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Search Results: 1 - 10 of 11102 matches for " Lia Hemerik "
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A Demo-Genetic Analysis of a Small Reintroduced Carnivore Population: The Otter (Lutra lutra) in The Netherlands
Maelle Seignobosc,Lia Hemerik,Hans Peter Koelewijn
International Journal of Ecology , 2011, DOI: 10.1155/2011/870853
Abstract: Assessing the viability of reintroduced animal populations is a complicated task. Reintroductions are usually carried out with a small number of individuals, thereby, limiting the possibilities for monitoring because of the possible negative effects of intensive monitoring on survival and reproduction. Moreover, reintroduction studies are part of a socioeconomic interplay of forces, thereby, also limiting monitoring possibilities. Also, knowledge of population demography and abundance can be incomplete or unattainable. Here, we illustrate how we combined traditional telemetry and novel non-invasive genetic methodology to construct a detailed life table of a small reintroduced otter population in The Netherlands. Combining an appropriate capture-mark-recapture framework with a matrix modelling approach provides, in general, useful insights for such populations. The data indicated that (i) male survival is lower than female survival, (ii) the reintroduced population is currently growing (estimated =1.26: range [1.06, 1.42]) and seems viable, (iii) increasing adult survival is currently the critical stage at which efforts of field managers should concentrate, and (iv) the modelling framework allowed us to determine the boundary conditions for the vital rates under which the population would go extinct. The applied approach directs at measurements that help field managers to implement the right conservation strategy after reintroductions.
A Demo-Genetic Analysis of a Small Reintroduced Carnivore Population: The Otter (Lutra lutra) in The Netherlands
Maelle Seignobosc,Lia Hemerik,Hans Peter Koelewijn
International Journal of Ecology , 2011, DOI: 10.1155/2011/870853
Abstract: Assessing the viability of reintroduced animal populations is a complicated task. Reintroductions are usually carried out with a small number of individuals, thereby, limiting the possibilities for monitoring because of the possible negative effects of intensive monitoring on survival and reproduction. Moreover, reintroduction studies are part of a socioeconomic interplay of forces, thereby, also limiting monitoring possibilities. Also, knowledge of population demography and abundance can be incomplete or unattainable. Here, we illustrate how we combined traditional telemetry and novel non-invasive genetic methodology to construct a detailed life table of a small reintroduced otter population in The Netherlands. Combining an appropriate capture-mark-recapture framework with a matrix modelling approach provides, in general, useful insights for such populations. The data indicated that (i) male survival is lower than female survival, (ii) the reintroduced population is currently growing (estimated : range [1.06, 1.42]) and seems viable, (iii) increasing adult survival is currently the critical stage at which efforts of field managers should concentrate, and (iv) the modelling framework allowed us to determine the boundary conditions for the vital rates under which the population would go extinct. The applied approach directs at measurements that help field managers to implement the right conservation strategy after reintroductions. 1. Introduction Reintroductions of extinct or nearly extinct species in a country are becoming nowadays a more accepted tool for the restoration of biodiversity [1]. Reintroduction attempts are, however, not undisputed [2]. On the one hand, several stakeholders are involved, each with their own priorities (e.g., government, field managers, scientists, and the general and local public) making the decision process surrounding reintroductions sometimes cumbersome. On the other hand, the number of released individuals is usually limited, and a new small population is created, with all the accompanying risks of extinction again [3]. Extensive monitoring of the released individuals for a longer time period, in order to derive guidelines for success or failure of attempts, is, therefore, of utmost importance [4]. Unfortunately, many reintroduction studies suffer from a lack of detailed observations for a longer time span [4–6], causing difficulties in explaining the success or failure of reintroduction attempts and preventing adequate advice to field managers in charge of reintroductions. Currently, most inferences in reintroduction
Heterogeneous Host Susceptibility Enhances Prevalence of Mixed-Genotype Micro-Parasite Infections
