Bolivia during the global crisis 1998-2004: towards a ‘macroeconomics of microfinance

The macroeconomic role of microfinance appears to have varied enormously between country cases, as notably exposed by the recent wave of macro-economic crises. For example, in Indonesia in the late 1990s microfinance appears to have played a notably counter-cyclical role, whereas in Bolivia, the main focus of this paper, its role was in most cases to intensify rather than restrain the crisis. We find part of the explanation for this in the behaviour of government towards microfinance (much more conciliatory towards defaulting debtors in the Bolivian case) and in the structure of demand (unfavourable, in Bolivia, to the distribution and service sector which is the main market for microenterprise). However, closer examination of the Bolivian case suggests that institutional design also played an important role. In particular, those organisations which provided savings, training and quasi-insurance services bucked the trend of rising default rates and falling lending through the crisis and did particularly well, whereas the new breed of consumer-credit microfinance organisations did particularly badly and in several cases went out of business. This experience suggests,in particular, that it may be appropriate to call into question the fashionable´ minimalist´ (credit-only) model of microfinance, as certainly in Bolivia it was principally the credit-plus institutions which proved more financially disciplined and more resilient to crisis

Growth in systems of vesicles and membranes

We present a theoretical study for the intermediate stages of the growth of membranes and vesicles in supersaturated solutions of amphiphilic molecules. The problem presents important differences with the growth of droplets in the classical theory of Lifshitz-Slyozov-Wagner, because the aggregates are extensive only in two dimensions, but still grow in a three dimensional bath. The balance between curvature and edge energy favours the nucleation of small planar membranes, but as they grow beyond a critical size they close themselves to form vesicles. We obtain a system of coupled equations describing the growth of planar membranes and vesicles, which is solved numerically for different initial conditions. Finally, the range of parameters relevant in experimental situations is discussed.Comment: 13 pages and 5 postscript figures. To appear in Phys. Rev

Uncertainties on the theoretical predictions for classical Cepheid pulsational quantities

The expected distribution of Cepheids within the instability strip is affected by several model inputs, reflecting upon the predicted Period-Luminosity relation. On the basis of new and updated sets of evolutionary and pulsational models, we quantitatively evaluated the effects on the theoretical PL relation of current uncertainties on the chemical abundances of Cepheids in the Large Magellanic Cloud and on several physical assumptions adopted in the evolutionary models. We analysed how the different factors influence the evolutionary and pulsational observables and the resulting PL relation. As a result, we found that present uncertainties on the most relevant H and He burning reaction rates do not influence in a relevant way the loop extension in temperature. On the contrary, current uncertainties on the LMC chemical composition significantly affect the loop extension and also reflect in the morphology of the instability strip; however their influence on the predicted pulsational parameters is negligible. We also discussed how overshooting and mass loss influence the ML relation and the pulsational parameters. In summary, the present uncertainties on the physical inputs adopted in the evolutionary codes and in the LMC chemical composition are negligible for the prediction of the main pulsational properties; the inclusion of overshooting in the previous H burning phase and/or of mass loss is expected to significantly change the resulting theoretical pulsational scenario for Cepheids, as well as the calibration of their distance scale. These systematic effects are expected to influence the theoretical Cepheid calibration of the secondary distance indicators and in turn the resulting evaluation of the Hubble constant.Comment: accepted for publication on A&