Black holes are incredibly fascinating objects. They largely populate the Universe we live in, attracting whole galaxies around them. They also attract the imagination of novel writers and scientists alike: they represent the ultimate frontier at which our knowledge and intellect can be put to the test. In 1974 Stephen Hawking, building upon suggestions that black holes have a finite temperature, predicted that the event horizon surrounding a black hole separates regions characterized by such an intense space-time distortion that photons and particles are literally ripped out of vacuum state. These photons are then seen from outside the black hole to be emitted as a continuous flux of radiation. Black holes glow, just as if they were light bulbs. Unfortunately, this truly amazing prediction has little hope of being verified directly from astrophysical black holes. The "glow" has an extremely low temperature, of the order of tens of nano-Kelvins and cannot be distinguished amongst the much higher cosmic background temperature. Fortunately, exactly 30 years ago, William Unruh noted that the same arguments that lead to black hole evaporation also predict that a thermal spectrum of sound waves should be given out from a flowing fluid whose velocity is made to vary from sub-sonic to super-sonic velocities. Sound waves will remain blocked at the transition between the sub- and super-sonic regions at what, to all effects, is the analogue of an horizon. It now turns out that horizons are apparently far more common than one may imagine. They appear in flowing tap water as it hits the sink and in a number of water or liquid based scenarios; they appear in flowing Bose-Einstein-Condensates, in polariton condensates and, most importantly for what concerns this project, in moving dielectric media. We may imagine moving a transparent glass sample at velocities close to that of light. We would then have a situation analogous to that of sound waves in a moving fluid: in the presence of a transition from sub-luminal to super-luminal speeds, light waves will not be able to move beyond the horizon point at which the medium velocity is exactly equal to the phase velocity of light. One of the PIs (U. Leonhardt) recently proposed an ingenious method to achieve such horizons in a very simple manner. An intense laser pulse propagating in glass will create a local perturbation in the refractive index that travels together with the pulse, i.e. it naturally travels at light speeds. Any light wave approaching the perturbation will be slowed down by the local increase in refractive index and will eventually be blocked at the horizon beyond which it will be never be able to propagate. Using this very simple proposal, the other project PI (D. Faccio) obtained the first evidence of spontaneous photon emission induced by the dielectric horizon. The perturbation is glowing and evaporating by shedding photons excited from the vacuum state, just as Hawking predicted black holes should do. This project aims at taking forth these results and taking studies on Hawking emission and horizon related effects to the next level. We are now able to plan real experiments that can give us for the first time real data describing how horizons interact with the quantum vacuum. Moreover, at the heart of Hawking emission lies a novel amplification mechanism that, due to the lack of any previous experimental possibilities, has never been truly investigated before. This new amplification channel will be studied and used to amplify light. The goal in mind is to create the first black hole laser in which light is trapped in between two separate horizons. Bouncing back and forth it is amplified at each rebound and finally exponentially explodes in laser-like amplification process. The impact of this project therefore goes well beyond investigation of Hawking effects and invests a number of fields, ranging from quantum field theories to nonlinear optics and photonic technologies.

Here we propose to investigate the synthesis and characterization of novel classes of metal-based nano-structuredparticles and composites with well-defined geometry and connectivity. The materials are obtained by a modular bottom-upapproach of metal-containing nanoparticles (NPs) with core-shell architecture as well as nanocomposites from metal NPsand block copolymers (BCs) as structure-directed agents. The aim of the proposed program is to understand theunderlying fundamental chemical, thermodynamic and kinetic formation principles enabling general and relativelyinexpensive wet-chemistry methodologies for the efficient creation of multiscale functional metal materials with noveloptical property profiles that may revolutionize the field of nanophotonics/plasmonics/ metamaterials, enabled by nmscalecontrol over the underlying structure over large dimensions. The proposed research includes synthesis of allnecessary organic/polymer and inorganic components, characterization of assembly structures using various scattering,optical and electron microscopy techniques, as well as thorough investigations of their optical properties includingsimulation and modeling efforts, and work towards major novel optics in the form of sub-wavelength imaging, highlysensitive hot-spot arrays over macroscopic dimensions for sensing, and sub-wavelength waveguiding. While the mainfocus of our proposed work lies on non-magnetic materials and the assessment of linear optical properties of thefabricated compounds, a crucial point is that we are aiming at synthesis approaches that can be generalized over a widerclass of materials systems. A final thrust of the program addresses a particularly topical exploitation area, where we willintegrate specific plasmonic structures into hybrid solar cells and characterize and optimize plasmon enhancedphotogeneration of charges and subsequent solar cell efficiency. If successful this will lead to a new generation, or classof photovolatics, namely plasmonic solar cells.

