Note: This page contains sample records for the topic heterogeneous student population from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: November 12, 2013.
1

Population heterogeneity and causal inference  

PubMed Central

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

Xie, Yu

2013-01-01

2

Minority Representation in Higher Education: The Impact of Population Heterogeneity.  

ERIC Educational Resources Information Center

|A study using national data on minority college students and institutional heterogeneity revealed that minority groups are better represented at some universities than others, relative to their proportions in the state population. State racial heterogeneity is a major determinant of African-American representation. For other minority groups,…

Mentzer, Marc S.

1993-01-01

3

Demographic heterogeneity, cohort selection, and population growth.  

PubMed

Demographic heterogeneity--variation among individuals in survival and reproduction--is ubiquitous in natural populations. Structured population models address heterogeneity due to age, size, or major developmental stages. However, other important sources of demographic heterogeneity, such as genetic variation, spatial heterogeneity in the environment, maternal effects, and differential exposure to stressors, are often not easily measured and hence are modeled as stochasticity. Recent research has elucidated the role of demographic heterogeneity in changing the magnitude of demographic stochasticity in small populations. Here we demonstrate a previously unrecognized effect: heterogeneous survival in long-lived species can increase the long-term growth rate in populations of any size. We illustrate this result using simple models in which each individual's annual survival rate is independent of age but survival may differ among individuals within a cohort. Similar models, but with nonoverlapping generations, have been extensively studied by demographers, who showed that, because the more "frail" individuals are more likely to die at a young age, the average survival rate of the cohort increases with age. Within ecology and evolution, this phenomenon of "cohort selection" is increasingly appreciated as a confounding factor in studies of senescence. We show that, when placed in a population model with overlapping generations, this heterogeneity also causes the asymptotic population growth rate lambda to increase, relative to a homogeneous population with the same mean survival rate at birth. The increase occurs because, even integrating over all the cohorts in the population, the population becomes increasingly dominated by the more robust individuals. The growth rate increases monotonically with the variance in survival rates, and the effect can be substantial, easily doubling the growth rate of slow-growing populations. Correlations between parent and offspring phenotype change the magnitude of the increase in lambda, but the increase occurs even for negative parent-offspring correlations. The effect of heterogeneity in reproductive rate on lambda is quite different: growth rate increases with reproductive heterogeneity for positive parent-offspring correlation but decreases for negative parent-offspring correlation. These effects of demographic heterogeneity on lambda have important implications for population dynamics, population viability analysis, and evolution. PMID:22073789

Kendall, Bruce E; Fox, Gordon A; Fujiwara, Masami; Nogeire, Theresa M

2011-10-01

4

Evolution of altruistic punishment in heterogeneous populations.  

PubMed

Evolutionary models for altruistic behavior typically make the assumption of homogeneity: each individual has the same costs and benefits associated with cooperating with each other and punishing for selfish behavior. In this paper, we relax this assumption by separating the population into heterogeneous classes, such that individuals from different classes differ in their ability to punish for selfishness. We compare the effects of introducing heterogeneity this way across two population models, that each represents a different type of population: the infinite and well-mixed population describes the way workers of social insects such as ants are organized, while a spatially structured population is more related to the way social norms evolve and are maintained in a social network. We find that heterogeneity in the effectiveness of punishment by itself has little to no effect on whether or not altruistic behavior will stabilize in a population. In contrast, heterogeneity in the cost that individuals pay to punish for selfish behavior allows altruistic behavior to be maintained more easily. Fewer punishers are needed to deter selfish behavior, and the individuals that punish will mostly belong to the class that pays a lower cost to do so. This effect is amplified when individuals that pay a lower cost for punishing inflict a higher punishment. The two population models differ when individuals that pay a low cost for punishing also inflict a lower punishment. In this situation, altruistic behavior becomes harder to maintain in an infinite and well-mixed population. However, this effect does not occur when the population is spatially structured. PMID:21903100

de Weerd, Harmen; Verbrugge, Rineke

2011-09-01

5

Latent variable modeling in heterogeneous populations  

Microsoft Academic Search

Common applications of latent variable analysis fail to recognize that data may be obtained from several populations with different sets of parameter values. This article describes the problem and gives an overview of methodology that can address heterogeneity. Artificial examples of mixtures are given, where if the mixture is not recognized, strongly distorted results occur. MIMIC structural modeling is shown

Bengt O. Muthén

1989-01-01

6

Population robustness arising from cellular heterogeneity  

PubMed Central

Heterogeneity between individual cells is a common feature of dynamic cellular processes, including signaling, transcription, and cell fate; yet the overall tissue level physiological phenotype needs to be carefully controlled to avoid fluctuations. Here we show that in the NF-?B signaling system, the precise timing of a dual-delayed negative feedback motif [involving stochastic transcription of inhibitor ?B (I?B)-? and -?] is optimized to induce heterogeneous timing of NF-?B oscillations between individual cells. We suggest that this dual-delayed negative feedback motif enables NF-?B signaling to generate robust single cell oscillations by reducing sensitivity to key parameter perturbations. Simultaneously, enhanced cell heterogeneity may represent a mechanism that controls the overall coordination and stability of cell population responses by decreasing temporal fluctuations of paracrine signaling. It has often been thought that dynamic biological systems may have evolved to maximize robustness through cell-to-cell coordination and homogeneity. Our analyses suggest in contrast, that this cellular variation might be advantageous and subject to evolutionary selection. Alternative types of therapy could perhaps be designed to modulate this cellular heterogeneity.

Paszek, Pawel; Ryan, Sheila; Ashall, Louise; Sillitoe, Kate; Harper, Claire V.; Spiller, David G.; Rand, David A.; White, Michael R. H.

2010-01-01

7

Stochastic population growth in spatially heterogeneous environments.  

PubMed

Classical ecological theory predicts that environmental stochasticity increases extinction risk by reducing the average per-capita growth rate of populations. For sedentary populations in a spatially homogeneous yet temporally variable environment, a simple model of population growth is a stochastic differential equation dZ(t) = ?Z(t)dt + ?Z(t)dW(t), t ? 0, where the conditional law of Z(t+?t)-Z(t) given Z(t) = z has mean and variance approximately z ??t and z²?²?t when the time increment ?t is small. The long-term stochastic growth rate lim(t??) t?¹ log Z(t) for such a population equals ? ? ?²/2 . Most populations, however, experience spatial as well as temporal variability. To understand the interactive effects of environmental stochasticity, spatial heterogeneity, and dispersal on population growth, we study an analogous model X(t) = (X¹(t) , . . . , X(n)(t)), t ? 0, for the population abundances in n patches: the conditional law of X(t+?t) given X(t) = x is such that the conditional mean of X(i)(t+?t) ? X(i)(t) is approximately [x(i)?(i) + ?(j) (x(j) D(ji) ? x(i) D(i j) )]?t where ?(i) is the per capita growth rate in the ith patch and D(ij) is the dispersal rate from the ith patch to the jth patch, and the conditional covariance of X(i)(t+?t)? X(i)(t) and X(j)(t+?t) ? X(j)(t) is approximately x(i)x(j)?(ij)?t for some covariance matrix ? = (?(ij)). We show for such a spatially extended population that if S(t) = X¹(t)+· · ·+ X(n)(t) denotes the total population abundance, then Y(t) = X(t)/S(t), the vector of patch proportions, converges in law to a random vector Y(?) as t ? ?, and the stochastic growth rate lim(t??) t?¹ log S(t) equals the space-time average per-capita growth rate ?(i)?(i)E[Y(i)(?)] experienced by the population minus half of the space-time average temporal variation E[?(i,j) ?(i j)Y(i)(?) Y(j)(?)] experienced by the population. Using this characterization of the stochastic growth rate, we derive an explicit expression for the stochastic growth rate for populations living in two patches, determine which choices of the dispersal matrix D produce the maximal stochastic growth rate for a freely dispersing population, derive an analytic approximation of the stochastic growth rate for dispersal limited populations, and use group theoretic techniques to approximate the stochastic growth rate for populations living in multi-scale landscapes (e.g. insects on plants in meadows on islands). Our results provide fundamental insights into "ideal free" movement in the face of uncertainty, the persistence of coupled sink populations, the evolution of dispersal rates, and the single large or several small (SLOSS) debate in conservation biology. For example, our analysis implies that even in the absence of density-dependent feedbacks, ideal-free dispersers occupy multiple patches in spatially heterogeneous environments provided environmental fluctuations are sufficiently strong and sufficiently weakly correlated across space. In contrast, for diffusively dispersing populations living in similar environments, intermediate dispersal rates maximize their stochastic growth rate. PMID:22427143

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

2012-03-18

8

Dynamics of selection in a heterogeneous population  

SciTech Connect

The dynamics of the number of diploid individuals with possible n {ge} 2 alleles of a gene not located in a sex chromosome was studied in a heterogeneous isolated population. It was demonstrated that if only selection is accounted for, the number of individuals carrying alleles that do not a provide maximal selective advantage approaches zero as the time of observation increases, whereas the number of individuals with various genotypes, but with a maximal selective advantage, approaches nonzero stationary values depending on their initial numbers. It was established that under certain conditions and even if processes of death-reproduction are taken into account, the mechanism of selection may have a dominating effect on population dynamics.

Volkov, I.K.; Chebotarev, A.N. [Moscow Technical Univ. (Russian Federation)

1995-01-01

9

Changing Student Populations.  

ERIC Educational Resources Information Center

|The needs and aspirations of nontraditional college students and adult part-time students should stimulate the teaching of basic skills in higher education to: enhance continued learning; promote interest in lifelong learning; and develop discerning consumers of education. (CM)|

Cross, K. Patricia

1982-01-01

10

Combinatorial control of heterogeneous cell populations  

NASA Astrophysics Data System (ADS)

In medicine, a recent pharmacological approach involves systematic discovery of combinatorial therapies, in which different drugs are simultaneously used to control different pathways associated with a cellular function. This control must occur with minimal response in other non-target cells exposed to treatment, i.e. it has to be selective. We have investigated the statistics of selective control of the human apoptosis (cell death) signaling network. We have built a model for a heterogeneous population of cells, characterized by a signaling network with identical topology, but having different link strengths. The control of the life/death signal is realized by acting with external perturbations, modeling the effect of drugs, on the nodes and on the signaling flow. Concepts from statistical physics and information theory, including entropy, frustration, and non-linearity have been used to characterize the general properties of selective control. This knowledge was used as a guide in designing algorithms for identifying selective perturbations. Some of these algorithms have been implemented in vitro in high throughput experiments on real cell lines where a large number of combinations of different drugs can be tested.

Piermarocchi, C.; Duxbury, P.; Paternostro, G.; Feala, J.; Tiziani, S.; Axelrod, J.; Chaudhury, A.; Choi, J.; McCulloch, A.; Cortes, J.

2010-03-01

11

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

12

Communicating Risk to Student Populations  

Microsoft Academic Search

Campus emergency managers often face challenges in encouraging participation by student populations. Students are often unconcerned about hazard mitigation on college campuses and are limited in the range of personal actions they can take. Communicating risk is complicated by social, cultural, linguistic, and technological barriers. Unlike crisis communication which is often acute, time sensitive information that dictates a sense of

Matt Stanley

2011-01-01

13

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

14

Predicting Agent Strategy Mix in Heterogeneous Populations  

Microsoft Academic Search

Prior research has identified agent behaviors or strate- gies that can develop and sustain mutually beneficial co- operative relationships with like-minded agents and can re - sist exploitation from selfish agents. Evolutionary tourna - ments with different strategies can model scenarios where agents periodically adopt strategies that are outperformi ng others in the population. However, such experiments can be computationally

Sabyasachi Saha; Sandip Sen

15

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

16

On the spread of epidemics in a closed heterogeneous population  

PubMed Central

Heterogeneity is an important property of any population experiencing a disease. Here we apply general methods of the theory of heterogeneous populations to the simplest mathematical models in epidemiology. In particular, an SIR (susceptible-infective-removed) model is formulated and analyzed when susceptibility to or infectivity of a particular disease is distributed. It is shown that a heterogeneous model can be reduced to a homogeneous model with a nonlinear transmission function, which is given in explicit form. The widely used power transmission function is deduced from the model with distributed susceptibility and infectivity with the initial gamma-distribution of the disease parameters. Therefore, a mechanistic derivation of the phenomenological model, which is believed to mimic reality with high accuracy, is provided. The equation for the final size of an epidemic for an arbitrary initial distribution of susceptibility is found. The implications of population heterogeneity are discussed, in particular, it is pointed out that usual moment-closure methods can lead to erroneous conclusions if applied for the study of the long-term behavior of the models.

Novozhilov, Artem S

2008-01-01

17

Growth rate determination of heterogeneous microbial population in swine manure  

Microsoft Academic Search

The effect of manure concentration on the growth of the heterogeneous microbial population under batch condition was studied.\\u000a Four manure concentrations were used in the study. The dehydrogenase activity was used as a measure of the active biomass\\u000a in the manure. The chemical oxygen demand test was used to measure the change in organic material caused by biological activities.\\u000a The

A. E. Ghaly; R. Kok; J. M. Ingrahm

1989-01-01

18

Molecular heterogeneity of familial hypercholesterolemia in the St. Petersburg population  

SciTech Connect

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

Mandel`shtam, M.Yu.; Lipovetskii, B.M.; Schvartsman, A.L.; Gaitskhoki, V.S. [Institute of Experimental Medicine, St. Petersburg (Russian Federation)

1995-04-01

19

Population regulation by habitat heterogeneity or individual adjustment?  

PubMed

1. The habitat heterogeneity (HHH) and individual adjustment (IAH) hypotheses are commonly proposed to explain a decrease in reproduction rate with increasing population density. Higher numbers of low-quality territories with low reproductive success as density increases lead to a decrease in reproduction under the HHH, while more competition at high density decreases reproduction across all territories under the IAH. 2. We analyse the influence of density and habitat heterogeneity on reproductive success in eight populations of long-lived territorial birds of prey belonging to four species. Sufficient reliability in distinguishing between population-wide, site-specific and individual quality effects on reproduction was granted through the minimal duration of 20 years of all data sets and the ability to control for individual quality in five of them. 3. Density increased in five populations but reproduction did not decrease in these. Territory occupancy as a surrogate of territory quality correlated positively with reproductive success but only significantly so in large data sets with more than 100 territories. 4. Reproductive success was always best explained by measures of territory quality in multivariate models. Direct or delayed (t-1) population density entered very few of the best models. Mixed models controlling for individual quality showed an increasing reproductive performance in older individuals and in those laying earlier, but measures of territory quality were also always retained in the best models. 5. We find strong support for the habitat heterogeneity hypothesis but weak support for the individual adjustment hypothesis. Both individual and site characteristics are crucial for reproductive performance in long-lived birds. Proportional occupancy of territories enables recognition of high-quality territories as preferential conservation targets. PMID:21950339

Krüger, Oliver; Chakarov, Nayden; Nielsen, Jan T; Looft, Volkher; Grünkorn, Thomas; Struwe-Juhl, Bernd; Møller, Anders P

2011-09-23

20

Confounding and heterogeneity in genetic association studies with admixed populations.  

PubMed

Association studies among admixed populations pose many challenges including confounding of genetic effects due to population substructure and heterogeneity due to different patterns of linkage disequilibrium (LD). We use simulations to investigate controlling for confounding by indicators of global ancestry and the impact of including a covariate for local ancestry. In addition, we investigate the use of an interaction term between a single-nucleotide polymorphism (SNP) and local ancestry to capture heterogeneity in SNP effects. Although adjustment for global ancestry can control for confounding, additional adjustment for local ancestry may increase power when the induced admixture LD is in the opposite direction as the LD in the ancestral population. However, if the induced LD is in the same direction, there is the potential for reduced power because of overadjustment. Furthermore, the inclusion of a SNP by local ancestry interaction term can increase power when there is substantial differential LD between ancestry populations. We examine these approaches in genome-wide data using the University of Southern California's Children's Health Study investigating asthma risk. The analysis highlights rs10519951 (P = 8.5 × 10(-7)), a SNP lacking any evidence of association from a conventional analysis (P = 0.5). PMID:23334005

Liu, Jinghua; Lewinger, Juan Pablo; Gilliland, Frank D; Gauderman, W James; Conti, David V

2013-01-18

21

Disaster Vulnerability of University Student Populations  

Microsoft Academic Search

Student populations at Gulf Coast universities and colleges are subjected to multiple forces working together making them an especially vulnerable sub-group to hazards. Research has suggested that college students represent a segment of the population that hazards research has frequently overlooked and maybe not fully appreciated in university emergency planning. Most prior research has focused on university disaster experiences, highlighting

Jamie Lynn Auletta

2012-01-01

22

Teaching the Growing Population of Nontraditional Students.  

ERIC Educational Resources Information Center

|This document contains three articles on teaching the growing population of nontraditional students. "The Changing Demographics of the Classroom" defines "nontraditional students"; reviews the characteristics, risk factors, and special needs of nontraditional students; and identifies the following services as particularly important to…

Wagner, June G.

2002-01-01

23

Cell population heterogeneity during growth of Bacillus subtilis  

PubMed Central

We have discovered that cells of Bacillus subtilis at the mid-exponential phase of growth are a mixed population of two strikingly different cell types. One type is single swimming cells (or cell doublets) in which the transcription factor for motility, ?D, is active (?D ON). The other type is long chains of sessile cells in which ?D is inactive (?D OFF). The population is strongly biased toward ?D-ON cells by the action of a novel regulatory protein called SwrA. SwrA stimulates the transcription of a large operon (the flagellum/chemotaxis operon), which includes the genes for ?D and an activator of ?D-directed gene expression, SwrB. Cell population heterogeneity could enable B. subtilis to exploit its present location through the production of sessile cells as well as to explore new environmental niches through the generation of nomadic cells.

Kearns, Daniel B.; Losick, Richard

2005-01-01

24

Epidemic thresholds in a heterogenous population with competing strains  

NASA Astrophysics Data System (ADS)

Among many epidemic models, one epidemic disease may transmit with the existence of other pathogens or other strains from the same pathogen. In this paper, we consider the case where all of the strains obey the susceptible-infected-susceptible mechanism and compete with each other at the expense of common susceptible individuals. By using the heterogenous mean-field approach, we discuss the epidemic threshold for one of two strains. We confirm the existence of epidemic threshold in both finite and infinite populations subject to underlying epidemic transmission. Simulations in the Barabasi—Albert (BA) scale-free networks are in good agreement with the analytical results.

Wu, Qing-Chu; Fu, Xin-Chu; Yang, Meng

2011-04-01

25

Modeling Populations Using Heterogeneous Data, with Application to GRBs  

NASA Astrophysics Data System (ADS)

Astronomers often follow up survey observations with supplemental observations that provide additional information about a subset of surveyed sources. A motivating example is gamma-ray bursts (GRBs): survey missions such as CGRO and Swift provide basic information (e.g., direction, peak flux) for all bursts, but for a subset of bursts with counterparts at other wavelengths, other data are available, such as host galaxy redshifts or isotropic energy estimates. This heterogeneity significantly complicates global (population-level) analyses. Building on our earlier Bayesian framework for analyzing GRB and other survey data, we have developed a "data fusion" methodology that can optimally combine survey data from various sources. Using analysis of the GRB spatial and luminosity distribution as a concrete example, we describe the overall approach, present preliminary results for GRBs, and highlight benefits of Bayesian data fusion over more conventional approaches. This work is partially funded by the NASA Swift GI program.

Loredo, Thomas; Wasserman, I.

2008-03-01

26

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

PubMed Central

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

Merler, Stefano; Ajelli, Marco

2010-01-01

27

Networks and Models with Heterogeneous Population Structure in Epidemiology  

NASA Astrophysics Data System (ADS)

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

Kao, R. R.

28

Proportional reasoning competence among different student populations  

NASA Astrophysics Data System (ADS)

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

Wong, King

2012-10-01

29

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

NASA Astrophysics Data System (ADS)

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

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

2010-11-01

30

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

USGS Publications Warehouse

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

Link, W.A.

2003-01-01

31

Social learning in a heterogeneous population: technology diffusion in the Indian Green Revolution  

Microsoft Academic Search

Information flows are weaker in a heterogeneous population when the performance of a new technology is sensitive to unobserved individual characteristics, preventing individuals from learning from neighbors' experiences. This characterization of social learning is tested with wheat and rice data from the Indian Green Revolution. The rice-growing regions display greater heterogeneity in growing conditions and the new rice varieties were

Kaivan Munshi

2004-01-01

32

Heterogeneity and Temporal Dynamics of Evolution of G1 Human Rotaviruses in a Settled Population  

Microsoft Academic Search

A rotavirus sample collection from 19 consecutive years was used to investigate the heterogeneity and the dynamics of evolution of G1 rotavirus strains in a geographically defined population. Phylogenetic analysis of the VP7 gene sequences of G1P(8) human rotavirus strains showed the circulation of a heterogeneous population comprising three lineages and seven sublineages. Increases in the circulation of G1 rotaviruses

Serenella Arista; Giovanni M. Giammanco; Simona De Grazia; Stefania Ramirez; Concetta Lo Biundo; Claudia Colomba; Antonio Cascio; Vito Martella

2006-01-01

33

Endemic disease in environments with spatially heterogeneous host populations  

Microsoft Academic Search

The main interest in epidemic models stems from their use in uncovering certain qualitative features of epidemic processes. A deterministic model of a general epidemic in a population with an arbitrary number of separate population centers is presented. The mixing within each center is assumed to be homogeneous, and the usual threshold theorem holds for each population. The mixing between

W. M. Post; D. L. DeAngelis; C. C. Travis

1983-01-01

34

The role of physiological heterogeneity in microbial population behavior  

Microsoft Academic Search

As the ability to analyze individual cells in microbial populations expands, it is becoming apparent that isogenic microbial populations contain substantial cell-to-cell differences in physiological parameters such as growth rate, resistance to stress and regulatory circuit output. Subpopulations exist that are manyfold different in these parameters from the population average, and these differences arise by stochastic processes. Such differences can

Michael C Konopka; Mary E Lidstrom

2010-01-01

35

Heterogeneous Adaptive Trajectories of Small Populations on Complex Fitness Landscapes  

Microsoft Academic Search

Background Small populations are thought to be adaptively handicapped, not only because they suffer more from deleterious mutations but also because they have limited access to new beneficial mutations, particularly those conferring large benefits. Methodology\\/Principal Findings Here, we test this widely held conjecture using both simulations and experiments with small and large bacterial populations evolving in either a simple or

Daniel E. Rozen; Michelle G. J. L. Habets; Andreas Handel; Visser de J. A. G. M

2008-01-01

36

Observed-Score Equating with a Heterogeneous Target Population  

ERIC Educational Resources Information Center

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

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

2012-01-01

37

Endemic disease in environments with spatially heterogeneous host populations  

SciTech Connect

The main interest in epidemic models stems from their use in uncovering certain qualitative features of epidemic processes. A deterministic model of a general epidemic in a population with an arbitrary number of separate population centers is presented. The mixing within each center is assumed to be homogeneous, and the usual threshold theorem holds for each population. The mixing between centers is nonhomogeneous. This model is used to identify the necessary and sufficient conditions under which a disease will become endemic in the general population when each population center is below the threshold required for establishment of the disease and does not mix with other centers. These conditions depend critically on the concavity of the infection rate function with respect to the length of exposure time. The application of these results to host-vector models is discussed. 16 references, 2 figures.

Post, W.M.; DeAngelis, D.L.; Travis, C.C.

1983-01-01

38

A mathematical model for the dynamics of malaria in mosquitoes feeding on a heterogeneous host population  

Microsoft Academic Search

We describe and develop a difference equation model for the dynamics of malaria in a mosquito population feeding on, infecting and getting infected from a heterogeneous population of hosts. Using the force of infection from different classes of humans to mosquitoes as parameters, we evaluate a number of entomological parameters, indicating malaria transmission levels, which can be compared to field

Nakul Chitnis; Thomas Smith; Richard Steketee

2008-01-01

39

Heterogeneous Adaptive Trajectories of Small Populations on Complex Fitness Landscapes  

Microsoft Academic Search

BackgroundSmall populations are thought to be adaptively handicapped, not only because they suffer more from deleterious mutations but also because they have limited access to new beneficial mutations, particularly those conferring large benefits.Methodology\\/Principal FindingsHere, we test this widely held conjecture using both simulations and experiments with small and large bacterial populations evolving in either a simple or a complex nutrient

Daniel E. Rozen; Michelle G. J. L. Habets; Andreas Handel; Rees Kassen

2008-01-01

40

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.

Stige, Signe Hjelen

2011-01-01

41

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

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

1995-01-01

42

Multi-resolution border segmentation for measuring spatial heterogeneity of mixed population biofilm bacteria  

Microsoft Academic Search

Multi-resolution image clustering and segmentation interactive system has been developed to analyze the interaction between clusters of heterogeneous microbial populations residing in biofilms. Biofilms are biological microorganisms attached to surfaces, which develop a complex heterogeneous three-dimensional structure. The hierarchical structural analysis concept underlying multi-resolution image segmentation is that the clusters will be more complex and noisy for higher-resolution while less

Saeid Belkasim; Gordana Derado; Rizi Aznita; Eric Gilbert; Heather O’Connell

2008-01-01

43

Summer Experiential Learning Program for Diverse Student Populations: Year One.  

National Technical Information Service (NTIS)

This report describes the transportation workshops conducted during June of 1993, under the Summer Experiential Learning Program for Diverse Student Populations. The goal of this project was to provide an opportunity to interest minority students in the r...

D. G. Fontane

1994-01-01

44

EVOLUTION OF VIRULENCE IN A HETEROGENEOUS HOST POPULATION  

Microsoft Academic Search

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

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

2000-01-01

45

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.

Stamatakis, Michail; Zygourakis, Kyriacos

2010-01-01

46

Quantitative analysis of population heterogeneity of the adaptive salt stress response and growth capacity of Bacillus cereus ATCC 14579  

Microsoft Academic Search

Bacterial populations can display heterogeneity with respect to both the adaptive stress response and growth capacity of individual cells. The growth dynamics of Bacillus cereus ATCC 14579 during mild and severe salt stress exposure were investigated for the population as a whole in liquid culture. To quantitatively assess the population heterogeneity of the stress response and growth capacity at a

Besten den H. M. W; Colin J. Ingham; Hylckama Vlieg van J. E. T; M.M. Beerthuyzen; T. Abee

2007-01-01

47

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

ERIC Educational Resources Information Center

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

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

2009-01-01

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

Evolution of cooperation in a heterogeneous population with influential individuals  

NASA Astrophysics Data System (ADS)

Influential individuals are introduced and integrated with the public goods game (PGG) to investigate their influence on the emergence and evolution of cooperation. In the model, some influential individuals whose behaviors can be controlled by us are introduced into a homogeneous population on a square lattice. The influential individuals can play three kinds of roles: I. exemplar, II. supervisor with the power to punish defectors, and III. supervisor with the power to reward cooperative co-players. It is found that the existence of influential individuals who play Role I turns out to be detrimental to cooperation and that the larger the number of influential individuals is, the more difficult it is for cooperation to be maintained. For those playing supervisory roles, both punishment and reward are found to be effective ways for the influential individuals to promote and stabilize cooperative behavior. By comparing the critical costs and the mean payoffs for a low multiplication factor under the role of punishment and the role of reward, it is found that reward is a more effective intervention measure than punishment for influential individuals seeking to improve cooperation and that reward leads to a higher mean payoff.

Zhuang, Qian; Wang, Dong; Fan, Ying; Di, Zengru

2012-02-01

50

The influence of habitat heterogeneity on host-pathogen population dynamics  

Microsoft Academic Search

The influence of spatial heterogeneity on the population dynamics of a naturally occurring invertebrate host-pathogen system\\u000a was experimentally investigated. At ten week intervals over a two year period, I quantified the spatial distribution of natural\\u000a populations of the terrestrial isopod crustacean Porcellio scaber infected with the isopod iridescent virus (IIV). During the seasonally dry periods of summer and early fall

Edwin D. Grosholz

1993-01-01

51

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

52

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.

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

2008-01-01

53

Bone marrow as a home of heterogenous populations of nonhematopoietic stem cells  

Microsoft Academic Search

Evidence is presented that bone marrow (BM) in addition to CD45positive hematopoietic stem cells contains a rare population of heterogenous CD45negative nonhematopoietic tissue committed stem cells (TCSC). These nonhematopoietic TCSC (i) are enriched in population of CXCR4+ CD34+ AC133+ lin? CD45? and CXCR4+ Sca-1+ lin? CD45? in humans and mice, respectively, (ii) display several markers of pluripotent stem cells (PSC)

M Kucia; R Reca; V R Jala; B Dawn; J Ratajczak; M Z Ratajczak

2005-01-01

54

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

55

Aggregation under structural stability: the change in consumption of a heterogeneous population  

Microsoft Academic Search

It is shown how one can effectively use cross-section data in modelling the change over time in aggregate consumption expenditure of a heterogeneous population. The starting point of our aggregation analysis is a dynamic behavioral relation on the household level. Based on certain hypotheses on the evolution of the distribution of income and household characteristics we derive explanatory variables for

Werner Hildenbrand; Alois Kneip

2002-01-01

56

Transient animals in a resident population of snow geese: Local emigration or heterogeneity?  

