curve Exponentiation Using Mixed Coordinates  

Microsoft Academic Search

. Elliptic curve cryptosystems, proposed by Koblitz ([11]) andMiller ([15]), can be constructed over a smaller field of definition thanthe ElGamal cryptosystems ([5]) or the RSA cryptosystems ([19]). Thisis why elliptic curve cryptosystems have begun to attract notice. In thispaper, we investigate efficient elliptic curve exponentiation. We propose anew coordinate system and a new mixed coordinates strategy, which significantlyimproves on

Henri Cohen; Atsuko Miyaji; Takatoshi Ono

1998-01-01

383

Characterization of DNA Polymorphisms in Three Populations of Hereford Cattle and Their Associations with Growth and Maternal EPD in Line 1 Herefords1,2  

Microsoft Academic Search

Three populations of Hereford cattle differing in inbreeding levels and genetic potential for growth were genotyped for seven DNA polymor- phisms. The populations were compared to determine differences in allele frequency and genetic variation. Significant differences in allele frequency among the populations were found at six of the seven polymor- phisms genotyped, and average genetic variation differed as expected when

D. E. Moody; D. Pomp; S. Newman; M. D. MacNeil

384

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

USGS Publications Warehouse

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

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

2011-01-01

385

Population growth of Brachionus macracanthus (Rotifera) in relation to cadmium toxicity: Influence of algal (Chlorella vulgaris) density  

Microsoft Academic Search

In the present work, we quantified the harmful effects of Cd to Brachionus macracanthus using both acute (median lethal) and chronic (population growth) toxicity tests. Chronic toxicity tests were conducted under 4 different concentrations (0.000625–0.005 mg L) of cadmium chloride at 23°C under 3 food (Chlorella vulgaris) levels (0.5 × 10, 1.0 × 10 and 2.0 × 10 cells mL)

S. Nandini; Diego De JesúS Chaparro-Herrera; Sara Leticia CáRdenas-Arriola; S. S. S. Sarma

2007-01-01

386

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

Microsoft Academic Search

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

S. Nandini; T. R. Rao

1997-01-01

387

Single dietary amino acids control resting egg production and affect population growth of a key freshwater herbivore  

Microsoft Academic Search

The enormous success of the genus Daphnia in freshwater ecosystems is at least partially due to their cyclical parthenogenetic life cycle, in which asexual and sexual\\u000a reproduction alternate periodically. This temporal change between reproductive strategies allows for (1) rapid population\\u000a growth via subitaneously developing eggs when environmental conditions are appropriate and (2) the maintenance of genetic\\u000a diversity via sexual reproduction

Ulrike Koch; Dominik Martin-Creuzburg; Hans-Peter Grossart; Dietmar Straile

388

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

PubMed

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

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

2014-03-25

389

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

PubMed Central

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

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

2014-01-01

390

Transforming growth factor-? decreases the cancer-initiating cell population within diffuse-type gastric carcinoma cells  

Microsoft Academic Search

Stem cells in normal tissues and cancer-initiating cells (CICs) are known to be enriched in side population (SP) cells. However, the factors responsible for the regulation of expression of ABCG2, involved in efflux of dyes, in SP cells have not been fully investigated. Here, we characterized the SP cells within diffuse-type gastric carcinoma, and examined the effects of transforming growth

S Ehata; E Johansson; R Katayama; S Koike; A Watanabe; Y Hoshino; Y Katsuno; A Komuro; D Koinuma; M R Kano; M Yashiro; K Hirakawa; H Aburatani; N Fujita; K Miyazono

2011-01-01

391

Energetics of growth and reproduction in a high-tidal population of the clam Ruditapes decussatus from Urdaibai Estuary (Basque Country, N. Spain)  

NASA Astrophysics Data System (ADS)

