spectral reflectance
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Difúzna reflexná spektrofotometria je neinvazívna vyšetrovacia metóda založená na optických vlastnostiach kože. Použitie metódy v klinickej praxi je široké, najvýznamnejšie je jej využitie pri hodnotení erytémov rôzneho pôvodu, pigmentových lézií, porúch pigmentácie a pri vyhodnocovaní kožných fototypov a kožných testov. Na našej klinike sme pomocou tejto metódy hodnotili absorpčné vlastnosti normálnej kože a kože s klinickými prejavmi vitiliga v experimentálnej skupine vybraných pacientov vo veku od 3 do 18 rokov života a vývoj cievnych malformácii u detí od novorodeneckého veku do 3 rokov života. Experimentálnym difúznym reflexným spektrofotometrom sme merali nepostihnutú oblasť kože v axile u detských pacientov s fototypom II, III, V a VI. U každého pacienta sa hodnotili spektrálne krivky a z nich obsah a absorpčná charakteristika oxyhemoglobínu, deoxyhemoglobínu a melanínu. Druhou vyšetrovanou skupinou boli pacienti s poruchami pigmentácie, najmä s prejavmi vitiliga. Následne sme sa zamerali na dermatologické choroby s klinickými prejavmi erytému, kde sme hodnotili pomocou spektrálnej absorpčnej krivky intenzitu erytematóznej zložky zápalovej reakcie a monitorovali vývoj cievnych malformácií, predovšetkým hemangiómov. Difúzna reflexná spektrofotometria umožňuje zaraďovať pacientov medzi jednotlivé fototypy, umožňuje monitorovať morfologické zmeny hemangiómu s rastom dieťaťa, určuje množstvo chromofórov, hlavne oxyhemoglobínu v erytematóznych léziách, melanínu v normálnej koži a jeho nedostatok v hypopigmentovaných a depigmentovaných oblastiach kože a v neposlednom rade poskytuje informácie o cievnom prekrvení vyšetrovanej lézie. Podľa našich dát získaných opakovanou neinvazívnou spektrálnou analýzou v oblasti viditeľného svetla je možné predpokladať budúci vývoj hemangiómov v detskom veku a správne manažovať fototerapiu pacientov s vitiligom.
Diffuse reflectance spectrophotometry is a non-invasive method to investigate optical properties of the skin. This method has a wide clinical use in dermatology, especially, in evaluation of erythematous skin diseases, pigmented skin lesions, disorders of pigmentation and skin tests. We used this method to evaluate normal skin and skin with clinical features of vitiligo within a group of children in age from 3 to 18 years and haemangiomas within a group of neonates to 3. year-old infants. We measured reflected visible light from different areas of normal skin, depigmented skin and haemangioma and made a spectral analysis of data acquired. Examinations with special probes are perfomed very quickly, in a non-invasive manner, and it is possible to repeat them more times without any discomfort or any negative impact on infants. This method helps to range patients into different phototype groups, gives unique opportunity to monitor morphological haemangiomas changes during growth of the infant, estimates amount of chromophores, mainly oxyhaemoglobine in erythematous lesions, melanin in normal skin, lack of this chromophore in hypopigmented and depigmented skin and determines blood perfusion in examined lesions. According to our data obtained by repeated non-invasive spectral analysis in visible light we can predict the future development of haemangiomas in childhood and manage phototherapy of vitiliginous skin.
