Different feeding and gustatory responses to ecdysone and 20-hydroxyecdysone by larvae of the silkworm,Bombyx mori

The feeding and gustatory responses to ecdysone and 20-hydroxyecdysone were investigated in the silkworm,Bombyx mori. 20-Hydroxyecdysone reduced feeding response strongly in fourth- and fifth-instar larvae, whereas ecdysone had no effect on feeding response. 20-Hydroxyecdysone stimulated the R receptor, the receptor to feeding deterrents, to a great degree. By contrast, ecdysone was much less effective for stimulating the R receptor. These results indicate that ecdysone and 20-hydroxyecdysone have different effects on feeding response due to different interactions with mouthpart chemoreceptors.     

Calcium Concentration Dependence of the Intergranular Film Thickness in Silicon Nitride

High-resolution electron microscopy and nano-beam analytical electron microscopy have been used to characterize both the intergranular silicate film thickness and its local composition in a series of high-purity Si₃N₄ ceramics doped with 0–450 at. ppm Ca. Calcium was detected at both two-grain junctions and triple junctions, even in the 80-ppm-Ca-doped specimen. The thickness of the intergranular film at two-grain junctions was found to depend sensitively on Ca content. In undoped material, the thickness was 1.0 ± 0.1 nm. With increasing Ca content, the thickness decreased in the dilute region (80 ppm Ca), but then increased. The variation in film thickness can be qualitatively understood in terms of the balance of three long-range forces acting normal to the film, namely the van der Waals dispersion force, a structural "steric" force, and an electrical-double-layer force. By comparing the measured thicknesses to those predicted, estimates for the structural correlation length and the inverse Debye length can be made. These estimates have values of ∼ 0.22 nm and approximately 0.3–0.5 nm, respectively, for the calcia-free and 80 ppm calcia materials.     

Stress distribution of coated film with a range of coated film thickness and elastic properties under a single EHL operating condition

In recent years, the techniques improving sliding performances have progressed by using coated films possessing superior tribological properties, to reduce the failures of the mechanical elements. Those techniques are often used under severe conditions such as elastohydrodynamic lubrication (EHL). In this paper, numerical three-dimensional analysis of the maximum shear stress applied into the coated film and substrate under a single EHL operating condition was performed with a range of coated film thickness and elastic properties. The strength of coated film as one of those techniques was evaluated numerically, resulting in an optimum design of coated film. As a result, coated films with a larger value of thickness and a smaller modulus of elasticity than that of substrate are preferable.     

High-velocity impact experiment of aluminum foam sample using powder gun

Porous materials such as aluminum foam have been investigated for possible use as impact shock absorbers in transportation aeronautic applications. However, the response of aluminum foam during impacts at high velocities of more than 100 m/s is not yet fully understood. A high-velocity impact experiment was therefore carried out to clarify impact shock absorption properties of aluminum foam. A one-stage powder gun was used to accelerate an aluminum foam sample to impact a rigid wall. Velocity and deformation of the aluminum foam sample during impact was studied using a digital high-speed video camera, while the pressure wave in the aluminum foam sample was measured using a PVDF gauge. The experimental observations revealed uneven collapse of the aluminum foam sample structure during high speed impact with a general stress plateau effect, typical for cellular material structures when subjected to quasi-static loading.     

H- beam extraction from a cesium seeded field effect transistor based radio frequency negative hydrogen ion source

H(-) beam was successfully extracted from a cesium seeded ion source operated using a field effect transistor inverter power supply as a radio frequency (RF) wave source. High density hydrogen plasma more than 10(19) m(-3) was obtained using an external type antenna with RF frequency of lower than 0.5 MHz. The source was isolated by an isolation transformer and H(-) ion beam was extracted from a single aperture. Acceleration current and extraction current increased with the increase of extraction voltage. Addition of a small amount of cesium vapor into the source enhanced the currents.     

Characterization of alicyclic polyimides based on cyclobutane ring dianhydride and aromatic diamine

Films of alicyclic polyamic acid and polyimide containing cyclobutane ring in dianhydride moiety and aromatic ring with p- or m-linkages in diamine moiety were characterized by infrared (IR) spectroscopy, dynamic viscoelasticity, differential-scanning calorimetry (DSC), density, and wide-angle X-ray diffraction analyses. Partially and fully imidized polyimides were obtained by varying the imidization temperature, e.g., 150°C, 250°C, and 350°C. It was found from the results of IR spectra, dynamic viscoelasticity, and DSC measurements that the imidization of alicyclic polyamic acid was reduced at about 150°C and needed a higher imidization temperature than aromatic polyamic acid. Alicyclic polyimide with m-linkage in the diamine moiety had a higher density and a much more ordered structure than with p-linkage. © 1994 John Wiley & Sons, Inc.     

