VictorJuiz/thesis huggingface dataset:
Electrode processes

The work presented in this thesis first characterises a high speed channel flow cell and then applies the system to the electro-reduction of nitromethane in aqueous solution. Potential step transient measurements are carried out with the current-time transients simulated using a model based on the absence of axial diffusion. The excellent agreement between theory and experiment confirms the proposed mass transport model and further demonstrates that the combination of current-time transients recorded using the high speed channel flow cell and numerical simulations provide a powerful tool to access homogeneous rate constants of the order 1 x 106s̄¹.
The high speed channel flow cell is then used in combination with a range of complementary electrochemical techniques, numerical modelling, in-situ ESR, single crystal experiments and kinetic isotope measurements to infer a mechanistic scheme for the complex electro-reduction pathway of nitromethane in aqueous solution. Platinum, gold, mercury/copper and mercury/gold electrodes are investigated enabling the most conclusive description of the reduction mechanism to date. The reaction pathway is shown to follow an ECEEE type process with the chemical step proceeding at the electrode surface. The heterogeneous rate constant, khet, describing the chemical step is calculated for each electrode surface. For platinum in the pH range 7.0 - 9.0 this value is 0.3 ± 0.06 cm s̄¹. For mercury/copper it is 0.18 cm s̄¹, for gold/mercury it is 0.06 cm s̄¹ and for Au it is 0.095 cm s̄¹. Consideration of these values shows a surprising independence of the heterogeneous rate constant on the chemical identity of the surface with all of the values being similar to within less than an order of magnitude. The reason for the apparent paradox of the observed surface indifference of the chemical reaction step is explained by a homogeneous H transfer from the carbon to the oxygen of the nitromethane radical anion, formed form the initial electron transfer step, occurring in the layer of solution immediately adjacent to the electrode solution as shown in the scheme below. The resulting species, •CH2 N(OH))ˉ then undergoes a rapid irreversible adsorption to the electrode surface and subsequent transformation to the final product the hydroxylamine, CH3NHOH. It is proposed that if the energy barrier to the adsorption of •CH2 N(OH))ˉ is less than that required for the H atom transfer then the reaction rate will be insensitive to the adsorption step and hence the chemical identity of the electrode. This introduces the concept of a whole new electrochemical process: the surface indifferent electrocatalytic reaction.

Advisor: Compton, R
Using uranium- and thorium-series isotopes as tracers for trace-metal inputs to the oceans

This thesis explores the use of U-Th series isotopes as tracers to study ocean mixing and chemical inputs to the open ocean from atmospheric dust, rivers, continental shelves and ocean sediments.
The use of Th isotopes as an improved tracer of dust input has been tested by measuring 232Th and 230Th concentrations of upper-ocean seawater at six stations along a meridional Atlantic section that spans the Saharan dust plume. The results of 232Th-derived dust fluxes show good agreements with dust model depositions, and suggest that thorium may be a more accurate tracer of dust input than Aluminium, which is frequently used for this purpose.
A new technique has been developed for the precise measurement of 228Ra/226Ra ratios and 228Ra and 226Ra concentrations in seawater by multi-collector ICP mass spectrometry (MC-ICP-MS). This methods offers improved analytical precision and detection limits relative to previous decay-counting approaches, though is more labour intensive. The accuracy of this method has been proved in the GEOTRACES Ra intercalibration, and shows consistent results with decay counting measurements from other labs. This technique has been applied to water samples in Loch Etive, a Scottish fjord, and in the Cape Basin during the UK-GEOTRACES cruise (GA10E) to investigate ocean mixing and trace-metal fluxes in the oceans.
In Loch Etive, Ra data provide an estimation of sedimentary 228Ra flux of 5.5 ± 0.3 (× 109 atoms m-2 yr-1) in the inner loch deep basin. Short-lived Ra isotope (223Raex) has also been used to estimate surface water transport rate, which is ~ 2.4 ±0.2 cm s-1 from the mouth to the head of the loch. In the Cape Basin, seawater 228Ra and 226Ra activities have been used to estimate vertical and horizontal mixing in the surface ocean. The horizontal mixing (Kx) from the continental shelf to the open ocean is 3.8 ± 0.8 (× 107 cm² s-1) and the vertical mixing (Kz) in the upper 400 m layer is 0.9 – 2.1 cm² s-1. These mixing rates enable the calculation of nutrient flux in the surface ocean. The calculated vertical nitrate fluxes in the Cape Basin are 0.4 – 0.5 mmol N m-2 d-1. This finding shed light on the nutrient inputs to the South Atlantic Subtropical Gyre.