Microsoft Academic Search

SUMMARY The estimation of survival rates from analysis of recapture of individually marked animals assumes that all individuals are equally likely to be re-encountered. This assumption is frequently violated in natural populations due to movements to and from the sampling area. We evaluated potential sources of heterogeneity using data from recaptures of 36000 individually marked female lesser snow geese, Anser

ROGER PRADEL; Evan Cooch; Fred Cooke

1995-01-01

57

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

58

Interactive effects of temporal correlations, spatial heterogeneity and dispersal on population persistence  

PubMed Central

It is an ecological truism that population persistence depends on a population's growth rate when rare. To understand the interplay between temporal correlations, spatial heterogeneity and dispersal on persistence, an analytic approximation for this growth rate is derived for partially mixing populations. Partial mixing has two effects on population growth. In the absence of temporal correlations in relative fitness, greater movement to patches with, on average, higher relative fitness increases population growth rates. In the absence of spatial heterogeneity in the average relative fitnesses, lower dispersal rates enhance population growth when temporal autocorrelations of relative fitness within a patch exceed temporal cross-correlations in relative fitness between patches. This approximation implies that metapopulations whose expected fitness in every patch is less than 1 can persist if there are positive temporal autocorrelations in relative fitness, sufficiently weak spatial correlations and the population disperses at intermediate rates. It also implies that movement into lower quality habitats increases the population growth rate whenever the net temporal variation in per capita growth rates is sufficiently larger than the difference in the means of these per capita growth rates. Moreover, temporal autocorrelations, whether they be negative or positive, can enhance population growth for optimal dispersal strategies.

Schreiber, Sebastian J.

2010-01-01

59

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

PubMed Central

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

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

2011-01-01

60

Direct-Imaging-Based Quantification of Bacillus cereus ATCC 14579 Population Heterogeneity at a Low Incubation Temperature?  

PubMed Central

Bacillus cereus ATCC 14579 was cultured in microcolonies on Anopore strips near its minimum growth temperature to directly image and quantify its population heterogeneity at an abusive refrigeration temperature. Eleven percent of the microcolonies failed to grow during low-temperature incubation, and this cold-induced population heterogeneity could be partly attributed to the loss of membrane integrity of individual cells.

den Besten, Heidy M. W.; Garcia, Diego; Moezelaar, Roy; Zwietering, Marcel H.; Abee, Tjakko

2010-01-01

61

Direct-imaging-based quantification of Bacillus cereus ATCC 14579 population heterogeneity at a low incubation temperature.  

PubMed

Bacillus cereus ATCC 14579 was cultured in microcolonies on Anopore strips near its minimum growth temperature to directly image and quantify its population heterogeneity at an abusive refrigeration temperature. Eleven percent of the microcolonies failed to grow during low-temperature incubation, and this cold-induced population heterogeneity could be partly attributed to the loss of membrane integrity of individual cells. PMID:20023091

den Besten, Heidy M W; Garcia, Diego; Moezelaar, Roy; Zwietering, Marcel H; Abee, Tjakko

2009-12-18

62

Circular stochastic fluctuations in SIS epidemics with heterogeneous contacts among sub-populations.  

PubMed

The conceptual difference between equilibrium and non-equilibrium steady state (NESS) is well established in physics and chemistry. This distinction, however, is not widely appreciated in dynamical descriptions of biological populations in terms of differential equations in which fixed point, steady state, and equilibrium are all synonymous. We study NESS in a stochastic SIS (susceptible-infectious-susceptible) system with heterogeneous individuals in their contact behavior represented in terms of subgroups. In the infinite population limit, the stochastic dynamics yields a system of deterministic evolution equations for population densities; and for very large but finite systems a diffusion process is obtained. We report the emergence of a circular dynamics in the diffusion process, with an intrinsic frequency, near the endemic steady state. The endemic steady state is represented by a stable node in the deterministic dynamics. As a NESS phenomenon, the circular motion is caused by the intrinsic heterogeneity within the subgroups, leading to a broken symmetry and time irreversibility. PMID:22273833

Wang, Jia-Zeng; Qian, Min; Qian, Hong

2012-01-16

63

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.

2012-01-01

64

Mapping the Misunderstood Population of Adult Students  

ERIC Educational Resources Information Center

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

Ashburn, Elyse

2007-01-01

65

Financial Aid and Student Dropout in Higher Education: A Heterogeneous Research Approach  

Microsoft Academic Search

This article draws on theoretical and empirical literature to develop a longitudinal research approach for investigating the\\u000a possible variations in aid effects on dropout risks. It considers that the student body is heterogeneous and thus may respond\\u000a to financial aid differently according to their socioeconomic and racial backgrounds. It further identifies key elements in\\u000a assessing the longitudinal impact of various

Rong Chen

66

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

SciTech Connect

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

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

2006-06-15

67

Orientation Courses: Meeting the Needs of Different Student Populations.  

ERIC Educational Resources Information Center

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

Higbee, Jeanne L.

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

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…

Jensen, Dallas R.

2003-01-01

70

KIR genotypic diversity can track ancestries in heterogeneous populations: a potential confounder for disease association studies.  

PubMed

Killer cell immunoglobulin-like receptors (KIR) are encoded by highly polymorphic genes that regulate the activation of natural killer (NK) cells and other lymphocyte subsets and likely play key roles in innate and adaptive immunity. Association studies increasingly implicate KIR in disease predisposition and outcome but could be confounded by unknown KIR genetic structure in heterogeneous populations. To examine this, we characterized the diversity of 16 KIR genes in 712 Northern Californians (NC) stratified by self-assigned ethnicities and compared the profiles of KIR polymorphism with other US and global populations using a reference database. Sixty-eight distinct KIR genotypes were characterized: 58 in 457 Caucasians (NCC), 17 in 47 African Americans (NCAA), 21 in 80 Asians (NCA), 20 in 74 Hispanics (NCH), and 18 in 54 "other" ethnicities (NCO). KIR genotype patterns and frequencies in the 4 defined ethnicities were compared with each other and with 34 global populations by phylogenetic analysis. Although there were no population-specific genotypes, the KIR genotype frequency patterns faithfully traced the ancestry of NCC, NCAA, and NCA but not of NCH whose ancestries are known to be more heterogeneous. KIR genotype frequencies can therefore track ethnic ancestries in modern urban populations. Our data emphasize the importance of selecting ethnically matched controls in KIR-based studies to avert spurious associations. PMID:21898189

Singh, Komal Manpreet; Phung, Yume T; Kohla, Mohamed S; Lan, Billy Y-A; Chan, Sharon; Suen, Diana L; Murad, Sahar; Rheault, Shana; Davidson, Peter; Evans, Jennifer; Singh, Manpreet; Dohil, Sofie; Osorio, Robert W; Wakil, Adil E; Page, Kimberly; Feng, Sandy; Cooper, Stewart L

2011-09-07

71

Synchrony of spatial populations: heterogeneous population dynamics and reddened environmental noise  

Microsoft Academic Search

Many species exhibit widespread spatial synchrony in population fluctuations. This pattern is of great ecological interest\\u000a and can be a source of concern when a species is rare or endangered. Moran’s theorem suggests that if two (or more) populations\\u000a sharing a common linear density-dependence in the renewal process are disturbed with correlated noise, they will become synchronized\\u000a with correlation matching

Zhiguang Liu; Meng Gao; Zizhen Li; Gaofeng Zhu

2009-01-01

72

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.

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

2013-01-01

73

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

2013-07-24

74

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

USGS Publications Warehouse

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

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

2009-01-01

75

Phenotypic heterogeneity within clonogenic ductal cell populations isolated from normal adult rat liver.  

PubMed

Oval cells represent a heterogeneous population composed of ductal cells, transitional cells with characteristics of both hepatocytes and bile ductal cells, and bipotential stem cells capable of differentiation along a biliary or hepatocytic lineage. In an attempt to define markers that would distinguish between individual cell types within the oval cell population, a number of investigators have utilized hybridoma technology to produce cell type-specific monoclonal antibodies. Several of these have proved to be of value in delineating lineage relationships during fetal development and carcinogenesis in the adult liver. Most recently, monoclonal antibodies specific for OC2 and OC3, two oval cell antigens identified in our laboratory, have been used in combination with magnetic beads or a fluorescence-activated cell sorter to isolate antigenically defined subpopulations from adult and fetal rat liver. Using OC2-positive fetal liver cells as an immunogen, we have produced a monoclonal antibody identifying a bile ductal antigen, designated BD1, that is differentially expressed by oval cells and normal ductal cells. This antigen shows a heterogeneous pattern of reactivity that defines three distinct cell populations in regenerating rat liver: a BD1-negative, [3H]thymidine-labeled cell population thought to contain hepatic stem cells; a BD1-positive, thymidine-negative population of terminally differentiated ductal cells; and a BD1-positive, [3H]thymidine-positive population of mature ductal cells. Analysis of BD1 expression in vitro on continuous lines of bile duct epithelial cells (BDEC) demonstrated that BD1 was rapidly increased in late G1 and lost during G2/M. High passage cultures of BDEC and primary cultures of oval cells expressed low or undetectable levels of BD1 and high passage BDEC failed to express BD1 when arrested in late G1. Taken together, these results suggested that oval cells and high passage BDEC might share a subtle defect in cell cycle regulation marked by an inability to upregulate the expression of BD1. PMID:8234371

Yang, L; Faris, R A; Hixson, D C

1993-12-01

76

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

PubMed

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

2013-09-11

77

The Origin of Phenotypic Heterogeneity in a Clonal Cell Population In Vitro  

PubMed Central

Background The spontaneous emergence of phenotypic heterogeneity in clonal populations of mammalian cells in vitro is a rule rather than an exception. We consider two simple, mutually non-exclusive models that explain the generation of diverse cell types in a homogeneous population. In the first model, the phenotypic switch is the consequence of extrinsic factors. Initially identical cells may become different because they encounter different local environments that induce adaptive responses. According to the second model, the phenotypic switch is intrinsic to the cells that may occur even in homogeneous environments. Principal Findings We have investigated the “extrinsic” and the “intrinsic” mechanisms using computer simulations and experimentation. First, we simulated in silico the emergence of two cell types in a clonal cell population using a multiagent model. Both mechanisms produced stable phenotypic heterogeneity, but the distribution of the cell types was different. The “intrinsic” model predicted an even distribution of the rare phenotype cells, while in the “extrinsic” model these cells formed small clusters. The key predictions of the two models were confronted with the results obtained experimentally using a myogenic cell line. Conclusions The observations emphasize the importance of the “ecological” context and suggest that, consistently with the “extrinsic” model, local stochastic interactions between phenotypically identical cells play a key role in the initiation of phenotypic switch. Nevertheless, the “intrinsic” model also shows some other aspects of reality: The phenotypic switch is not triggered exclusively by the local environmental variations, but also depends to some extent on the phenotypic intrinsic robustness of the cells.

Picot, Julien; Rameau, Philippe; Neildez, Thi My Anh; Landini, Gabriel; Laplace-Builhe, Corinne; Paldi, Andras

2007-01-01

78

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.

Liere, Heidi; Jackson, Doug; Vandermeer, John

2012-01-01

79

Epidemic size and probability in populations with heterogeneous infectivity and susceptibility  

NASA Astrophysics Data System (ADS)

We analytically address disease outbreaks in large, random networks with heterogeneous infectivity and susceptibility. The transmissibility Tuv (the probability that infection of u causes infection of v ) depends on the infectivity of u and the susceptibility of v . Initially, a single node is infected, following which a large-scale epidemic may or may not occur. We use a generating function approach to study how heterogeneity affects the probability that an epidemic occurs and, if one occurs, its attack rate (the fraction infected). For fixed average transmissibility, we find upper and lower bounds on these. An epidemic is most likely if infectivity is homogeneous and least likely if the variance of infectivity is maximized. Similarly, the attack rate is largest if susceptibility is homogeneous and smallest if the variance is maximized. We further show that heterogeneity in the infectious period is important, contrary to assumptions of previous studies. We confirm our theoretical predictions by simulation. Our results have implications for control strategy design and identification of populations at higher risk from an epidemic.

Miller, Joel C.

2007-07-01

80

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

81

Multi-resolution border segmentation for measuring spatial heterogeneity of mixed population biofilm bacteria.  

PubMed

Multi-resolution image clustering and segmentation interactive system has been developed to analyze the interaction between clusters of heterogeneous microbial populations residing in biofilms. Biofilms are biological microorganisms attached to surfaces, which develop a complex heterogeneous three-dimensional structure. The hierarchical structural analysis concept underlying multi-resolution image segmentation is that the clusters will be more complex and noisy for higher-resolution while less complex and smoother for lower-resolution image. This hierarchical structure analysis can be used to simplify the image storage and retrieval in well-mixed populations. We are proposing an algorithm that combines Fuzzy C-Means, SOM and LVQ neural networks to segment and identify clusters. The outcome of the image segmentation is quantified by the number of cluster objects of each kind of microorganism within sections of the biofilm, and the centroid distances between the identified cluster objects. Experimental evaluations of the algorithm showed its effectiveness in enumerating cluster objects of bacteria in dual-species biofilms at the substratum and measuring the associated intercellular distances. PMID:17936583

Belkasim, Saeid; Derado, Gordana; Aznita, Rizi; Gilbert, Eric; O'Connell, Heather

2007-10-23

82

Reflections on Introducing Students to Multicultural Populations and Diversity Content  

Microsoft Academic Search

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

Diane de Anda

2007-01-01

83

Transmission rates and adaptive evolution of pathogens in sympatric heterogeneous plant populations.  

PubMed Central

Diversification in agricultural cropping patterns is widely practised to delay the build-up of virulent races that can overcome host resistance in pathogen populations. This can lead to balanced polymorphism, but the long-term consequences of this strategy for the evolution of crop pathogen populations are still unclear. The widespread occurrence of sibling species and reproductively isolated sub-species among fungal and oomycete plant pathogens suggests that evolutionary divergence is common. This paper develops a mathematical model of host-pathogen interactions using a simple framework of two hosts to analyse the influences of sympatric host heterogeneity on the long-term evolutionary behaviour of plant pathogens. Using adaptive dynamics, which assumes that sequential mutations induce small changes in pathogen fitness, we show that evolutionary outcomes strongly depend on the shape of the trade-off curve between pathogen transmission on sympatric hosts. In particular, we determine the conditions under which the evolutionary branching of a monomorphic into a dimorphic population occurs, as well as the conditions that lead to the evolution of specialist (single host range) or generalist (multiple host range) pathogen populations.

Gudelj, I; van den Bosch, F; Gilligan, C A

2004-01-01

84

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

2011-02-28

85

How to Minimize the Attack Rate during Multiple Influenza Outbreaks in a Heterogeneous Population  

PubMed Central

Background If repeated interventions against multiple outbreaks are not feasible, there is an optimal level of control during the first outbreak. Any control measures above that optimal level will lead to an outcome that may be as sub-optimal as that achieved by an intervention that is too weak. We studied this scenario in more detail. Method An age-stratified ordinary-differential-equation model was constructed to study infectious disease outbreaks and control in a population made up of two groups, adults and children. The model was parameterized using influenza as an example. This model was used to simulate two consecutive outbreaks of the same infectious disease, with an intervention applied only during the first outbreak, and to study how cumulative attack rates were influenced by population composition, strength of inter-group transmission, and different ways of triggering and implementing the interventions. We assumed that recovered individuals are fully immune and the intervention does not confer immunity. Results/Conclusion The optimal intervention depended on coupling between the two population sub-groups, the length, strength and timing of the intervention, and the population composition. Population heterogeneity affected intervention strategies only for very low cross-transmission between groups. At more realistic values, coupling between the groups led to synchronization of outbreaks and therefore intervention strategies that were optimal in reducing the attack rates for each subgroup and the population overall coincided. For a sustained intervention of low efficacy, early intervention was found to be best, while at high efficacies, a delayed start was better. For short interventions, a delayed start was always advantageous, independent of the intervention efficacy. For most scenarios, starting the intervention after a certain cumulative proportion of children were infected seemed more robust in achieving close to optimal outcomes compared to a strategy that used a specified duration after an outbreak’s beginning as the trigger.

Fung, Isaac Chun-Hai; Antia, Rustom; Handel, Andreas

2012-01-01

86

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

PubMed

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

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

2013-03-13

87

Consequences of heterogeneity in survival probability in a population of Florida scrub-jays.  

PubMed

1. Using data on breeding birds from a 35-year study of Florida scrub-jays Aphelocoma coerulescens (Bosc 1795), we show that survival probabilities are structured by age, birth cohort, and maternal family, but not by sex. Using both accelerated failure time (AFT) and Cox proportional hazard models, the data are best described by models incorporating variation among birth cohorts and greater mortality hazard with increasing age. AFT models using Weibull distributions with the shape parameter > 1 were always the best-fitting models. 2. Shared frailty models allowing for family structure greatly reduce model deviance. The best-fitting models included a term for frailty shared by maternal families. 3. To ask how long a data set must be to reach qualitatively the same conclusions, we repeated the analyses for all possible truncated data sets of 2 years in length or greater. Length of the data set affects the parameter estimates, but not the qualitative conclusions. In all but three of 337 truncated data sets the best-fitting models pointed to same conclusions as the full data set. Shared frailty models appear to be quite robust. 4. The data are not adequate for testing hypotheses as to whether variation in frailty is heritable. 5. Substantial structured heterogeneity for survival exists in this population. Such structured heterogeneity has been shown to have substantial effects in reducing demographic stochasticity. PMID:17009755

Fox, Gordon A; Kendall, Bruce E; Fitzpatrick, John W; Woolfenden, Glen E

2006-07-01

88

Cell population-based model of dermal wound invasion with heterogeneous intracellular signaling properties  

PubMed Central

A deterministic model of dermal wound invasion, which accounts for the platelet-derived growth factor (PDGF) gradient sensing mechanism in fibroblasts mediated by cell surface receptors and the phosphoinositide 3-kinase (PI3K) signal transduction pathway, was previously described (Biophys J 2006; 90:2297–308). Here, we extend that work and implement a hybrid modeling strategy that treats fibroblasts as discrete entities endowed with heterogeneous properties, namely receptor, PI3K and 3? phosphoinositide phosphatase expression levels. Analysis of the model suggests that the wound environment fosters the advancement of cells within the population that are better fit to migrate and/or proliferate in response to PDGF stimulation. Thus, cell-to-cell variability results in a significantly higher rate of wound invasion as compared with the deterministic model, in a manner that depends on the way in which individual cell properties are sampled or inherited upon cell division.

Monine, Michael I

2008-01-01

89

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.

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

2012-01-01

90

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

2013-01-01

91

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

ERIC Educational Resources Information Center

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

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

2009-01-01

92

Light Microscopic Analysis of Mitochondrial Heterogeneity in Cell Populations and Within Single Cells  

Microsoft Academic Search

\\u000a \\u000a Abstract  Heterogeneity in the shapes of individual multicellular organisms is a daily experience. Likewise, even a quick glance through\\u000a the ocular of a light microscope reveals the morphological heterogeneities in genetically identical cultured cells, whereas\\u000a heterogeneities on the level of the organelles are much less obvious. This short review focuses on intracellular heterogeneities\\u000a at the example of the mitochondria and their

Stefan Jakobs; Stefan Stoldt; Daniel Neumann

93

Effect of reproductive modes and environmental heterogeneity in the population dynamics of a geographically widespread clonal desert cactus  

Microsoft Academic Search

The dynamics of plant populations in arid environments are largely affected by the unpredictable environmental conditions\\u000a and are fine-tuned by biotic factors, such as modes of recruitment. A single species must cope with both spatial and temporal\\u000a heterogeneity that trigger pulses of sexual and clonal establishment throughout its distributional range. We studied two populations\\u000a of the clonal, purple prickly pear

María C. Mandujano; Jordan Golubov; Laura F. Huenneke

2007-01-01

94

Toxicity of Increased Amounts of Chemicals and the Dose–Response Curves for Heterogeneous Microbial Populations in Soil  

Microsoft Academic Search

The paper deals with the interpretation and classification of dose–response curves in order to understand the way in which the heterogeneous soil microbial population behaves under chemical stress. The evaluation is based on a set of about 500 toxicity tests, in which geometrically increasing doses of toxicants were applied to soil samples. The responses of the microflora were measured by

Gerhard Welp; Gerhard W. Brümmer

1997-01-01

95

Analysis of heterogeneity and epistasis in physiological mixed populations by combined structural equation modelling and latent class analysis  

PubMed Central

Background Biological systems are interacting, molecular networks in which genetic variation contributes to phenotypic heterogeneity. This heterogeneity is traditionally modelled as a dichotomous trait (e.g. affected vs. non-affected). This is far too simplistic considering the complexity and genetic variations of such networks. Methods In this study on type 2 diabetes mellitus, heterogeneity was resolved in a latent class framework combined with structural equation modelling using phenotypic indicators of distinct physiological processes. We modelled the clinical condition "the metabolic syndrome", which is known to be a heterogeneous and polygenic condition with a clinical endpoint (type 2 diabetes mellitus). In the model presented here, genetic factors were not included and no genetic model is assumed except that genes operate in networks. The impact of stratification of the study population on genetic interaction was demonstrated by analysis of several genes previously associated with the metabolic syndrome and type 2 diabetes mellitus. Results The analysis revealed the existence of 19 distinct subpopulations with a different propensity to develop diabetes mellitus within a large healthy study population. The allocation of subjects into subpopulations was highly accurate with an entropy measure of nearly 0.9. Although very few gene variants were directly associated with metabolic syndrome in the total study sample, almost one third of all possible epistatic interactions were highly significant. In particular, the number of interactions increased after stratifying the study population, suggesting that interactions are masked in heterogenous populations. In addition, the genetic variance increased by an average of 35-fold when analysed in the subpopulations. Conclusion The major conclusions from this study are that the likelihood of detecting true association between genetic variants and complex traits increases tremendously when studied in physiological homogenous subpopulations and on inclusion of epistasis in the analysis, whereas epistasis (i.e. genetic networks) is ubiquitous and should be the basis in modelling any biological process.

Fenger, Mogens; Linneberg, Allan; Werge, Thomas; J?rgensen, Torben

2008-01-01

96

Heterogeneous Catalysis.  

ERIC Educational Resources Information Center

|Described is a heterogeneous catalysis course which has elements of materials processing embedded in the classical format of catalytic mechanisms and surface chemistry. A course outline and list of examples of recent review papers written by students are provided. (MVL)|

Miranda, R.

1989-01-01

97

Heterogeneous Catalysis.  

ERIC Educational Resources Information Center

Described is a heterogeneous catalysis course which has elements of materials processing embedded in the classical format of catalytic mechanisms and surface chemistry. A course outline and list of examples of recent review papers written by students are provided. (MVL)

Miranda, R.

1989-01-01

98

Genomic heterogeneity in a natural archaeal population suggests a model of tRNA gene disruption.  

PubMed

Understanding the mechanistic basis of the disruption of tRNA genes, as manifested in the intron-containing and split tRNAs found in Archaea, will provide considerable insight into the evolution of the tRNA molecule. However, the evolutionary processes underlying these disruptions have not yet been identified. Previously, a composite genome of the deep-branching archaeon Caldiarchaeum subterraneum was reconstructed from a community genomic library prepared from a C. subterraneum-dominated microbial mat. Here, exploration of tRNA genes from the library reveals that there are at least three types of heterogeneity at the tRNA(Thr)(GGU) gene locus in the Caldiarchaeum population. All three involve intronic gain and splitting of the tRNA gene. Of two fosmid clones found that encode tRNA(Thr)(GGU), one (tRNA(Thr-I)) contains a single intron, whereas another (tRNA(Thr-II)) contains two introns. Notably, in the clone possessing tRNA(Thr-II), a 5' fragment of the tRNA(Thr-I) (tRNA(Thr-F)) gene was observed 1.8-kb upstream of tRNA(Thr-II). The composite genome contains both tRNA(Thr-II) and tRNA(Thr-F), although the loci are >500 kb apart. Given that the 1.8-kb sequence flanked by tRNA(Thr-F) and tRNA(Thr-II) is predicted to encode a DNA recombinase and occurs in six regions of the composite genome, it may be a transposable element. Furthermore, its dinucleotide composition is most similar to that of the pNOB8-type plasmid, which is known to integrate into archaeal tRNA genes. Based on these results, we propose that the gain of the tRNA intron and the scattering of the tRNA fragment occurred within a short time frame via the integration and recombination of a mobile genetic element. PMID:22403667

Sugahara, Junichi; Fujishima, Kosuke; Nunoura, Takuro; Takaki, Yoshihiro; Takami, Hideto; Takai, Ken; Tomita, Masaru; Kanai, Akio

2012-03-05

99

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

100

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

NASA Astrophysics Data System (ADS)

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

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

2008-03-01

101

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

PubMed Central

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

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

2008-01-01

102

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

103

Heterogeneity of HLA-DRB1?04 and its associated haplotypes in the north indian population  

Microsoft Academic Search

HLA-DR4 has been implicated in several diseases including rheumatoid arthritis (RA) and type I diabetes, the strength of associations being ethnically variable. Unusually high level of heterogeneity in DR4-DQB1 haplotypes has been reported in the Indian population. The present study is an attempt to determine the genetic diversity of the HLA-DR4 allelic family and its associated DQA1-DQB1 haplotypic combinations in

Ritika Jaini; Gurvinder Kaur; Narinder K Mehra

2002-01-01

104

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

105

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.

Tashyreva, Daria; Elster, Josef; Billi, Daniela

2013-01-01

106

A novel staining protocol for multiparameter assessment of cell heterogeneity in Phormidium populations (cyanobacteria) employing fluorescent dyes.  

PubMed

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

2013-02-20

107

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.

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

2011-01-01

108

Modeling the Invasion and Spread of Contagious Diseases in Heterogeneous Populations  

Microsoft Academic Search

The evolution of disease requires a rm understanding of hetero- geneity among pathogen strains and hosts with regard to the processes of transmission, movement, recovery, and pathobiology. In this chapter, we build on the basic methodologies outlined in the previous chapter to address the question of how to model the invasion and spread of diseases in heterogeneous environments, without making

Wayne M. Getz; James O. Lloyd-Smith; Paul C. Cross; Shirli Bar-David; Philip L. Johnson; Travis C. Porco

109

Epidemic size and probability in populations with heterogeneous infectivity and susceptibility  

Microsoft Academic Search

We analytically address disease outbreaks in large, random networks with heterogeneous infectivity and susceptibility. The transmissibility Tuv the probability that infection of u causes infection of v depends on the infectivity of u and the susceptibility of v. Initially, a single node is infected, following which a large-scale epidemic may or may not occur. We use a generating function approach

Joel C. Miller

2007-01-01

110

Analysis of beta globin mutations in the Indian population: presence of rare and novel mutations and region-wise heterogeneity.  

PubMed

Beta thalassaemia is a major public health problem in India. A comprehensive database of the spectrum of mutations causing beta thalassaemia in the Indian population is necessary. This study in which a large number of patients with beta thalassaemia including those from certain regions that were not explored earlier shows a great heterogeneity of mutations. Several novel and rare alleles that have not been reported earlier in the Indian population have been identified, and mutations differ in frequency in different regions of the country. This information on the spectrum of mutations has implications for the control of beta thalassaemia in a population with complex ethnic background and also on the genotype-phenotype correlation of the disease. PMID:18294253

Edison, E S; Shaji, R V; Devi, S G; Moses, A; Viswabandhya, A; Mathews, V; George, B; Srivastava, A; Chandy, M

2008-02-20

111

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

PubMed Central

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

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

2012-01-01

112

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.

113

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

PubMed Central

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

Davey, H M; Kell, D B

1996-01-01

114

Dealing with heterogeneous populations in randomized wound trials: challenges and potential solutions.  

