Soft Matrices Suppress Cooperative Behaviors among Receptor-Ligand Bonds in Cell Adhesion

The fact that biological tissues are stable over prolonged periods of time while individual receptor-ligand bonds only have limited lifetime underscores the critical importance of cooperative behaviors of multiple molecular bonds, in particular the competition between the rate of rupture of closed bonds (death rate) and the rate of rebinding of open bonds (birth rate) in a bond cluster. We have recently shown that soft matrices can greatly increase the death rate in a bond cluster by inducing severe stress concentration near the adhesion edges. In the present paper, we report a more striking effect that, irrespective of stress concentration, soft matrices also suppress the birth rate in a bond cluster by increasing the local separation distance between open bonds. This is shown by theoretical analysis as well as Monte Carlo simulations based on a stochastic-elasticity model in which stochastic descriptions of molecular bonds and elastic descriptions of interfacial force/separation are unified in a single modeling framework. Our findings not only are important for understanding the role of elastic matrices in cell adhesion, but also have general implications on adhesion between soft materials

Executive remuneration in the EU: comparative law and practice

Executive pay practices are currently a "cause celebre" of corporate governance in the media, among regulators, in the marketplace, and in academia, in the US, the UK, and Europe. The purpose of this paper is to examine the approaches taken across Europe to the regulation of executive pay practices in listed companies. The outstanding feature of the regulation of executive pay across Europe is the extent to which it reflects the interconnection between pay and corporate governance. This link is expanded on in Part B with respect to the different rules found across European legal systems and how they address/prioritize the concerns which executive pay potentially raises. The role of public regulation is relatively important for disclosure of executive pay, while best practices and private codes generally have some impact on the way in which executive compensation is set for listed companies. On the whole, there is some convergence in continental Europe towards the Anglo-American model. The merits of full disclosure of executive remuneration are increasingly acknowledged in corporate governance codes and reports, while the use of remuneration committees is on the rise in the Continent. The research data on reported pay practices for 2001 among FTSE Eurotop300 companies reveal a reliance on performance-based pay generally and a somewhat variable adoption of share options programmes and other equity-based incentive contracts, which are generating difficulties in dispersed ownership systems. The executive pay problem may therefore be a particular cost of dispersed ownership, and the particular legal and policy responses, which are widely debated a specific feature of Anglo-American corporate governance. Nonetheless, the faultline between both systems, which is evident from the different approaches European states have taken, calls for particular care in the adoption of pan-European reforms but also in the transplanting of reforms based on the Anglo-American experience