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At least 451 records · Page 25Linked to original sources

Ultrafast integrated semiconductor optical modulator based on the plasma-dispersion effect.

We demonstrate integrated semiconductor optical devices with ultrafast temporal responses based on the plasma-dispersion effect. The geometry of the devices removes the dependence of the modulation time on the free-carrier dynamics. We present the theoretical analysis of the performance of such devices. We show that a silicon-based device with a free-carrier lifetime of 1.4 ns can be modulated on a time scale of only 20 ps. The ultrafast operation is verified experimentally.

Journal Article↗

Planar concentrators near the étendue limit.

Recently proposed aplanatic imaging designs are integrally combined with nonimaging flux boosters to produce an ultracompact planar glass-filled concentrator that performs near the étendue limit. Such optical devices are attractive for high-efficiency multijunction photovoltaics at high flux, with realistic power generation of 1 W from a 1 mm2 cell. When deployed in reverse, our designs provide collimation even for high-numerical-aperture light sources.

Journal Article↗

Optical-damage-free guided second-harmonic generation in 1% MgO-doped stoichiometric lithium tantalate.

Room-temperature cw second-harmonic generation from telecom wavelengths, with 30% W(-1) cm(-2) efficiency and second-harmonic power levels up to 41 mW, was achieved in buried waveguides fabricated by reverse-proton exchange in 1% MgO-doped stoichiometric lithium tantalate without any evidence of optical damage. The technology proves suitable for the realization of efficient nonlinear frequency converters and all-optical devices.

Journal Article↗

Achromatic optical vortex lens.

A vortex lens is a useful optical device having applications ranging from astronomy to microscopy. Current vortex masks operate across a narrow bandwidth. Two design schemes are proposed for creating a vortex across a bandwidth exceeding 100 nm in the visible region of the spectrum.

Journal Article↗

Investigation of resonant modes in thin microcavities by using electromagnetic theory.

A biharmonic differential equation for 3D thin microcavities with uniform thickness is investigated by use of electromagnetic theory, whose exact solution is determined to govern the electromagnetic field distribution inside the thin microcavities. The resonant field patterns of a thin microdisk and thin rectangular microcavity are obtained accordingly. The governing equation can be verified by comparing the results of the thin microdisk presented with the approximate ones in the literature. The fourth-order partial differential equation and its exact solution should be useful in possible applications of the thin microcavities for optical resonators in laser optics and optical devices.

Journal Article↗

Double plasma mirror for ultrahigh temporal contrast ultraintense laser pulses.

We present and characterize a very efficient optical device that employs the plasma mirror technique to increase the contrast of high-power laser systems. Contrast improvements higher than 10(4) with 50% transmission are shown to be routinely achieved on a typical 10 TW laser system when the pulse is reflected on two consecutive plasma mirrors. Used at the end of the laser system, this double plasma mirror preserves the spatial profile of the initial beam, is unaffected by shot-to-shot fluctuations, and is suitable for most high peak power laser systems. We use the generation of high-order harmonics as an effective test for the contrast improvement produced by the double plasma mirrors.

Journal Article↗

[Three-dimensional visualization of stationary flow behind artificial heart valves].

The visualization and quantitative analysis of flow offers a possibility for the hydrodynamic characterization of artificial heart valves. Different types of valves can be compared if velocity profile and the turbulent shear stress caused by the prosthesis are known. The tracer technique was selected, since it permits visualization also of turbulent flow through the valve. With the aid of a simple optical device the three-dimensional flow pattern behind the valve is determinable. The main features of the method are: The regions of interest can easily be identified. Velocity profiles can be determined and shear stress and turbulence intensities estimated. The experimental setup is simple, calibration is not necessary, and it can be used for turbulent flows. The method can be used only with transparent fluids and vessels; measurements in blood are not possible. Because of the large number of measuring points required the method is very time-consuming. The use of an automatic picture analyzing system would make it possible to increase the number of pictures processed, and thus increase resolution. The velocity profile of a three-finger-valve, the TAD 29, was established at a distance of 20 mm from the ring, and compared with known profiles from the literature. The valve has an opening angle of 70 degrees. All typical regions for the flow of an artificial heart valve, such as jet, stagnation gone, backflow and turbulence were demonstrated.

Blood Flow Velocity↗

The relationship between different subcutaneous adipose tissue layers, fat mass and leptin in obese children and adolescents.

