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Sample records for heterogeneous student population

  1. Population heterogeneity and causal inference

    PubMed Central

    Xie, Yu

    2013-01-01

    Population heterogeneity is ubiquitous in social science. The very objective of social science research is not to discover abstract and universal laws but to understand population heterogeneity. Due to population heterogeneity, causal inference with observational data in social science is impossible without strong assumptions. Researchers have long been concerned with two potential sources of bias. The first is bias in unobserved pretreatment factors affecting the outcome even in the absence of treatment. The second is bias due to heterogeneity in treatment effects. In this article, I show how “composition bias” due to population heterogeneity evolves over time when treatment propensity is systematically associated with heterogeneous treatment effects. A form of selection bias, composition bias, arises dynamically at the aggregate level even when the classic assumption of ignorability holds true at the microlevel. PMID:23530202

  2. STOCHASTIC POPULATION GROWTH IN SPATIALLY HETEROGENEOUS ENVIRONMENTS

    E-print Network

    McAuliffe, Jon

    STOCHASTIC POPULATION GROWTH IN SPATIALLY HETEROGENEOUS ENVIRONMENTS STEVEN N. EVANS, PETER L, a simple model of population growth is a continuous time Markov process Zt, t 0, where the conditional law t is small. The long-term stochastic growth rate limt t-1 log Zt for such a population equals µ - 2 2 . Most

  3. Eradication of infectious diseases in heterogeneous populations

    SciTech Connect

    Travis, C.C.; Lenhart, S.M.

    1987-04-01

    A model is presented of infectious disease in heterogeneous populations, which allows for variable intra- to intergroup contact ratios. The authors give necessary and sufficient conditions for disease eradication by means of vaccination. Smallpox is used as an illustrative example.

  4. Scale Reliability Evaluation with Heterogeneous Populations

    ERIC Educational Resources Information Center

    Raykov, Tenko; Marcoulides, George A.

    2015-01-01

    A latent variable modeling approach for scale reliability evaluation in heterogeneous populations is discussed. The method can be used for point and interval estimation of reliability of multicomponent measuring instruments in populations representing mixtures of an unknown number of latent classes or subpopulations. The procedure is helpful also…

  5. Optical metabolic imaging quantifies heterogeneous cell populations

    PubMed Central

    Walsh, Alex J.; Skala, Melissa C.

    2015-01-01

    The genetic and phenotypic heterogeneity of cancers can contribute to tumor aggressiveness, invasion, and resistance to therapy. Fluorescence imaging occupies a unique niche to investigate tumor heterogeneity due to its high resolution and molecular specificity. Here, heterogeneous populations are identified and quantified by combined optical metabolic imaging and subpopulation analysis (OMI-SPA). OMI probes the fluorescence intensities and lifetimes of metabolic enzymes in cells to provide images of cellular metabolism, and SPA models cell populations as mixed Gaussian distributions to identify cell subpopulations. In this study, OMI-SPA is characterized by simulation experiments and validated with cell experiments. To generate heterogeneous populations, two breast cancer cell lines, SKBr3 and MDA-MB-231, were co-cultured at varying proportions. OMI-SPA correctly identifies two populations with minimal mean and proportion error using the optical redox ratio (fluorescence intensity of NAD(P)H divided by the intensity of FAD), mean NAD(P)H fluorescence lifetime, and OMI index. Simulation experiments characterized the relationships between sample size, data standard deviation, and subpopulation mean separation distance required for OMI-SPA to identify subpopulations. PMID:25780745

  6. Genetic Heterogeneity in Algerian Human Populations

    PubMed Central

    Deba, Tahria; Calafell, Francesc; Benhamamouch, Soraya; Comas, David

    2015-01-01

    The demographic history of human populations in North Africa has been characterized by complex processes of admixture and isolation that have modeled its current gene pool. Diverse genetic ancestral components with different origins (autochthonous, European, Middle Eastern, and sub-Saharan) and genetic heterogeneity in the region have been described. In this complex genetic landscape, Algeria, the largest country in Africa, has been poorly covered, with most of the studies using a single Algerian sample. In order to evaluate the genetic heterogeneity of Algeria, Y-chromosome, mtDNA and autosomal genome-wide makers have been analyzed in several Berber- and Arab-speaking groups. Our results show that the genetic heterogeneity found in Algeria is not correlated with geography or linguistics, challenging the idea of Berber groups being genetically isolated and Arab groups open to gene flow. In addition, we have found that external sources of gene flow into North Africa have been carried more often by females than males, while the North African autochthonous component is more frequent in paternally transmitted genome regions. Our results highlight the different demographic history revealed by different markers and urge to be cautious when deriving general conclusions from partial genomic information or from single samples as representatives of the total population of a region. PMID:26402429

  7. 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…

  8. DEMOGRAPHIC PROCESSES: POPULATION DYNAMICS IN HETEROGENEOUS LANDSCAPES

    EPA Science Inventory

    Few topics have attracted the attention of ecologists more than fluctuations in the numbers of plants and animals through time and their variation in abundance through space. nderstanding population fluctuations, and thus population conservation, requires understanding the links ...

  9. The effect of heterogeneity in measles vaccination on population immunity.

    PubMed Central

    Glass, K.; Kappey, K.; Grenfell, B. T.

    2004-01-01

    High overall vaccination levels sometimes hide pockets of poor coverage. We adopted a meta-population framework to model local aggregation of populations, and used this to investigate the effects of vaccination heterogeneity. A recent survey of antibody levels in a community with low vaccination levels in The Netherlands enabled us to assess the relative importance of local and long-range infective contacts, and thus identify feasible levels of aggregation in the meta-population model. In the aggregated model, we found that heterogeneity in vaccination coverage can lead to a much increased rate of infection among unvaccinated individuals, with a simultaneous drop in the average age at infection. PMID:15310169

  10. Targeting the adaptability of heterogeneous aneuploidy population

    E-print Network

    Chen, Guangbo

    2015-05-31

    conserved role for Hsp90 chaperon complexes in kinetochore assembly. We found the induction of aneuploidy population potentiates adaptability. Continued growth in the presence of Hsp90 inhibitor resulted in emergence of drug-resistant colonies...

  11. Mitochondrial DNA polymorphism reveals hidden heterogeneity within some Asian populations.

    PubMed Central

    Chakraborty, R

    1990-01-01

    Use of data on mtDNA morph distributions from six Asian populations has shown that the observed number of different mtDNA morphs is too large when compared with the number expected on the basis of the observed gene diversity in the mtDNA genome. This excess number of morphs mainly occurs through an excess of rare morphs, and this discrepancy is more pronounced in a pooled sample of five Asian populations. It is suggested that this discrepancy is probably due to internal heterogeneity in each of the anthropologically defined populations. This analysis demonstrates the utility that population data for a single locus, such as the mtDNA genome, have for detecting hidden heterogeneity in populations, provided that the locus has substantial genetic variability, so that many variant alleles can be detected. PMID:2349953

  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. Heterogeneity in Immune Responses – From Populations to Single Cells

    PubMed Central

    Satija, Rahul; Shalek, Alex K.

    2014-01-01

    The mammalian immune system is tasked with protecting the host against a broad range of threats. Understanding how immune populations leverage cellular diversity to achieve this breadth and flexibility, particularly during dynamic processes such as differentiation and antigenic response, is a core challenge that is well suited for single cell analysis. Recent years have witnessed transformative and intersecting advances in nanofabrication and genomics that enable deep profiling of individual cells, affording exciting opportunities to study heterogeneity in the immune response at an unprecedented scope. In light of these advances, here we review recent work exploring how immune populations generate and leverage cellular heterogeneity at multiple molecular and phenotypic levels. Additionally, we highlight opportunities for single cell technologies to shed light on the causes and consequences of heterogeneity in the immune system. PMID:24746883

  14. 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…

  15. Demographic heterogeneity and the dynamics of open populations.

    PubMed

    Noonburg, Erik G; Chen, Adam; Shima, Jeffrey S; Swearer, Stephen E

    2015-05-01

    Individuals vary in their phenotype and propensity for growth and survival, but the demographic consequences of this remain poorly understood. We extend previous theoretical work on benthic marine populations and formulate a new model to evaluate how demographic heterogeneity among newly settled reef fish affects population stability. We simulated settlement, growth, and mortality of a small reef fish, the common triplefin (Forsterygion lapillurn) in an open "subpopulation" using a delay-differential equation model framework. We modeled demographic heterogeneity with a discrete number of "quality" types, motivated by our previous empirical observations: individuals were either "high quality" (immigrants from nearby subpopulations) or "low quality" (immigrants from distant subpopulations); in our model, quality influences how quickly individuals develop at a given competitor density. Our results demonstrate how demographic heterogeneity and juvenile competition interact to qualitatively alter the effects of settlement on population stability. Specifically, our model suggests that a mixture of quality types can stabilize the equilibrium even when equal settlement of either type alone would result in an unstable equilibrium. These results highlight the importance of among-individual variation in a metapopulation context, and suggest that in systems where dispersal influences individual quality, connectivity may serve to stabilize local populations. PMID:26236830

  16. Transcriptional and phenotypical heterogeneity of Trypanosoma cruzi cell populations.

    PubMed

    Seco-Hidalgo, Víctor; De Pablos, Luis Miguel; Osuna, Antonio

    2015-12-01

    Trypanosoma cruzi has a complex life cycle comprising pools of cell populations which circulate among humans, vectors, sylvatic reservoirs and domestic animals. Recent experimental evidence has demonstrated the importance of clonal variations for parasite population dynamics, survival and evolution. By limiting dilution assays, we have isolated seven isogenic clonal cell lines derived from the Pan4 strain of T. cruzi. Applying different molecular techniques, we have been able to provide a comprehensive characterization of the expression heterogeneity in the mucin-associated surface protein (MASP) gene family, where all the clonal isogenic populations were transcriptionally different. Hierarchical cluster analysis and sequence comparison among different MASP cDNA libraries showed that, despite the great variability in MASP expression, some members of the transcriptome (including MASP pseudogenes) are conserved, not only in the life-cycle stages but also among different strains of T. cruzi. Finally, other important aspects for the parasite, such as growth, spontaneous metacyclogenesis or excretion of different catabolites, were also compared among the clones, demonstrating that T. cruzi populations of cells are also phenotypically heterogeneous. Although the evolutionary strategy that sustains the MASP expression polymorphism remains unknown, we suggest that MASP clonal variability and phenotypic heterogeneities found in this study might provide an advantage, allowing a rapid response to environmental pressure or changes during the life cycle of T. cruzi. PMID:26674416

  17. Group testing in heterogeneous populations by using halving algorithms.

    PubMed

    Black, Michael S; Bilder, Christopher R; Tebbs, Joshua M

    2012-03-01

    Group (pooled) testing is often used to reduce the total number of tests that are needed to screen a large number of individuals for an infectious disease or some other binary characteristic. Traditionally, research in group testing has assumed that each individual is independent with the same risk of positivity. More recently, there has been a growing set of literature generalizing previous work in group testing to include heterogeneous populations so that each individual has a different risk of positivity. We investigate the effect of acknowledging population heterogeneity on a commonly used group testing procedure which is known as 'halving'. For this procedure, positive groups are successively split into two equal-sized halves until all groups test negatively or until individual testing occurs. We show that heterogeneity does not affect the mean number of tests when individuals are randomly assigned to subgroups. However, when individuals are assigned to subgroups on the basis of their risk probabilities, we show that our proposed procedures reduce the number of tests by taking advantage of the heterogeneity. This is illustrated by using chlamydia and gonorrhoea screening data from the state of Nebraska. PMID:25035521

  18. Classification method for heterogeneity in monoclonal cell population

    NASA Astrophysics Data System (ADS)

    Aburatani, S.; Tashiro, K.; Kuhara, S.

    2015-09-01

    Monoclonal cell populations are known to be composed of heterogeneous subpopulations, thus complicating the data analysis. To gain clear insights into the mechanisms of cellular systems, biological data from a homogeneous cell population should be obtained. In this study, we developed a method based on Latent Profile Analysis (LPA) combined with Confirmatory Factor Analysis (CFA) to divide mixed data into classes, depending on their heterogeneity. In general cluster analysis, the number of measured points is a constraint, and thereby the data must be classified into fewer groups than the number of samples. By our newly developed method, the measured data can be divided into groups depending on their latent effects, without constraints. Our method is useful to clarify all types of omics data, including transcriptome, proteome and metabolic information.

  19. Assessing Student Attitudes toward Heterogeneous Grouping: A Pilot Study.

    ERIC Educational Resources Information Center

    Poppish, Susan; And Others

    Evidence suggests that tracking of students on the secondary level may not only be discriminatory, but also counterproductive to the personal, educational, and economic potential of all students. The English and Social Studies department of Oak Hill High School, in Wales, Maine, developed an intervention program concerning heterogeneous grouping…

  20. Molecular heterogeneity of familial hypercholesterolemia in the St. Petersburg population

    SciTech Connect

    Mandel`shtam, M.Yu.; Lipovetskii, B.M.; Schvartsman, A.L.; Gaitskhoki, V.S.

    1995-04-01

    Inheritance of Taq I, BstE II, and Nco I restriction fragment length polymorphisms (RFLP) in three families from St. Petersburg with familial hypercholesterolemia (FH) was studied. In two of these families, polymorphic markers of the low density lipoprotein receptor (LDLR) gene cosegregated with the disease. This data confirmed FH diagnosis based on the analysis of blood plasma lipid levels. Three different RFLP haplotypes were associated with the disease, suggesting the presence of at least three point mutations in the LDLR gene in the population studied, i.e., suggesting molecular heterogeneity of FH in the St. Petersburg population. 23 refs., 6 figs., 3 tabs.

  1. 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

  2. Digital signaling decouples activation probability and population heterogeneity.

    PubMed

    Kellogg, Ryan A; Tian, Chengzhe; Lipniacki, Tomasz; Quake, Stephen R; Tay, Sava?

    2015-01-01

    Digital signaling enhances robustness of cellular decisions in noisy environments, but it is unclear how digital systems transmit temporal information about a stimulus. To understand how temporal input information is encoded and decoded by the NF-?B system, we studied transcription factor dynamics and gene regulation under dose- and duration-modulated inflammatory inputs. Mathematical modeling predicted and microfluidic single-cell experiments confirmed that integral of the stimulus (or area, concentration × duration) controls the fraction of cells that activate NF-?B in the population. However, stimulus temporal profile determined NF-?B dynamics, cell-to-cell variability, and gene expression phenotype. A sustained, weak stimulation lead to heterogeneous activation and delayed timing that is transmitted to gene expression. In contrast, a transient, strong stimulus with the same area caused rapid and uniform dynamics. These results show that digital NF-?B signaling enables multidimensional control of cellular phenotype via input profile, allowing parallel and independent control of single-cell activation probability and population heterogeneity. PMID:26488364

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

    SciTech Connect

    Ganusov, Vitaly V

    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.

  4. Sub-population analysis of deformability distribution in heterogeneous red blood cell population.

    PubMed

    Lee, Dong Woo; Doh, Il; Kuypers, Frans A; Cho, Young-Ho

    2015-12-01

    We present a method for sub-population analysis of deformability distribution using single-cell microchamber array (SiCMA) technology. It is a unique method allowing the correlation of overall cellular characteristics with surface and cytosolic characteristics to define the distribution of individual cellular characteristics in heterogeneous cell populations. As a proof of principle, reticulocytes, the immature sub-population of red blood cells (RBC), were recognized from RBC population by a surface marker and different characteristics on deformability between these populations were characterized. The proposed technology can be used in a variety of applications that would benefit from the ability to measure the distribution of cellular characteristics in complex populations, especially important to define hematologic disorders. PMID:26383009

  5. Index sorting resolves heterogeneous murine hematopoietic stem cell populations

    PubMed Central

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

    2015-01-01

    Recent advances in the cellular and molecular biology of single stem cells have uncovered significant heterogeneity in the functional properties of stem cell populations. This has prompted the development of approaches to study single cells in isolation, often performed using multiparameter flow cytometry. However, many stem cell populations are too rare to test all possible cell surface marker combinations, and virtually nothing is known about functional differences associated with varying intensities of such markers. Here we describe the use of index sorting for further resolution of the flow cytometric isolation of single murine hematopoietic stem cells (HSCs). Specifically, we associate single-cell functional assay outcomes with distinct cell surface marker expression intensities. High levels of both CD150 and EPCR associate with delayed kinetics of cell division and low levels of differentiation. Moreover, cells that do not form single HSC-derived clones appear in the 7AADdim fraction, suggesting that even low levels of 7AAD staining are indicative of less healthy cell populations. These data indicate that when used in combination with single-cell functional assays, index sorting is a powerful tool for refining cell isolation strategies. This approach can be broadly applied to other single-cell systems, both to improve isolation and to acquire additional cell surface marker information. PMID:26051918

  6. Friendship-based partner switching promotes cooperation in heterogeneous populations

    NASA Astrophysics Data System (ADS)

    Chen, Wei; Wu, Te; Li, Zhiwu; Wang, Long

    2016-02-01

    The forming of human social ties tends to be with similar individuals. This study concentrates on the emergence of cooperation among heterogeneous populations. A simple model is proposed by considering the impact of interplay between the evolution of strategies and that of social partnerships on cooperation dynamics. Whenever two individuals acquire the rewards by playing prisoner's dilemma game with each other, the friendship (friendship is quantified as the weight of a link) between the two individuals deepens. Individuals can switch off the social ties with the partners who are unfriendly and rewire to similar new ones. Under this partner switching mechanism, population structure is divided into several groups and cooperation can prevail. It is observed that the frequent tendency of partner switching can lead to the enhancement of cooperative behavior under the enormous temptation to defect. Moreover, the influence of discounting the relationship between different individuals is also investigated. Meanwhile, the cooperation prevails when the adjustment of friendships mainly depends on the incomes of selected individuals rather than that of their partners. Finally, it is found that too similar population fail to maximize the cooperation and there exists a moderate similarity that can optimize cooperation.

  7. Index sorting resolves heterogeneous murine hematopoietic stem cell populations.

    PubMed

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

    2015-09-01

    Recent advances in the cellular and molecular biology of single stem cells have uncovered significant heterogeneity in the functional properties of stem cell populations. This has prompted the development of approaches to study single cells in isolation, often performed using multiparameter flow cytometry. However, many stem cell populations are too rare to test all possible cell surface marker combinations, and virtually nothing is known about functional differences associated with varying intensities of such markers. Here we describe the use of index sorting for further resolution of the flow cytometric isolation of single murine hematopoietic stem cells (HSCs). Specifically, we associate single-cell functional assay outcomes with distinct cell surface marker expression intensities. High levels of both CD150 and EPCR associate with delayed kinetics of cell division and low levels of differentiation. Moreover, cells that do not form single HSC-derived clones appear in the 7AAD(dim) fraction, suggesting that even low levels of 7AAD staining are indicative of less healthy cell populations. These data indicate that when used in combination with single-cell functional assays, index sorting is a powerful tool for refining cell isolation strategies. This approach can be broadly applied to other single-cell systems, both to improve isolation and to acquire additional cell surface marker information. PMID:26051918

  8. Estimation of multiple transmission rates for epidemics in heterogeneous populations

    PubMed Central

    Cook, Alex R.; Otten, Wilfred; Marion, Glenn; Gibson, Gavin J.; Gilligan, Christopher A.

    2007-01-01

    One of the principal challenges in epidemiological modeling is to parameterize models with realistic estimates for transmission rates in order to analyze strategies for control and to predict disease outcomes. Using a combination of replicated experiments, Bayesian statistical inference, and stochastic modeling, we introduce and illustrate a strategy to estimate transmission parameters for the spread of infection through a two-phase mosaic, comprising favorable and unfavorable hosts. We focus on epidemics with local dispersal and formulate a spatially explicit, stochastic set of transition probabilities using a percolation paradigm for a susceptible–infected (S–I) epidemiological model. The S–I percolation model is further generalized to allow for multiple sources of infection including external inoculum and host-to-host infection. We fit the model using Bayesian inference and Markov chain Monte Carlo simulation to successive snapshots of damping-off disease spreading through replicated plant populations that differ in relative proportions of favorable and unfavorable hosts and with time-varying rates of transmission. Epidemiologically plausible parametric forms for these transmission rates are compared by using the deviance information criterion. Our results show that there are four transmission rates for a two-phase system, corresponding to each combination of infected donor and susceptible recipient. Knowing the number and magnitudes of the transmission rates allows the dominant pathways for transmission in a heterogeneous population to be identified. Finally, we show how failure to allow for multiple transmission rates can overestimate or underestimate the rate of spread of epidemics in heterogeneous environments, which could lead to marked failure or inefficiency of control strategies. PMID:18077378

  9. Modelling Lipid Competition Dynamics in Heterogeneous Protocell Populations

    E-print Network

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

    2014-01-30

    In addressing the origins of Darwinian evolution, recent experimental work has been focussed on the discovery of simple physical effects which would provide a relevant selective advantage to protocells competing with each other for a limited supply of lipid. In particular, data coming from Szostak's lab suggest that the transition from simple prebiotically plausible lipid membranes to more complex and heterogeneous ones, closer to real biomembranes, may have been driven by changes in the fluidity of the membrane and its affinity for the available amphiphilic compound, which in turn would involve changes in vesicle growth dynamics. Earlier work from the same group reported osmotically-driven competition effects, whereby swelled vesicles grow at the expense of isotonic ones. In this paper, we try to expand on these experimental studies by providing a simple mathematical model of a population of competing vesicles, studied at the level of lipid kinetics. In silico simulations of the model are able to reproduce qualitatively and often quantitatively the experimentally reported competition effects in both scenarios. We also develop a method for numerically solving the equilibrium of a population of competing model vesicles, which is quite general and applicable to different vesicle kinetics schemes.

  10. 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…

  11. Nuclear heterogeneity in conidial populations of Aspergillus flavus.

    PubMed

    Runa, Farhana; Carbone, Ignazio; Bhatnagar, Deepak; Payne, Gary A

    2015-11-01

    Aspergillus flavus is a major producer of aflatoxin and an opportunistic pathogen for a wide range of hosts. Understanding genotypic and phenotypic variation within strains of A. flavus is important for controlling disease and reducing aflatoxin contamination. A. flavus is multinucleate and predominantly haploid (n) and homokaryotic. Although cryptic heterokaryosis may occur in nature, it is unclear how nuclei in A. flavus influence genetic heterogeneity and if nuclear condition plays a role in fungal ecology. A. flavus mainly reproduces asexually by producing conidia. In order to observe whether conidia are homokaryotic or heterokaryotic, we labeled nuclei of A. flavus using two different nuclear localized fluorescent reporters. The reporter constructs (pYH2A and pCH2B), encode histones HH2A and HH2B fused at the C terminus with either yellow (EYFP) or cyan (ECFP) fluorescent proteins, respectively. The constructs were transformed into the double auxotrophic strain AFC-1 (-pyrG, -argD) to generate a strain containing each reporter construct. By taking advantage of the nutritional requirement for each strain, we were able to generate fusants between FR36 (-argD) expressing yellow fluorescence, and FR46 (-pyr4) expressing cyan fluorescence. Conidia from fusants between FR36 and FR46 showed three types of fluorescence: only EYFP, only ECFP or both EYFP+ECFP. Conidia containing nuclei expressing EYFP+ECFP were separated by Fluorescence-Activated Cell sorting (FACS) and were found to contain both yellow and cyan fluorescent markers in the same nucleus. Further characterization of conidia having only one nucleus but expressing both EYFP+ECFP fluorescence were found to be diploid (2n). Our findings suggest that A. flavus maintains nuclear heterogeneity in conidial populations. PMID:26362651

  12. Intrapersonal and Populational Heterogeneity of the Chemokine RANTES

    PubMed Central

    Oran, Paul E.; Sherma, Nisha D.; Borges, Chad R.; Jarvis, Jason W.; Nelson, Randall W.

    2013-01-01

    BACKGROUND Current immunoassays for the chemokine RANTES (regulated on activation, normal T-cell expressed and secreted) are not tailored for specific isoforms that exist endogenously, despite the fact that variants with modified activity are known to exist. This is surprising in view of this protein’s ubiquitous increased presence in many diseases and that the 2 established isoforms are truncated by enzymes also correlated to disease. An in-depth population survey of RANTES heterogeneity in the context of multiple diseases via a mass spectrometric immunoassay (MSIA) may resolve this issue. METHODS We developed an MSIA for RANTES and endogenous variants apparent in human plasma. Samples from multiple cohorts of individuals (type 2 diabetes, congestive heart failure, history of myocardial infarction, and cancer patients) were run in parallel with samples from healthy individuals (239 people total). We used 230 ?L of plasma per individual and tabulated relative percent abundance (RPA) values for identified isoforms. RESULTS We detected at least 19 variants, including the dipeptidyl peptidase IV (DPP-IV)-truncated variant. The majority of variants were unreported in the literature. Identifiable modifications included N- and/or C-terminal truncations, oxidation, glycation, and glycosylation. We observed statistically significant differences in RPA values for multiple variants between disease cohorts and recognized prospective disease-specific protein profiles for RANTES. CONCLUSIONS Because of widespread interest in the clinical value of RANTES, the protein diversity established here may aid in the design of future, fully quantitative assays. Equally important, an inclusive qualitative understanding of RANTES heterogeneity may present new insights into the relationship between RANTES and disease. PMID:20802101

  13. Deep-Sequencing of the Peach Latent Mosaic Viroid Reveals New Aspects of Population Heterogeneity

    E-print Network

    Perreault, Jean-Pierre

    Deep-Sequencing of the Peach Latent Mosaic Viroid Reveals New Aspects of Population Heterogeneity heterogeneity from a population dynamics perspective, a GF305-indicator peach tree was infected with a single variant of the Avsunviroidae family member Peach latent mosaic viroid (PLMVd). Six months post

  14. Lattice statistics for highly heterogeneous populations of rigid rectangular particles

    NASA Astrophysics Data System (ADS)

    Herzfeld, Judith

    1982-04-01

    DiMarzio's lattice model is used to calculate the configurational entropy of a population of rigid rectangular parallelepipeds which is arbitrarily heterogeneous in both lengths and widths. An analytical expression is obtained which is a product of a small number of terms and is readily applicable to statistical thermodynamic calculations. The limit of infinitesimal lattice cell size is considered as an approximation of a continuum description. In this continuum limit, the alignment transition for monodisperse nematogen is found to occur at a lower density, and with a smaller density discontinuity, than is predicted by the lattice model in its original form. Although, at a given density, the alignment and the pressure are generally greater in the continuum description than in the discrete description, the alignment and pressure are less at the transition in the continuum case than they are at the transition in the discrete case. Whereas the original lattice model predicts that no transition occurs for particles of axial ratio less than 3.65, in the continuum limit the transition disappears only when the axial ratio is less than 3.06. Alternative approaches for treating solvents are discussed.

  15. Functional heterogeneity of side population cells in skeletal muscle

    SciTech Connect

    Uezumi, Akiyoshi; Ojima, Koichi; Fukada, So-ichiro; Ikemoto, Madoka; Masuda, Satoru; Miyagoe-Suzuki, Yuko; Takeda, Shin'ichi . 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.

  16. 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

  17. 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).

  18. 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.

  19. Breeding site heterogeneity reduces variability in frog recruitment and population dynamics

    USGS Publications Warehouse

    McCaffery, Rebecca M.; Eby, Lisa A.; Maxell, Bryce A.; Corn, Paul Stephen

    2013-01-01

    Environmental stochasticity can have profound effects on the dynamics and viability of wild populations, and habitat heterogeneity provides one mechanism by which populations may be buffered against the negative effects of environmental fluctuations. Heterogeneity in breeding pond hydroperiod across the landscape may allow amphibian populations to persist despite variable interannual precipitation. We examined recruitment dynamics over 10 yr in a high-elevation Columbia spotted frog (Rana luteiventris) population that breeds in ponds with a variety of hydroperiods. We combined these data with matrix population models to quantify the consequences of heterogeneity in pond hydroperiod on net recruitment (i.e. number of metamorphs produced) and population growth rates. We compared our heterogeneous system to hypothetical homogeneous environments with only ephemeral ponds, only semi-permanent ponds, and only permanent ponds. We also examined the effects of breeding pond habitat loss on population growth rates. Most eggs were laid in permanent ponds each year, but survival to metamorphosis was highest in the semi-permanent ponds. Recruitment success varied by both year and pond type. Net recruitment and stochastic population growth rate were highest under a scenario with homogeneous semi-permanent ponds, but variability in recruitment was lowest in the scenario with the observed heterogeneity in hydroperiods. Loss of pond habitat decreased population growth rate, with greater decreases associated with loss of permanent and semi-permanent habitat. The presence of a diversity of pond hydroperiods on the landscape will influence population dynamics, including reducing variability in recruitment in an uncertain climatic future.

  20. Demographic Heterogeneity and the Dynamics of Open Populations1 Erik G. Noonburg1*

    E-print Network

    Shima, Jeff

    #12;Demographic Heterogeneity and the Dynamics of Open Populations1 2 Erik G. Noonburg1* , Adam Individuals vary in their phenotype and propensity for growth and survival, but the24 demographic consequences and formulate a new model to evaluate how demographic26 heterogeneity among newly settled reef fish affects

  1. An elaboration of theory about preventing outbreaks in homogeneous populations to include heterogeneity or preferential mixing.

    PubMed

    Feng, Zhilan; Hill, Andrew N; Smith, Philip J; Glasser, John W

    2015-12-01

    The goal of many vaccination programs is to attain the population immunity above which pathogens introduced by infectious people (e.g., travelers from endemic areas) will not cause outbreaks. Using a simple meta-population model, we demonstrate that, if sub-populations either differ in characteristics affecting their basic reproduction numbers or if their members mix preferentially, weighted average sub-population immunities cannot be compared with the proportionally-mixing homogeneous population-immunity threshold, as public health practitioners are wont to do. Then we review the effect of heterogeneity in average per capita contact rates on the basic meta-population reproduction number. To the extent that population density affects contacts, for example, rates might differ in urban and rural sub-populations. Other differences among sub-populations in characteristics affecting their basic reproduction numbers would contribute similarly. In agreement with more recent results, we show that heterogeneous preferential mixing among sub-populations increases the basic meta-population reproduction number more than homogeneous preferential mixing does. Next we refine earlier results on the effects of heterogeneity in sub-population immunities and preferential mixing on the effective meta-population reproduction number. Finally, we propose the vector of partial derivatives of this reproduction number with respect to the sub-population immunities as a fundamentally new tool for targeting vaccination efforts. PMID:26375548

  2. Proportional reasoning competence among different student populations

    NASA Astrophysics Data System (ADS)

    Wong, King

    2012-10-01

    A collaborative project between Western Washington University, Rutgers University, and New Mexico State University seeks to understand student's competence level on proportional reasoning. We have been collecting and analyzing data from introductory physics and science education courses using a set of assessment tasks. We utilize the notion of constructs to categorize student thinking according to repetitive patterns. Results suggest that, when students confront ratio and proportion problems, they often experience a gap between the mechanics of the mathematical operations and the conscious understanding of what they are doing. In this poster we will share results of our findings from different courses, institutions, and student populations. Supported by NSF grants DUE-1045227, DUE-1045231, DUE-1045250..

  3. Observed-Score Equating with a Heterogeneous Target Population

    ERIC Educational Resources Information Center

    Duong, Minh Q.; von Davier, Alina A.

    2012-01-01

    Test equating is a statistical procedure for adjusting for test form differences in difficulty in a standardized assessment. Equating results are supposed to hold for a specified target population (Kolen & Brennan, 2004; von Davier, Holland, & Thayer, 2004) and to be (relatively) independent of the subpopulations from the target population (see…

  4. Herbivore population regulation and resource heterogeneity in a stochastic environment.

    PubMed

    Hempson, G P; Illius, A W; Hendricks, H H; Bond, W J; Vetter, S

    2015-08-01

    Large-mammal herbivore populations are subject to the interaction of internal density-dependent processes and external environmental stochasticity. We disentangle these processes by linking consumer population dynamics, in a highly stochastic environment, to the availability of their key forage resource via effects on body condition and subsequent fecundity and mortality rates. Body condition and demographic rate data were obtained by monitoring 500 tagged female goats in the Richtersveld National Park, South Africa, over a three-year period. Identifying the key resource and pathway to density dependence for a population allows environmental stochasticity to be partitioned into that which has strong feedbacks to population stability, and that which does not. Our data reveal a density- dependent seasonal decline in goat body condition in response to concomitant density-dependent depletion of the dry-season forage resource. The loss in body condition reduced density-dependent pregnancy rates, litter sizes, and pre-weaning survival. Survival was lowest following the most severe dry season and for juveniles. Adult survival in the late-dry season depended on body condition in the mid-dry season. Population growth was determined by the length of the dry season and the population size in the previous year. The RNP goat population is thereby dynamically coupled primarily to its dry-season forage resource. Extreme environmental variability thus does not decouple consumer resource dynamics, in contrast to the views of nonequilibrium protagonists. PMID:26405742

  5. Phenotypic heterogeneity and evolutionary games in microbial populations

    E-print Network

    Healey, David W. (David Wendell)

    2015-01-01

    One of the most interesting discoveries of the last decade is the surprising degree of phenotypic variability between individual cells in clonal microbial populations, even in identical environments. While some variation ...

  6. A Stabilization Group Approach for Heterogeneous Populations of Trauma Clients

    PubMed Central

    Stige, Signe Hjelen

    2011-01-01

    High prevalence and long-lasting implications of human-inflicted trauma call for effective treatment approaches reaching clients in need of trauma-specific treatment. Numerous approaches exist, but often with limited empirical support. There is also a tendency toward segregating treatment approaches depending on type of exposure history and presenting symptoms. This might exclude clients in need of trauma-specific treatment; therefore, treatment approaches that can reach more heterogeneous groups of clients are needed. In this article, a group-based treatment approach adjusted to include clients with a wide range of trauma-related problems and traumatic experiences will be presented. A brief outline of the approach is presented, together with the theoretical and empirical background, to facilitate implementation by practitioners and empirical testing. PMID:22267901

  7. 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.

  8. Uncovering epidemiological dynamics in heterogeneous host populations using phylogenetic methods.

    PubMed

    Stadler, Tanja; Bonhoeffer, Sebastian

    2013-03-19

    Host population structure has a major influence on epidemiological dynamics. However, in particular for sexually transmitted diseases, quantitative data on population contact structure are hard to obtain. Here, we introduce a new method that quantifies host population structure based on phylogenetic trees, which are obtained from pathogen genetic sequence data. Our method is based on a maximum-likelihood framework and uses a multi-type branching process, under which each host is assigned to a type (subpopulation). In a simulation study, we show that our method produces accurate parameter estimates for phylogenetic trees in which each tip is assigned to a type, as well for phylogenetic trees in which the type of the tip is unknown. We apply the method to a Latvian HIV-1 dataset, quantifying the impact of the intravenous drug user epidemic on the heterosexual epidemic (known tip states), and identifying superspreader dynamics within the men-having-sex-with-men epidemic (unknown tip states). PMID:23382421

  9. 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

  10. Slow epidemic extinction in populations with heterogeneous infection rates

    NASA Astrophysics Data System (ADS)

    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=?wij proportional to the intensity of their contact wij, with a distribution P(wij) taken from face-to-face experiments analyzed in Cattuto [PLoS ONE1932-620310.1371/journal.pone.0011596 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.

  11. 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.

  12. 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…

  13. Hypervariable purine biosynthesis genes contribute to stress response population heterogeneity in Campylobacter jejuni

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Population heterogeneity gives bacteria a remarkable ability to survive and grow in swiftly changing environments because the generation of cells with variable phenotypes ensures that some will be successful in hostile conditions. Although pure laboratory cultures have historically been assumed to b...

  14. 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

  15. Modelling lipid competition dynamics in heterogeneous protocell populations.

    PubMed

    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

  16. Using Populism to Engage Students in Critical Thinking

    ERIC Educational Resources Information Center

    Peiser, Andrew

    2013-01-01

    Populism is a relevant issue in the teaching of American history. Historically, the standard interpretation of Populism perceived the movement as favorable. How educators handle conflicting views of Populism is important in engaging students in critical thinking. This article describes the history of American Populism, explains how Populism can be…

  17. Physiological heterogeneities in microbial populations and implications for physical stress tolerance

    PubMed Central

    2012-01-01

    Background Traditionally average values of the whole population are considered when analysing microbial cell cultivations. However, a typical microbial population in a bioreactor is heterogeneous in most phenotypes measurable at a single-cell level. There are indications that such heterogeneity may be unfavourable on the one hand (reduces yields and productivities), but also beneficial on the other hand (facilitates quick adaptation to new conditions - i.e. increases the robustness of the fermentation process). Understanding and control of microbial population heterogeneity is thus of major importance for improving microbial cell factory processes. Results In this work, a dual reporter system was developed and applied to map growth and cell fitness heterogeneities within budding yeast populations during aerobic cultivation in well-mixed bioreactors. The reporter strain, which was based on the expression of green fluorescent protein (GFP) under the control of the ribosomal protein RPL22a promoter, made it possible to distinguish cell growth phases by the level of fluorescence intensity. Furthermore, by exploiting the strong correlation of intracellular GFP level and cell membrane integrity it was possible to distinguish subpopulations with high and low cell membrane robustness and hence ability to withstand freeze-thaw stress. A strong inverse correlation between growth and cell membrane robustness was observed, which further supports the hypothesis that cellular resources are limited and need to be distributed as a trade-off between two functions: growth and robustness. In addition, the trade-off was shown to vary within the population, and the occurrence of two distinct subpopulations shifting between these two antagonistic modes of cell operation could be distinguished. Conclusions The reporter strain enabled mapping of population heterogeneities in growth and cell membrane robustness towards freeze-thaw stress at different phases of cell cultivation. The described reporter system is a valuable tool for understanding the effect of environmental conditions on population heterogeneity of microbial cells and thereby to understand cell responses during industrial process-like conditions. It may be applied to identify more robust subpopulations, and for developing novel strategies for strain improvement and process design for more effective bioprocessing. PMID:22799461

  18. 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

  19. 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

  20. 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

  1. Impact of small groups with heterogeneous preference on behavioral evolution in population evacuation.

    PubMed

    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

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

    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.

  3. 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

  4. 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

  5. Noise-Driven Phenotypic Heterogeneity with Finite Correlation Time in Clonal Populations

    PubMed Central

    Lee, UnJin; Skinner, John J.; Reinitz, John; Rosner, Marsha Rich; Kim, Eun-Jin

    2015-01-01

    There has been increasing awareness in the wider biological community of the role of clonal phenotypic heterogeneity in playing key roles in phenomena such as cellular bet-hedging and decision making, as in the case of the phage-? lysis/lysogeny and B. Subtilis competence/vegetative pathways. Here, we report on the effect of stochasticity in growth rate, cellular memory/intermittency, and its relation to phenotypic heterogeneity. We first present a linear stochastic differential model with finite auto-correlation time, where a randomly fluctuating growth rate with a negative average is shown to result in exponential growth for sufficiently large fluctuations in growth rate. We then present a non-linear stochastic self-regulation model where the loss of coherent self-regulation and an increase in noise can induce a shift from bounded to unbounded growth. An important consequence of these models is that while the average change in phenotype may not differ for various parameter sets, the variance of the resulting distributions may considerably change. This demonstrates the necessity of understanding the influence of variance and heterogeneity within seemingly identical clonal populations, while providing a mechanism for varying functional consequences of such heterogeneity. Our results highlight the importance of a paradigm shift from a deterministic to a probabilistic view of clonality in understanding selection as an optimization problem on noise-driven processes, resulting in a wide range of biological implications, from robustness to environmental stress to the development of drug resistance. PMID:26203903

  6. Order-Disorder Phase Transition in Heterogeneous Populations of Self-propelled Particles

    NASA Astrophysics Data System (ADS)

    Ariel, Gil; Rimer, Oren; Ben-Jacob, Eshel

    2015-02-01

    Biological systems are typically heterogeneous as individuals vary in their characteristics, their response to the external environment and to each other. For example, cell diversity plays a crucial role in the successful survival of many biological systems. Phenotypic heterogeneity is associated with cellular response to intercellular communications, the response to external environmental cues, motility modes, and proliferation rates. Here we study the effect of phenotypic diversity on the properties of collective motion in the context of the scalar noise model of collective migration. For simplicity, we study a population that is composed of two sub-populations, each with different sensitivities to external noise. We find that the two sub-populations interact non-additively: Within a large range of parameters, the dynamics of the system can be described by an equivalent homogeneous system with an effective temperature that depends on the average circular mean of the phenotypes. However, if one of the sub-populations is sufficiently "cold", it dominates the dynamics of the group as a whole.

