Definitive crystal structure of 1,1'-bis[1,2-dicarba-<i>clos</i>o-dodecaborane(11)]

In the title compound, C4H22B20, the two {1,2-closo-C2B10H11} cages are linked across a centre of inversion with a C—C distance of 1.5339 (11) Å. By careful analysis of the structure, it is established that the non-linking cage C atom is equally disordered over cage vertices 2 and 3

Colour constancy in dichromats and trichromats: dependence on task

An important topic in the field of colour vision is the impact of colour vision deficiencies on daily life tasks. Investigating the extent to which colour constancy (i.e. the ability to recognise surface colour under different illuminants) is preserved in colour vision- deficient observers can provide us with insight into the nature and function of trichromatic colour vision. The first chapter of this thesis provides a summary of the very basics of colour vision, colour vision deficiencies, as well as colour constancy. Studies conducted on the colour constancy abilities of colour-vision-deficient observers versus those with normal colour vision are reviewed. The second chapter presents and reports the aims and methods of the proposed experiment (which could not take place due to the COVID-19 pandemic). This experiment investigated the colour constancy abilities of trichromats versus dichromats using two different colour constancy tasks (2D achromatic adjustment vs. 3D blocks-copying/selection task) and aimed to show how colour constancy depends on observer type as well as task type. The third chapter comprises of a computerised simulation. This simulation aimed to model the colour constancy of “ideal” observers when presented with various surfaces and illuminants. These observers involve simulated normal trichromats, anomalous trichromats and dichromats. A variety of yellow, blue, green and red illuminant shifts (from neutral daylight) were used, and surface chromaticity and observer types were compared. Overall, whilst no three-way interaction between illuminant shift, surface chromaticity and observer type were found in the simulation, strong main effects were found. It is suggested that a combination of simulated and experimental research is needed to understand the colour constancy mechanisms underpinning dichromacy and trichromacy at multiple levels (cone-based, cognitive and computational)

Reduction-induced facile isomerisation of metallacarboranes:synthesis and crystallographic characterisation of 4-Cp-4,1,2-closo-CoC₂B₉H₁₁

One-electron reduction of 3-Cp-3,1,2-closo-CoC2B9H11 followed by heating to reflux in DME (b.p. 85 °C) induces isomerisation to 4-Cp-4,1,2-closo-CoC2B9H11.</p

Steric <i>versus</i> electronic factors in metallacarborane isomerisation: nickelacarboranes with 3,1,2-, 4,1,2- and 2,1,8-NiC₂B₉ architectures and pendant carborane groups, derived from 1,1′-bis(o-carborane)

Nickelacarborane derivatives of 1,1′-bis(o-carborane) allow comment on the factors important in the isomerisation of metallacarboranes.</p

Effectiveness and cost-effectiveness of a telehealth intervention to support the management of long-term conditions:study protocol for two linked randomized controlled trials

As the population ages, more people are suffering from long-term health conditions (LTCs). Health services around the world are exploring new ways of supporting people with LTCs and there is great interest in the use of telehealth: technologies such as the Internet, telephone and home self-monitoring

Molecular Beam Epitaxial Growth Optimization for Next Generation Optoelectronic Devices Based on III-V Semiconductors

