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Artículos de revistas sobre el tema "Optical indices"

Autor: Grafiati

Publicado: 25 de mayo de 2024

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1

Rubin, M., K. von Rottkay, S. J. Wen, N. Özer y J. Slack. "Optical indices of lithiated electrochromic oxides". Solar Energy Materials and Solar Cells 54, n.º 1-4 (julio de 1998): 49–57. http://dx.doi.org/10.1016/s0927-0248(97)00222-5.

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2

von Rottkay, K., M. Rubin y S. J. Wen. "Optical indices of electrochromic tungsten oxide". Thin Solid Films 306, n.º 1 (agosto de 1997): 10–16. http://dx.doi.org/10.1016/s0040-6090(97)00254-x.

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3

Larouche, Stéphane y Ludvik Martinu. "Optical filters with prescribed optical thickness and refined refractive indices". Applied Optics 47, n.º 22 (28 de julio de 2008): 4140. http://dx.doi.org/10.1364/ao.47.004140.

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4

Kosowski, Adrian. "Forwarding and optical indices of a graph". Discrete Applied Mathematics 157, n.º 2 (enero de 2009): 321–29. http://dx.doi.org/10.1016/j.dam.2008.03.002.

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5

Shreve, Cheney M., Gregory S. Okin y Thomas H. Painter. "Indices for estimating fractional snow cover in the western Tibetan Plateau". Journal of Glaciology 55, n.º 192 (2009): 737–45. http://dx.doi.org/10.3189/002214309789470996.

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AbstractSnow cover in the Tibetan Plateau is highly variable in space and time and plays a key role in ecological processes of this cold-desert ecosystem. Resolution of passive microwave data is too low for regional-scale estimates of snow cover on the Tibetan Plateau, requiring an alternate data source. Optically derived snow indices allow for more accurate quantification of snow cover using higher-resolution datasets subject to the constraint of cloud cover. This paper introduces a new optical snow index and assesses four optically derived MODIS snow indices using Landsat-based validation scenes: MODIS Snow-Covered Area and Grain Size (MODSCAG), Relative Multiple Endmember Spectral Mixture Analysis (RMESMA), Relative Spectral Mixture Analysis (RSMA) and the normalized-difference snow index (NDSI). Pearson correlation coefficients were positively correlated with the validation datasets for all four optical snow indices, suggesting each provides a good measure of total snow extent. At the 95% confidence level, linear least-squares regression showed that MODSCAG and RMESMA had accuracy comparable to validation scenes. Fusion of optical snow indices with passive microwave products, which provide snow depth and snow water equivalent, has the potential to contribute to hydrologic and energy-balance modeling in the Tibetan Plateau.

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6

Gasparri, D., L. Morelli, V. D. Ivanov, P. François, A. Pizzella, L. Coccato, E. M. Corsini, E. Dalla Bontà, L. Costantin y M. Cesetti. "Near-infrared spectroscopic indices for unresolved stellar populations – II. Index measurements". Monthly Notices of the Royal Astronomical Society 507, n.º 4 (24 de agosto de 2021): 4669–83. http://dx.doi.org/10.1093/mnras/stab2412.

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ABSTRACT We measured the equivalent width of a large set of near-infrared (NIR, 0.8–2.4$\ \mu$m) line-strength indices in XShooter medium-resolution spectra of the central regions of 14 galaxies. We found that two aluminum indices, Al at 1.31 μm and Al1 at 1.67 μm, and two CO indices, CO1 at 1.56 μm and CO4 at 1.64 μm, are tightly correlated with the velocity dispersion. Moreover, the NIR Al and CO1 indices show strong correlations with the optical Mg2 and Mgb indices, which are usually adopted as α/Fe-enhancement diagnostics. The molecular FeH1 index at 1.58 μm correlates tightly with the optical 〈Fe〉 and [MgFe]′ indices, which are used as total metallicity diagnostics. The NIR Paβ index at 1.28 μm has a behaviour similar to the optical Hβ index, which is a diagnostic of mean age. We defined two new composite indices, 〈Al〉 and [AlFeH], as possible candidates to be used as NIR diagnostics of total metallicity and α/Fe enhancement. The NIR 〈Al〉 index has a strong correlation with the optical Mg2 and Mgb indices, while the [AlFeH] index is tightly correlated with the optical 〈Fe〉 and [MgFe]′ indices. The distribution of the data points in the NIR Paβ–〈Al〉 and Paβ–[AlFeH] diagrams mimics that in the optical [MgFe]′–Hβ and Mgb–〈Fe〉 diagrams, which are widely used to constrain the properties of the unresolved stellar populations. We concluded that some NIR line-strength indices could be useful in studying stellar populations as well as in fine-tuning stellar population models.

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7

Gil, José Jorge y Eusebio Bernabeu. "Depolarization and Polarization Indices of an Optical System". Optica Acta: International Journal of Optics 33, n.º 2 (febrero de 1986): 185–89. http://dx.doi.org/10.1080/713821924.

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8

Qin, Fangli y R. K. Li. "Predicting refractive indices of the borate optical crystals". Journal of Crystal Growth 318, n.º 1 (marzo de 2011): 642–44. http://dx.doi.org/10.1016/j.jcrysgro.2010.08.037.

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9

Rodríguez-Caballero, E., P. Escribano, C. Olehowski, S. Chamizo, J. Hill, Y. Cantón y B. Weber. "Transferability of multi- and hyperspectral optical biocrust indices". ISPRS Journal of Photogrammetry and Remote Sensing 126 (abril de 2017): 94–107. http://dx.doi.org/10.1016/j.isprsjprs.2017.02.007.

