The nuclear matter liquid-gas phase transition is expected to be a signal of nuclear spinodal instabilities as a result of density fluctuations. Nuclear spinodal instabilities in symmetric nuclear matter are studied within a stochastic relativistic density-dependent model in semi-classical approximation. We use two parameterization for the Lagrange density, DDME1 and TW sets. The early growth of density fluctuations is investigated by employing relativistic Vlasov equation based on QHD and discussed the cluster size of the condensations from the early growth of density correlation functions. Expectations are that hot nuclear matter behaves unstable around &rho / b &asymp / &rho / 0/4 (below the saturation density) and at low temperatures. We therefore present our results at low temperature T=1 MeV and at higher temperature T=5 MeV, and also at a lower initial baryon density &rho / b = 0.2 &rho / 0 and a higher value &rho / b = 0.4 &rho / 0 where unstable behavior is within them. Calculations in density-dependent model are compared with the other calculations obtained in a relativistic non-linear model and in a Skyrme type nonivrelativistic model. Our results are consistent with them. Qualitatively similar results show that the physics of the quantities are model-independent. The size of clusterization is estimated in two ways, by using half-wavelength of the most unstable mode and from the width of correlation function at half maximum. Furthermore, the average speed of condensing fragments during the initial phase of spinodal decomposition are determined by using the current density correlation functions.

The relationship between spawning stock biomass (SSB) and 3 spatial distribution metrics (SDMs), measuring range, concentration, and density, using fisheries independent survey data for 10 demersal Northwest Atlantic fish populations (9 species), show metrics of density offer the best correlate of SSB. The concave, positive relationship between high density area (HDA) and SSB indicates that a decline in HDAs beyond a spatial threshold is associated with disproportionately large SSB declines in 6 populations. HDAs might indicate highly productive areas and/or positive fitness consequences, enhancing the ability of individuals to successfully spawn, locate prey, and evade predators. HDAs can help to assess the status of a population’s spatial structure and serve as a spatial reference point. By comparing spatial reference point locations relative to existing biomass reference points (based on MSY), scenarios are described wherein spatial reference points contribute to biomass reference points and to a precautionary approach to fisheries management.

Seawater-fresh groundwater natural equilibrium conditions in the aquifers of the Sel&ccedil / uk sub-basin may be disturbed by the discharge occurred during the past 30 years in order to supply water for irrigation and domestic purpose usage. Two dimensional density dependent cross sectional saturated flow and solute transport simulations were carried out to determine whether seawater intrusion has occurred in the Sel&ccedil / uk sub-basin due to the imposed discharge or the determined salt-water in the western section of the aquifers represents natural interface equilibrium conditions. The numerical simulation model was calibrated using field measurements. The results of the simulations suggest that the seawater intrusion has occurred in the study area since the pumping activity increased in the region. Five scenarios were simulated for future predictions: (1) Present recharge and discharge conditions are maintained, (2) Discharge increases at a rate of the municipality need as a result of increasing population, (3) Discharge decreases by 12% from the present value, (4) Discharge decreases by 25% from the present value, and (5) No discharge occurs or recharge amount equals to the present discharge amount condition supplied to the aquifer. These scenario results suggest that seawater intrusion in the Sel&ccedil / uk sub-basin would progress in the following years unless proper management measures are taken into consideration. KEYWORDS: seawater intrusion, density dependent groundwater flow, solute transport, contamination, Sel&ccedil / uk sub-basin.

Ph.D. thesis is focused on different aspects of ecology of several mustelid species in the Central European landscape. Particularly, nest predation, habitat and resting sites selection, predator-prey interactions as well as impact of fragmentation and urbanization on mustelids were described in 8 published papers or manuscripts.

