Out-of-Plane Negative Magnetoresistance of Bi2Sr1.6La0.4CuO6+δ Single Crystals in the Underdoped Region

In order to investigate a relationship between the carrier concentration and negative magnetoresistance in the underdoped region, we have performed out-of-plane electrical resistivity measurements for underdoped Bi ₂ Sr _1.6 La _0.4 CuO ₆₊ single crystals. Giant negative magnetoresistance has been observed in the most abundant carrier sample with = 0.12 in our experiment. The negative magnetoresistance reduces with decreasing carrier concentration.     

Preparation and morphology of as-prepared and highly stretch-aligned polyacetylene

The macroscopic morphology of as-prepared polyacetylene depends on the concentration of the catalyst system. At high catalyst concentration, polymerization occurs on the free surface of the catalyst solution to form a polyacetylene film which retards further polymerization because of the limited diffusion of acetylene monomer through the film. At lower concentrations, however, successive diffusion and polymerization is possible yielding a gelatinous mass. A continuous mass does not form at an extremely low concentration; the product is flock or powder. Despite these differences in macroscopic morphology, electron micrographs show that the fibrillar structure is a common feature of all forms of polyacetylene. However, the average fibril diameter of 200 Å may depend on the polymerization conditions. Orientation of the fibrils by combined mechanical and thermal treatment is possible to produce highly stretch-aligned films which show anisotropic properties.     

Cell cycle analysis of Chinese hamster ovary cells stimulated by phosphatidic acid in serum-free culture

When recombinant Chinese hamster ovary cells were treated with pertussis toxin or genistein, not only lysophosphatidic acid (LPA) but also phosphatidic acid (PA) failed to stimulate progression through the cell cycle in serum-free culture, suggesting that PA and LPA induce cell growth through the same signal transduction pathway. Cell cycle analysis also indicates that cell growth promoted by PA results in enhanced protein production.     

Rate of emulsion polymerization of styrene

In emulsion polymerization, the Smith and Ewart theory gives about two or three times the number of polymer particles obtained by experiment. In this paper, a reaction model is proposed which, from the standpoint of reactor design, can give an adequate explanation of the whole course of an emulsion polymerization of monomer highly insoluble in water. Among other things, the generating process of polymer particles is examined in detail. It is demonstrated experimentally that a new parameter proposed here, which represents the degree of difficulty of monomer initiation in micelles, is indispensable in explaining that process. Also confirmed is that monomer initiation takes place more easily in polymer particles than in micelles. According to the new model, the progress of polymerization, i.e., monomer conversion, the number of the polymer particles, and properties of polymer thus produced can be estimated with satisfactory accuracy. Furthermore, approximate equations are derived for easier estimation.     

Pulsed laser irradiation impact on two marine diatoms Skeletonema costatum and Chaetoceros gracilis

The ability of pulsed laser irradiations to cause damage on the biofouling organisms is recently being investigated. If this technique is employed in industries such as power generation wherein a large quantity of water is being used for the cooling purpose, many organisms other than the targeted would get affected. In this study, we have investigated the damage caused by the pulsed laser irradiations from an Nd:YAG laser (fluence 0.1J/cm(2)) for varying durations such as 2, 5, 10, 30, 60 and 300 s on two marine diatom species namely Skeletonema costatum and Chaetoceros gracilis. Upon exposure to low power laser irradiations, these diatom species showed mortalities between 52.6+/-9.3% to 97.7+/-3.1% in the case of S. costatum and 57.8+/-2.5% to 98.9+/-0.6% in the case of C. gracilis for 2 and 300 s of irradiations, respectively. The mortality increased with the increase in the duration of laser irradiation. The estimation of the chlorophyll a concentration in the irradiated samples showed a considerable reduction varying between 9.8% and 57% in C. gracilis and 3% and 70.3% in S. costatum for 2 and 300 s of irradiations, respectively. The laser-survived cells grew as the non-irradiated (control) samples. C. gracilis frustules were broken by the laser whilst, the cell materials were drained out of the frustules in the case of S. costatum. The study therefore showed that the low power pulsed laser irradiations could cause significant damage on the two species of planktonic diatoms.     

Spectral interferometric microscope with tandem liquid-crystal Fabry-Perot interferometers for extension of the dynamic range in three-dimensional step-height measurement

The maximum measurable range of a spectral interference microscope depends on the coherence length of the light transmitted by its tunable spectral filter. To achieve a large range in step-height measurement we have developed a new tunable spectral filter that uses tandem liquid-crystal Fabry-Perot interferometers (LC-FPIs), which can simultaneously attain both a high spectral resolution and a large tuning range. Fringe visibility measurements were carried out, and it was found that the coherence length of the light transmitted through tandem LC-FPIs is two times larger than that transmitted through a single LC-FPI. Using this novel tunable spectral filter, we developed a new spectral interference microscope for the measurement of three-dimensional shapes of discontinuous objects. Experimental results of step-height measurements both with a single LC-FPI and with tandem LC-FPIs are presented for a combination of standard steel gauge block sets with 1-, 99-, and 100-microm steps. A large range (1-100 microm) of measurement with submicrometer resolution was achieved with tandem LC-FPIs that was not possible with our previous system in which a single LC-FPI was used.     

Spectral interference Mirau microscope with an acousto-optic tunable filter for three-dimensional surface profilometry

A nonmechanical scanning Mirau-type spectral interference microscope has been developed for the measurement of three-dimensional surface profiles of discontinuous objects. An acousto-optic tunable filter (AOTF) is used as a high-resolution spectral filter, which scans the optical frequency of the broadband light emitted from a superluminescent diode. To generate spectral fringes that make full use of the limited coherence length of the filtered light we unbalanced the Mirau interferometric system by positioning the reference mirror nearly halfway between the top and the bottom of the step height. When the frequency of the broadband light source is scanned by an AOTF, the interference fringes move in opposite directions on the top and the bottom of the object. To uniquely determine the sign of the fringe movement over the large area of the object, we developed a three-dimensional Fourier-transform technique, and from the detected sign of the fringe movement and phase information, we determined the three-dimensional step height. Experimental results of the measurement of 100-microm step height are presented. The main advantages of the proposed system are that it provides nonmechanical scanning and a large measurement range without ambiguity in the sign of the phase.