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The Moon displays weak magnetic fields resulting from areas of the lunar crust that are remanently magnetised. The origins of the magnetic fields that produced this remanent magnetisation are still under discussion, and theories include among several, an ancient lunar dynamo, or processes occurring on the Moon as a result of impacts. Lunar crustal fields have been mapped globally by the Magnetometer (MAG) and Electron Reflectometer (ER) on the satellite Lunar Prospector, providing vector magnetic field measurements at an average altitude of 30 km, and estimates of the total surface field. This thesis presents global and regional models of the magnitude and direction of lunar magnetisation within a layer, produced from both the MAG and ER data independently and jointly using several inversion methods. The inverse modelling techniques are based on those developed for terrestrial and Martian data sets, employing equivalent source dipoles as basis functions, and Green’s functions relating a magnetic field observation to a spatially continuous magnetisation distribution. A unique magnetisation solution is selected having the smallest rootmean- square (RMS) magnetisation for a given fit to the data, controlled by a damping parameter. The non-uniqueness in magnetisation distributions and the determination of source parameters is discussed with the use of forward models to assist the interpretation of the crustal magnetisation models. Suites of magnetisation models for layers with thicknesses between 10 and 50 km, and with different dipole depths, are able to reproduce both the ER and MAG data well. Inverse models utilising the scalar ER data have been developed successfully, resulting in a joint inversion of the ER and MAG data for one of the strongest magnetic anomalies on the Moon, Reiner Gamma. The largest concentrations of strongly magnetised crust are, like the crustal fields themselves, located antipodal to the youngest large impact basins, and in some isolated areas associated with the strongest crustal fields. The magnetisation distributions show robust magnitudes with different data sets and modelling techniques showing the extent of magnetised sources, but can not be used to infer the direction of the magnetising fields. Average magnetisation values in magnetised regions of 30-40 mA/m are similar to the measured magnetisations of the Apollo samples and significantly weaker than crustal magnetisations for Mars and the Earth. A global preference for a 30 km thick magnetised layer suggests that a dynamo field may be more consistent with these magnetisation models. The magnetisation models in this thesis are the first global magnetisation models for the Moon, and the first to combine the vector MAG and the scalar ER data. These magnetisation models can be used to predict the crustal contribution to the lunar magnetic field environment at a particular location, and in the absence of reliable sample returns, provide valuable information on the magnitude of lunar crustal magnetisation.

The research area of magnetic field effects (MFE) on organic systems has been intensively studied during the last decade. It has been revealed that there are processes that are subject to low fields (< 50 mT) and processes that are subject to high fields (> 50 mT). While the low field processes are widely accepted to be a result of the suppression of the spin mixing caused by random hyperfine fields and spin-orbit coupling within the devices, the origin of the high field processes is still not clear. Although several mechanisms, like triplet-charge carrier interaction (TCI) and triplet-triplet annihilation (TTA), were proposed to explain the high field MFEs, how these processes are affected by a magnetic field is not well understood. This thesis presents a study of the role of excitons on MFEs using aluminium tris(8-hydroxyquinolinate) (Alq3) based diodes, focusing on the behaviour of high field effects on electroluminescence (MEL). In order to investigate the role of excitons on high field MEL, devices with different structures were designed to modify the population of exciton and excess charge carriers in the devices via controlling the injection of charge carriers. In this way, the exciton population dependent TTA and TCI processes can be studied further and even distinguished, since the TTA depends mainly on the population of triplets while the TCI depends on the exciton to charge carrier ratio. Steady state MFE measurements were performed, and results show that significant high field MEL decay can be seen in a device with extremely low triplet concentration. This indicates that TTA cannot be the underlying mechanism of high field MEL decay. The gradual trend of high field MEL, changing from a moderate increase to significant decays upon adjusting the hole and electron injection from balanced to severely hole dominated, suggests that this high field decay is exciton-hole interaction dependent. To decompose the role of singlets and triplets on high MELs, transient MFE measurements were performed on the Alq3 based standard devices. Since in Alq3 layer singlets feature a lifetime of ~ns and triplets feature a lifetime of ~ms, the behaviour of MEL at the rising edge and the falling edge of a pulse can provide a useful tool. Results show that an extra component occurs in the transient MEL at large current density and high fields. This indicates that the high field MEL is related to triplet-charge carrier interaction.

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Hydrogel smart polymers have achieved a great attention in the research area of drug delivery, MEMS/NEMS, microfluidics and sensor design because of their responsiveness to various environmental stimuli- pH, temperature, light, electric field, enzyme etc. This thesis presents the modeling, fabrication and study of the bending deformation of magnetic field sensitive hydrogel micro fibers called ferrogels. The objective is to externally actuate the ferrogel fibers by applying magnetic field, for the application of targeted drug delivery inside the alveoli of a human lung. Prediction of the bending deformation of the ferrogel fibers is done by the Multiphysics Finite Element Modeling in an Arbitrary Lagrangian Eulerian (ALE) framework. Ferrogel micro fibers are fabricated and the bending deforma-tion is studied experimentally by varying the aspect ratio of the fibers, volume fraction of the magnetic particle content of the fibers and the magnetic field strength. The numerical and experimental results are compared. This is the first attempt to numerically predict the bending deformation of ferrogel micro-fibers.

Thesis-University of California, November 1963. / TID 4500 (24th Ed.). Bibliography references : p. 94-97.

In the present experiment a gas discharge plasma generator was designed and constructed and a search was made for evidence of a plasma instability due to the influence of an externally applied magnetic field. The evidence for such an unstable mode of operation is too indirect to make a possible conclusion, but an approach to more certain identification will be indicated.

Conventional Extrinsic Fabry-Perot Interferometric (EFPI) sensors have been used to measure a variety of physical parameters like temperature, pressure and strain. A modified version of this geometry is successfully implemented to measure low-level magnetic field densities. A complete optical fiber based magnetometer system consisting of sensor head, laser source, opto-electronics, signal demodulation circuitry and display is designed, fabricated and tested. Various electronic signal demodulation schemes are discussed. The Quadrature Phase Shifted EFPI signal demodulation scheme, used in the system, is studied in detail. The scheme is designed and implemented in both analog and digital domain and the advantages and drawbacks of each type are presented. Primary limitations in the measurement of extremely low-level magnetic field densities are discussed and methods to overcome them using electronic signal processing schemes are suggested for future consideration. / Master of Science

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