PubMed

Chronic wounds have a great variety of etiologies and manifestations that influence wound healing. Such heterogeneity potentially threatens the validity and clinical usefulness of trials if not considered appropriately. In 82 randomized wound trials retrieved from 10 Cochrane reviews, we assessed if and how authors considered wound and other prognostically important characteristics in the conduct and analysis of wound trials. We assessed whether these characteristics were discussed, reflected in the eligibility criteria, used for prestratification or for adjustments to ensure comparability of treatment groups, and whether subgroup analyses were conducted to identify heterogeneity of treatment effects. Nine percent of all trials explicitly discussed characteristics that influence wound healing in the introduction and 43% in the Discussion section. Ninety percent of trials had at least one prognostically important characteristic as eligibility criterion. Only 11% of trials used prestratification, and 6% adjusted the results for imbalances between treatment groups. Twenty-seven percent performed subgroup analyses with prognostically important characteristics defining subgroups. Chronic wound trials use simple randomization, but rarely adapt the study design and analysis to take the heterogeneity of patients into consideration. Collaborative multicenter trials would overcome many of the limitations and provide statistical power to detect important treatment effects both overall and in subgroups. PMID:22672225

Vollenweider, Daniela; Ebneter, Ingrid; Mayer, Dieter; Hafner, Jürg; Steurer, Johann; Puhan, Milo A

2012-06-07

115

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

PubMed Central

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

2010-01-01

116

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

117

Recognising Language Impairment in Secondary School Student Populations  

ERIC Educational Resources Information Center

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

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

2011-01-01

118

Recognising language impairment in secondary school student populations  

Microsoft Academic Search

Up to 16% of students in mainstream secondary schools present with language impairment (LI). As with other learning difficulties, students with LI experience many academic, social, emotional and behavioral problems. Associated presenting behaviors may, however, be masking the primary language impairment. As a result, secondary school students with LI are under-recognised and may therefore be missing out on appropriate supports

Julia Starling; Natalie Munro; Leanne Togher; Joanne Arciuli

2011-01-01

119

Recognising language impairment in secondary school student populations  

Microsoft Academic Search

Up to 16% of students in mainstream secondary schools present with language impairment (LI). As with other learning difficulties, students with LI experience many academic, social, emotional and behavioral problems. Associated presenting behaviors may, however, be masking the primary language impairment. As a result, secondary school students with LI are under-recognised and may therefore be missing out on appropriate supports

Julia Starling; Natalie Munro; Leanne Togher; Joanne Arciuli

2010-01-01

120

Best practices for time-management of student groups with heterogeneous effort  

Microsoft Academic Search

The daily work of an engineer in industry is affected by project work; often more than one project at a time. Consequently, time and self-management is an important part of the education of future engineers and scientists. Students of electrical engineering and computer science at the University of Siegen have a student project work in their curricula to deepen hard

André Schäfer; Matthias Mielke; Rainer Brück

2012-01-01

121

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

ERIC Educational Resources Information Center

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

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

2013-01-01

122

Homeless and highly mobile students: A population-level description of the status of homeless students from three school districts  

Microsoft Academic Search

An increasing number of school-age children lack fixed, permanent housing, which negatively affects their school engagement, jeopardizing long-term school success. Much of the previous research on this problem has focused on specific interventions in specific jurisdictions on targeted populations, but seldom have researchers attempted to study homeless and highly mobile students at a population level. This descriptive study combined statewide

Anita M. Larson; Danielle M. Meehan

2011-01-01

123

LDL particle heterogeneity, and its association with other established cardiovascular risk factors in a young Indian industrial population  

PubMed Central

Objective Low density lipoprotein (LDL) particles are heterogeneous in terms of size, density, chemical composition and electric charge with certain particle of LDL being more atherogenic than the others. The present study aimed to look at the LDL particle heterogeneity, particle size and association with other cardiovascular disease (CVD) risk factors in young Indian industrial population. Methodology 600 employees of an industry of Delhi, aged 20-39 years were selected for the study. Data on demographics, individual characteristics associated with major risk factors of CVD, past medical history, clinical and anthropometric profile was collected. Fasting glucose, lipid profile, apolipoprotein (A1, B, and E), lipoprotein (a), high sensitive C-reactive protein (hsCRP) and insulin were estimated. LDL particle size was determined in ethylenediamminetetraacetate (EDTA) plasma by 3% polyacrylamide gel electrophoresis. Result We found a prevalence of small dense LDL phenotype (LDL size ? 26.3) in 27.4% of males and 24.0% of females. The mean waist circumference, blood pressure, triglycerides (TAG), cholesterol, hsCRP, apolipoprotein (A1, B and E) and insulin were higher in males whereas mean high density lipoprotein was higher in females. Females also had a significantly higher mean LDL particle diameter as compared to males. Conclusion TAG, physical activity and lipoprotein (a) correlated with small dense LDL in this young Indian population.

Lakshmy, Ramakrishnan; Dorairaj, Prabhakaran; Tarik, Mohamad; Gupta, Ruby; Reddy, Kolli Srinath

2012-01-01

124

Temporal stability of gene frequencies within genetically heterogeneous populations of the queen scallop Aequipecten (Chlamys) opercularis  

Microsoft Academic Search

The widely held assumption that gene frequencies within samples of multi-aged organisms are temporally stable has rarely been tested. In order to test this assumption in the commercially exploited bivalve scallop Aequipecten (Chlamys) opercularis (L.), 12 populations were sampled from around the UK over the period 1988–1990 and each was assayed at four putative polymorphic enzyme loci. Most populations were

R. I. Lewis; J. P. Thorpe

1994-01-01

125

Microhabitat heterogeneity and population ecology of an herbivorous rodent, Microtus californicus  

Microsoft Academic Search

Existing models of microtine population regulation and life history evolution rely on data derived from empirical studies which assume spatial homogeneity of the sampling unit, and infer that population dynamics can be described adequately by aggregation of individuals differing in sex, age and social status. These assumptions were not supported in the present study, and their application would have obscured

Andrew Cockburn; William Z. Lidicker

1983-01-01

126

Evolutionary Models of Color Categorization: Investigations based on Realistic Population Heterogeneity  

Microsoft Academic Search

These constraints are made operational in agent categorization and communication games. They produce a number of interesting consequences for stable, shared categorization solutions that are evolved in agent populations. It is found that the confusion patterns associated with a small fraction of color decient agents break symmetries in population categorization solutions, and conne the boundaries of color categories to a

Kimberly A. Jameson; Natalia L. Komarova

2008-01-01

127

Genetic heterogeneity of limb-girdle muscular dystrophy in Amish populations  

SciTech Connect

The autosomal recessive form of limb-girdle muscular dystrophy (LGMD2) is characterized by onset in childhood, progressive weakness predominantly of shoulder, pelvic and trunk muscles with sparing of facial muscles. A gene for LGMD2 was localized to chromosome 15q by Beckmann et al. in 1991 in Isle La Reunion families, subsequently confirmed in Amish families and in Brazilian families where genetic heterogeneity has been demonstrated. Analysis of LGM2 families for recombination events permitted the gene region to be restricted to an interval of about 7 cM defined by flanking markers D15S129 and D15S143. Extended haplotypes were established in the families on the basis of the segregation of multiple markers within this interval. Although the nine northern Indiana Amish families showed linkage of the gene to chromosome 15 markers (maximum lod score of 7.58 at {theta}=0.06 for D15S129 and 12.57 at {theta}=0.046 for D15S143), six large southern Indiana families with LGMD2, clinically indistinguishable from the LGMD2 in northern Indiana, were found to have a disease neither linked to chromosome 15 nor to chromosome 2 where a second localization has been reported. Although these two Indiana Amish LGMD2 kindreds contain some common ancestors and are clinically similar, the LGMD2 appears to be genetically heterogeneous.

Beckmann, J.S.; Allamand, V.; Broux, O. [CEPH, Paris (France)] [and others

1994-09-01

128

Single nucleotide polymorphisms of the protoporphyrinogen oxidase gene: inter-population heterogeneity of allelic variation.  

PubMed

Five single nucleotide polymorphisms (SNPs) in the protoporphyrinogen oxidase gene (PPOX) were used for inter-population comparisons of six South African populations and two non-South African Caucasian populations. Novel polymorphisms identified in the promoter region and exon 11 of the PPOX gene, as well as three known variants in exon 1 and intron 2, were analysed using single-strand conformation polymorphism (SSCP) and restriction enzyme analyses. Significant population differences were found for four of the five polymorphisms analysed. A G-to-A transition was found at nucleotide position -1081 and is the first polymorphism to be identified in the 5' promoter region of the gene. A novel A-to-C substitution at nucleotide position 3880 in exon 11 was not detected in subjects of European descent. This study represents the first inter-population comparison of allelic variation at the PPOX locus. The significant differences observed between populations demonstrate the importance of population considerations when marker association studies are performed at this locus. PMID:11513556

Warnich, L; Waso, H F; Groenewald, I M; Bester, A E; de Villiers, J N; Kotze, M J; Lynch, A G; Louw, J H

2001-08-01

129

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

Microsoft Academic Search

In Colombia, the mosquito Ochlerotatus taeniorhyn- chus has been identified as an efficient vector of the epidemic-epi- zootic Venezuelan equine encephalitis virus. We evaluated the ge- netic variability and heterogeneity of this mosquito in Colombian populations using eight microsatellite DNA loci. Two hundred and ten mosquito specimens collected from seven populations of the Co- lombian Atlantic coast (San Bernardo del

F. Bello; V. Becerra

130

Treatment of Bipolar Disorder in the University Student Population  

Microsoft Academic Search

University counseling centers are faced with the challenge of effectively treating bipolar students while also utilizing brief treatment frameworks and managing high patient volumes. Potential destabilization, particularly within the elevated mood phase, poses significant behavioral management issues for university clinicians and administrators, though for many years the common default position for university counseling centers has been to refer students with

Russ Federman

2010-01-01

131

Assessment of Learning Disabilities Among a Pharmacy Student Population1  

Microsoft Academic Search

American Association of Colleges of Pharmacy GAPS funding provided support to screen 214 pharmacy students enrolled in a Doctor of Pharmacy Program for dyslexia and other learning disabilities. The results have substantial implications for teaching, testing, and student performance in schools of pharmacy. In its simplest definition, dyslexia is \\

James A. Boyd; Constance A. McKenzie; Thomas J. Holmes Jr

1999-01-01

132

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

133

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

PubMed Central

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

2006-01-01

134

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

PubMed

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

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

2006-01-01

135

Heterogeneity in protein expression induces metabolic variability in a modeled Escherichia coli population  

PubMed Central

Stochastic gene expression can lead to phenotypic differences among cells even in isogenic populations growing under macroscopically identical conditions. Here, we apply flux balance analysis in investigating the effects of single-cell proteomics data on the metabolic behavior of an in silico Escherichia coli population. We use the latest metabolic reconstruction integrated with transcriptional regulatory data to model realistic cells growing in a glucose minimal medium under aerobic conditions. The modeled population exhibits a broad distribution of growth rates, and principal component analysis was used to identify well-defined subpopulations that differ in terms of their pathway use. The cells differentiate into slow-growing acetate-secreting cells and fast-growing CO2-secreting cells, and a large population growing at intermediate rates shift from glycolysis to Entner–Doudoroff pathway use. Constraints imposed by integrating regulatory data have a large impact on NADH oxidizing pathway use within the cell. Finally, we find that stochasticity in the expression of only a few genes may be sufficient to capture most of the metabolic variability of the entire population.

Labhsetwar, Piyush; Cole, John Andrew; Roberts, Elijah; Price, Nathan D.; Luthey-Schulten, Zaida A.

2013-01-01

136

Are New Generations of Female College-Student Populations Meeting Calcium Requirements: Comparison of American and Croatian Female Students  

PubMed Central

We compared calcium (Ca) sources and intake, as well as multivitamin/mineral supplement use between female students with nutrition/health background and those from general-student-populations. 314 participants 18–37 y, including 57 African-Americans and 54 Caucasian-Americans recruited from Nutrition and/or other Health Sciences departments (NHS), and 100 African-American and 103 Croatian women representing general-student-population (GSP), completed food frequency questionnaire assessing their usual Ca intake and supplement use. NHS populations met recommendations and consumed significantly more Ca, particularly from dairy sources, and were more likely to take supplements than GSP groups, suggesting that health education may influence Ca intake.

Douglas, Crystal C.; Rumbak, Ivana; Baric, Irena Colic; Kovacina, Marinela; Piasek, Martina; Ilich, Jasminka Z.

2010-01-01

137

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

138

Sample Heterogeneity and the Measurement Structure of the Multidimensional Students' Life Satisfaction Scale  

ERIC Educational Resources Information Center

|Several measurement assumptions were examined with the goal of assessing the validity of the Multidimensional Students' Life Satisfaction Scale (MSLSS), a measure of adolescents' satisfaction with their family, friends, living environment, school, self, and general quality of life. The data were obtained via a cross-sectional survey of 8,225…

Sawatzky, Richard; Ratner, Pamela A.; Johnson, Joy L.; Kopec, Jacek A.; Zumbo, Bruno D.

2009-01-01

139

The effectiveness of multi resolution image segmentation for measuring spatial heterogeneity in mixed population biofilms  

Microsoft Academic Search

Multi resolution image clustering and segmentation tools has been developed to measure the distance between clusters of homogeneous microbial populations within two-dimensional sections of biofilms visualized by confocal laser scanning microscopy. The concept underlying multi resolution image segmentation is that the number of clusters are larger for higher resolution image and smaller for lower resolution image. This hierarchical structure analysis

Saeid Belkasim; Gordana Derado; Eric Gilbert; H. O'Connell

2004-01-01

140

Reaction-diffusion processes and meta-population models in heterogeneous networks  

Microsoft Academic Search

Dynamical reaction-diffusion processes and meta-population models are standard model- ing approaches for a wide variety of phenomena in which local quantities - such as den- sity, potential and particles - diffuse and interact according to the physical laws. Here, we study the behavior of two basic reaction-diffusion processes (B ? A and A + B ? 2B) defined on networks

Vittoria Colizza; Romualdo Pastor-Satorras; Alessandro Vespignani

141

Peer bullying in a pre-registration student nursing population.  

PubMed

Peer bullying is a major problem in schools and workplaces including the National Health Service. Although there are a few published studies exploring the incidence of peer bullying among university students, none is specific to pre-registration nursing students. Nursing programmes are delivered across two campuses of the university however students registered at individual campuses do not mix which makes the experiences of each campus individual. The aim of this study was to explore the incidence and manifestation of peer bullying amongst pre-registration nursing students in the university setting. The study describes the reported incidence of the three types of peer bullying behaviour: physical, verbal and non-verbal bullying. Participants in their final year of adult nurse education were asked to explore their perceptions of peer bullying, the frequency of witnessed or experienced behaviour and the location of where this behaviour occurred on the university campuses via a quantitative questionnaire. In total 190 students were surveyed with 156 (82%) responding. Participants reported peer bullying is experienced by student nurses on university premises and that academic members of staff are sometimes present when this behaviour is demonstrated. Reported levels of bullying decreased during their 2nd and 3rd years of the course compared to the foundation year. This decrease may have been in response to the university's strong anti-bullying stance. PMID:22093882

Cooper, Brenda; Curzio, Joan

2011-11-16

142

Sleep Patterns and Predictors of Disturbed Sleep in a Large Population of College Students  

Microsoft Academic Search

PurposeTo characterize sleep patterns and predictors of poor sleep quality in a large population of college students. This study extends the 2006 National Sleep Foundation examination of sleep in early adolescence by examining sleep in older adolescents.

Hannah G. Lund; Brian D. Reider; Annie B. Whiting; J. Roxanne Prichard

2010-01-01

143

Genetic Diversity in Normal Cell Populations is the Earliest Stage of Oncogenesis Leading to Intra-Tumor Heterogeneity  

PubMed Central

Random mutations and epigenetic alterations provide a rich substrate for microevolutionary phenomena to occur in proliferating epithelial tissues. Genetic diversity resulting from random mutations in normal cells is critically important for understanding the genetic basis of oncogenesis. However, evaluation of the cell-specific role of individual (epi-)genetic alterations in living tissues is extremely difficult from a direct experimental perspective. For this purpose, we have developed a single cell model to describe the fate of every cell in the uterine epithelium and to simulate occurrence of the first cancer cell. Computational simulations have shown that a baseline mutation rate of two mutations per cell division is sufficient to explain sporadic endometrial cancer as a rare evolutionary consequence with an incidence similar to that reported in SEER data. Simulation of the entire oncogenic process has allowed us to analyze the features of the tumor-initiating cells and their clonal expansion. Analysis of the malignant features of individual cancer cells, such as de-differentiation status, proliferation potential, and immortalization status, permits a mathematical characterization of malignancy at the single cell level and a comparison of intra-tumor heterogeneity between individual tumors. We found, under the conditions specified, that cancer stem cells account for approximately 7% of the total cancer cell population. Therefore, our mathematical modeling describes the genetic diversity and evolution in a normal cell population at the early stages of oncogenesis and characterizes intra-tumor heterogeneity. This model has explored the role of accumulation of a large number of genetic alterations in oncogenesis as an alternative to traditional biological approaches emphasizing the driving role of a small number of genetic mutations. A quantitative description of the contribution of a large set of genetic alterations will allow the investigation of the impact of environmental factors on the growth advantage of and selection pressure on individual cancer cells for tumor progression.

Howk, Cory L.; Voller, Zachary; Beck, Brandon B.; Dai, Donghai

2013-01-01

144

Association of acculturation and country of origin with self-reported hypertension and diabetes in a heterogeneous Hispanic population  

PubMed Central

Background Hispanics are the fasting growing population in the U.S. and disproportionately suffer from chronic diseases such as hypertension and diabetes. Little is known about the complex interplay between acculturation and chronic disease prevalence in the growing and increasingly diverse Hispanic population. We explored the association between diabetes and hypertension prevalence among distinct U.S. Hispanic subgroups by country of origin and by degree of acculturation. Methods We examined the adult participants in the 2001, 2003, 2005, and 2007 California Health Interview Survey (CHIS). Using weighted logistic regression stratified by nativity, we measured the association between country of origin and self-reported hypertension and diabetes adjusting for participants’ demographics, insurance status, socio-economic status and degree of acculturation measured by citizenship, English language proficiency and the number of years of residence in the U.S. Results There were 33,633 self-identified Hispanics (foreign-born: 19,988; U.S.-born: 13,645). After multivariable adjustment, we found significant heterogeneity in self-reported hypertension and diabetes prevalence among Hispanic subgroups. Increasing years of U.S. residence was associated with increased disease prevalence. Among all foreign-born subgroups, only Mexicans reported lower odds of hypertension after adjustment for socioeconomic and acculturation factors. Both U.S.-born and foreign-born Mexicans had higher rates of diabetes as compared to non-Hispanic whites. Conclusions We found significant heterogeneity among Hispanics in self-reported rates of hypertension and diabetes by acculturation and country of origin. Our findings highlight the importance of disaggregation of Hispanics by country of origin and acculturation factors whenever possible.

2012-01-01

145

Sample Heterogeneity and the Measurement Structure of the Multidimensional Students’ Life Satisfaction Scale  

Microsoft Academic Search

Several measurement assumptions were examined with the goal of assessing the validity of the Multidimensional Students’ Life\\u000a Satisfaction Scale (MSLSS), a measure of adolescents’ satisfaction with their family, friends, living environment, school,\\u000a self, and general quality of life. The data were obtained via a cross-sectional survey of 8,225 adolescents in British Columbia,\\u000a Canada. Confirmatory factor and factor mixture analyses of

Richard Sawatzky; Pamela A. Ratner; Joy L. Johnson; Jacek A. Kopec; Bruno D. Zumbo

2009-01-01

146

Genetic variance estimates in a heterogenous potato population propagated from true seed (TPS)  

Microsoft Academic Search

Genetic variances were estimated for 11 traits in a potato breeding population propagated from true seed (TPS). Means were\\u000a high and no genetic variability was found for seed germination and transplant survival. Additive variance and heritability\\u000a were high for TPS production which was positively correlated with tuber yield. No additive variance was found for uniformity\\u000a of tuber size, but heritability

P. G. Thompson; H. A. Mendoza

1984-01-01

147

Cooperative action of coherent groups in broadly heterogeneous populations of interacting chemical oscillators  

PubMed Central

We present laboratory experiments on the effects of global coupling in a population of electrochemical oscillators with a multimodal frequency distribution. The experiments show that complex collective signals are generated by this system through spontaneous emergence and joint operation of coherently acting groups representing hierarchically organized resonant clusters. Numerical simulations support these experimental findings. Our results suggest that some forms of internal self-organization, characteristic for complex multiagent systems, are already possible in simple chemical systems.

Mikhailov, A. S.; Zanette, D. H.; Zhai, Y. M.; Kiss, I. Z.; Hudson, J. L.

2004-01-01

148

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

ERIC Educational Resources Information Center

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

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

149

The Inventory of Personality Organisation: its psychometric properties among student and clinical populations in Japan  

Microsoft Academic Search

BACKGROUND: The Inventory of Personality Organisation (IPO) is a self-report measure that reflects personality traits, as theorised by Kernberg. METHODS: In study 1, the Japanese version of the IPO was distributed to a population of Japanese university students (N = 701). The students were randomly divided into two groups. The factor structure derived from an exploratory factor analysis among one

Hiromi Igarashi; Hiroyoshi Kikuchi; Rikihachiro Kano; Hiroshi Mitoma; Masahiro Shono; Chieko Hasui; Toshinori Kitamura

2009-01-01

150

Measures of life stress and social support specific to an Asian student population  

Microsoft Academic Search

We designed two new measures—the Index of Life Stress (ILS) and the Index of Social Support (ISS)—to assist in the prediction of cultural adjustment for an Asian international student population. In the present study, these two measures were administered to 101 Asian international students. Stability estimates over 1 month were high: .97 for the ILS and .81 for the ISS.

Bin Yang; George A. Clum

1995-01-01

151

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

PubMed Central

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

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

2013-01-01

152

A dual reporter gene transgenic mouse demonstrates heterogeneity in hepatic fibrogenic cell populations.  

PubMed

Activation of hepatic stellate cells (HSCs) and other resident mesenchymal cells into myofibroblasts expressing alpha smooth muscle actin (alphaSMA) and collagen I is a key event in liver fibrogenesis. However, the temporal expression profiles of alphaSMA and collagen I genes in these cells is unknown. To address this question, we studied alphaSMA and collagen alpha1(I) transcriptional patterns in primary cultures of HSCs, and additionally, in an in vivo model of secondary biliary fibrosis using transgenic mice that express the Discomsoma sp. red fluorescent protein (RFP) and the enhanced green fluorescent protein (EGFP) reporter genes under direction of the mouse alphaSMA and collagen alpha1(I) promoter/enhancers, respectively. The alphaSMA-RFP mice were crossed with collagen-EGFP mice to generate double transgenic mice. Reporter gene expression in cultured HSCs demonstrated that both transgenes were induced at day 3 with continued expression through day 14. Interestingly, alphaSMA and collagen alpha1(I) transgenes were not coexpressed in all cells. Flow cytometry analysis showed three different patterns of gene expression: alphaSMA-RFP positive cells, collagen-EGFP positive cells, and cells expressing both transgenes. AlphaSMA-only and alphaSMA/collagen expressing cells showed higher expression levels of synaptophysin, reelin, MMP13, TIMP1, and ICAM-1 compared to collagen-only expressing cells, as assessed by real-time PCR. Following bile duct ligation, alphaSMA and collagen alpha1(I) transgenes were differentially expressed by peribiliary, parenchymal and vascular fibrogenic cells. Peribiliary cells preferentially expressed collagen alpha1(I), while parenchymal myofibroblasts expressed both alphaSMA and collagen alpha1(I). In conclusion, these data demonstrate heterogeneity of gene expression in myofibroblastic cells during active fibrogenesis. These reporter mice provide a useful tool to further characterize fibrogenic cell types and to evaluate antifibrotic drugs. PMID:15389867

Magness, Scott T; Bataller, Ramón; Yang, Liu; Brenner, David A

2004-11-01

153

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

PubMed Central

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

2012-01-01

154

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

NASA Astrophysics Data System (ADS)

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

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

155

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

156

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

157

Distribution of a naturally fluctuating ungulate population among heterogeneous plant communities: ideal and free?  

PubMed

1. Herbivore distribution is often assumed to follow the ideal free distribution (IFD) model. This assumes that organisms are omniscient about forage quality and availability within the area available to them and are free to move, with negligible cost, throughout this environment. If this were the case we would expect that, at lowest densities, all animals would be found in the best habitat patches, with less desirable habitats being occupied stepwise as population density increases. We test this using data from a naturally fluctuating population of feral Soay sheep. 2. We show that, although the distribution of individuals is correlated positively with food quality, in line with patterns reported for hill sheep in Scotland, their distribution does not conform to the predictions of the IFD model. We argue that it is the dynamic nature of their food resource that causes this departure from the predictions of the IFD model and make the case that the IFD model, in its unmodified form, is inappropriate for use in modelling distribution among patches containing dynamic resources. PMID:17032371

Jones, Owen R; Pilkington, Jill G; Crawley, Michael J

2006-11-01

158

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

159

Product News versus Advertising: An Exploration within a Student Population.  

ERIC Educational Resources Information Center

|An exploratory survey (part of a larger study) examined the relative effectiveness of news versus advertising as sources of product information. Subjects, 140 undergraduate students enrolled in an introductory public speaking course or a course in visual communication, completed a 5-page media interest survey. Results indicated that news rates…

Hallahan, Kirk

160

Treatment of Bipolar Disorder in the University Student Population  

ERIC Educational Resources Information Center

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

Federman, Russ

2011-01-01

161

Descriptive epidemiology of contact dermatitis in a university student population  

Microsoft Academic Search

Background: The frequency of irritant and allergic contact dermatitis has been compared in relatively few studies.Objective: This report describes the frequency of visits by university students to campus prepaid health plan dermatologists for irritant and allergic contact dermatitis compared with visits for other types of dermatitis and other skin problems.Methods: Prospective recording of specific dermatologic diagnoses was performed for all

Philip D. Shenefelt

1996-01-01

162

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

163

Treatment of Bipolar Disorder in the University Student Population  

ERIC Educational Resources Information Center

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

Federman, Russ

2011-01-01

164

Chronic disease projections in heterogeneous ageing populations: approximating multi-state models of joint distributions by modelling marginal distributions.  

PubMed

To quantify the effects of changes in risk factors for chronic diseases on morbidity and mortality, Markov-type multi-state models are used. However, with multiple risk factors and many diseases relating to these risk factors, these models contain a large number of states. In this paper, we present an alternative modelling methodology implemented in the National Institute for Public Health and the Environment chronic disease model. This model includes multiple states based on risk factor levels and disease stages but only keeps track of the marginal probability values. Starting from the multi-state model, differential equations are derived that describe the change of the marginal distribution for each risk factor class and disease stage, taking into account population heterogeneity and competing mortality risks. The model is illustrated by presenting results of a scenario affecting disease incidence by altering the risk factor distribution of the population. To show the strength of the approximating model, we compare its results to those of the multi-state Markov model. PMID:19516046

Hoogenveen, Rudolf T; van Baal, Pieter H M; Boshuizen, Hendriek C

2009-06-10

165

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

166

Population Heterogeneity of Agrobacterium tumefaciens in Galls of Populus L. from a Single Nursery  

PubMed Central

This study focused on the natural crown gall infections occurring in a Leuce poplar nursery. Soil effects on crown gall frequency were detected, indicating that contamination was due to a resident Agrobacterium tumefaciens population, which was present before seedling plantation. The crown gall frequency on poplar progenies varied from 3 to 67%, indicating the feasibility of improvement in crown gall resistance. Of 129 tumor isolates, 128 were pathogenic. These isolates were of biotype 1 or 2. Biochemical, serological, and antibiotic resistance typing results concurred, indicating the presence of four biotype 1 and two biotype 2 resident subpopulations. No significant change was noticed in the relative proportions of subpopulations from one year to another. Pathogenic subpopulations both in vitro and in planta were susceptible to Kerr K84 (P. B. New and A. Kerr, J. Appl. Bacteriol. 90:172-179, 1972). In addition, no serological cross-reactions were found to occur between K84 and the pathogenic subpopulations.

Nesme, Xavier; Michel, Marie-France; Digat, Bernard

1987-01-01

167

The impact of environmental heterogeneity on genetic architecture in a wild population of Soay sheep.  

PubMed

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

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

2009-02-09

168

The unconventional secretion of stress-inducible protein 1 by a heterogeneous population of extracellular vesicles.  