Within the next few years the number of devices connected to each other and the Internet will outnumber humans by almost 5:1. These connected devices will underpin everything from healthcare to transport to energy and manufacturing. At the same time, this growth is not just in the number or variety of devices, but also in the ways they communicate and share information with each other, building hyper-connected cyber-physical infrastructures that span most aspects of people's lives. For the UK to maximise the socio-economic benefits from this revolutionary change we need to address the myriad trust, identity, privacy and security issues raised by such large, interconnected infrastructures. Solutions to many of these issues have previously only been developed and tested on systems orders of magnitude less complex in the hope they would 'scale up'. However, the rapid development and implementation of hyper-connected infrastructures means that we need to address these challenges at scale since the issues and the complexity only become apparent when all the different elements are in place. There is already a shortage of highly skilled people to tackle these challenges in today's systems with latest estimates noting a shortfall of 1.8M by 2022. With an estimated 80Bn malicious scans and 780K records lost daily due to security and privacy breaches, there is an urgent need for future leaders capable of developing innovative solutions that will keep society one step ahead of malicious actors intent on compromising security, privacy and identity and hence eroding trust in infrastructures. The Centre for Doctoral Training (CDT) 'Trust, Identity, Privacy and Security - at scale' (TIPS-at-Scale) will tackle this by training a new generation of interdisciplinary research leaders. We will do this by educating PhD students in both the technical skills needed to study and analyse TIPS-at-scale, while simultaneously studying how to understand the challenges as fundamentally human too. The training involves close involvement with industry and practitioners who have played a key role in co-creating the programme and, uniquely, responsible innovation. The implementation of the training is novel due to its 'at scale' focus on TIPS that contextualises students' learning using relevant real-world, global problems revealed through project work, external speakers, industry/international internships/placements and masterclasses. The CDT will enrol ten students per year for a 4-year programme. The first year will involve a series of taught modules on the technical and human aspects of TIPS-at-scale. There will also be an introductory Induction Residential Week, and regular masterclasses by leading academics and industry figures, including delivery at industrial facilities. The students will also undertake placements in industry and research groups to gain hands-on understanding of TIPS-at-scale research problems. They will then continue working with stakeholders in industry, academia and government to develop a research proposal for their final three years, as well as undertake internships each year in industry and international research centres. Their interdisciplinary knowledge will continue to expand through masterclasses and they will develop a deep appreciation of real-world TIPS-at-scale issues through experimentation on state-of-the-art testbed facilities and labs at the universities of Bristol and Bath, industry and a city-wide testbed: Bristol-is-Open. Students will also work with innovation centres in Bath and Bristol to develop novel, interdisciplinary solutions to challenging TIPS-at-scale problems as part of Responsible Innovation Challenges. These and other mechanisms will ensure that TIPS-at-Scale graduates will lead the way in tackling the trust, identity, privacy and security challenges in future large, massively connected infrastructures and will do so in a way that considers wider sosocial responsibility.

Biological productivity (the growth of phytoplankton) is limited by the availability of iron (Fe) in at least 30% of the ocean. Fe is so insoluble in seawater that the large amounts entering from rivers cannot be transported far from the continental margins. The supply of Fe from dust falling on the ocean becomes the primary way to add Fe (and other elements important to life such as phosphorus) to the open ocean. The pattern and flux of Fe from the atmosphere to the surface ocean is therefore important for ocean ecosystems, and for the global carbon cycle (because ocean life consumes carbon). Despite this importance, the flux of dust and of its incorporated metals to the ocean is poorly known. It is challenging to measure this flux directly, and other observational approaches require quite fundamental assumptions, which limit accuracy. At present, therefore, most estimates of dust flux rely on atmospheric models, and are generally considered to be uncertain by a factor of ten, particularly in remote regions. In the proposed work, we will assess and use a new approach to quantify the inputs of dust and its associated micronutrients to the ocean. This approach relies on measurements of two biologically inactive, partially soluble components of dust: thorium (Th) and aluminium (Al). Two isotopes of Th are used in this assessment. 