Two-equation turbulence modeling of pulsatile flow in a stenosed tube.

The study of pulsatile flow in stenosed vessels is of particular importance because of its significance in relation to blood flow in human pathophysiology. To date, however, there have been few comprehensive publications detailing systematic numerical simulations of turbulent pulsatile flow through stenotic tubes evaluated against comparable experiments. In this paper, two-equation turbulence modeling has been explored for sinusoidally pulsatile flow in 75% and 90% area reduction stenosed vessels, which undergoes a transition from laminar to turbulent flow as well as relaminarization. Wilcox's standard k-omega model and a transitional variant of the same model are employed for the numerical simulations. Steady flow through the stenosed tubes was considered first to establish the grid resolution and the correct inlet conditions on the basis of comprehensive comparisons of the detailed velocity and turbulence fields to experimental data. Inlet conditions based on Womersley flow were imposed at the inlet for all pulsatile cases and the results were compared to experimental data from the literature. In general, the transitional version of the k-omega model is shown to give a better overall representation of both steady and pulsatile flow. The standard model consistently over predicts turbulence at and downstream of the stenosis, which leads to premature recovery of the flow. While the transitional model often under-predicts the magnitude of the turbulence, the trends are well-described and the velocity field is superior to that predicted using the standard model. On the basis of this study, there appears to be some promise for simulating physiological pulsatile flows using a relatively simple two-equation turbulence model.

Development and validation of the Conflict in Adolescent Dating Relationships Inventory.

Four studies examined the Conflict in Adolescent Dating Relationships Inventory (CADRI), a measure of abusive behavior among adolescent dating partners. Exploratory factor analysis was used to refine items based on high school participants with dating experience (N = 393; 49% female). Confirmatory factor analysis was used to derive and cross-validate the factor structure with participants from 10 high schools (N = 1,019, 55% female; ages 14-16). The model structure fit for all grades and both sexes, with physical abuse, verbal abuse, and threatening behavior most representative of the underlying "abuse" factor. In Studies 3 and 4, the second-order abuse factor showed acceptable test-retest reliability, partner agreement, and correlation (significant for males only) between observer ratings of dating partners' interactions and youths' CADRI scores. Results support the CADRI as a measure of abusive behavior in adolescent dating relationships.

The influence of early and recent life stress on severity of depression.

The influence of life stressors arising in different life stages on the severity of depression was examined in a sample of 123 depressive women, ranging from 22 to 64 years of age. In an interview, information was obtained on the incidence of certain life stressors in early and recent periods. The severity of depression was measured using the Beck Depression Inventory. The results indicate that experience of physical or sexual abuse before the age of 19 is strongly associated with severity of depression. Also, most women suffering from severe depression had previous and recent difficulties in their relationships with parents, partner or others and recent problems with self-esteem. A hypothetical model for predicting the severity of depression was evaluated. Difficulties experienced one year prior to assessment appeared to directly predict severity of depression. Difficulties with social relationships whose origin could be traced back to early periods and that had a continuing effect throughout life were found to be crucial factors for indirectly predicting the severity of depression.

Patient "no-shows"--a costly problem.

The cost of patients' failure to keep scheduled appointments can be significant. This article examines two methods of reducing this problem and evaluates their effectiveness: the reminder phone call and computer-generated reminder letters. The varying success rates of these two methods are discussed as they relate to several areas of the Radiology Department at the University of Texas Medical Branch at Galveston, Texas.

Patient "no-shows"--are we scheduling failure?

Radiology departments may inadvertently be contributing to their patient "no show" problems. This article continues the analysis of patients' failure to keep scheduled radiology appointments first described in "Patient 'No Shows'--A Costly Problem" (Radiology Management, 11:1) and illustrates "no-show" patterns in three examination groups in the Department of Radiology at the University of Texas Medical Branch, Galveston, Texas. The study shows a strong link between patients' failure to keep appointments and the length of time between scheduling and the performance of the examination.