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Components Separation Technique Combined with a Double-Mesh Repair for Large Midline Incisional Hernia Repair

Background The surgical treatment of large midline incisional hernias remains a challenge. The aim of this report is to present the results of a new technique for large midline incisional hernia repair which combines the components- separation technique with a double-prostheticmesh repair. Methods The records of all consecutive patients who received a double-mesh combined with the componentsseparation technique for ventral hernia repair were reviewed. The clinical, surgical, and follow-up data were analyzed. Results Nine patients [3 women, 6 men; median age = 62 years (range = 26-77)] were included in the study. Median transverse defect size was 20 cm (range = 15-25). The median duration of hospital stay was 8 days (range = 5-17). Postoperative complications occurred in 66% (6/9). Follow-up [median = 13 months (range = 3-49)] showed no recurrent hernias, but one patient had a small hernia after a relaparotomy for colon carcinoma recurrence. The overall occurrence of wound infections was 44% (4/9). There was no mortality. Conclusion The components-separation technique in combination with a double-mesh has shown a low recurrence rate in the short-term follow-up. However, there is a considerable occurrence of postoperative wound infections. Long-term results of the hernia recurrence rate have to be awaited

Paradoxes and Mechanisms for Choice under Risk

Experiments on choice under risk typically involve multiple decisions by individual subjects. The choice of mechanism for selecting decision(s) for payoff is an essential design feature unless subjects isolate each one of the multiple decisions. We report treatments with different payoff mechanisms but the same decision tasks. The data show large differences across mechanisms in subjects’ revealed risk preferences, a clear violation of isolation. We illustrate the importance of these mechanism effects by identifying their implications for classical tests of theories of decision under risk. We discuss theoretical properties of commonly used mechanisms, and new mechanisms introduced herein, in order to clarify which mechanisms are theoretically incentive compatible for which theories. We identify behavioral properties of some mechanisms that can introduce bias in elicited risk preferences – from cross-task contamination – even when the mechanism used is theoretically incentive compatible. We explain that selection of a payoff mechanism is an important component of experimental design in many topic areas including social preferences, public goods, bargaining, and choice under uncertainty and ambiguity as well as experiments on decisions under risk

Accommodating stake effects under prospect theory

One of the stylized facts underlying prospect theory is a four-fold pattern of risk preferences. People have been shown to be risk seeking for small probability gains and large probability losses, while being risk averse for large probability gains and small probability losses. Another fourfold pattern of risk preferences over outcomes, postulated by Harry Markowitz in 1952, has received much less attention and is currently not integrated into prospect theory. In two experiments, we show that risk preferences may change over outcomes. While we find people to be risk seeking for small outcomes, this turns to risk neutrality and later risk aversion as stakes increase. We then show how a one-parameter logarithmic utility function fits such stake effects significantly better under prospect theory than the power or exponential functions mostly used when fitting prospect theory models. We further investigate the extent to which the use of ill-suited functional forms to represent utility may result in violations of prospect theory, and whether such violations disappear when using logarithmic utility

A Revealed Reference Point for Prospect Theory

Without an instrument to identify the reference point, prospect theory includes a degree of freedom that makes the model difficult to falsify. To address this issue, we propose a foundation for prospect theory that advances existing approaches with three innovations. First, the reference point is not known a priori; if preferences are reference-dependent, the reference point is revealed from behavior. Second, the key preference axiom is formulated as a consistency property for attitudes towards probabilities; it entails both a revealed preference test for reference-dependence and a tool suitable for empirical measurement. Third, minimal assumptions are imposed for outcomes, thereby extending the model to general settings. By incorporating these three features we deliver general foundations for prospect theory that show how reference points can be identified and how the model can be falsified