Measurements of Two-Dimensional Distribution of Refrigerant Concentration in EHL Film Using Micro FT-IR and Effect of Variation of Concentration on Oil Film Thickness

The dissolution of refrigerant into a lubricant causes a decrease in viscosity of the oil and it gives a large effect on the lubrication of sliding parts in a refrigerant compressor. This paper describes an application of micro FT-IR to measure the two-dimensional concentration distribution of refrigerant held in solution in the EHL film surrounded by the refrigerant gas and discusses the refrigerant concentration variation in the vicinity of the Hertzian contact area. In order to measure the concentration distribution, an apparatus which can observe the EHL film in a point contact in the refrigerant atmosphere was developed. The refrigerant concentration was measured using micro FT-IR through a CaF₂ window from outside of the apparatus with polyol ester as a base oil in an atmosphere pressurized with HFC-134a refrigerant gas. The results indicate that the concentration of HFC-134a refrigerant reduces in the inlet boost region of EHL contact and the Hertzian contact area but in the side region of Hertzian contact area it is greater than that in the bulk fluid. In addition, the effect of the variation on the oil film thickness is discussed.     

Cautionary observations on preparing and interpreting brain images using molecular biology-based staining techniques

Though molecular biology-based visualization techniques such as antibody staining, in situ hybridization, and induction of reporter gene expression have become routine procedures for analyzing the structures of the brain, precautions to prevent misinterpretation have not always been taken when preparing and interpreting images. For example, sigmoidal development of the chemical processes in staining might exaggerate the specificity of a label. Or, adjustment of exposure for bright fluorescent signals might result in overlooking weak signals. Furthermore, documentation of a staining pattern is affected easily by recognized organized features in the image while other parts interpreted as "disorganized" may be ignored or discounted. Also, a higher intensity of a label per cell can often be confused with a higher percentage of labeled cells among a population. The quality, and hence interpretability, of the three-dimensional reconstruction with confocal microscopy can be affected by the attenuation of fluorescence during the scan, the refraction between the immersion and mounting media, and the choice of the reconstruction algorithm. Additionally, visualization of neurons with the induced expression of reporter genes can suffer because of the low specificity and low ubiquity of the expression drivers. The morphology and even the number of labeled cells can differ considerably depending on the reporters and antibodies used for detection. These aspects might affect the reliability of the experiments that involves induced expression of effector genes to perturb cellular functions. Examples of these potential pitfalls are discussed here using staining of Drosophila brain.     

Study on practical application of a new seismic damper using a Zn–Al alloy with a nanocrystalline microstructure

Superplastic Zn–Al alloy has some excellent properties needed for a seismic damper, such as high ductility, low work hardening and no harmful metal to human health. In addition, superplastic materials with ultra-fined grains exhibit the high-strain-rate superplasticity and/or low-temperature superplasticity. Some investigations were carried out for nano-sized Zn–Al alloy in order to develop a high-performance seismic damper capable of replacing conventional dampers, such as low-yield-point steel. First, the design for appropriate structure as a damping device using superplastic Zn–Al alloy was discussed by FEM analysis. Secondly, a bulk Zn–Al alloy with nanocrystalline microstructure was manufactured by thermo-mechanical controlling process (TMCP) technology, and the tensile properties of this alloy were compared with that of low-yield-point steel. Then, the full-size cyclic testing of the damping device was carried out in order to evaluate the response for earthquake. As a result, an ecological and high performance seismic damper, the so-called “maintenance-free seismic damper”, has been successfully developed and put into actual use in a high-rise building.     

Electron-energy-loss near edge structures of six-fold-coordinated Zn in MgO

Electron-energy-loss near edge structures (ELNES) at the Zn-L(2,3) edge and the O-K edge have been measured for 10 mol% ZnO-doped MgO, and were compared with spectra from reference materials. In order to interpret the spectra, first principles molecular orbital calculations were made using model clusters composed of 125 and 153 atoms. Photoabsorption cross sections (PACS) were computed at the Slater's transition state in which a half-filled core hole was included in the self-consistent calculations. The difference in the coordination numbers of Zn was found well distinguishable by the Zn-L(2,3)-edge ELNES. The experimental spectra in the first 25 eV were well reproduced by the theoretical PACS. In this energy region, the Zn-L(2,3)-edge ELNES from four-fold coordinated Zn showed four sets of peaks, whereas the six-fold coordinated Zn exhibits three sets of peaks. The origin of these peaks can be explained by the point symmetry within the first coordination unit. A small shift toward the lower energy side was observed in the O-K edge ELNES of the ZnO-doped MgO as compared with pure MgO. This can be ascribed to the lower energy of the Zn-4s orbital as compared with the Mg-3s orbital, which is the common mechanism to the difference in the band gap between MgO and ZnO.