An approach of designing and controlling free-form surfaces by using NURBS boundary Gregory patches

Designers require a means of designing complex free-form surfaces easily and intuitively. One general approach to designing such surfaces is to first define a curve mesh consisting of characteristic lines, such as cross sections and boundary curves, then to interpolate the curve mesh using free-form surfaces. NURBS surfaces are widely used but make the interpolation of an irregular curve mesh difficult. This has been a major limiting constraint on designers. In this paper, we propose a new surface representation that enables the smooth interpolation of an irregular curve mesh with NURBS curves and surfaces.     

Enhanced hepatic uptake of liposomes through complement activation depending on the size of liposomes

The objective of this study was to differentiate the roles of opsonins and phagocytic cells in the size-dependent hepatic uptake of liposomes in the submicron region. The extent of opsonization decreased with the decrease in size of liposomes (from 800 to 200 nm in diameter) and no enhancement of uptake was observed at 200 nm. There was no effect of liposome size on the uptake of unopsonized liposomes. Serum was pretreated with empty liposomes of each size and its opsonic activity was measured in the perfused liver. The small liposomes could not consume the opsonic activity, while the larger ones did so substantially. These results suggest that opsonins bind to liposomes depending on the size of liposomes and phagocytic cells take up liposomes in proportion to the extent of opsonization. Size-dependent liposome degradation in serum was also found, which was consistent with the size-dependent complement activation, because liposomes with this composition have been shown to be degraded by complement. The mechanism of opsonization was examined by treating serum at 56 degrees C for 30 min or with anti-C3 antiserum. Since both treatments inhibited the opsonic activity, the hepatic uptake of liposomes is considered to occur via complement receptor. In conclusion, the size of liposomes affected complement recognition, and the liposomes were taken up by the liver depending on the extent of opsonization.     

Effect of Mn on Aging of (Pb0.63Ba0.37)(Zr0.7Ti0.3)O3 Dielectric Ceramics

An aging model for relaxors is suggested on the basis of the transformation of a supercooled cubic lattice into a tetragonal lattice. Manganese ions distort the crystal lattice, and the distortion affects the phase transformation rate. As a result, the aging rate may be expected to change. The lattice constant of (Pb_0.63Ba_0.37)(Zr_0.7Ti_0.3)O₃+χ MnO mol% dielectric ceramics was used as a measure of the degree of the distortion. As the lattice constant decreased up to 0.5 MnO mol%, the aging rate increased, justifying the proposed model.     

Parallel Operation Techniques of GTO Inverter Sets for Large AC Motor Drives

Techniques are presented for using a high-power GTO in a PWM inverter and operating inverter sets in parallel to increase the inverter equipment capacity. The high-power GTO has both a very large turn-off gate current and turn-on gate current for overdrive. It is best to employ an isolation pulse transformer for current amplification as the gate circuit. Also, the high-power GTO, which has a relatively small nonrepetitive controllable current compared with that of a medium- or low-power GTO, in principle can be protected effectively against short circuit faults using fuses. In parallel set operation, the inverter equipment has four typical behavior patterns which arise from differences in GTO switching characteristics. Of these, the behavior pattern in which the current balance is optimized is explained. In addition, the method for designing an interphase reactor as a current balancer and the combination region of GTO characteristics have been given. By means of a parallel set operation test, it has been confirmed that a current unbalance can be suppressed to below ten percent of the peak load current.     

Performance of Y2O3∕Al multilayer coatings for the He-II radiation at 30.4 nm

We briefly report on the performance and stability of periodic multilayer mirrors containing Y(2)O(3) and Al layers designed for normal incidence reflection at the He-II emission line (30.4 nm). We found that Y(2)O(3)∕Al multilayer coatings had higher reflectivity (24.9%) at 30.4 nm and significantly lower reflectivity (1.3%) at 58.4 nm than the conventional coatings such as Mo∕Si. Furthermore, we investigated the temporal stability of the Y(2)O(3)∕Al multilayer coatings. Our sample was kept under vacuum, dry N(2) purge, and normal atmosphere for over three months, and there were no measurable changes in the reflectivity. These results suggest that we can use Y(2)O(3)∕Al multilayer coatings as standard mirrors for the He-II radiation.     

