Similar Absorption Coefficients Research Articles

Qualitative and Quantitative Detection of Pesticides With Terahertz Time-Domain Spectroscopy

This paper used the newly developed terahertz time-domain spectroscopy (THz-TDS) to detect pesticides, especially imidacloprid, qualitatively and quantitatively in the frequency range of 0.5-1.6 THz. All together, four pesticides and three food powders, as well as polyethylene, were investigated. Different weight ratios of imidacloprid in polyethylene and in sticky rice powder were detected and analyzed with the partial least squares (PLS) regression method. Results show that all four pesticides exhibit unique absorption peaks in the terahertz range, and can thus be easily discriminated between each other and from those food powders that show similar and featureless absorption coefficients. Differences in the refractive indices can also be observed between the pesticides and food powders. Imidacloprid can be identified with its absorption fingerprints in the imidacloprid and polyethylene and imidacloprid and sticky rice powder mixtures. We have achieved the relative error of less than 5% predicting the weight ratio of imidacloprid in these two mixtures with the PLS method, according to the linear relationship found between the absorption coefficient and the weight ratio. In all, the THz-TDS technique is quite promising for the nondestructive pesticide residual detection in food safety control in the near future.

Determination of solar optical properties of transparent polymer films using UV/vis spectroscopy

In this paper, 4- and 5-flux models were implemented and used for the determination of absorption and scattering coefficients of transparent polymer films by UV/vis/NIR spectroscopy. The models were applied for a systematic characterization of polar ethylene copolymer films in the solar radiation range. The investigated ethylene copolymer films were highly transparent in the solar range of radiation, with hemispheric transmittance values above 91% and hemispheric reflectance values of about 8%. Both models revealed a significant forward scattering behavior of the films. The 4-flux model fitted hemispheric and diffuse transmittance far better than the 5-flux model. Hemispheric reflectance values were overestimated by both models. Similar absorption coefficient values ranging from 0.4 to 0.6 cm −1 were obtained for all investigated films. While ethylene(acrylic acid/butylacrylate) terpolymer showed the lowest scattering coefficient (10.9 (5-flux) and 6.8 cm −1 (4-flux)), the highest scattering coefficient (26.2 (5-flux) and 35.2 cm −1 (4-flux)) was found for ethylene(butylacrylate) copolymer.

Site-specific infrared O-H absorption coefficients for water substitution into olivine

There are four ways by which OH - commonly substitutes into olivine, namely those associated with (1) Si vacancies, (2) Mg vacancies, (3) Ti, or (4) trivalent cations. The four mechanisms, which we label [Si], [Mg], [Ti], and [triv], respectively, may each be fingerprinted by their characteristic O-H stretching modes in the infrared spectrum. We show by comparing the integrated intensities of these characteristic infrared peaks against total water content analyzed by secondary ion mass spectrometry, obtained for a suite of synthetic olivines plus one natural olivine, that the different substitution mechanisms require different absorption coefficients (k). For [Ti], we find k = 0.18 ± 0.07, identical to the value previously obtained from natural olivines in which the water was mainly associated with [Ti] defects. Values of k for [Si] and [triv] are 0.57 ± 0.04 and 0.18 ± 0.05, respectively; that for [Mg] is too small to be accurately determined (0.03 ± 0.03). The values of k for [Ti] and [Si] defects differ by a factor of three even though their average wavenumbers are virtually the same. The [Ti] and [triv] defects, on the other hand, have very similar absorption coefficients at significantly different wavenumbers. This highlights the inadequacy of using wavenumber-dependent calibrations for olivine and presumably for NAMs in general. Different substitution mechanisms have their own crystallographic environments that determine their absorption coefficients. The large variation in absorption coefficients within a single mineral emphasizes the importance of distinguishing the substitution mechanism if meaningful quantitative results are to be obtained from infrared spectroscopy.

Fundamental study to develop a fiber-optic gap sensor for a rotary undulation pump

The rotary undulation pump is believed to be a good candidate for the next-generation artificial heart. Due to its complex movement, it is desirable to magnetically levitate the rotor and dynamically control the gap. In this article, the applicability of a fiber-optic gap sensor to the dynamic position control of the rotor in the rotary undulation pump was investigated. The fiber-optic gap sensor consisted of two plastic-core fibers and a reflection plate. Two 1-mm-diameter optical fibers were aligned parallel: one for source light propagation and the other for reflected light transmission. The basic properties of gap sensors using four different light sources were explored in five media (air, physiologic saline, and blood samples with three different hematocrit levels). The influence of the oxygen saturation level in the blood on sensing was investigated with two types of light sources. It is desirable to use a light source the wavelength of which shows similar absorption coefficients for both oxygenated blood and deoxygenated blood. The effect of the distance between the two fibers on the sensing and range was also investigated. The results indicated that the fiber-optic gap sensor is quite promising for the active control of rotor positioning in the rotary undulation pump.

