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1

Phenotypically heterogeneous populations in spatially heterogeneous environments  

NASA Astrophysics Data System (ADS)

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

Patra, Pintu; Klumpp, Stefan

2014-03-01

2

Eradication of infectious diseases in heterogeneous populations  

SciTech Connect

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

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

1987-04-01

3

Population dynamics on heterogeneous bacterial substrates  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

4

Specialization and Bet-Hedging in Heterogeneous Populations  

E-print Network

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

Rulands, Steffen; Frey, Erwin

2014-01-01

5

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

6

Evolutionary dynamics of social dilemmas in structured heterogeneous populations  

NASA Astrophysics Data System (ADS)

Real populations have been shown to be heterogeneous, in which some individuals have many more contacts than others. This fact contrasts with the traditional homogeneous setting used in studies of evolutionary game dynamics. We incorporate heterogeneity in the population by studying games on graphs, in which the variability in connectivity ranges from single-scale graphs, for which heterogeneity is small and associated degree distributions exhibit a Gaussian tale, to scale-free graphs, for which heterogeneity is large with degree distributions exhibiting a power-law behavior. We study the evolution of cooperation, modeled in terms of the most popular dilemmas of cooperation. We show that, for all dilemmas, increasing heterogeneity favors the emergence of cooperation, such that long-term cooperative behavior easily resists short-term noncooperative behavior. Moreover, we show how cooperation depends on the intricate ties between individuals in scale-free populations. complex networks | evolution of cooperation

Santos, F. C.; Pacheco, J. M.; Lenaerts, Tom

2006-02-01

7

Student Instructions Population Dynamics  

E-print Network

the population dynamics of wolves and bunnies that live in a meadow together. Figure 1. The Meadow. Population: "the wolves" 75 1" x 1" pink paper squares: "the bunnies" Instructions Overview: This simulation manager. The wolves (gray squares) will be randomly dropped onto the meadow (large sheet) covered

Spakowitz, Andrew J.

8

Evolutionary Game Dynamics in Populations with Heterogenous Structures  

PubMed Central

Evolutionary graph theory is a well established framework for modelling the evolution of social behaviours in structured populations. An emerging consensus in this field is that graphs that exhibit heterogeneity in the number of connections between individuals are more conducive to the spread of cooperative behaviours. In this article we show that such a conclusion largely depends on the individual-level interactions that take place. In particular, averaging payoffs garnered through game interactions rather than accumulating the payoffs can altogether remove the cooperative advantage of heterogeneous graphs while such a difference does not affect the outcome on homogeneous structures. In addition, the rate at which game interactions occur can alter the evolutionary outcome. Less interactions allow heterogeneous graphs to support more cooperation than homogeneous graphs, while higher rates of interactions make homogeneous and heterogeneous graphs virtually indistinguishable in their ability to support cooperation. Most importantly, we show that common measures of evolutionary advantage used in homogeneous populations, such as a comparison of the fixation probability of a rare mutant to that of the resident type, are no longer valid in heterogeneous populations. Heterogeneity causes a bias in where mutations occur in the population which affects the mutant's fixation probability. We derive the appropriate measures for heterogeneous populations that account for this bias. PMID:24762474

Maciejewski, Wes; Fu, Feng; Hauert, Christoph

2014-01-01

9

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

10

Item Response Theory Scaling with Heterogeneous Populations.  

ERIC Educational Resources Information Center

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

Blais, Jean-Guy

11

Student Heterogeneity and Diversity at Catholic Colleges  

ERIC Educational Resources Information Center

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

Elliott, Diane Cardenas

2012-01-01

12

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

13

The heterogeneous HLA genetic makeup of the Swiss population.  

PubMed

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

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

2012-01-01

14

Confounding and Heterogeneity in Genetic Association Studies with Admixed Populations  

PubMed Central

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.

2013-01-01

15

Non-linearity and heterogeneity in modeling of population dynamics.  

PubMed

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

Karev, Georgy P

2014-12-01

16

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

17

Heterogeneity of the Y chromosome in Afro-Brazilian populations.  

PubMed

Sixteen biallelic markers (SRY10831a, SRY10831b, SRY4064, SRY2627, 92R7, P2, P3, M34, M9, M3, M2, YAP, M60, M89, M213, M216) located in the nonrecombinant region of the Y chromosome were analyzed in 209 individuals belonging to six Brazilian populations: four Afro-Brazilian populations, one population of white European descendants, and one population of Japanese descendants. The results showed that most of the Y chromosomes of the Afro-Brazilians were from sub-Saharan Africa and that the proportion of Y chromosomes of European origin was greater than that of Y chromosomes of Amerindian origin. No typical African or Amerindian haplogroup was detected among Japanese individuals, and only one white individual showed a typical African haplogroup. Haplogroup P-92R7, which is highly frequent in the Portuguese and Italian populations, was the most frequent among whites (54%), and haplogroup K-M9, which shows wide geographic distribution and is absent in Africa, was the most frequent among Japanese individuals (65.6%). The two semi-isolated Afro-Brazilian populations showed the highest and the lowest genetic diversity, respectively. These differences probably reflect the effect of greater or smaller gene flow between a small isolated group and other populations. These findings show that the process of admixture does not occur homogeneously, with a tendency toward preferential marriages within the ethnic group and a clear direction in unions between European men and Amerindian or African women in the past. The results agree with historical and social data about the formation of the Brazilian population and reveal some of the factors that contribute to its heterogeneity. PMID:15222681

Abe-Sandes, Kiyoko; Silva, Wilson A; Zago, Marco A

2004-02-01

18

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

SciTech Connect

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

Ganusov, Vitaly V [Los Alamos National Laboratory

2008-01-01

19

Estimation of multiple transmission rates for epidemics in heterogeneous populations  

PubMed Central

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

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

2007-01-01

20

Dual Enrollment for Underrepresented Student Populations.  

ERIC Educational Resources Information Center

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

Hugo, Esther B.

2001-01-01

21

Modelling Lipid Competition Dynamics in Heterogeneous Protocell Populations  

E-print Network

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

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

2014-01-30

22

Functional heterogeneity of side population cells in skeletal muscle  

SciTech Connect

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

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

2006-03-17

23

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.

24

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

25

Breeding site heterogeneity reduces variability in frog recruitment and population dynamics  

USGS Publications Warehouse

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

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

2013-01-01

26

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

PubMed Central

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

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

2014-01-01

27

Heterogeneity of Australian Population Mortality and Implications for a Viable Life Annuity Market  

Microsoft Academic Search

Heterogeneity in mortality rates is known to exist in populations, undermining the use of age and sex as the only rating factors for life insurance and annuity products. Life insurers underwrite life products using a variety of rating factors to allow for this heterogeneity. In the case of life annuities, there is limited underwriting used. Life insurers rely on an

Shu Su; Michael Sherris

2011-01-01

28

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

PubMed Central

Recently, the impact of network structure on evolutionary dynamics has been at the center of attention when studying the evolutionary process of structured populations. This paper aims at finding out the key structural feature of network to capture its impact on evolutionary dynamics. To this end, a novel concept called heat heterogeneity is introduced to characterize the structural heterogeneity of network, and the correlation between heat heterogeneity of structure and outcome of evolutionary dynamics is further investigated on various networks. It is found that the heat heterogeneity mainly determines the impact of network structure on evolutionary dynamics on complex networks. In detail, the heat heterogeneity readjusts the selection effect on evolutionary dynamics. Networks with high heat heterogeneity amplify the selection effect on the birth-death process and suppress the selection effect on the death-birth process. Based on the above results, an effective algorithm is proposed to generate selection adjusters with desired size and average degree. PMID:24849192

Tan, Shaolin; Lü, Jinhu

2014-01-01

29

GLOBAL PRODUCTION INCREASED BY SPATIAL HETEROGENEITY IN A POPULATION DYNAMICS  

E-print Network

rates and the local subpopulation growth rates is provided under which the total carrying capacity is higher than the sum of the local carrying capacities, which is not intuitive. As we illustrate interest nowadays since many human activities tend to decrease the heterogeneities, which could result

Poggiale, Jean-Christophe

30

GLOBAL PRODUCTION INCREASED BY SPATIAL HETEROGENEITY IN A POPULATION DYNAMICS  

E-print Network

on the migration rates and the local subpopulation growth rates is provided under which the total carrying capacity is higher than the sum of the local carrying capacities, which is not intuitive. As we illustrate since many human activities tend to decrease the heterogeneities, which could result in a loss

Paris-Sud XI, Université de

31

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

PubMed Central

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

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

2010-01-01

32

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

Microsoft Academic Search

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

John Boulanger; Gordon Stenhouse; Robin Munro

2004-01-01

33

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

34

Using Populism to Engage Students in Critical Thinking  

ERIC Educational Resources Information Center

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

Peiser, Andrew

2013-01-01

35

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

PubMed Central

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

Stamatakis, Michail; Zygourakis, Kyriacos

2010-01-01

36

Slow epidemic extinction in populations with heterogeneous infection rates  

NASA Astrophysics Data System (ADS)

We explore how heterogeneity in the intensity of interactions between people affects epidemic spreading. For that, we study the susceptible-infected-susceptible model on a complex network, where a link connecting individuals i and j is endowed with an infection rate ?ij=?wij proportional to the intensity of their contact wij, with a distribution P(wij) taken from face-to-face experiments analyzed in Cattuto [PLoS ONE1932-620310.1371/journal.pone.0011596 5, e11596 (2010)]. We find an extremely slow decay of the fraction of infected individuals, for a wide range of the control parameter ?. Using a distribution of width a we identify two large regions in the a-? space with anomalous behaviors, which are reminiscent of rare region effects (Griffiths phases) found in models with quenched disorder. We show that the slow approach to extinction is caused by isolated small groups of highly interacting individuals, which keep epidemics alive for very long times. A mean-field approximation and a percolation approach capture with very good accuracy the absorbing-active transition line for weak (small a) and strong (large a) disorder, respectively.

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

2013-08-01

37

Neisseria gonorrhoeae population in Arkhangelsk, Russia: phenotypic and genotypic heterogeneity.  

PubMed

Reliable data concerning the incidence and phenotypic and genotypic characteristics of the Neisseria gonorrhoeae population in many eastern European countries are lacking. Clinically significant N. gonorrhoeae isolates (n = 76) from 76 consecutive patients in Arkhangelsk, Russia were characterised by antimicrobial susceptibility testing, serovar determination, porB gene sequencing and N. gonorrhoeae multi-antigen sequence typing (NG-MAST). The isolates were assigned to 12 different serovars, displayed 35 divergent porB sequences, and belonged to 40 different sequence types (STs). All the serovars, but only seven of the STs, had been identified previously in other countries. Twelve ST clusters of between two and 14 isolates were identified, which indicated that many multiple transmission networks exist in Arkhangelsk. The high number of unique STs (n = 28) may be a consequence of sub-optimal diagnostic procedures, ineffective partner tracing, local emergence of new STs, import of strains via sexual tourists, or foreign travel. The N. gonorrhoeae population circulating in Arkhangelsk was highly diverse and differed from the N. gonorrhoeae populations disseminated in some western European countries. Thorough knowledge concerning the incidence of gonorrhoea, antibiotic susceptibility and other phenotypic and genotypic characteristics of the N. gonorrhoeae strains circulating in eastern Europe is crucial. PMID:17596201

Unemo, M; Vorobieva, V; Firsova, N; Ababkova, T; Leniv, I; Haldorsen, B C; Fredlund, H; Skogen, V

2007-09-01

38

A heterogeneous population model for the analysis of bacterial growth kinetics  

Microsoft Academic Search

A two-compartment, heterogeneous population model (HPM) was derived using the simulation software SB ModelMaker© to describe the growth of Listeria monocytogenes in bacteriological media at 5–35 °C. The model assumed that, at time t = 0, the inoculum was distributed between two distinct compartments, Non-Growing and Growing, and that growth could be described by four parameters: initial total cell population

R. C. McKellar

1997-01-01

39

Coverage-adjusted estimators for mark-recapture in heterogeneous populations  

Microsoft Academic Search

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

J. Ashbridge; I. B. J. Goudie

2000-01-01

40

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...

41

The Innovation Diffusion Process in a Heterogeneous Population: A Micromodeling Approach  

Microsoft Academic Search

A model of the innovation diffusion process is developed using a micromodeling approach that explicitly considers the determinants of adoption at the individual level in a decision analytic framework, and incorporates heterogeneity in the population with respect to initial perceptions, preference characteristics, and responsiveness to information. The micromodelling approach provides a behavioral basis for explaining adoption at the disaggregate level

Rabik Ar Chatterjee; Jehoshua Eliashberg

1990-01-01

42

Modelling Lipid Competition Dynamics in Heterogeneous Protocell Populations  

PubMed Central

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

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

2014-01-01

43

A score-type test for heterogeneity in zero-inflated models in a stratified population.  

PubMed

We propose a score-type statistic to evaluate heterogeneity in zero-inflated models for count data in a stratified population, where heterogeneity is defined as instances in which the zero counts are generated from two sources. Evaluating heterogeneity in this class of models has attracted considerable attention in the literature, but existing testing procedures have primarily relied on the constancy assumption under the alternative hypothesis. In this paper, we extend the literature by describing a score-type test to evaluate homogeneity against general alternatives that do not neglect the stratification information under the alternative hypothesis. The limiting null distribution of the proposed test statistic is a mixture of chi-squared distributions that can be well approximated by a simple parametric bootstrap procedure. Our numerical simulation studies show that the proposed test can greatly improve efficiency over tests of heterogeneity that ignore the stratification information. An empirical application to dental caries data in early childhood further shows the importance and practical utility of the methodology in using the stratification profile to detect heterogeneity in the population. PMID:24488881

Cao, Guanqun; Hsu, Wei-Wen; Todem, David

2014-05-30

44

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. PMID:21305027

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

2011-01-01

45

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

PubMed

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

Wu, Jincheng; Tzanakakis, Emmanuel S

2013-01-01

46

Distinct Allelic Patterns of Nanog Expression Impart Embryonic Stem Cell Population Heterogeneity  

PubMed Central

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

Wu, Jincheng; Tzanakakis, Emmanuel S.

2013-01-01

47

High school students' understanding and problem solving in population genetics  

NASA Astrophysics Data System (ADS)

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

Soderberg, Patti D.

48

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

PubMed Central

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

2013-01-01

49

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

ERIC Educational Resources Information Center

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

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

2014-01-01

50

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

PubMed Central

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

2014-01-01

51

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

PubMed

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

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

2012-01-01

52

Individual movement behavior, matrix heterogeneity, and the dynamics of spatially structured populations  

PubMed Central

The dynamics of spatially structured populations is characterized by within- and between-patch processes. The available theory describes the latter with simple distance-dependent functions that depend on landscape properties such as interpatch distance or patch size. Despite its potential role, we lack a good mechanistic understanding of how the movement of individuals between patches affects the dynamics of these populations. We used the theoretical framework provided by movement ecology to make a direct representation of the processes determining how individuals connect local populations in a spatially structured population of Iberian lynx. Interpatch processes depended on the heterogeneity of the matrix where patches are embedded and the parameters defining individual movement behavior. They were also very sensitive to the dynamic demographic variables limiting the time moving, the within-patch dynamics of available settlement sites (both spatiotemporally heterogeneous) and the response of individuals to the perceived risk while moving. These context-dependent dynamic factors are an inherent part of the movement process, producing connectivities and dispersal kernels whose variability is affected by other demographic processes. Mechanistic representations of interpatch movements, such as the one provided by the movement-ecology framework, permit the dynamic interaction of birth–death processes and individual movement behavior, thus improving our understanding of stochastic spatially structured populations. PMID:19060193

Revilla, Eloy; Wiegand, Thorsten

2008-01-01

53

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

ERIC Educational Resources Information Center

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

Esmonde, Indigo; Langer-Osuna, Jennifer M.

2013-01-01

54

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

PubMed

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

Aspridou, Zafiro; Koutsoumanis, Konstantinos P

2015-02-01

55

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

56

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

SciTech Connect

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

Ormiston, B.G.

1980-11-01

57

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

PubMed Central

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

2014-01-01

58

Adapting Institutional Research to Changing Student Populations.  

ERIC Educational Resources Information Center

Institutional research (IR) in community/junior colleges in past years has been limited to gathering data for external agencies, concentrating on raw demographic data and student flow studies. IR should be directed toward providing data for administrative decisions and for successful maintenance of college operations. In spite of the heavy demands…

Cohen, Arthur M.

59

Impact of Roles Assignation on Heterogeneous Populations in Evolutionary Dictator Game  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

60

Impact of Roles Assignation on Heterogeneous Populations in Evolutionary Dictator Game  

PubMed Central

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

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

2014-01-01

61

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

PubMed

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

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

2014-11-01

62

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

PubMed Central

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

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

2014-01-01

63

Student understanding in mechanics: A large population survey  

NSDL National Science Digital Library

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

Gunstone, Richard

2005-10-20

64

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

PubMed Central

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

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

2014-01-01

65

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

PubMed

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

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

2014-01-01

66

Evidence That the Heterogeneity of a T4 Population Is the Result of Heritable Traits  

PubMed Central

Many bacteriophage populations display heterogeneity in their adsorption characteristics; a portion of the phage population remains free in solution throughout adsorption experiments (residual fraction). This residual fraction generally constitutes a minority of phages that exhibit significantly slower adsorption kinetics than the main phage stock (main fraction). While this phenomenon is likely the result of evolutionary driving forces, the present study demonstrates that the residual fraction is not always the result of phenotypic variations within a single genotype, as is generally thought. Experiments with phage T4 showed that two subgroups with distinct adsorption traits that were passed on to their progeny could be isolated from the original phage stock. Sequencing of genes involved in adsorption revealed two point mutations in gene 37 of residual fraction isolates, which resulted in modifications to the long tail-fiber, the organelle of attachment and host cell recognition. Adsorption studies consistently showed that T4 phage stocks amplified from residual fraction isolates had significantly lower adsorption efficiencies than those amplified from main fractions. The conducted experiments provide convincing evidence that the observed heterogeneity in T4 adsorption behavior is the result of conserved mutations to the phage genome and is not exclusively the result of phenotypic variations within the population. While it is believed high mutation rates exist to hasten phage adaptation, this study shows that this bet hedging strategy can also, in the short term, inadvertently handicap the phage's adsorption capabilities to a given host under normal infection conditions, resulting in the residual fraction observed in adsorption experiments. PMID:25551763

Storms, Zachary J.; Sauvageau, Dominic

2014-01-01

67

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

PubMed

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

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

2012-01-01

68

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

69

Population Genomics Reveals Chromosome-Scale Heterogeneous Evolution in a Protoploid Yeast  

PubMed Central

Yeast species represent an ideal model system for population genomic studies but large-scale polymorphism surveys have only been reported for species of the Saccharomyces genus so far. Hence, little is known about intraspecific diversity and evolution in yeast. To obtain a new insight into the evolutionary forces shaping natural populations, we sequenced the genomes of an expansive worldwide collection of isolates from a species distantly related to Saccharomyces cerevisiae: Lachancea kluyveri (formerly S. kluyveri). We identified 6.5 million single nucleotide polymorphisms and showed that a large introgression event of 1 Mb of GC-rich sequence in the chromosomal arm probably occurred in the last common ancestor of all L. kluyveri strains. Our population genomic data clearly revealed that this 1-Mb region underwent a molecular evolution pattern very different from the rest of the genome. It is characterized by a higher recombination rate, with a dramatically elevated A:T ? G:C substitution rate, which is the signature of an increased GC-biased gene conversion. In addition, the predicted base composition at equilibrium demonstrates that the chromosome-scale compositional heterogeneity will persist after the genome has reached mutational equilibrium. Altogether, the data presented herein clearly show that distinct recombination and substitution regimes can coexist and lead to different evolutionary patterns within a single genome. PMID:25349286

Friedrich, Anne; Jung, Paul; Reisser, Cyrielle; Fischer, Gilles; Schacherer, Joseph

2015-01-01

70

The Effect of Correlated Neuronal Firing and Neuronal Heterogeneity on Population Coding Accuracy in Guinea Pig Inferior Colliculus  

PubMed Central

It has been suggested that the considerable noise in single-cell responses to a stimulus can be overcome by pooling information from a large population. Theoretical studies indicated that correlations in trial-to-trial fluctuations in the responses of different neurons may limit the improvement due to pooling. Subsequent theoretical studies have suggested that inherent neuronal diversity, i.e., the heterogeneity of tuning curves and other response properties of neurons preferentially tuned to the same stimulus, can provide a means to overcome this limit. Here we study the effect of spike-count correlations and the inherent neuronal heterogeneity on the ability to extract information from large neural populations. We use electrophysiological data from the guinea pig Inferior-Colliculus to capture inherent neuronal heterogeneity and single cell statistics, and introduce response correlations artificially. To this end, we generate pseudo-population responses, based on single-cell recording of neurons responding to auditory stimuli with varying binaural correlations. Typically, when pseudo-populations are generated from single cell data, the responses within the population are statistically independent. As a result, the information content of the population will increase indefinitely with its size. In contrast, here we apply a simple algorithm that enables us to generate pseudo-population responses with variable spike-count correlations. This enables us to study the effect of neuronal correlations on the accuracy of conventional rate codes. We show that in a homogenous population, in the presence of even low-level correlations, information content is bounded. In contrast, utilizing a simple linear readout, that takes into account the natural heterogeneity, even of neurons preferentially tuned to the same stimulus, within the neural population, one can overcome the correlated noise and obtain a readout whose accuracy grows linearly with the size of the population. PMID:24358120

Zohar, Oran; Shackleton, Trevor M.; Palmer, Alan R.; Shamir, Maoz

2013-01-01

71

Competition in a spatially heterogeneous environment: modelling the risk of spread of a genetically engineered population.  

