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1

Phenotypically heterogeneous populations in spatially heterogeneous environments  

NASA Astrophysics Data System (ADS)

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

Patra, Pintu; Klumpp, Stefan

2014-03-01

2

PUNCH: Population Characterization of Heterogeneity.  

PubMed

Neuropsychiatric disorders are notoriously heterogeneous in their presentation, which precludes straightforward and objective description of the differences between affected and typical populations that therefore makes finding reliable biomarkers a challenge. This difficulty underlines the need for reliable methods to capture sample characteristics of heterogeneity using a single continuous measure, incorporating the multitude of scores used to describe different aspects of functioning. This study addresses this challenge by proposing a general method of identifying and quantifying the heterogeneity of any clinical population using a severity measure called the PUNCH (Population Characterization of Heterogeneity). PUNCH is a decision level fusion technique to incorporate decisions of various phenotypic scores, while providing interpretable weights for scores. We provide applications of our framework to simulated datasets and to a large sample of youth with Autism Spectrum Disorder (ASD). Next we stratify PUNCH scores in our ASD sample and show how severity moderates findings of group differences in diffusion weighted brain imaging data; more severely affected subgroups of ASD show expanded differences compared to age and gender matched healthy controls. Results demonstrate the ability of our measure in quantifying the underlying heterogeneity of the clinical samples, and suggest its utility in providing researchers with reliable severity assessments incorporating population heterogeneity. PMID:24799135

Tunc, Birkan; Ghanbari, Yasser; Smith, Alex R; Pandey, Juhi; Browne, Aaron; Schultz, Robert T; Verma, Ragini

2014-09-01

3

Estimating Marginal Treatment Effects in Heterogeneous Populations  

E-print Network

Estimating Marginal Treatment Effects in Heterogeneous Populations Robert Moffitt Johns Hopkins in heterogeneous populations. Building upon an insight of Heckman and Vytlacil, the conventional treatment effects model with heterogeneous effects is shown to imply that outcomes are a nonlinear function

Niebur, Ernst

4

Specialization and Bet Hedging in Heterogeneous Populations  

NASA Astrophysics Data System (ADS)

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

Rulands, Steffen; Jahn, David; Frey, Erwin

2014-09-01

5

Eradication of infectious diseases in heterogeneous populations  

SciTech Connect

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.

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

1987-04-01

6

Population dynamics on heterogeneous bacterial substrates  

NASA Astrophysics Data System (ADS)

How species invade new territories and how these range expansions influence the population's genotypes are important questions in the field of population genetics. The majority of work addressing these questions focuses on homogeneous environments. Much less is known about the population dynamics and population genetics when the environmental conditions are heterogeneous in space. To better understand range expansions in two-dimensional heterogeneous environments, we employ a system of bacteria and bacteriophage, the viruses of bacteria. Thereby, the bacteria constitute the environment in which a population of bacteriophages expands. The spread of phage constitutes itself in lysis of bacteria and thus formation of clear regions on bacterial lawns, called plaques. We study the population dynamics and genetics of the expanding page for various patterns of environments.

Mobius, Wolfram; Murray, Andrew W.; Nelson, David R.

2012-02-01

7

Individual histories and selection in heterogeneous populations  

PubMed Central

The strength of selection in populations has traditionally been inferred by measuring changes in bulk population parameters, such as mean reproductive rates. Untangling the effect of selection from other factors, such as specific responses to environmental fluctuations, poses a significant problem both in microbiology and in other fields, including cancer biology and immunology, where selection occurs within phenotypically heterogeneous populations of cells. Using “individual histories”—temporal sequences of all reproduction events and phenotypic changes of individuals and their ancestors—we present an alternative approach to quantifying selection in diverse experimental settings. Selection is viewed as a process that acts on histories, and a measure of selection that employs the distribution of histories is introduced. We apply this measure to phenotypically structured populations in fluctuating environments across different evolutionary regimes. Additionally, we show that reproduction events alone, recorded in the population’s tree of cell divisions, may be sufficient to accurately measure selection. The measure is thus applicable in a wide range of biological systems, from microorganisms—including species for which genetic tools do not yet exist—to cellular populations, such as tumors and stem cells, where detailed temporal data are becoming available. PMID:20616073

Leibler, Stanislas; Kussell, Edo

2010-01-01

8

Specialization and Bet-Hedging in Heterogeneous Populations  

E-print Network

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

Rulands, Steffen; Frey, Erwin

2014-01-01

9

Habitat heterogeneity affects population growth in goshawk Accipiter gentilis  

Microsoft Academic Search

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

Oliver Kruger; Jan Lindstrom

2001-01-01

10

Estimation of colloidal deposition from heterogeneous populations  

Microsoft Academic Search

This paper reports a study of size-heterogeneous colloid filtration in a new bed using different types of colloids under different conditions of flow and solution chemistry. Depth-wise variation of the particle-size-distributions fi(x), and the total liquid-phase colloid concentration, C(x) are measured which are used to estimate the depth-wise variation of the liquid-phase concentration for each distinct section of the heterogeneous

Jaideep Chatterjee; Shajahan Abdulkareem; Santosh Kumar Gupta

2010-01-01

11

Spreading dynamics on heterogeneous populations: Multitype network approach Alexei Vazquez  

E-print Network

. In the case of sexually transmitted diseases the reproductive num- ber is proportional to the rate of sexual diseases in heterogeneous populations. The population structure is de- scribed by a contact graph where vertices represent agents and edges represent disease transmission channels among them. The population

Vazquez, Alexei

12

Resource heterogeneity and ungulate population dynamics  

Microsoft Academic Search

It has been suggested that climatic variation has the effect on the dynamics of arid and semi-arid grazing systems of reducing animal numbers below the level at which they have much impact on vegetation or soils, and that spatial heterogeneity in resource availability serves to buffer herbivores against climatic variation. Modelling was used to test these hypotheses and to examine

A. W. Illius; T. G. O'Connor

2000-01-01

13

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 ...

14

Heterogeneous Heterozygosities in Mus musculus Populations  

Microsoft Academic Search

Both chance and adaptation have effects in determining the genetical constitution of local populations of any organism, but opinions differ widely over their relative importance. This study describes the frequencies of electrophoretically detected alleles at 22 loci in 1538 house mice (Mus musculus L.) from 27 population samples collected from the Faroe, Shetland and Orkney archipelagoes; the mainland of Great

R. J. Berry; Josephine Peters

1977-01-01

15

Student Instructions Population Dynamics  

E-print Network

to assume certain requirements for both species' survival and reproduction. In this simulation, we will use as population dynamics. A population of bunnies, for instance, may increase due to reproduction or migration to survive and reproduce. This process will be repeated for 20 rounds, and in each round, a varying number

Spakowitz, Andrew J.

16

Item Response Theory Scaling with Heterogeneous Populations.  

ERIC Educational Resources Information Center

Tools used in scaling proficiency scores from the Second International Assessment of Educational Progress (IAEP) are described. The second IAEP study, conducted in 1991, was an international comparative study of the mathematics and science skills of samples of 9- and 13-year-old students from 20 countries. This paper focuses on part of the second…

Blais, Jean-Guy

17

Mosquito Population Regulation and Larval Source Management in Heterogeneous Environments  

PubMed Central

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

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

2013-01-01

18

Low birth weight in a heterogenic population.  

PubMed

In order to elucidate some of the factors which influence the low birth weight rate, 22,815 deliveries were studied. It is already known that low birth weight (LBW) underlies the majority of infant deaths. It is also associated with an increased risk of permanent disability such as cerebral palsy, learning difficulties, and mental retardation of various degrees in survivors. In modern society these problems require major resources from the health budget. The Israeli population is composed of Jews and non-Jews, who differ not only in their religion but also in their customs. Most of the Jews are immigrants from many parts of the world who still retain many of the habits, customs and lifestyles of the societies they had lived in for many generations. We evaluated the LBW rate in these different groups. Jews and non-Jews have similar rates of LBW and similar mean birth weights. Other factors such as maternal age, parity, and hypertensive disorders of pregnancy showed some statistically significant differences. LBW rates increase from 6.9% in the babies of women aged 24-40 years to 8.5% in those less than 24 years, and 9.5% in those over 40. The risk of LBW was increased in primiparae to 10%. The highest rates were found in babies of mothers with hypertension. Pregnancy induced hypertension is associated with a LBW rate of 15.6% and chronic hypertension with a rate of 23%. Moderate and severe preeclampsia are important risk factors since they increase the rate to 15% and 47.1%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2746441

Mor-Yosef, S; Ezra, Y; Samueloff, A; Moussa, F; Schenker, J G

1989-01-01

19

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

ERIC Educational Resources Information Center

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…

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

2012-01-01

20

Consequences of dispersal heterogeneity for population spread and persistence.  

PubMed

Dispersal heterogeneity is increasingly being observed in ecological populations and has long been suspected as an explanation for observations of non-Gaussian dispersal. Recent empirical and theoretical studies have begun to confirm this. Using an integro-difference model, we allow an individual's diffusivity to be drawn from a trait distribution and derive a general relationship between the dispersal kernel's moments and those of the underlying heterogeneous trait distribution. We show that dispersal heterogeneity causes dispersal kernels to appear leptokurtic, increases the population's spread rate, and lowers the critical reproductive rate required for persistence in the face of advection. Wavespeed has been shown previously to be determined largely by the form of the dispersal kernel tail. We qualify this by showing that when reproduction is low, the precise shape of the tail is less important than the first few dispersal moments such as variance and kurtosis. If the reproductive rate is large, a dispersal kernel's asymptotic tail has a greater influence over wavespeed, implying that estimating the prevalence of traits which correlate with long-range dispersal is critical. The presence of multiple dispersal behaviors has previously been characterized in terms of long-range versus short-range dispersal, and it has been found that rare long-range dispersal essentially determines wavespeed. We discuss this finding and place it within a general context of dispersal heterogeneity showing that the dispersal behavior with the highest average dispersal distance does not always determine wavespeed. PMID:25348060

Stover, Joseph P; Kendall, Bruce E; Nisbet, Roger M

2014-11-01

21

Animal movements and population dynamics in heterogeneous landscapes  

Microsoft Academic Search

Organisms respond to environmental heterogeneity at different scales and in different ways. These differences are consequences\\u000a of how the movement characteristics of animals—their movement rates, directionality, turning frequencies, and turning angles—interact\\u000a with patch and boundary features in landscape mosaics. The interactions of movement patterns with landscape features in turn\\u000a produce spatial patterns in individual space-use, population dynamics and dispersion, gene

A. R. Johnsonl; J. A. Wiens; B. T. Milne; T. O. Crist

1992-01-01

22

The Heterogeneous HLA Genetic Makeup of the Swiss Population  

PubMed Central

This study aims at investigating the HLA molecular variation across Switzerland in order to determine possible regional differences, which would be highly relevant to several purposes: optimizing donor recruitment strategies in hematopoietic stem cell transplantation (HSCT), providing reliable reference data in HLA and disease association studies, and understanding the population genetic background(s) of this culturally heterogeneous country. HLA molecular data of more than 20,000 HSCT donors from 9–13 recruitment centers of the whole country were analyzed. Allele and haplotype frequencies were estimated by using new computer tools adapted to the heterogeneity and ambiguity of the data. Non-parametric and resampling statistical tests were performed to assess Hardy-Weinberg equilibrium, selective neutrality and linkage disequilibrium among different loci, both in each recruitment center and in the whole national registry. Genetic variation was explored through genetic distance and hierarchical analysis of variance taking into account both geographic and linguistic subdivisions in Switzerland. The results indicate a heterogeneous genetic makeup of the Swiss population: first, allele frequencies estimated on the whole national registry strongly deviate from Hardy-Weinberg equilibrium, by contrast with the results obtained for individual centers; second, a pronounced differentiation is observed for Ticino, Graubünden, and, to a lesser extent, Wallis, suggesting that the Alps represent(ed) a barrier to gene flow; finally, although cultural (linguistic) boundaries do not represent a main genetic differentiation factor in Switzerland, the genetic relatedness between population from south-eastern Switzerland and Italy agrees with historical and linguistic data. Overall, this study justifies the maintenance of a decentralized donor recruitment structure in Switzerland allowing increasing the genetic diversity of the national—and hence global—donor registry. It also indicates that HLA data of local donor recruitment centers can be used as reference data in both epidemiological and population genetic studies focusing on the genetic history of present European populations. PMID:22848484

Buhler, Stéphane; Nunes, José Manuel; Nicoloso, Grazia; Tiercy, Jean-Marie; Sanchez-Mazas, Alicia

2012-01-01

23

Modelling Lipid Competition Dynamics in Heterogeneous Protocell Populations  

E-print Network

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.

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

2014-01-30

24

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

PubMed

Populations of genetically uniform microorganisms exhibit phenotypic heterogeneity, where individual cells have varying phenotypes. Such phenotypes include fitness-determining traits. Phenotypic heterogeneity has been linked to increased population-level fitness in laboratory studies, but its adaptive significance for wild microorganisms in the natural environment is unknown. Here, we addressed this by testing heterogeneity in yeast isolates from diverse environmental sites, each polluted with a different principal contaminant, as well as from corresponding control locations. We found that cell-to-cell heterogeneity (in resistance to the appropriate principal pollutant) was prevalent in the wild yeast isolates. Moreover, isolates with the highest heterogeneity were consistently observed in the polluted environments, indicating that heterogeneity is positively related to survival in adverse conditions in the wild. This relationship with survival was stronger than for the property of mean resistance (IC(50)) of an isolate. Therefore, heterogeneity could be the major determinant of microbial survival in adverse conditions. Indeed, growth assays indicated that isolates with high heterogeneities had a significant competitive advantage during stress. Analysis of yeasts after cultivation for ??500 generations additionally showed that high heterogeneity evolved as a heritable trait during stress. The results showed that environmental stress selects for wild microorganisms with high levels of phenotypic heterogeneity. PMID:24000788

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

2014-06-01

25

Multiple Mutations in Heterogeneous Miltefosine-Resistant Leishmania major Population as Determined  

E-print Network

that resistance can be highly heterogeneous at the population level with individual clones derived from 6(2): e1512. doi:10.1371/journal.pntd.0001512 Editor: Peter J. Myler, SBRI, United States of America

Arnold, Jonathan

26

Characterizing the effect of population heterogeneity on evolutionary dynamics on complex networks  

NASA Astrophysics Data System (ADS)

Recently, the impact of network structure on evolutionary dynamics has been at the center of attention when studying the evolutionary process of structured populations. This paper aims at finding out the key structural feature of network to capture its impact on evolutionary dynamics. To this end, a novel concept called heat heterogeneity is introduced to characterize the structural heterogeneity of network, and the correlation between heat heterogeneity of structure and outcome of evolutionary dynamics is further investigated on various networks. It is found that the heat heterogeneity mainly determines the impact of network structure on evolutionary dynamics on complex networks. In detail, the heat heterogeneity readjusts the selection effect on evolutionary dynamics. Networks with high heat heterogeneity amplify the selection effect on the birth-death process and suppress the selection effect on the death-birth process. Based on the above results, an effective algorithm is proposed to generate selection adjusters with desired size and average degree.

Tan, Shaolin; Lü, Jinhu

2014-05-01

27

A Stabilization Group Approach for Heterogeneous Populations of Trauma Clients  

PubMed Central

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

Stige, Signe Hjelen

2011-01-01

28

Identification of heterogeneous cell populations in normal human intervertebral disc.  

PubMed Central

There is clear evidence that tissues related to the intervertebral disc, such as articular cartilage, contain several phenotypically different chondrocytic cell populations. Histological data for the disc suggest the same may be true for the annulus fibrosus and nucleus pulposus, but this has not been shown directly. For the first time, cells from adult human nondegenerative nucleus pulposus and annulus fibrosus were recovered after enzymatic digestion and maintained in an alginate bead culture system for up to 6 wk. The cells remained viable and produced matrix, but did not divide. Cultured cells were stained simultaneously for the presence of chondroitin sulphate and keratan sulphate, or types I and II collagen. The majority of the cells from both the annulus fibrosus and the nucleus pulposus produced both keratan sulphate and chondroitin sulphate (> 60%), a few only detectable levels of one or the other, but a significant population produced neither. This is an indication of a population of cells with a nonchondrocytic phenotype. In nondegenerative discs, the majority of the annulus fibrosus cells produced both types I and II collagen but the majority of nucleus pulposus cells produced only type II collagen. These observations are consistent with the presence of at least 2 phenotypically stable populations of cells in the adult human intervertebral disc and with the view that the phenotype of the major population of the annulus is different from that of the nucleus. Images Fig. 1 Fig. 2 PMID:7544335

Chelberg, M K; Banks, G M; Geiger, D F; Oegema, T R

1995-01-01

29

Uncovering epidemiological dynamics in heterogeneous host populations using phylogenetic methods  

PubMed Central

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

Stadler, Tanja; Bonhoeffer, Sebastian

2013-01-01

30

Slow epidemic extinction in populations with heterogeneous infection rates  

NASA Astrophysics Data System (ADS)

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.

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

2013-08-01

31

Phase II cancer clinical trials with heterogeneous patient populations.  

PubMed

The patient population for a Phase II trial often consists of multiple subgroups in terms of risk level. In this case, a popular design approach is to specify the response rate and the prevalence of each subgroup, to calculate the response rate of the whole population by the weighted average of the response rates across subgroups, and to choose a standard Phase II design such as Simon's optimal or minimax design to test the response rate for the whole population. In this case, although the prevalence of each subgroup is accurately specified, the observed prevalence among the accrued patients to the study may be quite different from the expected one because of the small sample size, which is typical in most Phase II trials. The fixed rejection value for a chosen standard Phase II design may be either too conservative (i.e., increasing the false rejection probability of the experimental therapy) if the trial accrues more high-risk patients than expected, or too anti-conservative (i.e., increasing the false acceptance probability of the experimental therapy) if the trial accrues more low-risk patients than expected. We can avoid such problems by adjusting the rejection values, depending on the observed prevalence from the trial. In this paper, we investigate the performance of the flexible designs compared with the standard design with fixed rejection values under various settings. PMID:22251176

Jung, Sin-Ho; Chang, Myron N; Kang, Sun J

2012-01-01

32

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

PubMed Central

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

Stamatakis, Michail; Zygourakis, Kyriacos

2010-01-01

33

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

Microsoft Academic Search

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

John Boulanger; Gordon Stenhouse; Robin Munro

2004-01-01

34

Modelling lipid competition dynamics in heterogeneous protocell populations.  

PubMed

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

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

2014-01-01

35

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

PubMed

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

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

2014-10-14

36

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

PubMed Central

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

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

2008-01-01

37

Population Heterogeneity and State Dependence: State of the Evidence and Directions for Future Research  

Microsoft Academic Search

Criminological research has consistently uncovered a positive correlationbetween past and current criminal behavior. Continuity in offending overtime can be attributed to at least two processes—populationheterogeneity and state dependence. A population heterogeneity processattributes stability in offending over time to differences in ananti-social characteristic (self-control, impulsivity, psychopathicpersonality) across persons that is established early in life andtime-stable thereafter. An implication of a population

Daniel Nagin; Raymond Paternoster

2000-01-01

38

Coverage-adjusted estimators for mark-recapture in heterogeneous populations  

Microsoft Academic Search

Consideration of coverage yields a new class of estimators of population size for the standard mark-recapture model which permits heterogeneity of capture probabilities. Real data and simulation studies are used to assess these coverage-adjusted estimators. The simulations highlight the need for estimators that perform well for a wide range of values of the mean and coefficient of variation of the

J. Ashbridge; I. B. J. Goudie

2000-01-01

39

Muscle satellite cell heterogeneity: in vitro and in vivo evidences for populations that fuse differently  

Microsoft Academic Search

During development, muscle growth results from the proliferation of satellite cells (SC) and their fusion with fibers. Several studies revealed heterogeneity of SC population notably based on the proliferation rate. Here, we examined the SC characteristics of turkey skeletal muscles in terms of proliferation and more specifically fusion, to define if the ability of these cells to fuse may represent

Karl Rouger; Mickael Brault; Nathalie Daval; Isabelle Leroux; Lydie Guigand; Julie Lesoeur; Bernard Fernandez; Yan Cherel

2004-01-01

40

Behavioral/Systems/Cognitive Heterogenous Population Coding of a Short-Term Memory  

E-print Network

Behavioral/Systems/Cognitive Heterogenous Population Coding of a Short-Term Memory and Decision in short-term memory tasks (Fuster and Alexander, 1971; Funahashi et al., 1989; Miller et al., 1991), en require the rapid storage of information in short-term memory followed by a computa- tion in which

Miller, Paul

41

Teachers’ Images of Gifted Students and the roles assigned to them in Heterogeneous Mathematics Classes  

Microsoft Academic Search

\\u000a The present study discusses the opportunities that are available to students with high mathematical abilities in school mathematics.\\u000a Our focus is on teaching mathematically able students (MAS) in heterogeneous mathematics classrooms. Based on individual interviews\\u000a with teachers, we describe images that teachers hold of mathematically gifted students. By analyzing multiple classroom observations,\\u000a we characterized the roles that the teachers assign

Roza Leikin; Ora Stanger

42

Physiological heterogeneities in microbial populations and implications for physical stress tolerance  

PubMed Central

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

2012-01-01

43

Using Populism to Engage Students in Critical Thinking  

ERIC Educational Resources Information Center

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…

Peiser, Andrew

2013-01-01

44

The scale of demographic heterogeneity in a population of Peromyscus leucopus  

Microsoft Academic Search

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

D. T. Krohne; A. B. Burgin

1990-01-01

45

Analysis of fluorescent reporters indicates heterogeneity in glucose uptake and utilization in clonal bacterial populations  

PubMed Central

Background In this study, we aimed at investigating heterogeneity in the expression of metabolic genes in clonal populations of Escherichia coli growing on glucose as the sole carbon source. Different metabolic phenotypes can arise in these clonal populations through variation in the expression of glucose transporters and metabolic enzymes. First, we focused on the glucose transporters PtsG and MglBAC to analyze the diversity of glucose uptake strategies. Second, we analyzed phenotypic variation in the expression of genes involved in gluconeogenesis and acetate scavenging (as acetate is formed and excreted during bacterial growth on glucose), which can reveal, for instance, phenotypic subpopulations that cross-feed through the exchange of acetate. In these experiments, E. coli MG1655 strains containing different transcriptional GFP reporters were grown in chemostats and reporter expression was measured with flow cytometry. Results Our results suggest heterogeneous expression of metabolic genes in bacterial clonal populations grown in glucose environments. The two glucose transport systems exhibited different level of heterogeneity. The majority of the bacterial cells expressed the reporters for both glucose transporters MglBAC and PtsG and a small fraction of cells only expressed the reporter for Mgl. At a low dilution rate, signals from transcriptional reporters for acetyl-CoA synthetase Acs and phosphoenolpyruvate carboxykinase Pck indicated that almost all cells expressed the genes that are part of acetate utilization and the gluconeogenesis pathway, respectively. Possible co-existence of two phenotypic subpopulations differing in acs expression occurred at the threshold of the switch to overflow metabolism. The overflow metabolism results in the production of acetate and has been previously reported to occur at intermediate dilution rates in chemostats with high concentration of glucose in the feed. Conclusions Analysis of the heterogeneous expression of reporters for genes involved in glucose and acetate metabolism raises new question whether different metabolic phenotypes are expressed in clonal populations growing in continuous cultures fed on glucose as the initially sole carbon source. PMID:24238347

2013-01-01

46

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

PubMed Central

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

2014-01-01

47

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

PubMed Central

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

Temunovic, Martina; Franjic, Jozo; Satovic, Zlatko; Grgurev, Marin; Frascaria-Lacoste, Nathalie; Fernandez-Manjarres, Juan F.

2012-01-01

48

Restructuring Laboratory Worksheets for Junior High School Biology Students in the Heterogeneous Classroom.  

ERIC Educational Resources Information Center

Presents samples of educational material adapted for laboratory use on the subject of the pH scale, dilution skills, and their relevance to biology. The experiments were developed for use in both ninth-grade heterogeneous and tracked classes in biology. Students were assessed for academic achievement in relation to their operational reasoning…

Witenoff, Shalamit; Lazarowitz, Reuven

1993-01-01

49

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

ERIC Educational Resources Information Center

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…

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

2014-01-01

50

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

PubMed

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

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

2013-09-01

51

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

PubMed Central

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

L'Herault, Vincent; Franke, Alastair; Lecomte, Nicolas; Alogut, Adam; Bety, Joel

2013-01-01

52

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

E-print Network

of interacting populations of heterogeneous oscillators Ernest Barreto,1,* Brian Hunt,2 Edward Ott,3 and Paul So1 oscillators in which the set of oscillators is composed of several distinct populations. The oscillators, and each population has its own such distribution. The coupling among the oscillators is global, however

Barreto, Ernest

53

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

SciTech Connect

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

Ormiston, B.G.

1980-11-01

54

Policy options for alcohol price regulation: the importance of modelling population heterogeneity.  

PubMed

Context and aims Internationally, the repertoire of alcohol pricing policies has expanded to include targeted taxation, inflation-linked taxation, taxation based on alcohol-by-volume (ABV), minimum pricing policies (general or targeted), bans of below-cost selling and restricting price-based promotions. Policy makers clearly need to consider how options compare in reducing harms at the population level, but are also required to demonstrate proportionality of their actions, which necessitates a detailed understanding of policy effects on different population subgroups. This paper presents selected findings from a policy appraisal for the UK government and discusses the importance of accounting for population heterogeneity in such analyses. Method We have built a causal, deterministic, epidemiological model which takes account of differential preferences by population subgroups defined by age, gender and level of drinking (moderate, hazardous, harmful). We consider purchasing preferences in terms of the types and volumes of alcoholic beverages, prices paid and the balance between bars, clubs and restaurants as opposed to supermarkets and off-licenses. Results Age, sex and level of drinking fundamentally affect beverage preferences, drinking location, prices paid, price sensitivity and tendency to substitute for other beverage types. Pricing policies vary in their impact on different product types, price points and venues, thus having distinctly different effects on subgroups. Because population subgroups also have substantially different risk profiles for harms, policies are differentially effective in reducing health, crime, work-place absence and unemployment harms. Conclusion Policy appraisals must account for population heterogeneity and complexity if resulting interventions are to be well considered, proportionate, effective and cost-effective. PMID:19839965

Meier, Petra Sylvia; Purshouse, Robin; Brennan, Alan

2010-03-01

55

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

PubMed Central

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

2014-01-01

56

High school students' understanding and problem solving in population genetics  

NASA Astrophysics Data System (ADS)

This study is an investigation of student understanding of population genetics and how students developed, used and revised conceptual models to solve problems. The students in this study participated in three rounds of problem solving. The first round involved the use of a population genetics model to predict the number of carriers in a population. The second round required them to revise their model of simple dominance population genetics to make inferences about populations containing three phenotype variations. The third round of problem solving required the students to revise their model of population genetics to explain anomalous data where the proportions of males and females with a trait varied significantly. As the students solved problems, they were involved in basic scientific processes as they observed population phenomena, constructed explanatory models to explain the data they observed, and attempted to persuade their peers as to the adequacy of their models. In this study, the students produced new knowledge about the genetics of a trait in a population through the revision and use of explanatory population genetics models using reasoning that was similar to what scientists do. The students learned, used and revised a model of Hardy-Weinberg equilibrium to generate and test hypotheses about the genetics of phenotypes given only population data. Students were also interviewed prior to and following instruction. This study suggests that a commonly held intuitive belief about the predominance of a dominant variation in populations is resistant to change, despite instruction and interferes with a student's ability to understand Hardy-Weinberg equilibrium and microevolution.

Soderberg, Patti D.

57

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

PubMed

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

Casper, B B; Cahill, J F

1998-12-01

58

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

PubMed Central

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

Wu, Jincheng; Tzanakakis, Emmanuel S.

2014-01-01

59

Ecological Complexity in a Coffee Agroecosystem: Spatial Heterogeneity, Population Persistence and Biological Control  

PubMed Central

Background Spatial heterogeneity is essential for the persistence of many inherently unstable systems such as predator-prey and parasitoid-host interactions. Since biological interactions themselves can create heterogeneity in space, the heterogeneity necessary for the persistence of an unstable system could be the result of local interactions involving elements of the unstable system itself. Methodology/Principal Findings Here we report on a predatory ladybird beetle whose natural history suggests that the beetle requires the patchy distribution of the mutualism between its prey, the green coffee scale, and the arboreal ant, Azteca instabilis. Based on known ecological interactions and the natural history of the system, we constructed a spatially-explicit model and showed that the clustered spatial pattern of ant nests facilitates the persistence of the beetle populations. Furthermore, we show that the dynamics of the beetle consuming the scale insects can cause the clustered distribution of the mutualistic ants in the first place. Conclusions/Significance From a theoretical point of view, our model represents a novel situation in which a predator indirectly causes a spatial pattern of an organism other than its prey, and in doing so facilitates its own persistence. From a practical point of view, it is noteworthy that one of the elements in the system is a persistent pest of coffee, an important world commodity. This pest, we argue, is kept within limits of control through a complex web of ecological interactions that involves the emergent spatial pattern. PMID:23029061

Liere, Heidi; Jackson, Doug; Vandermeer, John

2012-01-01

60

The Malthusian parameter and R0 for heterogeneous populations in periodic environments.  

PubMed

Since the classical stable population theory in demography by Sharpe and Lotka, the sign relation sign(?0)=sign(R0-1) between the basic reproduction number R0 and the Malthusian parameter (the intrinsic rate of natural increase) ?0 has played a central role in population theory and its applications, because it connects individual's average reproductivity described by life cycle parameters to growth character of the whole population. Since R0 is originally defined for linear population evolution process in a constant environment, it is an important extension if we could formulate the same kind of threshold principle for population growth in time-heterogeneous environments. Since the mid-1990s, several authors proposed some ideas to extend the definition of R0 so that it can be applied to population dynamics in periodic environments. In particular, the definition of R0 in a periodic environment by Bacaer and Guernaoui (J. Math. Biol. 53, 2006) is most important, because their definition of R0 in a periodic environment can be interpreted as the asymptotic per generation growth rate, so from the generational point of view, it can be seen as a direct extension of the most successful definition of R0 in a constant environment by Diekmann, Heesterbeek and Metz ( J. Math. Biol. 28, 1990). In this paper, we propose a new approach to establish the sign relation between R0 and the Malthusian parameter ?0 for linear structured population dynamics in a periodic environment. Our arguments depend on the uniform primitivity of positive evolutionary system, which leads the weak ergodicity and the existence of exponential solution in periodic environments. For typical finite and infinite dimensional linear population models, we prove that a positive exponential solution exists and the sign relation holds between the Malthusian parameter, which is defined as the exponent of the exponential solution, and R0 given by the spectral radius of the next generation operator by Bacaer and Guernaoui's definition. PMID:22901067

Inaba, Hisashi

2012-04-01

61

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

PubMed

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

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

2014-01-01

62

Impact of Roles Assignation on Heterogeneous Populations in Evolutionary Dictator Game  

PubMed Central

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

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

2014-01-01

63

Heterogeneity of uidA gene in environmental Escherichia coli populations.  

