Spectral studies of SnO2 nanofibres prepared by electrospinning method

Tin oxide nanofibres with 100-150 nm diameter has been prepared, for the first time by calcination of poly(vinyl acetate) (PVAc)/SnO2 composite fibres prepared by electrospinning method as precursor. Scanning electron microscopic images revealed cylindrical morphology of the fibres after calcination at 600 degrees C. Both, X-ray diffraction (XRD) and Raman spectral data confirmed the presence of phase pure tetragonal rutile tin oxide after calcination process. Room temperature photoluminescence (PL) spectra of tin oxide nanofibres under excitation at 325 nm wavelength show a strong green emission at 525 nm with a band gap of 2.41 eV. FT-IR spectra confirmed the formation of pure tin oxide after calcination at 600 degrees C and complete removal of PVAc during calcination. UV-vis spectrum of the fibres showed absorption at 315 nm due to the direct electron transfer in tin oxide.     

Pleckstrin homology domain of phospholipase C-gamma1 directly binds to 68-kDa neurofilament light chain

Phosphoinositide-specific phospholipase C-gamma1 (PLC-gamma1) has two pleckstrin homology (PH) domains: an amino-terminal domain (PH1) and a split PH domain (PH2). Here, we show that overlay assay of bovine brain tubulin pool with glutathione-S-transferase (GST)-PLC-gamma1 PH domain fusion proteins, followed by matrix-assisted laser-desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), identified 68-kDa neurofilament light chain (NF-L) as a binding protein of amino-terminal PH domain of PLC-gamma1. NF-L is known as a component of neuronal intermediate filaments, which are responsible for supporting the structure of myelinated axons in neuron. PLC-gamma1 and NF-L colocalized in the neurite in PC12 cells upon nerve growth factor stimulation. In vitro binding assay and immunoprecipitation analysis also showed a specific interaction of both proteins in differentiated PC12 cells. The phosphatidylinositol 4, 5-bisphosphate [PI(4,5)P(2)] hydrolyzing activity of PLC-gamma1 was slightly decreased in the presence of purified NF-L in vitro, suggesting that NF-L inhibits PLC-gamma1. Our results suggest that PLC-gamma1-associated NF-L sequesters the phospholipid from the PH domain of PLC-gamma1.     

Delayed allograft rejection by the suppression of class II transactivator

(CIITA) down-modulation on allograft rejection. To inhibit the function of CIITA, we constructed a series of CIITA mutants and found one exhibiting the dominant-negative effect on the regulation of major histocompatibility complex (MHC) class II expression. To test whether the CIITA dominant-negative mutant reduces immunogenicity, CIITA-transfected melanoma cells were injected into allogeneic host and assessed for immune evading activity against host immune cells. We demonstrated that the CIITA dominant-negative mutant allowed tumor nodules to develop earlier in the lung than control by this tumor challenge study. Furthermore, skin grafts deficient for CIITA also survived longer than wild-type in allogeneic hosts. Both the tumor challenge and skin graft studies suggest the inhibition of CIITA molecules in donor tissue would be beneficial to the control of allo-response.     

Fabrication of non-biofouling polyethylene glycol micro- and nanochannels by ultraviolet-assisted irreversible sealing

We present a simple and widely applicable method to fabricate micro- and nanochannels comprised entirely of crosslinked polyethylene glycol (PEG) by using UV-assisted irreversible sealing to bond partially crosslinked PEG surfaces. The method developed here can be used to form channels as small as approximately 50 nm in diameter without using a sophisticated experimental setup. The manufactured channel is a homogeneous conduit made completely from non-biofouling PEG, exhibits robust sealing with minimal swelling and can be used without additional surface modification chemistries, thus significantly enhancing reliability and durability of microfluidic devices. Furthermore, we demonstrate simple analytical assays using PEG microchannels combined with patterned arrays of supported lipid bilayers (SLBs) to detect ligand (biotin)-receptor (streptavidin) interactions.     

Formation of regular nanoscale undulations on a thin polymer film imprinted by a soft mold

We observed the formation of regular nanoscale undulations on a polystyrene film when imprinted by a soft poly(dimethylsiloxane) mold above the polymer's glass transition temperature. The shape of the wave was reminiscent of a buckling wave frequently observed for a metal film supported on an elastomeric substrate. We derived a simple theoretical model based on an anisotropic buckling of the polymer film rigidly bound to a substrate, which agrees well with the experiment.     