232Th, is present in continental rocks. If found dissolved in the open ocean, 232Th must have been recently added by dissolution of dust transported from the continents. Another isotope, 230Th, is formed within seawater by the decay of a uranium isotope. Its concentration in seawater reflects a competition between this known rate of formation, and removal due to its insoluble nature. We can therefore use 230Th to assess the removal rate of Th, including 232Th, from seawater. The 232Th removed must be replaced by input from dust to maintain the observed 232Th concentrations, so we can calculate the input of dust. There are two main challenges to the reconstruction of dust fluxes from Th isotopes. One is that the solubility of Th in dust, a critical term in the flux calculation, is not well known. Our new results indicate that Th is amongst a small group of elements whose solubility is very little impacted by transport of dust through the atmosphere, while the solubilities of Fe, Al and several other biologically active elements are all altered greatly during transport. Using aerosol samples collected on a series of research cruises, and at a sampling tower on Bermuda, we will assess the solubility of Th, the controls on how that varies during atmospheric transport, and its relationship to changes in Al and Fe solubility. We will also conduct laboratory studies on desert dust parent soils aimed at better understanding the unusual Th solubility in dust aerosols. Dust fluxes can also be calculated from dissolved Al concentrations, but these estimates are affected by changes in Al solubility during atmospheric transport. The second challenge is that we do not know how far 232Th from the continents might travel after input at the coast. We will address this by incorporating 232Th into an ocean model. Such models have a proven ability to reconstruct 230Th, and we will develop them to also model 232Th, and to indicate where 232Th is dominated by coastal inputs rather than by dust. These models will also be used to assess the uncertainty in using Th isotopes to reconstruct dust inputs. A large number of observations of Th isotopes in seawater has recently been measured during an international programme: GEOTRACES. We will add data from two further cruises, to complete a detailed coverage of Th and Al measurements for the Atlantic Ocean. Combined use of the Th and Al tracers will therefore allow us to produce robust maps of dust inputs (from Th) and soluble Fe inputs (by taking account of the changes in solubility during transport using Al) for the Atlantic (with associated maps of uncertainty).

Males of many different mammal, bird and invertebrate species respond to their social and sexual environment. These responses have profound effects on their reproductive success. For example, males of many species that perceive rivals transfer more sperm to females during mating, to increase their share of paternity. However, the complete pathway from the detection of cues from rival males, to effects on the composition of the male ejaculate through to ultimate reproductive success is not known. Nor do we know the effects on ageing for males of responding to rivals. The discovery of the pathway between rival detection and paternity represents the next key stage in understanding the evolution of male mating success. In this proposal we aim to provide the first case study, using the fruitfly. The fruitfly offers a unique opportunity, its genome has been sequenced and there are many different genetic reagents available with which to manipulate a male's perception of the number of rivals present. We have also generated a substantial amount of relevant and novel background data. For example, males respond to the presence of rivals before mating, and subsequently mate for longer when they do meet a female. More importantly, during those longer matings they transfer more of key ejaculate components, which increase the overall number of offspring fathered. Males appear to detect rivals by smelling a particular male pheromone. Importance for pure research: The work tackles questions of fundamental importance: how do males respond to rivals and what are the fitness consequences of doing so. When ejaculates are limiting (e.g. when males that mate just a few times become exhausted), males partition their ejaculates among different matings and different females, according to how many rival males are present. However, despite the wealth of studies showing that males do this, key questions remain: (i) what are molecular mechanisms by which males signal and perceive rivals? and (ii) what are the overall consequences, particularly the impact on ageing, for males that respond to the presence of rivals. These are the questions we will answer. Importance for applied research: Of equal importance, our work will provide techniques to improve insect pest control. Insect pests are the source of the world's most serious agricultural (and health) problems. Research is focusing on methods whose basic principles lie in biological control. However, males produced for control often have poor mating success. We aim to provide methods to improve this (e.g. simple husbandry rules to increase exposure to rivals or pheromones) using the fruitfly, which is the only species in which the relevant background data and genetic reagents are available. We plan to apply our findings to pests in the future. Methodology: We will manipulate male numbers and length of exposure to rivals, and the smell pathways that our work has highlighted as important. We can test the amount of ejaculate proteins transferred to females during mating using a method developed by our project partner, Mariana Wolfner from Cornell University. We can test for sperm transfer by staining and counting the sperm transferred. To test for the effects of responding to rivals on male ageing, we will compare the lifespan and reproductive success of males that mate following exposure, or not, to rivals. Timeliness and originality: Our proposal will provide the first investigation of the complete pathway by which males respond to rivals. The work is timely given the recent elucidation of smell receptors, our recent discoveries of changes to ejaculate composition in the presence of rivals and the recent surge of developments in genetic insect pest control.