Ocular biotribology and contact lens lubrication mechanisms

The work described in this thesis is concerned with mechanisms of contact lens lubrication. There are three major driving forces in contact lens design and development; cost, convenience, and comfort. Lubrication, as reflected in the coefficient of friction, is becoming recognised as one of the major factors affecting the comfort of the current generation of contact lenses, which have benefited from several decades of design and production improvements. This work started with the study of the in-eye release of soluble macromolecules from a contact lens matrix. The vehicle for the study was the family of CIBA Vision Focus® DAILIES® daily disposable contact lenses which is based on polyvinyl alcohol (PVA). The effective release of linear soluble PVA from DAILIES on the surface of the lens was shown to be beneficial in terms of patient comfort. There was a need to develop a novel characterisation technique in order to study these effects at surfaces; this led to the study of a novel tribological technique, which allowed the friction coefficients of different types of contact lenses to be measured reproducibly at genuinely low values. The tribometer needed the ability to accommodate the following features: (a) an approximation to eye lid load, (b) both new and ex-vivo lenses, (c) variations in substrate, (d) different ocular lubricants (including tears). The tribometer and measuring technique developed in this way was used to examine the surface friction and lubrication mechanisms of two different types of contact lenses: daily disposables and silicone hydrogels. The results from the tribometer in terms of both mean friction coefficient and the friction profiles obtained allowed various mechanisms used for surface enhancement now seen in the daily disposable contact lens sector to be evaluated. The three major methods used are: release of soluble macromolecules (such as PVA) from the lens matrix, irreversible surface binding of a macromolecule (such as polyvinyl pyrrolidone) by charge transfer and the simple polymer adsorption (e.g. Pluoronic) at the lens surface. The tribological technique was also used to examine the trends in the development of silicone hydrogel contact lenses. The focus of the principles in the design of silicone hydrogels has now shifted from oxygen permeability, to the improvement of surface properties. Presently, tribological studies reflect the most effective in vitro method of surface evaluation in relation to the in-eye comfort.

Non-Linear oil firm force coefficients for a journal bearing operating under aligned and misaligned conditions

It is well established that hydrodynamic journal bearings are responsible for self-excited vibrations and have the effect of lowering the critical speeds of rotor systems. The forces within the oil film wedge, generated by the vibrating journal, may be represented by displacement and velocity coefficient~ thus allowing the dynamical behaviour of the rotor to be analysed both for stability purposes and for anticipating the response to unbalance. However, information describing these coefficients is sparse, misleading, and very often not applicable to industrial type bearings. Results of a combined analytical and experimental investigation into the hydrodynamic oil film coefficients operating in the laminar region are therefore presented, the analysis being applied to a 120 degree partial journal bearing having a 5.0 in diameter journal and a LID ratio of 1.0. The theoretical analysis shows that for this type of popular bearing, the eight linearized coefficients do not accurately describe the behaviour of the vibrating journal based on the theory of small perturbations, due to them being masked by the presence of nonlinearity. A method is developed using the second order terms of Taylor expansion whereby design charts are provided which predict the twentyeight force coefficients for both aligned, and for varying amounts of journal misalignment. The resulting non-linear equations of motion are solved using a modified Newton-Raphson method whereby the whirl trajectories are obtained, thus providing a physical appreciation of the bearing characteristics under dynamically loaded conditions.

An investigation into the impact of safety features on the ergonomics of surgical scalpels

In the case of surgical scalpels, blade retraction and disposability have been incorporated into a number of commercial designs to address sharps injury and infection transmission issues. Despite these new designs, the traditional metal reusable scalpel is still extensively used and this paper attempts to determine whether the introduction of safety features has compromised the ergonomics and so potentially the take-up of the newer designs. Examples of scalpels have been analysed to determine the ergonomic impact of these design changes. Trials and questionnaires were carried out using both clinical and non-clinical user groups, with the trials making use of assessment of incision quality, cutting force, electromyography and video monitoring. The results showed that ergonomic performance was altered by the design changes and that while these could be for the worse, the introduction of safety features could act as a catalyst to encourage re-evaluation of the ergonomic demands of a highly traditional product.