PubMed

Previous studies have shown that Escherichia coli can be isolated from non-polluted rivers and from bromeliad axilae in pristine areas of tropical rain forests. Finding E. coli in pristine environments is unusual because this bacterium is thought to only survive in the gut of warm-blooded animals and thus its presence should indicate recent fecal contamination. The aims of this study were 1) to determine if E. coli is part of the native soil microbiota in tropical rain forests and 2) to determine if genetic heterogeneity exists among E. coil populations. High concentrations of total coliforms (10(4)-10(5) cells per 10 g of soil dry weight) and low concentrations of thermotolerant coliforms (10(1)-10(2) cells per 10 g dry soil, the majority of these were found to be E. coli) were detected. PCR using uidA-specific primers was done on DNA purified from E. coli isolates and the resulting amplicons analysed by denaturing-gradient gel electrophoresis (DGGE). Out of several hundred isolates, mixtures of nine different amplicons were consistently observed. The different patterns of DGGE observed indicate that the E. coli populations in these pristine soils are genetically heterogeneous. Fecal and environmental E. coli isolates were also analysed by pulsed-field gel electrophoresis (PFGE) which showed high DNA sequence variation among the E coli isolates. Because of these differences in the genomes, PFGE did not allow grouping of environmental versus human isolates of E. coli when compared side to side. The apparent genetic polymorphisms, as a result of genetic heterogeneity, observed in isolates from the same pristine site indicate that source tracking may be difficult to carry out using E. coli as the target organism. PMID:16209033

Lasalde, Clarivel; Rodriguez, Roberto; Toranzos, Gary A; Smith, Henry H

2005-09-01

64

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

PubMed Central

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

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

65

Forms of self-concept in gifted high school students enrolled in heterogeneous classes  

Microsoft Academic Search

Prior research has been devoted to understanding how to facilitate the integration of gifted young people (Intelligence Quotient,\\u000a ?130) into classroom settings. This study investigated a typology of self-concept in gifted French high school students. Eighty-four\\u000a participants, between the ages of 13 and 18 (mean age, 15.5; SD, 1.04), enrolled in heterogeneous classes completed the Genèse\\u000a des Perceptions de Soi

Aude Villatte; Mandarine Hugon; Myriam de Léonardis

66

Determining School Population Using Multiple Student Driven Methods  

NSDL National Science Digital Library

This activity is an introduction to population sampling techniques. Students' will identify weaknesses and strengths of a variety of techniques and determine the best applications of the various methods identified.

67

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

PubMed Central

Viroids are small circular single-stranded infectious RNAs characterized by a relatively high mutation level. Knowledge of their sequence heterogeneity remains largely elusive and previous studies, using Sanger sequencing, were based on a limited number of sequences. In an attempt to address sequence 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-inoculation, full-length circular conformers of PLMVd were isolated and deep-sequenced. We devised an original approach to the bioinformatics refinement of our sequence libraries involving important phenotypic data, based on the systematic analysis of hammerhead self-cleavage activity. Two distinct libraries yielded a total of 3,939 different PLMVd variants. Sequence variants exhibiting up to ?17% of mutations relative to the inoculated viroid were retrieved, clearly illustrating the high level of divergence dynamics within a unique population. While we initially assumed that most positions of the viroid sequence would mutate, we were surprised to discover that ?50% of positions remained perfectly conserved, including several small stretches as well as a small motif reminiscent of a GNRA tetraloop which are the result of various selective pressures. Using a hierarchical clustering algorithm, the different variants harvested were subdivided into 7 clusters. We found that most sequences contained an average of 4.6 to 6.4 mutations compared to the variant used to initially inoculate the plant. Interestingly, it was possible to reconstitute and compare the sequence evolution of each of these clusters. In doing so, we identified several key mutations. This study provides a reliable pipeline for the treatment of viroid deep-sequencing. It also sheds new light on the extent of sequence variation that a viroid population can sustain, and which may give rise to a quasispecies. PMID:24498066

Wang, Shengrui; Najmanovich, Rafael J.; Perreault, Jean-Pierre

2014-01-01

68

Understanding Sleep Disorders in a College Student Population.  

ERIC Educational Resources Information Center

College students' sleep habits are changing dramatically, and related sleep problems are increasing. Reviews the current literature on sleep problems, focusing on the college student population. The unique challenges of college settings are discussed as they apply to understanding sleep problems, and suggestions are made for professionals who work…

Jensen, Dallas R.

2003-01-01

69

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

PubMed Central

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

2013-01-01

70

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

PubMed Central

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

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

2012-01-01

71

Heterogeneity in genetic diversity among non-coding loci fails to fit neutral coalescent models of population history.  

PubMed

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

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

2012-01-01

72

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

PubMed

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

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

2014-08-30

73

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

PubMed Central

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

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

2014-01-01

74

Unsupervised segmentation, clustering, and groupwise registration of heterogeneous populations of brain MR images.  

PubMed

Population analysis of brain morphology from magnetic resonance images contributes to the study and understanding of neurological diseases. Such analysis typically involves segmentation of a large set of images and comparisons of these segmentations between relevant subgroups of images (e.g., "normal" versus "diseased"). The images of each subgroup are usually selected in advance in a supervised way based on clinical knowledge. Their segmentations are typically guided by one or more available atlases, assumed to be suitable for the images at hand. We present a data-driven probabilistic framework that simultaneously performs atlas-guided segmentation of a heterogeneous set of brain MR images and clusters the images in homogeneous subgroups, while constructing separate probabilistic atlases for each cluster to guide the segmentation. The main benefits of integrating segmentation, clustering and atlas construction in a single framework are that: 1) our method can handle images of a heterogeneous group of subjects and automatically identifies homogeneous subgroups in an unsupervised way with minimal prior knowledge, 2) the subgroups are formed by automatical detection of the relevant morphological features based on the segmentation, 3) the atlases used by our method are constructed from the images themselves and optimally adapted for guiding the segmentation of each subgroup, and 4) the probabilistic atlases represent the morphological pattern that is specific for each subgroup and expose the groupwise differences between different subgroups. We demonstrate the feasibility of the proposed framework and evaluate its performance with respect to image segmentation, clustering and atlas construction on simulated and real data sets including the publicly available BrainWeb and ADNI data. It is shown that combined segmentation and atlas construction leads to improved segmentation accuracy. Furthermore, it is demonstrated that the clusters generated by our unsupervised framework largely coincide with the clinically determined subgroups in case of disease-specific differences in brain morphology and that the differences between the cluster-specific atlases are in agreement with the expected disease-specific patterns, indicating that our method is capable of detecting the different modes in a population. Our method can thus be seen as a comprehensive image-driven population analysis framework that can contribute to the detection of novel subgroups and distinctive image features, potentially leading to new insights in the brain development and disease. PMID:23797244

Ribbens, Annemie; Hermans, Jeroen; Maes, Frederik; Vandermeulen, Dirk; Suetens, Paul

2014-02-01

75

Student understanding in mechanics: A large population survey  

NSDL National Science Digital Library

There has recently been a considerable growth in research probing student understanding in mechanics. Questions based on four such research probes were included in the end-of-high-school physics examination undertaken by some 5500 students. The results obtained give an indication of the extent to which various interpretations of some physical situations are held in a whole population. The possibilities of using research probes as a basis for assessment questions are also illustrated.

Gunstone, Richard

2005-10-20

76

Single-Cell Behavior and Population Heterogeneity: Solving an Inverse Problem to Compute the Intrinsic Physiological State Functions  

PubMed Central

The dynamics of isogenic cell populations can be described by cell population balance models that account for phenotypic heterogeneity. To utilize the predictive power of these models, however, we must know the rates of single-cell reaction and division and the bivariate partition probability density function. These three intrinsic physiological state (IPS) functions can be obtained by solving an inverse problem that requires knowledge of the phenotypic distributions for the overall cell population, the dividing cell subpopulation and the newborn cell subpopulation. We present here a robust computational procedure that can accurately estimate the IPS functions for heterogeneous cell populations. A detailed parametric analysis shows how the accuracy of the inverse solution is affected by discretization parameters, the type of non-parametric estimators used, the qualitative characteristics of phenotypic distributions and the unknown partitioning probability density function. The effect of finite sampling and measurement errors on the accuracy of the recovered IPS functions is also assessed. Finally, we apply the procedure to estimate the IPS functions of an E. coli population carrying an IPTG-inducible genetic toggle network. This study completes the development of an integrated experimental and computational framework that can become a powerful tool for quantifying single-cell behavior using measurements from heterogeneous cell populations. PMID:21930163

Spetsieris, Konstantinos; Zygourakis, Kyriacos

2011-01-01

77

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

PubMed

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

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

2005-01-01

78

Culture history and population heterogeneity as determinants of bacterial adaptation: the adaptomics of a single environmental transition.  

PubMed

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

Ryall, Ben; Eydallin, Gustavo; Ferenci, Thomas

2012-09-01

79

Predicting NCLEX-RN success in a diverse student population.  

PubMed

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

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

2011-05-01

80

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

PubMed Central

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

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

2014-01-01

81

Impact of spatial heterogeneity of neighborhoods on long-term population dynamics of sugar maple ( Acer saccharum)  

Microsoft Academic Search

We evaluated the impact of spatial heterogeneity resulting from disturbance and neighbor density on long-term population dynamics of sugar maple (Acer saccharum) in Brownfield Woods, an old-growth forest remnant in central Illinois. All trees with diameter at breast height (DBH)?7.6cm in eight discrete quadrats (48m×68m) and one large quadrat (216m×260m) were mapped in Brownfield Woods in 1951, 1988, and 2001.

Yiching Lin; Carol K. Augspurger

2008-01-01

82

Mindfulness-based stress reduction and health-related quality of life in a heterogeneous patient population  

Microsoft Academic Search

This study examined the effects of mindfulness-based stress reduction (MBSR) on health-related quality of life and physical and psychological symptomatology in a heterogeneous patient population. Patients (n=136) participated in an 8-week MBSR program and were required to practice 20 min of meditation daily. Pre- and post-intervention data were collected by using the Short-Form Health Survey (SF-36), Medical Symptom Checklist (MSCL)

Diane K Reibel; Jeffrey M Greeson; George C Brainard; Steven Rosenzweig

2001-01-01

83

Using heterogeneity of the patient-derived xenograft model to identify the chemoresistant population in ovarian cancer  

PubMed Central

A cornerstone of preclinical cancer research has been the use of clonal cell lines. However, this resource has underperformed in its ability to effectively identify novel therapeutics and evaluate the heterogeneity in a patient's tumor. The patient-derived xenograft (PDX) model retains the heterogeneity of patient tumors, allowing a means to not only examine efficacy of a therapy, but also basic tenets of cancer biology in response to treatment. Herein we describe the development and characterization of an ovarian-PDX model in order to study the development of chemoresistance. We demonstrate that PDX tumors are not simply composed of tumor-initiating cells, but recapitulate the original tumor's heterogeneity, oncogene expression profiles, and clinical response to chemotherapy. Combined carboplatin/paclitaxel treatment of PDX tumors enriches the cancer stem cell populations, but persistent tumors are not entirely composed of these populations. RNA-Seq analysis of six pair of treated PDX tumors compared to untreated tumors demonstrates a consistently contrasting genetic profile after therapy, suggesting similar, but few, pathways are mediating chemoresistance. Pathways and genes identified by this methodology represent novel approaches to targeting the chemoresistant population in ovarian cancer PMID:25209969

Dobbin, Zachary C.; Katre, Ashwini A.; Steg, Adam D.; Erickson, Britt K.; Shah, Monjri M.; Alvarez, Ronald D.; Conner, Michael G.; Schneider, David; Chen, Dongquan; Landen, Charles N.

2014-01-01

84

Student Difficulties with Trigonometric Vector Components Persist in Multiple Student Populations  

NSDL National Science Digital Library

Students in introductory physics courses sometimes struggle to correctly break down a single vector into its components when provided only with an arrow, a magnitude, a reference angle, and a coordinate system. Students struggle further when asked to break down a vector in an inclined coordinate system, such as the weight vector of a box on an inclined plane. Varying the placement of the angle consistently affects student error and response patterns across four physics student populations: algebra-based mechanics, algebra-based E&M, calculus-based mechanics, and calculus-based E&M. This suggests that student difficulties with trigonometric vector components are persistent and pervasive, even across different introductory physics courses, and are far below the requisite near-perfect accuracy needed for such fundamental skills. Student error and response patterns are discussed for both problem types.

Mikula, Brendon D.; Heckler, Andrew F.

2014-02-01

85

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

PubMed Central

Background Clinical evidence has long suggested there may be heterogeneity in the patterns and predictors of common mood and anxiety disorders; however, epidemiologic studies have generally treated these outcomes as homogenous entities. The objective of this study was to systematically review the epidemiologic evidence for potential patterns of heterogeneity of common mood and anxiety disorders over the lifecourse in the general population. Methods We reviewed epidemiologic studies examining heterogeneity in either the nature of symptoms experienced ("symptom syndromes") or in patterns of symptoms over time ("symptom trajectories"). To be included, studies of syndromes were required to identify distinct symptom subtypes, and studies of trajectories were required to identify distinct longitudinal patterns of symptoms in at least three waves of follow-up. Studies based on clinical or patient populations were excluded. Results While research in this field is in its infancy, we found growing evidence that, not only can mood and anxiety disorders be differentiated by symptom syndromes and trajectories, but that the factors associated with these disorders may vary between these subtypes. Whether this reflects a causal pathway, where genetic or environmental factors influence the nature of the symptom or trajectory subtype experienced by an individual, or whether individuals with different subtypes differed in their susceptibility to different environmental factors, could not be determined. Few studies addressed issues of comorbidity or transitions in symptoms between common disorders. Conclusion Understanding the diversity of these conditions may help us identify preventable factors that are only associated with some subtypes of these common disorders. PMID:19486530

Nandi, Arijit; Beard, John R; Galea, Sandro

2009-01-01

86

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

PubMed Central

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

Tashyreva, Daria; Elster, Josef; Billi, Daniela

2013-01-01

87

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

PubMed Central

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

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

2012-01-01

88

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

PubMed Central

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

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

2013-01-01

89

Populations  

NSDL National Science Digital Library

This chapter introduces population as a group of the same kind of organisms in a given space at a given time. The activities in this section will provide students with the opportunity to define population, estimate populations in a community, and count and compare populations within a community. Students will gain the knowledge in describing plant and animal populations living in a community. They will also experiment with plant populations to control growth and development, not to mention discuss the effects of abiotic conditions on a community.

Galle, Janet R.; Warren, Patricia A.

2005-01-01

90

The emergence of homogeneous norms in heterogeneous populations Dirk Helbing,1,2  

E-print Network

of a computational simulation model that homogeneous social norms may even come about in heterogeneous societies can lead to homogeneous behaviors even in well diversified societies. 1. Introduction Social norms can as "Cement of Society" (Elster 1989b). However, social norms are not unchangeable. They are flexible

91

An intuitive formulation for the reproductive number for the spread of diseases in heterogeneous populations  

E-print Network

An intuitive formulation for the reproductive number for the spread of diseases in heterogeneous the critical conditions for an epidemic to grow or die out. The reproductive number can provide signi appropriately for certain epidemiological models, and construct a simpli®ed formulation of the reproductive

Hyman, James "Mac"

92

Heterogeneities and Consequences of Plasmodium Species and Hookworm Coinfection: A Population Based Study in Uganda  

PubMed Central

Background. Previous studies have suggested that helminth infection exacerbates malaria, but few existing epidemiological studies adequately control for infection heterogeneities and confounding factors. In this study, we investigate spatial and household heterogeneities, predictors, and consequences of Plasmodium species and hookworm coinfection in rural communities in Uganda. Methods. A cross-sectional study was conducted among 1770 individuals aged 0–88 years in 4 villages. We recorded demographic, socioeconomic, and microgeographic factors during household surveys. We determined malaria parasitemia and hemoglobin concentration and collected stool samples on 2 consecutive days. For data analysis, we used a hierarchical, spatially explicit Bayesian framework. Results. Prevalence of Plasmodium-hookworm coinfection was 15.5% overall and highest among school-aged children. We found strong evidence of spatial and household clustering of coinfection and an enduring positive association between Plasmodium-species and hookworm infection among preschool-aged children (odds ratio [OR], 2.36; 95% Bayesian credible interval [BCI], 1.26–4.30) and adults (OR, 2.09; 95% BCI, 1.35–3.16) but not among school-aged children. Coinfection was associated with lower hemoglobin level only among school-aged children. Conclusions. Plasmodium-hookworm coinfection exhibits marked age dependency and significant spatial and household heterogeneity, and among preschool-aged children and adults, occurs more than would be expected by chance. Such heterogeneities provide insight into factors underlying observed patterns and the design of integrated control strategies. PMID:21187338

Kabatereine, Narcis B.; Bukirwa, Hasifa; Staedke, Sarah G.; Brooker, Simon

2011-01-01

93

Fiscal Policy Effects in a Heterogeneous-Agent Overlapping-Generations Economy with an Aging Population  

National Technical Information Service (NTIS)

Among the models that the Congressional Budget Office uses to analyze the economic effects of changes in federal fiscal policy is a life-cycle growth model with overlapping generations of heterogeneous households. In this paper, we extend a similar dynami...

S. Nishiyama

2013-01-01

94

Extreme genetic heterogeneity among the nine major tribal Taiwanese island populations detected with a new generation Y23 STR system.  

PubMed

The Taiwanese aborigines have been regarded as the source populations for the Austronesian expansion that populated Oceania to the east and Madagascar off Africa to the West. Although a number of genetic studies have been performed on some of these important tribes, the scope of the investigations has been limited, varying in the specific populations examined as well as the maker systems employed. This has made direct comparison among studies difficult. In an attempt to alleviate this lacuna, we investigate, for the first time, the genetic diversity of all nine major Taiwanese aboriginal tribes (Ami, Atayal, Bunun, Rukai, Paiwan, Saisat, Puyuma, Tsou and Yami) utilizing a new generation multiplex Y-STR system that allows for the genotyping of 23 loci from a single amplification reaction. This comprehensive approach examining 293 individuals from all nine main tribes with the same battery of forensic markers provides for the much-needed equivalent data essential for comparative analyses. Our results have uncovered that these nine major aboriginal populations exhibit limited intrapopulation genetic diversity and are highly heterogeneous from each other, possibly the result of endogamy, isolation, drift and/or unique ancestral populations. Specifically, genetic diversity, discrimination capacity, fraction of unique haplotypes and the most frequent haplotypes differ among the nine tribes, with the Tsou possessing the lowest values for the first three of these parameters. The phylogenetic analyses performed indicate that the genetic diversity among all nine tribes is greater than the diversity observed among the worldwide reference populations examined, indicating an extreme case of genetic heterogeneity among these tribes that have lived as close neighbors for thousands of years confined to the limited geographical area of an island. PMID:24911980

Zeng, Zhaoshu; Garcia-Bertrand, Ralph; Calderon, Silvia; Li, Li; Zhong, Mingxia; Herrera, Rene J

2014-09-01

95

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

PubMed

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

Deister, Christopher A; Dodla, Ramana; Barraza, David; Kita, Hitoshi; Wilson, Charles J

2013-01-01

96

BAYESIAN CAPTURERECAPTURE METHODS FOR ERROR DETECTION AND ESTIMATION OF POPULATION SIZE: HETEROGENEITY AND DEPENDENCE  

E-print Network

about software review and estimation of a cottontail rabbit population. Some key words: Capture­recapture; Closed population estimation; Gibbs sampling; Soft­ ware review; Variable capture probability #12; BAYESIAN CAPTURE­RECAPTURE METHODS FOR ERROR DETECTION AND ESTIMATION OF POPULATION SIZE

Basu, Sanjib

97

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

PubMed

Partial resistance to Phytophthora sojae in soybean is controlled by multiple quantitative trait loci (QTL). With traditional QTL mapping approaches, power to detect such QTL, frequently of small effect, can be limited by population size. Joint linkage QTL analysis of nested recombinant inbred line (RIL) populations provides improved power to detect QTL through increased population size, recombination, and allelic diversity. However, uniform development and phenotyping of multiple RIL populations can prove difficult. In this study, the effectiveness of joint linkage QTL analysis was evaluated on combinations of two to six nested RIL populations differing in inbreeding generation, phenotypic assay method, and/or marker set used in genotyping. In comparison to linkage analysis in a single population, identification of QTL by joint linkage analysis was only minimally affected by different phenotypic methods used among populations once phenotypic data were standardized. In contrast, genotyping of populations with only partially overlapping sets of markers had a marked negative effect on QTL detection by joint linkage analysis. In total, 16 genetic regions with QTL for partial resistance against P. sojae were identified, including four novel QTL on chromosomes 4, 9, 12, and 16, as well as significant genotype-by-isolate interactions. Resistance alleles from PI 427106 or PI 427105B contributed to a major QTL on chromosome 18, explaining 10-45% of the phenotypic variance. This case study provides guidance on the application of joint linkage QTL analysis of data collected from populations with heterogeneous assay conditions and a genetic framework for partial resistance to P. sojae. PMID:24247235

Lee, Sungwoo; Mian, M A Rouf; Sneller, Clay H; Wang, Hehe; Dorrance, Anne E; McHale, Leah K

2014-02-01

98

Homologies between heterogeneous extrachromosomal DNA populations of Halobacterium halobium and four new halobacterial isolates  

Microsoft Academic Search

Heterogeneous collections of covalently-closed circular DNA (cccDNA) comprise up to 10% of the total DNA of H. halobium and four other halophilic strains (SB3, GRA, GRB and GN101) recently isolated from different sources. All of these bacteria have purple membrane, bacterioruberin and gas vacuoles as characteristic phenotypic markers. Most of the major cccDNA species of these isolates are not homologous

Klaus Ebert; Werner Goebel; Felicitas Pfeifer

1984-01-01

99

Student population changes and progress in Belgian medical schools.  

PubMed

The present study was designed to analyse the evolution of student populations--undergraduates and graduates--in the 11 Belgian medical schools from 1969 to 1982. During this period, an overall 44% drop in the number of entrants was observed, while the number of medical graduates continued to rise until 1977, when it stabilized. French- and Flemish-speaking universities followed a similar trend. During the period under study, the proportion of women students virtually doubled from 25 to 44%. The total success rate averaged 39% for Belgian students and 24% for foreigners. By comparing success curves over the years, the various medical faculties were rated with a 'selectivity' score, indicating those significantly different from the national average. A separate classification was made for preclinical (3 years of 'Candidature') and clinical (4 years of 'Doctorat') phases since, among the 11 Belgian medical schools, four teach only preclinical subjects. Marked differences in failure rates were observed between candidature and doctoral education even within universities. PMID:2927340

Albert, A; Firket, H; Castermans, A

1989-01-01

100

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

PubMed

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

Møller, Anders Pape; Hobson, Keith A

2004-07-01

101

Combined effects between temporal heterogeneity of water supply, nutrient level, and population density on biomass of four broadly distributed herbaceous species.  

PubMed

Temporal heterogeneity of water supply affects grassland community productivity and it can interact with nutrient level and intraspecific competition. To understand community responses, the responses of individual species to water heterogeneity must be evaluated while considering the interactions of this heterogeneity with nutrient levels and population density. We compared responses of four herbaceous species grown in monocultures to various combinations of water heterogeneity, nutrient level, and population density: two grasses (Cynodon dactylon and Lolium perenne), a forb (Artemisia princeps), and a legume (Trifolium repens). Treatment effects on shoot and root biomass were analyzed. In all four species, shoot biomass was larger under homogeneous than under heterogeneous water supply. Shoot responses of L. perenne tended to be greater at high nutrient levels. Although root biomass was also larger under homogeneous water supply, effects of water heterogeneity on root biomass were not significant in the grasses. Trifolium repens showed marked root responses, particularly at high population density. Although greater shoot and root growth under homogeneous water supply appears to be a general trend among herbaceous species, our results suggested differences among species could be found in the degree of response to water heterogeneity and its interactions with nutrient level and intraspecific competition. PMID:21327692

Hagiwara, Yousuke; Kachi, Naoki; Suzuki, Jun-Ichirou

2012-01-01

102

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

ERIC Educational Resources Information Center

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…

Page, Jill

2013-01-01

103

Delineating Psychological and Biomedical Profiles in a Heterogeneous Fibromyalgia Population Using Cluster Analysis  

PubMed Central

The heterogeneity of patients meeting American College of Rheumatology (ACR) criteria for a diagnosis of fibromyalgia (FM) challenges our ability to understand the underlying pathogenesis and to optimize treatment of this enigmatic disorder. Our goal was to discern clinically relevant subgroups across multiple psychological and biomedical domains to better characterize the phenomenology of FM. Women meeting 1990 ACR criteria for FM (N=107) underwent psychological (childhood trauma, mood, anxiety, and stress) and biomedical (neuroendocrine, immune, metabolic) testing. Cluster analysis identified four distinct subgroups. Subgroups I, II and III exhibited profiles that included high psychological distress. Subgroup I was further distinguished by a history of childhood maltreatment and hypocortisolism, and these women reported the most pain and disability. Subgroup II evinced more physiological dysregulation and also reported high levels of pain, fatigue, and disability. Subgroup III was characterized by normal biomarkers and reported intermediate pain severity with higher global functioning. Subgroup IV was distinguished by their psychological wellbeing, reporting less disability and pain. Our findings underscore the heterogeneity of both psychological and physiological features among FM patients presenting with nearly identical TP counts. This subgroup categorization is compatible with hypothesized pathogenetic mechanisms of early trauma, stress system dysregulation, and pro-inflammatory bias, each prominent in some but not all FM patients. Appreciation of distinct FM subgroup features is invaluable for selecting the most appropriate treatment modalities. PMID:22200814

Loevinger, Barbara L.; Shirtcliff, Elizabeth A.; Muller, Daniel; Alonso, Carmen; Coe, Christopher L.

2013-01-01

104

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

Microsoft Academic Search

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

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

2010-01-01

105

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

Microsoft Academic Search

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

Pierre-Alexandre Landry; François-Joseph Lapointe

1999-01-01

106

What can we learn from genetic studies of systemic lupus erythematosus? Implications of genetic heterogeneity among populations in SLE.  

PubMed

Recent progress in genetics has expanded the number of the genes associated with SLE to more than 20 in the past 2 years. One might assign these candidate genetic factors into several pre-existing biological pathways: (i) innate immune response including TLR/interferon signaling pathways (IRF5, STAT4, TNFAIP3, and TREX1); (ii) adaptive immune response (HLA-DR, PTPN22, PDCD1, STAT4, LYN, BLK, and BANK1) including B, T cells, and antigen-presenting cells; and (iii) immune complex clearance mechanism (FCGRs, CRP, and ITGAM). In addition, there are also several genes and loci that could not be assigned into previous known pathways (KIAA1542, PXK, XKR6, ATG5, etc), providing possible novel mechanisms in SLE. It has also been evident that there are similarities and differences in SLE susceptibility loci across ethnic groups. Here we categorize the susceptible genes into four groups. The first group is the consistently associated genes with similar risk allele frequency between multiple ethnic populations such as STAT4, TNFAIP3, BANK1, and IRAK1/MECP2. The second group is the genes that are consistently associated but show marked difference in risk allele frequency (BLK, IRF5). The third group is the genes in which different risk variants exist within a gene or genetic loci (allelic heterogeneity) such as HLA-DR, FCGRs, and IRF5. The fourth group is the genes that show consistently discrepancy between populations such as PTPN22 and possibly ITGAM, PXK, and LYN (genetic heterogeneity). The possible explanations for differences of susceptible genetic factors between populations could be different genetic backgrounds, contribution of gene-gene or gene-environment interaction, and the relation between marker and causal variants. Therefore, efforts to identify ethnic-specific genetic factors or disease causing variants should be necessary for individualized therapy for SLE in future. PMID:20947557

Lee, H-S; Bae, S-C

2010-10-01

107

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

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,…

Kober, Nancy

2010-01-01

108

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

PubMed

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

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

2011-01-01

109

Relation Between Near Work and Myopia Progression in Student Population  

PubMed Central

Aim To determine relation between near work and myopia progression in student population. Causes of myopia occurrence are not sufficiently explained. Methods This retrospective-prospective, descriptive research included 100 students with verified myopia up to -3 Dsph. Ophthalmological examination and measurement diopter-hours variable (Dh) were done twice, in the period from January 2011 until January 2012. Results A multivariate regression analysis of impact on the difference of distance visual acuity without correction to the right and left eye and difference of automatic computer refractometry in cycloplegia of both eyes indicates that, diopter-hours variable (Dh) had statistically significant impact on increase of distance visual acuity difference (right eye OR: I measurement–Dh 1.489, II measurement–Dh 1.544, p<0.05; left eye OR: I measurement–Dh 1.602, II measurement–Dh 1.538, p<0.05) and automatic computer refractometry in cycloplegia (right eye OR: I measurement 1.361, II measurement 1.493, p<0.05; left eye OR: I measurement 0.931, II measurement 1.019, p<0.05) during both measurements. Conclusion Near work cause the increase of myopia. This research opened a perspective for other researches on the impact of near work on myopia. PMID:24944532

Muhamedagic, Lejla; Muhamedagic, Belma; Halilovic, Emina Alimanovic; Halimic, Jasmina Alajbegovic; Stankovic, Aleksa; Muracevic, Bedrana

2014-01-01

110

Organizational Factors Affecting the Continuation of an Instructional Innovation for Heterogeneous Populations.  

ERIC Educational Resources Information Center

This paper investigates the elementary school principal's role in helping to sustain implementation of a complex math and science program designed to foster the development of higher order thinking skills, particularly for language minority students. The study predicted a positive relationship between coordination and program continuation; if the…

Dahl, Rene Fukuhara

111

Antigenic and genetic heterogeneity of Borrelia burgdorferi populations transmitted by ticks  

Microsoft Academic Search

The genome of Borrelia burgdorferi encodes a large number of lipoproteins, many of which are expressed only at certain stages of the spirochete's life cycle. In the current study we describe the B. burgdorferi population structure with respect to the production of two lipoproteins [outer surface protein A (OspA) and outer surface protein C (OspC)] during transmission from the tick

Jun Ohnishi; Joseph Piesman; Aravinda M. de Silva

2001-01-01

112

Survival and competition of clonal plant populations in spatially and temporally heterogeneous habitats  

Microsoft Academic Search

Clonal populations are hierarchically organized: genetic individuals (genets) can consist of many physiological individuals (ramets). Each ramet takes up resources from its local environment, but the resource pattern can be reorganized within the clone by transport between ramets. Thus, an integrated clone is not directly subject to the pattern of resource availability in its habitat. Local shortages can be compensated,

B. Oborny; Á. Kun

2003-01-01

113

Stable Heterogeneity for the Production of Diffusible Factors in Cell Populations  

PubMed Central

The production of diffusible molecules that promote survival and growth is common in bacterial and eukaryotic cell populations, and can be considered a form of cooperation between cells. While evolutionary game theory shows that producers and non-producers can coexist in well-mixed populations, there is no consensus on the possibility of a stable polymorphism in spatially structured populations where the effect of the diffusible molecule extends beyond one-step neighbours. I study the dynamics of biological public goods using an evolutionary game on a lattice, taking into account two assumptions that have not been considered simultaneously in existing models: that the benefit of the diffusible molecule is a non-linear function of its concentration, and that the molecule diffuses according to a decreasing gradient. Stable coexistence of producers and non-producers is observed when the benefit of the molecule is a sigmoid function of its concentration, while strictly diminishing returns lead to coexistence only for very specific parameters and linear benefits never lead to coexistence. The shape of the diffusion gradient is largely irrelevant and can be approximated by a step function. Since the effect of a biological molecule is generally a sigmoid function of its concentration (as described by the Hill equation), linear benefits or strictly diminishing returns are not an appropriate approximations for the study of biological public goods. A stable polymorphism of producers and non-producers is in line with the predictions of evolutionary game theory and likely to be common in cell populations. PMID:25268125

Archetti, Marco

2014-01-01

114

The mutation spectrum of the phenylalanine hydroxylase (PAH) gene and associated haplotypes reveal ethnic heterogeneity in the Taiwanese population.  

