Publications by authors named "Luca Mercatelli"

18 Publications

  • Page 1 of 1

Sky radiance and spectral gradient are orienting cues for the sandhopper (Crustacea, Amphipoda).

J Exp Biol 2021 Jan 29;224(Pt 2). Epub 2021 Jan 29.

Dipartimento di Biologia, Università di Firenze, Via Romana 17/19, 50125 Firenze, Italy

The sandhopper relies on both the sun and the moon compasses to return to the belt of damp sand on the beach in which it lives buried during the day. In addition to the sun, the gradient of radiance and the spectral distribution across the sky could provide directional information that can potentially use to orient itself during the day even when the sun is not visible (e.g. cloudy sky). The scope of this work was (1) to determine the intensity levels of sky radiance that the sandhoppers use in their zonal recovery and (2) to investigate whether this species relies on the celestial spectral gradient in its zonal recovery. Sandhoppers were tested in the laboratory under artificial radiance or spectral gradients. Our results show that under an artificial sky simulating the natural radiance gradient on a cloudless day, sandhoppers orientated toward the correct seaward direction of their home beach; however, individuals lost their ability to use the intensity gradient as an orientation cue when the radiance was attenuated by at least 40%. Sandhoppers were also able to head in the correct seaward direction of their home beach at any time of the day by using the spectral gradient as their only source of visual orientation reference.
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http://dx.doi.org/10.1242/jeb.239574DOI Listing
January 2021

Optical Limiting of Carbon Nanohorn-Based Aqueous Nanofluids: A Systematic Study.

Nanomaterials (Basel) 2020 Oct 29;10(11). Epub 2020 Oct 29.

INAF, Astrophysical Observatory of Arcetri, Largo E. Fermi, 5, I-50125 Firenze, Italy.

Nowadays, the use of lasers has become commonplace in everyday life, and laser protection has become an important field of scientific investigation, as well as a security issue. In this context, optical limiters are receiving increasing attention. This work focuses on the identification of the significant parameters affecting optical limiting properties of aqueous suspensions of pristine single-wall carbon nanohorns. The study is carried out on the spectral range, spanning from ultraviolet to near-infrared (355, 532 and 1064 nm). Optical nonlinear properties are systematically investigated as a function of nanohorn morphology, concentration, dimensions of aggregates, sample preparation procedure, nanostructure oxidation and the presence and concentration of surfactants to identify the role of each parameter in the nonlinear optical behavior of colloids. The size and morphology of individual nanoparticles were identified to primarily determine optical limiting. A cluster size effect was also demonstrated, showing more effective optical limiting in larger aggregates. Most importantly, we describe an original approach to identify the dominant nonlinear mechanism. This method requires simple transmittance measurements and a fitting procedure. In our suspensions, nonlinearity was identified to be of electronic origin at a 532 nm wavelength, while at 355 nm, it was found in the generation of bubbles.
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http://dx.doi.org/10.3390/nano10112160DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7716216PMC
October 2020

Specializations in the compound eye of Talitrus saltator (Crustacea, Amphipoda).

J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2020 09 19;206(5):711-723. Epub 2020 Jun 19.

Department of Biology, University of Florence, Via Romana 17, 50125, Florence, Italy.

We investigated the eye regionalization in Talitrus saltator by morphological, electrophysiological and behavioural experiments. Each ommatidium possesses five radially arranged retinular cells producing a square fused rhabdom by R1-R4 cells; the smaller R5 exists between R1 and R4. The size of R5 rhabdomere is larger in the dorsal part and becomes smaller in the median and ventral parts of the eye. Spectral-sensitivity by electroretinograms were recorded from dorsal or ventral parts of the eye. The dorsal part possesses maxima at green and UV-blue region. The main response region in the ventral part is only from UV (390 nm) to blue (430 nm) decreasing at longer wavelengths. To evaluate the sandhoppers' celestial orientation, their eyes were painted black either in the dorsal or ventral part, under the natural sky or a blue filter with or without the vision of the sun. Sandhoppers with the dorsal region of the eyes painted and tested under the screened sun were more dispersed and their directions varied more than in other groups of individuals. Sandhoppers with this area of the eye obscured display considerable difficulties to head in a specific direction. This work suggests the existence of regional specializations in the eye of T. saltator.
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http://dx.doi.org/10.1007/s00359-020-01432-8DOI Listing
September 2020

Optical CAD Utilization for the Design and Testing of a LED Streetlamp.