We studied the relationships of subcutaneous adipose tissue layers (SAT-layers), body fat mass (FM) and waist-to-hip ratio (WHR) with leptin in obese children and adolescents. Twenty-nine obese children and adolescents (12 boys: age: 11.3 +/- 3.7 yr; body mass index [BMI]: 28.5 +/- 4) and 17 girls (age: 12.2 +/- 2.2 yr; BMI: 29.8 +/- 4.7) (mean +/- SD) were studied. FM was estimated by bioelectrical impedance. SAT-layers were determined at 15 different body sites from 1-neck to 15-calf by the Lipometer optical device. Leptin and insulin were determined by RIA. Maturity was associated with a greater thickness of certain SAT-layers from the upper body and with a lower thickness of SAT-layers from the abdominal region and lower extremities. Significant correlations were found for all estimates of adiposity and leptin (all p<0.001). Waist and hip circumferences were not correlated to leptin after adjustment for FM. SAT-layers from the upper body were significantly and positively correlated to leptin. Multiple regression analysis revealed FM as a main contributor to the variation in leptin (R2=0.53, p<0.0001). FM together with SAT-layers 5-front chest and 13-rear thigh explained 72% of the variation in leptin (p<0.0001). In a body fat distribution model, hip circumference together with SAT-layers 4-upper back and 2-triceps explained 75% of the variation in leptin (p< 0.0001). The results suggest that SAT-layers and their topography are main determinants for leptin in obese children and adolescents. Maturity in obese children is associated with higher values of upper body SAT-layers and lower values of abdominal and lower extremities SAT-layers. Whether leptin is under the control of certain subcutaneous adipose tissue depots from the upper body remains to be elucidated by longitudinal studies.

Adipose Tissue↗

Biophysical aspects of photodynamic therapy.

Over the last three decades photodynamic therapy (PDT) has been developed to a useful clinical tool, a viable alternative in the treatment of cancer and other diseases. Several disciplines have contributed to this development: chemistry in the development of new photosensitizing agents, biology in the elucidation of cellular processes involved in PDT, pharmacology and physiology in identifying the mechanisms of distribution of photosensitizers in an organism, and, last but not least, physics in the development of better light sources, dosimetric concepts and construction of imaging devices, optical sensors and spectroscopic methods for determining sensitizer concentrations in different tissues. Physics and biophysics have also helped to focus on the role of pH for sensitizer accumulation, dose rate effects, oxygen depletion, temperature, and optical penetration of light of different wavelengths into various types of tissue. These are all important parameters for optimally effective PDT. The present review will give a brief, physically based, overview of PDT and then discuss some of the main biophysical aspects of this therapeutic modality.

Animals↗

Plasmon resonance methods in GPCR signaling and other membrane events.

The existence of surface guided electromagnetic waves has been theoretically predicted from Maxwell's equations and investigated during the first decades of the 20th century. However, it is only since the late 1960's that they have attracted the interest of surface physicists and earned the moniker of "surface plasmon". With the advent of commercially available instruments and well established theories, the technique has been used to study a wide variety of biochemical and biotechnological phenomena. Spectral response of the resonance condition serves as a sensitive indicator of the optical properties of thin films immobilized within a wavelength of the surface. This enhanced surface sensitivity has provided a boon to the surface sciences, and fosters collaboration between surface chemistry, physics and the ongoing biological and biotechnological revolution. Since then, techniques based on surface plasmons such as Surface Plasmon Resonance (SPR), SPR Imaging, Plasmon Waveguide Resonance (PWR) and others, have been increasingly used to determine the affinity and kinetics of a wide variety of real time molecular interactions such as protein-protein, lipid-protein and ligand-protein, without the need for a molecular tag or label. The physical-chemical methodologies used to immobilize membranes at the surface of these optical devices are reviewed, pointing out advantages and limitations of each method. The paper serves to summarize both historical and more recent developments of these technologies for investigating structure-function aspects of these molecular interactions, and regulation of specific events in signal transduction by G-protein coupled receptors (GPCRs).

Cell Membrane↗

A conceptual design for cosmo-biology experiments in Earth's Orbit.

