9,730 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
Get PDFPosterior 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
The biomechanics of rigid contact lens removal
No full textThe removal of rigid contact lenses from the eye, using the eyelids, is a relatively simple procedure. However, there is a sequence of biomechanical events underlying this procedure which are not well understood. By using high-speed videokeratoscopy (50 Hz), we have shown that during the lid-pull procedure the cornea typically shows a significant increase in with-the-rule astigmatism by an average of 2.19 D (axial power). The average increase in steep K power was 1.22 D (S.D. ±1.05 D) and the average decrease in flat K power was 0.97 D (S.D. ±1.05 D). This change in corneal topography increases the edge lift of the lens at 12 and 6 O’clock locations of the lens, enhancing the removal process. When the subject blinks, as the lid margins reach the lens edge, the lens flexes and the eye retracts by an average of 0.66 mm (S.D. ±0.27 mm). This retraction again enhances the act of lens removal
Recovery of corneal topography and vision following opaque-tinted contact lens wear
No full textPurpose: To investigate corneal changes after wearing cosmetic tinted contact lens and the recovery of corneal topography. \ud
Methods: Seven subjects took part in the study. Three cosmetic tinted lens types and one control soft contact lens were investigated (Crazy Lens, WildEyes, FreshLook, and SofLens Comfort). Lenses were worn for 1 hour. Corneal topography data were measured before lens wear, with the contact lens in situ and at 0, 10, 20, 30, 60, 90, 120, and 150 minutes after lens removal. Height data difference maps were calculated and corneal recovery measured. Visual acuity was taken before lens removal and at 1, 10, 30, 60, 120, and 150 minutes after lens removal. Subjective ratings of haloes and ghosting following lens wear were also recorded. \ud
Results: For the Crazy Lens, concentric rings of steepening and flattening with a mean height change of 2.17 +/- 0.98 [mu]m (P < 0.05) were found in the central cornea at a location corresponding to the edge of the clear pupil diameter. Corneal recovery after removal of the Crazy Lens took up to 150 minutes. Visual acuity loss in high luminance during Crazy Lens wear was 0.29 LogMAR (P < 0.01). For the WildEyes and FreshLook lenses, smaller changes in corneal topography and vision were found after 1 hour of lens wear. \ud
Conclusions: Patients who wear cosmetic tinted lenses need to be aware of the potential for reduced visual performance, both during lens wear and for several hours after lens wear
An epidemiological assessment of lens opacifications that impaired vision in patients injected with radium-224
Get PDFThe incidence of lens opacifications that impaired vision (cataract) was analyzed among 831 patients who were injected with known dosages of 224Ra in Germany shortly after World War II. The dependence of the incidence on dosage, i.e., injected activity per unit body weight, and on time after treatment was determined. The observations are equally consistent with proportionality of the incidence of cataract to the square of dosage or with a linear dependence beyond a threshold of 0.5 MBq/kg. The possibility of a linear dependence without threshold was strongly rejected (P less than 0.001). The analysis of temporal dependences yielded a component that was correlated with the injected amount of 224Ra and a component that was uncorrelated. The former was inferred by a maximum likelihood analysis to increase approximately as the square of the time after treatment. The component unrelated to the treatment was found to increase steeply with age and to become dominant within the collective of patients between age 50 and 60. The relative magnitudes of the two components were such that a fraction of 55 to 60% of the total of 58 cataracts had to be ascribed to the dose-related incidence. Impaired vision due to cataract was diagnosed before age 54 in 25 cases. In terms of injected activity per unit body weight no dependence of the sensitivity on age was found; specifically there was no indication of a faster occurrence of the treatment-related cataracts in patients treated at older ages
On the Michael addition of water to C = C bonds
No full text?-Hydroxy carbonyl compounds are an important class of compounds often found as a common structural motif in natural products. Although the molecules themselves look rather simple, their synthesis can be challenging. Water addition to conjugated C = C bonds opens up a straightforward route for the preparation of ?-hydroxy carbonyl compounds. Moreover, water addition to C = C bonds benefits a lot from its simplicity and excellent atom economy. However, the enantioselective addition of water to ?,?