Materials (Basel) 2017 Aug 24;10(9). Epub 2017 Aug 24.

CNR-INO National Institute of Optics, Largo E. Fermi, 6-50125 Firenze, Italy.

The design and testing of LED lamps are vital steps toward broader use of LED lighting for outdoor illumination and traffic signalling. The characteristics of LED sources, in combination with the need to limit light pollution and power consumption, require a precise optical design. In particular, in every step of the process, it is important to closely compare theoretical or simulated results with measured data (obtained from a prototype). This work examines the various possibilities for using an optical CAD (Lambda Research ) to design and check a LED lamp for outdoor use. This analysis includes the simulations and testing on a prototype as an example; data acquired by measurement are inserted into the same simulation software, making it easy to compare theoretical and actual results.
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http://dx.doi.org/10.3390/ma10090985DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5615640PMC
August 2017

Lanthanum hexaboride for solar energy applications.

Sci Rep 2017 04 6;7(1):718. Epub 2017 Apr 6.

CNR-ISTEC, Institute of Science and Technology for Ceramics, Via Granarolo 64, I-48018, Faenza, Italy.

We investigate the optical properties of LaB - based materials, as possible candidates for solid absorbers in Concentrating Solar Power (CSP) systems. Bulk LaB materials were thermally consolidated by hot pressing starting from commercial powders. To assess the solar absorbance and spectral selectivity properties, room-temperature hemispherical reflectance spectra were measured from the ultraviolet to the mid-infrared, considering different compositions, porosities and surface roughnesses. Thermal emittance at around 1100 K has been measured. Experimental results showed that LaB can have a solar absorbance comparable to that of the most advanced solar absorber material in actual plants such as Silicon Carbide, with a higher spectral selectivity. Moreover, LaB has also the appealing characteristics to be a thermionic material, so that it could act at the same time both as direct high-temperature solar absorber and as electron source, significantly reducing system complexity in future concentrating solar thermionic systems and bringing a real innovation in this field.
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http://dx.doi.org/10.1038/s41598-017-00749-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5429614PMC
April 2017

Processing, Mechanical and Optical Properties of Additive-Free ZrC Ceramics Prepared by Spark Plasma Sintering.

Materials (Basel) 2016 Jun 18;9(6). Epub 2016 Jun 18.

INO-CNR, National Institute of Optics, Largo E. Fermi, 6, Firenze 50125, Italy.

In the present study, nearly fully dense monolithic ZrC samples are produced and broadly characterized from microstructural, mechanical and optical points of view. Specifically, 98% dense products are obtained by Spark Plasma Sintering (SPS) after 20 min dwell time at 1850 °C starting from powders preliminarily prepared by Self-propagating High-temperature Synthesis (SHS) followed by 20 min ball milling. A prolonged mechanical treatment up to 2 h of SHS powders does not lead to appreciable benefits. Vickers hardness of the resulting samples (17.5 ± 0.4 GPa) is reasonably good for monolithic ceramics, but the mechanical strength (about 250 MPa up to 1000 °C) could be further improved by suitable optimization of the starting powder characteristics. The very smoothly polished ZrC specimen subjected to optical measurements displays high absorption in the visible-near infrared region and low thermal emittance at longer wavelengths. Moreover, the sample exhibits goodspectral selectivity (2.1-2.4) in the 1000-1400 K temperature range. These preliminary results suggest that ZrC ceramics produced through the two-step SHS/SPS processing route can be considered as attractive reference materials for the development of innovative solar energy absorbers.
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http://dx.doi.org/10.3390/ma9060489DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5456769PMC
June 2016

Facility for assessing spectral normal emittance of solid materials at high temperature.