  7. 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

  8. Heterogeneity and diversity of ABO and Rh blood group genes in select Saudi Arabian populations.

    PubMed

    AlSuhaibani, E S; Kizilbash, N A; Malik, S

    2015-01-01

    In order to investigate the diversity of ABO and Rh blood group genes in the Saudi Arabian population, we assembled the phenotypic data of approximately 66,000 subjects from ten representative Saudi populations: Al-Khobar, Riyadh, Tabuk/Madina Al-Munawaara, Jeddah, Abha, South region, Sakaka, Domah, Al-Qurayat, and Sweer. The frequencies of p[A], q[B], and r[O] alleles at the ABO locus were observed to be 0.1688, 0.1242, and 0.7070, respectively, and the frequency of the D allele at the Rh locus was 0.7138. The heterozygosities at the ABO and Rh loci were 0.4563 and 0.4086, respectively, while the combined heterozygosity was 0.4324. Homogeneity tests revealed the population of Abha to be the most heterogeneous while that of Tabuk/Madina was found to be the least heterogeneous. Homogeneity was higher among the Northern populations while Southern populations demonstrated subdivisions and stratification. Gene diversity analyses yielded a total heterozygosity value of 0.4449. The coefficient of gene differentiation was 0.0090. Nei's genetic distance analyses showed that there was close affinity between the populations of Al-Khobar and Riyadh. The largest differences were observed between the populations of Sakaka and Domah. Furthermore, negative correlations were found between p[A] and r[O] alleles, and between q[B] and r[O] alleles at the ABO locus. Clinal analyses revealed that the r[O] allele showed an increasing trend from North-East to South-West, and conversely the q[B] allele exhibited a decreasing trend at these coordinates. These analyses present interesting aspects of the blood group allele distribution across the geography of Saudi Arabia. PMID:26214466

  9. Individual cell heterogeneity as variability source in population dynamics of microbial inactivation.

    PubMed

    Aspridou, Zafiro; Koutsoumanis, Konstantinos P

    2015-02-01

    A statistical modeling approach was applied for describing and evaluating the individual cell heterogeneity as variability source in microbial inactivation. The inactivation data (Nt vs time) of Salmonella enterica serotype Agona, with initial concentration N0 = 10(9) CFU/ml in acidified tryptone soy broth (pH 3.5), were transformed to (N0 - Nt)/N0 vs time leading to the cumulative probability distribution of the individual cell inactivation times (ti), which was further fitted to a variety of continuous distributions using @Risk software. The best-fitted ti distribution (Gamma) was used to predict the inactivation of S. Agona populations of various N0 using Monte Carlo simulation, with the number of iterations in each simulation being equal to N0 and the number of simulations representing the variability of the population inactivation behavior. The Monte Carlo simulation results for a population with N0 = 10,000 CFU/ml showed that the variability in the predicted inactivation behavior is negligible for concentrations down to 100 cells. As the concentration decreases below 100 cells, however, the variability increases significantly. The results also indicated that the D-value used in deterministic first order kinetic models is valid only for large populations. For small populations, D-value shows a high variability, originating from individual cell heterogeneity, and, thus, can be better characterized by a probability distribution rather than a uniform value. Validation experiments with small populations confirmed the variability predicted by the statistical model. The use of the proposed approach to quantify the variability in the inactivation of mixed microbial populations, consisting of subpopulations with different probability distributions of ti, was also demonstrated. PMID:25500387

  10. Multiple cell and population-level interactions with mouse embryonic stem cell heterogeneity.

    PubMed

    Cannon, Danielle; Corrigan, Adam M; Miermont, Agnes; McDonel, Patrick; Chubb, Jonathan R

    2015-08-15

    Much of development and disease concerns the generation of gene expression differences between related cells sharing similar niches. However, most analyses of gene expression only assess population and time-averaged levels of steady-state transcription. The mechanisms driving differentiation are buried within snapshots of the average cell, lacking dynamic information and the diverse regulatory history experienced by individual cells. Here, we use a quantitative imaging platform with large time series data sets to determine the regulation of developmental gene expression by cell cycle, lineage, motility and environment. We apply this technology to the regulation of the pluripotency gene Nanog in mouse embryonic stem cells. Our data reveal the diversity of cell and population-level interactions with Nanog dynamics and heterogeneity, and how this regulation responds to triggers of pluripotency. Cell cycles are highly heterogeneous and cycle time increases with Nanog reporter expression, with longer, more variable cycle times as cells approach ground-state pluripotency. Nanog reporter expression is highly stable over multiple cell generations, with fluctuations within cycles confined by an attractor state. Modelling reveals an environmental component to expression stability, in addition to any cell-autonomous behaviour, and we identify interactions of cell density with both cycle behaviour and Nanog. Rex1 expression dynamics showed shared and distinct regulatory effects. Overall, our observations of multiple partially overlapping dynamic heterogeneities imply complex cell and environmental regulation of pluripotent cell behaviour, and suggest simple deterministic views of stem cell states are inappropriate. PMID:26209649

  11. Assessing the Implicit Curriculum in Social Work Education: Heterogeneity of Students' Experiences and Impact on Professional Empowerment

    ERIC Educational Resources Information Center

    Peterson, N. Andrew; Farmer, Antoinette Y.; Donnelly, Louis; Forenza, Brad

    2014-01-01

    The implicit curriculum, which refers to a student's learning environment, has been described as an essential feature of an integrated professional social work curriculum. Very little is known, however, about the heterogeneity of students' experiences with the implicit curriculum, how this heterogeneity may be distributed across groups…

  12. Experimentally Verified Parameter Sets for Modelling Heterogeneous Neocortical Pyramidal-Cell Populations

    PubMed Central

    Harrison, Paul M.; Badel, Laurent; Wall, Mark J.; Richardson, Magnus J. E.

    2015-01-01

    Models of neocortical networks are increasingly including the diversity of excitatory and inhibitory neuronal classes. Significant variability in cellular properties are also seen within a nominal neuronal class and this heterogeneity can be expected to influence the population response and information processing in networks. Recent studies have examined the population and network effects of variability in a particular neuronal parameter with some plausibly chosen distribution. However, the empirical variability and covariance seen across multiple parameters are rarely included, partly due to the lack of data on parameter correlations in forms convenient for model construction. To addess this we quantify the heterogeneity within and between the neocortical pyramidal-cell classes in layers 2/3, 4, and the slender-tufted and thick-tufted pyramidal cells of layer 5 using a combination of intracellular recordings, single-neuron modelling and statistical analyses. From the response to both square-pulse and naturalistic fluctuating stimuli, we examined the class-dependent variance and covariance of electrophysiological parameters and identify the role of the h current in generating parameter correlations. A byproduct of the dynamic I-V method we employed is the straightforward extraction of reduced neuron models from experiment. Empirically these models took the refractory exponential integrate-and-fire form and provide an accurate fit to the perisomatic voltage responses of the diverse pyramidal-cell populations when the class-dependent statistics of the model parameters were respected. By quantifying the parameter statistics we obtained an algorithm which generates populations of model neurons, for each of the four pyramidal-cell classes, that adhere to experimentally observed marginal distributions and parameter correlations. As well as providing this tool, which we hope will be of use for exploring the effects of heterogeneity in neocortical networks, we also provide the code for the dynamic I-V method and make the full electrophysiological data set available. PMID:26291316

  13. 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.

  14. Experimentally Verified Parameter Sets for Modelling Heterogeneous Neocortical Pyramidal-Cell Populations.

    PubMed

    Harrison, Paul M; Badel, Laurent; Wall, Mark J; Richardson, Magnus J E

    2015-08-01

    Models of neocortical networks are increasingly including the diversity of excitatory and inhibitory neuronal classes. Significant variability in cellular properties are also seen within a nominal neuronal class and this heterogeneity can be expected to influence the population response and information processing in networks. Recent studies have examined the population and network effects of variability in a particular neuronal parameter with some plausibly chosen distribution. However, the empirical variability and covariance seen across multiple parameters are rarely included, partly due to the lack of data on parameter correlations in forms convenient for model construction. To addess this we quantify the heterogeneity within and between the neocortical pyramidal-cell classes in layers 2/3, 4, and the slender-tufted and thick-tufted pyramidal cells of layer 5 using a combination of intracellular recordings, single-neuron modelling and statistical analyses. From the response to both square-pulse and naturalistic fluctuating stimuli, we examined the class-dependent variance and covariance of electrophysiological parameters and identify the role of the h current in generating parameter correlations. A byproduct of the dynamic I-V method we employed is the straightforward extraction of reduced neuron models from experiment. Empirically these models took the refractory exponential integrate-and-fire form and provide an accurate fit to the perisomatic voltage responses of the diverse pyramidal-cell populations when the class-dependent statistics of the model parameters were respected. By quantifying the parameter statistics we obtained an algorithm which generates populations of model neurons, for each of the four pyramidal-cell classes, that adhere to experimentally observed marginal distributions and parameter correlations. As well as providing this tool, which we hope will be of use for exploring the effects of heterogeneity in neocortical networks, we also provide the code for the dynamic I-V method and make the full electrophysiological data set available. PMID:26291316

  15. 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.)

  16. Addressing population heterogeneity and distribution in epidemics models using a cellular automata approach

    PubMed Central

    2014-01-01

    Background The spread of an infectious disease is determined by biological and social factors. Models based on cellular automata are adequate to describe such natural systems consisting of a massive collection of simple interacting objects. They characterize the time evolution of the global system as the emergent behaviour resulting from the interaction of the objects, whose behaviour is defined through a set of simple rules that encode the individual behaviour and the transmission dynamic. Methods An epidemic is characterized trough an individual–based–model built upon cellular automata. In the proposed model, each individual of the population is represented by a cell of the automata. This way of modeling an epidemic situation allows to individually define the characteristic of each individual, establish different scenarios and implement control strategies. Results A cellular automata model to study the time evolution of a heterogeneous populations through the various stages of disease was proposed, allowing the inclusion of individual heterogeneity, geographical characteristics and social factors that determine the dynamic of the desease. Different assumptions made to built the classical model were evaluated, leading to following results: i) for low contact rate (like in quarantine process or low density population areas) the number of infective individuals is lower than other areas where the contact rate is higher, and ii) for different initial spacial distributions of infected individuals different epidemic dynamics are obtained due to its influence on the transition rate and the reproductive ratio of disease. Conclusions The contact rate and spatial distributions have a central role in the spread of a disease. For low density populations the spread is very low and the number of infected individuals is lower than in highly populated areas. The spacial distribution of the population and the disease focus as well as the geographical characteristic of the area play a central role in the dynamics of the desease. PMID:24725804

  17. 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

  18. 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

  19. Impact of roles assignation on heterogeneous populations in evolutionary dictator game.

    PubMed

    Deng, Xinyang; Liu, Qi; Sadiq, Rehan; Deng, Yong

    2014-01-01

    The evolution of cooperation is a hot and challenging topic in the field of evolutionary game theory. Altruistic behavior, as a particular form of cooperation, has been widely studied by the ultimatum game but not by the dictator game, which provides a more elegant way to identify the altruistic component of behaviors. In this paper, the evolutionary dictator game is applied to model the real motivations of altruism. A degree-based regime is utilized to assess the impact of the assignation of roles on evolutionary outcome in populations of heterogeneous structure with two kinds of strategic updating mechanisms, which are based on Darwin's theory of evolution and punctuated equilibrium, respectively. The results show that the evolutionary outcome is affected by the role assignation and that this impact also depends on the strategic updating mechanisms, the function used to evaluate players' success, and the structure of populations. PMID:25377303

  20. Statewide Survey of ESL Student Populations: Overview.

    ERIC Educational Resources Information Center

    Spicer, Scot L.; And Others

    In spring 1989, 25 community colleges conducted a survey of their English-as-a-Second-Language (ESL) students to project the need for ESL services at institutional and statewide levels, and to assess students' existing and desired levels of English proficiency, and the time and resources needed to achieve the desired level. In addition, the study…

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

    PubMed Central

    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.

    2014-01-01

    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

  2. Projection specificity in heterogeneous locus coeruleus cell populations: implications for learning and memory.

    PubMed

    Uematsu, Akira; Tan, Bao Zhen; Johansen, Joshua P

    2015-09-01

    Noradrenergic neurons in the locus coeruleus (LC) play a critical role in many functions including learning and memory. This relatively small population of cells sends widespread projections throughout the brain including to a number of regions such as the amygdala which is involved in emotional associative learning and the medial prefrontal cortex which is important for facilitating flexibility when learning rules change. LC noradrenergic cells participate in both of these functions, but it is not clear how this small population of neurons modulates these partially distinct processes. Here we review anatomical, behavioral, and electrophysiological studies to assess how LC noradrenergic neurons regulate these different aspects of learning and memory. Previous work has demonstrated that subpopulations of LC noradrenergic cells innervate specific brain regions suggesting heterogeneity of function in LC neurons. Furthermore, noradrenaline in mPFC and amygdala has distinct effects on emotional learning and cognitive flexibility. Finally, neural recording data show that LC neurons respond during associative learning and when previously learned task contingencies change. Together, these studies suggest a working model in which distinct and potentially opposing subsets of LC neurons modulate particular learning functions through restricted efferent connectivity with amygdala or mPFC. This type of model may provide a general framework for understanding other neuromodulatory systems, which also exhibit cell type heterogeneity and projection specificity. PMID:26330494

  3. Dynamic Heterogeneity of the Heart Valve Interstitial Cell Population in Mitral Valve Health and Disease

    PubMed Central

    Sauls, Kimberly; Koenig, Sara N.; Anstine, Lindsey J.; Garg, Vidu; Norris, Russell A.; Lincoln, Joy

    2015-01-01

    The heart valve interstitial cell (VIC) population is dynamic and thought to mediate lay down and maintenance of the tri-laminar extracellular matrix (ECM) structure within the developing and mature valve throughout life. Disturbances in the contribution and distribution of valve ECM components are detrimental to biomechanical function and associated with disease. This pathological process is associated with activation of resident VICs that in the absence of disease reside as quiescent cells. While these paradigms have been long standing, characterization of this abundant and ever-changing valve cell population is incomplete. Here we examine the expression pattern of Smooth muscle ?-actin, Periostin, Twist1 and Vimentin in cultured VICs, heart valves from healthy embryonic, postnatal and adult mice, as well as mature valves from human patients and established mouse models of disease. We show that the VIC population is highly heterogeneous and phenotypes are dependent on age, species, location, and disease state. Furthermore, we identify phenotypic diversity across common models of mitral valve disease. These studies significantly contribute to characterizing the VIC population in health and disease and provide insights into the cellular dynamics that maintain valve structure in healthy adults and mediate pathologic remodeling in disease states. PMID:26527432

  4. Mitochondrial DNA from El Mirador Cave (Atapuerca, Spain) Reveals the Heterogeneity of Chalcolithic Populations

    PubMed Central

    Pierini, Federica; Matas-Lalueza, Laura; Gigli, Elena; Lari, Martina; Civit, Sergi; Lozano, Marina; Vergès, Josep Maria; Caramelli, David; Ramírez, Oscar; Lalueza-Fox, Carles

    2014-01-01

    Previous mitochondrial DNA analyses on ancient European remains have suggested that the current distribution of haplogroup H was modeled by the expansion of the Bell Beaker culture (ca 4,500–4,050 years BP) out of Iberia during the Chalcolithic period. However, little is known on the genetic composition of contemporaneous Iberian populations that do not carry the archaeological tool kit defining this culture. Here we have retrieved mitochondrial DNA (mtDNA) sequences from 19 individuals from a Chalcolithic sample from El Mirador cave in Spain, dated to 4,760–4,200 years BP and we have analyzed the haplogroup composition in the context of modern and ancient populations. Regarding extant African, Asian and European populations, El Mirador shows affinities with Near Eastern groups. In different analyses with other ancient samples, El Mirador clusters with Middle and Late Neolithic populations from Germany, belonging to the Rössen, the Salzmünde and the Baalberge archaeological cultures but not with contemporaneous Bell Beakers. Our analyses support the existence of a common genetic signal between Western and Central Europe during the Middle and Late Neolithic and points to a heterogeneous genetic landscape among Chalcolithic groups. PMID:25116044

  5. Mitochondrial DNA from El Mirador cave (Atapuerca, Spain) reveals the heterogeneity of Chalcolithic populations.

    PubMed

    Gómez-Sánchez, Daniel; Olalde, Iñigo; Pierini, Federica; Matas-Lalueza, Laura; Gigli, Elena; Lari, Martina; Civit, Sergi; Lozano, Marina; Vergès, Josep Maria; Caramelli, David; Ramírez, Oscar; Lalueza-Fox, Carles

    2014-01-01

    Previous mitochondrial DNA analyses on ancient European remains have suggested that the current distribution of haplogroup H was modeled by the expansion of the Bell Beaker culture (ca 4,500-4,050 years BP) out of Iberia during the Chalcolithic period. However, little is known on the genetic composition of contemporaneous Iberian populations that do not carry the archaeological tool kit defining this culture. Here we have retrieved mitochondrial DNA (mtDNA) sequences from 19 individuals from a Chalcolithic sample from El Mirador cave in Spain, dated to 4,760-4,200 years BP and we have analyzed the haplogroup composition in the context of modern and ancient populations. Regarding extant African, Asian and European populations, El Mirador shows affinities with Near Eastern groups. In different analyses with other ancient samples, El Mirador clusters with Middle and Late Neolithic populations from Germany, belonging to the Rössen, the Salzmünde and the Baalberge archaeological cultures but not with contemporaneous Bell Beakers. Our analyses support the existence of a common genetic signal between Western and Central Europe during the Middle and Late Neolithic and points to a heterogeneous genetic landscape among Chalcolithic groups. PMID:25116044

  6. Discovery of Power-Law Growth in the Self-Renewal of Heterogeneous Glioma Stem Cell Populations

    PubMed Central

    Boman, Bruce M.; Fields, Jeremy Z.; Awaji, Miharu; Kozano, Hiroko; Tamura, Ryoi; Yamamoto, Seiji; Ogata, Toru; Yamada, Mitsuhiko; Endo, Shunro; Kurimoto, Masanori; Kuroda, Satoshi

    2015-01-01

    Background Accumulating evidence indicates that cancer stem cells (CSCs) drive tumorigenesis. This suggests that CSCs should make ideal therapeutic targets. However, because CSC populations in tumors appear heterogeneous, it remains unclear how CSCs might be effectively targeted. To investigate the mechanisms by which CSC populations maintain heterogeneity during self-renewal, we established a glioma sphere (GS) forming model, to generate a population in which glioma stem cells (GSCs) become enriched. We hypothesized, based on the clonal evolution concept, that with each passage in culture, heterogeneous clonal sublines of GSs are generated that progressively show increased proliferative ability. Methodology/Principal Findings To test this hypothesis, we determined whether, with each passage, glioma neurosphere culture generated from four different glioma cell lines become progressively proliferative (i.e., enriched in large spheres). Rather than monitoring self-renewal, we measured heterogeneity based on neurosphere clone sizes (#cells/clone). Log-log plots of distributions of clone sizes yielded a good fit (r>0.90) to a straight line (log(% total clones) = k*log(#cells/clone)) indicating that the system follows a power-law (y = xk) with a specific degree exponent (k = ?1.42). Repeated passaging of the total GS population showed that the same power-law was maintained over six passages (CV = ?1.01 to ?1.17). Surprisingly, passage of either isolated small or large subclones generated fully heterogeneous populations that retained the original power-law-dependent heterogeneity. The anti-GSC agent Temozolomide, which is well known as a standard therapy for glioblastoma multiforme (GBM), suppressed the self-renewal of clones, but it never disrupted the power-law behavior of a GS population. Conclusions/Significance Although the data above did not support the stated hypothesis, they did strongly suggest a novel mechanism that underlies CSC heterogeneity. They indicate that power-law growth governs the self-renewal of heterogeneous glioma stem cell populations. That the data always fit a power-law suggests that: (i) clone sizes follow continuous, non-random, and scale-free hierarchy; (ii) precise biologic rules that reflect self-organizing emergent behaviors govern the generation of neurospheres. That the power-law behavior and the original GS heterogeneity are maintained over multiple passages indicates that these rules are invariant. These self-organizing mechanisms very likely underlie tumor heterogeneity during tumor growth. Discovery of this power-law behavior provides a mechanism that could be targeted in the development of new, more effective, anti-cancer agents. PMID:26284929

  7. 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

  8. 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

  9. Psychoeducation in an Outpatient Setting--Designing a Heterogeneous Format for a Heterogeneous Population of Juvenile Delinquents.

    ERIC Educational Resources Information Center

    Carpenter, Patricia; Sugrue, Dennis P.

    1984-01-01

    Describes the G.I.T. (Getting It Together) program, a heterogeneous delinquent treatment program combining affective education and social skills training. Delinquents with immature personalities or neurotic features appeared to benefit more from the program than those with characterological disorders. (JAC)

  10. IL12B expression is sustained by a heterogenous population of myeloid lineages during tuberculosis

    PubMed Central

    Reeme, Allison E.; Miller, Halli E.; Robinson, Richard T.

    2015-01-01

    Summary IL12B is required for resistance to Mycobacterium tuberculosis (Mtb) infection, promoting the initiation and maintenance of Mtb-specific effector responses. While this makes the IL12-pathway an attractive target for experimental tuberculosis (TB) therapies, data regarding what lineages express IL12B after infection is established are limited. This is not obvious in the lung, an organ in which both hematopoietic and non-hematopoietic lineages produce IL12p40 upon pathogen encounter. Here, we use radiation bone marrow chimeras and Yet40 reporter mice to determine what lineages produce IL12p40 during experimental TB. We observed that hematopoietic IL12p40-production was sufficient to control Mtb, with no contribution by non-hematopoietic lineages. Furthermore, rather than being produced by a single subset, IL12p40 was produced by cells that were heterogenous in their size, granularity, autofluorescence and expression of CD11c, CD11b and CD8?. While depending on the timepoint and tissue examined, the surface phenotype of IL12p40-producers most closely resembled macrophages based on previous surveys of lung myeloid lineages. Importantly, depletion of CDllchi cells during infection had no affect on lung IL12p40-concentrations. Collectively, our data demonstrate that IL12p40 production is sustained by a heterogenous population of myeloid lineages during experimental TB, and that redundant mechanisms of IL12p40-production exist when CD11chi lineages are absent. PMID:23491716

  11. 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.

  12. Exposing medical students to expanding populations

    PubMed Central

    Lindenthal, JJ; DeLisa, JA; Heinrich, GF; Calderón Gerstein, WS

    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

  13. 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

  14. Population-level thermal performance of a cold-water ectotherm is linked to ontogeny and local environmental heterogeneity

    USGS Publications Warehouse

    Hossack, Blake R.; Corn, P. Stephen; , Winsor H. Lowe; , Molly A. H. Webb; , Mariah J. Talbott; , Kevin M. Kappenman

    2013-01-01

    5. Our experiments with a cold-water species show that population-level performance varies across small geographic scales and is linked to local environmental heterogeneity. This variation could influence the rate and mode of species-level responses to climate change, both by facilitating local persistence in the face of change

  15. 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

  16. Heterogeneity in ALSFRS-R decline and survival: a population-based study in Italy.

    PubMed

    Mandrioli, Jessica; Biguzzi, Sara; Guidi, Carlo; Sette, Elisabetta; Terlizzi, Emilio; Ravasio, Alessandro; Casmiro, Mario; Salvi, Fabrizio; Liguori, Rocco; Rizzi, Romana; Pietrini, Vladimiro; Borghi, Annamaria; Rinaldi, Rita; Fini, Nicola; Chierici, Elisabetta; Santangelo, Mario; Granieri, Enrico; Mussuto, Vittoria; De Pasqua, Silvia; Georgoulopoulou, Eleni; Fasano, Antonio; Ferro, Salvatore; D'Alessandro, Roberto

    2015-12-01

    Very few studies examined trend over time of the revised Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS-R) and factors influencing it; previous studies, then, included only patients attending tertiary ALS Centres. We studied ALSFRS-R decline, factors influencing this trend and survival in a population-based setting. From 2009 onwards, a prospective registry records all incident ALS cases among residents in Emilia Romagna (population: 4.4 million). For each patient, demographic and clinical details (including ALSFRS-R) are collected by caring physicians at each follow-up. Analysis was performed on 402 incident cases (1279 ALSFRS-R assessments). The average decline of the ALSFRS-R was 0.60 points/month during the first year after diagnosis and 0.34 points/month in the second year. ALSFRS-R decline was heterogeneous among subgroups. Repeated measures mixed model showed that ALSFRS-R score decline was influenced by age at onset (p < 0.01), phenotype (p = 0.01), body mass index (BMI) (p < 0.01), progression rate at diagnosis (?FS) (p < 0.01), El Escorial Criteria-Revised (p < 0.01), and FVC% at diagnosis (p < 0.01). Among these factors, at multivariate analysis, only age, site of onset and ?FS independently influenced survival. In this first population-based study on ALSFRS-R trend, we confirm that ALSFRS-R decline is not homogeneous among ALS patients and during the disease. Factors influencing ALSFRS-R decline may not match with those affecting survival. These disease modifiers should be taken into consideration for trials design and in clinical practice during discussions with patients on prognosis. PMID:26205535

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

    ERIC Educational Resources Information Center

    Zabrowski, Edward K.; And Others

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

  18. Student and School Staff Strategies to Combat Cyberbullying in an Urban Student Population

    ERIC Educational Resources Information Center

    Pelfrey, William V., Jr.; Weber, Nicole L.

    2015-01-01

    Research indicates that cyberbullying is occurring among middle and high school student populations at increasing rates. There is limited research, however, on strategies students use to combat cyberbullying, as well as how schools implement policies, intervention tactics, and prevention strategies. This qualitative study aimed to explore, among a…

  19. Culture History and Population Heterogeneity as Determinants of Bacterial Adaptation: the Adaptomics of a Single Environmental Transition

    PubMed Central

    Ryall, Ben; Eydallin, Gustavo

    2012-01-01

    Summary: Diversity in adaptive responses is common within species and populations, especially when the heterogeneity of the frequently large populations found in environments is considered. By focusing on events in a single clonal population undergoing a single transition, we discuss how environmental cues and changes in growth rate initiate a multiplicity of adaptive pathways. Adaptation is a comprehensive process, and stochastic, regulatory, epigenetic, and mutational changes can contribute to fitness and overlap in timing and frequency. We identify culture history as a major determinant of both regulatory adaptations and microevolutionary change. Population history before a transition determines heterogeneities due to errors in translation, stochastic differences in regulation, the presence of aged, damaged, cheating, or dormant cells, and variations in intracellular metabolite or regulator concentrations. It matters whether bacteria come from dense, slow-growing, stressed, or structured states. Genotypic adaptations are history dependent due to variations in mutation supply, contingency gene changes, phase variation, lateral gene transfer, and genome amplifications. Phenotypic adaptations underpin genotypic changes in situations such as stress-induced mutagenesis or prophage induction or in biofilms to give a continuum of adaptive possibilities. Evolutionary selection additionally provides diverse adaptive outcomes in a single transition and generally does not result in single fitter types. The totality of heterogeneities in an adapting population increases the chance that at least some individuals meet immediate or future challenges. However, heterogeneity complicates the adaptomics of single transitions, and we propose that subpopulations will need to be integrated into future population biology and systems biology predictions of bacterial behavior. PMID:22933562

  20. 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

  1. 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.

  2. Genetic heterogeneity of Beta thalassemia in Lebanon reflects historic and recent population migration.

    PubMed

    Makhoul, N J; Wells, R S; Kaspar, H; Shbaklo, H; Taher, A; Chakar, N; Zalloua, P A

    2005-01-01

    Beta thalassemia is an autosomal recessive disorder characterized by reduced (beta(+)) or absent (beta(0)) beta-globin chain synthesis. In Lebanon it is the most predominant genetic defect. In this study we investigated the religious and geographic distribution of the beta-thalassemia mutations identified in Lebanon, and traced their precise origins. A total of 520 beta-globin chromosomes from patients of different religious and regional backgrounds was studied. Beta thalassemia mutations were identified using Amplification Refractory Mutation System (ARMS) PCR or direct gene sequencing. Six (IVS-I-110, IVS-I-1, IVS-I-6, IVS-II-1, cd 5 and the C > T substitution at cd 29) out of 20 beta-globin defects identified accounted for more than 86% of the total beta-thalassemia chromosomes. Sunni Muslims had the highest beta-thalassemia carrier rate and presented the greatest heterogeneity, with 16 different mutations. Shiite Muslims followed closely with 13 mutations, whereas Maronites represented 11.9% of all beta-thalassemic subjects and carried 7 different mutations. RFLP haplotype analysis showed that the observed genetic diversity originated from both new mutational events and gene flow from population migration. This study provides information about the types and distribution of beta-thalassemia mutations within each religious group and geographic region, which is essential for the implementation of screening and prevention programs. PMID:15638828

  3. CHIP buffers heterogeneous Bcl-2 expression levels to prevent augmentation of anticancer drug-resistant cell population.

    PubMed

    Tsuchiya, M; Nakajima, Y; Waku, T; Hiyoshi, H; Morishita, T; Furumai, R; Hayashi, Y; Kishimoto, H; Kimura, K; Yanagisawa, J

    2015-08-27

    Many types of cancer display heterogeneity in various features, including gene expression and malignant potential. This heterogeneity is associated with drug resistance and cancer progression. Recent studies have shown that the expression of a major protein quality control ubiquitin ligase, carboxyl terminus of Hsc70-interacting protein (CHIP), is negatively correlated with breast cancer clinicopathological stages and poor overall survival. Here we show that CHIP acts as a capacitor of heterogeneous Bcl-2 expression levels and prevents an increase in the anticancer drug-resistant population in breast cancer cells. CHIP knockdown in breast cancer cells increased variation in Bcl-2 expression levels, an antiapoptotic protein, among the cells. Our results also showed that CHIP knockdown increased the proportion of anticancer drug-resistant cells. These findings suggest that CHIP buffers variation in gene expression levels, affecting resistance to anticancer drugs. In single-cell clones derived from breast cancer cell lines, CHIP knockdown did not alter the variation in Bcl-2 expression levels and the proportion of anticancer drug-resistant cells. In contrast, when clonal cells were treated with a mutagen, the variation in Bcl-2 expression levels and proportion of anticancer drug-resistant cells were altered by CHIP knockdown. These results suggest that CHIP masks genetic variations to suppress heterogeneous Bcl-2 expression levels and prevents augmentation of the anticancer drug-resistant population of breast cancer cells. Because genetic variation is a major driver of heterogeneity, our results suggest that the degree of heterogeneity in expression levels is decided by a balance between genetic variation and the buffering capacity of CHIP. PMID:25435366

  4. Joint effects of habitat heterogeneity and species' life-history traits on population dynamics in spatially structured landscapes.

    PubMed

    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

  5. 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

  6. 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.

  7. ECOLOGY AND POPULATION BIOLOGY Influence of Multiple Factors on Insect Colonization of Heterogeneous

    E-print Network

    Holt, Robert D.

    of Heterogeneous Landscapes: A Review and Case Study with Periodical Cicadas (Homoptera: Cicadidae) WILLIAM M. COOK of unmeasured habitat parameters. In this study of colonization by cicada Magicicada cassinii (FisherÞne-scale,within-patchvariationinlocalstemdensitycanbeimportanttotheinterpretation of insect dispersal and colonization. KEY WORDS cicadas, colonization, heterogeneous habitats, rough

  8. 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

  9. PERCEPTIONS OF THE CAPACITY FOR CHANGE AS A COMPONENT OF LEADERSHIP DEVELOPMENT AS REPORTED BY SELECT POPULATIONS OF COLLEGE STUDENTS: IMPLICATIONS FOR COLLEGE STUDENT LEADERSHIP DEVELOPMENT 

    E-print Network

    Durham Hynes, Sharra L.

    2010-01-16

    populations of interest were first generation college students, transfer students and male students. The purpose of the study was to determine the self-perceived capacity to adapt to change for selected college student populations based on the Social Change...

  10. The effects of selective history and environmental heterogeneity on inbreeding depression in experimental populations of Drosophila melanogaster.

    PubMed

    Long, Tristan A F; Rowe, Locke; Agrawal, Aneil F

    2013-04-01

    Inbreeding depression varies considerably among populations, but only some aspects of this variation have been thoroughly studied. Because inbreeding depression requires genetic variation, factors that influence the amount of standing variation can affect the magnitude of inbreeding depression. Environmental heterogeneity has long been considered an important contributor to the maintenance of genetic variation, but its effects on inbreeding depression have been largely ignored by empiricists. Here we compare inbreeding depression, measured in two environments, for 20 experimental populations of Drosophila melanogaster that have been maintained under four different selection regimes, including two types of environmentally homogeneous selection and two types environmentally heterogeneous selection. In line with theory, we find considerably higher inbreeding depression in populations from heterogeneous selection regimes. We also use our data set to test whether inbreeding depression is correlated with either stress or the phenotypic coefficient of variation (CV), as suggested by some recent studies. Though both of these factors are significant predictors of inbreeding depression in our study, there is an effect of assay environment on inbreeding depression that cannot be explained by either stress or CV. PMID:23535617

  11. Environmental heterogeneity generates opposite gene-by-environment interactions for two fitness-related traits within a population.

    PubMed

    Culumber, Zachary W; Schumer, Molly; Monks, Scott; Tobler, Michael

    2015-02-01

    Theory predicts that environmental heterogeneity offers a potential solution to the maintenance of genetic variation within populations, but empirical evidence remains sparse. The live-bearing fish Xiphophorus variatus exhibits polymorphism at a single locus, with different alleles resulting in up to five distinct melanistic "tailspot" patterns within populations. We investigated the effects of heterogeneity in two ubiquitous environmental variables (temperature and food availability) on two fitness-related traits (upper thermal limits and body condition) in two different tailspot types (wild-type and upper cut crescent). We found gene-by-environment (G × E) interactions between tailspot type and food level affecting upper thermal limits (UTL), as well as between tailspot type and thermal environment affecting body condition. Exploring mechanistic bases underlying these G × E patterns, we found no differences between tailspot types in hsp70 gene expression despite significant overall increases in expression under both thermal and food stress. Similarly, there was no difference in routine metabolic rates between the tailspot types. The reversal of relative performance of the two tailspot types under different environmental conditions revealed a mechanism by which environmental heterogeneity can balance polymorphism within populations through selection on different fitness-related traits. PMID:25496554

  12. Comparative Microsatellite Typing of New World Leishmania infantum Reveals Low Heterogeneity among Populations and Its Recent Old World Origin

    PubMed Central

    Kuhls, Katrin; Alam, Mohammad Zahangir; Cupolillo, Elisa; Ferreira, Gabriel Eduardo M.; Mauricio, Isabel L.; Oddone, Rolando; Feliciangeli, M. Dora; Wirth, Thierry; Miles, Michael A.; Schönian, Gabriele

    2011-01-01

    Leishmania infantum (syn. L. chagasi) is the causative agent of visceral leishmaniasis (VL) in the New World (NW) with endemic regions extending from southern USA to northern Argentina. The two hypotheses about the origin of VL in the NW suggest (1) recent importation of L. infantum from the Old World (OW), or (2) an indigenous origin and a distinct taxonomic rank for the NW parasite. Multilocus microsatellite typing was applied in a survey of 98 L. infantum isolates from different NW foci. The microsatellite profiles obtained were compared to those of 308 L. infantum and 20 L. donovani strains from OW countries previously assigned to well-defined populations. Two main populations were identified for both NW and OW L. infantum. Most of the NW strains belonged to population 1, which corresponded to the OW MON-1 population. However, the NW population was much more homogeneous. A second, more heterogeneous, population comprised most Caribbean strains and corresponded to the OW non-MON-1 population. All Brazilian L. infantum strains belonged to population 1, although they represented 61% of the sample and originated from 9 states. Population analysis including the OW L. infantum populations indicated that the NW strains were more similar to MON-1 and non-MON-1 sub-populations of L. infantum from southwest Europe, than to any other OW sub-population. Moreover, similarity between NW and Southwest European L. infantum was higher than between OW L. infantum from distinct parts of the Mediterranean region, Middle East and Central Asia. No correlation was found between NW L. infantum genotypes and clinical picture or host background. This study represents the first continent-wide analysis of NW L. infantum population structure. It confirmed that the agent of VL in the NW is L. infantum and that the parasite has been recently imported multiple times to the NW from southwest Europe. PMID:21666787

  13. A Novel Staining Protocol for Multiparameter Assessment of Cell Heterogeneity in Phormidium Populations (Cyanobacteria) Employing Fluorescent Dyes

    PubMed Central

    Tashyreva, Daria; Elster, Josef; Billi, Daniela

    2013-01-01

    Bacterial populations display high heterogeneity in viability and physiological activity at the single-cell level, especially under stressful conditions. We demonstrate a novel staining protocol for multiparameter assessment of individual cells in physiologically heterogeneous populations of cyanobacteria. The protocol employs fluorescent probes, i.e., redox dye 5-cyano-2,3-ditolyl tetrazolium chloride, ‘dead cell’ nucleic acid stain SYTOX Green, and DNA-specific fluorochrome 4?,6-diamidino-2-phenylindole, combined with microscopy image analysis. Our method allows simultaneous estimates of cellular respiration activity, membrane and nucleoid integrity, and allows the detection of photosynthetic pigments fluorescence along with morphological observations. The staining protocol has been adjusted for, both, laboratory and natural populations of the genus Phormidium (Oscillatoriales), and tested on 4 field-collected samples and 12 laboratory strains of cyanobacteria. Based on the mentioned cellular functions we suggest classification of cells in cyanobacterial populations into four categories: (i) active and intact; (ii) injured but active; (iii) metabolically inactive but intact; (iv) inactive and injured, or dead. PMID:23437052

  14. Modelling population heterogeneity in sensitivity and specificity of a multi-stage screen for obstructive sleep apnoea.

    PubMed

    ten Have, T R; Bixler, E O

    1997-09-15

    We propose a model-based approach for modelling population heterogeneity in terms of sensitivity and specificity of multi-stage screening procedures that consists of multiple tests ordered according to criteria such as cost and invasiveness. It is assumed that a patient proceeds to the next test only if they test positive for the current test. An overall positive result occurs if a patient tests positive for all tests. A dropout occurs when a subject tests positive for a test but does not proceed to subsequent tests. Chinchilli proposed estimates of sensitivity and specificity based upon ratios of multinomial sample probabilities for such a multi-stage procedure in a homogeneous population. The method proposed here accommodates population heterogeneity with generalized linear models and transformation-based confidence intervals. In contrast to the approach of Chinchilli, such an approach provides model-based tests of population differences, narrower confidence intervals that satisfy boundary constraints, and a method for accommodating dropouts without the need for prespecified weights. The proposed method is motivated by the need to assess age differences in the accuracy of a multi-stage test for obstructive sleep apnoea. PMID:9304769

  15. Explaining Spatial Heterogeneity in Population Dynamics and Genetics from Spatial Variation in Resources for a Large Herbivore

    PubMed Central

    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

  16. Rate response of neurons subject to fast or frozen noise: From stochastic and homogeneous to deterministic and heterogeneous populations

    NASA Astrophysics Data System (ADS)

    Alijani, Azadeh Khajeh; Richardson, Magnus J. E.

    2011-07-01

    The response of a neuronal population to afferent drive can be expected to be sensitive to both the distribution and dynamics of membrane voltages within the population. Voltage fluctuations can be driven by synaptic noise, neuromodulators, or cellular inhomogeneities: processes ranging from millisecond autocorrelation times to effectively static or “frozen” noise. Here we extend previous studies of filtered fluctuations to the experimentally verified exponential integrate-and-fire model. How fast or frozen fluctuations affect the steady-state rate and firing-rate response are both examined using perturbative solutions and limits of a 1 + 2 dimensional Fokker-Planck equation. The central finding is that, under conditions of a more-or-less constant population voltage variance, the firing-rate response is only weakly dependent on the fluctuation filter constant: The voltage distribution is the principal determinant of the population response. This result is unexpected given the nature of the systems underlying the extreme limits of fast and frozen fluctuations; the first limit represents a homogeneous population of neurons firing stochastically, whereas the second limit is equivalent to a heterogeneous population of neurons firing deterministically.

  17. 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

  18. Multilocus genotyping reveals high heterogeneity and strong local population structure of the Plasmodium vivax population in the Peruvian Amazon

    PubMed Central

    2010-01-01

    Background Peru is one of the Latin American countries with the highest malaria burden, mainly due to Plasmodium vivax infections. However, little is known about P. vivax transmission dynamics in the Peruvian Amazon, where most malaria cases occur. The genetic diversity and population structure of P. vivax isolates collected in different communities around Iquitos city, the capital of the Peruvian Amazon, was determined. Methods Plasmodium vivax population structure was determined by multilocus genotyping with 16 microsatellites on 159 P. vivax infected blood samples (mono-infections) collected in four sites around Iquitos city. The population characteristics were assessed only in samples with monoclonal infections (n = 94), and the genetic diversity was determined by calculating the expected heterozygosity and allelic richness. Both linkage disequilibrium and the genetic differentiation (?) were estimated. Results The proportion of polyclonal infections varied substantially by site (11% - 70%), with the expected heterozygosity ranging between 0.44 and 0.69; no haplotypes were shared between the different populations. Linkage disequilibrium was present in all populations (IAS 0.14 - 0.61) but was higher in those with fewer polyclonal infections, suggesting inbreeding and a clonal population structure. Strong population differentiation (? = 0.45) was found and the Bayesian inference cluster analysis identified six clusters based on distinctive allele frequencies. Conclusion The P. vivax populations circulating in the Peruvian Amazon basin are genetically diverse, strongly differentiated and they have a low effective recombination rate. These results are in line with the low and clustered pattern of malaria transmission observed in the region around Iquitos city. PMID:20525233

  19. Hispanics: A Diverse Population of Students to Influence the Landscape of Higher Education

    ERIC Educational Resources Information Center

    Page, Jill

    2013-01-01

    Hispanic students are a growing and pervasive population within higher education. This position paper examines population characteristics and educational patterns of Hispanic students that underscore failures of the higher education system in serving these students, in addition to institutional issues and cultural values that further complicate…

  20. 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

  1. Resolving Heterogeneity: Fluorescence-Activated Cell Sorting of Dynamic Cell Populations from Feeder-Free Mouse Embryonic Stem Cell Culture.

    PubMed

    Hölzenspies, Jurriaan; Dela Cruz, Gelo; M Brickman, Joshua

    2016-01-01

    Embryonic stem cell (ESC) culture comprises a mixture of cells that are primed to differentiate into different lineages. In conditions where ESCs self-renew, these primed populations continuously interconvert and consequently show highly dynamic coordinated changes in their expression of different sets of pluripotency and differentiation markers. It has become increasingly apparent that this transcriptional heterogeneity is an important characteristic of ESC culture. By sorting for specific populations of ESCs it is possible to enrich for cells with a capacity to colonize the embryo proper or the extra-embryonic lineages such as the descendents of the primitive endoderm or trophoblast. Here, we describe a method of isolating specific sub-sets of ESCs from the pluripotent cells present in in vitro ESC culture using SSEA1 antibody staining in combination with reporter lines and fluorescence activated cell sorting (FACS). PMID:26026884

  2. Determining the effects of a spatially heterogeneous selection pressure on bacterial population structure at the sub-millimetre scale.

    PubMed

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

    2010-11-01

    A key interest of microbial ecology is to understand the role of environmental heterogeneity in shaping bacterial diversity and fitness. However, quantifying relevant selection pressures and their effects is challenging due to the number of parameters that must be considered and the multiple scales over which they act. In the current study, a model system was employed to investigate the effects of a spatially heterogeneous mercuric ion (Hg(2+)) selection pressure on a population comprising Hg-sensitive and Hg-resistant pseudomonads. The Hg-sensitive bacteria were Pseudomonas fluorescens SBW25::rfp and Hg-resistant bacteria were P. fluorescens SBW25 carrying a gfp-labelled, Hg resistance plasmid. In the absence of Hg, the plasmid confers a considerable fitness cost on the host, with µ(max) for plasmid-carrying cells relative to plasmid-free cells of only 0.66. Two image analysis techniques were developed to investigate the structure that developed in biofilms about foci of Hg (cellulose fibres imbued with HgCl(2)). Both techniques indicated selection for the resistant phenotype occurred only in small areas of approximately 178-353 ?m (manually defined contour region analysis) or 275-350 ?m (daime analysis) from foci. Hg also elicited toxic effects that reduced the growth of both Hg-sensitive and Hg-resistant bacteria up to 250 ?m from foci. Selection for the Hg resistance phenotype was therefore highly localised when Hg was spatially heterogeneous. As such, for this model system, we define here the spatial scale over which selection operates. The ability to quantify changes in the strength of selection for particular phenotypes over sub-millimetre scales is useful for understanding the scale over which environmental variables affect bacterial populations. PMID:20512486

  3. 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,…

  4. Connectivity, passability and heterogeneity interact to determine fish population persistence in river networks.

    PubMed

    Samia, Yasmine; Lutscher, Frithjof; Hastings, Alan

    2015-09-01

    The movement of fish in watersheds is frequently inhibited by human-made migration barriers such as dams or culverts. The resulting lack of connectivity of spatial subpopulations is often cited as a cause for observed population decline. We formulate a matrix model for a spatially distributed fish population in a watershed, and we investigate how location and other characteristics of a single movement barrier impact the asymptotic growth rate of the population. We find that while population growth rate often decreases with the introduction of a movement obstacle, it may also increase due to a 'retention effect'. Furthermore, obstacle mortality greatly affects population growth rate. In practice, different connectivity indices are used to predict population effects of migration barriers, but the relation of these indices to population growth rates in demographic models is often unclear. When comparing our results with the dentritic connectivity index, we see that the index captures neither the retention effect nor the influences of obstacle mortality. We argue that structural indices cannot entirely replace more detailed demographic models to understand questions of persistence and extinction. We advocate the development of novel functional indices and characteristics. PMID:26311313

  5. Pooled-testing procedures for screening high volume clinical specimens in heterogeneous populations.

    PubMed

    Bilder, Christopher R; Tebbs, Joshua M

    2012-11-30

    Pooled testing is a procedure commonly used to reduce the cost of screening a large number of individuals for infectious diseases. In its simplest form, pooled testing works by compositing a set of individual specimens (e.g., blood or urine) into a common pool. If the pool tests negative, all individuals within it are diagnosed as negative. If the pool tests positive, retesting is needed to decode the positive individuals from the negative individuals. Traditionally, pooled testing has assumed that each individual has the same probability of being positive. However, this assumption is often unrealistic, especially when known risk factors can be used to measure distinct probabilities of positivity for each individual. In this paper, we investigate new pooled-testing algorithms that exploit the heterogeneity among individual probabilities and subsequently reduce the total number of tests needed, while maintaining accuracy levels similar to standard algorithms that do not account for heterogeneity. We apply these algorithms to data from the Infertility Prevention Project, a nationally implemented program supported by the Centers for Disease Control and Prevention. PMID:22415972

  6. Genomic analysis of a heterogeneous Mendelian phenotype: multiple novel alleles for inherited hearing loss in the Palestinian population.

