The N/Z, or ratio of neutron to proton, degree of freedom may be used to study intermediate energy nuclear collisions to give information about the origin of emitted collision fragments. Establishing under what conditions the onset of N/Z equilibrium occurs will give a better understanding of the physics of the equation of state through the use of simulation codes. If the nuclear equation of state can be elucidated in terms of the N/Z dependent component and how the N/Z dependent component varies with density, then the equilibrium ratio of protons to neutrons inside high density neutron stars can be inferred, allowing for prediction of cooling rates and supernovae mechanisms. In the current study, isotopic and isobaric ratios at thetalab=40o with cuts of 10% and 20% most central events, respectively, are studied for their N/Z equilibration signals. Light charged particles, or LCPs, are found to be emitted from systems which have not yet fully N/Z combined; the fragments with A=3 are emitted from the least equilibrated systems. Intermediate mass fragments, or IMFs, are seen to be emitted by N/Z equilibrated sources, within statistical error bars. The N/Z tracer method is used with ratios of isotopes and isobars to see how the amount of nuclear stopping or N/Z mixing changes as a function of the centrality of the event. The N/Z observable is used to reinvestigate earlier findings of the isotope and isobar ratio observables and shows the progression (or lack of it, in some cases) of the N/Z equilibration. This observable has proven to be a clear and sensitive tool to use when considering the differences in N/Z mixing of the systems at two energies.

Abstract The equilibrium of aqueous D-glucaric acid was investigated via Nuclear Magnetic Resonance (NMR) spectroscopy. The NMR spectra of all four species (D-glucaric acid, D-glucaro-1,4-lactone, D-glucaro-6,3- lactone and D-glucaro-1,4;6,3-lactone) were assigned. A 1H NMR spectroscopy method was developed to investigate the kinetics of equilibration of the starting species (D-glucaro-1,4-lactone and D-glucaro-1,4;6,3-dilactone). The equilibration was investigated under neutral conditions as well as conditions with increasing acidity. Each experiment set contained 50-100 1HNMR spectroscopy experiments that were run on the same sample using a program that built in delays. Dimethyl sulfoxide was used as an internal standard, and its signal size was used as a scale to report the changes in relative concentration of the four species throughout the experiment sets. Under neutral conditions D-glucaro-1,4-lactone is relatively stable against equilibration, while D-glucaro-1,4;6,3-dilactone is not. Under acidic conditions both compounds equilibrate within approximately 30,000 seconds. After equilibration under acidic conditions D-glucaric acid is the dominant species, while the relative concentration of D-glucaro-1,4-lactone is slightly higher than that of D-glucaro-6,3-lactone. The relative equilibrium concentration of D-glucaro-1,4;6,3-dilactone is low. A mechanism for the equilibration of aqueous D-glucaric acid was proposed and equilibrium constants and estimates of rate constants were derived from the experimental data. These rate constants were used in MATLAB simulations that were compared to the experimental data. MATLAB simulations were used to alter the rate constants to improve the fits between experimental data and simulated data.

I have developed a technique that improves the speed, reproducibility, and sensitivity of the measurement of degree of equilibration in ordinary chondrites. The Fast Electron Microprobe technique (FEM) technique provides a continuous quantitative scale for the amount of thermal processing a particular sample has experienced. The Fast Electron Microprobe technique (FEM) allows us to quickly collect sufficient data to determine the homogeneity and composition of olivine and low-Ca pyroxene in ordinary chondrite thin sections. I have studied several meteorites that are homogenous in olivine composition, but heterogeneous in low-Ca pyroxene composition. One of these samples (ALH 85033) has previously been classified as an L4. The FEM technique allows reproducible measurements of the degree of thermal metamorphism in ordinary chondrites, improving our understanding of thermal processing of asteroids in the early solar system.

No description available.

Lakes play an important role in the global carbon (C) cycle as they process carbon from terrestrial (allochthonous) and within lake (autochthonous) sources and may store C over long periods of time. Some arctic lakes contain high concentrations of dissolved organic carbon (DOC) that does not absorb light and thus remains colourless. The origin of this DOC remains unknown, but the sediment of these lakes have been suggested to accumulate primarily autochthonous (algal) C. I developed an experimental chamber for hydrogen (H) isotope pre-treatments and applied a novel H isotope tracing approach to determine the origin of the DOC and sediment C of a lake on SW Greenland known to contain colourless DOC. I hypothesized that autochthonous C was the prime source of DOC and sediment C, in line with previous theories. Analyses of algae and soil samples from the catchment revealed that local allochthonous and autochthonous C sources had a δ2H composition of -139 ‰ and -209 ‰, respectively. In contrast to my hypothesis, the analysed DOC had a mean δ2H isotopic composition of -147 ‰ indicating a dominance (ca 80-90 %) of allochthonous C. Similarly, the sediment had a mean δ2H isotopic composition of -155 ‰, suggesting that about 84 % of the C accumulating in the sediment was derived from terrestrial sources. The terrestrial origin was supported by field observations of high DOC seepage water (up to 70 mg L-1) with uncharacteristically low light absorption values entering the lake during high precipitation events. My results indicate that terrestrial processes are fundamental C sources for arctic lakes, even in regions with very low precipitation.

