411 |
Comparative study of Mobile IPv4 and Mobile IPv6Darwich, Jamal January 2011 (has links)
This thesis has compared the Mobile IPv4 and Mobile IPv6 to find out which of them performs better when it comes to send datagram from the correspondent node to the mobile node. The tests that were made to measure performance were latency, TCP/UDP throughput, loss and delay, as well as time measurement for connectivity loss for the mobile node while roaming. The tests were done using Cisco equipments and Microsoft Windows 7 Professional OS. Due to the hardware and software used, the route of datagram was the same in both scenarios since Cisco routers and Microsoft Windows 7 OS does not support route optimization for Mobile IPv6. The results showed that Mobile IPv4 performed better in all the tests done.
|
412 |
Investigating the role of larval dispersal models in the development of an 'ecologically coherent' network of deep sea marine protected areasRoss, Rebecca E. January 2016 (has links)
There is currently worldwide pressure to establish Marine Protected Area (MPA) networks which are self-sustaining and will persistently protect habitats and species. In order for MPA networks to be effective, the species targeted for conservation must be able to disperse between protected areas and maintain a gene-flow necessary for population sustainability and persistence. This warrants new research on how to quantify and map faunal dispersal to ensure that protection will be effective and sustainable. Population genetic methods have merit, with the ability to track parentage and gene flow between areas directly. However the costs, quantity of samples, and time required to genetically quantify dispersal for multiple species make these approaches prohibitive as the only method of assessment, especially in relatively inaccessible offshore waters. Dispersal modelling is now becoming more accessible and may fulfil immediate needs in this field (although ground truthing will be necessary in the future). There have been very few dispersal modelling studies focussed on deep sea or offshore areas, predominantly due to the lack of high resolution hydrodynamic models with sufficient geographic extent away from shore. Current conclusions have been drawn based on shallow water coastal studies, informing offshore MPA network size and spacing. However the differences between these two environments may mean that dispersal abilities are not comparable. Deep water receives less influence from wind and weather, and the scales are vastly different in terms of a) the depth ranges covered, b) the planktonic larval durations (PLDs) of animals, and c) the geographic areas concerned as a consequence. Global hydrodynamic models with reasonable resolution are now becoming more accessible. With the outputs from these models, and freely available particle simulators, it is becoming more practical to undertake offshore deep water dispersal studies. This thesis aims to undertake an analysis of these accessible modelling tools within a deep sea context. The guidelines which are currently available to dispersal modellers are yet to encompass the needs of deep water modellers which may require some additional considerations given the extended depth range covered and the different hydrodynamic drivers away from the air/sea interface. Chapter 1 reviews the larval dispersal process, the factors which may affect dispersal success, and those which should be incorporated into future predictions of dispersal. The current methods for assessing larval dispersal are explored covering genetics, elemental tagging and modelling approaches with an extended look at modelling considerations. Existing marine conservation policy is also touched on in the context of connectivity and larval dispersal. Chapter 2 is designed to inform future deep sea modellers on how to parameterise and understand a dispersal model. As models appear as a ‘black box’ to the majority of users, sensitivity tests can offer a way of scaling model inputs and tempering expectations from model outputs. A commonly used model pairing (the HYCOM hydrodynamic model and the Connectivity Modeling System) is assessed, using parameters which link to the temporal and spatial scales of mixing in the modelled system: timestep of particle tracer, horizontal and vertical positioning of release points, release frequency of larvae, and temporal range of simulation. All parameters were shown to have a decreased sensitivity with depth, with patterns reflecting local watermass structure. Future studies observing similar hydrodynamic conditions seeking to optimise their model set up would be advised to stratify their model release locations with depth. A means to incorporate all sensitivity test results into optimal input parameters for future studies is demonstrated. Chapter 3 investigates whether dispersal models provide any advantage over a “sphere of influence” estimate based on average current speeds and PLDs: there is no use pursuing dispersal modelling if the outputs are too erroneous to provide any advantage over a back-of-the-envelope calculation. This chapter examines the outputs of two dispersal models driven by two different hydrodynamic models in order to observe the variability in prediction between models. This model comparison revealed a greater disparity between hydrodynamic model predictions than has been previously understood by ecologists. The two models compared (POLCOMS and HYCOM) may equally be considered as suitable to promote realism in the study region, but slight differences in resolution and numerical error handling resulted in dispersal predictions from which opposing conclusions can be drawn. This chapter therefore emphasises the necessity for model ground truthing before predictions can be trusted. Chapter 4 assimilates the findings of the previous chapters and applies their advice to a study of MPA network dispersal connectivity. Using the hydrodynamic model which performed best in chapter 3 (HYCOM), a simulation was undertaken for cold water coral (Lophelia pertusa (Linnaeus 1758)) larval dispersal between already established MPAs in the NE Atlantic. As larval characters have only been observed ex situ, dispersal was simulated using two null models (passive and active vertical migration) and averaged to provide an intermediate prediction. A method for assessing dispersal within MPAs and MPA networks is offered based on the intermediate prediction, as well as a network wide assessment of the difference in dispersal patterns for passive and active larvae. It was found that the existing network performs well at supplying larvae to non-networked sites, but performs poorly at supplying other MPAs. The ‘best’ MPAs were central to the network and facilitated the traverse of regional gaps in suitable habitat. The ‘worst’ MPAs were peripheral to the network and small in size. Network-wide passive and active dispersal matrices had no significant difference between them. However site specific variability in the effect of vertical migration was detected subject to variability in local topographic barriers to dispersal, only some of which could be surmounted with vertical migration. All chapters aim to inform future deep sea dispersal modellers, and encourage exploration of this tool in other contexts, as well as marine conservation. The thesis cautions against the transplantation of shallow water assumptions to deep water environments, and advocates region specific studies and mandatory ground truthing of predictions. An upcoming study will ground truth the findings of this thesis with both genetic and oceanographic data, allowing the accuracy of study results to be quantified.