PubMed

The co-chaperone stress-inducible protein 1 (STI1) is released by astrocytes, and has important neurotrophic properties upon binding to prion protein (PrP(C)). However, STI1 lacks a signal peptide and pharmacological approaches pointed that it does not follow a classical secretion mechanism. Ultracentrifugation, size exclusion chromatography, electron microscopy, vesicle labeling, and particle tracking analysis were used to identify three major types of extracellular vesicles (EVs) released from astrocytes with sizes ranging from 20-50, 100-200, and 300-400 nm. These EVs carry STI1 and present many exosomal markers, even though only a subpopulation had the typical exosomal morphology. The only protein, from those evaluated here, present exclusively in vesicles that have exosomal morphology was PrP(C). STI1 partially co-localized with Rab5 and Rab7 in endosomal compartments, and a dominant-negative for vacuolar protein sorting 4A (VPS4A), required for formation of multivesicular bodies (MVBs), impaired EV and STI1 release. Flow cytometry and PK digestion demonstrated that STI1 localized to the outer leaflet of EVs, and its association with EVs greatly increased STI1 activity upon PrP(C)-dependent neuronal signaling. These results indicate that astrocytes secrete a diverse population of EVs derived from MVBs that contain STI1 and suggest that the interaction between EVs and neuronal surface components enhances STI1-PrP(C) signaling. PMID:23543276

Hajj, Glaucia N M; Arantes, Camila P; Dias, Marcos Vinicios Salles; Roffé, Martín; Costa-Silva, Bruno; Lopes, Marilene H; Porto-Carreiro, Isabel; Rabachini, Tatiana; Lima, Flávia R; Beraldo, Flávio H; Prado, Marco M A; Linden, Rafael; Martins, Vilma R

2013-03-31

169

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

PubMed

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

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

2000-01-01

170

Population Heterogeneity in Corynebacterium glutamicum ATCC 13032 caused by prophage CGP3.  

PubMed

The genome of Corynebacterium glutamicum type strain ATCC 13032 (accession number BX927147) contains three prophages, CGP1, CGP2, and CGP3. We recently observed that many genes within the CGP3 prophage region have increased mRNA levels in a dtxR deletion mutant that lacks the master regulator of iron homeostasis (J. Wennerhold and M. Bott, J. Bacteriol. 188:2907-2918, 2006). Here, we provide evidence that this effect is due to the increased induction of the prophage CGP3 in the dtxR mutant, possibly triggered by DNA damage caused by elevated intracellular iron concentrations. Upon induction, the CGP3 prophage region is excised from the genome and forms a circular double-stranded DNA molecule. Using quantitative real-time PCR, an average copy number of about 0.1 per chromosome was determined for circular CGP3 DNA in wild-type C. glutamicum. This copy number increased about 15-fold in the dtxR mutant. In order to visualize the CGP3 DNA within single cells, a derivative of the wild type was constructed that contained an array of tet operators integrated within the CGP3 region and a plasmid-encoded YFP-TetR fusion protein. As expected, one to two fluorescent foci that represented the chromosomally integrated CGP3 prophage were detected in the majority of cells. However, in a small fraction (2 to 4%) of the population, 4 to 10 CGP3 DNA molecules could be observed in a single cell. Interestingly, the presence of many CGP3 copies in a cell often was accompanied by an efflux of chromosomal DNA, indicating the lysis of the corresponding cell. However, evidence for the formation of functional infective CGP3 phage particles could not be obtained. PMID:18487330

Frunzke, Julia; Bramkamp, Marc; Schweitzer, Jens-Eric; Bott, Michael

2008-05-16

171

Population Heterogeneity in Corynebacterium glutamicum ATCC 13032 Caused by Prophage CGP3?  

PubMed Central

The genome of Corynebacterium glutamicum type strain ATCC 13032 (accession number BX927147) contains three prophages, CGP1, CGP2, and CGP3. We recently observed that many genes within the CGP3 prophage region have increased mRNA levels in a dtxR deletion mutant that lacks the master regulator of iron homeostasis (J. Wennerhold and M. Bott, J. Bacteriol. 188:2907-2918, 2006). Here, we provide evidence that this effect is due to the increased induction of the prophage CGP3 in the dtxR mutant, possibly triggered by DNA damage caused by elevated intracellular iron concentrations. Upon induction, the CGP3 prophage region is excised from the genome and forms a circular double-stranded DNA molecule. Using quantitative real-time PCR, an average copy number of about 0.1 per chromosome was determined for circular CGP3 DNA in wild-type C. glutamicum. This copy number increased about 15-fold in the dtxR mutant. In order to visualize the CGP3 DNA within single cells, a derivative of the wild type was constructed that contained an array of tet operators integrated within the CGP3 region and a plasmid-encoded YFP-TetR fusion protein. As expected, one to two fluorescent foci that represented the chromosomally integrated CGP3 prophage were detected in the majority of cells. However, in a small fraction (2 to 4%) of the population, 4 to 10 CGP3 DNA molecules could be observed in a single cell. Interestingly, the presence of many CGP3 copies in a cell often was accompanied by an efflux of chromosomal DNA, indicating the lysis of the corresponding cell. However, evidence for the formation of functional infective CGP3 phage particles could not be obtained.

Frunzke, Julia; Bramkamp, Marc; Schweitzer, Jens-Eric; Bott, Michael

2008-01-01

172

Pesticide residues in heterogeneous plant populations, a model-based approach applied to nematicides in banana (Musa spp.).  

PubMed

Nematicides are widely used to control plant-parasitic nematodes in intensive export banana (Musa spp.) cropping systems. Data show that the concentration of fosthiazate in banana fruits varies from zero to 0.035 g kg-1, under the maximal residue limit (MRL=0.05 mg kg-1). The fosthiazate concentration in fruit is described by a Gaussian envelope curve function of the interval between pesticide application and fruit harvest (preharvest interval). The heterogeneity of phenological stages in a banana population increases over time, and thus the preharvest interval of fruits harvested after a pesticide application varies over time. A phenological model was used to simulate the long-term harvest dynamics of banana at field scale. Simulations show that the mean fosthiazate concentration in fruits varies according to nematicide application program, climate (temperature), and planting date of the banana field. This method is used to assess the percentage of harvested bunches that exceed a residue threshold and to help farmers minimize fosthiazate residues in bananas. PMID:17305357

Tixier, Philippe; Chabrier, Christian; Malézieux, Eric

2007-02-17

173

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

PubMed

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

Haven, G G; Stolz, J W

174

Tumor cell heterogeneity.  

PubMed

The paper deals with the analysis of literary data on the tumor cell heterogeneity. Phenotypic, genetic and epigenetic mechanisms of heterogeneity are considered. The heterogeneity of metastasis is considered too. The importance for the biology of populations of tumor cells and the sensitivity of tumors to therapeutic treatment are discussed. PMID:24084451

Chekhun, V F; Sherban, S D; Savtsova, Z D

2013-09-01

175

Evaluation of a student-run smoking cessation clinic for a medically underserved population  

Microsoft Academic Search

Background  Smoking is common among medically underserved populations. Accessible resources to encourage and support smoking cessation\\u000a among these patients are limited. Volunteer medical student-run free smoking cessation clinics may provide an effective option\\u000a to help these individuals achieve smoking abstinence. In order to demonstrate the feasibility and cost-effectiveness of a\\u000a student-run clinic, we analyzed a case series of patients receiving care

Lindsay E Lough; Jon O Ebbert; Thomas G McLeod

2011-01-01

176

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

177

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

PubMed Central

The solution structure of the hepta-alanine polypeptide Ac-X2A7O2-NH2 (XAO) has been a matter of controversy in the current literature. On one side of the argument is a claim that the peptide adopts a mostly polyproline II (PPII) structure, with a <20% population of ? conformations at room temperature [Shi Z, Olson CA, Rose GA, Baldwin RL, Kallenbach NR (2002) Proc Natl Acad Sci USA 99:9190–9195], whereas the other side of the argument insists that the peptide exists as an ensemble of conformations, including multiple ?-turn structures [Makowska J, Rodziewicz-Motowidlo S, Baginska K, Vila JA, Liwo A, Chmurzynski L, Scheraga HA (2006) Proc Natl Acad Sci USA 103:1744–1749]. We have used an excitonic coupling model to simulate the amide I band of the FTIR, vibrational circular dichroism, and isotropic and anisotropic Raman spectra of XAO, where, for each residue, the backbone dihedral angle ? was constrained by using the reported 3JC?HNH values and a modified Karplus relation. The best reproduction of the experimental data could only be achieved by assuming an ensemble of conformations, which contains various ?-turn conformations (?26%), in addition to ?-strand (?23%) and PPII (?50%) conformations. PPII is the dominant conformation in segments not involved in turn formations. Most of the residues were found to sample the bridge region connecting the PPII and right-handed helix troughs in the Ramachandran plot, which is part of the very heterogeneous ensemble of conformations generally termed type IV ?-turn.

Schweitzer-Stenner, Reinhard; Measey, Thomas J.

2007-01-01

178

Genetic heterogeneity in populations of the Mediterranean shore crab, Carcinus aestuarii (Decapoda, Portunidae), from the Venice Lagoon  

NASA Astrophysics Data System (ADS)

Heterogeneity in genetic composition among recruits, mostly due to a large variance in reproductive success mediated by oceanographic processes, has been reported for marine species but is less understood in coastal lagoons' organisms. Temporal genetic variation in natural populations of the Mediterranean shore crab Carcinus aestuarii was quantified over a multi-year sample. A total of 486 adult crabs were collected at eight different sites of the Venice Lagoon during the period 2005-2007 and screened for genetic variation using 11 microsatellite loci. Two additional samples (N = 115) from neighbouring sites, located approximately 100 km North and South to the Venice Lagoon, were included for the sake of comparison. Our results show significant differences in allelic frequencies at the micro-geographic scale of the Venice Lagoon, observed between sites of collection, typologies of habitat, and areas with different class of ecological risk or pattern of hemocyanin expression. However, this pattern was not constant between years, with significant differences observed mainly in 2005 and 2006, but not in 2007. Our results indicate significant temporal differences suggesting the existence of dynamic processes that act on the genetic pool of this species. Although natural selection and gene flow might play a role, we suggest that genetic drift linked to large variation in the reproductive success of individuals is the most probable scenario to explain the local genetic patterns of differentiation in the Mediterranean shore crab. Our study, by providing the first evidence for the existence of genetic differences in this species at the micro-geographic scale, suggests that a better comprehension of the link between reproduction, recruitment and oceanography is critical to understand how colonization and maintenance of genetic variation is achieved in ephemeral and vulnerable environments such as coastal lagoons.

Marino, Ilaria Anna Maria; Barbisan, Federica; Gennari, Micol; Giomi, Folco; Beltramini, Mariano; Bisol, Paolo Maria; Zane, Lorenzo

2010-03-01

179

An Assessment of Barriers and Strategies for Recruitment and Retention of a Diverse Graduate Student Population  

ERIC Educational Resources Information Center

The purpose of this exploratory qualitative investigation was to: a) describe the barriers of recruitment and retention of diverse graduate student population at one of the predominantly white universities (PWUs) in the Midwestern US as perceived by the program coordinators and directors and b) identify successful strategies for improving the…

Quarterman, Jerome

2008-01-01

180

Student Recruitment of Special Populations. Special Programs Segment, De Anza College.  

ERIC Educational Resources Information Center

|De Anza College provides numerous services and programs to meet the needs of the disabled, the aged, and other special populations in the surrounding community. These services include: (1) the Tutorial Center; (2) the Physically Limited Program, which works with the student to assure full participation in the college's curriculum; (3) the…

Charles, Richard

181

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.

182

Assessing Undergraduate Learning Outcomes between Accelerated Degree and Traditional Student Populations  

ERIC Educational Resources Information Center

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

Rawls, Janita; Hammons, Stacy

2012-01-01

183

Body Dysmorphic Disorder: Gender differences and prevalence in a Pakistani medical student population  

Microsoft Academic Search

BACKGROUND: Body dysmorphic disorder (BDD) is a psychiatric disorder characterized by a preoccupation with an imagined or slight defect which causes significant distress or impairment in functioning. Few studies have assessed gender differences in BDD in a non clinical population. Also no study assessed BDD in medical students. This study was designed to determine the point prevalence of BDD in

Ather M Taqui; Mehrine Shaikh; Saqib A Gowani; Fatima Shahid; Asmatullah Khan; Syed M Tayyeb; Minahil Satti; Talha Vaqar; Saman Shahid; Afreen Shamsi; Hammad A Ganatra; Haider A Naqvi

2008-01-01

184

Assessing Undergraduate Learning Outcomes Between Accelerated Degree and Traditional Student Populations  

Microsoft Academic Search

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

Janita Rawls; Stacy Hammons

2012-01-01

185

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

PubMed

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

Bello, F; Becerra, V

2009-09-29

186

Detection of hepatitis C virus antibodies and specific hepatitis C virus ribonucleic acid sequences in cord bloods from a heterogeneous prenatal population  

Microsoft Academic Search

OBJECTIVE: Our aim was to quantify the prevalence of at-risk pregnancies for maternal-fetal hepatitis C virus transmission in a heterogeneous prenatal population by detection of both hepatitis C virus-specific antibody and hepatitis C virus ribonucleic acid sequencesin cord bloods from their deliveries.STUDY DESIGN: An anonymous serosurvey of 1432 consecutive umbilical cord blood samples were analyzed for hepatitis C virus antibodies

Neil S. Silverman; Michael Snyder; Richard L. Hodinka; Patricia McGillen; Gerald Knee

1995-01-01

187

Heterogeneity of the population of lymphoma NK\\/Ly and leukemia L-1210 cells according to the carbohydrate structure of cell surfaces: Immunocytochemical analysis of lectin binding  

Microsoft Academic Search

This paper investigates the heterogeneity of surface carbohydrate determinants in a population of ascites cells of lymphoma\\u000a NK\\/Ly and leukemia L-1210 according to the binding of lectins in lentil, wheat germs, peanut, and concavalin A. Bound lectins\\u000a were detected by an indirect immunochemical method using obtained by the authors colloidal gold-labeled polyclonal antilectin\\u000a antibodies with further development with silver acetate.

M. M. Lutsik; A. M. Yashchenko; V. I. Kovalishin; O. E. Pridatko; R. S. Stoika; M. D. Lutsik

2011-01-01

188

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

Microsoft Academic Search

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

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

1994-01-01

189

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

190

Detection of Chlamydia trachomatis in an Australian high school student population  

PubMed Central

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

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

2002-01-01

191

Background, expectations and beliefs of a chiropractic student population: a cross-sectional survey.  

PubMed

Purpose: Research encompassing the characteristics of chiropractic students is limited. The purpose of our study was to evaluate a current chiropractic student population enrolled at a chiropractic college concerning demographics, expectations, and beliefs. Methods: A 44-item survey was administered to volunteer participants. Direct verbal interaction in a classroom setting to potential participants was the recruitment strategy used. Data were collected and stored on a safe network. Percentages for all responses were calculated and means were recorded where appropriate. Results: A total of 664 students participated of 877 potential eligible candidates (75%). The respondents tended to be 21-25 years of age, Caucasian, and male. Most respondents expected to work in a private practice immediately following graduation and anticipated an annual income of at least $100,000 eventually. Respondents preferred the retaining of the term, "subluxation," and identified the importance of new and emerging scientific data. Additionally, respondents held the viewpoint that some non-musculoskeletal diseases can be treated effectively with spinal manipulation as a primary treatment. Conclusions: The majority of chiropractic students in our study were represented by specific demographic characteristics, and a strong favoritism toward the expectations of working in a private practice setting and earning at least $100,000 per year at some point in their career. Distinct beliefs are shared between chiropractic students and practicing chiropractors in North America, and certain aspects of students in our study are comparable to chiropractic students in similar studies. PMID:23362362

Gliedt, Jordan A; Briggs, Shaun; Williams, Joshua S M; Smith, Derek P; Blampied, Joseph

2012-01-01

192

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

193

Human Capital and Population Growth in Non-Metropolitan 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 paper examines this relationship for U.S. non-metropolitan counties and posits that student migration for higher education may play an important role. Students often move to an

John V Winters

2010-01-01

194

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

ERIC Educational Resources Information Center

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

Bill, Anthony; Henderson, Sally; Penman, John

2010-01-01

195

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

PubMed

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

Stycos, J M

1987-01-01

196

[Leprosy in the municipality of Buriticupu, State of Maranhão: active search among the student population].  

PubMed

This study had the aim of determining the coefficient of leprosy detection among the student population of the municipality of Buriticupu, State of Maranhão. An active case search method was used, covering a population of 14,653 students, in 53 schools within the municipal network. Clinical examination gave rise to a leprosy diagnosis for 20 students, which represents a detection coefficient of 13.6/10,000 students. Cutaneous lymph bacilloscopy was performed on all cases, and it was positive in two samples. The predominant clinical form was the indeterminate form, with 12 cases (60%), followed by the tuberculoid form, with five (25%) and the dimorphous form with two (10%). Biopsies were then taken from the lesions of 11 patients, and histopathological analysis showed common findings of hyperkeratosis, mononuclear inflammatory infiltrate and ectasia of vessels and isolated arrector pili muscles. The study also enabled identification of some other infectious skin diseases: pityriasis versicolor in 793, scabies in 361 and dermatophytosis in 119. A variety of nonspecific conditions were also detected, such as scars, nevi and excoriation, in 1,020 students. PMID:18200420

Silva, Antonio Rafael da; Portela, Edson Gustavo Lima; Matos, Wilma Batista de; Silva, Camila Cristina Bastos; Gonçalves, Eloisa da Graça do Rosario

197

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

1994-08-01

198

Gender differences in metabolic risk factor prevalence in a South African student population.  

PubMed

We determined selected risk factors for the metabolic syndrome and assessed the metabolic risk status (using IDF criteria) of third-year physiology students at Stellenbosch University (88 males and 178 females). Outcome measures included anthropometry [body mass index (BMI), waist circumference, waist-to-hip ratio], blood pressure (BP), resting pulse rate, and fasting blood glucose, total cholesterol and triglyceride levels. In addition, students completed a lifestyle questionnaire. A number of gender-based differences were found, with male students displaying a greater incidence of risk factors for the metabolic syndrome: 6% of males versus 3% of females displayed a cluster of three risk factors. Twenty-five per cent of female students (but only 14% of males) exhibited waist circumferences above the accepted range, which was positively correlated, for males and females, with both systolic and diastolic BP, and in females only, also with total cholesterol levels. Male students on average exercised more than their female counterparts, but also exhibited poorer eating habits. Average blood triglyceride levels for both male and female students exceeded the accepted threshold (1.85 +/- 1.62 mmol/l and 2.15 +/- 1.79 mmol/l, respectively). We concluded that metabolic risk factors were evident in a much younger population than commonly expected. Moreover, the gender-specific differences observed may impact on future risk assessment and preventative measures adopted. PMID:19575082

Smith, Carine; Essop, M Faadiel

199

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

200

The Inventory of Personality Organisation: its psychometric properties among student and clinical populations in Japan  

PubMed Central

Background The Inventory of Personality Organisation (IPO) is a self-report measure that reflects personality traits, as theorised by Kernberg. Methods In study 1, the Japanese version of the IPO was distributed to a population of Japanese university students (N = 701). The students were randomly divided into two groups. The factor structure derived from an exploratory factor analysis among one subsample was tested using a confirmatory factor structure among another subsample. In study 2, the factor-driven subscales of the IPO were correlated with other variables that would function as external criteria to validate the scale in a combined population of the students used in study 1 and psychiatric outpatients (N = 177). Results In study 1 the five-factor structure presented by the original authors was replicated in exploratory factor analyses in one subgroup of students. However, this was through reduction of the number of items (the number of the primary items was reduced from 57 to 24 whereas the number of the additional items was reduced from 26 to 13) due to low endorsement frequencies as well as low factor loadings on a designated factor. The new factor structure was endorsed by a confirmatory factor analysis in the other student subgroup. In study 2 the new five subscales of the Japanese IPO were likely to be correlated with younger age, more personality psychopathology (borderline and narcissistic), more dysphoric mood, less psychological well-being, more insecure adult attachment style, lower self-efficacy, and more frequent history of childhood adversity. The IPO scores were found to predict the increase in suicidal ideation in a week's time in a longitudinal follow-up. Conclusion Although losing more than 40% of the original items, the Japanese IPO may be a reliable and valid measure of Kernberg's personality organisation for Japanese populations.

Igarashi, Hiromi; Kikuchi, Hiroyoshi; Kano, Rikihachiro; Mitoma, Hiroshi; Shono, Masahiro; Hasui, Chieko; Kitamura, Toshinori

2009-01-01

201

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

PubMed

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

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

2013-01-01

202

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

203

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

204

Spatial heterogeneity of cyanobacterial communities and genetic variation of microcystis populations within large, shallow eutrophic lakes (Lake Taihu and Lake Chaohu, China).  

PubMed

Cyanobacteria, specifically Microcystis, usually form massive blooms in eutrophic freshwater lakes. Cyanobacterial samples were collected from eight sites of both Lake Taihu and Lake Chaohu in late summer to determine the diversity and distribution pattern of cyanobacteria and Microcystis in large, shallow, entropic lakes with significant spatial heterogeneity and long-term Microcystis bloom. Molecular methods based on denaturing gradient gel electrophoresis and clone library analysis were used. A similar heterogeneous distribution pattern of cyanobacteria in both lakes was observed. Most parts of these two lakes with high trophic level were dominated by Microcystis. However, in the regions with low trophic levels as well as low concentrations of chlorophyll a, Synechococcus occupied a considerable percentage. Different morphospecies and genotypes dominated the bloom-forming Microcystis populations in these two lakes. Microcystis viridis and Microcystis novacekii were dominant in Lake Chaohu, whereas Microcystis flos-aquae was dominant in Lake Taihu. Only 2 of thel3 Microcystis operational taxonomic units were shared between these two lakes. Analysis of molecular variance based on 16S to 23S internal transcribed spacer sequences indicated the significAnt genetic differentiation of Microcystis between these two lakes (F(ST) = 0.19, p < 0.001). However, only 19.46% of the genetic variability was explained by the population variation between lakes, whereas most (80.54%) of the genetic variability occurred within the lakes. Phylogenetic analysis revealed no phylogeographic structure of Microcystis population in these two lakes, as illustrated by their cosmopolitan nature. Our results revealed that spatial heterogeneity within lakes has more impact on the cyanobacterial diversity than geographical isolation in a local scale. PMID:23520854

Cai, Yuanfeng; Kong, Fanxiang; Shi, Limei; Yu, Yang

2012-01-01

205

Participation in Heterogeneous Communities  

Microsoft Academic Search

This paper studies what determines group formation and the degree of participation when the population is heterogeneous, both in terms of income and race or ethnicity. We are especially interested in whether and how much the degree of heterogeneity in communities influences the amount of participation in different types of groups. Using survey data on group membership and data on

Eliana La Ferrara

2000-01-01

206

Participation in Heterogeneous Communities  

Microsoft Academic Search

This paper studies both theoretically and empirically the determinants of group formation and of the degree of participation when the population is heterogeneous, both in terms of income and race or ethnicity. We are especially interested in whether and how much the degree of heterogeneity in communities influences the amount of participation in different types of groups. Using survey data

Alberto Alesina; Eliana La Ferrara

1999-01-01

207

Evaluation of a student-run smoking cessation clinic for a medically underserved population  

PubMed Central

Background Smoking is common among medically underserved populations. Accessible resources to encourage and support smoking cessation among these patients are limited. Volunteer medical student-run free smoking cessation clinics may provide an effective option to help these individuals achieve smoking abstinence. In order to demonstrate the feasibility and cost-effectiveness of a student-run clinic, we analyzed a case series of patients receiving care in a medical student-run Smoking Cessation Clinic (SCC) at the Rochester, Minnesota Salvation Army Good Samaritan Health Clinic (GSHC). Findings Between January 2005 and March 2009, 282 cigarette smokers seeking care at the SCC were analyzed. Student providers at the SCC conducted 1652 weekly individual counseling sessions averaging 18 minutes per encounter. Patients were offered a choice of pharmacotherapies including nicotine replacement therapy (NRT), bupropion, and varenicline for up to 12 weeks. Smoking abstinence was confirmed with exhaled carbon monoxide (CO). Thirty-two patients completed the entire 12-week program (11.3%). At last contact, 94 patients (33.3%) abstained from smoking for ? 7 days and 39 patients (13.8%) were continuously abstinent for ? 4 weeks. The 7-day point prevalence abstinence rates at last contact were 58.6% for varenicline, 41.2% for bupropion, 33.9% for NRT, and 23.5% for bupropion and NRT. Analyzing missing patients as smoking, the 7-day point prevalence abstinence rates were 7.1%, 8.9%, and 8.2%, at 1 month, 2 months, and 3 months after program enrollment, respectively. No serious adverse drug reactions were recorded. Conclusions Our medical student-run smoking cessation clinic provided an effective and safe experience for medically underserved patients who might not otherwise have access to conventional smoking cessation programs because of high cost, lack of insurance, or other disparities. Similar medical student initiatives focusing on healthy lifestyles may be feasible and beneficial for individuals with limited access to healthcare resources.

2011-01-01

208

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

Microsoft Academic Search

This article describes the development and evaluation of an NCI-sponsored short-term summer cancer research education program.\\u000a The study questions examined: the feasibility of conducting a cancer education program in special populations at multiple\\u000a US and international field sites for masters students; the merit and worth that students and faculty attribute to the program;\\u000a and students' scholarly and cancer-related career outcomes.

Amr S. Soliman; Patricia B. Mullan; Robert M. Chamberlain

2010-01-01

209

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.

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

2013-01-01

210

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

PubMed

Cultural competence is not limited to ethnicity, religion, or race but is inclusive of vulnerable groups, such as the homeless. The complex health and social issues related to homelessness requires educational instruction that supports students' ability to address and care for the multidimensional elements that surround this group. Exposure to homeless populations provides nursing students with increased awareness of the issues related to health disparities, while promoting introspective reflection on one's values and beliefs. To increase student exposure to working with homeless clients, a service-learning project using a critical social theory (CST) lens was offered at a homeless center. The students' response that clients were "just like" them, coupled with ambiguity regarding the complex social-economic-political issues surrounding the homeless, may indicate a need for further education regarding cultural understanding, sensitivity, and vulnerability. This project demonstrates the need for learning experiences that support advocacy and social responsibility for vulnerable groups. [J Nurs Educ. 2013;52(10):585-588.]. PMID:24040771

Stanley, Mary Jo

2013-09-13

211

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

ERIC Educational Resources Information Center

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

Fenster, Judy

2004-01-01

212

The prevalence of eating disorder pathology in a cross-ethnic population of female students in South Africa  

Microsoft Academic Search

Objective: The purpose of this study was to determine the prevalence of eating disorder pathology in female students representing South Africa's ethnically diverse population. A secondary aim was to explore relationships between eating disorder pathology, Body Mass Index (BMI), and socioeconomic status (SES). Method: In a questionnaire survey of a cross-section of South African college students, the Eating Disorder Inventory

Douglas Wassenaar; Daniel le Grange; Jacquie Winship; Lance Lachenicht

2000-01-01

213

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

214

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

215

CRITICAL EXAMINATION OF CANDIDATES' DIVERSITY COMPETENCE: RIGOROUS AND SYSTEMATIC ASSESSMENT OF CANDIDATES' EFFICACY TO TEACH DIVERSE STUDENT POPULATIONS  

Microsoft Academic Search

The National Center for Educational Statistics (NCES, 2010) continues to report substantial underachievement of diverse student populations in the nation's schools. After decades of focus on diversity and multicultural education, with integrating field and clinical practice, candidates continue to graduate without adequate knowledge, skills and dispositions to teach diverse students. The National Council of Accreditation of Teacher Education (NCATE) requires

Beatrice Hope Benton-Borghi; Young Mi Chang

2012-01-01

216

Heterogeneity in the Distribution of Bites by Anopheles Gambiae and Anopheles Funestus among Individuals of a Local Human Population.  

National Technical Information Service (NTIS)

The concept of 'female mosquito density per human' implies the existence of a female mosquito population which distributes its bites homogeneously among the local human population. Field data concerning Anopheles gambiae s.l. and A. funestus s.l. suggest ...

M. E. Uildriks J. Lines

1985-01-01

217

Population Size, Per Capita Income, and the Risk of Civil War: Regional Heterogeneity in the Structural Relationship Matters  

Microsoft Academic Search

A common finding in the empirical civil war literature is that population size and per capita income are highly significant predictors of civil war incidence and onset. This paper shows that the common finding of population size and per capita income having a significant average effect on civil war risk in a world sample breaks down once countryand year-specific unobservables

Markus Brückner

2011-01-01

218

Effect of school environment on dental students' perceptions of cultural competency curricula and preparedness to care for diverse populations.  

