Fabrication of aluminium foams from powder by hot extrusion and foaming

In order to produce aluminium foams for light-weight and energy absorbing structures of automobiles, a method for fabricating aluminium foam from powder mixed with a foaming agent by using a mould is proposed. The method consists of four sequential processes: powder compacting, extruding, foaming and moulding. In the experiment for fabricating aluminium foam from powder, the conditions of powder extrusion and foaming by the heated die are determined from the density of the aluminium foams made without a mould. The experimental results show that the relative density of the aluminium foam made under appropriate conditions is 0.22. In moulding of aluminium foam, a stainless steel pipe is used as a mould and the cylindrical aluminium foam is produced by filling into the pipe mould. The distribution of relative density within the aluminium foam bar is in a range of 0.2–0.3 by rapid cooling of the pipe. To examine the ratio of deformation energy to weight of the pipe including the aluminium foam, a compression test using a press is carried out. The deformation energy of the pipe can be increased with aluminium foam filled by the proposed method.     

Toxicity and tetramine contents of salivary glands from carnivorous gastropods

Salivary glands from 29 species of marine carnivorous gastropods in nine families were examined for lethal activity against mice and tetramine content. Mouse lethality was assayed by intravenous injection of buffer extracts into mice, and was detected in 14 species. Heat-stability tests confirmed that toxins in four species were thermolabile, while those in eight species were thermostable. Based on the tetramine contents determined by the colorimetric method using methanolic extracts, the thermostable toxins in seven species (Neptunea eulimatalamellosa, N. vinosa, N. arthritica, N. bulbacea, N. intersculpta f. pribiloffensis, N. intersculpta f. frater pilsbry and Hemifusus tuba) were considered to be tetramine contained at high levels (more than 900 micrograms/g salivary gland), but that in one species (Buccinum opisthoplectum) appeared to be a low-molecular-weight compound differing from tetramine. It is interesting that one (Hemifusus tuba) of the seven species containing high amounts of tetramine belongs to the family Melongenidae, although the other six Neptunea species are members of the family Buccinidae, as expected from previous studies.     

Characteristics of neutralization of acids by newly isolated fungal cells

Soil microorganisms play an important role in maintaining soil pH at levels suitable for other soil organisms. To clarify the biological neutralization mechanism in soil, we isolated soil microorganisms showing a high ability to neutralize acids and studied their characteristics. From our taxonomic study, three isolated strains were identified as filamentous fungi, namely Mucor sp., Aspergillus fumigatus, and Aureobasidium pullulans. These strains could secrete basic materials, such as ammonia, for neutralization, grow in the medium at pH 4.0 and increase the pH of the medium to approximately 8.0. These microbial cells could neutralize not only nitric acid but also sulfuric and hydrochloric acids. The strains could also grow by utilizing nitric acid as a sole nitrogen source. In the soil containing these organisms, the pH was maintained in the neutral range by the buffering action of basic materials that they secrete. These results suggest that these fungal cells are useful for protecting the soil from acidification by acid rain.     

Dynamic behavior of bubble domains at low drive field

Dynamic properties of bubble domains at low drive pulse field are examined by the bubble transport method. Important findings are as follows. 1) The bubble does not move unless the pulse duration exceeds a critical value which depends on the pulse amplitude. 2) A minimum pulse amplitude is also required for the bubble translation which depends on the pulse duration. 3) As the pulse duration goes to infinity, the minimum drive field approaches a constant value which is different from the dynamic coercivity. 4) As soon as the pulse duration exceeds the critical value, the bubble is displaced discontinuously by a finite distance independent of the drive field. All of these properties are adequately explained by a simple phenomenological theory, in which the domain wall is assumed to be connected by springs to pinning sites until the wall is displaced by a finite distance.     