|
413 |
Life histories predict genetic diversity and population structure within three species of octopus targeted by small-scale fisheries in Northwest MexicoDomínguez-Contreras, José F., Munguia-Vega, Adrian, Ceballos-Vázquez, Bertha P., Arellano-Martínez, Marcial, García-Rodríguez, Francisco J., Culver, Melanie, Reyes-Bonilla, Hector 15 February 2018 (has links)
The fishery for octopus in Northwest Mexico has increased to over 2,000 tons annually, but to date the specific composition of the catch has been ignored. With at least three main species targeted by artisanal fisheries in the region with distinct life histories, the lack of basic biological information about the distribution, metapopulation size and structure of each species could impede effective fisheries management to avoid overexploitation. We tested if different life histories of three species of octopus could help predict observed patterns of genetic diversity, population dynamics, structure and connectivity and how this information could be relevant to the sustainable management of the fishery. We sequenced two mitochondrial genes and genotyped seven nuclear microsatellite loci to identify the distribution of each species in 20 locations from the Gulf of California and the west coast of the Baja California peninsula. We tested five hypotheses derived from population genetic theory based on differences in the fecundity and dispersal potential for each species. We discovered that Octopus bimaculoides with low fecundity and direct development (without a planktonic phase) had lower average effective population size and genetic diversity, but higher levels of kinship, population structure, and richness of private alleles, than the other two species. These features indicated limited dispersal and high local recruitment. In contrast, O. bimaculatus and O. hubbsorum with higher fecundity and planktonic phase as paralarvae had higher effective population size and genetic diversity, and overall lower kinship and population structure than O. bimaculoides. These observations supported higher levels of gene flow over a larger geographical scale. O. bimaculatus with the longest planktonic paralarval duration and therefore larger dispersal potential had differences in the calculated parameters possibly associated with increased connectivity. We propose O. bimaculoides is more susceptible to over exploitation of small, isolated populations and could have longer recovery times than the other two species. This species may benefit from distinct fishery management within each local population. O. bimaculatus and O. hubbsorum may benefit from fishery management that takes into account metapopulation structure over larger geographic scales and the directionality and magnitude of larval dispersal driven by ocean currents and population connectivity among individuals of each locality. The distribution of each species and variations in their reproductive phenology is also important to consider when establishing marine reserves or seasonal fishing closures.
|
414 |
Functional neuroimaging of pathophysiological mesolimbic dopamine system and aberrant motivational salience in schizophreniaRichter, Anja 02 April 2017 (has links)
No description available.
