MRC Laboratory of Molecular Biology
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Built environment of Britain in 2040: Scenarios and strategies
No full text© 2020 Elsevier Ltd We are living through a convergence of crises. In 2020, when the ongoing Covid-19 global pandemic spread across the world, it brought economic instability in its wake. Sectors of the built environment (BE), among others, were hit hard by a public health crisis followed swiftly by an unprecedented economic downturn. In 2018, the Intergovernmental Panel on Climate Change (IPCC) report highlighted the need for rapid and drastic action on climate change by 2030 to prevent the disastrous effects of a world warmed by more than 1.5 °C above pre-industrial levels, raising the urgency of achieving the United Nations (UN) Sustainable Development Goals (SDGs) adopted by Member States in 2015. Even rapid decarbonisation, the report warned, would likely not be sufficient to address the intertwined problems of poverty, mass migration, politics and ecological collapse that the SDGs seek to address. Digital technology offers an opportunity to better understand and model solutions to these complex crises, but it is unclear how digital technology should be harnessed in the face of an uncertain future. Written at the beginning of this critical decade leading up to 2030, this paper looks ahead 20 years in the future to better understand the resources, technology, economy, governance, infrastructure, mobility and social factors that may shape the development of Britain's digital BE. By exploring four scenarios around the variables of i) the UK's compliance with the interconnected targets of the SDGs and ii) the size of the workforce relative to the dependent population (dependency), this paper concludes with the identification of key strategies that can lead to the sustainable development of the BE sectors, outlining a number of actions that should be combined with the path for recovery from Covid-19 and are based on digital technology and a green information economy that ensures a future better for everyone in a digital built Britain
Lateral Extensions to Nanowires for Controlling Nickel Silicidation Kinetics: Improving Contact Uniformity of Nanoelectronic Devices
No full textAlthough widely applied as contacts to nanoelectronic devices, metal silicides in nanostructures suffer from varying compositions and growth rates. To study the underlying kinetics and to control the reactions, we introduce local volume extensions ("polders") to silicon nanowires. This method allows to decouple the silicide growth process from variations in the metal supply and to gain a reduced length growth rate as long as the silicon reaction volume is available in the polders. In situ analyses are performed by scanning electron microscopy during the anneal to extract the growth rates. A deterministic limitation of silicide growth by nickel flux, NiSi2 reaction rate, and nickel diffusion is observed. The extracted maximal reaction rate at the NiSi2-Si interface allows to determine the activation energy. Subsequent transmission electron microscopy reveals an epitaxial {111} NiSi2-Si interface in the 〈011〉-oriented nanowire. It is also seen that the polders suppress Ni-rich silicide phases and give rise to the formation of a single-crystalline Ni-Si phase with a Ni/Si ratio close to 1:1. Retarded growth by the application of polders can almost stop the silicidation in nanowires at a defined point even for different Ni fluxes. This can help to reduce gate overlap and channel length variation, especially in Schottky-junction-based field-effect transistors. Geometric optimization of the polder regions with regard to the largest impact is discussed
Manipulating terahertz responses of GdFeO<inf>3</inf> ceramics by thickening and thermal methods
No full textElectric field-induced antiferromagnets with ultrahigh resonant frequencies without current flow in insulating materials is highly desired. This paper reports the terahertz (THz) responses of Γ4 in rare-earth orthoferrite GdFeO3 ceramics, which were manipulated using thickening and thermal methods. As the thickness was increased, the noise was greatly reduced, and increased peak heights of both the ferromagnetic resonances and antiferromagnetic resonances were observed. For the thermal control of THz responses in GdFeO3, the resonant frequencies of both the ferromagnetic resonances and antiferromagnetic resonances experienced a blue shift, and their peak heights increased. The detected shifts of the responses were determined by the changes in thermodynamic potential. Moreover, macroscopic properties were collected to verify the coexistence of ferromagnetism and antiferromagnetism
Extremum sensitivity analysis with polynomial Monte Carlo filtering
No full textGlobal sensitivity analysis is a powerful set of ideas and heuristics for understanding the importance and interplay between uncertain parameters in a computational model. Such a model is characterized by a set of input parameters and an output quantity of interest, where we typically assume that the inputs are independent and their marginal densities are known. If the output quantity is smooth, polynomial chaos can be used to extract Sobol’ indices. In this paper, we build on these well-known ideas by examining two different aspects of this paradigm. First, we study whether sensitivity indices can be computed efficiently if one leverages a polynomial ridge approximation—a polynomial fit over a subspace. Given the assumption of anisotropy in the dependence of a function, we show that sensitivity indices can be computed with a reduced number of model evaluations. Second, we discuss methods for evaluating sensitivities when constrained near output extrema. Methods based on the analysis of skewness are reviewed and a novel type of indices based on Monte Carlo filtering (MCF) – extremum Sobol’ indices – is proposed. We combine these two ideas by showing that these indices can be computed efficiently with ridge approximations, and explore the relationship between MCF-based indices and skewness-based indices empirically
Method for inferring the mechanical strain of GaN-on-Si epitaxial layers using optical profilometry and finite element analysis
No full textGaN-on-Si has become a useful fabrication route for many GaN devices and applications, but the mechanical stress incorporated throughout the material stack can impact the viability of this approach. The transfer printing of GaN membrane devices, a promising emerging technology, is most effective with flat membranes, but in practice many GaN structures released from their Si substrate are highly bowed due to the strain in the epitaxial nitride stack. Our approach uses the optical profiles of epitaxial wafers and membranes as inputs for inferring the mechanical strain state of the material by multi-variable numerical model fitting using COMSOL Multiphysics. This versatile, adaptable and scalable method was tested on samples from two GaN-on-Si wafers, revealing the relationship between built-in strain and material bow in principal-component fashion, returning 3-4×10−4 strain estimates for the AlGaN (compressive) and GaN (tensile) layers, and suggesting the occurrence of plastic deformation during transfer printing
Essential Emergency and Critical Care: a consensus among global clinical experts.