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10

He, Yingran, Sailing He, Jie Gao y Xiaodong Yang. "Nanoscale metamaterial optical waveguides with ultrahigh refractive indices". Journal of the Optical Society of America B 29, n.º 9 (29 de agosto de 2012): 2559. http://dx.doi.org/10.1364/josab.29.002559.

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11

Bueno, Juan M. "Indices of linear polarization for an optical system". Journal of Optics A: Pure and Applied Optics 3, n.º 6 (9 de octubre de 2001): 470–76. http://dx.doi.org/10.1088/1464-4258/3/6/308.

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12

Abreu-Gonzalez, Rodrigo, Marta Gonzalez-Hernandez, Cristina Pena-Betancor, Paloma Rodriguez-Esteve y Manuel Gonzalez De La Rosa. "New visual field indices of disharmony for early diagnosis of glaucoma, alone or associated with conventional parameters". European Journal of Ophthalmology 28, n.º 5 (6 de abril de 2018): 590–97. http://dx.doi.org/10.1177/1120672118762668.

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Purpose: To evaluate the specificity of new perimetric indices based on harmony, alone and in combination with structural data, for glaucoma detection. Methods: In this prospective observational cross-sectional study, one eye of 105 healthy subjects and 97 early and suspect glaucomas were sequentially included and examined with Cirrus optical coherence tomography, twice with OCULUS Smartfield perimeter (SPARK strategy) and twice with Humphrey Analyzer (24-2 SITA-Fast) at the Ophthalmology Department from the University Hospital La Candelaria. Disharmony in the visual field was evaluated including vertical threshold symmetry, threshold rank), and homogeneity (threshold standard deviation from its maximum) using the patient himself/herself as a reference. We also evaluated disharmony in combination with the mean deviation and the pattern standard deviation in a single index (mismatch) and various combinations of morphological and functional indices. Combinations used a new score based on values above certain critical cut-off levels of each index. Results: For 95% specificity, the highest sensitivities were as follows: vertical cup/disc ratio: 28.9%; SPARK threshold rank: 29.9%; and SITA-Fast threshold standard deviation: 28.9%. For the combined indices and 100% specificity, they were 5 SPARK indices mismatch: 10.3%; 5 SITA-Fast indices mismatch: 11.3%; 8 optical coherence tomography indices: 21.9%; 13 SPARK and optical coherence tomography indices: 27.8%; and 13 SITA-Fast and optical coherence tomography indices: 32.0%. Conclusion: Disharmony combined with normative value-based indices and/or optical coherence tomography indices is useful for very specific early diagnosis of glaucoma.

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13

Tanase, M. A., R. Kennedy y C. Aponte. "Fire severity estimation from space: a comparison of active and passive sensors and their synergy for different forest types". International Journal of Wildland Fire 24, n.º 8 (2015): 1062. http://dx.doi.org/10.1071/wf15059.

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Monitoring fire effects at landscape level is viable from remote sensing platforms providing repeatable and consistent measurements. Previous studies have estimated fire severity using optical and synthetic aperture radar (SAR) sensors, but to our knowledge, none have compared their effectiveness. Our study carried out such a comparison by using change detection indices computed from pre- and post-fire Landsat and L-band space-borne SAR datasets to estimate fire severity for seven fires located on three continents. Such indices were related to field-estimated fire severity through empirical models, and their estimation accuracy was compared. Empirical models based on the joint use of optical and radar indices were also evaluated. The results showed that optic-based indices provided more accurate fire severity estimates. On average, overall accuracy increased from 61% (SAR) to 76% (optical) for high-biomass forests. For low-biomass forests (i.e. aboveground biomass levels below the L-band saturation point), radar indices provided comparable results; overall accuracy was only slightly lower when compared with optical indices (69% vs 73%). The joint use of optical and radar indices decreased the estimation error and reduced misclassification of unburned forest by 9% for eucalypt and 3% for coniferous forests.

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14

Haug, K. "Continuum Distributions and Line Profiles of UX UMa-Type Novalike Systems". International Astronomical Union Colloquium 93 (1987): 91–102. http://dx.doi.org/10.1017/s0252921100104683.

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AbstractCombined UV, optical and, in part, IR continuum distributions of the UX UMa-systems CPD-48°1577, V3885 Sgr, RW Sex and of the recently discovered cataclysmic system PHL 227 were determined from multi-wavelength spectroscopic and photometric data to search for general characteristics of these systems. The observed variations of the UV to IR spectral indices are qualitatively very similar for all systems, whereas the absolute values show significant differences in the far and near UV ranges. The wavelength dependence of the optical and IR spectral indices as well as the variations of the Balmer line profiles lie within the range of model spectra of optically thick and stationary accretion disks with stellar atmosphere characteristics. The different behavior of the far UV spectral indices can be explained by the excess radiation from an extended and optically thick boundary layer, which depends mainly on the orbital inclination.

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15

Cai, Wenting, Shuhe Zhao, Yamei Wang, Fanchen Peng, Joon Heo y Zheng Duan. "Estimation of Winter Wheat Residue Coverage Using Optical and SAR Remote Sensing Images". Remote Sensing 11, n.º 10 (15 de mayo de 2019): 1163. http://dx.doi.org/10.3390/rs11101163.

