Estimation of the squeeze film effect in a surface acoustic wave motor

This paper describes the air film characteristic in the interface between the slider and stator substrate of a surface acoustic wave (SAW) motor, and the difference of the squeeze film effect by the form of the slider. Because the vibration amplitude of the SAW motor is several 10 nm order, analysis of pressure was performed by using the molecular gas-film lubrication (MGL) equation. In the analysis, the MGL equation was split into advection phase and nonadvection phase, and calculation of advection and nonadvection phases was performed by using the cubic interpolated propagation (CIP) method and the finite difference method, respectively. From analysis results it was found that the time to steady pressure of air film depends on the radius of projection arranged on the contact surface of the slider. Also found was that the steady pressure in the interface does not depend on the radius and height of the projection, but it depends on the minimum spacing between the slider and the stator substrate.     

Method to evaluate the effect of safety belt use by rear seat passengers on the injury severity of front seat occupants

Although the effectiveness of seat belts for reducing injury to rear seat passengers in traffic accidents has been well documented, the ratio of rear-seat passengers restrained by seatbelts remains lower than that of drivers or passengers in front seats. If passengers in rear seats do not wear seat belts, they may sustain unexpected injury to themselves when involved in accidents, and also endanger front occupants (drivers or front seat passengers). This paper focuses on the tendency of front seat occupants to sustain severer injuries due to forward movement of passengers in rear seats at the moment of frontal collisions, and evaluates the effectiveness of rear passengers' wearing seat belts in reducing injuries of front seat occupants. Since the occurrence of occupant injuries depends considerably on the crash severity, we proposed to use pseudo-delta V in regression analysis to represent velocity change during a collision when analyzing statistical accident data. As the crash severity can be estimated from pseudo-delta V, it becomes possible to make appropriate estimations even when the crash severity differs in data. The binary model derived from the ordered response model was used to evaluate the influence on the injury level based on pseudo-delta V, belted or unbelted status, gender and age. Occupants in cars with a hood in the case of car-to-car frontal collisions were extracted from the statistical data on accidents in Japan. Among 81,817 cars, where at least one passenger was present, a total of 6847 cars in which all passengers sustained injuries and which had at least one rear seat passenger aboard were analyzed. The number of killed or seriously injured drivers is estimated to decrease by around 25% if rear seat occupants come to wear seat belts. Also, the number of killed or seriously injured passengers in front seats is estimated to decrease by 28% if unbelted rear seat occupants come to wear seat belts. Thus, wearing of seat belts by previously unbelted rear seat passengers is considered effective in reducing not only injuries to the rear seat passengers themselves but also injuries to front seat occupants.     

Gymnema sylvestre leaf extract: a 52-week dietary toxicity study in Wistar rats

A 52-week study of oral-repeated-dose toxicity for the extraction powder of Gymnema sylvestre (GS), Indian-native genus, Metaplexis japonica, was conducted in both genders of Wistar rats. The rats were administered a graded dose of GS at 0.01, 0.10 and 1.00% of basal powder diet, along with a group fed solely with the basal powder diet without GS, for 52 weeks. General conditions were recorded daily. Body weights and food consumptions were recorded weekly up to 12 weeks, and thereafter at longer intervals. At 26 weeks, for an intermediate examination, and 52 weeks, for the final examination, animals were subjected to hematology, serum chemistry, and pathological examination. None of the animals died in the period up to 52 weeks. No exposure-related changes in body-weight, in the food consumption, in the hematological examinations, or in the serum biochemical examinations were recognized. No histopathological alterations were seen. Thus, it was concluded that there was no toxic effect in rats treated with GS at up to 1.00% in the diet for 52 weeks. The no-observable-effect level from this study is 1.00% GS, i.e., 504 mg/kg/day for male and 563 mg/kg/day for female as mean daily intake, for 52 weeks.     

pDUAL, a multipurpose, multicopy vector capable of chromosomal integration in fission yeast

A novel series of plasmid vectors named pDUAL have been developed. These vectors enable one to introduce not only multicopies of genes with episomal maintenance but also a single copy with chromosomal integration into the fission yeast, Schizosaccharomyces pombe. The multicopy plasmids can be easily converted to fragments for chromosomal integration by digestion of the plasmids with a certain restriction endonuclease before transformation of the yeast cells. The resultant fragments, lacking the autonomously replicating sequence, are designed for targeting into the chromosomal leu1 locus by homologous recombination. Whether the transformants are the results of episomal maintenance of the plasmid or homologous gene targeting can be readily checked by their requirement for uracil or leucine, or by the PCR diagnostic analysis. Furthermore, we propose the use of pDUAL derivatives for PCR-based chromosomal tagging of a gene to introduce several tags into 5'-terminus of a gene, employing a set of primers. Using these all-in-one vectors, a suitable mode of expression of a cloned gene can be selected for individual analysis without any complicated subcloning processes.     

Ion beam deposition of α-Ta films by nitrogen addition and improvement of diffusion barrier property

Ta thin films were deposited on Si (100) substrates by an ion beam deposition method at various substrate bias voltages under Ar + N₂ atmosphere with different pressure ratios of Ar and N₂. The effects of nitrogen pressure in the plasma gas and the substrate bias voltage on the surface morphology, crystalline microstructure, electrical resistivity and diffusion barrier property were investigated. It was found that the fraction of a metastable β-phase in the Ta film deposited at the substrate bias voltage of − 50 V films decreased by adding nitrogen gas, while the α-Ta phase became dominant. As a result, the Ta films deposited at the substrate bias voltage of − 50 V under Ar (9 Pa) + N₂ (3 Pa) atmosphere showed a dominant α-phase with good surface morphology, low resistivity, and superior thermal stability as a diffusion barrier.     

