The detection of kinin activity in contact lens wear

Many factors can be, and have been, attributed to the appearance of complications in lens wear, but the greatest is associated with deposition. Reduced acuity, irritation and inflammatory responses are often referred to as adverse reactions arising as a result of deposition. In this study, particular attention was paid to the potential role of adsorbed proteins in activating, mediating and/or stimulating a host immune response, i.e., the hypothesis that the adsorption of certain proteins from the tears and ocular surfaces may actively affect successful lens wear. In particular, the purpose of this study was to investigate the presence of a group of proteins previously undiscovered in the ocular environment. The intention was to target a family of proteins/glycoproteins that have become prominent recently in a variety of inflammatory responses and disorders at many other mucosal associated sites around the body, e.g. in nasal rhinitis and in joint inflammation. The protein cascade in question is the kinin family of inflammatory mediators. The aim was to investigate their presence in the ocular environment, specifically in relation to contact lens wear, and consequently assess the implications of their discovery. High molecular weight kininogen (HMWK), with its central role in kinin responses, was investigated initially as the marker of kinin activity, with subsequent members examined thereafter.

Diabetes and contact lens wear

The literature suggests that diabetic patients may have altered tear chemistry and tear secretion as well as structural and functional changes to the corneal epithelium, endothelium and nerves. These factors, together with a reported increased incidence of corneal infection, suggest that diabetic patients may be particularly susceptible to developing ocular complications during contact lens wear. Reports of contact lens-induced complications in diabetic patients do exist, although a number of these reports concern patients with advanced diabetic eye disease using lenses on an extended wear basis. Over the past decade or so, there have been published studies documenting the response of the diabetic eye to more modern contact lens modalities. The results of these studies suggest that contact lenses can be a viable mode of refractive correction for diabetic patients. Furthermore, new research suggests that the measurement of tear glucose concentration could, in future, be used to monitor metabolic control non-invasively in diabetic patients. This could be carried out using contact lenses manufactured from hydrogel polymers embedded with glucose-sensing agents or nanoscale digital electronic technology. The purpose of this paper is to review the literature on the anterior ocular manifestations of diabetes, particularly that pertaining to contact lens wear. © 2012 The Authors. Clinical and Experimental Optometry © 2012 Optometrists Association Australia.

Function of lipids - their fate in contact lens wear:an interpretive review

Lipids play a vital role in the body at many interfaces. Examples include the lubrication of articulating joints by synovial fluid, the coating of the lung by pulmonary surfactant and the functions of the tear film in the protection of the anterior eye. The role of the lipids is similar at each site - acting as boundary lubricants and reducing surface and interfacial tension. This review focuses on how and why contact lens wear can disrupt the normal function of lipids within the tear film and explains how the otherwise advantageous presence and function of tear lipids can become disadvantageous, causing problems for the wearer. Because the contact lens is some ten times thicker than the tear film, lipids deposited on the anterior surface become immobilised, reducing lipid turnover and thus leading to prolonged exposure to oxygen and light with consequent generation of degradation products. These degraded lipids reduce lens wettability and have additionally been linked to problems of contact lens discomfort and intolerance. Lipid problems are influenced by the thickness of the lens, the material, surface modification, mode of wear and ultimately the subject. The most influential of these variables is frequently the subject. © 2012.

The development of biomaterials for contact lens applications:effects of wear modality on materials design

The successful design of polymers for contact lens applications depends on the ability to provide a balance of properties appropriate to the ocular environment. Principal relevant aspects of the anterior eye are the tear film, eyelid and cornea, which govern the requirements for surface properties, modulus and oxygen permeability, respectively. Permeability requirements and the developing view of the needs of the cornea, in terms of oxygen consumption and the particular roles of fluorine and silicon in the design of silicone hydrogels, which have proved to be the most successful family of materials for this demanding application, are discussed. The contact lens field is complicated by the fact that contact lenses are used in a range of wear modalities, the extremes of which can conveniently be classified as lenses that are disposed of at the end of a single period of daily wear and those used for 30. days of successive day-and-night periods, frequently referred to as extended or continuous wear. As silicone hydrogels developed, in the decade following their launch there has been a progressive trend in properties taking both modulus and water content closer to those of conventional hydrogels. This is particularly evident in the family of daily disposable contact lenses that have appeared since 2008.

