Improving the applicability of radar rainfall estimates for urban pluvial flood modelling and forecasting

This work explores the possibility of improving the applicability of radar rainfall estimates (whose accuracy is generally insufficient) to the verification and operation of urban storm-water drainage models by employing a number of local gauge-based radar rainfall adjustment techniques. The adjustment techniques tested in this work include a simple mean-field bias (MFB) adjustment, as well as a more complex Bayesian radar-raingauge data merging method which aims at better preserving the spatial structure of rainfall fields. In addition, a novel technique (namely, local singularity analysis) is introduced and shown to improve the Bayesian method by better capturing and reproducing storm patterns and peaks. Two urban catchments were used as case studies in this work: the Cranbrook catchment (9 km2) in North-East London, and the Portobello catchment (53 km2) in the East of Edinburgh. In the former, the potential benefits of gauge-based adjusted radar rainfall estimates in an operational context were analysed, whereas in the latter the potential benefits of adjusted estimates for model verification purposes were explored. Different rainfall inputs, including raingauge, original radar and the aforementioned merged estimates were fed into the urban drainage models of the two catchments. The hydraulic outputs were compared against available flow and depth records. On the whole, the tested adjustment techniques proved to improve the applicability of radar rainfall estimates to urban hydrological applications, with the Bayesian-based methods, in particular the singularity sensitive one, providing more realistic and accurate rainfall fields which result in better reproduction of the urban drainage system’s dynamics. Further testing is still necessary in order to better assess the benefits of these adjustment methods, identify their shortcomings and improve them accordingly

Development of Superconducting Tuning Quadrupole Corrector (MQT) Prototypes for the LHC

The main quadrupoles of the Large Hadron Collider (LHC) are connected in families of focusing and defocusing magnets. In order to make tuning corrections in the machine a number of quadrupole corrector magnets (designated MQT) are necessary. These 56 mm diameter aperture magnets have to be compact, with a maximum length of 395 mm and a coil radial thickness of 5 to 7.5 mm, while generating a minimum field gradient of 110 T/m. Two design options have been explored, both using the "counter-winding" system developed at CERN for the fabrication of low cost corrector coils. The first design, with the poles composed of two double-pancake coils, each counter-wound using a single wire, superposed to create 4-layer coils, was developed and built by ACCEL Instruments GmbH. A second design where single coils were counter-wound using a 3-wire ribbon to obtain 6-layer coils was developed at CERN. This paper describes the two designs and reports on the performance of the prototypes during testing

Further Development of the Sextupole and Decapole Spool Corrector Magnets for the LHC

In the Large Hadron Collider (LHC) the main dipoles will be equipped with sextupole (MCS) and decapole (MCD) spool correctors to meet the very high demands of field quality required for the satisfactory operation of the machine. Each decapole corrector will in addition have an octupole insert (MCO) and the assembly of the two is designated MCDO. These correctors are needed in relatively large quantities, i.e. 2464 MCS Sextupoles and 1232 MCDO Decapole-Octupole assemblies. Half the number of the required spool correctors will be made in India through a collaboration between CERN and CAT (Centre for Advanced Technology, Indore, India), the other half will be built by European industry. The paper describes final choices concerning design, materials, production techniques, and testing so as to assure economic magnet manufacture but while maintaining a homogenous magnetic quality that results in a robust product

Intralaminar stimulation of the inferior colliculus facilitates frequency-specific activation in the auditory cortex

Objective. Auditory midbrain implants (AMI) provide inadequate frequency discrimination for open set speech perception. AMIs that can take advantage of the tonotopic laminar of the midbrain may be able to better deliver frequency specific perception and lead to enhanced performance. Stimulation strategies that best elicit frequency specific activity need to be identified. This research examined the characteristic frequency (CF) relationship between regions of the auditory cortex (AC), in response to stimulated regions of the inferior colliculus (IC), comparing monopolar, and intralaminar bipolar electrical stimulation. Approach. Electrical stimulation using multi-channel micro-electrode arrays in the IC was used to elicit AC responses in anaesthetized male hooded Wistar rats. The rate of activity in AC regions with CFs within 3 kHz (CF-aligned) and unaligned CFs was used to assess the frequency specificity of responses. Main results. Both monopolar and bipolar IC stimulation led to CF-aligned neural activity in the AC. Altering the distance between the stimulation and reference electrodes in the IC led to changes in both threshold and dynamic range, with bipolar stimulation with 400 µm spacing evoking the lowest AC threshold and widest dynamic range. At saturation, bipolar stimulation elicited a significantly higher mean spike count in the AC at CF-aligned areas than at CF-unaligned areas when electrode spacing was 400 µm or less. Bipolar stimulation using electrode spacing of 400 µm or less also elicited a higher rate of elicited activity in the AC in both CF-aligned and CF-unaligned regions than monopolar stimulation. When electrodes were spaced 600 µm apart no benefit over monopolar stimulation was observed. Furthermore, monopolar stimulation of the external cortex of the IC resulted in more localized frequency responses than bipolar stimulation when stimulation and reference sites were 200 µm apart. Significance. These findings have implications for the future development of AMI, as a bipolar stimulation strategy may improve the ability of implant users to discriminate between frequencies

