Encounter success of free-ranging marine predator movements across a dynamic prey landscape

Movements of wide-ranging top predators can now be studied effectively using satellite and archival telemetry. However, the motivations underlying movements remain difficult to determine because trajectories are seldom related to key biological gradients, such as changing prey distributions. Here, we use a dynamic prey landscape of zooplankton biomass in the north-east Atlantic Ocean to examine active habitat selection in the plankton-feeding basking shark Cetorhinus maximus. The relative success of shark searches across this landscape was examined by comparing prey biomass encountered by sharks with encounters by random-walk simulations of ‘model’ sharks. Movements of transmitter-tagged sharks monitored for 964 days (16754km estimated minimum distance) were concentrated on the European continental shelf in areas characterized by high seasonal productivity and complex prey distributions. We show movements by adult and sub-adult sharks yielded consistently higher prey encounter rates than 90% of random-walk simulations. Behavioural patterns were consistent with basking sharks using search tactics structured across multiple scales to exploit the richest prey areas available in preferred habitats. Simple behavioural rules based on learned responses to previously encountered prey distributions may explain the high performances. This study highlights how dynamic prey landscapes enable active habitat selection in large predators to be investigated from a trophic perspective, an approach that may inform conservation by identifying critical habitat of vulnerable species.

Unsafe driving behaviour and four wheel drive vehicles: observational study

Objective To assess the level of compliance with the new law in the United Kingdom mandating penalties for rising a hand held mobile phone while driving, to compare compliance with this law with the one on the use of seat belts, and to compare compliance with these laws between drivers of four wheel drive vehicles and drivers of normal cars. Design Observational study with two phases-one within the grace period, the other starting one week after penalties were imposed on drivers using such telephones. Setting Three busy sites in London. Participants Drivers of 38 182 normal cars and 2944 four wheel drive vehicles. Main outcome measures Proportions of drivers seen to be using hand held mobile phones and not using seat belts. Results Drivers of four wheel drive vehicles were more likely than drivers of other cars to be seen using hand held mobile phones (8.2% v 2.0%) and not complying with the law on seat belts (19.5% v 15.0%). Levels of non-compliance with both laws were slightly higher in the penalty phase of observation, and breaking one law was associated with increased likelihood of breaking the other. Conclusions The level of non-compliance with the law on the use of hand held mobile phones by drivers in London is high, as is non-compliance with the law on seat belts. Drivers of four wheel drive vehicles were four times more likely than drivers of other cars to be seen using hand held mobile phones and slightly more likely not to comply with the law on seat belts.

Fast stereo matching by iterated dynamic programming and quadtree subregioning

The application of energy minimisation methods for stereo matching has been demonstrated to produce high quality disparity maps. However the majority of these methods are known to be computationally expensive, requiring minutes or even hours of computation. We propose a fast minimisation scheme that produces strongly competitive results for significantly reduced computation, requiring only a few seconds of computation. In this paper, we present our iterated dynamic programming algorithm along with a quadtree subregioning process for fast stereo matching.

Tear film lipids:dynamic composition and clinical performance

Purpose: Meibomian-derived lipid secretions are well characterised but their subsequent fate in the ocular environment is less well understood. Phospholipids are thought to facilitate the interface between aqueous and lipid layers of the tear film and to be involved in ocular lubrication processes. We have extended our previous studies on phospholipid levels in the tear film to encompass the fate of polar and non-polar lipids in progressive accumulation and aging processes on both conventional and silicone-modified hydrogel lenses. This is an important aspect of the developing understanding of the role of lipids in the clinical performance of silicone hydrogels. Method: Several techniques were used to identify lipids in the tear film. Mass-spectrometric methods included Agilent 1100-based liquid chromatography coupled to mass spectrometry (LCMS) and Perkin Elmer gas chromatography mass spectrometry (GCMS). Thin layer chromatography (TLC) was used for separation of lipids on the basis of increasing solvent polarity. Routine assay of lipid extractions from patient-worn lenses was carried out using a Hewlett Packard 1090 liquid chromatograph coupled to both uv and Agilent 1100 fluorescence detection. A range of histological together with optical, and electron microscope techniques was used in deposit analysis. Results: Progressive lipid uptake was assessed in various ways, including: composition changes with wear time, differential lipid penetrate into the lens matrix and, particularly, the extent to which lipids become unextractable as a function of wear time. Solvent-based separation and HPLC gave consistent results indicating that the polarity of lipid classes decreased as follows: phospholipids/fatty acids > triglycerides > cholesterol/cholesteryl esters. Tear lipids were found to show autofluorescence—which underpinned the value of fluorescence microscopy and fluorescence detection coupled with HPLC separation. The most fluorescent lipids were found to be cholesteryl esters; histological techniques coupled with fluorescence microscopy indicated that white spots (’’jelly bumps’’) formed on silicone hydrogel lenses contain a high proportion of cholesteryl esters. Lipid profiles averaged for 30 symptomatic and 30 asymptomatic contact lens wearers were compiled. Peak classes were split into: cholesterol (C), cholesteryl esters (CE), glycerides (G), polar fatty acids/phospholipids (PL). The lipid ratio for ymptomatic/symptomatic was 0.6 ± 0.1 for all classes except one—the cholesterol ratio was 0.2 ± 0.05. Significantly the PL ratio was no different from that of any other class except cholesterol. Chromatography indicated that: lipid polarity decreased with depth of penetration and that lipid extractability decreased with wear time. Conclusions: Meibomian lipid composition differs from that in the tear film and on worn lenses. Although the same broad lipid classes were obtained by extraction from all lenses and all patients studied, quantities vary with wear and material. Lipid extractability diminishes with wear time regardless of the use of cleaning regimes. Dry eye symptoms in contact lens wear are frequently linked to lipid layer behaviour but seem to relate more to total lipid than to specific composition. Understanding the detail of lipid related processes is an important element of improving the clinical performance of materials and care solutions.