Keywords: uranium
geochemistry
thorium
iron
dust
ocean mixing
radium
isotope
nutrient
Advisor: Henderson, G
Teachers' understanding of the purposes of group work and their relationship with practice

Group work is commonly recommended as a student-centred instructional strategy which may enhance learning. Research in this area has predominantly used controlled interventions focusing on unproductive teacher assistance or specific strategies of doing group work to be applied by teachers. On the other hand, teachers’ own understanding and uses of group work in classrooms have been under-researched. Drawing on cultural-historical theory, this study scrutinises how and why teachers use group work, and how their enacted understanding is related to the broader contexts of teaching.
The present study consists of four teachers of English in two secondary schools in Hong Kong to discern their rationales for and implementation of group work. The analysis delves into the dynamics within the activity of teaching, which comprise the interrelations between teachers' biographies, their purposes for group work in classrooms and what was expected from these teachers within the school practices.
The Vygotskian perspective taken by this study entailed an inquiry into the teachers' intentional actions in everyday teaching. Each teacher was interviewed at the outset and end of the school-based fieldwork for their learning backgrounds and beliefs about teaching. In between these interviews each of them was observed in 15 lessons involving group work and undertook five to six stimulated recall (SR) interviews. These lesson video-recordings provided the stimuli for the SR interviews for probing the teacher’s pedagogic decisions while orchestrating students in small groups.
The data was analysed by deploying concepts from cultural-historical theory, particularly two organising frameworks developed within the approach. One is a pedagogic sequence proposed by Edwards (1995; in press) as a descriptor to categorise the teachers’ purposes for and actions in group work. The other is an adaptation of Hedegaard's (2012) planes of analysis for identifying the various motives and demands in the multi-layered setting of teaching where group work was located.
Group work as a pedagogic tool displayed the intra- and interpersonal dynamics in the activity of teaching. The findings indicate that the teachers' historically-constructed identities as learners of English oriented their intentions for group work and beliefs about teaching the subject. How the schools mediated societal expectations on teaching and learning had a considerable bearing on the teachers enacting their understanding. These institutional objectives and demands in practices created sets of opportunities for group work in the classrooms. The analysis thence was sited at the interface between the teachers' personal pedagogies and the multi-faceted social structure reflected in how education policy was mediated differently in different school contexts. The implications for teacher development are discussed.

Keywords: teacher agency
cultural-historical theory
pedagogy
group work
Advisor: Edwards, A
Constraints on nutritional compensation in acridids

Some aspects of the ability of locusts and grasshoppers (Acrididae) to compensate for nutritional shortfalls were studied, with a special emphasis on the factors which constrain this ability.
Chapter 1 investigates the effects over the short-term (12 h) of the plant-produced allelochemical tannic acid on the ability of Locusta migratoria (L.) and Schistocerca gregaria (Forskal) to compensate for dilution of dietary proteins and carbohydrates by increasing consumption. Tannic acid had no effect on compensatory feeding by L. migratoria, and stimulated feeding by S. gregaria.
Chapter 2 extends this study over the longer-term (fifth instar) for L. migratoria. Over this period, tannic acid restricted intake and reduced growth of those insects fed lowprotein diets, indicating an inhibitory effect on compensatory feeding for protein. In addition, the levels of dietary proteins influenced regulation for carbohydrate intake and, to a lesser extent, vice-versa. A detailed discussion is presented of the ways that some dietary components can influence the intake of others, and how failure to take this into account can lead to poor experimental design and interpretation.
Chapter 3 investigates some mechanisms involved in dietary selection by the grasshopper Schistocerca americana (Drury). It was found that S. americana conditioned on distinctly flavoured protein-inadequate diets then tested on nutritionally similar diets with the familiar or a novel flavour, tend to eat more of the novel-flavoured diets. This suggests that conditioned neophilia, possibly in conjunction with aversion learning, may be a factor facilitating dietary selection in acridids.
Chapter 4 investigates the patterns of feeding and dietary selection behaviour of the polyphagous grasshopper Taeniopoda eques (Burmeister) in its natural desert habitat. Despite the overwhelming thermoregulatory requirements and unpredictable variability inherent in ecological complexity, these insects nonetheless maintained a pattern of feeding comparable to that observed under controlled laboratory conditions. The patterns of dietary selection behaviour were concordant with some of the mechanisms observed to operate in the laboratory.
Chapter 5 addresses an important inadequacy in the methodology currently used to investigate some aspects of nutritional compensation. A computer-generated data set is used to illustrate how the analysis of the currently popular ratio-based nutritional indices may be flawed, and how this may be overcome using as an alternative the analysis of covariance.