Cytochemistry of gastric parietal cells with high-pressure freezing followed by freeze-substitution

Gastric parietal cells were examined for changes in their ultrastructure and distribution of the proton pump during feeding and fasting states in rats. The fundic glands from rats fed ad libitum or fasted with free access to water were cryofixed using high-pressure freezing followed by freeze-substitution in acetone containing osmium or acrolein and then embedded in Epon 812 or Lowicryl K4M resin, respectively. Excellent ultrastructural preservation was achieved. During the feeding state, intracellular canaliculi and numerous microvilli were well developed, while tubulovesicles were poorly developed. In contrast, during the fasting state, the microvilli in the narrowed space of the intracellular canaliculi were tightly packed and the tubulovesicles were enlarged. Ultrathin sections were immunostained with antibodies against the alpha- and beta-subunits of the proton pump, H+ x K(+)-ATPase, using the immunogold method. The labelling was strong and clearly localized in comparison with that obtained using the conventional chemical-fixation method. Each subunit was localized on the membrane of the microvilli, intracellular canaliculi and tubulovesicles. The distribution of subunit proteins varied between the two states. During ad libitum feeding, the immunolabelling was localized strongly on the membranes of the microvilli and intracellular canaliculi. In contrast, the labelling was strong on the tubulovesicle membrane in the fasting state. The results obtained with each anti-subunit antibody by H+ x K(+)-ATPase immunostaining revealed differences in distribution and labelling density between the feeding and fasting states.     

Robust disturbance-rejection problems for linear ω-periodicdiscrete-time systems

Two robust disturbance-rejection problems with state feedback and with incomplete-state feedback for linear ω-periodic discrete-time systems are studied in the framework of the so-called geometric approach. Also, some necessary conditions and/or sufficient conditions for the problems to be solvable are presented     

Isotopic separation of silicon atoms by atomic mirror

The isotopic separation of silicon by an atomic mirror has been demonstrated numerically, by which each silicon isotope encounters a different dipole force depending on the frequency detuning due to the different frequencies resonant to the silicon isotopes. It was found that the atomic mirror, which comprised a wave guide structure designed for the enhancement of evanescent waves at 252 nm, allows us to discriminate ²⁹Si from the other isotopes.     

A 500-MHz pipelined burst SRAM with improved SER immunity

This paper describes a 0.25-μm, 64 K×36 bit pipelined burst SRAM using a 6.156-μm² cell. It realizes over 500-MHz operation using a lower cost double metal process, Internal 16 K×144 organization by T-shaped bit line array reduces 20% of latency, 20% of active power, and 8.5% of die size. The low power also enables us to use lower cost thin quad flat type packages. Our solution to the soft error problem, a shallow triple well structure and four-transistor cell with stacked capacitor, improved soft error rate by 3.5 orders of magnitude compared with the conventional SRAM cell     

Antioxidative activities of some peptides isolated from hydrolyzed potato protein extract

Three peptides (5A, 5C and 6C), purified from potato protein hydrolysate fractions, possessed antioxidative activities. Isolation and purification were carried out using gel permeation chromatography and successive reverse-phase HPLC. These three peptide fractions were sequenced and identified as Phe-Gly-Glu-Arg, Phe-Asp-Arg-Arg and Phe-Gly-Glu-Arg-Arg, respectively. The fractions 5A, 5C and 6C inhibited linoleic acid oxidation by 55.3%, 58.5% and 61.7% using β-carotene decolorization assay system, while the inhibition ratio was 32.1%, 93.0% and 93.4% in the ferric thiocyanate assay system, respectively. The peptide fractions 5A, 5C and 6C also repressed lipid oxidation by 24.2%, 14.7% and 26.4% in the erythrocyte membrane ghost assay system, respectively. Oral administration of 100 mg/kg of body weight of the chemically synthesized peptides, 5A, 5C and 6C to rats (male Wistar) 30 min prior to ethanol injection reduced ethanol-induced gastric mucosal damage by 67.9%, 57.0% and 60.3%, respectively. Conclusively, these peptides have shown real potent antioxidative activities and could further be investigated for potential use as food additives.