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Cette thèse présente la conception et l'implémentation d'une nouvelle génération de puces à atomes, ouvrant de nouvelles perspectives expérimentales dans des micropièges magnétiques très anisotropes. Les propriétés thermiques des puces en nitrure d'aluminium sont étudiées en détail. Le dispositif a été optimisé pour piéger de plus grands nombres d'atomes et améliorer la qualité de l'imagerie, notamment en fabriquant un miroir de planéité sub-λ/10 à la surface de la puce.Nous étudions des gaz quasi-1D grâce à des images in situ de profils fluctuants et des méthodes précises de calibration et d'analyse statistique. Nous mesurons des fluctuations non-gaussiennes, ce qui permet de tester sensiblement la thermodynamique du gaz et donne une mesure de corrélations à trois corps. Nous étudions précisément la transition de quasicondensation et mesurons pour la première fois sa loi d'échelle. En régime 3D, c'est une condensation transverse qui déclenche la quasicondensation longitudinale, tandis qu'en régime 1D, la formation d'un quasicondensat est gouvernée par les interactions répulsives et non par la dégénérescence quantique.Obtenant des températures record pour des gaz 1D, nous observons des fluctuations subpoissoniennes lorsque les corrélations atomiques sont déterminées, au moins localement, par les fluctuations quantiques qui dominent les fluctuations thermiques. Nous discutons également la thermalisation étonnamment rapide mesurée en régime 1D profond qui suggère que des collisions effectives à 3 corps brisent l'intégrabilité du système. / This thesis presents the design and implementation of a new generation of atom chips, that open novel experimental possibilities with very anisotropic magnetic microtraps. The thermal properties of aluminum nitride atom chips are studied in detail. We have optimized the set-up in order to trap more atoms and image the clouds as precisely as possible. In particular we have fabricated a miror of sub-λ/10 planeity on top of the chip surface.We study quasi-1D gases using in situ pictures of the fluctuating density pro_les and precise methods for their calibration and statistical analysis. We measure non-gaussian fluctuations, which provides a sensitive test of the thermodynamics of the system and gives a measure of three-body correlations. We study precisely the quasicondensation transition, measuring its scaling for the first time. In the 3D regime, a transverse condensation triggers the longitudinal quasicondensation. In the 1D regime, on the contrary, the appearance of a quasicondensate is governed by repulsive interactions only, and not by quantum degeneracy.Reaching record temperatures for 1D gases, we observe subpoissonian fluctuations which indicate that atomic correlations are determined at least locally by quantum rather than thermal fluctuations. We also discuss our observation of surprizingly e_fficient thermalization deep in the 1D regime, suggesting that e_ffective 3-body collisions break the integrability of the system.

A Transparência Eletromagneticamente Induzida tem sido muito usada atualmente para implementação de memórias quânticas. Neste trabalho, estudamos este fenômeno, experimental e teoricamente, utilizando um sistema de dois níveis com degenerescências como modelo para o átomo. Tratamos o campo eletromagnético como quantizado e propomos um modelo linearizado para as flutuações que leva em consideração as forças quânticas de Langevin. Devido ao excesso de ruído de fase presente em nosso laser, a implementeção numérica do modelo levou em consideração apenas a autocorrelação de fase como fonte para o sinal de ruído observado. Este modelo mostrou um bom acordo qualitativo com os dados experimentais observados. Fizemos medidas de ruído de soma e subtração com o esquema de deteção balanceada, calculamos os coeficientes de correlação normalizado e mostramos que há regiões de correlação e anticorrelação que variam com a intensidade do feixe. Observamos também uma inversão de picos no sinal de soma não prevista pelo modelo à medida que diminuimos a intensidade. Esta inversão pode ser causada por contribuições das flutuações de amplitude do laser a baixas intensidades. / Electromagnetically Induced Transparency has attracted much attention recently as a source to implement quantum memories. In this work, we studied this phenomenon, both theoretically and experimentally, using a degenerate two-level system modeling the atoms. We quantize the electromagnetic field and propose a linearized model for fluctuations that takes into account the quantum Langevin forces. Because of the excess noise in the phase of our laser, the numerical implementation of the theoretical model takes into account only the phase autocorrelation term as a source for the observed noise. This model showed a good qualitative agreement with the experimental data. We made sum and subtraction noise measurements using the balanced detection scheme, we calculated the normalized correlation coefficient and we showed that there are regions of correlation and anticorrelation that change with laser intensity. We also observed a peak inversion of the sum signal as laser intensity becames smaller that was not predicted by the model with only phase noise. The cause for this inversion can be the contribution of laser amplitude noise at small intensities.