Advisor: Simpson, S
Bernays, E
Bernays, L
Industrial relations, flexibility, and the EU social dimension

This study sets out to explore employer response to the EU social dimension, in answer to the question, "How are employers in the UK and Germany responding to the EU social dimension, and why?" Using case study evidence from nine large British and German engineering companies, as well as material from employers' associations at all levels, it is argued that there is little employer support for extending the social dimension. Focusing on micro-economic aspects of the debate, it is also argued that a common feature in both British and German employer opposition is a concern for the impact of EU industrial relations regulation on firm-level flexibility. This stands in direct contradiction of the EU Commission's own contentions about the flexibility-enhancing effects of its social policy measures, and appears paradoxical in light of earlier research findings of a German flexibility advantage over UK rivals on account of the country's well-structured regulatory framework for industrial relations. Evidence from participant companies, however, suggests that, in the global environment of the late 1990s, much of Germany's former flexibility advantage has been eroded, and the regulation-induced limitations on both the pace and scale of change are increasingly onerous to German companies. German managers perceive a need for targeted deregulatory reform of their industrial relations system; by strengthening (and often extending) existing industrial relations regulation, EU social policy measures meet with firm disapproval. In the UK, by contrast, the changed context has contributed to a significant increase in firm-level flexibility. British companies now operate to levels of flexibility often in advance of their German counterparts, at far lower 'cost' in terms of the time taken, and the extent to which change measures are compromised, to reach agreement. For British managers, EU social policy measures are perceived as a threat to these beneficial arrangements, and vigorously opposed. The thesis concludes by suggesting that such fixed opposition, in the face of Commission determination to extend the EU social dimension, points to an escalation of the controversy surrounding the social dimension.
Automated image-based recognition and targeted laser transfection techniques for drug development and stem cell research

Advances in several areas of scientific research is currently hampered by the slow progress in developing a non-viral, high precision technique capable of safely and efficiently injecting targeted single cells with impermeable molecules. To date, one of the most promising techniques employs the laser to temporarily create a pore in the cell membrane to allow the entry of exogenous molecules. This technique has potentially wide applications.
In this thesis, I utilised the precision of laser transfection, also known as optoporation, to deliver two histone demethylase inhibitors (8-hydroxyquinoline and FMF1293) of the JmjC-domain protein JMJD3 into vital cells. The enzyme, JMJD3, demethylates histone H3 lysine K27, the methylation state of which has been shown in previous studies to regulate genes in such a way as to play a key role in the formation of tumours and even maintenance of stem cell pluripotency. The research here shows proof of principle that optoporation can be employed to quickly screen and test the efficacy of novel drugs by delivering them into cells at significantly low concentrations while still maintaining inhibition activity. I also used optoporation to deliver relatively large proteins such as bovine serum albumin (BSA), phalloidin and novel synthetic antibodies into living cells without fixatives. This offers the possibility of using reporter systems to monitor living cells over time. Finally, an attempt was made to generate iPS colonies by optoporating plasmid DNA into somatic cells, however, I find that this technique was unable to efficiently transfect and reprogram primary cells.
Two automated image-based systems that can be integrated into existing microscopes are presented here. First, an image processing algorithm that can quickly identify stem cell colonies non-invasively was implemented. When tested, the algorithm’s resulting specificity was excellent (95 – 98.5%). Second, because optoporation is a manual and time consuming procedure, an algorithm to automate optoporation by using image processing to locate the position of cells was developed. To my knowledge, this is the first publication of a system which automates optoporation of human fibroblasts in this way.

Keywords: image recognition
transfection
laser
histone demethylase inhibitor
optoporation
automation
JMJD3
stem cell colony
Advisor: Oppermann, U
Noble, A
Robust quantum phenomena for quantum information processing

This thesis is concerned with finding technologically useful quantum phenomena that are robust against real world imperfections. We examine three different areas covering techniques for spin measurement, photon preparation and error correction.
The first research chapter presents a robust spin-measurement procedure, using an amplification approach: the state of the spin is propagated over a two-dimensional array to a point where it can be measured using standard macroscopic state mea- surement techniques. Even in the presence of decoherence, our two-dimensional scheme allows a linear growth in the total spin polarisation - an important increase over the √t obtainable in one-dimension. The work is an example of how simple propagation rules can lead to predictable macroscopic behaviour and the techniques should be applicable in other state propagation schemes.
The next chapter is concerned with strategies for obtaining a robust and reliable single photon source. Using a microscopic model of electron-phonon interactions and a quantum master equation, we examine phonon-induced decoherence and assess its impact on the rate of production, and indistinguishability, of single photons emitted from an optically driven quantum dot system. We find that, above a certain threshold of desired indistinguishability, it is possible to mitigate the deleterious effects of phonons by exploiting a three-level Raman process for photon production. We introduce a master equation technique for quantum jump situations that should have wide application in other situations.
The final chapter focusses on toric error correcting codes. Toric codes form part of the class of surface codes that have attracted a lot of attention due to their ability to tolerate a high level of errors, using only local operations. We investigate the power of small scale toric codes and determine the minimum size of code necessary for a first experimental demonstration of toric coding power.

