Energetic particles are injected into the geosynchronous-orbit region of the Earth's magnetosphere during events called magnetospheric substorms. This injection process has been investigated utilizing the Magnetospheric Specification Model. Using time-dependent models of the magnetospheric electric and magnetic fields, we follow the ExB and gradient/curvature drifts of ions and electrons of differing energies within the modeling region. With allowance made for precipitation loss, the flux at each grid point is calculated from the initial and boundary condition fluxes. We used the data from the geomagnetic storm of March 22, 1979 to test the model's accuracy. Comparing predicted and observed geosynchronous particle fluxes, the model's predictions as to when the particles should arrive at various locations at the geosynchronous orbit are in good agreement with observations. However, assuming adiabatic drift of particles from the plasma sheet to the geosynchronous orbit region, with reasonable allowance for precipitation loss, the model obtains substorm fluxes that are about a factor of ten too high. This implies the existence of a powerful loss process that operates during a substorm on particles drifting between the middle plasma sheet and geosynchronous-orbit region.

We demonstrate a technique of measuring x-ray (or neutron) scattering with the momentum transfer parallel to the plane of membrane. This technique allows us to investigate the lateral organization of protein and peptide in the membrane. To resolve the question of whether gramicidin (GA) forms lateral aggregates, samples of GA in dilauroylphosphatidycholine (DLPC) bilayers (molar ratio 1:10) were investigated. Very clear scattering signals of GA were obtained, even for the peptide without a heavy atom attached. The experiment showed that the gramicidin channels did not aggregate and were randomly distributed in the membrane. The non-conducting state of gramicidin channel was also investigated. We use a synthetic GA analogue in which the formyl group of natural GA is replaced by a BOC group. The in-plane scattering measurements show that the gramicidin channel closes by dissociation into two monomers, each remains embedded and freely diffuses in its own monolayer.

The gluing and tensor product constructions of lattices are reviewed. A third construction, called shifting, is defined and its relationship to gluing and rational equivalence is investigated. There follows a discussion of a method, based on gluing, for systematically generating theta function identities. Gluing is used also as a device for constructing phenomenologically realistic superstring theories. Finally, these lattice methods are applied to recent work concerning vanishing cosmological constants in string theories. In addition, scattered throughout the thesis are a number of smaller results on lattices.

The calibration and quality control measurements of the ZEUS forward and rear calorimeters made using movable $ sp{60} Co$ sources are described. The types of assembly faults discovered from the runs taken first at CERN and then later at DESY from mid 1990 to early 1991 are presented. The WLS attenuation length as well as changes in the attenuation length of the scintillators can be monitored by the cobalt scans.

<p> Single molecule magnets (SMMs), such as Mn₁₂-acetate, are composed of transition metal ions and consists of identical molecules with large ground-state spin (<i>S</i> = 10) and a strong uniaxial anisotropy (65 K). Below about 3 K, Mn₁₂-acetate exhibits magnetic hysteresis with steps at specific values of longitudinal magnetic field due to resonant quantum tunneling between spin up and down projections along the easy axis. The intermolecular exchange interactions between spins on molecules are quite small and spins are considered to be independent and non-interacting. </p><p> However, the molecules do interact with each other both through magnetic dipolar interactions and through the lattice (e.g. phonons). I have investigated collective effects in SMMs due to these intermolecular interactions. In the thesis I will present experiments that explored magnetic ordering due to magnetic dipole interactions in Mn₁₂-acetate and Mn₁₂-acetate-MeOH. I will also present exper- iments on the onset of magnetic de agration in Mn₁₂-acetate due to a thermal instability.</p><p> The magnetic ordering studies involved investigating the effect of transverse fields on the susceptibility of single crystals of Mn₁₂-acetate and Mn₁₂-acetate- MeOH. Transverse fields increase quantum spin uctuations that suppress long- range order. However, the suppression of the Curie temperature by transverse fields in Mn₁₂-acetate is far more rapid than predicted by the Transverse-Field Ising Ferromagnetic Model (TFIFM) and instead agrees with the predictions of the Random-Field Ising Ferromagnet Model. It appears that solvent disorder in Mn₁₂-acetate gives rise to a distribution of random-fields that further suppress long-range order. Subsequent studies on Mn₁₂-acetate-MeOH, with the same spin and similar lattice constants but without solvent disorder as Mn₁₂-acetate, agrees with the TFIFM.</p><p> The magnetic de agration studies involved studying the instability that leads to the ignition of magnetic deflagration in a thermally driven Mn₁₂-acetate crystal. When spins prepared in a metastable state reverse, Zeeman energy is released that diffuses away. In some circumstances, the heat released cannot be compensated by thermal diffusion, resulting in an instability that gives rise to a front of rapidly reversing spins traveling through the crystal. We observed a sharp crossover from relaxation driven by heat diffusion to a self-sustained reversal front that propagates at a constant subsonic speed.</p>

