A finite element parametric study on the mechanical properties of J-shaped steel hysteresis devices

The present paper discusses the mechanical properties of J-shaped steel hysteresis devices, abbreviated to “J-dampers”, interposed between the upper structure of a spatial structure and its substructure. The mechanical properties of a J-damper, which are characterized by its key geometrical and material parameters, are evaluated through parametric analyses using an in-house Finite Element program. The hysteresis behavior of a J-damper is also modeled by a bi-linear elasto-plastic hysteresis model with the strain-hardening effect. Its elastic stiffness, yield strength and dimensionless hardening ratio, which are expressed as functions of the parameters, are formulated on the basis of mathematical models and the results of parametric studies. Finally, some remarks relevant to the application of the proposed hysteresis model are made for the design of the J-damper.     

Reexamination of grain-boundary sliding by diffusion

Steady-state sliding of grain boundaries is discussed by taking into account the change in the potential energy of an applied stress, when the sliding occurs by diffusional accommodation. The present analysis enables us to derive the sliding rates at boundaries of various shapes in a simple manner without knowing local stress fields. Sliding rate of a boundary containing second phase particles is also derived by similar calculations. The results are compared with previous calculations by other investigators, and it is found that the resultant expressions for the sliding rates are essentially identical to those derived from more complex analyses.     

Formation of dityrosine and other fluorescent amino acids by reaction of amino acids with lipid hydroperoxides

Formation of fluorescence by the reaction of various amino acids with lipid hydroperoxides,i.e., linoleic acid 13-monohydroperoxide, methyl linoleate 13-monohydroperoxide and phosphatidylcholine hydroperoxide, in the presence of methemoglobin was investigated. Two types of fluorescence were produced: fluorescent dityrosine (3,3′-dityrosine) from tyrosine, and unidentified fluorophores with α- and ε-amino groups of various amino acids. While the former was stable after treatment with borohydride, the latter fluorophores were readily destroyed. The rate of dityrosine formation was rapid, and the yield of dityrosine was dependent on the concentrations of tyrosine and the lipid hydroperoxides. Butylated hydroxytoluene and tocopherol inhibited the formation of dityrosine, but did not affect the formation of fluorophores on the amino groups. Dityrosine appears to be formed by radical reaction of the lipid hydroperoxides, while the other fluorophores seem to be created by nonradical mechanisms.     

Syntheses and structural properties of four Rb-aluminosilicate zeolites

Four types of Rb-aluminosilicate zeolites were hydrothermally synthesized in pure phase for the first time from Rb-aluminosilicate gels without using any organic structure-directing agent (SDA) under stirring conditions. The crystal structure of each zeolite was refined by Rietveld analysis of the X-ray diffraction (XRD) data. These crystal structures were confirmed to be Rb-mordenite, Rb-merlinoite, a new aluminosilicate zeolite with an ATT framework topology, and Rb-offretite denoted by RMA-1, RMA-2, RMA-3, and RMA-4, respectively. The Si/Al ratio of RMA-1 with an MOR topology varied from 5.3 to 8.0; however, the variation of the Si/Al ratios of the other zeolites was rather small. The crystal system of RMA-2 was tetragonal with space group I4/mmm, where two Rb sites were distributed at the center of an 8-membered ring (MR). On the other hand, two Rb sites in RMA-3 were located at the center of the 8-MR in small two cages. The structure of RMA-4 was identified as the OFF type with a local disorder or defect, which included a small amount of an intergrown ERI phase.     

Aerobic and anaerobic microbiology of empyema. A retrospective review in two military hospitals

The microbiology and clinical features of empyema were studied retrospectively in 197 patients whose specimens yielded bacterial growth after inoculation for aerobic and anaerobic bacteria. Three hundred forty-three organisms (216 aerobic or facultative and 127 anaerobic organisms) were isolated. Aerobic bacteria were isolated in 127 (64 percent) patients, anaerobic bacteria in 25 (13 percent), and mixed aerobic and anaerobic bacteria in 45 (23 percent). The predominant aerobic or facultative organisms were Streptococcus pneumoniae (70 isolates), Staphylococcus aureus (58), Escherichia coli (17), Klebsiella pneumoniae (16), and Haemophilus influenzae (12). The predominant anaerobes were pigmented Prevotella and Porphyromonas species (24), Bacteroides fragilis group (22), anaerobic cocci (36), and Fusobacterium species (20). beta-Lactamase-producing organisms were recovered in 49 (38 percent) of 128 tested specimens. These included all 42 tested S aureus and 15 B fragilis group, 4 of 9 K pneumoniae, 3 of 9 H influenzae, 3 of 8 pigmented Prevotella and Porphyromonas species, and 2 of 6 E coli. Most patients from whom S pneumoniae and H influenzae were recovered had pneumonia, and most patients with S aureus had pneumonia, aspiration pneumonia, and lung abscesses. The recovery of anaerobic bacteria was mostly associated with the concomitant diagnosis of aspiration pneumonia, and lung, subdiaphragmatic, dental, and oropharyngeal abscesses. These data highlight the importance of anaerobic bacteria in selected cases of empyema.     

Simultaneous fabrication of a composite with low thermal expansion and high strength in the eucryptite — yttria-stabilized PSZ system

Low thermal expansion coefficient and high mechanical strength have been attained simultaneously in a composite with microstructures in which the low thermal expansion grains are surrounded by a continuous texture of the grains with high strength. Alloying eucryptite with yttria-stabilized PSZ (partially stabilized zirconia) simultaneously achieved the low thermal expansion coefficient, 1.45 × 10^–6, and the high bending strength, 220 MPa, by adjusting the composition and controlling the microstructures by changing the starting powders and the milling durations. Grain size and reactions between the coupled materials determined the critical processing conditions.     

Serum rheumatoid factor induced by intraperitoneal administration of periodontopathic bacterial lipopolysaccharide in mice

Serum rheumatoid factor (RF) level and peritoneal and splenic CD5+B (B-1) cells in mice were examined after intraperitoneal administration of purified lipopoly-saccharides (LPS) from oral periodontopathic bacteria; Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans, Fusobacterium nucleatum and Capnocytophaga ochracea. F. nucleatum and C. ochracea LPS induced higher levels of serum IgM- and IgG-RF, while P. gingivalis LPS showed the least induction. In addition, wet weights of spleen and serum IgM and IgG concentration were markedly increased in F. nucleatum LPS injected group. On the other hand, the proportion of CD5+ B cells to lymphocytes in the peritoneal cavity and spleen did not increase. The reason for this was not clear but conventional B cells (CD5- B cells) might increase more rapidly with splenic enlargement than CD5+ B cells. These results suggested that RF induced by bacterial LPS may modulate immune responses against bacteria and plays an important role for defence and destruction of periodontal tissue.