PubMed

Phenylalanine hydroxylase (PAH) deficiency is responsible for most cases of phenylketonuria (PKU). In this study of the PAH mutation spectrum in the Taiwanese population, 139 alleles were identified including 34 different mutations. The V190G, Q267R and F392I mutations are first reported in this study. The most common mutations, R241C, R408Q and Ex6-96A>G, account for 23.2%, 12.0% and 9.2%, of the mutant alleles, respectively. Haplotype analysis shows that R241C and Ex6-96A>G are exclusively associated with haplotype 4.3 to suggest founder effects. On the other hand, R408Q is found on two distinct haplotypes suggesting recurrent mutations. The spectrum of PAH mutations in Taiwan shows various links to those of other Asian regions, yet remarkable differences exist. Notably, R408Q, E286K and -4173_-407del, accounting for 21% of all mutant alleles in Taiwan, are very rare or are undetected among PKU cohorts of other Asian regions to suggest local founder effects. Moreover, the low homozygosity value of 0.092 hints at a high degree of ethnic heterogeneity within the Taiwanese population. Our study of PAH mutation spectrum and the associated haplotypes is useful for subsequent study on the origin and migration pattern via Taiwan, an island at the historical crossroad of migration of ancient populations. PMID:24401910

Liang, Ying; Huang, Miao-Zeng; Cheng, Cheng-Yi; Chao, Hung-Kun; Fwu, Victor Tramjay; Chiang, Szu-Hui; Hsiao, Kwang-Jen; Niu, Dau-Ming; Su, Tsung-Sheng

2014-03-01

115

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

PubMed Central

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

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

2010-01-01

116

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

NASA Technical Reports Server (NTRS)

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.

Czerwinski, Mary; Nguyen, Trung

1994-01-01

117

Re-activated adult epicardial progenitor cells are a heterogeneous population molecularly distinct from their embryonic counterparts.  

PubMed

Cardiovascular disease remains the major cause of mortality, and cardiac cell therapy has recently emerged as a paradigm for heart repair. The epicardium is a layer of mesothelial cells covering the heart that during development contributes to different cardiovascular lineages, including cardiomyocytes, but which becomes quiescent after birth. We previously revealed that the peptide thymosin beta 4 (T?4) can reactivate adult epicardium-derived cells (EPDCs) after myocardial infarction (MI), to proliferate, and differentiate into cardiovascular derivatives. The aim of this study was to provide a lineage characterization of the adult EPDCs relative to the embryonic epicardial lineage and to determine prospective cell fate biases within the activated adult population during cardiovascular repair. Wt1(GFPCre/+) mice were primed with T?4 and MI induced by ligation of the left anterior descending coronary artery. Adult WT1(+) GFP(+) EPDCs were fluorescence-activated cell sorted (FACS) at 2, 4, and 7 days after MI. Embryonic WT1(+) GFP(+) EPDCs were isolated from embryonic hearts (E12.5) by FACS, and sorted cells were characterized by real-time quantitative reverse transcriptase-polymerase chain reaction (RT-qPCR) and immunostaining. Adult WT1(+) GFP(+) EPDCs were highly heterogeneous, expressing cardiac progenitor and mesenchymal stem markers. Based on the expression of stem cell antigen-1 (Sca-1), CD44, and CD90, we identified different subpopulations of EPDCs of varying cardiovascular potential, according to marker gene profiles, with a molecular phenotype distinct from the source embryonic epicardial cells at E12.5. Thus, adult WT1(+) GFP(+) cells are a heterogeneous population that when activated can restore an embryonic gene programme, but do not revert entirely to adopt an embryonic phenotype. Potential biases in cardiovascular cell fate suggest that discrete subpopulations of EPDCs might be clinically relevant for regenerative therapy. PMID:24702282

Bollini, Sveva; Vieira, Joaquim Miguel Nunes; Howard, Sara; Dubè, Karina Natasha; Balmer, Gemma Mary; Smart, Nicola; Riley, Paul Richard

2014-08-01

118

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

PubMed

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

Parker, J S; Wilby, A S

1989-02-01

119

Effect of physiological heterogeneity of E. coli population on antibiotic susceptivity test.  

PubMed

According to the instantaneous growth rate (dN/dt) of E. coli CVCC249 growing in batch culture, the entire growth progress was distinguished into four phases: accelerating growth phase, constant growth phase, decelerating growth phase and declining phase, in each of which obvious variation in physiological and biochemical properties was detected, including total DNA, total protein, and MTT-dehydrogenase activity, etc., that led to difference in their antibiotic susceptivity. Antibiotic susceptivity of the population sampled from each phase was tested by Concentration-killing Curve (CKC) approach following the formula N=N (0)/{1+exp[r.(x-BC (50))]}, showing as normal distribution at the individual cell level for an internal population, in which the median bactericidal concentration BC (50) represents the mean level of susceptivity, while the bactericidal span BC (1-99)=(2lnN (0))/r indicates the variation degree of the antibiotic susceptivity. Furthermore, tested by CKC approach, the antibiotic susceptivity of E. coli CVCC249 population in each physiological phase to gentamicin or enoxacin was various: susceptivity of the population in the constant growth phase and declining phase all increased compared with that in the accelerating growth phase for gentamicin but declined for enoxacin. The primary investigations revealed that the physiological phase should be taken into account in the context of antibiotic susceptivity and research into antimicrobial mechanism. However there are few reports concerned with this study. Further research using different kinds of antibiotics with synchronized continuous culture of different bacterial strains is required. PMID:17901932

Liu, YuQing; Zhang, HuaiQiang; Shen, JianZhong; Gao, PeiJi

2007-12-01

120

Ploidy frequencies in plants with ploidy heterogeneity: fitting a general gametic model to empirical population data  

PubMed Central

Genome duplication (polyploidy) is a recurrent evolutionary process in plants, often conferring instant reproductive isolation and thus potentially leading to speciation. Outcome of the process is often seen in the field as different cytotypes co-occur in many plant populations. Failure of meiotic reduction during gametogenesis is widely acknowledged to be the main mode of polyploid formation. To get insight into its role in the dynamics of polyploidy generation under natural conditions, and coexistence of several ploidy levels, we developed a general gametic model for diploid–polyploid systems. This model predicts equilibrium ploidy frequencies as functions of several parameters, namely the unreduced gamete proportions and fertilities of higher ploidy plants. We used data on field ploidy frequencies for 39 presumably autopolyploid plant species/populations to infer numerical values of the model parameters (either analytically or using an optimization procedure). With the exception of a few species, the model fit was very high. The estimated proportions of unreduced gametes (median of 0.0089) matched published estimates well. Our results imply that conditions for cytotype coexistence in natural populations are likely to be less restrictive than previously assumed. In addition, rather simple models show sufficiently rich behaviour to explain the prevalence of polyploids among flowering plants. PMID:23193129

Suda, Jan; Herben, Tomas

2013-01-01

121

School Enrollment in the United States: Social and Economic Characteristics of Students, October 1999. Population Characteristics. Current Population Reports.  

ERIC Educational Resources Information Center

This report highlights school enrollment trends and student social and economic characteristics using findings from data collected in the U.S. Census Bureau's Current Population Survey, October 1999. Overall, one-fourth of the U.S. population was enrolled in school in 1999. Nursery school enrollment equalled the record level set in 1995.…

Jamieson, Amie; Curry, Andrea; Martinez, Gladys

122

Influence of spatial and temporal heterogeneities on the estimation of demographic parameters in a continuous population using individual microsatellite data.  

PubMed Central

Drift and migration disequilibrium are very common in animal and plant populations. Yet their impact on methods of estimation of demographic parameters was rarely evaluated especially in complex realistic population models. The effect of such disequilibria on the estimation of demographic parameters depends on the population model, the statistics, and the genetic markers used. Here we considered the estimation of the product Dsigma2 from individual microsatellite data, where D is the density of adults and sigma2 the average squared axial parent-offspring distance in a continuous population evolving under isolation by distance. A coalescence-based simulation algorithm was used to study the effect on Dsigma2 estimation of temporal and spatial fluctuations of demographic parameters. Estimation of present-time Dsigma2 values was found to be robust to temporal changes in dispersal, to density reduction, and to spatial expansions with constant density, even for relatively recent changes (i.e., a few tens of generations ago). By contrast, density increase in the recent past gave Dsigma2 estimations biased largely toward past demographic parameters values. The method was also robust to spatial heterogeneity in density and estimated local demographic parameters when the density is homogenous around the sampling area (e.g., on a surface that equals four times the sampling area). Hence, in the limit of the situations studied in this article, and with the exception of the case of density increase, temporal and spatial fluctuations of demographic parameters appear to have a limited influence on the estimation of local and present-time demographic parameters with the method studied. PMID:15020488

Leblois, Raphael; Rousset, François; Estoup, Arnaud

2004-01-01

123

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

SciTech Connect

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.

Ormiston, B.G.

1984-07-01

124

A New Approach to Evaluation of University Teaching Considering Heterogeneity of Students' Preferences  

ERIC Educational Resources Information Center

Students' evaluations of teaching are increasingly used by universities to evaluate teaching performance. However, these evaluations are controversial mainly due to the fact that students value various aspects of excellent teaching differently. Therefore, in this paper we propose a new approach to students' evaluations of university…

Kuzmanovic, Marija; Savic, Gordana; Popovic, Milena; Martic, Milan

2013-01-01

125

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

ERIC Educational Resources Information Center

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

El-Koumy, Abdel Salam Abdel Khalek

2009-01-01

126

Catalog of Exemplary Vocational Education Programs for California Community Colleges' Special Student Populations.  

ERIC Educational Resources Information Center

This directory contains abstracts of 30 model programs for special population students at California community colleges. Programs are divided into four categories corresponding to the type of special population served. The seven programs for disadvantaged students are as follows: "Career Beginnings"; "Center for Computer Assisted Instruction and…

Evaluation and Training Inst., Los Angeles, CA.

127

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

PubMed

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

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

2012-08-01

128

1.0 SERVICES FOR SPECIAL POPULATIONS 1.1 Student Athletes  

E-print Network

contact in each college advising office, keeps track of the NCAA/MAC requirements and student athletes1.0 SERVICES FOR SPECIAL POPULATIONS 1.1 Student Athletes 1.1.a Athletic Advising Office 205, FAX x3953 · In addition to meeting University and college standards, student athletes must also meet

Viola, Ronald

129

Minor psychological problems in a multiracial student population in Rhodesia.  

PubMed

Experience in the student health service at the multiracial University of Rhodesia suggests that, although the aetiology and manifestations of minor psychological problems are affected by cultural factors, similarities between students of different races are more marked than are divergencies. The students' problems are similar to those reported from universities in other countries. PMID:746457

Smith, M E

1978-12-16

130

The wildlife orientations of selected Taiwanese student populations  

E-print Network

with an area of 105 square miles and has a population of over 2. 4 million people. Hualien is situated on the eastern coast of Taiwan with an area of 11. 2 square miles and has a population of around 100, 000 people. Therefore, the population densities... with an area of 105 square miles and has a population of over 2. 4 million people. Hualien is situated on the eastern coast of Taiwan with an area of 11. 2 square miles and has a population of around 100, 000 people. Therefore, the population densities...

Lin, Pei-Chien

2012-06-07

131

Heterogeneity in Risk of Pelvic Inflammatory Diseases After Chlamydia Infection: A Population-Based Study in Manitoba, Canada  

PubMed Central

Background.?The association between chlamydia infection and pelvic inflammatory disease (PID) is a key parameter for models evaluating the impact of chlamydia control programs. We quantified this association using a retrospective population-based cohort. Methods.?We used administrative health data sets to construct a retrospective population-based cohort of women and girls aged 12–24 years who were resident in Manitoba, Canada, between 1992 and 1996. We performed survival analysis on a subcohort of individuals who were tested for chlamydia to estimate the risk of PID diagnosed in a primary care, outpatient, or inpatient setting after ?1 positive chlamydia test. Results.?A total of 73 883 individuals contributed 625 621 person years of follow-up. Those with a diagnosis of chlamydia had an increased risk of PID over their reproductive lifetime compared with those who tested negative (adjusted hazard ratio [AHR], 1.55; 95% confidence interval [CI], 1.43–1.70). This risk increased with each subsequent infection: the AHR was 1.17 for first reinfection (95% CI, 1.06–1.30) and 1.35 for the second (95% CI, 1.04–1.75). The increased risk of PID from reinfection was highest in younger individuals (AHR, 4.55 (95% CI, 3.59–5.78) in individuals aged 12–15 years at the time of their second reinfection, compared with individuals older than 30 years). Conclusions.?There is heterogeneity in the risk of PID after a chlamydia infection. Describing the progression to PID in mathematical models as an average rate may be an oversimplification; more accurate estimates of the cost-effectiveness of screening may be obtained by using an individual-based measure of risk. Health inequalities may be reduced by targeting health promotion interventions at sexually active girls younger than 16 years and those with a history of chlamydia. PMID:25381374

Davies, Bethan; Ward, Helen; Leung, Stella; Turner, Katy M. E.; Garnett, Geoff P.; Blanchard, James F.; Yu, B. Nancy

2014-01-01

132

The Assessment of Risk Factors in a Student Population.  

ERIC Educational Resources Information Center

This paper identifies and assesses factors that may characterize students at risk of dropping out, based on a ninth grade class of Cincinnati (Ohio) public school students which was followed for five years, from 1984-85 to 1988-89. The paper aims to develop a quick, easy, and reliable method that teachers, counselors, and principals can use to…

Mueller, Elizabeth Jane

133

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

Microsoft Academic Search

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

Arijit Nandi; John R Beard; Sandro Galea

2009-01-01

134

Fertility values and acceptance of population control among college students  

E-print Network

each respondent was asked the following question: "Do you feel that the world, as it is today, is overpopulated?" Dichotomized responses were utilized to define those students perceiving or not perceiving overpopulation. Fertility Values A... class peers. Furthermore, a direct link was found between perception of overpopulation and fertility values. This relationship indicates that students who perceive the world as being overpopulated are more likely to have lower fertility values than...

West, Walter G.; Poole, Eric D.

1974-10-01

135

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

ERIC Educational Resources Information Center

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

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

2011-01-01

136

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)

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.

Moreno-Rueda, Gregorio; Pizarro, Manuel

2007-07-01

137

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

PubMed

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

Hassan, U; Bashir, R

2014-10-14

138

Antibody responses induced by Leish-Tec®, an A2-based vaccine for visceral leishmaniasis, in a heterogeneous canine population.  

PubMed

Zoonotic visceral leishmaniasis (VL) is a widespread disease, and dogs are the main reservoirs for human parasite transmission. Hence, development of an effective vaccine that prevents disease and reduces the transmission of VL is required. As euthanasia of seropositive dogs is recommended in Brazil for VL epidemiological control, to include anti-VL canine vaccines as a mass control measure it is necessary to characterize the humoral responses induced by vaccination and if they interfere with the reactivity of vaccinated dogs in serological diagnostic tests. Leish-Tec(®) is an amastigote-specific A2 recombinant protein vaccine against canine visceral leishmaniasis (CVL) that is commercially available in Brazil. Here, we tested the immunogenicity of Leish-Tec(®) in a heterogeneous dog population by measuring A2-specific antibody responses. Healthy dogs (n=140) of various breeds were allocated to two groups: one group received Leish-Tec(®) (n=70), and the other group received a placebo (n=70). Anti-A2 or anti-Leishmania promastigote antigen (LPA) antibody levels were measured by ELISA in serum samples collected before and after vaccination. An immunochromatographic test (DPP) based on the recombinant K28 antigen was also used for serodiagnosis of CVL. Vaccinated animals, except one, remained seronegative for anti-LPA total IgG and anti-K28 antibodies. Conversely, seropositivity for anti-A2 total IgG antibodies was found in 98% of animals after vaccination. This value decreased to 81.13% at 6 months before rising again (98%), after the vaccination boost. Anti-A2 IgG2 and IgG1 titers were also increased in vaccinated animals relative to control animals. These data indicate that Leish-Tec(®) is immunogenic for dogs of different genetic backgrounds and that humoral responses induced by vaccination can be detected by A2-ELISA, but do not interfere with the LPA-ELISA and DPP diagnostic tests for CVL. PMID:24863572

Testasicca, Miriam C de Souza; dos Santos, Mariana Silva; Machado, Leopoldo Marques; Serufo, Angela Vieira; Doro, Daniel; Avelar, Daniel; Tibúrcio, Ana Maria Leonardi; Abrantes, Christiane de Freitas; Machado-Coelho, George Luiz Lins; Grimaldi, Gabriel; Gazzinelli, Ricardo Tostes; Fernandes, Ana Paula

2014-08-29

139

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

PubMed

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

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

2014-08-01

140

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

ERIC Educational Resources Information Center

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…

Brown, Virginia; Nichols, Tracy R.

2013-01-01

141

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

ERIC Educational Resources Information Center

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…

Bouchat, Clarence J.

2008-01-01

142

Minority Student Response to the Anthropology of Asian Black Populations. Revised.  

ERIC Educational Resources Information Center

Since 1970, the University of Chicago has offered three undergraduate anthropology courses on Philippine Negrito and Malay and Thai aboriginal black populations. Between 1975 and 1981, 72 students, including American blacks, Filipinos, and other Asians, attended the courses. The instructor's observations of students' responses to the courses…

Warren, Charles P.

143

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

ERIC Educational Resources Information Center

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…

Castaneda, Lillian Vega

144

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

ERIC Educational Resources Information Center

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

Wagman, Janet Campbell

2005-01-01

145

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

Microsoft Academic Search

Bone marrow-derived mesenchymal stem cells consist of a developmentally heterogeneous population of cells obtained from colony\\u000a forming progenitors. As these colonies express the alpha-1 integrin (CD49a), here we single-cell FACS sorted CD49a+ cells\\u000a from bone marrow in order to create clones and then compared their colony forming efficiency and multilineage differentiation\\u000a capacity to the unsorted cells. Following selection, 40% of

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

2007-01-01

146

The wildlife orientation of selected student populations in Victoria, Texas  

E-print Network

vity scores by grade level in VISD students. Of the 12 wildlife-related act1vities used 1n this study, students gave the highest importance value to "went to the zoo", "watched a TV show on wild animals", and "went fishing". The lowest 1mportance..., and twelve c1ty parks. A special feature with1n Riverside Park is the Texas Zoo. This zoo houses only native Texas animals and is highly utilized by the elementary schools. Victor1a is only a 32-minute drive to the coast or the Coleto Creek Reservoir...

Kirkpatrick, Phyllis Ann Bradley

2012-06-07

147

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

ERIC Educational Resources Information Center

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…

Luyten, Hans; de Wolf, Inge

2011-01-01

148

Dental students' reflections on their experiences with a diverse patient population.  

PubMed

Recent developments, including national reports and new accreditation standards, have emphasized the need for dental students to be prepared to address the needs of a diverse patient population. The purpose of this study was to explore students' descriptions of and reflections on their day-to-day interactions with a diverse patient population in the clinical setting, using a qualitative approach. All dental students (sixty-six) enrolled in the third year of the D.M.D. program at a Midwestern dental school were required to write a paper reflecting on their experiences working with a diverse patient population in the general dental clinic of the school as part of a behavioral sciences course. All third-year dental students were invited to participate in the study. The students' papers were deidentified prior to data analysis. Forty-two students' papers describing a total of 126 patient-student interactions were reviewed. Data analysis resulted in identification of three key themes: 1) development of cultural awareness and recognition of the need to understand each patient as a unique individual, 2) desire to build rapport with all patients, and 3) realization that the development of cultural competence is a lifelong learning process requiring ongoing experiences working with a diverse patient population. Review of student reflection papers is valuable in providing faculty with an understanding of students' degree of development of cultural competence. A greater understanding of students' day-to-day experiences with a diverse patient population can provide insights for dental educators who develop cultural competence curricula. PMID:23929567

Victoroff, Kristin Zakariasen; Williams, Kristin A; Lalumandier, James

2013-08-01

149

Changing Patterns of Cervical Disease in a Student Population.  

ERIC Educational Resources Information Center

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)

Rosenthal, Dorothy L.; And Others

1982-01-01

150

Dental students' attitudes toward underserved populations across four years of dental school.  

PubMed

The objective of this study was to assess dental students' attitudes toward underserved populations across their four years of dental school. Students at the Herman Ostrow School of Dentistry of the University of Southern California were invited to take part in the study. Participating students completed a questionnaire on their attitudes toward the underserved at three time points: 1) during orientation week; 2) at the end of their second year after taking part in some community dental programs; and 3) at the end of their fourth year after they had completed all their mandatory and volunteer rotations in community dental programs. Students' attitudes were measured in four categories: societal expectations, dentist/student responsibility, personal efficacy, and access to care. First-year students scored 85 out of a maximum of 115 on the questionnaire. Female students scored higher than male students (P=0.006). Age, debt, and past history of volunteer work were not related to first-year students' total attitude scores; however, students with a history of volunteer experience scored higher on the dentist/student responsibility category (P=0.04). Students' attitude scores declined across the four years of dental school (P=0.001). The same patterns were evident for all categories except societal expectations. The decline was not related to age, gender, debt, or volunteer work experience. Follow-up studies are needed to help explain the factors that may be related to this decline. PMID:21828295

Habibian, Mina; Seirawan, Hazem; Mulligan, Roseann

2011-08-01

151

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

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.

Van Soest, S.; Ingeborgh Van Den Born, L.; Bergen, A.A.B. [Netherlands Ophthalmic Research Institute, Amsterdam (Netherlands)] [and others] [Netherlands Ophthalmic Research Institute, Amsterdam (Netherlands); and others

1994-08-01

152

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

PubMed Central

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

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

2014-01-01

153

Heterogeneous landscapes and the role of refuge on the population dynamics of a specialist predator and its prey  

Microsoft Academic Search

How, and where, a prey species survives predation by a specialist predator during low phases of population fluctuations or a cycle, and how the increase phase of prey population is initiated, are much-debated questions in population and theoretical ecology. The persistence of the prey species could be due mainly to habitats that act as refuges from predation and\\/or due to

Hannu Ylönen; Roger Pech; Stephen Davis

2003-01-01

154

The effects of spatial and temporal heterogeneity on the population dynamics of four animal species in a Danish landscape  

Microsoft Academic Search

BACKGROUND: Variation in carrying capacity and population return rates is generally ignored in traditional studies of population dynamics. Variation is hard to study in the field because of difficulties controlling the environment in order to obtain statistical replicates, and because of the scale and expense of experimenting on populations. There may also be ethical issues. To circumvent these problems we

Richard M Sibly; Jacob Nabe-Nielsen; Mads C Forchhammer; Valery E Forbes; Christopher J Topping

2009-01-01

155

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

Microsoft Academic Search

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

Christine Robitschek

2003-01-01

156

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

ERIC Educational Resources Information Center

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…

Tindall, Lloyd W.; And Others

157

A SocioEconomic Analysis of Student Population in Third Level Education  

Microsoft Academic Search

The pursuit of knowledge and the availability of an educational qualification has always been an aspiration of most citizens in developed and less developed economies worldwide. In modern Ireland, the educational system has prided itself as one of the more advanced models vis-a-vis student quality and educational participation structured and quality educational population. Eighty per cent of Irish school children

Pat McGarthy; Dermot Duffy

1999-01-01

158

Biomedical Social Science, Unit VI: Population Growth and Genetic Engineering. Student Text. Revised Version, 1977.  

ERIC Educational Resources Information Center

This collection of lessons and class activities covers two major concepts: (1) population growth and (2) genetic engineering. Lessons consist of readings, questions and answers, and problems of projects where appropriate. Issues are posed in as much as possible in a manner intended to cause the student to reach conclusions and values without being…

Biomedical Interdisciplinary Curriculum Project, Berkeley, CA.

159

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

ERIC Educational Resources Information Center

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…

Jurow, A. Susan

2004-01-01

160

The Effectiveness of "Study Unlimited" in Serving New Student Populations in the Community.  

ERIC Educational Resources Information Center

This study evaluates the effectiveness of Study Unlimited, an off-campus instructional program cooperatively offered at area public libraries by Black Hawk College and the River Bend Library System (Illinois), in serving "new" student populations (adults over 25, males employed full-time, housewives, ethnic minorities, and adults attending college…

Stevens, Mary A.

161

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

ERIC Educational Resources Information Center

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…

Freeth, Megan; Bullock, Tom; Milne, Elizabeth

2013-01-01

162

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

ERIC Educational Resources Information Center

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

Robitschek, Christine

2003-01-01

163

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

PubMed

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

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

2014-03-01

164

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

PubMed Central

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

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

2013-01-01

165

Assessment of heterogeneity between European Populations: a Baltic and Danish replication case-control study of SNPs from a recent European ulcerative colitis genome wide association study  

PubMed Central

Background Differences in the genetic architecture of inflammatory bowel disease between different European countries and ethnicities have previously been reported. In the present study, we wanted to assess the role of 11 newly identified UC risk variants, derived from a recent European UC genome wide association study (GWAS) (Franke et al., 2010), for 1) association with UC in the Nordic countries, 2) for population heterogeneity between the Nordic countries and the rest of Europe, and, 3) eventually, to drive some of the previous findings towards overall genome-wide significance. Methods Eleven SNPs were replicated in a Danish sample consisting of 560 UC patients and 796 controls and nine missing SNPs of the German GWAS study were successfully genotyped in the Baltic sample comprising 441 UC cases and 1156 controls. The independent replication data was then jointly analysed with the original data and systematic comparisons of the findings between ethnicities were made. Pearson's ?2, Breslow-Day (BD) and Cochran-Mantel-Haenszel (CMH) tests were used for association analyses and heterogeneity testing. Results The rs5771069 (IL17REL) SNP was not associated with UC in the Danish panel. The rs5771069 (IL17REL) SNP was significantly associated with UC in the combined Baltic, Danish and Norwegian UC study sample driven by the Norwegian panel (OR = 0.89, 95% CI: 0.79-0.98, P = 0.02). No association was found between rs7809799 (SMURF1/KPNA7) and UC (OR = 1.20, 95% CI: 0.95-1.52, P = 0.10) or between UC and all other remaining SNPs. We had 94% chance of detecting an association for rs7809799 (SMURF1/KPNA7) in the combined replication sample, whereas the power were 55% or lower for the remaining SNPs. Statistically significant PBD was found for OR heterogeneity between the combined Baltic, Danish, and Norwegian panel versus the combined German, British, Belgian, and Greek panel (rs7520292 (P = 0.001), rs12518307 (P = 0.007), and rs2395609 (TCP11) (P = 0.01), respectively). No SNP reached genome-wide significance in the combined analyses of all the panels. Conclusions This replication study supports an important role for the studied rs5771069 (IL17REL) SNP, but not for rs7809799 (SMURF1/KPNA7), in UC etiology in the Danish, Baltic, and Norwegian populations. Significant genetic heterogeneity was suggested for rs7520292, rs12518307, and rs2395609 (TCP11) in UC etiology between the Nordic and the other European populations. PMID:21995314

2011-01-01

166

Human Capital and Population Growth in Nonmetropolitan U.S. Counties: The Importance of College Student Migration  

Microsoft Academic Search

Researchers have consistently shown that the stock of human capital in an area, measured as the share of the adult population with a college degree, is a strong predictor of future population growth. This article examines this relationship for U.S. nonmetropolitan counties and posits that student migration for higher education may play an important role. Students often move to an

John V. Winters

2011-01-01

167

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

PubMed Central

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

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

2010-01-01

168

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

USGS Publications Warehouse

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.

Dorazio, R. M.

1997-01-01

169

Spatial heterogeneity and long-term changes in bivalve Anadara broughtoni population: influence of river run-off and fishery  

Microsoft Academic Search

A comparison was made of population of the economically important cockleAnadara (=Scapharca)broughtoni (Bivalvia, Arcidae) inhabiting different areas of the Razdolnaya River estuary at the head of Amurskii Bay (Peter the Great\\u000a Gulf, East Sea). Also, changes in cockle population density and structure, as well as in cockle growth rates during the last\\u000a 20 years were studied. In all years of

Alla V. Silina

2006-01-01

170

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

NASA Astrophysics Data System (ADS)

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.

Rose, Nancy L.

171

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

PubMed

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

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

2007-10-01

172

Seasonality of Month of Birth of Children and Adolescents with Type 1 Diabetes Mellitus in Homogenous and Heterogeneous Populations  

Microsoft Academic Search

Background: Type 1 childhood-onset diabetes mellitus has a multifactorial origin involving an interplay between genetic and en- vironmental factors. We have previously shown that many children who subsequently develop T1DM have a different seasonality of birth than the total live births of the same population, supporting the hypothesis that perinatal viral infection is a trigger for the autoim- mune process

Zvi Laron; Hadas Lewy; Igor Wilderman; Anna Casu; Jinny Willis; Maria Jose Redondo; Ingrid Libman; Neil White; Maria Craig

2005-01-01

173

Engaging Pharmacy Students with Diverse Patient Populations to Improve Cultural Competence  

PubMed Central

Objective To develop and implement learning activities within an advanced pharmacy practice experience (APPE) to improve students' cultural competence. Design During their AAPE at Community Access Pharmacy, students participated in topic discussions with faculty members, used interpreters to interview Hispanic patients, visited a Mexican grocery store, evaluated nontraditional medicine practices in the Hispanic community, and served as part of a patient care team at a homeless shelter and an HIV/AIDS clinic. The students reflected on these activities in daily logs and completed a final evaluation of their experiences. Assessment Forty-three students completed the rotation from 2004-2007. Almost all learned something new about counseling patients with cultural/language differences (98%) and became more aware of financial barriers to health care and potential solutions to overcome them (93%). Students' reflections were positive and showed progression toward cultural competence. Conclusion A culturally diverse patient population provided opportunities for APPE students to develop the skills necessary to become culturally competent pharmacists. Future work should focus on potential evaluation tools to assess curricular cultural competency outcomes in APPE's. PMID:19214278

2008-01-01

174

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

PubMed Central

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

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

175

Genetic heterogeneity of susceptibility gene in different ethnic populations: refining association study of PTPN22 for Graves' disease in a Chinese Han population.  

PubMed

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 (P(combined) = 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

Xue, Liqiong; Pan, Chunming; Gu, Zhaohui; 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

176

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

PubMed Central

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

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

2012-01-01

177

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

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…

Pender, Matea

2010-01-01

178

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

PubMed

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

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

2013-01-01

179

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

Greater knowledge of specific populations? perception of the capacity for change will assist leadership practitioners in the design and implementation of effective leadership programs. These leadership programs will hopefully prepare students...

