A surface acoustic wave on a ferroelectric layer-structure oxide

As a piezoelectric application of a ferroelectric material of layer-structure type, a surface acoustic wave device using a ceramic Pb_0.15 (NaBi)_0.425Bi₄Ti₄O₁₅, produced by a hot-forging technique is described. The surface acoustic wave on the substrate with the poling axis parallel to the free surface is Blustein-Gulyaev type and its velocity is 2812 m/s.     

Power law of molecular weight dependence of lateral growth rate of isotactic polypropylene

Molecular weight (M) dependence of the lateral growth rate (V) of α form crystal of isotactic polypropylene (iPP) was studied. Reliable equilibrium melting temperature determined in our previous study was used for the analysis of supercooling dependence of V. A power law of M of V, , was obtained, where H is a small constant (H = 0.7). The small H, which is similar to that of the hexagonal phase of polyethylene (H = 0.7) in comparison with the value of H = 1.7 for the orthorhombic phase of polyethylene, confirmed our prediction of smaller H for “rod like” chain polymers because of easier chain sliding within the interface between the crystalline phase and the melt. Thus, the universality of the important role of topological nature in polymer crystallization was confirmed. Lateral surface free energy (σ) of the α form of iPP was obtained as σ ≅ 1.59 × 10⁻⁶ J/cm².     

Molecular dynamics of DNA and nucleosomes in solution studied by fast-scanning atomic force microscopy

Nucleosome is a fundamental structural unit of chromatin, and the exposure from or occlusion into chromatin of genomic DNA is closely related to the regulation of gene expression. In this study, we analyzed the molecular dynamics of poly-nucleosomal arrays in solution by fast-scanning atomic force microscopy (AFM) to obtain a visual glimpse of nucleosome dynamics on chromatin fiber at single molecule level. The influence of the high-speed scanning probe on nucleosome dynamics can be neglected since bending elastic energy of DNA molecule showed similar probability distributions at different scan rates. In the sequential images of poly-nucleosomal arrays, the sliding of the nucleosome core particle and the dissociation of histone particle were visualized. The sliding showed limited fluctuation within ∼50 nm along the DNA strand. The histone dissociation occurs by at least two distinct ways: a dissociation of histone octamer or sequential dissociations of tetramers. These observations help us to develop the molecular mechanisms of nucleosome dynamics and also demonstrate the ability of fast-scanning AFM for the analysis of dynamic protein–DNA interaction in sub-seconds time scale.     

Alkoxyresorufin O-dealkylase assay using a rat hepatocyte spheroid microarray

Hepatocyte multicellular aggregates (spheroids), which maintain high expression of liver functions, have been advocated as a useful culture technique for various cell-based assays. In this study, we investigated the drug metabolic function of a hepatocyte spheroid microarray (HSM) chip, which contained an array of 672 spheroids of primary rat hepatocytes within a 100-mm² region in the center of a poly(methylmethacrylate) plate (24 × 24 mm) and used an alkoxyresorufin (ethoxy-, methoxy-, pentoxy- and benzyloxyresorufin) O-dealkylase assay system. Ethoxyresorufin O-dealkylase (EROD) activity of the HSM chip initiated by 3-methylcholanthrene (3-MC), an inducer of cytochrome P450 enzymes, was 5- to 10-fold higher than that of monolayer hepatocytes, with activity being maintained for at least 2 weeks. We also demonstrated that 3-MC induced EROD, methoxyresorufin O-dealkylase (MROD) and benzyloxyresorufin O-dealkylase (BROD) activities in the HSM chip, while sodium phenobarbital (P450 inducer) induced pentoxyresorufin O-dealkylase (PROD), BROD, EROD and MROD activities. Induction of these activities was confirmed by increased gene expression of the related P450 enzymes. These results showed that the HSM chip had a good response to P450 inducers and that function was maintained for long periods of time. The HSM chip therefore may be a promising cellular platform for drug metabolic assays using hepatocytes.     

Monitoring biofilm development in a microfluidic device using modified confocal reflection microscopy

The feasibility of a method to monitor biofilm development non-destructively in a microfluidic device was addressed. Here, we report that biofilm growth could be non-destructively monitored by an image analysis technique based on modification of confocal reflection microscopy.     