|
415 |
Gouvernance et politiques de science en région : une approche multi-acteurs et multi-niveaux / Governance and regional science policies : a multi-actors and multi-levels approachBenaim, Mickaël 03 May 2013 (has links)
Cette thèse se penche sur la gouvernance des politiques régionales de la science en France dans le contexte de l'Espace Européen de la Science. Nous proposons donc une typologie des régions européennes qui vise à offrir un regard différent sur ces espaces de collaborations, en considérant les connectivités locales-globales dans la théorie des Systèmes Régionaux d'Innovation. Puis au travers d'un modèle gravitaire nous mobilisons plusieurs formes de proximités pour expliquer ces collaborations, en introduisant des proximités culturelles à l'échelle régionale. Cette thèse questionne à la fois la place des autorités régionales dans les politiques scientifiques en régions ou des régions, mais aussi la vision de la science de ces régions (à travers de l'analyse des CPER et de comptes Twitter). Nos travaux préconisent une meilleure compréhension des acteurs dans le cadre cognitif où les liens entre Science et Innovation sont trop souvent supposés. Cette dernière approche est également l'occasion de mettre en avant l'insuffisante prise en compte des logiques des différents acteurs de l'innovation (au sens large) et la nécessaire coordination des politiques des différents niveaux impliqués. L'analyse du mode de gouvernance des politiques de soutien aux activités créatives dans l'espace transfrontalier du Rhin Supérieur, permettra d'illustrer ce cadre cognitif nouveau. / This thesis addresses the issue of governance of the regional science policies in France, in the context of the European Science Area. We propose a typology of European regions that offer a new point of view on collaborations spaces (better considerations of local vs global connectivity). Then we go through this issue by proposing a gravity model incorporating diverse forms of proximities to explain scientific collaboration in Europe (detailed analysis on cultural proximity at the regional level). We raise the issue of scientific policies made in regions or by regions in France (context of decentralization) and ask the view of these regions of science (through the analysis of CPER and Twitter). Finally we propose to go ahead with the cognitive framework (expectation on the effectiveness of the links between Science & Innovation) by analyzing the governance of creative industries policies in the Upper-Rhine region (using a failure story). This last approach will again raise the insufficient consideration of each actor’s motivations in the innovation process (in a broad sense) and the need for coordination of economic policies between each level involved.
|
416 |
Age-Related Changes in Perirhinal Cortex Sensitivity to Configuration and Part Familiarity and Connectivity to Visual CortexCacciamani, Laura, Wager, Erica, Peterson, Mary A., Scalf, Paige E. 15 September 2017 (has links)
The perirhinal cortex (PRC) is a medial temporal lobe (MTL) structure known to be involved in assessing whether an object is familiar (i.e., meaningful) or novel. Recent evidence shows that the PRC is sensitive to the familiarity of both whole object configurations and their parts, and suggests the PRC may modulate part familiarity responses in V2. Here, using functional magnetic resonance imaging (fMRI), we investigated age-related decline in the PRC's sensitivity to part/configuration familiarity and assessed its functional connectivity to visual cortex in young and older adults. Participants categorized peripherally presented silhouettes as familiar ("real-world") or novel. Part/configuration familiarity was manipulated via three silhouette configurations: Familiar (parts/configurations familiar), Control Novel (parts/configurations novel), and Part-Rearranged Novel (parts familiar, configurations novel). "Real-world" judgments were less accurate than "novel" judgments, although accuracy did not differ between age groups. The fMRI data revealed differential neural activity, however: In young adults, a linear pattern of activation was observed in left hemisphere (LH) PRC, with Familiar > Control Novel > Part-Rearranged Novel. Older adults did not show this pattern, indicating age-related decline in the PRC's sensitivity to part/configuration familiarity. A functional connectivity analysis revealed a significant coupling between the PRC and V2 in the LH in young adults only. Older adults showed a linear pattern of activation in the temporopolar cortex (TPC), but no evidence of TPC-V2 connectivity. This is the first study to demonstrate age-related decline in the PRC's representations of part/configuration familiarity and its covariance with visual cortex.