Durham Hynes, Sharra L.

2010-01-16

180

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

PubMed

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 the strongest balancing selection and DPB1 being compatible with neutrality. Comparisons of the allelic spectra reported by studies since 1990 indicate 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

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

2008-07-01

181

Molecular heterogeneity at the phenylalanine hydroxylase locus in the population of the south-west of England.  

PubMed Central

The phenylalanine hydroxylase gene locus has been studied in 35 independent phenylketonuric families in the south-west of England using RFLP haplotype patterns and allele specific oligonucleotide probes. Haplotype 3 was the most common pattern on mutant chromosomes and there was strict linkage disequilibrium between this haplotype and the splice mutation in exon 12. The R408W mutation in exon 12 occurred on both haplotypes 1 and 2. The R126Q mutation in exon 7 was found only on a rare haplotype 28 pattern. No gene carried the R158Q mutation. More than 60% of mutant genes did not carry these four mutations which were originally described in other European populations. We suggest that the splice mutation arose as a single event and spread throughout northern Europe by population migration and admixture. In addition, we believe the haplotype/mutation associations seen in our population are a reflection of the mixed ancestry of the inhabitants of the British Isles. PMID:1677425

Tyfield, L A; Osborn, M J; Holton, J B

1991-01-01

182

Predictors of Sexual Bother in a Population of Male North American Medical Students  

PubMed Central

Introduction The prevalence and associations of sexual bother in male medical students has not been extensively studied. Aims The aim of this study is to analyze predictors of sexual bother in a survey of male North American medical students. Methods Students enrolled in allopathic and osteopathic medical schools in North America between February 2008 and July 2008 were invited to participate in an internet-based survey of sexuality and sexual function. Main Outcome Measures The principle outcome measure was a single-item question inquiring about global satisfaction with sexual function. The survey also consisted of a questionnaire that included ethnodemographic factors, student status, sexual history, and a validated scale for the assessment of depression. Respondents completed the International Index of Erectile Function, the premature ejaculation diagnostic tool, and the Self-Esteem and Relationship Quality survey (SEAR). Descriptive statistics, analysis of variance, and multivariable logistic regression were utilized to analyze responses. Results There were 480 male subjects (mean age 26.3 years) with data sufficient for analysis. Forty-three (9%) reported sexual bother. Sexual bother was significantly more common in men with erectile dysfunction (ED), high risk of premature ejaculation (HRPE), depressive symptoms, and lower sexual frequency. However, after multivariate analysis including SEAR scores, ED, and HRPE were no longer independently predictive of sexual bother. Higher scores for all domains of the SEAR were associated with lower odds of sexual bother. Conclusions ED and HRPE are associated with sexual bother in this young and presumably healthy population. However, after controlling for relationship factors neither ED nor HRPE independently predicted sexual bother. It is plausible to hypothesize that sexual dysfunction from organic causes is rare in this population and is seldom encountered outside of relationship perturbations. Attention to relationship and psychological factors is likely of key importance in addressing sexual concerns in this population. PMID:21951580

Smith, James F.; Breyer, Benjamin N.; Shindel, Alan W.

2013-01-01

183

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

PubMed Central

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

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

2014-01-01

184

[Dietary, oral hygienic habits, dental surgeon attendance, and social background in police student's population].  

PubMed

The aim of the study was to survey the dietary, oral hygienic habits, dental surgeon attendance and their relations with each other and social background in the Police School of Miskolc, Hungary. In this study, based on a questionnaire, 792 students [(mean age: 20.43 +/- 1.25 ys (mean +/- S.D.)] participated. Statistical analysis was performed using SPSS for Windows 10.0 statistical software. The daily consumption of sweets was 30.8%. There was no significant difference between educational level of father and frequency of consumption of sweets. The frequency of consumption of sweets significantly decreased with increasing the number of siblings (p < 0.05). The daily consumption of soft drinks was 28.8%. In the examined population 10% of the students used dental floss, most of them (60.0%) cleaned their teeth twice a day. Frequency of tooth-cleaning was significantly increased parallel to increase the educational level of father (p<0.05). Dental surgeon attendance aimed check up was 28.4% beside the compulsory yearly visit. The "3-times-tooth-cleaning" students visited their dentists within last 12 months in significantly higher percent than those of without daily tooth-cleaning (p < 0.05). There is a need to improve those factors which can affect oral health in the examined population. PMID:19402311

Faragó, Ildikó; Márton, Sándor; Túry, Ferenc; Bagi, István; Madléna, Melinda

2009-02-01

185

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

PubMed

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

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

2014-03-01

186

Psychometric Properties of the Icelandic Version of the Beck Anxiety Inventory in a Clinical and a Student Population  

Microsoft Academic Search

The Beck Anxiety Inventory (BAI) is a widely used anxiety scale in clinical practice as well as in research. In the present study the objective was to assess the psychometric properties of the Icelandic version of the BAI in a patient and a student population. There was a total of 1674 participants, 607 outpatients and 1067 students. All participants completed

Bragi R. Sæmundsson; Fanney Þórsdóttir; Hafrún Kristjánsdóttir; Daníel Þ. Ólason; Jakob Smári; Jón F. Sigurðsson

2011-01-01

187

Evaluating the Phobias, Attitudes, and Cultural Competence of Master of Social Work Students Toward the LGBT Populations  

Microsoft Academic Search

Background. Evidence suggests there is bias toward lesbian, gay, bisexual, and transgender (LGBT) persons by social workers; unfortunately, little research has been conducted to examine Master of Social Work (MSW) students' views toward these populations. The purpose of this study was to develop an assessment scale to evaluate the attitudes, phobias, and cultural competence of MSW students toward the LGBT

Carmen Logie; Tana J. Bridge; Patrick D. Bridge

2007-01-01

188

The Values and Attitudes of Selected College Students on Some Topics Relevant to Human Population. Monograph No. 31.  

ERIC Educational Resources Information Center

Results of a study on attitudes of Filipino college students concerning human population issues are reported. A total of 74 University of the Philippines students, half of whom were enrolled in a natural science course, answered a 15-part questionnaire on dating, friendship, premarital sex, marital expectations, and birth control. Several…

Carballo, Jose Luis O.; And Others

189

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

PubMed Central

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

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

2014-01-01

190

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

ERIC Educational Resources Information Center

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

Van Peer, Christine

2006-01-01

191

Transition and Students with Twice Exceptionality  

ERIC Educational Resources Information Center

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

Prior, Susan

2013-01-01

192

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

PubMed Central

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

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; Lindstrom, Jaana; Lingaas-Holmen, Oddgeir; Mitchell, Sabrina L.; Narisu, Narisu; Robinson, Jennifer G.; Schumacher, Fred; Stancakova, 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.; Buzkova, 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.; Kesaniemi, Antero Y.; Kuusisto, Johanna; Laakso, Markku; Lakka, Timo A.; Lee, I-Te; Leppert, Mark F.; Matise, Tara C.; Moilanen, Leena; Nj?lstad, 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

193

Genetic polymorphisms of 15 STR loci within Turkish student population living in Sarajevo, Bosnia and Herzegovina.  

PubMed

Allele frequencies of 15 STRs included in the PowerPlex 16 System (D3S1358, TH01, D21S11, D18S51, Penta E, D5S818, D13S317, D7S820, D16S539, CSF1PO, Penta D, VWA, D8S1179, TPOX and FGA) were calculated from the referent sample of 100 unrelated individuals of both sexes from Turkish student population living in Sarajevo, Bosnia and Herzegovina. Buccal swab, as a source of DNA, was collected from the volunteers from whom the informed consent form was obtained. DNA extraction was performed using QIAamp DNA Micro kit by Qiagen. DNA template ranging from 0.5 to 2 ng was used to amplify 15 STR loci by PCR multiplex amplification which was performed by using the PowerPlex 16 kit (Promega Corp., Madison, WI, USA) according to the manufacturer's protocol. The amplifications were carried out in a PE Gene Amp PCR System thermal cycler (Applied Biosystems) and capillary electrophoresis was carried out in an ABI PRISM 310 Genetic Analyzer (Applied Biosystems) in accordance with the manufacturer's recommendations. The frequency of each locus was calculated from the numbers of each observed genotype. Deviation from Hardy-Weinberg equilibrium and observed heterozygosity were calculated. Data were analyzed by using Microsoft Excel workbook template--Powerstats V12 and the power of discrimination (PD), power of exclusion (PE), as well as other population genetic indices for the 15 STR loci were calculated. Obtained results contribute to existing Turkish DNA database, as well as insight of differences and similarities in comparison to population of Bosnia and Herzegovina. In addition, 13 autosomal STR loci frequencies (D3S1358, TH01, D21S11, D18S51, Penta E, D5S818, D13S317, D7S820, D16S539, CSFIPO, Penta D, VWA, D8S1 179, TPOX, and FGA) were studied in 15 different worldwide populations (Turkish, Bosnian, Croatian, Serbian, Montenegrin, Macedonian, Albanian, Kosovan, Greek, Russian, Japanese, Korean, Lithuanian, Iraqi, Belarusian). For the proof of corresponding data, two different Turkish population STR data obtained from previously published articles were compared with our data and this showed that our data correspond to these 2 previously published data. Further, STR allele frequency data for 13 loci for each population were obtained from previous scientific articles and the allele frequencies and genetic diversity among the 15 sample populations were compared. In addition, even though the populations are from different nationalities, the STR data are similar among the geographically close populations. The phylogenetic tree established among worldwide populations and genetic distance values show a great affinity among the 15populations. Our data is useful for anthropological and further comparative genetic studies of populations. PMID:24611350

Dogan, Serkan; Kovacevi?, Lejla; Marjanovi?, Damir

2013-12-01

194

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

ERIC Educational Resources Information Center

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

Lazenby, Sara

2011-01-01

195

CASCADE EFFECTS IN HETEROGENEOUS POPULATIONS  

E-print Network

. The clothes we wear, the cars we drive, and the food we eat are all influenced to varying extents by public of schoolchildren is well established: children may be motivated either to take drugs, or to `just say no if they are convinced of its popularity. This is why, for example, McDonald's advertises `billions and billions

Gordon, Geoffrey J.

196

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

PubMed

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

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

2014-06-01

197

"For most of us Africans, we don't just speak": a qualitative investigation into collaborative heterogeneous PBL group learning.  

PubMed

Collaborative approaches such as Problem Based Learning (PBL) may provide the opportunity to bring together diverse students but their efficacy in practice and the complications that arise due to the mixed ethnicity needs further investigation. This study explores the key advantages and problems of heterogeneous PBL groups from the students' and teachers' opinions. Focus groups were conducted with a stratified sample of second year medical students and their PBL teachers. We found that students working in heterogeneous groupings interact with students with whom they don't normally interact with, learn a lot more from each other because of their differences in language and academic preparedness and become better prepared for their future professions in multicultural societies. On the other hand we found students segregating in the tutorials along racial lines and that status factors disempowered students and subsequently their productivity. Among the challenges was also that academic and language diversity hindered student learning. In light of these the recommendations were that teachers need special diversity training to deal with heterogeneous groups and the tensions that arise. Attention should be given to create 'the right mix' for group learning in diverse student populations. The findings demonstrate that collaborative heterogeneous learning has two sides that need to be balanced. On the positive end we have the 'ideology' behind mixing diverse students and on the negative the 'practice' behind mixing students. More research is needed to explore these variations and their efficacy in more detail. PMID:21088990

Singaram, Veena S; van der Vleuten, Cees P M; Stevens, Fred; Dolmans, Diana H J M

2011-08-01

198

A study of student and administrator perceptions regarding the existence of student-to-student cruelty in the independent middle school population  

Microsoft Academic Search

The purpose of this study was (a) to investigate the extent of student-to-student cruelty as perceived by independent middle school students and administrators, (b) to analyze cruelty, and (c) to compare student and administrator perceptions. Most available research on student-to-student cruelty was conducted in public schools while limited data existed for independent schools. ^ One thousand, two hundred eleven (1,211)

Lester Frederick Frawley

2000-01-01

199

Heterogeneous noise enhances spatial reciprocity  

E-print Network

Recent research has identified the heterogeneity as crucial for the evolution of cooperation in spatial population. However, the influence of heterogeneous noise is still lack. Inspired by this interesting question, in this work, we try to incorporate heterogeneous noise into the evaluation of utility, where only a proportion of population possesses noise, whose range can also be tuned. We find that increasing heterogeneous noise monotonously promotes cooperation and even translates the full defection phase (of the homogeneous version) into the complete cooperation phase. Moreover, the promotion effect of this mechanism can be attributed to the leading role of cooperators who have the heterogeneous noise. These type of cooperators can attract more agents penetrating into the robust cooperator clusters, which is beyond the text of traditional spatial reciprocity. We hope that our work may shed light on the understanding of the cooperative behavior in the society.

Yao, Y

2014-01-01

200

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

ERIC Educational Resources Information Center

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…

Brown, Patrick J. P.

2010-01-01

201

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

ERIC Educational Resources Information Center

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…

Mills, Carol J.; Tissot, Sherri L.

1995-01-01

202

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

ERIC Educational Resources Information Center

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…

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

2014-01-01

203

Students with Dyslexia If you have dyslexia, you are not alone. It is thought that 10% of the population  

E-print Network

Students with Dyslexia If you have dyslexia, you are not alone. It is thought that 10% of the population shows signs of dyslexia with around 4% affected severely. When applying for jobs the following organisations appear positive about dyslexia, do not limit your applications to these alone. Choose employers

Royal Holloway, University of London

204

Population Connection: Population Education  

NSDL National Science Digital Library

Population Connection "is the national grassroots population organization that educates young people and advocates progressive action to stabilize world population at a level that can be sustained by Earth's resources." The Population Connection's Education Program develops "age-appropriate curricula to complement students' science and social science instruction about human population trends and their impacts on natural resources, environmental quality and human well-being." The Population Education website offers a variety of educational resources including downloadable classroom activities and readings, and newsletters for teachers and students. The site also provides information about professional development opportunities for educators and free population education workshops held at universities for pre-service teachers and graduate students.

205

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

ERIC Educational Resources Information Center

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…

Baughman, Kristen N.; Bruce, Jacklyn

2011-01-01

206

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

ERIC Educational Resources Information Center

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…

Jolly, J. Christopher

2008-01-01

207

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

NSDL National Science Digital Library

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

Pickard, Dawn M.; Pyle, Eric; Fetters, Marcia; Marcia Fetters, Dawn M. Pickard, and Eric Pyle

2003-02-01

208

Prevalence of ADHD in a sample of Italian students: a population-based study.  

PubMed

Attention-deficit/hyperactivity disorder (ADHD) is one of the most common diagnosis for children and adolescents, although the reported estimates for prevalence are extremely variable worldwide. In the present work we investigate the prevalence of ADHD in a sample of Italian students in a study divided in two phases. In Phase I, a total of 6183 schoolchildren (3178 males and 3005 females, aged range 5-15 years) were screened using the SDAI rating scale for teachers. In Phase II, the parents of children and adolescents who met high screen criteria according to SDAI (cut-off>14; n=471, 7.3%) were invited to complete a specific clinical-diagnostic assessment for ADHD with the help of an experienced clinician. Within the entire sample, 107 children dropped out and 12 had mental retardation, whereas 332 subjects (278 males and 54 females, age range 5-14 years) completed the Phase II of the study. One hundred ninety subjects (163 males and 27 females, male: female ratio 6:1, mean age 8 years) were diagnosed with ADHD, indicating a prevalence of 3%. ADHD subtypes included the following: combined (n=108; 56.8%), inattentive (n=48; 25.2%) and hyperactive/impulsive (n=33; 17.3%). Our findings are in line with other reports of ADHD prevalence in the European Countries, and may contribute to underline the impact of this phenomenon in the population, and the need of achieving an improvement in the quality of the public health mental service for the prevention and treatment of ADHD. PMID:23751299

Bianchini, Rio; Postorino, Valentina; Grasso, Rita; Santoro, Bartolo; Migliore, Salvatore; Burlò, Corrado; Tata, Carmela; Mazzone, Luigi

2013-09-01

209

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

NSDL National Science Digital Library

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

Patrick J.P. Brown (King College Biology)

2010-09-01

210

Rethinking Policy for At-Risk Students.  

ERIC Educational Resources Information Center

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…

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

211

International Students and Academic Assistance: Meeting the Needs of Another College Population  

Microsoft Academic Search

International students are attending U.S. colleges in large numbers. They often must work in a non-native language, English, and adjust to a new academic culture containing unfamiliar tasks, approaches to learning, and new patterns of relationships if they are to achieve. An emphasis on educating the whole student and a focus on the development of self-regulated learning in students make

Karen Irene Burrell; Dae Jin Kim

212

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

PubMed Central

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.

Franklin, Rachel S.

2014-01-01

213

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

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,…

Brown-Anfelouss, Marjorie

2012-01-01

214

Student Motivation and Study Strategies in University and College of Advanced Education Populations  

Microsoft Academic Search

A “study process complex” comprising three major motives (instrumental, intrinsic and achievement) and three cognate learning\\/study strategies (reproducing, meaning and organising), is described. The Study Process Questionnaire (SPQ) is an instrument designed to tap these motives and strategies in tertiary students. It is hypothesized that patterns of motivations and study strategies would be typically different between students in colleges of

John Biggs

1982-01-01

215

How Educational Media Can Benefit the International Student Population in the United States University Setting  

Microsoft Academic Search

This study investigated international students' access to the Internet, their use of web- based educational media, and the differences between those who utilized a website designed to decrease acculturative stress and those who did not. Results indicated that international students applying to universities in the United States have excellent ac- cess to the Internet, although in some areas it is

Kerry Purmensky

2005-01-01

216

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

ERIC Educational Resources Information Center

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…

FRANKLIN, ELTON

217

A Survey of Eating and Weight-Related Behaviors in a Medical University Student Population  

Microsoft Academic Search

The purpose of this study was to assess using a survey questionnaire the lifetime prevalence of several eating- and weight-related behaviors in medical, dental, and nursing students. The sample included 109 students: 59% were female, 67% were single, 84% were Caucasian, and average age was 26.5 years. The results indicated that the prevalence rates of food restriction, exercise, self-induced vomiting,

L. M. Varner; Jeff Crowson; Darlene Shaw

1998-01-01

218

Mapping Variables Related to Social Identity, Distress and Perceived Health in an Undergraduate Student Population  

Microsoft Academic Search

The relationship between students’ levels of self-categorisation or identification with their university, their problem-solving style, perceived social support, psychological distress and self-reported illness was investigated in a sample of 269 students (181 females and 88 males). Structural equation modelling shows that problem-solving style, perceived social support, and strength of identity, are the best predictors of both distress and illness, while

Tony Cassidy

2004-01-01

219

Students delivering health care to a vulnerable Appalachian population through interprofessional service-learning.  

PubMed

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 for students by partnering with the College of Pharmacy, the College of Clinical & Rehabilitative Health Sciences, and the local public housing authority. Select faculty from each college met and developed a plan to form student teams from all three colleges to conduct in-home comprehensive medical and nutrition assessments and medication chart reviews of high-risk older adults. Following the in-home visit, students and faculty discuss the assessment findings at planned interprofessional meetings. Students present their findings from each discipline's perspective and collaboratively set health priorities and develop intervention strategies and an inclusive follow-up plan. Excerpts from students' reflective narratives discussing the impact of the interprofessional service-learning experiences are shared. PMID:23362854

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

2013-01-01

220

Changing AIDS Risk Behavior: Effects of an Intervention Emphasizing AIDS Risk Reduction Information, Motivation, and Behavioral Skills in a College Student Population  

Microsoft Academic Search

This research used the Information–Motivation–Behavioral Skills (IMB) model of AIDS risk behavior change (J. D. Fisher & Fisher, 1992a) to reduce AIDS risk behavior in a college student population. College students received an IMB model-based intervention that addressed AIDS risk reduction information, motivation, and behavioral skills deficits that had been empirically identified in this population, or were assigned to a

Jeffrey D. Fisher; William A. Fisher; Stephen J. Misovich; Diane L. Kimble; Thomas E. Malloy

1996-01-01

221

How Do School Systems Manage Pupils' Heterogeneity?  

ERIC Educational Resources Information Center

School systems worldwide respond in particular ways to students' academic heterogeneity, and different countries have developed different strategies to manage such heterogeneity. Whereas some countries separate children according to distinctive educational routes (or tracks) at early ages, others rely on intensive use of grade retention, while…

Dupriez, Vincent; Dumay, Xavier; Vause, Anne

2008-01-01

222

Identifying the attitudes and traits of teachers with an at-risk student population in a multi-cultural urban high school  

Microsoft Academic Search

Purpose – To identify the attitudes and traits of teachers with an at-risk student population in a multi-cultural urban high school. Design\\/methodology\\/approach – A research team consisting of doctoral students and their faculty advisor used an appreciative inquiry model to identify attitudes and traits of teachers who supported effective teaching in an urban high school with a high at-risk student

Raymond L. Calabrese; Sherry Goodvin; Rae Niles

2005-01-01

223

On the definition and the computation of the basic reproduction ratio R 0 in models for infectious diseases in heterogeneous populations  

Microsoft Academic Search

The expected number of secondary cases produced by a typical infected individual during its entire period of infectiousness in a completely susceptible population is mathematically defined as the dominant eigenvalue of a positive linear operator. It is shown that in certain special cases one can easily compute or estimate this eigenvalue. Several examples involving various structuring variables like age, sexual

O. Diekmann; J. A. P. Heesterbeek; J. A. J. Metz

1990-01-01

224

On the definition and the computation of the basic reproduction ratio R0 in models for infectious diseases in heterogeneous populations  

Microsoft Academic Search

The expected number of secondary cases produced by a typical infected individual during its entire period of infectiousness in a completely susceptible population is mathematically defined as the dominant eigenvalue of a positive linear operator. It is shown that in certain special cases one can easily compute or estimate this eigenvalue. Several examples involving various structuring variables like age, sexual

O. Diekmann; J. A. P. Heesterbeek; J. A. J. Metz

1990-01-01

225

We do not explicitly consider heterogeneity in sexual activity, although the results are robust to consideration of contact networks and stratification of the population (see  

E-print Network

for each population. The model parameters g, R0 and N for New York City and Houston in Fig. 2b were York City and 6 in Houston, and m ¼ 0.03). The impact of different levels of coupling (1) on cross was assumed to follow a power law, in agreement with the decennial census estimates of the US city sizes

Weeks, Eric R.

226

Accommodating Change: The Process of Growth and Development amongst a Mature Student Population  

ERIC Educational Resources Information Center

Many commentators have noted that mature students speak of education changing them. One of the most positive outcomes is a heightened sense of self-belief and confidence, which pervades other areas of their lives, not just the academic environment. It is argued within this paper that such research tends to offer a somewhat simplistic account of…

Mercer, Jenny; Saunders, Danny

2004-01-01

227

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

ERIC Educational Resources Information Center

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…

Novogrodsky, Dorothy

2012-01-01

228

Social and Economic Characteristics of Students: October 1972. Current Population Reports, Series P-20, No. 260.  

ERIC Educational Resources Information Center

New information is presented in this report on recent changes in rates of school participation in the United States by age, sex, marital status, race, and income, and changes in field of study of college students. Included also for the first time is information on the enrollment status of persons 35 years old and over, and on the enrollment level…

Suter, Larry E.; And Others

229

The Inventory of College Students' Recent Life Experiences: A decontaminated hassles scale for a special population  

Microsoft Academic Search

The development and validation of a new decontaminated hassles measure, the Inventory of College Students' Recent Life Experiences, are described. An initial pool of 85 items was administered to 100 undergraduates along with the Perceived Stress Scale. Forty-nine items were selected based on significant correlations against the Perceived Stress Scale. The alpha reliability of the resultant final form of the

Paul M. Kohn; Kathryn Lafreniere; Maria Gurevich

1990-01-01

230

Cognition as a function of depression in a student population: Content and complexity of cognitions  

Microsoft Academic Search

Cognitive content and complexity were studied as functions of depression as measured by the Beck Depression Inventory in three groups of college students (N = 73): nondepressed, mildly depressed, and highly depressed. Subjects were administered six verions of Bieri's (Bieri, Atkins, Briar, Leaman, Miller, & Tripodi, 1966) Repertory Grid Test, on which they rated the three domains of persons in

J. M. Oliver; Judith McGee

1982-01-01

231

How One University Examined Graduation Rates of Its Undergraduate Student Population  

ERIC Educational Resources Information Center

The Office of Planning and Institutional Research (OPAIR), at the University of the West Indies, Mona Campus was asked to undertake an analysis of student throughput rates as part of a University-wide initiative involving the three campuses. Each Campus was provided with a template and guidelines for reporting the data. The exercise was intended…

Paterson, Nicola; Gordon, Garvin

2010-01-01

232

Using Mini-Grants and Service-Learning Projects to Prepare Students to Serve Underserved Populations  

Microsoft Academic Search

This article discusses a short term service-learning initiative developed by the Center for Community Health and Service Learning (CCHSL) at Morehouse School of Medicine, exploring how extramural mini-grant opportunities can be used to teach students and residents about community health assessment, health communication, and health promotion.

Meryl S. McNeal; Ayanna V. Buckner

2012-01-01

233

Using mini-grants and service-learning projects to prepare students to serve underserved populations.  

PubMed

This article discusses a short term service-learning initiative developed by the Center for Community Health and Service Learning (CCHSL) at Morehouse School of Medicine, exploring how extramural mini-grant opportunities can be used to teach students and residents about community health assessment, health communication, and health promotion. PMID:22643551

McNeal, Meryl S; Buckner, Ayanna V

2012-05-01

234

Preparing to teach diverse student populations: a British and American perspective  

Microsoft Academic Search

Demographic changes in Britain and the USA have resulted in schools that are more culturally diverse than they were a generation ago. In response to these changes, colleges and departments of education are attempting to prepare teachers who are able to work with students from a wide range of ethnic, racial and religious backgrounds. Teacher preparation programmes face the challenge

Thomas E. Deering

1997-01-01

235

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

ERIC Educational Resources Information Center

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…

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

2013-01-01

236

Polymorphisms in DNA-Repair Genes in a Cohort of Prostate Cancer Patients from Different Areas in Spain: Heterogeneity between Populations as a Confounding Factor in Association Studies  

PubMed Central

Background Differences in the distribution of genotypes between individuals of the same ethnicity are an important confounder factor commonly undervalued in typical association studies conducted in radiogenomics. Objective To evaluate the genotypic distribution of SNPs in a wide set of Spanish prostate cancer patients for determine the homogeneity of the population and to disclose potential bias. Design, Setting, and Participants A total of 601 prostate cancer patients from Andalusia, Basque Country, Canary and Catalonia were genotyped for 10 SNPs located in 6 different genes associated to DNA repair: XRCC1 (rs25487, rs25489, rs1799782), ERCC2 (rs13181), ERCC1 (rs11615), LIG4 (rs1805388, rs1805386), ATM (rs17503908, rs1800057) and P53 (rs1042522). The SNP genotyping was made in a Biotrove OpenArray® NT Cycler. Outcome Measurements and Statistical Analysis Comparisons of genotypic and allelic frequencies among populations, as well as haplotype analyses were determined using the web-based environment SNPator. Principal component analysis was made using the SnpMatrix and XSnpMatrix classes and methods implemented as an R package. Non-supervised hierarchical cluster of SNP was made using MultiExperiment Viewer. Results and Limitations We observed that genotype distribution of 4 out 10 SNPs was statistically different among the studied populations, showing the greatest differences between Andalusia and Catalonia. These observations were confirmed in cluster analysis, principal component analysis and in the differential distribution of haplotypes among the populations. Because tumor characteristics have not been taken into account, it is possible that some polymorphisms may influence tumor characteristics in the same way that it may pose a risk factor for other disease characteristics. Conclusion Differences in distribution of genotypes within different populations of the same ethnicity could be an important confounding factor responsible for the lack of validation of SNPs associated with radiation-induced toxicity, especially when extensive meta-analysis with subjects from different countries are carried out. PMID:23936089

Henriquez-Hernandez, Luis Alberto; Valenciano, Almudena; Foro-Arnalot, Palmira; Alvarez-Cubero, Maria Jesus; Cozar, Jose Manuel; Suarez-Novo, Jose Francisco; Castells-Esteve, Manel; Ayala-Gil, Adriana; Fernandez-Gonzalo, Pablo; Ferrer, Montse; Guedea, Ferran; Sancho-Pardo, Gemma; Craven-Bartle, Jordi; Ortiz-Gordillo, Maria Jose; Cabrera-Roldan, Patricia; Herrera-Ramos, Estefania; Lara, Pedro C.

2013-01-01

237

Simulating Population Growth.  

ERIC Educational Resources Information Center

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

Byington, Scott

1997-01-01

238

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

SciTech Connect

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

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

1993-10-01

239

Factor structure of the Hospital Anxiety and Depression Scale in Japanese psychiatric outpatient and student populations  

Microsoft Academic Search

BACKGROUND: The Hospital Anxiety and Depression Scale (HADS) is a common screening instrument excluding somatic symptoms of depression and anxiety, but previous studies have reported inconsistencies of its factor structure. The construct validity of the Japanese version of the HADS has yet to be reported. To examine the factor structure of the HADS in a Japanese population is needed. METHODS:

Tomomi Matsudaira; Hiromi Igarashi; Hiroyoshi Kikuchi; Rikihachiro Kano; Hiroshi Mitoma; Kiyoshi Ohuchi; Toshinori Kitamura

2009-01-01

240

Considerations for Changing Populations: Supporting Nontraditional Students in Acquiring Special Education Licensure.  

ERIC Educational Resources Information Center

This article describes a program at the University of Hawaii that recruits individuals with training in general education for a special education certification program. Program features include strategies for aligning course and field requirements and the infusion of cultural and linguistic considerations of the school population. (Contains…

Ornelles, Cecily; Goetz, Lori

2001-01-01

241

An Action Research Project on Preparing Teachers to Meet the Needs of Underserved Student Populations  

ERIC Educational Resources Information Center

The focus of this action research study was on the initial stage in reforming our teacher preparation programs. We designed, conducted, evaluated, and revised the components of our teacher preparation programs that were aimed at providing preservice teachers with the confidence and knowledge needed to meet the needs of youth populations

Buck, Gayle A.; Cordes, Jeanene G.

