Light-scattering Coefficient Research Articles

Spectral dependence of the scattering coefficient in case 1 and case 2 waters

An approximate linear relationship between the scattering coefficient and the wavelength of light in the visible is found in case 1 and case 2 waters. From this relationship, we estimate scattering at an unknown wavelength from scattering at a single measured wavelength. This approximation is based on measurements in a 1.5-m-thick surface layer collected with an AC9 instrument at 63 stations in the Arabian Sea, northern Gulf of Mexico, and coastal North Carolina. The light-scattering coefficient at 412 nm ranged from 0.2 to 15.1 m(-1) in these waters, and the absorption coefficient at 412 nm ranged from 0.2 to 4.0 m(-1). A separate data set for 100 stations from Oceanside, California, and Chesapeake Bay, Virginia, was used to validate the relationship. Although the Oceanside waters were considerably different from the developmental data set (based on absorption-to-scattering ratios and single-scattering albedos), the average error between modeled and measured scattering values was 6.0% for the entire test data set over all wavelengths (without regard to sign). The slope of the spectral scattering relationship decreases progressively from high-scattering, turbid waters dominated by suspended sediments to lower-scattering, clear waters dominated by phytoplankton.

Depolarized interaction-induced Rayleigh light scattering in gaseous SO2

The second light-scattering virial coefficient, B ρ, of SO2 has been extracted from measurements of the depolarization ratio ρ at gas pressures up to 1 MPa. The value calculated using our recent molecular-tensor theory of B ρ for nonlinear molecules agrees with the experimental value to within 5%, providing further evidence that a comprehensive dipole—induced-dipole theory of molecular interaction effects explains the observed phenomena adequately

Evaluation of Detergency with Consideration of Different Fiber Substrate Configurations

The effects of different fiber substrate configurations on the evaluation of detergency for new synthetic polyester fibers, “Shingosen” and “Tencel, ” were investigated. The light-scattering coefficient (S) and light-absorption coefficient (K) were separately obtained using Kubelka-Munk's two-constant equation and the Minato equation in order to consider the effect of the fabric substrate configuration. It was found that the light-scattering coefficients of “Shingosen” and “Tencel”, for which the two-constant value rather than the single-constant value was used, decreased more significantly with increases in the amount of residual soil on the fabrics compared to those of polyester and cotton fabrics made from conventional fibers. We proposed a new method for evaluating the detergency using only the light-absorption coefficient (K) instead of the K/S value corresponding to Kubelka-Munk's single-constant values.

Aerosol light-scattering coefficients and size distributions in a suburban area in Taiwan

Aerosol light-scattering coefficients and size distributions in a suburban area in Taiwan

Relationship Between Tinctorial Depth and Fiber Fineness in Dyed Polyester Fabrics.

The influence of fiber fineness and fabric structure on the tinctorial depth of dyed polyester fabrics was investigated. Plain weave and stitch fabrics composed of polyester filament yarns with different single-fiber finenesses were prepared. The single filaments of the yarn used had finenesses of 0.4, 0.7, 1.0, 2.0, 3.0, and 5.0 denier. The fabrics were dyed with disperse dyes (C. I. Disperse Yellow 5, Red 72 and Blue 148) in various tinctorial depths. The relationship between dye uptake on fabrics (Cf) and K/S value in the Kubelka-Munk function was examined at various wavelengths. Plots of Cf vs. (K/S)d-(K/S)o give a straight line at a particular wavelength for each fabric dyed with the same dye, suffixes d and o refer to dyed and undyed fabrics, respectively. In the K/S region of 10 or less, where Kubelka-Munk function could be applied, the change in the tinctorial depth with Cf and fineness of fiber (D) is expressed by the following equation.This equation shows that a smaller denier leads to lower values for (K/S)d-(K/S)o, which in turn proves that the denier of a single fiber is a significant factor in making the tinctorial depth appear lighter. It was clarified that each fabric has a unique effective surface area and a light-scattering coefficient determined by the fineness of the single fibers and the weaving structure. It was confirmed that the light-scattering coefficient of an undyed fabric could be used to estimate the effect of the fiber substrate on the tinctorial depth.

Calculation and measurement of the second light-scattering virial coefficients of nonlinear molecules: a study of ethene

The second light-scattering virial coefficient B ρ of ethene has been extracted from measurements of the depolarization ratio ρ at gas pressures up to 3·2 MPa. The value calculated using our recent molecular tensor theory of B ρ for axially symmetric molecules, underestimates the experimental value by 40%. A complete molecular tensor theory of B ρ for nonlinear molecules is presented, and leads to a calculated value for ethene which is within 2% of the experimental value.

Effect of Light-Scattering Properties on Tinctorial Depth of Dyed Fine-Denier Polyester Fabrics.

