Sequestration of distasteful compounds by some pharmacophagous insects

Several pharmacophagous insects have been shown to sequester specific kairomonal substances or their derivatives in their body tissues. Turnip sawflies,Athalia rosae, visit a plant,Clerodendron trichototmum (Verbenaceae), and feed voraciously on the leaf surface. Clerodendrins were characterized as the potent phagostimulants forA. rosae adults. The insect sequesters some of the analogs and becomes extremely bitter on its body surface. Some chrysomelid leaf beetles associated with cucurbitacins were found to store high concentrations of these bitter principles in their body. South American polyphagous beetles,Diabrotica speciosa andCerotoma arcuata, are strongly arrested by root components from the cucurbit plant,Ceratosanthes hilariana, and selectively accumulate 23,24-dihydrocucurbitacin D, effectively gaining bitterness. Similarly, four species of Asian pumpkin leaf beetles belonging to the genusAulacophora were shown to sequester the same compound in body tissue as the major bitter principle. Three phenylpropanoids closely related to methyl eugenol were found to accumulate in the rectal glands of the male Oriental fruit fly,Dacus dorsalis. One of the rectal gland components, 2-allyl-4,5-dimethoxyphenol was shown to be released in the air during courtship. In all of these cases, selectively sequestered compounds strongly deterred feeding by some predators, thus serving as allomones in this context. Kairomonal and pheromonal functions linked with allomonal sequestration by pharmacophagous feeding has also been suggested.     

Toughening of Silicon Nitride Matrix Composites by the Addition of Both Silicon Carbide Whiskers and Silicon Carbide Particles

Si₃N₄ matrix composites reinforced by SiC whiskers, SiC particles, or both were fabricated using the hot-pressing technique. The mechanical properties of the composites containing various amounts of these SiC reinforcing materials and different sizes of SiC particles were investigated. Fracture toughness of the composites was significantly improved by introducing SiC whiskers and particles together, compared with that obtained by adding SiC whiskers or SiC particles alone. On increasing the size of the added SiC particles, the fracture toughness of the composites reinforced by both whiskers and particles was increased. Their fracture toughness also showed a strong dependence on the amount of SiC particles (average size 40 μm) and was a maximum at the particle content of 10 vol%. The maximum fracture toughness of these composites was 10.5 MPa·m^1/2 and the flexural strength was 550 MPa after addition of 20 vol% of SiC whiskers and 10 vol% of SiC particles having an average particle size of 40 μm. These mechanical properties were almost constant from room temperature to temperatures around 1000°C. Fracture surface observations revealed that the reinforcing mechanisms acting in these composites were crack deflection and crack branching by SiC particles and pullout of SiC whiskers.     

Radiation from a Line Source Placed in Two-dimensional Photonic Crystals

A novel formulation of radiation from a localized line source placed in two-dimensional photonic crystals consisting of layered periodic arrays of parallel circular cylinders is presented. The method employs the spectral domain approach. The spectral response of the photonic crystals to the line source excitation is calculated using the lattice sums, the T-matrix of a circular cylinder, and the generalized reflection and transmission matrices of the layered system. The far-zone radiated field is obtained using the conventional asymptotic method to the spectral response. The radiation patterns of the localized line source sandwiched by two photonic crystals are numerically studied.     

Effects of Aliphatic Alcohols on Formation of Cyclodextrin from Soluble Starch by Bacillus macerans Cyclodextrin Glucanotransferase

Effects of aliphatic alcohols such as ethanol, n-butanol and n-decanol on the formation of cyclodextrin (CD) from soluble starch by Bacillus macerans cyclodextrin glucanotransferase (CGTase) were experimentally studied at 50°C and pH 6.0. The addition of such aliphatic alcohols caused an increase in α-CD yield, which extent was remarkable in n-butanol. From the incubation of α-CD with CGTase, such an increase was found to be due to a restriction on further transglycosylation of α-CD into β-CD by CGTase imposed by the aliphatic alcohols.     

Vibration fatigue reliability of BGA-IC package with Pb-free solder and Pb–Sn solder

In this paper, a new method is proposed for evaluating the high-cycle fatigue strength of BGA (Ball Grid Array) packages with Pb-free solder and Pb–Sn solder due to vibration. An attached weight induced mixed mode stress in the solder ball of a package was used. To consider the effect of the mixed mode stress that occurred in a solder ball and the frequency to fatigue strength of the solder ball, a test was carried out with the three kinds of weights (σ_n/τ_n = 4, 5, and 6) at various frequencies (10–27 Hz). To clarify the effect of frequency, a nonlinear analysis with a viscoplastic model was carried out within the range of 0.001–3450 Hz. From the continuous observation of the cross-section of the package and finite element method (FEM) analysis results, it was revealed that the maximum principal stress is the driving force to package failure. Although an intermetallic compound in both packages and a Pb-rich region in a Pb–Sn solder based package were confirmed by EDX microprobe analysis, they do not contribute to the initiation of a crack in a solder ball. The fatigue strength of the Pb-free solder and Pb solder was evaluated on the basis of the maximum principal stress calculated by FEM and the experimental results.     

