Determination of asbestos cement rooftop surface composition using regression analysis and hyper-spectral reflectance data in the visible and near-infrared ranges

The effects of asbestos on human health have spurred numerous studies examining its risks in urban environments. Recent works have shifted towards less-invasive techniques for remote detection and classification of asbestos-cement. In this context, this study combines visible (VIS) and near-infrared (NIR) reflectance data collected in-situ with reference signals from the USGS spectral library, utilizing optimized regression analysis to determine the surface composition of corrugated asbestos-cement rooftops. An outlier filter was successfully implemented to enhance the accuracy of regression calculations, achieving a high level of agreement with actual field observations. The regression analysis revealed varying proportions of weathered cement, hazardous asbestos fibers (specifically chrysotile and cummingtonite), and biological growth (such as lichens and moss). These results are consistent with previous research on the composition of asbestos-cement rooftops, including a comparable field study and XRD analysis conducted in 2019. This underscores the importance of using regression analysis, preceded by an outlier filtering step, on VIS and NIR reflectance data to ascertain the surface composition of asbestos-cement rooftops. This methodology holds potential for application to larger hyperspectral datasets across more extensive sample surfaces and areas.

Asymmetric metamaterial sandwich structure with NIM characteristics for THz imaging application

This study presented a unique, miniaturised asymmetric interconnected vertical stripe (IVS) design for terahertz (THz) frequency applications. Therefore, this research aimed to achieve a frequency response of 0 to 10 THz using a 5 × 5 µm2 Silicon (Si) substrate material. Meanwhile, various parametric examinations were conducted to investigate variations in the performance. For example, the unit cell selection process was carefully examined by using various design structures and modifying the structure by adding split gaps and connecting bars between vertical stripes. Furthermore, the proposed sandwich structure design was used to compute the absorbance and reflectance properties. All the analytical examinations were executed utilising the Computer Simulation Technology (CST) 2019 software. The introduced IVS metamaterial exhibits negative index behaviour and has a single resonance frequency of 5.23 THz with an acceptable magnitude of - 24.38 dB. Additionally, the quadruple-layer IVS structure exhibits optimised transmission coefficient behaviour between 3 and 6 THz and 7 to 9 THz, respectively. However, the magnitude of the transmission coefficient increased with the number of material layers. Besides that, the absorbance study shows that using a quadruple-layer structure obtains unique and promising results. Overall, the proposed asymmetric IVS metamaterial design achieves the required performance by using a compact structure rather than extending the dimensions of the design.

Detection of chlorophyll content based on optical properties of maize leaves

The chlorophyll content reflects plants' photosynthetic capacity, growth stage, and nitrogen status. Maize is one of the three widely planted gain crops in the world. In order to offer useful information for the development of chlorophyll content detectors of maize leaves, a single integrating sphere system was used to measure the transmittance and reflectance spectra of maize leaves over the wavelength range of 500-950 nm. The linear relationships of transmittance and reflectance with chlorophyll content were investigated. The feature wavelengths (FWs) sensitive to chlorophyll content were extracted from the full transmittance and reflectance spectra using the successive projections algorithm (SPA). The partial least squares regression (PLSR) models for predicting the chlorophyll content were established using the full spectra and extracted FWs. The results showed that there were obvious linear relationships between transmittance and reflectance with chlorophyll content of maize leaves and the best linear relationships were found at 709 nm and 714 nm, respectively, with the linear correlation coefficients of 0.801 and 0.696, and the root-mean-squares error (RMSEP) of 0.321 mg·g-1 and 0.405 mg·g-1, respectively. Eight and 6 FWs were extracted from the transmittance and reflectance spectra, respectively. The PLSR model established using the selected FWs from transmittance spectra had better prediction performance with RMSEP of 0.208 mg·g-1 than using full transmittance spectra. The built PLSR models using the full reflectance spectra and extracted FWs had poor robustness. This research offers some theoretical basis for developing a maize leaf chlorophyll content detector based on transmittance or reflectance.

Functional interactions between coat structure and colour in the determination of solar heat load on arid living kangaroos in summer: balancing crypsis and thermoregulation

Interactions of solar radiation with mammal fur are complex. Reflection of radiation in the visible spectrum provides colour that has various roles, including sexual display and crypsis, i.e., camouflage. Radiation that is absorbed by a fur coat is converted to heat, a proportion of which impacts on the skin. Not all absorption occurs at the coat surface, and some radiation penetrates the coat before being absorbed, particularly in lighter coats. In studies on this phenomenon in kangaroos, we found that two arid zone species with the thinnest coats had similar effective heat load, despite markedly different solar reflectances. These kangaroos were Red Kangaroos (Osphranter rufus) and Western Grey Kangaroos (Macropus fuliginosus).Here we examine the connections between heat flow patterns associated with solar radiation, and the physical structure of these coats. Also noted are the impacts of changing wind speed. The modulation of solar radiation and resultant heat flows in these coats were measured at wind speeds from 1 to 10 m s-1 by mounting them on a heat flux transducer/temperature-controlled plate apparatus in a wind tunnel. A lamp with a spectrum like solar radiation was used as a proxy for the sun. The integrated reflectance across the solar spectrum was higher in the red kangaroos (40 ± 2%) than in the grey kangaroos (28 ± 1%). Fur depth and insulation were not different between the two species, but differences occurred in fibre structure, notably in fibre length, fibre density and fibre shape. Patterns of heat flux within the species' coats occurred despite no overall difference in effective solar heat load. We consider that an overarching need for crypsis, particularly for the more open desert-adapted red kangaroo, has led to the complex adaptations that retard the penetrance of solar radiation into its more reflective fur.

Visible spectroscopy on lamb fat and muscle to authenticate the duration of pasture finishing

Pasture-based livestock systems are considered environmentally-sustainable and welfare-friendly farming systems that can meet consumer demand for good-quality produce. However, trust in products labelled as 'grass-fed' depends on the ability to reliably authenticate pasture origin. The two objectives of this study were (i) to test the ability of visible spectroscopy combined with discriminant analysis on lamb perirenal fat (PF), dorsal fat (DF) and longissimus thoracis et lumborum muscle to discriminate different durations of pasture-finishing; and (ii) to determine the timing of appearance of the pasture signature and its stabilization in these tissues. Four groups of 35 lambs were used over two years, i.e. lambs fed concentrate in-stall (L0) and lambs grazing alfalfa for 21d (L21), 42d (L42) and 63d (L63) before slaughter. No one tissue satisfactorily discriminated the four treatment groups, with ≤75% of lambs correctly classified. However, visible spectroscopy discriminated L0 from L21 + L42 + L63 lambs with an accuracy of 92.8%, 92.0%, and 85.3% lambs correctly classified on PF, DF and muscle, respectively, and discriminated L0 + L21 from L42 + L63 lambs with an accuracy of 90.1%, 76.5% and 92.3% on PF, DF and muscle, respectively. The pasture fingerprint or signature on the spectrum appeared in most lambs between 0 and 21d in PF and DF and between 0 and 42d in muscle. Pasture signature gradually stabilized with increasing time on pasture but was not entirely stabilized in any tissue within the range of grazing durations explored. These promising results need to be confirmed on larger datasets with different breeds and grazing conditions.

Applications of Ultraviolet and Sub-ultraviolet Dermatoscopy in Neoplastic and Non-neoplastic Dermatoses: A Systematic Review

Dermatoscopy is a non-invasive and cost-efficient imaging technique augmenting clinical examination in neoplastic and non-neoplastic dermatoses. Recently, novel dermatoscopic techniques based on principles of reflectance/absorption and excited fluorescence have been developed. However, comprehensive data on their applications are sparse, and terminology is inconsistent. In this systematic review, we addressed the principles of ultraviolet (UV) imaging and proposed categorization based on spectral characteristics and signal acquisition, as well as discussed documented and potential clinical applications, safety measures during examination, and limitations associated with reflectance and fluorescence dermatoscopy. A literature search was conducted in the PubMed medical database until 2 December 2023 according to PRISMA guidelines, and 28 papers fit the scope of this review, whereas additional relevant articles were included to provide broader context regarding the chosen terminology, chromophores described, safety of sub-UV/UV, and regulations for light-emitting devices. UV and sub-UV dermatoscopy, categorized into different methods on the basis of the emitted wavelength and signal acquisition process (reflectance versus fluorescence), augment conventional dermatoscopy by optimizing safety margins in melanoma, facilitating early detection of tumor recurrence, and enhancing visualization in non-neoplastic conditions, including pigmentation disorders, intertrigo, papulo-desquamative dermatoses, and beyond. The review highlights the limitations of these techniques, including difficulty in differentiating melanin from hemoglobin, challenges in evaluating uneven surfaces, and artifacts. Although UV dermatoscopy complements conventional dermatoscopy, clinicians should be aware of their peculiarities, artifacts, limitations, and safety concerns to optimize their diagnostic accuracy and ensure patient's safety.

