Optical fiber sensors using the method of polarization-rotated reflection

The method of polarization-rotated reflection is applied to sensors with polarization-maintaining optical fibers. By the use of this scheme, stable measurement can be realized because the fluctuation of the light propagation characteristics in the fiber is canceled automatically without any additional active phase compensation techniques. Several kinds of sensors were designed for the measurement of different physical values. A magnetic field sensor and a temperature sensor were built and the performances were tested to confirm their basic features experimentally.     

Absence of acetylcholine- and ionomycin-activated Cl- currents in submandibular cells of early postnatal rats

Using the whole-cell patch-clamp technique, we investigated developmental changes in the expression of an acetylcholine- (Ach-) activated Cl- conductance in rat submandibular acinar cells. ACh induced an oscillatory inward current in cells isolated from animals older than 5 weeks, but not in animals less than 2-3 weeks of age. The current/voltage (I/V) relationship of the ACh-induced current was that of an outward rectifier, and the current was inhibited by intracellular BAPTA, a Ca2+ buffer, indicating the current was Ca2+ activated. The ACh-induced current was also blocked in the presence of DPC and SITS, two Cl- current inhibitors in other tissues. Ionomycin mimicked the effect of ACh but in a nonoscillatory fashion. The appearance of the ionomycin-induced currents was also age related, as the current was not observed to occur in animals less than 2-3 weeks old. Since both ACh and ionomycin significantly increase cytosolic [Ca2+] in the acinar cells of young animals, the correlation between the age dependence of the ACh-activated Cl- current and the ionomycin-activated Cl- current responses suggests that the lack of responsiveness observed in the young animals is due to the absence of Ca2+-activated Cl- channels, rather than to a deficiency of a cellular mediator.     

Optical bistability and all-optical switching in novel waveguidejunctions with localized optical nonlinearity

We propose novel all-optical guided-wave devices using the structure with localized third-order optical nonlinearity where only a selected part of a waveguide both in a cross section and along a propagation direction is made from a Kerr-like nonlinear material and the rest are made from linear ones. Optical bistable devices and all-optical switching devices are realizable by utilizing bistable like nonlinear dispersion characteristics in selectively nonlinear guided-wave systems. Optical bistability and all-optical switching characteristics are analyzed in waveguide Y-junctions adopted the scheme by using a modified BPM combined with the normal mode analysis. The method to realize the guided-wave structure with localized nonlinearity is also discussed     

Growth of NiWO4 crystals from a Na2W2O7 flux

Well-formed rod crystals of NiWO₄ were grown from a Na₂W₂O₇ flux by a slow cooling method. The solubility of NiWO₄ in Na₂W₂O₇ increased with increasing temperature. At 1100 °C, NiWO₄ was dissolved in Na₂W₂O₇ at a concentration of about 45 mol %. The eutectic temperature was 615± 5 °C. Flux growth was conducted by heating mixtures at 1100 °C for 10 h, followed by cooling to 500 °C at a rate of 5 °C h^–1. The brownish and transparent crystals up to 15 mm in length were grown from the mixtures of about 40 g. The most suitable solute content was 30 mol %. The grown crystals were bounded by the {100}, {010}, {110}, {102}, and {111} faces. In certain instances, the {111} faces disappeared. The EPMA data showed that sodium from the flux used was not contained within the grown crystals. The crystals of NiWO₄ had a d.c. electrical resistivity of about 1 × 10¹¹ cm.     

Enhancement of nucleoside phosphorylation activity in an acid phosphatase

Escherichia blattae non-specific acid phosphatase (EB-NSAP)possesses a pyrophosphate-nucleoside phosphotransferase activity,which is C-5'-position selective. Current mutational and structuraldata were used to generate a mutant EB-NSAP for a potentialindustrial application as an effective and economical proteincatalyst in synthesizing nucleotides from nucleosides. First,Gly74 and Ile153 were replaced by Asp and Thr, respectively,since the corresponding replacements in the homologous enzymefrom Morganella morganii reduced the K_m value for inosine andthus increased the productivity of 5'-IMP. We determined thecrystal structure of G74D/I153T, which has a reduced K_m valuefor inosine, as expected. The tertiary structure of G74D/I153Twas virtually identical to that of the wild-type. In addition,neither of the introduced side chains of Asp74 and Thr153 isdirectly involved in the interaction with inosine in a hypotheticalbinding mode of inosine to EB-NSAP, although both residues aresituated near a potential inosine-binding site. These findingssuggested that a slight structural change caused by an aminoacid replacement around the potential inosine-binding site couldsignificantly reduce the K_m value. Prompted by this hypothesis,we designed several mutations and introduced them to G74D/I153T,to decrease the K_m value further. This strategy produced a S72F/G74D/I153Tmutant with a 5.4-fold lower K_m value and a 2.7-fold higherV_max value as compared to the wild-type EB-NSAP.     

