Measurements Of Absorption Research Articles

Concurrent measurements of phytoplankton productivity and light absorption from a global carbon hotspot: Variability, features, and causes

Concurrent measurements of phytoplankton productivity and light absorption from a global carbon hotspot: Variability, features, and causes

Ultrasonic Study of Novel Polymer Dextran in Aqueous Media at 12 MHz

Background: The characteristics of matter and the dynamics of molecular processes are examined by acoustic approaches. The primary techniques in molecular acoustics are the measure-ment of sound speed and sound absorption, as well as the relationship between these quantities and different physical variables including pressure, temperature, and wave frequency. Molecular acoustics emerged as a separate field in the 1930s. When it was discovered that many substances disperse the speed of sound during the transmission of sound waves through them and that the classical law, which states that the coefficient of absorption is proportional to the square of the frequency, however, it does not adequately describe how sound is absorbed. Objective: The ultrasonic technique is employed because it is one of the most popular techniques, which is very easy to use, and provides precise velocity results. With careful analysis of the results, the correlation between solute and solvent was discovered. In the pharmaceutical, agricultural, and cosmetics industries, dextran and its derivatives from a few select strains have found a wide range of uses. This is why we have chosen it for our study. For assessing the impact of temperature and con-centration on the aqueous medium containing the polymer dextran, ultrasonic properties are crucial. Pycnometer, Ostwald viscometer, and ultrasonic interferometer were used respectively to measure density (ρ), viscosity (η), and ultrasonic speed (u) at "303 K, 308 K, 313 K, 318 K, and 323 K." The experimental parameters are used to determine the acoustic parameters "adiabatic compressibility, Intermolecular free length, relaxation time, acoustic impedance, and Gibb's free energy". Method: To measure the density, viscosity, and ultrasonic velocity of the solution using a pycnome-ter, an Ostwald's viscometer, and an ultrasonic interferometer, and to calculate the thermo acoustical parameters based on the measured parameters. Result: Applications for examining the physico-chemical behaviour of aqueous dextran using ultra-sound include understanding the nature of molecular interactions. Conclusion: It was investigated how concentration and temperature affected the thermoacoustic char-acteristics of aqueous dextran. Hydrogen bonds, charge transfer complexes, and the dissolution of hy-drogen bonds and complexes are only a few examples of the forces that exist between molecules and how the analysis has interpreted their nature. Weak intermolecular forces exist. Other: Recent developments in ultrasonic techniques have made them an effective tool for evaluating information regarding the physical and chemical behaviour of liquid molecules.

Simulation, measurement and optimization of sound absorption in gradient impedance fiber-based composites

In order to achieve effective noise absorption by finite thickness fiber-based materials, fiber-based composites integrating porous, resonant and damping structures were prepared in this research. Here, the effects of gradient structure, number of constituent units, nonwovens thickness and micro-perforated membrane fabric (MPMF) arrangement on the noise reduction of the composites were simulated and measured. The results showed that the gradient fiber-based composite has excellent broadband sound absorption effect. Moreover, designing the arrangement of micro-perforated structures in the composite can further improve its noise reduction coefficient (NRC). The fiber-based composite (thickness of 1.34 cm) designed by the algorithm has an NRC of 0.51, which is much higher than other noise reduction products with the same thickness. The multi-layer fiber-based composites have the advantages of strong noise reduction capability, small thickness, simple processing and low manufacturing cost, which can be flexibly applied in various noise reduction fields.

Synthesis of ZnO Nanoparticle and Utilized as a Drug Carrier to Treat Leukemia

This study includes two parts, and the first was the preparation of the Zn(II)complex by reacting N-[4-(5-{(Z)-[(5-oxo-2-sulfanyl-4,5-dihydro-1H-imidazol-1-yl)imino]methyl}furan-2-yl)phenyl]acetamide with ZnCl2. The complex was characterized by using microscopic analysis such as UV-Vis spectrum, LC-MS, FTIR spectrophotometer, measurements of conductivity, magnetic susceptibility, and atomic absorption. The second part was the preparation of the ZnO nanoparticles by dissolving the Zn(II) complex in HNO3 and HCl and its use as a drug transporter to treat leukemia. FSEM, TEM, and XRD were examined for the characterization of ZnO nanoparticles that will be used in the synthesis of most medicines and drugs in the future.

