178,063 research outputs found

    On Iterative Algorithms for Quantitative Photoacoustic Tomography in the Radiative Transport Regime

    Full text link
    In this paper, we describe the numerical reconstruction method for quantitative photoacoustic tomography (QPAT) based on the radiative transfer equation (RTE), which models light propagation more accurately than diffusion approximation (DA). We investigate the reconstruction of absorption coefficient and/or scattering coefficient of biological tissues. Given the scattering coefficient, an improved fixed-point iterative method is proposed to retrieve the absorption coefficient for its cheap computational cost. And we prove the convergence. To retrieve two coefficients simultaneously, Barzilai-Borwein (BB) method is applied. Since the reconstruction of optical coefficients involves the solution of original and adjoint RTEs in the framework of optimization, an efficient solver with high accuracy is improved from~\cite{Gao}. Simulation experiments illustrate that the improved fixed-point iterative method and the BB method are the comparative methods for QPAT in two cases.Comment: 21 pages, 44 figure

    Optical properties of apple skin and flesh in the wavelength range from 350 to 2200 nm

    Get PDF
    Optical measurement of fruit quality is challenging due to the presence of a skin around the fruit flesh and the multiple scattering by the structured tissues. To gain insight in the light-tissue interaction, the optical properties of apple skin and flesh tissue are estimated in the 350-2200nm range for three cultivars. For this purpose, single integrating sphere measurements are combined with inverse adding- doubling. The observed absorption coefficient spectra are dominated by water in the near infrared and by pigments and chlorophyll in the visible region, whose concentrations are much higher in skin tissue. The scattering coefficient spectra show the monotonic decrease with increasing wavelength typical for biological tissues with skin tissue being approximately three times more scattering than flesh tissue. Comparison to the values from time-resolved spectroscopy reported in literature showed comparable profiles for the optical properties, but overestimation of the absorption coefficient values, due to light losses

    The Development of Transdermal Piroxicam Using HPMC Matrices With PVP K-30 as a Penetration Enhancer

    Get PDF
    The physicochemical properties such as solubility, partition coefficient, and membrane permeability of a drug are required for formulating and estimating drugs absorption that pass through biological membranes. The research studied about solubility, partition coefficient in octanol-phosphate buffer, rabbit skin permeability and release from the transdermal delivery system of piroxicam with addition of 6% PVP K-30 in vitro into phosphate buffer solution pH 7.4 at temperature 320 ± 10C. The results showed that the solubility of piroxicam was 904.44 ± 20.92 μg/mL. The values of log IPC and APC were 1.99 ± 0.01 and 0.08 ± 0.01, respectively. The flux, permeability coefficient, and diffusion coefficient of the piroxicam permeation process were 2.07 x 10-4 μg/cm2/sec, 4.96 x 10-6 cm/minute, and 4.13 x 10-8 cm2/minute, respectively. The release mechanism of piroxicam from transdermal delivery system was more dominant by diffusion than erosion. The fluxes of piroxicam release were 0,169 and 0,107 mg/cm2/minute for formulation with 2% HPMC and 4% HPMC, respectively

    Assessing the Harvest Maturity of Brazilian Mangoes

    Get PDF
    No clear criterion exists to determine the optimum time to harvest mango. Some empirical relations are used to assess maturity, such as shoulder development. Moreover, as a result of the typical growing conditions in tropical climates, a huge variation in maturity and ripeness exists, seriously hampering the export of fruit in the global chain. The consequence for consumers in western countries is that sometimes mangoes are overripe at the retailer, or have to be kept for several days, even weeks, to reach the edible state, provided they do not rot in the meantime. To ensure an edible quality, the chlorophyll content in the fruit flesh, measured at harvest by Time-resolved Reflectance Spectroscopy (TRS), could be used as a maturity criterion for mango fruit. Commercially grown fruit were harvested in Brazil and transported to Italy by plane. Fruits were measured using TRS at 630 nm for absorption coefficient (µa) and skin colour. The development of µa was followed on 60 fruits during 15 days of storage at 20°C. The remainders of fruit were used to measure firmness destructively. Absorption coefficient decreased during shelf life according to a logistic pattern, as expected for colour development. Taking the variation between the individual fruit into account, 72% of the variation was accounted for. Nevertheless, µa assessed at harvest could be converted into a biological shift factor (BSF), as an expression of the maturity at harvest of each individual fruit. This biological shift factor explained about 70% of the variation in firmness development in individual fruit. These preliminary results indicate that TRS methodology coupled with BSF theory could be useful in assessing maturity at harvest and assuring acceptable eating quality of mango

    Time-resolved reflectance measurements on layered tissues with strongly varying optical properties

