How much is policy driving the adoption of cover crops? Evidence from four EU regions.

EU agriculture is facing increasing expectations and pressure from society and policymakers to support environmental protection and climate change mitigation. Catch and cover crops (CCC) are an underused farming practice that can potentially contribute towards these goals. Previous research is sparse and has yielded few relevant insights into CCC adoption behaviour by farmers.

Quasiperiodic Bloch-like states in a surface-wave experiment.

Bloch-like surface waves associated with a quasiperiodic structure are observed in a classic wave propagation experiment which consists of pulse propagation with a shallow fluid covering a quasiperiodically drilled bottom. We show that a transversal pulse propagates as a plane wave with quasiperiodic modulation, displaying the characteristic undulatory propagation in this quasiperiodic system and reinforcing the idea that analogous concepts to Bloch functions can be applied to quasicrystals under certain circumstances.

Parametric Bragg resonances in waves on a shallow fluid over a periodically drilled bottom.

Bragg resonances involving strong interactions among Fourier wave components of a periodically drilled bottom and parametrically driven surface waves on a shallow liquid are experimentally shown to break down the secular dispersion relation of surface waves. When the fluid is sufficiently shallow, wave components that match reciprocal wave vectors of the bottom topography are dominant. Experimental evidence of band-gap phenomena in these surface waves are also shown.

The influence of family, school, and peers on adolescent drug misuse.

The socializing impact of the family is compared to that of peers during adolescent progressive involvement with drugs. This longitudinal study replicates in the school population of Madrid the work of Kandel and associates in the state of New York in an attempt to verify the "stepping-stone" hypothesis. Although the Madrid study detected a sequence of drug use similar to that in the New York study, the Spanish study hypothesized tobacco use to be the first stage and alcohol use the second.