State of irremovable water in solid polymer films examined by fourier transform infrared spectroscopy I: poly(ethylene glycol) dimethyl ether

The state of the sorbed water, including the water that cannot be removed by the reduced pressure and water-sorption processes, into poly(ethylene glycol) dimethyl ether (PEG-DME) film was examined by Fourier transform infrared (FT-IR) spectroscopy. The spectrum of the irremovable water could be obtained without a thermal treatment frequently used as the dehydration procedure. It was found that the irremovable water mainly existed in the crystalline region of PEG-DME film, and that its hydrogen-bonding (HB) structure differed from that of the water sorbed from the air. Moreover, the amount of water having the same HB structure as the irremovable water increased with the water contents. These findings could not be revealed by the spectrum of the sorbed water obtained by the conventional dehydration procedure. The experimental procedure examined here allowed us to investigate the true aspects of the irremovable water and the water-sorption processes.     

Acoustic pulse echoes probed with time-resolved X-ray triple-crystal diffractometry

Acoustic pulse echoes generated by femtosecond laser irradiation were detected using time-resolved x-ray triple-crystal diffractometry. The determined time-dependent longitudinal strain component for pulse echoes in silicon and gallium arsenide plates showed that the polarity of the strain pulse was dependent on the optically induced initial stress, and that the bipolar pulse waveform was gradually deformed and broadened in the course of propagation. The three-dimensional wave front distortion of pulse echoes was shown simply as the pulse duration broadening, which was consistent with a boundary roughness for an unpolished plate.     

Measurement of small chirp-parameter for Mach-Zehnder-type optical modulator

A new measurement method of chirp-parameters is proposed for electro-optic (EO) intensity modulators with the Mach-Zehnder (MZ) waveguide interferometer. This method is suitably applied for the measurement of the small chirp with operation at a specific RF-frequency. To determine the chirp-parameter, optical spectrum components of the modulated light are observed with varying the relative optical phase difference between the two arms of the MZ waveguide interferometer. The chirp-parameter of 0.17, which is a value small enough for EO intensity modulation, was successfully measured by the experiment.     

Effect of the number of molecules on the energetic efficiency in molecular motors using the Flashing Ratchet model

In this paper, we analyze the N-motor model based on the Flashing Ratchet model. There are two types of models. One of them consists of the Langevin equation and the other consists of the Fokker-Planck equation. By using the former equation, we calculate the velocity of N-motor models, and find several dependencies on the number of motors. We also find analytical expressions of the velocity as a function of the number of motors, which contribute to understanding the cooperativity of motors. In the latter equation, we modify the previously proposed N-motor model and develop methods to calculate the velocity, efficiency, and dissipation rates of the model. Specifically, we analyze single-particle, 2-particle, and infinite-particle molecular motor models. We show that the efficiency increases as the number of motors increases depending on the dissipation rates.     

Cerebral infarction associated with moyamoya disease: histogram-based quantitative analysis of diffusion tensor imaging -- a preliminary study

Moyamoya disease (MMD) is a rare disorder of unknown etiology in which terminal portions of the internal carotid arteries become steno-occlusive, with fine collateral "moyamoya vessels" formed secondarily, resulting in serial ischemic strokes throughout its clinical course. Whole-brain histogram (WBH) of diffusion tensor imaging (WBH-DTI) is an analytical tool whose feasibility has been ascertained in various pathologies. To elucidate whether WBH-DTI could detect any difference between ischemic MMD and normal controls, we examined 27 consecutive MMD patients without hemorrhage and 48 normal controls in this prospective study using a 3.0-T magnetic resonance scanner. WBHs of fractional anisotropy (FA) (WBH-FA) and mean diffusivity (MD) (WBH-MD) were compared among three groups: Group 1, MMD patients with infarct (n=15); Group 2, MMD patients without infarct (n=12); and Group 3, normal controls (n=48). Group 1 showed significantly higher peak height and significantly lower mean value on WBH-FA, as well as significantly lower peak height and significantly higher mean value on WBH-MD, compared with Groups 2 and 3. No significant difference was seen in parameters at either WBH-FA or WBH-MD between Groups 2 and 3. These results might reflect the pathological severity of each group, and WBH-DTI could feasibly detect differences between ischemic MMD with infarction and MMD without infarction and normal controls.     

