Structure and magnetic properties of Sm/Fe multilayers versus substrate temperature

Three Sm(2 Å)/Fe(3 Å) multilayers have been made using two electron beams in a high vacuum chamber onto very thin Kapton foils at different substrate temperatures, (Ts=40°C, 150°C and 230°C), with the same total thickness of 3000 Å. We have found that the substrate temperature strongly affects structure and magnetic properties of the samples. For a substrate temperature of 150°C the sample behaves as a three dimensional random magnet

Enhanced observability of quantum post-exponential decay using distant detectors

We study the elusive transition from exponential to post-exponential (algebraic) decay of the probability density of a quantum particle emitted by an exponentially decaying source, in one dimension. The main finding is that the probability density at the transition time, and thus its observability, increases with the distance of the detector from the source, up to a critical distance beyond which exponential decay is no longer observed. Solvable models provide explicit expressions for the dependence of the transition on resonance and observational parameters, facilitating the choice of optimal conditions

Brains versus Brawn: Labor Market Returns to Intellectual and Health Human Capital in a Poor Developing Country

Previous studies report that adult height has significant associations with wages even controlling for schooling. But schooling and height are imperfect measures of adult cognitive skills (“brains”) and strength (“brawn”); further they are not exogenous. Analysis of rich Guatemalan longitudinal data over 35 years finds that proximate determinants—adult reading comprehension skills and fat-free body mass—have significantly positive associations with wages, but only brains, and not brawn, is significant when both human capital measures are treated as endogenous. Even in a poor developing economy in which strength plausibly has rewards, labor market returns are increased by brains, not brawn.

Fragmented condensation in Bose-Hubbard trimers with tunable tunnelling

We consider a Bose-Hubbard trimer, i.e. an ultracold Bose gas populating three quantum states. The latter can be either different sites of a triple-well potential or three internal states of the atoms. The bosons can tunnel between different states with variable tunnelling strength between two of them. This will allow us to study; i) different geometrical configurations, i.e. from a closed triangle to three aligned wells and ii) a triangular configuration with a $\pi$-phase, i.e. by setting one of the tunnellings negative. By solving the corresponding three-site Bose-Hubbard Hamiltonian we obtain the ground state of the system as a function of the trap topology. We characterise the different ground states by means of the coherence and entanglement properties. For small repulsive interactions, fragmented condensates are found for the $\pi$-phase case. These are found to be robust against small variations of the tunnelling in the small interaction regime. A low-energy effective many-body Hamiltonian restricted to the degenerate manifold provides a compelling description of the $\pi$-phase degeneration and explains the low-energy spectrum as excitations of discrete semifluxon states

The Impact of Nutrition during Early Childhood on Education among Guatemalan Adults

Early childhood nutrition is thought to have important effects on education, broadly defined to include various forms of learning. We advance beyond previous literature on the effect of early childhood nutrition on education in developing countries by using unique longitudinal data begun during a nutritional experiment during early childhood with educational outcomes measured in adulthood. Estimating an intent-to-treat model capturing the effect of exposure to the intervention from birth to 36 months, our results indicate significantly positive, and fairly substantial, effects of the randomized nutrition intervention a quarter century after it ended: increased grade attainment by women (1.2 grades) via increased likelihood of completing primary school and some secondary school; speedier grade progression by women; a one-quarter SD increase in a test of reading comprehension with positive effects found for both women and men; and a one-quarter SD increase on nonverbal cognitive tests scores. There is little evidence of heterogeneous impacts with the exception being that exposure to the intervention had a larger effect on grade attainment and reading comprehension scores for females in wealthier households. The findings are robust to an array of alternative estimators of the standard errors and controls for sample attrition.education, schooling, Guatemala, nutrition, economic development, Latin America

The impact of an experimental nutritional intervention in childhood on education among Guatemalan adults:

"Studies have shown that malnourished children in developing countries score lower on tests of cognitive function and fail to acquire fine motor skills at the normal rate. Do the effects of nourishment—good or bad—in early childhood linger into adolescence and adulthood, or do they fade away after a few years? This paper provides new evidence of the effects of early childhood nutritional interventions on adult outcomes, using longitudinal data and methods well suited to address the concerns that have been raised about earlier studies." from Textmalnutrition, Children, Education, Nutrition,

Scattering of second-harmonic light from small spherical particles ordered in a crystalline lattice

Experimental evidence of scattering of second-harmonic light from the surface of spherical particles of optical dimensions is presented. This mechanism for second-harmonic generation is observed in a suspension of monodisperse spherical colloidal particles, ordered in a centrosymmetric crystalline lattice. In this periodic structure the mechanism of phase matching is provided by the bending of the photon dispersion curve near the Bragg reflection band. A simple theoretical analysis based on the Rayleigh-Gans scattering approximation shows that constructive interference of the second-harmonic light scattered from different portions of a single-sphere surface leads to a nonvanishing field with a quadrupolar distribution intensity pattern

Second harmonic generation in a photonic crystal

Phase matched second harmonic generation is observed experimentally in a centrosymmetric crystalline lattice of dielectric spheres of optical dimensions. The inversion symmetry is broken locally at the surface of each sphere in such a way that the scattered second harmonic light interferes constructively leading to a nonvanishing macroscopic field. Phase matching of the fundamental and second harmonic waves in such periodic lattice is observed to be naturally provided by the bending of the photondispersion curve at the edge of the Bragg reflection band of a given set of lattice planes

Second-harmonic generation in local modes of a truncated periodic structure

We present an experimental study of the generation of second-harmonic light in a one-dimensional periodic structure truncated by the introduction of a defect in the central period. We observed an enhancement of the nonlinear interaction in the vicinity of the defect when the second-harmonic wave was excited for modes within the forbidden zone or stop band. We also observed an enhancement near the band edge, where the group velocity approaches zero. Second-harmonic generation is completely suppressed for local modes within the forbidden band other than the defect mode