In order to monitor Potentially Toxic Elements (PTEs) in anthropogenic soils on brown coal mining dumpsites, a large number of samples and cumbersome, time-consuming laboratory measurements are required. Due to its rapidity, convenience and accuracy, reflectance spectroscopy within the Visible-Near Infrared (Vis-NIR) region has been used to predict soil constituents. This study evaluated the suitability of Vis-NIR (350-2500 nm) reflectance spectroscopy for predicting PTEs concentration, using samples collected on large brown coal mining dumpsites in the Czech Republic. Partial Least Square Regression (PLSR) and Support Vector Machine Regression (SVMR) with cross-validation were used to relate PTEs data to the reflectance spectral data by applying different preprocessing strategies. According to the criteria of minimal Root Mean Square Error of Prediction of Cross Validation (RMSEPcv) and maximal coefficient of determination (R2cv) and Residual Prediction Deviation (RPD), the SVMR models with the first derivative pretreatment provided the most accurate prediction for As (R2cv) = 0.89, RMSEPcv = 1.89, RPD = 2.63). Less accurate, but acceptable prediction for screening purposes for Cd and Cu (0.66 ˂ R2cv) ˂ 0.81, RMSEPcv = 0.0.8 and 4.08 respectively, 2.0 ˂ RPD ˂ 2.5) were obtained. The PLSR model for predicting Mn (R2cv) = 0.44, RMSEPcv = 116.43, RPD = 1.45) presented an inadequate model. Overall, SVMR models for the Vis-NIR spectra could be used indirectly for an accurate assessment of PTEs' concentrations.
We explored ability of reflectance vegetation indexes (VIs) related to chlorophyll fluorescence emission (R₆₈₆/R₆₃₀, R₇₄₀/R₈₀₀) and de-epoxidation state of xanthophyll cycle pigments (PRI, calculated as (R₅₃₁- R₅₇₀)/(R₅₃₁-R₅₇₀) to track changes in the CO₂ assimilation rate and Light Use Efficiency (LUE) in montane grassland and Norway spruce forest ecosystems, both at leaf and also canopy level. VIs were measured at two research plots using a ground-based high spatial/spectral resolution imaging spectroscopy technique. No significant relationship between VIs and leaf light-saturated CO₂ assimilation (A(MAX)) was detected in instantaneous measurements of grassland under steady-state irradiance conditions. Once the temporal dimension and daily irradiance variation were included into the experimental setup, statistically significant changes in VIs related to tested physiological parameters were revealed. ΔPRI and Δ(R₆₈₆/R₆₃₀) of grassland plant leaves under dark-to-full sunlight transition in the scale of minutes were significantly related to A(MAX) (R² = 0.51). In the daily course, the variation of VIs measured in one-hour intervals correlated well with the variation of Gross Primary Production (GPP), Net Ecosystem Exchange (NEE), and LUE estimated via the eddy-covariance flux tower. Statistical results were weaker in the case of the grassland ecosystem, with the strongest statistical relation of the index R₆₈₆/R₆₃₀ with NEE and GPP.
Four different polymorphs, A, C, D, and E, of succinobucol were isolated and characterized by means of solid-state nuclear magnetic resonance spectroscopy, single crystal and powder X-ray diffraction, differential scanning calorimetry, thermogravimetry, and attenuated total reflection-infrared spectroscopy. From a number of experiments, the same polymorphs (C, D, and E) and an equilibrium phase mixture B consisting of polymorphs C and D were repeatedly gained using different solvents or their mixtures. Although polymorph A was obtained directly from recrystallization only on few occasions, polymorphs C, D, and E proved to be metastable kinetic polymorphs, which slowly transform to a thermodynamically more stable form A during long-term storage. The single-crystal structures of polymorph C and D were determined by X-ray single-crystal diffraction.
