Sample records for heterogeneous student population

  1. Phenotypically heterogeneous populations in spatially heterogeneous environments.

    PubMed

    Patra, Pintu; Klumpp, Stefan

    2014-03-01

    The spatial expansion of a population in a nonuniform environment may benefit from phenotypic heterogeneity with interconverting subpopulations using different survival strategies. We analyze the crossing of an antibiotic-containing environment by a bacterial population consisting of rapidly growing normal cells and slow-growing, but antibiotic-tolerant persister cells. The dynamics of crossing is characterized by mean first arrival times and is found to be surprisingly complex. It displays three distinct regimes with different scaling behavior that can be understood based on an analytical approximation. Our results suggest that a phenotypically heterogeneous population has a fitness advantage in nonuniform environments and can spread more rapidly than a homogeneous population. PMID:24730780

  2. Spreading of Persistent Infections in Heterogeneous Populations

    E-print Network

    Sanz, J; Moreno, Y

    2010-01-01

    Up to now, the effects of having heterogeneous networks of contacts have been studied mostly for diseases which are not persistent in time, i.e., for diseases where the infectious period can be considered very small compared to the lifetime of an individual. Moreover, all these previous results have been obtained for closed populations, where the number of individuals does not change during the whole duration of the epidemics. Here, we go one step further and analyze, both analytically and numerically, a radically different kind of diseases: those that are persistent and can last for an individual's lifetime. To be more specific, we particularize to the case of Tuberculosis' (TB) infection dynamics, where the infection remains latent for a period of time before showing up and spreading to other individuals. We introduce an epidemiological model for TB-like persistent infections taking into account the heterogeneity inherent to the population structure. This sort of dynamics introduces new analytical and numer...

  3. Stochastic population growth in spatially heterogeneous environments

    E-print Network

    Evans, Steven N; Schreiber, Sebastian J; Sen, Arnab

    2011-01-01

    Classical ecological theory predicts that environmental stochasticity increases extinction risk by reducing the average per-capita growth rate of populations. To understand the interactive effects of environmental stochasticity, spatial heterogeneity, and dispersal on population growth, we study the following model for population abundances in $n$ patches: the conditional law of $X_{t+dt}$ given $X_t=x$ is such that when $dt$ is small the conditional mean of $X_{t+dt}^i-X_t^i$ is approximately $[x^i\\mu_i+\\sum_j(x^j D_{ji}-x^i D_{ij})]dt$, where $X_t^i$ and $\\mu_i$ are the abundance and per capita growth rate in the $i$-th patch respectivly, and $D_{ij}$ is the dispersal rate from the $i$-th to the $j$-th patch, and the conditional covariance of $X_{t+dt}^i-X_t^i$ and $X_{t+dt}^j-X_t^j$ is approximately $x^i x^j \\sigma_{ij}dt$. We show for such a spatially extended population that if $S_t=(X_t^1+...+X_t^n)$ is the total population abundance, then $Y_t=X_t/S_t$, the vector of patch proportions, converges in law...

  4. International Students: A Vulnerable Student Population

    ERIC Educational Resources Information Center

    Sherry, Mark; Thomas, Peter; Chui, Wing Hong

    2010-01-01

    This study examines the experiences of international students at The University of Toledo, where international students comprise approximately 10% of the student population. It highlights problems international students experience such as adapting to a new culture, English language problems, financial problems and lack of understanding from the…

  5. Specialization and Bet-Hedging in Heterogeneous Populations

    E-print Network

    Rulands, Steffen; Frey, Erwin

    2014-01-01

    Phenotypic heterogeneity is a strategy commonly used by bacteria to rapidly adapt to changing environmental conditions. Here, we study the interplay between phenotypic heterogeneity and genetic diversity in spatially extended populations. By analyzing the spatio-temporal dynamics, we show that the level of mobility and the type of competition qualitatively influence the persistence of phenotypic heterogeneity. While direct competition generally promotes persistence of phenotypic heterogeneity, specialization dominates in models with indirect competition irrespective of the degree of mobility.

  6. Habitat heterogeneity affects population growth in goshawk Accipiter gentilis

    Microsoft Academic Search

    Oliver Kruger; Jan Lindstrom

    2001-01-01

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

  7. The effect of population heterogeneities upon spread of infection.

    PubMed

    Clancy, Damian; Pearce, Christopher J

    2013-10-01

    It has often been observed that population heterogeneities can lead to outbreaks of infection being less frequent and less severe than homogeneous population models would suggest. We address this issue by comparing a model incorporating various forms of heterogeneity with a homogenised model matched according to the value of the basic reproduction number [Formula: see text]. We mainly focus upon heterogeneity in individuals' infectivity and susceptibility, though with some allowance also for heterogeneous patterns of mixing. The measures of infectious spread we consider are (i) the probability of a major outbreak; (ii) the mean outbreak size; (iii) the mean endemic prevalence level; and (iv) the persistence time. For each measure, we establish conditions under which heterogeneity leads to a reduction in infectious spread. We also demonstrate that if such conditions are not satisfied, the reverse may occur. As well as comparison with a homogeneous population, we investigate comparisons between two heterogeneous populations of differing degrees of heterogeneity. All of our results are derived under the assumption that the susceptible population is sufficiently large. PMID:22941453

  8. Are Heterogeneous or Homogeneous Groups More Beneficial to Students?

    ERIC Educational Resources Information Center

    Schullery, Nancy M.; Schullery, Stephen E.

    2006-01-01

    This study investigated the relative benefits to the student of working in homogeneous versus heterogeneous classroom groups. Correlation analysis of 18 desirable outcomes versus 8 personality-based heterogeneity variables reveals that heterogeneity associates with advantages as well as disadvantages. Ways in which group composition might be…

  9. The Adult Student Population.

    ERIC Educational Resources Information Center

    Snyder, Fred A.; Blocker, Clyde E.

    This study is concerned with the following topics on adult student attendance at Harrisburg Area Community College (HACC) during the 1969-70 academic year: student background, reason for attendance, enrollment in programs or courses, academic success, evidence of personal and occupational development. The report is based on the useable…

  10. Mosquito population regulation and larval source management in heterogeneous environments.

    PubMed

    Smith, David L; Perkins, T Alex; Tusting, Lucy S; Scott, Thomas W; Lindsay, Steven W

    2013-01-01

    An important question for mosquito population dynamics, mosquito-borne pathogen transmission and vector control is how mosquito populations are regulated. Here we develop simple models with heterogeneity in egg laying patterns and in the responses of larval populations to crowding in aquatic habitats. We use the models to evaluate how such heterogeneity affects mosquito population regulation and the effects of larval source management (LSM). We revisit the notion of a carrying capacity and show how heterogeneity changes our understanding of density dependence and the outcome of LSM. Crowding in and productivity of aquatic habitats is highly uneven unless egg-laying distributions are fine-tuned to match the distribution of habitats' carrying capacities. LSM reduces mosquito population density linearly with coverage if adult mosquitoes avoid laying eggs in treated habitats, but quadratically if eggs are laid in treated habitats and the effort is therefore wasted (i.e., treating 50% of habitat reduces mosquito density by approximately 75%). Unsurprisingly, targeting (i.e. treating a subset of the most productive pools) gives much larger reductions for similar coverage, but with poor targeting, increasing coverage could increase adult mosquito population densities if eggs are laid in higher capacity habitats. Our analysis suggests that, in some contexts, LSM models that accounts for heterogeneity in production of adult mosquitoes provide theoretical support for pursuing mosquito-borne disease prevention through strategic and repeated application of modern larvicides. PMID:23951118

  11. Mosquito Population Regulation and Larval Source Management in Heterogeneous Environments

    PubMed Central

    Smith, David L.; Perkins, T. Alex; Tusting, Lucy S.; Scott, Thomas W.; Lindsay, Steven W.

    2013-01-01

    An important question for mosquito population dynamics, mosquito-borne pathogen transmission and vector control is how mosquito populations are regulated. Here we develop simple models with heterogeneity in egg laying patterns and in the responses of larval populations to crowding in aquatic habitats. We use the models to evaluate how such heterogeneity affects mosquito population regulation and the effects of larval source management (LSM). We revisit the notion of a carrying capacity and show how heterogeneity changes our understanding of density dependence and the outcome of LSM. Crowding in and productivity of aquatic habitats is highly uneven unless egg-laying distributions are fine-tuned to match the distribution of habitats’ carrying capacities. LSM reduces mosquito population density linearly with coverage if adult mosquitoes avoid laying eggs in treated habitats, but quadratically if eggs are laid in treated habitats and the effort is therefore wasted (i.e., treating 50% of habitat reduces mosquito density by approximately 75%). Unsurprisingly, targeting (i.e. treating a subset of the most productive pools) gives much larger reductions for similar coverage, but with poor targeting, increasing coverage could increase adult mosquito population densities if eggs are laid in higher capacity habitats. Our analysis suggests that, in some contexts, LSM models that accounts for heterogeneity in production of adult mosquitoes provide theoretical support for pursuing mosquito-borne disease prevention through strategic and repeated application of modern larvicides. PMID:23951118

  12. Evolution of pathogens towards low R0 in heterogeneous populations.

    PubMed

    Kao, Rowland R

    2006-10-01

    Maximization of the basic reproduction ratio or R(0) is widely believed to drive the emergence of novel pathogens. The presence of exploitable heterogeneities in a population, such as high variance in the number of potentially infectious contacts, increases R(0) and thus pathogens that can exploit heterogeneities in the contact structure have an advantage over those that do not. However, exploitation of heterogeneities results in a more rapid depletion of the potentially susceptible neighbourhood for an infected host. Here a simple model of pathogen evolution in a heterogeneous environment is developed and placed in the context of HIV transmission. In this model, it is shown that pathogens may evolve towards lower R(0), even if this results in pathogen extinction. For sufficiently high transmissibility, two locally stable strategies exist for an evolving pathogen, one that exploits heterogeneities and results in higher R(0), and one that does not, and results in lower R(0). While the low R(0) strategy is never evolutionarily stable, invading strains with higher R(0) will also converge to the low R(0) strategy if not sufficiently different from the resident strain. Heterogenous transmission is increasingly recognized as fundamental to epidemiological dynamics and the evolution of pathogens; here, it is shown that the ability to exploit heterogeneity is a strategy that can itself evolve. PMID:16730749

  13. Effects of the Heterogeneity of Game Complexity and User Population in Learning Performance of Business Simulation Games

    ERIC Educational Resources Information Center

    Tao, Yu-Hui; Yeh, C. Rosa; Hung, Kung Chin

    2012-01-01

    Previous studies on business simulation games (BSGs) have concluded that improved performance may not be the primary benefit of using BSGs, due to mixed results between student performance and perceptions. Two relevant and insightful issues attract our attention, namely, the impacts of the heterogeneous student population and the different…

  14. Tit for tat in heterogeneous populations

    Microsoft Academic Search

    Martin A. Nowak; Karl Sigmund

    1992-01-01

    THE 'iterated prisoner's dilemma' is now the orthodox paradigm for the evolution of cooperation among selfish individuals. This viewpoint is strongly supported by Axelrod's computer tournaments, where 'tit for tat' (TFT) finished first1. This has stimulated interest in the role of reciprocity in biological societies1-8. Most theoretical investigations, however, assumed homogeneous populations (the setting for evolutionary stable strategies9,10) and programs

  15. Student Heterogeneity and Diversity at Catholic Colleges

    ERIC Educational Resources Information Center

    Elliott, Diane Cardenas

    2012-01-01

    The purpose of this study was to examine structural diversity at Catholic colleges; more specifically, the variation in the student body diversity characteristics of a sample of freshman students matriculated at Catholic colleges. For the purpose of this article, diversity characteristics include background characteristics associated with student

  16. Modeling Heterogeneity in Students Seeking College Counseling

    ERIC Educational Resources Information Center

    Nordberg, Samuel S.

    2013-01-01

    Objective: A series of four studies explored the heuristic value of a method of grouping students in counseling by the severity of symptoms across eight domains. Method: Participants were over 50,000 college students in counseling, assessed with the CCAPS-62 and -34 as part of routine clinical care. Latent Profile Analysis was used to group…

  17. Non-linearity and heterogeneity in modeling of population dynamics.

    PubMed

    Karev, Georgy P

    2014-12-01

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

  18. Explicit kinetic heterogeneity: mechanistic models for interpretation of labeling data in heterogeneous populations

    SciTech Connect

    Ganusov, Vitaly V [Los Alamos National Laboratory

    2008-01-01

    Estimation of division and death rates of lymphocytes in different conditions is vital for quantitative understanding of the immune system. Deuterium, in the form of deuterated glucose or heavy water, can be used to measure rates of proliferation and death of lymphocytes in vivo. Inferring these rates from labeling and delabeling curves has been subject to considerable debate with different groups suggesting different mathematical models for that purpose. We show that the three models that are most commonly used are in fact mathematically identical and differ only in their interpretation of the estimated parameters. By extending these previous models, we here propose a more mechanistic approach for the analysis of data from deuterium labeling experiments. We construct a model of 'kinetic heterogeneity' in which the total cell population consists of many sub-populations with different rates of cell turnover. In this model, for a given distribution of the rates of turnover, the predicted fraction of labeled DNA accumulated and lost can be calculated. Our model reproduces several previously made experimental observations, such as a negative correlation between the length of the labeling period and the rate at which labeled DNA is lost after label cessation. We demonstrate the reliability of the new explicit kinetic heterogeneity model by applying it to artificially generated datasets, and illustrate its usefulness by fitting experimental data. In contrast to previous models, the explicit kinetic heterogeneity model (1) provides a mechanistic way of interpreting labeling data; (2) allows for a non-exponential loss of labeled cells during delabeling, and (3) can be used to describe data with variable labeling length.

  19. Cluster analysis of the genetic heterogeneity and disease distributions in purebred dog populations

    Microsoft Academic Search

    G. J. Ubbink; J. van de Broek; H. A. W. Hazewinkel; J. Rothuizen

    1998-01-01

    Purebred dog populations have been subject to strong selection which has resulted in extreme differences between breeds and decreased heterogeneity within breeds. As a result, breed-specific inherited diseases have accumulated in many populations. The aim of this study was to analyse genetic heterogeneity in relation to the distribution of elbow dysplasia in labrador retrievers, portosystemic shunts in Irish wolfbounds, and

  20. Effects of Population Heterogeneity on Accuracy of DIF Detection

    ERIC Educational Resources Information Center

    Oliveri, María Elena; Ercikan, Kadriye; Zumbo, Bruno D.

    2014-01-01

    Heterogeneity within English language learners (ELLs) groups has been documented. Previous research on differential item functioning (DIF) analyses suggests that accurate DIF detection rates are reduced greatly when groups are heterogeneous. In this simulation study, we investigated the effects of heterogeneity within linguistic (ELL) groups on…

  1. Regional heterogeneity and gene flow maintain variance in a quantitative trait within populations of lodgepole pine

    PubMed Central

    Yeaman, Sam; Jarvis, Andy

    2006-01-01

    Genetic variation is of fundamental importance to biological evolution, yet we still know very little about how it is maintained in nature. Because many species inhabit heterogeneous environments and have pronounced local adaptations, gene flow between differently adapted populations may be a persistent source of genetic variation within populations. If this migration–selection balance is biologically important then there should be strong correlations between genetic variance within populations and the amount of heterogeneity in the environment surrounding them. Here, we use data from a long-term study of 142 populations of lodgepole pine (Pinus contorta) to compare levels of genetic variation in growth response with measures of climatic heterogeneity in the surrounding region. We find that regional heterogeneity explains at least 20% of the variation in genetic variance, suggesting that gene flow and heterogeneous selection may play an important role in maintaining the high levels of genetic variation found within natural populations. PMID:16769628

  2. The role of population heterogeneity and human mobility in the spread of pandemic influenza.

    PubMed

    Merler, Stefano; Ajelli, Marco

    2010-02-22

    Little is known on how different levels of population heterogeneity and different patterns of human mobility affect the course of pandemic influenza in terms of timing and impact. By employing a large-scale spatially explicit individual-based model, founded on a highly detailed model of the European populations and on a careful analysis of air and railway transportation data, we provide quantitative measures of the influence of such factors at the European scale. Our results show that Europe has to be prepared to face a rapid diffusion of a pandemic influenza, because of the high mobility of the population, resulting in the early importation of the first cases from abroad and highly synchronized local epidemics. The impact of the epidemic in European countries is highly variable because of the marked differences in the sociodemographic structure of European populations. R(0), cumulative attack rate and peak daily attack rate depend heavily on sociodemographic parameters, such as the size of household groups and the fraction of workers and students in the population. PMID:19864279

  3. The role of population heterogeneity and human mobility in the spread of pandemic influenza

    PubMed Central

    Merler, Stefano; Ajelli, Marco

    2010-01-01

    Little is known on how different levels of population heterogeneity and different patterns of human mobility affect the course of pandemic influenza in terms of timing and impact. By employing a large-scale spatially explicit individual-based model, founded on a highly detailed model of the European populations and on a careful analysis of air and railway transportation data, we provide quantitative measures of the influence of such factors at the European scale. Our results show that Europe has to be prepared to face a rapid diffusion of a pandemic influenza, because of the high mobility of the population, resulting in the early importation of the first cases from abroad and highly synchronized local epidemics. The impact of the epidemic in European countries is highly variable because of the marked differences in the sociodemographic structure of European populations. R0, cumulative attack rate and peak daily attack rate depend heavily on sociodemographic parameters, such as the size of household groups and the fraction of workers and students in the population. PMID:19864279

  4. Dual Enrollment for Underrepresented Student Populations.

    ERIC Educational Resources Information Center

    Hugo, Esther B.

    2001-01-01

    Reports that the dual enrollment program at Santa Monica College (SMC) in California aims to serve underrepresented student populations, particularly in light of the dismantling of affirmative action programs in California. The overall goal of the program is to increase the pool of students qualifying for competitive colleges and universities. (NB)

  5. Functional heterogeneity of side population cells in skeletal muscle

    SciTech Connect

    Uezumi, Akiyoshi [Department of Molecular Therapy, National Institute of Neuroscience, National Center of Neurology and Psychiatry, 4-1-1 Ogawa-higashi, Kodaira, Tokyo 187-8502 (Japan); Ojima, Koichi [Department of Molecular Therapy, National Institute of Neuroscience, National Center of Neurology and Psychiatry, 4-1-1 Ogawa-higashi, Kodaira, Tokyo 187-8502 (Japan); Fukada, So-ichiro [Department of Molecular Therapy, National Institute of Neuroscience, National Center of Neurology and Psychiatry, 4-1-1 Ogawa-higashi, Kodaira, Tokyo 187-8502 (Japan); Ikemoto, Madoka [Department of Molecular Therapy, National Institute of Neuroscience, National Center of Neurology and Psychiatry, 4-1-1 Ogawa-higashi, Kodaira, Tokyo 187-8502 (Japan); Masuda, Satoru [Department of Molecular Therapy, National Institute of Neuroscience, National Center of Neurology and Psychiatry, 4-1-1 Ogawa-higashi, Kodaira, Tokyo 187-8502 (Japan); Miyagoe-Suzuki, Yuko [Department of Molecular Therapy, National Institute of Neuroscience, National Center of Neurology and Psychiatry, 4-1-1 Ogawa-higashi, Kodaira, Tokyo 187-8502 (Japan); Takeda, Shin'ichi [Department of Molecular Therapy, National Institute of Neuroscience, National Center of Neurology and Psychiatry, 4-1-1 Ogawa-higashi, Kodaira, Tokyo 187-8502 (Japan)]. E-mail: takeda@ncnp.go.jp

    2006-03-17

    Skeletal muscle regeneration has been exclusively attributed to myogenic precursors, satellite cells. A stem cell-rich fraction referred to as side population (SP) cells also resides in skeletal muscle, but its roles in muscle regeneration remain unclear. We found that muscle SP cells could be subdivided into three sub-fractions using CD31 and CD45 markers. The majority of SP cells in normal non-regenerating muscle expressed CD31 and had endothelial characteristics. However, CD31{sup -}CD45{sup -} SP cells, which are a minor subpopulation in normal muscle, actively proliferated upon muscle injury and expressed not only several regulatory genes for muscle regeneration but also some mesenchymal lineage markers. CD31{sup -}CD45{sup -} SP cells showed the greatest myogenic potential among three SP sub-fractions, but indeed revealed mesenchymal potentials in vitro. These SP cells preferentially differentiated into myofibers after intramuscular transplantation in vivo. Our results revealed the heterogeneity of muscle SP cells and suggest that CD31{sup -}CD45{sup -} SP cells participate in muscle regeneration.

  6. Manipulation with heterogeneity within a species population formulated as an inverse problem

    NASA Astrophysics Data System (ADS)

    Horváth, D.; Brutovsky, B.; Ko?išová, J.; Šprinc, S.

    2010-11-01

    Dependence of the evolutionary dynamics on the population’s heterogeneity has been reliably recognized and studied within the frame of evolutionary optimization theory. As the causal relation between the heterogeneity and dynamics of environment has been revealed, the possibility to influence convergence rate of evolutionary processes by purposeful manipulation with environment emerges. For the above purposes we formulate the task as the inverse problem meaning that desired population heterogeneity, quantified by Tsallis information entropy, represents the model’s input and dynamics of environment leading to desired population heterogeneity is looked for. Here the presented abstract model of evolutionary motion within the inverse model of replicating species is case-independent and it is relevant for the broad range of phenomena observed at cellular, ecological, economic and social scales. We envision relevance of the model for anticancer therapy, in which the effort is to circumvent heterogeneity as it typically correlates with the therapy efficiency.

  7. Networks and Models with Heterogeneous Population Structure in Epidemiology

    NASA Astrophysics Data System (ADS)

    Kao, R. R.

    Heterogeneous population structure can have a profound effect on infectious disease dynamics, and is particularly important when investigating “tactical” disease control questions. At times, the nature of the network involved in the transmission of the pathogen (bacteria, virus, macro-parasite, etc.) appears to be clear; however, the nature of the network involved is dependent on the scale (e.g. within-host, between-host, or between-population), the nature of the contact, which ranges from the highly specific (e.g. sexual acts or needle sharing at the person-to-person level) to almost completely non-specific (e.g. aerosol transmission, often over long distances as can occur with the highly infectious livestock pathogen foot-and-mouth disease virus—FMDv—at the farm-to-farm level, e.g. Schley et al. in J. R. Soc. Interface 6:455-462, 2008), and the timescale of interest (e.g. at the scale of the individual, the typical infectious period of the host). Theoretical approaches to examining the implications of particular network structures on disease transmission have provided critical insight; however, a greater challenge is the integration of network approaches with data on real population structures. In this chapter, some concepts in disease modelling will be introduced, the relevance of selected network phenomena discussed, and then results from real data and their relationship to network analyses summarised. These include examinations of the patterns of air traffic and its relation to the spread of SARS in 2003 (Colizza et al. in BMC Med., 2007; Hufnagel et al. in Proc. Natl. Acad. Sci. USA 101:15124-15129, 2004), the use of the extensively documented Great Britain livestock movements network (Green et al. in J. Theor. Biol. 239:289-297, 2008; Robinson et al. in J. R. Soc. Interface 4:669-674, 2007; Vernon and Keeling in Proc. R. Soc. Lond. B, Biol. Sci. 276:469-476, 2009) and the growing interest in combining contact structure data with phylogenetics to identify real contact patterns as they directly relate to diseases of interest (Cottam et al. in PLoS Pathogens 4:1000050, 2007; Hughes et al. in PLoS Pathogens 5:1000590, 2009).

  8. Nonidentifiability of population size from capture-recapture data with heterogeneous detection probabilities

    USGS Publications Warehouse

    Link, W.A.

    2003-01-01

    Heterogeneity in detection probabilities has long been recognized as problematic in mark-recapture studies, and numerous models developed to accommodate its effects. Individual heterogeneity is especially problematic, in that reasonable alternative models may predict essentially identical observations from populations of substantially different sizes. Thus even with very large samples, the analyst will not be able to distinguish among reasonable models of heterogeneity, even though these yield quite distinct inferences about population size. The problem is illustrated with models for closed and open populations.

  9. Phenotypic heterogeneity is a selected trait in natural yeast populations subject to environmental stress

    PubMed Central

    Holland, Sara L; Reader, Tom; Dyer, Paul S; Avery, Simon V

    2014-01-01

    Populations of genetically uniform microorganisms exhibit phenotypic heterogeneity, where individual cells have varying phenotypes. Such phenotypes include fitness-determining traits. Phenotypic heterogeneity has been linked to increased population-level fitness in laboratory studies, but its adaptive significance for wild microorganisms in the natural environment is unknown. Here, we addressed this by testing heterogeneity in yeast isolates from diverse environmental sites, each polluted with a different principal contaminant, as well as from corresponding control locations. We found that cell-to-cell heterogeneity (in resistance to the appropriate principal pollutant) was prevalent in the wild yeast isolates. Moreover, isolates with the highest heterogeneity were consistently observed in the polluted environments, indicating that heterogeneity is positively related to survival in adverse conditions in the wild. This relationship with survival was stronger than for the property of mean resistance (IC50) of an isolate. Therefore, heterogeneity could be the major determinant of microbial survival in adverse conditions. Indeed, growth assays indicated that isolates with high heterogeneities had a significant competitive advantage during stress. Analysis of yeasts after cultivation for ??500 generations additionally showed that high heterogeneity evolved as a heritable trait during stress. The results showed that environmental stress selects for wild microorganisms with high levels of phenotypic heterogeneity. PMID:24000788

  10. Trapping single human osteoblast-like cells from a heterogeneous population using a dielectrophoretic microfluidic device

    PubMed Central

    Thomas, Rupert S. W.; Mitchell, Peter D.; Oreffo, Richard O. C.; Morgan, Hywel

    2010-01-01

    We describe a system for the isolation, concentration, separation, and recovery of human osteoblast-like cells from a heterogeneous population using dielectrophoretic ring traps. Cells flowing in a microfluidic channel are immobilized inside an electric field cage using negative dielectrophoresis. A planar ring electrode creates a closed trap while repelling surrounding cells. Target cells are identified by fluorescent labeling, and are trapped as they pass across a ring electrode by an automated system. We demonstrate recovery of small populations of human osteoblast-like cells with a purity of 100%, which in turn demonstrates the potential of such a device for cell selection from a heterogeneous population. PMID:20697594

  11. SOURCES OF HETEROGENEITY BIAS WHEN DNA MARK-RECAPTURE SAMPLING METHODS ARE APPLIED TO GRIZZLY BEAR (URSUS ARCTOS) POPULATIONS

    Microsoft Academic Search

    John Boulanger; Gordon Stenhouse; Robin Munro

    2004-01-01

    One of the challenges in estimating grizzly bear (Ursus arctos) population size using DNA methods is heterogeneity of capture probabilities. This study developed general tools to explore heterogeneity variation using data from a DNA mark-recapture project in which a proportion of the bear population had GPS collars. The Huggins closed population mark-recapture model was used to determine if capture probability

  12. High school students' understanding and problem solving in population genetics

    Microsoft Academic Search

    Patti D. Soderberg

    2005-01-01

    This study is an investigation of student understanding of population genetics and how students developed, used and revised conceptual models to solve problems. The students in this study participated in three rounds of problem solving. The first round involved the use of a population genetics model to predict the number of carriers in a population. The second round required them

  13. Index-sorting resolves heterogeneous murine hematopoietic stem cell populations

    E-print Network

    Schulte, Reiner; Wilson, Nicola K.; Prick, Janine C. M.; Cossetti, Chiara; Maj, Michael K.; Gottgens, Berthold; Kent, David G.

    2015-01-01

    to hold individual 1.4mL polypropylene round bottom tubes (See Methods and Figure 1A). Index sorting used as a tool for determining transcriptional differences in single stem cells. To develop a tool to understand the molecular heterogeneity within... . To create a fitting holder a 96 well polycarbonate rack typically used to hold individual 1.4mL polypropylene round bottom tubes was used. By removing the legs of the rack and shaving the bottom surface to be flat, we were able to create a rigid fit...

  14. Analytic Investigation Into Effect of Population Heterogeneity on Parameter Ratio Estimates

    SciTech Connect

    Schinkel, Colleen [Department of Physics, University of Alberta, Edmonton, AB (Canada); Department of Medical Physics, Cross Cancer Institute, Edmonton, AB (Canada); Carlone, Marco [Department of Medical Physics, Cross Cancer Institute, Edmonton, AB (Canada); Department of Oncology, University of Alberta, Edmonton, AB (Canada)], E-mail: marcocar@cancerboard.ab.ca; Warkentin, Brad [Department of Medical Physics, Cross Cancer Institute, Edmonton, AB (Canada); Fallone, B. Gino [Department of Physics, University of Alberta, Edmonton, AB (Canada); Department of Medical Physics, Cross Cancer Institute, Edmonton, AB (Canada); Department of Oncology, University of Alberta, Edmonton, AB (Canada)

    2007-11-15

    Purpose: A homogeneous tumor control probability (TCP) model has previously been used to estimate the {alpha}/{beta} ratio for prostate cancer from clinical dose-response data. For the ratio to be meaningful, it must be assumed that parameter ratios are not sensitive to the type of tumor control model used. We investigated the validity of this assumption by deriving analytic relationships between the {alpha}/{beta} estimates from a homogeneous TCP model, ignoring interpatient heterogeneity, and those of the corresponding heterogeneous (population-averaged) model that incorporated heterogeneity. Methods and Materials: The homogeneous and heterogeneous TCP models can both be written in terms of the geometric parameters D{sub 50} and {gamma}{sub 50}. We show that the functional forms of these models are similar. This similarity was used to develop an expression relating the homogeneous and heterogeneous estimates for the {alpha}/{beta} ratio. The expression was verified numerically by generating pseudo-data from a TCP curve with known parameters and then using the homogeneous and heterogeneous TCP models to estimate the {alpha}/{beta} ratio for the pseudo-data. Results: When the dominant form of interpatient heterogeneity is that of radiosensitivity, the homogeneous and heterogeneous {alpha}/{beta} estimates differ. This indicates that the presence of this heterogeneity affects the value of the {alpha}/{beta} ratio derived from analysis of TCP curves. Conclusions: The {alpha}/{beta} ratio estimated from clinical dose-response data is model dependent-a heterogeneous TCP model that accounts for heterogeneity in radiosensitivity will produce a greater {alpha}/{beta} estimate than that resulting from a homogeneous TCP model.

  15. A Mathematical and Computational Approach for Integrating the Major Sources of Cell Population Heterogeneity

    PubMed Central

    Stamatakis, Michail; Zygourakis, Kyriacos

    2010-01-01

    Several approaches have been used in the past to model heterogeneity in bacterial cell populations, with each approach focusing on different source(s) of heterogeneity. However, a holistic approach that integrates all the major sources into a comprehensive framework applicable to cell populations is still lacking. In this work we present the mathematical formulation of a cell population master equation (CPME) that describes cell population dynamics and takes into account the major sources of heterogeneity, namely stochasticity in reaction, DNA-duplication, and division, as well as the random partitioning of species contents into the two daughter cells. The formulation also takes into account cell growth and respects the discrete nature of the molecular contents and cell numbers. We further develop a Monte Carlo algorithm for the simulation of the stochastic processes considered here. To benchmark our new framework, we first use it to quantify the effect of each source of heterogeneity on the intrinsic and the extrinsic phenotypic variability for the well-known two-promoter system used experimentally by Elowitz et al. (2002). We finally apply our framework to a more complicated system and demonstrate how the interplay between noisy gene expression and growth inhibition due to protein accumulation at the single cell level can result in complex behavior at the cell population level. The generality of our framework makes it suitable for studying a vast array of artificial and natural genetic networks. Using our Monte Carlo algorithm, cell population distributions can be predicted for the genetic architecture of interest, thereby quantifying the effect of stochasticity in intracellular reactions or the variability in the rate of physiological processes such as growth and division. Such in silico experiments can give insight into the behavior of cell populations and reveal the major sources contributing to cell population heterogeneity. PMID:20685607

  16. Sucrose octaacetate tasting in a heterogeneous population of CFW mice.

    PubMed

    Gannon, K S; Whitney, G

    1989-05-01

    Three experiments investigated the genetic underpinnings of the sucrose octaacetate (SOA) avoidance-indifference dimorphism that exists among outbred CFW mice. In the first experiment, results from 687 subjects across three generations of segregation were consistent with predictions from a single-autosomal, two-allele model, with dominance for the avoidance (Taster) phenotype. In the second experiment, heterogeneous CFW Tasters and Nontasters were mated with SWR/J (Taster) and C57BL/6J (Nontaster) inbred mice. The SWR and CFW mice are both derived from Swiss mice, and the results were consistent with the possibility that the Taster animals share an allele which is identical by descent. The second and third experiments also investigated sensitivity to SOA across an extended range of concentrations. Nontaster CFWs avoided SOA at the near-saturation 10(-3) M concentration but did not avoid any weaker concentrations. Taster CFWs avoided all concentrations down to approximately 10(-6) M SOA. PMID:2757593

  17. Follow the leader: Herding behavior in heterogeneous populations

    NASA Astrophysics Data System (ADS)

    Mosquera-Doñate, Guillem; Boguñá, Marián

    2015-05-01

    Here we study the emergence of spontaneous collective leadership in large populations. In standard models of opinion dynamics, herding behavior is only obeyed at the local scale due to the interaction of single agents with their neighbors; while at the global scale, such models are governed by purely diffusive processes. Surprisingly, in this paper we show that the combination of a strong separation of time scales within the population and a hierarchical organization of the influences of some agents on the others induces a phase transition between a purely diffusive phase, as in the standard case, and a herding phase where a fraction of the agents self-organize and lead the global opinion of the whole population.

  18. EVOLUTION OF VIRULENCE IN A HETEROGENEOUS HOST POPULATION

    Microsoft Academic Search

    Roland R. Regoes; Martin A. Nowak; Sebastian Bonhoeffer

    2000-01-01

    There is a large body of theoretical studies that investigate factors that affect the evolution of virulence, that is parasite-induced host mortality. In these studies the host population is assumed to be genetically homogeneous. However, many parasites have a broad range of host types they infect, and trade-offs between the parasite virulence in different host types may exist. The aim

  19. Slow epidemic extinction in populations with heterogeneous infection rates.

    PubMed

    Buono, C; Vazquez, F; Macri, P A; Braunstein, L A

    2013-08-01

    We explore how heterogeneity in the intensity of interactions between people affects epidemic spreading. For that, we study the susceptible-infected-susceptible model on a complex network, where a link connecting individuals i and j is endowed with an infection rate ?(ij)=?w(ij) proportional to the intensity of their contact w(ij), with a distribution P(w(ij)) taken from face-to-face experiments analyzed in Cattuto et al. [PLoS ONE 5, e11596 (2010)]. We find an extremely slow decay of the fraction of infected individuals, for a wide range of the control parameter ?. Using a distribution of width a we identify two large regions in the a-? space with anomalous behaviors, which are reminiscent of rare region effects (Griffiths phases) found in models with quenched disorder. We show that the slow approach to extinction is caused by isolated small groups of highly interacting individuals, which keep epidemics alive for very long times. A mean-field approximation and a percolation approach capture with very good accuracy the absorbing-active transition line for weak (small a) and strong (large a) disorder, respectively. PMID:24032889

  20. Modelling Spread of Oncolytic Viruses in Heterogeneous Cell Populations

    NASA Astrophysics Data System (ADS)

    Ellis, Michael; Dobrovolny, Hana

    2014-03-01

    One of the most promising areas in current cancer research and treatment is the use of viruses to attack cancer cells. A number of oncolytic viruses have been identified to date that possess the ability to destroy or neutralize cancer cells while inflicting minimal damage upon healthy cells. Formulation of predictive models that correctly describe the evolution of infected tumor systems is critical to the successful application of oncolytic virus therapy. A number of different models have been proposed for analysis of the oncolytic virus-infected tumor system, with approaches ranging from traditional coupled differential equations such as the Lotka-Volterra predator-prey models, to contemporary modeling frameworks based on neural networks and cellular automata. Existing models are focused on tumor cells and the effects of virus infection, and offer the potential for improvement by including effects upon normal cells. We have recently extended the traditional framework to a 2-cell model addressing the full cellular system including tumor cells, normal cells, and the impacts of viral infection upon both populations. Analysis of the new framework reveals complex interaction between the populations and potential inability to simultaneously eliminate the virus and tumor populations.

  1. Basal p21 controls population heterogeneity in cycling and quiescent cell cycle states.

    PubMed

    Overton, K Wesley; Spencer, Sabrina L; Noderer, William L; Meyer, Tobias; Wang, Clifford L

    2014-10-14

    Phenotypic heterogeneity within a population of genetically identical cells is emerging as a common theme in multiple biological systems, including human cell biology and cancer. Using live-cell imaging, flow cytometry, and kinetic modeling, we showed that two states--quiescence and cell cycling--can coexist within an isogenic population of human cells and resulted from low basal expression levels of p21, a Cyclin-dependent kinase (CDK) inhibitor (CKI). We attribute the p21-dependent heterogeneity in cell cycle activity to double-negative feedback regulation involving CDK2, p21, and E3 ubiquitin ligases. In support of this mechanism, analysis of cells at a point before cell cycle entry (i.e., before the G1/S transition) revealed a p21-CDK2 axis that determines quiescent and cycling cell states. Our findings suggest a mechanistic role for p21 in generating heterogeneity in both normal tissues and tumors. PMID:25267623

  2. Basal p21 controls population heterogeneity in cycling and quiescent cell cycle states

    PubMed Central

    Overton, K. Wesley; Spencer, Sabrina L.; Noderer, William L.; Meyer, Tobias; Wang, Clifford L.

    2014-01-01

    Phenotypic heterogeneity within a population of genetically identical cells is emerging as a common theme in multiple biological systems, including human cell biology and cancer. Using live-cell imaging, flow cytometry, and kinetic modeling, we showed that two states—quiescence and cell cycling—can coexist within an isogenic population of human cells and resulted from low basal expression levels of p21, a Cyclin-dependent kinase (CDK) inhibitor (CKI). We attribute the p21-dependent heterogeneity in cell cycle activity to double-negative feedback regulation involving CDK2, p21, and E3 ubiquitin ligases. In support of this mechanism, analysis of cells at a point before cell cycle entry (i.e., before the G1/S transition) revealed a p21–CDK2 axis that determines quiescent and cycling cell states. Our findings suggest a mechanistic role for p21 in generating heterogeneity in both normal tissues and tumors. PMID:25267623

  3. L'INSEE/GENES Estimating Marginal Treatment Effects in Heterogeneous Populations

    E-print Network

    Weaver, Harold A. "Hal"

    of heterogeneity in returns. Estimation d'effets de traitement marginaux dans des populations h?t?rog?nes R populations h?t?rog?nes. S'appuyant sur un aper?u de Heckman et Vytlacil, on montre que le mod?le conventionnel des effets de traitement avec effets h?t?rog?nes implique que les r?sultats sont une fonction non

  4. Anomalous diffusion of heterogeneous populations characterized by normal diffusion at the individual level

    PubMed Central

    Hapca, Simona; Crawford, John W; Young, Iain M

    2008-01-01

    The characterization of the dispersal of populations of non-identical individuals is relevant to most ecological and epidemiological processes. In practice, the movement is quantified by observing relatively few individuals, and averaging to estimate the rate of dispersal of the population as a whole. Here, we show that this can lead to serious errors in the predicted movement of the population if the individuals disperse at different rates. We develop a stochastic model for the diffusion of heterogeneous populations, inspired by the movement of the parasitic nematode Phasmarhabditis hermaphrodita. Direct observations of this nematode in homogeneous and heterogeneous environments reveal a large variation in individual behaviour within the population as reflected initially in the speed of the movement. Further statistical analysis shows that the movement is characterized by temporal correlations and in a heterogeneously structured environment the correlations that occur are of shorter range compared with those in a homogeneous environment. Therefore, by using the first-order correlated random walk techniques, we derive an effective diffusion coefficient for each individual, and show that there is a significant variation in this parameter among the population that follows a gamma distribution. Based on these findings, we build a new dispersal model in which we maintain the classical assumption that individual movement can be described by normal diffusion, but due to the variability in individual dispersal rates, the diffusion coefficient is not constant at the population level and follows a continuous distribution. The conclusions and methodology presented are relevant to any heterogeneous population of individuals with widely different diffusion rates. PMID:18708322

  5. The Effect of Population Heterogeneity on Statistical Power in the Design and Evaluation of Interventions

    ERIC Educational Resources Information Center

    Jiang, Depeng; Pepler, Debra; Yao, Hongxing

    2010-01-01

    Do interventions work and for whom? For this article, we examined the influence of population heterogeneity on power in designing and evaluating interventions. On the basis of Monte Carlo simulations in Study 1, we demonstrated that the power to detect the overall intervention effect is lower for a mixture of two subpopulations than for a…

  6. DETECTION HETEROGENEITY AND ABUNDANCE ESTIMATION IN POPULATIONS OF GOLDEN-CHEEKED WARBLERS

    E-print Network

    Weckerly, Floyd "Butch" - Department of Biology, Texas State University

    DETECTION HETEROGENEITY AND ABUNDANCE ESTIMATION IN POPULATIONS OF GOLDEN-CHEEKED WARBLERS abundance of Golden- cheeked Warblers (Setophaga chrysoparia) in two years at six study sites 2013. Key words: abundance estimators, detection probability, Golden-cheeked Warbler, N-mixture model

  7. Modelling Lipid Competition Dynamics in Heterogeneous Protocell Populations

    PubMed Central

    Shirt-Ediss, Ben; Ruiz-Mirazo, Kepa; Mavelli, Fabio; Solé, Ricard V.

    2014-01-01

    Recent experimental work in the field of synthetic protocell biology has shown that prebiotic vesicles are able to ‘steal’ lipids from each other. This phenomenon is driven purely by asymmetries in the physical state or composition of the vesicle membranes, and, when lipid resource is limited, translates directly into competition amongst the vesicles. Such a scenario is interesting from an origins of life perspective because a rudimentary form of cell-level selection emerges. To sharpen intuition about possible mechanisms underlying this behaviour, experimental work must be complemented with theoretical modelling. The aim of this paper is to provide a coarse-grain mathematical model of protocell lipid competition. Our model is capable of reproducing, often quantitatively, results from core experimental papers that reported distinct types vesicle competition. Additionally, we make some predictions untested in the lab, and develop a general numerical method for quickly solving the equilibrium point of a model vesicle population. PMID:25024020

  8. Effect of Population Heterogenization on the Reproducibility of Mouse Behavior: A Multi-Laboratory Study

    PubMed Central

    Richter, S. Helene; Garner, Joseph P.; Zipser, Benjamin; Lewejohann, Lars; Sachser, Norbert; Touma, Chadi; Schindler, Britta; Chourbaji, Sabine; Brandwein, Christiane; Gass, Peter; van Stipdonk, Niek; van der Harst, Johanneke; Spruijt, Berry; Võikar, Vootele; Wolfer, David P.; Würbel, Hanno

    2011-01-01

    In animal experiments, animals, husbandry and test procedures are traditionally standardized to maximize test sensitivity and minimize animal use, assuming that this will also guarantee reproducibility. However, by reducing within-experiment variation, standardization may limit inference to the specific experimental conditions. Indeed, we have recently shown in mice that standardization may generate spurious results in behavioral tests, accounting for poor reproducibility, and that this can be avoided by population heterogenization through systematic variation of experimental conditions. Here, we examined whether a simple form of heterogenization effectively improves reproducibility of test results in a multi-laboratory situation. Each of six laboratories independently ordered 64 female mice of two inbred strains (C57BL/6NCrl, DBA/2NCrl) and examined them for strain differences in five commonly used behavioral tests under two different experimental designs. In the standardized design, experimental conditions were standardized as much as possible in each laboratory, while they were systematically varied with respect to the animals' test age and cage enrichment in the heterogenized design. Although heterogenization tended to improve reproducibility by increasing within-experiment variation relative to between-experiment variation, the effect was too weak to account for the large variation between laboratories. However, our findings confirm the potential of systematic heterogenization for improving reproducibility of animal experiments and highlight the need for effective and practicable heterogenization strategies. PMID:21305027

  9. Distinct allelic patterns of nanog expression impart embryonic stem cell population heterogeneity.

    PubMed

    Wu, Jincheng; Tzanakakis, Emmanuel S

    2013-01-01

    Nanog is a principal pluripotency regulator exhibiting a disperse distribution within stem cell populations in vivo and in vitro. Increasing evidence points to a functional role of Nanog heterogeneity on stem cell fate decisions. Allelic control of Nanog gene expression was reported recently in mouse embryonic stem cells. To better understand how this mode of regulation influences the observed heterogeneity of NANOG in stem cell populations, we assembled a multiscale stochastic population balance equation framework. In addition to allelic control, gene expression noise and random partitioning at cell division were considered. As a result of allelic Nanog expression, the distribution of Nanog exhibited three distinct states but when combined with transcriptional noise the profile became bimodal. Regardless of their allelic expression pattern, initially uniform populations of stem cells gave rise to the same Nanog heterogeneity within ten cell cycles. Depletion of NANOG content in cells switching off both gene alleles was slower than the accumulation of intracellular NANOG after cells turned on at least one of their Nanog gene copies pointing to Nanog state-dependent dynamics. Allelic transcription of Nanog also raises issues regarding the use of stem cell lines with reporter genes knocked in a single allelic locus. Indeed, significant divergence was observed in the reporter and native protein profiles depending on the difference in their half-lives and insertion of the reporter gene in one or both alleles. In stem cell populations with restricted Nanog expression, allelic regulation facilitates the maintenance of fractions of self-renewing cells with sufficient Nanog content to prevent aberrant loss of pluripotency. Our findings underline the role of allelic control of Nanog expression as a prime determinant of stem cell population heterogeneity and warrant further investigation in the contexts of stem cell specification and cell reprogramming. PMID:23874182

  10. Extreme heterogeneity in parasitism despite low population genetic structure among monarch butterflies inhabiting the Hawaiian Islands.

    PubMed

    Pierce, Amanda A; de Roode, Jacobus C; Altizer, Sonia; Bartel, Rebecca A

    2014-01-01

    Host movement and spatial structure can strongly influence the ecology and evolution of infectious diseases, with limited host movement potentially leading to high spatial heterogeneity in infection. Monarch butterflies (Danaus plexippus) are best known for undertaking a spectacular long-distance migration in eastern North America; however, they also form non-migratory populations that breed year-round in milder climates such as Hawaii and other tropical locations. Prior work showed an inverse relationship between monarch migratory propensity and the prevalence of the protozoan parasite, Ophryocystis elektroscirrha. Here, we sampled monarchs from replicate sites within each of four Hawaiian Islands to ask whether these populations show consistently high prevalence of the protozoan parasite as seen for monarchs from several other non-migratory populations. Counter to our predictions, we observed striking spatial heterogeneity in parasite prevalence, with infection rates per site ranging from 4-85%. We next used microsatellite markers to ask whether the observed variation in infection might be explained by limited host movement and spatial sub-structuring among sites. Our results showed that monarchs across the Hawaiian Islands form one admixed population, supporting high gene flow among sites. Moreover, measures of individual-level genetic diversity did not predict host infection status, as might be expected if more inbred hosts harbored higher parasite loads. These results suggest that other factors such as landscape-level environmental variation or colonization-extinction processes might instead cause the extreme heterogeneity in monarch butterfly infection observed here. PMID:24926796

  11. Extreme Heterogeneity in Parasitism Despite Low Population Genetic Structure among Monarch Butterflies Inhabiting the Hawaiian Islands

    PubMed Central

    Pierce, Amanda A.; de Roode, Jacobus C.; Altizer, Sonia; Bartel, Rebecca A.

    2014-01-01

    Host movement and spatial structure can strongly influence the ecology and evolution of infectious diseases, with limited host movement potentially leading to high spatial heterogeneity in infection. Monarch butterflies (Danaus plexippus) are best known for undertaking a spectacular long-distance migration in eastern North America; however, they also form non-migratory populations that breed year-round in milder climates such as Hawaii and other tropical locations. Prior work showed an inverse relationship between monarch migratory propensity and the prevalence of the protozoan parasite, Ophryocystis elektroscirrha. Here, we sampled monarchs from replicate sites within each of four Hawaiian Islands to ask whether these populations show consistently high prevalence of the protozoan parasite as seen for monarchs from several other non-migratory populations. Counter to our predictions, we observed striking spatial heterogeneity in parasite prevalence, with infection rates per site ranging from 4–85%. We next used microsatellite markers to ask whether the observed variation in infection might be explained by limited host movement and spatial sub-structuring among sites. Our results showed that monarchs across the Hawaiian Islands form one admixed population, supporting high gene flow among sites. Moreover, measures of individual-level genetic diversity did not predict host infection status, as might be expected if more inbred hosts harbored higher parasite loads. These results suggest that other factors such as landscape-level environmental variation or colonization-extinction processes might instead cause the extreme heterogeneity in monarch butterfly infection observed here. PMID:24926796

  12. Fundamental form of a population TCP model in the limit of large heterogeneity

    SciTech Connect

    Carlone, Marco C.; Warkentin, Brad; Stavrev, Pavel; Fallone, B. Gino [Department of Medical Physics, Cross Cancer Institute, 11560 University Avenue, Edmonton (Canada); Department of Medical Physics, Cross Cancer Institute and Department of Oncology, University of Alberta, 11560 University Avenue, Edmonton (Canada)

    2006-06-15

    A population tumor control probability (TCP) model for fractionated external beam radiotherapy, based on Poisson statistics and in the limit of large parameter heterogeneity, is studied. A reduction of a general eight-parameter TCP equation, which incorporates heterogeneity in parameters characterizing linear-quadratic radiosensitivity, repopulation, and clonogen number, to an equation with four parameters is obtained. The four parameters represent the mean and standard deviation for both clonogen number and a generalized radiosensitivity that includes linear-quadratic and repopulation descriptors. Further, owing to parameter inter-relationship, it is possible to express these four parameters as three ratios of parameters in the large heterogeneity limit. These ratios can be directly linked to two defining features of the TCP dose response: D{sub 50} and {gamma}{sub 50}. In the general case, the TCP model can be written in terms of D{sub 50}, {gamma}{sub 50} and a third parameter indicating the ratio of the levels of heterogeneity in clonogen number and generalized radiosensitivity; however, the third parameter is unnecessary when either of these two sources of heterogeneity is dominant. It is shown that heterogeneity in clonogen number will have little impact on the TCP formula for clinical scenarios, and thus it will generally be the case that the fundamental form of the Poisson-based population TCP model can be specified completely in terms of D{sub 50} and {gamma}{sub 50}: TCP=(1/2) erfc[{radical}({pi}){gamma}{sub 50}(D{sub 50}/D-1)]. This implies that limited radiobiological information can be determined by the analysis of dose response data: information about parameter ratios can be ascertained, but knowledge of absolute values for the fundamental radiobiological parameters will require independent auxiliary measurements.

  13. The scale of demographic heterogeneity in a population of Peromyscus leucopus

    Microsoft Academic Search

    D. T. Krohne; A. B. Burgin

    1990-01-01

    The patterns of spatial heterogeneity in density and demography were studied in a population of Peromyscus leucopus inhabiting a deciduous forest in west-central Indiana. A series of 9 live-trapping grids sampled densities from 3 spatial scales: 3 ha, 80 ha and 350 km2. We found high levels of variation within all three spatial scales. There was as much variation within

  14. Impact of Small Groups with Heterogeneous Preference on Behavioral Evolution in Population Evacuation

    PubMed Central

    Wang, Tao; Huang, Keke; Wang, Zhen; Zheng, Xiaoping

    2015-01-01

    Up to now, there have been a great number of mechanisms to explain the individual behavior and population traits, which seem of particular significance in evolutionary biology and social behavior analysis. Among them, small groups and heterogeneity are two useful frameworks to the above issue. However, vast majority of existing works separately consider both scenarios, which is inconsistent with realistic cases in our life. Here we propose the evolutionary games of heterogeneous small groups (namely, different small groups possess different preferences to dilemma) to study the collective behavior in population evacuation. Importantly, players usually face completely different dilemmas inside and outside the small groups. By means of numerous computation simulations, it is unveiled that the ratio of players in one certain small group directly decides the final behavior of the whole population. Moreover, it can also be concluded that heterogeneous degree of preference for different small groups plays a key role in the behavior traits of the system, which may validate some realistic social observations. The proposed framework is thus universally applicable and may shed new light into the solution of social dilemmas. PMID:25793637

  15. Single-cell Migration Chip for Chemotaxis-based Microfluidic Selection of Heterogeneous Cell Populations

    PubMed Central

    Chen, Yu-Chih; Allen, Steven G.; Ingram, Patrick N.; Buckanovich, Ronald; Merajver, Sofia D.; Yoon, Euisik

    2015-01-01

    Tumor cell migration toward and intravasation into capillaries is an early and key event in cancer metastasis, yet not all cancer cells are imbued with the same capability to do so. This heterogeneity within a tumor is a fundamental property of cancer. Tools to help us understand what molecular characteristics allow a certain subpopulation of cells to spread from the primary tumor are thus critical for overcoming metastasis. Conventional in vitro migration platforms treat populations in aggregate, which leads to a masking of intrinsic differences among cells. Some migration assays reported recently have single-cell resolution, but these platforms do not provide for selective retrieval of the distinct migrating and non-migrating cell populations for further analysis. Thus, to study the intrinsic differences in cells responsible for chemotactic heterogeneity, we developed a single-cell migration platform so that individual cells’ migration behavior can be studied and the heterogeneous population sorted based upon chemotactic phenotype. Furthermore, after migration, the highly chemotactic and non-chemotactic cells were retrieved and proved viable for later molecular analysis of their differences. Moreover, we modified the migration channel to resemble lymphatic capillaries to better understand how certain cancer cells are able to move through geometrically confining spaces. PMID:25984707

  16. FIGG: Simulating populations of whole genome sequences for heterogeneous data analyses

    PubMed Central

    2014-01-01

    Background High-throughput sequencing has become one of the primary tools for investigation of the molecular basis of disease. The increasing use of sequencing in investigations that aim to understand both individuals and populations is challenging our ability to develop analysis tools that scale with the data. This issue is of particular concern in studies that exhibit a wide degree of heterogeneity or deviation from the standard reference genome. The advent of population scale sequencing studies requires analysis tools that are developed and tested against matching quantities of heterogeneous data. Results We developed a large-scale whole genome simulation tool, FIGG, which generates large numbers of whole genomes with known sequence characteristics based on direct sampling of experimentally known or theorized variations. For normal variations we used publicly available data to determine the frequency of different mutation classes across the genome. FIGG then uses this information as a background to generate new sequences from a parent sequence with matching frequencies, but different actual mutations. The background can be normal variations, known disease variations, or a theoretical frequency distribution of variations. Conclusion In order to enable the creation of large numbers of genomes, FIGG generates simulated sequences from known genomic variation and iteratively mutates each genome separately. The result is multiple whole genome sequences with unique variations that can primarily be used to provide different reference genomes, model heterogeneous populations, and can offer a standard test environment for new analysis algorithms or bioinformatics tools. PMID:24885193

  17. Single-cell Migration Chip for Chemotaxis-based Microfluidic Selection of Heterogeneous Cell Populations.

    PubMed

    Chen, Yu-Chih; Allen, Steven G; Ingram, Patrick N; Buckanovich, Ronald; Merajver, Sofia D; Yoon, Euisik

    2015-01-01

    Tumor cell migration toward and intravasation into capillaries is an early and key event in cancer metastasis, yet not all cancer cells are imbued with the same capability to do so. This heterogeneity within a tumor is a fundamental property of cancer. Tools to help us understand what molecular characteristics allow a certain subpopulation of cells to spread from the primary tumor are thus critical for overcoming metastasis. Conventional in vitro migration platforms treat populations in aggregate, which leads to a masking of intrinsic differences among cells. Some migration assays reported recently have single-cell resolution, but these platforms do not provide for selective retrieval of the distinct migrating and non-migrating cell populations for further analysis. Thus, to study the intrinsic differences in cells responsible for chemotactic heterogeneity, we developed a single-cell migration platform so that individual cells' migration behavior can be studied and the heterogeneous population sorted based upon chemotactic phenotype. Furthermore, after migration, the highly chemotactic and non-chemotactic cells were retrieved and proved viable for later molecular analysis of their differences. Moreover, we modified the migration channel to resemble lymphatic capillaries to better understand how certain cancer cells are able to move through geometrically confining spaces. PMID:25984707

  18. Environmental heterogeneity explains the genetic structure of Continental and Mediterranean populations of Fraxinus angustifolia Vahl.

    PubMed

    Temunovi?, Martina; Franji?, Jozo; Satovic, Zlatko; Grgurev, Marin; Frascaria-Lacoste, Nathalie; Fernández-Manjarrés, Juan F

    2012-01-01

    Tree species with wide distributions often exhibit different levels of genetic structuring correlated to their environment. However, understanding how environmental heterogeneity influences genetic variation is difficult because the effects of gene flow, drift and selection are confounded. We investigated the genetic variation and its ecological correlates in a wind-pollinated Mediterranean tree species, Fraxinus angustifolia Vahl, within a recognised glacial refugium in Croatia. We sampled 11 populations from environmentally divergent habitats within the Continental and Mediterranean biogeographical regions. We combined genetic data analyses based on nuclear microsatellite loci, multivariate statistics on environmental data and ecological niche modelling (ENM). We identified a geographic structure with a high genetic diversity and low differentiation in the Continental region, which contrasted with the significantly lower genetic diversity and higher population divergence in the Mediterranean region. The positive and significant correlation between environmental and genetic distances after controlling for geographic distance suggests an important influence of ecological divergence of the sites in shaping genetic variation. The ENM provided support for niche differentiation between the populations from the Continental and Mediterranean regions, suggesting that contemporary populations may represent two divergent ecotypes. Ecotype differentiation was also supported by multivariate environmental and genetic distance analyses. Our results suggest that despite extensive gene flow in continental areas, long-term stability of heterogeneous environments have likely promoted genetic divergence of ashes in this region and can explain the present-day genetic variation patterns of these ancient populations. PMID:22905171

  19. Environmental Heterogeneity Explains the Genetic Structure of Continental and Mediterranean Populations of Fraxinus angustifolia Vahl

    PubMed Central

    Temunovi?, Martina; Franji?, Jozo; Satovic, Zlatko; Grgurev, Marin; Frascaria-Lacoste, Nathalie; Fernández-Manjarrés, Juan F.