Temporal and spectral responses of a softening Duffing oscillator undergoing route-to-chaos

Because nonlinear responses are oftentimes transient and consist of complex amplitude and frequency modulations, linearization would inevitably obscure the temporal transition attributable to the nonlinear terms, thus also making all inherent nonlinear effects inconspicuous. It is shown that linearization of a softening Duffing oscillator underestimates the variation of the frequency response, thereby concealing the underlying evolution from bifurcation to chaos. In addition, Fourier analysis falls short of capturing the time evolution of the route-to-chaos and also misinterprets the corresponding response with fictitious frequencies. Instantaneous frequency along with the empirical mode decomposition is adopted to unravel the multi-components that underlie the bifurcation-to-chaos transition, while retaining the physical features of each component. Through considering time and frequency responses simultaneously, a better understanding of the particular Duffing oscillator is achieved.     

Pitch reduction lithography by pressure-assisted selective wetting and thermal reflow

We report on a new pitch reduction lithographic technique by utilizing pressure-assisted selective wetting and thermal reflow. The primary line-and-space pattern of low molecular weight polystyrene (PS) (Mw=17,300) was formed by solvent-assisted capillary force lithography (CFL), on which a diluted photoresist (PR) solution was selectively filled into the spaces by the application of a slight pressure (200 g cm(-2)). Subsequent removal of the PS pattern by toluene and ashing process led to a line pattern with approximately 50% pitch reduction. It was observed that the size reduction and space to width ratios were controllable by changing PR concentration and ashing time.     

Hydrogen permeation characteristics of rolled V85Al10Co5 alloys

Thin sheets of V₈₅Al₁₀Co₅ alloy were produced by a thermo-mechanical treatment consisting in successive hot rolling, cold rolling steps and annealing treatment at high temperature followed by either air cooling or water quenching. Though the values of hydrogen permeability measured for these sheets were significantly reduced as a consequence of the rolling process, the annealing treatment restored almost the hydrogen permeation properties to those of the alloy in the cast condition. EBSD analyses suggested that the post-annealing treatment performed at 1100 °C for 3 min after cold rolling induced a recrystallization of the grains resulting in a preferred orientation along the {002} planes. For the sample annealed and water quenched, the value of the hydrogen flux reached about 45 ml/cm².min, which is more than twice the value of the flux obtained for thin foils of Pd alloys tested under identical conditions.     

Comparative analysis of characteristics of Si, Mg, and undoped GaN

We have grown undoped, Si- and Mg-doped GaN epilayers using metalorganic chemical vapor deposition. The grown samples have electron Hall mobilities (carrier concentrations) of 798 cm²/V s (7×10¹⁶ cm⁻³) for undoped GaN and 287 cm²/V s (2.2×10¹⁸ cm⁻³) for Si-doped GaN. Mg-doped GaN shows a high hole concentration of 8×10¹⁷ cm⁻³ and a low resistivity of 0.8 Ω cm. When compared with undoped GaN, Si and Mg dopings increase the threading dislocation density in GaN films by one order and two orders, respectively. Besides, it was observed that the Mg doping causes an additional biaxial compressive stress of 0.095 GPa compared with both undoped and Si-doped GaN layers, which is due to the incorporation of large amount of Mg atoms (4–5×10¹⁹ cm⁻³).     

A Complementary Metal-Oxide-Semiconductor Vision Chip for Edge and Motion Detection with a Function for Output Offset Cancellation

We have designed and fabricated a complementary metal-oxide-semiconductor (CMOS) vision chip by modeling cells of the human retina as hardware that are involved in edge and motion detection. There are several fluctuation factors which affect the characteristics of metal-oxide-semiconductor field effect transistors (MOSFETs) through the CMOS fabrication process and this effect appears as the output offset of the vision chip, which is composed of pixel arrays and readout circuits. The vision chip which detects edge and motion information from an input image is used for the input stage of other systems. Therefore, the output offset of the vision chip determines the efficiency of the entire system. In order to eliminate the offset at the output stage, we designed a vision chip utilizing the correlated double sampling (CDS) technique. The chip has been fabricated using a 0.6 m standard CMOS process. With reliable output characteristics, this chip can be used at the input stage for various applications. © 2005 The Optical Society of Japan