An L1 positioned dust cloud as an effective method of space-based geoengineering

In this paper a method of geoengineering is proposed involving clouds of dust placed in the vicinity of the L1 point as an alternative to the use of thin film reflectors. The aim of this scheme is to reduce the manufacturing requirement for space-based geoengineering. It has been concluded that the mass requirement for a cloud placed at the classical L1 point, to create an average solar insolation reduction of 1.7%, is 2.93x109 kg yr-1 whilst a cloud placed at a displaced equilibrium point created by the inclusion of the effect of solar radiation pressure is 8.87x108 kg yr-1. These mass ejection rates are considerably less than the mass required in other unprocessed dust cloud methods proposed and, for a geoengineering period of 10 years, they are comparable to thin film reflector geoengineering requirements. It is envisaged that the required mass of dust can be extracted from captured near Earth asteroids, whilst stabilised in the required position using the impulse provided by solar collectors or mass drivers used to eject material from the asteroid surface

The international development of the ‘Social Norms’ approach to drug education and prevention

Binge drinking has sparked considerable interest and concern. However despite this interest little is known about the lay understanding of binge drinking and whether there are differences in understanding by gender, age and level of deprivation. Aims: This study investigated the beliefs and attitudes of a sample in the Inverclyde area to binge drinking. Methods: Using both cluster and quota sampling, 586 subjects completed a structured interview, using open questions about their beliefs on binge drinking and was it a problem generally and locally. Findings: Definitions of binge drinking tended to concentrate on intoxication and some described a dependent drinking pattern. Causes and solutions offered were varied but pointed up levels of deprivation in respect of jobs and entertainment. More subjects regarded binge drinking as a problem in society than locally, which is consistent with research suggesting that misperceptions of others’ drinking increases with social distance. Differences in beliefs were found by age and level of deprivation but not gender. It was marked that no subject offered the ‘official’ definition of bingeing or even an approximation of it. Conclusions: Further research is required if future mass media campaigns and interventions are to be relevant to the population

Needs assessment of gossamer structures in communications platform end-of-life disposal

The use of a gossamer structure is considered in application to end-of-life disposal of communications platforms. A wide-ranging survey of end-of-life disposal techniques and strategies is presented for comparison against a gossamer structure prior to a down-selection of viable competing techniques; solar sailing, high and low-thrust propulsion, and electrodynamic tethers. A parametric comparison of the down-selection competing techniques is presented where it was found that exploiting solar radiation pressure on the gossamer structure was of limited value. In general terms, it was found that if a spacecraft propulsion system remains functioning at the end-of-life then this will likely provide the most efficient means of re-orbiting, especially when the propulsion system is only used to lower the orbit to a point where atmospheric drag will cause the orbit to decay within the required timeframe. Atmospheric drag augmentation was found to be of most benefit for end-of-life disposal when an entirely passive means is required, allowing the device to act as a ‘fail-safe’, which if the spacecraft suffers a catastrophic failure would activate. The use of an atmospheric drag augmentation system is applicable to only low and medium mass spacecraft, or spacecraft that are unlikely to survive atmospheric re-entry, hence minimizing risk to human life

The feasibility of using an L1 positioned dust cloud as a method of space-based geoengineering

In this paper a method of geoengineering is proposed involving clouds of dust placed in the vicinity of the L1 point as an alternative to the use of thin film reflectors. The aim of this scheme is to reduce the manufacturing requirement for space-based geoengineering. It has been concluded that the mass requirement for a cloud placed at the classical L1 point, to create an average solar insolation reduction of 1.7%, is 7.60x1010 kg yr−1 whilst a cloud placed at a displaced equilibrium point created by the inclusion of the effect of solar radiation pressure is 1.87x1010 kg yr−1. These mass ejection rates are considerably less than the mass required in other unprocessed dust cloud methods proposed and are comparable to thin film reflector geoengineering requirements. Importantly, unprocessed dust sourced in-situ is seen as an attractive scheme compared to highly engineered thin film reflectors. It is envisaged that the required mass of dust can be extracted from captured near Earth asteroids, whilst stabilised in the required position using the impulse provided by solar collectors or mass drivers used to eject material from the asteroid surface

Use of orbiting reflectors to decrease the technological challenges of surviving the lunar night

