141,465 research outputs found
The soft-focus lens and Anglo-American pictorialism
No full textElectronic version excludes illustrations for which permission has not been granted by the rights holderThe history, practice and aesthetic of the soft focus lens in photography is elucidated and developed from its earliest statements of need to the current time with a particular emphasis on its role in the development of the Pictorialist movement. Using William Crawford's concept of photographic 'syntax', the use of the soft focus lens is explored as an example of how technology shapes style.
A detailed study of the soft focus lenses from the earliest forms to the present is presented, enumerating the core properties of pinhole, early experimental and commercial soft focus lenses. This was researched via published texts in period journals, advertising, private correspondence, interviews, and the lenses themselves. The author conducted a wide range of in-studio experiments with both period and contemporary soft focus lenses to evaluate their character and distinct features, as well as to validate source material.
Nodal points of this history and development are explored in the critical debate between the diffuse and sharp photographic image, beginning with the competition between the calotype and daguerreotype. The role of George Davison's The Old Farmstead is presented as well as the invention of the first modern soft focus lens, the Dallmeyer-Bergheim, and its function in the development of the popular Pictorialist lens, the Pinkham & Smith Semi-Achromatic. The trajectory of the soft focus lens is plotted against the Pictorialist movement, noting the correlation betwixt them, and the modern renaissance of soft focus lenses and the diffuse aesthetic.
This thesis presents a unique history of photography modeled around the determining character of technology and the interdependency of syntax, style and art
The Influence of extracellular matrix on lens epithelial cell viability
No full textPosterior capsular opacification is the main complication of cataract surgery and results from the proliferation, migration and differentiation of lens epithelial cells remaining in the capsular bag. To better understand this pathological cell behaviour, 1 investigated the interactions between lens epithelial cells and the bovine lens capsule in vitro and their effect on cell viability. As determined by a colorimetric cell proliferation assay, in vitro culture of cells directly on the bovine lens capsule resulted in maintained cell viability in the presence of staurosporine in both lens epithelial cell lines tested, but in neither of the two non-lens cell lines tested. As determined by immunoblotting and reverse-transcriptase polymerase chain reaction (RT-PCR), cell viability on the bovine lens capsule could further be correlated to the presence of both ɑA-crystallin and αB-crystallin expression. A positive correlation of cell viability on the lens capsule with vimentin and HSP27 expression was also found in a smaller set of cell lines. As determined by gelatin zymography and immunoblotting, MMP-2 was expressed by lens epithelial cells, led to the release of FGF-2 and IGF-1 from the lens capsule and correlated with lens epithelial cell viability. Taken together, these results suggest that the lens capsule can act as a store of releasable growth factors available to the lens epithelial cells, with effects on their protein expression and cell viability
Chromatin remodeling enzyme Brg1 is required for mouse lens fiber cell terminal differentiation and its denucleation
No full textBackground: Brahma-related gene 1 (Brg1, also known as Smarca4 and Snf2 beta) encodes an adenosine-5'-triphosphate (ATP)-dependent catalytical subunit of the (switch/sucrose nonfermentable) (SWI/SNF) chromatin remodeling complexes. SWI/SNF complexes are recruited to chromatin through multiple mechanisms, including specific DNA-binding factors (for example, heat shock transcription factor 4 (Hsf4) and paired box gene 6 (Pax6)), chromatin structural proteins (for example, high-mobility group A1 (HMGA1)) and/or acetylated core histones. Previous studies have shown that a single amino acid substitution (K798R) in the Brg1 ATPase domain acts via a dominant-negative (dn) mechanism. Genetic studies have demonstrated that Brg1 is an essential gene for early (that is, prior implantation) mouse embryonic development. Brg1 also controls neural stem cell maintenance, terminal differentiation of multiple cell lineages and organs including the T-cells, glial cells and limbs. Results: To examine the roles of Brg1 in mouse lens development, a dnBrg1 transgenic construct was expressed using the lens-specific alpha A-crystallin promoter in postmitotic