An expert elicitation of climate, energy and economic uncertainties

Critical energy policy decisions rely on expert assessments of key future uncertainties. But existing modelling techniques that help form these expert assessments often ignore the existence of uncertainty. Consequently, techniques to measure these uncertainties are of increasing importance. We use one technique, expert elicitation, to assess six key uncertain parameters with 25 UK energy experts across academia, government and industry. We obtain qualitative descriptions of the uncertain parameters and a novel data set of probability distributions describing individual expert beliefs. We conduct a sensitivity analysis on weights for a linear opinion pool and show that aggregated median beliefs in 2030 are: for oil price $120/barrel (90$34/tCO2e (90% CI: 5, 256) and for levelised cost of low-carbon electricity 17.1 US cents/kWh (90% CI: 8.3, 31.0). The quantitative results could inform model validation, help benchmark policy makers’ beliefs or provide probabilistic inputs to models

Nonunitary quantum computation in the ground space of local Hamiltonians

A central result in the study of quantum Hamiltonian complexity is that the k-local Hamiltonian problem is quantum-Merlin-Arthur–complete. In that problem, we must decide if the lowest eigenvalue of a Hamiltonian is bounded below some value, or above another, promised one of these is true. Given the ground state of the Hamiltonian, a quantum computer can determine this question, even if the ground state itself may not be efficiently quantum preparable. Kitaev’s proof of QMA-completeness encodes a unitary quantum circuit in QMA into the ground space of a Hamiltonian. However, we now have quantum computing models based on measurement instead of unitary evolution; furthermore, we can use postselected measurement as an additional computational tool. In this work, we generalize Kitaev’s construction to allow for nonunitary evolution including postselection. Furthermore, we consider a type of postselection under which the construction is consistent, which we call tame postselection. We consider the computational complexity consequences of this construction and then consider how the probability of an event upon which we are postselecting affects the gap between the ground-state energy and the energy of the first excited state of its corresponding Hamiltonian. We provide numerical evidence that the two are not immediately related by giving a family of circuits where the probability of an event upon which we postselect is exponentially small, but the gap in the energy levels of the Hamiltonian decreases as a polynomial

Multiple populations within globular clusters in Early-type galaxies Exploring their effect on stellar initial mass function estimates

It is now well-established that most (if not all) ancient globular clusters host multiple popula- tions, that are characterised by distinct chemical features such as helium abundance variations along with N-C and Na-O anti-correlations, at fixed [Fe/H]. These very distinct chemical fea- tures are similar to what is found in the centres of the massive early-type galaxies and may influence measurements of the global properties of the galaxies. Additionally, recent results have suggested that M/L variations found in the centres of massive early-type galaxies might be due to a bottom-heavy stellar initial mass function. We present an analysis of the effects of globular cluster-like multiple populations on the integrated properties of early-type galaxies. In particular, we focus on spectral features in the integrated optical spectrum and the global mass-to-light ratio that have been used to infer variations in the stellar initial mass function. To achieve this we develop appropriate stellar population synthesis models and take into account, for the first time, an initial-final mass relation which takes into consideration a varying He abundance. We conclude that while the multiple populations may be present in massive early-type galaxies, they are likely not responsible for the observed variations in the mass- to-light ratio and IMF sensitive line strengths. Finally, we estimate the fraction of stars with multiple populations chemistry that come from disrupted globular clusters within massive ellipticals and find that they may explain some of the observed chemical patterns in the centres of these galaxies

Comparing verbal media for alarm handling: Speech versus textual displays

The rise of computers in command and control domains has meant that control operations can be performed via desk-based visual display terminals. This trend has also produced the potential to display information to operators in a variety of formats. Of particular interest has been the use of text-based displays for alarm presentation. There are possible limitations to the use of text for alarm presentation, not least of which is the need for a dedicated alarms display screen (or, at least, a display page). Given the capability of computers to synthesize speech, it is possible that speech-based alarms could generate the same information as text-based displays without the need for dedicated screen space. In this paper an experimental comparison of speech-based and text-based displays for presentation of alarms is reported. The findings show that speech leads to longer response times than text displays, but that it has minimal effect on the efficacy of fault handling. The results are discussed within the alarm initiated activities framework and implications for alarm system design are outlined

Physical inactivity and its predictors among adolescents in Saudi Arabia: A cross-sectional comparison between cities with and without a Healthy Cities Program.

