Science.gov

Sample records for accelerated population growth

  1. Population growth.

    PubMed

    1984-01-01

    Despite efforts to reduce population growth, the World Bank projects a world population of 10 billion by 2050, with 7 billion living in developing countries. From October 1979 to September 1984, the US Agency for International Development (AID) funded the Research Triangle Institute's (RTI) Integrated Population and Development Planning (IPDP) project to assess rapid population growth effects in 25 developing countries. In October 1984, US AID extended funding for the program, nicknamed INPLAN, for 3 years, at a cost of $6.3 million. Up to 50% of people in developing countries are under age 15, a fact that guarantees large population increases for the next 50-75 years. Also, many regions have been slow to correlate high fertility with socioeconomic development, and in some areas, fertility is actually increasing. INPLAN aims to make governments more aware of population dynamics and to provide training and tools for effective development planning. 40% of INPLAN's work will be done in Africa, 25% in Latin America, and 20% in Asia, with some activity in the Near East. One project in Egypt, involving the use of model generation by microcomputer, was developed by RTI to show rural to urban migration and rapid population growth affects on the educational system. INPLAN expects to develop several other planning sector models on labor force and employment, health and family planning, food supply, housing, and urban development, and apply them to 20-25 countries. Another project provided 9 microcomputer systems and training to Nigerian government agencies. IMPLAN will purchase and distribute 60 such systems in the future.

  2. Simulating Population Growth.

    ERIC Educational Resources Information Center

    Byington, Scott

    1997-01-01

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

  3. Population growth and economic growth.

    PubMed

    Narayana, D L

    1984-01-01

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

  4. Modeling Exponential Population Growth

    ERIC Educational Resources Information Center

    McCormick, Bonnie

    2009-01-01

    The concept of population growth patterns is a key component of understanding evolution by natural selection and population dynamics in ecosystems. The National Science Education Standards (NSES) include standards related to population growth in sections on biological evolution, interdependence of organisms, and science in personal and social…

  5. Impact of Population Growth

    ERIC Educational Resources Information Center

    Ehrlich, Paul R.; Holdren, John P.

    1971-01-01

    Discusses the interrelated crises in population growth, natural resources, and environmental quality. Major problems include population control, redirection of technology, closed resource cycles, equitable opportunity distribution and prosperity. Population growth is regarded as causing a disportionate world-wide negative environmental impact.…

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

    PubMed

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

    2004-07-01

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

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

    USGS Publications Warehouse

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

    2004-01-01

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

  8. The accelerating growth of online tagging systems

    NASA Astrophysics Data System (ADS)

    Wu, L. F.

    2011-09-01

    Research on the growth of online tagging systems not only is interesting in its own right, but also yields insights for website management and semantic web analysis. Traditional models that describing the growth of online systems can be divided between linear and nonlinear versions. Linear models, including the BA model [A.L. Barabasi, R. Albert, Science 286, 509 (1999)], assume that the average activity of users is a constant independent of population. Hence the total activity is a linear function of population. On the contrary, nonlinear models suggest that the average activity is affected by the size of the population and the total activity is a nonlinear function of population. In the current study, supporting evidences for the nonlinear growth assumption are obtained from data on Internet users' tagging behavior. A power law relationship between the number of new tags (F) and the population (P), which can be expressed as F~Pγ (γ > 1), is found. I call this pattern accelerating growth and find it relates the to time-invariant heterogeneity in individual activities. I also show how a greater heterogeneity leads to a faster growth.

  9. Population growth and consumption.

    PubMed

    Chalkley, K

    1997-04-01

    The relationship between population growth, resource consumption, and environmental degradation is complex. The rise in "greenhouse gases" that will cause climatic change is clearly due to human activity, and pollutants are often concentrated in densely populated areas. However, even an area with a negative population growth, such as Russia, can experience severe environmental degradation due to poor management. Consumption patterns have the most effect on ozone depletion, while population growth threatens biodiversity of and within species through the destruction of ecosystems. Migration joins population growth and social factors, such as land inequality, as major causes of deforestation, and global demand for water is expected to increase faster than the rate of population growth. Coastal development and over-fishing threaten to deplete the oceans, while soil quality is threatened by inappropriate land use. Estimates of the earth's carrying capacity range from less than 3 billion to more than 44 billion people, indicating how difficult it is to assess this figure. Development efforts throughout the world may lead to human gains that will ultimately be negated by environmental losses. These factors have led to growing support for environmentally sustainable development.

  10. Global population growth.

    PubMed

    Langmore, J

    1992-07-01

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

  11. U.S. Population Growth.

    ERIC Educational Resources Information Center

    Dillner, Harry

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

  12. Population Growth: Crisis and Challenge.

    ERIC Educational Resources Information Center

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

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

  13. The repercussion of population growth.

    PubMed

    Barnes, A C

    1981-08-01

    It is self-evident that, "in a finite world, infinite population growth is impossible." Population growth rates are now higher than ever before in history. In addition, there is a certain level of momentum built in, i.e., even achievement of zero population growth would be accompanied by real increases in the population level due to the age-sex structure of the population. While birth, death, and population growth rates can be calculated arithmetically, their repercussions for quality of life indices cannot. With unlimited population growth, life becomes less worth living. A brief examination is made of the following indices of quality of life and the implications for them of unlimited growth: 1) educational facilities and information media; 2) food and nutrition; 3) housing and clothing; 4) health facilities and sanitation; 5) job availability; 6) waste disposal and the quality of the environment; and 7) energy supply and transportation. Except at the local level, it is unlikely that these facilities can grow exponentially with rapid population growth. Population control must ultimately rest on many individual decisions taken at the personal level.

  14. The coming acceleration of global population ageing.

    PubMed

    Lutz, Wolfgang; Sanderson, Warren; Scherbov, Sergei

    2008-02-07

    The future paths of population ageing result from specific combinations of declining fertility and increasing life expectancies in different parts of the world. Here we measure the speed of population ageing by using conventional measures and new ones that take changes in longevity into account for the world as a whole and for 13 major regions. We report on future levels of indicators of ageing and the speed at which they change. We show how these depend on whether changes in life expectancy are taken into account. We also show that the speed of ageing is likely to increase over the coming decades and to decelerate in most regions by mid-century. All our measures indicate a continuous ageing of the world's population throughout the century. The median age of the world's population increases from 26.6 years in 2000 to 37.3 years in 2050 and then to 45.6 years in 2100, when it is not adjusted for longevity increase. When increases in life expectancy are taken into account, the adjusted median age rises from 26.6 in 2000 to 31.1 in 2050 and only to 32.9 in 2100, slightly less than what it was in the China region in 2005. There are large differences in the regional patterns of ageing. In North America, the median age adjusted for life expectancy change falls throughout almost the entire century, whereas the conventional median age increases significantly. Our assessment of trends in ageing is based on new probabilistic population forecasts. The probability that growth in the world's population will end during this century is 88%, somewhat higher than previously assessed. After mid-century, lower rates of population growth are likely to coincide with slower rates of ageing.

  15. Human Population: Fundamentals of Growth and Change.

    ERIC Educational Resources Information Center

    Stauffer, Cheryl Lynn, Ed.

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

  16. Front acceleration by dynamic selection in Fisher population waves

    NASA Astrophysics Data System (ADS)

    Bénichou, O.; Calvez, V.; Meunier, N.; Voituriez, R.

    2012-10-01

    We introduce a minimal model of population range expansion in which the phenotypes of individuals present no selective advantage and differ only in their diffusion rate. We show that such neutral phenotypic variability (i.e., that does not modify the growth rate) alone can yield phenotype segregation at the front edge, even in absence of genetic noise, and significantly impact the dynamical properties of the expansion wave. We present an exact asymptotic traveling wave solution and show analytically that phenotype segregation accelerates the front propagation. The results are compatible with field observations such as invasions of cane toads in Australia or bush crickets in Britain.

  17. Population Growth: Stretching the Limits.

    ERIC Educational Resources Information Center

    Brouse, Deborah E.

    1990-01-01

    Three population education activities that can be used to illustrate the effects of uncontrolled population growth are presented. Included are "Crowding Can Be Seedy," which uses seeds; "Something for Everyone," which illustrates competition for resources; and "More or Less," which illustrates the relationship between humans and the environment.…

  18. Impaired lymphatic function accelerates cancer growth

    PubMed Central

    Steinskog, Eli Sihn Samdal; Sagstad, Solfrid Johanne; Wagner, Marek; Karlsen, Tine Veronica; Yang, Ning; Markhus, Carl Erik; Yndestad, Synnøve; Wiig, Helge; Eikesdal, Hans Petter

    2016-01-01

    Increased lymphangiogenesis is a common feature of cancer development and progression, yet the influence of impaired lymphangiogenesis on tumor growth is elusive. C3HBA breast cancer and KHT-1 sarcoma cell lines were implanted orthotopically in Chy mice, harboring a heterozygous inactivating mutation of vascular endothelial growth factor receptor-3, resulting in impaired dermal lymphangiogenesis. Accelerated tumor growth was observed in both cancer models in Chy mice, coinciding with reduced peritumoral lymphangiogenesis. An impaired lymphatic washout was observed from the peritumoral area in Chy mice with C3HBA tumors, and the number of macrophages was significantly reduced. While fewer macrophages were detected, the fraction of CD163+ M2 macrophages remained constant, causing a shift towards a higher M2/M1 ratio in Chy mice. No difference in adaptive immune cells was observed between wt and Chy mice. Interestingly, levels of pro- and anti-inflammatory macrophage-associated cytokines were reduced in C3HBA tumors, pointing to an impaired innate immune response. However, IL-6 was profoundly elevated in the C3HBA tumor interstitial fluid, and treatment with the anti-IL-6 receptor antibody tocilizumab inhibited breast cancer growth. Collectively, our data indicate that impaired lymphangiogenesis weakens anti-tumor immunity and favors tumor growth at an early stage of cancer development. PMID:27329584

  19. Population growth, inequality and poverty.

    PubMed

    Rodgers, G

    1983-01-01

    In this discussion of population growth, inequality, and poverty, the type of relationships that can be observed in intercountry comparisons are explored, reviewing the findings of several other authors, presenting some new estimates using an International Labor Office data bank, considering some basic conceptual problems, and examining some of the theoretical and empirical issues that call for investigation at the national level. Intercountry comparisons, despite their limitations, appear to be the easiest starting point for empirical analysis. The approach adopted by most researchers has been to select 1 or more population indicators and a measure of national income inequality and to explain intercountry differences in 1 or both of these variables in terms of each other and of other indicators of economic and social development. Underlying this methodology is the assumption that there are aspects of demographic and economic change that are common to all countries included in the study, so that differences between countries give some guide to the likely evolution over time within any 1 country. This can be accepted at best with reservations, but given the scarcity of data on the evolution of inequality over time, a working hypothesis of this type appears unavoidable. But, as many of the factors likely to cause population growth and inequality operate over extended periods of time, a dynamic model is indicated. A simpler model, which pays particular attention to lags and variations over time, may generate new insights. A summary of the results of a new international cross-section analysis set up on these lines is presented. Results suggest that contrary to expectations, reducing population growth does not seem to generate longterm benefits for the poor in this model, though some short term gains are found. Increasing equality does appear to generate some decline in population growth, as well as persistent gains in incomes among the poor, but the reductions in

  20. Rotary plant growth accelerating apparatus. [weightlessness

    NASA Technical Reports Server (NTRS)

    Dedolph, R. D. (Inventor)

    1975-01-01

    Rotary plant growth accelerating apparatus for increasing plant yields by effectively removing the growing plants from the constraints of gravity and increasing the plant yield per unit of space is described. The apparatus is comprised of cylindrical plant beds supported radially removed from a primary axis of rotation, with each plant bed being driven about its own secondary axis of rotation and simultaneously moved in a planetary path about the primary axis of rotation. Each plant bed is formed by an apertured outer cylinder, a perforated inner cylinder positioned coaxially, and rooting media disposed in the space between. A rotatable manifold distributes liquid nutrients and water to the rooting media through the perforations in the inner cylinders as the plant beds are continuously rotated by suitable drive means.

  1. Modeling Population Growth and Extinction

    ERIC Educational Resources Information Center

    Gordon, Sheldon P.

    2009-01-01

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

  2. Population Growth: Family Planning Programs.

    ERIC Educational Resources Information Center

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

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

  3. Nutrition, Development, and Population Growth

    ERIC Educational Resources Information Center

    Berg, Alan

    1973-01-01

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

  4. Political economy of population growth.

    PubMed

    Mehta, S; Mehta, H S

    1987-01-01

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

  5. Anomalous Growth of Aging Populations

    NASA Astrophysics Data System (ADS)

    Grebenkov, Denis S.

    2016-04-01

    We consider a discrete-time population dynamics with age-dependent structure. At every time step, one of the alive individuals from the population is chosen randomly and removed with probability q_k depending on its age, whereas a new individual of age 1 is born with probability r. The model can also describe a single queue in which the service order is random while the service efficiency depends on a customer's "age" in the queue. We propose a mean field approximation to investigate the long-time asymptotic behavior of the mean population size. The age dependence is shown to lead to anomalous power-law growth of the population at the critical regime. The scaling exponent is determined by the asymptotic behavior of the probabilities q_k at large k. The mean field approximation is validated by Monte Carlo simulations.

  6. Environmental impact of population growth

    NASA Astrophysics Data System (ADS)

    Naylor, Rosamond; Matson, Pamela

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

  7. Population growth and global warming.

    PubMed

    Short, R V

    2009-01-01

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

  8. The challenge of population growth.

    PubMed

    Smith, A W

    1984-03-02

    A precarious balance exists on earth between food and people, and at this time 800 million people are starving or close to starvation. When agriculture began, say 10,000 years ago, human populations were low. They stayed roughly in balance with the food supply. After agriculture, food supplies increased as did populations. The discovery of the New World opened vast resources, more land. Human numbers began to climb. Inventions and machines increased the ability to exploit resources. With modern medicine came a decline in death rates while birthrates remained high. The result is the 20th century population now totals 4.7 billion. By 2000, it will probably reach 6.1 billion and 7.8 billion by 2020. There will be insufficient cropland to produce the food all these people will need. People have been moving into sprawling urban centers of the poor countries. They come in search of jobs because there is not enough land to support them in rural areas. They increase the numbers of the unemployed and live in squalid shanty towns. Each agricultural or industrial advance that has occurred has been overwhelmed by ever increasing numbers of people in many less developed nations. There appears to be no "catching up" with the world's soaring rate of population. About 40 years ago this dilemma began to alarm some people. Fairfield Osborn and William Vogt believed that food and economic aid should continue but would be only a stopgap until developing countries were able to control their population growth. This meant cutting the birthrate. They reasoned that the best way to accomplish this was to educate people about contraceptives and other methods of limiting fertility. Private foundations funded educational programs, and many governments began giving out contraceptives at little or no cost. Despite such efforts, populations continued to increase in places that could least support more people. Already controversial, population control programs began to offer various incentives to

  9. Modeling Reliability Growth in Accelerated Stress Testing

    DTIC Science & Technology

    2013-12-01

    HASS and HASA Explained, Milwaukee, WI: Quality Press, 2009. [13] A. J. Porter, "Failure Mode Verification: Applying Highly Accelerated Life Testing...and Production Conference - Proceedings of the Technical Program, Des Plaines, IL, 1998. [16] M. Silverman, "Summary of HALT and HASS results at

  10. Accelerated growth of calcium silicate hydrates: Experiments and simulations

    SciTech Connect

    Nicoleau, Luc

    2011-12-15

    Despite the usefulness of isothermal calorimetry in cement analytics, without any further computations this brings only little information on the nucleation and growth of hydrates. A model originally developed by Garrault et al. is used in this study in order to simulate hydration curves of cement obtained by calorimetry with different known hardening accelerators. The limited basis set of parameters used in this model, having a physical or chemical significance, is valuable for a better understanding of mechanisms underlying in the acceleration of C-S-H precipitation. Alite hydration in presence of four different types of hardening accelerators was investigated. It is evidenced that each accelerator type plays a specific role on one or several growth parameters and that the model may support the development of new accelerators. Those simulations supported by experimental observations enable us to follow the formation of the C-S-H layer around grains and to extract interesting information on its apparent permeability.

  11. [The accelerated aging of the population in Brazil].

    PubMed

    Cassab, Amanda Kampa

    2013-01-01

    Formerly a young country, Brazil is now undergoing a period of acceleration in the ageing of its population. The Brazilian geriatric heathcare sector must prepare itself to advocate and optimise the care of elderly patients. The training of professionals in gerontology must be a priority and public policies need to evolve.

  12. Population and growth causality in developing countries.

    PubMed

    Kapuria-foreman, V

    1995-07-01

    This study empirically tests the null hypotheses of no causality between population growth and economic growth and of no causality between economic growth and population growth in 15 developing countries. The model follows the Cheng Hsiao form with lag lengths to minimize Akaike's Final Prediction Error (FPE). Equations are run separately for each country. Lag lengths and Granger causality test were chosen according to three steps. 1) Each of the variables was regressed on its own lagged values with a maximum lag of five years. A lag length was chosen that minimized FPE, which was calculated for each regression. 2) Bivariate regressions were run with a fixed lag length for population growth and mixed lag lengths for the other variable, until the lag length which minimized FPE was determined. 3) The last step involved checking the lag length of population growth by keeping the lag fixed for economic growth. The economic growth measure was gross domestic product per capita. Findings indicate that in seven countries the null hypothesis of no causality between population growth and economic growth, either positive or negative, cannot be rejected (Ghana, Sri Lanka, Bolivia, Philippines, Syria, Thailand, and Argentina). In Nepal, India, China, Guatemala, Peru, Turkey, Chile, and Mexico lagged values of population growth improve predictions of economic growth. Higher economic growth has no significant effect on population growth rates in Nepal, Bolivia, Philippines, Guatemala, Peru, Thailand, Argentina, and Mexico. Interaction between economic growth and population growth was found in India, China, Turkey, and Chile. The direction of causation tests indicate that population growth has a significant positive impact on income growth in China, Guatemala, Turkey, Chile, and Mexico. India shows a negative impact of population growth on income. A significant negative impact of economic growth on population growth is evident only in Sri Lanka. There is weak evidence of a

  13. Population growth rates: issues and an application.

    PubMed Central

    Godfray, H Charles J; Rees, Mark

    2002-01-01

    Current issues in population dynamics are discussed in the context of The Royal Society Discussion Meeting 'Population growth rate: determining factors and role in population regulation'. In particular, different views on the centrality of population growth rates to the study of population dynamics and the role of experiments and theory are explored. Major themes emerging include the role of modern statistical techniques in bringing together experimental and theoretical studies, the importance of long-term experimentation and the need for ecology to have model systems, and the value of population growth rate as a means of understanding and predicting population change. The last point is illustrated by the application of a recently introduced technique, integral projection modelling, to study the population growth rate of a monocarpic perennial plant, its elasticities to different life-history components and the evolution of an evolutionarily stable strategy size at flowering. PMID:12396521

  14. Hispanic Population Growth and Rural Income Inequality

    ERIC Educational Resources Information Center

    Parrado, Emilio A.; Kandel, William A.

    2010-01-01

    We analyze the relationship between Hispanic population growth and changes in U.S. rural income inequality from 1990 through 2000. Applying comparative approaches used for urban areas we disentangle Hispanic population growth's contribution to inequality by comparing and statistically modeling changes in the family income Gini coefficient across…

  15. Population growth and earth's human carrying capacity.

    PubMed

    Cohen, J E

    1995-07-21

    Earth's capacity to support people is determined both by natural constraints and by human choices concerning economics, environment, culture (including values and politics), and demography. Human carrying capacity is therefore dynamic and uncertain. Human choice is not captured by ecological notions of carrying capacity that are appropriate for nonhuman populations. Simple mathematical models of the relation between human population growth and human carrying capacity can account for faster-than-exponential population growth followed by a slowing population growth rate, as observed in recent human history.

  16. Population growth. Its magnitude and implications for development.

    PubMed

    Birdsall, N

    1984-09-01

    A summary of the 1984 World Development Report is provided. The 3 major points stressed in the report were: 1) rapid population growth adversely affects development, 2) governments must adopt policies to reduce fertility, and 3) policies adopted by many countries have effectively reduced fertility. World population growth began accelerating at 0.5%/year in the 18th century, and by 1950 the annual acceleration rate was 2%. Most of the increase in population size is occurring in less developed countries, and this increase is due in part to the recent decline in mortality experienced by these countries. Of the 80 million individuals who will be added to the world's population in 1984, 70 million will be in the developing countries. Since 1965 the population growth rate for developing countries as a group declined from 2.4% to 2%. However, because of the high proportion of younger aged individuals in developing countries, the decline in fertility is expected to level off. According to World Bank population projections, the world population will stabilize at around 11 billion in 2150. During the interium, the population of developing countries will increase from its present level of 3.6 billion to 8.4 billion, and the population of developed countries will increase from 1.2 billion to 1.4 billion. These projections are probably overly optimistic. The adverse impact on development of rapid population growth is due to several factors. 1st, resources which could be used for investment must instead be used to fulfill the consumption needs of an increased number of people. 2nd, increases in the labor force must be absorbed by the agricultural sector, and this reduces agricultural productivity. 3rd, rapid population growth increases management problems. The adaption of policies by governments to reduce fertility is a necessary step in halting population growth. For poor families, children provide economic security. Therefore, governments must act to improve the economic

  17. Crystal growth of energetic materials during high acceleration

    SciTech Connect

    Lanzerotti, M.Y.D.; Autera, J.; Borne, L.; Sharma, J.

    1996-07-01

    Studies of the growth of crystals of energetic materials under conditions of high acceleration in an ultracentrifuge are reported. When a saturated solution is accelerated in an ultracentrifuge, the solute molecules move individually through the solvent molecules to form a crystal at the outer edge of the tube if the solute is more dense than the solvent. Since there is no evaporation or temperature variation, convection currents caused by simultaneous movement of solvent and solute are minimized and crystal defects are potentially minimized. Crystal growth is controlled by the g-level of the acceleration. In addition, solution inclusions and bubbles migrate out of the saturated solution as a result of the pressure gradient induced by the g-force. The authors present results of TNT, RDX, and TNAZ grown at high g from various solutions.

  18. Metropolitan population growth in Arab countries.

    PubMed

    Vaidyanathan, K E

    1977-01-01

    A study or urban population growth in Arab countries has 3 objectives: 1) examination at the micro level of recent demographic trends in selected metropolitan areas of the Arab world and their relationship to changes in the total and urban populations in the respective countries; 2) estimation of net migration by sex and broad age groups for each metropolitan area; and 3) analysis of the pattern of variation in the metropolitan growth rates and their components, migration and natural increase. The study covers the cities proper or urban agglomerations, which includes the suburbs, whose population exceeded 100,000 in the most recent census. Altogether, the study covers 49 metropolitan areas from 9 Arab countries--Algeria; Morocco; Tunisia; Libya; Egypt; Sudan; Syria; Iraq; and Kuwait. Analysis revealed that metropolitan growth rates do follow geographic patterns. In countries with an oil-based economy, metropolitan growth rates are high; in countries with unexploited resources they are slightly below the 1st group; and countries which have pressure on land have low metropolitan growth rates. Population size of the metropolitan area appears to be an important factor associated with variations in metropolitan growth rates and net migration rates. Natural increase emerges as the predominant factor in metropolitan growth, but the differentials in the growth rates are more clearly associated with variations in net migration rates. As all the possibilities of analysis of relationships of metropolitan growth have not been exhausted, it is proposed to examine additional variables as possible factors associated with the speed of metropolitan growth.

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

    ERIC Educational Resources Information Center

    Peck, Jennifer Marks

    1974-01-01

    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…

  20. Growth rate, population entropy, and perturbation theory.

    PubMed

    Demetrius, L

    1989-04-01

    This paper is concerned with the connection between two classes of population variables: measures of population growth rate--the Malthusian parameter, the net reproduction rate, the gross reproduction rate, and the mean life expectancy; and measures of demographic heterogeneity--population entropy. It is shown that the entropy functions predict the response of the growth rate parameters to perturbations in the age-specific fecundity and mortality schedule. These results are invoked to introduce the notion of environmental intensity. The intensity function, expressed in terms of the entropy parameters, is applied to give a comparative study of the effect of environmental factors on the dynamics of Swedish and French populations.

  1. A Revisionist Look at Population and Growth.

    ERIC Educational Resources Information Center

    Holden, Constance

    1986-01-01

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

  2. The containment of world population growth.

    PubMed

    Caldwell, J C

    1975-12-01

    The world has reached the present position of unprecedentedly rapid population growth not by achieving uniquely high fertility but by bringing about extraordinarily low mortality. The high growth rate and the built-in momentum of the age structure are obstacles to achievement of an acceptable standard of living for most of the world's population. Although government population programs have the potential to curb this growth rate, this potential has not been realized, and such programs are too often perceived both by their administrators and the population concerned as an end in themselves rather than a means toward a better standard of living. It is in this latter perspective, and in the context of the total development process, that population programs should be implemented.

  3. Population growth and development: the Kenyan experience.

    PubMed

    Nyamwange, M

    1995-01-01

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

  4. Population priorities: the challenge of continued rapid population growth

    PubMed Central

    Turner, Adair

    2009-01-01

    Rapid population growth continues in the least developed countries. The revisionist case that rapid population could be overcome by technology, that population density was advantageous, that capital shallowing is not a vital concern and that empirical investigations had not proved a correlation between high population growth and low per capita income was both empirically and theoretically flawed. In the modern world, population density does not play the role it did in nineteenth-century Europe and rates of growth in some of today's least developed nations are four times than those in nineteenth-century Europe, and without major accumulation of capital per capita, no major economy has or is likely to make the low- to middle-income transition. Though not sufficient, capital accumulation for growth is absolutely essential to economic growth. While there are good reasons for objecting to the enforced nature of the Chinese one-child policy, we should not underestimate the positive impact which that policy has almost certainly had and will have over the next several decades on Chinese economic performance. And a valid reticence about telling developing countries that they must contain fertility should not lead us to underestimate the severely adverse impact of high fertility rates on the economic performance and prospects of many countries in Africa and the Middle East. PMID:19770149

  5. Population priorities: the challenge of continued rapid population growth.

    PubMed

    Turner, Adair

    2009-10-27

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

  6. Stochastic population growth in spatially heterogeneous environments.

    PubMed

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

    2013-02-01

    Classical ecological theory predicts that environmental stochasticity increases extinction risk by reducing the average per-capita growth rate of populations. For sedentary populations in a spatially homogeneous yet temporally variable environment, a simple model of population growth is a stochastic differential equation dZ(t) = μZ(t)dt + σZ(t)dW(t), t ≥ 0, where the conditional law of Z(t+Δt)-Z(t) given Z(t) = z has mean and variance approximately z μΔt and z²σ²Δt when the time increment Δt is small. The long-term stochastic growth rate lim(t→∞) t⁻¹ log Z(t) for such a population equals μ − σ²/2 . Most populations, however, experience spatial as well as temporal variability. To understand the interactive effects of environmental stochasticity, spatial heterogeneity, and dispersal on population growth, we study an analogous model X(t) = (X¹(t) , . . . , X(n)(t)), t ≥ 0, for the population abundances in n patches: the conditional law of X(t+Δt) given X(t) = x is such that the conditional mean of X(i)(t+Δt) − X(i)(t) is approximately [x(i)μ(i) + Σ(j) (x(j) D(ji) − x(i) D(i j) )]Δt where μ(i) is the per capita growth rate in the ith patch and D(ij) is the dispersal rate from the ith patch to the jth patch, and the conditional covariance of X(i)(t+Δt)− X(i)(t) and X(j)(t+Δt) − X(j)(t) is approximately x(i)x(j)σ(ij)Δt for some covariance matrix Σ = (σ(ij)). We show for such a spatially extended population that if S(t) = X¹(t)+· · ·+ X(n)(t) denotes the total population abundance, then Y(t) = X(t)/S(t), the vector of patch proportions, converges in law to a random vector Y(∞) as t → ∞, and the stochastic growth rate lim(t→∞) t⁻¹ log S(t) equals the space-time average per-capita growth rate Σ(i)μ(i)E[Y(i)(∞)] experienced by the population minus half of the space-time average temporal variation E[Σ(i,j) σ(i j)Y(i)(∞) Y(j)(∞)] experienced by the population. Using this characterization of the

  7. Stochastic population growth in spatially heterogeneous environments

    PubMed Central

    Evans, Steven N.; Ralph, Peter L.; Sen, Arnab

    2016-01-01

    Classical ecological theory predicts that environmental stochasticity increases extinction risk by reducing the average per-capita growth rate of populations. For sedentary populations in a spatially homogeneous yet temporally variable environment, a simple model of population growth is a stochastic differential equation dZt = μZtdt + σ ZtdWt, t ≥ 0, where the conditional law of Zt+Δt − Zt given Zt = z has mean and variance approximately zμΔt and z2σ2Δt when the time increment Δt is small. The long-term stochastic growth rate limt→∞ t−1 log Zt for such a population equals μ−σ22. Most populations, however, experience spatial as well as temporal variability. To understand the interactive effects of environmental stochasticity, spatial heterogeneity, and dispersal on population growth, we study an analogous model Xt=(Xt1,…,Xtn), t ≥ 0, for the population abundances in n patches: the conditional law of Xt+Δt given Xt = x is such that the conditional mean of Xt+Δti−Xti is approximately [xiμi +∑j (xj Dji − xi Dij)]Δt where μi is the per capita growth rate in the ith patch and Dij is the dispersal rate from the ith patch to the jth patch, and the conditional covariance of Xt+Δti−Xti and Xt+Δtj−Xtj is approximately xixjσijΔt for some covariance matrix Σ = (σij). We show for such a spatially extended population that if St=Xt1+⋯+Xtn denotes the total population abundance, then Yt = Xt /St, the vector of patch proportions, converges in law to a random vector Y∞ as t → ∞, and the stochastic growth rate limt→∞ t−1 log St equals the space-time average per-capita growth rate ∑iμi𝔼[Y∞j] experienced by the population minus half of the space-time average temporal variation 𝔼[∑i,jσijY∞iY∞j] experienced by the population. Using this characterization of the stochastic growth rate, we derive an explicit expression for the stochastic growth rate for populations living in two patches, determine which

  8. Epistasis can accelerate adaptive diversification in haploid asexual populations.

    PubMed

    Griswold, Cortland K

    2015-03-07

    A fundamental goal of the biological sciences is to determine processes that facilitate the evolution of diversity. These processes can be separated into ecological, physiological, developmental and genetic. An ecological process that facilitates diversification is frequency-dependent selection caused by competition. Models of frequency-dependent adaptive diversification have generally assumed a genetic basis of phenotype that is non-epistatic. Here, we present a model that indicates diversification is accelerated by an epistatic basis of phenotype in combination with a competition model that invokes frequency-dependent selection. Our model makes use of a genealogical model of epistasis and insights into the effects of balancing selection on the genealogical structure of a population to understand how epistasis can facilitate diversification. The finding that epistasis facilitates diversification may be informative with respect to empirical results that indicate an epistatic basis of phenotype in experimental bacterial populations that experienced adaptive diversification.

  9. Population growth and environmental degradation in Malawi.

    PubMed

    Kalipeni, E

    1992-01-01

    Malawi has been ranked by the World Bank as one of the poorest countries in Africa. Malawi's only resources are its people and fertile soil, which comprises about 55% of land area. Environmental degradation and population growth conditions in Malawi were used to illustrate the model of environmental degradation linked to population pressure on land resources and government development strategies that favored large-scale agricultural farms. The result has been deforestation, overgrazing, overuse of land for subsistence, and increased population density. The argument was that population growth in some developing countries has been so rapid that environmental collapse is the result. The theoretical framework linking population growth, environment, and resources emphasized processes: 1) the precursor stage of underlying causes; 2) the problem phase with potential ecological and economic decline; and 3) consequences (environmental decline, reduction in food production systems, and reduction in standard of living). The precursors were identified as an agrarian society, lack of a population policy, and emphasis on large families. The problems were rapid population growth and immigration from Mozambique, which led to increased demand for trees for fuel and consequent deforestation, increased demand for arable land and consequent landlessness, increased investment in livestock and consequent overgrazing, and continued population momentum which was a financial burden to government and resulted in increased labor competition. The ecological consequences were soil erosion, degradation of vegetation, and water supply contamination and decline. Eventually, famines will occur and lead to disease, migration, deserted villages, urbanization, unemployment, ethnic conflicts, and political unrest. Population was estimated at 8.75 million in 1990, with exponential growth expected. Completed family size was 6.6 children per woman. Even replacement fertility would mean growth for 50 more

  10. Impact of accelerated plant growth on seed variety development

    NASA Astrophysics Data System (ADS)

    Christophersen, Eric

    1998-01-01

    The commercial lives of agricultural seed products have steadily declined in recent years. The introduction of genetically engineered crop seeds in 1966 has accentuated that trend. Widespread grower demand for genetically engineered seed requires competitive response by industry followers in order to avert market share losses to the industry leaders. Limitations on plant transformation technology, regulatory requirements and patent impediments require companies to rapidly convert transformed lines into elite commercial products. Massive multigenerational backcrossing efforts are required to distribute genetically engineered traits into a broad product mix. Significant incidents of expression failures, or ``gene silencing,'' have occurred unexpectedly, requiring product substitution strategies. First-to-market strategies, competitive response, broad germplasm conversion and rescue of product failures all share the element of urgency. Technologies which reliably accelerate product development rates can expect favorable reception by commercial seed developers. A growth chamber which dramatically accelerates the rate of plant growth is described.

  11. Emittance growth mechanisms for laser-accelerated proton beams.

    PubMed

    Kemp, Andreas J; Fuchs, J; Sentoku, Y; Sotnikov, V; Bakeman, M; Antici, P; Cowan, T E

    2007-05-01

    In recent experiments the transverse normalized rms emittance of laser-accelerated MeV ion beams was found to be < 0.002 mm mrad, which is at least 100 times smaller than the emittance of thermal ion sources used in accelerators [T. E. Cowan, Phys. Rev. Lett. 92, 204801 (2004)]. We investigate the origin for the low emittance of laser-accelerated proton beams by studying several candidates for emittance-growth mechanisms. As our main tools, we use analytical models and one- and two-dimensional particle-in-cell simulations that have been modified to include binary collisions between particles. We find that the dominant source of emittance is filamentation of the laser-generated hot electron jets that drive the ion acceleration. Cold electron-ion collisions that occur before ions are accelerated contribute less than ten percent of the final emittance. Our results are in qualitative agreement with the experiment, for which we present a refined analysis relating emittance to temperature, a better representative of the fundamental beam physics.

  12. Modeling Nonlinear Change via Latent Change and Latent Acceleration Frameworks: Examining Velocity and Acceleration of Growth Trajectories

    ERIC Educational Resources Information Center

    Grimm, Kevin; Zhang, Zhiyong; Hamagami, Fumiaki; Mazzocco, Michele

    2013-01-01

    We propose the use of the latent change and latent acceleration frameworks for modeling nonlinear growth in structural equation models. Moving to these frameworks allows for the direct identification of "rates of change" and "acceleration" in latent growth curves--information available indirectly through traditional growth…

  13. Population growth and sustainable development in China.

    PubMed

    Gui, S

    1998-12-01

    This article identifies the adverse impacts of population growth in China and offers suggestions for attaining sustainable development. Although China has below replacement level fertility, population will continue to increase. Chinese demographers project that the total fertility rate will average 2.1 each year until 2010, 2.1 until 2050, or 1.88 until 2010 and 1.6 during 2010-2050 under high, medium, and low variants, respectively. Total population would number 1.69 billion, 1.50 billion, or 1.46 billion under various projections, respectively, by 2050. Continued growth is expected to seriously slow economic development, to hinder improvements in the quality of and full use of human resources, to depress increases in per-capita economic development levels, and to impact on reasonable use of resources and environmental protection. The averting of 5 million births would save 35.5 billion yuan. Population growth has reduced the per-capita share of cultivated land from 0.19 to 0.08 hectares during 1952-95. There are about 150-190 million surplus rural laborers. Registered unemployment in cities was 3.1% in 1997. 11.5 million were laid-off workers. The working-age population will exceed 900 million during 2007-26. China's gross national product (GNP) was the 8th highest in the world in 1990, but its per-capita GNP was in 100th place. China's abundant natural resources are seriously reduced when population is considered. Environmental damage is already evident. Population growth needs to be controlled through family planning, an old-age social security program, and long-term population policies. Society needs healthier births and childbearing and better educated children.

  14. Keynes on population and economic growth.

    PubMed

    Toye, J

    1997-01-01

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

  15. UN lowers projection on future population growth.

    PubMed

    1999-01-01

    The new projections of future population growth released by the UN Population Division in late October 1998 are lower than previous projections. This has happened, as reported, owing to a number of reasons, including an expected increase in AIDS-related deaths. However, the projections suggest than even in the countries hardest hit by AIDS the population will keep growing because of continuing high birth rates. The projection, routinely updated every 2 years, suggests that the world will reach 6 billion in 1999. By the middle of the next century, global population will be between 7.3 and 10.7 billion. Under the medium variant projections reflecting a middle range of assumptions regarding future birth rates, the world would reach 8.9 billion in 2050. This is nearly half a billion lower than under the medium variant in the 1996 projections. Almost all future population growth, about 97%, is projected to occur in developing regions. Populations in the developed regions on the other hand are projected to stabilize and even decrease in some cases. By 2050 nearly 60 countries, including all of Europe, China and Japan, would experience a decline in population size according to the medium variant projections.

  16. Impact of demographic policy on population growth.

    PubMed

    Podyashchikh, P

    1968-01-01

    Various bourgeois theories, including the reactionary Malthusianism and its variants, challenge the Marxist-Leninist revolutionary theory on the growth of population. Bourgeois science maintains that unchanging biological laws of proliferation form the foundation of social life. Malthus, in his "An Essay on the Principle of Population," contends that population increases in a geometric rate, while means of subsistence tend to increase only in an arithmetic rate: neither the way of production nor social conditions but this law of nature in control of proliferation had been the cause of overpopulation, which again leads to misery, hunger, and unemployment. From this follows the possible conclusion that the working classes should be concerned not about how to change the social order but how to reduce the number of childbirths. Progressive science views the laws of social life in a totally different way. Marxism-Leninism teaches that population size, despite the markedly important role played by it in historical progress, fails to represent that main force of social progress which determines the mode of production and of the distribution of material goods, but just the reverse: the mode of production determines the growth of population, the changes in its density and composition. Marxism-Leninism teaches that each historical stage of production (slavery, feudalism, capitalism) has its own special, historically valid demographic law. Bourgeois science maintains that humankind faces an absolute overpopulation caused by the means of production lagging behind the growth of population. Actually this is only a relative overpopulation due to the fact that capitalistic production is subjected to the interests of increasing capitalistic profit and not to those of meeting the demands of population. In socialist countries, production is incessantly developing and expanding, and employment of the entire productive population is ensured. Consequently, the problem of relative

  17. Stochastic dynamics and logistic population growth

    NASA Astrophysics Data System (ADS)

    Méndez, Vicenç; Assaf, Michael; Campos, Daniel; Horsthemke, Werner

    2015-06-01

    The Verhulst model is probably the best known macroscopic rate equation in population ecology. It depends on two parameters, the intrinsic growth rate and the carrying capacity. These parameters can be estimated for different populations and are related to the reproductive fitness and the competition for limited resources, respectively. We investigate analytically and numerically the simplest possible microscopic scenarios that give rise to the logistic equation in the deterministic mean-field limit. We provide a definition of the two parameters of the Verhulst equation in terms of microscopic parameters. In addition, we derive the conditions for extinction or persistence of the population by employing either the momentum-space spectral theory or the real-space Wentzel-Kramers-Brillouin approximation to determine the probability distribution function and the mean time to extinction of the population. Our analytical results agree well with numerical simulations.

  18. Stochastic dynamics and logistic population growth.

    PubMed

    Méndez, Vicenç; Assaf, Michael; Campos, Daniel; Horsthemke, Werner

    2015-06-01

    The Verhulst model is probably the best known macroscopic rate equation in population ecology. It depends on two parameters, the intrinsic growth rate and the carrying capacity. These parameters can be estimated for different populations and are related to the reproductive fitness and the competition for limited resources, respectively. We investigate analytically and numerically the simplest possible microscopic scenarios that give rise to the logistic equation in the deterministic mean-field limit. We provide a definition of the two parameters of the Verhulst equation in terms of microscopic parameters. In addition, we derive the conditions for extinction or persistence of the population by employing either the momentum-space spectral theory or the real-space Wentzel-Kramers-Brillouin approximation to determine the probability distribution function and the mean time to extinction of the population. Our analytical results agree well with numerical simulations.

  19. Design issues for population growth models

    PubMed Central

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

    2010-01-01

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

  20. Safety Evaluation of Transgenic Tilapia with Accelerated Growth.

    PubMed

    Guillén; Berlanga; Valenzuela; Morales; Toledo; Estrada; Puentes; Hayes; de la Fuente J

    1999-01-01

    Recent advances in modern marine biotechnology have permitted the generation of new strains of economically important fish species through the transfer of growth hormone genes. These transgenic fish strains show improved growth performance and therefore constitute a better alternative for aquaculture programs. Recently, we have obtained a transgenic tilapia line with accelerated growth. However, before introducing this line into Cuban aquaculture, environmental and food safety assessment was required by national authorities. Experiments were performed to evaluate the behavior of transgenic tilapia in comparison to wild tilapia as a way to assess the environmental impact of introducing transgenic tilapia into Cuban aquaculture. Studies were also conducted to evaluate, according to the principle of substantial equivalence, the safety of consuming transgenic tilapia as food. Behavior studies showed that transgenic tilapia had a lower feeding motivation and dominance status than controls. Food safety assessment indicated that tilapia growth hormone has no biological activity when administered to nonhuman primates. Furthermore, no effects were detected in human healthy volunteers after the consumption of transgenic tilapia. These results showed, at least under the conditions found in Cuba, no environmental implications for the introduction of this transgenic tilapia line and the safety in the consumption of tiGH-transgenic tilapia as an alternative feeding source for humans. These results support the culture and consumption of these transgenic tilapia.

  1. Antisomatostatin-induced growth acceleration in chinook salmon (Oncorhynchus tshawytscha).

    PubMed

    Mayer, I; McLean, E; Kieffer, T J; Souza, L M; Donaldson, E M

    1994-10-01

    Since somatostatin (SRIF) inhibits the release of growth hormone (GH), its immunoneutralization may provide an alternative to GH therapy as a means of enhancing somatic growth in fish. The present study examined the feasibility of accelerating growth in juvenile chinook salmon by means of antiSRIF administration. Yearling salmon of Nicola River stock (BC, Canada) were injected intraperitoneally every 5 days, for a total of 40 days, with either SRIF (1 μg g-1 body wt.), antiSRIF (SOMA-10, 1 μg g(-1)), recombinant bovine GH (rbGH, 2.5 μg g(-1)), recombinant porcine GH (rpGH, 2.5 μg g(-1)) or saline (controls). No significant differences were observed in length, weight or final condition factor (k) between the SRIF-treated and control fish over the experimental period. However, the fish treated with the antiSRIF were significantly (p ≤ 0.05) longer and heavier than the control salmon after 25 and 30 days respectively. Furthermore, antiSRIF treatment caused a lowering in k when compared to the control salmon. Fish injected with rbGH or rpGH were significantly longer and heavier than all other groups (p ≤ 0.05), after only 5 days. GH treated groups also returned higher k when compared against all other treatments (p ≤ 0.05). No differences were observed in growth between the two rGH treatments over the experimental period.

  2. Genetic mixture of multiple source populations accelerates invasive range expansion.

    PubMed

    Wagner, Natalie K; Ochocki, Brad M; Crawford, Kerri M; Compagnoni, Aldo; Miller, Tom E X

    2017-01-01

    population growth) during the initial stages of invasion but no consistent effects on dispersal ability. Our work is the first to demonstrate that genetic mixture can alter the course of spatial expansion, the stage of invasion typically associated with the greatest ecological and economic impacts. We suggest that similar effects of genetic mixture may be a common feature of biological invasions in nature, but that these effects can easily go undetected.

  3. Preloading To Accelerate Slow-Crack-Growth Testing

    NASA Technical Reports Server (NTRS)

    Gyekenyesi, John P.; Choi, Sung R.; Pawlik, Ralph J.