Wopke van der Werf ,Lia Hemerik ,Just M. Vlak,Mark P. Zwart
PLOS Computational Biology , 2011, DOI: 10.1371/journal.pcbi.1002097
Abstract: Dose response in micro-parasite infections is usually shallower than predicted by the independent action model, which assumes that each infectious unit has a probability of infection that is independent of the presence of other infectious units. Moreover, the prevalence of mixed-genotype infections was greater than predicted by this model. No probabilistic infection model has been proposed to account for the higher prevalence of mixed-genotype infections. We use model selection within a set of four alternative models to explain high prevalence of mixed-genotype infections in combination with a shallow dose response. These models contrast dependent versus independent action of micro-parasite infectious units, and homogeneous versus heterogeneous host susceptibility. We specifically consider a situation in which genome differences between genotypes are minimal, and highly unlikely to result in genotype-genotype interactions. Data on dose response and mixed-genotype infection prevalence were collected by challenging fifth instar Spodoptera exigua larvae with two genotypes of Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV), differing only in a 100 bp PCR marker sequence. We show that an independent action model that includes heterogeneity in host susceptibility can explain both the shallow dose response and the high prevalence of mixed-genotype infections. Theoretical results indicate that variation in host susceptibility is inextricably linked to increased prevalence of mixed-genotype infections. We have shown, to our knowledge for the first time, how heterogeneity in host susceptibility affects mixed-genotype infection prevalence. No evidence was found that virions operate dependently. While it has been recognized that heterogeneity in host susceptibility must be included in models of micro-parasite transmission and epidemiology to account for dose response, here we show that heterogeneity in susceptibility is also a fundamental principle explaining patterns of pathogen genetic diversity among hosts in a population. This principle has potentially wide implications for the monitoring, modeling and management of infectious diseases.
Rapid Establishment of a Regular Distribution of Adult Tropical Drosophila Parasitoids in a Multi-Patch Environment by Patch Defence Behaviour
Peter W. de Jong, Lia Hemerik, Gerrit Gort, Jacques J. M. van Alphen
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0020870
Abstract: Females of the larval parasitoid of Drosophila, Asobara citri, from sub-Saharan Africa, defend patches with hosts by fighting and chasing conspecific females upon encounter. Females of the closely related, palearctic species Asobara tabida do not defend patches and often search simultaneously in the same patch. The effect of patch defence by A. citri females on their distribution in a multi-patch environment was investigated, and their distributions were compared with those of A. tabida. For both species 20 females were released from two release-points in replicate experiments. Females of A. citri quickly reached a regular distribution across 16 patches, with a small variance/mean ratio per patch. Conversely, A. tabida females initially showed a clumped distribution, and after gradual dispersion, a more Poisson-like distribution across patches resulted (variance/mean ratio was closer to 1 and higher than for A. citri). The dispersion of A. tabida was most probably an effect of exploitation: these parasitoids increasingly made shorter visits to already exploited patches. We briefly discuss hypotheses on the adaptive significance of patch defence behaviour or its absence in the light of differences in the natural history of both parasitoid species, notably the spatial distribution of their hosts.
Evolutionary Trajectory of White Spot Syndrome Virus (WSSV) Genome Shrinkage during Spread in Asia
Mark P. Zwart,Bui Thi Minh Dieu,Lia Hemerik,Just M. Vlak
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0013400
Abstract: White spot syndrome virus (WSSV) is the sole member of the novel Nimaviridae family, and the source of major economic problems in shrimp aquaculture. WSSV appears to have rapidly spread worldwide after the first reported outbreak in the early 1990s. Genomic deletions of various sizes occur at two loci in the WSSV genome, the ORF14/15 and ORF23/24 variable regions, and these have been used as molecular markers to study patterns of viral spread over space and time. We describe the dynamics underlying the process of WSSV genome shrinkage using empirical data and a simple mathematical model.
