On the high-temperature corrosion of Fe-Cr alloys in sulfur vapor

The mechanism of sulfidation of Fe-Cr alloys ranging from 8 to 97 wt.% chromium was determined from studies of scale structures, surface morphologies of scale, and reaction kinetics. Although the kinetics of sulfidation were quite similar to those previously determined by Mrowec et al., the structures in the present work were different, being triplex in nature. The growth mechanism of each layer was determined, and the overall sulfidation behavior was compared to the oxidation behavior. Many similarities between the two corrosion processes were observed.     

Solid-state microwave relay systems in Japan

In response to the rapidly increasing demand for communication facilities, microwave relay systems have played an important role in Japan's telecommunications network because of their economy and capability for broadband transmission. Their progress has been marked during the past 20 years and this development has been supported by advances in such diverse fields as radio propagation, antennas, microwave and electronic circuitry, electron devices, and, particularly, in solid-state techniques. This article reviews the history of microwave relay systems and describes the past and expected future contributions of the solid-state technology to these systems.     

Purification, bacteriolytic activity, and specificity of beta-lytic protease from Lysobacter sp. IB-9374

Lysobacter sp. IB-9374, which was isolated from soil as a high lysyl endopeptidase-producing strain (Chohnanet al., FEMS Microbiol. Lett., 213, 13-20, 2002), was found to produce a beta-lytic protease capable of lysing gram-positive bacteria such as Staphylococcus aureus, Microccocuseus, and Bacillus subtilis. The Lysobacter strain secreted the beta-lytic protease into the culture medium at a 2.4-fold higher level than Achromobacter lyticus. The enzyme was highly purified through a series of six steps with a high yield. The enzyme was strongly inhibited by tetraethylene-pentamine and 1,10-phenanthroline. The purified enzyme lysed more efficiently almost all the gram-positive bacteria tested than lysozyme, lysostaphin, and mutanolysin. The enzyme was very similar to Achromobacter beta-lytic protease containing one zinc atom in terms of amino acid composition and N-terminal sequence. The nucleotide sequence revealed that the mature enzyme was composed of 179 amino acid residues with additional 198 amino acids at the amino-terminal end of the enzyme. The deduced amino acid sequence of the mature enzyme coincided with that of the Achromobacter enzyme, although the prepro-region showed a 41% sequence identity with the counterpart. These results indicate that Lysobacter sp. is a useful strain for an efficient large-scale preparation of beta-lytic protease capable of lysing bacteria.     

Characterization of polymer-adhesive interfaces on a nanometre scale by elemental mapping and image EELS using EFTEM

Energy-filtering transmission electron microscopy (EFTEM) was applied for investigating interfaces between a polymer and an adhesive. The sample employed in this work is polybutylene terephtharate (PBT) sheets laminated with an epoxy adhesive. It was found that heat aging of the PBT at 180 degrees C in air for > 9 h prior to adhesion decreases the adhesion strength drastically. To investigate this unfavourable aging effect on the adhesion strength, we performed elemental mapping and image EELS using EFTEM. A weak boundary layer with a thickness of < 50 nm was visualized at the PBT-adhesive interface by elemental mapping in the sample subjected to the heat aging and image EELS revealed the origin of this layer. Thus, we clearly correlated the nanoscale interfacial structure with the adhesion strength by EFTEM.     

A spherical aberration-corrected 200 kV TEM

A spherical aberration (Cs)-corrected 200 kV TEM was newly developed. The column of the microscope was extended by 25 cm and the inner yoke of the objective lens was modified to insert some parts of the corrector elements. The corrector has two hexapole elements that play a main role in Cs correction and they are placed at a position equivalent to the coma-free point of the objective lens by using two transfer doublet lenses. The Cs correction was successfully carried out by means of the third-order aberration that was generated in the two extended hexapoles. The Cs can be corrected to the desired value and also can be overcompensated in order to produce a negative Cs, as with the corrected Cs of -23 microm shown in this work. The optical system of the corrector does not produce second- and fourth-order aberrations, and can correct residual aberrations up to the third order. All of the corrector elements are computer-controlled and the third-order aberrations are quite stable after they are properly corrected. The resolution of 0.135 nm was experimentally confirmed by the Young's fringe method. Image simulations of a silicon [110] single crystal were made with various Cs and defocus values to demonstrate the effectiveness of arbitral control of Cs.     

An authorization-based trust model for multiagent systems

In this paper an authorization-based trust model (ABTM) is described which is designed for managing access to services in a semi-open distributed environment. This is called a multiagent-based smart office environment. In this model, "trust" is defined as a set of authorization attributes that are granted by the owner of a service to the user of the service. Central to this model is a trust manager that redelegates authorizations from the service owner to the requesting user, based on access control policies that are specified by role labels which are assigned to a set of agents. The ABTM scheme is different from a centralized scheme, in which authorizations are granted directly by an authority. It is also different from a fully distributed system,where authorizations are granted based solely on the discretion of the owner of the services. The design philosophy is the separation of trust management and trust application to allow efficient management of access control in large-scale and dynamic environment, such as those that exist in multiagent systems.     

Effect of Fe2O3 crystallite size on its mechanochemical reaction with La2O3 to form LaFeO3

Fe₂O₃ powders with different crystallite sizes prepared by heating FeOOH at various temperatures were ground with La₂O₃ powder using a planetary ball mill to investigate the effect of crystallite size on mechanochemical synthesis of LaFeO₃. Fe₂O₃ powder with smaller crystallite size obtained by heating at lower temperature reacts more easily with La₂O₃ than that with larger size. The mechanochemical reaction proceeds with an increase in grinding time. Specific surface area of the LaFeO₃ powder synthesized has a large value of over 11 m²/g. The mechanochemical process can be also applied to synthesize other iron complex oxides with rare earth elements such as Pr, Nd and Sm.