The lateral and ventromedial prefrontal cortex work as a dynamic integrated system:evidence from FMRI connectivity analysis

Recent functional magnetic resonance imaging (fMRI) investigations of the interaction between cognition and reward processing have found that the lateral prefrontal cortex (PFC) areas are preferentially activated to both increasing cognitive demand and reward level. Conversely, ventromedial PFC (VMPFC) areas show decreased activation to the same conditions, indicating a possible reciprocal relationship between cognitive and emotional processing regions. We report an fMRI study of a rewarded working memory task, in which we further explore how the relationship between reward and cognitive processing is mediated. We not only assess the integrity of reciprocal neural connections between the lateral PFC and VMPFC brain regions in different experimental contexts but also test whether additional cortical and subcortical regions influence this relationship. Psychophysiological interaction analyses were used as a measure of functional connectivity in order to characterize the influence of both cognitive and motivational variables on connectivity between the lateral PFC and the VMPFC. Psychophysiological interactions revealed negative functional connectivity between the lateral PFC and the VMPFC in the context of high memory load, and high memory load in tandem with a highly motivating context, but not in the context of reward alone. Physiophysiological interactions further indicated that the dorsal anterior cingulate and the caudate nucleus modulate this pathway. These findings provide evidence for a dynamic interplay between lateral PFC and VMPFC regions and are consistent with an emotional gating role for the VMPFC during cognitively demanding tasks. Our findings also support neuropsychological theories of mood disorders, which have long emphasized a dysfunctional relationship between emotion/motivational and cognitive processes in depression.

S100A4 downregulates filopodia formation through increased dynamic instability

Cell migration requires the initial formation of cell protrusions, lamellipodia and/or filopodia, the attachment of the leading lamella to extracellular cues and the formation and efficient recycling of focal contacts at the leading edge. The small calcium binding EF-hand protein S100A4 has been shown to promote cell motility but the direct molecular mechanisms responsible remain to be elucidated. In this work, we provide new evidences indicating that elevated levels of S100A4 affect the stability of filopodia and prevent the maturation of focal complexes. Increasing the levels of S100A4 in a rat mammary benign tumor derived cell line results in acquired cellular migration on the wound healing scratch assay. At the cellular levels, we found that high levels of S100A4 induce the formation of many nascent filopodia, but that only a very small and limited number of those can stably adhere and mature, as opposed to control cells, which generate fewer protrusions but are able to maintain these into more mature projections. This observation was paralleled by the fact that S100A4 overexpressing cells were unable to establish stable focal adhesions. Using different truncated forms of the S100A4 proteins that are unable to bind to myosin IIA, our data suggests that this newly identified functions of S100A4 is myosin-dependent, providing new understanding on the regulatory functions of S100A4 on cellular migration.