    2004-01-01

    An accelerated-testing methodology has been developed for measuring the slow-crack-growth (SCG) behavior of brittle materials. Like the prior methodology, the accelerated-testing methodology involves dynamic fatigue ( constant stress-rate) testing, in which a load or a displacement is applied to a specimen at a constant rate. SCG parameters or life prediction parameters needed for designing components made of the same material as that of the specimen are calculated from the relationship between (1) the strength of the material as measured in the test and (2) the applied stress rate used in the test. Despite its simplicity and convenience, dynamic fatigue testing as practiced heretofore has one major drawback: it is extremely time-consuming, especially at low stress rates. The present accelerated methodology reduces the time needed to test a specimen at a given rate of applied load, stress, or displacement. Instead of starting the test from zero applied load or displacement as in the prior methodology, one preloads the specimen and increases the applied load at the specified rate (see Figure 1). One might expect the preload to alter the results of the test and indeed it does, but fortunately, it is possible to account for the effect of the preload in interpreting the results. The accounting is done by calculating the normalized strength (defined as the strength in the presence of preload the strength in the absence of preload) as a function of (1) the preloading factor (defined as the preload stress the strength in the absence of preload) and (2) a SCG parameter, denoted n, that is used in a power-law crack-speed formulation. Figure 2 presents numerical results from this theoretical calculation.

  4. Growth of India's scheduled caste population, 1971-81: a spatial analysis.

    PubMed

    Gosal, R P

    1990-01-01

    The author analyzes the spatial distribution and the rapid growth rate of India's scheduled caste population since 1971 and finds that "there are wide regional disparities in their rates of population growth. Areas with relatively high growth rates are associated with (i) accelerated process of urbanisation and industrialisation, (ii) expansion in mining activity, and (iii) intensification and commercialisation of agricultural development based on irrigation. By contrast, areas experiencing low rates of growth are associated with (i) continuing high mortality rate, and (ii) net out-migration arising from scarcity of resources, acute poverty and subjection to deprivations...."

  5. The accelerated growth of the worldwide air transportation network

    NASA Astrophysics Data System (ADS)

    Azzam, Mark; Klingauf, Uwe; Zock, Alexander

    2013-01-01

    Mobility by means of air transportation has a critical impact on the global economy. Especially against the backdrop of further growth and an aggravation of the energy crisis, it is crucial to design a sustainable air transportation system. Current approaches focus on air traffic management. Nevertheless, also the historically evolved network offers great potential for an optimized redesign. But the understanding of its complex structure and development is limited, although modern network science supplies a great set of new methods and tools. So far studies analyzing air transportation as a complex network are based on divers and poor data, which are either merely regional or strongly bounded time-wise. As a result, the current state of research is rather inconsistent regarding topological coefficients and incomplete regarding network evolution. Therefore, we use the historical, worldwide OAG flight schedules data between 1979 and 2007 for our study. Through analyzing by far the most comprehensive data base so far, a better understanding of the network, its evolution and further implications is being provided. To our knowledge we present the first study to determine that the degree distribution of the worldwide air transportation network is non-stationary and is subject to densification and accelerated growth, respectively.

  6. Bioelectrochemical system accelerates microbial growth and degradation of filter paper.

    PubMed

    Sasaki, Kengo; Hirano, Shin-Ichi; Morita, Masahiko; Sasaki, Daisuke; Matsumoto, Norio; Ohmura, Naoya; Igarashi, Yasuo

    2011-01-01

    Bioelectrochemical reactors (BERs) with a cathodic working potential of -0.6 or -0.8 V more efficiently degraded cellulosic material, i.e., filter paper (57.4-74.1% in 3 days and 95.9-96.3% in 7 days) than did control reactors without giving exogenous potential (15.4% in 3 days and 64.2% in 7 days). At the same time, resultant conversions to methane and carbon dioxide in cathodic working chamber of BERs by application of electrochemical reduction in 3 days of operation were larger than control reactors. However, cumulative methane production in cathodic BERs was similar to those in control reactors after 7 days of operation. Microscopic observation and 16S rRNA gene analysis showed that microbial growth in the entire consortium was higher after 2 days of operation of cathodic BERs as compared with the control reactors. In addition, the number of methanogenic 16S rRNA gene copies in cathodic BERs was higher than in control reactors. Moreover, archaeal community structures constructed in cathodic BERs consisted of hydrogenotrophic methanogen-related organisms and differed from those in control reactors after 2 days of operation. Specifically, the amount of Methanothermobacter species in cathodic BERs was higher within archaeal communities than in those control reactors after 2 days of operation. Electrochemical reduction may be effective for accelerating microbial growth in the start-up period and thereby increasing microbial treatment of cellulosic waste and methane production.

  7. Population divergence in compensatory growth responses and their costs in sticklebacks

    PubMed Central

    Ab Ghani, Nurul Izza; Merilä, Juha

    2015-01-01

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

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

    ERIC Educational Resources Information Center

    Kent, Mary Mederios

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

  9. Estimation of population growth or decline in genetically monitored populations.

    PubMed Central

    Beaumont, Mark A

    2003-01-01

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

  10. Human population growth and the demographic transition.

    PubMed

    Bongaarts, John

    2009-10-27

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

  11. Accelerated Near-Threshold Fatigue Crack Growth Behavior of an Aluminum Powder Metallurgy Alloy

    NASA Technical Reports Server (NTRS)

    Piascik, Robert S.; Newman, John A.

    2002-01-01

    Fatigue crack growth (FCG) research conducted in the near threshold regime has identified a room temperature creep crack growth damage mechanism for a fine grain powder metallurgy (PM) aluminum alloy (8009). At very low DK, an abrupt acceleration in room temperature FCG rate occurs at high stress ratio (R = Kmin/Kmax). The near threshold accelerated FCG rates are exacerbated by increased levels of Kmax (Kmax less than 0.4 KIC). Detailed fractographic analysis correlates accelerated FCG with the formation of crack-tip process zone micro-void damage. Experimental results show that the near threshold and Kmax influenced accelerated crack growth is time and temperature dependent.

  12. Fitness and density-dependent population growth in Drosophila melanogaster

    SciTech Connect

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

    1981-03-01

    The density-dependent rates of population growth were determined for 26 populations of Drosophila melanogaster maintained in the serial transfer system. Twenty-five populations were homozygous for an entire chromosome 2 sampled from nature; the other was a random heterozygous population. Rates of population growth around the carrying capacity cannot explain the large fitness depression of these lines. However, the homozygous lines show large differences in rates of population growth at low densities relative to the random heterozygous standard. The average relative fitness of the homozygous lines, as determined from the growth rates at the lowest density, is 0.51.

  13. Population growth and education development in China.

    PubMed

    Wei, J

    1988-09-01

    Using data from the 1982 national census and the 1982 national 1 per 1000 fertility sampling survey, this paper examines population growth and educational development in China. From 1949-1979, an average of 22 million people were born each year. In 1985, the birth rate was 20.9 and the natural increase rate was 14.9 per 1000. In 1949, the average numbers of students per 10,000 in university, middle school, and primary school were 2.2, 23, and 450, respectively. In 1982, the numbers were 1.4, 465, and 1324, respectively. Rapid population growth impedes educational development either by reducing educational quality to maintain enrollment or by reducing the quantity to maintain educational quality. Among those over age 12, roughly 1/3 were illiterate. Nonetheless, China has made significant progress in education. The illiteracy rate among 12-14 year olds is below 10%, and more than 1/4 of women have a primary school education. Among women ages 25-34, about 3/5 had a primary school education. The illiteracy rate among rural women age 20-44 is 6 times that of their urban counterparts. Women with a primary school education have about 2 times the fertility level of women with a college education, while the general fertility rate for women with a middle school education is about 1/4 lower than those with a primary school education. The higher the educational level, the lower the number of children ever born. Contraceptive use rates among women with a primary school education are significantly higher than those of illiterate women. Without education and development, the family planning program and birth control cannot be successful in China.

  14. Population growth rate and its determinants: an overview.

    PubMed Central

    Sibly, Richard M; Hone, Jim

    2002-01-01

    We argue that population growth rate is the key unifying variable linking the various facets of population ecology. The importance of population growth rate lies partly in its central role in forecasting future population trends; indeed if the form of density dependence were constant and known, then the future population dynamics could to some degree be predicted. We argue that population growth rate is also central to our understanding of environmental stress: environmental stressors should be defined as factors which when first applied to a population reduce population growth rate. The joint action of such stressors determines an organism's ecological niche, which should be defined as the set of environmental conditions where population growth rate is greater than zero (where population growth rate = r = log(e)(N(t+1)/N(t))). While environmental stressors have negative effects on population growth rate, the same is true of population density, the case of negative linear effects corresponding to the well-known logistic equation. Following Sinclair, we recognize population regulation as occurring when population growth rate is negatively density dependent. Surprisingly, given its fundamental importance in population ecology, only 25 studies were discovered in the literature in which population growth rate has been plotted against population density. In 12 of these the effects of density were linear; in all but two of the remainder the relationship was concave viewed from above. Alternative approaches to establishing the determinants of population growth rate are reviewed, paying special attention to the demographic and mechanistic approaches. The effects of population density on population growth rate may act through their effects on food availability and associated effects on somatic growth, fecundity and survival, according to a 'numerical response', the evidence for which is briefly reviewed. Alternatively, there may be effects on population growth rate of

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

    PubMed

    Sanders, T G

    1982-01-01

    The rate of population increase dropped to less than 2.5% annually in Brazil between 1970-80, but 26 million more people were born. The 1980 census also provides details of continuing urbanization, settlement of the farthest frontiers, and changes in racial composition. The direct cause of the drop in population increase was a drop of about 15% in the fertility rate that had been projected for the decade. Brazil's rate of population increase declined impressively despite the fact that the country continued to make progress in reducing mortality. The greatest improvement occurred between 1930-60. The mortality rate averaged 20.9/1000 between 1940-50 but dropped to 14.2/1000 between 1950-60. Even though the crude death rate dropped 28% in the 1970-80 decade and each child born in 1980 can expect to live 6.5 years longer than a child born in 1970, the life expectancy of 62 years compares with Colombia and El Salvador, which are much poorer countries. In Brazil as a whole the crude birthrate in the 15-19 age group was 66/1000 in 1980. It was 46/1000 in 1970, an increase of nearly 50%. In urban areas the rate increased from 37/1000 to 57/1000 and in the countryside from 59/1000 to 89/1000. The crude birthrate went down slightly in Brazil from 1970-80 from 34 to 32/1000. The total fertility rate (TFR) dropped in the same period from 4.9ll to 3.983. The question that arises is whether fertility rates will increase, with women in the youngest age group continuing to have more children during their reproductive years. Internal migration plays a major role in the distribution of the population. Between 1970-80 there were changes in the migration pattern from the previous decade. All the rapidly growing areas, defined as the frontier, have high fertility rates, but much of their growth results from migration. Between 1960-70 and 1970-80 the most rapidly growing areas of the frontier changed. Few are aware of the extent to which Brazil is becoming a country of large cities

  16. Population Growth and Poverty in the Developing World.

    ERIC Educational Resources Information Center

    Birdsall, Nancy

    1980-01-01

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

  17. [The necessity of controlling population growth in Algeria].

    PubMed

    Sari, D

    1990-01-01

    The case is made for controlling Algeria's rapid rate of population growth. The author notes that at the present rate of growth the population is doubling every 20 years. The decline in the labor market and increases in unemployment and underemployment are also examined. The need for strong population policies and programs is stressed.

  18. Intrinsic normalized emittance growth in laser-driven electron accelerators

    NASA Astrophysics Data System (ADS)

    Migliorati, M.; Bacci, A.; Benedetti, C.; Chiadroni, E.; Ferrario, M.; Mostacci, A.; Palumbo, L.; Rossi, A. R.; Serafini, L.; Antici, P.

    2013-01-01

    Laser-based electron sources are attracting strong interest from the conventional accelerator community due to their unique characteristics in terms of high initial energy, low emittance, and significant beam current. Extremely strong electric fields (up to hundreds of GV/m) generated in the plasma allow accelerating gradients much higher than in conventional accelerators and set the basis for achieving very high final energies in a compact space. Generating laser-driven high-energy electron beam lines therefore represents an attractive challenge for novel particle accelerators. In this paper we show that laser-driven electrons generated by the nowadays consolidated TW laser systems, when leaving the interaction region, are subject to a very strong, normalized emittance worsening which makes them quickly unusable for any beam transport. Furthermore, due to their intrinsic beam characteristics, controlling and capturing the full beam current can only be achieved improving the source parameters.

  19. National health expenditure projections: modest annual growth until coverage expands and economic growth accelerates.

    PubMed

    Keehan, Sean P; Cuckler, Gigi A; Sisko, Andrea M; Madison, Andrew J; Smith, Sheila D; Lizonitz, Joseph M; Poisal, John A; Wolfe, Christian J

    2012-07-01

    For 2011-13, US health spending is projected to grow at 4.0 percent, on average--slightly above the historically low growth rate of 3.8 percent in 2009. Preliminary data suggest that growth in consumers' use of health services remained slow in 2011, and this pattern is expected to continue this year and next. In 2014, health spending growth is expected to accelerate to 7.4 percent as the major coverage expansions from the Affordable Care Act begin. For 2011 through 2021, national health spending is projected to grow at an average rate of 5.7 percent annually, which would be 0.9 percentage point faster than the expected annual increase in the gross domestic product during this period. By 2021, federal, state, and local government health care spending is projected to be nearly 50 percent of national health expenditures, up from 46 percent in 2011, with federal spending accounting for about two-thirds of the total government share. Rising government spending on health care is expected to be driven by faster growth in Medicare enrollment, expanded Medicaid coverage, and the introduction of premium and cost-sharing subsidies for health insurance exchange plans.

  20. Population Growth and a Sustainable Environment.

    ERIC Educational Resources Information Center

    Mortimore, Michael; Tiffen, Mary

    1994-01-01

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

  1. Detecting differential growth of microbial populations with Gaussian process regression

    PubMed Central

    Tonner, Peter D.; Darnell, Cynthia L.; Engelhardt, Barbara E.; Schmid, Amy K.

    2017-01-01

    Microbial growth curves are used to study differential effects of media, genetics, and stress on microbial population growth. Consequently, many modeling frameworks exist to capture microbial population growth measurements. However, current models are designed to quantify growth under conditions for which growth has a specific functional form. Extensions to these models are required to quantify the effects of perturbations, which often exhibit nonstandard growth curves. Rather than assume specific functional forms for experimental perturbations, we developed a general and robust model of microbial population growth curves using Gaussian process (GP) regression. GP regression modeling of high-resolution time-series growth data enables accurate quantification of population growth and allows explicit control of effects from other covariates such as genetic background. This framework substantially outperforms commonly used microbial population growth models, particularly when modeling growth data from environmentally stressed populations. We apply the GP growth model and develop statistical tests to quantify the differential effects of environmental perturbations on microbial growth across a large compendium of genotypes in archaea and yeast. This method accurately identifies known transcriptional regulators and implicates novel regulators of growth under standard and stress conditions in the model archaeal organism Halobacterium salinarum. For yeast, our method correctly identifies known phenotypes for a diversity of genetic backgrounds under cyclohexamide stress and also detects previously unidentified oxidative stress sensitivity across a subset of strains. Together, these results demonstrate that the GP models are interpretable, recapitulating biological knowledge of growth response while providing new insights into the relevant parameters affecting microbial population growth. PMID:27864351

  2. A Longitudinal Assessment of Early Acceleration of Students in Mathematics on Growth in Mathematics Achievement

    ERIC Educational Resources Information Center

    Ma, X.

    2005-01-01

    Early acceleration of students in mathematics (in the form of early access to formal abstract algebra) has been a controversial educational issue. The current study examined the rate of growth in mathematics achievement of accelerated gifted, honors, and regular students across the entire secondary years (Grades 7-12), in comparison to their…

  3. Early rapid growth, early birth: Accelerated fetal growth and spontaneous late preterm birth

    PubMed Central

    Kusanovic, Juan Pedro; Erez, Offer; Espinoza, Jimmy; Gotsch, Francesca; Goncalves, Luis; Hassan, Sonia; Gomez, Ricardo; Nien, Jyh Kae; Frongillo, Edward A.; Romero, Roberto

    2011-01-01

    The past two decades in the United States have seen a 24 % rise in spontaneous late preterm delivery (34 to 36 weeks) of unknown etiology. This study tested the hypothesis that fetal growth was identical prior to spontaneous preterm (n=221, median gestational age at birth 35.6 weeks) and term (n=3706) birth among pregnancies followed longitudinally in Santiago, Chile. The hypothesis was not supported: Preterm-delivered fetuses were significantly larger than their term-delivered peers by mid-second trimester in estimated fetal weight, head, limb and abdominal dimensions, and they followed different growth trajectories. Piecewise regression assessed time-specific differences in growth rates at 4-week intervals from 16 weeks. Estimated fetal weight and abdominal circumference growth rates faltered at 20 weeks among the preterm-delivered, only to match and/or exceed their term-delivered peers at 24–28 weeks. After an abrupt decline at 28 weeks attenuating growth rates in all dimensions, fetuses delivered preterm did so at greater population-specific sex and age-adjusted weight than their peers from uncomplicated pregnancies (p<0.01). Growth rates predicted birth timing: one standard score of estimated fetal weight increased the odds ratio for preterm birth from 2.8 prior to 23 weeks, to 3.6 (95% confidence interval, 1.82–7.11, p<0.05) between 23 and 27 weeks. After 27 weeks, increasing size was protective (OR: 0.56, 95% confidence interval, 0.38–0.82, p=0.003). These data document, for the first time, a distinctive fetal growth pattern across gestation preceding spontaneous late preterm birth, identify the importance of mid-gestation for alterations in fetal growth, and add perspective on human fetal biological variability. PMID:18988282

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

    PubMed

    Johnson, Christopher N; Brook, Barry W

    2011-12-22

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

  5. Volatility and Growth in Populations of Rural Associations

    ERIC Educational Resources Information Center

    Wollebaek, Dag

    2010-01-01

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

  6. Population growth and development: the case of Bangladesh.

    PubMed

    Nakibullah, A

    1998-04-01

    In a poor, overly populated country such as Bangladesh, some believe that a high rate of population growth is a cause of poverty which impedes economic development. Population growth would therefore be exogenous to economic development. However, others believe that rapid population growth is a consequence rather than a cause of poverty. Population growth is therefore endogenous to economic development. Findings are presented from an investigation of whether population growth has been exogenous or endogenous with respect to Bangladesh's development process during the past 3 decades. The increase in per capita real gross domestic product (GDP) is used as a measure of development. Data on population, real GDP per capita, and real investment share of GDP are drawn from the Penn World Table prepared by Summers and Heston in 1991. The data are annual and cover the period 1959-90. Analysis of the data indicate that population growth is endogenous to Bangladesh's development process. These findings are reflected both in the Granger causality tests and the decompositions of variances of detrended real GDP per capita and population growth.

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

    PubMed

    Ngendakumana, M

    1988-04-01

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

  8. Winter temperatures limit population growth rate of a migratory songbird

    PubMed Central

    Woodworth, Bradley K.; Wheelwright, Nathaniel T.; Newman, Amy E.; Schaub, Michael; Norris, D. Ryan

    2017-01-01

    Understanding the factors that limit and regulate wildlife populations requires insight into demographic and environmental processes acting throughout the annual cycle. Here, we combine multi-year tracking data of individual birds with a 26-year demographic study of a migratory songbird to evaluate the relative effects of density and weather at the breeding and wintering grounds on population growth rate. Our results reveal clear support for opposing forces of winter temperature and breeding density driving population dynamics. Above-average temperatures at the wintering grounds lead to higher population growth, primarily through their strong positive effects on survival. However, population growth is regulated over the long term by strong negative effects of breeding density on both fecundity and adult male survival. Such knowledge of how year-round factors influence population growth, and the demographic mechanisms through which they act, will vastly improve our ability to predict species responses to environmental change and develop effective conservation strategies for migratory animals. PMID:28317843

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

    PubMed

    Lesser, Mark R; Jackson, Stephen T

    2012-05-01

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

  10. Accelerated Threshold Fatigue Crack Growth Effect-Powder Metallurgy Aluminum Alloy

    NASA Technical Reports Server (NTRS)

    Piascik, R. S.; Newman, J. A.

    2002-01-01

    Fatigue crack growth (FCG) research conducted in the near threshold regime has identified a room temperature creep crack growth damage mechanism for a fine grain powder metallurgy (PM) aluminum alloy (8009). At very low (Delta) K, an abrupt acceleration in room temperature FCG rate occurs at high stress ratio (R = K(sub min)/K(sub max)). The near threshold accelerated FCG rates are exacerbated by increased levels of K(sub max) (K(sub max) = 0.4 K(sub IC)). Detailed fractographic analysis correlates accelerated FCG with the formation of crack-tip process zone micro-void damage. Experimental results show that the near threshold and K(sub max) influenced accelerated crack growth is time and temperature dependent.

  11. The application of exogenous cellulase to improve soil fertility and plant growth due to acceleration of straw decomposition.

    PubMed

    Han, Wei; He, Ming

    2010-05-01

    The effects of exogenous cellulase application on straw decomposition, soil fertility, and plant growth were investigated with nylon bag and pot experiments. Cellulase application promoted straw decomposition, and the decomposition rates of rice and wheat straw increased by 6.3-26.0% and 6.8-28.0%, respectively, in the nylon bag experiments. In pot experiments soil-available N and P contents, soil cellulase activity, and growth of rice seedlings increased. Soil respiration rate and microbial population were unaffected. Seventy Ug(-1) was the optimal cellulase concentration for plant growth. The exogenous cellulase persisted in soil for more than 100days. Although the data show that exogenous cellulase application can enhance soil fertility and plant growth in the short-term due to the acceleration of straw decomposition and has the potential to be an environment-friendly approach to manage straw, cellulase application to soil seems currently not economical.

  12. The population growth and desertification crisis.

    PubMed

    Milas, S

    1985-01-01

    Desertification is a result of overexploitation of the land through overcultivation, overgrazing, deforestation, and poor irrigation practices. This process is a result of the growing imbalance between population, resources, environment, and development. The principle problem causing desertification is not population increase per se; rather, it is due to mismanagement of the land. However, rapidly increasing population densities in the drylands of Africa, Asia, and Latin America have upset the former balance upon which subsistence agriculture depended, including long fallow periods to allow the land to regain its fertility. Arable land for the world as a whole is projected to decrease from its 1975 level of .31 ha/person to .15 ha/person by the year 2000. Population increases in the remaining croplands are expected to produce further encroachment on rangelands and forests and increased ecologic degradation, in turn producing further population pressure, poverty, land degradation, and desertification. The basic need is for better resource utilization. Halting desertification requires the restoration of the balance between man and land. Development, good resource management, and use of appropriate technologic advances are key factors. There is also a crucial need for each country to relate its population policy to its resource base and development plans. Population increase cannot continue indefinitely without regard for the realities of resources, development, and the environment.

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

    NASA Astrophysics Data System (ADS)

    Hüsler, A. D.; Sornette, D.

    2014-10-01

    We analyze the growth rates of human population and of atmospheric carbon dioxide by comparing the relative merits of two benchmark models, the exponential law and the finite-time-singular (FTS) power law. The later results from positive feedbacks, either direct or mediated by other dynamical variables, as shown in our presentation of a simple endogenous macroeconomic dynamical growth model describing the growth dynamics of coupled processes involving human population (labor in economic terms), capital and technology (proxies by CO2 emissions). Human population in the context of our energy intensive economies constitutes arguably the most important underlying driving variable of the content of carbon dioxide in the atmosphere. Using some of the best databases available, we perform empirical analyses confirming that the human population on Earth has been growing super-exponentially until the mid-1960s, followed by a decelerated sub-exponential growth, with a tendency to plateau at just an exponential growth in the last decade with an average growth rate of 1.0% per year. In contrast, we find that the content of carbon dioxide in the atmosphere has continued to accelerate super-exponentially until 1990, with a transition to a progressive deceleration since then, with an average growth rate of approximately 2% per year in the last decade. To go back to CO2 atmosphere contents equal to or smaller than the level of 1990 as has been the broadly advertised goals of international treaties since 1990 requires herculean changes: from a dynamical point of view, the approximately exponential growth must not only turn to negative acceleration but also negative velocity to reverse the trend.

  14. [Five recommendations for controlling population growth in China].

    PubMed

    Lui, Z; Wu, C P; Lin, F D

    1980-10-01

    The rapid population growth rate (2% annually from 1949 to 1978) caused great difficulties for China's national economy because it increased the burden of families, communities, and government. It caused employment problems and slowed increases in living standards and educational levels. The best way to control population growth is based on a combination of political education and effective economic measures. The recommendations are: 1) coordinate employment, food rationing, salaries, bonuses, health treatment, age and condition of retirement, preschool care and education with family planning programs, maintain the elderly's living standard, and give preference to childless and single child families; 2) educate people about family planning and incorporate population growth and family planning into political and economics courses in high school and college; 3) incorporate population control into national economic plans; 4) prohibit families with 3 children and advocate 1 child per couple; and 5) establish a permanent population committee to plan, develop, and implement population policies and related research.

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

    ERIC Educational Resources Information Center

    Groth, Edward, III

    This paper, one in a series of occasional publications, discusses trends in food production and population growth, emphasizing how environmental quality will be affected. The series is intended to increase understanding of the interrelationships between population growth and socioeconomic and cultural patterns throughout the world, and to…

  16. Population Projections and Growth: Proposals or Porphecies?

    ERIC Educational Resources Information Center

    Taylor, Chris

    1974-01-01

    Presents a review charging the Canadian governments with reacting to population projections as if they were public prophecy. Projections throughout 1930-40 are summarized and tabulated as well as those in the years 1950-60 and recent years. (EB)

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

    PubMed

    Loriaux, M

    1991-12-01

    Africa, currently one of the least densely populated continents, is growing so rapidly that its population will comprise some 1.5 billion inhabitants around 2020, and Africans will be more numerous than the population of the developed world. Attitudes about Africa's population size vary widely; many educated Africans believe that low density is a greater disadvantage than overpopulation, but most specialists believe the population of the developing world, and of Africa especially, to be too large, the prospects of significant voluntary reduction are dim. The rate of population growth has thus attracted attention as a factor amenable to modification. Africa's demographic transition remains largely in the future. Its case is unique because of the rate of demographic growth and because the phase of rapid growth will apparently continue far longer in Africa than in any other continent. The widening gap between population growth rates and rates of economic development in Africa inspires great pessimism about the future wellbeing of the population. Population officials urge that demographic growth be slowed in order to reduce pressure on economic and ecological resources and to gain time for social and economic development. But despite the consensus of international organizations, such as the UN Fund for Population, on the desirability of slowing population growth to encourage and permit economic growth, there has actually been relatively little progress since the time of Malthus in understanding the relationship between population, development, and the environment. Some recent works suggest that demographic growth has benefits as well as disadvantages, and the net impact on development is uncertain. Demographic pressure is in this view a far more potent force for innovation than is usually recognized. Population is not just an exogenous variable in development, but it is at the heart of the process. There can be no true integration of population into development until

  18. Poverty-led higher population growth in Bangladesh.

    PubMed

    Nakibullah, A; Rahman, A

    1996-01-01

    This article discusses the issue whether population growth is exogenous or endogenous in the economic development of Bangladesh. Overpopulation adversely affects food supplies, foreign exchange, and human resources. Moreover, it depresses savings per capita and retards growth of physical capital per labor. Underdeveloped countries, like Bangladesh, are faced with the problem of allocating resources between infrastructure, education, and health service that are essential for human capital development and population control measures. With this, determination whether fertility is exogenous or endogenous is important for policy purposes in the context of Bangladesh. Results showed that there is a correlation between population growth and real gross domestic products per capita. Based on Granger causality test, population growth is endogenous in the development process of Bangladesh and its overpopulation is due to poverty. Thus, there is a need for appropriate policy to take measures to improve human capital and decrease fertility rates.

  19. Arabidopsis thaliana root growth kinetics and lunisolar tidal acceleration.

    PubMed

    Fisahn, Joachim; Yazdanbakhsh, Nima; Klingele, Emile; Barlow, Peter

    2012-07-01

    • All living organisms on Earth are continually exposed to diurnal variations in the gravitational tidal force due to the Sun and Moon. • Elongation of primary roots of Arabidopsis thaliana seedlings maintained at a constant temperature was monitored for periods of up to 14 d using high temporal- and spatial-resolution video imaging. The time-course of the half-hourly elongation rates exhibited an oscillation which was maintained when the roots were placed in the free-running condition of continuous illumination. • Correlation between the root growth kinetics collected from seedlings initially raised under several light protocols but whose roots were subsequently in the free-running condition and the lunisolar tidal profiles enabled us to identify that the latter is the probable exogenous determinant of the rhythmic variation in root elongation rate. Similar observations and correlations using roots of Arabidopsis starch mutants suggest a central function of starch metabolism in the response to the lunisolar tide. The periodicity of the lunisolar tidal signal and the concomitant adjustments in root growth rate indicate that an exogenous timer exists for the modulation of root growth and development. • We propose that, in addition to the sensitivity to Earthly 1G gravity, which is inherent to all animals and plants, there is another type of responsiveness which is attuned to the natural diurnal variations of the lunisolar tidal force.

  20. Bunch self-focusing regime of laser wakefield acceleration with reduced emittance growth.

    PubMed

    Reitsma, A J W; Goloviznin, V V; Kamp, L P J; Schep, T J

    2002-01-07

    A new regime of laser wakefield acceleration of an injected electron bunch is described. In this regime, the bunch charge is so high that the bunch wakefields play an important role in the bunch dynamics. In particular, the transverse bunch wakefield induces a strong self-focusing that suppresses the transverse emittance growth arising from misalignment errors. The decelerating longitudinal bunch wakefield, however, is not so strong that it completely cancels the accelerating laser wakefield. In fact, the induced energy spread can be compensated by exploiting phase slippage effects. These features make the new regime interesting for high beam quality laser wakefield acceleration.

  1. Agriculture, population growth, and statistical analysis of the radiocarbon record.

    PubMed

    Zahid, H Jabran; Robinson, Erick; Kelly, Robert L

    2016-01-26

    The human population has grown significantly since the onset of the Holocene about 12,000 y ago. Despite decades of research, the factors determining prehistoric population growth remain uncertain. Here, we examine measurements of the rate of growth of the prehistoric human population based on statistical analysis of the radiocarbon record. We find that, during most of the Holocene, human populations worldwide grew at a long-term annual rate of 0.04%. Statistical analysis of the radiocarbon record shows that transitioning farming societies experienced the same rate of growth as contemporaneous foraging societies. The same rate of growth measured for populations dwelling in a range of environments and practicing a variety of subsistence strategies suggests that the global climate and/or endogenous biological factors, not adaptability to local environment or subsistence practices, regulated the long-term growth of the human population during most of the Holocene. Our results demonstrate that statistical analyses of large ensembles of radiocarbon dates are robust and valuable for quantitatively investigating the demography of prehistoric human populations worldwide.

  2. Agriculture, population growth, and statistical analysis of the radiocarbon record

    PubMed Central

    Zahid, H. Jabran; Robinson, Erick; Kelly, Robert L.

    2016-01-01

    The human population has grown significantly since the onset of the Holocene about 12,000 y ago. Despite decades of research, the factors determining prehistoric population growth remain uncertain. Here, we examine measurements of the rate of growth of the prehistoric human population based on statistical analysis of the radiocarbon record. We find that, during most of the Holocene, human populations worldwide grew at a long-term annual rate of 0.04%. Statistical analysis of the radiocarbon record shows that transitioning farming societies experienced the same rate of growth as contemporaneous foraging societies. The same rate of growth measured for populations dwelling in a range of environments and practicing a variety of subsistence strategies suggests that the global climate and/or endogenous biological factors, not adaptability to local environment or subsistence practices, regulated the long-term growth of the human population during most of the Holocene. Our results demonstrate that statistical analyses of large ensembles of radiocarbon dates are robust and valuable for quantitatively investigating the demography of prehistoric human populations worldwide. PMID:26699457

  3. Effects of population growth on the success of invading mutants.

    PubMed

    Ashcroft, Peter; Smith, Cassandra E R; Garrod, Matthew; Galla, Tobias

    2017-03-18

    Understanding if and how mutants reach fixation in populations is an important question in evolutionary biology. We study the impact of population growth has on the success of mutants. To systematically understand the effects of growth we decouple competition from reproduction; competition follows a birth-death process and is governed by an evolutionary game, while growth is determined by an externally controlled branching rate. In stochastic simulations we find non-monotonic behaviour of the fixation probability of mutants as the speed of growth is varied; the right amount of growth can lead to a higher success rate. These results are observed in both coordination and coexistence game scenarios, and we find that the 'one-third law' for coordination games can break down in the presence of growth. We also propose a simplified description in terms of stochastic differential equations to approximate the individual-based model.

  4. Parameter Estimates in Differential Equation Models for Population Growth

    ERIC Educational Resources Information Center

    Winkel, Brian J.

    2011-01-01

    We estimate the parameters present in several differential equation models of population growth, specifically logistic growth models and two-species competition models. We discuss student-evolved strategies and offer "Mathematica" code for a gradient search approach. We use historical (1930s) data from microbial studies of the Russian biologist,…

  5. A Role for M-Matrices in Modelling Population Growth

    ERIC Educational Resources Information Center

    James, Glyn; Rumchev, Ventsi

    2006-01-01

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

  6. Coenzyme Q10 prevents accelerated cardiac aging in a rat model of poor maternal nutrition and accelerated postnatal growth.

    PubMed

    Tarry-Adkins, Jane L; Blackmore, Heather L; Martin-Gronert, Malgorzata S; Fernandez-Twinn, Denise S; McConnell, Josie M; Hargreaves, Iain P; Giussani, Dino A; Ozanne, Susan E

    2013-01-01

    Studies in human and animals have demonstrated that nutritionally induced low birth-weight followed by rapid postnatal growth increases the risk of metabolic syndrome and cardiovascular disease. Although the mechanisms underlying such nutritional programming are not clearly defined, increased oxidative-stress leading to accelerated cellular aging has been proposed to play an important role. Using an established rodent model of low birth-weight and catch-up growth, we show here that post-weaning dietary supplementation with coenzyme Q10, a key component of the electron transport chain and a potent antioxidant rescued many of the detrimental effects of nutritional programming on cardiac aging. This included a reduction in nitrosative and oxidative-stress, telomere shortening, DNA damage, cellular senescence and apoptosis. These findings demonstrate the potential for postnatal antioxidant intervention to reverse deleterious phenotypes of developmental programming and therefore provide insight into a potential translatable therapy to prevent cardiovascular disease in at risk humans.

  7. The New Population Debate: Two Views on Population Growth and Economic Development. Population Trends and Public Policy, Number 7.

    ERIC Educational Resources Information Center

    King, Timothy; Kelley, Allen C.

    Articles representing two views on the issue of rapid population growth and economic development are presented. Although the authors present different perspectives, they agree on many of the fundamentals. For example, both reject alarmism about impending "population explosions" and the use of population as a scapegoat for all Third World…

  8. The old age security hypothesis and optimal population growth.

    PubMed

    Bental, B

    1989-03-01

    The application of the Samuelson-Diamond overlapping generations framework to the old age security hypothesis indicates that government intervention schemes can influence the relationship between population growth and capital accumulation. The most direct means of optimizing population growth is through taxes or subsidies that relate to the intergenerational transfer of wealth. A pay-as-you-go social security scheme, in which payment is predicated on the number of children the receiver has and is financed by taxes levied on the working population, emerges as the most likely intervention to produce the optimal steady state equilibrium. This system is able to correct any distortions the private sector may build into it. In contrast, a child support system, in which the government subsidizes or taxes workers according to their family size, can guarantee the optimal capital:labor ratio but not the optimal population growth rate. Thus, if the government seeks to decrease the population growth rate, the appropriate intervention is to levy a lump-sum social-security tax on workers and transfer the revenues to the old; the direction should be reversed if the goal is to increase population growth. Another alternative, a lump sum social security system, can guarantee optimal population growth but not a desirable capital:labor ratio. Finally, the introduction of money as a valued commodity into an economy with a high capital:labor ratio will also serve to decrease the population growth rate and solve the intergenerational transfer problem through the private sector without any need for government intervention.

  9. Population growth and economic development revisited with reference to Asia.

    PubMed

    Jha, S C; Deolalikar, A B; Pernia, E M

    1993-01-01

    "This article takes another look at the old issue of population growth and economic development in the context of recent developments and with the benefit of the increasing stock of knowledge on the subject. It first presents a demographic perspective; then it analyzes the implications of population growth with respect to such integral aspects of economic development as human capital accumulation, income distribution and poverty, the environment, and sustainable economic growth. The approach in each case is to review the theoretical considerations, survey the empirical evidence, and then draw policy implications. An overall conclusion with implications for policy caps the paper." The geographical focus is on Asia.

  10. Metropolitan migration and population growth in selected developing countries.

    PubMed

    1983-01-01

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

  11. Transgenic tobacco plants overexpressing the Nicta; CycD3; 4 gene demonstrate accelerated growth rates.

    PubMed

    Guo, Jia; Wang, Myeong Hyeon

    2008-07-31

    D-type cyclins control the onset of cell division and the response to extracellular signals during the G1 phase. In this study, we transformed a D-type cyclin gene, Nicta;CycD3;4, from Nicotiana tabacum using an Agrobacterium-mediated method. A predicted 1.1 kb cyclin gene was present in all of the transgenic plants, but not in wild-type. Northern analyses showed that the expression level of the Nicta;CycD3;4 gene in all of the transgenic plants was strong when compared to the wild-type plants, suggesting that Nicta;CycD3;4 gene driven by the CaMV 35S promoter was being overexpressed. Our results revealed that transgenic plants overexpressing Nicta;CycD3;4 had an accelerated growth rate when compared to wild-type plants, and that the transgenic plants exhibited a smaller cell size and a decreased cell population in young leaves when compared to wild-type plants.

  12. Steady-state thermodynamics for population growth in fluctuating environments

    NASA Astrophysics Data System (ADS)

    Sughiyama, Yuki; Kobayashi, Tetsuya J.

    2017-01-01

    We report that population dynamics in fluctuating environments is characterized by a mathematically equivalent structure to steady-state thermodynamics. By employing the structure, population growth in fluctuating environments is decomposed into housekeeping and excess parts. The housekeeping part represents the integral of the stationary growth rate for each condition during a history of the environmental change. The excess part accounts for the excess growth induced by environmental fluctuations. Focusing on the excess growth, we obtain a Clausius inequality, which gives the upper bound of the excess growth. The equality is shown to be achieved in quasistatic environmental changes. We also clarify that this bound can be evaluated by the "lineage fitness", which is an experimentally observable quantity.

  13. Minimization of three-dimensional beam emittance growth in rare-isotope accelerator

    NASA Astrophysics Data System (ADS)

    Oh, B. H.; Yoon, M.

    2016-12-01

    In this paper, we describe a research to minimize the three-dimensional (3D) emittance growth (EG) in the RAON accelerator, a heavy ion accelerator currently being developed in Korea to produce various rare isotopes. The emittance minimization is performed using the multi-objective genetic algorithm and the simplex method. We use them to analyze the driver linac for the in-flight fragmentation separator of the RAON facility and show that redesign of the 90-degree bending section of the RAON accelerator together with adjustment of optics in the upstream and downstream superconducting linacs can limit the 3D EG to 20 % in the entire region of the driver linac. Effects of various magnet and rf accelerating cavity errors on the beam-EG are also discussed.

  14. Population growth and the development of a central place system

    NASA Astrophysics Data System (ADS)

    Cromley, Robert G.; Hanink, Dean M.

    2008-12-01

    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.

  15. Integrating Frameworks from Early Childhood Intervention and School Psychology to Accelerate Growth for All Young Children

    ERIC Educational Resources Information Center

    VanDerHeyden, Amanda M.; Snyder, Patricia

    2006-01-01

    Knowing what behaviors adults can engage in to accelerate child growth toward desired outcomes is fundamental to achieving the promise of early education and intervention. Once adequate progress-monitoring measures are developed, patterns of child performance over time and in response to certain interventions can be quantified. The ability to…

  16. Nigerian population growth and its implications for economic development.

    PubMed

    Okpala, A O

    1990-12-01

    The population of Nigeria is growing at a rate of 3.75%/year indicating a doubling of the population every 22 years. Demographers estimated the population to be 91,178,000 in 1985. Even though population density is high (288 people/square mile), it is not equally distributed. It is highest in the south and southwest urban areas such as Lagos (1045 people/square mile) and lowest in the northeast (75 people/square mile). Moreover rural-urban migration is growing. A major reason for rural-urban migration is the dual nature of the economy in Nigeria. In urban areas, economic development brings about higher standards of living, but, in rural areas, a subsistence economy predominates. This coupled with rapid population growth results in small or no growth in per capita income. Only if the government were to integrate redistribution policies into complete economic development plans should it consider redistributing the population. It should stress rural development (e.g., incentives for firms to set up in rural areas). Further it should move some government offices to rural areas. The government also needs to adopt population policies encouraging the lowering of fertility levels. If it were to provide education through the secondary and prevocational education level free of charge, educated women will lower their fertility. Sex education should be included in the curriculum. Further the government must play an active role in family planning programs, especially educating rural women about family planning. It should also use the mass media to promote small family size, but it should not dictate family size. It also needs to recognize that population growth puts much pressure on the environment. For example, population growth causes soil erosion, nutrient exhaustion, rapid deforestation, and other problems which render the land unusable for agriculture.

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

    PubMed

    Conroy, M E

    1980-01-01

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

  18. Increased diffuse radiation fraction does not significantly accelerate plant growth

    NASA Astrophysics Data System (ADS)

    Angert, Alon; Krakauer, Nir

    2010-05-01

    A recent modelling study (Mercado et al., 2009) claims that increased numbers of scattering aerosols are responsible for a substantial fraction of the terrestrial carbon sink in recent decades because higher diffuse light fraction enhances plant net primary production (NPP). Here we show that observations of atmospheric CO2 seasonal cycle and tree ring data indicate that the relation between diffuse light and NPP is actually quite weak on annual timescales. The inconsistency of these data with the modelling results may arise because the relationships used to quantify the enhancement of NPP were calibrated with eddy covariance measurements of hourly carbon uptake. The effect of diffuse-light fraction on carbon uptake could depend on timescale, since this effect varies rapidly as sun angle and cloudiness change, and since plants can respond dynamically over various timescales to change in incoming radiation. Volcanic eruptions, such as the eruption of Mount Pinatubo in 1991, provide the best available tests for the effect of an annual-scale increase in the diffuse light fraction. Following the Pinatubo Eruption, in 1992 and 1993, a sharp decrease in the atmospheric CO2 growth rate was observed. This could have resulted from enhanced plant carbon uptake. Mercado et al. (2009) argue that largely as a result of the (volcanic aerosol driven) increase in diffuse light fraction, NPP was elevated in 1992, particularly between 25° N-45° N where annual NPP was modelled to be ~0.8 PgC (~10%) above average. In a previous study (Angert et al., 2004) a biogeochemical model (CASA) linked to an atmospheric tracer model (MATCH), was used to show that a diffuse-radiation driven increase in NPP in the extratropics will enhance carbon uptake mostly in summer, leading to a lower CO2 seasonal minimum. Here we use a 'toy model' to show that this conclusion is general and model-independent. The model shows that an enhanced sink of 0.8 PgC, similar to that modelled by Mercado et al. (2009

  19. Modeling Bacterial Population Growth from Stochastic Single-Cell Dynamics

    PubMed Central

    Molina, Ignacio; Theodoropoulos, Constantinos

    2014-01-01

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

  20. Modeling bacterial population growth from stochastic single-cell dynamics.

    PubMed

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

    2014-09-01

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

  1. Population growth, human development, and deforestation in biodiversity hotspots.

    PubMed

    Jha, S; Bawa, K S

    2006-06-01

    Human population and development activities affect the rate of deforestation in biodiversity hotspots. We quantified the effect of human population growth and development on rates of deforestation and analyzed the relationship between these causal factors in the 1980s and 1990s. We compared the averages of population growth, human development index (HDI, which measures income, health, and education), and deforestation rate and computed correlations among these variables for countries that contain biodiversity hotspots. When population growth was high and HDI was low there was a high rate of deforestation, but when HDI was high, rate of deforestation was low, despite high population growth. The correlation among variables was significant for the 1990s but not for the 1980s. The relationship between population growth and HDI had a regional pattern that reflected the historical process of development. Based on the changes in HDI and deforestation rate over time, we identified two drivers of deforestation: policy choice and human-development constraints. Policy choices that disregard conservation may cause the loss of forests even in countries that are relatively developed. Lack of development in other countries, on the other hand, may increase the pressure on forests to meet the basic needs of the human population. Deforestation resulting from policy choices may be easier to fix than deforestation arising from human development constraints. To prevent deforestation in the countries that have such constraints, transfer of material and intellectual resources from developed countries may be needed. Popular interest in sustainable development in developed countries can facilitate the transfer of these resources.

  2. Latino Population Growth and Hospital Uncompensated Care in California

    PubMed Central

    O’Brien, Matthew J.; Mennis, Jeremy; Alos, Victor A.; Grande, David T.; Roby, Dylan H.; Ortega, Alexander N.