- MeSH
- diferenciální skenovací kalorimetrie MeSH
- krystalizace MeSH
- krystalografie rentgenová MeSH
- magnetická rezonanční spektroskopie MeSH
- molekulární modely MeSH
- prášková difrakce MeSH
- probukol analogy a deriváty analýza chemie MeSH
- spektrofotometrie infračervená MeSH
- termogravimetrie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Modeling central auditory neurons in response to complex sounds not only helps understanding neural processing of speech signals but can also provide insights for biomimetics in neuro-engineering. While modeling responses of midbrain auditory neurons to synthetic tones is rather good, modeling those to environmental sounds is less satisfactory. Environmental sounds typically contain a wide range of frequency components, often with strong and transient energy. These stimulus features have not been examined in the conventional approach of auditory modeling centered on spectral selectivity. To this end, we firstly compared responses to an environmental sound of auditory midbrain neurons across 3 subpopulations of neurons with frequency selectivity in the low, middle and high ranges; secondly, we manipulated the sound energy, both in power and in spectrum, and compared across these subpopulations how their modeled responses were affected. The environmental sound was recorded when a rat was drinking from a feeding bottle (called the 'drinking sound'). The sound spectrum was divided into 20 non-overlapping frequency bands (from 0 to 20 kHz, at 1 kHz width) and presented to an artificial neural model built on a committee machine with parallel spectral inputs to simulate the known tonotopic organization of the auditory system. The model was trained to predict empirical response probability profiles of neurons to the repeated sounds. Results showed that model performance depended more on the strong energy components than on the spectral selectivity. Findings were interpreted to reflect general sensitivity to rapidly changing sound intensities at the auditory midbrain and in the cortex.
- MeSH
- akustická stimulace metody MeSH
- krysa rodu rattus MeSH
- mezencefalon * fyziologie MeSH
- neurony fyziologie MeSH
- řeč MeSH
- zvířata MeSH
- zvuk * MeSH
- Check Tag
- krysa rodu rattus MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
Light-harvesting complex II (LHCII) from the marine green macroalga Bryopsis corticulans is spectroscopically characterized to understand the structural and functional changes resulting from adaptation to intertidal environment. LHCII is homologous to its counterpart in land plants but has a different carotenoid and chlorophyll (Chl) composition. This is reflected in the steady-state absorption, fluorescence, linear dichroism, circular dichroism and anisotropic circular dichroism spectra. Time-resolved fluorescence and two-dimensional electronic spectroscopy were used to investigate the consequences of this adaptive change in the pigment composition on the excited-state dynamics. The complex contains additional Chl b spectral forms - absorbing at around 650 nm and 658 nm - and lacks the red-most Chl a forms compared with higher-plant LHCII. Similar to plant LHCII, energy transfer between Chls occurs on timescales from under hundred fs (mainly from Chl b to Chl a) to several picoseconds (mainly between Chl a pools). However, the presence of long-lived, weakly coupled Chl b and Chl a states leads to slower exciton equilibration in LHCII from B. corticulans. The finding demonstrates a trade-off between the enhanced absorption of blue-green light and the excitation migration time. However, the adaptive change does not result in a significant drop in the overall photochemical efficiency of Photosystem II. These results show that LHCII is a robust adaptable system whose spectral properties can be tuned to the environment for optimal light harvesting.
The recently introduced resin composites with a universal shade are claimed to match any tooth color. In this study, it was examined how composite thickness affects the color adjustment of conventional and universal-shade composites to background dentin. Thirty sound human central incisors of various shade were used, and color differences between their intact labial surfaces, exposed dentin surfaces and composite restorations (thickness 1-3 mm) were evaluated. In addition, the translucency, light transmission characteristics, and spectral reflectance of the composites were measured. The results showed that universal-shade composites outperformed conventional composites of A2 shade in the adjustment of hue and chroma (p<0.05) but not in lightness (p>0.05). The color adjustment potential of all composites significantly decreased as their thickness increased (p<0.05). The effect of thickness on Omnichroma and Omnichroma Flow was less marked, presumably because of their higher translucency (p<0.05) and structural coloration which induces light reflectance in the yellow-to-red range.