    2012-01-01

    Tree species with wide distributions often exhibit different levels of genetic structuring correlated to their environment. However, understanding how environmental heterogeneity influences genetic variation is difficult because the effects of gene flow, drift and selection are confounded. We investigated the genetic variation and its ecological correlates in a wind-pollinated Mediterranean tree species, Fraxinus angustifolia Vahl, within a recognised glacial refugium in Croatia. We sampled 11 populations from environmentally divergent habitats within the Continental and Mediterranean biogeographical regions. We combined genetic data analyses based on nuclear microsatellite loci, multivariate statistics on environmental data and ecological niche modelling (ENM). We identified a geographic structure with a high genetic diversity and low differentiation in the Continental region, which contrasted with the significantly lower genetic diversity and higher population divergence in the Mediterranean region. The positive and significant correlation between environmental and genetic distances after controlling for geographic distance suggests an important influence of ecological divergence of the sites in shaping genetic variation. The ENM provided support for niche differentiation between the populations from the Continental and Mediterranean regions, suggesting that contemporary populations may represent two divergent ecotypes. Ecotype differentiation was also supported by multivariate environmental and genetic distance analyses. Our results suggest that despite extensive gene flow in continental areas, long-term stability of heterogeneous environments have likely promoted genetic divergence of ashes in this region and can explain the present-day genetic variation patterns of these ancient populations. PMID:22905171

  20. 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…

  1. Landscape heterogeneity drives intra-population niche variation and reproduction in an arctic top predator.

    PubMed

    L'hérault, Vincent; Franke, Alastair; Lecomte, Nicolas; Alogut, Adam; Bêty, Joël

    2013-09-01

    While intra-population variability in resource use is ubiquitous, little is known of how this measure of niche diversity varies in space and its role in population dynamics. Here we examined how heterogeneous breeding environments can structure intra-population niche variation in both resource use and reproductive output. We investigated intra-population niche variation in the Arctic tundra ecosystem, studying peregrine falcon (Falco peregrinus tundrius, White) breeding within a terrestrial-marine gradient near Rankin Inlet, Nunavut, Canada. Using stable isotope analysis, we found that intra-population niches varied at the individual level; we examined within-nest and among-nest variation, though only the latter varied along the terrestrial-marine gradient (i.e., increased among-nest variability among birds nesting within the marine environment, indicating higher degree of specialization). Terrestrial prey species (small herbivores and insectivores) were consumed by virtually all falcons. Falcons nesting within the marine environment made use of marine prey (sea birds), but depended heavily on terrestrial prey (up to 90% of the diet). Using 28-years of peregrine falcon nesting data, we found a positive relationship between the proportion of terrestrial habitat surrounding nest sites and annual nestling production, but no relationship with the likelihood of successfully rearing at least one nestling reaching 25 days old. Annually, successful inland breeders raised 0.47 more young on average compared to offshore breeders, which yields potential fitness consequences for this long-living species. The analyses of niche and reproductive success suggest a potential breeding cost for accessing distant terrestrial prey, perhaps due to additional traveling costs, for those individuals with marine nest site locations. Our study indicates how landscape heterogeneity can generate proximate (niche variation) and ultimate (reproduction) consequences on a population of generalist predator. We also show that within-individual and among-individual variation are not mutually exclusive, but can simultaneously arise and structure intra-population niche variation. PMID:24101979

  2. Landscape heterogeneity drives intra-population niche variation and reproduction in an arctic top predator

    PubMed Central

    L'Hérault, Vincent; Franke, Alastair; Lecomte, Nicolas; Alogut, Adam; Bêty, Joël

    2013-01-01

    While intra-population variability in resource use is ubiquitous, little is known of how this measure of niche diversity varies in space and its role in population dynamics. Here we examined how heterogeneous breeding environments can structure intra-population niche variation in both resource use and reproductive output. We investigated intra-population niche variation in the Arctic tundra ecosystem, studying peregrine falcon (Falco peregrinus tundrius, White) breeding within a terrestrial-marine gradient near Rankin Inlet, Nunavut, Canada. Using stable isotope analysis, we found that intra-population niches varied at the individual level; we examined within-nest and among-nest variation, though only the latter varied along the terrestrial-marine gradient (i.e., increased among-nest variability among birds nesting within the marine environment, indicating higher degree of specialization). Terrestrial prey species (small herbivores and insectivores) were consumed by virtually all falcons. Falcons nesting within the marine environment made use of marine prey (sea birds), but depended heavily on terrestrial prey (up to 90% of the diet). Using 28-years of peregrine falcon nesting data, we found a positive relationship between the proportion of terrestrial habitat surrounding nest sites and annual nestling production, but no relationship with the likelihood of successfully rearing at least one nestling reaching 25 days old. Annually, successful inland breeders raised 0.47 more young on average compared to offshore breeders, which yields potential fitness consequences for this long-living species. The analyses of niche and reproductive success suggest a potential breeding cost for accessing distant terrestrial prey, perhaps due to additional traveling costs, for those individuals with marine nest site locations. Our study indicates how landscape heterogeneity can generate proximate (niche variation) and ultimate (reproduction) consequences on a population of generalist predator. We also show that within-individual and among-individual variation are not mutually exclusive, but can simultaneously arise and structure intra-population niche variation. PMID:24101979

  3. In vitro heterogeneity of osteogenic cell populations at various equine skeletal sites

    PubMed Central

    McDuffee, Laurie A.; Anderson, Gail I.; Wright, Glenda M.; Ryan, Daniel A.J.

    2006-01-01

    Bone cell cultures were evaluated to determine if osteogenic cell populations at different skeletal sites in the horse are heterogeneous. Osteogenic cells were isolated from cortical and cancellous bone in vitro by an explant culture method. Subcultured cells were induced to differentiate into boneforming osteoblasts. The osteoblast phenotype was confirmed by immunohistochemical testing for osteocalcin and substantiated by positive staining of cells for alkaline phosphatase and the matrix materials collagen and glycosaminoglycans. Bone nodules were stained by the von Kossa method and counted. The numbers of nodules produced from osteogenic cells harvested from different skeletal sites were compared with the use of a mixed linear model. On average, cortical bone sites yielded significantly greater numbers of nodules than did cancellous bone sites. Between cortical bone sites, there was no significant difference in nodule numbers. Among cancellous sites, the radial cancellous bone yielded significantly more nodules than did the tibial cancellous bone. Among appendicular skeletal sites, tibial metaphyseal bone yielded significantly fewer nodules than did all other long bone sites. This study detected evidence of heterogeneity of equine osteogenic cell populations at various skeletal sites. Further characterization of the dissimilarities is warranted to determine the potential role heterogeneity plays in differential rates of fracture healing between skeletal sites. PMID:17042380

  4. In vitro heterogeneity of osteogenic cell populations at various equine skeletal sites.

    PubMed

    McDuffee, Laurie A; Anderson, Gail I; Wright, Glenda M; Ryan, Daniel A J

    2006-10-01

    Bone cell cultures were evaluated to determine if osteogenic cell populations at different skeletal sites in the horse are heterogeneous. Osteogenic cells were isolated from cortical and cancellous bone in vitro by an explant culture method. Subcultured cells were induced to differentiate into bone-forming osteoblasts. The osteoblast phenotype was confirmed by immunohistochemical testing for osteocalcin and substantiated by positive staining of cells for alkaline phosphatase and the matrix materials collagen and glycosaminoglycans. Bone nodules were stained by the von Kossa method and counted. The numbers of nodules produced from osteogenic cells harvested from different skeletal sites were compared with the use of a mixed linear model. On average, cortical bone sites yielded significantly greater numbers of nodules than did cancellous bone sites. Between cortical bone sites, there was no significant difference in nodule numbers. Among cancellous sites, the radial cancellous bone yielded significantly more nodules than did the tibial cancellous bone. Among appendicular skeletal sites, tibial metaphyseal bone yielded significantly fewer nodules than did all other long bone sites. This study detected evidence of heterogeneity of equine osteogenic cell populations at various skeletal sites. Further characterization of the dissimilarities is warranted to determine the potential role heterogeneity plays in differential rates of fracture healing between skeletal sites. PMID:17042380

  5. Effect of distance-related heterogeneity on population size estimates from point counts

    USGS Publications Warehouse

    Efford, M.G.; Dawson, D.K.

    2009-01-01

    Point counts are used widely to index bird populations. Variation in the proportion of birds counted is a known source of error, and for robust inference it has been advocated that counts be converted to estimates of absolute population size. We used simulation to assess nine methods for the conduct and analysis of point counts when the data included distance-related heterogeneity of individual detection probability. Distance from the observer is a ubiquitous source of heterogeneity, because nearby birds are more easily detected than distant ones. Several recent methods (dependent double-observer, time of first detection, time of detection, independent multiple-observer, and repeated counts) do not account for distance-related heterogeneity, at least in their simpler forms. We assessed bias in estimates of population size by simulating counts with fixed radius w over four time intervals (occasions). Detection probability per occasion was modeled as a half-normal function of distance with scale parameter sigma and intercept g(0) = 1.0. Bias varied with sigma/w; values of sigma inferred from published studies were often 50% for a 100-m fixed-radius count. More critically, the bias of adjusted counts sometimes varied more than that of unadjusted counts, and inference from adjusted counts would be less robust. The problem was not solved by using mixture models or including distance as a covariate. Conventional distance sampling performed well in simulations, but its assumptions are difficult to meet in the field. We conclude that no existing method allows effective estimation of population size from point counts.

  6. Cluster analysis of the genetic heterogeneity and disease distributions in purebred dog populations.

    PubMed

    Ubbink, G J; van de Broek, J; Hazewinkel, H A; Rothuizen, J

    1998-02-28

    Purebred dog populations have been subject to strong selection which has resulted in extreme differences between breeds and decreased heterogeneity within breeds. As a result, breed-specific inherited diseases have accumulated in many populations. The aim of this study was to analyse genetic heterogeneity in relation to the distribution of elbow dysplasia in labrador retrievers, portosystemic shunts in Irish wolfhounds, and hepatic copper toxicosis, in Bedlington terriers. Decreased heterogeneity was demonstrated in the multiple genetic interrelations in the three populations. In pedigrees containing seven generations of ancestors, the average number of common ancestors in all pair-wise combinations of dogs was five to six (range 0 to 18). These complex interrelationships were resolved by a cluster analysis on matrices of relatedness. This analysis gave clusters of highly related animals, the average relatedness of these clusters, and the average relatedness of the entire population, as expressions of its genetic variability. The mean relatedness was 0.032 for Irish wolfhounds and Bedlington terriers, and 0.002 for labrador retrievers. The labrador retriever cohort was resolved into 31 clusters, and all cases of elbow dysplasia were concentrated in five highly related clusters with an overall incidence of 17 per cent. The Bedlington terrier cohort consisted of 12 clusters which all contained cases of copper toxicosis, with an overall incidence of 46 per cent. The Irish wolfhounds were divided into 14 clusters with a disease incidence of 4 per cent. Dogs with portosystemic shunts were found in four averagely related clusters. A genetic distribution became obvious only when relatedness due to common ancestors of the cases was used as a criterion, and the cases were then concentrated in five highly related clusters. PMID:9533291

  7. Population-level responses to nutrient heterogeneity and density by Abutilon theophrasti (Malvaceae): an experimental neighborhood approach.

    PubMed

    Casper, B B; Cahill, J F

    1998-12-01

    An experimental approach was used to examine the effects of spatial nutrient heterogeneity and planting density on the sizes of plants within populations of Abutilon theophrasti. Planting locations were generated using random numbers and replicated among populations growing on two different scales of heterogeneity and homogeneous soils. The same quantity of nutrients (dehydrated cow manure) was added to each population, regardless of the spatial nutrient distribution. The higher density was achieved by adding additional planting locations to those present at the lower density. Plant biomass was compared among ten planting locations present in all populations. Plants in seven locations were smaller at the higher density, but the spatial distribution of nutrients affected plant size in only two locations. At the population level, the higher density reduced mean plant biomass and increased both total biomass and the coefficient of variation in biomass, a measure of size inequality. Only when populations on both scales of heterogeneity were together compared with those on homogeneous soils were population-level measurements found to be significantly affected by soil treatment; heterogeneity resulted in decreased total biomass and an increase in the coefficient of variation, apparently due to an increase in the number of small plants in the population. These results, together with the finding that fine root biomass increased in nutrient-enriched patches, suggest that on heterogeneous soils most plants were able to access nutrient patches. PMID:21680329

  8. Role of temperate forest heterogeneity in determining the population ecology of Peromyscus leucopus

    SciTech Connect

    Ormiston, B.G.

    1980-11-01

    Population density levels of small mammals are often roughly correlated with local forest productivity. In a highly productive forest the total number of individual small mammals (all species) may exceed 100/hectare. Low productivity forests may harbor few or none at all. Thus, the potential exists for using small mammal populations as indicators of local forest composition and quality. Changes in the density levels of species used for this purpose (indicator species) may so reflect the dynamics of forest structure and productivity. The white-footed mouse, Peromyscus leucopus, is common in temperate deciduous forests throughout the northeastern United States. Its ubiquitous distribution is a required feature for studying the effects of variation in forest components upon a representative consumer. The goal of this study was to collect baseline data on P. leucopus populations responding to spatial and temporal forest heterogeneity, and so evaluate its potential as an indicator species.

  9. Power in Numbers: Student Participation in Mathematical Discussions in Heterogeneous Spaces

    ERIC Educational Resources Information Center

    Esmonde, Indigo; Langer-Osuna, Jennifer M.

    2013-01-01

    Mathematics classrooms are conceptualized as heterogeneous spaces in which multiple figured worlds come into contact. The study explores how a group of high school students drew upon several figured worlds as they navigated mathematical discussions. (Contains 5 excerpts and 2 footnotes.)

  10. Assessing Heterogeneous Student Bodies Using a Methodology that Encourages the Acquisition of Skills Valued by Employers

    ERIC Educational Resources Information Center

    Perdigones, Alicia; Garcia, Jose Luis; Valino, Vanesa; Raposo, Cecilia

    2009-01-01

    This work compares the results of three assessment systems used in two Spanish universities (the "Universidad Politecnica de Madrid" and the "Universidad Catolica de Avila"): the traditional system based on final examinations, continuous assessment with periodic tests and a proposed system (specially designed for heterogeneous student bodies)…

  11. The Effects of Heterogeneous and Homogeneous Groupings on Student Attitudes and Student Performance in Eighth and Ninth Grade Social Studies Classes.

    ERIC Educational Resources Information Center

    Marascuilo, Leonard A.

    This study attempts to determine whether or not ability grouping is desirable for effective instruction. Parents volunteered their children for assignment to a heterogeneous social studies class. Students were divided into a Volunteer Group, a Non-volunteer Group and a Non-response Group. Students for the heterogeneous classes were randomly…

  12. Heterogeneity of intrinsic biophysical properties among cochlear nucleus neurons improves the population coding of temporal information

    PubMed Central

    Ahn, J.; Kreeger, L. J.; Lubejko, S. T.; Butts, D. A.

    2014-01-01

    Reliable representation of the spectrotemporal features of an acoustic stimulus is critical for sound recognition. However, if all neurons respond with identical firing to the same stimulus, redundancy in the activity patterns would reduce the information capacity of the population. We thus investigated spike reliability and temporal fluctuation coding in an ensemble of neurons recorded in vitro from the avian auditory brain stem. Sequential patch-clamp recordings were made from neurons of the cochlear nucleus angularis while injecting identical filtered Gaussian white noise currents, simulating synaptic drive. The spiking activity in neurons receiving these identically fluctuating stimuli was highly correlated, measured pairwise across neurons and as a pseudo-population. Two distinct uncorrelated noise stimuli could be discriminated using the temporal patterning, but not firing rate, of the spike trains in the neural ensemble, with best discrimination using information at time scales of 5–20 ms. Despite high cross-correlation values, the spike patterns observed in individual neurons were idiosyncratic, with notable heterogeneity across neurons. To investigate how temporal information is being encoded, we used optimal linear reconstruction to produce an estimate of the original current stimulus from the spike trains. Ensembles of trains sampled across the neural population could be used to predict >50% of the stimulus variation using optimal linear decoding, compared with ?20% using the same number of spike trains recorded from single neurons. We conclude that heterogeneity in the intrinsic biophysical properties of cochlear nucleus neurons reduces firing pattern redundancy while enhancing representation of temporal information. PMID:24623512

  13. Wide proteolytic activity survey reinforces heterogeneity among Trypanosoma cruzi TCI and TCII wild populations.

    PubMed

    Fampa, Patrícia; Lisboa, Cristiane Varella; Zahner, Viviane; Jansen, Ana Maria; Ramirez, Marcel Ivan

    2010-11-01

    Chagas disease, caused by the flagellate protozoan Trypanosoma cruzi, is characterized by considerable variation in both incidence and infection severity. This variation has been attributed to a set of complex features including the host genetic background, environmental and social factors, and the genetic heterogeneity of parasite populations. Using biochemical and molecular markers these populations can be divided into two major groups (TCI and TCII). In a previous work, our group identified cysteine and metalloprotease activities as good markers for differentiating TCI from TCII wild isolates, with a higher level of heterogeneity observed among TCII isolates. In this investigation, we applied the protease activity assay to a sample of 49 sylvatic T. cruzi isolates that had been previously assessed in terms of their Swiss mice infection patterns. Protease activity profiles were determined at pH 5.5 and 10.0 and was compared with the original host species, phylogenetic lineage, and mice infection characteristics. Substantial variability, with molecular weights ranging from 35 to 220 kDa for active proteases at pH 5.5, and of 30 to 90 kDa for active proteases at pH 10.0, was observed in gelatin substrate gels, with no phenetic separation between TCI and TCII groups or original hosts. The combinatorial expression of proteases recorded among individual isolates may account for the diverse behavior observed for parasite populations in nature. PMID:20420537

  14. Deconstructing stem cell population heterogeneity: Single-cell analysis and modeling approaches

    PubMed Central

    Wu, Jincheng; Tzanakakis, Emmanuel S.

    2014-01-01

    Isogenic stem cell populations display cell-to-cell variations in a multitude of attributes including gene or protein expression, epigenetic state, morphology, proliferation and proclivity for differentiation. The origins of the observed heterogeneity and its roles in the maintenance of pluripotency and the lineage specification of stem cells remain unclear. Addressing pertinent questions will require the employment of single-cell analysis methods as traditional cell biochemical and biomolecular assays yield mostly population-average data. In addition to time-lapse microscopy and flow cytometry, recent advances in single-cell genomic, transcriptomic and proteomic profiling are reviewed. The application of multiple displacement amplification, next generation sequencing, mass cytometry and spectrometry to stem cell systems is expected to provide a wealth of information affording unprecedented levels of multiparametric characterization of cell ensembles under defined conditions promoting pluripotency or commitment. Establishing connections between single-cell analysis information and the observed phenotypes will also require suitable mathematical models. Stem cell self-renewal and differentiation are orchestrated by the coordinated regulation of subcellular, intercellular and niche-wide processes spanning multiple time scales. Here, we discuss different modeling approaches and challenges arising from their application to stem cell populations. Integrating single-cell analysis with computational methods will fill gaps in our knowledge about the functions of heterogeneity in stem cell physiology. This combination will also aid the rational design of efficient differentiation and reprogramming strategies as well as bioprocesses for the production of clinically valuable stem cell derivatives. PMID:24035899

  15. Heterogeneity of intrinsic biophysical properties among cochlear nucleus neurons improves the population coding of temporal information.

    PubMed

    Ahn, J; Kreeger, L J; Lubejko, S T; Butts, D A; MacLeod, K M

    2014-06-01

    Reliable representation of the spectrotemporal features of an acoustic stimulus is critical for sound recognition. However, if all neurons respond with identical firing to the same stimulus, redundancy in the activity patterns would reduce the information capacity of the population. We thus investigated spike reliability and temporal fluctuation coding in an ensemble of neurons recorded in vitro from the avian auditory brain stem. Sequential patch-clamp recordings were made from neurons of the cochlear nucleus angularis while injecting identical filtered Gaussian white noise currents, simulating synaptic drive. The spiking activity in neurons receiving these identically fluctuating stimuli was highly correlated, measured pairwise across neurons and as a pseudo-population. Two distinct uncorrelated noise stimuli could be discriminated using the temporal patterning, but not firing rate, of the spike trains in the neural ensemble, with best discrimination using information at time scales of 5-20 ms. Despite high cross-correlation values, the spike patterns observed in individual neurons were idiosyncratic, with notable heterogeneity across neurons. To investigate how temporal information is being encoded, we used optimal linear reconstruction to produce an estimate of the original current stimulus from the spike trains. Ensembles of trains sampled across the neural population could be used to predict >50% of the stimulus variation using optimal linear decoding, compared with ?20% using the same number of spike trains recorded from single neurons. We conclude that heterogeneity in the intrinsic biophysical properties of cochlear nucleus neurons reduces firing pattern redundancy while enhancing representation of temporal information. PMID:24623512

  16. Cluster detection of diseases in heterogeneous populations: an alternative to scan methods.

    PubMed

    Ramis, Rebeca; Gómez-Barroso, Diana; López-Abente, Gonzalo

    2014-05-01

    Cluster detection has become an important part of the agenda of epidemiologists and public health authorities, the identification of high- and low-risk areas is fundamental in the definition of public health strategies and in the suggestion of potential risks factors. Currently, there are different cluster detection techniques available, the most popular being those using windows to scan the areas within the studied region. However, when these areas are heterogeneous in populations' sizes, scan window methods can lead to inaccurate conclusions. In order to perform cluster detection over heterogeneously populated areas, we developed a method not based on scanning windows but instead on standard mortality ratios (SMR) using irregular spatial aggregation (ISA). Its extension, i.e. irregular spatial aggregation with covariates (ISAC), includes covariates with residuals from Poisson regression. We compared the performance of the method with the flexible shaped spatial scan statistic (FlexScan) using mortality data for stomach and bladder cancer for 8,098 Spanish towns. The results show a collection of clusters for stomach and bladder cancer similar to that detected by ISA and FlexScan. However, in general, clusters detected by FlexScan were bigger and include towns with SMR, which were not statistically significant. For bladder cancer, clusters detected by ISAC differed from those detected by ISA and FlexScan in shape and location. The ISA and ISAC methods could be an alternative to the traditional scan window methods for cluster detection over aggregated data when the areas under study are heterogeneous in terms of population. The simplicity and flexibility of the methods make them more attractive than methods based on more complicated algorithms. PMID:24893029

  17. Mapping the Misunderstood Population of Adult Students

    ERIC Educational Resources Information Center

    Ashburn, Elyse

    2007-01-01

    Adult students are not well documented, are frequently left out of discussions of higher-education policy, and are not fully understood by the colleges they attend, says a report ("Returning to Learning: Adults' Success in College is Key to America's Future") released this week by the Lumina Foundation for Education. As a result, those students

  18. Fertility values and acceptance of population control among college students

    E-print Network

    West, Walter G.; Poole, Eric D.

    1974-10-01

    FERTILITY VALUES AND ACCEPTANCE OF POPULATION CONTROL AMONG COLLEGE STUDENTS* Walter G. West Virginia Commonwealth University Eric D. Poole Washington State University **This paper attempts to determine the effects of relevant social factors... on college students' fertility values, examining how these variables and fertility values are associated with attitudes toward govern mental population control. Having hypothesized that fertility values will vary by religion, social class, race...

  19. Quasi-one-dimensional waves in rodent populations in heterogeneous habitats: A consequence of elevational gradients on

    E-print Network

    Kenkre, V.M.

    Quasi-one-dimensional waves in rodent populations in heterogeneous habitats: A consequence and distribution of animal populations on the landscape is determined by the availability of suitable habitat, allowing normally unsuitable (suboptimal) adjacent habitat to periodically become more hospitable for short

  20. Cancer research in Asian American, Native Hawaiian, and Pacific Islander populations: accelerating cancer knowledge by acknowledging and leveraging heterogeneity.

    PubMed

    Gomez, Scarlett Lin; Glaser, Sally L; Horn-Ross, Pamela L; Cheng, Iona; Quach, Thu; Clarke, Christina A; Reynolds, Peggy; Shariff-Marco, Salma; Yang, Juan; Lee, Marion M; Satariano, William A; Hsing, Ann W

    2014-11-01

    The Asian American, Native Hawaiian, and Pacific Islander population is large, growing, and extremely heterogeneous. Not only do they bear unique burdens of incidence and outcomes for certain cancer types, they exhibit substantial variability in cancer incidence and survival patterns across the ethnic groups. By acknowledging and leveraging this heterogeneity through investing in cancer research within these populations, we have a unique opportunity to accelerate the availability of useful and impactful cancer knowledge. See all the articles in this CEBP Focus section, "Cancer in Asian and Pacific Islander Populations." PMID:25368394

  1. FACULTYHIGHEST POPULATION OF INTERNATIONAL STUDENTS AT TU DELFT IN 2013

    E-print Network

    Kuzmanov, Georgi

    POPULATION OF INTERNATIONAL STUDENTS AT TU DELFT IN 2013 INTERNATIONAL STUDENTS PER FACULTY COUNTRIES. INDIA 221 5. GERMANY 206 2. CHINA 316 3. IRAN 136 4. INDIA 134 5. GREECE 104 2. CHINA 244 3. INDONESIA 95 4. SURINAME 88 5. GERMANY 70 2. CHINA 225 3. INDONESIA 85 4. GERMANY 75 4. SURINAME 75 2. CHINA

  2. Orientation Courses: Meeting the Needs of Different Student Populations.

    ERIC Educational Resources Information Center

    Higbee, Jeanne L.

    A model that includes three distinct syllabi for orientation courses for different subgroups of the college or university freshman population is presented. Among the groups with special needs are underprepared students who may be motivated but need skill development, and underachieving students characterized by untapped potential. One means of…

  3. Populational Heterogeneity vs. Temporal Fluctuation in Escherichia coli Flagellar Motor Switching

    PubMed Central

    Bai, Fan; Che, Yong-Suk; Kami-ike, Nobunori; Ma, Qi; Minamino, Tohru; Sowa, Yoshiyuki; Namba, Keiichi

    2013-01-01

    The dynamic switching of the bacterial flagellar motor regulates cell motility in bacterial chemotaxis. It has been reported under physiological conditions that the switching bias of the flagellar motor undergoes large temporal fluctuations, which reflects noise propagating in the chemotactic signaling network. On the other hand, nongenetic heterogeneity is also observed in flagellar motor switching, as a large group of switching motors show different switching bias and frequency under the same physiological condition. In this work, we present simultaneous measurement of groups of Escherichia coli flagellar motor switching and compare them to long time recording of single switching motors. Consistent with previous studies, we observed temporal fluctuations in switching bias in long time recording experiments. However, the variability in switching bias at the populational level showed much higher volatility than its temporal fluctuation. These results suggested stable individuality in E. coli motor switching. We speculate that uneven expression of key regulatory proteins with amplification by the ultrasensitive response of the motor can account for the observed populational heterogeneity and temporal fluctuations. PMID:24209857

  4. Full-length haplotype reconstruction to infer the structure of heterogeneous virus populations.

    PubMed

    Giallonardo, Francesca Di; Töpfer, Armin; Rey, Melanie; Prabhakaran, Sandhya; Duport, Yannick; Leemann, Christine; Schmutz, Stefan; Campbell, Nottania K; Joos, Beda; Lecca, Maria Rita; Patrignani, Andrea; Däumer, Martin; Beisel, Christian; Rusert, Peter; Trkola, Alexandra; Günthard, Huldrych F; Roth, Volker; Beerenwinkel, Niko; Metzner, Karin J

    2014-08-01

    Next-generation sequencing (NGS) technologies enable new insights into the diversity of virus populations within their hosts. Diversity estimation is currently restricted to single-nucleotide variants or to local fragments of no more than a few hundred nucleotides defined by the length of sequence reads. To study complex heterogeneous virus populations comprehensively, novel methods are required that allow for complete reconstruction of the individual viral haplotypes. Here, we show that assembly of whole viral genomes of ?8600 nucleotides length is feasible from mixtures of heterogeneous HIV-1 strains derived from defined combinations of cloned virus strains and from clinical samples of an HIV-1 superinfected individual. Haplotype reconstruction was achieved using optimized experimental protocols and computational methods for amplification, sequencing and assembly. We comparatively assessed the performance of the three NGS platforms 454 Life Sciences/Roche, Illumina and Pacific Biosciences for this task. Our results prove and delineate the feasibility of NGS-based full-length viral haplotype reconstruction and provide new tools for studying evolution and pathogenesis of viruses. PMID:24972832

  5. Application of phasor plot and autofluorescence correction for study of heterogeneous cell population.

    PubMed

    Szmacinski, Henryk; Toshchakov, Vladimir; Lakowicz, Joseph R

    2014-04-01

    Protein-protein interactions in cells are often studied using fluorescence resonance energy transfer (FRET) phenomenon by fluorescence lifetime imaging microscopy (FLIM). Here, we demonstrate approaches to the quantitative analysis of FRET in cell population in a case complicated by a highly heterogeneous donor expression, multiexponential donor lifetime, large contribution of cell autofluorescence, and significant presence of unquenched donor molecules that do not interact with the acceptor due to low affinity of donor-acceptor binding. We applied a multifrequency phasor plot to visualize FRET FLIM data, developed a method for lifetime background correction, and performed a detailed time-resolved analysis using a biexponential model. These approaches were applied to study the interaction between the Toll Interleukin-1 receptor (TIR) domain of Toll-like receptor 4 (TLR4) and the decoy peptide 4BB. TLR4 was fused to Cerulean fluorescent protein (Cer) and 4BB peptide was labeled with Bodipy TMRX (BTX). Phasor displays for multifrequency FLIM data are presented. The analytical procedure for lifetime background correction is described and the effect of correction on FLIM data is demonstrated. The absolute FRET efficiency was determined based on the phasor plot display and multifrequency FLIM data analysis. The binding affinity between TLR4-Cer (donor) and decoy peptide 4BB-BTX (acceptor) was estimated in a heterogeneous HeLa cell population. PMID:24770662

  6. Application of phasor plot and autofluorescence correction for study of heterogeneous cell population

    PubMed Central

    Szmacinski, Henryk; Toshchakov, Vladimir; Lakowicz, Joseph R.

    2014-01-01

    Abstract. Protein-protein interactions in cells are often studied using fluorescence resonance energy transfer (FRET) phenomenon by fluorescence lifetime imaging microscopy (FLIM). Here, we demonstrate approaches to the quantitative analysis of FRET in cell population in a case complicated by a highly heterogeneous donor expression, multiexponential donor lifetime, large contribution of cell autofluorescence, and significant presence of unquenched donor molecules that do not interact with the acceptor due to low affinity of donor-acceptor binding. We applied a multifrequency phasor plot to visualize FRET FLIM data, developed a method for lifetime background correction, and performed a detailed time-resolved analysis using a biexponential model. These approaches were applied to study the interaction between the Toll Interleukin-1 receptor (TIR) domain of Toll-like receptor 4 (TLR4) and the decoy peptide 4BB. TLR4 was fused to Cerulean fluorescent protein (Cer) and 4BB peptide was labeled with Bodipy TMRX (BTX). Phasor displays for multifrequency FLIM data are presented. The analytical procedure for lifetime background correction is described and the effect of correction on FLIM data is demonstrated. The absolute FRET efficiency was determined based on the phasor plot display and multifrequency FLIM data analysis. The binding affinity between TLR4-Cer (donor) and decoy peptide 4BB-BTX (acceptor) was estimated in a heterogeneous HeLa cell population. PMID:24770662

  7. The side population of ovarian cancer cells defines a heterogeneous compartment exhibiting stem cell characteristics

    PubMed Central

    Boesch, Maximilian; Zeimet, Alain G.; Reimer, Daniel; Schmidt, Stefan; Gastl, Guenther; Parson, Walther; Spoeck, Franziska; Hatina, Jiri

    2014-01-01

    Cancer stem cells (CSC) are believed to be involved in tumor evasion of classical antitumor therapies and have thus become an attractive target for further improvement of anticancer strategies. However, the existence and identity of CSC are still a matter of controversy. In a systematic screen of 13 ovarian cancer cell lines we show that cells with stem cell properties are reliably detectable as a minor population, characterized by ABC transporter expression resulting in the side population (SP) phenotype. In different cell lines, either ABCG2 or ABCB1 was found to be responsible for this effect. Purified SP cells featured virtually all characteristics of bona fide CSC, including clonogenicity, asymmetric division and high tumorigenicity in vivo. Using in-depth phenotyping by multicolor flow cytometry, we found that among the investigated ovarian cancer cell lines the SP compartment exhibits tremendous heterogeneity and is composed of multiple phenotypically distinct subpopulations. Thus, our study confirms previous results showing that CSC are contained within the SP. However, the exact identity of the CSC is still disguised by the high complexity of the CSC-containing compartment. Further functional studies are needed to determine whether a single cellular subset can unambiguously be defined as CSC or whether multiple stem cell-like cells with different properties coexist. Moreover, the observed heterogeneity may reflect a high level of plasticity and likely influences tumor progression, escape from immune-surveillance and development of resistance to anticancer therapies and should therefore be considered in the development of new treatment strategies. PMID:25216521

  8. The side population of ovarian cancer cells defines a heterogeneous compartment exhibiting stem cell characteristics.

    PubMed

    Boesch, Maximilian; Zeimet, Alain G; Reimer, Daniel; Schmidt, Stefan; Gastl, Guenther; Parson, Walther; Spoeck, Franziska; Hatina, Jiri; Wolf, Dominik; Sopper, Sieghart

    2014-08-30

    Cancer stem cells (CSC) are believed to be involved in tumor evasion of classical antitumor therapies and have thus become an attractive target for further improvement of anticancer strategies. However, the existence and identity of CSC are still a matter of controversy. In a systematic screen of 13 ovarian cancer cell lines we show that cells with stem cell properties are reliably detectable as a minor population, characterized by ABC transporter expression resulting in the side population (SP) phenotype. In different cell lines, either ABCG2 or ABCB1 was found to be responsible for this effect. Purified SP cells featured virtually all characteristics of bona fide CSC, including clonogenicity, asymmetric division and high tumorigenicity in vivo. Using in-depth phenotyping by multicolor flow cytometry, we found that among the investigated ovarian cancer cell lines the SP compartment exhibits tremendous heterogeneity and is composed of multiple phenotypically distinct subpopulations. Thus, our study confirms previous results showing that CSC are contained within the SP. However, the exact identity of the CSC is still disguised by the high complexity of the CSC-containing compartment. Further functional studies are needed to determine whether a single cellular subset can unambiguously be defined as CSC or whether multiple stem cell-like cells with different properties coexist. Moreover, the observed heterogeneity may reflect a high level of plasticity and likely influences tumor progression, escape from immune-surveillance and development of resistance to anticancer therapies and should therefore be considered in the development of new treatment strategies. PMID:25216521

  9. Heterogeneity in Genetic Diversity among Non-Coding Loci Fails to Fit Neutral Coalescent Models of Population History

    PubMed Central

    Peters, Jeffrey L.; Roberts, Trina E.; Winker, Kevin; McCracken, Kevin G.

    2012-01-01

    Inferring aspects of the population histories of species using coalescent analyses of non-coding nuclear DNA has grown in popularity. These inferences, such as divergence, gene flow, and changes in population size, assume that genetic data reflect simple population histories and neutral evolutionary processes. However, violating model assumptions can result in a poor fit between empirical data and the models. We sampled 22 nuclear intron sequences from at least 19 different chromosomes (a genomic transect) to test for deviations from selective neutrality in the gadwall (Anas strepera), a Holarctic duck. Nucleotide diversity among these loci varied by nearly two orders of magnitude (from 0.0004 to 0.029), and this heterogeneity could not be explained by differences in substitution rates alone. Using two different coalescent methods to infer models of population history and then simulating neutral genetic diversity under these models, we found that the observed among-locus heterogeneity in nucleotide diversity was significantly higher than expected for these simple models. Defining more complex models of population history demonstrated that a pre-divergence bottleneck was also unlikely to explain this heterogeneity. However, both selection and interspecific hybridization could account for the heterogeneity observed among loci. Regardless of the cause of the deviation, our results illustrate that violating key assumptions of coalescent models can mislead inferences of population history. PMID:22384117

  10. The genetic structure of a Venturia inaequalis population in a heterogeneous host population composed of different Malus species

    PubMed Central

    2013-01-01

    Background Adaptation, which induces differentiation between populations in relation to environmental conditions, can initiate divergence. The balance between gene flow and selection determines the maintenance of such a structure in sympatry. Studying these two antagonistic forces in plant pathogens is made possible because of the high ability of pathogens to disperse and of the strong selective pressures exerted by their hosts. In this article, we analysed the genetic structure of the population of the apple scab fungus, Venturia inaequalis, in a heterogeneous environment composed of various Malus species. Inferences were drawn from microsatellite and AFLP data obtained from 114 strains sampled in a single orchard on nine different Malus species to determine the forces that shape the genetic structure of the pathogen. Results Using clustering methods, we first identified two specialist subpopulations: (i) a virulent subpopulation sampled on Malus trees carrying the Rvi6 resistance gene; and (ii) a subpopulation infecting only Malus trees that did not carry this resistance gene. A genome scan of loci on these two subpopulations did not detect any locus under selection. Additionally, we did not detect any other particular substructure linked to different hosts. However, an isolation-by-distance (IBD) pattern at the orchard scale revealed free gene flow within each subpopulation. Conclusions Our work shows a rare example of a very strong effect of a resistance gene on pathogen populations. Despite the high diversity of Malus hosts, the presence of Rvi6 seems sufficient to explain the observed genetic structure. Moreover, detection of an IBD pattern at the orchard scale revealed a very low average dispersal distance that is particularly significant for epidemiologists and landscape managers for the design of scab control strategies PMID:23497223

  11. Exposing medical students to expanding populations.

    PubMed

    Lindenthal, J J; DeLisa, J A; Heinrich, G F; Calderón Gerstein, W S

    2015-01-01

    Physicians are required to advocate for and counsel patients based on the best science and the interests of the individual while avoiding discrimination, ensuring equal access to health and mental services. Nonetheless, the communication gap between physician and patients has long been observed. To this end, the Institute for the Public Understanding of Health and Medicine of the Rutgers University New Jersey Medical School has expanded its efforts. This report describes two new programs: a legacy lecture series for medical students and an international "experience", in Huancayo, Peru, for medical students and faculty. The MiniMed outreach program, now in its ninth year and first described in this journal in 2012, was designed to empower the powerless to communicate more effectively with clinicians, thus improving both the effectiveness of the physician-patient relationship and health care outcomes. The approach of the two new programs and their effects on patients, particularly the underserved, and medical students and faculty, are outlined in the following article. PMID:25834472

  12. A finite mixture model for genotype and environment interactions: detecting latent population heterogeneity.

    PubMed

    Gillespie, Nathan A; Neale, Michael C

    2006-06-01

    Approaches such as DeFries-Fulker extremes regression (LaBuda et al., 1986) are commonly used in genetically informative studies to assess whether familial resemblance varies as a function of the scores of pairs of twins. While useful for detecting such effects, formal modeling of differences in variance components as a function of pairs' trait scores is rarely attempted. We therefore present a finite mixture model which specifies that the population consists of latent groups which may differ in (i) their means, and (ii) the relative impact of genetic and environmental factors on within-group variation and covariation. This model may be considered as a special case of a factor mixture model, which combines the features of a latent class model with those of a latent trait model. Various models for the class membership of twin pairs may be employed, including additive genetic, common environment, specific environment or major locus (QTL) factors. Simulation results based on variance components derived from Turkheimer and colleagues (2003), illustrate the impact of factors such as the difference in group means and variance components on the feasibility of correctly estimating the parameters of the mixture model. Model-fitting analyses estimated group heritability as .49, which is significantly greater than heritability for the rest of the population in early childhood. These results suggest that factor mixture modeling is sufficiently robust for detecting heterogeneous populations even when group mean differences are modest. PMID:16790151

  13. Emergence of cooperation in phenotypically heterogeneous populations: a replicator dynamics analysis

    NASA Astrophysics Data System (ADS)

    Barreira da Silva Rocha, A.; Escobedo, R.; Laruelle, A.

    2015-06-01

    The emergence of cooperation is analyzed in heterogeneous populations where two kinds of individuals exist according to their phenotypic appearance. Phenotype recognition is assumed for all individuals: individuals are able to identify the type of every other individual, but fail to recognize their own type. Individuals thus behave under partial information conditions. The interactions between individuals are described by the snowdrift game, where individuals can either cooperate or defect. The evolution of such populations is studied in the framework of evolutionary game theory by means of the replicator dynamics. Overlapping generations are considered, so the replicator equations are formulated in discrete-time form. The stability analysis of the dynamical system is carried out and a detailed description of the behavior of trajectories starting from the interior of the state-space is given. We find that the four monomorphic states are unstable and that a polymorphic state exists which is a global attractor for non-degenerate initial states of the population. The result for the discrete-time replicator coincides with the one of the continuous case.

  14. Functional Differentiation of a Population of Electrically-Coupled Heterogeneous Elements in a Microcircuit

    PubMed Central

    Sasaki, Kosei; Cropper, Elizabeth C; Weiss, Klaudiusz R; Jing, Jian

    2013-01-01

    Although electrical coupling is present in many microcircuits, the extent to which it will determine neuronal firing patterns and network activity remains poorly understood. This is particularly true when the coupling is present in a population of heterogeneous, or intrinsically distinct circuit elements. We examine this question in the Aplysia californica feeding motor network in five electrically-coupled identified cells, B64, B4/5, B70, B51 and a newly-identified interneuron B71. These neurons exhibit distinct activity patterns during the radula retraction phase of motor programs. In a subset of motor programs, retraction can be flexibly extended by adding a phase of network activity (hyper-retraction). This is manifested most prominently as an additional burst in the radula closure motoneuron B8. Two neurons that excite B8 (B51 and B71) and one that inhibits it (B70) are active during hyper-retraction. Consistent with their near synchronous firing, B51 and B71 showed one of the strongest coupling ratios in this group of neurons. Nonetheless, by manipulating their activity, we found that B51 preferentially acted as a driver of B64/B71 activity, whereas B71 played a larger role in driving B8 activity. In contrast, B70 was weakly coupled to other neurons and its inhibition of B8 counter-acted the excitatory drive to B8. Finally, the distinct firing patterns of the electrically-coupled neurons were fine-tuned by their intrinsic properties and the largely chemical cross-inhibition between some of them. Thus, the small microcircuit of Aplysia feeding network is advantageous in understanding how a population of electrically-coupled heterogeneous neurons may fulfill specific network functions. PMID:23283325

  15. Combined Single-Cell Functional and Gene Expression Analysis Resolves Heterogeneity within Stem Cell Populations

    PubMed Central

    Wilson, Nicola K.; Kent, David G.; Buettner, Florian; Shehata, Mona; Macaulay, Iain C.; Calero-Nieto, Fernando J.; Sánchez Castillo, Manuel; Oedekoven, Caroline A.; Diamanti, Evangelia; Schulte, Reiner; Ponting, Chris P.; Voet, Thierry; Caldas, Carlos; Stingl, John; Green, Anthony R.; Theis, Fabian J.; Göttgens, Berthold

    2015-01-01

    Summary Heterogeneity within the self-renewal durability of adult hematopoietic stem cells (HSCs) challenges our understanding of the molecular framework underlying HSC function. Gene expression studies have been hampered by the presence of multiple HSC subtypes and contaminating non-HSCs in bulk HSC populations. To gain deeper insight into the gene expression program of murine HSCs, we combined single-cell functional assays with flow cytometric index sorting and single-cell gene expression assays. Through bioinformatic integration of these datasets, we designed an unbiased sorting strategy that separates non-HSCs away from HSCs, and single-cell transplantation experiments using the enriched population were combined with RNA-seq data to identify key molecules that associate with long-term durable self-renewal, producing a single-cell molecular dataset that is linked to functional stem cell activity. Finally, we demonstrated the broader applicability of this approach for linking key molecules with defined cellular functions in another stem cell system. PMID:26004780

  16. Autosomal dominant ataxia: Genetic evidence for locus heterogeneity from a cuban founder-effect population

    PubMed Central

    Auburger, Georg; Diaz, Guillermo Orozco; Capote, Raul Ferreira; Sanchez, Suzana Gispert; Perez, Marta Paradoa; del Cueto, Marianela Estrada; Meneses, Mirna Garcia; Farrall, Martin; Williamson, Robert; Chamberlain, Susan; Baute, Luis Heredero

    1990-01-01

    The locus for autosomal dominant ataxia with a diagnosis of olivo-ponto-cerebellar atrophy at autopsy has been previously assigned to chromosome 6p. However, evidence for two alternative locations has been reported. We have recently described a large potential founder-effect population of such patients in the Holguin province of Cuba. With an estimated 1,000 patients available for analysis, this extensive cluster of families provides a unique opportunity for the definitive localization of the genetic mutation. Linkage analysis between the disease locus in this population and markers within and flanking the HLA region on chromosome 6 were undertaken in 12 families comprising over 100 affected individuals. Despite similarity in the clinical phenotype between those families where the disease locus has been reported to be linked to the HLA locus and the Cuban patients, no evidence of linkage to this region could be demonstrated in the latter. The disease locus was excluded from a 96-cM genetic interval of the short arm of chromosome 6, encompassing the F13A1–HLA–GLO1–MUT/D6S4 loci. These data strongly support the existence of genetic heterogeneity for the disease. PMID:1971152

  17. Combined Single-Cell Functional and Gene Expression Analysis Resolves Heterogeneity within Stem Cell Populations.

    PubMed

    Wilson, Nicola K; Kent, David G; Buettner, Florian; Shehata, Mona; Macaulay, Iain C; Calero-Nieto, Fernando J; Sánchez Castillo, Manuel; Oedekoven, Caroline A; Diamanti, Evangelia; Schulte, Reiner; Ponting, Chris P; Voet, Thierry; Caldas, Carlos; Stingl, John; Green, Anthony R; Theis, Fabian J; Göttgens, Berthold

    2015-06-01

    Heterogeneity within the self-renewal durability of adult hematopoietic stem cells (HSCs) challenges our understanding of the molecular framework underlying HSC function. Gene expression studies have been hampered by the presence of multiple HSC subtypes and contaminating non-HSCs in bulk HSC populations. To gain deeper insight into the gene expression program of murine HSCs, we combined single-cell functional assays with flow cytometric index sorting and single-cell gene expression assays. Through bioinformatic integration of these datasets, we designed an unbiased sorting strategy that separates non-HSCs away from HSCs, and single-cell transplantation experiments using the enriched population were combined with RNA-seq data to identify key molecules that associate with long-term durable self-renewal, producing a single-cell molecular dataset that is linked to functional stem cell activity. Finally, we demonstrated the broader applicability of this approach for linking key molecules with defined cellular functions in another stem cell system. PMID:26004780

  18. Parasite strain coexistence in a heterogeneous host population Darren M. Green, Istvan Z. Kiss and Rowland R. Kao

    E-print Network

    Kiss, Istvan Zoltan

    Parasite strain coexistence in a heterogeneous host population Darren M. Green, Istvan Z. Kiss and Rowland R. Kao Green, D. M., Kiss, I. Z. and Kao, R. R. 2006. Parasite strain coexistence to parasite attack allows a lower transmission rate to sustain an epidemic than is required in homogeneous

  19. Reflections on Introducing Students to Multicultural Populations and Diversity Content

    ERIC Educational Resources Information Center

    de Anda, Diane

    2007-01-01

    The aim of this article is to identify factors the author feels facilitate learning in introductory courses focused on multicultural populations and related issues. These are reflections based on observations of patterns over a number of years, in a variety of teaching settings and structures, and with a very diverse body of students, and include…

  20. The Effect on Mathematics Achievement and Attitude of Homogeneous and Heterogeneous Grouping of Gifted Sixth-Grade Students.

    ERIC Educational Resources Information Center

    Hunt, Barbara

    1997-01-01

    Comparison of gifted, average ability, and low ability sixth grade students (total n=208), in either homogeneous or heterogeneous instructional settings, found a positive effect for achievement in mathematics for the gifted students in the homogeneous grouping. No significant difference in mathematics achievement based on grouping was found for…

  1. High Achieving Students' Interactions and Performance on Complex Mathematical Tasks as a Function of Homogeneous and Heterogeneous Pairings.

    ERIC Educational Resources Information Center

    Fuchs, Lynn S.; Fuchs, Douglas; Hamlett, Carol L.; Karns, Kathy

    1998-01-01

    Interactions and performances of 10 high-achieving third- and fourth-grade students on complex mathematics tasks were studied as a function of paring with other high-achieving (homogeneous) or low-achieving (heterogeneous pairing) students. Homogeneous dyads operate more collaboratively, generate more cognitive conflict, and create better quality…

  2. Spatial Genetic Heterogeneity in Populations of a Newly Invasive Whitefly in China Revealed by a Nation-Wide Field Survey

    PubMed Central

    Li, Xian-Chun; Guo, Dong; Tao, Yun-Li; Liu, Bai-Ming; Zhang, You-Jun

    2013-01-01

    Background Even though introductions of exotic species provide ready-made experiments of rapid evolution, few studies have examined the genetic structure of an exotic species shortly after its initial introduction and subsequent spread. To determine the genetic structure of its populations during the initial introduction, we investigated the invasive sweet potato whitefly (Bemisia tabaci Q, commonly known as B. tabaci biotype Q) in China, which was introduced in approximately 2003. A total of 619 B. tabaci Q individuals in 20 provinces throughout China were collected and analyzed using five microsatellite loci. Results The introduced populations of B. tabaci Q in China represent eight genetic clusters with different geographic distributions. The populations in Yunnan Province, where B. tabaci Q was first detected, are genetically different from the other populations in China. Conclusion The introduced populations of B. tabaci Q in China have high spatial genetic heterogeneity. Additional research is required to determine whether the heterogeneity results from multiple introductions, rapid evolution following one or few introductions, or some combination of multiple introductions and rapid evolution. The heterogeneity, however, is inconsistent with a single introduction at Yunnan Province, where B. tabaci Q was first detected, followed by spread. PMID:24302995

  3. On the Bayesian estimation of a closed population size in the presence of heterogeneity and model uncertainty.

    PubMed

    King, R; Brooks, S P

    2008-09-01

    We consider the estimation of the size of a closed population, often of interest for wild animal populations, using a capture-recapture study. The estimate of the total population size can be very sensitive to the choice of model used to fit to the data. We consider a Bayesian approach, in which we consider all eight plausible models initially described by Otis et al. (1978, Wildlife Monographs 62, 1-135) within a single framework, including models containing an individual heterogeneity component. We show how we are able to obtain a model-averaged estimate of the total population, incorporating both parameter and model uncertainty. To illustrate the methodology we initially perform a simulation study and analyze two datasets where the population size is known, before considering a real example relating to a population of dolphins off northeast Scotland. PMID:18047534

  4. Predicting NCLEX-RN success in a diverse student population.

    PubMed

    Alameida, Marshall D; Prive, Alice; Davis, Harvey C; Landry, Lynette; Renwanz-Boyle, Andrea; Dunham, Michelle

    2011-05-01

    Many schools of nursing have implemented standardized testing using platforms such as those developed by Assessment Technologies Institute (ATI) to better prepare students for success on the National Council Licensure Examination for Registered Nurses® (NCLEX-RN). This study extends and replicates the research on standardized testing to predict first-time pass success in a diverse student population and across two prelicensure program types. The final sample consisted of 589 students who graduated between 2003 and 2009. Demographic data, as well as academic performance and scores on the ATI RN Comprehensive Predictor, were analyzed. The findings in this study indicate that scores on the ATI RN Comprehensive Predictor were positively, significantly associated with first-time pass success. Students in jeopardy of failing the NCLEX-RN on their first attempt can be identified prior to graduation and remediation efforts can be strengthened to improve their success. PMID:21366169

  5. Fine specificity of anti-citrullinated peptide antibodies discloses a heterogeneous antibody population in rheumatoid arthritis

    PubMed Central

    Goules, J D; Goules, A V; Tzioufas, A G

    2013-01-01

    Anti-citrullinated peptide antibodies (ACPA) are highly specific for rheumatoid arthritis (RA). However, the predominant B cell epitopes have not yet been defined. The aim of this study was to examine the reactivity of ACPA against different peptides derived from citrullinated proteins and to investigate whether or not these antibodies constitute a homogeneous population. For this purpose, sera from patients with RA (n = 141), systemic lupus erythematosus (SLE) (n = 60), Sjögren's syndrome (SS) (n = 54) and healthy controls (n = 100) were tested for their reactivity against six citrullinated peptides derived from peptidyl arginine deiminase (PAD), vimentin (vim), alpha-enolase (enol), fibrin, type II collagen (col-II) and filaggrin, respectively. A non-citrullinated control peptide derived from PAD was used as control (ctrlPAD621–40). Antibody reactivity against each individual peptide was evaluated by enzyme-linked immunosorbent assay (ELISA). Specificity and cross-reactivity of ACPA were tested by using two prototype sera with homologous and cross-inhibition assays. Specificity of ACPA from two prototype sera was confirmed by purification of anti-peptide antibodies and homologous-inhibition experiments. We found that sera from patients with RA reacted diversely with the six citrullinated peptides. More specifically, PAD211–30 displayed 29·08% sensitivity, vim60–75 29·08%, enol5–21 37·59%, fibrin617–31 31·21%, col-II358–75 29·97% and filaggrin306–24 28·37%, while control ctrlPAD621–40 showed no reactivity. All reactive peptides were found to be highly specific for RA. A notable cross-reaction (>70%) was found mainly between filaggrin and the majority of anti-citrullinated peptide antibodies. We concluded that ACPA in RA constitute a heterogeneous population with limited cross-reactivity and without a predominant epitope. PMID:23711220

  6. Parasexual Ploidy Reduction Drives Population Heterogeneity Through Random and Transient Aneuploidy in Candida albicans

    PubMed Central

    Hickman, Meleah A.; Paulson, Carsten; Dudley, Aimee; Berman, Judith

    2015-01-01

    The opportunistic pathogen Candida albicans has a large repertoire of mechanisms to generate genetic and phenotypic diversity despite the lack of meiosis in its life cycle. Its parasexual cycle enables shifts in ploidy, which in turn facilitate recombination, aneuploidy, and homozygosis of whole chromosomes to fuel rapid adaptation. Here we show that the tetraploid state potentiates ploidy variation and drives population heterogeneity. In tetraploids, the rate of losing a single heterozygous marker [loss of heterozygosity (LOH)] is elevated ?30-fold higher than the rate in diploid cells. Furthermore, isolates recovered after selection for LOH of one, two, or three markers were highly aneuploid, with a broad range of karyotypes including strains with a combination of di-, tri-, and tetrasomic chromosomes. We followed the ploidy trajectories for these tetraploid- and aneuploid-derived isolates, using a combination of flow cytometry and double-digestion restriction-site-associated DNA analyzed with next-generation sequencing. Isolates derived from either tetraploid or aneuploid isolates predominately resolved to a stable euploid state. The majority of isolates reduced to the conventional diploid state; however, stable triploid and tetraploid states were observed in ?30% of the isolates. Notably, aneuploid isolates were more transient than tetraploid isolates, resolving to a euploid state within a few passages. Furthermore, the likelihood that a particular isolate will resolve to the same ploidy state in replicate evolution experiments is only ?50%, supporting the idea that the chromosome loss process of the parasexual cycle is random and does not follow trajectories involving specific combinations of chromosomes. Together, our results indicate that tetraploid progenitors can produce populations of progeny cells with a high degree of genomic diversity, from altered ploidy to homozygosis, providing an excellent source of genetic variation upon which selection can act. PMID:25991822

  7. Spike triggered hormone secretion in vasopressin cells; a model investigation of mechanism and heterogeneous population function.

    PubMed

    MacGregor, Duncan J; Leng, Gareth

    2013-01-01

    Vasopressin neurons generate distinctive phasic patterned spike activity in response to elevated extracellular osmotic pressure. These spikes are generated in the cell body and are conducted down the axon to the axonal terminals where they trigger Ca²? entry and subsequent exocytosis of hormone-containing vesicles and secretion of vasopressin. This mechanism is highly non-linear, subject to both frequency facilitation and fatigue, such that the rate of secretion depends on both the rate and patterning of the spike activity. Here we used computational modelling to investigate this relationship and how it shapes the overall response of the neuronal population. We generated a concise single compartment model of the secretion mechanism, fitted to experimentally observed profiles of facilitation and fatigue, and based on representations of the hypothesised underlying mechanisms. These mechanisms include spike broadening, Ca²? channel inactivation, a Ca²? sensitive K? current, and releasable and reserve pools of vesicles. We coupled the secretion model to an existing integrate-and-fire based spiking model in order to study the secretion response to increasing synaptic input, and compared phasic and non-phasic spiking models to assess the functional value of the phasic spiking pattern. The secretory response of individual phasic cells is very non-linear, but the response of a heterogeneous population of phasic cells shows a much more linear response to increasing input, matching the linear response we observe experimentally, though in this respect, phasic cells have no apparent advantage over non-phasic cells. Another challenge for the cells is maintaining this linear response during chronic stimulation, and we show that the activity-dependent fatigue mechanism has a potentially useful function in helping to maintain secretion despite depletion of stores. Without this mechanism, secretion in response to a steady stimulus declines as the stored content declines. PMID:23966850

  8. Fine specificity of anti-citrullinated peptide antibodies discloses a heterogeneous antibody population in rheumatoid arthritis.

    PubMed

    Goules, J D; Goules, A V; Tzioufas, A G

    2013-10-01

    Anti-citrullinated peptide antibodies (ACPA) are highly specific for rheumatoid arthritis (RA). However, the predominant B cell epitopes have not yet been defined. The aim of this study was to examine the reactivity of ACPA against different peptides derived from citrullinated proteins and to investigate whether or not these antibodies constitute a homogeneous population. For this purpose, sera from patients with RA (n = 141), systemic lupus erythematosus (SLE) (n = 60), Sjögren's syndrome (SS) (n = 54) and healthy controls (n = 100) were tested for their reactivity against six citrullinated peptides derived from peptidyl arginine deiminase (PAD), vimentin (vim), alpha-enolase (enol), fibrin, type II collagen (col-II) and filaggrin, respectively. A non-citrullinated control peptide derived from PAD was used as control (ctrlPAD(621-40)). Antibody reactivity against each individual peptide was evaluated by enzyme-linked immunosorbent assay (ELISA). Specificity and cross-reactivity of ACPA were tested by using two prototype sera with homologous and cross-inhibition assays. Specificity of ACPA from two prototype sera was confirmed by purification of anti-peptide antibodies and homologous-inhibition experiments. We found that sera from patients with RA reacted diversely with the six citrullinated peptides. More specifically, PAD(211-30) displayed 29·08% sensitivity, vim(60-75) 29·08%, enol(5-21) 37·59%, fibrin(617-31) 31·21%, col-II(358-75) 29·97% and filaggrin(306-24) 28·37%, while control ctrlPAD(621-40) showed no reactivity. All reactive peptides were found to be highly specific for RA. A notable cross-reaction (>70%) was found mainly between filaggrin and the majority of anti-citrullinated peptide antibodies. We concluded that ACPA in RA constitute a heterogeneous population with limited cross-reactivity and without a predominant epitope. PMID:23711220

  9. Normative data for vestibular evoked myogenic potential in different age groups among a heterogeneous Indian population.

