The cornea is the anterior most surface of the eye and plays a critical role in vision. A thin fluid layer, the tear film, coats the outer surface of the cornea and serves to protect, nourish, and lubricate the cornea. At the same time, the tear film is responsible for creating a smooth continuous surface, where the majority of refraction takes place in the eye. A significant component of vision quality is determined by the shape of the cornea and stability of the tear film. A dual interferometer system for measuring the dynamic corneal topography is designed, built, verified, and qualified by testing on human subjects. The system consists of two coaligned simultaneous phase-shifting polarization-splitting Twyman-Green interferometers. The primary interferometer measures the surface of the tear film while the secondary interferometer tracks the absolute position of the cornea, which provides enough information to reconstruct the absolute shape of the cornea. The results are high-resolution and high-accuracy surface topography measurements of the in vivo tear film and cornea that are captured at standard camera frame rates. (C) 2016 Society of Photo-Optical Instrumentation Engineers (SPIE)

A catarata, enfermidade ocular de etiopatogenia complexa, é uma das principais causas de perda de visão, em cães. As causas da doença são diversas, predominando a origem genética, seguida pelo diabetes mellitus. O tratamento da catarata é estritamente cirúrgico, sendo a facoemulsificação, atualmente, considerada a técnica de eleição na conduta terapêutica. O procedimento cirúrgico demanda a realização de incisão corneana para acesso à câmara anterior. A despeito das incisões reduzidas requeridas na sua consecução, comparativamente a outras técnicas como facectomias intra e extracapsulares, alterações da inervação corneana podem ser acarretadas, principalmente em pacientes diabéticos. A córnea é um dos tecidos mais densamente inervados do organismo, por isso, assume-se que, em maior ou menor grau, tais incisões possam comprometer sua sensibilidade e, também, influenciar na produção lacrimal. Portanto, visando avaliar tais consequências, concebeu-se aferir a sensibilidade corneana e a produção lacrimal aquosa, em cães diabéticos submetidos à facoemulsificação. Estes parâmetros foram investigados em dez cães diabéticos com idade, sexo, raça e peso variáveis. O procedimento cirúrgico foi realizado somente em um olho (olho tratado - OT) e o olho contralateral foi considerado como controle (olho controle - OC). A sensibilidade da córnea foi mensurada com o estesiômetro de Cochet-Bonnet e a produção lacrimal pelo teste da lágrima de Schirmer. Também foi medida a pressão intraocular e verificada a ocorrência ou não de hiperemia conjuntival, blefarospasmo e edema de córnea para detecção de complicações pós-operatórias. Os parâmetros foram aferidos previamente ao procedimento cirúrgico (M0 - valores basais) e, posteriormente, após sete (M1), 15 (M2), 30 (M3), 90 (M4) e 180 dias (M5). Houve diferença estatística nos valores de estesiometria (em cm e g/mm2) (p=0,0138), em OT, entre M0 e todos os momentos pós-operatórios (M1 a M5). Em OT, individualmente, evidenciou-se diferença entre os tempos M0 e M1 (p<0,005). Também houve diferença entre OC e OT (p<0,0032) quanto aos valores da estesiometria. Não foram verificadas diferenças significativas nos demais parâmetros avaliados, nos diferentes momentos pós-operatórios e entre OC e OT. / The cataract is an ocular disease of complex etiopathogenesis and one of the main causes of blindness in dogs. The disease sources are diverse and genetic origin is predominant, followed by diabetes mellitus. The treatment of cataract is strictly surgical and, nowadays, the phacoemulsification is the technique more indicated. The surgical procedure requires a corneal incision to access the anterior chamber. Despite minor incisions required (compared to other techniques such as intra and extracapsular facectomy), corneal innervation may be injured, especially in diabetic patients. Therefore, these incisions may compromise the sensitivity and also the lacrimal production. This study aimed to evaluate these consequences, through measurement of the corneal sensitivity and the aqueous lacrimal production in diabetic dogs submitted to phacoemulsification. The parameters were investigated in ten diabetic dogs with different ages, genders, breeds and weights. The surgical procedure was performed in one eye (treated eye - TE) and the contralateral eye was the control (control eye - CE). Corneal sensitivity was measured with the Cochet-Bonnet esthesiometer and lacrimal production with the Schirmer tear test, in both eyes. The intraocular pressure was also measured and the occurrence or not of conjunctival hyperemia, blepharospasm and corneal edema was verified for the detection of postoperative complications. The parameters were measured prior to the surgery (M0 - baseline values) and after seven (M1), 15 (M2), 30 (M3), 90 (M4) and 180 days (M5). Significant differences were observed in the values of esthesiometry (in cm and g/mm2) (p = 0.0138), in TE, between M0 and postoperative moments. There was a significant difference between M0 and M1, in TE (p <0.005). There was also a significant difference between CE and TE (p <0.0032) for the esthesiometry. The other parameters did not show significant differences in the postoperative moments and between CE and TE.