Novel high water content hydrogels

Hydrogels may be described as cross-linked hydrophilic polymers that swell but do not dissolve in water. The production of high water content hydrogels was the subject of investigation. Based upon copolymer compositions that had already achieved commercial success as biomaterials, new monomers were added or substituted in and the effects observed. The addition of N-isopropyl acrylamide to an acrylamide-based composition that had previously been designed to become a contact lens, produced materials that showed smart effects in that the water content showed dependence on the temperature of the hydrating solution. Such thermo-responsive materials have potential uses in drug delivery, ultrafiltration and cell culture surfaces. Proteoglycans in nature have an important role to play in structural support where a highly hydrophilic structure maintains lubricious surfaces. Certain functional groups that impart this hydrophilicity are present in certain sulphonate monomers, Bis(3-sulphopropyl ester) itaconate, dipotassium salt (SPI), 3-Sulphopropyl ester acrylate, potassium salt (SPA) and Sodium 2-(acrylamido)-2-methyl propane sulphonate (NaAMPS). These monomers were incorporated into a HEMA-based copolymer that had been designed initially as a contact lens and the resulting effects examined. Highly hydrophilic materials resulted that showed reduced protein deposition over the neutral core material. It is postulated that a sulphonate group would have a larger number of hydration shells around it than for example methacrylic acid, leading to more dynamic exchange and so reducing the adsorption of biological solutes. A cationic monomer was added to bring back the net anionic nature of the sulphonate hydrogels and the effects studied. Ionic interactions were found to cause a reduction in the water content of the resulting materials as the mobility of the network decreased, leading to stiffer but less extensible materials. The presence of a net dominant charge, whether negative or positive, appeared to act to reduce protein deposition, but increasing equivalence in the amount of both charges served to present a more 'neutral' surface and deposition subsequently increased. The grafting of hydrophilic hydrogel layers onto silicone elastomer was attempted and the results evaluated using dynamic contact angle measurements. Following plasma oxidation to reduce the surface energy barrier to aqueous grafting chemistry, it was found that the wettability of the modified elastomers could be significantly enhanced by such treatment. The SPA-grafted material in particular hinted at an osmotic drive for rehydration that may be exploited in biomaterials.

Global non-dynamic refinement of radial orbit error for altimetric earth satellites

The accuracy of altimetrically derived oceanographic and geophysical information is limited by the precision of the radial component of the satellite ephemeris. A non-dynamic technique is proposed as a method of reducing the global radial orbit error of altimetric satellites. This involves the recovery of each coefficient of an analytically derived radial error correction through a refinement of crossover difference residuals. The crossover data is supplemented by absolute height measurements to permit the retrieval of otherwise unobservable geographically correlated and linearly combined parameters. The feasibility of the radial reduction procedure is established upon application to the three day repeat orbit of SEASAT. The concept of arc aggregates is devised as a means of extending the method to incorporate longer durations, such as the 35 day repeat period of ERS-1. A continuous orbit is effectively created by including the radial misclosure between consecutive long arcs as an infallible observation. The arc aggregate procedure is validated using a combination of three successive SEASAT ephemerides. A complete simulation of the 501 revolution per 35 day repeat orbit of ERS-1 is derived and the recovery of the global radial orbit error over the full repeat period is successfully accomplished. The radial reduction is dependent upon the geographical locations of the supplementary direct height data. Investigations into the respective influences of various sites proposed for the tracking of ERS-1 by ground-based transponders are carried out. The potential effectiveness on the radial orbital accuracy of locating future tracking sites in regions of high latitudinal magnitude is demonstrated.

Combining data driven programming with component based software development:with applications in geovisualisation and dynamic data driven application systems

Software development methodologies are becoming increasingly abstract, progressing from low level assembly and implementation languages such as C and Ada, to component based approaches that can be used to assemble applications using technologies such as JavaBeans and the .NET framework. Meanwhile, model driven approaches emphasise the role of higher level models and notations, and embody a process of automatically deriving lower level representations and concrete software implementations. The relationship between data and software is also evolving. Modern data formats are becoming increasingly standardised, open and empowered in order to support a growing need to share data in both academia and industry. Many contemporary data formats, most notably those based on XML, are self-describing, able to specify valid data structure and content, and can also describe data manipulations and transformations. Furthermore, while applications of the past have made extensive use of data, the runtime behaviour of future applications may be driven by data, as demonstrated by the field of dynamic data driven application systems. The combination of empowered data formats and high level software development methodologies forms the basis of modern game development technologies, which drive software capabilities and runtime behaviour using empowered data formats describing game content. While low level libraries provide optimised runtime execution, content data is used to drive a wide variety of interactive and immersive experiences. This thesis describes the Fluid project, which combines component based software development and game development technologies in order to define novel component technologies for the description of data driven component based applications. The thesis makes explicit contributions to the fields of component based software development and visualisation of spatiotemporal scenes, and also describes potential implications for game development technologies. The thesis also proposes a number of developments in dynamic data driven application systems in order to further empower the role of data in this field.

