Mechanical Analysis of Polycarbonate/Polysiloxane Block Copolymers and Blends

Polydimethylsiloxane (PDMS) can be used to react with polycarbonate (PC) to generate PC-PDMS multiblock copolymers and PC/PC-PDMS-PC triblock blends to overcome the notch sensitivity of PC while maintaining its transparency. It was found in this study that PDMS can act as a rubber particle to absorb energy and promote multicrazing. As a result, the incorporation of PDMS can increase PC's toughness. Meanwhile, high optical clarity can be observed even at 62 wt% PDMS in the multiblock copolymers with uniform morphology. However, PC/PC-PDMS-PC triblock blends damage PC's transparency and become opaque due to the phase separation. Furthermore, compared to compression molding, injection molding introduces shear due to the decrease of the area at the nozzle, which leads to the orientation of polymer chains and, subsequently, better properties of specimens

Illness Experiences and Racial Identity in Sickness: a Memoir

In the Iranian American writer Porochista Khakpour’s powerful memoir Sick: a Memoir, Khakpour’s racial identity plays an important part in her illness experiences. Different from traditional American autopathographies, Sick mixes Khakpour’s illness experiences and autobiographical experiences. The memoir is not only about the mysterious Lyme disease and its symptoms but about the feeling of alienation and homelessness and the trauma of being an outsider in America. Khakpour’s experiences of living with Lyme becomes a trope of her experiences of living in America as an racial other. In combining illness and racial experiences, Sick enriches the genre of autopathography which is mainly white and middle-class and provides a new perspective to observe illness in a multi-cultural context

Puritan Jeremiad and American Myth: Sacvan Bercovitch’s Study in the Puritan Rhetoric and Imagination

Sacvan Bercovitch is the most influential and prominent Americanist and literary and cultural critic after Perry Miller. In a close textual reading of classic Puritan texts, Bercovitch concludes that the major legacy of Puritan New England is not religious, or moral, or institutional, but in the realm of rhetoric. Rhetoric for Bercovitch is more than verbal ornamentation. It is a set of aesthetic devices that constitute a particular structure of perception, a particular pattern of thought and mode of expression. Bercovitch tries to grasp the imaginative structure and symbolic pattern of American thought underlying in rhetorical devices and believes that the Puritan rhetoric is the primary force that drives and shapes the American imagination. Bercovitch analyzes the Puritan jeremiad, a particular Puritan literary mode, to be a case of his study in the Puritan rhetoric. By the rhetorical device of typology, the Puritans identified America as the new promised land foretold in Scripture. Their migration to New England was a flight from another Babylon or Egypt; their conflicts with the Indians were foreshadowed by Joshua’s conquest of Cannan; and New England would in due time be the site of new Jerusalem. Considered as “a kind of imperialism by interpretation” by Bercovtich, the Puritan typology enables the immigrants to usurp the very meaning of the story of the ancient Jews. The Puritan jeremiad survives the decline of Puritanism and persists throughout the 18th and 19th century in all forms of the literature. It bespeaks an “ideological consensus” and helps sustain the myth of America through three hundred years of turbulence and change in American history

Electrical impedance spectroscopy-based nondestructive testing for imaging defects in concrete structures

An electrical impedance spectroscopy-based nondestructive testing (NDT) method is proposed to image both cracks and reinforcing bars in concrete structures. The method utilizes the frequency-dependent behavior of thin insulating cracks: low-frequency electrical currents are blocked by insulating cracks, whereas high-frequency currents can pass through the conducting bars without being blocked by thin cracks. Rigorous mathematical analysis relates the geometric structures of the cracks and bars to the frequency-dependent Neumann-to-Dirichlet data. Various numerical simulations support the feasibility of the proposed method