Exact testing with random permutations
Jesse Hemerik,Jelle Goeman
Statistics , 2014,
Abstract: The way in which random permutations have been used in various permutation-based methods leads to anti-conservativeness, especially in multiple testing contexts. Problems arise in particular for Westfall and Young's maxT method, a more recent method by Meinshausen and a global test that we introduce. We illustrate this using simulations. We solve the problem of anti-conservativeness by proving that an exact test is obtained, if the identity map is added to the randomly drawn permutations.
Forces in Struggle in the Country and the City Today in Brazil: Beyond a Dualistic Understanding  [PDF]
lia Regina Vendramini
Current Urban Studies (CUS) , 2015, DOI: 10.4236/cus.2015.31006
Abstract: Is it still possible to distinguish the line that separates the country and the city? How do rural and urban workers produce their life today? What are the characteristics that distinguish or approximate them? What movements of resistance have been observed? These questions guide our reflections about the relationship between urban and rural space. Based on a study in the urban pe-riphery and in encampments and settlements of the Landless Rural Workers Movements in Brazil, we seek to understand alternative forms of occupation of space today.
A nursing interface terminology: Evaluation of face validity  [PDF]
Maria Eulàlia Juvé Udina
Open Journal of Nursing (OJN) , 2012, DOI: 10.4236/ojn.2012.23030
Abstract: A range of different language systems for nursing diagnosis, interventions and outcomes are currently available. Nursing terminologies are intended to support nursing practice but they have to be evaluated. This study aims to assess the results of an expert survey to establish the face validity of a nursing interface terminology. The study applied a descriptive design with a cross-sectional survey strategy using a written questionnaire administered to expert nurses working in hospitals. Sample size was estimated at 35 participants. The questionnaire included topics related to validity and reliability criteria for nursing controlled vocabularies described in the literature. Mean global score and criteria scoring at least 7 were considered main outcome measures. The analysis included descriptive statistics with a confidence level of 95%. The mean global score was 8.1. The mean score for the validity criteria was 8.4 and 7.8 for reliability and applicability criteria. Two of the criteria for reliability and applicability evaluation did not achieve minimum scores. According to the experts’ responses, this terminology meets face validity, but that improvements are required in some criteria and further research is needed to completely demonstrate its metric properties.
Is the ATIC terminology oriented to nursing phenomena?  [PDF]
Maria Eulàlia Juvé-Udina
Open Journal of Nursing (OJN) , 2012, DOI: 10.4236/ojn.2012.24057
Abstract: The main goal of this observational and descriptive study is to evaluate whether the diagnosis axis of a nursing interface terminology meets the content validity criterion of being nursing-phenomena oriented. Nursing diagnosis concepts were analyzed in terms of presence in the nursing literature, type of articles published and areas of disciplinary interest. The search strategy was conducted in three databases with limits in relation to period and languages. The final analysis included 287 nursing diagnosis concepts. The results showed that most of the concepts were identified in the scientific literature, with a homogeneous distribution of types of designs. Most of these concepts (87.7%) were studied from two or more areas of disciplinary interest. Validity studies on disciplinary controlled vocabularies may contribute to demonstrate the nursing influence on patients’ outcomes.
Evolution of the Number of Students in Elementary and Secondary School in Portugal and Population Ageing  [PDF]
Cecília Rosa, Edgar Pereira
Open Journal of Social Sciences (JSS) , 2017, DOI: 10.4236/jss.2017.57008
Abstract: In this work, we present an application of a mathematical model structured in classes (see [1]) for the study of the influence of population ageing in the evolution of the number of students in elementary school and in secondary school in Portugal, from 1995/96 to 2014/15 (see [2]). Based on historical data, some scenarios of projection are presented, with the aim of quantifying the young student population and its relation with the structure of the population age for the next school years in Portugal (from 2016/2017 to 2020/2021), in the various study cycles. Furthermore, we make a comparative analysis between the projection results presented here and in references [3] and [4]. The dynamic of the model comprises two stages: the first one represents the flow of students that go from one school year to the next, as well as the flow of students that enter or leave the educational system in a certain cycle of studies. The second stage represents the flow of students that go to the next cycle of studies. The simulations were done using Matlab.
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