PubMed

In recent years regulations have been developed to address the risks of releasing genetically engineered organisms into the natural environment. These risks are generally considered to be proportional to the exposure multiplied by the hazard. Exposure is, in part, determined by the spatial spread of the organisms, a component of risk suited to mathematical analysis. In this paper we exampine a mathematical model describing the spread of organisms introduced into a hetereogeneous environment, focusing on the risk of spread and plausibility of containment strategies. Two competing populations are assumed, one the natural species and the other an engineered species or strain, both of which move randomly in a spatially heterogenous environment consisting of alternating favourable and unfavourable patches. The classical Lotka-Volterra competition model with diffusion is used. Analyses of the possible spread and invasion of engineered organisms are thus reduced to finding periodic travelling wave solutions to the model equations. We focus on whether a very small number of engineered organisms can spatially invade a natural population. Initially we investigate the problem for spatially periodic diffusion coefficients and demonstrate that, under the right circumstances and a large enough unfavourable patch, invasion does not succeed. However, if spatially periodic carrying capacities are assumed along with spatially varying diffusion rates, the situation is far more complex. In this case containment of the engineered species is no longer only a simple function of the unfavourable patch length. By using perturbation solutions to the nonuniform steady states, approximate invasion conditions are obtained. PMID:8813010

Cruywagen, G C; Kareiva, P; Lewis, M A; Murray, J D

1996-02-01

72

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

PubMed

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

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

2014-12-01

73

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

74

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

E-print Network

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

Kiss, Istvan Zoltan

75

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

USGS Publications Warehouse

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

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

2013-01-01

76

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

PubMed Central

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

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

2013-01-01

77

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

PubMed Central

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

Ryall, Ben; Eydallin, Gustavo

2012-01-01

78

Spike Triggered Hormone Secretion in Vasopressin Cells; a Model Investigation of Mechanism and Heterogeneous Population Function  

PubMed Central

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

MacGregor, Duncan J.; Leng, Gareth

2013-01-01

79

Feline herpesvirus 1 and feline calicivirus infections in a heterogeneous cat population of a rescue shelter.  

PubMed

Feline herpesvirus 1 (FeHV-1) and feline calicivirus (FCV), associated with upper respiratory tract disease, are highly prevalent in cats worldwide. With the aim to investigate the importance of feline respiratory viruses in a heterogeneous population of cats, samples were taken in a rescue shelter in Liège, Belgium, between March 2005 and August 2006. Reverse transcription polymerase chain reaction (RT-PCR) and polymerase chain reaction (PCR) were performed to diagnose FCV and FeHV-1 infection in the sampled cats. The prevalence rate (33.1%) was higher for FCV than for FeHV-1 (20.1%) whereas prevalence rate of co-infection with both viruses was 10%. Gingivitis was more common in FCV infections (odds ratio (OR)=2.83) whereas respiratory signs were more often observed with FeHV-1 infections. The average age was significantly higher in FCV positive cats (38 months) than in FeHV-1 positive cats (29.9 months). The second and the fourth quarters of the year and the two first quarters were significantly more at risk than the others in the case of FeHV-1 and FCV infection, respectively. Age was found to be a confounding factor. High prevalence of both infections strengthens the importance of applying hygienic and preventive measures in rescue shelters where cats with an unknown status of vaccination are introduced. PMID:19577497

Zicola, Angélique; Saegerman, Claude; Quatpers, Dominique; Viandier, Julie; Thiry, Etienne

2009-12-01

80

A comprehensive molecular characterization of beta thalassemia in a highly heterogeneous population.  

PubMed

In Iran, the prevalence of beta-thalassemia trait is approximately 4-8% in most areas, and in Mazandaran province 10% of the population are carriers. Twenty four beta-globin gene mutations were identified in 1635 persons with beta-thalassemia trait using reverse dot blot and restriction fragment length polymorphism analysis. The predominant mutations included IVSII-1 (G-A) (61%), codon 30 (G-C) (7.5%), codon 22 (-7bp) (6.2%), codon 8 (-AA) (5.4%) and IVSI-5 (G-C) (3.6%). These mutations were in different haplotypes, with IVSII-1 being the most heterogeneous. Other less frequent mutations included IVS-II-745 (C-G), codon 44 (-C), codon 39 (C-T), codon 5 (-CT), IVS I-110 (G-A), IVSI-130 (G-C), Fr8/9 (+G), IVSI-1 (G-A), and IVSI (-25bp). All rare mutations except IVSI-130 were encountered in a unique haplotype. The diversity of these mutations reflects the historical admixture of genes in the region. The high prevalence of IVSII-1 (G-A) compared to other parts of the country and the world suggests a founder effect. Our data provide a basis for genetic counseling and prenatal diagnosis. PMID:21493114

Akhavan-Niaki, Haleh; Derakhshandeh-Peykar, Poupak; Banihashemi, Ali; Mostafazadeh, Amrollah; Asghari, Beheshteh; Ahmadifard, Mohammad-Reza; Azizi, Mandana; Youssefi, Ali; Elmi, Maryam Mitra

2011-06-15

81

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

PubMed

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

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

2014-06-01

82

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

PubMed Central

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 used detailed simulations of the simultaneous behaviours of interacting animals in an accurate facsimile of a real Danish landscape. The models incorporate as much as possible of the behaviour and ecology of skylarks Alauda arvensis, voles Microtus agrestis, a ground beetle Bembidion lampros and a linyphiid spider Erigone atra. This allows us to quantify and evaluate the importance of spatial and temporal heterogeneity on the population dynamics of the four species. Results Both spatial and temporal heterogeneity affected the relationship between population growth rate and population density in all four species. Spatial heterogeneity accounted for 23–30% of the variance in population growth rate after accounting for the effects of density, reflecting big differences in local carrying capacity associated with the landscape features important to individual species. Temporal heterogeneity accounted for 3–13% of the variance in vole, skylark and spider, but 43% in beetles. The associated temporal variation in carrying capacity would be problematic in traditional analyses of density dependence. Return rates were less than one in all species and essentially invariant in skylarks, spiders and beetles. Return rates varied over the landscape in voles, being slower where there were larger fluctuations in local population sizes. Conclusion Our analyses estimated the traditional parameters of carrying capacities and return rates, but these are now seen as varying continuously over the landscape depending on habitat quality and the mechanisms of density dependence. The importance of our results lies in our demonstration that the effects of spatial and temporal heterogeneity must be accounted for if we are to have accurate predictive models for use in management and conservation. This is an area which until now has lacked an adequate theoretical framework and methodology. PMID:19549327

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

2009-01-01

83

Populations  

NSDL National Science Digital Library

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

Galle, Janet R.; Warren, Patricia A.

2005-01-01

84

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

PubMed Central

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

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

2014-01-01

85

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

PubMed

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

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

2014-04-01

86

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

PubMed Central

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

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

2014-01-01

87

Fertility values and acceptance of population control among college students  

E-print Network

not be applicable for a select college sample. Obviously, the college campus today resembles a quasi-meiting pot that breeds a student subculture. It may be expected that certain variables which are salient for the general population fail to have an important... - What more can we do now?" Bio Science 20:854-857. 116^Kansàs^òurnàì?d'f^SociMc^ igyÓ'-^tt't^tltrfl-'Pabli^à'Tùr itNè-SOdàT Sciences. New York: McGraw- Hill Book Co. Prescott, D. M. 1969 "An editorial." Bio Science 19:205. Rabin, A. I. 1965...

West, Walter G.; Poole, Eric D.

1974-10-01

88

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

89

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

Microsoft Academic Search

The spatial heterogeneity of bacterial populations at a shallow-water hydrothermal vent in the Aegean Sea close to the island of Milos (Greece) was examined at two different times by using acridine orange staining for total cell counts, cultivation-based techniques, and denaturing gradient gel electrophoresis (DGGE) analysis of PCR-amplified 16S rRNA gene fragments. Concurrent with measurements of geochemical parameters, samples were

STEFAN M. SIEVERT; THORSTEN BRINKHOFF; GERARD MUYZER; WIEBKE ZIEBIS; JAN KUEVER

1999-01-01

90

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

PubMed

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

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

2015-02-01

91

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

PubMed Central

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

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

2014-01-01

92

Comparative microsatellite typing of new world leishmania infantum reveals low heterogeneity among populations and its recent old world origin.  

PubMed

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

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

2011-06-01

93

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

PubMed Central

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

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

2011-01-01

94

Population.  

ERIC Educational Resources Information Center

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

King, Pat; Landahl, John

95

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

PubMed Central

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

Tashyreva, Daria; Elster, Josef; Billi, Daniela

2013-01-01

96

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

E-print Network

Service, SavannahRiverPlant,Aiken,SC 298014 Abstract: Protein variation in 218 white-tailed deer (OdocoileusBiochemical Variation and Genetic Heterogeneity in South Carolina Deer Populations Author(s): P. R

Avise, John

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

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

USGS Publications Warehouse

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

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

2009-01-01

99

Cellular heterogeneity in the mouse esophagus implicates the presence of a non-quiescent epithelial stem cell population  

PubMed Central

SUMMARY Because the esophageal epithelium lacks a defined stem cell niche, it is unclear whether all basal epithelial cells in the adult esophagus are functionally equivalent. In this study, we showed that basal cells in the mouse esophagus contained a heterogeneous population of epithelial cells, similar to other rapidly cycling tissues such as the intestine or skin. Using a combination of cell surface markers, we separated primary esophageal tissue into distinct cell populations that harbored differences in stem cell potential. We also utilized an in vitro 3-D organoid assay to demonstrate that Sox2, Wnt, and bone morphogenetic protein (BMP) signaling regulate esophageal self-renewal. Finally, we labeled proliferating basal epithelial cells in vivo to show differing cell cycle profiles and proliferation kinetics. Based on our results, we propose that a non-quiescent stem cell population resides in the basal epithelium of the mouse esophagus. PMID:25373907

DeWard, Aaron D.; Cramer, Julie; Lagasse, Eric

2014-01-01

100

Heterogeneous reaction rates in an ionic liquid: quantitative results from two-dimensional multiple population-period transient spectroscopy.  

PubMed

The hypotheses that ionic liquids are structurally heterogeneous at the molecular level and, even further, that this heterogeneity can transfer to the rates of reactions run in ionic liquids is being actively debated. Here, this hypothesis is tested using multiple population-period transient spectroscopy (MUPPETS), an emerging type of multidimensional measurement that resolves the kinetics of subensembles within a heterogeneous sample. A previous MUPPETS study of the excited-state twisting and electronic relaxation of auramine indicated that an ionic-liquid solvent induces rate dispersion due to a combination of heterogeneous and homogeneous processes, but those data could not quantitatively separate these contributions [Khurmi, C.; Berg, M. A. J. Phys. Chem. Lett.2010, 1, 161]. New MUPPETS data that include phase resolution and subtraction of thermal gratings are presented here and are successfully modeled. The total range of reaction rates (10--90%) is a factor of 70. If the solvent effect is viewed as a set of local viscosities, the viscosity distribution is broad and highly asymmetric. However, if the solvent is viewed as changing a reaction barrier, the data correspond to a Gaussian distribution of barrier heights. The relaxation of each subensemble is nonexponential with an initial induction period, but the shape of the decay is invariant across the rate distribution. A small (2%), long-lived component is identified as a part of the homogeneous kinetic scheme and thus as a secondary channel for excited-state relaxation, not as an impurity or alternative ground-state form of auramine. On the basis of these results, we suggest that the primary cause of rate heterogeneity is a long-lived local electric field acting on the charge redistribution during the reaction. PMID:21630702

Sahu, Kalyanasis; Kern, Sean J; Berg, Mark A

2011-07-14

101

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

PubMed

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

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

2014-09-01

102

Relation Between Near Work and Myopia Progression in Student Population  

PubMed Central

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

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

2014-01-01

103

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

NASA Astrophysics Data System (ADS)

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

Fu, Guiyuan; Zhang, Weidong; Li, Zhijun

2015-02-01

104

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

PubMed

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

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

2014-07-01

105

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

PubMed

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

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

2014-02-01

106

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

PubMed

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

Møller, Anders Pape; Hobson, Keith A

2004-07-01

107

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

PubMed Central

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

Møller, Anders Pape; Hobson, Keith A.

2004-01-01

108

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

PubMed

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

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

2012-01-01

109

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. PMID:8987359

Davey, H M; Kell, D B

1996-01-01

110

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.

111

Genetic heterogeneity in natural populations of Drosophila melanogaster for ability to withstand dessication  

Microsoft Academic Search

Strains set up from single inseminated females of D. melanogaster derived from two wild populations have been shown to differ in their ability to withstand dessication, as measured by mortalities after 16 hours in a dry environment, thus there are genes segregating in wild populations for ability to withstand dessication. A more detailed study on strains from one of the

P. A. Parsons

1970-01-01

112

Correlation of B type natriuretic peptides with clinical and echocardiographic parameters in heterogeneous population of patients with symptoms suggestive of heart failure  

Microsoft Academic Search

Purpose: NT-proBNP and BNP concentrations in CHF correlate with NYHA class and LVEF. Little research has been conducted to compare the clinical performance of these two natriuretic peptides in heterogeneous CHF population. Purpose: to evaluate and compare the clinical performance of NT-proBNP and BNP in heterogeneous group of CHF patients on the basis of these peptides' correlation with NYHA class,

Piechota WN; Piechota WT; Bejm J; Wierzbowski R

113

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. PMID:16460646

2006-01-01

114

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

115

The Trouble with Diversity: Fork-Join Networks with Heterogenous Customer Population  

E-print Network

Consider a feedforward network of single-server stations populated by multiple job types. Each job requires the completion of a number of tasks whose order of execution is determined by a set of deterministic precedence ...

Nguyen, Viên

116

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

Microsoft Academic Search

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

Pierre-Alexandre Landry; François-Joseph Lapointe

1999-01-01

117

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

PubMed Central

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

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

2014-01-01

118

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. PMID:23908403

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

2013-01-01

119

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

ERIC Educational Resources Information Center

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

El-Koumy, Abdel Salam Abdel Khalek

2009-01-01

120

A Model Biology Curriculum for Heterogeneous Seventh Grade Biology Classes Containing Culturally Deprived Students (In Israel). I. The Theoretical Foundation of the Model  

ERIC Educational Resources Information Center

Describes an experimental seventh grade biology course designed as part of an Israeli education reform program intended to provide a more heterogeneous mixing of disadvantaged students from Asian-African backgrounds and advantaged students from European-American backgrounds. (See SE 514 546 for a related article.) (MLH)

Kaplan, Eugene H.

1975-01-01

121

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

NASA Astrophysics Data System (ADS)

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

Gutierrez A., Natalia A.

2014-06-01

122

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

PubMed Central

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

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

2014-01-01

123

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. PMID:23577323

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

2013-01-01

124

CCAST: a model-based gating strategy to isolate homogeneous subpopulations in a heterogeneous population of single cells.  

PubMed

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

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

2014-07-01

125

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.

126

Not All Smokers Die Young: A Model for Hidden Heterogeneity within the Human Population  

PubMed Central

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

Levine, Morgan; Crimmins, Eileen

2014-01-01

127

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

PubMed Central

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

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

2010-01-01

128

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

NASA Technical Reports Server (NTRS)

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

Czerwinski, Mary; Nguyen, Trung

1994-01-01

129

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

ERIC Educational Resources Information Center

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

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

2013-01-01

130

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

PubMed

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

Parker, J S; Wilby, A S

1989-02-01

131

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

PubMed

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

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

2015-02-01

132

Self-Organising Interaction Patterns of Homogeneous and Heterogeneous Multi-Agent Populations  

Microsoft Academic Search

The organic computing (OC) initiative deals with new design concepts, which facilitate the development of technical systems with life-like properties such as self-organization, self-optimization and self-configuration in order to make them robust, flexible and adaptive. In this paper, we systematically investigate different interaction patterns in self-organizing agent populations using a multi-robot observation scenario from the pursuit (predator-prey) domain. We create

Emre Cakar; Christian Müller-schloer

2009-01-01

133

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

PubMed Central

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

Leblois, Raphael; Rousset, François; Estoup, Arnaud

2004-01-01

134

Guidelines for Death Notification in College Student Populations  

ERIC Educational Resources Information Center

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

Hamilton, Lou Ann

2008-01-01

135

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

136

Heterogeneous dopamine populations project to specific subregions of the primate amygdala.  

PubMed

Amygdala dysfunction has been reported among patients with various psychiatric disorders, and dopamine is critical to the amygdala's ability to mediate fear conditioning. Recent work indicates that the midbrain dopaminergic neurons have heterogeneous receptor and membrane channel profiles, as well as differential physiologic responses to discrete stimuli. To begin understanding how dopamine affects amygdala physiology and pathology in higher primates, we mapped the inputs from the midbrain dopaminergic neurons to various amygdala nuclei in the monkey using retrograde and anterograde tracing techniques, and single and double immunofluorescence histochemistry for tracer and tyrosine hydroxylase, a dopamine marker. Our results show that the primate amygdala as a whole receives broad input, mostly from the dorsal tier of the substantia nigra, pars compacta, and the A8-retrorubral field. Input from the A10-ventral tegmental area, while present, was less prominent. These results differ from data in the rat, where the midline A10-ventral tegmental area is a major source of dopamine to the amygdala "mesolimbic" pathway. Both the "amygdala proper" and the "extended amygdala" receive the majority of their input from the dorsal tier of the substantia nigra and A8-retrorubral field, but the extended amygdala receives additional modest input from the ventral tier. In addition, the "extended amygdala" structures have a denser input than the "amygdala proper," with the exception of the lateral core of the central nucleus, which receives no input. Our anterograde studies confirm these findings, and revealed fine, diffuse terminal fibers in the amygdala proper, but a denser network of fibers in the extended amygdala outside the lateral core of the central nucleus. These results indicate that the entire extent of the dorsal tier beyond the A10-ventral tegmental area may regulate the amygdala in primates, and subsequently serve as a source of dysfunction in primate psychopathology. PMID:19914353

Cho, Y T; Fudge, J L

2010-02-17

137

The wildlife orientation of selected student populations in Victoria, Texas  

E-print Network

vity scores by grade level in VISD students. Of the 12 wildlife-related act1vities used 1n this study, students gave the highest importance value to "went to the zoo", "watched a TV show on wild animals", and "went fishing". The lowest 1mportance... be developed and extended. In th1s study it may be argued that those students with the h1ghest values pertaining to wildlife would be those who scored high in preferences, attitudes, and act1vities, i. e. , the "action" orientation. Conversely, those...

Kirkpatrick, Phyllis Ann Bradley

2012-06-07

138

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

139

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

ERIC Educational Resources Information Center

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

Brehe Pixler, Priscilla

2009-01-01

140

Linguistically and Culturally Diverse Students. Populations: African American & Hmong. Language Sample Analysis Companion Guide.  

ERIC Educational Resources Information Center

The information in this guide should help speech and language pathologists and others who are responsible for the assessment of students from the target populations, African Americans and Hmong students in Wisconsin. The guide provides information pertaining to cultural factors influencing learning and language and recommended procedures for…

Freiberg, Christine

141

A Brief Screening Instrument for Assessing Parental Alcoholism in College Student Populations  

Microsoft Academic Search

The Children of Alcoholics Short Screening Instrument (CASSI), a four-item Likert-type scale, was developed to fulfill the need for a screening instrument to identify children of alcoholics (COAs) in college student populations. A sample of 369 college students was surveyed to assess the psychometric properties of the CASSI; the scale had a Cronbach alpha reliability coefficient of .94 and a

Karen Vail-Smith; Sharon M. Knight; Thomas W. Durham

1996-01-01

142

Investigation of populations heterogeneous according to O-antigen in Vibrio cholerae cultures.  

PubMed

The O-antigenic composition of 36 cultures of Vibrio cholerae agglutinating simultaneously with 01 cholera sera and 0 sera to NAG vibrios of the Sakazaki collection was investigated. It has been established experimentally that under the effect of medium and environmental conditions such cultures dissociate to subcultures differing in their affiliation to different serological groups according to 0 antigen. The passage of these cultures in the organism of susceptible animals promotes preservation of 01-group clones whereas the passage in peptone water or prolonged storage under unfavourable conditions result in the predominance of clones of different serological affiliation. The proposition has been put forward that the observed vibrio cultures are genotypically capable of producing, besides the 01 group, a number of 0 antigens. Phenotypical manifestation of the antigenic structure in the respective individuals of the population depends on the conditions of the environment. PMID:6206130

Andrusenko, I T; Aleksandrova, I K; Pidtilok, E A; Ved'mina, E A; Givental', N I; Pasternak, N A; Shenderovich, V A; Sobolev, V R

1984-01-01

143

Molecular identity and heterogeneity of Trichomonad parasites in a closed avian population.  