    PubMed

    Walsh, Tom; Abu Rayan, Amal; Abu Sa'ed, Judeh; Shahin, Hashem; Shepshelovich, Jeanne; Lee, Ming K; Hirschberg, Koret; Tekin, Mustafa; Salhab, Wa'el; Avraham, Karen B; King, Mary-Claire; Kanaan, Moien

    2006-01-01

    Recessively inherited phenotypes are frequent in the Palestinian population, as the result of a historical tradition of marriages within extended kindreds, particularly in isolated villages. In order to characterise the genetics of inherited hearing loss in this population, we worked with West Bank schools for the deaf to identify children with prelingual, bilateral, severe to profound hearing loss not attributable to infection, trauma or other known environmental exposure. Of 156 families enrolled, hearing loss in 17 families (11 per cent) was due to mutations in GJB2 (connexin 26), a smaller fraction of GJB2-associated deafness than in other populations. In order to estimate how many different genes might be responsible for hearing loss in this population, we evaluated ten families for linkage to all 36 known human autosomal deafness-related genes, fully sequencing hearing-related genes at any linked sites in informative relatives. Four families harboured four novel alleles of TMPRSS3 (988DeltaA = 352stop), otoancorin (1067A > T = D356V) and pendrin (716T > A = V239D and 1001G > T = 346stop). In each family, all affected individuals were homozygous for the critical mutation. Each allele was specific to one or a few families in the cohort; none were widespread. Since epidemiological tests of association of mutations with deafness were not feasible for such rare alleles, we used functional and bioinformatics approaches to evaluate their consequences. In six other families, hearing loss was not linked to any known gene, suggesting that these families harbour novel genes responsible for this phenotype. We conclude that inherited hearing loss is highly heterogeneous in this population, with most extended families acting as genetic isolates in this context. We also conclude that the same genes are responsible for hearing loss in this population as elsewhere, so that gene discovery in these families informs the genetics of hearing loss worldwide. PMID:16460646

  7. Populating the i2b2 database with heterogeneous EMR data: a semantic network approach.

    PubMed

    Mate, Sebastian; Bürkle, Thomas; Köpcke, Felix; Breil, Bernhard; Wullich, Bernd; Dugas, Martin; Prokosch, Hans-Ulrich; Ganslandt, Thomas

    2011-01-01

    In an ongoing effort to share heterogeneous electronic medical record (EMR) data in an i2b2 instance between the University Hospitals Münster and Erlangen for joint cancer research projects, an ontology based system for the mapping of EMR data to a set of common data elements has been developed. The system translates the mappings into local SQL scripts, which are then used to extract, transform and load the facts data from each EMR into the i2b2 database. By using Semantic Web standards, it is the authors' goal to reuse the laboriously compiled "mapping knowledge" in future projects, such as a comprehensive cancer ontology or even a hospital-wide clinical ontology. PMID:21893800

  8. A role for E-cadherin in ensuring cohesive migration of a heterogeneous population of non-epithelial cells

    PubMed Central

    Campbell, Kyra; Casanova, Jordi

    2015-01-01

    Collective cell migration is a key process underlying the morphogenesis of many organs as well as tumour invasion, which very often involves heterogeneous cell populations. Here we investigated how such populations can migrate cohesively in the Drosophila posterior midgut, comprised of epithelial and mesenchymal cells and show a novel role for the epithelial adhesion molecule E-cadherin (E-Cad) in mesenchymal cells. Despite a lack of junctions at the ultrastructure level, reducing E-Cad levels causes mesenchymal cells to detach from one another and from neighbouring epithelial cells; as a result, coordination between the two populations is lost. Moreover, Bazooka and recycling mechanisms are also required for E-Cad accumulation in mesenchymal cells. These results indicate an active role for E-Cad in mediating cohesive and ordered migration of non-epithelial cells, and discount the notion of E-Cad as just an epithelial feature that has to be switched off to enable migration of mesenchymal cells. PMID:26272476

  9. Computing Ro in a population with heterogeneity in sexual activity and proportionate mixing using a STM-solver

    NASA Astrophysics Data System (ADS)

    Gutierrez A., Natalia A.

    2014-06-01

    A model to determinate the reproductive basic number, detonated Ro, for the case of population with heterogeneity in sexual activity and proportionate mixing is solved using computer algebra and SMT solvers. Specifically Maple and Z3 were used. The code for the solution of the model was written in Z3-Python, but it can also be played by Z3-SMT-Lib. Ro represents an algebraic synthesis of every epidemiological parameter. Numerical simulations were done to prove the effectiveness of the model and the code. The algebraic structure of Ro suggests the possible control measurements that should be implemented to avoid the propagation of the sexual transmitted diseases. The obtained results are important on the computational epidemiology field. As a future investigation, it is suggested to apply the STM solvers to analyze models for other kinds of epidemic diseases.

  10. Stage-dependent responses to emergent habitat heterogeneity: consequences for a predatory insect population in a coffee agroecosystem

    PubMed Central

    Liere, Heidi; Perfecto, Ivette; Vandermeer, John

    2014-01-01

    Interactions among members of biological communities can create spatial patterns that effectively generate habitat heterogeneity for other members in the community, and this heterogeneity might be crucial for their persistence. For example, stage-dependent vulnerability of a predatory lady beetle to aggression of the ant, Azteca instabilis, creates two habitat types that are utilized differently by the immature and adult life stages of the beetle. Due to a mutualistic association between A. instabilis and the hemipteran Coccus viridis – which is A. orbigera main prey in the area – only plants around ant nests have high C. viridis populations. Here, we report on a series of surveys at three different scales aimed at detecting how the presence and clustered distribution of ant nests affect the distribution of the different life stages of this predatory lady beetle in a coffee farm in Chiapas, Mexico. Both beetle adults and larvae were more abundant in areas with ant nests, but adults were restricted to the peripheries of highest ant activity and outside the reach of coffee bushes containing the highest densities of lady beetle larvae. The abundance of adult beetles located around trees with ants increased with the size of the ant nest clusters but the relationship is not significant for larvae. Thus, we suggest that A. orbigera undergoes an ontogenetic niche shift, not through shifting prey species, but through stage-specific vulnerability differences against a competitor that renders areas of abundant prey populations inaccessible for adults but not for larvae. Together with evidence presented elsewhere, this study shows how an important predator is not only dependent on the existence of two qualitatively distinct habitat types, but also on the spatial distribution of these habitats. We suggest that this dependency arises due to the different responses that the predator's life stages have to this emergent spatial pattern. PMID:25473473

  11. Differing effects of attention in single-units and populations are well predicted by heterogeneous tuning and the normalization model of attention.

    PubMed

    Hara, Yuko; Pestilli, Franco; Gardner, Justin L

    2014-01-01

    Single-unit measurements have reported many different effects of attention on contrast-response (e.g., contrast-gain, response-gain, additive-offset dependent on visibility), while functional imaging measurements have more uniformly reported increases in response across all contrasts (additive-offset). The normalization model of attention elegantly predicts the diversity of effects of attention reported in single-units well-tuned to the stimulus, but what predictions does it make for more realistic populations of neurons with heterogeneous tuning? Are predictions in accordance with population-scale measurements? We used functional imaging data from humans to determine a realistic ratio of attention-field to stimulus-drive size (a key parameter for the model) and predicted effects of attention in a population of model neurons with heterogeneous tuning. We found that within the population, neurons well-tuned to the stimulus showed a response-gain effect, while less-well-tuned neurons showed a contrast-gain effect. Averaged across the population, these disparate effects of attention gave rise to additive-offsets in contrast-response, similar to reports in human functional imaging as well as population averages of single-units. Differences in predictions for single-units and populations were observed across a wide range of model parameters (ratios of attention-field to stimulus-drive size and the amount of baseline response modifiable by attention), offering an explanation for disparity in physiological reports. Thus, by accounting for heterogeneity in tuning of realistic neuronal populations, the normalization model of attention can not only predict responses of well-tuned neurons, but also the activity of large populations of neurons. More generally, computational models can unify physiological findings across different scales of measurement, and make links to behavior, but only if factors such as heterogeneous tuning within a population are properly accounted for. PMID:24600380

  12. 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.

  13. A heterogeneous population code for elapsed time in rat medial agranular cortex

    PubMed Central

    Matell, Matthew S.; Shea-Brown, Eric; Gooch, Cindy; Wilson, A. George; Rinzel, John

    2010-01-01

    The neural mechanisms underlying the temporal control of behavior are largely unknown. Here we recorded from the medial agranular cortex in rats trained to respond on a temporal production procedure for probabilistically available food reward. Due to variability in estimating the time of food availability, robust responding typically bracketed the expected duration, starting some time before and ending some time after the signaled delay. This response period provided an analytic “steady-state” window during which the subject actively timed their behavior. Remarkably, during these response periods, a variety of firing patterns were seen which could be broadly described as ramps, peaks, and dips, with different slopes, directions, and times at which maxima or minima occur. Regularized linear discriminant analysis indicated that these patterns provided sufficiently reliable information to discriminate the elapsed duration of responding within these response periods. Modeling this across neuron variability showed that the utilization of ramps, dips, and peaks with different slopes and minimal/maximal rates at different times led to a substantial improvement in temporal prediction errors, suggesting that heterogeneity in the neural representation of elapsed time may facilitate temporally controlled behavior. PMID:21319888

  14. 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

  15. Dynamic phase microscopy, a new method to detect viable and killed spores and to estimate the heterogeneity of spore populations

    NASA Astrophysics Data System (ADS)

    Tychinsky, Vladimir P.; Mulyukin, Andrey L.; Lisovskii, Vitalii V.; Nikolaev, Yury A.; Kretushev, Aleksander V.; Vyshenskaya, Tatyana V.; Suzina, Nataliya E.; Duda, Vitalii I.; El-Registan, Galina I.

    One of the challenging tasks in monitoring studies is to estimate heterogeneity of microbial populations by the physiological state and potential viability of individual cells, especially with regard of their ability to withstand various environmental assaults. Previously, we described some approaches based on electron microscopy methods to discriminate vegetative, dormant, and dead cells in both aged microbial cultures and environmental samples, including permafrost. We propose to extend the arsenal of microscopy methods for monitoring studies by a new non-invasive and informative method - dynamic phase microscopy (DPM). The substantial advantage of DPM is that it gives quantitative (digitized) data of undestroyed (living) microscopic objects, exemplified in our work by Bacillus licheniformis spores. Using DPM made it possible to record interference images of objects (spores) and to produce picture of their "phase thickness" (PT) that is the optical path difference in nm. Thus, it was demonstrated the remarkable difference in the PT of spores at different physiological states: dormant, germinating, and heat-killed spores had PT values of 80, 40-50, and 20 nm, respectively. The other found criterion to distinguish between spores was the PT fluctuations. In contrast to dormant and killed spores, the PT of germinating spores oscillated with amplitude of up to 7 nm, with typical frequencies of 1.3 and 3.4 Hz. A combination of the recorded PT values and PT fluctuations gave a key to detect viable and dead cells. Under the conditions that did not support germination (the lack of nutrients), we were able to follow the response of a single dormant spore and a spore population to heating from 25 °C to 70 °C. Thus, a very small temperature change (from 40 °C to 42 °C) under conditions non-favorable for germination, caused a drastic decrease in the spores' PT; the second drop in the PT values was observed during heating from 60 °C to 70 °C. These changes were reversible: after cessation of heating, PT values became similar to dormant spores. So, DPM allowed us to track the first, reversible stage of activation, when a spore maintains the attributes of the dormant state. Under the conditions that favor germination (in the presence of nutrients), irreversible changes in the PT and spore diameter, d, were detectable in a single germinating spore and spore population. In addition, DPM allowed an easy estimation of the heterogeneity of spore populations. It is a great advantage of DPM that it makes possible to reveal the ability of spores to respond to various stimuli with or without further germination and outgrowth - the salient feature of a living cell. DPM may have a high potential in general microbiology and astrobiology, enabling to: (1) estimate the heterogeneity of spore populations either under standard conditions and subjected to solar radiation and simulated extraterrestrial factors; (2) to track a response of spores to changing conditions at the early germination stage, even if they do not enter further outgrowth; (3) to develop some approaches for monitoring studies and appraisal of the physiological state of dormant cells in situ, in samples of dry soils, permafrost, etc. regarded as models for searching life beyond the Earth.

  16. Unexpected genetic heterogeneity for primary ciliary dyskinesia in the Irish Traveller population.

    PubMed

    Casey, Jillian P; McGettigan, Paul A; Healy, Fiona; Hogg, Claire; Reynolds, Alison; Kennedy, Breandan N; Ennis, Sean; Slattery, Dubhfeasa; Lynch, Sally A

    2015-02-01

    We present a study of five children from three unrelated Irish Traveller families presenting with primary ciliary dyskinesia (PCD). As previously characterized disorders in the Irish Traveller population are caused by common homozygous mutations, we hypothesised that all three PCD families shared the same recessive mutation. However, exome sequencing showed that there was no pathogenic homozygous mutation common to all families. This finding was supported by histology, which showed that each family has a different type of ciliary defect; transposition defect (family A), nude epithelium (family B) and absence of inner and outer dynein arms (family C). Therefore, each family was analysed independently using homozygosity mapping and exome sequencing. The affected siblings in family A share a novel 1?bp duplication in RSPH4A (NM_001161664.1:c.166dup; p.Arg56Profs*11), a radial-spoke head protein involved in ciliary movement. In family B, we identified three candidate genes (CCNO, KCNN3 and CDKN1C), with a 5-bp duplication in CCNO (NM_021147.3:c.258_262dup; p.Gln88Argfs*8) being the most likely cause of ciliary aplasia. This is the first study to implicate CCNO, a DNA repair gene reported to be involved in multiciliogenesis, in PCD. In family C, we identified a ?3.5-kb deletion in DYX1C1, a neuronal migration gene previously associated with PCD. This is the first report of a disorder in the relatively small Irish Traveller population to be caused by >1 disease gene. Our study identified at least three different PCD genes in the Irish Traveller population, highlighting that one cannot always assume genetic homogeneity, even in small consanguineous populations. PMID:24824133

  17. 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

  18. 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

  19. 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

  20. Heterogeneity of respiratory dendritic cell subsets and lymphocyte populations in inbred mouse strains

    PubMed Central

    2012-01-01

    Background Inbred mouse strains are used in different models of respiratory diseases but the variation of critical respiratory leukocyte subpopulations across different strains is unknown. Methods By using multiparameter flow cytometry we have quantitated respiratory leukocyte subsets including dendritic cells subpopulations, macrophages, classical T and B cells, natural killer cells, ??TCR+ T cells and lineage-negative leukocytes in the five most common inbred mouse strains BALB/c, C57BL/6, DBA/2, 129SV and C3H. To minimize confounding environmental factors, age-matched animals were received from the same provider and were housed under identical specific-pathogen-free conditions. Results Results revealed significant strain differences with respect to respiratory neutrophils (p=0.005; up to 1.4 fold differences versus C57BL/6 mice), eosinophils (p=0.029; up to 2.7 fold), certain dendritic cell subsets (p?0.0003; up to 3.4 fold), T (p<0.001; up to 1.6 fold) and B lymphocyte subsets (p=0.005; up to 0.4 fold), ?? T lymphocytes (p=0.003; up to 1.6 fold), natural killer cells (p<0.0001; up to 0.6 fold) and lineage-negative innate leukocytes (p?0.007; up to 3.6 fold). In contrast, total respiratory leukocytes, macrophages, total dendritic cells and bronchoalveolar lavage leukocytes did not differ significantly. Stimulation of respiratory leukocytes via Toll-like receptor 4 and 9 as well as CD3/CD28 revealed significant strain differences of TNF-? and IL-10 production. Conclusion Our study demonstrates significant strain heterogeneity of respiratory leukocyte subsets that may impact respiratory immunity in different disease models. Additionally, the results may help identification of optimal strains for purification of rare respiratory leukocyte subsets for ex vivo analyses. PMID:23066782

  1. Coalescent Times and Patterns of Genetic Diversity in Species with Facultative Sex: Effects of Gene Conversion, Population Structure, and Heterogeneity.

    PubMed

    Hartfield, Matthew; Wright, Stephen I; Agrawal, Aneil F

    2016-01-01

    Many diploid organisms undergo facultative sexual reproduction. However, little is currently known concerning the distribution of neutral genetic variation among facultative sexual organisms except in very simple cases. Understanding this distribution is important when making inferences about rates of sexual reproduction, effective population size, and demographic history. Here we extend coalescent theory in diploids with facultative sex to consider gene conversion, selfing, population subdivision, and temporal and spatial heterogeneity in rates of sex. In addition to analytical results for two-sample coalescent times, we outline a coalescent algorithm that accommodates the complexities arising from partial sex; this algorithm can be used to generate multisample coalescent distributions. A key result is that when sex is rare, gene conversion becomes a significant force in reducing diversity within individuals. This can reduce genomic signatures of infrequent sex (i.e., elevated within-individual allelic sequence divergence) or entirely reverse the predicted patterns. These models offer improved methods for assessing null patterns of molecular variation in facultative sexual organisms. PMID:26584902

  2. Acculturation, dietary practices and risk for childhood obesity in an ethnically heterogeneous population of Latino school children in the San Francisco bay area.

    PubMed

    Wojcicki, Janet M; Schwartz, Norah; Jiménez-Cruz, Arturo; Bacardi-Gascon, Montserrat; Heyman, Melvin B

    2012-08-01

    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

  3. Diverse levels of an inwardly rectifying potassium conductance generate heterogeneous neuronal behavior in a population of dorsal cochlear nucleus

    E-print Network

    Doiron, Brent

    Diverse levels of an inwardly rectifying potassium conductance generate heterogeneous neuronal. Diverse levels of an inwardly rectifying potassium conductance generate heterogeneous neuronal behavior of a Ba2 -sensitive, inwardly rectifying potassium conductance (Kir). Variability in Kir maximal

  4. Faculty of Medicine, Primary Care and Population Sciences PhD/DM students Name Title Email

    E-print Network

    Huang, Xun

    Faculty of Medicine, Primary Care and Population Sciences ­ PhD/DM students Name Title Email Primary Supervisor in Faculty of Medicine, Primary Care and Population Sciences Professor Paul Roderick Fraser. Dmt1g15@soton.ac.uk Primary Supervisor in Faculty of Medicine, Primary Care and Population

  5. Population Heterogeneity in the Salience of Multiple Risk Factors for Adolescent Delinquency

    PubMed Central

    Lanza, Stephanie T.; Cooper, Brittany R.; Bray, Bethany C.

    2014-01-01

    Purpose To present mixture regression analysis as an alternative to more standard regression analysis for predicting adolescent delinquency. We demonstrate how mixture regression analysis allows for the identification of population subgroups defined by the salience of multiple risk factors. Methods We identified population subgroups (i.e., latent classes) of individuals based on their coefficients in a regression model predicting adolescent delinquency from eight previously established risk indices drawn from the community, school, family, peer, and individual levels. The study included N = 37,763 tenth-grade adolescents who participated in the Communities that Care Youth Survey. Standard, zero-inflated, and mixture Poisson and negative binomial regression models are considered. Results Standard and mixture negative binomial regression models are selected as optimal. The five-class regression model is interpreted based on the class-specific regression coefficients, indicating that risk factors have varying salience across classes of adolescents. Conclusions Standard regression shows that all risk factors are significantly associated with delinquency. Mixture regression provides more nuanced information, suggesting a unique set of risk factors that are salient for different subgroups of adolescents. Implications for the design of subgroup-specific interventions are discussed. PMID:24231260

  6. 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.

  7. 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

  8. Investigating Population Heterogeneity and Interaction Effects of Covariates: The Case of a Large-Scale Assessment for Teacher Licensure in Saudi Arabia

    ERIC Educational Resources Information Center

    Dimitrov, Dimiter M.; Al-Saud, Faisal Abdullah Al-Mashari; Alsadaawi, Abdullah Saleh

    2015-01-01

    This article investigates the population heterogeneity of test data for the case of teacher licensure assessments in Saudi Arabia. The results from factor mixture modeling of the data (N = 15,962) on the construct of "promoting learning" revealed the presence of two latent classes of examinees based on their performance profiles across…

  9. Biochemical Variation and Genetic Heterogeneity in South Carolina Deer Populations Author(s): P. R. Ramsey, J. C. Avise, M. H. Smith, D. F. Urbston

    E-print Network

    Avise, John

    Service, SavannahRiverPlant,Aiken,SC 298014 Abstract: Protein variation in 218 white-tailed deer (OdocoileusBiochemical Variation and Genetic Heterogeneity in South Carolina Deer Populations Author(s): P. R and upland subpopulations were recognized from 6 years of data from controlled hunts. The swamp herd had

  10. 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

  11. Spatial Heterogeneity of Bacterial Populations along an Environmental Gradient at a Shallow Submarine Hydrothermal Vent near Milos Island (Greece)

    PubMed Central

    Sievert, Stefan M.; Brinkhoff, Thorsten; Muyzer, Gerard; Ziebis, Wiebke; Kuever, Jan

    1999-01-01

    The spatial heterogeneity of bacterial populations at a shallow-water hydrothermal vent in the Aegean Sea close to the island of Milos (Greece) was examined at two different times by using acridine orange staining for total cell counts, cultivation-based techniques, and denaturing gradient gel electrophoresis (DGGE) analysis of PCR-amplified 16S rRNA gene fragments. Concurrent with measurements of geochemical parameters, samples were taken along a transect from the center of the vent to the surrounding area. Most-probable-number (MPN) counts of metabolically defined subpopulations generally constituted a minor fraction of the total cell counts; both counting procedures revealed the highest cell numbers in a transition zone from the strongly hydrothermally influenced sediments to normal sedimentary conditions. Total cell counts ranged from 3.2 × 105 cells ml?1 in the water overlying the sediments to 6.4 × 108 cells g (wet weight) of sediment?1. MPN counts of chemolithoautotrophic sulfur-oxidizing bacteria varied between undetectable and 1.4 × 106 cells g?1. MPN counts for sulfate-reducing bacteria and dissimilatory iron-reducing bacteria ranged from 8 to 1.4 × 105 cells g?1 and from undetectable to 1.4 × 106 cells g?1, respectively. DGGE revealed a trend from a diverse range of bacterial populations which were present in approximately equal abundance in the transition zone to a community dominated by few populations close to the center of the vent. Temperature was found to be an important parameter in determining this trend. However, at one sampling time this trend was not discernible, possibly due to storm-induced disturbance of the upper sediment layers. PMID:10473383

  12. Model for acid-mediated tumour invasion with chemotherapy intervention II: Spatially heterogeneous populations.

    PubMed

    Holder, Andrew B; Rodrigo, Marianito R

    2015-12-01

    This paper extends the model for acid-mediated tumour invasion with chemotherapy intervention examined in part I. The model presented in part I considers the interaction between tumour cells, normal cells, acid and drug in a well mixed (i.e. spatially homogeneous) setting, which is governed by a system of nonlinear differential equations. The model examined here removes the assumption that the populations are spatially homogeneous resulting in a system of nonlinear partial differential equations. Numerical simulations of this model are presented for different treatment methods displaying several possible behaviours. Asymptotic approximations are also derived for a special case of the treatment method and set of parameter values. This analysis then allows us to draw conclusions about the effectiveness of treating acid-mediated tumours with chemotherapy. PMID:26459059

  13. Hemoglobin Constant Spring among Southeast Asian Populations: Haplotypic Heterogeneities and Phylogenetic Analysis

    PubMed Central

    Jomoui, Wittaya; Fucharoen, Goonnapa; Sanchaisuriya, Kanokwan; Nguyen, Van Hoa; Fucharoen, Supan

    2015-01-01

    Background Hemoglobin Constant Spring (Hb CS) is an abnormal Hb caused by a mutation at the termination codon of ?2-globin gene found commonly among Southeast Asian and Chinese people. Association of Hb CS with ?°-thalassemia leads to a thalassemia intermedia syndrome commonly encountered in the region. We report chromosome background and addressed genetic origins of Hb CS observed in a large cohort of Hb CS among Southeast Asian populations. Materials and Methods A study was done on 102 Vietnamese (aged 15–49 year-old) and 40 Laotian (aged 18–39 year-old) subjects with Hb CS and results compared with 120 Hb CS genes in Thailand. Hematological parameters were recorded and Hb analysis was performed using capillary electrophoresis. Hb CS mutation and thalassemia genotypes were defined by DNA analysis. Six DNA polymorphisms within ?-globin gene cluster including 5’Xba I, Bgl I, Inter-zeta HVR, AccI, RsaI and ?PstI 3’, were determined using PCR-RFLP assay. Results Nine different genotypes of Hb CS were observed. In contrast to the Thai Hb CS alleles which are mostly linked to haplotype (+—S + + -), most of the Vietnamese and the Laotian Hb CS genes were associated with haplotype (+—M + + -), both of which are different from that of the European Hb CS. Conclusions Hb CS is commonly found in combination with other thalassemias among Southeast Asian populations. Accurate genotyping of the cases requires both hematologic and DNA analyses. At least two independent origins are associated with the Hb CS gene which could indirectly explain the high prevalence of this Hb variant in the region. PMID:26683994

  14. Heterogeneous population effects of an alcohol excise tax increase on sexually transmitted infections morbidity

    PubMed Central

    Staras, Stephanie A S; Livingston, Melvin D; Christou, Alana M; Jernigan, David H; Wagenaar, Alexander C

    2014-01-01

    Background and Aims Alcohol taxes reduce population-level excessive alcohol use and alcohol-related morbidity and mortality, yet little is known about the distribution of the effects of alcohol taxation across race/ethnicity and age subgroups. We examined the race/ethnicity- and age group-specific effects of an excise alcohol tax increase on a common and routinely collected alcohol-related morbidity indicator, sexually transmitted infections. Methods We used an interrupted time series design to examine the effect of a 2009 alcohol tax increase in Illinois, USA on new cases of two common sexually transmitted infections (chlamydia and gonorrhea) reported to the US National Notifiable Disease Surveillance System from January 2003 to December 2011 (n = 108 repeated monthly observations). We estimated the effects of the tax increase on infection rates in the general population and within specific race/ethnicity and age subgroups using mixed models accounting for temporal trends and median income. Results Following the Illinois alcohol tax increase, state-wide rates of gonorrhea decreased 21% [95% confidence Interval (CI) = ?25.7, ?16.7] and chlamydia decreased 11% [95% CI = ?17.8, ?4.4], resulting in an estimated 3506 fewer gonorrhea infections and 5844 fewer chlamydia infections annually. The null hypothesis of homogenous effects by race/ethnicity and age was rejected (P < 0.0001). Significant reductions were observed among non-Hispanic blacks: gonorrhea rates decreased 25.6% (95% CI = ?30.0, ?21.0) and chlamydia rates decreased 14.7% (95% CI = ?20.9, ?8.0). Among non-Hispanics, point estimates suggest decreases were highest among 25–29-year-olds. Conclusions Increased alcohol taxes appear to reduce sexually transmitted infections, especially among subpopulations with high disease burdens, such as non-Hispanic blacks. PMID:24450730

  15. 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

  16. 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

  17. Capillary electrophoresis for fast detection of heterogeneous population in colistin-resistant Gram-negative bacteria.

    PubMed

    Sautrey, Guillaume; Duval, Raphaël E; Chevalley, Alicia; Fontanay, Stéphane; Clarot, Igor

    2015-10-01

    It has been shown that diverse strains of bacteria can be separated according to their characteristic surface properties by means of CE. We employed here this analytical technique to the study of colistin-resistance in Gram-negative bacteria, which involves the selection of mutants with modified outer membrane composition resulting in changes of surface cell properties. In the same way as with molecular entities, we performed firstly the validation of an ITP-based CE method for three common pathogenic Gram-negative bacteria namely Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae. Secondly, we compared the electrophoretic profiles of bacterial samples from a colistin-susceptible clinical isolate of K. pneumoniae and from the corresponding colistin-resistant derivative. By a simple CE run taking a few minutes, the coexistence of several bacterial subpopulations in the colistin-resistant derivative was clearly evidenced. This work encourages further research that would allow applications of CE in clinical laboratory for a daily monitoring of bacterial population in cared patients when "last-chance" colistin treatment is initiated against multidrug-resistant bacteria. PMID:26101140

  18. Dynamic phase microscopy, a new method to detect viable and killed spores and to estimate the heterogeneity of spore populations

    NASA Astrophysics Data System (ADS)

    Tychinsky, V. P.; Mulyukin, A. L.; Lisovskii, V. V.; Nikolaev, Yu. A.; Kretushev, A. V.; Vyshenskaya, T. V.; Suzina, N. E.; Duda, V. I.; El-Registan, G. I.

    One of the challenging tasks in monitoring studies is to estimate heterogeneity of microbial populations by the physiological state and potential viability of individual cells especially with regard of their ability to withstand various environmental assaults Previously we described some approaches based on electron microscopy methods to discriminate vegetative dormant and dead cells in both aged microbial cultures and environmental samples including permafrost In this communication we propose to extend the arsenal of microscopy methods for monitoring studies by a new non-invasive and informative method - dynamic phase microscopy DPM The substantial advantage of DPM is that it gives quantitative digitized data of un-destroyed living microscopic objects exemplified in our work by Bacillus licheniformis spores Using DPM made it possible to record interference images of objects spores and to produce picture of their phase thickness PT that is the optical path difference in nm Thus it was demonstrated the remarkable difference in the PT of spores at different physiological states dormant germinating and heat-killed spores had PT values of 80 nm 40-50 nm and 20 nm respectively The other found criterion to distinguish between spores was the PT fluctuations In contrast to dormant and killed spores the PT of germinating spores oscillated with amplitude of up to 7 nm with typical frequencies of 1 3 and 3 4 Hz A combination of the recorded PT values and PT fluctuations gave a key to detect viable and dead cells Under the conditions that did not

  19. School Enrollment--Social and Economic Characteristics of Students: October 1985 and 1984. Current Population Reports: Population Characteristics.

    ERIC Educational Resources Information Center

    Bruno, Rosalind R.

    1988-01-01

    Using data from the October supplements to the Current Population Survey (CPS), collected in 1984 and 1985, this report presents statistical information on students in the United States attending nursery school through college by age, race, Spanish origin, sex, marital status, household relationship, residence, and family income. The data are…

  20. Guidelines for Death Notification in College Student Populations

    ERIC Educational Resources Information Center

    Hamilton, Lou Ann

    2008-01-01

    College is a time for intellectual growth and also an important time for psychological and emotional maturation and the development of coping skills. The death loss of a family member or friend is a relatively common experience for college students. How students and family members are notified of a death can have a long-standing impact on their…

  1. With Educational Benefits for All: Campus Inclusion through Learning Communities Designed for Underserved Student Populations

    ERIC Educational Resources Information Center

    Fink, John E.; Hummel, Mary L.

    2015-01-01

    This chapter explores the practices of learning communities designed for specific, underserved student populations, highlighting on-campus examples and culminating with a synthesized list of core practices from these "inclusive" learning communities.

  2. Heterogeneity of Borrelia burgdorferi Sensu Stricto Population and Its Involvement in Borrelia Pathogenicity: Study on Murine Model with Specific Emphasis on the Skin Interface

    PubMed Central

    Kern, Aurélie; Schnell, Gilles; Bernard, Quentin; Bœuf, Amandine; Jaulhac, Benoît; Collin, Elody; Barthel, Cathy

    2015-01-01

    Lyme disease is a multisystemic disorder caused by B. burgdorferi sl. The molecular basis for specific organ involvement is poorly understood. The skin plays a central role in the development of Lyme disease as the entry site of B. burgdorferi in which specific clones are selected before dissemination. We compared the skin inflammatory response (antimicrobial peptides, cytokines and chemokines) elicited by spirochete populations recovered from patients presenting different clinical manifestations. Remarkably, these spirochete populations induced different inflammatory profiles in the skin of C3H/HeN mice. As spirochete population transmitted into the host skin is heterogeneous, we isolated one bacterial clone from a population recovered from a patient with neuroborreliosis and compared its virulence to the parental population. This clone elicited a strong cutaneous inflammatory response characterized by MCP-1, IL-6 and antimicrobial peptides induction. Mass spectrometry of this clone revealed 110 overexpressed proteins when compared with the parental population. We further focused on the expression of nine bacterial surface proteins. bb0347 coding for a protein that interacts with host fibronectin, allowing bacterial adhesion to vascular endothelium and extracellular matrix, was found to be induced in host skin with another gene bb0213 coding for a hypothetical protein. These findings demonstrate the heterogeneity of the B. burgdorferi ss population and the complexity of the interaction involved early in the skin. PMID:26197047

  3. Prevalence of oral mucosal lesions among Pre-University students of Kodava population in Coorg District

    PubMed Central

    Sandeepa, N C; Jaishankar, H P; Sharath, Chandra B; Abhinetra, M S; Darshan, D D; Deepika, Nappalli

    2013-01-01

    Background: To know the prevalence of oral mucosal lesions among Pre-University students of Kodava population in Coorg District. This survey also aims to find out tobacco or other habits among students and related changes in the oral environment. Materials & Methods: 900 PU students of Kodava population were included. 300 students from each taluk were randomly selected, after the consent. Questions were asked to reveal the systemic diseases, abnormal oral habits, use of tobacco &alcohol. Each student was examined for oral mucosal lesions and recording was based on WHO oral health assessment form. Results: Oral mucosal lesions were similar to studies done in other population but with a slightly higher frequency of few lesions. Incidence of substance use was noted, but with no signs of significant changes in the oral mucosa. Conclusion: Prevalence of oral mucosal lesions varies among each population indicating the need for study in each population to format health policy. Substance use was noted among 16-17 yr age group indicates the need for early preventive measures among adolescents to avoid future serious health problems. How to cite this article: Sandeepa N C, Jaishankar H P, Sharath C B, Abhinetra M S, Darshan D D, Nappalli D. Prevalence of oral mucosal lesions among Pre-University students of Kodava population in Coorg District. J Int Oral Health 2013; 5(3):35-41. PMID:24155600

  4. Pregnant and Parenting Students on Campus: Policy and Program Implications for a Growing Population

    ERIC Educational Resources Information Center

    Brown, Virginia; Nichols, Tracy R.

    2013-01-01

    The number of pregnant and parenting students in higher education is increasing. Research suggests this population experiences added pressure and stress while pursuing their education. Few resources exist for these students and the universities who provide services do not adequately promulgate them to the campus community. The research presented…

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

    ERIC Educational Resources Information Center

    Bouchat, Clarence J.

    2008-01-01

    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…

  6. Connections: Linking Population and the Environment. Student Resource Book and Teacher's Guide.

    ERIC Educational Resources Information Center

    Crews, Kimberly A., Ed.; Cancellier, Patricia, Ed.

    A teacher's guide and student resource book developed by geography, social studies and economics teachers comprise this teaching kit. The kit was developed to help seventh through twelfth grade students understand the links between population and the environment in the context of sustainable development. The goal of the project is to develop…

  7. Improving Programs of Schools Serving Culturally and Linguistically Diverse Student Populations.

    ERIC Educational Resources Information Center

    Castaneda, Lillian Vega

    The Metropolitan Educational Trends and Research Outcomes Center conducts Improving Programs of Schools Serving Culturally and Linguistically Diverse Student Populations, a survey to identify programs that have successfully addressed the needs of ethnically, linguistically, and culturally diverse students. This report presents a cross-sites…

  8. 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…

  9. Class Size Effects on Student Achievement: Heterogeneity across Abilities and Fields

    ERIC Educational Resources Information Center

    De Paola, Maria; Ponzo, Michela; Scoppa, Vincenzo

    2013-01-01

    In this paper, we analyze class size effects on college students exploiting data from a project offering special remedial courses in mathematics and language skills to freshmen enrolled at an Italian medium-sized public university. To estimate the effects of class size, we exploit the fact that students and teachers are virtually randomly assigned…

  10. The relative influence of climate, environmental heterogeneity, and human population on the distribution of vertebrate species richness in south-eastern Spain

    NASA Astrophysics Data System (ADS)

    Moreno-Rueda, Gregorio; Pizarro, Manuel

    2007-07-01

    In view of the many factors affect species richness, this study examines the relative influence of environmental heterogeneity, climate, human disturbance and spatial structure with respect to the species-richness distribution of terrestrial vertebrates in an area of south-eastern Spain with a Mediterranean climate. We show that environmental heterogeneity was the primary factor determining species richness (20.3% of variance), with the effect of temperature and precipitation being lower (11.6%). Climate had greater importance in determining the species richness of ectotherms (amphibians and reptiles) than of endotherms (mammals and birds). Species richness had less spatial autocorrelation in mammals and birds than in ectotherms. Also, a positive correlation was found between species richness and human population density, especially in reptiles and mammals. Orders and families more sensitive to human presence, such as snakes, raptors, ungulates, and carnivores, showed no relationship (or a negative one) with the human population. This study highlights the importance of environmental heterogeneity (topographic heterogeneity and habitat diversity) for vertebrate conservation in zones with a Mediterranean climate.

  11. Changes in Student Populations and Average Test Scores of Dutch Primary Schools

    ERIC Educational Resources Information Center

    Luyten, Hans; de Wolf, Inge

    2011-01-01

    This article focuses on the relation between student population characteristics and average test scores per school in the final grade of primary education from a dynamic perspective. Aggregated data of over 5,000 Dutch primary schools covering a 6-year period were used to study the relation between changes in school populations and shifts in mean…

  12. Cooperation in Heterogeneous Populations

    E-print Network

    Sigmund, Karl

    deals with stochastic reactive strategies for the Iterated Prisoner's Dilemma. It considerspopulations days of game theory, the Prisoner'sDilemma (PD) has beenviewedas a major paradigm on the mathematicalaspectsof the game,a wide varietyof researchon its psychological,biological,political, and economicalim

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

    E-print Network

    West, Walter G.; Poole, Eric D.

    1974-10-01

    , 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 and perception of overpopulation, the findings... accepted as an ideal, more and more observers argue that the urgency of overpopulation demands compulsion (Ehrlich, 1968-, Hardin. 1968; Lamson, 1970; Prescott, 1969; Chasteen, 1971). Indeed, many authorities have concluded that population control can...

  14. 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

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

    PubMed Central

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

    2014-01-01

    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

  16. Responding to Diversity in the Urban Student Population.

    ERIC Educational Resources Information Center

    Kemp, Leroy

    1992-01-01

    Urban educators must highly value the diversity of language, culture, and cognitive styles their students bring to the classroom. Holistic, interactive instruction builds on youngsters' interpretations of various forms of intelligence, whether musical, linguistic, interpersonal, intrapersonal, bodily kinesthetic, or spatial. Cooperative learning…

  17. 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,…

  18. Changing Patterns of Cervical Disease in a Student Population.

    ERIC Educational Resources Information Center

    Rosenthal, Dorothy L.; And Others

    1982-01-01

    The Cytology Service at the University of California at Los Angeles (UCLA) Center for Health Sciences has examined about 4000 pap smears (each year) from the UCLA Student Health Service between 1973-1978. An apparently significant increase in abnormal pap smears in young college-age women is reported. (Authors/CJ)

  19. Assignment of a gene for autosomal recessive retinitis pigmentosa (RP12) to chromosome 1q31-q32.1 in an inbred and genetically heterogeneous disease population

    SciTech Connect

    Van Soest, S.; Ingeborgh Van Den Born, L.; Bergen, A.A.B.

    1994-08-01

    Linkage analysis was carried out in a large family segregating for autosomal recessive retinitis pigmentosa (arRP), originating from a genetically isolated population in The Netherlands. Within the family, clinical heterogeneity was observed, with a major section of the family segregating arRP with characteristic para-arteriolar preservation of the retinal pigment epithelium (PPRPE). In the remainder of the arRP patients no PPRPE was found. Initially, all branches of the family were analyzed jointly, and linkage was found between the marker F13B, located at 1q31-q32.1, and RP12 ({Zeta}{sub max} = 4.99 at 8% recombination). Analysis of linkage heterogeneity between five branches of the family yielded significant evidence for nonallelic genetic heterogeneity within this family, coinciding with the observed clinical differences. Multipoint analysis, carried out in the branches that showed linkage, favored the locus order 1cen-D1S158-(F13B, RP12)-D1S53-1qter ({Zeta}{sub max} = 9.17). The finding of a single founder allele associated with the disease phenotype supports this localization. This study reveals that even in a large family, apparently segregating for a single disease entity, genetic heterogeneity can be detected and resolved successfully. 35 refs., 5 figs.

  20. 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

  1. Methodological approach for substantiating disease freedom in a heterogeneous small population. Application to ovine scrapie, a disease with a strong genetic susceptibility.

    PubMed

    Martinez, Marie-José; Durand, Benoit; Calavas, Didier; Ducrot, Christian

    2010-06-01

    Demonstrating disease freedom is becoming important in different fields including animal disease control. Most methods consider sampling only from a homogeneous population in which each animal has the same probability of becoming infected. In this paper, we propose a new methodology to calculate the probability of detecting the disease if it is present in a heterogeneous population of small size with potentially different risk groups, differences in risk being defined using relative risks. To calculate this probability, for each possible arrangement of the infected animals in the different groups, the probability that all the animals tested are test-negative given this arrangement is multiplied by the probability that this arrangement occurs. The probability formula is developed using the assumption of a perfect test and hypergeometric sampling for finite small size populations. The methodology is applied to scrapie, a disease affecting small ruminants and characterized in sheep by a strong genetic susceptibility defining different risk groups. It illustrates that the genotypes of the tested animals influence heavily the confidence level of detecting scrapie. The results present the statistical power for substantiating disease freedom in a small heterogeneous population as a function of the design prevalence, the structure of the sample tested, the structure of the herd and the associated relative risks. PMID:20347494

  2. Year Survey Time Population Responsibility Notes 2013/14 Departmental Focus Groups Spring Undergraduates Student Life IRT draws the sample

    E-print Network

    Lin, King-Ip "David"

    Year Survey Time Population Responsibility Notes 2013/14 Departmental Focus Groups Spring Undergraduates Student Life IRT draws the sample Comprehensive Program Review/AAAHC Spring Department Health Center Comprehensive Program Review Spring Department Student Activities Comprehensive Program Review

  3. Eating and body attitudes related to noncompetitive bodybuilding in military and general Hungarian male student populations.