2005-01-01

242

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

PubMed

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

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

2014-04-01

243

A novel online Food Recall Checklist for use in an undergraduate student population: a comparison with diet diaries  

PubMed Central

Background University students are commonly overlooked when diet of populations is measured and there is a lack of comprehensive dietary assessment in whole university student populations. To measure diet of undergraduate students, a new online 121-item Food Recall Checklist (FoRC) was designed as an alternative to a non-weighed record (food diary). This article reports the comparison between the new dietary assessment method (FoRC) and the food diary as a measure of energy (kJ), fat (g), Non-Starch Polysaccharide (NSP) (g), fruit and vegetables (g), breakfast cereal (g) and bread (g) and alcohol (units) intake. Methods Fifty-three students at the University of Aberdeen completed four days of FoRC then four days food diary. Median agreement and correlation between the two methods was assessed for foods and nutrients using the Spearman's rank correlation co-efficient and the Wilcoxon signed ranks test. Agreement between FoRC and food diary was assessed using the Bland-Altman method. Results The mean time taken to complete FoRC for one day was 7.4 minutes. Intakes of fat (g and % food energy), NSP and bread were similar between FoRC and the food diary. Median energy intake was 8185 kJ in the food diary and 8007 kJ in FoRC. However, FoRC recorded significantly lower intakes of energy and alcohol and significantly higher intakes of fruit and vegetables and breakfast cereal compared with the food diary. There was considerable variation in agreement between methods at the individual level. For all variables except alcohol and percentage energy from fat, correlation co-efficients were statistically significant and greater than 0.5. Conclusion At the group level, four days of FoRC showed good median agreement with the food diary and there was high correlation between methods for most foods and nutrients. This suggests that this novel method of assessing diet can provide a useful alternative for assessing group mean intakes but that individual intakes may need to be interpreted with care. PMID:19228392

Comrie, Fiona; Masson, Lindsey F; McNeill, Geraldine

2009-01-01

244

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

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…

Jarnagin, Lea Marie

2010-01-01

245

How is an Electronic Screening and Brief Intervention Tool on Alcohol Use Received in a Student Population? A Qualitative and Quantitative Evaluation  

PubMed Central

Background A previous study among Antwerp college and university students showed that more male (10.2%–11.1%) than female (1.8%–6.2%) students are at risk for problematic alcohol use. The current literature shows promising results in terms of feasibility and effectiveness for the use of brief electronic interventions to address this health problem in college and university students. We evaluated this type of intervention and cite existing literature on the topic. Objective To develop a website, www.eentjeteveel.be, to motivate college and university students with problematic alcohol use to reduce alcohol consumption and increase their willingness to seek help. Method The website contained a questionnaire (Alcohol Use Disorders Identification Test [AUDIT]) for students to test their alcohol use. According to their answers, the students immediately received personalized feedback (personal AUDIT score and additional information on risks associated with alcohol use) and a suggestion for further action. Afterward, students could send an email to a student counselor for questions, guidance, or advice. To obtain in-depth qualitative information on the opinions and experiences of students, we held 5 focus group discussions. The topics were publicity, experiences, impressions, and effects of the website. We analyzed the quantitative results of the online test in SPSS 15.0. Results More than 3500 students visited www.eentjeteveel.be; over half were men (55.0%). A total of 34 students participated in the focus group discussions. The mixture of quantitative and qualitative methods to evaluate the intervention allowed a thorough analysis and provided complementary results. The intervention was well received by the student population. However, some minor aspects should be reconsidered, such as website publicity and providing students with options that were added after intermediate evaluation. The intervention increased the motivation of students to think about their alcohol use but could not stimulate them to change their behavior. The website attracted relatively more male than female students and more students in the high-risk group than in the low-risk group. The high-risk group was more inclined to seek advice or guidance (23/400, 6%; ?2 2 = 32.4, P < .001) than the low-risk group (34/1714, 2%; ?2 2 = 32.4, P < .001). Conclusions We gained unique insight into students’ experiences, opinions, and perceptions with regard to the intervention. The results show that the intervention was positively received in the population, and the willingness to seek help was increased. However, real behavior change needs further research. The results of this study can assist health providers and researchers in better understanding college and university students’ perceptions of eHealth initiatives. PMID:22525340

Van Royen, Paul; Vriesacker, Bart; De Mey, Leen; Van Hal, Guido

2012-01-01

246

An Action Research Project on Preparing Teachers to Meet the Needs of Underserved Student Populations  

NASA Astrophysics Data System (ADS)

The focus of this action research study was on the initial stage in reforming our teacher preparation programs. We designed, conducted, evaluated, and revised the components of our teacher preparation programs that were aimed at providing preservice teachers with the confidence and knowledge needed to meet the needs of youth populations underserved in science education. The conceptual framework of this study predicted that providing preservice teachers with experiences in teaching science to at-risk youth in a nonformal educational setting and that exploring these experiences in a seminar setting will increase the teachers confidence and knowledge in regard to teaching science to children from underserved populations. The community-based experience allowed for an experience in which 20 preservice teachers taught in a situation in which at-risk youth were the majority, thus spotlighting their needs in a manner traditionally not experienced by these prospective teachers. A two-phase methodological design (J. Creswell, 1994) was utilized to answer the questions: (a) Did the plan lead to the desired outcomes? and (b) What strategies fostered or hindered progress toward the desired outcomes? The findings of this study were utilized to develop our next action step in preparing teachers to foster science literacy for All Americans.

Buck, Gayle A.; Cordes, Jeanene G.

2005-02-01

247

Population Explosion  

NSDL National Science Digital Library

A series of experiments explore the effects of increased population growth on a population of Fast Plants. Through these inquiries, students will better understand the many substantial and pertinent issues surrounding human population explosion on Earth.These experiments can be adjusted toward middle, high school or post-secondary levels.

Program, The W.

248

Examining unusual digit span performance in a population of postsecondary students assessed for academic difficulties.  

PubMed

Methods of identifying poor test-related motivation using the Wechsler Adult Intelligence Scale Digit Span subtest are based on identification of performance patterns that are implausible if the test taker is investing full effort. No studies to date, however, have examined the specificity of such measures, particularly when evaluating persons with either known or suspected learning or attention disorders. This study investigated performance of academically challenged students on three measures embedded in the Wechsler Adult Intelligence Scale-III, namely, low Digit Span, high Vocabulary-Digit span (Voc-DS), and low Reliable Digit Span scores. Evaluating subjects believed to be investing full effort in testing, it was found that both Digit Span and Reliable Digit Span had high specificity, although both showed relatively lower sensitivity. In contrast, VOC-DS was especially weak in both sensitivity and specificity, with an apparent false positive rate of 28%. Use of VOC-DS is therefore not appropriate for those with a history of learning or attention problems. PMID:19915200

Harrison, Allyson G; Rosenblum, Yoni; Currie, Shannon

2010-09-01

249

Bird Populations  

NSDL National Science Digital Library

In this lesson, students will study bird migratory patterns and the methods that researchers use to study them. Students will be introduced to the concepts of the study of bird movements. The lesson is given in two parts: 1) gathering data about bird populations, and 2) monitoring the movements of bird populations.To assess student learning, they will write a short answer essay explaining the differences between the four types of population movements described in the Movements of Bird Populations resource. Students should be able to describe what kinds of patterns might be observed in each type and how observing and studying each pattern gives scientists the evidence they need to understand the movement of bird populations.

American Association for the Advancement of Science (;)

2005-06-23

250

Population Growth  

NSDL National Science Digital Library

This series of activities explores the mathematical and environmental aspects of population growth. Using archived census and demographic data as well as up-to-the-minute population estimates from the U.S. Census Bureau, students learn how to model population growth and study the implications of a changing population. The project provides instructions, activities, back-up information, data links, reference materials, on-line help, and an instructor guide. Although intended for high school students, activities 1 through 5 and 9 avoid higher mathematics and offer students work on statistical and historical aspects of population growth appropriate for the middle school level. This on-line project is part of the Center for Improved Engineering and Science Education (CIESE) program, which has developed internet activities for the elementary, middle, and high school level student.

2007-12-12

251

The experience of implementing an interprofessional research methods course for student health professionals of population health and clinical practice. Getting the right fit  

Microsoft Academic Search

Purpose: This paper reports on the adaptation of an existing interpretive and critical research methods course in nursing for postgraduate student health professionals in a School of Population Health and Clinical Practice. Methods: A cyclical approach of inquiry, reflection and planning was undertaken by the teaching team to make changes to the existing course for implementation for the current and

Anne Wilson

2009-01-01

252

Special Student Populations in Vocational and Technical Education. Private Sector Involvement in Vocational and Technical Education. Analysis of Distribution of Funds for Secondary and Postsecondary Vocational Education.  

ERIC Educational Resources Information Center

After analyzing the needs of special student populations in vocational and technical education in South Carolina, private sector involvement in vocational and technical education, and the distribution of funds for secondary and postsecondary vocational education in the state, the South Carolina Council on Vocational and Technical Education…

South Carolina State Council on Vocational and Technical Education, Columbia.

253

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

"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…

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

2012-01-01

254

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

ERIC Educational Resources Information Center

"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…

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

2012-01-01

255

The Nation's Report Card: Mega-States--An Analysis of Student Performance in the Five Most Heavily Populated States in the Nation. NCES 2013-450  

ERIC Educational Resources Information Center

California, Florida, Illinois, New York, and Texas enroll close to 40 percent of the nation's public school students. The importance of these "Mega-States" goes beyond the sheer size of their population. They now serve more than half of the nation's English language learners (ELL), as well as some of the largest concentrations of children from…

National Center for Education Statistics, 2013

2013-01-01

256

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

ERIC Educational Resources Information Center

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

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

2014-01-01

257

Moral and Social Norms in Heterogeneous Populations  

Microsoft Academic Search

This paper presents an idealized model of social interaction, where preferences are private information and individuals cannot condition their behavior on the identity of whom they are interacting with. An optimal decentralized benchmark is identified, where each individual imposes some restriction on what people interacting with him cannot do. Social norms arise in the model as a consequence of reciprocating

Matteo Richiardi

258

The Role of African American Mentor Teachers in Preparing White Preservice Teachers for African American Student Populations  

ERIC Educational Resources Information Center

How do we bridge the mismatch between teachers and students based on race and ethnicity currently in our nation's schools? The teaching force remains overwhelmingly White, while the percentage of K-12 students of color continues to rise. Because of cultural dissonance, teachers may not understand the needs of their students. This study shows…

Moule, Jean; Higgins, Karen M.

2007-01-01

259

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

ERIC Educational Resources Information Center

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…

Decker, Jody F.; Slawson, Robin M.

2012-01-01

260

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

E-print Network

to such heterogeneous environments can lead to corresponding patterns of population genetic structure. To what extentThe effects of migration and drift on local adaptation to a heterogeneous environment F. BLANQUART, Idaho Introduction Populations often experience spatial heterogeneity in their environment. Adaptation

261

The Heterogeneous HLA Genetic Makeup of the Swiss Stephane Buhler1  

E-print Network

The Heterogeneous HLA Genetic Makeup of the Swiss Population Ste´phane Buhler1 *, Jose´ Manuel studies, and understanding the population genetic background(s) of this culturally heterogeneous country and linguistic subdivisions in Switzerland. The results indicate a heterogeneous genetic makeup of the Swiss

Citi, Sandra

262

Preparing to care for an aging population: medical student reflections on their clinical mentors within a new geriatrics curriculum.  

PubMed

Reflective writing techniques such as journaling help provide insights into the process by which medical students are mentored and develop into practicing physicians. The authors sought to analyze medical students' journals regarding their mentored experiences within a new geriatrics curriculum at a U.S. medical school. Thirty preclinical and clinical medical student journalers participated in this project. The authors employed qualitative analytic techniques using an interdisciplinary team process. Three major themes emerged: (a) exposure to clinical mentors challenged medical students' preconceptions regarding older adults and geriatric medicine; (b) students learned new medical knowledge and techniques from observing their mentors; and (c) students provided positive and negative assessments of their mentors. Reflective journaling provides important insights into the process by which medical students draw upon mentored clinical experiences during their training. Such mentorship may be particularly relevant to promoting their interest in geriatrics. PMID:24138182

Farrell, Timothy W; Shield, Renée R; Wetle, Terrie; Nanda, Aman; Campbell, Susan

2013-01-01

263

Students.  

ERIC Educational Resources Information Center

Educational consumerism continues to be the major focus of litigation involving students. Disputes over admissions practices, grades, academic terminations, and financial aid comprised the largest proportion of cases reported this year. The section on academic affairs is the largest single section. As the job market gets tighter and the cost of…

Gehring, Donald D.; Young, D. Parker

264

Diffusion and Surface Reaction in Heterogeneous Catalysis  

ERIC Educational Resources Information Center

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)

Baiker, A.; Richarz, W.

1978-01-01

265

Integration of the K-12 LGBTQI Student Population in School Counselor Education Curricula: The Current State of Affairs  

Microsoft Academic Search

A national survey of 123 school counselor educators investigated how participants integrated K–12 lesbian, gay, bisexual, transgender, questioning, intersex (LGBTQI) students’ needs and concerns into school counseling curricula. Results indicated 91.9% of participants integrated the K–12 LGBTQI students’ needs and concerns for a median pedagogical duration of one, 3-hour session within a single course, focusing on students’ knowledge and awareness

Melissa Luke; Kristopher M. Goodrich; Janna L. Scarborough

2011-01-01

266

Towards Inverse Modeling of Intratumoral Heterogeneity  

E-print Network

Development of resistance limits efficiency of present anticancer therapies and preventing it remains big challenge in cancer research. It is accepted, at intuitive level, that the resistance emerges as a consequence of cancer cells heterogeneity at molecular, genetic and cellular levels. At the same time, population heterogeneity stands as one of fundamental prerequisite of evolutionary theory, which was accepted long time ago as an instructive conceptual framework to understand cancer behavior. Produced by many sources, tumor heterogeneity is extremely complex time dependent statistical characteristics which may be quantified by the measures defined in many different ways, most of them coming from statistical mechanics. While genetic intratumor diversity is well accepted as necessary prerequisite of evolution, the role of non-genetic intratumor diversity in cancer progression is not yet satisfactorily explained. In the paper we construct formal framework which provides to analyze phenotypic heterogeneity re...

Brutovsky, Branislav

2014-01-01

267

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

ERIC Educational Resources Information Center

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,…

Pattillo, Stephen Prescott

2011-01-01

268

Teacher Education Students as Tutors for a Diverse K-12 Population: A Model Tutorial Program for University-School Collaboration.  

ERIC Educational Resources Information Center

The Teaching/Learning Center (T/LC) at the Jacksonville State University College of Education (Alabama) is Level 2 in a 5-level teacher education program that is intended to build student competency through reflection and revision of the student's teaching practices. T/LC is a practicum laboratory for preservice teachers and an on-campus,…

Zenanko, Marsha A; Zenanko, Mike

269

Optimal Heterogeneity for Coding in Spiking Neural Networks  

NASA Astrophysics Data System (ADS)

The effect of cellular heterogeneity on the coding properties of neural populations is studied analytically and numerically. We find that heterogeneity decreases the threshold for synchronization, and its strength is nonlinearly related to the network mean firing rate. In addition, conditions are shown under which heterogeneity optimizes network information transmission for either temporal or rate coding, with high input frequencies leading to different effects for each coding strategy. The results are shown to be robust for more realistic conditions.

Mejias, J. F.; Longtin, A.

2012-06-01

270

Quantifying heterogeneity: flow cytometry of bacterial cultures  

Microsoft Academic Search

Flow cytometry is a technique which permits the characterisation of individual cells in populations, in terms of distributions in their properties such as DNA content, protein content, viability, enzyme activities and so on. We review the technique, and some of its recent applications to microbiological problems. It is concluded that cellular heterogeneity, in both batch and continuous axenic cultures, is

Douglas B. Kell; Hazel M. Ryder; Arseny S. Kaprelyants; Hans V. Westerhoff

1991-01-01

271

Heterogeneity of FFA responses or multiplexing?  

PubMed

Recent work using cluster analysis of brain activity during movies revealed distinct clusters that respond to faces and different non-face categories in the fusiform face area (FFA). Because of the limited heterogeneity observed, these results could mean that the FFA contains one population of cells capable of representing multiple categories. PMID:24360882

Ross, David A; McGugin, Rankin W; Gauthier, Isabel

2014-04-01

272

Adaptation Driven by Spatial Heterogeneities  

NASA Astrophysics Data System (ADS)

Biological evolution and ecology are intimately linked, because the reproductive success or "fitness" of an organism depends crucially on its ecosystem. Yet, most models of evolution (or population genetics) consider homogeneous, fixed-size populations subjected to a constant selection pressure. To move one step beyond such "mean field" descriptions, we discuss stochastic models of evolution driven by spatial heterogeneity. We imagine a population whose range is limited by a spatially varying environmental parameter, such as a temperature or the concentration of an antibiotic drug. Individuals in the population replicate, die and migrate stochastically. Also, by mutation, they can adapt to the environmental stress and expand their range. This way, adaptation and niche expansion go hand in hand. This mode of evolution is qualitatively different from the usual notion of a population climbing a fitness gradient. We analytically calculate the rate of adaptation by solving a first passage time problem. Interestingly, the joint effects of reproduction, death, mutation and migration result in two distinct parameter regimes depending on the relative time scales of mutation and migration. We argue that the proposed scenario may be relevant for the rapid evolution of antibiotic resistance.

Hermsen, Rutger

2011-03-01

273

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

E-print Network

??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… (more)

Pattillo, Stephen

2011-01-01

274

Dynamic heterogeneity and life histories.  

PubMed

Biodemography is increasingly focused on the large and persistent differences between individuals within populations in fitness components (age at death, reproductive success) and fitness-related components (health, biomarkers) in humans and other species. To study such variation we propose the use of dynamic models of observable phenotypes of individuals. Phenotypic change in turn determines variation among individuals in their fitness components over the life course. We refer to this dynamic accumulation of fitness differences as dynamic heterogeneity and illustrate it for an animal population in which longitudinal data are studied using multistate capture-mark-recapture models. Although our approach can be applied to any characteristic, for our empirical example we use reproduction as the phenotypic character to define stages. We indicate how our stage-structured model describes the nature of the variation among individual characteristics that is generated by dynamic heterogeneity. We conclude by discussing our ongoing and planned work on animals and humans. We also discuss the connections between our work and recent work on human mortality, disability and health, and life course theory. PMID:20738276

Tuljapurkar, Shripad; Steiner, Ulrich K

2010-08-01

275

Dynamic Heterogeneity and Life Histories  

PubMed Central

Biodemography is increasingly focused on the large and persistent differences between individuals within populations in fitness components (age at death, reproductive success) and fitness related components (health, biomarkers) in humans and other species. To study such variation we propose the use of dynamic models of observable phenotypes of individuals. Phenotypic change in turn determines variation among individuals in their fitness components over the life course. We refer to this dynamic accumulation of fitness differences as dynamic heterogeneity and illustrate it for an animal population in which longitudinal data are studied using multi-state capture-mark-recapture models. For our empirical example we use reproduction as the phenotypic character to define stages though our approach can be applied to any characteristic. We indicate how our stage-structured model describes the nature of the variation among individual characteristics that is generated by dynamic heterogeneity. We conclude by discussing our ongoing and planned work on animals and humans. We also discuss the connections between our work and recent work on human mortality, disability and health, and life course theory. PMID:20738276

Tuljapurkar, Shripad; Steiner, Ulrich K.

2012-01-01

276

The Graduate and Professional Student Association (GPSA) of FAU represents FAU's graduate and professional student population. We advocate for the interests of graduate and professional students University-wide and strive to enrich  

E-print Network

will not be reviewed. Email all application materials to gpsa@fau.edu OR bring your application to Student Union room Graduate and Professional Student Association 777 Glades Road, Student Union Room 234 Boca Raton, FL 33431 Engineering Business Medicine (Graduate Programs) Design & Social Inquiry Nursing Education Science Employment

Fernandez, Eduardo

277

Frequency of partial edentulism and awareness to restore the same: a cross sectional study in the age group of 18-25 years among kerala student population.  

PubMed

Treating partial edentulousness forms a major share of prosthodontic clinical practice. The purpose of this study was to find out the frequency of partial edentulism, its arch distribution status, awareness to restore, and the ratio of removable to fixed prosthesis among a student sample aged 18-25 years. The methodology selected was a questionnaire survey followed by clinical examination of the student community from Tirur taluk, Malappuram district, Kerala. The results showed that the frequency of partial edentulism among the surveyed group was significant with predominance in maxillary posterior edentulousness in men and mandibular posterior edentulousness in women. Though there was not any significant gender difference in the partial edentulism, women were more aware than men to restore it. All restored cases were with fixed bridges and no anterior edentulousness was found. The study also revealed a lack of awareness and need to educate the population. PMID:24431776

Abdurahiman, V T; Abdul Khader, M; Sanju John Jolly

2013-12-01

278

Heterogeneous atmospheric chemistry  

NASA Technical Reports Server (NTRS)

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.

Schryer, D. R.

1982-01-01

279

Towards heterogeneous distributed debugging  

SciTech Connect

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.

Damodaran-Kamal, S.K.

1995-04-01

280

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

PubMed Central

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

2010-01-01

281

The Use of Conceptual versus Physical Models in Teaching Action Research to Culturally Diverse Student Populations: A Preliminary Analysis.  

ERIC Educational Resources Information Center

Graduate business administration students (n=55) were asked which model they used for action research projects: conceptual or a physical model visually depicting action research. The physical model was favored by 69%; most agreed that it helped them understand the process of action research, was easy to use, and flexibly applied to various…

McMurray, Adela J.

2002-01-01

282

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

ERIC Educational Resources Information Center

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…

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

2013-01-01

283

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

ERIC Educational Resources Information Center

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…

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

2012-01-01

284

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

PubMed Central

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

2012-01-01

285

Phenotypic heterogeneity: differential stress resistance among individual cells of the yeast Saccharomyces cerevisiae  

Microsoft Academic Search

Overview Phenotypic heterogeneity describes non-genetic vari- ation that exists between individual cells within isogenic populations. Such heterogeneity is readily evident in the dierential sensitivity to stress of genetically identical cells and can be fundamental to the fitness and per- sistence of an organism. Consequently, phenotypic heterogeneity is currently receiving increased attention from the scientific community. Here, we present the first

Edward R. Sumner; Simon V. Avery

2002-01-01

286

Matrix Multiplication on Heterogeneous Platforms  

Microsoft Academic Search

In this paper, we address the issue of implementing matrix multiplication on heterogeneous platforms. We target two different classes of heterogeneous computing resources: heterogeneous networks of workstations and collections of heterogeneous clusters. Intuitively, the problem is to load balance the work with different speed resources while minimizing the communication volume. We formally state this problem in a geometric framework and

Olivier Beaumont; Vincent Boudet; Fabrice Rastello; Yves Robert

2001-01-01

287

Phylogenetic Quantification of Intra-tumour Heterogeneity  

PubMed Central

Intra-tumour genetic heterogeneity is the result of ongoing evolutionary change within each cancer. The expansion of genetically distinct sub-clonal populations may explain the emergence of drug resistance, and if so, would have prognostic and predictive utility. However, methods for objectively quantifying tumour heterogeneity have been missing and are particularly difficult to establish in cancers where predominant copy number variation prevents accurate phylogenetic reconstruction owing to horizontal dependencies caused by long and cascading genomic rearrangements. To address these challenges, we present MEDICC, a method for phylogenetic reconstruction and heterogeneity quantification based on a Minimum Event Distance for Intra-tumour Copy-number Comparisons. Using a transducer-based pairwise comparison function, we determine optimal phasing of major and minor alleles, as well as evolutionary distances between samples, and are able to reconstruct ancestral genomes. Rigorous simulations and an extensive clinical study show the power of our method, which outperforms state-of-the-art competitors in reconstruction accuracy, and additionally allows unbiased numerical quantification of tumour heterogeneity. Accurate quantification and evolutionary inference are essential to understand the functional consequences of tumour heterogeneity. The MEDICC algorithms are independent of the experimental techniques used and are applicable to both next-generation sequencing and array CGH data. PMID:24743184

Schwarz, Roland F.; Trinh, Anne; Sipos, Botond; Brenton, James D.; Goldman, Nick; Markowetz, Florian

2014-01-01

288

[Biochemical heterogeneity of mitochondria].  

PubMed

Rat liver mitochondria were fractionated on the basis of their sedimentation coefficients in the gradient of ficoll. The fractions ("heavy", "middle" and "light" mitochondria) were heterogeneous with regard to the content of protein, DNA, cytochrome a + a3 and respiratory activity. Heterogeneity of mitochondria did not result from the damage or microsomal and lysosomal contamination. The biosynthesis of DNA, RNA and proteins in the different fractions of mitochondria was studied. In vivo incorporation of radioactive precursor into RNA was highest in the fractions of "middle" mitochondria, whereas in vitro the "heavy" mitochondria showed maximum activity in the synthesis of RNA. In vitro DNA synthes was maximum in the fractions of "heavy" mitochondria, protein synthesis in "heavy" and "light" mitochondria. Activity of the synthesis of RNA, DNA and proteins in vitro depends on the content of DNA and cytochrome a + a3 in the different fractions of mitochondria. It is supposed that heterogeneity of mitochondria may be connected with their biogenesis. PMID:1053068

Adrianov, N V; Blednov, Iu A; Shuppe, N G

1976-01-01

289

Alcohol-related injury among Greek-letter college students: Defining a target population for secondary prevention  

PubMed Central

Members of Greek-letter societies are the heaviest drinkers on college campuses, and experience more alcohol-related problems than their peers. This study reports the results of a web-based survey administered to stratified random samples of college students from ten North Carolina universities. Greek-letter status was a significant independent risk factor for increased injury (both experienced and caused to others), even after adjusting for drinking behaviors. Prevention, screening, and intervention strategies are discussed in the context of these results. PMID:22689586

O'Brien, Mary Claire; McNamara, Robert S; McCoy, Thomas P; Sutfin, Erin L; Wolfson, Mark; Rhodes, Scott D

2013-01-01

290

Alcohol-related injury among Greek-letter college students: defining a target population for secondary prevention.  

PubMed

Members of Greek-letter societies are the heaviest drinkers on college campuses, and experience more alcohol-related problems than their peers. This study reports the results of a web-based survey administered to stratified random samples of college students from 10 North Carolina universities. Greek-letter status was a significant independent risk factor for increased injury (both experienced and caused to others), even after adjusting for drinking behaviors. Prevention, screening, and intervention strategies are discussed in the context of these results. PMID:22689586

O'Brien, Mary Claire; McNamara, Robert S; McCoy, Thomas P; Sutfin, Erin L; Wolfson, Mark; Rhodes, Scott D

2013-04-01

291

Why Teach Population Education?  

ERIC Educational Resources Information Center

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…

Cook-Fuller, Charlotte; And Others

292

'Heterogeneous Beliefs and Instability'  

Microsoft Academic Search

While Rational Expectations have dominated the paradigm of expectations formation, they have been more recently challenged on the empirical ground such as, for instance, in the dynamics of the exchange rate. This challenge has led to the introduction of heterogeneous expectations in economic modeling. More specifically, the forecasts of the market participants have been drawn from competing views. Two behaviours

Laurence Lasselle; Serge Svizzero; Clem Tisdell

2001-01-01

293

2, 983998, 2002 Heterogeneous  

E-print Network

contrail ice particles to be potentially important for heterogeneous chlorine activation and ozone contrails and aircraft induced ice clouds. 1. Introduction In view of the present and anticipated growth) and water vapor (H2O) emissions (WMO, 1994; Brasseur et al., 1998), aerosols and contrails formed

Paris-Sud XI, Université de

294

Dynamical patterns of epidemic outbreaks in complex heterogeneous networks  

Microsoft Academic Search

We present a thorough inspection of the dynamical behavior of epidemic phenomena in populations with complex and heterogeneous connectivity patterns. We show that the growth of the epidemic prevalence is virtually instantaneous in all networks characterized by diverging degree fluctuations, independently of the structure of the connectivity correlation functions characterizing the population network. By means of analytical and numerical results,

Marc Barthélemy; Alain Barrat; Romualdo Pastor-Satorras; Alessandro Vespignani

2005-01-01

295

Heterogeneity of Clara Cell Glutathione A Possible Basis for Differences in Cellular Responses to Pulmonary Cytotoxicants  

Microsoft Academic Search

Clara-cell populations show a high degree of variation in sus- ceptibility to injury by bioactivated cytotoxicants. Because glutathione (GSH) is critical for detoxification of electrophilic metabolites, heterogeneity in Clara cell GSH levels may lead to a wide range of cytotoxic responses. This study was de- signed to define the distinct GSH pools within Clara cells, characterize heterogeneity within the population,

Jay A. A. West; Christine H. Chichester; Alan R. Buckpitt; Nancy K. Tyler; Patricia Brennan; Cimity Helton; Charles G. Plopper

296

Population: Basic Statistics  

NSDL National Science Digital Library

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

Rhinehart, Ken; Pratte, John

297

Conceptualizing a tool to optimize therapy based on dynamic heterogeneity  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

298

Conceptualizing a Tool to Optimize Therapy Based on Dynamic Heterogeneity  

PubMed Central

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

Liao, David; Estevez-Salmeron, Luis; Tlsty, Thea D.

2012-01-01

299

Exploiting heterogeneity in sensor networks  

Microsoft Academic Search

The presence of heterogeneous nodes (i.e., nodes with an enhanced energy capacity or communication capability) in a sensor network is known to increase network reliability and lifetime. However, questions of where, how many, and what types of heterogeneous resources to deploy remain largely unexplored. We focus on energy and link heterogeneity in ad hoc sensor net- works and consider resource-aware

Mark D. Yarvis; Nandakishore Kushalnagar; Harkirat Singh; Anand Rangarajan; York Liu; Suresh Singh

2005-01-01

300

Heterogeneity of Rhizobium lipopolysaccharides.  