PubMed

Columbids (pigeons and doves) are the primary host of Trichomonas gallinae, the flagellate protozoon which causes avian trichomoniasis, a widespread, often lethal disease. Although predominantly apathogenic, the organism is paradigmatic for the study of strain-specific virulence, with some strains causing greater than 75% mortality and epizootic die-offs in wildlife populations. In recent years, research on this important emerging pathogen has been neglected and genetic variation within the parasite has not hitherto been investigated. The pink pigeon (Columba mayeri), endemic to Mauritius and one of the world's rarest pigeons, suffers high levels of nestling/fledgling mortality from trichomoniasis. As a closed oceanic island population with recorded life-history parameters for all birds, this species represents a unique resource for the study of this host-parasite interaction. To investigate genetic variation within T. gallinae in Mauritian columbids, isolates were collected from pink pigeons and another widespread species, the Madagascar turtle-dove (Streptopelia picturata). Comparison of the 5.8S region of rDNA and surrounding internally transcribed spacer regions (ITS) showed no sequence variation between isolates or with an unrelated but previously sequenced T. gallinae isolate (Genbank). This confirmed all 24 isolates as T. gallinae, and defined this section of the genome as a good species marker. In contrast, Random Amplified Polymorphic DNA (RAPD) analysis of the isolates revealed considerable genotypic variation between isolates. RAPD genotypes appeared to correlate with geographic distribution and host species, suggesting inter-species transmission and rapid host adaptation by the parasite. PMID:17320488

Gaspar da Silva, Daniela; Barton, Emma; Bunbury, Nancy; Lunness, Patricia; Bell, Diana J; Tyler, Kevin M

2007-07-01

144

Analysis of biochemical genetic data on Jewish populations: II. Results and interpretations of heterogeneity indices and distance measures with respect to standards.  

PubMed Central

A nonparametric statistical methodology is used for the analysis of biochemical frequency data observed on a series of nine Jewish and six non-Jewish populations. Two categories of statistics are used: heterogeneity indices and various distance measures with respect to a standard. The latter are more discriminating in exploiting historical, geographical and culturally relevant information. A number of partial orderings and distance relationships among the populations are determined. Our concern in this study is to analyze similarities and differences among the Jewish populations, in terms of the gene frequency distributions for a number of genetic markers. Typical questions discussed are as follows: These Jewish populations differ in certain morphological and anthropometric traits. Are there corresponding differences in biochemical genetic constitution? How can we assess the extent of heterogeneity between and within groupings? Which class of markers (blood typings or protein loci) discriminates better among the separate populations? The results are quite surprising. For example, we found the Ashkenazi, Sephardi and Iraqi Jewish populations to be consistently close in genetic constitution and distant from all the other populations, namely the Yemenite and Cochin Jews, the Arabs, and the non-Jewish German and Russian populations. We found the Polish Jewish community the most heterogeneous among all Jewish populations. The blood loci discriminate better than the protein loci. A number of possible interpretations and hypotheses for these and other results are offered. The method devised for this analysis should prove useful in studying similarities and differences for other groups of populations for which substantial biochemical polymorphic data are available. PMID:380330

Karlin, S; Kenett, R; Bonné-Tamir, B

1979-01-01

145

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

146

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

147

Preparation of Agricultural Education Students to Work with Diverse Populations  

ERIC Educational Resources Information Center

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

Talbert, B. Allen; Edwin, James

2008-01-01

148

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

149

Changing Patterns of Cervical Disease in a Student Population.  

ERIC Educational Resources Information Center

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

Rosenthal, Dorothy L.; And Others

1982-01-01

150

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 In this communication we propose to extend the arsenal of microscopy methods for monitoring studies by a new non-invasive and informative method - dynamic phase microscopy DPM The substantial advantage of DPM is that it gives quantitative digitized data of un-destroyed living microscopic objects exemplified in our work by Bacillus licheniformis spores Using DPM made it possible to record interference images of objects spores and to produce picture of their phase thickness PT that is the optical path difference in nm Thus it was demonstrated the remarkable difference in the PT of spores at different physiological states dormant germinating and heat-killed spores had PT values of 80 nm 40-50 nm and 20 nm respectively The other found criterion to distinguish between spores was the PT fluctuations In contrast to dormant and killed spores the PT of germinating spores oscillated with amplitude of up to 7 nm with typical frequencies of 1 3 and 3 4 Hz A combination of the recorded PT values and PT fluctuations gave a key to detect viable and dead cells Under the conditions that did not

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

151

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

152

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

PubMed

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

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

2014-08-01

153

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

Microsoft Academic Search

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

Arijit Nandi; John R Beard; Sandro Galea

2009-01-01

154

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

155

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

PubMed

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

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

2014-10-01

156

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

PubMed

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

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

2014-08-29

157

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

PubMed

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

Hassan, U; Bashir, R

2014-11-21

158

Human immunodeficiency virus-associated oral Kaposi's sarcoma. A heterogeneous cell population dominated by spindle-shaped endothelial cells.  

PubMed Central

Cell lineage and cell function antigens were studied immunohistochemically in human immunodeficiency virus-associated oral Kaposi's sarcoma to provide insight into tumor pathogenesis. All tumors were composed predominantly of spindle cells that expressed endothelium-associated antigens, CD34 and CD36 (factor VIII-related antigen was expressed by considerably fewer numbers of tumor cells). Infrequently, spindle tumor cells also expressed actin. Factor XIIIa positive spindle and dendritic stromal cells comprised up to 9% of the tumor cell population. Other spindle and dendritic cells expressing macrophage-associated antigen, CD68, accounted for up to 15% of the tumor cells. Mast cells occurred frequently within and around tumors. Leukocyte function antigen (CD18) was expressed by approximately 13% of tumor cells, and its ligand, intercellular adhesion molecule (ICAM), was expressed by some tumor-associated capillaries (which also expressed endothelial leukocyte adhesion molecule, ELAM) and occasional stromal cells. Staining for proliferating cell nuclear antigen was noted in both interstitial and vascular lining cells. All tumors were non-reactive for human Papillomavirus antigen and HIV p24 antigen. Oral KS is a heterogeneous cellular proliferation composed predominantly of endothelial or endothelium-related spindle cells. Other spindle/dendritic (XIIIa-positive and CD68-positive) cells and mast cells are also present and may contribute to tumor development. ICAM and ELAM expression within tumors may assist infiltration of macrophages and other inflammatory cells into these lesions. Images Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 PMID:8100400

Regezi, J. A.; MacPhail, L. A.; Daniels, T. E.; DeSouza, Y. G.; Greenspan, J. S.; Greenspan, D.

1993-01-01

159

MODELLING STUDENTS' LEARNING OF INTRODUCTORY STATISTICS  

Microsoft Academic Search

In this exploratory study, we followed approximately 1000 students (Economics and Business) in their freshman year at the University of Maastricht (Netherlands). Those students attended three compulsory courses in Quantitative Methods, each having an important component of statistics. Our population of students exhibits a strong heterogeneity with respect to several aspects: attitude towards and prior knowledge of mathematics and statistics,

Dirk Tempelaar

2002-01-01

160

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

161

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

E-print Network

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

Carin, Lawrence

162

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

ERIC Educational Resources Information Center

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

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

2014-01-01

163

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

ERIC Educational Resources Information Center

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

Freeth, Megan; Bullock, Tom; Milne, Elizabeth

2013-01-01

164

Evaluation of the Technical Evidence of Assessments for Special Student Populations  

ERIC Educational Resources Information Center

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

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

2007-01-01

165

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

ERIC Educational Resources Information Center

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

Yost, Thomas E.

166

Student Difficulties With Trigonometric Vector Components Persist In Multiple Student Populations  

E-print Network

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

Heckler, Andrew F.

167

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

PubMed Central

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 Pakistani medical students and the gender differences in prevalence of BDD, body foci of concern and symptoms of BDD. Methods The medical students enrolled in a medical university in Karachi, Pakistan filled out a self-report questionnaire which assessed clinical features of BDD. BDD was diagnosed according to the DSM-IV criteria. Results Out of the 156 students, 57.1% were female. A total of 78.8% of the students reported dissatisfaction with some aspect of their appearance and 5.8% met the DSM-IV criteria for BDD. The male to female ratio for BDD was 1.7. Regarding gender differences in body foci of concern, the top three reported foci of concern in male students were head hair (34.3%), being fat (32.8%), skin (14.9%) and nose(14.9%), whereas in females they were being fat (40.4%), skin (24.7%) and teeth (18%). Females were significantly more concerned about being fat (p = 0.005). Male students were significantly more concerned about being thin (p = 0.01) and about head hair (p = 0.012). Conclusion BDD is fairly common in our medical student population, with a higher prevalence in males. Important gender differences in BDD symptomatology and reported body foci of concern were identified which reflected the influence of media on body image perception. The impact of cultural factors on the prevalence as well as gender differences in BDD symptomatology was also established. PMID:18400091

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

2008-01-01

168

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

NASA Astrophysics Data System (ADS)

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

Rose, Nancy L.

169

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

170

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

171

Engaging Pharmacy Students with Diverse Patient Populations to Improve Cultural Competence  

PubMed Central

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

2008-01-01

172

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

PubMed Central

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

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

2013-01-01

173

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

PubMed

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

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

2014-12-01

174

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

PubMed

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

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

2014-03-01

175

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

176

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

ERIC Educational Resources Information Center

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

Ho, Ya-Ting

2014-01-01

177

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

178

District-Wide Strategy To Monitor the Placement and Performance of Students From Ethnically Diverse Populations: a Case Study  

Microsoft Academic Search

Disproportionate representation of students from ethnically diverse populations in special education has been a concern at every level from the judicial system and federal legislation to the parents of identified children. Yet, over-referral itself may not be the problem. Rather, the failure may be for students of varying ethnicities to make improvements once identified and receiving services in special education.

Tracey E. Hall

1998-01-01

179

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

USGS Publications Warehouse

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

Dorazio, R.M.

1997-01-01

180

Mutational heterogeneity: A key ingredient of bet-hedging and evolutionary divergence?: The broad spectrum of mutations and their flexible frequency in populations provides a source of risk avoidance and alternative evolutionary strategies.  

PubMed

Here, we propose that the heterogeneity of mutational types in populations underpins alternative pathways of evolutionary adaptation. Point mutations, deletions, insertions, transpositions and duplications cause different biological effects and provide distinct adaptive possibilities. Experimental evidence for this notion comes from the mutational origins of adaptive radiations in large, clonal bacterial populations. Independent sympatric lineages with different phenotypes arise from distinct genetic events including gene duplication, different insertion sequence movements and several independent point mutations. The breadth of the mutational spectrum in the ancestral population should be viewed as a form of bet-hedging, reducing the risk of evolutionary dead ends and complementing the phenotypic and epigenetic heterogeneities that improve the survival capabilities of a population. Different mutational events arise from distinct cellular processes and are subject to separate environmental impacts, so the availability of any particular type of mutation may constrain or promote adaptive pathways in populations. PMID:25370372

Ferenci, Thomas; Maharjan, Ram

2015-02-01

181

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

PubMed Central

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

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

2013-01-01

182

Gustatory expression pattern of the human TAS2R bitter receptor gene family reveals a heterogenous population of bitter responsive taste receptor cells.  

PubMed

Human bitter taste is mediated by approximately 25 members of the human TAS2 receptor (hTAS2R) gene family. The hTAS2R genes are expressed in taste buds of gustatory papillae on the tongue surface. Because many naturally occurring bitter compounds are toxic, bitter taste receptors are believed to serve as warning sensors against the ingestion of toxic food compounds. An important question is whether bitter taste receptor cells are a homogeneous, broadly tuned population of cells, which uniformly express all bitter taste receptor genes, or not. Gene expression analyses in rodents demonstrated an essentially overlapping expression of TAS2R genes indicating a broad tuning, whereas functional in vivo analyses suggest a narrow tuning. The present study demonstrates the expression of all 25 human TAS2R genes in taste receptor cells of human circumvallate papillae. As shown by in situ hybridization experiments, the expression of hTAS2R genes differs in both the apparent level of expression and the number of taste receptor cells expressing these genes, suggesting a heterogeneous bitter taste receptor cell population. Differences in gene expression levels were verified by quantitative reverse transcription-PCR experiments for a subset of hTAS2R genes. Direct evidence for the heterogeneity of bitter taste receptor cells is provided by dual-labeling in situ hybridizations with selected pairs of hTAS2R gene-specific probes. Functional coexpression experiments in heterologous cells show competition among hTAS2Rs, indicating a possible biological reason for the observed expression pattern. From the data, we conclude that human bitter taste receptor cells are tuned to detect a limited subset of bitter stimuli. PMID:18003842

Behrens, Maik; Foerster, Susann; Staehler, Frauke; Raguse, Jan-Dirk; Meyerhof, Wolfgang

2007-11-14

183

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

184

Single-molecule resolution of protein dynamics on polymeric membrane surfaces: the roles of spatial and population heterogeneity.  

PubMed

Although polymeric membranes are widely used in the purification of protein pharmaceuticals, interactions between biomolecules and membrane surfaces can lead to reduced membrane performance and damage to the product. In this study, single-molecule fluorescence microscopy provided direct observation of bovine serum albumin (BSA) and human monoclonal antibody (IgG) dynamics at the interface between aqueous buffer and polymeric membrane materials including regenerated cellulose and unmodified poly(ether sulfone) (PES) blended with either polyvinylpyrrolidone (PVP), polyvinyl acetate-co-polyvinylpyrrolidone (PVAc-PVP), or polyethylene glycol methacrylate (PEGM) before casting. These polymer surfaces were compared with model surfaces composed of hydrophilic bare fused silica and hydrophobic trimethylsilane-coated fused silica. At extremely dilute protein concentrations (10(-3)-10(-7) mg/mL), protein surface exchange was highly dynamic with protein monomers desorbing from the surface within ?1 s after adsorption. Protein oligomers (e.g., nonspecific dimers, trimers, or larger aggregates), although less common, remained on the surface for 5 times longer than monomers. Using newly developed super-resolution methods, we could localize adsorption sites with ?50 nm resolution and quantify the spatial heterogeneity of the various surfaces. On a small anomalous subset of the adsorption sites, proteins adsorbed preferentially and tended to reside for significantly longer times (i.e., on "strong" sites). Proteins resided for shorter times overall on surfaces that were more homogeneous and exhibited fewer strong sites (e.g., PVAc-PVP/PES). We propose that strong surface sites may nucleate protein aggregation, initiated preferentially by protein oligomers, and accelerate ultrafiltration membrane fouling. At high protein concentrations (0.3-1.0 mg/mL), fewer strong adsorption sites were observed, and surface residence times were reduced. This suggests that at high concentrations, adsorbed proteins block strong sites from further protein adsorption. Importantly, this demonstrates that strong binding sites can be modified by changing solution conditions. Membrane surfaces are intrinsically heterogeneous; by employing single-molecule techniques, we have provided a new framework for understanding protein interactions with such surfaces. PMID:25611782

Langdon, Blake B; Mirhossaini, Roya B; Mabry, Joshua N; Sriram, Indira; Lajmi, Ajay; Zhang, Yanxia; Rojas, Orlando J; Schwartz, Daniel K

2015-02-18

185

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

PubMed Central

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

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

2013-01-01

186

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

PubMed

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

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

2014-01-01

187

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

PubMed Central

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

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

2014-01-01

188

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

PubMed

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

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

2013-12-01

189

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

PubMed

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

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

2014-01-01

190

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

PubMed

Non-native plant species can provide native generalist insects, including pests, with novel food and habitats. It is hypothesized that local and landscape-level abundances of non-native plants can affect the population size of generalist insects, although generalists are assumed to be less sensitive to habitat connectivity than specialists. In a heterogeneous landscape in Japan, the relationship between the density of a native pest of rice (Stenotus rubrovittatus (Matsumura) (Heteroptera: Miridae)) and the abundance of Italian ryegrass (Lolium multiflorum Lam. (Poales: Poaceae)), a non-native meadow grass known to facilitate S. rubrovittatus, was analyzed. Statistical analyses of data on bug density, vegetation, and the spatial distribution of fallow fields and meadows dominated by Italian ryegrass, obtained by field surveys, demonstrated that local and landscape-level abundances of Italian ryegrass (the unmowed meadow areas within a few hundred meters of a sampling plot) positively affected bug density before its immigration into rice fields. Our findings suggest that a generalist herbivorous insect that prefers non-native plants responds to spatial availability and connectivity of plant species patches at the metapopulation level. Fragmentation by selective mowing that decreases the total area of source populations and increases the isolation among them would be an effective and environmentally-friendly pest management method. PMID:25368057

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

2014-01-01

191

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

PubMed Central

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

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

2014-01-01

192

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

PubMed

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

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

2014-08-01

193

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

PubMed

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

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

2014-06-01

194

Choices and Motivations: The Why and How of Portuguese Students' Enrolment Choices  

ERIC Educational Resources Information Center

The student population is becoming increasingly diversified and heterogeneous. In a climate of decreasing traditional enrolments in the Portuguese higher education system and increasing competition for students, it becomes essential to understand the reasons and motivations that attract students to higher education and which are the more relevant…

Tavares, Orlanda; Ferreira, Jose Brites

2012-01-01

195

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

PubMed

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

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

2014-12-01

196

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. PMID:22778910

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

2012-01-01

197

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

E-print Network

to implement practices in schools, districts, and school communities that address the needs and challenges they have faced (Hakuta, 2011). 3 Growth of English Language Learner Populations According to Hoefer (2007) in his statement to the House...). According to 2011 NAEP data, the state scored lower than only 8 states in 4th grade reading and 7 states in 4th grade math. However, 80% of students tested were White, 1% of students tested were Black, 14% of students tested were Hispanic, and 3% were...

Shannon, Keri Leigh

2014-01-31

198

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).

199

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

PubMed Central

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

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

2014-01-01

200

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. PMID:23028425

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

2012-01-01

201

The Use of a Heterogeneously Controlled Mouse Population Reveals a Significant Correlation of Acute Phase Parasitemia with Mortality in Chagas Disease  

PubMed Central

Chagas disease develops upon infection with the protozoan parasite Trypanosoma cruzi and undergoes an acute phase characterized by massive parasite replication and the presence of parasites in the blood. This condition is known as acute phase parasitemia. This initial stage may result in a cure, in the development of the chronic stages of the disease or in the death of the infected host. Despite intensive investigation related to the characterization of the acute and chronic phases of the disease, the cause-effect relationship of acute phase parasitemia to the outcome of the disease is still poorly understood. In this study, we artificially generated a heterogeneously controlled mouse population by intercrossing F1 mice obtained from a parental breeding of highly susceptible A/J with highly resistant C57BL/6 mouse strains. This F2 population was infected and used to assess the correlation of acute phase parasitemia with the longevity of the animals. We used nonparametric statistical analyses and found a significant association between parasitemia and mortality. If males and females were evaluated separately, we found that the former were more susceptible to death, although parasitemia was similar in males and females. In females, we found a strong negative correlation between parasitemia and longevity. In males, however, additional factors independent of parasitemia may favor mouse mortality during the development of the disease. The correlations of acute phase parasitemia with mortality reported in this study may facilitate an appropriate prognostic approach to the disease in humans. Moreover, these results illustrate the complexity of the mammalian genetic traits that regulate host resistance during Chagas disease. PMID:24651711

Sanches, Tiago L. M.; Cunha, Larissa D.; Silva, Grace K.; Guedes, Paulo M. M.; Silva, João Santana; Zamboni, Dario S.

2014-01-01

202

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

SciTech Connect

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

Bowen, Brenda

2013-09-30

203

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

204

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

E-print Network

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

Royal Holloway, University of London

205

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

ERIC Educational Resources Information Center

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

Eklund, Julie Ann

2009-01-01

206

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

ERIC Educational Resources Information Center

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

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

2014-01-01

207

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

PubMed Central

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

Mullan, Patricia B.; Chamberlain, Robert M.

2014-01-01

208

Lectin binding of F9 embryonal carcinoma cells: evidence for population heterogeneity and developmentally regulated high-Mr cell surface proteins  

Microsoft Academic Search

Summary Undifferentiated F9 embryonal carcinoma (EC) cells bound fluorochrome-coupled Helix pomatia agglutinins (HPA) and peanut agglutinins (PNA) homogeneously, but were distinctly heterogeneous in their binding of Dolichos biflorus agglutinin (DBA) conjugates. Upon chemically induced differ- entiation the proportion of cells binding the DBA conjugates increased, but a distinct heterogeneity in the intensity of binding remained among the par- ietal endoderm

JUKKA TIENARI; ISMO VIRTANEN; EERO LEHTONEN

1989-01-01

209

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

ERIC Educational Resources Information Center

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

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

2014-01-01

210

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

211

Factors Affecting the Graduation Rates of University Students from Underrepresented Populations  

ERIC Educational Resources Information Center

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

Creighton, Linda M.

2007-01-01

212

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

213

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.

214

Teaching students to work with vulnerable populations through a patient advocacy course.  

PubMed

Nursing students need an in-depth understanding of how social determinants, such as poverty, unsafe housing, and illiteracy, impact the health of patients. The authors describe how a patient advocacy service-learning course increased students' awareness and proficiency in working with the challenges low-income, vulnerable individuals face as they attempt to improve their lives and health. Course learning objectives, essential requirements, and student reflections are presented. PMID:24978016

Bell, Meghan L; Buelow, Janet R

2014-01-01

215

Assessing the Validity and Reliability of a Questionnaire on Dietary Fibre-related Knowledge in a Turkish Student Population  

PubMed Central

This study aimed to validate a questionnaire on dietary fibre (DF)-related knowledge in a Turkish student population. Participants (n=360) were either undergraduate students who have taken a nutrition course for 14 weeks (n=174) or those in another group who have not taken such a nutrition course (n=186). Test-retest reliability, internal reliability, and construct validity of the questionnaire were determined. Overall internal reliability (Cronbach's alpha=0.90) and test-retest reliability (0.90) were high. Significant differences (p<0.001) between the scores of the two groups of students indicated that the questionnaire had satisfactory construct validity. It was found that one-fifth of the students were unsure of the correct answer for any item, and 52.5% of them were not aware that DF had to be consumed on a daily basis. Only 36.4 to 44.2% of the students were able to correctly identify the food sources of DF. PMID:24592591

Deniz, Melike S.