RPIOSL: construction of the radiation transfer model for rice leaves

The radiative transfer model of vegetation leaves simulates the transmission mechanism of light inside the vegetation and simulates the reflectivity of blades according to the change law of different components in the process of plant growth. Based on the PIOSL model, this paper combines PIOSL with the structure of rice leaves to construct a radiation transfer model for rice leaves. The parameters of each layer of the RPIOSL model are determined by the Non-dominated Sorting Genetic Algorithm-III. (NSGA-III.) algorithm. The reflectance spectra of 218 rice leaf samples in different periods were simulated using the RPIOSL model. The results show that the mean (RMSE) between the simulated and measured spectra of the constructed RPIOSL model is 0.1074, which is 0.0191 lower than that of the PROSPECT model. Among them, the spectral simulation effect of RPIOSL model in yellow and red light band is the best, and the RMSE at tillering period, jointing period, heading period and grouting period are 0.0584, 0.0576, 0.0724 and 0.0820, respectively. Therefore, the establishment of the RPIOSL model can accurately describe the interaction mechanism between light, which is of great significance for the rapid acquisition of rice growth information and accurate crop management.

Effect of shear strain on the electronic and optical properties of Al-doped stanane

CONTEXT

The quasi-metallic properties of stanene limit its prospects in optoelectronic devices. Based on first-principles calculations, a systematic study is conducted on the tuning effects of surface hydrogenation and Al atom doping on the electronic and optical properties of stanene. Surface hydrogenation serves as an ideal way to open the forbidden band of stanene, and Al atom doping further increases hydrogenated stanene (stanane) band gap to 0.460 eV. Deformation has a minor impact on the stability of the stanane-Al structure, while shear strain can effectively modulate the band gap engineering of the doped system, reducing the band gap value from 0.460 to 0.170 eV. Deformation induces a redshift in the absorption peak and reflectance, also slowing down the rate of decrease in the absorption coefficient, and enhancing the peak value of light reflectance, which is positively correlated with the degree of shear strain. These findings hold promise for expanding the potential application of monolayer stanane in semiconductor devices.

METHODS

All calculations are performed using CASTEP module in Materials Studio based on the density functional theory (DFT). The Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA) is employed to describe the exchange-correlation energy (Perdew et al., Phys Rev Lett 77(18), 1996). We construct models for both stanene and stanane. The original unit cell of stanene has two Sn atoms, while stanane consists of two Sn atoms and two H atoms, and expand them to a 3 × 3 × 1 supercell with a vacuum layer of 20 Å in height to prevent interlayer coupling. After convergence testing, the plane-wave cutoff energy is set to 450 eV, and the energy convergence threshold is set to 1 × 10-5 eV. The maximum residual stress for each atom is set to 0.01 eV/Å. Brillouin zone sampling is performed using a 6 × 6 × 1 k-point mesh based on the Monkhorst-Pack method (Monkhorst and Pack, Phys Rev B 13(12), 1976). The k-point accuracy of the density of states and optical properties is 9 × 9 × 1. All calculations are performed using the more advanced OTFG ultrasoft pseudopotential, and structural relaxations are performed using supercells to ensure that the model is fully relaxed. We use the HSE06 functional to calculate the energy band structures of stanane-Al deformed to 0%, 4%, and 8%, resulting in band gap values of 1.465 eV, 1.368 eV, and 1.016 eV, respectively. These values are significantly higher than those obtained using the PBE functional (0.460 eV, 0.397 eV, and 0.170 eV). However, the shapes and trends of the band structures obtained from both PBE and HSE06 calculations are similar. Additionally, the calculation time needed by HSE06 is greatly longer than PBE, which exceeds the capabilities of our computer hardware, and cannot support all subsequent calculations. To investigate the influence of deformations on the variation of band gap values and to conserve computational resources, the subsequent calculations in this study use the PBE functional.

Updating "Angle-dependent spectral reflectance material dataset based on 945 nm time-of-flight camera measurements" with extended data to cover reflectance measurements mainly for vehicle varnish and moss rubber

An updated dataset based on angle-dependent spectral reflectance measurements taken for an angle range of 0° to 80° with 10° incremental steps and pictures for most measurements of the whole dataset are presented in this article. It covers two new material types regarding the material classification scheme presented in the original paper [1]: vehicle varnish and moss rubber. Vehicle varnish samples are prepared on flat steel plates to enable proper angle-dependent acquisition of the data with the same angle adjustable measurement device already presented in the original paper. The moss rubber material has a behavior similar to a Lambertian reflector and thus serves for diffuse reflectance measurement purposes. The extended dataset, including the original dataset, is published open access on the open repository Zenodo with record number 8322076 in a new version 1.1.1 [2], and currently contains 314 measurements with the addition of 70 new varnish and moss rubber measurements. The new version of the dataset further includes pictures of most of the measurements to depict how the data were acquired. The pictures enable material mapping such as the link between the measured data in the near infrared spectrum at a wavelength of λ = 945 n m and the picture taken in the optical spectrum.

Supervised classification combined with genetic algorithm variable selection for a fast identification of polymeric microdebris using infrared reflectance

Pollution caused by plastics and, in particular, microplastics has become a source of environmental concern for Society. Their ubiquity, with millions of tons of plastic debris spilled in both land and sea, requires efficient technological improvements in the ways residues are collected, handled, characterized and recycled. For reliable decision-making, dependable chemical information is essential to assess both the nature of the plastics found in the environment and their fate. In this work an efficient method to identify the polymeric composition of microplastic fragments is proposed. It combines infrared reflectance spectra and chemometric methods. A breakthrough result is that the models include polymers weathered under both dry (shoreline) and submerged (in sea water) conditions and, hence, they are very promising as a starting point for eventual practical applications. In addition, no spectral processing is required after the initial measurement. SYNOPSIS: This approach to identify microplastics in aquatic environments combines infrared measurements and multivariate data analysis to fight against (micro)plastic pollution.

The northernmost hyperspectral FLoX sensor dataset for monitoring of high-Arctic tundra vegetation phenology and Sun-Induced Fluorescence (SIF)

A hyperspectral field sensor (FloX) was installed in Adventdalen (Svalbard, Norway) in 2019 as part of the Svalbard Integrated Arctic Earth Observing System (SIOS) for monitoring vegetation phenology and Sun-Induced Chlorophyll Fluorescence (SIF) of high-Arctic tundra. This northernmost hyperspectral sensor is located within the footprint of a tower for long-term eddy covariance flux measurements and is an integral part of an automatic environmental monitoring system on Svalbard (AsMovEn), which is also a part of SIOS. One of the measurements that this hyperspectral instrument can capture is SIF, which serves as a proxy of gross primary production (GPP) and carbon flux rates. This paper presents an overview of the data collection and processing, and the 4-year (2019-2021) datasets in processed format are available at: https://thredds.met.no/thredds/catalog/arcticdata/infranor/NINA-FLOX/raw/catalog.html associated with https://doi.org/10.21343/ZDM7-JD72 under a CC-BY-4.0 license. Results obtained from the first three years in operation showed interannual variation in SIF and other spectral vegetation indices including MERIS Terrestrial Chlorophyll Index (MTCI), EVI and NDVI. Synergistic uses of the measurements from this northernmost hyperspectral FLoX sensor, in conjunction with other monitoring systems, will advance our understanding of how tundra vegetation responds to changing climate and the resulting implications on carbon and energy balance.

Application of analytical performance specifications for urine test strip methods: Importance of reflectance signals

INTRODUCTION

Urinalysis is essential for diagnosing kidney-related medical conditions. Urine test strip analysis serves as an initial and efficient screening method for reflex testing with accurate quantitative methods.

