Tesi sul tema "Population"
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1
Koegler, Xavier. "Population protocols, games and large populations". Paris 7, 2012. http://www.theses.fr/2012PA077132.
Testo completoAbstract (sommario):
Le modèle des populations protocols a été proposé pour capturer les spécificités de réseaux opportunistes constitués d'une population d'agents mobiles à la mémoire limitée capables de communications sans fil par paires. L'objet de cette thèse est d'étendre la compréhension et l'analyse des population protocols ainsi que leurs liens avec d'autres modèles de dynamiques de populations. La première contribution de cette thèse est l'étude de la traduction en terme de protocoles de population de la dynamique d'une population d'agents jouant à un jeu de manière répétée les uns contre les autres et adaptant leur stratégie selon le comportement de PAVLOV. Nous montrons que les protocoles issus de tels jeux sont aussi puissants que les protocoles de population généraux. La deuxième contribution consiste à étudier des hypothèse de symétrie dans les jeux et dans les transitions d'un protocole de population, pour montrer que, si les protocoles de population symétriques sont équivalents aux protocoles généraux, les jeux symétriques sont, eux, significativement moins puissants. La troisième contribution est de montrer comment étudier le comportement d'une protocole de population lorsque la taille de la population tend vers l'infini en approchant la dynamique résultante à l'aide d'une équation différentielle ordinaire et de définir un calcul par grande population comme la convergence de cette équation différentielle vers un équilibre stable. La quatrième et dernière contribution de la thèse est la caractérisation des nombres calculables en ce sens comme étant très exactement les réels algébriques des [0,1]Population protocols were introduced to capture the specifies of opportunistic networks of tny mobile agents with limited memory and capable of wireless communication in pairs. This thesis aims at extending the understanding and analysis of population protocols as well as their links to other models of population dynamics including ones from game theory. The first contribution of this thesis is to translate in terms of population protocols the dynamics of a population of agents playing a game repeatedly against each-other and adapting their strategy according to the PAVLOV behaviour. We show that protocols born from games are exactly as powerful as general population protocols. The second contribution consists in the study of the impact of symmetry on games and in the transitions of a population protocol to show that, if symmetric population protocols are equivalent to general protocols, symmetric games are significantly less powerful. The third contribution is to show how the dynamic of a population protocol can be approximated by an ordinary differential equation when the population grows to infinity. We then define a computation by a large population to be the convergence of this differential equation to a stable equilibrium. The fourth and final contribution of this thesis is the characterisation of the numbers computable in the above sense as exactly the algebraic real numbers in [0,1]
2
Lundy, Ian J. "Theoretical population genetics of spatially structured populations /". Title page, contents and summary only, 1997. http://web4.library.adelaide.edu.au/theses/09PH/09phl962.pdf.
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3
Martien, Karen Kay Fear. "Conservation of spatially structured populations : lessons from population genetics /". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2000. http://wwwlib.umi.com/cr/ucsd/fullcit?p9979969.
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4
Gagnon, Nicolas. "Mesure et analyse de l'effet fondateur dans les populations de Charlevoix et du Bas-Saint-Laurent". Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1998. http://theses.uqac.ca.
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5
Self, Eric C. "Population analysis a methodology for understanding populations in COIN environments". Thesis, Monterey, California. Naval Postgraduate School, 2008. http://hdl.handle.net/10945/3810.
Testo completoAbstract (sommario):
This thesis outlines a methodology for use by tactical operators to better understand the dynamics of the population whose support they are attempting to gain. In turn, these operators (Army soldiers, Marines, Special Forces, SEALs, Civil Affairs, etc.) can use this information to more effectively develop strategy, plan operations, and conduct tactical missions. Our methodology provides a heuristic model, called the "3 x 5 P.I.G.S.P.E.E.R. Model," that can be applied in any environment and will help bridge the gap between strategic theory and tactical implementation. We believe that our methodology can be utilized to increase the operator's understanding of the environment, and improve both non-kinetic and kinetic combat operations. As a counterinsurgency (COIN) force progresses from kinetic combat operations (those attempting to gain a security foothold in a non-permissive environment) to operations focused on gaining the support of the population, our methodology will aid in collecting human intelligence (HUMINT). Our methodology shows that by providing security, working through locals, building trust and cooperation, and identifying opportunities to leverage the local populace's needs, COIN forces will be able to handle their own security.
6
Burke, Mark C. Self Eric C. "Population analysis a methodology for understanding populations in COIN environments /". Monterey, Calif. : Naval Postgraduate School, 2008. http://edocs.nps.edu/npspubs/scholarly/theses/2008/Dec/08Dec%5FBurkeM.pdf.
Testo completoAbstract (sommario):
Thesis (M.S. in Defense Analysis)--Naval Postgraduate School, December 2008.Thesis Advisor(s): Gregg, Heather. "December 2008." Description based on title screen as viewed on January 30, 2009. Includes bibliographical references (p. 71-74). Also available in print.
7
Grillenberger, Bernd K. "Biogeography, population genetics and mating systems of natural Nasonia populations". [S.l. : Groningen : s.n. ; University Library Groningen] [Host], 2009. http://irs.ub.rug.nl/ppn/317.
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8
McRae, Allan F. "Quantitative and population genetic analyses of domesticated and wild sheep populations". Thesis, University of Edinburgh, 2005. http://hdl.handle.net/1842/15362.