Quantitative impurity profiling by principal component analysis of high-performance liquid chromatography–diode array detection data

Related organic impurities generally have approximately similar molar absorption coefficients ( ɛ) due to their structural similarities. On the assumption that all peaks in an impurity profiling chromatogram have approximately the same maximum molar absorption coefficients ( ɛ max) and the chromatogram contains one major peak and several much smaller ones, all of which are completely separated, integration of the summed score vectors from the principal component analysis (PCA) decomposition of high-performance liquid chromatography–diode array detection (HPLC–DAD) data will give areas that are quantitatively proportional to the actual content of the compounds. Due to the sequential nature of PCA, the first principal component (PC) will primarily be related to the main compound and all peaks showing a similar spectrum, while the second PC will be related to the impurities with a spectrum different from the main peak. Summing the two score vectors thus makes it possible to take account of different spectra in the score chromatogram, which make the method proposed give better quantitative estimates of the impurities than any single wavelength chromatogram. Multivariate curve resolution alternating least squares (MCR-ALS) is used for comparison. The results are presented for two examples of simulated HPLC–DAD data as well as for three examples of real HPLC–DAD data from impurity profiling. The results show that integration of the score chromatograms can handle differences in the unknown ɛ max of the peaks and take account of the different spectra of the impurity peaks, giving quantitative estimates of the content of the impurities that closely correspond to the reference values. The results obtained are also better than integration with the best possible separate wavelength. The method could be a straightforward approach to impurity profiling in order to obtain a good estimate of the content or relative response factors of small chromatographic impurity peaks without knowledge of their molar absorption coefficients and without any precalibration.

Determination of the absorption length of CO 2, Nd:YAG and high power diode laser radiation for a selected grouting material

The laser beam absorption lengths of CO 2, Nd:YAG and a high power diode laser (HPDL) radiation for a newly developed SiO 2/Al 2O 3-based tile grout have been determined through the application of Beer–Lambert’s law. The findings revealed marked differences in the absorption lengths despite the material having similar beam absorption coefficients for the lasers. The absorption lengths for the SiO 2/Al 2O 3-based tile grout for CO 2, Nd:YAG and HPDL radiation were calculated as being 232±11, 193±4 and 183±8 μm , respectively. Moreover, this method of laser beam absorption length determination, which has hitherto been used predominantly with lasers operated in the pulsed mode, is shown to be valid for use with lasers operated in the continuous wave (CW) mode, depending upon the material being treated.

Temperature dependence of absorption in ice at 532 nm

A YAG laser was used to emit nanosecond pulses of light at 532 nm at depths from 1185 to 2200 m in Antarctic ice, corresponding to temperatures increasing from 229 to 249 K. From the timing distributions of photons arriving at phototubes at distances up to 100 m and at similar depths, the scattering and absorption coefficients were measured, and the temperature dependence of absorptivity at 532 nm was determined. Despite the absorptivity being many orders of magnitude lower at 532 nm than in the near ultraviolet and near infrared, the fractional increase of absorptivity, a(-1)da/dT = 0.01 K(-1), was the same in the visible, ultraviolet, and infrared. Analysis of published data at other wavelengths shows that a(-1)da/dT is ~0.01 K(-1) from 175 nm to ~1 cm, above which it increases strongly from 1 cm to 10 m. That temperature dependence applies only in regions not close to absorption bands.

Novel Laser Ablation Resists for Excimer Laser Ablation Lithography. Influence of Photochemical Properties on Ablation

The ablation characteristics of various polymers were studied at low and high fluences. The polymers can be divided into three groups, i.e., polymers containing triazene and ester groups, the same polymers without the triazene group, and polyimide as reference polymer. At high fluences, similar ablation parameters, i.e., etch rates and effective absorption coefficients, were obtained for all polymers. The main difference is the absence of carbon deposits for the designed polymers. At low fluences, very pronounced differences are detected. The polymers containing the photochemically most active group (triazene) exhibit the lowest threshold of ablation and the highest etch rates, followed by the designed polyesters and then polyimide. Neither the linear nor the effective absorption coefficients reveal a clear influence on the ablation characteristics. The thermal properties of the designed polymers also have only minor influence on the ablation activity. The amount of detected gaseous products follows the s...

