Characterisation of mechanical loss in fused silica ribbons for use in gravitational wave detector suspensions

The majority of work contained in this thesis involves characterisation of the mechanical losses in fused silica ribbon fibres to determine their potential for use in suspending the 40kg test masses for Advanced LIGO. The design of fibres is discussed here, demonstrating the advantages of rectangular cross sections over the circular cross sections already used in GEO600, with experimental work used to show the viability of this suspension scheme. The losses of a number of modes of oscillation of fibres were investigated using different suspension designs to reduce excess loss mechanisms. Measurements made of the material loss of the fused silica, using cantilever bending modes of a fibre held at one end, gave values slightly higher than those used in the design of noise curves for Advanced LIGO. The measurements also showed a reduced thermoelastic damping effect from that theoretically calculated from which an altered value for the Young’s modulus of the fibres was found compared to the value for bulk fused silica. Measurements performed using the violin modes and pendulum modes of the fibres showed that, while excess loss mechanisms were characterised and in the case of the violin mode measurement shown to be negligible, the level of dilution of loss calculated theoretically was not achieved. The source of increased loss is thought to be due to the energy being concentrated closer to lossy welded regions of the fibre. The losses measured for the linear pendulum were the lowest ever measured. Measurements of the vertical bounce mode of a small mass suspended between two fibres has shown clear evidence that there is no intrinsic stress dependence of the material loss of fused silica and has given further evidence that the majority of loss in the fibres comes from a thin highly dissipative layer on the surface. The strength of ribbon fibres has been shown to be sufficient to carry the working load of the Advanced LIGO masses, with a 20kg test suspension being created, however there was a wide variation in measured fibre breaking strengths thought to be due to bending in the fibre coupling longitudinal force into shear stress. Issues regarding thermal stress at welds are discussed with suggested solutions for construction of Advanced LIGO suspensions

Perfect State Transfer: Beyond Nearest-Neighbor Couplings

In this paper we build on the ideas presented in previous works for perfectly transferring a quantum state between opposite ends of a spin chain using a fixed Hamiltonian. While all previous studies have concentrated on nearest-neighbor couplings, we demonstrate how to incorporate additional terms in the Hamiltonian by solving an Inverse Eigenvalue Problem. We also explore issues relating to the choice of the eigenvalue spectrum of the Hamiltonian, such as the tolerance to errors and the rate of information transfer.Comment: 8 pages, 2 figures. Reorganised, more detailed derivations provided and section on rate of information transfer adde

Femtomolar detection of Tau proteins in undiluted plasma using surface plasmon resonance

The ability to directly detect Tau protein and other neurodegenerative biomarkers in human plasma at clinically relevant concentrations continues to be a significant hurdle for the establishment of diagnostic tests for Alzheimer’s disease (AD). In this article, we introduce a new DNA aptamer/antibody sandwich assay pairing and apply it for the detection of human Tau 381 in undiluted plasma at concentrations as low as 10 fM. This was achieved on a multichannel surface plasmon resonance (SPR) platform with the challenge of working in plasma overcome through the development of a tailored mixed monolayer surface chemistry. In addition, a robust methodology was developed involving various same chip control measurements on reference channels to which the detection signal was normalized. Comparative measurements in plasma between SPR and enzyme-linked immunosorbent assay (ELISA) measurements were also performed to highlight both the 1000-fold performance enhancement of SPR and the ability to measure both spiked and native concentrations that are not achievable with ELISA

A rigid triple of conjugacy classes in G 2

We produce a rigid triple of classes in the algebraic group G 2 in characteristic 5, and use it to show that the finite groups G 2(5 n ) are not (2, 5, 5)-generate

Gel electrophoretic analysis of differently shaped interacting and non-interacting bioconjugated nanoparticles

The use of a simple gel electrophoretic method to study mixtures of differently shaped biofunctionalized nanoparticles (NP's) that undergo bioaffinity interactions is demonstrated. Both gold nanorods (NR's) and quasi-spherical nanoparticles (qNS's) were functionalized with an interacting antigen and antibody pairing (alpha-1 antitrypsin (AAT) protein and antiAAT) or non-interacting antibody controls (antiBNP). Gel-based measurements were accompanied with transmission electron microscopy (TEM) and UV-vis spectroscopy analysis before and after separation. Initial measurements of NR and qNS bioconjugates suspended individually were applied to optimize the gel separation conditions and it was demonstrated that higher particle uniformities could be obtained relative to the initial stock solutions. A series of NR and qNS mixtures prepared at various stoichiometric ratios were then compared for both interacting (antiAAT–AAT) and non-interacting (antiAAT–antiBNP) particle conjugates. Both gel images and extinction measurements were utilized to demonstrate reduced NP concentrations transported along the gel due to bioaffinity-induced NP assembly. This confirmed that gel electrophoresis can be extended to identifying particle aggregation associated with protein bioaffinity interactions as well as being an established tool for separating particles based on size, shape and surface chemistry

Glycoprotein Ib-V-IX, a Receptor for von Willebrand Factor, Couples Physically and Functionally to the Fc Receptor y-Chain, Fyn, and Lyn to Activate Human Platelets

