Decomposition driven interface evolution for layers of binary mixtures: {II}. Influence of convective transport on linear stability

We study the linear stability with respect to lateral perturbations of free surface films of polymer mixtures on solid substrates. The study focuses on the stability properties of the stratified and homogeneous steady film states studied in Part I [U. Thiele, S. Madruga and L. Frastia, Phys. Fluids 19, 122106 (2007)]. To this aim, the linearized bulk equations and boundary equations are solved using continuation techniques for several different cases of energetic bias at the surfaces, corresponding to linear and quadratic solutal Marangoni effects. For purely diffusive transport, an increase in film thickness either exponentially decreases the lateral instability or entirely stabilizes the film. Including convective transport leads to a further destabilization as compared to the purely diffusive case. In some cases the inclusion of convective transport and the related widening of the range of available film configurations (it is then able to change its surface profile) change the stability behavior qualitatively. We furthermore present results regarding the dependence of the instability on several other parameters, namely, the Reynolds number, the Surface tension number and the ratio of the typical velocities of convective and diffusive transport.Comment: Published in Physics of Fluic

The Vector Valued Quartile Operator

Certain vector-valued inequalities are shown to hold for a Walsh analog of the bilinear Hilbert transform. These extensions are phrased in terms of a recent notion of quartile type of a UMD (Unconditional Martingale Differences) Banach space X. Every known UMD Banach space has finite quartile type, and it was recently shown that the Walsh analog of Carleson's Theorem holds under a closely related assumption of finite tile type. For a Walsh model of the bilinear Hilbert transform however, the quartile type should be sufficiently close to that of a Hilbert space for our results to hold. A full set of inequalities is quantified in terms of quartile type.Comment: 32 pages, 5 figures, incorporates referee's report, to appear in Collect. Mat

Aggregating Performance Measures in Multi-Task Agencies

It has been argued in the multi-task agency literature that effort distortion can be mitigated by applying several performance measures in incentive contracts. This paper analyzes the efficient aggregation of multiple performance measures aimed at motivating non-distorted effort. It demonstrates that non-distorted effort can be induced by combining a sufficient quantity of informative performance measures. However, this is only optimal if the required aggregation concurrently maximizes the precision of the agent`s performance evaluation. This paper further illustrates how the optimal performance evaluation is affected by the ability of individual agents to perform relevant tasks.Multi-task agencies, effort distortion, performance measurement, incentives

Performance Measurement in Multi-Task Agencies

This paper analyzes a multi-task agency model with a risk-neutral and financially constrained agent. The agent's performance evaluation is thereby incongruent, i.e. it does not perfectly reflect the relative contribution of the agent's multi-dimensional effort to firm's profit. This paper elaborates on the improvement of the agent's performance evaluation through the costly acquisition of additional performance measures aimed at inducing the agent to implement a more efficient effort allocation across tasks. It contrasts two alternatives for the principal: (i) to centrally invest in the information acquisition; or (ii), to delegate this task to a supervisor. This paper demonstrates that the principal generally favors delegation for a sufficiently incongruent measurement of the agent's performance, and a centralized investment, otherwise.Multi-task agencies; performance measurement; distortion; congruity; limited liability; incentives

East Timor's transition to independence: Building up an economy from scratch

After the extensive destruction caused by the violence that followed the vote for independence on August 30th, 1999, the reconstruction of East Timor's infrastructure inevitably was the top priority. Supported by massive aid inflows, achievements in this area have been quite remarkable. As a result, East Timor's production capacity is likely to return to pre-crisis levels within a few years. The much more difficult task is to initiate and then sustain a long-run development process. This requires a whole bundle of measures of which only a part has been introduced up to now. At the macroeconomic level, three policy areas figure most prominently. First, to ensure a certain degree of macroeconomic stability as a prerequisite for growth, it is recommended to implement a combination of a Currency Board regime for the exchange rate and a sound fiscal policy based on a broad domestic revenue base. Second, permanent growth can only be achieved via the accumulation of physical and human capital. Secure property rights and a transparent investment code are among the essential conditions for physical capital formation. Human capital formation can be fostered by reallocating public resources towards basic services, which were seriously neglected under Indonesian rule. Third, a country like East Timor with its very small domestic market and its limited technical knowledge can reap large benefits from adopting an open trade and foreign investment regime. From a sectoral perspective, agriculture will remain the backbone of the economy in the foreseeable future. Incentives that lead to a more dynamic development of this sector are thus of particular importance, not only for growth but also for poverty alleviation as the vast majority of poor people live in rural areas. Such incentives include a market-oriented pricing policy, a stable and competitive exchange rate, access to credit, a basic rural infrastructure, and the provision of adequate research and extension facilities. A development strategy based on agriculture alone would, however, leave the economy vulnerable to shocks. Only a diversification of production will open the way to more robust growth. One significant step in this direction could be the exploitation of existing oil fields. If future oil revenues live up to expectations, the main policy challenge will be to avoid an overvaluation of the domestic currency (Dutch Disease). In the medium run, the establishment of labor-intensive industries could be another step towards a more diversified economy. Whether this option can be realized will depend to a large extent on East Timor's ability to import capital and know-how via foreign direct investment. Overall, if political stability prevails, the outlook for sustained progress seems better than in many other low-income countries, where the international community is less consistently engaged and where much stronger vested interests block reform efforts. At the moment, the most significant danger for long-term development in East Timor arises from the uncertainty of land and property rights, which is likely to hamper investment and agricultural development. Moreover, it has to be kept in mind that various important measures, such as investments in education, will take considerable time to materialize fully. --