This thesis presents the first ever measurement of the noise emitted by magnetic monopoles and the development of an exquisitely sensitive magnetic-field-noise spectrometer based on a superconducting quantum interference device (SQUID) that enabled it. Magnetic monopoles are highly elusive elementary particles exhibiting quantized magnetic charge. The prospects for studying them brightened recently with the theoretical discovery that the thermally excited states in certain classes of magnetic insulators exhibit all the characteristics of magnetic monopoles. Furthermore, in 2018, it was predicted that the random motion of magnetic monopoles inside would generate a very specific kind of magnetization noise. In this thesis, the author describes a new experimental technique, so-called spin noise spectroscopy, and the subsequent discovery of virtually all of the predicted features of the magnetic noise expected from a dense fluid of magnetic monopoles in crystals of Dy2Ti2O7. Remarkably, because this magnetic monopole noise occurs in the frequency range below 20kHz, when amplified by the SQUID it is actually audible to humans.

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In 1269 Petrus Peregrinus observed lines of force around a lodestone and noted that they were concentrated at two points which he designated as the north and south poles of the magnet. Subsequent observation has confirmed that all magnetic objects have paired regions of' opposite polarity, that is, all magnets are dipoles. It is easy to conceive of an isolated pole, which J.J. Thomson did in 1904 when he set his famous problem of the motion of an electron in the field of a magnetic charge. In 1931 P.A.M. Dirac solved this problem quantum mechanically and showed that the existence of a single magnet pole anywhere in the universe could explain the mystery of charge quantization. By late 1981, theoretical interest in monopoles had reached the point where a meeting was organized at the International Centre for Theoretical Physics in Trieste. Many mathematical properties of monopoles were discussed at length but there was only a solitary account describing experiments. This imbalance did not so much reflect the meeting's venue as it indicated the relative theoretical and experimental effort at that point.

These lecture notes discusses the developments both in the theoretical understanding of the physics and mathematics of magnetic monopoles as well as the ways in which they can be detected experimentally.The subject has now become highly interdisciplinary and recent monopole meetings have attracted participants from low temperature physics at one extreme to cosmology at the other.

Principles and applications of SQUIDs serves as a textbook and a multi-author collection of critical reviews. Providing both basic aspects and recent progress in SQUIDs technology, it offers a realistic and stimulating picture of the state of the art. It can also contribute to a further development of the field for commercial applications.

Functional Magnetic Resonance Imaging (fMRI) has become a standard tool for mapping the working brain's activation patterns, both in health and in disease. It is an interdisciplinary field and crosses the borders of neuroscience, psychology, psychiatry, radiology, mathematics, physics and engineering. Developments in techniques, procedures and our understanding of this field are expanding rapidly. In this second edition of Introduction to Functional Magnetic Resonance Imaging, Richard Buxton – a leading authority on fMRI – provides an invaluable guide to how fMRI works, from introducing the basic ideas and principles to the underlying physics and physiology. He covers the relationship between fMRI and other imaging techniques and includes a guide to the statistical analysis of fMRI data. This book will be useful both to the experienced radiographer, and the clinician or researcher with no previous knowledge of the technology.