    2015-01-01

    Objectives. We examined the association between the size and growth of Latino populations and hospitals’ uncompensated care in California. Methods. Our sample consisted of general acute care hospitals in California operating during 2000 and 2010 (n = 251). We merged California hospital data with US Census data for each hospital service area. We used spatial analysis, multivariate regression, and fixed-effect models. Results. We found a significant association between the growth of California’s Latino population and hospitals’ uncompensated care in the unadjusted regression. This association was still significant after we controlled for hospital and community population characteristics. After we added market characteristics into the final model, this relationship became nonsignificant. Conclusions. Our findings suggest that systematic support is needed in areas with rapid Latino population growth to control hospitals’ uncompensated care, especially if Latinos are excluded from or do not respond to the insurance options made available through the Affordable Care Act. Improving availability of resources for hospitals and providers in areas with high Latino population growth could help alleviate financial pressures. PMID:26066960

  3. Expert Group Meeting on Population Growth and Demographic Structure.

    PubMed

    1993-01-01

    As part of the preparation for the forth-coming UN International Conference on Population and Development, an expert group met in Paris, France, in November 1992 to discuss population growth and demographic structure. As part of the demographic background for the meeting provided by the UN Population Division, participants were informed that although the world population growth rate began to decline in the late 1970s, this decline has not yet resulted in declining absolute numbers, and the annual increment to the world population was not expected to decline to the level that existed in 1985 until the period 2020-25. World population increased from 2.5 billion in 1950 to 5.3 billion in 1990. The medium variant population projection of the UN shows world population at 6.3 billion in 2000 and 8.5 billion in 2025 (the high variant shows 9.4 billion in 2025 and the low variant shows 7.6 billion). Population aging is expected to reach unparalleled levels in 2010-20. The meeting then considered the topics of population growth and socioeconomic development, confronting poverty in developing countries, demographic impacts of development patterns, demographic and health transitions, population growth and employment, social change and the elderly in developing countries, and social development and ageing in developed countries, The expert group meeting then prepared 19 recommendations aimed at governments, social institutions, and the international community. The recommendations call for political commitment to human resources development and population and development programs, especially in least developed countries, alleviation of poverty and social inequality, and equality of access to social and health resources that will lead to reduced mortality and fertility. Governments are urged to place a high priority on education and on increasing women's access to education and to remove barriers to economic independence for women. Health-sector priorities should be reassessed

  4. The Population Growth Consequences of Variation in Individual Heterozygosity

    PubMed Central

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

    2011-01-01

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

  5. Explosive genetic evidence for explosive human population growth.

    PubMed

    Gao, Feng; Keinan, Alon

    2016-12-01

    The advent of next-generation sequencing technology has allowed the collection of vast amounts of genetic variation data. A recurring discovery from studying larger and larger samples of individuals had been the extreme, previously unexpected, excess of very rare genetic variants, which has been shown to be mostly due to the recent explosive growth of human populations. Here, we review recent literature that inferred recent changes in population size in different human populations and with different methodologies, with many pointing to recent explosive growth, especially in European populations for which more data has been available. We also review the state-of-the-art methods and software for the inference of historical population size changes that lead to these discoveries. Finally, we discuss the implications of recent population growth on personalized genomics, on purifying selection in the non-equilibrium state it entails and, as a consequence, on the genetic architecture underlying complex disease and the performance of mapping methods in discovering rare variants that contribute to complex disease risk.

  6. Maximizing oyster-reef growth supports green infrastructure with accelerating sea-level rise

    PubMed Central

    Ridge, Justin T.; Rodriguez, Antonio B.; Joel Fodrie, F.; Lindquist, Niels L.; Brodeur, Michelle C.; Coleman, Sara E.; Grabowski, Jonathan H.; Theuerkauf, Ethan J.

    2015-01-01

    Within intertidal communities, aerial exposure (emergence during the tidal cycle) generates strong vertical zonation patterns with distinct growth boundaries regulated by physiological and external stressors. Forecasted accelerations in sea-level rise (SLR) will shift the position of these critical boundaries in ways we cannot yet fully predict, but landward migration will be impaired by coastal development, amplifying the importance of foundation species’ ability to maintain their position relative to rising sea levels via vertical growth. Here we show the effects of emergence on vertical oyster-reef growth by determining the conditions at which intertidal reefs thrive and the sharp boundaries where reefs fail, which shift with changes in sea level. We found that oyster reef growth is unimodal relative to emergence, with greatest growth rates occurring between 20–40% exposure, and zero-growth boundaries at 10% and 55% exposures. Notably, along the lower growth boundary (10%), increased rates of SLR would outpace reef accretion, thereby reducing the depth range of substrate suitable for reef maintenance and formation, and exacerbating habitat loss along developed shorelines. Our results identify where, within intertidal areas, constructed or natural oyster reefs will persist and function best as green infrastructure to enhance coastal resiliency under conditions of accelerating SLR. PMID:26442712

  7. Maximizing oyster-reef growth supports green infrastructure with accelerating sea-level rise.

    PubMed

    Ridge, Justin T; Rodriguez, Antonio B; Joel Fodrie, F; Lindquist, Niels L; Brodeur, Michelle C; Coleman, Sara E; Grabowski, Jonathan H; Theuerkauf, Ethan J

    2015-10-07

    Within intertidal communities, aerial exposure (emergence during the tidal cycle) generates strong vertical zonation patterns with distinct growth boundaries regulated by physiological and external stressors. Forecasted accelerations in sea-level rise (SLR) will shift the position of these critical boundaries in ways we cannot yet fully predict, but landward migration will be impaired by coastal development, amplifying the importance of foundation species' ability to maintain their position relative to rising sea levels via vertical growth. Here we show the effects of emergence on vertical oyster-reef growth by determining the conditions at which intertidal reefs thrive and the sharp boundaries where reefs fail, which shift with changes in sea level. We found that oyster reef growth is unimodal relative to emergence, with greatest growth rates occurring between 20-40% exposure, and zero-growth boundaries at 10% and 55% exposures. Notably, along the lower growth boundary (10%), increased rates of SLR would outpace reef accretion, thereby reducing the depth range of substrate suitable for reef maintenance and formation, and exacerbating habitat loss along developed shorelines. Our results identify where, within intertidal areas, constructed or natural oyster reefs will persist and function best as green infrastructure to enhance coastal resiliency under conditions of accelerating SLR.

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

    PubMed

    Madulu, N F

    1995-03-01

    Population strategies to relieve the density pressures on land and resources in Tanzania have not considered the basic causes of population growth. Resettlement results in the same environmental degradation as in the original settlement. There should be a reduction in the population growth and planning of proper land use and resource exploitation before resettlement. Rural development must include a decline in the dependency on subsistence agriculture. Population in Tanzania increased by 213% during 1948-88. An absolute increase in population size during 1978-88 is recorded despite a slight decline in the rate of growth. Death rates declined, but birth rates were relatively stable at around 50 per 1000 population. Regions with the highest growth rates were Dar es Salaam (4.8%), Rukwa (4.3%), Arusha (3.8%), Mbeya (3.1%), and Ruvuma (3.2%). The regions with the lowest rates were Tanga and Kilimanjaro (2.1%), Coast (2.1%), Lindi (2%), and Mtwara (1.4%). Low growth rates are attributed to low fertility and high infertility. Other factors affecting high growth rates are culture, rates of natural increase, intensity of internal and international migration, climatic conditions, and availability of resources. In 1988 46% of the population was under 15 years old. Per capita land availability declined from 11.8 hectares in 1948 to 3.8 hectares in 1988. The number of landless peasants increased. Productivity declined, and distances to farms increased. The total fertility rate was 6.5 children per woman in 1988 and 6.1 during 1991-92. Slight declines were apparent in the crude birth rate also. High fertility was a response to universal marriage, low contraceptive use (7% using modern methods during 1991-92), declining lactation periods, high mortality rates, and old traditions favoring large families. Children were used extensively in time-consuming and labor-intensive activities, such as fetching water. The mean number of children ever born was higher among women with 1

  9. Meteorological limits on the growth and development of screwworm populations

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

    A program to evaluate the use of remotely sensed data as an additional tool in existing and projected efforts to eradicate the screwworm began in 1973. Estimating weather conditions by use of remotely sensed data was part of the study. Next, the effect of weather on screwworm populations was modeled. A significant portion of the variation in screwworm population growth and development has been traced to weather-related parameters. This report deals with the salient points of the weather and the screwworm population interaction.

  10. Capital accumulation, endogenous population growth, and Easterlin cycles.

    PubMed

    Feichtinger, G; Dockner, E J

    1990-01-01

    "In this paper we attempt to explain the occurrence of population cycles in industrialised economies where the birth rate depends on the difference between the actual and the expected consumption rate. This model of an endogenously growing population brings together Easterlin's idea of an adapting aspiration level with the neoclassical optimal growth paradigm. It is shown that in this highly aggregated demo-economic system (i.e., without inclusion of the age structure of a population) swings both in the economic and demographic variables may exist. The reason behind this 'strange' optimal behaviour is identified to be an intertemporal substitution effect between current and future levels of consumption."

  11. Seed population for about 1 MeV per nucleon heavy ions accelerated by interplanetary shocks

    NASA Technical Reports Server (NTRS)

    Tan, L. C.; Mason, G. M.; Klecker, B.; Hovestadt, D.

    1989-01-01

    Data obtained between 1977 and 1982 by the ISEE 1 and ISEE 3 satellites on the composition of heavy ions of about 1 MeV per nucleon, accelerated in interplanetary shock events which followed solar flare events, are examined. It was found that the average relative abundances for C, O, and Fe in the shock events were very close to those found for energetic ions in the solar flares, suggesting that, at these energies, the shock accelerated particles have the solar energetic particles as their seed population. This hypothesis is supported by the fact that the Fe/O ratio in the solar particle events is very strongly correlated with the Fe/O ratio in associated diffusive shock events.

  12. Effects of body size and temperature on population growth.

    PubMed

    Savage, Van M; Gilloly, James F; Brown, James H; Charnov, Eric L

    2004-03-01

    For at least 200 years, since the time of Malthus, population growth has been recognized as providing a critical link between the performance of individual organisms and the ecology and evolution of species. We present a theory that shows how the intrinsic rate of exponential population growth, rmax, and the carrying capacity, K, depend on individual metabolic rate and resource supply rate. To do this, we construct equations for the metabolic rates of entire populations by summing over individuals, and then we combine these population-level equations with Malthusian growth. Thus, the theory makes explicit the relationship between rates of resource supply in the environment and rates of production of new biomass and individuals. These individual-level and population-level processes are inextricably linked because metabolism sets both the demand for environmental resources and the resource allocation to survival, growth, and reproduction. We use the theory to make explicit how and why rmax exhibits its characteristic dependence on body size and temperature. Data for aerobic eukaryotes, including algae, protists, insects, zooplankton, fishes, and mammals, support these predicted scalings for rmax. The metabolic flux of energy and materials also dictates that the carrying capacity or equilibrium density of populations should decrease with increasing body size and increasing temperature. Finally, we argue that body mass and body temperature, through their effects on metabolic rate, can explain most of the variation in fecundity and mortality rates. Data for marine fishes in the field support these predictions for instantaneous rates of mortality. This theory links the rates of metabolism and resource use of individuals to life-history attributes and population dynamics for a broad assortment of organisms, from unicellular organisms to mammals.

  13. Proximate causes of adaptive growth rates: growth efficiency variation among latitudinal populations of Rana temporaria.

    PubMed

    Lindgren, B; Laurila, A

    2005-07-01

    In ectothermic organisms, declining season length and lower temperature towards higher latitudes often select for latitudinal variation in growth and development. However, the energetic mechanisms underlying this adaptive variation are largely unknown. We investigated growth, food intake and growth efficiency of Rana temporaria tadpoles from eight populations along a 1500 km latitudinal gradient across Sweden. To gain an insight into the mechanisms of adaptation at organ level, we also examined variation in tadpole gut length. The tadpoles were raised at two temperatures (16 and 20 degrees C) in a laboratory common garden experiment. We found increased growth rate towards higher latitudes, regardless of temperature treatment. This increase in growth was not because of a higher food intake rate, but populations from higher latitudes had higher growth efficiency, i.e. they were more efficient at converting ingested food into body mass. Low temperature reduced growth efficiency most strongly in southern populations. Relative gut length increased with latitude, and tadpoles at low temperature tended to have longer guts. However, variation in gut length was not the sole adaptive explanation for increased growth efficiency as latitude and body length still explained significant amounts of variation in growth efficiency. Hence, additional energetic adaptations are probably involved in growth efficiency variation along the latitudinal gradient.

  14. Is There Hidden Potential for Rural Population Growth in Sweden?

    ERIC Educational Resources Information Center

    Niedomysl, Thomas; Amcoff, Jan

    2011-01-01

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

  15. The Educational Effects of Rapid Rural Population Growth.

    ERIC Educational Resources Information Center

    Ross, Peggy J.; Green, Bernal L.

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

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

    ERIC Educational Resources Information Center

    Daley, Michael; Hillier, Douglas

    1981-01-01

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

  17. Role of abortion in control of global population growth.

    PubMed

    Mumford, S D; Kessel, E

    1986-03-01

    No nation desirous of reducing its growth rate to 1% or less can expect to do so without the widespread use of abortion. This observational study, based on the experience of 116 of the world's largest countries, supports the contention that abortion is essential to any national population growth control effort. The principal findings are: Except for a few countries with ageing populations and very high contraceptive prevalence rates, developed countries will need to maintain abortion rates generally in the range of 201-500 abortions per 1000 live births if they are to maintain growth rates at levels below 1%. The current rate in the USA is 426 abortions per 1000 live births. Developing countries, on the other hand, are faced with a different and more difficult set of circumstances that require even greater reliance on abortion. No developing nation wanting to reduce its growth to less than 1% can expect to do so without the widespread use of abortion, generally at a rate greater than 500 abortions per 1000 live births. Widespread availability of abortion is a necessary but not sufficient condition to achieve growth rates below 1%. A high contraceptive prevalence is essential as well in order to achieve growth rates below 1%. A high contraceptive prevalence is a necessary but not sufficient condition to achieve population growth rates below 1%. A high rate of abortion (generally 201-500 or more abortions per 1000 live births in the developed and greater than 500 abortions per 1000 live births in the developing countries) is essential to achieve growth rates below 1%. The different and more difficult set of circumstances faced by developing countries that will necessitate even higher abortion rates than developed countries includes a young population with resultant rapidly growing numbers of young fertile women, poor contraceptive use-effectiveness, low prevalence of contraception, and poor or non-existent systems for providing contraceptives. These data show that

  18. MENTAL RETARDATION AND ACCELERATED GROWTH: INAPPROPRIATE SECRETION OF HUMAN GROWTH HORMONE,

    DTIC Science & Technology

    he had periodic elevations of the fasting plasma growth hormone levels and regularly had a paradoxical fall in the hormone level associated with...insulin-induced hypoglycemia. The human growth hormone response to arginine infusion was perfectly normal. It is suggested that the occasional elevations...in human growth hormone under fasting conditions and the paradoxical response to insulin are compatible with the hypothesis that this patient

  19. Early Acceleration of Mathematics Students and its Effect on Growth in Self-esteem: A Longitudinal Study

    NASA Astrophysics Data System (ADS)

    Ma, Xin

    2002-11-01

    The Longitudinal Study of American Youth (LSAY) database was employed to examine the educational practice of early acceleration of students of mathematics on the development of their self-esteem across the entire secondary grade levels. Students were classified into three different academic categories (gifted, honors, and regular). Results indicated that, in terms of the development of their self-esteem, gifted students benefited from early acceleration, honors students neither benefited nor were harmed by early acceleration, and regular students were harmed by early acceleration. Early acceleration in mathematics promoted significant growth in self-esteem among gifted male students and among gifted, honors, and regular minority students. When students were accelerated, schools showed similar average growth in self-esteem among gifted students and regular students and a large effect of general support for mathematics on the average growth in self-esteem among honors students.

  20. Habitat-Specific Population Growth of a Farmland Bird

    PubMed Central

    Arlt, Debora; Forslund, Pär; Jeppsson, Tobias; Pärt, Tomas

    2008-01-01

    Background To assess population persistence of species living in heterogeneous landscapes, the effects of habitat on reproduction and survival have to be investigated. Methodology/Principal Findings We used a matrix population model to estimate habitat-specific population growth rates for a population of northern wheatears Oenanthe oenanthe breeding in farmland consisting of a mosaic of distinct habitat (land use) types. Based on extensive long-term data on reproduction and survival, habitats characterised by tall field layers (spring- and autumn-sown crop fields, ungrazed grasslands) displayed negative stochastic population growth rates (log λs: −0.332, −0.429, −0.168, respectively), that were markedly lower than growth rates of habitats characterised by permanently short field layers (pastures grazed by cattle or horses, and farmyards, log λs: −0.056, +0.081, −0.059). Although habitats differed with respect to reproductive performance, differences in habitat-specific population growth were largely due to differences in adult and first-year survival rates, as shown by a life table response experiment (LTRE). Conclusions/Significance Our results show that estimation of survival rates is important for realistic assessments of habitat quality. Results also indicate that grazed grasslands and farmyards may act as source habitats, whereas crop fields and ungrazed grasslands with tall field layers may act as sink habitats. We suggest that the strong decline of northern wheatears in Swedish farmland may be linked to the corresponding observed loss of high quality breeding habitat, i.e. grazed semi-natural grasslands. PMID:18714351

  1. Numerical analysis of the sensitivity of crystal growth experiments to spacecraft residual acceleration

    NASA Technical Reports Server (NTRS)

    Alexander, J. I. D.; Amiroudine, Sakir; Ouazzani, Jalil; Rosenberger, Franz

    1992-01-01

    An analysis is conducted of the sensitivity of the Bridgman-Stockbarger crystal growth method, using an idealized model for a range of operating and boundary conditions over a variety of accelerations. Attention is given to the dopant nonuniformity at the melt-crystal interface. The largest compositional nonuniformities are found to occur for disturbances whose amplitudes are greater than 10 exp 6 g, and frequencies below 0.1 Hz.

  2. Consequences of bounds on longitudinal emittance growth for the design of recirculating linear accelerators

    SciTech Connect

    Berg, J. S.

    2015-05-03

    Recirculating linear accelerators (RLAs) are a cost-effective method for the acceleration of muons for a muon collider in energy ranges from a couple GeV to a few 10s of GeV. Muon beams generally have longitudinal emittances that are large for the RF frequency that is used, and it is important to limit the growth of that longitudinal emittance. This has particular consequences for the arc design of the RLAs. I estimate the longitudinal emittance growth in an RLA arising from the RF nonlinearity. Given an emittance growth limitation and other design parameters, one can then compute the maximum momentum compaction in the arcs. I describe how to obtain an approximate arc design satisfying these requirements based on the deisgn in [1]. Longitudinal dynamics also determine the energy spread in the beam, and this has consequences on the transverse phase advance in the linac. This in turn has consequences for the arc design due to the need to match beta functions. I combine these considerations to discuss design parameters for the acceleration of muons for a collider in an RLA from 5 to 63 GeV.

  3. Hydrogen accelerated fatigue crack growth of friction stir welded X52 steel pipe

    DOE PAGES

    Ronevich, Joseph Allen; Somerday, Brian P.; Feng, Zhili

    2016-11-17

    Friction stir welded steel pipelines were tested in high pressure hydrogen gas to examine the effects of hydrogen accelerated fatigue crack growth. Fatigue crack growth rate (da/dN) vs. stress-intensity factor range (ΔK) relationships were measured for an X52 friction stir welded pipe tested in 21 MPa hydrogen gas at a frequency of 1 Hz and R = 0.5. Tests were performed on three regions: base metal (BM), center of friction stir weld (FSW), and 15 mm off-center of the weld. For all three material regions, tests in hydrogen exhibited accelerated fatigue crack growth rates that exceeded an order of magnitudemore » compared to companion tests in air. Among tests in hydrogen, fatigue crack growth rates were modestly higher in the FSW than the BM and 15 mm off-center tests. Select regions of the fracture surfaces associated with specified ΔK levels were examined which revealed intergranular fracture in the BM and 15 mm off-center specimens but an absence of intergranular features in the FSW specimens. In conclusion, the X52 friction stir weld and base metal tested in hydrogen exhibited fatigue crack growth rate relationships that are comparable to those for conventional arc welded steel pipeline of similar strength found in the literature.« less

  4. Hydrogen accelerated fatigue crack growth of friction stir welded X52 steel pipe

    SciTech Connect

    Ronevich, Joseph Allen; Somerday, Brian P.; Feng, Zhili

    2016-11-17

    Friction stir welded steel pipelines were tested in high pressure hydrogen gas to examine the effects of hydrogen accelerated fatigue crack growth. Fatigue crack growth rate (da/dN) vs. stress-intensity factor range (ΔK) relationships were measured for an X52 friction stir welded pipe tested in 21 MPa hydrogen gas at a frequency of 1 Hz and R = 0.5. Tests were performed on three regions: base metal (BM), center of friction stir weld (FSW), and 15 mm off-center of the weld. For all three material regions, tests in hydrogen exhibited accelerated fatigue crack growth rates that exceeded an order of magnitude compared to companion tests in air. Among tests in hydrogen, fatigue crack growth rates were modestly higher in the FSW than the BM and 15 mm off-center tests. Select regions of the fracture surfaces associated with specified ΔK levels were examined which revealed intergranular fracture in the BM and 15 mm off-center specimens but an absence of intergranular features in the FSW specimens. In conclusion, the X52 friction stir weld and base metal tested in hydrogen exhibited fatigue crack growth rate relationships that are comparable to those for conventional arc welded steel pipeline of similar strength found in the literature.

  5. Contrasting signatures of population growth for mitochondrial DNA and Y chromosomes among human populations in Africa.

    PubMed

    Pilkington, Maya Metni; Wilder, Jason A; Mendez, Fernando L; Cox, Murray P; Woerner, August; Angui, Thiep; Kingan, Sarah; Mobasher, Zahra; Batini, Chiara; Destro-Bisol, Giovanni; Soodyall, Himla; Strassmann, Beverly I; Hammer, Michael F

    2008-03-01

    A history of Pleistocene population expansion has been inferred from the frequency spectrum of polymorphism in the mitochondrial DNA (mtDNA) of many human populations. Similar patterns are not typically observed for autosomal and X-linked loci. One explanation for this discrepancy is a recent population bottleneck, with different rates of recovery for haploid and autosomal loci as a result of their different effective population sizes. This hypothesis predicts that mitochondrial and Y chromosomal DNA will show a similar skew in the frequency spectrum in populations that have experienced a recent increase in effective population size. We test this hypothesis by resequencing 6.6 kb of noncoding Y chromosomal DNA and 780 basepairs of the mtDNA cytochrome c oxidase subunit III (COIII) gene in 172 males from 5 African populations. Four tests of population expansion are employed for each locus in each population: Fu's Fs statistic, the R(2) statistic, coalescent simulations, and the mismatch distribution. Consistent with previous results, patterns of mtDNA polymorphism better fit a model of constant population size for food-gathering populations and a model of population expansion for food-producing populations. In contrast, none of the tests reveal evidence of Y chromosome growth for either food-gatherers or food-producers. The distinct mtDNA and Y chromosome polymorphism patterns most likely reflect sex-biased demographic processes in the recent history of African populations. We hypothesize that males experienced smaller effective population sizes and/or lower rates of migration during the Bantu expansion, which occurred over the last 5,000 years.

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

    PubMed

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

    2007-10-01

    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

  7. DCC functions as an accelerator of thalamocortical axonal growth downstream of spontaneous thalamic activity

    PubMed Central

    Castillo-Paterna, Mar; Moreno-Juan, Verónica; Filipchuk, Anton; Rodríguez-Malmierca, Luis; Susín, Rafael; López-Bendito, Guillermina

    2015-01-01

    Controlling the axon growth rate is fundamental when establishing brain connections. Using the thalamocortical system as a model, we previously showed that spontaneous calcium activity influences the growth rate of thalamocortical axons by regulating the transcription of Robo1 through an NF-κB-binding site in its promoter. Robo1 acts as a brake on the growth of thalamocortical axons in vivo. Here, we have identified the Netrin-1 receptor DCC as an accelerator for thalamic axon growth. Dcc transcription is regulated by spontaneous calcium activity in thalamocortical neurons and activating DCC signaling restores normal axon growth in electrically silenced neurons. Moreover, we identified an AP-1-binding site in the Dcc promoter that is crucial for the activity-dependent regulation of this gene. In summary, we have identified the Dcc gene as a novel downstream target of spontaneous calcium activity involved in axon growth. Together with our previous data, we demonstrate a mechanism to control axon growth that relies on the activity-dependent regulation of two functionally opposed receptors, Robo1 and DCC. These two proteins establish a tight and efficient means to regulate activity-guided axon growth in order to correctly establish neuronal connections during development. PMID:25947198

  8. Deterministic versus stochastic aspects of superexponential population growth models

    NASA Astrophysics Data System (ADS)

    Grosjean, Nicolas; Huillet, Thierry

    2016-08-01

    Deterministic population growth models with power-law rates can exhibit a large variety of growth behaviors, ranging from algebraic, exponential to hyperexponential (finite time explosion). In this setup, selfsimilarity considerations play a key role, together with two time substitutions. Two stochastic versions of such models are investigated, showing a much richer variety of behaviors. One is the Lamperti construction of selfsimilar positive stochastic processes based on the exponentiation of spectrally positive processes, followed by an appropriate time change. The other one is based on stable continuous-state branching processes, given by another Lamperti time substitution applied to stable spectrally positive processes.

  9. Accelerate!

    PubMed

    Kotter, John P

    2012-11-01

    The old ways of setting and implementing strategy are failing us, writes the author of Leading Change, in part because we can no longer keep up with the pace of change. Organizational leaders are torn between trying to stay ahead of increasingly fierce competition and needing to deliver this year's results. Although traditional hierarchies and managerial processes--the components of a company's "operating system"--can meet the daily demands of running an enterprise, they are rarely equipped to identify important hazards quickly, formulate creative strategic initiatives nimbly, and implement them speedily. The solution Kotter offers is a second system--an agile, networklike structure--that operates in concert with the first to create a dual operating system. In such a system the hierarchy can hand off the pursuit of big strategic initiatives to the strategy network, freeing itself to focus on incremental changes to improve efficiency. The network is populated by employees from all levels of the organization, giving it organizational knowledge, relationships, credibility, and influence. It can Liberate information from silos with ease. It has a dynamic structure free of bureaucratic layers, permitting a level of individualism, creativity, and innovation beyond the reach of any hierarchy. The network's core is a guiding coalition that represents each level and department in the hierarchy, with a broad range of skills. Its drivers are members of a "volunteer army" who are energized by and committed to the coalition's vividly formulated, high-stakes vision and strategy. Kotter has helped eight organizations, public and private, build dual operating systems over the past three years. He predicts that such systems will lead to long-term success in the 21st century--for shareholders, customers, employees, and companies themselves.

  10. On the effect of accelerated winds on the wave growth through detailed laboratory measurements.

    NASA Astrophysics Data System (ADS)

    Ocampo-Torres, Francisco J.; Branger, Hubert; Osuna, Pedro; Hernández, Aldo

    2013-04-01

    The possible influence of accelerated winds on air-water momentum fluxes is being studied through detailed laboratory measurements in a large wind-wave flume. Wind stress over the water surface, waves and surface drift are measured in the 40m long wind-wave tank at IRPHE, Marseille. While momentum fluxes are estimated directly through the eddy correlation method in a station about the middle of the tank, they provide information corresponding to rather short non-dimensional fetch not previously reported. Wave evolution along the tank is determined through a series of wave gauges, and the wind-induced surface drift is obtained at one of the first measuring stations at the beginning of the tank. At each experimental run very low wind was on (about 1m/s) for a certain period and suddenly it was constantly accelerated to reach about 13 m/s (as well as 8 and 5 m/s during different runs) in about 15 sec to as long as 600 sec. The wind was kept constant at that high speed for 2 to 10 min, and then suddenly and constantly decelerate to 0. Data from the constant high winds provided us with reference equilibrium conditions for at least 3 different wind speed. We, nevertheless, focus in the recordings while wind was being constantly accelerated expecting some contribution to the understanding of gustiness, the implied wind wave growth and the onset of surface drift. Wind-wave growth is observed to lag behind the wind stress signal, and furthermore, a two regime wind stress is noticed, apparently well correlated with a) the incipient growth and appearance of the first waves and b) the arrival of waves from the up-wind section of the tank. Results of non-dimensional wave energy as a function of non-dimensional fetch represent an extension of at least 2 decades shorter non-dimensional fetch to the wave growth curves typically found in the literature. The linear tendency of wave growth compares very well only when wind is reaching its maximum, while during the accelerated wind

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

    PubMed

    Banguero, H

    1983-05-01

    This work uses Keynesian principles and an analysis of the Colombian population in the 1970s to argue that the Colombian policy of slowing population growth, which was adopted with the aim of improving the general welfare of the population, has had shortterm negative effects on effective demand and thus on the level of employment and welfare. These negative effects were caused by the inflexibility of income distribution, which prevented expansion of the internal market, complicated by the stagnant condition of the external sector and the budget deficit. The results of the Colombian case study demonstrate how the deceleration of population growth beginning in the 1960s had a significant impact on the levels of consumption and savings and on the patterns of consumption, leading to low levels of investment and little dynamism. Although the current Colombian economic recession is aggravated by contextual factors such as the world economic recession, the high cost of capital, the industrial recession, and declining food production among others, at the core of the crisis are longer term structural determinants such as the decline in the rate of population growth and the highly unequal distribution of income and wealth, which have contributed to a shrinking of the internal market for some types of goods. Given the unlikelihood of renewed rapid population growth, the Keynesian model suggests that the only alternative for increasing aggregate demand is state intervention through public spending and investment and reorientation of the financial system to achieve a dynamic redistribution of income. Based on these findings and on proposals of other analysts, a stragegy for revitalization is proposed which would imply a gradual income redistribution to allow increased consumption of mass produced goods by the low income groups. Direct consumption subsidies would be avoided because of their inflationary and import-expanding tendencies; rather, incentives and support would be

  12. Deep resequencing reveals excess rare recent variants consistent with explosive population growth

    PubMed Central

    Coventry, Alex; Bull-Otterson, Lara M.; Liu, Xiaoming; Clark, Andrew G.; Maxwell, Taylor J.; Crosby, Jacy; Hixson, James E.; Rea, Thomas J.; Muzny, Donna M.; Lewis, Lora R.; Wheeler, David A.; Sabo, Aniko; Lusk, Christine; Weiss, Kenneth G.; Akbar, Humeira; Cree, Andrew; Hawes, Alicia C.; Newsham, Irene; Varghese, Robin T.; Villasana, Donna; Gross, Shannon; Joshi, Vandita; Santibanez, Jireh; Morgan, Margaret; Chang, Kyle; IV, Walker Hale; Templeton, Alan R.; Boerwinkle, Eric; Gibbs, Richard; Sing, Charles F.

    2010-01-01

    Accurately determining the distribution of rare variants is an important goal of human genetics, but resequencing of a sample large enough for this purpose has been unfeasible until now. Here, we applied Sanger sequencing of genomic PCR amplicons to resequence the diabetes-associated genes KCNJ11 and HHEX in 13,715 people (10,422 European Americans and 3,293 African Americans) and validated amplicons potentially harbouring rare variants using 454 pyrosequencing. We observed far more variation (expected variant-site count ∼578) than would have been predicted on the basis of earlier surveys, which could only capture the distribution of common variants. By comparison with earlier estimates based on common variants, our model shows a clear genetic signal of accelerating population growth, suggesting that humanity harbours a myriad of rare, deleterious variants, and that disease risk and the burden of disease in contemporary populations may be heavily influenced by the distribution of rare variants. PMID:21119644

  13. Tuning calcite morphology and growth acceleration by a rational design of highly stable protein-mimetics

    SciTech Connect

    Chen, Chunlong; Qi, Jiahui; Tao, Jinhui; Zuckermann, Ronald; De Yoreo, James J.

    2014-09-05

    In nature, proteins play a significant role in biomineral formation. One of the ultimate goals of bioinspired materials science is to develop highly stable synthetic molecules that mimic the function of these natural proteins by controlling crystal formation. Here, we demonstrate that both the morphology and the degree of acceleration or inhibition observed during growth of calcite in the presence of peptoids can be rationally tuned by balancing the electrostatic interactions (EI) and hydrophobic interactions (HI), with HI playing the dominant role. While either strong EI or HI inhibit growth and suppress (104) face expression, correlations between peptoid-crystal binding energies and observed changes in calcite growth indicate moderate EI allow peptoids to weakly adsorb while moderate HI cause disruption of surface-adsorbed water layers, leading to growth acceleration with retained expression of (104) faces. This study provides fundamental principles for designing peptoids as crystallization promoters, and offers a straightforward screening method based on macroscopic crystal morphology. Because peptoids are sequence-specific, highly stable, and easily synthesized, peptoid-enhanced crystallization offers a broad range of potential applications.

  14. Growth rates in a captive population of Tonkean macaques.

    PubMed

    Sanna, Andrea; De Marco, Arianna; Thierry, Bernard; Cozzolino, Roberto

    2015-07-01

    Measuring variations in body mass is necessary to gain a deeper understanding of the evolution of life-history patterns, and it provides information on the timing of sexual maturity and the development of sexual dimorphism. In this study, we collected longitudinal data on body mass from infancy to adulthood in a captive population of Tonkean macaques (Macaca tonkeana). Tests to evaluate whether social group, maternal age, and dominance rank influenced growth rates showed that they had no significant effect. We investigated the timing and magnitude of breaking points in the growth paths of males and females, and checked whether these breaking points could correspond to specific reproductive and morphological developmental events. We found that male and female Tonkean macaques have roughly equivalent body masses until around the age of four, when males go through an adolescent growth spurt and females continue to grow at a constant rate. Males not only grow faster than females, but they also continue to grow for nearly one and a half years after females have attained their full body mass. Growth rate differences account for approximately two-thirds of the body mass sexual dimorphism; only the remaining third results from continued male growth beyond the age where full body mass is reached in females. We also discovered remarkable correspondences between the timing of testicular enlargement and the adolescent growth spurt in males, and between dental development and slowdown breaking points in both sexes.

  15. Sweden Faces Zero Population Growth. Population Bulletin, Vol. 35, No. 2, June, 1980.

    ERIC Educational Resources Information Center

    Gendell, Murray

    This bulletin examines the causes of the fertility decline in Sweden and the concerns and ambivalence of Swedes about zero population growth (ZPG). The fertility decline is attributed to many causes. In recent years there has been a drop in marriage rates and a sharp increase in non-marital cohabitation. The decline is also related to the…

  16. Minimal models of growth and decline of microbial populations.

    PubMed

    Juška, Alfonsas

    2011-01-21

    Dynamics of growth and decline of microbial populations were analysed and respective models were developed in this investigation. Analysis of the dynamics was based on general considerations concerning the main properties of microorganisms and their interactions with the environment which was supposed to be affected by the activity of the population. Those considerations were expressed mathematically by differential equations or systems of the equations containing minimal sets of parameters characterizing those properties. It has been found that: (1) the factors leading to the decline of the population have to be considered separately, namely, accumulation of metabolites (toxins) in the medium and the exhaustion of resources; the latter have to be separated again into renewable ('building materials') and non-renewable (sources of energy); (2) decline of the population is caused by the exhaustion of sources of energy but no decline is predicted by the model because of the exhaustion of renewable resources; (3) the model determined by the accumulation of metabolites (toxins) in the medium does not suggest the existence of a separate 'stationary phase'; (4) in the model determined by the exhaustion of energy resources the 'stationary' and 'decline' phases are quite discernible; and (5) there is no symmetry in microbial population dynamics, the decline being slower than the rise. Mathematical models are expected to be useful in getting insight into the process of control of the dynamics of microbial populations. The models are in agreement with the experimental data.

  17. Bacterial populations growth under co- and counter-flow condition

    NASA Astrophysics Data System (ADS)

    Tesser, Francesca; Zeegers, Jos C. H.; Clercx, Herman J. H.; Toschi, Federico

    2014-11-01

    For organisms living in a liquid ecosystem, flow and flow gradients play a major role on the population level: the flow has a dual role as it transports the nutrient while dispersing the individuals. In absence of flow and under homogeneous conditions, the growth of a population towards an empty region is usually described by a reaction diffusion equation. The solution predicts the expansion as a wave front (Fisher wave) proceeding at constant speed, till the carrying capacity is reached everywhere. The effect of fluid flow, however, is not well understood and the interplay between transport of individuals and nutrient opens a wide scenario of possible behaviors. In this work, we experimentally observe non-motile E. coli bacteria spreading inside rectangular channels in a PDMS microfluidic device. By use of a fluorescent microscope we analyze the dynamics of the population density subjected to different co- and counter-flow conditions and shear rates.

  18. Stochastic resonance in a generalized Von Foerster population growth model

    SciTech Connect

    Lumi, N.; Mankin, R.

    2014-11-12

    The stochastic dynamics of a population growth model, similar to the Von Foerster model for human population, is studied. The influence of fluctuating environment on the carrying capacity is modeled as a multiplicative dichotomous noise. It is established that an interplay between nonlinearity and environmental fluctuations can cause single unidirectional discontinuous transitions of the mean population size versus the noise amplitude, i.e., an increase of noise amplitude can induce a jump from a state with a moderate number of individuals to that with a very large number, while by decreasing the noise amplitude an opposite transition cannot be effected. An analytical expression of the mean escape time for such transitions is found. Particularly, it is shown that the mean transition time exhibits a strong minimum at intermediate values of noise correlation time, i.e., the phenomenon of stochastic resonance occurs. Applications of the results in ecology are also discussed.

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

    NASA Astrophysics Data System (ADS)

    Lambert, Guillaume; Kussell, Edo

    2013-03-01

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

  20. Is faster economic growth compatible with reductions in carbon emissions? The role of diminished population growth

    NASA Astrophysics Data System (ADS)

    Casey, Gregory; Galor, Oded

    2017-01-01

    We provide evidence that lower fertility can simultaneously increase income per capita and lower carbon emissions, eliminating a trade-off central to most policies aimed at slowing global climate change. We estimate the effect of lower fertility on carbon emissions, accounting for the fact that changes in fertility patterns affect carbon emissions through three channels: total population, the age structure of the population, and economic output. Our analysis proceeds in two steps. First, we estimate the elasticity of carbon emissions with respect to population and income per capita in an unbalanced yearly panel of cross-country data from 1950-2010. We demonstrate that the elasticity with respect to population is nearly seven times larger than the elasticity with respect to income per capita and that this difference is statistically significant. Thus, the regression results imply that 1% slower population growth could be accompanied by an increase in income per capita of nearly 7% while still lowering carbon emissions. In the second part of our analysis, we use a recently constructed economic-demographic model of Nigeria to estimate the effect of lower fertility on carbon emissions, accounting for the impacts of fertility on population growth, population age structure, and income per capita. We find that by 2100 C.E. moving from the medium to the low variant of the UN fertility projection leads to 35% lower yearly emissions and 15% higher income per capita. These results suggest that population policies could be part of the approach to combating global climate change.

  1. Education and Skills for Development in South Africa: Reflections on the Accelerated and Shared Growth Initiative for South Africa

    ERIC Educational Resources Information Center

    McGrath, S.; Akoojee, Salim

    2007-01-01

    In July 2005, President Mbeki announced the launch of the Accelerated and Shared Growth Initiative for South Africa (AsgiSA), a new development strategy designed to help the South African state meet the ANC's 2004 election pledges, namely: (1) halve unemployment; (2) halve poverty; (3) accelerate employment equity; and (4) improve broad-based…

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

    PubMed

    Greenspan, A

    1994-12-01

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

  3. In vivo acceleration of skin growth using a servo-controlled stretching device.

    PubMed

    Chin, Michael S; Ogawa, Rei; Lancerotto, Luca; Pietramaggiori, Giorgio; Schomacker, Kevin T; Mathews, Jasmine C; Scherer, Saja S; Van Duyn, Paul; Prsa, Michael J; Ottensmeyer, Mark P; Veves, Aristidis; Orgill, Dennis P

    2010-06-01

    Tension is a principal force experienced by skin and serves a critical role in growth and development. Optimal tension application regimens may be an important component for skin tissue engineering and dermatogenesis. In this study, we designed and tested a novel servo-controlled skin-stretching device to apply predetermined tension and waveforms in mice. The effects of static and cyclical stretching forces were compared in 48 mice by measuring epidermal proliferation, angiogenesis, cutaneous perfusion, and principal growth factors using immunohistochemistry, real-time reverse transcriptase-polymerase chain reaction, and hyperspectral imaging. All stretched samples had upregulated epidermal proliferation and angiogenesis. Real-time reverse transcriptase-polymerase chain reaction of epidermal growth factor, transforming growth factor beta1, and nerve growth factor demonstrated greater expression in cyclically stretched skin when compared to static stretch. Hypoxia-induced factor 1alpha was significantly upregulated in cyclically stretched skin, but poststretch analysis demonstrated well-oxygenated tissue, collectively suggesting the presence of transient hypoxia. Waveform-specific mechanical loads may accelerate tissue growth by mechanotransduction and as a result of repeated cycles of temporary hypoxia. Further analysis of mechanotransduction signaling pathways may provide additional insight to improve skin tissue engineering methods and optimize our device.

  4. Plant growth promoting rhizobacteria and endophytes accelerate phytoremediation of metalliferous soils.

    PubMed

    Ma, Y; Prasad, M N V; Rajkumar, M; Freitas, H

    2011-01-01

    Technogenic activities (industrial-plastic, textiles, microelectronics, wood preservatives; mining-mine refuse, tailings, smelting; agrochemicals-chemical fertilizers, farm yard manure, pesticides; aerosols-pyrometallurgical and automobile exhausts; biosolids-sewage sludge, domestic waste; fly ash-coal combustion products) are the primary sources of heavy metal contamination and pollution in the environment in addition to geogenic sources. During the last two decades, bioremediation has emerged as a potential tool to clean up the metal-contaminated/polluted environment. Exclusively derived processes by plants alone (phytoremediation) are time-consuming. Further, high levels of pollutants pose toxicity to the remediating plants. This situation could be ameliorated and accelerated by exploring the partnership of plant-microbe, which would improve the plant growth by facilitating the sequestration of toxic heavy metals. Plants can bioconcentrate (phytoextraction) as well as bioimmobilize or inactivate (phytostabilization) toxic heavy metals through in situ rhizospheric processes. The mobility and bioavailability of heavy metal in the soil, particularly at the rhizosphere where root uptake or exclusion takes place, are critical factors that affect phytoextraction and phytostabilization. Developing new methods for either enhancing (phytoextraction) or reducing the bioavailability of metal contaminants in the rhizosphere (phytostabilization) as well as improving plant establishment, growth, and health could significantly speed up the process of bioremediation techniques. In this review, we have highlighted the role of plant growth promoting rhizo- and/or endophytic bacteria in accelerating phytoremediation derived benefits in extensive tables and elaborate schematic sketches.

  5. Population growth and poverty in the developing world.

    PubMed

    Birdsall, N

    1980-12-01

    The links between rapid population growth and the absolute poverty currently affecting 780 million people in the developing countries (excluding China and other centrally planned economies) were examined. Absolute poverty is defined as having less than the income necessary to ensure a daily diet of 2150 calories per person ($200 per person a year in 1970 United States dollars). Focus is on poverty and demography in the developing world (defining poverty; income, fertility and life expectancy; demographic change and poverty), effect of poverty on fertility, family planning programs and the poor, and the outlook for the future. Rapid population growth stretches both national and family budgets thin with the increasing numbers of children to be fed and educated and workers to be provided with jobs. Slower per capita income growth, lack of progress in reducing income inequality, and more poverty are the probable consequences. Many characteristics of poverty can cause high fertility -- high infant mortality, lack of education for women in particular, too little family income to invest in children, inequitable shares in national income, and the inaccessibility of family planning. Experience in China, Indonesia, Taiwan, Colombia, Korea, Sri Lanka, Cuba and Costa Rica demonstrate that birthrates can decline rapidly in low income groups and countries when basic health care, education, and low-cost or free family planning services are made widely available.

  6. Population growth and United States politics in the 1970s.

    PubMed

    Nash, A E

    1973-01-01

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

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

    PubMed

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

    2010-03-01

    Rodents that have multi-annual cycles of density are known to have flexible growth strategies, and the "Chitty effect", whereby adults in the high-density phase of the cycle exhibit larger average body mass than during the low phase, is a well-documented feature of cyclic populations. Despite this, there have been no studies that have repeatedly monitored individual vole growth over time from all phases of a density cycle, in order to evaluate whether such variation in body size is due to differences in juvenile growth rates, differences in growth periods, or differential survival of particularly large or small voles. This study compares growth trajectories from voles during the peak, increase and crash phases of the cycle in order to evaluate whether voles are exhibiting fast or slow growth strategies. We found that although voles reach highest asymptotic weights in the peak phase and lowest asymptotes during the crash, initial growth rates were not significantly different. This suggests that voles attain larger body size during the peak phase as a result of growing for longer.

