Design of highly nonlinear dispersion-flattened square photonic crystal fiber for medical applications

In this paper, we report the design of a highly nonlinear dispersion flattened high-index-core square photonic crystal fiber (PCF) for applications in optical coherence tomography (OCT). The finite-difference method with an anisotropic perfectly matched boundary layer is used as a numerical simulation tool. A set of optimized design parameters numerically resulted in a nonlinear coefficient of 79.9W⁻¹ km⁻¹ and a dispersion of −0:186 ps/(nm·km) at a wavelength of approximately 1.06 μm. Owing to its high nonlinear coefficient and flattened dispersion, the PCF is expected to be suitable for broadband supercontinuum generation, which is considered very important in OCT medical applications.     

Another realization of Kerr/CFT correspondence

We study another realization of the Kerr/CFT correspondence. By imposing new asymptotic conditions for the near-horizon geometry of Kerr black hole, an asymptotic symmetry which contains all of the exact isometries can be obtained. In particular, the Virasoro algebra can be realized as an enhancement of symmetry of the AdS geometry. By using this asymptotic symmetry, we discuss finite temperature effects and show the correspondence concretely.     

Down-mixing of multi-channel audio for sound field reproduction based on spatial covariance

This article describes a method for automatic down-mixing multi-channel audio content on the basis of spatial covariance. Such a down-mixing method should be able to convert the signal of the original multi-channel audio system into that for an alternative system with the lesser number of channels, while maintaining the spatial impression of sound. Moreover, it should take into account the listener’s position and transfer function. Wave surface control and convolving the head related transfer function are techniques used in sound field control or reproduction. We consider that the spatial impressions of a sound field, which we perceive through our ears, are reproduced by preserving the relative relationship between observation points even if the wave surface is not completely controlled. Takahashi et al. proposed a new sound field reproduction method that we named “SOund field Reproduction based on sPAtial Covariance” (SORPAC). SORPAC can control the point-to-point covariance in a sound field. We expect that this sound field reproduction method based on spatial covariance can be applied to down-mixing of multi-channel content because SORPAC does not require the listener’s position or transfer function. This article describes SORPAC and its characteristics. We used SORPAC for down-mixing audio content. We confirmed that SORPAC-based down-mixing could accurately reproduce the interaural cross correlation (IACC) in relation to the listener’s position.     

Stereoselective Complex Formation between Polybutadiene and Cyclodextrins in Bulk

Polybutadienes (PBs) are found to form inclusion complexes with cyclodextrins (CDs) stereoselectively to give crystalline compounds in bulk. These complexes have been isolated and characterized by means of ¹H NMR and ¹³C CP/MAS NMR spectroscopy, and X‐ray diffraction. Although α‐CD did not form inclusion complexes with any kinds of PBs in aqueous solutions, α‐CD did form inclusion complexes with PBs having 1,4‐cis‐ and 1,4‐trans‐butadiene units in bulk by heating at 100 °C. On the other hand, PB having 79% of a 1,2‐structure did not form inclusion complexes with α‐CD. The yield of the inclusion complexes increases with an increase in the content of the 1,4‐cis‐structure of PB and decreases with the molecular weights of the PBs.

     

Ac vortex-dependent torsional oscillation response and onset temperature T0 in solid 4He

Detailed studies of ac velocity V_{ac} and T dependence of torsional oscillator responses of solid 4He are reported. A characteristic onset temperature T_{0} approximately 0.5 K is found, below which a significant V_{ac}-dependent change occurs in the energy dissipation for the samples at approximately 32 bar and for one at 49 bar. A V_{ac} dependence of the so-called "nonclassical rotational inertia" fraction also appears below approximately T_{0}. The log(V_{ac}) linear dependence, which suggests involvement of quantized vorticies, was examined in the nonclassical rotational inertia fraction. We find a common 1/T;{2} dependence for this linear slope change in all of the samples for 30相似文献   

Photochromism induced by infrared two-photon absorption

An IR laser of 940 nm wavelength induced photochromic reaction in acrylate that contained both spirobenzopyran and rare-earth doped oxide (Gd(2)O(2)S:YbEr). The rare-earth elements were excited by two 940 nm photons and emitted a 550 nm photon, which caused photochromic isomerization of spirobenzopyran. This acrylate turned to its original orange color by either thermal relaxation or ultraviolet irradiation, and was bleached again by IR laser irradiation.     

