The adsorption of fibrinogen from human plasma onto various surfaces was investigated under differing conditions of plasma composition. Previous studies by Vroman have indicated that fibrinogen is only transiently adsorbed from normal human blood plasma, possibly due to displacement by high molecular weight kininogen (HMWK). It is possible that this "Vroman Effect" is a manifestation of the activation of the intrinsic clotting pathway responsible, in part, for thrombus formation on artificial surfaces. The effect was studied using dilutions of human plasma from 0.01% to 20.0% of normal concentration trace-labelled with a small amount of ¹²⁵I labelled fibrinogen. Adsorption of fibrinogen to various materials, including glass and several potentially useful biomaterials was measured. Fibrinogen is initially adsorbed apparently under diffusion limitation and later displaced at a rate which depends on the type of material being tested. There does not appear to be a direct relationship between material properties (contact angle, biocompatibility) and the "Vroman Effect". Studies comparing the effect for a series of clotting factor deficient plasmas seem to indicate that plasminogen and HWNK are the main displacing agents on glass. Factors XI and XII, prekallikrein and other components do not appear to be involved. An attempt to mathematically model the effect was hampered by the lack of adequate models to describe even one-component protein adsorption. An isotherm equation was developed based on a theoretical model of protein exchange and spreading on the surface. The resulting parameter estimates based on data for different surfaces were well conditioned and may provide a good in vitro basis for comparing materials. It is hoped that the theoretical model will also be compatible with dynamic adsorption and ultimately a multicomponent system such as plasma (and the Vroman Effect). This work may lead to a better understanding of blood-material interactions and may provide the basis for a simple in vitro test for the characterization of potential biomaterials. / Thesis / Master of Engineering (ME)

Artificial surfaces are increasingly more common in a number of sports including football, rugby and hockey. Each specific sport has mechanical properties designed to suit the requirements of the sport which can be achieved through appropriate selection of surface specification, as well as the appropriate selection of footwear. In player-surface interactions, traction is a key system property that needs to be measured for comfort, performance and any potential injury risk. Many of the current industry tests used to measure traction are simplistic and have limitations when used in tests. The aim of the thesis was to make a contribution to knowledge with regard to the mobilisation of traction and apply this to the understanding of shoe-surface interactions. This was achieved by completing a number of objectives. These included reviewing current knowledge of player-surface interaction behaviour in relation to traction and obtaining relevant human boundary conditions for biofidelic mechanical test development. The mechanisms of traction were then investigated and the variables in the mobilisation of traction identified. The traction forces developed were quantified with appropriate measurement systems. Mechanical test equipment was then developed along with protocols to replicate the translational and rotational lower limb behaviour during sport specific behaviour. This included the standard FIFA rotational device being modified to include two sensors which record continuous data throughout a trial to allow for more than a peak torque value to be analysed. In addition, a piece of equipment to measure translational traction was developed and constructed to support the rotational traction device and help to understand the mobilisation of traction. The device pulled a tray containing a surface sample, with a shoe/plate placed on the sample. The horizontal force was measured, as well as the amount of stud penetration into the surface. It was also necessary to characterise the state of the surface and the effects that any changes may have on the traction that is mobilised. Testing completed involved repeated testing on both the rotational and translational to allow for comparison. Changes in the surface properties were made such as the number of fibres in a set area and the rubber infill density as well as shoe properties such as stud spacing, stud type and number of studs. In the results, the initial stiffness response of the surface was often focussed on as it was stated that this may be a better indicator of the mechanisms involved in the traction mobilised by subjects, compared to peak torque. This is due to actual foot rotation measured in subject testing being observed to be much smaller than the rotation/distance required to produce the peak force. The larger angles/displacements were also considered to help inform the mechanisms of traction. The final objective was to refine the mechanisms based on the experimental design. This all adds to the contribution of knowledge regarding the mobilisation of traction. A key outcome from the thesis is the effect the surface and shoe properties have on traction, therefore it is essential to state the specification when reporting results otherwise comparisons are not able to be made. The mechanism of traction has not previously been fully understood, with this thesis beginning to understand the details of how the change in surface or shoe properties affect how the surface reacts during shoe-surface interactions.

Research interest: In recent years we have seen the emergence of commercial applications at high frequencies, such as the top part of the microwave band and the millimeter and sub-millimeter bands, and it is expected a big increase in the coming years. This growing demand requires a rapid development of low-cost technology with good performance at these frequencies, where common technologies, such as microstrip and standard waveguides, have some shortcomings. In particular, existing solutions for high-gain planar scanning antennas at these frequencies su er from the disadvantages of these technologies giving rise to high-cost products not suitable for high volume production. Objectives: The main objective of this thesis is to study the feasibility of a new proposal to improve existing solutions to date for low-cost high-gain planar scanning antennas at high frequencies. This overall objective has resulted in another central objective of this thesis, which is the research of new quasi-TEM waveguides that are more appropriate than current technologies for the realization of circuits and components at these frequency bands. These guided solutions make use of periodic or arti cial surfaces in order to con- ne and channel the elds within these waveguides. Methodology: The work follows a logical sequence of speci c tasks aimed at achieving the main objective of this thesis. Chapter 2 presents the proposed guiding solution and shows its performance numerical and experimentally. The optimized design of high-gain antennas based on waveguide slot arrays requires the development of e cient ad-hoc codes. The implementation and validation of this code is presented in Chapter 3, where a new method for the analysis of corrugated surfaces is proposed, and in Chapter 4, which extends this code to the analysis of waveguide slot arrays. The process design and optimization of a two-dimensional array is described in Chapter 5, where a preliminary experimental validation is also described. Moreover, the proposed guiding solution has inspired the development of a new guiding technology of wider bandwidth and more versatile for the realization of circuits and components at high frequencies. Chapter 6 presents the contributions to the study of this technology and its application to the design of circuits. / Alfonso Alós, E. (2011). New quasi-TEM waveguides using artificial surfaces and their application to antennas and circuits [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/11073