Search results for "Refractive"

Precise structural investigation of symmetric diblock copolymer thin films with resonant soft X-ray reflectivity

2013

Symmetric diblock copolymers are known to form lamellar structures in the bulk of an organic thin film. Polymer/polymer and polymer/substrate interfaces play a critical role in this application. Here, we report the investigation of multiple buried interfaces by using a novel technique resonant soft X-ray reflectivity which benefits from enhanced contrast between different polymers near the carbon K-edge. This allows us to obtain a precise interface structure. We also present an alternative method to determine optical constants of polymers by fitting X-ray reflectivity of polymers with known structural parameters at specific soft X-ray energies. This approach is compared with the way of obta…

1981

A new interferometer has been designed in order to perform measurements of refractive indices and refractive index increments on liquid systems under elevated pressure at different temperatures. The method of measurement, the calibration of the instrument and the treatment of data are described. With a series of test measurements on trans-decalin it is shown that with this instrument reliable results are obtained.

Refractive Indices and Deviations in Refractive Indices of Trifluoromethanesulfonate-Based Ionic Liquids in Water

2011

Refractive indices were determined for four different ionic liquid + water binary systems, from (288.15 to 338.15) K, and covering the entire composition range. The four ionic liquids used were 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, 3-butyl-1-ethylimidazolium trifluoromethanesulfonate, 3-butyl-1-methylimidazolium trifluoromethanesulfonate, and 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate, all of them being completely miscible in water. From the experimental data, deviations in refractive indices, defined on a volume fraction basis, have been calculated and fitted to an extended version of the Redlich–Kister equation. The behavior of the deviations in refractive in…

The role of dry eye disease in cataract and refractive surgery

2019

El síndrome de ojo seco (DED) puede jugar un papel importante en las cirugías oftálmicas con fines refractivos tanto corneales (tratamiento corneal laser) como cristalinianas (cirugía de catarata) pero también en aquellas cuyo fin es controlar la presión intraocular en pacientes que sufren de glaucoma. El objetivo principal de esta tesis se refiere a la aplicación de una serie de pruebas diagnósticas, de mínimamente a no-invasivas, sugeridas por el Tear Film & Ocular Society Dry Eye WorkShop II (TFOS DEWS II) que pueden ayudar a mejorar los resultandos refractivos y visuales en la cirugía oftálmica actual. La cirugía de cristalino, particularmente la cirugía moderna de catarata y la refract…

<title>Refractive properties of separate erythrocytes of Chernobyl clean-up workers at different pH</title>

2000

This study is focused on the modifications in erythrocytes of Chernobyl nuclear power plant accident clean-up workers as a late health effect of short-term impact of high level radioactive contamination. As a result, a new method based on erythrocyte (RBC) refractive index properties at different pH has been elaborated. According to the light dispersion theory for fluids refractive index is associated with molecules mass m. This feature is widely used for estimation of cell dry mass. But there is another refractive index dependency from molecules charge q regardless of its sing. This feature is not being used for cell quantitative and qualitative characterization. In this study, RBC were in…

Theoretical study of Fe doping and oxidation–reduction influence on the photorefractive effect in BaTiO_3

1993

We numerically solve charge-transport and Poisson equations for photorefractive BaTiO3 single crystals with a band model, using four impurity levels, Fe2+–Fe3+, Fe3+–Fe4+, VO••–VO•, and VO•-VOx. Densities and photoinduced spatial distributions of each population are computed as a function of annealing O partial pressure. Space-charge field and beam-coupling gain are also computed as a function of annealing O partial pressure, temperature, Fe concentration, grating wave vector, and light intensity. We discuss the intervening mechanism of impurity centers and the correlations between experimental conditions of crystal growth, oxidation–reduction treatments, and measurement parameters.

Visual defects in subjects with Down’s syndrome

1995

Because the incidence of other visual defects is much higher in cases of Down’s syndrome than in individuals with other forms of retardation (Gardiner, 1967; Aitchison et al., 1990), we tested the color vision of a population of Down’s syndrome patients, using Ishihara plates and the Davico anomaloscope. The Down’s syndrome group had a significantly higher proportion of color deficiencies than either normal controls or a matched mentally retarded population. Refractive errors were corrected with static retinoscopy, and spatial contrast sensitivity was measured with the Vistech test.

FLUMO: FLexible Underwater MOdem

2019

The last years have seen a growing interest in underwater acoustic communications because of its applications in marine research, oceanography, marine commercial operations, the offshore oil industry and defense. High-speed communication in the underwater acoustic channel has been challenging because of limited bandwidth, extended multipath, refractive properties of the medium, severe fading, rapid time variation and large Doppler shifts. In this paper, we show an implementation of a flexible Software-Defined Acoustic (SDA) underwater modem, where modulation parameters are completely tunable to optimize performance. In particular, we develop the system architecture following two key ideas. …

Schematic eye models to mimic the behavior of the accommodating human eye

2018

A simplified version of the human eye is known as schematic eye model. Since the first attempts in the middle of the 19th century, numerous approaches describing new schematic eye models have been introduced. Some of them are able to describe the accommodation ability of the human eye. Accommodative schematic eyes could be of great interest since they are able to explain the functionality of the human eye and they can be easily used for different research purposes. Some of these include the design and testing of multifocal ophthalmic solutions, evaluation of the effect of optical aberrations on the retinal image quality, and study of the optical performance of the eye at different distances…

A new trifocal corneal inlay for presbyopia

2021

[EN] Corneal inlays (CIs) are the most recent surgical procedure for the treatment of presbyopia in patients who want complete independence from the use of glasses or contact lenses. Although refractive surgery in presbyopic patients is mostly performed in combination with cataract surgery, when the implantation of an intraocular lens is not necessary, the option of CIs has the advantage of being minimally invasive. Current designs of CIs are, either: small aperture devices, or refractive devices, however, both methods do not have good performance simultaneously at intermediate and near distances in eyes that are unable to accommodate. In the present study, we propose the first design of a …