Remarkable effect of addition of In and Pb on the reduction of N2O by CO over SiO2 supported Pd catalysts

The effect of addition of In and Pb on the reduction of N₂O by CO was studied over SiO₂ supported Pd catalysts, using a closed gas circulation system as well as in-situ infrared spectroscopy. Formation of intermetallic compounds such as Pd_0.48In_0.52, Pd₃Pb and Pd₃Pb₂ was observed which caused a drastic enhancement of the rate of N₂ formation. The infrared spectroscopic analyses revealed a weakening of the adsorption strength of CO on Pd metal by the formation of intermetallic compounds, which is likely the main reason for the enhancement of the reaction rate. From a kinetic investigation as well as in situ FT-IR observation during the N₂O-CO reaction, a redox mechanism was proposed involving the oxidation of the surface by N₂O followed by its reduction by CO. Over Pd/SiO₂, the former process seems to be the rate limiting step because of the inhibition of N₂O activation by strongly adsorbed CO. By adding In or Pb, the rate limiting step shifted to the latter process, which resulted in a large enhancement in the rate of N₂ formation.     

Depth profiling study on the migration of tritium in titanium induced by deuterium-ion bombardment

A thin titanium layer with uniformly absorbed tritium (T/Ti ˜1.0) was bombarded by 390 keV D₃⁺ ions (130 keV per deuteron). Bombardment was performed at low (111 K) and room temperatures up to fluences of 5.9 × 10¹⁸ D/cm² and 3.0 × 10¹⁸ D/cm², respectively. Depth profiles of tritium up to a depth of 0.8 mg/cm² (˜1.8 μm) were measured and the change of the profile with fluence was investigated by means of the T(d, )n nuclear reaction. At both of the temperatures, a dip was formed on the depth profile of tritium at the depth around the projected range, indicating that the deuteron bombardment induced the migration of tritium against the concentration gradient. At the low temperature, the dip showed a gradual growth with fluence and saturation of the growth at the higher fluences, which could not be described by the existing model for isotope mixing. The spectrum of protons from the D(d, p)T reaction obtained in the same measurement suggested that the release of deuterium suddenly started at the final stage of the present bombardment. The dip formed at room temperature was larger than that at the low temperature. The migration of tritium induced by the bombardment is discussed on the basis of the experimental results obtained.     

Polarisation conservation in single-mode fibres

There exist proper orthogonal elliptical polarisation states, which are maintained over long fibre length without converting. When one of the proper polarisation states is excited, orthogonal polarisation less than ?40 dB is confirmed after 5 km single-mode fibre transmission. It is also proposed that twisted single-mode fibres show a high degree of polarisation for any incident polarisation state. The polarisation characteristics are hardly affected by external perturbations.     

Theory of magnetically polarizable superconductors. II

A microscopic theory of superconductors containing a magnetically polarizable medium is given. By taking into account the Zeeman effect, we derive the crossover behavior from a second- to a first-order phase transition, the magnetization curve in the high-field region, and the magnetization jump at the first-order phase transition temperature. The theory gives a qualitative account of the magnetic behavior, including the remarkable convex curvature of the magnetization curves, observed in the ferromagnetic superconductor ErRh₄B₄ with applied external field parallel to the magnetic easy axis.     

Amorphous Pd---Si alloys for hydrogen-permeable and catalytically active membranes

Amorphous Pd_xSi_1-x(x=0.8,0.825,0.85) in the form of ribbon was prepared by a single-roller melt spinning technique to examine hydrogen permeability and catalytic activity for dehydrogenation. As a result, it was found that the amorphous specimens had higher tenacity and higher permeability of hydrogen than its crystallized form. Also, the surface of the amorphous specimen showed a catalytic activity for dehydrogenation of cyclohexane, while no activity was observed in the untreated. Taking advantage of both hydrogen permeability and catalytic activity, the amorphous Pd_xSi_1-x would be expected to be a candidate for a catalytic membrane.     