Rapid enumeration of low numbers of moulds in tea based drinks using an automated system

Aseptically prepared cold drinks based on tea have become popular worldwide. Contamination of these drinks with harmful microbes is a potential health problem because such drinks are kept free from preservatives to maximize aroma and flavour. Heat-tolerant conidia and ascospores of fungi can survive pasteurization, and need to be detected as quickly as possible. We were able to rapidly and accurately detect low numbers of conidia and ascospores in tea-based drinks using fluorescent staining followed by an automated counting system. Conidia or ascospores were inoculated into green tea and oolong tea, and samples were immediately filtered through nitrocellulose membranes (pore size: 0.8 μm) to concentrate fungal propagules. These were transferred onto potato dextrose agar and incubated for 23 h at 28 °C. Fungi germinating on the membranes were fluorescently stained for 30 min. The stained mycelia were counted selectively within 90 s using an automated counting system (MGS-10LD; Chuo Electric Works, Osaka, Japan). Very low numbers (1 CFU/100 ml) of conidia or ascospores could be rapidly counted, in contrast to traditional labour intensive techniques. All tested mould strains were detected within 24 h while conventional plate counting required 72 h for colony enumeration. Counts of slow-growing fungi (Cladosporium cladosporioides) obtained by automated counting and by conventional plate counting were close (r² = 0.986). Our combination of methods enables counting of both fast- and slow-growing fungi, and should be useful for microbiological quality control of tea-based and also other drinks.     

Segregation behaviors and radial distribution of dopant atoms in silicon nanowires

Gaining an understanding the dynamic behaviors of dopant atoms in silicon nanowires (SiNWs) is the key to achieving low-power and high-speed transistor devices using SiNWs. The segregation behavior of boron (B) and phosphorus (P) atoms in B- and P-doped SiNWs during thermal oxidation was closely observed using B local vibrational peaks and Fano broadening in optical phonon peaks of B-doped SiNWs by micro-Raman scattering. Electron spin resonance (ESR) signals from conduction electrons were used for P-doped SiNWs. Our results showed that B atoms preferentially segregate in the surface oxide layer, whereas P atoms tend to accumulate in the Si region around the interface of SiNWs. The radial distribution of P atoms in SiNWs was also investigated to prove the difference segregation behaviors between of P and B atoms.     

Prediction of vortex penetration depth at thermal stratification by cavity flow in a branch pipe with closed end (effect of heat radiation condition on temperature fluctuations)

In a branch pipe with one closed end, the cavity flow penetrates into the branch pipe from the main loop and a thermal boundary layer occurs because the cavity flow is a hot fluid, but heat removal causes a colder fluid in the branch pipe. This thermal stratification may affect the structural integrity. Therefore, a pipe design standard to suppress thermal fatigue should be established. The pipe design standard consists of the maximum penetration depth L_sv and the minimum penetration depth L_sh. In order to establish an evaluation method for L_sh, a visualization test and a temperature fluctuation test were carried out. A theoretical formula for thermal stratification was introduced from the heat balance model. Then the model was used to obtain an empirical equation from the map of fluid temperature fluctuation. This method can predict the vortex penetration depth by cavity flow in horizontal branch pipes. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(1):38–55, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20135     

Room-temperature continuous-wave operation of GaN-based laser diodes grown by raised-pressure metalorganic chemical vapor deposition

We report our new raised-pressure metalorganic chemical vapor deposition (RP-MOCVD) technique and the room-temperature continuous-wave (cw) operation of GaN-based laser diodes grown using this technique. We have found that both the defect density as measured by etch-pit density and optical pumping threshold-powder density decreases as the growth pressure is increased beyond 1 atm. We fabricated GaN-based laser diodes and achieved lasing under cw conditions at 20°C. The threshold current density was 3.5 kA/cm² and the operation voltage at threshold was 16.8 V.     

The Ceramide Synthase Subunit Lac1 Regulates Cell Growth and Size in Fission Yeast

Cell division produces two viable cells of a defined size. Thus, all cells require mechanisms to measure growth and trigger cell division when sufficient growth has occurred. Previous data suggest a model in which growth rate and cell size are mechanistically linked by ceramide-dependent signals in budding yeast. However, the conservation of mechanisms that govern growth control is poorly understood. In fission yeast, ceramide synthase is encoded by two genes, Lac1 and Lag1. Here, we characterize them by using a combination of genetics, microscopy, and lipid analysis. We showed that Lac1 and Lag1 co-immunoprecipitate and co-localize at the endoplasmic reticulum. However, each protein generates different species of ceramides and complex sphingolipids. We further discovered that Lac1, but not Lag1, is specifically required for proper control of cell growth and size in Schizosaccharomyces pombe. We propose that specific ceramide and sphingolipid species produced by Lac1 are required for normal control of cell growth and size in fission yeast.