Comprendre les adaptations qui permettent aux espèces de vivre dans des environnements variables, temporellement et spatialement, est essentiel pour prédire la façon dont elles peuvent répondre aux changements globaux actuels et futurs. De nombreuses études à long terme ont montré que les fluctuations climatiques affectaient la dynamique des populations, mais l'influence relative des processus de sélection d'habitat et de densité-dépendance sur la sélection d'habitat est encore mal connue et expliquée. L'objectif de cette thèse est donc d'étudier, d'une part, par une approche corrélative, la sélection d'habitat densité-dépendante à quatre échelles spatiales différentes, chez une population de cigognes blanches (Ciconia ciconia) en augmentation; et d'autre part, par une approche mécaniste, d'étudier les effets relatifs du climat, de l'habitat et de l'expérience des reproducteurs en termes de fitness (nombre de jeunes produits, condition corporelle des jeunes et sexe-ratio) chez cet oiseau, suivi depuis 30 ans dans un milieu sensible, les zones humides de l'ouest de la France, en Charente-Maritime. Ce travail a contribué à identifier des mécanismes qui conduisent aux décisions de sélection d'habitat de nidification qui restaient encore mal compris, et appuie les travaux qui montrent que la dégradation des habitats par les activités humaines peut influer sur les décisions de sélection d'habitat. De plus, ces résultats apportent des informations essentielles à la compréhension des adaptations de cette population dans un environnement variable, ce qui permet de prédire plus efficacement le devenir de la population face aux changements environnementaux futurs. / Understanding adaptations that allow species to live in temporally and spatially variable environments is crucial to predict how species may respond to current and future global changes. Long-term studies have shown that climatic variations affect the dynamic of populations. However, the relative influence of habitat selection and density-dependence processes is still poorly understood and explained. The aim of this thesis is, firstly by a correlative approach, to investigate the density-dependent habitat selection at varying spatial scales in an increasing white stork (Ciconia ciconia) population. Secondly, by a mechanistic approach, we studied the relative effects of climate, habitat and breeder experience in terms of reproductive fitness (fledging success, body condition and sex ratio) in this population monitored for 30 years in a sensitive wetland in Charente-Maritime, western France. This work helped identifying the mechanisms that lead to nesting habitat selection. This work supports research showing that habitat degradation by human activities may affect habitat selection decisions. In addition, these results provide crucial information to understand the adaptations of this population in a changing environment, which allows predicting more efficiently the response of the population to future environmental changes.

<p> The light even-even nuclei have been studied using the den~ity dependent effective interaction of Sprung and Banerjeee The nuclei were studied initially, using a harmonic variational procedure, to deter mine the most appropriate parameters of t he force for the Hartree Fock study. </p> <p> This chosen force was then used in a comparative study of spherical nuclei to d e termine the inadequacies of our Hartn~e Fock approach, as opposed to the spherical basis calculations of Campi. Some deformed nuclei were then examined and our results were compared with those of K. Lassey and A. B. Volkov , and of J. Zofka and G. Ripka. </p> / Thesis / Master of Science (MSc)

No description available.

No description available.