Energetics of growth and reproduction were studied in a high-tidal population of the clam Ruditapes decussatus living in the Mundaka Estuary in the Biosphere Reserve of Urdaibai (Basque Country, North Spain). The study included an analysis of growth rings on the shells to establish the growth curve as well as seasonal patterns of growth and body condition, and estimates of the breeding cycle including quantification of the reproductive output and reproductive effort. The simultaneous determination of the seasonal course of metabolism allowed estimates of assimilation, growth efficiency and reproductive costs. Growth rates were consistently lower in this population than in other populations from similar latitudes, and this effect is interpreted in terms of nutritional restrictions caused by the high tidal position of the population. Assimilation rapidly increased from March to July, as a consequence of optimal nutritional conditions and increasing water temperatures. Somatic growth (spring) and gonadal development (early summer) both took place during this period. Negative growth was restricted to the winter and late summer and was associated with poor nutritional conditions (winter) and high rates of metabolic expenditure induced by high temperatures (late summer). Net growth efficiencies (ranging from 27% in 1-y-old to 6% in 7-y-old individuals) ranked among the lowest recorded for populations of marine bivalves. Reduced reproductive-effort values were consistent with the poor growing conditions that appeared to characterise this population of clams.

Urrutia, M. B.; Ibarrola, I.; Iglesias, J. I. P.; Navarro, E.

1999-08-01

392

Predators with multiple ontogenetic niche shifts have limited potential for population growth and top-down control of their prey.  

PubMed

Catastrophic collapses of top predators have revealed trophic cascades and community structuring by top-down control. When populations fail to recover after a collapse, this may indicate alternative stable states in the system. Overfishing has caused several of the most compelling cases of these dynamics, and in particular Atlantic cod stocks exemplify such lack of recovery. Often, competition between prey species and juvenile predators is hypothesized to explain the lack of recovery of predator populations. The predator is then considered to compete with its prey for one resource when small and to subsequently shift to piscivory. Yet predator life history is often more complex than that, including multiple ontogenetic diet shifts. Here we show that no alternative stable states occur when predators in an intermediate life stage feed on an additional resource (exclusive to the predator) before switching to piscivory, because predation and competition between prey and predator do not simultaneously structure community dynamics. We find top-down control by the predator only when there is no feedback from predator foraging on the additional resource. Otherwise, the predator population dynamics are governed by a bottleneck in individual growth occurring in the intermediate life stage. Therefore, additional resources for predators may be beneficial or detrimental for predator population growth and strongly influence the potential for top-down community control. PMID:23778226

van Leeuwen, Anieke; Huss, Magnus; Gårdmark, Anna; Casini, Michele; Vitale, Francesca; Hjelm, Joakim; Persson, Lennart; de Roos, André M

2013-07-01

393

Population structure, growth and production of the surf clam Donax serra (Bivalvia, Donacidae) on two Namibian sandy beaches  

NASA Astrophysics Data System (ADS)

Population structure, growth and production of the surf clam Donax serra (Bivalvia, Donacidae), inhabiting highly exposed sandy beaches of Namibia, were investigated between November 1997 and December 1999. From length-frequency distribution and tagging-recapture data, a von Bertalanffy growth function with an asymptotic length ( L ?) of 82 mm and a growth constant ( K) of 0.274 yr -1 was established. Regarding growth performance of Donacidae, D. serra fits in a group of species inhabiting cold temperate and upwelling regions. The intertidal biomass of the studied population ranged between 141 and 546 g ash-free dry mass (AFDM) m -2 yr -1. Individual production was maximal at 56.5 mm shell length (0.83 g AFDM ind. -1 yr -1), and annual production ranged between 167 and 637 g AFDM m -2 yr -1, resulting in productivity values (P/ B¯) between 1.167 and 1.589 yr -1. These data underline the importance of D. serra for the beach/surf ecosystem. Further, the findings of this study are crucial to support future aquaculture or exploitation activities and management.

Laudien, J.; Brey, T.; Arntz, W. E.

2003-10-01

394

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

EPA Science Inventory

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

395

Overcrowding and Population Growth: The Nature and Relevance of Animal Behavior.  