2013-01-01

216

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

217

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

ERIC Educational Resources Information Center

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

FRANKLIN, ELTON

218

Identifying Rural Disadvantaged Gifted Students. Project SPRING: Special Populations Resource Information Network for the Gifted.  

ERIC Educational Resources Information Center

This manual was developed as part of a project to identify and serve the needs of gifted and talented economically disadvantaged elementary and secondary level populations. Section I presents a leader's manual for a workshop that discusses innovative procedures for identifying bright children in all cultures and populations. The workshop examines…

Spicker, Howard H.; Poling, S. Nancy

219

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

ERIC Educational Resources Information Center

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

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

2013-01-01

220

Highly Specific Separation of Heterogeneous Cell Populations by Lectin-Coated Beads: Application for the Isolation of Inner Medullary Collecting Duct Cells  

Microsoft Academic Search

Conditions for the highly specific selection of a cell type by the use of lectin-coated magnetic beads are reported for the isolation of inner medullary collecting duct (IMCD) cells from a heterogeneous inner medullary cell suspension, containing both single cells and tubular fragments of variable size. The lectin Dolichos Biflorus Agglutinin (DBA), which binds in rat inner medulla exclusively to

Clemens Grupp; Ilka Troche; Jürgen Steffgen; Sigrid Langhans; David I. Cohen; Lydia Brandl; Gerhard A. Müller

1998-01-01

221

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

PubMed

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

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

2013-01-01

222

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

223

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

Microsoft Academic Search

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

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

2007-01-01

224

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

225

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

ERIC Educational Resources Information Center

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

Topor, Irene; Rosenblum, L. Penny

2013-01-01

226

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

227

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

228

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

Microsoft Academic Search

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

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

2009-01-01

229

ApoE genotype does not predict lipid response to changes in dietary saturated fatty acids in a heterogeneous normolipidemic population. The DELTA Research Group. Dietary Effects on Lipoproteins and Thrombogenic Activity.  

PubMed

Recent studies have suggested that variations in apoE genotypes may influence the magnitude of plasma lipid changes in response to dietary interventions. We examined the ability of apoE genotype to predict plasma lipid response to reductions in percent of calories from total fat (TF) and saturated fat (SF) in a normolipidemic study population (n = 103) heterogeneous with respect to age, gender, race, and menopausal status. Three diets, an average American diet (34.3% TF, 15.0% SF), an AHA Step 1 diet (28.6% TF, 9.0% SF), and a low saturated fat (Low-Sat) diet (25.3% TF, 6.1% SF) were each fed for a period of 8 weeks in a three-way crossover design. Cholesterol was kept constant at 275 mg/d; monounsaturated and polyunsaturated fat were kept constant at approximately 13% and 6.5% of calories, respectively. Fasting lipid levels were measured during each of the final 4 weeks of each diet period. Participants were grouped by apoE genotype: E2 (E2/2, E2/3, E2/4); E3 (E3/3); E4 (E3/4, E4/4). Relative to the average American diet, both the Step 1 and Low-Sat diets significantly reduced total cholesterol, LDL cholesterol, and HDL cholesterol in all three apoE genotype groups. No evidence of a significant diet by genotype interaction, however, could be identified for any of the measured lipid and lipoprotein end points. Additional analysis of the data within individual population subgroup (men and women, blacks and whites) likewise provided no evidence of a significant diet by genotype interaction. Thus, in a heterogeneous, normolipidemic study population, apoE genotype does not predict the magnitude of lipid response to reductions in dietary saturated fat. PMID:9409276

Lefevre, M; Ginsberg, H N; Kris-Etherton, P M; Elmer, P J; Stewart, P W; Ershow, A; Pearson, T A; Roheim, P S; Ramakrishnan, R; Derr, J; Gordon, D J; Reed, R

1997-11-01

230

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

E-print Network

The Open University Student Employability Policy Statement a) The University acknowledges undertakes to provide student centered support for employability skills development which: · responds of the student employability policy is to ensure that The Open University explicitly addresses and supports

Bandara, Arosha

231

Population Explosion  

NSDL National Science Digital Library

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

The Wisconsin Fast Plants Program

232

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

NASA Astrophysics Data System (ADS)

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

Buck, Gayle A.; Cordes, Jeanene G.

2005-02-01

233

Population Growth  

NSDL National Science Digital Library

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

2007-12-12

234

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

235

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

236

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

237

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

PubMed Central

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

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

2014-01-01

238

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

ERIC Educational Resources Information Center

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

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

2012-01-01

239

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

ERIC Educational Resources Information Center

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

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

2012-01-01

240

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

241

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

PubMed Central

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

2014-01-01

242

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

ERIC Educational Resources Information Center

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

Ben-Tsur, Dalia

2009-01-01

243

Heterogeneity in cancer stem cells.  

PubMed

Accumulating evidence suggests that cancer stem cells (CSCs) are heterogeneous populations and their phenotypes are unstable. A number of intrinsic and extrinsic mechanisms contribute to CSC phenotypic variation. The existence of various CSC subpopulations which would lead to a rapid relapse after primary treatments might pose a problem for CSC targeted therapeutics. In order to develop more effective approaches to cancer therapeutics, more CSC-related surface markers or targeting molecules, as well as some novel targeting strategies should be explored. This review summarized the origin and performance of heterogeneity in CSCs and discussed their therapeutic implications. PMID:25444897

Wang, Anxin; Chen, Lisha; Li, Chunlin; Zhu, Yimin

2015-02-01

244

Deer Population  

NSDL National Science Digital Library

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

School, Maryland V.

245

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

246

Heterogeneous pumice populations in the 2.08-Ma Cerro Gal??n Ignimbrite: Implications for magma recharge and ascent preceding a large-volume silicic eruption  

USGS Publications Warehouse

Triggering mechanisms of large silicic eruptions remain a critical unsolved problem. We address this question for the ~2. 08-Ma caldera-forming eruption of Cerro Gal??n volcano, Argentina, which produced distinct pumice populations of two colors: grey (5%) and white (95%) that we believe may hold clues to the onset of eruptive activity. We demonstrate that the color variations correspond to both textural and compositional variations between the clast types. Both pumice types have bulk compositions of high-K, high-silica dacite to low-silica rhyolite, but there are sufficient compositional differences (e. g., ~150 ppm lower Ba at equivalent SiO2 content and 0.03 wt.% higher TiO2 in white pumice than grey) to suggest that the two pumice populations are not related by simple fractionation. Trace element concentrations in crystals mimic bulk variations between clast types, with grey pumice containing elevated Ba, Cu, Pb, and Zn concentrations in both bulk samples (average Cu, Pb, and Zn concentrations are 27, 35, and 82 in grey pumice vs. 11, 19, and 60 in white pumice) and biotite phenocrysts and white pumice showing elevated Li concentrations in biotite and plagioclase phenocrysts. White and grey clasts are also texturally distinct: White pumice clasts contain abundant phenocrysts (44-57%), lack microlites, and have highly evolved groundmass glass compositions (76.4-79.6 wt.% SiO2), whereas grey pumice clasts contain a lower percentage of phenocrysts/microphenocrysts (35-49%), have abundant microlites, and have less evolved groundmass glass compositions (69.4-73.8 wt.% SiO2). There is also evidence for crystal transfer between magma producing white and grey pumice. Thin highly evolved melt rims surround some fragmental crystals in grey pumice clasts and appear to have come from magma that produced white pumice. Furthermore, based on crystal compositions, white bands within banded pumice contain crystals originating in grey magma. Finally, only grey pumice clasts form breadcrusted surface textures. We interpret these compositional and textural variations to indicate distinct magma batches, where grey pumice originated from an originally deeper, more volatile-rich dacite recharge magma that ascended through and mingled with the volumetrically dominant, more highly crystalline chamber that produced white pumice. Shortly before eruption, the grey pumice magma stalled within shallow fractures, forming a vanguard magma phase whose ascent may have provided a trigger for eruption of the highly crystalline rhyodacite magma. We suggest that in the case of the Cerro Gal??n eruption, grey pumice provides evidence not only for cryptic silicic recharge in a large caldera system but also a probable trigger for the eruption. ?? 2011 Springer-Verlag.

Wright, H.M.N.; Folkes, C.B.; Cas, R.A.F.; Cashman, K.V.

2011-01-01

247

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

248

Classroom and Site-Based Leadership Development: Increasing Achievement and Participation for All Students with an Emphasis on Underserved Populations.  

ERIC Educational Resources Information Center

Outcomes of two leadership programs designed to increase achievement and participation for all students are reviewed in this paper, which addresses educational disparity. The first program, the Gender/Ethnic Expectations and Students Achievement (GESA) program, has four goals: to reduce the disparity in the frequency and quality of student/teacher…

Grayson, Dolores A.

249

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

250

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

ERIC Educational Resources Information Center

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

Moule, Jean; Higgins, Karen M.

2007-01-01

251

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

PubMed

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

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

2013-01-01

252

The role of a student-run clinic in providing primary care for Calgary’s homeless populations: a qualitative study  

PubMed Central

Background Despite the increasing popularity of Student-Run Clinics (SRCs) in Canada, there is little existing literature exploring their role within the Canadian healthcare system. Generalizing American literature to Canadian SRCs is inappropriate, given significant differences in healthcare delivery between the two countries. Medical students at the University of Calgary started a SRC serving Calgary’s homeless population at the Calgary Drop-In and Rehabilitation Centre (CDIRC). This study explored stakeholders’ desired role for a SRC within Calgary’s primary healthcare system and potential barriers it may face. Methods Individual and group semi-structured interviews were undertaken with key stakeholders in the SRC project: clients (potential patients), CDIRC staff, staff from other stakeholder organizations, medical students, and faculty members. Convenience sampling was used in the recruitment of client participants. Interview transcripts were analyzed using a coding template which was derived from the literature. Results Participants identified factors related to the clinic and to medical students that suggest there is an important role for a SRC in Calgary. The clinic was cited as improving access to primary healthcare for individuals experiencing homelessness. It was suggested that students may be ideally suited to provide empathetic healthcare to this population. Barriers to success were identified, including continuity of care and the exclusion of some subsets of the homeless population due to location. Conclusions SRCs possess several unique features that may make them a potentially important primary healthcare resource for the homeless. Participants identified numerous benefits of the SRC to providing primary care for homeless individuals, as well as several important limitations that need to be accounted for when designing and implementing such a program. PMID:23866968

2013-01-01

253

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 an…

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

2012-01-01

254

Identifying subgroup markers in heterogeneous populations.  

PubMed

Traditional methods that aim to identify biomarkers that distinguish between two groups, like Significance Analysis of Microarrays or the t-test, perform optimally when such biomarkers show homogeneous behavior within each group and differential behavior between the groups. However, in many applications, this is not the case. Instead, a subgroup of samples in one group shows differential behavior with respect to all other samples. To successfully detect markers showing such imbalanced patterns of differential signal, a different approach is required. We propose a novel method, specifically designed for the Detection of Imbalanced Differential Signal (DIDS). We use an artificial dataset and a human breast cancer dataset to measure its performance and compare it with three traditional methods and four approaches that take imbalanced signal into account. Supported by extensive experimental results, we show that DIDS outperforms all other approaches in terms of power and positive predictive value. In a mouse breast cancer dataset, DIDS is the only approach that detects a functionally validated marker of chemotherapy resistance. DIDS can be applied to any continuous value data, including gene expression data, and in any context where imbalanced differential signal is manifested. PMID:24062158

de Ronde, Jorma J; Rigaill, Guillem; Rottenberg, Sven; Rodenhuis, Sjoerd; Wessels, Lodewyk F A

2013-11-01

255

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

PubMed

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

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

2013-12-01

256

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

257

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

ERIC Educational Resources Information Center

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

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

2013-01-01

258

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

ERIC Educational Resources Information Center

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

Smith, Gary R.

2009-01-01

259

The competing benefits of noise and heterogeneity in neural coding.  

PubMed

Noise and heterogeneity are both known to benefit neural coding. Stochastic resonance describes how noise, in the form of random fluctuations in a neuron's membrane voltage, can improve neural representations of an input signal. Neuronal heterogeneity refers to variation in any one of a number of neuron parameters and is also known to increase the information content of a population. We explore the interaction between noise and heterogeneity and find that their benefits to neural coding are not independent. Specifically, a neuronal population better represents an input signal when either noise or heterogeneity is added, but adding both does not always improve representation further. To explain this phenomenon, we propose that noise and heterogeneity operate using two shared mechanisms: (1) temporally desynchronizing the firing of neurons in the population and (2) linearizing the response of a population to a stimulus. We first characterize the effects of noise and heterogeneity on the information content of populations of either leaky integrate-and-fire or FitzHugh-Nagumo neurons. We then examine how the mechanisms of desynchronization and linearization produce these effects, and find that they work to distribute information equally across all neurons in the population in terms of both signal timing (desynchronization) and signal amplitude (linearization). Without noise or heterogeneity, all neurons encode the same aspects of the input signal; adding noise or heterogeneity allows neurons to encode complementary aspects of the input signal, thereby increasing information content. The simulations detailed in this letter highlight the importance of heterogeneity and noise in population coding, demonstrate their complex interactions in terms of the information content of neurons, and explain these effects in terms of underlying mechanisms. PMID:24877735

Hunsberger, Eric; Scott, Matthew; Eliasmith, Chris

2014-08-01

260

ATTITUDES TOWARD FAMILY TYPE AND FAMILY SIZE IN WEST AFRICA: A STUDY OF NORMS AMONG A GHANAIAN STUDENT POPULATION  

Microsoft Academic Search

Recently a number of attempts have been made to stimulate more anthropologists to apply the perspectives and concepts of their discipline to population studies. Pleas have also been made for further understanding of the social determinants of fertility, in particular through the exploration of processes occurring in the reproductive unit. This paper, using an anthropological approach, tests a widely held

Christine Oppong

1974-01-01

261

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

2010-12-01

262

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

263

The evidence of glioblastoma heterogeneity.  

PubMed

Cancers are composed of heterogeneous combinations of cells that exhibit distinct phenotypic characteristics and proliferative potentials. Because most cancers have a clonal origin, cancer stem cells (CSCs) must generate phenotypically diverse progenies including mature CSCs that can self-renew indefinitely and differentiated cancer cells that possess limited proliferative potential. However, no convincing evidence exists to suggest that only single CSCs are representative of patients' tumors. To investigate the CSCs' diversity, we established 4 subclones from a glioblastoma patient. These subclones were subsequently propagated and analyzed. The morphology, the self-renewal and proliferative capacities of the subclones differed. Fluorescence-activated cell sorting and cDNA-microarray analyses revealed that each subclone was composed of distinct populations of cells. Moreover, the sensitivities of the subclones to an inhibitor of epidermal growth factor receptor were dissimilar. In a mouse model featuring xenografts of the subclones, the progression and invasion of tumors and animal survival were also different. Here, we present clear evidence that a brain tumor contains heterogeneous subclones that exhibit dissimilar morphologies and self-renewal and proliferative capacities. Our results suggest that single cell-derived subclones from a patient can produce phenotypically heterogeneous self-renewing progenies in both in vitro and in vivo settings. PMID:25623281

Soeda, Akio; Hara, Akira; Kunisada, Takahiro; Yoshimura, Shin-Ichi; Iwama, Toru; Park, Deric M

2015-01-01

264

The Evidence of Glioblastoma Heterogeneity  

PubMed Central

Cancers are composed of heterogeneous combinations of cells that exhibit distinct phenotypic characteristics and proliferative potentials. Because most cancers have a clonal origin, cancer stem cells (CSCs) must generate phenotypically diverse progenies including mature CSCs that can self-renew indefinitely and differentiated cancer cells that possess limited proliferative potential. However, no convincing evidence exists to suggest that only single CSCs are representative of patients' tumors. To investigate the CSCs' diversity, we established 4 subclones from a glioblastoma patient. These subclones were subsequently propagated and analyzed. The morphology, the self-renewal and proliferative capacities of the subclones differed. Fluorescence-activated cell sorting and cDNA-microarray analyses revealed that each subclone was composed of distinct populations of cells. Moreover, the sensitivities of the subclones to an inhibitor of epidermal growth factor receptor were dissimilar. In a mouse model featuring xenografts of the subclones, the progression and invasion of tumors and animal survival were also different. Here, we present clear evidence that a brain tumor contains heterogeneous subclones that exhibit dissimilar morphologies and self-renewal and proliferative capacities. Our results suggest that single cell-derived subclones from a patient can produce phenotypically heterogeneous self-renewing progenies in both in vitro and in vivo settings. PMID:25623281

Soeda, Akio; Hara, Akira; Kunisada, Takahiro; Yoshimura, Shin-ichi; Iwama, Toru; Park, Deric M.

2015-01-01

265

On comparing heterogeneity across biomarkers.  

PubMed

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

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

2014-11-25

266

Maternal genetic correlations in the seed rain: effects of frugivore activity in heterogeneous landscapes  

E-print Network

the maternal genetic correlations in a vertebrate-generated seed rain of a Prunus mahaleb population located, heterogeneous landscape, maternal progenies, maternal richness, microhabitat, Prunus mahaleb, seed dispersal

Jordano, Pedro

267

Exploiting heterogeneous parallelism with the Heterogeneous Programming Library$  

E-print Network

. In this paper we present the Heterogeneous Programming Library (HPL), which permits the development outlining the programmability advantages of HPL. Keywords: programmability, heterogeneity, parallelism on compiler technology. In this paper we present the Heterogeneous Programming Library (HPL), a new

Fraguela, Basilio B.

268

Heterogeneous Semantics in Ptolemy  

E-print Network

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

California at Irvine, University of

269

The readiness of health profession students to comply with a hypothetical program of forced migration of a minority population.  

PubMed

The readiness of Jewish Israeli medical, psychology, and social work students to cooperate in a hypothetical government program involving expulsion of Arabs from Israel was explored via research scenarios that pointedly used terms reminiscent of Holocaust events. Strong moral sensitivity was expected on the part of the study subjects as both Jewish Israelis and vocationally committed to human welfare. The authors argue that the readiness of as many as one-third of the sample to "follow orders" is a disturbing sign, calling for greater vigilance in defense of human rights and values. PMID:2248360

Charny, I W; Fromer, D

1990-10-01

270

Dynamic heterogeneity and life histories.  

PubMed

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

Tuljapurkar, Shripad; Steiner, Ulrich K

2010-08-01

271

The Co-occurrence of DSM-IV Alcohol Abuse in DSM-IV Alcohol Dependence: Results of the National Epidemiologic Survey on Alcohol and Related Conditions on Heterogeneity That Differ by Population Subgroup  

Microsoft Academic Search

preemptedbydependence,althoughthesymptomsofeach disorderaredifferent.Consequently,littleisknownabout the extent to which dependence occurs with or without abuse. The distinction is important because of potential heterogeneity in dependence as a phenotype in genetic research, as well as potential underestimation of alco- hol dependence when surveys cover dependence symp- toms only among those who screen positive for alcohol abuse.

Deborah S. Hasin; Bridget F. Grant

2004-01-01

272

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

PubMed

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

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

2014-05-01

273

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

274

Spatially correlated heterogeneous aspirations to enhance network reciprocity  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

275

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

PubMed

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

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

2014-12-01

276

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

277

Teaching about Population Issues.  

ERIC Educational Resources Information Center

This teaching guide on population issues contains 19 activities for students in grades 7-12. The objective is to analyze population issues that have resulted from human population dynamics. In this guide, four categories of activities are included: some are discussion starters, some provide factual data, some focus on thinking skills, and some are…

Otero, George G., Jr., Comp.

278

Deconstructing transcriptional heterogeneity in pluripotent stem cells.  

PubMed

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

Kumar, Roshan M; Cahan, Patrick; Shalek, Alex K; Satija, Rahul; DaleyKeyser, A Jay; Li, Hu; Zhang, Jin; Pardee, Keith; Gennert, David; Trombetta, John J; Ferrante, Thomas C; Regev, Aviv; Daley, George Q; Collins, James J

2014-12-01

279

Student led part Introduction  

E-print Network

Overview Student led part Introduction Mathematical Biology ­ Matrix Population Projection Models;Overview Student led part Introduction The second lecture focuses on matrix (P)opulation (P)rojection (M)odels­ Stuart Townley Math Bio ­ Matrix PPMs 2/ 5 #12;Overview Student led part Introduction The second lecture

Knobloch,Jürgen

280

Towards heterogeneous distributed debugging  

SciTech Connect

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

Damodaran-Kamal, S.K.

1995-04-01

281

National Articulation and Transfer Network (NATN): Building an Alternative Pathway for Underserved Student Populations To Access Historically Black Colleges and Universities (HBCU), Hispanic Serving Institutions (HSI) & Tribal Colleges and Universities (TCU).  

ERIC Educational Resources Information Center

This is a report on the National Articulation and Transfer Network (NATN) program, which seeks to increase the achievement and aspirations of students from underserved population, namely African Americans, Hispanics, and Native Americans. More than 150 Historically Black Colleges and Universities (HBCU), Hispanic Serving Institutions (HSI), and…

City Coll. of San Francisco, CA.