lens fiber cells. Morphological studies revealed abnormal lens fiber cell differentiation in transgenic lenses resulting in cataract. Electron microscopic studies showed abnormal lens suture formation and incomplete karyolysis (that is, denucleation) of lens fiber cells. To identify genes regulated by Brg1, RNA expression profiling was performed in embryonic day 15.5 (E15.5) wild-type and dnBrg1 transgenic lenses. In addition, comparisons between differentially expressed genes in dnBrg1 transgenic, Pax6 heterozygous and Hsf4 homozygous lenses identified multiple genes coregulated by Brg1, Hsf4 and Pax6. DNase II beta, a key enzyme required for lens fiber cell denucleation, was found to be downregulated in each of the Pax6, Brg1 and Hsf4 model systems. Lens-specific deletion of Brg1 using conditional gene targeting demonstrated that Brg1 was required for lens fiber cell differentiation, for expression of DNase II beta, for lens fiber cell denucleation and indirectly for retinal development. Conclusions: These studies demonstrate a cell-autonomous role for Brg1 in lens fiber cell terminal differentiation and identified DNase II beta as a potential direct target of SWI/SNF complexes. Brg1 is directly or indirectly involved in processes that degrade lens fiber cell chromatin. The presence of nuclei and other organelles generates scattered light incompatible with the optical requirements for the lens
Lid massage and symptoms of dryness in soft contact lens wearers
No full textWe have compared the efficacy of an in-eye lubricant and lid massage (gently massaging the surface of the lens through the upper lid) in a group of 13 soft lens wearers who regularly suffer from symptoms of dryness. Subjects used each technique for 1 week in a crossover study and recorded in a diary the symptoms experienced, duration of relief from symptoms, and improvement in vision, and, at the end of the study, they made a choice of preferred technique. Most subjects found longest relief from symptoms following use of the in-eye lubricant; however, the majority preferred to continue using the lid-massage technique alone or in combination with the in-eye lubricant. At a follow-up 1 year later, the majority of subjects continued to use lid massage to relieve dryness symptoms. We suggest that lid massage can provide a useful supplementary technique for many soft contact lens wearers who experience symptoms of dryness. \ud
Author Keywords: Author Keywords: Dryness; contact lenses; lid massage; lens lubricants; tea
The Contact Lens Impact on Quality of Life (CLIQ) questionnaire: development and validation
No full textNoPURPOSE. To develop and validate a questionnaire for the measurement of the impact of contact lenses on quality of life (QoL): The Contact Lens Impact on Quality of Life (CLIQ) Questionnaire. METHODS. The questionnaire was developed and validated using conventional methods and Rasch analysis to assure content validity, repeatability, construct validity, and low respondent burden. Item identification and selection (647 items) were performed with an extensive literature review, professional advice, and lay focus groups. Item reduction used focus groups and data obtained from 161 subjects completing a 90-item pilot questionnaire. Validity and reliability, from data of 128 additional subjects, were assessed using Rasch analysis, intraclass correlation coefficient, and Bland-Altman limits of agreement. RESULTS. A 28-item CLIQ Questionnaire was developed and shown to have good validity and reliability by Rasch analysis statistics: real person separation, 2.02; model person separation, 2.17; reliability, 0.80; root mean square measurement error, 2.73; mean square ± SD infit, 1.01 ± 0.18; outfit, 1.01 ± 0.19. The items (mean score, 49.8 ± 4.9) were well targeted to the subjects (mean score, 51.2 ± 6.2) with a mean difference of 1.35 (scale range, 0-100) units. Test-retest intraclass correlation coefficient (0.86) and coefficient of repeatability (±8.00 units) demonstrated good repeatability. CONCLUSIONS. Rasch analysis and standard psychometric analyses demonstrated that the 28-item CLIQ Questionnaire is a valid and reliable measure of QoL in contact lens wearers. A scoring algorithm is provided for CLIQ Questionnaire users to convert raw scores into the Rasch analysis-derived linear person measures
Oeuvres philosophiques de Bossuet
No full textContiene: Le traité de la connaissance de Dieu et de soi-même ; Le traité du libre arbitre ; La logique ; divers fragment
A survey of corneal curvature changes from corneal lens wear