-unsaturated carbonyl (Michael) acceptors still represents a chemically very challenging reaction, due to the poor nucleophilicity of water and its small size, which make regio- and stereoinduction difficult. Equally, the often unfavorable equilibrium of water-addition reactions remains to be solved. In contrast, enzymes such as fumarase, malease, citraconase, aconitase, and enoyl-CoA hydratase have been successfully used on industrial scale, and their excellent (enantio-) selectivities are highly valued. Unfortunately, most hydratases are part of the primary metabolism where perfect substrate specificity is required. This very high substrate selectivity severely limits their practical applicability in organic synthesis. Thus, a straightforward approach with broad applicability still had not been described. The aim of the research presented in this thesis was to take up this challenge and dedicated to the search for a Michael hydratase with a more relaxed substrate specificity for the preparation of important ?-hydroxy carbonyl compounds. The stereospecificity of enzyme-catalysed reactions has been a fruitful source of information about the mechanisms of enzyme catalysis and vice versa; the application of stereospecifically labelled substrates allows for studying the course of the reaction. It offers a very promising opportunity to comprehensively understand the precise mechanistic and kinetic details of even the most complex enzymatic reactions. Thus Chapter 1 provides unifying ideas for stereochemistry of the enzymatic water addition to C = C bonds. This enhances our understanding of the chemistry of water addition to C = C bonds, and further allows us to find more hydratases from natural sources or obtained via protein engineering. In Chapter 2, a direct, enantioselective Michael addition of water in water to prepare important ?-hydroxy carbonyl compounds using whole cells of Rhodococcus strains is described. Good yields and excellent enantioselectivities were achieved with this method. This opens up an entirely new approach for the preparation of important ?-hydroxy carbonyl compounds. Deuterium labelling studies demonstrate that a Michael hydratase catalyzes the water addition exclusively with anti-stereochemistry, which belongs to the family members of hydratases: oleate hydratase, fumarase, malease, aconitase and type II dehydroquinase with a preference for the anti-addition; whereas, type I dehydroquinase, enoyl-CoA hydratase and artificial hydratase exclusive prefer for the syn-addition, as discussed in Chapter 1. The biocatalytic reaction system was carefully optimized for gram-scale synthesis, resulting in good conversions and excellent enantioselectivities. Under the optimized conditions, whole cells could be reused for 4 cycles without significant loss of activity while maintaining up to 90% ee. Since whole cells from Rhodococcus strains were used to catalyse the Michael addition of water in water to a series of ?,?-unsaturated carbonyl compounds, and when the work presented in Chapter 2 started, no genomic information of Rhodococcus strains was publically available, we sequenced and annotated the strain R. rhodochrous ATCC 17895. This is described in Chapter 3 together with features of the R. rhodochrous ATCC 17895. It is a Gram-positive aerobic bacterium with a rod-like morphology. The 6,869,887 bp long genome contains 6,609 protein-coding genes and 53 RNA genes. Our study suggests the Michael hydratase has not been described before. In the work presented in Chapter 2, we found that most ?-hydroxy ketones are not commercially available or commercially expensive as we mentioned in the first paragraph, which made the stereoselectivity determination of Michael addition products difficult. Indeed, many seemingly simple molecules have to be prepared via multi-step syntheses, in particular so if they are optically active. Therefore a straightforward approach to enantiomerically enriched (R)- and (S)-3-hydroxycyclopentanone was established by kinetic resolution in Chapter 4. This methodology allows us to prepare more ?-hydroxy carbonyl compounds structurally closely related to 3-hydroxycyclopentanone. The isolated chiral alcohols were used to determine the stereochemistry of the Michael addition of water in Chapter 2, saving us a lot of laboratory work. Moreover, unexpected stereoselective reduction of conjugated C = C bonds was discovered during studies on the enantioselective Michael addition of water. As mentioned in Chapter 2, the whole cells of R. rhodochrous ATCC 17895 reduced ?,?-unsaturated cyclic ketones into the corresponding ketones as initially undesired side reaction for the addition of water to C = C bonds. Therefore, ene-reductase activity was also investigated in Chapter 5. A series of substrates, including activated ketones, aldehydes, amines and nitro-compounds were screened for ene-reductase activity using whole cells of R. rhodochrous ATCC 17895. This showed that R. rhodochrous is a very promising catalyst for the reduction of C = C bonds and harbours ene-reductases. Indeed, looking for the annotated ene reductase from the genome of R. rhodochrous ATCC 17895 as described in Chapter 3, three candidates were observed and were classified as ene-reductases by amino acid sequence alignment with the known Old Yellow Enzymes (OYEs). Thus, the putative ene-reductase genes from R. rhodochrous ATCC 17895 were heterologously overexpressed in Escherichia coli and one of the encoded proteins was purified and characterized for their biocatalytic and biochemical properties. Based on these accomplishments it can be concluded that we have discovered a new Michael hydratase and three new ene reductases from Rhodococcus strains. Genome sequence and annotation of strain R. rhodochrous ATCC 17895 has been done, offering an excellent opportunity for the discovering novel enzymes, for instance, the Michael hydratase and S-selective ene reductase. The important chiral ?