Appl Opt 2015 Oct;54(29):8700-5

Spectral emittance is a key topic in the study of new compositions, depositions, and mechanical machining of materials for solar absorption and for renewable energies in general. The present work reports on the realization and testing of a new experimental facility for the measurement of directional spectral emittance in the range of 2.5-20 μm. Our setup provides emittance spectral information in a completely controlled environment at medium-high temperatures up to 1200 K. We describe the layout and first tests on the device, comparing the results obtained for hafnium carbide and tantalum diboride ultrarefractory ceramic samples to previous quasi-monochromatic measurements carried out in the PROMES-CNRS (PROcedes, Materiaux et Energie Solaire- Centre National de la Recherche Scientifique, France) solar furnace, obtaining a good agreement. Finally, to assess the reliability of the widely used approach of estimating the spectral emittance from room-temperature reflectance spectrum, we compared the calculation in the 2.5-17 μm spectral range to the experimental high-temperature spectral emittance, obtaining that the spectral trend of calculated and measured curves is similar but the calculated emittance underestimates the measured value.
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http://dx.doi.org/10.1364/AO.54.008700DOI Listing
October 2015

Fat emulsions as diffusive reference standards for tissue simulating phantoms?

Appl Opt 2012 Oct;51(30):7176-82

Dipartimento di Fisica e Astronomia dell'Università degli Studi di Firenze, Firenze, Italy.

Intralipid 20% was recently suggested as a diffusive reference standard for tissue simulating phantoms. In this work, we extend previously obtained results to other fat emulsions, specifically Intralipid 10%, Intralipid 30%, Lipovenoes 10%, Lipovenoes 10% PhosphoLipid Reduced, Lipovenoes 20%, Lipofundin S 10%, and Lipofundin S 20%. Of particular importance for practical applications, our measurements carried out at a wavelength of 751 nm show the following features. First, these products show high stability and small batch-to-batch variations in their diffusive optical properties, similar to Intralipid 20%. Second, the absorption coefficient of Intralipid, Lipovenoes, and Lipofundin S are very similar and their measured values are within the experimental errors; moreover the reduced scattering coefficient of Intralipid 20%, Lipovenoes 20%, and Lipofundin S 20% are similar and their measured values are within 5%. Third, the reduced scattering coefficient of Intralipid 10% and Intralipid 30% can be scaled from that of Intralipid 20% with an error of 9% and 2%, respectively. A similar scaling property is valid for Lipovenoes and Lipofundin S. We have verified that this scaling property depends on the composition of the fat emulsions: If the ingredients exactly scale with the concentration then the reduced scattering coefficient almost exactly scale as well.
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http://dx.doi.org/10.1364/AO.51.007176DOI Listing
October 2012

The skylight gradient of luminance helps sandhoppers in sun and moon identification.

J Exp Biol 2012 Aug;215(Pt 16):2814-9

Dipartimento Di Biologia Evoluzionistica, Università di Firenze, Via Romana 17, 50125 Firenze, Italy.

To return to the ecologically optimal zone of the beach, the sandhopper Talitrus saltator (Montagu) maintains a constant sea-land direction based on the sun and moon compasses. In this study, we investigated the role of the skylight gradient of luminance in sun and moon identification under natural and artificial conditions of illumination. Clock-shifted (inverted) sandhoppers tested under the sun (during their subjective night) and under the full moon (during their subjective day) exhibit orientation in accordance with correct identification of the sun and the moon at night. Tested in artificial conditions of illumination at night without the artificial gradient of luminance, the artificial astronomical cue is identified as the moon even when the conditions of illumination allow sun compass orientation during the day. When the artificial gradient of luminance is added, the artificial astronomical cue is identified as the sun. The role of the sky gradient of luminance in sun and moon identification is discussed on the basis of present and past findings.
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http://dx.doi.org/10.1242/jeb.069542DOI Listing
August 2012

Carbon nanohorn-based nanofluids: characterization of the spectral scattering albedo.

Nanoscale Res Lett 2012 Feb 1;7(1):96. Epub 2012 Feb 1.

National Research Council-National Institute of Optics (CNR-INO), Largo E, Fermi, 6, Florence, 50125, Italy.

