Improvement of photonuclear reaction model below 140 MeV in the PHITS code

The photonuclear reaction model in the particle and heavy ion transport code system (PHITS) code is improved for incident photon energies below 140 MeV. Japanese Evaluated Nuclear Data Library (JENDL) Photonuclear Data File 2004 (JENDL/PD-2004) is adopted to determine the total reaction cross section. The statistical decay model after excitation of the nucleus in PHITS is improved by modifying the decay widths for light nuclei under the isospin selection rule to reasonably reproduce the proton and neutron emission in the de-excitation process. The quasideuteron disintegration process is newly introduced into PHITS to handle the photonuclear reaction up to 140 MeV of incident photon energy. The accuracy of the improvements was verified by comparison with the experimental literature data. The improved PHITS can contribute to various practical applications such as neutron dose estimation in X-ray therapy.     

Two‐Photon Fluorescent Imaging of Myelination in the Spinal Cord

Myelination is a fundamental biological process in the vertebrate nervous system. Damage to or malformation of myelin can lead to various neurological diseases; for example, demyelination in the spinal cord is a major cause of paralysis of patients suffering from multiple sclerosis and related diseases. The ability to directly track myelin levels in the spinal cord is needed in order to assess the efficacy of therapeutics in promoting myelin repair. To address this unmet need, 4‐((E)‐4‐((E)‐4‐aminostyryl)‐2,5‐dimethoxystyryl)‐N‐methylaniline, known as Case Imaging Compound (CIC), has been developed as a myelin‐targeted fluorescent imaging agent that selectively binds to myelin. CIC was synthesized via an improved route and evaluated as a fluorescent probe for two‐photon fluorescent imaging of myelin in the spinal cord in both demyelinated and dysmyelinated models. In vitro and ex vivo tissue staining both suggest that CIC selectively binds to in animal models. Further evaluation in animal models indicated that CIC is sensitive to differences in myelin content in healthy versus pathological myelin. CIC could potentially be useful in the development and evaluation of novel therapies for multiple sclerosis and other demyelinating diseases.     

Exploitation of inline photon density wave spectroscopy for titania particle syntheses

In this work, inline (or in-situ) monitoring of titania particle formation with photon density wave spectroscopy is shown to provide helpful information for process optimization for higher particle yields. Titania particles have been synthesized by the controlled hydrolysis of tetraethyl orthotitanate. Without calibration or dilution, photon density wave spectroscopy provides access to dispersions' reduced scattering coefficient μ_s'. Hence, information can be obtained inline about processes that are otherwise challenging for established particle characterization methods. Photon density wave spectroscopy results suggest that the titania particles disintegrate over time after their formation. Consistent with that hypothesis, a decreasing particle yield with reaction time has been observed. The disintegration can be hindered by adding a sufficient amount of hexadecylamine, such that the particle yield after 24 h can be increased by 44% for the given syntheses.     

燃烧法合成稀土纳米长余辉发光材料SrO·xAl2O3:Eu2+,Dy3+

应用燃烧法在空气中较低的温度(<900℃)下成功地合成了SrO·xAl2O3∶Eu2+,Dy3+稀土纳米长余辉发光材料,并研究了炉温、反应物中铝锶比、助溶剂和可燃物等对发光材料性能的影响。研究结果表明,反应物置于温度为600℃的高温炉中时燃烧得到的产物性能最好,发光粉的粒径在70nm左右,发射光谱的最大波长在520nm左右。与其它合成方法相比,该方法具有合成温度低、反应时间短,获得的产物疏松、硬度小、粒度小等优点。     

Rigorous simulation of nonlinear optomechanical coupling in micro- and nano-structured resonant cavities

A numerical method aimed to predict the optomechanical dynamics in micro- and nano-structured resonant cavities is introduced here. The rigorousness of it is ensured by exploiting the harmonic version of the transformation optics (TO) technique and by considering all the energy-transduction contributions of electrostriction, radiation pressure, photoelasticity and moving boundaries. Since our full-wave approach implements a multi-modal analysis and also considers material losses, from both a mechanical and an optical point of view, a considerable step further has been made in respect to the standard optomechanical perturbative theory. The efficiency and the versatility of the strategy are tested by analysing the optomechanical behaviour of a corrugated Si-based nanobeam and comparing numerical results to experimental ones from the literature.     

Proposal for an advanced hybrid K-edge/XRF densitometry (HKED) using a monochromatic photon beam from laser Compton scattering

The general purpose Monte Carlo electron-gamma shower computer code (EGS5) was used to obtain the U, Np, and Pu X-ray response from the hybrid K-edge/XRF densitometry (HKED). In the present simulation, we adopt a monochromatic, linearly polarized photon beam generated by using inverse Compton scattering of laser light with high-energy electrons from an energy recovery linac. The simulation has been carried out under various conditions of the U, Np, and Pu concentrations to investigate the effect of counting rates as well as counting precision. The results of the simulation show that the assessment time for low concentration Pu input solutions is reduced by improving the signal-to-background ratios. It is also shown that the Np concentration is determined with the counting precision of 0.67-1.8% in standard deviation during 1 h live time measurement for a 3N HNO₃ sample solution (1.1-1.3 g/cm²) including U (10-200 g/L), Np (0.1 g/L), and Pu (10 g/L).     

On photo-oxidation of single molecules

Fluorescence and fluorescence excitation spectra of terrylene in 9,10-dibromoanthracene matrix were studied at 5 K. Characteristic singlet oxygen phosphorescence, O₂(¹Δ_g) → O₂(³Σ_g) with the line maximum at 1272.5 nm, was observed after excitation of terrylene molecules embedded into one of its two sites. It indicates that singlet oxygen, precursor in photo-oxidation of aromatic molecules, can be created only for those oxygen molecules which can form weak van der Waals complex with terrylene. According to quantum-chemical calculations terrylene and oxygen can form complex with the bonding energy 141 cm⁻¹, in which oxygen molecule is located along the long axis of terrylene, ∼0.3 nm apart, with the molecular axis inclined by 110°.