The development of a model system and high throughput assay for the study of interactions between zinc finger proteins and DNA

It has been recognised for some time that a full code of amino acid-based recognition of DNA sequences would be useful. Several approaches, which utilise small DNA binding motifs called zinc fingers, are presently employed. None of the current approaches successfully combine a combinatorial approach to the elucidation of a code with a single stage high throughput screening assay. The work outlined here describes the development of a model system for the study of DNA protein interactions and the development of a high throughput assay for detection of such interactions. A zinc finger protein was designed which will bind with high affinity and specificity to a known DNA sequence. For future work it is possible to mutate the region of the zinc finger responsible for the specificity of binding, in order to observe the effect on the DNA / protein interactions. The zinc finger protein was initially synthesised as a His tagged product. It was not possible however to develop a high throughput assay using the His tagged zinc finger protein. The gene encoding the zinc finger protein was altered and the protein synthesised as a Glutathione S-Transferase (GST) fusion product. A successful assay was developed using the GST protein and Scintillation Proximity Assay technology (Amersham Pharmacia Biotech). The scintillation proximity assay is a dynamic assay that allows the DNA protein interactions to be studied in "real time". This assay not only provides a high throughput method of screening zinc finger proteins for potential ligands but also allows the effect of addition of reagents or competitor ligands to be monitored.

Incorporation and release of macromolecules from biodegradable polymer vehicles

The initial objective of this work was to evaluate and introduce fabrication techniques based on W/0/W double emulsion and 0/W single emulsion systems with solvent evaporation for the incorporation of a surrogate macromolecule (BSA) into microspheres and microcapsules fabricated using P(HB-HV}, PEA and their blends. Biodegradation, expressed as changes in the gross and ultrastructural morphology of BSA loaded microparticulates with time was monitored using SEM concomitant with BSA release. Spherical microparticulates were successfully fabricated using both the W/0/W and 0/W emulsion systems. Both microspheres and microcapsules released BSA over a period of 24 to 26 days. BSA release from P(HB-HV)20% PCL 11 microcapsules increased steadily with time, while BSA release from all other microparticulates was characterised by an initial lag phase followed by exponential release lasting 6-11 days. Microcapsules were found to biodegrade more rapidly than microspheres fabricated from the same polymer. The incubation of microparticulates in newborn calf serum; synthetic gastric juice and pancreatin solution showed that microspheres and microcapsules were susceptible to enzymatic biodegradation. The in vitro incubation of microparticulates in Hank's buffer demonstrated limited biodegradation of microspheres and microcapsules by simple chemical hydrolysis. BSA release was thought to ocurr as a result of the macromolecule diffusing through either inherent micropores or via pores and channels generated in situ by previously dissolved BSA. However, in all cases, irrespective of percentage loading or fabrication polymer, low encapsulation efficiencies were obtained with W/0/W and 0/W techniques (4.2±0.9%- 15.5±0.5%,n=3), thus restricting the use of these techniques for the generation of microparticulate sustained drug delivery devices. In order to overcome this low encapsulation efficiency, a W/0 single emulsion technique was developed and evaluated in an attempt to minimise the loss of the macromolecule into the continuous aqueous phase and increase encapsulation efficiency. Poly(lactide-co-glycolide) [PLCG] 75:25 and 50:50, PEA alone and PEA blended with PLCG 50:50 to accelerate biodegradation, were used to microencapsulate the water soluble antibiotic vancomycin, a putative replacement for gentamicin in the control of bacterial infection in orthopaedic surgery especially during total hip replacement. Spherical microspheres (17.39±6.89~m,n=74-56.5±13.8~m,n=70) were successfully fabricated with vancomycin loadings of 10, 25 and 50%, regardless of the polymer blend used. All microspheres remained structurally intact over the period of vancomycin release and exhibited high percentage yields( 40. 75±2 .86%- 97.16±4.3%,n=3)and encapsulation efficiencies (47.75±9.0%- 96.74±13.2%,n=12). PLCG 75:25 microspheres with a vancomycin loading of 50% were judged to be the most useful since they had an encapsulation efficiency of 96.74+13.2%, n=12 and sustained therapeutically significant vancomycin release (15-25μg/ml) for up to 26 days. This work has provided the means for the fabrication of a spectrum of prototype biodegradable microparticulates, whose biodegradation has been characterised in physiological media and which have the potential for the sustained delivery of therapeutically useful macromolecules including water soluble antibiotics for orthopaedic applications.