Shortwave absorption by wildfire smoke dominated by dark brown carbon

Wildfires emit large amounts of black carbon and light-absorbing organic carbon, known as brown carbon, into the atmosphere. These particles perturb Earth’s radiation budget through absorption of incoming shortwave radiation. It is generally thought that brown carbon loses its absorptivity after emission in the atmosphere due to sunlight-driven photochemical bleaching. Consequently, the atmospheric warming effect exerted by brown carbon remains highly variable and poorly represented in climate models compared with that of the relatively nonreactive black carbon. Given that wildfires are predicted to increase globally in the coming decades, it is increasingly important to quantify these radiative impacts. Here we present measurements of ensemble-scale and particle-scale shortwave absorption in smoke plumes from wildfires in the western United States. We find that a type of dark brown carbon contributes three-quarters of the short visible light absorption and half of the long visible light absorption. This strongly absorbing organic aerosol species is water insoluble, resists daytime photobleaching and increases in absorptivity with night-time atmospheric processing. Our findings suggest that parameterizations of brown carbon in climate models need to be revised to improve the estimation of smoke aerosol radiative forcing and associated warming.

Complex refractive index and single scattering albedo of Icelandic dust in the shortwave part of the spectrum

Abstract. Icelandic dust can impact the radiative budget in high-latitude regions directly by affecting light absorption and scattering and indirectly by changing the surface albedo after dust deposition. This tends to produce a positive radiative forcing. However, the limited knowledge of the spectral optical properties of Icelandic dust prevents an accurate assessment of these radiative effects. Here, the spectral single scattering albedo (SSA) and the complex refractive index (m=n-ik) of Icelandic dust from five major emission hotspots were retrieved between 370–950 nm using online measurements of size distribution and spectral absorption (βabs) and scattering (βsca) coefficients of particles suspended in a large-scale atmospheric simulation chamber. The SSA(λ) estimated from the measured βabs and βsca increased from 0.90–0.94 at 370 nm to 0.94–0.96 at 950 nm in Icelandic dust from the different hotspots, which falls within the range of mineral dust from northern Africa and eastern Asia. The spectral complex refractive index was retrieved by minimizing the differences between the measured βabs and βsca and those computed using the Mie theory for spherical and internally homogeneous particles, using the size distribution data as input. The real part of the complex refractive index (n(λ)) was found to be 1.60–1.61 in the different samples and be independent of wavelength. The imaginary part (k(λ)) was almost constant with wavelength and was found to be around 0.004 at 370 nm and 0.002–0.003 at 950 nm. The estimated complex refractive index was close to the initial estimates based on the mineralogical composition, also suggesting that the high magnetite content observed in Icelandic dust may contribute to its high absorption capacity in the shortwave part of the spectrum. The k(λ) values retrieved for Icelandic dust are at the upper end of the reported range for low-latitude dust (e.g., from the Sahel). Furthermore, Icelandic dust tends to be more absorbing towards the near-infrared. In Icelandic dust, k(λ) between 660–950 nm was 2–8 times higher than most of the dust samples sourced in northern Africa and eastern Asia. This suggests that Icelandic dust may have a stronger positive direct radiative forcing on climate that has not been accounted for in climate predictions.

Optical Properties and Refractive Index of Wintertime Aerosol at a Highly Polluted North‐Indian Site

