A new approach to grain boundary engineering for nanocrystalline materials.

A new approach to grain boundary engineering (GBE) for high performance nanocrystalline materials, especially those produced by electrodeposition and sputtering, is discussed on the basis of some important findings from recently available results on GBE for nanocrystalline materials. In order to optimize their utility, the beneficial effects of grain boundary microstructures have been seriously considered according to the almost established approach to GBE. This approach has been increasingly recognized for the development of high performance nanocrystalline materials with an extremely high density of grain boundaries and triple junctions. The effectiveness of precisely controlled grain boundary microstructures (quantitatively characterized by the grain boundary character distribution (GBCD) and grain boundary connectivity associated with triple junctions) has been revealed for recent achievements in the enhancement of grain boundary strengthening, hardness, and the control of segregation-induced intergranular brittleness and intergranular fatigue fracture in electrodeposited nickel and nickel alloys with initial submicrometer-grained structure. A new approach to GBE based on fractal analysis of grain boundary connectivity is proposed to produce high performance nanocrystalline or submicrometer-grained materials with desirable mechanical properties such as enhanced fracture resistance. Finally, the potential power of GBE is demonstrated for high performance functional materials like gold thin films through precise control of electrical resistance based on the fractal analysis of the grain boundary microstructure.

[Drug sensitivity test of Campylobacter jejuni strains isolated from human diarrheal stools, chicken meat, and chicken feces, and gene mutation of quinolone-resistant strains].

In basic studies on campylobacteriosis, we tested 53 strains from human diarrhea stools and 102 strains from chicken meat and feces obtained between 2002 and 2006 for drug sensitivity to different drugs and gene mutation in quinolone-resistant strains. 1) Of 15 drugs tested, all were resistant to one or more of the following 10 drugs: CEX, 99.4%: ABPC, 59.4%; NA, 40.6%; NFLX, 40.0%; TC and CPFX, 39.4%; PIPC, 38.1%; MINO, 30.3%; KM, 3.2%; and SM, 2.6%. 2) Of 155 drug-resistant strains, 28 (18.1%) were resistant to single drugs and 127 (81.9%) were resistant to multiple drugs. The most frequent pattern of multipledrug resistance was ABPC/PIPC/CEX, followed by ABPC/PIPC/CEX/TC/MINO/NA/NFLX/CPFX. 3) Mutation of GyrA (Thr86 --> Ile) was detected in 43 (97.7%) of 44 quinolone-resistant strains. We found that resistance to beta-lactams, quinolones, and tetracycline antibiotics was high, and most resistant strains were resistant to multiple drugs. We also found that most quinolone-resistant strains had GyrA mutation.

Effects of a collagenolytic cell wall component from Fusobacterium necrophorum subsp. necrophorum on rabbit tissue-culture cells.

The effects on rabbit tissue-cultured cells of collagenolytic cell wall component (CCWC) from Fusobacterium necrophorum subsp. necrophorum were investigated. Scanning electron microscopy demonstrated that CCWC damaged the cell surfaces of the rabbit granulocytes and hepatocytes but the effects of the cells differed from each other. Granulocytes appeared smooth and morphologically irregular whereas hepatocytes looked rough and had tiny holes in the cell membranes. Differences in cell viability were observed in MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulphophenyl)-2H-tetrazolium, inner salt) assay. The findings suggest that cytotoxic activity in vivo may well contribute to the establishment of an initial injury in visceral tissues, and the action of CCWC could increase the chances of survival for an invading F. necrophorum subsp. necrophorum at the first stages of infection.

Pokrovsky-Talapov critical behavior and rough-to-rough ridges of the sigma3 coincidence tilt boundary in Mo.

