Current cancer therapies are highly cytotoxic and their delivery to exclusively the affected site is poorly controlled, resulting in unavoidable and often severe side effects. In an effort to overcome such issues, magnetic nanoparticles have been recently gaining relevance in the areas of biomedical applications and therapeutics, opening pathways to alternative methods. This led to the concept of magnetic particle hyperthermia in which magnetic nano beads are heated by a high power magnetic field. The increase in temperature kills the cancer cells, which are more susceptible to heat in comparison to healthy cells. In this dissertation, the possibility to kill cancer cells with magnetic nanowires is evaluated. The idea is to exploit a magnetomechanical effect, where nanowires cause cancer cell death through vibrating in a low power magnetic field. Specifically, the magnetic nanowires effects to cells in culture and their ability to induce cancer cell death, when combined with an alternating magnetic field, was investigated. Nickel and iron nanowires of 35 nm diameter and 1 to 5 μm long were synthesized by electrodeposition into nanoporous alumina templates, which were prepared using a two-step anodization process on highly pure aluminum substrates. For the cytotoxicity studies, the nanowires were added to cancer cells in culture, varying the incubation time and the concentration. The cell-nanowire interaction was thoroughly studied at the cellular level (mitochondrial metabolic activity, cell membrane integrity and, apoptosis/necrosis assay), and optical level (transmission electron and confocal microscopy). Furthermore, to investigate their therapeutic potential, an alternating magnetic field was applied varying its intensity and frequency. After the magnetic field application, cells health was measured at the mitochondrial activity level. Cytotoxicity results shed light onto the cellular tolerance to the nanowires, which helped in establishing the appropriate nanowire concentrations to use the nanowires + alternating magnetic field combination as a cancer treatment. Different levels of cancer cell death were achieved by changing the incubation time of the nanowires with the cells and the alternating magnetic field parameters. Cell viability was significantly affected in terms of mitochondrial activity and cell membrane integrity after applying the treatment (nanowires + alternating magnetic field) using a low-frequency alternating magnetic. Theoretical calculations considering the magnetic and viscous torques showed that the nanowires vibrate as a consequence of the applied magnetic field. This, alongside the fact that no temperature increase was measured during the treatment, makes the magnetomechanical effect the most probable action mechanism in the applied treatment that is inducing cell death. Inducing cancer cell death via magnetomechanical action using magnetic nanowires resulted in killing up to 60% of cancer cells with only 10 minutes of treatment. The required magnetic field for treatment is in a low power regime, which is safe, does not cause any discomfort to the patients, and can be generated with compact and cheap instruments.

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A single crystal of colemanite, which is ferroelectric at temperatures below about -2.0° C., has been investigated by means of nuclear magnetic resonance (n.m.r.) techniques, over a temperature range 52° C. to -136° C. The splitting b^11 the n.m.r. signal in colemanite, caused by the perturbation of the nuclear Zeeman levels by the interactions between the nuclear electric quadrupole moment and the electric field gradients existing at the boron sites at room temperature and at -40°C., has been fully analysed, using the procedure developed by lookoff and coworkers. The quadrupole coupling constants, the asymmetry para­meters and the orientations of the principal axes of the electric field gradient tensors at room temperature and -40° C. are given in Tables XXV - XXII. A selected set of B^11 n.m.r. lines has been examined over the temperature range 52°C. to -136°C. This investigation suggests that the ferroelectric transition is second-order and not the order-disorder or martensitic type. The transition temperature itself has been found to depend upon the history of the crystal, but is apparently about 2°C. higher than previously reported temperatures of about -2.0° C. In addition, a previously unknown phase in colemanite is reported. A large temperature hysteresis loop is associated with the transition to the new phase; on cooling, the transition takes place at about -80°C, whereas on heating, the transition takes place at about -35° C. The point groups for the three phases have been determined as 2/m., 2 and 1 going from room temperature to -80° C., respectively. The resets of the n.m.r. investigation have been interpreted, as far as possible at present, in terms of the crystal. structure. / Thesis / Doctor of Philosophy (PhD)

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<p> Magnetic susceptibility data indicate that Tb2Mo2O7 undergoes a spin glass transition at 25 K. The crystal structure is consistent with the fully ordered pyrochlore model. Short range order, involving ferromagnetic and antiferromagnetic correlations, is observed down to 8 K by neutron scattering. </p> <p> Sr2Cr03F and SrLaCr04 have the same magnetic structure. The neutron diffraction data are consistent with two different models. In both cases the magnetic cell is √2a and c and the magnetic moments lie out of the plane. However, in one model the in-plane projection is canted and in the other it is colinear. Sr2Cr03F has a Tc value of 132(2) K and a susceptibility maximum at 280 K. SrLaCr04 has a Tc value of approximately 200 K and a susceptibility maximum near 400 K. The critical· exponent β for Sr2Cr03F is 0.26(4). The (100) magnetic reflection of both SrLaCr04 and Sr2Cr03F shows short range order correlations above Tc. </p> / Thesis / Master of Science (MSc)

This thesis explores a method to fabricate magnetic membranes with asymmetric distribution of particles and their testing as actuators. Focus of this research is to fabricate thin polymeric sheets and thickness range of 120-125µm, with asymmetric distribution of magnetic nano particles, employing micromagnets during the fabrication. The micromagnets are used to localize the magnetic particles during the curing process at selected locations. The effect of the asymmetric distribution of magnetic particles in the membrane is used for the first time. Magnetite (Fe3O4) is used as the magnetic particles that is embedded into a polymeric membrane made of polydimethylsiloxane (PDMS); the membrane is then tested in terms of deflection observed by using a high-resolution camera. From the perspective of the biomedical application, PDMS is chosen for its excellent biocompatibility and mechanical properties, and Fe3O4 for its non-toxic nature. Since magnetic actuation does not require onboard batteries or other power systems, it is very convenient to use in embedded devices or where the access is made difficult. A comparative study of membranes with asymmetric and randomly distributed particles is carried out in this thesis. The asymmetric distribution of magnetic particles can benefit applications involving localized and targeted treatments and precision medicine.

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