282

Characterization of Paper Heterogeneity  

NASA Astrophysics Data System (ADS)

Paper and paperboard are the most widely-used green materials in the world because they are renewable, recyclable, reusable, and compostable. Continued and expanded use of these materials and their potential use in new products requires a comprehensive understanding of the variability of their mechanical properties. This work develops new methods to characterize the mechanical properties of heterogeneous materials through a combination of techniques in experimental mechanics, materials science and numerical analysis. Current methods to analyze heterogeneous materials focus on crystalline materials or polymer-crystalline composites, where material boundaries are usually distinct. This work creates a methodology to analyze small, continuously-varying stiffness gradients in 100% polymer systems and is especially relevant to paper materials where factors influencing heterogeneity include local mass, fiber orientation, individual pulp fiber properties, local density, and drying restraint. A unique approach was used to understand the effect of heterogeneity on paper tensile strength. Additional variation was intentionally introduced, in the form of different size holes, and their effect on strength was measured. By modifying two strength criteria, an estimate of strength in the absence of heterogeneity was determined. In order to characterize stiffness heterogeneity, a novel load fixture was developed to excite full-field normal and shear strains for anisotropic stiffness determination. Surface strains were measured with digital image correlation and were analyzed with the VFM (Virtual Fields Method). This approach led to VFM-identified stiffnesses that were similar to values determined by conventional tests. The load fixture and VFM analyses were used to measure local stiffness and local stiffness variation on heterogeneous anisotropic materials. The approach was validated on simulated heterogeneous materials and was applied experimentally to three different paperboards. The analyses were used to create upper and lower stiffness bounds; the scale of the bounds were related to the coefficient of variations of stiffness and grammage variations. This work contributes to understanding of heterogeneous material behavior by characterizing strength loss due to variability and determining stiffness bounds in materials in which heterogeneity varies gradually and is complicated by several, interrelated physical properties.

Considine, John M.

283

Individual heterogeneity and identifiability in capture?recapture models  

USGS Publications Warehouse

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

Link, W.A.

2004-01-01

284

Determining Bird Populations Through Counting  

NSDL National Science Digital Library

This activity is a field investigation where students gather population data on bird species. The students will create bar graphs and interpret their findings. Based on their experiences and data, they will write an answer to the guiding question.

285

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

286

Heterogeneity of small plasmids from halophilic archaea.  

PubMed Central

Small multicopy plasmids in three strains of halophilic archaea, SB3, GRB, and GN101, were found to be present in a cell as a population of related but not identical sequences. Two types of heterogeneity were observed: macroheterogeneity, represented by two major plasmid sequence versions homologous to each other by 80%, and microheterogeneity, in which individual plasmids differ by one or a few nucleotide substitutions. Images PMID:8094388

Akhmanova, A S; Kagramanova, V K; Mankin, A S

1993-01-01

287

Students' Attitude Towards Mathematics  

ERIC Educational Resources Information Center

Students' success in mathematics depends upon attitude towards mathematics. It also influences the participation rate of learners. This study was based on a survey of high school students about their attitudes towards mathematics. Students of both the gender constitute the population of this study. Sample of the study was 685 students (male = 379…

Farooq, Muhammad Shahid; Shah, Syed Zia Ullah

2008-01-01

288

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

289

Site occupancy models with heterogeneous detection probabilities  

USGS Publications Warehouse

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

Royle, J.A.

2006-01-01

290

Monocyte and macrophage heterogeneity.  

PubMed

Heterogeneity of the macrophage lineage has long been recognized and, in part, is a result of the specialization of tissue macrophages in particular microenvironments. Circulating monocytes give rise to mature macrophages and are also heterogeneous themselves, although the physiological relevance of this is not completely understood. However, as we discuss here, recent studies have shown that monocyte heterogeneity is conserved in humans and mice, allowing dissection of its functional relevance: the different monocyte subsets seem to reflect developmental stages with distinct physiological roles, such as recruitment to inflammatory lesions or entry to normal tissues. These advances in our understanding have implications for the development of therapeutic strategies that are targeted to modify particular subpopulations of monocytes. PMID:16322748

Gordon, Siamon; Taylor, Philip R

2005-12-01

291

Conceptualizing a tool to optimize therapy based on dynamic heterogeneity  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

292

World Population Activity I: Excel  

NSDL National Science Digital Library

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

Activity and Starting Point page by R.M. MacKay. Clark College, Physics and Meteorology.

293

Evolution of cooperation through the heterogeneity of random networks  

NASA Astrophysics Data System (ADS)

We use the standardized variance (?st) of the degree distribution of a random network as an analytic measure of its heterogeneity. We show that ?st accurately predicts, quantitatively, the success of cooperators in an evolutionary prisoner’s dilemma. Moreover, we show how the generating functional expression for ?st suggests an intrinsic interpretation for the heterogeneity of the network that helps explain local mechanisms through which cooperators thrive in heterogeneous populations. Finally, we give a simple relationship between ?st , the cooperation level, and the epidemic threshold of a random network that reveals an appealing connection between epidemic disease models and the evolutionary prisoner’s dilemma.

Devlin, Stephen; Treloar, Thomas

2009-01-01

294

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, students in this lesson work in small groups to design experiments that determine how environmental factors affect yeast population growth.

Engineering K-Phd Program

295

Heterogeneous waste processing  

DOEpatents

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

2000-01-01

296

HETEROGENEOUS MODELING AND  

E-print Network

PTOLEMY II HETEROGENEOUS CONCURRENT MODELING AND DESIGN IN JAVA Edited by: Christopher Hylands: INTRODUCTION TO PTOLEMY II Authors: Shuvra S. Bhattacharyya Elaine Cheong John Davis, II Mudit Goel Bart of Electrical Engineering and Computer Sciences University of California at Berkeley http://ptolemy

297

HETEROGENEOUS MODELING AND  

E-print Network

PTOLEMY II HETEROGENEOUS CONCURRENT MODELING AND DESIGN IN JAVA Edited by: Christopher Brooks TO PTOLEMY II Authors: Shuvra S. Bhattacharyya Christopher Brooks Elaine Cheong John Davis, II Mudit Goel of Electrical Engineering and Computer Sciences University of California at Berkeley http://ptolemy

298

-PTOLEMY II -HETEROGENEOUS CONCURRENT  

E-print Network

-PTOLEMY II - HETEROGENEOUS CONCURRENT MODELING AND DESIGN IN JAVA John Davis, II Mudit Goel University of California at Berkeley http://ptolemy.eecs.berkeley.edu Memorandum UCB/ERL M99/40 Document Contents Part 1: Using Ptolemy II 1. Introduction 1-1 1.1.Modeling and Design 1-1 1.2.Architecture Design 1

299

-PTOLEMY II -HETEROGENEOUS CONCURRENT  

E-print Network

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

300

HETEROGENEOUS MODELING AND  

E-print Network

PTOLEMY II HETEROGENEOUS CONCURRENT MODELING AND DESIGN IN JAVA Edited by: Christopher Hylands of California at Berkeley http://ptolemy.eecs.berkeley.edu Document Version 2.0.1 for use with Ptolemy II 2 Concurrent Modeling and Design Contents Part 1: Using Ptolemy II 1. Introduction 1-1 1.1.Modeling and Design

301

Coordinating heterogeneous parallelism  

Microsoft Academic Search

Our goal is to produce a client-server based programming environment to enable massively parallel symbolic computing on heterogeneous ensembles of parallel hardware. Multiple users should be able to log on as clients and use any combination of the resources available, via a single simple language. We want our users to have control over the Kind of parallelism employed by their

Duncan J. Batey; Julian A. Padget

1995-01-01

302

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

303

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

304

Quality of mental health care at a student-run clinic: care for the uninsured exceeds that of publicly and privately insured populations.  

PubMed

Diagnosing and treating depression in a primary care practice is an important, yet difficult task, especially for safety-net practices serving the uninsured. In the United States healthcare system, there is a mismatch between the need for mental health care and access to services. This disparity is most striking among the uninsured. Mental health disorders are more prevalent among the uninsured, and even when diagnosed with mental illness, they are less likely to obtain necessary treatment than insured patients. Given the increasing burden of depression on society, growing numbers of uninsured and negative repercussions of untreated mental illness, improvements in screening and management protocols are becoming more important in primary care practices serving this population. The quality of depression treatment at commercial and public insurance plans in New York City (NYC) and New York State (NYS) were compared to that of the East Harlem Health Outreach Partnership (EHHOP), the student-run clinic of the Mount Sinai School of Medicine. Based on the comparison, the study made recommendations for an integrated, on-site mental health service program at the community health clinic. A cohort of 49 depressed patients were evaluated and treated at the EHHOP clinic. The quality of the mental health care was evaluated according to variables from the Healthcare Effectiveness Data and Information Set (HEDIS). Indicators of quality included demographics, method of diagnosis, type of pharmacological treatment, referral to specialty care, patient adherence to follow-up care and adherence to pharmacologic treatment. When compared to insured patients in NYS, more EHHOP patients had the appropriate number of physician contacts after being diagnosed with depression than patients with commercial health plans (P = 0.008) and Medicaid (P = 0.09). Similarly, a greater number of EHHOP patients had better acute phase (P = 0.001; P = 0.096) and continuous phase (P = 0.049; P = 0.88) pharmacologic treatment than patients with commercial health plans and Medicaid, respectively. EHHOP meets and, in some areas, exceeds the quality of depression treatment when compared to insured populations. Even though EHHOP already surpasses these indicators, the clinic can improve its diagnostic capabilities, prescription medication adherence, and referral care follow-through by creating an on-site mental health clinic. PMID:21298472

Liberman, Kate M; Meah, Yasmin S; Chow, Andrew; Tornheim, Jeffrey; Rolon, Omayra; Thomas, David C

2011-10-01

305

Using Classwide Peer Tutoring To Teach Beginning Algebra Problem-Solving Skills in Heterogeneous Classrooms.  

ERIC Educational Resources Information Center

This study compared the effectiveness of using classwide peer tutoring (CWPT) in 14 heterogeneous eighth-grade math classrooms with traditional independent student practice to teach problem-solving skills to students in beginning algebra. Both CWPT and independent practice were equally effective strategies with students identified as at risk or…

Allsopp, David H.

1997-01-01

306

Heterogeneous Supercomputing: Problems and Issues  

Microsoft Academic Search

While promising feasible solutions to several shortcomings of homogeneous parallel computing, Heterogeneous Supercomputing (HSC) poses new problems to be solved. In this paper, we outline the issues and problems arising in using heterogeneous environments for parallel solutions to various applications. Preliminary solutions to a set of problems in heterogeneous supercomputing are presented. As an example application, implementation of image understanding

Ashfaq Khokhar; Viktor K. Prasanna; Muhammad Shaaban; Cho-Li Wang

1992-01-01

307

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

308

World Population  

NSDL National Science Digital Library

Access and visualize world population data using the user friendly MyWorld GIS software. Data includes total population, population density, projected population, male and female population, and age specific population, etc.

This starting point example compiled by R.M. MacKay. utilizes the MyWorld (more info) Geographic Information System (GIS) software created at Norhtwestern University.

309

The World Population Dilemma.  

ERIC Educational Resources Information Center

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

Population Reference Bureau, Inc., Washington, DC.

310

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

PubMed Central

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

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

2014-01-01

311

Dressing up for School Work? Supporting a Collaborative Environment with Heterogeneous Technologies  

Microsoft Academic Search

This paper approaches heterogeneity and heterogeneous technology as assets, rather than limitations, in the development of computer supported cooperative work. We demonstrate how heterogeneous technologies sustain teachers' and students' school work by presenting four different prototypes (the HyConExplorer, the eCell, the iGameFloor and the eBag) that complement one another because they offer different functionalities and are, at the same time,

Christina Brodersen; Ole Sejer Iversen

2007-01-01

312

Population: Age Structure  

NSDL National Science Digital Library

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

Laposata, Matt

313

-PTOLEMY II -HETEROGENEOUS  

E-print Network

-PTOLEMY II - HETEROGENEOUS CONCURRENT MODELING AND DESIGN IN JAVA John Davis, II Ron Galicia Mudit University of California at Berkeley http://ptolemy.eecs.berkeley.edu Document Version 0.1.1 February 12.2.8. Timed CSP and Timed PN 1-5 1.3.Choosing Models of Computation 1-6 1.4.Visual Syntaxes 1-6 1.5.Ptolemy II

314

PTOLEMY II HETEROGENEOUS  

E-print Network

­PTOLEMY II ­ HETEROGENEOUS CONCURRENT MODELING AND DESIGN IN JAVA John Davis, II Ron Galicia Mudit University of California at Berkeley http://ptolemy.eecs.berkeley.edu Document Version 0.1.1 February 12 Syntaxes 1­6 1.5. Ptolemy II 1­7 1.5.1. Package Structure 1­7 1.5.2. Overview of Key Classes 1­9 1

315

Heterogeneous atmospheric bromine chemistry  

Microsoft Academic Search

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

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

1996-01-01

316

Thermodynamics and Human Population  

NASA Astrophysics Data System (ADS)

This paper discusses a Fermi-problem exercise through which I take students in several of my college courses. Students work in teams, determining the average daily Caloric needs per person. Then they use insolation values to determine the size of a collection area needed to absorb the previously determined daily energy requirements. Adjustments to the size of the collection area are made based on energy absorption per biological trophic level, as well as the consideration that most diets are a mixture of plant- and animal-derived elements. Finally, using the total amount of farmland available on the planet, students calculate a maximum population value. Although the maximum population values derived herewith should not be considered authoritative, the exercise has three beneficial purposes: 1) a chance to talk about the modeling process and extrapolations, 2) an unexpected application of physics to social contexts, and 3) raising student awareness of population and energy issues.

Cordry, Sean M.

2010-09-01

317

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

318

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

E-print Network

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

Bernard, Samuel

319

A Variational Approach to Upscaling Heterogeneous Media  

E-print Network

. Coon, Columbia University January 28, 2010 A Variational Approach to Upscaling Heterogeneous Media- p.1 #12;Heterogeneous Media What makes a medium heterogeneous? · Large relative variation in material to Upscaling Heterogeneous Media- p.2 #12;Heterogeneous Media What makes a medium heterogeneous? · Large

MacLachlan, Scott

320

Foldamers with Heterogeneous Backbones  

PubMed Central

Conspectus The functions carried out by proteins and nucleic acids provide the foundation for life, and chemists have begun to ask whether it is possible to design synthetic oligomers that approach the structural and functional complexity of these biopolymers. The study of foldamers, non-natural oligomers with discrete folding propensities, has demonstrated that a variety of synthetic backbones can show biopolymer-like conformational behavior. Early work in this area focused on oligomers comprised of a single type of monomer subunit, but recent efforts have highlighted the potential of mixed or “heterogeneous” backbones to expand the structural and functional repertoire of foldamers. In this Account, we illustrate the promise of heterogeneous backbone foldamers by focusing on examples containing both ?- and ?-amino acid residues. The use of heterogeneous backbone foldamers offers advantages over homogeneous backbone counterparts, including access to many new molecular shapes, based on variations in the stoichiometries and patterns of subunit combination, and improved prospects for side chain diversification. Recent efforts to develop ?/?-peptide foldamers can be divided into two conceptually distinct classes. The first includes entities prepared by a “block” strategy, in which ?-peptide segments and ?-peptide segments are combined to form a hybrid oligomer. The second class encompasses designs in which ?- and ?-amino acid monomers are interspersed in a regular pattern throughout an oligomer sequence. A variety of secondary structures has been generated from ?/?-peptides via these approaches. Helical secondary structures available to ?/?-peptides have recently been parlayed into higher order structure, specifically, helix bundle quaternary structure. Desirable biological functions have been elicited from ?/?-peptide foldamers. Efforts to mimic naturally occurring host-defense ?-peptides have yielded new antimicrobial agents and led to a re-examination of the long-held views regarding structure-activity relationships among ?-peptides and other amphiphilic oligomers. Foldamers offer new platforms for mimicry of molecular surfaces involved in specific protein-protein recognition events; recent achievements with ?/?-peptide inhibitors of protein-protein interactions involved in apoptotic signaling have revealed benefits of heterogeneous backbones relative to homogeneous backbones for foldamer-based designs. These initial successes in the development of ?/?-peptides with specific biological activities highlight the potential of heterogeneous backbone foldamers for biomedical applications and provide guidelines for the future work on new target functions. PMID:18590282

Horne, W. Seth; Gellman, Samuel H.

2008-01-01

321

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,

322

State Population Projections  

NSDL National Science Digital Library

In this lesson plan students create graphs and analyze data based on the data provided by the United States Census Bureau. Students choose five states to focus on and create a bar graph for each, then students compare the data represented in the graphs and answer questions about the data. The lesson includes student activity sheet, the link to the U.S. Census Bureau is no longer active, please follow this link instead: http://www.census.gov/population/projections/files/stateproj/stpjpop.txt

Burton, Grace M.; Midgett, Carol

2008-01-01

323

TEACHING STATISTICS AND RESEARCH METHODS TO HETEROGENEOUS GROUPS: THE WESTMINSTER EXPERIENCE.  

E-print Network

Teachers of statistics are often faced with the task of teaching their subject to heterogeneous groups of students. At the University of Westminster we are faced with groups of students who are all studying psychology but have very different academic and social backgrounds. To teach statistics and research methods successfully to such heterogeneous groups we have developed teaching and learning strategies to enhance student experience of the course. These strategies encompass curriculum design and student support and include interventions using blended learning, study groups, reflective learning journals and the management of statistics anxiety.

Alan Porter; Tina Cartwright; Rosemary Snelgar

324

The Role of Teacher Education Programs in Creating Culturally Competent Teachers: A Moral Imperative for Ensuring the Academic Success of Diverse Student Populations  

ERIC Educational Resources Information Center

While it is clear that culturally and linguistically diverse students have the greatest need for quality instructional programs, many researchers argue that they are less likely to be taught with the most effective evidence-based instruction. Banks (2002) contends that the challenges facing educators in meeting the needs of multicultural students

Taylor, Roben W.

2010-01-01

325

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

326

Inter-tumor heterogeneity.  

PubMed

Advances in the molecular study of cancer have focused on biomarkers in the setting of tumor-driving mutations within the great heterogeneity of the tumor genomic landscape. It is clearly recognized now that even two tumors originating from the same organ even if histological they appear similar their behavior and response to therapy can be different. These findings have increased interest and research to find truly prognostic and predictive biomarkers to serve as tools in better assessing the natural course of disease and response to treatments in the hope of truly individualizing cancer therapy in the future. PMID:22854659

Cusnir, Mike; Cavalcante, Ludmila

2012-08-01

327

Inter-tumor heterogeneity  

PubMed Central

Advances in the molecular study of cancer have focused on biomarkers in the setting of tumor-driving mutations within the great heterogeneity of the tumor genomic landscape. It is clearly recognized now that even two tumors originating from the same organ even if histological they appear similar their behavior and response to therapy can be different. These findings have increased interest and research to find truly prognostic and predictive biomarkers to serve as tools in better assessing the natural course of disease and response to treatments in the hope of truly individualizing cancer therapy in the future. PMID:22854659

Cusnir, Mike; Cavalcante, Ludmila

2012-01-01

328

Tumor heterogeneity: causes and consequences  

PubMed Central

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

Marusyk, Andriy; Polyak, Kornelia

2009-01-01

329

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

PubMed

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

Pollack, Alexia E

2010-01-01

330

Teaching Population Concepts. Revised Edition.  

ERIC Educational Resources Information Center

This edition is designed to help teachers provide their students with some basic population concepts with stress placed on the elements of decision making. In the first section of the pamphlet, some of the basic concepts of population study are presented. These include populations, growth rates, birth and death rates, doubling time, migration, age…

King, Pat; Landahl, John

331

Anthropogenic Biomes ver. 1 Anthropogenic biomes represent heterogeneous  

E-print Network

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

Columbia University

332

1 Evolving Heterogeneous Neural Agents by Local Selection  

Microsoft Academic Search

Evolutionary algorithms have been applied to the synthesis of neural architec- tures, but they normally lead to uniform populations. Homogeneous solutions, however, are inadequate for certain applications and models. For these cases, local selection may produce the desired heterogeneity in the evolving neural networks. This chapter describes algorithms based on local selection, and dis- cusses the main differences distinguishing them

Filippo Menczer; Melania Degeratu

2000-01-01

333

Heterogeneous photonic integrated circuits  

NASA Astrophysics Data System (ADS)

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

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

2012-01-01

334

Heterogeneity of reactive astrocytes.  

PubMed

Astrocytes respond to injury and disease in the central nervous system (CNS) with a process referred to as reactive astrogliosis. Recent progress demonstrates that reactive astrogliosis is not a simple all-or-none phenomenon, but is a finely gradated continuum of changes that range from reversible alterations in gene expression and cell hypertrophy, to scar formation with permanent tissue rearrangement. There is now compelling evidence that reactive astrocytes exhibit a substantial potential for heterogeneity at multiple levels, including gene expression, cell morphology, topography (distance from lesions), CNS regions, local (among neighboring cells), cell signaling and cell function. Structural and functional changes are regulated in reactive astrocytes by many different potential signaling events that occur in a context dependent manner. It is noteworthy that different stimuli of astrocyte reactivity can lead to similar degrees of GFAP upregulation while causing substantially different changes in transcriptome profiles and cell function. Thus, it is not possible to equate simple and uniform measures such as cell hypertrophy and upregulation of GFAP expression with a single, uniform concept of astrocyte reactivity. Instead, it is necessary to recognize the considerable potential for heterogeneity and determine the functional implications of astrocyte reactivity in a context specific manner as regulated by specific signaling events. PMID:24361547

Anderson, Mark A; Ao, Yan; Sofroniew, Michael V

2014-04-17

335

Heterogeneity in expected longevities.  