Fabrication of ultrathin and highly uniform silicon on insulator by numerically controlled plasma chemical vaporization machining

Metal-oxide semiconductor field-effect transistors fabricated on a silicon-on-insulator (SOI) wafer operate faster and at a lower power than those fabricated on a bulk silicon wafer. Scaling down, which improves their performances, demands thinner SOI wafers. In this article, improvement on the thinning of SOI wafers by numerically controlled plasma chemical vaporization machining (PCVM) is described. PCVM is a gas-phase chemical etching method in which reactive species generated in atmospheric-pressure plasma are used. Some factors affecting uniformity are investigated and methods for improvements are presented. As a result of thinning a commercial 8 in. SOI wafer, the initial SOI layer thickness of 97.5+/-4.7 nm was successfully thinned and made uniform at 7.5+/-1.5 nm.     

Dynamic study of intramembranous particles in human fresh erythrocytes using an "in vitro cryotechnique"

For analyses of dynamic ultrastructures of erythrocyte intramembranous particles (IMPs) in situ, a quick-freezing method was used to stabilize the flow behavior of erythrocytes embedded in vitreous ice. Fresh human blood was jetted at various pressures through artificial tubes, in which the flowing erythrocytes were elongated from biconcave discoid shapes to elliptical ones, and quickly frozen in liquid isopentane-propane cryogen (-193 degrees C). They were freeze-fractured using a scalpel in liquid nitrogen, and routinely prepared for replica membranes. Many IMPs were observed on the protoplasmic freeze-fracture face (P-face) of the erythrocyte membranes. Some control erythrocytes under nonflowing or stationary conditions showed IMPs with their random distribution. However, other jetted erythrocytes under flowing conditions showed variously sized IMPs with much closer distribution. They were also arranged into parallel rows in some parts, and aggregated together. This quick-freezing method enabled for the first time the visualization of time-dependent topology and the molecular alteration of IMPs in dynamically flowing erythrocytes.     

Tribological properties of asperity arrays coated with self-assembled monolayers

The effects of a self-assembled monolayer (SAM) coating on the friction and pull-off forces were determined by using two-dimensional asperity arrays on silicon wafers. The arrays were coated with SAM composed of one of five different alkylchlorsilanes. First, two-dimensional asperity arrays were created by using a focussed ion beam (FIB) system to mill patterns on silicon plates. Each silicon plate had different patterns of equally spaced asperities. Each pattern (5 × 5 μm²) had a different radius of curvature of the asperity peaks, ranging from about 200 to 2500 nm. Then, each silicon plate was immersed in a solution of a different alkylchlorsilane in hexane (either hexyltrichlorosilane, octyltrichlorosilane, dodecyltrichlorosilane, tetradecyltrichlorosilane, or octadecyltrichlorosilane), thus coating the asperity arrays with SAM. The friction and pull-off forces on the SAM-coated arrays were measured by using an atomic force microscope (AFM) that had a square flat probe. The pull-off force for SAM-coated silicon was roughly proportional to the radius of curvature of the asperity peaks. The magnitude of the pull-off force corresponded approximately to the capillary force calculated by using the contact angle of water on the surface of SAM. The friction coefficient correlated with the inverse of the alkyl-chain length of the SAM.     

Fundamental experiments for the development of high-performance cold plates in a feasability study on space solar power system

To realize a concept of solar power satellite with high power generation, it is a promising method to transfer the power by laser beam using active mirror type amplifiers where cooling of the laser material accepting highly condensed sunray is inevitable. To remove high heat flux density from a large area, a structure of cold plate consisted of two parallel plates is devised and the effective liquid supply directly to the bottom of flattened bubbles due to nucleate boiling is realized by the auxiliary liquid feeder. The critical heat flux is increased by more than 1.5 times from that without the additional liquid supply. The technology can be applied not only to space but widely to the development of high-performance cold plates employed on ground.