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As an important part of the farmland ecosystem, crop residues provide a barrier against water erosion, and improve soil quality. Timely and accurate estimation of crop residue coverage (CRC) on a regional scale is essential for understanding the condition of ecosystems and the interactions with the surrounding environment. Satellite remote sensing is an effective way of regional CRC estimation. Both optical remote sensing and microwave remote sensing are common means of CRC estimation. However, CRC estimation based on optical imagery has the shortcomings of signal saturation in high coverage areas and susceptibility to weather conditions, while CRC estimation using microwave imagery is easily influenced by soil moisture and crop types. Synergistic use of optical and microwave remote sensing information may have the potential to improve estimation accuracy. Therefore, the objectives of this study were to: (i) Analyze the correlation between field measured CRC and satellite derived variables based on Sentinel-1 and Sentinel-2, (ii) investigate the relationship of CRC with new indices (OCRI-RPs) which combine optical crop residues indices (OCRIs) and radar parameters (RPs), and (iii) to estimate CRC in Yucheng County based on OCRI-RPs by optimal subset regression. The correlations between field measured CRC and satellite derived variables were evaluated by coefficient of determination (R2) and root mean square error (RMSE). The results showed that the normalized difference tillage index (NDTI) and radar indices 2 (RI2) had relatively higher correlations with field measured CRC in OCRIs and RPs (R2 = 0.570, RMSE = 6.560% and R2 = 0.430, RMSE = 7.052%, respectively). Combining OCRIs with RPs by multiplying each OCRI with each RP could significantly improve the ability of indices to estimate CRC, as NDTI × RI2 had the highest R2 value of 0.738 and lowest RMSE value of 5.140%. The optimal model for CRC estimation by optimal subset regression was constructed by NDI71 × σ V V 0 and NDTI × σ V H 0 , with a R2 value of 0.770 and a RMSE value of 4.846%, which had a great improvement when compared with the best results in OCRIs and RPs. The results demonstrated that the combination of optical remote sensing information and microwave remote sensing information could improve the accuracy of CRC estimation.

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16

Barczak, K., T. Pustelny, D. Dorosz y J. Dorosz. "New Optical Glasses with High Refractive Indices for Applications in Optical Current Sensors". Acta Physica Polonica A 116, n.º 3 (septiembre de 2009): 247–49. http://dx.doi.org/10.12693/aphyspola.116.247.

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17

Kováč, Daniel, Alexander Ač, Ladislav Šigut, Karel Klem y Otmar Urban. "Optical indicators of plant physiological activity". Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis 60, n.º 3 (2012): 101–10. http://dx.doi.org/10.11118/actaun201260030101.

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Retrieving information on the plant physiological status from spectral reflectance is a challenging task in many ways. The easiest way to get the information is through normalized vegetation indices, that are based on a normalization of reflectance in specific wavebands. Beside the most common spectral indices such as Photochemical Reflectance Index PRI or Normalized Difference Vegetation Index NDVI, several new indices has been proposed during the past decade as potential physiological indicators. In this paper, the performance of several of them for determining the physiological status of the foliage is evaluated on an experimental Norway spruce needles (Picea abies (L.) Karst) plot. Four needle classess of 27 years old spruce have been sampled throughout cloudy and sunny day. Needle classes were represented by the needles of the branchlets of the 4th, 7th, 9th and 12th whorls. Study was conducted on one-year old needles and sampling ran over several times a day to separate influence of dynamic processess on parameters. Results show that the ratio of reflectance in the green and red region (presented as ratio of reflectance at 560 nm and 694 nm) outperforms the others examinated vegetation indices, and suggest that it would be best suited for the characterization of the leaf status. Being always the highest in the uppermost part of the crown and the lowest in shaded part of the crown, parameter is strictly stratificated throughout the crown. Furthermore, parameter values correspond with intensity of physiological processess ongoing in needles during midday. The values of the other indicators seem to be affected by leaf pigment content and morphology too much. Neither PRI nor NDVI were able to distinguish differences in needle properties sufficiently.

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18

Irshad, R., R. G. Grainger, D. M. Peters, R. A. McPheat, K. M. Smith y G. Thomas. "Laboratory measurements of the optical properties of sea salt aerosol". Atmospheric Chemistry and Physics 9, n.º 1 (13 de enero de 2009): 221–30. http://dx.doi.org/10.5194/acp-9-221-2009.

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Abstract. The extinction spectra of laboratory generated sea salt aerosols have been measured from 1 μm to 20 μm using a Bruker 66v/S FTIR spectrometer. Concomitant measurements include temperature, pressure, relative humidity and the aerosol size distribution. The refractive indices of the sea salt aerosol have been determined using a simple harmonic oscillator band model (Thomas et al., 2004) for aerosol with relative humidities at eight different values between 0.4% to 86%. The resulting refractive index spectra show significant discrepancies when compared to existing sea salt refractive indices calculated using volume mixing rules (Shettle and Fenn, 1979). Specifically, an additional band is found in the refractive indices of dry sea salt aerosol and the new data shows increased values of refractive index at almost all wavelengths. This implies that the volume mixing rules, currently used to calculate the refractive indices of wet sea salt aerosols, are inadequate. Furthermore, the existing data for the real and imaginary parts of the refractive indices of dry sea salt aerosol are found not to display the Kramers-Kronig relationship. This implies that the original data used for the volume mixing calculations is also inaccurate.

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19

Somashekar, R. y M. S. Madhava. "Refractive Indices, Densities and Optical Anisotropy of Cholesteryl Oleate". Molecular Crystals and Liquid Crystals 147, n.º 1 (enero de 1987): 79–84. http://dx.doi.org/10.1080/00268948708084625.

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20

Gan, Heng-Soon, Hamid Mokhtar y Sanming Zhou. "Forwarding and optical indices of 4-regular circulant networks". Journal of Discrete Algorithms 35 (noviembre de 2015): 27–39. http://dx.doi.org/10.1016/j.jda.2015.09.002.