During the use phase of products, a series of obsolescing factors contribute to why a product is disposed of. Currently the visual state of a product is considered primarily in terms of aesthetic obsolescence which is synonymous with influential factors such as changes in fashion or personal preferences in style. The physical condition of a product is not commonly understood within the context of product replacement and the physical changes due to use are not understood fully. The research contributes to and provides original empirical research findings for the current literature on product lifetime extension, material semantics, the circular economy, emotionally durable design and material culture. Through an initial exploratory study (Photographic Analysis (PA) Study) of previously unexplained types of wear and damage that occur on portable electronic devices a taxonomy of damage (TOD) was established which provided the nomenclature for further studies. The second study (Retrospective Assessment (RA) Study) established the attitudes to wear based on the wear type, location, material and the stage during ownership that the wear occurred at. The RA Study highlighted the differences in the attitudinal responses to differing types of wear and damage and identified the differences in the temporal assessments of wear and damage. A third study (Real Time Assessment (RTA) Study) aimed to confirm or repudiate the findings found in the RA Study. The focus during the study was attitudes to the wear and damage in relation to the differences in materials, the location of the wear and the type of wear and damage was also looked at and led to a fuller understanding of how products and materials are perceived during the use phase; a stage of the product lifetime that is not currently well understood in terms of users aesthetic or cosmetic sensibilities. The final study (Semantic Perception of Materials (SPM) Study) focused on the visual and tactile perceptions of materials. The study established attitudinal perceptions of wear and damage of materials with a quantitative research methodology which has produced a better understanding of material semantics within the context of electronic objects. Through the four studies, discussion topics arose and major findings of the doctoral study were drawn out and seen to be interesting enough for further research and study. These discussions include the importance of including cosmetic obsolescence into the lexicon of product obsolescence and product lifetime extension literature, the differences in the perceptions of materials when they are within the context of a product or being assessed as samples, how differing product contexts affect user perceptions of wear and damage on materials and the potential inclusion of a material wear index that could inform the material selection process that goes further than the technical aspects outlined in current material selection tools and literature.