PubMed

Reports of oral health disparities among racial, ethnic, and socioeconomic sectors of the U.S. population have hastened development of strategies to address this issue. Among these strategies is revising dental school curricula in order to develop more culturally competent graduates. The present study uses data from the 2003 American Dental Education Association (ADEA) survey of dental school seniors to assess students' perceptions of the adequacy of their cultural competency training. We hypothesize that these perceptions are influenced by multiple student characteristics and contextual factors, including a school's status with respect to the Pipeline, Professions, and Practice initiative of the Robert Wood Johnson Foundation and The California Endowment. Response data from ADEA survey items reflecting student perceptions of adequacy of curriculum time devoted to cultural competency and their preparedness to treat an ethnically and culturally diverse population were analyzed to assess the influence of selected student and contextual factors. Student gender, marital status, and level of educational debt were found to influence the curriculum time variable, and students at California schools reported higher perceived preparedness levels than students at dental schools nationwide. Dental school environments promoting acceptance and respect of diverse ethnicities/cultures and student race/ethnicity were significantly associated with students' perception of the adequacy of curriculum time for cultural competency and students' perception of their preparedness to provide oral health care for racially and culturally diverse groups. The findings provide insight for development of cultural competency curricula and direction for future study in this area. PMID:17554098

Hewlett, Edmond R; Davidson, Pamela L; Nakazono, Terry T; Baumeister, Sebastian E; Carreon, Daisy C; Freed, James R

2007-06-01

219

Murine Bone Marrow Lin?Sca-1+CD45? Very Small Embryonic-Like (VSEL) Cells Are Heterogeneous Population Lacking Oct-4A Expression  

PubMed Central

Murine very small embryonic-like (VSEL) cells, defined by the Lin?Sca-1+CD45? phenotype and small size, were described as pluripotent cells and proposed to be the most primitive hematopoietic precursors in adult bone marrow. Although their isolation and potential application rely entirely on flow cytometry, the immunophenotype of VSELs has not been extensively characterized. Our aim was to analyze the possible heterogeneity of Lin?Sca+CD45? population and investigate the extent to which VSELs characteristics may overlap with that of hematopoietic stem cells (HSCs) or endothelial progenitor cells (EPCs). The study evidenced that murine Lin?Sca-1+CD45? population was heterogeneous in terms of c-Kit and KDR expression. Accordingly, the c-Kit+KDR?, c-Kit?KDR+, and c-Kit?KDR? subpopulations could be distinguished, while c-Kit+KDR+ events were very rare. The c-Kit+KDR? subset contained almost solely small cells, meeting the size criterion of VSELs, in contrast to relatively bigger c-Kit?KDR+ cells. The c-Kit?KDR?FSClow subset was highly enriched in Annexin V-positive, apoptotic cells, hence omitted from further analysis. Importantly, using qRT-PCR, we evidenced lack of Oct-4A and Oct-4B mRNA expression either in whole adult murine bone marrow or in the sorted of Lin?Sca-1+CD45?FSClow population, even by single-cell qRT-PCR. We also found that the Lin?Sca-1+CD45?c-Kit+ subset did not exhibit hematopoietic potential in a single cell-derived colony in vitro assay, although it comprised the Sca-1+c-Kit+Lin? (SKL) CD34?CD45?CD105+ cells, expressing particular HSC markers. Co-culture of Lin?Sca-1+CD45?FSClow with OP9 cells did not induce hematopoietic potential. Further investigation revealed that SKL CD45?CD105+ subset consisted of early apoptotic cells with fragmented chromatin, and could be contaminated with nuclei expelled from erythroblasts. Concluding, murine bone marrow Lin?Sca-1+CD45?FSClow cells are heterogeneous population, which do not express the pluripotency marker Oct-4A. Despite expression of some hematopoietic markers by a Lin?Sca-1+CD45?c-Kit+KDR? subset of VSELs, they do not display hematopoietic potential in a clonogenic assay and are enriched in early apoptotic cells.

Nowak, Witold Norbert; Szade, Agata; Kachamakova-Trojanowska, Neli; Zukowska, Monika; Jozkowicz, Alicja; Dulak, Jozef

2013-01-01

220

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.

Lopez-Sepulcre, Andres; Kokko, Hanna; Norris, Ken

2010-01-01

221

'Pragmatic randomized controlled trial of individually prescribed exercise versus usual care in a heterogeneous cancer survivor population': A feasibility study PEACH Trial: Prescribed exercise after chemotherapy  

PubMed Central

Background Many cancer survivors suffer a range of physical and psychological symptoms which may persist for months or years after cessation of treatment. Despite the known benefits of exercise and its potential to address many of the adverse effects of treatment, the role of exercise as well as optimum duration, frequency, and intensity in this population has yet to be fully elucidated. Many cancer rehabilitation programmes presented in the literature are very long and have tight eligibility criteria which make them non-applicable to the majority of cancer survivors. This paper presents the protocol of a novel 8-week intervention which aims to increase fitness, and address other physical symptoms in a heterogeneous cancer survivor population. Methods/design The aim is to recruit 64 cancer survivors 2-6 months after completion of chemotherapy, usually adjuvant, with curative intent. Subjects will be recruited through oncology clinics in a single institution and randomised to usual care or an exercise intervention. The exercise intervention consists of two specifically tailored supervised moderate intensity aerobic exercise sessions weekly over 8-weeks. All participants will be assessed at baseline (0 weeks), at the end of the intervention (8 weeks), and at 3-month follow-up. The primary outcome measure is fitness, and secondary patient-related outcome measures include fatigue, quality of life, and morphological outcomes. A further secondary outcome is process evaluation including adherence to and compliance with the exercise program. Discussion This study will provide valuable information about the physical outcomes of this 8-week supervised aerobic programme. Additionally, process information and economic evaluation will inform the feasibility of implementing this program in a heterogeneous population post cessation of chemotherapy. Trial Registration NCT01030887

2010-01-01

222

Spatial heterogeneity of mitochondrial DNA and allozymes among populations of white-tailed deer and mule deer.  

PubMed

A white-tailed deer (Odocoileus virginianus) population in northeastern Minnesota and a mule deer (O. hemionus) population in the Bridger Mountains Montana, have previously been shown to be spatially subdivided into contiguous subpopulations. We assessed the degree of genetic differentiation among subpopulations and tested the hypothesis that differentiation will be greater for mitochondrial DNA (mtDNA) than for nuclear-encoded allozymes. Differentiation of the white-tailed deer subpopulations was significant for two allozyme loci but not for mtDNA, and the overall degree of differentiation was low. Gene flow, recent founding of the subpopulations, and polygamous breeding structure may all have contributed to this pattern. Greater differentiation was evident among disjunct populations than between the contiguous subpopulations of white-tailed deer. The contiguous mule deer subpopulations were significantly differentiated for mtDNA and one allozyme locus. Differentiation was greater for mtDNA than for allozymes. These results are consistent with demographic data that indicate mule deer males disperse more than do females. Disjunct mule deer populations may be similar or dramatically different in mtDNA haplotype frequencies that do not necessarily vary with geographic distance. Current and historical gene flow and breeding structure will influence population genetic patterns. PMID:1849522

Cronin, M A; Nelson, M E; Pac, D F

223

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/.

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

224

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

PubMed

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

2012-10-12

225

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

2008-06-09

226

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

PubMed Central

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

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

2008-01-01

227

Heterogeneity of cell death.  

PubMed

Cell death constitutes a number of heterogeneous processes. Despite the dynamic nature of cell death, studies of cell death have primarily focused on apoptosis, and cell death has often been viewed as static events occurring in linear pathways. In this article we review cell death heterogeneity with specific focus on 4 aspects of cell death: the type of cell death; how it is induced; its mechanism(s); the results of cell death, and the implications of cell death heterogeneity for both basic and clinical research. This specifically reveals that cell death occurs in multiple overlapping forms that simultaneously occur within a population. Network and pathway heterogeneity in cell death is also discussed. Failure to integrate cell death heterogeneity within analyses can lead to inaccurate predictions of the amount of cell death that takes place in a tumor. Similarly, many molecular methods employed in cell death studies homogenize a population removing heterogeneity between individual cells and can be deceiving. Finally, and most importantly, cell death heterogeneity is linked to the formation of new genome systems through induction of aneuploidy and genome chaos (rapid genome reorganization). PMID:23548436

Stevens, J B; Abdallah, B Y; Liu, G; Horne, S D; Bremer, S W; Ye, K J; Huang, J Y; Kurkinen, M; Ye, C J; Heng, H H Q

2013-04-03

228

Handling Heterogeneous Academic Curricula  

Microsoft Academic Search

Academic programs follow very heterogeneous curricula. A first roadmap to overcome this still unsolved problem was stated in the Bologna-process. In this paper, we propose a framework heading this goal. It enables students to integrate classes from other institutions into their own curriculum even if the curriculum at the corresponding institution differs. In order to allow class substitutions, we propose

Richard Hackelbusch

2006-01-01

229

Social Engagement and Student Body Diversity at Elite American Colleges  

Microsoft Academic Search

Putnam has concluded that trust in others and civic and social engagement in the community are inversely related to the racial and ethnic diversity of the population. In this paper, we examine how measures of social engagement among college students vary with student body racial and ethnic heterogeneity at elite U.S. colleges. We find that socialization measures from the Fiske

Sharissa Barrow; Douglas Coate

2009-01-01

230

Differences in repair in heterogeneous cell populations in vivo and in vitro following high LET irradiation (neutrons).  

PubMed Central

The shape of cell survival curves following X-irradiation when the X-rays were given immediately after neutron irradiation has been examined in two cell lines in vitro (Ehrlich ascites and V79) and in the stem cells of the mouse jejunum. The changes in the shape of the X-ray survival curve following neutron irradiation are different in all the cell systems examined. Some of the changes observed may be associated with a change in the cell profile following neutron irradiation due to the more even cell age killing pattern of neutrons through the cell cycle compared with X-rays. It is unlikely that this can account for all changes in shape observed and it is postulated that some cells following neutron irradiation are more sensitive to X-rays than the unirradiated population or than X-irradiated cells at the same level of survival. This increased sensitivity may be associated with a non-reversible sublethal damage or a saturation of the repair potential caused largely by the alpha or heavy recoil (HR) particles produced by the neutrons in the cell nucleus. The damage is observed when the probability of alpha or HR particles being produced within the cell nucleus, without killing the cell, is high.

Hornsey, S.; Lunec, J.; Griffin, C.

1984-01-01

231

Expression Profiling of a Heterogeneous Population of ncRNAs Employing a Mixed DNA/LNA Microarray  

PubMed Central

Mammalian transcriptomes mainly consist of non protein coding RNAs. These ncRNAs play various roles in all cells and are involved in multiple regulation pathways. More recently, ncRNAs have also been described as valuable diagnostic tools. While RNA-seq approaches progressively replace microarray-based technologies for high-throughput expression profiling, they are still not routinely used in diagnostic. Microarrays, on the other hand, are more widely used for diagnostic profiling, especially for very small ncRNA (e.g., miRNAs), employing locked nucleic acid (LNA) arrays. However, LNA microarrays are quite expensive for high-throughput studies targeting longer ncRNAs, while DNA arrays do not provide satisfying results for the analysis of small RNAs. Here, we describe a mixed DNA/LNA microarray platform, where directly labeled small and longer ncRNAs are hybridized on LNA probes or custom DNA probes, respectively, enabling sensitive and specific analysis of a complex RNA population on a unique array in one single experiment. The DNA/LNA system, requiring relatively low amounts of total RNA, which complies with diagnostic references, was successfully applied to the analysis of differential ncRNA expression in mouse embryonic stem cells and adult brain cells.

Skreka, Konstantinia; Zywicki, Marek; Karbiener, Michael; Huttenhofer, Alexander; Scheideler, Marcel; Rederstorff, Mathieu

2012-01-01

232

Who Pays for Student Diversity? Population Changes and Educational Policy. Twelfth Annual Yearbook of the American Education Finance Association, 1991.  

ERIC Educational Resources Information Center

|Issues of finance undergird all education policy decisions, and demographic changes have clear financial impact. This edited volume outlines demographic trends, focuses on minority and other special student populations in urban and rural settings, and relates the findings to policies. Contained in the book are the following papers: (1) "The Power…

Ward, James Gordon, Ed.; Anthony, Patricia, Ed.

233

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

234

Critical Examination of Candidates' Diversity Competence: Rigorous and Systematic Assessment of Candidates' Efficacy to Teach Diverse Student Populations  

ERIC Educational Resources Information Center

|The National Center for Educational Statistics (NCES, 2010) continues to report substantial underachievement of diverse student populations in the nation's schools. After decades of focus on diversity and multicultural education, with integrating field and clinical practice, candidates continue to graduate without adequate knowledge, skills and…

Benton-Borghi, Beatrice Hope; Chang, Young Mi

2011-01-01

235

PS2-26: Coordinating Heterogeneous Data and Mixed Collection Methods to Support Population-Based Cancer Screening Research  

PubMed Central

Background/Aims The central goal of Population-Based Research Optimizing Screening through Personalized Regimens (PROSPR), a recently-funded NCI initiative, is to develop multi-site, transdisciplinary research to improve the screening process for breast, colon, and cervical cancer. To support this goal, we aim to collect, document, and manage data for the entire colorectal cancer (CRC) screening process at Group Health (GH), an integrated health system and PROSPR Research Center. We describe the data sources, types, and collection methods being used to assemble the breadth of relevant information on patients, providers, tests, pathology, treatment, and outcomes this effort requires. Methods To characterize the CRC screening process for GH members enrolled from 1993–2015, we employed administrative databases, previous CRC studies, data partnerships, and GH’s EpicCare-based electronic medical record (EMR). These resources contain both structured data and unstructured text requiring the use of multiple collection methods, including programmatic extraction, natural language processing (NLP), and manual abstraction. Results We are programmatically extracting demographic information on patients and providers from well-established administrative databases. Information on stool-based tests is extracted from lab databases and EpicCare. Colonoscopy and corresponding pathology notes are available as unstructured text in EpicCare for GH-performed procedures, and we are employing NLP to extract information on family history, test indication, and results from these notes. Scanned notes from contracted colonoscopy providers require manual abstraction; however, through partnership with our largest contracted provider, we receive electronic transfers of this information as structured data, minimizing manual review. For colonoscopies occurring prior to GH’s 2005 implementation of EpicCare, we rely on data from five previously-conducted CRC studies. Treatment information is extracted from pharmacy and utilization databases, and CRC outcomes are available as structured data through partnerships with our local cancer registries. Conclusions Under the auspices of an ambitious initiative such as PROSPR, documenting the entire screening process can be achieved by creating a comprehensive data collection system that coordinates all available data sources and maximizes their value with appropriate collection methods. Efficiencies can be gained by using data from prior studies and developing external data partnerships for access to higher-quality data.

Kamineni, Aruna; Halgrim, Scott; Gundersen, Gabrielle; Fuller, Sharon; Hart, Gene; Carrell, David; Rutter, Carolyn

2013-01-01

236

[Fat and oil consumption in a university student population in Buenos Aires].  

PubMed

The purpose of this study was to evaluate the fat and oil intake and their distribution according to the dietary origin in students of the University of Buenos Aires. A 7 day dietary record of students (49 males and 127 females) attendant to the 1989 Course of Nutrition, School of Pharmacy and Biochemistry, to obtain in Pharmacy and Biochemistry was collected. This information was processed in a PC Computer (VAN Program, Lujan University, Argentina) to obtain the energy and fat daily intake, according to the Dietary Composition Tables compiled by INCAP; missing data were completed t with the German, Italian or Argentine Tables. The results obtained were (average daily intake +/- SD) for females and males, respectively: Energy (Kcal): 1805 +/- 5431 and 2551 +/- 712; total fat (g): 65.6 +/- 21.8 and 87.8 +/- 28.7; percentage of energy provided by fat: 33.0 and 31.1. The distribution of fat intake according to its dietary source was (g/100 g): meat: 33.3; oils: 15.5; diary products: 19.3; cakes and pasta: 11.6; cereals (bread, crackers, etc.): 8.3; separate animal fat: 5.1; legumes and oil seeds: 1.4; eggs: 2.9; poultry: 1.5; margarines: 0.6; fish: 0.3; viscera: 0.3. These data show that the fat intake is not excessive, about 30% of the energy intake; but the high percentage of animal fat might be one of the risk factors responsible for the high incidence of cardiovascular diseases in the population of Buenos Aires. PMID:1342175

Rovirosa, A; Ribonetto, C; del Cerro, A; Luz de Portela, M; Río, M E

1992-12-01

237

Population Expanding with the Phalanx Model and Lineages Split by Environmental Heterogeneity: A Case Study of Primula obconica in Subtropical China  

PubMed Central

Background Current and historical events have both affected the current distribution patterns and intraspecific divergence of plants. While numerous studies have focused on the Qinghai-Tibetan Plateau (QTP), the impacts of such events on the flora of subtropical China remain poorly understood. Subtropical China is famous for its highly complex topography and the limited impact from glaciation during the Pleistocene; this may have resulted in a different genetic legacy for species in this region compared to fully glaciated areas. Methodology/Principal Findings We used plastid and nuclear DNA sequence data and distribution modeling to analyze the divergence patterns and demographic history of Primula obconica Hance, a widespread herbaceous montane species in subtropical China. The phylogenetic analysis revealed two major lineages (lineage A and lineage B), representing a west-east split into the Yunnan and Eastern groups, and the Sichuan and Central groups, respectively. The Eastern and Central groups comprised relatively new derived haplotypes. Nested Clade Analysis and Bayesian Skyline Plot analyses both indicated that P. obconica mainly experienced a gradual expansion of populations. In addition, the simulated distribution of P. obconica during the Last Glacial Maximum was slightly larger than its present-day distribution. Conclusion/Significance Our results are the first to identify a west-east migration of P. obconica. The gradual expansion pattern and a larger potential distribution range in cold periods detected for P. obconica indicate that the population expansion of this species is consistent with the phalanx model. In addition, the current patterns of genetic differentiation have persisted as a result of the extensive environmental heterogeneity that exists in subtropical China.

Yan, Hai-Fei; Zhang, Cai-Yun; Wang, Feng-Ying; Hu, Chi-Ming; Ge, Xue-Jun; Hao, Gang

2012-01-01

238

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

239

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…

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

240

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

PubMed

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. PMID:20826770

Brown, Patrick J P

2010-09-01

241

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

242

The effect of coloured filters on the rate of reading in an adult student population.  

PubMed

Meares-Irlen Syndrome is characterised by visual stress (visual discomfort) and visual perceptual distortions that can be alleviated by individually prescribed coloured filters. The benefit from coloured filters can be demonstrated with the Wilkins Rate of Reading Test (WRRT). Previous research using individually prescribed coloured overlays (sheets of plastic placed on a page) found that between one-fifth and one-third of unselected school-children show a significant (> 5%) improvement in their rate of reading with their chosen overlay. This 5% cut-off has good sensitivity and specificity for predicting those children who will continue to voluntarily use their overlay for a sustained period. Previous research has concentrated on children, and we sought to investigate the immediate effect of overlays on rate of reading in an adult population. Subjects were 113 unselected university students who answered a symptom questionnaire and were tested with the Wilkins Intuitive Overlays and WRRT. Some symptoms were common: 73% reported sore or tired eyes when reading and 40% reported four to 12 headaches a year. One hundred of the subjects chose an overlay as improving their immediate perception of text. These subjects were significantly more likely to report perceptual distortions and visual discomfort on viewing text than subjects who did not choose an overlay. The 100 subjects read 3.8% faster with the overlay than without any overlay (p < 0.00001), whereas the 13 subjects who did not choose an overlay read 1.7% slower with a placebo overlay than without (p = 0.37). Of the subjects who chose an overlay, 38% read more than 5% faster with the overlay and 2% read more than 25% faster. These results are comparable with those obtained for children. We conclude that Meares-Irlen Syndrome is likely to be as common in adults as it is in children. PMID:12477018

Evans, Bruce J W; Joseph, Florence

2002-11-01

243

Reliability of a telephone-based Glasgow Outcome Scale assessment using a structured interview in a heterogenous population of patients and examiners.  

PubMed

A reliable telephone-based Glasgow Outcome Scale (GOS) assessment would be advantageous to both patients and investigators. Using a previously published structured GOS interview and scoring system, the aim of this study was to assess the reliability of telephone-based GOS scores compared to those obtained face-to-face in a heterogenous population of patients and examiners. Sixty-six patients hospitalized for a variety of acute neurological injuries underwent two GOS interviews approximately 90 days after injury. From a pool of six examiners, structured interviews were conducted using a standardized data form containing nine yes/no questions. One interview was conducted face-to-face and the other interview was conducted by telephone, the order being randomly selected. A different examiner conducted the second interview, and was unaware of the findings of the first interview. From this data, a separate investigator assigned GOS scores using standardized criteria. Concordant GOS scores were obtained in 71% (47/66) of patients and discordant scores in 29% (19/66); kappa = 0.56 +/- 0.08 (SE) (95% CI kappa = 0.40-0.73). Patient-, examiner-, and interview-related characteristics had no significant associations with GOS concordance, although patient sex had a significant association with discrepant responses to one specific question (work at previous capacity). When used by multiple examiners to assess patients with diverse neurological conditions, use of a structured GOS examination does not guarantee a reliable telephone-based GOS score. Determination of whether patient sex influences the validity of the structured face-to-face GOS interview is worthy of future study. PMID:17892406

LeGrand, Scott A; Hindman, Bradley J; Dexter, Franklin; Moss, Linda G; Todd, Michael M

2007-09-01

244

Comparison of vocational interests and attitudes of learning-impaired high school students with different cognitive patterns  

Microsoft Academic Search

Research has shown that individuals with learning impairments often have a difficult time finding and maintaining appropriate employment. They may limit their career options and fail to make vocational choices which reflect their cognitive strengths. The population of individuals with learning impairments is cognitively heterogeneous, and their career choices should reflect a fair degree of vocational heterogeneity.^ Students with learning

William Francis Ivory

1996-01-01

245

Heterogeneous voter models  

NASA Astrophysics Data System (ADS)

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

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

2010-07-01

246

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

ERIC Educational Resources Information Center

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

Davis, Jeff

2011-01-01

247

Factorial and Structural Validity of Holland's Hexagonal Model for an Asian Student Population.  

ERIC Educational Resources Information Center

|A study examined the utility of Holland's hexagonal model as a culturally appropriate theoretical framework for U.S. career psychologists working with Asian international students. Chinese-descent international students enrolled in three Southeastern universities (n=170) completed three instruments: Holland's Self-Directed Search (SDS), an…

Tay, Kenneth Kim; Hill, Joseph A.; Ward, Connie M.

248

Smoking Cessation Delivered by Medical Students Is Helpful to Homeless Population  

ERIC Educational Resources Information Center

Objective: The authors pilot a smoking-cessation outreach for the homeless that extends medical students' tobacco cessation education. Method: In this prospective study, second-year medical students administered cognitive behavior therapy or unstructured support to homeless subjects to help them quit smoking. Self-report and biological measures…

Spector, Andrew; Alpert, Hilary; Karam-Hage, Maher

2007-01-01

249

Cardiovascular disease risk factors in the population of secondary school students in Ciechanów.  

PubMed

The aim of this paper was to determine the frequency of occurrence of cardiovascular disease risk factors among the secondary school students in Ciechanów. The study comprised 150 students attending high school, mechanical technical secondary school and a vocational school complex in Ciechanów (province of Mazovia). All the examined students were 17-18 years of age. The study was in the form of an auditory questionnaire. It was conducted in February 2002. To evaluate the state of students' nourishment we used the so-called body mass index (BMI). For the needs of this paper, to examine the amounts of alcohol consumed, the following conversion factor was used: standard portion = 10g pure ethanol. The results were analyzed in accordance with the sex of the examined persons. Among the examined students no cases of obesity or diabetes were found. One third of the polled persons had inherited susceptibility to cardiovascular diseases. 27.3% of the polled secondary school students smoke cigarettes every day (usually 5-10 a day). This fact increases the risk of cardiovascular diseases. The problem of alcohol abuse concerned 6% students, but only every tenth of them declared being a teetotaler. Three fourths of the polled persons regarded the level of their physical activity as moderate. About one third of the examined students accomplish their physical activity exclusively within Physical Education classes. The form of exercise done on their own most frequently was slow and brisk walking. The students usually nourish regularly, eating breakfast, lunch and dinner every day. They eat fruit, cutting down on animal fats and salt. Most of the examined students are exposed to stressful situations, both in their home environment (56.6%) and at school (84.7%). Long-lasting and overlapping stress intensifies the risk of cardiovascular diseases. More than a half of the polled persons ascribe to themselves type A personality features, which makes them more susceptible to coronary heart disease, than type B personality. PMID:15314965

Zo?nierczuk-Kieliszek, Dorota; Pacian, Anna; Koz?owska-Panek, Ewa

2003-01-01

250

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

ERIC Educational Resources Information Center

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

Facing the Future, Lopez Island, WA.

251

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

ERIC Educational Resources Information Center

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

Facing the Future, Lopez Island, WA.

252

Heterogeneity in breast cancer.  

PubMed

Breast cancer is a heterogeneous disease. There is a high degree of diversity between and within tumors as well as among cancer-bearing individuals, and all of these factors together determine the risk of disease progression and therapeutic resistance. Advances in technologies such as whole-genome sequencing and functional viability screens now allow us to analyze tumors at unprecedented depths. However, translating this increasing knowledge into clinical practice remains a challenge in part due to tumor evolution driven by the diversity of cancer cell populations and their microenvironment. The articles in this Review series discuss recent advances in our understanding of breast tumor heterogeneity, therapies tailored based on this knowledge, and future ways of assessing and treating heterogeneous tumors. PMID:21965334

Polyak, Kornelia

2011-10-03

253

[Assignment of students for the Royal School of Medicine on the basis of ethnic minority population in the Ottoman Empire].  

PubMed

Tibhane-i Amire (Royal School of Medicine) was founded in 1827 in order to train Muslim physicians and surgeons equipped with modern medical knowledge ("novel medicine"). Following the Declaration of Tanzimat (Imperial Decree of Reformation) Non-Muslims were permitted to enroll to the School of Medicine just after the decree on January 16, 1841. At the beginning, to room, board and educate students of different religions and sects were not approved. But the Chief Physician and the Dean of the School of Medicine solved the problem by undertaking all the responsibilities. The first year following the afore-mentioned decree, 38 Christian students were enrolled and their number increased to 76 in the next year. In 1847, 29 students from the Jewish community were accepted to the School, for whom all the facilities covering their religious deeds, needs and customs were provided. The same year some Serbian students were accepted and special treatment was requested, since they were kins to the Serbian Prince. Greeks and Walachians were also accepted to the School, as there had not been any political restriction. In 1851 the total student number was 459, among whom there were 14 Non-Muslims. The same year, day students were also admitted as boarders, since it was hard to go to school in winter. In 1857, the Armenian Patriarch was given an audience by the Grand Vizier on an official demand stating that the assignment to them was not in proportion with their population, so it should be increased. This was approved by the Superior Council of Tanzimat. In 1855 the Greek Patriarch demanded officially that this decree should be withdrawn by stating that the Greek population was much larger than the Armenian's. Upon this, the council rearranged the assignment based on a reliable source and determined that it ought to be 30 for Armenians, 46 for Jews and Latin community, 74 for Greeks (including 15 Bulgarians) and totally 150 Non-Muslims. Together with 300 Muslim students, the student number reached up to 450. ... PMID:11625086

Altinta?, A

1995-01-01

254

Population.  

ERIC Educational Resources Information Center

In an effort to help meet the growing interest and concern about the problems created by the rapid growth of population, The International Planned Parenthood Federation has prepared this booklet with the aim of assisting the study of the history and future trends of population growth and its impact on individual and family welfare, national,…

International Planned Parenthood Federation, London (England).

255

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

256

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

PubMed Central

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

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

2013-01-01

257

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

258

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

259

Training and Resource Needs of Teachers Who Provide HIV Education to Special Population Students  

ERIC Educational Resources Information Center

This study identified substantial training and resource needs for special education (SPED), transitional bilingual education/ English as a Second Language (TBE/ESL), and general education (GENED) HIV education teachers relative to providing appropriate, effective HIV education to students with disabilities (SWD) and language minority/Limited…

Sawyer, Richard J.; Blake, Susan; Ledsky, Rebecca; Goodenow, Carol; Evans, Doug

2004-01-01

260

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

261

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

262

Profile of the Graduate Student Population in U.S. Medical Schools.  

ERIC Educational Resources Information Center

|Medical school surveys in 1994-95 and 1995-96 (n=104 schools) found that PhDs accounted for 25-30% of medical school enrollments; in some institutions, it was about half. Trend is toward interdisciplinary rather than departmental degrees. Number of student supported by National Institutes of Health (NIH) research grants was nearly twice that for…

Ammons, Stanley W.; Kelly, Douglas E.

1997-01-01

263

Knowledge of and Attitudes Toward Evolution in a Population of Community College Students  

Microsoft Academic Search

Much attention has been given to the opposition toward the teaching of evolution at the K-12 level and the movement to include alternative theories, such as Intelligent Design (ID), in the science curriculum. However, very little is known regarding the attitudes of community college students toward the study of evolution and the inclusion of ID in biology courses. This lack

Patricia Flower

264

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

ERIC Educational Resources Information Center

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

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

265

Effects of daytime naps on performance and mood in a college student population  

Microsoft Academic Search

Studied the effects of daytime naps on performance and mood in 18 healthy male university students who habitually slept 1\\/2 hr-2 hrs in the afternoon. Measurements were obtained from an auditory reaction time task and a mood adjective checklist 20 min before and after a control condition and 2 EEG recorded afternoons of sleep. The experimental conditions comprised a 2-hr

John M. Taub; Peter E. Tanguay; Douglas Clarkson

1976-01-01

266

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

267

Heterogeneous Gossip  

NASA Astrophysics Data System (ADS)

Gossip-based information dissemination protocols are considered easy to deploy, scalable and resilient to network dynamics. Load-balancing is inherent in these protocols as the dissemination work is evenly spread among all nodes. Yet, large-scale distributed systems are usually heterogeneous with respect to network capabilities such as bandwidth. In practice, a blind load-balancing strategy might significantly hamper the performance of the gossip dissemination.