    PubMed

    Lukács, Liza; Murányi, István; Túry, Ferenc

    2007-02-01

    Pathological eating attitudes and extreme weight control practices occur most commonly in certain female populations. In some young male occupation groups, such as in the armed forces, the appearance of physical strength and muscularity has particular importance. We studied body and eating attitudes and the prevalence of bodybuilding and steroid abuse in 480 military college and 752 general college male students. The Eating Disorder Inventory was used for all subjects. General college students had higher body mass index values than did military students. The prevalence of bodybuilding and steroid abuse was significantly greater in the military population. Comparisons between the study groups and within groups showed significantly different scores on certain Eating Disorder Inventory subscales. The study revealed that male military college students have some protective factors against the psychopathological features of eating disorders. PMID:17357769

  4. Vocational education students: a difficult-to-reach population at risk for smoking-related cancer.

    PubMed

    Corcoran, R D; Allegrante, J P

    1989-05-01

    Vocational education high school students comprise a significant proportion of the school-based population. Recent studies indicate vocational education students are at greater risk for cigarette smoking behavior than their non-vocational education counterparts. Vocational students have higher prevalence rates of smoking than do non-vocational students and are more likely to report that they expect to be smoking in the future. Characteristics of adolescents who participate in vocational education and their cigarette smoking behavior are reviewed, as well as the need to develop, implement, and evaluate new educational approaches designed to prevent cigarette smoking and the use of other tobacco products in this difficult-to-reach population. PMID:2739362

  5. A student-oriented study tool for heterogeneous HyperCard courseware.

    PubMed Central

    Rathe, R.; Garren, T.

    1991-01-01

    Several computer-assisted instruction initiatives at our institution rely on a shared laserdisc for image storage and HyperCard for interactive programming. This paper furnishes a brief overview of problems encountered with multimedia projects and how we are attempting to overcome them using a generic, student-oriented study tool. The tool provides bookmarks, annotations, quotations, and other utilities across our entire HyperCard courseware collection. PMID:1807701

  6. School Enrollment--Social and Economic Characteristics of Students: October 1986. Current Population Reports: Population Characteristics.

    ERIC Educational Resources Information Center

    Bruno, Rosalind R.

    1988-01-01

    This report presents detailed tabulations of data from the Current Population Survey on school enrollment in October 1986, and summary time series of data collected since the inception of the survey in 1946. School enrollment data are shown by the following personal and school characteristics: (1) age; (2) race; (3) Hispanic origin; (4) sex; (5)…

  7. The effect of homogeneous and heterogeneous review pairs on student achievement and attitude when utilizing computer-assisted instruction in middle-level Earth science classes

    NASA Astrophysics Data System (ADS)

    Lyon, Ellen Beth

    1998-09-01

    This research project investigated the influence of homogeneous (like-ability) review pairs coupled with heterogeneous (mixed-ability) cooperative learning groups using computer-assisted instruction (CAI) on academic achievement and attitude toward science in eighth grade Earth science students. Subjects were placed into academic quartiles (Hi, Med-Hi, Med-Lo, and Lo) based on achievement. Cooperative learning groups of four (one student from each academic quartile) were formed in all classes, within which students completed CAI through a software package entitled Geoscience Education Through Interactive Technology, or GETITspTM. Each day, when computer activities were completed, students in the experimental classes were divided into homogeneous review pairs to review their work. The students in the control classes were divided into heterogeneous review pairs to review their work. The effects of the experimental treatment were measured by pretest, posttest, and delayed posttest measures, by pre- and post-student attitude scales, and by evaluation of amendments students made to their work during the time spent in review pairs. Results showed that student achievement was not significantly influenced by placement in homogeneous or heterogeneous review pairs, regardless of academic quartile assignment. Student attitude toward science as a school subject did not change significantly due to experimental treatment. Achievement retention of students in experimental and control groups within each quartile showed no significant difference. Notebook amendment patterns showed some significant differences in a few categories. For the Hi quartile, there were significant differences in numbers of deletion amendments and substitution amendments between the experimental and the control group. In both cases, subjects in the experimental group (homogeneous review pairs) made greater number of amendments then those in the control group (heterogeneous review pairs). For the Lo quartile, there was a significant difference in the number of grammar/usage/mechanics (GUM) amendments between the experimental and control groups. The experimental group made far more GUM amendments than the control group. This research highlights the fact that many factors may influence a successful learning environment in which CAI is successfully implemented. Educational research projects should be designed and used to help teachers create learning environments in which CAI is maximized.

  8. Heterogeneous populations of cells mediate spontaneous synchronous bursting in the developing hippocampus through a frequency-dependent mechanism.

    PubMed

    Menendez de la Prida, L; Sanchez-Andres, J V

    2000-01-01

    Under normal conditions, hippocampal slices from newborn rats and rabbits (postnatal days 0-8) show spontaneous synchronous bursts known as giant depolarizing potentials. These bursts are recorded from CA3, CA1 and the fascia dentata in both intact slices and isolated hipocampal regions. Giant depolarizing potentials are network-driven events resulting from the synergistic activation of N-methyl-D-aspartate, alpha-amino-3-hydroxy-5-methyl-4-isoxadepropionate and GABA(A) receptors, the latter playing an excitatory role. Recently, we showed that they spontaneously emerge in an all-or-none manner after the increase of synaptic and cellular activity beyond a threshold frequency [Menendez de la Prida L. and Sanchez-Andres J. V. (1999) J. Neurophysiol. 82, 202-208]. Under this framework, background levels of spontaneous activity at individual neurons build up network synchronization 100-300ms prior to the onset of giant depolarizing potentials. However, the role of distinct cellular populations and connectivity in determining the threshold frequency has not been examined. By performing simultaneous intracellular recordings from pyramidal cells, non-pyramidal cells and interneurons, we investigated their participation in the generation of giant depolarizing potentials. Electrodes containing Neurobiotin were used to examine the cellular morphology. We found that giant depolarizing potentials were not initiated from a single pacemaker cellular group; instead, they involved recurrent cooperation among these groups, which contributed differently according to their intrinsic firing capability. In all the neurons examined, the onset of these bursts took place in an all-or-none frequency-dependent manner, both spontaneously (depending on the frequency of the excitatory postsynaptic potentials) or when triggered by extracellular stimulation. The CA3 threshold of frequency was at 12Hz in both pyramidal cells and interneurons, while in the fascia dentata it was 17Hz. The application of 6-cyano-7-nitroquinoxaline-2,3-dione increased CA3 threshold of frequency up to 50Hz, suggesting that it is determined by combined synaptic components. We examined the role of postsynaptic summation on the threshold of frequency. Heterogeneity is present among the cellular groups, pyramidal neurons from CA1 and CA3 showing less evidence of postsynaptic summation prior to giant depolarizing potentials. Cells showing stronger evidence of postsynaptic summation were more typically recorded at the hilus, the granule layer of the fascia dentata and the CA3/CA4 area. Nevertheless, for a given cell, not all the giant depolarizing potentials were preceded by summation of postsynaptic potentials. These outcomes, together with the long and variable time delays recorded between different areas, strongly suggest that giant depolarizing potentials are locally generated from different initiation sites and not from a single region. We discuss these results in view of the principles underlying hyperexcitability in hippocampal slices, i.e. the intrinsic firing properties of individual cells and the connectivity patterns. PMID:10799755

  9. Teaching Population Balances for Chemical Engineering Students: Application to Granulation Processes

    ERIC Educational Resources Information Center

    Bucala, Veronica; Pina, Juliana

    2007-01-01

    The population balance equation (PBE) is a useful tool to predict particle size distributions in granulation processes. When PBE is taught to advanced chemical engineering students, the internal coordinates (particle properties) are particularly hard to understand. In this paper, the flow of particles along different coordinates is carefully…

  10. Generalizing in Interaction: Middle School Mathematics Students Making Mathematical Generalizations in a Population-Modeling Project

    ERIC Educational Resources Information Center

    Jurow, A. Susan

    2004-01-01

    Generalizing or making claims that extend beyond particular situations is a central mathematical practice and a focus of classroom mathematics instruction. This study examines how aspects of generality are produced through the situated activities of a group of middle school mathematics students working on an 8-week population-modeling project. The…

  11. 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…

  12. 54 Journal of Student Research in Environmental Science at Appalachian Land Loss and Displaced Population of

    E-print Network

    Thaxton, Christopher S.

    54 Journal of Student Research in Environmental Science at Appalachian Land Loss and Displaced Program, Appalachian State University, Boone, NC Abstract The land loss and displaced population the amount of sunlight that is absorbed. The coastal region of North Carolina is one of the state's most

  13. 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…

  14. The Distribution of and Relationship between Autistic Traits and Social Anxiety in a UK Student Population

    ERIC Educational Resources Information Center

    Freeth, Megan; Bullock, Tom; Milne, Elizabeth

    2013-01-01

    Traits associated with autism and social anxiety were assessed in a UK student population (n = 1325) using the Autism-spectrum Quotient and the Liebowitz Social Anxiety Scale. Clinically relevant levels of autistic traits were observed in 3.3% of the cohort; 10.1% of the cohort reported clinically relevant levels of social anxiety; 1.8% of the…

  15. Faculty of Medicine, Primary Care and Population Sciences PhD/MD students Name Title Email

    E-print Network

    Molinari, Marc

    Faculty of Medicine, Primary Care and Population Sciences ­ PhD/MD students Name Title Email Primary Supervisor in Faculty of Medicine, PCPS Professor Paul Roderick Sara Afshar Multimorbidities: its14@soton.ac.uk Primary Supervisor in Faculty of Medicine, PCPS Dr Julie Parkes Emma Richards

  16. Detection of Chlamydia trachomatis in an Australian high school student population

    PubMed Central

    Debattista, J; Martin, P; Jamieson, J; Crane, K; Dolton, I; Russell-Hall, S; DeSilva, J; Hargrave, R; Robinson, T; Ryan, N; Mortlock, M

    2002-01-01

    Objective: To assess the prevalence of Chlamydia trachomatis infections among an Australian high school adolescent population. Methods: Over a 4 year period, 14 high schools were selected in which an infertility prevention programme targeting C trachomatis was delivered to senior student populations. Coded first catch urine specimens were analysed by Amplicor PCR and infected students treated. Data retrospectively obtained from chlamydia screening programmes conducted among disadvantaged young people detached from formal education were also collated for comparison. Results: Of a total student test population of 1174, 15 (1.3%; 95% CI 0.7% to 2.1%) were diagnosed with C trachomatis. Of 516 females and 658 males, 12 (2.3%; 95% CI 1.1% to 4.1%) and 3 (0.5%; 95% CI 0.1% to 1.4%) were tested positive respectively. Data collated for three populations of disadvantaged youth returned at total of 89 C trachomatis infections out of 560 people (15.9% 95%CI 13.0–19.2%). Conclusion: The overall prevalence of C trachomatis infection among this population of senior high school adolescents is low, and significantly differs from the higher chlamydia rates detected in disadvantaged adolescents detached from formal schooling (p<0.0001). PMID:12238652

  17. Students teaching AIDS to students: addressing AIDS in the adolescent population.

    PubMed

    Haven, G G; Stolz, J W

    1989-01-01

    Adolescents are at high risk for developing acquired immunodeficiency syndrome (AIDS) because of their sexual curiosity and exploration, drug experimentation, and lack of knowledge. At present, the only way to reduce this risk is through education. In an effort to increase AIDS education among adolescents, a program called Students Teaching AIDS to Students (STATS) is proposed. The goal of this project is to help train medical students to become AIDS educators in the schools, churches, and youth organizations of their local communities. The project involves preparation and distribution of a package of materials which can be used by medical students to initiate a STATS program. The package consists of a manual which explains the essentials of starting a youth health education project, suggests how to gain approval for the project within the community, and contains curriculums with basic AIDS information and exercises. The curriculum material is tailored for presentation to students over two school-class periods on separate days and contains age-appropriate information. Another component of the package is the slide show tailored to explain STATS to school boards, parent groups, and the leaders of other youth organizations. A video tape to help answer difficult questions put by students has been selected to be part of the curriculum for school grade levels 7 to 12. These materials are geared to facilitate the start of a successful AIDS education program for adolescents. PMID:2493665

  18. A Survey to Identify University Student Attitudes toward the Role of Government in Controlling Human Population Growth.

    ERIC Educational Resources Information Center

    Yost, Thomas E.

    The purpose of this study was to obtain, measure, and evaluate the attitudes of postsecondary students on domestic population issues in order to determine the extent of support for a national government-controlled population stabilization program. A total of 125 students enrolled in either the American government or general sociology course at the…

  19. [Biostatistical support for decision making in drug licensing and reimbursement exemplified by implications of heterogeneous findings in subgroups of the study population].

    PubMed

    Gonnermann, A; Kottas, M; Koch, Armin

    2015-03-01

    In the context of both drug licensing and reimbursement, the target population is sometimes restricted to a specific subgroup. In the setting of drug licensing the discussion concerns a negative benefit/risk assessment in a relevant subgroup. For reimbursement the debate involves the detection of an additional benefit compared with standard treatment, which can in some situations not be accepted for the overall study population. In their Methods Paper, the Institute for Quality and Efficiency in Health Care (IQWiG) refers to published articles that name criteria for the evaluation of credibility to claim a therapeutic effect on the basis of results in the subgroups of a study population (BMJ 340:850-854, 2010). A number of these criteria have found their way into the regulatory debate, which was recently published in a draft guideline of the European Medicines Agency (EMA). However, the significance of the interaction/heterogeneity test has been mentioned as one criterion for the credibility of a finding in a subgroup of the study population. This aspect is critically challenged in our paper. In our estimation, the application of this criterion hinders the critical discussion of whether a global treatment effect is applicable to relevant subgroups of a study population and the potential implications of this. We feel that biostatistical support for decision-making strategies should be the same in both worlds, even though in some instances the outcomes in a specific situation may be different, depending on the objective to be demonstrated. PMID:25566838

  20. Analysis of survival, gene expression and behavior following chill-coma in the medfly Ceratitis capitata: effects of population heterogeneity and age.

    PubMed

    Pujol-Lereis, Luciana Mercedes; Rabossi, Alejandro; Quesada-Allué, Luis Alberto

    2014-12-01

    The medfly Ceratitis capitata is an agricultural pest distributed worldwide thanks, in part, to its phenotypic plasticity of thermal tolerance. Cold exposure has been shown to reduce C. capitata survival, which may affect its distribution in areas with subfreezing temperatures. When insects are increasingly cooled, they attain a critical thermal threshold and enter a chill-coma state characterized by cessation of movement. It is not clear how a rapid cold exposure affects the physiological state of medflies, and how this is influenced by age and population heterogeneity. In order to approach these questions, C. capitata single-sex laboratory populations of 15 and 30 days old were subjected to a chill-coma recovery assay, and separated according to their recovery time in three subgroups: Fast-Subgroups, Intermediate-Subgroups, and Slow-Subgroups. Thereafter, we analyzed their survival, behavioral, and gene expression outputs. In female and old male populations, we found that flies with the slowest recovery time had a reduced life expectancy, a higher initial mortality rate, and a worse climbing performance compared with flies that recovered faster. Therefore, we were able to separate subgroups that developed chilling-injury from subgroups that had a reversible full recovery after cold exposure. The gene expression analysis of the heat shock protein genes hsp70 and hsp83 showed no clear association with the parameters studied. Interestingly, thorax expression levels of the Cu/Zn superoxide dismutase gene were elevated during the recovery phase in the Fast-Subgroups, but remained constant in the Slow-Subgroups that developed chilling-injury. On the other hand, none of the young male subgroups seemed to have suffered irreversible damage. Thus, we concluded that depending on age and population heterogeneity, chill-coma recovery time points out significant differences on individual cold tolerance. Moreover, the inability to properly induce the antioxidant defense system to counteract the oxidative damage caused by cold seems to contribute to the development of chilling-injury. PMID:25449902

  1. 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

  2. Two Test Items to Explore High School Students' Beliefs of Sample Size When Sampling from Large Populations

    ERIC Educational Resources Information Center

    Bill, Anthony; Henderson, Sally; Penman, John

    2010-01-01

    Two test items that examined high school students' beliefs of sample size for large populations using the context of opinion polls conducted prior to national and state elections were developed. A trial of the two items with 21 male and 33 female Year 9 students examined their naive understanding of sample size: over half of students chose a…

  3. 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.

  4. Evolution effects on genes, individuals and populations (4 HEC) In this postgraduate student course organized at the Ultuna campus we will highlight the nature

    E-print Network

    Evolution ­ effects on genes, individuals and populations (4 HEC) In this postgraduate student population genetic processes (i.e. selection, genetic drift and gene flow, mutation), molecular evolution

  5. [Attitudes of Costa Rican students and teachers on sex and population education].

    PubMed

    Stycos, J M

    1987-01-01

    Students in 34 secondary schools and the last year of primary school throughout Costa Rica were interviewed to determine the attitudes of older students toward sex and population education. The sex, grade level, and geographic region of residence were considered key study variables. To ensure an adequate number of cases in each geographic region, the sample was stratified into 4 zones: downtown San Jose, the rest of metropolitan San Jose, other cantons of the central valley, and cantons outside the central valley. Various smaller studies were also conducted, including brief intelligence tests for 190 students, interviews with 286 parents, focus group debates in 8 schools, surveys of 10 teachers in each school, and interviews with Ministry of Education and other officials. The final questionnaire was very long, consisting of 281 questions as well as data about the student's residence. Although students cooperated in filling out the questionnaires, it was too long and 27% of all students failed to complete it. The average student completed 91% of the questions, but fewer than 1/2 of the 6th year primary students were able to complete it. Costa Rican students gain at least a partial understanding of sex at an early age. Almost all secondary students and 71% of the 6th year primary students knew 1 or more contraceptive methods. Most acquired contraceptive information before the age of 12, often from the mass media. 2/3 said their parents had been important sources of information on sex. Most students said they had received some information on sex or family planning in school, but no influence was seen on knowledge or attitudes. The survey results revealed considerable misinformation about sex and family planning. The attitude of Costa Rican students toward equality of the sexes appears conservative, but it becomes less so as their grade level advances, especially for girls. The majority of students had tolerant or indifferent attitudes toward premarital fertility, the ideal age at marriage, and having 1 or 2 children beyond their ideal average of 2 or 3 children. The 173 out-of-school youths who completed the surveys were even more family oriented and conservative and less well informed about family planning and demographic growth than were the students. Grade level was the most important factor explaining differences in knowledge and attitude toward the issues raised in the survey. Geographic region and socioeconomic level of the parents and much less influence. Special questionnaires administered to 327 teachers in the same secondary schools revealed that they assigned the highest priority to sex education of 8 possible educational innovations. Most teachers assigned a lower priority to population education. Major conclusions of the study were that Costa Rican students would welcome a more systematic program of sex education, but greater attention is required to train teachers in the method and content of sex education and population education. PMID:12269046

  6. Benchmarking Student Diversity at Public Universities in the United States: Accounting for State Population Composition

    PubMed Central

    Franklin, Rachel S.

    2014-01-01

    Regions rely at least partially on the internal production of a qualified workforce in order to maintain their economic competitiveness. Increasingly, at least from a university or corporate point of view, a qualified workforce is viewed as one that is racially and ethnically diverse. However, the conceptualization and measurement of ethnic and racial diversity in higher education appears to be often based on normative values rather than solid benchmarks, making any regional comparisons or goals difficult to specify. Ideally, at least as a starting point, public state universities would, while attempting to increase overall student diversity, benchmark their progress against the state population composition. This paper combines enrollment data from the National Center for Education Statistics (NCES) with U.S. Census Bureau population estimates data to provide a point of comparison for state universities. The paper has two goals: first a university-level comparison of diversity scores, as measured by the interaction index and, second, an analysis of how university student population composition compares to that of the population the university was originally intended to serve – the state population. PMID:25506123

  7. 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…

  8. 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.

  9. Characteristics of the population of deaf and hard of hearing students with emotional disturbance in Illinois.

    PubMed

    Sinnott, Cheri L; Jones, Thomas W

    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 general population of deaf and hard of hearing students in many ways, including higher incidences of prematurity, prenatal trauma, and perinatal trauma. They were more likely to have had a later onset of hearing loss, to live in single-parent homes, to belong to an ethnic minority, to live in an urban or suburban area, and to qualify for low-income health care. Many had histories of abuse, 50% were regularly medicated, and 15% were assigned to surrogate parents. PMID:16212016

  10. Selection using the alpha-1 integrin (CD49a) enhances the multipotentiality of the mesenchymal stem cell population from heterogeneous bone marrow stromal cells.

    PubMed

    Rider, David A; Nalathamby, Thenmozhi; Nurcombe, Victor; Cool, Simon M

    2007-10-01

    Bone marrow-derived mesenchymal stem cells consist of a developmentally heterogeneous population of cells obtained from colony forming progenitors. As these colonies express the alpha-1 integrin (CD49a), here we single-cell FACS sorted CD49a+ cells from bone marrow in order to create clones and then compared their colony forming efficiency and multilineage differentiation capacity to the unsorted cells. Following selection, 40% of the sorted CD49a+ cells formed colonies, whereas parental cells failed to form colonies following limited dilution plating at 1 cell/well. Following ex vivo expansion, clones shared a similar morphology to the parental cell line, and also demonstrated enhanced proliferation. Further analysis by flow cytometry using a panel of multilineage markers demonstrated that the CD49a+ clones had enhanced expression of CD90 and CD105 compared to unsorted cells. Culturing cells in adipogenic, osteogenic or chondrogenic medium for 7, 10 and 15 days respectively and then analysing them by quantitative PCR demonstrated that CD49a+ clones readily underwent multlineage differentiation into fat, bone and cartilage compared to unsorted cells. These results thus support the use of CD49a selection for the enrichment of mesenchymal stem cells, and describes a strategy for selecting the most multipotential cells from a heterogeneous pool of bone marrow mononuclear stem cells. PMID:17694277

  11. Integrating Population and Clinical Medicine: A New Third-Year Curriculum to Prepare Medical Students for the Care of Individuals, Panels, and Populations.

    PubMed

    White, Jordan; Riese, Alison; Clyne, Brian; Vanvleet, Marcia W; George, Paul

    2015-09-01

    Population and Clinical Medicine (PCM) I & II constitute two of the nine courses established for the Warren Alpert Medical School of Brown University's (AMS) innovative dual-degree Primary Care-Population Medicine (PC-PM) program. The courses will run consecutively during students' third year in the program, in conjunction with the Longitudinal Integrated Clerkship (LIC). Throughout the courses, students will examine the intersection between population and clinical medicine with a focus on vulnerable populations, the social and community context of care, quality improvement, and leadership. In addition to attending class sessions in which students will engage with leaders in relevant fields, students will also draw from patient and population-level experiences in the LIC to plan and implement two projects: a community-based intervention to address a particular health issue, and a quality improvement project to change a small aspect of care delivery at a clinical site. Finally, leadership skills development sessions will be incorporated, and leadership practice will occur during implementation of student projects. PMID:26324973

  12. 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

  13. Efficacy and safety of entecavir treatment in a heterogeneous CHB population from a ‘real-world’ clinical practice setting in China.

    PubMed

    Hou, J-L; Jia, J-D; Wei, L; Zhao, W; Wang, Y M; Cheng, M; Tang, X; Tan, D-M; Ren, H; Tang, H; Cohen, D; Llamoso, C

    2013-11-01

    Chronic hepatitis B infection is an important cause of liver-related mortality in China. This study assessed the efficacy and safety of entecavir in a heterogeneous patient population from a ‘real-world’ clinical practice setting in China. This prospective, observational cohort provides 48-week data on 2600 patients from 50 sites in China who received entecavir (0.5 or 1.0 mg) and were assessed for virologic, serologic and biochemical responses. Patients were nucleos(t)ide-na€?ve or -experienced and had compensated or decompensated liver function. At Week 48, 1545/2424 (64%) patients with compensated liver disease and 30/44 (68%) patients with decompensated liver disease achieved HBV DNA<50 IU/mL. Greater proportions of nucleos(t)ide-na€?ve than nucleos(t)ide-experienced (69% vs 53%), and adefovir-experienced than lamivudine/ telbivudine-experienced (62% vs 52%) patients achieved this endpoint. Most patients with HBV DNA<50 IU/mL also achieved HBV DNA<12 IU/L (60%, 45% and 61% of nucleos(t)ide-na€?ve, nucleos(t)ide-experienced and decompensated patients, respectively). In patients with compensated liver disease, ALT values normalized in 1532/1792 patients (85%), and HBeAg loss and HBeAg seroconversion were observed in 17% and 15% of treatment-na€?ve and 15% and 11% of treatment-experienced patients. Entecavir was generally well tolerated. Adverse event rates were comparable between treatment-na€?ve and treatment-experienced patients with compensated liver disease, but were higher in decompensated than in compensated patients, consistent with previous reports in these patients with more advanced disease. Four patients discontinued treatment due to adverse events. In a ‘real-world’ setting, entecavir was efficacious and well tolerated throughout 48 weeks in a heterogeneous Chinese CHB population. PMID:23876210

  14. Joint QTL analyses for partial resistance to Phytophthora sojae using six nested inbred populations with heterogeneous conditions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Partial resistance to Phytophthora sojae in soybean is controlled by multiple quantitative trait loci (QTL). With traditional QTL mapping approaches, power to detect these QTL, frequently of small effect, can be limited by population size. Joint linkage QTL analysis of nested recombinant inbred li...

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

    E-print Network

    Kenkre, V.M.

    can be clearly discerned in data collected on mouse populations in the Cibola National Forest (New of Bristol, Bristol, UK d Valles Caldera National Preserve, P.O. Box 359, Jemez Springs, NM 87025, USA e for investigations of the spread of the Hantavirus epidemic in mice we have built a system of interacting reaction

  16. Method To Purify and Analyze Heterogeneous Senescent Cell Populations Using a Microfluidic Filter with Uniform Fluidic Profile.

    PubMed

    Kim, Minseok S; Jo, Seonghyeon; Park, Joon Tae; Shin, Hyun Young; Kim, Sun Soo; Gurel, Ogan; Park, Sang Chul

    2015-10-01

    To precisely purify and study aged (senescent) cells, we have designed, fabricated, and demonstrated a novel diamond-structure (DS) microfluidic filter. Nonuniform flow velocities within the microfilter channel can compromise microfluidic filter performance, but with this new diamond structure, further optimized via simulation, we achieve a uniform microfilter flow field, improving the throughput of size-based separation of senescent cells, as obtained by 39-passaged human dermal fibroblasts. After separating these aged cells into two groups, consisting of large- and small-sized cells, we assessed senescence by measuring lipofuscin accumulation and ?-galactosidase activity. Our results reveal that even though these senescent cells had been equivalently passaged in culture, a high degree of size distribution and senescent phenotype heterogeneity was observed. In particular, the smaller-sized cells tended to express a younger phenotype while the larger aged cells demonstrated an older phenotype. We suggest that size-based separation of senescent cells, subtyped into small- and large-sized cohorts, offers an alternative method to purify such aged cells, thereby enabling more precise study of the mechanisms of aging, autophagy impairment, and rejuvenation. PMID:26322520

  17. Balancing selection and heterogeneity across the classical human leukocyte antigen loci: a meta-analytic review of 497 population studies

    PubMed Central

    Solberg, Owen D.; Mack, Steven J.; Lancaster, Alex K.; Single, Richard M.; Tsai, Yingssu; Sanchez-Mazas, Alicia; Thomson, Glenys

    2008-01-01

    This paper presents a meta-analysis of high-resolution human leukocyte antigen (HLA) allele frequency data describing 497 population samples. Most of the datasets were compiled from studies published in eight journals from 1990 to 2007; additional datasets came from the International Histocompatibility Workshops and from the AlleleFrequencies.net database. In all, these data represent approximately 66,800 individuals from throughout the world, providing an opportunity to observe trends that may not have been evident at the time the data were originally analyzed, especially with regard to the relative importance of balancing selection among the HLA loci. Population genetic measures of allele frequency distributions were summarized across populations by locus and geographic region. A role for balancing selection maintaining much of HLA variation was confirmed. Further, the breadth of this meta-analysis allowed the ranking of the HLA loci, with DQA1 and HLA-C showing strongest balancing selection and DPB1 being compatible with neutrality. Comparisons of the allelic spectra reported by studies since 1990 suggest that most of the HLA alleles identified since 2000 are very-low-frequency alleles. The literature-based allele-count data, as well as maps summarizing the geographic distributions for each allele, are available online. PMID:18638659

  18. An Individual-Based Model of the Evolution of Pesticide Resistance in Heterogeneous Environments: Control of Meligethes aeneus Population in Oilseed Rape Crops

    PubMed Central

    Stratonovitch, Pierre; Elias, Jan; Denholm, Ian; Slater, Russell; Semenov, Mikhail A.

    2014-01-01

    Preventing a pest population from damaging an agricultural crop and, at the same time, preventing the development of pesticide resistance is a major challenge in crop protection. Understanding how farming practices and environmental factors interact with pest characteristics to influence the spread of resistance is a difficult and complex task. It is extremely challenging to investigate such interactions experimentally at realistic spatial and temporal scales. Mathematical modelling and computer simulation have, therefore, been used to analyse resistance evolution and to evaluate potential resistance management tactics. Of the many modelling approaches available, individual-based modelling of a pest population offers most flexibility to include and analyse numerous factors and their interactions. Here, a pollen beetle (Meligethes aeneus) population was modelled as an aggregate of individual insects inhabiting a spatially heterogeneous landscape. The development of the pest and host crop (oilseed rape) was driven by climatic variables. The agricultural land of the landscape was managed by farmers applying a specific rotation and crop protection strategy. The evolution of a single resistance allele to the pyrethroid lambda cyhalothrin was analysed for different combinations of crop management practices and for a recessive, intermediate and dominant resistance allele. While the spread of a recessive resistance allele was severely constrained, intermediate or dominant resistance alleles showed a similar response to the management regime imposed. Calendar treatments applied irrespective of pest density accelerated the development of resistance compared to ones applied in response to prescribed pest density thresholds. A greater proportion of spring-sown oilseed rape was also found to increase the speed of resistance as it increased the period of insecticide exposure. Our study demonstrates the flexibility and power of an individual-based model to simulate how farming practices affect pest population dynamics, and the consequent impact of different control strategies on the risk and speed of resistance development. PMID:25531104

  19. Awareness of Risk Factors for Breast, Lung and Cervical Cancer in a UK Student Population.

    PubMed

    Sherman, Susan M; Lane, Emily L

    2015-12-01

    The objective of this study is to identify levels of risk awareness for breast, lung and cervical cancer, in a UK student population. A sample of male (N?=?62) and female (N?=?58) university students, mean age 21.62 years completed a questionnaire identifying which risk factors they knew for each cancer. Analysis of variance was used to compare differences in risk awareness across gender and cancer types. Risk factor awareness was highest for lung cancer (0.78), mid-range for breast cancer (0.61) and lowest for cervical cancer (0.47). Women had greater risk factor awareness (0.67) than males (0.57) across all three cancers. There is also significant belief in mythic risk factors such as stress (from 14 to 40 % across the three cancers). Previous research has demonstrated that risk factor awareness increases with educational status, yet even in a university student population, in which the majority of females would have been offered the HPV vaccination, risk factor awareness for cancers is variable. More health education is needed particularly around the risk factors for cervical cancer. PMID:25510367

  20. Sexual behaviour and condom use as a protection against sexually transmitted infections in student population.

    PubMed

    Dijani?, Tomislav; Kozul, Karlo; Miskulin, Maja; Medi?, Alan; Jurcev-Savicevi?, Anamarija; Burazin, Jelena

    2014-03-01

    The aim of the study was to determine the differences in sexual behaviour and condom use as a protection against sexually transmitted infections (STI) between the first-year and the last-year students. Data were collected by filling anonymous and consented questionnaire in June of 2011 at University of Josip Juraj Strossmayer in Osijek, Croatia. Out of 857 students in the planned sample, 462 (53.9%) filled out the questionnaire, and 353/462 (76.4%) were sexually active. Data from sexually active students were processed and statistically significant results between first-year and the last-year students were presented. Studied sample consisted of 192/353 (54.4%) first-year students and 161/353 (45.6%) last-year students. Average age of sexual initiation for the first-year students was 17.28 +/- 1.29 years, a for the last-year students 18.45 +/- 2.14 years, and the difference is significant (Man-Whitney test = 10335.00, p < 0.01). First-year students have lower number of sexual partners (chi2 = 28.005, p < 0.01), during relationship they had lower number of intercourses with the third person (2 = 17.947, p < 0.01), and feel that lower number of their friends were already sexually active at the time of their own sexual initiation (chi2 = 18.350, p < 0.01). First-year students more often inform their partners about existing or previous STI (chi2 = 14.476, p < 0.01) and curiosity significantly influenced their decision regarding sexual initiation (chi2 = 8.689, p < 0.05). First-year students more often used condom at their first sexual intercourse (chi2 = 7.275, p < 0.01), and more rarely used withdrawal (chi2 = 6.380, p < 0.05). At their last sexual intercourse, first-year students more often used any kind of protection (chi2 = 3.853, p < 0.05),more often used condom (chi2 = 11.110, p < 0.01) and withdrawal (chi2 = 5.156, p < 0.05), and more rarely used contraceptive pills (chi2 = 4.405, p < 0.05). First-year students more often use condom in a permanent relationship (chi2 = 13.384, p < 0.05), and also plan to use it during following intercourse in the permanent relationship (chi2 = 17.575, p < 0.01). Growing condom use and decreasing risky sexual behaviour among students, as well as other adolescents and young adults needs to be maintained. Youth should learn before sexual initiation that only correct condom use at every sexual intercourse protects them against STI and human immunodeficiency virus (HIV). Sexual education and STI/HIV prevention programmes, positive role of media (television) and civil organisations that communicate with the youth can help that. Such changes among adolescents and young adults should have to be seen in student population as well. PMID:24851594

  1. 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…

  2. Culturally Diverse and Underserved Populations of Gifted Students in the United States and in Taiwan: Equitable Access to Gifted Education

    ERIC Educational Resources Information Center

    Ho, Ya-Ting

    2014-01-01

    There is a continuing increase in the African American and Hispanic student populations in public schools. The students who are invited to gifted programs are overwhelmingly White. This is the situation in schools in the United States and also in Taiwan. Misunderstanding or unawareness of culture difference among educators might contribute to…

  3. The phenotype of freshly isolated and cultured human bone marrow allostimulatory cells: possible heterogeneity in bone marrow dendritic cell populations.

    PubMed Central

    Egner, W; Hart, D N

    1995-01-01

    Putative dendritic cells (DC) and their precursors have been obtained from human bone marrow but their origin and relationship to other myeloid cells remains obscure. A minor bone marrow mononuclear cell (BMMC) population, which contains the most potent allostimulatory cells and lacks mature cell lineage markers (CD3, CD11b, CD14, CD15, CD16, CD19, CD57 and glycophorin A; lineage-negative) was enriched by immunoselection. These preparations, which contain cells with similar characteristics to freshly isolated human blood DC, were further subdivided by serial fluorescent-activated cell sorting (FACS). Potent allostimulatory cells were detected in the CD34, CD33 and CD4 positive and negative subpopulations. Cells with putative DC morphology were present in both the CD33 and CD4 positive and negative fractions. No significant CD13 or Thy-1 staining was seen in the lineage-negative population. In vitro culture of lineage-negative BMMC for 7 days in conditioned medium resulted in a up to fivefold expansion of cells and generated many lineage-positive progeny. This lineage-positive population was as allostimulatory as the negative progeny. Likewise, the CD14-positive and the CD14-negative cell progeny were equally allostimulatory. In contrast, the freshly isolated lineage-positive BMMC (containing CD14-positive monocytes) remained poor stimulators of the mixed lymphocyte reaction (MLR), even after culture in the presence of cytokines. These data suggest that there are at least two phenotypically diverse forms of potent allostimulatory cells in the lineage-negative fraction of human BM, at least some of which express the early haemopoietic precursor antigens CD34 or CD33. Some of these precursors generate CD14-positive allostimulatory cells upon in vitro culture, suggesting an intimate link between DC ontogeny and myeloid differentiation. Images Figure 3 Figure 8 PMID:7558157

  4. 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

  5. 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

  6. 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…

  7. 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

  8. Neural Population Evidence of Functional Heterogeneity along the CA3 Transverse Axis: Pattern Completion versus Pattern Separation.

    PubMed

    Lee, Heekyung; Wang, Cheng; Deshmukh, Sachin S; Knierim, James J

    2015-09-01

    Classical theories of associative memory model CA3 as a homogeneous attractor network because of its strong recurrent circuitry. However, anatomical gradients suggest a functional diversity along the CA3 transverse axis. We examined the neural population coherence along this axis, when the local and global spatial reference frames were put in conflict with each other. Proximal CA3 (near the dentate gyrus), where the recurrent collaterals are the weakest, showed degraded representations, similar to the pattern separation shown by the dentate gyrus. Distal CA3 (near CA2), where the recurrent collaterals are the strongest, maintained coherent representations in the conflict situation, resembling the classic attractor network system. CA2 also maintained coherent representations. This dissociation between proximal and distal CA3 provides strong evidence that the recurrent collateral system underlies the associative network functions of CA3, with a separate role of proximal CA3 in pattern separation. PMID:26298276

  9. Modeling population heterogeneity in viral dynamics for chronic hepatitis C infection: Insights from Phase 3 telaprevir clinical studies.

    PubMed

    Haseltine, Eric L; Kimko, Holly; Luo, Haobin; Tolsma, John; Bartels, Doug J; Kieffer, Tara L; Garg, Varun

    2015-12-01

    Viral dynamic modelling has proven useful for designing clinical studies and predicting treatment outcomes for patients infected with the hepatitis C virus. Generally these models aim to capture and predict the on-treatment viral load dynamics from a small study of individual patients. Here, we explored extending these models (1) to clinical studies with numerous patients and (2) by incorporating additional data types, including sequence data and prior response to interferon. Data from Phase 3 clinical studies of the direct-acting antiviral telaprevir (T; total daily dose of 2250 mg) combined with pegylated-interferon alfa and ribavirin (PR) were used for the analysis. The following data in the treatment-naïve population were reserved to verify the model: (1) a T/PR regimen where T was dosed every 8 h for 8 weeks (T8(q8h)/PR) and (2) a T/PR regimen where T was dosed twice daily for 12 weeks (T12(b.i.d.)/PR). The resulting model accurately predicted (1) sustained virologic response rates for both of these dosing regimens and (2) viral breakthrough characteristics of the T8(q8h)/PR regimen. Since the observed viral variants depend on the T exposure, the second verification suggested that the model was correctly sensitive to the different T regimen even though the model was developed using data from another T regimen. Furthermore, the model predicted that b.i.d. T dosing was comparable to q8h T dosing in the PR-experienced population, a comparison that has not been made in a controlled clinical study. The methods developed in this work to estimate the variability occurring below the limit of detection for the viral load were critical for making accurate predictions. PMID:26289844

  10. Medical students' attitudes toward underserved populations: changing associations with choice of primary care versus non-primary care residency.

    PubMed

    Wayne, Sharon; Timm, Craig; Serna, Lisa; Solan, Brian; Kalishman, Summers

    2010-05-01

    The number of medical students entering primary care residencies continues to decrease. The association between student attitudes toward underserved populations and residency choice has received little attention even though primary care physicians see a larger proportion of underserved patients than most other specialists. We evaluated attitudes toward underserved populations in 826 medical students using a standardized survey, and used logistic regression to assess the effect of attitudes, along with other variables, on selection of a primary care residency. We compared results between two groups defined by year of entry to medical school (1993-99 and 2000-05) to determine whether associations differed by time period. Students' attitudes regarding professional responsibility toward underserved populations remained high over the study period; however, there was a statistically. significant association between positive attitudes and primary care residency in the early cohort only. This association was not found in the more recent group. PMID:20453348

  11. Dissecting tumor metabolic heterogeneity: Telomerase and large cell size metabolically define a sub-population of stem-like, mitochondrial-rich, cancer cells

    PubMed Central

    Lamb, Rebecca; Ozsvari, Bela; Bonuccelli, Gloria; Smith, Duncan L.; Pestell, Richard G.; Martinez-Outschoorn, Ubaldo E.; Clarke, Robert B.; Sotgia, Federica; Lisanti, Michael P.

    2015-01-01

    Tumor cell metabolic heterogeneity is thought to contribute to tumor recurrence, distant metastasis and chemo-resistance in cancer patients, driving poor clinical outcome. To better understand tumor metabolic heterogeneity, here we used the MCF7 breast cancer line as a model system to metabolically fractionate a cancer cell population. First, MCF7 cells were stably transfected with an hTERT-promoter construct driving GFP expression, as a surrogate marker of telomerase transcriptional activity. To enrich for immortal stem-like cancer cells, MCF7 cells expressing the highest levels of GFP (top 5%) were then isolated by FACS analysis. Notably, hTERT-GFP(+) MCF7 cells were significantly more efficient at forming mammospheres (i.e., stem cell activity) and showed increased mitochondrial mass and mitochondrial functional activity, all relative to hTERT-GFP(?) cells. Unbiased proteomics analysis of hTERT-GFP(+) MCF7 cells directly demonstrated the over-expression of 33 key mitochondrial proteins, 17 glycolytic enzymes, 34 ribosome-related proteins and 17 EMT markers, consistent with an anabolic cancer stem-like phenotype. Interestingly, MT-CO2 (cytochrome c oxidase subunit 2; Complex IV) expression was increased by >20-fold. As MT-CO2 is encoded by mt-DNA, this finding is indicative of increased mitochondrial biogenesis in hTERT-GFP(+) MCF7 cells. Importantly, most of these candidate biomarkers were transcriptionally over-expressed in human breast cancer epithelial cells in vivo. Similar results were obtained using cell size (forward/side scatter) to fractionate MCF7 cells. Larger stem-like cells also showed increased hTERT-GFP levels, as well as increased mitochondrial mass and function. Thus, this simple and rapid approach for the enrichment of immortal anabolic stem-like cancer cells will allow us and others to develop new prognostic biomarkers and novel anti-cancer therapies, by specifically and selectively targeting this metabolic sub-population of aggressive cancer cells. Based on our proteomics and functional analysis, FDA-approved inhibitors of protein synthesis and/or mitochondrial biogenesis, may represent novel treatment options for targeting these anabolic stem-like cancer cells. PMID:26323205

  12. Dissecting tumor metabolic heterogeneity: Telomerase and large cell size metabolically define a sub-population of stem-like, mitochondrial-rich, cancer cells.

