Wavelength Of Nm Research Articles

A novel algorithm to extrapolate ultraviolet absorption of chromophoric dissolved organic matter from remote sensing ocean color

Accurate estimation of the absorption of chromophoric dissolved organic matter (CDOM) in ultraviolet (UV) wavelength range is crucial for understanding photochemical and biochemical processes in the global ocean. Here, we propose a novel UV absorption extrapolation (UVAE) algorithm. It extrapolates the absorption coefficients (ag(λ) where λ is the wavelength in nm) of CDOM in the UV wavelength range from ocean color data in the visible wavelength range observed by satellite remote sensing. The extrapolation is based on the assumption that three characteristic Gaussian bands describe the CDOM UV–visible absorption spectra (275–443 nm). The UVAE algorithm retrieves the ag(275), ag(295), ag(330), and ag(380) using the characteristics of the spectral slope (S) of the absorbance spectra of CDOM at specific wavelength intervals, namely 275–295, 295–330, 330–380, and 380–443 nm. With the UVAE algorithm, the spatial variability of CDOM spectral features can be captured on a global scale using data from the Moderate-resolution Imaging Spectroradiometer (MODIS) Aqua mission. The retrieved ag(275), ag(295), ag(330), and ag(380) values match well with in-situ observed values, with mean absolute percent differences (MAPDs) of 19.2 %, 26.1 %, 36.9 %, and 46.6 %, respectively. The performance of the UVAE algorithm demonstrates a significant improvement compared to that of existing algorithms, especially for ag(λ) at lower wavelengths.

Simulation of Heat Transfer in Single-Crystal Lithium Niobate in Interaction with Continuous-Wave Laser Radiation

The paper presents the simulation results of heat transfer in single-crystal lithium niobate (LiNbO3) in the form of cylinder of diameter mm and height mm in interaction with continuous-wave laser radiation with the output power of W and the wavelength of nm. The density of the LiNbO3 crystal is kg/m3; the thermal conductivity along the [001] direction is W/(m×K); the thermal conductivity in the (001) plane is W/(m×K); the specific heat at constant pressure is J/(kg×K); the absorption coefficient is %/cm @ 1064 nm. The laser beam propagates along the optical axis of the crystal. The laser beam intensity profile is represented as a Gaussian function, and the absorption of laser radiation of the single-crystal lithium niobate is described by Beer-Lambert’s law. The numerical solution of the non-stationary heat conduction problem is obtained by meshless scheme using anisotropic radial basis functions. The time interval of the non-stationary boundary-value problem is 2 h 30 min. The results of numerical calculations of the temperature distribution inside and on the surface of the single-crystal lithium niobate at times s are presented. The time required to achieve the steady-state heating mode of the LiNbO3 crystal, as well as its temperature range over the entire time interval, have been determined. The accuracy of the approximate solution of the boundary-value problem at the n-th iteration is estimated by the value of the norm of relative residual . The results of the numerical solution of the non-stationary heat conduction problem obtained by meshless method show its high efficiency even at a small number of interpolation nodes.

Diode like high-contrast asymmetric transmission of linearly polarized waves based on plasmon-tunneling effect coupling to electromagnetic radiation modes

We present a narrow-band optical diode with a high-contrast forward-to-backward ratio at the near-infrared region. The design has a forward transmission of approximately , and a backward one of less than , yielding a contrast ratio of greater than dB at a wavelength of nm. The structure is composed of a one-dimensional diffraction grating on top of a dielectric slab waveguide, both of which are made of silicon nitride (Si3N4), and all together are placed over a silver (Ag) thin film embedded on a dielectric substrate. Utilizing a dielectric-based diffraction grating waveguide on a thin silver layer leads to the simultaneous excitation of two surface plasmon modes known as long- and short-range surface plasmon polaritons (SPPs) at both interfaces of the metallic layer. The plasmon-tunneling effect, which is the result of the coupling of SPPs excited at the upper interface of the metallic layer to the radiation modes, provides a high asymmetric transmission (AT) property. The spectral response of the proposed high-contrast AT device is verified using both rigorous coupled-wave analysis as an analytical approach and finite difference time domain as a numerical one.

A systematic review of the effective laser wavelength range in delivering photobiomodulation for pain relief in active orthodontic treatment

This systematic review aimed to establish an effective wavelength range for PhotoBioModulation (PBM) to relieve pain in orthodontic treatments. The electronic literature search was carried out in the following databases: PubMed, ISI Web of Science, Scopus, and Cochrane. In the initial search, 255 papers were obtained. Deleting duplicates in the search left 180 items. One manually searched study was included for a total of 181 studies. According to PRISMA guidelines and a thorough analysis of their methodology, the final sample was composed of 13 RCTs. The final statistical analysis was performed in 11 studies. The statistical analysis sought to strengthen the collected data, determining the correlation coefficient (r) for the same time interval (24h) using a scale equivalent to the standard value (0-10cm). Aiming to reduce the effect of heterogeneity, the difference in cm between control group (GC) and experimental group (EG) averages was considered the outcome. This difference was correlated with the wavelength in nm, calculating the Pearson linear correlation coefficient, and calculating a logarithmic correlation. The dispersion of the data obtained in the experimental groups at each given wavelength showed that the most significant number of studies were in the ranges of 780-830nm. The correlation between the wavelength and the difference between the control and experimental group averages, either linear (R2=0.0564, r=0.237) or logarithmic (R2=0.0688, r=0.262) was not significant (P>0.90). Therefore, pain reduction after 24h is not significantly dependent of wavelength. The majority of RCTs related to pain relief in orthodontic treatment showed 780-830nm as the most effective photobiomodulation wavelength range for orthodontic pain relief. However, pain reduction after 24h is not significantly dependent of wavelength. The protocol was registered in PROSPERO (CRD42019119799).