Testo completoAbstract (sommario):
In Chapter 2, a directed linkage scam for loci involved in body weight and carcass composition traits is performed in a commercial Charollais sheep population. Five chromosomes were investigated based on prior evidence for major genes effecting the studied traits in other breeds. A maximum likelihood variance component analysis using identity-by-descent values estimated by Markov chain Monte Carlo methods was performed on a complex pedigree containing a total of 570 sheep. Of the total of nine QTL detected, the estimated position of only one overlapped with the regions showing major genes that were used in chromosome selection. During the analysis of the Charollais sheep population, a region of the genome showing a significant deviation from the published sheep linkage map was detected. This region is examined in more detail in Chapter 3, with the addition of further microsatellite markers as well as the investigation of this region in two further sheep breeds. With the inclusion of the published linkage map, this demonstrated a total of three linkage maps across four populations. Such heterogeneity in linkage maps across sheep breeds has important consequences for the design and analysis fine-mapping studies. The significance of a QTL linkage peak is not readily evaluated with general pedigrees. The extension of permutation methodology that is commonly used with structured pedigrees to more general pedigrees is investigated in Chapter 4. Chapter 5 examines the population dynamics of a well studied wild Soay sheep population. A unified statistical framework is developed for all major aspects of the life cycle of the sheep. This forms the basis of a simulation model of the population that is used to predict the amount of linkage disequilibrium in the population (Chapter 6) and the effective population size of the population (Chapter 7). The examination of the linkage disequilibrium structure in a population is an important step in the design of studies with the aim of fine-mapping quantitative trait loci. The simulated population showed significant decline of linkage disequilibrium with genetic distance and low levels of background linkage disequilibrium, indicating that the Soay sheep population is a viable resource for linkage disequilibrium fine mapping. Through the use of the simulation model, the effective population size of the Soay sheep population was estimated to be approximately 0.17 of its census population size. This is approximately half the value obtained with the use of a general predictive equation.
9
Cole-Showers, Curtis Lanre. "Population structure and demographics in Nigerian populations utilizing Y-chromosome markers". University of the Western Cape, 2014. http://hdl.handle.net/11394/5326.
Testo completoAbstract (sommario):
Philosophiae Doctor - PhDNigeria is peopled by ethnically and linguistically diverse populations of which little were known until the last few millennial. The absence of major natural geographical barrier increases the possibility of the populations being affected by the same demographic events. The aim of this thesis was to ascertain the genetic variations and demographics in five major Nigerian populations using Y-markers. This was done by determining the genetic structures of the Afro-asiatic speaking Hausa (n=78) of Northern Nigeria and the Niger Congo speaking populations of Igbo (n=119), Yoruba (n=238), Bini (n=13) and Ijaw (n=15) of Southern Nigeria all spread over 22 geographical origins and four (North, South east, south west and South south) geographical regions. They were compared with more than 2000 individuals from 46 populations of 20 other African and Middle Eastern countries, in published literature. The Scientific Working Group on DNA Analysis Methods (SWGDAM) recommended Y-Short Tandem Repeats (STRs) and nine Y-Single Nucleotide Polymorphisms (SNPs) haplogroups were typed with multiplex Polymerase Chain Reaction (PCR), Restriction Fragment Length Polymorphisms (RFLP) and High Resolution Melting (HRM). Summary statistics and measures of diversity were determined. Population structure was assessed with Population Pairwise Differences, hierarchical Analysis of Molecular Variance, Multidimensional scaling and correspondence analysis plots. Mantel’s test was used to assess the correlation of genetic distances with geographic distances. Demographic inferences were assessed with lineage based Network reconstruction, Spatial autocorrelation plots, effective migrants per population and both Inter and Intra-lineages Times to the Most Recent Common Ancestor (TMRCA). The patterns of diversity of the Y-markers showed a North-South gradient and a notable sub-structure among the Hausa populations. The Niger-Congo speakers displayed rare presence of haplogroups R and E1b1b but a preponderance of E1b1a7. Overall, the Y markers showed high diversities and significant genetic sub-structure within the Hausa populations of Nigeria with stronger linguistic than geographical bias. The demographic evaluations gave credence for genetic validation of both historical records and archeological findings among these Nigerian populations. These populations showed stronger affiliations with other sub-Saharan African populations rather than with North African or Middle Eastern populations, lacking evidence for the Middle Eastern origins of the male founders of these populations. Finally, the contribution of these Nigerian dataset would greatly enhance the Africa meta-population on the YHRD with more than 274 new haplotypes of forensic estimation significance.
10
Koons, David Nelson Grand James Barry. "Transient population dynamics and population momentum in vertebrates". Auburn, Ala, 2005. http://repo.lib.auburn.edu/EtdRoot/2005/SPRING/Forestry_and_Wildlife_Sciences/Dissertation/KOONS_DAVID_55.pdf.
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11
Leslie, Stephen. "Inference of Population Stratification Using Population Genetic Data". Thesis, University of Oxford, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.504423.
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12
Arrhenius, Gustaf S. H. "Population axiology". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq49968.pdf.
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13
Hubbard, Amelia R. "AN EXAMINATION OF POPULATION HISTORY, POPULATION STRUCTURE, AND BIOLOGICAL DISTANCE AMONG REGIONAL POPULATIONS OF THE KENYAN COAST USING GENETIC AND DENTAL DATA". The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1337195794.
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14
Håkansson, Nina. "Population growth : analysis of an age structure population model". Thesis, Linköping University, Department of Mathematics, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-4392.
Testo completoAbstract (sommario):
This report presents an analysis of a partial differential equation, resulting from population model with age structure. The existence and uniqueness of a solution to the equation are proved. We look at stability of the solution. The asymptotic behaviour of the solution is treated. The report also contains a section about the connection between the solution to the age structure population model and a simple model without age structure.
15
Méléard, Sylvie, e Sylvie Roelly. "Evolutive two-level population process and large population approximations". Universität Potsdam, 2013. http://opus.kobv.de/ubp/volltexte/2013/6460/.
Testo completoAbstract (sommario):
We are interested in modeling the Darwinian evolution of a population described by two levels of biological parameters: individuals characterized by an heritable phenotypic trait submitted to mutation and natural selection and cells in these individuals influencing their ability to consume resources and to reproduce. Our models are rooted in the microscopic description of a random (discrete) population of individuals characterized by one or several adaptive traits and cells characterized by their type. The population is modeled as a stochastic point process whose generator captures the probabilistic dynamics over continuous time of birth, mutation and death for individuals and birth and death for cells. The interaction between individuals (resp. between cells) is described by a competition between individual traits (resp. between cell types). We are looking for tractable large population approximations. By combining various scalings on population size, birth and death rates and mutation step, the single microscopic model is shown to lead to contrasting nonlinear macroscopic limits of different nature: deterministic approximations, in the form of ordinary, integro- or partial differential equations, or probabilistic ones, like stochastic partial differential equations or superprocesses.
16
Bycroft, Clare. "Genomic data analyses for population history and population health". Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:c8a76d94-ded6-4a16-b5af-09bbad6292a2.