Keywords: surface codes
spin amplification
single photon source
Advisor: Benjamin, S
Lovett, B
Digital holographic microscopy for three-dimensional studies of bacteria

Holography has the ability to render three-dimensional information of a recorded scene by capturing both the amplitude and phase of light incident on the recording medium. The application of digital camera technology and high-speed computing means digital holograms can be analysed numerically and novel applications can be found for this technology. This thesis explores the potential for both inline and off-axis digital holographic microscopy to study the three-dimensional swimming behaviour of bacteria.
A high-magnification (225x) digital holographic microscope was designed and constructed with the ability to switch easily between inline and off-axis imaging modalities. Hardware aspects, in particular the illumination source, the choice of camera and data transfer rates, were considered. Novel strategies for off-axis holography combining dark field microscopy were designed and implemented.
The localisation accuracy of the inline imaging modality was assessed by studying samples of polystyrene microspheres. The microscope is sensitive to stage drift on the order of angstroms per second and can successfully localise microspheres in dilute suspensions at least 100μm from the objective specimen plane. As a simple test of the capabilities of the microscope, the diffusion coefficient of a 0.5μm microsphere was found to be isotropic and consistent with the theoretical value.
Amplitude and phase image reconstructions from the off-axis modality are demonstrated. High-magnification dark field off-axis holographic microscopy is shown to be superior to inline microscopy in localising 100nm gold nanoparticles. An artifact from our method of dark-field imaging, however, restricts the depth range to 15μm.
A lower-magnification (45x) configuration of the microscope was used to study the 3D swimming behaviour of wild type Escherichia coli as a qualitative demonstration of the potential for this instrument in microbiological applications.

Keywords: three-dimensional microscopy
3D imaging
microscopy
micro-organism motility
digital holographic microscopy
optics
holography
bacterial motility
Advisor: Berry, R
Sensory control of ocular accommodation

The investigations described in this thesis have examined how, with particular reference to optical cues, the retinal image is analysed by the brain so as to generate the appropriate signals for controlling accommodation. This line of research involved behavioural studies on trained monkeys (Macaca mulatto), human psychophysical studies, mathematical analysis of the capabilities of visual neurons in detecting defocus and single unit studies in an anaesthetized preparation. The chromatic, temporal and binocular aspects of accommodation control were considered.
CHROMATIC: The accuracy of accommodation in monkeys was found to be reduced in the absence of chromatic cues. The nature of the neural processing that might be involved in utilising chromatic cues to accommodation was investigated, both theoretically and electrophysiologically, and a specific neural model was constructed.
TEMPORAL: The effects on human accommodation of varying the temporal parameters of simple grating stimuli were investigated. These experiments provided information about both the sensory mechanisms involved in accommodation control and the possible role of temporal cues to accommodation. The temporal variability of accommodation (and accommodative-vergence) were examined in the rhesus monkey.
BINOCULAR: The nature of the binocular interactions in accommodation control were investigated, in both man and monkey, by presenting conflicting blur cues to the two eyes and recording the accommodation response. In the presence of such conflicting cues, the accommodative response was best described as a weighted average of the inputs to the two eyes.
In addition to providing insights into the sensory guidance of accommodation, these studies have also permitted a detailed comparison of accommodative function in man and the rhesus monkey. There was a striking similarity between these two species in all areas studied; ie. role of chromatic cues, temporal variability and nature of binocular interactions. Thus the rhesus monkey appears to be an excellent experimental model for investigating the accommodation control system.

Advisor: Judge, S
An analytical and experimental study of large strain soil consolidation

This thesis is concerned with large strain soil consolidation and a large portion of the work is devoted to the theoretical development in modelling this phenomenon. An experimental programme based on a specially designed oedometer is also included. The governing equations are formulated in Chapter 2, where both the material and the space coordinates are considered. In space coordinate the problem is a moving boundary problem, and special numerical techniques for the idealized case of a thin soil layer are developed in Chapter 3. In Chapter 4 the consolidation of a normally consolidated stratum and a dredged fill are considered with a linear soil model, and the consolidation of a deposit undergoing continuous sedimentation is considered in Chapter 5. The material coordinate is used in the analysis which also includes the effect of self weight of soil. These problems are again considered in Chapter 6 and Chapter 7 with a nonlinear soil model. A specially designed oedometer for testing very soft soil is described in Chapter 8, and the experimental results are discussed in Chapter 9. These are compared with the theoretical solutions developed in Chapter 3, and good agreement has been obtained.

Keywords: large strain
consolidation
soil
Advisor: Sills, G