Investigation of the propagation of pollutants in water reservoirs

A mathematical model for investigating the problem of the propagation of pollutants in water reservoirs on salvoed (instantaneous) discharge is suggested. To calculate dilution, a method developed on the basis of the equation of turbulent diffusion in cylindrical coordinates is suggested. The method allows one to determine the concentration of pollutants at an arbitrary distance from the place of their discharge. The conditions for the formation of local pollution zones in a water reservoir are considered.     

Investigation of concentrically and eccentrically layered droplets by light scattering

Two pairs of immiscible liquid compounds are chosen to prepare levitated layered droplets with and without density difference between core and layer phases. The droplets are examined by light scattering along two orthogonal directions. A layered droplet without phase density difference is unambiguously identified as a concentric sphere by matching the observed scattering spectra with those calculated from the Aden-Kerker extension of Mie theory. For layered droplets with phase density difference, only the scattering spectrum from one of the scattering directions can be matched theoretically. These observations suggest that a static layered droplet is predominantly eccentric even though the embedded core is large by volume, as predicted from fluid mechanics. The consistency of the light-scattering characterization with the diffusion theory governing the evaporation of concentrically and eccentrically layered droplets is also established.     

Monte carlo procedure for investigating light propagation and imaging of highly scattering media

A Monte Carlo procedure has been developed to study photon migration through highly scattering nonhomogeneous media. When two scaling relationships are used, the temporal response when scattering or absorbing inhomogeneities are introduced can be evaluated in a short time from the results of only one simulation carried out for the homogeneous medium. Examples of applications to the imaging of defects embedded into a diffusing slab, a model usually used for optical mammography, are given. Comparisons with experimental results show the correctness of the results obtained.     

表面效应对动态光散射纳米粒径测量的影响

为探究表面效应对动态光散射法测量纳米粒度的影响,设计一种宽度可调的样品池,采用基于高速线阵CCD的动态光散射测量系统,对不同粒径的标准SiO_2颗粒进行测量。结果表明:样品池宽度小于1.3 mm时,粒径测量值随通道宽度减小线性增大,宽度为0.6 mm时,粒径测量值与自由空间中的测量值差距超过5%;样品池宽度较小时,颗粒布朗运动受到明显影响,动态光散射仪中使用微量样品池时,应根据样品池宽度对测量结果进行修正。     

Optical rotatory-dispersion-type spatial light modulator and characteristics of the modulated light

Among known temporal-spatial light modulation methods, there is no realistic method that can precisely control a light pulse simultaneously in the temporal and spatial domains. By careful consideration of the symmetries and topological properties of electromagnetic waves, a novel spatial light modulator has been developed to create different far-field patterns for each wavelength of linearly polarized light composed of various wavelength components. The system consists of an optical rotatory dispersion device, which is like a Faraday rotator, and a spatial light modulator with parallel-alignment nematic liquid-crystal cells. Numerical simulation results show the effectiveness of this new spatial light modulation method.     

Investigation of the effects of microbubble shell disruption on population scattering and implications for modeling contrast agent behavior

In a previous study, quantitative measurement of nonlinear scattering revealed some quantitative discrepancies with a model for ultrasound scattering by a population ensemble of microbubbles. This study is designed to investigate the effect of the shell on single-pulse scattering by a population of contrast microbubbles. Nonlinear scattering was measured shortly (15 /spl mu/s) after exposure to a previous ultrasound pulse with variable intensity. The short time delay eliminated the influence of gas diffusion and focused the study on the consequence of ultrasound exposure. The results suggest that single-pulse scattering is dependent on the disruption properties of the bubble shell and confirm the significance of the shell properties.     

Revised Kubelka-Munk theory. III. A general theory of light propagation in scattering and absorptive media

A generally applicable theoretical model describing light propagating through turbid media is proposed. The theory is a generalization of the revised Kubelka-Munk theory, extending its applicability to accommodate a wider range of absorption influences. A general expression for a factor taking into account the effect of scattering on the total photon path traversed in a turbid medium is derived. The extended model is applied to systems of ink-dyed paper sheets-mixtures of wood fibers with dyes-which represent examples of systems that have thus far eluded the original Kubelka-Munk model. The results of simulations of the spectral dependence of Kubelka-Munk coefficients of absorption and scattering show that they compare very well with those derived from experimental results.     

Stimulated light scattering in transparent liquid particles: effect of the descartes ring

We consider some peculiarities of the evolution of processes of stimulated scattering in liquid transparent particles in the presence of ponderomotive action of a light field. We observed the occurrence of sharp deformations in the Descartes ring zone, which exceeds by more than 1 order of magnitude the deformations of the remaining particle surface. Investigation of the dynamics of the evolution of droplet deformations has made it possible to consider these deformations as the main cause of suppression of stimulated scattering indicated in the experiments. An analytical expression was derived to evaluate the decrease of the Q factor of droplet quasi-normal eigenmodes caused by perturbation of the particle shape from the spherical. Our study revealed that the larger the Q factor of the droplet eigenmodes, the greater the influence of surface deformation.     