ERIC Educational Resources Information Center

This paper provides a descriptive overview of research on the consequences of overcrowding and the development of high population densities in animals, and speculates on the relevance of these studies for similar human phenomena. Three major foci are distinguished: (1) the effect of high population densities on animal behavior; (2) the nature of…

Stettner, Laurence J.

396

Snowbirds and Water Coolers: How Aging Populations Can Drive Economic Growth  

Microsoft Academic Search

This article focuses on how private industry can make simple, yet effective changes to transform aging populations into important economic participants. Through three case studies—of BMW, CVS, and Tesco—this essay details how these businesses are gaining a competitive edge by integrating aging populations into their business models, both as customers and as productive employees. This essay argues that private industry

Michael W. Hodin; Mark Hoffmann

2011-01-01

397

Snowbirds and Water Coolers: How Aging Populations Can Drive Economic Growth  

Microsoft Academic Search

: This article focuses on how private industry can make simple, yet effective changes to transform aging populations into important economic participants. Through three case studies—of BMW, CVS, and Tesco—this essay details how these businesses are gaining a competitive edge by integrating aging populations into their business models, both as customers and as productive employees. This essay argues that private

Michael W. Hodin; Mark Hoffmann

2011-01-01

398

Growth of newly established alien populations: comparison of North American gypsy moth colonies with invasion theory  

Microsoft Academic Search

A common characteristic observed in many biological invasions is the existence of a lag between the time of arrival by the alien population and the time when established populations are noticed. Consider- able advances have been made in modeling the expansion of invading species, and there is often remarkable congruence between the behavior of these models with spread of actual

Andrew M. Liebhold; Patrick C. Tobin

2006-01-01

399

Growth and Sex Distribution in an Anadromous Population of Arctic Char in Northern Norway  

Microsoft Academic Search

Presmolt Arctic char Salvelinus alpinus in the River Halselva watershed, northern Norway, were analysed with respect to growth and sex distribution. Two main hypotheses were tested: (1) females dominate among the first-time sea migrants; and (2) age at smoltification depends on presmolt growth rate. Our results showed no significant difference in sex distribution of first-time migrants. There was a low

Rita Strand; Tor G. Heggberget

1994-01-01

400

Cephalopod hatchling growth: the effects of initial size and seasonal temperatures  

Microsoft Academic Search

Temperature is known to have a strong influence on cephalopod growth during the early exponential growth phase. Most captive\\u000a growth studies have used constant temperature regimes and assumed that populations are composed of identically sized individuals\\u000a at hatching, overlooking the effects of seasonal temperature variation and individual hatchling size heterogeneity. This study\\u000a investigated the relative roles of initial hatchling size

Stephen C. Leporati; Gretta T. Pecl; Jayson M. Semmens

2007-01-01

401

Genotype-restricted growth and aging patterns in hematopoietic stem cell populations of allophenic mice  

PubMed Central

We have studied contributions to hematopoiesis of genetically distinct stem cell populations in allophenic mice. Chimeras were made by aggregating embryos of inbred strains known to differ with respect to stem cell population kinetics. One partner strain (DBA/2) has previously been shown to normally have a stem cell (CFU-S) population of which 24% are in S-phase of the cell cycle, whereas the homologous population of the other partner strain (C57BL/6) was characterized by having only 2.6% in cycle (7). Contributions of the chimeric stem cell population to mature blood cell pools were studied throughout the life of the mice and intrinsic differences in stem cell function and aging were reflected in dynamic patterns of blood cell composition. The DBA/2 stem cell population was eclipsed by stem cells of the C57BL/6 genotype and, after 1.5-3 yr, the hemato-lymphoid composition of 22 of 27 mice studied for this long had shifted by at least 25 percentage points toward the C57BL/6 genotype. 8 of the 27 had hematolymphoid populations solely of C57BL/6 origin. To test whether or not a population of stem cells with an inherently higher cycling rate (DBA/2) might have a competitive advantage during repopulation, we engrafted allophenic marrow into lethally irradiated (C57BL/6 x DBA/2)F1 recipients. DBA/2 hematopoiesis was predominant early, far outstripping its representation in the marrow graft. Perhaps as a consequence of inherently greater DBA/2 stem cell proliferation, the populations of developmentally more restricted precursor populations (CFU-E, BFU-E, CFU-GM, CFU-GEMM) showed an overwhelming DBA/2 bias in the first 2-3 mo after engraftment. However, as in the allophenic mice themselves during the aging process, the C57BL/6 genotypic representation was ascendant over the subsequent months. The shift toward C57BL/6 genotype was first documented in the marrow and spleen precursor cell populations and was subsequently reflected in the circulating, mature blood cells. Bone marrow-derived stromal cell cultures from engrafted mice were studied and genotypic analyses showed donor representation in stromal cell populations that reflected donor hematopoietic contributions in the same recipient. Results from these studies involving two in vivo settings (allophenic mice and engraftment by allophenic marrow) are consistent with the notion that a cell autonomous difference in stem cell proliferation confers on one population a competitive repopulating advantage, but at the expense of longevity.

