Capillary pinching in a pinched microchannel

We report a study of the capillary pinching of a gas bubble by a wetting liquid inside a pinched channel. The capillary pinching induces very reproducible bubbling, at a very well-defined frequency. There are two regimes associated with drip and jet bubbling. In the latter, we show that highly monodispersed bubbles are formed by our pinched channel. The dynamics of the bubble formation also shows two distinct regimes: a long-duration elongation of the air bubble and a rapid relaxation of the interface after interface breakup. The slow regime depends on the flux imposed and the channel geometry. The rapid deformation dynamic regime depends very weakly on the boundary conditions. Scaling arguments are proposed in the context of the lubrication approximation to describe the two regimes

Smoothness of the flow map for low-regularity solutions of the Camassa-Holm equations

It was recently proven by De Lellis, Kappeler, and Topalov that the periodic Cauchy problem for the Camassa-Holm equations is locally well-posed in the space Lip (T) endowed with the topology of H^1 (T). We prove here that the Lagrangian flow of these solutions are analytic with respect to time and smooth with respect to the initial data. These results can be adapted to the higher-order Camassa-Holm equations describing the exponential curves of the manifold of orientation preserving diffeomorphisms of T using the Riemannian structure induced by the Sobolev inner product H^l (T), for l in N, l > 1 (the classical Camassa-Holm equation corresponds to the case l=1): the periodic Cauchy problem is locally well-posed in the space W^{2l-1,infty} (T) endowed with the topology of H^{2l-1} (T) and the Lagrangian flows of these solutions are analytic with respect to time with values in W^{2l-1,infty} (T) and smooth with respect to the initial data. These results extend some earlier results which dealt with more regular solutions. In particular our results cover the case of peakons, up to the first collision

On the ferromagnetism equations with large variations solutions

We exhibit some large variations solutions of the Landau-Lifschitz equations as the exchange coefficient ε^2 tends to zero. These solutions are described by some asymptotic expansions which involve some internals layers by means of some large amplitude fluctuations in a neighborhood of width of order ε of an hypersurface contained in the domain. Despite the nonlinear behaviour of these layers we manage to justify locally in time these asymptotic expansions

Employment protection reform in search economies

The design of employment protection legislation (EPL) is of particular importance in the European debate on the contours of labor market reform. In this article we appeal to an equilibrium unemployment model to investigate the virtues of EPL reform which reduces the red tape and legal costs associated with layos and introduces a U.S.-style experiencerating system, which we model as a combination of a layo tax and a payroll subsidy. The reform considered shows that it is possible to improve the eciency of employment protection policies without aecting the extent of worker protection on the labor market. These results are consistent with the conventional wisdom that experience rating is desirable, not only as an integral component of unemployment-compensation nance, as most studies acknowledge, but also as part and parcel of a virtuous EPL system.Search and Matching Models; Employment Protection; State-Contingent Layo Tax; Experience-Rating

Education and the welfare gains from employment protection

In this paper, we generalize the study of the return to education undertaken in e.g. Laing, Palivos and Wang (1995) or Burdett and Smith (2002) to an environment where the link between education and employment stability is taken into account. This enables us to study how an European-like and Employment Protection Legislation (EPL) with heavily regulated long-term contracts and more flexible short-term contracts affects the return to schooling, equilibrium unemployment and welfare. In this context, we show that ¯ring costs and temporary employment have opposite effects on the rate of use of human capital and thus, on educational investments. We furthermore demonstrate that a laissez faire economy with no regulation is inefficient as it is characterized by insufficient educational investments leading to excess job destruction and inadequate job creation. By stabilizing employment relationships, firing costs may spur educational investments and therefore lead to welfare and productivity gains, though a first-best policy would be to subsidize education. However, there is little chance for a dual (European-like) EPL to raise the incentives to schooling and aggregate welfare.human capital; job destruction; matching frictions; efficiency

Employment Protection Reform in Search Economies

The design of employment protection legislation (EPL) is of particular importance in the European debate on the contours of labor market reform. In this article we appeal to an equilibrium unemployment model to investigate the virtues of EPL reform which reduces the red tape and legal costs associated with layoffs and introduces a U.S.-style experience- rating system, which we model as a combination of a layoff tax and a payroll subsidy. The reform considered shows that it is possible to improve the efficiency of employment protection policies without affecting the extent of worker protection on the labor market. These results are consistent with the conventional wisdom that experience rating is desirable, not only as an integral component of unemployment-compensation finance, as most studies acknowledge, but also as part and parcel of a virtuous EPL system.Search and Matching Models, Employment Protection, State-Contingent Layoff Tax, Experience-Rating

Education and the Welfare Gains from Employment Protection

This paper studies the impact of an European-like labor market regulation on the return to schooling, equilibrium unemployment and welfare. We show that firing costs and temporary employment have opposite effects on educational choices. We furthermore demonstrate that a laissez faire economy with no regulation is inefficient as it is characterized by insufficient educational investments leading to excess job destruction and inadequate job creation. By stabilizing employment relationships, firing costs may spur educational investments and therefore lead to welfare and productivity gains, though a first-best policy would be to subsidize education. However, there is little chance for a dual labor market, as is common in many European countries, with heavily regulated long-term contracts and more flexible short-term contracts to raise the incentives to schooling and aggregate welfare.human capital, job destruction, matching frictions, efficiency

Education and the Welfare Gains from Employment Protection

This paper studies the impact of an European-like labor market regulation on the return to schooling, equilibrium unemployment and welfare. We show that firing costs and temporary employment have opposite effects on educational choices. We furthermore demonstrate that a laissez faire economy with no regulation is inefficient as it is characterized by insufficient educational investments leading to excess job destruction and inadequate job creation. By stabilizing employment relationships, firing costs may spur educational investments and therefore lead to welfare and productivity gains, though a first-best policy would be to subsidize education. However, there is little chance for a dual labor market, as is common in many European countries, with heavily regulated long-term contracts and more flexible short-term contracts to raise the incentives to schooling and aggregate welfare.Human capital, job destruction, matching frictions, efficiency