Determination of the absorption length of CO2 and high power diode laser radiation for a high volume alumina-based refractory material

The laser beam absorption lengths of CO2 (10.6μm wavelength) and a high power diode laser (HPDL) (810nm wavelength) radiation for an Al2O3/SiO2-based refractory have been determined through the application of Beer–Lambert’s law. The findings revealed marked differences in the absorption lengths despite the material having similar beam absorption coefficients for both lasers. The absorption lengths for the Al2O3/SiO2-based refractory of CO2 and a HPDL radiation were calculated as being 345±22 and 198±15μm, respectively. Moreover, this method of laser beam absorption length determination, which has hitherto been used predominantly with lasers operated in the pulsed mode, is shown to be valid for use with lasers operated in the continuous wave (CW) mode, depending upon the material being treated.

Role of Scattering Coefficients in Extended Near-Infrared Diffuse Reflection Spectrometry

The role of the bulk scattering coefficient in extended near-infrared diffuse reflection (DR) spectrometry of materials with similar or identical absorption coefficients is demonstrated. Spectral differences that arise from intraclass variation in scattering coefficient strongly affect the ability to interpret certain spectral regions. Profound intraclass differences in both band intensities and band shapes in the DR spectra of both polyethylene and polystyrene samples are shown. The effects of saturation and Fresnel reflection are discussed. The enhancement of absorption by the matrix and other analytes in DR spectrometry through the addition of a liquid with an index of refraction which matches that of the matrix is also demonstrated.

Estimating primary production at depth from remote sensing

By use of a common primary-production model and identical photosynthetic parameters, four different methods were used to calculate quanta (Q) and primary production (P) at depth for a study of high-latitude North Atlantic waters. The differences among the four methods relate to the use of pigment information in the upper water column. Methods 1 and 2 use pigment biomass (B) as an input and a subtropical, empirical relation between K(d) (diffuse attenuation coefficient) and B to estimate Q at depth. Method 1 uses measured B, but Method 2 uses B derived from the Coastal Zone Color Scanner (subtropical algorithm) as inputs. Methods 3 and 4 use the phytoplankton absorption coefficient (a(ph)) instead of B as input, and Method B uses empirically derived a(ph)(440) and K(d) values, and Method 4 uses analytically derived a(ph)(440) and a (total absorption coefficient) values based on the same remote measurements as Method 2. When the calculated and the measured values of Q(z) and P(z) were compared, Method 4 provided the closest results [for P(z), r(2) = 0.95 (n = 24), and for Q(z), r(2) = 0.92 (n = 11)]. Method 1 yielded the worst results [for P(z), r(2) = 0.56 and for Q(z), r(2) = 0.81]. These results indicate that one of the greatest uncertainties in the remote estimation of P can come from a potential mismatch of the pigment-specific absorption coefficient (a(ph)*), which is needed implicitly in current models or algorithms based on B. We point out that this potential mismatch can be avoided if we arrange the models or algorithms so that they are based on the pigment absorption coefficient (a(ph)). Thus, except for the accuracy of the photosynthetic parameters and the above-surface light intensity, the accuracy of the remote estimation of P depends on how accurately a(ph) can be estimated, but not how accurately B can be estimated. Also, methods to derive a(ph) empirically and analytically from remotely sensed data are introduced. Curiously, combined application of subtropical algorithms for both B and K(d) to subarctic waters apparently compensates to some extent for effects that are due to their similar and implicit pigment-specific absorption coefficients for the calculation of Q(z).

Acoustophoresis separation method

First Page

The use of color in image enhancement of X-ray microtomographs

This paper examines the effectiveness in displaying monochrome images as color images and presents a pseudo-color enhancement technique for enhancing features in x-ray microtomographs of biological and inorganic materials. The technique utilizes the knowledge that the gray levels (intensities) in the image represent the linear absorption coefficients of the elements in the material and assigns pixels with similar gray levels and hence similar absorption coefficients to a color. Since each color in the pseudo-color enhanced image represents a range of gray levels and this corresponds to an element or phase in the material, its microstructure can easily be determined. This paper also discusses the problems associated with the selection of colors and presents a scheme which uses the CIE 1976 L ∗u ∗v ∗ uniform color space to select 256 colors for replacing the 256 gray shades used to represent the monochrome image.

