Hadamard transform microchip electrophoresis combined with diode laser fluorometry

The application of a Hadamard transform technique to microchip electrophoresis is described. The sample is electrokinetically injected into a separation channel and is then detected by diode laser-induced fluorometry. The sample and buffer solutions are introduced into the channel by controlling the high voltages applied to the solutions, according to a code determined by a Hadamard matrix. The S/N ratio of the signal in the electropherogram can be improved by a factor of 5 in comparison with that obtained by a conventional single-injection method, although an 8-fold improvement is theoretically predicted when a 255-order matrix is used.     

Diffuse reflection of ceramics coated with dielectric thin films

We have studied the diffuse reflection properties of ceramics in the presence of dielectric thin films on the surface. A simple optical model was proposed in which interference effects in a thin film were considered for light scattered out of a ceramic in various directions. Measurements were performed on angle-resolved reflection spectra of a thin-film-coated alumina ceramic in the case of normal incidence. They showed that the presence of the thin film on the ceramic's surface modified the angular distributions of scattered radiation from that of a bare ceramic, which suggested a way to tailor the scattering properties of a diffuse reflector as needed.     

Hadamard transform capillary electrophoresis combined with absorption spectrometry

A novel injection device for applying absorption spectrometry to Hadamard transform (HT) capillary electrophoresis is described. A small hole, at the center part of the capillary, functions as an inlet port for the sample. The hole is immersed in a sample solution and the end of the capillary that is usually employed for sample introduction is immersed in a buffer solution. An ultraviolet absorption detector is placed between the sample injection port and the other end of the capillary filled with a buffer solution. A high potential is continuously applied between the injection port and the end of the capillary, which allows the sample solution to be introduced into the separation capillary. By application of a higher potential modulated according to a Hadamard code between both ends of the capillary, the buffer solution is injected into the separation capillary. In some preliminary experiments, this injection device was utilized to introduce a single sample segment into a capillary. As expected, a single peak was observed in the electropherogram for a sample containing a single component. This device was then employed for multiple sample injection in HT capillary electrophoresis. An 8-fold improvement in the S/N ratio was observed when the HT technique was used, in which a 255-order of a Hadamard matrix was used, as expected from theory. The present approach was also utilized for the sensitive detection of a sample comprised of multiple components.     

Elastic properties of a crossply SiC f /Ti composite at elevated temperatures

Using electromagnetic acoustic resonance (EMAR), we measured the complete set of elastic constants and internal friction of a silicon-carbide-fiber-reinforced Ti-6Al-4V-matrix cross-ply composite between room temperature and 1000 K. This material exhibits tetragonal symmetry and possesses six independent C _ij . By changing the magnetic-field direction, we selected two vibration groups among the eight vibration groups of a rectangular parallelepiped. The elastic constants showed anomalous temperature dependence around 650 K and internal friction Q ⁻¹ increased rapidly above that temperature; neither the C _ij nor Q ⁻¹ returned to the before-heating values. We attributed this to disbonding between the matrix alloy and SiC, and between SiC and the carbon core within the fiber caused by oxidation of carbon, which is supported by the microstructure observation. We present the temperature derivatives of the composite C _ij and estimate those of the fiber C _ij by comparing the matrix-C _ij derivatives.     

Nickel sulfides as a cathode for all-solid-state ceramic lithium batteries

The nickel sulfide, Ni₃S₂, was examined as a potential cathode material of the all-solid-state-lithium-batteries using thio-LISICON, Li₂S–GeS₂–P₂S₅, as the solid-electrolyte. Ni₃S₂and Li₂S–GeS₂–P₂S₅ system, was synthesized with a new sintering system, which proceed under a flowing argon in the reusable quartz tube. The highest ionic conductivity 2.39×10⁻³$2.39\times 10^{-3}$ S cm⁻¹ was observed for a sample prepared at 700 °C with 10% of excess P₂S₅, and bear comparison with the maximum conductivity reported for the thio-LISICON, Li_3.35Ge_0.35P_0.65S₄. An all-solid-state-lithium-battery based on, Ni₃S₂/Li_3.35Ge_0.35P_0.65S₄/Li–Al alloy, showed electrochemical capacities of greater than ∼$\sim$300 mAh g⁻¹ after 30 cycles. The cycling performances of the cells were found to be dependent on the Ni₃S₂/thio-LISICON compositions in the cathode mixture, with a cell containing 60 wt.% of Ni₃S₂ exhibiting the most stable reversible capacities. As the depth of the first discharge capacity also influences the cycling properties, Ni₃S₂ consumed during the discharge reaction may play an important role in the nickel reduction mechanism.     

