Biometric authentication is the process of establishing an individual's identity based on measurable characteristics of their anatomy, physiology or behavior. Biometrics do not share many of the limitations of traditional authentication mechanisms, as the characteristics used for biometric authentication cannot be lost, forgotten or easily replicated. Despite these advantages, there are unresolved problems with the use and acceptability of biometrics and the technology has not seen the strong uptake that many predicted. There is a significant literature discussing the implications of biometric technology use, though much of this work is theoretical in nature and there is comparatively little empirically grounded work with a focus on the biometric user experience. This thesis presents research investigating biometric authentication from a user-centric perspective. The principal aims of this research were to deepen our understanding of the usability and acceptability of biometric authentication and use this knowledge to improve design. A series of controlled evaluations are presented, where biometric systems and different aspects of system design were investigated. To understand wider implementation issues, a field trial of a biometric system in a real-world environment was also carried out. A second strand of research focused on how biometrics are perceived and both survey and interview approaches were used to explore this issue. In general the empirical work can be characterized by a trend of structured, quantitative methodologies leading into less-structured approaches as contextual and experiential aspects of system use were investigated. A framework for the biometric user experience is presented based on this work. The framework is used to structure the design guidelines and knowledge emerging from this work. A methodology for the user-centric evaluation of biometrics is also proposed. The results from this project further our understanding of usable system design, but biometrics have proven to be an emotive technology and implementation remains a complex issue.

Due to the huge amount of DNA and the small space in which this is stored, cells package DNA into condensed chromatin. During DNA replication, repair or transcription, cells need to reorganize chromatin structure in order to gain access to the DNA. To do so they use a wide range of enzyme that can modify chromatin structure such as acetyltransferases, methyltransferases and others. Chromatin remodelling is also accomplished by ATP dependent and independent histone chaperones. One of the ATP independent histone chaperones is FACT (facilitate chromatin transcription), which is a heterocomplex of SSRP1 and Spt16. Studies on FACT showed that it is implicated in DNA replication, transcription and repair. To date little is known about its mechanism of action; but based on recent structural studies of its individual domains, it has been proposed that FACT reorganizes nucleosome by eviction of the heterocomplex H2A/H2B. Nevertheless, how FACT reorganizes nucleosomes remains elusive. Studies conducted in several cancer cell lines have shown that FACT is overexpressed in these cells and that knockdown of FACT reduces cells proliferation suggesting that FACT may be a cancer therapeutic target. Here I report the structure of human Spt16 N-terminal domain, which resembles an aminopeptidase domain lacking a catalytic centre. Sequence conservation and electrostatic surface analyses of this domain reveal some acidic regions that might be associated with histone binding. Indeed, ITC analysis showed that this domain binds both histone H2A/H2B and (H3/H4)2 at mid-low μM affinity. Interestingly, Spt16 N-terminal domain showed a sequential binding event both for G. gallus and X. laevis histone dimer H2A/H2B. On the onset of my project there was no structure for Spt16 middle domain. To gain insight into FACT mechanism of action, I determined the structure of D. rerio Spt16 middle domain. Surprisingly this domain resembles a double PH domain, which is similar to the POB3 middle domain and RTT106 except for having a U-turn motif at its C-terminus. Sequence conservation and electrostatic surface analyses of this domain reveal two possible surfaces for histone binding. Interestingly, ITC analysis showed Spt16 middle domain has weak binding affinity for both histone H2A/H2B and (H3/H4)2 with the latter displaying a double binding event. Moreover, ITC analysis showed that Spt16 middle domain binds histone H2A/H2B via the U-turn motif consistent with the recent published data. Finally, I investigated the solution structure of SSRP1 by using AUC and SAXS analysis. I found that SSRP1 is an elongated homodimer, which assumes an open v conformation. Mutations in PH2 or PH3 domain alone resulted in the formation of monomer suggesting that SSRP1 homodimer may assume an asymmetric conformation. Interestingly, PH2 and PH3 domain mutants displayed weaker histone binding affinity than wild type suggesting that homodimerization plays a role in histone binding.

No description available.