- MeSH
- barva MeSH
- dentin * MeSH
- lidé MeSH
- složené pryskyřice * chemie MeSH
- testování materiálů MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
This study reports on the successful use of a machine learning approach using attenuated total reflectance Fourier transform infrared (ATR FT-IR) spectroscopy for the classification and prediction of a donor's sex from the fingernails of 63 individuals. A significant advantage of ATR FT-IR is its ability to provide a specific spectral signature for different samples based on their biochemical composition. The infrared spectrum reveals unique vibrational features of a sample based on the different absorption frequencies of the individual functional groups. This technique is fast, simple, non-destructive, and requires only small quantities of measured material with minimal-to-no sample preparation. However, advanced multivariate techniques are needed to elucidate multiplex spectral information and the small differences caused by donor characteristics. We developed an analytical method using ATR FT-IR spectroscopy advanced with machine learning (ML) based on 63 donors' fingernails (37 males, 26 females). The PLS-DA and ANN models were established, and their generalization abilities were compared. Here, the PLS scores from the PLS-DA model were used for an artificial neural network (ANN) to create a classification model. The proposed ANN model showed a greater potential for predictions, and it was validated against an independent dataset, which resulted in 92% correctly classified spectra. The results of the study are quite impressive, with 100% accuracy achieved in correctly classifying donors as either male or female at the donor level. Here, we underscore the potential of ML algorithms to leverage the selectivity of ATR FT-IR spectroscopy and produce predictions along with information about the level of certainty in a scientifically defensible manner. This proof-of-concept study demonstrates the value of ATR FT-IR spectroscopy as a forensic tool to discriminate between male and female donors, which is significant for forensic applications.
The color-matching ability of single-shade composites Omnichroma (OMN) and Omnichroma Flow (OCF) is ensured by structural color, which arises from monodisperse 260 nm spherical fillers. This study evaluated how filler load influences the color adjustment potential of composite restorations to human teeth of various shades. The performance of composites containing the 260 nm spherical fillers -OMN (79 wt%), OCF (71 wt%), and experimental composites R1 (65 wt%), and R2 (60 wt%)- was compared to two conventional A2-shade composites and a transparent composite. Additionally, the translucency parameter, spectral reflectance, and light transmission properties were assessed. Composites with a lower load of the 260 nm spherical fillers exhibited lower light diffusion and lower reflectance in the yellow-to-red range (580-650 nm), which is characteristic for the structural color of OMN and OCF. The best color adjustment was achieved with OCF, presumably due to its high translucency and uniform spectral reflectance.
- MeSH
- barva MeSH
- lidé MeSH
- složené pryskyřice * chemie MeSH
- testování materiálů MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
Leaf chlorophyll content is an important physiological parameter which can serve as an indicator of nutritional status, plant stress or senescence. Signals proportional to the chlorophyll content can be measured non-destructively with instruments detecting leaf transmittance (e.g., SPAD-502) or reflectance (e.g., showing normalized differential vegetation index, NDVI) in red and near infrared spectral regions. The measurements are based on the assumption that only chlorophylls absorb in the examined red regions. However, there is a question whether accumulation of other pigments (e.g., anthocyanins) could in some cases affect the chlorophyll meter readings. To answer this question, we cultivated tomato plants (Solanum lycopersicum L.) for a long time under low light conditions and then exposed them for several weeks (4 h a day) to high sunlight containing the UV-A spectral region. The senescent leaves of these plants evolved a high relative content of anthocyanins and visually revealed a distinct blue color. The SPAD and NDVI data were collected and the spectra of diffusive transmittance and reflectance of the leaves were measured using an integration sphere. The content of anthocyanins and chlorophylls was measured analytically. Our results show that SPAD and NDVI measurement can be significantly affected by the accumulated anthocyanins in the leaves with relatively high anthocyanin content. To describe theoretically this effect of anthocyanins, concepts of a specific absorbance and a leaf spectral polarity were developed. Corrective procedures of the chlorophyll meter readings for the anthocyanin contribution are suggested both for the transmittance and reflectance mode.
- MeSH
- algoritmy MeSH
- anthokyaniny analýza metabolismus MeSH
- chemické modely MeSH
- chlorofyl analýza metabolismus MeSH
- chloroplasty metabolismus MeSH
- listy rostlin metabolismus MeSH
- počítačová simulace MeSH
- Solanum lycopersicum chemie metabolismus účinky záření MeSH
- světlo MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
