Migration, Remittances and Moral Hazard. Evidence from the Kayes Area (Western Mali)

This article uses recent survey data from the Kayes area (Western Mali) to estimate the effect of migration and remittances on the technical efficiency of agricultural households. A theoretical model is developed, which shows that the more insurance is provided by the migrants, the less incentive their families have to work. A production function using panel data with household-specific fixed effects is estimated to test this hypothesis. The probability of being financially supported by migrants is found to significantly contribute to technical inefficiency. This result should help agricultural policy makers formulate more efficient development strategies in the area.technical inefficiency, moral hazard, risk-coping strategy, migration

Contingent Loan Repayment in the Philippines.

Using data from the Philippines, this article seeks to understand how households in the study area apparently manage to avoid falling into a debt trap in spite of frequent borrowing. Findings suggest that this is achieved via three institutional features. First, most informal debt carries no interest. Second, for all debts, repayment is postponed in case of a borrower’s difficulty; this is the only insurance feature of debt repayment. Third, while debt principal is seldom forgiven or reduced, interest‐bearing debt does not carry additional interest if debt repayment is delayed. This prevents interest charges from accumulating and debt from snowballing.Dette; Crédit;

Transversal magnetotransport in Weyl semimetals: Exact numerical approach

Magnetotransport experiments on Weyl semimetals are essential for investigating the intriguing topological and low-energy properties of Weyl nodes. If the transport direction is perpendicular to the applied magnetic field, experiments have shown a large positive magnetoresistance. In this work, we present a theoretical scattering matrix approach to transversal magnetotransport in a Weyl node. Our numerical method confirms and goes beyond the existing perturbative analytical approach by treating disorder exactly. It is formulated in real space and is applicable to mesoscopic samples as well as in the bulk limit. In particular, we study the case of clean and strongly disordered samples.Comment: 10 pages, 4 figure

Anatomy of Topological Surface States: Exact Solutions from Destructive Interference on Frustrated Lattices

The hallmark of topological phases is their robust boundary signature whose intriguing properties---such as the one-way transport on the chiral edge of a Chern insulator and the sudden disappearance of surface states forming open Fermi arcs on the surfaces of Weyl semimetals---are impossible to realize on the surface alone. Yet, despite the glaring simplicity of non-interacting topological bulk Hamiltonians and their concomitant energy spectrum, the detailed study of the corresponding surface states has essentially been restricted to numerical simulation. In this work, however, we show that exact analytical solutions of both topological and trivial surface states can be obtained for generic tight-binding models on a large class of geometrically frustrated lattices in any dimension without the need for fine-tuning of hopping amplitudes. Our solutions derive from local constraints tantamount to destructive interference between neighboring layer lattices perpendicular to the surface and provide microscopic insights into the structure of the surface states that enable analytical calculation of many desired properties. We illustrate our general findings on a large number of examples in two and three spatial dimensions. Notably, we derive exact chiral Chern insulator edge states on the spin orbit-coupled kagome lattice, and Fermi arcs relevant for various recently synthesized pyrochlore iridate slabs. Remarkably, each of the pyrochlore slabs exhibit Fermi arcs although only the ones with a magnetic one-in-three-out configuration feature bulk Weyl nodes in realistic parameter regimes. Our approach furthermore signal the absence of topological surface states, which we illustrate for a class of models akin to the trivial surface of Hourglass materials KHg$X$.Comment: 24 pages, 17 figure

Migration, self selection and returns to education in the WAEMU.

Using data from labour force surveys conducted simultaneously in the capital cities of seven West African Economic and Monetary Union countries, we estimate a model of residential location choice in which expected earnings play a role. The model is first estimated in a reduced form. Estimates are then used to correct for the endogeneity of locational choice in the earnings equations estimated for each country. We find that migration behaviour has a significant effect in shaping earnings differentials between education levels and between the seven capital cities. Corrected predicted earnings in each country are then used as an independent variable in a structural multinomial logit of residential choice. Results show that individuals tend to reside in countries in which their expected earnings are higher than elsewhere.Migration; Self-selection; West Africa;

Organic substances against Monilia laxa on apricot – in-vitro and on-farm experiments

Natural substances against Monilia laxa were onfarm and in-vitro tested. According to on-farm tests, some products reached interesting efficacies. The fluctuation of the year and parcel pressures, makes it difficult to perform the results

Boundaries of boundaries: a systematic approach to lattice models with solvable boundary states of arbitrary codimension

We present a generic and systematic approach for constructing D-dimensional lattice models with exactly solvable d-dimensional boundary states localized to corners, edges, hinges and surfaces. These solvable models represent a class of "sweet spots" in the space of possible tight-binding models---the exact solutions remain valid for any tight-binding parameters as long as they obey simple locality conditions that are manifest in the underlying lattice structure. Consequently, our models capture the physics of both (higher-order) topological and non-topological phases as well as the transitions between them in a particularly illuminating and transparent manner.Comment: 19 pages, 12 figure