Structure and Selected Properties of Intraocular Implants (PMMA, Acrylic)

2019 ◽  
Vol 56 (3) ◽  
pp. 621-624
Author(s):  
Marcin Gacek ◽  
Jerzy Wyslocki ◽  
Joanna Gondro ◽  
Franciszek Badura ◽  
Slawomir Letkiewicz
Keyword(s):  
Uv Radiation ◽  
Light Transmission ◽  
Visible Spectrum ◽  
Amorphous Structure ◽  
Intraocular Lenses ◽  
Light Spectrum ◽  
Implant Surgery ◽  
Clear Vision ◽  
Implant Coating ◽  
A Minor

This paper presents the results of an investigation into the structure and properties of intraocular lenses (IOL) that are available on the ophthalmological market. The majority of implants of this type are based on acrylics or poly(methyl methacrylate) (PMMA). The acrylic lenses can be curled, which allows the making of just a minor incision during the associated implant surgery. The drawback of PMMA implants is their high rigidity, resulting in the need for a larger incision during the implant surgery. The benefits accrued from wearing such an implant are (1) the correction of focus for clear vision and (2) protection of the retina against UV-A radiation. X-ray diffractometry has confirmed the amorphous structure of all of the lenses investigated in this paper. The absorption and transmittance of the selected implants have been measured; differences found in the directional values of the transmittance and absorbance suggest the presence of differences in the implant coating (such as: different thickness or lack of coating on one side). It has been found that the PMMA-based implants exhibit the better properties with a level of light transmission in the visible spectrum of almost 40% and total protection against UV radiation. The acrylic implants feature lower transmittance in the visible light spectrum, and two of the investigated acrylic lenses failed to provide adequate protection against the UV radiation.

Influence of UV radiation on the light transmission of a polymer optical fiber

1993 ◽  
Vol 59 (1-2) ◽  
pp. 528-532 ◽  
Author(s):  
P. M. Pakhomov ◽  
M. A. Maryukov ◽  
V. M. Levin ◽  
A. S. Chegolya
Keyword(s):  
Optical Fiber ◽  
Uv Radiation ◽  
Light Transmission ◽  
Polymer Optical Fiber

scholarly journals LIQUID LIGHT FILTER FOR THE VISIBLE SPECTRUM BASED ON HYDROPHILIC SOLUTIONS

2021 ◽  
Vol 6 ◽  
pp. 225-229
Author(s):  
Konstantin S. Nikitin ◽  
Victor S. Efremov
Keyword(s):  
Light Transmission ◽  
Visible Spectrum ◽  
Light Filter ◽  
Principal Possibility

The principal possibility of designing a liquid light filter using hydrophilic solutions is considered. Search for hydrophilic solutions with the most uniform light transmission at all wavelengths of the visible spectrum.

An experiment on dispersion

1933 ◽  
Vol 29 (3) ◽  
pp. 417-422
Author(s):  
R. C. Evans
Keyword(s):  
White Light ◽  
Visible Spectrum ◽  
Anomalous Dispersion ◽  
The Other ◽  
Sharp Edge ◽  
Light Spectrum ◽  
Minimum Deviation ◽  
Other Hand ◽  
As If

In the spectrum formed by a grating the red is more deviated than the blue, while in that formed by a prism, which does not exhibit anomalous dispersion in the visible spectrum, the reverse is the case. If, then, white light is passed first through a grating and then through a prism, the nature of the spectrum produced will depend on the relative dispersions of the grating and prism. If throughout the spectrum the dispersion of the prism is less than that of the grating, the sequence of colours will be the same as that in the spectrum due to the grating alone, red being more deviated than blue. If, on the other hand, the dispersion of the prism is throughout the spectrum greater than that of the grating, the sequence of colours will be reversed. On account of the rapid increase in the dispersion of glass near the blue end of the spectrum, it may, however, be possible that the dispersion of the prism exceeds that of the grating in the blue while in the red the reverse is the case. Under these conditions both red and blue will be more deviated than some intermediate colour for which the dispersions of the grating and prism are equal. The spectrum will thus have a sharp edge of this colour at the end of minimum deviation, while in the direction of greater deviation it will at each point consist of two superimposed colours. It is as if an ordinary white light spectrum was folded back on itself about the sharp edge.

