Evaluating crack tip stress field in a thin glass plate under thermal load

The stress field around a propagating crack tip in a quenched thin glass plate is discussed through experimental and theoretical analyses. Instantaneous phase-stepping photoelasticity using a CCD camera equipped with a pixelated micro-retarder array is used for measuring the crack tip stress field. From the successive phase maps of principal direction, the position and the velocity of the crack tip are evaluated. On the other hand, the fracture parameters, that is, the stress intensity factors and the T-stress are determined from the phase maps of the retardation. Experimental results obtained for a straight crack show good agreement with those obtained by theory of elasticity. The results also indicate that the direction of the crack propagation arising in the quenching process is not determined by the direction of the maximum principal stress. Furthermore, the results show that the T-stress criterion is inappropriate to evaluate the crack path instability in a quenched thin glass plate.     

Dielectric properties of Permalloy granular composite materials

Dielectric and electrical properties of Permalloy granular composite materials have been studied considering the application to left-handed meta-materials. Surface oxidized Permalloy particles have high surface electrical resistance; the eddy current effect in the composite structure is suppressed. The electrical conductivity of compacted Permalloy particles increases with increasing temperature and indicates the semiconductive layer formation on the particle. The low frequency ac electrical conductivity of Permalloy composite materials shows a drastic increase in the particle content between 50 and 60 vol.%. Electrical permittivity spectra of Permalloy composites show a non-metallic characteristic and the enhancement of permittivity is observed with increase of Permalloy particle content.     

Influence of heating and laser irradiation on the Raman D band in single-wall carbon nanotubes

Fine structure of the Raman D band in single-wall carbon nanotubes (SWNTs) was investigated by heating and laser irradiation. It is shown that the D band is composed of three components at ～ 1313, 1340, and 1355 cm^? 1, denoted by D₁, D₂, and D₃, respectively. The D₁ and D₂ intensities significantly increase with laser irradiation in air and vacuum, respectively. The D₃ intensity drastically increases with heating in air. From these results, it is suggested that the fine structure of the D band is attributed to different kinds of defects introduced in SWNTs.     

Numerical simulation of solidification for aluminum-base multicomponent alloy

Solidification simulation of an aluminum-base multicomponent alloy was carried out by a method combining thermodynamic analysis using Thermo-Calc and heat-transfer calculation. An Al-9.5% Si-3% Cu-1% Mg-0.8% Fe (all mass%) aluminum-base multicomponent alloy was used for the simulation. The effect of latent heat on the heat-transfer calculation was considered by using an enthalpy method. The temperature-enthalpy curves for both an equilibrium state and nonequilibrium state with assumptions of no diffusion in the solid were calculated by using Thermo-Calc. A small casting with a cylindrical shape was used for the heat-transfer simulation. The vertical cross section of the casting was divided into rectangular grids, and the enthalpy change of each grid was numerically calculated. The calculated enthalpies in the grids were converted for each time-step into temperatures by using the temperature-enthalpy curve. A casting experiment was carried out under the same conditions as those of the simulation, and the calculated cooling curves obtained under the nonequilibrium condition agreed with the experimental ones.     

In vitro determination of basement membrane invasion predicts liver metastases in human gastrointestinal carcinoma

We described previously (H. Imamura, et al., Cancer Res., 54: 3620-3624, 1994) a quantitative and reproducible 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay for tumor cell invasiveness that uses a water-repellent, paraffin-treated Chemotaxicell chamber to produce a uniform Matrigel layer. In the present experiments, we studied 71 human gastrointestinal carcinomas, including 53 maintained as xenografts in nude mice and 18 fresh surgical specimens. We found a correlation between metastatic behavior and the percent invasion (PI) calculated from the MTT assay. Tumors producing liver metastases had a significantly higher PI than did tumors without liver metastases (P < 0.01), and seven of nine fresh tumors with a PI greater than 1.0 showed liver metastases within 2 years. No significant correlations were noted between the PI and clinicopathological factors. In the tumor xenografts, type IV collagenase activity was significantly higher in tumors with clinically evident liver metastases than in those without liver metastases (P < 0.05). Colorectal carcinomas with liver metastases and a high PI showed higher expression of matrix metalloproteinase 9 than matrix metalloproteinase 2 as assessed by gelatin zymography. Thus, the invasion-MTT assay is clinically useful for predicting liver metastases. Type IV collagenase plays an important role in the development of liver metastases from human gastrointestinal carcinoma.     