Molecular beam epitaxy (MBE) has been serving as the best tool for group III-V compound growths due to its capability of depositing epilayers with high single-crystalline quality, high purity and Angstrom-scale thickness precision. In spite of decades of work, further optimizations of MBE growth conditions are required in order to meet the increasing demands of next-generation and novel devices. For instance, low temperature (LT) deposition far away from thermal equilibrium growth conditions brings several benefits such as suppressed undesirable interface inter-diffusion, dopant diffusion and segregation. More importantly, it has been proven to be a very useful method in forming non-stoichiometric III-V compounds. Although this creates defects like group V antisites and interstitials, they can be utilized in making terahertz (THz) photoconductive antennas (PCAs). Since the development of THz technology in the late 20th century, THz PCAs have been drawing tremendous research interest due to their low-cost and portability. The amount of embedded excess As which alters the LT grown III-V material properties is sensitive to the V/III flux ratio, and more importantly, the growth temperature at the range of ∼200–300◦C. It is crucial to determine a critical substrate temperature that simultaneously maximizes the excess As incorporation without losing single crystallinity, as both features are essential for high-performance broadband THz PCAs applications. However, substrate temperature monitoring becomes difficult when the growth is switched to the LT regime. Conventional substrate temperature measurement techniques such as pyrometry have limited precision at LT due to the exponential decrease of the substrate thermal radiation intensity with the temperature, hence an alternative means for precise temperature monitoring is required. InAlGaAs has been an emerging candidate for 1319 nm laser-pumped, high-efficiency photonic power converters (PPCs). To acquire smooth surface morphology and minimize crystalline defects, such quaternary material is preferred to be lattice-matched on InP(001) substrates. A clear correlation between group III compositions, lattice constant and bandgap of InAlGaAs, as well as a reproducible approach to grow lattice-matched InAlGaAs structures need to be established to optimize the PPC performance. This thesis conducts a comprehensive study of optimizing MBE growth conditions of several III-V materials, including LT GaAs, mid-temperature (MT) and LT InGaAs-InAlAs superlattice (SL), and InAlGaAs, with parameters such as substrate temperature, As overpressure and doping concentration being repetitively tuned. In particular, an integrated spectral pyrometry (ISP) technique is proposed, which is particularly well suited to monitor the growth temperature of InAs and InSb. Potentially, ISP can also be applied to other LT growths with semiconductors of smaller bandgaps when pyrometer does not work. In-growth and post-growth surface morphologies were investigated with the aid of reflection high energy electron diffraction (RHEED) and Nomarski microscopy. LT GaAs and InGaAs-InAlAs SL based THz PCAs were characterized with 780 and 1550 nm pumped time-domain spectroscopy (TDS) measurements and the correlation between THz signal amplitude, pulse width and bandwidth with growth and annealing temperatures are discussed. The material properties of InAlGaAs structures were investigated with an emphasis on discussing challenges of lattice mismatch and in-growth flux drift studied by high-resolution x-ray diffraction (HRXRD) fitting. The performance of InAlGaAs p-n junctions was optimized by MBE. State-of-the-art 1319 nm pumped single-junction (SJ) and two-junction (TJ) PPC devices are presented. The effects of growth temperature on current-voltage characteristics and unintentionally strained InAlGaAs epilayers on quantum efficiency are discussed

Morphological and Doppler UHR-OCT Imaging of Retinal Degeneration Induced by Sodium Iodate Toxicity in a Rat Model

A high speed, high resolution spectral domain optical coherence tomography (SD-OCT) system was used to study in-vivo early morphological changes and optical nerve head (ONH) blood flow in the Long Evans rat retina, induced by administration of sodium iodate (NaIO3). Linear and circular scanned OCT images were acquired at the same location in the retina from healthy control rats and from rats injected with 40mg/kg of NaIO3 solution at 1, 3, 6 12, 24, 72 and 168 hours post drug administration. Morphological OCT images showed changes in the optical reflectance and layer thickness of the photoreceptor IS and OS. The formation of a new low reflective layer between the photoreceptor OS and the RPE was observed in all tested rats. This new layer appeared as early as 1 hour, increased in thickness after 6 hours, and disappeared by 12 hours post NaIO3 injection. The low optical reflectance and the dynamics of this new layer suggest that it was most likely fluid accumulation. Comparison with H&E stained histological sections and IgG immunohistochemistry revealed minimal photoreceptor OS cell swelling at hour 1, detachment of the OS from the RPE by hour 3, and breaking of the blood-retina barrier with significant fluid accumulation by hour 6 post NaIO3 injection. The Doppler Optical Micro-Angiography (DOMAG) algorithm was used to carry out quantitative analysis of the ONH blood flow. Estimation of flow rate on each ONH vessel was done by measurements of the Doppler angle, vessel size and the axial velocity. This study has demonstrated that the capability of UHR-OCT to study optical reflectance and layer thickness changes, rearrangement and detachment of the photoreceptor OS and RPE layers, together with flow rate estimation of retinal blood vessels. Therefore, it can serve as markers in future non-invasive, in-vivo studies of disease or drug induced retinal degeneration in ophthalmic research

Digital Quantum Simulation of the Statistical Mechanics of a Frustrated Magnet

Many problems of interest in physics, chemistry and computer science are equivalent to problems defined on systems of interacting spins. However, most such problems require computational resources that are out of reach with classical computers. A promising solution to overcome this challenge is quantum simulation. Several 'analogue' quantum simulations of interacting spin systems have been realized experimentally, where ground states were prepared using adiabatic techniques. Here we report a 'digital' quantum simulation of thermal states; a three-spin frustrated magnet was simulated using a nuclear magnetic resonance quantum information processor, and we were able to explore the phase diagram of the system at any simulated temperature and external field. These results help to identify the challenges for performing quantum simulations of physical systems at finite temperatures, and suggest methods that may be useful in simulating thermal open quantum systems.Chemistry and Chemical Biolog