Combustion synthesis of LaSi3N5:Eu2+ phosphor powders

LaSi₃N₅:Eu²⁺ phosphor powders were prepared by a highly efficient combustion synthesis method. It was found that the compositions of the raw powder mixtures had great influences on the phase compositions and particle morphologies of the synthesized powders. By selecting appropriate starting compositions and combustion parameters, single phase LaSi₃N₅:Eu²⁺ phosphors could be synthesized. When excited by a UV light, the LaSi₃N₅:Eu²⁺ phosphors emitted green light. The wavelength and intensity of the emission spectra were affected by the amount of Eu²⁺ dopant. With increasing amount of Eu²⁺ dopant, concentration quenching could occur and emission spectra shifted to longer wavelengths.     

Preliminary spectrum shifter design for intermediate energy nuclear data benchmark experiments with DT neutrons

Integral benchmark experiments with DT neutrons are not always sufficient for nuclear data benchmarking in the MeV region, below 10 MeV. A neutron spectrum shifter, which will be placed between a sample and a DT neutron source, is effective to moderate DT neutrons incident to the sample. In order to estimate effects of the spectrum shifter, the ratio of the contribution of 14 MeV neutrons in the leakage neutron and gamma-ray spectra was calculated with MCNP-4C for an experimental configuration at FNS of JAEA, Japan. The calculations were carried out for a Li₂TiO₃ sample with a Be, D₂O, or ⁷LiD spectrum shifter. It was found out that the Be shifter was superior to others and the Be shifter was effective to decrease the contribution of 14 MeV neutrons especially for secondary gamma-ray spectrum measurements.     

Self-flux synthesis and photoluminescent properties of LiAl5O8

Pure-phase LiAl₅O₈ was selected as an oxide ceramic red phosphor material without dopants (color centers) and was synthesized using a self-flux method. The LiAl₅O₈ was formed by heating a powder mixture consisting of γ-Al₂O₃:Li₂SO₄ = 1:2 (molar ratio) at over 1100 °C for 1 h. Photoluminescence (PL) properties for the synthesized LiAl₅O₈ were investigated. The maximum intensity of the excitation spectrum for the photoluminescent emission of LiAl₅O₈ synthesized was at 274 nm. The peak intensity of the emission spectrum was at a wavelength of 667 nm (red color). The intensity of the peak emission spectrum increased with the heating temperature, i.e., the maximum peak intensity of the red emission spectrum was detected for the LiAl₅O₈ synthesized by heating at 1500 °C for 1 h.     

Detection of relative and uniform motion

We measured the lowest velocity (velocity threshold) for discriminating motion direction in relative and uniform motion stimuli, varying the contrast and the spatial frequency of the stimulus gratings. The results showed significant differences in the effects of contrast and spatial frequency on the threshold, as well as on the absolute threshold level between the two motion conditions, except when the contrast was 1% or lower. Little effect of spatial frequency was found for uniform motion, whereas a bandpass property with a peak at approximately 5 cycles per degree was found for relative motion. It was also found that contrast had little effect on uniform motion, whereas the threshold decreased with increases in contrast up to 85% for relative motion. These differences cannot be attributed to possible differences in eye movements between the relative and the uniform motion conditions, because the spatial-frequency characteristics differed in the two conditions even when the presentation duration was short enough to prevent eye movements. The differences also cannot be attributed to detecting positional changes, because the velocity threshold was not determined by the total distance of the stimulus movements. These results suggest that there are two different motion pathways: one that specializes in relative motion and one that specializes in uniform or global motion. A simulation showed that the difference in the response functions of the two possible pathways accounts for the differences in the spatial-frequency and contrast dependency of the velocity threshold.     

Histidine 210 mutant of a trypsin-type Achromobacter protease I shows broad optimum pH range

Achromobacter protease I (API), a lysine-specific serine protease, shows one order of magnitude higher activity than bovine trypsin, while its optimum pH is in the alkaline region at about pH 9. To improve the optimum pH range, mutant enzyme His 210 replaced by Ser(H210S), Ala (H210A), and Lys (H210K) were constructed. The optimum pH of H210S shifted from about pH 9 (wild-type enzyme) to about pH 7, retaining its high activity. The putative electrostatic interaction between His 210 and catalytic Asp 113 was elucidated by the optimum-pH shift of H210K and H210A. These results indicate that this unconserved His 210 in API, which plays a key role in generating the useful peptidase, broadened the optimum-pH range without decreasing lysylendo-peptidase activity.     

Laser Thomson scattering and optical emission studies of striated PDP micro‐discharge plasmas

Abstract— Properties of a plasma‐display‐panel (PDP) like discharge were examined by emission and laser Thomson scattering (LTS) measurements. Emission measurements were performed using an intensified CCD camera. By varying several external parameters such as the amplitude of the input voltage, gas composition, and pressure, the influence of these parameters on the discharge behavior was studied. Results of emission measurements showed that they were in good agreement with similar emission measurements on real PDP cells. LTS measurements were performed for the striated PDP‐like discharge at a pressure of 100 Torr and the results showed clear modulations in both profiles of electron density and electron temperature.     

Processing and Thermal Conductivity of Sintered Reaction-Bonded Silicon Nitride. I: Effect of Si Powder Characteristics

This paper will present sintered reaction-bonded silicon nitride (SRBSN) material with a high thermal conductivity of 121 W·(m·K)⁻¹, which has been successfully prepared from a coarse Si powder with lower levels of oxygen and aluminum impurities, using a mixture of Y₂O₃ and MgSiN₂ as sintering additives, by nitriding at 1400°C for 8 h and subsequent post-sintering at 1900°C for 12 h at a nitrogen pressure of 1 MPa N₂. This thermal conductivity value is higher than that of the materials prepared from high-purity α-Si₃N₄ powder (UBE SN-E10) with the same additive composition under the same sintering conditions. In order to study the effects of Si powder characteristics on the processing, microstructure, and thermal conductivity of SRBSN, the other type of fine powder with higher native oxygen and metallic impurity (typically Al and Fe) contents was also used. The effects of Si particle size, native oxygen, and metallic impurities on the nitriding process, post-sintering process, and thermal conductivity of the resultant SRBSN materials were discussed in detail. This work demonstrates that the improvement in thermal conductivity of SRBSN could be achieved by using higher purity coarse Si powder with lower levels of oxygen and aluminum impurities. In addition, this work also shows that the nitriding temperature has no significant effect on the microstructure and thermal conductivity of SRBSN during post-sintering, although it does affect the characteristics of RBSN formed during nitridation.     

Responses of maxillary sensilla styloconica inBombyx mori to glucosides fromOsmunda japonica,a nonhost plant

We isolated glucosides from the royal fern,Osmunda japonica, which elicit a deterrent response in larvae ofBombyx mori. These compounds were absent in taro (Colocasia antiquorum) and castor-oil plant (Ricinus communis) leaves and did not evoke responses of sensory cells in the lateral and medial sensilla styloconica ofSpodoptera litura. This glucoside extract of the royal fern leaves stimulates receptors generally associated with deterrent. It is also possible that this compound may act as a behavioral deterrent, and from actual feeding tests, it is suggested that this compound may prevent feeding in some monophagous insects, such asBombyx mori. The deterrent glucoside possesses a noncyclic aglycon.