PubMed

We develop a new methodology to compute differences in the expected longevity of individuals of a given cohort who are in different socioeconomic groups at a certain age. We address the two main problems associated with the standard use of life expectancy: (1) that people's socioeconomic characteristics change, and (2) that mortality has decreased over time. Our methodology uncovers substantial heterogeneity in expected longevities, yet much less heterogeneity than what arises from the naive application of life expectancy formulae. We decompose the longevity differences into differences in health at age 50, differences in the evolution of health with age, and differences in mortality conditional on health. Remarkably, education, wealth, and income are health-protecting but have very little impact on two-year mortality rates conditional on health. Married people and nonsmokers, however, benefit directly in their immediate mortality. Finally, we document an increasing time trend of the socioeconomic gradient of longevity in the period 1992-2008, and we predict an increase in the socioeconomic gradient of mortality rates for the coming years. PMID:25391225

Pijoan-Mas, Josep; Ríos-Rull, José-Víctor

2014-12-01

336

Sequences and structural organization of phospholipase A2 genes from Vipera aspis aspis, V. aspis zinnikeri and Vipera berus berus venom. Identification of the origin of a new viper population based on ammodytin I1 heterogeneity.  

PubMed

We used a PCR-based method to determine the genomic DNA sequences encoding phospholipases A2 (PLA2s) from the venoms of Vipera aspis aspis (V. a. aspis), Vipera aspis zinnikeri (V. a. zinnikeri), Vipera berus berus (V. b. berus) and a neurotoxic V. a. aspis snake (neurotoxic V. a. aspis) from a population responsible for unusual neurotoxic envenomations in south-east France. We sequenced five groups of genes, each corresponding to a different PLA2. The genes encoding the A and B chains of vaspin from the neurotoxic V. a. aspis, PLA2-I from V. a. zinnikeri, and the anticoagulant PLA2 from V. b. berus are described here. Single nucleotide differences leading to amino-acid substitutions were observed both between genes encoding the same PLA2 and between genes encoding different PLA2s. These differences were clustered in exons 3 and 5, potentially altering the biological activities of PLA2. The distribution and characteristics of the PLA2 genes differed according to the species or subspecies. We characterized for the first time genes encoding neurotoxins from the V. a. aspis and V. b. berus snakes of central France. Genes encoding ammodytins I1 and I2, described previously in Vipera ammodytes ammodytes (V. am. ammodytes), were also present in V. a. aspis and V. b. berus. Three different ammodytin I1 gene sequences were characterized: one from V. b. berus, the second from V. a. aspis, V. a. zinnikeri and the neurotoxic V. a. aspis, and the third from the neurotoxic V. a. aspis. This third sequence was identical with the reported sequence of the V. am. ammodytes ammodytin I1 gene. Genes encoding monomeric neurotoxins of V. am. ammodytes venom, ammodytoxins A, B and C, and the Bov-B LINE retroposon, a phylogenetic marker found in V. am. ammodytes genome, were identified in the genome of the neurotoxic V. a. aspis. These results suggest that the population of neurotoxic V. a. aspis snakes from south-east France may have resulted from interbreeding between V. a. aspis and V. am. ammodytes. PMID:12823540

Guillemin, Isabelle; Bouchier, Christiane; Garrigues, Thomas; Wisner, Anne; Choumet, Valérie

2003-07-01

337

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

PubMed Central

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

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

2013-01-01

338

Heterogeneity of human Platelets  

PubMed Central

Human platelets have been separated into two extreme density populations by centrifugation in specific density media. A large-heavy platelet population with specific gravity > 1.055 and a light-small population with specific gravity < 1.046 were obtained, each representing approximately 15-20% of the total population volume. The average volume per platelet of the separated large-heavy and light-small platelet populations was 12 and 5 ?3 respectively. When data are expressed per milliliter platelets or per gram wet weight, the large-heavy platelet population had a 2-fold greater glycogen content, 1.3-fold greater orthophosphate content, 1.3-fold greater total adenine nucleotide content, 4.2-fold greater rate of glycogenolysis, 2.6-fold greater rate of glycolysis, 2.9-fold greater rate of protein synthesis, and 5.7-fold greater rate of glycogen synthesis. Significant differences were not obtained with respect to total lipid content or total lipid synthesis. The large-heavy platelet had a 2.5-fold greater resistance to osmotic shock as measured by adenosine triphosphate (ATP) or adenosine diphosphate (ADP) release. These data, as well as diisopropyl fluorophosphate (DFP32) survival curves in rabbits, indicate that large-heavy platelets have a greater metabolic potential and suggest that they may be the young platelets which progress with age to light-small platelets with a diminished metabolic potential. PMID:5771188

Karpatkin, Simon; Charmatz, Arthur

1969-01-01

339

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

E-print Network

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

Bakian, Amanda V.

2011-01-01

340

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

E-print Network

This thesis describes the identification and characterization of a novel 'layer' of intrinsic non-genetic functional heterogeneity within the seemingly homogeneous naive CD8? T cell population in their survival and ...

Mahajan, Vinay Subhash

2009-01-01

341

Cancer heterogeneity—a multifaceted view  

PubMed Central

Cancers of various organs have been categorized into distinct subtypes after increasingly sophisticated taxonomies. Additionally, within a seemingly homogeneous subclass, individual cancers contain diverse tumour cell populations that vary in important cancer-specific traits such as clonogenicity and invasive potential. Differences that exist between and within a given tumour type have hampered significantly both the proper selection of patients that might benefit from therapy, as well as the development of new targeted agents. In this review, we discuss the differences associated with organ-specific cancer subtypes and the factors that contribute to intra-tumour heterogeneity. It is of utmost importance to understand the biological causes that distinguish tumours as well as distinct tumour cell populations within malignancies, as these will ultimately point the way to more rational anti-cancer treatments. EMBO reports advance online publication 12 July 2013; doi:10.1038/embor.2013.92 PMID:23846313

Melo, Felipe De Sousa E; Vermeulen, Louis; Fessler, Evelyn; Medema, Jan Paul

2013-01-01

342

Heterogeneity in Waardenburg syndrome.  

PubMed Central

Heterogeneity of Waardenburg syndrome is demonstrated in a review of 1,285 patients from the literature and 34 previously unreported patients in five families in the Netherlands. The syndrome seems to consist of two genetically distinct entities that can be differentiated clinically: type I, Waardenburg syndrome with dystopia canthorum; and type II, Waardenburg syndrome without dystopia canthorum. Both types have an autosomal dominant mode of inheritance. The incidence of bilateral deafness in the two types of the syndrome was found in one-fourth with type I and about half of the patients with type II. This difference has important consequences for genetic counseling. Images Fig. 7 Fig. 8 Fig. 9 PMID:331943

Hageman, M J; Delleman, J W

1977-01-01

343

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

344

Measuring Proximity between Heterogeneous Data  

Microsoft Academic Search

Measuring proximity (or similarity) underlies many algorithms in information processing (by humans or indeed animals, or by machines). When the data involved are heterogeneous this issue is further complicated. This paper discusses some of the difficulties of measuring similarity between heterogeneous data and possible directions for addressing these difficulties using computational intelligence\\/fuzzy set based techniques. An important concept underlying the

Anca Ralescu; Michihiko Minoh

2007-01-01

345

Heterogeneous Programming Library Programming Manual  

E-print Network

Heterogeneous Programming Library Programming Manual HPL Team August 23, 2013 #12;Contents 1.2.1 HPL automatic variables . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.2.2 Control flow variables 17 1 #12;1 Introduction The Heterogeneous Programming Library (HPL) provides a programming

Fraguela, Basilio B.

346

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

347

Discriminating cellular heterogeneity using microwell-based RNA cytometry  

PubMed Central

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

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

2014-01-01

348

Quantitative Population Ecology  

NSDL National Science Digital Library

Dr. Alexei Sharov of the Department of Entomology at Virginia Tech has put together this excellent teaching resource on quantitative population ecology. The online resource contains thirteen lecture handouts and eight labs, targeting beginning graduate or advanced undergraduate students; the course requires a basic understanding of statistics and ecology. Each chapter contains a concise introduction to the topic plus several more detailed subsections. The chapters are well organized and easy to navigate, and include useful color illustrations and mathematical equations. For educators and students of quantitative population ecology alike, this exceptional resource is hard to beat.

349

Competition in phenotypically variable and uniform populations of the tadpole shrimp Triops longicaudatus (Notostraca: Triopsidae)  

Microsoft Academic Search

Life-history parameters (growth, reproduction, and survival) were measured from one genetically heterogeneous and three homogeneous populations of tadpole shrimp (Triops longicaudatus) raised under three competitive levels: 5, 10, and 16 shrimp per 38-1 aquarium. Comparisons were made between the homogeneous populations (three monomorphic selfing lines) and a heterogeneous population (a mixture of the three lines) to test for increased productivity

Clay Sassaman

1990-01-01

350

Population Structures and Cohorts  

NSDL National Science Digital Library

This module provides a gentle introduction to the use of StudentChip software and census data to investigate basic population issues. In the first part of this module, you will use data from the 1990 U.S. census to create population pyramids for several racial and ethnic groups. These population pyramids provide the ability to view the age and sex structure of a population. They not only allow us to view the cumulative impacts of past patterns of fertility, mortality, and migration, but also provide hints about what a particular population is likely to look like in the future. In the second part of the module you will continue our exploration of basic U.S. population structures by comparing some of the basic characteristics of a number of distinct birth cohorts.

Crowder, Kyle

2009-04-20

351

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

ERIC Educational Resources Information Center

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

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

2014-01-01

352

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

353

Spatial heterogeneity study of vegetation coverage at Heihe River Basin  

NASA Astrophysics Data System (ADS)

Spatial heterogeneity of the animal-landscape system has three major components: heterogeneity of resource distributions in the physical environment, heterogeneity of plant tissue chemistry, heterogeneity of movement modes by the animal. Furthermore, all three different types of heterogeneity interact each other and can either reinforce or offset one another, thereby affecting system stability and dynamics. In previous studies, the study areas are investigated by field sampling, which costs a large amount of manpower. In addition, uncertain in sampling affects the quality of field data, which leads to unsatisfactory results during the entire study. In this study, remote sensing data is used to guide the sampling for research on heterogeneity of vegetation coverage to avoid errors caused by randomness of field sampling. Semi-variance and fractal dimension analysis are used to analyze the spatial heterogeneity of vegetation coverage at Heihe River Basin. The spherical model with nugget is used to fit the semivariogram of vegetation coverage. Based on the experiment above, it is found, (1)there is a strong correlation between vegetation coverage and distance of vegetation populations within the range of 0?28051.3188m at Heihe River Basin, but the correlation loses suddenly when the distance greater than 28051.3188m. (2)The degree of spatial heterogeneity of vegetation coverage at Heihe River Basin is medium. (3)Spatial distribution variability of vegetation occurs mainly on small scales. (4)The degree of spatial autocorrelation is 72.29% between 25% and 75%, which means that spatial correlation of vegetation coverage at Heihe River Basin is medium high.

Wu, Lijuan; Zhong, Bo; Guo, Liyu; Zhao, Xiangwei

2014-11-01

354

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

PubMed Central

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

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

2013-01-01

355

Systemic Equity Pedagogy in Science Education: A Mixed-Method Analysis of High Achieving High Schools of Culturally Diverse Student Populations in Texas  

E-print Network

administrators and teachers face the challenges found in culturally diverse classrooms (Kahle, 1998; Hewson, Kahle, Scantlebury, & Davies, 2001; Hammond, 2006; Rodriquez, 2001). Furthermore, Borman et al. (1005) identified key factors, or ?drivers... targeted by systemic reform included promoting equitable teaching practices, meeting curriculum standards, reducing the achievement gap, and developing students prepared for college (Borman et al., 2005; Edmonds, 1979; Hammond, 2006; Hewson, Kahle...

Blocker, Tyrone Dewayne

2013-08-14

356

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

357

Assessing Life Styles, Stressors and Health Status among a Predominantly African American On-Campus and Off-Campus Student Population  

ERIC Educational Resources Information Center

Students who attend college and reside on campus often have to contend with social problems such as alcohol and drug abuse, HIV/AIDS infection, courtship, sex and marriage, home and family and other social-psychological issues while trying to maintain academically and matriculate to graduation. Earlier research from the 1995 National College…

Hicks, Terence; Herndon, Michael; Hilton, Adriel; Attoh, Prince; Armstrong, Vikki

2013-01-01

358

Relationship of spirituality, subjective well-being, and psychological well-being in a population of African-American college students  

Microsoft Academic Search

The purpose of this study was to examine the relationship of four variables: spirituality, religiosity, subjective well-being, and psychological well-being. Subjects were 51 male and 106 female African American college students recruited from various undergraduate classes. Each participant completed a demographic questionnaire concerning religious activity and a battery of surveys including the Spiritual Involvement and Beliefs Scale, the Scales of

Mary Elizabeth Walker

2009-01-01

359

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

SciTech Connect

The objective of this project was to characterize the influence that naturally complex geologic media has on anomalous dispersion and to determine if the nature of dispersion can be estimated from the underlying heterogeneous media. The UNM portion of this project was to provide detailed representations of aquifer heterogeneity through producing highly-resolved models of outcrop analogs to aquifer materials. This project combined outcrop-scale heterogeneity characterization (conducted at the University of New Mexico), laboratory experiments (conducted at Sandia National Laboratory), and numerical simulations (conducted at Sandia National Laboratory and Colorado School of Mines). The study was designed to test whether established dispersion theory accurately predicts the behavior of solute transport through heterogeneous media and to investigate the relationship between heterogeneity and the parameters that populate these models. The dispersion theory tested by this work was based upon the fractional advection-dispersion equation (fADE) model. Unlike most dispersion studies that develop a solute transport model by fitting the solute transport breakthrough curve, this project explored the nature of the heterogeneous media to better understand the connection between the model parameters and the aquifer heterogeneity. We also evaluated methods for simulating the heterogeneity to see whether these approaches (e.g., geostatistical) could reasonably replicate realistic heterogeneity. The UNM portion of this study focused on capturing realistic geologic heterogeneity of aquifer analogs using advanced outcrop mapping methods.

Weissmann, Gary S

2013-12-06

360

An investigation into trends in Advanced Placement test taking in science and mathematics among student sub-populations using a longitudinal growth model  

NASA Astrophysics Data System (ADS)

The lack of preparation, participation, and equal access of students in mathematics and the science education continues to afflict America's high school system (Ratliff, 2001). Additionally, gender and ethnic status have become significant factors as females and minority subgroups such as African Americans and Hispanics continue to be underrepresented in these two subject fields. Recognizing and understanding these trends is extremely important for the future of this country. As fewer minorities and females become involved in advanced mathematics and science curriculum there will be a continued lack of minorities and females in mathematics and science careers. Additionally, this insufficient representation leads to fewer numbers of females and minorities in industry and educational leadership positions in mathematics and science to promote participation and equality in these fields. According to Brainard and Carlin (2003) as trends currently stand, these two groups will be under-represented in the fields of math and science and will continue to be denied economic and social power. Thus, a better understanding of these trends in participation in mathematics and science among these groups of students is warranted. This study is intended to accomplish four objectives. The first objective is to identify the extent to which opportunities are increasing or decreasing for students in high schools taking mathematics and science Advanced Placement exams by examining six years of student testing data from the College Board. A second objective is to identify features of high schools that relate to greater expansion in Advanced Placement test taking for females and minority groups in the areas of both math and science. A third objective is to explore whether, and to what extent, any social or educational features such as economic status, regional school and living locations, and ethnic backgrounds have enhanced or reduced Advanced Placement testing in these schools. Lastly, the fourth objective is to determine which courses are showing the greatest growth rates in minority and female students among mathematics and science subject areas.

Campbell, D. Michael

361

Mechanism of heterogeneous  

NASA Astrophysics Data System (ADS)

The present article describes a novel theoretical approach to the mechanism of heterogeneous nucleation of pores in metallic systems. The proposed mechanism is based on the behavior of foreign particles at the advancing solid/liquid (S/L) interface. Foreign substrates act as a barrier to the fluid flow as well as to the diffusion field at the S/L interface, giving rise to enhanced gas segregation and viscous pressure drop. Mathematical analyses have been employed to pre- dict the gas segregation and pressure drop in the gap between the particle and the S/L interface. The equations which arise are solved using available experimental data in the literature. An order of magnitude analysis is done, and it is shown that pressures in the range of the activation barrier (fracture pressure) can be obtained in normal castings. The effect of particle properties and solidification parameters, such as wettability, density, thermal conductivity, solidification rate and morphology of S/L interface, are discussed. A complete assessment of all possible kinds of particles is not possible, since the material values and experimental parameters are not known in most of the cases. To consolidate the mechanism, therefore, further quantitative measurements of material values, interfacial energies in particular, are required on systems of interest.

Mohanty, P. S.; Samuel, F. H.; Gruzleski, J. E.

1993-08-01

362

Perspectives on heterogeneous photochemistry.  

PubMed

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

Friend, Cynthia M

2014-10-01

363

Generalized principles of stochasticity can be used to control dynamic heterogeneity  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

364

Node assignment in heterogeneous computing  

NASA Technical Reports Server (NTRS)

A number of node assignment schemes, both static and dynamic, are explored for the Algorithm to Architecture Mapping Model (ATAMM). The architecture under consideration consists of heterogeneous processors and implements dataflow models of real-time applications. Terminology is developed for heterogeneous computing. New definitions are added to the ATAMM for token and assignment classifications. It is proved that a periodic execution is possible for dataflow graphs. Assignment algorithms are developed and proved. A design procedure is described for satisfying an objective function in an heterogeneous architecture. Several examples are provided for illustration.

Som, Sukhamoy

1993-01-01

365

Landscape heterogeneity shapes host-parasite interactions and results in apparent plant-virus codivergence.  

PubMed

Knowledge on how landscape heterogeneity shapes host-parasite interactions is central to understand the emergence, dynamics and evolution of infectious diseases. However, this is an underexplored subject, particularly for plant-virus systems. Here, we analyse how landscape heterogeneity influences the prevalence, spatial genetic structure, and temporal dynamics of Pepper golden mosaic and Pepper huasteco yellow vein begomoviruses infecting populations of the wild pepper Capsicum annuum glabriusculum (chiltepin) in Mexico. Environmental heterogeneity occurred at different nested spatial scales (host populations within biogeographical provinces), with levels of human management varying among host population within a province. Results indicate that landscape heterogeneity affects the epidemiology and genetic structure of chiltepin-infecting begomoviruses in a scale-specific manner, probably related to conditions favouring the viruses' whitefly vector and its dispersion. Increased levels of human management of the host populations were associated with higher virus prevalence and erased the spatial genetic structure of the virus populations. Also, environmental heterogeneity similarly shaped the spatial genetic structures of host and viruses. This resulted in the congruence between host and virus phylogenies, which does not seem to be due to host-virus co-evolution. Thus, results provide evidence of the key role of landscape heterogeneity in determining plant-virus interactions. PMID:23379795

Rodelo-Urrego, M; Pagán, I; González-Jara, P; Betancourt, M; Moreno-Letelier, A; Ayllón, M A; Fraile, A; Piñero, D; García-Arenal, F

2013-04-01

366

Ocean Predator/Prey Populations  

NSDL National Science Digital Library

Susan Kelly Topic: Population change Course type: Introductory undergraduate course Description Modeling impact of change in food web Learning Goals or Outcomes Students will see how changes on one trophic level ...

367

Population and Development Issues.  

ERIC Educational Resources Information Center

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

Cohen, Sharon; Garran, Christopher

1998-01-01

368

Population Geography: Problems, Concepts, and Prospects.  

ERIC Educational Resources Information Center

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

Peters, Gary L.; Larkin, Robert P.

369

Tomographic Characterization of Aquifer Heterogeneity  

E-print Network

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

Lyle, Shane

2011-05-31

370

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

371

Heterogeneity of Aspergillus niger microcolonies in liquid shaken cultures.  

PubMed

The fungus Aspergillus niger forms (sub)millimeter microcolonies within a liquid shaken culture. Here, we show that such microcolonies are heterogeneous with respect to size and gene expression. Microcolonies of strains expressing green fluorescent protein (GFP) from the promoter of the glucoamlyase gene glaA or the ferulic acid esterase gene faeA were sorted on the basis of diameter and fluorescence using the Complex Object Parametric Analyzer and Sorter (COPAS) technology. Statistical analysis revealed that the liquid shaken culture consisted of two populations of microcolonies that differ by 90 ?m in diameter. The population of small microcolonies of strains expressing GFP from the glaA or faeA promoter comprised 39% and 25% of the culture, respectively. Two populations of microcolonies could also be distinguished when the expression of GFP in these strains was analyzed. The population expressing a low level of GFP consisted of 68% and 44% of the culture, respectively. We also show that mRNA accumulation is heterogeneous within microcolonies of A. niger. Central and peripheral parts of the mycelium were isolated with laser microdissection and pressure catapulting (LMPC), and RNA from these samples was used for quantitative PCR analysis. This analysis showed that the RNA content per hypha was about 45 times higher at the periphery than in the center of the microcolony. Our data imply that the protein production of A. niger can be improved in industrial fermentations by reducing the heterogeneity within the culture. PMID:21169437

de Bekker, Charissa; van Veluw, G Jerre; Vinck, Arman; Wiebenga, L Ad; Wösten, Han A B

2011-02-01

372

Medical Student Surgery Elective in Rural Haiti: A Novel Approach to Satisfying Clerkship Requirements While Providing Surgical Care to an Underserved Population  

Microsoft Academic Search

Background  The addition of global health programs to medical school training results in graduates with enhanced clinical skills and increased\\u000a sensitivity to cost issues. Funding from U.S. medical schools has been unable to meet student demand, and therefore it is\\u000a often a critical limiting factor to the lack of development of these programs. We describe an alternative approach for global\\u000a health

Anthony Chin-Quee; Laura White; Ira Leeds; Jana MacLeod; Viraj A. Master

2011-01-01

373

Off-Campus Student Services Dear Neighbor,  

E-print Network

-Campus Student Services Stephanie.Salazar@asu.edu · Participation in the Fall and Spring Housing Fair the university and its off-campus student population. This program supports the mission of Off-Campus Student1 get Off-Campus Student Services connected #12;2 2 Dear Neighbor, Off-Campus Student Services

Hall, Sharon J.

