2 resultados para modulus of continuity

em Duke University


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This thesis examines the discourse(s) of crisis in the Parsi diaspora. Treating crisis as a common variable, rather than a singular and unique event across various Parsi communities, I investigate the dimensions of crisis that bind separated Parsi communities in anxiety through a shared language, cultural experience, and historical memory. Turning first to India and then Hong Kong as my case studies, I analyze “crisis,” that has often been identified in terms of demographic decay or postcolonial decline, in the context of more subtle debates around racial purity and trust funds. Crisis, for the Parsi diaspora, while indicating a critical moment in the present, also serves to reveal the underlying and pre-existing socio-economic and cultural tensions in the communities. Relying largely on life-story interviews, online blogs and articles, and archival work, I portray the crisis not as a unique and sporadic event, but rather as one of continuity and complexity, albeit manifesting each time in different and unique guises, that continues to disrupt as well as unite the Parsi diaspora today.

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Our long-term goal is the detection and characterization of vulnerable plaque in the coronary arteries of the heart using intravascular ultrasound (IVUS) catheters. Vulnerable plaque, characterized by a thin fibrous cap and a soft, lipid-rich necrotic core is a precursor to heart attack and stroke. Early detection of such plaques may potentially alter the course of treatment of the patient to prevent ischemic events. We have previously described the characterization of carotid plaques using external linear arrays operating at 9 MHz. In addition, we previously modified circular array IVUS catheters by short-circuiting several neighboring elements to produce fixed beamwidths for intravascular hyperthermia applications. In this paper, we modified Volcano Visions 8.2 French, 9 MHz catheters and Volcano Platinum 3.5 French, 20 MHz catheters by short-circuiting portions of the array for acoustic radiation force impulse imaging (ARFI) applications. The catheters had an effective transmit aperture size of 2 mm and 1.5 mm, respectively. The catheters were connected to a Verasonics scanner and driven with pushing pulses of 180 V p-p to acquire ARFI data from a soft gel phantom with a Young's modulus of 2.9 kPa. The dynamic response of the tissue-mimicking material demonstrates a typical ARFI motion of 1 to 2 microns as the gel phantom displaces away and recovers back to its normal position. The hardware modifications applied to our IVUS catheters mimic potential beamforming modifications that could be implemented on IVUS scanners. Our results demonstrate that the generation of radiation force from IVUS catheters and the development of intravascular ARFI may be feasible.