Influence of γ Irradiation on the Mechanical Strength and In Vitro Biodegradation of Porous Hydroxyapatite/Collagen Composite

Gamma irradiation treatment (GIT) is the most widely used sterilization method for biomaterials in spite of the potential to degrade polymers. The adverse effects of GIT on the mechanical properties and biological stabilities of porous hydroxyapatite/collagen (HAp/Col) composites were investigated in this study. Those properties of a porous HAp/Col composite stabilized by dehydrothermal treatment (DHT) drastically decreased by GIT in the same manner as conventional pure Col materials. DHT after GIT could partially eliminate the adverse effects, due to the introduction of cross-linkage among the degraded Col molecules.     

Dysfunction of nitric oxide induces protein kinase C activation resulting in vasospasm after subarachnoid hemorrhage

We hypothesize that the interaction between protein kinase C (PKC) and nitric oxide (NO) plays a role in the modulation of cerebral vascular tone, and the disturbance of this interaction following subarachnoid hemorrhage (SAH) results in vasospasm. To prove this hypothesis with direct evidence, PKC activities of smooth muscle cells of canine basilar arteries in the control and in the SAH groups were measured by an enzyme immunoassay method. N omega-nitro-L arginine (L-NA), an inhibitor of NO production, enhanced PKC activity. This enhancement was inhibited neither by 8-bromo-guanosine 3',5'-cyclic monophosphate (8-bromo-cGMP) nor SIN-1, a NO releasing agent. PKC activity in the SAH was significantly higher than in the control; however, no further enhancement was produced with L-NA. In the SAH, PKC activity was not inhibited either by 8-bromo-cGMP or SIN-1. We conclude that NO maintains an appropriate vascular tone through inactivation of PKC, and that this effect is disturbed following SAH, resulting in PKC-dependent vascular contraction, such as vasospasm. On the other hand, once PKC has been activated, NO precursors do not inhibit PKC. These facts indicate NO inactivates PKC through the inhibition of phosphatidylinositol breakdown.     

Hand-mirror cells acute lymphoblastic leukemia (L3)

To our knowledge, this report represents the first confirmed case in Japan of a 15-year-old boy with acute lymphoblastic leukemia (ALL).L3 with hand-mirror cells (HMC) in the bone marrow. HMC lymphoid leukemia is an unusual variant of ALL in which the bone marrow lymphoblasts manifest distinctive hand-mirror morphologic features. HMC lymphoblast is characterized by an asymmetric foot-like cytoplasmic process that extends from the portion of the cell, thus giving it the light-microscopic appearance responsible for its name. Besides ALL, HMC has been reported in acute myeloblastic leukemia (AML), blastic crisis of chronic myelogenous leukemia, non-Hodgkin's lymphoma, and infectious mononucleosis. HMC has been reported to be prevalent in ALL.L1 and L2 as compared with L3.     

Chemical sensing by an electrical oscillator: Detection and quantification of cationic surfactants

A new chemical sensing system using an electrical oscillator has been developed. This sensing system measures the electrical ‘non-linearity’ at the surface of an electrode immersed in a test solution: a sinusoidal voltage is applied to the electrode and the higher harmonics of the output current are obtained by Fourier transformation. This sensing system has been used to detect and quantify surfactant molecules in solutions. The relative intensity P₂/P₁ of the peaks of the second (P₂) and first (P₁) harmonics in the output current was found to be linearly correlated with the logarithms of the concentrations of cationic surfactants such as cetylpyridium bromide (CPB) and cetyl-N,N,N-trimethylammonium bromide (CTAB), but not with those of the anionic surfactant sodium dodecyl sulfate (SDS) or the neutral surfactant Triton X-100. The reproducibility of this sensing system was shown to be excellent.     

Velocity and turbulence measurements in a cylindrical bath subject to centric bottom gas injection

Laser Doppler velocimeter (LDV) measurements were made to clarify the fluid flow behavior in a bath subject to centric bottom gas injection. Correlations of the axial mean velocity and turbulence components in the gas-liquid two-phase flow region,i.e., in the bubbling jet region, were proposed as functions of the inner diameter of nozzle, gas flow rate, and densities of gas and liquid. Measured values of the flow rate, momentum, and kinetic energy of water rising upward were approximated satisfactorily by these empirical correlations. In addition, the Reynolds shear stress was calculated and compared with measured values. Formerly Graduate Student, Osaka University,