Experimental Determination of Fracture Toughness of CFRP in Mode II by Raman Spectroscopy

Fracture toughness of Mode II of carbon fiber reinforced plastic (CFRP) was investigated using end notched flexure (ENF) specimens and a Raman coating method. Distribution of shear strain near the crack tip of CFRP was measured by Raman spectroscopy. A thin film of PbO on the measured surface of the ENF specimen was deposited by physical vapor deposition (PVD) as pretreatment to measure the strain by Raman spectroscopy. Fracture toughness of CFRP in Mode II was determined using the Raman results. The results coincided closely with those measured by the compliance method and FEM analyses (finite element method).     

Microfabrication of polytetrafluoroethylene using SR direct etching

Polytetrafluoroethylene (PTFE) is a very attractive material for various fields because of its chemical resistance, insulation properties, and hydrophobic properties. However, it is difficult to fabricate PTFE microstructures with conventional techniques such as semiconductor processes or micromachining. We have succeeded in the fabrication of high‐aspect‐ratio microfluidics parts from PTFE by direct in‐vacuum photo‐etching utilizing synchrotron radiation (SR) at energy levels from 2 to 12 keV. This paper presents an analysis of the mechanisms of the PTFE microfabrication process and describes newly discovered processing characteristics of PTFE. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 178(4): 49–54, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21152     

Characterization of bacterial biofilm communities in tertiary treatment processes for wastewater reclamation and reuse

The concern with wastewater reuse as a sustainable water resource in urban areas has been growing. For the reclamation and distribution of wastewater, biofilm development deserves careful attention from the point of view of its promotion (e.g. biofiltration) and inhibition (e.g. clogging and hygiene problems). As the first step to control biofilm development, bacterial biofilm communities in tertiary treatment processes were characterized by using molecular biological methods. The result of clone library analysis showed that Nitrospirae-related (nitrite-oxydizing bacteria) and Acidobacteria-related (probably oligotrophic bacteria) groups were dominant. The ratio of the Nitrospirae-related group to the Acidobacteria-related group was associated with ammonia load, whereas other operational conditions (process, media, temperature, salt) did not clearly affect the phylum-level community or the dominant sequence of nitrifying bacteria. The result of real-time PCR also indicated that high ammonia load promotes the proliferation of nitrite- and ammonia-oxidizing bacteria. Regarding water supply systems, some researchers also have suggested the dominance of Nitrospirae- and Acidobacteria-related groups in biofilm formed on water distribution pipes. In tertiary wastewater treatment, therefore, it is concluded that oligotrophic and autotrophic bacteria are the dominant groups in biofilm samples because assimilable organic carbon is too poor to proliferate various heterotrophic bacteria.     

Epidermal growth factor stimulates the tyrosine phosphorylation of SHPS-1 and association of SHPS-1 with SHP-2, a SH2 domain-containing protein tyrosine phosphatase

SHPS-1 is a 120 kDa glycosylated receptor-like protein that contains immunoglobulin-like domains in its extracellular region and four potential tyrosine phosphorylation for SH2 domain binding sites in its cytoplasmic region. Epidermal growth factor (EGF) stimulated the rapid tyrosine phosphorylation of SHPS-1 and subsequent association of SHPS-1 with SHP-2, a protein tyrosine phosphatase containing SH2 domains, in Chinese hamster ovary cells overexpressing human EGF receptors. In the cells overexpressing SHPS-1, the tyrosine phosphorylation of SHPS-1 was more evident than that observed in parent cells. However, overexpression of SHPS-1 alone did not affect the activation of MAP kinase in response to EGF. These results suggest that SHPS-1 may be involved in the recruitment of SHP-2 from the cytosol to the plasma membrane in response to EGF.     

Preparation and characterization of the new quaternary chalcogenides Tl-III-IV-S4 (III = Al,Ga, In; IV = Si,Ge)

Five new chalcogenides: TlInSiS₄, TlInGeS₄, TlGaSiS₄, TlGaGeS₄, TlAlGeS₄ were synthesized by the evacuated silica tube method. The crystals are isotypic and belong to the orthorhombic system with space group Pbnm and lattice parameters in the range of, a: 11.53 –11.74, b: 16.50–17.04, c: 7.036–7.353 Å. Infrared and photoacoustic spectra of those compounds are also reported.     

Stress distribution in a segmented coating film on metal fibre under tensile loading

When a coating film on a metal fibre or wire is brittle, it exhibits multiple-fracture under loading. In order to describe the exerted tensile stress on the segments of a coating film as a function of the distance from the end of the segments and as a function of applied stress, a new approximate calculation method is presented, assuming that the interfacial bonding strength is high enough and no interfacial debonding occurs. Using the present calculation method, effects of geometrical factors such as fibre diameter, thickness of coating film and length of segment as well as those of mechanical factors such as Young's modulus, shear modulus and the yield stress of the fibre and the coating film on the exerted tensile stress on the segments and also on the exerted shear stress at the interface are described in a quantitative manner.     

