Self-control and savings

We reconsider the well-established paradigm of a rational individual's choice of a consumption schedule, building on the idea that human beings devote resources to withstand their desire for immediate consumption, i.e. to become more patient, thereby making less remote the pleasure derived from deferred consumption. We construct an infinite-horizon model of a small open economy, in which individuals can accumulate a stock of personal capital that reduces the discount on future consumption. Personal capital captures the effect of a conumer's past experience and choices on his future utilities. Our main results are: i) when individuals are heterogenous with respect to ability to become patient all individuals exhibit the same rate of time preference in the long run; ii) effort is rewarded in the long run to the extent that individuals who need to make more effort to become patient are wealthier and enjoy a higher level of utility bin the steady state. The latter result stems from the complementarity between personal capital and deferred consumption. JEL Classification: E13

Potential Irreversible Catastrophic Shifts of the Assimilative Capacity of the Environment

Pollution accumulation may result in more or less severe losses of natural self-cleaning capacities. We study a polluting resource management problem submitted to a potential shift from a high to a low pollution self-regeneration regime be crossed some critical pollution stock threshold. We rst describe the optimal resource exploitation policy absent the threshold. When at the threshold, the society has two options: either stabilizing the pollution level to avoid the loss of natural self-cleaning capacity or deliberately cross the threshold and switch to the low regeneration regime. We show under fairly general assumptions that there exists a unique critical pollution stock level such that thresholds located below this level will induce a switch from the high to the low regeneration regime while thresholds located above it will imply maintaining the high regime forever. We characterize the optimal policies in these two scenarios and show that triggering the low regeneration regime requires an upward jump of the resource consumption rate at the optimal switching time.

Statistical Estimation of Mechanical Parameters of Clarinet Reeds Using Experimental and Numerical Approaches

A set of 55 clarinet reeds is observed by holography, collecting 2 series of measurements made under 2 different moisture contents, from which the resonance frequencies of the 15 first modes are deduced. A statistical analysis of the results reveals good correlations, but also significant differences between both series. Within a given series, flexural modes are not strongly correlated. A Principal Component Analysis (PCA) shows that the measurements of each series can be described with 3 factors capturing more than $90\%$ of the variance: the first is linked with transverse modes, the second with flexural modes of high order and the third with the first flexural mode. A forth factor is necessary to take into account the individual sensitivity to moisture content. Numerical 3D simulations are conducted by Finite Element Method, based on a given reed shape and an orthotropic model. A sensitivity analysis revels that, besides the density, the theoretical frequencies depend mainly on 2 parameters: $E_L$ and $G_{LT}$. An approximate analytical formula is proposed to calculate the resonance frequencies as a function of these 2 parameters. The discrepancy between the observed frequencies and those calculated with the analytical formula suggests that the elastic moduli of the measured reeds are frequency dependent. A viscoelastic model is then developed, whose parameters are computed as a linear combination from 4 orthogonal components, using a standard least squares fitting procedure and leading to an objective characterization of the material properties of the cane \textit{Arundo donax}

Sustainable rural livelihoods to analyse family farming dynamics: A comparative perspective

The very nature of family farming makes it a complex scientific subject, being at the same time a social form of production and an economic agent. Its nature challenges disciplines that most of the time overlook dimensions that do not fit in with their own framework leading to partial views in anthropology, sociology, political science or economics, just to mention the most common disciplinary focus on rural societies. We suggest exploring the well-known Sustainable Rural Livelihood framework as a comprehensive and open conceptual design to address the evolution of family farming. While the entry point concerns individuals, it also considers the social structures and institutions in which they are embedded. It also contemplates natural, social and human assets in addition to physical and financial ones. The activity system developed by each individual within its social setting goes beyond sectorial approaches; the strategies developed are contextualized and influenced by policies. To illustrate how this framework can be implemented, we developed a case study approach in contrasting rural contexts ranging from Argentina, Brazil or Nicaragua for Latin American situations, to Indonesia, China or India for Asia, or to Mali, Cameroon or Mozambique for African illustrations. The cases will not be extensively presented here as we choose to highlight some of the main findings and crosscutting themes as ways and means of adapting to changing contexts. We also discuss the challenges and perspectives faced by family farming from other forms of production and provide some insight into "blind" issues: the social drawbacks and political dimensions linked to agriculture related to broader territorial and national concerns

Non-classical field state stabilization in a cavity by reservoir engineering

We propose an engineered reservoir inducing the relaxation of a cavity field towards non-classical states. It is made up of two-level atoms crossing the cavity one at a time. Each atom-cavity interaction is first dispersive, then resonant, then dispersive again. The reservoir pointer states are those produced by an effective Kerr Hamiltonian acting on a coherent field. We thereby stabilize squeezed states and quantum superpositions of multiple coherent components in a cavity having a finite damping time. This robust method could be implemented in state-of-the-art experiments and lead to interesting insights into mesoscopic quantum state superpositions and into their protection against decoherence.Comment: submitted to Phys.Rev.Let