Testo completoAbstract (sommario):
Many of the patterns of genetic variation we observe today have arisen via the complex dynamics of interactions and isolation of historic human populations. In this thesis, we focus on two important features of the genetics of populations that can be used to learn about human history: population structure and admixture. The Iberian peninsula has a complex demographic history, as well as rich linguistic and cultural diversity. However, previous studies using small genomic regions (such as Y-chromosome and mtDNA) as well as genome-wide data have so far detected limited genetic structure in Iberia. Larger datasets and powerful new statistical methods that exploit information in the correlation structure of nearby genetic markers have made it possible to detect and characterise genetic differentiation at fine geographic scales. We performed the largest and most comprehensive study of Spanish population structure to date by analysing genotyping array data for ~1,400 Spanish individuals genotyped at ~700,000 polymorphic loci. We show that at broad scales, the major axis of genetic differentiation in Spain runs from west to east, while there is remarkable genetic similarity in the north-south direction. Our analysis also reveals striking patterns of geographically-localised and subtle population structure within Spain at scales down to tens of kilometres. We developed and applied new approaches to show how this structure has arisen from a complex and regionally-varying mix of genetic isolation and recent gene-flow within and from outside of Iberia. To further explore the genetic impact of historical migrations and invasions of Iberia, we assembled a data set of 2,920 individuals (~300,000 markers) from Iberia and the surrounding regions of north Africa, Europe, and sub-Saharan Africa. Our admixture analysis implies that north African-like DNA in Iberia was mainly introduced in the earlier half (860 - 1120 CE) of the period of Muslim rule in Iberia, and we estimate that the closest modern-day equivalents to the initial migrants are located in Western Sahara. We also find that north African-like DNA in Iberia shows striking regional variation, with near-zero contributions in the Basque regions, low amounts (~3%) in the north east of Iberia, and as high as (~11%) in Galicia and Portugal. The UK Biobank project is a large prospective cohort study of ~500,000 individuals from across the United Kingdom, aged between 40-69 at recruitment. A rich variety of phenotypic and health-related information is available on each participant, making the resource unprecedented in its size and scope. Understanding the role that genetics plays in phenotypic variation, and its potential interactions with other factors, provides a critical route to a better understanding of human biology and population health. As such, a key component of the UK Biobank resource has been the collection of genome-wide genetic data (~805,000 markers) on every participant using purpose-designed genotyping arrays. These data are the focus of the second part of this thesis. In particular, we designed and implemented a quality control (QC) pipeline on behalf of the current and future use of this multi-purpose resource. Genotype data on this scale offers novel opportunities for assessing quality issues, although the wide range of ancestral backgrounds in the cohort also creates particular challenges. We also conducted a set of analyses that reveal properties of the genetic data, including population structure and familial relatedness, that can be important for downstream analyses. We find that cryptic relatedness is common among UK Biobank participants (~30% have at least one first cousin relative or closer), and a full range of human population structure is present in this cohort: from world-wide ancestral diversity to subtle population structure at sub-national geographic scales. Finally, we performed a genome-wide association scan on a well-studied and highly polygenic phenotype: standing height. This provided a further test of the effectiveness of our QC, as well as highlighting the potential of the resource to uncover novel regions of association.
17
Herbots, Hilde Maria Jozefa Dominiek. "Stochastic models in population genetics : genealogy and genetic differentiation in structured populations". Thesis, Queen Mary, University of London, 1994. http://qmro.qmul.ac.uk/xmlui/handle/123456789/1482.
Testo completoAbstract (sommario):
The theory of probability and stochastic processes is applied to a current issue in population genetics, namely that of genealogy and genetic differentiation in subdivided populations. It is proved that under a reasonable model for reproduction and migration, the ancestral process of a sample from a subdivided population converges weakly, as the subpopulation sizes tend to infinity, to a continuous-time Markov chain called the "structured coalescent". The moment-generating function, the mean and the cond moment of the time since the most recent common ancestor (called the "coalescence time") of a pair of genes are calculated explicitly for a range of models of population structure. The value of Wright's coefficient FST, which serves as a measure of the subpopulation differentiation and which can be related to the coalescence times of pairs of genes sampled within or among subpopulations, is calculated explicitly for various models of population structure. It is shown that the dependence of FST on the mutation rate may be more marked than is generally believed, particularly when gene flow is restricted to an essentially one-dimensional habitat with a large number of subpopulations. Several more general results about genealogy and subpopulation differentiation are proved. Simple relationships are found between moments of within and between population coalescence times. Weighting each subpopulation by its relative size, the asymptotic behaviour of FST at large mutation rates is independent of the details of population structure. Two sets of symmetry conditions on the population structure are found for which the mean coalescence time of a pair of genes from a single subpopulation is independent of the migration rate and equal to that of two individuals from a panmictic population of the same total size. Under graph-theoretic conditions on the population structure, there is a uniform relationship between the FST value of a pair of neighbouring subpopulations, in the limit of zero mutation rate, and the migration rate
18
Champagnon, Jocelyn. "Conséquences des introductions d’individus dans les populations exploitées : l’exemple du Canard Colvert Anas platyrhynchos". Thesis, Montpellier 2, 2011. http://www.theses.fr/2011MON20147/document.
Testo completoAbstract (sommario):
Le renforcement des populations naturelles exploitées par des individus captifs est rarement évalué, bien qu'il puisse induire des modifications notables sur la population naturelle à de nombreux niveaux : démographie, comportement, morphologie, génétique, pathogènes. Ce travail de thèse concerne les introductions de canards colverts Anas platyrhynchos réalisées à des fins cynégétiques. Cette pratique est très répandue en Europe, depuis plus de trente ans. Du fait de leur domestication en élevage, les canards lâchés subissent une mortalité naturelle très forte comparée aux oiseaux sauvages, à laquelle s'ajoute une plus grande vulnérabilité à la chasse. Une différenciation génétique marquée permet de discriminer les oiseaux lâchés de leurs congénères sauvages. Des croisements entre les deux groupes sont détectés, mais l'introgression reste limitée. Globalement, la contribution démographique et génétique des individus d'élevage à la population sauvage est faible, même si une modification morphologique attribuable aux lâchers a été constatée dans la population sauvage en trente ans. Les conséquences écologiques pour la population réceptrice semblent donc limitées, mais une vigilance continue doit s'exercer concernant la diffusion de pathogènes (forte prévalence occasionnelle de virus Influenza A dans les élevages) et les risques génétiques associés au renforcement sur le long termeThe consequences of releasing captive-reared game animals into the wild have received little attention, despite their potential impact for receiving populations in terms of demography, behaviour, morphometrics, genetics and pathogens. The present study considers Mallards Anas platyrhynchos released for hunting purposes, an increasing practice in Europe over the last 30 years. Because of domestication process in game farm facilities, our study shows high natural mortality of these ducks once released compared to wild Mallards, in addition to high vulnerability to hunting. A clear genetic differentiation allows discrimination of released and wild Mallards. Hybridization with wild Mallards exists, but did not result into significant introgression. Generally, genetic as well as demographic contributions of captive-bred birds to the natural population were low, but a morphological modification associated with releases was recorded over 30 years in natural population. Ecological consequences of the releases for the wild population seem to be limited, but caution should be maintained on the possible transmission of pathogens (occasionally high prevalence of avian Influenza A in some breeding facilities) and the genetic risks associated with long-term releases
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Ward, Eric John. "Incorporating model selection and decision analysis into population dynamics modeling /". Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/5319.