Metabolic and morphological alterations induced by proteolysis-inducing factor from Walker tumour-bearing rats in C2C12 myotubes

BACKGROUND: Patients with advanced cancer suffer from cachexia, which is characterised by a marked weight loss, and is invariably associated with the presence of tumoral and humoral factors which are mainly responsible for the depletion of fat stores and muscular tissue. METHODS: In this work, we used cytotoxicity and enzymatic assays and morphological analysis to examine the effects of a proteolysis-inducing factor (PIF)-like molecule purified from ascitic fluid of Walker tumour-bearing rats (WF), which has been suggested to be responsible for muscle atrophy, on cultured C2C12 muscle cells. RESULTS: WF decreased the viability of C2C12 myotubes, especially at concentrations of 20-25 mug.mL-1. There was an increase in the content of the pro-oxidant malondialdehyde, and a decrease in antioxidant enzyme activity. Myotubes protein synthesis decreased and protein degradation increased together with an enhanced in the chymotrypsin-like enzyme activity, a measure of functional proteasome activity, after treatment with WF. Morphological alterations such as cell retraction and the presence of numerous cells in suspension were observed, particularly at high WF concentrations. CONCLUSION: These results indicate that WF has similar effects to those of proteolysis-inducing factor, but is less potent than the latter. Further studies are required to determine the precise role of WF in this experimental model. © 2008 Yano et al; licensee BioMed Central Ltd.

Predicting success with silicone-hydrogel contact lenses in new wearers

Purpose: to evaluate changes in tear metrics and ocular signs induced by six months of silicone-hydrogel contact lens wear and the difference in baseline characteristics between those who successfully continued in contact lens wear compared to those that did not. Methods: Non-invasive Keratograph, Tearscope and fluorescein tear break-up times (TBUTs), tear meniscus height, bulbar and limbal hyperaemia, lid-parallel conjunctival folds (LIPCOF), phenol red thread, fluorescein and lissamine-green staining, and lid wiper epitheliopathy were measured on 60 new contact lens wearers fitted with monthly silicone-hydrogels (average age 36 ± 14 years, 40 females). Symptoms were evaluated by the Ocular Surface Disease Index (OSDI). After six months full time contact lens wear the above metrics were re-measured on those patients still in contact lens wear (n= 33). The initial measurements were also compared between the group still wearing lenses after six months and those who had ceased lens wear (n= 27). Results: There were significant changes in tear meniscus height (p= 0.031), bulbar hyperaemia (p= 0.011), fluorescein TBUT (p= 0.027), corneal (p= 0.007) and conjunctival (p= 0.009) staining, LIPCOF (p= 0.011) and lid wiper epitheliopathy (p= 0.002) after six months of silicone-hydrogel wear. Successful wearers had a higher non-invasive (17.0 ± 8.2. s vs 12.0 ± 5.6. s; p= 0.001) and fluorescein (10.7 ± 6.4. s vs 7.5 ± 4.7. s; p= 0.001) TBUT than drop-outs, although OSDI (cut-off 4.2) was also a strong predictor of success. Conclusion: Silicone-hydrogel lenses induced significant changes in the tear film and ocular surface as well as lid margin staining. Wettability of the ocular surface is the main factor affecting contact lens drop-out. © 2013 British Contact Lens Association.

What is the optimum artificial treament for dry eye?