Simple in‐field evaluation of moisture content in curing forage using normalized differece vegetation index (NDVI)

AbstractProduction of hay at a proper moisture level is critical to reduce the spontaneous heating and nutrient loss during the preservation phase. Herein, we explored a new method for estimating the moisture content (MC) of field curing forages that uses a portable spectroradiometer (400–900 nm) and a hand‐held normalized difference vegetation index (NDVI) meter. The spatial distributions were assessed by a multispectral camera with unmanned aerial vehicle (UAV) platform. Field spectral measurements were conducted daily at 10 random plots over six trials at four forage fields across the entire curing period. Multispectral imagery acquisition by UAV flights was conducted at one trial. The MC (wet basis) was determined using a forced‐air oven. For 400–900 nm spectral reflectance measured by the spectroradiometer, we conducted linear regression analyses between the MC and all available combinations of a normalized difference spectral index (NDSI(Band1, Band2) = (ρBand1 − ρBand2)/(ρBand1 + ρBand2), where ρλ is the apparent reflectance and λ is the wavelength in nm). The combinations that are generally used as greenness indices showed high coefficients of determination, for example, red and near infrared (R2 = .76, RMSE = 10.66%) and green and red (R2 = .81, RMSE = 9.57%). The NDVI meter and multispectral imagery showed the feasibility of NDVI (R2 = .79, RMSE = 8.58% and R2 = .89, RMSE = 6.74%, respectively) as a parameter to estimate the MC. We were able to verify the spatial variability of the MC in the field based on the NDVI imagery, which indicates that our method provides information for site‐specific management (e.g., partial swath manipulation) and for decision‐making regarding the harvest time and location.

Optical properties of size fractions of suspended particulate matter in littoral waters of Québec

Abstract. Mass-specific absorption (ai∗(λ)) and scattering (bi∗(λ)) coefficients were derived for four size fractions (i = 0.2–0.4, 0.4–0.7, 0.7–10, and > 10 µm, λ = wavelength in nm) of suspended particulate matter (SPM) and with samples obtained from surface waters (i.e., 0–2 m depth) of the Saint Lawrence Estuary and Saguenay Fjord (SLE-SF) during June of 2013. For the visible–near-infrared spectral range (i.e., λ = 400–710 nm), mass-specific absorption coefficients of total SPM (i.e., particulates > 0.2 µm) (hereafter aSPM∗) had low values (e.g., < 0.01 m2 g−1 at λ = 440 nm) in areas of the lower estuary dominated by particle assemblages with relatively large mean grain size and high particulate organic carbon and chlorophyll a per unit of mass of SPM. Conversely, largest aSPM∗ values (i.e., > 0.05 m2 g−1 at λ = 440 nm) corresponded with locations of the upper estuary and SF where particulates were mineral-rich and/or their mean diameter was relatively small. The variability of two optical proxies (the spectral slope of particulate beam attenuation coefficient and the mass-specific particulate absorption coefficient, hereafter γ and Svis, respectively) with respect to changes in particle size distribution (PSD) and chemical composition was also examined. The slope of the PSD was correlated with bi∗(550) (Spearman rank correlation coefficient ρs up to 0.37) and ai∗(440) estimates (ρs up to 0.32) in a comparable way. Conversely, the contribution of particulate inorganic matter to total mass of SPM (FSPMPIM) had a stronger correlation with ai∗ coefficients at a wavelength of 440 nm (ρs up to 0.50). The magnitude of γ was positively related to FSPMi or the contribution of size fraction i to the total mass of SPM (ρs up to 0.53 for i = 0.2–0.4 µm). Also, the relation between γ and FSPMPIM variability was secondary (ρs = −0.34, P > 0.05). Lastly, the magnitude of Svis was inversely correlated with aSPM∗(440) (ρs = −0.55, P = 0.04) and FSPMPIM (ρs = −0.62, P = 0.018) in sampling locations with a larger marine influence (i.e., lower estuary).

Photonic crystal fiber long-period gratings for biochemical sensing

We present experimental results showing that long-period gratings in photonic crystal fibers can be used as sensitive biochemical sensors. A layer of biomolecules was immobilized on the sides of the holes of the photonic crystal fiber and by observing the shift in the resonant wavelength of a long-period grating it was possible to measure the thickness of the layer. The long-period gratings were inscribed in a large-mode area silica photonic crystal fiber with a CO2 laser. The thicknesses of a monolayer of poly-L-lysine and double-stranded DNA was measured using the device. We find that the grating has a sensitivity of approximately 1.4nm/1nm in terms of the shift in resonance wavelength in nm per nm thickness of biomolecule layer.