-hydroxy carbonyl compounds can be prepared by kinetic resolution of racemic alcohols using lipases or the direct enantioselective Michael addition of water using whole cells of Rhodococcus strains. The isolated products from kinetic resolution were readily used for the stereochemistry determination of Michael addition of water in water, completes the story of water addition to C = C bonds.BiotechnologyApplied Science
Transcriptionally correlated subcellular dynamics of MBNL1 during lens development and their implication for the molecular pathology of myotonic dystrophy type 1
No full textThis work is supported by the Scottish Universities Life Science Alliance (SULSA) and the Biotechnology and Biological Sciences Research Council (BBSRC) via a Ph.D. studentship to S.M.C.DM1 (myotonic dystrophy type 1) is caused by elongation of a CTG repeat in the DMPK (dystrophia myotonica-protein kinase) gene. mRNA transcripts containing these CUGexp (CUG expansion) repeats form accumulations, or foci, in the nucleus of the cell. The pathogenesis of DM1 is proposed to result from inappropriate patterns of alternative splicing caused by sequestration of the developmentally regulated alternative splicing factor MBNL1 (muscleblind-like 1) by these foci. Since eye lens cataract is a common feature of DM1 we have examined the distribution and dynamics of MBNL1 in lens epithelial cell lines derived from patients with DM1. The results of the present study demonstrate that only a small proportion of nuclear MBNL1 accumulates in CUGexp pre-mRNA foci. MBNL1 is, however, highly mobile and changes localization in response to altered transcription and splicing activity. Moreover, immunolocalization studies in lens sections suggest that a change in MBNL1 distribution is important during lens growth and differentiation. Although these data suggest that the loss of MBNL1 function due to accumulation in foci is an unlikely explanation for DM1 symptoms in the lens, they do demonstrate a strong relationship between the subcellular MBNL1 localization and pathways of cellular differentiation, providing an insight into the sensitivity of the lens to changes in MBNL1 distribution.Peer reviewe
Laser Refractive Lens Surgery using an Intraocular Femtosecond Laser
No full textThis video shows an intraocular femtosecond laser (Alcon LenSx Lasers, Inc, Ft. Worth, TX, USA) used to perform laser refractive lens surgery. The laser uses build-in optical coherence tomography (OCT) to image the cornea, lens capsule and lens. Nucleus liquefaction, capsulorhexis and corneal incisions are then positioned on the screen, and the laser performs lens liquefaction followed by capsulorhexis and corneal incisions. Irrigation/aspiration only is used to remove the liquefied lens nucleus, and an intraocular lens is implanted. Laser refractive lens surgery provides a far more accurate size and position of the capsulorhexis than the manual technique and enables the surgeon to combine the lens surgery with intracorneal refractive incision to correct astigmatism
Electrically tunable soft solid lens inspired by reptile and bird accommodation
No full textElectrically tunable lenses are conceived as deformable adaptive optical components able to change focus without motor-controlled translations of stiff lenses. In order to achieve large tuning ranges, large deformations are needed. This requires new technologies for the actuation of highly stretchable lenses. This paper presents a configuration to obtain compact tunable lenses entirely made of soft solid matter (elastomers). This was achieved by combining the advantages of dielectric elastomer actuation (DEA) with a design inspired by the accommodation of reptiles and birds. An annular DEA was used to radially deform a central solid-body lens. Using an acrylic elastomer membrane, a silicone lens and a simple fabrication method, we assembled a tunable lens capable of focal length variations up to 55%, driven by an actuator four times larger than the lens. As compared to DEA-based liquid lenses, the novel architecture halves the required driving voltages, simplifies the fabrication process and allows for a higher versatility in design. These new lenses might find application in systems requiring large variations of focus with low power consumption, silent operation, low weight, shock tolerance, minimized axial encumbrance and minimized changes of performance against vibrations and variations in temperature
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