Dry eye disease is a common clinical condition whose aetiology and management challenges clinicians and researchers alike. Practitioners have a number of dry eye tests available to clinically assess dry eye disease, in order to treat their patients effectively and successfully. This thesis set out to determine the most relevant and successful key tests for dry eye disease diagnosis/ management. There has been very little research on determining the most effective treatment options for these patients; therefore a randomised controlled study was conducted in order to see how different artificial treatments perform compared to each other, whether the preferred treatment could have been predicted from their ocular clinical assessment, and if the preferred treatment subjectively related to the greatest improvement in ocular physiology and tear film stability. This research has found: 1. From the plethora of ocular the tear tests available to utilise in clinical practice, the tear stability tests as measured by the non-invasive tear break (NITBUT) up time and invasive tear break up time (NaFL TBUT) are strongly correlated. The tear volume tests are also related as measured by the phenol red thread (PRT) and tear meniscus height (TMH). Lid Parallel Conjunctival Folds (LIPCOF) and conjunctival staining are significantly correlated to one another. Symptomology and osmolarity were also found to be important tests in order to assess for dry eye. 2. Artificial tear supplements do work for ocular comfort, as well as the ocular surface as observed by conjunctival staining and the reduction LIPCOF. There is no strong evidence of one type of artificial tear supplement being more effective than others, and the data suggest that these improvements are more due to the time than the specific drops. 3. When trying to predict patient preference for artificial tears from baseline measurements, the individual category of artificial tear supplements appeared to have an improvement in at least 1 tear metric. Undoubtedly, from the study the patients preferred artificial tear supplements’ were rated much higher than the other three drops used in the study and their subjective responses were statistically significant than the signs. 4. Patients are also willing to pay for a community dry eye service in their area of £17. In conclusion, the dry eye tests conducted in the study correlate with one another and with the symptoms reported by the patient. Artificial tears do make a difference objectively as well as subjectively. There is no optimum artificial treatment for dry eye, however regular consistent use of artificial eye drops will improve the ocular surface.

International session at the BCLA conference

Full text: It seems a long time ago now since we were at the BCLA conference. The excellent FIFA World Cup in Brazil kept us occupied over the summer as well as Formula 1, Wimbledon, Tour de France, Commonwealth Games and of course exam paper marking! The BCLA conference this year was held in Birmingham at the International Convention Centre which again proved to be a great venue. The number of attendees overall was up on previous years, and at a record high of 1500 people. Amongst the highlights at this year's annual conference was the live surgery link where Professor Sunil Shah demonstrated the differences in technique between traditional phacoemulsification cataract surgery and femtosecond assisted phacoemulsification cataract surgery. Dr. Raquel Gil Cazorla, a research optometrist at Aston University, assisted in the procedure including calibrating the femtosecond laser. Another highlight for me was the session that I chaired, which was the international session organised by IACLE (International Association of CL Educators). There was a talk by Mirjam van Tilborg about dry eye prevalence in the Netherlands and how it was managed by medical general practitioners (GPs) or optometrists. It was interesting to know that there are only 2 schools of optometry there and currently under 1000 registered optometrists there. It also seems that GPs were more likely to blame CL as the cause for dry eye whereas optometrists who had a fuller range of tests were better at solving the issue. The next part of the session included the presentation of 5 selected posters from around the world. The posters were also displayed in the main poster area but were selected to be presented here as they had international relevance. The posters were: 1. Motivators and Barriers for Contact Lens Recommendation and Wear by Nilesh Thite (India) 2. Contact lens hygiene among Saudi wearers by Dr. Ali Masmaly (Saudi) 3. Trends of contact lens prescribing and patterns of contact lens practice in Jordan by Dr. Mera Haddad (Jordan) 4. Contact Lens Behaviour in Greece by Dr. Dimitra Makrynioti (Greece) 5. How practitioners inform ametropes about the benefits of contact lenses and overcome the potential barriers: an Italian survey, by Dr. Fabrizio Zeri (Italy) It was interesting to learn about CL practice in different parts, for example the CL wearing population ration in Saudi Arabia is around 1:2 Male:Female (similar to other parts of the world) and although the sale of CL is restricted to registered practitioners there are many unregistered outlets, like clothing stores, that flout the rules. In Jordan some older practitioners will still advise patients to use tap water or even saliva! But thankfully the newer generation of practitioners have been educated not to advise this. In Greece one of the concerns was that some practitioners may advise patients to use disposable lenses for longer than they should and again it seems to be the practitioners with inadequate education that would do this. In India it was found that cost was one barrier to using contact lenses but also some practitioners felt that they shouldn’t offer CLs due to cost too. In Italy sensitive eyes and CL care and maintenance were the barriers to CL wear but the motivators were vision and comfort and aesthetics. Finally the international session ended with the IACLE travel award and educator awards presented by IACLE president Shehzad Naroo and BCLA President Andrew Yorke. The travel award went to Wang Ling, Jinling Institute of Technology, Nanjing, China. There were 3 regional Contact Lens Educator of the Year Awards sponsored by Coopervision and presented by Dr. J.C. Aragorn of Coopervision. 1. Asia Pacific Region – Dr. Rajeswari Mahadevan of Sankara Nethralaya Medical Research Foundation, Chennai, India 2. Americas Region – Dr. Sergio Garcia of University of La Salle, Bogotá and the University Santo Tomás, Bucaramanga, Colombia 3. Europe/Africa – Middle East Region: Dr. Eef van der Worp, affiliated with the University of Maastricht, the Netherlands The posters above were just a small selection of those displayed at this year's BCLA conference. If you missed the BCLA conference then you can see the abstracts for all posters and talks in a virtual issue of CLAE very soon. The poster competition was kindly sponsored by Elsevier. The poster winner this year was: Joan Gispets – Corneal and Anterior Chamber Parameters in Keratoconus The 3 runners up were: Debby Yeung – Scleral Lens Central Corneal Clearance Assessment with Biomicroscopy Sarah L. Smith – Subjective Grading of Lid Margin Staining Heiko Pult – Impact of Soft Contact Lenses on Lid Parallel Conjunctival Folds My final two highlights are a little more personal. Firstly, I was awarded Honorary Life Fellowship of the BCLA for my work with the Journal, and I would like to thank the BCLA, Elsevier, the editorial board of CLAE, the reviewers and the authors for their support of my role. My final highlight from the BCLA conference this year was the final presentation of the conference – the BCLA Gold Medal award. The recipient this year was Professor Philip Morgan with his talk ‘Changing the world with contact lenses’. Phil was the person who advised me to go to my first BCLA conference in 1994 (funnily he didn’t attend himself as he was busy getting married!) and now 20 years later he was being honoured with the accolade of being the BCLA Gold Medallist. The date of his BCLA medal addressed was shared with his father's birthday so a double celebration for Phil. Well done to outgoing BCLA President Andy Yorke and his team at the BCLA (including Nick Rumney, Cheryl Donnelly, Sarah Greenwood and Amir Khan) on an excellent conference. And finally welcome to new President Susan Bowers. Copyright © 2014 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

