Theory, models and biology

Theoretical ideas have a rich history in many areas of biology, and new theories and mathematical models have much to offer in the future

An Effective Membrane Model of the Immunological Synapse

The immunological synapse is a patterned collection of different types of receptors and ligands that forms in the intercellular junction between T Cells and antigen presenting cells (APCs) during recognition. The synapse is implicated in information transfer between cells, and is characterized by different spatial patterns of receptors at different stages in the life cycle of T cells. We obtain a minimalist model that captures this experimentally observed phenomenology. A functional RG analysis provides further insights.Comment: 6 pages, 3 figures, submitted for publicatio

Evidence of a compensated semimetal with electronic correlations at the CNP of twisted double bilayer graphene

Recently, magic-angle twisted bilayer graphene (MATBLG) has shown the emergence of various interaction-driven novel quantum phases at the commensurate fillings of the moir'e superlattice, while the charge neutrality point (CNP) remains mostly a vanilla insulator. Here, we show an emerging phase of nearly compensated semimetallicity at the CNP of twisted double bilayer graphene (TDBLG), a close cousin of MATBLG, with signatures of electronic correlation. Using electrical and thermal transport, we find almost two orders of magnitude enhancement of the thermopower in magnetic fields much smaller than the extreme quantum limit, accompanied by a large magnetoresistance($\sim 2500\%$) at CNP. This provides indisputable experimental evidence that TDBLG near CNP is a compensated semimetal. Moreover, at low temperatures, we observe an unusual sublinear temperature dependence of resistance. A recent theory predicts the formation of an excitonic metal near CNP, where small electron and hole pockets coexist. We understand the sublinear temperature dependence in terms of critical fluctuations in this theory

Networking Cities after Paris: Weighing the Ambition of Urban Climate Change Experimentation

Over the past few decades, cities have repeatedly demonstrated high levels of ambition with regard to climate action. Global environmental governance has been marked by a proliferation of policy actions taken by local governments around the world to demonstrate their potential to advance climate change mitigation and adaptation. Leading ‘by example’ and demonstrating the extent of action that it is possible to deliver, cities have aspired to raise the ambition of national and international climate governance and put action into practice via a growing number of ‘climate change experiments’ delivered on the ground. Yet accounts of the potential of cities in global environmental governance have often stopped short of a systematic valuation of the nature and impact of the networked dimension of this action. This article addresses this by assessing the nature, and challenges faced by, urban climate governance in the post-Paris era, focusing on the ‘experimentation’ undertaken in cities and the city networks shaping this type of governance. First, we unpack the concept of ‘urban climate change experimentation’, the ways in which it is networked, and the forces driving it. In the second and third parts of the article, we discuss two main pitfalls of networked urban experimentation in its current form, focusing on issues of scaling experiments and the nature of experimentation. We call for increased attention to ‘scaling up’ experiments beyond urban levels of governance, and to transformative experimentation with governance and politics by and in cities. Finally, we consider how these pitfalls allow us to weigh the potential of urban climate ambition, and consider the pathways available for supporting urban climate change experimentation

Collective modes of a quasi two-dimensional Bose condensate in large gas parameter regime

We have theoretically studied the collective modes of a quasi two-dimensional (Q2D) Bose condensate in the large gas parameter regime by using a formalism which treats the interaction energy beyond the mean-field approximation. In the calculation we use the perturbative expansion for the interaction energy by incorporating the Lee, Huang and Yang (LHY) correction term. The results show that incorporation of this higher order term leads to detectable modifications in the mode frequencies.Comment: 10 pages, 2 figure

Water management at BedZED - Some lessons

Copyright © 2008 ICE Publishing Ltd. Permission is granted by ICE Publishing to print one copy for personal use. Any other use of these PDF files is subject to reprint fees.The Beddington zero fossil energy development (BedZED) in London, UK, is something of a modern icon in terms of assembling simultaneously on the same site new construction methods, the best of available ‘green’ technology and social engineering combined with new peri-urban lifestyles. The development also includes a number of ‘alternative’ water systems. As with many innovative and exploratory departures, however, not everything went according to plan. This paper describes the bold vision, highlights some of the issues and seeks to learn and disseminate lessons for the future, with special reference to the integrated water and wastewater services