MATERIALS AND METHODS

Freshly voided urines (n = 206) were analysed using two urine test strip brands on UC-MAX (Menarini) and cobas u 601 (Roche Diagnostics) instruments. Ordinal scale categories and reflectance signals (if available) were both used for the comparison with reference quantitative methods for glucose, proteins and albumin (cobas 503). Samples were considered positive when glucose > 15 or ≥ 54 mg/dL, proteins ≥ 200 mg/L and albumin ≥ 10 mg/L. Optimized reflectance thresholds were calculated by ROC curve analysis. Analytical performance specifications (APS) for trueness of test strip were gathered from the EFLM guideline (FPD, FNG, FNC).

RESULTS

Reflectance signals were significantly lower in urine samples considered positive by the reference method (p < 0.0001). Reflectance signals were also correlated with quantitative measurements, showing strong correlation (0.754 to 0.969). Only the use of optimized reflectance thresholds on cobas u 601 achieved at least the minimum EFLM APS (FPD < 20%, FNG < 50% and FNC < 10%).

CONCLUSION

The use of reflectance signals from urine test strips enhanced accuracy for glucose, proteins, and albumin measurement and may contribute to improve diagnosis of diverse kidney-related conditions.

Leaf chlorophyll fluorescence and reflectance of oakleaf lettuce exposed to metal and metal(oid) oxide nanoparticles

BACKGROUND

Most nanoparticles (NPs) have a significant impact on the structure and function of the plant photosynthetic apparatus. However, their spectrum of action varies significantly, from beneficial stimulation to toxicity, depending on the type of NPs, the concentration used and plant genotypic diversity. Photosynthetic performance can be assessed through chlorophyll a fluorescence (ChlF) measurements. These data allow to indirectly obtain detailed information about primary light reactions, thylakoid electron transport reactions, dark enzymatic stroma reactions, slow regulatory processes, processes at the pigment level. It makes possible, together with leaf reflectance performance, to evaluate photosynthesis sensitivity to stress stimuli.

RESULTS

We investigated effects of different metal and metal(oid) oxide nanoparticles on photosynthesis of oakleaf lettuce seedlings by monitoring the chlorophyll a fluorescence light radiation and reflectance from the leaves. Observations of ChlF parameters and changes in leaf morphology were carried out for 9 days in two-day intervals. Spectrophotometric studies were performed at 9th day. Suspensions of NPs with the following concentrations were used: 6% TiO2, SiO2; 3% CeO2, SnO2, Fe2O3; 0.004% (40 ppm) Ag; 0.002% (20 ppm) Au. Nanoparticles were applied directly on the leaves which caused small symptoms of chlorosis, necrosis and leaf veins deformation, but the plants fully recovered to the initial morphological state at 9th day. Leaf reflectance analysis showed an increase in FRI for SiO2-NPs and CeO2-NPs treatments and ARI2 for Fe2O3, however, WBI and PRI coefficients for the latter nanoparticle were lower than in control. Chlorophyll a fluorescence parameters have changed due to NPs treatment. Fe2O3-NPs caused an increase in Fv/F0, PIABS, ET0/RC, DI0/RC, ABS/RC in different time points in comparison to control, also Ag, Au and SnO2 treatment caused an increase in Fv/F0, PIABS or ET0/RC, respectively. On the other hand, TiO2-NPs caused a decrease in Fv/Fm and Fv/F0 parameters, but an increase in DI0/RC value was observed. SnO2-NPs decreased PIABS, but increased ET0/RC than compared to control. Nanoparticles affected the shape of the O-J-I-P curve in slight manner, however, further analyses showed unfavourable changes within the PSII antenna, manifested by a slowdown in the transport of electrons between the Chl molecules of the light-harvesting complex II and the active center of PSII due to NPs application.

CONCLUSION

Changes in ChlF parameters and leaf reflectance values clearly proved the significant influence of NPs on the functioning of the photosynthetic apparatus, especially right after NPs application. The nature of these changes was strictly depended on the type of nanoparticles and sometimes underwent very significant changes over time. The greatest changes in ChlF parameters were caused by Fe2O3 nanoparticles, followed by TiO2-NPs. After slight response of O-J-I-P curves to treatment of the plants with NPs the course of the light phase of photosynthesis stabilized and at 9th day were comparable to the control curve.

Electronic structure and optical properties of Br- and Cl-doped rutile TiO2 for application in self-cleaning and photovoltaic panel's coatings: first-principle calculations

Development of novel self-cleaning technologies, especially those based on semiconductor photocatalysis system, is one of the most important research problems in environmental cleanup. Titanium dioxide (TiO₂) is a well-known semiconductor photocatalyst that has a strong photocatalytic activity in the ultra-violet part of the spectrum while its photocatalytic efficiency is very limited within the visible range due to its large band gap. In the field of photocatalytic materials, doping is an efficient method to increase the spectral response and promote charge separation. However, the type of dopant is not the only important factor, but also its position in the material lattice. In the present study, we have carried out first-principle calculations based on density functional theory to explore how particular doping configuration, such as Br or Cl doping at an O site, may influence the electronic structure and the charge density distribution within rutile TiO₂. Furthermore, optical properties such as the absorption coefficient, the transmittance, and reflectance spectra have also been derived from the calculated complex dielectric function and examined to see whether this doping configuration has any effect on the use of the material as a self-cleaning coating on photovoltaic panels.

Characterization of leaf surface phenotypes based on light interaction

BACKGROUND

Leaf surface phenotypes can indicate plant health and relate to a plant's adaptations to environmental stresses. Identifying these phenotypes using non-invasive techniques can assist in high-throughput phenotyping and can improve decision making in plant breeding. Identification of these surface phenotypes can also assist in stress identification. Incorporating surface phenotypes into leaf optical modelling can lead to improved biochemical parameter retrieval and species identification.

RESULTS

In this paper, leaf surface phenotypes are characterized for 349 leaf samples based on polarized light reflectance measured at Brewster's Angle, and microscopic observation. Four main leaf surface phenotypes (glossy wax, glaucous wax, high trichome density, and glabrous) were identified for the leaf samples. The microscopic and visual observations of the phenotypes were used as ground truth for comparison with the spectral classification. In addition to surface classification, the microscope images were used to assess cell size, shape, and cell cap aspect ratios; these surface attributes were not found to correlate significantly with spectral measurements obtained in this study. Using a quadratic discriminant analysis function, a series of 10,000 classifications were run with the data randomly split between training and testing datasets, with 150 and 199 samples, respectively. The average correct classification rate was 72.9% with a worst-case classification of 60.3%.

CONCLUSIONS

Leaf surface phenotypes were successfully correlated with spectral measurements that can be obtained remotely. Remote identification of these surface phenotypes will improve leaf optical modelling and biochemical parameter estimations. Phenotyping of leaf surfaces can inform plant breeding decisions and assist with plant health monitoring.

Characterization of fresh PM deposits on calcareous stone surfaces: Seasonality, source apportionment and soiling potential

Particulate matter (PM) pollution is one of the major threats to cultural heritage outdoors. It has been recently implied that organic aerosols will prevail over inorganic carbon particulates in the future, changing the main mechanisms of damage caused by poor air quality to calcareous heritage in particular. We studied fresh particulate deposits on marble and limestone surfaces exposed to urban air in sheltered and unsheltered configurations. Due to different air pollution sources in different seasons, the amount and composition of surface deposits varied throughout the year. The main and most constant contributor to PM_2.5 (particles smaller than 2.5 μm) were primary traffic emissions (30 %), followed by secondary formation of acidic inorganic aerosols, such as sulphate in summer and nitrate in winter (33 % altogether), and seasonal biomass-burning emissions (14 %). Although biomass burning is the major source of primary organic aerosols including the light-absorbing fraction that prevailed over black carbon (BC) in colder months (up to 60 % carbonaceous aerosol mass), we show that surface darkening causing the soiling effect is still governed by the minor BC fraction of atmospheric aerosols, which remained below 20 % of the carbonaceous aerosol mass throughout the year. This, however, can change in remote environments affected by biomass-burning emissions, such as winter resorts, or by rigorous BC mitigation measures in the future. In the short run, sheltered positions were less affected by different removal processes, but we show that surface deposits are not simply additive when considering longer periods of time. This must be taken into account when extrapolating surface accumulation to longer time scales.