Comprehensive process maps for synthesizing high density aluminum oxide-carbon nanotube coatings by plasma spraying for improved mechanical and wear properties

Plasma sprayed aluminum oxide ceramic coating is widely used due to its outstanding wear, corrosion, and thermal shock resistance. But porosity is the integral feature in the plasma sprayed coating which exponentially degrades its properties. In this study, process maps were developed to obtain Al2O3-CNT composite coatings with the highest density (i.e. lowest porosity) and improved mechanical and wear properties. Process map is defined as a set of relationships that correlates large number of plasma processing parameters to the coating properties. Carbon nanotubes (CNTs) were added as reinforcement to Al2O 3 coating to improve the fracture toughness and wear resistance. Two novel powder processing approaches viz spray drying and chemical vapor growth were adopted to disperse CNTs in Al2O3 powder. The degree of CNT dispersion via chemical vapor deposition (CVD) was superior to spray drying but CVD could not synthesize powder in large amount. Hence optimization of plasma processing parameters and process map development was limited to spray dried Al2O3 powder containing 0, 4 and 8 wt. % CNTs. An empirical model using Pareto diagram was developed to link plasma processing parameters with the porosity of coating. Splat morphology as a function of plasma processing parameter was also studied to understand its effect on mechanical properties. Addition of a mere 1.5 wt. % CNTs via CVD technique showed ∼27% and ∼24% increase in the elastic modulus and fracture toughness respectively. Improved toughness was attributed to combined effect of lower porosity and uniform dispersion of CNTs which promoted the toughening by CNT bridging, crack deflection and strong CNT/Al2O3 interface. Al2O 3-8 wt. % CNT coating synthesized using spray dried powder showed 73% improvement in the fracture toughness when porosity reduced from 4.7% to 3.0%. Wear resistance of all coatings at room and elevated temperatures (573 K, 873 K) showed improvement with CNT addition and decreased porosity. Such behavior was due to improved mechanical properties, protective film formation due to tribochemical reaction, and CNT bridging between the splats. Finally, process maps correlating porosity content, CNT content, mechanical properties, and wear properties were developed.

Tool cutting force modeling and wear estimation of micro -end-milling operations

The applications of micro-end-milling operations have increased recently. A Micro-End-Milling Operation Guide and Research Tool (MOGART) package has been developed for the study and monitoring of micro-end-milling operations. It includes an analytical cutting force model, neural network based data mapping and forecasting processes, and genetic algorithms based optimization routines. MOGART uses neural networks to estimate tool machinability and forecast tool wear from the experimental cutting force data, and genetic algorithms with the analytical model to monitor tool wear, breakage, run-out, cutting conditions from the cutting force profiles. ^ The performance of MOGART has been tested on the experimental data of over 800 experimental cases and very good agreement has been observed between the theoretical and experimental results. The MOGART package has been applied to the micro-end-milling operation study of Engineering Prototype Center of Radio Technology Division of Motorola Inc. ^

Tool cutting force modeling and wear estimation of micro-end-milling operations

The applications of micro-end-milling operations have increased recently. A Micro-End-Milling Operation Guide and Research Tool (MOGART) package has been developed for the study and monitoring of micro-end-milling operations. It includes an analytical cutting force model, neural network based data mapping and forecasting processes, and genetic algorithms based optimization routines. MOGART uses neural networks to estimate tool machinability and forecast tool wear from the experimental cutting force data, and genetic algorithms with the analytical model to monitor tool wear, breakage, run-out, cutting conditions from the cutting force profiles. The performance of MOGART has been tested on the experimental data of over 800 experimental cases and very good agreement has been observed between the theoretical and experimental results. The MOGART package has been applied to the micro-end-milling operation study of Engineering Prototype Center of Radio Technology Division of Motorola Inc.