No full textBACKGROUND: Globally, critical illness results in millions of deaths every year. Although many of these deaths are potentially preventable, the basic, life-saving care of critically ill patients are often overlooked in health systems. Essential Emergency and Critical Care (EECC) has been devised as the care that should be provided to all critically ill patients in all hospitals in the world. EECC includes the effective care of low cost and low complexity for the identification and treatment of critically ill patients across all medical specialties. This study aimed to specify the content of EECC and additionally, given the surge of critical illness in the ongoing pandemic, the essential diagnosis-specific care for critically ill patients with COVID-19. METHODS: In a Delphi process, consensus (>90% agreement) was sought from a diverse panel of global clinical experts. The panel iteratively rated proposed treatments and actions based on previous guidelines and the WHO/ICRC's Basic Emergency Care. The output from the Delphi was adapted iteratively with specialist reviewers into a coherent and feasible package of clinical processes plus a list of hospital readiness requirements. RESULTS: The 269 experts in the Delphi panel had clinical experience in different acute medical specialties from 59 countries and from all resource settings. The agreed EECC package contains 40 clinical processes and 67 requirements, plus additions specific for COVID-19. CONCLUSION: The study has specified the content of care that should be provided to all critically ill patients. Implementing EECC could be an effective strategy for policy makers to reduce preventable deaths worldwide
Practicable assessment of cochlear size and shape from clinical CT images
No full textThere is considerable interpersonal variation in the size and shape of the human cochlea, with evident consequences for cochlear implantation. The ability to characterize a specific cochlea, from preoperative computed tomography (CT) images, would allow the clinician to personalize the choice of electrode, surgical approach and postoperative programming. In this study, we present a fast, practicable and freely available method for estimating cochlear size and shape from clinical CT. The approach taken is to fit a template surface to the CT data, using either a statistical shape model or a locally affine deformation (LAD). After fitting, we measure cochlear size, duct length and a novel measure of basal turn non-planarity, which we suggest might correlate with the risk of insertion trauma. Gold-standard measurements from a convenience sample of 18 micro-CT scans are compared with the same quantities estimated from low-resolution, noisy, pseudo-clinical data synthesized from the same micro-CT scans. The best results were obtained using the LAD method, with an expected error of 8–17% of the gold-standard sample range for non-planarity, cochlear size and duct length
A design method for flexible retaining walls in clay
No full textDesign of retaining walls in clay is typically based on ultimate limit state calculations to prevent collapse, with arbitrary factors of safety used to limit deformations. These factors of safety do not take into account the different rates of strength mobilisation in the wide variety of clays found worldwide. As there is substantial uncertainty in this approach, conventional design tends to lead to excessive conservatism with associated high cost. The novel analysis procedure based on the fraction of the strength of soil mobilised for a given wall displacement developed here allows rapid assessment of wall deformations and stresses by way of a simple two-parameter constitutive model which can be easily calibrated using conventional triaxial data. The model is validated based on field and model case histories with a variety of different clays and propping conditions and is shown to exhibit good performance in predicting the behaviour of published case histories based on soil parameters extracted from previously published soil test data. This novel analysis provides for the first time a route for practising engineers to carry out fast, efficient design at early stages of the design process by considering many potential wall geometries without the computational overhead of complex finite-element or finite-difference numerical models
Design of a pressure modulator using fast-acting bistable valves
No full textFast-acting pneumatic valves, combined with a slip-control braking algorithm, have recently been used to improve the straight-line braking performance of an experimental heavy goods vehicle, on low friction roads, by 16%. This paper describes how the fast-acting valves, which were central to the aforementioned research, were designed for use on a commercial vehicle. Design equations, as well as a generalized design method, are first presented for the fast-acting bistable pneumatic valve. A pressure observer is developed to predict the brake chamber pressure in cases where a pressure transducer is mounted upstream. A simple fault detection algorithm is then introduced, which utilizes some of the calculations made in the pressure observer, and is shown to correctly identify faults on a real vehicle. Performance comparisons are made between the new modulator and a conventional heavy goods vehicle electro-pneumatic brake system. Closed-loop frequency response tests show that the control bandwidth of brake chamber pressure on a heavy goods vehicle can be increased from 1.5 Hz to 10 Hz using the new hardware