    PubMed

    Lamb, Rebecca; Ozsvari, Bela; Bonuccelli, Gloria; Smith, Duncan L; Pestell, Richard G; Martinez-Outschoorn, Ubaldo E; Clarke, Robert B; Sotgia, Federica; Lisanti, Michael P

    2015-09-01

    Tumor cell metabolic heterogeneity is thought to contribute to tumor recurrence, distant metastasis and chemo-resistance in cancer patients, driving poor clinical outcome. To better understand tumor metabolic heterogeneity, here we used the MCF7 breast cancer line as a model system to metabolically fractionate a cancer cell population. First, MCF7 cells were stably transfected with an hTERT-promoter construct driving GFP expression, as a surrogate marker of telomerase transcriptional activity. To enrich for immortal stem-like cancer cells, MCF7 cells expressing the highest levels of GFP (top 5%) were then isolated by FACS analysis. Notably, hTERT-GFP(+) MCF7 cells were significantly more efficient at forming mammospheres (i.e., stem cell activity) and showed increased mitochondrial mass and mitochondrial functional activity, all relative to hTERT-GFP(-) cells. Unbiased proteomics analysis of hTERT-GFP(+) MCF7 cells directly demonstrated the over-expression of 33 key mitochondrial proteins, 17 glycolytic enzymes, 34 ribosome-related proteins and 17 EMT markers, consistent with an anabolic cancer stem-like phenotype. Interestingly, MT-CO2 (cytochrome c oxidase subunit 2; Complex IV) expression was increased by >20-fold. As MT-CO2 is encoded by mt-DNA, this finding is indicative of increased mitochondrial biogenesis in hTERT-GFP(+) MCF7 cells. Importantly, most of these candidate biomarkers were transcriptionally over-expressed in human breast cancer epithelial cells in vivo. Similar results were obtained using cell size (forward/side scatter) to fractionate MCF7 cells. Larger stem-like cells also showed increased hTERT-GFP levels, as well as increased mitochondrial mass and function. Thus, this simple and rapid approach for the enrichment of immortal anabolic stem-like cancer cells will allow us and others to develop new prognostic biomarkers and novel anti-cancer therapies, by specifically and selectively targeting this metabolic sub-population of aggressive cancer cells. Based on our proteomics and functional analysis, FDA-approved inhibitors of protein synthesis and/or mitochondrial biogenesis, may represent novel treatment options for targeting these anabolic stem-like cancer cells. PMID:26323205

  13. Molecular heterogeneity in a patient-derived glioblastoma xenoline is regulated by different cancer stem cell populations.

    PubMed

    Garner, Jo Meagan; Ellison, David W; Finkelstein, David; Ganguly, Debolina; Du, Ziyun; Sims, Michelle; Yang, Chuan He; Interiano, Rodrigo B; Davidoff, Andrew M; Pfeffer, Lawrence M

    2015-01-01

    Malignant glioblastoma (GBM) is a highly aggressive brain tumor with a dismal prognosis and limited therapeutic options. Genomic profiling of GBM samples has identified four molecular subtypes (Proneural, Neural, Classical and Mesenchymal), which may arise from different glioblastoma stem-like cell (GSC) populations. We previously showed that adherent cultures of GSCs grown on laminin-coated plates (Ad-GSCs) and spheroid cultures of GSCs (Sp-GSCs) had high expression of stem cell markers (CD133, Sox2 and Nestin), but low expression of differentiation markers (?III-tubulin and glial fibrillary acid protein). In the present study, we characterized GBM tumors produced by subcutaneous and intracranial injection of Ad-GSCs and Sp-GSCs isolated from a patient-derived xenoline. Although they formed tumors with identical histological features, gene expression analysis revealed that xenografts of Sp-GSCs had a Classical molecular subtype similar to that of bulk tumor cells. In contrast xenografts of Ad-GSCs expressed a Mesenchymal gene signature. Adherent GSC-derived xenografts had high STAT3 and ANGPTL4 expression, and enrichment for stem cell markers, transcriptional networks and pro-angiogenic markers characteristic of the Mesenchymal subtype. Examination of clinical samples from GBM patients showed that STAT3 expression was directly correlated with ANGPTL4 expression, and that increased expression of these genes correlated with poor patient survival and performance. A pharmacological STAT3 inhibitor abrogated STAT3 binding to the ANGPTL4 promoter and exhibited anticancer activity in vivo. Therefore, Ad-GSCs and Sp-GSCs produced histologically identical tumors with different gene expression patterns, and a STAT3/ANGPTL4 pathway is identified in glioblastoma that may serve as a target for therapeutic intervention. PMID:25955030

  14. Molecular Heterogeneity in a Patient-Derived Glioblastoma Xenoline Is Regulated by Different Cancer Stem Cell Populations

    PubMed Central

    Garner, Jo Meagan; Ellison, David W.; Finkelstein, David; Ganguly, Debolina; Du, Ziyun; Sims, Michelle; Yang, Chuan He; Interiano, Rodrigo B.; Davidoff, Andrew M.; Pfeffer, Lawrence M.

    2015-01-01

    Malignant glioblastoma (GBM) is a highly aggressive brain tumor with a dismal prognosis and limited therapeutic options. Genomic profiling of GBM samples has identified four molecular subtypes (Proneural, Neural, Classical and Mesenchymal), which may arise from different glioblastoma stem-like cell (GSC) populations. We previously showed that adherent cultures of GSCs grown on laminin-coated plates (Ad-GSCs) and spheroid cultures of GSCs (Sp-GSCs) had high expression of stem cell markers (CD133, Sox2 and Nestin), but low expression of differentiation markers (?III-tubulin and glial fibrillary acid protein). In the present study, we characterized GBM tumors produced by subcutaneous and intracranial injection of Ad-GSCs and Sp-GSCs isolated from a patient-derived xenoline. Although they formed tumors with identical histological features, gene expression analysis revealed that xenografts of Sp-GSCs had a Classical molecular subtype similar to that of bulk tumor cells. In contrast xenografts of Ad-GSCs expressed a Mesenchymal gene signature. Adherent GSC-derived xenografts had high STAT3 and ANGPTL4 expression, and enrichment for stem cell markers, transcriptional networks and pro-angiogenic markers characteristic of the Mesenchymal subtype. Examination of clinical samples from GBM patients showed that STAT3 expression was directly correlated with ANGPTL4 expression, and that increased expression of these genes correlated with poor patient survival and performance. A pharmacological STAT3 inhibitor abrogated STAT3 binding to the ANGPTL4 promoter and exhibited anticancer activity in vivo. Therefore, Ad-GSCs and Sp-GSCs produced histologically identical tumors with different gene expression patterns, and a STAT3/ANGPTL4 pathway is identified in glioblastoma that may serve as a target for therapeutic intervention. PMID:25955030

  15. 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

  16. 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

    2015-12-01

    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

  17. 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.

  18. CASCADE EFFECTS IN HETEROGENEOUS POPULATIONS

    E-print Network

    Murphy, Robert F.

    ) is well known in the marketing literature: consumers are much more likely to buy a product' of hamburgers sold, and why companies such as Nike and Reebok spend millions of dollars annually on celebrity market share even if the altern

  19. 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…

  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. Heterogeneous voter models

    NASA Astrophysics Data System (ADS)

    Masuda, Naoki; Gibert, N.; Redner, S.

    2010-07-01

    We introduce the heterogeneous voter model (HVM), in which each agent has its own intrinsic rate to change state, reflective of the heterogeneity of real people, and the partisan voter model (PVM), in which each agent has an innate and fixed preference for one of two possible opinion states. For the HVM, the time until consensus is reached is much longer than in the classic voter model. For the PVM in the mean-field limit, a population evolves to a preference-based state, where each agent tends to be aligned with its internal preference. For finite populations, discrete fluctuations ultimately lead to consensus being reached in a time that scales exponentially with population size.

  4. [Phenotypic characterization of species of Malassezia in healthy skin of an university student population].

    PubMed

    Rodríguez-Valero, Sofía; Mesa, Luz Mila; Gonzalez-Morán, Evelyn; Delmonte, María Lucía; Robertiz, Sandra; Valero, Alejandro

    2005-12-01

    The yeasts of the Malassezia genus are part of the normal skin of man and other vertebrates. The description of new species for this genus has induced on their study in several countries. For this reason, is important to do research in order to get epidemiologic data about Malassezia species in tropical countries like Venezuela, where the new Malassezia species have not been reported. This study was made on healthy skin of a university student population. The samples were taken from different body areas and inoculated in Dixon modified medium and Sabouraud dextrose agar medium e incubated at 32 degrees C. The identification was achieved following the key of species described by Gueho et al. and the tween diffusion test proposed by Guillot et al. In this investigation the isolated specie was M. furfur, corresponding the major positive percentage to the age group from 16 to 20 years old (66.7%). The presence of Malassezia was predominant on shoulder and chest (33.3% and 26.6%). There were not found significant differences between the evaluated groups, as was demonstrated by the applied statistical tests, exact Fisher's test and Chi square test. It is important to continue the investigations on other age groups, in order to establish the prevalent species in our region and evaluate their pathogenic potential. PMID:16353540

  5. Second International Mathematics Study; Longitudinal, Classroom Process Surveys for Population A: Students, Teachers, and Schools, 1981-1982 [machine-readable data file].

    ERIC Educational Resources Information Center

    Wolfe, Richard G.

    The Second International Mathematics Study (SIMS) of the International Association for the Evaluation of Educational Achievement (IEA) was conducted in 20 countries on two sampled populations: Population A of 13-year-olds and Population B of students studying mathematics in their final year of secondary school. Mathematics achievement was measured…

  6. Rethinking Policy for At-Risk Students.

    ERIC Educational Resources Information Center

    Wong, Kenneth K., Ed.; Wang, Margaret C., Ed.

    As the school-age population in the United States becomes increasingly culturally diverse and economically heterogeneous, public schools are confronted with issues of program specialization and social integration. Programs designed for students with special needs often take the form of discrete instructional structures. One consequence of targeted…

  7. The Interaction Effects of GPA on Other Determinants of Student Attrition in a Homogeneous Population.

    ERIC Educational Resources Information Center

    Bean, John P.

    Variables that best explain variance in student attrition for 168 freshmen students from a college of agriculture within a major midwestern university were studied in 1979. Variables were selected from a theoretical causal model of student attrition (Bean, 1981), a review of the literature (Bean, 1978), and five empirical investigations conducted…

  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. 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…

  10. Pluralistic Ignorance among Student-Athlete Populations: A Factor in Academic Underperformance

    ERIC Educational Resources Information Center

    Levine, Joshua; Etchison, Sara; Oppenheimer, Daniel M.

    2014-01-01

    It is well documented that student-athletes underperform academically. Some researchers have suggested that this underperformance is because student-athletes lack motivation in academic endeavors. In contrast, we find that most student-athletes hold positive private attitudes towards academic achievement, but also believe that their peers do not.…

  11. A pilot investigation of "metaphor blindness" in a college student population.

    PubMed

    Jalal, Baland; Ramachandran, Vilayanur S

    2014-06-01

    Previous research from our group suggests that patients with lesions in the left inferior parietal lobule (IPL)-which is concerned with abstract numerical cognition and cross-modal association (which is consistent with its strategic location at the crossroads between the temporal, parietal and occipital lobes) have difficulty understanding proverbs and metaphors (Ramachandran and Hubbard, 2001). In the current pilot investigation, we report "metaphor blindness" in a college student population; that is, either the complete inability or difficulty for otherwise intellectually non-challenged individuals to comprehend metaphors of language. Participants (N=205) read 12 metaphorical ("The detective jumped at the clue") and 12 literal ("The accident was a fall") sentences and had to decide whether the sentences conveyed a metaphorical or literal meaning. The mean accuracy for these metaphorical sentences was 11.0 (SD=2.3; RNG=0-12); the mean accuracy for literal sentences was 7.2 (SD=1.8; RNG=2-10). We found that 5% of participants (11/205) were unable or had difficulty understanding metaphors (i.e., were statistical outliers), while their score for literal sentences felt within a normal statistical range M=8.3 (SD=2.3; RNG=5-10). Follow-up control procedures were conducted in order to help ascertain that the results were not due to low verbal IQ and task difficulty. Likewise, none of the "metaphor blind" participants reported any psychiatric or neurological histories that would impair language comprehension, including strokes, brain injuries, language problems dyslexia, and signs of late language onset. The results are very preliminary and future studies are needed to confirm these findings. We suggest that brain modules may be specialized even for subtle functions like metaphor and their formation in embryogenesis may be controlled by small handfuls of genes whose expression can go awry--as in "metaphor blindness". PMID:24661940

  12. Guide to Population Issues for Students and Teachers [and] Curriculum Guide.

    ERIC Educational Resources Information Center

    Facing the Future, Lopez Island, WA.

    As the world grapples with increasing environmental, social, and security problems, population is rarely considered a cause or contributing factor. The relationship of population to the human condition, and to the condition of the Earth, is often subtle and complex. But population growth affects almost every aspect of life from education to…

  13. 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

  14. The Roles of Population, Place, and Institution in Student Diversity in American Higher Education

    PubMed Central

    Franklin, Rachel S.

    2014-01-01

    Student racial and ethnic diversity in higher education is an important and timely topic, as institutions, policy-makers, and economists increasingly recognize the value that accrues at many levels of having a skilled and diverse student body and workforce. Students benefit from learning in a diverse environment; firms may benefit from a diverse workforce; and more demographically diverse regions make experience higher rates of economic growth. However, the forces governing institution-level student diversity are poorly understood, as little prior research on the topic exists. This paper uses school enrollment data to parse out the contribution institutional characteristics, geographical setting, and local demographic characteristics make to student body diversity at each level of study. Results indicate that geographical location and local demographic composition play a role in student body diversity, as do the type and orientation of the institution. Institutional characteristics explain a lot of the variation in student body diversity and actual location of schools matters less than the demographic composition of young people around that location. Two broad conclusions emerge with regard to schools seeking to increase their student diversity. First, some may find their efforts hampered by circumstances outside their control (location, for example). Second, the influence of public/private status and even school size suggest further research on the ways in which these factors influence student diversity so that eventual policy action can be more effective. PMID:25425748

  15. Efficient Hybrid Security Mechanisms for Heterogeneous Sensor Networks

    E-print Network

    La Porta, Tom

    Terms--Heterogeneous sensor networks, probabilistic key management, probabilistic authentication, hybridEfficient Hybrid Security Mechanisms for Heterogeneous Sensor Networks Patrick Traynor, Student network security. Ç 1 INTRODUCTION THE deployment of wireless sensor networks is becoming more common

  16. A Meta-Analytic Evaluation of the FRIENDS Program for Preventing Anxiety in Student Populations

    ERIC Educational Resources Information Center

    Maggin, Daniel M.; Johnson, Austin H.

    2014-01-01

    The purpose of this review was to evaluate the methodological strength and overall effectiveness of the research underlying the FRIENDS program for preventing anxiety in students at low and elevated risk for developing anxiety disorders. Meta-analytic findings provided mixed results, with low-risk students exposed to the program having…

  17. Ohio's At-Risk Student Population: A Decade of Rising Risk

    ERIC Educational Resources Information Center

    Vesely, Randall S.

    2013-01-01

    Educators face increasing demands to raise student achievement, to improve classroom instruction, and to demonstrate accountability in an environment of high stakes testing. However, meeting these demands is challenging in the face of numerous risk factors that jeopardize the academic success of elementary and secondary students. To that end, the…

  18. Student as Institutional Mirror: What Campuses Can Learn from Nontraditional Populations

    ERIC Educational Resources Information Center

    Davis, Jeff

    2011-01-01

    College campuses look different today, at the beginning of the twenty-first century, than they did 50 years ago. The buildings and signage may look almost the same, but the students who learn in those buildings definitely do not. Increased access and the diversity movement have resulted in younger and older students sitting side by side in the…

  19. 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…

  20. 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…

  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. Simulating Population Growth.

    ERIC Educational Resources Information Center

    Byington, Scott

    1997-01-01

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

  4. 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)

  5. How Spanish Primary School Students Interpret the Concepts of Population and Species

    ERIC Educational Resources Information Center

    Jiménez-Tejada, María-Pilar; Sánchez-Monsalve, Cristina; González-García, Francisco

    2013-01-01

    This article presents research concerning the way in which primary school pupils in southern Spain interpret the concepts of population and species. The results show that, for the concept of population, there was an intense anthropocentrism in pupils' responses, while for the concept of species, only animals were considered as living…

  6. Positive Mental Health and Well-Being among a Third Level Student Population

    PubMed Central

    Davoren, Martin P.; Fitzgerald, Eimear; Shiely, Frances; Perry, Ivan J.

    2013-01-01

    Introduction Much research on the health and well-being of third level students is focused on poor mental health leading to a dearth of information on positive mental health and well-being. Recently, the Warwick Edinburgh Mental Well-being scale (WEMWBS) was developed as a measurement of positive mental health and well-being. The aim of this research is to investigate the distribution and determinants of positive mental health and well-being in a large, broadly representative sample of third level students using WEMWBS. Methods Undergraduate students from one large third level institution were sampled using probability proportional to size sampling. Questionnaires were distributed to students attending lectures in the randomly selected degrees. A total of 2,332 self-completed questionnaires were obtained, yielding a response rate of 51% based on students registered to relevant modules and 84% based on attendance. One-way ANOVAs and multivariate logistic regression were utilised to investigate factors associated with positive mental health and well-being. Results The sample was predominantly female (62.66%), in first year (46.9%) and living in their parents’ house (42.4%) or in a rented house or flat (40.8%). In multivariate analysis adjusted for age and stratified by gender, no significant differences in WEMWBS score were observed by area of study, alcohol, smoking or drug use. WEMWBS scores were higher among male students with low levels of physical activity (p=0.04). Men and women reporting one or more sexual partners (p<0.001) were also more likely to report above average mental health and well-being. Conclusion This is the first study to examine positive mental health and well-being scores in a third level student sample using WEMWBS. The findings suggest that students with a relatively adverse health and lifestyle profile have higher than average mental health and well-being. To confirm these results, this work needs to be replicated across other third level institutions. PMID:24009778

  7. 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…

  8. A Profile of the Aboriginal and Torres Strait Islander Higher Education Student Population

    ERIC Educational Resources Information Center

    Wilks, Judith; Wilson, Katie

    2015-01-01

    This paper brings together recent statistics relating to the participation of Aboriginal and Torres Strait Islander students in higher education. A number of key statistical realities relating to their enrolment into, retention during, and completion of, their university courses are depicted. Foremost among these realities is that despite…

  9. Students Delivering Health Care to a Vulnerable Appalachian Population through Interprofessional Service-Learning

    ERIC Educational Resources Information Center

    Lee, Michelle L.; Hayes, Patricia A.; McConnell, Peggy; Henry, Robin M.

    2013-01-01

    Interprofessional student service-learning experiences are integrated into the preventive care of older adult residents of public housing in Appalachia. Receiving a Health Resources and Services Administration grant provided the College of Nursing at East Tennessee State University the opportunity to expand interprofessional clinical experiences…

  10. Writing to Learn Ecology: A Study of Three Populations of College Students

    ERIC Educational Resources Information Center

    Balgopal, Meena M.; Wallace, Alison M.; Dahlberg, Steven

    2012-01-01

    Being an ecologically literate citizen involves making decisions that are based on ecological knowledge and accepting responsibility for personal actions. Using writing-to-learn activities in college science courses, we asked students to consider personal dilemmas that they or others might have in response to how human choices can impact coastal…

  11. 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…

  12. Analysis of the Learning Styles of Diverse Student Populations and Implications for Higher Education Instructional Change

    ERIC Educational Resources Information Center

    Novogrodsky, Dorothy

    2012-01-01

    Higher education is one of the last institutions of learning to embrace the challenge of learner diversity that exists everywhere today (Dunn & Griggs, 2000; Rowley, Lujan, Dolence, 1998). This investigation explored the relationships between perceived preferred instructional strategies and student learning styles of learning-style aware…

  13. Nonoutbreak Surveillance of Group A Streptococci Causing Invasive Disease in Portugal Identified Internationally Disseminated Clones among Members of a Genetically Heterogeneous Population?

    PubMed Central

    Friães, A.; Ramirez, M.; Melo-Cristino, J.

    2007-01-01

    The typing of 160 invasive Streptococcus pyogenes isolates confirmed the importance of pulsed-field gel electrophoresis and multilocus sequence typing for defining clones. The results identified an extremely diverse population and highlighted the importance of both internationally disseminated and local clones not previously associated with invasive disease. PMID:17460058

  14. Heterogeneity in Melanoma.

    PubMed

    Shannan, Batool; Perego, Michela; Somasundaram, Rajasekharan; Herlyn, Meenhard

    2016-01-01

    Melanoma is among the most aggressive and therapy-resistant human cancers. While great strides in therapy have generated enthusiasm, many challenges remain. Heterogeneity is the most pressing issue for all types of therapy. This chapter summarizes the clinical classification of melanoma, of which the research community now adds additional layers of classifications for better diagnosis and prediction of therapy response. As the search for new biomarkers increases, we expect that biomarker analyses will be essential for all clinical trials to better select patient populations for optimal therapy. While individualized therapy that is based on extensive biomarker analyses is an option, we expect in the future genetic and biologic biomarkers will allow grouping of melanomas in such a way that we can predict therapy outcome. At this time, tumor heterogeneity continues to be the major challenge leading inevitably to relapse. To address heterogeneity therapeutically, we need to develop complex therapies that eliminate the bulk of the tumor and, at the same time, the critical subpopulations. PMID:26601857

  15. Evidence of hearing loss in a 'normally-hearing' college-student population.

    PubMed

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

    2011-03-01

    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

  16. 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

  17. Population heterogeneity of trait anger and differential associations of trait anger facets with borderline personality features, neuroticism, depression, Attention Deficit Hyperactivity Disorder (ADHD), and alcohol problems.

    PubMed

    Lubke, Gitta H; Ouwens, Klaasjan G; de Moor, Marleen H M; Trull, Timothy J; Boomsma, Dorret I

    2015-12-15

    Anger is an emotion consisting of feelings of variable intensity ranging from mild irritation to intense fury. High levels of trait anger are associated with a range of psychiatric, interpersonal, and health problems. The objectives of this study were to explore heterogeneity of anger as measured by the Spielberger Trait Anger Scale (STAS), and to assess the association of the different anger facets with a selection of psychiatric disorders covering externalizing and internalizing problems, personality disorders, and substance use. Factor mixture models differentiated between a high and low scoring class (28% vs. 72%), and between three factors (anger-temperament, anger-reaction, and immediacy of an anger response). Whereas all psychiatric scales correlated significantly with the STAS total score, regressing the three STAS factors on psychiatric behaviors model showed a more detailed pattern. Only borderline affect instability and depression were significantly associated with all three factors in both classes whereas other problem behaviors were associated only with 1 or 2 of the factors. Alcohol problems were associated with immediacy only in the high scoring class, indicating a non-linear relation in the total sample. Taking into account these more specific associations is likely to be beneficial when investigating differential treatment strategies. PMID:26454404

  18. Multi-event capture–recapture modeling of host–pathogen dynamics among European rabbit populations exposed to myxoma and Rabbit Hemorrhagic Disease Viruses: common and heterogeneous patterns

    PubMed Central

    2014-01-01

    Host–pathogen epidemiological processes are often unclear due both to their complexity and over-simplistic approaches used to quantify them. We applied a multi-event capture–recapture procedure on two years of data from three rabbit populations to test hypotheses about the effects on survival of, and the dynamics of host immunity to, both myxoma virus and Rabbit Hemorrhagic Disease Virus (MV and RHDV). Although the populations shared the same climatic and management conditions, MV and RHDV dynamics varied greatly among them; MV and RHDV seroprevalences were positively related to density in one population, but RHDV seroprevalence was negatively related to density in another. In addition, (i) juvenile survival was most often negatively related to seropositivity, (ii) RHDV seropositives never had considerably higher survival, and (iii) seroconversion to seropositivity was more likely than the reverse. We suggest seropositivity affects survival depending on trade-offs among antibody protection, immunosuppression and virus lethality. Negative effects of seropositivity might be greater on juveniles due to their immature immune system. Also, while RHDV directly affects survival through the hemorrhagic syndrome, MV lack of direct lethal effects means that interactions influencing survival are likely to be more complex. Multi-event modeling allowed us to quantify patterns of host–pathogen dynamics otherwise difficult to discern. Such an approach offers a promising tool to shed light on causative mechanisms. PMID:24708296

  19. 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

  20. Survey of mobile phone use and their chronic effects on the hearing of a student population.

    PubMed

    Davidson, Harry C; Lutman, Mark E

    2007-03-01

    Mobile phone ownership and usage is now widespread and public concern has developed over possible harmful physiological effects of their use. This study aimed to investigate the prevalence of student mobile phone ownership and any possible chronic effects of usage on hearing, tinnitus and balance. Questionnaires for electronic self-completion were distributed to University of Southampton postgraduates, and 117 out of 160 returned met the criteria for analysis. A total of 94% were current mobile phone users, and only 2% had never used a mobile phone. Duration of ownership and daily usage ranged from 0-7 years and 0-45 minutes respectively. Text-messaging was more popular than talking. High or long-term users reported no worse hearing, tinnitus, or balance than low or short-term users. The results of this study confirm that the prevalence of mobile phone ownership amongst students is extremely high. However there appear to be no harmful effects of mobile phone usage on their audiovestibular systems within the range of exposure of the study, insofar as can be detected by the self-report method employed. PMID:17365064

  1. Heterogeneous Evolution of HIV-1 CRF01_AE in Men Who Have Sex with Men (MSM) and Other Populations in China

    PubMed Central

    Peng, Xiaorong; Wu, Haibo; Peng, Xiuming; Jin, Changzhong; Wu, Nanping

    2015-01-01

    Introduction The HIV epidemic in men who have sex with men (MSM) continues to grow in most countries. However, the phylodynamic and virological differences among HIV-1 strains circulating in MSM and other populations are not well characterized. Methods Nearly full-length genomes (NFLGs) of the HIV-1 CRF01_AE were obtained from the Los Alamos HIV database. Phylogenetic analyses were conducted using the NFLG, gag, pol and env genes, using the maximum likelihood method. Selection pressure analyses at the codon level were performed for each gene in the phylogenetic clusters using PAML. Results Sequences isolated from MSM in China clustered in Clusters 1 (92.5%) and 2 (85.71%). The major risk factor for Cluster 3 was heterosexual transmission (62.16%). The ratio of non-synonymous to synonymous substitutions in the env gene (0.7–0.75) was higher than the gag (0.26–0.34) or pol (0.21–0.26) genes. In env gene, Cluster 1 (4.56×10-3subs/site/year) and 2 (6.01×10-3subs/site/year) had higher evolutionary rates than Cluster 3 (1.14×10-3subs/site/year). Positive selection affected 4.2–6.58% of the amino acid sites in the env gene. Two sites (HXB2:136 and 316) evolved similarly in Clusters 1 and 2, but not Cluster 3. Conclusion The HIV-1 CRF01_AE in MSM is evolving differently than in other populations. PMID:26623642

  2. 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

  3. 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.

  4. Herpes simplex virus type 1 prereplicative sites are a heterogeneous population: only a subset are likely to be precursors to replication compartments.

    PubMed Central

    Lukonis, C J; Burkham, J; Weller, S K

    1997-01-01

    When herpes simplex virus type 1 (HSV-1) DNA replication is blocked by viral polymerase inhibitors, such as phosphonoacetic acid (PAA) or acyclovir (ACV), UL29 (ICP8) localizes to numerous punctate nuclear foci which are called prereplicative sites. Since this pattern can form in cells infected with mutants which are defective in UL5, UL8, UL9, or UL52 in the presence of polymerase inhibitors (C. J. Lukonis and S. K. Weller, J. Virol. 70:1751-1758, 1996; L. M. Liptak, S. L. Uprichard, and D. M. Knipe, J. Virol. 70:1759-1767, 1996), we previously proposed that it is unlikely that these numerous UL29 foci actually represent a functional subassembly of viral replication proteins that could lead to the formation of replication compartments (C. J. Lukonis and S. K. Weller, J. Virol. 70:1751-1758, 1996). In this paper, we have investigated the requirement for formation of the prereplicative site pattern by using double mutants of HSV. From the analysis of mutants lacking both UL5 and UL9, we conclude that neither viral helicase is required for the prereplicative site pattern to form as long as a polymerase inhibitor is present. From the analysis of mutants defective in both UL30 and UL5, we suggest that the prereplicative site pattern can form under conditions in which viral and/or cellular polymerases are inhibited. Furthermore, reexamination of the UL29 staining pattern in cells infected with wild-type virus in the presence of PAA reveals that at least two different UL29 staining patterns can be detected in these cells. One population of cells contains numerous (greater than 20) punctate UL29 foci which are sites of cellular DNA synthesis. In another population of cells, fewer punctate foci (less than 15) are detected, and these structures do not colocalize with sites of cellular DNA synthesis. Instead, they colocalize with PML, a component of nuclear matrix structures known as ND10. We propose that ND10-associated UL29 sites represent domains at which replication compartments form. PMID:9151871

  5. 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…

  6. 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…

  7. Postsecondary Educational Decision-Making among First-Generation College-Bound Students in Okinawa Prefecture, with Consideration of the Population Problem in Japan

    ERIC Educational Resources Information Center

    Amaki, Yuki

    2010-01-01

    In correspondence to an overall decline in the Japanese population, the number of young students in Japan has been dramatically decreasing to the extent that the Japanese government has predicted a situation in which as of 2009 admissions places in Japanese universities will be equal to the number of applicants. Currently, approximately fifty…

  8. 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…

  9. Very Low Ventricular Pacing Rates Can Be Achieved Safely in a Heterogeneous Pacemaker Population and Provide Clinical Benefits: The CANadian Multi-Centre Randomised Study-Spontaneous AtrioVEntricular Conduction pReservation (CAN-SAVE R) Trial

    PubMed Central

    Thibault, Bernard; Ducharme, Anique; Baranchuk, Adrian; Dubuc, Marc; Dyrda, Katia; Guerra, Peter G; Macle, Laurent; Mondésert, Blandine; Rivard, Léna; Roy, Denis; Talajic, Mario; Andrade, Jason; Nitzsché, Rémi; Khairy, Paul

    2015-01-01

    Background It is well recognized that right ventricular apical pacing can have deleterious effects on ventricular function. We performed a head-to-head comparison of the SafeR pacing algorithm versus DDD pacing with a long atrioventricular delay in a heterogeneous population of patients with dual-chamber pacemakers. Methods and Results In a multicenter prospective double-blinded randomized trial conducted at 10 centers in Canada, 373 patients, age 71±11 years, with indications for dual chamber DC pacemakers were randomized 1:1 to SafeR or DDD pacing with a long atrioventricular delay (250 ms). The primary objective was twofold: (1) reduction in the proportion of ventricular paced beats at 1 year; and (2) impact on atrial fibrillation burden at 3 years, defined as the ratio between cumulative duration of mode-switches divided by follow-up time. Statistical significance of both co-primary end points was required for the trial to be considered positive. At 1 year of follow-up, the median proportion of ventricular-paced beats was 4.0% with DDD versus 0% with SafeR (P<0.001). At 3 years of follow-up, the atrial fibrillation burden was not significantly reduced with SafeR versus DDD (median 0.00%, interquartile range [0.00% to 0.23%] versus median 0.01%, interquartile range [0.00% to 0.44%], respectively, P=0.178]), despite a persistent reduction in the median proportion of ventricular-paced beats (10% with DDD compared to 0% with SafeR). Conclusions A ventricular-paced rate <1% was safely achieved with SafeR in a population with a wide spectrum of indications for dual-chamber pacing. However, the lower percentage of ventricular pacing did not translate into a significant reduction in atrial fibrillation burden. Clinical Trial Registration URL: https://www.clinicaltrials.gov/ Unique identifier: NCT01219621. PMID:26206737

  10. Dynamic stem cell heterogeneity.

    PubMed

    Krieger, Teresa; Simons, Benjamin D

    2015-04-15

    Recent lineage-tracing studies based on inducible genetic labelling have emphasized a crucial role for stochasticity in the maintenance and regeneration of cycling adult tissues. These studies have revealed that stem cells are frequently lost through differentiation and that this is compensated for by the duplication of neighbours, leading to the consolidation of clonal diversity. Through the combination of long-term lineage-tracing assays with short-term in vivo live imaging, the cellular basis of this stochastic stem cell loss and replacement has begun to be resolved. With a focus on mammalian spermatogenesis, intestinal maintenance and the hair cycle, we review the role of dynamic heterogeneity in the regulation of adult stem cell populations. PMID:25852198

  11. Academic Studies amid Violent Conflict: A Study of the Impact of Ongoing Conflict on a Student Population

    ERIC Educational Resources Information Center

    Ben-Tsur, Dalia

    2009-01-01

    This paper explores the impact of violent conflict on undergraduate students. In order to strengthen student resilience during periods of heightened insecurity, teachers and institutions must identify the difficulties that their students may be experiencing. Based on a case study of students in Israel, this paper identifies specific difficulties…

  12. Impact of Heterogeneous Human Activities on Epidemic Spreading

    E-print Network

    Yang, Zimo; Zhou, Tao

    2011-01-01

    Recent empirical observations suggest a heterogeneous nature of human activities. The heavy-tailed inter-event time distribution at population level is well accepted, while whether the individual acts in a heterogeneous way is still under debate. Motivated by the impact of temporal heterogeneity of human activities on epidemic spreading, this paper studies the susceptible-infected model on a fully mixed population, where each individual acts in a completely homogeneous way but different individuals have different mean activities. Extensive simulations show that the heterogeneity of activities at population level remarkably affects the speed of spreading, even though each individual behaves regularly. Further more, the spreading speed of this model is more sensitive to the change of system heterogeneity compared with the model consisted of individuals acting with heavy-tailed inter-event time distribution. This work refines our understanding of the impact of heterogeneous human activities on epidemic spreading...

  13. An Evaluation of Behavioral Health Compliance and Microbial Risk Factors on Student Populations within a High-Density Campus

    ERIC Educational Resources Information Center

    Decker, Jody F.; Slawson, Robin M.

    2012-01-01

    Objective: The aim of this Canadian study was to assess student behavioral response to disease transmission risk, while identifying high microbial deposition/transmission sites. Participants: A student survey was conducted during October 2009. Methods: The methods included a survey of students to assess use of health services, vaccination…

  14. Heterogeneous Crystal Populations: Signatures, Genesis and Chronologies

    NASA Astrophysics Data System (ADS)

    Reid, M. R.; Vazquez, J. A.

    2005-12-01

    The ongoing development of accessory phase-based techniques helps to illuminate possible scenarios for the physical state of magmatic systems between eruptions. These, in turn, may aid in the detection of magmas in the crust. At Long Valley caldera, eastern California, ion microprobe analyses of 238U-230Th in zircon from the youthful Inyo Dome rhyolites show that even though their ages are mainly younger than the 760 k.y. old caldera-forming Bishop Tuff, they are significantly older than eruption (up to 200 k.y. and more). Do these ages date the timing of magma emplacement and show that liquid was present in the system for at least 200 k.y.? Or do the ages represent sampling by the ion beam of bimodal age domains, meaning that they could have been rapidly mobilized from voluminous crystal mushes residual after the Bishop Tuff (e.g., Hildreth, 2004)? Additionally or alternatively, could the "old" zircons be derived via assimilation of young, hydrothermally altered intrusive rocks (Schmitt and Simon, 2004)? The majority of 238U-206Pb analyses of zircons from Deer Mountain (13 of 20) are consistent with a single crystallization age that is somewhat older than previously obtained by 238U-230Th disequilibrium dating; the remaining zircon ages are younger and range to within error of the eruption age. The absence of Bishop Tuff-aged zircons indicates that if crystal mush contributes to the Inyo Dome rhyolites, its remobilization must have involved reheating to temperatures in excess of zircon saturation conditions (T>~800°C). Ion microprobe U-Th ages of allanites from South Deadman Dome range from 150 to <10 ka, in contrast to virtually all of the zircon ages which are >100 ka. The ca. 2-fold ranges in MnO/MgO and La/Nd in the same allanites overlap and extend the range of compositions we obtained for rhyolites from Toba caldera (Vazquez and Reid, 2005). The South Deadman Dome allanites could, by analogy to experimental results for a Toba rhyolite, have crystallized between the temperature interval of ~765°C to ~745°C. Taken at face value, the temperature-age distributions of allanite and zircon are therefore suggestive of a broad cooling trend. In detail, however, the T-t evolution defined by the allanites is one of a protracted interval of INCREASING temperature before eruption. We infer that intrusions of hotter, less evolved magma progressively hybridized the magma reservoir. Given the rarity with which zircons contemporary with the allanites have (as yet) been detected, the thermochemical conditions of that reservoir were sufficiently well buffered so that extensive (re)crystallization of zircon did not occur. Repose of a crystal-rich magma is indicated. This abstract is dedicated to the pioneering work of Stan Hart and Nobu Shimizu who showed how the Cameca 3f, Serial No. 1, could be used to investigate the isotopic and chemical evolution of crystals.

  15. Diffusion and Surface Reaction in Heterogeneous Catalysis

    ERIC Educational Resources Information Center

    Baiker, A.; Richarz, W.

    1978-01-01

    Ethylene hydrogenation on a platinum catalyst, electrolytically applied to a tube wall, is a good system for the study of the interactions between diffusion and surface reaction in heterogeneous catalysis. Theoretical background, apparatus, procedure, and student performance of this experiment are discussed. (BB)

  16. 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…

  17. 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,…

  18. An Administrative Concern: Science Teachers' Instructional Efficacy Beliefs regarding Racially, Culturally, Economically, and Linguistically Diverse Student Populations

    ERIC Educational Resources Information Center

    Tuck Bonner, Natalie Christine

    2009-01-01

    A teacher's sense of {instructional} efficacy has been considered a critical variable in student academic performance. Researchers Tschannen-Moran and Hoy Woolfolk (2001, p.783) defined teachers' {instructional} efficacy as a teacher's judgment of his or her capabilities to bring about desired outcomes of student engagement and learning, even…

  19. 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

  20. 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. PMID:25425168

  1. 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

  2. Welcoming Blue-Collar Scholars into the Ivory Tower: Developing Class-Conscious Strategies for Student Success. Series on Special Student Populations

    ERIC Educational Resources Information Center

    Soria, Krista M.

    2015-01-01

    "Welcoming Blue-Collar Scholars Into the Ivory Tower" is the first volume in a new book series designed to explore how institutional policies, practices, and cultures shape learning, development, and success for students who have been historically underserved or given limited consideration in the design of higher education contexts.…

  3. Heterogeneous Semantics in Ptolemy

    E-print Network

    Zakhor, Avideh

    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

  4. Developing Dental Students' Awareness of Health Care Disparities and Desire to Serve Vulnerable Populations Through Service-Learning.

    PubMed

    Behar-Horenstein, Linda S; Feng, Xiaoying; Roberts, Kellie W; Gibbs, Micaela; Catalanotto, Frank A; Hudson-Vassell, Charisse M

    2015-10-01

    Service-learning in dental education helps students integrate knowledge with practice in an underserved community setting. The aim of this study was to explore how a service-learning experience affected a small group of dental students' beliefs about cultural competence, professionalism, career development, desire to practice in a community service setting, and perceptions about access and disparities issues. Prior to beginning their first year of dental school, five first-year dental students at one U.S. dental school participated in a six-week service-learning program in which they interned at one of three at-risk settings in order to experience health care delivery there. After the program, 60 reflective writing assignments completed by the participants were analyzed using grounded theory methods; interviews with the students were used to corroborate the findings from that analysis. Seven themes identified in the journal reflections and interview findings showed enhanced awareness of social health care issues and patient differences, as well as a social justice orientation and desire to address disparities. Building on this study, future research should explore the curricular components of service-learning programs to ensure students receive ample opportunity to reflect upon their experiences in order to integrate previously held assumptions with their newfound knowledge. PMID:26427778

  5. The Community College Effect Revisited: The Importance of Attending to Heterogeneity and Complex Counterfactuals*

    PubMed Central

    Brand, Jennie E.; Pfeffer, Fabian T.; Goldrick-Rab, Sara

    2015-01-01

    Community colleges are controversial educational institutions, often said to simultaneously expand college opportunities and diminish baccalaureate attainment. We assess the seemingly contradictory functions of community colleges by attending to effect heterogeneity and to alternative counterfactual conditions. Using data on postsecondary outcomes of high school graduates of Chicago Public Schools, we find that enrolling at a community college penalizes more advantaged students who otherwise would have attended four-year colleges, particularly highly selective schools; however, these students represent a relatively small portion of the community college population, and these estimates are almost certainly biased. On the other hand, enrolling at a community college has a modest positive effect on bachelor's degree completion for disadvantaged students who otherwise would not have attended college; these students represent the majority of community college goers. We conclude that discussions among scholars, policymakers, and practitioners should move beyond considering the pros and cons of community college attendance for students in general to attending to the implications of community college attendance for targeted groups of students. PMID:25825705

  6. Spatially correlated heterogeneous aspirations to enhance network reciprocity

    NASA Astrophysics Data System (ADS)

    Tanimoto, Jun; Nakata, Makoto; Hagishima, Aya; Ikegaya, Naoki

    2012-02-01

    Perc & Wang demonstrated that aspiring to be the fittest under conditions of pairwise strategy updating enhances network reciprocity in structured populations playing 2×2 Prisoner's Dilemma games (Z. Wang, M. Perc, Aspiring to the fittest and promoted of cooperation in the Prisoner's Dilemma game, Physical Review E 82 (2010) 021115; M. Perc, Z. Wang, Heterogeneous aspiration promotes cooperation in the Prisoner's Dilemma game, PLOS one 5 (12) (2010) e15117). Through numerical simulations, this paper shows that network reciprocity is even greater if heterogeneous aspirations are imposed. We also suggest why heterogeneous aspiration fosters network reciprocity. It distributes strategy updating speed among agents in a manner that fortifies the initially allocated cooperators' clusters against invasion. This finding prompted us to further enhance the usual heterogeneous aspiration cases for heterogeneous network topologies. We find that a negative correlation between degree and aspiration level does extend cooperation among heterogeneously structured agents.

  7. Update of Project to Introduce Technology in Urban Schools Which Have Low Achievement and Economically Poor Student Populations

    ERIC Educational Resources Information Center

    Smith, Gary R.

    2009-01-01

    This document provides new insights into events which occurred in a project funded by a Technology Literacy Challenge Fund grant awarded by Michigan Department of Education(MDE) in 2000. One purpose of this document is to update the formal report of the project which introduced new technology for use by low achieving students who are studying in…

  8. 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…

  9. Use of Trans Fat Information on Food Labels and Its Determinants in a Multiethnic College Student Population

    ERIC Educational Resources Information Center

    Jasti, Sunitha; Kovacs, Szilvia

    2010-01-01

    Objectives: To examine the correlates of trans fat knowledge and trans fat label use; to examine the influence of trans fat knowledge, trans fat label use, and dietary attitudes on intake of high trans fat food. Design: Cross-sectional survey. Setting: An urban commuter college. Subjects: Two hundred twenty-two college students. Variables…

  10. Preparing Elementary Pre-Service Teachers from a Non-Traditional Student Population to Teach with Technology

    ERIC Educational Resources Information Center

    An, Heejung; Wilder, Hilary; Lim, Keol

    2011-01-01

    This article documents the development of a two-stage curriculum intended to improve elementary teacher candidates' understanding of technology integration. Most students in the program came from low-income districts and lacked technology experience. The first stage of the curriculum consisted of a prerequisite basic technology skills course…

  11. 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…

  12. Junior Biology, Populations.

    ERIC Educational Resources Information Center

    Hamilton City Board of Education (Ontario).

