208 research outputs found
Fortissat Science Alliance podcast: Layla Mathieson
No full textLayla Mathieson was an EPSRC/MRC OPTIMA CDT PhD student studying optical medical imaging alongside an integrated Masters in healthcare innovation and entrepreneurship at the University of Edinburgh. She took part in the Fortissat Science Alliance podcast recordings in September 2021.What is the Fortissat Science Alliance?The Fortissat Science Alliance was a Wellcome Trust & Children In Need "Curiosity" project. This scheme provided informal STEM learning opportunities for young people who attended the community centre Getting Better Together Shotts (GBT Shotts) between 2019 and 2023. Due to the COVID-19 pandemic, deliveries had to pivot online so the podcast was founded. These recordings were made via Zoom with warm-up STEM activities sent to every young person in advance, along with a profile page for each researcher, so that they were relaxed and able to ask excellent questions.Link to episode on Spotify.Depending on the broadcast date, podcast deliveries were co-sponsored by Glasgow Science Festival, EXPLORATHON 2021, or EXPLORATHON 2022/23.For the duration of the project, it was supported jointly by Children in Need and the Wellcome Trust. In 2021, EXPLORATHON episodes were supported by the European Commission [grant agreement ID 101036101]. In 2022-23, EXPLORATHON episodes were supported by the Engineering & Physical Sciences Research Council [grant number EP/X020894/1]. Layla was supported by the EPSRC/MRC Centre for Doctoral Training in Optical Medical Imaging (OPTIMA).Author contributions to contentLayla Mathieson was the guest featured on this episode. Rebecca Hay was the youth worker coordinating the young people who conducted the interviews as well as co-editing and broadcasting the recordings. Iain Hamilton co-edited the episodes. Kirsty Ross was the STEM consultant for the project and uploaded completed episodes to Figshare.</p
Flexible [my]LED-based optical cochlear implant for high-resolution stimulation
No full textThis thesis describes the first functional optical cochlear implant (oCI) based on integrated μLEDs successfully applied in vivo. In order to integrate the highest possible number of individually addressable μLEDs, different routing schemes implementing single- and multi-layer metallization have been evaluated. Based on conclusions drawn during the intense evaluation of the first oCI generation (oCI-1), a new single layer interconnection approach is developed, characterized, and found in a given range of complexity to be more efficient than the commonly used multilayer based multiplexing scheme commonly used for LED arrays. After comparing various light-emitting diode (LED) routing schemes such as common contact, multiplexing and tri-state switching, the most suitable approaches are transferred into two different optical cochlear implant (oCI) designs, namely oCI-1 and the second oCI generation (oCI-2) differing mainly in the way the μLEDs are interfaced. For both design generations a detailed process development is performed and analyzed. All relevant design and process parameters are evaluated in related parameter studies in order to extract the best parameter set. The key process steps developed for oCI-1 are (i) the homogeneous deposition of down to 5-μm-thin epoxy layers using spin-coating, (ii) the reliable wafer-level bonding based on indium used to transfer μLEDs with lateral dimensions down to 60_60 μm2 from the epitaxial sapphire substrate to the polymeric carrier, and (iii) the optimized laser lift-off (LLO) enabling the release of 6-μm-thin μLEDs embedded in a polymeric matrix from the sapphire wafer. The detailed process know-how acquired during the fabrication of oCI-1 implants is subsequently transferred into the layout and process design of the oCI-2 generation. Exemplarily, the epoxy deposition by spin-coating as developed in the case of oCI-1 is applied as well, but also transferred into a planarization step that is one of the key technological steps of oCI-2. The oCI-2 implants utilize the μLED sapphire growth-substrate not only to realize the μLEDs. The substrate also serves as the carrier substrate for the entire fabrication. The single-sided μLED process of the oCI-2 variant allows to implement both μLED contacts facing the same direction. This single-sided processing allows the epoxy substrate to be processed around the μLED mesas once they are realized by dry etching and metal layer deposition. The electroplated metal lines interfacing the μLEDs apply appropriate interconnection schemes and are sandwiched between planarized epoxy layers. For both design generations, a variety of process steps have been implemented in order to optimize the device performance. This includes (i) low-resistive and highly-reflective contacts to the gallium nitride (GaN) to increase the backside reflection in the case of oCI-1, (ii) side-mirrors integrated into the μLED passivation to reduce stray light, (iii) surface roughening of GaN using wet-chemical etching to increase the outcoupling efficiency of photons, (iv) the integration of micro lenses and conical concentrators to increase the peak intensity and confine the emission angle, and (v) the application of transparent, low-resistance n-contacts based on indium tin oxide to increase the emission surface and thus the optical power. In order to connect both types of oCIs several assembly methods are investigated. Based these tests it is concluded, that flip-chip bonding of polyimide-based ribbon cables enables the most reliable interfacing of the μLED arrays. A dedicated process is developed to bond contact pads of different height. This flip-chip bonding process is also identified as the process which is easiest to encapsulate by silicone underfill and provides the highest assembly yield. The complete encapsulation of the oCI and ribbon cable is done by a newly developed molding process which ensures that the sidewalls of the ultra-thin optical probes are encapsulated with a sufficient silicone thickness. The encapsulation procedure, including a preceding washing step applied prior to silicone deposition, is evaluated in a parameter study. Based on in vivo tests performed in cooperation with project partners, it is concluded that a single μLED is capable of efficiently stimulating optogenetically modified nerve cells in the cochlea. It is further demonstrated that the μLED arrays of the oCIs reduce the spectral spread, compared to a clinical style electrical cochlear implant, by up to 5 octaves
Modelling semiconductor pixel detectors
