Structural study of degraded ZnMgSSe blue light emitters

Using electroluminescence (EL) topography and transmission electron microscopy (TEM), we investigated the nonluminescent regions which form while current is being injected into ZnMgSSe/ZnSSe/ZnCdSe-based blue light emitters. Small dark spots were observed just after turn-on and spread out forming rough nonluminescent triangles in the <100> directions in the EL image of the active region. TEM studies showed that the small dark spots are pre-existing stacking faults originating at the substrate/epitaxial layer interface. The nonluminescent triangles were found to be a dense region of dislocation dipoles and dislocation loops. Each dipole was aligned along two <110> directions in the {111} planes. The Burgers vectors were of the type a/2<011> inclined at 45° to the (001) junction plane.     

Identification of Sialylated Oligosaccharides Derived from Ovine and Caprine Caseinomacropeptide by Graphitized Carbon Liquid Chromatography–Electrospray Ionization Ion Trap Tandem Mass Spectrometry

Isolation and characterization of oligosaccharides from caseinomacropeptide (CMP) are important in understanding the biological and functional properties of CMP. However, it is difficult to achieve this goal, due to the high degree of isomerism present in these types of compounds. In this study, the sialylated oligosaccharides derived from ovine and caprine CMP were released as oligosaccharide alditols by reductive β-elimination and subsequently separated and characterized using graphite carbon column liquid chromatography–negative electrospray ionization ion trap tandem mass spectrometry (LC/ESI(?)-MSⁿ). Although, the chromatographic resolution of isomeric oligosaccharides was not achieved perfectly, the characteristic tandem mass spectra of these compounds allowed differentiating and confirming unequivocally the structure of each one of the oligosaccharides. In CMP of both species, four trisaccharides and four tetrasaccharides were identified as O-glycans. Their chemical structures were identified to be Galβ1-3(NeuAcα2-6)GalNAcol, NeuAcα2-3Galβ1-3GalNAcol, Galβ1-3(NeuGcα2-6)GalNAcol, NeuGcα2-3Galβ1-3GalNAcol, NeuAcα2-3Galβ1-3(NeuGcα2-6)GalNAcol, NeuGcα2-3Galβ1-3(NeuAcα2-6)GalNAcol, NeuAcα2-3Galβ1-3(NeuAcα2-6)GalNAcol, and NeuGcα2-3Galβ1-3(NeuGcα2-6)GalNAcol. The LC/MSⁿ methodology using an ion trap-type mass analyzer shown in this study is of general applicability for determination of short O-glycan oligosaccharides.     

Humanization of lepidopteran insect-cell-produced glycoproteins

The insect cell-baculovirus expression vector system, widely used for glycoprotein production, is not ideal for pharmaceutical glycoprotein production due to the characteristics of the N-glycans in the expressed products. Insect cells lack several enzymes required for mammalian-type N-glycan synthesis and contain a specific N-acetylglucosaminidase that stunts the growth of chains and a core alpha-1,3-fucosyltransferase that yields potentially allergenic glycoforms. Current knowledge on N-glycan processing in lepidopteran insect cells is summarized, and strategies to develop better glycoprotein expression systems suitable for pharmaceutical glycoprotein production are discussed.     

Segmented chirped grating for coarse wavelength division demultiplexing with multimode optical fibers

A chirped grating segmented into partitions each having a constant blaze angle to use in a demultiplexer for coarse wavelength division multiplexing with multimode optical fibers is developed. Its designed configuration utilizes a resonance region to achieve high diffraction efficiency and large dispersion. The width, blaze angle, and diffraction order of each partition were optimized by vector diffraction analysis. The diffraction loss of the manufactured grating was less than 1.5 dB, and polarization-dependent loss was less than 0.6 dB within a wavelength width of at least 70 nm. It is confirmed that a demultiplexer with the developed chirped grating had a wide passband and low cross talk.     

Aberration properties in a chirped grating for coarse wavelength division demultiplexing

We studied the imaging performance of a chirped grating for a demultiplexer designed for coarse wavelength division multiplexing using a wavefront aberration analysis and the ray tracing simulation. The demultiplexer was composed of a chirped grating, cylindrical lenses, and a waveguide. The best image point and the spot shape focused by the chirped grating were effectively calculated with the wavefront aberration. We applied the aberration analysis to design a waveguide to connect branched beams to photodetectors, and we confirmed the demultiplexing performance experimentally.     

Composition dependence of the oxygen-evolution reaction rate on Ir x Ti1−x O2 mixed-oxide electrodes

Mudcrack-free oxide films of Ir _x Ti_1–x O₂ (0 < x 1) on titanium substrates were obtained, and the effects of the oxide composition on the rate of oxygen-evolution reaction were investigated. At x 0.6, Ir-rich grains appear on the mudcrack-free surface. In the purely single-phase region (0 < x 0.5), the pseudo-capacitive charge is proportional to the surface composition, x _s, and the exchange-current density for the oxygen-evolution reaction increases linearly with x _s at 0.2 x _s 0.5, with an extrapolated intercept at x _s 0.15, below which the oxides are inactive.     

Super‐ductile PBT alloy with excellent heat resistance

A super‐ductile PBT alloy with excellent heat resistance was successfully fabricated by reactive blending of poly(butylene terephthalate) (PBT) with poly(ethylene‐co‐glycidyl methacrylate) together with linear low density polyethylene (LLDPE) and hydrogenated styrene‐butadiene‐styrene block copolymer (SEBS). It possesses a unique tensile stress–strain curve with no yielding point and large elongation at break, moreover, the alloy did not show serious deterioration of the mechanical properties by high temperature annealing at 150°C for 96 h. The structure‐properties relationship is discussed on the basis of transmission electron microscopy, differential scanning calorimetry, dynamic mechanical analysis, and wide‐angle X‐ray diffraction analysis. The outstanding ductile nature seems to come from the negative pressure effect of LLDPE (or LLDPE/SEBS) particles that dilates the PBT ligament matrix to enhance the local segment motions. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers.     

Bidirectional optical coupler for plastic optical fibers

We have developed a low-loss bidirectional optical coupler for high-speed optical communication with plastic optical fibers (POFs). The coupler, which is fabricated by an injection molding method that uses poly (methyl methacrylate), has an antisymmetric tapered shape. We show that the coupler has low insertion and branching losses. The tapered shape of the receiving branch reduces beam diameter and increases detection efficiency coupling to a photodetector, whose area is smaller than that of the plastic optical fiber. The possibility of more than 15-m bidirectional transmission with a signaling bit rate up to 500 Mbits/s for simplex step-index POFs is demonstrated.     

Quantum fidelity and dynamical scar states on chaotic billiard system

It is found that the decay rate of the quantum fidelity is suppressed, when the periodic orbit scars in the accumulation of the time-evolving wavefunction become obvious in two-dimensional (2D) nanostructure. The fidelity is numerically evaluated by the time-evolution of the wavepacket inside a 2D chaotic nanostructure: the stadium, which is the typical chaotic system. The suppression is apparent in the Lyapunov regime, where the decay rate does not depend on the strength of the perturbation.