1990-01-01

402

The Population Game: A Socially Significant Laboratory Activity  

NASA Astrophysics Data System (ADS)

A game-like activity using dice-like cubes can bring population growth home to all students, scientists, and nonscientists alike, while demonstrating many aspects of probability and uncertainty that are too often ignored in the physics curriculum. The activity can proceed at a variety of levels of sophistication and complication, from a simple demonstration of exponential growth through an elaborate modeling of life expectancy, advanced versus primitive societies, family planning, birth rate, and population momentum. Variations can demonstrate radioactive decay, resource depletion, and the approach of a thermodynamic system to statistical equilibrium.

Hobson, Art

2003-04-01

403

Truncated ?-exponential models for tidal stellar systems  

NASA Astrophysics Data System (ADS)

We introduce a parametric family of models in order to characterize the properties of astrophysical systems in quasi-stationary evolution under the influence of evaporation. We start from a one-particle distribution f? q, p??, ?e that is based on an appropriate deformation of Maxwell–Boltzmann form with inverse temperature ? and, in particular, a power-law truncation at the escape energy ?e with exponent ? > 0. This deformation is implemented using a generalized ?-exponential function obtained from the fractional integration of an ordinary exponential. As shown in this work, this proposal generalizes models of tidal stellar systems that predict particle distributions with isothermal cores and polytropic haloes, e.g. Michie–King models. We perform an analysis of the thermodynamic features of these models and their associated distribution profiles. A nontrivial consequence of this study is that profiles with isothermal cores and polytropic haloes are only obtained for low energies when the deformation parameter ? < ?c ? 2.13.

Gomez-Leyton, Y. J.; Velazquez, L.

2014-04-01

404

Exponentially tapered non-uniform transmission lines  

Microsoft Academic Search

We solve the transmission line equations for a non-uniform transmission line (NUTL). The analytical method used is different to the Kuroda's one. First we find the solution in terms of voltage and current waves, then the expression of input impedance that allow us to find the R=const and X=const loci. In particular the solution is found for an exponential NUTL.

L. Vegni; F. Urbani; A. Toscano

1997-01-01

405

Soundness of Symbolic Equivalence for Modular Exponentiation  

Microsoft Academic Search

In this paper, we study the Dynamic Decisional Diffie-Hellman (3DH) problem,a powerfulgeneralizationoftheDecisionalDiffie-Hellman(DDH)prob- lem. Our main result is that DDH implies 3DH. This result leads to significantly simpler proofs for protocols by relying directly on the more general problem. Our second contribution is a computationally sound symbolic technique for reasoning about protocols that use symmetric encryption and modular exponentiation. We show

Yassine Lakhnech; Laurent Mazare; Bogdan Warinschi

406

Exponential mixing for the Teichmüller flow  

Microsoft Academic Search

We study the dynamics of the Teichmüller flow in the moduli space of Abelian differentials (and more generally, its restriction\\u000a to any connected component of a stratum). We show that the (Masur-Veech) absolutely continuous invariant probability measure\\u000a is exponentially mixing for the class of Hölder observables. A geometric consequence is that the action in the moduli space has a spectral

