Thesis (Ph.D.)--Kent State University, 2009. / Title from PDF t.p. (viewed Jan. 12, 2010). Advisor: Laura G. Leff. Keywords: Bacteria; modeled reduced gravity; response; gene expression; physiology. Includes bibliographical references (p. 200-204).

Thesis (Ph. D.)--University of Chicago, Department of Physics, August, 2003. / Includes bibliographical references. Also available on the Internet.

Thesis (M. Sc.)--York University, 2001. Graduate Programme in Kinesiology and Health Science. / Typescript. Title on thesis acceptance page: Effects of aging on the cardiovascular responses to a push-pull tilting manoeuvre. Includes bibliographical references (leaves 65-73). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pMQ71587.

Several groups produce estimates of the Earth's time-varying gravitational field with data provided by the NASA/DLR Gravity Recovery and Climate Experiment (GRACE) mission. These unprecedented highly accurate global data sets track the time-variable transport of mass across and underneath the surface of the Earth and give insight into secular, seasonal, and sub seasonal variations in the global water supply. Knowledge gained from these products can inform and be incorporated into ocean and hydrological models and advise environmental policy planning. Therefore, a complete understanding of the accuracy and variations between these different fields is necessary, and the most accurate possible solutions desired. While the various gravity fields are similar, differences in processing strategies and tuning parameters result in solutions with regionally specific variations and error patterns. This study analyzed the spatial, temporal, and spectral variations between four different gravity field products. The knowledge gained in this analysis was used to develop an ensemble solution that harnesses the best characteristics of each individual field to create an optimal model. Multiple methods were used to combine and analyze the individual and ensemble solutions. First a simple mean model was created; then the different solutions were weighted based on the formal error estimates as well as the monthly deviation from the arithmetic mean ensemble. These ensemble models as well as the four individual data center solutions were analyzed for bias, long term trend, and regional variations between the solutions, evaluated statistically to assess the noise and scatter within the solutions, and compared to independent hydrological models. Therefore, the form and cause of the deviations between the models, as well as the impact of these variations, is characterized. The three ensemble solutions constructed in this analysis were all effective at reducing noise in the models and better correlate to hydrological processes than any individual solution. However, the scale of these improvements is constrained by the relative variation between the individual solutions as the deviation of these individual data products from the hydrological model output is much larger than the variations between the individual and ensemble solutions. / text

The Gravity Recovery and Climate Experiment (GRACE) project has two primary goals: to determine the Earth’s mean gravitational field over the lifetime of the mission and to observe the time-variable nature of the gravitational field. The Center for Space Research's (CSR) Release 4 (RL04) GRACE solutions are currently created via a least-squares process that assimilates data collected over a month using a simple boxcar window and determines a spherical harmonic representation of the monthly gravitational field. The nature of this technique obscures the time-variable gravity field on time scales shorter than one month and spatial scales shorter than a few hundred kilometers. A computational algorithm is developed here that allows increased temporal resolution of the GRACE gravity information, thus allowing the Earth's time-variable gravity to be more clearly observed. The primary technique used is a sliding-window algorithm attached to a weighted version of batch least squares estimation. A number of different temporal windowing functions are evaluated. Their results are investigated via both spectral and spatial analyses, and globally as well as in localized regions. In addition to being compared to each other, the solutions are also compared to external models and data sets, as well as to other high-frequency GRACE solutions made outside CSR. The results demonstrate that a GRACE solution made from at least eight days of data will provide a well-conditioned solution. A series of solutions made with windows of at least that length is capable of observing the expected near-annual signal. The results also indicate that the signals at frequencies greater than 3 cycles/year are often smaller than the GRACE errors, making detection unreliable. Altering the windowing technique does not noticeably improve the resolution, since the spectra of the expected errors and the expected non-annual signals are very similar, leading any window to affect them in the same manner. / text

No description available.

The General theory of Relativity (GR) brought gravity into accord with the principles of locality and relativity. Since its discovery it has been preeminent, recognized as the most accurate description of gravity on the many scales where it has been tested. During this period, seemingly radical predictions like the existence of black holes and the expansion of the Universe have been verified and testify to the great leap of insight that GR represented in our understanding of space and time. However not all precision observations of astrophysical systems have yielded easily to interpretation within GR, and with the discovery of cosmic acceleration, there is genuine concern that General Relativity may be incomplete when describing the Universe on the largest sizes imaginable. In this uncertainty, many theoretical models have been proposed. In this thesis we shall first outline the motivation behind a certain subset of these models and the known issues that arise in interpreting these models as alternative theories of gravity. Then focus on one variety of theory the f(R) modifications to gravity. Demonstrating that many of the known instabilities have a common origin and that they are avoided when treating these theories via perturbative constraints. In the second part of this work we examine the astrophysical impact of modifications to gravity, first in the case of high mass neutron stars, then subsequently on corrections to the line profile of neutral hydrogen from violations of the equivalence principle. Finally we explore the phenomenology of modifications to gravity that produce late-Universe acceleration. In particular, what solutions are allowed and what range of accelerations are predicted as a result. Furthermore we explore how a correction to gravity at large scales would impact the growth and evolution of cosmological perturbations.

No description available.

We construct a 4d Lorentzian spin foam model capable of describing both spacelike and timelike surfaces. To do so we use a coherent state approach inspired by the Riemannian FK model. Using the coherent state method we reproduce the results of the EPRL model for Euclidean tetrahedra and extend the model to include Lorentzian tetrahedra. The coherent states of spacelike/timelike triangles are found to correspond to elements of the discrete/continuous series of SU(1,1). It is found that the area spectrum of both spacelike and timelike surfaces is quantized. A path integral for the quantum theory is defined as a product of vertex amplitudes. The states corresponding to timelike triangles are constructed in a basis diagonalised with respect to a noncompact generator. A derivation of the matrix elements of the generators of SL(2,C) in this basis is provided.

We propose a Generalized Uncertainty Principle (GUP) consistent with String Theory, Black Hole Physics and Doubly Special Relativity. This modifies all quantum mechanical Hamiltonians and predicts quantum gravity corrections. We compute corrections to the Lamb shift, simple harmonic oscillator, Landau levels, and the tunneling current. When applied to an elementary particle, it suggests that the space must be quantized, and that all measurable lengths are quantized in units of a fundamental length. We investigated whether GUP can explain the violation of the equivalence principle at small length scales that was observed experimentally. We investigated the consequences of GUP on Liouville theorem. We examined GUP effect on post inflation preheating, and show that it predicts an increase or a decrease in parametric resonance and a change in particle production. The effect of GUP on the creation of black holes is investigated to justify the experimental results from the Large Hadron Collider. / viii, 154 leaves ; 30 cm