  8. Acceleration and localization of subcritical crack growth in a natural composite material

    NASA Astrophysics Data System (ADS)

    Lennartz-Sassinek, S.; Main, I. G.; Zaiser, M.; Graham, C. C.

    2014-11-01

    Catastrophic failure of natural and engineered materials is often preceded by an acceleration and localization of damage that can be observed indirectly from acoustic emissions (AE) generated by the nucleation and growth of microcracks. In this paper we present a detailed investigation of the statistical properties and spatiotemporal characteristics of AE signals generated during triaxial compression of a sandstone sample. We demonstrate that the AE event amplitudes and interevent times are characterized by scaling distributions with shapes that remain invariant during most of the loading sequence. Localization of the AE activity on an incipient fault plane is associated with growth in AE rate in the form of a time-reversed Omori law with an exponent near 1. The experimental findings are interpreted using a model that assumes scale-invariant growth of the dominating crack or fault zone, consistent with the Dugdale-Barenblatt "process zone" model. We determine formal relationships between fault size, fault growth rate, and AE event rate, which are found to be consistent with the experimental observations. From these relations, we conclude that relatively slow growth of a subcritical fault may be associated with a significantly more rapid increase of the AE rate and that monitoring AE rate may therefore provide more reliable predictors of incipient failure than direct monitoring of the growing fault.

  9. Growth in an English population from the Industrial Revolution.

    PubMed

    Mays, S; Brickley, M; Ives, R

    2008-05-01

    The rapid urbanization of the Industrial Revolution in 18th-19th century England presented new health challenges. Our aim is to investigate using English skeletal remains whether the living conditions for an urban working class group in the Industrial Revolution negatively impacted upon their skeletal growth compared with a population from a rural agrarian parish. The Industrial Revolution skeletal material is from St Martin's Churchyard, Birmingham (SMB), West Midlands. It dates primarily from the first half of the nineteenth century when Birmingham was a major manufacturing center. The rural group is from Wharram Percy (WP), North Yorkshire, and dates from 10th-19th century AD. The methodology involves plotting diaphyseal bone lengths versus dental age for subadults. No overall difference was found between the two populations in bone length-for-age among the 2- to 18-year cohort. However the younger parts of the SMB cohort were smaller than at WP; the opposite was true of the older parts of the cohort. Growth rate, as inferred from crosssectional data, appeared greater at SMB than at WP. The only result consistent with expectations is the larger bone dimensions in young children from WP, but this likely reflects prolonged breastfeeding at WP not differences in urban and rural environments. That the deleterious health effects that we know accompanied the major transition in human society from a rural agrarian to an urban industrialized living environment should be little manifest in skeletal endochondral growth data is discouraging for those who would use such methodology to monitor health in earlier populations.

  10. Population growth of Yellowstone grizzly bears: Uncertainty and future monitoring

    USGS Publications Warehouse

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

    2007-01-01

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

  11. Two-tank suspended growth process for accelerating the detoxification kinetics of hydrocarbons requiring initial monooxygenation reactions.

    PubMed

    Dahlen, Elizabeth P; Rittmann, Bruce E

    2002-01-01

    An experimental evaluation demonstrated that suspended growth systems operated in a two-tank accelerator/aerator configuration significantly increased the overall removal rates for phenol and 2,4-dichlorophenol (2,4-DCP), aromatic hydrocarbons that require initial monooxygenations. The accelerator tank is a small volume that receives the influent and recycled biomass. It has a high ratio of electron donor (BOD) to electron acceptor (O2). Biomass in the accelerator should be enriched in reduced nicotinamide adenine dinucleotide (NADH + H+) and have a very high specific growth rate, conditions that should accelerate the kinetics of monooxygenation reactions. For the more slowly degraded 2,4-DCP, the average percentage removal increased from 74% to 93%, even though the volume of the two-tank system was smaller than that of the one-tank system in most experiments. The average volumetric and biomass-specific removal rates increased by 50% and 100%, respectively, in the two-tank system, compared to a one-tank system. The greatest enhancement in 2,4-DCP removal occurred when the accelerator tank comprised approximately 20% of the system volume. Biomass in the accelerator tank was significantly enriched in NADH + H+ when its dissolved oxygen (DO) concentration was below 0.25 mg/L, a situation having a high ratio of donor to acceptor. The accelerator biomass had its highest NADH + H+ content for the experiments that had the highest rate of 2,4-DCP removal. Biomass in the accelerator also had a much higher specific growth rate than in the aerator or the system overall, and the specific growth rate in the accelerator was inversely correlated to the accelerator volume.

  12. Herbivory: effects on plant abundance, distribution and population growth

    PubMed Central

    Maron, John L; Crone, Elizabeth

    2006-01-01

    Plants are attacked by many different consumers. A critical question is how often, and under what conditions, common reductions in growth, fecundity or even survival that occur due to herbivory translate to meaningful impacts on abundance, distribution or dynamics of plant populations. Here, we review population-level studies of the effects of consumers on plant dynamics and evaluate: (i) whether particular consumers have predictably more or less influence on plant abundance, (ii) whether particular plant life-history types are predictably more vulnerable to herbivory at the population level, (iii) whether the strength of plant–consumer interactions shifts predictably across environmental gradients and (iv) the role of consumers in influencing plant distributional limits. Existing studies demonstrate numerous examples of consumers limiting local plant abundance and distribution. We found larger effects of consumers on grassland than woodland forbs, stronger effects of herbivory in areas with high versus low disturbance, but no systematic or unambiguous differences in the impact of consumers based on plant life-history or herbivore feeding mode. However, our ability to evaluate these and other patterns is limited by the small (but growing) number of studies in this area. As an impetus for further study, we review strengths and challenges of population-level studies, such as interpreting net impacts of consumers in the presence of density dependence and seed bank dynamics. PMID:17002942

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

    PubMed

    Lincoln, D W

    1993-01-01

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

  14. Social policy and population growth in South-East Asia.

    PubMed

    You Poh Seng Rao, B; Shantakumar, G

    1974-01-01

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

  15. Solving the problem of negative populations in approximate accelerated stochastic simulations using the representative reaction approach.

    PubMed

    Kadam, Shantanu; Vanka, Kumar

    2013-02-15

    Methods based on the stochastic formulation of chemical kinetics have the potential to accurately reproduce the dynamical behavior of various biochemical systems of interest. However, the computational expense makes them impractical for the study of real systems. Attempts to render these methods practical have led to the development of accelerated methods, where the reaction numbers are modeled by Poisson random numbers. However, for certain systems, such methods give rise to physically unrealistic negative numbers for species populations. The methods which make use of binomial variables, in place of Poisson random numbers, have since become popular, and have been partially successful in addressing this problem. In this manuscript, the development of two new computational methods, based on the representative reaction approach (RRA), has been discussed. The new methods endeavor to solve the problem of negative numbers, by making use of tools like the stochastic simulation algorithm and the binomial method, in conjunction with the RRA. It is found that these newly developed methods perform better than other binomial methods used for stochastic simulations, in resolving the problem of negative populations.

  16. [Environmental pollution and population growth in Latin America].

    PubMed

    Viel, B

    1983-01-01

    3 factors are always involved in causation of infectious disease: the causal organism, an adverse environment, and nutritional status. As knowledge of degenerative and mental illnesses advances, their relationship to environmental problems becomes clearer. Health in the human being as in all living things is the product of ecological equilibrium. In countries with high mortality rates, the majority of deaths occur in the early years of life. Countries enjoying low mortality rates are those that have protected themselves against environmental deterioration. The Roman civilization, the 1st to have large cities, built aqueducts to protect the water supply from contamination. With the disappearance of the Roman Empire the concern for purity of the water supply also disappeared, and the cities of the Middle Ages became breeding grounds for epidemics. In the early 19th century John Snow demonstrated the role of water in the transmission of cholera and thereafter the concern with potable water and sewage disposal was reborn. The Industrial Revolution eventually allowed sufficient accumulation of wealth to permit improved nutrition. Environmental sanitation and improved food supply produced a new ecological equilibrium, and Western Europe began to have lower and lower mortality rates. Paralleling the decline in deaths a new spirit of responsible parenthood and delayed marriage was lowering birth rates. Population growth, which never exceeded 1%, had the additional escape valve of emigration to America and Australia. The true cause of environmental degradation is man. When human beings were few their contaminants were readily obsorbed by the environment, but as they proliferate the environment is increasingly unable to absorb their pollution by natural processes. Industrial fumes, deforestation, and polluted rivers are only the symptoms of contamination. In the developed countries, technological innovations minimizing industrial pollution and lower population growth are

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

    PubMed

    Verliat, S

    1994-01-01

    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.

  18. TP508 accelerates fracture repair by promoting cell growth over cell death

    SciTech Connect

    Li Xinmin; Wang Hali; Touma, Edward; Qi Yuchen; Rousseau, Emma; Quigg, Richard J.; Ryaby, James T.

    2007-12-07

    TP508 is a synthetic 23-amino acid peptide representing a receptor-binding domain of human thrombin. We have previously shown that a single injection of TP508 accelerates fracture healing in a rat femoral fracture model. To understand how TP508 acts at the protein level during fracture healing, we compared the translational profiles between saline-control and fractured femur at six time points after TP508 treatment using the second generation of BD Clontech{sup TM} Antibody Microarray. Here, we demonstrate that TP508 accelerates fracture healing by modulating expression levels of proteins primarily involved in the functional categories of cell cycle, cellular growth and proliferation, and cell death. The majority of those proteins are physically interrelated and functionally overlapped. The action of those proteins is highlighted by a central theme of promoting cell growth via balance of cell survival over cell death signals. This appears to occur through the stimulation of several bone healing pathways including cell cycle-G1/S checkpoint regulation, apoptosis, JAK/STAT, NF-{kappa}B, PDGF, PI3K/AKT, PTEN, and ERK/MAPK.

  19. The trade-off between maturation and growth during accelerated development in frogs.

    PubMed

    Mueller, Casey A; Augustine, Starrlight; Kooijman, Sebastiaan A L M; Kearney, Michael R; Seymour, Roger S

    2012-09-01

    Developmental energetics are crucial to a species' life history and ecology but are poorly understood from a mechanistic perspective. Traditional energy and mass budgeting does not distinguish between costs of growth and maturation, making it difficult to account for accelerated development. We apply a metabolic theory that uniquely considers maturation costs (Dynamic Energy Budget theory, DEB) to interpret empirical data on the energetics of accelerated development in amphibians. We measured energy use until metamorphosis in two related frogs, Crinia georgiana and Pseudophryne bibronii. Mass and energy content of fresh ova were comparable between the species. However, development to metamorphosis was 1.7 times faster in C. georgiana while P. bibronii produced nine times the dry biomass at metamorphosis and had lower mass-specific oxygen requirements. DEB theory explained these patterns through differences in ontogenetic energy allocation to maturation. P. bibronii partitioned energy in the same (constant) way throughout development whereas C. georgiana increased the fraction of energy allocated to maturation over growth between hatching and the onset of feeding. DEB parameter estimation for additional, direct-developing taxa suggests that a change in energy allocation during development may result from a selective pressure to increase development rate, and not as a result of development mode.

  20. Acceleration of puberty during growth hormone therapy in a child with septo-optic dysplasia.

    PubMed

    Catlı, Gönül; Altıncık, Ayça; Anık, Ahmet; Demir, Korcan; Güleryüz, Handan; Abacı, Ayhan; Böber, Ece

    2014-01-01

    Septo-optic dysplasia (SOD) is a heterogeneous disorder of the central nervous system characterized by various endocrinological and neurological findings. It is a complex disease caused by a combination of genetic and environmental factors. Herein, we report the case of a 5.5-year-old girl who presented with short stature and strabismus. Ophthalmological examination revealed bilateral optic nerve hypoplasia. Ectopic posterior pituitary and bilateral optic hypoplasia were detected on brain magnetic resonance imaging. The presence of bilateral optic nerve hypoplasia and hypopituitarism led to the diagnosis of SOD. An abated growth hormone (GH) response was found in the GH stimulation test and GH replacement therapy was initiated. At the end of the first year of clinical follow-up, secondary hypothyroidism was detected and L-thyroxine was added to the treatment. At the age of 8.25 years, thelarche was noted and 6 months later, the patient presented with menarche. At this time, the bone age was 12 years and the basal luteinizing hormone level was 7 mIU/mL. These findings indicated acceleration in the process of pubertal development. We report this case (i) to emphasize the need to investigate hypopituitarism in cases with bilateral optic nerve hypoplasia and (ii) to draw attention to the fact that during the follow-up of SOD cases receiving GH therapy, inappropriate acceleration of growth velocity and rapid improvement in bone age may be predictive of central precocious puberty development.

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

    PubMed

    Pimentel, D

    1991-01-01

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

  2. Tree growth acceleration and expansion of alpine forests: The synergistic effect of atmospheric and edaphic change

    PubMed Central

    Silva, Lucas C. R.; Sun, Geng; Zhu-Barker, Xia; Liang, Qianlong; Wu, Ning; Horwath, William R.

    2016-01-01

    Many forest ecosystems have experienced recent declines in productivity; however, in some alpine regions, tree growth and forest expansion are increasing at marked rates. Dendrochronological analyses at the upper limit of alpine forests in the Tibetan Plateau show a steady increase in tree growth since the early 1900s, which intensified during the 1930s and 1960s, and have reached unprecedented levels since 1760. This recent growth acceleration was observed in small/young and large/old trees and coincided with the establishment of trees outside the forest range, reflecting a connection between the physiological performance of dominant species and shifts in forest distribution. Measurements of stable isotopes (carbon, oxygen, and nitrogen) in tree rings indicate that tree growth has been stimulated by the synergistic effect of rising atmospheric CO2 and a warming-induced increase in water and nutrient availability from thawing permafrost. These findings illustrate the importance of considering soil-plant-atmosphere interactions to understand current and anticipate future changes in productivity and distribution of forest ecosystems. PMID:27652334

  3. Tree growth acceleration and expansion of alpine forests: The synergistic effect of atmospheric and edaphic change.

    PubMed

    Silva, Lucas C R; Sun, Geng; Zhu-Barker, Xia; Liang, Qianlong; Wu, Ning; Horwath, William R

    2016-08-01

    Many forest ecosystems have experienced recent declines in productivity; however, in some alpine regions, tree growth and forest expansion are increasing at marked rates. Dendrochronological analyses at the upper limit of alpine forests in the Tibetan Plateau show a steady increase in tree growth since the early 1900s, which intensified during the 1930s and 1960s, and have reached unprecedented levels since 1760. This recent growth acceleration was observed in small/young and large/old trees and coincided with the establishment of trees outside the forest range, reflecting a connection between the physiological performance of dominant species and shifts in forest distribution. Measurements of stable isotopes (carbon, oxygen, and nitrogen) in tree rings indicate that tree growth has been stimulated by the synergistic effect of rising atmospheric CO2 and a warming-induced increase in water and nutrient availability from thawing permafrost. These findings illustrate the importance of considering soil-plant-atmosphere interactions to understand current and anticipate future changes in productivity and distribution of forest ecosystems.

  4. Crack growth in Ti-8Al-1Mo-1V with real-time and accelerated flight by flight loading

    NASA Technical Reports Server (NTRS)

    Imig, L. A.

    1975-01-01

    Crack growth in Ti-8Al-lMo-lV was measured and calculated for real time and accelerated simulations of supersonic airplane loading and heating. Crack-growth rates calculated on the assumption that an entire flight could be represented by a single cycle predicted the experimental rates poorly. Calculated crack growth rates were slower than the experimental rates for all tests with flight-by-flight loading. For room temperature accelerated tests, the calculated rates agreed well with the experimental rates; but the calculations became progressively less accurate for progressively more complex test conditions (tests that included elevated temperature).

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

    PubMed

    Sharpless, J

    1995-01-01

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

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

    PubMed

    Lesser, Mark R; Jackson, Stephen T

    2013-03-01

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

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

    PubMed

    Charles, Florence; Rugani, Nathalie; Gontard, Nathalie

    2005-05-01

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

  8. The dynamical analogy between microbial growth on mixtures of substrates and population growth of competing species.

    PubMed

    Narang, A

    1998-07-05

    There is a similarity between the metabolic dynamics of a microbial species growing on a mixture of two substrates and the dynamics of growth of two competing populations. Specifically, the enzymes catalyzing the uptake and catabolism of substrates exhibit phenomena analogous to extinction and coexistence."Extinction" of the enzymes associated with one of the substrates results in sequential utilization of the substrates (diauxie) (Monod, 1942). "Coexistence" of the enzymes associated with the substrates results in simultaneous utilization of the substrates (Egli, 1995). Here, we formulate a simple model that shows the basis for this dynamical similarity: The equations describing the evolution of the enzyme levels are dynamical analogs of the Lotka-Volterra model for two competing species. The analogy suggests ways of capturing the experimentally observed preculture-dependent growth patterns, i.e., growth patterns that vary depending on the physiological state of the preculture.

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

    PubMed Central

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

    2014-01-01

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

  10. Population. Headline Series.

    ERIC Educational Resources Information Center

    Oppenheimer, Valerie K.

    Useful as background reading or secondary classroom material, this pamphlet reviews several dimensions of world population growth and control. The first of seven chapters, World Population Growth: Past, Present and Future, discusses some of the reasons for the greatly accelerated growth since 1950, and points out that even significantly rapid…

  11. Food shortages in sub-Saharan Africa and population growth.

    PubMed

    Munisi, S E

    1982-12-01

    Food problems faced by sub-Saharan African nations center around the widening gap between food needs and availablity. Food shortages are suggested to originate from poor distribution and as a result of natural disasters; not as a consequence of population growth. Imperialism, colonialism, and neocolonial exploitation has encouraged African economic and cultural backwardness; a situation in which high population growth can have grave consequences. Fertility control is promoted by industrialized governments as a means of solving socioeconomic problems. However, fertility control may not be justified in many African nations which experience high infant mortality and labor intensive agriculture. Although the number of people who can be fed in any circumstance is ultimately finite, Africa's situation could be improved. If presently uninhabitable land was made suitable for settlement, land shortage from overpopulation would not be problematic for a long time. Modernization of agricultural practices could have a substantial impact of food production. At present, innovations are largely associated with the production of export crops which has often necessitated food imports. Food aid for relief in emergencies or for support of regions with chronic shortages is appropriate and beneficial, however, in some cases food aid can be detrimental, e.g., by lowering food prices thus burdening small farmers. Food aid tends to create dependency, not self-sufficiency. Malnutrition and hunger are symptoms of underdevelopment. At the policy level, a food and nutrition strategy should include rural development designed to improve income redistribution, agricultural modernization, and measures to influence the production of various foods to ensure a balanced diet, and nutrition and health intervention programs for vulnerable groups. In addition to overall agricultural development, 2 general recommendations are offered: increased production of staple food stuffs and a concentrated effort to

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

    PubMed Central

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

    2016-01-01

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

  13. Carcinogenic Parasite Secretes Growth Factor That Accelerates Wound Healing and Potentially Promotes Neoplasia

    PubMed Central

    Smout, Michael J.; Sotillo, Javier; Laha, Thewarach; Papatpremsiri, Atiroch; Rinaldi, Gabriel; Pimenta, Rafael N.; Chan, Lai Yue; Johnson, Michael S.; Turnbull, Lynne; Whitchurch, Cynthia B.; Giacomin, Paul R.; Moran, Corey S.; Golledge, Jonathan; Daly, Norelle; Sripa, Banchob; Mulvenna, Jason P.

    2015-01-01

    Abstract Infection with the human liver fluke Opisthorchis viverrini induces cancer of the bile ducts, cholangiocarcinoma (CCA). Injury from feeding activities of this parasite within the human biliary tree causes extensive lesions, wounds that undergo protracted cycles of healing, and re-injury over years of chronic infection. We show that O. viverrini secreted proteins accelerated wound resolution in human cholangiocytes, an outcome that was compromised following silencing of expression of the fluke-derived gene encoding the granulin-like growth factor, Ov-GRN-1. Recombinant Ov-GRN-1 induced angiogenesis and accelerated mouse wound healing. Ov-GRN-1 was internalized by human cholangiocytes and induced gene and protein expression changes associated with wound healing and cancer pathways. Given the notable but seemingly paradoxical properties of liver fluke granulin in promoting not only wound healing but also a carcinogenic microenvironment, Ov-GRN-1 likely holds marked potential as a therapeutic wound-healing agent and as a vaccine against an infection-induced cancer of major public health significance in the developing world. PMID:26485648

  14. Recombinant Human Epidermal Growth Factor Accelerates Recovery of Mouse Small Intestinal Mucosa After Radiation Damage

    SciTech Connect

    Lee, Kang Kyoo; Jo, Hyang Jeong; Hong, Joon Pio; Lee, Sang-wook Sohn, Jung Sook; Moon, Soo Young; Yang, Sei Hoon; Shim, Hyeok; Lee, Sang Ho; Ryu, Seung-Hee; Moon, Sun Rock

    2008-07-15

    Purpose: To determine whether systemically administered recombinant human epidermal growth factor (rhEGF) accelerates the recovery of mouse small intestinal mucosa after irradiation. Methods and Materials: A mouse mucosal damage model was established by administering radiation to male BALB/c mice with a single dose of 15 Gy applied to the abdomen. After irradiation, rhEGF was administered subcutaneously at various doses (0.04, 0.2, 1.0, and 5.0 mg/kg/day) eight times at 2- to 3-day intervals. The evaluation methods included histologic changes of small intestinal mucosa, change in body weight, frequency of diarrhea, and survival rate. Results: The recovery of small intestinal mucosa after irradiation was significantly improved in the mice treated with a high dose of rhEGF. In the mice that underwent irradiation without rhEGF treatment, intestinal mucosal ulceration, mucosal layer damage, and severe inflammation occurred. The regeneration of villi was noticeable in mice treated with more than 0.2 mg/kg rhEGF, and the villi recovered fully in mice given more than 1 mg/kg rhEGF. The frequency of diarrhea persisting for more than 3 days was significantly greater in the radiation control group than in the rhEGF-treated groups. Conclusions: Systemic administration of rhEGF accelerates recovery from mucosal damage induced by irradiation. We suggest that rhEGF treatment shows promise for the reduction of small intestinal damage after irradiation.

  15. TUSC3 Loss Alters the ER Stress Response and Accelerates Prostate Cancer Growth in vivo

    NASA Astrophysics Data System (ADS)

    Horak, Peter; Tomasich, Erwin; Vaňhara, Petr; Kratochvílová, Kateřina; Anees, Mariam; Marhold, Maximilian; Lemberger, Christof E.; Gerschpacher, Marion; Horvat, Reinhard; Sibilia, Maria; Pils, Dietmar; Krainer, Michael

    2014-01-01

    Prostate cancer is the most prevalent cancer in males in developed countries. Tumor suppressor candidate 3 (TUSC3) has been identified as a putative tumor suppressor gene in prostate cancer, though its function has not been characterized. TUSC3 shares homologies with the yeast oligosaccharyltransferase (OST) complex subunit Ost3p, suggesting a role in protein glycosylation. We provide evidence that TUSC3 is part of the OST complex and affects N-linked glycosylation in mammalian cells. Loss of TUSC3 expression in DU145 and PC3 prostate cancer cell lines leads to increased proliferation, migration and invasion as well as accelerated xenograft growth in a PTEN negative background. TUSC3 downregulation also affects endoplasmic reticulum (ER) structure and stress response, which results in increased Akt signaling. Together, our findings provide first mechanistic insight in TUSC3 function in prostate carcinogenesis in general and N-glycosylation in particular.

  16. TUSC3 Loss Alters the ER Stress Response and Accelerates Prostate Cancer Growth in vivo

    PubMed Central

    Horak, Peter; Tomasich, Erwin; Vaňhara, Petr; Kratochvílová, Kateřina; Anees, Mariam; Marhold, Maximilian; Lemberger, Christof E.; Gerschpacher, Marion; Horvat, Reinhard; Sibilia, Maria; Pils, Dietmar; Krainer, Michael

    2014-01-01

    Prostate cancer is the most prevalent cancer in males in developed countries. Tumor suppressor candidate 3 (TUSC3) has been identified as a putative tumor suppressor gene in prostate cancer, though its function has not been characterized. TUSC3 shares homologies with the yeast oligosaccharyltransferase (OST) complex subunit Ost3p, suggesting a role in protein glycosylation. We provide evidence that TUSC3 is part of the OST complex and affects N-linked glycosylation in mammalian cells. Loss of TUSC3 expression in DU145 and PC3 prostate cancer cell lines leads to increased proliferation, migration and invasion as well as accelerated xenograft growth in a PTEN negative background. TUSC3 downregulation also affects endoplasmic reticulum (ER) structure and stress response, which results in increased Akt signaling. Together, our findings provide first mechanistic insight in TUSC3 function in prostate carcinogenesis in general and N-glycosylation in particular. PMID:24435307

  17. Acceleration of wound healing by growth hormone-releasing hormone and its agonists.

    PubMed

    Dioufa, Nikolina; Schally, Andrew V; Chatzistamou, Ioulia; Moustou, Evi; Block, Norman L; Owens, Gary K; Papavassiliou, Athanasios G; Kiaris, Hippokratis

    2010-10-26

    Despite the well-documented action of growth hormone-releasing hormone (GHRH) on the stimulation of production and release of growth hormone (GH), the effects of GHRH in peripheral tissues are incompletely explored. In this study, we show that GHRH plays a role in wound healing and tissue repair by acting primarily on wound-associated fibroblasts. Mouse embryonic fibroblasts (MEFs) in culture and wound-associated fibroblasts in mice expressed a splice variant of the receptors for GHRH (SV1). Exposure of MEFs to 100 nM and 500 nM GHRH or the GHRH agonist JI-38 stimulated the expression of α-smooth muscle actin (αSMA) based on immunoblot analyses as well as the expression of an αSMA-β-galactosidase reporter transgene in primary cultures of fibroblasts isolated from transgenic mice. Consistent with this induction of αSMA expression, results of transwell-based migration assays and in vitro wound healing (scratch) assays showed that both GHRH and GHRH agonist JI-38 stimulated the migration of MEFs in vitro. In vivo, local application of GHRH or JI-38 accelerated healing in skin wounds of mice. Histological evaluation of skin biopsies showed that wounds treated with GHRH and JI-38 were both characterized by increased abundance of fibroblasts during the early stages of wound healing and accelerated reformation of the covering epithelium at later stages. These results identify another function of GHRH in promoting skin tissue wound healing and repair. Our findings suggest that GHRH may have clinical utility for augmenting healing of skin wounds resulting from trauma, surgery, or disease.

  18. Population.

    ERIC Educational Resources Information Center

    International Planned Parenthood Federation, London (England).

    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,…

  19. Exposure to omega-3 fatty acids at early age accelerate bone growth and improve bone quality.

    PubMed

    Koren, Netta; Simsa-Maziel, Stav; Shahar, Ron; Schwartz, Betty; Monsonego-Ornan, Efrat

    2014-06-01

    Omega-3 fatty acids (FAs) are essential nutritional components that must be obtained from foods. Increasing evidence validate that omega-3 FAs are beneficial for bone health, and several mechanisms have been suggested to mediate their effects on bone, including alterations in calcium absorption and urinary calcium loss, prostaglandin synthesis, lipid oxidation, osteoblast formation and inhibition of osteoclastogenesis. However, to date, there is scant information regarding the effect of omega-3 FAs on the developing skeleton during the rapid growth phase. In this study we aim to evaluate the effect of exposure to high levels of omega-3 FAs on bone development and quality during prenatal and early postnatal period. For this purpose, we used the fat-1 transgenic mice that have the ability to convert omega-6 to omega-3 fatty acids and the ATDC5 chondrogenic cell line as models. We show that exposure to high concentrations of omega-3 FAs at a young age accelerates bone growth through alterations of the growth plate, associated with increased chondrocyte proliferation and differentiation. We further propose that those effects are mediated by the receptors G-protein coupled receptor 120 (GPR120) and hepatic nuclear factor 4α, which are expressed by chondrocytes in culture. Additionally, using a combined study on the structural and mechanical bone parameters, we show that high omega-3 levels contribute to superior trabecular and cortical structure, as well as to stiffer bones and improved bone quality. Most interestingly, the fat-1 model allowed us to demonstrate the role of maternal high omega-3 concentration on bone growth during the gestation and postnatal period.

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

    PubMed

    Khalatbari, P

    1986-07-01

    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.

  1. Microwave effect in the fast synthesis of microporous materials: which stage between nucleation and crystal growth is accelerated by microwave irradiation?

    PubMed

    Jhung, Sung Hwa; Jin, Taihuan; Hwang, Young Kyu; Chang, Jong-San

    2007-01-01

    Microporous materials, such as silicalite-1 and VSB-5 molecular sieves, have been synthesized by both microwave irradiation (MW) and conventional electric heating (CE). The accelerated syntheses by microwave irradiation can be quantitatively investigated by various heating modes conducted in two steps such as MW-MW, MW-CE, CE-MW, and CE-CE (in the order of nucleation-crystal growth). In the case of synthesis by MW-CE or CE-MW, the heating modes were changed for the second step just after the appearance of X-ray diffraction peaks in the first step. We have quantitatively demonstrated that the microwave irradiation accelerates not only the nucleation but also crystal growth. However, the contribution to decrease the synthesis time by microwave irradiation is larger in the nucleation stage than in the step of crystal growth. The crystal size increases in the order of MW-MWgrowth and small crystal size observed in the synthesis from microwave-nucleated precursor can be explained in terms of the fact that the microwave-nucleated samples have higher population of nuclei with smaller size than the samples nucleated by conventional heating.

  2. A critical point of male gonad development: neuroendocrine correlates of accelerated testicular growth in rats during early life.

    PubMed

    Dygalo, Nikolay N; Shemenkova, Tatjana V; Kalinina, Tatjana S; Shishkina, Galina T

    2014-01-01

    Testis growth during early life is important for future male fertility and shows acceleration during the first months of life in humans. This acceleration coincides with the peak in gonadotropic hormones in the blood, while the role of hypothalamic factors remains vague. Using neonatal rats to assess this issue, we found that day 9 of life is likely critical for testis development in rats. Before this day, testicular growth was proportional to body weight gain, but after that the testes showed accelerated growth. Hypothalamic kisspeptin and its receptor mRNA levels begin to elevate 2 days later, at day 11. A significant increase in the mRNA levels for gonadotropin-releasing hormone (GnRH) receptors in the hypothalamus between days 5 and 7 was followed by a 3-fold decrease in GnRH mRNA levels in this brain region during the next 2 days. Starting from day 9, hypothalamic GnRH mRNA levels increased significantly and positively correlated with accelerated testicular growth. Triptorelin, an agonist of GnRH, at a dose that had no effect on testicular growth during "proportional" period, increased testis weights during the period of accelerated growth. The insensitivity of testicular growth to GnRH during "proportional" period was supported by inability of a 2.5-fold siRNA knockdown of GnRH expression in the hypothalamus of the 7-day-old animals to produce any effect on their testis weights. GnRH receptor blockade with cetrorelix was also without effect on testis weights during "proportional" period but the same doses of this GnRH antagonist significantly inhibited "accelerated" testicular growth. GnRH receptor mRNA levels in the pituitary as well as plasma LH concentrations were higher during "accelerated" period of testicular growth than during "proportional" period. In general, our data defined two distinct periods in rat testicular development that are primarily characterized by different responses to GnRH signaling.

  3. The structural alteration of gut microbiota in low-birth-weight mice undergoing accelerated postnatal growth

    PubMed Central

    Wang, Jingjing; Tang, Huang; Wang, Xiaoxin; Zhang, Xu; Zhang, Chenhong; Zhang, Menghui; Zhao, Yufeng; Zhao, Liping; Shen, Jian

    2016-01-01

    The transient disruption of gut microbiota in infancy by antibiotics causes adult adiposity in mice. Accelerated postnatal growth (A) leads to a higher risk of adult metabolic syndrome in low birth-weight (LB) humans than in normal birth-weight (NB) individuals, but the underlying mechanism remains unclear. Here, we set up an experiment using LB + A mice, NB + A mice, and control mice with NB and normal postnatal growth. At 24 weeks of age (adulthood), while NB + A animals had a normal body fat content and glucose tolerance compared with controls, LB + A mice exhibited excessive adiposity and glucose intolerance. In infancy, more fecal bacteria implicated in obesity were increased in LB + A pups than in NB + A pups, including Desulfovibrionaceae, Enterorhabdus, and Barnesiella. One bacterium from the Lactobacillus genus, which has been implicated in prevention of adult adiposity, was enhanced only in NB + A pups. Besides, LB + A pups, but not NB + A pups, showed disrupted gut microbiota fermentation activity. After weaning, the fecal microbiota composition of LB + A mice, but not that of NB + A animals, became similar to that of controls by 24 weeks. In infancy, LB + A mice have a more dysbiotic gut microbiome compared to NB + A mice, which might increase their risk of adult metabolic syndrome. PMID:27277748

  4. National health spending in 2011: overall growth remains low, but some payers and services show signs of acceleration.

    PubMed

    Hartman, Micah; Martin, Anne B; Benson, Joseph; Catlin, Aaron

    2013-01-01

    In 2011 US health care spending grew 3.9 percent to reach $2.7 trillion, marking the third consecutive year of relatively slow growth. Growth in national health spending closely tracked growth in nominal gross domestic product (GDP) in 2010 and 2011, and health spending as a share of GDP remained stable from 2009 through 2011, at 17.9 percent. Even as growth in spending at the national level has remained stable, personal health care spending growth accelerated in 2011 (from 3.7 percent to 4.1 percent), in part because of faster growth in spending for prescription drugs and physician and clinical services. There were also divergent trends in spending growth in 2011 depending on the payment source: Medicaid spending growth slowed, while growth in Medicare, private health insurance, and out-of-pocket spending accelerated. Overall, there was relatively slow growth in incomes, jobs, and GDP in 2011, which raises questions about whether US health care spending will rebound over the next few years as it typically has after past economic downturns.

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

    ERIC Educational Resources Information Center

    Williams, James D.

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

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

    ERIC Educational Resources Information Center

    Perry, Marc

    2002-01-01

    Examines population growth during the 1990s for a variety of geographic levels including regions, divisions, states, metropolitan areas, counties, and large cities. Compares growth rates for the 1990s with earlier decades to provide an historical context for present-day trends in population growth and decline. Discusses how differential population…

  7. Modelling the unsteady growth state population balance for a nonlinear growth model in an MSMPR crystallizer

    SciTech Connect

    Carver, C.; Chipman, N.A.; Carleson, T.E.

    1994-03-01

    The precipitation of zirconium and other metal species as hydroxides (hydrous oxides) from simulated nuclear waste process solutions has been investigated as a potential method to reduce radioactive waste volumes. The reaction of ammonium hexaflourozirconate was used to simulate these waste streams. Studies were conducted to investigate the unsteady state response of crystallization in mixed suspension, mixed product removal (MSMPR) crystallizer. Size distributions below 40 {mu}m from laboratory batch and MSMPR data indicate size-dependent growth may be occurring because they may fit the Abegg, Stevens and Larson (ASL) model. However, these distributions also may fit a transient growth model based on the Method of Lines numerical solution to the unsteady state population balance equation. The development of the Method of Lines solution as well as experimental agreement with both models were studied.

  8. The formation of kappa-distribution accelerated electron populations in solar flares

    SciTech Connect

    Bian, Nicolas H.; Stackhouse, Duncan J.; Kontar, Eduard P.; Emslie, A. Gordon E-mail: d.stackhouse.1@research.gla.ac.uk E-mail: emslieg@wku.edu

    2014-12-01

    Driven by recent RHESSI observations of confined loop-top hard X-ray sources in solar flares, we consider stochastic acceleration of electrons in the presence of Coulomb collisions. If electron escape from the acceleration region can be neglected, the electron distribution function is determined by a balance between diffusive acceleration and collisions. Such a scenario admits a stationary solution for the electron distribution function that takes the form of a kappa distribution. We show that the evolution toward this kappa distribution involves a 'wave front' propagating forward in velocity space, so that electrons of higher energy are accelerated later; the acceleration timescales with energy according to τ{sub acc} ∼ E {sup 3/2}. At sufficiently high energies escape from the finite-length acceleration region will eventually dominate. For such energies, the electron velocity distribution function is obtained by solving a time-dependent Fokker-Planck equation in the 'leaky-box' approximation. Solutions are obtained in the limit of a small escape rate from an acceleration region that can effectively be considered a thick target.

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

    PubMed

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

    2012-01-22

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

  10. 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 ...

  11. Comparison of accelerated ion populations observed upstream of the bow shocks at Venus and Mars

    NASA Astrophysics Data System (ADS)

    Yamauchi, M.; Futaana, Y.; Fedorov, A.; Frahm, R. A.; Winningham, J. D.; Dubinin, E.; Lundin, R.; Barabash, S.; Holmström, M.; Mazelle, C.; Sauvaud, J.-A.; Zhang, T. L.; Baumjohann, W.; Coates, A. J.; Fraenz, M.

    2011-03-01

    Foreshock ions are compared between Venus and Mars at energies of 0.6~20 keV using the same ion instrument, the Ion Mass Analyser, on board both Venus Express and Mars Express. Venus Express often observes accelerated protons (2~6 times the solar wind energy) that travel away from the Venus bow shock when the spacecraft location is magnetically connected to the bow shock. The observed ions have a large field-aligned velocity compared to the perpendicular velocity in the solar wind frame, and are similar to the field-aligned beams and intermediate gyrating component of the foreshock ions in the terrestrial upstream region. Mars Express does not observe similar foreshock ions as does Venus Express, indicating that the Martian foreshock does not possess the intermediate gyrating component in the upstream region on the dayside of the planet. Instead, two types of gyrating protons in the solar wind frame are observed very close to the Martian quasi-perpendicular bow shock within a proton gyroradius distance. The first type is observed only within the region which is about 400 km from the bow shock and flows tailward nearly along the bow shock with a similar velocity as the solar wind. The second type is observed up to about 700 km from the bow shock and has a bundled structure in the energy domain. A traversal on 12 July 2005, in which the energy-bunching came from bundling in the magnetic field direction, is further examined. The observed velocities of the latter population are consistent with multiple specular reflections of the solar wind at the bow shock, and the ions after the second reflection have a field-aligned velocity larger than that of the de Hoffman-Teller velocity frame, i.e., their guiding center has moved toward interplanetary space out from the bow shock. To account for the observed peculiarity of the Martian upstream region, finite gyroradius effects of the solar wind protons compared to the radius of the bow shock curvature and effects of cold ion

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

    ERIC Educational Resources Information Center

    Carter, Ashley J. R.

    1999-01-01

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

  13. Dysfunctional Transforming Growth Factor-β Receptor II Accelerates Prostate Tumorigenesis in the TRAMP Mouse Model

    PubMed Central

    Pu, Hong; Collazo, Joanne; Jones, Elisabeth; Gayheart, Dustin; Sakamoto, Shinichi; Vogt, Adam; Mitchell, Bonnie; Kyprianou, Natasha

    2009-01-01

    The contribution of a dysfunctional TGF-β type II receptor (TGFβRII) to prostate cancer initiation and progression was investigated in an in vivo mouse model. Transgenic mice harboring the dominant-negative mutant TGF-β type II receptor (DNTGFβRII) in mouse epithelial cell were crossed with the TRAMP prostate cancer transgenic mouse to characterize the in vivo consequences of inactivated TGF-β signaling on prostate tumor initiation and progression. Histopathological diagnosis of prostate specimens from the TRAMP+/DNTGFβRII double transgenic mice, revealed the appearance of early malignant changes and subsequently highly aggressive prostate tumors at a younger age, compared to littermates TRAMP+/Wt TGFβRII mice. Immunohistochemical and western blotting analysis revealed significantly increased proliferative and apoptotic activities, as well as vascularity and macrophage infiltration that correlated with an elevated VEGF and MCP-1 protein levels in prostates from TRAMP+/DNTGFβRII+ mice. An epithelial-mesenchymal transition (EMT)-effect was also detected in prostates of TRAMP+/DNTGFβRII mice, as documented by the loss of epithelial markers (E-cadherin and β-catenin) and upregulation of mesenchymal markers (N-cadherin) and EMT-transcription factor Snail. A significant increase in the androgen receptor (AR) mRNA and protein levels was associated with the early onset of prostate tumorigenesis in TRAMP+/DNTGFβRII mice. Our results indicate that in vivo disruption of TGF-β signaling accelerates the pathological malignant changes in the prostate by altering the kinetics of prostate growth and inducing EMT. The study also suggests that a dysfunctional TGFβRII augments AR expression and promotes inflammation in early stage tumor growth thus conferring a significant contribution by TGF-β to prostate cancer progression. PMID:19738062

  14. Overexpression of insulin-like growth factor-II induces accelerated myoblast differentiation.

    PubMed

    Stewart, C E; James, P L; Fant, M E; Rotwein, P

    1996-10-01

    Previous studies have shown that exogenous insulin-like growth factors (IGFs) can stimulate the terminal differentiation of skeletal myoblasts in culture and have established a correlation between the rate and the extent of IGF-II secretion by muscle cell lines and the rate of biochemical and morphological differentiation. To investigate the hypothesis that autocrine secretion of IGF-II plays a critical role in stimulating spontaneous myogenic differentiation in vitro, we have established C2 muscle cell lines that stably express a mouse IGF-II cDNA under control of the strong, constitutively active Moloney sarcoma virus promoter, enabling us to study directly the effects of IGF-II overproduction. Similar to observations with other muscle cell lines, IGF-II overexpressing myoblasts proliferated normally in growth medium containing 20% fetal serum, but they underwent enhanced differentiation compared with controls when incubated in low-serum differentiation medium. Accelerated differentiation of IGF-II overexpressing C2 cells was preceded by the rapid induction of myogenin mRNA and protein expression (within 1 h, compared with 24-48 h in controls) and was accompanied by an enhanced proportion of the retinoblastoma protein in an underphosphrylated and potentially active form, by a marked increase in activity of the muscle-specific enzyme, creatine phosphokinase, by extensive myotube formation by 48 h, and by elevated secretion of IGF binding protein-5 when compared with controls. These results confirm a role for IGF-II as an autocrine/paracrine differentiation factor for skeletal myoblasts, and they define a model cell system that will be useful in determining the biochemical mechanisms of IGF action in cellular differentiation.

  15. Hypercholesterolemia induces angiogenesis and accelerates growth of breast tumors in vivo.

    PubMed

    Pelton, Kristine; Coticchia, Christine M; Curatolo, Adam S; Schaffner, Carl P; Zurakowski, David; Solomon, Keith R; Moses, Marsha A

    2014-07-01

    Obesity and metabolic syndrome are linked to an increased prevalence of breast cancer among postmenopausal women. A common feature of obesity, metabolic syndrome, and a Western diet rich in saturated fat is a high level of circulating cholesterol. Epidemiological reports investigating the relationship between high circulating cholesterol levels, cholesterol-lowering drugs, and breast cancer are conflicting. Here, we modeled this complex condition in a well-controlled, preclinical animal model using innovative isocaloric diets. Female severe combined immunodeficient mice were fed a low-fat/no-cholesterol diet and then randomized to four isocaloric diet groups: low-fat/no-cholesterol diet, with or without ezetimibe (cholesterol-lowering drug), and high-fat/high-cholesterol diet, with or without ezetimibe. Mice were implanted orthotopically with MDA-MB-231 cells. Breast tumors from animals fed the high-fat/high-cholesterol diet exhibited the fastest progression. Significant differences in serum cholesterol level between groups were achieved and maintained throughout the study; however, no differences were observed in intratumoral cholesterol levels. To determine the mechanism of cholesterol-induced tumor progression, we analyzed tumor proliferation, apoptosis, and angiogenesis and found a significantly greater percentage of proliferating cells from mice fed the high-fat/high-cholesterol diet. Tumors from hypercholesterolemic animals displayed significantly less apoptosis compared with the other groups. Tumors from high-fat/high-cholesterol mice had significantly higher microvessel density compared with tumors from the other groups. These results demonstrate that hypercholesterolemia induces angiogenesis and accelerates breast tumor growth in vivo.