Optical Characterization of MBE Grown Zinc-Blende AlGaN

Zinc-blende AlGaN epilayers were grown by plasma-assisted MBE on thick (001) SiC deposited by CVD on Si substrates. Alloy compositions were controlled in situ by reflection high energy diffraction (RHEED) oscillations, and confirmed by Rutherford backscattering (RBS) post growth analysis. The zinc-blende nature of our samples was assessed by RHEED analysis. From reflectivity measurements at room temperature, we deduce the variation of the lowest direct absorption edge of zinc-blende AlGaN as a function of the Al content x, E0(x) = 3.25 (1 — x) + 6.05x — 1.4x (1 — x), E0 in eV. The dispersion of the refractive index n of cubic AlN was also extracted from our reflectivity and RBS data, and fitted by a Sellmeier-type relation, n2 = 3.05 + 1.38 λ2/(λ2—1802), λ being the wavelength in nm.

Development of a new technique for high-energy secondary-electron measurements in plasma immersion ion implantation

A scintillation technique was applied to directly monitor high-energy secondary electrons during the process of plasma immersion ion implantation (PIII). The spectral peak of the scintillation appeared at the wavelength of nm, and the temporal behaviour of the secondary electrons was measured with a response time as short as several microseconds. A maximum absolute secondary-electron flux for a target peak voltage of 25 kV reached at a measuring point, which showed good agreement with a calculated value. The kinetic energy of the secondary electrons was also measured by penetration depth into an aluminium layer coated on the scintillator surface, revealing acceleration of the secondary electrons up to an energy corresponding to the sheath voltage.

Light transmittance of the human cornea from 320 to 700 nm for different ages

In vivo relative corneal transmittance was estimated using Tan's [(1971) Vision in the ultraviolet, thesis, University of Utrecht, The Netherlands] data on scotopic spectral sensitivity in aphakic eyes. This was combined with in vitro corneal transmittance data and in vivo light scattering data to arrive at absolute data. All data combined, the following function (no age dependence is found) resulted: log(transmittance) = −0.016 −c *λ −4(λ = wavelength in nm, λ > 310nm). c = 85 *10 3nm 4 for direct transmittance (acceptance angle of the order of 1 deg) and c = 21*10 8nm 4 for total transmittance (acceptance angle close to 180 deg).

A spectral model of the beam attenuation coefficient in the ocean and coastal areas

A large set (∼ 100 data points at each wavelength) of multispectral beam attenuation, c(λ), data at nine wavelengths (440, 450, 490, 520, 535, 550, 565, 630, and 670 nm) is used to develop a spectral model of the beam attenuation coefficient. The relationship c(λ) − cW(λ) =[c(490 nm) − cW(490 nm)](1.563 − 1.149 × 10−3 λ) describes the spectral variation of c(λ) where cW(λ) is the pure water beam attenuation and λ is the wavelength in nm. From a subset of the data a relationship of chloropyll (Chl) to c(490) was found to be c(490) = 0.39 Chl0.57; however there is significant scatter in this relationship. The spectral c model was tested with independent data sets and the average percent difference of the measured to predicted values ranged from 0.4 to 5% for the different spectral bands.

A Handy Indicator of Resolution in Raman Spectroscopy

There are now numerous spectroscopy laboratories located throughout North America and in the rest of the world in which an Instruments S. A. U-1000 Ramanor spectrometer is employed to collect Raman data. Often, these measurements involve the use of different laser lines to excite the Raman spectra. During the course of our own work over the past six years on this type of instrument, we have needed to have knowledge of the actual resolution in wavenumbers rather than simply the slit-width settings in microns for a variety of argon- and krypton-ion laser lines. To aid us in this endeavor, we have constructed the curve shown in Fig. 1 using information provided by Instruments S. A. for the dispersion of the 1.0-m double monochromator of the U-1000 spectrometer when equipped with two 1800 grooves/mm−1 holographic gratings. The equation for this curve is: Res. = {(0.2254 − 1.436∗10−3∗λ + 3.959∗10−6∗λ2 − 5.645∗10−9∗λ3 + 4.073∗10−12∗λ4 − 1.177∗10−15∗λ5)∗μ} [1a] or μ = Res./(0.2254 − 1.436∗10−3∗λ + 3.959∗10−6∗λ2 − 5.645∗10−9∗λ3 + 4.073∗10−12∗λ4 − 1.177∗10−15∗λ5) [1b] where the resolution is given in cm−1, λ is the wavelength in nm, and μ is the slit width in μm. The equation governs the range of the U-1000 monochromator from 300.0 to 909.1 nm. The resolutions for commonly used wavelengths, in Raman spectroscopy, are given in Table I. Furthermore, since for a given wavelength the plot of slit width vs. resolution is linear, the equations of the lines for the wavelengths shown in Table I are listed in Table II. It is hoped that this handy resolution guide will prove useful to other members of the Raman spectroscopic community.