Flux vector formulation for photon propagation in the biological tissue

We present a generalized delta-Eddington phase function to simplify the radiative transfer equation to an integral equation with respect to the photon flux vector. The solution of the integral equation is highly accurate to model the photon propagation in the biological tissue over a broad range of optical parameters, especially in the visible light spectrum where the diffusion approximation breaks down. The methodology is validated in the Monte Carlo simulation and can be applied in various optical imaging applications.     

Spectrally resolved reflectometric measurement of polarization mode dispersion in an optical fiber link with polarization-dependent loss

In an optical fiber link with polarization-dependent loss (PDL), we demonstrate that although the complex polarization mode dispersion vector cannot be fully obtained by the reflectometric measurement, the spectrally resolved differential group delay (DGD) and differential attenuation slope (DAS) can be explicitly determined by such measurements performed simultaneously in the optical frequency domain and the fiber length domain. In principle, this technique can be used to realize the spectrally resolved and spatially resolved measurement of DGD and DAS in an optical fiber link having PDL based on distributed Rayleigh backscattering. We report the experimental result based on the far-end Fresnel reflection to confirm the validity of the proposed method.     

First-principles study on the metallic antiferromagnet Co[PhPO3]·H2O

The electronic structure and the magnetic properties of transition metal phosphonate Co(PhPO₃)·H₂O have been studied by first-principles within the density-functional theory (DFT) and the full potential linearized augmented plane wave (FP-LAPW) method. The total energy, the total magnetic moment, the atomic spin magnetic moments and the density of states(DOS) of Co(PhPO₃)·H₂O were all calculated. The calculations reveal that the title compound is a metallic antiferromagnet and has a metallic ferromagnetic metastable state, which are in good agreement with the experiment. The spin magnetic moment of Co(PhPO₃)·H₂O is about 4.93 _μB${\mu }_{\mathrm{B}}$ per molecule, and it is mainly assembled at the cobalt atom, at the same time, with a little contribution from the P, O1, O2, O3.     

Bleaching effect of a 405-nm diode laser irradiation used with titanium dioxide and 3.5% hydrogen peroxide

A 405-nm diode laser has recently been developed for soft tissue problems in dentistry. A new in-office bleaching agent consisting of a titanium dioxide photocatalyst and 3.5% hydrogen peroxide has proven to react well with light irradiated at a wavelength of around 400 nm. In this study, we evaluated the bleaching efficacy of a newly developed 405-nm diode laser on bovine teeth treated with a bleaching agent composed of titanium dioxide and 3.5% hydrogen peroxide. Sixteen bovine incisors were randomly divided into two groups: Group A, irradiated by the 405-nm diode laser at 200 mW; Group B, irradiated by the 405-nm diode laser at 400 mW. The bleaching agent with titanium dioxide and 3.5% hydrogen peroxide was applied to bovine enamel and irradiated for 1 min. The specimens were then washed and dried, and the same procedure was repeated nine more times. After irradiation, we assessed the effects of bleaching on the enamel by measuring the color of the specimens with a spectrophotometer and examining the enamel surfaces with a scanning electron microscope. L* rose to a high score, reaching a significantly higher post-treatment level in comparison to pretreatment. In a comparison of the color difference (ΔE) between Group A and Group B, the specimens in Group B showed significantly higher values after 10 min of irradiation for the post-treatment. No remarkable differences in the enamel surface morphology were found between the unbleached and bleached enamel. The use of a 405-nm diode laser in combination with a bleaching agent of titanium dioxide and 3.5% hydrogen peroxide may be an effective method for bleaching teeth without the risk of tooth damage.     

Changes in metal specificity due to iron ligand substitutions in reaction centers fromRhodobacter sphaeroides

Bacterial reaction centers have a single nonheme iron that is located between two bound quinones, Q_A and Q_B, which are the primary and secondary electron acceptors during photosynthesis, respectively. InRhodobacter sphaeroides, the iron is coordinated by four nitrogen atoms, contributed by histidines at L190, L230, M219, and M266, and two oxygen atoms, contributed by Glu at M234. The roles of these ligands in determining the metal-binding specificity and electron transfer properties of the quinones were investigated by mutagenesis. Each of the four His ligands was changed to Glu, Gln, and Cys, whereas Glu was changed to His, Gln, Cys, and Asp. All mutants supported photosynthetic growth except for those with substitutions of Glu or Cys at L190 or M219. The metal specificity of isolated mutant RCs was determined by measurements using atomic absorption and 35 GHz electron paramagnetic resonance spectroscopy. The M234 mutants had a lesser iron specificity than the wild type with a mole fraction of 0.7 to 0.8 iron but retained a total metal content of 1.0. All His mutants had an even lower iron content with mole fractions of 0.04 to 0.16. The His to Cys at M266 mutant had a significantly greater amount of bound zinc that was further enhanced when the strain was grown in zinc-supplemented media. The charge recombination rates from Q _B ^?. , which ranged from 0.5 to 1 s^?1 in the mutants, were comparable to the 1 s^?1 value for the wild type. Charge recombination from Q _A ^?. showed complex kinetics, with rates of 15 to 30 s^?1 for the L190, L230, and M234 mutants and 200 s^?1 for the M266 mutants compared with 8 s^?1 for the wild type. The faster rates in the mutants most likely reflected a smaller free energy difference between Q _A ^?. and Φ _A ^? , a nearby bacteriopheophytin, with the smaller energy difference facilitating indirect recombination. All of the mutants transferred electrons to the secondary quinone, with rates (1200 to 4700 s^?1) comparable to that of the native (3700 s^?1). The data demonstrate that neither the ligands nor the bound metal play a critical role in the electron transfer processes at the acceptor side.     

Chemical Composition of Flowers of Gossypium hirsutum

Chemistry of Natural Compounds -