Retificação plana tangencial dos ferros fundidos nodular, vermicular e cinzento em várias condições de corte

In a scenario of increasing competitiveness of the global industrial sector and with a consumer market increasingly demanding, there is an increased demand for new materials and, consequently, possibilities to explore new research and technological advances towards the development of new manufacturing methods or the improvement of existing technologies. In the case of cast irons, new grades of them have been developed so that their mechanical properties have been improved, making them more competitive with steel, expanding the applications and thus represents great economic gain for metallurgy and manufacturing sectors. This increases the interest and creates new opportunities to study these materials and identify how they respond in terms of the surface integrity, tool wear, cutting forces, among others, when machined by grinding operation. In this context, due to the lack of results from grinding of cast irons and studies comparing grindability among several grades of cast irons found in the literature, this work aims to generate scientific and technological contribution to the metallurgical and metal working sector through roughness results (Ra and Rz parameters) and evaluation and analysis of the subsurface integrity of three cast iron grades (gray, compacted graphite and nodular). The machining trials were performed on a surface grinding machine with silicon carbide grinding wheel at different cutting conditions. The input variables were the radial depth of cut (15 and 30 μm), worktable speed, vw (5 and 10 m/min) and the abrasive grain size of the grinding wheel. The results showed that surface roughness increased with the radial depth of cut for all materials tested; and the lowest values were obtained for gray cast iron. Also, roughness was sensitive to variation of worktable speed and the lowest values were obtained after machining with vw = 5 m/min. With respect to the abrasive grain size, as it decreased the roughness values increased to gray and nodular cast iron grades. Furthermore, grinding burns marks were observed on the surfaces of nodular cast iron and compacted graphite iron grades after grinding the smallest grain size, contrary to what is usually reported in literature. However, no evidence of severe thermal damages below the machined surfaces of all cast iron grades was observed after analyzing the results of hardness and the SEM micrograph images.

Influence of cutting parameters and tool wear on martensitic stainless steel surface integrity after a face milling process

Surface finish is one of the most relevant aspects of machining operations, since it is one of the principle methods to assess quality. Also, surface finish influences mechanical properties such as fatigue behavior, wear, corrosion, etc. The feed, the cutting speed, the cutting tool material, the workpiece material and the cutting tool wear are some of the most important factors that affects the surface roughness of the machined surface. Due to the importance of the martensitic 416 stainless steel in the petroleum industry, especially in valve parts and pump shafts, this material was selected to study the influence of the feed per tooth and cutting speed on tool wear and surface integrity. Also the influence of tool wear on surface roughness is analyzed. Results showed that high values of roughness are obtained when using low cutting speed and feed per tooth and by using these conditions tool wear decreases prolonging tool life. Copyright © 2009 by ASME.

Empirical expression of tool wear when face milling 416 SS

During a machining process, cutting parameters must be taken into account, since depending on them the cutting edge starts to wear out to the point that tool can fail and needs to be change, which increases the cost and time of production. Since wear is a negative phenomenon on the cutting tool, due to the fact that tool life is reduced, it is important to optimize the cutting variables to be used during the machining process, in order to increase tool life. This research is focused on the influence of cutting parameters such as cutting speed, feed per tooth and axial depth of cut on tool wear during a face milling operation. The Taguchi method is applied in this study, since it uses a special design of orthogonal array to study the entire parameters space, with only few numbers of experiments. Also a relationship between tool wear and the cutting parameters is presented. For the studies, a martensitic 416 stainless steel was selected, due to the importance of this material in the machining of valve parts and pump shafts. Copyright © 2009 by ASME.

Wear and its effects on dental topography measures in howling monkeys (Alouatta palliata).

OBJECTIVES: Three dental topography measurements: Dirichlet Normal Energy (DNE), Relief Index (RFI), and Orientation Patch Count Rotated (OPCR) are examined for their interaction with measures of wear, within and between upper and lower molars in Alouatta palliata. Potential inferences of the "dental sculpting" phenomenon are explored. MATERIALS AND METHODS: Fifteen occluding pairs of howling monkey first molars (15 upper, 15 lower) opportunistically collected from La Pacifica, Costa Rica, were selected to sample wear stages ranging from unworn to heavily worn as measured by the Dentine Exposure Ratio (DER). DNE, RFI, and OPCR were measured from three-dimensional surface reconstructions (PLY files) derived from high-resolution CT scans. Relationships among the variables were tested with regression analyses. RESULTS: Upper molars have more cutting edges, exhibiting significantly higher DNE, but have significantly lower RFI values. However, the relationships among the measures are concordant across both sets of molars. DER and EDJL are curvilinearly related. DER is positively correlated with DNE, negatively correlated with RFI, and uncorrelated with OPCR. EDJL is not correlated with DNE, or RFI, but is positively correlated with OPCR among lower molars only. DISCUSSION: The relationships among these metrics suggest that howling monkey teeth adaptively engage macrowear. DNE increases with wear in this sample presumably improving food breakdown. RFI is initially high but declines with wear, suggesting that the initially high RFI safeguards against dental senescence. OPCR values in howling monkey teeth do not show a clear relationship with wear changes.