PubMed Central

The lipopolysaccharides ( LPSs ) from strains of Rhizobium leguminosarum, Rhizobium trifolii, and Rhizobium phaseoli were isolated and partially characterized by mild acid hydrolysis and by polyacrylamide gel electrophoresis. Mild acid hydrolysis results in a precipitate which can be removed by centrifugation or extraction with chloroform. The supernatant contains polysaccharides which, in general, are separated into two fractions ( LPS1 and LPS2 ) by Sephadex G-50 gel filtration chromatography. The higher-molecular-weight LPS1 fractions among the various Rhizobium strains are highly variable in composition and reflect the variability reported in the intact LPSs (R. W. Carlson and R. Lee, Plant Physiol. 71:223-228, 1983; Carlson et al., Plant Physiol. 62:912-917, 1978; Zevenhuizen et al., Arch. Microbiol. 125:1-8, 1980). The LPS1 fraction of R. leguminosarum 128C53 has a higher molecular weight than all other LPS1 fractions examined. All LPS2 fractions examined are oligosaccharides with a molecular weight of ca. 600. The major sugar component of all LPS2 oligosaccharides is uronic acid. The LPS2 compositions are similar for strains of R. leguminosarum and R. trifolii, but the LPS2 from R. phaseoli was different in that it contained glucose, a sugar not found in the other LPS2 fractions or found only in trace amounts. Polyacrylamide gel electrophoretic analysis shows that each LPS contains two banding regions, a higher-molecular-weight heterogeneous region often containing many bands and a lower-molecular-weight band. The lower-molecular-weight bands of all LPSs have the same electrophoretic mobility, which is greater than that of lysozyme. The banding pattern of the heterogeneous regions varies among the different Rhizobium strains. In the case of R. leguminosarum 128C53 LPS, the heterogeneous region of a higher molecular weight than is this region from all other Rhizobium strains examined and consists of many bands separated from one another by a small and apparently constant molecular weight interval. When the heterogeneous region of R. Leguminosarum 128C53 LPS was cut from the gel and analyzed, its composition was found to be that of the intact LPS, whereas the lower-molecular-weight band contains only sugars found in the LPS2 oligosaccharide. In the case of R. leguminosarum 128C63 and R. trifolii 0403 LPSs, the heterogeneous regions are similar and consist of several band s separated by a large-molecular-weight interval with a the major band of these heterogeneous regions having the lowest molecular weight with an electrophoretic mobility near that of beta-lactoglobulin. The heterogeneous region from R. phaseoli 127K14 consists of several bands with electrophoretic mobilities near that of beta-lactoglobulin, whereas this region from R. trifolii 162S7 shows a continuous staining region, indicating a great deal of heterogeneity. The results described in this paper are discussed with regard to the reported properties of Escherichia coli and Salmonella LPSs. Images PMID:6725208

Carlson, R W

1984-01-01

301

Heterogeneous HPC Environments  

Microsoft Academic Search

Directions of software technologies for innovative HPC environments are discussed according to the industrial user requirements\\u000a for heterogeneous multidisciplinary applications, performance portability, rapid prototyping and software reuse, integration\\u000a and interoperability of standard tools. The various issues are demonstrated with reference to the PQE2000 project and its\\u000a programming environment SkIE (Skeleton-based Integrated Environment). Modules developed by a variety of standard languages

Marco Vanneschi

1998-01-01

302

Heterogeneous atmospheric bromine chemistry  

Microsoft Academic Search

This paper considers the effect of heterogeneous bromine reactions on stratospheric photochemistry. We have considered reactions on both sulfate aerosols and on polar stratospheric clouds (PSCs). It is shown that the hydrolysis of BrONO2 on sulfate aerosols enhances the HOBr concentration, which in turn enhances the OH and HO2 concentrations, thereby reducing the HC1 lifetime and concentration. The hydrolysis of

D. J. Lary; M. P. Chipperfield; R. Toumi; T. Lenton

1996-01-01

303

Modeling Mitochondrial Population Genetics  

Microsoft Academic Search

Indirect tests have detected recombination in diverse animal mitochondrial DNA (mtDNA), including mammals. These results have far reaching implications for evolution and ecology, as virtually all animal population genetics studies assume mtDTA is clonally inherited. For the first time, we demonstrated that the molecular patterns detected by these tests could alternatively be explained by mutation rate heterogeneity, or clusters of

Stephanie Sun

2009-01-01

304

Experimental protocol for manipulating plant-induced soil heterogeneity.  

PubMed

Coexistence theory has often treated environmental heterogeneity as being independent of the community composition; however biotic feedbacks such as plant-soil feedbacks (PSF) have large effects on plant performance, and create environmental heterogeneity that depends on the community composition. Understanding the importance of PSF for plant community assembly necessitates understanding of the role of heterogeneity in PSF, in addition to mean PSF effects. Here, we describe a protocol for manipulating plant-induced soil heterogeneity. Two example experiments are presented: (1) a field experiment with a 6-patch grid of soils to measure plant population responses and (2) a greenhouse experiment with 2-patch soils to measure individual plant responses. Soils can be collected from the zone of root influence (soils from the rhizosphere and directly adjacent to the rhizosphere) of plants in the field from conspecific and heterospecific plant species. Replicate collections are used to avoid pseudoreplicating soil samples. These soils are then placed into separate patches for heterogeneous treatments or mixed for a homogenized treatment. Care should be taken to ensure that heterogeneous and homogenized treatments experience the same degree of soil disturbance. Plants can then be placed in these soil treatments to determine the effect of plant-induced soil heterogeneity on plant performance. We demonstrate that plant-induced heterogeneity results in different outcomes than predicted by traditional coexistence models, perhaps because of the dynamic nature of these feedbacks. Theory that incorporates environmental heterogeneity influenced by the assembling community and additional empirical work is needed to determine when heterogeneity intrinsic to the assembling community will result in different assembly outcomes compared with heterogeneity extrinsic to the community composition. PMID:24686854

Brandt, Angela J; del Pino, Gaston A; Burns, Jean H

2014-01-01

305

Molecular Diversity After a Range Expansion in Heterogeneous Environments  

PubMed Central

Recent range expansions have probably occurred in many species, as they often happen after speciation events, after ice ages, or after the introduction of invasive species. While it has been shown that range expansions lead to patterns of molecular diversity distinct from those of a pure demographic expansion, the fact that many species do live in heterogeneous environments has not been taken into account. We develop here a model of range expansion with a spatial heterogeneity of the environment, which is modeled as a gamma distribution of the carrying capacities of the demes. By allowing temporal variation of these carrying capacities, our model becomes a new metapopulation model linking ecological parameters to molecular diversity. We show by extensive simulations that environmental heterogeneity induces a loss of genetic diversity within demes and increases the degree of population differentiation. We find that metapopulations with low average densities are much more affected by environmental heterogeneity than metapopulations with high average densities, which are relatively insensitive to spatial and temporal variations of the environment. Spatial heterogeneity is shown to have a larger impact on genetic diversity than temporal heterogeneity. Overall, temporal heterogeneity and local extinctions are not found to leave any specific signature on molecular diversity that cannot be produced by spatial heterogeneity. PMID:17028329

Wegmann, Daniel; Currat, Mathias; Excoffier, Laurent

2006-01-01

306

Identifying and Quantifying Heterogeneity in High Content Analysis: Application of Heterogeneity Indices to Drug Discovery  

PubMed Central

One of the greatest challenges in biomedical research, drug discovery and diagnostics is understanding how seemingly identical cells can respond differently to perturbagens including drugs for disease treatment. Although heterogeneity has become an accepted characteristic of a population of cells, in drug discovery it is not routinely evaluated or reported. The standard practice for cell-based, high content assays has been to assume a normal distribution and to report a well-to-well average value with a standard deviation. To address this important issue we sought to define a method that could be readily implemented to identify, quantify and characterize heterogeneity in cellular and small organism assays to guide decisions during drug discovery and experimental cell/tissue profiling. Our study revealed that heterogeneity can be effectively identified and quantified with three indices that indicate diversity, non-normality and percent outliers. The indices were evaluated using the induction and inhibition of STAT3 activation in five cell lines where the systems response including sample preparation and instrument performance were well characterized and controlled. These heterogeneity indices provide a standardized method that can easily be integrated into small and large scale screening or profiling projects to guide interpretation of the biology, as well as the development of therapeutics and diagnostics. Understanding the heterogeneity in the response to perturbagens will become a critical factor in designing strategies for the development of therapeutics including targeted polypharmacology. PMID:25036749

Gough, Albert H.; Chen, Ning; Shun, Tong Ying; Lezon, Timothy R.; Boltz, Robert C.; Reese, Celeste E.; Wagner, Jacob; Vernetti, Lawrence A.; Grandis, Jennifer R.; Lee, Adrian V.; Stern, Andrew M.; Schurdak, Mark E.; Taylor, D. Lansing

2014-01-01

307

A Variational Approach to Upscaling Heterogeneous Media  

E-print Network

A Variational Approach to Upscaling Heterogeneous Media Scott MacLachlan Department of Computer to Upscaling Heterogeneous Media- p.1 #12;Heterogeneous Media What makes a medium heterogeneous? · Large in spatial scales A Variational Approach to Upscaling Heterogeneous Media- p.2 #12;Heterogeneous Media What

MacLachlan, Scott

308

Heterogeneous Differential Evolution for Numerical Optimization  

PubMed Central

Differential evolution (DE) is a population-based stochastic search algorithm which has shown a good performance in solving many benchmarks and real-world optimization problems. Individuals in the standard DE, and most of its modifications, exhibit the same search characteristics because of the use of the same DE scheme. This paper proposes a simple and effective heterogeneous DE (HDE) to balance exploration and exploitation. In HDE, individuals are allowed to follow different search behaviors randomly selected from a DE scheme pool. Experiments are conducted on a comprehensive set of benchmark functions, including classical problems and shifted large-scale problems. The results show that heterogeneous DE achieves promising performance on a majority of the test problems. PMID:24683329

Wang, Wenjun; Sun, Hui; Rahnamayan, Shahryar

2014-01-01

309

Heterogeneous differential evolution for numerical optimization.  

PubMed

Differential evolution (DE) is a population-based stochastic search algorithm which has shown a good performance in solving many benchmarks and real-world optimization problems. Individuals in the standard DE, and most of its modifications, exhibit the same search characteristics because of the use of the same DE scheme. This paper proposes a simple and effective heterogeneous DE (HDE) to balance exploration and exploitation. In HDE, individuals are allowed to follow different search behaviors randomly selected from a DE scheme pool. Experiments are conducted on a comprehensive set of benchmark functions, including classical problems and shifted large-scale problems. The results show that heterogeneous DE achieves promising performance on a majority of the test problems. PMID:24683329

Wang, Hui; Wang, Wenjun; Cui, Zhihua; Sun, Hui; Rahnamayan, Shahryar

2014-01-01

310

Linking growth, survival, and heterogeneity through vitality.  

PubMed

We model the cross-stage effect of juvenile growth on future cohort survival with vitality, a single stochastic measure of an organism's survival capacity that results in death when it reaches 0. In this construct, the distribution of vitality at the end of a growth treatment stage, which is a measure of survival capacity heterogeneity, determines a cohort's susceptibility to starvation in a subsequent challenge stage. The model predicts that the treatment-stage duration and mass gain determine the mean and variance of the initial vitality distribution of the challenge stage, which in turn determine the effect of a challenge-stage stressor on survival. Studies linking the effect of juvenile growth on time to starvation for chinook salmon and yellow perch are compared to model predictions. The feasibility of predicting survival and heterogeneity in overwintering fish populations from first-year growth is considered. Some limitations and potential extensions of the model to other scenarios are discussed. PMID:18171141

Anderson, James J; Gildea, Molly C; Williams, Drew W; Li, Ting

2008-01-01

311

Gradient Heterogeneous Surface  

NASA Astrophysics Data System (ADS)

The strength of the interfacial interaction and the length scale over which the interaction occurs are two important factors to understand the polymer blends (Lsp 100 nm), diblock copolymers (Lb 30 nm), cell recognition, random heteropolymer, adhesion (ex. Protein, cell) and wettability on a surface. This has important implications in pattern recognition applications, biosensors and random recognition processes. A gradient pattern is produced on a surface with two different surface energies, analogous to a gradient checkerbroad. Indirectly, this would give some insight on random heteropolymer and multifunctional disordered surfaces and biomimetic recognition between polymer and surfaces. To achieve this, a gradient surface is created to vary the lateral size scale correlation of heterogeneity. Two possible routes will be presented to vary different size scale, for example, from micron to nano scale. Then, the gradient surface will be used as a template to vary the surface interaction, i.e. having one domain hydrophilic and hydrophobic the other. And finally, this lateral size scale correlation having two different interaction sites is used to examine the phase separation of polymer blend films, cell recognition, and diblock copolymer films on this gradient heterogenous surface.

Tsai, Irene; Kimura, Masahiro; Lin, Zhiqun; Stockton, Rebecca; Fadeev, Alex; Jacobson, Bruce; Russell, Thomas P.

2002-03-01

312

Heterogeneous photonic integrated circuits  

NASA Astrophysics Data System (ADS)

Photonic Integrated Circuits (PICs) have been dichotomized into circuits with high passive content (silica and silicon PLCs) and high active content (InP tunable lasers and transceivers) due to the trade-off in material characteristics used within these two classes. This has led to restrictions in the adoption of PICs to systems in which only one of the two classes of circuits are required to be made on a singular chip. Much work has been done to create convergence in these two classes by either engineering the materials to achieve the functionality of both device types on a single platform, or in epitaxial growth techniques to transfer one material to the next, but have yet to demonstrate performance equal to that of components fabricated in their native substrates. Advances in waferbonding techniques have led to a new class of heterogeneously integrated photonic circuits that allow for the concurrent use of active and passive materials within a photonic circuit, realizing components on a transferred substrate that have equivalent performance as their native substrate. In this talk, we review and compare advances made in heterogeneous integration along with demonstrations of components and circuits enabled by this technology.

Fang, Alexander W.; Fish, Gregory; Hall, Eric

2012-01-01

313

Tumor heterogeneity: causes and consequences  

PubMed Central

With rare exceptions, spontaneous tumors originate from a single cell. Yet, at the time of clinical diagnosis, the majority of human tumors display startling heterogeneity in many morphological and physiological features, such as expression of cell surface receptors, proliferative and angiogenic potential. To a substantial extent, this heterogeneity might be attributed to morphological and epigenetic plasticity, but there is also strong evidence for the co-existence of genetically divergent tumor cell clones within tumors. In this perspective, we summarize the sources of intra-tumor phenotypic heterogeneity with emphasis on genetic heterogeneity. We review experimental evidence for the existence of both intra-tumor clonal heterogeneity as well as frequent evolutionary divergence between primary tumors and metastatic outgrowths. Furthermore, we discuss potential biological and clinical implications of intra-tumor clonal heterogeneity. PMID:19931353

Marusyk, Andriy; Polyak, Kornelia

2009-01-01

314

Using Extensible Heterogeneous Database Transformers  

Microsoft Academic Search

\\u000a Transforming a heterogeneous data model to another heterogeneous data model involves mapping of structural information and\\u000a data layout. For performing the transformation processes this paper presents a flexible and extensible approach for heterogeneous\\u000a database transformation using XML. Basics steps involved are forward transformation and reverse transformation. Between these\\u000a two steps lie two XML documents; one representing the database structure; the

F. Furman Haddix; Kalyan Pydipati

2006-01-01

315

Heterogeneous belief and asset returns  

NASA Astrophysics Data System (ADS)

Based on DSSW model, this paper introduces the noise traders with heterogeneous belief. With an equilibrium analysis, this paper examines the return of risky asset. The results show that the belief biases, the probability of economy state, the degree of the heterogeneous noise trader's aversion risk, the coefficient between heterogeneous noise traders are all the factors that have effects on the risky asset pricing and the return of risky asset.

Lei-Sun, Wen-Zou, Hui

2014-10-01

316

World Population Activity I: Excel  

NSDL National Science Digital Library

(Activity 1 of 2) This activity is primarily intended as an introductory tutorial on using Excel. Students use Excel to explore population dynamics using the Logistic equation for (S-shaped) population growth.

Activity And Starting Point Page By R.m. Mackay. Clark College, Physics A.

317

Using mixtures to model heterogeneity in ecological capture-recapture studies.  

PubMed

Modelling heterogeneity of capture is an important problem in estimating animal abundance from capture-recapture data, with underestimation of abundance occurring if different animals have intrinsically high or low capture probabilities. Mixture models are useful in many cases to model the heterogeneity. We summarise mixture model results for closed populations, using a skink data set for illustration. New mixture models for heterogeneous open populations are discussed, and a closed population model is shown to have new and potentially effective applications in community analysis. PMID:19067335

Pledger, Shirley; Phillpot, Polly

2008-12-01

318

Changing Student Characteristics: Implications for New Student Orientation.  

ERIC Educational Resources Information Center

Describes the characteristics of today's college student population, noting ways in which they differ from the students of the past and exploring what the characteristics of these students means for the design and conduct of orientation programs. (SLD)

Zis, Stacey L.

2002-01-01

319

Adventures With The Fish Pond: Population Modeling  

NSDL National Science Digital Library

This activity builds on the population decay M&M activity and will introduce students to recursive equations and uses calculators as an efficient tool for exploring population models. Students will describe what happens to the fish population from one year to another. Each pair of students will have an activity sheet to go along with the activity, and a calculator is needed.

Math, Pbs T.; Pbs

2010-01-01

320

Accessing and Investigating Population Data  

NSDL National Science Digital Library

In this activity, students investigate population projections from 1990-2100 using data from the U.S. Census Bureau Web. Using the five specific population pyramids, students investigate population projection data for the United States over a 110-year period. They examine how the population data is distributed over time and explain what factors might contribute to these trends. An activity sheet and thoughtful questions, included in the lesson plan, guide the class investigation.

Burton, Grace M.; Midgett, Carol

2000-01-01

321

The Pegasus Heterogeneous Multidatabase System  

Microsoft Academic Search

Pegasus, a heterogeneous multidatabase management system that responds to the need for effective access and management of shared data across in a wide range of applications, is described. Pegasus provides facilities for multidatabase applications to access and manipulate multipole autonomous heterogeneous distributed object-oriented relational, and other information systems through a uniform interface. It is a complete data management system that

Rafi Ahmed; Philippe De Smedt; Weimin Du; William Kent; Mohammad A. Ketabchi; Witold Litwin; Abbas Rafii; Ming-chien Shan

1991-01-01

322

Anthropogenic Biomes ver. 1 Anthropogenic biomes represent heterogeneous  

E-print Network

Anthropogenic Biomes ver. 1 Africa Anthropogenic biomes represent heterogeneous landscape mosaics defined by population density and vegetation cover. The 21 biomes are grouped into six major categories: Ellis, E. C. and N. Ramankutty. 2008. Putting people in the map: anthropogenic biomes of the world. http

Columbia University

323

Characterizing Mutational Heterogeneity in a Glioblastoma Patient with Double Recurrence  

Microsoft Academic Search

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

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

2012-01-01

324

Heterogeneity of an earth  

NASA Astrophysics Data System (ADS)

The study of magnetic anomaly field structure of the Barents Sea water area along seismic and extended profiles intersecting known fields is carried out. Geomagnetic and density sections down to 40 km depth are constructed. This allowed the estimation of heterogeneities of the Barents Sea water area deep structure. The analysis of geomagnetic and density sections along extended profiles showed the confinedness of oil-and-gas bearing provinces to deep permeable zones characterized by reduced magnetic and density features. Based on the analysis of permeable zones, regional diagnostic features similar to those obtained earlier in oil-and-gas bearing provinces in other regions, for example, in Timan-Pechora, Volga-Urals and Siberian, as well as in the Northern and Norwegian seas water areas, are revealed. The analysis of magnetic and gravity fields over the region area allowed the delineation of weakened zones as intersection areas of weakly magnetic areals with reduced density. Within the Barents Sea water area, permeable areas with lenticular-laminated structure of the upper and lower Earth's crust containing weakly magnetic areals with reduced rock density within the depth range of 8-12 and 15-20 km are revealed. Such ratio of magnetic and density heterogeneities in the Earth's crust is characteristic for zones with proved oil-and-gas content in the European part of the Atlantic Ocean water area. North Kildin field on 1 AR profile is confined to a trough with thick weakly magnetic stratum discontinuously traced to a depth of 6-10 km. At a depth of approximately 15 km, a lens of weakly magnetic and porous formations is observed. Ludlov field in the North Barents trough is confined to a zone of weakly magnetic rocks with reduced density traced to a depth of 8-9 km. Deeper, at ?=15 km, a lenticular areal of weakly magnetic formations with reduced density is observed. The profile transecting the Stockman field shows that it is located in the central part of a permeable zone. Ledovoe field is in the northern margin of the same zone. SPAN calculations of magnetic and gravity fields in areal option allowed obtaining the distribution of permeable weakly magnetic zones in the Barents Sea water area. The most significant ones are confined to Franz-Victoria trough, Severnaya depression, Malygin saddle, Bjarmeland syneclise, Murmansk-Kurentsovo monocline, Southern Lunin trough and depression, Northern Stockman depression, and Southern Barents syneclise.

Litvinova, T.; Petrova, A.

2009-04-01

325

Variability in fault size scaling due to rock strength heterogeneity: a finite element investigation  

E-print Network

-softening, Von Mises rheology with Gaussian heterogeneity in yield strength distributed randomly throughoutVariability in fault size scaling due to rock strength heterogeneity: a finite element conjugate, normal fault populations in cross-section. The deforming material is modelled using a strain

Cowie, Patience

326

Heterogeneity and plasticity of epidermal stem cells  

PubMed Central

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

Schepeler, Troels; Page, Mahalia E.; Jensen, Kim B.

2014-01-01

327

The World Population Dilemma.  

ERIC Educational Resources Information Center

This book is the third in a series published by the Population Reference Bureau aimed at illuminating the facts and consequences of human population dynamics for secondary and college-age students. Many illustrations, charts and graphs are included in this volume to help the reader grasp a number of the current ideas and concepts that are used in…

Population Reference Bureau, Inc., Washington, DC.

328

Heterogeneity in the penumbra  

PubMed Central

Original experimental studies in nonhuman primate models of focal ischemia showed flow-related changes in evoked potentials that suggested a circumferential zone of low regional cerebral blood flow with normal K+ homeostasis, around a core of permanent injury in the striatum or the cortex. This became the basis for the definition of the ischemic penumbra. Imaging techniques of the time suggested a homogeneous core of injury, while positing a surrounding ‘penumbral' region that could be salvaged. However, both molecular studies and observations of vascular integrity indicate a more complex and dynamic situation in the ischemic core that also changes with time. The microvascular, cellular, and molecular events in the acute setting are compatible with heterogeneity of the injury within the injury center, which at early time points can be described as multiple ‘mini-cores' associated with multiple ‘mini-penumbras'. These observations suggest the progression of injury from many small foci to a homogeneous defect over time after the onset of ischemia. Recent observations with updated imaging techniques and data processing support these dynamic changes within the core and the penumbra in humans following focal ischemia. PMID:21731034

del Zoppo, Gregory J; Sharp, Frank R; Heiss, Wolf-Dieter; Albers, Gregory W

2011-01-01

329

On Heterogeneous Covert Networks  

NASA Astrophysics Data System (ADS)

Covert organizations are constantly faced with a tradeoff between secrecy and operational efficiency. Lindelauf, Borm and Hamers [13] developed a theoretical framework to determine optimal homogeneous networks taking the above mentioned considerations explicitly into account. In this paper this framework is put to the test by applying it to the 2002 Jemaah Islamiyah Bali bombing. It is found that most aspects of this covert network can be explained by the theoretical framework. Some interactions however provide a higher risk to the network than others. The theoretical framework on covert networks is extended to accommodate for such heterogeneous interactions. Given a network structure the optimal location of one risky interaction is established. It is shown that the pair of individuals in the organization that should conduct the interaction that presents the highest risk to the organization, is the pair that is the least connected to the remainder of the network. Furthermore, optimal networks given a single risky interaction are approximated and compared. When choosing among a path, star and ring graph it is found that for low order graphs the path graph is best. When increasing the order of graphs under consideration a transition occurs such that the star graph becomes best. It is found that the higher the risk a single interaction presents to the covert network the later this transition from path to star graph occurs.

Lindelauf, Roy; Borm, Peter; Hamers, Herbert

330

Perspectives on heterogeneous photochemistry.  

PubMed

Heterogeneous photochemistry has a potentially important role in production of energy, in environmental remediation and in sustainable production of chemicals. Photochemical efficiency depends on both materials properties and the desired chemical reaction that is promoted through creation of an excited state. A detailed understanding of the interplay between materials properties and reactivity requires a molecular-scale approach that determines the elementary steps in the overall process. This personal account summarizes the role of defects in determining the photochemical and thermal reactions on rutile titania, a model for semiconductor metal oxide photocatalysts that defects, e.g., Ti interstitials present in the subsurface region, and O adatoms on the surface, have a substantial impact on the efficiency for photochemical conversion through modification of molecular binding and also through likely modification of charge carrier dynamics. Design of materials must include engineering of the optical and electronic properties of the semiconductor photocatalyst, and understanding of the key photochemical steps involved in specific processes to ensure proper alignment of their electronic states with the band structure of the material. Thus, fundamental surface science studies and development of time-dependent theoretical methods that map out the reaction mechanism for photochemical processes on materials with controlled composition and structure are critical. PMID:25131154

Friend, Cynthia M

2014-10-01

331

Enhancing Student Development in Community Colleges.  

ERIC Educational Resources Information Center

Reviews student development theories and their application to different student populations, including underrepresented students. Discusses students who are transfer-bound, those of nontraditional ages, and those involved in vocational education. (MAB)

Ortiz, Anna M.

1995-01-01

332

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

E-print Network

The Adult Learner and Student Veteran Undergraduate Experience Adult learner, nontraditional Homeless or on the brink of becoming homeless These students comprise approximately 15 student, or may have a disability. Adult learners and veterans are a marginalized, student population

Boone, Randall B.

333

Retrograde signaling from functionally heterogeneous plastids  

PubMed Central

Structural and functional components of chloroplast are encoded by genes localized both to nuclear and plastid genomes of plant cell. Development from etioplasts to chloroplasts is triggered by light receptors that activate the expression of photosynthesis-associated nuclear genes (PhaNGs). In addition to photoreceptor-mediated pathways, retrograde signals from the chloroplast to the nucleus activate or repress the expression of nuclear genes involved in acclimatory or stress responses in plant leaves. A plant mesophyll cell contains up to 100 chloroplasts that function autonomously, raising intriguing questions about homogeneity and coordination of retrograde signals transmitted from chloroplast to nucleus. We have previously demonstrated that the knockout of the chloroplast regulatory protein, chloroplast NADPH-dependent thioredoxin reductase (NTRC) leads to a heterogeneous population of chloroplasts with a range of different functional states. The heterogeneous chloroplast population activates both redox-dependent and undifferentiated plastid-generated retrograde signaling pathways in the mutant leaves. Transcriptome data from the ntrc knockout lines suggest that the induction of the redox-dependent signaling pathway depends on light conditions and leads to activation of stress-responsive gene expression. Analysis of mutants in different developmental stages allows to dissect signals from normal and anomalous chloroplasts. Thus, the signals derived from anomalous chloroplasts repress expression of PhaNGs as well as genes associated with light receptor signaling and differentiation of stomata, implying interaction between retrograde pathways and plant development. Analysis of the nuclear gene expression in mutants of retrograde signaling pathways in ntrc background would reveal the components that mediate signals generated from heterogeneous plastids to nucleus. PMID:23267363

Lepisto, Anna; Toivola, Jouni; Nikkanen, Lauri; Rintamaki, Eevi

2012-01-01

334

Molecular typing of nasal carriage isolates of Staphylococcus aureus from an Irish university student population based on toxin gene PCR, agr locus types and multiple locus, variable number tandem repeat analysis  

Microsoft Academic Search

Forty-eight Staphylococcus aureus isolates collected from a young, healthy, Irish university student population from 1995 to 2004 were screened for 16 enterotoxin (SE) and enterotoxin-like (SEl) genes (sea-see, seg-sei, selj-selo, selq, selu), and for the toxic shock toxin syndrome toxin-1 gene, tst. All of the isolates harboured at least one SE or SEl gene and 66.7% possessed a classical SE

Mark M. Collery; Davida S. Smyth; Jane M. Twohig; Anna C. Shore; David C. Coleman; Cyril J. Smyth

2008-01-01

335

Multipath Aggregation of Heterogeneous Access Dominik Kaspar  

E-print Network

Multipath Aggregation of Heterogeneous Access Networks by Dominik Kaspar Doctoral Dissertation heterogeneity introduces packet reordering, which can negatively affect the performance of transport protocols with the attempt to find solutions that achieve increased data throughput by concurrently utilizing heterogeneous

Sahay, Sundeep

336

Behavioral responses of Willow Flycatchers, Empidonax traillii, to a heterogeneous environment.  

E-print Network

?? Spatial heterogeneity impacts population and community-level dynamics including species-level dispersal patterns, the use and availability of refugia, predator/prey dynamics, and reproductive fitness. Understanding how… (more)

Bakian, Amanda V.

2011-01-01

337

Intrinsic heterogeneity in the survival and proliferation capacities of naïve CD8? T cells  

E-print Network

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 ...

Mahajan, Vinay Subhash

2009-01-01

338

An exploratory examination of the associations among racial and ethnic discrimination, racial climate, and trauma-related symptoms in a college student population.  

PubMed

In this study, we examined the association among perceptions of racial and/or ethnic discrimination, racial climate, and trauma-related symptoms among 289 racially diverse college undergraduates. Study measures included the Perceived Stress Scale, the Perceived Ethnic Discrimination Questionnaire, the Posttraumatic Stress Disorder Checklist-Civilian Version, and the Racial Climate Scale. Results of a multivariate analysis of variance (MANOVA) indicated that Asian and Black students reported more frequent experiences of discrimination than did White students. Additionally, the MANOVA indicated that Black students perceived the campus racial climate as being more negative than did White and Asian students. A hierarchical regression analysis showed that when controlling for generic life stress, perceptions of discrimination contributed an additional 10% of variance in trauma-related symptoms for Black students, and racial climate contributed an additional 7% of variance in trauma symptoms for Asian students. PMID:21133577

Pieterse, Alex L; Carter, Robert T; Evans, Sarah A; Walter, Rebecca A

2010-07-01

339

Population: Age Structure  

NSDL National Science Digital Library

One of the primary tools that demographers use to understand population is the age structure diagram, a graphic representation that shows the distribution by ages of females and males within a certain population. This lesson describes how these diagrams are constructed and interpreted. It includes an activity in which students use online data on Native American populations from the United States Census Bureau to construct their own diagrams.

Laposata, Matt

340

Chimera states in heterogeneous networks  

E-print Network

Chimera states in networks of coupled oscillators occur when some fraction of the oscillators synchronise with one another, while the remaining oscillators are incoherent. Several groups have studied chimerae in networks of identical oscillators, but here we study these states in a heterogeneous model for which the natural frequencies of the oscillators are chosen from a distribution. We obtain exact results by reduction to a finite set of differential equations. We find that heterogeneity can destroy chimerae, destroy all states except chimerae, or destabilise chimerae in Hopf bifurcations, depending on the form of the heterogeneity.

Carlo R. Laing

2008-09-23

341

Discriminating cellular heterogeneity using microwell-based RNA cytometry  

PubMed Central

Discriminating cellular heterogeneity is important for understanding cellular physiology. However, it is limited by the technical difficulties of single-cell measurements. Here, we develop a two-stage system to determine cellular heterogeneity. In the first stage, we perform multiplex single-cell RNA-cytometry in a microwell array containing over 60,000 reaction chambers. In the second stage, we use the RNA-cytometry data to determine cellular heterogeneity by providing a heterogeneity likelihood score. Moreover, we use Monte-Carlo simulation and RNA-cytometry data to calculate the minimum number of cells required for detecting heterogeneity. We applied this system to characterize the RNA distributions of aging related genes in a highly purified mouse hematopoietic stem cell population. We identified genes that reveal novel heterogeneity of these cells. We also show that changes in expression of genes such as Birc6 during aging can be attributed to the shift of relative portions of cells in the high-expressing subgroup versus low-expressing subgroup. PMID:24667995

Dimov, Ivan K.; Lu, Rong; Lee, Eric P.; Seita, Jun; Sahoo, Debashis; Park, Seung-min; Weissman, Irving L.; Lee, Luke P.

2014-01-01

342

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

E-print Network

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

Bernard, Samuel

343

Fundamentals of Populations and Population Growth  

NSDL National Science Digital Library

This activity reinforces the concepts covered in the lecture presented during LESSON 3 of this unit. It takes the student through the definition of a population. Graphing skills are tested and the difference between the independent and dependent variables is explained. The S-shaped and Boom and Bust growth rate curves are next compared and contrasted. The activity then asks the student to analyze a data table and to plot its points. Students gain personal application of the lesson material. And relate the material to the grand challenge of this unit.

Vu Bioengineering Ret Program

344

Portable performance on heterogeneous architectures  

E-print Network

Trends in both consumer and high performance computing are bringing not only more cores, but also increased heterogeneity among the computational resources within a single machine. In many machines, one of the greatest ...