Measuring active volume using electrical resistance tomography in a gas-sparged model anaerobic digester

Inadequate mixing in anaerobic digesters fitted with gas sparging systems is caused by many factors, and leads to dead zones where sludge remains stagnant. The present study explores a range of gas sparging configurations that can be implemented to maximize active volume, and validates electrical resistance tomography (ERT) as an effective measurement tool for analysing mixing conditions without the need for visual access to the liquid volume. Air was used as the gas phase, and xanthan gum Keltrol-T (XGKT) solutions at concentrations of 0.15 and 0.4 wt% were selected as transparent simulant fluids for their rheological similarity to digested sludge. Gas flow rate, sparger nozzle orientation (upward-facing vs. downward-facing), and nozzle height were varied, and mixing performance was assessed using flow visualisation experiments. Results were then replicated with ERT for comparison. It was found that the 0.15 wt% XGKT solution achieved almost complete mixing for all configurations, while the 0.4 wt% XGKT solution developed stable, unmixed regions. Gas flow rate made little difference to the final mixed volume suggesting lower power input does not sacrifice steady-state active volume in the reactor. Positioning the nozzle closer to the bottom of the vessel and sparging gas downward both reduced inactive volume. ERT measurements matched flow visualisation results closely, and were able to capture details that flow visualisation ignores. It has been shown that there is great potential for implementing ERT as a method for researching flow behaviours in complex opaque materials, especially the formation and progression of active volume

Midbrain responses to micro-stimulation of the cochlea using high density thin-film arrays

A broader activation of auditory nerve fibres than normal using a cochlear implant contributes to poor frequency discrimination. As cochlear implants also deliver a restricted dynamic range, this hinders the ability to segregate sound sources

Heterogeneous Catalysis of Carbon Species Formation in Space

The formation of primary nanocarbon materials (PAHs, fullerenes, CNT, etc.) in stellar outflows from carbon-rich stars is well-known and expected to follow gas-phase soot formation mechanisms akin to those observed in low-oxygen flames in the laboratory. However, there are other well-established chemistries that can produce such materials through catalytic processes involving small saturated (e.g., [1]) and unsaturated (e.g., [2]) hydrocarbons as a found in aged, cold dense environments. The catalytic centres in such chemistry are commonly first row transition elements, in particular iron and nickel clusters. Moreover, there are even reports of aromatic molecule formation from acetylene on simple olivine mimic surfaces [3] without any catalytic metal participation. There is therefore a strong case for investigations of the surface-promoted formation of these materials in relation to a range of astrophysical environments from warming cores and corinos, through protoplanetary disks to evolved stellar systems and exo-planetary atmospheres. In this presentation, we will outline the activities planned in a new programme entitled Astrocatalysis: In Operando Studies of Catalysis and Photocatalysis of Space-abundant Transition Metals funded by the UK EPSRC exploring the role of transition metal catalysis in astrophysical environments. As part of that programme, we will integrate experimental surface science studies of nanocarbon formation on small atom number (1-3) molecular species and on larger metallic clusters in the Astrochemistry Group at Heriot-Watt University (HWU) with computational investigations on these systems through collaboration with the Rimola Group at the Universitat Autonoma de Barcelona.AcknowledgementsJA acknowledges EPSRC for a DTP Studentship to support his PhD studies. VC and MRSM acknowledge the support of the EPSRC through responsive mode grant no. EP/W023024/1 Astrocatalysis: In Operando Studies Of Catalysis And Photocatalysis Of Space-abundant Transition Metals. AR is indebted to the EU Horizon 2020 research and innovation programme through the European Research Council (ERC) project "Quantum Chemistry on Interstellar Grains” (QUANTUMGRAIN, Grant No. 865657) and to the MICINN for the project PID2021-126427NB-I00.References[1] M. Pudukudy, Z. Yaakoba, M. Z. Mazukia, M. S. Takriff, and S. S. Jahayaca, Applied Catalysis B: Environmental, 218, 298-316 (2017)[2] W. J. Lee, S. S. A. Syed-Hassan, and C. -Z. Li, Fuel Processing Technology, 104, 319-324 (2012)[3] V. L. Frankland, A. D. James, J. D. C. Sánchez, T. P. Mangan, K. Willacy, A. R. Poppe, and J. M. C. Plane, Icarus, 278, 88-99 (2016)<br/