No full textThe fact that variations in corneal curvature occur as a result os wearing PMMA contact lenses has been reported many times (1-8). The nature of these curvature changes and the factors influencing them are, however, still not well defined. Estimates of the frequency of corneal curvature changes in contact lens wearers vary from 24% (9) TO 100% (5) with a full range of intermediate values. Similar uncertainty is evident in the findings on the extent and direction of these curvature changes. Values for the magnitude of the change range from zero to 2.25D (10) while changes up to 6.00D in corneal aastigmatism have been reported.(11,12)With regard to the direction fo the corneal curvature change, th most commonly expressed view in the early contat lens literature was that contat lens mold the corneal curvature to its own shape. (13-18) A flat lens would flatten the apical curve, a steep lens would steepen the corneal curvature, and in all cases a reduction in corneal astigmatism would result. Reports of surveys of keratometric changes give only partial support to the molding hypothesis (1-9). They show that the curvature changes are more complex than a simple molding of the the corneal curvature, since a lens fitted in any particular way can produce either corneal steepening or flattening, and either an increase or decrease in astigmatism. there are several reasons for this uncertainty in describing the curvature variation. The studies used different types of lenses, particularly in the fitting relationship of the lens to the cornea, and both wearing and measurement times differ from study to study. As well, different criteria for the presence of a change in curvature have been used. Analysis of tthe results of these surveys is further confused by the universal difficulty in adequately describing the curvature changes. The influence of these variables is made harder to ascertain because of ommission of some of the relevant information by almost all studies
Withdrawal from the lens of freshwater in a tropical island: The two interface case
No full textFresh water held in the soil beneath a tropical island is one source of drinking water for the island population. If recharge through rainfall is insufficient, this resource may drain away. This work considers the circumstances under which artificial recharge will maintain the lens of freshwater. A Green function approach is used to derive an integral equation that is solved numerically for the case in which there exist two interfaces - one between salt and freshwater and one between freshwater and air. There appear to be bounds on the flow rates that produce steady interface shapes, but the height of the seepage faces is affected much more by the density ratios than the flow rates. Several different scenarios of withdrawal and influx are considered with a goal of determining some optimal management strategies
Passive Microstrip Transmitarray Lens for Ku Band
No full textThe aim of this paper is to introduce a novel 12 GHz radiating design based on the idea of transmitarray lens device. In this document, an overview of the functioning of this kind of devices is given and the proposed transmitarray lens is studied, with architecture discussion and selection, as well as some ideas about the design, and manufacturing. In the document, some design, manufacturing and validation of the constituting elements of the lens (radiating elements, transmission circuits and transitions) are presented, together with a complete prototype of assembled transmitarray lens. Radiation pattern measurements in anechoic chamber, as well as gain and directivity values are offered
The effectiveness of early lens extraction with intraocular lens implantation for the treatment of primary angle-closure glaucoma (EAGLE): study protocol for a randomized controlled trial
No full textGlaucoma is the leading cause of irreversible blindness. Although primary open-angle glaucoma is more common, primary angle-closure glaucoma (PACG) is more likely to result in irreversible blindness. By 2020, 5·3 million people worldwide will be blind because of PACG. The current standard care for PACG is a stepped approach of a combination of laser iridotomy surgery (to open the drainage angle) and medical treatment (to reduce intraocular pressure). If these treatments fail, glaucoma surgery (eg, trabeculectomy) is indicated. It has been proposed that, because the lens of the eye plays a major role in the mechanisms leading to PACG, early clear lens extraction will improve glaucoma control by opening the drainage angle. This procedure might reduce the need for drugs and glaucoma surgery, maintain good visual acuity, and improve quality of life compared with standard care.EAGLE aims to evaluate whether early lens extraction improves patient-reported, clinical outcomes, and cost-effectiveness, compared with standard care
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