Groups of closely spaced minor moraines allow for observations of moraine formation and ice-marginal fluctuations on short timescales, helping to better understand glacier retreat and predict its geomorphological effects. Some minor moraines can be classified as annual moraines given sufficient chronological control, which implies a seasonal climatic driver of ice-marginal fluctuations. This leads to moraines being utilised as very specific, short-term records of glacier fluctuations and climate change. This research is common in lowland, maritime settings, but remains sparse in high-mountain settings. This study presents the detailed geomorphological and sedimentological results of minor moraines at two high-mountain settings in the European Alps. Geomorphological investigations included mapping and measurements through field observations and remotely-sensed imagery. Detailed sedimentological investigations followed excavation of moraines and include multiple scales of observation and measurements to support interpretations of sediment transport and deposition. Additionally, ground-penetrating radar data were collected in one foreland. Minor moraines at Schwarzensteinkees, Austria, formed as push or combined push and freeze-on moraines in two groups between approximately 1850 and 1930. The existence of a former proglacial lake appears to have exerted a strong control on moraine formation. Modern minor moraines at Silvrettagletscher, Switzerland, exist primarily on reverse bedrock slopes and have formed since approximately 1850 through push, freeze-on, and controlled moraine mechanisms. The presence of these bedrock slopes, and in some areas englacial debris septa, appear to exert the primary controls on moraine formation. The foreland of Gornergletscher, Switzerland, has been revisited using aerial imagery to assess if moraines are still forming annually, and this has been confirmed. These findings show a range of mechanisms responsible for moraine formation, which are then compared to previously published research on minor moraines to elucidate any common drivers of minor and annual moraine formation globally. This includes a global database of forelands where minor moraines have been studied, created as part of this research and presented as a table and Google Earth file, both easily accessible and freely available online, for use by other researchers when exploring similar topics.

Power quality is an issue of ever increasing importance, and with ever increasingcustomer expectations on such issues, the significance of supplying customers withhigh quality power can never be underestimated. One of the most important mattersthat define power of good quality is the voltage level each customer is supplied with.Most appliances are designed to operate satisfactorily only within a narrow range ofsupply voltages. Inappropriate supply voltages can not only result in poor performingappliances, it can also cause equipment damage, increase distribution losses anddecrease the revenue for the power supplier.The point that is electrically closest to the consumers, where the voltage is activelyregulated and monitored, is usually in a zone substation, where on load tap changerson the zone substation transformers ensure that the voltage in the distribution networkis kept within appropriate limits. The supply voltage is therefore directly reliant oncorrect operation and functionality of the on load tap changers and their controllingautomatic voltage regulators. The main objective that this thesis seeks to achieve is todetermine the most effective method of voltage control to be utilised with differenttypes of zone substations, primarily with respect to the algorithms utilised in theautomatic voltage regulator.Metering data from the distribution network has been utilised to examine the presentvoltage performance of the distribution network. Different reasons that can causevoltage fluctuations and unpredictable voltage performance are investigated anddiscussed. Voltage levels that are investigated are steady-state voltages, hencetransients, flicker, and sags and swells of short duration have not been taken intoconsideration. The present voltage levels are also examined in network models, withthe aim to investigate the impact of altered methods of voltage control in zonesubstations. The accuracy of the utilised network models is also investigated, bycomparing metering data to modelled voltage levels.This thesis is undertaken with the assistance of Ergon Energy Corporation Limited, acorporation owned and operated by the Queensland Government. Ergon Energy ownsand operates the subtransmission and distribution network in regional Queensland. Itis intended that this thesis will aid understanding of the voltage performance of thedistribution network, and that it will bring clarity to how the voltage in thedistribution network should be controlled in order to achieve optimum voltageperformance. / Uppsatsnivå: C

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Physics, 1980. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Vita. / Bibliography: leaves 211-214. / by Peter Eric Bosted. / Ph.D.

abstract: Fluctuations with a power spectral density depending on frequency as $1/f^\alpha$ ($0<\alpha<2$) are found in a wide class of systems. The number of systems exhibiting $1/f$ noise means it has far-reaching practical implications; it also suggests a possibly universal explanation, or at least a set of shared properties. Given this diversity, there are numerous models of $1/f$ noise. In this dissertation, I summarize my research into models based on linking the characteristic times of fluctuations of a quantity to its multiplicity of states. With this condition satisfied, I show that a quantity will undergo $1/f$ fluctuations and exhibit associated properties, such as slow dynamics, divergence of time scales, and ergodicity breaking. I propose that multiplicity-dependent characteristic times come about when a system shares a constant, maximized amount of entropy with a finite bath. This may be the case when systems are imperfectly coupled to their thermal environment and the exchange of conserved quantities is mediated through their local environment. To demonstrate the effects of multiplicity-dependent characteristic times, I present numerical simulations of two models. The first consists of non-interacting spins in $0$-field coupled to an explicit finite bath. This model has the advantage of being degenerate, so that its multiplicity alone determines the dynamics. Fluctuations of the alignment of this model will be compared to voltage fluctuations across a mesoscopic metal-insulator-metal junction. The second model consists of classical, interacting Heisenberg spins with a dynamic constraint that slows fluctuations according to the multiplicity of the system's alignment. Fluctuations in one component of the alignment will be compared to the flux noise in superconducting quantum interference devices (SQUIDs). Finally, I will compare both of these models to each other and some of the most popular models of $1/f$ noise, including those based on a superposition of exponential relaxation processes and those based on power law renewal processes. / Dissertation/Thesis / Doctoral Dissertation Physics 2018