Detection of norovirus RNA in bivalve molluscs by using bacteria-culture-employed method (A3T method)

Norovirus (NV) RNA has rarely been detected in foods despite the use of highly sensitive methods such as RT-PCR and real-time RT-PCR. In the modified method (A3T method) reported previously, a bacterial culture process was introduced into the standard protocol for NV detection to remove some inhibitor(s) present in food ingredients. To confirm the efficiency of the A3T method and to examine NV contamination in bivalve molluscs, we tried to detect NV RNA in bivalve molluscs on the market and in oyster samples associated with foodborne outbreaks by using the standard method and the A3T method. NV RNAs were detected in 20 samples (18.0%) of 111 bivalve molluscs, including oysters, on the market by use of the A3T method, while only one sample (0.9%) was positive according to the standard method. NV RNA was also detected in 10 of 35 oyster samples related to foodborne outbreaks by the A3T method. Those results show that the A3T method is suitable for the detection of NV in bivalve molluscs in general laboratories.     

Radar cross-section measurement method using a spatial filtering within a near zone

A spatial filtering is a useful method for suppressing unwanted reflection from undesired scatters on radar cross-section (RCS) measurements. Highly accurate RCS measurements for stealth-designed targets are generally performed by using full-scale models. However, it is difficult to carry out a measurement of a large full-scale target, because a vast RCS measurement site which satisfies the far-field criterion without undesired scatters is required. In this paper, we have applied the filtering method to RCS measurements in a near field and investigated the validity of that method by varying the scanning angular span. First, a distribution of scattering sources including undesired scatters is predicted from near-field spherical- or cylindrical-scanning data. Next, undesired scatters are suppressed using the spatial filtering. Finally, RCS values of the test target are calculated by taking the Fourier transform of the filtered scattering source distribution. Using electromagnetic simulations, we have validated the RCS measurement method by comparing predicted RCS with reference data as far-field RCS of the test target. As a result, predicted RCS profiles closely matched with reference data. In conclusion, the proposed method is useful for RCS measurements within the unsuitable near zone. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Energy transmission transformer for a wireless capsule endoscope: analysis of specific absorption rate and current density in biological tissue

This paper reports on the electromagnetic influences on the analysis of biological tissue surrounding a prototype energy transmission system for a wireless capsule endoscope. Specific absorption rate (SAR) and current density were analyzed by electromagnetic simulator in a model consisting of primary coil and a human trunk including the skin, fat, muscle, small intestine, backbone, and blood. First, electric and magnetic strength in the same conditions as the analytical model were measured and compared to the analytical values to confirm the validity of the analysis. Then, SAR and current density as a function of frequency and output power were analyzed. The validity of the analysis was confirmed by comparing the analytical values with the measured ones. The SAR was below the basic restrictions of the International Commission on Nonionizing Radiation Protection (ICNIRP). At the same time, the results for current density show that the influence on biological tissue was lowest in the 300-400 kHz range, indicating that it was possible to transmit energy safely up to 160 mW. In addition, we confirmed that the current density has decreased by reducing the primary coil's current.     

Micropatterned organoid culture of rat hepatocytes and HepG2 cells

The culture of liver cell organoids (multicellular aggregates) such as spheroids or cylindroids, which can strongly express liver functions, has been advocated as a useful technique that has advantages over monolayer culture. This paper describes a micropatterning technique for obtaining spheroids and cylindroids by using rat hepatocytes or HepG2 cells. We developed culture chips that comprised multiple, circular or rectangular microwells; the bottom surface of each microwell was modified with collagen to create a cell adhesion area, and the entire microwell, excluding the collagen-coated spots, was modified with polyethylene glycol (PEG) to create a nonadhesive area. Rat hepatocytes and HepG2 cells formed uniform spheroids and cylindroids on the circular and rectangular chips, respectively. Consequently, two-dimensional micropatterned chips containing homogeneous spheroids or cylindroids were generated. The expression of liver functions (protein secretion and ammonia removal) was greater in the spheroids and cylindroids than in the monolayer culture, and this expression was maintained for at least 2 weeks of culture. Thus, this chip technology has potential for use in various applications that involve organoid culture.