On Pareto Sets in Multi-Criteria Optimization

Здравко Д. Славов - В тази работа се разглеждат Паретовските решения в непрекъсната многокритериална оптимизация. Обсъжда се ролята на някои предположения, които влияят на характеристиките на Паретовските множества. Авторът се е опитал да премахне предположенията за вдлъбнатост на целевите функции и изпъкналост на допустимата област, които обикновено се използват в многокритериалната оптимизация. Резултатите са на базата на конструирането на ретракция от допустимата област върху Парето-оптималното множество.

Using Covariance as a Similarity Measure for Document Language Identification in Hard Contexts

2000 Mathematics Subject Classification: C2P99.

Incorporating Water Sensitive Urban Design (WSUD) practices into the planning context:the conceptual case for lot-scale developments

In recent decades, a number of sustainable strategies and polices have been created to protect and preserve our water environments from the impacts of growing communities. The Australian approach, Water Sensitive Urban Design (WSUD), defined as the integration of urban planning and design with the urban water cycle management, has made considerable advances on design guidelines since 2000. WSUD stormwater management systems (e.g. wetlands, bioretentions, porous pavement etc), also known as Best Management Practices (BMPs) or Low Impact Development (LID), are slowly gaining popularity across Australia, the USA and Europe. There have also been significant improvements in how to model the performance of the WSUD technologies (e.g. MUSIC software). However, the implementation issues of these WSUD practices are mainly related to ongoing institutional capacity. Some of the key problems are associated with a limited awareness of urban planners and designers; in general, they have very little knowledge of these systems and their benefits to the urban environments. At the same time, hydrological engineers should have a better understanding of building codes and master plans. The land use regulations are equally as important as the physical site conditions for determining opportunities and constraints for implementing WSUD techniques. There is a need for procedures that can make a better linkage between urban planners and WSUD engineering practices. Thus, this paper aims to present the development of a general framework for incorporating WSUD technologies into the site planning process. The study was applied to lot-scale in the Melbourne region, Australia. Results show the potential space available for fitting WSUD elements, according to building requirements and different types of housing densities. © 2011 WIT Press.