    PubMed

    Khan, Feroze K; Balraj, Achamma; Lepcha, Anjali

    2014-06-01

    To establish normative data of vestibular evoked myogenic potential in different age groups among a heterogeneous Indian population. Prospective study design using a sample of convenience. Eighty five normal controls ranging between the ages 7 and 71 years were asked to provide a written signed consent for the study. Demographic characteristics of the patients were summarized using descriptive statistical methods using SPSS-17 analysing software. The outcome variable (VEMP recording) was expressed in percentiles as function of age. In all patients the stimulus which gave the best response was 95 dB (97.7 %) and 100 dB (95 %). The mean of wave latencies (p1 & n1) for 95-VEMP were, 11.2 ± 3.2 and 17.3 ± 4.7 ms on the right and 11.0 ± 2.8 and 17.0 ± 4.2 ms on the left respectively. The amplitude was 45.1 ± 54 mV on right and 46.9 ± 61.6 mV on the left. The mean of latency difference was 0.87 ms. The VEMP is a relatively simple test. The VEMP response rate was maximum in the younger age group; the optimum intensity was 95 dB. The asymmetry ratio interpretation should be done according to the age specific values. PMID:24822153

  10. Evidence of a sophisticatedly heterogeneous population of human umbilical vein endothelial cells.

    PubMed

    Zheng, Y-W; Nie, Y-Z; Tsuchida, T; Zhang, R-R; Aoki, K; Sekine, K; Ogawa, M; Takebe, T; Ueno, Y; Sakakibara, H; Hirahara, F; Taniguchi, H

    2014-05-01

    Induction and promotion of angiogenesis play a role in a diverse range of physiologic and pathophysiologic processes that are especially relevant to the field of regenerative medicine. For assessing vasculogenesis and neo-angiogenesis, identifying angiogenic factors, angiocrine factors, and vascular niche, facilitating tissue-repair and tumor growth, efficiently generating induced pluripotent stem cells, and coculturing with organ-specific stem cells, isolation and characterization of the subpopulation of human umbilical vein endothelial cells (HUVECs) and their endothelial progenitor cells (EPCs) are needed. In this study, primary HUVECs were collected from fresh umbilical cords and fractionated and characterized with the use of flow cytometry. Clonal colony assay showed that endothelial colony-forming units in culture frequently existed in fresh HUVECs. Antigenic profiling demonstrated that undifferentiated EPCs in HUVECs had normal endothelial marker CD31 with a subpopulation of cells positive for hematopoietic stem cell marker CD34 and c-Kit. With continuing passages, EPC markers CD34 and vascular endothelial growth factor receptor 2 expression decreased dramatically. Moreover, a distinct subpopulation with different proliferative capability and angiogenesis from the early-passage HUVECs was shown. In conclusion, it is possible to isolate accurately and to enrich EPCs or hematoangioblast-like cells from a heterogeneous population of HUVECs, and to explore the differential process with flow cytometry for further investigations. PMID:24815173

  11. Using noise to control heterogeneity of isogenic populations in homogenous environments

    NASA Astrophysics Data System (ADS)

    Szyma?ska, Paulina; Gritti, Nicola; Keegstra, Johannes M.; Soltani, Mohammad; Munsky, Brian

    2015-07-01

    We explore the extent to which the phenotypes of individual, genetically identical cells can be controlled independently from each other using only a single homogeneous environmental input. We show that such control is theoretically impossible if restricted to a deterministic setting, but it can be achieved readily if one exploits heterogeneities introduced at the single-cell level due to stochastic fluctuations in gene regulation. Using stochastic analyses of a bistable genetic toggle switch, we develop a control strategy that maximizes the chances that a chosen cell will express one phenotype, while the rest express another. The control mechanism uses UV radiation to enhance identically protein degradation in all cells. Control of individual cells is made possible only by monitoring stochastic protein fluctuations and applying UV control at favorable times and levels. For two identical cells, our stochastic control law can drive protein expression of a chosen cell above its neighbor with a better than 99% success rate. In a population of 30 identical cells, we can drive a given cell to remain consistently within the top 20%. Although cellular noise typically impairs predictability for biological responses, our results show that it can also simultaneously improve controllability for those same responses.

  12. Population-based initiatives in college mental health: students helping students to overcome obstacles.

    PubMed

    Kirsch, Daniel J; Pinder-Amaker, Stephanie L; Morse, Charles; Ellison, Marsha L; Doerfler, Leonard A; Riba, Michelle B

    2014-12-01

    College students' need for mental health care has increased dramatically, leaving campus counseling and mental health centers struggling to meet the demand. This has led to the investigation and development of extra-center, population-based interventions. Student-to-student support programs are but one example. Students themselves are a plentiful, often-untapped resource that extends the reach of mental health services on campus. Student-to-student programs capitalize on students' natural inclination to assist their peers. A brief review of the prevalence and effects of mental disorders in the college population is provided, followed by a broad overview of the range of peer-to-peer programs that can be available on college campuses. Two innovative programs are highlighted: (1) a hospital- and community-based program, the College Mental Health Program (CMHP) at McLean Hospital, and 2) the Student Support Network (SSN) at Worcester Polytechnic Institute. The subsequent section reviews the literature on peer-to-peer programs for students with serious and persistent mental illness for which there is a small but generally positive body of research. This lack of an empirical basis in college mental health leads the authors to argue for development of broad practice-research networks. PMID:25308393

  13. Synchronization in networks of networks: The onset of coherent collective behavior in systems of interacting populations of heterogeneous oscillators

    NASA Astrophysics Data System (ADS)

    Barreto, Ernest; Hunt, Brian; Ott, Edward; So, Paul

    2008-03-01

    The onset of synchronization in networks of networks is investigated. Specifically, we consider networks of interacting phase oscillators in which the set of oscillators is composed of several distinct populations. The oscillators in a given population are heterogeneous in that their natural frequencies are drawn from a given distribution, and each population has its own such distribution. The coupling among the oscillators is global, however, we permit the coupling strengths between the members of different populations to be separately specified. We determine the critical condition for the onset of coherent collective behavior, and develop the illustrative case in which the oscillator frequencies are drawn from a set of (possibly different) Cauchy-Lorentz distributions. One motivation is drawn from neurobiology, in which the collective dynamics of several interacting populations of oscillators (such as excitatory and inhibitory neurons and glia) are of interest.

  14. Joint Effects of Habitat Heterogeneity and Species’ Life-History Traits on Population Dynamics in Spatially Structured Landscapes

    PubMed Central

    Ye, Xinping; Skidmore, Andrew K.; Wang, Tiejun

    2014-01-01

    Both habitat heterogeneity and species’ life-history traits play important roles in driving population dynamics, yet there is little scientific consensus around the combined effect of these two factors on populations in complex landscapes. Using a spatially explicit agent-based model, we explored how interactions between habitat spatial structure (defined here as the scale of spatial autocorrelation in habitat quality) and species life-history strategies (defined here by species environmental tolerance and movement capacity) affect population dynamics in spatially heterogeneous landscapes. We compared the responses of four hypothetical species with different life-history traits to four landscape scenarios differing in the scale of spatial autocorrelation in habitat quality. The results showed that the population size of all hypothetical species exhibited a substantial increase as the scale of spatial autocorrelation in habitat quality increased, yet the pattern of population increase was shaped by species’ movement capacity. The increasing scale of spatial autocorrelation in habitat quality promoted the resource share of individuals, but had little effect on the mean mortality rate of individuals. Species’ movement capacity also determined the proportion of individuals in high-quality cells as well as the proportion of individuals experiencing competition in response to increased spatial autocorrelation in habitat quality. Positive correlations between the resource share of individuals and the proportion of individuals experiencing competition indicate that large-scale spatial autocorrelation in habitat quality may mask the density-dependent effect on populations through increasing the resource share of individuals, especially for species with low mobility. These findings suggest that low-mobility species may be more sensitive to habitat spatial heterogeneity in spatially structured landscapes. In addition, localized movement in combination with spatial autocorrelation may increase the population size, despite increased density effects. PMID:25232739

  15. Use of posterior predictive checks as an inferential tool for investigating individual heterogeneity in animal population vital rates

    PubMed Central

    Chambert, Thierry; Rotella, Jay J; Higgs, Megan D

    2014-01-01

    The investigation of individual heterogeneity in vital rates has recently received growing attention among population ecologists. Individual heterogeneity in wild animal populations has been accounted for and quantified by including individually varying effects in models for mark–recapture data, but the real need for underlying individual effects to account for observed levels of individual variation has recently been questioned by the work of Tuljapurkar et al. (Ecology Letters, 12, 93, 2009) on dynamic heterogeneity. Model-selection approaches based on information criteria or Bayes factors have been used to address this question. Here, we suggest that, in addition to model-selection, model-checking methods can provide additional important insights to tackle this issue, as they allow one to evaluate a model's misfit in terms of ecologically meaningful measures. Specifically, we propose the use of posterior predictive checks to explicitly assess discrepancies between a model and the data, and we explain how to incorporate model checking into the inferential process used to assess the practical implications of ignoring individual heterogeneity. Posterior predictive checking is a straightforward and flexible approach for performing model checks in a Bayesian framework that is based on comparisons of observed data to model-generated replications of the data, where parameter uncertainty is incorporated through use of the posterior distribution. If discrepancy measures are chosen carefully and are relevant to the scientific context, posterior predictive checks can provide important information allowing for more efficient model refinement. We illustrate this approach using analyses of vital rates with long-term mark–recapture data for Weddell seals and emphasize its utility for identifying shortfalls or successes of a model at representing a biological process or pattern of interest. We show how posterior predictive checks can be used to strengthen inferences in ecological studies. We demonstrate the application of this method on analyses dealing with the question of individual reproductive heterogeneity in a population of Antarctic pinnipeds. PMID:24834335

  16. BI515: Population Genetics This course is designed to provide students with a general introduction to population genetics,

    E-print Network

    Sorenson, Michael

    SYLLABUS BI515: Population Genetics Fall 2014 This course is designed to provide students with a general introduction to population genetics, which examines the interaction of basic evolutionary processes (including mutation, natural selection, genetic drift, inbreeding, recombination, and gene flow

  17. Heterogeneous capture rates in low density populations and consequences for capture-recapture analysis of camera-trap data

    Microsoft Academic Search

    Bart J. HarmsenRebecca; Rebecca J. Foster; C. Patrick Doncaster

    2011-01-01

    Closed population capture-recapture analysis of camera-trap data has become the conventional method for estimating the abundance\\u000a of individually recognisable cryptic species living at low densities, such as large felids. Often these estimates are the\\u000a only information available to guide wildlife managers and conservation policy. Capture probability of the target species using\\u000a camera traps is commonly heterogeneous and low. Published studies

  18. Population.

    ERIC Educational Resources Information Center

    King, Pat; Landahl, John

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

  19. Understanding Internet Searching Performance in a Heterogeneous Portal for K-12 Students: Search Success, Search Time, Strategy, and Effort

    ERIC Educational Resources Information Center

    Zhang, Yin; Robins, David; Holmes, Jason; Salaba, Athena

    2009-01-01

    This study sought to better understand search performance using an online portal containing a collection of heterogeneous library resources for K-12 students. Search performance is examined in terms of search success, search time, strategy, and effort. This study revealed unsuccessful searches tended to take longer than successful searches;…

  20. Understanding Internet Searching Performance in a Heterogeneous Portal for K-12 Students: Search Success, Search Time, Strategy, and Effort

    Microsoft Academic Search

    Yin Zhang; David Robins; Jason Holmes; Athena Salaba

    2009-01-01

    This study sought to better understand search performance using an online portal containing a collection of heterogeneous library resources for K-12 students. Search performance is examined in terms of search success, search time, strategy, and effort. This study revealed unsuccessful searches tended to take longer than successful searches; preference of search strategy (searching vs. browsing) did not affect search success

  1. Explaining spatial heterogeneity in population dynamics and genetics from spatial variation in resources for a large herbivore.

    PubMed

    Contasti, Adrienne L; Tissier, Emily J; Johnstone, Jill F; McLoughlin, Philip D

    2012-01-01

    Fine-scale spatial variation in genetic relatedness and inbreeding occur across continuous distributions of several populations of vertebrates; however, the basis of observed variation is often left untested. Here we test the hypothesis that prior observations of spatial patterns in genetics for an island population of feral horses (Sable Island, Canada) were the result of spatial variation in population dynamics, itself based in spatial heterogeneity in underlying habitat quality. In order to assess how genetic and population structuring related to habitat, we used hierarchical cluster analysis of water sources and an indicator analysis of the availability of important forage species to identify a longitudinal gradient in habitat quality along the length of Sable Island. We quantify a west-east gradient in access to fresh water and availability of two important food species to horses: sandwort, Honckenya peploides, and beach pea, Lathyrus japonicas. Accordingly, the population clusters into three groups that occupy different island segments (west, central, and east) that vary markedly in their local dynamics. Density, body condition, and survival and reproduction of adult females were highest in the west, followed by central and east areas. These results mirror a previous analysis of genetics, which showed that inbreeding levels are highest in the west (with outbreeding in the east), and that there are significant differences in fixation indices among groups of horses along the length of Sable Island. Our results suggest that inbreeding depression is not an important limiting factor to the horse population. We conclude that where habitat gradients exist, we can anticipate fine-scale heterogeneity in population dynamics and hence genetics. PMID:23118900

  2. Mechanisms of population genetic heterogeneity among molting common mergansers on Kodiak Island, Alaska: implications for assessments of migratory connectivity

    USGS Publications Warehouse

    Pearce, John M.; Zwiefelhofer, Denny; Maryanski, Nate

    2009-01-01

    Quantifying population genetic heterogeneity within nonbreeding aggregations can inform our understanding of patterns of site fidelity, migratory connectivity, and gene flow between breeding and nonbreeding areas. However, characterizing mechanisms that contribute to heterogeneity, such as migration and dispersal, is required before site fidelity and migratory connectivity can be assessed accurately. We studied nonbreeding groups of Common Mergansers (Mergus merganser) molting on Kodiak Island, Alaska, from 2005 to 2007, using banding data to assess rates of recapture, mitochondrial (mt) DNA to determine natal area, and nuclear microsatellite genotypes to assess dispersal. Using baseline information from differentiated mtDNA haplogroups across North America, we were able to assign individuals to natal regions and document population genetic heterogeneity within and among molting groups. Band-recovery and DNA data suggest that both migration from and dispersal among natal areas contribute to admixed groups of males molting on Kodiak Island. A lack of differentiation in the Common Merganser's nuclear, bi-parentally inherited DNA, observed across North America, implies that dispersal can mislead genetic assessments of migratory connectivity and assignments of nonbreeding individuals to breeding areas. Thus multiple and independent data types are required to account for such behaviors before accurate assessments of migratory connectivity can be made.

  3. Niche-Dependent Gene Expression Profile of Intratumoral Heterogeneous Ovarian Cancer Stem Cell Populations

    PubMed Central

    Abelson, Sagi; Shamai, Yeela; Berger, Liron; Skorecki, Karl; Tzukerman, Maty

    2013-01-01

    Intratumoral heterogeneity challenges existing paradigms for anti-cancer therapy. We have previously demonstrated that the human embryonic stem cells (hESC)-derived cellular microenvironment in immunocompromised mice, enables functional distinction of heterogeneous tumor cells, including cells which do not grow into a tumor in a conventional direct tumor xenograft platform. We have identified and characterized six cancer cell subpopulations each clonally expanded from a single cell, derived from human ovarian clear cell carcinoma of a single tumor, to demonstrate striking intratumoral phenotypic heterogeneity that is dynamically dependent on the tumor growth microenvironment. These cancer cell subpopulations, characterized as cancer stem cell subpopulations, faithfully recapitulate the full spectrum of histological phenotypic heterogeneity known for human ovarian clear cell carcinoma. Each of the six subpopulations displays a different level of morphologic and tumorigenic differentiation wherein growth in the hESC-derived microenvironment favors growth of CD44+/aldehyde dehydrogenase positive pockets of self-renewing cells that sustain tumor growth through a process of tumorigenic differentiation into CD44-/aldehyde dehydrogenase negative derivatives. Strikingly, these derivative cells display microenvironment-dependent plasticity with the capacity to restore self-renewal markers and CD44 expression. In the current study, we delineate the distinct gene expression and epigenetic profiles of two such subpopulations, representing extremes of phenotypic heterogeneity in terms of niche-dependent self-renewal and tumorigenic differentiation. By combining Gene Set Enrichment, Gene Ontology and Pathway-focused array analyses with methylation status, we propose a suite of robust differences in tumor self-renewal and differentiation pathways that underlie the striking intratumoral phenotypic heterogeneity which characterize this and other solid tumor malignancies. PMID:24358304

  4. Student Engagement in Higher Education: Theoretical Perspectives and Practical Approaches for Diverse Populations

    Microsoft Academic Search

    Quaye

    2009-01-01

    STUDENT ENGAGEMENT IN HIGHER EDUCATION is an important volume that fills a longstanding void in the higher education and student affairs literature. The editors and authors make clear that diverse populations of students experience college differently and encounter group-specific barriers to success. Informed by relevant theories, each chapter focuses on a different population for whom research confirms that engagement and

  5. Opinion dynamics of modified Hegselmann-Krause model in a group-based population with heterogeneous bounded confidence

    NASA Astrophysics Data System (ADS)

    Fu, Guiyuan; Zhang, Weidong; Li, Zhijun

    2015-02-01

    Continuous opinion dynamics in a group-based population with heterogeneous bounded confidences is considered in this paper. A slightly modified Hegselmann-Krause model is proposed, and agents are classified into three categories: open-minded-, moderate-minded-, and closed-minded-agents, while the whole population is divided into three subgroups accordingly. We study how agents of each category and the population size can affect opinion dynamics. It is observed that the number of final opinion clusters is dominated by the closed-minded agents; open-minded agents cannot contribute to forming opinion consensus and the existence of open-minded agents may diversify the final opinions instead; for the fixed population size and proportion of closed-minded agents, the relative size of the largest final opinion cluster varies along concave-parabola-like curve as the proportion of open-minded agents increases, and there is a tipping point when the number of open-minded agents is almost equal to that of moderate-minded agents; for the fixed proportion of the three categories in the population, as the population size becomes larger, the number of final opinion clusters will reach a plateau. Some of the results are different from the previous studies.

  6. Implications of interacting microscale habitat heterogeneity and disturbance events on Folsomia candida (Collembola) population dynamics: a modeling approach.

    PubMed

    Meli, Mattia; Palmqvist, Annemette; Forbes, Valery E

    2014-07-01

    The authors implemented a fractal algorithm in a spatially explicit individual-based model to generate landscapes with different microscale patterns of habitat fragmentation and disturbance events and studied their effects on population dynamics of the collembolan Folsomia candida. Among human activities that may cause habitat destruction, the present study focused on agricultural practices. Soil organisms living in a cultivated field are subjected to habitat loss and fragmentation as well as disturbance events generated by the application of agrochemicals and related activities. In addition, they are exposed to natural stressors, which might influence the effects of chemicals on populations. The authors designed simulation experiments that incorporate these 3 factors and investigated their effects on populations of F. candida in the presence or absence of behavioral avoidance of contaminated habitat. Simulation results show that spatial autocorrelation of contamination has different effects on population growth and equilibrium size according to the percentage of clean habitat. This pattern changes when avoidance behavior is excluded from the model, as does population recovery after a series of disturbance events. The model suggests that a combination of heterogeneous contamination and multiple stressors can lead to unexpected effects of toxicants at the population level. Individual-based models can help to understand these effects and therefore add ecological realism to environmental risk assessment of chemicals and can help to explore the effects of different risk management options. PMID:24549590

  7. Between-airport heterogeneity in air toxics emissions associated with individual cancer risk thresholds and population risks

    PubMed Central

    2009-01-01

    Background Airports represent a complex source type of increasing importance contributing to air toxics risks. Comprehensive atmospheric dispersion models are beyond the scope of many applications, so it would be valuable to rapidly but accurately characterize the risk-relevant exposure implications of emissions at an airport. Methods In this study, we apply a high resolution atmospheric dispersion model (AERMOD) to 32 airports across the United States, focusing on benzene, 1,3-butadiene, and benzo [a]pyrene. We estimate the emission rates required at these airports to exceed a 10-6 lifetime cancer risk for the maximally exposed individual (emission thresholds) and estimate the total population risk at these emission rates. Results The emission thresholds vary by two orders of magnitude across airports, with variability predicted by proximity of populations to the airport and mixing height (R2 = 0.74–0.75 across pollutants). At these emission thresholds, the population risk within 50 km of the airport varies by two orders of magnitude across airports, driven by substantial heterogeneity in total population exposure per unit emissions that is related to population density and uncorrelated with emission thresholds. Conclusion Our findings indicate that site characteristics can be used to accurately predict maximum individual risk and total population risk at a given level of emissions, but that optimizing on one endpoint will be non-optimal for the other. PMID:19426510

  8. Novel Microchip-Based Tools Facilitating Live Cell Imaging and Assessment of Functional Heterogeneity within NK Cell Populations

    PubMed Central

    Forslund, Elin; Guldevall, Karolin; Olofsson, Per E.; Frisk, Thomas; Christakou, Athanasia E.; Wiklund, Martin; Önfelt, Björn

    2012-01-01

    Each individual has a heterogeneous pool of NK cells consisting of cells that may be specialized towards specific functional responses such as secretion of cytokines or killing of tumor cells. Many conventional methods are not fit to characterize heterogeneous populations as they measure the average response of all cells. Thus, there is a need for experimental platforms that provide single cell resolution. In addition, there are transient and stochastic variations in functional responses at the single cell level, calling for methods that allow studies of many events over extended periods of time. This paper presents a versatile microchip platform enabling long-term microscopic studies of individual NK cells interacting with target cells. Each microchip contains an array of microwells, optimized for medium or high-resolution time-lapse imaging of single or multiple NK and target cells, or for screening of thousands of isolated NK-target cell interactions. Individual NK cells confined with target cells in small microwells is a suitable setup for high-content screening and rapid assessment of heterogeneity within populations, while microwells of larger dimensions are appropriate for studies of NK cell migration and sequential interactions with multiple target cells. By combining the chip technology with ultrasonic manipulation, NK and target cells can be forced to interact and positioned with high spatial accuracy within individual microwells. This setup effectively and synchronously creates NK-target conjugates at hundreds of parallel positions in the microchip. Thus, this facilitates assessment of temporal aspects of NK-target cell interactions, e.g., conjugation, immune synapse formation, and cytotoxic events. The microchip platform presented here can be used to effectively address questions related to fundamental functions of NK cells that can lead to better understanding of how the behavior of individual cells add up to give a functional response at the population level. PMID:23060879

  9. Dendritic cells (DCs) constitute a heterogenous popu-lation of professional, bone-marrow-derived antigen-

    E-print Network

    Cai, Long

    Dendritic cells (DCs) constitute a heterogenous popu- lation of professional, bone,2 . Under steady-state conditions, they exist as conventional DCs (cDCs) or precursor DCs (pre-DCs the extracellular environment3 . The abil- ity of DCs to respond to endogenous and exogenous danger signals links

  10. Firing rate and pattern heterogeneity in the globus pallidus arise from a single neuronal population

    PubMed Central

    Dodla, Ramana; Barraza, David; Kita, Hitoshi; Wilson, Charles J.

    2013-01-01

    Intrinsic heterogeneity in networks of interconnected cells has profound effects on synchrony and spike-time reliability of network responses. Projection neurons of the globus pallidus (GPe) are interconnected by GABAergic inhibitory synapses and in vivo fire continuously but display significant rate and firing pattern heterogeneity. Despite being deprived of most of their synaptic inputs, GPe neurons in slices also fire continuously and vary greatly in their firing rate (1–70 spikes/s) and in regularity of their firing. We asked if this rate and pattern heterogeneity arises from separate cell types differing in rate, local synaptic interconnections, or variability of intrinsic properties. We recorded the resting discharge of GPe neurons using extracellular methods both in vivo and in vitro. Spike-to-spike variability (jitter) was measured as the standard deviation of interspike intervals. Firing rate and jitter covaried continuously, with slow firing being associated with higher variability than faster firing, as would be expected from heterogeneity arising from a single physiologically distinct cell type. The relationship between rate and jitter was unaffected by blockade of GABA and glutamate receptors. When the firing rate of individual neurons was altered with constant current, jitter changed to maintain the rate-jitter relationship seen across neurons. Long duration (30–60 min) recordings showed slow and spontaneous bidirectional drift in rate similar to the across-cell heterogeneity. Paired recordings in vivo and in vitro showed that individual cells wandered in rate independently of each other. Input conductance and rate wandered together, in a manner suggestive that both were due to fluctuations of an inward current. PMID:23114208

  11. Heterogeneity in stable isotope profiles predicts coexistence of populations of barn swallows Hirundo rustica differing in morphology and reproductive performance.

    PubMed Central

    Møller, Anders Pape; Hobson, Keith A.

    2004-01-01

    Population studies assume that individuals belonging to a study population are homogeneous for natal and breeding origin, although this assumption is rarely tested. We tested for heterogeneity in stable-isotope profiles (delta15N, delta13C, deltaD) of feathers grown in the African winter quarters from a Danish breeding population of adult barn swallows, Hirundo rustica. Deuterium isotope values did not provide useful information on population segregation of wintering swallows in Africa. However, both delta15N and delta13C values showed a clearly bimodal distribution with 6% belonging to one category and the remaining birds belonging to another category, resulting in this population comprising three categories of birds. Adults belonging to the two categories of delta13C isotope profiles differed weakly in morphology for several different characters. The frequency and the size of second broods differed between categories of delta13C isotope profiles. Phenotypes of nestlings from the first brood in terms of tarsus length, body mass and T-cell response differed significantly between the two delta15N isotope categories, suggesting that conditions during winter carried over to the breeding season at least as late as the first brood. Polymorphism can be maintained only if fitness is similar for birds from categories of isotope profiles. We suggest that fluctuating selection or migration-selection balance may maintain the observed polymorphism. PMID:15306333

  12. Improving Achievement for the Growing Latino Population Is Critical to the Nation's Future. Student Achievement Policy Brief #3: Latino Students

    ERIC Educational Resources Information Center

    Kober, Nancy

    2010-01-01

    More than one-fifth of the nation's public school students are Latino. By 2025, the share of Latino children is projected to increase to nearly 3 in 10 school-age children (Fry & Passel, 2009). The fast-growing Latino student population will shape the nation's future, so it is critical that these students are well-prepared for college, careers,…

  13. Flow cytometry and cell sorting of heterogeneous microbial populations: the importance of single-cell analyses.

    PubMed Central

    Davey, H M; Kell, D B

    1996-01-01

    The most fundamental questions such as whether a cell is alive, in the sense of being able to divide or to form a colony, may sometimes be very hard to answer, since even axenic microbial cultures are extremely heterogeneous. Analyses that seek to correlate such things as viability, which is a property of an individual cell, with macroscopic measurements of culture variables such as ATP content, respiratory activity, and so on, must inevitably fail. It is therefore necessary to make physiological measurements on individual cells. Flow cytometry is such a technique, which allows one to analyze cells rapidly and individually and permits the quantitative analysis of microbial heterogeneity. It therefore offers many advantages over conventional measurements for both routine and more exploratory analyses of microbial properties. While the technique has been widely applied to the study of mammalian cells, is use in microbiology has until recently been much more limited, largely because of the smaller size of microbes and the consequently smaller optical signals obtainable from them. Since these technical barriers no longer hold, flow cytometry with appropriate stains has been used for the rapid discrimination and identification of microbial cells, for the rapid assessment of viability and of the heterogeneous distributions of a wealth of other more detailed physiological properties, for the analysis of antimicrobial drug-cell interactions, and for the isolation of high-yielding strains of biotechnological interest. Flow cytometric analyses provide an abundance of multivariate data, and special methods have been devised to exploit these. Ongoing advances mean that modern flow cytometers may now be used by nonspecialists to effect a renaissance in our understanding of microbial heterogeneity. PMID:8987359

  14. The dynamic balance of import and export of zinc in Escherichia coli suggests a heterogeneous population response to stress

    PubMed Central

    Takahashi, Hiroki; Oshima, Taku; Hobman, Jon L.; Doherty, Neil; Clayton, Selina R.; Iqbal, Mudassar; Hill, Philip J.; Tobe, Toru; Ogasawara, Naotake; Kanaya, Shigehiko; Stekel, Dov J.

    2015-01-01

    Zinc is essential for life, but toxic in excess. Thus all cells must control their internal zinc concentration. We used a systems approach, alternating rounds of experiments and models, to further elucidate the zinc control systems in Escherichia coli. We measured the response to zinc of the main specific zinc import and export systems in the wild-type, and a series of deletion mutant strains. We interpreted these data with a detailed mathematical model and Bayesian model fitting routines. There are three key findings: first, that alternate, non-inducible importers and exporters are important. Second, that an internal zinc reservoir is essential for maintaining the internal zinc concentration. Third, our data fitting led us to propose that the cells mount a heterogeneous response to zinc: some respond effectively, while others die or stop growing. In a further round of experiments, we demonstrated lower viable cell counts in the mutant strain tested exposed to excess zinc, consistent with this hypothesis. A stochastic model simulation demonstrated considerable fluctuations in the cellular levels of the ZntA exporter protein, reinforcing this proposal. We hypothesize that maintaining population heterogeneity could be a bet-hedging response allowing a population of cells to survive in varied and fluctuating environments. PMID:25808337

  15. Paucity of class I MHC gene heterogeneity between individuals in the endangered Hawaiian monk seal population

    Microsoft Academic Search

    Brian M. Aldridge; Lizabeth Bowen; Brett R. Smith; George A. Antonelis; Frances Gulland; Jeffrey L. Stott

    2006-01-01

    The Hawaiian monk seal population has experienced precipitous declines in the last 50 years. In this study, we provide evidence that individuals from remaining endangered population exhibit alarming uniformity in class I major histocompatibility (MHC) genes. The peripheral blood leukocyte-derived mRNA of six captive animals rescued from a stranding incident on the French frigate shoals in the Hawaiian archipelago was used

  16. The genetic heterogeneity of deer mouse populations ( Peromyscus maniculatus ) in an insular landscape

    Microsoft Academic Search

    Pierre-Alexandre Landry; François-Joseph Lapointe

    1999-01-01

    A survey of the genetic variability in deer mouse populations was performed using specimens collected from six different\\u000a islands on a lake covering approximately 50 km2. Random amplified polymorphic DNA (RAPD) was used to measure the extent of the genetic differences in this insular system.\\u000a An analysis of molecular variance (AMOVA) revealed that populations are clearly separated at this microgeographic

  17. High Levels of Heterogeneity in the HIV Cascade of Care across Different Population Subgroups in British Columbia, Canada

    PubMed Central

    Lourenço, Lillian; Colley, Guillaume; Nosyk, Bohdan; Shopin, Dmitry; Montaner, Julio S. G.; Lima, Viviane D.

    2014-01-01

    Background The HIV cascade of care (cascade) is a comprehensive tool which identifies attrition along the HIV care continuum. We executed analyses to explicate heterogeneity in the cascade across key strata, as well as identify predictors of attrition across stages of the cascade. Methods Using linked individual-level data for the population of HIV-positive individuals in BC, we considered the 2011 calendar year, including individuals diagnosed at least 6 months prior, and excluding individuals that died or were lost to follow-up before January 1st, 2011. We defined five stages in the cascade framework: HIV ‘diagnosed’, ‘linked’ to care, ‘retained’ in care, ‘on HAART’ and virologically ‘suppressed’. We stratified the cascade by sex, age, risk category, and regional health authority. Finally, multiple logistic regression models were built to predict attrition across each stage of the cascade, adjusting for stratification variables. Results We identified 7621 HIV diagnosed individuals during the study period; 80% were male and 5% were <30, 17% 30–39, 37% 40–49 and 40% were ?50 years. Of these, 32% were MSM, 28% IDU, 8% MSM/IDU, 12% heterosexual, and 20% other. Overall, 85% of individuals ‘on HAART’ were ‘suppressed’; however, this proportion ranged from 60%–93% in our various stratifications. Most individuals, in all subgroups, were lost between the stages: ‘linked’ to ‘retained’ and ‘on HAART’ to ‘suppressed’. Subgroups with the highest attrition between these stages included females and individuals <30 years (regardless of transmission risk group). IDUs experienced the greatest attrition of all subgroups. Logistic regression results found extensive statistically significant heterogeneity in attrition across the cascade between subgroups and regional health authorities. Conclusions We found that extensive heterogeneity in attrition existed across subgroups and regional health authorities along the HIV cascade of care in B.C., Canada. Our results provide critical information to optimize engagement in care and health service delivery. PMID:25541682

  18. The Heterogeneous Second-Language Population in US Colleges and the Impact on Writing Program Design

    ERIC Educational Resources Information Center

    di Gennaro, Kristen

    2012-01-01

    To effectively address the needs of second language (L2) learners in college writing courses, many postsecondary institutions, especially those located in cities with high concentrations of immigrants, offer college-level courses for L2 students. Such courses include noncredit English language courses in an intensive English program, developmental…

  19. CCAST: A Model-Based Gating Strategy to Isolate Homogeneous Subpopulations in a Heterogeneous Population of Single Cells

    PubMed Central

    Anchang, Benedict; Do, Mary T.; Zhao, Xi; Plevritis, Sylvia K.

    2014-01-01

    A model-based gating strategy is developed for sorting cells and analyzing populations of single cells. The strategy, named CCAST, for Clustering, Classification and Sorting Tree, identifies a gating strategy for isolating homogeneous subpopulations from a heterogeneous population of single cells using a data-derived decision tree representation that can be applied to cell sorting. Because CCAST does not rely on expert knowledge, it removes human bias and variability when determining the gating strategy. It combines any clustering algorithm with silhouette measures to identify underlying homogeneous subpopulations, then applies recursive partitioning techniques to generate a decision tree that defines the gating strategy. CCAST produces an optimal strategy for cell sorting by automating the selection of gating markers, the corresponding gating thresholds and gating sequence; all of these parameters are typically manually defined. Even though CCAST is optimized for cell sorting, it can be applied for the identification and analysis of homogeneous subpopulations among heterogeneous single cell data. We apply CCAST on single cell data from both breast cancer cell lines and normal human bone marrow. On the SUM159 breast cancer cell line data, CCAST indicates at least five distinct cell states based on two surface markers (CD24 and EPCAM) and provides a gating sorting strategy that produces more homogeneous subpopulations than previously reported. When applied to normal bone marrow data, CCAST reveals an efficient strategy for gating T-cells without prior knowledge of the major T-cell subtypes and the markers that best define them. On the normal bone marrow data, CCAST also reveals two major mature B-cell subtypes, namely CD123+ and CD123- cells, which were not revealed by manual gating but show distinct intracellular signaling responses. More generally, the CCAST framework could be used on other biological and non-biological high dimensional data types that are mixtures of unknown homogeneous subpopulations. PMID:25078380

  20. A new musculoskeletal assessment in a student population.

    PubMed

    Singer, K P

    1986-01-01

    A common finding in repetition activities (typing, running, swimming . . .), are overuse syndromes arising from a mechanical imbalance affecting overstressed soft tissues and joints. A more subtle corollary, occasioned by a sedentary life-style, is an imbalance between postural and phasic muscle groups leading to joint dysfunction. Postural and phasic muscles as defined by V Janda (New Zealand Manip Ther Assoc Tech Newsletter 2: 1-3, 1977) interplay in complex patterns which determine strength and coordination for normal function. Joint pathology, and central or peripheral nervous system impairment, all lead to compensatory changes in the muscle function, namely the tendency for postural muscles to become tight and for phasic muscles to weaken. Faulty posture through muscle imbalance compromises joint mechanics predisposing to dysfunction. Appropriate management of musculoskeletal disorders should recognize the role of imbalance between postural and phasic muscles in both the etiology and sequelae of the disorder. A musculoskeletal examination of 35 students was undertaken to develop assessment skills, devise a recording form, and refine a test sequence to assist data collection. The principal finding of tightness in postural muscles is consistent with the theory that these muscles undergo adaptive shortening. This survey provided the opportunity to examine the incidence of muscle imbalance in a young adult population and to prepare guidelines for future study. J Orthop Sports Phys Ther 1986;8(1):34-41. PMID:18802249

  1. Population differences in the timing of diapause: adaptation in a spatially heterogeneous environment

    Microsoft Academic Search

    Nelson G. Hairston; Emily J. Olds

    1984-01-01

    Populations of the planktonic copepod, Diaptomus sanguineus, live in permanent and temporary freshwater ponds in Rhode Island. All ponds in which they occur become uninhabitable at some time during the year, but the nature and timing of the harsh period varies both spatially and temporally. Females produce discrete clutches either of subitaneous eggs which hatch immediately or of diapausing eggs

  2. Extensive survey of 12 X-STRs reveals genetic heterogeneity among Brazilian populations.

    PubMed

    Ribeiro-Rodrigues, Elzemar Martins; Palha, Teresinha de Jesus Brabo Ferreira; Bittencourt, Eloisa Auler; Ribeiro-Dos-Santos, Andrea; Santos, Sidney

    2011-05-01

    The admixed Brazilian population shows high levels of genetic variability, which resulted from the contribution of three main ethnicities, Amerindian, European, and African. However, due to its huge territory, admixing has been asymmetrical, i.e., the relative contribution from each ethnicity has been unequal in the five geopolitical regions of the country. The aim of this study was to describe genetic variability using a panel of short-tandem repeats on the X chromosome (X-STR) in order to perform a comprehensive evaluation of the usefulness of such markers for forensic purposes in Brazil. Twelve X-STR (DXS9895, DXS7132, DXS6800, DXS9898, DXS6789, DXS7133, GATA172D05, DXS7130, HPRTB, GATA31E08, DXS7423, and DXS10011) were chosen and tested in a sample of 2,234 individuals belonging to 16 out of the 27 Brazilian States, representing all of its five geopolitical regions. No markers showed significant deviation from the Hardy-Weinberg equilibrium, even when analyses were partitioned to represent geopolitical regions. Genetic diversity per locus ranged from 67% (DSX7133) to 95% (DXS10011), and the State of Ceará showed the highest average genetic diversity (79% for all 12 X-STR markers). Considering the Brazilian population as a whole, the power of discrimination of the 12 X-STR panel in females (PDF) was 0.999999999999994, while the power of discrimination in males (PDM) was 0.9999999969. Such high values suggest the potential of that panel to be used in forensic applications and relatedness tests among individuals. Comparisons among the Brazilian populations investigated revealed significant differences when they were compared among each other, a pattern that was maintained when additional populations from Europe and Latin America were compared to Brazilians. Our results highlight the need and usefulness of specific genetic database for forensic purposes in Brazilian populations. PMID:21404027

  3. The Impact of Multi-Dimensional Behavioral Interventions in Student Conduct Processes: Achieving Increased Learning Outcomes in Adult Student Populations

    ERIC Educational Resources Information Center

    Braddix, D'Andre Cortez

    2012-01-01

    As adult students constitute nearly half of all undergraduates in the United States, college practitioners need to identify effective disciplinary strategies for this population when violations of institutional rules and regulations occur. The purpose of this quasi-experimental, action research study was to modify the student conduct process for…

  4. Future Directions in Painful Knee Osteoarthritis: Harnessing Complexity in a Heterogeneous Population

    PubMed Central

    George, Steven Z.; Maluf, Katrina S.; Stevens-Lapsley, Jennifer E.

    2014-01-01

    This perspective article proposes a conceptual model for the pain experience for individuals diagnosed with knee osteoarthritis (OA). Pain in knee OA is likely a heterogeneous, multifactorial phenomenon that involves not only the OA disease process but also elements specific to patient psychology and pain neurophysiology. The relevant contributions to the pain experience for any individual patient remain difficult, if not impossible, to definitively determine, and the rationale for many clinical treatment decisions arises primarily from a mechanistic understanding of OA pathophysiology. The Osteoarthritis Research Society International (OARSI) recently identified “phenotyping” of OA pain as a research priority to “better target pain therapies to individual patients.” This perspective article proposes that contributions from 3 domains—knee pathology, psychological distress, and pain neurophysiology—should be considered equally important in future efforts to understand pain phenotypes in knee OA. Ultimately, characterization of pain phenotypes may aid in the understanding of the pain experience and the development of interventions specific to pain for individual patients. PMID:24179141

  5. Human factors involvement in bringing the power of AI to a heterogeneous user population

    NASA Technical Reports Server (NTRS)

    Czerwinski, Mary; Nguyen, Trung

    1994-01-01

    The Human Factors involvement in developing COMPAQ QuickSolve, an electronic problem-solving and information system for Compaq's line of networked printers, is described. Empowering customers with expert system technology so they could solve advanced networked printer problems on their own was a major goal in designing this system. This process would minimize customer down-time, reduce the number of phone calls to the Compaq Customer Support Center, improve customer satisfaction, and, most importantly, differentiate Compaq printers in the marketplace by providing the best, and most technologically advanced, customer support. This represents a re-engineering of Compaq's customer support strategy and implementation. In its first generation system, SMART, the objective was to provide expert knowledge to Compaq's help desk operation to more quickly and correctly answer customer questions and problems. QuickSolve is a second generation system in that customer support is put directly in the hands of the consumers. As a result, the design of QuickSolve presented a number of challenging issues. Because the produce would be used by a diverse and heterogeneous set of users, a significant amount of human factors research and analysis was required while designing and implementing the system. Research that shaped the organization and design of the expert system component as well.

  6. Not all smokers die young: a model for hidden heterogeneity within the human population.

    PubMed

    Levine, Morgan; Crimmins, Eileen

    2014-01-01

    The ability of some individuals to reach extreme old age in the presence of clearly high exposure to damaging factors may signal an innate biological advantage. For this study we used data on 4,655 current and never smokers, ages 50 and above, from NHANES III to examine whether long-lived smokers represent a biologically resilient phenotype that could facilitate our understanding of heterogeneity in the aging process. Using a proportional hazards model, our results showed that while smoking significantly increased mortality in most age groups, it did not increase the mortality risk for those who were age 80 and over at baseline. Additionally when comparing the adjusted means of biomarkers between never and current smokers, we found that long-lived smokers (80+) had similar inflammation, HDL, and lung function levels to never smokers. Given that factors which allow some individuals to withstand smoking may also enable others to cope with everyday biological stressors, the investigation of long-lived smokers may eventually allow us to identify molecular and genetic mechanisms which enable longevity extension. PMID:24520332

  7. Extreme chromosomal heterogeneity in a small-island population of Rumex acetosa.

    PubMed

    Parker, J S; Wilby, A S

    1989-02-01

    Chromosome analyses of 227 mature plants of the dioecious species Rumex acetosa collected on the small island of Skomer have revealed an extremely high level of unique and polymorphic variation. The three common polymorphisms in this species--supernumerary segments on chromosomes 1 and 6, and B-chromosomes--are widespread on the island and the frequency of supernumerary segment 1 is higher than in all 37 mainland populations previously studied. Novel variants, unknown elsewhere, occur in each polymorphism. Fourteen different chromosome rearrangements are unique to the island, and eleven of these were detected in 67 plants from a small area which had undergone a population crash in 1977. It is argued that the genome of R. acetosa is undergoing rapid reorganisation on this small island which may be associated with an enforced shift towards inbreeding in this dioecious species. PMID:2732084

  8. Heterogeneity of genetic architecture of body size traits in a free-living population

    PubMed Central

    Bérénos, Camillo; Ellis, Philip A; Pilkington, Jill G; Lee, S Hong; Gratten, Jake; Pemberton, Josephine M

    2015-01-01

    Knowledge of the underlying genetic architecture of quantitative traits could aid in understanding how they evolve. In wild populations, it is still largely unknown whether complex traits are polygenic or influenced by few loci with major effect, due to often small sample sizes and low resolution of marker panels. Here, we examine the genetic architecture of five adult body size traits in a free-living population of Soay sheep on St Kilda using 37 037 polymorphic SNPs. Two traits (jaw and weight) show classical signs of a polygenic trait: the proportion of variance explained by a chromosome was proportional to its length, multiple chromosomes and genomic regions explained significant amounts of phenotypic variance, but no SNPs were associated with trait variance when using GWAS. In comparison, genetic variance for leg length traits (foreleg, hindleg and metacarpal) was disproportionately explained by two SNPs on chromosomes 16 (s23172.1) and 19 (s74894.1), which each explained >10% of the additive genetic variance. After controlling for environmental differences, females heterozygous for s74894.1 produced more lambs and recruits during their lifetime than females homozygous for the common allele conferring long legs. We also demonstrate that alleles conferring shorter legs have likely entered the population through a historic admixture event with the Dunface sheep. In summary, we show that different proxies for body size can have very different genetic architecture and that dense SNP helps in understanding both the mode of selection and the evolutionary history at loci underlying quantitative traits in natural populations. PMID:25753777

  9. Heterogeneity of genetic architecture of body size traits in a free-living population.

    PubMed

    Bérénos, Camillo; Ellis, Philip A; Pilkington, Jill G; Lee, S Hong; Gratten, Jake; Pemberton, Josephine M

    2015-04-01

    Knowledge of the underlying genetic architecture of quantitative traits could aid in understanding how they evolve. In wild populations, it is still largely unknown whether complex traits are polygenic or influenced by few loci with major effect, due to often small sample sizes and low resolution of marker panels. Here, we examine the genetic architecture of five adult body size traits in a free-living population of Soay sheep on St Kilda using 37 037 polymorphic SNPs. Two traits (jaw and weight) show classical signs of a polygenic trait: the proportion of variance explained by a chromosome was proportional to its length, multiple chromosomes and genomic regions explained significant amounts of phenotypic variance, but no SNPs were associated with trait variance when using GWAS. In comparison, genetic variance for leg length traits (foreleg, hindleg and metacarpal) was disproportionately explained by two SNPs on chromosomes 16 (s23172.1) and 19 (s74894.1), which each explained >10% of the additive genetic variance. After controlling for environmental differences, females heterozygous for s74894.1 produced more lambs and recruits during their lifetime than females homozygous for the common allele conferring long legs. We also demonstrate that alleles conferring shorter legs have likely entered the population through a historic admixture event with the Dunface sheep. In summary, we show that different proxies for body size can have very different genetic architecture and that dense SNP helps in understanding both the mode of selection and the evolutionary history at loci underlying quantitative traits in natural populations. PMID:25753777

  10. Recognising Language Impairment in Secondary School Student Populations

    ERIC Educational Resources Information Center

    Starling, Julia; Munro, Natalie; Togher, Leanne; Arciuli, Joanne

    2011-01-01

    Up to 16% of students in mainstream secondary schools present with language impairment (LI). As with other learning difficulties, students with LI experience many academic, social, emotional and behavioral problems. Associated presenting behaviors may, however, be masking the primary language impairment. As a result, secondary school students with…

  11. [Genetic heterogeneity in natural populations of Microphallus piriformes and M. pygmaeus parthenites (Trematoda: Microphallidae)].

    PubMed

    Khalturin, K V; Mikha?lova, N A; Granovich, A I

    2000-01-01

    The random amplified polymorphic DNA (RAPD) technique was applied for the studies of genetic heterogeny between several natural populations of trematodes belonging to the Microphallida family. Initially, the metacercariae from the daughter sporocysts infestating Littorina saxatilis and Littorina littorea periwinkles were used. Comparison of the banding patterns obtained for the different metacercariae within one sporocyst gave an unpredicted results. For two of three studied species (M. pygmaeus and M. pseudopygmaeus), the considerable differences in RAPD patterning was detected. According to the classical point of view, the process of cercariae (metacercariae in case of the "pygmaeus" group of microphallides) formation does not include DNA recombination. Because of that, all metacercariae within one single sporocyst should be genetically identical. However, data obtained clearly shows that at least in some cases it is not so. We can hardly believe that such result could be a methodological artifact, for not single difference in a RAPD patterns was recorded between the metacercariae within sporocysts of M. piriformes. Moreover, even the 100 fold dilution of the total DNA used for PCR amplification does not change the banding patterns. Hence, our results can not be explained by slight fluctuations in the DNA concentrations between the samples. The most evident conclusion is that we came across yet strange, but real phenomenon--some degree of genetic difference within the progeny of each of the sporocysts--metacercariae. However, the detailed study is needed to understand and interpret these observations correctly. Amplification of the total DNA extracted from the whole sporocysts (containing metacercariae) never showed any differences in RAPD patterns between the parasites been derived from one infestated snail (local parasite hemipopulation). That allowed us to compare different parasite populations referring the RAPD pattern of one sporocyst from a snail to as a representative of one local hemipopulation. Analysis of the RAPD-loci frequencies showed a considerable genetic differences between the subpopulations of M. piriformes, infestating different paraxenic intermediate hosts--L. saxatilis and L. obtusata. This phenomenon was statistically significant for 2 localities of 3 studied. No heterogeny within populations was recorded for M. pygmaeus. Both M. piriformes and M. pygmaeus are characterized by the genetic differentiation in the microgeographic scale (within the Chupa bay of the White sea, the longest distance between the analyzed localities is 20 km). According to the frequencies of the RAPD-loci, parasites from the sheltered locality differ significantly from the parasites of other two localities exposed to the open sea. For both species the degree of genetic similarity between the populations correlates positively with the distance between the localities. We can suppose that the population structure of microphallids depended mainly upon the population structures of their intermediate hosts, definitive hosts and geographical structure of the areal. However, taking into consideration the low motility of snails, we believe that the distribution, migration and species composition of the definitive hosts play the key role in the genetic structuring of M. pygmaeus and M. piriformes hemipopulations. As an addition, the RAPD analysis of the parasite populations from the Barents Sea (East cost of Murman peninsula) and North Sea (Western cost of Sweden) revealed no significant genetic differences between the worms from those places and from the White Sea. However in case of this macrogeographic comparison, insufficient number of samples does not allow us to draw any final conclusions. PMID:11212616

  12. Acculturation, Dietary Practices and Risk for Childhood Obesity in an Ethnically Heterogeneous Population of Latino School Children in the San Francisco Bay Area

    PubMed Central

    Schwartz, Norah; Jiménez-Cruz, Arturo; Bacardi-Gascon, Montserrat; Heyman, Melvin B.

    2015-01-01

    Previous studies have found increased acculturation to the US lifestyle increases risk for obesity in Latinos. However, methodologies differ, and results in children are inconsistent. Moreover, previous studies have not evaluated risk factors within the heterogeneous US population. We recruited 144 self-identified Latino school children and their mother or father in grades 4–6 in San Francisco parochial schools and South San Francisco public schools using an information letter distributed to all students. Children and parents had weights, heights, demographic information, dietary patterns and lifestyle variables collected in English or Spanish through an interview format. A high percentage of our children were overweight [?85th percentile body mass index (BMI)] (62.5%) and obese (?95th percentile BMI) (45.2%). Correspondingly parents also had a high percentage of overweight (BMI ? 25 & <30) (40.8%) and obesity (BMI ? 30) (45.3%). Mexico was the country of origin for 62.2% of parents, and 26.6% were from Central or South America. In multivariate logistic analysis, speaking Spanish at home was an independent risk factor for obesity [odds ratio (OR) 2.97, 95% confidence interval (CI) 1.28–6.86]. Eating breakfast daily (OR 0.34, 95% CI 0.15–0.78) and consumption of tortas (a Mexican fast food sandwich) (OR 0.45, 95% CI 0.21–1.00) were associated with decreased risk. In stratified analysis, significant differences in risk factors existed between Mexican origin versus Central/South American Latino children. The processes of acculturation likely impact eating and lifestyle practices differentially among Latino groups. Interventions should focus on ensuring that all children eat a nutritious breakfast and take into consideration ethnicity when working with Latino populations. PMID:22101726

  13. The Effects of Homogeneous versus Heterogeneous Reading-Style Grouping on EFL Students' Non-Preferred Reading Style and Reading Comprehension

    ERIC Educational Resources Information Center

    El-Koumy, Abdel Salam Abdel Khalek

    2009-01-01

    The purpose of this study was to investigate the effects of homogeneous versus heterogeneous reading-style grouping on EFL students' non-preferred reading style and reading comprehension. The study used a pretest-posttest experimental design. The original subjects of the study (N=86) were Egyptian English major senior students during the 2005/2006…

  14. A simulation model for the diffusion of a new technology in an environment populated by heterogeneous agents. The case of business to business (B2B) ecommerce.

    E-print Network

    Gallo, Giorgio

    1 A simulation model for the diffusion of a new technology in an environment populated). In the literature of technology diffusion several types of structural heterogeneity have been introduced. Among by variables describing, on one hand, the expectations regarding the diffusion of technology among customers

  15. Allelic heterogeneity in NCF2 associated with systemic lupus erythematosus (SLE) susceptibility across four ethnic populations

    PubMed Central

    Kim-Howard, Xana; Sun, Celi; Molineros, Julio E.; Maiti, Amit K.; Chandru, Hema; Adler, Adam; Wiley, Graham B.; Kaufman, Kenneth M.; Kottyan, Leah; Guthridge, Joel M.; Rasmussen, Astrid; Kelly, Jennifer; Sánchez, Elena; Raj, Prithvi; Li, Quan-Zhen; Bang, So-Young; Lee, Hye-Soon; Kim, Tae-Hwan; Kang, Young Mo; Suh, Chang-Hee; Chung, Won Tae; Park, Yong-Beom; Choe, Jung-Yoon; Shim, Seung Cheol; Lee, Shin-Seok; Han, Bok-Ghee; Olsen, Nancy J.; Karp, David R.; Moser, Kathy; Pons-Estel, Bernardo A.; Wakeland, Edward K.; James, Judith A.; Harley, John B.; Bae, Sang-Cheol; Gaffney, Patrick M.; Alarcón-Riquelme, Marta; Looger, Loren L.; Nath, Swapan K.; Acevedo, Eduardo; Acevedo, Eduardo; La Torre, Ignacio García-De; Maradiaga-Ceceña, Marco A.; Cardiel, Mario H.; Esquivel-Valerio, Jorge A.; Rodriguez-Amado, Jacqueline; Moctezuma, José Francisco; Miranda, Pedro; Perandones, Carlos; Aires, Buenos; Castel, Cecilia; Laborde, Hugo A.; Alba, Paula; Musuruana, Jorge; Goecke, Annelise; Foster, Carola; Orozco, Lorena; Baca, Vicente

    2014-01-01

    Recent reports have associated NCF2, encoding a core component of the multi-protein NADPH oxidase (NADPHO), with systemic lupus erythematosus (SLE) susceptibility in individuals of European ancestry. To identify ethnicity-specific and -robust variants within NCF2, we assessed 145 SNPs in and around the NCF2 gene in 5325 cases and 21 866 controls of European-American (EA), African-American (AA), Hispanic (HS) and Korean (KR) ancestry. Subsequent imputation, conditional, haplotype and bioinformatic analyses identified seven potentially functional SLE-predisposing variants. Association with non-synonymous rs17849502, previously reported in EA, was detected in EA, HS and AA (PEA = 1.01 × 10?54, PHS = 3.68 × 10?10, PAA = 0.03); synonymous rs17849501 was similarly significant. These SNPs were monomorphic in KR. Novel associations were detected with coding variants at rs35937854 in AA (PAA = 1.49 × 10?9), and rs13306575 in HS and KR (PHS = 7.04 × 10?7, PKR = 3.30 × 10?3). In KR, a 3-SNP haplotype was significantly associated (P = 4.20 × 10?7), implying that SLE predisposing variants were tagged. Significant SNP–SNP interaction (P = 0.02) was detected between rs13306575 and rs17849502 in HS, and a dramatically increased risk (OR = 6.55) with a risk allele at each locus. Molecular modeling predicts that these non-synonymous mutations could disrupt NADPHO complex assembly. The risk allele of rs17849501, located in a conserved transcriptional regulatory region, increased reporter gene activity, suggesting in vivo enhancer function. Our results not only establish allelic heterogeneity within NCF2 associated with SLE, but also emphasize the utility of multi-ethnic cohorts to identify predisposing variants explaining additional phenotypic variance (‘missing heritability’) of complex diseases like SLE. PMID:24163247

  16. Allelic heterogeneity in NCF2 associated with systemic lupus erythematosus (SLE) susceptibility across four ethnic populations.

    PubMed

    Kim-Howard, Xana; Sun, Celi; Molineros, Julio E; Maiti, Amit K; Chandru, Hema; Adler, Adam; Wiley, Graham B; Kaufman, Kenneth M; Kottyan, Leah; Guthridge, Joel M; Rasmussen, Astrid; Kelly, Jennifer; Sánchez, Elena; Raj, Prithvi; Li, Quan-Zhen; Bang, So-Young; Lee, Hye-Soon; Kim, Tae-Hwan; Kang, Young Mo; Suh, Chang-Hee; Chung, Won Tae; Park, Yong-Beom; Choe, Jung-Yoon; Shim, Seung Cheol; Lee, Shin-Seok; Han, Bok-Ghee; Olsen, Nancy J; Karp, David R; Moser, Kathy; Pons-Estel, Bernardo A; Wakeland, Edward K; James, Judith A; Harley, John B; Bae, Sang-Cheol; Gaffney, Patrick M; Alarcón-Riquelme, Marta; Looger, Loren L; Nath, Swapan K

    2014-03-15

    Recent reports have associated NCF2, encoding a core component of the multi-protein NADPH oxidase (NADPHO), with systemic lupus erythematosus (SLE) susceptibility in individuals of European ancestry. To identify ethnicity-specific and -robust variants within NCF2, we assessed 145 SNPs in and around the NCF2 gene in 5325 cases and 21 866 controls of European-American (EA), African-American (AA), Hispanic (HS) and Korean (KR) ancestry. Subsequent imputation, conditional, haplotype and bioinformatic analyses identified seven potentially functional SLE-predisposing variants. Association with non-synonymous rs17849502, previously reported in EA, was detected in EA, HS and AA (P(EA) = 1.01 × 10(-54), PHS = 3.68 × 10(-10), P(AA) = 0.03); synonymous rs17849501 was similarly significant. These SNPs were monomorphic in KR. Novel associations were detected with coding variants at rs35937854 in AA (PAA = 1.49 × 10(-9)), and rs13306575 in HS and KR (P(HS) = 7.04 × 10(-7), P(KR) = 3.30 × 10(-3)). In KR, a 3-SNP haplotype was significantly associated (P = 4.20 × 10(-7)), implying that SLE predisposing variants were tagged. Significant SNP-SNP interaction (P = 0.02) was detected between rs13306575 and rs17849502 in HS, and a dramatically increased risk (OR = 6.55) with a risk allele at each locus. Molecular modeling predicts that these non-synonymous mutations could disrupt NADPHO complex assembly. The risk allele of rs17849501, located in a conserved transcriptional regulatory region, increased reporter gene activity, suggesting in vivo enhancer function. Our results not only establish allelic heterogeneity within NCF2 associated with SLE, but also emphasize the utility of multi-ethnic cohorts to identify predisposing variants explaining additional phenotypic variance ('missing heritability') of complex diseases like SLE. PMID:24163247

  17. The 8p23 Inversion Polymorphism Determines Local Recombination Heterogeneity across Human Populations

    PubMed Central

    Alves, Joao M.; Chikhi, Lounès; Amorim, António; Lopes, Alexandra M.