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21

Kozlova, N. S., O. A. Busanov, E. V. Zabelina, A. P. Kozlova y V. M. Kasimova. "Optical properties and refractive indices of Gd3Al2Ga3O12:Се3+ crystals". Crystallography Reports 61, n.º 3 (mayo de 2016): 474–78. http://dx.doi.org/10.1134/s1063774516030160.

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22

Lo, Yuan-Hsun, Hung-Lin Fu, Yijin Zhang y Wing Shing Wong. "The undirected optical indices of complete m-ary trees". Discrete Applied Mathematics 285 (octubre de 2020): 173–81. http://dx.doi.org/10.1016/j.dam.2020.05.006.

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23

Kozlova, Nina S., Oleg A. Buzanov, Valentina M. Kasimova, Anna P. Kozlova y Evgeniya V. Zabelina. "Optical characteristics of single crystal Gd3Al2Ga3O12 : Ce". Modern Electronic Materials 4, n.º 1 (1 de mayo de 2018): 7–12. http://dx.doi.org/10.3897/j.moem.4.1.33240.

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New emerging high-energy radiation detection techniques are based on the use of rare-earth ion doped materials. There is a great demand for new inorganic scintillators for medical applications, including X-ray and g radiation detection. In these applications, the new scintillating materials must comply with the main requirements such as high optical quality, high light yield, short response time etc. Materials satisfying these requirements include Gd3Al2Ga3O12: Ce (GAGG : Ce) scintillating single crystals. By now the optical characteristics of GAGG : Ce have been studied insufficiently. We have therefore measured the spectral reflectance and transmittance characteristics of these crystals using optical spectroscopy in the 200–750 nm range. We have also measured the absorbance and refractive indices and the extinction coefficients, and assessed the optical band gap for GAGG : Ce crystals. For measuring the refractive indices, we have used two spectrophotometric methods, i.e. by the measured Brewster angle and by the reflectance for low incidence angles, i.e., close to the normal. Based on the results we have drawn up the dispersion functions of the refractive indices.

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24

Yeh, Yen Liang, Cheng Chi Wang, Ming Jyi Jang, Yen Pin Lin y Kuang Sheng Chen. "Determining the Thickness and Refractive Index of a Birefringence by Using an Improved Accurate Measurement System". Key Engineering Materials 364-366 (diciembre de 2007): 510–15. http://dx.doi.org/10.4028/www.scientific.net/kem.364-366.510.

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This paper presents a high-precision, non-destructive measurement system for determining the thickness and refractive indices of birefringent optical wave plates. Significantly, the proposed method enables the two refractive indices of the optical sample to be measured simultaneously. The performance of the proposed system is verified using a commercial quartz optical wave plate with known refractive indices of 1.5518 e n = and 1.5427 o n = , respectively, and a thickness of 452.1428 μm. The experimentally determined values of the refractive indices are found to be 1.55190 e n = and 1.54281 o n = , respectively, while the thickness is found to be 452.189 μm, corresponding to an experimental error of approximately 0.046 μm. The measurement resolution of the proposed system exceeds that of the interferometer hardware itself and provides a simple yet highly accurate means of measuring the principal optical parameters of birefringent glass wave plates.

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25

Gu, Lingxiao, Yanmin Shuai, Congying Shao, Donghui Xie, Qingling Zhang, Yaoming Li y Jian Yang. "Angle Effect on Typical Optical Remote Sensing Indices in Vegetation Monitoring". Remote Sensing 13, n.º 9 (27 de abril de 2021): 1699. http://dx.doi.org/10.3390/rs13091699.

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Optical remote sensing indices play an important role in vegetation information extraction and have been widely serving ecology, agriculture and forestry, urban monitoring, and other communities. Remote sensing indices are constructed from individual bands depending on special characteristics to enhance the typical spectral features for the identification or distinction of surface land covers. With the development of quantitative remote sensing, there is a rapid increasing requirement for accurate data processing and modeling. It is well known that the geometry-induced variation observed in surface reflectance is not ignorable, but the situation of uncertainty thereby introduced into these indices still needs further detailed understanding. We adopted the ground multi-angle hyperspectrum, spectral response function (SRF) of Thematic Mapper (TM), Enhanced Thematic Mapper (ETM+), Operational Land Imager (OLI), Moderate-Resolution Imaging Spectroradiometer (MODIS), and Multi-Spectral Instrument (MSI) optical sensors and simulated their sensor-like spectral reflectance; then, we investigated the potential angle effect uncertainty on optical indices that have been frequently involved in vegetation monitoring and examined the forward/backward effect over both the ground-based level and the actual Landsat TM/ETM+ overlapped region. Our results on the discussed indices and sensors show as following: (1) Identifiable angle effects exist with a more elevated influence than that introduced by band difference among sensors; (2) The absolute difference between forward and backward direction can reach up to −0.03 to 0.1 within bands of the TM/ETM+ overlapped region; (3) The investigation at ground level indicates that there are different variations of angle effect transmitted to each remote sensing index. Regarding cases of crop canopy at various growth phases, most of the discussed indices have more than a 20% relative difference to nadir value except Normalized Difference Vegetation Index (NDVI) and Normalized Difference Water Index (NDWI) with the magnitude lower than 10%, and less than 16% of Normalized Burn Ratio (NBR). For the case of wax maturity stage, the relative difference to nadir value of Enhanced Vegetation Index (EVI), Soil-Adjusted Vegetation Index (SAVI), Ratio Vegetation Index (RVI), Char Soil Index (CSI), NBR, Normalized Difference Moisture Index (NDMI), and SWIR2/NIR exceeded 50%, while the values for NBR and NDMI can reach up to 115.8% and 206.7%, respectively; (4) Various schemes of index construction imply different propagation of angle effect uncertainty. The “difference” indices can partially suppress the directional influence, while the “ratio” indices show high potential to amplify the angle effect. This study reveals that the angle-induced uncertainty of these indices is greater than that induced by the spectrum mismatch among sensors, especially under the case of senescence. In addition, based on this work, indices with a suppressed potential of angle effect are recommended for vegetation monitoring or information retrieval to avoid unexpected effects.