Phothilimthana, Phitchaya Mangpo

345

Tomographic Characterization of Aquifer Heterogeneity  

E-print Network

aquifer tests, such as slug and pumping tests, predict hydraulic conductivity values without detailed information about aquifer heterogeneity. The multiple source and receiver signals of a hydraulic tomography aquifer test can estimate interwell...

Lyle, Shane

2011-05-31

346

The Influence of Student Characteristics on the Use of Adaptive E-Learning Material  

ERIC Educational Resources Information Center

Adaptive e-learning materials can help teachers to educate heterogeneous student groups. This study provides empirical data about the way academic students differ in their learning when using adaptive e-learning materials. Ninety-four students participated in the study. We determined characteristics in a heterogeneous student group by collecting…

van Seters, J. R.; Ossevoort, M. A.; Tramper, J.; Goedhart, M. J.

2012-01-01

347

Heterogeneity in background fitness acts as a suppressor of selection.  

PubMed

We introduce the concept of heterogeneity in background fitness to evolutionary dynamics in finite populations. Background fitness is specific to an individual but not linked to its strategy. It can be thought of as a property that is related to the physical or societal position of an individual, but is not dependent on the strategy that is adopted in the evolutionary process under consideration. In our model, an individual's total fitness is the sum of its background fitness and the fitness derived from using a specific strategy. This approach has important implications for the imitation of behavioural strategies: if we imitate others for their success, but can only adopt their behaviour and not their social and economic ties, we may imitate in vain. We study the effect of heterogeneity in background fitness on the fixation of a mutant strategy with constant fitness. We find that heterogeneity suppresses selection, but also decreases the time until a novel strategy either takes over the population or is lost again. We derive analytical solutions of the fixation probability in small populations. In the case of large total background fitness in a population with maximum inequality, we find a particularly simple approximation of the fixation probability. Numerical simulations suggest that this simple approximation also holds for larger population sizes. PMID:24211522

Hauser, Oliver P; Traulsen, Arne; Nowak, Martin A

2014-02-21

348

Dynamic equilibrium of heterogeneous and interconvertible multipotent hematopoietic cell subsets  

PubMed Central

Populations of hematopoietic stem cells and progenitors are quite heterogeneous and consist of multiple cell subsets with distinct phenotypic and functional characteristics. Some of these subsets also appear to be interconvertible and oscillate between functionally distinct states. The multipotent hematopoietic cell line EML has emerged as a unique model to study the heterogeneity and interconvertibility of multipotent hematopoietic cells. Here we describe extensive phenotypic and functional heterogeneity of EML cells which stems from the coexistence of multiple cell subsets. Each of these subsets is phenotypically and functionally heterogeneous, and displays distinct multilineage differentiation potential, cell cycle profile, proliferation kinetics, and expression pattern of HSC markers and some of the key lineage-associated transcription factors. Analysis of their maintenance revealed that on a population level all EML cell subsets exhibit cell-autonomous interconvertible properties, with the capacity to generate all other subsets and re-establish complete parental EML cell population. Moreover, all EML cell subsets generated during multiple cell generations maintain their distinct phenotypic and functional signatures and interconvertible properties. The model of EML cell line suggests that interconvertible multipotent hematopoietic cell subsets coexist in a homeostatically maintained dynamic equilibrium which is regulated by currently unknown cell-intrinsic mechanisms. PMID:24903657

Weston, Wendy; Zayas, Jennifer; Perez, Ruben; George, John; Jurecic, Roland

2014-01-01

349

An investigation of the effects of selected factors on the success of Black college students as compared to the general population at a predominately White institution  

Microsoft Academic Search

This study focused on academic and non-academic factors that may affect the academic success of Black and Non-Black college students on a predominately White college campus. The students completed 5 assessments and a demographic questionnaire which measured various factors which may have an effect on academic success. The 126 participants were freshmen or sophomores. There were 29 Black and 97

Cheri Yevette Anderson

1998-01-01

350

Heterogeneous effects of heterogeneity : Disentangling heterogeneity positive and negative effects on performance  

Microsoft Academic Search

Purpose – The aim of the paper is to test the Heterogeneity Construct as a second-order construct determined by dimensions expressing the resource utilization process carried out by firms, and to test the different impacts of Heterogeneity sub-dimensions on firm's performance. Design\\/methodology\\/approach – After collecting data on the machine tools industry, two models are tested by Lisrel. The first model

Andrea Lanza; Antonella Pellegrino; Guiseppina Simone

2008-01-01

351

Principles of Population Health Science Population Health 795  

E-print Network

. Students may audio record lectures for their own personal use (i.e. not for distribution) with permission1 Principles of Population Health Science Population Health 795 A course in the Program in Population Health Fall 2012 University of Wisconsin-Madison, School of Medicine and Public Health The lecture

Sheridan, Jennifer

352

Final Technical Report - Investigation into the Relationship between Heterogeneity and Heavy-Tailed Solute Transport  

SciTech Connect

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.

Weissmann, Gary S

2013-12-06

353

Embedded Learning Strategy Instruction: Story-Structure Pedagogy in Heterogeneous Secondary Literature Classes  

ERIC Educational Resources Information Center

The effects of using the Embedded Story-Structure (ESS) Routine in a literature course were investigated. A heterogeneous group of 79 ninth graders, including 14 students with LD, were randomly assigned to one of two conditions, with instruction occurring in groups of 12 to 14 students in general education literature classes over a nine-day…

Faggella-Luby, Michael; Schumaker, Jean S.; Deshler, Donald D.

2007-01-01

354

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

ERIC Educational Resources Information Center

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…

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

2014-01-01

355

Dealing with spatial heterogeneity  

NASA Astrophysics Data System (ADS)

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

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

2005-03-01

356

A Variational Approach to Upscaling Heterogeneous Media  

E-print Network

A Variational Approach to Upscaling Heterogeneous Media Scott MacLachlan Department of Mathematics. Coon, Columbia University January 28, 2010 A Variational Approach to Upscaling Heterogeneous Media- p.1 #12;Heterogeneous Media What makes a medium heterogeneous? · Large relative variation in material

MacLachlan, Scott

357

Cognitive decline in the elderly: an analysis of population heterogeneity  

PubMed Central

Background: studies of cognitive ageing at the group level suggest that age is associated with cognitive decline; however, there may be individual differences such that not all older adults will experience cognitive decline. Objective: to evaluate patterns of cognitive decline in a cohort of older adults initially free of dementia. Design, setting and subjects: elderly Catholic clergy members participating in the Religious Orders Study were followed for up to 15 years. Cognitive performance was assessed annually. Methods: performance on a composite global measure of cognition was analysed using random effects models for baseline performance and change over time. A profile mixture component was used to identify subgroups with different cognitive trajectories over the study period. Results: from a sample of 1,049 participants (mean age 75 years), three subgroups were identified based on the distribution of baseline performance and change over time. The majority (65%) of participants belonged to a slow decline class that did not experience substantial cognitive decline over the observation period [?0.04 baseline total sample standard deviation (SD) units/year]. About 27% experienced moderate decline (?0.19 SD/year), and 8% belonged to a class experiencing rapid decline (?0.57 SD/year). A subsample analysis revealed that when substantial cognitive decline does occur, the magnitude and rate of decline is correlated with neuropathological processes. Conclusions: in this sample, the most common pattern of cognitive decline is extremely slow, perceptible on a time scale measured by decades, not years. While in need of cross validation, these findings suggest that cognitive changes associated with ageing may be minimal and emphasise the importance of understanding the full range of age-related pathologies that may diminish brain function. PMID:21890481

Hayden, Kathleen M.; Reed, Bruce R.; Manly, Jennifer J.; Tommet, Douglas; Pietrzak, Robert H.; Chelune, Gordon J.; Yang, Frances M.; Revell, Andrew J.; Bennett, David A.; Jones, Richard N.

2011-01-01

358

Use of gene expression to characterize heterogeneous liver cell populations  

E-print Network

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 ...

Schreiber, Brent M. (Brent Matthew), 1981-

2004-01-01

359

Ethane: A Heterogeneous Parallel Search Algorithm for Heterogeneous Platforms  

E-print Network

In this paper we present Ethane, a parallel search algorithm specifically designed for its execution on heterogeneous hardware environments. With Ethane we propose an algorithm inspired in the structure of the chemical compound of the same name, implementing a heterogeneous island model based in the structure of its chemical bonds. We also propose a schema for describing a family of parallel heterogeneous metaheuristics inspired by the structure of hydrocarbons in Nature, HydroCM (HydroCarbon inspired Metaheuristics), establishing a resem- blance between atoms and computers, and between chemical bonds and communication links. Our goal is to gracefully match computers of different power to algorithms of different behavior (GA and SA in this study), all them collaborating to solve the same problem. The analysis will show that Ethane, though simple, can solve search problems in a faster and more robust way than well-known panmitic and distributed algorithms very popular in the literature.

Domínguez, Julián

2011-01-01

360

Optimal Control of Heterogeneous Systems with Endogenous Domain of Heterogeneity  

SciTech Connect

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.

Belyakov, Anton O., E-mail: anton.belyakov@tuwien.ac.at [Vienna University of Technology, ORCOS, Institute of Mathematical Methods in Economics (Austria); Tsachev, Tsvetomir, E-mail: tsachev@math.bas.bg [Bulgarian Academy of Sciences, Institute of Mathematics and Informatics (Bulgaria); Veliov, Vladimir M., E-mail: veliov@tuwien.ac.at [Vienna University of Technology, ORCOS, Institute of Mathematical Methods in Economics (Austria)

2011-10-15

361

Generalized principles of stochasticity can be used to control dynamic heterogeneity.  

PubMed

It is increasingly appreciated that phenotypic stochasticity plays fundamental roles in biological systems at the cellular level and that a variety of mechanisms generates phenotypic interconversion over a broad range of time scales. The ensuing dynamic heterogeneity can be used to understand biological and clinical processes involving diverse phenotypes in different cell populations. The same principles can be applied, not only to populations composed of cells, but also to populations composed of molecules, tissues, and multicellular organisms. Stochastic units generating dynamic heterogeneity can be integrated across various length scales. We propose that a graphical tool we have developed, called a metronomogram, will allow us to identify factors that suitably influence the restoration of homeostatic heterogeneity so as to modulate the consequences of dynamic heterogeneity for desired outcomes. PMID:23197162

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

2012-12-01

362

Generalized principles of stochasticity can be used to control dynamic heterogeneity  

PubMed Central

It is increasingly appreciated that phenotypic stochasticity plays fundamental roles in biological systems at the cellular level and that a variety of mechanisms generates phenotypic interconversion over a broad range of time scales. The ensuing dynamic heterogeneity can be used to understand biological and clinical processes involving diverse phenotypes in different cell populations. The same principles can be applied, not only to populations composed of cells, but also to populations composed of molecules, tissues, and multicellular organisms. Stochastic units generating dynamic heterogeneity can be integrated across various length scales. We propose that a graphical tool we have developed, called a metronomogram, will allow us to identify factors that suitably influence the restoration of homeostatic heterogeneity so as to modulate the consequences of dynamic heterogeneity for desired outcomes. PMID:23197162

Liao, David; Estevez-Salmeron, Luis; Tlsty, Thea D.

2012-01-01

363

Online Student Support Services  

ERIC Educational Resources Information Center

Community colleges serve a population of students that is more varied than any other segment of higher education. Commuter, adult, distance education, returning, part-time, working and transfer students have academic support needs that are varied and decentralized. However, frequently these students do not receive or cannot access the support…

Smith, Burck

2005-01-01

364

Motivating Students To Read.  

ERIC Educational Resources Information Center

This report describes a research study in which motivational strategies were used to increase student enjoyment of reading and to foster a life-long love of reading. The targeted populations consisted of primary and middle grade students in three different urban midwestern settings. The problem of motivating students to read was documented through…

Green, Patricia; Kandyba, Christine; McDonald, Colleen; Stevens, Tricia

365

Organizational Heterogeneity of Vertebrate Genomes  

PubMed Central

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

Frenkel, Svetlana; Kirzhner, Valery; Korol, Abraham

2012-01-01

366

Heterogeneous information-based artificial stock market  

NASA Astrophysics Data System (ADS)

In this paper, an information-based artificial stock market is considered. The market is populated by heterogeneous agents that are seen as nodes of a sparsely connected graph. Agents trade a risky asset in exchange for cash. Besides the amount of cash and assets owned, each agent is characterized by a sentiment. Moreover, agents share their sentiments by means of interactions that are identified by the graph. Interactions are unidirectional and are supplied with heterogeneous weights. The agent's trading decision is based on sentiment and, consequently, the stock price process depends on the propagation of information among the interacting agents, on budget constraints and on market feedback. A central market maker (clearing house mechanism) determines the price process at the intersection of the demand and supply curves. Both closed- and open-market conditions are considered. The results point out the validity of the proposed model of information exchange among agents and are helpful for understanding the role of information in real markets. Under closed market conditions, the interaction among agents' sentiments yields a price process that reproduces the main stylized facts of real markets, e.g. the fat tails of the returns distributions and the clustering of volatility. Within open-market conditions, i.e. with an external cash inflow that results in asset price inflation, also the unitary root stylized fact is reproduced by the artificial stock market. Finally, the effects of model parameters on the properties of the artificial stock market are also addressed.

Pastore, S.; Ponta, L.; Cincotti, S.

2010-05-01

367

Reporting heterogeneity in self-assessed health among elderly Europeans  

PubMed Central

Introduction Self-assessed health (SAH) is a frequently used measure of individuals’ health status. It is also prone to reporting heterogeneity. To control for reporting heterogeneity objective measures of true health need to be included in an analysis. The topic becomes even more complex for cross-country comparisons, as many key variables tend to vary strongly across countries, influenced by cultural and institutional differences. This study aims at exploring the key drivers for reporting heterogeneity in SAH in an international context. To this end, country specific effects are accounted for and the objective health measure is concretized, distinguishing effects of mental and physical health conditions. Methods We use panel data from the SHARE-project which provides a rich dataset on the elderly European population. To obtain distinct indicators for physical and mental health conditions two indices are constructed. Finally, to identify potential reporting heterogeneity in SAH a generalized ordered probit model is estimated. Results We find evidence that in addition to health behaviour, health care utilization, mental and physical health condition as well as country characteristics affect reporting behaviour. We conclude that observed and unobserved heterogeneity play an important role when analysing SAH and have to be taken into account. PMID:23036352

2012-01-01

368

Quantifying tumour heterogeneity with CT  

PubMed Central

Abstract Heterogeneity is a key feature of malignancy associated with adverse tumour biology. Quantifying heterogeneity could provide a useful non-invasive imaging biomarker. Heterogeneity on computed tomography (CT) can be quantified using texture analysis which extracts spatial information from CT images (unenhanced, contrast-enhanced and derived images such as CT perfusion) that may not be perceptible to the naked eye. The main components of texture analysis can be categorized into image transformation and quantification. Image transformation filters the conventional image into its basic components (spatial, frequency, etc.) to produce derived subimages. Texture quantification techniques include structural-, model- (fractal dimensions), statistical- and frequency-based methods. The underlying tumour biology that CT texture analysis may reflect includes (but is not limited to) tumour hypoxia and angiogenesis. Emerging studies show that CT texture analysis has the potential to be a useful adjunct in clinical oncologic imaging, providing important information about tumour characterization, prognosis and treatment prediction and response. PMID:23545171

Miles, Kenneth A.

2013-01-01

369

Static heterogeneities in liquid water  

NASA Astrophysics Data System (ADS)

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.

Stanley, H. Eugene; Buldyrev, Sergey V.; Giovambattista, Nicolas

2004-10-01

370

Functional heterogeneity in the basophil cell lineage  

PubMed Central

CD4+ T-helper type 2 (Th2) cells, characterized by their expression of interleukin (IL)-4, IL-5, IL-9 and IL-13, are required for immunity to helminth parasites and promote the pathological inflammation associated with asthma and allergic diseases. Recent reports from a number of laboratories have indicated that basophils can influence the induction and/or effector stages of Th2 cytokine-mediated inflammation. However, the impact of basophils appears to depend on the anatomical location and nature of the infectious or inflammatory stimulus. This review will highlight the factors that regulate basophil development and activation and will describe known basophil effector functions. Further, we will discuss the recent identification of phenotypic and functional heterogeneity within murine and human basophil populations and discuss how these findings may explain the context-dependent influence of basophils on either the propagation, regulation or effector phases of Th2 cytokine-associated inflammation. PMID:22608258

Siracusa, Mark C.; Tait Wojno, Elia D.; Artis, David

2013-01-01

371

Phase Transformations in Heterogeneous Steels  

E-print Network

.4 Conclusions 135 References 161 CHAPTER SEVEN ALLOTRIOMORPHIC FERRITE FORMATION IN A HETEROGENEOUS STEEL 7.1 Introduction 163 7.2 Theoretical Analysis 163 7.3 Dilatometry 168 7.4 Conclusions 170 IV References 190 CHAPTER EIGHT COMPLETE CALCULATION... OF MICROSTRUCTURAL EVOLUTION IN HETEROGENEOUS AUTOMOBILE STEELS 8.1 Introduction 191 8.2 Dilatometry 191 8.3 Transformation to bainitic ferrite 194 8.4 Martensitic transformation in 'US83' steel 196 8.5 Conclusions 197 References 229 CHAPTER NINE SUMMARY AND FURTHER...

Khan, Shahid Amin

1990-05-08

372

Using Particulate Drawings to Determine and Improve Students' Conceptions of Pure Substances and Mixtures  

Microsoft Academic Search

Students were interviewed to identify the ways in which they classify particulate drawings as pure substances or heterogeneous or homogeneous mixtures. Those who successfully classified the heterogeneous and homogeneous mixtures used a \\

Michael J. Sanger

2000-01-01

373

Individual heterogeneity in reproductive rates and cost of reproduction in a long-lived vertebrate  

PubMed Central

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

Chambert, Thierry; Rotella, Jay J; Higgs, Megan D; Garrott, Robert A

2013-01-01

374

Emergence of heterogeneity in a noncompetitive resource allocation problem  

NASA Astrophysics Data System (ADS)

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.

Matzke, Christina; Challet, Damien

2011-07-01

375

Measuring Heterogeneity in Forensic Databases  

E-print Network

Measuring Heterogeneity in Forensic Databases Using Hierarchical Bayes Models: Computational Method in Forensic Databases Using Hierarchical Bayes Models''. It supplies details of the Markov Chain Monte Carlo technique employed. Some Key Words: DNA fingerprint, Gibbs Sampling, Markov Chain Monte Carlo. 1 #12; From

376

Behavioral heterogeneity in stock prices  

Microsoft Academic Search

We estimate a dynamic asset pricing model characterized by heterogeneous boundedly rational agents. The fundamental value of the risky asset is publicly available to all agents, but they have different beliefs about the persistence of deviations of stock prices from the fundamental benchmark. An evolutionary selection mechanism based on relative past profits governs the dynamics of the fractions and switching

H. Peter Boswijk; Cars H. Hommes; Sebastiano Manzan

2007-01-01

377

A Dynamic Heterogeneous Beliefs CAPM  

Microsoft Academic Search

We reconsider the derivation of the traditional capital asset pricing model (CAPM) in the discrete time setting for a portfolio of one riskless asset and many risky assets. In contrast to the standard setting, it is assumed that agents are heterogeneous in their conditional means and covariances of the risky returns, and that their beliefs about future returns - based

Carl Chiarella; Xue-Zhong He; Roberto Dieci

2006-01-01

378

Social Capital and Community Heterogeneity  

ERIC Educational Resources Information Center

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…

Coffe, Hilde

2009-01-01

379

Genetic heterogeneity of Alport syndrome  

Microsoft Academic Search

Genetic heterogeneity of Alport syndrome. Forty-one families have been studied with stringent diagnostic criteria of Alport syndrome: proven renal disease with hematuria affecting at least two relatives, neural hearing loss in at least one affected individual, and evolution to renal failure in at least one affected individual. The proportion of affected offsprings of affected females does not significantly differ from

Josué Feingold; Etienne Bois; Agnès Chompert; Michel Broyer; Marie-Claire Gubler; Jean-Pierre Grünfeld

1985-01-01

380

Marketing models of consumer heterogeneity  

Microsoft Academic Search

The distribution of consumer preferences plays a central role in many marketing activities. Pricing and product design decisions, for example, are based on an understand- ing of the di?erences among consumers in price sensitivity and valuation of product attributes. In addition, marketing activities which target specific households require household level parameter estimates. Thus, the modeling of consumer heterogeneity is the

Greg M. Allenby; Peter E. Rossi

1999-01-01

381

Heterogeneous media events processing systems  

Microsoft Academic Search

A key challenge to the successful application of the data modeling, storage and retrieval is the processing of relevant media to determine the events that are represented by them. Towards this goal, we are developing a heterogeneous media events processing system that combines human expertise with algorithmic processing capabilities. In doing so, we seek to leverage the fact that computers

Pilho Kim; Ramesh Jain

2004-01-01

382

Intratumoral heterogeneity in kidney cancer  

PubMed Central

Clear cell renal cell carcinoma (CCRCC) is characterized by mutation of the VHL gene and loss of a segment of chromosome 3. A new study using multi-region exome sequencing has identified substantial intratumoral heterogeneity within large primary CCRCCs, which has profound implications for understanding tumor evolution and for developing effective therapies. PMID:24569233

Ricketts, Christopher J.; Linehan, W. Marston

2014-01-01

383

A Staff Development Program Designed To Reach the Partnership School's Goals: Cooperative Learning Strategies, Coaching Sessions and a Narrowed Academic Performance Gap among Student Populations.  

ERIC Educational Resources Information Center

This paper describes the design and implementation of a staff-development program at Vivian Field Junior High School in Carrollton, Texas. The school is a member of the Texas Partnership School Initiative, which was created to give schools latitude in raising student achievement. The goal of the staff-development program was to identify gains in…

Cook, Kathy; Karr-Kidwell, PJ

384

Intra-tumor heterogeneity: lessons from microbial evolution and clinical implications  

PubMed Central

Multiple subclonal populations of tumor cells can coexist within the same tumor. This intra-tumor heterogeneity will have clinical implications and it is therefore important to identify factors that drive or suppress such heterogeneous tumor progression. Evolutionary biology can provide important insights into this process. In particular, experimental evolution studies of microbial populations, which exist as clonal populations that can diversify into multiple subclones, have revealed important evolutionary processes driving heterogeneity within a population. There are transferrable lessons that can be learnt from these studies that will help us to understand the process of intra-tumor heterogeneity in the clinical setting. In this review, we summarize drivers of microbial diversity that have been identified, such as mutation rate and environmental influences, and discuss how knowledge gained from microbial experimental evolution studies may guide us to identify and understand important selective factors that promote intra-tumor heterogeneity. Furthermore, we discuss how these factors could be used to direct and optimize research efforts to improve patient care, focusing on therapeutic resistance. Finally, we emphasize the need for longitudinal studies to address the impact of these potential tumor heterogeneity-promoting factors on drug resistance, metastatic potential and clinical outcome. PMID:24267946

2013-01-01

385

Genes regulated by the Escherichia coli SOS repressor LexA exhibit heterogenous expression  

Microsoft Academic Search

BACKGROUND: Phenotypic heterogeneity may ensure that a small fraction of a population survives environmental perturbations or may result in lysis in a subpopulation, to increase the survival of siblings. Genes involved in DNA repair and population dynamics play key roles in rapid responses to environmental conditions. In Escherichia coli the transcriptional repressor LexA controls a coordinated cellular response to DNA

Simona Kamenšek; Zdravko Podlesek; Osnat Gillor; Darja Žgur-Bertok

2010-01-01

386

Community-based participatory research to decrease smoking prevalence in a high-risk young adult population: an evaluation of the Students Against Nicotine and Tobacco Addiction (SANTA) project.  

PubMed

Students Against Nicotine and Tobacco Addiction is a community-based participatory research project that engages local medical and mental health providers in partnership with students, teachers, and administrators at the Minnesota-based Job Corps. This intervention contains multiple and synchronous elements designed to allay the stress that students attribute to smoking, including physical activities, nonphysical activities, purposeful modifications to the campus's environment and rules/policies, and on-site smoking cessation education and peer support. The intent of the present investigation was to evaluate (a) the types of stress most predictive of smoking behavior and/or nicotine dependence, (b) which activities students are participating in, and (c) which activities are most predictive of behavior change (or readiness to change). Quantitative data were collected through 5 campus-wide surveys. Response rates for each survey exceeded 85%. Stressors most commonly cited included struggles to find a job, financial problems, family conflict, lack of privacy or freedom, missing family or being homesick, dealing with Job Corps rules, and other-unspecified. The most popular activities in which students took part were physically active ones. However, activities most predictive of beneficent change were nonphysical. Approximately one third of respondents were nicotine dependent at baseline. Nearly half intended to quit within 1 month and 74% intended to quit within 6 months. Interventions perceived as most helpful toward reducing smoking were nonphysical in nature. Future efforts with this and comparable populations should engage youth in advancing such activities within a broader range of activity choices, alongside conventional education and support. PMID:24079815

Mendenhall, Tai J; Harper, Peter G; Henn, Lisa; Rudser, Kyle D; Schoeller, Bill P

2014-03-01

387

Local sparse bump hunting reveals molecular heterogeneity of colon tumors‡  

PubMed Central

The question of molecular heterogeneity and of tumoral phenotype in cancer remains unresolved. To understand the underlying molecular basis of this phenomenon, we analyzed genome-wide expression data of colon cancer metastasis samples, as these tumors are the most advanced and hence would be anticipated to be the most likely heterogeneous group of tumors, potentially exhibiting the maximum amount of genetic heterogeneity. Casting a statistical net around such a complex problem proves difficult because of the high dimensionality and multi-collinearity of the gene expression space, combined with the fact that genes act in concert with one another and that not all genes surveyed might be involved. We devise a strategy to identify distinct subgroups of samples and determine the genetic/molecular signature that defines them. This involves use of the local sparse bump hunting algorithm, which provides a much more optimal and biologically faithful transformed space within which to search for bumps. In addition, thanks to the variable selection feature of the algorithm, we derived a novel sparse gene expression signature, which appears to divide all colon cancer patients into two populations: a population whose expression pattern can be molecularly encompassed within the bump and an outlier population that cannot be. Although all patients within any given stage of the disease, including the metastatic group, appear clinically homogeneous, our procedure revealed two subgroups in each stage with distinct genetic/molecular profiles. We also discuss implications of such a finding in terms of early detection, diagnosis and prognosis. PMID:22052459

Dazard, Jean-Eudes; Rao, J. Sunil; Markowitz, Sanford

2013-01-01

388

Immigrant College Students' Academic Obstacles  

ERIC Educational Resources Information Center

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…

Soria, Krista M.; Stebleton, Michael

2013-01-01

389

The dangers of heterogeneous network computing: heterogeneous networks considered harmful  

SciTech Connect

This report addresses the issue of writing reliable numerical software for networks of heterogeneous computers. Much software has been written for distributed memory parallel computers and in principal such software could readily be ported to networks of machines, such as a collection of workstations connected by Ethernet, but if such a network is not homogeneous there are special challenges that need to be addressed. The symptoms can range from erroneous results returned without warning to deadlock. Some of the problems are straightforward to solve, but for others the solutions are not so obvious and indeed in some cases, such as the method of bisection which we shall discuss in the report, we have not yet decided upon a satisfactory solution that does not incur an unacceptable overhead. Making software robust on heterogeneous systems often requires additional communication. In this report we describe and illustrate the problems and, where possible, suggest solutions so that others may be aware of the potential pitfalls and either avoid them or, if that is not possible, ensure that their software is not used on heterogeneous networks.

Demmel, J.; Stanley, K. [California Univ., Berkeley, CA (United States); Dongarra, J. [Oak Ridge National Lab., TN (United States); Hammarling, S.; Osstrouchov, S. [Tennessee Univ., Knoxville, TN (United States)

1996-12-31

390

Understanding the consequences of seed dispersal in a heterogeneous environment.  

PubMed

Plant distributions are in part determined by environmental heterogeneity on both large (landscape) and small (several meters) spatial scales. Plant populations can respond to environmental heterogeneity via genetic differentiation between large distinct patches, and via phenotypic plasticity in response to heterogeneity occurring at small scales relative to dispersal distance. As a result, the level of environmental heterogeneity experienced across generations, as determined by seed dispersal distance, may itself be under selection. Selection could act to increase or decrease seed dispersal distance, depending on patterns of heterogeneity in environmental quality with distance from a maternal home site. Serpentine soils, which impose harsh and variable abiotic stress on non-adapted plants, have been partially invaded by Erodium cicutarium in northern California, USA. Using nearby grassland sites characterized as either serpentine or non-serpentine, we collected seeds from dense patches of E. cicutarium on both soil types in spring 2004 and subsequently dispersed those seeds to one of four distances from their maternal home site (0, 0.5, 1, or 10 m). We examined distance-dependent patterns of variation in offspring lifetime fitness, conspecific density, soil availability, soil water content, and aboveground grass and forb biomass. ANOVA revealed a distinct fitness peak when seeds were dispersed 0.5 m from their maternal home site on serpentine patches. In non-serpentine patches, fitness was reduced only for seeds placed back into the maternal home site. Conspecific density was uniformly high within 1 m of a maternal home site on both soils, whereas soil water content and grass biomass were significantly heterogeneous among dispersal distances only on serpentine soils. Structural equation modeling and multigroup analysis revealed significantly stronger direct and indirect effects linking abiotic and biotic variation to offspring performance on serpentine soils than on non-serpentine soils, indicating the potential for soil-specific selection on seed dispersal distance in this invasive species. PMID:19739374

Baythavong, Brooke S; Stanton, Maureen L; Rice, Kevin J

2009-08-01

391

Scaling laws for heterogeneous wireless networks  

E-print Network

This thesis studies the problem of determining achievable rates in heterogeneous wireless networks. We analyze the impact of location, traffic, and service heterogeneity. Consider a wireless network with n nodes located ...

Niesen, Urs

2009-01-01

392

Heterogeneous Multiprocessor System Design with ESPAM  

E-print Network

Heterogeneous Multiprocessor System Design with ESPAM: Integration of Hardware IP Cores MASTER . . . . . . . . . . . . . . . . . . . . . . . . . 9 2 Heterogeneous Multiprocessor System Generation 11 2.1 IP Core Integration in ESPAM­ Basic . . . . . . . . . . . . . . . . . . . . . . . . 54 3.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 #12;iv Contents 4

Emmerich, Michael

393

American Sign Language & Heterogeneous Communication Systems.  

ERIC Educational Resources Information Center

This study seeks to understand American Sign Language (ASL) as heterogeneous communication and to use it as a model for developing in other modalities alternative heterogeneous communication systems with the same advantages. (26 references) (CK)

Macken, Elizabeth; And Others

1995-01-01

394

Spatiotemporal heterogeneity in recruitment of larval parasites to shore crab intermediate hosts: the influence of shorebird definitive hosts  

Microsoft Academic Search

Parasitism is a major biotic determinant of animal population dynamics and community structure. Temporal and spatial heterogeneity in parasitism is commonly observed in intermediate host populations. Understanding the causes of temporal and spatial variation in the recruitment of parasites is crucial if we are to manage host populations and animal communities effectively. Here, the temporal and spatial dynamics of Profilicollis

A. David M. Latham; Robert Poulin

2003-01-01

395

Student Affairs DECKER STUDENT  

E-print Network

College Health), where students deliver wellness messages through short, focused conversations with fellow, nutrition, stress management, and more Health education services are available to all registered studentsStudent Affairs DECKER STUDENT HEALTH SERVICES CENTER HEALTH.BINGHAMTON.EDU The Decker Student

Suzuki, Masatsugu

396

The Effect of Student Evaluations on Academic Success  

ERIC Educational Resources Information Center

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…

Artz, Benjamin; Welsch, David M.