Directed cell motility plays a key role in many areas of biology, with cells able to reorient quickly in response to changes of an extracellular stimuli. A complex signalling network directs this response, which motivates the use of conceptual mathematical models that replicate aspects of this behaviour and can be more readily analysed. Comparisons between such models have more focused on the qualitative differences between them. We wished to construct a framework for the rigorous comparison between models, using cell repolarisation in response to shear ow change. We fitted three reaction-diffusion models of cell polarity to experimental data of dictyostelium amoeba repolarising in response to mechanical shear flow. Experiments performed under different conditions were fitted simultaneously, to provide models with a range of cellular dynamics, with the models being fit to spatio-temporal data of cortex fluorescence of an F-actin reporter. All models were able to give a satisfactory t, with parameter identifiability determined using the pro le likelihood. The Meinhardt and Levchenko models were able to obtain better fits than the Otsuji model. Analysis of the model behaviour and parameter identifiability prompted alterations of the models, which resulted in a fully identi able two-variable Meinhardt model. Simulations of the Meinhardt and Levchenko models were used to test their behaviour over time frames past which the models had been tfitted. This motivated changes to the model parameters to obtain the desired long-term behaviour. Further simulations were run to elicit the model response to a changing external signal beyond that seen in the fitting, with the models being able to adapt to a moving signal, and respond to multiple simultaneous signals. Further fitting of the Meinhardt and Levchenko models was conducted using single cell data. The models were able to t well to data taken from both repolarising and unstimulated cells, showing that these models are able to replicate both mean and single cell spatio-temporal imaging data.

1. With freshwater ecosystems worldwide at significant risk from global change, there is an urgent need to understand the processes involved and to develop adaptive responses. Riparian management might offer a means of increasing resilience to global change in headwaters, but evidence is scarce. This thesis investigates the potential effects of riparian management on the storage, processing and downstream export of resource subsidies – dominantly as terrestrial litter – that enter streams from the riparian zone. 2. In a large scale field study over four years, natural and experimental systems were used to test the hypothesis that riparian woodlands enhance stream ecosystem resilience to climatically mediated changes in flow regimes. Specific work included assessments of benthic organic matter stocks and export in contrasting catchments (broadleaf woodland, conifer plantations or sheep-grazed moorland), flow manipulations in mesocosms, and a large-scale field experiment simulating riparian broadleaved tree planting. 3. Standing stocks of particulate organic matter (POM) were influenced by flow regime, and declined following larger and longer flow-events, but event frequency had no apparent impact. Experimental data showed also that coarse fractions of POM in transport were significantly elevated in the early stages of simulated floods. 4. Despite flow effects on POM dynamics, streams bordered by broadleaves maintained consistently higher standing stocks of POM than conifer or moorland streams. Broadleaved streams also transported the highest concentrations of carbon in the form of high-quality FPOM. Leaf litter additions of stream channels did not reproduce these effects, possibly because the scale was insufficient to mimic real riparian woodlands. 5. While predicted flow changes under a warmer climate might affect the storage and flux of organic matter, riparian broadleaves are likely to mitigate these effects in stream ecosystems. This project illustrates the value of blending catchment-scale studies with field-based mesocosms to understanding complex global change processes.

No description available.