AbstractEstimation of aerosol radiative forcing continues to suffer from large uncertainties, partially from a lack of observations of aerosol optical properties. Limited measurements of the atmospheric aerosol imaginary refractive index (iRI) have been made, especially in some of the world's most polluted regions. In this study, we measured aerosol optical and micro‐physical properties at a regional site, Rohtak, India, representative of polluted cities in the Indo‐Gangetic plains in northern India. The average PM2.5 measured during the campaign was 163 μg/m3 with a single‐scatter albedo of 0.7, indicating the presence of strongly absorbing aerosol components. Measurements of aerosol absorption, scattering, and particle number size distributions were used to estimate the effective refractive index using an established Mie inversion technique. The calculated iRI was spectrally invariant in the visible region with values ranging between 0.076 and 0.145. Brown carbon absorption, estimated using an existing Mie optimization method, ranged 34–88 Mm−1, with strongly absorbing mass absorption cross‐sections (∼1.9 m2/g). Higher iRI were observed during periods with higher brown carbon absorption, which are likely directly emitted from combustion sources. Low volatility organic carbon fractions dominated during these periods, with likely persistence of atmospheric absorption. The iRI values are at the upper end of previously reported ranges of urban aerosol iRI. In a sensitivity analysis to measured parameters, the absorption had the dominant effect on estimated iRI. Measured single scatter albedos, were lower than those from climate model simulations over the region, demonstrating the need for intrinsic property measurements to evaluate and constrain climate models.

Investigation of the optoelectronic and structural properties of FA(1−x)BixPbBr6I3 of perovskite mixed halide films

In this study, we analyzed the structural and optical characteristics of pure FAPbBr2I mixed halide perovskites and doped with a large proportion of bismuth. Previous work has demonstrated that the replacement of 2/3 of the iodine by bromine in the perovskite FAPbI3 limits its phase transition and thus increases its stability. However, this improvement in stability is accompanied by an increase in the band gap, from 1.45 to about 2 eV. It has been found that bismuth doping of certain perovskite materials makes it possible, in addition to increasing their stability, to significantly reduce their band gap, although certain authors still contest this phenomenon. Thus, we synthesized thin layers of perovskite FAPbBr2I doped with bismuth and studied the effect of this doping on the crystalline structure and the layers' optical characteristics thanks to analyses by X-ray diffraction, scanning electron microscopy and measurements of absorption and photoluminescence. The structural analysis results showed that bismuth diffuses very slowly into the crystal, resulting in a reduction in crystal size and a smoother surface. Moreover, measurements of the absorption coefficient revealed a significant reduction in the band gap, going from 2.08 eV with 0% bismuth to 1.45 eV with 20% bismuth. However, photoluminescence measurements gave much higher bandgap values. We believe that a phenomenon related to the addition of bismuth is responsible for this discrepancy.

Extending the limitations in the prediction of PAMPA permeability with machine learning algorithms

Gastrointestinal absorption is a key factor amongst the ADME-related (absorption, distribution, metabolism and excretion) pharmacokinetic properties; therefore, it has a major role in drug discovery and drug safety determinations. The Parallel Artificial Membrane Permeability Assay (PAMPA) can be considered as the most popular and well-known screening assay for the measurement of gastrointestinal absorption. Our study provides quantitative structure-property relationship (QSPR) models based on experimental PAMPA permeability data for almost four hundred diverse molecules, which is a great extension of the applicability of the models in the chemical space. Two- and three-dimensional molecular descriptors were applied for the model building in every case. We have compared the performance of a classical partial least squares regression (PLS) model with two major machine learning algorithms: artificial neural networks (ANN) and support vector machine (SVM). Due to the applied gradient pH in the experiments, we have calculated the descriptors for the model building at pH values of 7.4 and 6.5, and compared the effect of pH on the performance of the models. After a complex validation protocol, the best model had an R2=0.91 for the training set, and R2= 0.84 for the external test set. The developed models are capable for the robust and fast prediction of new compounds with an excellent accuracy compared to the previous QSPR models.

Measurement of Time Dependent Reflection, Transmission, and Absorption in Laser Driven Silicon and GaAs Switches for 250 GHz Radiation.

The reflectance and transmittance of Si and GaAs wafers irradiated by a 6 ns pulsed, 532 nm laser have been studied for s- and p-polarized 250 GHz radiation as a function of laser fluence and time. The measurements were carried out using precision timing of the and signals, allowing an accurate determination of the absorptance where . Both wafers had a maximum reflectance above 90% for a laser fluence . Both also showed an absorptance peak of ~50% lasting ~2 ns during the risetime of the laser pulse. Experimental results were compared with a stratified medium theory using the Vogel model for the carrier lifetime and the Drude model for permittivity. Modeling showed that the large absorptance at the early part of the rise of the laser pulse was due to the creation of a lossy, low carrier density layer. For Si, the measured and were in very good agreement with theory on both the nanosecond time scale and the microsecond scale. For GaAs, the agreement was very good on the nanosecond scale but only qualitatively correct on the microsecond scale. These results may be useful for planning applications of laser driven semiconductor switches.