The full characterization of the optical properties of nanofluids consisting of single-wall carbon nanohorns of different morphologies in aqueous suspensions is carried out using a novel spectrophotometric technique. Information on the nanofluid scattering and absorption spectral characteristics is obtained by analyzing the data within the single scattering theory and validating the method by comparison with previous monochromatic measurements performed with a different technique. The high absorption coefficient measured joint to the very low scattering albedo opens promising application perspectives for single-wall carbon nanohorn-based fluid or solid suspensions. The proposed approximate approach can be extended also to other low-scattering turbid media.PACS: 78.35.+c Brillouin and Rayleigh scattering, other light scattering; 78.40.Ri absorption and reflection spectra, fullerenes and related materials; 81.05.U- carbon/carbon-based materials; 78.67.Bf optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures, nanocrystals, nanoparticles, and nanoclusters.
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http://dx.doi.org/10.1186/1556-276X-7-96DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3292941PMC
February 2012

Absorption and scattering properties of carbon nanohorn-based nanofluids for direct sunlight absorbers.

Nanoscale Res Lett 2011 Apr 4;6(1):282. Epub 2011 Apr 4.

National Institute of Optics, National Council of Research, Firenze, 50125, Italy.

In the present work, we investigated the scattering and spectrally resolved absorption properties of nanofluids consisting in aqueous and glycol suspensions of single-wall carbon nanohorns. The characteristics of these nanofluids were evaluated in view of their use as sunlight absorber fluids in a solar device. The observed nanoparticle-induced differences in optical properties appeared promising, leading to a considerably higher sunlight absorption with respect to the pure base fluids. Scattered light was found to be not more than about 5% with respect to the total attenuation of light. Both these effects, together with the possible chemical functionalization of carbon nanohorns, make this new kind of nanofluids very interesting for increasing the overall efficiency of the sunlight exploiting device. PACS: 78.40.Ri, 78.35.+c, 78.67.Bf, 88.40.fh, 88.40.fr, 81.05.U.
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http://dx.doi.org/10.1186/1556-276X-6-282DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3211347PMC
April 2011

Colorimetric comparison of light-filtering intraocular lenses and human crystalline lenses at various ages.

J Cataract Refract Surg 2011 Apr;37(4):758-62

Department of Clinical Physiopathology, University of Florence, Florence, Italy.

Purpose: To perform colorimetric characterization of 2 blue light-filtering intraocular lens (IOL) models and an IOL that filters ultraviolet-violet (UV-v) light and compare the charactizations with those of a standard UV light-filtering IOL and the human crystalline lens at various ages.

Setting: Department of Clinical Physiopathology, University of Florence, and National Institute of Applied Optics, CNR, Florence, Italy.

Design: Experimental study.

Methods: Three IOLs of each model with different dioptric powers (16.0, 21.0, and 26.0 diopters) were analyzed. The colorimetric coordinates of the IOLs were calculated by measuring their transmission spectra using a microspectroscopy technique. Subsequently, a parameter (ΔE) that was proportional to the perceived color differences was defined. The results of the IOLs and of the human crystalline lens at different ages (4, 22, 41, 53, and 72 years; values taken from the literature) were compared. The colorimetric analysis was performed using Commission Internationale de l'Éclairage standards.

Results: The maximum ΔE value was with the standard UV light-filtering IOL at any crystalline lens age and was greatest with a 72-year-old human lens. The minimum ΔE value was obtained for both blue light-filtering IOLs with middle-aged human lenses.

Conclusions: None of the analyzed IOLs had the same colorimetric performance of the human crystalline lens. The 2 blue light-filtering IOLs best reproduced yellowing of the human lens at 40 to 50 years of age.

Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.
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http://dx.doi.org/10.1016/j.jcrs.2010.10.053DOI Listing
April 2011

Seawater Ca2+ concentration influences solar orientation in Talitrus saltator (Crustacea, Amphipoda).

J Exp Biol 2009 Mar;212(Pt 6):797-801

Dipartimento di Biologia Evoluzionistica, Via Romana 17, Università di Firenze, Firenze, 50125, Italy.