The adhesion molecule von Willebrand factor (vWF) activates platelets upon binding 2 surface receptors, glycoprotein (GP) Ib-V-IX and integrin aIIbb3. We have used 2 approaches to selectively activate GP Ib using either the snake venom lectin alboaggregin-A or mutant recombinant forms of vWF (DA1-vWF and RGGS-vWF) with selective binding properties to its 2 receptors. We show that activation of GP Ib induces platelet aggregation, secretion of 5-hydroxy tryptamine (5-HT), and an increase in cytosolic calcium. Syk becomes tyrosine phosphorylated and activated downstream of GP Ib, and associates with several tyrosinephosphorylated proteins including the Fc receptor g-chain through interaction with Syk SH2 domains. GP Ib physically associates with the g-chain in GST-Syk-SH2 precipitates from platelets stimulated through GP Ib, and 2 Src family kinases, Lyn and Fyn, also associate with this signaling complex. In addition, GP Ib stimulation couples to tyrosine phosphorylation of phospholipase Cg2. The Src familyspecific inhibitor PP1 dose-dependently inhibits phosphorylation of Syk, its association with tyrosine-phosphorylated g-chain, phosphorylation of PLCg2, platelet aggregation, and 5-HT release. The results indicate that, upon activation, GP Ib is physically associated with FcR g-chain and members of the Src family kinases, leading to phosphorylation of the g-chain, recruitment, and activation of Syk. Phosphorylation of PLCg2 also lies downstream of Src kinase activation and may critically couple early signaling events to functional platelet responses

From the pursuit of excellence to the quest for significance: Promotion of a Childsafe South Africa

Trauma represents a major burden of disease in South Africa. Children are disproportionately affected by trauma; rightly, childhood trauma can be referred to as ‘the neglected childhood killer disease’. Unlike the field of infectious diseases, where vaccinations and prevention are the norm, paediatric trauma is usually ignored and prevention strategies are scarce. In this article, we review paediatric trauma and its effect on our society in light of the development of more effective child safety promotion strategies

The sedimentary legacy of a palaeo-ice stream on the shelf of the southern Bellingshausen Sea: Clues to West Antarctic glacial history during the Late Quaternary

A major trough ("Belgica Trough") eroded by a palaeo-ice stream crosses the continental shelf of the southern Bellingshausen Sea (West Antarctica) and is associated with a trough mouth fan ("Belgica TMF") on the adjacent continental slope. Previous marine geophysical and geological studies investigated the bathymetry and geomorphology of Belgica Trough and Belgica TMF, erosional and depositional processes associated with bedform formation, and the temporal and spatial changes in clay mineral provenance of subglacial and glaciomarine sediments. Here, we present multi-proxy data from sediment cores recovered from the shelf and uppermost slope in the southern Bellingshausen Sea and reconstruct the ice-sheet history since the last glacial maximum (LGM) in this poorly studied area of West Antarctica. We combined new data (physical properties, sedimentary structures, geochemical and grain-size data) with published data (shear strength, clay mineral assemblages) to refine a previous facies classification for the sediments. The multi-proxy approach allowed us to distinguish four main facies types and to assign them to the following depositional settings: 1) subglacial, 2) proximal grounding-line, 3) distal sub-ice shelf/sub-sea ice, and 4) seasonal open-marine. In the seasonal open-marine fades we found evidence for episodic current-induced winnowing of near-seabed sediments on the middle to outer shelf and at the uppermost slope during the late Holocene. In addition, we obtained data on excess Pb-210 activity at three core sites and 44 AMS C-14 dates from the acid-insoluble fraction of organic matter (AIO) and calcareous (micro-) fossils, respectively, at 12 sites. These chronological data enabled us to reconstruct, for the first time, the timing of the last advance and retreat of the West Antarctic Ice Sheet (WAIS) and the Antarctic Peninsula Ice Sheet (APIS) in the southern Bellingshausen Sea. We used the down-core variability in sediment provenance inferred from clay mineral changes to identify the most reliable AIO C-14 ages for ice-sheet retreat. The palaeo-ice stream advanced through Belgica Trough after similar to 36.0 corrected C-14 ka before present (B.P.). It retreated from the outer shelf at similar to 25.5 ka B.P, the middle shelf at similar to 19.8 ka B.P., the inner shelf in Eltanin Bay at similar to 12.3 ka B.P., and the inner shelf in Ronne Entrance at similar to 6.3 ka B.P. The retreat of the WAIS and APIS occurred slowly and stepwise, and may still be in progress. This dynamical ice-sheet behaviour has to be taken into account for the interpretation of recent and the prediction of future mass-balance changes in the study area. The glacial history of the southern Bellingshausen Sea is unique when compared to other regions in West Antarctica, but some open questions regarding its chronology need to be addressed by future work. (C) 2010 Elsevier Ltd. All rights reserved

Inkjet printing of oral dosage forms to solubilize BCS Class II drugs

Oral drug delivery remains the preferred method of administration but BCS Class II drugs are not ideally suited to this due to their inherent poor solubility. Although a number of methods to increase solubility already exist, there is a need for less damaging methods of production which are more flexible to the needs of the patient. The innovative formulation method of inkjet printing has been suggested for this purpose as it has the capacity to produce highly precise dosing in a continuous manner. The Optomec Aerosol Jet 200 Printer utilised in the current study has never been used in pharmaceutical research before and it is highly interesting as it functions in a manner akin to a miniaturised spray dryer. Due to the low dose content of a single layer, formulations can be easily tailored to the patient’s individual requirements by changing the size and speed of deposition, utilising different nozzle sizes and layering to increase the overall dose. Raman spectroscopy, scanning electron microscopy and powder x-ray diffraction suggest that printing the drug alone results in a crystalline product. However, in the presence of a polymer it seems to form a less crystalline product suggesting the polymer is promoting solid dispersion formation in a similar manner to a spray dryer. Completely amorphous formulations are achieved on application of a premixed "ink" with a polymer content of 75% or more, allowing up to 25% drug loading. Drug release increases 10-fold on printing relative to a comparable powder blend and thus inkjet printing can be considered to be a viable method of improving the overall performance of the drug. The next steps will be to utilize this established methodology to produce innovative controlled release on a small scale