Numerical Simulations for the Design of Novel Integrated Parallel Reception, Excitation, and Shimming (iPRES) Coil Arrays

Magnetic field inhomogeneity results in image artifacts including signal loss, image blurring and distortions, leading to decreased diagnostic accuracy. Conventional multi-coil (MC) shimming method employs both RF coils and shimming coils, whose mutual interference induces a tradeoff between RF signal-to-noise (SNR) ratio and shimming performance. To address this issue, RF coils were integrated with direct-current (DC) shim coils to shim field inhomogeneity while concurrently emitting and receiving RF signal without being blocked by the shim coils. The currents applied to the new coils, termed iPRES (integrated parallel reception, excitation and shimming), were optimized in the numerical simulation to improve the shimming performance. The objectives of this work is to offer a guideline for designing the optimal iPRES coil arrays to shim the abdomen.

In this thesis work, the main field () inhomogeneity was evaluated by root mean square error (RMSE). To investigate the shimming abilities of iPRES coil arrays, a set of the human abdomen MRI data was collected for the numerical simulations. Thereafter, different simplified iPRES(N) coil arrays were numerically modeled, including a 1-channel iPRES coil and 8-channel iPRES coil arrays. For 8-channel iPRES coil arrays, each RF coil was split into smaller DC loops in the x, y and z direction to provide extra shimming freedom. Additionally, the number of DC loops in a RF coil was increased from 1 to 5 to find the optimal divisions in z direction. Furthermore, switches were numerically implemented into iPRES coils to reduce the number of power supplies while still providing similar shimming performance with equivalent iPRES coil arrays.

The optimizations demonstrate that the shimming ability of an iPRES coil array increases with number of DC loops per RF coil. Furthermore, the z direction divisions tend to be more effective in reducing field inhomogeneity than the x and y divisions. Moreover, the shimming performance of an iPRES coil array gradually reach to a saturation level when the number of DC loops per RF coil is large enough. Finally, when switches were numerically implemented in the iPRES(4) coil array, the number of power supplies can be reduced from 32 to 8 while keeping the shimming performance similar to iPRES(3) and better than iPRES(1). This thesis work offers a guidance for the designs of iPRES coil arrays.

“Newter”-ing the Nicodemite: Reception of John Calvin’s Quatre sermons (1552) in Sixteenth-Century England

This dissertation examines the publication history of a single work: John Calvin’s 1552 Quatre sermons de M. Jehan Calvin traictans des matières fort utiles pour nostre temps, avec briefve exposition du Pseaume lxxxvii. Overlooked for both its contribution to Calvin’s wider corpus and its surprising popularity in English translation, successive editions of Quatre sermons display how Calvin’s argument against the behavior of so-called “Nicodemites” was adapted to various purposes unrelated to refuting religious dissimulation. The present study contributes to research in Calvin’s anti-Nicodemism by highlighting the fruitfulness of focusing on a discrete work and its reception. Borrowing a term (“Newter”) from John Field’s 1579 translation of Quatre sermons, this study’s title adumbrates its argument. English translators capitalized on the intrinsic malleability of a nameless and faceless opponent, the Nicodemite, and the adaptability of Quatre sermons’ genre as a collection of sermons to reshape—or, if you will, disfigure—both Calvin’s original foes and his case against them to advance various new agenda. Yet they were not the first to use the reformer’s sermons this way. They could have learned this from Calvin himself.

My examination of Quatre sermons opens by setting the work in the context of Calvin’s other writings and his political situation (Introduction, chapters one and two). Calvin’s unrelenting literary assault on French Nicodemism over three decades has long been recognized for its consistency and negativity. Yet scholars have tended to neglect how Calvin’s polemic against religious dissimulation could exhibit significant flexibility according to the needs of his context. Whereas Calvin’s preface promises simply to revisit his previous argument against participation in the Mass, his approach to Nicodemism in Quatre sermons seems adapted to accomplish goals beyond decrying false worship, offering a carefully-crafted apology for Calvin’s pastoral authority directed at his political situation. Repeatedly emphasizing God’s purpose to bless his children through the ministry of a rightly-ordered church, Quatre sermons marks a shift in Calvin’s anti-Nicodemite rhetoric away from purely negative critique, stressing instead God’s provision of spiritual nurture via political exile. Read in light of Calvin’s 1552 context, two audiences emerge: sermons ostensibly targeting believers in France who hid their faith also appear especially designed to silence Calvin’s foes in Geneva.

The remainder of the study examines the reception of Quatre sermons in the rapidly shifting religious and social contexts of Marian and Elizabethan England, where it appeared in more unique editions than any of Calvin’s writings besides the Institutio and the reformer’s 1542/45 Genevan Catechism. Calvin’s anti-Nicodemism has not been examined for its distinct contribution to the overall English reception of his thought. Five English versions of Quatre sermons appeared between 1553 and 1584—four of these under a Protestant queen, a situation quite different from the French context Calvin addressed. After situating Calvin’s position within the currents of Tudor Protestant anti-Nicodemism (chapter three), I place each of the five translations in its particular context, investigating prefaces, appendices, marginalia, and translation methods to discover how and why individuals used Quatre sermons (chapters four to six). Like Calvin in 1552, those who brought Quatre sermons to English readers were not primarily concerned with Nicodemism. Rather, the malleability of Calvin’s Nicodemite as polemical opponent and the flexibility of Quatre sermons as a sequence of discrete, interrelated parts made it popular with those eager to press Calvin into the service of a variety of diverse goals he could not have imagined, including turning his anti-Nicodemism against fellow members of the English church.

Rhetoric, Roman Values, and the Fall of the Republic in Cicero's Reception of Plato

This dissertation seeks to identify what makes Cicero’s approach to politics unique. The author's methodology is to turn to Cicero’s unique interpretation of Plato as the crux of what made his thinking neither Stoic nor Aristotelian nor even Platonic (at least, in the usual sense of the word) but Ciceronian. As the author demonstrates in his reading of Cicero’s correspondences and dialogues during the downward spiral of a decade that ended in the fall of the Republic (that is, from Cicero’s return from exile in 57 BC to Caesar’s crossing of the Rubicon in 49 BC), it is through Cicero's reading of Plato that the former develops his characteristically Ciceronian approach to politics—that is, his appreciation for the tension between the political ideal on the one hand and the reality of human nature on the other as well as the need for rhetoric to fuse a practicable compromise between the two. This triangulation of political ideal, human nature, and rhetoric is developed by Cicero through his dialogues "de Oratore," "de Re publica," and "de Legibus."