MRC Laboratory of Molecular Biology
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Deriving equations from sensor data using dimensional function synthesis
No full textWe present a new method for deriving functions that model the relationship between multiple signals in a physical system. The method, which we call dimensional function synthesis, applies to data streams where the dimensions of the signals (e.g., length, mass, etc.) are known. The method comprises two phases: a compile-time synthesis phase and a subsequent calibration using sensor data. We implement dimensional function synthesis and use the implementation to demonstrate efficiently summarizing multimodal sensor data for two physical systems using 90 laboratory experiments and 10,000 synthetic idealized measurements. The results show that our technique can generate models in less than 300 ms on average across all the physical systems we evaluated. This is a marked improvement when compared to an average of 16 s for training neural networks of comparable accuracy on the same computing platform. When calibrated with sensor data, our models outperform traditional regression and neural network models in inference accuracy in all the cases we evaluated. In addition, our models perform better in training latency (up to 1096X improvement) and required arithmetic operations in inference (up to 34X improvement). These significant gains are largely the result of exploiting information on the physics of signals that has hitherto been ignored
A clustering approach to clean cooking transition pathways for low-income households in Bangalore
No full textImproving access to clean cooking is a key part of India's strategy to reduce energy poverty and tackle the health impacts of solid biomass fuel use. Currently policies to promote uptake of clean cooking fuels do not account for local socio-economic and cultural context. However, lack of access to clean cooking is a multi-dimensional problem that requires an understanding of both socio-economic macro-scale trends, as well as household and community behaviour at a micro-scale. This study uses data science approaches to integrate quantitative and qualitative data from a survey of low-income households in Bangalore, to identify dominant socio-economic characteristics, behaviours, and decision-making that act as barriers to clean cooking across a community. Key barriers identified include awareness and access to subsidy programmes, safety concerns, as well as weak community networks. Low income households can also be adversely affected by kerosene restrictions intended to promote LPG uptake. The clean cooking transition pathways identified can support targeting of local policy interventions to address barriers to clean cooking faced by different groups of households
Similar outcomes, different paths: Tracing the relationship between neighborhood-scale built environment and travel behavior using activity-based modelling
No full textThe relationship between the built environment and travel behavior has long been a hot research topic. However, most existing research focus on aggregate measures of the patterns of daily travel (e.g. vehicle miles travelled, total distance travelled), while the mechanisms and processes that lead to these outcomes are much less researched. We therefore propose an activity-based model that simulates people's detailed decision making in daily travel and the influences of the neighborhood-scale built environment throughout the process, using Beijing as the study case. More specifically, it deals with eight activity types, eleven most common activity plans, 652 traffic analysis zones, six time slots and four travel modes. The model is then applied to simulate how people's travel behavior would change in response to changes in the built environment. The simulation is implemented by changing the built environment conditions. The major advantage of the model lies in its ability to ‘trace back’ the influence of the built environment on aggregate travel outcomes to detailed travel aspects, such as activity frequency, travel distance for various purposes, mode choice, etc. The simulation results show that although compact design generally reduce VMT, the mechanisms of influence by different built environment variables vary, e.g. through a major impact on the mode choice or through distributed impacts on several travel aspects
High-fidelity simulation training with PPE may optimise resuscitation outcomes in the COVID-19 era
No full textExciton–phonon coupling strength in single-layer MoSe<inf>2</inf> at room temperature
No full textSingle-layer transition metal dichalcogenides are at the center of an ever increasing research effort both in terms of fundamental physics and applications. Exciton–phonon coupling plays a key role in determining the (opto)electronic properties of these materials. However, the exciton–phonon coupling strength has not been measured at room temperature. Here, we use two-dimensional micro-spectroscopy to determine exciton–phonon coupling of single-layer MoSe2. We detect beating signals as a function of waiting time induced by the coupling between A excitons and A′1 optical phonons. Analysis of beating maps combined with simulations provides the exciton–phonon coupling. We get a Huang–Rhys factor ~1, larger than in most other inorganic semiconductor nanostructures. Our technique offers a unique tool to measure exciton–phonon coupling also in other heterogeneous semiconducting systems, with a spatial resolution ~260 nm, and provides design-relevant parameters for the development of optoelectronic devices
On the assessment of seismic performance of bridge piers on caisson foundations subjected to strong ground motions
No full textSubstructure method is widely used to evaluate the seismic performance of caisson foundations supporting bridge piers subjected to strong ground motions, mainly because of its simplicity. However, the strongly-simplifying assumption of linear viscous-elastic behaviour for the foundation soil limits its applicability to flexible systems subjected to low-intensity earthquakes, for which irreversible strains and pore water pressure build-up are not anticipated. Furthermore, lumped-parameter models are typically adopted in calculations in which soil-foundation compliance is reproduced via dynamic impedance functions, whose dependency on frequency of excitation is often neglected. Modification of free-field motion leading to foundation input motion (FIM), due to the presence of caisson embedment, is also mostly ignored. The influence of these simplifying assumptions on the seismic performance of bridge piers on caisson foundations is assessed in this paper through a parametric study, where soil-caisson-bridge pier-deck systems differing in geometric and mechanical properties are subjected to real seismic records. Dynamic analyses were carried out in the time domain with the finite element method, using a 3D continuum and a lumped-parameter model for the foundation soil. In the 3D model both the linear viscous-elastic and the nonlinear soil behaviour were assumed, while linear viscous-elastic behaviour was assumed in the lumped-parameter model. The influence of inelastic soil behaviour was assessed by comparing the seismic performance of the systems obtained with the 3D model, while the role of FIM was evaluated by comparing the results of the dynamic analyses computed assimilating the soil to a linear elastic medium
SARS-CoV-2 transmission risk from asymptomatic carriers: Results from a mass screening programme in Luxembourg.