Optical reflectometric measurement of SARS-CoV-2 (COVID-19) RNA based on cationic cysteamine-capped gold nanoparticles

The coronavirus disease (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged as a major public health outbreak in late 2019 and was proclaimed a global pandemic in March 2020. A reflectometric-based RNA biosensor was developed by using cysteamine-stabilized gold nanoparticles (cysAuNPs) as the colorimetric probe for bioassay of COVID-19 RNA (SARS-CoV-2 RNA) sequence. The cysAuNPs aggregated in the presence of DNA probes via cationic and anionic electrostatic attraction between the positively charged cysteamine ligands and the negatively charged sugar-phosphate backbone of DNA, whilst in the presence of target RNAs, the specific recognition between DNA probes and targets depleted the electrostatic interaction between the DNA probes and cysAuNPs signal probe, leading to dispersed particles. This has rendered a remarkable shifting in the surface plasmon resonance (SPR) on the basis of visual color change of the RNA biosensor from red to purplish hue at the wavelength of 765 nm. Optical evaluation of SARS-CoV-2 RNA by means on reflectance transduction of the RNA biosensor based on cysAuNPs optical sensing probes demonstrated rapid response time of 30 min with high sensitivity, good linearity and high reproducibility across a COVID-19 RNA concentration range of 25 nM to 200 nM, and limit of detection (LOD) at 0.12 nM. qPCR amplification of SARS-CoV-2 viral RNA showed good agreement with the proposed RNA biosensor by using spiked RNA samples of the oropharyngeal swab from COVID-19 patients. Therefore, this assay is useful for rapid and early diagnosis of COVID-19 disease including asymptomatic carriers with low viral load even in the presence of co-infection with other viruses that manifest similar respiratory symptoms.

Concordance of Objectively Detected Retinal Nerve Fiber Bundle Defects in En Face OCT Images with Conventional Structural and Functional Changes in Glaucoma

PURPOSE

To assess how objectively detected defects in retinal nerve fiber bundle (RNFB) reflectance on en face OCT images relate to circumpapillary retinal nerve fiber layer thickness (cpRNFLT) and visual field defects.

DESIGN

Cross-sectional study.

PARTICIPANTS

Sixteen participants with early glaucoma and 29 age-matched healthy controls, of whom 22 had usable en face images for the establishment of normative levels of RNFB reflectance.

METHODS

All the participants underwent cpRNFLT scans, visual field examination, and wide-field OCT. En face reflectivity was assessed objectively using the Summary of Multiple Anatomically Adjusted Slabs method. En face defects were deemed concordant with cpRNFLT when they had at least 1 cpRNFLT point with P < 0.01, within ± 15° of the predicted insertion on the optic disc. Visual fields were examined using custom suprathreshold perimetry and SITA Standard 24-2. For each visual field location, the corresponding reflectance was deemed abnormal if any en face superpixel within ± 1° was abnormal. The overall, positive, and negative agreements were measured in each participant.

MAIN OUTCOME MEASURES

Proportion of concordant defects between en face reflectance analysis and cpRNFLT (%) as well as overall, positive, and negative agreements between en face reflectance analysis and visual field results.

RESULTS

Most en face abnormalities had concordant cpRNFLT defects in the mapped sector (median proportion concordant, 0.85; interquartile range, 0.74-0.95). In eyes with glaucoma, a median of 8.1% (range, 2.4%-23.7%) and 14.9% (range, 3.5%-29.1%) locations showed corresponding en face and visual field defects using 24-2 and custom perimetry, respectively. Both the perimetric strategies had moderate-to-good raw agreement with en face analysis (0.66-0.68), with stronger agreement on normal findings than on defects (0.77-0.78 and 0.4-0.44).

CONCLUSIONS

Objectively extracted reflectance defects showed strong concordance with conventional cpRNFLT damage and good agreement with perimetry, which could be enhanced by further minimization of image artifacts.

Distinguishing thermally altered bones from debris using imaging and fluorescence spectrometry

Bushfires and mass disasters from which result fatal fire victims are two types of events in which Forensic Anthropology acts aiding in the recovery of human remains and the identification of the victims. This is a challenging job since bones that have undergone fire-caused alterations can be unrecognizable. Therefore, collecting evidence at the scene is very important and should be thorough. To evaluate the potential of the application of optical techniques for the recovery and analysis of burnt skeletal material in forensic contexts, this exploratory study focused on analysing reflectance and luminescence properties of bone to differentiate between skeletal remains and debris. The sample includes burnt human bones, as well as non-human bones and debris (like metal, fabric, and others). The reflectance experiments revealed to be quite ineffective, not showing a response pattern that allowed for discrimination between skeletal remains and debris. Three techniques were used to detect luminescence, which included imaging (with a camera), fluorescence spectrometry, and laser-induced fluorescence spectroscopy (excitation: 440 nm). Luminescence results were more promising, registering a positive response for several samples, with a general consistency of results between the different methodologies. Nevertheless, burning conditions and individual characteristics (e.g., pathologies) can introduce limitations to the techniques.

Weathering-independent differentiation of microplastic polymers by reflectance IR spectrometry and pattern recognition

The presence and effects of microplastics in the environment is being continuously studied, so the need for a reliable approach to ascertain the polymer/s constituting them has increased. To characterize them, infrared (IR) spectrometry is commonly applied, either reflectance or attenuated total reflectance (ATR). A common problem when considering field samples is their weathering and biofouling, which modify their spectra. Hence, relying on spectral matching between the unknown spectrum and spectral databases is largely defective. In this paper, the use of IR spectra combined with pattern recognition techniques (principal components analysis, classification and regression trees and support vector classification) is explored first time to identify a collection of typical polymers regardless of their ageing. Results show that it is possible to identify them using a reduced suite of spectral wavenumbers with coherent chemical meaning. The models were validated using two datasets containing artificially weathered polymers and field samples.

Intraocular reflectance of the ocular fundus and its impact on increased retinal hazard

PURPOSE

Inside the eye light can be reflected multiple times due to light-tissue interactions and the spherical geometry of the eye. Due to these optical properties, a defined retinal area is not only illuminated by direct light but also by indirect, reflected light from the inner side of the eyewall. During illumination for ophthalmic surgery, this could lead to an unintended increase in intraocular retinal irradiance, which was already discussed in previous studies but without a detailed consideration of spectral differences and a potential influence of pigmentation. In this study this effect is investigated wavelength-dependent to see if different wavelengths lead to different increase in irradiance, with a special focus on the raise in photochemical and thermal hazard to the retina. It is also examined whether this effect is dependent on the pigmentation of the eye.

METHODS

The reflectance properties of either less or highly pigmented porcine eyes are measured in the wavelength range between 350 and 1100nm with an integrating sphere and a spectrometer. With these reflectance spectra the wavelength-dependent Sphere Multiplier M of porcine eyes can be calculated, which represents the increase of radiance due to multiple reflections inside a sphere compared to a planar diffuser of the same size. Based on measurements of the emitted irradiance of ophthalmic illumination fibers the increase in photochemical and thermal retinal hazard due to these multiple reflections is calculated for eyes with small and high amounts of pigmentation.

RESULTS

The reflectance of the inner eyewall in the range between 350 and 1100nm is significantly higher for eyes with low pigmentation (between 4.90% and 37.44% reflectance) in comparison to eyes with a high amount of pigmentation (between 4.30% and 28.88% reflectance). The Sphere Multiplier for the inner side of the eyewall (sclera, choroid and retina) ranges between 1.13 and 1.59 and between 1.13 and 1.48 for eyes with low and high pigmentation, respectively, in the range between 350 and 1100nm. The reflectance, as well as the Sphere Multiplier, is strongly wavelength-dependent due to the absorption spectra of melanin and hemoglobin, which are located in the eye. With increasing wavelength, the reflection properties and the Sphere Multiplier also increases. With this, the photochemical retinal hazard of highly pigmented eyes increases by (14.11± 0.09)% and of lightly pigmented eyes by (16.75±0.35)% compared to if the reflection properties are not considered. The thermal retinal hazard increases by (14.30±0.07)% for highly pigmented eyes and by (19.65±0.17)% for low pigmented eyes.

CONCLUSION

This study demonstrates that the anatomy and pigmentation of the eye plays an important role for the reflectance properties of the eye and for the photochemical and thermal hazard to the retina.

