Angular dependences of critical current density in YBCO thin films with crossed columnar defects

We investigated the dependences of the critical current density J_c on the magnetic field angle θ in YBa₂Cu₃O_7−δ thin films with the crossed configurations of the columnar defects (CDs). To install the crossed CDs, the films were irradiated using the high energetic Xe ions at two angles relative to the c-axis. The additional peak around the c-axis appears in the J_c(θ) for all irradiated films. In lower magnetic fields, the height of the J_c(θ) peak caused by the crossed CDs with the crossing angles θ_i = ±10° was higher than that for the parallel CDs. It is considered that the correlation of the flux pinning by the crossed CDs along the c-axis occurs even in the case of θ_i = ±25°, which was also suggested by the kink behaviors of the scaling parameters of the current–voltage characteristics near 1/3 of the matching field. In higher magnetic fields, on the other hand, the height and width of the J_c(θ) peak for the crossed CD configurations rapidly reduce with increasing the magnetic field compared to the parallel ones. In the crossed CD configurations, the dispersion in the direction of CDs would prevent the correlation of flux pinning along the c-axis in high magnetic fields, which occurs in the parallel CD configurations due to the collective pinning of flux lines including the interstitial flux lines between the directly pinned flux lines by CDs.     

Non-linear forced vibrations of a beam carrying concentrated mass under gravity

The non-linear dynamic behavior of a simply supported beam, with ends restrained to remain a fixed distance apart, carrying a concentrated mass and subjected to a harmonic exciting force at an arbitrary point under the influence of gravity is analysed. By using the one mode approximation and applying Galerkin's method, the governing equation of motion is reduced to the well known Duffing type equation. The harmonic balance method is applied to solve the equation and the dynamic response of a concentrated mass is derived. The effects of the weight, the location, and the vibratory amplitude of the concentrated mass on the natural frequency are also discussed.     

Graft Copolymerization of Benzyl Methacrylate onto Poly(Acryloyl-L-valine) Microspheres by Using the Photoreaction of Side Carboxyl Groups with Lead Tetraacetate

N-Acryloyl-L-valine (ALV) was found to yield polymer microspheres when it was polymerized with a radical initiator in acetophenone. The resulting microspheres showed thermochromism in aromatic solvents such as benzonitrile, methyl benzoate, and acetophenone. Graft copolymerization of benzyl methacrylate (BzMA) onto poly(ALV) microspheres was carried out in benzonitrile by using the photoreaction of carboxyl groups in poly (ALV) with Pb(OAc)₄. The grafting efficiency was not very high (15–28%). Methyl methacrylate as the second monomer gave a higher grafting efficiency (56%) although the polymer yield was considerably lower. The resulting graft copolymer was characterized by IR spectroscopy and thermogravimetry. The grafted poly (ALV) microspheres were well dispersed in benzene. A benzene solution of grafted poly(ALV) microspheres and homopoly(BzMA) gave a film with finely dispersed poly (ALV) microspheres.     

Effect of superficial velocity on pressure fluctuations in a gas–solid fluidized bed: A stochastic analysis

The characteristics of a gas–solid fluidized bed are influenced by complicated and stochastic phenomena, e.g. jetting and the bubbling of the fluidizing medium and the motion of the fluidized particles. In this study pressure fluctuations due to the bubble movement were measured by means of a pressure probe over a range of time. The resultant time series have been analysed by determining their autocorrelation function and power spectrum with emphasis on the examination of the effect of the superficial velocity of the fluidizing gas. A stochastic model of bubble motion in a fluidized bed has been developed. This model visualizes the bubble motion in a fluidized bed to consist of the random movement, generating irregular signals, and the linear movement, generating wave-like signals. A theoretical autocorrelation function and a power spectral density function have been derived based on the model.     

Analysis for catecholamines and related compounds based on luminescence at room temperature and at 77 k

The luminescence characteristics of 34 catecholamines and related compounds at room temperature and at 77 K are reported. Neutral, basic and acidic mixtures were used as solvents. Limits of detection, linear ranges and analytical precision were determined for each case. Analytically useful luminescence was obtained at 77 K. In neutral and acidic solutions, both fluorescence and phosphorescence could be used qualitatively and quantitatively; in basic solutions, the phosphorescence was valuable at concentrations as low as 10⁶–10^-9 M, depending on the compound.     

Transition State of Heat Denaturation of Methionine Aminopeptidase from a Hyperthermophile

Heat denaturation of methionine aminopeptidase from a hyperthermophile Pyrococcus furiosus (PfMAP) was studied by differential scanning calorimetry at acid pH. Analysis of the calorimetric data has shown that denaturation of PfMAP is non-equilibrium at heating rates from 0.125 to 2 K min^–1. This means that the protein structure at these conditions is metastable and its stability (the apparent temperature of denaturation T _m) is under kinetic control. It was shown that heat denaturation of this protein is a one-step kinetic process. The enthalpy of the process and its activation energy were measured as functions of temperature. The obtained data allowed us to estimate the heat capacity increment and the change in the number of bound protons during activation of the molecule. The data also suggest that the conformation of PfMAP at the transition state only slightly differs from its native conformation with respect to compactness, hydration extent and hydroxyl protonation. This revised version was published online in July 2006 with corrections to the Cover Date.     

A wide spectral band photodetector with PtSi/p-Si Schottky-barrier

The photoresponse of a front-illuminated PtSi Schottky-barrier detector is measured in the wavelength range between 0.4 and 5.2m. In the wavelength range longer than 1.1m, the detection mechanism is the internal photoemission. On the other hand, the intrinsic mechanism becomes dominant in the wavelength range shorter than 1.1m. The measured data are in good agreement with values calculated from these two detection mechanisms. The photoresponse depends on the PtSi thickness in both wavelength ranges. For getting a high responsivity, it is important to make a thin uniform metal film. The visible and the thermal image with a PtSi Schottky-barrier wide spectral band imager are also demonstrated.     

Distribution of Polyphenols and a Surfactant Component in Skin during Aerosol OT Microemulsion-Enhanced Intradermal Delivery

As for most other polyphenols, intradermal delivery of curcumin and resveratrol is limited; however, it was significantly improved by a microemulsion using Aerosol OT (Aerosol OT microemulsion) and Tween 80 (Tween 80 microemulsion) as surfactants. Aerosol OT microemulsion was more effective and the incorporation ratio of these polyphenols into skin by Aerosol OT microemulsion was five-fold or ten-fold that by Tween 80 microemulsion. To clarify the mechanism of the enhancement we examined the distribution of these polyphenols and the surfactant component, Aerosol OT, using excised guinea pig skin and Yucatan micropig (YMP) skin. During permeation, polyphenols distributed deep in the skin. In particular, a small molecule, resveratrol, was mainly present in the dermis in YMP skin. Aerosol OT also distributed deep in the skin. These findings suggest the possible involvement of the interaction of surfactant molecules with skin components in the enhanced delivery process of polyphenols. The distribution ratio between the dermis and epidermis of the polyphenols, including quercetin, in the presence of Aerosol OT microemulsion decreased with the increase of molecular weight in YMP skin, suggesting the possibility that distribution to the dermis is regulated by the molecular size.