1,721,013 research outputs found
Self-mixing superluminescent diode optical tomography
No full textSelf-mixing superluminescent diode optical tomograph
Autofluorescence of ocular tissues: a promising diagnostic technique in ophthalmology
No full textIn the past, ocular diagnosis through fluorometric systems has been mainly based onto exogenous agents. Recently, a number of diagnostic techniques has been proposed for diagnosis of ocular pathologies, which are based upon the naturally occurring fluorescent emission of ocular tissues. In this paper, we discuss major advantages and drawbacks of these techniques, focusing in particular our attention on a novel diagnostic technique based onto autofluorescence of corneal tissue
Autofluorescence of Ocular tissues: an update of measurement techniques for research and diagnosis
No full textOphthalmic diagnosis through measurements of ocular tissues autofluorescence has recently reached its first clinical maturity. This technique is intrinsically non-invasive and, thanks to the availability of a new family of measuring instruments, is becoming reliable even if performed in a few seconds and is of no burden to the patient. Diagnostic methods based on ocular tissue autofluorescence could become important tools in the prevention of a number of diseases which may lead to blindness, and therefore have a great social impact. The present paper is intended to give, from one side, an update of the rationale concerning fluorophores in the eye and their absorption and fluorescence properties; from the other, it offers an overview of ophthalmic fluorescence techniques aimed at the detection, quantitation and discrimination of ocular autofluorescing substances, highlighting their usefulness as a diagnostic aid in the early detection and prevention of ocular diseases
Corneal autofluorescence in presence of diabetic retinopathy
No full textRecently corneal autofluorescence has been proposed as an ocular diagnostic tool for diabetic retinopathy. The method is based on the sensible increase of the natural fluorescence of corneal tissue within specific wavelength in presence of early stage of diabetic retinopathy. The main advantages of this method are that the corneal autofluorescence has been demonstrated to be not age-related and that the cornea is readily accessible to be investigated. In this study 47 insulin-dependent diabetes mellitus and 51 non-insulin- dependent diabetes mellitus patients aged 20 - 90 years have been considered. Patients were selected from the Eye Clinic of S. Raffaele Hospital. The modified Airlie House classification was used to grade the diabetic retinopathy. Corneal autofluorescence has been measured by using both a specifically designed instrument and the Fluorotron Master. Corneal autofluorescence mean value for each diabetic retinopathy measured by using both the instruments correlated with the retinopathy grade
Design and performance of a new fluorometer for corneal autofluorescence measurement
No full textAn optical instrument for in-vivo corneal autofluorescence measurements in the human eye is described. This instrument measures corneal autofluorescence without burden to the patient. The corneal tissues are excited tangentially by wavelengths in the spectral region of 450 to 500 nm and the fluorescence emitted by the corneal tissue passing through a suitable set of barrier filters is collected by a miniature photomultiplier. Autofluorescence data are recorded in sixteen measurement cycles during a period of 10 seconds and the average value has been considered. The instrument demonstrates good safety characteristics
Self mixing low-coherence interferometry
No full textIn this paper a novel low-coherence interferometer using a self-mixing super luminescent diode is described. The optical scheme presented uses the photodiode on the back- face of a commercial super luminescent diode to detect the interference signal. The low-coherence interferometer, here proposed, for the first time sums up a Fizeau interferomete
Low-noise front end electronics for solid state fluorometers
No full textNew steady-state fluorometric systems are based on solid state-optoelectronic components such as blue light-emitting diodes, avalanche photodiodes, and standard photodiodes. In the latter case, the noise performance of the front-end electronics limits the sensitivity of the instrumentation. However, signal detection performed by standard photodiode is appealing in low-cost applications. In this article, a low-noise electronic setup which processes the signal from photodetectors without internal amplification is presented. Low-noise preamplification and optimal signals shaping allow to minimize the fluorometric measurement uncertainty. The circuit has been accordingly developed and tested in operation. Using a low-cost silicon photodiode, a minimum equivalent noise power less than 1 pW/ has been obtained at a shaping time of 200 μs. The circuit exhibits excellent rejection to continuous ambient light and partially suppresses the alternating components
La collana della storia della tecnologia italiana
No full textStoria delle misure nella società dal1875: successi, insuccessi e ... occasioni perdute
a cura di Franco Docchio, Michele Gasparetto, Luca Mar
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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