Hyperspectral time series datasets of maize during the grain filling period

OBJECTIVES

Remotely sensed hyperspectral data are increasingly being used to assess crop development and growth throughout the growing season. Large datasets capturing key growth stages can be useful to researchers studying many physiological plant responses. A time series analysis of hyperspectral reflectance measurements taken during the grain filling period and published within a publicly accessible database are described herein. These datasets document the spectral reflectance pattern of the canopy within the visible and near-infrared portion of the electromagnetic spectrum during the late stages of the grain filling period as plants approach and reach physiological maturity.

DATA DESCRIPTION

Included within the data repository are canopy-level hyperspectral datasets collected in 2017 and 2018. Data is included in its raw form, as well as with several manipulations to smooth and standardize the raw data. Data are released as comma separated value spreadsheets as well as Microsoft Excel open XLSX spreadsheets. These are accompanied by README text files which further describe the data and supplemental files that record hybrids used and plant phenology for each year of data collection.

Scaling photosynthetic function and CO2 dynamics from leaf to canopy level for maize - dataset combining diurnal and seasonal measurements of vegetation fluorescence, reflectance and vegetation indices with canopy gross ecosystem productivity

Recent advances in leaf fluorescence measurements and canopy proximal remote sensing currently enable the non-destructive collection of rich diurnal and seasonal time series, which are required for monitoring vegetation function at the temporal and spatial scales relevant to the natural dynamics of photosynthesis. Remote sensing assessments of vegetation function have traditionally used actively excited foliar chlorophyll fluorescence measurements, canopy optical reflectance data and vegetation indices (VIs), and only recently passive solar induced chlorophyll fluorescence (SIF) measurements. In general, reflectance data are more sensitive to the seasonal variations in canopy chlorophyll content and foliar biomass, while fluorescence observations more closely relate to the dynamic changes in plant photosynthetic function. With this dataset we link leaf level actively excited chlorophyll fluorescence, canopy proximal reflectance and SIF, with eddy covariance measurements of gross ecosystem productivity (GEP). The dataset was collected during the 2017 growing season on maize, using three automated systems (i.e., Monitoring Pulse-Amplitude-Modulation fluorimeter, Moni-PAM; Fluorescence Box, FloX; and from eddy covariance tower). The data were quality checked, filtered and collated to a common 30 minutes timestep. We derived vegetation indices related to canopy functioning (e.g., Photochemical Reflectance Index, PRI; Normalized Difference Vegetation Index, NDVI; Chlorophyll Red-edge, Clre) to investigate how SIF and VIs can be coupled for monitoring vegetation photosynthesis. The raw datasets and the filtered and collated data are provided to enable new processing and analyses.

Fast and dark: The case of Mezquite lizards at extreme altitude

Sprint speed is a major performance trait in animal fitness involved in escaping from predators, obtaining food, and defending territory. Biotic and abiotic factors may influence sprint speed in lizards. Temperature decreases at higher altitude. Therefore, lizards at high elevations may require longer basking times to reach optimal body temperatures, increasing their vulnerability to predation and decreasing their time for other activities such as foraging or reproduction. Here, we tested whether the maximum sprint speed of a lizard that shows conservative thermal ecology varied along an altitudinal gradient comprising low (2500 m), middle (3400 m) and high-altitude (4300 m) populations. We also tested whether sprint speed was related to dorsal reflectance at different ecologically relevant temperatures. Given that the lizard Sceloporus grammicus shows conservative thermal ecology with altitude, we expected that overall average sprint speed would not vary with altitude. However, given that darker lizards heat up quicker, we expected that darker lizards would be faster than lighter lizards. Our results suggest that S. grammicus at high altitude are faster and darker at 30 °C, while lizards from low and middle altitude are faster and lighter in color at 20 °C than high altitude lizards. Also, our results suggest a positive relationship between sprint speed and dorsal skin reflectance at 10 and 20 °C. Sprint speed was also affected by snout-vent length, leg length, and leg thickness at 10 °C. These results suggest that, even though predation pressure is lower at extreme altitudes, other factors such as vegetation cover or foraging mode have influenced sprint speed.

Interference of CDOM in remote sensing of suspended particulate matter (SPM) based on MODIS in the Persian Gulf and Oman Sea

The spatial and temporal variability of suspended particulate matter (SPM) in the Persian Gulf and Oman Sea coastal waters has remained challenging to understand among researchers. Here, for the first time in the region, we parametrized SPM concentration in the study area utilizing derived remote sensing reflectance (R_rs) values from Moderate-resolution Imaging Spectroradiometer (MODIS), using 555 and 667 nm wavelengths. Likewise, the findings showed that the developed optical model based on the optical ratio of R_rs (667)/R_rs (555) was sensitive to the concentration of Chromophoric dissolved organic matter (CDOM) in the seawater, within the visible wavelengths less than 600 nm. Comparing the new estimates of the SPM concentration with in situ measurements by Spearman's Rank correlation for validation revealed that the association between estimated and measured SPM concentration would be considered statistically significant (ρ up to 0.86, p < 0.05). This study increased the average accuracy of the estimates up to 73%.

Can flowers affect land surface albedo and soil microclimates?

The phenology of vegetation, namely leaf-out and senescence, can influence the Earth's climate over regional spatial scales and long time periods (e.g., over 30 years or more), in addition to microclimates over local spatial scales and shorter time periods (weeks to months). However, the effects of flowers on climate and microclimate are unknown. We investigate whether flowers can influence light reflected by the land surface and soil microclimate in a subalpine meadow. We conducted a flower removal experiment with a common sunflower species, Helianthella quinquenervis, for 3 years (2015, 2017, and 2019). The flower removal treatment simulates the appearance of the meadow when Helianthella flowers earlier under climate change and loses its flowers to frost (other plant structures are not damaged by frost). We test the hypotheses that a reduction in cover of yellow flowers leads to a greener land surface, lower reflectance, warmer and drier soils, and increased plant water stress. Flower removal plots are greener, reflect less light, exhibit up to 1.2 °C warmer soil temperatures during the warmest daylight hours, and contain ca. 1% less soil moisture compared to controls. However, soils were warmer in only 2 of the 3 years, when flower abundance was high. Helianthella water use efficiency did not differ between removal and control plots. Our study provides evidence for a previously undocumented effect of flowers on soil microclimate, an effect that is likely mediated by climate change and flowering phenology. Many anthropogenic environmental changes alter landscape albedo, all of which could be mediated by flowers: climate change, plant invasions, and agriculture. This study highlights how further consideration of the effects of flowers on land surface albedo could improve our understanding of the effects of vegetation on microclimate.

Finite-difference Time-domain (FDTD) Optical Simulations: A Primer for the Life Sciences and Bio-Inspired Engineering

Light influences most ecosystems on earth, from sun-dappled forests to bioluminescent creatures in the ocean deep. Biologists have long studied nano- and micro-scale organismal adaptations to manipulate light using ever-more sophisticated microscopy, spectroscopy, and other analytical equipment. In combination with experimental tools, simulations of light interacting with objects can help researchers determine the impact of observed structures and explore how variations affect optical function. In particular, the finite-difference time-domain (FDTD) method is widely used throughout the nanophotonics community to efficiently simulate light interacting with a variety of materials and optical devices. More recently, FDTD has been used to characterize optical adaptations in nature, such as camouflage in fish and other organisms, colors in sexually-selected birds and spiders, and photosynthetic efficiency in plants. FDTD is also common in bioengineering, as the design of biologically-inspired engineered structures can be guided and optimized through FDTD simulations. Parameter sweeps are a particularly useful application of FDTD, which allows researchers to explore a range of variables and modifications in natural and synthetic systems (e.g., to investigate the optical effects of changing the sizes, shape, or refractive indices of a structure). Here, we review the use of FDTD simulations in biology and present a brief methods primer tailored for life scientists, with a focus on the commercially available software Lumerical FDTD. We give special attention to whether FDTD is the right tool to use, how experimental techniques are used to acquire and import the structures of interest, and how their optical properties such as refractive index and absorption are obtained. This primer is intended to help researchers understand FDTD, implement the method to model optical effects, and learn about the benefits and limitations of this tool. Altogether, FDTD is well-suited to (i) characterize optical adaptations and (ii) provide mechanistic explanations; by doing so, it helps (iii) make conclusions about evolutionary theory and (iv) inspire new technologies based on natural structures.