Design of Fully Balanced Analog Systems Based on Ordinary and/or Modified Single-Ended Opamps

The system architectures, which allow a high performance fully balanced (FB) system based on ordinary/modified single-ended opamps to be implemented, are investigated and the basic and general requirements are formulated. Two new methods of an FB analog system design, which contribute towards achieving both a high performance IC system implementation and a great reduction of the design time are presented. It is shown that a single-ended system based on any type of opamp (rail-to-rail, constant g _m , etc.), realized in any technology (CMOS, bipolar, BiCMOS, GaAs), can be easily and effectively converted to its FB counterpart in a very practical way. Using the proposed rules, any FB system implementation with opamps (data converter, modulator, filter, etc.) requires only a single-ended system version design and the drawbacks related to a conventional FB system design are avoided. The principles of the design are pointed out and they are verified by experimental results.     

Bi2SiO5 Doping Concentration Effects on the Electrical Properties of SrBi2Ta2O9 Films

In this paper, we investigated the microstructure and electrical properties of Bi₂SiO₅ (BSO) doped SrBi₂Ta₂O₉ (SBT) films deposited by chemical solution deposition. X-ray diffraction observation indicated that the crystalline structures of all the BSO-doped SBT films are nearly the same as those of a pure SBT film. Through BSO doping, the 2Pr and 2Ec values of SBT films were changed from 15.3 μC/cm² and 138 kV/cm of pure SBT to 1.45 μC/cm² and 74 kV/cm of 10 wt.% BSO-doped SBT. The dielectric constant at 1 MHz for SBT varied from 199 of pure SBT to 96 of 10 wt.% BSO-doped SBT. The doped SBT films exhibited higher leakage current than that of non-doped SBT films. Nevertheless, all the doped SBT films still had small dielectric loss and low leakage current. Our present work will provide useful insights into the BSO doping effects to the SBT films, and it will be helpful for the material design in the future nonvolatile ferroelectric memories.     

Effect of ethyl alcohol on growth and intracellular alanine racemase of psychrotrophs

The psychrotrophic alanine racemase from Pseudomonas fluorescens, a typical psychrotroph, is less resistant to organic solvents than the enzymes from thermophilic and mesophilic bacteria (Okubo et al., J. Home Econ. Jpn., 46: 1135-1140, 1995). To further elucidate this difference, we examined the effect of ethyl alcohol on the growth and intracellular alanine racemase activity of three typical psychrotrophs-P. fluorescens, Bacillus psychrosaccharolyticus and B. psychrophilus-in comparison with two mesophiles, Escherichia coli and B. subtilis. Although all the bacteria grew to the early stationary phase when cultivated at 22 degrees C for 36 h in the absence of ethyl alcohol, the growth of the psychrotrophs was more effectively suppressed by the addition of 3 and 5% ethyl alcohol to the medium than that of the mesophiles. The intracellular alanine racemase activity of the psychrotrophs was also more markedly reduced in the presence of ethyl alcohol than that of the mesophiles. When bacterial cells of each strain grown at 22 degrees C for 36 h in the absence of alcohol were suspended in 0-5 % ethyl alcohol solution and incubated at 30 degrees C for 1 h, both the survival ratio and intracellular alanine racemase activity of the psychrotrophs were lower than those of the mesophiles. Thus, ethyl alcohol effectively reduced both the growth of the psychrotrophs and their intracellular alanine racemase activity. Low concentrations of various other alcohols also repressed the growth of the psychrotrophs at 10 degrees C.     

Chemical sensing by an electrical oscillator: Detection and quantification of cationic surfactants

A new chemical sensing system using an electrical oscillator has been developed. This sensing system measures the electrical ‘non-linearity’ at the surface of an electrode immersed in a test solution: a sinusoidal voltage is applied to the electrode and the higher harmonics of the output current are obtained by Fourier transformation. This sensing system has been used to detect and quantify surfactant molecules in solutions. The relative intensity P₂/P₁ of the peaks of the second (P₂) and first (P₁) harmonics in the output current was found to be linearly correlated with the logarithms of the concentrations of cationic surfactants such as cetylpyridium bromide (CPB) and cetyl-N,N,N-trimethylammonium bromide (CTAB), but not with those of the anionic surfactant sodium dodecyl sulfate (SDS) or the neutral surfactant Triton X-100. The reproducibility of this sensing system was shown to be excellent.     

The influence of dopant species on thermal stability of NiSi film

We investigated the relationship between thermal stability of NiSi films and the implanted dopant species on Si substrates. The most stable NiSi layer appeared on Boron-implanted Si substrate, where the formation of pseudo-epitaxial transrotational structure was observed, just in case that the dose of boron is more than 5e15 atoms/cm². This unique crystallographic orientation of NiSi film on Boron-implanted substrate is a key role of thermal stability because thermal stress at grain boundary can be diminished by peculiar arrangement of transrotational domains, owing to the anisotropy in coefficient of thermal expansion (CTE) of NiSi.