Individual-based models have been applied to study a broad spectrum of problems across multiple disciplines, such as the spread of epidemics or the outcome of social dilemma. They are used to investigate the macroscopic effects that arise from the microscopic dynamics of interacting individuals. Fixation describes the taking over of the population by a single type of individual or species. It is a prominent feature in the field of population genetics, which interprets many biological scenarios of evolution. Equilibration describes the process of reaching a heterogeneous steady state. In this thesis we analyse these macroscopic features through techniques derived from statistical physics and the theory of stochastic processes. Birth-death processes are used to describe the interaction of two types of individual in a population, such as competing strains of bacteria. These interactions are often specified using the framework of evolutionary game theory. The environment in which the population evolves can have a crucial impact on selection. In systems where the environment switches between multiple states we develop a general theory to calculate the fixation time statistics of a mutant individual in a population of wild-types, as well as the stationary distributions when mutations are present in the dynamics. In some birth--death processes, and in particular those described by evolutionary game theory, the mean fixation time contains only limited information. By diagonalising the master equation that describes the process, we are able to obtain closed-form expressions for the complete fixation time distributions. Individual-based models can also be used to describe the accumulation of mutations in a cell. This has important consequences for the initiation and progression of cancer. We find that such systems exhibit metastable states in the dynamics, and we can exploit the separation of timescales between relaxing to the quasi-stationary state and reaching fixation to characterise these phenomena. In this scenario we employ the WKB method to describe the population-level dynamics. Although this method has been used to describe numerous stochastic processes, a clear and coherent description is lacking in the literature. Through the use of multiple examples, including the aforementioned cancer initiation model, we carefully explain the multitude of constructs and equations that result from the application of this methodThe analytical characterisation of the evolutionary dynamics that are observed in these stochastic processes has resulted in a greater understanding of fixation and equilibration. This thesis promotes the benefits of analytical, or even semi-analytical methods, and on a more general level contributes toward a more complete understanding of evolutionary processes.

<p> A series of 2-substituted Δ^3-1,3,4-oxadiazolines (i) were synthesized by oxidation of the corresponding hydrazones with lead-tetraacetate in alcohol, eq A. (See Diagram A in Thesis)</p> <p> These oxadiazolines, upon thermolysis, generated carbonyl ylide intermediates (ii). These ylides are known to undergo fragmentation into carbenes and carbonyl compounds, eq B. (See Diagram B in Thesis)</p> <p> A new series of products were found from the thermolysis of these types of oxadiazolines, ester azines iv and v. A possible mechanism for the formation of these ester azines involves carbene attack on the oxadiazoline to give an azomethine imine intermediate (iii) which can subsequently rearrange to give the azines and carbonyl compounds, eq C. (See Diagram C in Thesis)</p> <p> This mechanism is supported by the observation that the overall yields of ester azines rise with increasing initial concentration of oxadiazoline whereas the yield of propene, a rearrangement product of dimethyl carbene, falls with increasing initial concentration of oxadiazoline.</p> <p> The ester azines (R=CH3, CH2CH3 and CH(CH3)2) were found to be uniconfigurational and the E-configuration was assigned to ester azine iv and the E,E-configuration was assigned to ester azine v. Ester azines (R=C(CH3)3) were found to exist as configurational isomers. Equilibration studies were carried out on these ester azines and the thermodynamic parameters ΔG°, ΔH° and ΔS° were found for equilibration shown in eq D. (See Diagram D in Thesis)</p> <p> Changing the R' substituent of i to OCH2CCl3 or OCH2CF3 did not stop fragmentation of the derived ylide. Ester azines were found from the thermolysis of these oxadiazolines also. They were found to be uniconfigurational and were assigned the E-configuration.</p> / Thesis / Master of Science (MSc)

No description available.