An insight into spectral composition of light available for photosynthesis via remotely assessed absorption coefficient at leaf and canopy levels

Non-invasive comparative analysis of the spectral composition of energy absorbed by crop species at leaf and plant levels was carried out using the absorption coefficient retrieved from leaf and plant reflectance as an informative metric. In leaves of three species with contrasting leaf structures and photosynthetic pathways (maize, soybean, and rice), the blue, green, and red fractions of leaf absorption coefficients were 48, 20, and 32%, respectively. The fraction of green light in the total budget of light absorbed at the plant level was higher than at the leaf level approaching the size of the red fraction (24% green vs. 25.5% red) and surpassing it inside the canopy. The plant absorption coefficient in the far-red region (700-750 nm) was significant reaching 7-10% of the absorption coefficient in green or red regions. The spectral composition of the absorbed light in the three species was virtually the same. Fractions of light in absorbed PAR remained almost invariant during growing season over a wide range of plant chlorophyll content. Fractions of absorption coefficient in the green, red, and far-red were in accord with published results of quantum yield for CO2 fixation on an absorbed light basis. The role of green and far-red light in photosynthesis was demonstrated in simple experiments in natural conditions. The results show the potential for using leaf and plant absorption coefficients retrieved from reflectance to quantify photosynthesis in each spectral range.

Multimodal imaging as optical biopsy system for gastritis diagnosis in humans, and input of the mouse model

BACKGROUND

Gastric inflammation is a major risk factor for gastric cancer. Current endoscopic methods are not able to efficiently detect and characterize gastric inflammation, leading to a sub-optimal patients' care. New non-invasive methods are needed. Reflectance mucosal light analysis is of particular interest in this context. The aim of our study was to analyze reflectance light and specific autofluorescence signals, both in humans and in a mouse model of gastritis.

METHODS

We recruited patients undergoing gastroendoscopic procedure during which reflectance was analysed with a multispectral camera. In parallel, the gastritis mouse model of Helicobacter pylori infection was used to investigate reflectance from ex vivo gastric samples using a spectrometer. In both cases, autofluorescence signals were measured using a confocal microscope.

FINDINGS

In gastritis patients, reflectance modifications were significant in near-infrared spectrum, with a decrease between 610 and 725 nm and an increase between 750 and 840 nm. Autofluorescence was also modified, showing variations around 550 nm of emission. In H. pylori infected mice developing gastric inflammatory lesions, we observed significant reflectance modifications 18 months after infection, with increased intensity between 617 and 672 nm. Autofluorescence was significantly modified after 1, 3 and 6 months around 550 and 630 nm. Both in human and in mouse, these reflectance data can be considered as biomarkers and accurately predicted inflammatory state.

INTERPRETATION

In this pilot study, using a practical measuring device, we identified in humans, modification of reflectance spectra in the visible spectrum and for the first time in near-infrared, associated with inflammatory gastric states. Furthermore, both in the mouse model and humans, we also observed modifications of autofluorescence associated with gastric inflammation. These innovative data pave the way to deeper validation studies on larger cohorts, for further development of an optical biopsy system to detect gastritis and finally to better surveil this important gastric cancer risk factor.

FUNDING

The project was funded by the ANR EMMIE (ANR-15-CE17-0015) and the French Gastroenterology Society (SNFGE).

Inversion reflectance by apple tree canopy ground and unmanned aerial vehicle integrated remote sensing data

To obtain accurate spatially continuous reflectance from Unmanned Aerial Vehicle (UAV) remote sensing, UAV data needs to be integrated with the data on the ground. Here, we tested accuracy of two methods to inverse reflectance, Ground-UAV-Linear Spectral Mixture Model (G-UAV-LSMM) and Minimum Noise Fraction-Pixel Purity Index-Linear Spectral Mixture Model (MNF-PPI-LSMM). At wavelengths of 550, 660, 735 and 790 nm, which were obtained by UAV multispectral observations, we calculated the canopy abundance based on the two methods to acquire the inversion reflectance. The correlation of the inversion and measured reflectance values was stronger in G-UAV-LSMM than MNF-PPI-LSMM. We conclude that G-UAV-LSMM is the better model to obtain the canopy inversion reflectance.

A Biaxial Strain Sensor Using a Single MoS2 Grating

In this paper, we report a new type of MoS₂-based grating sensor for in-plane biaxial strain gauges with a precision limit of ~ 1‰. The MoS₂ grating is numerically simulated with different biaxial strains up to 5%. Our first-principles calculations reveal that the strain sensitivity of the MoS₂ reflectance spectrum can be considered an additional strain sensor integrated with the grating structure, enabling the mapping of in-plane biaxial strains. Our experimental studies on a prototype MoS₂-grating sensor further confirm that a strain component perpendicular to the grating period can cause intensity peak shifts in the grating's first-order diffraction patterns. This work opens a new path towards the sensing of in-plane biaxial strain within a single-grating device. Our new approach is applicable for other materials that have predictable reflectance response under biaxial strains and the capacity to form a two-dimensional single-crystal layer.

A dataset composed of multiangular spectral libraries and auxiliary data at tree, leaf, needle, and bark level for three common European tree species

This article describes a dataset of multiangular scattering properties of small trees (height = 0.38–0.7 m) at visible, near-infrared, and shortwave-infrared wavelengths (350–2500 nm), and provides supporting auxiliary data that comprise leaf, needle, and bark spectra, and structural characteristics of the trees. Multiangular spectra were measured for 18 trees belonging to three common European tree species: Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) H. Karst), and sessile oak (Quercus petraea (Matt.) Liebl.). The measurements were performed in 47 different view angles across a hemisphere, using a laboratory goniometer and a non-imaging spectrometer. Leaf and needle spectra were measured for each tree, using a non-imaging spectrometer coupled to an integrating sphere. Bark spectra were measured for one sample tree per species. In addition, leaf and needle fresh mass, surface area of leaves, needles, and woody parts, silhouette area, and spherically averaged silhouette to total area ratio (STAR) for each tree were measured or derived from the measurements. The data are useful for modeling the shortwave reflectance characteristics of small trees and potentially forests, and thus benefit climate modeling or interpretation of remote sensing data.

Biomimetic Nanopillar-Based Biosensor for Label-Free Detection of Influenza A Virus

Since the first emergence of influenza viruses, they have caused the flu seasonally worldwide. Precise detection of influenza viruses is required to prevent the spreading of the disease. Herein, we developed an optical biosensor using peptide-immobilized nanopillar structures for the label-free detection of influenza viruses. The spin-on-glass nanopillar structures were fabricated by nanoimprint lithography. A sialic acid-mimic peptide, which can specifically bind to hemagglutinin on the surface of the influenza virus, was immobilized onto the nanopillars via polymerized dopamine. The constructed nanopillar sensor enabled us to detect influenza A viruses in the range of 10³-10⁵ plaque-forming units through simple measurements of reflectance. Our findings suggest that biomimetic modification of nanopillar structures can be an alternative method for the immunodiagnosis of influenza viruses.

Fully Automated Optical Hematocrit Measurement From Dried Blood Spots

The impact of the hematocrit (HCT) on the dried blood spot's (DBS) spreading area is one of the most important hurdles which prevents the full acceptance of quantitative microsampling strategies. Several destructive- and non-destructive strategies to assess the HCT from a DBS post-sampling have been presented. Unfortunately, the current methods are either labor-intensive, require a complicated algorithm, or are not automatable. Here, we present a novel setup that permits the fully automated reflectance analysis to measure the HCT from a DBS. The underlying principle is based on the concept presented by Capiau et al. for the non-destructive single-wavelength measurement of the HCT. The novel module was embedded within the DBS-MS 500 platform to enable high-throughput analysis of hematocrit values in combination with automated DBS extraction. The novel setup was assessed and optimized for the probe to card distance, stability, anti-coagulant, spotting volume, scan number, calibration variability, accuracy, and precision. It showed excellent inter-day (≤3.7%) and intra-day (≤1.16%) precision, as well as high accuracy when analyzing authentic samples 101%±7% (range:87%-127%). Besides, the simple and straightforward application of an HCT correction for DBS was demonstrated during a pharmacokinetic study with diclofenac involving three subjects. Thereby, the sample's HCT and the HCT impact on the analyte was assessed and compensated. In conclusion, the novel setup enables quantitative analysis of non-volumetric samples in an automated fashion without compromising the concept of cost-effective, minimally invasive sampling.