374

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

375

Cellular Respiration and Population Growth  

NSDL National Science Digital Library

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

Engineering K-Phd Program

376

Optimized caching in systems with heterogeneous client populations  

Microsoft Academic Search

Supporting on-demand access to large widely shared data, such as popular video objects, requires effec tive use of regional (proxy) servers that store some of the da ta close to the clients. The proxy caching problem is more complex in the context of continuous media files because of the ne ed to consider bandwidth as well as storage constraints at

Derek L. Eager; Michael C. Ferris; Mary K. Vernon

2000-01-01

377

Routing in Delay-Tolerant Networks Comprising Heterogeneous Node Populations  

Microsoft Academic Search

Communication networks are traditionally assumed to be connected. However, emerging wireless applications such as vehicular networks, pocket-switched networks, etc., coupled with volatile links, node mobility, and power outages, will require the network to operate despite frequent disconnections. To this end, opportunistic routing techniques have been proposed, where a node may store-and-carry a message for some time, until a new forwarding

Thrasyvoulos Spyropoulos; Thierry Turletti; Katia Obraczka

2009-01-01

378

Spatial Heterogeneity in Mycorrhizal Populations and Communities: Scales and Mechanisms  

Microsoft Academic Search

The importance of a spatial context in understanding the ecology and evolution of organisms has become increasingly clear.\\u000a Although there is a growing awareness of the importance of mycorrhizal fungi in many communities and ecosystems, much of this\\u000a understanding is based on a spatially homogenized view of these soil fungi. This homogenized approach may limit our understanding\\u000a of how these

Benjamin E. Wolfe; Jeri L. Parrent; Alexander M. Koch; Benjamin A. Sikes; Monique Gardes; John N. Klironomos

379

Social Mobility Models for Heterogeneous Populations Burton Singer; Seymour Spilerman  

E-print Network

?zity Act of 1964. TVe wish to thank S e i l Henry and I . Richard Savage for their comments on a n earlier, 1960; Hodge, 1966; Blumen, Mogan, and AIcCarthy, 1955), income dynamics (Smith and Cain, 1967; JIc

Fienberg, Stephen E.

380

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

PubMed Central

Individual variation in reproductive success is a key feature of evolution, but also has important implications for predicting population responses to variable environments. Although such individual variation in reproductive outcomes has been reported in numerous studies, most analyses to date have not considered whether these realized differences were due to latent individual heterogeneity in reproduction or merely random chance causing different outcomes among like individuals. Furthermore, latent heterogeneity in fitness components might be expressed differently in contrasted environmental conditions, an issue that has only rarely been investigated. Here, we assessed (i) the potential existence of latent individual heterogeneity and (ii) the nature of its expression (fixed vs. variable) in a population of female Weddell seals (Leptonychotes weddellii), using a hierarchical modeling approach on a 30-year mark–recapture data set consisting of 954 individual encounter histories. We found strong support for the existence of latent individual heterogeneity in the population, with “robust” individuals expected to produce twice as many pups as “frail” individuals. Moreover, the expression of individual heterogeneity appeared consistent, with only mild evidence that it might be amplified when environmental conditions are severe. Finally, the explicit modeling of individual heterogeneity allowed us to detect a substantial cost of reproduction that was not evidenced when the heterogeneity was ignored. PMID:23919151

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

2013-01-01

381

Genetic Heterogeneity of Hepatitis C Virus in Association with Antiviral Therapy Determined by Ultra-Deep Sequencing  

Microsoft Academic Search

Background and AimsThe hepatitis C virus (HCV) invariably shows wide heterogeneity in infected patients, referred to as a quasispecies population. Massive amounts of genetic information due to the abundance of HCV variants could be an obstacle to evaluate the viral genetic heterogeneity in detail.MethodsUsing a newly developed massive-parallel ultra-deep sequencing technique, we investigated the viral genetic heterogeneity in 27 chronic

Akihiro Nasu; Hiroyuki Marusawa; Yoshihide Ueda; Norihiro Nishijima; Ken Takahashi; Yukio Osaki; Yukitaka Yamashita; Tetsuro Inokuma; Takashi Tamada; Takeshi Fujiwara; Fumiaki Sato; Kazuharu Shimizu; Tsutomu Chiba; Yoshio Yamaoka

2011-01-01

382

Population Density: How Much Space Do You Have?  

NSDL National Science Digital Library

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

Integrated Teaching And Learning Program

383

Improving Student Engagement.  

ERIC Educational Resources Information Center

This action research project implemented and evaluated an intervention for improving student engagement in the learning process. The targeted population consisted of first, third, and fifth grade students in a small, traditional, middle class community, located in central Illinois. Evidence of non-engaged behaviors were documented from teacher…

Beuscher, Shonna; Keuer, Lynn; Muehlich, Sharon; Tyra, Carol

384

Challenging Students to Achieve  

ERIC Educational Resources Information Center

With the specter of No Child Left Behind hanging over their heads, educators should be wary of using disaggregated data to track selected populations of students and their progress through school. Such data can be misleading by showing that students are doing well, although they may be taking classes that are not challenging. Although the myth of…

VanSciver, James H.

2004-01-01

385

Genomic Heterogeneity and Structural Variation in Soybean Near Isogenic Lines  

PubMed Central

Near isogenic lines (NILs) are a critical genetic resource for the soybean research community. The ability to identify and characterize the genes driving the phenotypic differences between NILs is limited by the degree to which differential genetic introgressions can be resolved. Furthermore, the genetic heterogeneity extant among NIL sub-lines is an unaddressed research topic that might have implications for how genomic and phenotypic data from NILs are utilized. In this study, a recently developed high-resolution comparative genomic hybridization (CGH) platform was used to investigate the structure and diversity of genetic introgressions in two classical soybean NIL populations, respectively varying in protein content and iron deficiency chlorosis (IDC) susceptibility. There were three objectives: assess the capacity for CGH to resolve genomic introgressions, identify introgressions that are heterogeneous among NIL sub-lines, and associate heterogeneous introgressions with susceptibility to IDC. Using the CGH approach, introgression boundaries were refined and previously unknown introgressions were revealed. Furthermore, heterogeneous introgressions were identified within seven sub-lines of the IDC NIL “IsoClark.” This included three distinct introgression haplotypes linked to the major iron susceptible locus on chromosome 03. A phenotypic assessment of the seven sub-lines did not reveal any differences in IDC susceptibility, indicating that the genetic heterogeneity among the lines does not have a significant impact on the primary NIL phenotype. PMID:23630538

Stec, Adrian O.; Bhaskar, Pudota B.; Bolon, Yung-Tsi; Nolan, Rebecca; Shoemaker, Randy C.; Vance, Carroll P.; Stupar, Robert M.

2013-01-01

386

Heterogeneous components of chitosans.  

PubMed

The main objectives of the research were to compare the components of partially N-deacetylated chitins prepared identically from native chitin and a chitin regenerated from a heavily deacetylated chitosan. Additionally, to determine if any of the water-soluble components would serve as substrates in a study of a Chitinase isolated from soy bean hull. The brief heating of suspended chitins in 20% (w/w) NaOH resulted in similar degrees of N-deacetylation, the native chitin giving DAc 0.84 and the regenerated chitin DAc 0.79-0.72, with DAc indicating the proportion of glucosamine residues that are acetylated. Evidence for the nature of the hydrolysis of acetamido groups was provided by analyses of the water-soluble and -insoluble Smith degradation products. The water-soluble fraction derived from the native chitin comprised very small amounts of erythrityl N-acetyl glucosaminoside (GlcNAc1E), erythrityl N,N'-diacetyl chitobioside (GlcNAc2E), and erythrityl N,N',N''-triacetyl chitotrioside (GlcNAc3E), each identified by MALDI-TOF mass spectrometry of the butanoyl derivative. The water-insoluble products, as analyzed by light scattering detection method of their butanoyl esters and corrected for their composition, had a molecular weight (Mw) of 25 kDa, corresponding to about 120 N-acetyl glucosaminyl repeating residues (DPw), contrasting to that of 140 kDa with DPw of 680 for the parent chitin. Much of the decrease in the molecular weight of the polymer occurs by the loss of sugar residues by alkaline peeling at reducing terminals. For the regenerated chitin (DAc 1.0), prepared by N-reacetylation of a commercial chitosan (DAc 0.15), the resulting Smith products comprised erythritol and a series of N-acetyl glucosaminyl erythritol homologues of up to at least 39 N-acetyl glucosaminyl repeating residues, reflecting greater heterogeneity in the hydrolysis of acetamido groups along the polymer chain than what was seen for the native chitin. Of the water-soluble Smith products, GlcNAc5-7E were good substrates for chitinase isolated from soybean hull. PMID:20957998

Yang, Byung Y; Ding, Qiong; Montgomery, Rex

2010-11-01

387

Cooperation in a Game of Chicken with Heterogeneous Agents: An experimental study  

E-print Network

of population heterogeneity on cooperative behaviour. For that purpose, they introduce two different types to the main predictions that the structure of the population as well as the structure of the payoffs affect barely cooperate or not cooperate at all. The most investigated two- and multiple- person games (prisoner

Paris-Sud XI, Université de

388

The Heterogeneous HLA Genetic Makeup of the Swiss Stephane Buhler1  

E-print Network

the genetic diversity of the national--and hence global--donor registry. It also indicates that HLA data genetic studies focusing on the genetic history of present European populations. Citation: Buhler S, NunesThe Heterogeneous HLA Genetic Makeup of the Swiss Population Ste´phane Buhler1 *, Jose´ Manuel

Citi, Sandra

389

HABITAT QUALITY AND HETEROGENEITY INFLUENCE DISTRIBUTION AND BEHAVIOR IN AFRICAN BUFFALO ( SYNCERUS CAFFER )  

Microsoft Academic Search

Top-down effects of predators on prey behavior and population dynamics have been extensively studied. However, some populations of very large herbivores appear to be regulated primarily from the bottom up. Given the importance of food resources to these large herbivores, it is reasonable to expect that forage heterogeneity (variation in quality and quantity) affects individual and group behaviors as well

John A. Winnie; Paul Cross; Wayne Getz

2008-01-01

390

The effect of host heterogeneity and parasite intragenomic interactions on parasite  

E-print Network

The effect of host heterogeneity and parasite intragenomic interactions on parasite population Bank, Sheffield S10 2TN, UK Understanding the processes that shape the genetic structure of parasite populations and the functional consequences of different parasite genotypes is critical for our ability

Paterson, Steve

391

Heterogeneous information-based artificial stock market  

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

392

Epigenetic Heterogeneity in HIV-1 Latency Establishment.  

PubMed

Despite prolonged antiretroviral therapy, HIV-1 persists as transcriptionally inactive proviruses. The HIV-1 latency remains a principal obstacle in curing AIDS. It is important to understand mechanisms by which HIV-1 latency is established to make the latent reservoir smaller. We present a molecular characterization of distinct populations at an early phase of infection. We developed an original dual-color reporter virus to monitor LTR kinetics from establishment to maintenance stage. We found that there are two ways of latency establishment i.e., by immediate silencing and slow inactivation from active infection. Histone covalent modifications, particularly polycomb repressive complex 2 (PRC2)-mediated H3K27 trimethylation, appeared to dominate viral transcription at the early phase. PRC2 also contributes to time-dependent LTR dormancy in the chronic phase of the infection. Significant differences in sensitivity against several stimuli were observed between these two distinct populations. These results will expand our understanding of heterogeneous establishment of HIV-1 latency populations. PMID:25572573

Matsuda, Yuka; Kobayashi-Ishihara, Mie; Fujikawa, Dai; Ishida, Takaomi; Watanabe, Toshiki; Yamagishi, Makoto

2015-01-01

393

Students-Teach-Students.  

ERIC Educational Resources Information Center

Students-Teach-Students is a program that trains teams of high school students to present a smoking education program and role-model to fifth graders, helping them to overcome peer pressure to smoke cigarettes and marijuana. Surveys show that a significant percentage of students first begin to experiment with smoking cigarettes and marijuana…

Tokarz, Edward, Jr.; Sullivan, Richard D.

394

Noise and heterogeneity in bacterial communication  

NASA Astrophysics Data System (ADS)

Many bacterial species engage in a sophisticated chemical communication behavior known as quorum sensing: Individual cells release small diffusible molecules into their environment while simultaneously detecting the local concentration of these molecules. Important collective behaviors of the bacterial population are triggered once the signal concentration accumulates to a certain level. Although quorum sensing is widespread in microbiology, the physical environment of bacteria is often very heterogeneous and diffusion may be inefficient. Meanwhile the genetic circuitry that generates and detects the chemical signal is microscopic and subject to stochasticity. This raises interesting physical questions about how much information is actually carried by these chemical signals, and what an individual cell can learn about its environment through this mechanism. I will present a general introduction to quorum sensing with emphasis on our experimental studies of the role of noise and microenvironment on this phenomenon.

Hagen, Stephen

2010-10-01

395

The effects of spatial population dataset choice on estimates of population at risk of disease  

Microsoft Academic Search

BACKGROUND: The spatial modeling of infectious disease distributions and dynamics is increasingly being undertaken for health services planning and disease control monitoring, implementation, and evaluation. Where risks are heterogeneous in space or dependent on person-to-person transmission, spatial data on human population distributions are required to estimate infectious disease risks, burdens, and dynamics. Several different modeled human population distribution datasets are

Andrew J Tatem; Nicholas Campiz; Peter W Gething; Robert W Snow; Catherine Linard

2011-01-01

396

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

397

River Meandering in Heterogeneous Floodplains  

NASA Astrophysics Data System (ADS)

Freely-meandering natural rivers typically evolve into complex planforms characterized by compound loops or multilobes or into irregular patterns. It is widely acknowledged that spatial heterogeneity in floodplain erodibility should affect the planform evolution of meandering rivers; however, past studies have not systematically explored the importance of this effect. In this study, we systematically analyze how the scale, magnitude, and stochasticity of floodplain erosional variability influence meander evolution and the emergence of bend complexity and planform irregularity. We employ a physically-based model of meander morphodynamics and stochastically-generated heterogeneous landscapes with a range of spatial scales that represent spatial heterogeneity (i.e., patchiness) in floodplain erosional resistance. The heterogeneous mosaics of differential resistance with different scales of patchiness are meant to represent spatial arrangements of factors influencing migration and varying with scale, such as sedimentological complexity, patches of floodplain vegetation, and human activities. We also evaluate the effects of stochasticity in bank erodibility on the spatial characteristics of planform evolution. The results show that both the spatial scale of heterogeneity and the magnitude of variability in erodibility have a strong influence on meander evolution. The planform morphologies generated by simulations with spatially-heterogeneous landscapes are remarkably similar, both visually and in their spectral signatures, to those of natural meandering rivers. Landscapes with patch sizes larger than the initial meander size promote the evolution of highly elongated, upstream-skewed meanders with high variability in amplitudes. As patch size becomes smaller than the initial meander size, bend complexity and planform irregularities increase, resulting in downstream-skewed bends and compound loops or multilobes. Fine-grained heterogeneity results in meanders similar to those for a homogenous floodplain. Moreover, the sensitivity of autogenic meandering processes to stochastic variability in the environment leads to different patterns of planform evolution even in landscapes with the same mean spatial heterogeneity and magnitude of variability. The explicit integration of environmental heterogeneity and stochasticity characterizing landscape patterns and processes into the morphodynamic models of river meandering can significantly enhance our understanding of meandering dynamics at landscape scale, and thus, help improve our ability to forecast, manage, and restore integrated meandering river-floodplain systems, particularly in the presence of environmental change.

Guneralp, I.; Rhoads, B. L.

2011-12-01

398

The Evolution of Heterogeneities Altered by Mutational Robustness, Gene Expression Noise and Bottlenecks in Gene Regulatory Networks  

PubMed Central

Intra-population heterogeneity is commonly observed in natural and cellular populations and has profound influence on their evolution. For example, intra-tumor heterogeneity is prevalent in most tumor types and can result in the failure of tumor therapy. However, the evolutionary process of heterogeneity remains poorly characterized at both genotypic and phenotypic level. Here we study the evolution of intra-population heterogeneities of gene regulatory networks (GRN), in particular mutational robustness and gene expression noise as contributors to the development of heterogeneities. By in silico simulations, it was found that the impact of these factors on GRN can, under certain conditions, promote phenotypic heterogeneity. We also studied the effect of population bottlenecks on the evolution of GRN. When the GRN population passes through such bottlenecks, neither mutational robustness nor population fitness was observed to be substantially altered. Interestingly, however, we did detect a significant increase in the number of potential “generator” genes which can substantially induce population fitness, when stimulated by mutational hits. PMID:25541720

Zhang, Zhihua

2014-01-01

399

Organizational Heterogeneity of Vertebrate Genomes  

PubMed Central

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

Frenkel, Svetlana; Kirzhner, Valery; Korol, Abraham

2012-01-01

400

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

401

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

402

Kid's PACK: Population Awareness Campaign Kit.  

ERIC Educational Resources Information Center

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

Zero Population Growth, Inc., Washington, DC.

403

Career Development Needs of Students.  

ERIC Educational Resources Information Center

Undecided college students, those students who have entered college without declaring a major field of study, make up a significant population. Counselors can help undecided college students by using a four-step career decision-making model, consisting of the steps of self-awareness, career information, decision-making, and an action plan. In the…

Boyd, Patti A.

404

Static heterogeneities in liquid water  

NASA Astrophysics Data System (ADS)

The thermodynamic behavior of water seems to be closely related to static heterogeneities. These static heterogeneities are related to the local structure of water molecules, and when properly characterized, may offer an economical explanation of thermodynamic data. The key feature of liquid water is not so much that the existence of hydrogen bonds, first pointed out by Linus Pauling, but rather the local geometry of the liquid molecules is not spherical or oblong but tetrahedral. In the consideration of static heterogeneities, this local geometry is critical. Recent experiments suggested more than one phase of amorphous solid water, while simulations suggest that one of these phases is metastable with respect to another, so that in fact there are only two stable phases.

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

2004-10-01

405

Quantifying tumour heterogeneity with CT  

PubMed Central

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

Miles, Kenneth A.

2013-01-01

406

Asymmetric diffusion in heterogeneous media  

NASA Astrophysics Data System (ADS)

Diffusion in heterogeneous media (i.e., layers with discontinuous values of the diffusivity parameter) is found in different situations, including geology, catalyst, physiology and separation processes. This work considers an array of rectangular layers of different diffusivity as a simple model for studying diffusivity in heterogeneous media. Random walk simulations adapted for transport across interfaces between different materials are used for showing that heterogeneous media exhibit asymmetric transport in the sense that the diffusive flux depends of the transport direction. It is shown that Brownian particles run preferentially along the direction of decreasing diffusivity. An uphill diffusion effect is found when particles move from high to low diffusivity layers. In terms of Fick’s modeling, asymmetric transport is explained from the presence of a jump in the particle density at layer interfaces.

Alvarez-Ramirez, J.; Dagdug, L.; Meraz, M.

2014-02-01

407

Simulator for heterogeneous dataflow architectures  

NASA Technical Reports Server (NTRS)

A new simulator is developed to simulate the execution of an algorithm graph in accordance with the Algorithm to Architecture Mapping Model (ATAMM) rules. ATAMM is a Petri Net model which describes the periodic execution of large-grained, data-independent dataflow graphs and which provides predictable steady state time-optimized performance. This simulator extends the ATAMM simulation capability from a heterogenous set of resources, or functional units, to a more general heterogenous architecture. Simulation test cases show that the simulator accurately executes the ATAMM rules for both a heterogenous architecture and a homogenous architecture, which is the special case for only one processor type. The simulator forms one tool in an ATAMM Integrated Environment which contains other tools for graph entry, graph modification for performance optimization, and playback of simulations for analysis.

Malekpour, Mahyar R.

1993-01-01

408

Community Health Nursing Student Experience in Nicaragua  

Microsoft Academic Search

International clinical experiences can provide excellent opportunities for nursing students to practice community health nursing, enhance their global perspective, and increase their cultural awareness of vulnerable populations. Selected students from the Georgetown University nursing program spent part of their winter intercession in Nicaragua, working with a vulnerable population in an impoverished community. Students cared for families, worked in clinics, conducted

Rita L. Ailinger; Suzanne B. Molloy; Elida Ramirez Sacasa

2009-01-01

409

Spoon River College Student Retention Project.  

ERIC Educational Resources Information Center

As part of a student retention project conducted at Spoon River College (SRC), specific populations served by SRC were identified; strategies to increase retention of particular student populations were developed; students in need of assistance were identified; and a transfer graduate follow-up study and two cohort tracking studies involving all…

Gardner, Janet L.

410

Population Biology Graduate Group Bylaws of the Population Biology Graduate Group  

E-print Network

Population Biology Graduate Group Bylaws of the Population Biology Graduate Group Amended and Approved: February 1, 1994 I. Definition of the Graduate Group in Population Biology The purpose of this graduate group is to bring together faculty and graduate students interested in population biology

Wainwright, Peter C.

411

Creep Ruptures in Heterogeneous Materials  

NASA Astrophysics Data System (ADS)

We present creep experiments on fiber composite materials with different controlled heterogeneity. All samples exhibit a power-law relaxation of the strain rate in the primary creep regime (Andrade's law) followed by a power-law acceleration up to rupture. We discover that the rupture time is proportional to the duration of the primary creep regime, showing the interplay between the two regimes and offering a method of rupture prediction. These experimental results are rationalized by a mean-field model of representative elements with nonlinear viscoelastic rheology and with a large heterogeneity of strengths.