Comparison of Ba/Ca and d18OWATER as freshwater proxies: a multi-species core-top study on planktonic foraminifera from the vicinity of the Orinoco River mouth

Past river run-off is an important measure for the continental hydrological cycle and the as-sessment of freshwater input into the ocean. However, paleosalinity reconstructions applying different proxies in parallel often show offsets between the respective methods. Here, we compare the established foraminiferal Ba/Ca and d18OWATER salinity proxies for their capability to record the highly seasonal Orinoco freshwater plume in the eastern Caribbean. For this purpose we obtained a data set comprising Ba/Ca and d18OWATER determined on multiple spe-cies of planktonic foraminifera from core tops distributed around the Orinoco river mouth. Our findings indicate that interpretations based on either proxy could lead to different conclu-sions. In particular, Ba/Ca and d18OWATER diverge in their spatial distribution due to different governing factors. Apparently, the Orinoco freshwater plume is best tracked by Ba/Ca ratios of G. ruber (pink and sensu lato morphotypes), while d18OWATER based on the same species is more related to the local precipitation-evaporation balance overprinting the riverine freshwater contribution. Other shallow dwelling species (G. sacculifer, O. universa) show a muted response to the freshwater discharge, most likely due to their ecological and habitat prefer-ences. Extremely high Ba/Ca ratios recorded by G. ruber are attributed to Ba2+-desorption from suspended matter derived from the Orinoco. Samples taken most proximal to the freshwater source do not show pronounced Ba/Ca or d18OWATER anomalies. Here, the suspension loaded freshwater lid developing during maximum discharge suppresses foraminiferal populations. Both proxies are therefore biased towards dry season conditions at these sites, when surface salinity is only minimally reduced.

Incorporação do resíduo de cascalho de perfuração de poços de petróleo em formulações cerâmicas

During its operations, the oil industry generates a lot of waste, including gravel from drilling. Control of environmental impacts caused by this waste represents a major challenge. Such impacts can be minimized when it is given an appropriate management by being properly treated and properly disposed or recycled. The properties of these materials can be greatly influenced when a waste is added to its composition. This work aims to study the incorporation of gravel waste oil-well drilling in the standard body for production of red ceramic from a ceramic industry in São Gonçalo do Amarante / RN. The success of the incorporation can minimize costs in the production of ceramic pieces and reduce the environmental impacts caused by waste. The raw materials used were collected, characterized, and formulated with the percentages of 0%, 20% and 40% by weight of substitution of residue were synthesized at temperatures of 900, 1.010 and 1.120 °C using 30 minute firing intervals, 1 hour and 30min and 2 hours and 30 minutes, based on a factorial design 2³. Samples were then subjected to the tests of Water Absorption, Linear Retraction Firing, Flexural Rupture Strength, Apparent Porosity and Apparent Specific mass and Scanning Electron Microscopy (SEM) of break section. The results showed that the use of the residue for the manufacture of the ceramic products is possible (tiles, bricks and massive hollow bricks) replacing the clay to 40%, meeting the requirements of the standard and the literature for the technological properties of the final product.