  16. High expression of connective tissue growth factor accelerates dissemination of leukaemia.

    PubMed

    Wells, J E; Howlett, M; Halse, H M; Heng, J; Ford, J; Cheung, L C; Samuels, A L; Crook, M; Charles, A K; Cole, C H; Kees, U R

    2016-09-01

    To improve treatment of acute lymphoblastic leukaemia (ALL), a better understanding of disease development is needed to tailor new therapies. Connective tissue growth factor (CTGF/CCN2) is highly expressed in leukaemia cells from the majority of paediatric patients with B-lineage ALL (pre-B ALL). CTGF is a matricellular protein and plays a role in aggressive cancers. Here we have genetically engineered leukaemia cells to modulate CTGF expression levels. Elevated CTGF levels accelerated disease dissemination and reduced survival in NOD/SCID mice. In vitro studies showed that CTGF protein induces stromal cell proliferation, promotes adhesion of leukaemia cells to stromal cells and leads to overexpression of genes associated with cell cycle and synthesis of extracellular matrix (ECM). Corresponding data from our leukaemia xenograft models demonstrated that CTGF leads to increased proliferation of non-leukaemia cells and deposition of ECM in the bone marrow. We document for the first time a functional role of CTGF in altering disease progression in a lymphoid malignancy. The findings provide support for targeting the bone marrow microenvironment in aggressive forms of leukaemia.

  17. Accelerated Aging Experiments for Prognostics of Damage Growth in Composite Materials

    NASA Technical Reports Server (NTRS)

    Saxena, Abhinav; Goebel, Kai Frank; Larrosa, Cecilia C.; Janapati, Vishnuvardhan; Roy, Surajit; Chang, Fu-Kuo

    2011-01-01

    Composite structures are gaining importance for use in the aerospace industry. Compared to metallic structures their behavior is less well understood. This lack of understanding may pose constraints on their use. One possible way to deal with some of the risks associated with potential failure is to perform in-situ monitoring to detect precursors of failures. Prognostic algorithms can be used to predict impending failures. They require large amounts of training data to build and tune damage model for making useful predictions. One of the key aspects is to get confirmatory feedback from data as damage progresses. These kinds of data are rarely available from actual systems. The next possible resource to collect such data is an accelerated aging platform. To that end this paper describes a fatigue cycling experiment with the goal to stress carbon-carbon composite coupons with various layups. Piezoelectric disc sensors were used to periodically interrogate the system. Analysis showed distinct differences in the signatures of growing failures between data collected at conditions. Periodic X-radiographs were taken to assess the damage ground truth. Results after signal processing showed clear trends of damage growth that were correlated to damage assessed from the X-ray images.

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

    ERIC Educational Resources Information Center

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

    This report, the third in a series of five reports of the Comparative Study of Population Growth and Agricultural Change, describes a study of the two states of India (Punjaband and Orissa) which attempted to clarify the relationship between population pressure and agricultural change through a time series analysis. This study: (1) outlines trends…

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

    PubMed

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

    2010-10-01

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

  20. Ocean Acidification Accelerates the Growth of Two Bloom-Forming Macroalgae

    PubMed Central

    Young, Craig S.; Gobler, Christopher J.

    2016-01-01

    While there is growing interest in understanding how marine life will respond to future ocean acidification, many coastal ecosystems currently experience intense acidification in response to upwelling, eutrophication, or riverine discharge. Such acidification can be inhibitory to calcifying animals, but less is known regarding how non-calcifying macroalgae may respond to elevated CO2. Here, we report on experiments performed during summer through fall with North Atlantic populations of Gracilaria and Ulva that were grown in situ within a mesotrophic estuary (Shinnecock Bay, NY, USA) or exposed to normal and elevated, but environmentally realistic, levels of pCO2 and/or nutrients (nitrogen and phosphorus). In nearly all experiments, the growth rates of Gracilaria were significantly increased by an average of 70% beyond in situ and control conditions when exposed to elevated levels of pCO2 (p<0.05), but were unaffected by nutrient enrichment. In contrast, the growth response of Ulva was more complex as this alga experienced significantly (p<0.05) increased growth rates in response to both elevated pCO2 and elevated nutrients and, in two cases, pCO2 and nutrients interacted to provide a synergistically enhanced growth rate for Ulva. Across all experiments, elevated pCO2 significantly increased Ulva growth rates by 30% (p<0.05), while the response to nutrients was smaller (p>0.05). The δ13C content of both Gracilaria and Ulva decreased two-to-three fold when grown under elevated pCO2 (p<0.001) and mixing models demonstrated these macroalgae experienced a physiological shift from near exclusive use of HCO3- to primarily CO2 use when exposed to elevated pCO2. This shift in carbon use coupled with significantly increased growth in response to elevated pCO2 suggests that photosynthesis of these algae was limited by their inorganic carbon supply. Given that eutrophication can yield elevated levels of pCO2, this study suggests that the overgrowth of macroalgae in eutrophic

  1. The effects of invertebrate herbivores on plant population growth: a meta-regression analysis.

    PubMed

    Katz, Daniel S W

    2016-09-01

    Over the last two decades, an increasing number of studies have quantified the effects of herbivory on plant populations using stage-structured population models and integral projection models, allowing for the calculation of plant population growth rates (λ) with and without herbivory. In this paper, I assembled 29 studies and conducted a meta-regression to determine the importance of invertebrate herbivores to population growth rates (λ) while accounting for missing data. I found that invertebrate herbivory often induced important reductions in plant population growth rates (with herbivory, λ was 1.08 ± 0.36; without herbivory, λ was 1.28 ± 0.58). This relationship tended to be weaker for seed predation than for other types of herbivory, except when seed predation rates were very high. Even so, the amount by which studies reduced herbivory was a poor predictor of differences in population growth rates-which strongly cautions against using measured herbivory rates as a proxy for the impact of herbivores. Herbivory reduced plant population growth rates significantly more when potential growth rates were high, which helps to explain why there was less variation in actual population growth rates than in potential population growth rates. The synthesis of these studies also shows the need for future studies to report variance in estimates of λ and to quantify how λ varies as a function of plant density.

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

    ERIC Educational Resources Information Center

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

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

  3. Recent Population Growth and Change among Asian-Americans.

    ERIC Educational Resources Information Center

    Vann, Barbara H.; Ryu, Jai P.

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

  4. Anabolic therapy with growth hormone accelerates protein gain in surgical patients requiring nutritional rehabilitation.

    PubMed Central

    Byrne, T A; Morrissey, T B; Gatzen, C; Benfell, K; Nattakom, T V; Scheltinga, M R; LeBoff, M S; Ziegler, T R; Wilmore, D W

    1993-01-01

    OBJECTIVE: The authors investigated the effects of exogenous growth hormone (GH) on protein accretion and the composition of weight gain in a group of stable, nutritionally compromised postoperative patients receiving standard hypercaloric nutritional therapy. SUMMARY BACKGROUND DATA: A significant loss of body protein impairs normal physiologic functions and is associated with increased postoperative complications and prolonged hospitalization. Previous studies have demonstrated that standard methods of nutritional support enhance the deposition of fat and extracellular water but are ineffective in repleting body protein. METHODS: Fourteen patients requiring long-term nutritional support for severe gastrointestinal dysfunction received standard nutritional therapy (STD) providing approximately 50 kcal/kg/day and 2 g of protein/kg/day during an initial 7-day equilibrium period. The patients then continued on STD (n = 4) or, in addition, received GH 0.14 mg/kg/day (n = 10). On day 7 of the equilibrium period and again after 3 weeks of treatment, the components of body weight were determined; these included body fat, mineral content, lean (nonfat and nonmineral-containing tissue) mass, total body water, extracellular water (ECW), and body protein. Daily and cumulative nutrient balance and substrate oxidation studies determined the distribution, efficiency, and utilization of calories for protein, fat, and carbohydrate deposition. RESULTS: The GH-treated patients gained minimal body fat but had significantly more lean mass (4.311 +/- 0.6 kg vs. 1.988 +/- 0.2 kg, p < or = 0.03) and more protein (1.417 +/- 0.3 kg vs. 0.086 +/- 0.1 kg, p < or = 0.03) than did the STD-treated patients. The increase in lean mass was not associated with an inappropriate expansion of ECW. In contrast, patients receiving STD therapy tended to deposit a greater proportion of body weight as ECW and significantly more fat than did GH-treated patients (1.004 +/- 0.3 kg vs. 0.129 +/- 0.2 kg, p < 0

  5. Taking Exception. Reduced mortality leads to population growth: an inconvenient truth.

    PubMed

    Shelton, James D

    2014-05-01

    Reduced mortality has been the predominant cause of the marked global population growth over the last 3/4 of a century. While improved child survival increases motivation to reduce fertility, it comes too little and too late to forestall substantial population growth. And, beyond motivation, couples need effective means to control their fertility. It is an inconvenient truth that reducing child mortality contributes considerably to the population growth destined to compromise the quality of life of many, particularly in sub-Saharan Africa. Vigorous child survival programming is of course imperative. Wide access to voluntary family planning can help mitigate that growth and provide many other benefits.

  6. Effect of Residual Accelerations on the Crystal Growth of II-VI Semiconductors in Low Earth Orbit

    NASA Technical Reports Server (NTRS)

    Gillies, D. C.; Su, C.-H.; Szofran, F. R.; Scripa, R. N.; Cobb, S. D.; Lehoczky, S. L.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    The paper compares and summarizes the effects of residual acceleration during crystal growth on the compositional variation of two II-VI solid solution binary alloys (Hg(0.8)Cd(0.2)Te and Hg(0.84)Zn(0.16)Te). The crystals were grown by directional solidification on the second United States Microgravity Payload (USMP-2) and the first United States Microgravity Laboratory (USML-1) missions, respectively. For both alloys, changes in the direction and magnitude of the quasisteady acceleration vector (approximately 0.4- 1 mu g) caused large changes in the radial compositional distribution that demonstrates the importance of residual accelerations, even in the submicrogravity range, for large density gradients in the melt and slow solidification rates. The observed compositional variations will be correlated to changes in the radial flow velocities ahead of the solidification interface.

  7. A Photometer for Measuring Population Growth in Yeast.

    ERIC Educational Resources Information Center

    Tatina, Robert; Hartley, Tamela; Thomas, Danita

    1999-01-01

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

  8. Growth under elevated atmospheric CO(2) concentration accelerates leaf senescence in sunflower (Helianthus annuus L.) plants.

    PubMed

    de la Mata, Lourdes; Cabello, Purificación; de la Haba, Purificación; Agüera, Eloísa

    2012-09-15

    Some morphogenetic and metabolic processes were sensitive to a high atmospheric CO(2) concentration during sunflower primary leaf ontogeny. Young leaves of sunflower plants growing under elevated CO(2) concentration exhibited increased growth, as reflected by the high specific leaf mass referred to as dry weight in young leaves (16 days). The content of photosynthetic pigments decreased with leaf development, especially in plants grown under elevated CO(2) concentrations, suggesting that high CO(2) accelerates chlorophyll degradation, and also possibly leaf senescence. Elevated CO(2) concentration increased the oxidative stress in sunflower plants by increasing H(2)O(2) levels and decreasing activity of antioxidant enzymes such as catalase and ascorbate peroxidase. The loss of plant defenses probably increases the concentration of reactive oxygen species in the chloroplast, decreasing the photosynthetic pigment content as a result. Elevated CO(2) concentration was found to boost photosynthetic CO(2) fixation, especially in young leaves. High CO(2) also increased the starch and soluble sugar contents (glucose and fructose) and the C/N ratio during sunflower primary leaf development. At the beginning of senescence, we observed a strong increase in the hexoses to sucrose ratio that was especially marked at high CO(2) concentration. These results indicate that elevated CO(2) concentration could promote leaf senescence in sunflower plants by affecting the soluble sugar levels, the C/N ratio and the oxidative status during leaf ontogeny. It is likely that systemic signals produced in plants grown with elevated CO(2), lead to early senescence and a higher oxidation state of the cells of these plant leaves.

  9. Hypercholesterolemia Induces Angiogenesis and Accelerates Growth of Breast Tumors in Vivo

    PubMed Central

    Pelton, Kristine; Coticchia, Christine M.; Curatolo, Adam S.; Schaffner, Carl P.; Zurakowski, David; Solomon, Keith R.; Moses, Marsha A.

    2015-01-01

    Obesity and metabolic syndrome are linked to an increased prevalence of breast cancer among postmenopausal women. A common feature of obesity, metabolic syndrome, and a Western diet rich in saturated fat is a high level of circulating cholesterol. Epidemiological reports investigating the relationship between high circulating cholesterol levels, cholesterol-lowering drugs, and breast cancer are conflicting. Here, we modeled this complex condition in a well-controlled, preclinical animal model using innovative isocaloric diets. Female severe combined immunodeficient mice were fed a low-fat/no-cholesterol diet and then randomized to four isocaloric diet groups: low-fat/no-cholesterol diet, with or without ezetimibe (cholesterol-lowering drug), and high-fat/high-cholesterol diet, with or without ezetimibe. Mice were implanted orthotopically with MDA-MB-231 cells. Breast tumors from animals fed the high-fat/high-cholesterol diet exhibited the fastest progression. Significant differences in serum cholesterol level between groups were achieved and maintained throughout the study; however, no differences were observed in intratumoral cholesterol levels. To determine the mechanism of cholesterol-induced tumor progression, we analyzed tumor proliferation, apoptosis, and angiogenesis and found a significantly greater percentage of proliferating cells from mice fed the high-fat/high-cholesterol diet. Tumors from hypercholesterolemic animals displayed significantly less apoptosis compared with the other groups. Tumors from high-fat/high-cholesterol mice had significantly higher microvessel density compared with tumors from the other groups. These results demonstrate that hypercholesterolemia induces angiogenesis and accelerates breast tumor growth in vivo. PMID:24952430

  10. Estimating Reading Growth Attributable to Accelerated Reader at One American School in the Caribbean

    ERIC Educational Resources Information Center

    Foster, David K.; Foster, Dean P.

    2014-01-01

    This article provides a statistical analysis of the reading gains observed at one American school in the Caribbean that was using Accelerated Reader. It provides an estimate of the number of hours students needed to read to advance their reading performance an additional year. The authors estimate how much Accelerated Reader contributed to the…

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

    PubMed

    Yang, S; Liu, W

    1992-06-01

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

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

    ERIC Educational Resources Information Center

    Siegler, Theodore R.

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

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

    ERIC Educational Resources Information Center

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

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

  14. Practical application of the Bristol Perinatal Growth Chart to Mediterranean populations.

    PubMed

    Pecorari, D; Costa, L; Barbone, F

    1985-01-01

    The Bristol Perinatal Growth Chart (gestogram) has been applied to different Mediterranean populations and compared to traditional percentile intrauterine growth charts. The opinion is stressed that the gestogram system can successfully replace traditional intrauterine growth charts and offers the advantage of greater simplicity and adaptability.

  15. The demographic consequences of mutualism: ants increase host-plant fruit production but not population growth.

    PubMed

    Ford, Kevin R; Ness, Joshua H; Bronstein, Judith L; Morris, William F

    2015-10-01

    The impact of mutualists on a partner's demography depends on how they affect the partner's multiple vital rates and how those vital rates, in turn, affect population growth. However, mutualism studies rarely measure effects on multiple vital rates or integrate them to assess the ultimate impact on population growth. We used vital rate data, population models and simulations of long-term population dynamics to quantify the demographic impact of a guild of ant species on the plant Ferocactus wislizeni. The ants feed at the plant's extrafloral nectaries and attack herbivores attempting to consume reproductive organs. Ant-guarded plants produced significantly more fruit, but ants had no significant effect on individual growth or survival. After integrating ant effects across these vital rates, we found that projected population growth was not significantly different between unguarded and ant-guarded plants because population growth was only weakly influenced by differences in fruit production (though strongly influenced by differences in individual growth and survival). However, simulations showed that ants could positively affect long-term plant population dynamics through services provided during rare but important events (herbivore outbreaks that reduce survival or years of high seedling recruitment associated with abundant precipitation). Thus, in this seemingly clear example of mutualism, the interaction may actually yield no clear benefit to plant population growth, or if it does, may only do so through the actions of the ants during rare events. These insights demonstrate the value of taking a demographic approach to studying the consequences of mutualism.

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

    ERIC Educational Resources Information Center

    Newman, Constance

    Although earnings generally increased in rural areas in the 1990s, Hispanic population growth led to lower wages for at least one segment of the rural population--workers with a high school degree (skilled workers), particularly men in this skill group. Using data from the Bureau of Economic Analysis and the Current Population Survey, this report…

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

    PubMed Central

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

    2012-01-01

    Somatic growth patterns represent a major component of organismal fitness and may vary among sexes and populations due to genetic and environmental processes leading to profound differences in life-history and demography. This study considered the ontogenic, sex-specific and spatial dynamics of somatic growth patterns in ten populations of the world’s largest lizard the Komodo dragon (Varanus komodoensis). The growth of 400 individual Komodo dragons was measured in a capture-mark-recapture study at ten sites on four islands in eastern Indonesia, from 2002 to 2010. Generalized Additive Mixed Models (GAMMs) and information-theoretic methods were used to examine how growth rates varied with size, age and sex, and across and within islands in relation to site-specific prey availability, lizard population density and inbreeding coefficients. Growth trajectories differed significantly with size and between sexes, indicating different energy allocation tactics and overall costs associated with reproduction. This leads to disparities in maximum body sizes and longevity. Spatial variation in growth was strongly supported by a curvilinear density-dependent growth model with highest growth rates occurring at intermediate population densities. Sex-specific trade-offs in growth underpin key differences in Komodo dragon life-history including evidence for high costs of reproduction in females. Further, inverse density-dependent growth may have profound effects on individual and population level processes that influence the demography of this species. PMID:23028983

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

    PubMed

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

    2012-01-01

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

  19. Accelerating 21st Century Economic Growth by Implementation of the Lunar Solar Power System

    NASA Astrophysics Data System (ADS)

    Criswell, D. R.

    2002-01-01

    The World Energy Council (1) makes this declaration. "Given this dramatically uneven distribution and the limited evidence of improvement in economic growth in many developing countries, WEC at the 17th World Congress in Houston in September 1998 concluded that the number one priority in sustainable energy development today for all decision-makers in all countries is to extend access to commercial energy services to the people who do not now have it and to those who will come into the world in the next two decades, largely in developing countries, without such access." By ~2050 the global systems should supply 10 billion people approximately 6.7 kilowatts of thermal power per person or 61,360 kWt-h/y-person of energy. The economic equivalent is ~2 - 3 kWe of electric power per person. The energy must be environmentally clean. The energy must be sufficiently low in cost that the 2 billion poorest people, who now make 1,000 /y-person, can be provided with the new power. A survey of twenty-five options for providing adequate commercial electric power, including solar power satellites in orbit about Earth, concludes that only the Lunar Solar Power System can meet the WEC challenge (2, 3, 4, 5). Maurice Strong is the former CEO of Ontario Hydro and organizer of the 1992 Rio Environmental Summit. Quoting Strong - "I have checked it (LSP System) out with a number of experts, all of whom confirmed that the idea, which has been mooted for some time, may now be ripe to carry forward. --- The project would deliver net new energy to the Earth that is independent of the biosphere, would produce no CO2 or other polluting emissions and have minimal environmental impact compared with other energy sources." (6). Electric energy provided by the LSP System can accelerate terrestrial economic growth in several ways. A cost of less than 1 cent per kilowatt electric hour seems achievable. This allows poor nations to buy adequate energy. Increasing per capita use of electric power is

  20. Effects of climate change on plant population growth rate and community composition change.

    PubMed

    Chang, Xiao-Yu; Chen, Bao-Ming; Liu, Gang; Zhou, Ting; Jia, Xiao-Rong; Peng, Shao-Lin

    2015-01-01

    The impacts of climate change on forest community composition are still not well known. Although directional trends in climate change and community composition change were reported in recent years, further quantitative analyses are urgently needed. Previous studies focused on measuring population growth rates in a single time period, neglecting the development of the populations. Here we aimed to compose a method for calculating the community composition change, and to testify the impacts of climate change on community composition change within a relatively short period (several decades) based on long-term monitoring data from two plots-Dinghushan Biosphere Reserve, China (DBR) and Barro Colorado Island, Panama (BCI)-that are located in tropical and subtropical regions. We proposed a relatively more concise index, Slnλ, which refers to an overall population growth rate based on the dominant species in a community. The results indicated that the population growth rate of a majority of populations has decreased over the past few decades. This decrease was mainly caused by population development. The increasing temperature had a positive effect on population growth rates and community change rates. Our results promote understanding and explaining variations in population growth rates and community composition rates, and are helpful to predict population dynamics and population responses to climate change.

  1. Tumor growth accelerated by chemotherapy-induced senescent cells is suppressed by treatment with IL-12 producing cellular vaccines

    PubMed Central

    Simova, Jana; Sapega, Olena; Imrichova, Terezie; Stepanek, Ivan; Kyjacova, Lenka; Mikyskova, Romana; Indrova, Marie; Bieblova, Jana; Bubenik, Jan; Bartek, Jiri; Hodny, Zdenek; Reinis, Milan

    2016-01-01

    Standard-of-care chemo- or radio-therapy can induce, besides tumor cell death, also tumor cell senescence. While senescence is considered to be a principal barrier against tumorigenesis, senescent cells can survive in the organism for protracted periods of time and they can promote tumor development. Based on this emerging concept, we hypothesized that elimination of such potentially cancer-promoting senescent cells could offer a therapeutic benefit. To assess this possibility, here we first show that tumor growth of proliferating mouse TC-1 HPV-16-associated cancer cells in syngeneic mice becomes accelerated by co-administration of TC-1 or TRAMP-C2 prostate cancer cells made senescent by pre-treatment with the anti-cancer drug docetaxel, or lethally irradiated. Phenotypic analyses of tumor-explanted cells indicated that the observed acceleration of tumor growth was attributable to a protumorigenic environment created by the co-injected senescent and proliferating cancer cells rather than to escape of the docetaxel-treated cells from senescence. Notably, accelerated tumor growth was effectively inhibited by cell immunotherapy using irradiated TC-1 cells engineered to produce interleukin IL-12. Collectively, our data document that immunotherapy, such as the IL-12 treatment, can provide an effective strategy for elimination of the detrimental effects caused by bystander senescent tumor cells in vivo. PMID:27448982

  2. [Establishing legal system completely and controlling the excessive population growth].

    PubMed

    Zou, P

    1988-05-01

    China during the early years of Socialism concentrated on economic development. Population problems were given a low priority. But now, at this point in China's history, it is necessary to maintain the stability and uniformity of the birth policy through legislation, alter attitudes toward childbearing through legal education, and protect through laws the enthusiastic nature of family planning work of cadres. Without legislation, family planning work cannot endure. It is the proper time to promulgate "Family Planning Law", the body of laws written by the State Council after 5 years of research in family planning work. Critics of this view feel that conditions in rural areas are not ripe for such a law, or that because China is large and populous, laws are not the proper method for controlling population, or that legal restrictions would bring unforeseen consequences in the future. But China's population problem is immediate and dire, and conditions are indeed ripe for passing this law.

  3. Population size, survival, growth, and movements of Rana sierrae

    USGS Publications Warehouse

    Fellers, Gary M.; Kleeman, Patrick M.; Miller, David A. W.; Halstead, Brian J.; Link, William

    2013-01-01

    Based on 2431 captures of 757 individual frogs over a 9-yr period, we found that the population of R. sierrae in one meadow–stream complex in Yosemite National Park ranged from an estimated 45 to 115 adult frogs. Rana sierrae at our relatively low elevation site (2200 m) grew at a fast rate (K = 0.73–0.78), had high overwintering survival rates (44.6–95%), lived a long time (up to 16 yr), and tended to be fairly sedentary during the summer (100% minimum convex polygon annual home ranges of 139 m2) but had low year-to-year site fidelity. Even though the amphibian chytrid fungus (Batrachochytrium dendrobatidis, Bd) has been present in the population for at least 13 yr, there was no clear downward trend as might be expected from reports of R. sierrae population declines associated with Bd or from reports of widespread population decline of R. sierrae throughout its range.

  4. Assessing the anticipated growth response of northern conifer populations to a warming climate.

    PubMed

    Pedlar, John H; McKenney, Daniel W

    2017-03-07

    The growth response of trees to ongoing climate change has important implications for future forest dynamics, accurate carbon accounting, and sustainable forest management. We used data from black spruce (Picea mariana) and jack pine (Pinus banksiana) provenance trials, along with published data for three other northern conifers, to identify a consistent growth response to climate warming in which cold-origin populations are expected to benefit and warm-origin populations are expected to decline. Specifically, populations from across the geographic range of a species appear to grow well at temperatures characteristic of the southern portion of the range, indicating significant potential for a positive growth response to climate warming in cold-origin populations. Few studies have quantified and compared this pattern across multiple species using provenance data. We present a forest regeneration strategy that incorporates these anticipated growth responses to promote populations that are both local to the planting site and expected to grow well under climate change.

  5. Assessing the anticipated growth response of northern conifer populations to a warming climate

    NASA Astrophysics Data System (ADS)

    Pedlar, John H.; McKenney, Daniel W.

    2017-03-01

    The growth response of trees to ongoing climate change has important implications for future forest dynamics, accurate carbon accounting, and sustainable forest management. We used data from black spruce (Picea mariana) and jack pine (Pinus banksiana) provenance trials, along with published data for three other northern conifers, to identify a consistent growth response to climate warming in which cold-origin populations are expected to benefit and warm-origin populations are expected to decline. Specifically, populations from across the geographic range of a species appear to grow well at temperatures characteristic of the southern portion of the range, indicating significant potential for a positive growth response to climate warming in cold-origin populations. Few studies have quantified and compared this pattern across multiple species using provenance data. We present a forest regeneration strategy that incorporates these anticipated growth responses to promote populations that are both local to the planting site and expected to grow well under climate change.

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

    PubMed

    Steinmann, G; Komlos, J

    1988-08-01

    The authors propose an economic model capable of simulating the 4 main historical stages of civilization: hunting, agricultural, industrial, and postindustrial. An output-maximizing society to respond to changes in factor endowments by switching technologies. Changes in factor proportions arise through population growth and capital accumulation. A slow rate of exogenous technical process is assumed. The model synthesizes Malthusian and Boserupian notions of the effect of population growth on per capita output. Initially the capital-diluting effect of population growth dominates. As population density increases, however, and a threshold is reached, the Boserupian effect becomes crucial, and a technological revolution occurs. The cycle is thereafter repeated. After the second economic revolution, however, the Malthusian constraint dissolves permanently, as population growth can continue without being constrained by diminishing returns to labor. By synthesizing Malthusian and Boserupian notions, the model is able to capture the salient features of economic development in the very long run.

  7. Assessing the anticipated growth response of northern conifer populations to a warming climate

    PubMed Central

    Pedlar, John H.; McKenney, Daniel W.

    2017-01-01

    The growth response of trees to ongoing climate change has important implications for future forest dynamics, accurate carbon accounting, and sustainable forest management. We used data from black spruce (Picea mariana) and jack pine (Pinus banksiana) provenance trials, along with published data for three other northern conifers, to identify a consistent growth response to climate warming in which cold-origin populations are expected to benefit and warm-origin populations are expected to decline. Specifically, populations from across the geographic range of a species appear to grow well at temperatures characteristic of the southern portion of the range, indicating significant potential for a positive growth response to climate warming in cold-origin populations. Few studies have quantified and compared this pattern across multiple species using provenance data. We present a forest regeneration strategy that incorporates these anticipated growth responses to promote populations that are both local to the planting site and expected to grow well under climate change. PMID:28266577

  8. Source Population and Acceleration Location of Suprathermal Heavy Ions in Corotating Interaction Regions

    NASA Astrophysics Data System (ADS)

    Filwett, R. J.; Desai, M. I.; Dayeh, M. A.; Broiles, T. W.

    2017-03-01

    We have analyzed the ∼20–320 keV nucleon‑1 suprathermal (ST) heavy ion abundances in 41 corotating interaction regions (CIRs) observed by the Wind spacecraft from 1995 January to 2008 December. Our results are: (1) the CIR Fe/CNO and NeS/CNO ratios vary with the sunspot number, with values being closer to average solar energetic particle event values during solar maxima and lower than nominal solar wind values during solar minima. The physical mechanism responsible for the depleted abundances during solar minimum remains an open question. (2) The Fe/CNO increases with energy in the 6 events that occurred during solar maximum, while no such trends are observed for the 35 events during solar minimum. (3) The Fe/CNO shows no correlation with the average solar wind speed. (4) The Fe/CNO is well correlated with the corresponding upstream ∼20–320 keV nucleon‑1 Fe/CNO and not with the solar wind Fe/O measured by ACE in 31 events. Using the correlations between the upstream ∼20–40 keV nucleon‑1 Fe/CNO and the ∼20–320 keV nucleon‑1 Fe/CNO in CIRs, we estimate that, on average, the ST particles traveled ∼2 au along the nominal Parker spiral field line, which corresponds to upper limits for the radial distance of the source or acceleration location of ∼1 au beyond Earth orbit. Our results are consistent with those obtained from recent surveys, and confirm that CIR ST heavy ions are accelerated more locally, and are at odds with the traditional viewpoint that CIR ions seen at 1 au are bulk solar wind ions accelerated between 3 and 5 au.

  9. Seed dispersal by pulp consumers, not "legitimate" seed dispersers, increases Guettarda viburnoides population growth.

    PubMed

    Loayza, Andrea P; Knight, Tiffany

    2010-09-01

    We examined the effect of seed dispersal by Purplish Jays (Cyanocorax cyanomelas; pulp consumers) and the Chestnut-eared Araçari (Pteroglossus castanotis; "legitimate" seed dispersers) on population growth of the small tree Guettarda viburnoides (Rubiaceae) in northeastern Bolivian savannas. Because each bird species differs with respect to feeding and post-feeding behavior, we hypothesized that seed dispersal by each species will contribute differently to the rate of increase of G. viburnoides, but that seed dispersal by either species will increase population growth when compared to a scenario with no seed dispersal. To examine the effects of individual dispersers on the future population size of G. viburnoides, we projected population growth rate using demographic models for G. viburnoides that explicitly incorporate data on quantitative and qualitative aspects of seed dispersal by each frugivore species. Our model suggests that seed dispersal by C. cyanomelas leads to positive population growth of G. viburnoides, whereas seed dispersal by P. castanotis has a detrimental effect on the population growth of this species. To our knowledge, this is the first study to report negative effects of a "legitimate" seed disperser on the population dynamics of the plant it consumes. Our results stress the importance of incorporating frugivore effects into population projection matrices, to allow a comprehensive analysis of the effectiveness of different dispersers for plant population dynamics.

  10. Population growth through history and the escape from the Malthusian trap: a homeostatic simulation model.

    PubMed

    Artzrouni, M; Komlos, J

    1985-01-01

    "A Malthusian simulation model is proposed to describe the growth of human population from the Neolithic through the Industrial Revolution. The economy is composed of a subsistence sector and a capital-producing sector. Our model captures the 'incessant contest' between population growth and the means of subsistence. When the per capita agricultural output falls below a biological minimum, the growth rate of the population is subject, in a random fashion, to perturbations that can take on disastrous proportions." It is suggested that "the slow accumulation of capital (and the buildup of the population of the capital-producing sector) eventually enables the population to overcome the constraints of the hostile economic environment. Our simulations (complete with confidence intervals) yield numerically realistic estimates of the population that eventually escapes from the Malthusian menace and grows unhindered during the Industrial Revolution." (summary in FRE, ITA)

  11. Mating behavior, population growth, and the operational sex ratio: a periodic two-sex model approach.

    PubMed

    Jenouvrier, Stéphanie; Caswell, Hal; Barbraud, Christophe; Weimerskirch, Henri

    2010-06-01

    We present a new approach to modeling two-sex populations, using periodic, nonlinear two-sex matrix models. The models project the population growth rate, the population structure, and any ratio of interest (e.g., operational sex ratio). The periodic formulation permits inclusion of highly seasonal behavioral events. A periodic product of the seasonal matrices describes annual population dynamics. The model is nonlinear because mating probability depends on the structure of the population. To study how the vital rates influence population growth rate, population structure, and operational sex ratio, we used sensitivity analysis of frequency-dependent nonlinear models. In nonlinear two-sex models the vital rates affect growth rate directly and also indirectly through effects on the population structure. The indirect effects can sometimes overwhelm the direct effects and are revealed only by nonlinear analysis. We find that the sensitivity of the population growth rate to female survival is negative for the emperor penguin, a species with highly seasonal breeding behavior. This result could not occur in linear models because changes in population structure have no effect on per capita reproduction. Our approach is applicable to ecological and evolutionary studies of any species in which males and females interact in a seasonal environment.

  12. Sorafenib suppresses growth and survival of hepatoma cells by accelerating degradation of enhancer of zeste homolog 2.

    PubMed

    Wang, Shanshan; Zhu, Yu; He, Hongyong; Liu, Jing; Xu, Le; Zhang, Heng; Liu, Haiou; Liu, Weisi; Liu, Yidong; Pan, Deng; Chen, Lin; Wu, Qian; Xu, Jiejie; Gu, Jianxin

    2013-06-01

    Enhancer of zeste homolog 2 (EZH2) is a mammalian histone methyltransferase that contributes to the epigenetic silencing of target genes that regulate cancer cell growth and survival. It is overexpressed in hepatocellular carcinoma (HCC) with a clinical significance that remains obscure. Sorafenib, a multikinase inhibitor, has been used as a first-line therapeutic drug and shown clinical efficiency for advanced-stage HCC patients. In the present study, we found that sorafenib lowered the protein level of EZH2 through accelerating proteasome-mediated EZH2 degradation in hepatoma cells. Overexpression of EZH2 reversed sorafenib-induced cell growth arrest, cell cycle arrest, and cell apoptosis dependent on histone methyltransferase activity in hepatoma cells. More importantly, shRNA-mediated EZH2 knockdown or EZH2 inhibition with 3-deazaneplanocin A treatment promoted sorafenib-induced hepatoma cell growth arrest and apoptosis. Sorafenib altered the hepatoma epigenome by reducing EZH2 and H3K27 trimethylation. These results revealed a novel therapeutic mechanism underlying sorafenib treatment in suppressing hepatoma growth and survival by accelerating EZH2 degradation. Genetic deletion or pharmacological ablation of EZH2 made hepatoma cells more sensitive to sorafenib, which helps provide a strong framework for exploring innovative combined therapies for advanced-stage HCC patients.

  13. Quantitative Modeling of Growth and Dispersal in Population Models.

    DTIC Science & Technology

    1986-01-01

    partial differential equations. Applications to dispersal and nonlinear growth/predation models arc dnsity- depresented . Computational iresults using...depend only on size x. The ideas we present here can be readily modified to treat theoretically and computationally the more general case where g and m

  14. Oscillations and accelerations of ice crystal growth rates in microgravity in presence of antifreeze glycoprotein impurity in supercooled water.

    PubMed

    Furukawa, Yoshinori; Nagashima, Ken; Nakatsubo, Shun-Ichi; Yoshizaki, Izumi; Tamaru, Haruka; Shimaoka, Taro; Sone, Takehiko; Yokoyama, Etsuro; Zepeda, Salvador; Terasawa, Takanori; Asakawa, Harutoshi; Murata, Ken-Ichiro; Sazaki, Gen

    2017-03-06

    The free growth of ice crystals in supercooled bulk water containing an impurity of glycoprotein, a bio-macromolecule that functions as 'antifreeze' in living organisms in a subzero environment, was observed under microgravity conditions on the International Space Station. We observed the acceleration and oscillation of the normal growth rates as a result of the interfacial adsorption of these protein molecules, which is a newly discovered impurity effect for crystal growth. As the convection caused by gravity may mitigate or modify this effect, secure observations of this effect were first made possible by continuous measurements of normal growth rates under long-term microgravity condition realized only in the spacecraft. Our findings will lead to a better understanding of a novel kinetic process for growth oscillation in relation to growth promotion due to the adsorption of protein molecules and will shed light on the role that crystal growth kinetics has in the onset of the mysterious antifreeze effect in living organisms, namely, how this protein may prevent fish freezing.

  15. Oscillations and accelerations of ice crystal growth rates in microgravity in presence of antifreeze glycoprotein impurity in supercooled water

    NASA Astrophysics Data System (ADS)

    Furukawa, Yoshinori; Nagashima, Ken; Nakatsubo, Shun-Ichi; Yoshizaki, Izumi; Tamaru, Haruka; Shimaoka, Taro; Sone, Takehiko; Yokoyama, Etsuro; Zepeda, Salvador; Terasawa, Takanori; Asakawa, Harutoshi; Murata, Ken-Ichiro; Sazaki, Gen

    2017-03-01

    The free growth of ice crystals in supercooled bulk water containing an impurity of glycoprotein, a bio-macromolecule that functions as ‘antifreeze’ in living organisms in a subzero environment, was observed under microgravity conditions on the International Space Station. We observed the acceleration and oscillation of the normal growth rates as a result of the interfacial adsorption of these protein molecules, which is a newly discovered impurity effect for crystal growth. As the convection caused by gravity may mitigate or modify this effect, secure observations of this effect were first made possible by continuous measurements of normal growth rates under long-term microgravity condition realized only in the spacecraft. Our findings will lead to a better understanding of a novel kinetic process for growth oscillation in relation to growth promotion due to the adsorption of protein molecules and will shed light on the role that crystal growth kinetics has in the onset of the mysterious antifreeze effect in living organisms, namely, how this protein may prevent fish freezing.

  16. Oscillations and accelerations of ice crystal growth rates in microgravity in presence of antifreeze glycoprotein impurity in supercooled water

    PubMed Central

    Furukawa, Yoshinori; Nagashima, Ken; Nakatsubo, Shun-ichi; Yoshizaki, Izumi; Tamaru, Haruka; Shimaoka, Taro; Sone, Takehiko; Yokoyama, Etsuro; Zepeda, Salvador; Terasawa, Takanori; Asakawa, Harutoshi; Murata, Ken-ichiro; Sazaki, Gen

    2017-01-01

    The free growth of ice crystals in supercooled bulk water containing an impurity of glycoprotein, a bio-macromolecule that functions as ‘antifreeze’ in living organisms in a subzero environment, was observed under microgravity conditions on the International Space Station. We observed the acceleration and oscillation of the normal growth rates as a result of the interfacial adsorption of these protein molecules, which is a newly discovered impurity effect for crystal growth. As the convection caused by gravity may mitigate or modify this effect, secure observations of this effect were first made possible by continuous measurements of normal growth rates under long-term microgravity condition realized only in the spacecraft. Our findings will lead to a better understanding of a novel kinetic process for growth oscillation in relation to growth promotion due to the adsorption of protein molecules and will shed light on the role that crystal growth kinetics has in the onset of the mysterious antifreeze effect in living organisms, namely, how this protein may prevent fish freezing. PMID:28262787

  17. Student-Teacher Population Growth Model. Working Paper.

    ERIC Educational Resources Information Center

    Zabrowski, Edward K.; And Others

    This mathematical model of the educational system calculates information on population groups by sex, race, age, and educational level. The model can be used to answer questions about what would happen to the flows of students and teachers through the formal educational system if these flows are changed at various stages. The report discusses the…

  18. The Revival of Population Growth in Nonmetropolitan America.

    ERIC Educational Resources Information Center

    Beale, Calvin L.

    Population grew faster in nonmetro than in metro countries of the United States between 1970 and 1973. This trend reverses the previous pattern of inmigration to cities. Among the reasons for increases in rural areas and small towns are: (1) decentralization of manufacturing and other industry; (2) increased settlement of retired people; (3)…

  19. Calculating the Financial Impact of Population Growth on Education.

    ERIC Educational Resources Information Center

    Cline, Daniel H.

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

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

    PubMed Central

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

    2002-01-01

    While the concept of population growth rate has been of central importance in the development of the theory of population dynamics, few empirical studies consider the intrinsic growth rate in detail, let alone how it may vary within and between populations of the same species. In an attempt to link theory with data we take two approaches. First, we address the question 'what growth rate patterns does theory predict we should see in time-series?' The models make a number of predictions, which in general are supported by a comparative study between time-series of harvesting data from 352 red grouse populations. Variations in growth rate between grouse populations were associated with factors that reflected the quality and availability of the main food plant of the grouse. However, while these results support predictions from theory, they provide no clear insight into the mechanisms influencing reductions in population growth rate and regulation. In the second part of the paper, we consider the results of experiments, first at the individual level and then at the population level, to identify the important mechanisms influencing changes in individual productivity and population growth rate. The parasitic nematode Trichostrongylus tenuis is found to have an important influence on productivity, and when incorporated into models with their patterns of distribution between individuals has a destabilizing effect and generates negative growth rates. The hypothesis that negative growth rates at the population level were caused by parasites was demonstrated by a replicated population level experiment. With a sound and tested model framework we then explore the interaction with other natural enemies and show that in general they tend to stabilize variations in growth rate. Interestingly, the models show selective predators that remove heavily infected individuals can release the grouse from parasite-induced regulation and allow equilibrium populations to rise. By contrast, a

  1. Accelerated crossing of fitness valleys through division of labor and cheating in asexual populations

    NASA Astrophysics Data System (ADS)

    Komarova, Natalia L.; Urwin, Erin; Wodarz, Dominik

    2012-12-01

    Complex traits can require the accumulation of multiple mutations that are individually deleterious. Their evolution requires a fitness valley to be crossed, which can take relatively long time spans. A new evolutionary mechanism is described that accelerates the emergence of complex phenotypes, based on a ``division of labor'' game and the occurrence of cheaters. If each intermediate mutation leads to a product that can be shared with others, the complex type can arise relatively quickly as an emergent property among cooperating individuals, without any given individual having to accumulate all mutations. Moreover, the emergence of cheaters that destroy cooperative interactions can lead to the emergence of individuals that have accumulated all necessary mutations on a time scale that is significantly faster than observed in the absence of cooperation and cheating. Application of this mechanism to somatic and microbial evolution is discussed, including evolutionary processes in tumors, biofilms, and viral infections.

  2. Increased human occupation and agricultural development accelerates the population contraction of an estuarine delphinid

    PubMed Central

    Lin, Wenzhi; Karczmarski, Leszek; Xia, Jia; Zhang, Xiyang; Yu, Xinjian; Wu, Yuping

    2016-01-01

    Over the past few thousand years, human development and population expansion in southern China have led to local extirpation and population contraction of many terrestrial animals. At what extent this early human-induced environmental change has also affected coastal marine species remains poorly known. We investigated the demographic history of the Indo-Pacific humpback dolphin (Sousa chinensis) in the Pearl River Delta (PRD); an obligatory inshore species known for its susceptibility to anthropogenic impacts in one of China’s most developed coastal regions. Although the deltaic evolution of PRD has been influenced by climate since the Holocene, ~74% reduction of the dolphin’s effective population size occurred within the last 2000 years, consistent with ~61% habitat contraction during this period. This considerable and recent population contraction may have been due to land use practices and deforestation in the upper/middle Pearl River region, all leading to increasing sedimentation rate in the estuarine area. As anthropogenic impacts within the drainage of Pearl River affected a vast area, coastal dolphins and large terrestrial mammals in southern China may share a similar demographic history, whilst the demographic and biogeographic history of the PRD humpback dolphins may be symptomatic of similar processes that this species may have undergone elsewhere in the region. PMID:27759106

  3. GPU-Accelerated Population Annealing Algorithm: Frustrated Ising Antiferromagnet on the Stacked Triangular Lattice

    NASA Astrophysics Data System (ADS)

    Borovský, Michal; Weigel, Martin; Barash, Lev Yu.; Žukovič, Milan

    2016-02-01

    The population annealing algorithm is a novel approach to study systems with rough free-energy landscapes, such as spin glasses. It combines the power of simulated annealing, Boltzmann weighted differential reproduction and sequential Monte Carlo process to bring the population of replicas to the equilibrium even in the low-temperature region. Moreover, it provides a very good estimate of the free energy. The fact that population annealing algorithm is performed over a large number of replicas with many spin updates, makes it a good candidate for massive parallelism. We chose the GPU programming using a CUDA implementation to create a highly optimized simulation. It has been previously shown for the frustrated Ising antiferromagnet on the stacked triangular lattice with a ferromagnetic interlayer coupling, that standard Markov Chain Monte Carlo simulations fail to equilibrate at low temperatures due to the effect of kinetic freezing of the ferromagnetically ordered chains. We applied the population annealing to study the case with the isotropic intra- and interlayer antiferromagnetic coupling (J2/|J1| = -1). The reached ground states correspond to non-magnetic degenerate states, where chains are antiferromagnetically ordered, but there is no long-range ordering between them, which is analogical with Wannier phase of the 2D triangular Ising antiferromagnet.

  4. Quantitative trait loci mapping in an F2 Duroc x Pietrain resource population: I. Growth traits.

    PubMed

    Edwards, D B; Ernst, C W; Tempelman, R J; Rosa, G J M; Raney, N E; Hoge, M D; Bates, R O

    2008-02-01

    body fat tissue on SSC 8. These results will facilitate fine-mapping efforts to identify genes controlling growth and body composition of pigs that can be incorporated into marker-assisted selection programs to accelerate genetic improvement in pig populations.