A conceptual design was developed for a cosmo-biology experiment. It is intended to expose simulated interstellar ice materials deposited on dust grains to the space environment. The experimental system consists of a cryogenic system to keep solidified gas sample, and an optical device to select and amplify the ultraviolet part of the solar light for irradiation. By this approach, the long lasting chemical evolution of icy species could be examined in a much shorter time of exposure by amplification of light intensity. The removal of light at longer wavelength, which is ineffective to induce photochemical reactions, reduces the heat load to the cryogenic system that holds solidified reactants including CO as a constituent species of interstellar materials. Other major hardware components were also defined in order to achieve the scientific objectives of this experiment. Those are a cold trap maintained at liquid nitrogen temperature to prevent the contamination of the sample during the exposure, a mechanism to exchange multiple samples, and a system to perform bake-out of the sample exposure chamber. This experiment system is proposed as a candidate payload implemented on the exposed facility of Japanese Experiment Module on International Space Station.

Cold Temperature↗

A study on the clinical usefulness of digitalized random-dot stereoacuity test.

Existing methods of stereoacuity testing need specific glasses or optical device for use. We have designed a new stereoacuity test for the digitalized, random-dot stereogram and researched its clinical usefulness. A digitalized, random-dot, stereoacuity test card was created with a computer program that used a preferred symbol and the designed system was tested along with the Randot preschool stereoacuity, Titmus-fly and Lang tests to compare their sensitivity and specificity. The mean success rate of the digitalized, random-dot test was 98.2%, while the rates of the Randot preschool stereoacuity, Titmus-fly and Lang tests were 89.3%, 74.2% and 86.1%, respectively. Sensitivity and specificity of the new test were 100% and 95.3%, respectively, which were not that different from those of the Randot preschool stereoacuity, Titmus-fly and Lang tests. We found that the digitalized, random-dot, stereoacuity test has a high success rate and can be appropriately used in medical examinations and follow-up tests for strabismus patients.

Age Distribution↗

Providing low vision rehabilitation services with occupational therapy and ophthalmology: a program description.

This article describes a low vision rehabilitation program operating within a hospital-based outpatient rehabilitation clinic. The program uses a team approach combining ophthalmology and occupational therapy services. Patients are referred to the program by their primary care physician for a low vision evaluation completed jointly by the ophthalmologist and occupational therapist. The ophthalmology portion of the evaluation includes assessment of visual acuity, contrast sensitivity function, and macular perimetry with a scanning laser ophthalmoscope. The occupational therapy evaluation focuses on assessing the functional limitations experienced by the patient due to the vision loss and determining how the patient is best able to use remaining vision to complete daily activities. Occupational therapy treatment emphasizes training the patient to use remaining vision as efficiently and effectively as possible to complete daily activities and includes training in use of optical devices. Because of the specialized nature of the service provided, additional postgraduate preparation is needed to enable occupational therapists to provide effective low vision rehabilitation.

Activities of Daily Living↗

Considerations in evaluation and treatment of the child with low vision.

Habilitation of infants and children with visual impairments should be based on a thorough understanding of their visual capabilities and limitations. Comprehensive evaluation of visual function includes measurement of visual acuity, contrast sensitivity, visual field, color vision, adaptation, visual sphere, accommodation, and oculomotor functions. It is best completed through a team approach that uses therapists, special educators, and physicians. A complete evaluation also includes examination of the effect of other motor functions on the use of vision. Nearly all aspects of a child's vision can be measured in play situations with tests that are easy to use. However, further education of nonphysician team members in refractive errors, optics, and function of optical devices may be necessary to ensure an accurate and thorough evaluation.

Adaptation, Ocular↗

[Comments on the possibility of the use of the ND-YAG laser in chronic hypertrophic rhinopathy].

Impediment of breath through the nose because of turbinal hypertrophy is an often repeated symptom in chronic rhinitis. In the course of years several procedures for clear the nasal congestion, with more or less satisfactory outcomes, has been tested. The introduction of Nd:Yag laser has allowed a new treatment of the hypertrophic turbinates, thanks to the advantage of its conduction through the flexible optical fibers of the traditional optical devices, even connected to the video system. Treatment can be achieved in the outpatients department with local anesthesia. Results are favorable and forebode new horizons in the surgery of chronic hypertrophic rhinopathies.

Chronic Disease↗

[Comparative studies of two different systems for bonding composites with tissue of the tooth].