Crescimento urbano e seus impactos no sistema de drenagem de uma bacia em Natal/RN

The uncontrolled growth of most Brazilian cities is not accompanied by the development of urban infrastructure. With increasing soil sealing, runoff and decreased infiltration volume, impacts on water resources and on population of the areas affected by urban growth are inevitable. This study aims to evaluate the use and occupation of a watershed and analyze the drainage system in order to control the impact using tools to integrate urban development with the drainage of rainwater in an important watershed in the Natal City, Rio Grande do Norte State. The study involved the characterization of the basin XII.4 on the land use and occupation, for the years 2005 and 2014. With the application of SWMM model was possible to analyze the impacts caused by the urbanization process in the existing drainage system, showing the two years analyzed have their areas very close to percentage saturation of impervious areas. Although the region is still predominantly single family residential, suffers increasing verticalization of mainly commercial buildings. The drainage system is inefficient for the area's needs by the year 2005. The drainage system was also tested for four variations of land use by developing scenarios. Scenario 1 is related to the year 2014, considered current. Scenario 2 was adopted the maximum rate of 80% for land use, allowed for the Natal City. Scenario 3 gives the critical condition of land use, with the area 100% impervious. Scenario 4 is applied to the existence of LID (Low Impact Device). The scenarios analysis showed that all indicate deficiency at some point of the drainage system as a result of the high degree of occupation of the area that generate higher flows than the initial drainage system capacity. With the study it became clear that the adoption of non-structural tools are effective in reducing flooding and improving the drainage system capacity.

Crescimento urbano e seus impactos no sistema de drenagem de uma bacia em Natal/RN

The uncontrolled growth of most Brazilian cities is not accompanied by the development of urban infrastructure. With increasing soil sealing, runoff and decreased infiltration volume, impacts on water resources and on population of the areas affected by urban growth are inevitable. This study aims to evaluate the use and occupation of a watershed and analyze the drainage system in order to control the impact using tools to integrate urban development with the drainage of rainwater in an important watershed in the Natal City, Rio Grande do Norte State. The study involved the characterization of the basin XII.4 on the land use and occupation, for the years 2005 and 2014. With the application of SWMM model was possible to analyze the impacts caused by the urbanization process in the existing drainage system, showing the two years analyzed have their areas very close to percentage saturation of impervious areas. Although the region is still predominantly single family residential, suffers increasing verticalization of mainly commercial buildings. The drainage system is inefficient for the area's needs by the year 2005. The drainage system was also tested for four variations of land use by developing scenarios. Scenario 1 is related to the year 2014, considered current. Scenario 2 was adopted the maximum rate of 80% for land use, allowed for the Natal City. Scenario 3 gives the critical condition of land use, with the area 100% impervious. Scenario 4 is applied to the existence of LID (Low Impact Device). The scenarios analysis showed that all indicate deficiency at some point of the drainage system as a result of the high degree of occupation of the area that generate higher flows than the initial drainage system capacity. With the study it became clear that the adoption of non-structural tools are effective in reducing flooding and improving the drainage system capacity.

Electropermanent magnetic anchoring for surgery and endoscopy

The use of magnets for anchoring of instrumentation in minimally invasive surgery and endoscopy has become of increased interest in recent years. Permanent magnets have significant advantages over electromagnets for these applications; larger anchoring and retraction force for comparable size and volume without the need for any external power supply. However, permanent magnets represent a potential hazard in the operating field where inadvertent attraction to surgical instrumentation is often undesirable. The current work proposes an interesting hybrid approach which marries the high forces of permanent magnets with the control of electromagnetic technology including the ability to turn the magnet OFF when necessary. This is achieved through the use of an electropermanent magnet, which is designed for surgical retraction across the abdominal and gastric walls. Our electropermanent magnet, which is hand-held and does not require continuous power, is designed with a center lumen which may be used for trocar or needle insertion. The device in this application has been demonstrated successfully in the porcine model where coupling between an intraluminal ring magnet and our electropermanent magnet facilitated guided insertion of an 18 Fr Tuohy needle for guidewire placement. Subsequent investigations have demonstrated the ability to control the coupling distance of the system alleviating shortcomings with current methods of magnetic coupling due to variation in transabdominal wall thicknesses. With further refinement, the magnet may find application in the anchoring of endoscopic and surgical instrumentation for minimally invasive interventions in the gastrointestinal tract.