Frey, Davide; Guerraoui, Rachid; Kermarrec, Anne-Marie; Koldehofe, Boris; Mogensen, Martin; Monod, Maxime; Quéma, Vivien

268

Bringing Lunar and Planetary Science and Exploration to Underrepresented and Underutilized Student Populations  

NASA Astrophysics Data System (ADS)

In order to reach the nation's best talent and brainpower, NASA must inform and inspire all populations including those that have been underutilized and underserved in the past, such as females, African-Americans and Native Americans.

Levine, A. S.

2007-03-01

269

Evidence of hearing loss in a "normally-hearing" college-student population  

PubMed Central

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

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

2011-01-01

270

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

271

Special education and education reform in Mexico: providing quality education to a diverse student population  

Microsoft Academic Search

This paper discusses the reform of basic education in Mexico and the restructuring of special education services that is occurring within the context of that reform. Recent developments in the transformation of educational services for diverse populations are identified and discussed. The activities of the General Directorate of Special Education of the Public Education Secretariat in the Federal District of

Eliseo Guajardo Ramos; Todd V. Fletcher

1998-01-01

272

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

ERIC Educational Resources Information Center

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

Smith, Clayton; Gottheil, Susan

2011-01-01

273

Cellular heterogeneity and molecular evolution in cancer.  

PubMed

Intratumor heterogeneity represents a major obstacle to effective cancer treatment and personalized medicine. However, investigators are now elucidating intratumor heterogeneity at the single-cell level due to improvements in technologies. Better understanding of the composition of tumors, and monitoring changes in cell populations during disease progression and treatment, will improve cancer diagnosis and therapeutic design. Measurements of intratumor heterogeneity may also be used as biomarkers to predict the risk of progression and therapeutic resistance. We summarize important considerations related to intratumor heterogeneity during tumor evolution. We also discuss experimental approaches that are commonly used to infer intratumor heterogeneity and describe how these methodologies can be translated into clinical practice. PMID:23092187

Almendro, Vanessa; Marusyk, Andriy; Polyak, Kornelia

2012-10-22

274

Organizational Crisis Preparedness in Heterogeneous Societies: The OCPH Model  

Microsoft Academic Search

The populations of European societies are heterogeneous and a crucial part of effective crisis preparedness is to customize contingency planning and crisis communication to these populations. The aim of this study is therefore to develop a theoretically based model of organizations' crisis preparedness in heterogeneous societies. Through theoretical and empirical analyses the model for ‘Organizational Crisis Preparedness in Heterogeneous societies’,

Anna Olofsson

2011-01-01

275

Incidence of head injury: lasting effects among college students and working adults in the general population.  

PubMed

224 (21%) of 1067 persons in a nonclinical population surveyed had one or more head injuries resulting in unconsciousness. They had a total of 306 head injuries with 113 (31%) of them resulting in lasting neurological effects. Both in a pilot project and in the main study, headache was the most commonly reported of an array of symptoms that are essentially a postconcussion syndrome. PMID:9017750

Triplett, G; Hill, C; Freeman, L; Rajan, U; Templer, D I

1996-12-01

276

Psychosocial factors and reading difficulties: students with reading difficulties drawn from a representative population sample.  

PubMed

In a representative sample of 2,464 Norwegian adolescents, aged 12-15 years, 7.8% (n= 191) reported reading difficulties (RD). No gender difference was found. Adolescents with RD were compared to classmates on psychosocial variables. In univariate analysis, RD adolescents report higher levels of depressive symptoms, more school stress, worried more about going to school, had lower school grades and lower attachment to parents than those without RD. They also scored lower on Global Self-worth and on Social Acceptance scales. Further, they reported reduced levels of psycho-functioning during the previous year because of mental health problems, they had received more help and had used more medication for such problems. In a multivariate logistic regression analysis, receiving help for mental health problems and reduced psycho-functioning showed the strongest associations with student RD status. No gender interactions were found. The study demonstrated important differences between adolescents with and without RD. PMID:18466186

Undheim, Anne Mari; Sund, Anne Mari

2008-05-06

277

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

SciTech Connect

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

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

1992-01-01

278

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

279

Predicting Population Curves.  

ERIC Educational Resources Information Center

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

Bunton, Matt

2003-01-01

280

The role of controlled propagation on an endangered species: demographic effects of habitat heterogeneity among captive and native populations of the socorro isopod (Crustacea: Flabellifera)  

Microsoft Academic Search

The Socorro isopod, Thermosphaeroma thermophilum, became the focus of a novel conservation strategy when apparent extirpation of the species from the wild prompted construction\\u000a of the Socorro Isopod Propagation Facility (SIPF) near the native spring in Socorro, New Mexico, USA. We subjected captive\\u000a populations to 4 habitat treatments over 2 consecutive 50-month experimental trials. Native populations of T. thermophilum remained

Brian K. Lang; Douglas A. Kelt; Stephen M. Shuster

2006-01-01

281

A Study To Determine How the Office of Student Affairs Can Better Serve the Student Population at Arizona State University at Tempe.  

ERIC Educational Resources Information Center

In 1985, the Office of Student Affairs (OSA) at Arizona State University offered 10 major categories of services to students. Its austere budget allocation was noted as a significant obstacle to an increase in its professional office staff; this led to a concern that the provision of student services was not being optimized. A study was conducted…

Campbell, Charles R.

282

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

283

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

284

The effect of pasture on starling ( Sturnus vulgaris) breeding success and population density in a heterogeneous agricultural landscape in southern Sweden  

Microsoft Academic Search

Populations of European starlings have declined over large parts of northern and western Europe during the last 20 years. It has been suggested that reduced availability of pasture in the agricultural landscape was one reason for this decline. To investigate this, breeding colonies for starlings were established in southern Sweden, in agricultural landscapes with different availabilities of pasture. Agricultural land-use

H. G. Smith; M. Bruun

2002-01-01

285

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

PubMed Central

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

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

2007-01-01

286

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

287

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

ERIC Educational Resources Information Center

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

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

2005-01-01

288

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

289

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

290

The evolution of life histories heterogeneous environments\\  

Microsoft Academic Search

Summary Natural populations live in heterogeneous environments, where habitat variation drives the evolution of phenotypic plasticity. The key feature of population structure addressed in this paper is the net flow of individuals from source (good) to sink (poor) habitats. These movements make it necessary to calculate fitness across the full range of habitats encountered by the population, rather than independently

TADEUSZ J. KAWECKI; STEPHEN C. STEARNS

291

[Eating before of an unselected student population of the 7th to 10th grade in a Berlin school].  

PubMed

In 1990 a study of 32 girls and 44 boys in Grades 7 to 10 in a former "East Berlin" school in the borough of Prenzlauer Berg was carried out in continuation of an "East-West Berlin Study on Eating Disorders in Adolescents" which we had initiated in the mid-eighties. The Eating Attitudes Test (EAT), Eating Disorder Inventory (EDI), State of Comfort Scale (SCS) were used in a one-step study design together with complementary clinical and sociodemographic data, including body weight, height and BMI. On the whole, all students were well aware of their own body measurements and had definite ideas about their ideal body weight. Boys were less sure about their real weight, while girls showed some insecurity in defining their ideal weight. Regardless of weight parameters, girls were more strongly preoccupied with issues specific to eating disorders, such as dissatisfaction with their own body, the quest for a slim figure and diet. They were more severely affected by perceptions of insufficiency. 44% of all girls and 4% of the boys said they had problems with their body weight. These students' intensive preoccupation with issues specific to eating disorders was dependent on their actual body weight. They exhibited more clearly pronounced psychological characteristics of eating disorders. Eating-related and psychological characteristics of eating disorders were significantly more pronounced in girls with irregular menstruation. The correlation between irregular menstruation and individually perceived weight problems was significant. These results are discussed in greater detail with due consideration of the need for understanding the specific dynamics of eating attitudes in the general population. PMID:9553228

Hein, J; Neumärker, K J; Neumärker, U

1998-03-01

292

Pricing Strategies Under Heterogeneous Service Requirements.  

National Technical Information Service (NTIS)

This paper analyzes a communication network, used by customers with heterogeneous service requirements. We investigate priority queueing as a way to establish service differentiation. It is assumed that there is an infinite population of customers, who jo...

M. R. H. Mandjes

2004-01-01

293

Heterogeneity of ITS1 sequences in the biting midge Culicoides impunctatus (Goetghebuer) suggests a population in Argyll, Scotland, may be genetically distinct.  

PubMed

Ribosomal DNA (rDNA) internal transcribed spacer 1 (ITS1) is a useful genomic region for understanding evolutionary and genetic relationships. In the current study, variation in ITS1 from eight Culicoides species was analysed by PCR, DNA restriction analysis, cloning, and sequencing. ITS1 variants were essentially homogenized within a species, as sequences were identical or closely related. However, Culicoides impunctatus ITS1 sequences derived from one (Argyll) of five populations contained considerable genomic diversity. The secondary structure of each ITS1 was computed. The structure aided the production of an accurate alignment and the identification of a large indel. A phylogenetic analysis was performed. Some of the sequences from the diverse Argyll C. impunctatus population were more related to Culicoides imicola, a vector of animal pathogens in the Old World, than they were to the other C. impunctatus sequences. Thus, the rDNA ITS1 regions of individuals in the Argyll C. impunctatus population were not conforming to the general theory of rDNA homogenization through molecular drive. PMID:15190372

Ritchie, Allyson; Blackwell, Alison; Malloch, Gaynor; Fenton, Brian

2004-06-01

294

White blood cell count, sex and age are major determinants of heterogeneity of platelet indices in an adult general population: results from the MOLI-SANI project  

PubMed Central

Background The understanding of non-genetic regulation of platelet indices - platelet count, plateletcrit, mean platelet volume, and platelet distribution width - is limited. The association of these platelet indices with a number of biochemical, environmental and clinical variables was studied in a large cohort of the general population. Design and Methods Men and women (n=18,097, 52% women, 56±12 years) were randomly recruited from various villages in Molise (Italy) in the framework of the population-based cohort study “Moli-sani”. Hemochromocytometric analyses were performed using an automatic analyzer (Beckman Coulter, IL, Milan, Italy). Associations of platelet indices with dependent variables were investigated by multivariable linear regression analysis. Results Full models including age, sex, body mass index, blood pressure, smoking, menopause, white and red blood cell counts, mean corpuscular volume, D-dimers, C-reactive protein, high-density lipoproteins, low-density lipoproteins, triglycerides, glucose, and drug use explained 16%, 21%, 1.9% and 4.7% of platelet count, plateletcrit, mean platelet volume and platelet distribution width variability, respectively; variables that appeared to be most strongly associated were white blood cell count, age, and sex. Platelet count, mean platelet volume and plateletcrit were positively associated with white blood cell count, while platelet distribution width was negatively associated with white blood cell count. Platelet count and plateletcrit were also positively associated with C-reactive protein and D-dimers (P<0.0001). Each of the other variables, although associated with platelet indices in a statistically significant manner, only explained less than 0.5% of their variability. Platelet indices varied across Molise villages, independently of any other platelet count determinant or characteristics of the villages. Conclusions The association of platelet indices with white blood cell count, C-reactive protein and D-dimers in a general population underline the relation between platelets and inflammation.

Santimone, Iolanda; Di Castelnuovo, Augusto; De Curtis, Amalia; Spinelli, Maria; Cugino, Daniela; Gianfagna, Francesco; Zito, Francesco; Donati, Maria Benedetta; Cerletti, Chiara; de Gaetano, Giovanni; Iacoviello, Licia

2011-01-01

295

Time-series analysis of two hydrothermal plumes at 9°50'N East Pacific Rise reveals distinct, heterogeneous bacterial populations.  

PubMed

We deployed sediment traps adjacent to two active hydrothermal vents at 9°50'N on the East Pacific Rise (EPR) to assess the variability in bacterial community structure associated with plume particles on the timescale of weeks to months, to determine whether an endemic population of plume microbes exists, and to establish ecological relationships between bacterial populations and vent chemistry. Automated rRNA intergenic spacer analysis (ARISA) indicated that there are separate communities at the two different vents and temporal community variations between each vent. Correlation analysis between chemistry and microbiology indicated that shifts in the coarse particulate (>1 mm) Fe/(Fe+Mn+Al), Cu, V, Ca, Al, (232) Th, and Ti as well as fine-grained particulate (<1 mm) Fe/(Fe+Mn+Al), Fe, Ca, and Co are reflected in shifts in microbial populations. 16S rRNA clone libraries from each trap at three time points revealed a high percentage of Epsilonproteobacteria clones and hyperthermophilic Aquificae. There is a shift toward the end of the experiment to more Gammaproteobacteria and Alphaproteobacteria, many of whom likely participate in Fe and S cycling. The particle-attached plume environment is genetically distinct from the surrounding seawater. While work to date in hydrothermal environments has focused on determining the microbial communities on hydrothermal chimneys and the basaltic lavas that form the surrounding seafloor, little comparable data exist on the plume environment that physically and chemically connects them. By employing sediment traps for a time-series approach to sampling, we show that bacterial community composition on plume particles changes on timescales much shorter than previously known. PMID:22221398

Sylvan, J B; Pyenson, B C; Rouxel, O; German, C R; Edwards, K J

2012-01-04

296

Effectiveness of the Brief Alcohol and Screening Intervention for College Students (BASICS) Program with a Mandated Population  

ERIC Educational Resources Information Center

Objective: This study evaluated the effectiveness of a large-scale intervention designed to reduce alcohol abuse among adjudicated college students. Participants: Participants were college students mandated to attend a Brief Alcohol Screening and Intervention for College Students (BASICS) program and a randomly selected comparison group of…

DiFulvio, Gloria T.; Linowski, Sally A.; Mazziotti, Janet S.; Puleo, Elaine

2012-01-01

297

The Impact of Engagement with Extracurricular Activities on the Student Experience and Graduate Outcomes for Widening Participation Populations  

ERIC Educational Resources Information Center

|This research examined extracurricular activity (ECA) effects on students' experiences, outcomes and future job prospects. A survey of diverse undergraduate students, along with alumni and potential employer interviews, revealed differences in students' engagement with ECAs beyond the classroom. Variations between "traditional" and "widening…

Stuart, Mary; Lido, Catherine; Morgan, Jessica; Solomon, Lucy; May, Steve

2011-01-01

298

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

299

Nerve terminals of squid photoreceptor neurons contain a heterogeneous population of mRNAs and translate a transfected reporter mRNA.  

PubMed

It is now well established that the distal structural/functional domains of the neuron contain 2a diverse population of mRNAs that program the local synthesis of protein. However, there is still a paucity of information on the composition and function of these mRNA populations in the adult nervous system. To generate empirically, hypotheses regarding the function of the local protein synthetic system, we have compared the mRNAs present in the squid giant axon and its parental cell bodies using differential mRNA display as an unbiased screen. The results of this screen facilitated the identification of 31 mRNAs that encoded cytoskeletal proteins, translation factors, ribosomal proteins, molecular motors, metabolic enzymes, nuclear-encoded mitochondrial mRNAs, and a molecular chaperone. Results of cell fractionation and RT-PCR analyses established that several of these mRNAs were present in polysomes present in the presynaptic nerve terminal of photoreceptor neurons, indicating that these mRNAs were being actively translated. Findings derived from in vitro transfection studies established that these isolated nerve terminals had the ability to translate a heterologous reporter mRNA. Based upon these data, it is hypothesized that the local protein synthetic system plays an important role in the maintenance/remodelling of the cytoarchitecture of the axon and nerve terminal, maintenance of the axon transport and mRNA translation systems, as well as contributing to the viability and function of the local mitochondria. PMID:15305855

Gioio, Anthony E; Lavina, Zeno Scotto; Jurkovicova, Dana; Zhang, Hengshan; Eyman, Maria; Giuditta, Antonio; Kaplan, Barry B

2004-08-01

300

Quasi-one-dimensional waves in rodent populations in heterogeneous habitats: a consequence of elevational gradients on spatio-temporal dynamics.  

PubMed

Wave propagation can be clearly discerned in data collected on mouse populations in the Cibola National Forest (New Mexico, USA) related to seasonal changes. During an exploration of the construction of a methodology for investigations of the spread of the Hantavirus epidemic in mice we have built a system of interacting reaction diffusion equations of the Fisher-Kolmogorov-Petrovskii-Piskunov type. Although that approach has met with clear success recently in explaining Hantavirus refugia and other spatiotemporal correlations, we have discovered that certain observed features of the wave propagation observed in the data we mention are impossible to explain unless modifications are made. However, we have found that it is possible to provide a tentative explanation/description of the observations on the basis of an assumed Allee effect proposed to exist in the dynamics. Such incorporation of the Allee effect has been found useful in several of our recent investigations both of population dynamics and pattern formation and appears to be natural to the observed system. We report on our investigation of the observations with our extended theory. PMID:23219492

Abramson, Guillermo; Giuggioli, Luca; Parmenter, Robert R; Kenkre, V M

2012-12-04

301

Resource heterogeneity can facilitate cooperation  

PubMed Central

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

Kun, Adam; Dieckmann, Ulf

2013-01-01

302

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

ERIC Educational Resources Information Center

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

Griffin, Kimberly A.; Muniz, Marcela M.

2011-01-01

303

The challenge of gene expression profiling in heterogeneous clinical samples.  

PubMed

Almost all samples used in tumor biology, such as tissues and bodily fluids, are heterogeneous, i.e., consist of different cell types. Evaluating the degree of heterogeneity in samples can increase our knowledge on processes such as clonal selection and metastasis. In addition, generating expression profiles from specific sub populations of cells can reveal their distinct functions. Tissue heterogeneity also poses a challenge, as it can confound the interpretation of gene expression data. This chapter will (1) give a brief overview on how heterogeneity may influence gene expression profiling data and (2) describe the methods that are currently available to assess transcriptional biomarkers in a heterogeneous cell population. PMID:22652627

Rodr?guez-Gonzalez, F German; Mustafa, Dana A M; Mostert, Bianca; Sieuwerts, Anieta M

2012-05-29

304

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

305

Integrating web applications to provide an effective distance online learning environment for students  

Microsoft Academic Search

The Human Physiology online course offered by the Department of Physiology at the University of Toronto (www.physiology.utoronto.ca) offers a quality online learning experience and promotes flexibility to its students in terms of time and location, allowing self-directed learning within a semi-structured frame-work. The online course population has expanded, including a more heterogeneous group of students. In addition to the traditional

C. Perumalla; J. Mak; N. Kee; S. Matthews

2011-01-01

306

Thalassaemia and Glucose6Phosphate Dehydrogenase Screening in 13- to 14YearOld Students of the Sardinian Population: Preliminary Findings  

Microsoft Academic Search

Objectives: In this paper we describe the outline and results of a 7-year screening programme for thalassaemias and glucose-6-phosphate dehydrogenase (G6PD) deficiency in 13- to 14-year-old students from the Sardinian population. Method: This programme had several steps: formal education on thalassaemia, request of informed consent by parents, blood testing and genetic counselling. Results:Out of 63,285 subjects tested, 6,521 (10.3%) were

A. Cao; R. Congiu; M. C. Sollaino; M. F. Desogus; F. R. Demartis; D. Loi; M. Cau; R. Galanello

2008-01-01

307

[Review on landscape heterogeneity].  

PubMed

On the base of precedent studies, the occurring mechanism, classification, measurement methods, and the important role of landscape heterogeneity in landscape ecology were reviewed. The inner and outer uncertain factors result in landscape heterogeneity. Landscape heterogeneity has close relations with landscape stability, landscape design, architecture, management and disturbance, scale and ecological diversity in ecology. Complexity of landscape heterogeneity research, non-system of measurement indices and methods, difficulties and limitations of landscape heterogeneity modelling were all discussed respectively. In addition, it is suggested that the theory and methods of ecological complexity should be used to improve landscape heterogeneity research. PMID:12222062

Zhao, Yutao; Yu, Xinxiao; Guang, Wenbin

2002-04-01

308

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

ERIC Educational Resources Information Center

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

Tuck Bonner, Natalie Christine

2009-01-01

309

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

ERIC Educational Resources Information Center

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

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

2012-01-01

310

One medical school's effort to ready the workforce for the future: preparing medical students to care for populations who are publicly insured.  

PubMed

This article describes the development, implementation, and evaluation of a curriculum project designed to prepare medical students to care for populations who have Medicaid or a low socioeconomic status (SES). The setting for the project was a community-based medical school, the College of Human Medicine (CHM) at Michigan State University. This article describes a four-year process of curriculum development and offers examples of specific changes that CHM made to courses and clerkships. CHM modified 25% of preclinical courses, five core clerkships of year three, and two clerkships (Senior Surgery and Senior Internal Medicine) of year four. The authors describe highlights of outcomes in student performance, course and clerkship ratings, attitudes, professional goals, student self-assessment of their skills, and feedback from residency program directors. The authors identified four items on the Association of American Medical Colleges (AAMC) Graduation Questionnaire as related to the project and tracked them as an outcome measure of student attitudes related to the social responsibility of physicians. Attitudes of the students who experienced the modified curriculum showed greater agreement with AAMC Graduation Questionnaire items than the previous class at CHM and than their classmates across the country. The majority of residency program directors rated CHM graduates as more skilled than their peers in applying cultural competence, working with patients who have Medicaid or a low SES, and using community resources. The authors discuss factors that contributed to the successful implementation of curricular changes as well as challenges to their implementation. PMID:18580078

Turner, Jane L; Farquhar, Lynda

2008-07-01

311

Stoichiometry and population dynamics  

Microsoft Academic Search

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

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

2004-01-01

312

Population Peril  

NSDL National Science Digital Library

Rising air temperatures have changed the extent and timing of sea ice formation in the Arctic, forcing some polar bear populations to go longer each year without food. In this activity, students assume the role of graduate students advising an intern part

Constible, Juanita; Sandro, Luke; Lee Jr., Richard E.

2008-10-01

313

Impact of heterogeneous human activities on epidemic spreading  

NASA Astrophysics Data System (ADS)

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

Yang, Zimo; Cui, Ai-Xiang; Zhou, Tao

2011-11-01

314

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

315

Statistical Treatment Rules for Heterogeneous Populations  

Microsoft Academic Search

An important objective of empirical research on treatment response is to provide decision makers with information useful in choosing treatments. This paper studies minimax-regret treatment choice using the sample data generated by a classical randomized experiment. Consider a utilitarian social planner who must choose among the feasible statistical treatment rules, these being functions that map the sample data and observed

Charles F. Manski

2004-01-01

316

Heterogeneous Crystal Populations: Signatures, Genesis and Chronologies  

NASA Astrophysics Data System (ADS)

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

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

2005-12-01

317

Do Your Homework! Investigating the Role of Culturally Relevant Pedagogy in Comprehensive School Reform Models Serving Diverse Student Populations  

ERIC Educational Resources Information Center

|Like the African proverb, "It takes a village to raise a child", many educational researchers charge that it takes a comprehensive school reform to raise student achievement. With the passing of the No Child Left Behind legislation in 2002, national officials authorized the Comprehensive School Reform program to support low performing schools as…

Durden, Tonia

2008-01-01

318

The Paradoxes of Freedom: A Thematic Approach to Teaching a Compulsory Composition Course to a Multi-Ethnic Student Population.  

ERIC Educational Resources Information Center

|A composition teacher at a New York City community college where cooperative education is stressed found that focusing the writing of his multiethnic students on the theme of freedom helped them look at their lives differently, revealing the contradictions involved in their beliefs, ideals, and prejudices. The course began with a discussion of…

Lynch, Daniel J.

319

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

ERIC Educational Resources Information Center

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

Jasti, Sunitha; Kovacs, Szilvia

2010-01-01

320

The Impact of Rapid Automatized Naming and Phonological Awareness on the Reading Fluency of a Minority Student Population  

ERIC Educational Resources Information Center

The purpose of this study was to explore the relationship between phonological awareness (PA) and rapid automatized naming (RAN) on the reading fluency (RF) of students from traditionally underrepresented groups. The study included 86 participants attending 1st through 4th grade within an inner-city charter school located in a high-poverty, urban…

Taub, Gordon E.; Szente, Judit

2012-01-01

321

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

ERIC Educational Resources Information Center

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

DiMino, John; Blau, Gary

2012-01-01

322

The Relationship Between Wait Time After Triage and Show Rate for Intake in a Nonurgent Student Population  

Microsoft Academic Search

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

John DiMino; Gary Blau

2012-01-01

323

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

ERIC Educational Resources Information Center

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

Jasti, Sunitha; Kovacs, Szilvia

2010-01-01

324

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

325

Quantifying network heterogeneity  

NASA Astrophysics Data System (ADS)

Despite degree distributions give some insights about how heterogeneous a network is, they fail in giving a unique quantitative characterization of network heterogeneity. This is particularly the case when several different distributions fit for the same network, when the number of data points is very scarce due to network size, or when we have to compare two networks with completely different degree distributions. Here we propose a unique characterization of network heterogeneity based on the difference of functions of node degrees for all pairs of linked nodes. We show that this heterogeneity index can be expressed as a quadratic form of the Laplacian matrix of the network, which allows a spectral representation of network heterogeneity. We give bounds for this index, which is equal to zero for any regular network and equal to one only for star graphs. Using it we study random networks showing that those generated by the Erdös-Rényi algorithm have zero heterogeneity, and those generated by the preferential attachment method of Barabási and Albert display only 11% of the heterogeneity of a star graph. We finally study 52 real-world networks and we found that they display a large variety of heterogeneities. We also show that a classification system based on degree distributions does not reflect the heterogeneity properties of real-world networks.

Estrada, Ernesto

2010-12-01

326

Quantifying network heterogeneity.  

PubMed

Despite degree distributions give some insights about how heterogeneous a network is, they fail in giving a unique quantitative characterization of network heterogeneity. This is particularly the case when several different distributions fit for the same network, when the number of data points is very scarce due to network size, or when we have to compare two networks with completely different degree distributions. Here we propose a unique characterization of network heterogeneity based on the difference of functions of node degrees for all pairs of linked nodes. We show that this heterogeneity index can be expressed as a quadratic form of the Laplacian matrix of the network, which allows a spectral representation of network heterogeneity. We give bounds for this index, which is equal to zero for any regular network and equal to one only for star graphs. Using it we study random networks showing that those generated by the Erdös-Rényi algorithm have zero heterogeneity, and those generated by the preferential attachment method of Barabási and Albert display only 11% of the heterogeneity of a star graph. We finally study 52 real-world networks and we found that they display a large variety of heterogeneities. We also show that a classification system based on degree distributions does not reflect the heterogeneity properties of real-world networks. PMID:21230700

Estrada, Ernesto

2010-12-02

327

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.

2012-01-01

328

Lipid rafts: heterogeneity on the high seas.  

PubMed Central

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

Pike, Linda J

2004-01-01

329

Translating research into practice: targeting negative thinking as a modifiable risk factor for depression prevention in the college student population.  

PubMed

This article describes the effects of an evidence-based depression prevention intervention on the depressive symptomatology, negative thinking, and self-esteem in college students. A feasibility study was conducted using pre-test post-test design sampling a total of 12 college students. Participants underwent 4-weeks of psychological treatment using Peden's cognitive behavioral group intervention. The Beck Depression Inventory, Crandell Cognitions Inventory, and Rosenberg Self-Esteem Scale were administered at two time points: prior to the intervention (T1) and 4weeks later (T2). Paired t-test analysis found participants had significantly decreased depressive symptoms and negative thinking, and significantly increased self-esteem from T1 to T2. PMID:23706889

Buchanan, Jenna L

2013-04-16

330

What else are psychotherapy trainees learning? A qualitative model of students' personal experiences based on two populations.  