Dynamic light scattering investigation of CTAB/swelling agent/water mixture for designing of hierarchical ZSM-5 zeolites with favorable mesoporosity

Journal of Materials Science - In this project, a series of hierarchical ZSM-5 zeolites with various mesopore sizes were synthesized by using trimethylbenzene (TMB), decane and dodecanethiol as...     

Influence of bubbles on scattering of light in the ocean

The scattering and backscattering properties of bubble populations in the upper ocean are estimated with Mie theory and a generalized bubble size spectrum based on in situ observations. Optical properties of both clean bubbles and bubbles coated with an organic film are analyzed; the results are compared with the corresponding optical properties of micro-organisms of similar size. Given a bubble number density (from ~10(5) to ~10(7) m(-3)) frequently found at sea, the bubble populations significantly influence the scattering process in the ocean, especially in oligotrophic waters. Bubbles appear to make a large contribution to the missing terms in constructing the observed total backscattering coefficient of the ocean. This contribution to backscattering is strongly enhanced if the bubbles are coated with organic film. The injection of bubbles will shift ocean color toward the green, resembling phytoplankton blooms, and hence introducing error in ocean color remote sensing if its effect is not corrected.     

Investigation of the temporal spread of an ultrashort light pulse on transmission through a highly scattering medium

An experimental and theoretical investigation of the temporal spread of an ultrashort light pulse on transmission through a highly scattering medium has been made. For the strongly diffuse light, the transmitted pulse may be described by a universal function whose duration can be directly related to the width of the sample. For sufficiently scattering samples, experimental data and the diffusion approximation indicate that the output pulse duration scales with the square root of the sample width.     

Near-infrared light propagation in an adult head model. I. Modeling of low-level scattering in the cerebrospinal fluid layer

Adequate modeling of light propagation in a human head is important for quantitative near-infrared spectroscopy and optical imaging. The presence of a nonscattering cerebrospinal fluid (CSF) that surrounds the brain has been previously shown to have a strong effect on light propagation in the head. However, in reality, a small amount of scattering is caused by the arachnoid trabeculae in the CSF layer. In this study, light propagation in an adult head model with discrete scatterers distributed within the CSF layer has been predicted by Monte Carlo simulation to investigate the effect of the small amount of scattering caused by the arachnoid trabeculae in the CSF layer. This low scattering in the CSF layer is found to have little effect on the mean optical path length, a parameter that can be directly measured by a time-resolved experiment. However, the partial optical path length in brain tissue that relates the sensitivity of the detected signal to absorption changes in the brain is strongly affected by the presence of scattering within the CSF layer. The sensitivity of the near-infrared signal to hemoglobin changes induced by brain activation is improved by the effect of a low-scattering CSF layer.     

The effect of the size factor of nanodiamonds in suspensions on optical power limiting and nonlinear laser light scattering

The results of experimental studies of optical power limiting (OPL) and nonlinear light scattering (NLS) at a wavelength of 532 nm in suspensions of detonation-synthesis modified nanodiamonds (MNDs) with different grain-size compositions are described. It is found that, at the same nanoparticle concentration, OPL and NLS are more efficient in suspensions with large MNDs. It is shown that MND suspensions can exhibit a stable long-term operation as OPL in a field of laser pulses with a power density of 0.2 GW/cm² at a repetition frequency of 1 Hz.     

Investigation of the influence of temperature on threshold value and pulse duration of stimulated Brillouin scattering in liquid water

The threshold value and pulse duration of stimulated Brillouin scattering (SBS) have been measured over the temperature range 10–45°C in liquid water. Also, a theoretical analysis based on the temperature dependence of SBS has been carried out. The results show that the threshold value of SBS decreases with an increase of temperature, whereas the measured pulse duration increases with an increase of temperature.     

Description and time reduction of a Monte Carlo code to simulate propagation of polarized light through scattering media

Propagation of polarized light through a scattering medium has been studied with a Monte Carlo code to obtain polarized backscattered images. Studies of these backscattered patterns obtained with polarized illumination can be used as a technique to characterize the medium anisotropy factor g. First we present the different steps of the Monte Carlo simulation that describe polarized light propagation in a turbid medium. Monte Carlo is a good tool to simulate the backscattered polarized light but is time-consuming. Therefore, we consider two ways to decrease the computation time. The first way deals with angle sampling of the light direction. The second takes advantage of backscattered image symmetry to divide the simulation time by a factor of 4. By combining these two techniques we significantly decrease the code computation time.     

