Surface thermodynamics of osteoblasts: relation between hydrophobicity and bone active biomaterials

Surface tensions of rat calvaria osteoblasts were determined by measuring the cell–liquid–vapor contact angle with sessile drops of water on the cell monolayer. The results indicated the hydrophobic character of osteoblastic cells with a contact angle of 26.89° (0.29°). This value could explain the ability of osteoblasts to specifically attach onto hydrophobic surfaces like titanium or hydroxyapatite. The first cellular step of bone healing requires the presence of osteoblasts and their adhesion to biomaterial surfaces is the crucial phase of the osteointegration process. The presence of a monolayer of a newly discovered hydrophobic bacterial exopolysaccharide on coverglass slides appeared to strongly encourage adhesion of osteoblastic cells. In that, providing surfaces with this hydrophobic material induced a selective adsorption of osteoblast cells and might enhance osteointegration.     

Use of conduction models in the study of “low temperature” carbons

The frequency (10-10⁸ Hz) and temperature (100–400 K) dependence of the ac conductivity of anthracene carbons is explained within two theoretical models. The properties of carbon heat treated up to 600°C are correctly explained by means of a model where the current flow is due to electron hops over a potential barrier between localized sites.The conductivity of the carbon heat-treated up to 650°C is interpreted using a theory proposed by Mott and Davis. The spatial densities of states are determined in both cases.     

Frequency-dependent protonic conduction and high resolution 1H NMR of KDP around 298 K

Measurements of the dc conductivity, polarisation conductivity, and high resolution ¹H NMR have been carried out on KDP (KH₂PO₄) around 298 K. Comparisons between the different results are reported and an interpretation is proposed in order to clarify the protonic motion within the bulk material.     

Study of hydrated Na-faujasite zeolites by thermally stimulated currents technique

The dielectric relaxation of the two faujasite zeolites NaX and NaY as a function of their hydration state, has been studied. The technique of thermally stimulated current (TSC) has been used. Two distinct processes of cationic relaxation have been identified. They correspond to local hops of cations of sites III' and II of the supercage. Analysis of the observed TSC peaks has been performed by the thermal windowing method (TSC/RMA). The activation energies of the two relaxations have been determined as a function of the adsorbed water molecules. The influence of the water molecules on the movement of the cations in the considered sites was explained. Paper presented at the 3rd Euroconference on Solid State Ionics, Teulada, Sardinia, Italy, Sept. 15–22, 1996     

Tests for specific nonparametric relations between two distribution functions with applications

Let (X,Y) be a random vector and let G and H be the marginal distributions of X and Y, respectively. In this paper, we propose two tests, one of Kolmogorov‐Smirnov type and the other of Wilcoxon type, for the null hypothesis Ψ(G) = H against the alternative Ψ(G) < H, where Ψ() is a function such that Ψ(G) is a distribution function. The tests are based on the empirical distribution functions of the observations on X and Y, which are dependent. We obtain their asymptotic null distributions. A suspected relationship between the distribution functions of two dependent outcomes can be specified as a hypothesis to be tested in examples like the load sharing models, record values, and auction bidding models. As an application, we consider in detail the problem of testing the effect of load sharing in two component parallel systems.