Nous avons étudié le transfert de chaleur et de matière au cours de l'histoire de la Terre primitive à de multiples échelles en utilisant des modèles numériques. Deux systèmes différents sont abordés. Tout d’abord, nous nous concentrons sur les premiers stades de la formation du noyau terrestre lorsque le fer se sépare des silicates et descend vers l'intérieur de la planète. Au cours de la différenciation, des interactions chimiques et thermiques se produisent entre les gouttes de fer dispersées dans des silicates fondus formant un océan de magma. Nous étudions le transport chimique des éléments traces à l'intérieur et autour des gouttes. Nous tirons quelques relations fonctionnelles dépendante du régime dynamique d'écoulement et montrons que le système tend à être en équilibre chimique extrêmement rapidement par rapport à l'échelle de temps de la descente de la goutte de fer. Peu de temps après la fin de l'accrétion de la Terre, la fusion extensive de son intérieur profond ainsi que la formation d'un océan de magma en surface a lieu. Comme le rayonnement de la chaleur dans l'espace est très efficace, les silicates fondus superficiels cristallisent très rapidement. L'histoire thermique de la couche liquide enterrée, appelée océan de magma basal (OMB), se déroule sur une longue période de temps et il est proposé que ses restes soient aujourd'hui observables sous forme de poches partiellement fondues au dessus de frontière noyau-manteau. Nous déterminons les paramètres régissant un système convectif dans lequel se produit une transition solide/liquide. Les lois d'échelle ainsi obtenues ont été appliquées à l'OMB et indiquent que la différence de température qui peut être maintenue dans les couches limites supérieure et inférieure de l'OMB est infime. Par conséquent, la température du noyau suit la température de liquidus à la base du manteau et ainsi la vitesse de refroidissement de l'OMB doit être la même que celle du noyau de la Terre. / We have studied the heat and mass transfer during the early Earth history at multiple scales and for multiple systems by means of numerical computing. Two different systems are approached. Firstly, we focus on the early stages of the Earth core formation when iron segregates from silicates and descends toward the interior of the planet. During the differentiation there are chemical and thermal interactions between dispersed iron blobs and surrounding molten silicates. We study the chemical transport of trace elements within and around the drops. We derive functional relations between critical parameters and show that the system tends to be in chemical equilibrium.During the accretion process of the Earth, extensive melting of its deep interior as well as formation of shallow magma oceans occurred.As heat radiation into space happens with high efficiency, surface molten silicates crystallize very rapidly, in about 10 My. The thermal history of the buried liquid layer, called the basal magma ocean (BMO), proceeds over a long time and it is proposed that its remnants are nowadays observable as partial melts in the core-mantle boundary region.We develop numerical models of the thermal history of the crystallizing basal magma ocean that enable to study coupling between the mantle and the core in the presence of the BMO. We derive parametrized relations for this convective system that undergoes solidification/melting. Obtained scaling equations applied to the BMO indicate that the temperature difference that can be maintained across the top and bottom boundaries of the BMO is minute. Hence, the temperature of the core follows the temperature of liquidus at the bottom of the mantle and thus the rate of the BMO cooling must be the same as that of the Earth's core.

The stable isotope ratio of non-exchangeable hydrogen (δ2Hn) emerged as a promising new tool for source attribution in aquatic ecology, which can better discriminate between the organic matter sources. However, determining the absolute isotopic values is problematic due to the functional groups with hydrogen (H) that can easily exchange with the ambient water. This can lead to significant uncertainties in the absolute isotopic values, which eventually translates into errors in source attribution. However, controlled H exchange experiments with dual water equilibrations can alleviate this problem. However, current methods report significant variation in the absolute values, likely originating in partial H exchange, uncertainty in fractionation factors between exchangeable H and ambient water, and residual moisture. Here I used two methods for H exchange based on steam and liquid water using novel equipment for sample preparation called the Isobox. I evaluated the exchangeable H fraction in materials commonly analysed in ecology. Furthermore, I have investigated how these methods and associated analytical uncertainties can influence the mathematical mixing models used to resolve the source attribution using known sample mixtures made with soils and algae. The results show that 1) H exchange experiments using liquid water equilibration provide a higher exchangeable H fraction than the steam-based method, which was approximately three times higher. 2) The two-source mixing model proved to effectively determine the source attribution with known soil and algae mixtures, as evidenced by both water and steam equilibration. However, prior exposure to isotopically divergent waters can lead to source attribution errors, particularly with steam-based methods that provide low exchangeable H fractions. 3) When labile H is fully exchanged, source attribution does not depend on absolute δ2Hn determination, and simple one-water equilibration is sufficient. 4) Additional uncertainties in source attribution could originate from fractionation factors and δ2H measurement variability. The findings of this study conclude that the variations in fractionation factors did not significantly alter the mixing model as the error was below 5%. 5) Based on these experiments, I recommend keeping the analytical uncertainty of δ2H below ±5‰, which amounts to about a 6% error factor in source attribution. Finally, these experiments and analyses show how the methods can generate reliable data, depending on the research questions and whether absolute or relative isotopic values are required. This study provides different analytical pathways.