    2014-01-01

    For decades, chromosomal inversions have been regarded as fascinating evolutionary elements as they are expected to suppress recombination between chromosomes with opposite orientations, leading to the accumulation of genetic differences between the two configurations over time. Here, making use of publicly available population genotype data for the largest polymorphic inversion in the human genome (8p23-inv), we assessed whether this inhibitory effect of inversion rearrangements led to significant differences in the recombination landscape of two homologous DNA segments, with opposite orientation. Our analysis revealed that the accumulation of genetic differentiation is positively correlated with the variation in recombination profiles. The observed recombination dissimilarity between inversion types is consistent across all populations analyzed and surpasses the effects of geographic structure, suggesting that both structures (orientations) have been evolving independently over an extended period of time, despite being subjected to the very same demographic history. Aside this mainly independent evolution, we also identified a short segment (350 kb, <10% of the whole inversion) in the central region of the inversion where the genetic divergence between the two structural haplotypes is diminished. Although it is difficult to demonstrate it, this could be due to gene flow (possibly via double-crossing over events), which is consistent with the higher recombination rates surrounding this segment. This study demonstrates for the first time that chromosomal inversions influence the recombination landscape at a fine-scale and highlights the role of these rearrangements as drivers of genome evolution. PMID:24682157

  18. A Nonlocal Model for Contact Attraction and Repulsion in Heterogeneous Cell Populations.

    PubMed

    Painter, K J; Bloomfield, J M; Sherratt, J A; Gerisch, A

    2015-06-01

    Instructing others to move is fundamental for many populations, whether animal or cellular. In many instances, these commands are transmitted by contact, such that an instruction is relayed directly (e.g. by touch) from signaller to receiver: for cells, this can occur via receptor-ligand mediated interactions at their membranes, potentially at a distance if a cell extends long filopodia. Given that commands ranging from attractive to repelling can be transmitted over variable distances and between cells of the same (homotypic) or different (heterotypic) type, these mechanisms can clearly have a significant impact on the organisation of a tissue. In this paper, we extend a system of nonlocal partial differential equations (integrodifferential equations) to provide a general modelling framework to explore these processes, performing linear stability and numerical analyses to reveal its capacity to trigger the self-organisation of tissues. We demonstrate the potential of the framework via two illustrative applications: the contact-mediated dispersal of neural crest populations and the self-organisation of pigmentation patterns in zebrafish. PMID:25963245

  19. Population and habitat dynamics of the white-footed mouse (Peromyscus leucopus) in a heterogeneous forest

    SciTech Connect

    Ormiston, B.G.

    1984-07-01

    Movements and demography of white-footed mice (Peromyscus leucopus) were determined by live-trapping and radiotelemetry in contiguous upland and lowland forest habitat to assess the extent of variation in local habitat distribution due to season, age, and sex factors. Mice were marked and recaptured monthly in 1980 and 1981 from April through December on a continuous 20 ha trapping grid, thus yielding 1486 captures of 397 individuals. Locations and activity of 43 mice were determined by radiotracking. Various measures of habitat suitability, including adult density, sex ratio, reproduction, persistence, home range size, and immigration, indicated a seasonal cycle of habitat suitability. Upland habitat appeared better for overwintering, and lowland habitat was superior relative to the upland from June through October. Tendencies for breeding females to be restricted to lowland, and for lowland males to display greater mean body weights and smaller home range sizes than upland males, were attributed to greater food availability in the lowland over this period. Individual P. leucopus use local habitats opportunistically, but variations in habitat distribution between the age- and sex-classes of the population noted during the breeding season suggest that local habitats provide a spatial framework for behavioral population regulation in P. leucopus. 49 references, 5 figures, 10 tables.

  20. A millifluidic study of cell-to-cell heterogeneity in growth-rate and cell-division capability in populations of isogenic cells of Chlamydomonas reinhardtii.

    PubMed

    Damodaran, Shima P; Eberhard, Stephan; Boitard, Laurent; Rodriguez, Jairo Garnica; Wang, Yuxing; Bremond, Nicolas; Baudry, Jean; Bibette, Jérôme; Wollman, Francis-André

    2015-01-01

    To address possible cell-to-cell heterogeneity in growth dynamics of isogenic cell populations of Chlamydomonas reinhardtii, we developed a millifluidic drop-based device that not only allows the analysis of populations grown from single cells over periods of a week, but is also able to sort and collect drops of interest, containing viable and healthy cells, which can be used for further experimentation. In this study, we used isogenic algal cells that were first synchronized in mixotrophic growth conditions. We show that these synchronized cells, when placed in droplets and kept in mixotrophic growth conditions, exhibit mostly homogeneous growth statistics, but with two distinct subpopulations: a major population with a short doubling-time (fast-growers) and a significant subpopulation of slowly dividing cells (slow-growers). These observations suggest that algal cells from an isogenic population may be present in either of two states, a state of restricted division and a state of active division. When isogenic cells were allowed to propagate for about 1000 generations on solid agar plates, they displayed an increased heterogeneity in their growth dynamics. Although we could still identify the original populations of slow- and fast-growers, drops inoculated with a single progenitor cell now displayed a wider diversity of doubling-times. Moreover, populations dividing with the same growth-rate often reached different cell numbers in stationary phase, suggesting that the progenitor cells differed in the number of cell divisions they could undertake. We discuss possible explanations for these cell-to-cell heterogeneities in growth dynamics, such as mutations, differential aging or stochastic variations in metabolites and macromolecules yielding molecular switches, in the light of single-cell heterogeneities that have been reported among isogenic populations of other eu- and prokaryotes. PMID:25760649

  1. A Millifluidic Study of Cell-to-Cell Heterogeneity in Growth-Rate and Cell-Division Capability in Populations of Isogenic Cells of Chlamydomonas reinhardtii

    PubMed Central

    Damodaran, Shima P.; Eberhard, Stephan; Boitard, Laurent; Rodriguez, Jairo Garnica; Wang, Yuxing; Bremond, Nicolas; Baudry, Jean; Bibette, Jérôme; Wollman, Francis-André

    2015-01-01

    To address possible cell-to-cell heterogeneity in growth dynamics of isogenic cell populations of Chlamydomonas reinhardtii, we developed a millifluidic drop-based device that not only allows the analysis of populations grown from single cells over periods of a week, but is also able to sort and collect drops of interest, containing viable and healthy cells, which can be used for further experimentation. In this study, we used isogenic algal cells that were first synchronized in mixotrophic growth conditions. We show that these synchronized cells, when placed in droplets and kept in mixotrophic growth conditions, exhibit mostly homogeneous growth statistics, but with two distinct subpopulations: a major population with a short doubling-time (fast-growers) and a significant subpopulation of slowly dividing cells (slow-growers). These observations suggest that algal cells from an isogenic population may be present in either of two states, a state of restricted division and a state of active division. When isogenic cells were allowed to propagate for about 1000 generations on solid agar plates, they displayed an increased heterogeneity in their growth dynamics. Although we could still identify the original populations of slow- and fast-growers, drops inoculated with a single progenitor cell now displayed a wider diversity of doubling-times. Moreover, populations dividing with the same growth-rate often reached different cell numbers in stationary phase, suggesting that the progenitor cells differed in the number of cell divisions they could undertake. We discuss possible explanations for these cell-to-cell heterogeneities in growth dynamics, such as mutations, differential aging or stochastic variations in metabolites and macromolecules yielding molecular switches, in the light of single-cell heterogeneities that have been reported among isogenic populations of other eu- and prokaryotes. PMID:25760649

  2. Heterogeneous atypical cell populations are present in blood of metastatic breast cancer patients

    PubMed Central

    2014-01-01

    Introduction Circulating tumor cells (CTCs) are commonly isolated from the blood by targeting the epithelial cell adhesion molecule (EpCAM) through positive selection. However, EpCAM can be downregulated during metastatic progression, or it can be initially not present. We designed the present prospective trial to characterize CTCs as well as other circulating cell populations in blood samples from women with metastatic breast cancer without EpCAM-dependent enrichment and/or isolation technology. Methods A total of 32 patients with metastatic breast cancer were enrolled, and blood samples were processed using a previously described negative depletion immunomagnetic methodology. Samples from healthy volunteers were run as controls (n?=?5). Multistep sequential labeling was performed to label and fix cell-surface markers followed by permeabilization for cytokeratins (CK) 8, 18 and 19. Multiparametric flow cytometry (FCM) analysis was conducted using a BD LSR II flow cytometer or a BD FACSAria II or FACSAria III cell sorter. Immunocytochemical staining on postenrichment specimens for DAPI, EpCAM, CD45, CK, epidermal growth factor receptor and vimentin was performed. Expression of these markers was visualized using confocal microscopy (CM). Results CD45-negative/CK-positive (CD45? CK+) populations with EpCAM?+?and EpCAM???expression were identified with both FCM and CM from the negatively enriched patient samples. In addition, EpCAM?+?and EpCAM???populations that were CK?+?and coexpressing the pan-hematopoietic marker CD45 were also noted. There were more CK?+?EpCAM???events/ml than CK?+?EpCAM?+?events/ml in both the CD45? and CD45+ fractions (both statistically significant at P???0.0005). The number of CK?+?CD45? and CK?+?CD45+ events per milliliter in blood samples (regardless of EpCAM status) was higher in patient samples than in normal control samples (P???0.0005 and P???0.026, respectively). Further, a significant fraction of the CK?+?CD45+ events also expressed CD68, a marker associated with tumor-associated macrophages. Higher levels of CD45-CK?+?EpCAM???were associated with worse overall survival (P?=?0.0292). Conclusions Metastatic breast cancer patients have atypical cells that are CK?+?EpCAM???circulating in their blood. Because a substantial number of these patients do not have EpCAM?+?CTCs, additional studies are needed to evaluate the role of EpCAM???circulating cells as a prognostic and predictive marker. PMID:24602188

  3. The wildlife orientations of selected Taiwanese student populations 

    E-print Network

    Lin, Pei-Chien

    1986-01-01

    comparisons. 18 3 ImpOrtance values for selected wildlife-related activities by Taiwanese students (N = 791). 4 ANOVA comparisons of wildlife attitude and perception scores of Taiwanese students (N = 791) given the bird, butterfly, spider, and snake. DF... related to invertebrates and snakes, and addressing human cross-cultural (ethnic and international) comparisons. Therefore, this study compared student wildlife orientations toward two invertebrates (spider and butterfly) and vertebrates (snake...

  4. Population heterogeneity and dynamics in starter culture and lag phase adaptation of the spoilage yeast Zygosaccharomyces bailii to weak acid preservatives.

    PubMed

    Stratford, Malcolm; Steels, Hazel; Nebe-von-Caron, Gerhard; Avery, Simon V; Novodvorska, Michaela; Archer, David B

    2014-07-01

    The food spoilage yeast Zygosaccharomyces bailii shows great resistance to weak-acid preservatives, including sorbic acid (2, 4-hexadienoic acid). That extreme resistance was shown to be due to population heterogeneity, with a small sub-population of cells resistant to a variety of weak acids, probably caused by a lower internal pH reducing the uptake of all weak acids. In the present paper, it was found that resistant cells were extremely rare in exponential cultures, but increased by up to 8000-fold in stationary phase. Inoculation of media containing sorbic acid with a population of Z. bailii cells gave rise to what appeared to be a prolonged lag phase, suggesting adaptation to the conditions before the cells entered the period of exponential growth. However, the apparent lag phase caused by sorbic acid was largely due to the time required for the resistant sub-population to grow to detectable levels. The slow growth rate of the sub-population was identical to that of the final total population. The non-resistant bulk population remained viable for 3 days but had lost viability by 6 days and, during that time, there was no indication of any development of resistance in the bulk population. The sub-population growing in sorbic acid showed very high population diversity in colony size and internal pH. After removal of sorbic acid, the population rapidly reverted back to the normal, largely non-resistant, population distribution. The data presented suggest that a reevaluation of the lag phase in microbial batch culture is required, at least for the resistance of Z. bailii to sorbic acid. Furthermore, the significance of phenotypic diversity and heterogeneity in microbial populations is discussed more broadly with potential relevance to bacterial "persisters", natural selection and evolution. PMID:24813627

  5. The Henry street consortium population-based competencies for educating public health nursing students.

    PubMed

    Schaffer, Marjorie A; Cross, Sharon; Keller, Linda O; Nelson, Pamela; Schoon, Patricia M; Henton, Pat

    2011-01-01

    The Henry Street Consortium, a collaboration of nurse educators from universities and colleges and public health nurses (PHNs) from government, school, and community agencies, developed 11 population-based competencies for educating nursing students and the novice PHN. Although many organizations have developed competency lists for experts, the Consortium developed a set of competencies that clearly define expectations for the beginning PHN. The competencies are utilized by both education and practice. They guide nurse educators and PHNs in the creation of learning experiences that develop population-based knowledge and skills for baccalaureate nursing students. Public health nursing leaders use the competencies to frame their expectations and orientations for nurses who are new to public health nursing. This paper explains the meaning of each of the 11 population-based competencies and provides examples of student projects that demonstrate competency development. Strategies are suggested for nurse educators and PHNs to promote effective population-based student projects in public health agencies. PMID:21198818

  6. Estimating locus heterogeneity in autosomal dominant polycystic kidney disease (ADPKD) in the Spanish population.

    PubMed Central

    Peral, B; San Millán, J L; Hernández, C; Valero, A; Lathrop, G M; Beckmann, J S; Moreno, F

    1993-01-01

    Although most mutations causing ADPKD in European populations have been mapped to the PKD1 locus on chromosome 16, some of them appear to be unlinked to this locus. To evaluate the incidence of unlinked mutations in Spain we have typed 31 Spanish families from different geographical sites for six closely linked DNA polymorphic marker loci flanking PKD1 detected by probes D16S85, D16S21, D16S259, D16S125, D16S246, and D16S80. Multilocus linkage analysis indicated that in 26 families the disease resulted from PKD1 mutations, whereas in three families it resulted from mutations in a locus other than PKD1. The two other families were not informative. Using the HOMOG test, the incidence of the PKD1 linked mutations in Spain is 85%. Multipoint linkage analysis in the 26 PKD1 families showed that the disease locus lies in the interval between D16S259(pGGG1) and D16S125(26.6). PMID:7905535

  7. The Impact of Environmental Heterogeneity on Genetic Architecture in a Wild Population of Soay Sheep

    PubMed Central

    Robinson, Matthew R.; Wilson, Alastair J.; Pilkington, Jill G.; Clutton-Brock, Tim H.; Pemberton, Josephine M.; Kruuk, Loeske E. B.

    2009-01-01

    This work demonstrates that environmental conditions experienced by individuals can shape their development and affect the stability of genetic associations. The implication of this observation is that the environmental response may influence the evolution of traits in the wild. Here, we examined how the genetic architecture of a suite of sexually dimorphic traits changed as a function of environmental conditions in an unmanaged population of Soay sheep (Ovis aries) on the island of Hirta, St. Kilda, northwest Scotland. We examined the stability of phenotypic, genetic, and environmental (residual) covariance in males during the first year of life between horn length, body weight, and parasite load in environments of different quality. We then examined the same covariance structures across environments within and between the adult sexes. We found significant genotype-by-environment interactions for lamb male body weight and parasite load, leading to a change in the genetic correlation among environments. Horn length was genetically correlated with body weight in males but not females and the genetic correlation among traits within and between the sexes was dependent upon the environmental conditions experienced during adulthood. Genetic correlations were smaller in more favorable environmental conditions, suggesting that in good environments, loci are expressed that have sex-specific effects. The reduction in genetic correlation between the sexes may allow independent evolutionary trajectories for each sex. This study demonstrates that the genetic architecture of traits is not stable under temporally varying environments and highlights the fact that evolutionary processes may depend largely upon ecological conditions. PMID:19204380

  8. Student Populations Served by College of Business Degree Programs

    E-print Network

    Johnson, Eric E.

    land grant status, the BBA program primarily serves students from New Mexico but seeks to add diversity students are male and over 40% are Hispanic with small percentages of Black, Asian, and American Indian programs at other universities both domestic and international. About 28% are Hispanic, 2% American Indian

  9. Extramarital Sexual Attitudes and Norms of an Undergraduate Student Population.

    ERIC Educational Resources Information Center

    Medora, Nilufer P.; Burton, Mary M.

    1981-01-01

    A study of 200 single undergraduate students' opinions on extramarital sexual behavior indicates (1) fraternity/sorority membership does not predict students' opinions, (2) females are more conservative than males, and (3) religiosity is negatively correlated with extramarital sexual permissiveness. (CM)

  10. Measuring the effectiveness of research-based curriculum at a university serving a diverse student population

    NASA Astrophysics Data System (ADS)

    Loverude, M. E.

    2004-09-01

    California State University Fullerton is a regional comprehensive university that serves a diverse student population. Over half of the undergraduate students at CSUF are members of minority groups, and just under half spoke a language other than English at home while growing up. We have tested research-based curricular materials, including Tutorials in Introductory Physics, in courses at CSUF. In some cases, these materials are successful. However, in many cases student outcomes are significantly different from those reported at large research universities. Informally, many faculty believe that the student population at CSUF is significantly different from those at more selective universities. In what ways can the tools of PER be used to measure, describe, and understand the differences between student populations? Are the standard methods of PER suitable for answering questions of this type?

  11. [Dynamical electrical states of heterogeneous populations of ion channels in the membranes of excitable cells].

    PubMed

    Korogod, S M; Kulagina, I B

    2012-01-01

    In computer models, we studied instantaneous (time-varying) current-voltage relationships (iIVs) of populations of ion channels characteristic of the membrane of different type excitable cells, of which the responses to electrical stimuli essentially differ: giant squid axon (Hodgkin-Huxley model), cardiomyocyte, dendrites of CA3 hippocampal pyramidal neurons and Purkinje neurons of the cerebellum. The membrane potential was stepped from the rest level to a certain depolarization test level that was clamped for a certain time, and the total current was measured at different moments after the step onset. For each iIV zero-current points (potentials) were determined. A set of such points, which were situated on the limb of iIV positive slop and corresponded to the state of high membrane depolarization (excitation state, upstate) at different time moments, were used to characterize the dynamics of the excitation state in time. With these indicators the axon membrane was characterized by a single excitation state that rapidly occurred (0.25 ms) and was short-lasting (decayed from -45 to 40 mV during life-time of 5.5 ms). There were two such states of the membrane of cardiomyocyte. The first one was early, rapidly occurring and short-living (rapidly relaxing). It occurred shortly after the depolarization start and lasted for 14.5 ms. The second one was late, slowly rising and long-lasting (occurred with a 7.5-ms delay, increased from 11 to 46 mV in 39 ms and then relaxed lasting for 623 ms in total). The dendritic membrane ofCA3 neurons had one long-lasting excitation state that occurred shortly after the depolarization shift, first rapidly relaxed during 3 ms from initial 30 mV level to -10 mV and then slowly, in 80 ms, stabilized at the level of -20 mV. In the Purkinje neuron membrane two short-lasting and one very long-lasting excitation states were revealed. The first state of very high (>100 mV) depolarization relaxed to 4 mV in 0.8 ms. Shortly before its vanishing, at 0.7 ms, the second short-lasting state emerged, which relaxed in 1 ms from -22 mV to -48 mV. At 1.8 ms a new excitation state emerged, which after a transient relaxation stabilized at -29.65 mV starting from 88 ms. Thus, iIVs allowed disclosing a fine organization of the states of electrical excitation of the membrane and revealing, in populations of ion channels of different content, existence of different number of the mentioned states, which differ from each other in occurrence time and life-time. PMID:22946313

  12. Heterogeneity of Taiwan's indigenous population: possible relation to prehistoric Mongoloid dispersals.

    PubMed

    Lin, M; Chu, C C; Lee, H L; Chang, S L; Ohashi, J; Tokunaga, K; Akaza, T; Juji, T

    2000-01-01

    Taiwan's 9 indigenous tribes (Tsou, Bunun, Paiwan, Rukai, Atayal, Saisiat, Ami, Puyuma, Yami) are highly homogeneous within each tribe, but diversified among the different tribes due to long-term isolation, most probably since Taiwan became an island about 12,000 years ago. Homogeneity of each tribe is evidenced by many HLA-A,B,C alleles having the world's highest ever reported frequencies, e.g. A24 (86.3%), A26 (18.8%), Cw10 (36.8%), Cw7 (66%), Cw8 (32.1%), B13 (27.9%), B62 (37.4%), B75 (18%), B39 (53.5%), B60 (33.3%), and B48 (24%). Also, all of these tribes have HLA class I haplotype frequencies greater than 10%, with A24-Cw7-B39 in Saisiat (44.5%) being the highest, suggesting Taiwan's indigenous tribes are probably the most homogeneous ( the "purest") population in the world. A24-Cw8-B48, A24-Cw10-B60 and A24-Cw9-B61 found common to many Taiwan indigenous tribes, have also been observed in Maori, Papua New Guinea Highlanders, Orochons, Mongolians, Inuit, Japanese, Man, Buryat, Yakut, Tlingit, Tibetans and Thais. These findings suggest Taiwan's indigenous groups are more or less genetically related to both northern and southern Asians. Principal component analysis and the phylogenetic tree (using the neighbor-joining method) showed close relationship between the indigenous groups and Oceanians. This relationship supports the hypothesis that Taiwan was probably on the route of prehistoric Mongoloid dispersals that most likely took place along the coastal lowland of the Asian continent (which is under the sea today). Cultural anthropology also suggests a relationship between Taiwan's indigenous tribes and southern Asians and to a lesser extent, northern Asians. However, the indigenous groups show little genetic relationship to current southern and northern Han Chinese. PMID:10703601

  13. An Analysis of Supports for Persistence for the Military Student Population

    ERIC Educational Resources Information Center

    Mentzer, Bruce; Black, Ellen Lowrie; Spohn, R. Terry

    2015-01-01

    This study sought to describe the correlation of academic, financial, and social supports to the persistence of a military student population: veterans, active duty and their families. The study also contrasted these relationships with those of nonmilitary students and looked at the results of both groups together to determine how supports…

  14. Mild Disability Students and Everyday Mathematics: Serving the Needs of This Population

    ERIC Educational Resources Information Center

    Brehe Pixler, Priscilla

    2009-01-01

    No Child Left Behind requires school districts to demonstrate adequate yearly progress in mathematics for all students, including the sub-population of disabled students. Given that more than 200 Ohio school districts have implemented Everyday Mathematics (EM) to achieve this mandate, districts need to know if this standards-based program meets…

  15. Geography, the Integrating Discipline: Explaining China's Population-Driven Geopolitics to Students

    Microsoft Academic Search

    Clarence J. Bouchat

    2009-01-01

    This article demonstrates geography's role as an integrative discipline and its utility in connecting students to the world around them. A case study links China's demography and its geopolitics to the lives of U.S. students. The relationship of China's population pressures to its resulting economic growth, need for economic resources, and geopolitical efforts are examined using the concepts and holistic

  16. Genetic variability and heterogeneity of Venezuelan equine encephalitis virus vector Ochlerotatus taeniorhynchus (Diptera: Culicidae) populations of the Colombian Atlantic coast, based on microsatellite loci.

    PubMed

    Bello, F; Becerra, V

    2009-01-01

    In Colombia, the mosquito Ochlerotatus taeniorhynchus has been identified as an efficient vector of the epidemic-epizootic Venezuelan equine encephalitis virus. We evaluated the genetic variability and heterogeneity of this mosquito in Colombian populations using eight microsatellite DNA loci. Two hundred and ten mosquito specimens collected from seven populations of the Colombian Atlantic coast (San Bernardo del Viento, Coveñas, Cartagena, Barranquilla, Ciénaga, Dibulla, and Riohacha) were analyzed. We found five polymorphic microsatellite loci, with 19 alleles giving 62.5% polymorphism; the mean number of alleles per locus was 3.8. The mean expected heterogeneity ranged from 0.568 to 0.660. Most of the polymorphic microsatellite loci were in Hardy-Weinberg disequilibrium, due to both deficit and excess of heterozygotes. The Fst statistic gave a total value of 0.0369, reflecting low genetic differentiation among the populations and, as a consequence, a low degree of structuring among them, while gene flow was high (Nm = 6.52); these findings point to genetic homogeneity among these populations. There was no significant linkage disequilibrium between genotype pairs of the various populations. We concluded that this mosquito is distributed in local populations along the Colombian Atlantic coast; these findings will be useful for developing strategies for controlling this vector. PMID:19866436

  17. The heterogeneous HLA genetic composition of the Brazilian population and its relevance to the optimization of hematopoietic stem cell donor recruitment.

    PubMed

    Fabreti-Oliveira, R A; Nascimento, E; Fonseca, C G; Santos, M A

    2014-08-01

    The aim of this study was to investigate the human leukocyte antigen (HLA) molecular variation across the Brazilian population in order to determine possible regional differences, which would be highly relevant to optimizing donor recruitment strategies in hematopoietic stem cell transplantation (HSCT) and understanding the population genetic background of this heterogeneous country. HLA data of 551 HSCT donors from five Brazilian regions were characterized by high-resolution DNA alleles at the HLA-A, -B, -C, -DRB1 and -DQB1 loci and compared with other populations in Brazil and worldwide populations. Allele and haplotype frequencies were estimated. The analysis was performed to assess Hardy-Weinberg equilibrium (HWE) and linkage disequilibrium (LD) among different loci in each recruitment center. Genetic variation was explored through genetic distance analyzed by using a new algorithm based on linear algebra, taking into account geographic regions of Brazil. The results indicated a heterogeneous genetic composition of the Brazilian population, such that HLA allele and haplotype frequencies exhibit different distributions among Brazilian regions, which has important implications for donor matching. In addition, a pronounced differentiation was observed by the absence of clustering of the regional populations in the reduced-dimension space. These data may be useful for increasing donor recruitment with more genetic representativeness in the Brazilian Volunteer Bone Marrow Donors Registry (REDOME). PMID:24724906

  18. Epidemiologic heterogeneity of common mood and anxiety disorders over the lifecourse in the general population: a systematic review

    Microsoft Academic Search

    Arijit Nandi; John R Beard; Sandro Galea

    2009-01-01

    BACKGROUND: Clinical evidence has long suggested there may be heterogeneity in the patterns and predictors of common mood and anxiety disorders; however, epidemiologic studies have generally treated these outcomes as homogenous entities. The objective of this study was to systematically review the epidemiologic evidence for potential patterns of heterogeneity of common mood and anxiety disorders over the lifecourse in the

  19. Preparation of Agricultural Education Students to Work with Diverse Populations

    ERIC Educational Resources Information Center

    Talbert, B. Allen; Edwin, James

    2008-01-01

    This study investigated how agricultural education programs prepare teacher education students for work in diverse situations. It assessed the extent to which agricultural education programs are infusing diversity, multiculturalism, and pluralism into their curriculum as courses, field experiences, and in-service for current teachers. This census…

  20. Treatment of Bipolar Disorder in the University Student Population

    ERIC Educational Resources Information Center

    Federman, Russ

    2011-01-01

    University counseling centers are faced with the challenge of effectively treating bipolar students while also utilizing brief treatment frameworks and managing high patient volumes. Potential destabilization, particularly within the elevated mood phase, poses significant behavioral management issues for university clinicians and administrators,…

  1. Coincidence detection of heterogeneous cell populations from whole blood with coplanar electrodes in a microfluidic impedance cytometer.

    PubMed

    Hassan, U; Bashir, R

    2014-11-21

    Particle counting finds many industrial applications especially in medical healthcare. In particular, cell counting from whole blood is used pervasively for disease diagnostics. Microfluidic impedance cytometry is fast, requires a small volume of blood, can be used at point of care and can perform absolute enumeration of different cell types in the sample. Coincidence detection is very essential for accurate counting results and becomes more significant while counting specific target cells, e.g. CD4(+) or CD8(+) T cell count in HIV/AIDS patient blood samples. In heterogeneous samples, e.g. blood, cell differentiation for all coincidence occurrences is essential in addition to the coincidence detection for accurate cell enumeration. In this paper, we have characterized the coincidence detection with cell differentiation using a microfluidic impedance biochip. The pure population of leukocytes is obtained after all erythrocytes are lysed on-chip from whole blood. Leukocytes were counted electrically as they pass over coplanar microfabricated electrodes bonded to the 15 ?m × 15 ?m cross section counting channel while generating a bipolar pulse for each cell passage. We have developed a mathematical model to simulate the electrical cell pulse and its coincidences. We show that coincidence detection can be characterized into three main types based on the range of time delay at which the coincidence occurs. We have also characterized cell differentiation for all the three coincidence types and show that multiple coincidences of different types can also occur. We used healthy and HIV-infected patient blood samples and used our coincidence detection technique to count CD4(+) and CD8(+) T cells and show the improvement in accuracy of cell counts compared to that without coincidence detection. We have also shown the improvement in the erythrocyte counting with coincidence detection in diluted whole blood samples. PMID:25231594

  2. The alanine-rich XAO peptide adopts a heterogeneous population, including turn-like and polyproline II conformations.

    PubMed

    Schweitzer-Stenner, Reinhard; Measey, Thomas J

    2007-04-17

    The solution structure of the hepta-alanine polypeptide Ac-X(2)A(7)O(2)-NH(2) (XAO) has been a matter of controversy in the current literature. On one side of the argument is a claim that the peptide adopts a mostly polyproline II (PPII) structure, with a <20% population of beta conformations at room temperature [Shi Z, Olson CA, Rose GA, Baldwin RL, Kallenbach NR (2002) Proc Natl Acad Sci USA 99:9190-9195], whereas the other side of the argument insists that the peptide exists as an ensemble of conformations, including multiple beta-turn structures [Makowska J, Rodziewicz-Motowidlo S, Baginska K, Vila JA, Liwo A, Chmurzynski L, Scheraga HA (2006) Proc Natl Acad Sci USA 103:1744-1749]. We have used an excitonic coupling model to simulate the amide I band of the FTIR, vibrational circular dichroism, and isotropic and anisotropic Raman spectra of XAO, where, for each residue, the backbone dihedral angle varphi was constrained by using the reported (3)J(CalphaHNH) values and a modified Karplus relation. The best reproduction of the experimental data could only be achieved by assuming an ensemble of conformations, which contains various beta-turn conformations ( approximately 26%), in addition to beta-strand ( approximately 23%) and PPII ( approximately 50%) conformations. PPII is the dominant conformation in segments not involved in turn formations. Most of the residues were found to sample the bridge region connecting the PPII and right-handed helix troughs in the Ramachandran plot, which is part of the very heterogeneous ensemble of conformations generally termed type IV beta-turn. PMID:17416675

  3. Stress indicators based on airborne thermal imagery for field phenotyping a heterogeneous tree population for response to water constraints.

    PubMed

    Virlet, Nicolas; Lebourgeois, Valentine; Martinez, Sébastien; Costes, Evelyne; Labbé, Sylvain; Regnard, Jean-Luc

    2014-10-01

    As field phenotyping of plant response to water constraints constitutes a bottleneck for breeding programmes, airborne thermal imagery can contribute to assessing the water status of a wide range of individuals simultaneously. However, the presence of mixed soil-plant pixels in heterogeneous plant cover complicates the interpretation of canopy temperature. Moran's Water Deficit Index (WDI = 1-ETact/ETmax), which was designed to overcome this difficulty, was compared with surface minus air temperature (T s-T a) as a water stress indicator. As parameterization of the theoretical equations for WDI computation is difficult, particularly when applied to genotypes with large architectural variability, a simplified procedure based on quantile regression was proposed to delineate the Vegetation Index-Temperature (VIT) scatterplot. The sensitivity of WDI to variations in wet and dry references was assessed by applying more or less stringent quantile levels. The different stress indicators tested on a series of airborne multispectral images (RGB, near-infrared, and thermal infrared) of a population of 122 apple hybrids, under two irrigation regimes, significantly discriminated the tree water statuses. For each acquisition date, the statistical method efficiently delineated the VIT scatterplot, while the limits obtained using the theoretical approach overlapped it, leading to inconsistent WDI values. Once water constraint was established, the different stress indicators were linearly correlated to the stem water potential among a tree subset. T s-T a showed a strong sensitivity to evaporative demand, which limited its relevancy for temporal comparisons. Finally, the statistical approach of WDI appeared the most suitable for high-throughput phenotyping. PMID:25080086

  4. What Is the Impact of Heterogeneous Grouping versus Homogeneous Grouping on Secondary School Student Performance? Technical Report Submitted to the Morgan School, Clinton, CT.

    ERIC Educational Resources Information Center

    Schindelman, Laura; Szoo, Jennifer

    Based on a review of current literature, this report provides information on the impact of heterogeneous grouping versus homogeneous grouping on secondary student performance. Following a definition of ability grouping and arguments for and against its employment in current educational practice, the document examines five significant factors…

  5. The Effects of an Inquiry-Internet Research Project on Motivation, Self-Efficacy, and Academic Autonomy in Heterogenously Grouped High School Latin I Students

    ERIC Educational Resources Information Center

    Wagman, Janet Campbell

    2005-01-01

    The purpose of this study was to analyze and induce change to lessen the achievement gap in heterogeneously grouped high school Latin classes where some students may be at academic risk, due to insufficient knowledge, inability to connect with the subject, and poor performances. The researcher engaged in action research, a branch of qualitative…

  6. Forms of Self-Concept in Gifted High School Students Enrolled in Heterogeneous Classes

    ERIC Educational Resources Information Center

    Villatte, Aude; Hugon, Mandarine; de Leonardis, Myriam

    2011-01-01

    Prior research has been devoted to understanding how to facilitate the integration of gifted young people (Intelligence Quotient, greater than or equal to 130) into classroom settings. This study investigated a typology of self-concept in gifted French high school students. Eighty-four participants, between the ages of 13 and 18 (mean age, 15.5;…

  7. Circular Labor Migration and HIV in India: Exploring Heterogeneity in Bridge Populations Connecting Areas of High and Low HIV Infection Prevalence

    PubMed Central

    Rai, Tanvi; Lambert, Helen S.; Borquez, Annick B.; Saggurti, Niranjan; Mahapatra, Bidhubhushan; Ward, Helen

    2014-01-01

    Background.?The emerging human immunodeficiency virus (HIV) epidemics in rural areas of India are hypothesized to be linked to circular migrants who are introducing HIV from destination areas were the prevalence of HIV infection is higher. We explore the heterogeneity in potential roles of circular migrants in driving an HIV epidemic in a rural area in north India and examine the characteristics of the “sustaining bridge population”, which comprises individuals at risk of HIV acquisition at destination and of HIV transmission into networks at origin capable of sustaining an epidemic. Methods.?Results of a behavioral survey of 639 male migrants from Azamgarh district, India, were analyzed using ?2 tests and logistic regression. Results.?We estimated the size of various subgroups defined by specific sexual behaviors across different locations and over time. Only 20% fit our definition of a sustaining bridge population, with the majority making no apparent contribution to geographical connectedness between high- and low-prevalence areas. However, we found evidence of sexual contacts at origin that could potentially sustain an epidemic once HIV is introduced. Variables associated with sustaining bridge population membership were self-perceived HIV risk, current migrant status, and age. Conclusions.?Circular migrants represent a heterogeneous population in terms of their role as a bridge group. Self-perception of heightened risk could be exploited in designing prevention programs. PMID:25381375

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

    ERIC Educational Resources Information Center

    Robitschek, Christine

    2003-01-01

    This study tested the validity of scores on the Personal Growth Initiative Scale (PGIS; C. Robitschek, 1998, 1999) with a Mexican American college student sample. Results indicated that the PGIS scores appear to be culturally relevant for this population, with scores on the PGIS having many similar relations with other variables that have been…

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

    Microsoft Academic Search

    Christine Robitschek

    2003-01-01

    This study tested the validity of scores on the Personal Growth Initiative Scale (PGIS; C. Robitschek, 1998, 1999) with a Mexican American college student sample. Results indicated that the PGIS scores appear to be culturally relevant for this population, with scores on the PGIS having many similar relations with other variables that have been found in prior research with mostly

  10. Integrating Vocational & Academic Education. A Handbook Featuring Four Demonstration Sites Including Students from Special Populations.

    ERIC Educational Resources Information Center

    Tindall, Lloyd W.; And Others

    This handbook describes the processes and techniques used to develop, implement, and evaluate four integrated vocational and academic learning programs in Wisconsin that included students from special populations. The handbook contains seven chapters. Chapter 1 presents an overview of the project, including the request for proposal process and…

  11. Bayesian Modeling of Space-Time Properties of Infectious Disease in a College Student Population

    E-print Network

    Carin, Lawrence

    Bayesian Modeling of Space-Time Properties of Infectious Disease in a College Student Population 1Z statistical model is developed for analysis of the time-evolving properties of infectious disease of the model results. Keywords: Infectious disease, Bayesian, semi-Markov I. INTRODUCTION There has been

  12. Assessing Undergraduate Learning Outcomes between Accelerated Degree and Traditional Student Populations

    ERIC Educational Resources Information Center

    Rawls, Janita; Hammons, Stacy

    2012-01-01

    This study investigated learning outcomes in both traditional and accelerated degree populations. Using the National Survey of Student Engagement, outcomes were examined relating to critical thinking, oral and written communication, and cultural and global understanding. Literature from life stage development and degree delivery mode areas were…

  13. Evaluation of the Technical Evidence of Assessments for Special Student Populations

    ERIC Educational Resources Information Center

    Sato, Edynn; Rabinowitz, Stanley; Worth, Peter; Gallagher, Carole; Lagunoff, Rachel; Crane, Eric

    2007-01-01

    Recent research has shown that the technical adequacy of assessments for special student populations is relatively undeveloped compared to their general education counterparts; that is, the technical evidence provided and the methods by which this evidence is established do not necessarily account for the unique characteristics of special needs…

  14. Experiences of the Student Population at an Urban University: How Do They Use a Joint Library?

    ERIC Educational Resources Information Center

    Molteni, Valeria E.; Goldman, Crystal; Oulc'hen, Enora

    2014-01-01

    The King Library in San José, California, is a unique combination of academic and public library. It serves the diverse populations of the City of San José and San José State University (SJSU). This article provides analysis of data collected in a study on the concept of "library as place" and SJSU students' sense of belonging…

  15. Teaching about vulnerable populations: nursing students' experience in a homeless center.

    PubMed

    Stanley, Mary Jo

    2013-10-01

    Cultural competence is not limited to ethnicity, religion, or race but is inclusive of vulnerable groups, such as the homeless. The complex health and social issues related to homelessness requires educational instruction that supports students' ability to address and care for the multidimensional elements that surround this group. Exposure to homeless populations provides nursing students with increased awareness of the issues related to health disparities, while promoting introspective reflection on one's values and beliefs. To increase student exposure to working with homeless clients, a service-learning project using a critical social theory (CST) lens was offered at a homeless center. The students' response that clients were "just like" them, coupled with ambiguity regarding the complex social-economic-political issues surrounding the homeless, may indicate a need for further education regarding cultural understanding, sensitivity, and vulnerability. This project demonstrates the need for learning experiences that support advocacy and social responsibility for vulnerable groups. PMID:24040771

  16. Genome-Wide Association Analysis for Blood Lipid Traits Measured in Three Pig Populations Reveals a Substantial Level of Genetic Heterogeneity

    PubMed Central

    Yang, Hui; Huang, Xiaochang; Zeng, Zhijun; Zhang, Wanchang; Liu, Chenlong; Fang, Shaoming; Huang, Lusheng; Chen, Congying

    2015-01-01

    Serum lipids are associated with myocardial infarction and cardiovascular disease in humans. Here we dissected the genetic architecture of blood lipid traits by applying genome-wide association studies (GWAS) in 1,256 pigs from Laiwu, Erhualian and Duroc × (Landrace × Yorkshire) populations, and a meta-analysis of GWAS in more than 2,400 pigs from five diverse populations. A total of 22 genomic loci surpassing the suggestive significance level were detected on 11 pig chromosomes (SSC) for six blood lipid traits. Meta-analysis of GWAS identified 5 novel loci associated with blood lipid traits. Comparison of GWAS loci across the tested populations revealed a substantial level of genetic heterogeneity for porcine blood lipid levels. We further evaluated the causality of nine polymorphisms nearby or within the APOB gene on SSC3 for serum LDL-C and TC levels. Of the 9 polymorphisms, an indel showed the most significant association with LDL-C and TC in Laiwu pigs. But the significant association was not identified in the White Duroc × Erhualian F2 resource population, in which the QTL for LDL-C and TC was also detected on SSC3. This indicates that population-specific signals may exist for the SSC3 QTL. Further investigations are warranted to validate this assumption. PMID:26121138

  17. Variation in DNA methylation transmissibility, genetic heterogeneity and fecundity-related traits in natural populations of the perennial herb Helleborus foetidus.

    PubMed

    Herrera, Carlos M; Medrano, Mónica; Bazaga, Pilar

    2014-03-01

    Inferences about the role of epigenetics in plant ecology and evolution are mostly based on studies of cultivated or model plants conducted in artificial environments. Insights from natural populations, however, are essential to evaluate the possible consequences of epigenetic processes in biologically realistic scenarios with genetically and phenotypically heterogeneous populations. Here, we explore associations across individuals between DNA methylation transmissibility (proportion of methylation-sensitive loci whose methylation status persists unchanged after male gametogenesis), genetic characteristics (assessed with AFLP markers), seed size variability (within-plant seed mass variance), and realized maternal fecundity (number of recently recruited seedlings), in three populations of the perennial herb Helleborus foetidus along a natural ecological gradient in southeastern Spain. Plants (sporophytes) differed in the fidelity with which DNA methylation was transmitted to descendant pollen (gametophytes). This variation in methylation transmissibility was associated with genetic differences. Four AFLP loci were significantly associated with transmissibility and accounted collectively for ~40% of its sample-wide variance. Within-plant variance in seed mass was inversely related to individual transmissibility. The number of seedlings recruited by individual plants was significantly associated with transmissibility. The sign of the relationship varied between populations, which points to environment-specific, divergent phenotypic selection on epigenetic transmissibility. Results support the view that epigenetic transmissibility is itself a phenotypic trait whose evolution may be driven by natural selection, and suggest that in natural populations epigenetic and genetic variation are two intertwined, rather than independent, evolutionary factors. PMID:24471446

  18. Cord Blood Lin?CD45? Embryonic-Like Stem Cells Are a Heterogeneous Population That Lack Self-Renewal Capacity

    PubMed Central

    Alvarez-Gonzalez, Cesar; Duggleby, Richard; Vagaska, Barbora; Querol, Sergio; Gomez, Susana G.; Ferretti, Patrizia; Madrigal, Alejandro

    2013-01-01

    Human umbilical cord blood (hUCB) has been proposed to contain not only haematopoietic stem cells, but also a rare pluripotent embryonic-like stem cell (ELSc) population that is negative for hematopoietic markers (Lin?CD45?) and expresses markers typical of pluripotent cells. The aim of this work was to isolate, characterise and expand this ELSc fraction from hUCB, as it may provide a valuable cell source for regenerative medicine applications. We found that we could indeed isolate a Lin?CD45? population of small cells (3–10 µm diameter) with a high nucleus to cytoplasm ratio that expressed the stem cell markers CD34 and CXCR4. However, in contrast to some previous reports, this fraction was not positive for CD133. Furthermore, although these cells expressed transcripts typical of pluripotent cells, such as SOX2, OCT3/4, and NANOG, they were not able to proliferate in any of the culture media known to support stem cell growth that we tested. Further analysis of the Lin?CD45? population by flow cytometry showed the presence of a Lin?CD45?Nestin+ population that were also positive for CD34 (20%) but negative for CXCR4. These data suggest that the Lin?CD45? stem cell fraction present in the cord blood represents a small heterogeneous population with phenotypic characteristics of stem cells, including a Lin?CD45?Nestin+ population not previously described. This study also suggests that heterogeneity within the Lin?CD45? cell fraction is the likely explanation for differences in the hUCB cell populations described by different groups that were isolated using different methods. These populations have been widely called “embryonic-like stem cell” on the basis of their phenotypical similarity to embryonic stem cells. However, the fact they do not seem to be able to self-renew casts some doubt on their identity, and warns against defining them as “embryonic-like stem cell” at this stage. PMID:23840798

  19. Determining the Effects of a Spatially Heterogeneous Selection Pressure on Bacterial Population Structure at the Submillimetre Scale

    Microsoft Academic Search

    Frances R. Slater; Kenneth D. Bruce; Richard J. Ellis; Andrew K. Lilley; Sarah L. Turner

    2010-01-01

    A key interest of microbial ecology is to understand the role of environmental heterogeneity in shaping bacterial diversity\\u000a and fitness. However, quantifying relevant selection pressures and their effects is challenging due to the number of parameters\\u000a that must be considered and the multiple scales over which they act. In the current study, a model system was employed to\\u000a investigate the

  20. Student Difficulties With Trigonometric Vector Components Persist In Multiple Student Populations

    E-print Network

    Heckler, Andrew F.

    system, such as the weight vector of a box on an inclined plane. Varying the placement of the angle, and a coordinate system. Students struggle further when asked to break down a vector in an inclined coordinate randomly assigned to one of four conditions, each consisting of two "simple" problems and one inclined

  1. Embedding Evolution: Exploring Changes in Students' Conceptual Development, Beliefs, and Motivations in a Population Ecology Unit

    NASA Astrophysics Data System (ADS)

    Rose, Nancy L.

    The purpose of this study was to explore student changes in conceptual development, epistemology, and motivations when evolution concepts are embedded and explicit reflective discourse is used in a unit for population ecology. The two research problems were: (1) What changes are observed in student's conceptual development, epistemology, and motivations when there is explicit reflective discourse within a population ecology unit with embedded evolution?, and (2) In what ways does explicit reflection influence students' mental models within a population ecology unit with embedded evolution? This mixed-method, quasi-experimental study assessed two regular high school biology classes in a small, urban, Midwestern high school. Students in this study had not studied evolution within any formal chapters, but had been immersed in a curriculum with embedded evolution. The study was conducted over a four-week period in a population ecology unit near the beginning of second semester. Instruction emphasized basic conceptions in population ecology. Five key intervention activities included evolutionary concepts as part of an embedded curriculum. The independent variable was explicit reflective discourse with one or two intervention questions after completion of these activities. Data included pre- and posttest surveys measuring (a) evolutionary understanding of natural selection, (b) science beliefs, and (c) science motivations. Written artifacts included (a) explanations to scenarios, (b) pre- and post-argument reflections revealing student's science beliefs and science motivations resultant from two argumentations, and (c) three, pre-, post-, and 6-week final concept maps constructed from 12 concepts. All data sources provided descriptive data. Conceptual change was interpreted from an ontological, epistemological, and motivational perspective. The experimental class receiving explicit reflective discourse showed greater overall increases in conceptual development. Students in both classes constructed teleological and proximate explanations. Overall, the experimental class gave greater numbers of evolutionary explanations. Scored propositions from concept maps showed a mixture of synthetic and scientific conceptions in both classes, however the experimental group showed greater scientific quality. Students in both classes exhibited direct-process ontology. Both classes had high degrees of epistemological and motivational commitments demonstrated by their engagement and subsequent improvements in conceptual development in both evolutionary and ecological conceptions.

  2. Limits of Generalizing in Education Research: Why Criteria for Research Generalization Should Include Population Heterogeneity and Uses of Knowledge Claims

    ERIC Educational Resources Information Center

    Ercikan, Kadriye; Roth, Wolff-Michael

    2014-01-01

    Context: Generalization is a critical concept in all research designed to generate knowledge that applies to all elements of a unit (population) while studying only a subset of these elements (sample). Commonly applied criteria for generalizing focus on experimental design or representativeness of samples of the population of units. The criteria…

  3. Addressing the Needs of Racially/Culturally Diverse Student Populations in Higher Education: An Analysis of Educational Practices for Disadvantaged Youth

    ERIC Educational Resources Information Center

    Pender, Matea

    2010-01-01

    The recent growth in the racial and cultural heterogeneity of college students in the United States has increased the demand for higher educational policies that will accommodate the needs of an increasingly diverse collective student body (Kao & Thompson, 2003). Traditionally, underrepresented minority students (i.e., African American, Hispanic…

  4. Noncognitive Predictors of Academic Performance and Persistence in Horizontal and Vertical Transfer Students by Academic Level

    ERIC Educational Resources Information Center

    Davis, Christopher A.

    2010-01-01

    College students increasingly are transferring among institutions of higher education in pursuit of their educational goals. The existing research on transfer students, however, does not adequately explore the unique characteristics of this heterogeneous population. The literature on transfer students suggests that transfer students are at-risk…

  5. Evolutionary conservation advice for despotic populations: habitat heterogeneity favours conflict and reduces productivity in Seychelles magpie robins

    PubMed Central

    López-Sepulcre, Andrés; Kokko, Hanna; Norris, Ken

    2010-01-01

    Individual preferences for good habitat are often thought to have a beneficial stabilizing effect for populations. However, if individuals preferentially compete for better-quality territories, these may become hotspots of conflict. We show that, in an endangered species, this process decreases the productivity of favoured territories to the extent that differences in productivity between territories disappear. Unlike predictions from current demographic theory on site-dependent population regulation (ideal despotic distribution), we show that population productivity is reduced if resources are distributed unevenly in space. Competition for high-quality habitat can thus have detrimental consequences for populations even though it benefits individuals. Manipulating conflict (e.g. by reducing variation in habitat quality) can therefore prove an effective conservation measure in species with strong social or territorial conflict. PMID:20534612

  6. Modelling heterogeneity in the recoveries of marked animal populations with covariates of individual animals, groups of animals or recovery time

    USGS Publications Warehouse

    Dorazio, R.M.

    1997-01-01

    A general framework is developed for modelling rates of survival and recovery of marked animal populations in terms of auxiliary information collected at the time of marking. The framework may be used to estimate differences in survival or recovery among individual animals, groups of animals, and recovery times. Analyses of the recoveries of tagged fish and banded bird populations are used to illustrate the specification and selection of various models.

  7. Genetic heterogeneity in a single year-class from a panmictic population of adult blue rockfish ( Sebastes mystinus )

    Microsoft Academic Search

    Martha O. Burford; Ralph J. Larson

    2007-01-01

    We used microsatellite genetic markers to investigate adult population structure and the formation of a new year-class in\\u000a Sebastes mystinus (blue rockfish). Since S. mystinus may live as long as 45 years and reach reproductive age at approximately 5 years, the adult population may contain as many\\u000a as eight generations of reproductive adults. We investigated whether the juveniles of the 2000 year-class and

  8. Homogeneous Grouping and Heterogeneous Grouping.

    ERIC Educational Resources Information Center

    Ediger, Marlow

    This paper discusses how to group students for reading instruction. The paper first considers the reasons for heterogeneous grouping, where there are mixed levels of reading achievement among the students in the classroom. It then discusses some weaknesses in advocating heterogeneous grouping. There are individualized plans for reading instruction…

  9. "That's so gay!" Exploring college students' attitudes toward the LGBT population.

    PubMed

    Holland, Laurel; Matthews, Todd L; Schott, Melinda R

    2013-01-01

    Traditional students are often introduced to unfamiliar subcultures for the first time on the college campus. Recent high school graduates find themselves transitioning from an atmosphere in which homophobia is likely to be tolerated and possibly even expected to an educational setting in which diversity is promoted. Research shows that the college years are influential in the re-socialization of core values, yet very little work focuses on the ideological shifts that may take place in attitudes toward the lesbian, gay, bisexual, and transgendered (LGBT) population. The research presented in this study includes a modified version of LaMar and Kite's Component Measure, which has been broken down into 6 distinctive components of tolerance. In addition to examining religion, gender, and race--factors that have been correlated in past research with differing levels of tolerance toward the LGBT community--this study adds politics, sexual orientation, academic class standing, and college of major--variables that have received little or no attention in this literature. Higher levels of LGBT tolerance are consistently observed across the indexes among women, more liberal Christian traditions, non-Christian faiths, the non-religious, and those who self-identify as LGBT. The distinctive contribution of this study is that students in the College of Arts and Sciences and students further along in their college careers are also more tolerant. Based on these findings, recommendations are made for inter-college curriculum changes that integrate students in all disciplines and students of all classifications. PMID:23469818

  10. LoFreq: a sequence-quality aware, ultra-sensitive variant caller for uncovering cell-population heterogeneity from high-throughput sequencing datasets

    PubMed Central

    Wilm, Andreas; Aw, Pauline Poh Kim; Bertrand, Denis; Yeo, Grace Hui Ting; Ong, Swee Hoe; Wong, Chang Hua; Khor, Chiea Chuen; Petric, Rosemary; Hibberd, Martin Lloyd; Nagarajan, Niranjan

    2012-01-01

    The study of cell-population heterogeneity in a range of biological systems, from viruses to bacterial isolates to tumor samples, has been transformed by recent advances in sequencing throughput. While the high-coverage afforded can be used, in principle, to identify very rare variants in a population, existing ad hoc approaches frequently fail to distinguish true variants from sequencing errors. We report a method (LoFreq) that models sequencing run-specific error rates to accurately call variants occurring in <0.05% of a population. Using simulated and real datasets (viral, bacterial and human), we show that LoFreq has near-perfect specificity, with significantly improved sensitivity compared with existing methods and can efficiently analyze deep Illumina sequencing datasets without resorting to approximations or heuristics. We also present experimental validation for LoFreq on two different platforms (Fluidigm and Sequenom) and its application to call rare somatic variants from exome sequencing datasets for gastric cancer. Source code and executables for LoFreq are freely available at http://sourceforge.net/projects/lofreq/. PMID:23066108

  11. A new model for teaching to a diverse population of students

    NASA Astrophysics Data System (ADS)

    Weissmann, G. S.; Ibarra, R.

    2014-12-01

    Why do the geosciences suffer from low diversity in our students and workforce? We wonder if something is missing in the way we approach Earth Science learning. Diversity is important not only to produce a population of students that better reflects the overall US population, but also to draw on a diverse approach to understanding important concepts such as found in integrated approaches like Earth Systems Science or Environmental Science. By exploring social science research in culture and diversity, my exposure to Context Diversity Theory appears to show ways to enhance our ability to tackle these large-scale problems in Earth Sciences while attracting diverse students and helping them thrive in the academic setting. The theory postulates that a growing number of individuals now entering higher education bring with them a mix of characteristics described as their "cultural context" (high and low). Context Diversity Theory represents ways of knowing and doing as a binary continuum. One end member of this continuum has individuals approaching the world through a reductionist approach (e.g., low context). The other end member uses a more constructivist approach to science (e.g., high context). While both approaches are successful at describing various aspects of the natural world, our educational system emphasizes the low context perspective. However, many of our students from underrepresented groups may understand the world from a high context perspective. A Multicontextual model would use a balanced approach to evaluating our world, expanding on the commonly low context approach in education. Thus, a reframing process based on Context Diversity Theory may help develop strategies that expand disciplinary culture(s) while not changing the cultural approach of people participating in it. This Multicontextual approach may significantly enhance our ability to develop new approaches to interdisciplinary research while building a strong framework that allows all students to thrive in our programs.

  12. Transition and Students with Twice Exceptionality

    ERIC Educational Resources Information Center

    Prior, Susan

    2013-01-01

    "Twice exceptional" is one of the terms used to describe students who have giftedness and a disability. This is a small heterogeneous population of individual learners who are underserved in special, gifted, and mainstream education settings. Despite the availability of research on transition for students with disabilities, there is…

  13. Genetic Heterogeneity of Susceptibility Gene in Different Ethnic Populations: Refining Association Study of PTPN22 for Graves’ Disease in a Chinese Han Population

    PubMed Central

    Zhao, Shuangxia; Han, Bing; Liu, Wei; Yang, Shaoying; Yu, Shasha; Sun, Yixuan; Liang, Jun; Gao, Guanqi; Zhang, Xiaomei; Yuan, Guoyue; Li, Changgui; Du, Wenhua; Chen, Gang; Chen, Jialun; Song, Huaidong

    2013-01-01

    In our previous studies, we presumed subtypes of Graves’ disease (GD) may be caused by different major susceptibility genes or different variants of a single susceptibility gene. However, more evidence is needed to support this hypothesis. Single-nucleotide polymorphism (SNP) rs2476601 in PTPN22 is the susceptibility loci of GD in the European population. However, this polymorphism has not been found in Asian populations. Here, we investigate whether PTPN22 is the susceptibility gene for GD in Chinese population and further determine the susceptibility variant of PTPN22 in GD. We conducted an imputation analysis based on the results of our genome-wide association study (GWAS) in 1,536 GD patients and 1,516 control subjects. Imputation revealed that 255 common SNPs on a linkage disequilibrium (LD) block containing PTPN22 were associated with GD (P<0.05). Nine tagSNPs that captured the 255 common variants were selected to be further genotyped in a large cohort including 4,368 GD patients and 4,350 matched controls. There was no significant difference between the nine tagSNPs (P>0.05) in either the genotype distribution or allelic frequencies between patients and controls in the replication study. Although the combined analysis exhibited a weak association signal (Pcombined = 0.003263 for rs3811021), the false positive report probability (FPRP) analysis indicated it was most likely a false positive finding. Our study did not support an association of common SNPs in PTPN22 LD block with GD in Chinese Han population. This suggests that GD in different ethnic population is probably caused by distinct susceptibility genes. PMID:24386393

  14. Language Shift and the Inclusion of Indigenous Populations in Large-Scale Assessment Programs

    ERIC Educational Resources Information Center

    Solano-Flores, Guillermo; Backhoff, Eduardo; Contreras-Niño, Luis A.; Vázquez-Muñoz, Mariana

    2015-01-01

    Indicators of academic achievement for bilingual students can be inaccurate due to linguistic heterogeneity. For indigenous populations, language shift (the gradual replacement of one language by another) is a factor that can increase this heterogeneity and poses an additional challenge for valid testing. We investigated whether and how indigenous…

  15. ECL 290 Population Genetic Software Winter 2007 Plan and student assignments as of: 1/21/2007

    E-print Network

    Ernest, Holly

    ECL 290 Population Genetic Software Winter 2007 Plan and student assignments as of: 1/21/2007 Course instructors: Bernie May, Holly Ernest, John Eadie Objectives of course ----learn key genetic data that will be added to our lab web sites Students assigned as their group's contact person (see below) should get

  16. Can Welfare Mothers Hack It in College? A Comparison of Achievement between TANF Recipients and General Population Community College Students

    ERIC Educational Resources Information Center

    Fenster, Judy

    2004-01-01

    The achievement of a group of undergraduate students enrolled in a pilot program for welfare recipients in the form of TANF (Temporary Aid to Needy Families) was compared with the achievement of general population students at an urban community college. Grades attained in a basic level, introductory Psychology course were used to measure academic…

  17. Enrichment of live unlabelled cardiomyocytes from heterogeneous cell populations using manipulation of cell settling velocity by magnetic field

    PubMed Central

    Sofla, Aarash; Cirkovic, Bojana; Hsieh, Anne; Miklas, Jason W.; Filipovic, Nenad; Radisic, Milica

    2013-01-01

    The majority of available cardiomyocyte markers are intercellular proteins, limiting our ability to enrich live cardiomyocytes from heterogeneous cell preparations in the absence of genetic labeling. Here, we describe enrichment of live cardiomyocytes from the hearts of adult mice in a label-free microfluidic approach. The separation device consisted of a vertical column (15?mm long, 700??m diameter), placed between permanent magnets resulting in a field strength of 1.23?T. To concentrate the field at the column wall, the column was wrapped with 69??m diameter nickel wire. Before passing the cells through the column, the cardiomyocytes in the cell suspension had been rendered paramagnetic by treatment of the adult mouse heart cell preparation with sodium nitrite (2.5?mM) for 20?min on ice. The cell suspension was loaded into the vertical column from the top and upon settling, the non-myocytes were removed by the upward flow from the column. The cardiomyocytes were then collected from the column by applying a higher flow rate (144??l/min). We found that by applying a separation flow rate of 4.2??l/min in the first step, we can enrich live adult cardiomyocytes to 93%?±?2% in a label-free manner. The cardiomyocytes maintained viability immediately after separation and upon 24?h in culture. PMID:24404002

  18. Projecting Enrollments for Delta College: Explosive Population Growth Will Enlarge and Diversify Delta's Student Body. Research Report.