OBJECTIVES: To estimate the prevalence of insufficient physical activity and excessive screen time among adolescents living in cities participating in the Healthy Cities Program (HCP) and cities not running the program in the Qassim region of Saudi Arabia. METHODS: We surveyed 1133 adolescents from the Qassim region using systematic random sampling between April and September 2017. Multivariable logistic regression analyses were conducted to investigate the predictors of insufficient levels of PA and excessive screen time. RESULTS: The prevalence of <60 minutes of moderate- to vigorous-intensity physical activity/day was 82.4% and <3 days of vigorous intensity physical activity/week among adolescents was 59%. There was no significant association between living in healthy cities (HCPs) and insufficient levels of physical activity. The odds of excessive screen time were higher in HCPs than in cities not running the program (NHCPs) (OR: 1.49). The odds of insufficient daily PA (OR: 2.19) are higher among girls than boys. Increasing age is positively associated with insufficient weekly PA (OR: 1.19). The prevalence of excessive recreational screen time is 84.6% with higher odds in HCPs than in NHCPs (OR: 1.51). CONCLUSION: Our findings report a lack of evidence of any impact of the HCP on adolescents' physical activity behaviors. This outcome warrants a further in-depth evaluation of the process and outcomes of the HCP in Saudi Arabia

UK MARKAL Modelling - Examining Decarbonisation Pathways in the 2020s on the Way to Meeting the 2050 Emissions Target

CCC will provide advice on the 4th carbon budget period – covering 2023-2027 – in December 2010. As part of the underpinning evidence base for this advice, CCC commissioned this major energy modelling study, focusing on mid-term (2020-2030) uncertainties in the feasibility, costs and trade-offs of alternate pathways towards meeting the 2050 target

Critical mid-term uncertainties in long-term decarbonisation pathways

Over the next decade, large energy investments are required in the UK to meet growing energy service demands and legally binding emission targets under a pioneering policy agenda. These are necessary despite deep mid-term (2025–2030) uncertainties over which national policy makers have little control. We investigate the effect of two critical mid-term uncertainties on optimal near-term investment decisions using a two-stage stochastic energy system model. The results show that where future fossil fuel prices are uncertain: (i) the near term hedging strategy to 2030 differs from any one deterministic fuel price scenario and is structurally dissimilar to a simple ‘average’ of the deterministic scenarios, and (ii) multiple recourse strategies from 2030 are perturbed by path dependencies caused by hedging investments. Evaluating the uncertainty under a decarbonisation agenda shows that fossil fuel price uncertainty is very expensive at around £20 billion. The addition of novel mitigation options reduces the value of fossil fuel price uncertainty to £11 billion. Uncertain biomass import availability shows a much lower value of uncertainty at £300 million. This paper reveals the complex relationship between the flexibility of the energy system and mitigating the costs of uncertainty due to the path-dependencies caused by the long-life times of both infrastructures and generation technologies

Effect of structural disorder on quantum oscillations in graphite

PublishedWe have studied the effect of structural disorder on the de Haas van Alphen and Shubnikov de Haas quantum oscillations measured in natural, Kish, and highly oriented pyrolytic graphite samples at temperatures down to 30 mK and at magnetic fields up to 14 T. The measurements were performed on different samples characterized by means of x-ray diffractometry, transmission electron microscopy, and atomic-force microscopy techniques. Our results reveal a correlation between the amplitude of quantum oscillations and the sample surface roughness.This work was carried out with the support of CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico—Brasil) and FAPESP (Fundação de Amparo a Pesquisa do Estado de São Paulo)

Formation of misfit dislocations in strained-layer GaAs/In_xGa_1–xAs/GaAs heterostructures during postfabrication thermal processing

It is demonstrated that relaxation of GaAs/InxGa1–xAs/GaAs strained-layer heterostructures can be brought about by postfabrication thermal processing. Misfit dislocations are introduced into the structure during thermal processing, even though the thickness of the strained layer is well below the critical value predicted by the Matthews–Blakeslee model. The misfit dislocations are observed to be of both 60° mixed type and 90° pure edge type. As no relaxation occurs at the lower temperatures encountered during fabrication by molecular-beam epitaxy, it can be inferred that the critical condition for the formation of misfit dislocations is not only a function of strained-layer thickness and composition, but also of temperature. This observation cannot be accounted for by differential thermal expansion or diffusion across the strained-layer interfaces, but the temperature-dependent Peierls force may offer an explanation. The high temperature required to produce relaxation of these structures suggests that they are sufficiently thermally stable for most practical applications