Cytochemical energy-filtering transmission electron microscopy of mitochondrial free radical formation in paraquat cytotoxicity.

The generation of oxygen free radicals was investigated using cytochemistry and its energy-filtering transmission electron microscopy in reference to the toxic mediator for the herbicide paraquat. When isolated intact mitochondria from rat livers were incubated in a medium containing paraquat and NADH, a mitochondrial NADH-quinone oxidoreductase activity generated superoxide anions to cause the destruction of mitochondria which resulted in cell death. The superoxide anions were immediately converted into hydrogen peroxide, which then formed cerium perhydroxide deposits in the presence of cerium ions and precipitated on the outer surface of the mitochondrial outer membrane. This localization was also specifically identified by energy spectral imaging and image-electron energy loss spectral analyses. Precipitation reaction was scavenged by the addition of either cytochrome c or catalase and inhibited by dicoumarol (an inhibitor of NAD(P)H-quinone oxidoreductases). These cytochemical energy-filtering transmission electron microscopic results indicated that paraquat generated free radicals from the outer membrane of mitochondria.     

Liquidus and solidus temperatures of Ni-solid solution in Ni-Al-X (X: V, Nb and Ta) ternary systems

A systematic investigation was carried out to determine both liquidus and solidus surfaces of the Ni-solid solution (γ) in the Ni-Al-X ternary phase diagrams successively by differential thermal analysis (DTA) technique. Each of the Group V elements of the periodic table, V, Nb, and Ta, was chosen as a ternary additive X in the present study. The γ-solvus was also taken into account in determining a temperature range for a solid solution treatment above the γ-solvus, i.e., “the window,” as well as the maximum solubility limit of γ-Ni solid solution.     

Optical and electrical anisotropies of polydiacetylene derivative film aligned by shear stress

The molecular alignment of polydiacetylene (PDA) derivatives and their optical and electrical properties of thin films based on PDA derivatives have been studied. The PDA derivatives were aligned depending on the direction of applied shear stress in the film. From measurements of the polarized absorption and current–voltage characteristics, the optical and electrical anisotropies have been observed, that was discussed by taking the PDA main chain alignment into consideration.     

Multiple roles for endothelin in melanocyte development: regulation of progenitor number and stimulation of differentiation

Melanocytes in the skin are derived from the embryonic neural crest. Recently, mutations in endothelin 3 and the endothelin receptor B genes have been shown to result in gross pigment defects, indicating that this signalling pathway is required for melanocyte development. We have examined the effects of endothelins on melanocyte progenitors in cultures of mouse neural crest. Firstly, they stimulate an increase in progenitor number and act synergistically with another factor, Steel factor, in the survival and proliferation of the progenitors. These findings are consistent with findings from mice with natural mutations in the endothelin receptor B gene, which show an early loss of melanocyte progenitors. Secondly, endothelins induce differentiation of the progenitors into fully mature pigmented melanocytes. This finding is consistent with the expression of endothelins in the skin of mice at the initiation of pigmentation. The melanocytes generated in endothelin-treated cultures also become responsive to alpha melanocyte-stimulating hormone, which then acts to regulate the activity of the pigmentation pathway. These findings indicate two key roles for endothelin in melanocyte development: regulation of expansion of the progenitor pool and differentiation of progenitors into mature melanocytes.     

Dynamic local lattice distortion in YBa2Cu4O8

Significant changes in the local atomic structure and lattice dynamics were observed by pulsed neutron inelastic scattering measurements on YBa₂Cu₄O₈ both around the superconducting transition temperature and around the spin-gap temperature. These observations and earlier results of numerical calculations on the enhancement of electron-lattice interaction by electron correlation lead to a novel picture of unconventional lattice-induced superconductivity related to antiferroelectric instability.     

High bit rate and programmable multiwavelength generator based onRaman soliton effect in DSF

A wavelength tunable multiwavelength pulse source with clock rate tunability is described. A tuning range of 32 nm and multiwavelength generation were achieved at a 10 GHz clock rate and a quasi-320 GHz OTDM signal. The device consists of a programmable PLC multiplexer and employs amplitude-to-wavelength conversion based on the Raman soliton effect     

In Situ Observation of Wear Process Before and During Scuffing in Sliding Contact

In this study, a direct observation of a point contact area was conducted to understand the scuffing phenomenon. The contact area was produced between a rotating sapphire disc and a stationary steel ball and it was lubricated using n-hexadecane. The image detected by a colour digital CCD camera, load, and friction were synchronously recorded by a computer during the test. It was found that wear debris produced in the contact area played an important role in the wear process, which includes running-in and scuffing. In the test, debris particles accumulated in the inlet zone, and some particles entered the contact area to cause abrasive wear of the ball surface, even in the light-load stages. During the running-in process, the abrasive wear by debris particles changed the conformity between the sliding surfaces. In the high-load stage, just before the occurrence of scuffing, the whole contact area was flattened at once. When scuffing occurred, the contact area suddenly expanded. The conformity of the contact area was dramatically changed during its expansion. The flattening of the whole contact area and dramatic expansion with changing the conformity seemed to play important roles in scuffing.     

Effects of Particle Strength of Feedstock Powders on Properties of Warm-Sprayed WC-Co Coatings

Warm spray (WS) process, which can control the temperature of a combustion gas jet used to propel powder, has been successfully applied to deposit WC-Co coatings. Detrimental reactions resulting from dissolution of WC into Co binder and decarburization were suppressed effectively by keeping the WC-Co particles’ temperature below the m.p. of the binder phase. In this study, three nano-structured WC-12Co powders with different particle strengths were prepared by changing the sintering conditions of spray-dried powder and were deposited by WS. The deposition efficiency and porosity of the coatings decreased with increasing the particle strength. The coating deposited from the powder with very low particle strength showed significant phase changes, while those deposited from the higher particle strengths showed almost no change. Particle Image Velocimetry revealed significant disintegration of the weakest powder, which explains the changes observed. The hardness and wear properties of the former coating, therefore, were inferior to the other two.