The influence of optical properties on the tinctorial depth of dyed polyester fabrics consisting of single fibers of different deniers and different cross-sectional shapes was investigated. Dyes were applied over a wide concentration range, using three disperse dyes of different hue. To assess the optical properties of the dyed fabrics, light-scattering and light-absorption coefficients were obtained using the Kubelka-Munk and Minato methods, respectively. New Shingosen fabric, woven with especially fine microfibers, had a higher light-scattering coefficient than fabrics made from conventional fibers, regardless of the uptake or hue of the dyes used. This was ascribed to the increased surface area of the Shingosen fabric changing both the surface reflectivity and light-scattering properties. The higher light scattering coefficient led to a lower K/S value. The latter value was correlated with perceived depth, and consequently, the perceived depth of the Shingosen fabric tended to be weak.

Light Scattering from Associating Polymers in Solution

The effects of polymolecularity on the second and third light-scattering virial coefficients are calculated for some sample distributions and compared to the values obtained from an approximate treatment by Burchard and coworkers. It is concluded that the Burchard scheme, designed to facilitate the evaluation of light scattering data for associating systems, is generally reliable.

Effects of Different Microorganisms on Pulp and Paper Properties

Abstract Pretreatment of wood chips with some microorganisms including white-rot fungi and streptomyces improves the strength properties of mechanical pulps. We studied the effect of these white-rot fungi and streptomyces on the mechanical properties of handsheets. Strength and optical properties were compared in handsheets prepared from mechanical pulp of treated and untreated wood chips. The fungal pretreatments resulted in handsheet strength properties better than the control and also better than streptomyces when compared at an equivalent freeness. Fungal pretreatments decreased brightness and light-scattering coefficients but did not adversely affect opacity. Lignin content of the chips was reduced by fungal pretreatments.

Measurement and interpretation of the second light-scattering virial coefficients of linear and quasi-linear molecules

Measurements are reported of the depolarization ratios of CO2, N2, CH3CH3, CH3Cl and CO at gas pressures up to 5·2 MPa, and the first and second light-scattering virial coefficients are extracted. The apparatus and experimental procedures are described briefly. Experimental values of the second light-scattering virial coefficient are compared with calculated theoretical values. For CO2, N2 and CH3Cl the agreement is within 10%, and for CO and CH3CH3 it is within 20%.

Optical investigations of dust storms during U.S.S.R.-U.S. experiments in Tadzhikistan, 1989

The results of studies on dust aerosol optical properties obtained during the U.S.S.R.-U.S. experiment are discussed. The ground-based and aircraft measurements carried out during the experiment allow the estimation of characteristic values of aerosol optical depth, aerosol light-scattering coefficients, the degree of linear polarization, and aureole phase functions for different atmospheric conditions in Central Soviet Asia. Two dust storms were observed for which the recorded aerosol optical depth at λ = 0.55 μm {τa(0.55)} reached 1.5 on 16 and 17 September 1989, and 3.5 on 20 and 21 September 1989. The optical characteristics (spectral dependence of the optical depth, degree of linear polarization) were similar for two dust episodes.

Higher-order dipole-dipole, dipole-quadrupole and field gradient contributions to the second light-scattering virial coefficient

Theory of the second light-scattering virial coefficient Bp is extended to include in the scattered intensity terms that have not previously been considered, namely dipole-dipole intensities of the fifth power in the molecular polarizability α as well as additional contributions arising from field gradient effects and induced quadrupole moments in the molecular interactions. Numerical calculations for ten gases show that terms in α5 make a significant contribution to B ρ of up to nearly 20%. In polar molecules, terms in α2 A (where A describes the dipole induced by a field gradient, or the quadrupole induced by a field) make contributions of up to 9%. Indications are that in molecules with a centre of inversion, for which A is zero, field gradient and quadrupole effects will generally lead to contributions of less than 1%.

Calculations of second light-scattering virial coefficients of linear and quasi-linear molecules

The molecular theory of the second light-scattering virial coefficient B ρ is briefly reviewed, and tensor expressions for contributions to B ρ of linear molecules, correct to the fourth power of the polarizability in the depolarized scattered intensity, are presented. These expressions are evaluated numerically by computer for nine gases and, where possible, compared with published experimental values. The results identify molecules which may be fruitfully investigated experimentally. The calculations also demonstrate the usefulness of an algebraic package (in this case Derive) in the accurate performance by computer of tedious manipulations often encountered in the theory of molecular interactions.

Polycrystalline materials for magneto-optical devices

The replacement of single-crystal compounds by polycrystalline compounds in some magneto-optical devices is proposed. For this purpose a characterized polycrystalline, Cd(0.55)Mn(0.45) Te, has been manufactured. Its Verdet constant and cutoff wavelength are identical to those of single crystals of the same composition. Optical transmission is lower in polycrystals because they have larger light-scattering coefficients; hence they are not well suited for applications such as isolators but are adequate for magnetometers, modulators, and similar devices.

The second virial coefficient of polydisperse polymer samples in a good solvent

In this paper we present analytical expressions for the osmotic and light-scattering second virial coefficients of polydisperse polymer samples in a good solvent. They are derived using the Schulz and the Lognormal molecular weight distribution respectively. The effect of interpenetrating coils is taken into account. Comparison is made with expressions already derived by Casassa using a hard sphere model. The reduction of the obtained expressions to simple scaling laws is discussed.