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26

S. Hussein, Hany, Mohamed Hagag y Mohammed Farrag. "Extended Spatial-Index LED Modulation for Optical MIMO-OFDM Wireless Communication". Electronics 9, n.º 1 (16 de enero de 2020): 168. http://dx.doi.org/10.3390/electronics9010168.

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An efficient optical modulation technique for multi-input multi-output (MIMO) orthogonal frequency division multiplexing (OFDM) visible light communication system is proposed in this paper. The proposed modulation technique is termed as extended spatial-index light-emitting diode (LED) modulation. In the proposed technique, the indices (the spatial domain) of the LEDs are exploited in a dynamic style to not only get rid of the optical OFDM time-domain ( OFDM t d ) shaping problem but also to expand the LED indices spatial modulation domain. The indices of the active LEDs in the proposed technique are changed from the two LEDs active situation to the situation where all or several LEDs are active. Moreover, within the selected active LED indices, the power weight distribution and the positions of the OFDM components are varied to expand the resultant spatial domain. Therefore, the proposed technique offers a considerable spectral efficiency improvement over the up-to-date LED index OFDM modulation schemes even with a lower number of LEDs. The key idea of the proposed technique is to maximize the LEDs’ indices spatial position (spatial domain) utilization, where both the power weight allocation and the positions of the complex OFDM time domain components are varying several times over the same active LED indices combination, which improve the optical system spectral efficiency. The simulation results asserted the superiority of the proposed technique, as it improves both the average bit error rate (ABER) and the achievable data rate (R) compared with existing up-to-date OFDM-LED index modulations with even lower computational complexity.

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27

Willey, Ronald R. y Olaf Stenzel. "Designing Optical Coatings with Incorporated Thin Metal Films". Coatings 13, n.º 2 (6 de febrero de 2023): 369. http://dx.doi.org/10.3390/coatings13020369.

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In the world of nanomaterials and meta-materials, thin films are used which are an order of magnitude thinner than historically used in optical thin film coatings. A problem stems from the island structure that is seen as the film nucleates and grows until there is coalescence or percolation of the islands into a nearly continuous film. The application problem is that the indices of refraction, n and k, vary with thickness from zero thickness up to some thickness such as 30 or 40 nanometers for silver. This behavior will be different from material to material and deposition process to deposition process; it is hardly modeled by simple mathematical functions. It has been necessary to design with only fixed thicknesses and associated indices instead. This paper deals with a tool for the practical task of designing optical thin films in this realm of non-bulk behavior of indices of refraction; no new research is reported here. Historically, two applications are known to have encountered this problem because of their thin metal layers which are on the order of 10 nm thick: (1) architectural low emittance (Low-E) coatings on window glazing with thin silver layers, and (2) black mirrors which transmit nothing and reflect as little as possible over the visible spectrum with thin layers of chromium or related metals. The contribution reported here is a tool to remove this software limitation and model thin layers whose indices vary in thickness.

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28

Chen, Meirun y Jianguo Qian. "On f-fault tolerant arc-forwarding and optical indices of all-optical folded hypercubes". Information Processing Letters 109, n.º 15 (julio de 2009): 828–31. http://dx.doi.org/10.1016/j.ipl.2009.04.006.

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29

Cruz y Cruz, Sara, Alejandro Romero-Osnaya y Oscar Rosas-Ortiz. "Balanced Gain-and-Loss Optical Waveguides: Exact Solutions for Guided Modes in Susy-QM". Symmetry 13, n.º 9 (27 de agosto de 2021): 1583. http://dx.doi.org/10.3390/sym13091583.

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The construction of exactly solvable refractive indices allowing guided TE modes in optical waveguides is investigated within the formalism of Darboux–Crum transformations. We apply the finite-difference algorithm for higher-order supersymmetric quantum mechanics to obtain complex-valued refractive indices admitting all-real eigenvalues in their point spectrum. The new refractive indices are such that their imaginary part gives zero if it is integrated over the entire domain of definition. This property, called condition of zero total area, ensures the conservation of optical power so the refractive index shows balanced gain and loss. Consequently, the complex-valued refractive indices reported in this work include but are not limited to the parity-time invariant case.

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30

Ouirimi, Amani, Alex Chamberlain Chime, Nixson Loganathan, Mahmoud Chakaroun, Daan Lenstra y Alexis P. A. Fischer. "Design, Fabrication and Validation of Mixed Order Distributed Feed-Back Organic Diode Laser Cavity". Photonics 10, n.º 6 (8 de junio de 2023): 670. http://dx.doi.org/10.3390/photonics10060670.

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In the context of the quest for the organic laser diode, we address a key challenge to design and fabricate high-quality factor cavities compatible with electrical excitation of organic semiconductors. More precisely, we present the design of DFB micro-cavities for integration in organic laser diodes and their validation under optical pumping. To design high-quality factor mixed-order DFB micro-cavities, we consider the half- and quarter-wavelength multilayered system and use the optical waveguide analysis to quantify the effective indices of the high and low indices, and the matrix transfer method to calculate the reflectances. Matrices of DFB micro-cavities made from different doses and different grating periods were fabricated. We then identified those showing laser emission under optical pumping as an indication of optimal matching of their resonance wavelength with respect to the electroluminescence peak of the organic gain material. Potential applications of organic laser diodes deal with light communication, spectroscopy, sensors, and other applications where heterogenous integration is important.