    ERIC Educational Resources Information Center

    Evans, John W.

    In 1990, a study was conducted at California's San Joaquin Delta Community College (SJDCC) to examine student enrollment trends and to analyze alternative population projections. The purpose of the study was to prepare SJDCC for the fiscal, managerial, and educational challenges which the growing, ethnically diverse population would bring.…

  19. Education on Population Matters in Europe: Results from a Comparative Survey among Students in Five European Countries

    ERIC Educational Resources Information Center

    Van Peer, Christine

    2006-01-01

    In 1996-1997, within the framework of the European Observatory for Population Education and Information, a comparative survey was conducted among students in final classes of secondary education in several European countries. On the one hand, the survey attempted to assess the effects of education on population in terms of knowledge acquired; the…

  20. Spatial homogeneity and temporal heterogeneity of red drum (Sciaenops ocellatus) microsatellites: effective population sizes and management implications.

    PubMed

    Chapman, Robert W; Ball, A O; Mash, Lisa R

    2002-12-01

    The red drum (Sciaenops ocellatus) is one of a number of species that occupy estuarine waters as juveniles and migrate to open ocean waters as adults. This species has experienced dramatic declines in population numbers over the past 2 decades, which has prompted increasing fishery restriction. In addition, hatchery augmentation has been initiated by several states to increase the abundance of juveniles in local areas. In South Carolina hatchery-reared fish have made significant (20%) contributions to the juvenile population on very local scales. As hatchery-reared fish are typically produced by a small number of individuals, the genetic consequences of augmentation programs are of concern. In this article we assess genetic variation at 5 microsatellite loci in S. ocellatus. The data indicate little geographic differentiation among samples collected along the Atlantic Coast of the United States, but substantial differences among year classes taken from South Carolina. The gene frequency differences among year classes were used to estimate the effective population size (Nc) of S. ocellatus in South Carolina and suggested that Ne was less than 300 from 1990 to 1993 and increased to about 1000 in 1994 and 1995. Whether this increase reflects the effectiveness of management regulations or simply a random fluctuation in S. ocellatus populations is not clear. The data suggest that a limited number of individuals produce the bulk of a given year class and support the sweepstakes hypothesis. Given the small Ne and estimates of the contribution of hatchery-reared fish to the wild stock, it is suggested that programs have the potential to increase, rather than decrease; Ne in the wild. PMID:14961234

  1. Landscape effects of a non-native grass facilitate source populations of a native generalist bug, Stenotus rubrovittatus, in a heterogeneous agricultural landscape.

    PubMed

    Yoshioka, A; Takada, M B; Washitani, I

    2014-01-01

    Non-native plant species can provide native generalist insects, including pests, with novel food and habitats. It is hypothesized that local and landscape-level abundances of non-native plants can affect the population size of generalist insects, although generalists are assumed to be less sensitive to habitat connectivity than specialists. In a heterogeneous landscape in Japan, the relationship between the density of a native pest of rice (Stenotus rubrovittatus (Matsumura) (Heteroptera: Miridae)) and the abundance of Italian ryegrass (Lolium multiflorum Lam. (Poales: Poaceae)), a non-native meadow grass known to facilitate S. rubrovittatus, was analyzed. Statistical analyses of data on bug density, vegetation, and the spatial distribution of fallow fields and meadows dominated by Italian ryegrass, obtained by field surveys, demonstrated that local and landscape-level abundances of Italian ryegrass (the unmowed meadow areas within a few hundred meters of a sampling plot) positively affected bug density before its immigration into rice fields. Our findings suggest that a generalist herbivorous insect that prefers non-native plants responds to spatial availability and connectivity of plant species patches at the metapopulation level. Fragmentation by selective mowing that decreases the total area of source populations and increases the isolation among them would be an effective and environmentally-friendly pest management method. PMID:25205015

  2. Landscape Effects of a Non-Native Grass Facilitate Source Populations of a Native Generalist Bug, Stenotus rubrovittatus, in a Heterogeneous Agricultural Landscape

    PubMed Central

    Yoshioka, A.; Takada, M. B.; Washitani, I.

    2014-01-01

    Non-native plant species can provide native generalist insects, including pests, with novel food and habitats. It is hypothesized that local and landscape-level abundances of non-native plants can affect the population size of generalist insects, although generalists are assumed to be less sensitive to habitat connectivity than specialists. In a heterogeneous landscape in Japan, the relationship between the density of a native pest of rice (Stenotus rubrovittatus (Matsumura) (Heteroptera: Miridae)) and the abundance of Italian ryegrass (Lolium multiflorum Lam. (Poales: Poaceae)), a non-native meadow grass known to facilitate S. rubrovittatus, was analyzed. Statistical analyses of data on bug density, vegetation, and the spatial distribution of fallow fields and meadows dominated by Italian ryegrass, obtained by field surveys, demonstrated that local and landscape-level abundances of Italian ryegrass (the unmowed meadow areas within a few hundred meters of a sampling plot) positively affected bug density before its immigration into rice fields. Our findings suggest that a generalist herbivorous insect that prefers non-native plants responds to spatial availability and connectivity of plant species patches at the metapopulation level. Fragmentation by selective mowing that decreases the total area of source populations and increases the isolation among them would be an effective and environmentally-friendly pest management method. PMID:25205015

  3. Effect of heterogeneity of human population in cell radiosensitivity on the extrapolation of dose-response relationships to low doses

    SciTech Connect

    Filyushkin, I.V.; Bragin, Yu.N.; Khandogina, E.K.

    1989-09-01

    Presented are the results of an investigation of the dose-response relationship for the yield of chromosome aberrations in peripheral blood lymphocytes of persons with some hereditary diseases which represent the high risk group with respect to the increased incidence of malignant tumors and decreased life span. Despite substantially different absolute radiosensitivities of chromosomes, the variations of the alpha/beta ratio determining the extrapolation of experimental dose-response relationships to low doses did not prove to be too high, the mean deviation from the control being 15%. This points to the possible practical use of the dose-response relationships averaged over the human population as a whole.

  4. Evolution of aging: individual life history trade-offs and population heterogeneity account for mortality patterns across species.

    PubMed

    Le Cunff, Y; Baudisch, A; Pakdaman, K

    2014-08-01

    A broad range of mortality patterns has been documented across species, some even including decreasing mortality over age. Whether there exist a common denominator to explain both similarities and differences in these mortality patterns remains an open question. The disposable soma theory, an evolutionary theory of aging, proposes that universal intracellular trade-offs between maintenance/lifespan and reproduction would drive aging across species. The disposable soma theory has provided numerous insights concerning aging processes in single individuals. Yet, which specific population mortality patterns it can lead to is still largely unexplored. In this article, we propose a model exploring the mortality patterns which emerge from an evolutionary process including only the disposable soma theory core principles. We adapt a well-known model of genomic evolution to show that mortality curves producing a kink or mid-life plateaus derive from a common minimal evolutionary framework. These mortality shapes qualitatively correspond to those of Drosophila melanogaster, Caenorhabditis elegans, medflies, yeasts and humans. Species evolved in silico especially differ in their population diversity of maintenance strategies, which itself emerges as an adaptation to the environment over generations. Based on this integrative framework, we also derive predictions and interpretations concerning the effects of diet changes and heat-shock treatments on mortality patterns. PMID:24925106

  5. An Untapped Resource for Increasing College Attainment: Estimating the Population of Potential First-Generation Students in Wisconsin. WISCAPE Policy Brief

    ERIC Educational Resources Information Center

    Lazenby, Sara

    2011-01-01

    Potential first-generation students make up a large segment of Wisconsin's teenage population. To increase the pool of educated workers in Wisconsin, policymakers must work to recruit, retain, and graduate these students. Estimates of the size of the first-generation student population in the state are crucial for these efforts. This brief…

  6. Phylogenetic and clonality analysis of Bacillus pumilus isolates uncovered a highly heterogeneous population of different closely related species and clones.

    PubMed

    Branquinho, Raquel; Meirinhos-Soares, Luís; Carriço, João A; Pintado, Manuela; Peixe, Luísa V

    2014-12-01

    Bacillus pumilus is a Gram-positive bacterium with a wide range of attributed applications, namely as a plant growth promoting rhizobacteria (PGPR), animal, and human probiotic. However, a rare putative role in human diseases has been reported, namely in food poisoning or as anthrax-like cutaneous infectious agent. This species is difficult to distinguish from its closely related species on the basis of phenotypic or biochemical characteristics and 16S rRNA gene sequences. In this study, the phylogenetic analysis of gyrB and rpoB gene sequences of a collection of isolates previously identified as B. pumilus, assigned most of them (93%, 38 of 41 isolates) to B. safensis or to the new recently described B. invictae. Moreover, we extended the previously reported recognized habitats of these species and unveiled a human health or biotechnological relevance (e.g. as implicated in food poisoning or PGPR) for them. Additionally, we demonstrated that both B. safensis and B. invictae species encompass a clonally diverse population, which can justify their great adaptation ability to different niches, with evidence of clonal-host specificity. PMID:25230950

  7. A heterogeneous population of alpha 1-adrenoceptors mediates contraction of the isolated follicle wall from the bovine ovary.

    PubMed

    Kannisto, P; Owman, C; Schmidt, G; Sjöberg, N O

    1988-08-01

    Strips from Graafian follicles of bovine ovaries were tested for their contractile response in vitro in order to characterize the type of post-junctional alpha-adrenoceptor involved. Electrically induced contractions were inhibited concentration-dependently by the alpha 1-antagonist, prazosin. Besides noradrenaline the alpha 1-selective agonists, methoxamine and phenylephrine, caused the strips to contract, whereas the alpha 2-selective agonists clonidine, oxymetazoline and B-HT920 were without effect. However, the alpha 1-selective antagonist prazosin gave a line with a slope less than unity in the Schild plots with noradrenaline and methoxamine. From results obtained with or without the presence of two classes of neuronal uptake blockers (desipramine and cocaine) it is concluded that the post-junctional alpha 1-receptor population is inhomogeneous. The regular appearance of the Schild plot obtained with phenylephrine may be due to involvement also of a component of noradrenaline release by this agonist. The pA2 value in the test with phenylephrine was 9.27, with a corresponding kB of 3.81 +/- 1.15 X 10(-10) M. PMID:2906513

  8. Trans-Ethnic Fine-Mapping of Lipid Loci Identifies Population-Specific Signals and Allelic Heterogeneity That Increases the Trait Variance Explained

    PubMed Central

    Wu, Ying; Waite, Lindsay L.; Jackson, Anne U.; Sheu, Wayne H-H.; Buyske, Steven; Absher, Devin; Arnett, Donna K.; Boerwinkle, Eric; Bonnycastle, Lori L.; Carty, Cara L.; Cheng, Iona; Cochran, Barbara; Croteau-Chonka, Damien C.; Dumitrescu, Logan; Eaton, Charles B.; Franceschini, Nora; Guo, Xiuqing; Henderson, Brian E.; Hindorff, Lucia A.; Kim, Eric; Kinnunen, Leena; Komulainen, Pirjo; Lee, Wen-Jane; Le Marchand, Loic; Lin, Yi; Lindström, Jaana; Lingaas-Holmen, Oddgeir; Mitchell, Sabrina L.; Narisu, Narisu; Robinson, Jennifer G.; Schumacher, Fred; Stan?áková, Alena; Sundvall, Jouko; Sung, Yun-Ju; Swift, Amy J.; Wang, Wen-Chang; Wilkens, Lynne; Wilsgaard, Tom; Young, Alicia M.; Adair, Linda S.; Ballantyne, Christie M.; B?žková, Petra; Chakravarti, Aravinda; Collins, Francis S.; Duggan, David; Feranil, Alan B.; Ho, Low-Tone; Hung, Yi-Jen; Hunt, Steven C.; Hveem, Kristian; Juang, Jyh-Ming J.; Kesäniemi, Antero Y.; Kuusisto, Johanna; Laakso, Markku; Lakka, Timo A.; Lee, I-Te; Leppert, Mark F.; Matise, Tara C.; Moilanen, Leena; Njølstad, Inger; Peters, Ulrike; Quertermous, Thomas; Rauramaa, Rainer; Rotter, Jerome I.; Saramies, Jouko; Tuomilehto, Jaakko; Uusitupa, Matti; Wang, Tzung-Dau; Mohlke, Karen L.

    2013-01-01

    Genome-wide association studies (GWAS) have identified ?100 loci associated with blood lipid levels, but much of the trait heritability remains unexplained, and at most loci the identities of the trait-influencing variants remain unknown. We conducted a trans-ethnic fine-mapping study at 18, 22, and 18 GWAS loci on the Metabochip for their association with triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C), respectively, in individuals of African American (n?=?6,832), East Asian (n?=?9,449), and European (n?=?10,829) ancestry. We aimed to identify the variants with strongest association at each locus, identify additional and population-specific signals, refine association signals, and assess the relative significance of previously described functional variants. Among the 58 loci, 33 exhibited evidence of association at P<1×10?4 in at least one ancestry group. Sequential conditional analyses revealed that ten, nine, and four loci in African Americans, Europeans, and East Asians, respectively, exhibited two or more signals. At these loci, accounting for all signals led to a 1.3- to 1.8-fold increase in the explained phenotypic variance compared to the strongest signals. Distinct signals across ancestry groups were identified at PCSK9 and APOA5. Trans-ethnic analyses narrowed the signals to smaller sets of variants at GCKR, PPP1R3B, ABO, LCAT, and ABCA1. Of 27 variants reported previously to have functional effects, 74% exhibited the strongest association at the respective signal. In conclusion, trans-ethnic high-density genotyping and analysis confirm the presence of allelic heterogeneity, allow the identification of population-specific variants, and limit the number of candidate SNPs for functional studies. PMID:23555291

  9. Trans-ethnic fine-mapping of lipid loci identifies population-specific signals and allelic heterogeneity that increases the trait variance explained.

    PubMed

    Wu, Ying; Waite, Lindsay L; Jackson, Anne U; Sheu, Wayne H-H; Buyske, Steven; Absher, Devin; Arnett, Donna K; Boerwinkle, Eric; Bonnycastle, Lori L; Carty, Cara L; Cheng, Iona; Cochran, Barbara; Croteau-Chonka, Damien C; Dumitrescu, Logan; Eaton, Charles B; Franceschini, Nora; Guo, Xiuqing; Henderson, Brian E; Hindorff, Lucia A; Kim, Eric; Kinnunen, Leena; Komulainen, Pirjo; Lee, Wen-Jane; Le Marchand, Loic; Lin, Yi; Lindström, Jaana; Lingaas-Holmen, Oddgeir; Mitchell, Sabrina L; Narisu, Narisu; Robinson, Jennifer G; Schumacher, Fred; Stan?áková, Alena; Sundvall, Jouko; Sung, Yun-Ju; Swift, Amy J; Wang, Wen-Chang; Wilkens, Lynne; Wilsgaard, Tom; Young, Alicia M; Adair, Linda S; Ballantyne, Christie M; B?žková, Petra; Chakravarti, Aravinda; Collins, Francis S; Duggan, David; Feranil, Alan B; Ho, Low-Tone; Hung, Yi-Jen; Hunt, Steven C; Hveem, Kristian; Juang, Jyh-Ming J; Kesäniemi, Antero Y; Kuusisto, Johanna; Laakso, Markku; Lakka, Timo A; Lee, I-Te; Leppert, Mark F; Matise, Tara C; Moilanen, Leena; Njølstad, Inger; Peters, Ulrike; Quertermous, Thomas; Rauramaa, Rainer; Rotter, Jerome I; Saramies, Jouko; Tuomilehto, Jaakko; Uusitupa, Matti; Wang, Tzung-Dau; Boehnke, Michael; Haiman, Christopher A; Chen, Yii-Der I; Kooperberg, Charles; Assimes, Themistocles L; Crawford, Dana C; Hsiung, Chao A; North, Kari E; Mohlke, Karen L

    2013-03-01

    Genome-wide association studies (GWAS) have identified ~100 loci associated with blood lipid levels, but much of the trait heritability remains unexplained, and at most loci the identities of the trait-influencing variants remain unknown. We conducted a trans-ethnic fine-mapping study at 18, 22, and 18 GWAS loci on the Metabochip for their association with triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C), respectively, in individuals of African American (n = 6,832), East Asian (n = 9,449), and European (n = 10,829) ancestry. We aimed to identify the variants with strongest association at each locus, identify additional and population-specific signals, refine association signals, and assess the relative significance of previously described functional variants. Among the 58 loci, 33 exhibited evidence of association at P<1 × 10(-4) in at least one ancestry group. Sequential conditional analyses revealed that ten, nine, and four loci in African Americans, Europeans, and East Asians, respectively, exhibited two or more signals. At these loci, accounting for all signals led to a 1.3- to 1.8-fold increase in the explained phenotypic variance compared to the strongest signals. Distinct signals across ancestry groups were identified at PCSK9 and APOA5. Trans-ethnic analyses narrowed the signals to smaller sets of variants at GCKR, PPP1R3B, ABO, LCAT, and ABCA1. Of 27 variants reported previously to have functional effects, 74% exhibited the strongest association at the respective signal. In conclusion, trans-ethnic high-density genotyping and analysis confirm the presence of allelic heterogeneity, allow the identification of population-specific variants, and limit the number of candidate SNPs for functional studies. PMID:23555291

  10. Heterogeneous cell-cycle behavior in response to UVB irradiation by a population of single cancer cells visualized by time-lapse FUCCI imaging.

    PubMed

    Miwa, Shinji; Yano, Shuya; Kimura, Hiroaki; Yamamoto, Mako; Toneri, Makoto; Murakami, Takashi; Hayashi, Katsuhiro; Yamamoto, Norio; Fujiwara, Toshiyoshi; Tsuchiya, Hiroyuki; Hoffman, Robert M

    2015-06-18

    The present study analyzed the heterogeneous cell-cycle dependence and fate of single cancer cells in a population treated with UVB using a fluorescence ubiquitination-based cell-cycle (FUCCI) imaging system. HeLa cells expressing FUCCI were irradiated by 100 or 200 J/m(2) UVB. Modulation of the cell-cycle and apoptosis were observed by time-lapse confocal microscopy imaging every 30 min for 72 h. Correlation between cell survival and factors including cell-cycle phase at the time of the irradiation of UVB, mitosis and the G1/S transition were analyzed using the Kaplan-Meier method along with the log rank test. Time-lapse FUCCI imaging of HeLa cells demonstrated that UVB irradiation induced cell-cycle arrest in S/G2/M phase in the majority of the cells. The cells irradiated by 100 or 200 J/m(2) UVB during G0/G1 phase had a higher survival rate than the cells irradiated during S/G2/M phase. A minority of cells could escape S/G2/M arrest and undergo mitosis which significantly correlated with decreased survival of the cells. In contrast, G1/S transition significantly correlated with increased survival of the cells after UVB irradiation. UVB at 200 J/m(2) resulted in a greater number of apoptotic cells. PMID:25946083

  11. Heterogeneous pattern of selective pressure for PRRT2 in human populations, but no association with autism spectrum disorders.

    PubMed

    Huguet, Guillaume; Nava, Caroline; Lemière, Nathalie; Patin, Etienne; Laval, Guillaume; Ey, Elodie; Brice, Alexis; Leboyer, Marion; Szepetowski, Pierre; Gillberg, Christopher; Depienne, Christel; Delorme, Richard; Bourgeron, Thomas

    2014-01-01

    Inherited and de novo genomic imbalances at chromosome 16p11.2 are associated with autism spectrum disorders (ASD), but the causative genes remain unknown. Among the genes located in this region, PRRT2 codes for a member of the synaptic SNARE complex that allows the release of synaptic vesicles. PRRT2 is a candidate gene for ASD since homozygote mutations are associated with intellectual disability and heterozygote mutations cause benign infantile seizures, paroxysmal dyskinesia, or hemiplegic migraine. Here, we explored the contribution of PRRT2 mutations in ASD by screening its coding part in a large sample of 1578 individuals including 431 individuals with ASD, 186 controls and 961 individuals from the human genome Diversity Panel. We detected 24 nonsynonymous variants, 1 frameshift (A217PfsX8) and 1 in-frame deletion of 6 bp (p.A361_P362del). The frameshift mutation was observed in a control with no history of neurological or psychiatric disorders. The p.A361_P362del was observed in two individuals with autism from sub-Saharan African origin. Overall, the frequency of PRRT2 deleterious variants was not different between individuals with ASD and controls. Remarkably, PRRT2 displays a highly significant excess of nonsynonymous (pN) vs synonymous (pS) mutations in Asia (pN/pS?=?4.85) and Europe (pN/pS?=?1.62) compared with Africa (pN/pS?=?0.26; Asia vs Africa: P?=?0.000087; Europe vs Africa P?=?0.00035; Europe vs Asia P?=?P?=?0.084). We also showed that whole genome amplification performed through rolling cycle amplification could artificially introduce the A217PfsX8 mutation indicating that this technology should not be performed prior to PRRT2 mutation screening. In summary, our results do not support a role for PRRT2 coding sequence variants in ASD, but provide an ascertainment of its genetic variability in worldwide populations that should help researchers and clinicians to better investigate the role of PRRT2 in human diseases. PMID:24594579

  12. Heterogeneous Pattern of Selective Pressure for PRRT2 in Human Populations, but No Association with Autism Spectrum Disorders

    PubMed Central

    Huguet, Guillaume; Nava, Caroline; Lemière, Nathalie; Patin, Etienne; Laval, Guillaume; Ey, Elodie; Brice, Alexis; Leboyer, Marion; Szepetowski, Pierre; Gillberg, Christopher; Depienne, Christel; Delorme, Richard; Bourgeron, Thomas

    2014-01-01

    Inherited and de novo genomic imbalances at chromosome 16p11.2 are associated with autism spectrum disorders (ASD), but the causative genes remain unknown. Among the genes located in this region, PRRT2 codes for a member of the synaptic SNARE complex that allows the release of synaptic vesicles. PRRT2 is a candidate gene for ASD since homozygote mutations are associated with intellectual disability and heterozygote mutations cause benign infantile seizures, paroxysmal dyskinesia, or hemiplegic migraine. Here, we explored the contribution of PRRT2 mutations in ASD by screening its coding part in a large sample of 1578 individuals including 431 individuals with ASD, 186 controls and 961 individuals from the human genome Diversity Panel. We detected 24 nonsynonymous variants, 1 frameshift (A217PfsX8) and 1 in-frame deletion of 6 bp (p.A361_P362del). The frameshift mutation was observed in a control with no history of neurological or psychiatric disorders. The p.A361_P362del was observed in two individuals with autism from sub-Saharan African origin. Overall, the frequency of PRRT2 deleterious variants was not different between individuals with ASD and controls. Remarkably, PRRT2 displays a highly significant excess of nonsynonymous (pN) vs synonymous (pS) mutations in Asia (pN/pS?=?4.85) and Europe (pN/pS?=?1.62) compared with Africa (pN/pS?=?0.26; Asia vs Africa: P?=?0.000087; Europe vs Africa P?=?0.00035; Europe vs Asia P?=?P?=?0.084). We also showed that whole genome amplification performed through rolling cycle amplification could artificially introduce the A217PfsX8 mutation indicating that this technology should not be performed prior to PRRT2 mutation screening. In summary, our results do not support a role for PRRT2 coding sequence variants in ASD, but provide an ascertainment of its genetic variability in worldwide populations that should help researchers and clinicians to better investigate the role of PRRT2 in human diseases. PMID:24594579

  13. Preparing for patient-centered care: assessing nursing student knowledge, comfort, and cultural competence toward the Latino population.

    PubMed

    Mayo, Rachel M; Sherrill, Windsor W; Truong, Khoa D; Nichols, Christina M

    2014-06-01

    As the Latino population continues to grow throughout the United States, cultural competence training of nursing students at the baccalaureate level has become a priority. This study aimed to explore undergraduate nursing students' attitudes and beliefs toward Latino patients and their perceived readiness to provide care to Latino patients. A cross-sectional survey was conducted at four major nursing schools in the southeastern United States, which is the region that has seen the highest percentage of growth in the Latino population. Results from multivariable regression suggest that social interaction with Latino individuals and cultural immersion in a Spanish-speaking country predict student knowledge, cultural competence, and comfort with Latino patients. Direct influence by nursing programs, such as clinical experience, coursework, and language proficiency, are positively associated with the designed outcomes, but these relationships are not statistically significant. Our findings suggest that dosage of training matters. Implications for student recruitment, selection, and training are discussed. PMID:24766083

  14. Large epidemic thresholds emerge in heterogeneous networks of heterogeneous nodes

    E-print Network

    Yang, Hui; Gross, Thilo

    2015-01-01

    One of the famous results of network science states that networks with heterogeneous connectivity are more susceptible to epidemic spreading than their more homogeneous counterparts. In particular, in networks of identical nodes it has been shown that heterogeneity can lower the epidemic threshold at which epidemics can invade the system. Network heterogeneity can thus allow diseases with lower transmission probabilities to persist and spread. Here, we point out that for real world applications, this result should not be regarded independently of the intra-individual heterogeneity between people. Our results show that, if heterogeneity among people is taken into account, networks that are more heterogeneous in connectivity can be more resistant to epidemic spreading. We study a susceptible-infected-susceptible model with adaptive disease avoidance. Results from this model suggest that this reversal of the effect of network heterogeneity is likely to occur in populations in which the individuals are aware of t...

  15. Identifying Academic Potential in Students from Underrepresented Populations: Is Using the Ravens Progressive Matrices a Good Idea?

    Microsoft Academic Search

    Carol J. Mills; Sherri L. Tissot

    1995-01-01

    Increasing concern has been focused on the under-representation of African-American and Hispanic students in programs for the academically talented. The Raven's Progressive Matrices (RPM) has been suggested as a possible instrument to help remedy this situation, although little research has been conducted about its viability in identifying academic potential in minority populations. A sample of low-income minority students was given

  16. Estimate of dietary exposure to sulphites using Brazilian students as a sample population.

    PubMed

    Popolim, W D; De V C Penteado, M

    2005-11-01

    In Brazil, there is neither a register of the use of sulphites by the food industry nor is research being undertaken on their dietary exposure to the population. The objective of the work reported here was to estimate the dietary exposure to sulphites in two different groups of high school students, a fee-paying school group and a state school group. The data were collected through a 24-hour dietary recall, which provided estimates of sulphited foods and beverages in the diet. The Maximum Permitted Level (MPL), established by the Brazilian legislation for each of the sulphited food and beverages, was used to measure the dietary exposure to this additive. On this basis none of the students could have exceeded the Acceptable Daily Intake (ADI) of 0.70 mg SO2/kg bw/day, with a average dietary exposure of 0.07 mg SO2/kg bw/day (p<0.001), with no significant statistical difference (p=0.643) between fee-paying and state school students. Highly exposed consumers (dietary exposure to more than 50% of the ADI, or either, 0.35 mg SO2/kg bw/day, to the maximum of 0.52 mg SO2/kg bw/dia) represented 4.5% of the researched samples and reached these levels of intake due to a consumption beyond 500 ml/day of industrialized packaged fruit juices, and, in the fee-paying school, for associating its consumption with alcoholic beverages like beer and wine. PMID:16332633

  17. Gambling and Attention Deficit Hyperactivity Disorders (ADHD) in a Population of French Students.

    PubMed

    Romo, L; Rémond, J J; Coeffec, A; Kotbagi, G; Plantey, S; Boz, F; Kern, L

    2014-12-01

    Attention deficit disorder with or without hyperactivity (ADD/ADHD) is a neurodevelopmental disorder that can be exacerbated by psychosocial factors. Various studies confirm that the severity of a psychiatric disorder, particularly when it comes to ADHD, is strongly correlated with the amount of use. This study (1) evaluated the association between ADHD and gambling among young students; (2) determined which symptom among ADHD's three symptoms (attention deficit, hyperactivity, or impulsivity) had the strongest association with video game addiction and gambling; and (3) determined the impact of the association between ADHD and video game addiction and gambling on self-esteem and academic performance of students. A total of 720 students (445 males and 274 females) were recruited from eight higher educational institutions of Ile de France. They all completed a battery of questionnaire consisting of Canadian Problem Gambling Index, UPPS Impulsive Behavior Scale, Wender Utah Rating Scale (WURS), Adult ADHD Self-Report Scale (ASRS) and Rosenberg scales, and socio-demographic data. 13.33 % of the participants had symptoms of ADHD during childhood (WURS scale score) and 40.41 % of them have symptoms of ADHD in adulthood (ASRS score). Finally, among the participants, 37.5 % had excessive gambling addiction, have positive results on WURS and ASRS scales, thus having a probable ADHD, whereas 14.55 % had no gambling addiction. The results demonstrated that adult ADHD was associated with gambling addiction. Significant associations were observed between ADHD and impulsivity, academic difficulties and gambling addiction. The association between ADHD and gambling seems to be common among vulnerable populations such as adolescents and could be related to variables such as self-esteem, which appears to potentially worsen the prognosis. Further research on this relationship is needed to optimize prevention strategies and effective treatment. PMID:25466366

  18. Migraine headaches in adolescents: a student population-based study in Monreale.

    PubMed

    Raieli, V; Raimondo, D; Cammalleri, R; Camarda, R

    1995-02-01

    We assessed the prevalence of migraine headaches in an epidemiological survey of an 11 to 14-year-old student population. Migraine headaches were classified on the basis of questionnaires and neurological examination using the operational diagnostic criteria of the International Headache Society. Prevalence of migraine without aura (IHS code 1.1) was 2.35%; that of migraine with aura (IHS code 1.2) was 0.62%. Migraine without aura was equally distributed among males and females, whereas migraine with aura was preponderant in the female cohort. The prevalence of migraine headaches in males was constant through the ages studied, whereas the prevalence of migraine headaches in females reached a peak at age 12 and plateaued over the following two years. Although the new IHS classification criteria of migraines are reliable and exhaustive, some subcriteria may not be valid in a juvenile population. For instance, the duration of the pain in young migraineurs is often briefer than in adults, and the intensity of pain was almost always described as moderate or severe. Therefore, in order to increase the reliability and comprehensiveness of the IHS classification, minor modifications should be made. PMID:7758099

  19. Training Students to Analyze Spatial and Temporal Heterogeneities in Reservoir and Seal Petrology, Mineralogy, and Geochemistry: Implications for CO{sub 2} Sequestration Prediction, Simulation, and Monitoring

    SciTech Connect

    Bowen, Brenda

    2013-09-30

    The objective of this project was to expose and train multiple students in geological tools that are essential to reservoir characterization and geologic sequestration including but not limited to advanced petrological methods, mineralogical methods, and geochemical methods; core analysis, and geophysical well-log interpretation. These efforts have included training of multiple students through geologically based curriculum and research using advanced petrological, mineralogical, and geochemical methods. In whole, over the last 3+ years, this award has supported 5,828 hours of student research, supporting the work of several graduate and undergraduate students. They have all received training directly related to ongoing CO{sub 2} sequestration demonstrations. The students have all conducted original scientific research on topics related to understanding the importance of lithological, textural, and compositional variability in formations that are being targeted as CO{sub 2} sequestration reservoirs and seals. This research was linked to the Mount Simon Sandstone reservoir and overlying Eau Claire Formation seal in the Illinois Basin- a system where over one million tons of CO{sub 2} are actively being injected with the first large-scale demonstration of anthropogenic CO{sub 2} storage in the U.S. Student projects focused specifically on 1) reservoir porosity characterization and evaluation, 2) petrographic, mineralogical, and geochemical evidence of fluid-related diagenesis in the caprock, 3) textural changes in reservoir samples exposed to experimental CO{sub 2} + brine conditions, 4) controls on spatial heterogeneity in composition and texture in both the reservoir and seal, 5) the implications of small-scale fractures within the reservoir, and 6) petrographic and stable isotope analyses of carbonates in the seal to understand the burial history of the system. The student-led research associated with this project provided real-time and hands-on experience with a relevant CO{sub 2} system, provided relevant information to the regional partnerships who are working within these formations, and provides more broadly applicable understanding and method development for other carbon capture and storage systems.

  20. Process-Oriented Guided-Inquiry Learning in an Introductory Anatomy and Physiology Course with a Diverse Student Population

    ERIC Educational Resources Information Center

    Brown, Patrick J. P.

    2010-01-01

    Process-oriented guided-inquiry learning (POGIL), a pedagogical technique initially developed for college chemistry courses, has been implemented for 2 yr in a freshman-level anatomy and physiology course at a small private college. The course is populated with students with backgrounds ranging from no previous college-level science to junior and…

  1. The Dominance Concept Inventory: A Tool for Assessing Undergraduate Student Alternative Conceptions about Dominance in Mendelian and Population Genetics

    ERIC Educational Resources Information Center

    Abraham, Joel K.; Perez, Kathryn E.; Price, Rebecca M.

    2014-01-01

    Despite the impact of genetics on daily life, biology undergraduates understand some key genetics concepts poorly. One concept requiring attention is dominance, which many students understand as a fixed property of an allele or trait and regularly conflate with frequency in a population or selective advantage. We present the Dominance Concept…

  2. Exploring Dual Credit Data Alignment, Student Populations, and Coursework Patterns in Texas Using a P-16 Framework

    ERIC Educational Resources Information Center

    Eklund, Julie Ann

    2009-01-01

    This multi-faceted study of dual credit programs in Texas was motivated by perceived discrepancies in dual credit data reporting and a lack of comprehensive, state-level information about dual credit student populations and coursework patterns. Using a P-16 framework, the author explored alignment issues that influence the delivery of dual credit…

  3. Identifying Academic Potential in Students from Under-Represented Populations: Is Using the Ravens Progressive Matrices a Good Idea?

    ERIC Educational Resources Information Center

    Mills, Carol J.; Tissot, Sherri L.

    1995-01-01

    The Raven's Progressive Matrices (RPM) and the Raven's Advanced Progressive Matrices (APM) were evaluated as possible instruments for identifying academically talented students in minority populations. A significantly higher proportion of minority children scored well on the RPM than on a traditional measure. Issues and concerns about using the…

  4. Physiological heterogeneity in biofilms

    Microsoft Academic Search

    Michael J. Franklin; Philip S. Stewart

    2008-01-01

    Biofilms contain bacterial cells that are in a wide range of physiological states. Within a biofilm population, cells with diverse genotypes and phenotypes that express distinct metabolic pathways, stress responses and other specific biological activities are juxtaposed. The mechanisms that contribute to this genetic and physiological heterogeneity include microscale chemical gradients, adaptation to local environmental conditions, stochastic gene expression and

  5. Case Studies of Non-Traditional High Risk Students: Does Social and Academic Integration Apply? AIR 1988 Annual Forum Paper.

    ERIC Educational Resources Information Center

    Walleri, R. Dan; Peglow-Hoch, Marcia

    Increasing recent research on nontraditional students has uncovered anomalies and inconsistencies in Tinto's model of student persistence patterns, especially with regard to academic and social integration. It is hypothesized that these inconsistencies are a product of the heterogeneous nature of nontraditional student populations, combined with…

  6. Research Training of Students in Minority and International Settings: Lessons Learned from Cancer Epidemiology Education in Special Populations

    PubMed Central

    Mullan, Patricia B.; Chamberlain, Robert M.

    2014-01-01

    This article describes the development and evaluation of an NCI-sponsored short-term summer cancer research education program. The study questions examined: the feasibility of conducting a cancer education program in special populations at multiple US and international field sites for masters students; the merit and worth that students and faculty attribute to the program; and students' scholarly and cancer-related career outcomes. Developing a new curriculum, increasing the pool of mentors, utilizing and increasing the number of field sites, and program dissemination were also evaluated. Evidence of the program's success included students' completion of field experiences at multiple sites and their subsequent 70% project-related publication rate, with 79% of trainees reporting themselves as likely to pursue future cancer-related careers. Evaluation-guided future plans for the program include implementing faculty development to further enhance the program outcomes. PMID:20352397

  7. Rightward dominance in temporal high-frequency electrical asymmetry corresponds to higher resting heart rate and lower baroreflex sensitivity in a heterogeneous population

    PubMed Central

    Tegeler, Charles H; Shaltout, Hossam A; Tegeler, Catherine L; Gerdes, Lee; Lee, Sung W

    2015-01-01

    Objective Explore potential use of a temporal lobe electrical asymmetry score to discriminate between sympathetic and parasympathetic tendencies in autonomic cardiovascular regulation. Methods 131 individuals (82 women, mean age 43.1, range 13–83) with diverse clinical conditions completed inventories for depressive (CES-D or BDI-II) and insomnia-related (ISI) symptomatology, and underwent five-minute recordings of heart rate and blood pressure, allowing calculation of heart rate variability and baroreflex sensitivity (BRS), followed by one-minute, two-channel, eyes-closed scalp recordings of brain electrical activity. A temporal lobe high-frequency (23–36 Hz) electrical asymmetry score was calculated for each subject by subtracting the average amplitude in the left temporal region from amplitude in the right temporal region, and dividing by the lesser of the two. Results Depressive and insomnia-related symptomatology exceeding clinical threshold levels were reported by 48% and 50% of subjects, respectively. Using a cutoff value of 5% or greater to define temporal high-frequency asymmetry, subjects with leftward compared to rightward asymmetry were more likely to report use of a sedative-hypnotic medication (42% vs. 22%, P = 0.02). Among subjects with asymmetry of 5% or greater to 30% or greater, those with rightward compared to leftward temporal high-frequency asymmetry had higher resting heart rate (?5% asymmetry, 72.3 vs. 63.8, P = 0.004; ?10%, 71.5 vs. 63.0, P = 0.01; ?20%, 72.2 vs. 64.2, P = 0.05; ?30%, 71.4 vs. 64.6, P = 0.05). Subjects with larger degrees of rightward compared to leftward temporal high-frequency asymmetry had lower baroreflex sensitivity (?40% asymmetry, 10.6 vs. 16.4, P = 0.03; ?50% asymmetry, 10.4 vs. 16.7, P = 0.05). Conclusion In a heterogeneous population, individuals with rightward compared to leftward temporal high-frequency electrical asymmetry had higher resting heart rate and lower BRS. Two-channel recording of brain electrical activity from bilateral temporal regions appears to hold promise for further investigation as a means to assess cortical activity associated with autonomic cardiovascular regulation.

  8. The Unique Leadership Needs of Minority Student Populations: Crafting a Leadership Identity

    ERIC Educational Resources Information Center

    Baughman, Kristen N.; Bruce, Jacklyn

    2011-01-01

    The purpose of this qualitative study was to determine how college-level minority student leaders make meaning of those leadership experiences. Semi-structured interviews were conducted with 12 students. Major findings noted a strong personal motivation to participate in student leadership positions. Further research on the impact of familial…

  9. Factors Affecting the Graduation Rates of University Students from Underrepresented Populations

    ERIC Educational Resources Information Center

    Creighton, Linda M.

    2007-01-01

    One of the most pressing issues facing American universities is the number of students who fail to graduate. Nearly one out of five four-year institutions graduate fewer than one-third of its first-time, full-time degree-seeking first-year students within six years. Although there are various explanations for attrition, students often leave for…

  10. Teacher's Understanding, Perceptions, and Experiences of Students in Foster Care: A Forgotten Population

    ERIC Educational Resources Information Center

    Watson-Davis, Darneika

    2010-01-01

    The purpose of this study is to examine elementary teacher's understanding, perceptions, and experiences of working with students in foster care. The researcher examined whether teachers are informed about students in foster care, determined teacher's understanding of the foster care system, and how their students are affected. The results…

  11. Raising the Question #9: Is the Student-Athlete Population Unique? and Why Should We Care?

    ERIC Educational Resources Information Center

    Jolly, J. Christopher

    2008-01-01

    There are unique aspects of the student-athlete collegiate experience that create substantial challenges for student-athletes' academic success. Athletic culture, extreme time demands on student-athletes, and the often uneasy marriage between athletics and academics in the university setting all contribute to the difficulties that many…

  12. The Impact of an Economically Disadvantaged Student Population on School Climate

    ERIC Educational Resources Information Center

    Null, Curtis F.

    2012-01-01

    The purpose of this study was to determine the relationship between student poverty levels, defined by the number of students identified as economically disadvantaged by qualifying for free and reduced lunch and school climate. The literature review examined school climate and culture, effects of student socioeconomic (SES) status on education,…

  13. Process-oriented guided-inquiry learning in an introductory anatomy and physiology course with a diverse student population

    NSDL National Science Digital Library

    Patrick J.P. Brown (King College Biology)

    2010-09-01

    Process-oriented guided-inquiry learning (POGIL), a pedagogical technique initially developed for college chemistry courses, has been implemented for 2 yr in a freshman-level anatomy and physiology course at a small private college. The course is populated with students with backgrounds ranging from no previous college-level science to junior and senior biology, biochemistry, and forensic science majors. Fifty percent of the lectures in the course were replaced with POGIL activities, performed in class by students working collaboratively in small groups. The introduction of POGIL pedagogy into the second half of a two-semester anatomy and physiology course significantly improved student performance on summative evaluations. Overall course scores increased from a mean score of 76% to 89% in the three semesters after POGIL was introduced. Performance on the same multiple-choice final exam rose from a mean of 68% to 88% over the same time period. Most significantly, the rate of students earning a D or F in the course was halved in the first two semesters after POGIL was introduced and was 0% in the third semester. Student satisfaction with the method was high, and most students perceived the value of this form of instruction.

  14. Making Science Accessible: Strategies to Meet the Needs of a Diverse Student Population

    NSDL National Science Digital Library

    Dawn M. Pickard

    2003-02-01

    Despite the sincere interest of many teachers to address the varying educational needs of their students (Scruggs and Mastropieri 1994), the current emphasis on inclusion remains a source of frustration, misunderstanding, and distrust by some teachers, parents, and students. Many regular educators are ill prepared or supported to accept the challenges of teaching students with special needs. One of the dilemmas that they often face is how to modify these activities so that they are accessible to a wider range of students. This article offers suggestions for modifying favorite activities so that they are accessible to students with hearing, visual, motor, or learning disabilities.

  15. The Dominance Concept Inventory: A Tool for Assessing Undergraduate Student Alternative Conceptions about Dominance in Mendelian and Population Genetics

    PubMed Central

    Perez, Kathryn E.; Price, Rebecca M.

    2014-01-01

    Despite the impact of genetics on daily life, biology undergraduates understand some key genetics concepts poorly. One concept requiring attention is dominance, which many students understand as a fixed property of an allele or trait and regularly conflate with frequency in a population or selective advantage. We present the Dominance Concept Inventory (DCI), an instrument to gather data on selected alternative conceptions about dominance. During development of the 16-item test, we used expert surveys (n = 12), student interviews (n = 42), and field tests (n = 1763) from introductory and advanced biology undergraduates at public and private, majority- and minority-serving, 2- and 4-yr institutions in the United States. In the final field test across all subject populations (n = 709), item difficulty ranged from 0.08 to 0.84 (0.51 ± 0.049 SEM), while item discrimination ranged from 0.11 to 0.82 (0.50 ± 0.048 SEM). Internal reliability (Cronbach's alpha) was 0.77, while test–retest reliability values were 0.74 (product moment correlation) and 0.77 (intraclass correlation). The prevalence of alternative conceptions in the field tests shows that introductory and advanced students retain confusion about dominance after instruction. All measures support the DCI as a useful instrument for measuring undergraduate biology student understanding and alternative conceptions about dominance. PMID:26086665

  16. Systems Mapping for Hematopoietic Progenitor Cell Heterogeneity

    PubMed Central

    Zhou, Linghua; Shen, Yong; Jiang, Libo; Yin, Danni; Guo, Jingxin; Zheng, Hui; Sun, Hao; Wu, Rongling; Guo, Yunqian

    2015-01-01

    Cells with the same genotype growing under the same conditions can show different phenotypes, which is known as “population heterogeneity”. The heterogeneity of hematopoietic progenitor cells has an effect on their differentiation potential and lineage choices. However, the genetic mechanisms governing population heterogeneity remain unclear. Here, we present a statistical model for mapping the quantitative trait locus (QTL) that affects hematopoietic cell heterogeneity. This strategy, termed systems mapping, integrates a system of differential equations into the framework for systems mapping, allowing hypotheses regarding the interplay between genetic actions and cell heterogeneity to be tested. A simulation approach based on cell heterogeneity dynamics has been designed to test the statistical properties of the model. This model not only considers the traditional QTLs, but also indicates the methylated QTLs that can illustrate non-genetic individual differences. It has significant implications for probing the molecular, genetic and epigenetic mechanisms of hematopoietic progenitor cell heterogeneity. PMID:25970338

  17. Characteristics of the Population of Deaf and Hard of Hearing Students with Emotional Disturbance in Illinois

    ERIC Educational Resources Information Center

    Sinnott, C. L.; Jones, T. W.

    2005-01-01

    The study summarizes a database for the years 1994-1999 on deaf and hard of hearing students in Illinois with a diagnosis of emotional disturbance (N = 115). Data are reported on the group's demographic, domestic, etiologic, communication-related, and intervention-related characteristics. These dually diagnosed students differed from Illinois's…

  18. Human Population. (Student Resource Book IV in the Investigating Your Environemnt Program).

    ERIC Educational Resources Information Center

    Biological Sciences Curriculum Study, Boulder, CO.

    These resource papers encourage the student to discover for himself the contributions to a problem made through original literature. Since some of the papers are controversial or contradict one another, the student will need to evaluate them to determine his position. It is hoped that these papers will foster an appreciation of the work of the…

  19. CHARACTERISTICS OF THE STUDENT POPULATION, UNIVERSITY OF ALABAMA RESIDENT CENTER, HUNTSVILLE, ALABAMA.

    ERIC Educational Resources Information Center

    FRANKLIN, ELTON

    THE MAIN PURPOSE OF THIS 1959 SURVEY WAS TO ANALYZE SOME OF THE BASIC CHARACTERISTICS OF STUDENTS AT THE UNIVERSITY OF ALABAMA RESIDENT CENTER, HUNTSVILLE. FINDINGS WERE TABULATED IN SUMMARY FORM AND BY MAJOR FIELDS OF ACADEMIC INTEREST. OF THE STUDENTS (LARGELY YOUNG ADULTS), 51 PERCENT WERE IN ENGINEERING. ONLY 16 PERCENT WERE FEMALE. MOST…

  20. Developing a learner centered environment to meet the needs of a growing urban commuter student population

    Microsoft Academic Search

    Lourdes Sánchez-Contreras; Rosa M. Gómez; Joseph Ramos; Benjamin C. Flores; Helmut Knaust

    The Colleges of Engineering and Science at the University of Texas at El Paso have developed a multi-faceted system based on peer support to address the particular needs of science and engineering majors. At the core of this strategy is a strong commitment to develop the critical thinking and leadership skills of a selected cohort of undergraduate students. These students

  1. Factors Influencing Successful Student Outcomes between Transfer and Native Populations in a Postsecondary Environment

    ERIC Educational Resources Information Center

    Tinney, Tina Molero

    2012-01-01

    Institutions of higher education have experienced increased scrutiny. Legislative and policy developments rapidly impact institutional accountability and student access. While various accountability measures are available to assess institutional quality and student success, information currently collected is not sufficient for a broader…

  2. Underachieving Gifted Students and Ways to Improve School Performance of at Risk Student Population Who Have High Potential: Improving Writing Performance in Underachieving Gifted Students

    ERIC Educational Resources Information Center

    Brown-Anfelouss, Marjorie

    2012-01-01

    Giftedness has often been equated with being academically talented or being a high achiever in school. However, there is often concern about the gifted students who could be described as unmotivated and underachieving in one or many academic areas. At the Jones Street School, a school for gifted elementary students, the location of this study,…

  3. Predicting Population Curves.

    ERIC Educational Resources Information Center

    Bunton, Matt

    2003-01-01

    Uses graphs to involve students in inquiry-based population investigations on the Wisconsin gray wolf. Requires students to predict future changes in the wolf population, carrying capacity, and deer population. (YDS)

  4. Modeling Population Heterogeneity in Appearance and Performance-Enhancing Drug (APED) Use: Applications of Mixture Modeling in 400 Regular APED Users

    Microsoft Academic Search

    Thomas Hildebrandt; James W. Langenbucher; Sasha J. Carr; Pilar Sanjuan

    2007-01-01

    Appearance- and performance-enhancing drugs (APEDs) constitute a wide range of substances, including anabolic–androgenic steroids, nonsteroidal anabolics, and licit and illicit ergo\\/thermogenics. A great deal of heterogeneity exists in APED use patterns among weight-lifting men, and, consequently, little is known about how these patterns are related to side effect profiles or risk potential. In the current study, a sample of 400

  5. Heterogeneous Students in Homogeneous Classrooms.

    ERIC Educational Resources Information Center

    Brown, Carol Bentley

    1985-01-01

    Describes the science program at Incarnate Word, a private Catholic girls' college preparatory school in San Antonio (Texas). Focuses on the chemistry curriculum and the instructional strategies/materials (such as learning activity packets) used in the curriculum. (JN)

  6. Side population\\/ABCG2-positive cells represent a heterogeneous group of haemopoietic cells: implications for the use of adult stem cells in transplantation and plasticity protocols

    Microsoft Academic Search

    C S Naylor; E Jaworska; K Branson; M J Embleton; R Chopra

    2005-01-01

    Murine side population (SP) cells may have an increased ability to engraft lethally irradiated mice and lack CD34 expression. Strategies using CD34 as a primary marker of haemopoietic stem cells may therefore result in the exclusion of a primitive stem cell population. The molecular basis for the murine SP phenotype has been attributed to the multidrug-resistance transporter ABCG2. This study

  7. English Language Learners: Experiences of Teachers of Students with Visual Impairments Who Work with This Population

    ERIC Educational Resources Information Center

    Topor, Irene; Rosenblum, L. Penny

    2013-01-01

    Introduction: This article presents a study that gathered data from 66 teachers of students with visual impairments about their preparation to work with children who are visually impaired and are learning English, and their knowledge of instructional strategies and methods of instruction. Methods: An online five-part survey was available to…

  8. Psychometric Analyses of the College Student Reasons for Living Inventory Using a Clinical Population.

    ERIC Educational Resources Information Center

    Westefeld, John S.; Scheel, Karen; Maples, Michael R.

    1998-01-01

    The usefulness of the College Student Reason for Living Inventory (CSRLI) for assessment of suicidal risk was evaluated among clients presenting for counseling (N=87) at a large university counseling center. Scores were compared to the Beck Depression Inventory and other measures. Data analysis is presented and discussed. (Author/EMK)

  9. The Incidence of Potentially Gifted Students within a Special Education Population

    ERIC Educational Resources Information Center

    Barnard-Brak, Lucy; Johnsen, Susan K.; Hannig, Alyssa Pond; Wei, Tianlan

    2015-01-01

    From a sample of 13,176 children with disabilities who were a part of the Special Education Elementary Longitudinal Study, 330 students achieved a score at the 90th percentile or higher on the Woodcock-Johnson III. These children represent some 9.1% of children who have disabilities nationally and who might be identified as gifted or academically…

  10. Preparing Administrators To Serve Diverse Populations Of Students With Learning Challenges

    Microsoft Academic Search

    Ronald A. Styron; A. Parker

    2008-01-01

    The notion of integrating a curriculum is more than connecting pieces so that students can see the bigger design—in effective curriculum integration models, knowledge is meaningfully related and connects in such a way that it is relevant to other areas of learning as well as to real life (Morris, 2003). This work details the integrated efforts of two university departments,

  11. Directory of California Community Colleges Exemplary Programs and Materials for Handicapped Population Students.

    ERIC Educational Resources Information Center

    Educational Evaluation and Research, Inc., Menlo Park, CA.

    The directory presents information on model programs, curriculum materials, and guides regarding Handicapped Student Programs and Services (HSPS) funds in California community colleges. Materials were identified via criteria which considered them exemplary and then selected by an advisory committee. Citations are organized in five major topics…

  12. BIRTH AND DEATH PROJECTIONS USED IN PRESENT STUDENT-TEACHER POPULATION GROWTH MODELS.

    ERIC Educational Resources Information Center

    OKADA, TETSUO

    A BRIEF DESCRIPTION OF THE METHODOLOGY USED IN DYNAMOD II TO PROJECT BIRTHS AND DEATHS IS PRESENTED. THE COMPUTATION OF DEATH RATES FOLLOWED THE METHOD USED BY THE DEPARTMENT OF HEALTH, EDUCATION AND WELFARE, MORTALITY DIVISION--DEATH RATE FOR AGE INTERVAL I THROUGH J EQUALS SUMMATION OF NUMBER OF DEATHS AT AGES I THROUGH J/SUMMATION OF POPULATION

  13. Increasing Accessibility: Lessons Learned in Retaining Special Population Students in Canada

    ERIC Educational Resources Information Center

    Smith, Clayton; Gottheil, Susan

    2011-01-01

    In Canada, changing demographics and increased competition--as well as social values based on equity--have inspired efforts to increase the postsecondary education (PSE) participation rates of youths from under-represented/under-served groups. Despite its population having the highest level of educational attainment among those of OECD countries,…

  14. Stoichiometry and population dynamics

    Microsoft Academic Search

    Tom Andersen; James J. Elser; Dag O. Hessen

    2004-01-01

    Population dynamics theory forms the quantitative core from which most ecologists have developed their intuition about how species interactions, heterogeneity, and biodiversity play out in time. Throughout its development, theoretical population biology has built on variants of the Lotka-Volterra equations and in nearly all cases has taken a single-currency approach to understanding population change, abstracting populations as aggregations of individuals

  15. Identification of repeat sequence heterogeneity at the polymorphic short tandem repeat locus HUMTH01[AATG][sub n] and reassignment of alleles in population analysis by using a locus-specific allelic ladder

    SciTech Connect

    Puers, C. (Institute for Forensic Medicine, Muenster (Germany)); Schumm, J.W. (Promega Corp., Madison, WI (United States)); Hammond, H.A.; Caskey, C.T.; Jin, L.

    1993-10-01

    An allelic ladder containing amplified sequences of seven alleles of the polymorphic human tyrosine hydroxylase locus, HUMTH01, was constructed and employed as a standard marker. Sequence analysis of each ladder component indicates that fragments differ by integral multiples of the AATG core repeat sequence characteristic of this locus. Individual alles are designated [open quotes]5[close quotes] through [open quotes]11,[close quotes] according to the number of complete reiterations of the core repeat contained within them. Comparison of the HUMTH01 allelic ladder with DNA samples amplified at this locus revealed core repeat length heterogeneity (i.e., deletions or insertions shorter than one core repeat) within the human population. In particular, a common allele was identified which migrates more quickly than allele 10, but more slowly than allele 9, on electrophoresis through a denaturing polyacrylamide gel. Sequence analysis of this allele, designated [open quotes]10-1,[close quotes] reveals lack of a single adenine normally present in the seventh copy of the AATG. The allelic ladder was used to reevaluate previously published population data. Results of testing for Hardy-Weinberg equilibrium and population substructure were not altered significantly by these modifications. 29 refs., 1 fig., 3 tabs.

  16. Host heterogeneity dominates West Nile virus transmission

    Microsoft Academic Search

    A. Marm Kilpatrick; Peter Daszak; Matthew J. Jones; Peter P. Marra; Laura D. Kramer

    2006-01-01

    Heterogeneity in host populations and communities can have large effects on the transmission and control of a pathogen. In extreme cases, a few individuals give rise to the majority of secondary infections, which have been termed super spreading events. Here, we show that transmission of West Nile virus (WNV) is dominated by extreme heterogeneity in the host community, resulting in

  17. Cognitive patterns and depression: study of a Japanese university student population.

    PubMed

    Tanaka, Nao; Uji, Masayo; Hiramura, Hidetoshi; Chen, Zi; Shikai, Noriko; Kitamura, Toshinori

    2006-06-01

    According to Beck's cognitive theory, individuals who endure negative self-schemas (dysfunctional attitudes) are more likely to present automatic thoughts consisting of negative schemata of oneself and one's world while experiencing depression. In order to examine the relationships between depression, automatic thought, and dysfunctional attitude, 329 Japanese university students were given a set of questionnaires, including the Center for Epidemiologic Studies Depression Scale (CES-D), Automatic Thought Questionnaire-revised (ATQ-R), and Dysfunctional Attitude Scale (DAS). A structural equation model revealed that depression was predicted predominantly by automatic thought, which was in turn predicted by dysfunctional attitude. The male gender had a tendency to predict dysfunctional attitude. The link between a student's depression and dysfunctional attitude was mediated by automatic thought. PMID:16732754

  18. Money Attitude, Self-esteem, and Compulsive Buying in a Population of Medical Students

    PubMed Central

    Lejoyeux, Michel; Richoux-Benhaim, Charlotte; Betizeau, Annabelle; Lequen, Valérie; Lohnhardt, Hannah

    2011-01-01

    This study tried to determine the prevalence of compulsive buying (CB) and to identify among compulsive buyers a specific relation to money, a different buying style, and a lowered level of self-esteem. We included 203 medical students and diagnosed CB with the Mc Elroy criteria and a specific questionnaire. The money attitude was characterized by the Yamauchi and Templer's scale and self-esteem with the Rosenberg scale. 11% of the medical students presented compulsive buying (CB+). Sex ratio and mean ages were comparable in the CB+ and control groups. CB+ students drank less alcohol and smoked an equivalent number of cigarettes. Compulsive buyers had higher scores of distress (tendency to be hesitant, suspicious, and doubtful attitude toward situations involving money) and bargain missing (fear of missing a good opportunity to buy an item). They bought more often gifts for themselves, items they use less than expected and choose goods increasing their self-esteem. Their score of self-esteem was not different from the one from controls. PMID:21556283

  19. Evidence of hearing loss in a “normally-hearing” college-student population

    PubMed Central

    Le Prell, C. G.; Hensley, B.N.; Campbell, K. C. M.; Hall, J. W.; Guire, K.