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20
Laine, Kari. "Long-term variations in plant quality and quantity in relation to cyclic microtine rodents at Kilpisjärvi, Finnish Lapland". Oulu, Finland : University of Oulu, 1988. http://catalog.hathitrust.org/api/volumes/oclc/18696609.html.
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21
Orsi, Maia. "Population synthesis models for IMF studies". Thesis, Liverpool John Moores University, 2014. http://researchonline.ljmu.ac.uk/4525/.
Testo completoAbstract (sommario):
Population synthesis models (PSMs) are fundamental tools to study the star formation history and IMF of unresolved stellar populations using spectral features. This work presents a new set of PSMs constructed using theoretical isochrones and two state-ofthe- art synthetic spectral libraries. The BT-Settl and Munari libraries were chosen for their ability to predict the observed values of Lick-type and IMF-sensitive indices in individual stars of the solar neighbourhood. The BT-Settl library was used to sample the cool main sequence stars and the Munari library for the rest of the evolutionary phases. The PSMs cover a range of metallicities with [Fe/H]= 0, -1.31 and -1.81 for scaled-solar and α-enhanced metal mixtures. The models were used to study the behaviour of the IMF indices defined in the literature and the results are in good agreement with what other PSMs have determined. The PSMs in this work predict a strong degeneracy between age, metallicity and IMF. I used the models to study which are the main evolutionary phases contributing to each IMF-sensitive index and found that most indices reach their final integrated values before the turn off. The post-main sequence stars contribute mainly to the continuum of these bands. Uncertainties in the the effective temperature of the isochrones can affect IMF estimates. The PSMs were applied to extragalactic globular clusters (GCs) and early-type galaxies (ETGs) using data from the literature. I determined the ages, metallicities and IMFs of these systems using index combinations in the optical and infrared. I explored how the morphology of the Horizontal Branch (HB) and dynamical evolution (which are key uncertainties in the modelling of GCs) can affect the IMF predictions. In a population with a Milky Way IMF, dynamical evolution can make the IMF indices mimic a bottom-light IMF. HB morphology has no impact on the IMF estimates at low [Fe/H]. In the IMF index-index diagrams for GCs, the results are significantly affected by the unknown sodium abundances of these systems. Using the PSMs in this work the best index combination to determine the IMF is CaH1 and TiO2. The ETGs and the [Fe/H]=0 GCs appear to have a bottom-heavy IMF with x ~ 3:0. These results are discussed in the work.
22
Hens, H. (Hilde). "Population genetics and population ecology in management of endangered species". Doctoral thesis, Oulun yliopisto, 2017. http://urn.fi/urn:isbn:9789526215853.
Testo completoAbstract (sommario):
Abstract Knowledge of the determinants of the viability of populations is essential in order to undertake effective conservation and management of endangered species. In this study, long-term demographic data was combined with genetic data to study the viability of an endangered orchid species, Epipactis atrorubens. The genetic analyses revealed low levels of genetic variation and the presence of population genetic differentiation independent of the spatial scale. Low levels of seed-mediated gene flow, possibly linked to low seedling recruitment, is the likely cause of the low levels of gene flow. Indications of slow post-glacial colonisation rates were found, which together with the low gene flow predict a limited capacity of the species to shift its range to more suitable habitats after environmental change. Low genetic variation as a proxy for low evolutionary potential also suggests that the species has limited capacity to adapt to new environmental conditions. Furthermore, poor seedling recruitment lowers population viability in small populations, as highlighted by the low population growth rates. In addition, we found a strong effect of stochasticity that limits the viability of populations. Both the genetic and demographic analyses indicated low viability of the studied species and that seedling recruitment could be the main determinant for the viabilityTiivistelmä Luonnonsuojelun perusta on populaatioiden elinkykyyn vaikuttavien tekijöiden tuntemus. Tässä väitöskirjatyössä tutkittiin uhanalaisen orkidean, tummaneidonvaipan (Epipactis atrorubens), elinkykyyn vaikuttavia tekijöitä yhdistämällä pitkäaikaisseurannoilla kerätyt demografiset aineistot geneettisin menetelmin kerättyihin aineistoihin. Lajin populaatioiden geneettisen muuntelun määrän havaittiin olevan pieni ja populaatioiden todettiin olevan geneettisesti erilaistuneita maantieteellisestä skaalasta riippumatta. Geneettisen erilaistumisen syy voi olla alhainen geenivirta, joka on seurausta vähäisestä siemendispersaalista ja huonosta taimettumisesta. Populaatioiden evolutiivista historiaa tutkittaessa havaittiin merkkejä hitaasta jääkauden jälkeisestä kolonisaatiosta, mikä yhdessä alhaisen geenivirran kanssa ennustaa, että lajilla on huono kyky siirtyä sille sopivammille alueille, jos ympäristö muuttuu. Huonoa evolutiivista potentiaalia kuvastava vähäinen geneettinen muuntelu ennustaa, että lajilla on huono kyky sopeutua uusiin ympäristöoloihin. Tämän lisäksi huono taimettuminen laskee elinkykyä etenkin pienissä populaatioissa, mikä näkyy muun muassa pienten populaatioiden matalina kasvukertoimina. Stokastinen vaihtelu vaikutti elinkykyä alentavasti, mikä pitäisikin huomioida nykyistä paremmin elinkykyanalyyseissä. Sekä geneettiset että demografiset analyysit osoittivat taimettumisen mahdollisesti olevan määräävä tekijä tummaneidonvaipan populaatioiden elinkyvylle
23
Okobo, Nicodème. "La population scolaire au Congo : analyse démographique d'une sous-population". Bordeaux 4, 2004. http://www.theses.fr/2004BOR40008.