Artur Avila; Sébastien Gouëzel; Jean-Christophe Yoccoz

2006-01-01

407

On Some Exponential Functionals of Brownian Motion  

Microsoft Academic Search

\\u000a In this paper, distributional questions which arise in certain mathematical finance models are studied: the distribution of\\u000a the integral over a fixed time interval [0, T]of the exponential of Brownian motion with drift is computed explicitly, with the help of computations previously made by\\u000a the author for Bessel processes. The moments of this integral are obtained independently and take a

Marc Yor

408

Statistical features of the Stretched Exponentials Densities  

NASA Astrophysics Data System (ADS)

A derivation of the Stretched Exponentials Probability Densities from a maximum entropy principle is given. The informational entropy is constrained such that the v-moment, langle|x|vrangle, must be finite. Also higher order moments are computed. Moreover, conditions for a central limit theorem are satified. From the physical point of view, we discuss the role of the entropy defining stationary states associated to complex systems.

Luévano, José-Rubén

2013-12-01

409

Sex-based prevalence of growth faltering in an urban pediatric population  

PubMed Central

Objective To determine the sex-based prevalence of growth faltering in a pediatric primary care setting. Study design 33,476 children attending four urban pediatric primary care practices affiliated with a tertiary pediatric hospital from July 2002 to June 2005 were studied. Growth faltering was defined as height: <5th percentile or z-score dropping by ?1.5 standard deviations (SD) before age 18 months or ?1 SD thereafter. Growth faltering and non-faltering groups were compared by sex, race, age, number of clinic visits, insurance and by US census tract, socioeconomic status and parental education. Similar comparisons were made for children with height z-scores below ?2.25 SD. Results Growth faltering was present in 3,007 (9%) children. Univariate and multivariate logistic regression analyses revealed growth faltering to significantly associate with younger age (P<0.0001), white race (P<0.0001), fewer clinic visits (P<0.0001) and Medicaid insurance (P<0.005), but not sex nor within residential census tract, median income or proportion with less than high school education. Height below ?2.25 SD associated with male sex (P<0.01), Medicaid insurance (P<0.01) and more primary care visits (P<0.0005). Conclusion Sex disparity in subspecialty growth center referrals (2:1 male:female) was not due to male predominance in growth faltering among children in the urban primary care setting.

Grimberg, Adda; Ramos, Mark; Grundmeier, Robert; Feemster, Kristen A.; Pati, Susmita; Cucchiara, Andrew J.; Stallings, Virginia A.

2013-01-01

410

The use of resighting data to estimate the rate of population growth of the snail kite in Florida  

USGS Publications Warehouse

The rate of population growth (lambda) is an important demographic parameter used to assess the viability of a population and to develop management and conservation agendas. We examined the use of resighting data to estimate lambda for the snail kite population in Florida from 1997-2000. The analyses consisted of (1) a robust design approach that derives an estimate of lambda from estimates of population size and (2) the Pradel (1996) temporal symmetry (TSM) approach that directly estimates lambda using an open-population capture-recapture model. Besides resighting data, both approaches required information on the number of unmarked individuals that were sighted during the sampling periods. The point estimates of lambda differed between the robust design and TSM approaches, but the 95% confidence intervals overlapped substantially. We believe the differences may be the result of sparse data and do not indicate the inappropriateness of either modelling technique. We focused on the results of the robust design because this approach provided estimates for all study years. Variation among these estimates was smaller than levels of variation among ad hoc estimates based on previously reported index statistics. We recommend that lambda of snail kites be estimated using capture-resighting methods rather than ad hoc counts.

Dreitz, V.J.; Nichols, J.D.; Hines, J.E.; Bennetts, R.E.; Kitchens, W.M.; Deangelis, D.L.

