My choice, my actions: self-determination, not instrumental value of outcomes enhances outcome monitoring during learning.

Freedom of choice enhances our sense of agency. During goal-directed behavior, the freedom to choose between different response options increases the neural processing of positive and negative feedback, indicating enhanced outcome monitoring under conditions of high agency experience. However, it is unclear whether this enhancement is predominantly driven by an increased salience of self- compared to externally determined action outcomes or whether differences in the perceived instrumental value of outcomes contribute to outcome monitoring in goal-directed tasks.

Freedom of choice boosts midfrontal theta power during affective feedback processing of goal-directed actions.

Sense of agency, the feeling of being in control of one's actions and their effects, is particularly relevant during goal-directed actions. During feedback learning, action effects provide information about the best course of action to reinforce positive and prevent negative outcomes. However, it is unclear whether agency experience selectively affects the processing of negative or positive feedback during the performance of goal-directed actions.

Two-dimensional color-mapping of turbulent shear stress distribution downstream of two aortic bioprosthetic valves in vitro.

Since artificial heart valve related complications such as thrombus formation, hemolysis and calcification are considered related to flow disturbances caused by the inserted valve, a thorough hemodynamic characterization of heart valve prostheses is essential. In a pulsatile flow model, fluid velocities were measured one diameter downstream of a Hancock Porcine (HAPO) and a Ionescu-Shiley Pericardial Standard (ISPS) aortic valve. Hot-film anemometry (HFA) was used for velocity measurements at 41 points in the cross-sectional area of the ascending aorta.

Estimation of shear stress-related blood damage in heart valve prostheses--in vitro comparison of 25 aortic valves.

The hemodynamics of heart valve prostheses can be reproducibly investigated in vitro within circulatory mock loops. By measuring the downstream velocity and shear stress fields the shear stresses which are clinically responsible for damage to platelets and red blood cells can be determined. The mechanisms of damage and the effects of shear stresses on blood corpuscles were investigated by Wurzinger et al.

The geometry of the aortic root in health, at valve disease and after valve replacement.

For the design of aortic valve prostheses with a separation-free flow field and minimum pressure drop the geometry of the aortic root is of high importance, since an appropriate adjustment of the prostheses to the surrounding geometry could largely reduce the risk of thromboembolic complications. For the investigation of the geometry of the aortic root 604 angiographic films out of a total stock of 15,000 of the Medical Clinic I were evaluated. The film material was preclassified into five clinical categories according to the patient's data.

Estimation of turbulent shear stresses in pulsatile flow immediately downstream of two artificial aortic valves in vitro.

Measuring turbulent shear stresses is of major importance in artificial heart valve evaluation. Bi- and unidirectional fluid velocity measurements enable calculation of Reynolds shear stress [formula: see text] and Reynolds normal stress [formula: see text]. tau is important due to the relation to hemolysis and thrombus formation, but sigma is the only obtainable parameter in vivo.

Velocity and shear stress distribution downstream of mechanical heart valves in pulsatile flow.

Ten mechanical valves (TAD 27 mm): Starr-Edwards Silastic Ball, Björk-Shiley Standard, Björk-Shiley Concave-Convex, Björk-Shiley Monostrut, Hall-Kaster (Medtronic-Hall), OmniCarbon, Bicer Val, Sorin, Saint-Jude Medical and Hemex (Duromedics) are investigated in a comparative in vitro study. The velocity and turbulent shear stress profiles of the valves were determined by Laser Doppler anemometry in two different downstream axes within a model aortic root. Depending on the individual valve design, velocity peaks up to 1.

An in vitro study of prosthetic heart valve sound.

Patients with an implanted mechanical heart valve sometimes experience the closing sounds of the valve as disturbing. To study the generation of valve sounds in general, a pulse duplicator study was carried out, testing eight commonly used types of prosthetic valves in the aortic position. Pulse rate was set at 70 beats/min, stroke volume at 70 ml and mean 'aortic' pressure at 100 mmHg.

Three-dimensional visualization of velocity fields downstream of six mechanical aortic valves in a pulsatile flow model.

Velocity fields downstream of 27 mm Björk-Shiley Standard, Björk-Shiley Convex-Concave, Björk-Shiley Monostrut, Hall-Kaster (Medtronic-Hall), St. Jude Medical and Starr-Edwards Silastic Ball aortic valves were studied in a pulsatile mock circulation. Stroke volume was 70 cm3 and frequency 71 min-1 and 88 min-1.

Turbulent stress measurements downstream of six mechanical aortic valves in a pulsatile flow model.

In a pulsatile flow model aortic Björk-Shiley Standard, Convex-Concave and Monostrut valves were investigated together with the Hall-Kaster (Medtronic-Hall), St Jude Medical and Starr-Edwards Silastic Ball valve using hot-film anemometry. Three-dimensional visualization of average systolic Reynolds normal stresses (RNS) reflected the design of the valves. Mean average RNS were used for comparison of the fluid dynamic performance along with Velocity Energy Ratio (VER100) and Turbulence Energy Ratio (TER) as a relative turbulence intensity for pulsatile flow.

In vitro stress measurements in the vicinity of six mechanical aortic valves using hot-film anemometry in steady flow.

Based on hot-film anemometry, point velocity measurements in the total cross sectional area 1 and 2 diameters downstream of: Björk-Shiley Standard, Convex-Concave and Monostrut, Hall-Kaster (Medtronic-Hall), St. Jude Medical and Starr-Edwards Silastic Ball aortic valves were made. The spatial distribution of Reynolds Normal Stresses (RNS) was visualized three-dimensionally in order to point out where and to what extent the highest RNSs were found.

Three-dimensional visualization of axial velocity profiles downstream of six different mechanical aortic valve prostheses, measured with a hot-film anemometer in a steady state flow model.

Hot-film anemometry was used for in vitro steady-state measurements downstream of six mechanical aortic valve prostheses at flow rates 10, 20 and 30 l.min-1. Three-dimensional visualizations of velocity profiles at two downstream levels were made with the valves rotated 0 and 60 degrees in relation to the sinuses of valsalvae.