Humic Acid Removal by Electrocoagulation Process from Natural Aqueous Environments

Humic acid results in formation of highly toxic and carcinogenic byproducts during the disinfection process of water by chlorine. In this study, removal of industrial humic acid from artificial and natural aqueous media is investigated using electrocoagulation process. To reach the goal, first, humic acid-contaminated water samples with concentrations of 20 mg/L were prepared in a reactor with the effective volume of 1 L, equipped with iron electrodes. Then, the effects of pH (2 up to 9) and electric potential of 30 V was studied by measurement of UV radiation absorption and total organic materials methods, on the coagulation process in removal of humic acid within 80 min. According to the results of this study, the best efficiency in removal of humic acid was obtained as 92.69 by electrochemical process when the parameters were adjusted as; potential difference of 50 V, 80 min reaction time, pH 5, and electric conductivity of 3000 I¼S/cm. In the optimum condition, the efficiency of humic acid removal from natural water was obtained as 68.8. The results indicated that, the electrochemical process equipped with iron electrodes could remove humic acid from aqueous media, efficiently. © 2018 The Authors.

Simulated Inherent Optical Properties of Aquatic Particles using The Equivalent Algal Populations (EAP) model

Paired measurements of phytoplankton absorption and backscatter, the inherent optical properties central to the interpretation of ocean colour remote sensing data, are notoriously rare. We present a dataset of Chlorophyll a (Chl a) -specific phytoplankton absorption, scatter and backscatter for 17 different phytoplankton groups, derived from first principles using measured in vivo pigment absorption and a well-validated semi-analytical coated sphere model which simulates the full suite of biophysically consistent phytoplankton optical properties. The optical properties of each simulated phytoplankton cell are integrated over an entire size distribution and are provided at high spectral resolution. The model code is additionally included to enable user access to the complete set of wavelength-dependent, angularly resolved volume scattering functions. This optically coherent dataset of hyperspectral optical properties for a set of globally significant phytoplankton groups has potential for use in algorithm development towards the optimal exploitation of the new age of hyperspectral satellite radiometry.

Measurements of Nitrile Rubber Absorption of Hydrocarbons: Trends for Sustainable Aviation Fuel Compatibility

The commercial aviation sector is seeking to reach net zero CO2 emissions by 2050, with sustainable aviation fuel (SAF) being the most important lever. However, SAF is currently limited by ASTM specifications to a maximum of 50%v blending with conventional jet fuel. One reason for the current blend limit is motivation to maintain o-ring swelling consistent with 100% petroleum fuel. This work explores the relationships between o-ring swelling of SAF blend components, model compounds, and various blends in nitrile rubber compared to conventional fuel swelling. Specifically, optical dilatometry measurements were used to gather swell propensity data for 39 different hydrocarbon dopants at 8%v in an iso-alkane solution, 4 dopants at 7 different concentrations, and 19 different fuels or fuel blends. This study also highlights the advantages of using swell measurements, such as those employed here, as a quality control metric instead of the current 8%v aromatics requirement. Notably, the potential is shown to maintain swelling in the conventional fuel range with fuels composed of less than 8%v aromatics.

The results of atmospheric parameters measurements in the millimeter wavelength range on the radio astronomy observatory “Suffa Plateau”

The results of measurements of atmospheric absorption and the amount of precipitated water on the Suffa Plateau for the period from January, 2015 to November, 2020, are presented. The measurements of atmospheric parameters in the 2 and 3 mm range of the radio waves spectrum were carried out using the MIAP-2 radiometer. The results of more than six years of measurements have show that on the Suffa Plateau, atmospheric parameters in the above range remain fairly stable. The median value of the atmospheric absorption and the amount of precipitated water over the entire observation period were 0.14 and 0.12 Nep and 5.91 and 9.83 mm, respectively, for the ranges of 2 and 3 mm.