The role of salinity in the ecophysiology of many intertidal invertebrates has been extensively investigated. Calcium (Ca(2+)), magnesium (Mg(2+)), potassium (K(+)) and sodium (Na(+)) are the major constituents of seawater and it has been demonstrated that sandhoppers tested under the sun in diluted seawater (3.5 per thousand) head seaward, instead of going landward as expected. Therefore, the variation in seawater salinity (from 35 per thousand to 3.5 per thousand) influences their directional choice. This paper investigates the contribution of different cations to the sea-land directional choice of Talitrus saltator (Crustacea, Amphipoda) by the sun compass orientation mechanism. Results of releases carried out in basic seawater selectively deprived of Ca(2+), Mg(2+) or K(+) and containing the same concentration of Na(+) indicate that only the reduction in Ca(2+) concentration affects the capacity of solar orientation. The pH does not influence the directional choice of sandhoppers and nor do small variations in salinity in the range 32-39 per thousand. Moreover, the clear photopositive tendency registered in experiments of phototaxis in Ca(2+)-deprived seawater indicates that the absence of Ca(2+) does not affect the normal functioning of the visual cells. Therefore, our results show that Ca(2+) seawater concentration is important for the correct functioning of one of the principal mechanisms of orientation in supralittoral amphipods and it could affect their survival in the field.
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http://dx.doi.org/10.1242/jeb.025452DOI Listing
March 2009

A new method based on contact surface profilometry for quantitative measurement of resorbed bone volume.

Phys Med 2005 January - March;21(1):41-6

Dept. of Clinical Physiopathology, Medical Physics Sect. University of Florence, Viale Pieraccini 6, I 50139 Florence (Italy).

Bone is a dynamic tissue. Its continuous remodeling depends on the balance between bone formation and bone resorption. These two processes are carried out by specialized cells called osteoblast and ostreoclast respectively. The osteoclastic bone resorption consists in degradation of the mineral and collagen components of bone. The study of bone turnover requires accurate assessment of osteoclastic bone resorption, that becomes even more important in pathologic bone loss due to the uncoupling between bone formation and bone resorption. Osteoclastic activity is diffucult to measure. Many techniques, generally based on the detection of the resorbing lacunae (lacunae (pits) due to the bone degradation, allow to estimate bone resorption, but none of them quantitatively and directly measures the volume of resorbed bone. We propose a reliable and relatively simple method, based on contact surfact profilometry, to evaluate directly and quantitatively the volume of resorbed bone. The method has the following advantages:
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http://dx.doi.org/10.1016/S1120-1797(05)80018-3DOI Listing
October 2012

AcrySof Natural intraocular lens optical characteristics during and after different doses of ultraviolet-visible light illumination.

J Cataract Refract Surg 2006 Nov;32(11):1961-5

Department of Oto-Neuro-Ophthalmological Surgical Sciences-Eye Clinic, University of Florence, Italy.

Purpose: To determine the optical transmission properties of a recently introduced intraocular lens (IOL) (AcrySof Natural SN60AT, Alcon Laboratories) and compare them with those of a conventional IOL (AcrySof SA60AT, Alcon Laboratories) after ultraviolet (UV)-visible light irradiation.

Setting: Eye Clinic and Department of Clinical Physiopathology, University of Florence, and the National Institute of Applied Optics, Florence, Italy.

Methods: Two IOLs, the AcrySof Natural with a UV and blue-light filter and the AcrySof without a blue-light filter, were studied. Three IOLs of each model with different dioptric powers were examined in two experimental setups. The samples were stressed with very high irradiance to reproduce light aging, and the transmission properties of the IOLs were studied.

Results: No significant decrease in transmission was found at a UV-visible light dose equivalent to 100 years of light aging.

Conclusion: The AcrySof Natural IOL has stable optical characteristics.
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http://dx.doi.org/10.1016/j.jcrs.2006.06.024DOI Listing
November 2006

Green land and blue sea: a coloured landscape in the orientation of the sandhopper Talitrus saltator (Montagu) (Amphipoda, Talitridae).

