Detection of Rice Yellow Mottle at the Asymptomatic Stage by Hyperspectral Fluorescence and Reflectance Spectroscopies

Rice yellow mottle is considered the most destructive disease threatening rice production in Africa. Early detection of this infection in rice is essential to limit its expansion and proliferation. However, there is no research devoted to the spectral detection of rice yellow mottle virus (RYMV) infection, especially in the asymptomatic or early stages. This work proposes the use of hyperspectral fluorescence and reflectance data at leaf level for the detection of this disease in asymptomatic stages. A greenhouse experiment was therefore conducted to collect hyperspectral fluorescence and reflectance data at different stages of infection. These data allowed to calculate nine vegetation indices: one from fluorescence spectra and eight from reflectance spectra. A t-test made it possible to identify, from the second day after infection, four relevant reflectance vegetation indices to discriminate healthy leaves from those infected: these are Photochemical Reflectance Index (PRI), Transformed Chlorophyll Absorption in Reflectance Index (TCARI), Structure Intensive Pigment Index (SIPI) and Simple Ratio Pigment Index (SRPI). The fluorescence index was less sensitive in detecting infection. The four significant vegetation indices for the detection of RYMV were then used to build and evaluate models for discriminating plants according to their health status by the supervised classification of support vector machine (SVM) at different stages of infection. The maximum overall accuracy is 92.5% six days after inoculation (6 DAI). The sixth day after inoculation would be the adequate day to detect RYMV. This plants discrimination was validated by the mean reflectance spectra and by the histograms showing the differences between the average reflectance vegetation indices values of the two types of plants. Our results demonstrate the feasibility of differentiating RYMV-infected samples. They suggest that support vector machine learning models could be developed to diagnose RYMV-infected plants based on vegetation indices derived from spectral profiles at early stages of disease development.

Charge Transfer Spectra (CTS) in CaS:Ce^(3+) Phosphors

This paper describes the excitation spectra nearby 220hm of CaS:Ce^(3+),Na^+ and CaS:Ce^(3+),X^-(X=F,Cl or Br).It is considered that the charge transfer excitation is caused by electron transfer of S^(2-)on 3p^6 to the 4f shell of Ce^(3+).It has been discussed that,when halogen ions act as coactivators,this excitation band shifts to low- er wavenumber.

Effect of HITRAN Database Improvement on Retrievals of Atmospheric Carbon Dioxide from Reflected Sunlight Spectra in the 1.61-μm Spectral Window

A large number of experimental and theoretical investigations of carbon dioxide （CO 2 ） spectra have been conducted since the most recent update of the High-Resolution Transmission Molecular Absorption （HITRAN） database. To maintain optimal parameters, the HITRAN 2004 CO 2 line list has been completely replaced by HITRAN 2008 data in the near-infrared region from 4300 cm-1 to 7000 cm-1 . To examine the effect of this change on the retrieval of CO 2 vertical column data from reflected sunlight spectra in the 1.61-μm spectral window, synthetic measurements for a given atmospheric state and instrument setup were generated and compared using radiative transfer model with the line-transition parameters from the HITRAN 2004 and 2008 databases. Simulated retrievals were then performed based on the optimal estimation retrieval theory. The results show that large systematic errors in atmospheric CO 2 column retrievals were induced by the differences in the HITRAN laboratory line parameters in the 1.61-μm region. The retrieved CO 2 columns were underestimated by 10 ppm using the HITRAN 2004 data, and improvements resulting from the use of the improved HITRAN database were more pronounced at a higher spectral resolution.

Structure,room-temperature magnetic and optical properties of Mn-doped TiO_2 nano powders prepared by the sol-gel process

TiO2 nano powders with Mn concentration of 0 at%-12 at% were synthesized by the sol-gel process, and were annealed at 500 ℃ and 800 ℃ in air for 2 hrs. X-ray diffraction （XRD） measurements indicate that the Mn-TiO2 nano powders with Mn concentration of 1 at% and 2 at% annealed at 500 and 800 ℃ are of pure anatase and rutile, respectively. The scanning electron microscope （SEM） observations reveal that the crystal grain size increases with the annealing temperature, and the high resolution transmission electron microscopy （HRTEM） investigations further indicate that the samples are well crystallized, confirming that Mn has doped into the TiO2 crystal lattice effectively. The room temperature ferromagnetism, which could be explained within the scope of the bound magnetic polaron （BMP） theory, is detected in the Mn-TiO2 samples with Mn concentration of 2 at%, and the magnetization of the powders annealed at 500 ℃ is stronger than that of the sample treated at 800 ℃. The UV-VIS diffuse reflectance spectra results demonstrate that the absorption of the TiO2 powders could be enlarged by the enhanced trapped electron absorption caused by Mn doping.

Structural and optical properties of Al_(1-x)In_xN epilayers on GaN template grown by metalorganic chemical vapor deposition

This paper reports that Al1-xInxN epilayers were grown on GaN template by metalorganic chemical vapor deposition with an In content of 7%--20%. X-ray diffraction results indicate that all these Al1-xInxN epilayers have a relatively low density of threading dislocations. Rutherford backscattering/channeling measurements provide the exact compositional information and show that a gradual variation in composition of the Al1-xInxN epilayer happens along the growth direction. The experimental results of optical reflection clearly show the bandgap energies of Al1-xInxN epilayers. A bowing parameter of 6.5~eV is obtained from the compositional dependence of the energy gap. The cathodoluminescence peak energy of the Al1-xInxN epilayer is much lower than its bandgap, indicating a relatively large Stokes shift in the Al1-xInxN sample.

