361,368 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
Integrated lenses for microfluidic systems
No full textGreater integration of optical devices is required in microfluidic systems for on-chip functionality, with lenses being key components. In this paper several candidate lens types are compared and simulations are presented which show that the paraxial kinoform lens offers optimum performance for efficiency and compactness in weak guiding system
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
Marketing Education through the lens of S-D Logic
No full textThis paper provides a theoretical contribution to the marketing literature by exploring ‘value creation' and ‘value in use' as applied to marketing education and from a service-dominant logic perspective. In 2004 Vargo and Lusch published a seminal article on the ideas and conceptions around Service-dominant (S-D) logic much of which has its roots in relationship marketing research and other concepts.
In the education (and more specifically Higher Education) field marketing is a relatively new area of research but one that is likely to grow in significance in the light of the potential environmental and political changes. This paper seeks to extend debate in the field of marketing education by viewing it through the lens of SD Logic and establishes a number of research themes which need to be addressed. It further suggests a conceptual framework which needs further development and testing
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
Does HIV accelerate the aging process? An assessment of clinical, ophthalmic and serum parameters in HIV-infected individuals in South Africa
No full textHIV-infected individuals are at increased risk of age-related non-AIDS morbidity and mortality compared with HIV-uninfected persons. It is speculated that HIV-infected individuals may not only be aging chronologically, but also undergoing accelerated biological aging. This is supported by clinical reports of conditions classically associated with the normal aging process appearing at an earlier age in HIV-infected persons compared to age-matched controls.
Chronological age is an imprecise measure of biological aging due to inter-individual differences in rates of aging and therefore ‘biomarkers of aging’ may be used to assess biological age. The eye may be a uniquely useful site as a model of aging. It is easily accessible for examination and several components can be measured and assessed objectively e.g. lens density, retinal vascular calibre, corneal endothelial cell counts and the retinal nerve fibre layer thickness.
This case-control study of 504 adults recruited from one district in Cape Town, South Africa assessed whether HIV-infected individuals have more advanced ocular aging, systemic frailty and cellular senescence than an HIV-uninfected group of similar age. Accelerated biological aging was demonstrated in HIV-infected individuals compared to their uninfected counterparts. HIV infection was also associated with frailty. Ocular parameters provided evidence of greater aging within the HIV-infected group, particularly objective measurement of retinal vascular calibre and lens density. These data suggest that as well as increased biological aging at a cellular and systemic level, ocular aging occurs as part of the accelerated aging phenotype in HIV infection.
This study provides novel data about accelerated biological aging in sub-Saharan Africa and a platform for addressing future research questions relating to accelerated aging trajectories in HIV infection, the relative contributions of the infection and antiretroviral therapy, and whether biological age is dependent upon the duration of untreated disease or nadir CD4 count. As the HIV-infected population continues to age and expand, accelerated biological aging may have wideranging implications for the burden and management of HIV-related morbidity
Accuracy of Intraocular Lens Power Estimation in Eyes Having Phacovitrectomy for Rhegmatogenous Retinal Detachment
No full textPurpose: To evaluate the accuracy of intraocular lens power estimation in eyes having phacovitrectomy for rhegmatogenous retinal detachment.
Methods: Retrospective case review of 100 consecutive eyes that underwent phacovitrectomy for rhegmatogenous retinal detachment. Axial lengths were measured using optical biometry and/or ultrasound A-scan. Achieved and predicted refraction were compared to calculate the mean postoperative refractive prediction error and the mean absolute prediction error. Factorial analysis of variance models were developed to assess outcome on the whole and that between the subgroups.
Results: Ninety-five eyes had postoperative refraction: 41 macula-on (43%) and 54 macula-off (57%). The mean postoperative prediction error was -0.34 +/- 0.89 diopters. There was no statistical significant difference in the refractive outcomes between macula-on and macula-off groups (P > 0.05). Overall, using mean absolute prediction error as the outcome measure, optical biometry was more accurate than ultrasound (P = 0.040). However, significantly more ultrasound-measured axial lengths were selected for intraocular lens power estimation in macula-off group compared with the macula-on group (P = 0.016).
Conclusion: Combined phacovitrectomy in rhegmatogenous retinal detachment included a small biometric error that was within the tolerable range in most cases. Both optical biometry and ultrasound should be used to estimate axial lengths, for macula-off rhegmatogenous retinal detachment cases, to improve the accuracy of intraocular lens power calculation
Pax6 interactions with chromatin and identification of its novel direct target genes in lens and forebrain.
No full textPax6 encodes a specific DNA-binding transcription factor that regulates the development of multiple organs, including the eye, brain and pancreas. Previous studies have shown that Pax6 regulates the entire process of ocular lens development. In the developing forebrain, Pax6 is expressed in ventricular zone precursor cells and in specific populations of neurons; absence of Pax6 results in disrupted cell proliferation and cell fate specification in telencephalon. In the pancreas, Pax6 is essential for the differentiation of α-, β- and δ-islet cells. To elucidate molecular roles of Pax6, chromatin immunoprecipitation experiments combined with high-density oligonucleotide array hybridizations (ChIP-chip) were performed using three distinct sources of chromatin (lens, forebrain and β-cells). ChIP-chip studies, performed as biological triplicates, identified a total of 5,260 promoters occupied by Pax6. 1,001 (133) of these promoter regions were shared between at least two (three) distinct chromatin sources, respectively. In lens chromatin, 2,335 promoters were bound by Pax6. RNA expression profiling from Pax6⁺/⁻ lenses combined with in vivo Pax6-binding data yielded 76 putative Pax6-direct targets, including the Gaa, Isl1, Kif1b, Mtmr2, Pcsk1n, and Snca genes. RNA and ChIP data were validated for all these genes. In lens cells, reporter assays established Kib1b and Snca as Pax6 activated and repressed genes, respectively. In situ hybridization revealed reduced expression of these genes in E14 cerebral cortex. Moreover, we examined differentially expressed transcripts between E9.5 wild type and Pax6⁻/⁻ lens placodes that suggested Efnb2, Fat4, Has2, Nav1, and Trpm3 as novel Pax6-direct targets. Collectively, the present studies, through the identification of Pax6-direct target genes, provide novel insights into the molecular mechanisms of Pax6 gene control during mouse embryonic development. In addition, the present data demonstrate that Pax6 interacts preferentially with promoter regions in a tissue-specific fashion. Nevertheless, nearly 20% of the regions identified are accessible to Pax6 in multiple tissues
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