Testo completoAbstract (sommario):
L'éducation a toujours été considérée, en tout temps et en tout lieu, comme une variable essentielle dans le développement socio-économique et culturel des nations et des peuples. Le Congo, comme la plupart des pays dans le monde en général, et en Afrique en particulier a toujours été conscient de ce rôle déterminant de l'éducation. C'est pourquoi, il a édicté une loi scolaire en 1965, nationalisant son système éducatif, le rendant gratuit et obligatoire pour tout enfant vivant sur le territoire. Cette loi a eut évidemment des effets considérables sur le développement du système d'enseignement et l'évolution de la population scolaire. L'analyse démographique de cette sous-population, même si elle reste encore difficile à mener en raison de l'insuffisance d'informations statistiques, a montré que celle-ci a augmenté très rapidement au Congo, dès l'année de la mise en place de la loi. Cela s'est traduit par une élévation appréciable du niveau de scolarisation de la jeunesse congolaise. Cette massification du système d'enseignement ne s'est pas faite sans douleur car en démocratisant totalement le système éducatif sans se préoccuper des moyens d'accueil et d'encadrement nécéssaires à sa bonne marche (classes surchargées, ratio maitre-éléves très élévé, part des dépenses publiques allouées à l'enseignement primaire assez faible), celui-ci allait rapidement connaitre une baisse de son rendement interne. . .
24
Klenzendorf, Sybille A. "Population dynamics of Virginia's hunted black bear (Ursus americanus) population". Diss., Connect to this title online, 2002. http://scholar.lib.vt.edu/theses/available/etd-02122002-160752/.
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Sester-Huss, Elisabeth Mariko [Verfasser], e Peter [Akademischer Betreuer] Pfaffelhuber. "Population genetic models with selection, fluctuating environments and population structure". Freiburg : Universität, 2020. http://d-nb.info/1206095830/34.
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Bel-Air, Françoise de. "Population, politique et politiques de population en Jordanie, 1948-1998". Paris, EHESS, 2003. http://www.theses.fr/2003EHES0115.
Testo completoAbstract (sommario):
Posant d'emblée la portée politique des comportements (migrations, nuptialité, structures familiales et fécondité) et des politiques démographiques, on examine comment "la démographie entre dans la stratégie de pouvoir des groupes ou influence la politique des Etats". Les exodes de Palestine en 1948 et 1967 et l'émigration vers les pays du Golfe après 1973 ont été instrumentalisés par le régime hachémite, pour une affirmation de l'arabité de la Jordanie et une rentiérisation de l'Etat. Les structures du pouvoir sont reproduites, dans les relations Etat-société mais aussi entre sexes et entre générations. La Guerre du Golfe affecte cet équilibre macro et micropolitique. A partir des années 1990, l'émergence de politiques de contrôle de la fécondité est le signe d'une substitution de l'aide internationale au développement à la rente migratoire. Parallèlement, l'ouverture de nouveaux champs migratoires permet un contrôle des effets du changement social et de la contestation politiqueFrom the outset, taking into consideration the political significance of demographic behaviour (migration patterns, marriage, family structures and fertility) and of population policies, we investigate how "demography is part of power strategies of groups or influences States' policies". Exodus from Palestine in 1948 and 1967, labour migration to the Gulf States after 1973 have been instrumentalised by the Hashemite regime, in order to promote the Arab identity of Jordan, as well as to set up a rentier State and economy. Structures of power distribution are thus produced, ine the State-society, as well as gender and intergenerational relationships. The Gulf War upset this micro and macropolitical balance. From the 1990's onwards, the emergence of fertility control policies signals an attempt to replace migratory revenue by international aid for development. Also, the emergence of new migration patterns allows for controlling the effects of social change and lack of political participation
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Williams, Mari. "Japanese population decline". Connect to resource, 2006. http://hdl.handle.net/1811/6454.
Testo completoAbstract (sommario):
Thesis (Honors)--Ohio State University, 2006.Title from first page of PDF file. Document formatted into pages: contains 13 p.; also includes graphics. Includes bibliographical references (p. 13). Available online via Ohio State University's Knowledge Bank.
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Kern, Andrew David. "Drosophila population genomics /". For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2005. http://uclibs.org/PID/11984.
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Zeineddine, Mohammed. "Evolutionary population phenomena". Thesis, Royal Holloway, University of London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425699.
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Childs, Dylan Zachary. "Structured population models". Thesis, Imperial College London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.404400.
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Muzhi, Li, e A. Tkachenko. "Human population crisis". Thesis, Видавництво СумДУ, 2009. http://essuir.sumdu.edu.ua/handle/123456789/8171.
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Corcoran, Pádraic. "Neurospora tetrasperma from Natural Populations : Toward the Population Genomics of a Model Fungus". Doctoral thesis, Uppsala universitet, Evolutionsbiologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-208791.