  5. Genetic variation facilitates seedling establishment but not population growth rate of a perennial invader

    PubMed Central

    Li, Shou-Li; Vasemägi, Anti; Ramula, Satu

    2016-01-01

    Background and Aims Assessing the demographic consequences of genetic variation is fundamental to invasion biology. However, genetic and demographic approaches are rarely combined to explore the effects of genetic variation on invasive populations in natural environments. This study combined population genetics, demographic data and a greenhouse experiment to investigate the consequences of genetic variation for the population fitness of the perennial, invasive herb Lupinus polyphyllus. Methods Genetic and demographic data were collected from 37 L. polyphyllus populations representing different latitudes in Finland, and genetic variation was characterized based on 13 microsatellite loci. Associations between genetic variation and population size, population density, latitude and habitat were investigated. Genetic variation was then explored in relation to four fitness components (establishment, survival, growth, fecundity) measured at the population level, and the long-term population growth rate (λ). For a subset of populations genetic variation was also examined in relation to the temporal variability of λ. A further assessment was made of the role of natural selection in the observed variation of certain fitness components among populations under greenhouse conditions. Key Results It was found that genetic variation correlated positively with population size, particularly at higher latitudes, and differed among habitat types. Average seedling establishment per population increased with genetic variation in the field, but not under greenhouse conditions. Quantitative genetic divergence (QST) based on seedling establishment in the greenhouse was smaller than allelic genetic divergence (F′ST), indicating that unifying selection has a prominent role in this fitness component. Genetic variation was not associated with average survival, growth or fecundity measured at the population level, λ or its variability. Conclusions The study suggests that although genetic

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

    PubMed

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

    2014-01-01

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

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

    ERIC Educational Resources Information Center

    Goudy, Willis

    2002-01-01

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

  8. The changing face of the Australian population: growth in centenarians.

    PubMed

    Richmond, Robyn L

    2008-06-16

    At the time of the 2006 Census, there were 3154 centenarians in Australia, 797 men (25%) and 2357 women (75%). This number is expected to increase to 12,000 by 2020. In Australia we are experiencing a demographic transition in which the proportions of people in the oldest age groups are increasing while the proportions in the youngest age groups are decreasing. Centenarians are the fastest growing age segment of the Australian population. Their numbers have increased by 8.5% per year over the past 25 years. In 2006, they represented 0.12% (3154/2,644,469) of the population aged 65 years and over. More than half of centenarians live in private dwellings, with 27% of men and 14% of women living on their own. Government policies are starting to address the issues of an ageing population, including provisions for financial support, improved access to medical services, and appropriate housing and transport facilities. However, we need specific social, medical and financial estimates of the impact of living to 100 years and beyond.

  9. Low energy emulsion-based fermentation enabling accelerated methane mass transfer and growth of poly(3-hydroxybutyrate)-accumulating methanotrophs.

    PubMed

    Myung, Jaewook; Kim, Minkyu; Pan, Ming; Criddle, Craig S; Tang, Sindy K Y

    2016-05-01

    Methane is a low-cost feedstock for the production of polyhydroxyalkanoate biopolymers, but methanotroph fermentations are limited by the low solubility of methane in water. To enhance mass transfer of methane to water, vigorous mixing or agitation is typically used, which inevitably increases power demand and operational costs. This work presents a method for accelerating methane mass transfer without agitation by growing methanotrophs in water-in-oil emulsions, where the oil has a higher solubility for methane than water does. In systems without agitation, the growth rate of methanotrophs in emulsions is five to six times that of methanotrophs in the medium-alone incubations. Within seven days, cells within the emulsions accumulate up to 67 times more P3HB than cells in the medium-alone incubations. This is achieved due to the increased interfacial area of the aqueous phase, and accelerated methane diffusion through the oil phase.

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

    USGS Publications Warehouse

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

    2007-01-01

    Variation in population dynamics is inherently related to life history characteristics of species, which vary markedly even within phylogenetic groups such as passerine birds. We computed the finite rate of population change (??) from a matrix projection model and from mark-recapture observations for 23 bird species breeding in northern Arizona. We used sensitivity analyses and a simulation model to separate contributions of different life history traits to population growth rate. In particular we focused on contrasting effects of components of reproduction (nest success, clutch size, number of clutches, and juvenile survival) versus adult survival on ??. We explored how changes in nest success or adult survival coupled to costs in other life history parameters affected ?? over a life history gradient provided by our 23 Arizona species, as well as a broader sample of 121 North American passerine species. We further examined these effects for more than 200 passeriform and piciform populations breeding across North America. Model simulations indicate nest success and juvenile survival exert the largest effects on population growth in species with moderate to high reproductive output, whereas adult survival contributed more to population growth in long-lived species. Our simulations suggest that monitoring breeding success in populations across a broad geographic area provides an important index for identifying neotropical migratory populations at risk of serious population declines and a potential method for identifying large-scale mechanisms regulating population dynamics. ?? 2007 Elsevier B.V. All rights reserved.

  11. [Age structure and growth pattern of Polytrichum juniperum populations in a mire of Changbai Mountains].

    PubMed

    Bu, Zhaojun; Yan, Yunfei; Dai, Dan; Wang, Xianwei

    2005-01-01

    In this paper, the age structure and growth pattern of two Polytrichum juniperum populations with and without sporophytes in Hani mire of Changbai Mountains were studied by 'innate annual marker' method. The ramets of both populations were composed of 6 age classes, and their quantity and biomass showed a declining age structure, which was more obvious in the sporophyte produced population. No significant difference of biomass was found (P > 0.05) between the two populations. The dry material accumulation of the ramets in both populations increased with aging, and showed similar patterns of linear function. The ramets mean height of sporophyte-produced population was 6.17% shorter (P < 0.05) than the another, because sporophyte production limited the height growth. The ramets mean height also increased with aging, and showed similar patterns of linear function. In non-sporophyte produced population, the variation coefficient of ramets height was only 2.44%, which indicated the significance of similar height for ramets survival. In sporophyte produced population, the variation coefficient of ramets height was 25.07%, while that of ramets biomass was 8.25%, suggesting the significance of similar biomass to the reproduction of population. The biomass of ramets had a significantly positive correlation with height in both populations (P < 0.001), and no allometric growth was showed.

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

    PubMed Central

    2011-01-01

    Background Human activities, such as agriculture, hunting, and habitat modification, exert a significant effect on native species. Although many species have suffered population declines, increased population fragmentation, or even extinction in connection with these human impacts, others seem to have benefitted from human modification of their habitat. Here we examine whether population growth in an insectivorous bat (Tadarida brasiliensis mexicana) can be attributed to the widespread expansion of agriculture in North America following European settlement. Colonies of T. b. mexicana are extremely large (~106 individuals) and, in the modern era, major agricultural insect pests form an important component of their food resource. It is thus hypothesized that the growth of these insectivorous bat populations was coupled to the expansion of agricultural land use in North America over the last few centuries. Results We sequenced one haploid and one autosomal locus to determine the rate and time of onset of population growth in T. b. mexicana. Using an approximate Maximum Likelihood method, we have determined that T. b. mexicana populations began to grow ~220 kya from a relatively small ancestral effective population size before reaching the large effective population size observed today. Conclusions Our analyses reject the hypothesis that T. b. mexicana populations grew in connection with the expansion of human agriculture in North America, and instead suggest that this growth commenced long before the arrival of humans. As T. brasiliensis is a subtropical species, we hypothesize that the observed signals of population growth may instead reflect range expansions of ancestral bat populations from southern glacial refugia during the tail end of the Pleistocene. PMID:21457563

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

    PubMed

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

    2000-07-14

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

  14. The growth of XXX females: population-based studies.

    PubMed

    Ratcliffe, S G; Pan, H; McKie, M

    1994-01-01

    Longitudinal measurements of height, sitting height and leg length are compared between 11 XXX girls identified by cytogenetic screening, and 16 chromosomally normal controls from the same population using a nonparametric method. While height velocity did not differ between the two groups either during the pubertal or the mid-childhood spurts, leg length velocity was significantly increased during the mid-childhood spurt, between 4 and 9 years of age. A further contribution to the increased leg length came from the slower decline in leg length velocity at the end of the pubertal spurt. The possible mechanisms involved in these changes are discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

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

    ERIC Educational Resources Information Center

    Morrison, Peter A.; Wheeler, Judith P.

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

  17. Population Change: Do You Know the Trends in Your Community? Coping with Growth.

    ERIC Educational Resources Information Center

    Butler, Lorna Michael

    To help government agency representatives and community leaders understand local population trends, particularly in rapid growth situations, this publication outlines a simple framework for analyzing population changes and provides useful criteria that can be applied when considering management and policy alternatives. It is noted that two…

  18. Progress on plasma accelerators

    SciTech Connect

    Chen, P.

    1986-05-01

    Several plasma accelerator concepts are reviewed, with emphasis on the Plasma Beat Wave Accelerator (PBWA) and the Plasma Wake Field Accelerator (PWFA). Various accelerator physics issues regarding these schemes are discussed, and numerical examples on laboratory scale experiments are given. The efficiency of plasma accelerators is then revealed with suggestions on improvements. Sources that cause emittance growth are discussed briefly.

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

    PubMed

    Feld, S

    2000-03-01

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

  20. Accelerated Growth Rate and Increased Drought Stress Resilience of the Model Grass Brachypodium distachyon Colonized by Bacillus subtilis B26.

    PubMed

    Gagné-Bourque, François; Mayer, Boris F; Charron, Jean-Benoit; Vali, Hojatollah; Bertrand, Annick; Jabaji, Suha

    2015-01-01

    Plant growth-promoting bacteria (PGB) induce positive effects in plants, for instance, increased growth and reduced abiotic stresses susceptibility. The mechanisms by which these bacteria impact the host plant are numerous, diverse and often specific. Here, we studied the agronomical, molecular and biochemical effects of the endophytic PGB Bacillus subtilis B26 on the full life cycle of Brachypodium distachyon Bd21, an established model species for functional genomics in cereal crops and temperate grasses. Inoculation of Brachypodium with B. subtilis strain B26 increased root and shoot weights, accelerated growth rate and seed yield as compared to control plants. B. subtilis strain B26 efficiently colonized the plant and was recovered from roots, stems and blades as well as seeds of Brachypodium, indicating that the bacterium is able to migrate, spread systemically inside the plant, establish itself in the aerial plant tissues and organs, and is vertically transmitted to seeds. The presence of B. subtilis strain B26 in the seed led to systemic colonization of the next generation of Brachypodium plants. Inoculated Brachypodium seedlings and mature plants exposed to acute and chronic drought stress minimized the phenotypic effect of drought compared to plants not harbouring the bacterium. Protection from the inhibitory effects of drought by the bacterium was linked to upregulation of the drought-response genes, DREB2B-like, DHN3-like and LEA-14-A-like and modulation of the DNA methylation genes, MET1B-like, CMT3-like and DRM2-like, that regulate the process. Additionally, total soluble sugars and starch contents increased in stressed inoculated plants, a biochemical indication of drought tolerance. In conclusion, we show a single inoculation of Brachypodium with a PGB affected the whole growth cycle of the plant, accelerating its growth rates, shortening its vegetative period, and alleviating drought stress effects. These effects are relevant to grasses and cereal

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

    PubMed

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

    2014-04-01

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

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

    SciTech Connect

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

    2015-10-22

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

  4. [Population growth in Plasencia in the nineteenth century].

    PubMed

    Sanchez De La Calle, J A

    1993-01-01

    "Using sources such as parish registers, civil registers, records of the town hall, inquiries, [censuses] and list of inhabitants, we have been able to confirm the existence of four different stages in the demographic development of Plasencia [Spain]. The first one, between 1800 and 1815, is characterized by a scarce growing.... The second one, between 1816 and 1839, shows a certain increase which is restrained at the end of the 30s because of some epidemic illness (cholera and various fevers). The period between 1840 and 1871 is a stage of slow growing due to many subsistence crises. The fourth stage, 1872-1899, continues the same outline with a great rising of mortality, which does not prevent the rising of population in Plasencia caused by a high rate of inmigration." (SUMMARY IN ENG AND FRE)

  5. Endogenous population growth and the exploitation of renewable resources.

    PubMed

    Prskawetz, A; Feichtinger, G; Wirl, F

    1994-01-01

    The authors consider a demo-economic model where the economy consists of two sectors ("hunting and farming" and "industry"), and both sectors depend directly or indirectly on the explanation of a renewable resource. The primary sector harvests a renewable resource (fish, corn, or wood) which is used as the input into industrial production, the secondary sector of our economy. Labor is divided up between these two sectors under the assumption of competitive labor markets. A system of two nonlinear differential equations for the resources and the population is studied by phase space analysis. Using the Hopf bifurcation theorem, the authors obtain two different routes to limit cycles and prove numerically the existence of a stable Malthusian limit cycle.

  6. A MULTI-PATCH MALARIA MODEL WITH LOGISTIC GROWTH POPULATIONS*

    PubMed Central

    GAO, DAOZHOU; RUAN, SHIGUI

    2013-01-01

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

  7. Agricultural change and population growth: a brief survey on the case of China in historical perspective.

    PubMed

    Liu, T

    1986-03-01

    A historical review of the relationship between agricultural change and population growth in China is presented. "This paper will try to discuss four aspects of agricultural change that are related to population growth. They are: (1) expansion of agricultural frontier, (2) changes in cultivation methods and land use, (3) improvements in agricultural technology, and (4) irrigation and water-control. Each of these aspects [is] treated briefly with temporal and spatial perspectives...." The relevance of the Boserup theory that population pressure leads to agricultural development is considered in the Chinese context. It is found that some evidence supports the theory. (summary in CHI)

  8. Stringent restriction from the growth of large-scale structure on apparent acceleration in inhomogeneous cosmological models.

    PubMed

    Ishak, Mustapha; Peel, Austin; Troxel, M A

    2013-12-20

    Probes of cosmic expansion constitute the main basis for arguments to support or refute a possible apparent acceleration due to different expansion rates in the Universe as described by inhomogeneous cosmological models. We present in this Letter a separate argument based on results from an analysis of the growth rate of large-scale structure in the Universe as modeled by the inhomogeneous cosmological models of Szekeres. We use the models with no assumptions of spherical or axial symmetries. We find that while the Szekeres models can fit very well the observed expansion history without a Λ, they fail to produce the observed late-time suppression in the growth unless Λ is added to the dynamics. A simultaneous fit to the supernova and growth factor data shows that the cold dark matter model with a cosmological constant (ΛCDM) provides consistency with the data at a confidence level of 99.65%, while the Szekeres model without Λ achieves only a 60.46% level. When the data sets are considered separately, the Szekeres with no Λ fits the supernova data as well as the ΛCDM does, but provides a very poor fit to the growth data with only 31.31% consistency level compared to 99.99% for the ΛCDM. This absence of late-time growth suppression in inhomogeneous models without a Λ is consolidated by a physical explanation.

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

    SciTech Connect

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

    1995-12-31

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

  10. The ocean blues. Navigating the course of population growth.

    PubMed

    Sarkar, D

    1996-01-01

    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

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

    USGS Publications Warehouse

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

    2011-01-01

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

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

    USGS Publications Warehouse

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

    2015-07-14

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

  13. Sexual Reproduction in a Simple Growth Population Model

    NASA Astrophysics Data System (ADS)

    Lemos, Carlos Gentil Oro; Santos, Marcio

    2012-05-01

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

  14. Evidence of accelerated beak growth associated with avian keratin disorder in black-capped chickadees (Poecile atricapillus)

    USGS Publications Warehouse

    Van Hemert, Caroline R.; Handel, Colleen M.; O'Hara, Todd M.

    2012-01-01

    We recently documented an epizootic of beak deformities in more than 2,000 Blackcapped Chickadees (Poecile atricapillus) and other wild bird species in North America. This emerging avian disease, which has been termed avian keratin disorder, results in gross overgrowth of the rhamphotheca, the outer, keratinized layer of the beak. To test the hypothesis that the beak deformities characteristic of this disorder are associated with accelerated keratin production, we measured rates of beak growth and wear in affected Black-capped Chickadees (n=16) and a control sample of unaffected chickadees (n=14) collected from south-central (61°09'-61°38'N, 149°11' -149°48'W) and interior Alaska (64°51' -64°53'N, 147°49' -147°59'W). Rates of absolute growth were 50-100% higher in affected birds than they were in control birds and exceeded records from other passerine species. These results suggest that abnormally rapid epidermal growth is the primary physical mechanism by which beak deformities develop and are maintained in affected chickadees. Although beak overgrowth typically worsened over time, differential patterns of wear influenced the severity and morphology of deformities. In some cases, the effects of accelerated keratin growth were partially mitigated by frequent breakage of rhamphothecal tips. However, mortalities occurred in 9 of 16 birds (56%) with beak deformities during the study, suggesting that avian keratin disorder results in severe health consequences for affected birds. Additional study of factors that control beak keratin production is needed to understand the pathogenesis of this debilitating disease in wild birds.

  15. Evidence of accelerated beak growth associated with avian keratin disorder in Black-capped Chickadees (Poecile atricapillus)

    USGS Publications Warehouse

    Van Hemert, Caroline; Handel, Colleen M.; O'Hara, Todd M.

    2012-01-01

    We recently documented an epizootic of beak deformities in more than 2,000 Blackcapped Chickadees (Poecile atricapillus) and other wild bird species in North America. This emerging avian disease, which has been termed avian keratin disorder, results in gross overgrowth of the rhamphotheca, the outer, keratinized layer of the beak. To test the hypothesis that the beak deformities characteristic of this disorder are associated with accelerated keratin production, we measured rates of beak growth and wear in affected Black-capped Chickadees (n=16) and a control sample of unaffected chickadees (n=14) collected from south-central (61°09′−61°38′N, 149°11′ −149°48′W) and interior Alaska (64°51′ −64°53′N, 147°49′ −147°59′W). Rates of absolute growth were 50–100% higher in affected birds than they were in control birds and exceeded records from other passerine species. These results suggest that abnormally rapid epidermal growth is the primary physical mechanism by which beak deformities develop and are maintained in affected chickadees. Although beak overgrowth typically worsened over time, differential patterns of wear influenced the severity and morphology of deformities. In some cases, the effects of accelerated keratin growth were partially mitigated by frequent breakage of rhamphothecal tips. However, mortalities occurred in 9 of 16 birds (56%) with beak deformities during the study, suggesting that avian keratin disorder results in severe health consequences for affected birds. Additional study of factors that control beak keratin production is needed to understand the pathogenesis of this debilitating disease in wild birds.

  16. Enterococcus faecium LKE12 Cell-Free Extract Accelerates Host Plant Growth via Gibberellin and Indole-3-Acetic Acid Secretion.

    PubMed

    Lee, Ko-Eun; Radhakrishnan, Ramalingam; Kang, Sang-Mo; You, Young-Hyun; Joo, Gil-Jae; Lee, In-Jung; Ko, Jae-Hwan; Kim, Jin-Ho

    2015-09-01

    The use of microbial extracts containing plant hormones is a promising technique to improve crop growth. Little is known about the effect of bacterial cell-free extracts on plant growth promotion. This study, based on phytohormonal analyses, aimed at exploring the potential mechanisms by which Enterococcus faecium LKE12 enhances plant growth in oriental melon. A bacterial strain, LKE12, was isolated from soil, and further identified as E. faecium by 16S rDNA sequencing and phylogenetic analysis. The plant growth-promoting ability of an LKE12 bacterial culture was tested in a gibberellin (GA)-deficient rice dwarf mutant (waito-C) and a normal GA biosynthesis rice cultivar (Hwayongbyeo). E. faecium LKE12 significantly improved the length and biomass of rice shoots in both normal and dwarf cultivars through the secretion of an array of gibberellins (GA1, GA3, GA7, GA8, GA9, GA12, GA19, GA20, GA24, and GA53), as well as indole-3-acetic acid (IAA). To the best of our knowledge, this is the first study indicating that E. faecium can produce GAs. Increases in shoot and root lengths, plant fresh weight, and chlorophyll content promoted by E. faecium LKE12 and its cell-free extract inoculated in oriental melon plants revealed a favorable interaction of E. faecium LKE12 with plants. Higher plant growth rates and nutrient contents of magnesium, calcium, sodium, iron, manganese, silicon, zinc, and nitrogen were found in cell-free extract-treated plants than in control plants. The results of the current study suggest that E. faecium LKE12 promotes plant growth by producing GAs and IAA; interestingly, the exogenous application of its cell-free culture extract can be a potential strategy to accelerate plant growth.

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

    PubMed

    Lachish, Shelly; Jones, Menna; McCallum, Hamish

    2007-09-01

    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.

  18. Catalysis of protein folding by chaperones accelerates evolutionary dynamics in adapting cell populations.

    PubMed

    Cetinbaş, Murat; Shakhnovich, Eugene I

    2013-01-01

    Although molecular chaperones are essential components of protein homeostatic machinery, their mechanism of action and impact on adaptation and evolutionary dynamics remain controversial. Here we developed a physics-based ab initio multi-scale model of a living cell for population dynamics simulations to elucidate the effect of chaperones on adaptive evolution. The 6-loci genomes of model cells encode model proteins, whose folding and interactions in cellular milieu can be evaluated exactly from their genome sequences. A genotype-phenotype relationship that is based on a simple yet non-trivially postulated protein-protein interaction (PPI) network determines the cell division rate. Model proteins can exist in native and molten globule states and participate in functional and all possible promiscuous non-functional PPIs. We find that an active chaperone mechanism, whereby chaperones directly catalyze protein folding, has a significant impact on the cellular fitness and the rate of evolutionary dynamics, while passive chaperones, which just maintain misfolded proteins in soluble complexes have a negligible effect on the fitness. We find that by partially releasing the constraint on protein stability, active chaperones promote a deeper exploration of sequence space to strengthen functional PPIs, and diminish the non-functional PPIs. A key experimentally testable prediction emerging from our analysis is that down-regulation of chaperones that catalyze protein folding significantly slows down the adaptation dynamics.

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

    PubMed

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

    2013-06-01

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

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

    PubMed

    El Cheikh, R; Bernard, S; El Khatib, N

    2014-12-21

    The circadian clock and the cell cycle are two tightly coupled oscillators. Recent analytical studies have shown counter-intuitive effects of circadian gating of the cell cycle on growth rates of proliferating cells which cannot be explained by a molecular model or a population model alone. In this work, we present a combined molecular-population model that studies how coupling the circadian clock to the cell cycle, through the protein WEE1, affects a proliferating cell population. We show that the cell cycle can entrain to the circadian clock with different rational period ratios and characterize multiple domains of entrainment. We show that coupling increases the growth rate for autonomous periods of the cell cycle around 24 h and above 48 h. We study the effect of mutation of circadian genes on the growth rate of cells and show that disruption of the circadian clock can lead to abnormal proliferation. Particularly, we show that Cry 1, Cry 2 mutations decrease the growth rate of cells, Per 2 mutation enhances it and Bmal 1 knockout increases it for autonomous periods of the cell cycle less than 21 h and decreases it elsewhere. Combining a molecular model to a population model offers new insight on the influence of the circadian clock on the growth of a cell population. This can help chronotherapy which takes benefits of physiological rhythms to improve anti-cancer efficacy and tolerance to drugs by administering treatments at a specific time of the day.

  1. A heterogeneous population model for the analysis of bacterial growth kinetics.

    PubMed

    McKellar, R C

    1997-05-20

    A two-compartment, heterogeneous population model (HPM) was derived using the simulation software SB ModelMaker to describe the growth of Listeria monocytogenes in bacteriological media at 5-35 degrees C. The model assumed that, at time t = 0, the inoculum was distributed between two distinct compartments, Non-Growing and Growing, and that growth could be described by four parameters: initial total cell population (N0), final maximum cell population (Nmax), maximum specific growth rate (mu(max)), and initial cell population in the Growing compartment (G0). The model was fitted to the data by optimizing the four parameters, and lag phase duration (lambda) was calculated. The resulting values of mu(max) and lambda were similar to those determined using the modified Gompertz equation. A new parameter, w0, was defined which relates to the proportion of the initial cell population capable of growth, and is a measure of the initial physiological state of the cells. A modified model in which mu(max) was replaced with a temperature function, and w0 replaced G0, was used to predict the effect of temperature on the growth of L. monocytogenes. The results of this study raise questions concerning the current definition of the lag phase.

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

    PubMed

    Wulf, D; Klitsch, M

    1986-01-01

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

  3. India's fertility declines, but it still leads world in population growth.

    PubMed

    Visaria, L; Visaria, P

    1995-10-01

    Despite its fertility decline, India still has the world's second largest population size. Over the decades fertility declined to 3.6 in 1992 per woman. However great or rapid the decline, the population growth rate is an estimated 1.9% a year. Only three countries in the world have a higher rate of growth: Nigeria, Pakistan, and Bangladesh. Fertility decline is attributed to increased literacy, urbanization, industrialization, modern communication and transportation, and women's status. The availability of government family planning services has also contributed to the fertility decline. Although female literacy has risen rapidly to 39% in 1991, male literacy is still higher at 64%. Girls lag behind in school attendance in both rural and urban areas. Fertility decline has occurred faster in urban areas, which are concentrated in cities of over 100,000 people. The childbearing period has declined, and childbearing is delayed. Contraceptive usage has grown dramatically since 1970 to around 40%, depending upon the data source. Population growth is attributed to improvements in health and mortality. Life expectancy has increased to 60 years, and infant mortality declined to 74 per 1000 live births. The age structure of the population is young due to demographic changes. Growth will continue for several decades due to population momentum. India is expected to surpass China as the most populous country in the world before 2050.

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

    PubMed

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

    2010-10-01

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

  5. Physical Growth of the Shuar: Height, Weight, and BMI References for an Indigenous Amazonian Population

    PubMed Central

    URLACHER, SAMUEL S.; BLACKWELL, AARON D.; LIEBERT, MELISSA A.; MADIMENOS, FELICIA C.; CEPON-ROBINS, TARA J.; GILDNER, THERESA E.; SNODGRASS, J. JOSH; SUGIYAMA, LAWRENCE S.

    2015-01-01

    Objectives Information concerning physical growth among small-scale populations remains limited, yet such data are critical to local health efforts and to foster basic understandings of human life history and variation in childhood development. Using a large dataset and robust modeling methods, this study aims to describe growth from birth to adulthood among the indigenous Shuar of Amazonian Ecuador. Methods Mixed-longitudinal measures of height, weight, and BMI were collected from Shuar participants (n = 2,463; age 0–29 years). Centile growth curves and tables were created for each anthropometric variable of interest using GAMLSS. Pseudo-velocity and LMS curves were generated to further investigate Shuar patterns of growth and to facilitate comparison with U.S. CDC and multinational WHO growth references. Results The Shuar are small throughout life and exhibit complex patterns of growth that differ substantially from those of international references. Similar to other Amazonians, Shuar growth in weight compares more favorably to references than growth in height, resulting in BMI curves that approximate international medians. Several additional characteristics of Shuar development are noteworthy, including large observed variation in body size early in life, significant infant growth faltering, extended male growth into adulthood, and a markedly early female pubertal growth spurt in height. Phenotypic plasticity and genetic selection in response to local environmental factors may explain many of these patterns. Conclusions Providing a detailed reference of growth for the Shuar and other Amazonian populations, this study possesses direct clinical application and affords valuable insight into childhood health and the ecology of human growth. PMID:26126793

  6. A highly invasive subpopulation of MDA-MB-231 breast cancer cells shows accelerated growth, differential chemoresistance, features of apocrine tumors and reduced tumorigenicity in vivo

    PubMed Central

    Mirisola, Valentina; Esposito, Alessia Isabella; Reverberi, Daniele; Matis, Serena; Maffei, Massimo; Giaretti, Walter; Viale, Maurizio; Gangemi, Rosaria; Emionite, Laura; Astigiano, Simonetta; Cilli, Michele; Bachmeier, Beatrice E.; Killian, Peter H.; Albini, Adriana; Pfeffer, Ulrich

    2016-01-01

    The acquisition of an invasive phenotype is a prerequisite for metastasization, yet it is not clear whether or to which extent the invasive phenotype is linked to other features characteristic of metastatic cells. We selected an invasive subpopulation from the triple negative breast cancer cell line MDA-MB-231, performing repeated cycles of preparative assays of invasion through Matrigel covered membranes. The invasive sub-population of MDA-MB-231 cells exhibits stronger migratory capacity as compared to parental cells confirming the highly invasive potential of the selected cell line. Prolonged cultivation of these cells did not abolish the invasive phenotype. ArrayCGH, DNA index quantification and karyotype analyses confirmed a common genetic origin of the parental and invasive subpopulations and revealed discrete structural differences of the invasive subpopulation including increased ploidy and the absence of a characteristic amplification of chromosome 5p14.1-15.33. Gene expression analyses showed a drastically altered expression profile including features of apocrine breast cancers and of invasion related matrix-metalloproteases and cytokines. The invasive cells showed accelerated proliferation, increased apoptosis, and an altered pattern of chemo-sensitivity with lower IC50 values for drugs affecting the mitotic apparatus. However, the invasive cell population is significantly less tumorigenic in orthotopic mouse xenografts suggesting that the acquisition of the invasive capacity and the achievement of metastatic growth potential are distinct events. PMID:27626697

  7. Respective impact of climate and fisheries on the growth of an albatross population.

    PubMed

    Rolland, V; Nevoux, M; Barbraud, C; Weimerskirch, H

    2009-07-01

    Climate and human activities such as fisheries impact many animal species. However, the demographic processes through which the population vital rates are affected, and the sensitivity of their growth rates, are poorly understood. The Black-browed Albatross, Thalassarche melanophrys, is a long-lived threatened seabird species. Previous studies have shown that the adult survival and breeding success of the population breeding at Kerguelen are affected by sea surface temperature anomalies (SSTA) during both the breeding and the nonbreeding season, and by tuna long-lining in Tasmanian waters through bycatch mortality. Here, using long-term demographic data from a Black-browed Albatross colony monitored for 26 years at Kerguelen, we estimate all demographic parameters from early to adult stages of the life cycle in order to build a fully parameterized population model and predict population growth rates under several scenarios of climate and fishing effort. The observed population growth rate (1.003) indicates that the population was stable or slightly increasing, and our population model gives a close estimate of 1.008. Population growth rate is more sensitive to survival of experienced breeders and accordingly to a change in SSTA during incubation and to tuna long-lining effort (both affecting survival of experienced breeders) than to other demographic parameters/environmental covariates. The population stability results from multiple factors and complex relationships between demographic parameters and environmental conditions, and therefore population equilibrium is precarious. If fishing effort remains stable at its current level and positive SSTA increase, or inversely if fishing effort decreases and SSTA remain similar to present values, then the population would increase. However, if fishing effort increases by 20% (i.e., to 40 million hooks) on the wintering grounds, without any change in SSTA, then the population would decrease at 0.9% per year. If fishing

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

    PubMed Central

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

    2014-01-01

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

  9. Fibrin biomatrix-conjugated platelet-derived growth factor AB accelerates wound healing in severe thermal injury.

    PubMed

    Mittermayr, Rainer; Branski, Ludwik; Moritz, Martina; Jeschke, Marc G; Herndon, David N; Traber, Daniel; Schense, Jason; Gampfer, Jörg; Goppelt, Andreas; Redl, Heinz

    2016-05-01

    Controlled delivery of growth factors from biodegradable biomatrices could accelerate and improve impaired wound healing. The study aim was to determine whether platelet-derived growth factor AB (PDGF.AB) with a transglutaminase (TG) crosslinking substrate site released from a fibrin biomatrix improves wound healing in severe thermal injury. The binding and release kinetics of TG-PDGF.AB were determined in vitro. Third-degree contact burns (dorsum of Yorkshire pigs) underwent epifascial necrosectomy 24 h post-burn. Wound sites were covered with autologous meshed (3:1) split-thickness skin autografts and either secured with staples or attached with sprayed fibrin sealant (FS; n = 8/group). TG-PDGF.AB binds to the fibrin biomatrix using the TG activity of factor XIIIa, and is subsequently released through enzymatic cleavage. Three doses of TG-PDGF.AB in FS (100 ng, 1 µg and 11 µg/ml FS) were tested. TG-PDGF.AB was bound to the fibrin biomatrix as evidenced by western blot analysis and subsequently released by enzymatic cleavage. A significantly accelerated and improved wound healing was achieved using sprayed FS containing TG-PDGF.AB compared to staples alone. Low concentrations (100 ng-1 µg TG-PDGF.AB/ml final FS clot) demonstrated to be sufficient to attain a nearly complete closure of mesh interstices 14 days after grafting. TG-PDGF.AB incorporated in FS via a specific binding technology was shown to be effective in grafted third-degree burn wounds. The adhesive properties of the fibrin matrix in conjunction with the prolonged growth factor stimulus enabled by this binding technology could be favourable in many pathological situations associated with wound-healing disturbances. Copyright © 2013 John Wiley & Sons, Ltd.

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

    PubMed

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

    2011-08-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  12. Natural growth of the population of Plovdiv, Bulgaria for the period 1895-1995.

    PubMed

    Dimitrov, I

    1998-01-01

    A study of the natural growth rate of the population using female cohorts by birth year has been carried out for the first time in our country. The study comprises 14 cohorts. The following characteristics are recorded: birth year, social group, educational level, number of live births, age of marriage, infant mortality rate, proto- and intergenetic intervals. Our report presents the key indicators of natural growth of population in the studied cohorts. A consistent trend of decreasing the number of livebirths is established. In the first studied cohort (1895-1899) the average number of offspring per woman is 3.94, reaching a level of 1.77 in the 1960-1964 cohort. The indicators for natural growth of population exhibit a similar trend. The summary fertility rate in the reference period decreases with more than 2 points--from 4.47 in 1895-1899 to 1.73 in 1960-1964. Likewise, the total reproduction rate goes down from 2.54 to 0.78 for the same period. Considerable changes have occurred in the indicators total period fertility rate and marriage fertility rate of women. For a period of 110 years the former has decreased 3.5 times, the latter--8 times. The drastic drop of the indicators of natural growth of the population is accounted for by an intricate complex of social, economic, psychological and biological factors. The marked aging of the population and the decrease of the percentage of women in active fertility age play a certain role in this process. The ascertained changes in the reproductive behavior and age structure of the female population are factors intensifying the unfavorable trends in the natural growth rate of the population in our country.

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

    PubMed

    Stutz, Aaron Jonas

    2014-01-01

    To Malthus, rapid human population growth-so evident in 18th Century Europe-was obviously unsustainable. In his Essay on the Principle of Population, Malthus cogently argued that environmental and socioeconomic constraints on population rise were inevitable. Yet, he penned his essay on the eve of the global census size reaching one billion, as nearly two centuries of super-exponential increase were taking off. Introducing a novel extension of J. E. Cohen's hallmark coupled difference equation model of human population dynamics and carrying capacity, this article examines just how elastic population growth limits may be in response to demographic change. The revised model involves a simple formalization of how consumption costs influence carrying capacity elasticity over time. Recognizing that complex social resource-extraction networks support ongoing consumption-based investment in family formation and intergenerational resource transfers, it is important to consider how consumption has impacted the human environment and demography--especially as global population has become very large. Sensitivity analysis of the consumption-cost model's fit to historical population estimates, modern census data, and 21st Century demographic projections supports a critical conclusion. The recent population explosion was systemically determined by long-term, distinctly pre-industrial cultural evolution. It is suggested that modern globalizing transitions in technology, susceptibility to infectious disease, information flows and accumulation, and economic complexity were endogenous products of much earlier biocultural evolution of family formation's embeddedness in larger, hierarchically self-organizing cultural systems, which could potentially support high population elasticity of carrying capacity. Modern super-exponential population growth cannot be considered separately from long-term change in the multi-scalar political economy that connects family formation and

  14. The impact of population change on the growth of mega-cities.

    PubMed

    Guest, P

    1994-03-01

    The population dynamics of population growth in mega-cities and the contributions of migration to urban growth are described. The policy implications are identified as the need for a continued emphasis on fertility declines, because reductions will have a beneficial effect on reducing the pace of growth of mega-cities. The short-term goal of policy should be to provide urban contraceptive services to female migrants, who should be targeted specifically as a special group. Natural increase will be the main source of growth of mega-cities, and women who migrated during the 1990s will be a part of that natural increase. Reductions in population growth will make it easier for governments to provide services and to manage the large population size in mega-cities, which will continue to exist as long as economic activities are centralized and economic development promotes urbanization and spatial concentration. The emergence of mega-cities with populations of many millions has been a recent and increasing phenomena. The largest cities in 1980 were Tokyo with 16.9 million followed by New York City with 15.6 million. By 1990, the largest mega-cities were Mexico City with 20.2 million, Tokyo with 18.1 million, Sao Paulo with 17.4 million, and New York with 16.2 million. By the year 2000, the expectation is that Mexico City will have 25.6 million, Sao Paulo 22.1 million, Tokyo 19.0 million, Shanghai 17.0 million, and New York 16.8 million. The rankings will change, but the pattern clearly reflects the growth of mega-cities in developing countries. The age structure of urban populations is conducive to population growth. The main component of urban growth in Asia has been migration. Age structure changes have affected migration and will continue to affect fertility in mega-cities. Mega-cities will attract a young population because of the tourist and personnel services sectors which employ large numbers of young people, because of the demand for educated workers who tend to

  15. Capital accumulation, aspiration adjustment, and population growth: limit cycles in an Easterlin-type model.

    PubMed

    Feichtinger, G; Sorger, G

    1990-01-01

    "One of the recent interesting hypotheses of population growth is due to Easterlin who suggests the possibility of self-generating fluctuations in birth numbers. The present paper tries to answer the question whether feedback mechanisms produce persistent oscillations in population growth. A system of two nonlinear differential equations for the per capita capital stock and the aspiration level is studied by a phase portrait analysis. Using the Poincare-Bendixson theorem we derive sufficient conditions for the existence of a stable limit cycle." (SUMMARY IN FRE)

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

    PubMed Central

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

    2013-01-01

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

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

    PubMed

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

    2013-01-01

    Field experiments were conducted to evaluate plant population and N-fertilizer effects on yield and yield components of maize (Zea mays L.). Three levels of plant populations (53000, 66000, and 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.

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

    PubMed Central

    2014-01-01

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

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

    PubMed

    Bianca, Carlo; Guerrini, Luca

    2014-01-01

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

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

    ERIC Educational Resources Information Center

    La Fleur, Mary Ann

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

  1. Using a population growth model to simulate response of Plodia interpunctella Hübner to temperature and diet

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Response to temperature and diet are major factors in the potential population growth of Plodia interpunctella Hübner, a damaging pest of many stored products. A population growth model was used to simulate population development on an optimal wheat-based diet and a sub-optimal diet of raisins at 20...

  2. Crowding out the Future: World Population Growth, U.S. Immigration, and Pressures on Natural Resources [and] Teacher's Guide.

    ERIC Educational Resources Information Center

    Fox, Robert W.; Mehlman, Ira H.

    Using text, graphics, satellite imagery, and data this publication with accompanying teacher's guide seeks to illustrate three main points concerning world population: (1) rapid world population growth is placing untenable immigration pressures on the United States; (2) immigration and U.S. population growth patterns generally are regionally…

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

    USGS Publications Warehouse

    Hansen, Michael J.; Nate, Nancy A.

    2014-01-01

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

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

    PubMed

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

    2016-11-01

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

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

    USGS Publications Warehouse

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

    2003-01-01

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

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

    ERIC Educational Resources Information Center

    Mahar, Dennis J., Ed.; And Others

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

  7. Population growth rate and carrying capacity for springtails Folsomia candida exposed to ivermectin.

    PubMed

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

    2006-04-01

    Forecasting the effects of stressors on the dynamics of natural populations requires assessment of the joint effects of a stressor and population density on the population response. The effects can be depicted as a contour map in which the population response, here assessed by population growth rate, varies with stress and density in the same way that the height of land above sea level varies with latitude and longitude. We present the first complete map of this type using as our model Folsomia candida exposed to five different concentrations of the widespread anthelmintic veterinary medicine ivermectin in replicated microcosm experiments lasting 49 days. The concentrations of ivermectin in yeast were 0.0, 6.8, 28.8, 66.4, and 210.0 mg/L wet weight. Increasing density and chemical concentration both significantly reduced the population growth rate of Folsomia candida, in part through effects on food consumption and fecundity. The interaction between density and ivermectin concentration was "less-than-additive," implying that at high density populations were able to compensate for the effects of the chemical. This result demonstrates that regulatory protocols carried out at low density (as in most past experiments) may seriously overestimate effects in the field, where densities are locally high and populations are resource limited (e.g., in feces of livestock treated with ivermectin).

  8. Population increase, economic growth, educational inequality, and income distribution: some recent evidence.

    PubMed

    Ram, R

    1984-04-01

    The relationship between population increase, economic growth, education and income inequality was examined in a cross-section study based on data from 26 developing and 2 developed countries. As other studies have noted, high population growth is associated with a less equal income distribution. A 1 percentage point reduction in the rate of population growth tends to raise the income share of the poorest 80% in the less developed world by almost 5 percentage points and is associated with a 1.7 percentage point increase in the income share of the poorest 40%. The relationship between short-run income growth and equality, on the other hand, is strong and positive. Estimates suggest that a 1 percentage point increase in the short-run rate of growth of the gross domestic product (GDP) increases the income share of the bottom 80% by about 2 percentage points and that of the poorest 40% by almost 1 percentage point. Although higher mean schooling appears to be a mild equalizer, educational inequality does not appear to have an adverse effect on income distribution. Overall, these results challenge the widely held belief that there must be a growth-equity trade-off. Moreover, they suggest that the impact of educational inequality on income distribution may be different from that observed in earlier studies, implying a need for caution in using these earlier results as a basis for educational policy development.

  9. Accelerating the dynamics of infrequent events: Combining hyperdynamics and parallel replica dynamics to treat epitaxial layer growth

    SciTech Connect

    Voter, A.F.; Germann, T.C.

    1998-12-31

    During the growth of a surface, morphology-controlling diffusion events occur over time scales that far exceed those accessible to molecular dynamics (MD) simulation. Kinetic Monte Carlo offers a way to reach much longer times, but suffers from the fact that the dynamics are correct only if all possible diffusion events are specified in advance. This is difficult due to the concerted nature of many of the recently discovered surface diffusion mechanisms and the complex configurations that arise during real growth. Here the authors describe two new approaches for this type of problem. The first, hyperdynamics, is an accelerated MD method, in which the trajectory is run on a modified potential energy surface and time is accumulated as a statistical property. Relative to regular MD, hyperdynamics can give computational gains of more than 10{sup 2}. The second method offers a way to parallelize the dynamics efficiently for systems too small for conventional parallel MD algorithms. Both methods exploit the infrequent-event nature of the diffusion process. After an introductory description of these methods, the authors present preliminary results from simulations combining the two approaches to reach near-millisecond time scales on systems relevant to epitaxial metal growth.

  10. Threshold effect of growth rate on population variability of Escherichia coli cell lengths

    PubMed Central

    2017-01-01

    A long-standing question in biology is the effect of growth on cell size. Here, we estimate the effect of Escherichia coli growth rate (r) on population cell size distributions by estimating the coefficient of variation of cell lengths (CVL) from image analysis of fixed cells in DIC microscopy. We find that the CVL is constant at growth rates less than one division per hour, whereas above this threshold, CVL increases with an increase in the growth rate. We hypothesize that stochastic inhibition of cell division owing to replication stalling by a RecA-dependent mechanism, combined with the growth rate threshold of multi-fork replication (according to Cooper and Helmstetter), could form the basis of such a threshold effect. We proceed to test our hypothesis by increasing the frequency of stochastic stalling of replication forks with hydroxyurea (HU) treatment and find that cell length variability increases only when the growth rate exceeds this threshold. The population effect is also reproduced in single-cell studies using agar-pad cultures and ‘mother machine’-based experiments to achieve synchrony. To test the role of RecA, critical for the repair of stalled replication forks, we examine the CVL of E. coli ΔrecA cells. We find cell length variability in the mutant to be greater than wild-type, a phenotype that is rescued by plasmid-based RecA expression. Additionally, we find that RecA-GFP protein recruitment to nucleoids is more frequent at growth rates exceeding the growth rate threshold and is further enhanced on HU treatment. Thus, we find growth rates greater than a threshold result in increased E. coli cell lengths in the population, and this effect is, at least in part, mediated by RecA recruitment to the nucleoid and stochastic inhibition of division. PMID:28386413

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

    USGS Publications Warehouse

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

    2006-01-01

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

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

    PubMed

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

    2015-01-01

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

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

    USGS Publications Warehouse

    Mech, L. David; Fieberg, John

    2015-01-01

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

  14. Accelerated adhesion of grafted skins by laser-induced stress wave-based gene transfer of hepatocyte growth factor

    NASA Astrophysics Data System (ADS)

    Aizawa, Kazuya; Sato, Shunichi; Saitoh, Daizoh; Tsuda, Hitoshi; Ashida, Hiroshi; Obara, Minoru

    2009-02-01

    In our previous study, we delivered plasmid DNA coding for human hepatocyto growth factor (hHGF) to rat skin grafts based on laser-induced stress wave (LISW), by which production of CD31-positive cells in the grafted skins was found to be enhanced, suggesting improved angiogenesis. In this study, we validated the efficacy of this method to accelerate adhesion of grafted skins; reperfusion and reepithelialization in the grafted skins were examined. As a graft, dorsal skin of a rat was exsected and its subcutaneous fat was removed. Plasmid DNA expression vector for hHGF was injected into the graft; on its back surface a laser target with a transparent sheet for plasma confinement was placed, and irradiated with three nanosecond laser pulses at a laser fluence of 1.2 J/cm2 (532 nm; spot diameter, 3 mm) to generate LISWs. After the application of LISWs, the graft was transplanted onto its donor site. We evaluated blood flow by laser Doppler imaging and analyzed reepithelialization based on immunohistochemistry as a function of postgrafting time. It was found that both reperfusion and reepithelialization were significantly enhanced for the grafts with gene transfection than for normal grafts; reepithelialization was completed within 7 days after transplantation with the transfected grafts. These findings demonstrate that adhesion of grafted skins can be accelerated by delivering HGF gene to the grafts based on LISWs.