No description available.

This Thesis is concerned with the computation and interpretation of Cerenkov light pulse shapes from digitised pulses. The experiment to measure the characteristics of extensive air showers in the energy range 10(^15) eV - 10(^18) eV was conducted at the University of Durham EAS array in Dugway, UTAH, USA between 1977 and 1980. Systematic environmental monitoring of the experiment has been carried out to quantify weather conditions and assess data quality. Computer programs have been developed and tested to retrieve pulse shape information from digitised Cerenkov light data. Three main data fitting methods are investigated and compared, and the theories underlying them are outlined. A sample of the Dugway data has been analysed in detail after pulse shape reconstruction using unimodal quartic splines. The measured pulse shape parameters are interpreted to show the electron cascade development of the extensive air showers, and related to a proposed primary energy estimator. Suggestions are made for further pulse shape reconstruction techniques.

The surface modification of polyethylene by Corona and Plasma discharges is studied by X-Ray photoelectron spectroscopy and multiple internal reflection spectroscopy. Wettabilities are used to observe changes in surface energy and the strengths of bonds formed using adhesives are measured. A short account is given of the importance to manufacturers of being able to increase the surface energies of polymers. The conditions needed to establish the corona discharge and the nature of the corona discharge are discussed. The reactions occurring within the plasma formed by the discharge and the various reactive species formed are considered and the effects of these species are discussed. Plasma discharges at low pressures and their effects on polymer surfaces are also considered. The surface modification of polyethylene by both corona and plasma discharges is shown to be associated with an increase in the oxygen functionality of the surface. The relationships between the increase in oxygen and carbon functionalities are discussed and the possible groups formed are suggested. Many of these are polar in character and include hydroxyl, carbonyl, carboxylic, carbonate and hydroperoxide groups together with ether and possibly peroxide (non polar) groups. These groups are found to be produced even when only traces of oxygen are present. The use of nitrogen gas is shown to produce high levels of amine and amide functions. The polar groups are believed to be largely responsible for the increased wettabilities of the surfaces and partly responsible for the increased adhesive strength. In this latter case cross linking at the surface is also believed to be important. Some evidence is put forward, from the heat treatment of plasma treated polyethylene, for free radicals being involved in some of the reactions at the surface- The fact that free radicals are not detected after the surface modification in many instances is thought tube due to the fact that they often react completely with oxygen as fast as they are formed. The surface charging of polyethylene during corona discharge is examined and shown to be largely due to deeply trapped electrons rather than merely superficial charges. A comparison is made between corona and plasma discharges and the suitability of each method in different situations is considered. The structure and bonding in the perchlorodiphenyl aminyl radical is investigated to see if this could helping the investigation of the effects of corona and plasma treatment of polyethylene. The results, though interesting in themselves, reveal that the multiplet splitting effect is too small for this effect to be used in investigating surface changes in polyethylene.

No description available.

No description available.