A sample of 61 subjects from an introductory psychology class was administered a battery of psychological tests, among them the Rorschach and the MMPI. The purpose was to determine the behavioral correlates, if any, of the two Rorschach variables, Mean Reaction Time, and Fluctuation in Time of First Response. This was accomplished by using multivariate statistical techniques, i.e. a factor analysis followed by a stepwise multiple regression. The results were ambiguous. While not statistically significant, they suggest that the MMPI variables of Social Introversion and Psychopathic Deviant are more closely related to the two dependent variables than previous literature would suggest. One variable, anxiety, which has been shown by previous research to be associated with Mean Reaction Time, was found to be not associated by the present investigation. Explanations and suggestions for further research were discussed.

Maintaining optimum levels of dissolved oxygen (DO) in natural water systems has become crucial for scientists and decision makers. In general, DO concentrations less than 5 mg/L stress many types of aquatic organisms including fishes. Uncontrolled growth of aquatic autotrophs (i.e., algae and macrophytes) may alter DO concentration if the growth exceeded the capacity of the aquatic food web structure. Primary production and respiration, the two main metabolic processes associated with aquatic autotrophs, were estimated, compared, and critiqued for three streams in Northern Utah, USA. These streams have been under consideration for many years due to their impaired water quality, as they supply water to Cutler Reservoir, the sink of all the transported sediment and nutrients. This study includes estimation of the metabolic rates, examination of the driving/limiting factors, examination of the consequences of the relevant rates on water quality, and a comparison of two methods of estimation of the metabolic rates. The outcome of this research will help scientists and decision makers build knowledgeable strategies to manage DO in the streams based on the given critiques on the cause and effect of the respective metabolic rates. It will also help reduce the cost and time associated with the frequent need to use physical field measurements to estimate metabolic rates in rivers and streams.

Our view of phytoplankton has historically revolved around their inability to control their location in space. The term phytoplankton itself underscores this particular difference between phytoplankton and their sessile terrestrial counterparts. Yet there are other differences between land plants and the phytoplankton that are perhaps equally important, beyond this sessile-planktonic dichotomy, to their growth, survival, and productivity. For example, phytoplankton are microbes and thus are short-lived, with generational scales on the order of days or less. An intriguing question to ask is how today���s pelagic ecology would differ, had this temporal difference between plants and phytoplankton been initially emphasized, perhaps by naming these microbes phytoephemera instead? This dissertation addresses certain aspects of the ecology of phytoplankton that result from their having short generational scales. Because they are so short lived, phytoplankton need to adjust their photosynthetic physiology to cope with more rapid changes in irradiance than may matter to longer-lived plants. Photoacclimation on the hours-plus time scales has been studied extensively in the phytoplankton, because its temporal scales match those of vertical mixing processes in the ocean. Yet most phytoplankton exhibit faster photosynthetic responses as well, down to the time scales of seconds. These photosynthetic responses have received considerably less attention in phytoplankton ecology. This dissertation specifically examines these rapid, seconds-to-hour scale photosynthetic responses in phytoplankton. First, the physiological bases of rapid photosynthetic regulation were examined using a numerical model that shows how specific physiological changes in phytoplankton photosystems either constrain or enhance light harvesting. This model is stochastic, and thus replicates certain nonlinear aspects of light harvesting better than equation-based analytical models. Also in this dissertation, a laboratory study is described that examined rapid photosynthetic regulation in three model phytoplankton. Results suggest that rapid photosynthetic regulation is not only constrained to higher eukaryotic phytoplankton, but also occurs in the two dominant marine photosynthetic prokaryotes, Synechococcus and Prochlorococcus. Finally, rapid photosynthetic responses were examined in field assemblages at Station ALOHA in the North Pacific. This ocean region experiences considerable cloud cover, which may result in a strong degree of rapid photosynthetic responses, even in near-surface assemblages. / Graduation date: 2007