Ubiquitous nature of ambient metastable aerosol

The potential for atmospheric aerosol particles to exist as metastable aqueous droplets instead of in their thermodynamically favoured crystalline solid phase has many implications for atmospheric physics and chemistry. Aqueous droplets are larger than their dry counterparts1 and generally scatter more light2,3. Also, the existence of an aqueous phase influences the oxidation, equilibrium vapour pressure and mass-transfer kinetics of trace gases4–9. Here we report observations at three urban and rural sites, showing that metastable droplets existed more than 50% of the time when the ambient relative humidity was between ∼45 and 75%. At one site, more than 10% of the aerosol's light-scattering coefficient was attributed to metastable liquid H2O when the relative humidity was greater than 55%. These results indicate that metastable droplets are ubiquitous in nature, although the full ramifications of these observations are still unclear.

Carbonaceous Particles and Regional Haze in the Western United States

In rural areas of the western United States, atmospheric mass concentrations of participate organic carbon are comparable to those of sulfate. At the low humidities characteristic of this region, atmospheric light-scattering coefficients are empirically as sensitive to carbon concentrations as they are to sulfate concentrations. The abundance and scattering effectiveness of organic particles imply that they are major contributors to the impairment of scenic views.

Arctic hazes in summer over Greenland and the North American Arctic. I: Incidence and origins

Airborne observations during August 1985 over Greenland and the North American Arctic revealed that dense, discrete haze layers were common above 850 mb. No such hazes were found near the surface in areas remote from local sources of particles. The haze layers aloft were characterized by large light-scattering coefficients due to dry particles (maximum value 1.24 × 10−4m−1) and relatively high total particle concentrations (maximum value 3100 cm−3). Sulfate was the dominant ionic component of the aerosol (0.06 – 1.9 μg m−3); carbon soot was also present. Evidence for relatively fresh aerosols, accompanied by NO2 and O3 depletion, was found near, but not within, the haze layers. The hazes probably derived from anthropogenic sources and/or biomass burning at midlatitudes.

Efficient scavenging of aerosol sulfate by liquid-water clouds

Continuous aircraft measurements of aerosol sulfate concentration, [SO 4 2−], (flame-photometric detector) and light-scattering coefficient, b scat, (integrating nephelometer) in cloud interstitial air and in associated clear air are reported for several locations in the eastern United States. Measurements were made in situations where, on the basis of other physical and chemical measurements, it can be argued that the cloud air and the clear air have similar history and composition. It is found in cloud interstitial air that [SO 4 2−] approaches zero and b scat approaches the Rayleigh scattering coefficient of air. Sulfate concentration and b scat in successive subsaturated regions along a given flight path at a given altitude were frequently nearly constant or slowly varying, the pattern presented appearing to be that of a fairly uniform concentration of sulfatecontaining, light-scattering aerosol from which segments had been removed in regions corresponding to the presence of cloud. The strong decrease in both [SO 4 2−] and b scat within cloud interstitial air relative to clear air is attributed to nearly complete uptake of sulfate-containing and light-scattering aerosol particles into cloud droplets. From comparison of the in-cloud signal to the non-cloud signal it is possible to set an upper bound to the fraction of unscavenged sulfate aerosol (frequently as low as 0.25) and to b scat (frequently as low as 0.1), although for both quantities the measurements would be consistent with essentially complete scavenging. Additionally, the observation in these situations that no cloud-free regions exhibited the low values of [SO 4 2−] and b scat characteristic of the in-cloud regions is indicative of the return of the dissolved material to the air as clear-air aerosol upon cloud evaporation.

Sulfate and nitrate chemistry in cumuliform clouds

Continuous aircraft measurements of aerosol sulfate concentration, [SO42−], (flame-photometric detector) and light-scattering coefficient, bscat, (integrating nephelometer) in cloud interstitial air and in associated clear air are reported for several locations in the eastern United States. Measurements were made in situations where, on the basis of other physical and chemical measurements, it can be argued that the cloud air and the clear air have similar history and composition. It is found in cloud interstitial air that [SO42−] approaches zero and bscat approaches the Rayleigh scattering coefficient of air. Sulfate concentration and bscat in successive subsaturated regions along a given flight path at a given altitude were frequently nearly constant or slowly varying, the pattern presented appearing to be that of a fairly uniform concentration of sulfatecontaining, light-scattering aerosol from which segments had been removed in regions corresponding to the presence of cloud. The strong decrease in both [SO42−] and bscat within cloud interstitial air relative to clear air is attributed to nearly complete uptake of sulfate-containing and light-scattering aerosol particles into cloud droplets. From comparison of the in-cloud signal to the non-cloud signal it is possible to set an upper bound to the fraction of unscavenged sulfate aerosol (frequently as low as 0.25) and to bscat (frequently as low as 0.1), although for both quantities the measurements would be consistent with essentially complete scavenging. Additionally, the observation in these situations that no cloud-free regions exhibited the low values of [SO42−] and bscat characteristic of the in-cloud regions is indicative of the return of the dissolved material to the air as clear-air aerosol upon cloud evaporation.