2013-01-01

397

Matrix-Matrix Multiplication on Heterogeneous Platforms  

Microsoft Academic Search

In this paper, we address the issue of implementing matrix-matrix multiplication on heterogeneous platforms. We target two different classes of heterogeneous computing resources: heterogeneous networks of workstations, and collections of heterogeneous clusters. Intuitively, the problem is to load balance the work with different-speed resources while minimizing the communication volume. We formally state this problem and prove its NP-completeness. Next we

Olivier Beaumont; Vincent Boudet; Fabrice Rastello; Yves Robert

2000-01-01

398

Memory Space Representation Heterogeneous Network Process Migration  

E-print Network

Memory Space Representation for Heterogeneous Network Process Migration Kasidit Chanchio Xian@bit.csc.lsu.edu http://www.csc.lsu.edu/~scs/ Abstract A major difficulty of heterogeneous process migration is how and effective for heterogeneous network process migration. 1. Introduction As network computing becomes

Sun, Xian-He

399

DISSECTING PREFERENCE HETEROGENEITY IN CONSUMER STATED CHOICES  

Microsoft Academic Search

This paper investigates alternative methods to account for preference heterogeneity in choice experiments. The main interest lies in assessing the different results obtainable when investigating heterogeneity in various ways. This comparison can be performed on the basis of model performance and, more interesting, by evaluating willingness to pay measures. Preference heterogeneity analysis relates to the methods used to search for

Edoardo Marcucci; Valerio Gatta

2011-01-01

400

Effective toughness of heterogeneous media  

NASA Astrophysics Data System (ADS)

We propose a versatile approach to computing the effective toughness of heterogeneous media. This approach focusses on the material property independent of the details of the boundary condition. The key idea is what we call a surfing boundary condition, where a steadily propagating crack opening displacement is applied as a boundary condition to a large domain while the crack set is allowed to evolve as it chooses. The approach is verified and used to study examples in brittle fracture. We demonstrate that effective toughness is different from effective or weighted surface area of the crack set. Furthermore, we demonstrate that elastic heterogeneity can have a profound effect on fracture toughness: it can be a significant toughening mechanism and it can lead to toughness asymmetry wherein the toughness depends not only on the direction but also on the sense of propagation. The role of length-scale is also discussed.

Hossain, M. Z.; Hsueh, C.-J.; Bourdin, B.; Bhattacharya, K.

2014-11-01

401

Vertical heterogeneity of a forest floor invertebrate food web as indicated by stable-isotope analysis  

Microsoft Academic Search

Diverse populations of invertebrates constitute the food web in detritus layers of a forest floor. Heterogeneity in trophic\\u000a interactions within such a species-rich community food web may affect the dynamic properties of biological communities such\\u000a as stability. To examine the vertical heterogeneity in trophic interactions among invertebrates in litter and humus layers,\\u000a we studied differences in species composition and variations

Yutaka Okuzaki; Ichiro Tayasu; Noboru Okuda; Teiji Sota

2009-01-01

402

Asynchrony, fragmentation, and scale determine benefits of landscape heterogeneity to mobile herbivores  

Microsoft Academic Search

Understanding the ways that resource heterogeneity shapes the performance of individuals and the dynamics of populations offers\\u000a a central challenge in contemporary ecology. Emerging evidence shows that herbivores track heterogeneity in nutritional quality\\u000a of vegetation by responding to phenological differences in plants, differences that result from spatial and temporal variation\\u000a in conditions favoring plant growth. Theory predicts that when spatial

Kate R. SearleN; N. T. Hobbs; Stefan R. Jaronski

2010-01-01

403

Phenotypic plasticity and performance of Taraxacum officinale (dandelion) in habitats of contrasting environmental heterogeneity  

Microsoft Academic Search

Ecological theory predicts a positive association between environmental heterogeneity of a given habitat and the magnitude\\u000a of phenotypic plasticity exhibited by resident plant populations. Taraxacum officinale (dandelion) is a perennial herb from Europe that has spread worldwide and can be found growing in a wide variety of habitats.\\u000a We tested whether T. officinale plants from a heterogeneous environment in terms

Marco A. Molina-Montenegro; Cristian Atala; Ernesto Gianoli

2010-01-01

404

Health Perceptions, Self and Body Image, Physical Activity and Nutrition among Undergraduate Students in Israel  

PubMed Central

Purpose This study examines health perceptions, self and body image, physical exercise and nutrition among undergraduate students. Methods A structured, self-reported questionnaire was administered to more than 1500 students at a large academic institute in Israel. The study population was heterogenic in both gender and fields of academic study. Results High correlations between health perceptions, appropriate nutrition, and positive self and body image were found. The relationships between these variables differed between the subpopulation in the sample and the different genders. Engagement in physical exercise contributed to positive body image and positive health perceptions more than engagement in healthy nutrition. Nutrition students reported higher frequencies of positive health perceptions, positive self and body image and higher engagement in physical exercise in comparison to all other students in the sample. Conclusions This study suggests, as have many before, that successful health promotion policy should reflect a collectivist rather than an individualist ethos by providing health prerequisites through a public policy of health-promotion, where the academic settings support a healthy lifestyle policy, by increasing availability of a healthy, nutritious and varied menu in the cafeterias, and offering students various activities that enhance healthy eating and exercise. Implications and contribution This study examined health perceptions, self-image, physical exercise and nutrition among undergraduate students and found high correlations between these topics. Nutrition students reported higher frequencies of positive health perceptions, and positive self and body image and engaged more in physical exercise when compared with all other students in the sample. PMID:23516503

Korn, Liat; Gonen, Ester; Shaked, Yael; Golan, Moria

2013-01-01

405

Heterogeneity of Reduced Bovine ?-Casein  

Microsoft Academic Search

The heterogeneity and some properties of K-casein were investigated. K-Casein preparations independently were pre- pared from milk from a single cow by the modified urea-sulfuric acid method and by the gel filtration method. The two preparations were fractionated by di- ethylaminoethyl-cellulose chromatog- raphy to one fraction, P-l, eluted with the front and 5 fractions, P-2 to P-6, eluted with increasing

H. Doi; F. Ibuki; M. Kanamori

1979-01-01

406

High-throughput heterogeneous catalysis  

NASA Astrophysics Data System (ADS)

This comprehensive review of the literature (over 250 references) deals with high-throughput experimentation in heterogeneous catalysis. Approaches to library design for catalyst discovery and optimization are described and discussed. Special focus is placed on advanced methods for knowledge discovery such as high-throughput kinetic modeling and QSAR. An inventory of successful case studies in catalysis is reported. Finally, recent developments in relevant electronic data and knowledge management are described.

Farrusseng, David

2008-11-01

407

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

ERIC Educational Resources Information Center

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…

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

408

Osteoclast fusion is based on heterogeneity between fusion partners.  

PubMed

Bone-resorbing osteoclasts are formed through fusion of mononucleated precursors. Their choice of partners during the fusion process remains unclear. We hypothesized that osteoclasts are selective in their choice of fusion partner and that this selectivity is based on heterogeneity among the cells with respect to their maturation stage and their expression and cellular organization of fusion factors. Support for this hypothesis was found from immunofluorescence staining of the osteoclast fusion factors CD47, dendritic cell-specific transmembrane protein (DC-STAMP), and syncytin-1. These stainings revealed heterogeneous localization patterns of all three factors within a given culture of osteoclasts. CD47 was found to be localized primarily in small osteoclasts and preosteoclasts, which were also positive for DC-STAMP but negative for cathepsin K expression. A role of CD47 in the early osteoclast fusion steps was also suggested from experiments with a CD47 blocking antibody, which resulted in an inhibition of the fusion of small osteoclasts. Conversely, blocking of connexin 43 affected the fusion of larger osteoclasts with four or more nuclei. The suggestion that different fusion factors function at different stages of osteoclast fusion supports the idea of heterogeneity in the osteoclast population; our results suggest that osteoclast fusion is indeed based on heterogeneity. Considering the in vivo environment in which osteoclasts develop and fuse, our findings seem very applicable and provide novel, important insight into key issues in bone and fusion research. PMID:24862648

Hobolt-Pedersen, Anne-Sofie; Delaissé, Jean-Marie; Søe, Kent

2014-07-01

409

Heterogeneity and Allometric Growth of Human Collaborative Tagging Behavior  

E-print Network

Allometric growth is found in many tagging systems online. That is, the number of new tags (T) is a power law function of the active population (P), or T P^gamma (gamma!=1). According to previous studies, it is the heterogeneity in individual tagging behavior that gives rise to allometric growth. These studies consider the power-law distribution model with an exponent beta, regarding 1/beta as an index for heterogeneity. However, they did not discuss whether power-law is the only distribution that leads to allometric growth, or equivalently, whether the positive correlation between heterogeneity and allometric growth holds in systems of distributions other than power-law. In this paper, the authors systematically examine the growth pattern of systems of six different distributions, and find that both power-law distribution and log-normal distribution lead to allometric growth. Furthermore, by introducing Shannon entropy as an indicator for heterogeneity instead of 1/beta, the authors confirm that the positive...

Wu, Lingfei

2011-01-01

410

Population Geography: Problems, Concepts, and Prospects.  

ERIC Educational Resources Information Center

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

Peters, Gary L.; Larkin, Robert P.

411

Effects of child abuse history on borderline personality traits, negative life events, and depression: a study among a university student population in Japan.  

PubMed

To simultaneously examine the impact of childhood abuse history on borderline personality traits, negative life events, and depression, undergraduate students (N=243) were studied by questionnaire surveys with one week intervals. Neglect and emotional abuse as well as sexual maltreatment predicted borderline personality traits and baseline depression. Baseline depression as well as the impact of negative life events occurring the week prior predicted depression a week later. However, after considering the baseline depression level, child abuse history failed to predict the follow-up depression level. Borderline personality traits did not moderate these findings. Childhood emotional and sexual abuse history may influence depression and borderline personality traits. PMID:20488554

Igarashi, Hiromi; Hasui, Chieko; Uji, Masayo; Shono, Masahiro; Nagata, Toshiaki; Kitamura, Toshinori

2010-12-30

412

Large-scale replication and heterogeneity in Parkinson disease genetic loci  

PubMed Central

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

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; Boyle, R.S; Sellbach, A; O'Sullivan, J.D.; Sutherland, G.T.; Siebert, G.A; Dissanayaka, N.N.W; Van Broeckhoven, Christine; Theuns, Jessie; Crosiers, David; Pickut, Barbara; Engelborghs, Sebastiaan; Meeus, Bram; De Deyn, Peter P.; Cras, Patrick; Rogaeva, Ekaterina; Lang, Anthony E; Agid, Y; Anheim, M; Bonnet, A-M; Borg, M; Brice, A; Broussolle, E; Corvol, JC; Damier, P; Destée, A; Dürr, A; Durif, F; Lesage, S; Lohmann, E; Pollak, P; Rascol, O; Tison, F; Tranchant, C; Viallet, F; Vidailhet, M; Tzourio, Christophe; Amouyel, Philippe; Loriot, Marie-Anne; Mutez, Eugénie; Duflot, Aurélie; Legendre, Jean-Philippe; Waucquier, Nawal; Gasser, Thomas; Riess, Olaf; Berg, Daniela; Schulte, Claudia; Klein, Christine; Djarmati, Ana; Hagenah, Johann; Lohmann, Katja; Auburger, Georg; Hilker, Rüdiger; van de Loo, Simone; Dardiotis, Efthimios; Tsimourtou, Vaia; Ralli, Styliani; Kountra, Persa; Patramani, Gianna; Vogiatzi, Cristina; Hattori, Nobutaka; Tomiyama, Hiroyuki; Funayama, Manabu; Yoshino, Hiroyo; Li, Yuanzhe; Imamichi, Yoko; Toda, Tatsushi; Satake, Wataru; Lynch, Tim; Gibson, J. Mark; Valente, Enza Maria; Ferraris, Alessandro; Dallapiccola, Bruno; Ialongo, Tamara; Brighina, Laura; Corradi, Barbara; Piolti, Roberto; Tarantino, Patrizia; Annesi, Ferdinanda; Jeon, Beom S.; Park, Sung-Sup; Aasly, J; Opala, Grzegorz; Jasinska-Myga, Barbara; Klodowska-Duda, Gabriela; Boczarska-Jedynak, Magdalena; Tan, Eng King; Belin, Andrea Carmine; Olson, Lars; Galter, Dagmar; Westerlund, Marie; Sydow, Olof; Nilsson, Christer; Puschmann, Andreas; Lin, JJ; Maraganore, Demetrius M.; Ahlskog, J, Eric; de Andrade, Mariza; Lesnick, Timothy G.; Rocca, Walter A.; Checkoway, Harvey; Ross, Owen A; Wszolek, Zbigniew K.; Uitti, Ryan J.

2012-01-01

413

Effects of soil nutrient heterogeneity on intraspecific competition in the invasive, clonal plant Alternanthera philoxeroides  

PubMed Central

Background and Aims Fine-scale, spatial heterogeneity in soil nutrient availability can increase the growth of individual plants, the productivity of plant communities and interspecific competition. If this is due to the ability of plants to concentrate their roots where nutrient levels are high, then nutrient heterogeneity should have little effect on intraspecific competition, especially when there are no genotypic differences between individuals in root plasticity. We tested this hypothesis in a widespread, clonal species in which individual plants are known to respond to nutrient heterogeneity. Methods Plants derived from a single clone of Alternanthera philoxeroides were grown in the greenhouse at low or high density (four or 16 plants per 27·5 × 27·5-cm container) with homogeneous or heterogeneous availability of soil nutrients, keeping total nutrient availability per container constant. After 9 weeks, measurements of size, dry mass and morphology were taken. Key Results Plants grew more in the heterogeneous than in the homogeneous treatment, showing that heterogeneity promoted performance; they grew less in the high- than in the low-density treatment, showing that plants competed. There was no interactive effect of nutrient heterogeneity and plant density, supporting the hypothesis that heterogeneity does not affect intraspecific competition in the absence of genotypic differences in plasticity. Treatments did not affect morphological characteristics such as specific leaf area or root/shoot ratio. Conclusions Results indicate that fine-scale, spatial heterogeneity in the availability of soil nutrients does not increase competition when plants are genetically identical, consistent with the suggestion that effects of heterogeneity on competition depend upon differences in plasticity between individuals. Heterogeneity is only likely to increase the spread of monoclonal, invasive populations such as that of A. philoxeroides in China. PMID:22207612

Zhou, Jian; Dong, Bi-Cheng; Alpert, Peter; Li, Hong-Li; Zhang, Ming-Xiang; Lei, Guang-Chun; Yu, Fei-Hai

2012-01-01

414

Cellular Respiration and Population Growth  

NSDL National Science Digital Library

Through two lessons and their associated activities, students explore cellular respiration and population growth in yeasts. Yeast cells are readily obtained and behave predictably, so they are very suitable for use in middle school classrooms. Students are presented with information that enables them to recognize that yeasts are unicellular organisms that are useful to humans.

Engineering K-Phd Program

415

Not Simply More of the Same: Distinguishing between Patient Heterogeneity and Parameter Uncertainty.  

PubMed

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

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

2014-11-01

416

Ethnogenetic heterogeneity of rheumatoid arthritis-implications for pathogenesis.  

PubMed

Autoimmune diseases such as rheumatoid arthritis and systemic lupus erythematosus are generally considered multifactorial-that is, they involve both genetic and environmental factors. Technical advances in human genetics over the past 5 years have enabled the survey of the entire human genome for disease susceptibility genes and have contributed to a greater understanding of the molecular mechanisms underlying autoimmunity. Among the genetic predisposition factors identified to date, some variants have been found to be restricted to specific ethnic groups, which might reflect migration history and the natural selection that shaped genetic variation in these populations. Other genetic factors could also have exerted different magnitudes of risk for the disease among the different populations, which might be explained by their interactions with other genetic and environmental factors. These pieces of evidence suggest that substantial heterogeneity exists in the genetics underlying autoimmunity among different ethnic populations. This Review discusses the genetic heterogeneity in autoimmunity, with a focus on rheumatoid arthritis, between Asian and European populations. In addition to the most-studied and well-characterized gene HLA-DRB1, we will also describe examples of the gene-environment interactions between PADI4 and smoking, and the gene-gene interactions between PTPN22 and FCRL3. PMID:20234359

Kochi, Yuta; Suzuki, Akari; Yamada, Ryo; Yamamoto, Kazuhiko

2010-05-01

417

Host plant quality, spatial heterogeneity, and the stability of mite predator-prey dynamics.  

PubMed

Population dynamics models suggest that both the over-all level of resource productivity and spatial variability in productivity can play important roles in community dynamics. Higher productivity environments are predicted to destabilize consumer-resource dynamics. Conversely, greater heterogeneity in resource productivity is expected to contribute to stability. Yet the importance of these two factors for the dynamics of arthropod communities has been largely overlooked. I manipulated nutrient availability for strawberry plants in a multi-patch experiment, and measured effects of overall plant quality and heterogeneity in plant quality on the stability of interactions between the phytophagous mite Tetranychus urticae and its predator Phytoseiulus persimilis. Plant size, leaf N content and T. urticae population growth increased monotonically with increasing soil nitrogen availability. This gradient in plant quality affected two correlates of mite population stability, population variability over time (i.e., coefficient of variation) and population persistence (i.e., proportion of plant patches colonized). However, the highest level of plant quality did not produce the least stable dynamics, which is inconsistent with the "paradox of enrichment". Heterogeneity in plant productivity had modest effects on stability, with the only significant difference being less variable T. urticae densities in the heterogeneous compared to the corresponding homogeneous treatment. These results are generally congruent with metapopulation theory and other models for spatially segregated populations, which predict that stability should be governed largely by relative movement rates of predators and prey--rather than patch quality. PMID:21053057

Daugherty, Matthew P

2011-04-01

418

Population. Environmental Ecological Education Project.  

ERIC Educational Resources Information Center

This unit on population, designed for senior high school students, is divided into six packets with the following major topics: general introduction to the effects of a growing population, urbanization, family structures, family planning, consumption, environmental decay, and controlling the environment. Each packet contains a list of the topical…

Parkway School District, Chesterfield, MO.

419

The Issue of Student Access: Fall 1990 to Fall 1993. Student Equity Report #1.  

ERIC Educational Resources Information Center

The Coast Community College District (CCCD) in Southern California conducted a study to determine how representative the district and college student populations were of the primary service population. Recent increases in community college credit student fees significantly affected the defined student and service population. For the purpose of…

Sanchez, Jorge R.

420

Population Density: How Much Space Do You Have?  

NSDL National Science Digital Library

Students learn about population density within environments and ecosystems. They determine the density of a population and think about why population density and distribution information is useful to engineers for city planning and design as well as for resource allocation.

Integrated Teaching And Learning Program

421

THEORETICAL POPULATION BIOLOGY 36, 34-58 (1989) Ecogenetic Models, Competition,  

E-print Network

, Berkeley, California 94720 VEIJO KAITALA Systems Analysis Laboratory, Helsinki University of Technology disruptive selection in heterogeneous environments. These equations have both a genetic and a population under disruptive selection in density regulated sympatric populations exploiting heterogeneousenviron

Getz, Wayne M.

422

Quantitative Characterization of Cellular Membrane-Receptor Heterogeneity through Statistical and Computational Modeling  

PubMed Central

Cell population heterogeneity can affect cellular response and is a major factor in drug resistance. However, there are few techniques available to represent and explore how heterogeneity is linked to population response. Recent high-throughput genomic, proteomic, and cellomic approaches offer opportunities for profiling heterogeneity on several scales. We have recently examined heterogeneity in vascular endothelial growth factor receptor (VEGFR) membrane localization in endothelial cells. We and others processed the heterogeneous data through ensemble averaging and integrated the data into computational models of anti-angiogenic drug effects in breast cancer. Here we show that additional modeling insight can be gained when cellular heterogeneity is considered. We present comprehensive statistical and computational methods for analyzing cellomic data sets and integrating them into deterministic models. We present a novel method for optimizing the fit of statistical distributions to heterogeneous data sets to preserve important data and exclude outliers. We compare methods of representing heterogeneous data and show methodology can affect model predictions up to 3.9-fold. We find that VEGF levels, a target for tuning angiogenesis, are more sensitive to VEGFR1 cell surface levels than VEGFR2; updating VEGFR1 levels in the tumor model gave a 64% change in free VEGF levels in the blood compartment, whereas updating VEGFR2 levels gave a 17% change. Furthermore, we find that subpopulations of tumor cells and tumor endothelial cells (tEC) expressing high levels of VEGFR (>35,000 VEGFR/cell) negate anti-VEGF treatments. We show that lowering the VEGFR membrane insertion rate for these subpopulations recovers the anti-angiogenic effect of anti-VEGF treatment, revealing new treatment targets for specific tumor cell subpopulations. This novel method of characterizing heterogeneous distributions shows for the first time how different representations of the same data set lead to different predictions of drug efficacy. PMID:24827582

Weddell, Jared C.; Imoukhuede, P. I.

2014-01-01

423

Dynamic heterogeneity and DNA methylation in embryonic stem cells.  

PubMed

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

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

2014-07-17

424

Epidemic spreading in metapopulation networks with heterogeneous infection rates  

NASA Astrophysics Data System (ADS)

In this paper, we study epidemic spreading in metapopulation networks wherein each node represents a subpopulation symbolizing a city or an urban area and links connecting nodes correspond to the human traveling routes among cities. Differently from previous studies, we introduce a heterogeneous infection rate to characterize the effect of nodes' local properties, such as population density, individual health habits, and social conditions, on epidemic infectivity. By means of a mean-field approach and Monte Carlo simulations, we explore how the heterogeneity of the infection rate affects the epidemic dynamics, and find that large fluctuations of the infection rate have a profound impact on the epidemic threshold as well as the temporal behavior of the prevalence above the epidemic threshold. This work can refine our understanding of epidemic spreading in metapopulation networks with the effect of nodes' local properties.

Gong, Yong-Wang; Song, Yu-Rong; Jiang, Guo-Ping

2014-12-01

425

Dynamic Heterogeneity and DNA Methylation in Embryonic Stem Cells  

PubMed Central

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

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

2014-01-01

426

Cellulose conversion under heterogeneous catalysis.  

PubMed

In view of current problems such as global warming, high oil prices, food crisis, stricter environmental laws, and other geopolitical scenarios surrounding the use of fossil feedstocks and edible resources, the efficient conversion of cellulose, a non-food biomass, into energy, fuels, and chemicals has received much attention. The application of heterogeneous catalysis could allow researchers to develop environmentally benign processes that lead to selective formation of value-added products from cellulose under relatively mild conditions. This Minireview gives insight into the importance of biomass utilization, the current status of cellulose conversion, and further transformation of the primary products obtained. PMID:19021143

Dhepe, Paresh L; Fukuoka, Atsushi

2008-01-01

427

Temperature chaos and quenched heterogeneities.  

PubMed

We present a treatable generalization of the Sherrington-Kirkpatrick (SK) model which introduces correlations in the elements of the coupling matrix through multiplicative disorder on the single variables and investigate the consequences on the phase diagram. We define a generalized qEA parameter and test the structural stability of the SK results in this correlated case evaluating the de Almeida-Thouless line of the model. As a main result we demonstrate the increase of temperature chaos effects due to heterogeneities. PMID:24730812

Barucca, Paolo; Parisi, Giorgio; Rizzo, Tommaso

2014-03-01

428

Becoming Researchers: Community College ESL Students, Information Literacy, and the Library  

E-print Network

with ESL instructors or the office of international studentsESL students, with the important exception of well- educated international students,ESL students are a growing majority (ICAS, 2006). Adding to this population, international students

Patterson, David Jay

2011-01-01

429

GenHtr: a tool for comparative assessment of genetic heterogeneity in microbial genomes generated by massive short-read sequencing  

Microsoft Academic Search

BACKGROUND: Microevolution is the study of short-term changes of alleles within a population and their effects on the phenotype of organisms. The result of the below-species-level evolution is heterogeneity, where populations consist of subpopulations with a large number of structural variations. Heterogeneity analysis is thus essential to our understanding of how selective and neutral forces shape bacterial populations over a

GongXin Yu

2010-01-01

430

Linguistic Minority Students Go to College: Preparation, Access, and Persistence  

ERIC Educational Resources Information Center

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…

Kanno, Yasuko, Ed.; Harklau, Linda, Ed.

2012-01-01

431

Mantle Heterogeneity: What is the message from geochemistry?  

NASA Astrophysics Data System (ADS)

Ubiquitous heterogeneity in the Earth's mantle has been documented by numerous chemical and isotopic analyses of oceanic basalts. Despite about four decades of research and the continuously increasing number of data, however, the way in which compositional heterogeneity is manifest in the Earth's mantle, as well as the origin and processes leading to mantle heterogeneity remain fundamental questions. A statistical analysis of the large amount of available isotope data in oceanic basalts shows that two principal compositional vectors capture about 95% of the isotopic variation. Care must be taken, however, to directly equate basalt and mantle isotopic composition, because partial melting, and melt mixing during melt extraction lead to a biased representation and subdued compositional variability in the basalts compared to their mantle sources. This is perhaps best documented by the isotopic disparity between MORB and abyssal peridotites, which are isotopically by far more depleted and variable than MORB. In contrast, enriched isotope signatures in ocean island basalts (OIB) closely represent those of their average enriched mantle source components. The main principal vector of the MORB and OIB isotopic distribution (about two-thirds of the variation) corresponds to the generation and subduction of oceanic plates. Mass exchange between the lower and upper continental crust and the mantle accounts for most of the remaining third of the MORB-OIB isotopic variation. This simple conceptual framework attributes mantle heterogeneity mainly to the large-scale cycling between the Earth's two major lithophile element reservoirs, the mantle and the oceanic and continental crust. Formation and evolution of mantle heterogeneity is therefore a continuous process that is largely governed by plate-tectonic processes, and unlikely to result in just a few large-scale mantle reservoirs, which subsequently interact and mingle during intra-mantle processing. To what extent heterogeneous mantle materials preserve their inherent compositional heterogeneity depends on the physics and fluid dynamics of the mantle. Once formed, by continuous depletion through partial melting (depleted mantle) and by transport into the mantle, heterogeneous materials become stretched, reduced in size and at present, they are more or less statistically distributed. Large-scale statistical differences caused by differences in the relative abundance of the distinct mantle materials may result in large-scale compositional "domains" (e.g. DUPAL or SOPITA ). Alternatively these putative domains could be an artifact resulting from different sampling of a similar population of mantle components. At mid-ocean ridges, for example, the observed degree of isotopic variability decreases as the scale of melting, or rate of processing of mantle material (as measured by the spreading rate), increases. This observation also shows that the scale of mantle components is small compared to the maximum dimension over which melts are produced and mixed beneath ridges, i.e. certainly on the kilometer scale of the melting region but perhaps even smaller. Further support for this sub-kilometer scale of mantle heterogeneity comes from theoretical melting models, the depth-dependent sampling of isotopically distinct source materials observed in Icelandic basalts, the isotopic heterogeneity observed in melt inclusions, and the sub-kilometer scale isotopic heterogeneity observed in abyssal peridotites. These observations further show that, despite intra-mantle processing by convective stirring, both enriched and highly depleted isotopic materials survive, i.e. to a large extent they retain their physico-chemical integrity, and escape equilibration with ambient, compositionally distinct material over geologic timescales (> 1 Ga).

Stracke, Andreas

2010-05-01

432

Teachers' PET Project. Population Education Training.  

ERIC Educational Resources Information Center

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.…

Zero Population Growth, Inc., Washington, DC.

433

Kid's PACK: Population Awareness Campaign Kit.  

ERIC Educational Resources Information Center

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

Zero Population Growth, Inc., Washington, DC.

434

Groundwater pumping by heterogeneous users  

NASA Astrophysics Data System (ADS)

Farm size is a significant determinant of both groundwater-irrigated farm acreage and groundwater-irrigation-application rates per unit land area. This paper analyzes the patterns of groundwater exploitation when resource users in the area overlying a common aquifer are heterogeneous. In the presence of user heterogeneity, the common resource problem consists of inefficient dynamic and spatial allocation of groundwater because it impacts income distribution not only across periods but also across farmers. Under competitive allocation, smaller farmers pump groundwater faster if farmers have a constant marginal periodic utility of income. However, it is possible that larger farmers pump faster if the Arrow-Pratt coefficient of relative risk-aversion is sufficiently decreasing in income. A greater farm-size inequality may either moderate or amplify income inequality among farmers. Its effect on welfare depends on the curvature properties of the agricultural output function and the farmer utility of income. Also, it is shown that a flat-rate quota policy that limits the quantity of groundwater extraction per unit land area may have unintended consequences for the income distribution among farmers.

Saak, Alexander E.; Peterson, Jeffrey M.

2012-08-01

435

Dispersivity in heterogeneous permeable media  

SciTech Connect

When one fluid displaces another through a one-dimensional porous medium, the composition changes from pure displacing fluid at the inlet to pure displaced fluid some distance downstream. The distance over which an arbitrary percentage of this change occurs is defined as the mixing zone length, which increases with increasing average distance traveled by the displacement front. For continuous injection, the mixing zone size can be determined from a breakthrough curve as the time required for the effluent displacing fluid concentration to change from, say, 10% to 90%. In classical dispersion theory, the mixing zone grows in proportion to the square root of the mean distance traveled, or, equivalently, to the square root of the mean breakthrough time. In a multi-dimensional heterogeneous medium, especially at field scales, the size of the mixing zone grows almost linearly with mean distance or travel time. If an observed breakthrough curve is forced to fit the, clinical theory, the resulting effective dispersivity, instead of being constant, also increases almost linearly with the spatial or temporal scale of the problem. This occurs because the heterogeneity in flow properties creates a corresponding velocity distribution along the different flow pathways from the inlet to the outlet of the system. Mixing occurs mostly at the outlet, or wherever the fluid is sampled, rather than within the medium. In this paper, we consider the effects. of this behavior on radionuclide or other contaminant migration.

Chesnut, D.A.

1994-01-01

436

Harnessing Technology to Improve Formative Assessment of Student Conceptions in STEM: Forging a National Network  

ERIC Educational Resources Information Center

Concept inventories, consisting of multiple-choice questions designed around common student misconceptions, are designed to reveal student thinking. However, students often have complex, heterogeneous ideas about scientific concepts. Constructed-response assessments, in which students must create their own answer, may better reveal students'…

Haudek, Kevin C.; Kaplan, Jennifer J.; Knight, Jennifer; Long, Tammy; Merrill, John; Munn, Alan; Nehm, Ross; Smith, Michelle; Urban-Lurain, Mark

2011-01-01