Testo completoAbstract (sommario):
The study of DNA sequence variation is a powerful approach to study genome evolution, and to reconstruct evolutionary histories of species. In this thesis, I have studied genetic variation in the fungus Neurospora tetrasperma and other closely related Neurospora species. I have focused on N. tetrasperma in my research because it has large regions of suppressed recombination on its mating-type chromosomes, had undergone a recent change in reproductive mode and is composed of multiple reproductively isolated lineages. Using DNA sequence data from a large sample set representing multiple species of Neurospora I estimated that N. tetrasperma evolved ~1 million years ago and that it is composed of at least 10 lineages. My analysis of the type of asexual spores produced using newly described N. tetrasperma populations in Britain revealed that lineages differ considerably in life history characteristics that may have consequences for their evolution. A comparative genomic analysis using three genomes of N. tetrasperma and the genome of N. crassa revealed that the mat a chromosomes in the lineages examine have been introgressed from other Neurospora species and that this introgression has reduced levels of molecular degeneration on the mating-type chromosomes. Finally, I generated a population genomic dataset composed of 92 N. tetrasperma genomes and two genomes of other Neurospora species. Analysis of these genomes revealed that all strains of N. tetrasperma have large regions of suppressed recombination on their mating-type chromosomes ranging from 69-84% of the chromosome and that the extent of divergence between mating-type chromosomes within lineages varies greatly (from 1.3 to 3.2%). I concluded that the source of this great divergence mating-type chromosome is large-scale introgression from other Neurospora species, and that these introgressed tracts have become fixed within N. tetrasperma lineages. I also discovered that genes within non-recombining introgressed regions of the mating-type chromosome have severely reduced levels of genetic variation as compared to the autosomes, and exhibit signatures of reduced molecular degeneration. My analysis of variation in coding regions revealed that positive selection on the introgressed regions has resulted in the removal of deleterious mutations and is responsible for the reductions in molecular degeneration observed.
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Olsson, Fredrik. "Inbreeding, Effective Population Sizes and Genetic Differentiation : A Mathematical Analysis of Structured Populations". Doctoral thesis, Stockholms universitet, Matematiska institutionen, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-115708.
Testo completoAbstract (sommario):
This thesis consists of four papers on various aspects of inbreeding, effective population sizes and genetic differentiation in structured populations, that is, populations that consist of a number of subpopulations. Three of the papers concern age structured populations, where in the first paper we concentrate on calculating the variance effective population size (NeV) and how NeV depends on the time between measurements and the weighting scheme of age classes. In the third paper we develop an estimation procedure of NeV which uses age specific demographic parameters to obtain approximately unbiased estimates. A simulation method for age structured populations is presented in the fourth paper. It is applicable to models with multiallelic loci in linkage equilibrium. In the second paper, we develop a framework for analysis of effective population sizes and genetic differentiation in geographically subdivided populations with a general migration scheme. Predictions of gene identities and gene diversities of the population are presented, which are used to find expressions for effective population sizes (Ne) and the coefficient of gene differentiation (GST). We argue that not only the asymptotic values of Ne and GST are important, but also their temporal dynamic patterns. The models presented in this thesis are important for understanding how different age decomposition, migration and reproduction scenarios of a structured population affect quantities, such as various types of effective sizes and genetic differentiation between subpopulations.At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Submitted.
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黃道全 e Richard Huang. "Spatial variation in Cellana grata populations: the interplay of population dynamics and foodavailability". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31243125.
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Hindle, Bethan J. "Unravelling the effects of environmental variation on the population dynamics of structured populations". Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/19466/.
Testo completoAbstract (sommario):
Complex environmental effects, combined with little temporal replication in most data sets, make investigating the ecological consequences of rapid climate change difficult with current tools. Structured population models are widely used to explore population responses to environmental variation. I develop and apply new statistical methods to parameterise such models. First I describe a structural equation model (SEM) approach for capturing temporal covariation among demographic rates via latent variable(s). When rates are positively correlated the latent variable(s) act as axes of ‘environmental quality’. This provides a simpler target for identifying the drivers of variation, than treating each process independently. Where drivers cannot be identified perturbing the latent variable(s) may represent the best alternative for exploring population-level responses to environmental change. Quantifying the effects of underlying drivers allows population viability under different management strategies to be predicted. Such studies frequently assume a stationary environment, despite rapid climate change. Where climatic drivers are included, single temporal windows of influence are typically chosen a priori. I show forecasted climate change alters predicted population viability under different management regimes in a rare fire-adapted herb. I illustrate that the effect of a single climatic variable may differ over time, suggesting a priori selection of single temporal windows can decrease predictive performance. I use the SEM approach to show that most (co)variation in survival and fecundity across different age-sex classes in a Soay sheep population is driven by a single environmental axis. I show climatic conditions during the energetically expensive autumn rut are nearly as important for overwinter mortality as the winter periods focused on in previous studies. I explore how density dependence, a temporal trend, population structure, and environmental variation interact to drive dynamics in this population. Throughout this thesis I apply novel methods that increase our ability to accurately forecast population dynamics under environmental change.
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Robin, Annie. "Synthese de population : un modele de la galaxie et de ses populations stellaires". Besançon, 1989. http://www.theses.fr/1989BESA2049.
Testo completoAbstract (sommario):
On construit un modele detaille de notre galaxie base sur la comprehension de la structure galactique suivant differents points de vue: cinematique, dynamique, evolution stellaire et evolution galactique. Pour cela on utilise un parametre cle: l'age des etoiles. La distribution theorique des ages des etoiles dans le voisinage solaire decoule d'un modele d'evolution stellaire et galactique. Les equations de boltzmann et de poisson contraignent par l'intermediaire du potentiel les lois de densite des etoiles du disque galactique. On produit ainsi une distribution des etoiles dans toute la galaxie en fonction de leurs parametres intrinseques: magnitude absolue, temperature effective, age, metallicite, qu'on peut aisement transformer en observables telles que magnitude apparente, couleurs, type spectral, mouvements propres et vitesses radiales en tenant compte de l'absorption interstellaire et des gradients de metallicite et de vitesse. Les contraintes proviennent soit des donnees du voisinage solaire, soit des denombrements d'etoiles a grandes distances. Le modele a produit un certain nombre de nouveaux resultats sur la structure galactique et les populations stellaires. Le plus important concerne la determination par une methode originale et autocoherente de la densite de masse au voisinage du soleil. Celle-ci est compatible avec la densite de masse observee ce qui refute l'hypothese d'existence d'une quantite significative de masse cachee dans le disque. D'autres resultats ont ete obtenus, tels que la determination de la densite locale d'etoiles du halo, l'existence de la population intermediaire, la calibration des magnitudes absolues et de l'age des geantes rouges, l'echelle de longueur du disque galactique et la fonction de luminosite et l'age des naines blanches. Le modele produit des predictions de distributions d'etoiles dans toute la galaxie, sauf le centre, en fonction des parametres observa
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Silva, Mónica Almeida e. "Population biology of bottlenose dolphins in the Azores archipelago". St Andrews : University of St Andrews thesis, 2007. https://research-repository.st-andrews.ac.uk/handle/10023/215.