PubMed

Abstract After an introductory course in experiential-integrative psychotherapy, 21 graduate students provided personal narratives of their experiences, which were analyzed using the grounded theory method. Results produced 37 hierarchically organized experiences, revealing that students perceived multiple changes in both professional (i.e., skill acquisition and learning related to the therapeutic process) and personal (i.e., self growth in a more private sphere) domains. Analysis also highlighted key areas of difficulties in training. By adding the personal accounts of graduate trainees, this study enriches and extends Pascual-Leone et al.'s (2012) findings on undergraduates' experiences, raising the number of cases represented in the model to 45. Findings confirm the model of novice trainee experiences while highlighting the unique experiences of undergraduate vs. graduate trainees. PMID:23964814

Pascual-Leone, Antonio; Rodriguez-Rubio, Beatriz; Metler, Samantha

2013-06-25

331

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

NASA Astrophysics Data System (ADS)

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

Tuck Bonner, Natalie Christine

332

Heterogeneous Chip Multiprocessors  

Microsoft Academic Search

Heterogeneous (or asymmetric) chip multiprocessors present unique opportunities for improving system throughput, reducing processor power, and mitigating Amdahl's law. On-chip heterogeneity allow the processor to better match execution resources to each application's needs and to address a much wider spectrum of system loads - from low to high thread parallelism - with high efficiency.

Rakesh Kumar; Dean M. Tullsen; Norman P. Jouppi; Parthasarathy Ranganathan

2005-01-01

333

Heterogeneous particle swarm optimizers  

Microsoft Academic Search

Particle swarm optimization (PSO) is a swarm intelligence technique originally inspired by models of flocking and of social influence that assumed homogeneous individuals. During its evolution to become a practical optimization tool, some heterogeneous variants have been proposed. However, heterogeneity in PSO algorithms has never been explicitly studied and some of its potential effects have therefore been overlooked. In this

Marco Antonio Montes de Oca; Jorge Peña; Thomas Stützle; Carlo Pinciroli; Marco Dorigo

2009-01-01

334

Heterogeneous Specification and the Heterogeneous Tool Set  

Microsoft Academic Search

features (like modalities, higher-order polymorphism, and calculi for concurrent systems) shall be combined. In such cases, a true combination of all the used logics will quickly become too complex. Hence, heterogeneous spec- ification provide a weaker form of logic combination (corresponding to weighted colimits), where basically the logics are put side by side, but can interact via logic translations. Using

Till Mossakowski

2005-01-01

335

Students' attitudes towards suicide  

Microsoft Academic Search

Attitudes of 800 college students from nine institutions were assessed by means of a 100 item Suicide Opinion Questionnaire. The results indicate both wide heterogeneity and communality of attitudes. Students see depression but not mental illness as a predisposing aspect. They exhibit considerable individual differences and intraindividual indecision as to religious precepts vis-a-vis suicide, see suicide as a “cry for

George Domino; Linda Gibson; Steven Poling; Laurie Westlake

1980-01-01

336

Heterogeneity of intracellular replication of bacterial pathogens.  

PubMed

Intracellular growth of bacterial pathogens is usually measured at the whole population level, which masks potential cell-to-cell variation. More direct measurements of replication using microscopy and Flow Cytometry have revealed extensive heterogeneity among populations of intracellular bacteria. Heterogeneity could result from differential exposure to nutritional deprivation and host cell antimicrobial activities, as well as variability in production or efficacy of virulence molecules. Furthermore, bacteria have evolved specific mechanisms to generate epigenetic variation. These include unequal partitioning of proteins during cell division, genetic phase variation and activation of toxin/antitoxin systems. An important aspect of heterogeneity concerns the generation of viable, non-replicating bacteria. These are predicted to confer tolerance to host-induced stress and antibiotics, and to be sources of persistent infection. PMID:23485258

Helaine, Sophie; Holden, David W

2013-02-26

337

Divergent selection and heterogeneous genomic divergence  

Microsoft Academic Search

Levels of genetic differentiation between populations can be highly variable across the genome, with divergent selection contributing to such heterogeneous genomic divergence. For example, loci under divergent selection and those tightly physically linked to them may exhibit stronger differentiation than neutral regions with weak or no linkage to such loci. Divergent selection can also increase genome-wide neutral differentiation by reducing

PATRIK NOSIL; DANIEL J. FUNK; DANIEL ORTIZ-BARRIENTOS

2009-01-01

338

Hand osteoarthritis—a heterogeneous disorder  

Microsoft Academic Search

Hand osteoarthritis (OA) is a prevalent disorder. Hand OA is not one single disease, but a heterogeneous group of disorders. Radiographic signs of hand OA, such as osteophytes or joint space narrowing, can be found in up to 81% of the elderly population. Several hand OA subsets—such as nodal interphalangeal OA, thumb base OA and erosive OA—can be discriminated. Furthermore,

Wing-Yee Kwok; Margreet Kloppenburg

2011-01-01

339

DR3 Heterogeneity in American Blacks.  

National Technical Information Service (NTIS)

The heterogeneity of DR3-associated haplotypes in American Blacks is striking when compared with that in the Caucasoid populations. In American Blacks, only 7.7% of DR3-positive individuals are Dw3. Three DR3-associated haplotypes are generally observed i...

A. H. Johnson T. Fang-Tang S. Rosen-Bronson F. M. Robbins N. Steiner

1989-01-01

340

Psychometric Properties of the Arabic Version of the Obsessive Compulsive Beliefs Questionnaire-44 in a Student Population  

PubMed Central

Objective We examined the psychometric properties of the Arabic version of the Obsessive Compulsive Beliefs Questionnaire-44 (OBQ-44) in a sample of Kuwait University students. This questionnaire was developed by the Obsessive Compulsive Cognitions Working Group in order to assess belief domains believed to be crucial in the development of obsessive compulsive symptoms. Method The Arabic version of the OBQ-44 was developed according to the standard translation and back-translation methods. The Arabic versions of the OBQ-44, the Maudsley Obsessive - Compulsive Inventory (MOCI), and Beck Depression Inventory-Revised (BDI-II) were then administered on a sample of 200 Kuwait University students from the faculty of humanities chosen through random cluster sampling. Retest was administered within a 4 week time period. Results The results of principle component factor analysis with varimax rotation indicated 6 factors which overlapped to a high degree. A 3 factor solution was chosen based on the scree plot and factor loadings which explained 36.12% of the variance. The factors were labeled as responsibility and threat estimation (RT), importance and control of thought (ICT) and perfectionism/Certainty (PC). The reliability coefficient of the three factors and the total score were assessed using three methods: Internal consistency, Test-retest reliability and Split-half reliability. Results showed an acceptable internal consistency for the Arabic version of the OBQ-44. Regarding the validity of OBQ-44, the instrument correlated with the total score of MOCI and most of its subscales. Conclusion These data support the reliability and validity of the OBQ-44 in a sample of Kuwait University students.

Rahat, Maryam; Mohamadi, Norolah

2012-01-01

341

Factors that correlate with the U.S. Medical Licensure Examination Step-2 scores in a diverse medical student population.  

PubMed Central

OBJECTIVE: To assess factors that correlate with performance on U.S. Medical Licensure Examination (USMLE) Step-2 examination. Our hypothesis was that demographic factors, faculty assessments and other standardized test scores will correlate with students' performance on USMLE Step 2. STUDY DESIGN: A comparison of standardized examinations and demographic factors with USMLE Step-2 scores as the outcome variable was accomplished using the educational records of 171 medical students. RESULTS: Mean USMLE Step 2, USMLE Step 1, NBME-OB/GYN and MCAT scores, respectively, were 190.63, 194.53, 67.47 and 24.03. Positive correlations of USMLE Step 2 were: USMLE Step-1 scores (r=0.681, p=0.000); MCAT scores (r=0.524, p=0.000); NBME-OB/GYN scores (r=0.614, p=0.000); year of OB/GYN rotation (r=0.432, p=0.000); faculty grades (r=0.400, p=0.000); undergraduate GPA (r=0.287, p=0.000); and science GPA (r=0.255, p=0.002). Negative correlations of USMLE Step 2 were students' increasing age (r=-0.405, p=0.000), increasing number of MCAT attempts (r=-0.182, p=0.000) and increasing number of NBME-OB/GYN attempts (r=-0.310, p=0.000). There was no correlation with gender or race. Logistic regression analysis showed that a failing NBME-OB/GYN score (p=0.008), failing USMLE Step-1 score (p=0.01), failing faculty grade (p=0.029) and multiple MCAT attempts (p=0.033) independently increased the risk of failing USMLE Step 2. CONCLUSIONS: Premedical test-taking abilities (MCAT scores), results of preclinical standardized tests (USMLE Step 1) and performance on clinical rotations (NBME-OB/GYN score and faculty grade) correlate significantly with USMLE scores. These findings may assist educators in selecting medical students at risk of performing poorly on the USMLE Step-2 examinations.

Ogunyemi, Dotun; Taylor-Harris, De Shawn

2005-01-01

342

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

2012-06-11

343

Heterogeneity in Cushing's disease.  

PubMed

Some patients with Cushing's disease respond to neuropharmacological treatment, whereas others do not. This apparent heterogeneity has been attributed to the existence of a separate form of Cushing's disease of putative neurointermediate lobe origin as opposed to Cushing's disease of anterior pituitary origin. The present review summarizes recent observations in human and canine Cushing's disease which mitigate against this view. We propose that heterogeneity in Cushing's disease is related to heterogeneity of the normal anterior pituitary corticotroph. However, the most fundamental questions concerning the pathogenesis of Cushing's disease remain unanswered. PMID:2192296

Croughs, R J; Rijnberk, A; Koppeschaar, H P

1990-04-01

344

World Population: Facts in Focus. World Population Data Sheet Workbook. Population Learning Series.  

ERIC Educational Resources Information Center

This workbook teaches population analysis using world population statistics. To complete the four student activity sheets, the students refer to the included "1988 World Population Data Sheet" which lists nations' statistical data that includes population totals, projected population, birth and death rates, fertility levels, and the gross national…

Crews, Kimberly A.

345

Conditional Likelihood Models for Heterogeneity in Longitudinal (Panel) Data.  

National Technical Information Service (NTIS)

The report develops econometric models for heterogeneity in panel data. The conditional likelihood approach, which requires few and unrestrictive assumptions about the distribution of unobservables in the population, is used. The techniques are applied to...

N. M. Kiefer

1980-01-01

346

Challenging Student Behaviour  

ERIC Educational Resources Information Center

|The issue of poor student behaviour within higher education institutions (HEIs) has been well documented in recent years. Although the number of reported cases constitutes a very small percentage of the overall student population in the UK, the impact of student misconduct on the rest of the student body and staff in HEIs can be substantial. For…

Jones, Glyn; Philp, Clare

2011-01-01

347

On the relationship between autistic traits and executive functioning in a non-clinical Dutch student population.  

PubMed

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 examined by means of a random number generation test and a phonemic fluency test. Using appropriate dependent measures, the following EF components were examined: 1) inhibition of prepotent responding, 2) simple output inhibition, 3) working memory monitoring and updating, and 4) switching. No significant relationship was found between the AQ and each of the four components of EF. However, two TCI subscales were reliably correlated with either the working memory or the shifting component. These results were discussed in view of the concept of an autism spectrum with respect to executive abilities. PMID:22700989

Maes, Joseph H R; Vissers, Constance Th W M; Egger, Jos I M; Eling, Paul A T M

2012-06-14

348

Debugging heterogeneous applications with Pangaea  

Microsoft Academic Search

Heterogeneous computing environments pose special challenges for debugging. They present the same difficulties as parallel computing environments, including asynchronous communication, non-detenninism, and increased state information. In addition, debugging in heterogeneous environments is complicated by the distribution of work across diverse computational platforms and heterogeneous communication networks. In this paper we describe Pangaea, a tool for debugging heterogeneous applications targeted to

Leesa Hicks; Francine Berman

1996-01-01

349

The Role of Postsecondary Education in Welfare ReformOhio’s Jobs Student Retention Program  

Microsoft Academic Search

The 1996 federal welfare reform legislation encourages quick employment over education and training for the nation’s welfare recipients. However, some argue that a one-size-fits-all approach ignores the heterogeneity of this population. This article presents findings from a net impact evaluation of Ohio’s JOBS Student Retention Program (JSRP), a program designed to facilitate success for public assistance recipients at 2-year community

Kevin Hollenbeck; Jean Kimmel

2002-01-01

350

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

351

AGEING AND PERSONAL RETIREMENT SAVINGS PLAN PARTICIPATION WITH HETEROGENEITY IN PREFERENCES: THE PORTUGUESE CASE  

Microsoft Academic Search

This paper analyses the relationship between ageing and personal retirement savings plan participation in the Portuguese population, taking into account heterogeneity and endogeneity in preferences. A mixed logit model is used to analyse the determinants of retirement saving behaviour, allowing for heterogeneity and endogeneity in the responses. We find considerable heterogeneity among individuals (in terms of socio- economic variables such

Carlos Pestana Barrosa

352

Host heterogeneity and disease endemicity: a moment-based approach.  

PubMed

This paper investigates the possibility of understanding the effects of host heterogeneity on disease levels through the use of moment approximations. The approach is to avoid assumptions about the distribution of mixing rates (or other parameters) in the population, by treating the low-order moments of the distribution as estimable parameters. This approach, while approximate, can greatly reduce the number of parameters needed to explore the effects of population heterogeneity on disease dynamics. This makes the approach useful for both inference and prediction, and also for gaining insight into the qualitative effects of heterogeneity on the spread of disease. This paper focuses on populations with variations in mixing rate and random mixing. It is shown that moment-based approximations can provide good quantitative estimates of disease dynamics, as well as aiding in qualitative under- standing, over a respectable range of parameters. It is hoped that this approach will provide a useful complement to more traditional box models of heterogeneity. PMID:10607525

Dushoff, J

1999-12-01

353

Junior Biology, Populations.  

ERIC Educational Resources Information Center

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

Hamilton City Board of Education (Ontario).

354

Heterogeneous waste processing  

SciTech Connect

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

Vanderberg, L.A.; Sauer, N.N.; Brainard, J.R.; Foreman, T.M.; Hanners, J.L.

2000-06-20

355

Heterogeneous High Performance Computer  

Microsoft Academic Search

This paper discusses the proven concept of marrying the computing capabilities of a cluster computer with the reconfigurability of adaptive computing systems into a 48 node heterogeneous high performance computer (HHPC) with 34 TOPS peak performance. This system has shown over two years of success supporting the Signal and Image Processing (SIP), Forces Modeling and Simulation (FMS), Computational Electromagnetics and

Virginia W. Ross

2005-01-01

356

Improved Heterogeneous Distance Functions  

Microsoft Academic Search

Instance-based learning techniques typically handle continuous and linear input values well, but often do not handle nominal input attributes appropriately. The Value Difference Metric (VDM) was designed to find reasonable distance values between nominal attribute values, but it largely ignores continuous attributes, requiring discretization to map continuous values into nominal values. This paper proposes three new heterogeneous distance functions, called

D. Randall Wilson; Tony R. Martinez

1997-01-01

357

Fluctuations and membrane heterogeneity  

Microsoft Academic Search

Biological membranes contain many specialized domains, ranging from tens of nanometers to several microns in size and characterized by different concentrations and compositions of protein. Because these domains influence membrane function, considerable attention has focused on understanding their origin. Here it is shown that number fluctuations and nonspecific interprotein interactions can lead to considerable heterogeneity in the distribution of membrane

James R. Abney; Bethe A. Scalettar

1995-01-01

358

Heterogeneity of Dutch rainfall  

Microsoft Academic Search

Rainfall data for the Netherlands have been used in this study to investigate aspects of heterogeneity of rainfall, in particular local differences in rainfall levels, time trends in rainfall, and local differences in rainfall trend. The possible effect of urbanization and industrialization on the distribution of rainfall has also been studied. Consideration has been given to whether local differences in

J. V. Witter

1984-01-01

359

The heterogeneous home  

Microsoft Academic Search

Due to several recent trends, the domestic environment has become more homogeneous and undifferentiated. Draw- ing on concepts from environmental psychology, we critique these trends. We propose heterogeneity as a new framework for domestic design, and we present design sketches that il- lustrate how ubiquitous computing technologies can inter- act with the domestic environment to create a more varied and

Ryan Aipperspach; Ben Hooker; Allison Woodruff

2008-01-01

360

Peer Consultants: A New Role for Student Paraprofessionals.  

ERIC Educational Resources Information Center

Describes a student organization development program composed of undergraduate paraprofessionals who provide services to student organizations. Discusses selection and training of students, service delivery, and populations served. (JAC)

Presser, Nan R.; And Others

1984-01-01

361

Liver NKT cells: an account of heterogeneity  

Microsoft Academic Search

The liver is a rich provenance of an unconventional group of T cells called natural killer T (NKT) cells that coexpress NKR-P1, a type II membrane glycoprotein of the C-type lectin superfamily (NK1.1). Accumulating evidence suggests that NKT cells comprise a far more heterogeneous population than originally thought. In addition to ‘classical’ NKT cells, which are restricted by CD1d, ‘nonclassical’

Masashi Emoto; Stefan H. E. Kaufmann

2003-01-01

362

Mathematical analysis of epidemiological models with heterogeneity  

SciTech Connect

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

Van Ark, J.W.

1992-01-01

363

Habitat Heterogeneity of Cycas micronesica Seed Chemistry in Guam's Forest  

Microsoft Academic Search

Understanding spatial structure of secondary metabolites with abiotic and biotic chorographers of chemical heterogeneity in natural populations may allow deeper insights into their function at the plant and community levels. Cycads are an ancient group of plants characterized by opulent secondary chemistry. Cycas micronesica K.D. Hill seed chemistry was determined in seven populations throughout Guam to determine if steryl glucosides

THOMAS E. MARLER; VIVIAN LEE; CHRISTOPHER A. SHAW

2007-01-01

364

Impact of Sorbic Acid on Germination and Outgrowth Heterogeneity of Bacillus cereus ATCC 14579 Spores  

PubMed Central

Population heterogeneity complicates the predictability of the outgrowth kinetics of individual spores. Flow cytometry sorting and monitoring of the germination and outgrowth of single dormant spores allowed the quantification of acid-induced spore population heterogeneity at pH 5.5 and in the presence of sorbic acid. This showed that germination efficiency was not a good predictor for heterogeneity in final outgrowth.

van Melis, Clint C. J.; Sanders, Jan Willem; Nierop Groot, Masja N.; Abee, Tjakko

2012-01-01

365

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

Microsoft Academic Search

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

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

2003-01-01

366

Genetic Hitchhiking under Heterogeneous Spatial Selection Pressures  

PubMed Central

During adaptive evolutionary processes substantial heterogeneity in selective pressure might act across local habitats in sympatry. Examples are selection for drug resistance in malaria or herbicide resistance in weeds. In such setups standard population-genetic assumptions (homogeneous constant selection pressures, random mating etc.) are likely to be violated. To avoid misinferences on the strength and pattern of natural selection it is therefore necessary to adjust population-genetic theory to meet the specifics driving adaptive processes in particular organisms. We introduce a deterministic model in which selection acts heterogeneously on a population of haploid individuals across different patches over which the population randomly disperses every generation. A fixed proportion of individuals mates exclusively within patches, whereas the rest mates randomly across all patches. We study how the allele frequencies at neutral markers are affected by the spread of a beneficial mutation at a closely linked locus (genetic hitchhiking). We provide an analytical solution for the frequency change and the expected heterozygosity at the neutral locus after a single copy of a beneficial mutation became fixed. We furthermore provide approximations of these solutions which allow for more obvious interpretations. In addition, we validate the results by stochastic simulations. Our results show that the application of standard population-genetic theory is accurate as long as differences across selective environments are moderate. However, if selective differences are substantial, as for drug resistance in malaria, herbicide resistance in weeds, or insecticide resistance in agriculture, it is necessary to adapt available theory to the specifics of particular organisms.

Schneider, Kristan A.; Kim, Yuseob

2013-01-01

367

Genetic structure of human populations  

Microsoft Academic Search

The difficulty of extrapolating from inbred mouse strains used for the assessment of toxicological responses to the human population that may be exposed to the potentially toxic substance is discussed. Conventional risk estimation procedures assume little heterogeneity among members of the population in their response to a substance. This ignores the inherent genetic diversity present in human populations. Measurement of

William J. Schull

1979-01-01

368

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

369

The significance of biological heterogeneity  

Microsoft Academic Search

Heterogeneity of expression for a variety of characteristics is found among malignant cells in the organism and in culture. Normal cells are relatively uniform when organized in a tissue, but become heterogeneous for many characteristics when they are dispersed and grown in monolayer culture. The heterogenizing effect of growth in culture indicates that the morphology and behavior of normal cells

Harry Rubin

1990-01-01

370

Exploiting Hierarchy in Heterogeneous Environments  

Microsoft Academic Search

Heterogeneous cluster environmentsare becomingan in- creasingly popular platform for executing parallel applica- tions. Efficient heterogeneous parallel applications must account for the differences inherent in such an environ- ment. Specifically, faster machines should possess more data items than their slower counterparts and communi- cation should be minimized over slow network links. We propose the -Heterogeneous Bulk Synchronous Parallel (HBSP ) model,

Tiffani L. Williams; Rebecca J. Parsons

2001-01-01

371

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

372

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

373

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

374

Area-heterogeneity tradeoff and the diversity of ecological communities  

PubMed Central

For more than 50 y ecologists have believed that spatial heterogeneity in habitat conditions promotes species richness by increasing opportunities for niche partitioning. However, a recent stochastic model combining the main elements of niche theory and island biogeography theory suggests that environmental heterogeneity has a general unimodal rather than a positive effect on species richness. This result was explained by an inherent tradeoff between environmental heterogeneity and the amount of suitable area available for individual species: for a given area, as heterogeneity increases, the amount of effective area available for individual species decreases, thereby reducing population sizes and increasing the likelihood of stochastic extinctions. Here we provide a comprehensive evaluation of this hypothesis. First we analyze an extensive database of breeding bird distribution in Catalonia and show that patterns of species richness, species abundance, and extinction rates are consistent with the predictions of the area–heterogeneity tradeoff and its proposed mechanisms. We then perform a metaanalysis of heterogeneity–diversity relationships in 54 published datasets and show that empirical data better fit the unimodal pattern predicted by the area–heterogeneity tradeoff than the positive pattern predicted by classic niche theory. Simulations in which species may have variable niche widths along a continuous environmental gradient are consistent with all empirical findings. The area–heterogeneity tradeoff brings a unique perspective to current theories of species diversity and has important implications for biodiversity conservation.

Allouche, Omri; Kalyuzhny, Michael; Moreno-Rueda, Gregorio; Pizarro, Manuel; Kadmon, Ronen

2012-01-01

375

Early Identification of Reading Difficulties Using Heterogeneous Developmental Trajectories  

Microsoft Academic Search

Serious conceptual and procedural problems associated with current diagnostic methods call for alternative approaches to assessing and diagnosing students with reading problems. This study presents a new analytic model to improve the classification and prediction of children's reading development. Growth mixture modeling was used to identify the presence of 10 different heterogeneous developmental patterns. In all, 411 children in kindergarten

Christy Kim Boscardin; Bengt O. Muthén; David J. Francis; Eva L. Baker

2008-01-01

376

Restructuring Heterogeneous Classes for Cognitive Development: Social Interactive Perspective.  

ERIC Educational Resources Information Center

|Describes a study of students in grades three, four, and five that tried an educational application derived from the social constructivism view based on theories of Vygotsky and Piaget to improve cognitive development in a heterogeneous class. Path analysis showed that complex learning techniques are related to cognitive development. (Author/LRW)|

Ben-Ari, Rachel; Kedem-Friedrich, Peri

2000-01-01

377

Science Education and ESL Students  

ERIC Educational Resources Information Center

|The number of students who learn English as a second language (ESL) in U.S. schools has grown significantly in the past decade. This segment of the student population increased by 56% between the 1994-95 and 2004-05 school years (NCLR 2007). As the ESL student population increases, many science teachers struggle to tailor instructional materials,…

Allen, Heather; Park, Soonhye

2011-01-01

378

Hispanic Student Achievement. Research Brief  

ERIC Educational Resources Information Center

|What are the factors affecting the achievement of Hispanic high school youth? Hispanic Americans are the largest growing population in the United States. Currently, Hispanic students make up more than 20% of the U.S. school population and, in 23 of the 50 states, Hispanic students outnumber African American and Asian students. During the 1970s…

Hansen, Angela L.

2005-01-01

379

Population Issues. Resources in Technology.  

ERIC Educational Resources Information Center

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

Technology Teacher, 1991

1991-01-01

380

Evolution of Cooperation in Evolutionary Games for Heterogeneous Interactions  

NASA Astrophysics Data System (ADS)

When a population structure is modelled as a square lattice, the cooperation may be improved for an evolutionary prisoner dilemma game or be inhibited for an evolutionary snowdrift game. In this work, we investigate cooperation in a population on a square lattice where the interaction among players contains both prisoner dilemma game and snowdrift game. The heterogeneity in interaction is introduced to the population in two different ways: the heterogenous character of interaction assigned to every player (HCP) or the heterogenous character of interaction assigned to every link between any two players (HCL). The resonant enhancement of cooperation in the case of HCP is observed while the resonant inhibition of cooperation in the case of HCL is prominent. The explanations on the enhancement or inhibition of cooperation are presented for these two cases.

Qian, Xiao-Lan; Yang, Jun-Zhong

2012-04-01

381

Female Student Athletes and Student Athletes of Color.  

ERIC Educational Resources Information Center

|Addresses the experiences of the growing population of women student athletes and student athletes of color. Proposes a culturally responsive approach for student affairs professionals working with these athletes that supports the students in managing internal and external conflict related to their identities and roles. (Contains 40 references.)…

Person, Dawn R.; Benson-Quaziena, Marcella; Rogers, Ann Marie

2001-01-01

382

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

383

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

384

Biclustering with heterogeneous variance.  

PubMed

In cancer research, as in all of medicine, it is important to classify patients into etiologically and therapeutically relevant subtypes to improve diagnosis and treatment. One way to do this is to use clustering methods to find subgroups of homogeneous individuals based on genetic profiles together with heuristic clinical analysis. A notable drawback of existing clustering methods is that they ignore the possibility that the variance of gene expression profile measurements can be heterogeneous across subgroups, and methods that do not consider heterogeneity of variance can lead to inaccurate subgroup prediction. Research has shown that hypervariability is a common feature among cancer subtypes. In this paper, we present a statistical approach that can capture both mean and variance structure in genetic data. We demonstrate the strength of our method in both synthetic data and in two cancer data sets. In particular, our method confirms the hypervariability of methylation level in cancer patients, and it detects clearer subgroup patterns in lung cancer data. PMID:23836637

Chen, Guanhua; Sullivan, Patrick F; Kosorok, Michael R

2013-07-08

385

Heterogeneous broadband network  

NASA Astrophysics Data System (ADS)

Although the vision for the future Integrated Broadband Communication Network (IBCN) is an all optical network, it is certain that for a long period to come, the network will remain very heterogeneous, with a mixture of different physical media (fiber, coax and twisted pair), transmission systems (PDH, SDH, ADSL) and transport protocols (TCP/IP, AAL/ATM, frame relay). In the current work towards the IBCN, the ATM concept is considered the generic network protocol for both public and private network, with the ability to use different underlying transmission protocols and, through adaptation protocols, provide the appropriate services (old as well as new) to the customer. One of the major difficulties of heterogeneous network is the restriction that is usually given by the lowest common denominator, e.g. in terms of single channel capacity. A possible way to overcome these limitations is by extending the ATM concept with a multilink capability, that allows us to use separate resources as one common. The improved flexibility obtained by this protocol extension further allows a real time optimization of network and call configuration, without any impact on the quality of service seen from the user. This paper describes an example of an ATM based multilink protocol that has been experimentally implemented within the RACE project 'STRATOSPHERIC'. The paper outlines the complexity of introducing an extra network functionality compared with the added value, such as an improved ability to recover an error due to a malfunctioning network component.

Dittmann, Lars

1995-11-01

386

E-Inclusion through text messaging: The emergence of an administrative ecology within an university student population via the use of a mobile academic information delivery system  

Microsoft Academic Search

The investigation evaluated the impact of incorporating mobile technology and in particular the introduction of on-demand Short Messaging Service (SMS) - also known as text messaging - into the information exchange between universities and the students. The impact of the technology on the creation of a new mode of information exchange that augments the existing student learning experience was assessed.

Joan Richardson; John Lenarcic

387

Students Against Nicotine and Tobacco Addiction (S.A.N.T.A.): Community-Based Participatory Research in a High-Risk Young Adult Population  

Microsoft Academic Search

Students Against Nicotine and Tobacco Addiction (S.A.N.T.A.) is a community-based participatory research project involving an active collaboration between University health providers and Job Corps students, administrators, teachers, counselors, and staff. In this article, we describe the project, its evolution, and key strategies that have employed over the course of the initiative and its ongoing efforts.

Tai Mendenhall; Heather Whipple; Peter Harper; Sonny Haas

2008-01-01

388

Heterogeneity of asthma in society.  