Investigation on the synergistic effect of a combination of chemical enhancers and modulated iontophoresis for transdermal delivery of insulin

Purpose: The main objective of this study was to assess the flux enhancement of insulin transdermally by utilizing a complex of chemical enhancers in combination with modulated iontophoresis. Methods: The experiments were performed on porcine epidermis model under three different circumstances, namely, (a) 1-hour modulated iontophoresis alone; (b) pretreatment with vehicle and chemical enhancer combinations and (c) combination of (a) and (b). The mechanism of action of the enhancers was studied using infra-red spectra by derivative and curve-fitting techniques and Confocal laser scanning microscopy. The efficacy of the optimized combination was tested in vivo in streptozocin-diabetic Wistar rats. Results: A blend of 1,8 cineole, oleic acid and sodium deoxycholate in propylene glycol : ethanol (7:3) resulted in 45% enhancement, when permeation was performed in combination with iontophoresis as compared to the latter alone. In-depth analysis of infra-red spectra revealed that each of the enhancers acted differentially on lipid-protein domains of the stratum corneum thereby supporting the observed synergism. Movement of fluorescently labeled insulin depicted highlighted follicular regions and paracellular accumulation of the probe after iontophoresis and chemical enhancer treatment respectively. Presence of the fluorescent peptide in these regions 4 hour after treatment with the combination reinforced the results of the permeation studies. Finally the combination of modulated iontophoresis with chemical enhancer blend resulted in lowering of blood glucose for 8 hour in vivo. Conclusions: The study proved the applicability of modulated iontophoresis with chemical pretreatment in delivering insulin transdermally.     

On the effect of oxygen and water vapor on the propagation of fatigue cracks in 2024-T3 alclad sheet

The propagation of fatigue cracks in 2024-T3 alclad sheet under fluctuating tension in different atmospheres has been studied. Of the principal contituents of air, water vapor had a much more severe effect than oxygen; in wet pure argon the endurance was much shorter than in dry pure oxygen. In air, other circumstances remaining unaltered, the endurance increased continuously at a reduction of the water vapour content; the endurance at a water content of the air of 20 ppm being about 6 times as long as in air saturated with water. Between the limits of 30°Jo and 100% relative humidity, as occurring in normal air, the endurance was only slightly affected. The thermodynamics and the mechanisms of the reactions of oxygen and water vapor with the metal are discussed.

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Zusammenfassung Die Fortpflanzungsgeschwindigkeit von Ermüdungsrissen in verschiedenen Casatmosphären wurde studiert für plattiertes 2024-T3 Blech. Von den Bestandteilen der Luft hatte Wasserdampf einen gröszeren Effekt als Sauerstoff; im naszen reinen Argon war die Lebensdauer viel kürzer als im trockenen reinen Sauerstoff. Bei Herabsetzung des Wasserdampfgehaltes nahm die Lebensdauer kontinuierlich zu. Die Lebensdauer unter wechselader Zugbelastung war bei einem Wassergehalt der Luft von 20 p.p.m. etwa 6 × gröszer als in gesättiger Luft. Die Lebensdauer wurde ka um beeinfluszt durch Änderungen in der relativen Feuchtigkeit der Luft zwischen den Grenzen 30 – 100 %, welche Feuchtigkeitsnormal in der Luft vorkommen. Die Thermodynamik und der Mechanismus der Reaktionen von Sauerstoff und Wasserdampf mit deco Metall werden diskutiert.

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Résumé La propagation des fissures en fatique dans des atmosphères différentes a été étudiée pour des tôles minces de 2024-T3 plaquées. Parmi les ingrédients de l' air la vapeur d' eau avait une influence plus importance que l' oxygène, L'endurance en argon pur à grande humidité était inférieure à celle en oxygène sec pur. Réduction de la teneur en vapeur d' eau résultait dans une croissance continue de l' endurance: en air avec 20 p. p.m. d' eau l' endurance de la tôle était presque 6 × lonque qu' en air saturé, L'endurance était à peine influencée pas des altérations de l'humidité relative de l'air entre les limites 30 – 100 %, comme se produisant en pratique. La thermodynamique et le mécanisme des réactions de l'oxygène et de la vapeur d' eau avec le métal sont discutés.

     

Local-field resonance in light scattering by a single water droplet with spherical dielectric inclusions

Light scattering by an evaporating water droplet several micrometers in size with spherical dielectric inclusions was investigated. The evolution of the droplet radius and the effective refractive index was determined. A deviation from predictions by standard effective-medium theories in the form of a resonance was encountered. Simple analysis of the phenomenon was conducted, and a qualitative explanation was proposed.     

Time-resolved studies of light propagation in paper

A method for time-resolved recording of light scattering in thin, highly scattering media is described. Subpicosecond pulses from a high-power Ti:sapphire laser are used, and single-shot recordings of the scattered light are made with a fast streak camera. The method is applied to the study of light scattering in paper, and a 1-ps resolution is demonstrated. The dependence of the light scattering on the basis of weight and density of the paper has been studied. A white-light continuum generated from the high-power pulses by the use of self phase modulation in water is used to study the wavelength dependence of the scattering process. A model for the propagation of light in paper has been developed and used in Monte Carlo simulations. The experimental results are used for testing this model, and absorption and scattering parameters are determined from that comparison.