1,721,054 research outputs found
Simultaneous surgery in bilateral congenital cataract.
No full textPURPOSE:
To assess the efficiency of simultaneous surgery in bilateral congenital cataract not only in patients with a high anesthesiologic risk profile.
METHODS:
A retrospective study was carried out on 40 bilateral congenital cataract patients (80 eyes) who presented to the outpatient department of pediatric ophthalmology of the University Federico II of Naples in the period from 1990 to 2005. All patients had undergone cataract extraction from both eyes in a single surgical session. Visual rehabilitation was achieved in all patients by corneal lenses; successively 25 patients had a secondary intraocular lens implant in the posterior chamber after a period of 2.5-3 years.
RESULTS:
The mean age at cataract surgery was 7 months (1-17 months). Visual acuity (VA) was assessed in 52 eyes: 8 eyes (15%) presented VA or=20/40. Ocular motility disorders were seen in 28 patients (70%). Eight patients had postoperative complications: the formation of secondary membranes in five patients, and secondary glaucoma in three patients. There were no cases of endophthalmitis.
CONCLUSIONS:
Simultaneous surgery in bilateral congenital cataract may be taken into consideration not only for patients with a high anesthesiologic risk profile
Modeling and Simulation of a High Sensitivity E-Field Sensor based on Disk Resonator and MOS Structure in SOI Technology
No full textA novel miniaturised high sensitivity Electric-field sensor based on a whispering gallery mode disk resonator is presented This device joins the potentials of silicon-on-insulator (SOI) technology with the potentials of high Q-factor disk resonator
Accurate physical modelling of multi quantum well ring lasers
No full textThe aim of this paper is to present a model including the fundamental physical effects of the multi quantum well (MQW) ring laser for the understanding of the optical mode behaviour and the control of the oscillating mode in semiconductor injection ring laser. The fully physical model is derived from a quantum mechanical approach and don't depend on any semi-empirical approximation. The ring laser behaviour is related to its physical and technological constraints, as the backscattering effect and ring radius
Nonlinear and dispersive effects in SOI optical waveguides
No full textIn this chapter, nonlinear optical propagation of ultrafast pulses in silicon-oninsulator rib waveguides is theoretically investigated. Two photon absorption, free carrier dispersion, self- and cross-phase modulation induced by Kerr effect, walk-off, group velocity dispersion, third-order dispersion, self-steeping and polarization coupling are taken into account by a very general modeling under sub-picosecond regime. Pulse compression as induced by the soliton generation are presented and discusse
Optimization of Bragg reflectors in AlGaAs/GaAs VCSELs
No full textIn this paper a detailed investigation of the distributed Bragg reflectors in GaAs-based vertical cavity surface emitting lasers is presented. The influence of layer doping concentration, number of periods, oxide aperture and AlxGa1-xAs alloy composition on output emission power and threshold current has been found. Both oxidized and non oxidized structures have been considered. A number of interpolation curves are extracted and presented for design and fabrication purposes. Although the results are presented for GaAs-based structures, the theoretical approach is very general
Modeling of noncollinear multifrequency acoustooptic interaction in guided-wave Bragg cells
No full textWe present an original detailed theoretical modeling of guided-wave noncollinear acoustooptic (AO) interaction produced by a multifrequency surface acoustic wave (SAW) in planar guided-wave structures, The modeling of the multifrequency AO interaction is based on a modified version of the coupled-mode theory, The first-and third-order diffraction efficiency and optimum dynamic range of the Bragg cell have been calculated as a function of acoustic power, acoustic radiofrequency, and optical waveguide parameters in Y-cut Ti:LiNbO3 planar waveguides, Polynomial approximations, describing the first and third order diffraction efficiency versus normalized acoustic power in the cases of two-and three-frequency interactions, are derived and presented for the first time for arbitrarly large RF signals
Anti-parity-time-symmetric integrated optical gyroscopes
No full textParity-time-symmetric optical gyroscopes are gaining interest for the enhanced sensitivity shown by exceptional points. The real splitting of anti-PT-symmetric gyroscopes is more reliable for stability and readout scheme than the complex splitting of parity-time-symmetric gyroscopes
Lithium niobate guided-wave beam-former for steering phased array antennas
No full textWe present the theoretical investigation, design, and simulation of a novel guided-wave optical processor for L-band-transmission beam forming in a linear array of phased active antennas. The proposed configuration includes two contradirectional surface acoustic-wave transducers, and it is based on a Y-cut, X-propagating Ti:LiNbO3 planar waveguide supporting the lowest-order modes of both polarizations (TE0 and TM0) at the free-space wavelength lambda = 0.85 mum. A detailed comparison between the processor we propose and other optical and electronic architectures reported in the literature is carried out, exhibiting a number of significant advantages in terms of weight, total chip size, and power consumption, when the number of antenna elements is greater than 50
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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