Investigation of Depth Variations of the Bamboo Twigs for its Acoustical Performance

This study aims to determine the relationship between variations in the depth of bamboo twigs with the sound absorption coefficient. The sample consisted of 12 bamboo twigs made up of three types of depth variations. Measurement of sound absorption of bamboo twigs using two microphone impedance tubes and B & K Lab shop software version 16. Standardization ISO 10534-2:1998 [1] was used to test parameters between 100 and 1600 Hz. This type of research is a comparative quantitative approach, data processing using Pulse Lab shop version 16 and visualized into a curve graph using Microsoft Excel. The results showed that the bamboo twig material with a depth of 50 mm was better than 25 mm with an absorption coefficient (α) of 0,68 at a frequency of 1600 Hz. While the material with a thickness of 75 mm only absorbs at a frequency of 1100 Hz with a maximum absorption coefficient of 0,57. According to ISO 11654 [2], it shows that bamboo twigs have the potential to be used as sound-absorbing materials. The sound absorption coefficient value of bamboo twigs rises from low to high frequency with increasing twig depth.

Searching for Spectroscopic Signatures of Ongoing Quenching in SDSS Galaxies

In this paper, we estimate the “star formation change parameter,” SFR79, which characterizes the current SFR relative to the average during the last 800 Myr, for ∼300,000 galaxies selected from the Sloan Digital Sky Survey (SDSS). The goals are to examine, in a much larger and independent sample, the trends previously reported in a sample of star-forming (SF) MaNGA galaxies and also to search for spectroscopic signatures of ongoing quenching in the so-called “Green Valley,” which is generally believed to contain galaxies that are migrating from the SF population to the quenched population of galaxies. Measuring SFR79 for our large sample of SDSS galaxies, we first confirm the basic results of SF galaxies published by Wang & Lilly. We then discuss in detail the calibration and meaning of SFR79 for galaxies that are well below the SFMS and establish the expected statistical signature of systematic ongoing quenching from modeling the z ∼ 0 quenching rate of the SF population. We conclude that it is not possible at present to establish unambiguous observational evidence for systematic ongoing quenching processes, due to limitations both in the noise of the observational data, in particular in the measurements of Hδ absorption, and in the calibration of SFR79, as well as biases introduced by the necessity of selecting objects with significant Hα emission. We do however see plausible indications of ongoing quenching, which are quantitatively consistent with expectations from “growth+quenching” models of galaxy evolution and a typical e-folding timescale for quenching of ∼500 Myr.

Nonlinear Interferometry for Quantum-Enhanced Measurements of Multiphoton Absorption.

Multiphoton absorption is of vital importance in many spectroscopic, microscopic, or lithographic applications. However, given that it is an inherently weak process, the detection of multiphoton absorption signals typically requires large field intensities, hindering its applicability in many practical situations. In this Letter, we show that placing a multiphoton absorbent inside an imbalanced nonlinear interferometer can enhance the precision of multiphoton cross section estimation with respect to strategies based on photon-number measurements using coherent or even squeezed light directly transmitted through the medium. In particular, the power scaling of the sensitivity with photon flux can be increased by 1 order compared with transmission measurements of the sample with coherent light, such that the measurement precision at any given intensity can be greatly enhanced. Furthermore, we show that this enhanced measurement precision is robust against experimental imperfections leading to photon losses, which usually tend to degrade the detection sensitivity. We trace the origin of this enhancement to an optimal degree of squeezing which has to be generated in a nonlinear SU(1,1) interferometer.

Synthesis and photophysical properties of fluorescent 8,9‐diarylbenzo[def]carbazoles

AbstractBackgroundBenzocarbazole has attracted much attention from scientists in the past few decades for a variety of applications in materials science.ObjectiveHerein we report the synthesis and photophysical properties of N‐acyl and N‐free 8,9‐diarylbenzo[def]carbazoles.MethodsThese benzo[def]carbazoles were prepared by Pd(II)‐catalyzed C‐H bond activation and deacetylation as the key steps, and their photophysical properties were studied by measurement of absorption and emission spectra in chloroform at room temperature.ResultsThe 8,9‐diarylbenzo[def]carbazoles show lower LUMO energy levels and smaller HOMO/LUMO gap compared to the parent benzo[def]carbazole, and the N‐unprotected 8,9‐diarylbenzo[def]carbazoles show more red‐shifted fluorescent emission compared to the N‐acyl ones. The absorption and emissionmaxima of these 8,9‐diaryl‐substituted benzo[def]carbazoles in CHCl3 were in the ranges of 278–350 and 365–426 nm, respectively, and with quantum yields (ΦF) up to 0.62.ConclusionsWe have demonstrated the photophysical properties of 8,9‐diaryl substituted benzo[def]carbazoles with or without N‐acetyl group. These 8,9‐diaryl substituted benzo[def]carbazoles could be good candidates for the future development of functional organic molecules.

