Direction-dependent turning leads to anisotropic diffusion and persistence

Cells and organisms follow aligned structures in their environment, a process that can generate persistent migration paths. Kinetic transport equations are a popular modelling tool for describing biological movements at the mesoscopic level, yet their formulations usually assume a constant turning rate. Here we relax this simplification, extending to include a turning rate that varies according to the anisotropy of a heterogeneous environment. We extend known methods of parabolic and hyperbolic scaling and apply the results to cell movement on micropatterned domains. We show that inclusion of orientation dependence in the turning rate can lead to persistence of motion in an otherwise fully symmetric environment and generate enhanced diffusion in structured domains

Nanoscale quantum dot infrared sensors with photonic crystal cavity

We report high performance infrared sensors that are based on intersubband transitions in nanoscale self-assembled quantum dots combined with a microcavity resonator made with a high-index-contrast two-dimensional photonic crystal. The addition of the photonic crystal cavity increases the photocurrent, conversion efficiency, and the signal to noise ratio (represented by the specific detectivity D*) by more than an order of magnitude. The conversion efficiency of the detector at Vb=–2.6 V increased from 7.5% for the control sample to 95% in the PhC detector. In principle, these photonic crystal resonators are technology agnostic and can be directly integrated into the manufacturing of present day infrared sensors using existing lithographic tools in the fabrication facility

Nonlinear localized waves in a periodic medium

We analyze the existence and stability of nonlinear localized waves in a periodic medium described by the Kronig-Penney model with a nonlinear defect. We demonstrate the existence of a novel type of stable nonlinear band-gap localized states, and also reveal an important physical mechanism of the oscillatory wave instabilities associated with the band-gap resonances.Comment: 4 pages, 5 figure

Visual portrayals of fun in the sun in European news outlets misrepresent heatwave risks

This is the author accepted manuscript. Available on open access from Wiley via the DOI in this recordData availability statement: The data that support the findings of this study are available from the corresponding author upon reasonable request.The ways in which news media communicate about heatwaves can influence how society conceptualises and addresses heatwave risks. We examined visual news coverage of the 2019 heatwaves in France, Germany, the Netherlands and UK, using content and visual critical discourse analyses. Many visuals were positively valenced (in contrast to article texts), framing heatwaves as ‘fun in the sun’. The most prevalent type of images in all countries were photographs of people having fun in or by water. When images did depict the danger of heat extremes, people were largely absent. We conclude that this visual framing of heatwaves is problematic: first, by displacing concerns of vulnerability, it marginalises the experiences of those vulnerable to heatwaves; and second, it excludes opportunities for imagining a more resilient future. We conclude with suggestions to diversify the visual discourse on climate change and heatwaves in the news media.Leverhulme TrustEconomic and Social Research Council (ESRC

An Inverse-Problem Approach to Designing Photonic Crystals for Cavity QED Experiments

Photonic band gap (PBG) materials are attractive for cavity QED experiments because they provide extremely small mode volumes and are monolithic, integratable structures. As such, PBG cavities are a promising alternative to Fabry-Perot resonators. However, the cavity requirements imposed by QED experiments, such as the need for high Q (low cavity damping) and small mode volumes, present significant design challenges for photonic band gap materials. Here, we pose the PBG design problem as a mathematical inversion and provide an analytical solution for a two-dimensional crystal. We then address a planar (2D crystal with finite thickness) structure using numerical techniques.Comment: 12 pages, 8 figures, preprint available from http://minty.caltech.edu/MabuchiLa