The Poetics of Service: Making in the Age of Experience

This article proposes a framework for service storytelling by analyzing its key elements with Aristotle's Poetics and synthesizing them using the temporal structure of Joseph Campbell's Hero's Journey. Poetics refer to the art of making that is concerned with the general pattern of human experience. We use this framework to study the four causes of storytelling: material cause, efficient cause, formal cause, and end cause. The Hero's Journey is a cyclical model that encompasses both an ordinary and a special world. We utilize this model to synthesize the four causes into a phasic flow, including deficiency, growth, personalization, and transformation.

A DES-SST Based Assessment of Hydrodynamic Performances of the Wetted and Cavitating PPTC Propeller

The paper describes an investigation of the hydrodynamic performances of a five-bladed controllable pitch propeller, whose geometry was provided by Schiffbau-Versuchsanstalt (SVA) Potsdam GmbH Model Basin. Both cavitating and non-cavitating regimes are numerically simulated for different advance ratio coefficients. The numerical approach is based on a finite volume approach in which closure to the turbulence is achieved through detached eddy simulation (DES). Propeller open water (POW) characteristics are computed, and the numerical solutions are validated through extensive comparisons with experimental data. In addition, the bi-phasic flow for the cavitating regime is simulated, for which comparisons with the cavitation sketches are performed to check the ability of the solver to estimate the cavitation extent. Grid convergence tests are performed for both working regimes together with validation and verification checks, not only to size the level of the numerical errors, but also to prove the robustness of the chosen numerical approach. Finally, a set of final remarks will conclude the present research.

Pericardial effusion and cardiac tamponade

Cardiac tamponade results from an increase in pericardial pressure that is sufficient to impede cardiac filling, resulting in high venous filling pressures, low cardiac output, and end-organ hypoperfusion. Most often this is due to the accumulation of a pericardial effusion though there are other possible causes. Patients usually present with features of cardiogenic shock, though some may initially be normotensive or hypertensive. Echocardiography can diagnose the presence of pericardial disease, especially pericardial effusion. Any associated haemodynamic sequelae can often be inferred by static and dynamic two-dimensional echocardiographic and Doppler measured intracardiac flow velocity abnormalities. These include atrial and ventricular wall inversion or collapse, and increased respiratory phasic flow velocities in tricuspid and mitral inflow. The concepts of transmural pressure, pericardial restraint, interventricular dependence, and cardiorespiratory interactions underpin the understanding and limitations of these echocardiographic findings. However, the impact of positive pressure ventilation remains problematic with respect to the interpretation of Doppler-derived intracardiac flow velocity variation. Echocardiography can also identify conditions that may confound the interpretation of accepted echocardiographic criteria (e.g. right ventricular hypertrophy, hypovolaemia, isolated chamber compression after cardiac surgery) and diagnose conditions that may mimic or exaggerate tamponade pathophysiology such as large compressive pleural effusion. Finally, echocardiographic criteria can aid stratification of the risk of tamponade in patients with pericardial effusion, and if necessary, guide percutaneous pericardiocentesis.

Mechanisms of myocardium-coronary vessel interaction

The mechanisms by which the contracting myocardium exerts extravascular forces (intramyocardial pressure, IMP) on coronary blood vessels and by which it affects the coronary flow remain incompletely understood. Several myocardium-vessel interaction (MVI) mechanisms have been proposed, but none can account for all the major flow features. In the present study, we hypothesized that only a specific combination of MVI mechanisms can account for all observed coronary flow features. Three basic interaction mechanisms (time-varying elasticity, myocardial shortening-induced intracellular pressure, and ventricular cavity-induced extracellular pressure) and their combinations were analyzed based on physical principles (conservation of mass and force equilibrium) in a realistic data-based vascular network. Mechanical properties of both vessel wall and myocardium were coupled through stress analysis to simulate the response of vessels to internal blood pressure and external (myocardial) mechanical loading. Predictions of transmural dynamic vascular pressure, diameter, and flow velocity were determined under each MVI mechanism and compared with reported data. The results show that none of the three basic mechanisms alone can account for the measured data. Only the combined effect of the cavity-induced extracellular pressure and the shortening-induced intramyocyte pressure provides good agreement with the majority of measurements. These findings have important implications for elucidating the physical basis of IMP and for understanding coronary phasic flow and coronary artery and microcirculatory disease.

Inflammation parallels severity of chronic venous insufficiency

Objective: This study was designed to assess the haemodynamic flow changes in patients with chronic venous insufficiency (CVI). Methods: Duplex scanning was used to evaluate prospectively the flow characteristics in the lower limb circulation and the number of enlarged lymph nodes in the groin of normal subjects, patients with CVI classes 2, 4, 5 and 6, and patients with acute cellulitis. Phasicity and continuous flow patterns were assessed in the venous system, while the arterial system was evaluated for tri-phasic flow, absence of flow reversal and absence of flow reversal with hyperaemic flow (increased peak systolic and end diastolic velocities). Additionally, the number and size of the groin lymph nodes around the saphenofemoral junction were recorded. Results: Patients with more severe class 4-6 CVI demonstrated an increased prevalence of abnormal flow patterns within the venous system of the leg compared to the normal phasic flow pattern seen in the absence of disease ( P < 0.001). Within the arterial system, significant changes were also observed in all three arteries studied in the legs of patients with class 4-6 CVI ( P < 0.001). For both the arterial and venous systems, no difference was noted between control limbs vs class 2 diseases or class 4-6 diseases vs cellulitis. With respect to the evaluation of inguinal lymph nodes, patients with class 2 disease were approximately four times as likely to have positive lymph nodes, and patients with more severe CVI were approximately 13 times as likely to have significant lymph nodes present. Conclusions: This study demonstrated that patients with more advanced stages of CVI had arterial and venous flow increases similar to those seen in an acute inflammatory condition such as cellulitis. These changes were most pronounced in the perforating and subcutaneous vessels in the leg.