    Twenty-one studies related to populations are included in this student manual for a junior high school biology course. Each activity or study provides questions, diagrams, experiments, and/or descriptive material to which the student must respond. Population studies pertain to individual plants and animals, their physical environments, reactions…

  13. 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…

  14. Vibrational resonance in a heterogeneous scale free network of neurons

    NASA Astrophysics Data System (ADS)

    Uzuntarla, Muhammet; Yilmaz, Ergin; Wagemakers, Alexandre; Ozer, Mahmut

    2015-05-01

    Vibrational resonance (VR) is a phenomenon whereby the response of some dynamical systems to a weak low-frequency signal can be maximized with the assistance of an optimal intensity of another high-frequency signal. In this paper, we study the VR in a heterogeneous neural system having a complex network topology. We consider a scale-free network of neurons where the heterogeneity is in the intrinsic excitability of the individual neurons. It is shown that emergence of VR in heterogeneous neuron population requires less energy than a homogeneous population. We also find that electrical coupling strength among neurons plays a key role in determining the weak signal processing capacity of the heterogeneous population. Lastly, we investigate the influence of interneuronal link density on the VR and demonstrate that the energy needed to obtain the resonance grows with the increase in average degree.

  15. An administrative concern: Science teachers' instructional efficacy beliefs regarding racially, culturally, economically, and linguistically diverse student populations

    NASA Astrophysics Data System (ADS)

    Tuck Bonner, Natalie Christine

    A teacher's sense of {instructional} efficacy has been considered a critical variable in student academic performance. Researchers Tschannen-Moran and Hoy Woolfolk (2001, p.783) defined teachers' {instructional} efficacy as a teacher's judgment of his or her capabilities to bring about desired outcomes of student engagement and learning, even among those students who may be difficult or unmotivated. There has been a substantial amount of research which reveals a strong correlation among teacher efficacy, teaching performance, and student achievement (Goddard & Goddard, et.al., 2000; Hackett; Hackett, 1995; Pajares, 1997 as cited in Villereal, 2005). This research study explored the content area of science and teacher's personal perception of their competency level in teaching science to all learners regardless of socio-economic, ethnicity/race or gender for grade levels Pre-K to 12. Lewthwaite states that a science teacher's personal teacher attributes or intrinsic factors such as science teaching self-efficacy, professional science knowledge, science teaching, instructional methodologies, interest in science, and motivation to teach science are critical dimensions and noted barriers in the delivery of science programs on elementary level campuses (Lewthwaite, Stableford & Fisher, 2001). This study focused on teacher instructional efficacy issues which may affect diverse learners' classroom and state-mandated assessment academic performance outcomes. A SPSS analysis of data was obtained from the following teacher survey instruments: The Bandura Teacher Efficacy Scale, the SEBEST, and the SETAKIST. Research findings revealed that a majority of science teachers surveyed believe they can effectively teach learners of diverse backgrounds, but responded with a sense of lower efficaciousness in teaching English Language Learners. There was also a statistically significant difference found between a state science organization and a national science organization's instructional efficacy beliefs in effectively teaching science content to females.

  16. A Statistical Portrait of the Multicultural/Multiethnic Student Population in Portland Public Schools. 1986-87.

    ERIC Educational Resources Information Center

    Portland Public Schools, OR. Research and Evaluation Dept.

    This second annual consolidated report of key statistics covers the status of culturally diverse children in the Portland (Oregon) School District during the 1986-87 school year. The district enrollment by ethnic group as of October 1, 1986, included 37,907 White, 7,913 Black, 3,881 Asian, 1,111 Hispanic, and 1,068 American Indian students, with a…

  17. Stability of Heterogeneous Ecosystem

    NASA Astrophysics Data System (ADS)

    Liu, Yang-Yu; Yan, Gang; Barabasi, Alber-Laszlo

    2014-03-01

    Stability of ecosystem measures the tendency of a community to return to equilibrium after environmental 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 ecosystems. Here we show that for networks with mixed interactions of competition and mutualism the degree heterogeneity always destabilizes the ecosystem. Surprisingly, for predator-prey interactions (e.g., food webs) high heterogeneity is destabilizing yet moderate heterogeneity is stabilizing. These findings deepen our understanding of the stability of real ecosystems and may also have implications in studying the stability of more general complex dynamical systems.

  18. Towards heterogeneous distributed debugging

    SciTech Connect

    Damodaran-Kamal, S.K.

    1995-04-01

    Several years of research and development in parallel debugger design have given up several techniques, though implemented in a wide range of tools for an equally wide range of systems. This paper is an evaluation of these myriad techniques as applied to the design of a heterogeneous distributed debugger. The evaluation is based on what features users perceive as useful, as well as the ease of implementation of the features using the available technology. A preliminary architecture for such a heterogeneous tool is proposed. Our effort in this paper is significantly different from the other efforts at creating portable and heterogeneous distributed debuggers in that we concentrate on support for all the important issues in parallel debugging, instead of simply concentrating on portability and heterogeneity.

  19. Heterogeneous atmospheric chemistry

    NASA Technical Reports Server (NTRS)

    Schryer, D. R.

    1982-01-01

    The present conference on heterogeneous atmospheric chemistry considers such topics concerning clusters, particles and microparticles as common problems in nucleation and growth, chemical kinetics, and catalysis, chemical reactions with aerosols, electron beam studies of natural and anthropogenic microparticles, and structural studies employing molecular beam techniques, as well as such gas-solid interaction topics as photoassisted reactions, catalyzed photolysis, and heterogeneous catalysis. Also discussed are sulfur dioxide absorption, oxidation, and oxidation inhibition in falling drops, sulfur dioxide/water equilibria, the evidence for heterogeneous catalysis in the atmosphere, the importance of heterogeneous processes to tropospheric chemistry, soot-catalyzed atmospheric reactions, and the concentrations and mechanisms of formation of sulfate in the atmospheric boundary layer.

  20. A stochastic model for tumor heterogeneity

    E-print Network

    Simone, Giuseppina

    2015-01-01

    Phenotype variations define heterogeneity of biological and molecular systems, which play a crucial role in several mechanisms. Heterogeneity has been demonstrated in tumor cells. Here, samples from blood of patients affected from colon tumor were analyzed and fished with a microfluidic assay based on galactose active moieties, and incubated, for culturing, in SCID mice. Following the experimental investigation, a model based on Markov theory was implemented and discussed to explain the equilibrium existing between phenotypes of subpopulations of cells sorted using the microfluidic assay. The model in combination with the experimental results had many implications for tumor heterogeneity. It displayed interconversion of phenotypes, as observed after experiments. The interconversion generates of metastatic cells and implies that targeting the CTCs will be not an efficient method to prevent tumor recurrence. Most importantly, understanding the transitions between cell phenotypes in cell population can boost the...

  1. Exploration of heterogeneity in distributed research network drug safety analyses.

    PubMed

    Hansen, Richard A; Zeng, Peng; Ryan, Patrick; Gao, Juan; Sonawane, Kalyani; Teeter, Benjamin; Westrich, Kimberly; Dubois, Robert W

    2014-12-01

    Distributed data networks representing large diverse populations are an expanding focus of drug safety research. However, interpreting results is difficult when treatment effect estimates vary across datasets (i.e., heterogeneity). In a previous study, risk estimates were generated for selected drugs and potential adverse outcomes. Analyses were replicated across eight distributed data sources using an identical analytic structure. To evaluate heterogeneity of risk estimates across data sources, the estimates were combined with summary-level data characterizing the population of each data source. Meta-analysis, meta-regression, and plots of the influence on overall results versus contribution to heterogeneity were examined and used to illustrate an approach to heterogeneity assessment. Heterogeneity, as measured by the I-squared statistic, was high with variability across outcomes. Plots of the relationship between influence on overall results and contribution to heterogeneity suggest that certain datasets and characteristics were influential but there was variability dependent on the drug and outcome being assessed. Exploratory meta-regression identified many possible influential factors, but may be subject to ecological bias and false positive conclusions. Distributed data network drug safety analyses can produce heterogeneous risk estimates that may not be easily explained. Approaches illustrated here can be useful for research that is subject to similar problems with heterogeneity. PMID:26052957

  2. 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…

  3. 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.

  4. 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...

  5. Heterogeneous conductorlike solvation model

    NASA Astrophysics Data System (ADS)

    Si, Dejun; Li, Hui

    2009-07-01

    A heterogeneous conductorlike solvation model (conductorlike screening model/conductorlike polarizable continuum model) that uses different local effective dielectrics for different portions of the solute cavity surface is implemented for quantum chemical Hartree-Fock and Kohn-Sham methods. A variational treatment is used to form the heterogeneous solvation operator, so a simple analytic expression of the energy gradients, which are vital for geometry optimization and molecular dynamics simulation, is derived and implemented. Using the new Fixed Points with Variable Areas surface tessellation scheme, continuous and smooth potential energy surfaces as well as analytic gradients are obtained for this heterogeneous model. Application of the heterogeneous solvation model to a realistic quantum model consisting of 101 atoms for the type-1 Cu center in rusticyanin shows that the desolvation due to protein burial can likely raise the reduction potential by ˜200 mV and, including the heterogeneity in geometry optimization, can likely affect the results by ˜2 kcal/mol or ˜70 mV.

  6. 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 (R²?=?.57) and patients (R²?=?.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

  7. Mathematical analysis of epidemiological models with heterogeneity

    SciTech Connect

    Van Ark, J.W.

    1992-01-01

    For many diseases in human populations the disease shows dissimilar characteristics in separate subgroups of the population; for example, the probability of disease transmission for gonorrhea or AIDS is much higher from male to female than from female to male. There is reason to construct and analyze epidemiological models which allow this heterogeneity of population, and to use these models to run computer simulations of the disease to predict the incidence and prevalence of the disease. In the models considered here the heterogeneous population is separated into subpopulations whose internal and external interactions are homogeneous in the sense that each person in the population can be assumed to have all average actions for the people of that subpopulation. The first model considered is an SIRS models; i.e., the Susceptible can become Infected, and if so he eventually Recovers with temporary immunity, and after a period of time becomes Susceptible again. Special cases allow for permanent immunity or other variations. This model is analyzed and threshold conditions are given which determine whether the disease dies out or persists. A deterministic model is presented; this model is constructed using difference equations, and it has been used in computer simulations for the AIDS epidemic in the homosexual population in San Francisco. The homogeneous version and the heterogeneous version of the differential-equations and difference-equations versions of the deterministic model are analyzed mathematically. In the analysis, equilibria are identified and threshold conditions are set forth for the disease to die out if the disease is below the threshold so that the disease-free equilibrium is globally asymptotically stable. Above the threshold the disease persists so that the disease-free equilibrium is unstable and there is a unique endemic equilibrium.

  8. Site occupancy models with heterogeneous detection probabilities

    USGS Publications Warehouse

    Royle, J. Andrew

    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.

  9. Managing Power Heterogeneity

    NASA Astrophysics Data System (ADS)

    Pruhs, Kirk

    A particularly important emergent technology is heterogeneous processors (or cores), which many computer architects believe will be the dominant architectural design in the future. The main advantage of a heterogeneous architecture, relative to an architecture of identical processors, is that it allows for the inclusion of processors whose design is specialized for particular types of jobs, and for jobs to be assigned to a processor best suited for that job. Most notably, it is envisioned that these heterogeneous architectures will consist of a small number of high-power high-performance processors for critical jobs, and a larger number of lower-power lower-performance processors for less critical jobs. Naturally, the lower-power processors would be more energy efficient in terms of the computation performed per unit of energy expended, and would generate less heat per unit of computation. For a given area and power budget, heterogeneous designs can give significantly better performance for standard workloads. Moreover, even processors that were designed to be homogeneous, are increasingly likely to be heterogeneous at run time: the dominant underlying cause is the increasing variability in the fabrication process as the feature size is scaled down (although run time faults will also play a role). Since manufacturing yields would be unacceptably low if every processor/core was required to be perfect, and since there would be significant performance loss from derating the entire chip to the functioning of the least functional processor (which is what would be required in order to attain processor homogeneity), some processor heterogeneity seems inevitable in chips with many processors/cores.

  10. Student Health Services Division of Student Affairs

    E-print Network

    Missouri-Rolla, University of

    quality medical care for the student population on the Missouri S&T campus. Promoting a healthy student of Electronic Health Records · Revised focus on customer service with collection of student satisfaction data the Division and the University. · 14,000 student visits in 2011 · Most recent satisfaction results: · 92

  11. Individual heterogeneity in life histories and eco-evolutionary dynamics

    PubMed Central

    Vindenes, Yngvild; Langangen, Øystein

    2015-01-01

    Individual heterogeneity in life history shapes eco-evolutionary processes, and unobserved heterogeneity can affect demographic outputs characterising life history and population dynamical properties. Demographic frameworks like matrix models or integral projection models represent powerful approaches to disentangle mechanisms linking individual life histories and population-level processes. Recent developments have provided important steps towards their application to study eco-evolutionary dynamics, but so far individual heterogeneity has largely been ignored. Here, we present a general demographic framework that incorporates individual heterogeneity in a flexible way, by separating static and dynamic traits (discrete or continuous). First, we apply the framework to derive the consequences of ignoring heterogeneity for a range of widely used demographic outputs. A general conclusion is that besides the long-term growth rate lambda, all parameters can be affected. Second, we discuss how the framework can help advance current demographic models of eco-evolutionary dynamics, by incorporating individual heterogeneity. For both applications numerical examples are provided, including an empirical example for pike. For instance, we demonstrate that predicted demographic responses to climate warming can be reversed by increased heritability. We discuss how applications of this demographic framework incorporating individual heterogeneity can help answer key biological questions that require a detailed understanding of eco-evolutionary dynamics. PMID:25807980

  12. Astrocyte heterogeneity in the brain: from development to disease

    PubMed Central

    Schitine, Clarissa; Nogaroli, Luciana; Costa, Marcos R.; Hedin-Pereira, Cecilia

    2015-01-01

    In the last decades, astrocytes have risen from passive supporters of neuronal activity to central players in brain function and cognition. Likewise, the heterogeneity of astrocytes starts to become recognized in contrast to the homogeneous population previously predicted. In this review, we focused on astrocyte heterogeneity in terms of their morphological, protein expression and functional aspects, and debate in a historical perspective the diversity encountered in glial progenitors and how they may reflect mature astrocyte heterogeneity. We discussed data that show that different progenitors may have unsuspected roles in developmental processes. We have approached the functions of astrocyte subpopulations on the onset of psychiatric and neurological diseases. PMID:25852472

  13. Population Issues. Resources in Technology.

    ERIC Educational Resources Information Center

    Technology Teacher, 1991

    1991-01-01

    Presents information about the problems caused by increasing population. Discusses the environmental impact and the ways that technology can be used to solve problems of overpopulation. Includes possible student outcomes and a student quiz. (JOW)

  14. HETEROGENEOUS MODELING AND

    E-print Network

    California at Berkeley, University of

    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

  15. -PTOLEMY II -HETEROGENEOUS CONCURRENT

    E-print Network

    California at Berkeley, University of

    -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

  16. HETEROGENEOUS MODELING AND

    E-print Network

    California at Berkeley, University of

    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

  17. -PTOLEMY II -HETEROGENEOUS CONCURRENT

    E-print Network

    California at Berkeley, University of

    -PTOLEMY II - HETEROGENEOUS CONCURRENT MODELING AND DESIGN IN JAVA John Davis, II Christopher of Electrical Engineering and Computer Sciences University of California at Berkeley http://ptolemy with Ptolemy II 1.0 March 15, 2001 This project is supported by the Defense Advanced Research Projects Agency

  18. HETEROGENEOUS MODELING AND

    E-print Network

    California at Berkeley, University of

    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

  19. Heterogeneous waste processing

    DOEpatents

    Vanderberg, Laura A. (Los Alamos, NM); Sauer, Nancy N. (Los Alamos, NM); Brainard, James R. (Los Alamos, NM); Foreman, Trudi M. (Los Alamos, NM); Hanners, John L. (Los Alamos, NM)

    2000-01-01

    A combination of treatment methods are provided for treatment of heterogeneous waste including: (1) treatment for any organic compounds present; (2) removal of metals from the waste; and, (3) bulk volume reduction, with at least two of the three treatment methods employed and all three treatment methods emplyed where suitable.

  20. Scales of mantle heterogeneity

    NASA Astrophysics Data System (ADS)

    Moore, J. C.; Akber-Knutson, S.; Konter, J.; Kellogg, J.; Hart, S.; Kellogg, L. H.; Romanowicz, B.

    2004-12-01

    A long-standing question in mantle dynamics concerns the scale of heterogeneity in the mantle. Mantle convection tends to both destroy (through stirring) and create (through melt extraction and subduction) heterogeneity in bulk and trace element composition. Over time, these competing processes create variations in geochemical composition along mid-oceanic ridges and among oceanic islands, spanning a range of scales from extremely long wavelength (for example, the DUPAL anomaly) to very small scale (for example, variations amongst melt inclusions). While geochemical data and seismic observations can be used to constrain the length scales of mantle heterogeneity, dynamical mixing calculations can illustrate the processes and timescales involved in stirring and mixing. At the Summer 2004 CIDER workshop on Relating Geochemical and Seismological Heterogeneity in the Earth's Mantle, an interdisciplinary group evaluated scales of heterogeneity in the Earth's mantle using a combined analysis of geochemical data, seismological data and results of numerical models of mixing. We mined the PetDB database for isotopic data from glass and whole rock analyses for the Mid-Atlantic Ridge (MAR) and the East Pacific Rise (EPR), projecting them along the ridge length. We examined Sr isotope variability along the East Pacific rise by looking at the difference in Sr ratio between adjacent samples as a function of distance between the samples. The East Pacific Rise exhibits an overall bowl shape of normal MORB characteristics, with higher values in the higher latitudes (there is, however, an unfortunate gap in sampling, roughly 2000 km long). These background characteristics are punctuated with spikes in values at various locations, some, but not all of which are associated with off-axis volcanism. A Lomb-Scargle periodogram for unevenly spaced data was utilized to construct a power spectrum of the scale lengths of heterogeneity along both ridges. Using the same isotopic systems (Sr, Nd and Pb), we correlated isotopic data from oceanic islands and seamounts with geophysical measurements and observations in order to determine whether the mantle source component end-members are related to geophysical structure. For this, data obtained from the GeoROC database and other sources were first carefully examined for consistency and then correlated with recent global upper mantle tomographic models of seismic attenuation and velocity structure. Complementing this approach is a fractal analysis of dynamical models of mantle mixing. A variety of published numerical mixing models show a fractal distribution of heterogeneities, consistent with a marble-cake mantle.

  1. Towards inverse modeling of intratumor heterogeneity

    NASA Astrophysics Data System (ADS)

    Brutovsky, Branislav; Horvath, Denis

    2015-08-01

    Development of resistance limits efficiency of present anticancer therapies and preventing it remains a big challenge in cancer research. It is accepted, at the intuitive level, that resistance emerges as a consequence of the heterogeneity of cancer cells at the molecular, genetic and cellular levels. Produced by many sources, tumor heterogeneity is extremely complex time dependent statistical characteristics which may be quantified by measures defined in many different ways, most of them coming from statistical mechanics. In this paper, we apply the Markovian framework to relate population heterogeneity to the statistics of the environment. As, from an evolutionary viewpoint, therapy corresponds to a purposeful modi- fication of the cells' fitness landscape, we assume that understanding general relationship between the spatiotemporal statistics of a tumor microenvironment and intratumor heterogeneity will allow to conceive the therapy as an inverse problem and to solve it by optimization techniques. To account for the inherent stochasticity of biological processes at cellular scale, the generalized distancebased concept was applied to express distances between probabilistically described cell states and environmental conditions, respectively.

  2. -PTOLEMY II -HETEROGENEOUS

    E-print Network

    California at Berkeley, University of

    -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

  3. PTOLEMY II HETEROGENEOUS

    E-print Network

    California at Berkeley, University of

    ­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

  4. Phenotypic Heterogeneity in Mycobacterial Stringent Response

    E-print Network

    Sayantari Ghosh; Kamakshi Sureka; Bhaswar Ghosh; Indrani Bose; Joyoti Basu; Manikuntala Kundu

    2011-02-03

    A common survival strategy of microorganisms subjected to stress involves the generation of phenotypic heterogeneity in the isogenic microbial population enabling a subset of the population to survive under stress. In a recent study, a mycobacterial population of M. smegmatis was shown to develop phenotypic heterogeneity under nutrient depletion. The observed heterogeneity is in the form of a bimodal distribution of the expression levels of the Green Fluorescent Protein (GFP) as reporter with the gfp fused to the promoter of the rel gene. The stringent response pathway is initiated in the subpopulation with high rel activity.In the present study, we characterize quantitatively the single cell promoter activity of the three key genes, namely, mprA, sigE and rel, in the stringent response pathway with gfp as the reporter. The origin of bimodality in the GFP distribution lies in two stable expression states, i.e., bistability. We develop a theoretical model to study the dynamics of the stringent response pathway. The model incorporates a recently proposed mechanism of bistability based on positive feedback and cell growth retardation due to protein synthesis. Based on flow cytometry data, we establish that the distribution of GFP levels in the mycobacterial population at any point of time is a linear superposition of two invariant distributions, one Gaussian and the other lognormal, with only the coefficients in the linear combination depending on time. This allows us to use a binning algorithm and determine the time variation of the mean protein level, the fraction of cells in a subpopulation and also the coefficient of variation, a measure of gene expression noise.The results of the theoretical model along with a comprehensive analysis of the flow cytometry data provide definitive evidence for the coexistence of two subpopulations with overlapping protein distributions.

  5. Heterogeneities in granular dynamics.

    PubMed

    Mehta, A; Barker, G C; Luck, J M

    2008-06-17

    The absence of Brownian motion in granular media is a source of much complexity, including the prevalence of heterogeneity, whether static or dynamic, within a given system. Such strong heterogeneities can exist as a function of depth in a box of grains; this is the system we study here. First, we present results from three-dimensional, cooperative and stochastic Monte Carlo shaking simulations of spheres on heterogeneous density fluctuations. Next, we juxtapose these with results obtained from a theoretical model of a column of grains under gravity; frustration via competing local fields is included in our model, whereas the effect of gravity is to slow down the dynamics of successively deeper layers. The combined conclusions suggest that the dynamics of a real granular column can be divided into different phases-ballistic, logarithmic, activated, and glassy-as a function of depth. The nature of the ground states and their retrieval (under zero-temperature dynamics) is analyzed; the glassy phase shows clear evidence of its intrinsic ("crystalline") states, which lie below a band of approximately degenerate ground states. In the other three phases, by contrast, the system jams into a state chosen randomly from this upper band of metastable states. PMID:18541918

  6. A Student Profile.

    ERIC Educational Resources Information Center

    Maine Univ., Augusta.

    A survey of graduates and students from the University of Maine at Augusta (UMA) was conducted in Spring 1980 to provide a profile of new and continuing students and to assess the vocational success of recent UMA graduates. The survey sample included: (1) 461 students selected from the entire UMA population; (2) 49 students enrolled in UMA's…

  7. From Single-Cell Genetic Architecture to Cell Population Dynamics: Quantitatively Decomposing the Effects of Different Population

    E-print Network

    Bernard, Samuel

    From Single-Cell Genetic Architecture to Cell Population Dynamics: Quantitatively Decomposing, Texas ABSTRACT Phenotypic cell-to-cell variability or cell population heterogeneity originates from two fundamentally different sources: unequal partitioning of cellular material at cell division and stochastic

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

    NASA Astrophysics Data System (ADS)

    Yang, Hui; Tang, Ming; Gross, Thilo

    2015-08-01

    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 network heterogeneity, i.e. a broad degree distribution, 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. However, it has been pointed out that networks in which the properties of nodes are intrinsically heterogeneous can be very resilient to disease spreading. Heterogeneity in structure can enhance or diminish the resilience of networks with heterogeneous nodes, depending on the correlations between the topological and intrinsic properties. Here, we consider a plausible scenario where people have intrinsic differences in susceptibility and adapt their social network structure to the presence of the disease. We show that the resilience of networks with heterogeneous connectivity can surpass those of networks with homogeneous connectivity. For epidemiology, this implies that network heterogeneity should not be studied in isolation, it is instead the heterogeneity of infection risk that determines the likelihood of outbreaks.

  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. Is the universal scaling for the dilemma strength still available in populations with heterogeneous connectivity or activities?. Comment on "Universal scaling for the dilemma strength in evolutionary games" by Z. Wang et al.

    NASA Astrophysics Data System (ADS)

    Xia, Cheng-Yi; Wang, Lin

    2015-09-01

    The emergence and maintenance of cooperative behavior are widely observed in various realistic systems, such as cellular organisms, vertebrates, and human society [1]. Understanding the ubiquity of cooperation is a challenging problem, attracting great interest from diverse communities. The development of evolutionary game theory contributes to valuable tools for studying the origin of cooperative behavior and solving related social dilemmas [2]. Five key reciprocal mechanisms to promote the cooperation, including direct reciprocity, indirect reciprocity, network reciprocity, group selection, and kin selection, have been identified [3], inspiring much effort in exploring the effects of game dynamics and population's connectivity structure on the patterns of cooperation. Most of current works generate conclusions by focusing on specific game models or mechanisms, which imply the probable existence of some effective and universal laws.

  11. Emergent heterogeneity in declining tuberculosis epidemics

    PubMed Central

    Colijn, Caroline; Cohen, Ted; Murray, Megan

    2009-01-01

    Tuberculosis is a disease of global importance: over 2 million deaths are attributed to this infectious disease each year. Even in areas where tuberculosis is in decline, there are sporadic outbreaks which are often attributed either to increased host susceptibility or increased strain transmissibility and virulence. Using two mathematical models, we explore the role of the contact structure of the population, and find that in declining epidemics, localized outbreaks may occur as a result of contact heterogeneity even in the absence of host or strain variability. We discuss the implications of this finding for tuberculosis control in low incidence settings. PMID:17540410

  12. Interconnecting heterogeneous database management systems

    NASA Technical Reports Server (NTRS)

    Gligor, V. D.; Luckenbaugh, G. L.

    1984-01-01

    It is pointed out that there is still a great need for the development of improved communication between remote, heterogeneous database management systems (DBMS). Problems regarding the effective communication between distributed DBMSs are primarily related to significant differences between local data managers, local data models and representations, and local transaction managers. A system of interconnected DBMSs which exhibit such differences is called a network of distributed, heterogeneous DBMSs. In order to achieve effective interconnection of remote, heterogeneous DBMSs, the users must have uniform, integrated access to the different DBMs. The present investigation is mainly concerned with an analysis of the existing approaches to interconnecting heterogeneous DBMSs, taking into account four experimental DBMS projects.

  13. Micronesica 39(2): 297-314, 2007 Habitat Heterogeneity of Cycas micronesica Seed Chemistry

    E-print Network

    Marler, Thomas E.

    was determined in seven populations throughout Guam to determine if steryl glucosides would segregate among the heterogeneity. Seed gameto- phyte content of steryl glucosides stigmasterol -D-glucoside and sitosterol -D

  14. 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 ...

  15. 307Department of Epidemiology and Population Health Department of

    E-print Network

    307Department of Epidemiology and Population Health Department of Epidemiology and Population H. Research Associate: Tohme, Rania A. The Department of Epidemiology and Population Health offers courses in epidemiology, biostatistics, and population health to graduate students in the Faculty

  16. Distinct population structure for co-occurring Anopheles goeldii and Anopheles triannulatus in Amazonian Brazil

    PubMed Central

    McKeon, Sascha Naomi; Moreno, Marta; Sallum, Maria Anise; Povoa, Marinete Marins; Conn, Jan Evelyn

    2013-01-01

    To evaluate whether environmental heterogeneity contributes to the genetic heterogeneity in Anopheles triannulatus, larval habitat characteristics across the Brazilian states of Roraima and Pará and genetic sequences were examined. A comparison with Anopheles goeldii was utilised to determine whether high genetic diversity was unique to An. triannulatus. Student t test and analysis of variance found no differences in habitat characteristics between the species. Analysis of population structure of An. triannulatus and An. goeldii revealed distinct demographic histories in a largely overlapping geographic range. Cytochrome oxidase I sequence parsimony networks found geographic clustering for both species; however nuclear marker networks depicted An. triannulatus with a more complex history of fragmentation, secondary contact and recent divergence. Evidence of Pleistocene expansions suggests both species are more likely to be genetically structured by geographic and ecological barriers than demography. We hypothesise that niche partitioning is a driving force for diversity, particularly in An. triannulatus. PMID:23903977

  17. 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

  18. Query Expansion Using Heterogeneous Thesauri.

    ERIC Educational Resources Information Center

    Mandala, Rila; Tokunaga, Takenobu; Tanaka, Hozumi

    2000-01-01

    Proposes a method to improve the performance of information retrieval systems by expanding queries using heterogeneous thesauri. Experiments show that using heterogeneous thesauri with an appropriate weighting method results in better retrieval performance than using only one type of thesaurus. (Author/LRW)

  19. Spatial heterogeneity lowers rather than increases host-parasite specialization.

    PubMed

    Hesse, E; Best, A; Boots, M; Hall, A R; Buckling, A

    2015-09-01

    Abiotic environmental heterogeneity can promote the evolution of diverse resource specialists, which in turn may increase the degree of host-parasite specialization. We coevolved Pseudomonas fluorescens and lytic phage ?2 in spatially structured populations, each consisting of two interconnected subpopulations evolving in the same or different nutrient media (homogeneous and heterogeneous environments, respectively). Counter to the normal expectation, host-parasite specialization was significantly lower in heterogeneous compared with homogeneous environments. This result could not be explained by dispersal homogenizing populations, as this would have resulted in the heterogeneous treatments having levels of specialization equal to or greater than that of the homogeneous environments. We argue that selection for costly generalists is greatest when the coevolving species are exposed to diverse environmental conditions and that this can provide an explanation for our results. A simple coevolutionary model of this process suggests that this can be a general mechanism by which environmental heterogeneity can reduce rather than increase host-parasite specialization. PMID:26135011

  20. Functional heterogeneity at dopamine release sites

    PubMed Central

    Daniel, James A.; Galbraith, Sally; Iacovitti, Lorraine; Abdipranoto, Andrea; Vissel, Bryce

    2010-01-01

    Although drugs used to treat several neurological diseases are presumed to target synapses that secrete dopamine (DA), relatively little is known about synaptic vesicle (SV) release mechanisms at single DA synapses. We found that the relative probability of release (Pr) varied between individual DA synapses. Furthermore, DA terminals generally exhibited lower Pr than glutamatergic hippocampal (Hpc) terminals, suggesting that DA release is less reliable than the release of glutamate. Our mathematical model of fluorescence loss shows that Pr is regulated by two independent and heterogeneous elements. Firstly, the size of the recycling SV pool regulates Pr. Secondly, Pr is also independently regulated by additional factors, which are reflected in the time constant of FM 1-43 destaining, ?. We found that the observed difference in Pr between Hpc and DA neurons results because the recycling SV pool is smaller in DA neurons than in Hpc neurons. However, ? does not vary between these two neuron populations. We also identified a population of functional non-synaptic boutons in DA axons, which are not associated with a postsynaptic element and which are not functionally different to boutons that formed conventional synapses. Our work provides a new approach to the study of SV exocytosis in DA neurons and shows that synaptic terminals of DA neurons are functionally heterogeneous and differ from excitatory terminals in mechanisms that regulate Pr. PMID:19923300

  1. The U.S. Homeless Student Population: Homeless Youth Education, Review of Research Classifications and Typologies, and the U.S. Federal Legislative Response

    ERIC Educational Resources Information Center

    Rahman, Mai Abdul; Turner, J. Fidel; Elbedour, Salman

    2015-01-01

    Background: The drastic surge in the number of homeless families in the United States (U.S.) has resulted in an increase in the number of homeless students attending U.S. public schools. Meanwhile, the U.S. public school system is struggling to meet the educational needs of their homeless students. Objective: This study examined the historical…

  2. Immunization Against Infection Propagation In Heterogeneous Networks

    E-print Network

    Koutsoukos, Xenofon D.

    Immunization Against Infection Propagation In Heterogeneous Networks Waseem Abbas, Sajal Bhatia to the effects such node heterogeneity might have in the overall infection (or immunization) process propa- gation, heterogeneous networks, immunization I. INTRODUCTION Infection propagation models have

  3. From science to humanities, ethics to medicine, we are partners in a world where collaboration is imperative to solve the world's issues and meet the needs of a diverse and multi-faceted student population. Our aim is to prepare leaders of change and prom

    E-print Network

    Matrajt, Graciela

    is imperative to solve the world's issues and meet the needs of a diverse and multi-faceted student populationFrom science to humanities, ethics to medicine, we are partners in a world where collaboration

  4. Heterogeneous mitochondrial DNA D-loop sequences in bovine tissue.

    PubMed

    Hauswirth, W W; Van de Walle, M J; Laipis, P J; Olivo, P D

    1984-07-01

    Mitochondrial DNA from bovine tissue contains heterogeneous sequences located within an evolutionary conserved cytosine homopolymer sequence near the 5' end of the D-loop region. This part of the mammalian mitochondrial genome is known to contain the origin of heavy strand DNA synthesis and the major transcriptional promoter for each strand. Nucleotide sequence analysis of cloned DNA and electrophoretic analysis of appropriate small fragments from animal tissue reveal a population of length polymorphs containing from nine to 19 cytosine residues. No individual length species represents more than 40% of the population. These data imply a state of significant intraanimal mtDNA sequence heterogeneity, which most likely occurs intracellularly as well. The localization of variability to a homopolymer run suggests that replication slip-page generated the sequence population. We also report that when recombinant clones containing this region are repeatedly passaged in E. coli, they begin to regenerate length variation similar to that seen in animal mtDNA. PMID:6744410

  5. When High Achievers and Low Achievers Work in the Same Group: The Roles of Group Heterogeneity and Processes in Project-Based Learning

    ERIC Educational Resources Information Center

    Wing-Yi Cheng, Rebecca; Lam, Shui-Fong; Chung-Yan Chan, Joanne

    2008-01-01

    Background: There has been an ongoing debate about the inconsistent effects of heterogeneous ability grouping on students in small group work such as project-based learning. Aim: The present research investigated the roles of group heterogeneity and processes in project-based learning. At the student level, we examined the interaction effect…

  6. Exploring the Complexities of Experimental Design: Using an On-line Reaction Time Program as a Teaching Tool for Diverse Student Populations

    PubMed Central

    Pollack, Alexia E.

    2010-01-01

    Students are rarely given an opportunity to think deeply about experimental design or asked to develop experimental protocols on their own. Without participating in these endeavors, they are often unaware of the many decisions necessary to construct a precise methodology. This article describes an on-line reaction time program, and how I have used this program as a teaching tool for students to explore experimental design. This approach can be tailored to meet the level of any undergraduate student – from non-science majors to upper-level biology/psychology/neuroscience majors, affording all students the opportunity to think like a scientist. Described is how I use the reaction time program for a whole class demonstration and discussion, as well as, how it can be used for a written assignment in which each student designs and conducts his/her own experiment outside of the classroom. Comments from several students, who did the written assignment, are included to provide a sense of their thoughts and considerations. When students are given a simple method, such as the measurement of reaction time, it allows them to focus exclusively on developing precise methodology, which taps into types of thinking that they are not often asked to exhibit in other science classes. PMID:23494764

  7. Theory of heterogeneous viscoelasticity

    E-print Network

    Walter Schirmacher; Giancarlo Ruocco; Valerio Mazzone

    2015-10-20

    We review a new theory of viscoelasticity of a glass-forming viscous liquid near and below the glass transition. In our model we assume that each point in the material has a specific viscosity, which varies randomly in space according to a fluctuating activation free energy. We include a Maxwellian elastic term and assume that the corresponding shear modulus fluctuates as well with the same distribution as that of the activation barriers. The model is solved in coherent-potential approximation (CPA), for which a derivation is given. The theory predicts an Arrhenius-type temperature dependence of the viscosity in the vanishing-frequency limit, independent of the distribution of the activation barriers. The theory implies that this activation energy is generally different from that of a diffusing particle with the same barrier-height distribution. If the distribution of activation barriers is assumed to have Gaussian form, the finite-frequency version of the theory describes well the typical low-temperature alpha relaxation peak of glasses. Beta relaxation can be included by adding another Gaussian with center at much lower energies than that responsible for the alpha relaxation. At high frequencies our theory reduces to the description of an elastic medium with spatially fluctuating elastic moduli (heterogeneous elasticity theory), which explains the occurrence of the boson-peak-related vibrational anomalies of glasses.

  8. 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. )

    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.

  9. Inconsistencies in DIF Detection for Sub-Groups in Heterogeneous Language Groups

    ERIC Educational Resources Information Center

    Ercikan, Kadriye; Roth, Wolff-Michael; Simon, Marielle; Sandilands, Debra; Lyons-Thomas, Juliette

    2014-01-01

    Diversity and heterogeneity among language groups have been well documented. Yet most fairness research that focuses on measurement comparability considers linguistic minority students such as English language learners (ELLs) or Francophone students living in minority contexts in Canada as a single group. Our focus in this research is to examine…

  10. A Comparison of Written Chinese Achievement among Heritage Learners in Homogeneous and Heterogeneous Groups.

    ERIC Educational Resources Information Center

    Shen, Helen H.

    2003-01-01

    Examines effects of grouping practice on written Chinese achievement among heritage learners in college Chinese classes. Subjects were two groups of heritage students, a homogeneous group and a heterogeneous group. Results suggest in college level Chinese language classes, tracking based on linguistic background can improve heritage students'…

  11. 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.

  12. Heterogeneity of human platelets

    PubMed Central

    Karpatkin, Simon; Strick, Nathan

    1972-01-01

    Human platelets were separated by desity-centrifugation into heavy and light populations. Heavy platelets have an average volume approximately twofold greater than light platelets, and have previously been shown to be young platelets. All 11 enzymes of the Embden-Meyerhof pathway plus the five related enzymes: phosphoglucomutase, glucose-6-P dehydrogenase, 6-P-gluconic dehydrogenase, ?-glycerol-P dehydrogenase, and glutathione reductase (TPNH) were examined in cell lysates from total, heavy, and light platelet populations. Apparent Km for individual enzymes were measured in a total platelet population. Empirical Vmax of the individual enzymes were measured in total, heavy, and light platelet populations. The three apparent rate-limiting enzymes for glycolysis were hexokinase, phosphofructokinase, and glyceraldehyde-3-P dehydrogenase. Heavy platelets contained approximately twofold greater enzyme activity (per gram wet weight) than light platelets for 7 of the 16 enzymes measured: hexokinase, phosphohexoisomerase, phosphofructokinase, glyceraldehyde-3-P dehydrogenase, phosphoglycerokinase, lactic dehydrogenase, and phosphoglucomutase. Heavy platelets also contained 1.9-fold greater reduced glutathione (GSH), 1.7-fold greater DPNH, and 1.2-fold greater TPNH than light platelets. Heavy platelets contained 1.8-fold less lipid peroxidation products (malonyl aldehyde equivalents) than light platelets and were 2.4-fold more resistant to lipid peroxidation catalyzed by 0.1 mM FeCl3. Sterile incubation of heavy platelets, in vitro for 17 hr, resulted in a significant loss of enzyme activity for the “elevated” seven enzymes when compared with the remainder. Reducing agents such as GSH (0.1 mM), ascorbic acid (0.1 mM), and dithiothreitol (0.01 mM), when added to the incubation mixture, significantly reduced the in vitro loss of activity. In vitro incubation was also associated with a significant loss of GSH and DPNH and a 1.8-fold increase in lipid peroxidation products. PMID:4262550

  13. 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,…

  14. Population Issues & Policies Population Issues

    E-print Network

    Huang, Youqin

    ? How? Is population growth detrimental to economic development? Does population growth lead to environmental degradation? Figure 3.1 The basic (and wrong) Malthusian ideas about the growth of population1 Unit 6: Population Issues & Policies Population Issues Can we feed the growing world population

  15. 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...

  16. Attitudes of Black and of White College Students Toward Student Personnel Services

    ERIC Educational Resources Information Center

    Amprey, Joseph L. Jr.; Gilbert, Arthur C. F.

    1977-01-01

    The purpose of this study was to compare the attitudes of black students with those of white students on predominantly white student populated campuses and on predominantly black student populated campuses to determine if on either type of campus the attitudes of the majority element of the student body was more favorable. (Author/AM)

  17. Fault heterogeneity and earthquake scaling

    NASA Astrophysics Data System (ADS)

    Hetherington, Alison; Steacy, Sandy

    2007-08-01

    There is an on-going debate in the seismological community as to whether stress drop is independent of earthquake size and this has important implications for earthquake physics. Here we investigate this question in a simple 2D cellular automaton that includes heterogeneity. We find that when the range of heterogeneity is low, the scaling approaches that of constant stress drop. However, clear deviations from the constant stress drop model are observed when the range of heterogeneity is large. Further, fractal distributions of strength show more significant departures from constant scaling than do random ones. Additionally, sub-sampling the data over limited magnitude ranges can give the appearance of constant stress drop even when the entire data set does not support this. Our results suggest that deviations from constant earthquake scaling are real and reflect the heterogeneity of natural fault zones, but may not provide much information about the physics of earthquakes.

  18. Tomographic Characterization of Aquifer Heterogeneity

    E-print Network

    Lyle, Shane

    2011-05-31

    The Darcy's Law proportionality constant, hydraulic conductivity, describes the relative ease or rate at which water can move through a permeable medium and its fine-scale heterogeneity determines preferential flow rates and pathways. Traditional...

  19. 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)

  20. 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.

  1. Population education resources.

    PubMed

    Larkin, R P; Peters, G L

    1981-01-01

    This article provides information on those population education materials and services which are available from the Population Reference Bureau (PRB) and explores their usefulness in secondary school and college environments. PRB data sheets are a most useful source of information. Demographic and socioeconomic information (birth and death rates, natural increase, population doubling times, projections for the year 2000, life expectancies, per capita gross national product, etc.) are included. The World's Women Data Sheet is a special publication issued to mark the midway point of the UN Decade for Women. 161 countries are included with information on demographic, health, employment, and educational status of women. There is a nominal cost for these data sheets. To help students learn about population dynamics and world patterns of population, mapping exercises can be developed. The Population Bulletin is published 6 times/year and each issue concentrates on specific aspects of population. The 28 bulletins which have been published since January 1976 are listed. The PRB Chart Series is a multicolor graphic presentation of topical issues in population and development trends worldwide. A total of 26 charts in 4 series have been produced and cover such topics as world population growth, urbanization, world energy consumption, age structure in the U.S., and adolescent pregnancy in the U.S. This material is best used with high school students. A monthly international population news magazine called Intercom is desinged to inform about worldwide trends and activities in population and family planning. It is published in both English and Spanish and is a useful source of current information in capsulized form. For population educators there is the bimonthly newsletter Interchange. PRB's teaching-learning modules are valuable publications for teachers. Thus far there are 9, each of which is a self-contained unit with classroom activities for junior high to college students. Each one outlines a problem and then presents methods which can stimulate discussion and provoke interest. 2 special publications on special interest topics (Population Handbook; Population Education: Sources and Resources) are described. PRB may well be the best single source of population education materials which will hopefully be used and incorporated into teaching. PMID:12178557

  2. Heterogeneity in motor driven transport

    NASA Astrophysics Data System (ADS)

    Tabei, Ali

    2015-03-01

    I will discuss quantitative analysis of particle tracking data for motor driven vesicles inside an insulin secreting cell. We use this method to study the dynamical and structural heterogeneity inside the cell. I will discuss our effort to explain the origin of observed heterogeneity in intracellular transport. Finally, I will explain how analyzing directional correlations in transport trajectories reveals self-similarity in the diffusion media.