Potical Energy Gap and Below Gap Optical Absorption of Fullerene Films Measured By Constant Photocurrent Method and Photothermal Deflection Spectroscopy

CPM spectra of the fullerene film was measured to obtain the below gap absorption. The optical energy gap E_o was obtained by using the Tauc's plots. E_o did not change so much with the intercalated impurities. The absorption due to intercalated impurities was found below 1.6eV.     

Study of charge storage behavior in metal-alumina-silicon dioxide-silicon(MAOS) field effect transistor

The basic characteristics and charge storage behavior of metal-alumina-silicon dioxide-silicon(MAOS) field effect transistors have been investigated as a function of the oxide thickness. The typical charge storage behaviors have also been measured on devices with SiO₂ films of 50 Å and Al₂O₃ films of 700 Å and the results are interpreted in terms of electron and hole transport processes across thin SiO₂ layer and electron injection from Al electrode by tunneling mechanism. In the MAOS structure, the shift of threshold voltage from initial state is within about 23 V and can be reversibly controlled, more than 10⁶-times at least, by alternate electric fields under suitable stressing condition. It is considered that the charge storage time is practically infinite at room temperature and of the order of 10⁶ hr at 150°C. The failure behaviors of device parameters under the repeated field stressing and cycles can be also accounted for in terms of electron accumulation within Al₂O₃ films and at interfaces between Al₂O₃ and SiO₂ films.     

Long-term study of patients with pulmonary tuberculosis sequelae after bilateral thoracoplasty-airway obstruction and its causes

Chest roentgenograms and results of pulmonary-function tests in patients with pulmonary tuberculosis sequelae 30 years after bilateral thoracoplasty were studied retrospectively to detect airway obstruction in these patients and to determine its causes. For periods of more than 10 years, vital capacity (VC) changed at a rate of 15.5 +/- 5.0 ml/year, and forced expiratory volume in one second as a percent of VC (FEV1%) changed at a rate of 0.546% +/- 0.380% per year (n = 13). Thirty years after thoracoplasty, the VC was 920 +/- 180 ml (%VC = 28.4% +/- 5.3%), and the FEV1% was 66.2% +/- 13.7% (n = 21). Thus, mild airway obstruction was found in about half of the cases. For each patient, the distance from the hilum to the diaphragm was measured along the mid-clavicular line on the side with fewer ribs resected, and this distance was divided by the patient's height. The results of that computation was found to be significantly and negatively related to FEV1% (r = -0.681, which suggests that longer bronchi in the lower and middle lobes on that side were associated with lower values of FEV1%. These findings are similar to those in patients with pulmonary tuberculous sequelae after total pneumonectomy. Over an average of 26 years, scoliosis, the vertebra showing the most bending, the intrapulmonary lesion, and the position of the diaphragm did not change, but the cardio-thoracic ratio increased.     

Characterization of Cat-CVD grown Si–C and Si–C–O dielectric films for ULSI applications

Si–C films with the Si compositions ranging from 40 to 70% have been grown by Cat-CVD using dimethylsilane [DMSi, Si(CH₃)₂H₂] compounds. Tetraethoxysilane [TEOS, Si(OC₂H₅)₄] and dimethyldimethoxysilane [DMDMOS, Si(CH₃)₂(OCH₃)₂] gas source gave us Si–C–O (C-doped SiO_x) films with wide ternary alloy compositions. The dielectric constant of a Si–C film has been evaluated by C–V measurements (at 1 MHz) using Al/Si–C/n-Si(001)/Cu MIS structure. The relative dielectric constant value of a Si–C film was estimated to be 3.0. The resistivity of the Si–C layer with 1 mm diameter and 0.24 μm thickness was estimated to be more than 24.5 Gohm·cm. These results gave us promising characteristics of Si–C and Si–C–O films grown by alkylsilane- and alcoxysilane-based Cat-CVD.