The Use of Color in Image Enhancement of X-Ray Microtomographs

This paper examines the effectiveness in displaying monochrome images as color images and presents a pseudo-color enhancement technique for enhancing features in x-ray microtomographs of biological and inorganic materials. The technique utilizes the knowledge that the gray levels (intensities) in the image represent the linear absorption coefficients of the elements in the material and assigns pixels with similar gray levels and hence similar absorption coefficients to a color. Since each color in the pseudo-color enhanced image represents a range of gray levels and this corresponds to an element or phase in the material, its microstructure can easily be determined. This paper also discusses the problems associated with the selection of colors and presents a scheme which uses the CIE 1976 L*u*v* uniform color space to select 256 colors for replacing the 256 gray shades used to represent the monochrome image.

The role of emissivities in radiative transport calculations

The radiation flux in gases with spectrally similar absorption coefficient, under the condition of thermal emission, can be expressed in terms of the Planck function and the emissivity function. With the use of the relations between the emissivity and the modified emissivity, the emissivity and the integrated band emissivity, and the modified emissivity and the Rosseland mean absorption coefficient, the general flux expression reduces to the various approximations in their respective limits. For these absorbing gases, therefore, the emissivity assumes a fundamental role in radiative transport calculations.

Physical and chemical studies on glycoproteins: III. The microheterogeneity of fetuin, a fetal calf serum glycoprotein

Fetuin was isolated by alcohol-metal ion fractionation. Although the homogeneity of the preparation has been demonstrated by many conventional techniques, microheterogeneity was clearly demonstrated by resolution into eight components on starch gel electrophoresis at pH 4.2. The microheterogeneity did not result from the method of preparation because normal fetal calf serum and fetuin prepared by ammonium sulfate fractionation had the same electrophoretic pattern. Furthermore, the identical bands, characteristic of the purified fetuin, were present in sera collected from five fetal calves. Treatment with neuraminidase reduced the number of bands from eight to three, indicating that sialic acid is primarily responsible for the microheterogeneity observed. Fetuin which was denatured in 8 m urea or reduced with 2-mercaptoethanol in 8 m urea failed to show definite electrophoretic bands; the importance of tertiary structure as a contributory factor to the microheterogeneity is suggested. Purified fetuin was resolved into several fractions by chromatography on DEAE-Sephadex; each fraction contained 2–3 of the bands found on electrophoresis and reveals that the fetuin variants arise from discrete structural differences. The fractions showed similar immunochemical properties, sedimentation constants, and absorption coefficients at 278 mμ. The sialic acid, hexose and hexosamine content increased significantly according to the order of elution. The increase in carbohydrate was accompanied by a small decrease in peptide content. Amino acid analysis revealed virtually no relative difference between the fractions; minor differences were demonstrated by peptide mapping. It was concluded that the microheterogeneity results primarily from differences in the number and arrangement of the sialic acid residues at the surface of the molecule. Conformational variations of the polypeptide portion of the fetuin molecule may also play a contributing role.

Neutron Microradiography of a Cadmium–Tin Alloy

X-RAY microradiography investigation of the internal structure of various alloys is a complementary tool to standard metallography. However, for alloys containing two or more elements with similar X-ray absorption coefficients, X-ray microradiography becomes difficult if not impossible. In an attempt to find a transmission method which could be used in its place, it was decided to use neutrons instead of X-rays.

The Absorption of Ultrasonic Waves in Benzene Solutions of Methyl Metacrylate in Different Polymerization Stages

Measurements of ultrasonic absorption are performed by a pulse method in benzene solutions of nine sorts of methyl metacrylate specimens of different intermediate polymerization stages, including the monomers and the final product of polymerization. In the case of the monomer, the absorption decreases rapidly with concentration. Solutions of the polymers without unreacted monomers show a similar absorption coefficient to that of benzene itself, in spite of the remarkably high viscosity. For the intermediate products the fraction of polymers is estimated from the absorption coefficient, assuming that only the unreacted monomers have influence on the absorption. For the solutions of the specimens in which the fraction of polymers is fairly large, the above assumption requires some modifications. In this case some parts of unreacted monomer molecules seem to be enclosed in the network structures of polymers and deprived of their influence upon the absorption.

On the Ultrasonic Absorption in Binary Mixtures of Unassociated Liquids

Measurements of absorption coefficient were carried out in a binary mixture formed by two unassociated liquids having similar absorption coefficients. The curve absorption coefficient versus mole fraction has a minimum at an intermediate concentration. A theoretical interpretation of experimental results is presented.