J Exp Biol 2006 Jul;209(Pt 13):2509-14

Dipartimento di Biologia Animale e Genetica, Università di Firenze, Via Romana 17, 50125 Firenze, Italy.

The use of the landscape in the zonal recovery of Talitrus saltator (Montagu) was demonstrated in the past using natural and artificial landscapes. Here we evaluate the importance of colour in the landscape orientation of sandhoppers. Adult individuals of T. saltator were released in a Plexiglas bowl under the sun, with a view of an artificial landscape: a black cardboard strip or a pair of differently coloured filters, each occupying 180 degrees of the horizon. Our results not only confirm the influence of the black and white artificial landscape-based compass cue on the zonal orientation of T. saltator, but also show that vision of a blue and green artificial landscape affects the direction of orientation; in fact, the orientation agreed with the directional indication of the landscape even when it contrasted with the sun compass indication. The same result was obtained with a blue-grey and green-grey landscape, but not with pairs of grey filters. Therefore, in the sandhoppers' visual world, a coloured landscape that matches the prevalent natural field colours greatly contributes to their directional choice.
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http://dx.doi.org/10.1242/jeb.02300DOI Listing
July 2006

Moon orientation in adult and young sandhoppers under artificial light.

Proc Biol Sci 2005 Oct;272(1577):2189-94

Dipartimento di Biologia Animale e Genetica, Università di Firenze, Via Romana 17, 50125 Firenze, Italy.

Our experiments, carried out at night and during the day on adults and laboratory-born young of the sandhopper Talitrus saltator, deal with the identification and use of the moon as an orientating factor. Sandhoppers were released in an apparatus (a Plexiglas dome) that produced a scenario similar to the natural one (with artificial sky, moon or sun illuminated at different intensities). When tested at night, the adult and young sandhoppers used the artificial moon like the natural one, independently of the intensity of illumination of the artificial sky and moon. In other words, sandhoppers tested at night always identified the artificial moon as the moon and never as the sun. In daytime releases, the seaward orientation failed at low intensities of artificial sky and sun illumination (3.07 and 1.55 microW cm2, respectively), whereas the sun compass was used effectively at higher levels of artificial sun and sky illumination. The innate ability of moon compass orientation in inexpert young sandhoppers was demonstrated even under artificial light.
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http://dx.doi.org/10.1098/rspb.2005.3199DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1559952PMC
October 2005

Optical characterization of a radiochromic film by total reflectance and transmittance measurements.

Med Phys 2004 Jul;31(7):2147-54

Laser Center for Medical Application-CEO, Department of Clinical Physiopathology, University of Florence, and Sezione A INFM, Viale G. Pieraccini 6, 50139 Florence, Italy.

The GafChromic film (GCF) MD-55-2, a radiochromic material, was examined for its optical properties through total reflectance and transmittance measurements in visible spectrum (400-700 nm). By using a multilayer model of the film and Kubelka-Munk's (KM) theory, absorption and scattering coefficients of the film sensitive layer (K and S, respectively) were obtained from measurements of irradiated and nonirradiated slides. This has allowed calculation of the absorbance A(KM) of the sensitive layer of the GCF. The model easily splits scattering from absorption. Unlike absorption, scattering is essentially insensitive to irradiation dose and decreases slowly as the wavelength increases. The scattering effect is predominant over absorption in the 400-500 nm range, while beyond 600 nm absorption prevails. The A(KM) absorbance of the sensitive layer was calculated using the K coefficient and compared with the optical densities (OD) measured considering only ballistic photons (as in a standard spectrophotometer) as well as the optical densities measured collecting all the transmitted photons (as in many densitometers). The values of A(KM) found were always lower than OD measured by the other methods and they had the best linearity on the whole visible range. These data support the hypothesis that the sensitive layer reacts to irradiation more linearly than that shown by measurements using standard commercial devices. However, in the 600-680 nm range, correction is not very important because absorption is predominant over scattering. When GCF is used for imaging, scattering produces a loss of spatial information. Consequently, it is necessary to collect only ballistic photons and to correct absorbance by K and S coefficients.
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http://dx.doi.org/10.1118/1.1764701DOI Listing
July 2004