Shape-sensitive reflectance by nanostructured metal attached on an optical waveguide-mode sensor

The optical reflectance of He-Ne laser light on a waveguide-mode sensor was measured as a function of light incident angle, in the case of either a metal (Au, Cr or Pt) film or nanoparticles being attached to the waveguide surface of the sensor. A dip appears in the reflectance spectrum as a function of incident angle at the angle where waveguide-mode excitation is induced. It is found that the dip moves toward a lower angle in the case that the attached metal is of a film shape, while it shifts toward a higher angle when the metal is an ensemble of nanoparticles. This difference in the direction of shift can be explained well by theoretical calculations using average refractive indices of the metal-containing layers. The present result indicates that one can estimate whether a metal nanostructure is film-like or an ensemble of spherical nanoparticles by the sensor.     

Growth and characterization of Fe3O4 films

Iron oxide films were grown on sapphire substrates by pulsed laser deposition at substrate temperatures between 100 and 700 °C. X-ray diffraction, Raman spectroscopy, and vibrational sample magnetometer analysis revealed that structural and magnetic properties of the iron oxide films strongly depend on the substrate temperature during growth. Single phase Fe₃O₄ film was successfully grown on sapphire substrate at a substrate temperature of 500 °C. The saturation magnetic moment of the single phase Fe₃O₄ film is 499 emu/cm³, which is in good agreement with the value reported for bulk magnetite, suggesting the Fe₃O₄ film is of high crystal quality without antiphase boundaries.     

Substituent effect on structure and physical properties of semicrystalline Diels-Alder network polymers

Semicrystalline cross-linked polymers were synthesized using the Diels-Alder (DA) reaction between furyl-telechelic poly(ε-caprolactone) prepolymers (PCLF₂-x. x (substituent in the vicinity of furan) = A (amide), E (ester) and U (urethane)) and a tris-maleimide linker (M₃). The equilibrium of the thermoreversible DA reaction shifted by changing the substituent, that is, the dissociation of PCLF₂-x and M₃ during the retro-DA reaction was significant in the order of PCLF₂-E-M₃ > PCLF₂-U-M₃ > PCLF₂-A-M₃, while the association during the DA reaction was effective in the reversed order. This can be attributed not only to the difference in electron density in furan rings (PCLF₂-A ≈ PCLF₂-U > PCLF₂-E) but also to the presence of hydrogen-bonding between CO in maleimide and N-H in the amide or urethane bond in the vicinity of furan and its strength (PCLF₂-A-M₃ > PCLF₂-U-M₃) and the absence for PCLF₂-E-M₃. The shift of reaction equilibrium resulted in effective modulation of structures and physical properties of crystallization-first (CRY^1st) and cross-linking-first (CL^1st) network polymers.     

Improvement of lasing properties of europium (III) complexes by increase of emission quantum yield

Deuterated Eu(III) complexes of tris-(hexafluoroacetylacetonato)europium(III) dehydrates (Eu(hfa-H)₃(H₂O)₂), tris-(hexafluoroacetylacetonato)europium(III) bis(triphenylphospine oxide) (Eu(hfa-H)₃(TPPO)₂), tris(hexafluoroacetylacetonato) europium(III) 1,1′-biphenyl-2,2′-diylbis (diphenylphosphine oxide) (Eu(hfa-H)₃(BIPHEPO)) were prepared by the exchange reaction via keto-enol tautomerism of the Eu(III) complexes with CD₃OD. The emission quantum yields of the deuterated Eu(III) complexes were higher than those of corresponding non-deuterated Eu(III) complexes. The lasing properties of Eu(III) complexes in polymer thin film were measured by photo-pumping of Nd: YAG laser (355 nm). Percentages of ASE components in whole emission were increased by deuteration of the Eu(III) complexes.