FDTD Simulation of Light Propagation Inside a-Si:H Structures

2010 ◽  
Vol 1245 ◽  
Author(s):  
Alessandro Fantoni ◽  
Pedro Pinho
Keyword(s):  
Light Absorption ◽  
Electromagnetic Waves ◽  
Light Propagation ◽  
Light Transmission ◽  
Visible Spectrum ◽  
Propagation Model ◽  
Interface Roughness ◽  
Fdtd Simulation ◽  
Doping Density ◽  
Surface And Interface

AbstractWe have developed a computer program based on the Finite Difference Time Domain (FDTD) algorithm able to simulate the propagation of electromagnetic waves with wavelengths in the range of the visible spectrum within a-Si:H p-i-n structures. Understanding of light transmission, reflection and propagation inside semiconductor structures is crucial for development of photovoltaic devices. Permitting 1D analysis of light propagation over time evolution, our software produces results in well agreement with experimental values of the absorption coefficient. It shows the light absorption process together with light reflection effects at the incident surface as well as at the semiconductor interfaces. While the effects of surface reflections are easily taken into account by the algorithm, light absorption represents a more critical point, because of its non-linear dependence from conductivity. Doping density, density of states and photoconductivity calculation are therefore crucial parameters for a correct description of the light absorption-transmission phenomena through a light propagation model.The results presented in this paper demonstrate that is possible to describe the effect of the light-semiconductor interaction through the application of the FDTD model to a a-Si:H solar cell. A more general application of the model to 2D geometries will permit the analysis of the influence of surface and interface roughness on the device photovoltaic efficiency.

Intrinsic platelet reactivity before start with clopidogrel as predictor for on-clopidogrel platelet function and long-term clinical outcome

2015 ◽  
Vol 114 (07) ◽  
pp. 109-114 ◽  
Author(s):  
Christian M. Valina ◽  
Timo Bömicke ◽  
Michael Amann ◽  
Christian Stratz ◽  
Thomas Nührenberg ◽  
...  
Keyword(s):  
Clinical Outcome ◽  
Platelet Function ◽  
Light Transmission ◽  
Platelet Reactivity ◽  
Clinical Trial Registration ◽  
Coronary Stent Implantation ◽  
Insufficient Response ◽  
A Minor ◽  
Intrinsic Reactivity

SummaryHigh on-clopidogrel platelet reactivity is associated with worse clinical outcome. Previous data suggest that intrinsic platelet reactivity before initiation of clopidogrel contributes significantly to on-clopidogrel platelet reactivity. It is unknown whether intrinsic reactivity can sufficiently predict on-clopidogrel reactivity and therefore identify patients with insufficient response to clopidogrel before initiation of treatment and at risk for worse clinical outcome. This analysis included 765 consecutive patients undergoing elective coronary stent implantation. Platelet reactivity was assessed by light transmission aggregometry (5 µM ADP) before administration of clopidogrel 600mg and after intake of first maintenance dose of clopidogrel on day 1 following coronary stenting. Patients were followed for up to seven years. The combined primary endpoint was death of any cause or non-fatal myocardial infarction. Intrinsic and on-clopidogrel platelet reactivity were significant correlated (r=0.31; p < 0.001). Among all tested clinical and genetic factors including the cytochrome P450 2C19*2 polymorphism, intrinsic platelet reactivity was the strongest predictor for on-clopidogrel platelet reactivity. However, intrinsic platelet reactivity could only explain 8 % of variability of on-clopidogrel platelet function. Only on-treatment platelet reactivity was predictive for long-term clinical outcome (HR 1.47, 95 % CI 1.05–2.05; p = 0.02) whereas intrinsic platelet reactivity was not (HR 1.03, 95 % CI 0.74–1.43; p = 0.86). In conclusion, intrinsic platelet reactivity before initiation of clopidogrel is the strongest predictor of early on-clopidogrel platelet reactivity but can only explain a minor proportion of its variability and is not significantly associated with clinical outcome. Thus, baseline testing cannot substitute on-clopidogrel platelet function testing.Clinical Trial Registration: ClinicalTrials.gov (Identifier: NCT00457236).