|
417 |
Evaluation of conservation efficiency for gorgonian species at a regional scale based on an existing Marine Protected Area network and modeling scenarios accounting for hydrodynamical connectivity / Évaluation de l'efficacité de conservation pour les espèces de gorgones à l'échelle régionale sur la base d'un réseau des aires marines protégées existantes et des scénarios de modélisation hydrodynamiquePadrón, Mariana 24 November 2015 (has links)
La connectivité est supposée influencer fortement la dynamique et la pérennité des populations d’organismes marins. Ainsi, étudier l’évolution et le maintien des patrons de connectivité au sein des populations marines semble essentiel pour la planification spatiale, la création et la gestion des Aires Marines Protégées (AMP). Cependant, comprendre la complexité des processus régissant la connectivité entre les populations marines nécessite l’utilisation d’outils, qui associent des modèles biophysiques et des informations caractérisant les relations entre démographie et génétique, résultant des échanges larvaires entre les populations. L’objectif de cette thèse de doctorat est donc, d’évaluer les patrons de connectivité génétique au sein des populations de gorgones à une échelle régionale et d'explorer les processus induisant la connectivité observée, grâce à des simulations de modèles prenant en compte les connectivités hydrologique, démographique et génétique. Le premier chapitre présente un modèle de métapopulation spatialement explicite qui, grâce à l’utilisation de matrices de connectivité stochastique, permet d’évaluer l’effet de la démographie sur la fréquence des allèles dans une métapopulation d’espèces marines benthiques sessiles. Le modèle est alors utilisé pour déterminer l’effet des traits démographiques et de la structure de connectivité sur la diversité génétique de la métapopulation. Le deuxième chapitre présente une analyse des patrons de connectivité génétique de deux espèces communes et largement répandues de gorgones, à une échelle régionale : Paramuricea clavata en mer de Ligure et Eunicella singularis dans le Golfe du Lion. Les deux espèces présentent de forts patrons de structure génétique à l’échelle régionale, bien que leur capacité de dispersion ne semble pas limitante (>100m). Le troisième chapitre vise à tester si la dispersion larvaire seule permet d'expliquer la connectivité réalisée d’E. singularis dans le Golfe du Lion, en appliquant le modèle présenté dans le Chapitre 1, et en comparant les patrons de structure génétique modélisés, aux résultats obtenus dans le Chapitre 2, par les méthodes empiriques d’analyse de données génétiques. Les patrons de structure génétique modélisés en ne prenant en compte que la structure spatiale de dispersion sont similaires à ceux observés entre les populations d’E. singularis dans cette région, suggérant le rôle prépondérant de la connectivité hydrologique dans la distribution régionale de l'espèce, tant au niveau démographique que génétique. La capacité d’évaluer le développement des structures génétiques entre populations, sous différents scénarios démographiques et hydrologiques, avec le modèle de paysage sous-marin présenté dans le Chapitre 1 s'avère donc un outil efficace pour la planification spatiale et la pérennité des populations marine. / Connectivity is expected to strongly influence the dynamics and persistence of marine populations. Studying the development and maintenance of connectivity patterns among marine populations is, thus, essential for spatial planning and the proper design and management of Marine Protected Areas (MPAs). However, understanding the complex processes driving marine population connectivity requires the use of tools that integrate bio-physical models with information regarding the demographic and genetic linkages resulting from the larval exchange among populations. Therefore, the aim of this PhD dissertation is to evaluate the patterns of genetic connectivity among gorgonian populations at a regional scale, and disentangle the processes that shape the observed connectivity by using model simulations accounting for hydrological, demographic and genetic connectivity. The first chapter presents a spatially explicit metapopulation model that, using stochastic connectivity matrices, assesses the effect of demography on allele frequencies in a marine metapopulation of sessile benthic species. The model is then used to evaluate the effect of demographic traits and connectivity structure on the genetic diversity of a marine metapopulation. The second chapter examines the patterns of genetic connectivity of two common and widely distributed gorgonian species at a regional scale: Paramuricea clavata in the Ligurian Sea, and Eunicella singularis in the Gulf of Lions. Both species exhibit strong patterns of genetic structure at a regional scale, although the dispersal capacity of each species does not seem limited (>100 m). The third chapter discerns among the potential processes shaping the realized connectivity of E. singularis in the Gulf of Lions by applying the model presented in Chapter 1, and comparing the modeled patterns of genetic structure to the results obtained from empirical genetic data in Chapter 2. Modeled and empirical results show similar patterns of genetic structure among populations of E. singularis in the region. Genetic and demographic differentiation among populations is demonstrated to result from the spatial structure of dispersal alone. The ability to evaluate the expected development of genetic structure among populations under different demographic and hydrological scenarios using the seascape model presented in Chapter 1 provides a useful tool with relevance for marine spatial planning and the persistence of marine populations.