A Novel Validated RP-HPLC Method For the Estimation of Salmeterol By DOE

Background: Salmeterol is a long-acting beta agonist (LABAs) Salmeterol is hypothesized to bind to 2 sites on the beta-2 adrenoceptor. The saligenin moiety binds to the active site of the beta-2 adrenoceptor. The hydrophilic tail of salmeterol binds to leucine residues in the exo-site of the beta-2 adrenoceptor almost irreversibly, allowing salmeterol to persist in the active site, which is responsible for its long duration of action. Method: A new, simple, accurate, rapid, precise, reproducible and cost-effective RP-HPLC method for the quantitative estimation of Salmeterol in bulk and pharmaceutical dosage form. The developed RP-HPLC method for the quantitative estimation of Salmeterol is based on measurement of absorption at maximum wavelength 254 nm using Phosphate buffer: Methanol PH 2.5 (35:65 v/v) as a solvent. The stock solution of Salmeterol was prepared, and subsequent suitable dilution was prepared in mobile phase to obtained standard curve. The standard solution shows absorption maxima at 254 nm. Results: The Salmeterol obeyed Beer Lambert’s law in the concentration range of 20-100μg/ml with regression 0.999 at 254 nm. The overall % recovery was found to be 99.78% for Salmeterol which reflects that the method was free from the interference of the impurities and other excipients, used in the bulk and marketed dosage form. The low value of % RSD was indicative of accuracy and reproducibility of the method. The % RSD for inter-day and intra-day precision was found to be 0.2 for Salmeterol respectively which is <2% hence proved that method is precise. Conclusion: In the present study, novel reverse phase High performance liquid chromatography method for simultaneous determination of Salmeterol in pharmaceutical dosage form was developed. The developed method was validated for various parameters such as accuracy, precision, ruggedness, linearity, robustness, system suitability, specificity as per ICH guidelines.

Doe Approach: A Validated Rp -Hplc Method For The Determination Of Dapagliflozin

Background: Dapagliflozin is a competitive inhibitor of sodium / glucose co transporter 2 (SGLT2). It will Inhibiting the reabsorption of filtered glucose in the kidney leads to elevated urinary glucose excretion, thereby lowering blood Method: A new, simple, accurate, rapid, precise, reproducible and cost-effective RP-HPLC method for the quantitative estimation of Dapagliflozin in bulk and pharmaceutical dosage form. The developed RP-HPLC method for the quantitative estimation of Dapagliflozin is based on measurement of absorption at maximum wavelength 254 nm using 0.1% urea: methanol (35:65% v/v) as a solvent. The stock solution for Dapagliflozin was prepared, and subsequent suitable dilution was prepared in mobile phase to obtained standard curve. The standard solution of Dapagliflozin shows absorption maxima at 254 nm. Results: Dapagliflozin will obeys Beers -Lamberts law in the concentration range of 20 - 100μg/ml with regression 0.999 at 254nm.The overall % recovery was found to be 101.59% for Dapagliflozin which reflects that the method was free from the interference of impurities and other impurities, used in bulk and marketed dosage forms. The low value of % RSD was indicative of accuracy and reproducibility of the method. The % RSD for inter-day and intra-day precision was found to be 0.1 for Dapagliflozin respectively which is & it <2% hence proved that method is precise. Conclusion: The results of analysis have been validated as per International Conference on Harmonization (ICH) guidelines. The developed method can be adopted in routine analysis of Dapagliflozin in bulk and tablet dosage form. The Proposed method was found to be rapid, accurate, precise, specific, robust, rugged and economical.