Slow equivariant lump dynamics on the two sphere

The low-energy, rotationally equivariant dynamics of n CP^1 lumps on S^2 is studied within the approximation of geodesic motion in the moduli space of static solutions. The volume and curvature properties of this moduli space are computed. By lifting the geodesic flow to the completion of an n-fold cover of the moduli space, a good understanding of nearly singular lump dynamics within this approximation is obtained.Comment: 12 pages, 3 figure

Magnetic bubble refraction and quasibreathers in inhomogeneous antiferromagnets

The dynamics of magnetic bubble solitons in a two-dimensional isotropic antiferromagnetic spin lattice is studied, in the case where the exchange integral J(x,y) is position dependent. In the near continuum regime, this system is described by the relativistic O(3) sigma model on a spacetime with a spatially inhomogeneous metric, determined by J. The geodesic approximation is used to describe low energy soliton dynamics in this system: n-soliton motion is approximated by geodesic motion in the moduli space of static n-solitons, equipped with the L^2 metric. Explicit formulae for this metric for various natural choices of J(x,y) are obtained. From these it is shown that single soliton trajectories experience refraction, with 1/J analogous to the refractive index, and that this refraction effect allows the construction of simple bubble lenses and bubble guides. The case where J has a disk inhomogeneity (taking the value J_1 outside a disk, and J_2<J_1 inside) is considered in detail. It is argued that, for sufficiently large J_1/J_2 this type of antiferromagnet supports approximate quasibreathers: two or more coincident bubbles confined within the disk which spin internally while their shape undergoes periodic oscillations with a generically incommensurate period.Comment: Conference proceedings paper for talk given at Nonlinear Physics Theory and Experiment IV, Gallipoli, Italy, June 200

Emissions budgets for shipping in a 2°C and a 4°C global warming scenario, and implications for operational efficiency

To achieve the widely accepted goal of keeping global temperature rise below 2°C above pre-industrial levels, greenhouse gas emissions must reduce drastically over the coming decades. Under this premise, the assumption that the shipping industry realises the same proportionate CO2 emission reductions as all other sectors on average has strong implications. This paper begins by considering an appropriate global CO2 emissions budget associated with a temperature rise of 2°C. Next, a range of future demand scenarios for international transport shipping are presented. Meeting the demand in any of the scenarios, while remaining within the emissions budget, requires stringent increases in overall operational efficiency. Different emissions and efficiency trajectories – with efficiency expressed in terms of the Energy Efficiency Operational Indicator (EEOI) – in line with the 2°C target are analysed. The potential short and long term levers of operational efficiency are explored

Drosophila Photoreceptor Axon Guidance and Targeting Requires the Dreadlocks SH2/SH3 Adapter Protein

AbstractMutations in the Drosophila gene dreadlocks (dock) disrupt photoreceptor cell (R cell) axon guidance and targeting. Genetic mosaic analysis and cell-type-specific expression of dock transgenes demonstrate dock is required in R cells for proper innervation. Dock protein contains one SH2 and three SH3 domains, implicating it in tyrosine kinase signaling, and is highly related to the human proto-oncogene Nck. Dock expression is detected in R cell growth cones in the target region. We propose Dock transmits signals in the growth cone in response to guidance and targeting cues. These findings provide an important step for dissection of signaling pathways regulating growth cone motility

Location location location: a carbon footprint calculator for transparent travel to the UN Climate Conference 2022

Addressing the large carbon footprint of conferences such as the United Nations Climate Change Convention Conference of the Parties (COP) will be important for maintaining public confidence in climate policy. Transparency is also a vital aspect of creating equitable outcomes in climate policies, as those most likely to be affected or who can create change on the ground are often unable to attend in person because of the high financial costs as well as having a large carbon footprint. The selection of host locations for the regular meetings of the UN Climate Change Convention is based on a rotation amongst the five UN regions, which for 2022 was Africa. Here, we present a carbon footprint calculator for travel to COP 27 in Sharm El-Sheikh, Egypt, weighing the benefits of certain routes and modes of transport. The calculator demonstrates the well-known carbon efficiency of coach and rail over flights but shows that these benefits were partly diminished in the case of COP 27 due to insufficient transport links from Europe to the conference location. However, we also highlight some of the benefits of hosting a COP in the Global South, particularly in the context of climate justice. Users of the calculator are invited to consider all their options for travel and acknowledge the issue of climate justice through careful selection of carbon offsets

Location location location: A carbon footprint calculator for transparent travel to COP27

Addressing the large carbon footprint of conferences such as the UN Climate Change Convention Conference of the Parties (COP) will be important for maintaining public confidence in climate policy. Transparency is also a vital aspect of creating equitable outcomes in climate policies, as often those most likely to be affected or who are able to create change on the ground are often unable to attend in person because of the high financial costs as well as having a large carbon footprint. The selection of host locations for the regular meetings of the UN Climate Change Convention is based on a rotation in amongst the five UN regions, which for 2022 is Africa. Here, we present UCL’s own carbon footprint calculator and use it to weigh the benefits of certain modes of transport to the 2021 COP 26 in Glasgow, UK and the 2022 COP 27 to be held in Sharm El-Sheikh, Egypt. The calculator demonstrates the well-known carbon-efficiency of coach and rail over flights, but shows that these benefits are only partly mitigated in the case of COP 27 due to insufficient transport links from Europe to the conference location. However, we also highlight some of the benefits of hosting a COP in the global South, particularly in the context of climate justice. Incorporating these principles into the calculator, we invite visitors to COP this year to carefully consider their options for carbon offsetting and how the tenets of climate justice could be integrated into the carbon accounting framework