In this paper the feasibility of using lunar reflectors to decrease the technological challenges of surviving the lunar night is investigated. This is achieved by attempting to find orbits in the two-body problem where the argument of periapsis is constantly Sun-pointing to maximise the time spent by the reflectors over the night-side of the Moon. Using these orbits the ability of reflectors of varying sizes to provide sufficient illumination to a target point on the surface is determined for scenarios where a latitude band is constantly illuminated and a scenario where a specific point is tracked. The optimum masses required for these far-term scenarios are large. However, a nearer-term scenario using low altitude orbits suggest that the effective duration of the lunar night can be reduced by up to 50% using a set of 300 parabolic reflectors of 100m radius with a total system mass of 370 tonnes. A system is also demonstrated that will allow a partial illumination of the craters in the Moon’s polar region for a mass up to 700kg

Dielectric response of modified Hubbard models with neutral-ionic and Peierls transitions

The dipole P(F) of systems with periodic boundary conditions (PBC) in a static electric field F is applied to one-dimensional Peierls-Hubbard models for organic charge-transfer (CT) salts. Exact results for P(F) are obtained for finite systems of N = 14 and 16 sites that are almost converged to infinite chains in deformable lattices subject to a Peierls transition. The electronic polarizability per site, \alpha_{el} = (\partial P/\partial F)_0, of rigid stacks with alternating transfer integrals t(1 +/- \delta) diverges at the neutral-ionic transition for \delta = 0 but remains finite for \delta > 0 in dimerized chains. The Peierls or dimerization mode couples to charge fluctuations along the stack and results in large vibrational contributions, \alpha_{vib}, that are related to \partial P/\partial \delta and that peak sharply at the Peierls transition. The extension of P(F) to correlated electronic states yields the dielectric response \kappa of models with neutral-ionic or Peierls transitions, where \kappa peaks >100 are found with parameters used previously for variable ionicity \rho and vibrational spectra of CT salts. The calculated \kappa accounts for the dielectric response of CT salts based on substituted TTFs (tetrathiafulvalene) and substituted CAs (chloranil). The role of lattice stiffness appears clearly in models: soft systems have a Peierls instability at small \rho and continuous crossover to large \rho, while stiff stacks such as TTF-CA have a first-order transition with discontinuous \rho that is both a neutral-ionic and Peierls transition. The transitions are associated with tuning the electronic ground state of insulators via temperature or pressure in experiments, or via model parameters in calculations.Comment: 10 pages, 9 figures; J.Chem.Phys., in pres

Improving the Logarithmic Accuracy of the Angular-Ordered Parton Shower

Monte Carlo event generators are a key tool for making theoretical predictions that can be compared with the results of collider experiments, our most accurate probes of fundamental particle physics. New developments in the way parton shower accuracy is assessed have led us to re-examine the accuracy of the angular-ordered parton shower in the Herwig 7 event generator, focussing on the way recoil is handled after successive emissions. We first discuss how the evolution variable is defined in the Herwig angular-ordered shower and how the choice of this definition determines the recoil scheme. We then show how the recoil scheme can affect the logarithmic accuracy of final-state radiation produced by the algorithm. As part of this investigation we consider a new interpretation of the evolution variable intended to mitigate problems with previous iterations of the shower. To test this, simulated events for each scheme are compared with experimental data from both LEP and the LHC. Next we extend our analysis to initial-state radiation and perform the same process of assessing the logarithmic accuracy of different interpretations of the evolution variable. This time, we compare simulated events for each scheme with LHC data for the vector boson production. Additionally, we consider the impact that the choice of NLO matching scheme has on the accuracy of these simulations, with reference to the same LHC data

Deciphering the Tectonics of the Greater Caucasus from Post-Collisional Volcanism