Introduction: The measurement of tear film stability/regularity is very critical in the diagnosis of dry eye. The tear breakup time, which is used as a diagnostic tool in diagnosing dry eye, is very subjective in nature and variations among individual clinicians exists. The exact mechanism of the tear breakup is also unclear due to the involvement of so many other factors other than the tear film itself. As the prevalence of dry eye is increasing, the need for an objective technique which can be used universally to differentiate between dry eye and normal values increases. Studies have shown that aberrations can be used as an objective technique in diagnosing dry eye, as there is a direct involvement of the tear film in the optics of the eye. However, very few studies have studied the dynamic nature of the anterior surface using aberrations and suggested using dynamic surface aberrations as an objective measure of surface quality. Hence, a series of studies were conducted to understand the aberrations produced by the anterior surface of the eye (tear film and corneal surface) and to measure objectively the anterior surface quality using surface aberrometry. The objectives of each study chapter are as follows: Chapter 3 i): To obtain the noise associated with the instrument using a non-dynamic measuring surface, and ii) to design appropriate acquisition settings for the measurements with ocular surface. Chapter 4: To determine ??) the spectral characteristics of the Placido disc light sources of two corneal analysers, ????) the thermal characteristic for a variety of inanimate objects, human ocular surface and the adnexa in the presence of Placido disc light source at normal working distance, and ??????) to compare the ocular surface aberrations obtained using both the corneal analysers Chapter 5: To determine i) the optimal method for acquisition with respect to normal physiological processes, by examining the blink regimen and head position that elicits the most consistent response over the largest region on repeated measurement; and i??) the largest region selected for analysis by investigating the effect on the individual and summary aberration metrics of the inclusion of non-measurement areas (i.e. where the Placido disc cannot be projected onto the cornea or contact lens). The proportion of non-measurement area that elicits a significantly different result will be determined. Chapter 6: To evaluate ??) a new method of analyzing dynamic ocular surface aberrations using segmented liner regression, and ????) the inter-ocular characteristics of the dynamic ocular surface aberrations using the segmented linear regression. Methods: Chapter 3: The characteristics of the surface aberrometer and the noise associated with the measurements of surface aberrations were evaluated using a non-dynamic surface (model eye). Measurements were obtained in different frame rates and focus positions to evaluate the optimal acquisition technique. At each focus position, a set of three repeated measurements were obtained to analyse the repeatability of the measurements obtained using a surface aberrometer. Chapter 4: The spectral characteristics of the Placido disc light source were obtained by using a PR650 SpectraScan photometer and the thermal characteristics of the objects were obtained using THI-500 non-contact infrared thermometer. The surface aberration measurements were compared between the corneal analysers. The spectral measures were obtained from the light sources, whereas the thermal measures were obtained from three different surfaces and surface of the eye and adnexa of ten participants. The dynamic anterior surface aberrations were obtained after obtaining the thermal measurements from the surface of the eye. Chapter 5: Twelve participants were enrolled by screening twenty participants. Participants were screened with their habitual lenses for contact lens wettability and non-invasive tear breakup time (NITBUT) without contact lenses. The participants were enrolled according to the inclusion and exclusion criteria and categorized into normal and dry eye group for study visits. The measurements of NITBUT and surface aberrations were obtained with and without contact lenses, and study lens wettability were also obtained in two visits on consecutive days. The surface aberration measurements were obtained in natural and forced blinking condition and in two different head positions. All the measurements were randomized between eye and between instruments. Chapter 6: Seventeen non- symptomatic and non- contact lens participants were recruited in this study. NITBUT and dynamic anterior surface aberration measurements were obtained. The order of the measurements was randomized between the eyes. Two open intervals of at least 10 sec and a maximum of 15 sec were used in the analysis of segmented fit. The dynamic vertical prism coefficients and higher order aberrations were used for the analysis. Results: Chapter 3: i. Data acquisition at an inter-frame interval of 0.25s gave the least number of dropped frames across focus positions, therefore this is the preferred frame rate for data acquisition. ii. Data obtained in the initial ~15s reflects the focusing procedure and needs to be manually removed prior to analysis of tear dynamics. iii. Even in the optimal focus position there were significant (small) differences in the distributions between repeated measures. For this reason repeated samples have to be obtained where possible. iv. The green and red focus positions showed the most consistency within repeated measurements. The variability of the measurements was also more similar between the red and green focus positions than the blue focus positions, both at the extreme positions of defocus and with incremental defocus away from the optimal focus position. When obtaining the dynamic sampling of human ocular surface measurements, the optimal position of focus should be obtained at the blink such that as the tear film dissipates between blinks the measurements are obtained in the (relatively) red focus position. Chapter 4: i. CA200 is the preferred device because of the consistent luminance. ii. Although aberrations were not significantly different between devices, the HOA RMS were higher with the CA200 and, combined with different luminance and possible tear response, indicates the devices are not interchangeable. In both instruments, there was no indication that there was a thermal response induced by the power of the light source. Therefore, this aspect of the source does not likely contribute to any difference in the aberrations measured by the two devices Chapter 5: i. Obtain data in the straight-ahead position, as there is no significant increase in target size with head turn. ii. With the CA100F, the forced blink paradigm is preferred as this enables blink dynamics to be examined. With the CA200F, either forced or natural blink paradigms are interpretable for tear dynamics. iii. Differentiation between dry eye and normal groups was best determined with the slope of the RMS aberrations within a blink. iv. Differentiation between performance with and without a contact lens in the dry eye and normal groups was best determined by analysing the width of the confidence interval of the moving average. Chapter 6: i. The location breakpoints one and two are significantly different between eye, open eye interval and order of the measurements for both vertical prism and HOA RMS values. ii. The highest positive slope for the HOA RMS was, on average, higher in the second eye measured (p= 0.0407) and tended to occur later after the blink (p= 0.0676). iii. The location of breakpoint 2 is not significantly different from the NITBUT values (p>0.05), even though the correlation was found to be low and not significant. iv. The average HOA RMS for segmented fit parameter intervals of vertical prism was found to be higher in the second open eye interval compared to first open eye interval. Conclusion: From the results of each chapter, it was observed that choosing the blink paradigm is very important to obtain and analyse the dynamic anterior surface aberrations. Choosing a forced blink paradigm (chapter 5) was showed to be useful when the information regarding blink location were not available. The repeatability of the measurements using a non-dynamic surface (chapter 3) shows that the measurements of surface aberrations are repeatable and it is important to choose a criterion closer to the natural tear film dynamics to obtain more repeatable measurements of anterior surface aberrations (chapter 4, 5 and 6). It also shows that the three phased segmented linear regression techniques can be used to analyse the anterior surface aberrations. The segmented linear regression technique was able to differentiate different stages of the tear film and the location of the second breakpoint calculated using segmented regression was closer to the clinical values of tear breakup time, indicating a possible use of segmented linear regression as an objective measure of surface quality.