Different effects of inorganic and dimethylated arsenic compounds on cell morphology, cytoskeletal organization, and DNA synthesis in cultured Chinese hamster V79 cells

Changes in cytoskeletal organization of cultured V79 cells exposed to arsenite and dimethylarsinic acid (DMAA), a methylated derivative of inorganic arsenics, and related changes, such as mitotic arrest and induction of multinucleated cells, were investigated in comparison with their effects on DNA synthesis. DMAA caused mitotic arrest and induction of multinucleated cells with a delay of 12 h relative to the mitotic arrest. By contrast, arsenite at equitoxic concentrations to DMAA was less effective than DMAA in causing mitotic arrest and in inducing multinucleated cells. Post-mitotic incubation of cells arrested in metaphase by 6 h incubation with 10 mM DMAA showed that the incidence of multinucleated cells increased conversely with a rapid decrease in metaphase cells. This suggests that metaphase-arrested cells can escape from metaphase, resulting in the appearance of multinucleated cells. The mitotic arrest caused by DMAA was accompanied by disruption of the microtubule network. By contrast, both arsenite and DMAA did not cause disorganization of actin stress fibers even when incubated at concentrations that caused a marked retardation of cell growth. Cells exposed to arsenite for 6 h showed marked inhibition of DNA synthesis, whereas inhibition by DMAA was not observed. When incubation was prolonged by 18 h, the arsenite-induced inhibition of DNA synthesis was mitigated. By contrast, inhibition of DNA synthesis by DMAA occurred in parallel with an increase in the population of mitotic cells. These results suggest that DMAA caused growth retardation and morphological changes via disruption of the microtubule network, and that arsenite-induced retardation of cell growth and inhibition of DNA synthesis were not attributable to the cytoskeletal changes.     

High-Temperature oxidation of cathodically hydrogen-charged two-phase (Ti3Al,TiAl) titanium aluminides

Ti-42A1, Ti-45A1, and Ti-5OA1 (at. pct) titanium aluminides, which were cathodically hydrogen charged in a 5 pct H₂SO₄ solution for charging times between 1.8 ks (0.5 hours) and 14.4 ks (4 hours), were oxidized in a static air under atmospheric pressure at temperatures between 1170 K (897 °C) and 1350 K (1077 °C). All the hydrogen-charged alloys, as well as alloys without hydrogen charging, followed parabolic oxidation kinetics. The weight gains of the alloys after hydrogen charging for normally less than 3.6 ks (1 hour) were 20 to 30 pct less than those without hydrogen charging. In the alloys charged with hydrogen for more than 7.2 ks (2 hours), the weight gains increased with increasing the charging time. The activation energies of oxidation indicated that the oxidation-controlling factor would change after a charging time of 7.2 ks (2 hours) in all the alloys. The decrease in the activation energies with charging time was more drastic in the Ti-5OA1 alloy, which suggested that hydrogen damage, such as cracking, was more severe in the Ti-50Al alloy than in the Ti-42A1 or Ti-45A1 alloys. The formation of cracks during hydrogen charging provides titanium-diffusion paths and accelerates formation of rutile (TiO₂) scale on the surface of the alloys. The TiO₂ on the alloys after hydrogen charging formed at a comparatively lower temperature than that on the alloys without charging.     

Growth and coarsening of g. p. Zones in Al- Zn alloys

The structural changes during the precipitation of G. P. zones in Al-Zn binary alloys have been investigated by means of anin situ small-angle scattering technique using synchrotron radiation. Defining a specific time, normalized by the half-completion time, the time-dependent evolution of the precipitation process can be divided into three periods, independent of alloy composition and quench-ing conditions. The structural and kinetic features of the first two periods have been analyzed in detail. The first stage represents a growing process of clusters with diffuse interface into the well-defined G. P. zones. The average size of these clusters increases, and the density decreases. The second stage corresponds to the Ostwald ripening process. This mechanism is described by utilizing a modified Lifshitz-Slyozov-Wagner theory.     

A computer simulation on tensile strength of surface-Damaged fibers

The strength of surface-damaged fibers was studied by means of a computer simulation experiment based on the Monte-Carlo method using a simple model which assumes that the surface flaws can be regarded as mode I notches on fiber surfaces, the strength of undamaged fibers obeys the Weibull distribution function, and the largest flaw determines the strength of damaged fibers. Normal and exponential distribution functions were taken as the flaw size distribution function. By employing the present simulation method, the effects of average flaw size, coefficient of variation of flaw size, density of flaws, and gage length on average strength and its coefficient of variation were studied. It was found that the surface-damaged fibers can retain their full strength only when the average flaw size is small, the coefficient of variation of flaw size is small, density of flaw size is low, and gage length is short. Otherwise the average strength of damaged fibers was reduced seriously. It was emphasized that the scatter of size of flaws and density of flaws strongly affect the strength of fibers as well as flaw size and gage length.