Surface depth analysis for fluorinated block copolymer films by X-ray photoelectron spectroscopy using C60 cluster ion beam

X-ray photoelectron spectroscopy (XPS) using fullerene (C₆₀) cluster ion bombardment was applied to films of a fluorinated block copolymer. Spectra so obtained were essentially different from those using Ar ion beam. Structure in the surface region with the depth down to 60 nm drawn on the basis of XPS with C₆₀ beam was essentially the same as the one drawn by the result using dynamic secondary ion mass spectrometry, which is a well-established method for the depth analysis of polymers. This implies that XPS using C₆₀ beam enables one to gain access to the depth analysis of structure in polymer films with the depth range over the analytical depth of conventional XPS, that is, three times inelastic mean-free path of photoelectrons.     

Nanoscale imaging of mineral crystals inside biological composite materials using X-ray diffraction microscopy

We for the first time applied x-ray diffraction microscopy to the imaging of mineral crystals inside biological composite materials--intramuscular fish bone--at the nanometer scale resolution. We identified mineral crystals in collagen fibrils at different stages of mineralization. Based on the experimental results and biomineralization analyses, we suggested a dynamic model to account for the nucleation and growth of mineral crystals in the collagen matrix. The results obtained from this study not only further our understanding of the complex structure of bone, but also demonstrate that x-ray diffraction microscopy will become an important tool to study biological materials.     

Improvement of magnetic properties and read/write characteristics in SmCo5 perpendicular thin films

An SmCo₅ alloy is a promising candidate for ultra-high density magnetic recording media because of its strong uniaxial magnetocrystalline anisotropy, whose constant, K_u, is more than 1.1×10⁸ erg/cm³. Recently, we successfully obtained high perpendicular magnetic anisotropy for a sputter-deposited SmCo₅ thin film by introducing a Cu/Ti dual underlayer. However, it is necessary to improve magnetic properties and read/write (R/W) characteristics for applying SmCo₅ thin films to perpendicular magnetic recording media. In this study, we focused on reduction of magnetic domain size and change of a magnetization reversal process of SmCo₅ perpendicular magnetic thin films by introducing carbon (C) atoms into the constituent Cu underlayer. The magnetic domain size became small and the ratio of coercivity (H_c) against magnetic anisotropy (H_k) which is an index of the magnetization reversal process was increased by adding C atoms. We also evaluated the R/W characteristics of SmCo₅ double-layered media including C atoms. The medium noise was decreased and signal-to-noise ratio increased by introducing the C. The addition of C into the Cu underlayer is effective for changing the magnetization reversal process, reducing medium noise and increasing SNR.     

Compatibilizer-aided toughening in polymer blends consisting of brittle polymer particles dispersed in a ductile polymer matrix

Blending brittle polymer particles in a ductile polymer matrix is a new way to obtain toughened plastics. Although the nylon-6/poly(acrylonitrile-co-styrene) (SAN) system is a ductile/brittle combination, the blend does not result in a toughened plastic. We have investigated the effect of adding a small amount of a third component, poly(styrene-co-maleic anhydride) (SMA), to the nylon/SAN system. SMA significantly improves the tensile and impact strength of the blend. Morphological observations indicate a finer dispersion of the SAN particles when SMA is present in the blend. The improved dispersion is attributed to the formation of nylon-SMA graft copolymer, and infrared analysis supports this supposition. That is, a “compatibilizer” seems to be produced during melt mixing of the ternary system. The role that the compatibilizer plays in improving the stress transfer in the two-phase system and its potential to induce a brittle-ductile transition of the glassy SAN particles are considered to explain the toughening mechanism.     

Measurement of sound-pressure distribution in replicas of the oral cavity.

The spatial distributions of sound pressure in artificial oral cavities were measured to examine the characteristics of wave propagation in the vocal tract. The measurement was performed with plaster replicas of the oral cavity, and pure tones were used as the driving signals to obtain both amplitude and phase distributions at varied frequencies. Plane-wave propagation, which has been widely assumed for speech production models, was examined from the measured spatial distributions of sound pressure. Trajectories of media particles and vectorial maps of acoustic intensity, which can be computed from the measured pressure distributions, were also presented to visualize the acoustic field in the oral cavity. The results showed that at certain frequencies there existed points where sound pressure was absolutely zero, with the phase spatially circulating around them. Up to about 4 kHz, except at these certain frequencies, the wave front was almost one-dimensional, though an amplitude gradient was seen in the vertical direction.