    Get PDF
    Most biological tissues consist of layers with different optical properties. A few examples are the skin, the esophagus, the stomach and the wall of arteries. An understanding of how the light propagates in such layered systems is a prerequisite for any light based therapy or diagnostic scheme. In this study we investigate the influence of different kinds of layers on time resolved reflectance measurements. Experiments were performed on layered gel phantoms and the results compared to Monte Carlo simulations and diffusion theory. It is shown that when a low absorbing medium is situated on top of a high absorbing medium, the absorption coefficient of the lower layer is accessible if the differences in the absorption coefficient are only small. In the case of large difference the optical properties of the upper layer dominate the signal and shield information on the lowest layer. The degree of this shielding effect depends on layer thickness as well as optical properties. In the case of an almost absorption and scattering free layer in between two normal tissues, an overall increase of the signal is visible. However, the overall shape of the curve is about preserved. The apparent scattering coefficient is slightly decreased, while the apparent absorption coefficient is unaltered

    Spectral absorption of unpolarized light through nano-materials in the absence of a magnetic field

    Get PDF
    A study of optical properties, such as light absorption, of a colloidal nano-material, provides information on the biphasic, solid - liquid system microstructure. The nano-material under study is a magnetic liquid (ferrofluid). The disperser agent is petroleum mineral oil and the dispersed material is a brown spar powder (nano-particles). The stabilizer is oleic acid. Light absorption through ferrofluid samples reveals the tendency of solid particles in a colloidal solution to form aggregates. The paper emphasizes the linear dependence between the spectral absorption coefficient, concentration and wavelength. The aggregates cause deviations of the extinction coefficient from values according to the Bouger-Lambert-Beer law. Fe3O4 aggregates sized 58.76 nm are formed in the system. The average number of nano-particles forming aggregates is 6. The magnetic liquid to be studied is secure stable and, thus, trustful in technological and biological applications

    Фиторемедиация городских почв цинерарией серебристой (Cineraria Silverdust L.)

    Full text link
    The article presents the results of experimental studies on the study of the remediation ability of cineraria silvery (Cineraria Silverdust L.) to biological absorption of heavy metals from the soil. The biological absorption coefficient (Ax) and the translocation coefficient (G) for four metals were considered as assessment criteria: lead, zinc, copper, cadmium

    Measurement method of optical properties of ex vivo biological tissues of rats in the near-infrared range

    Get PDF
    An optical fiber-based supercontinuum setup and a custom-made spectrophotometer that can measure spectra from 1100 to 2300 nm, are used to describe attenuation properties from different ex vivo rat tissues. Our method is able to differentiate between scattering and absorption coefficients in biological tissues. Theoretical assumptions combined with experimental measurements demonstrate that, in this infrared range, tissue attenuation and absorption can be accurately measured, and scattering can be described as the difference between both magnitudes. Attenuation, absorption, and scattering spectral coefficients of heart, brain, spleen, retina, and kidney are given by applying these theoretical and experimental methods. Light through these tissues is affected by high scattering, resulting in multiple absorption events, and longer wavelengths should be used to obtain lower attenuation values. It can be observed that the absorption coefficient has a similar behavior in the samples under study, with two main zones of absorption due to the water absorption bands at 1450 and 1950 nm, and with different absolute absorption values depending on the constituents of each tissue. The scattering coefficient can be determined, showing slight differences between retina and brain samples, and among heart, spleen and kidney tissues

    Phyto-assessment of Soil Heavy Metal Accumulation in Tropical Grasses

    Get PDF
    Tropical grasses are fast growing and often used for phytoremediation. Three different types of tropical grasses: Vetiver (V. zizanoides), Imperata (I. cylindrical) and Pennisetum (P. purpureum) tested in different growth media of spiked heavy metal contents under the glasshouse environment of RimbaIlmu for 60-day. The growth performance, metals tolerance and phyto-assessment of cadmium (Cd), lead (Pb), zinc (Zn) and copper (Cu) in shoots and roots were assessed using flame atomic absorption spectrometry (FAAS).Tolerance index (TI), translocation factor (TF), biological accumulation coefficient (BAC), biological concentration factor (BCF), and uptake efficacy was applied to evaluate the metal translocation ability among all three grasses. All three grasses showed significantly higher (p\u3c0.05) accumulation of the total heavy metals in the spiked metal treatment compared with other tested treatments. Vetiver accumulated remarkably higher total concentration of Cd (93.08 ± 3.81 mg/kg) and Zn (1284.00 ± 234.83 mg/kg) than both Imperata and Pennisetum. The overall trend of heavy metals accumulation for all three grasses followed the order of Zn\u3ePb\u3eCd\u3eCu. The results of study suggested that both Imperata and Pennisetum are commendable and potential phytoextractors for Zn as well as phytostabilizers for Cd, Pb and Cu, respectively
    corecore