Institutional Change and Product Composition: Does the Initial Quality of Institutions Matter?

We argue that the quality of institutions that enforce contracts and protect property rights influences the costs of producing high-value added (complex) versus low-value added (simple) products. Since data is hardly available for domestic transactions, we generate predictions about the relationship between the quality of institutions and product composition with an international trade model and use a rich international trade data set for empirical tests. We find that improvements in institutional quality increase the share and volume of a country's complex product exports. However, the initial quality of institutions is important, since in countries with the least developed institutions, the share of complex products in exports is generally small and, institutional reform has almost no influence on simple product exports. These findings cast doubts on the efficacy of institutional reform in countries with underdeveloped institutions.Complex and simple products, volume effect of institutions, compositional effect of institutions

Prediction and near-field observation of skull-guided acoustic waves

Ultrasound waves propagating in water or soft biological tissue are strongly reflected when encountering the skull, which limits the use of ultrasound-based techniques in transcranial imaging and therapeutic applications. Current knowledge on the acoustic properties of the cranial bone is restricted to far-field observations, leaving its near-field properties unexplored. We report on the existence of skull-guided acoustic waves, which was herein confirmed by near-field measurements of optoacoustically-induced responses in ex-vivo murine skulls immersed in water. Dispersion of the guided waves was found to reasonably agree with the prediction of a multilayered flat plate model. It is generally anticipated that our findings may facilitate and broaden the application of ultrasound-mediated techniques in brain diagnostics and therapy.Comment: 7 pages, 5 figures, appendix with 2 figure

On the Γ\Gamma-limit for a non-uniformly bounded sequence of two phase metric functionals

In this study we consider the $\Gamma$-limit of a highly oscillatory Riemannian metric length functional as its period tends to 0. The metric coefficient takes values in either $\{1,\infty\}$ or $\{1,\beta \varepsilon^{-p}\}$ where $\beta,\varepsilon > 0$ and $p \in (0,\infty)$. We find that for a large class of metrics, in particular those metrics whose surface of discontinuity forms a differentiable manifold, the $\Gamma$-limit exists, as in the uniformly bounded case. However, when one attempts to determine the $\Gamma$-limit for the corresponding boundary value problem, the existence of the $\Gamma$-limit depends on the value of $p$. Specifically, we show that the power $p=1$ is critical in that the $\Gamma$-limit exists for $p < 1$, whereas it ceases to exist for $p \geq 1$. The results here have applications in both nonlinear optics and the effective description of a Hamiltonian particle in a discontinuous potential.Comment: 31 pages, 1 figure. Submitte

Food Stamps as Money and Income

Food Stamps represent nearly $11 billion of personal income in the United States. The coupons that are issued to represent the purchasing power available to recipients are also reserves for the commercial banking system.This study asks how closely these coupons are substitutable for what is usually considered as money, and how well Food Stamps function as a fiscal stabilizer (whether they increase consumption more than does ordinary income). The results, based on estimates for 1959-1981, suggest that Food Stamp coupons are perfectly substitutable for Ml, and a revised money-supply series including "Food Stamp Money" is included in an Appendix. Estimates of consumption functions indicate that the MPC out of income in the form of Food Stamps is higher than that out of ordinary income. Taken together, the results suggest that the Food Stamp program is an automatic fiscal and monetary stabilizer -- under its provisions, both the money stock and disposable income are increased during a recession.

Fisher-Wright model with deterministic seed bank and selection

Seed banks are a common characteristics to many plant species, which allow storage of genetic diversity in the soil as dormant seeds for various periods of time. We investigate an above-ground population following a Fisher-Wright model with selection coupled with a deterministic seed bank assuming the length of the seed bank is kept constant and the number of seeds is large. To assess the combined impact of seed banks and selection on genetic diversity, we derive a general diffusion model. The applied techniques outline a path of approximating a stochastic delay differential equation by an appropriately rescaled stochastic differential equation, which is a common issue in statistical physics. We compute the equilibrium solution of the site-frequency spectrum and derive the times to fixation of an allele with and without selection. Finally, it is demonstrated that seed banks enhance the effect of selection onto the site-frequency spectrum while slowing down the time until the mutation-selection equilibrium is reached