PubMed

There has been an increased interest in studying other factors that affect asthma pathogenesis and cause heterogeneity in prevalence and incidence of asthma. The reason there are such varied expression patterns of disease in asthmatics is because of multiple variables that affect the pathogenesis of asthma. As an exemplar of an epidemiologic variable, we will discuss geographical location, obesity and vitamin D status of the individual, and their effects on asthma burden in humans. There is varying data regarding the prevalence or severity of asthma in urban versus rural setting which is likely related to the difference of the populations studied, complexity of causal variables involved, and local geographic factors. In addition to cross-sectional and cohort studies in humans, animal models and studies have established a link between asthma and obesity by investigating the mechanisms affecting both disease processes. The complicated interrelationship between obesity and asthma is an active area of epidemiological and experimental research with new insights being discovered at a rapid pace. Finally, vitamin D, an important immunomodulator thought to be important in pathogenesis of asthma, has both mechanistic and therapeutic implications in treatment of asthma. The influences of these factors on the clinical expression of asthma are discussed below. PMID:24162901

Divekar, Rohit; Calhoun, William J

2014-01-01

389

Voter models on heterogeneous networks.  

PubMed

We study simple interacting particle systems on heterogeneous networks, including the voter model and the invasion process. These are both two-state models in which in an update event an individual changes state to agree with a neighbor. For the voter model, an individual "imports" its state from a randomly chosen neighbor. Here the average time TN to reach consensus for a network of N nodes with an uncorrelated degree distribution scales as N mu1 2/mu2, where mu k is the kth moment of the degree distribution. Quick consensus thus arises on networks with broad degree distributions. We also identify the conservation law that characterizes the route by which consensus is reached. Parallel results are derived for the invasion process, in which the state of an agent is "exported" to a random neighbor. We further generalize to biased dynamics in which one state is favored. The probability for a single fitter mutant located at a node of degree k to overspread the population-the fixation probability--is proportional to k for the voter model and to 1k for the invasion process. PMID:18517592

Sood, V; Antal, Tibor; Redner, S

2008-04-22

390

Voter Models on Heterogeneous Networks  

PubMed Central

We study simple interacting particle systems on heterogeneous networks, including the voter model and the invasion process. These are both two-state models in which in an update event an individual changes state to agree with a neighbor. For the voter model, an individual “imports” its state from a randomly-chosen neighbor. Here the average time TN to reach consensus for a network of N nodes with an uncorrelated degree distribution scales as N?12/?2, where ?k is the kth moment of the degree distribution. Quick consensus thus arises on networks with broad degree distributions. We also identify the conservation law that characterizes the route by which consensus is reached. Parallel results are derived for the invasion process, in which the state of an agent is “exported” to a random neighbor. We further generalize to biased dynamics in which one state is favored. The probability for a single fitter mutant located at a node of degree k to overspread the population—the fixation probability—is proportional to k for the voter model and to 1/k for the invasion process.

Sood, V.; Antal, Tibor; Redner, S.

2008-01-01

391

Separation of SSEA-4 and TRA1–60 Labelled Undifferentiated Human Embryonic Stem Cells from A Heterogeneous Cell Population Using Magnetic-Activated Cell Sorting (MACS) and Fluorescence-Activated Cell Sorting (FACS)  

Microsoft Academic Search

A major concern in human embryonic stem cell (hESC)-derived cell replacement therapy is the risk of tumorigenesis from undifferentiated\\u000a hESCs residing in the population of hESC-derived cells. Separation of these undifferentiated hESCs from the differentiated\\u000a derivatives using cell sorting methods may be a plausible approach in overcoming this problem. We therefore explored magnetic\\u000a activated cell sorting (MACS) and fluorescence activated

Chui Yee Fong; Gary S. L. Peh; Kalamegam Gauthaman; Ariff Bongso

2009-01-01

392

Student input, student motivation  

Microsoft Academic Search

This study has examined the extent that attitudes and beliefs regarding student-centered learning and motivation were affected by students involved in a six-week collaborative language learning activity where they were allowed to use their own materials. The participants of the study were Japanese EFL university students. All participating students completed a questionnaire before and after the learning activity quantifying and

Mami Ueda

393

Population Growth in Yeasts  

NSDL National Science Digital Library

This lesson is the second of two that explore cellular respiration and population growth in yeasts. In the first lesson, students set up a simple way to indirectly observe and quantify the amount of respiration occurring in yeast-molasses cultures. Based on questions that arose during the first lesson and its associated activity, in this lesson students work in small groups to design experiments that will determine how environmental factors affect yeast population growth.

Engineering K-Ph.d. Program

394

Dynamic heterogeneity for the physical oncologist  

NSDL National Science Digital Library

Biological systems (e.g. cells) can make stochastic transitions between phenotypes (e.g. states of relatively increased or decreased drug resistance). This means that an initially drug-sensitive population can generate relatively drug-resistant subpopulations. This video presents a metronomogram, which is a tool for understanding whether such stochastic transitions can provide an opportunity for therapeutic treatment. Citation: Liao D, Estevez-Salmeron L, and Tlsty TD (2012) "Conceptualizing a tool to optimize therapy based on dynamic heterogeneity," Phys. Biol. 9:065005.

Liao, David

395

Spatial Heterogeneity of Autoinducer Regulation Systems  

PubMed Central

Autoinducer signals enable coordinated behaviour of bacterial populations, a phenomenon originally described as quorum sensing. Autoinducer systems are often controlled by environmental substances as nutrients or secondary metabolites (signals) from neighbouring organisms. In cell aggregates and biofilms gradients of signals and environmental substances emerge. Mathematical modelling is used to analyse the functioning of the system. We find that the autoinducer regulation network generates spatially heterogeneous behaviour, up to a kind of multicellularity-like division of work, especially under nutrient-controlled conditions. A hybrid push/pull concept is proposed to explain the ecological function. The analysis allows to explain hitherto seemingly contradicting experimental findings.

Hense, Burkhard A.; Muller, Johannes; Kuttler, Christina; Hartmann, Anton

2012-01-01

396

Asset Pricing with Heterogeneous Consumers  

Microsoft Academic Search

Empirical difficulties encountered by representative-consumer models are resolved in an economy with heterogeneity in the form of uninsurable, persistent, and heteroscedastic labor income shocks. Given the joint process of arbitrage-free labor prices, dividends, and aggregate income satisfying a certain joint restriction, it is shown that this process is supported in the equilibrium of an economy with judiciously modeled income heterogeneity.

George M. Constantinides; Darrell Duffie

1996-01-01

397

Fault heterogeneity and earthquake scaling  

Microsoft Academic Search

There is an on-going debate in the seismological community as to whether stress drop is independent of earthquake size and this has important implications for earthquake physics. Here we investigate this question in a simple 2D cellular automaton that includes heterogeneity. We find that when the range of heterogeneity is low, the scaling approaches that of constant stress drop. However,

Alison Hetherington; Sandy Steacy

2007-01-01

398

An Adaptive Heterogeneous Software DSM  

Microsoft Academic Search

This paper presents a mechanism to run parallel ap- plications in heterogeneous, dynamic environments while maintaining thread synchrony. A heterogeneous software DSM is used to provide synchronization constructs similar to Pthreads, while providing for individual thread mobility. An asymmetric data conversion scheme is adopted to restore thread states among different computers during thread mi- gration. Within this framework we create

John Paul Walters; Hai Jiang; Vipin Chaudhary

2006-01-01

399

Heterogeneous flywheel modeling and optimization  

Microsoft Academic Search

The modeling or representation of heterogeneous objects is a recent research topic extensively published. Today, several rapid prototyping technologies are at a point where building heterogeneous components has become realizable; thus, methodologies to design these objects for manufacturing have to be developed. In this paper, we demonstrate how to apply Kumar and Dutta's modeling techniques to two different kinds of

Jinhua Huang; Georges M. Fadel

2000-01-01

400

Taming heterogeneity - the Ptolemy approach  

Microsoft Academic Search

Modern embedded computing systems tend to be heterogeneous in the sense of being composed of subsystems with very different characteristics, which communicate and interact in a variety of ways-synchronous or asynchronous, buffered or unbuffered, etc. Obviously, when designing such systems, a modeling language needs to reflect this heterogeneity. Today's modeling environments usually offer a variant of what we call amorphous

Johan Eker; Jörn W. Janneck; Edward A. Lee; Jie Liu; Xiaojun Liu; JOZSEF LUDVIG; Stephen Neuendorffer; SONIA SACHS; Yuhong Xiong

2003-01-01

401

Heterogeneous agents in financial markets  

Microsoft Academic Search

In the previous decades, evidence against the efficient market hypothesis has been mounting. As a result, the behavioral finance literature has emerged, which embeds psychological influences in financial economics. The current thesis fits within the behavioral finance literature, and is focused on the fact that bounded rationality also implies heterogeneity between investors. Heterogeneous agents models describe the behavior of individuals

Remco C. J. Zwinkels

2009-01-01

402

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

403

Heterogeneous Computing: Challenges and Opportunities  

Microsoft Academic Search

The issues and problems posed by heterogeneous computing are discussed. They include design of algorithms for applications, partitioning and mapping of application tasks, interconnection requirements, and the design of programming environments. The use of heterogeneous computing in image understanding is reviewed. An example vision task is presented, and the different types of parallelism used in the example are identified.

Ashfaq A. Khokhar; Viktor K. Prasanna; Muhammad E. Shaaban; Cho-li Wang

1993-01-01

404

Data manipulation in heterogeneous databases  

SciTech Connect

Many important information systems applications require access to data stored in multiple heterogeneous databases. This paper examines a problem in inter-database data manipulation within a heterogeneous environment, where conventional techniques are no longer useful. To solve the problem, a broader definition for join operator is proposed. Also, a method to probabilistically estimate the accuracy of the join is discussed.

Chatterjee, A.; Segev, A.

1991-10-01

405

Droplet Dynamics on Heterogeneous Substrates  

NASA Astrophysics Data System (ADS)

Describing the dynamics of contact lines on heterogeneous substrates is important in fields ranging from coating technologies over microfluidics to enhanced oil recovery. The vast majority of studies on contact line dynamics considers the case of ideal, homogeneous substrates. Modelling chemically heterogeneous surfaces by introducing periodic variations in the wettability, we investigate the depinning and subsequent motion of 2D droplets driven by a body force. To this end, we study the time evolution of a sharp interface using Stokes dynamics together with Navier slip condition at the substrate, employing a boundary element formalism. The heterogeneity is represented by a position dependent microscopic contact angle. This allows us to quantify the modified droplet mobility, the spectrum of pinned and depinned solutions, and their dependence on periodicity and strength of the heterogeneity. Understanding the emergence of dynamic contact angles on heterogeneous substrates may open a new perspective on the relation of molecular and hydrodynamic models of contact line motion.

Herde, Daniel; Thiele, Uwe; Herminghaus, Stephan; Brinkmann, Martin

2011-11-01

406

[Population and environment. Requests for interdisciplinary analysis].  

PubMed

Serious difficulties impede interdisciplinary research involving demographers, ecologists, and other students of the environment. The 1st problem concerns definitions of the different subject areas. Demographers have focused on the dynamics of some indicators that reflect complex and heterogeneous population processes. The relative autonomy of demography as a discipline was gained through an empirical orientation reflected in the statistical treatment of causality. But the traditional demographic paradigm is insufficient for untangling the causal mechanisms underlying population dynamics. Environmental disciplines on the other hand face methodologic difficulties in transcending a strictly biological focus to incorporate aspects of cultural and social influence on ecological processes. "Human ecology", a possible meeting ground for ecological and demographic studies, is more of an ambitious program of transdisciplinary research than an independent discipline. Relations between the environment and development processes, including population aspects, are of increasing international concern. A conceptual base has developed in Latin America which emphasizes the global and structural aspects of the environment and of development styles. It has been extremely difficult to apply the entire conceptualization to the concrete environmental problems that are of current interest to both civil society and governments. It may be time to replace the umbrella term "environment", defining it in more specific, systemic, and operational terms. It is time to delimit study topics in terms of concrete problems. A good example would be the situation of Lake Chapala, the largest lake in Mexico. Damage caused to it cannot be assessed by referring to the "population explosion" or an "overall development style". Environmental, economic, and sociodemographic aspects will however necessarily enter the analysis. Fragile and unstable situations are of special interest in the study of relations between population and the biophysical environment. Such areas can transform the structural conditions of population processes. A combined analysis of spatial distribution of populations and natural resources is urgently needed. For such an analysis, it would be useful to organize demographic data into large ecological zones. PMID:12158041

Tudela, F

1991-01-01

407

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

408

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

409

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

410

Angiotensin II receptor heterogeneity  

SciTech Connect

The possibility of receptor heterogeneity in the angiotensin II (AII) system has been suggested previously, based on differences in Kd values or sensitivity to thiol reagents. One of the authors earliest indications was the frequent observation of incomplete inhibition of the binding of AII to adrenal cortical membranes. Autoradiographic studies demonstrated that all of the labeling of the rat adrenal was blocked by unlabeled AII or saralasin, but not by DuP 753. The predominant receptor in the rat adrenal cortex (80%) is sensitive to dithiothreitol (DTT) and DuP 753, and is designated AII-1. The residual sites in the adrenal cortex and almost all of the sites in the rat adrenal medulla are insensitive to both DTT and DuP 753, but were blocked by EXP655. These sites have been confirmed by ligand binding studies and are designated AII-2. The rabbit adrenal cortex is unique in yielding a nonuniform distribution of AII-2 sites around the outer layer of glomerulosa cells. In the rabbit kidney, the sites on the glomeruli are AII-1, but the sites on the kidney capsule are AII-2. Angiotensin III appears to have a higher affinity for AII-2 sites since it inhibits the binding to the rabbit kidney capsule but not the glomeruli. Elucidation of the distribution and function of these diverse sites should permit the development of more selective and specific therapeutic strategies.

Herblin, W.F.; Chiu, A.T.; McCall, D.E.; Ardecky, R.J.; Carini, D.J.; Duncia, J.V.; Pease, L.J.; Wong, P.C.; Wexler, R.R.; Johnson, A.L. (DuPont Merck Pharmaceutical Company, Wilmington, DE (USA))

1991-04-01

411

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.

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

2013-01-01

412

Faculty Perceptions of Students' Business Communication Needs  

Microsoft Academic Search

Today's student populations comprise more minority students, more students for whom English is a second language, and more older students than in the past. These changes prompted this descriptive study in which business faculty members' perceptions about the business commumcation curriculum are examined. Faculty perceive their students to have problems with basic writing skills as well as with sophisticated writing

Susan Plutsky

1996-01-01

413

Asset return and wealth dynamics with reference dependent preferences and heterogeneous beliefs  

Microsoft Academic Search

We study a model of a financial market populated with heterogenous agents whose preferences exhibit dependence on some reference level of wealth. Investment decisions of the agents are myopic and are based upon the demand for the risky asset derived from an S-shaped utility maximization. The specific demand form allows to model both heterogeneity of the system relative to the

Sergiy Gerasymchuk

2008-01-01

414

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.

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

2012-01-01

415

Increasing Student Interpersonal Relationships.  

ERIC Educational Resources Information Center

|A program for increasing the social skills development of fourth grade students is described. The targeted population consisted of fourth grade students in a growing, low socio-economic status, urban community including a public housing development. The problems of poor social skills and disruptive behavior were documented through observations,…

Williams, Linda

416

Strengthening Student Writing Skills.  

ERIC Educational Resources Information Center

This action research project describes a program to increase the basic writing ability and improve the attitude of sixth grade students. The targeted classroom was located in a unit district 45 miles northwest of a large metropolitan area. The district's population consists of a large amount of minority students and low-income families. Evidence…

Korbel, Teresa M.

417

Hand osteoarthritis--a heterogeneous disorder.  

PubMed

Hand osteoarthritis (OA) is a prevalent disorder. Hand OA is not one single disease, but a heterogeneous group of disorders. Radiographic signs of hand OA, such as osteophytes or joint space narrowing, can be found in up to 81% of the elderly population. Several hand OA subsets--such as nodal interphalangeal OA, thumb base OA and erosive OA--can be discriminated. Furthermore, the experience of symptoms and the course of the disease differ between patients. Studies that used well-defined study populations with longitudinal follow-up have shown that similarities and differences can be observed in the pathogenesis, epidemiology and risk factors of the various hand OA subsets. Erosive OA in particular, characterized by erosive lesions on radiographical images, has a higher clinical burden and worse outcome than nonerosive hand OA. Imaging modalities (such as ultrasonography) have increased our knowledge of the role of inflammation of the disease. Our understanding of the heterogeneous nature of hand OA can eventually lead to increased knowledge of the pathogenesis of, and ultimately new treatment modalities for, this complex disease. PMID:22105244

Kloppenburg, Margreet; Kwok, Wing-Yee

2011-11-22

418

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

419

An Age-Based Inspection and Replacement Policy for Heterogeneous Components  

Microsoft Academic Search

This paper considers a hybrid maintenance policy for a single component from a heterogeneous population. The component is placed in a socket, and the component and socket together comprise the system. The s-population of components consists of two sub-populations with different failure characteristics. By supposing that a component may be in a defective but operating state, so that there exists

Philip A. Scarf; Cristiano A. V. Cavalcante; Richard A. Dwight; Peter Gordon

2009-01-01

420

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

ERIC Educational Resources Information Center

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

Lamothe, Alain R.

2013-01-01

421

?LKÖ?RET?M 8. SINIF Ö?RENC?LER?N?N L?SE G?R?? SINAVLARINDAK? ÇEVRE VE POPULASYON KONUSUYLA ?LG?L? GRAF?K SORULARINI ALGILAMA VE YORUMLAMALARINDAK? YANILGILARI THE MISTAKES OF 8. CLASS STUDENTS IN PRIMARY SCHOOLS IN PERCEPTION ON INTERPRETATION OF GRAPHIC QUESTIONS ABOUT THE SUBJECT OF ENVIRONMENT AND POPULATION IN THE H?GH SCHOOL ENTRANCE EXAMS  

Microsoft Academic Search

The aim of this study is to define these conceptual mistakes in the students' interpretation and perception of the graphic questions about the subject of environment and population and on population. The models of this quantative study are the 8. class students of 5 primary schools which are chosen by coincidence in the center county. The test consists of 20

Yusuf SÜLÜN; Nevin KOZCU

422

Heterogeneous Degradation of Oxygenated Intermediates.  

National Technical Information Service (NTIS)

Issues surrounding the importance of including heterogeneous processes when determining the fate of oxygenated intermediates in the troposphere are discussed. Results of recent investigations are reviewed and preliminary data from a laboratory study are p...

E. O. Edney

1994-01-01

423

Dynamic heterogeneity in amorphous materials  

NASA Astrophysics Data System (ADS)

Amorphous solids are mechanically rigid while possessing a disordered structure similar to that of dense liquids. Recent research indicates that dynamical heterogeneity, spatio-temporal fluctuations in local dynamical behavior, might help understanding the statistical mechanics of glassy states.

Berthier, Ludovic

2011-05-01

424

Knowledge Discovery in Heterogeneous Environments.  

National Technical Information Service (NTIS)

This chapter addresses the topic of knowledge discovery in heterogeneous environments. It begins with an overview of the knowledge- discovery process. Because of the importance of using clean, consistent data in the knowledge-discovery process, the chapte...

M. N. Kamel M. G. Ceruti

2002-01-01

425

Homogeneous, Heterogeneous, and Enzymatic Catalysis.  

ERIC Educational Resources Information Center

Discusses three areas of catalysis: homegeneous, heterogeneous, and enzymatic. Explains fundamentals and economic impact of catalysis. Lists and discusses common industrial catalysts. Provides a list of 107 references. (MVL)

Oyama, S. Ted; Somorjai, Gabor A.

1988-01-01

426

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

427

Multilanguage design of heterogeneous systems  

Microsoft Academic Search

Multilanguage solutions are required for the design of heterogeneous s ystems where different parts belong to d ifferent application classes e.g. control\\/data or continuous\\/discrete. The main p roblem that needs to b e solved when d ealing with multilanguage design is the refinement of communication between heterogeneous subsystems. This paper discusses the basic concepts of multilanguage design and introduces MUSIC

Philippe Coste; F. Hessel; Ph. Le Marrec; Zoltan Sugar; M. Romdhani; Rodolph Suescun; Nacer-Eddine Zergainoh; A. A. Jarraya

1999-01-01

428

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

429

Heterogeneity shapes groups growth in social online communities  

NASA Astrophysics Data System (ADS)

Many complex systems are characterized by broad distributions capturing, for example, the size of firms, the population of cities or the degree distribution of complex networks. Typically this feature is explained by means of a preferential growth mechanism. Although heterogeneity is expected to play a role in the evolution, it is usually not considered in the modeling probably due to a lack of empirical evidence on how it is distributed. We characterize the intrinsic heterogeneity of groups in an online community and then show that together with a simple linear growth and an inhomogeneous birth rate it explains the broad distribution of group members.

Grabowicz, P. A.; Eguíluz, V. M.

2012-01-01

430

College Students Come of Age.  

ERIC Educational Resources Information Center

Universities today attract a student population less homogeneous than those of past generations. The majority of all college students are women, and adults 25 years and older account for over 40% of all college enrollments. A study was conducted to examine inherent similarities and differences among college students with age a critical factor.…

Epstein, Howard V.

431

Student Climate Survey, Spring 1998.  

ERIC Educational Resources Information Center

Every three years, Truckee Meadows Community College (Nevada) administers a student climate survey that measures the attitudes, perceptions, and opinions of its student population. The instrument used to survey the student body was designed with three basic objectives in mind: (1) validate the institutional mission; (2) obtain input regarding the…

Truckee Meadows Community Coll., Sparks, NV.

432

Increasing Student Intrinsic Reading Motivation.  

ERIC Educational Resources Information Center

|This report describes a program for increasing intrinsic reading motivation. The targeted population consisted of lower primary students in a growing middle class community, located in northern Illinois. The problems of aliterate students were documented through teacher observations and student surveys. Analysis of probable cause data revealed…

Lippe, Mary; Weber, Dana

433

Student Climate Survey, Spring 1998.  

ERIC Educational Resources Information Center

|Every three years, Truckee Meadows Community College (Nevada) administers a student climate survey that measures the attitudes, perceptions, and opinions of its student population. The instrument used to survey the student body was designed with three basic objectives in mind: (1) validate the institutional mission; (2) obtain input regarding the…

Truckee Meadows Community Coll., Sparks, NV.

434

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

435

Do Students Expect Compensation for Wage Risk?  

ERIC Educational Resources Information Center

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

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

2011-01-01

436

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

437

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

438

Spiral waves in systems with fractal heterogeneity  

NASA Astrophysics Data System (ADS)

The influence of fractal heterogeneity on a spiral wave in an excitable system is numerically studied based on the Barkley model. The heterogeneity is implemented by letting the diffusive coefficient in the heterogeneous area be different from the other area. The results show that fruitful transitions of the spiral tip trajectories are induced by the fractal heterogeneity. In particular, when the heterogeneity increases to a sufficiently high level the spiral tip trajectory always changes to a stable rotating trajectory (closed-circle tip trajectory), whatever transitions have been induced by a lower level of heterogeneity. We qualitatively ascribe the transitions to the attraction on the spiral tip exerted by the heterogeneous area.

Tang, Jun; Luo, Jin-Ming; Ma, Jun; Yi, Ming; Yang, Xian-Qing

2013-11-01

439

Seismic response in heterogeneous media.  

NASA Astrophysics Data System (ADS)

One of the aims of our research in the last few years has been to try to establish a comprehensive knowledge of the seismic response in heterogeneous media. There are many situations in geophysical exploration, where the interpreter, having to face seismic data acquired and processed with standard methods, has very little to interpret below heterogeneous layers. Basalts are an example of highly heterogenous media. Examination of flood basalts in the field show a high level of heterogeneity. The individual flows are highly fractured and are separated by layers of unconsolidated ash and clay. The top and bottom surfaces of the flows are highly irregular with each flow filling in topography on the previous flow. We used geological observations on basalts and defined models using statistical properties derived from basalts. However our results are applicable to any target imaging beneath strongly scattering structures. We have worked on highly heterogeneous models derived from borehole log data, digital imagery and seismic data. Through synthetic simulations, we have investigated the wave propagation through highly heterogeneous layers. It is the wave scattering through these heterogeneities (body and interface) that obscures underlying structures. Scattering from rough interfaces seems to have the most detrimental effect on imaging at depth, creating a serious distortion to the wavefront. Body scattering becomes more important with increasing thickness of the layer (number of wavelengths in the thickness). Also, as heterogeneity increases, the higher frequencies will get preferentially scattered. Only the lower frequencies retain the coherency necessary for successful imaging at the target. All this information is extremely useful both at the acquisition and processing stages. In summary, the coherent seismic wave that passes through a heterogenous layer preferentially loses high frequency energy, and in addition the wavefield is highly attenuated, distorted, and is seriously contaminated by the scattered energy. More detailed wave attenuation studies are currently part of our research work. Having already seen that highly absorbing layers can improve the imaging of lower structures, we are now focusing our attention on measuring the (scattering and intrinsic) attenuation, on both synthetic and real data.

Martini, F.; Bean, C. J.

2003-04-01

440

Spatial Patterns in European Rabbit Abundance After a Population Collapse  

Microsoft Academic Search

Assessing the associations between spatial patterns in population abundance and environmental heterogeneity is critical for understanding various population processes and for managing species and communities. This study evaluates responses in the abundance of the European rabbit (Oryctolagus cuniculus), an important prey for predators of conservation concern in Mediterranean ecosystems, to environmental heterogeneity at different spatial scales. Multi-scale habitat models of

Néstor Fernández; Pabellon de Peru ´

2005-01-01

441

Heterogeneous ice nucleation: bridging stochastic and singular freezing behavior  

NASA Astrophysics Data System (ADS)

Heterogeneous ice nucleation, a primary pathway for ice formation in the atmosphere, has been described alternately as being stochastic, in direct analogy with homogeneous nucleation, or singular, with ice nuclei initiating freezing at deterministic temperatures. We present an idealized model that bridges these stochastic and singular descriptions of heterogeneous ice nucleation. This "soccer ball" model treats statistically similar particles as being covered with surface sites (patches of finite area) characterized by different nucleation barriers, but with each surface site following the stochastic nature of ice embryo formation. The model provides a phenomenological explanation for seemingly contradictory experimental results obtained in our research groups. We suggest that ice nucleation is fundamentally a stochastic process but that for realistic atmospheric particle populations this process can be masked by the heterogeneity of surface properties. Full evaluation of the model will require experiments with well characterized ice nucleating particles and the ability to vary both temperature and waiting time for freezing.

Niedermeier, D.; Shaw, R. A.; Hartmann, S.; Wex, H.; Clauss, T.; Voigtländer, J.; Stratmann, F.

2011-01-01

442

Reaction Selectivity in Heterogeneous Catalysis  

SciTech Connect

The understanding of selectivity in heterogeneous catalysis is of paramount importance to our society today. In this review we outline the current state of the art in research on selectivity in heterogeneous catalysis. Current in-situ surface science techniques have revealed several important features of catalytic selectivity. Sum frequency generation vibrational spectroscopy has shown us the importance of understanding the reaction intermediates and mechanism of a heterogeneous reaction, and can readily yield information as to the effect of temperature, pressure, catalyst geometry, surface promoters, and catalyst composition on the reaction mechanism. DFT calculations are quickly approaching the ability to assist in the interpretation of observed surface spectra, thereby making surface spectroscopy an even more powerful tool. HP-STM has revealed three vitally important parameters in heterogeneous selectivity: adsorbate mobility, catalyst mobility, and selective site-blocking. The development of size controlled nanoparticles from 0.8 to 10 nm, of controlled shape, and of controlled bimetallic composition has revealed several important variables for catalytic selectivity. Lastly, DFT calculations may be paving the way to guiding the composition choice for multi-metallic heterogeneous catalysis for the intelligent design of catalysts incorporating the many factors of selectivity we have learned.

Somorjai, Gabor A.; Kliewer, Christopher J.

2009-02-02

443

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

ERIC Educational Resources Information Center

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

Ngai, Phyllis Bo-yuen

2006-01-01

444

Heterogeneity reduces sensitivity of cell death for TNF-Stimuli  

PubMed Central

Background Apoptosis is a form of programmed cell death essential for the maintenance of homeostasis and the removal of potentially damaged cells in multicellular organisms. By binding its cognate membrane receptor, TNF receptor type 1 (TNF-R1), the proinflammatory cytokine Tumor Necrosis Factor (TNF) activates pro-apoptotic signaling via caspase activation, but at the same time also stimulates nuclear factor ?B (NF-?B)-mediated survival pathways. Differential dose-response relationships of these two major TNF signaling pathways have been described experimentally and using mathematical modeling. However, the quantitative analysis of the complex interplay between pro- and anti-apoptotic signaling pathways is an open question as it is challenging for several reasons: the overall signaling network is complex, various time scales are present, and cells respond quantitatively and qualitatively in a heterogeneous manner. Results This study analyzes the complex interplay of the crosstalk of TNF-R1 induced pr