|
418 |
Model konektivity krajiny pro vydru říční / Model of landscape connectivity for European otterBureš, Jan January 2017 (has links)
Model of landscape connectivity for European otter Abstract Landscape connectivity is one of the main functions that mitigate the effects of landscape fragmentation on organisms. It allows organisms to move through habitat areas to natural habitat. Given of the overall decline in biodiversity, conservation of landscape connectivity is one of the main objectives of current nature protection. The greatest impact of landscape fragmentation on the population of European otters is mortality on roads. The most of the dead otters are found every year in the Jihočeský and Vysočina regions. That is why this region is an adequate model area for determining the connectivity of the landscape from the perspective of otters. This thesis deals with landscape fragmentation, habitat connectivity and landscape resistance. CIRCUISCAPE is the main tool used to solve connectivity modelling. From the resulting connectivity, landscape resistance and mortality values, risk areas for migration were selected. The telemetry data from the area around Dačice were used to validate this model. Keywords: habitat connectivity - landscape resistance - telemetry - European otter
|
419 |
Estimating Landscape Quality And Genetic Structure Of Recovering American Marten Populations In The Northeastern United StatesAylward, Cody Michael 01 January 2017 (has links)
The American marten (Martes americana) is an endangered species in Vermont and a Regional Species of Greatest Conservation Need in the northeastern United States. Though historically widespread in northeastern forests, their range presumably contracted to northern Maine and the High Peaks region of the Adirondacks by the early 1900s. Regionally, populations appear to be in recovery. Natural recolonization is believed to have occurred in New Hampshire, northeastern Vermont and the western Adirondacks. A reintroduction effort in southern Vermont that was originally declared unsuccessful is now believed to be the source of a recently detected population in the area. However, our current knowledge of distribution, population history and population connectivity relies primarily on occurrence data from harvest records, which are limited in scope and resolution. In Vermont, where population size is estimated to be extremely low, more robust estimates of population status may be critical to continued recovery.
I genotyped individuals from Maine, New York, New Hampshire, northeastern Vermont and southern Vermont at ten microsatellite loci and amplified a 320 base pair segment of the control region of mtDNA to estimate the source(s) of the two Vermont populations using statistical tests of genetic differentiation. I also used Bayesian and stochastic genetic clustering methods to estimate population genetic structure in the northeastern United States. Genetic structure exists at multiple scales in the region as a result of natural barriers to gene flow, human-mediated gene flow, and lineage sorting in relic populations. My results suggest that New Hampshire is a major source of colonization of northeastern Vermont and the population in southern Vermont is either a remnant of the reintroduction or a pre-reintroduction relic that has experienced introgression from the reintroduction stock. I identified three regions where relic populations perceived to be extirpated in the 1900s may have persisted.
I also developed an occupancy model for American marten in the northeastern United States using mixed-effects logistic regression based on expert opinion data. Eighteen experts from Maine, New Hampshire, Vermont and New York with backgrounds in trapping, wildlife management, and wildlife science participated in the survey. Experts were asked to estimate the probability of marten occupancy at 30 sites in the northeastern United States. Three top models described the data. Habitat covariates in those models were 1) percent canopy cover, 2) percent spruce-fir forest cover, 3) winter temperature, 4) elevation, and 5) road density. An AIC-weighted average of these three models had significant predictive ability (area under an ROC curve = 0.88) with respect to occurrence records in the northeastern United States. In addition, the model predicted that high quality habitat existed patchily along the central and northern Green Mountain spine in Vermont – where no occurrence records exist for at least a century. Top-scoring movement corridors between southern Vermont and nearby populations in northeastern Vermont/New Hampshire and New York occurred in the northern and central Green Mountains and across high resistance movement barriers in the Champlain valley. Corridors to New York were considered strong movement barriers and are unlikely to facilitate gene flow.
|
420 |
Do lentic and lotic communities respond similarly to drying?Rosset, Véronique, Ruhi, Albert, Bogan, Michael T., Datry, Thibault 07 1900 (has links)
Disturbance is a central factor shaping composition, structure, and dynamics of local communities. Drying is a disturbance that occurs in aquatic ecosystems globally and can strongly influence their communities. Although the effects of drying may depend on ecosystem connectivity and the dispersal abilities of resident species, there have been no comparisons of community responses to drying between lentic and lotic ecosystems across different climates. Here, we predicted that drying would have stronger effects on aquatic communities in isolated lentic ecosystems than in dendritic lotic ecosystems, owing to the higher hydrological connectivity of the latter, and that drying would have stronger effects on passive than on active dispersers, because of the potentially higher recolonizing ability of the latter. We tested these predictions by comparing alpha diversity, phylogenetic relatedness, and beta diversity for active and passive dispersers, in both ecosystem types across five climatic regions. Drying caused greater declines in alpha diversity in lentic than in lotic ecosystems. Communities that experienced drying were more similar to one another than those of perennial sites, and this pattern was especially pronounced in lentic ecosystems. In contrast, drying did not influence the contributions of turnover and richness gradients to beta diversity. Additionally, dispersal mode did not influence community responses to drying. Relatively weaker effects of drying in lotic compared to lentic systems were likely due to the hydrological connectivity among perennial and temporary river sites, which may facilitate dispersal of organisms to escape drying and recolonize rewetted sites. Collectively, our results suggest that habitat connectivity may ameliorate (and fragmentation may worsen) the impacts of drying disturbance. This is an important finding in light of increasing drying and concomitant aquatic habitat fragmentation under global change.
|
Page generated in 0.0364 seconds