Optimization of Cooling Protocols for Hearts Destined for Transplantation

Design and analysis of conceptually different cooling systems for the human heart preservation are numerically investigated. A heart cooling container with required connections was designed for a normal size human heart. A three-dimensional, high resolution human heart geometric model obtained from CT-angio data was used for simulations. Nine different cooling designs are introduced in this research. The first cooling design (Case 1) used a cooling gelatin only outside of the heart. In the second cooling design (Case 2), the internal parts of the heart were cooled via pumping a cooling liquid inside both the heart’s pulmonary and systemic circulation systems. An unsteady conjugate heat transfer analysis is performed to simulate the temperature field variations within the heart during the cooling process. Case 3 simulated the currently used cooling method in which the coolant is stagnant. Case 4 was a combination of Case 1 and Case 2. A linear thermoelasticity analysis was performed to assess the stresses applied on the heart during the cooling process. In Cases 5 through 9, the coolant solution was used for both internal and external cooling. For external circulation in Case 5 and Case 6, two inlets and two outlets were designed on the walls of the cooling container. Case 5 used laminar flows for coolant circulations inside and outside of the heart. Effects of turbulent flow on cooling of the heart were studied in Case 6. In Case 7, an additional inlet was designed on the cooling container wall to create a jet impinging the hot region of the heart’s wall. Unsteady periodic inlet velocities were applied in Case 8 and Case 9. The average temperature of the heart in Case 5 was +5.0oC after 1500 s of cooling. Multi-objective constrained optimization was performed for Case 5. Inlet velocities for two internal and one external coolant circulations were the three design variables for optimization. Minimizing the average temperature of the heart, wall shear stress and total volumetric flow rates were the three objectives. The only constraint was to keep von Mises stress below the ultimate tensile stress of the heart’s tissue.

American Perceptions of British Regional Dialects

Sociolinguists have discussed problematic language ideologies, such as Standard Language Ideology (Lippi-Green 1997) extensively and social perceptions of Standard English in the U.S and U.K are well documented. However, most work in this area has focused on perceptions of dialects within national contexts. This study makes a novel contribution to the study of language attitudes, investigating perceptions of British regional dialects within the U.S. A survey was created to gauge perceptions of five British regional dialects (Liverpool, Leeds, Birmingham, Newcastle, London). 49 survey participants listened to audio clips of British regional dialect speakers and then completed a mapping activity, answered perception questions, and ranked each speaker on specific qualities. Results showed that speaker region had a significant effect on perception of almost all variables at a statistically significant rate, despite unfamiliarity with all but the London dialect. Results suggest that although participants are largely unfamiliar with varieties of English in England outside of London, they assessed them by recruiting pre-existing stereotypes about vernacular dialects.