Experimental data and calibration processes to a new and simple device dedicated to the thermo-optical properties of a polycarbonate construction material

Thermo-optical properties of construction materials are important factors while designing a building. Human comfort and environmental issues are the main reasons inciting researchers to work in this field. For instance, the thermal conductivity coefficient, the optical reflectance, the optical transmittance and the optical absorbance of materials are frequently measured properties in civil engineering. Currently, each of these physical coefficients is measured separately by various devices. A new experimental device is therefore designed to measure these properties in a single unit. The data presented in the article consists of the experimentation process of designing a new type device. This paper includes data for calibration, measurements and validation for the elements of the new device. This data has been collected in the laboratory and is made available for reproducibility and improvement research in the field of thermo-optical properties of construction materials. This data article is related to the original research article of Fakra et al. denoted "A new simple experimental device for measuring the thermo-optical properties of translucent construction materials." [1].

Time-to-arrival estimations to simulated pedestrians

Driving a vehicle requires individuals' awareness of their surroundings to prevent collisions with other vehicles, objects, and pedestrians. While previous research has investigated time-to-arrival (TTA) in real-world and simulated driving situations, there is little information on how pedestrian reflectance and time of day impact TTA. The present study investigated how vehicle velocity, viewing time, pedestrian reflectance, and time of day affected individuals' estimates of TTA. We used recorded driver-perspective footage of a vehicle approaching simulated pedestrians at different velocities during daytime and nighttime. We found that TTA was consistently underestimated, with the most accurate TTA estimates occurring at the lowest vehicle velocity. We also found TTA accuracy was better during daytime conditions. Pedestrian reflectance did not produce a significant main effect, but it did interact significantly with both velocity and time of day. These results suggest that multiple variables are responsible for TTA estimation. A better understanding of what factors may affect TTA estimates helps both researchers who investigate the phenomenon and laypersons who strive for safe driving practices.

Towards a generic approach to remote non-invasive estimation of foliar carotenoid-to-chlorophyll ratio

Changes of chlorophyll (Chl) and carotenoid (Car) contents and their ratio (Car/Chl) represent a sensitive indicator of vegetation photosynthetic activity, developmental changes, and stress responses. The goal of this study was to design methods for estimating Car/Chl in plants across species, seasonal changes and ontogenetic phases requiring no species-specific parameterization. Four tree species (maple, chestnut, beech, and elm), wild vine shrub, and two crops species (maize and soybean) featuring contrasting leaf structure and photosynthetic pathways, a wide variation of pigment content and composition were studied. Two models based on leaf pigment absorption coefficients retrieved from reflectance spectra were proposed and tested. The first model uses the ratio of absorption coefficients at 500 and 700 nm and the second one-the difference between absorption coefficients at 500 and 660 nm. Both models accurately described Car/Chl changes in the range from 0.15 to 0.6 with determination coefficients R² of 0.87 for the first model and 0.82 for the second; algorithms for Car/Chl estimation did not require parameterization for each species accurately assessing Car/Chl with normalized root mean square error below 11 % and 14 %, respectively. The findings of a close relationship between leaf absorption coefficients, retrieved from reflectance, and Car/Chl present the first step towards accurate generic quantification of pigment composition and hence the progression of developmental stages, impact of stresses, and potential photosynthetic activity.

TiO2-coated 2D photonic crystals for reflectometric determination of malachite green

A "detect and destroy" strategy is reported for the spectroscopic determination and photocatalytic degradation of Malachite Green (MG) in aqueous solutions. The intensity of the reflection peak maxima from the TiO₂-coated 2D-photonic crystal (PhC) at 633 nm wavelength undergoes a gradual decrease with increasing concentrations of MG. The determination of MG was readily achieved in the nanomolar range due to the quenching of the reflection intensity of the peak, measured using a fiber optic probe. The assay works in the 1.0 nM to 10 μM MG concentration range with a detection limit of 1.3 nM. The same TiO₂-coated 2D-PhC surface can photocatalytically degrade MG in aqueous solutions under UV irradiation. The photocatalytic degradation in the presence of TiO₂-coated 2D-PhC becomes evident as the blue color of MG changes to colorless with increasing irradiation time. The decrease in absorption is detected at 617 nm. It was found that the photocatalytic efficiency of TiO₂ was synergistically enhanced in the presence of 2D-PhCs. It is concluded that each component of the TiO₂-coated 2D-PhC system plays a key role in the detection and degradation of MG. Graphical abstractSchematic representation for reflectometric detection and photocatalytic degradation of hazardous Malachite Green dye using TiO₂-coated two-dimensional photonic crystals.

Non-destructive methodologies applied to track the occurrence of natural micropollutants in watering: Glycine max as a biomonitor

Groundwater is habitually used for watering purposes in rural areas where the rainfall is not enough to adequately cover the crop requirements. However, groundwater sources could be naturally contaminated with trace micropollutants like As and associated elements (B, V and F) adversely affecting the plant health. In this work, non-destructive methodologies based on reflectance and chlorophyll emission processes were applied to assess the presence of micropollutants in watering by using a widespread crop (soybean plant). One of the most substantial results is that the co-occurrence of As, V, B and F in the watering solution clearly produced a synergistic effect in the plants. In fact, both reflectance and fluorescence techniques were proved in this work to be effective in detecting non-destructively stress by multielement treatment. Particularly, for reflectance measurements the most sensitive parameters were the derivative peak area between 480 and 560 nm and the chlorophyll content. Furthermore, it was demonstrated that it is possible to successfully use a portable hyperspectral spectroradiometer instead of a conventional spectrophotometer as the determinations performed with both instruments were positively correlated. Concerning fluorescence, variable emission of chlorophyll-a was more sensitive to stress than steady-state emission. The parameter Fv/F0 was a valuable indicator of stress but the quantum yields of PSII and NPQ stood out as the most sensitive indices with variations of around 60 and 100% respectively.

Convergent evolution of super black plumage near bright color in 15 bird families

We examined extremely low-reflectance, velvety black plumage patches in 32 bird species from 15 families and five orders and compared them with 22 closely related control species with normal black plumage. We used scanning electron microscopy to investigate microscopic feather anatomy, and applied spectrophotometry and hyperspectral imaging to measure plumage reflectance. Super black plumages are significantly darker and have more broadband low reflectance than normal black plumages, and they have evolved convergently in 15 avian families. Super black feather barbules quantitatively differ in microstructure from normal black feathers. Microstructural variation is significantly correlated with reflectance: tightly packed, strap-shaped barbules have lower reflectance. We assigned these super black feathers to five heuristic classes of microstructure, each of which has evolved multiple times independently. All classes have minimal exposed horizontal surface area and 3D micrometer-scale cavities greater in width and depth than wavelengths of light. In many species, barbule morphology varied between the super black exposed tip of a feather and its (i) concealed base or (ii) iridescently colored spot. We propose that super black plumages reduce reflectance, and flatten reflectance spectra, through multiple light scattering between the vertically oriented surfaces of microscale cavities, contributing to near-complete absorption of light by melanin. All super black plumage patches identified occur adjacent to brilliant colored patches. Super black plumage lacks all white specular reflections (reference points used to calibrate color perception), thus exaggerating the perceived brightness of nearby colors. We hypothesize that this sensory bias is an unavoidable by-product of color correction in variable light environments.

Data of plant diversity, spectral reflectance at specie level and satellite spectral variables from the largest dry forest nucleus in South America

The use of satellite remote sensing makes it possible to acquire useful information about the environment, since it presents tools capable of assisting the practical search of information related to species richness. Here we present data on richness and Shannon index from phytosociological researches, vegetation indices and individual bands spectral reflectance from satellite images and leaf-level spectral reflectance from eight Caatinga species. For further interpretation of the data presented in this article, please see the research article “Predicting plant species richness with satellite images in the largest dry forest nucleus in South America” [1].

