Mechanotransduction and growth factor signalling to engineer cellular microenvironments

Engineering cellular microenvironments involves biochemical factors, the extracellular matrix (ECM) and the interaction with neighbouring cells. This progress report provides a critical overview of key studies that incorporate growth factor (GF) signalling and mechanotransduction into the design of advanced microenvironments. Materials systems have been developed for surface-bound presentation of GFs, either covalently tethered or sequestered through physico-chemical affinity to the matrix, as an alternative to soluble GFs. Furthermore, some materials contain both GF and integrin binding regions and thereby enable synergistic signalling between the two. Mechanotransduction refers to the ability of the cells to sense physical properties of the ECM and to transduce them into biochemical signals. Various aspects of the physics of the ECM, i.e. stiffness, geometry and ligand spacing, as well as time-dependent properties, such as matrix stiffening, degradability, viscoelasticity, surface mobility as well as spatial patterns and gradients of physical cues are discussed. To conclude, various examples illustrate the potential for cooperative signalling of growth factors and the physical properties of the microenvironment for potential applications in regenerative medicine, cancer research and drug testing

Employment Protection Legislation and Plant-Level Productivity in India

Using plant-level data from the Annual Survey of Industries (ASI) for the fiscal years from 1998-99 through 2007-08, this study provides plant-level cross-state/time-series evidence of the impact of employment protection legislation (EPL) on total factor productivity (TFP) and labor productivity in India. Identification of the effect of EPL follows from a difference-in-differences estimator inspired by Rajan and Zingales (1998) that takes advantage of the state-level variation in labor regulation and heterogeneous industry characteristics. The fundamental identification assumption is that EPL is more likely to restrict firms operating in industries with higher labor intensity and/or higher sales volatility. Our results show that firms in labor intensive or more volatile industries benefited the most from labor reforms in their states. Our point estimates indicate that, on average, firms in labor intensive industries and in flexible labor markets have TFP residuals 14% higher than those registered for their counterparts in states with more stringent labor laws. However, no important differences are identified among plants in industries with low labor intensity when comparing states with high and low levels of EPL reform. Similarly, the TFP of plants in volatile industries and in states that experienced more pro-employer reforms is 11% higher than that of firms in volatile industries and in more restrictive states; however, the TFP residuals of plants in industries with low labor intensity are 11% lower in high EPL reform states than in states with lower levels of EPL reform. In sum, the evidence presented here suggests that the high labor costs and rigidities imposed through Indian federal labor laws are lessened by labor market reforms at the state level.

Concentration of Vacancies at Metal Oxide Surfaces: Case Study of MgO (100)

We investigate effects of doping on formation energy and concentration of oxygen vacancies at a metal oxide surface, using MgO (100) as an example. Our approach employs density-functional theory, where the performance of the exchange-correlation functional is carefully analyzed, and the functional is chosen according to a fundamental condition on DFT ionization energies. The approach is further validated by CCSD(T) calculations for embedded clusters. We demonstrate that the concentration of oxygen vacancies at a doped oxide surface is largely determined by formation of a macroscopically extended space charge region

Three-particle States in Nonrelativistic Four-fermion Model

On a nonrelativistic contact four-fermion model we have shown that the simple Lambda-cut-off prescription together with definite fine-tuning of the Lambda dependency of "bare"quantities lead to self-adjoint semi-bounded Hamiltonian in one-, two- and three-particle sectors. The fixed self-adjoint extension and exact solutions in two-particle sector completely define three-particle problem. The renormalized Faddeev equations for the bound states with Fredholm properties are obtained and analyzed.Comment: 9 pages, LaTex, no figure