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31

Hackett, R. "Relating active optical sensor measurements to barley yield". Advances in Animal Biosciences 8, n.º 2 (1 de junio de 2017): 162–66. http://dx.doi.org/10.1017/s204047001700125x.

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The objective of this work was to determine the most appropriate growth stage to make reflectance measurements that would indicate yield in high yielding winter barley crops. The results indicated that where different rates of fertiliser N were applied, at the same crop growth stages, the best relationship between vegetation indices, calculated on the basis of reflectance measurements, and grain yield were found to occur from booting to early grain fill. Where the timing of fertiliser N inputs was different, for a given level of fertiliser N addition, poor correlations between vegetation indices and grain yield during the stem elongation phase were observed.

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32

Zhang, Huixian, Daniel Fiifi Tawia Hagan, Ricardo Dalagnol y Yi Liu. "Forest Canopy Changes in the Southern Amazon during the 2019 Fire Season Based on Passive Microwave and Optical Satellite Observations". Remote Sensing 13, n.º 12 (8 de junio de 2021): 2238. http://dx.doi.org/10.3390/rs13122238.

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Canopy dynamics associated with fires in tropical forests play a critical role in the terrestrial carbon cycle and climate feedbacks. The aim of this study was to characterize forest canopy dynamics in the southern Amazon during the 2019 fire season (July–October) using passive microwave-based vegetation optical depth (VOD) and three optical-based indices. First, we found that precipitation during July–October 2019 was close to the climatic means, suggesting that there were no extreme hydrometeorological events in 2019 and that fire was the dominant factor causing forest canopy anomalies. Second, based on the active fire product (MCD14ML), the total number of active fires over each grid cell was calculated for each month. The number of active fires during the fire season in 2019 was above average, particularly in August and September. Third, we compared the anomalies of VOD and optical-based indices (the normalized difference vegetation index (NDVI), the enhanced vegetation index (EVI), and the normalized burn ratio (NBR)) against the spatiotemporal distribution of fires during July–October 2019. Spatially, the location with a concentrated distribution of significant negative VOD anomalies was matched with the grid cells with fire activities, whereas the concentrated distribution of strong negative anomalies in optical-based indices were found in both burned and unburned grid cells. When we focused on the temporal pattern over the grid cells with fire activity, the VOD and the optical-based indices behaved similarly from July to October 2019, i.e., the magnitude of negative anomalies became stronger with increased fire occurrences and reached the peak of negative anomalies in September before decreasing in October. A discrepancy was observed in the magnitude of negative anomalies of the optical-based indices and the VOD; the magnitude of optical-based indices was larger than the VOD in August–September and recovered much faster than the VOD over the grid cells with relatively low fire activity in October. The most likely reason for their different responses is that the VOD represents the dynamics of both photosynthetic (leaf) and nonphotosynthetic (branches) biomass, whereas optical-based indices are only sensitive to photosynthetic (leaf) active biomass, which recovers faster. Our results demonstrate that VOD can detect the spatiotemporal of canopy dynamics caused by fire and postfire canopy biomass recovery over high-biomass rainforest, which enables more comprehensive assessments, together with classic optical remote sensing approaches.

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33

L. Zhang, X., G. J. Wu, C. L. Zhang, T. L. Xu y Q. Q. Zhou. "What's the real role of iron-oxides in the optical properties of dust aerosols?" Atmospheric Chemistry and Physics Discussions 15, n.º 4 (26 de febrero de 2015): 5619–62. http://dx.doi.org/10.5194/acpd-15-5619-2015.

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Abstract. Iron oxides compounds constitute an important component of mineral dust aerosol. Several previous studies have shown that these minerals are strong absorbers at visible wavelengths and thus that they play a critical role in the overall climate forcing caused by dust aerosol. When compiling a database of complex refractive indices of possible mineral species of iron-oxides to study their optical properties, we found that uniformly continuous optical constants for a single type of iron-oxides in the wavelength range between 0.2 and 50 μm is very scarce and that the use of hematite to represent all molecular or mineral iron-oxides types is a popular hypothesis. However, the crucial problem is that three continuous datasets for complex refractive indices of hematite are employed in climate models, but there are significant differences between them. Thus, the real role of iron-oxides in the optical properties of dust aerosols becomes a key scientific question, and we address this problem by considering different refractive indices, size distributions, and more logical weight fractions and mixing states of hematite. Based on the microscopic observations, a semi-external mixture that employs an external mixture between Fe-aggregates and other minerals and partly internal mixing between iron-oxides and aluminosilicate particles is advised as the optimal approximation. The simulations demonstrate that hematite with a spectral refractive indices from Longtin et al. (1988) shows approximately equal absorbing capacity to the mineral illite over the whole wavelength region from 0.55 to 2.5 μm, and only enhances the optical absorption of aerosol mixture at λ < 0.55 μm. Using the dataset from Querry (1985) may overestimate the optical absorption of hematite at both visible and near-infrared wavelengths. More laboratory measurements of the refractive index of iron-oxides, especially for hematite and goethite in the visible spectrum, should therefore be taken into account when assessing the effect of mineral dust on climate forcing.

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34

Shopa, Yaroslav y Nazar Ftomyn. "Optical Activity of Langatate Crystals". Solid State Phenomena 200 (abril de 2013): 129–33. http://dx.doi.org/10.4028/www.scientific.net/ssp.200.129.