No full textBackground: To accompany the lifting of COVID-19 lockdown measures, Luxembourg implemented a mass screening (MS) programme. The first phase coincided with an early summer epidemic wave in 2020. Methods: rRT-PCR-based screening for SARS-CoV-2 was performed by pooling of samples. The infrastructure allowed the testing of the entire resident and cross-border worker populations. The strategy relied on social connectivity within different activity sectors. Invitation frequencies were tactically increased in sectors and regions with higher prevalence. The results were analysed alongside contact tracing data. Findings: The voluntary programme covered 49% of the resident and 22% of the cross-border worker populations. It identified 850 index cases with an additional 249 cases from contact tracing. Over-representation was observed in the services, hospitality and construction sectors alongside regional differences. Asymptomatic cases had a significant but lower secondary attack rate when compared to symptomatic individuals. Based on simulations using an agent-based SEIR model, the total number of expected cases would have been 42·9% (90% CI [-0·3, 96·7]) higher without MS. Mandatory participation would have resulted in a further difference of 39·7% [19·6, 59·2]. Interpretation: Strategic and tactical MS allows the suppression of epidemic dynamics. Asymptomatic carriers represent a significant risk for transmission. Containment of future outbreaks will depend on early testing in sectors and regions. Higher participation rates must be assured through targeted incentivisation and recurrent invitation. Funding: This project was funded by the Luxembourg Ministries of Higher Education and Research, and Health
Soot-free low-NO<inf>x</inf>aeronautical combustor concept: The lean azimuthal flame for kerosene sprays
No full textAn ultralow emission combustor concept based on "flameless oxidation"is demonstrated in this paper for aviation kerosene. Measurements of gas emissions, as well as of the size and number of nanoparticles via scanning mobility particle sizing, are carried out at the combustor outlet, revealing simultaneously sootfree and single-digit NOx levels for operation at atmospheric conditions. Such performance, achieved with direct spray injection of the fuel without any external preheating or prevaporization, is attributed to the unique mixing configuration of the combustor. The combustor consists of azimuthally arranged fuel sprays at the upstream boundary and reverse-flow air jets injected from downstream. This creates locally sequential combustion, good mixing with hot products, and a strong whirling motion that increases residence time and homogenizes the mixture. Under ideal conditions, a clean, bright-blue kerosene flame is observed, free of soot luminescence. Although soot is intermittently formed during operation around optimal conditions, high-speed imaging of the soot luminescence shows that particles are subjected to long residence times at O2-rich conditions and high temperatures, which likely promotes their oxidation. As a result, only nanoparticles in the 2-10 nm range are measured at the outlet under all tested conditions. The NOx emissions and completeness of the combustion are strongly affected by the splitting of the air flow. Numerical simulations confirm the trend observed in the experiment and provide more insight into the mixing and air dilution
Adsorption and diffusion of alkali atoms on FeX<inf>2</inf> (X = Se, S) surfaces for potassium-ion battery applications
No full textThe adsorption and diffusion behaviors of alkali atoms on all stable surfaces of FeX2 (X = Se, S) were studied by DFT calculation to investigate its application potential as electrode material for potassium-ion battery applications. The surface energies of all possible surfaces of FeSe2 and FeS2 are calculated to identify the stable ones with Wulff construction, and these surfaces were FeS2(0 0 1), FeSe2(1 1 0), and the FeSe2(0 0 1) surface, and the stable adsorption sites on those surfaces were also identified. Based on the chosen positions, the diffusion paths of the alkali atoms on these surfaces were examined to obtain the diffusion energy barrier of all these surfaces. It turned out that the lowest energy barrier was only 0.06 eV which occurred on FeS2(0 0 1) surface and FeSe2(1 1 0) surface. According to this research, FeSe2 offered both suitable negative adsorption energy and a relatively small diffusion barrier, which made it a promising electrode material of potassium-ion batteries
Tellurium nanowire gate-all-around MOSFETs for Sub-5 nm applications
No full textThe nanowire (NW) and gate-all-around (GAA) technologies are regarded as the ultimate solutions to sustain Moore's law benefitting from the exceptional gate control ability. Herein, we conduct a comprehensive ab initio quantum transportation calculation at different diameters (single trigonal-tellurium NW (1Te) and three trigonal-tellrium NW (3Te)) sub-5 nm tellurium (Te) GAA NW metal-oxide-semiconductor field-effect transistors (MOSFETs). The results claim that the performance of 1Te FETs is superior to that of 3Te FETs. Encouragingly, the single Te (1Te) n-type MOSFET with 5 nm gate length achieves International Technology Roadmap for Semiconductors (ITRS) high-performance (HP) and low-dissipation (LP) goals simultaneously. Especially, the HP on-state current reaches 6479 μA/μm, 7 times higher than the goal (900 μA/μm). Moreover, the subthreshold swing of the n-type 1Te FETs even hits a thermionic limit of 60 mV/dec. In terms of the spin-orbit coupling effect, the drain currents of devices are further improved, particularly the p-type Te FETs can also achieve the ITRS HP goal. Hence, the GAA Te MOSFETs provide a feasible approach for state-of-the-art sub-5 nm device applications