The Staunton River is a high gradient, second order stream approximately 6 km in length located on the eastern slope of the Blue Ridge Mountains in Shenandoah National Park, VA. In June 1995, a catastrophic flood and debris flow altered the instream habitat and <i>Salvelinus fontinalis</i> population of the Staunton River. The debris flow scoured the streambed, deposited new substrate materials, removed trees from the riparian zone, and eliminated fish from a 1.9km section of the stream. By June 1998, both young-of-year (YOY) and age 1+ <i>S. fontinalis</i> had recolonized the debris flow affected area. The event provided a rare opportunity to examine recovery of the <i>S. fontinalis</i> population and instream habitat in addition to addressing potential effects of the debris flow on movement, activity, and growth of fish in the debris flow affected and unaffected areas of the stream. Post-recolonization movement and activity were monitored using two-way fish traps (weirs), mark-recapture techniques, and radio telemetry. The weirs failed to produce any movement data. Most fish (91%) in the mark-recapture study had range sizes less than 100m, however biases common to mark-recapture study designs (low recapture rate, flawed logic, etc.) hampered interpretation of results. For example, subsequent recapture of individually marked fish indicated that as many as 54% of marked fish confirmed to have been alive at the time of a recapture session were not recaptured. Radio telemetry provided information on <i>S. fontinalis</i> movement and activity at seasonal and diel scales during summer and fall. Differences in movement and activity between the debris flow affected and unaffected areas were minimal when compared to seasonal variations. During summer, range sizes were near 0m and crepuscular activity patterns were observed. During the fall range size increased and diel activity was concentrated in the mid-afternoon with a much higher peak than during summer. Basin-wide visual estimation technique (BVET) fish population surveys performed each spring and fall from 1993 = 1999 provided pre- and post-event fish population abundance and density estimates. Post-event fish growth in the debris flow affected and unaffected areas was monitored using mark-recapture techniques. Abundance and density of both YOY and age 1+ <i>S. fontinalis</i> exceeded pre-event levels within 2-3 years. Growth of YOY and age 1+ fish was significantly greater in the debris flow affected area until spring 1999. Population density appeared to have a strong negative influence on growth. The observed changes in fish growth and differences in fish size associated with population density would be of minimal importance to the typical angler but may suggest a mechanism by which <i>S. fontinalis</i> populations can quickly recover from catastrophic events. BVET habitat surveys provided information on total stream area, number of pools and riffles, pool and riffle surface area and depth, substrate composition, and large woody debris (LWD) before (1993), immediately following (1995), and four years post-event (1999). Immediately following the debris flow, the stream channel was highly disordered which resulted in an increase in the total number of habitat units and a decrease in average habitat unit surface area, total stream area, and average depth when compared with pre-event conditions. In addition, substrate composition had shifted from small to large diameter particles and LWD loading had increased in both debris flow affected and unaffected areas. Four years after the event, the total number of habitat units, average habitat unit surface area, total stream area, and average depth had all returned to near pre-debris flow levels and substrate composition had begun to shift towards smaller particle sizes. Changes in LWD loading from 1995-1999 reflected changes in the riparian zone following the debris flow. In the unaffected area, where riparian trees remained intact, LWD loading increased, whereas in the debris flow affected area, where riparian trees were eliminated, LWD loading decreased. For the most part the effects of the debris flow, although immediately dramatic, were in the long term minimal. The debris flow affected area was recolonized rapidly and abundance and density quickly rebounded past pre-event levels. Differences in fish growth between the affected and unaffected area were short lived. Any effect the debris flow affected area may have had on movement or activity was minimal when compared with seasonal variations. Most habitat characteristics reverted to near pre-event levels just four years after the flood and debris flow. Although a number of factors will influence recovery time from such events, these results indicate that immediate management action, such as stocking or habitat modifications, are not necessary in all cases. / Master of Science

Utilizing the analytical solution of the steady state sharp interface saltwater intrusion model in coastal aquifers, a multi-objective optimization formulation of pumping rates and well locations in a coastal aquifer is formulated to solve problems in water management practice. The proposed optimization problem uses progressive genetic algorithm technique and the method developed is applied to the previous work of Cheng et al. [2000]. Through this analysis, several other applications are provided to demonstrate the use of the model in practical applications. This work is the first to optimize pumping rates as well as well locations simultaneously in coastal aquifer management. Known the limitation of the analytical solution, the work is expanded to cover the physics of saltwater intrusion in a more realistic way. This is variable density flow in a variably saturated porous medium. In this method, mixing between two fluids such as saltwater and freshwater can be described and the porous medium is also expanded to cover saturated and unsaturated zones together. One of the objectives is to develop a three dimensional physical model, verify the model, and apply to various applications in coastal aquifers. The developed model, TechFlow, is used to investigate instability issues associated with the numerical solution of the Elder problem in the perspective that includes physical instability issues associated with density differences used in numerical solutions, sensitivity of the solution to idealization irregularity, and the importance of accurate estimation of the velocity field and its association to the grid density levels that is necessary to solve the problem accurately. Saltwater intrusion hydrodynamics in a beach under the influence of tidal effects is also investigated using TechFlow. Based on the results of TechFlow with the use of various boundary conditions for the transport equation, the saltwater intrusion hydrodynamics in a beach under the influence of tidal effects shows unique dynamics. These solutions are primarily affected by density differences, tidal effects on a mild slope, variably saturated porous medium and finite domain solution condition. TechFlow is also used to investigate saltwater upconing beneath pumping wells both two- and three-dimensional applications.