Preparation and Characterization of La0.67–x Li3x TiO3 Solid-State Electrolyte Used for Electrochromic Mirrors

With the aim of producing all-solid-state electrochromic mirrors, La0.67–xLi3xTiO3 (LLTO) and the WO3 were prepared by electron beam deposition. The LLTO (with x = 0.11) powder was synthesized by thermally ball-grinding method and the Li+ ionic conductivity of the LLTO ceramic targets was found to be of ca. 3.25 × 10–3 S/cm. Using LLTO targets for e-beam evaporation, 300 nm-thick films with the Li+ ionic conductivity of 5.50 × 10–5 S/cm were deposited. Combining LLTO films with WO3/ITO and LiMn2O4 layers, all-solid-state electrochromic mirrors with a laminar structure of Al/LiMn2O4/LLTO/WO3/ITO were prepared. The reversible reflectance of the mirrors was well controlled by applying polarized potentials onto the ITO electrode. The obtained results suggest useful applications for electrochromic windows working as a smart reflectance mirror that can be used for auto rear-view mirrors.

Leaf spectral signatures differ in plant species colonizing habitats along a hydrological gradient

Aims We aimed at determining differences in the leaf spectral signatures of plant species groups growing in habitats along the hydrological gradient of an intermittent wetland and to define leaf traits that explain their variability.We want to contribute to the understanding of the causes for plant spectrum variability at leaf and community levels.Methods We measured leaf reflectance spectra(300-887 nm)of representative plant species from different habitats and analyzed spectral differences among species groups.To explain leaf spectra variability within a group,we performed detailed analyses of leaf morphological and biochemical traits in selected species.Important FindingsThe reflectance spectra of the different species groups differed most in the green,yellow and red spectral ranges.The reflectance spectra of submerged leaves of hydrophytes with simple structures were explained by their biochemical traits(carotenoids),while for more complex aerial leaves,morphological traits were more important.In submerged and natant leaves of amphiphytes,total mesophyll and spongy tissue thickness were the most important traits,and these explained 44%and 47%,respectively,of the spectrum variability of each plant group.In general,the redundancy analysis biplots show that samples of different plant species colonizing the same habitat form separate clusters and are related to the explanatory variables in different ways.The redundancy analysis biplots of helophytes and wet meadow species show clustering of graminoids and dicots into two distinct groups.Leaf encrustation(prickle hair properties and epidermis thickness)is important for graminoids,while leaf thickness and specific leaf area have more important roles in dicots.Our results show that knowledge of the species composition and leaf traits is necessary to interpret the reflectance spectra of such plant communities.

The application of proximal visible and near-infrared spectroscopy to estimate soil organic matter on the Triffa Plain of Morocco

Soil organic matter (SOM) is a fundamental soil constituent. The estimation of this parameter in the laboratory using the classical method is complex time-consuming and requires the use of chemical re-agents. The objectives of this study were to assess the accuracy of two laboratory measurement setups of the VIS-NIR spectroscopy in estimating SOM content and determine the important spectral bands in the SOM estimation model. A total of 115 soil samples were collected from the non-root zone (0-20 cm) of soil in the study area of the Triffa Plain and then analysed for SOM in the laboratory by the Walkley-Black method. The reflectance spectra of soil samples were measured by two protocols, Contact Probe (CP) and Pistol Grip (PG)) of the ASD spectroradiometer (350-2500 nm) in the laboratory. Partial least squares regression (PLSR) was used to develop the prediction models. The results of coefficient of determination (R2) and the root mean square error (RMSE) showed that the pistol grip offers reasonable accuracy with an R2=0.93 and RMSE=0.13 compared to the contact probe protocol with an R2=0.85 and RMSE = 0.19. The near-Infrared range were more accurate than those in the visible range for pre-dicting SOM using the both setups (CP and PG). The significant wavelengths contributing to the pre-diction of SOM for (PG) setup were at:424, 597, 1432, 1484, 1830,1920, 2200, 2357 and 2430 nm, while were at 433, 587, 1380, 1431, 1929, 2200 and 2345 nm for (CP) setup.

Reliable and broad-range layer identification of Au-assisted exfoliated large area MoS_(2)and WS_(2)using reflection spectroscopic fingerprints

The emerging Au-assisted exfoliation technique enables the production of a wealth of large-area and high-quality ultrathin two dimensional(2D)crystals.Fast,damage-free,and reliable determination of the layer number of such 2D films can greatly promote layer-dependent physical studies and device applications.Here,an optical method has been developed for simple,high throughput,and accurate determination of the layer number for Au-assisted exfoliated MoS_(2)and WS_(2)films in a broad thickness range.The method is based on quantitative analysis of layer-dependent white light reflection spectra(WLRS),revealing that the intensity of exciton-induced reflection peaks can be used as a clear indicator for identifying the layer number.The simple yet robust method will facilitate fundamental studies on layer-dependent optical,electrical,and thermal properties and device applications of 2D materials.The technique can also be readily combined with photoluminescence(PL)and Raman spectroscopies to study other layer-dependent physical properties of 2D materials.

Rare earth complexes with noncyclic polyether-methionine Schiff base

A novel Schiff base (TAMET) was synthesized by the condensation of tetraglycol aldehyde with methionine and a mild oxidant CrO3. (C5H5N)2 was selected for the reaction. Seven new rare earth complexes with this Schiff base have been synthesized and characterized by elemental analysis, TG-DTA, molar Conductivity, magnetic susceptibility and IR, especially 1H NMR spectra. Information was obtained from reflectance spectra and the coordination of sulfur atom to rare earths was discussed. The experimental results show that these compounds have some biological activity and could dispose of O2?-.