Effect of obliquity of incident light on the performance of silicon solar cells

The aim of this work is to investigate the effect of angle of incident light on the performance of silicon solar cell. In this regard, numerical calculations have been performed to obtain the reflectance for double layer antireflection coating (DLARC) of Si₃N₄ at various angles of incidence (i.e.0o,15o,30o,45o,and60o) using transfer matrix method. Reflectances obtained, are found to increases with increase in angle of incidence. Calculated reflectances have been further used in the PC1D simulator as external reflectance files to study the performance of silicon solar cell. As a result of the simulation, the conversion efficiency (and short circuit current) of solar cell is found to decrease by 1.7% (0.062 mA/cm²) with increase in angle of incidence from 0oto60o.

Tracing water and energy fluxes and reflectance in an arid ecosystem using the integrated model SCOPE

Transpiration plays a critical role in the water cycle of terrestrial ecosystems, especially for arid ecosystems in which water availability is typically the main constraint for plant growth. Although remote sensing has provided insights into transpiration across different temporal and spatial scales, its potential has not been fully exploited. This is due to a lack of synchronous observations of fluxes and reflectance. Only a few models have attempted to incorporate both radiative transfer and physiological processes. In this study, we calibrated the newly developed Soil, Canopy Observation, Photochemistry and Energy fluxes (SCOPE) model to trace synchronous fluxes of water, energy and reflectance, and thus, their interplays, in a typical arid ecosystem dominated by Haloxylon ammodendron based on long-term continuous field measurements. An initial global sensitivity analysis is conducted to identify parameters that have the greatest impact on model output before subsequent calibration with field data. The resulting calibrated model gives insight into the interplay between reflectance, energy and water fluxes in an arid ecosystem. The calibrated model is thus a useful tool to understand land surface fluxes and radiative transfer processes theoretically, from which additional reflectance information can be exploited to trace the physiological status of ecosystems.

Vividly coloured poppy flowers due to dense pigmentation and strong scattering in thin petals

The flowers of poppies (Papaveraceae) exhibit bright colours, despite their thin and floppy petals. We investigated the optical properties of flowers of Papaver rhoeas, P. dubium, Meconopsis cambrica and Argemone polyanthemos using a combined approach of anatomy, spectrophotometry and optical modelling. The petals of Papaver flowers are composed of only three cell layers, an upper and lower epidermal layer, which are densely filled with pigment, and an unpigmented mesophyll layer. Dense pigmentation together with strong scattering structures, composed of serpentine cell walls and air cavities, cause the striking poppy colours. We discuss how various aspects of the optical signal contribute to the flower's visibility to pollinators.

A low-cost and open-source platform for automated imaging

BACKGROUND

Remote monitoring of plants using hyperspectral imaging has become an important tool for the study of plant growth, development, and physiology. Many applications are oriented towards use in field environments to enable non-destructive analysis of crop responses due to factors such as drought, nutrient deficiency, and disease, e.g., using tram, drone, or airplane mounted instruments. The field setting introduces a wide range of uncontrolled environmental variables that make validation and interpretation of spectral responses challenging, and as such lab- and greenhouse-deployed systems for plant studies and phenotyping are of increasing interest. In this study, we have designed and developed an open-source, hyperspectral reflectance-based imaging system for lab-based plant experiments: the HyperScanner. The reliability and accuracy of HyperScanner were validated using drought and salt stress experiments with Arabidopsis thaliana.

RESULTS

A robust, scalable, and reliable system was created. The system was built using open-sourced parts, and all custom parts, operational methods, and data have been made publicly available in order to maintain the open-source aim of HyperScanner. The gathered reflectance images showed changes in narrowband red and infrared reflectance spectra for each of the stress tests that was evident prior to other visual physiological responses and exhibited congruence with measurements using full-range contact spectrometers.

CONCLUSIONS

HyperScanner offers the potential for reliable and inexpensive laboratory hyperspectral imaging systems. HyperScanner was able to quickly collect accurate reflectance curves on a variety of plant stress experiments. The resulting images showed spectral differences in plants shortly after application of a treatment but before visual manifestation. HyperScanner increases the capacity for spectroscopic and imaging-based analytical tools by providing more access to hyperspectral analyses in the laboratory setting.

Linking phytoplankton pigment composition and optical properties: A framework for developing remote-sensing metrics for monitoring cyanobacteria

This study has been performed in the framework of a research program aiming to develop a low-cost aerial sensor for the monitoring of cyanobacteria in freshwater ecosystems that could be used for early detection. Several empirical and mechanistic remote-sensing tools have been already developed and tested at large scales and have proven useful in monitoring cyanobacterial blooms. However, the effectiveness of these tools for early detection is hard to assess because such work requires the detection of low concentrations of characteristic pigments amid complex ecosystems exhibiting several confounding factors (turbidity, blooms of other species, etc.). We developed a framework for performing high-throughput measurements of the absorbance and reflectance of small volumes (∼ = 20 mL) of controlled mixtures of phytoplankton species and studied the potential of this framework to validate remote-sensing proxies of cyanobacteria concentration. The absorption and reflectance spectra of single and multiple cultures carried a specific signal that allowed for the quantitative analysis of culture mixes. This specific signal was shown to be related to known pigment absorbance spectra. The concentrations of chlorophyll-a and -b, phycocyanin and phycoerythrin could be obtained from direct absorbance measurements and were correlated with the concentration obtained after pigment extraction (R² ≥ 0.96 for all pigments). A systematic test of every possible two-band and three-band normalized difference between optical indices was then performed, and the coincidental correlation with chlorophyll-b (absent in cyanobacteria) was used as an indicator of non-specificity. Two-band indices were shown to suffer from non-specificity issues and could not yield strong and specific relationships with phycocyanin or phycoerythrin (maximum R² < 0.5). On the other hand, the three-band modified normalized difference indices yielded strong specific relationships (R² > 0.8).

Significant Delay in the Detection of Desaturation between Finger Transmittance and Earlobe Reflectance Oximetry Probes during Fiberoptic Bronchoscopy: Analysis of 104 Cases

PURPOSE

There is clinical significance to a delay in response time for detecting desaturation by pulse oximetry. Our aim in this study was to compare the response time of the reflectance and transmittance saturation probes during fiberoptic bronchoscopy (FOB) under monitored anesthesia care.

METHODS

A prospective study included 104 patients scheduled for FOB. Patients were monitored with transmittance (finger) and reflectance (ear) oximetry probes. The response time was evaluated during desaturation and resaturation. We also acquired blood tests for arterial oxygen saturation to assess the agreement with the oximetry probes.

RESULTS

Ninety patients had a desaturation episode during FOB and were included in the final analysis. Mean time difference between the reflectance ear probe (reference probe) and transmittance finger probe for the detection of desaturation (SpO2 = 90%) was + 36 s (CI 27.0-45.0, P < 0.001). The time difference between probes at end of desaturation episode (SpO2 = 95%) was + 31 s (CI 19.0-43.0; P < 0.001). A significant difference in response time was evident throughout the episode in all saturation values. The reflectance ear probe showed better agreement with arterial blood gases. The bias (and precision) for the earlobe and finger oximeters were of 0.24 (1.04) and 2.31 (3.37), respectively.

CONCLUSION

The data displayed by a centrally located reflectance probe are more accurate and allows for earlier identification, treatment, and resolution of desaturation events. In light of these data and the added value of the reflectance probe ability to measure transcutaneous PCO₂, we recommend monitoring bronchoscopy by a reflectance oximetry probe.

Luminance gradients and non-gradients as a cue for distinguishing reflectance and illumination in achromatic images: A computational approach

The brain analyses the visual world through the luminance patterns that reach the retina. Formally, luminance (as measured by the retina) is the product of illumination and reflectance. Whereas illumination is highly variable, reflectance is a physical property that characterizes each object surface. Due to memory constraints, it seems plausible that the visual system suppresses illumination patterns before object recognition takes place. Since many combinations of reflectance and illumination can give rise to identical luminance values, finding the correct reflectance value of a surface is an ill-posed problem, and it is still an open question how it is solved by the brain. Here we propose a computational approach that first learns filter kernels ("receptive fields") for slow and fast variations in luminance, respectively, from achromatic real-world images. Distinguishing between luminance gradients (slow variations) and non-gradients (fast variations) could serve to constrain the mentioned ill-posed problem. The second stage of our approach successfully segregates luminance gradients and non-gradients from real-world images. Our approach furthermore predicts that visual illusions that contain luminance gradients (such as Adelson's checker-shadow display or grating induction) may occur as a consequence of this segregation process.