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Klaoudatos, D. "Reproductive ecology, population genetics and population dynamics of selected Decapod crustaceans". Thesis, Swansea University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637807.
Testo completoAbstract (sommario):
The reproductive ecology of three species of Decapod crabs, the shore crab (Carcinus maenas), the velvet crab (Necora puber) and the edible crab (Cancer pagurus), were studied in Swansea Bay and South Gower. Spawning occurs over winter and spring (shore crab), winter (edible crab), and summer (velvet crab). Berried females occur in spring and summer (shore crab), winter spring and summer (edible crab), summer and autumn (velvet crab). Eggs hatch in spring and summer (shore crab, edible crab), summer and winter (velvet crab). Copulation occurs in summer and autumn (shore crab), summer, autumn and winter (edible crab, velvet crab). Shore crabs from Swansea Queen’s Dock have a different reproductive cycle compared to the shore crabs from Tawe Barrage Impoundment and Mumbles Pier. More than one spawning periods or an extended spawning period was indicated for the shore crabs in the Docks. The genetic makeup of the shore crab populations present in Swansea Queen’s Dock and Mumbles Pier was compared using SSCP and cloning analysis of the 16S rRNA. Four different haplotypes were identified all of which were present in the Docks and one in the Pier, with low level of genetic divergence, and close relationship of the identified haplotypes with published shore crab haplotypes. AMOVA showed no significant difference between the study populations and published shore crab haplotypes. However, all identified haplotypes were different from published shore crab haplotypes, indicating a degree of reproductive isolation of the Swansea shore crab populations. Analysis of the permit return data for 1980-2002 of the edible and velvet crab fishery for the South Wales Sea Fisheries Committee District indicated that a combination of factors including overfishing, environmental conditions, and the “Sea Empress” oil spill in 1996 have contributed to a decline in landings that continues to date with limited signs of recovery.
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Nussey, Daniel H. "Phenotypic plasticity and population genetic structure in a wild vertebrate population". Thesis, University of Edinburgh, 2005. http://hdl.handle.net/1842/15544.
Testo completoAbstract (sommario):
My thesis focuses on maternal phenotypic plasticity in two neonatal traits and population genetic structure at different spatial scales in a wild red deer (Cervus elaphus) population on the Isle of Rum, Scotland. Specifically, I present: • An analysis of offspring birth weight-spring temperature plasticity in female red deer using linear regression to measure individual reaction norms. I found evidence of variation in plasticity between females and show that early experiences of high population density reduce female plasticity. • The description of a mixed-effects linear model approach to analysing phenotypic plasticity from a reaction norm perspective, and application of this model to birth date in the Rum deer population. I use the model to examine variation in phenotypic plasticity between females and selection on plasticity at different population density levels. • An examination of population history and structure in red deer from across the Isle of Rum using mitochondria) DNA and microsatellite markers. Analysis revealed that deer in this introduced population came from geographically isolated ancestral populations, and there was genetic evidence for strongly male-biased dispersal. Recent management practices on the island may have led to spatial variation in effective male dispersal on Rum. • A comparison of fine-scale spatial genetic structure between male and female deer in the North Block study area using microsatellite markers and census data. There was evidence of structure at extremely fine spatial scales amongst females but not males, and a decline in the structure amongst females over time. • An analysis of the spatial distribution of different mtDNA haplotypes in male and female red deer across the North Block. There was evidence for spatial structuring of haplotypes in both sexes.
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Paltiel, Charles J. "An analysis of the 1994-1996 northern Strait of Georgia oyster survey". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ51440.pdf.
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41
Dooley, Claire. "Allee effects : empirical analyses of wild British butterfly populations and theoretical implications for population synchrony". Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:97da58d7-2bf3-45ca-a563-5394c7b97050.
Testo completoAbstract (sommario):
An Allee effect is a density-dependent process that can be responsible for the extinction of small populations. This thesis focuses on the detection of Allee effects, along with other density-dependent processes, and their influence on population synchrony. In chapter 2 I investigate the spatial variation in influential density-dependent processes and density-independent weather factors for the large skipper butterfly Ochlodes sylvanus across its British range. I find both qualitative and quantitative spatial variation in these processes and factors driving population dynamics. In chapter 3, I develop and test a Bayesian methodology, that I then use in chapter 4 to analyse local population level dynamics for 38 British butterfly species. For 35 of these species I found population level Allee effects and also found that phylogeny significant influenced a species’ susceptibility to Allee effects. Finally, in chapter 5 I examine the influence Allee effects have on network population synchrony in a theoretical framework.
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Waldick, Ruth. "Assessing the status of the endangered North Atlantic right whale using genetic and demographic data". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ66244.pdf.
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43
Hancock, Andrew. "The biology and fishery of Roe's abalone Haliotis roei Gray in south-western Australia, with emphasis on the Perth fishery /". Connect to this title, 2004. http://theses.library.uwa.edu.au/adt-WU2004.0068.
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44
Rohrer, Wendy L. "A biosystematic study of the rare plant Paronychia virginica Sprengel (Caryophyllaceae) employing morphometric and allozyme analyses". Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/46520.
Testo completoAbstract (sommario):
Paronychia virginica Spreng. (Caryophyllaceae) is a perennial evergreen herb of exposed, relatively xeric habitats. Approximately 10 mid-Appalachian populations remain in Virginia, West Virginia, and Maryland and are disjunct from populations located primarily in Texas, Oklahoma, and Arkansas. A study was conducted to test the hypothesis that eastern and western populations differ significantly and, therefore, represent at least two distinct taxa. Statistical analyses of 8 qualitative and 24 quantitative morphological characters indicated very highly significant (P < 0.001) variation between eastern and western populations of P. virginica. Characters differing most significantly included sepal pubescence, awn length, awn pubescence, awn curvature, length-width ratio of leaves, and shape of leaf apices. Starch gel electrophoresis was performed and six enzyme systems/nine loci (EST-2, EST-3, LAP, MDH-1, MDH-2, PGI, PGM-1, PGM-2, and SKDH) were identified as being consistently scorable and informative. Although gene flow between populations of P. virginica was shown to be restricted (mean FST = 0.353), populations are maintaining relatively high levels of genetic diversity. Genetic variability was quantified for each population and mean values for number of alleles per locus (A), percent loci polymorphic (P), and expected heterozygosity (HEXP) were found to be 1.95, 47.22%, and 0.204, respectively, exceeding those values reported for seed plants, widespread species, and endemic species. Hierarchical F statistics suggest higher levels of genetic variability within individual populations than among populations, regardless of geographic location. All statistically significant (P < 0.05) deviations from Hardy-Weinberg equilibrium indicated a deficiency in heterozygotes at the respective loci. Considering results from both the morphometric and allozyme analyses, the current author suggests recognizing two distinct subspecies, P. virginica subsp. virginica in the eastern U.S. and P. virginica subsp. scoparia in the south-central U.S. Conservation efforts should be focused on the maintenance of existing populations in both eastern and western regions of the U.S. in order to preserve the genetic and evolutionary potential of these taxa.Master of Science
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Bergeron, Josée. "Contribution différentielle des ancêtres d'origine acadienne au bassin génétique des populations régionales du Québec /". Thèse, Chicoutimi : Ste-Foy : Université du Québec à Chicoutimi. Université Laval, 2005. http://theses.uqac.ca.
