Parametric geometry modeling of the carotid artery bifurcation: the need for new flow metrics
Although well established correlations now exist between regions of reversed flow and sites of arterial disease [1], little evidence is available for methodologies that systematically compare how geometrical differences affect such relationships. Drawing on techniques developed in aerodynamic design, a parametric tuning-fork geometry model of the carotid artery bifurcation - based on the glass models described in [2] - is here employed to investigate the impact of bulb size and the angle of the internal carotid artery (ICA) on time-averaged shear stress. Since we seek to directly compare the effect of varying these geometric parameters, we demonstrate the need for a new metric, the integral of negative mean shear stress (INMSS), to highlight the stronger correlation between the extent of reversed flow and bulb width relative to the angle of the ICA.
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The Implicit Influence of Idioms
Communicators use analogies in strategic discourse to invite inferences about ambiguous situations that reinforce their own construals of these situations. For example, in the short-lived political debate preceding the U.S.’s entry into the 1991 Persian Gulf conflict, supporters of our involvement likened it to WW II (a war most Americans believe we “won”), whereas opponents called attention to its similarities with the Vietnam War (which many consider a “defeat”). Several years earlier, Gilovich (1981) found that political science students were far more likely to recommend intervention in a hypothetical foreign policy crisis when irrelevant features of the scenario (e.g., the location used for press briefings) called to mind WW II (Winston Churchill Hall) rather than Vietnam (e.g., Dean Rusk Hall). The presence of analogical cues did not, however, lead students to judge the scenario as being more similar to one of the previous conflicts than the other. Subsequent reasoning research has also found that seemingly trivial cues can compel people to unwittingly employ historical analogies in their judgments and decisions. The reported research explores idioms’ potential as an unobtrusive means of introducing analogies into decision scenarios. Many of the conventional figurative expressions we use to describe abstract concepts have a common analogical derivation (e.g., Lakoff & Johnson, 1980). For example, the idioms we use to describe corporate organizations reflect analogies to families (e.g., parent company), sports (sales team), ecological systems (e.g., business climate), and other source domains. In business correspondence, corporate executives tend to favor organizational idioms derived from analogies that cohere with their own beliefs about management (Morgan, 1997). How might this preference influence their correspondents’ perceptions of the firm? Although there is no evidence that derivational analogies are automatically activated during idiom comprehension (McGlone, 2001), people are able to recognize analogical consistency among idioms (Nayak & Gibbs, 1990). This recognition indicates that the underlying analogy is available in memory and can be accessed to participate in post-comprehension mental processes. Analogical access of this sort does not, however, guarantee that people have introspective access to its impact on their judgments (Nisbett & Wilson, 1977). Thus the analogical consistency between idioms in a problem and response option may lead people to favor the option, but nevertheless overlook the unremarkable presence of cliche expressions in the scenario as a factor influencing their choice. To investigate this possibility, we asked 126 undergraduates at The College of New Jersey to read a brief description of an organizational decision scenario, choose one of two response options provided, and explain the reasons for their choice. Participants read one of 3 versions of the scenario: one containing family-derived idioms for organization, a second containing sports-derived idioms, or a neutral control. Scenario versions were crossed with family, sports, and control versions of each response option in a factorial design. The results indicated that participants reliably preferred response options that were analogically consistent with the scenario, relative to neutral or inconsistent alternatives. However, fewer than 8% of participants who made consistent choices referred to the idioms or their derivational analogy when explaining their choices, instead referring to scenario attributes that did not differ across scenario or response option versions. These results suggest that idioms can exert an implicit influence on decision-making, compelling people to apply analogical knowledge without subjective awareness.