Made available in DSpace on 2014-06-11T19:32:51Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-11-10Bitstream added on 2014-06-13T19:22:34Z : No. of bitstreams: 1 souza_cn_dr_guara.pdf: 5417862 bytes, checksum: 45f7392a335fde8b9a67ef7d60be0ce9 (MD5) / Este trabalho tem como objetivo avaliar a influência dos tempos de fotopolimerização nas resinas odontológicas, onde quatro resinas compostas foram utilizadas, sendo três micro híbridas e uma nanoparticulada. Esses compósitos foram submetidos ao desgaste abrasivo de esfera rotativa pelo método de ball cratering. Para tal ação foi projetado e construído um dispositivo de desgaste por micro abrasão de esfera rotativa livre de três corpos. Os corpos de prova foram confeccionados e embutidos em uma matriz de alumínio, com uma profundidade de 2mm. Usam-se o aparelho LED RADII, com os tempos de exposição de 20, 30 e 40 segundos e uma esfera com 15 mm de diâmetro de aço temperada, retificada e revenida. A lama abrasiva utilizada nesse estudo foi uma solução composta por 20% de talco (USP/200) e 80% de soro fisiológico, na quantidade de 3 gotas por segundo. Para comprovação dos resultados obtidos, utilizaram-se os testes de: Espectroscopia por Dispersão de Energia (EDS), Infravermelho por Transformada de Fourier (FT-IR), Análise Termogravimétrica (TGA), micro dureza Vickers, ensaio de desgaste de micro abrasão por esfera rotativa pelo método de ball cratering e a análise da superfície desgastada por Microscopia Eletrônica de Varredura (MEV). Esta análise foi realizada para verificar o real mecanismo de desgaste ocorrido. Os resultados obtidos comprovam que o tempo recomendado pelos fabricantes, tem a capacidade suficiente de fotopolimerizar toda a matriz orgânica, comprovaram também que a resina nanoparticulada obteve em todos os ensaios os melhores resultados em relação às resinas híbridas, e que a cultura do acréscimo de até 20s além do recomendado não tem influência direta em relação ao desgaste abrasivo. / This work has as an objective to evaluate the influence of photopolymerization in odontological resins, where composed four resins were used, being three of them micro hybrid and one nanoparticulated. These composites were submitted to abrasive wear and tear of rotative sphere by the method ball cratering. For such action a device of micro abrasion of rotative sphere was designed and built free of three bodies. The bodies of proof were produced and put in a matrix of aluminum with a depth of 2mm. The device used was a LED RADII, with exposition time of 20, 30 and 40 seconds and a sphere of 15mm diameter made of tempered steel, rectified and soften, the abrasive lama used in this study was a solution composed by 20% of powder (USP/200) and 80% of physiological serum released at 3 drops per second. For verification of the results obtained the tests of Energy Dispersion Spectrograph (EDS) was used, transformed Infra red of Fourier (FT-IR), Thermogravimetric Analysis (TGA) Vickers micro hardness, wear and tear of micro abrasion by rotative sphere by the method ball cratering and the analysis of worn superficies by Sweeping Electronic Microscopy (SEM). This analysis was carried out to verify the real mechanism of the worn occurred. The results obtained prove that the time recommended by the manufacturer has enough capacity to photopolymerized all the organic matrix, it also proved that the resin nanoparticulated obtained in all the essays the best results in what concerns to the hybrid resins. And the culture of the addition of 20 seconds besides what is recommended has no direct influence in relation to the abrasive wear and tear.