The as-grown shape of the cylindric tilt grain boundary (GB) in Mo bicrystals grown by the floating zone method has been studied with the electron backscattering diffraction method. The seed crystals were misoriented such that the coincidence site lattice (CSL) with lowest possible inverse density of coincidence sites, a Sigma=3 was grown. The flat (100)(Sigma3CSL) facets were observed forming smooth edges (no slope discontinuity) with rounded rough GB portions. Rough GBs curve away from the plane of the (100)(Sigma3CSL) facet as x(beta) with beta=1.69+/-0.07 on one side and beta=1.72+/-0.07 on the other side. Therefore, GB roughening belongs to the Pokrovsky-Talapov universality class. Slope discontinuities between two rounded rough GB portions were also observed. This is the first experimental observation of such first-order rough-to-rough ridges predicted by the Davidson-den-Nijs model.

[Isolation and serotypes of Vero toxin-producing Escherichia coli (VTEC) from pigeons and crows].

To clarify the source and route of infection with Vero toxin-producing Escherichia coli (VTEC) in humans, we sampled gastrointestinal contents and isolated VTEC from wild birds captured to exterminate harmful birds between August 1997 and January 1998. Pigeons were caught in Sagamihara-shi and crows were caught in Sagamihara-shi, Kawasaki-shi, Yokohama-shi, and the Tokyo metropolitan area. The following results were obtained. 1) VTEC was isolated from 32 of 521 birds (6.1%) examined. Among pigeons, VTEC was isolated from 25 of 262 birds (9.5%) captured in Sagamihara-shi. Among crows, VTEC was isolated from 7 of 184 birds (3.8%) captured in Sagamihara-shi, but not isolated from any bird of 11.4, and 60 birds captured in Yokohama-shi, Kawasaki-shi, and the Tokyo metropolitan area, respectively. 2) Toxin was typed in 33 isolates. There were four VT1-producing isolates (6.5%), 27 VT2-producing isolates (88.7%), and two VT1, VT2-producing isolates (4.8%). 3) The serotypes of the isolates were: O78: H-, 10; O152: H-, 7; O153: H19.2; O164: H-, 1; O128: H-, 1; O164/143: H-, and O1: HUT, 1. The serotype was unknown in 10 isolates. Among 10 isolates for which the serotype could not be determined, auto-aggregation was observed in one isolate. 4) EaeA was investigated in the 33 isolates, and 31 isolates (93.9%) possessed eaeA. The above findings showed that strains with same toxin types and serotypes of human diarrhea-derived VTEC were isolated from pigeons and crows, and the isolates frequently possessed eaeA, which is considered to have an important association with its pathology, suggesting that birds are involved in VTEC infection in humans as a source of infection.

[Isolation and serotyping of Vero toxin-producing Escherichia coli (VTEC) from pig].

As a part of basic studies to elucidate the source of infection of Verotoxin-producing Escherichia coli (VTEC) infectious disease, fresh feces were collected from pigs raised in Kanto District (A and B Prefectures) and Kyushu District (C and D Prefectures) between April and October in 2000, and isolation, serotyping, toxin typing, and drug sensitivity test of VTEC were performed. 1) Of 411 fecal samples tested, VTEC was isolated from 44 samples (10.7%), consisting of 12 of 112 samples (10.7%) from A Prefecture, nine of 100 samples (9.0%) from B Prefecture, 18 of 99 samples (18.2%) from C Prefecture, and five of 100 samples (5.0%) from D Prefecture. 2) Forty-five isolates were serotyped. Four isolates (8.9%) were typed as type 3, but the remaining 41 isolates (91.1%) could not be typed. The four typed isolates consisted of two O112ac:H- isolates and one each of O126:H- and O157:H7. 3) Toxin was typed in 45 isolates. Twenty-seven (60.0%) and 17 isolates (37.8%) produced VT 2 and VT1, respectively, and one isolate (2.2%) produced both VT1 and VT2. 4) Drug sensitivity tests of 45 isolates were performed. All 45 isolates (100%) were multidrug-resistant that were resistant to multiple drugs. Nineteen, nine, four, four, seven, one, and one isolates were resistant to five, six, two, three, four eight, and nine drugs, respectively. The above findings confirmed contamination in all districts, although the VTEC isolation rate varied among the sampling districts. Serotyping clarified the presence of O157:H7 and O112ac:H- that are detected in human VTEC infectious disease. The drug sensitivity tests clarified the presence of many multidrug-resistant strains.