    2011-01-01

    We report pure-tone hearing threshold findings in 56 college students. All subjects reported normal hearing during telephone interviews, yet not all subjects had normal sensitivity as defined by well-accepted criteria. At one or more test frequencies (0.25–8 kHz), 7% of ears had thresholds ?25 dB HL and 12% had thresholds ?20 dB HL. The proportion of ears with abnormal findings decreased when three-frequency pure-tone-averages were used. Low-frequency PTA hearing loss was detected in 2.7% of ears and high-frequency PTA hearing loss was detected in 7.1% of ears; however, there was little evidence for “notched” audiograms. There was a statistically reliable relationship in which personal music player use was correlated with decreased hearing status in male subjects. Routine screening and education regarding hearing loss risk factors are critical as college students do not always self-identify early changes in hearing. Large-scale systematic investigations of college students’ hearing status appear to be warranted; the current sample size was not adequate to precisely measure potential contributions of different sound sources to the elevated thresholds measured in some subjects. PMID:21288064

  20. Explanations of sleep paralysis among Egyptian college students and the general population in Egypt and Denmark.

    PubMed

    Jalal, Baland; Simons-Rudolph, Joseph; Jalal, Bamo; Hinton, Devon E

    2014-04-01

    This cross-cultural study compared explanations of sleep paralysis (SP) in two countries and two groups with different levels of education in one country. Comparisons were made between individuals having experienced SP at least once in a lifetime from Cairo, Egypt (n?=?89), Copenhagen, Denmark (n?=?59), and the American University in Cairo, Egypt (n?=?44). As hypothesized, participants from the general Egyptian population were more likely to endorse supernatural causal explanation of their SP compared to participants from Denmark; participants from the American University in Cairo were less likely to endorse supernatural causes of their SP compared to participants from the general Egyptian population. Moreover, participants from the American University in Cairo were marginally significantly more likely to endorse supernatural causes of their SP compared to participants from Denmark. Additionally, we explored which culturally bound explanations and beliefs about SP existed in Egypt and Denmark. We found that nearly half (48%) of the participants from the general Egyptian population believed their SP to be caused by the Jinn, a spirit-like creature with roots in Islamic tradition, which constitutes a culturally bound interpretation of the phenomenology of SP in this region of the world. Case studies are presented to illustrate these findings. PMID:24084761

  1. Tobacco Smoking in HIV-Infected versus General Population in France: Heterogeneity across the Various Groups of People Living with HIV

    PubMed Central

    Tron, Laure; Lert, France; Spire, Bruno; Dray-Spira, Rosemary

    2014-01-01

    Background Although the various groups of people living with HIV (PLWHIV) considerably differ regarding socioeconomic and behavioral characteristics, their specificities regarding tobacco smoking have been poorly investigated. We aimed to assess patterns of tobacco consumption across the various groups of PLWHIV and to compare them to the general population, accounting for the specific socioeconomic profile of PLWHIV. Methods We used data of the ANRS-Vespa2 study, a national representative survey on PLWHIV conducted in France in 2011. Prevalence of past and current tobacco consumption, heavy smoking and strong nicotine dependence were assessed among the various groups of PLWHIV as defined by transmission category, gender and geographic origin, and compared to the French general population using direct standardization and multivariate Poisson regression models, accounting for gender, age, education and geographic origin. Results Among the 3,019 participants aged 18–85 years (median time since HIV diagnosis: 12 years), 37.5% were current smokers and 22.1% were past smokers, with marked differences across the various groups of PLWHIV. Compared to the general population, the prevalence of regular smoking was increased among HIV-infected men who have sex with men (MSM) (adjusted prevalence rate ratio (aPRR): 1.19, 95% confidence interval (95% CI): 1.07–1.32), French-native women (aPRR: 1.32, 95% CI: 1.10–1.57), and heterosexual French-native men (although not significantly, aPRR: 1.19, 95% CI: 0.98–1.45). Additionally, HIV-infected MSM were significantly less likely to be ex-smokers (aPRR: 0.73, 95% CI: 0.64–0.82) than the general population and similar trends were observed among heterosexual French-native men (aPRR: 0.89, 95% CI: 0.78–1.02) and women (aPRR: 0.84, 95% CI: 0.70–1.01). HIV-infected sub-Saharan African migrants were less likely to be regular smokers than the general population. Conclusions Smoking constitutes a major concern in various groups of PLWHIV in France including MSM and heterosexual French-natives, probably resulting from PLWHIV being less likely to quit smoking than their counterparts in the general population. PMID:25202968

  2. GM-CSF Mouse Bone Marrow Cultures Comprise a Heterogeneous Population of CD11c(+)MHCII(+) Macrophages and Dendritic Cells.

    PubMed

    Helft, Julie; Böttcher, Jan; Chakravarty, Probir; Zelenay, Santiago; Huotari, Jatta; Schraml, Barbara U; Goubau, Delphine; Reis E Sousa, Caetano

    2015-06-16

    Dendritic cells (DCs) are key players in the immune system. Much of their biology has been elucidated via culture systems in which hematopoietic precursors differentiate into DCs under the aegis of cytokines. A widely used protocol involves the culture of murine bone marrow (BM) cells with granulocyte-macrophage colony-stimulating factor (GM-CSF) to generate BM-derived DCs (BMDCs). BMDCs express CD11c and MHC class II (MHCII) molecules and share with DCs isolated from tissues the ability to present exogenous antigens to T cells and to respond to microbial stimuli by undergoing maturation. We demonstrate that CD11c(+)MHCII(+) BMDCs are in fact a heterogeneous group of cells that comprises conventional DCs and monocyte-derived macrophages. DCs and macrophages in GM-CSF cultures both undergo maturation upon stimulation with lipopolysaccharide but respond differentially to the stimulus and remain separable entities. These results have important implications for the interpretation of a vast array of data obtained with DC culture systems. PMID:26084029

  3. How two Chicago public schools are changing to meet the needs of a diverse student population

    SciTech Connect

    Murphy, P.; Slaughter, R. (Chicago Public Schools, IL (United States))

    1992-01-01

    The Chicago Public School System contains a wide range of high schools, which, even with the same funding sources and operating principles, have different levels of educational resources available to be focused on each educational activity. However, the basic curriculum objectives for each subject are the same across the system. Across all these approaches, a basic core curriculum is required to be met and outcome standards achieved. The Illinois Goal Assessment Program has forced all schools to look at their curriculum to re-evaluate what they are teaching and why. Algebra should include data analysis and statistics. Geometry is moving moving from proof writing to application. In the inner city, neighborhood, and selective schools, real efforts are being made to make mathematics accessible to all students.

  4. The fractionation experiment: reducing heterogeneity to investigate age-specific mortality in Drosophila

    Microsoft Academic Search

    Aziz A. Khazaeli; Scott D. Pletcher; James W. Curtsinger

    1998-01-01

    Age-specific mortality rates decelerate at older ages in both genetically homogenous and heterogeneous populations of Drosophila. One explanation proposed for deceleration is population heterogeneity. This hypothesis suggests that a population consists of sub-populations that differ in mortality characteristics and that the deceleration is the result of selective survival of stronger individuals. Here we describe an experiment that fractionates populations into

  5. Molecular heterogeneity of the XbaI defined 44kb allele of the CYP2D locus within the Caucasian population.

    PubMed Central

    Mura, C; Gerard, N; Vincent-Viry, M; Galteau, M M; Jacqz-Aigrain, E; Krishnamoorthy, R

    1993-01-01

    1. Cytochrome P450 debrisoquine (CYP2D6) activity is polymorphic and under genetic control. Most Caucasians are extensive metabolizers, but 5%-10% are poor metabolizers. 2. Restriction fragment length polymorphism analysis of the CYP2D6 locus identifies a 29kb XbaI fragment, either normal (D6-wt) or mutated, and three mutated XbaI alleles (44kb, 11.5kb and 16 + 9kb). The 44kb allele was initially considered as a poor metabolizer allele owing to a D6-B mutation, but cases of 44kb allele not carrying the D6-B, and therefore potentially functional, have been found. The degree of molecular heterogeneity of this allele was investigated by phenotype and genotype analysis of families. 3. Thirty-one French Caucasian families, representing 117 individuals, possessing at least one 44kb allele in each family were selected. Phenotypes were determined using dextromethorphan, and the XbaI, NcoI and BamH1 RFLPs of 42 independent chromosomes were analyzed. 4. 80% of the XbaI 44kb alleles carried the CYP2D6-B mutation and had an additional NcoI fragment (12.5kb or 4.8kb). The remaining 20% did not carry the CYP2D6-B or A mutations and had no extra NcoI fragment. 5. Information on three families demonstrated that 44kb alleles not carrying the CYP2D6-B mutation were associated with the extensive metabolizer phenotype. 6. We conclude that a substantial percentage of XbaI 44kb alleles is associated with a functional CYP2D gene, and therefore, that the XbaI 44kb allele is not consistently a poor metaboliser allele. PMID:8095148

  6. Establishing evaluation indicators on the population knowledge, attitudes, practices and skills (KAPS) of secondary school teachers and students in the Philippines.

    PubMed

    Mercado, C

    1985-06-01

    This study was conducted to establish evaluation indicators to be used as a basis in evaluating the integration of the population education program (POPED) of the Ministry of Education, Culture, and Sports within the Philippine 2ndary school curriculum. Questionnaires were used to determine existing knowledge, attitude, practice and skills (KAPS) of 3,136 high school students and 490 teachers, and data was analyzed for significant relationships between KAPS concerning POPED and demographic characteristics, exposure to population information sources, type of school attended, and exposure to POPED. KAPS and teaching method determine KAPS of the student. Data indicate that 81% of teachers had integrated POPED into the curriculum; only 19% of these had attended training on POPED. 93% utilized a lecture-discussion method in teaching POPED. Knowledge tests given to students and teachers were the same, covering demography, family size, age at marriage, responsible parenthood, use-effectiveness of methods, and population and development. Teachers performed better than students in questions on knowledge; on attitude statements teachers showed a slightly more favorable attitude towards POPED issues, most favorable to responsible parenthood, and least favorable to age at marriage. Mean preferred age at marriage (25) and mean desired number of children (3) was the same for teachers and students; teachers desired wider child spacing than students (3.3 years vs. 2.7 years). 84% of teachers used or wanted to use a family planning method, 76% of students felt they would use a method after marriage. Factors useful in predicting KAPS of teachers and students on POPED are: region of residence, age, sex, educational level, marital status, grade average, type of school, and exposure to various sources of POPED information. PMID:12314294

  7. Rationale and Development of a General Population Well-Being Measure: Psychometric Status of the GP-CORE in a Student Sample

    ERIC Educational Resources Information Center

    Sinclair, Alice; Barkham, Michael; Evans, Chris; Connell, Janice; Audin, Kerry

    2005-01-01

    This paper presents the rationale, development, and psychometric status of a non-clinical self-report measure for the general population (GP) ? including students ? derived from the Clinical Outcomes in Routine Evaluation-Outcome Measure (CORE-OM) and hence termed the GP-CORE. In contrast to the CORE-OM, the GP-CORE does not comprise items…

  8. Changes in Student Populations and Teacher Workforce in Low-Performing Chicago Schools Targeted for Reform. Summary. Issues & Answers. REL 2012-No. 123

    ERIC Educational Resources Information Center

    de la Torre, Marisa; Allensworth, Elaine; Jagesic, Sanja; Sebastian, James; Salmonowicz, Michael; Meyers, Coby; Gerdeman, R. Dean

    2012-01-01

    "Turning around" chronically low-performing schools is of increasing interest to educators and policymakers, as highlighted by the U.S. Department of Education's (2010) recent call to rapidly improve the nation's 5,000 lowest performing schools. Yet there is little rigorous research on changes in student populations and teacher workforce in…

  9. Changes in Student Populations and Teacher Workforce in Low-Performing Chicago Schools Targeted for Reform. Issues & Answers. REL 2012-No. 123

    ERIC Educational Resources Information Center

    de la Torre, Marisa; Allensworth, Elaine; Jagesic, Sanja; Sebastian, James; Salmonowicz, Michael; Meyers, Coby; Gerdeman, R. Dean

    2012-01-01

    "Turning around" chronically low-performing schools is of increasing interest to educators and policymakers, as highlighted by the U.S. Department of Education's (2010) recent call to rapidly improve the nation's 5,000 lowest performing schools. Yet there is little rigorous research on changes in student populations and teacher workforce in…

  10. Deer Population

    NSDL National Science Digital Library

    Maryland Virtual High School

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

  11. Resource heterogeneity can facilitate cooperation

    PubMed Central

    Kun, Ádám; Dieckmann, Ulf

    2013-01-01

    Although social structure is known to promote cooperation, by locally exposing selfish agents to their own deeds, studies to date assumed that all agents have access to the same level of resources. This is clearly unrealistic. Here we find that cooperation can be maintained when some agents have access to more resources than others. Cooperation can then emerge even in populations in which the temptation to defect is so strong that players would act fully selfishly if their resources were distributed uniformly. Resource heterogeneity can thus be crucial for the emergence and maintenance of cooperation. We also show that resource heterogeneity can hinder cooperation once the temptation to defect is significantly lowered. In all cases, the level of cooperation can be maximized by managing resource heterogeneity. PMID:24088665

  12. Heterogeneous pumice populations in the 2.08-Ma Cerro Galán Ignimbrite: Implications for magma recharge and ascent preceding a large-volume silicic eruption

    USGS Publications Warehouse

    Wright, Heather M.; Folkes, Christopher B.; Cas, Ray A.F.; Cashman, Katharine V.

    2011-01-01

    Triggering mechanisms of large silicic eruptions remain a critical unsolved problem. We address this question for the ~2.08-Ma caldera-forming eruption of Cerro Galán volcano, Argentina, which produced distinct pumice populations of two colors: grey (5%) and white (95%) that we believe may hold clues to the onset of eruptive activity. We demonstrate that the color variations correspond to both textural and compositional variations between the clast types. Both pumice types have bulk compositions of high-K, high-silica dacite to low-silica rhyolite, but there are sufficient compositional differences (e.g., ~150 ppm lower Ba at equivalent SiO2 content and 0.03 wt.% higher TiO2 in white pumice than grey) to suggest that the two pumice populations are not related by simple fractionation. Trace element concentrations in crystals mimic bulk variations between clast types, with grey pumice containing elevated Ba, Cu, Pb, and Zn concentrations in both bulk samples (average Cu, Pb, and Zn concentrations are 27, 35, and 82 in grey pumice vs. 11, 19, and 60 in white pumice) and biotite phenocrysts and white pumice showing elevated Li concentrations in biotite and plagioclase phenocrysts. White and grey clasts are also texturally distinct: White pumice clasts contain abundant phenocrysts (44–57%), lack microlites, and have highly evolved groundmass glass compositions (76.4–79.6 wt.% SiO2), whereas grey pumice clasts contain a lower percentage of phenocrysts/microphenocrysts (35–49%), have abundant microlites, and have less evolved groundmass glass compositions (69.4–73.8 wt.% SiO2). There is also evidence for crystal transfer between magma producing white and grey pumice. Thin highly evolved melt rims surround some fragmental crystals in grey pumice clasts and appear to have come from magma that produced white pumice. Furthermore, based on crystal compositions, white bands within banded pumice contain crystals originating in grey magma. Finally, only grey pumice clasts form breadcrusted surface textures. We interpret these compositional and textural variations to indicate distinct magma batches, where grey pumice originated from an originally deeper, more volatile-rich dacite recharge magma that ascended through and mingled with the volumetrically dominant, more highly crystalline chamber that produced white pumice. Shortly before eruption, the grey pumice magma stalled within shallow fractures, forming a vanguard magma phase whose ascent may have provided a trigger for eruption of the highly crystalline rhyodacite magma. We suggest that in the case of the Cerro Galán eruption, grey pumice provides evidence not only for cryptic silicic recharge in a large caldera system but also a probable trigger for the eruption.

  13. Mentors Are from Venus and Mars: Exploring the Benefits of Homogeneous and Heterogeneous Gender Pairings in the Mentoring Relationships of Female Senior Student Affairs Officers

    ERIC Educational Resources Information Center

    Jarnagin, Lea Marie

    2010-01-01

    While the number of women entering the student affairs profession has increased, gender equity at the senior level of leadership remains elusive in the student affairs profession. In comparison to their presence in graduate preparation programs and lower levels of administration women continue to lag behind men in their rate of advancement to the…

  14. The Strategies and Struggles of Graduate Diversity Officers in the Recruitment of Doctoral Students of Color

    ERIC Educational Resources Information Center

    Griffin, Kimberly A.; Muniz, Marcela M.

    2011-01-01

    The growing heterogeneity of American society is increasingly reflected in the undergraduate student population, yet there has been less change within graduate education. As graduate education is the pipeline to the professoriate, we must have a better understanding of how to promote institutional change toward greater graduate diversity. This…

  15. The Relationship between Mississippi Accreditation Ranking and Socio-Economic Status of Student Populations in Accredited Schools

    ERIC Educational Resources Information Center

    Leonard, Ed; Box, Jennifer A. L.

    2009-01-01

    Socio-economic status (SES) of students has long been viewed as having a strong impact on student achievement. While the nature and strength of the relationship between SES and student achievement may be open to some debate, the almost universal acceptance of SES as an important variable in student achievement outcomes has implications for funding…

  16. The Open University Student Employability Policy Statement a) The University acknowledges the diversity of the OU student population and the need to

    E-print Network

    Bandara, Arosha

    The Open University Student Employability Policy Statement a) The University acknowledges and motivations of students are distinct and varied in relation to career and personal development. The University of the student employability policy is to ensure that The Open University explicitly addresses and supports

  17. Cell heterogeneity during the cell cycle

    Microsoft Academic Search

    Z. Darzynkiewicz; H. Crissman; F. Traganos; J. Steinkamp

    1982-01-01

    Using flow cytometry, populations of Chinese hamster ovary cells, asynchronous and synchronized in the cycle, were measured with respect to cellular RNA- and protein-content, as well as cell light scatter properties. Heterogeneities of cell populations were expressed as coefficients of variation (c.v.) in percent of the respective mean values. Populations of cells immediately after mitosis have about 15% higher c.v.

  18. Establishing the reliability and validity of the Zagazig Depression Scale in a UK student population: an online pilot study

    Microsoft Academic Search

    Ahmed K Ibrahim; Shona J Kelly; Emily C Challenor; Cris Glazebrook

    2010-01-01

    BACKGROUND: It is thought that depressive disorders will be the second leading cause of disability worldwide by 2020. Recently, there is a steady increase in the number of university students diagnosed and treated as depression patients. It can be assumed that depression is a serious mental health problem for university students because it affects all age groups of the students

  19. The effects of migration and drift on local adaptation to a heterogeneous environment

    E-print Network

    The effects of migration and drift on local adaptation to a heterogeneous environment F. BLANQUART Recherche, Montpellier Cedex 5, France Department of Biological Sciences, University of Idaho, Moscow, Idaho Introduction Populations often experience spatial heterogeneity in their environment. Adaptation

  20. The Impact of a Language Learning Task on Instructional Outcomes in Two Student Populations: High-Ability and Average-Ability Students.

    ERIC Educational Resources Information Center

    Nikolova, Ofelia; Taylor, Gregory

    2003-01-01

    High-ability (n=97) and average-ability students (n=84) were asked to read a Spanish passage on a computer and use glosses provided for certain words to aid in comprehension or create glosses using a Spanish-English dictionary and annotation software (experimental task). High-ability students performed significantly better after the experimental…

  1. Salience of Nationality in Students' Spontaneous Self-Concept: A Comparative Study of a Nationally Homogeneous and a Heterogeneous School Context

    ERIC Educational Resources Information Center

    Murdock, Elke; Hirt, Franziska S.; Ferring, Dieter

    2014-01-01

    The study on which this article is based investigated the salience of nationality in adolescents' self-concept as a function of the diversity of the school context. According to the distinctiveness postulate, people selectively attend to and encode aspects that are most distinctive. We therefore predicted that students in the nationally…

  2. Monocyte and macrophage heterogeneity

    Microsoft Academic Search

    Philip R. Taylor; Siamon Gordon

    2005-01-01

    Heterogeneity of the macrophage lineage has long been recognized and, in part, is a result of the specialization of tissue macrophages in particular microenvironments. Circulating monocytes give rise to mature macrophages and are also heterogeneous themselves, although the physiological relevance of this is not completely understood. However, as we discuss here, recent studies have shown that monocyte heterogeneity is conserved

  3. A Comparison of a Sub-Population of Santa Monica College Students to Other Community College Students in the Southern California Area: An Analysis of the Results from the Community College Student Experiences Questionnaire.

    ERIC Educational Resources Information Center

    Ackermann, Susan P.

    Drawing from a nationwide pilot test of the Community College Student Experiences Questionnaire (CCSEQ), a study was conducted to compare Santa Monica College (SMC) students (N=106) with students attending nine other Southern California community colleges (N=498). The CCSEQ was designed to provide information on the relationship between students'…

  4. Are Student Veterans a Traditional, Nontraditional, or Special Population? A Study of Veterans on the Auburn University Campus

    ERIC Educational Resources Information Center

    Pattillo, Stephen Prescott

    2011-01-01

    This non-experimental study used, with the Educational Testing Service's permission, an updated 1946 Student Opinion Questionnaire (originally designed to compare WWII veterans and nonveterans) to collect data regarding student backgrounds, attitudes and motives, worries and concerns, use of time, and perceptions of respect concerning nonveterans,…

  5. Characteristics and Predictors of Health Problems from Use among High-Frequency Cannabis Users in a Canadian University Student Population

    ERIC Educational Resources Information Center

    Fischer, Benedikt; Dawe, Meghan; Mcguire, Fraser; Shuper, Paul A; Jones, Wayne; Rudzinski, Katherine; Rehm, Jurgen

    2012-01-01

    Aims: Assess key cannabis use, risk and outcome characteristics among high-frequency cannabis users within a university student sample in Toronto, Canada. Methods: N = 134 active universities students (ages of 18-28) using cannabis at least three times per week were recruited by mass advertisement, telephone-screened and anonymously assessed by an…

  6. Lipid rafts: heterogeneity on the high seas.

    PubMed Central

    Pike, Linda J

    2004-01-01

    Lipid rafts are membrane microdomains that are enriched in cholesterol and glycosphingolipids. They have been implicated in processes as diverse as signal transduction, endocytosis and cholesterol trafficking. Recent evidence suggests that this diversity of function is accompanied by a diversity in the composition of lipid rafts. The rafts in cells appear to be heterogeneous both in terms of their protein and their lipid content, and can be localized to different regions of the cell. This review summarizes the data supporting the concept of heterogeneity among lipid rafts and outlines the evidence for cross-talk between raft components. Based on differences in the ways in which proteins interact with rafts, the Induced-Fit Model of Raft Heterogeneity is proposed to explain the establishment and maintenance of heterogeneity within raft populations. PMID:14662007

  7. Accounting for Geographic Heterogeneity in Recreation Demand Models

    Microsoft Academic Search

    Kavita Sardana; James Michael Bowker; John C. Bergstrom; C. Meghan Starbuck; Donald B. K. English

    2008-01-01

    Spatial differences in site characteristics and user populations may result in heterogeneity of recreation preferences and values across geographic regions. Non-linear mixed effects models provide a potential means of accounting for this heterogeneity. This approach was tested by estimating a national-level recreation demand model with encouraging results.

  8. Photoluminescence study of heterogeneous terahertz quantum cascade lasers

    Microsoft Academic Search

    Joshua R. Freeman; Anthony Brewer; Harvey E. Beere; David A. Ritchie

    2011-01-01

    We present a study of heterogeneous terahertz quantum cascade lasers using micro-probe photoluminescence. Simulations and experiments are first presented on a homogeneous terahertz quantum cascade laser; these indicate that the population of the upper laser level and the energy of laser transition can be tracked by this technique. We then focus on heterogeneous terahertz quantum cascade lasers and demonstrate the

  9. Repetitive skin-picking in a student population and comparison with a sample of self-injurious skin-pickers.

    PubMed

    Keuthen, N J; Deckersbach, T; Wilhelm, S; Hale, E; Fraim, C; Baer, L; O'Sullivan, R L; Jenike, M A

    2000-01-01

    The prevalence of skin-picking and its associated characteristics were documented in a nonclinical sample of 105 college students. Subjects completed a self-report skin-picking inventory and several paper-and-pencil scales. Students who endorsed skin-picking were compared to a clinical sample of self-injurious skin-pickers (n = 31) reported on previously. Of the student subjects, 78.1% (n = 82) endorsed some degree of skin-picking and four subjects satisfied criteria for severe, self-injurious picking. Student subjects significantly differed from the clinical sample-of self-injurious skin-pickers in the duration, focus, and extent of picking, techniques used, reasons for picking, associated emotions, and picking sequelae. PMID:10849452

  10. Administrator's Perceptions on Growing Populations of Students who are English Language Learners in the State of Wyoming 

    E-print Network

    Shannon, Keri Leigh

    2014-01-31

    purposeful sampling, as voices from all district leaders would provide more clarity to the research questions. Literature review focused on the challenges that school districts face with a growing English language learner population, the challenges...

  11. Endothelial Cell Heterogeneity

    PubMed Central

    Aird, William C.

    2012-01-01

    The endothelial lining of blood vessels shows remarkable heterogeneity in structure and function, in time and space, and in health and disease. An understanding of the molecular basis for phenotypic heterogeneity may provide important insights into vascular bed-specific therapies. First, we review the scope of endothelial heterogeneity and discuss its proximate and evolutionary mechanisms. Second, we apply these principles, together with their therapeutic implications, to a representative vascular bed in disease, namely, tumor endothelium. PMID:22315715

  12. The Adult Learner and Student Veteran Undergraduate Experience Adult learner, nontraditional student, adult student, and student over traditional age are terms used

    E-print Network

    Boone, Randall B.

    The Adult Learner and Student Veteran Undergraduate Experience Adult learner, nontraditional student, adult student, and student over traditional age are terms used interchangeably in reference student, or may have a disability. Adult learners and veterans are a marginalized, student population

  13. On comparing heterogeneity across biomarkers.

    PubMed

    Steininger, Robert J; Rajaram, Satwik; Girard, Luc; Minna, John D; Wu, Lani F; Altschuler, Steven J

    2015-06-01

    Microscopy reveals complex patterns of cellular heterogeneity that can be biologically informative. However, a limitation of microscopy is that only a small number of biomarkers can typically be monitored simultaneously. Thus, a natural question is whether additional biomarkers provide a deeper characterization of the distribution of cellular states in a population. How much information about a cell's phenotypic state in one biomarker is gained by knowing its state in another biomarker? Here, we describe a framework for comparing phenotypic states across biomarkers. Our approach overcomes the current limitation of microscopy by not requiring costaining biomarkers on the same cells; instead, we require staining of biomarkers (possibly separately) on a common collection of phenotypically diverse cell lines. We evaluate our approach on two image datasets: 33 oncogenically diverse lung cancer cell lines stained with 7 biomarkers, and 49 less diverse subclones of one lung cancer cell line stained with 12 biomarkers. We first validate our method by comparing it to the "gold standard" of costaining. We then apply our approach to all pairs of biomarkers and use it to identify biomarkers that yield similar patterns of heterogeneity. The results presented in this work suggest that many biomarkers provide redundant information about heterogeneity. Thus, our approach provides a practical guide for selecting independently informative biomarkers and, more generally, will yield insights into both the connectivity of biological networks and the complexity of the state space of biological systems. © 2014 International Society for Advancement of Cytometry. PMID:25425168

  14. On comparing heterogeneity across biomarkers

    PubMed Central

    Steininger, Robert J.; Rajaram, Satwik; Girard, Luc; Minna, John D.; Wu, Lani F.; Altschuler, Steven J.

    2015-01-01

    Microscopy reveals complex patterns of cellular heterogeneity that can be biologically informative. However, a limitation of microscopy is that only a small number of biomarkers can typically be monitored simultaneously. Thus, a natural question is whether additional biomarkers provide a deeper characterization of the distribution of cellular states in a population. How much information about a cell’s phenotypic state in one biomarker is gained by knowing its state in another biomarker? Here, we describe a framework for comparing phenotypic states across biomarkers. Our approach overcomes the current limitation of microscopy by not requiring co-staining biomarkers on the same cells; instead we require staining of biomarkers (possibly separately) on a common collection of phenotypically diverse cell lines. We evaluate our approach on two image datasets: 33 oncogenically diverse lung cancer cell lines stained with 7 biomarkers, and 49 less diverse subclones of one lung cancer cell line stained with 12 biomarkers. We first validate our method by comparing it to the “gold standard” of co-staining. We then apply our approach to all pairs of biomarkers and use it to identify biomarkers that yield similar patterns of heterogeneity. The results presented in this work suggest that many biomarkers provide redundant information about heterogeneity. Thus, our approach provides a practical guide for selecting independently informative biomarkers and, more generally, will yield insights into both the connectivity of biological networks and the complexity of the state space of biological systems. PMID:25425168

  15. Heterogeneity in responses to a universal prevention program.

    PubMed

    Sandell, Rolf; Kimber, Birgitta

    2013-12-01

    Because universal or primary prevention strategies often target heterogeneous populations, their effects may likewise be expected to be heterogeneous. We sought to explore the heterogeneity of outcomes of previously published results of a longitudinal Swedish study of a school-based socio-emotional learning program. By applying latent class regression analysis to two measures of well-being, we found three significantly different classes with different change trajectories that yielded different outcomes. We conclude that restricting outcome analyses of primary prevention programs to sample means may conceal important heterogeneity regarding individual outcomes. PMID:23990404

  16. Establishing the reliability and validity of the Zagazig Depression Scale in a UK student population: an online pilot study

    PubMed Central

    2010-01-01

    Background It is thought that depressive disorders will be the second leading cause of disability worldwide by 2020. Recently, there is a steady increase in the number of university students diagnosed and treated as depression patients. It can be assumed that depression is a serious mental health problem for university students because it affects all age groups of the students either younger or older equally. The current study aims to establish the reliability and validity of the Zagazig Depression scale in a UK sample. Methods The study was a cross-sectional online survey. A sample of 133 out of 275 undergraduate students from a range of UK Universities in the academic year 2008-2009, aged 20.3 ± 6.3 years old were recruited. A modified back translated version of Zagazig Depression scale was used. In order to validate the Zagazig Depression scale, participants were asked to complete the Patient Health Questionnaire. Statistical analysis includes Kappa analysis, Cronbach's alpha, Spearman's correlation analysis, and Confirmatory Factor analysis. Results Using the recommended cut-off of Zagazig Depression scale for possible minor depression it was found that 30.3% of the students have depression and higher percentage was identified according to the Patient Health Questionnaire (37.4%). Females were more depressed. The mean ZDS score was 8.3 ± 4.2. Rates of depression increase as students get older. The reliability of The ZDS was satisfactory (Cronbach's alpha was .894). For validity, ZDS score was strongly associated with PHQ, with no significant difference (p-value > 0.05), with strong positive correlation (r = +.8, p-value < 0.01). Conclusion The strong, significant correlation between the PHQ and ZDS, along with high internal consistency of the ZDS as a whole provides evidence that ZDS is a reliable measure of depressive symptoms and is promising for the use of the translated ZDS in a large-scale cross-culture study. PMID:21143972

  17. Heterogeneous Semantics in Ptolemy

    E-print Network

    California at Irvine, University of

    Modeling Heterogeneous Semantics in Ptolemy with Modular Actor Interfaces Chris Shaver working analyses and forms of verification that cross the boundaries of heterogeneous composition. #12;Ptolemy II be understood in clear mathematical terms. From "A Modular Formal Semantics for Ptolemy", Tripakis et al

  18. E-Service-Learning: The Evolution of Service-Learning to Engage a Growing Online Student Population

    ERIC Educational Resources Information Center

    Waldner, Leora S.; McGorry, Sue Y.; Widener, Murray C.

    2012-01-01

    E-service-learning (electronic service-learning)--online course instruction and/or service--holds massive potential to transform both service-learning and online learning by freeing service-learning from geographical constraints and by equipping online learning with a powerful and much-needed tool to promote engagement. Students are increasingly…

  19. The Relationship between Wait Time after Triage and Show Rate for Intake in a Nonurgent Student Population

    ERIC Educational Resources Information Center

    DiMino, John; Blau, Gary

    2012-01-01

    Ideally, students requesting services should be seen quickly at their university counseling center to increase the likelihood of a successful treatment outcome. However, in these times of ever-increasing demand for university counseling services and the challenges of securing resources to keep up with that demand, the reality of prompt…

  20. On the Relationship between Autistic Traits and Executive Functioning in a Non-Clinical Dutch Student Population

    ERIC Educational Resources Information Center

    Maes, Joseph HR; Vissers, Constance ThWM; Egger, Jos IM; Eling, Paul ATM

    2013-01-01

    We examined the association between autistic traits and different aspects of executive functioning (EF), using non-clinical Social Science and Science students as participants. Autistic traits, and associated personality traits, were measured using the Autism Quotient (AQ) and the Temperament and Character Inventory (TCI), respectively. EF was…

  1. Dynamics of Adaptation in Spatially Heterogeneous Metapopulations

    PubMed Central

    Papaïx, Julien; David, Olivier; Lannou, Christian; Monod, Hervé

    2013-01-01

    The selection pressure experienced by organisms often varies across the species range. It is hence crucial to characterise the link between environmental spatial heterogeneity and the adaptive dynamics of species or populations. We address this issue by studying the phenotypic evolution of a spatial metapopulation using an adaptive dynamics approach. The singular strategy is found to be the mean of the optimal phenotypes in each habitat with larger weights for habitats present in large and well connected patches. The presence of spatial clusters of habitats in the metapopulation is found to facilitate specialisation and to increase both the level of adaptation and the evolutionary speed of the population when dispersal is limited. By showing that spatial structures are crucial in determining the specialisation level and the evolutionary speed of a population, our results give insight into the influence of spatial heterogeneity on the niche breadth of species. PMID:23424618

  2. Dynamics of adaptation in spatially heterogeneous metapopulations.

    PubMed

    Papaïx, Julien; David, Olivier; Lannou, Christian; Monod, Hervé

    2013-01-01

    The selection pressure experienced by organisms often varies across the species range. It is hence crucial to characterise the link between environmental spatial heterogeneity and the adaptive dynamics of species or populations. We address this issue by studying the phenotypic evolution of a spatial metapopulation using an adaptive dynamics approach. The singular strategy is found to be the mean of the optimal phenotypes in each habitat with larger weights for habitats present in large and well connected patches. The presence of spatial clusters of habitats in the metapopulation is found to facilitate specialisation and to increase both the level of adaptation and the evolutionary speed of the population when dispersal is limited. By showing that spatial structures are crucial in determining the specialisation level and the evolutionary speed of a population, our results give insight into the influence of spatial heterogeneity on the niche breadth of species. PMID:23424618

  3. Why Teach Population Education?

    ERIC Educational Resources Information Center

    Cook-Fuller, Charlotte; And Others

    Population education can help students develop coping skills and make responsible decisions as members of a family, a community, a nation, and a world. For example, by studying and understanding the impact of changes in population growth rates, compositional characteristics, and migration shifts, students, as future citizens, will be better able…

  4. The Effect of Grouping on the Behaviors of Eighth Grade Students.

    ERIC Educational Resources Information Center

    Hamm, William H.; Clawson, Kenneth

    To investigate the effect of heterogeneous and homogeneous instructional groupings used in a middle school eighth grade on selected student behaviors, 120 students were assigned to a heterogeneous group and 120 students to a homogeneous group based on several factors. The heterogeneous group was comprised of all students enrolled in the school…

  5. Gender differences in alcohol-related non-consensual sex; cross-sectional analysis of a student population

    PubMed Central

    2012-01-01

    Background Sexual offences are a global public health concern. Recent changes in the law in England and Wales have dramatically altered the legal landscape of sexual offences, but sexual assaults where the victim is voluntarily intoxicated by alcohol continue to have low conviction rates. Worldwide, students are high consumers of alcohol. This research aimed to compare male and female students in relation to their knowledge and attitudes about alcohol and sexual activity and to identify factors associated with being the victim of alcohol-related non-consensual sex. Methods 1,110 students completed an online questionnaire. Drinking levels were measured using the Alcohol Use Disorder Identification Test. Non-consensual sexual experiences were measured using the Sexual Experience Survey. Univariate and multivariate analyses were undertaken using chi square and backwards stepwise logistic regression respectively. Results A third of respondents had experienced alcohol-related non-consensual sex. Male and female students differed in the importance they gave to cues in deciding if a person wished to have sex with them and their understanding of the law of consent. 82.2% of women who had experienced alcohol-related non-consensual sex were hazardous drinkers compared to 62.9% who drank at lower levels (P < 0.001). Differences existed between men and women, and between those who had and had not experienced alcohol-related non-consensual sex, in relation to assessments of culpability in scenarios depicting alcohol-related intercourse. A third of respondents believed that a significant proportion of rapes were false allegations; significantly more men than women responded in this way. Conclusions Alcohol-related coerced sexual activity is a significant occurrence among students; attitudinal and knowledge differences between males and females may explain this. Educational messages that focus upon what is deemed acceptable sexual behaviour, the law and rape myths are needed but are set against a backdrop where drunkenness is commonplace. PMID:22433420

  6. Population: Basic Statistics

    NSDL National Science Digital Library

    Ken Rhinehart

    This lesson reinforces the idea that Earth's population, including the population of the United States, is gowing at a dramatic rate. It discusses some of the basics of demography, the study of population and its changes, and introduces key terms used to describe a population. The lesson inlcudes an activity in which students use an online reference to look up some population statistics and answer questions related to them.

  7. A Study of Adolescents Who Provide Tobacco to Other Adolescents in a Racial\\/Ethnic Diverse Population

    Microsoft Academic Search

    Steven E. Shive; Grace X. Ma; Patricia M. Legos; Earl S. Shive

    2003-01-01

    This study examined the sources of tobacco and the adolescent provision of tobacco to other adolescents in an ethnically\\/racially diverse, large heterogeneous urban, adolescent population in Philadelphia, Pennsylvania. A stratified multistage purposive sampling procedure was used to select an ethnically\\/racially diverse sample, which consisted of 569 students in grades 8-10 in five public and nonpublic funded schools. A logistical regression

  8. Deconstructing transcriptional heterogeneity in pluripotent stem cells

    PubMed Central

    Shalek, Alex K.; Satija, Rahul; DaleyKeyser, AJay; Li, Hu; Zhang, Jin; Pardee, Keith; Gennert, David; Trombetta, John J.; Ferrante, Thomas C.; Regev, Aviv; Daley, George Q.; Collins, James J.

    2014-01-01

    SUMMARY Pluripotent stem cells (PSCs) are capable of dynamic interconversion between distinct substates, but the regulatory circuits specifying these states and enabling transitions between them are not well understood. We set out to characterize transcriptional heterogeneity in PSCs by single-cell expression profiling under different chemical and genetic perturbations. Signaling factors and developmental regulators show highly variable expression, with expression states for some variable genes heritable through multiple cell divisions. Expression variability and population heterogeneity can be influenced by perturbation of signaling pathways and chromatin regulators. Strikingly, either removal of mature miRNAs or pharmacologic blockage of signaling pathways drives PSCs into a low-noise ground state characterized by a reconfigured pluripotency network, enhanced self-renewal, and a distinct chromatin state, an effect mediated by opposing miRNA families acting on the c-myc / Lin28 / let-7 axis. These data illuminate the nature of transcriptional heterogeneity in PSCs. PMID:25471879

  9. Teaching Population Geography.

    ERIC Educational Resources Information Center

    Carey, George W.; Schwartzberg, Julie

    Written under the sponsorship of the Population Council, with the financial support of the Population Instructional Materials Project, this work is intended to provide the thoughtful teacher of the social sciences with some suggestions and techniques for introducing population study to students in terms of concrete case studies which explore the…

  10. Validity and reliability of portfolio assessment of student competence in two dental school populations: a four-year study.

    PubMed

    Gadbury-Amyot, Cynthia C; McCracken, Michael S; Woldt, Janet L; Brennan, Robert L

    2014-05-01

    The purpose of this study was to empirically investigate the validity and reliability of portfolio assessment in two U.S. dental schools using a unified framework for validity. In the process of validation, it is not the test that is validated but rather the claims (interpretations and uses) about test scores that are validated. Kane's argument-based validation framework provided the structure for reporting results where validity claims are followed by evidence to support the argument. This multivariate generalizability theory study found that the greatest source of variance was attributable to faculty raters, suggesting that portfolio assessment would benefit from two raters' evaluating each portfolio independently. The results are generally supportive of holistic scoring, but analytical scoring deserves further research. Correlational analyses between student portfolios and traditional measures of student competence and readiness for licensure resulted in significant correlations between portfolios and National Board Dental Examination Part I (r=0.323, p<0.01) and Part II scores (r=0.268, p<0.05) and small and non-significant correlations with grade point average and scores on the Western Regional Examining Board (WREB) exam. It is incumbent upon the users of portfolio assessment to determine if the claims and evidence arguments set forth in this study support the proposed claims for and decisions about portfolio assessment in their respective institutions. PMID:24789826

  11. Quality of diet, screened by the Mediterranean diet quality index and the evaluation of the content of advanced glycation endproducts, in a population of high school students from Emilia Romagna

    Microsoft Academic Search

    Valeria Tarabusi; Carla Cavazza; Francesca Pasqui; Alessandra Gambineri; Renato Pasquali

    2010-01-01

    This observational study aims to evaluate the eating habits of a population of high school students from Emilia Romagna. 492\\u000a students aged between 15 and 19 years (265 females and 227 males) were personally interviewed by a dietician regarding their\\u000a dietary habits, used to assess the macro and micronutrient composition of the diet, the quality of the diet according to the

  12. The Effect Heterogeneity of Central Examinations: Evidence from TIMSS, TIMSS-Repeat and PISA

    ERIC Educational Resources Information Center

    Wobmann, Ludger

    2005-01-01

    This paper uses extensive student-level micro databases of three international student achievement tests to estimate heterogeneity in the effect of external exit examinations on student performance along three dimensions. First, quantile regressions show that the effect tends to increase with student ability--but it does not differ substantially…

  13. New Evidence on Linear Regression and Treatment Effect Heterogeneity

    Microsoft Academic Search

    Tymon S?oczy?ski

    2012-01-01

    In this paper I provide new evidence on the implications of treatment effect heterogeneity for least squares estimation when the effects are inappropriately assumed to be homogenous. I prove that under a set of benchmark assumptions linear regression provides a consistent estimator of the population average treatment effect on the treated times the population proportion of the nontreated individuals plus

  14. Individual heterogeneity and identifiability in capture?recapture models

    USGS Publications Warehouse

    Link, W.A.

    2004-01-01

    Individual heterogeneity in detection probabilities is a far more serious problem for capture?recapture modeling than has previously been recognized. In this note, I illustrate that population size is not an identifiable parameter under the general closed population mark?recapture model Mh. The problem of identifiability is obvious if the population includes individuals with pi= 0, but persists even when it is assumed that individual detection probabilities are bounded away from zero. Identifiability may be attained within parametric families of distributions for pi, but not among parametric families of distributions. Consequently, in the presence of individual heterogeneity in detection probability, capture?recapture analysis is strongly model dependent.

  15. Motives for eating tasty foods associated with binge-eating. Results from a student and a weight-loss seeking population.

    PubMed

    Boggiano, M M; Burgess, E E; Turan, B; Soleymani, T; Daniel, S; Vinson, L D; Lokken, K L; Wingo, B C; Morse, A

    2014-12-01

    The aim of this study was to use the Palatable Eating Motives Scale (PEMS) to determine if and what motives for eating tasty foods (e.g., junk food, fast food, and desserts) are associated with binge-eating in two diverse populations. BMI and scores on the PEMS, Yale Food Addiction Scale (YFAS), and Binge-eating Scale (BES) were obtained from 247 undergraduates at the University of Alabama at Birmingham (UAB) and 249 weight-loss seeking patients at the UAB EatRight program. Regression analyses revealed that eating tasty foods to forget worries and problems and help alleviate negative feelings (i.e., the 4-item Coping motive) was associated with binge-eating independently of any variance in BES scores due to sex, age, ethnicity, BMI, other PEMS motives, and YFAS scores in both students (R(2)?=?.57) and patients (R(2)?=?.55). Coping also was associated with higher BMI in students (p?students, the motives Conformity and Reward Enhancement were also independently associated with binge-eating. For this younger sample with a greater range of BES scores, eating for these motives, but not for Social ones, may indicate early maladaptive eating habits that could later develop into disorders characterized by binge-eating if predisposing factors are present. Thus, identifying one's tasty food motive or motives can potentially be used to thwart the development of BED and obesity, especially if the motive is Coping. Identifying one's PEMS motives should also help personalize conventional treatments for binge-eating and obesity toward improved outcomes. PMID:25169880

  16. Emerging heterogeneities in Italian customs

    E-print Network

    Agliari, Elena; Galluzzi, Andrea; Javarone, Marco Alberto; Pizzoferrato, Andrea; Tantari, Daniele

    2015-01-01

    Since its unification, more than a century ago, Italy has experienced strong social and economical diversities between its southern and northern regions. In the last decades, Italy has undergone a severe economical and political crisis reflecting corruption at various levels of social stratification as well as a poor involvement of its population in the number of elections that occurred. This might be explained by a lack of confidence, or interest in the country as a whole, as if the primary social and political focus of its citizens could still lay at smaller regional scales, possibly evidencing the persistence of different cultural heritages. In order to shed lights on the possible existence of such heterogeneities, we perform a statistical-mechanics-driven analysis focusing on key social quantifiers, namely the evolution of autochthonous marriages (as family still plays as a fundamental brick in the edification of social aggregates) and of mixed marriages, namely those involving a foreign-born and a native...

  17. Cell heterogeneity during the cell cycle

    SciTech Connect

    Darzynkiewicz, Z. (Memorial Sloan-Kettering Cancer Center, New York, NY); Crissman, H.; Traganos, F.; Steinkamp, J.

    1982-12-01

    Using flow cytometry, populations of Chinese hamster ovary cells, asynchronous and synchronized in the cycle, were measured with respect to cellular RNA- and protein-content, as well as cell light scatter properties. Heterogeneities of cell populations were expressed as coefficients of variation (c.v.) in percent of the respective mean values. Populations of cells immediately after mitosis have about 15% higher c.v. than mitotic cell populations, regardless of whether RNA, proteins, or light scatter are measured. These data indicate that cytoplasmic constituents are unequally distributed into the daughter cells during cytokinesis and that unequal cytokinesis generates intercellular metabolic variability during the cycle. An additional increase in heterogeneity, although of smaller degree, occurs during G/sub 2/ phase. Populations of S-phase cells are the most uniform, having 20-30% lower c.v. than the postmitotic cells. Cell progression through S does not involve any significant increase in intercellular variability with respect to RNA or protein content. In unperturbed exponentially growing cultures a critical RNA content is required for G/sub 1/ cells prior to their entrance into S. The cell residence times in the equalization compartments are exponentially distributed, which may reflect the randomness generated by the uneven division of metabolic constituents to daughter cells during cytokinesis. The cell heterogeneities were presently estimated at two metabolic levels, transcription (RNA content) and translation (proteins). The most uniform were populations stained for RNA and the highest variability was observed after staining of proteins. This suggests that the regulatory mechanisms equalizing cells in the cell cycle may operate primarily at the level of DNA transcription.

  18. Site occupancy models with heterogeneous detection probabilities

    USGS Publications Warehouse

    Royle, J.A.

    2006-01-01

    Models for estimating the probability of occurrence of a species in the presence of imperfect detection are important in many ecological disciplines. In these ?site occupancy? models, the possibility of heterogeneity in detection probabilities among sites must be considered because variation in abundance (and other factors) among sampled sites induces variation in detection probability (p). In this article, I develop occurrence probability models that allow for heterogeneous detection probabilities by considering several common classes of mixture distributions for p. For any mixing distribution, the likelihood has the general form of a zero-inflated binomial mixture for which inference based upon integrated likelihood is straightforward. A recent paper by Link (2003, Biometrics 59, 1123?1130) demonstrates that in closed population models used for estimating population size, different classes of mixture distributions are indistinguishable from data, yet can produce very different inferences about population size. I demonstrate that this problem can also arise in models for estimating site occupancy in the presence of heterogeneous detection probabilities. The implications of this are discussed in the context of an application to avian survey data and the development of animal monitoring programs.

  19. Conceptualizing a Tool to Optimize Therapy Based on Dynamic Heterogeneity

    PubMed Central

    Liao, David; Estévez-Salmerón, Luis; Tlsty, Thea D.

    2012-01-01

    Complex biological systems often display a randomness paralleled in processes studied in fundamental physics. This simple stochasticity emerges owing to the complexity of the system and underlies a fundamental aspect of biology called phenotypic stochasticity. Ongoing stochastic fluctuations in phenotype at the single-unit level can contribute to two emergent population phenotypes. Phenotypic stochasticity not only generates heterogeneity within a cell population, but also allows reversible transitions back and forth between multiple states. This phenotypic interconversion tends to restore a population to a previous composition after that population has been depleted of specific members. We call this tendency homeostatic heterogeneity. These concepts of dynamic heterogeneity can be applied to populations composed of molecules, cells, individuals, etc. Here we discuss the concept that phenotypic stochasticity both underlies the generation of heterogeneity within a cell population and can be used to control population composition, contributing, in particular, to both the ongoing emergence of drug resistance and an opportunity for depleting drug-resistant cells. Using notions of both “large” and “small” numbers of biomolecular components, we rationalize our use of Markov processes to model the generation and eradication of drug-resistant cells. Using these insights, we have developed a graphical tool, called a metronomogram, that we propose will allow us to optimize dosing frequencies and total course durations for clinical benefit. PMID:23197078

  20. Conceptualizing a tool to optimize therapy based on dynamic heterogeneity

    NASA Astrophysics Data System (ADS)

    Liao, David; Estévez-Salmerón, Luis; Tlsty, Thea D.

    2012-12-01

    Complex biological systems often display a randomness paralleled in processes studied in fundamental physics. This simple stochasticity emerges owing to the complexity of the system and underlies a fundamental aspect of biology called phenotypic stochasticity. Ongoing stochastic fluctuations in phenotype at the single-unit level can contribute to two emergent population phenotypes. Phenotypic stochasticity not only generates heterogeneity within a cell population, but also allows reversible transitions back and forth between multiple states. This phenotypic interconversion tends to restore a population to a previous composition after that population has been depleted of specific members. We call this tendency homeostatic heterogeneity. These concepts of dynamic heterogeneity can be applied to populations composed of molecules, cells, individuals, etc. Here we discuss the concept that phenotypic stochasticity both underlies the generation of heterogeneity within a cell population and can be used to control population composition, contributing, in particular, to both the ongoing emergence of drug resistance and an opportunity for depleting drug-resistant cells. Using notions of both ‘large’ and ‘small’ numbers of biomolecular components, we rationalize our use of Markov processes to model the generation and eradication of drug-resistant cells. Using these insights, we have developed a graphical tool, called a metronomogram, that we propose will allow us to optimize dosing frequencies and total course durations for clinical benefit. The authors dedicate this paper to Dr Barton Kamen who inspired its initiation and enthusiastically supported its pursuit.

  1. The effect of landscape heterogeneity on host–parasite dynamics

    Microsoft Academic Search

    Min Su; Wenlong Li; Zizhen Li; Fengpan Zhang; Cang Hui

    2009-01-01

    Environmental heterogeneity has been shown to have a profound effect on population dynamics and biological invasions, yet\\u000a the effect of its spatial structure on the dynamics of disease invasion in a spatial host–parasite system has received little\\u000a attention. Here we explore the effect of environment heterogeneity using the pair approximation and the stochastic spatially\\u000a explicit simulation in which the lost

  2. Continuous Trading Dynamically Effectively Complete Market with Heterogeneous Beliefs

    Microsoft Academic Search

    Zhenjiang Qin

    2012-01-01

    In a framework of heterogeneous beliefs, I investigate a two-date consumption model with continuous trading over the interval [0; T], in which information on the aggregate consumption at time T is revealed by an Ornstein-Uhlenbeck Bridge. This information structure allows investors to speculate on the heterogeneous posterior variance of dividend throughout [0; T). The market populated with many time-additive exponential-utility

  3. CAUSAL INFERENCE AND HETEROGENEITY BIAS IN SOCIAL SCIENCE*

    PubMed Central

    Xie, Yu

    2013-01-01

    Because of population heterogeneity, causal inference with observational data in social science may suffer from two possible sources of bias: (1) bias in unobserved pretreatment factors affecting the outcome even without treatment; and (2)bias due to heterogeneity in treatment effects. Even when we control for observed covariates, these two biases may occur if the classic ignorability assumption is untrue. In cases where the ignorability assumption is true, “composition bias” can occur if treatment propensity is systematically associated with heterogeneous treatment effects. PMID:23970824

  4. How Well Does Growth Mixture Modeling Identify Heterogeneous Growth Trajectories? A Simulation Study Examining GMM's Performance Characteristics

    Microsoft Academic Search

    James Peugh; Xitao Fan

    2012-01-01

    Growth mixture modeling (GMM) has become a more popular statistical method for modeling population heterogeneity in longitudinal data, but the performance characteristics of GMM enumeration indexes in correctly identifying heterogeneous growth trajectories are largely unknown. Few empirical studies have addressed this issue. This study considered both homogeneous (a k = 1 growth trajectory) and heterogeneous (k = 3 different but

  5. World Population Activity I: Excel

    NSDL National Science Digital Library

    Activity and Starting Point page by R.M. MacKay. Clark College, Physics and Meteorology.

    (Activity 1 of 2) This activity is primarily intended as an introductory tutorial on using Excel. Students use Excel to explore population dynamics using the Logistic equation for (S-shaped) population growth.

  6. Problematic Internet use, excessive alcohol consumption, their comorbidity and cardiovascular and cortisol reactions to acute psychological stress in a student population.

    PubMed

    Bibbey, Adam; Phillips, Anna C; Ginty, Annie T; Carroll, Douglas

    2015-06-01

    Background and aims Problematic Internet use and excessive alcohol consumption have been associated with a host of maladaptive outcomes. Further, low (blunted) cardiovascular and stress hormone (e.g. cortisol) reactions to acute psychological stress are a feature of individuals with a range of adverse health and behavioural characteristics, including dependencies such as tobacco and alcohol addiction. The present study extended this research by examining whether behavioural dependencies, namely problematic Internet use, excessive alcohol consumption, and their comorbidity would also be associated with blunted stress reactivity Methods A large sample of university students (N = 2313) were screened using Internet and alcohol dependency questionnaires to select four groups for laboratory testing: comorbid Internet and alcohol dependence (N = 17), Internet dependence (N = 17), alcohol dependence (N = 28), and non-dependent controls (N = 26). Cardiovascular activity and salivary cortisol were measured at rest and in response to a psychological stress protocol comprising of mental arithmetic and public speaking tasks. Results Neither problematic Internet behaviour nor excessive alcohol consumption, either individually or in combination, were associated with blunted cardiovascular or cortisol stress reactions. Discussion It is possible that problematic Internet behaviour and excessive alcohol consumption in a student population were not related to physiological reactivity as they may not reflect ingrained addictions but rather an impulse control disorder and binging tendency. Conclusions The present results serve to indicate some of the limits of the developing hypothesis that blunted stress reactivity is a peripheral marker of the central motivational dysregulation in the brain underpinning a wide range of health and behavioural problems. PMID:26014670

  7. Adventures With The Fish Pond: Population Modeling

    NSDL National Science Digital Library

    PBS TeacherSource - Math

    2010-01-01

    This activity builds on the population decay M&M activity and will introduce students to recursive equations and uses calculators as an efficient tool for exploring population models. Students will describe what happens to the fish population from one year to another. Each pair of students will have an activity sheet to go along with the activity, and a calculator is needed.

  8. Accessing and Investigating Population Data

    NSDL National Science Digital Library

    Grace M. Burton

    2000-01-01

    In this activity, students investigate population projections from 1990-2100 using data from the U.S. Census Bureau Web. Using the five specific population pyramids, students investigate population projection data for the United States over a 110-year period. They examine how the population data is distributed over time and explain what factors might contribute to these trends. An activity sheet and thoughtful questions, included in the lesson plan, guide the class investigation.