  3. Nuclear heterogeneity in conidial populations of Aspergillus flavus

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Aspergillus flavus is a major producer of aflatoxin and an opportunistic pathogen for a wide range of hosts. Understanding genotypic and phenotypic variations within strains of A. flavus is important for controlling disease and reducing aflatoxin contamination. A. flavus is multinucleate and predomi...

  4. Spreading dynamics on heterogeneous populations: Multitype network approach Alexei Vazquez

    E-print Network

    Vazquez, Alexei

    for the probability distribution of the outbreak size as a function of time. I demonstrate that the expected outbreak matrix and the characteristic distance between agents on the contact graph. Finally, I discuss the impact The globalization of human interactions has created a fer- tile ground for the fast and broad spread of infectious

  5. 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 ...

  6. 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

  7. 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…

  8. 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

  9. Heterogeneous Oxidation of Catechol.

    PubMed

    Pillar, Elizabeth A; Zhou, Ruixin; Guzman, Marcelo I

    2015-10-15

    Natural and anthropogenic emissions of aromatic hydrocarbons from biomass burning, agro-industrial settings, and fossil fuel combustion contribute precursors to secondary aerosol formation (SOA). How these compounds are processed under humid tropospheric conditions is the focus of current attention to understand their environmental fate. This work shows how catechol thin films, a model for oxygenated aromatic hydrocarbons present in biomass burning and combustion aerosols, undergo heterogeneous oxidation at the air-solid interface under variable relative humidity (RH = 0-90%). The maximum reactive uptake coefficient of O3(g) by catechol ?O3 = (7.49 ± 0.35) × 10(-6) occurs for 90% RH. Upon exposure of ca. 104-?m thick catechol films to O3(g) mixing ratios between 230 ppbv and 25 ppmv, three main reaction pathways are observed. (1) The cleavage of the 1,2 carbon-carbon bond at the air-solid interface resulting in the formation of cis,cis-muconic acid via primary ozonide and hydroperoxide intermediates. Further direct ozonolysis of cis,cis-muconic yields glyoxylic, oxalic, crotonic, and maleic acids. (2) A second pathway is evidenced by the presence of Baeyer-Villiger oxidation products including glutaconic 4-hydroxy-2-butenoic and 5-oxo-2-pentenoic acids during electrospray ionization mass spectrometry (MS) and ion chromatography MS analyses. (3) Finally, indirect oxidation by in situ produced hydroxyl radical (HO(•)) results in the generation of semiquinone radical intermediates toward the synthesis of polyhydoxylated aromatic rings such as tri-, tetra-, and penta-hydroxybenzene. Remarkably, heavier polyhydroxylated biphenyl and terphenyl products present in the extracted oxidized films result from coupling reactions of semiquinones of catechol and its polyhydroxylated rings. The direct ozonolysis of 1,2,3- and 1,2,4-trihydroxybenezene yields 2- and 3-hydroxy-cis,cis-muconic acid, respectively. The production of 2,4- or 3,4-dihdroxyhex-2-enedioic acid is proposed to result from the sequential processing of cis,cis-muconic acid, 2- and 3-hydroxy-cis,cis-muconic acid. Overall, these reactions contribute precursors to form aqueous SOA from aromatics in atmospheric aerosols and brown clouds. PMID:26403273

  10. Population and Development Issues.

    ERIC Educational Resources Information Center

    Cohen, Sharon; Garran, Christopher

    1998-01-01

    Describes a unit on demographics for a high school world-history course that addresses questions of uneven population growth and the "problem of global overpopulation." Provides a detailed outline of the two-day unit including unit and daily goals and objectives, daily activities and questions, and ideas for further student research. (DSK)

  11. Population Workbook: A Series of Learning Exercises in Population Studies for Undergraduates.

    ERIC Educational Resources Information Center

    Lawrence Univ., Appleton, WI. Dept. of Sociology.

    This series of population exercises for undergraduate use aims at bringing the student to the realization that he is a population actor and that his attitudes, values, and behavior are the raw material of population analysis. The following exercises engage the student by personal involvement and by case study approach in the use of demographic…

  12. Population Geography: Problems, Concepts, and Prospects.

    ERIC Educational Resources Information Center

    Peters, Gary L.; Larkin, Robert P.

    This book introduces secondary students to population geography. Material from other disciplines is included because the study of population is multidisciplinary. It is presented in eleven chapters. The introduction considers definitions of concepts and aspects of population geography, explaining the emphasis on spatial patterns of population

  13. 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

  14. Optimal Control of Heterogeneous Systems with Endogenous Domain of Heterogeneity

    SciTech Connect

    Belyakov, Anton O.; Tsachev, Tsvetomir; Veliov, Vladimir M.

    2011-10-15

    The paper deals with optimal control of heterogeneous systems, that is, families of controlled ODEs parameterized by a parameter running over a domain called domain of heterogeneity. The main novelty in the paper is that the domain of heterogeneity is endogenous: it may depend on the control and on the state of the system. This extension is crucial for several economic applications and turns out to rise interesting mathematical problems. A necessary optimality condition is derived, where one of the adjoint variables satisfies a differential inclusion (instead of equation) and the maximization of the Hamiltonian takes the form of 'min-max'. As a consequence, a Pontryagin-type maximum principle is obtained under certain regularity conditions for the optimal control. A formula for the derivative of the objective function with respect to the control from L{sub {infinity}} is presented together with a sufficient condition for its existence. A stylized economic example is investigated analytically and numerically.

  15. Immigrant College Students' Academic Obstacles

    ERIC Educational Resources Information Center

    Soria, Krista M.; Stebleton, Michael

    2013-01-01

    Immigrant college student populations continue to grow on college campuses across the nation; yet, little is known about the experiences of immigrant students. This paper examines differences in perceived academic obstacles between immigrant students and non-immigrant students at six large, public research universities (n = 56,000). The…

  16. Metastable dynamics in heterogeneous neural fields.

    PubMed

    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

  17. 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

  18. Organizational Heterogeneity of Vertebrate Genomes

    PubMed Central

    Frenkel, Svetlana; Kirzhner, Valery; Korol, Abraham

    2012-01-01

    Genomes of higher eukaryotes are mosaics of segments with various structural, functional, and evolutionary properties. The availability of whole-genome sequences allows the investigation of their structure as “texts” using different statistical and computational methods. One such method, referred to as Compositional Spectra (CS) analysis, is based on scoring the occurrences of fixed-length oligonucleotides (k-mers) in the target DNA sequence. CS analysis allows generating species- or region-specific characteristics of the genome, regardless of their length and the presence of coding DNA. In this study, we consider the heterogeneity of vertebrate genomes as a joint effect of regional variation in sequence organization superimposed on the differences in nucleotide composition. We estimated compositional and organizational heterogeneity of genome and chromosome sequences separately and found that both heterogeneity types vary widely among genomes as well as among chromosomes in all investigated taxonomic groups. The high correspondence of heterogeneity scores obtained on three genome fractions, coding, repetitive, and the remaining part of the noncoding DNA (the genome dark matter - GDM) allows the assumption that CS-heterogeneity may have functional relevance to genome regulation. Of special interest for such interpretation is the fact that natural GDM sequences display the highest deviation from the corresponding reshuffled sequences. PMID:22384143

  19. 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.

  20. How Well Does Growth Mixture Modeling Identify Heterogeneous Growth Trajectories? A Simulation Study Examining GMM's Performance Characteristics

    ERIC Educational Resources Information Center

    Peugh, James; Fan, Xitao

    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…

  1. Dealing with spatial heterogeneity

    NASA Astrophysics Data System (ADS)

    Marsily, Gh.; Delay, F.; Gonçalvès, J.; Renard, Ph.; Teles, V.; Violette, S.

    2005-03-01

    Heterogeneity can be dealt with by defining homogeneous equivalent properties, known as averaging, or by trying to describe the spatial variability of the rock properties from geologic observations and local measurements. The techniques available for these descriptions are mostly continuous Geostatistical models, or discontinuous facies models such as the Boolean, Indicator or Gaussian-Threshold models and the Markov chain model. These facies models are better suited to treating issues of rock strata connectivity, e.g. buried high permeability channels or low permeability barriers, which greatly affect flow and, above all, transport in aquifers. Genetic models provide new ways to incorporate more geology into the facies description, an approach that has been well developed in the oil industry, but not enough in hydrogeology. The conclusion is that future work should be focused on improving the facies models, comparing them, and designing new in situ testing procedures (including geophysics) that would help identify the facies geometry and properties. A world-wide catalog of aquifer facies geometry and properties, which could combine site genesis and description with methods used to assess the system, would be of great value for practical applications. On peut aborder le problème de l'hétérogénéité en s'efforçant de définir une perméabilité équivalente homogène, par prise de moyenne, ou au contraire en décrivant la variation dans l'espace des propriétés des roches à partir des observations géologiques et des mesures locales. Les techniques disponibles pour une telle description sont soit continues, comme l'approche Géostatistique, soit discontinues, comme les modèles de faciès, Booléens, ou bien par Indicatrices ou Gaussiennes Seuillées, ou enfin Markoviens. Ces modèles de faciès sont mieux capables de prendre en compte la connectivité des strates géologiques, telles que les chenaux enfouis à forte perméabilité, ou au contraire les faciès fins de barrières de perméabilité, qui ont une influence importante sur les écoulement, et, plus encore, sur le transport. Les modè les génétiques récemment apparus ont la capacité de mieux incorporer dans les modèles de faciès les observations géologiques, chose courante dans l'industrie pétrolière, mais insuffisamment développée en hydrogéologie. On conclut que les travaux de recherche ultérieurs devraient s'attacher à développer les modèles de faciès, à les comparer entre eux, et à mettre au point de nouvelles méthodes d'essais in situ, comprenant les méthodes géophysiques, capables de reconnaître la géométrie et les propriétés des faciès. La constitution d'un catalogue mondial de la géométrie et des propriétés des faciès aquifères, ainsi que des méthodes de reconnaissance utilisées pour arriver à la détermination de ces systèmes, serait d'une grande importance pratique pour les applications. La heterogeneidad se puede manejar por medio de la definición de características homogéneas equivalentes, conocidas como promediar o tratando de describir la variabilidad espacial de las características de las rocas a partir de observaciones geológicas y medidas locales. Las técnicas disponibles para estas descripciones son generalmente modelos geoestadísticos continuos o modelos de facies discontinuos como los modelos Boolean, de Indicador o de umbral de Gaussian y el modelo de cadena de Markow. Estos modelos de facies son mas adecuados para tratar la conectvidad de estratos geológicos (por ejemplo canales de alta permeabilidad enterrados o barreras de baja permeabilidad que tienen efectos importantes sobre el flujo y especialmente sobre el transporte en los acuíferos. Los modelos genéticos ofrecen nuevas formas de incorporar más geología en las descripciones de facies, un enfoque que está bien desarollado en la industria petrolera, pero insuficientemente en la hidrogeología. Se concluye que los trabajos futuros deberían estar más enfocados en mejorar los modelos de facies, en establecer comparaciones y en

  2. Tubulin heterogeneity in the trypanosome Crithidia fasciculata.

    PubMed Central

    Russell, D G; Miller, D; Gull, K

    1984-01-01

    The interphase cell of Crithidia fasciculata has three discrete tubulin populations: the subpellicular microtubules, the axonemal microtubules, and the nonpolymerized cytoplasmic pool protein. These three tubulin populations were independently and selectively purified, yielding, in each case, microtubule protein capable of self-assembly. All three preparations polymerized to form ribbons and sheets rather than the more usual microtubular structures. Analyses of the tubulin by two-dimensional polyacrylamide gel electrophoresis, isoelectric focusing, and peptide mapping indicated that the beta-tubulin complex remained constant regardless of source but that some heterogeneity was present in the alpha subunit. Cytoplasmic pool alpha tubulins (alpha 1/alpha 2) were the only alpha isotypes in the cytoplasm and also formed most of the alpha tubulin species in the pellicular fraction. Flagellar alpha tubulin (alpha 3) was the sole alpha isotype in the flagella; it appeared in small amounts in the pellicular fraction but was completely absent from the cytoplasm. In vitro translation products from polyadenylated RNA from C. fasciculata were also examined by two-dimensional polyacrylamide gel electrophoresis and possessed a protein corresponding to alpha 1/alpha 2 tubulin but lacked any alpha 3 tubulin. The alpha 3 polypeptide arose from a post-translational modification of a precursor polypeptide not identifiable by two-dimensional polyacrylamide gel electrophoresis as alpha 3. Peptide mapping data indicated that cytoplasmic alpha tubulin is the most likely precursor. These results demonstrate alpha-tubulin heterogeneity in this organism and also how close the relationship between flagellar and cytoskeletal tubulins can be among lower eucaryotes. Images PMID:6717441

  3. 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…

  4. Comparing Linear Relationships between E-Book Usage and University Student and Faculty Populations: The Differences between E-Reference and E-Monograph Collections

    ERIC Educational Resources Information Center

    Lamothe, Alain R.

    2013-01-01

    This paper reports the results from a quantitative study examining the strength of linear relationships between Laurentian University students and faculty members and the J. N. Desmarais Library's reference and monograph e-book collections. The number of full-text items accessed, searches performed, and undergraduate, graduate, and faculty…

  5. 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…

  6. 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…

  7. Emergence of heterogeneity in a noncompetitive resource allocation problem

    NASA Astrophysics Data System (ADS)

    Matzke, Christina; Challet, Damien

    2011-07-01

    Tuning one’s shower in some hotels may turn into a challenging coordination game with imperfect information. The temperature sensitivity increases with the number of agents, making the problem possibly unlearnable. Because there is in practice a finite number of possible tap positions, identical agents are unlikely to reach even approximately their favorite water temperature. We show that a population of agents with homogeneous strategies is evolutionary unstable, which gives insights into the emergence of heterogeneity, the latter being tempting but risky.

  8. 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.

  9. The heterogeneous explosive reaction zone

    SciTech Connect

    Mader, C.L.; Kershner, J.D.

    1989-01-01

    The calculated reaction zone of PBX-9404 using solid HMX Arrhenius kinetics is stable to perturbations. The calculated reaction zone Von Neumann spike pressure agrees with the experimental observations within experimental uncertainty associated with different experimental techniques. The calculated homogengeous explosive reaction zone thickness is larger than observed for the heterogeneous explosive. The effect of two volume percent air holes on the reaction zone was modeled using the three-dimensional Eulerian reactive hydrodynamic code, 3DE. The air holes perturb the reaction zone. A complicated, time-dependent, multidimensional reaction region proceeds through the heterogeneous explosive. The experimentally observed reaction zone characteristic of heterogeneous explosives are mean values of an irregular, three-dimensional reaction region. 20 refs., 6 figs.

  10. Managing for Biodiversity and Livestock: A Scale-Dependent Approach for Promoting Vegetation Heterogenity in Western Great Plains Grasslands

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Grasslands with heterogeneous vegetation structure and composition support a greater number of plant and animal species. To increase habitat diversity for wildlife, improve overall grassland health, and help recover declining grassland bird populations, management strategies should maintain or maxim...

  11. Dynamic fracture of heterogeneous materials

    SciTech Connect

    Stout, M.G.; Liu, C.; Addessio, F.L.; Williams, T.O.; Bennett, J.G.; Haberman, K.S.; Asay, B.W.

    1998-12-31

    This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The objective of this project was to investigate the fundamental aspects of the process of dynamic fracture propagation in heterogeneous materials. The work focused on three important, but poorly understood, aspects of dynamic fracture for materials with a heterogeneous microstructure. These were: the appropriateness of using a single-parameter asymptotic analysis to describe dynamic crack-tip deformation fields, the temperature rises at the tip and on the flanks of a running crack, and the constitutive modeling of damage initiation and accumulation.

  12. Grassroots Suggestions for Linking Native-Language Learning, Native American Studies, and Mainstream Education in Reservation Schools with Mixed Indian and White Student Populations

    ERIC Educational Resources Information Center

    Ngai, Phyllis Bo-yuen

    2006-01-01

    Indigenous-language education is critical in the rural and small-town communities with mixed native and non-native populations that constitute the headwaters of many dying tongues. Emerging from interviews conducted in 2002 and 2003 on the Flathead Indian Reservation with 89 study participants holding diverse perspectives is the need for a…

  13. Kid's PACK: Population Awareness Campaign Kit.

    ERIC Educational Resources Information Center

    Zero Population Growth, Inc., Washington, DC.

    This fun and educational kit is designed specifically for elementary students. The "Kid's PACK" (Population Awareness Campaign Kit) entertains and informs children on the environment and human population growth through stories, games, and concrete ideas for making a difference. In three booklets, the "Kid's PACK" offers elementary students

  14. Teachers' PET Project. Population Education Training.

    ERIC Educational Resources Information Center

    Zero Population Growth, Inc., Washington, DC.

    Six population education activities presented in both English and Spanish are part of this activity pack. The first, "Population Riddles," helps students to understand just how much one billion is. The second, "Everything Is Connected," helps students to identify ways that factors in human society and the natural environment are interdependent.…

  15. Fault heterogeneity and earthquake scaling

    NASA Astrophysics Data System (ADS)

    Hetherington, A.; Steacy, S.

    2006-12-01

    There is an on-going debate in the seismological community as to whether stress drop is independent of earthquake size. The problem is generally illustrated in plots of seismic moment vs. source radius and in some instances the same diagram has been used to support either the argument that stress drop scales with increasing earthquake size or that it is constant. Data from multiple studies tend to support the constant stress drop view whereas results from small data sets tend to support the opposite. Here we investigate this question in a simple 2D cellular automaton that includes heterogeneity. Each cell in the 512 x 64 model is assigned a maximum and minimum breaking strength, and the distributions of these strengths are drawn from either random or fractal distributions. We find that when the range of heterogeneity is low (i.e. the difference between maximum and minimum breaking strength), the scaling approaches that of constant stress drop. However, clear deviations from the constant stress drop model are observed when the range of heterogeneity is large. Further, fractal distributions of strength show more significant scaling than do random ones. These results suggest that the potential departures in earthquake scaling may be real and may reflect heterogeneity in the earthquake source process.

  16. Electoral Competition in Heterogeneous Districts

    ERIC Educational Resources Information Center

    Callander, Steven

    2005-01-01

    This paper considers a model of elections in which parties compete simultaneously for multiple districts. I show that if districts are heterogeneous, then a unique two-party equilibrium exists under plurality rule in which further entry is deterred. The equilibrium requires that parties choose noncentrist policy platforms and not converge to the…

  17. Floodplain heterogeneity and meander migration

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The impact of horizontal heterogeneity of floodplain soils on rates and patterns of meander migration is analyzed with a Ikeda et al. (1981)-type model for hydrodynamics and bed morphodynamics, coupled with a physically-based bank erosion model according to the approach developed by Motta et al. (20...

  18. Modeling and Tolerating Heterogeneous Failures

    E-print Network

    Kondo, Derrick

    - size-fits all #12;Goal · Design application-centric failure model ­Considering component failure-tolerance algorithms #12;Approach · Analyze 5 years of event logs of production HPC system · Develop failure modelModeling and Tolerating Heterogeneous Failures in Large Parallel Systems Eric Heien1

  19. Social Capital and Community Heterogeneity

    ERIC Educational Resources Information Center

    Coffe, Hilde

    2009-01-01

    Recent findings indicate that more pronounced community heterogeneity is associated with lower levels of social capital. These studies, however, concentrate on specific aspects in which people differ (such as income inequality or ethnic diversity). In the present paper, we introduce the number of parties in the local party system as a more…

  20. Within patient microevolution of Mycobacterium tuberculosis correlates with heterogeneous responses to treatment

    PubMed Central

    Liu, Qingyun; Via, Laura E.; Luo, Tao; Liang, Lili; Liu, Xin; Wu, Sufang; Shen, Qingyu; Wei, Wang; Ruan, Xianglin; Yuan, Xing; Zhang, Guolong; Barry, Clifton E.; Gao, Qian

    2015-01-01

    Genetic heterogeneity of Mycobacterium tuberculosis (MTB) within a patient has caused great concern as it might complicate antibiotic treatment and cause treatment failure. But the extent of genetic heterogeneity has not been described in detail nor has its association with heterogeneous treatment response. During treatment of a subject with MDR-TB, serial computed tomography (CT) scans showed this subject had six anatomically discrete lesions and they responded to treatment with disparate kinetics, suggesting heterogeneous MTB population may exist. To investigate this heterogeneity, we applied deep whole genome sequencing of serial sputum isolates and discovered that the MTB population within this patient contained three dominant sub-clones differing by 10?~?14 single nucleotide polymorphisms (SNPs). Differential mutation patterns in known resistance alleles indicated these sub-clones had different drug-resistance patterns, which may explain the heterogeneous treatment responses between lesions. Our results showed clear evidence of branched microevolution of MTB in vivo, which led to a diverse bacterial community. These findings indicated that complex sub-populations of MTB might coexist within patient and contribute to lesions’ disparate responses to antibiotic treatment. PMID:26620446

  1. Within patient microevolution of Mycobacterium tuberculosis correlates with heterogeneous responses to treatment.

    PubMed

    Liu, Qingyun; Via, Laura E; Luo, Tao; Liang, Lili; Liu, Xin; Wu, Sufang; Shen, Qingyu; Wei, Wang; Ruan, Xianglin; Yuan, Xing; Zhang, Guolong; Barry, Clifton E; Gao, Qian

    2015-01-01

    Genetic heterogeneity of Mycobacterium tuberculosis (MTB) within a patient has caused great concern as it might complicate antibiotic treatment and cause treatment failure. But the extent of genetic heterogeneity has not been described in detail nor has its association with heterogeneous treatment response. During treatment of a subject with MDR-TB, serial computed tomography (CT) scans showed this subject had six anatomically discrete lesions and they responded to treatment with disparate kinetics, suggesting heterogeneous MTB population may exist. To investigate this heterogeneity, we applied deep whole genome sequencing of serial sputum isolates and discovered that the MTB population within this patient contained three dominant sub-clones differing by 10?~?14 single nucleotide polymorphisms (SNPs). Differential mutation patterns in known resistance alleles indicated these sub-clones had different drug-resistance patterns, which may explain the heterogeneous treatment responses between lesions. Our results showed clear evidence of branched microevolution of MTB in vivo, which led to a diverse bacterial community. These findings indicated that complex sub-populations of MTB might coexist within patient and contribute to lesions' disparate responses to antibiotic treatment. PMID:26620446

  2. Large-scale replication and heterogeneity in Parkinson disease genetic loci

    PubMed Central

    Ioannidis, John P.A.; Aasly, Jan O.; Annesi, Grazia; Brice, Alexis; Van Broeckhoven, Christine; Bertram, Lars; Bozi, Maria; Crosiers, David; Clarke, Carl; Facheris, Maurizio; Farrer, Matthew; Garraux, Gaetan; Gispert, Suzana; Auburger, Georg; Vilariño-Güell, Carles; Hadjigeorgiou, Georgios M.; Hicks, Andrew A.; Hattori, Nobutaka; Jeon, Beom; Lesage, Suzanne; Lill, Christina M.; Lin, Juei-Jueng; Lynch, Timothy; Lichtner, Peter; Lang, Anthony E.; Mok, Vincent; Jasinska-Myga, Barbara; Mellick, George D.; Morrison, Karen E.; Opala, Grzegorz; Pramstaller, Peter P.; Pichler, Irene; Park, Sung Sup; Quattrone, Aldo; Rogaeva, Ekaterina; Ross, Owen A.; Stefanis, Leonidas; Stockton, Joanne D.; Satake, Wataru; Silburn, Peter A.; Theuns, Jessie; Tan, Eng-King; Toda, Tatsushi; Tomiyama, Hiroyuki; Uitti, Ryan J.; Wirdefeldt, Karin; Wszolek, Zbigniew; Xiromerisiou, Georgia; Yueh, Kuo-Chu; Zhao, Yi; Gasser, Thomas; Maraganore, Demetrius; Krüger, Rejko

    2012-01-01

    Objective: Eleven genetic loci have reached genome-wide significance in a recent meta-analysis of genome-wide association studies in Parkinson disease (PD) based on populations of Caucasian descent. The extent to which these genetic effects are consistent across different populations is unknown. Methods: Investigators from the Genetic Epidemiology of Parkinson's Disease Consortium were invited to participate in the study. A total of 11 SNPs were genotyped in 8,750 cases and 8,955 controls. Fixed as well as random effects models were used to provide the summary risk estimates for these variants. We evaluated between-study heterogeneity and heterogeneity between populations of different ancestry. Results: In the overall analysis, single nucleotide polymorphisms (SNPs) in 9 loci showed significant associations with protective per-allele odds ratios of 0.78–0.87 (LAMP3, BST1, and MAPT) and susceptibility per-allele odds ratios of 1.14–1.43 (STK39, GAK, SNCA, LRRK2, SYT11, and HIP1R). For 5 of the 9 replicated SNPs there was nominally significant between-site heterogeneity in the effect sizes (I2 estimates ranged from 39% to 48%). Subgroup analysis by ethnicity showed significantly stronger effects for the BST1 (rs11724635) in Asian vs Caucasian populations and similar effects for SNCA, LRRK2, LAMP3, HIP1R, and STK39 in Asian and Caucasian populations, while MAPT rs2942168 and SYT11 rs34372695 were monomorphic in the Asian population, highlighting the role of population-specific heterogeneity in PD. Conclusion: Our study allows insight to understand the distribution of newly identified genetic factors contributing to PD and shows that large-scale evaluation in diverse populations is important to understand the role of population-specific heterogeneity. Neurology® 2012;79:659–667 PMID:22786590

  3. Flammability of Heterogeneously Combusting Metals

    NASA Technical Reports Server (NTRS)

    Jones, Peter D.

    1998-01-01

    Most engineering materials, including some metals, most notably aluminum, burn in homogeneous combustion. 'Homogeneous' refers to both the fuel and the oxidizer being in the same phase, which is usually gaseous. The fuel and oxidizer are well mixed in the combustion reaction zone, and heat is released according to some relation like q(sub c) = delta H(sub c)c[((rho/rho(sub 0))]exp a)(exp -E(sub c)/RT), Eq. (1) where the pressure exponent a is usually close to unity. As long as there is enough heat released, combustion is sustained. It is useful to conceive of a threshold pressure beyond which there is sufficient heat to keep the temperature high enough to sustain combustion, and beneath which the heat is so low that temperature drains away and the combustion is extinguished. Some materials burn in heterogeneous combustion, in which the fuel and oxidizer are in different phases. These include iron and nickel based alloys, which burn in the liquid phase with gaseous oxygen. Heterogeneous combustion takes place on the surface of the material (fuel). Products of combustion may appear as a solid slag (oxide) which progressively covers the fuel. Propagation of the combustion melts and exposes fresh fuel. Heterogeneous combustion heat release also follows the general form of Eq.(1), except that the pressure exponent a tends to be much less than 1. Therefore, the increase in heat release with increasing pressure is not as dramatic as it is in homogeneous combustion. Although the concept of a threshold pressure still holds in heterogeneous combustion, the threshold is more difficult to identify experimentally, and pressure itself becomes less important relative to the heat transfer paths extant in any specific application. However, the constants C, a, and E(sub c) may still be identified by suitable data reduction from heterogeneous combustion experiments, and may be applied in a heat transfer model to judge the flammability of a material in any particular actual-use situation. In order to support the above assertions, two investigations are undertaken: 1) PCT data are examined in detail to discover the pressure dependence of heterogeneous combustion experiment results; and 2) heterogeneous combustion in a PCT situation is described by a heat transfer model, which is solved first in simplified form for a simple actual-use situation, and then extended to apply to PCT data reduction (combustion constant identification).

  4. 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.

  5. Freezing Rate Due to Heterogeneous Nucleation.

    NASA Astrophysics Data System (ADS)

    Vali, Gabor

    1994-07-01

    The heterogeneous nucleation of ice from supercooled water is influenced by the nature of the foreign nuclei that serve as the sites for ice embryo formation, and by the stochastic nature of the process of embryo growth to critical size. The relative roles of these two factors have been the subject of some debate, especially as they influence the way nucleation of ice is modeled in clouds. `Freezing rate' is defined as the time-dependent rate at which a population of macroscopically identical samples (e.g., drops in a volume of air) freeze due to the nuclei contained in them. Freezing rate is the combined result of nucleus content and of time dependence. The time-dependent freezing rate model (TDFR) is consistent with available empirical evidence. For droplets cooled at rates of the order of 1°C per min, the nucleus content, or nucleus spectrum, predicts the freezing rate with reasonable accuracy. For samples exposed to a fixed temperature, the time dependence of the freezing rate becomes important, but the probability of freezing is not the same for each individual of the sample population. Stochastic models are not supported by the results. Application of the TDFR model and use of measured freezing nucleus data for precipitation provide a basis for the description of ice formation via immersion-freezing nucleation in cloud models. Limitations to full development of these models arise from inadequate knowledge about the freezing nucleus content of cloud water as a function of cloud evolution.

  6. Using the University Student Depression Inventory to Investigate the Effect of Demographic Variables on Students' Depression

    ERIC Educational Resources Information Center

    Khawaja, Nigar G.; Duncanson, Krystle

    2008-01-01

    Depression is a problem in the student population and may impact students of any age, gender and ethnicity. Previous studies have indicated student demographic characteristics are associated with depression; however, these studies have not utilised scales specifically designed to measure depression in the student population. The aim of the present…

  7. Not simply more of the same: distinguishing between patient heterogeneity and parameter uncertainty.

    PubMed

    Vemer, Pepijn; Goossens, Lucas M A; Rutten-van Mölken, Maureen P M H

    2014-11-01

    In cost-effectiveness (CE) Markov models, heterogeneity in the patient population is not automatically taken into account. We aimed to compare methods of dealing with heterogeneity on estimates of CE, using a case study in chronic obstructive pulmonary disease (COPD). We first present a probabilistic sensitivity analysis (PSA) in which we sampled only from distributions representing parameter uncertainty. This ignores any heterogeneity. Next, we explored heterogeneity by presenting results for subgroups, using a method that samples parameter uncertainty simultaneously with heterogeneity in a single-loop PSA. Finally, we distinguished parameter uncertainty from heterogeneity in a double-loop PSA by performing a nested simulation within each PSA iteration. Point estimates and uncertainty differed substantially between methods. The incremental CE ratio (ICER) ranged from € 4900 to € 13,800. The single-loop PSA led to a substantially different shape of the CE plane and an overestimation of the uncertainty compared with the other 3 methods. The CE plane for the double-loop PSA showed substantially less uncertainty and a stronger negative correlation between the difference in costs and the difference in effects compared with the other methods. This came at the cost of higher calculation times. Not accounting for heterogeneity, subgroup analysis and the double-loop PSA can be viable options, depending on the decision makers' information needs. The single-loop PSA should not be used in CE research. It disregards the fundamental differences between heterogeneity and sampling uncertainty and overestimates uncertainty as a result. PMID:25216723

  8. Consumer heterogeneity, uncertainty, and product policies

    E-print Network

    Lin, Song

    2015-01-01

    This dissertation consists of three essays on the implications of consumer heterogeneity and uncertainty for firms' strategies. The first essay analyzes how firms should develop add-on policies when consumers have heterogeneous ...

  9. 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…

  10. Heterogeneous Viscoelasticity: A Combined Theory of Dynamic and Elastic Heterogeneity

    NASA Astrophysics Data System (ADS)

    Schirmacher, Walter; Ruocco, Giancarlo; Mazzone, Valerio

    2015-07-01

    We present a heterogeneous version of Maxwell's theory of viscoelasticity based on the assumption of spatially fluctuating local viscoelastic coefficients. The model is solved in coherent-potential approximation. The theory predicts an Arrhenius-type temperature dependence of the viscosity in the vanishing-frequency limit, independent of the distribution of the activation energies. It is shown that this activation energy is generally different from that of a diffusing particle with the same barrier-height distribution, which explains the violation of the Stokes-Einstein relation observed frequently in glasses. At finite but low frequencies, the theory describes low-temperature asymmetric alpha relaxation. As examples, we report the good agreement obtained for selected inorganic, metallic, and organic glasses. At high frequencies, the theory reduces to heterogeneous elasticity theory, which explains the occurrence of the boson peak and related vibrational anomalies.

  11. Heterogeneous Viscoelasticity: A Combined Theory of Dynamic and Elastic Heterogeneity.

    PubMed

    Schirmacher, Walter; Ruocco, Giancarlo; Mazzone, Valerio

    2015-07-01

    We present a heterogeneous version of Maxwell's theory of viscoelasticity based on the assumption of spatially fluctuating local viscoelastic coefficients. The model is solved in coherent-potential approximation. The theory predicts an Arrhenius-type temperature dependence of the viscosity in the vanishing-frequency limit, independent of the distribution of the activation energies. It is shown that this activation energy is generally different from that of a diffusing particle with the same barrier-height distribution, which explains the violation of the Stokes-Einstein relation observed frequently in glasses. At finite but low frequencies, the theory describes low-temperature asymmetric alpha relaxation. As examples, we report the good agreement obtained for selected inorganic, metallic, and organic glasses. At high frequencies, the theory reduces to heterogeneous elasticity theory, which explains the occurrence of the boson peak and related vibrational anomalies. PMID:26182108

  12. 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

  13. 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

  14. 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…

  15. Bird Populations

    EPA Science Inventory

    This indicator describes changes in bird populations in the contiguous U.S and southern Canada from 1966 to 2003. Bird populations are an important component of biological diversity, and trends in bird populations can reflect the influences of changes in landscape and habi...

  16. Name of the Institution Polytechnique Montral City: Montreal (population: 1 692 082)

    E-print Network

    Meunier, Michel

    (population: 1 692 082) Province: Québec (population: 7 979 663) Country: Canada (population of its student population (7200 students, 24.2 % of whom are international students from 123 provided highquality university instruction in engineering at all levels by focusing on human values

  17. Combinatorial probabilistic chromatin interactions produce transcriptional heterogeneity

    PubMed Central

    Voss, Ty C.; Schiltz, R. Louis; Sung, Myong-Hee; Johnson, Thomas A.; John, Sam; Hager, Gordon L.

    2009-01-01

    Summary Gene regulation often appears deterministic in the average cell population, but transcription is a probabilistic process at the single-cell level. Although many mechanisms are invoked to account for this behavior, it is difficult to determine how cell-to-cell variation in the interactions of transcription factors with target chromatin impact transcriptional output. Here, we use cells that contain a 200-copy tandem array of promoter or reporter gene units to simultaneously visualize transient interaction, equilibrium or steady-state binding of fluorescent-protein-labeled glucocorticoid receptor with its DNA response elements, the recruitment of diverse coregulators, and transcriptional output at the single-cell level. These regulatory proteins associate with target chromatin via a probabilistic mechanism that produces cell-to-cell variability in binding. The multiple steps of this process are partially independent and differ between individual regulators. The association level of each regulator influences the transcriptional output in individual cells, but this does not account for all transcriptional heterogeneity. Additionally, specific combinatorial interactions of the glucocorticoid receptor and coregulators with response elements regulate transcription at the single-cell level. Like many endogenous genes, the average array transcriptional activity evolves over time. This apparently deterministic average temporal promoter progression involves changes in the probability that specific combinatorial glucocorticoid receptor and coregulator interactions will occur on the response elements in single cells. These data support the emerging `return-to-template' transcription model, which mechanistically unifies the observed extremely transient interactions between the transcription factor and response elements, cell-to-cell variability in steady-state association of factors with chromatin, and the resulting heterogeneous gene expression between individual cells. PMID:19126674

  18. Stabilizing population.

    PubMed

    Brown, L; Mitchell, J

    1998-04-01

    This article is a reprint of the Worldwatch Institute's "State of the World Report," Chapter 10: "Building a New Economy." 16 countries reached zero population growth by 1997. 33 countries have stabilized population, which amounts to 14% of world population. It is estimated that by 2050 population will include an additional 3.6 billion people beyond the present 6 billion. About 60% of the added population will be in Asia, an increase from 3.4 billion in 1995 to 5.4 billion in 2050. China's current population of 1.2 billion will reach 1.5 billion. India's population is expected to rapidly rise from 930 million to 1.53 billion. Populations in the Middle East and North Africa are expected to double in size. Sub-Saharan population is expected to triple in size. By 2050, Nigeria will have 339 million people, which was the entire population of Africa in 1960. There is a great need to stabilize population in a number of currently unstabilized countries. In 1971, Bangladesh and Pakistan had the same population; however, by 2050, Pakistan, without a strong commitment to reducing population growth, will have 70 million more people than Bangladesh. Population stabilization will depend on removal of physical and social barriers that prevent women from using family planning services and thereby help them control their own unwanted fertility. Stabilization will require poverty alleviation and removal of the need for large families. Family size is reduced with lower infant and child mortality risk, increased education, a higher legal age of marriage, and investment in stabilization programs. Solutions to global population growth cannot wait for health reform and budget deficit reductions. PMID:12293723

  19. Characterizing mutational heterogeneity in a glioblastoma patient with double recurrence.

    PubMed

    Nickel, Gabrielle C; Barnholtz-Sloan, Jill; Gould, Meetha P; McMahon, Sarah; Cohen, Andrea; Adams, Mark D; Guda, Kishore; Cohen, Mark; Sloan, Andrew E; LaFramboise, Thomas

    2012-01-01

    Human cancers are driven by the acquisition of somatic mutations. Separating the driving mutations from those that are random consequences of general genomic instability remains a challenge. New sequencing technology makes it possible to detect mutations that are present in only a minority of cells in a heterogeneous tumor population. We sought to leverage the power of ultra-deep sequencing to study various levels of tumor heterogeneity in the serial recurrences of a single glioblastoma multiforme patient. Our goal was to gain insight into the temporal succession of DNA base-level lesions by querying intra- and inter-tumoral cell populations in the same patient over time. We performed targeted "next-generation" sequencing on seven samples from the same patient: two foci within the primary tumor, two foci within an initial recurrence, two foci within a second recurrence, and normal blood. Our study reveals multiple levels of mutational heterogeneity. We found variable frequencies of specific EGFR, PIK3CA, PTEN, and TP53 base substitutions within individual tumor regions and across distinct regions within the same tumor. In addition, specific mutations emerge and disappear along the temporal spectrum from tumor at the time of diagnosis to second recurrence, demonstrating evolution during tumor progression. Our results shed light on the spatial and temporal complexity of brain tumors. As sequencing costs continue to decline and deep sequencing technology eventually moves into the clinic, this approach may provide guidance for treatment choices as we embark on the path to personalized cancer medicine. PMID:22536362

  20. The Northwest Guilford High School Heterogeneous Grouping, Algebra IA and IB, and Guided Studies Programs. Evaluation Report.

    ERIC Educational Resources Information Center

    Harman, Patrick; And Others

    Northwest Guilford High School, Guilford County (North Carolina), is an essentially rural, largely white school that serves about 1,200 students from all socioeconomic levels. An evaluation was conducted of a heterogeneous grouping project involving students in a 2-year sequence of algebra for those who scored below the 40th percentile on a…

  1. Disseminated Museum Displays and Participation of Students from Underrepresented Populations in Polar Research: Education and Outreach for Joint Projects in GPS and Seismology Solid Earth Science Community

    NASA Astrophysics Data System (ADS)

    Eriksson, S. C.; Wilson, T. J.; Anandakrishnan, S.; Aster, R. C.; Johns, B.; Anderson, K.; Taber, J.

    2006-12-01

    Two Antarctic projects developed by solid earth scientists in the GPS and seismology communities have rich education and outreach activities focused on disseminating information gleaned from this research and on including students from underrepresented groups. Members of the UNAVCO and IRIS research consortia along with international partners from Australia, Canada, Chile, Germany, Italy, New Zealand and the U.K. aim to deploy an ambitious GPS/seismic network to observe the Antarctic glaciological and geologic system using a multidisciplinary and internationally coordinated approach. The second project supports this network. UNAVCO and IRIS are designing and building a reliable power and communication system for autonomous polar station operation which use the latest power and communication technologies for ease of deployment and reliable multi-year operation in severe polar environments. This project will disseminate research results through an IPY/POLENET web-based museum style display based on the next-generation "Museum Lite" capability primarily supported by IRIS. "Museum Lite" uses a standard PC, touch-screen monitor, and standard Internet browsers to exploit the scalability and access of the Internet and to provide customizable content in an interactive setting. The unit is suitable for research departments, public schools, and an assortment of public venues, and can provide wide access to real-time geophysical data, ongoing research, and general information. The POLENET group will work with members of the two consortia to provide content about the project and polar science in general. One unit is to be installed at Barrow's Ilisagvit College through the Barrow Arctic Science Consortium, one at McMurdo Station in Antarctica, and two at other sites to be determined (likely in New Zealand/Australia and in the U.S.). In January, 2006, Museum Lite exhibit was installed at the Amundsen-Scott South Pole Station. Evaluation of this prototype is underway. These projects also have a special focus on engaging underrepresented groups in polar science through coalitions with existing recruitment networks and strong, currently operating programs such as the joint UNAVCO-IRIS-USGS program called Research Experiences in Solid Earth Science for Students (RESESS) that provides multi-year research experiences, ongoing mentorship, and a learning community. Undergraduate students will participate in polar research or in development of the new polar equipment.

  2. 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

  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. Kinetic Heterogeneities at Dynamical Crossovers

    E-print Network

    T. K. Haxton; A. J. Liu

    2010-06-16

    We perform molecular dynamics simulations of a model glass-forming liquid to measure the size of kinetic heterogeneities, using a dynamic susceptibility $\\chi_{\\rm ss}(a, t)$ that quantifies the number of particles whose dynamics are correlated on the length scale $a$ and time scale $t$. By measuring $\\chi_{\\rm ss}(a, t)$ as a function of both $a$ and $t$, we locate local maxima $\\chi^\\star$ at distances $a^\\star$ and times $t^\\star$. Near the dynamical glass transition, we find two types of maxima, both correlated with crossovers in the dynamical behavior: a smaller maximum corresponding to the crossover from ballistic to sub-diffusive motion, and a larger maximum corresponding to the crossover from sub-diffusive to diffusive motion. Our results indicate that kinetic heterogeneities are not necessarily signatures of an impending glass or jamming transition.

  5. Renewal-anomalous-heterogeneous files

    E-print Network

    Ophir Flomenbom

    2010-08-13

    Renewal-anomalous-heterogeneous files are solved. A simple file is made of Brownian hard spheres that diffuse stochastically in an effective 1D channel. Generally, Brownian files are heterogeneous: the spheres' diffusion coefficients are distributed and the initial spheres' density is non-uniform. In renewal-anomalous files, the distribution of waiting times for individual jumps is exponential as in Brownian files, yet obeys: {\\psi}_{\\alpha} (t)~t^(-1-{\\alpha}), 0, obeys, ~[_{nrml}]^{\\alpha}, where _{nrml} is the MSD in the corresponding Brownian file. This scaling is an outcome of an exact relation (derived here) connecting probability density functions of Brownian files and renewal-anomalous files. It is also shown that non-renewal-anomalous files are slower than the corresponding renewal ones.

  6. Do Students Expect Compensation for Wage Risk?

    ERIC Educational Resources Information Center

    Schweri, Juerg; Hartog, Joop; Wolter, Stefan C.