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A calculation technique based on the polarizability theory for optical activity (OA) is applied to derive optical rotatory power (ORP) for the La3Ga5.5Ta0.5O14 (LGT). Dispersions of both the ordinary and extraordinary refractive indices and the ORP are calculated. A comparison of the observed and calculated OA parameters confirms validity of our theoretical calculations.

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35

Ryzhikov, P. S. y V. A. Makarov. "Intrinsic symmetry of nonlocal nonlinear optical susceptibilities". Laser Physics Letters 19, n.º 3 (10 de febrero de 2022): 035401. http://dx.doi.org/10.1088/1612-202x/ac503f.

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Abstract The permutation symmetry relations of the nth order nonlocal nonlinear optical susceptibilities emerging in the absence of absorption are obtained from the basic statements of electrodynamics. The values of the nth order nonlocal nonlinear susceptibility tensor components with swapped frequencies and indices corresponding to the generated electric field and the electric field under the operator of differentiation in the constitutive equation only differ by their signs and signs of the interchanged frequencies. Additionally, there exist n 2 − n relations between three components of this tensor with cyclically permuted indices and frequencies corresponding to the generated field, the field under the operator of differentiation in the constitutive equation and one of the remaining fields involved into nonlinear process under consideration.

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36

Kasim, Azman, H. Azhan, S. Akmal Syamsyir, Mardhiah Abdullah y M. R. S. Nasuha. "Optical Properties of Nd Doped Lead Borotellurite Glass". Materials Science Forum 846 (marzo de 2016): 193–98. http://dx.doi.org/10.4028/www.scientific.net/msf.846.193.

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Many trivalent rare earth ions such as Er3+, Tm3+, Ho3+, Pr3+ and Nd3+ were doped as absorption and emission centers in glass hosts. In this work, lead borotellurite (PBT) glass doped with neodymium ion (Nd3+) has been prepared and characterized by mean of their optical properties. The UV-Vis measurement has been carried out in order to determine the optical band gap energy, reflective indices and the polarizability. Optical absorption spectra of the glass samples are recorded in the range 400–900 nm at room temperature From the result, there are six significant absorption peaks that corresponds to 525 nm, 584 nm, 683 nm, 747 nm, 805 nm and 878 nm wavelength have been observed with the most predominant peak to be used as excitation wavelength is found centered at 584 nm. The energy band gaps as well as the refractive indices were found to vary from 2.50eV to 2.59eV and from 1.89 to 1.96 with mol% of Nd content respectively. Meanwhile, the polarizability shows a similar trend of results to refractive indices as it varies from 5.56 x 10-24 cm3 to 5.63 x 10-24 cm3. These results will be discussed further in details.

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37

Karaca, Cihan, Rodney B. Thompson, M. Teresa Peña-Fleitas, Marisa Gallardo y Francisco M. Padilla. "Evaluation of Absolute Measurements and Normalized Indices of Proximal Optical Sensors as Estimators of Yield in Muskmelon and Sweet Pepper". Remote Sensing 15, n.º 8 (20 de abril de 2023): 2174. http://dx.doi.org/10.3390/rs15082174.

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The generally established protocol for leaf measurement with proximal optical sensors is to use the most recently fully expanded leaf. However, differences in the nitrogen (N) status of lower and upper leaves could possibly be used to enhance optical sensor measurement. Normalized indices that consider both upper and lower leaves have been proposed to improve the assessment of crop N status and yield estimation. This study evaluated whether normalized indices improved the estimation of crop yield from measurements with three different proximal optical sensors: (i) SPAD-502 leaf chlorophyll meter, (ii) Crop Circle ACS 470 canopy reflectance sensor, and (iii) Multiplex fluorescence meter. The study was conducted with sweet pepper (Capsicum annuum L.) and muskmelon (Cucumis melo L.) in plastic greenhouses in Almeria, Spain. Measurements were made on the latest (most recent) leaf (L1), and the second (L2), third (L3) and fourth (L4) fully expanded leaves. Yield estimation models, using linear regression analysis, were developed and validated from the absolute and normalized measurements of the three optical sensors. Overall, the calibration and validation results indicated that the absolute measurements generally had better yield estimation performance than the normalized indices for all the leaves and different leaf profiles. In both species, there was a better performance at the early phenological stages, such as the vegetative and flowering stages, for the absolute and normalized indices for the three optical sensors. Absolute proximal optical sensor measurements on the lower leaves (L2, L3 and L4) slightly improved yield estimation compared to the L1 leaf. Normalized indices that included the L4 leaf (L1–L4) had better yield estimation compared to those using L2 and L3 (e.g., L1–L2 and L1–L3). Of the normalized indices evaluated, the yield performance of the Relative Index (RI), Relative Difference Index (RDI), and Normalized Difference Index (NDI) were very similar, and generally superior to the Difference Index (DI). Overall, the results of this study demonstrated that for three different proximal optical sensors in both muskmelon and sweet pepper (i) normalized indices did not improve yield estimation, and (ii) that absolute measurements on lower leaves (L2, L3 and L4) slightly improved yield estimation performance.

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38

YIN XIN, Lyu MENG-KAI y CHENG DUAN-PING. "THE REFRACTIVE INDICES AND NONLINEAR OPTICAL PROPERTY OF KIO3 CRYSTAL". Acta Physica Sinica 36, n.º 11 (1987): 1492. http://dx.doi.org/10.7498/aps.36.1492.

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39

Olshavsky, Michael y Harry R. Allcock. "Polyphosphazenes with High Refractive Indices: Optical Dispersion and Molar Refractivity". Macromolecules 30, n.º 14 (julio de 1997): 4179–83. http://dx.doi.org/10.1021/ma961628q.

