Punctuated equilibrium in a non-linear system of action

Coleman's equilibrium model of social development, the Linear System of Action, is extended to cover the dynamics of societal transitions. The model implemented has the characteristics of a dissipative system. A variation and selection algorithm favoring the retention of relatively dependent actors forces the system away from equilibrium, while exchange of control, according to Coleman the driving force behind social action, accounts for dissipation, pulling the social system back to equilibrium. This Non-linear System of Action self-organizes into a critical state, as confirmed by the robust power law distribution of exchange of control for a wide range of model sizes. Related punctuated equilibrium dynamics and structural change are of special interest, as these are closely connected to hypotheses on social dynamics developed in the literature on societal transitions

Complex dynamics in a transactional model of societal transitions

Article accepted for publucation in InterJournal 2006Transitions are structural innovations of societal systems in reaction to wicked problems threatening development. In this paper we develop a transactional model of transitions based on Coleman’s linear system of action. The model implemented has the characteristics of a dissipative system. A variation and selection algorithm favoring the selection of relatively dependent actors into the social system forces the system away from equilibrium. Exchange of control, according to Coleman the driving force behind social action, accounts for dissipation and brings the social system back to equilibrium. We expect the Transactional Model of Transitions to show complex dynamics. Power law behavior and punctuated equilibrium are of special interest, as these are closely connected to hypotheses on social dynamics developed in the literature on societal transitions and system innovations. We present simulation results for various variation and selection procedures, interpret their meaning in the light of societal transitions and system innovations and discuss their conformity with actual social processes. Our results show that the Transactional Model of Transitions indeed shows complex dynamics, mirrors some of the characteristics of transition dynamics and is promising for further research on Transition Management. We did not yet find conclusive evidence of evolution to the edge of chaos, self-organized criticality and/or power law behavior

Cardiac catheterization under echocardiographic control in a pregnant woman

A 22 year old woman had signs of rheumatic mitral and aortic valve disease early in pregnancy. Cardiac catheterization was performed during her third month of pregnancy under two-dimensional echocardiographic control without the use of ionizing radiation. Severe mitral stenosis with mild aortic stenosis was found. Five cubic centimeters of 5 percent dextrose in water were injected by hand to obtain left ventriculograms and supravalvular aortograms of sufficient quality to diagnose valvular regurgitation. The use of "echo-catheterization" may have significant advantages in selected clinical situations

Transthoracic three-dimensional echocardiography in adult patients with congenital heart disease

Objectives: This study sought to assess both the feasibility and potential role of transthoracic three-dimensional echocardiography for the evaluation of adult patients with congenital heart disease. Background: The unrestricted views with depth perception provided by three-dimensional echocardiography with dynamic volume-rendered display may enhance visualization of cardiac structures and detection of abnormalities in patients with congenital heart defects. Methods: We studied 33 patients with various heart defects (mitral valve anomalies in 9, aortic valve anomalies in 5, subaortic membrane in 5, ventricular septal defect in 4, transposition of the great arteries in 3, tetralogy of Fallot in 2, other defects in 5). Cross-sectional images of the specific region of interest were acquired from either the parasternal or apical window with the rotational technique (2° interval with electrocardiographic and respiratory gating) and postprocessed for resampling in cubic format. From these three-dimensional data sets a multitude of cut planes were selected, presented in volume-rendered dynamic display and analyzed by two observers for comparison with standard two-dimensional images to assess their additional information. Results: Three-dimensional reconstruction was possible in all patients. Structures of interest were evaluated from unusual viewpoints, providing both cardiologists and surgeons with immediate feedback. When compared with standard two-dimensional images, additional information was provided for 12 patients (36%). The mitral valve, aortoseptal continuity and interatrial septum were the structures for which three-dimensional echocardiography was most useful. Conclusions: Transthoracic three-dimensional echocardiography is feasible and facilitates spatial recognition of the intracardiac anatomy in a significant proportion of patients and enhances diagnostic confidence of complex congenital heart disease