  15. Biomaterials with persistent growth factor gradients in vivo accelerate vascularized tissue formation.

    PubMed

    Akar, Banu; Jiang, Bin; Somo, Sami I; Appel, Alyssa A; Larson, Jeffery C; Tichauer, Kenneth M; Brey, Eric M

    2015-12-01

    Gradients of soluble factors play an important role in many biological processes, including blood vessel assembly. Gradients can be studied in detail in vitro, but methods that enable the study of spatially distributed soluble factors and multi-cellular processes in vivo are limited. Here, we report on a method for the generation of persistent in vivo gradients of growth factors in a three-dimensional (3D) biomaterial system. Fibrin loaded porous poly (ethylene glycol) (PEG) scaffolds were generated using a particulate leaching method. Platelet derived growth factor BB (PDGF-BB) was encapsulated into poly (lactic-co-glycolic acid) (PLGA) microspheres which were placed distal to the tissue-material interface. PLGA provides sustained release of PDGF-BB and its diffusion through the porous structure results in gradient formation. Gradients within the scaffold were confirmed in vivo using near-infrared fluorescence imaging and gradients were present for more than 3 weeks. The diffusion of PDGF-BB was modeled and verified with in vivo imaging findings. The depth of tissue invasion and density of blood vessels formed in response to the biomaterial increased with magnitude of the gradient. This biomaterial system allows for generation of sustained growth factor gradients for the study of tissue response to gradients in vivo.

  16. Accelerated growth plate mineralization and foreshortened proximal limb bones in fetuin-A knockout mice.

    PubMed

    Seto, Jong; Busse, Björn; Gupta, Himadri S; Schäfer, Cora; Krauss, Stefanie; Dunlop, John W C; Masic, Admir; Kerschnitzki, Michael; Zaslansky, Paul; Boesecke, Peter; Catalá-Lehnen, Philip; Schinke, Thorsten; Fratzl, Peter; Jahnen-Dechent, Willi

    2012-01-01

    The plasma protein fetuin-A/alpha2-HS-glycoprotein (genetic symbol Ahsg) is a systemic inhibitor of extraskeletal mineralization, which is best underscored by the excessive mineral deposition found in various tissues of fetuin-A deficient mice on the calcification-prone genetic background DBA/2. Fetuin-A is known to accumulate in the bone matrix thus an effect of fetuin-A on skeletal mineralization is expected. We examined the bones of fetuin-A deficient mice maintained on a C57BL/6 genetic background to avoid bone disease secondary to renal calcification. Here, we show that fetuin-A deficient mice display normal trabecular bone mass in the spine, but increased cortical thickness in the femur. Bone material properties, as well as mineral and collagen characteristics of cortical bone were unaffected by the absence of fetuin-A. In contrast, the long bones especially proximal limb bones were severely stunted in fetuin-A deficient mice compared to wildtype littermates, resulting in increased biomechanical stability of fetuin-A deficient femora in three-point-bending tests. Elevated backscattered electron signal intensities reflected an increased mineral content in the growth plates of fetuin-A deficient long bones, corroborating its physiological role as an inhibitor of excessive mineralization in the growth plate cartilage matrix--a site of vigorous physiological mineralization. We show that in the case of fetuin-A deficiency, active mineralization inhibition is a necessity for proper long bone growth.

  17. Accelerated crack growth, residual stress, and a cracked zinc coated pressure shell

    NASA Technical Reports Server (NTRS)

    Dittman, Daniel L.; Hampton, Roy W.; Nelson, Howard G.

    1987-01-01

    During a partial inspection of a 42 year old, operating, pressurized wind tunnel at NASA-Ames Research Center, a surface connected defect 114 in. long having an indicated depth of a 0.7 in. was detected. The pressure shell, constructed of a medium carbon steel, contains approximately 10 miles of welds and is cooled by flowing water over its zinc coated external surface. Metallurgical and fractographic analysis showed that the actual detect was 1.7 in. deep, and originated from an area of lack of weld penetration. Crack growth studies were performed on the shell material in the laboratory under various loading rates, hold times, and R-ratios with a simulated shell environment. The combination of zinc, water with electrolyte, and steel formed an electrolytic cell which resulted in an increase in cyclic crack growth rate by as much as 500 times over that observed in air. It was concluded that slow crack growth occurred in the pressure shell by a combination of stress corrosion cracking due to the welding residual stress and corrosion fatigue due to the cyclic operating stress.

  18. Accelerated Growth Plate Mineralization and Foreshortened Proximal Limb Bones in Fetuin-A Knockout Mice

    PubMed Central

    Gupta, Himadri S.; Schäfer, Cora; Krauss, Stefanie; Dunlop, John W. C.; Masic, Admir; Kerschnitzki, Michael; Zaslansky, Paul; Boesecke, Peter; Catalá-Lehnen, Philip; Schinke, Thorsten; Fratzl, Peter; Jahnen-Dechent, Willi

    2012-01-01

    The plasma protein fetuin-A/alpha2-HS-glycoprotein (genetic symbol Ahsg) is a systemic inhibitor of extraskeletal mineralization, which is best underscored by the excessive mineral deposition found in various tissues of fetuin-A deficient mice on the calcification-prone genetic background DBA/2. Fetuin-A is known to accumulate in the bone matrix thus an effect of fetuin-A on skeletal mineralization is expected. We examined the bones of fetuin-A deficient mice maintained on a C57BL/6 genetic background to avoid bone disease secondary to renal calcification. Here, we show that fetuin-A deficient mice display normal trabecular bone mass in the spine, but increased cortical thickness in the femur. Bone material properties, as well as mineral and collagen characteristics of cortical bone were unaffected by the absence of fetuin-A. In contrast, the long bones especially proximal limb bones were severely stunted in fetuin-A deficient mice compared to wildtype littermates, resulting in increased biomechanical stability of fetuin-A deficient femora in three-point-bending tests. Elevated backscattered electron signal intensities reflected an increased mineral content in the growth plates of fetuin-A deficient long bones, corroborating its physiological role as an inhibitor of excessive mineralization in the growth plate cartilage matrix - a site of vigorous physiological mineralization. We show that in the case of fetuin-A deficiency, active mineralization inhibition is a necessity for proper long bone growth. PMID:23091616

  19. Sex differentiation in postnatal growth rate: a test in a wild boar population.

    PubMed

    Gaillard, J -M; Pontier, D; Brandt, S; Jullien, J-M; Allainé, D

    1992-05-01

    In wild boar individual growth rate is linear between 0.5 and 6 months after birth, based on successive body weight measurements. Contrary to expectation for a dimorphic and polygynous mammal like wild boar, no sexual dimorphism in growth rate could be detected between 0.5 and 6 months. We argue that high total maternal invesment in offspring due to large litter size and/or strong selection for early reproduction in this population with a short generation time could explain this absence of early differentiation in postnatal growth rate according to offspring sex.

  20. Minimization of transverse beam-emittance growth in the 90-degree bending section of the RAON rare-isotope accelerator

    NASA Astrophysics Data System (ADS)

    Oh, B. H.; Yoon, M.

    2016-11-01

    The major contribution of the transverse beam emittance growth (EG) in a RAON heavy-ion accelerator comes from the bending section, which consists of a charge-stripping section, a matching section, and a charge-selection section in sequence. In this paper, we describe our research to minimize the two-dimensional EG in the 90-degree bending section of the RAON currently being developed in Korea. The EG minimization was achieved with the help of multi-objective genetic algorithms and the simplex method. We utilized those algorithms to analyze the 90-degree bending section in a driver linac for the in-flight fragmentation system. Horizontal and vertical EGs were limited to below 10 % in the bending section by adjustment of the transverse beam optics upstream from the charge-stripping section, redesign of the charge-selection section, and optimization of the vertical beam optics at the entrance of a charge-selection section.

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

    USGS Publications Warehouse

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

    2014-01-01

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

  2. Arabidopsis thaliana root elongation growth is sensitive to lunisolar tidal acceleration and may also be weakly correlated with geomagnetic variations

    PubMed Central

    Barlow, Peter W.; Fisahn, Joachim; Yazdanbakhsh, Nima; Moraes, Thiago A.; Khabarova, Olga V.; Gallep, Cristiano M.

    2013-01-01

    Background Correlative evidence suggests a relationship between the lunisolar tidal acceleration and the elongation rate of arabidopsis roots grown under free-running conditions of constant low light. Methods Seedlings of Arabidopsis thaliana were grown in a controlled-climate chamber maintained at a constant temperature and subjected to continuous low-level illumination from fluorescent tubes, conditions that approximate to a ‘free-running’ state in which most of the abiotic factors that entrain root growth rates are excluded. Elongation of evenly spaced, vertical primary roots was recorded continuously over periods of up to 14 d using high temporal- and spatial-resolution video imaging and were analysed in conjunction with geophysical variables. Key Results and Conclusions The results confirm the lunisolar tidal/root elongation relationship. Also presented are relationships between the hourly elongation rates and the contemporaneous variations in geomagnetic activity, as evaluated from the disturbance storm time and ap indices. On the basis of time series of root elongation rates that extend over ≥4 d and recorded at different seasons of the year, a provisional conclusion is that root elongation responds to variation in the lunisolar force and also appears to adjust in accordance with variations in the geomagnetic field. Thus, both lunisolar tidal acceleration and the geomagnetic field should be considered as modulators of root growth rate, alongside other, stronger and more well-known abiotic environmental regulators, and perhaps unexplored factors such as air ions. Major changes in atmospheric pressure are not considered to be a factor contributing to oscillations of root elongation rate. PMID:23532042

  3. Truncated serine/arginine-rich splicing factor 3 accelerates cell growth through up-regulating c-Jun expression.

    PubMed

    Kano, Shizuka; Nishida, Kensei; Nishiyama, Chihiro; Akaike, Yoko; Kajita, Keisuke; Kurokawa, Ken; Masuda, Kiyoshi; Kuwano, Yuki; Tanahashi, Toshihito; Rokutan, Kazuhito

    2013-01-01

    Serine/arginine-rich splicing factor 3 (SRSF3), a member of the SRSF family, plays a wide-ranging role in gene expression. The human SRSF3 gene generates a major mRNA isoform encoding a functional, full-length protein and a PTC-containing isoform (SRSF3-PTC). The latter is expected to be degraded through the nonsense-mediated mRNA decay system. However, it was reported that SRSF3-PTC mRNA was produced under stressful conditions and translated into a truncated SRSF3 protein (SRSF3-TR). To disclose unknown functions of SRSF3-TR, we established Flp-In-293 cells stably expressing SRSF3-TR. The SRSF3-TR-expressing cells increased mRNA and protein levels of positive regulators for G1 to S phase transition (cyclin D1, cyclin D3, CDC25A, and E2F1) and accelerated their growth. c-Jun is required for progression through the G1 phase, the mechanism by which involves transcriptional control of the cyclin D1 gene. We also found that the JUN promoter activity was significantly increased in the Flp-In-293 cells stably expressing SRSF3-TR, compared with mock-transfected control cells. The SRSF3-TR-expressing cells increased c-Jun and Sp-1 levels, which are important for the positive autoregulation and basal transcription of JUN, respectively. Our results suggest that stress-inducible SRSF3-TR may participate in the acceleration of cell growth through facilitating c-Jun-mediated G1 progression under stressful conditions.

  4. Theory of a microfluidic serial dilution bioreactor for growth of planktonic and biofilm populations.

    PubMed

    Hsu, Sze-Bi; Yang, Ya-Tang

    2016-04-01

    We present the theory of a microfluidic bioreactor with a two-compartment growth chamber and periodic serial dilution. In the model, coexisting planktonic and biofilm populations exchange by adsorption and detachment. The criteria for coexistence and global extinction are determined by stability analysis of the global extinction state. Stability analysis yields the operating diagram in terms of the dilution and removal ratios, constrained by the plumbing action of the bioreactor. The special case of equal uptake function and logistic growth is analytically solved and explicit growth curves are plotted. The presented theory is applicable to generic microfluidic bioreactors with discrete growth chambers and periodic dilution at discrete time points. Therefore, the theory is expected to assist the design of microfluidic devices for investigating microbial competition and microbial biofilm growth under serial dilution conditions.

  5. Meeting the Sustainable Development Goals leads to lower world population growth

    PubMed Central

    Abel, Guy J.; Barakat, Bilal; KC, Samir; Lutz, Wolfgang

    2016-01-01

    Here we show the extent to which the expected world population growth could be lowered by successfully implementing the recently agreed-upon Sustainable Development Goals (SDGs). The SDGs include specific quantitative targets on mortality, reproductive health, and education for all girls by 2030, measures that will directly and indirectly affect future demographic trends. Based on a multidimensional model of population dynamics that stratifies national populations by age, sex, and level of education with educational fertility and mortality differentials, we translate these goals into SDG population scenarios, resulting in population sizes between 8.2 and 8.7 billion in 2100. Because these results lie outside the 95% prediction range given by the 2015 United Nations probabilistic population projections, we complement the study with sensitivity analyses of these projections that suggest that those prediction intervals are too narrow because of uncertainty in baseline data, conservative assumptions on correlations, and the possibility of new policies influencing these trends. Although the analysis presented here rests on several assumptions about the implementation of the SDGs and the persistence of educational, fertility, and mortality differentials, it quantitatively illustrates the view that demography is not destiny and that policies can make a decisive difference. In particular, advances in female education and reproductive health can contribute greatly to reducing world population growth. PMID:27911797

  6. Meeting the Sustainable Development Goals leads to lower world population growth.

    PubMed

    Abel, Guy J; Barakat, Bilal; Kc, Samir; Lutz, Wolfgang

    2016-12-13

    Here we show the extent to which the expected world population growth could be lowered by successfully implementing the recently agreed-upon Sustainable Development Goals (SDGs). The SDGs include specific quantitative targets on mortality, reproductive health, and education for all girls by 2030, measures that will directly and indirectly affect future demographic trends. Based on a multidimensional model of population dynamics that stratifies national populations by age, sex, and level of education with educational fertility and mortality differentials, we translate these goals into SDG population scenarios, resulting in population sizes between 8.2 and 8.7 billion in 2100. Because these results lie outside the 95% prediction range given by the 2015 United Nations probabilistic population projections, we complement the study with sensitivity analyses of these projections that suggest that those prediction intervals are too narrow because of uncertainty in baseline data, conservative assumptions on correlations, and the possibility of new policies influencing these trends. Although the analysis presented here rests on several assumptions about the implementation of the SDGs and the persistence of educational, fertility, and mortality differentials, it quantitatively illustrates the view that demography is not destiny and that policies can make a decisive difference. In particular, advances in female education and reproductive health can contribute greatly to reducing world population growth.

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

    PubMed Central

    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

    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. PMID:22893556

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

    USGS Publications Warehouse

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

    2015-01-01

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

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

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

    ERIC Educational Resources Information Center

    Wallace, Robert L.

    2005-01-01

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

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

    ERIC Educational Resources Information Center

    Ninbet, Steven; Hurley, Gabrielle; Weldon, Elizabeth

    2006-01-01

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

  12. Notes on the Age of Maternity, Population Growth and Family Structure in the Past

    ERIC Educational Resources Information Center

    Mendels, Franklin F.

    1978-01-01

    Emphasizes that the age of marriage was effective in determining the birth rate and the rate of population growth; measures the magnitude of the effects of the age of marriage; and offers some observations on the relationships between age of marriage, age of male and female fertility, and family structure. (Author)

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

    ERIC Educational Resources Information Center

    McDonald, Michael A.; And Others

    1996-01-01

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

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

    ERIC Educational Resources Information Center

    Jacobsen, Judith E.

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

  15. A Novel Aldehyde Dehydrogenase-3 Activator (Alda-89) Protects Submandibular Gland Function from Irradiation without Accelerating Tumor Growth

    PubMed Central

    Xiao, Nan; Cao, Hongbin; Chen, Che-Hong; Kong, Christina S.; Ali, Rehan; Chan, Cato; Sirjani, Davud; Graves, Edward; Koong, Albert; Giaccia, Amato; Mochly-Rosen, Daria; Le, Quynh-Thu

    2013-01-01

    Purpose To determine the effect of Alda-89 (an ALDH3 activitor) on (1) the function of irradiated (RT) submandibular gland (SMG) in mice, (2) its toxicity profile and (3) its effect on the growth of head and neck cancer (HNC) in vitro and in vivo. Experimental Design Adult mice were infused with Alda-89 or vehicle before, during and after RT. Saliva secretion was monitored weekly. Hematology, metabolic profile and post-mortem evaluation for toxicity were examined at the time of sacrifice. Alda-89 or vehicle was applied to HNC cell lines in vitro, and SCID mice transplanted with HNC in vivo with or without radiation; HNC growth was monitored. The ALDH3A1 and ALDH3A2 protein expression was evaluated in 89 HNC patients and correlated to freedom from relapse (FFR) and overall survival (OS). Results Alda-89 infusion significantly resulted in more whole saliva production and a higher percentage of preserved acini after RT compared to vehicle control. There was no difference in the complete blood count, metabolic profile, and major organ morphology between the Alda-89 and vehicle groups. Compared to vehicle control, Alda-89 treatment did not accelerate HNC cell proliferation in vitro, nor did it affect tumor growth in vivo with or without RT. Higher expression of ALDH3A1 or ALDH3A2 was not significantly associated with worse FFR or OS in either HPV-positive or HPV-negative group. Conclusion Alda-89 preserves salivary function after RT without affecting HNC growth or causing measurable toxicity in mice. It is a promising candidate to mitigate RT-related xerostomia. PMID:23812668

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

    PubMed Central

    Stutz, Aaron Jonas

    2014-01-01

    To Malthus, rapid human population growth—so evident in 18th Century Europe—was obviously unsustainable. In his Essay on the Principle of Population, Malthus cogently argued that environmental and socioeconomic constraints on population rise were inevitable. Yet, he penned his essay on the eve of the global census size reaching one billion, as nearly two centuries of super-exponential increase were taking off. Introducing a novel extension of J. E. Cohen's hallmark coupled difference equation model of human population dynamics and carrying capacity, this article examines just how elastic population growth limits may be in response to demographic change. The revised model involves a simple formalization of how consumption costs influence carrying capacity elasticity over time. Recognizing that complex social resource-extraction networks support ongoing consumption-based investment in family formation and intergenerational resource transfers, it is important to consider how consumption has impacted the human environment and demography—especially as global population has become very large. Sensitivity analysis of the consumption-cost model's fit to historical population estimates, modern census data, and 21st Century demographic projections supports a critical conclusion. The recent population explosion was systemically determined by long-term, distinctly pre-industrial cultural evolution. It is suggested that modern globalizing transitions in technology, susceptibility to infectious disease, information flows and accumulation, and economic complexity were endogenous products of much earlier biocultural evolution of family formation's embeddedness in larger, hierarchically self-organizing cultural systems, which could potentially support high population elasticity of carrying capacity. Modern super-exponential population growth cannot be considered separately from long-term change in the multi-scalar political economy that connects family formation and

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

    PubMed

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

    2012-01-01

    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.

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

    PubMed

    Mensforth, R P

    1985-10-01

    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.

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

    PubMed Central

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

    2012-01-01

    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

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

    PubMed

    Howat, Peter; Stoneham, Melissa

    2011-12-01

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

  1. Association with pathogenic bacteria affects life-history traits and population growth in Caenorhabditis elegans.

    PubMed

    Diaz, S Anaid; Mooring, Eric Q; Rens, Elisabeth G; Restif, Olivier

    2015-04-01

    Determining the relationship between individual life-history traits and population dynamics is an essential step to understand and predict natural selection. Model organisms that can be conveniently studied experimentally at both levels are invaluable to test the rich body of theoretical literature in this area. The nematode Caenorhabditis elegans, despite being a well-established workhorse in genetics, has only recently received attention from ecologists and evolutionary biologists, especially with respect to its association with pathogenic bacteria. In order to start filling the gap between the two areas, we conducted a series of experiments aiming at measuring life-history traits as well as population growth of C. elegans in response to three different bacterial strains: Escherichia coli OP50, Salmonella enterica Typhimurium, and Pseudomonas aeruginosa PAO1. Whereas previous studies had established that the latter two reduced the survival of nematodes feeding on them compared to E. coli OP50, we report for the first time an enhancement in reproductive success and population growth for worms feeding on S. enterica Typhimurium. Furthermore, we used an age-specific population dynamic model, parameterized using individual life-history assays, to successfully predict the growth of populations over three generations. This study paves the way for more detailed and quantitative experimental investigation of the ecology and evolution of C. elegans and the bacteria it interacts with, which could improve our understanding of the fate of opportunistic pathogens in the environment.

  2. The Probiotic Mixture VSL#3 Accelerates Gastric Ulcer Healing by Stimulating Vascular Endothelial Growth Factor

    PubMed Central

    Dharmani, Poonam; De Simone, Claudio; Chadee, Kris

    2013-01-01

    Studies assessing the effect and mechanism of probiotics on diseases of the upper gastrointestinal tract (GI) including gastric ulcers are limited despite extensive work and promising results of this therapeutic option for other GI diseases. In this study, we investigated the mechanisms by which the probiotic mixture VSL#3 (a mixture of eight probiotic bacteria including Lactobacilli, Bifidobacteria and Streptococcus species) heals acetic acid induced gastric ulcer in rats. VSL#3 was administered orally at low (6×109 bacteria) or high (1.2×1010 bacteria) dosages from day 3 after ulcer induction for 14 consecutive days. VSL#3 treatments significantly enhanced gastric ulcer healing in a dose-dependent manner. To assess the mechanism(s) whereby VSL#3 exerted its protective effects, we quantified the gene expression of several pro-inflammatory cytokines, protein and expression of stomach mucin-Muc5ac, regulatory cytokine-IL-10, COX-2 and various growth factors. Of all the components examined, only expression and protein production of VEGF was increased 332-fold on day 7 in the ulcerated tissues of animals treated with VSL#3. Predictably, animals treated with VEGF neutralizing antibody significantly delayed gastric ulcer healing in VSL#3 treated animals. This is the first report to demonstrate high efficacy of the probiotic mixture VSL#3 in enhancing gastric ulcer healing. Probiotic efficacy was effective at higher concentrations of VSL#3 by specifically increasing the expression and production of angiogenesis promoting growth factors, primarily VEGF. PMID:23484048

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

    PubMed

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

    2006-03-07

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

  4. The growth hormone receptor gene is associated with mandibular height in a Chinese population.

    PubMed

    Zhou, J; Lu, Y; Gao, X H; Chen, Y C; Lu, J J; Bai, Y X; Shen, Y; Wang, B K

    2005-11-01

    Genetic influences are important in the determination of mandibular morphology, and growth hormone receptor (GHR) is believed to have an important influence on the growth of craniofacial bone. In this study, we used quantitative trait locus methods to evaluate the relationship between craniofacial morphology and single-nucleotide polymorphisms (SNPs) in GHR in an unselected healthy Chinese population. We systematically screened the 10 exons and nearby introns of GHR and identified 6 SNPs. Using 4 SNPs as markers, we studied the relationships between genotypes and craniofacial linear measurements. Individuals with the genotype CC of polymorphism I526L had a significantly greater mandibular ramus length (condylion-gonion/ articulare-gonion) than those with genotype AC or AA. Haplotype analysis showed that there were also significant differences between the long and short mandibular height groups in an extreme population. Our results indicate that the GHR gene polymorphism I526L is associated with mandibular height in the Chinese population.

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

    PubMed Central

    Hone, Jim; Sibly, Richard M

    2002-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-09-01

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

  7. Comparing growth patterns among field populations of cereal aphids reveals factors limiting their maximum abundance.

    PubMed

    Honek, A; Jarosik, V; Dixon, A F G

    2006-06-01

    Cereal stands in central Europe are commonly infested with three species of aphids that may become serious pests. With increasing abundance, the proportion of a particular species in the total aphid population may remain constant, suggesting a density-independent exponential growth, or the proportion can change, suggesting density-dependent constraints on growth. The constraints that affect particular species, and thus their relative abundance, were studied. The proportionality between maximum abundances of the cereal aphids was studied using a 10-year census of the numbers of aphids infesting 268 winter wheat plots. For two species their abundance on leaves and ears was compared. With increasing aphid density the maximum abundance of Rhopalosiphum padi (Linnaeus) remained proportional, but not that of Sitobion avenae (Fabricius), which was constrained by the smaller surface area of ears compared to leaves. There was no evidence of inter-specific competition. Maximum abundance of R. padi and Metopolophium dirhodum (Walker) on leaves did not change proportionally as the proportion of M. dirhodum decreased with increasing overall aphid density. This decrease was probably caused by the restricted distribution of M. dirhodum, which is confined to leaves, where space is limiting. No change in proportion between populations was detected when the average densities were below 0.54 aphids per leaf or ear. Non-proportional relationships between aphid populations appeared to be due to spatial constraints, acting upon the more abundant population. Detecting the limitation of population growth can help with the assessment of when density-independent exponential growth is limited by density-dependent factors. This information may help in the development of models of cereal aphid population dynamics.

  8. Carbon dioxide enrichment alters plant community structure and accelerates shrub growth in the shortgrass steppe.

    PubMed

    Morgan, Jack A; Milchunas, Daniel G; LeCain, Daniel R; West, Mark; Mosier, Arvin R

    2007-09-11

    A hypothesis has been advanced that the incursion of woody plants into world grasslands over the past two centuries has been driven in part by increasing carbon dioxide concentration, [CO(2)], in Earth's atmosphere. Unlike the warm season forage grasses they are displacing, woody plants have a photosynthetic metabolism and carbon allocation patterns that are responsive to CO(2), and many have tap roots that are more effective than grasses for reaching deep soil water stores that can be enhanced under elevated CO(2). However, this commonly cited hypothesis has little direct support from manipulative experimentation and competes with more traditional theories of shrub encroachment involving climate change, management, and fire. Here, we show that, although doubling [CO(2)] over the Colorado shortgrass steppe had little impact on plant species diversity, it resulted in an increasingly dissimilar plant community over the 5-year experiment compared with plots maintained at present-day [CO(2)]. Growth at the doubled [CO(2)] resulted in an approximately 40-fold increase in aboveground biomass and a 20-fold increase in plant cover of Artemisia frigida Willd, a common subshrub of some North American and Asian grasslands. This CO(2)-induced enhancement of plant growth, among the highest yet reported, provides evidence from a native grassland suggesting that rising atmospheric [CO(2)] may be contributing to the shrubland expansions of the past 200 years. Encroachment of shrubs into grasslands is an important problem facing rangeland managers and ranchers; this process replaces grasses, the preferred forage of domestic livestock, with species that are unsuitable for domestic livestock grazing.

  9. Adding Biotin to Parenteral Nutrition Solutions Without Lipid Accelerates the Growth of Candida albicans

    PubMed Central

    Kuwahara, Takashi; Kaneda, Shinya; Shimono, Kazuyuki

    2016-01-01

    Background: We have previously demonstrated that Candida albicans requires multivitamins (MVs) or lipid to increase rapidly in parenteral nutrition (PN) solutions. In this study, in detail, the effects of vitamins on the growth of C. albicans in PN solutions without lipid were investigated. Methods: In the 1st experiment, a commercial PN solution without lipid was supplemented with water-soluble vitamins (SVs: vitamins B1, B2, B6, B12 and C, folic acid, nicotinamide, biotin and panthenol), water-insoluble vitamins (IVs: vitamins A, D, E and K) or both (MVs). In the 2nd experiment, the test solutions were prepared by supplementing the PN solution with one of each or all of the SVs. In the 3rd experiment, another commercial peripheral PN (PPN) solution without lipid was supplemented with SVs, nicotinic acid, biotin or both nicotinic acid and biotin. In each of the experiments, a specified number of C. albicans organisms was added to each test solution, and all of the test solutions were allowed to stand at room temperature (23-26ºC). The number of C. albicans was counted at 0, 24, 48 and 72 hours after the addition of the organism. Results: In the 1st experiment, the C. albicans increased rapidly in the PN solution supplemented with the SVs, but increased slowly without the SVs, regardless of the addition of the IVs. In the 2nd experiment, the C. albicans increased rapidly in the PN solution supplemented with the SVs or biotin, but increased slowly with each of the other water-soluble vitamins. In the 3rd experiment, the C. albicans increased rapidly in the PPN solution supplemented with the SVs or biotin, but increased slowly with the addition of nicotinic acid. Conclusions: These results suggested that adding MVs or SVs to PN solutions without lipid promotes the growth of C. albicans, and that this effect is mostly attributable to biotin. PMID:27648003

  10. Toward intelligent synthetic neural circuits: directing and accelerating neuron cell growth by self-rolled-up silicon nitride microtube array.

    PubMed

    Froeter, Paul; Huang, Yu; Cangellaris, Olivia V; Huang, Wen; Dent, Erik W; Gillette, Martha U; Williams, Justin C; Li, Xiuling

    2014-11-25

    In neural interface platforms, cultures are often carried out on a flat, open, rigid, and opaque substrate, posing challenges to reflecting the native microenvironment of the brain and precise engagement with neurons. Here we present a neuron cell culturing platform that consists of arrays of ordered microtubes (2.7-4.4 μm in diameter), formed by strain-induced self-rolled-up nanomembrane (s-RUM) technology using ultrathin (<40 nm) silicon nitride (SiNx) film on transparent substrates. These microtubes demonstrated robust physical confinement and unprecedented guidance effect toward outgrowth of primary cortical neurons, with a coaxially confined configuration resembling that of myelin sheaths. The dynamic neural growth inside the microtube, evaluated with continuous live-cell imaging, showed a marked increase (20×) of the growth rate inside the microtube compared to regions outside the microtubes. We attribute the dramatic accelerating effect and precise guiding of the microtube array to three-dimensional (3D) adhesion and electrostatic interaction with the SiNx microtubes, respectively. This work has clear implications toward building intelligent synthetic neural circuits by arranging the size, site, and patterns of the microtube array, for potential treatment of neurological disorders.

  11. Toward Intelligent Synthetic Neural Circuits: Directing and Accelerating Neuron Cell Growth by Self-Rolled-Up Silicon Nitride Microtube Array

    PubMed Central

    2015-01-01

    In neural interface platforms, cultures are often carried out on a flat, open, rigid, and opaque substrate, posing challenges to reflecting the native microenvironment of the brain and precise engagement with neurons. Here we present a neuron cell culturing platform that consists of arrays of ordered microtubes (2.7–4.4 μm in diameter), formed by strain-induced self-rolled-up nanomembrane (s-RUM) technology using ultrathin (<40 nm) silicon nitride (SiNx) film on transparent substrates. These microtubes demonstrated robust physical confinement and unprecedented guidance effect toward outgrowth of primary cortical neurons, with a coaxially confined configuration resembling that of myelin sheaths. The dynamic neural growth inside the microtube, evaluated with continuous live-cell imaging, showed a marked increase (20×) of the growth rate inside the microtube compared to regions outside the microtubes. We attribute the dramatic accelerating effect and precise guiding of the microtube array to three-dimensional (3D) adhesion and electrostatic interaction with the SiNx microtubes, respectively. This work has clear implications toward building intelligent synthetic neural circuits by arranging the size, site, and patterns of the microtube array, for potential treatment of neurological disorders. PMID:25329686

  12. Accelerated adhesion of grafted skin by laser-induced stress wave-based gene transfer of hepatocyte growth factor

    NASA Astrophysics Data System (ADS)

    Aizawa, Kazuya; Sato, Shunichi; Terakawa, Mitsuhiro; Saitoh, Daizoh; Tsuda, Hitoshi; Ashida, Hiroshi; Obara, Minoru

    2009-11-01

    Gene therapy using wound healing-associated growth factor gene has received much attention as a new strategy for improving the outcome of tissue transplantation. We delivered plasmid DNA coding for human hepatocyte growth factor (hHGF) to rat free skin grafts by the use of laser-induced stress waves (LISWs); autografting was performed with the grafts. Systematic analysis was conducted to evaluate the adhesion properties of the grafted tissue; angiogenesis, cell proliferation, and reepithelialization were assessed by immunohistochemistry, and reperfusion was measured by laser Doppler imaging as a function of time after grafting. Both the level of angiogenesis on day 3 after grafting and the increased ratio of blood flow on day 4 to that on day 3 were significantly higher than those in five control groups: grafting with hHGF gene injection alone, grafting with control plasmid vector injection alone, grafting with LISW application alone, grafting with LISW application after control plasmid vector injection, and normal grafting. Reepithelialization was almost completed on day 7 even at the center of the graft with LISW application after hHGF gene injection, while it was not for the grafts of the five control groups. These findings demonstrate the validity of our LISW-based HGF gene transfection to accelerate the adhesion of grafted skins.

  13. [The population growth in the city of Beijing and our present tasks (author's transl)].

    PubMed

    Qian, L J; Xu, B; Huang, S Y

    1980-04-01

    Concern for the rapid population growth since 1949 of China's second largest city, Beijing, is discussed in terms of population control, migration, and rises in the productive development of the city. From 1949 to 1963 the natural rate of population increased from 7.5 to 35.3%; however, after the introduction of a birth control program in 1971, the natural increase of population declined to 4.02% in 1977. From 1949-1978, the average birth rate was 145,000/year while the average death rate was 46,500/year, leaving the annual average increase in population at 98,000. The natural population increased by 2,340,000 from 1949-1978. The massive population growth since 1949 affected the economic development of the city as well as the country. Cultivated land near Beijing increased from 1949-1952, but because of urban development the land for cultivation decreased by 1,527,000 market acres from that available in 1949 (7,965,000 market acres). Population density increased from 430 persons/ square kilometer in 1962 to 506 persons/ square kilometer in 1978. From 1953 to 1978, production and consumption rates fluctuated with a net balance of only 2020 million catties in the 26 years, causing the need for products to be imported from other areas of the country. Unemployment is exacerbated by the lack of jobs and increasing numbers of people. Transportation problems also have developed. New efforts are being made to inform people of population control by the Beijing Population Association begun in 1979, because Beijing's population will continue to increase until 1989 due to the baby boom years during the fifties which created a 2nd boom in the late 1970s as well as the lack of education on population control. Other programs are being developed to, 1) educate people on economical measures of reducing the population, 2) promote governmental departments to improve birth control programs by means of social security services, child health agencies, and nursing schools, 3

  14. Contrasting Responses of Arctic Tussock Tundra to Early Season Snow Melt: Growth Acceleration Versus Frost Damage

    NASA Astrophysics Data System (ADS)

    Oberbauer, S. F.; Starr, G.; Pop, E. W.; Ahlquist, L. E.; Parker, I. C.

    2003-12-01

    Climate warming scenarios for the Arctic include early snow melt marking the beginning of the growing season. From the perspective of the vegetation, early snow melt may have advantageous or disadvantageous effects. With warm weather following snow melt, bud break and flowering will occur early providing a longer period for growth and photosynthesis. However, if very cold weather follows snowmelt, plants will be exposed directly to freezing conditions that plants under the snow would not. Such exposed plants may suffer freeze damage and delayed bud break. We have been experimentally manipulating snow cover at Toolik Lake, Alaska, since 1995. In 9 years of early snow removal treatments, in only two years has the second scenario occurred, in 2001 and 2002. Here we document the effects of very cold conditions following snow removal on green biomass as assessed by NDVI of treatment plots relative to controls. In 2001 evergreens shrubs were killed, bud break was delayed, and NDVI was lower on treatment plots relative to controls. In contrast, in a year with warm spring temperatures following snow melt, 1999, NDVI on treatment plots was significantly greater than that of controls. Cold conditions following snow melt may lead to death of shrubs and delayed budbreak, effects that will carry over throughout the growing season and ultimately, affect community composition and ecosystem function.

  15. Lack of fibroblast growth factor 21 accelerates metabolic liver injury characterized by steatohepatities in mice

    PubMed Central

    Liu, Xingkai; Zhang, Ping; Martin, Robert C; Cui, Guozhen; Wang, Guangyi; Tan, Yi; Cai, Lu; Lv, Guoyue; Li, Yan

    2016-01-01

    Fibroblast growth factor 21 (FGF21) concentrations are increased in human subjects who either have type 2 diabetes or nonalcoholic fatty liver disease (NAFLD). While excessive fat in the liver promotes the release of pro-inflammatory cytokines, NAFLD progresses from steatosis to non alcoholic steatohepatitis (NASH), a more aggressive form of hepatic damage, and lastly toward cirrhosis and HCC. In our previous study, loss of FGF21 is associated with hyper-proliferation, aberrant p53, and HCC development in diabetes mice. In this study, we proposed to investigate the liver metabolic disorders by diabetes and the potential roles of FGF21 played in NASH and potential carcinogenetic transformation of HCC. NASH was induced in FGF21 knockout (FGF21KO) mice by streptozotocin administration or fed with high fat diet (HFD). The pathological transformation of steatohepatities as well as parameters of inflammation, lipid metabolism, cellular events, mesenchymal-epithelial transition (MET) and Wnt/β-catenin signaling was determined in the FGF21 KO diabetic mice and HFD fed mice. We found that mice lacking the FGF21 gene are more prone to develop NASH. A compromised microenvironment of NASH, which could facilitate the HCC carcinogenetic transformation, was found in FGF21 KO mice under metabolic disorders by diabetes and HFD feeding. This study provided further evidence that lack of FGF21 worsened the metabolic disorders in NASH and could render a tumor microenvironment for HCC initiation and progression in the liver of diabetes mice. PMID:27293995

  16. Hepatocyte Growth Factor Prevents Acute Renal Failure of Accelerates Renal Regeneration in mice

    NASA Astrophysics Data System (ADS)

    Kawaida, Kouichi; Matsumoto, Kunio; Shimazu, Hisaaki; Nakamura, Toshikazu

    1994-05-01

    Although acute renal failure is encountered with administration of nephrotoxic drugs, ischemia, or unilateral nephrectomy, there has been no effective drug which can be used in case of acute renal failure. Hepatocyte growth factor (HGF) is a potent hepatotropic factor for liver regeneration and is known to have mitogenic, motogenic, and morphogenic activities for various epithelial cells, including renal tubular cells. Intravenous injection of recombinant human HGF into mice remarkably suppressed increases in blood urea nitrogen and serum creatinine caused by administration of cisplatin, a widely used antitumor drug, or HgCl_2, thereby indicating that HGF strongly prevented the onset of acute renal dysfunction. Moreover, exogenous HGF stimulated DNA synthesis of renal tubular cells after renal injuries caused by HgCl_2 administration and unilateral nephrectomy and induced reconstruction of the normal renal tissue structure in vivo. Taken together with our previous finding that expression of HGF was rapidly induced after renal injuries, these results allow us to conclude that HGF may be the long-sought renotropic factor for renal regeneration and may prove to be effective treatment for patients with renal dysfunction, especially that caused by cisplatin.

  17. The intrinsic growth rate as a predictor of population viability under climate warming.

    PubMed

    Amarasekare, Priyanga; Coutinho, Renato M

    2013-11-01

    1. Lately, there has been interest in using the intrinsic growth rate (rm) to predict the effects of climate warming on ectotherm population viability. However, because rm is calculated using the Euler-Lotka equation, its reliability in predicting population persistence depends on whether ectotherm populations can achieve a stable age/stage distribution in thermally variable environments. Here, we investigate this issue using a mathematical framework that incorporates mechanistic descriptions of temperature effects on vital rates into a stage-structured population model that realistically captures the temperature-induced variability in developmental delays that characterize ectotherm life cycles. 2. We find that populations experiencing seasonal temperature variation converge to a stage distribution whose intra-annual pattern remains invariant across years. As a result, the mean annual per capita growth rate also remains constant between years. The key insight is the mechanism that allows populations converge to a stationary stage distribution. Temperature effects on the biochemical processes (e.g. enzyme kinetics, hormonal regulation) that underlie life-history traits (reproduction, development and mortality) exhibit well-defined thermodynamical properties (e.g. changes in entropy and enthalpy) that lead to predictable outcomes (e.g. reduction in reaction rates or hormonal action at temperature extremes). As a result, life-history traits exhibit a systematic and predictable response to seasonal temperature variation. This in turn leads to temporally predictable temperature responses of the stage distribution and the per capita growth rate. 3. When climate warming causes an increase in the mean annual temperature and/or the amplitude of seasonal fluctuations, the population model predicts the mean annual per capita growth rate to decline to zero within 100 years when warming is slow relative to the developmental period of the organism (0.03-0.05°C per year) and to

  18. Fifty years of population growth and absorption of labor in Brazil: from 1950 to 2000.

    PubMed

    Paiva, P D

    1997-01-01

    For a long time, the Brazilian population has grown at a relatively high rate, and only recently has the process of demographic transition intensified in the country. While the associated decline in fertility could result in a future decline in the size of the working-age population, it could also lead to an increase in female participation in the labor market. Brazil's economy is performing well, with gross domestic product (GDP) growing at an average annual rate of 7.1% during 1947-80. Marked growth in industrial employment opportunities has accompanied this growth in GDP. The size of the informal sector, however, has not decreased in similar proportion, while the 1981-83 economic crisis caused urban employment levels to drop, especially in industry and construction. Moreover, the level of rural-urban migration has increased and the agricultural employment index has fallen. The author evaluates past growth trends of the Economically Active Population (EAP) and of employment in Brazil, and assesses the potential growth of the labor force until the year 2000.

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

    USGS Publications Warehouse

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

    2015-01-01

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

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

    PubMed

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

    1999-01-01

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

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

    PubMed

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

    2015-02-01

    Globally, greenhouse gas budgets are dominated by natural sources, and aquatic ecosystems are a prominent source of methane (CH(4)) to the atmosphere. Beaver (Castor canadensis and Castor fiber) populations have experienced human-driven change, and CH(4) emissions associated with their habitat remain uncertain. This study reports the effect of near extinction and recovery of beavers globally on aquatic CH4 emissions and habitat. Resurgence of native beaver populations and their introduction in other regions accounts for emission of 0.18-0.80 Tg CH(4) year(-1) (year 2000). This flux is approximately 200 times larger than emissions from the same systems (ponds and flowing waters that became ponds) circa 1900. Beaver population recovery was estimated to have led to the creation of 9500-42 000 km(2) of ponded water, and increased riparian interface length of >200 000 km. Continued range expansion and population growth in South America and Europe could further increase CH(4) emissions.

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

    PubMed

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

    2014-05-01

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

  3. Trans-generational influences of sulfamethoxazole on lifespan, reproduction and population growth of Caenorhabditis elegans.

    PubMed

    Yu, Zhenyang; Sun, Guohua; Liu, Yanjun; Yin, Daqiang; Zhang, Jing

    2017-01-01

    Trans-generational effects are increasingly used to indicate long-term influences of environmental pollutants. However, such studies can be complex and yield inconclusive results. In this study, the trans-generational effects of sulfamethoxazole (SMX) on Caenorhabditis elegans on lifespan, reproduction and population growth were tested for 7 consecutive generations, which included gestating generation (F0), embryo-exposed generation (F1), germline-exposed generation (F2), the first non-exposed generation (F3) and the three following generations (F4-F6). Results showed that lifespan was significantly affected by embryo exposure (F1) at 400µm SMX with a value as low as 47% of the control. The reproduction (a total brood size as 49% of the control) and population growth (81% of the control) were significantly affected in germline exposure (F2). Lifespan and reproduction were severely inhibited in non-exposed generations, confirming the real trans-generational effects. Notably, initial reproduction and reproduction duration showed opposite generation-related changes, indicating their interplay in the overall brood size. The population growth rate was well correlated with median lethal time, brood size and initial reproduction, which indicated that the population would increase when the nematodes lived longer and reproduced more offspring within shorter duration.