  9. HETEROGENEOUS MODELING AND

    E-print Network

    PTOLEMY II HETEROGENEOUS CONCURRENT MODELING AND DESIGN IN JAVA Edited by: Christopher Hylands: INTRODUCTION TO PTOLEMY II Authors: Shuvra S. Bhattacharyya Elaine Cheong John Davis, II Mudit Goel Bart of Electrical Engineering and Computer Sciences University of California at Berkeley http://ptolemy

  10. -PTOLEMY II -HETEROGENEOUS CONCURRENT

    E-print Network

    -PTOLEMY II - HETEROGENEOUS CONCURRENT MODELING AND DESIGN IN JAVA John Davis, II Mudit Goel University of California at Berkeley http://ptolemy.eecs.berkeley.edu Memorandum UCB/ERL M99/40 Document Contents Part 1: Using Ptolemy II 1. Introduction 1-1 1.1.Modeling and Design 1-1 1.2.Architecture Design 1

  11. HETEROGENEOUS MODELING AND

    E-print Network

    PTOLEMY II HETEROGENEOUS CONCURRENT MODELING AND DESIGN IN JAVA Edited by: Christopher Brooks TO PTOLEMY II Authors: Shuvra S. Bhattacharyya Christopher Brooks Elaine Cheong John Davis, II Mudit Goel of Electrical Engineering and Computer Sciences University of California at Berkeley http://ptolemy

  12. HETEROGENEOUS MODELING AND

    E-print Network

    PTOLEMY II HETEROGENEOUS CONCURRENT MODELING AND DESIGN IN JAVA Edited by: Christopher Hylands of California at Berkeley http://ptolemy.eecs.berkeley.edu Document Version 2.0.1 for use with Ptolemy II 2 Concurrent Modeling and Design Contents Part 1: Using Ptolemy II 1. Introduction 1-1 1.1.Modeling and Design

  13. HETEROGENEOUS MODELING AND

    E-print Network

    Hybinette, Maria

    PTOLEMY II HETEROGENEOUS CONCURRENT MODELING AND DESIGN IN JAVA Edited by: Christopher Brooks, Edward A. Lee, Xiaojun Liu, Steve Neuendorffer, Yang Zhao, Haiyang Zheng VOLUME 1: INTRODUCTION of the University of California. All rights reserved. "Java" is a registered trademark of Sun Microsystems. #12

  14. Identifying and Quantifying Heterogeneity in High Content Analysis: Application of Heterogeneity Indices to Drug Discovery

    PubMed Central

    Gough, Albert H.; Chen, Ning; Shun, Tong Ying; Lezon, Timothy R.; Boltz, Robert C.; Reese, Celeste E.; Wagner, Jacob; Vernetti, Lawrence A.; Grandis, Jennifer R.; Lee, Adrian V.; Stern, Andrew M.; Schurdak, Mark E.; Taylor, D. Lansing

    2014-01-01

    One of the greatest challenges in biomedical research, drug discovery and diagnostics is understanding how seemingly identical cells can respond differently to perturbagens including drugs for disease treatment. Although heterogeneity has become an accepted characteristic of a population of cells, in drug discovery it is not routinely evaluated or reported. The standard practice for cell-based, high content assays has been to assume a normal distribution and to report a well-to-well average value with a standard deviation. To address this important issue we sought to define a method that could be readily implemented to identify, quantify and characterize heterogeneity in cellular and small organism assays to guide decisions during drug discovery and experimental cell/tissue profiling. Our study revealed that heterogeneity can be effectively identified and quantified with three indices that indicate diversity, non-normality and percent outliers. The indices were evaluated using the induction and inhibition of STAT3 activation in five cell lines where the systems response including sample preparation and instrument performance were well characterized and controlled. These heterogeneity indices provide a standardized method that can easily be integrated into small and large scale screening or profiling projects to guide interpretation of the biology, as well as the development of therapeutics and diagnostics. Understanding the heterogeneity in the response to perturbagens will become a critical factor in designing strategies for the development of therapeutics including targeted polypharmacology. PMID:25036749

  15. Heterogeneity Maintenance in Glioblastoma: a social network

    PubMed Central

    Bonavia, Rudy; Inda, Maria-del-Mar; Cavenee, Webster; Furnari, Frank

    2011-01-01

    Glioblastoma multiforme (GBM), the most common intracranial tumor in adults, is characterized by extensive heterogeneity at the cellular and molecular levels. This insidious feature arises inevitably in almost all cancers and has great significance for the general outcome of the malignancy because it confounds our understanding of the disease and also intrinsically contributes to the tumor’s aggressiveness and poses an obstacle to the design of effective therapies. The classical view that heterogeneity arises as the result of a tumor’s “genetic chaos”, as well as the more contemporary cancer stem cell (CSC) hypothesis tend to identify a single cell population as the therapeutic target: the prevailing clone over time in the first case and the CSC in the latter. However, there is growing evidence that the different tumor cell populations may not be simple bystanders. Rather, they can establish a complex network of interactions between each other and with the tumor microenvironment that eventually strengthens tumor growth and increases chances to escape therapy. These differing but complementary ideas about the origin and maintenance of tumor heterogeneity and its importance in GBM will be reviewed here. PMID:21628493

  16. Astrocyte morphology, heterogeneity, and density in the developing African giant rat (Cricetomys gambianus).

    PubMed

    Olude, Matthew A; Mustapha, Oluwaseun A; Aderounmu, Oluwatunde A; Olopade, James O; Ihunwo, Amadi O

    2015-01-01

    Astrocyte morphologies and heterogeneity were described in male African giant rats (AGR; Cricetomys gambianus, Waterhouse) across three age groups (five neonates, five juveniles, and five adults) using Silver impregnation method and immunohistochemistry against glial fibrillary acidic protein. Immunopositive cell signaling, cell size and population were least in neonates, followed by adults and juveniles, respectively. In neonates, astrocyte processes were mostly detected within the glia limitans of the mid and hind brain; their cell bodies measuring 32 ± 4.8 ?m in diameter against 91 ± 5.4 ?m and 75 ± 1.9 ?m in juveniles and adults, respectively. Astrocyte heterogeneity in juvenile and adult groups revealed eight subtypes to include fibrous astrocytes chiefly in the corpus callosum and brain stem, protoplasmic astrocytes in the cortex and dentate gyrus (DG); radial glia were found along the olfactory bulb (OB) and subventricular zone (SVZ); velate astrocytes were mainly found in the cerebellum and hippocampus; marginal astrocytes close to the pia mater; Bergmann glia in the molecular layer of the cerebellum; perivascular and periventricular astrocytes in the cortex and third ventricle, respectively. Cell counts from twelve anatomical regions of the brain were significantly higher in juveniles than in adults (p ? 0.01) using unpaired student t-test in the cerebral cortex, pia, corpus callosum, rostral migratory stream, DG, and cerebellum. Highest astrocyte count was found in the DG, while the least count was in the brain stem and sub cortex. Astrocytes along the periventricular layer of the OB are believed to be part of the radial glia system that transport newly formed cells towards the hippocampus and play roles in neurogenesis migration and homeostasis in the AGR. Therefore, astrocyte heterogeneity was examined across age groups in the AGR to determine whether age influences astrocytes population in different regions of the AGR brain and discuss possible functional roles. PMID:26074782

  17. Astrocyte morphology, heterogeneity, and density in the developing African giant rat (Cricetomys gambianus)

    PubMed Central

    Olude, Matthew A.; Mustapha, Oluwaseun A.; Aderounmu, Oluwatunde A.; Olopade, James O.; Ihunwo, Amadi O.

    2015-01-01

    Astrocyte morphologies and heterogeneity were described in male African giant rats (AGR; Cricetomys gambianus, Waterhouse) across three age groups (five neonates, five juveniles, and five adults) using Silver impregnation method and immunohistochemistry against glial fibrillary acidic protein. Immunopositive cell signaling, cell size and population were least in neonates, followed by adults and juveniles, respectively. In neonates, astrocyte processes were mostly detected within the glia limitans of the mid and hind brain; their cell bodies measuring 32 ± 4.8 ?m in diameter against 91 ± 5.4 ?m and 75 ± 1.9 ?m in juveniles and adults, respectively. Astrocyte heterogeneity in juvenile and adult groups revealed eight subtypes to include fibrous astrocytes chiefly in the corpus callosum and brain stem, protoplasmic astrocytes in the cortex and dentate gyrus (DG); radial glia were found along the olfactory bulb (OB) and subventricular zone (SVZ); velate astrocytes were mainly found in the cerebellum and hippocampus; marginal astrocytes close to the pia mater; Bergmann glia in the molecular layer of the cerebellum; perivascular and periventricular astrocytes in the cortex and third ventricle, respectively. Cell counts from twelve anatomical regions of the brain were significantly higher in juveniles than in adults (p ? 0.01) using unpaired student t-test in the cerebral cortex, pia, corpus callosum, rostral migratory stream, DG, and cerebellum. Highest astrocyte count was found in the DG, while the least count was in the brain stem and sub cortex. Astrocytes along the periventricular layer of the OB are believed to be part of the radial glia system that transport newly formed cells towards the hippocampus and play roles in neurogenesis migration and homeostasis in the AGR. Therefore, astrocyte heterogeneity was examined across age groups in the AGR to determine whether age influences astrocytes population in different regions of the AGR brain and discuss possible functional roles. PMID:26074782

  18. Exploiting heterogeneity in sensor networks

    Microsoft Academic Search

    Mark D. Yarvis; Nandakishore Kushalnagar; Harkirat Singh; Anand Rangarajan; York Liu; Suresh Singh

    2005-01-01

    The presence of heterogeneous nodes (i.e., nodes with an enhanced energy capacity or communication capability) in a sensor network is known to increase network reliability and lifetime. However, questions of where, how many, and what types of heterogeneous resources to deploy remain largely unexplored. We focus on energy and link heterogeneity in ad hoc sensor net- works and consider resource-aware

  19. From Conflict to Harmony: A Heterogeneous Group in a Business Communication Class in Turkey.

    ERIC Educational Resources Information Center

    Usluata, Ayseli

    1997-01-01

    Describes how the teacher of a course in business communication for first-year students at a university in Turkey used group work and collaborative learning strategies to help students experience the value of working with others and develop intercultural communication skills. Notes that, at semester's end, 85% of students favored heterogeneous

  20. Heterogeneous Differential Evolution for Numerical Optimization

    PubMed Central

    Wang, Wenjun; Sun, Hui; Rahnamayan, Shahryar

    2014-01-01

    Differential evolution (DE) is a population-based stochastic search algorithm which has shown a good performance in solving many benchmarks and real-world optimization problems. Individuals in the standard DE, and most of its modifications, exhibit the same search characteristics because of the use of the same DE scheme. This paper proposes a simple and effective heterogeneous DE (HDE) to balance exploration and exploitation. In HDE, individuals are allowed to follow different search behaviors randomly selected from a DE scheme pool. Experiments are conducted on a comprehensive set of benchmark functions, including classical problems and shifted large-scale problems. The results show that heterogeneous DE achieves promising performance on a majority of the test problems. PMID:24683329

  1. Spatial Heterogeneity, Host Movement and Mosquito-Borne Disease Transmission

    PubMed Central

    Acevedo, Miguel A.; Prosper, Olivia; Lopiano, Kenneth; Ruktanonchai, Nick; Caughlin, T. Trevor; Martcheva, Maia; Osenberg, Craig W.; Smith, David L.

    2015-01-01

    Mosquito-borne diseases are a global health priority disproportionately affecting low-income populations in tropical and sub-tropical countries. These pathogens live in mosquitoes and hosts that interact in spatially heterogeneous environments where hosts move between regions of varying transmission intensity. Although there is increasing interest in the implications of spatial processes for mosquito-borne disease dynamics, most of our understanding derives from models that assume spatially homogeneous transmission. Spatial variation in contact rates can influence transmission and the risk of epidemics, yet the interaction between spatial heterogeneity and movement of hosts remains relatively unexplored. Here we explore, analytically and through numerical simulations, how human mobility connects spatially heterogeneous mosquito populations, thereby influencing disease persistence (determined by the basic reproduction number R0), prevalence and their relationship. We show that, when local transmission rates are highly heterogeneous, R0 declines asymptotically as human mobility increases, but infection prevalence peaks at low to intermediate rates of movement and decreases asymptotically after this peak. Movement can reduce heterogeneity in exposure to mosquito biting. As a result, if biting intensity is high but uneven, infection prevalence increases with mobility despite reductions in R0. This increase in prevalence decreases with further increase in mobility because individuals do not spend enough time in high transmission patches, hence decreasing the number of new infections and overall prevalence. These results provide a better basis for understanding the interplay between spatial transmission heterogeneity and human mobility, and their combined influence on prevalence and R0. PMID:26030769

  2. Spatial heterogeneity, host movement and mosquito-borne disease transmission.

    PubMed

    Acevedo, Miguel A; Prosper, Olivia; Lopiano, Kenneth; Ruktanonchai, Nick; Caughlin, T Trevor; Martcheva, Maia; Osenberg, Craig W; Smith, David L

    2015-01-01

    Mosquito-borne diseases are a global health priority disproportionately affecting low-income populations in tropical and sub-tropical countries. These pathogens live in mosquitoes and hosts that interact in spatially heterogeneous environments where hosts move between regions of varying transmission intensity. Although there is increasing interest in the implications of spatial processes for mosquito-borne disease dynamics, most of our understanding derives from models that assume spatially homogeneous transmission. Spatial variation in contact rates can influence transmission and the risk of epidemics, yet the interaction between spatial heterogeneity and movement of hosts remains relatively unexplored. Here we explore, analytically and through numerical simulations, how human mobility connects spatially heterogeneous mosquito populations, thereby influencing disease persistence (determined by the basic reproduction number R0), prevalence and their relationship. We show that, when local transmission rates are highly heterogeneous, R0 declines asymptotically as human mobility increases, but infection prevalence peaks at low to intermediate rates of movement and decreases asymptotically after this peak. Movement can reduce heterogeneity in exposure to mosquito biting. As a result, if biting intensity is high but uneven, infection prevalence increases with mobility despite reductions in R0. This increase in prevalence decreases with further increase in mobility because individuals do not spend enough time in high transmission patches, hence decreasing the number of new infections and overall prevalence. These results provide a better basis for understanding the interplay between spatial transmission heterogeneity and human mobility, and their combined influence on prevalence and R0. PMID:26030769

  3. Heterogeneous HPC Environments

    Microsoft Academic Search

    Marco Vanneschi

    1998-01-01

    Directions of software technologies for innovative HPC environments are discussed according to the industrial user requirements\\u000a for heterogeneous multidisciplinary applications, performance portability, rapid prototyping and software reuse, integration\\u000a and interoperability of standard tools. The various issues are demonstrated with reference to the PQE2000 project and its\\u000a programming environment SkIE (Skeleton-based Integrated Environment). Modules developed by a variety of standard languages

  4. PTOLEMY II HETEROGENEOUS

    E-print Network

    ­PTOLEMY II ­ HETEROGENEOUS CONCURRENT MODELING AND DESIGN IN JAVA John Davis, II Ron Galicia Mudit University of California at Berkeley http://ptolemy.eecs.berkeley.edu Document Version 0.1.1 February 12 Syntaxes 1­6 1.5. Ptolemy II 1­7 1.5.1. Package Structure 1­7 1.5.2. Overview of Key Classes 1­9 1

  5. -PTOLEMY II -HETEROGENEOUS

    E-print Network

    -PTOLEMY II - HETEROGENEOUS CONCURRENT MODELING AND DESIGN IN JAVA John Davis, II Ron Galicia Mudit University of California at Berkeley http://ptolemy.eecs.berkeley.edu Document Version 0.1.1 February 12.2.8. Timed CSP and Timed PN 1-5 1.3.Choosing Models of Computation 1-6 1.4.Visual Syntaxes 1-6 1.5.Ptolemy II

  6. Surface heterogeneity of minerals

    Microsoft Academic Search

    Frédéric Villiéras; Laurent J. Michot; Frédérique Bardot; Manuel Chamerois; Céline Eypert-Blaison; Michèle François; Gilles Gérard; Jean-Maurice Cases

    2002-01-01

    The precise study of adsorption mechanisms at solid–liquid interfaces requires a good analysis of the surface heterogeneity of the studied solids. For that purpose, molecular probe technique is one of the most powerful, especially at solid–gas interfaces. Indeed, low-pressure gas adsorption coupled to modelling of derivative adsorption isotherms as a function of logarithm of pressure allows to study qualitatively and

  7. The Effect of Homogeneous vs. Heterogeneous Matching-Item Format on Test Performance and Reliability.

    ERIC Educational Resources Information Center

    Allison, Donald E.

    1984-01-01

    Reports that no significant difference in reliability appeared between a heterogeneous and a homogeneous form of the same general science matching-item test administered to 316 sixth-grade students but that scores on the heterogeneous form of the test were higher, independent of the examinee's sex or intelligence. (SB)

  8. Population Growth Curves

    NSDL National Science Digital Library

    2014-09-18

    Using Avida-ED freeware, students control a few factors in an environment populated with digital organisms, and then compare how changing these factors affects population growth. They experiment by altering the environment size (similar to what is called carrying capacity, the maximum population size that an environment can normally sustain), the initial organism gestation rate, and the availability of resources. How systems function often depends on many different factors. By altering these factors one at a time, and observing the results, students are able to clearly see the effect of each one.

  9. The Early College High School Model as a Means of Reducing or Eliminating the Achievement Gap for Students from Traditionally Underrepresented Populations

    ERIC Educational Resources Information Center

    Bramucci, Matthew G.

    2014-01-01

    The existence of a gap in academic performance between various groups of students, such as minority and non-minority students or socioeconomically disadvantaged and advantaged students, has been the subject of public discourse and research for many years. Research has indicated numerous reasons for the existence of this gap and its impact on…

  10. Damage studies in heterogeneous aluminium alloys using X-ray tomography

    Microsoft Academic Search

    J. J. Gammage; D. S. Wilkinson; J. D. Embury; E. Maire

    2005-01-01

    The role of damage on the mechanical response of a heterogeneous material was investigated through X-ray tomography combined with in situ tensile deformation. This technique enables one to follow the same population of damage-nucleating particles throughout a tensile test. The results indicate that heterogeneity in the spatial distribution of particles does influence the damage process. In particular, particles that are

  11. An Age-Based Inspection and Replacement Policy for Heterogeneous Components

    Microsoft Academic Search

    Philip A. Scarf; Cristiano A. V. Cavalcante; Richard A. Dwight; Peter Gordon

    2009-01-01

    This paper considers a hybrid maintenance policy for a single component from a heterogeneous population. The component is placed in a socket, and the component and socket together comprise the system. The s-population of components consists of two sub-populations with different failure characteristics. By supposing that a component may be in a defective but operating state, so that there exists

  12. Peer Consultants: A New Role for Student Paraprofessionals.

    ERIC Educational Resources Information Center

    Presser, Nan R.; And Others

    1984-01-01

    Describes a student organization development program composed of undergraduate paraprofessionals who provide services to student organizations. Discusses selection and training of students, service delivery, and populations served. (JAC)

  13. Voter models on heterogeneous networks.

    PubMed

    Sood, V; Antal, Tibor; Redner, S

    2008-04-01

    We study simple interacting particle systems on heterogeneous networks, including the voter model and the invasion process. These are both two-state models in which in an update event an individual changes state to agree with a neighbor. For the voter model, an individual "imports" its state from a randomly chosen neighbor. Here the average time TN to reach consensus for a network of N nodes with an uncorrelated degree distribution scales as N mu1 2/mu2, where mu k is the kth moment of the degree distribution. Quick consensus thus arises on networks with broad degree distributions. We also identify the conservation law that characterizes the route by which consensus is reached. Parallel results are derived for the invasion process, in which the state of an agent is "exported" to a random neighbor. We further generalize to biased dynamics in which one state is favored. The probability for a single fitter mutant located at a node of degree k to overspread the population-the fixation probability--is proportional to k for the voter model and to 1k for the invasion process. PMID:18517592

  14. Voter models on heterogeneous networks

    NASA Astrophysics Data System (ADS)

    Sood, V.; Antal, Tibor; Redner, S.

    2008-04-01

    We study simple interacting particle systems on heterogeneous networks, including the voter model and the invasion process. These are both two-state models in which in an update event an individual changes state to agree with a neighbor. For the voter model, an individual “imports” its state from a randomly chosen neighbor. Here the average time TN to reach consensus for a network of N nodes with an uncorrelated degree distribution scales as N?12/?2 , where ?k is the kth moment of the degree distribution. Quick consensus thus arises on networks with broad degree distributions. We also identify the conservation law that characterizes the route by which consensus is reached. Parallel results are derived for the invasion process, in which the state of an agent is “exported” to a random neighbor. We further generalize to biased dynamics in which one state is favored. The probability for a single fitter mutant located at a node of degree k to overspread the population—the fixation probability—is proportional to k for the voter model and to 1/k for the invasion process.

  15. Voter Models on Heterogeneous Networks

    PubMed Central

    Sood, V.; Antal, Tibor; Redner, S.

    2008-01-01

    We study simple interacting particle systems on heterogeneous networks, including the voter model and the invasion process. These are both two-state models in which in an update event an individual changes state to agree with a neighbor. For the voter model, an individual “imports” its state from a randomly-chosen neighbor. Here the average time TN to reach consensus for a network of N nodes with an uncorrelated degree distribution scales as N?12/?2, where ?k is the kth moment of the degree distribution. Quick consensus thus arises on networks with broad degree distributions. We also identify the conservation law that characterizes the route by which consensus is reached. Parallel results are derived for the invasion process, in which the state of an agent is “exported” to a random neighbor. We further generalize to biased dynamics in which one state is favored. The probability for a single fitter mutant located at a node of degree k to overspread the population—the fixation probability—is proportional to k for the voter model and to 1/k for the invasion process. PMID:18517592

  16. Heterogeneity of asthma in society.

    PubMed

    Divekar, Rohit; Calhoun, William J

    2014-01-01

    There has been an increased interest in studying other factors that affect asthma pathogenesis and cause heterogeneity in prevalence and incidence of asthma. The reason there are such varied expression patterns of disease in asthmatics is because of multiple variables that affect the pathogenesis of asthma. As an exemplar of an epidemiologic variable, we will discuss geographical location, obesity and vitamin D status of the individual, and their effects on asthma burden in humans. There is varying data regarding the prevalence or severity of asthma in urban versus rural setting which is likely related to the difference of the populations studied, complexity of causal variables involved, and local geographic factors. In addition to cross-sectional and cohort studies in humans, animal models and studies have established a link between asthma and obesity by investigating the mechanisms affecting both disease processes. The complicated interrelationship between obesity and asthma is an active area of epidemiological and experimental research with new insights being discovered at a rapid pace. Finally, vitamin D, an important immunomodulator thought to be important in pathogenesis of asthma, has both mechanistic and therapeutic implications in treatment of asthma. The influences of these factors on the clinical expression of asthma are discussed below. PMID:24162901

  17. Dynamic heterogeneity for the physical oncologist

    NSDL National Science Digital Library

    David Liao

    Biological systems (e.g. cells) can make stochastic transitions between phenotypes (e.g. states of relatively increased or decreased drug resistance). This means that an initially drug-sensitive population can generate relatively drug-resistant subpopulations. This video presents a metronomogram, which is a tool for understanding whether such stochastic transitions can provide an opportunity for therapeutic treatment. Citation: Liao D, Estevez-Salmeron L, and Tlsty TD (2012) "Conceptualizing a tool to optimize therapy based on dynamic heterogeneity," Phys. Biol. 9:065005.

  18. Understanding tumor heterogeneity as functional compartments - superorganisms revisited

    Microsoft Academic Search

    Thomas GP Grunewald; Saskia M Herbst; Jürgen Heinze; Stefan Burdach

    2011-01-01

    Compelling evidence broadens our understanding of tumors as highly heterogeneous populations derived from one common progenitor.\\u000a In this review we portray various stages of tumorigenesis, tumor progression, self-seeding and metastasis in analogy to the\\u000a superorganisms of insect societies to exemplify the highly complex architecture of a neoplasm as a system of functional \\

  19. 1 Evolving Heterogeneous Neural Agents by Local Selection

    Microsoft Academic Search

    Filippo Menczer; Melania Degeratu

    2000-01-01

    Evolutionary algorithms have been applied to the synthesis of neural architec- tures, but they normally lead to uniform populations. Homogeneous solutions, however, are inadequate for certain applications and models. For these cases, local selection may produce the desired heterogeneity in the evolving neural networks. This chapter describes algorithms based on local selection, and dis- cusses the main differences distinguishing them

  20. Heterogeneity of keratan sulfate substituted on human chondrocytic large proteoglycans.

    PubMed

    Block, J A; Inerot, S E; Kimura, J H

    1992-04-15

    Newly synthesized 35S-labeled chondrocytic keratan sulfate chains were generated by chondrocytes of human chondrosarcoma cell line 105KC and were analyzed for heterogeneity of regional substitution, hydrodynamic size, and charge density. After isolation of the high density large chondrocytic proteoglycans and sequential digestions with chondroitinase ABC, L-1-tosylamido-2-phenylethyl chloromethyl ketone-treated trypsin, and alpha-chymotrypsin, followed by Superose 6 chromatography, two populations of keratan sulfate-containing proteoglycan fragments were identified and pooled separately. Keratan sulfate chains from each of the regions were compared after release by Pronase digestion, and differences in substitution patterns were observed; keratan sulfate chains of greater polydispersity, as well as a population of larger hydrodynamic size, were present in only one of the two regions. Alkaline/borohydride treatment confirmed both the existence of a population of uniquely large keratan sulfate chains and its restriction to a single region of proteoglycan fragments. In addition to heterogeneity of hydrodynamic size, the keratan sulfate chains exhibited regional heterogeneity of charge density and hence, of sulfation patterns. Analysis by Mono Q chromatography identified distinct groups of keratan sulfate that segregated by charge density and whose proportionate composition differed between the proteoglycan regions. Furthermore, the most highly charged species were unique to a single region and encompassed the chains of larger hydrodynamic size. This suggests that there may be regional heterogeneity of keratan sulfate chains substituted along a single class of proteoglycans and identifies a novel population of large, highly sulfated chondrocytic keratan sulfate chains. PMID:1559968

  1. Intrinsic heterogeneity in the survival and proliferation capacities of naïve CD8? T cells

    E-print Network

    Mahajan, Vinay Subhash

    2009-01-01

    This thesis describes the identification and characterization of a novel 'layer' of intrinsic non-genetic functional heterogeneity within the seemingly homogeneous naive CD8? T cell population in their survival and ...

  2. Tumor heterogeneity: causes and consequences

    PubMed Central

    Marusyk, Andriy; Polyak, Kornelia

    2009-01-01

    With rare exceptions, spontaneous tumors originate from a single cell. Yet, at the time of clinical diagnosis, the majority of human tumors display startling heterogeneity in many morphological and physiological features, such as expression of cell surface receptors, proliferative and angiogenic potential. To a substantial extent, this heterogeneity might be attributed to morphological and epigenetic plasticity, but there is also strong evidence for the co-existence of genetically divergent tumor cell clones within tumors. In this perspective, we summarize the sources of intra-tumor phenotypic heterogeneity with emphasis on genetic heterogeneity. We review experimental evidence for the existence of both intra-tumor clonal heterogeneity as well as frequent evolutionary divergence between primary tumors and metastatic outgrowths. Furthermore, we discuss potential biological and clinical implications of intra-tumor clonal heterogeneity. PMID:19931353

  3. Teaching Population Concepts. Revised Edition.

    ERIC Educational Resources Information Center

    King, Pat; Landahl, John

    This edition is designed to help teachers provide their students with some basic population concepts with stress placed on the elements of decision making. In the first section of the pamphlet, some of the basic concepts of population study are presented. These include populations, growth rates, birth and death rates, doubling time, migration, age…

  4. Heterogeneity in expected longevities.

    PubMed

    Pijoan-Mas, Josep; Ríos-Rull, José-Víctor

    2014-12-01

    We develop a new methodology to compute differences in the expected longevity of individuals of a given cohort who are in different socioeconomic groups at a certain age. We address the two main problems associated with the standard use of life expectancy: (1) that people's socioeconomic characteristics change, and (2) that mortality has decreased over time. Our methodology uncovers substantial heterogeneity in expected longevities, yet much less heterogeneity than what arises from the naive application of life expectancy formulae. We decompose the longevity differences into differences in health at age 50, differences in the evolution of health with age, and differences in mortality conditional on health. Remarkably, education, wealth, and income are health-protecting but have very little impact on two-year mortality rates conditional on health. Married people and nonsmokers, however, benefit directly in their immediate mortality. Finally, we document an increasing time trend of the socioeconomic gradient of longevity in the period 1992-2008, and we predict an increase in the socioeconomic gradient of mortality rates for the coming years. PMID:25391225

  5. Heterogeneity and plasticity of epidermal stem cells

    PubMed Central

    Schepeler, Troels; Page, Mahalia E.; Jensen, Kim B.

    2014-01-01

    The epidermis is an integral part of our largest organ, the skin, and protects us against the hostile environment. It is a highly dynamic tissue that, during normal steady-state conditions, undergoes constant turnover. Multiple stem cell populations residing in autonomously maintained compartments facilitate this task. In this Review, we discuss stem cell behaviour during normal tissue homeostasis, regeneration and disease within the pilosebaceous unit, an integral structure of the epidermis that is responsible for hair growth and lubrication of the epithelium. We provide an up-to-date view of the pilosebaceous unit, encompassing the heterogeneity and plasticity of multiple discrete stem cell populations that are strongly influenced by external cues to maintain their identity and function. PMID:24961797

  6. Heterogeneity in spending change at retirement

    PubMed Central

    Hurd, Michael D.; Rohwedder, Susann

    2014-01-01

    The simple one-good model of life-cycle consumption requires that consumption be continuous over retirement; yet prior research based on partial measures of consumption or on synthetic panels indicates that spending drops at retirement, a result that has been called the retirement-consumption puzzle. Using panel data on total spending, nondurable spending and food spending, we find that spending declines at small rates at retirement, rates that could be explained by mechanisms such as the cessation of work-related expenses, unexpected retirement due to a health shock or by the substitution of time for spending. We find substantial heterogeneity in spending change at retirement: in the upper half of the wealth distribution spending increased. In the low-wealth population where spending did decline at higher rates, the main explanation for the decline appears to be early retirement due to poor health, possibly augmented by a short planning horizon by a minority of the population. PMID:24524026

  7. Discriminating cellular heterogeneity using microwell-based RNA cytometry.

    PubMed

    Dimov, Ivan K; Lu, Rong; Lee, Eric P; Seita, Jun; Sahoo, Debashis; Park, Seung-min; Weissman, Irving L; Lee, Luke P

    2014-01-01

    Discriminating cellular heterogeneity is important for understanding cellular physiology. However, it is limited by the technical difficulties of single-cell measurements. Here we develop a two-stage system to determine cellular heterogeneity. In the first stage, we perform multiplex single-cell RNA cytometry in a microwell array containing over 60,000 reaction chambers. In the second stage, we use the RNA cytometry data to determine cellular heterogeneity by providing a heterogeneity likelihood score (HLS). Moreover, we use Monte-Carlo simulation and RNA cytometry data to calculate the minimum number of cells required for detecting heterogeneity. We apply this system to characterize the RNA distributions of ageing-related genes in a highly purified mouse haematopoietic stem cell population. We identify genes that reveal novel heterogeneity of these cells. We also show that changes in expression of genes such as Birc6 during ageing can be attributed to the shift of relative portions of cells in the high-expressing subgroup versus low-expressing subgroup. PMID:24667995

  8. Compiler Architectures for Heterogeneous Systems

    Microsoft Academic Search

    Kathryn S. Mckinley; Sharad K. Singhai; Glen E. Weaver; Charles C. Weems

    1995-01-01

    . Heterogeneous parallel systems incorporate diverse models of parallelism within a single machine or across machines and are better suited for diverse applications [25, 43, 30]. These systems are already pervasive in industrial and academic settings and offer a wealth of underutilized resources for achieving high performance. Unfortunately, heterogeneity complicates software development. We believe that compilers can and should assist

  9. Taming heterogeneity - the Ptolemy approach

    Microsoft Academic Search

    Johan Eker; Jörn W. Janneck; Edward A. Lee; Jie Liu; Xiaojun Liu; JOZSEF LUDVIG; Stephen Neuendorffer; SONIA SACHS; Yuhong Xiong

    2003-01-01

    Modern embedded computing systems tend to be heterogeneous in the sense of being composed of subsystems with very different characteristics, which communicate and interact in a variety of ways-synchronous or asynchronous, buffered or unbuffered, etc. Obviously, when designing such systems, a modeling language needs to reflect this heterogeneity. Today's modeling environments usually offer a variant of what we call amorphous

  10. Integrating Autonomous Heterogeneous Information Sources

    Microsoft Academic Search

    Rex Jakobovits

    1997-01-01

    this paper, most attempts at implementing a multidatabase system have had their handsfull dealing with the heterogeneities of much simpler domains. This is crossoverresearch, combining complex data type management with integration issues [SSU96].This paper is a survey of the existing computer science research approaches to achievinginteroperability between autonomous heterogeneous data sources.B. Schematic Conflicts

  11. Detecting Latent Heterogeneity Judea Pearl

    E-print Network

    California at Los Angeles, University of

    to a program benefit most from the program; the alternative calls for revising recruiting policies. Heterogeneity also introduces bias if one ventures to estimate average effects us- ing linear or constant-406 December 2012 #12;of the model. A straightforward way of assessing heterogeneity is to estimate

  12. Heterogeneous flywheel modeling and optimization

    Microsoft Academic Search

    Jinhua Huang; Georges M. Fadel

    2000-01-01

    The modeling or representation of heterogeneous objects is a recent research topic extensively published. Today, several rapid prototyping technologies are at a point where building heterogeneous components has become realizable; thus, methodologies to design these objects for manufacturing have to be developed. In this paper, we demonstrate how to apply Kumar and Dutta's modeling techniques to two different kinds of

  13. Heterogeneity in background fitness acts as a suppressor of selection.

    PubMed

    Hauser, Oliver P; Traulsen, Arne; Nowak, Martin A

    2014-02-21

    We introduce the concept of heterogeneity in background fitness to evolutionary dynamics in finite populations. Background fitness is specific to an individual but not linked to its strategy. It can be thought of as a property that is related to the physical or societal position of an individual, but is not dependent on the strategy that is adopted in the evolutionary process under consideration. In our model, an individual's total fitness is the sum of its background fitness and the fitness derived from using a specific strategy. This approach has important implications for the imitation of behavioural strategies: if we imitate others for their success, but can only adopt their behaviour and not their social and economic ties, we may imitate in vain. We study the effect of heterogeneity in background fitness on the fixation of a mutant strategy with constant fitness. We find that heterogeneity suppresses selection, but also decreases the time until a novel strategy either takes over the population or is lost again. We derive analytical solutions of the fixation probability in small populations. In the case of large total background fitness in a population with maximum inequality, we find a particularly simple approximation of the fixation probability. Numerical simulations suggest that this simple approximation also holds for larger population sizes. PMID:24211522

  14. Ventilation heterogeneity in obesity.

    PubMed

    Pellegrino, Riccardo; Gobbi, Alessandro; Antonelli, Andrea; Torchio, Roberto; Gulotta, Carlo; Pellegrino, Giulia Michela; Dellacà, Raffaele; Hyatt, Robert E; Brusasco, Vito

    2014-05-01

    Obesity is associated with important decrements in lung volumes. Despite this, ventilation remains normally or near normally distributed at least for moderate decrements in functional residual capacity (FRC). We tested the hypothesis that this is because maximum flow increases presumably as a result of an increased lung elastic recoil. Forced expiratory flows corrected for thoracic gas compression volume, lung volumes, and forced oscillation technique at 5-11-19 Hz were measured in 133 healthy subjects with a body mass index (BMI) ranging from 18 to 50 kg/m(2). Short-term temporal variability of ventilation heterogeneity was estimated from the interquartile range of the frequency distribution of the difference in inspiratory resistance between 5 and 19 Hz (R5-19_IQR). FRC % predicted negatively correlated with BMI (r = -0.72, P < 0.001) and with an increase in slope of either maximal (r = -0.34, P < 0.01) or partial flow-volume curves (r = -0.30, P < 0.01). Together with a slight decrease in residual volume, this suggests an increased lung elastic recoil. Regression analysis of R5-19_IQR against FRC % predicted and expiratory reserve volume (ERV) yielded significantly higher correlation coefficients by nonlinear than linear fitting models (r(2) = 0.40 vs. 0.30 for FRC % predicted and r(2) = 0.28 vs. 0.19 for ERV). In conclusion, temporal variability of ventilation heterogeneities increases in obesity only when FRC falls approximately below 65% of predicted or ERV below 0.6 liters. Above these thresholds distribution is quite well preserved presumably as a result of an increase in lung recoil. PMID:24651986

  15. Dynamic equilibrium of heterogeneous and interconvertible multipotent hematopoietic cell subsets.

    PubMed

    Weston, Wendy; Zayas, Jennifer; Perez, Ruben; George, John; Jurecic, Roland

    2014-01-01

    Populations of hematopoietic stem cells and progenitors are quite heterogeneous and consist of multiple cell subsets with distinct phenotypic and functional characteristics. Some of these subsets also appear to be interconvertible and oscillate between functionally distinct states. The multipotent hematopoietic cell line EML has emerged as a unique model to study the heterogeneity and interconvertibility of multipotent hematopoietic cells. Here we describe extensive phenotypic and functional heterogeneity of EML cells which stems from the coexistence of multiple cell subsets. Each of these subsets is phenotypically and functionally heterogeneous, and displays distinct multilineage differentiation potential, cell cycle profile, proliferation kinetics, and expression pattern of HSC markers and some of the key lineage-associated transcription factors. Analysis of their maintenance revealed that on a population level all EML cell subsets exhibit cell-autonomous interconvertible properties, with the capacity to generate all other subsets and re-establish complete parental EML cell population. Moreover, all EML cell subsets generated during multiple cell generations maintain their distinct phenotypic and functional signatures and interconvertible properties. The model of EML cell line suggests that interconvertible multipotent hematopoietic cell subsets coexist in a homeostatically maintained dynamic equilibrium which is regulated by currently unknown cell-intrinsic mechanisms. PMID:24903657

  16. Stability of Heterogeneous Ecological Systems

    E-print Network

    Yan, Gang; Liu, Yang-Yu

    2014-01-01

    Stability of ecological system measures the tendency of a community to return to equilibrium after small perturbation, which is severely constrained by the underlying network structure. Despite significant advances in uncovering the relationship between stability and network structure, little attention has been paid to the impact of the degree heterogeneity that exists in real ecological systems. Here we show that for networks with mixed interactions of competition and mutualism the degree heterogeneity always destabilizes ecological system. For ecological networks with predator-prey interactions (e.g., food webs) constructed from either simple network models or a realistic food web model (cascade model) high heterogeneity is always destabilizing, yet moderate heterogeneity is stabilizing. Surprisingly, for ecological network generated from the niche model, the degree heterogeneity is always destabilizing. These findings deepen our understanding of the stability of real ecological systems and may also have im...

  17. Population Structures and Cohorts

    NSDL National Science Digital Library

    Crowder, Kyle

    This module provides a gentle introduction to the use of StudentChip software and census data to investigate basic population issues. In the first part of this module, you will use data from the 1990 U.S. census to create population pyramids for several racial and ethnic groups. These population pyramids provide the ability to view the age and sex structure of a population. They not only allow us to view the cumulative impacts of past patterns of fertility, mortality, and migration, but also provide hints about what a particular population is likely to look like in the future. In the second part of the module you will continue our exploration of basic U.S. population structures by comparing some of the basic characteristics of a number of distinct birth cohorts.

  18. Individual Human Cytotoxic T Lymphocytes Exhibit Intraclonal Heterogeneity during Sustained Killing.

    PubMed

    Vasconcelos, Zilton; Müller, Sabina; Guipouy, Delphine; Yu, Wong; Christophe, Claire; Gadat, Sébastien; Valitutti, Salvatore; Dupré, Loïc

    2015-06-01

    The killing of antigen-bearing cells by clonal populations of cytotoxic T lymphocytes (CTLs) is thought to be a rapid phenomenon executed uniformly by individual CTLs. We combined bulk and single-CTL killing assays over a prolonged time period to provide the killing statistics of clonal human CTLs against an excess of target cells. Our data reveal efficiency in sustained killing at the population level, which relied on a highly heterogeneous multiple killing performance at the individual level. Although intraclonal functional heterogeneity was a stable trait in clonal populations, it was reset in the progeny of individual CTLs. In-depth mathematical analysis of individual CTL killing data revealed a substantial proportion of high-rate killer CTLs with burst killing activity. Importantly, such activity was delayed and required activation with strong antigenic stimulation. Our study implies that functional heterogeneity allows CTL populations to calibrate prolonged cytotoxic activity to the size of target cell populations. PMID:26027932

  19. Final Technical Report - Investigation into the Relationship between Heterogeneity and Heavy-Tailed Solute Transport

    SciTech Connect

    Weissmann, Gary S

    2013-12-06

    The objective of this project was to characterize the influence that naturally complex geologic media has on anomalous dispersion and to determine if the nature of dispersion can be estimated from the underlying heterogeneous media. The UNM portion of this project was to provide detailed representations of aquifer heterogeneity through producing highly-resolved models of outcrop analogs to aquifer materials. This project combined outcrop-scale heterogeneity characterization (conducted at the University of New Mexico), laboratory experiments (conducted at Sandia National Laboratory), and numerical simulations (conducted at Sandia National Laboratory and Colorado School of Mines). The study was designed to test whether established dispersion theory accurately predicts the behavior of solute transport through heterogeneous media and to investigate the relationship between heterogeneity and the parameters that populate these models. The dispersion theory tested by this work was based upon the fractional advection-dispersion equation (fADE) model. Unlike most dispersion studies that develop a solute transport model by fitting the solute transport breakthrough curve, this project explored the nature of the heterogeneous media to better understand the connection between the model parameters and the aquifer heterogeneity. We also evaluated methods for simulating the heterogeneity to see whether these approaches (e.g., geostatistical) could reasonably replicate realistic heterogeneity. The UNM portion of this study focused on capturing realistic geologic heterogeneity of aquifer analogs using advanced outcrop mapping methods.

  20. Science Education and ESL Students

    ERIC Educational Resources Information Center

    Allen, Heather; Park, Soonhye

    2011-01-01

    The number of students who learn English as a second language (ESL) in U.S. schools has grown significantly in the past decade. This segment of the student population increased by 56% between the 1994-95 and 2004-05 school years (NCLR 2007). As the ESL student population increases, many science teachers struggle to tailor instructional materials,…

  1. Motivating Students To Read.

    ERIC Educational Resources Information Center

    Green, Patricia; Kandyba, Christine; McDonald, Colleen; Stevens, Tricia

    This report describes a research study in which motivational strategies were used to increase student enjoyment of reading and to foster a life-long love of reading. The targeted populations consisted of primary and middle grade students in three different urban midwestern settings. The problem of motivating students to read was documented through…

  2. Systemic Equity Pedagogy in Science Education: A Mixed-Method Analysis of High Achieving High Schools of Culturally Diverse Student Populations in Texas 

    E-print Network

    Blocker, Tyrone Dewayne

    2013-08-14

    The purpose of this study was to identify and describe the associations between systemic equity pedagogy (SEP) practices in highly diverse high schools and their students' science achievement and college readiness. This study focuses on science...

  3. Systemic Equity Pedagogy in Science Education: A Mixed-Method Analysis of High Achieving High Schools of Culturally Diverse Student Populations in Texas

    E-print Network

    Blocker, Tyrone Dewayne

    2013-08-14

    programs in ten highly diverse Texas high schools serving students who exhibit high science achievement and college readiness. According to the Policy Research Group in Science Education, only two percent of all culturally diverse high schools within...

  4. Embedded Learning Strategy Instruction: Story-Structure Pedagogy in Heterogeneous Secondary Literature Classes

    ERIC Educational Resources Information Center

    Faggella-Luby, Michael; Schumaker, Jean S.; Deshler, Donald D.

    2007-01-01

    The effects of using the Embedded Story-Structure (ESS) Routine in a literature course were investigated. A heterogeneous group of 79 ninth graders, including 14 students with LD, were randomly assigned to one of two conditions, with instruction occurring in groups of 12 to 14 students in general education literature classes over a nine-day…

  5. Diffusion in heterogeneous media

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Liu, L.

    2012-12-01

    Diffusion in heterogeneous media has been investigated for over forty years. However, the fundamental equations for bulk (effective) diffusivity in multi-phase systems were incorrect because of the use of an inappropriate similarity between diffusion and other physical properties such as thermal conductivity. The mistake has permeated through the literature and textbooks. Specifically, the role of concentration partitioning between different phases in diffusion was not considered in such similarity relations. In this work, we present the correct method to derive such relations in heterogeneous media. Barrer [1] used the similarity between diffusivity and thermal conductivity to derive the relation between the bulk (effective) diffusivity and the individual-phase diffusivities. The approach was followed by many others [2-4]. Unfortunately the similarity approach by Barrer [1] is incorrect because there is also dissimilarity. The key difference is that, even though heat conduction and mass diffusion are characterized by a similar flux equation, in heat conduction, T is continuous across phase boundaries, whereas in diffusion, C is usually not continuous across phase boundaries. The concentration in each phase plays a major role in controlling the contribution by the phase to the bulk diffusive flux and hence the bulk diffusivity. For example, if the concentration of a component in a phase is very low, even if the diffusivity in the phase is high, the contribution of diffusion in that phase to the bulk diffusion flux can still be negligible. Hence, previous models for diffusivity in composite materials or multi-mineral rocks, no matter how sophisticated, are fundamentally wrong because the foundation is a mistake. Correcting the mistake is straightforward. The mass flux can be written in terms of chemical potential and mobility [5,6]. Because chemical potential is continuous across phase boundaries, the relation between bulk mobility and individual-phase mobilities is the same as that between bulk heat conductivity and individual-phase heat conductivities. That is, all previous relations for diffusion cannot be directly applied to diffusivities, but can be applied to mobilities. Then, from the relation between diffusivity and mobility, the correct equations can be obtained, as will be shown in the presentation. [1] Barrer (1968) Diffusion in Polymers, Academic Press, 165. [2] Crank (1975) The Mathematics of Diffusion, Clarendon Press. [3] Brady (1983) Am. J. Sci. 283A, 181. [4] Torquato et al. (1999) J. Appl. Phys. 85, 1560. [5] Lesher (1994) J Geophys. Res. 99, 9585. [6] Zhang (1993) J Geophys. Res. 98, 11901.

  6. Information Represented Graphically: History of Populations

    NSDL National Science Digital Library

    Illuminations National Council of Mathematics

    2009-07-26

    In this lesson, students will describe and explain change of population data displayed in circle graphs and make written predictions from the information. Students will justify their explanation. Lesson 3 of a three-lesson unit.

  7. Chimera states in heterogeneous networks

    E-print Network

    Carlo R. Laing

    2008-12-17

    Chimera states in networks of coupled oscillators occur when some fraction of the oscillators synchronise with one another, while the remaining oscillators are incoherent. Several groups have studied chimerae in networks of identical oscillators, but here we study these states in a heterogeneous model for which the natural frequencies of the oscillators are chosen from a distribution. We obtain exact results by reduction to a finite set of differential equations. We find that heterogeneity can destroy chimerae, destroy all states except chimerae, or destabilise chimerae in Hopf bifurcations, depending on the form of the heterogeneity.

  8. Heterogeneous ice nucleation: bridging stochastic and singular freezing behavior

    NASA Astrophysics Data System (ADS)

    Niedermeier, D.; Shaw, R. A.; Hartmann, S.; Wex, H.; Clauss, T.; Voigtländer, J.; Stratmann, F.

    2011-01-01

    Heterogeneous ice nucleation, a primary pathway for ice formation in the atmosphere, has been described alternately as being stochastic, in direct analogy with homogeneous nucleation, or singular, with ice nuclei initiating freezing at deterministic temperatures. We present an idealized model that bridges these stochastic and singular descriptions of heterogeneous ice nucleation. This "soccer ball" model treats statistically similar particles as being covered with surface sites (patches of finite area) characterized by different nucleation barriers, but with each surface site following the stochastic nature of ice embryo formation. The model provides a phenomenological explanation for seemingly contradictory experimental results obtained in our research groups. We suggest that ice nucleation is fundamentally a stochastic process but that for realistic atmospheric particle populations this process can be masked by the heterogeneity of surface properties. Full evaluation of the model will require experiments with well characterized ice nucleating particles and the ability to vary both temperature and waiting time for freezing.

  9. STUDENT ABILITIES, GROUPING PATTERNS, AND CLASSROOM INTERACTION.

    ERIC Educational Resources Information Center

    DREWS, ELIZABETH M.

    A STUDY WAS MADE TO DETERMINE THE EFFECT OF HETEROGENEOUS AND HOMOGENEOUS GROUPING IN NINTH-GRADE ENGLISH CLASSES. ON THE BASES OF IQ AND READING LANGUAGE SKILLS, STUDENTS WERE GROUPED AT THREE ABILITY LEVELS AND PLACE IN HETEROGENEOUS, HOMOGENEOUS SUPERIOR, HOMOGENEOUS SLOW, AND HOMOGENEOUS AVERAGE CLASSES. TEACHER VARIABLES WERE REDUCED BY…

  10. Angiotensin II receptor heterogeneity

    SciTech Connect

    Herblin, W.F.; Chiu, A.T.; McCall, D.E.; Ardecky, R.J.; Carini, D.J.; Duncia, J.V.; Pease, L.J.; Wong, P.C.; Wexler, R.R.; Johnson, A.L. (DuPont Merck Pharmaceutical Company, Wilmington, DE (USA))

    1991-04-01

    The possibility of receptor heterogeneity in the angiotensin II (AII) system has been suggested previously, based on differences in Kd values or sensitivity to thiol reagents. One of the authors earliest indications was the frequent observation of incomplete inhibition of the binding of AII to adrenal cortical membranes. Autoradiographic studies demonstrated that all of the labeling of the rat adrenal was blocked by unlabeled AII or saralasin, but not by DuP 753. The predominant receptor in the rat adrenal cortex (80%) is sensitive to dithiothreitol (DTT) and DuP 753, and is designated AII-1. The residual sites in the adrenal cortex and almost all of the sites in the rat adrenal medulla are insensitive to both DTT and DuP 753, but were blocked by EXP655. These sites have been confirmed by ligand binding studies and are designated AII-2. The rabbit adrenal cortex is unique in yielding a nonuniform distribution of AII-2 sites around the outer layer of glomerulosa cells. In the rabbit kidney, the sites on the glomeruli are AII-1, but the sites on the kidney capsule are AII-2. Angiotensin III appears to have a higher affinity for AII-2 sites since it inhibits the binding to the rabbit kidney capsule but not the glomeruli. Elucidation of the distribution and function of these diverse sites should permit the development of more selective and specific therapeutic strategies.

  11. Heterogeneity in the penumbra

    PubMed Central

    del Zoppo, Gregory J; Sharp, Frank R; Heiss, Wolf-Dieter; Albers, Gregory W

    2011-01-01

    Original experimental studies in nonhuman primate models of focal ischemia showed flow-related changes in evoked potentials that suggested a circumferential zone of low regional cerebral blood flow with normal K+ homeostasis, around a core of permanent injury in the striatum or the cortex. This became the basis for the definition of the ischemic penumbra. Imaging techniques of the time suggested a homogeneous core of injury, while positing a surrounding ‘penumbral' region that could be salvaged. However, both molecular studies and observations of vascular integrity indicate a more complex and dynamic situation in the ischemic core that also changes with time. The microvascular, cellular, and molecular events in the acute setting are compatible with heterogeneity of the injury within the injury center, which at early time points can be described as multiple ‘mini-cores' associated with multiple ‘mini-penumbras'. These observations suggest the progression of injury from many small foci to a homogeneous defect over time after the onset of ischemia. Recent observations with updated imaging techniques and data processing support these dynamic changes within the core and the penumbra in humans following focal ischemia. PMID:21731034

  12. Heterogeneity of Aspergillus niger microcolonies in liquid shaken cultures.

    PubMed

    de Bekker, Charissa; van Veluw, G Jerre; Vinck, Arman; Wiebenga, L Ad; Wösten, Han A B

    2011-02-01

    The fungus Aspergillus niger forms (sub)millimeter microcolonies within a liquid shaken culture. Here, we show that such microcolonies are heterogeneous with respect to size and gene expression. Microcolonies of strains expressing green fluorescent protein (GFP) from the promoter of the glucoamlyase gene glaA or the ferulic acid esterase gene faeA were sorted on the basis of diameter and fluorescence using the Complex Object Parametric Analyzer and Sorter (COPAS) technology. Statistical analysis revealed that the liquid shaken culture consisted of two populations of microcolonies that differ by 90 ?m in diameter. The population of small microcolonies of strains expressing GFP from the glaA or faeA promoter comprised 39% and 25% of the culture, respectively. Two populations of microcolonies could also be distinguished when the expression of GFP in these strains was analyzed. The population expressing a low level of GFP consisted of 68% and 44% of the culture, respectively. We also show that mRNA accumulation is heterogeneous within microcolonies of A. niger. Central and peripheral parts of the mycelium were isolated with laser microdissection and pressure catapulting (LMPC), and RNA from these samples was used for quantitative PCR analysis. This analysis showed that the RNA content per hypha was about 45 times higher at the periphery than in the center of the microcolony. Our data imply that the protein production of A. niger can be improved in industrial fermentations by reducing the heterogeneity within the culture. PMID:21169437

  13. Individual heterogeneity in reproductive rates and cost of reproduction in a long-lived vertebrate

    PubMed Central

    Chambert, Thierry; Rotella, Jay J; Higgs, Megan D; Garrott, Robert A

    2013-01-01

    Individual variation in reproductive success is a key feature of evolution, but also has important implications for predicting population responses to variable environments. Although such individual variation in reproductive outcomes has been reported in numerous studies, most analyses to date have not considered whether these realized differences were due to latent individual heterogeneity in reproduction or merely random chance causing different outcomes among like individuals. Furthermore, latent heterogeneity in fitness components might be expressed differently in contrasted environmental conditions, an issue that has only rarely been investigated. Here, we assessed (i) the potential existence of latent individual heterogeneity and (ii) the nature of its expression (fixed vs. variable) in a population of female Weddell seals (Leptonychotes weddellii), using a hierarchical modeling approach on a 30-year mark–recapture data set consisting of 954 individual encounter histories. We found strong support for the existence of latent individual heterogeneity in the population, with “robust” individuals expected to produce twice as many pups as “frail” individuals. Moreover, the expression of individual heterogeneity appeared consistent, with only mild evidence that it might be amplified when environmental conditions are severe. Finally, the explicit modeling of individual heterogeneity allowed us to detect a substantial cost of reproduction that was not evidenced when the heterogeneity was ignored. PMID:23919151

  14. Ocean Predator/Prey Populations

    NSDL National Science Digital Library

    Susan Kelly Topic: Population change Course type: Introductory undergraduate course Description Modeling impact of change in food web Learning Goals or Outcomes Students will see how changes on one trophic level ...

  15. Female Student Athletes and Student Athletes of Color.

    ERIC Educational Resources Information Center

    Person, Dawn R.; Benson-Quaziena, Marcella; Rogers, Ann Marie

    2001-01-01

    Addresses the experiences of the growing population of women student athletes and student athletes of color. Proposes a culturally responsive approach for student affairs professionals working with these athletes that supports the students in managing internal and external conflict related to their identities and roles. (Contains 40 references.)…

  16. Homogeneous, Heterogeneous, and Enzymatic Catalysis.

    ERIC Educational Resources Information Center

    Oyama, S. Ted; Somorjai, Gabor A.

    1988-01-01

    Discusses three areas of catalysis: homegeneous, heterogeneous, and enzymatic. Explains fundamentals and economic impact of catalysis. Lists and discusses common industrial catalysts. Provides a list of 107 references. (MVL)

  17. Heterogeneous Multi-Robot Cooperation

    E-print Network

    Parker, Lynne E.

    1994-02-01

    This report addresses the problem of achieving cooperation within small- to medium- sized teams of heterogeneous mobile robots. I describe a software architecture I have developed, called ALLIANCE, that facilitates ...

  18. HETEROGENOUS DEGRADATION OF OXYGENATED INTERMEDIATES

    EPA Science Inventory

    Issues surrounding the importance of including heterogeneous processes when determining the fate of oxygenated intermediates in the troposphere are discussed. esults of recent investigations are reviewed and preliminary data from a laboratory study are presented. n the laboratory...

  19. QUANTIFYING SITE QUALITY IN A HETEROGENEOUS LANDSCAPE: RECRUITMENT OF A REEF FISH

    Microsoft Academic Search

    Jeffrey S. Shima; Craig W. Osenberg; Colette M. St. Mary

    2008-01-01

    Heterogeneity in site quality can play an important role in patterns of abundance and population dynamics. Yet, estimating site quality in natural systems can be problematic because site quality can (1) vary through ontogeny for a focal organism, leading to shifts in site quality with age, (2) be confounded with (or masked by) variation in traits of individuals populating the

  20. The effect of host heterogeneity and parasite intragenomic interactions on parasite

    E-print Network

    Paterson, Steve

    The effect of host heterogeneity and parasite intragenomic interactions on parasite population Bank, Sheffield S10 2TN, UK Understanding the processes that shape the genetic structure of parasite populations and the functional consequences of different parasite genotypes is critical for our ability

  1. Population-focused nursing: advocacy for vulnerable populations in an RN-BSN program.

    PubMed

    Jones, Melissa; Smith, Paul

    2014-01-01

    The purpose of this article is to describe an innovative learning activity for online RN-BSN students designed to foster advocacy for vulnerable populations. The Vulnerable Population Advocacy Assignment, included as a component of the online Population-Focused Nursing class, provides students with the opportunity to identify and develop an awareness of issues impacting vulnerable populations and to advocate for policy changes that will influence the health of individuals, families, and populations. RN-BSN students build on previous knowledge and skills in professional communication and advocacy as they develop a policy statement designed to address health disparities impacting local, national, and global populations. PMID:24611961

  2. On the evolution of migration in heterogeneous environments.

    PubMed

    Blanquart, François; Gandon, Sylvain

    2014-06-01

    Populations often experience variable conditions, both in time and space. Here we develop a novel theoretical framework to study the evolution of migration under the influence of spatially and temporally variable selection and genetic drift. First, we examine when polymorphism is maintained at a locus under heterogeneous selection, as a function of the pattern of spatial heterogeneity and the migration rate. In a second step, we study how levels of migration evolve under the joint action of kin competition and local adaptation at a polymorphic locus. This analysis reveals the existence of evolutionary bistability, whereby a low or a high migration rate may evolve depending on the initial conditions. Last, we relax several assumptions regarding selection heterogeneity commonly made in previous studies and explore the consequences of more complex spatial and temporal patterns of variability in selection on the evolution of migration. We found that small modifications in the pattern of environmental heterogeneity may have dramatic effects on the evolution of migration. This work highlights the importance of considering more general scenarios of environmental heterogeneity when studying the evolution of life-history traits in ecologically complex settings. PMID:24571236

  3. Reporting heterogeneity in self-assessed health among elderly Europeans

    PubMed Central

    2012-01-01

    Introduction Self-assessed health (SAH) is a frequently used measure of individuals’ health status. It is also prone to reporting heterogeneity. To control for reporting heterogeneity objective measures of true health need to be included in an analysis. The topic becomes even more complex for cross-country comparisons, as many key variables tend to vary strongly across countries, influenced by cultural and institutional differences. This study aims at exploring the key drivers for reporting heterogeneity in SAH in an international context. To this end, country specific effects are accounted for and the objective health measure is concretized, distinguishing effects of mental and physical health conditions. Methods We use panel data from the SHARE-project which provides a rich dataset on the elderly European population. To obtain distinct indicators for physical and mental health conditions two indices are constructed. Finally, to identify potential reporting heterogeneity in SAH a generalized ordered probit model is estimated. Results We find evidence that in addition to health behaviour, health care utilization, mental and physical health condition as well as country characteristics affect reporting behaviour. We conclude that observed and unobserved heterogeneity play an important role when analysing SAH and have to be taken into account. PMID:23036352

  4. The effects of spatial population dataset choice on estimates of population at risk of disease

    Microsoft Academic Search

    Andrew J Tatem; Nicholas Campiz; Peter W Gething; Robert W Snow; Catherine Linard

    2011-01-01

    BACKGROUND: The spatial modeling of infectious disease distributions and dynamics is increasingly being undertaken for health services planning and disease control monitoring, implementation, and evaluation. Where risks are heterogeneous in space or dependent on person-to-person transmission, spatial data on human population distributions are required to estimate infectious disease risks, burdens, and dynamics. Several different modeled human population distribution datasets are

  5. Developing the methods of modeling heterogeneous components

    Microsoft Academic Search

    Ke-Zhang Chen; Xin-An Feng

    2003-01-01

    In order to represent, analyze, optimize, and manufacture a component made of multi-heterogeneous materials for high-tech applications, a computer model of the heterogeneous component needs to be built first. Heterogeneous materials include composite, functionally graded materials, and heterogeneous materials with a periodic microstructure. Current modeling techniques focus only on capturing the geometric information and cannot satisfy the requirements from modeling

  6. Quantifying heterogeneity and dynamics of clonal fitness in response to perturbation.

    PubMed

    Frick, Peter L; Paudel, Bishal B; Tyson, Darren R; Quaranta, Vito

    2015-07-01

    The dynamics of heterogeneous clonal lineages within a cell population, in aggregate, shape both normal and pathological biological processes. Studies of clonality typically relate the fitness of clones to their relative abundance, thus requiring long-term experiments and limiting conclusions about the heterogeneity of clonal fitness in response to perturbation. We present, for the first time, a method that enables a dynamic, global picture of clonal fitness within a mammalian cell population. This novel assay allows facile comparison of the structure of clonal fitness in a cell population across many perturbations. By utilizing high-throughput imaging, our methodology provides ample statistical power to define clonal fitness dynamically and to visualize the structure of perturbation-induced clonal fitness within a cell population. We envision that this technique will be a powerful tool to investigate heterogeneity in biological processes involving cell proliferation, including development and drug response. PMID:25600161

  7. Use of gene expression to characterize heterogeneous liver cell populations

    E-print Network

    Schreiber, Brent M. (Brent Matthew), 1981-

    2004-01-01

    Non-parenchymal cells (NPC's) are integral to recreate the native hepatic microenvironment and necessary to maintain in vivo liver function. A variety of in vitro culture systems have been developed to address different ...