2002-01-01

411

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

NSDL National Science Digital Library

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

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

2005-05-21

412

Benchmarking Exponential Growth of Educational Reform: The Sustainability Index  

ERIC Educational Resources Information Center

After decades of reform efforts in public school systems in the United States, there is minimal student achievement progress to measure. This article addresses the ongoing challenges and complexities of the sustainability of educational reform through a review of the literature and the proposal of a Sustainability Index as a metric to benchmark…

Garcia, Ray

2009-01-01

413

Teachers Explore Linear and Exponential Growth: Spreadsheets as Cognitive Tools  

ERIC Educational Resources Information Center

This article addresses some of the issues relevant to the cognitive goals of information and communication technology (ICT) integration in the mathematics classroom. It focuses on the development of conceptual understanding through multiple representations. Specifically, it informs about a group of middle school mathematics teachers' learning and…

Alagic, Mara; Palenz, Diana

2006-01-01

414

Growth monitoring still has a place in selected populations of children.  

PubMed

In 1998, a multiprofessional group developed a consensus on growth monitoring in the UK. While routine serial measurements were not recommended in healthy children, it is clear that there is a subset of children at increased risk of growth-modifying disease who may benefit from growth monitoring. This subset includes children with genetic disorders at increased risk of thyroid dysfunction. Symptoms and signs of thyroid dysfunction are non-specific in the early stages of disease and are easily mistaken for features of an underlying genetic disorder. In this article, we report the case of a 2.8-year-old girl with 18q deletion syndrome who was profoundly weak, hypotonic and poorly responsive at diagnosis of Grave's disease. She was tall and her bone age was 2 years advanced, indicating long-standing disease. Growth monitoring of this patient should have enabled earlier diagnosis and avoided a serious and potentially fatal episode. PMID:22700067

Hussain, M; John, C M; Mohamed, K; Zbaeda, M; Ng, S M; Chanderasekaran, S; Didi, M; Blair, J C

2011-01-01

415

[Population problems in Latin America].  

PubMed

Accelerated urban growth is one of the main impediments to rapid development in Latin America. Birth rates are closely tied to development, and improved living standards in urban areas induce migration to cities. The Brazilian urban population exceeded 70% of the total population in 1980, while rural population declined. During the period of 1950-70 high demographic growth occurred as a result of high fertility and the drop of mortality. From the 1970s fertility declined from the under 20 years of age, a fact that will sustain high fertility for sometime. Education exerted an impact on fertility: in 1980 illiterate women averaged 6 children vs. 2.6 children for women with 8 years of education and 2.2 children for those with 12 years. Migration was another major factor: in 1950 the urban population of Latin America amounted to 40 million, and it reached 142 million in 1974. Every year about 8.7 million people are added to the urban population. In 1950 those who resided in an urban area made up 9.2%, in 1975 they increased to 22%, but all urban residents amount to about 40% of the total population. This urbanization has also produced major income differentials. In Argentina 20% of the poorest people get 4.5% of total income, while 10% of the richest get 35%. In Brazil 20% of the poorest receive 2% of income, while 10% of the richest get 50.5% of total income. Unfortunately, the Brazilian model is more typical of Latin America. It is a fundamental premise that balanced population growth and economic development go hand in hand, and the improvement of living standards is essential for the reduction of exponential population growth. PMID:12178391

Faissol, S

1990-01-01

416

Study of the growth and development of chlorella populations in the culture as a whole  

Microsoft Academic Search

Summary  The cytomorphology of two species ofChlorella was studied under conditions in which growth and reproduction processes were more or less dissociated. In media of different\\u000a compositions it was found possible to carry out a typical and reproducible study of the trend of growth and development of\\u000a the culture as a whole. Chlorella cells reproduce basically by division of the nucleus,

R. ?etovský; Irena Klášterská

1961-01-01

417

Reliability growth via testing  

Microsoft Academic Search

Observed data values are typically assumed to come from an infinite population of items in reliability and survival analysis applications. The case of a finite population of items with exponentially distributed lifetimes is considered here. The data set consists of the lifetimes of a large number of items that are known to have exponentially distributed failure times with a failure

Lawrence M. Leemis

2010-01-01

418