scholarly journals Harvesting Solar Energy from Asphalt Pavement

2021 ◽  
Vol 13 (22) ◽  
pp. 12807
Author(s):  
Md Fahim Tanvir Hossain ◽  
Samer Dessouky ◽  
Ayetullah B. Biten ◽  
Arturo Montoya ◽  
Daniel Fernandez
Keyword(s):  
Solar Energy ◽  
Energy Harvester ◽  
Light Transmission ◽  
Low Cost ◽  
Visible Spectrum ◽  
Weather Conditions ◽  
Element Analysis ◽  
Energy Harvesters ◽  
Wide Range ◽  
Self Powered

This study aims at designing and developing a new technique to harvest solar energy from asphalt pavements. The proposed energy harvester system consists of a pavement solar box with a transparent polycarbonate sample and a thin-film solar panel. This device mechanism can store energy in a battery charged over daytime and later convert it into electric power as per demand. A wide range of polycarbonate samples containing different thicknesses, elastic moduli, and light transmission properties were tested to select the most efficient materials for the energy harvester system. Transmittance Spectroscopy was conducted to determine the percent light transmission property of the polycarbonate samples at different wavelengths in the visible spectrum. Finite Element Analysis modeling of the pavement–tire load system was conducted to design the optimal energy harvester system under static load. It was followed by the collection of data on the generated power under different weather conditions. The energy harvesters were also subjected to vehicular loads in the field. The results suggest that the proposed pavement solar box can generate an average of 23.7 watts per square meter continuously over 6 h a day under sunny conditions for the weather circumstances encountered in South Texas while providing a slightly smaller power output in other weather circumstances. It is a promising self-powered and low-cost installation technique that can be implemented at pedestrian crossings and intersections to alert distracted drivers at the time of pedestrian crossing, which is likely to improve pedestrian safety.

Enhancement of plasticity in Zr-based bulk metallic glasses

2007 ◽  
Vol 22 (9) ◽  
pp. 2454-2459 ◽  
Author(s):  
X.D. Wang ◽  
L. Yang ◽  
J.Z. Jiang ◽  
K. Saksl ◽  
H. Franz ◽  
...  
Keyword(s):  
Metallic Glasses ◽  
Concentration Ratio ◽  
Bulk Metallic Glasses ◽  
Amorphous Structure ◽  
Catastrophic Failure ◽  
X Ray Diffraction ◽  
Present Evidence ◽  
X Ray ◽  
The Stability ◽  
A Minor

We present evidence that a minor adjustment in Zr/Ni concentration ratio can dramatically enhance the plasticity of monolithic Zr-based bulk metallic glasses (BMGs) from about 2.2% for Zr65Al8Ni10Cu17 BMG to 14% for Zr62Al8Ni13Cu17 BMG. No deformation-induced nanocrystallization appears in a 55% strained Zr62Al8Ni13Cu17 BMG without catastrophic failure while pre-existing nanocrystals in Zr65Al8Ni10Cu17 BMG result in its limited plasticity. Also note that the stability of Zr62Al8Ni13Cu17 BMG against crystallization upon deformation is somewhat higher than that of Zr65Al8Ni10Cu17 BMG. As determined by x-ray diffraction using synchrotron radiation, the enhanced plasticity of Zr62Al8Ni13Cu17 BMG seems to be related to the relative homogeneity of the amorphous structure.

Refractive index matching for high light transmission composite systems

2018 ◽  
Vol 52 (24) ◽  
pp. 3299-3307 ◽  
Author(s):  
Erin Keaney ◽  
John Shearer ◽  
Artee Panwar ◽  
Joey Mead
Keyword(s):  
Refractive Index ◽  
Light Transmission ◽  
Polymer System ◽  
Visible Spectrum ◽  
Optical Polymer ◽  
Index Matching ◽  
Dispersion Data ◽  
Refractive Index Matching ◽  
Transparent Composite ◽  
Index Match

Transparent optical polymer/filler systems can be produced into complex shapes for a range of applications, such as lenses, shields, and containers. This work used refractive index liquids as a model for polymer matrices to investigate the degree of refractive index match required to maintain high transmission in an inorganic-filled polymer system (cubic calcium fluoride with particle size of 1 to 5 µm) over the visible spectrum. It was determined that in order to achieve a transparent composite (>85% transmission with 10 mm pathlength) with this filler (using literature reported dispersion data), the materials must have a refractive index match within ±0.007 for 1.6 vol.% loading. With a loading of 3.1 vol.%, the matching range required was reduced to approximately ±0.002.

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