Factors influencing microstructural development in equal-channel angular pressing

Processing through the imposition of severe plastic deformation (SPD) provides an opportunity for achieving very significant grain refinement in bulk materials. Although different SPD procedures are available, the process of equal-channel angular pressing (ECAP) is especially attractive because it can be scaled easily to produce relatively large samples. This paper describes the principles of ECAP processing and demonstrates the potential for achieving unusual mechanical properties in the samples subjected to ECAP. Special emphasis is placed on the possibility of attaining a high strain rate superplastic forming capability in the as-pressed materials: examples are presented for an Al−Mg−Sc alloy prepared in the laboratory by casting and for a commercial Al-2024 alloy. This article is based on a presentation made in the 2002 Korea-US symposium on the “Phase Transformations of Nano-Materials,” organized as a special program of the 2002 Annual Meeting of the Korean Institute of Metals and Materials, held at Yonsei University, Seoul, Korea on October 25–26, 2002.     

SH3BP2 Deficiency Ameliorates Murine Systemic Lupus Erythematosus

Background: The adaptor protein Src homology 3 domain-binding protein 2 (SH3BP2) is widely expressed in immune cells. It controls intracellular signaling pathways. The present study was undertaken to investigate the role of SH3BP2 in a murine systemic lupus erythematosus model. Methods: For the lupus model, we used Fas^lpr/lpr mice. Clinical and immunological phenotypes were compared between Fas^lpr/lpr and SH3BP2-deficient Fas^lpr/lpr mice. Splenomegaly and renal involvement were assessed. Lymphocyte subsets in the spleen were analyzed by flow cytometry. To examine the role of SH3BP2 in specific cells, B cell-specific SH3BP2-deficient lupus mice were analyzed; T cells and bone marrow-derived dendritic cells and macrophages were analyzed in vitro. Results: SH3BP2 deficiency significantly reduced lupus-like phenotypes, presented as splenomegaly, renal involvement, elevated serum anti-dsDNA antibody, and increased splenic B220⁺CD4⁻CD8⁻ T cells. Notably, SH3BP2 deficiency in B cells did not rescue the lupus-like phenotypes. Furthermore, SH3BP2 deficiency did not substantially affect the characteristics of T cells and macrophages in vitro. Interestingly, SH3BP2 deficiency suppressed the differentiation of dendritic cells in vitro and reduced the number of dendritic cells in the spleen of the lupus-prone mice. Conclusions: SH3BP2 deficiency ameliorated lupus-like manifestations. Modulating SH3BP2 expression could thus provide a novel therapeutic approach to autoimmune diseases.     

Antimicrobial Activities of LL-37 Fragment Mutant-Poly (Lactic-Co-Glycolic) Acid Conjugate against Staphylococcus aureus,Escherichia coli,and Candida albicans

Various peptides and their derivatives have been reported to exhibit antimicrobial activities. Although these activities have been examined against microorganisms, novel methods have recently emerged for conjugation of the biomaterials to improve their activities. Here, we prepared CKR12-PLGA, in which CKR12 (a mutated fragment of human cathelicidin peptide, LL-37) was conjugated with poly (lactic-co-glycolic) acid (PLGA), and compared the antimicrobial and antifungal activities of the conjugated peptide with those of FK13 (a small fragment of LL-37) and CKR12 alone. The prepared CKR12-PLGA was characterized by dynamic light scattering and measurement of the zeta potential, critical micellar concentration, and antimicrobial activities of the fragments and conjugate. Although CKR12 showed higher antibacterial activities than FK13 against Staphylococcus aureus and Escherichia coli, the antifungal activity of CKR12 was lower than that of FK13. CKR12-PLGA showed higher antibacterial activities against S. aureus and E. coli and higher antifungal activity against Candida albicans compared to those of FK13. Additionally, CKR12-PLGA showed no hemolytic activity in erythrocytes, and scanning and transmission electron microscopy suggested that CKR12-PLGA killed and disrupted the surface structure of microbial cells. Conjugation of antimicrobial peptide fragment analogues was a successful approach for obtaining increased microbial activity with minimized cytotoxicity.     

Hot-Pressing of TiC-Graphite Composite Materials

Monolithic TiC and TiC-graphite composites were hot-pressed at temperatures ranging from 1800 to 2100 °C and with graphite contents up to 30 wt%. Densification behavior was compared for both monolith and composites based on results of microstructural observation and mechanical tests. Monolithic TiC was well densified at the hot- pressing temperature of 1800 °C; significant grain growth and an accompanying decrease in the flexural strength occurred with an increase in hot- pressing temperature. Conversely, the 10 wt% graphite-containing TiC composite required higher temperatures (1900 to ~2000 °C) to reach a similar degree of densification approaching that of monolithic TiC. As with densification, flexural strength of the composite increased with an increase in hot- pressing temperature. Graphite dispersions in the composites inhibited grain growth of TiC. Contrary to the equiaxed nature of the monolithic TiC grains, in the composite system, the graphite grains were flattened to thin platelets that aligned perpendicular to the hot- pressing axis. Apparent anisotropy in the microstructure was observed in the composites. At a fixed hot-pressing temperature, the relative density of the composites decreased with increasing graphite content.