    2011-01-01

    We use a unique data set about the wage distribution that Swiss students expect for themselves ex ante, deriving parametric and non-parametric measures to capture expected wage risk. These wage risk measures are unfettered by heterogeneity which handicapped the use of actual market wage dispersion as risk measure in earlier studies. Students in…

  7. Computer Aided Design Modeling for Heterogeneous Objects

    E-print Network

    Gupta, Vikas; Tandon, Puneet

    2010-01-01

    Heterogeneous object design is an active research area in recent years. The conventional CAD modeling approaches only provide geometry and topology of the object, but do not contain any information with regard to the materials of the object and so can not be used for the fabrication of heterogeneous objects (HO) through rapid prototyping. Current research focuses on computer-aided design issues in heterogeneous object design. A new CAD modeling approach is proposed to integrate the material information into geometric regions thus model the material distributions in the heterogeneous object. The gradient references are used to represent the complex geometry heterogeneous objects which have simultaneous geometry intricacies and accurate material distributions. The gradient references helps in flexible manipulability and control to heterogeneous objects, which guarantees the local control over gradient regions of developed heterogeneous objects. A systematic approach on data flow, processing, computer visualizat...

  8. Dynamic Heterogeneity and DNA Methylation in Embryonic Stem Cells

    PubMed Central

    Singer, Zakary S.; Yong, John; Tischler, Julia; Hackett, Jamie A.; Altinok, Alphan; Surani, M. Azim; Cai, Long; Elowitz, Michael B.

    2014-01-01

    Summary Cell populations can be strikingly heterogeneous, composed of multiple cellular states, each exhibiting stochastic noise in its gene expression. A major challenge is to disentangle these two types of variability and to understand the dynamic processes and mechanisms that control them. Embryonic stem cells (ESCs) provide an ideal model system to address this issue because they exhibit heterogeneous and dynamic expression of functionally important regulatory factors. We analyzed gene expression in individual ESCs using single-molecule RNA-FISH and quantitative time-lapse movies. These data discriminated stochastic switching between two coherent (correlated) gene expression states and burst-like transcriptional noise. We further showed that the “2i” signaling pathway inhibitors modulate both types of variation. Finally, we found that DNA methylation plays a key role in maintaining these metastable states. Together, these results show how ESC gene expression states and dynamics arise from a combination of intrinsic noise, coherent cellular states, and epigenetic regulation. PMID:25038413

  9. Optimal surveillance and eradication of invasive species in heterogeneous landscapes.

    PubMed

    Epanchin-Niell, Rebecca S; Haight, Robert G; Berec, Ludek; Kean, John M; Liebhold, Andrew M

    2012-08-01

    Cost-effective surveillance strategies are needed for efficient responses to biological invasions and must account for the trade-offs between surveillance effort and management costs. Less surveillance may allow greater population growth and spread prior to detection, thereby increasing the costs of damages and control. In addition, surveillance strategies are usually applied in environments under continual invasion pressure where the number, size and location of established populations are unknown prior to detection. We develop a novel modeling framework that accounts for these features of the decision and invasion environment and determines the long term sampling effort that minimises the total expected costs of new invasions. The optimal solution depends on population establishment and growth rates, sample sensitivity, and sample, eradication, and damage costs. We demonstrate how to optimise surveillance systems under budgetary constraints and find that accounting for spatial heterogeneity in sampling costs and establishment rates can greatly reduce management costs. PMID:22642613

  10. International Students' Confidence and Academic Success

    ERIC Educational Resources Information Center

    Telbis, Nicola Miky; Helgeson, Lars; Kingsbury, Cheryl

    2014-01-01

    Research shows that the international student population is showing significant growth. This article deals with issues affecting a growing international student population. Studies show that foreign students are encountering difficulties in social adaptability, language barriers, academic ability, and financial need. There is evidence that a…

  11. DREAMing: a simple and ultrasensitive method for assessing intratumor epigenetic heterogeneity directly from liquid biopsies

    PubMed Central

    Pisanic, Thomas R.; Athamanolap, Pornpat; Poh, Weijie; Chen, Chen; Hulbert, Alicia; Brock, Malcolm V.; Herman, James G.; Wang, Tza-Huei

    2015-01-01

    Many cancers comprise heterogeneous populations of cells at primary and metastatic sites throughout the body. The presence or emergence of distinct subclones with drug-resistant genetic and epigenetic phenotypes within these populations can greatly complicate therapeutic intervention. Liquid biopsies of peripheral blood from cancer patients have been suggested as an ideal means of sampling intratumor genetic and epigenetic heterogeneity for diagnostics, monitoring and therapeutic guidance. However, current molecular diagnostic and sequencing methods are not well suited to the routine assessment of epigenetic heterogeneity in difficult samples such as liquid biopsies that contain intrinsically low fractional concentrations of circulating tumor DNA (ctDNA) and rare epigenetic subclonal populations. Here we report an alternative approach, deemed DREAMing (Discrimination of Rare EpiAlleles by Melt), which uses semi-limiting dilution and precise melt curve analysis to distinguish and enumerate individual copies of epiallelic species at single-CpG-site resolution in fractions as low as 0.005%, providing facile and inexpensive ultrasensitive assessment of locus-specific epigenetic heterogeneity directly from liquid biopsies. The technique is demonstrated here for the evaluation of epigenetic heterogeneity at p14ARF and BRCA1 gene-promoter loci in liquid biopsies obtained from patients in association with non-small cell lung cancer (NSCLC) and myelodysplastic/myeloproliferative neoplasms (MDS/MPN), respectively. PMID:26304549

  12. Modelling deuterium labelling of lymphocytes with temporal and/or kinetic heterogeneity.

    PubMed

    De Boer, Rob J; Perelson, Alan S; Ribeiro, Ruy M

    2012-09-01

    To study the kinetics of lymphocytes, models have divided the cell population into subpopulations with different turnover rates. These have been called 'kinetic heterogeneity models' so as to distinguish them from 'temporal heterogeneity models', in which a cell population may have different turnover rates at different times, e.g. when resting versus when activated. We model labelling curves for temporally heterogeneous populations, and predict that they exhibit equal biphasic up- and downslopes. We show when cells divide only once upon activation, these slopes are dominated by the slowest exponent, yielding underestimates of the average turnover rate. When cells undergo more than one division, the labelling curves allow fitting of the two exponential slopes in the temporal heterogeneity model. The same data can also be described with a two-compartment kinetic heterogeneity model. In both instances, the average turnover rate is correctly estimated. Because both models assume a different cell biology but describe the data equally well, the parameters of either model have no simple biological interpretation, as each parameter could reflect a combination of parameters of another biological process. Thus, even if there are sufficient data to reliably estimate all exponentials, one can only accurately estimate an average turnover rate. We illustrate these issues by re-fitting labelling data from healthy and HIV-infected individuals. PMID:22513720

  13. 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.

    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.

  14. Differential effects of excitatory and inhibitory heterogeneity on the gain and asynchronous state of sparse cortical networks

    PubMed Central

    Mejias, Jorge F.; Longtin, André

    2014-01-01

    Recent experimental and theoretical studies have highlighted the importance of cell-to-cell differences in the dynamics and functions of neural networks, such as in different types of neural coding or synchronization. It is still not known, however, how neural heterogeneity can affect cortical computations, or impact the dynamics of typical cortical circuits constituted of sparse excitatory and inhibitory networks. In this work, we analytically and numerically study the dynamics of a typical cortical circuit with a certain level of neural heterogeneity. Our circuit includes realistic features found in real cortical populations, such as network sparseness, excitatory, and inhibitory subpopulations of neurons, and different cell-to-cell heterogeneities for each type of population in the system. We find highly differentiated roles for heterogeneity, depending on the subpopulation in which it is found. In particular, while heterogeneity among excitatory neurons non-linearly increases the mean firing rate and linearizes the f-I curves, heterogeneity among inhibitory neurons may decrease the network activity level and induces divisive gain effects in the f-I curves of the excitatory cells, providing an effective gain control mechanism to influence information flow. In addition, we compute the conditions for stability of the network activity, finding that the synchronization onset is robust to inhibitory heterogeneity, but it shifts to lower input levels for higher excitatory heterogeneity. Finally, we provide an extension of recently reported heterogeneity-induced mechanisms for signal detection under rate coding, and we explore the validity of our findings when multiple sources of heterogeneity are present. These results allow for a detailed characterization of the role of neural heterogeneity in asynchronous cortical networks. PMID:25309409

  15. An Interview with Mara Sapon-Shevin: Implications for Students and Teachers of Labeling Students as Learning Disabled/Gifted.

    ERIC Educational Resources Information Center

    Walther-Thomas, Chriss; Brownell, Mary

    1999-01-01

    This interview with Mara Sapon-Shevin discusses her interest in students with learning disabilities and giftedness, the negative effects of labeling students, what teachers can do to improve the social climate and peer acceptance in heterogeneous classrooms, and the need for teachers to teach all students as if they are gifted. (CR)

  16. Population Blocks.

    ERIC Educational Resources Information Center

    Smith, Martin H.

    1992-01-01

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

  17. MAINE POPULATION

    EPA Science Inventory

    MEPOP250 depicts Maine's 1950-1990 population data by town or Census in unorganized territories. Populations were compiled from US Census Bureau data where available or from Maine Municipal Information (mainly for older records). Unorganized towns with very low or zero pop...

  18. The Factor Structure of the Internet Addiction Tool with University Students in Jordan.

    PubMed

    Ahmad, Muayyad; Alzayyat, Abdulkarim; Al-Gamal, Ekhlas

    2015-09-01

    Internet addiction is a growing phenomenon affecting people in varying ways around the globe. This study examined the factor structure and internal reliability of the Internet Addiction Test (IAT) with a heterogeneous sample of university students in Jordan. The study used a cross-sectional design, and all the questionnaires were completed in classrooms. A sample of 587 students from seven universities in Jordan was obtained. The exploratory and confirmatory factor analyses of the 20-item IAT revealed that a four-factor solution offered the most parsimonious explanation of the data. The IAT reliably assesses distinct domains of Internet addiction. These domains are Excessive Use, Loss/Suffer, Attached To, and Impaired Social Relations. Thus, it is recommended to use the obtained four factors when assessing Internet addiction among a similar population. PMID:26440876

  19. Today's Higher Education Students: Issues of Admission, Retention, Transfer, and Attrition in Relation to Changing Student Demographics.

    ERIC Educational Resources Information Center

    Andres, Lesley; Carpenter, Susan

    The paper discusses retention models for the nontraditional student population, including transfer students, older adult learners, commuters, part-time students, graduate students, women, students with disabilities, and ethnic minorities. Since 1975, leading research in the field of postsecondary student retention has been grounded on Tinto's…

  20. Macrophage heterogeneity in tissues: phenotypic diversity and functions

    PubMed Central

    Gordon, Siamon; Plüddemann, Annette; Martinez Estrada, Fernando

    2014-01-01

    During development and throughout adult life, macrophages derived from hematopoietic progenitors are seeded throughout the body, initially in the absence of inflammatory and infectious stimuli as tissue-resident cells, with enhanced recruitment, activation, and local proliferation following injury and pathologic insults. We have learned a great deal about macrophage properties ex vivo and in cell culture, but their phenotypic heterogeneity within different tissue microenvironments remains poorly characterized, although it contributes significantly to maintaining local and systemic homeostasis, pathogenesis, and possible treatment. In this review, we summarize the nature, functions, and interactions of tissue macrophage populations within their microenvironment and suggest questions for further investigation. PMID:25319326

  1. Shock Initiation of Heterogeneous Explosives

    SciTech Connect

    Reaugh, J E

    2004-05-10

    The fundamental picture that shock initiation in heterogeneous explosives is caused by the linking of hot spots formed at inhomogeneities was put forward by several researchers in the 1950's and 1960's, and more recently. Our work uses the computer hardware and software developed in the Advanced Simulation and Computing (ASC) program of the U.S. Department of Energy to explicitly include heterogeneities at the scale of the explosive grains and to calculate the consequences of realistic although approximate models of explosive behavior. Our simulations are performed with ALE-3D, a three-dimensional, elastic-plastic-hydrodynamic Arbitrary Lagrange-Euler finite-difference program, which includes chemical kinetics and heat transfer, and which is under development at this laboratory. We developed the parameter values for a reactive-flow model to describe the non-ideal detonation behavior of an HMX-based explosive from the results of grain-scale simulations. In doing so, we reduced the number of free parameters that are inferred from comparison with experiment to a single one - the characteristic defect dimension. We also performed simulations of the run to detonation in small volumes of explosive. These simulations illustrate the development of the reaction zone and the acceleration of the shock front as the flame fronts start from hot spots, grow, and interact behind the shock front. In this way, our grain-scale simulations can also connect to continuum experiments directly.

  2. Socially Aware Heterogeneous Wireless Networks.

    PubMed

    Kosmides, Pavlos; Adamopoulou, Evgenia; Demestichas, Konstantinos; Theologou, Michael; Anagnostou, Miltiades; Rouskas, Angelos

    2015-01-01

    The development of smart cities has been the epicentre of many researchers' efforts during the past decade. One of the key requirements for smart city networks is mobility and this is the reason stable, reliable and high-quality wireless communications are needed in order to connect people and devices. Most research efforts so far, have used different kinds of wireless and sensor networks, making interoperability rather difficult to accomplish in smart cities. One common solution proposed in the recent literature is the use of software defined networks (SDNs), in order to enhance interoperability among the various heterogeneous wireless networks. In addition, SDNs can take advantage of the data retrieved from available sensors and use them as part of the intelligent decision making process contacted during the resource allocation procedure. In this paper, we propose an architecture combining heterogeneous wireless networks with social networks using SDNs. Specifically, we exploit the information retrieved from location based social networks regarding users' locations and we attempt to predict areas that will be crowded by using specially-designed machine learning techniques. By recognizing possible crowded areas, we can provide mobile operators with recommendations about areas requiring datacell activation or deactivation. PMID:26110402

  3. Socially Aware Heterogeneous Wireless Networks

    PubMed Central

    Kosmides, Pavlos; Adamopoulou, Evgenia; Demestichas, Konstantinos; Theologou, Michael; Anagnostou, Miltiades; Rouskas, Angelos

    2015-01-01

    The development of smart cities has been the epicentre of many researchers’ efforts during the past decade. One of the key requirements for smart city networks is mobility and this is the reason stable, reliable and high-quality wireless communications are needed in order to connect people and devices. Most research efforts so far, have used different kinds of wireless and sensor networks, making interoperability rather difficult to accomplish in smart cities. One common solution proposed in the recent literature is the use of software defined networks (SDNs), in order to enhance interoperability among the various heterogeneous wireless networks. In addition, SDNs can take advantage of the data retrieved from available sensors and use them as part of the intelligent decision making process contacted during the resource allocation procedure. In this paper, we propose an architecture combining heterogeneous wireless networks with social networks using SDNs. Specifically, we exploit the information retrieved from location based social networks regarding users’ locations and we attempt to predict areas that will be crowded by using specially-designed machine learning techniques. By recognizing possible crowded areas, we can provide mobile operators with recommendations about areas requiring datacell activation or deactivation. PMID:26110402

  4. Heterogeneous Glasses and Sustainable Cement

    NASA Astrophysics Data System (ADS)

    Del Gado, Emanuela

    2015-03-01

    Calcium-silicate hydrate (C-S-H) is the main binding agent in cement and concrete. It forms at the beginning of cement hydration, it progressively densifies as cement hardens and is ultimately responsible for the performances of concrete. This hydration product is a cohesive nano-scale heterogeneous glass, whose structure and mechanics are still poorly understood, in spite of its practical importance. I will review some of the open questions for this fascinating material and discuss a statistical physics approach recently developed, which allows us to investigate the structural arrest and solidification under the out-of-equilibrium conditions typical of cement hydration and the role of the nano-scale structure in C-S-H mechanics upon hardening. Our approach unveils how some distinctive features of the kinetics of cement hydration can be related to changes in the morphology of this glassy material and elucidates the role of nano-scale mechanical heterogeneities in the hardened C-S-H.

  5. TEACHER AND STUDENT NOTES How Do We Levitate the Train?

    E-print Network

    Fermilab Experiment E831

    or Macintosh) with connection to printer (one per group of 3-4 students) · Spreadsheet software (The be as heterogeneous as one can make them, allowing for the fact that advanced physics classes can be less than

  6. Population Dynamics

    PubMed Central

    Juliano, Steven A.

    2007-01-01

    This chapter reviews aspects of population dynamics that may be conceptually important for biological control of mosquitoes. Density dependent population regulation among immature stages has important implications for biological control of mosquito populations, primarily because it can lead to compensatory or overcompensatory mortality due to additions of a biological control agent. This can result in control efforts leading to no change in the target population, or actual increases in the target population, respectively. Density dependent effects, and compensatory or overcompensatory mortality, appear to be most common in mosquitoes from container or highly ephemeral habitats. In permanent ground water habitats generalist predators appear to limit mosquito populations and so render mortality additive. Thus, biological control in permanent ground water habitats seems to have the highest likelihood of producing a satisfactory result. A central premise of classical biological control is that pest populations are reduced by enemies to stable equilibrium levels that are both below the pre-control equilibrium level, and well below the level producing detrimental effects. This premise results in predictions that successful biological control is likely to involve specialist enemies (usually parasitoids), with short generation times relative to the victim, high rates of successful search, rapid rates of increase, and needing only a few victims to complete their life cycle. These predictions largely fail for mosquito systems, in which successful biological control seems to be associated with generalist enemies that can kill a large portion of the target population, often causing local extinction, and can persist in the absence of the target organism. Biological control of mosquitoes appears to be inherently unstable, thus contrasting sharply with classical biological control. This review suggests a need for better data on density dependent regulation of mosquito populations. PMID:17853611

  7. WHEN TO SLOW DOWN: ELK RESIDENCY RATES ON A HETEROGENEOUS LANDSCAPE

    E-print Network

    Turner, Monica G.

    WHEN TO SLOW DOWN: ELK RESIDENCY RATES ON A HETEROGENEOUS LANDSCAPE DEAN P. ANDERSON,* JAMES D simply returning frequently to selected areas. We studied a population of North American elk (Cervus influence residency time in localized areas. We used global positioning system telemetry data from 7 elk

  8. CHARACTERIZATION OF NATURAL KILLER CELLS' CYTOTOXIC HETEROGENEITY USING AN ARRAY OF SONO-CAGES

    E-print Network

    CHARACTERIZATION OF NATURAL KILLER CELLS' CYTOTOXIC HETEROGENEITY USING AN ARRAY OF SONO of natural killer (NK) cells' cytotoxic response against cancer cells. We report a fraction of inactive NK cells within the tested population (36%), as well as the existence of few `serial killers

  9. Spatial Heterogeneity in Response of Male Greater Sage-Grouse Lek Attendance to Energy Development

    E-print Network

    Beck, Jeffrey L.

    Spatial Heterogeneity in Response of Male Greater Sage-Grouse Lek Attendance to Energy Development of the Intermountain West is the greater sage-grouse (Centrocercusurophasianus). Sage-grouse have been petitioned 64% of the extant sage- grouse population in the eastern portion of their range. Consequently

  10. Impact of heterozygosity and heterogeneity on cotton (Gossypium hirsutum L.) lint yield stability

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An 18-environment field study was undertaken to observe lint yield stability in four population types of cotton (Gossypium hirsutum L.) that included: pure lines grown in pure stands (homozygous/homogeneous), pure lines grown in blended stands (homozygous/ heterogeneous), hybrids grown in pure stand...

  11. Assessing SNPs Versus RAPDs for Predicting Heterogeneity and Screening Efficiency in Wild Potato (Solanum) Species

    E-print Network

    Douches, David S.

    Assessing SNPs Versus RAPDs for Predicting Heterogeneity and Screening Efficiency in Wild Potato January 2015 # The Potato Association of America 2015 Abstract Knowing how genetic diversity is partitioned among and within wild potato species populations is impor- tant for efficient sampling

  12. Population policy.

    PubMed

    1987-03-01

    Participants in the Seminar on Population Policies for Top-level Policy Makers and Program Managers, meeting in Thailand during January 1987, examined the challenges now facing them regarding the implementation of fertility regulation programs in their respective countries -- Bangladesh, China, India, Indonesia, Malaysia, Nepal, Pakistan, the Philippines, the Republic of Korea, and Thailand. This Seminar was organized to coincide with the completion of an Economic and Social Commission for Asia and the Pacific (ESCAP) study investigating the impact and efficiency of family planning programs in the region. Country studies were reviewed at the Seminar along with policy issues about the status of women, incentive and disincentive programs, and socioeconomic factors affecting fertility. In Bangladesh the government recognizes population growth as its top priority problem related to the socioeconomic development of the country and is working to promote a reorientation strategy from the previous clinic-oriented to a multidimensional family welfare program. China's family planning program seeks to postpone marraige, space the births of children between 3-5 years, and promote the 1-child family. Its goal is to reduce the rate of natural increase from 12/1000 in 1978 to 5/1000 by 1985 and 0 by 2000. India's 7th Five-Year-Plan (1986-90) calls for establishing a 2-child family norm by 2000. In Indonesia the government's population policy includes reducing the rate of population growth, achieving a redistribution of the population, adjusting economic factors, and creating prosperous families. The government of Indonesia reversed its policy to reduce the population growth rate in 1984 and announced its goal of achieving a population of 70 million by 2100 in order to support mass consumption industries. It has created an income tax deduction system favoring large families and maternity benefits for women who have up to 5 children as incentives. Nepal's official policy is to decrease fertility, control international migration, and modify the spatial distribution of the population. To reduce its population growth rate, Pakistan has adopted a multi-sectoral, multidimensional approach to family planning. The policy of the government of the Philippines is to bring the population growth rate in line with the availability of natural resources and employment opportunities. In its 5-year plan covering 1982-86, the government of the Republic of Korea emphasized social development, attempting to more fully integrate population and development policies and programs within relevant sectors. To reduce its population growth rate to 1.3% by 1992, the government of Thailand is expanding the reach of its family planning program. PMID:12341036

  13. Improving Student Behavior through Character Education.

    ERIC Educational Resources Information Center

    Battersby, Mary Jo; And Others

    This report describes a program for building and reinforcing character development in order to increase appropriate student-to-student and student-to-teacher behaviors. The targeted population consists of primary and intermediate elementary students in a growing middle class community in Elk Grove, Illinois, a suburb of Chicago. The problems of…

  14. Population Growth Change Population Size or Density

    E-print Network

    Caraco, Thomas

    1 Population Growth Change Population Size or Density Model Measurable Quantity (Observable Unbounded Growth Useful: Small Population Ecological Invasion, Dynamics of Rarity #12;8 2. b ) Estimate Population Size: N Consider Single Population Assume Identical Individuals 1. Plants, Sessile

  15. Soil Heterogeneity Effects on Tallgrass Prairie Community Heterogeneity: An Application of

    E-print Network

    Blair, John

    Soil Heterogeneity Effects on Tallgrass Prairie Community Heterogeneity: An Application seeded to native prairie species. Our objective was to determine whether resource heterogeneity was attributed to net photo- synthesis rates equivalent to or higher than those of the native prairie plants

  16. A Decade of Population Change in Texas. 

    E-print Network

    Skrabanek, R. L.

    1963-01-01

    Universal screening for behavior is the use of a measure of social, emotional or behavioral function across an entire population with a goal of preventing future difficulties by intervening with students identified by the ...

  17. HETEROGENEOUS REBURNING BY MIXED FUELS

    SciTech Connect

    Wei-Yin Chen; Benson B. Gathitu

    2005-01-14

    Recent studies of heterogeneous reburning, i.e., reburning involving a coal-derived char, have elucidated its variables, kinetics and mechanisms that are valuable to the development of a highly efficient reburning process. Young lignite chars contain catalysts that not only reduce NO, but they also reduce HCN that is an important intermediate that recycles to NO in the burnout zone. Gaseous CO scavenges the surface oxides that are formed during NO reduction, regenerating the active sites on the char surface. Based on this mechanistic information, cost-effective mixed fuels containing these multiple features has been designed and tested in a simulated reburning apparatus. Remarkably high reduction of NO and HCN has been observed and it is anticipated that mixed fuel will remove 85% of NO in a three-stage reburning process.

  18. Data Integration for Heterogenous Datasets

    PubMed Central

    2014-01-01

    Abstract More and more, the needs of data analysts are requiring the use of data outside the control of their own organizations. The increasing amount of data available on the Web, the new technologies for linking data across datasets, and the increasing need to integrate structured and unstructured data are all driving this trend. In this article, we provide a technical overview of the emerging “broad data” area, in which the variety of heterogeneous data being used, rather than the scale of the data being analyzed, is the limiting factor in data analysis efforts. The article explores some of the emerging themes in data discovery, data integration, linked data, and the combination of structured and unstructured data. PMID:25553272

  19. Genetic heterogeneity of hepatocellular carcinoma

    SciTech Connect

    Unsal, H.; Isselbacher, K.J. ); Yakicier, C.; Marcais, C.; Ozturk, M. ); Kew, M. ); Volkmann, M. ); Zentgraf, H. )

    1994-01-18

    The authors studied 80 hepatocellular carcinomas from three continents for p53 gene (TP53) mutations and hepatitis B virus (HBV) sequences. p53 mutations were frequent in tumors from Mozambique but not in tumors from South Africa, China, and Germany. Independent of geographic origin, most tumors were positive for HBV sequences. X gene coding sequences of HBV were detected in 78% of tumors, whereas viral sequences in the surface antigen- and core antigen-encoding regions were present in less than 35% of tumors. These observations indicate that hepatocellular carcinomas are genetically heterogeneous. Mozambican-types of hepatocellular carcinomas are characterized by a high incidence of p53 mutations related to aflatoxins. In other tumors, the rarity of p53 mutations combined with the frequent presence of viral X gene coding sequences suggests a possible interference of HBV with the wild-type p53 function.

  20. Heterogeneous Reburning By Mixed Fuels

    SciTech Connect

    Anderson Hall

    2009-03-31

    Recent studies of heterogeneous reburning, i.e., reburning involving a coal-derived char, have elucidated its variables, kinetics and mechanisms that are valuable to the development of a highly efficient reburning process. Young lignite chars contain catalysts that not only reduce NO, but they also reduce HCN that is an important intermediate that recycles to NO in the burnout zone. Gaseous CO scavenges the surface oxides that are formed during NO reduction, regenerating the active sites on the char surface. Based on this mechanistic information, cost-effective mixed fuels containing these multiple features has been designed and tested in a simulated reburning apparatus. Remarkably high reduction of NO and HCN has been observed and it is anticipated that mixed fuel will remove 85% of NO in a three-stage reburning process.

  1. Heterogeneous fuel for hybrid rocket

    NASA Technical Reports Server (NTRS)

    Stickler, David B. (Inventor)

    1996-01-01

    Heterogeneous fuel compositions suitable for use in hybrid rocket engines and solid-fuel ramjet engines, The compositions include mixtures of a continuous phase, which forms a solid matrix, and a dispersed phase permanently distributed therein. The dispersed phase or the matrix vaporizes (or melts) and disperses into the gas flow much more rapidly than the other, creating depressions, voids and bumps within and on the surface of the remaining bulk material that continuously roughen its surface, This effect substantially enhances heat transfer from the combusting gas flow to the fuel surface, producing a correspondingly high burning rate, The dispersed phase may include solid particles, entrained liquid droplets, or gas-phase voids having dimensions roughly similar to the displacement scale height of the gas-flow boundary layer generated during combustion.

  2. Understanding the Executive Functioning Heterogeneity in Schizophrenia

    ERIC Educational Resources Information Center

    Raffard, Stephane; Bayard, Sophie

    2012-01-01

    Schizophrenia is characterized by heterogeneous brain abnormalities involving cerebral regions implied in the executive functioning. The dysexecutive syndrome is one of the most prominent and functionally cognitive features of schizophrenia. Nevertheless, it is not clear to what extend executive deficits are heterogeneous in schizophrenia…

  3. Task and Machine Heterogeneities: Higher Moments Matter

    E-print Network

    Maciejewski, Anthony A. "Tony"

    Task and Machine Heterogeneities: Higher Moments Matter Abdulla M. Al-Qawasmeh 1 , Anthony A.potter}@colostate.edu jtsmith@digitalglobe.com Abstract - One type of heterogeneous computing (HC) systems consists of machines in this matrix represents the ETC of a specific task on a specific machine when executed exclusively. Heuristics

  4. Population growth.

    PubMed

    1984-01-01

    Despite efforts to reduce population growth, the World Bank projects a world population of 10 billion by 2050, with 7 billion living in developing countries. From October 1979 to September 1984, the US Agency for International Development (AID) funded the Research Triangle Institute's (RTI) Integrated Population and Development Planning (IPDP) project to assess rapid population growth effects in 25 developing countries. In October 1984, US AID extended funding for the program, nicknamed INPLAN, for 3 years, at a cost of $6.3 million. Up to 50% of people in developing countries are under age 15, a fact that guarantees large population increases for the next 50-75 years. Also, many regions have been slow to correlate high fertility with socioeconomic development, and in some areas, fertility is actually increasing. INPLAN aims to make governments more aware of population dynamics and to provide training and tools for effective development planning. 40% of INPLAN's work will be done in Africa, 25% in Latin America, and 20% in Asia, with some activity in the Near East. One project in Egypt, involving the use of model generation by microcomputer, was developed by RTI to show rural to urban migration and rapid population growth affects on the educational system. INPLAN expects to develop several other planning sector models on labor force and employment, health and family planning, food supply, housing, and urban development, and apply them to 20-25 countries. Another project provided 9 microcomputer systems and training to Nigerian government agencies. IMPLAN will purchase and distribute 60 such systems in the future. PMID:12314095

  5. Addressing challenges of heterogeneous tumor treatment through bispecific protein-mediated pretargeted drug delivery.

    PubMed

    Yang, Qi; Parker, Christina L; McCallen, Justin D; Lai, Samuel K

    2015-12-28

    Tumors are frequently characterized by genomically and phenotypically distinct cancer cell subpopulations within the same tumor or between tumor lesions, a phenomenon termed tumor heterogeneity. These diverse cancer cell populations pose a major challenge to targeted delivery of diagnostic and/or therapeutic agents, as the conventional approach of conjugating individual ligands to nanoparticles is often unable to facilitate intracellular delivery to the full spectrum of cancer cells present in a given tumor lesion or patient. As a result, many cancers are only partially suppressed, leading to eventual tumor regrowth and/or the development of drug-resistant tumors. Pretargeting (multistep targeting) approaches involving the administration of 1) a cocktail of bispecific proteins that can collectively bind to the entirety of a mixed tumor population followed by 2) nanoparticles containing therapeutic and/or diagnostic agents that can bind to the bispecific proteins accumulated on the surface of target cells offer the potential to overcome many of the challenges associated with drug delivery to heterogeneous tumors. Despite its considerable success in improving the efficacy of radioimmunotherapy, the pretargeting strategy remains underexplored for a majority of nanoparticle therapeutic applications, especially for targeted delivery to heterogeneous tumors. In this review, we will present concepts in tumor heterogeneity, the shortcomings of conventional targeted systems, lessons learned from pretargeted radioimmunotherapy, and important considerations for harnessing the pretargeting strategy to improve nanoparticle delivery to heterogeneous tumors. PMID:26407672

  6. c-di-GMP heterogeneity is generated by the chemotaxis machinery to regulate flagellar motility

    PubMed Central

    Kulasekara, Bridget R; Kamischke, Cassandra; Kulasekara, Hemantha D; Christen, Matthias; Wiggins, Paul A; Miller, Samuel I

    2013-01-01

    Individual cell heterogeneity is commonly observed within populations, although its molecular basis is largely unknown. Previously, using FRET-based microscopy, we observed heterogeneity in cellular c-di-GMP levels. In this study, we show that c-di-GMP heterogeneity in Pseudomonas aeruginosa is promoted by a specific phosphodiesterase partitioned after cell division. We found that subcellular localization and reduction of c-di-GMP levels by this phosphodiesterase is dependent on the histidine kinase component of the chemotaxis machinery, CheA, and its phosphorylation state. Therefore, individual cell heterogeneity in c-di-GMP concentrations is regulated by the activity and the asymmetrical inheritance of the chemotaxis organelle after cell division. c-di-GMP heterogeneity results in a diversity of motility behaviors. The generation of diverse intracellular concentrations of c-di-GMP by asymmetric partitioning is likely important to the success and survival of bacterial populations within the environment by allowing a variety of motility behaviors. DOI: http://dx.doi.org/10.7554/eLife.01402.001 PMID:24347546

  7. Dynamics of single-species population growth: stability or chaos

    SciTech Connect

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

    1981-01-01

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

  8. Population Problems, Teacher's Guide. Environmental Education Unit, Twelfth Grade Sociology.

    ERIC Educational Resources Information Center

    Little Rock School District, AR.

    Human population growth and the implications of increasing population on the well-being of men and nations is examined in this twelfth grade curriculum guide which is part of a series for grades 4 through 12. The primary functions of the unit are to introduce the student to reasons for population growth, results of overextended populations, and…

  9. Heterogeneous expression of apolipoprotein-E by human macrophages

    PubMed Central

    Tedla, Nicodemus; Glaros, Elias N; Brunk, Ulf T; Jessup, Wendy; Garner, Brett

    2004-01-01

    Apolipoprotein-E (apoE) is expressed at high levels by macrophages. In addition to its role in lipid transport, macrophage-derived apoE plays an important role in immunoregulation. Previous studies have identified macrophage subpopulations that differ substantially in their ability to synthesize specific cytokines and enzymes, however, potential heterogeneous macrophage apoE expression has not been studied. Here we examined apoE expression in human THP-1 macrophages and monocyte-derived macrophages (MDM). Using immunocytochemistry and flow cytometry methods we reveal a striking heterogeneity in macrophage apoE expression in both cell types. In phorbol-ester-differentiated THP-1 macrophages, 5% of the cells over-expressed apoE at levels more than 50-fold higher than the rest of the population. ApoE over-expressing THP-1 macrophages contained condensed/fragmented nuclei and increased levels of activated caspase-3 indicating induction of apoptosis. In MDM, 3–5% of the cells also highly over-expressed apoE, up to 50-fold higher than the rest of the population; however, this was not associated with obvious nuclear alterations. The apoE over-expressing MDM were larger, more granular, and more autofluorescent than the majority of cells and they contained numerous vesicle-like structures that appeared to be coated by apoE. Flow cytometry experiments indicated that the apoE over-expressing subpopulation of MDM were positive for CD14, CD11b/Mac-1 and CD68. These observations suggest that specific macrophage subpopulations may be important for apoE-mediated immunoregulation and clearly indicate that subpopulation heterogeneity should be taken into account when investigating macrophage apoE expression. PMID:15500620

  10. Heterogeneity shapes invasion: host size and environment influence susceptibility to a nonnative pathogen.

    PubMed

    Kauffman, Matthew J; Jules, Erik S

    2006-02-01

    Theoretical study of invasion dynamics has suggested that spatial heterogeneity should strongly influence the rate and extent of spreading organisms. However, empirical support for this prediction is scant, and the importance of understanding heterogeneity for real-world systems has remained ambiguous. This study quantified the influence of host and environmental heterogeneity on the dynamics of a 19-year disease invasion by the exotic and fatal pathogen, Phytophthora lateralis, within a stream population of its host tree, Port Orford cedar (Chamaecyparis lawsoniana). Using dendrochronology, we reconstructed the invasion history along a 1350-m length of infected stream, which serves as the only route of pathogen dispersal. Contrary to theoretical predictions, the temporal progression of the disease invasion was not related to a host's downstream spatial position, but instead was determined by two sources of heterogeneity: host size and proximity to the stream channel. These sources of heterogeneity influenced both the epidemic and endemic dynamics of this pathogen invasion. This analysis provides empirical support for the influence of heterogeneity on the invasion dynamics of a commercially important forest pathogen and highlights the need to incorporate such natural variability into both invasion theory and methods aimed at controlling future spread. PMID:16705970

  11. Signal Threshold Adaptation for Vertical Handoff in Heterogeneous Wireless Networks

    E-print Network

    Liang, Ben

    Signal Threshold Adaptation for Vertical Handoff in Heterogeneous Wireless Networks Ahmed H. Zahran. Keywords: heterogeneous wireless networks, seamless integration, vertical handoff, application signal in heterogeneous wireless system Mobility management is a main challenge in the converged network. It ad- dresses

  12. Threshold-Based Media Streaming Optimization for Heterogeneous

    E-print Network

    Sreenan, Cormac J.

    Threshold-Based Media Streaming Optimization for Heterogeneous Wireless Networks Ahmed H. Zahran heterogeneous network. In this paper, we propose a generic practical framework that optimizes media streaming management algorithms and optimization framework. Index Terms--Media streaming algorithm, heterogeneous

  13. Genome-wide meta-analysis identifies multiple novel associations and ethnic heterogeneity of psoriasis susceptibility

    PubMed Central

    Yin, Xianyong; Low, Hui Qi; Wang, Ling; Li, Yonghong; Ellinghaus, Eva; Han, Jiali; Estivill, Xavier; Sun, Liangdan; Zuo, Xianbo; Shen, Changbing; Zhu, Caihong; Zhang, Anping; Sanchez, Fabio; Padyukov, Leonid; Catanese, Joseph J.; Krueger, Gerald G.; Duffin, Kristina Callis; Mucha, Sören; Weichenthal, Michael; Weidinger, Stephan; Lieb, Wolfgang; Foo, Jia Nee; Li, Yi; Sim, Karseng; Liany, Herty; Irwan, Ishak; Teo, Yikying; Theng, Colin T. S.; Gupta, Rashmi; Bowcock, Anne; De Jager, Philip L.; Qureshi, Abrar A.; de Bakker, Paul I. W.; Seielstad, Mark; Liao, Wilson; Ståhle, Mona; Franke, Andre; Zhang, Xuejun; Liu, Jianjun

    2015-01-01

    Psoriasis is a common inflammatory skin disease with complex genetics and different degrees of prevalence across ethnic populations. Here we present the largest trans-ethnic genome-wide meta-analysis (GWMA) of psoriasis in 15,369 cases and 19,517 controls of Caucasian and Chinese ancestries. We identify four novel associations at LOC144817, COG6, RUNX1 and TP63, as well as three novel secondary associations within IFIH1 and IL12B. Fine-mapping analysis of MHC region demonstrates an important role for all three HLA class I genes and a complex and heterogeneous pattern of HLA associations between Caucasian and Chinese populations. Further, trans-ethnic comparison suggests population-specific effect or allelic heterogeneity for 11 loci. These population-specific effects contribute significantly to the ethnic diversity of psoriasis prevalence. This study not only provides novel biological insights into the involvement of immune and keratinocyte development mechanism, but also demonstrates a complex and heterogeneous genetic architecture of psoriasis susceptibility across ethnic populations. PMID:25903422

  14. The roles of competition and environmental heterogeneity in the maintenance of behavioral variation and covariation.

    PubMed

    Dochtermann, Ned A; Jenkins, Stephen H; Swartz, Maryke J; Hargett, Allison C

    2012-06-01

    Many models of selection predict that populations will lose variation in traits that affect fitness. Nonetheless, phenotypic variation is commonly observed in natural populations. We tested the influences of competition and spatial heterogeneity on behavioral variation within and among populations of Merriam's kangaroo rats (Dipodomys merriami) and tested for the differential expression of trait correlations. We found that populations of D. merriami exhibited more aggression at sites with more competition. Contrary to theoretical predictions and empirical results in other systems, the sites with the greatest spatial heterogeneity and highest levels of competition did not exhibit the most behavioral variation among individuals. However, the greatest within-individual behavioral variability in boldness (response to cues of predator presence) was exhibited where spatial heterogeneity was highest. Aggression and boldness of D. merriami were highly repeatable, that is, individuals behaved in a consistent manner over time, and the two behaviors were also highly correlated. Interestingly, the strength of this correlation was greatest where the competitive community was least diverse. These findings add to increasing evidence that natural populations of animals exhibit patterns of behavioral covariance, or personality structure, and suggest that competitive variation may act to erode personality structure. PMID:22834374

  15. Main Screen: students and advisors will use during the advising engagement and is prepopulated with degree plans per major. Sequences plan by terms; term courses populated by degree plans per each major.

    E-print Network

    Barrash, Warren

    1 #12;2 #12;3 #12;4 #12;5 #12;6 #12;7 #12;8 #12;9 #12;10 #12;Main Screen: students and advisors by either the student or advisor Advisor Message: allows advisor to leave message for student on that particular course. Students view only; Advisors: create/edit; Pencil icon: blank message; pencil with note

  16. Contact heterogeneity in deer mice: implications for Sin Nombre virus transmission

    PubMed Central

    Clay, Christine A.; Lehmer, Erin M.; Previtali, Andrea; St. Jeor, Stephen; Dearing, M. Denise

    2009-01-01

    Heterogeneities within disease hosts suggest that not all individuals have the same probability of transmitting disease or becoming infected. This heterogeneity is thought to be due to dissimilarity in susceptibility and exposure among hosts. As such, it has been proposed that many host–pathogen systems follow the general pattern whereby a small fraction of the population accounts for a large fraction of the pathogen transmission. This disparity in transmission dynamics is often referred to as ‘20/80 Rule’, i.e. approximately 20 per cent of the hosts are responsible for 80 per cent of pathogen transmission. We investigated the role of heterogeneity in contact rates among potential hosts of a directly transmitted pathogen by examining Sin Nombre virus (SNV) in deer mice (Peromyscus maniculatus). Using foraging arenas and powder marking, we documented contacts between wild deer mice in Great Basin Desert, central Utah. Our findings demonstrated heterogeneity among deer mice, both in frequency and in duration of contacts with other deer mice. Contact dynamics appear to follow the general pattern that a minority of the population accounts for a majority of the contacts. We found that 20 per cent of individuals in the population were responsible for roughly 80 per cent of the contacts observed. Larger-bodied individuals appear to be the functional group with the greatest SNV transmission potential. Contrary to our predictions, transmission potential was not influenced by breeding condition or sex. PMID:19129136

  17. Single-Cell-Kinetics Approach to Discover Functionally Distinct Subpopulations within Phenotypically Uniform Populations of Cells

    E-print Network

    Krylov, Sergey

    - genesis, carcinogenesis, and tissue regeneration requires the classification of highly heterogeneous cells: tumor-initiating cells (TICs) and bulk tumor cells (BTCs).2 Stem cells can also be roughly classified into two populations: cycling stem cells and dormant stem cells.3 Cell heterogeneity is typically

  18. The Orientation Student Profile Card: Improving the Collection of Student Demographic Information

    ERIC Educational Resources Information Center

    Clapp, Marlene; Young, Michael

    2010-01-01

    Bridgewater State University (BSU) is a public institution that falls under the Carnegie classification of Master's Colleges and Universities. BSU is committed to serving students in the New England region. This student population includes a sizeable number of underrepresented students. BSU is dealing with intense pressure to serve these students

  19. 34 CFR 403.205 - What are the State's responsibilities for members of special populations?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...responsibilities for members of special populations? 403.205 Section 403.205 ...responsibilities for members of special populations? The State board shall— (a...students who are members of special populations and their parents, teachers,...

  20. 34 CFR 403.193 - What are the information requirements regarding special populations?

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...information requirements regarding special populations? 403.193 Section 403.193 ...information requirements regarding special populations? (a)(1) Each local educational...students who are members of special populations and their parents information...