The objective of studies was the clinical evaluation concerning the influence of the bonding systems Syntac and Gluma exerted on the quality of compositive fillings in various types of defects in humans, in comparison to fillings, in which Compa Bond resin was used. The question was studied to answer whether there were any significant differences in respect of the assessed parameters between fillings by Syntac system and the fillings by Gluma system with preservation and marginal adaptation being taken into consideration. The studies were performed on 98 patients of both sexes, therein 56 women and 42 men. The assessment included 248 classified fillings, namely: 82 of Tetric material, 78 of Pekalux material and 88 of C-Fill MH and C-Molar materials. The fillings were estimated directly after placement, as well as after 6, 12, and 24 months, under artificial light by making use of dental mirror, a probe and an optic device (magnifying glass of fivefold magnification), on the basis of own card of investigations for compositive fillings. The dental pulp reaction to thermic simuli and faradic current was also taken into account. Fillings classified by grades 0 degree and 1 degree were defined as clinically acceptable, while 2 degrees and 3 degrees as clinically unacceptable. The statistical analysis was carried out by means of Chi 2 test. The number of Tetric and Pekalux materials fillings lost after 24 months of studies was substantially lower than the number of lost fillings made of C-Fill MH and C-Molar materials. The loss only concerned defects of non-carious origin, namely wedge shaped defects and pathological attrition of teeth (Tab. 1 and Tab. 2). The fillings by Syntac system are characterized by better marginal adaptation as compared with fillings, wherein the Gluma system was applied, however, no statistically significant differences between these groups were disclosed (Tab. 3). Significant differences were found to appear between the groups, of fillings, in which use was made of bonding systems Syntac and Gluma on the one hand, and the fillings set up by Compa Bond resin on the other. Assessing the colour, smoothness of surface and the anatomical shape of the fillings after 24 months no essential differences between the studied material groups were revealed. Secondary caries and post-procedural sensitivity involved only the cases, in which Compa Bond resin and C-Fill MH material were employed. After 24 months of studies the percentage of clinically acceptable fillings claimed to be as follows: Tetric 93.51%, Pekalux 91.55%, C-Fill MH and C-Molar 75.36%. Thus, it was disclosed that there were significantly more clinically acceptable fillings made of Tetric and Pekalux materials than of C-Fill MH and C-Molar materials. The Syntac and Gluma systems exerted significant influence on better preservation and marginal adaptation of fillings mainly in defects of non carious origin, in comparison to the fillings in which the conventional Compa Bond resin was being used. In cases, wherein Syntac and Gluma systems were applied, no post-procedural hypersensitivity was recorded. This ailment was evidenced in 4.5% of cases after implementing Compa Bond resin.

Adhesiveness↗

IPM-FISH, a new M-FISH approach using IRS-PCR painting probes: application to the analysis of seven human prostate cell lines.

We have developed an alternative multicolor karyotyping technique based on multiplex fluorescence in situ hybridization (M-FISH) and our own optical device with a specific filter set. The most innovative part of our development is the use of interspersed polymerase chain reaction (IRS-PCR) painting probes that show an R-band pattern simultaneous to the combinatorial labeling. This allows us not only to recognize the origin of chromosomal fragments, but to identify the breakpoints as well. We have used this technique to analyze seven cell lines: four prostate cancer cell lines (CA-HPV-10, LNCaP, DU145, and PC3), and three normal transformed epithelial prostate cell lines (PNT1B, PNT2, and PZ-HPV-7). In order to validate our IRS-PCR multiplex FISH (IPM-FISH) technique and to complement the results, we applied comparative genomic hybridization (CGH) and FISH analysis, showing good correlation with the IPM-FISH results. To date, molecular and cytogenetic studies have identified several chromosomal regions that are altered in human prostate cancer; several candidate genes have been suggested. However, reliable markers for predicting the aggressiveness of early prostate cancer are not yet available. Our results show several common, unbalanced rearrangements in the cell lines. These rearrangements are similar to regions already implicated in prostate cancer, validating these cell lines as a good model system.

Cell Line, Transformed↗

[Functional improvement after vision rehabilitation in low monocular vision after myopic macular degeneration and retinal detachment].

PURPOSE: We present a case of a 62 year-old woman, with a single eye functional vision (VA of 0.16) who improved her vision after following a vision rehabilitation program, which included optical and non-optical devices for daily performance. CONCLUSIONS: A correct optometric evaluation and a training program are key factors to improve quality of life in low vision patients, whose ocular pathology allows no other treatment.

Female↗