No full textIn this thesis the work will focus on the modelling of highly pixellated solid-state devices. Results are presented on the performance of a pixellated spectroscopic silicon detector - the Dash-E detector. The electronic noise is measured to be 228 eV with the system observed to be close to the Fano limit at room temperature. The characteristic X-rays of Mn-55, Cu, Rb, Mo, Ag and Ba have been used to examine the spectroscopic performance of the detectors. Good linearity over the required energy range 1 keV to 25 keV has been observed. A higher than expected background is evident in all of the spectra taken - approximately a 1:1 correspondence in the peak counts to background counts. The modelled performance of a 3-D GaAs detector is analysed. The effect of the metallic column-like electrode structure on the particle interactions is simulated via the Monte Carlo code MCNP. The effective dead area due to these electrodes is reduced from 8 % to 4.5 % due to the secondary particle interactions. The modelled structure becomes depleted at 50 V with a slight over-depletion of 75 V necessary to minimise the inter-electrode low field regions. The principle benefit of these depletion voltages is that they remain constant for whatever detection thickness that fabrication allows. The charge transport in the devices are also examined, with the damage effects of dry-etching included - a technique used to form the electrode holes in the GaAs material. Full charge collection can be expected after 200 ps in most cases. The effect of reducing the charge carrier lifetime and examining the charge collection efficiency has been utilised to explore how these detectors would respond in a harsh radiation environment. It is predicted that over critical carrier lifetimes (10 ps to 0.1 ns) an improvement of 40 % over conventional detectors can be expected. This also has positive implications for fabricating detectors, in this geometry, from materials which might otherwise be considered substandard. An analysis of charge transport in CdZnTe pixel detectors has been performed. The analysis starts with simulation studies into the formation of contacts and their influence on the internal electric field of planar detectors. The models include a number of well known defect states and these are balanced to give an agreement with a typical experimental I-V curve. The charge transport study extends to the development of a method for studying the effect of charge sharing in highly pixellated detectors. The case of X-ray, as well as higher energy #gamma#-ray, interactions are considered. The charge lost is studied for these interactions over a range of pixel sizes (1#mu#m to 10 mm). The aforementioned Dash-E detector has been used to obtain experimental data for comparison with the models developed, with close agreement being observed. The combination of MCNP and MEDICI is used to form a complete picture of photon interactions in semiconducting materials and also compares well with experiment. The models predict that the dominant term in the sharing of charge is due to diffusion and that the difference with photon energy is due to the energy given to the photoelectron. (author)Available from British Library Document Supply Centre-DSC:DXN047631 / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo
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Genome-wide analysis identifies genetic effects on reproductive success and ongoing natural selection at the FADS locus
No full textThis manuscript represents a large collaboration with many "middle" contributing authors, including the author requesting this waiver (Daniel Chasman). Iain Mathieson, Felix R. Day, Nicola Barban, Felix C. Tropf, and David M. Brazel are the starred (equal contribution) first authors; Melinda C. Mills, and John R.B. Perry are the starred last authors. Corresponding: Iain Mathieson, Melinda C. Mills, and John Perry are the corresponding authors.
Please note that while the uploaded version of the manuscript has been accepted, there may still be changes that would be incorporated in the final publication.Identifying genetic determinants of reproductive success may highlight mechanisms underlying fertility and identify alleles under present-day selection. Using data in 785,604 individuals of European ancestry, we identified 43 genomic loci associated with either number of children ever born (NEB) or childlessness. These loci span diverse aspects of reproductive biology, including puberty timing, age at first birth, sex hormone regulation, endometriosis and age at menopause. Missense variants in ARHGAP27 were associated with higher NEB but shorter reproductive lifespan, suggesting a trade-off at this locus between reproductive ageing and intensity. Other genes implicated by coding variants include PIK3IP1, ZFP82 and LRP4, and our results suggest a new role for the melanocortin 1 receptor (MC1R) in reproductive biology. As NEB is one component of evolutionary fitness, our identified associations indicate loci under present-day natural selection. Integration with data from historical selection scans highlighted an allele in the FADS1/2 gene locus that has been under selection for thousands of years and remains so today. Collectively, our findings demonstrate that a broad range of biological mechanisms contribute to reproductive success.Accepted Manuscrip
Programmable active pixel sensor to investigate neural interactions within the retina
No full textDetection of the visual scene by the eye and the resultant neural interactions of the retina-brain system give us our perception of sight. We have developed an Active Pixel Sensor (APS) to be used as a tool for both furthering understanding of these interactions via experimentation with the retina and to make developments towards a realisable retinal prosthesis. The sensor consists of 469 pixels in a hexagonal array. The pixels are interconnected by a programmable neural network to mimic lateral interactions between retinal cells. Outputs from the sensor are in the form of biphasic current pulse trains suitable to stimulate retinal cells via a biocompatible array. The APS will be described with initial characterisation and test results
Chaplains in the Royal Australian Navy : 1912 to the Vietnam war
No full textKnown in naval slang as ‘sin-bosuns’, chaplains have served as an integral part of the Royal Australian Navy for a century. From Keith Mathieson, who supported his shipmates in a Japanese prisoner-of-war camp, to the first Australian navy chaplain to be killed in active service, George Stubbs on HMAS Sydney, this book profiles chaplains serving at sea and in naval establishments, both in war and peace. Rowan Strong examines the chaplains’ role as religious ministers, counsellors, and clergy prepared to challenge naval culture from a religious standpoint. He also looks at the forces of change, including denominational rivalry and cooperation, tensions between religious and military roles, and shifts in Australian society. Royal Australian Navy chaplains have sought to serve both God and country; this book reveals the difficulties and successes of that task
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