Despite intense persecution over the last century, the jaguar (Panthera onca) has sustained a wide geographic distribution, perhaps due to its elusive nature and rather flexible ecology. This study investigated jaguar ecology under anthropogenic pressures in Belize, Central America. A suite of methods including camera-trap surveys, diet analysis, discussions with local stakeholders, and population simulations were used to study a population of jaguars spanning the boundary of a protected forest. Camera-trap data combined with capture-recapture population models are increasingly used to estimate the density of mammals such as jaguars with individually identifiable coat patterns. A review of current methods highlighted problems associated with estimating the sizes of lowdensity populations. Simulations to assess the robustness of the method found that camera failure can negatively or positively bias the abundance estimate, depending on the particular nature of capture histories. The most commonly used model estimator in the literature was nevertheless robust to failures of up to 10% of trap-occasions. Pooling trap-occasions reduced the effect of camera failure. Sub-sampling data from large-scale surveys indicated a threshold survey area of ~170 km2, below which estimates of density were inflated and unreliable. For surveys exceeding this threshold size, jaguar density varied across the landscape from the protected forest to the human-influenced lands such that <30% contiguous forest precipitated reduction. Reduced densities with distance from contiguous forest and proximity to human habitation may result principally from direct conflicts with people. The influence of anthropogenic factors on the coexistence of jaguars and pumas (Puma concolor) was investigated by comparing their habitat use and feeding ecology. Diet was analysed from the largest sample to date of scats from one area identified to species. Jaguars and pumas made similar use of the secondary rainforest, despite differences in diet. Although both cats relied heavily on one species of small prey (5-10 kg), for jaguars this was the nine-banded armadillo (Dasypus novemcinctus) while for pumas it was the paca (Agouti paca). Both cats took some larger prey, mainly white-lipped peccaries (Dictolyes pecari) by jaguars and red brocket deer (Mazama americana) by pumas. Energetics models indicated that reproduction may be limited for either species if large prey are unavailable for females with dependents. Outside the forest block, jaguars rarely ate large wild prey species; instead, a diet of smaller wild prey was supplemented with large domestic stock. Pumas were scarce outside the protected forest, possibly reflecting a reluctance to utilise domestic species near human developments and competition with humans for their preferred prey of paca and deer, which are also prized regionally as game species. Human-induced mortality of jaguars outside the protected forest was mainly associated with livestock predation. Both sexes were equally active on pastures and were persecuted at a similar rate. Many of those killed were young individuals in good body condition, suggesting high turnover rates augmented by immigration. Population simulations indicated that the observed levels of human-induced mortality could be maintained only with immigration from the protected forest. Without natal dispersers (2-4 year olds) immigrating in, the hunted population had zero probability of persisting beyond 20 years. Simulations indicated that the jaguar populations inhabiting the two main protected forest blocks in Belize could persist in isolation and maintain low levels of emigration to the unprotected population. However the probability of all three populations persisting for 100 years fell to ~50% if the migration of natal dispersers from the protected to unprotected population exceeded ~12% per year.

The majority of lipids that interact with a transmembrane protein act as a solvent for the protein, forming a shell around it; these lipids are called annular or boundary lipids. However, some lipids interact in a more specific way, binding between transmembrane α-helices or at protein-protein interfaces, and these lipids are referred to as non-annular lipids. The crystal structure of the bacterial potassium channel KcsA shows a non-annular lipid molecule bound at the subunit interfaces in the homotetrameric structure, and binding of this non-annular lipid has been shown to be essential for channel function, making KcsA an ideal candidate for the study of lipid-protein interactions. Recently, a third type of binding site at the hydrophobic inner cavity of the pore of potassium channels has been proposed for fatty acid molecules, where binding was suggested to cause block of ion flux. Fatty acids are known to affect ion channel activity, but it is not yet certain how they act. Here, fluorescence spectroscopy and electron spin resonance (ESR) are combined to analyse the interaction of fatty acids with the annular and non-annular sites, and with the hydrophobic inner cavity of the pore on KcsA. To study fatty acid binding by fluorescence spectroscopy, KcsA was reconstituted in bilayers of phosphatidylcholine (PC) containing brominated fatty acid. Quenching of the Trp fluorescence of wild type KcsA by brominated fatty acids allows an analysis of their interaction with annular sites on the channel and interaction at non-annular sites was studied using a Trp mutant of KcsA. The results shown that fatty acids can bind with an affinity rather similar to that of PC to both annular and non-annular sites, but uncharged fatty acid analogues show limited binding, emphasising the importance of charged interactions in these systems. In ESR studies KcsA was reconstituted in PC membranes containing a small amount of spin labelled fatty acid. Spin labelled lipids in contact with the protein show a different ESR spectrum from those in the bulk lipid due to the different mobilities of their acyl chains. The ESR spectra show that the spin labelled fatty acid bound to KcsA is strongly immobilised and binds with high affinity. It is proposed that the fatty acid binds to the hydrophobic cavity with a dissociation constant of ca. 0.22 μM. The studies show that fatty acids can bind to the channel at a variety of sites, suggesting that ion channel function could be modulated directly by interactions with fatty acids. Other studies here presented focused on the influence of the annular lipids on the aggregation of KcsA. Protein-protein contacts are important for membrane protein association and activity, but little is known about the influence that the lipid bilayer can have on protein-protein association. ESR experiments with spin labelled phospholipids show that at lipid:channel molar ratios of ca. 100:1 or higher, KcsA is solvated by ca. 31 annular phospholipid molecules, as expected from its crystal structure, but that, at lower lipid content, protein-protein contacts become favourable and KcsA aggregates. The ESR data also show that aggregation is reduced in bilayers of anionic phosphatidylglycerol (PG) in comparison to bilayers of zwitterionic PC, as confirmed by quenching experiments where brominated PG was able to quench wild type KcsA more efficiently than brominated PC at the low lipid:channel molar ratios. The results highlight the importance that the lipid bilayer composition can have on membrane protein association.