Tooth wear in Irish teenagers: a laboratory and epidemiological study

Aim: To investigate the characteristics, development and determinants of toothwear among Irish schoolchildren. Methods: A cross-sectional (examination at 16-years-old) and longitudinal (examinations at 5-,12-,14-years) study were conducted. Two indices were used to measure toothwear, children/parents completed a demographic profile and questionnaire on oral hygiene and dietary practices, health, and lifestyle in both studies. Saliva was collected from consenting 16-year-olds. The explanatory variables for the cross-sectional and longitudinal study were derived from children/parents responses. Differences in salivary profiles were determined for subsets; the protein concentration was determined with Bradford protein assay and protein carbonyl concentration (a protein oxidation marker) was determined spectrophotometrically. Gel-electrophoresis and mass spectrometry determined proteins and ion chromatography inorganic ions. Statistical significance was accepted at p<0.05. Results: At 16-years-old the prevalence of toothwear with dentine visible was 44%. No difference in salivary flow rates existed. In unstimulated saliva a higher mean, protein carbonyl (p<0.0001) and total calcium concentration (p<0.002) existed for the group with moderate toothwear. In stimulated saliva the moderate toothwear group had a lower mean protein concentration(p<0.0001). The 2-DE protein spots prepared for a sub-group differed between those with toothwear and without. Mass spectrometry, identified one of the different proteins as IgA. For 16-year-olds, the self-reported factors indicated that brushing after breakfast was associated with lower toothwear scores(p<0.03). Nail-biting, being asthmatic or reporting a dry mouth were associated with higher toothwear scores(all p<0.05). Eating an apple daily or less was associated with less toothwear(p<0.002). In the longitudinal study toothwear into dentine at age five or 12-years was associated with more toothwear at age 14(all p<0.05). Discussion: The results illustrate the multifactorial aetiology of toothwear. The biochemical and physical correlates of saliva with toothwear requires further research. Conclusion: The impact of previous toothwear, salivary, dietary and personal factors on toothwear in the early permanent dentition is demonstrated.

Imputing accelerometer non-wear time when assessing children's moderate-to-vigorous physical activity

BACKGROUND: Moderate-to-vigorous physical activity (MVPA) is an important determinant of children’s physical health, and is commonly measured using accelerometers. A major limitation of accelerometers is non-wear time, which is the time the participant did not wear their device. Given that non-wear time is traditionally discarded from the dataset prior to estimating MVPA, final estimates of MVPA may be biased. Therefore, alternate approaches should be explored. OBJECTIVES: The objectives of this thesis were to 1) develop and describe an imputation approach that uses the socio-demographic, time, health, and behavioural data from participants to replace non-wear time accelerometer data, 2) determine the extent to which imputation of non-wear time data influences estimates of MVPA, and 3) determine if imputation of non-wear time data influences the associations between MVPA, body mass index (BMI), and systolic blood pressure (SBP). METHODS: Seven days of accelerometer data were collected using Actical accelerometers from 332 children aged 10-13. Three methods for handling missing accelerometer data were compared: 1) the “non-imputed” method wherein non-wear time was deleted from the dataset, 2) imputation dataset I, wherein the imputation of MVPA during non-wear time was based upon socio-demographic factors of the participant (e.g., age), health information (e.g., BMI), and time characteristics of the non-wear period (e.g., season), and 3) imputation dataset II wherein the imputation of MVPA was based upon the same variables as imputation dataset I, plus organized sport information. Associations between MVPA and health outcomes in each method were assessed using linear regression. RESULTS: Non-wear time accounted for 7.5% of epochs during waking hours. The average minutes/day of MVPA was 56.8 (95% CI: 54.2, 59.5) in the non-imputed dataset, 58.4 (95% CI: 55.8, 61.0) in imputed dataset I, and 59.0 (95% CI: 56.3, 61.5) in imputed dataset II. Estimates between datasets were not significantly different. The strength of the relationship between MVPA with BMI and SBP were comparable between all three datasets. CONCLUSION: These findings suggest that studies that achieve high accelerometer compliance with unsystematic patterns of missing data can use the traditional approach of deleting non-wear time from the dataset to obtain MVPA measures without substantial bias.