Effect of electrically degenerated layer on the carrier transport property of ZnO epitaxial thin films

ZnO films were prepared on (1 1 1) YSZ and (0 0 0 1) sapphire by pulsed laser deposition method. Effect of lattice mismatch on the carrier transport properties of ZnO epitaxial thin films was investigated. The carrier mobility of the ZnO films on YSZ was larger than that of ZnO/sapphire due to smaller lattice mismatch when the thickness was below 150 nm. The effect of electrically degenerated layer on the carrier transport property increased with decreasing the film thickness of ZnO film. The carrier density and electron mobility of 20 nm-thick-ZnO film on either substrate were regardless of the temperature. We concluded that the dominant carrier scattering mechanism in ZnO ultra thin films is double Schottky barriers at the grain boundary and that their height depends on the carrier concentration.     

Secondary ion species containing nitrogen atoms from plasma-enhanced chemical vapor deposited silicon oxide films on silicon

Secondary ion species from plasma-enhanced chemical vapor deposited (PECVD) SiO₂ films have been investigated using time-of-flight secondary ion mass spectrometry (TOF-SIMS). Comparative studies of PECVD SiO₂ films prepared using a mixture of SiH₄/N₂O reaction gas at 400 °C with thermally oxidized SiO₂ films grown at 900 °C were carried out in the mid-range mass spectra from 95 to 165 amu. Small amounts of ion species containing nitrogen atoms, including Si₂O₂N⁺, Si₃O₂N⁺and Si₃O₃N⁺, were detected in the SiO₂ bulk from the PECVD SiO₂ films. Furthermore, large amounts of Si₃O₂N⁺ and Si₂O₃N⁻ were found at the interface between silicon and the SiO₂ films. Depth analysis showed that the intensity peak shapes of these ion species containing nitrogen atoms at the interface were closely coincident with those of Si₃O₃⁺ corrected by subtracting the influence of the SiO₂ matrix. The variation in the spectra of these ion species clearly indicates that two types of structures of oxynitride exist for the PECVD SiO₂ films in the SiO₂ bulk films and at the interface. These are likely produced by the reaction of reactive gas with SiO₂ and silicon surfaces where dangling bonds of silicon may exist in the different form.     

Characterization of a magnetic carrier encapsulating europium and ferrite nanoparticles for biomolecular recognition and imaging

In this study, FG beads (ferrite nanoparticles in the core covered with poly-(styrene-co-glycidyl methacrylate)) were made into fluorescent magnetic carriers (FMCs) containing the fluorescent substance, europium ion (Eu³⁺) complex. The developed FMCs showed several notable features such as high fluorescence intensity and high dispersibility in water. More importantly, FMCs did not leak Eu³⁺ complex. It is expected that the FMCs will be a useful tool for biomolecular recognition and imaging and contribute to advancement of a wide range of research fields, including cell biology and molecular imaging.     

A high-resolution code for turbulent boundary layers

A new high-resolution code for the direct simulation of incompressible boundary layers over a flat plate is described. It can accommodate a wide range of pressure gradients, and general time-dependent boundary conditions such as incoming wakes or wall forcing. The consistency orders of the advective and pressure-correction steps are different, but it is shown that the overall resolution is controlled by the higher-order advection step. The formulation of boundary conditions to ensure global mass conservation in the presence of arbitrary forcing is carefully analyzed. Two validation boundary layers with and without a strong adverse pressure gradient are presented, with maximum Reynolds numbers Re_θ≈2000${\mathit{Re}}_{\theta }\approx 2000$. They agree well with the available experiments. Turbulent inflow conditions for the zero-pressure case are implemented by a recycling method, and it is shown that at least the initial 300 momentum thicknesses have to be discarded before the effect of the artificial inflow is forgotten. It is argued that this is not a defect of the method used to generate the inflow, but a property of the boundary layer.