An investigation of the dynamic characteristics of a bolted-rotor system

A Jeffcott rotor consists of a disc at the centre of an axle supported at its end by bearings. A bolted Jeffcott rotor is formed by two discs, each with a shaft on one side. The discs are held together by spring loaded bolts near the outer edge. When the rotor turns there is tendency for the discs to separate on one side. This effect is more marked if the rotor is unbalanced, especially at resonance speeds. The equations of motion of the system have been developed with four degrees of freedom to include the rotor and bearing movements in the respective axes. These equations which include non-linear terms caused by the rotor opening, are subjected to external force such from rotor imbalance. A simulation model based on these equations was created using SIMULINK. An experimental test rig was used to characterise the dynamic features. Rotor discs open at a lateral displacement of the rotor of 0.8 mm. This is the threshold value used to show the change of stiffness from high stiffness to low stiffness. The experimental results, which measure the vibration amplitude of the rotor, show the dynamic behaviour of the bolted rotor due to imbalance. Close agreement of the experimental and theoretical results from time histories, waterfall plots, pseudo-phase plots and rotor orbit plot, indicated the validity of the model and existence of the non-linear jump phenomenon.

Automobile friction materials: a test instrument and technique for determining dynamic mechanical properties in relation to brake squeal

This study is primarily concerned with the problem of break-squeal in disc brakes, using moulded organic disc pads. Moulded organic friction materials are complex composites and due to this complexity it was thought that they are unlikely to be of uniform composition. Variation in composition would under certain conditions of the braking system, cause slight changes in its vibrational characteristics thus causing resonance in the high audio-frequency range. Dynamic mechanical propertes appear the most likely parameters to be related to a given composition's tendency to promote squeal. Since it was necessary to test under service conditions a review was made of all the available commercial test instruments but as none were suitable it was necessary to design and develop a new instrument. The final instrument design, based on longitudinal resonance, enabled modulus and damping to be determined over a wide range of temperatures and frequencies. This apparatus has commercial value since it is not restricted to friction material testing. Both used and unused pads were tested and although the cause of brake squeal was not definitely established, the results enabled formulation of a tentative theory of the possible conditions for brake squeal. The presence of a temperature of minimum damping was indicated which may be of use to braking design engineers. Some auxilIary testing was also performed to establish the effect of water, oil and brake fluid and also to determine the effect of the various components of friction materials.

Flexible high speed machinery

The thesis describes an investigation into methods for the design of flexible high-speed product processing machinery, consisting of independent electromechanically actuated machine functions which operate under software coordination and control. An analysis is made of the elements of traditionally designed cam-actuated, mechanically coupled machinery, so that the operational functions and principal performance limitations of the separate machine elements may be identified. These are then used to define the requirements for independent actuators machinery, with a discussion of how this type of design approach is more suited to modern manufacturing trends. A distributed machine controller topology is developed which is a hybrid of hierarchical and pipeline control. An analysis is made, with the aid of dynamic simulation modelling, which confirms the suitability of the controller for flexible machinery control. The simulations include complex models of multiple independent actuators systems, which enable product flow and failure analyses to be performed. An analysis is made of high performance brushless d.c. servomotors and their suitability for actuating machine motions is assessed. Procedures are developed for the selection of brushless servomotors for intermittent machine motions. An experimental rig is described which has enabled the actuation and control methods developed to be implemented. With reference to this, an evaluation is made of the suitability of the machine design method and a discussion is given of the developments which are necessary for operational independent actuators machinery to be attained.

Formability of high strength aluminium sheet

An initial review of the subject emphasises the need for improved fuel efficiency in vehicles and the possible role of aluminium in reducing weight. The problems of formability generally in manufacture and of aluminium in particular are discussed in the light of published data. A range of thirteen commercially available sheet aluminium alloys have been compared with respect to mechanical properties as these affect forming processes and behaviour in service. Four alloys were selected for detailed comparison. The formability and strength of these were investigated in terms of underlying mechanisms of deformation as well as the microstructural characteristics of the alloys including texture, particle dispersion, grain size and composition. In overall terms, good combinations of strength and ductility are achievable with alloys of the 2xxx and 6xxx series. Some specific alloys are notably better than others. The strength of formed components is affected by paint baking in the final stages of manufacture. Generally, alloys of the 6xxx family are strengthened while 2xxx and 5xxx become weaker. Some anomalous behaviour exists, however. Work hardening of these alloys appears to show rather abrupt decreases over certain strain ranges which is probably responsible for the relatively low strains at which both diffuse and local necking occur. Using data obtained from extended range tensile tests, the strain distribution in more complex shapes can be successfully modelled using finite element methods.Sheet failure during forming occurs by abrupt shear fracture in many instances. This condition is favoured by states of biaxial tension, surface defects in the form of fine scratches and certain types of crystallographic texture. The measured limit strains of the materials can be understood on the basis of attainment of a critical shear stress for fracture.