  4. [Some fundamental problems concerning the relationship between population growth and economic development].

    PubMed

    Huang, Z

    1983-05-29

    The population growth rate is closely related to the quality of economic life, available funds for individual and social consumption, national income to be used for reproduction, and the labor employment situation. Since liberation, socialism has not been able to show its superiority, mainly because of China's large population figure, low economic productivity, low national income, and poor management in the relationship between consumption and accumulation. In order to solve these problems, we need to adequately control the pace of the population growth and match the rate of population growth with the pace of economic development. A way to increase national income is through saving and avoiding unnecessary waste. Social expenditures on education, culture, science, health and medical care, social welfare, and investment in the promotion of people's wisdom should all be increased. Meanwhile, the living standard of the people needs to be raised, and capital accumulation should also be managed so that funds will be available for industrial and economic enterprises. Existing inefficient production enterprises should be properly reorganized so that full employment may be achieved. In this way, the national economy will have more prosperity, and the people will benefit more from the Socialist policy.

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

    PubMed

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

    2015-01-01

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

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

    PubMed

    Kozusko, F; Bourdeau, M

    2011-12-01

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

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

    PubMed Central

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

    2015-01-01

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

  8. Chile confronts its environmental health future after 25 years of accelerated growth

    PubMed Central

    Pino, Paulina; Iglesias, Verónica; Garreaud, René; Cortés, Sandra; Canals, Mauricio; Folch, Walter; Burgos, Soledad; Levy, Karen; Naeher, Luke P.; Steenland, Kyle

    2015-01-01

    Background Chile has recently been reclassified by the World Bank from an upper middle income country to a higher income country. There has been great progress in the last 20–30 years in relation to air and water pollution in Chile. Yet after 25 years of unrestrained growth there remain clear challenges posed by air and water, as well as climate change. Methods: In late 2013 a three-day workshop on environmental health was held in Santiago, bringing together researchers and government policy makers. As a follow-up to that workshop, here we review the progress made in environmental health in the past 20–30 years, and discuss the challenges of the future. We focus on air and water pollution, and climate change, which we believe are among the most important areas of environmental health in Chile. Results Air pollution in some cities remains among the highest in the continent. Potable water is generally available, but weak state supervision has led to serious outbreaks of infectious disease and ongoing issues with arsenic exposure in some regions. Climate change modeling in Chile is quite sophisticated, and a number of the impacts of climate change can be reasonably predicted in terms of which areas of the country are most likely to be affected by increased temperature and decreased availability of water, as well as expansion of vector territory. Some health effects, including change vector-borne diseases and excess heat mortality, can be predicted. However, there has yet to be an integration of such research with government planning. Conclusion While great progress has been made, currently there are a number of problems. We suspect that the Chilean experience in environmental health may be of some use for other Latin American countries with rapid economic development. PMID:26615070

  9. Boundary layer infusion of basic fibroblast growth factor accelerates intimal hyperplasia in endarterectomized canine artery.

    PubMed

    Chen, C; Li, J; Mattar, S G; Pierce, G F; Aukerman, L; Hanson, S R; Lumsden, A B

    1997-05-01

    We examined the effects of human recombinant basic fibroblast growth factor (bFGF) on the proliferation and migration of cultured dog smooth muscle cells (SMCs) and endothelial cells (ECs) and the effect of continuous local boundary layer infusion of bFGF on intimal hyperplasia in endarterectomized dog artery. In vitro proliferation and migration of dog SMCs or ECs were performed using direct counting and Boyden's chamber, respectively. At a dose of 10 ng/mL, bFGF significantly promoted both SMC and EC proliferation (7- and 4-fold, respectively) and migration (2.3- and 1.9-fold, respectively). Six dogs underwent bilateral carotid endarterectomies. A newly designed local infusion device with an osmotic pump continuously delivered bFGF to one artery or vehicle solution to the contralateral artery for 14 days. The intimal thickness and area in the bFGF-treated vessels were increased by 72 and 81%, respectively, compared with control arteries (P < 0.05). As assessed by the bromodeoxyuridine index, the proliferative activity was increased by 73% in bFGF-treated arteries (P = 0.03). Furthermore, cell proliferation at the distal anastomoses of local infusion device was significantly increased in the bFGF-infused grafts compared with distal anastomoses in the control grafts (13.24 +/- 1.24% versus 5.24 +/- 1.01%, P < 0.01). These data demonstrate that human recombinant bFGF has a potent effect on dog SMC and EC proliferation and migration, and that local infusion of exogenous bFGF significantly enhances the intimal hyperplasia formation and cell proliferation to vascular injury. We conclude that the bFGF pathway may contribute to the development of intimal hyperplastic lesions.

  10. Living bacteria rheology: population growth, aggregation patterns, and collective behavior under different shear flows.

    PubMed

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

    2014-08-01

    The activity of growing living bacteria was investigated using real-time and in situ rheology-in stationary and oscillatory shear. Two different strains of the human pathogen Staphylococcus aureus-strain COL and its isogenic cell wall autolysis mutant, RUSAL9-were considered in this work. For low bacteria density, strain COL forms small clusters, while the mutant, presenting deficient cell separation, forms irregular larger aggregates. In the early stages of growth, when subjected to a stationary shear, the viscosity of the cultures of both strains increases with the population of cells. As the bacteria reach the exponential phase of growth, the viscosity of the cultures of the two strains follows different and rich behaviors, with no counterpart in the optical density or in the population's colony-forming units measurements. While the viscosity of strain COL culture keeps increasing during the exponential phase and returns close to its initial value for the late phase of growth, where the population stabilizes, the viscosity of the mutant strain culture decreases steeply, still in the exponential phase, remains constant for some time, and increases again, reaching a constant plateau at a maximum value for the late phase of growth. These complex viscoelastic behaviors, which were observed to be shear-stress-dependent, are a consequence of two coupled effects: the cell density continuous increase and its changing interacting properties. The viscous and elastic moduli of strain COL culture, obtained with oscillatory shear, exhibit power-law behaviors whose exponents are dependent on the bacteria growth stage. The viscous and elastic moduli of the mutant culture have complex behaviors, emerging from the different relaxation times that are associated with the large molecules of the medium and the self-organized structures of bacteria. Nevertheless, these behaviors reflect the bacteria growth stage.

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

    PubMed

    Barr, Brannon; Wolverton, Steve

    2014-10-01

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

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

    NASA Astrophysics Data System (ADS)

    Barr, Brannon; Wolverton, Steve

    2014-10-01

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

  13. Measuring selection in human populations using the growth rate per generation.

    PubMed

    Ewbank, Douglas

    2016-04-19

    Estimates of the speed of evolution between generations depend on the association between individual traits and a measure of fitness. The two most frequently used measures of fitness are the net reproduction rate and the 1-year growth factor implied by the fertility and mortality rates. Results based on the two lead to very different results. The reason is that the 1-year growth factor is not a measure of change between generations. Therefore, studies of changes between generations should use the amount of growth over the length of a generation. This is especially important for studies of human populations because of the long length of generation. In addition, estimates based on a single year's growth are overly sensitive to data on individuals who fail to reproduce. The effects of using a generational measure are demonstrated using data from Kenya and Ukraine. These results demonstrate that using a 1-year growth rate to measure fitness leads to estimates that understate the rate at which evolution changes the characteristics of a human population.

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

    PubMed

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

    2016-01-01

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

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

    PubMed Central

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

    2016-01-01

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

  16. Recombinant growth factor mixtures induce cell cycle progression and the upregulation of type I collagen in human skin fibroblasts, resulting in the acceleration of wound healing processes.

    PubMed

    Lee, Do Hyun; Choi, Kyung-Ha; Cho, Jae-We; Kim, So Young; Kwon, Tae Rin; Choi, Sun Young; Choi, Yoo Mi; Lee, Jay; Yoon, Ho Sang; Kim, Beom Joon

    2014-05-01

    Application of growth factor mixtures has been used for wound healing and anti-wrinkles agents. The aim of this study was to evaluate the effect of recombinant growth factor mixtures (RGFM) on the expression of cell cycle regulatory proteins, type I collagen, and wound healing processes of acute animal wound models. The results showed that RGFM induced increased rates of cell proliferation and cell migration of human skin fibroblasts (HSF). In addition, expression of cyclin D1, cyclin E, cyclin-dependent kinase (Cdk)4, and Cdk2 proteins was markedly increased with a growth factor mixtures treatment in fibroblasts. Expression of type I collagen was also increased in growth factor mixtures-treated HSF. Moreover, growth factor mixtures-induced the upregulation of type I collagen was associated with the activation of Smad2/3. In the animal model, RGFM-treated mice showed accelerated wound closure, with the closure rate increasing as early as on day 7, as well as re-epithelization and reduced inflammatory cell infiltration than phosphate-buffered saline (PBS)-treated mice. In conclusion, the results indicated that RGFM has the potential to accelerate wound healing through the upregulation of type I collagen, which is partly mediated by activation of Smad2/3-dependent signaling pathway as well as cell cycle progression in HSF. The topical application of growth factor mixtures to acute and chronic skin wound may accelerate the epithelization process through these molecular mechanisms.

  17. Population Growth of the Generalist Mite Tyrophagus putrescentiae (Acari: Acaridida) Following Adaptation to High- or Low-Fat and High- or Low-Protein Diets and the Effect of Dietary Switch.

    PubMed

    Erban, Tomas; Rybanska, Dagmar; Hubert, Jan

    2015-12-01

    Tyrophagus putrescentiae (Schrank, 1781) is a cosmopolitan generalist feeder that prefers foodstuffs of high-fat and high-protein content. Our aim was to investigate the population growth of T. putrescentiae after long-term nutritional adaptation to two distinct diets that are commonly infested in the synanthropic environment. Crushed dry dog food kernels provided a high-fat, high-protein, and low-carbohydrate diet, whereas wholemeal spelt flour provided a low-protein, low-fat, and high-carbohydrate diet. After >6 mo of nutritional adaptation, each of the two populations were used in two 28-d population growth tests: one that mites remained on their adaptation diet (homogenous diet treatment) and one that mites underwent a dietary switch (dietary switch treatment). Dietary treatment, nutritional adaptation, and their interaction all significantly influenced population growth. The homogenous diet treatment showed 7.5 times higher growth on the dog food diet than on flour. In the dietary switch, flour-adapted mites switching to dog food experienced five times greater population growth than the flour-adapted mites remained on flour, whereas the dog food-adapted population showed a 2.8-fold decrease in population growth when transferred to the flour. A comparison of means between the two dietary switch treatments showed a 1.9-fold higher population growth after flour-adapted mites were shifted to dog food than when the dog food-adapted mites were shifted to flour. We demonstrated that T. putrescentiae is able survive and reproduce for many generations on dry dog food and flour with different levels of success. High-fat and -protein food accelerated T. putrescentiae population growth compared with the high-carbohydrate diet.

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

    PubMed

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

    2010-03-22

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

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

    PubMed

    Salgado, Mauricio

    2015-09-07

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

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

    USGS Publications Warehouse

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

    2007-01-01

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

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

    PubMed Central

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

    2010-01-01

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

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

    PubMed Central

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

    2010-01-01

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

  3. The factors of urban population growth: net inmigration versus natural increase.

    PubMed

    Ledent, J

    1982-10-01

    "As a country evolves from a traditional to an advanced society, the part of urban growth that is due to net inmigration follows a simple pattern, which can be described by an inverted U-shaped curve: it first increases, then passes through a maximum, and decreases thereafter. This hypothesis is confirmed by quantitative analysis using time-series and cross-section data. The analysis suggests that in the second half of this century natural increase often provides a slightly higher contribution to urban population growth than net inmigration." (summary in FRE, ITA, JPN, )

  4. Periodic matrix population models: growth rate, basic reproduction number, and entropy.

    PubMed

    Bacaër, Nicolas

    2009-10-01

    This article considers three different aspects of periodic matrix population models. First, a formula for the sensitivity analysis of the growth rate lambda is obtained that is simpler than the one obtained by Caswell and Trevisan. Secondly, the formula for the basic reproduction number R0 in a constant environment is generalized to the case of a periodic environment. Some inequalities between lambda and R0 proved by Cushing and Zhou are also generalized to the periodic case. Finally, we add some remarks on Demetrius' notion of evolutionary entropy H and its relationship to the growth rate lambda in the periodic case.

  5. [Relationship between growth potential of pine, population density of Monochamus alternatus and pathogenicity of Bursaphlenchus xyloophilus].

    PubMed

    Ding, Y; Lü, C; Han, B; Pou, H; Wu, M

    2001-06-01

    The results showed that the growth potential of pine (x) is negative related to the population density of Monochamus alternatus (y) and the pathoyenecity of Bursaphlenchus xyloophilus (z). But the population density of Monochamus alternatus is positively related to the pathogenicity of Bursaphlenchus xyloophilus. Three linear equations regression line were established as y = 1793.771 - 16404.47x, z = 31.80989 - 241.9274x, y = -407.611 + 70.51478z. Correlation coefficient is -0.8139, -0.8770 and +0.9864 respectively.

  6. Impacts of population growth, urbanisation and sanitation changes on global human Cryptosporidium emissions to surface water.

    PubMed

    Hofstra, Nynke; Vermeulen, Lucie C

    2016-10-01

    Cryptosporidium is a pathogenic protozoan parasite and is a leading cause of diarrhoea worldwide. The concentration of Cryptosporidium in the surface water is a determinant for probability of exposure and the risk of disease. Surface water concentrations are expected to change with population growth, urbanisation and changes in sanitation. The objective of this paper is to assess the importance of future changes in population, urbanisation and sanitation on global human emissions of Cryptosporidium to surface water. The GloWPa-Crypto H1 (the Global Waterborne Pathogen model for Human Cryptosporidium emissions version 1) model is presented and run for 2010 and with scenarios for 2050. The new scenarios are based on the Shared Socio-economic Pathways (SSPs) developed for the climate community. The scenarios comprise assumptions on sanitation changes in line with the storylines and population and urbanisation changes from the SSPs. In SSP1 population growth is limited, urbanisation large and sanitation and waste water treatment strongly improve. SSP1* is the same as SSP1, but waste water treatment does not improve. SSP3 sees large population growth, moderate urbanisation and sanitation and waste water treatment fractions that are the same as in 2010. Total global Cryptosporidium emissions to surface water for 2010 are estimated to be 1.6×10(17) oocysts per year, with hotspots in the most urbanised parts of the world. In 2050 emissions are expected to decrease by 24% or increase by 52% and 70% for SSP1, SSP3 and SSP1* respectively. The emissions increase in all scenarios for countries in the Middle East and Africa (MAF) region, while emissions in large parts in Europe decrease in scenarios SSP1 and SSP3. Improving sanitation by connecting the population to sewers, should be combined with waste water treatment, otherwise (SSP1*) emissions in 2050 are expected to be much larger than in a situation with strong population growth and slow development of safe water and

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

    ERIC Educational Resources Information Center

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

    2005-01-01

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

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

    ERIC Educational Resources Information Center

    Hobart, Christine L.

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

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

    USGS Publications Warehouse

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

    2006-01-01

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

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

    PubMed

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

    2010-01-01

    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.

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

    PubMed

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

    2009-03-01

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

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

    PubMed Central

    1992-01-01

    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

  13. Evidence of exponential growth of an anammox population in an anaerobic batch culture.

    PubMed

    Yasuda, Tomoko; Waki, Miyoko; Yoshinaga, Ikuo; Amano, Teruki; Suzuki, Kazuyoshi; Tanaka, Yasuo; Yamagishi, Takao; Suwa, Yuichi

    2011-01-01

    Twenty-five replicates of growth medium for anaerobic ammonium oxidation (anammox) containing (15)N-labeled ammonium and non-labeled nitrite were inoculated into an anammox enrichment culture at low density, and anaerobically incubated batchwise. In the headspace, (29)N(2) partial pressure linearly increased via anammox in 25 vials, confirming that anammox populations were viable in all subcultures. On prolonged incubation, exponential increases in (29)N(2) were not observed in all but 13 subcultures, suggesting that the anammox population may not proliferate unless all conditions for growth are satisfied. The estimated first-order rate coefficients in those 13 subcultures varied from 0.0029 to 0.0048 h(-1).

  14. Trends and predicted trends in presentations of older people to Australian emergency departments: effects of demand growth, population aging and climate change.

    PubMed

    Burkett, Ellen; Martin-Khan, Melinda G; Scott, Justin; Samanta, Mayukh; Gray, Leonard C

    2016-07-29

    . ED presentation growth was found to exceed population growth in all age groups. The rate of ED presentations per head of population was highest among those aged ≥85 years. ED utilisation projections to 2050, using standard Australian Bureau of Statistics population modelling, with and without adjustment for current ED growth, were developed. The projections demonstrated linear growth in ED presentation for those aged 0-84 years, with growth in ED presentations of the ≥85 year age group demonstrating marked acceleration after 2030.What are the implications for practitioners? Growth in ED presentations exceeding population growth suggests that current models of acute health care delivery require review to ensure that optimal care is delivered in the most fiscally efficient manner. Trends in presentation of older people emphasise the imperative for ED workforce planning and education in care of this complex patient cohort, and the requirement to review funding models to incentivise investment in ED avoidance and substitutive care models targeting older people.

  15. Fetal Growth and Risk of Stillbirth: A Population-Based Case–Control Study

    PubMed Central

    Bukowski, Radek; Hansen, Nellie I.; Willinger, Marian; Reddy, Uma M.; Parker, Corette B.; Pinar, Halit; Silver, Robert M.; Dudley, Donald J.; Stoll, Barbara J.; Saade, George R.; Koch, Matthew A.; Rowland Hogue, Carol J.; Varner, Michael W.; Conway, Deborah L.; Coustan, Donald; Goldenberg, Robert L.

    2014-01-01

    Background Stillbirth is strongly related to impaired fetal growth. However, the relationship between fetal growth and stillbirth is difficult to determine because of uncertainty in the timing of death and confounding characteristics affecting normal fetal growth. Methods and Findings We conducted a population-based case–control study of all stillbirths and a representative sample of live births in 59 hospitals in five geographic areas in the US. Fetal growth abnormalities were categorized as small for gestational age (SGA) (<10th percentile) or large for gestational age (LGA) (>90th percentile) at death (stillbirth) or delivery (live birth) using population, ultrasound, and individualized norms. Gestational age at death was determined using an algorithm that considered the time-of-death interval, postmortem examination, and reliability of the gestational age estimate. Data were weighted to account for the sampling design and differential participation rates in various subgroups. Among 527 singleton stillbirths and 1,821 singleton live births studied, stillbirth was associated with SGA based on population, ultrasound, and individualized norms (odds ratio [OR] [95% CI]: 3.0 [2.2 to 4.0]; 4.7 [3.7 to 5.9]; 4.6 [3.6 to 5.9], respectively). LGA was also associated with increased risk of stillbirth using ultrasound and individualized norms (OR [95% CI]: 3.5 [2.4 to 5.0]; 2.3 [1.7 to 3.1], respectively), but not population norms (OR [95% CI]: 0.6 [0.4 to 1.0]). The associations were stronger with more severe SGA and LGA (<5th and >95th percentile). Analyses adjusted for stillbirth risk factors, subset analyses excluding potential confounders, and analyses in preterm and term pregnancies showed similar patterns of association. In this study 70% of cases and 63% of controls agreed to participate. Analysis weights accounted for differences between consenting and non-consenting women. Some of the characteristics used for individualized fetal growth estimates were missing

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

    PubMed

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

    2014-09-01

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

  17. Prenatal growth acceleration in maxillary deciduous canines of children with Down syndrome: histological and chemical composition study.

    PubMed

    Keinan, David; Smith, Patricia; Zilberman, Uri

    2007-10-01

    Previous studies have reported that the abnormal development of the second deciduous molar in Down syndrome and cerebral palsy begins before birth. In view of these results we have turned our attention to the earlier stages of dental development in utero, represented by the primary canine, in order to see if we can identify more precisely the origin and timing of developmental insults in these conditions. The study was carried out on exfoliated or extracted maxillary primary canines of children with Down syndrome (DS) and cerebral palsy (CP) and they were compared to a control group of children with no adverse medical history. Thin sections were made through the mid-sagittal bucco-palatinal axis. Using a light microscope, the width of prenatal enamel and postnatal enamel, defined by the neonatal line was measured on each section at a standardized location. The chemical composition of the enamel was then measured at three different locations using an energy dispersive spectrophotometer (ESR) in a high vacuum mode. The total enamel width in DS and controls was similar and greater than that of CP canines. Significantly more enamel was laid down prenatally in DS teeth than in controls or CP and it was more highly mineralized. These results for DS canines differ from those previously published for the later developing second primary molars. They support the hypothesis of accelerated growth in the early stages of intra-uterine development, prior to the establishment of reduced growth trajectories in the later stages. The results for CP teeth showed that more prenatal enamel was laid down prenatally than in controls. Mineralization in CP was poor during the first two trimesters and improved significantly during the last trimester. While this approach is retrospective, we propose that it may aid in identifying the onset of developmental anomalies of unknown etiology that are expressed in later life.

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

    PubMed

    Picard, Nicolas; Liang, Jingjing

    2014-01-01

    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 (λ) 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 λ to matrix dimension was linked to the existence of fast pathways (i.e. the fraction of individuals that systematically move up a class), whose proportion increases when class width increases. We showed that for matrix population models with growth transition only from class i to class i + 1, λ 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 λ 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 λ. Moreover, λ 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 λ for tree species.

  19. Population growth and allergen accumulation of Dermatophagoides pteronyssinus cultured at 20 and 25 °C.

    PubMed

    Yella, Lakshmi; Morgan, Marjorie S; Arlian, Larry G

    2011-02-01

    The house dust mites, Dermatophagoides pteronyssinus and D. farinae are cultured commercially and in research laboratories and material is harvested from these cultures to make extracts that are used for diagnosis, immunotherapy and research. Temperature and other climatic conditions can influence population growth rates, dynamics of allergen production, and the associated endotoxin, enzyme and protein levels of the mite material harvested from these cultures. Here we determined how temperature affected these parameters. Dermatophagoides pteronyssinus was cultured at 20 and 25 °C at 75% relative humidity, and at 2-week intervals the concentrations of mites, Der p 1 and Der p 2 allergens, endotoxin, and selected enzymes were determined. Mite density increased exponentially but growth rate and final population density were greater at 25 °C compared to 20 °C. The combined allergen (Der p 1 + Der p 2) concentrations accumulated in the cultures at about the same rate at both temperatures. However, individual Der p 1 and Der p 2 accumulation rates varied independently at the two temperatures. Der p 1 accumulated faster at 20 °C whereas Der p 2 accumulated faster at 25 °C. The amount of Der p 1 in whole cultures was greater than the amount of Der p 2. The concentration of allergen for washed mites harvested from the cultures was much less than for the whole cultures. Our study demonstrated that temperature is an important factor in population growth and the dynamics of allergen production in cultured mites.

  20. Population growth, interest rate, and housing tax in the transitional China

    NASA Astrophysics Data System (ADS)

    He, Ling-Yun; Wen, Xing-Chun

    2017-03-01

    This paper combines and develops the models in Lastrapes (2002) and Mankiw and Weil (1989), which enables us to analyze the effects of interest rate and population growth shocks on housing price in one integrated framework. Based on this model, we carry out policy simulations to examine whether the housing (stock or flow) tax reduces the housing price fluctuations caused by interest rate or population growth shocks. Simulation results imply that the choice of housing tax tools depends on the kind of shock that housing market faces. In the situation where the housing price volatility is caused by the population growth shock, the flow tax can reduce the volatility of housing price while the stock tax makes no difference to it. If the shock is resulting from the interest rate, the policy maker should not impose any kind of the housing taxes. Furthermore, the effect of one kind of the housing tax can be strengthened by that of the other type of housing tax.

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

    PubMed

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

    2007-02-01

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

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

    NASA Astrophysics Data System (ADS)

    Farooq, M.; Muslim, M.

    2014-11-01

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

  3. Loss of Mig6 accelerates initiation and progression of mutant epidermal growth factor receptor-driven lung adenocarcinoma

    PubMed Central

    Maity, Tapan K.; Venugopalan, Abhilash; Linnoila, Ilona; Cultraro, Constance M.; Giannakou, Andreas; Nemati, Roxanne; Zhang, Xu; Webster, Joshua D.; Ritt, Daniel; Ghosal, Sarani; Hoschuetzky, Heinz; Simpson, R. Mark; Biswas, Romi; Politi, Katerina; Morrison, Deborah K.; Varmus, Harold E.; Guha, Udayan

    2015-01-01

    Somatic mutations in the epidermal growth factor receptor (EGFR) kinase domain drive lung adenocarcinoma. We have previously identified MIG6, an inhibitor of ERBB signaling and a potential tumor suppressor, as a target for phosphorylation by mutant EGFRs. Here we demonstrate that Mig6 is a tumor suppressor for the initiation and progression of mutant EGFR-driven lung adenocarcinoma in mouse models. Mutant EGFR-induced lung tumor formation was accelerated in Mig6-deficient mice, even with Mig6 haploinsufficiency. We demonstrate that constitutive phosphorylation of MIG6 at Y394/395 in EGFR-mutant human lung adenocarcinoma cell lines is associated with an increased interaction of MIG6 with mutant EGFR, which may stabilize EGFR protein. MIG6 also fails to promote mutant EGFR degradation. We propose a model whereby increased tyrosine phosphorylation of MIG6 decreases its capacity to inhibit mutant EGFR. Nonetheless, the residual inhibition is sufficient for Mig6 to delay mutant EGFR-driven tumor initiation and progression in mouse models. PMID:25735773

  4. Carbon nanotubes functionalized with fibroblast growth factor accelerate proliferation of bone marrow-derived stromal cells and bone formation

    NASA Astrophysics Data System (ADS)

    Hirata, Eri; Ménard-Moyon, Cécilia; Venturelli, Enrica; Takita, Hiroko; Watari, Fumio; Bianco, Alberto; Yokoyama, Atsuro

    2013-11-01

    Multi-walled carbon nanotubes (MWCNTs) were functionalized with fibroblast growth factor (FGF) and the advantages of their use as scaffolds for bone augmentation were evaluated in vitro and in vivo. The activity of FGF was assessed by measuring the effect on the proliferation of rat bone marrow stromal cells (RBMSCs). The presence of FGF enhanced the proliferation of RBMSCs and the FGF covalently conjugated to the nanotubes (FGF-CNT) showed the same effect as FGF alone. In addition, FGF-CNT coated sponges were implanted between the parietal bone and the periosteum of rats and the formation of new bone was investigated. At day 14 after implantation, a larger amount of newly formed bone was clearly observed in most pores of FGF-CNT coated sponges. These findings indicated that MWCNTs accelerated new bone formation in response to FGF, as well as the integration of particles into new bone during its formation. Scaffolds coated with FGF-CNT could be considered as promising novel substituting materials for bone regeneration in future tissue engineering applications.

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

    PubMed

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

    2014-12-01

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

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

    USGS Publications Warehouse

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

    2000-01-01

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

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

    PubMed Central

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

    2002-01-01

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

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

    PubMed

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

    2007-01-01

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

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed

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

    2015-12-22

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

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

    PubMed

    Leta, Samson; Mesele, Frehiwot

    2014-01-01

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

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

    PubMed

    Shaw, R P

    1992-02-01

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

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

    PubMed Central

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

    2014-01-01

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

  14. Determining individual variation in growth and its implication for life-history and population processes using the empirical Bayes method.

    PubMed

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

    2014-09-01

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

  15. Influence of Molecular Noise on the Growth of Single Cells and Bacterial Populations

    PubMed Central

    Schmidt, Mischa; Creutziger, Martin; Lenz, Peter

    2012-01-01

    During the last decades experimental studies have revealed that single cells of a growing bacterial population are significantly exposed to molecular noise. Important sources for noise are low levels of metabolites and enzymes that cause significant statistical variations in the outcome of biochemical reactions. In this way molecular noise affects biological processes such as nutrient uptake, chemotactic tumbling behavior, or gene expression of genetically identical cells. These processes give rise to significant cell-to-cell variations of many directly observable quantities such as protein levels, cell sizes or individual doubling times. In this study we theoretically explore if there are evolutionary benefits of noise for a growing population of bacteria. We analyze different situations where noise is either suppressed or where it affects single cell behavior. We consider two specific examples that have been experimentally observed in wild-type Escherichia coli cells: (i) the precision of division site placement (at which molecular noise is highly suppressed) and (ii) the occurrence of noise-induced phenotypic variations in fluctuating environments. Surprisingly, our analysis reveals that in these specific situations both regulatory schemes [i.e. suppression of noise in example (i) and allowance of noise in example (ii)] do not lead to an increased growth rate of the population. Assuming that the observed regulatory schemes are indeed caused by the presence of noise our findings indicate that the evolutionary benefits of noise are more subtle than a simple growth advantage for a bacterial population in nutrient rich conditions. PMID:22238678

  16. Early Stages Of Biome Shift in Boreal Alaska: Climate Sensitivity of Tree Growth and Accelerated Tree Mortality

    NASA Astrophysics Data System (ADS)

    Juday, G. P.; Grant, T.; Alix, C. M.; Spencer, D. L.; Beck, P. S.

    2012-12-01

    The boreal forest region of Alaska is characterized by a major east-west climate gradient, in addition to a widely appreciated north-south gradient. Low elevations of the eastern and central Interior experience warm summer temperatures and low annual precipitation, while coastal western Alaska has cool summer temperatures and greater precipitation. In the Interior the four dominant tree species of white and black spruce, aspen, and Alaska birch on low elevation sites nearly all register a strong negative radial growth relationship to summer temperatures, concentrated in May and July. Precipitation, particularly in late winter and midsummer, plays a supplemental role as a positive factor in growth. Floodplain white spruce along the Yukon and Kuskokwim Rivers transition from negative temperature response to positive response in western Alaska near the tree limit. Populations of white spruce on treeline sites display both negative growth response to July temperature and positive response to spring temperatures, with the negative response dominant in the east and the positive response dominant in the west. Across boreal Alaska summer temperatures increased abruptly in 1974, and have remained at historically high levels since. Correspondingly, climatic favorability for radial growth of Interior trees on most low elevation sites has been at extreme low levels particularly in the 21st century. Satellite-based NDVI coverage confirms that forest growth reduction is widespread in boreal Alaska since the 1980s. Defoliating and wood boring insects have reached outbreak population levels across most of boreal Alaska, partly from release of direct temperature control on the insects and partly from increased tree host susceptibility. Major outbreak species include aspen leaf miner, spruce engraver beetle, and spruce budworm. About a dozen tall willow species have been subjected to widespread attack by willow leaf blotch miner, and a new disease and defoliating insect have spread

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

    EPA Science Inventory

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

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

    USGS Publications Warehouse

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

    2008-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Bagan, H.; Yamagata, Y.

    2012-12-01

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

  20. Acceleration of wound healing in gastric ulcers by local injection of neutralising antibody to transforming growth factor beta 1.

    PubMed Central

    Ernst, H; Konturek, P; Hahn, E G; Brzozowski, T; Konturek, S J

    1996-01-01

    BACKGROUND: Application of neutralising antibodies (NAs) to transforming growth factor beta 1 (TGF beta 1) improves wound healing in experimental glomerulonephritis and dermal incision wounds. TGF beta 1 has been detected in the stomach, but despite the fact that this cytokine plays a central part in wound healing no information is available to determine if modulation of the TGF beta 1 profile influences the healing of gastric ulcers. This study examines gastric ulcer healing in the rat after local injection of NAs to TGF beta 1. METHOD: Chronic gastric ulcers were induced in Wistar rats by the application of 100% acetic acid to the serosal surface of the stomach. Immediately after ulcer induction and on day 2, NAs to TGF beta 1 (50 micrograms), TGF beta 1 (50 ng), saline or control antibodies (IgG; 50 micrograms) were locally injected into the subserosa. Controls received no subserosal injections. Animals were killed on day 5 or 11, the ulcer area was measured planimetrically, sections were embedded in paraffin wax, and stained with trichrome or haematoxylin and eosin. Depth of residual ulcer was assessed on day 11 by a scale of 0-3, the percentage of connective tissue was determined by a semiquantitative matrix score and granulocytes and macrophages in the ulcer bed were also assessed. RESULTS: The application of NAs to TGF beta 1 led to a significant acceleration of gastric ulcer healing on day 11 (0.6 (SD 0.8) v 3.7 (SD 2.6) mm2), a reduction in macrophages (23.7 (SD 22.6) v 38 (26) per 40 x power field) and granulocytes (8.5 (SD 5.6) v 20 (10) per 40 x power field), fewer histological residual ulcers (mean 1 (SD 0.9) v 2 (1.1)), a reduced matrix score, and a regenerative healing pattern. Excessive scarring was seen in the TGF beta 1 treated group. CONCLUSION: Further treatment of gastric ulcers may induce a new treatment modality by local injection of NA to TGF beta 1 in an attempt to accelerate and improve ulcer healing. Images Figure 2 Figure 3 PMID:8991853

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

    PubMed

    Rhein, E

    1994-08-25

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

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

    PubMed

    Short, R V

    2001-01-01

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

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

    PubMed

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

    2012-03-15

    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.

  4. Does Size Matter? A Study of Risk Perceptions of Global Population Growth.

    PubMed

    Dawson, Ian G J; Johnson, Johnnie E V

    2017-01-01

    The global human population now exceeds 7 billion and is projected to reach 10 billion around 2060. While population growth has been associated with certain benefits (e.g., economies of scale, technological advancements), theoretical models, probabilistic projections, and empirical evidence also indicate that this growth could increase the likelihood of many adverse events (e.g., climate change, resource shortages) and the impact of these events, as more people are exposed to the outcomes. While concerns about these issues are well-documented in the academic literature, there is little evidence concerning the public's perceptions of the risks associated with global population growth (GPG) and how these perceptions are likely to influence related decisions. To address these issues, we conducted a U.K.-based study that examined respondents' risk perceptions of GPG, their willingness to embrace mitigation/precautionary behaviors, and reasons for variations in these two factors. We found that GPG is perceived as a moderate-to-high risk, with concerns about the increased likelihood of resource shortages, ecological damage, and violent conflict being foremost. Respondents believed that the worst effects of GPG would arrive around 2050 and would be experienced by the world's poorest people. Respondents who perceived greater levels of risk from GPG were generally those who indicated a greater willingness to embrace mitigation behaviors (e.g., reduce resource consumption) and preventative actions (e.g., support political action to limit growth). We discuss how our findings might be utilized to better manage the potential challenges associated with GPG and we suggest several directions for further research.

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

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

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

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

    USGS Publications Warehouse

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

    2015-01-01

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

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

    SciTech Connect

    Vidal, J.; Smith, S.L.

    1985-09-01

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

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

    PubMed

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

    2007-01-01

    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.

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

    PubMed

    Jasmin, Jean-Nicolas; Zeyl, Clifford

    2012-12-01

    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.

  10. Influence of projected ocean warming on population growth potential in two North Atlantic copepod species

    NASA Astrophysics Data System (ADS)

    Stegert, Christoph; Ji, Rubao; Davis, Cabell S.

    2010-10-01

    Copepods of the genera Pseudocalanus and Centropages play an important role in the North Atlantic ecosystems and have distinctive spatial and temporal patterns depending on physiological adaptation to different environmental conditions. To examine the possible impact of climate change on these biogeographic patterns, potential population growth rate was computed for each species using IPCC projections of sea surface temperature together with chlorophyll distributions from SeaWiFS climatology and published laboratory data on temperature and food-dependent life-history parameters. The results indicate that the predicted temperature increase throughout the North Atlantic will cause temporal and spatial shifts in copepod species population growth potential. The Centropages population is projected to increase in mid-latitudinal shelf areas, e.g. the Gulf of Maine and the North Sea, due to shorter generation times and a longer growing season, while Pseudocalanus is predicted to be less abundant in these regions after 2050. These shifts potentially have a significant impact on the future demographics of pelagic fish species for which the copepods are the major food source.

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

    PubMed Central

    Taylor, Marylee C.; Schroeder, Matthew B.

    2014-01-01

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

  12. Endless urban growth? On the mismatch of population, household and urban land area growth and its effects on the urban debate.

    PubMed

    Haase, Dagmar; Kabisch, Nadja; Haase, Annegret

    2013-01-01

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

  13. Growth Factor-Activated Stem Cell Circuits and Stromal Signals Cooperatively Accelerate Non-Integrated iPSC Reprogramming of Human Myeloid Progenitors

    PubMed Central

    Park, Tea Soon; Huo, Jeffrey S.; Peters, Ann; Talbot, C. Conover; Verma, Karan; Zimmerlin, Ludovic; Kaplan, Ian M.; Zambidis, Elias T.

    2012-01-01

    Nonviral conversion of skin or blood cells into clinically useful human induced pluripotent stem cells (hiPSC) occurs in only rare fractions (∼0.001%–0.5%) of donor cells transfected with non-integrating reprogramming factors. Pluripotency induction of developmentally immature stem-progenitors is generally more efficient than differentiated somatic cell targets. However, the nature of augmented progenitor reprogramming remains obscure, and its potential has not been fully explored for improving the extremely slow pace of non-integrated reprogramming. Here, we report highly optimized four-factor reprogramming of lineage-committed cord blood (CB) myeloid progenitors with bulk efficiencies of ∼50% in purified episome-expressing cells. Lineage-committed CD33+CD45+CD34− myeloid cells and not primitive hematopoietic stem-progenitors were the main targets of a rapid and nearly complete non-integrated reprogramming. The efficient conversion of mature myeloid populations into NANOG+TRA-1-81+ hiPSC was mediated by synergies between hematopoietic growth factor (GF), stromal activation signals, and episomal Yamanaka factor expression. Using a modular bioinformatics approach, we demonstrated that efficient myeloid reprogramming correlated not to increased proliferation or endogenous Core factor expressions, but to poised expression of GF-activated transcriptional circuits that commonly regulate plasticity in both hematopoietic progenitors and embryonic stem cells (ESC). Factor-driven conversion of myeloid progenitors to a high-fidelity pluripotent state was further accelerated by soluble and contact-dependent stromal signals that included an implied and unexpected role for Toll receptor-NFκB signaling. These data provide a paradigm for understanding the augmented reprogramming capacity of somatic progenitors, and reveal that efficient induced pluripotency in other cell types may also require extrinsic activation of a molecular framework that commonly regulates self

  14. Results With Accelerated Partial Breast Irradiation in Terms of Estrogen Receptor, Progesterone Receptor, and Human Growth Factor Receptor 2 Status

    SciTech Connect

    Wilder, Richard B.; Curcio, Lisa D.; Khanijou, Rajesh K.; Eisner, Martin E.; Kakkis, Jane L.; Chittenden, Lucy; Agustin, Jeffrey; Lizarde, Jessica; Mesa, Albert V.; Macedo, Jorge C.; Ravera, John; Tokita, Kenneth M.

    2010-11-01

    Purpose: To report our results with accelerated partial breast irradiation (APBI) in terms of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER-2/neu) status. Methods and Materials: Between February 2003 and June 2009, 209 women with early-stage breast carcinomas were treated with APBI using multicatheter, MammoSite, or Contura brachytherapy to 34 Gy in 10 fractions twice daily over 5-7 days. Three patient groups were defined by receptor status: Group 1: ER or PR (+) and HER-2/neu (-) (n = 180), Group 2: ER and PR (-) and HER-2/neu (+) (n = 10), and Group 3: ER, PR, and HER-2/neu (-) (triple negative breast cancer, n = 19). Median follow-up was 22 months. Results: Group 3 patients had significantly higher Scarff-Bloom-Richardson scores (p < 0.001). The 3-year ipsilateral breast tumor control rates for Groups 1, 2, and 3 were 99%, 100%, and 100%, respectively (p = 0.15). Group 3 patients tended to experience relapse in distant sites earlier than did non-Group 3 patients. The 3-year relapse-free survival rates for Groups 1, 2, and 3 were 100%, 100%, and 81%, respectively (p = 0.046). The 3-year cause-specific and overall survival rates for Groups 1, 2, and 3 were 100%, 100%, and 89%, respectively (p = 0.002). Conclusions: Triple negative breast cancer patients typically have high-grade tumors with significantly worse relapse-free, cause-specific, and overall survival. Longer follow-up will help to determine whether these patients also have a higher risk of ipsilateral breast tumor relapse.

  15. Population growth rate and genetic variability of small and large populations of Red flour beetle (Tribolium castaneum) following multigenerational exposure to copper.

    PubMed

    Laskowski, Ryszard; Radwan, Jacek; Kuduk, Katarzyna; Mendrok, Magdalena; Kramarz, Paulina

    2015-07-01

    We reared large (1000 individuals) and small (20 individuals) populations of Tribolium castaneum on diet contaminated with copper in order to determine if the size of a population affects its ability to adapt to adverse environmental conditions. After 10 generations, we used microsatellite markers to estimate and subsequently compare the genetic variability of the copper-treated populations with that of the control populations, which were reared on uncontaminated medium. Additionally, we conducted a full cross-factorial experiment which evaluated the effects of 10 generations of "pre-exposure" to copper on a population's fitness in control and copper-contaminated environments. In order to distinguish results potentially arising from genetic adaptation from those due to non-genetic effects associated to parental exposure to copper, we subjected also F11 generation, originating from parents not exposed to copper, to the same cross-factorial experiment. The effects of long-term exposure to copper depended on population size: the growth rates of small populations that were pre-exposed to copper were inhibited compared to those of small populations reared in uncontaminated environments. Large Cu-exposed populations had a higher growth rate in the F10 generation compared to the control groups, while the growth rate of the F11 generation was unaffected by copper exposure history. The only factor that had a significant effect on genetic variability was population size, but this was to be expected given the large difference in the number of individuals between large and small populations. Neither copper contamination nor its interaction with population size affected the number of microsatellite alleles retained in the F10 generation.

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

    PubMed

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

    2011-12-01

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

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

    PubMed

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

    2011-10-22

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

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

    PubMed Central

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

    2011-01-01

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

  19. Intrauterine growth retardation and preterm delivery: prenatal risk factors in an indigent population.

    PubMed

    Wen, S W; Goldenberg, R L; Cutter, G R; Hoffman, H J; Cliver, S P

    1990-01-01

    Prenatally ascertained risk factors for low birth weight were evaluated in a population of 17,000 indigent women for their specific effect on intrauterine growth retardation and on the rate of preterm delivery. In a univariate analysis, intrauterine growth retardation occurred more frequently in women who were black, single, primiparous, less than 17 or greater than 30 years old, short, thin, had a previous preterm delivery, consumed alcohol, took drugs, or gained limited weight. Preterm delivery occurred significantly more frequently in women who were black, single, thin, less than 17 or greater than 30 years old, had less than a twelfth grade education, or gained limited weight. In logistic regression analyses, race, parity, maternal age, a history of preterm delivery, smoking, short stature, low weight, and low weight gain remained significant risk factors of intrauterine growth retardation. Of these factors, smoking, short stature, low weight, and low weight gain showed the greatest correlation. Factors significantly related to preterm delivery included black race, single marital status, younger or older ages, previous preterm delivery, smoking, low weight, and very low or high weight gain. A previous preterm delivery and very low maternal weight had the greatest correlation. Identification of specific risk factors of both intrauterine growth retardation and preterm delivery should aid in the development of strategies to reduce the prevalence of these conditions.

  20. Long-term growth of Desert Tortoises (Gopherus agassizii) in a southern Nevada population

    USGS Publications Warehouse

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

    2012-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Fedotov, Sergei; Moss, David; Campos, Daniel

    2008-08-01

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

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

    PubMed Central

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

    2013-01-01

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

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

    PubMed

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

    2013-07-22

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

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

    PubMed

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

    2012-12-01

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

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

    PubMed

    Dixon, B

    1995-01-01

    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

  6. A Stable Finite-Difference Scheme for Population Growth and Diffusion on a Map

    PubMed Central

    Callegari, S.; Lake, G. R.; Tkachenko, N.; Weissmann, J. D.; Zollikofer, Ch. P. E.

    2017-01-01

    We describe a general Godunov-type splitting for numerical simulations of the Fisher–Kolmogorov–Petrovski–Piskunov growth and diffusion equation on a world map with Neumann boundary conditions. The procedure is semi-implicit, hence quite stable. Our principal application for this solver is modeling human population dispersal over geographical maps with changing paleovegetation and paleoclimate in the late Pleistocene. As a proxy for carrying capacity we use Net Primary Productivity (NPP) to predict times for human arrival in the Americas. PMID:28085882

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

    PubMed

    Kapitsa, S

    1997-01-01

    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.

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

    PubMed

    Rowland, R H

    1997-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

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

    PubMed

    Patterson, J G; Shrestha, N R

    1988-01-01

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

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

    USGS Publications Warehouse

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

    2005-01-01

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