Testo completoAbstract (sommario):
Thèse (M.Med.Exp.) -- Université du Québec à Chicoutimi, programme en extension de l'Université Laval, 2005.Bibliogr.: f. [94]-103. Document électronique également accessible en format PDF. CaQCU
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Banks, John E. "The effects of landscape heterogeneity on insect populations : a study of pattern and scale /". Thesis, Connect to this title online; UW restricted, 1997. http://hdl.handle.net/1773/5166.
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Larson, Shawn Elizabeth. "Genetic and endocrine related variability of sea otters, Enhydra lutris /". Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/5360.
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Mäki-Petäys, H. (Hannaleena). "Conservation and management of populations in a fragmented forest landscape:behavioural ecology meets population genetics". Doctoral thesis, University of Oulu, 2007. http://urn.fi/urn:isbn:9789514283482.
Testo completoAbstract (sommario):
Abstract
The effects of habitat loss and fragmentation on the genetic structure and vulnerability of populations strongly depend on the behaviour of a particular species. In this thesis, I examined the effects of forest fragmentation on genetic population structure with the aim of identifying and evaluating the different genetic and behavioural factors important for species conservation and management on different geographical scales. The species studied were the mound building red wood ants Formica lugubris and F. aquilonia, and a lekking bird, the capercaillie, Tetrao urogallus.
Habitat loss and fragmentation affected the genetic structure in both wood ants and capercaillie. In general, the effects were related to the time since fragmentation and to the level of habitat loss and isolation from the other existing populations. The loss of genetic diversity due to population fragmentation was less observable than the differences in population structure. The response to habitat fragmentation was further dependent on species characteristics such as dispersal and mating behaviour. Sociality affected the genetic vulnerability of wood ant populations by decreasing gene diversity, increasing inbreeding depression and restricting gene flow between subpopulations. The results on the capercaillie in turn suggested that lekking behaviour restricts dispersal of both sexes, thus elevating the occurrence of inbreeding between individuals.
The present study provided important information on species conservation and management in terms of better understanding species' biology and behaviour, as well as increased knowledge concerning the genetic issues that should be taken into account when planning conservation actions. By examining the genetic structure of the species it was possible to clarify the conservation status including the effective population size, the question of origin, and the genetic vulnerability (genetic diversity, inbreeding and inbreeding depression) of the populations and/or species. Overall, the results emphasised the importance of preserving the effective population size and the connectivity of habitat patches when planning species specific management strategies. There were great differences in conservation needs among the species, which should be taken into account especially in local management actions.
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Downing, Beatrice Catherine. "Disruption and disease : how does population management affect disease risk in wild bird populations?" Thesis, University of Exeter, 2017. http://hdl.handle.net/10871/29259.
Testo completoAbstract (sommario):
Despite the ubiquity of wildlife management, from reintroductions and supplemental feeding to culling and habitat destruction, very little is known of the effects of management practices on species’ social dynamics. Species’ social structure has the potential to affect not only behaviour and evolution but also the transmission of information or disease. Understanding the effects of population management on social behaviour and organisation is a key step in understanding these species’ ecology. This thesis examines the differences between individuals’ roles in the social structure and what this means for the transmission of disease. It demonstrates how similarity in movement behaviour scales with increasing social circles, how seasonality in movement and seasonality in association rates covary as well as detailing post-cull behavioural changes. It finds that there is the potential for certain individuals (most likely non-breeding individuals) to transmit infection far and wide. It reveals the similarities in movement behaviour and body condition that birds share with their pair and social group. It emphasises the importance of autumn and winter movement in the transmission of infectious disease and it follows the short- and long-term changes in social structure and movement behaviour following a cull. Cull survivors were observed to retain a higher proportion of associations with their previous associates and moved less far in the year following the cull than in the year preceding it. This is the first application of social network analysis to quantify social structure before and after culling. The findings suggest that culling an infected population may facilitate rather than constrain the transmission of disease.
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Levin, Alex Ph D. (Alexander) Massachusetts Institute of Technology. "Graphs, matrices, and populations : linear algebraic techniques in theoretical computer science and population genetics". Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/83695.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Department of Mathematics, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 149-155).
In this thesis, we present several algorithmic results for problems in spectral graph theory and computational biology. The first part concerns the problem of spectral sparsification. It is known that every dense graph can be approximated in a strong sense by a sparse subgraph, known as a spectral sparsifier of the graph. Furthermore, researchers have recently developed efficient algorithms for computing such approximations. We show how to make these algorithms faster, and also give a substantial improvement in space efficiency. Since sparsification is an important first step in speeding up approximation algorithms for many graph problems, our results have numerous applications. In the second part of the thesis, we consider the problem of inferring human population history from genetic data. We give an efficient and principled algorithm for using single nucleotide polymorphism (SNP) data to infer admixture history of various populations, and apply it to show that Europeans have evidence of mixture with ancient Siberians. Finally, we turn to the problem of RNA secondary structure design. In this problem, we want to find RNA sequences that fold to a given secondary structure. We propose a novel global sampling approach, based on the recently developed RNAmutants algorithm, and show that it has numerous desirable properties when compared to existing solutions. Our method can prove useful for developing the next generation of RNA design algorithms.
by Alex Levin.
Ph.D.