Supraspinatus (SSP) tendon tear leads to intramuscular fat accumulation in the SSP muscle and the mechanisms are currently unknown. The purpose of this study was to investigate changes in vascularization of the SSP muscle and the relationship to intramuscular fat accumulation following SSP tendon detachment with or without reattachment. One hundred and six rabbits underwent SSP tendon detachment. In groups of ten, thirty rabbits were sacrificed 4, 8, and 12 weeks following detachment. Forty rabbits underwent detachment and immediate reattachment and were sacrificed in groups of ten following 0, 1, 2, and 6 weeks of healing. In groups of twelve, the remaining thirty-six rabbits underwent SSP tendon reattachment 4, 8, and 12 weeks after detachment and were sacrificed 12 weeks later. Vascularization was quantified in each specimen using CD31 immunohistochemistry. Four weeks after SSP tendon detachment, there was an increase in vascularization of the distal SSP muscle that reached significance after 12 weeks of detachment (p=0.024). We found that vascularization was positively correlated with intramuscular fat accumulation after detachment only (r=0.29; p=0.008). After SSP tendon reattachment, immediate or delayed, the correlation between vascularization and intramuscular fat accumulation was not observed. Microscopically, some SSP muscle vascular structures in the reattachment group had thicker vascular walls which were further quantified using αSMA immunohistochemistry. The delayed reattachment group showed an increase in vascular wall thickness in the distal portion of the SSP muscle at 4+12 (p=0.012) and 12+12 (p=0.012) weeks and in the proximal portion at 4+12 (p=0.024) weeks. Further investigation is required to demonstrate a cause/effect relationship between increased vascularization and intramuscular fat accumulation in the context of rotator cuff tear and success of surgical repair.

A tear in the subducting Nazca slab is located between the end of the Pampean flat slab and normally subducting oceanic lithosphere. Tomographic studies suggest mantle material flows through this opening. The best way to probe this hypothesis is through observations of seismic anisotropy, such as shear wave splitting. We examine patterns of shear wave splitting using data from two seismic deployments in Argentina that lay updip of the slab tear. We observe a simple pattern of plate-motion-parallel fast splitting directions, indicative of plate-motion-parallel mantle flow, beneath the majority of the stations. Our observed splitting contrasts previous observations to the north and south of the flat slab region. Since plate-motion-parallel splitting occurs only coincidentally with the slab tear, we propose mantle material flows through the opening resulting in Nazca plate-motion-parallel flow in both the subslab mantle and mantle wedge.

No description available.

<p> Hydroxypropyl guar (HPG) is an effective ingredient in lubricant eye drops used by patients with dry eye disease. The overall goal of the work described in this thesis is to understand the physical-chemical properties of HPG in the presence ofmodel surfaces and solutes with view to understanding the behavior of HPG in the tear film. </p> <p> HPG behaviors are complex because borate ions bind to HPG, which converts nonionic HPG into anionic polyelectrolyte, RPG-borate. The borate binding constants are very low, meaning the charges on RPG-borate are labile. Another consequence ofweak binding is that the equilibrium electrolyte concentration with HPG-borate is relatively high. Mathematical models were developed to predict the structure of HPG-borate as functions of pH. </p> <p> This thesis probes the question "When does HPG-borate behave as an anionic polyelectrolyte?" This work shows that HPG-borate exhibits deviant behaviors of an anionic polyelectrolyte: does not interact with cationic surfactants below the CMC; does not interact with lysozyme (cationic protein), and does not adsorb onto cationic liposomes. By contrast, anionic polyelectrolytes such as carboxymethyl guar display generic behaviors. On the other hand, HPG-borate forms polyelectrolyte complexes with cationic polyelectrolytes at low ionic strength and other work from our laboratory has shown that HPG-borate flocculates cationic polystyrene latex. </p> <p> This complex range of RPG-borate behaviors was rationalized by proposing that the labile nature ofthe charge groups means that the charge density on RPG-borate is regulated by the local electrostatic environment. Near a cationic surface HPG-borate charge density increases whereas near an anionic surface the charge density is lower. </p> <p> Anionic liposome interactions with HPG-borate were characterized. HPG concentrations close to clinical levels induced depletion flocculation ofthe anionic liposomes. This is the first example we have found depletion interactions were proposed for the tear film. </p> <p> To summarize the main implications for the ophthalmic application of HPG are: 1) under ophthalmic conditions HPG-borate behaves as a nonionic water soluble polymer; 2) RPG-borate will adsorb onto hydrophobic domains but will not interact with lysozyme; 3) depletion interactions are important and have the potential to stabilize the lipid layer and destabilize emulsion droplets and other dispersed species in the tear film. </p> / Thesis / Doctor of Philosophy (PhD)

No description available.