In the widely accepted core accretion model of planet formation, small rocky and/or icy bodies (planetesimals) accrete to form protoplanetary cores. Gas giant planets are believed to have solid cores that must reach a critical mass, ∼10 Earth masses (ME), after which there is rapid inflow of gas from the gas disk. In order to accrete the gas giants’ massive atmospheres, this step must occur within the gas disk’s lifetime (1 − 10 million years). Numerical simulations of solid body accretion in the outer Solar System are performed using two integrators. The goal of these simulations is to investigate the effects of important dynamical processes instead of specifically recreating the formation of the Solar System’s giant planets. The first integrator uses the Symplectic Massive Body Algorithm (SyMBA) with a modification to allow for planetesimal fragmentation. Due to computational constraints, this code has some physical limitations, specifically that the planetesimals themselves cannot grow, so protoplanets must be seeded in the simulations. The second integrator, the Lagrangian Integrator for Planetary Accretion and Dynamics (LIPAD), is more computationally expensive. However, its treatment of planetesimals allows for growth of potential giant planetary cores from a disk consisting only of planetesimals. Thus, this thesis’ preliminary simulations use the first integrator to explore a wider range of parameters while the main simulations use LIPAD to further investigate some specific processes. These simulations are the first use of LIPAD to study giant planet formation and they identify a few important dynamical processes affecting core formation. Without any fragmentation, cores tend to grow to ∼2ME. When planetesimal fragmentation is included, the resulting fragments are easier to accrete and larger cores are formed (∼4ME). But, in half of the runs, the fragments force the entire system to migrate towards the Sun. In other half, outward migration via scattering off a large number of planetesimal helps the protoplanets grow and survive. However, in a preliminary set of simulations including protoplanetary fragmentation, very few collisions are found to result in accretion so it is difficult for any cores to form. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2012-08-20 14:48:39.443

The giant panda (Ailuropoda melanoleuca) is an endangered species and many efforts are being made to ensure its survival, including numerous research studies. However, there has been little investigation of spatial memory in the giant panda. Spatial memory is an important mechanism for survival in the wild, allowing an animal to find and remember the location of food, mates, den sites and avoid predators. Memory assessment in non-human species typically involves the use of recognition, as opposed to recall tasks. The current study tested spatial memory recall in 1.1 giant pandas using a delayed response memory task. The design required a delayed response to a previously lighted location, with varying lengths of delay between the observation phase and the test phase. The male subject reached criterion at 2-, 3-, 4-, 5-, 6-, and 10-second delays. The female subject reached criterion at 2-, 3-, 4-, 5-, 6-, 10-, and 15-second delays. The results support the hypothesis that giant pandas have working memory recall ability for spatial location.

Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references. Also available on the World Wide Web.

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The present study examined the relationship between early rearing experience and reproductive competence in captive adult giant pandas (Ailuropoda melanoleuca) and spectacled bears (Tremarctos ornatus). Life history information of 52 giant pandas and 34 spectacled bears were obtained from the International Studbook and by interviewing staff at institutions housing the subjects. The early rearing experience variables included duration of mother rearing, social access within 1-yr period following maternal separation, and birth origin. Correlation, Chi-square, and logistic regression analyses were used to analyze the data. Contrary to findings from studies with other animals, the results generally suggest that early rearing experience is not related to adult reproductive success in giant pandas and spectacled bears. Alternative explanation and limitation of the study were discussed; suggestions were made for future study.

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The scattering mechanisms responsible for Giant Magneto-Resistance (OMR) in magnetic multilayers are believed to be related to many aspects of the multilayer structure. X-ray scattering techniques provide a powerful method with which to study the bulk and interface morphology in these systems, and are therefore crucial in developing an understanding of the dominant factors influencing the magnitude of the OMR. Reflectivity measurements performed on a series of Co/Cu multilayers, sputter deposited onto etched silicon, reveal no variation in the interface roughness with etching voltage, the thickness of the individual layers also remaining constant. The observed decrease in the OMR cannot, therefore, be attributed to variations in spacer thickness or interfacial spin-independent scattering. Electron and X-ray Diffraction measurements suggest the reduction in GMR is due to a loss of antiferromagnetic coupling associated with a transformation of the texture from a randomly oriented to well oriented (111) polycrystalline texture, and subsequent reduction in the volume fraction of (100) oriented grains. Interfaces within Co/Cu are found to propagate with a high degree of conformality with increasing bilayer number, with an out-of-plane correlation length well in excess of 300Å. In contrast, the Co/Pt system exhibits a limiting out-of-plane correlation length of the order of 350Å arising from a columnar growth mode. X-ray Reflectivity and Diffraction measurements provide no structural interpretation for the 3-fold enhancement in the rate of increase of the saturation conductivity, as a function of spacer thickness, in Fe/Au (100) compared to Fe/Au (111), or why large oscillations in the GMR occur for the (100) orientation only. Such observations are, however, consistent with the existence of a channelling mechanism in Fe/Au (100). Grazing Incidence Fluorescence data indicates that Nb acts as a surfactant in Fe/Au (111) growth on sapphire. The influence of different defect types within multilayers has also been observed.