Mirror symmetry and aging: The role of stimulus figurality and attention to colour

Symmetry perception studies have generally used two stimulus types: figural and dot patterns. Here, we designed a novel figural stimulus—a wedge pattern—made of centrally aligned pseudorandomly positioned wedges. To study the effect of pattern figurality and colour on symmetry perception, we compared symmetry detection in multicoloured wedge patterns with nonfigural dot patterns in younger and older adults. Symmetry signal was either segregated or nonsegregated by colour, and the symmetry detection task was performed under two conditions: with or without colour-based attention. In the first experiment, we compared performance for colour-symmetric patterns that varied in the number of wedges (24 vs. 36) and number of colours (2 vs. 3) and found that symmetry detection was facilitated by attention to colour when symmetry and noise signals were segregated by colour. In the second experiment, we compared performance for wedge and dot patterns on a sample of younger and older participants. Effects of attention to colour in segregated stimuli were magnified for wedge compared with dot patterns, with older and younger adults showing different effects of attention to colour on performance. Older adults significantly underperformed on uncued wedge patterns compared with dot patterns, but their performance improved greatly through colour cueing, reaching performance levels similar to young participants. Thus, while confirming the age-related decline in symmetry detection, we found that this deficit could be alleviated in figural multicoloured patterns by attending to the colour that carries the symmetry signal.Output Status: Forthcoming/Available Onlin

Climate-related migration and the climate-security-migration nexus in the Central American Dry Corridor

The Central American Dry Corridor (CADC) is among the most climate-vulnerable regions worldwide. Climate change, commonly referred to as a “threat multiplier” of pre-existing socioeconomic issues, already undermines rural livelihoods by reducing agricultural yields and income opportunities. This paper provides a review of climate-related migration in the CADC region while identifying the specific pathways by which climate change manifests itself as a threat multiplier to migration. Different forms of human mobility (seasonal/temporal/permanent and internal/international migration) are increasingly attempted as adaptation strategies by affected households to diversify incomes and offset climate impacts. Preferred intra-regional migrant destinations tend to be less climate-vulnerable and also less violent. Notably, climate change is not isolated from socioeconomic and political migration drivers. Erosion of rural livelihoods reduces the costs of engaging in illicit coping strategies (e.g., illegal crop production) and simultaneously favours rapid urbanisation, which is linked to (forced) gang recruitment, primarily affecting the youth. These processes contribute to extraordinarily high violence levels, which are a major push factor for migration on their own, ultimately challenging state authority. Moreover, as outmigration from the region is projected to increase, the observed securitisation of borders, particularly along the USA-Mexico border and the Mexico-Guatemala border, while unfit to limit migration attempts, make migration more desperate and dangerous, allowing organised crime to step in and exploit migration as an economic undertaking. Thus, for the CADC, the depoliticised and simplistic narrative of migration serving as adaptation must be questioned. Policy coherence and state capacity for addressing climate-security-migration nexus challenges are critical needs

Many-body Landau-Zener dynamics in coupled 1D Bose liquids

The Landau-Zener model of a quantum mechanical two-level system driven with a linearly time dependent detuning has served over decades as a textbook paradigm of quantum dynamics. In their seminal work [L. D. Landau, Physik. Z. Sowjet. 2, 46 (1932); C. Zener, Proc. Royal Soc. London 137, 696 (1932)], Landau and Zener derived a non-perturbative prediction for the transition probability between two states, which often serves as a reference point for the analysis of more complex systems. A particularly intriguing question is whether that framework can be extended to describe many-body quantum dynamics. Here we report an experimental and theoretical study of a system of ultracold atoms, offering a direct many-body generalization of the Landau-Zener problem. In a system of pairwise tunnel-coupled 1D Bose liquids we show how tuning the correlations of the 1D gases, the tunnel coupling between the tubes and the inter-tube interactions strongly modify the original Landau-Zener picture. The results are explained using a mean-field description of the inter-tube condensate wave-function, coupled to the low-energy phonons of the 1D Bose liquid.Comment: 13 pages, 10 figures

Spin polarization in low-energy electron diffraction from Au(110): theory and experiment

Feder R, Müller N, Wolf D. Spin polarization in low-energy electron diffraction from Au(110): theory and experiment. Zeitschrift für Physik, B: Condensed Matter. 1977;28(4):265-271.A special LEED system has been constructed, in which the gun is movable in front of the grids and diffracted beams can be extracted through a probe hole in the screen. The polarization is subsequently measured by means of Mott scattering. The Au(110) surface is of particular interest, because it shows a reversible structure transition, which manifests itself in LEED intensities as a change from a (1 × 2) pattern at low temperatures to a (1 × 1) pattern at higher temperatures. For the (1 × 1) structure, spin polarization was measured, with values up to 70%, and calculated for a number of beams as a function of energy and scattering angle. Theoretical and experimental results are in reasonable agreement. In particular, the polarization is found to depend sensitively on geometrical, electronic and vibronic properties of the surface. The experimental work was sponsored by the Deutsche Forschungsgemeinschaft, Sonderforschungsbereich 12