Plodia interpunctella (Hübner) is a major pest of raw and processed stored food products and the purpose of this work was to design and determine whether an entomopathogen based autodissemination approach would be an efficacious product for its control. A comparison of the retention, horizontal transmission and effect on mating of two electrostatic entomopathogen delivery powders (Entomag™ and Entostat™) was made to evaluate their potential as a component of an autodissemination method for the control of P. interpunctella. Both powders were shown to have some effects on mating behaviour and ability of treated males to locate a pheromone source when applied in high doses. However, no effects were observed at rates consistent with the amount of powder that was actually taken up when the moths visited a prototype bait station device. Male and females lost 69.9 and 64.3% by weight respectively of Entomag by 48h after exposure but lost more Entostat, 89.8% and 75.9%, over the same period. Critical to the efficacy of autodissemination is the transfer of powder from males to females and on average a 49% greater weight of Entostat was transferred than Entomag. In addition to this the electrostatic charge on each powder was measured, with Entostat charging significantly more (to the negative polarity) than Entomag. The respective distances that a charged particle could levitate by virtue of electrostatic forces to an insect, were modelled, with Entostat predicted as levitating over a greater distance to the moth than Entomag under scenarios where the insect was either neutral or charged (neutral particle = 2.8 mm, compared to 1.9 mm; charged particle = 21.7 mm, compared to 6.8 mm). A novel technique for determining powder uptake by P. interpuncetlla was developed based on image analysis. This determined the regions of the moth’s body to which particles were more likely to adhere. This study confirmed that pit-fall style powder dispensers were more effective at delivering powder to the head of the moth, where powder appeared to be most readily horizontally transferred between conspecifics. Finally, an individual based modelling approach was taken to determine the overall suitability of Beauveria bassiana autodissemination as a controlling strategy for P. interpunctella. The model suggested that a maximum of only 62% of male moths would become contaminated with entomopathogen and that this would be insufficient to cause a decline in the overall population.

Bacteria dominate the remineralization of organic carbon in marine systems. Examining patterns of abundance, diversity and distribution is critical to understanding the contribution of bacteria to global biogeochemical cycles. In the oligotrophic deep sea, the role of bacterial communities is intimately linked to the flux of organic matter from primary productivity in surface waters. Deep-sea sediments are a major site of nutrient regeneration, supporting bacteria that comprise up to 90% of the benthic biomass and account for almost 45% of all respiration that occurs in the deep sea. The study of benthic bacterial communities in relation to organic matter flux may help to further scientific understanding of the contribution of bacteria to trends in the carbon cycle that have global significance. In this study, the bacterial abundance and diversity in deep-sea sediments beneath two zones of contrasting productivity in the Southern Ocean were compared. Sediments were taken at two abyssal sites, to the east and south of the Crozet Island Archipelago, in the Indian Ocean sector of the Southern Ocean. To the east of the islands, enhanced productivity levels are generated by seasonal blooms in marked contrast to the southerly, oligotrophic site where high nutrient, low chlorophyll conditions, predominate. Bacterial abundance was examined in sediment to a depth of 20 cm. No significant difference in abundance was found between sites, although a trend in decreasing abundance with vertical sediment depth was observed. Fluorescence in situ hybridisation (FISH) showed consistent distribution of different bacterial groups at both sites, where the gamma- and alpha-Proteobacteria were dominant. Similar denaturing gradient gel electrophoresis (DGGE) profiles were observed for both sites. A comparison of the eutrophic and oligotrophic surface sediment clone libraries found that approximately 36% of operational taxonomic units were common to both sites, however, richness was higher at the oligotrophic site. The results indicated a consistency in abundance and community structure between the two sediments, which may reflect shared biogeochemical characteristics. Both sites supported the same dominant community members. Differences in richness were observed between sites among the less dominant bacteria and these differences might reflect the contrasting productivity regimes of the overlying water.