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40

Mozume, T., T. Simoyama y H. Ishikawa. "Indices of refraction of AlGaAsSb by an optical waveguide technique". Journal of Applied Physics 102, n.º 11 (diciembre de 2007): 113111. http://dx.doi.org/10.1063/1.2818101.

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41

Shi, L. P., E. Y. B. Pun y P. S. Chung. "Wavelength dispersion of effective refractive indices of Rb:KTiOPO4 optical waveguides". IEEE Photonics Technology Letters 8, n.º 7 (julio de 1996): 912–14. http://dx.doi.org/10.1109/68.502268.

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42

Silverstein, Steven M., Danielle Paterno, Lindsay Cherneski y Stuart Green. "Optical coherence tomography indices of structural retinal pathology in schizophrenia". Psychological Medicine 48, n.º 12 (13 de diciembre de 2017): 2023–33. http://dx.doi.org/10.1017/s0033291717003555.

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AbstractBackgroundPrior optical coherence tomography (OCT) studies of schizophrenia have identified thinning of retinal layers. However, findings have varied across reports, and most studies have had serious methodological limitations. To address unresolved issues, we determined whether: (1) retinal thinning in schizophrenia occurs independently of comorbid medical conditions that affect the retina; (2) thinning is independent of antipsychotic medication dose; (3) optic nerve parameters are abnormal in schizophrenia; and (4) OCT indices are related to visual and cognitive impairments common in schizophrenia.MethodsA total of 32 people with schizophrenia and 32 matched controls participated. Spectral domain OCT generated data on retinal nerve fiber layer (RNFL), macula, and ganglion cell-inner plexiform layer (GCL-IPL) thickness, in addition to cup volume and the cup-to-disc ratio at the optic nerve head. Subjects with schizophrenia also completed measures of symptoms, visual processing, and IQ.ResultsThe groups did not differ on RNFL, macula, or GCL-IPL thickness. However, thinning of these layers was related to the presence of diabetes or hypertension across the sample as a whole. The schizophrenia group demonstrated enlarged cup volume and an enlarged cup-to-disc ratio in both eyes, which were unrelated to medical comorbidity, but were related to increased cognitive symptoms.ConclusionsPast reports of retinal thinning may be artifacts of medical comorbidity that is over-represented in schizophrenia, or other confounds. However, optic nerve head abnormalities may hold promise as biomarkers of central nervous system abnormality, including cognitive decline, in schizophrenia.

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43

Luzanov, A. V., V. V. Ivanov y R. M. Minyaev. "Disymmetry indices based on optical rotational polarizability of chiral molecules". Journal of Structural Chemistry 39, n.º 2 (septiembre de 1998): 261–67. http://dx.doi.org/10.1007/bf02873627.

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44

Adamiv, V. T., Ya V. Burak, M. M. Romanyuk, G. M. Romanyuk y I. M. Teslyuk. "New nonlinear optical LiKB4O7 single crystals: Dispersion of refractive indices". Optical Materials 29, n.º 11 (julio de 2007): 1501–4. http://dx.doi.org/10.1016/j.optmat.2006.07.018.

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45

Šimon, V., G. Pizzichini y R. Hudec. "Color indices of optical afterglows of long GRBs in theSwiftera". EAS Publications Series 61 (2013): 271–73. http://dx.doi.org/10.1051/eas/1361043.

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46

Olshavsky, Michael A. y Harry R. Allcock. "Polyphosphazenes with High Refractive Indices: Synthesis, Characterization, and Optical Properties". Macromolecules 28, n.º 18 (agosto de 1995): 6188–97. http://dx.doi.org/10.1021/ma00122a028.

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47

Priyadarshi, A., L. Shimin, E. H. Wong, R. Rajoo, S. G. Mhaisalkar y V. Kripesh. "Refractive indices variation with temperature and humidity of optical adhesive". Journal of Electronic Materials 34, n.º 11 (noviembre de 2005): 1378–84. http://dx.doi.org/10.1007/s11664-005-0194-2.

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48

Shultis, J. Kenneth. "Calculated sensitivities of several optical radiometric indices for vegetation canopies". Remote Sensing of Environment 38, n.º 3 (diciembre de 1991): 211–28. http://dx.doi.org/10.1016/0034-4257(91)90090-s.

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49

Lusty, M. E. y M. H. Dunn. "Refractive indices and thermo-optical properties of dye laser solvents". Applied Physics B Photophysics and Laser Chemistry 44, n.º 3 (noviembre de 1987): 193–98. http://dx.doi.org/10.1007/bf00692324.

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50

Goodarzi, F. y B. S. Norford. "Optical Properties of Graptolite Epiderm A Review". Bulletin of the Geological Society of Denmark 35 (1 de junio de 1987): 141–47. http://dx.doi.org/10.37570/bgsd-1986-35-15.

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Studies of optical properties of the skeletal materials of graptolites show progressive changes of reflectance, bireflectance, refractive index and absorptive index with maximum temperatures caused by depths of burial, metamorphism or tectonic disturbance. Samples of Lower Ordovician to Upper Silurian graptolites were selected from across Canada, at locations where the Conodont Alteration Indices of adjacent conodont collections provide temperature control. Maximum reflectance in oil and bireflectance appear to be the characters most diagnostic of maximum temperature and show progressively higher rates of increase at higher temperatures. These factors show potential for sensitive discrimination of temperatures at high levels of Conodont Alteration Indices. Besides depth of burial, variables that have some effect on the optical properties include the composition of rock matrix, thermal metamorphism, mineralization and oxidation. The effects of morphological orientation and the taxonomical attributes of graptolites as yet are uncertain.

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