The southern margin of the Eurasian plate is a well-studied region of continental collision. The Caucasus mountains lie at the centre of the Alpine-Himalayan orogenic belt, and differs from their better studied neighbours by the presence of intense, largely mantle derived post-collisional magmatism. Volcanism began 5-15 Ma after the initial collision occurred, and after the crust had already thickened to 45-60 km. This thesis presents bulk rock and mineral element and isotope geochemistry to assess the role of asthenosphere, lithosphere and crust in generating contemporaneous volcanism across the region. Broad similarities are seen between volcanism in the Greater and Lesser Caucasus, dominated by calc-alkaline basalt-dacite (48-72 wt% SiO2) compositions. High Mg# cores (>85) of olivines suggest significant fractionation has occurred. Trace element patterns show a distinctive supra-subduction setting, suggesting the fluid-enriched source remained in place, and hydrated >10 Ma following collision. Isotope ratios require an asthenospheric component in the early Lesser Caucasus melts, whilst sediment-enrichment of the source is observed across the region. Little interaction with the thickened crust is observed. For the Lesser Caucasus, a model of Palaeo-Tethyan slab breakoff is proposed, resulting in asthenospheric upwelling and melting of an enriched lithosphere. Small-scale convection continues to produce drips, leading to episodic pulses of magmatism. Subduction of back-arc crust with slab breakoff is proposed beneath the Greater Caucasus, allowing melting of enriched lithosphere, with distinguishable fluid, and slab-melt components. Although contemporaneous, and volcanism in the Lesser and Greater Caucasus being geochemically similar in many respects, a shared source is ruled out because of tectonic constraints. Strike-slip faulting, the result of a tectonic regime shift at 5 Ma, determined the location of volcanoes. Although the style of post-collisional magmatism may not be characteristic of all continental collision zones, where present it has a high preservation potential. It may therefore play a significant role in the formation, and composition of continental crust that is largely unrecognised in models of continental crust evolution

Space mission applications of high area-to-mass-ratio orbital dynamics

High area-to-mass-ratio spacecraft experience a signifcant perturbation due to surface forces, such as solar radiation pressure and aerodynamic drag. Hence, their orbits do not evolve in the manner of traditional satellites. They undergo strong changes in eccentricity and argument of pericentre due to solar radiation pressure, and in semi-major axis due to aerodynamic drag. These effects can be exploited for a number of applications, providing solutions to existing problems for space mission design. In this thesis an analytical Hamiltonian model of the orbital evolution of high area-to-massratio objects is used to identify potential mission applications on decreasing length-scale. These applications are then investigated using numerical methods and validated against high-precision orbit propagations. On the metre-scale, applications for small satellites, of 100 kg mass or less, are developed. Firstly, a passive orbit manoeuvre from geostationary transfer orbit to low Earth orbit is investigated. This method has the potential to enable a new range of piggy-back launches for small satellites. Using the same insights, the strategy of solar radiation pressure augmented deorbiting is presented. The deorbiting method can enable passive end-of-life removal from very high altitude orbits. On the millimetre-scale, an orbit control method for so-called SpaceChips is developed. The method uses electrochromic coatings to allow the SpaceChip to alter its optical properties and thus modulate the perturbation due to solar radiation pressure. Different control algorithms are discussed and evaluated. Finally, on the micrometre-scale, a dispersion strategy for a planetary dust ring extracted from a captured asteroid is presented. The long-lived dust ring is designed to reduce the solar input to the global climate system and mitigate global warming. Heliotropic orbits are used as a means of passively controlling the ring.High area-to-mass-ratio spacecraft experience a signifcant perturbation due to surface forces, such as solar radiation pressure and aerodynamic drag. Hence, their orbits do not evolve in the manner of traditional satellites. They undergo strong changes in eccentricity and argument of pericentre due to solar radiation pressure, and in semi-major axis due to aerodynamic drag. These effects can be exploited for a number of applications, providing solutions to existing problems for space mission design. In this thesis an analytical Hamiltonian model of the orbital evolution of high area-to-massratio objects is used to identify potential mission applications on decreasing length-scale. These applications are then investigated using numerical methods and validated against high-precision orbit propagations. On the metre-scale, applications for small satellites, of 100 kg mass or less, are developed. Firstly, a passive orbit manoeuvre from geostationary transfer orbit to low Earth orbit is investigated. This method has the potential to enable a new range of piggy-back launches for small satellites. Using the same insights, the strategy of solar radiation pressure augmented deorbiting is presented. The deorbiting method can enable passive end-of-life removal from very high altitude orbits. On the millimetre-scale, an orbit control method for so-called SpaceChips is developed. The method uses electrochromic coatings to allow the SpaceChip to alter its optical properties and thus modulate the perturbation due to solar radiation pressure. Different control algorithms are discussed and evaluated. Finally, on the micrometre-scale, a dispersion strategy for a planetary dust ring extracted from a captured asteroid is presented. The long-lived dust ring is designed to reduce the solar input to the global climate system and mitigate global warming. Heliotropic orbits are used as a means of passively controlling the ring