Polymer-Functionalised Nanograins of Mg-Doped Amorphous Calcium Carbonate via a Flow-Chemistry Approach

Calcareous biominerals typically feature a hybrid nanogranular structure consisting of calcium carbonate nanograins coated with organic matrices. This nanogranular organisation has a beneficial effect on the functionality of these bioceramics. In this feasibility study, we successfully employed a flow-chemistry approach to precipitate Mg-doped amorphous calcium carbonate particles functionalized by negatively charged polyelectrolytes—either polyacrylates (PAA) or polystyrene sulfonate (PSS). We demonstrate that the rate of Mg incorporation and, thus, the ratio of the Mg dopant to calcium in the precipitated amorphous calcium carbonate (ACC), is flow rate dependent. In the case of the PAA-functionalized Mg-doped ACC, we further observed a weak flow rate dependence concerning the hydration state of the precipitate, which we attribute to incorporated PAA acting as a water sorbent; a behaviour which is not present in experiments with PSS and without a polymer. Thus, polymer-dependent phenomena can affect flow-chemistry approaches, that is, in syntheses of functionally graded materials by layer-deposition processes

Why football players may benefit from the ‘shadow of the transfer system’

Transfer restrictions have a long tradition in professional sports but came under heavy attack in recent years (e.g. Bosman ruling, Monti system). Based on a bargaining model with stochastic player productivity, we show that less restrictive transfer rules reallocate ex post bargaining power from players to clubs. This reallocation is efficient and in the ex ante self-interest of players. The right to charge transfer fees enables clubs to insure their players. The players, in turn, benefit by converting risky future income into riskless current income. Overall, player utility is higher under more than under less restrictive transfer rules