  8. Selective Adaptation in Networks of Heterogeneous Populations: Model, Simulation,

    E-print Network

    Meir, Ron

    Israel Institute of Technology, Haifa, Israel, 2 Faculty of Medicine, Technion Israel Institute of Technology, Haifa, Israel Biological systems often change their responsiveness when subject to persistent or depression, is explained in terms of net loss or gain of exciting or restoring resources. For instance, one

  9. [Experimental substantiation of population heterogeneity in methicillin resistant Staphylococcus aureus].

    PubMed

    Musina, L T; Gladkova, K K; Dmitrenko, O A; Gladkova, E G; Semina, I E; Petrash, P; Dalmatov, V V; Nikolaeva, T N; Reshed'ko, G K; Adarchenko, A A

    1994-05-01

    A comprehensive intraspecies typing of the cultures of MRSA collected during inspection of drug resistance in causative agents of intrahospital infections was performed. The following parameters were investigated: antibiotic resistance, toxin production, sensitivity to the phages of the International Set and the phages of an experimental collection providing the isolation of strains with definite specificity of the restriction-modification system. Different clones of methicillin resistant S. aureus were found to be circulating on the territory of the CIS. PMID:7857156

  10. Routing in Delay-Tolerant Networks Comprising Heterogeneous Node Populations

    Microsoft Academic Search

    Thrasyvoulos Spyropoulos; Thierry Turletti; Katia Obraczka

    2009-01-01

    Communication networks are traditionally assumed to be connected. However, emerging wireless applications such as vehicular networks, pocket-switched networks, etc., coupled with volatile links, node mobility, and power outages, will require the network to operate despite frequent disconnections. To this end, opportunistic routing techniques have been proposed, where a node may store-and-carry a message for some time, until a new forwarding

  11. Spatial Heterogeneity in Mycorrhizal Populations and Communities: Scales and Mechanisms

    Microsoft Academic Search

    Benjamin E. Wolfe; Jeri L. Parrent; Alexander M. Koch; Benjamin A. Sikes; Monique Gardes; John N. Klironomos

    The importance of a spatial context in understanding the ecology and evolution of organisms has become increasingly clear.\\u000a Although there is a growing awareness of the importance of mycorrhizal fungi in many communities and ecosystems, much of this\\u000a understanding is based on a spatially homogenized view of these soil fungi. This homogenized approach may limit our understanding\\u000a of how these

  12. Host heterogeneity dominates West Nile virus transmission.

    PubMed

    Kilpatrick, A Marm; Daszak, Peter; Jones, Matthew J; Marra, Peter P; Kramer, Laura D

    2006-09-22

    Heterogeneity in host populations and communities can have large effects on the transmission and control of a pathogen. In extreme cases, a few individuals give rise to the majority of secondary infections, which have been termed super spreading events. Here, we show that transmission of West Nile virus (WNV) is dominated by extreme heterogeneity in the host community, resulting in highly inflated reproductive ratios. A single relatively uncommon avian species, American robin (Turdus migratorius), appeared to be responsible for the majority of WNV-infectious mosquitoes and acted as the species equivalent of a super spreader for this multi-host pathogen. Crows were also highly preferred by mosquitoes at some sites, while house sparrows were significantly avoided. Nonetheless, due to their relative rarity, corvids (crows and jays) were relatively unimportant in WNV amplification. These results challenge current beliefs about the role of certain avian species in WNV amplification and demonstrate the importance of determining contact rates between vectors and host species to understand pathogen transmission dynamics. PMID:16928635

  13. Heterogeneity of mesenchymal stromal cell preparations.

    PubMed

    Ho, A D; Wagner, W; Franke, W

    2008-01-01

    As an archetype of human adult stem cells that can readily be harvested, enriched and expanded in vitro, mesenchymal stromal cells (MSC) have been reported to be of significance for regenerative medicine. The literature is replete with reports on their developmental potentials in pre-clinical model systems. Different preparative protocols have been shown to yield MSC-like cell cultures or even cell lines, from starting materials as diverse as bone marrow, fat tissue, fetal cord blood and peripheral blood. However, MSC are still ill-defined by physical, phenotypic and functional properties. The quality of preparations from different laboratories varies tremendously and the cell products are notoriously heterogeneous. The source and freshness of the starting material, culture media used, presence of animal sera, cytokines, cell density, number of passages upon culture, etc., all have a significant impact on the (1) cell type components and heterogeneity of the initial population, (2) differential expansion of specific subsets, with different potentials of the end products, and (3) long-term functional fate of MSC as well as other types of progenitor cells that are co-cultivated with them. Consequently, there is an urgent need for the development of reliable reagents, common guidelines and standards for MSC preparations and of precise molecular and cellular markers to define subpopulations with diverse pathways of differentiation and divergent potentials. PMID:18574765

  14. Epigenetic heterogeneity in HIV-1 latency establishment.

    PubMed

    Matsuda, Yuka; Kobayashi-Ishihara, Mie; Fujikawa, Dai; Ishida, Takaomi; Watanabe, Toshiki; Yamagishi, Makoto

    2015-01-01

    Despite prolonged antiretroviral therapy, HIV-1 persists as transcriptionally inactive proviruses. The HIV-1 latency remains a principal obstacle in curing AIDS. It is important to understand mechanisms by which HIV-1 latency is established to make the latent reservoir smaller. We present a molecular characterization of distinct populations at an early phase of infection. We developed an original dual-color reporter virus to monitor LTR kinetics from establishment to maintenance stage. We found that there are two ways of latency establishment i.e., by immediate silencing and slow inactivation from active infection. Histone covalent modifications, particularly polycomb repressive complex 2 (PRC2)-mediated H3K27 trimethylation, appeared to dominate viral transcription at the early phase. PRC2 also contributes to time-dependent LTR dormancy in the chronic phase of the infection. Significant differences in sensitivity against several stimuli were observed between these two distinct populations. These results will expand our understanding of heterogeneous establishment of HIV-1 latency populations. PMID:25572573

  15. Epigenetic Heterogeneity in HIV-1 Latency Establishment

    PubMed Central

    Matsuda, Yuka; Kobayashi-Ishihara, Mie; Fujikawa, Dai; Ishida, Takaomi; Watanabe, Toshiki; Yamagishi, Makoto

    2015-01-01

    Despite prolonged antiretroviral therapy, HIV-1 persists as transcriptionally inactive proviruses. The HIV-1 latency remains a principal obstacle in curing AIDS. It is important to understand mechanisms by which HIV-1 latency is established to make the latent reservoir smaller. We present a molecular characterization of distinct populations at an early phase of infection. We developed an original dual-color reporter virus to monitor LTR kinetics from establishment to maintenance stage. We found that there are two ways of latency establishment i.e., by immediate silencing and slow inactivation from active infection. Histone covalent modifications, particularly polycomb repressive complex 2 (PRC2)-mediated H3K27 trimethylation, appeared to dominate viral transcription at the early phase. PRC2 also contributes to time-dependent LTR dormancy in the chronic phase of the infection. Significant differences in sensitivity against several stimuli were observed between these two distinct populations. These results will expand our understanding of heterogeneous establishment of HIV-1 latency populations. PMID:25572573

  16. Assessing Life Styles, Stressors and Health Status among a Predominantly African American On-Campus and Off-Campus Student Population

    ERIC Educational Resources Information Center

    Hicks, Terence; Herndon, Michael; Hilton, Adriel; Attoh, Prince; Armstrong, Vikki

    2013-01-01

    Students who attend college and reside on campus often have to contend with social problems such as alcohol and drug abuse, HIV/AIDS infection, courtship, sex and marriage, home and family and other social-psychological issues while trying to maintain academically and matriculate to graduation. Earlier research from the 1995 National College…

  17. The Elementary School Classroom. The Study of the Built Environment Through Student and Teacher Responses. The Elementary School and Its Population, Phase 2.

    ERIC Educational Resources Information Center

    Artinian, Vrej-Armen

    An extensive investigation of elementary school classrooms was conducted through the collection and statistical analysis of student and teacher responses to questions concerning the educational environment. Several asepcts of the classroom are discussed, including the spatial, thermal, luminous, and aural environments. Questions were organized so…

  18. The Effects of a Service-Learning Introductory Diversity Course on Pre-Service Teachers' Attitudes toward Teaching Diverse Student Populations

    ERIC Educational Resources Information Center

    Lucas, Dawn Jacoby

    2011-01-01

    This study examined the impact of a service-based course in diversity on pre-service teachers attitudes toward the inclusion of diverse learners (ethnically, socioeconomically, and disabled) in the general classroom. One-hundred and ten students at a private liberal arts university in North Carolina completed the Pluralism and Diversity Attitude…

  19. The Effect of Student Evaluations on Academic Success

    ERIC Educational Resources Information Center

    Artz, Benjamin; Welsch, David M.

    2013-01-01

    This article uses longitudinal student-level data from the American University of Sharjah, a large comprehensive university in the Middle East, to examine the relationship between student evaluations of teachers and current and future student achievement. Our model strategies control for the observed and unobserved heterogeneity of students and…

  20. Cellular Respiration and Population Growth

    NSDL National Science Digital Library

    2014-09-18

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

  1. Metastable dynamics in heterogeneous neural fields

    PubMed Central

    Schwappach, Cordula; Hutt, Axel; beim Graben, Peter

    2015-01-01

    We present numerical simulations of metastable states in heterogeneous neural fields that are connected along heteroclinic orbits. Such trajectories are possible representations of transient neural activity as observed, for example, in the electroencephalogram. Based on previous theoretical findings on learning algorithms for neural fields, we directly construct synaptic weight kernels from Lotka-Volterra neural population dynamics without supervised training approaches. We deliver a MATLAB neural field toolbox validated by two examples of one- and two-dimensional neural fields. We demonstrate trial-to-trial variability and distributed representations in our simulations which might therefore be regarded as a proof-of-concept for more advanced neural field models of metastable dynamics in neurophysiological data. PMID:26175671

  2. Population. Environmental Ecological Education Project.

    ERIC Educational Resources Information Center

    Parkway School District, Chesterfield, MO.

    This unit on population, designed for senior high school students, is divided into six packets with the following major topics: general introduction to the effects of a growing population, urbanization, family structures, family planning, consumption, environmental decay, and controlling the environment. Each packet contains a list of the topical…

  3. Reaction Selectivity in Heterogeneous Catalysis

    SciTech Connect

    Somorjai, Gabor A.; Kliewer, Christopher J.

    2009-02-02

    The understanding of selectivity in heterogeneous catalysis is of paramount importance to our society today. In this review we outline the current state of the art in research on selectivity in heterogeneous catalysis. Current in-situ surface science techniques have revealed several important features of catalytic selectivity. Sum frequency generation vibrational spectroscopy has shown us the importance of understanding the reaction intermediates and mechanism of a heterogeneous reaction, and can readily yield information as to the effect of temperature, pressure, catalyst geometry, surface promoters, and catalyst composition on the reaction mechanism. DFT calculations are quickly approaching the ability to assist in the interpretation of observed surface spectra, thereby making surface spectroscopy an even more powerful tool. HP-STM has revealed three vitally important parameters in heterogeneous selectivity: adsorbate mobility, catalyst mobility, and selective site-blocking. The development of size controlled nanoparticles from 0.8 to 10 nm, of controlled shape, and of controlled bimetallic composition has revealed several important variables for catalytic selectivity. Lastly, DFT calculations may be paving the way to guiding the composition choice for multi-metallic heterogeneous catalysis for the intelligent design of catalysts incorporating the many factors of selectivity we have learned.

  4. The Issue of Student Access: Fall 1990 to Fall 1993. Student Equity Report #1.

    ERIC Educational Resources Information Center

    Sanchez, Jorge R.

    The Coast Community College District (CCCD) in Southern California conducted a study to determine how representative the district and college student populations were of the primary service population. Recent increases in community college credit student fees significantly affected the defined student and service population. For the purpose of…

  5. Population crises and population cycles

    Microsoft Academic Search

    Claire Russell; W. M. S. Russell

    2000-01-01

    To prevent a population irretrievably depleting its resources, mammals have evolved a behavioural and physiological response to population crisis. When a mammalian population becomes dangerously dense, there is a reversal of behaviour. Co?operation and parental behaviour are replaced by competition, dominance and aggressive violence, leading to high mortality, especially of females and young, and a reduced population. The stress of

  6. Heterogeneity in host-parasitoid interactions: 'Aggregation of risk' and the 'CV(2) > 1 Rule'.

    PubMed

    Taylor, A D

    1993-11-01

    In host-parasitoid interactions the coefficient of variation (CV) of the risk of parasitism measures, at least approximately, the stabilizing influence of many forms of heterogeneity. This realization emphasizes the underlying similarity of these heterogeneities, and should end two decades of confusion about how to study them in nature. The first applications of this approach suggest that roughly one-third of systems studied show substantial measurable heterogeneity. Proper use of the CV measure, however, requires that the density-dependent processes linking this static phenomenon to temporal population dynamics also be examined; this has yet to be done for any system. PMID:21236211

  7. Static heterogeneities in liquid water

    NASA Astrophysics Data System (ADS)

    Stanley, H. Eugene; Buldyrev, Sergey V.; Giovambattista, Nicolas

    2004-10-01

    The thermodynamic behavior of water seems to be closely related to static heterogeneities. These static heterogeneities are related to the local structure of water molecules, and when properly characterized, may offer an economical explanation of thermodynamic data. The key feature of liquid water is not so much that the existence of hydrogen bonds, first pointed out by Linus Pauling, but rather the local geometry of the liquid molecules is not spherical or oblong but tetrahedral. In the consideration of static heterogeneities, this local geometry is critical. Recent experiments suggested more than one phase of amorphous solid water, while simulations suggest that one of these phases is metastable with respect to another, so that in fact there are only two stable phases.

  8. Understanding the consequences of seed dispersal in a heterogeneous environment.

    PubMed

    Baythavong, Brooke S; Stanton, Maureen L; Rice, Kevin J

    2009-08-01

    Plant distributions are in part determined by environmental heterogeneity on both large (landscape) and small (several meters) spatial scales. Plant populations can respond to environmental heterogeneity via genetic differentiation between large distinct patches, and via phenotypic plasticity in response to heterogeneity occurring at small scales relative to dispersal distance. As a result, the level of environmental heterogeneity experienced across generations, as determined by seed dispersal distance, may itself be under selection. Selection could act to increase or decrease seed dispersal distance, depending on patterns of heterogeneity in environmental quality with distance from a maternal home site. Serpentine soils, which impose harsh and variable abiotic stress on non-adapted plants, have been partially invaded by Erodium cicutarium in northern California, USA. Using nearby grassland sites characterized as either serpentine or non-serpentine, we collected seeds from dense patches of E. cicutarium on both soil types in spring 2004 and subsequently dispersed those seeds to one of four distances from their maternal home site (0, 0.5, 1, or 10 m). We examined distance-dependent patterns of variation in offspring lifetime fitness, conspecific density, soil availability, soil water content, and aboveground grass and forb biomass. ANOVA revealed a distinct fitness peak when seeds were dispersed 0.5 m from their maternal home site on serpentine patches. In non-serpentine patches, fitness was reduced only for seeds placed back into the maternal home site. Conspecific density was uniformly high within 1 m of a maternal home site on both soils, whereas soil water content and grass biomass were significantly heterogeneous among dispersal distances only on serpentine soils. Structural equation modeling and multigroup analysis revealed significantly stronger direct and indirect effects linking abiotic and biotic variation to offspring performance on serpentine soils than on non-serpentine soils, indicating the potential for soil-specific selection on seed dispersal distance in this invasive species. PMID:19739374

  9. Population Biology Graduate Group Bylaws of the Population Biology Graduate Group

    E-print Network

    Wainwright, Peter C.

    Population Biology Graduate Group Bylaws of the Population Biology Graduate Group Amended and Approved: February 1, 1994 I. Definition of the Graduate Group in Population Biology The purpose of this graduate group is to bring together faculty and graduate students interested in population biology

  10. Linguistic Minority Students Go to College: Preparation, Access, and Persistence

    ERIC Educational Resources Information Center

    Kanno, Yasuko, Ed.; Harklau, Linda, Ed.

    2012-01-01

    Currently, linguistic minority students--students who speak a language other than English at home--represent 21% of the entire K-12 student population and 11% of the college student population. Bringing together emerging scholarship on the growing number of college-bound linguistic minority students in the K-12 pipeline, this ground-breaking…

  11. Relating Single Cell Heterogeneity To Genotype During Cancer Progression

    NASA Astrophysics Data System (ADS)

    Rajaram, Satwik

    2013-03-01

    Progression of normal cells towards cancer is driven by a series of genetic changes. Traditional population-averaged measurements have found that cell signalling activities are increasingly altered during this progression. Despite the fact that cancer cells are known to be highly heterogeneous, the response of individual pathways to specific genetic changes remains poorly characterized at a single cell level. Do signalling alterations in a pathway reflect a shift of the whole population, or changes to specific subpopulations? Are alterations to pathways independent, or are cells with alterations in one pathway more likely to be abnormal in another due to crosstalk? We are building a computational framework that analyzes immunofluorescence microscopy images of cells to identify alterations in individual pathways at a single-cell level. A primary novelty of our approach is a ``change of basis'' that allows us to understand signalling in cancer cells in terms of the much better understood patterns of signalling in normal cells. This allows us to model heterogeneous populations of cancer cells as a mixture of distinct subpopulations, each with a specific combination of signalling pathways altered beyond the normal baseline. We used this framework to analyze human bronchial epithelial cell lines containing a series of genetic modifications commonly seen in lung cancer. We confirmed expected trends (such as a population-wide epithelial mesenchymal transition following the last of our series of modifications) and are presently studying the relation between the mutational profiles of cancer cells and pathway crosstalk. Our framework will help establish a more natural basis for future investigations into the phenotype-genotype relationship in heterogeneous populations.

  12. Faculty Perceptions of Students' Business Communication Needs

    Microsoft Academic Search

    Susan Plutsky

    1996-01-01

    Today's student populations comprise more minority students, more students for whom English is a second language, and more older students than in the past. These changes prompted this descriptive study in which business faculty members' perceptions about the business commumcation curriculum are examined. Faculty perceive their students to have problems with basic writing skills as well as with sophisticated writing

  13. Molecular characterization of heterogeneous mesenchymal stem cells with single-cell transcriptomes

    PubMed Central

    Li, Zhongjun; Zhang, Chao; Weiner, Leslie P.; Zhang, Yiqiang; Zhong, Jiang F.

    2013-01-01

    Mesenchymal stem cells (MSC) are heterogeneous cell populations with promising therapeutic potentials in regenerative medicine. The therapeutic values of MSC in various clinical situations have been reported. Clonal assays (expansion of MSC from a single cell) demonstrated that multiple types of cells with different developmental potential exist in a MSC population. Due to the heterogeneous nature of MSC, molecular characterization of MSC in the absence of known biomarkers is a challenge for cell therapy with MSC. Here, we review potential therapeutic applications of MSC and discuss a systematic approach for molecular characterization of heterogeneous cell population using single-cell transcriptome analysis. Differentiation/maturation of cells is orchestrated by sequential expression of a series of genes within a cell. Therefore, single-cell mRNA expression (transcriptome) profiles from consecutive developmental stages are more similar than those from disparate stages. Bioinformatic analysis can cluster single-cell transcriptome profiles from consecutive developmental stages into a dendrogram based on the similarity matrix of these profiles. Because a single-cell is an ultimately “pure” sample in expression profiling, these dendrograms can be used to classify individual cells into molecular subpopulations within a heterogeneous cell population without known biomarkers. This approach is especially powerful in studying cell populations with little molecular information and few known biomarkers, for example the MSC populations. The molecular understanding will provide novel targets for manipulating MSC differentiation with small molecules and other drugs to enable safer and more effective therapeutic applications of MSC. PMID:23266308

  14. Population Pasta

    NSDL National Science Digital Library

    This website is part of National Geographic's Xpeditions Hall and includes lesson plans and activities related to the topic of population statistics. It covers overpopulation problems, U.S. problems with population, how to interpret population statistics, and issues in India and China. These lesson plans were written by educators and have been tested in the classroom.

  15. Counting Populations

    ERIC Educational Resources Information Center

    Damonte, Kathleen

    2004-01-01

    Scientists use sampling to get an estimate of things they cannot easily count. A population is made up of all the organisms of one species living together in one place at the same time. All of the people living together in one town are considered a population. All of the grasshoppers living in a field are a population. Scientists keep track of the…

  16. Understanding Population.

    ERIC Educational Resources Information Center

    Mothner, Ira

    Activities and concerns of Ford Foundation supported population research and training centers are described in this report. The centers are concerned with population growth, consequences of growth for human welfare, forces that determine family planning, interrelations among population variables, economics of contraceptive distribution, and…

  17. Homogeneity and heterogeneity as situational properties: Producing – and moving beyond? – race in post-genomic science

    PubMed Central

    Shim, Janet K; Darling, Katherine Weatherford; Lappe, Martine D; Thomson, L Katherine; Lee, Sandra Soo-Jin; Hiatt, Robert A; Ackerman, Sara L

    2015-01-01

    In this article, we explore current thinking and practices around the logics of difference in gene–environment interaction research in the post-genomic era. We find that scientists conducting gene–environment interaction research continue to invoke well-worn notions of racial difference and diversity, but use them strategically to try to examine other kinds of etiologically significant differences among populations. Scientists do this by seeing populations not as inherently homogeneous or heterogeneous, but rather by actively working to produce homogeneity along some dimensions and heterogeneity along others in their study populations. Thus we argue that homogeneity and heterogeneity are situational properties – properties that scientists seek to achieve in their study populations, the available data, and other aspects of the research situation they are confronting, and then leverage to advance post-genomic science. Pointing to the situatedness of homogeneity and heterogeneity in gene–environment interaction research underscores the work that these properties do and the contingencies that shape decisions about research procedures. Through a focus on the situational production of homogeneity and heterogeneity more broadly, we find that gene–environment interaction research attempts to shift the logic of difference from solely racial terms as explanatory ends unto themselves, to racial and other dimensions of difference that may be important clues to the causes of complex diseases. PMID:25272613

  18. Heterogeneous porous media in hydrology

    NASA Astrophysics Data System (ADS)

    Ababou, Rachid

    In natural geologic formations, flow and transport-related processes are perturbed by multidimensional and anisotropic material heterogeneities of diverse sizes, shapes, and origins (bedding, layering, inclusions, fractures, grains, for example). Heterogeneity tends to disperse and mix transported quantities and may initiate new transfer mechanisms not seen in ideally homogeneous porous media. Effective properties such as conductivity and dispersivity may not be simple averages of locally measured quantities.The special session, “Effective Constitutive Laws for Heterogeneous Porous Media,” convened at AGU's 1992 Fall Meeting in San Francisco, addressed these issue. Over forty-five contributions, both oral and poster, covering a broad range of physical phenomena were presented. The common theme was the macroscale characterization and modeling of flow and flow-related processes in geologic media that are heterogeneous at various scales (from grain size or fracture aperture, up to regional scales). The processes analyzed in the session included coupled hydro-mechanical processes; Darcy-type flow in the saturated, unsaturated, or two-phase regimes; tracer transport, dilution, and dispersion. These processes were studied for either continuous (porous) or discontinuous (fractured) media.

  19. Teaching about Heterogeneous Response Models

    ERIC Educational Resources Information Center

    Murray, Michael P.

    2014-01-01

    Individuals vary in their responses to incentives and opportunities. For example, additional education will affect one person differently than another. In recent years, econometricians have given increased attention to such heterogeneous responses and to the consequences of such responses for interpreting regression estimates, especially…

  20. Marketing models of consumer heterogeneity

    Microsoft Academic Search

    Greg M. Allenby; Peter E. Rossi

    1999-01-01

    The distribution of consumer preferences plays a central role in many marketing activities. Pricing and product design decisions, for example, are based on an understand- ing of the di?erences among consumers in price sensitivity and valuation of product attributes. In addition, marketing activities which target specific households require household level parameter estimates. Thus, the modeling of consumer heterogeneity is the

  1. Adrenoleukodystrophy: heterogeneity in two brothers

    Microsoft Academic Search

    G M Elrington; D E Bateman; M J Jeffrey; N F Lawton

    1989-01-01

    A man with hypoadrenalism died from a rapidly progressive pseudobulbar palsy, due to adult onset adrenoleukodystrophy. This diagnosis suggested that his brother, with a longstanding spastic paraparesis, suffered from adrenomyeloneuropathy. Both cases were confirmed biochemically. The heterogeneity of expression of this x-linked disorder is described, with the consequent difficulty in diagnosis and nomenclature.

  2. Adrenoleukodystrophy: heterogeneity in two brothers.

    PubMed Central

    Elrington, G M; Bateman, D E; Jeffrey, M J; Lawton, N F

    1989-01-01

    A man with hypoadrenalism died from a rapidly progressive pseudobulbar palsy, due to adult onset adrenoleukodystrophy. This diagnosis suggested that his brother, with a longstanding spastic paraparesis, suffered from adrenomyeloneuropathy. Both cases were confirmed biochemically. The heterogeneity of expression of this x-linked disorder is described, with the consequent difficulty in diagnosis and nomenclature. Images PMID:2538572

  3. Special Education and Student Services.

    ERIC Educational Resources Information Center

    Brazeau, Karen; And Others

    This report examines the current status and plans for special education, student services, and special projects and studies in Oregon. The first section offers an overview of special education long-range planning in secondary and transition programs, the student population with severe emotional disturbance, low incidence populations, families, the…

  4. Brandeis University International Student & Scholar

    E-print Network

    Snider, Barry B.

    Finance 33 81 114 Genetic Counseling 3 2 5 General Studies/Undeclared 251 251 Health Policy / Management 7 OF CONTENTS OVERVIEW OF INTERNATIONAL STUDENT & SCHOLAR POPULATION | 3 DETAILED INFORMATION ON INTERNATIONAL STUDENT POPULATION | 4 Basic Data | 4 Academic Level | 4 School | 4 New & Continuing Enrollments | 4 Visa

  5. Instructing African American Students.

    ERIC Educational Resources Information Center

    Young, Clara Y.; Wright, James V.; Laster, Joseph

    2005-01-01

    Closing the educational achievement gap has been a schooling issue since Brown v. Board of Topeka, Kansas decision. Generally, the learning achievement of elementary and secondary African-American student has been an issue in majority school populations across the United States. And evidence of performance of these students appears to be more…

  6. Scaling laws for heterogeneous wireless networks

    E-print Network

    Niesen, Urs

    2009-01-01

    This thesis studies the problem of determining achievable rates in heterogeneous wireless networks. We analyze the impact of location, traffic, and service heterogeneity. Consider a wireless network with n nodes located ...

  7. Are family, neighbourhood and school social capital associated with higher self-rated health among Croatian high school students? A population-based study

    PubMed Central

    Novak, Dario; Suzuki, Etsuji; Kawachi, Ichiro

    2015-01-01

    Objectives We investigated the associations between self-rated health and social capital among Croatian high school students. Design A cross-sectional survey among high school students was carried out in the 2013–2014 school year. Setting High schools in Croatia. Participants Subjects were 3427 high school students (1688 males and 1739 females), aged 17–18?years. Main outcome measure Self-rated health was assessed by the single item: “How do you perceive your health?”. Possible responses were arranged along a five-item Likert-type scale: 1 very poor, 2 poor, 3 fair, 4 good, 5 excellent. The outcome was binarised as ‘good health’ (excellent, good or fair) versus ‘poor health’ (poor or very poor). Methods We calculated ORs and 95% CIs for good self-rated health associated with family, neighbourhood and school social capital, while adjusting for gender, self-perceived socioeconomic status, psychological distress, physical activity and body mass index. We used generalised estimating equations using an exchangeable correlation matrix with robust SEs. Results Good self-rated health was significantly associated with higher family social capital (OR 2.43; 95% CI 1.55 to 3.80), higher neighbourhood trust (OR 2.02; 95% CI 1.48 to 2.76) and higher norms of reciprocity at school (OR 1.79; 95% CI 1.13 to 2.84). When all of the social capital variables were entered simultaneously, good self-rated health remained significantly associated with higher family social capital (OR 1.98; 95% CI 1.19 to 3.30), neighbourhood trust (OR 1.77; 95% CI 1.25 to 2.51) and reciprocity at school (OR 1.71; 95% CI 1.08 to 2.73). Conclusions Higher levels of social capital were independently associated with higher self-rated health among youth. Intervention and policies that leverage community social capital might serve as an avenue for health promotion in youth. PMID:26056122

  8. US Populations

    NSDL National Science Digital Library

    1998-01-01

    The SEER (Surveillance, Epidemiology, and End Results) Program of the National Cancer Institute has recently released this collection of US population data files. The collection includes data files for county level populations from 1973 to 1996 for every state in the US. Data files containing the total US population from 1973 to 1996 as well as files containing total populations for each state from 1973 to 1996 are also included. The data are available for downloading in ASCII format as self-extracting DOS executable files. Users should note that documentation for the population data files is in .pdf format.

  9. Population Growth

    NSDL National Science Digital Library

    2009-01-01

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

  10. Population Explosion

    NSDL National Science Digital Library

    The Concord Consortium

    2012-01-13

    Many factors influence the success and survival rate of a population of living things. Explore several factors that can determine the survival of a population of sheep in this NetLogo model. Start with a model of unlimited grass available to the sheep and watch what happens to the sheep population! Next try to keep the population under control by removing sheep periodically. Change the birthrate, grass regrowth rate, and the amount of energy rabbits get from the grass to keep a stable population.

  11. Population Structures and Cohorts

    NSDL National Science Digital Library

    Kyle Crowder

    This activity is used in a Populations Problems class for undergraduate students. This activity looks at population in the in the 1990s and the labor force and educational attainment over time in the United States. This activity uses four customized data sets; one made from the 1990 census and three made from census trend data combining census information from 1950-1990. It guides students through data manipulation using WebCHIP software found at DataCounts!. To open WebCHIP with the dataset for the activity, please see instructions and links in the exercise documents under teaching materials. For more information on how to use WebCHIP, see the How To section on DataCounts!

  12. Biosystematic studies on Capsella bursa-pastoris ( Brassicaceae ): Enzyme polymorphism in natural populations

    Microsoft Academic Search

    Klaus Bosbach; Herbert Hurka

    1981-01-01

    The genetic variability of natural populations ofCapsella bursapastoris in North- and Middle-Europe has been estimated by means of enzyme assays. Zymograms of 81 populations have been developed. 17 loci could be identified, and 8 of them can be heterozygous. Genetic variability is greater between populations than within. No correlation between actual population sizes and genetic heterogeneity could be detected. Some

  13. Exploiting Heterogeneity for Sensor Network Security

    Microsoft Academic Search

    Jens Mache; Chieh-yih Wan; Mark D. Yarvis

    2008-01-01

    Many sensor network deployments are heterogeneous: a large number of regular nodes perform sensing, while some nodes have better energy resources and\\/or more computational capacity. Whereas the effect of heterogeneous nodes on network reliability and lifetime has been studied [3], we here focus on exploiting heterogeneity for security. For security and privacy, the identity of nodes must be authenticated and

  14. Modeling the Energy Efficiency of Heterogeneous Clusters

    E-print Network

    Teo, Yong-Meng

    Modeling the Energy Efficiency of Heterogeneous Clusters Lavanya Ramapantulu, Bogdan Marius Tudor allocation on heterogeneous clusters ­ Throughput vs. power [Heath et al. 2005] ­ Pikachu: dynamic load on heterogeneous clusters ­ Unexplored from energy-time performance perspective 10-Sep-14 ICPP 2014 7 #12;Objective

  15. Understanding cancer stem cell heterogeneity and plasticity

    Microsoft Academic Search

    Dean G Tang

    2012-01-01

    Heterogeneity is an omnipresent feature of mammalian cells in vitro and in vivo. It has been recently realized that even mouse and human embryonic stem cells under the best culture conditions are heterogeneous containing pluripotent as well as partially committed cells. Somatic stem cells in adult organs are also heterogeneous, containing many subpopulations of self-renewing cells with distinct regenerative capacity.

  16. Geophysics of Chemical Heterogeneity in the Mantle

    E-print Network

    Stixrude, Lars

    , transition zone Abstract Chemical heterogeneity, produced by the near-surface rock cycle and dom- inated.annualreviews.org byUniversityCollegeLondonon12/06/12.Forpersonaluseonly. #12;MANTLE HETEROGENEITY, THE ROCK CYCLE, AND PLATE TECTONICS The rock cycle is a heterogeneity-producing engine that serves as the cornerstone

  17. The dangers of heterogeneous network computing: heterogeneous networks considered harmful

    SciTech Connect

    Demmel, J.; Stanley, K. [California Univ., Berkeley, CA (United States); Dongarra, J. [Oak Ridge National Lab., TN (United States); Hammarling, S.; Osstrouchov, S. [Tennessee Univ., Knoxville, TN (United States)

    1996-12-31

    This report addresses the issue of writing reliable numerical software for networks of heterogeneous computers. Much software has been written for distributed memory parallel computers and in principal such software could readily be ported to networks of machines, such as a collection of workstations connected by Ethernet, but if such a network is not homogeneous there are special challenges that need to be addressed. The symptoms can range from erroneous results returned without warning to deadlock. Some of the problems are straightforward to solve, but for others the solutions are not so obvious and indeed in some cases, such as the method of bisection which we shall discuss in the report, we have not yet decided upon a satisfactory solution that does not incur an unacceptable overhead. Making software robust on heterogeneous systems often requires additional communication. In this report we describe and illustrate the problems and, where possible, suggest solutions so that others may be aware of the potential pitfalls and either avoid them or, if that is not possible, ensure that their software is not used on heterogeneous networks.

  18. Population Index

    NSDL National Science Digital Library

    Two excellent bibliographic resources for population studies are the "Population Index" from the Office of Population Research at Princeton University, and "Population Organizations: Finder's Guide" from the Center for Demography and Ecology at the University of Wisconsin-Madison. "Population Index" is a quarterly publication that has been available since 1935. It "covers all fields of interest to demographers, including fertility, mortality, population size and growth, migration, nuptiality and the family, research methodology, projections and predictions, historical demography, and demographic and economic interrelations. Input is derived from original publications including monographs, journal articles, other serial publications, working papers, doctoral dissertations, machine-readable data files, and relevant acquisitions lists and bibliographies." About 3,500 citations are produced annually. Full text for the Index is available at the "Population Index" Web site for 1986-present (Vol. 52-present). Indexes can be searched by author, subject matter, geographical region, or publication year. There is now an experimental free text search capability for the 1994-present issues. "Population Organizations: Finder's Guide" is a no frills "practical tool for population professionals who need a single source for the quick location of organizations that publish and distribute or post population or family planning documents." It contains hundreds of citations, providing organization addresses, phone and FAX numbers, and Internet addresses when available. The Guide is updated every six months and is maintained by Ruth Sandor, Director of the Library of the Center for Demography and Ecology. Office of Population Research, Princeton University: http://opr.princeton.edu/ "Population Organizations: Finder's Guide": gopher://cde2.ssc.wisc.edu:70/00/addazlis gopher to: cde2.ssc.wisc.edu select: Population Organizations: Finder's Guide Center for Demography and Ecology, University of Wisconsin-Madison: http://www.ssc.wisc.edu/cde/

  19. Community Health Nursing Student Experience in Nicaragua

    Microsoft Academic Search

    Rita L. Ailinger; Suzanne B. Molloy; Elida Ramirez Sacasa

    2009-01-01

    International clinical experiences can provide excellent opportunities for nursing students to practice community health nursing, enhance their global perspective, and increase their cultural awareness of vulnerable populations. Selected students from the Georgetown University nursing program spent part of their winter intercession in Nicaragua, working with a vulnerable population in an impoverished community. Students cared for families, worked in clinics, conducted

  20. Assembling thefacebook: Using heterogeneity to understand online social network assembly

    E-print Network

    Jacobs, Abigail Z; Ugander, Johan; Clauset, Aaron

    2015-01-01

    Online social networks represent a popular and highly diverse class of social media systems. Despite this variety, each of these systems undergoes a general process of online social network assembly, which represents the complicated and heterogeneous changes that transform newly born systems into mature platforms. However, little is known about this process. For example, how much of a network's assembly is driven by simple growth? How does a network's structure change as it matures? How does network structure vary with adoption rates and user heterogeneity, and do these properties play different roles at different points in the assembly? We investigate these and other questions using a unique dataset of online connections among the roughly one million users at the first 100 colleges admitted to Facebook, captured just 20 months after its launch. We first show that different vintages and adoption rates across this population of networks reveal temporal dynamics of the assembly process, and that assembly is onl...

  1. A mathematical model of subpopulation kinetics for the deconvolution of leukaemia heterogeneity.

    PubMed

    Fuentes-Garí, María; Misener, Ruth; García-Munzer, David; Velliou, Eirini; Georgiadis, Michael C; Kostoglou, Margaritis; Pistikopoulos, Efstratios N; Panoskaltsis, Nicki; Mantalaris, Athanasios

    2015-07-01

    Acute myeloid leukaemia is characterized by marked inter- and intra-patient heterogeneity, the identification of which is critical for the design of personalized treatments. Heterogeneity of leukaemic cells is determined by mutations which ultimately affect the cell cycle. We have developed and validated a biologically relevant, mathematical model of the cell cycle based on unique cell-cycle signatures, defined by duration of cell-cycle phases and cyclin profiles as determined by flow cytometry, for three leukaemia cell lines. The model was discretized for the different phases in their respective progress variables (cyclins and DNA), resulting in a set of time-dependent ordinary differential equations. Cell-cycle phase distribution and cyclin concentration profiles were validated against population chase experiments. Heterogeneity was simulated in culture by combining the three cell lines in a blinded experimental set-up. Based on individual kinetics, the model was capable of identifying and quantifying cellular heterogeneity. When supplying the initial conditions only, the model predicted future cell population dynamics and estimated the previous heterogeneous composition of cells. Identification of heterogeneous leukaemia clones at diagnosis and post-treatment using such a mathematical platform has the potential to predict multiple future outcomes in response to induction and consolidation chemotherapy as well as relapse kinetics. PMID:26040591

  2. Effective toughness of heterogeneous media

    NASA Astrophysics Data System (ADS)

    Hossain, M. Z.; Hsueh, C.-J.; Bourdin, B.; Bhattacharya, K.

    2014-11-01

    We propose a versatile approach to computing the effective toughness of heterogeneous media. This approach focusses on the material property independent of the details of the boundary condition. The key idea is what we call a surfing boundary condition, where a steadily propagating crack opening displacement is applied as a boundary condition to a large domain while the crack set is allowed to evolve as it chooses. The approach is verified and used to study examples in brittle fracture. We demonstrate that effective toughness is different from effective or weighted surface area of the crack set. Furthermore, we demonstrate that elastic heterogeneity can have a profound effect on fracture toughness: it can be a significant toughening mechanism and it can lead to toughness asymmetry wherein the toughness depends not only on the direction but also on the sense of propagation. The role of length-scale is also discussed.

  3. MS/PhD Population Health Graduate Program

    E-print Network

    Sheridan, Jennifer

    MS/PhD Population Health Graduate Program CURRENT UW-MADISON GRADUATE STUDENTS APPLYING FOR THE POPULATION HEALTH PROGRAM A current graduate student at UW-Madison can apply for the MS or PhD graduate program in Population Health Sciences. Your first step is to contact the Graduate Program Coordinator

  4. Population and Climate Change

    NASA Astrophysics Data System (ADS)

    O'Neill, Brian C.; Landis MacKellar, F.; Lutz, Wolfgang

    2000-11-01

    Population and Climate Change provides the first systematic in-depth treatment of links between two major themes of the 21st century: population growth (and associated demographic trends such as aging) and climate change. It is written by a multidisciplinary team of authors from the International Institute for Applied Systems Analysis who integrate both natural science and social science perspectives in a way that is comprehensible to members of both communities. The book will be of primary interest to researchers in the fields of climate change, demography, and economics. It will also be useful to policy-makers and NGOs dealing with issues of population dynamics and climate change, and to teachers and students in courses such as environmental studies, demography, climatology, economics, earth systems science, and international relations.

  5. Integrating heterogeneous network monitoring data

    Microsoft Academic Search

    Chi Zhang; Bin Liu; Xun Su; Heidi L. Alvarez; Julio Ibarra

    2008-01-01

    In this paper, we investigate the integration of heterogeneous network monitoring data. Specifically, we will synchronize and integrate flow-level records, exemplified by Cisco NetFlow, and packet-level traces, exemplified by NLANR PMA. The integration can facilitate cross-validation and complementary utility. However, finding the correspondences of timestamps\\/flows\\/packets between the PMA and Netflow is non-trivial, because they have different levels of granularity, different

  6. Molecular mechanism of heterogeneous catalysis

    Microsoft Academic Search

    R. S. Swathi; K. L. Sebastian

    2008-01-01

    Gerhard Ertl, the German physical chemist, was awarded the Nobel Prize in chemistry for the year 2007, for his contributions\\u000a in the area of surface science. His painstaking work led to a microscopic understanding of heterogeneous catalysis in industrially\\u000a important chemical reactions. These include the Haber-Bosch process for the production of ammonia, and the catalytic oxidation\\u000a of carbon monoxide.

  7. The Impact of Homogeneous vs. Heterogeneous Collaborative Learning Groups in Multicultural Classes on the Achievement and Attitudes of Nine Graders towards Learning Science

    ERIC Educational Resources Information Center

    Faris, Ahmed O.

    2009-01-01

    The current study aims at investigating the impact of homogeneous versus heterogeneous collaborative learning grouping in multicultural classes on the students' achievements and attitudes towards learning science. In the present study, heterogeneity was unpacked through two dimensions: the cultural background, represented by the different…

  8. Soft Dielectrics: Heterogeneity and Instabilities

    NASA Astrophysics Data System (ADS)

    Rudykh, Stephan; Debotton, Gal; Bhattacharya, Kaushik

    2012-02-01

    Dielectric Elastomers are capable of large deformations in response to electrical stimuli. Heterogeneous soft dielectrics with proper microstructures demonstrate much stronger electromechanical coupling than their homogeneous constituents. In turn, the heterogeneity is an origin for instability developments leading to drastic change in the composite microstructure. In this talk, the electromechanical instabilities are considered. Stability of anisotropic soft dielectrics is analyzed. Ways to achieve giant deformations and manipulating extreme material properties are discussed. 1. S. Rudykh and G. deBotton, ``Instabilities of Hyperelastic Fiber Composites: Micromechanical Versus Numerical Analyses.'' Journal of Elasticity, 2011. http://dx.doi.org/2010.1007/s10659-011-9313-x 2. S. Rudykh, K. Bhattacharya and G. deBotton, ``Snap-through actuation of thick-wall electroactive balloons.'' International Journal of Non-Linear Mechanics, 2011. http://dx.doi.org/10.1016/j.ijnonlinmec.2011.05.006 3. S. Rudykh and G. deBotton, ``Stability of Anisotropic Electroactive Polymers with Application to Layered Media.'' Zeitschrift f"ur angewandte Mathematik und Physik, 2011. http://dx.doi.org/10.1007/s00033-011-0136-1 4. S. Rudykh, A. Lewinstein, G. Uner and G. deBotton, ``Giant Enhancement of the Electromechanical Coupling in Soft Heterogeneous Dielectrics.'' 2011 http://arxiv.org/abs/1105.4217v1

  9. Heterogeneity of chromosome 17 and erbB-2 gene copy number in primary and metastatic bladder cancer

    SciTech Connect

    Sauter, G.; Mihatsch, M.J.; Gasser, T.C. [Univ. of Basel (Switzerland)

    1995-09-01

    To study the relationship of tumor genomic heterogeneity with bladder cancer phenotype and p53 gene alterations, 139 primary bladder tumors were examined by dual labeling fluorescence in situ hybridization (FISH) using probes for chromosome 17 centromere (p17H8) and p53 (17p13.1). The number of different aneusomic populations >5% (and monosomic populations >20%) of cells served as a marker for heterogeneity. Nuclear p53 overexpression and Ki67 labeling index (Ki67 LI) were determined by immunohistochemistry. The number of aneusomic populations was 0 in 53 tumors, 1 in 18, 2 in 47, 3 in 9, and >3 in 11 tumors. Presence of aneusomy was associated with tumor grade and stage (P < 0.0001 each). Ki67 LI was low in disomic tumors (11.0 {+-} 7.7), higher in tumors with 1-3 aneusomic populations (17.4 {+-} 11.3), and highest in tumors with >3 aneusomic populations (25.8 {+-} 10.9; P = 0.02 for >3 vs. 1-3 populations). Aneusomy and heterogeneity were associated with p53 alterations. Aneusomy was seen in 35% of tumors with neither p53 expression nor p53 deletion but in 97% of tumors with both p53 deletion and expression. Nine of 11 tumors with >3 aneusomic populations exhibited both p53 deletion and overexpression. To study genomic heterogeneity in tumor progression, two recurrences and three metastases of a tumor with known erbB-2 amplification were examined for centromere 17 and erbB-2 copy number. A considerable heterogeneity in centromere 17 and erbB-2 gene copy number was found in both recurrences and metastases, indicating a marked genomic instability in these metastatic cells. These results show that genomic heterogeneity is common in bladder cancer. Highly heterogeneous tumors might represent a particularly aggressive subtype of bladder carcinoma. 28 refs., 4 figs., 3 tabs.

  10. Population Biology: How Do Populations Change Over Time?

    NSDL National Science Digital Library

    This classroom activity asks students to consider the question: "How do populations change over time?" The material is adaptable and may be used for grades K-12. The activity demonstrates the process of natural selection. The class will "perform a simulation of a population of fictional birds as they try to survive through several generations after a drastic change in their environment." Students will learn more about the concepts of natural selection, adaptation, genetic diversity, variation and carrying capacity. In addition to the main classroom activity, a knowledge mapping exercise, alternative ideas for instructors, a glossary and a lesson SemNet are included.

  11. Genetic variability and population structure of Poecilia latipinna

    Microsoft Academic Search

    Dan E. Simanek

    1978-01-01

    THE pattern of genetic variability among natural populations is commonly attributed to the influence of environmental heterogeneity on natural selection1,2. However, I report here that in Poecilia latipinna (Pisces: Poeciliidae), a small ovoviviparous fish, genetic variability is more closely related to local population structure, in particular, the adult sex ratio.

  12. Forecasting spatially structured populations: the role of dispersal and scale

    Microsoft Academic Search

    Cailin Xu; Mark S. Boyce; Madhav Gadgil; Vidyanand Nanjundiah

    2005-01-01

    We forecasted spatially structured population models with complex dynamics, focusing on the effect of dispersal and spatial scale on the predictive capability of nonlinear forecasting (NLF). Dispersal influences NLF ability by its influence on population dynamics. For simple 2-cell models, when dispersal is small, our ability to predict abundance in subpopulations decreased and then increased with increasing dispersal. Spatial heterogeneity,

  13. Population dynamics of bacterial persistence.

    PubMed

    Patra, Pintu; Klumpp, Stefan

    2013-01-01

    Persistence is a prime example of phenotypic heterogeneity, where a microbial population splits into two distinct subpopulations with different growth and survival properties as a result of reversible phenotype switching. Specifically, persister cells grow more slowly than normal cells under unstressed growth conditions, but survive longer under stress conditions such as the treatment with bactericidal antibiotics. We analyze the population dynamics of such a population for several typical experimental scenarios, namely a constant environment, shifts between growth and stress conditions, and periodically switching environments. We use an approximation scheme that allows us to map the dynamics to a logistic equation for the subpopulation ratio and derive explicit analytical expressions for observable quantities that can be used to extract underlying dynamic parameters from experimental data. Our results provide a theoretical underpinning for the study of phenotypic switching, in particular for organisms where detailed mechanistic knowledge is scarce. PMID:23675428

  14. Influence of Multiple Factors on Insect Colonization of Heterogeneous Landscapes: A Review and Case Study with Periodical Cicadas (Homoptera: Cicadidae)

    Microsoft Academic Search

    William M. Cook; Robert D. Holt

    2006-01-01

    The literature on herbivorous insects in heterogeneous habitats has addressed insect population responses to patch size, distance from source populations, habitat edges, and variation in host stem density. Studies typically conclude that insect colonists respond positively to the area of host plant patches, but there is little consensus on how insects respond to variation in host density at the patch

  15. Evolution of intratumoral phenotypic heterogeneity: the role of trait inheritance

    PubMed Central

    Gallaher, Jill; Anderson, Alexander R. A.

    2013-01-01

    A tumour is a heterogeneous population of cells that competes for limited resources. In the clinic, we typically probe the tumour by biopsy, and then characterize it by the dominant genetic clone. But genotypes are only the first link in the chain of hierarchical events that leads to a specific cell phenotype. The relationship between genotype and phenotype is not simple, and the so-called genotype to phenotype map is poorly understood. Many genotypes can produce the same phenotype, so genetic heterogeneity may not translate directly to phenotypic heterogeneity. We therefore choose to focus on the functional endpoint, the phenotype as defined by a collection of cellular traits (e.g. proliferative and migratory ability). Here, we will examine how phenotypic heterogeneity evolves in space and time and how the way in which phenotypes are inherited will drive this evolution. A tumour can be thought of as an ecosystem, which critically means that we cannot just consider it as a collection of mutated cells but more as a complex system of many interacting cellular and microenvironmental elements. At its simplest, a growing tumour with increased proliferation capacity must compete for space as a limited resource. Hypercellularity leads to a contact-inhibited core with a competitive proliferating rim. Evolution and selection occurs, and an individual cell's capacity to survive and propagate is determined by its combination of traits and interaction with the environment. With heterogeneity in phenotypes, the clone that will dominate is not always obvious as there are both local interactions and global pressures. Several combinations of phenotypes can coexist, changing the fitness of the whole. To understand some aspects of heterogeneity in a growing tumour, we build an off-lattice agent-based model consisting of individual cells with assigned trait values for proliferation and migration rates. We represent heterogeneity in these traits with frequency distributions and combinations of traits with density maps. How the distributions change over time is dependent on how traits are passed on to progeny cells, which is our main enquiry. We bypass the translation of genetics to behaviour by focusing on the functional end result of inheritance of the phenotype combined with the environmental influence of limited space. PMID:24511380

  16. Educational Goals of Teachers in Heterogeneous and Homogeneous Classes in Elementary and Junior High Schools.

    ERIC Educational Resources Information Center

    Rich, Yisrael

    1993-01-01

    Teachers of low-achieving homogeneous, high-achieving homogeneous, and academically heterogeneous classes in elementary and junior high schools in Israel were interviewed to determine their allegiance to academic, personal, and social goals for students. In contrast to results of U.S. research, academic goals dominated for teachers in all…

  17. Cooperative CBI: The Effects of Heterogeneous versus Homogeneous Grouping on the Learning of Progressively Complex Concepts.

    ERIC Educational Resources Information Center

    Hooper, Simon; Hannafin, Michael J.

    1988-01-01

    Describes study that compared the achievement of high and low ability eighth-grade students working cooperatively during computer-based instruction. Homogeneous and heterogeneous grouping based on ability are explained, posttest results are analyzed, and implications for instructional design are discussed. (23 references) (Author/LRW)

  18. Phenotypic Heterogeneity, a Phenomenon That May Explain Why Quorum Sensing Does Not Always Result in Truly Homogenous Cell Behavior.

    PubMed

    Grote, Jessica; Krysciak, Dagmar; Streit, Wolfgang R

    2015-08-15

    Phenotypic heterogeneity describes the occurrence of "nonconformist" cells within an isogenic population. The nonconformists show an expression profile partially different from that of the remainder of the population. Phenotypic heterogeneity affects many aspects of the different bacterial lifestyles, and it is assumed that it increases bacterial fitness and the chances for survival of the whole population or smaller subpopulations in unfavorable environments. Well-known examples for phenotypic heterogeneity have been associated with antibiotic resistance and frequently occurring persister cells. Other examples include heterogeneous behavior within biofilms, DNA uptake and bacterial competence, motility (i.e., the synthesis of additional flagella), onset of spore formation, lysis of phages within a small subpopulation, and others. Interestingly, phenotypic heterogeneity was recently also observed with respect to quorum-sensing (QS)-dependent processes, and the expression of autoinducer (AI) synthase genes and other QS-dependent genes was found to be highly heterogeneous at a single-cell level. This phenomenon was observed in several Gram-negative bacteria affiliated with the genera Vibrio, Dinoroseobacter, Pseudomonas, Sinorhizobium, and Mesorhizobium. A similar observation was made for the Gram-positive bacterium Listeria monocytogenes. Since AI molecules have historically been thought to be the keys to homogeneous behavior within isogenic populations, the observation of heterogeneous expression is quite intriguing and adds a new level of complexity to the QS-dependent regulatory networks. All together, the many examples of phenotypic heterogeneity imply that we may have to partially revise the concept of homogeneous and coordinated gene expression in isogenic bacterial populations. PMID:26025903

  19. Population crises and population cycles.

    PubMed

    Russell, C; Russell, W M

    2000-01-01

    To prevent a population irretrievably depleting its resources, mammals have evolved a behavioural and physiological response to population crisis. When a mammalian population becomes dangerously dense, there is a reversal of behaviour. Co-operation and parental behaviour are replaced by competition, dominance and aggressive violence, leading to high mortality, especially of females and young, and a reduced population. The stress of overpopulation and the resulting violence impairs both the immune and the reproductive systems. Hence epidemics complete the crash of the population, and reproduction is slowed for three or four generations, giving the resources ample time to recover. In some mammal species, crisis and crisis response recur regularly, leading to cycles of population growth and relapse, oscillating about a fixed mean. Population crisis response and population cycles have been equally prominent in the history of human societies. But in man successive advances in food production have made possible growing populations, though with every such advance population soon outgrew resources again. Hence human cycles have been superimposed on a rising curve, producing a saw-tooth graph. Because advances in food production amounted to sudden disturbances in the relations between human populations and their environments, the crisis response in man has failed to avert famine and resource damage. In the large human societies evolved since the coming of settled agriculture and cities, the basic effects of violence, epidemics, famine and resource damage have been mediated by such specifically human disasters as inflation, unemployment, and political tyranny. An account of past crises, periods of relative relief from population pressure, and resulting cycles, is given for a number of regions: China, North Africa and Western Asia, the northern Mediterranean, and north-western Europe. The paper ends with an account of the present world-wide population crisis, and the solution made possible by Malthus's discovery that, unlike animals, we can choose to check population growth by reducing the birth-rate, instead of raising the death-rate, as in other mammals, by the population crisis response. PMID:11130632

  20. Heterogeneous persister cells formation in Acinetobacter baumannii.

    PubMed

    Barth, Valdir Cristóvão; Rodrigues, Belisa Ávila; Bonatto, Grasiela Daiane; Gallo, Stephanie Wagner; Pagnussatti, Vany Elisa; Ferreira, Carlos Alexandre Sanchez; de Oliveira, Sílvia Dias

    2013-01-01

    Bacterial persistence is a feature that allows susceptible bacteria to survive extreme concentrations of antibiotics and it has been verified in a number of species, such as Escherichia coli, Pseudomonas aeruginosa, Staphylococcus spp., Mycobacterium spp. However, even though Acinetobacter baumannii is an important nosocomial pathogen, data regarding its persistence phenotype are still lacking. Therefore, the aim of this study was to evaluate the persistence phenotype in A. baumannii strains, as well as its variation among strains after treatment with polymyxin B and tobramycin. Stationary cultures of 37 polymyxin B-susceptible clinical strains of A. baumannii were analyzed for surviving cells after exposure to 15 µg/mL of polymyxin B for 6 h, by serial dilutions and colony counting. Among these, the 30 tobramycin-susceptible isolates also underwent tobramycin treatment at a concentration of 160 µg/mL and persister cells occurrence was evaluated equally. A high heterogeneity of persister cells formation patterns among isolates was observed. Polymyxin B-treated cultures presented persister cells corresponding from 0.0007% to 10.1% of the initial population and two isolates failed to produce detectable persister cells under this condition. A high variability could also be observed when cells were treated with tobramycin: the persister fraction corresponded to 0.0003%-11.84% of the pre-treatment population. Moreover, no correlation was found between persister subpopulations comparing both antibiotics among isolates, indicating that different mechanisms underlie the internal control of this phenotype. This is the first report of persister cells occurrence in A. baumannii. Our data suggest that distinct factors regulate the tolerance for unrelated antibiotics in this species, contrasting the multi-drug tolerance observed in other species (eg. dormancy-mediated tolerance). Supporting this observation, polymyxin B--an antibiotic that is believed to act on non-dividing cells as well--failed to eradicate persister cells in the majority of the isolates, possibly reflecting a disconnection between persistence and dormancy. PMID:24391945