National scale modelling to test UK population growth and infrastructure scenarios

This paper describes an exploratory methodology used to study the national scale issues of population growth and infrastructure implementation across the UK. The project was carried out for the Government Office for Science in 2015, focussing on two key questions: how could a “spatially driven” scenario provoke new thinking on accommodating forecast growth, and; what would be the impact of transport infrastructure investments within this context. Addressing these questions required the construction of a national scale spatial model that also needed to integrate datasets on population and employment. Models were analysed and profiled initially to identify existing relationships between the distribution of population and employment against the spatial network. Based on these profiles, an experimental methodology was used to firstly identify cities with the potential to accommodate growth, then secondly to allocate additional population proportionally. This raises important questions for discussion around which cities provide the benchmark for growth and why, as well as what the optimal spatial conditions for population growth may be, and how this growth should be accommodated locally. Later the model was used to study the impact of High Speed Rail. As these proposed infrastructure changes improve service (capacity, frequency, journey time), rather than creating new topological connections, the model was adapted to be able to produce time based catchments as an output. These catchments could then be expressed in terms of the workforce population within an hour of every city (a potential travel to work area), as well as the number of employment opportunities within an hour of every household

Apparatus to control and visualize the impact of a high-energy laser pulse on a liquid target

We present an experimental apparatus to control and visualize the response of a liquid target to a laser-induced vaporization. We use a millimeter-sized drop as target and present two liquid-dye solutions that allow a variation of the absorption coefficient of the laser light in the drop by seven orders of magnitude. The excitation source is a Q-switched Nd:YAG laser at its frequency-doubled wavelength emitting nanosecond pulses with energy densities above the local vaporization threshold. The absorption of the laser energy leads to a large-scale liquid motion at timescales that are separated by several orders of magnitude, which we spatiotemporally resolve by a combination of ultra-high-speed and stroboscopic high-resolution imaging in two orthogonal views. Surprisingly, the large-scale liquid motion at upon laser impact is completely controlled by the spatial energy distribution obtained by a precise beam-shaping technique. The apparatus demonstrates the potential for accurate and quantitative studies of laser-matter interactions.Comment: Submitted to Review of Scientific Instrument

Road centre line simplification principles for angular segment analysis

Angular segment analysis is one of the most fundamental analyses in space syntax practice that helps understand movement, land-use and other socio-economic patterns. It was initially applied in axial segment maps and later was used in road centre line maps as an attempt to overcome the 'segment problem' (Turner, 2005). Furthermore, the growing need to examine large urban systems has led to the wide use of road centre line maps instead of the previously hand-drawn axial maps. However, this transition to such datasets has lacked systematic studies on what is required to convert a road centre line map into a segment map, in order to produce reliable results of the angular segment analysis. To date, no consensual methodology has been developed within the space syntax community. This paper attempts to clarify what a road centre line segment represents spatially and suggests principles and rules to simplify a road centre line map to a segment map. Based on previous experience, the simplification mostly relies on the following two principles: reducing the number of nodes in the dual graph representation of a street network; optimising the angular change between adjacent nodes of the dual graph when space allows it. In addition to the above general principles, we discuss rules for special and complex cases, e.g. roundabouts, underpasses, bridges etc. To evaluate these rules and principles comparisons are carried out between traditional axial and RCL unsimplified and simplified segment maps, to develop a good understanding of how changes in dual graph representation of a street network can affect space syntax measure of 'choice'. Correlations of angular segment choice values are performed in order to evaluate which simplification technique can approximate better the axial representation of actual human activity. The results show that using a raw road centre line data set raises several inconsistencies in the analysis results, and the progressive application of the different simplification techniques brings these results closer to those of a traditional axial segment map, and thus to a better representation of socio-economic activity. The purpose of simplification is to minimise inconsistencies to ensure maximum accuracy in the results of angular segment analysis

Ion distribution and ablation depth measurements of a fs-ps laser-irradiated solid tin target

The ablation of solid tin surfaces by an 800-nanometer-wavelength laser is studied for a pulse length range from 500 fs to 4.5 ps and a fluence range spanning 0.9 to 22 J/cm^2. The ablation depth and volume are obtained employing a high-numerical-aperture optical microscope, while the ion yield and energy distributions are obtained from a set of Faraday cups set up under various angles. We found a slight increase of the ion yield for an increasing pulse length, while the ablation depth is slightly decreasing. The ablation volume remained constant as a function of pulse length. The ablation depth follows a two-region logarithmic dependence on the fluence, in agreement with the available literature and theory. In the examined fluence range, the ion yield angular distribution is sharply peaked along the target normal at low fluences but rapidly broadens with increasing fluence. The total ionization fraction increases monotonically with fluence to a 5-6% maximum, which is substantially lower than the typical ionization fractions obtained with nanosecond-pulse ablation. The angular distribution of the ions does not depend on the laser pulse length within the measurement uncertainty. These results are of particular interest for the possible utilization of fs-ps laser systems in plasma sources of extreme ultraviolet light for nanolithography.Comment: 8 pages, 7 figure

ULTRA HIGH FIELD MR CAROTID VESSEL WALL IMAGING: COMPARISON BETWEEN 7T AND 3T

Cardiovascular Aspects of Radiolog

A sparse spin qubit array with integrated control electronics

Current implementations of quantum computers suffer from large numbers of control lines per qubit, becoming unmanageable with system scale up. Here, we discuss a sparse spin-qubit architecture featuring integrated control electronics significantly reducing the off-chip wire count. This quantum-classical hardware integration closes the feasibility gap towards a CMOS quantum computer.Comment: Paper accompanying an invited talk at the 2019 IEEE International Electron Devices Meeting (IEDM), December 7-11, 201