Nechad, H.; Helmstetter, A.; El Guerjouma, R.; Sornette, D.

2005-01-01

412

Spatial localization in heterogeneous systems.  

PubMed

We study spatial localization in the generalized Swift-Hohenberg equation with either quadratic-cubic or cubic-quintic nonlinearity subject to spatially heterogeneous forcing. Different types of forcing (sinusoidal or Gaussian) with different spatial scales are considered and the corresponding localized snaking structures are computed. The results indicate that spatial heterogeneity exerts a significant influence on the location of spatially localized structures in both parameter space and physical space, and on their stability properties. The results are expected to assist in the interpretation of experiments on localized structures where departures from spatial homogeneity are generally unavoidable. PMID:24580293

Kao, Hsien-Ching; Beaume, Cédric; Knobloch, Edgar

2014-01-01

413

Dynamic fracture of heterogeneous materials  

SciTech Connect

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

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

1998-12-31

414

Spatial localization in heterogeneous systems  

NASA Astrophysics Data System (ADS)

We study spatial localization in the generalized Swift-Hohenberg equation with either quadratic-cubic or cubic-quintic nonlinearity subject to spatially heterogeneous forcing. Different types of forcing (sinusoidal or Gaussian) with different spatial scales are considered and the corresponding localized snaking structures are computed. The results indicate that spatial heterogeneity exerts a significant influence on the location of spatially localized structures in both parameter space and physical space, and on their stability properties. The results are expected to assist in the interpretation of experiments on localized structures where departures from spatial homogeneity are generally unavoidable.

Kao, Hsien-Ching; Beaume, Cédric; Knobloch, Edgar

2014-01-01

415

Heterogeneity of chromosome 17 and erbB-2 gene copy number in primary and metastatic bladder cancer  

Microsoft Academic Search

To study the relationship of tumor genomic heterogeneity with bladder cancer phenotype and p53 gene alterations, 139 primary bladder tumors were examined by dual labeling fluorescence in situ hybridization (FISH) using probes for chromosome 17 centromere (p17H8) and p53 (17p13.1). The number of different aneusomic populations >5% (and monosomic populations >20%) of cells served as a marker for heterogeneity. Nuclear

Guido Sauter; M. J. Mihatsch; Thomas C. Gasser; Frederic M. Waldman

1995-01-01

416

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

Microsoft Academic Search

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

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

2010-01-01

417

MULTIPLE DATA SOURCES IMPROVE DNA-BASED MARK–RECAPTURE POPULATION ESTIMATES OF GRIZZLY BEARS  

Microsoft Academic Search

A fundamental challenge to estimating population size with mark-recapture methods is heterogeneous capture probabilities and subsequent bias of population estimates. Confronting this problem usually requires substantial sampling effort that can be difficult to achieve for some species, such as carnivores. We developed a methodology that uses two data sources to deal with heterogeneity and applied this to DNA mark-recapture data

John Boulanger; Katherine C. Kendall; Jeffrey B. Stetz; David A. Roon; Lisette P. Waits; David Paetkau

2008-01-01

418

Locus heterogeneity disease genes encode proteins with high interconnectivity in the human protein interaction network  

PubMed Central

Mutations in genes potentially lead to a number of genetic diseases with differing severity. These disease genes have been the focus of research in recent years showing that the disease gene population as a whole is not homogeneous, and can be categorized according to their interactions. Locus heterogeneity describes a single disorder caused by mutations in different genes each acting individually to cause the same disease. Using datasets of experimentally derived human disease genes and protein interactions, we created a protein interaction network to investigate the relationships between the products of genes associated with a disease displaying locus heterogeneity, and use network parameters to suggest properties that distinguish these disease genes from the overall disease gene population. Through the manual curation of known causative genes of 100 diseases displaying locus heterogeneity and 397 single-gene Mendelian disorders, we use network parameters to show that our locus heterogeneity network displays distinct properties from the global disease network and a Mendelian network. Using the global human proteome, through random simulation of the network we show that heterogeneous genes display significant interconnectivity. Further topological analysis of this network revealed clustering of locus heterogeneity genes that cause identical disorders, indicating that these disease genes are involved in similar biological processes. We then use this information to suggest additional genes that may contribute to diseases with locus heterogeneity. PMID:25538735

Keith, Benjamin P.; Robertson, David L.; Hentges, Kathryn E.

2014-01-01

419

Large-scale replication and heterogeneity in Parkinson disease genetic loci  

PubMed Central

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

Ioannidis, John P.A.; Aasly, Jan O.; Annesi, Grazia; Brice, Alexis; Van Broeckhoven, Christine; Bertram, Lars; Bozi, Maria; Crosiers, David; Clarke, Carl; Facheris, Maurizio; Farrer, Matthew; Garraux, Gaetan; Gispert, Suzana; Auburger, Georg; Vilariño-Güell, Carles; Hadjigeorgiou, Georgios M.; Hicks, Andrew A.; Hattori, Nobutaka; Jeon, Beom; Lesage, Suzanne; Lill, Christina M.; Lin, Juei-Jueng; Lynch, Timothy; Lichtner, Peter; Lang, Anthony E.; Mok, Vincent; Jasinska-Myga, Barbara; Mellick, George D.; Morrison, Karen E.; Opala, Grzegorz; Pramstaller, Peter P.; Pichler, Irene; Park, Sung Sup; Quattrone, Aldo; Rogaeva, Ekaterina; Ross, Owen A.; Stefanis, Leonidas; Stockton, Joanne D.; Satake, Wataru; Silburn, Peter A.; Theuns, Jessie; Tan, Eng-King; Toda, Tatsushi; Tomiyama, Hiroyuki; Uitti, Ryan J.; Wirdefeldt, Karin; Wszolek, Zbigniew; Xiromerisiou, Georgia; Yueh, Kuo-Chu; Zhao, Yi; Gasser, Thomas; Maraganore, Demetrius; Krüger, Rejko; Boyle, R.S; Sellbach, A; O'Sullivan, J.D.; Sutherland, G.T.; Siebert, G.A; Dissanayaka, N.N.W; Van Broeckhoven, Christine; Theuns, Jessie; Crosiers, David; Pickut, Barbara; Engelborghs, Sebastiaan; Meeus, Bram; De Deyn, Peter P.; Cras, Patrick; Rogaeva, Ekaterina; Lang, Anthony E; Agid, Y; Anheim, M; Bonnet, A-M; Borg, M; Brice, A; Broussolle, E; Corvol, JC; Damier, P; Destée, A; Dürr, A; Durif, F; Lesage, S; Lohmann, E; Pollak, P; Rascol, O; Tison, F; Tranchant, C; Viallet, F; Vidailhet, M; Tzourio, Christophe; Amouyel, Philippe; Loriot, Marie-Anne; Mutez, Eugénie; Duflot, Aurélie; Legendre, Jean-Philippe; Waucquier, Nawal; Gasser, Thomas; Riess, Olaf; Berg, Daniela; Schulte, Claudia; Klein, Christine; Djarmati, Ana; Hagenah, Johann; Lohmann, Katja; Auburger, Georg; Hilker, Rüdiger; van de Loo, Simone; Dardiotis, Efthimios; Tsimourtou, Vaia; Ralli, Styliani; Kountra, Persa; Patramani, Gianna; Vogiatzi, Cristina; Hattori, Nobutaka; Tomiyama, Hiroyuki; Funayama, Manabu; Yoshino, Hiroyo; Li, Yuanzhe; Imamichi, Yoko; Toda, Tatsushi; Satake, Wataru; Lynch, Tim; Gibson, J. Mark; Valente, Enza Maria; Ferraris, Alessandro; Dallapiccola, Bruno; Ialongo, Tamara; Brighina, Laura; Corradi, Barbara; Piolti, Roberto; Tarantino, Patrizia; Annesi, Ferdinanda; Jeon, Beom S.; Park, Sung-Sup; Aasly, J; Opala, Grzegorz; Jasinska-Myga, Barbara; Klodowska-Duda, Gabriela; Boczarska-Jedynak, Magdalena; Tan, Eng King; Belin, Andrea Carmine; Olson, Lars; Galter, Dagmar; Westerlund, Marie; Sydow, Olof; Nilsson, Christer; Puschmann, Andreas; Lin, JJ; Maraganore, Demetrius M.; Ahlskog, J, Eric; de Andrade, Mariza; Lesnick, Timothy G.; Rocca, Walter A.; Checkoway, Harvey; Ross, Owen A; Wszolek, Zbigniew K.; Uitti, Ryan J.

2012-01-01

420

Relating Single Cell Heterogeneity To Genotype During Cancer Progression  

NASA Astrophysics Data System (ADS)

Progression of normal cells towards cancer is driven by a series of genetic changes. Traditional population-averaged measurements have found that cell signalling activities are increasingly altered during this progression. Despite the fact that cancer cells are known to be highly heterogeneous, the response of individual pathways to specific genetic changes remains poorly characterized at a single cell level. Do signalling alterations in a pathway reflect a shift of the whole population, or changes to specific subpopulations? Are alterations to pathways independent, or are cells with alterations in one pathway more likely to be abnormal in another due to crosstalk? We are building a computational framework that analyzes immunofluorescence microscopy images of cells to identify alterations in individual pathways at a single-cell level. A primary novelty of our approach is a ``change of basis'' that allows us to understand signalling in cancer cells in terms of the much better understood patterns of signalling in normal cells. This allows us to model heterogeneous populations of cancer cells as a mixture of distinct subpopulations, each with a specific combination of signalling pathways altered beyond the normal baseline. We used this framework to analyze human bronchial epithelial cell lines containing a series of genetic modifications commonly seen in lung cancer. We confirmed expected trends (such as a population-wide epithelial mesenchymal transition following the last of our series of modifications) and are presently studying the relation between the mutational profiles of cancer cells and pathway crosstalk. Our framework will help establish a more natural basis for future investigations into the phenotype-genotype relationship in heterogeneous populations.

Rajaram, Satwik

2013-03-01

421

Student Services Student Services  

E-print Network

with academic faculty to build an environment maximizing student growth and academic success. To achieve and facilitates academic success through services and programs designed to support adult learners and student facilitates the academic success of adult learners and student veterans through individual meetings, referrals

422

Scalable streaming for heterogeneous clients  

Microsoft Academic Search

Periodic broadcast protocols enable the efficient streaming of highly popular media files to large numbers of concurrent clients. Most previous periodic broadcast protocols, how- ever, assume that all clients can receive at the same rate, and also assume that available bandwidth is not time-varying. In this paper, we first develop a new periodic broadcast proto- col, Optimized Heterogeneous Periodic Broadcast

Liqi Shi; Phillipa Sessini; Anirban Mahanti; Zongpeng Li; Derek L. Eager

2006-01-01

423

SYMMETRY AND HETEROGENEITY IN HIGH  

E-print Network

SYMMETRY AND HETEROGENEITY IN HIGH TEMPERATURE SUPERCONDUCTORS #12;#12;Kluwer Academic Publishers Dordrecht/Boston/London Published in cooperation with NATO Scientific Affairs Division SYMMETRY AND EXCHANGE-LIKE PAIRING SCENARIOS 1 I.1 Symmetry and Higher Superconductivity in the Lower Elements N. W

424

Molecular ingredients of heterogeneous catalysis  

SciTech Connect

The purpose of this paper is to present a review and status report to those in theoretical chemistry of the rapidly developing surface science of heterogeneous catalysis. The art of catalysis is developing into science. This profound change provides one with opportunities not only to understand the molecular ingredients of important catalytic systems but also to develop new and improved catalyst. The participation of theorists to find answers to important questions is sorely needed for the sound development of the field. It is the authors hope that some of the outstanding problems of heterogeneous catalysis that are identified in this paper will be investigated. For this purpose the paper is divided into several sections. The brief Introduction to the methodology and recent results of the surface science of heterogeneous catalysis is followed by a review of the concepts of heterogeneous catalysis. Then, the experimental results that identified the three molecular ingredients of catalysis, structure, carbonaceous deposit and the oxidation state of surface atoms are described. Each section is closed with a summary and a list of problems that require theoretical and experimental scrutiny. Finally attempts to build new catalyst systems and the theoretical and experimental problems that appeared in the course of this research are described.

Somorjai, G.A.

1982-06-01

425

Modeling large heterogeneous RF structures  

SciTech Connect

Large heterogeneous structures are difficult to model on a numerical grid because of the limitations on computing resources, so that alternate approaches such as equivalent circuits and mode-matching have been developed to treat this problem. This paper will describe the three methods and will analyze a structure representative of the SLAC and JLC detuned structures to compare the efficacy of each approach.

Li, Zenghai; Ko, Kwok; Srinivas, V. [Stanford Univ., CA (United States); Higo, Toshiyasu [KEK, Ibaraki (Japan)

1996-11-01

426

Adrenoleukodystrophy: heterogeneity in two brothers  

Microsoft Academic Search

A man with hypoadrenalism died from a rapidly progressive pseudobulbar palsy, due to adult onset adrenoleukodystrophy. This diagnosis suggested that his brother, with a longstanding spastic paraparesis, suffered from adrenomyeloneuropathy. Both cases were confirmed biochemically. The heterogeneity of expression of this x-linked disorder is described, with the consequent difficulty in diagnosis and nomenclature.

G M Elrington; D E Bateman; M J Jeffrey; N F Lawton

1989-01-01

427

Modeling intrinsic heterogeneity and growth of cancer cells.  

PubMed

Intratumoral heterogeneity has been found to be a major cause of drug resistance. Cell-to-cell variation increases as a result of cancer-related alterations, which are acquired by stochastic events and further induced by environmental signals. However, most cellular mechanisms include natural fluctuations that are closely regulated, and thus lead to asynchronization of the cells, which causes intrinsic heterogeneity in a given population. Here, we derive two novel mathematical models, a stochastic agent-based model and an integro-differential equation model, each of which describes the growth of cancer cells as a dynamic transition between proliferative and quiescent states. These models are designed to predict variations in growth as a function of the intrinsic heterogeneity emerging from the durations of the cell-cycle and apoptosis, and also include cellular density dependencies. By examining the role all parameters play in the evolution of intrinsic tumor heterogeneity, and the sensitivity of the population growth to parameter values, we show that the cell-cycle length has the most significant effect on the growth dynamics. In addition, we demonstrate that the agent-based model can be approximated well by the more computationally efficient integro-differential equations when the number of cells is large. This essential step in cancer growth modeling will allow us to revisit the mechanisms of multidrug resistance by examining spatiotemporal differences of cell growth while administering a drug among the different sub-populations in a single tumor, as well as the evolution of those mechanisms as a function of the resistance level. PMID:25457229

Greene, James M; Levy, Doron; Fung, King Leung; Souza, Paloma S; Gottesman, Michael M; Lavi, Orit

2015-02-21

428

Spatial Control of Rabies on Heterogeneous Landscapes  

PubMed Central

Rabies control in terrestrial wildlife reservoirs relies heavily on an oral rabies vaccine (ORV). In addition to direct ORV delivery to protect wildlife in natural habitats, vaccine corridors have been constructed to control the spread; these corridors are often developed around natural barriers, such as rivers, to enhance the effectiveness of vaccine deployment. However, the question of how to optimally deploy ORV around a river (or other natural barrier) to best exploit the barrier for rabies control has not been addressed using mathematical models. Given an advancing epidemic wave, should the vaccine be distributed on both sides of barrier, behind the barrier, or in front of it? Here, we introduce a new mathematical model for the dynamics of raccoon rabies on a spatially heterogeneous landscape that is both simple and realistic. We demonstrate that the vaccine should always be deployed behind a barrier to minimize the recurrence of subsequent epidemics. Although the oral rabies vaccine is sufficient to induce herd immunity inside the vaccinated area, it simultaneously creates a demographic refuge. When that refuge is in front of a natural barrier, seasonal dispersal from the vaccine corridor into an endemic region sustains epidemic oscillations of raccoon rabies. When the vaccine barrier creates a refuge behind the river, the low permeability of the barrier to host movement limits dispersal of the host population from the protected populations into the rabies endemic area and limits subsequent rabies epidemics. PMID:17183654

Russell, Colin A.; Real, Leslie A.; Smith, David L.

2006-01-01

429

Population Genetics  

Microsoft Academic Search

\\u000a \\u000a Population genetics is the study of evolutionary genetics at the population level focusing on the exchange of alleles and genes within and between\\u000a populations as well as the forces that cause or maintain these exchanges. This exchange of genes and alleles causes changes\\u000a in the specific allele and hence genotype frequencies within and between populations. Studying this evolution helps us

Jill S. Barnholtz-Sloan; Hemant K. Tiwari

430

Teachers Use of a Differentiated Curriculum for Gifted Students  

ERIC Educational Resources Information Center

Teachers have the responsibility to educate a diverse group of students in heterogeneous classes. One way in which teachers meet this challenge is to differentiate the curriculum to meet the needs, interests, and abilities of each student. One particular group of students in need of a differentiated curriculum to maximize learning potential is the…

Marotta-Garcia, Christina

2011-01-01

431

Counting Populations  

ERIC Educational Resources Information Center

Scientists use sampling to get an estimate of things they cannot easily count. A population is made up of all the organisms of one species living together in one place at the same time. All of the people living together in one town are considered a population. All of the grasshoppers living in a field are a population. Scientists keep track of the…

Damonte, Kathleen

2004-01-01

432

Heterogeneity in hormone responses and patterns of collagen synthesis in cloned dermal fibroblasts.  

PubMed Central

Fibroblasts cultured from normal human dermis are heterogeneous with respect to growth kinetics, synthetic function, and morphologic features. There are many examples of clonal heterogeneity in apparently homogeneous connective tissue cell populations, and it has been suggested that selection of cell populations with particular phenotypic features is the basis for the development of pathologic connective tissue changes in inflammatory disorders. In these studies we report characterization of the pattern of matrix biosynthesis and responses to hormones in cells cloned from normal human dermis. The results indicate that cloned dermal fibroblasts are heterogeneous with respect to synthesis of collagens as well as their responses to prostaglandin E2 and parathyroid hormone. Selective expansion of clonal populations with unique patterns of matrix synthesis and cell surface receptors could provide the basis for abnormal connective tissue remodeling in certain pathologic states. PMID:2155928

Goldring, S R; Stephenson, M L; Downie, E; Krane, S M; Korn, J H

1990-01-01

433

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

ERIC Educational Resources Information Center

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

Walther-Thomas, Chriss; Brownell, Mary

1999-01-01

434

Population Explosion  

NSDL National Science Digital Library

Many factors influence the success and survival rate of a population of living things. Explore several factors that can determine the survival of a population of sheep in this NetLogo model. Start with a model of unlimited grass available to the sheep and watch what happens to the sheep population! Next try to keep the population under control by removing sheep periodically. Change the birthrate, grass regrowth rate, and the amount of energy rabbits get from the grass to keep a stable population.

Consortium, The C.

2012-01-13

435

Population Growth  

NSDL National Science Digital Library

These activities explore population growth rates and its consequences with regard to the distribution of natural resources. Population growth is perhaps the most important environmental issue of our time. As population increases and as people seek to raise their standard of living, more stress is put on our earth’s finite resources.One aspect of the population issue is the sheer magnitude of the numbers involved. World population did not reach 1 billion until the year 1800. Since then it has grown exponentially to reach our current 6.7 billion.

2009-01-01

436

International Student Persistence: Integration or Cultural Integrity?  

ERIC Educational Resources Information Center

As diverse student populations expand in colleges and universities in the United States, attention must be given to preserving students' cultural integrity. Dominant theories of student persistence contend that integration, not cultural preservation is necessary to student success. This qualitative study examines the experiences of one group of…

Andrade, Maureen S.

2007-01-01

437

Suicidal Behavior among Latina College Students  

ERIC Educational Resources Information Center

Latina college students are one of the fastest-growing segments of the college student population. Although there is evidence suggesting Latina high school students are at increased risk of engaging in suicidal behavior, it is unclear Bwhether this risk continues in college. Over the course of 3 years, 554 Latina college students, the majority of…

Chesin, Megan S.; Jeglic, Elizabeth L.

2012-01-01

438

Improving Student Reading by Implementing Phonics Programs.  

ERIC Educational Resources Information Center

This report describes phonics programs that will increase students' fluency and independent reading skills. The targeted population consisted of second grade students in a growing affluent community and first grade students in a large metropolitan city. The first and second grade students demonstrated a lack of awareness between phonemes and their…

Appleton, Beth; Karlson, Stephanie; Mendez, Donna

439

Geophysics of Chemical Heterogeneity in the Mantle  

E-print Network

, transition zone Abstract Chemical heterogeneity, produced by the near-surface rock cycle and dom- inated.annualreviews.org byUniversityCollegeLondonon12/06/12.Forpersonaluseonly. #12;MANTLE HETEROGENEITY, THE ROCK CYCLE, AND PLATE TECTONICS The rock cycle is a heterogeneity-producing engine that serves as the cornerstone

Stixrude, Lars

440

Understanding cancer stem cell heterogeneity and plasticity  

Microsoft Academic Search

Heterogeneity is an omnipresent feature of mammalian cells in vitro and in vivo. It has been recently realized that even mouse and human embryonic stem cells under the best culture conditions are heterogeneous containing pluripotent as well as partially committed cells. Somatic stem cells in adult organs are also heterogeneous, containing many subpopulations of self-renewing cells with distinct regenerative capacity.

Dean G Tang

2012-01-01