Solution copolymerization of ethylene with α-olefin by vanadium catalyst

Summary Copolymerization of ethylene with an -olefin, i.e. propylene, butene-1 and 4-methyl-pentene-1(4-MP-1), was carried out by vanadium catalyst prepared by treating VOCl₃ with (n-C₈H₁₇)₃Al in decane in combination with Et₃Al and CHCl₃. The copolymerization system was homogeneous at a temperature as high as 170 °C. It has been revealed that the monomer insertion reaction of irregular direction, i.e. the insertion giving rise to the growing end of secondary alkyl / catalyst bond, occurs occasionally at the propagation of the -olefin comonomer. The irregular insertion takes place most frequently with 4-MP-1. The chain transfer with hydrogen takes place more preferentially at the irregular propagation end in comparison with the regular one.     

A method of coding LSP residual signals using wavelets for speech synthesis

This paper presents a method of using wavelet analysis for speech coding and synthesis by rule. It is a coding system where LSP residual signal is transformed into wave‐let coefficients. As wavelet analysis is implemented effectively by filter banks, our method requires less computation than multipulse coding and others where complicated prediction procedures are essential. To achieve good‐quality speech at low bit rates, we verified allocation of different bits onto the wavelet coefficients, with more bits in lower frequencies, and less in higher. The synthesized speech by Haar wavelet with 16.538 kbit/s has nearly the same perceptual quality with 6 bits µlog PCM (66.15 kbit/s). We are convinced that the coding method of LSP residual signals using wavelet analysis is an effective approach to synthesize speech. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(3): 54–61, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10326     

Preparation of Tetragonal Barium Titanate Thin Film on Titanium Metal Substrate by Hydrothermal Method

Tetragonal BaTiO₃ thin films were prepared directly on Ti metal substrates in Ba(OH)₂ solutions by a hydrothermal method at temperatures 400° to 800°C for 5 to 240 min. The film thickness estimated from weight gain of Ti plate was in the range from 0.5 to 2.5 μm, and it increased with increasing treatment temperature, treatment time, and Ba(OH)₂ concentration. Rectangular crystals having {100} and {001} faces grew idiomorphically with approximate crystal size of 0.3 to 2.0 μm. The tetragonality of the BaTiO₃ films became apparent when the average crystal size exceeded about 1 μm. Lattice parameters of the films were a = 3.994 Å, c = 4.035 Å, and c/a = 1.010. The films formed above 600°C had preferred orientation showing stronger XRD peaks of h 00 and 00 l than the other peaks.     

Design and performance of 0.1-μm CMOS devices usinglow-impurity-channel transistors (LICT's)

0.1-μm CMOS devices using low-impurity-channel transistors (LICTs) with dual-polysilicon gates have been fabricated by nondoped epitaxial growth technology, high-pressure oxidation of field oxide, and electron-beam lithography. These devices, with gate lengths of 0.135 μm, achieved normal transistor operation at both 300 and 77 K using 1.5-V supply voltage. Maximum transconductances are 203 mS/mm for nMOS transistors and 124 mS/mm for pMOS transistors at 300 K. Low-impurity channels grown on highly doped wells provide low threshold voltages of about 0.35 V for nMOS transistors and about -0.15 V for pMOS transistors at 77 K, and preserve good turn-offs with subthreshold swings of 25 mV/decade at 77 K. LICTs suppress short-channel effects more effectively, compared with conventional devices with nearly uniform dopings     

Elastic Effect on Domain Morphology and Kinetics of Spinodal Decomposition in the Tetragonal System

A method was proposed for calculation of the effect of elastic strain on spinodal decomposition in the tetragonal system. An effective free energy for the composition field was derived by eliminating elastic fields which are coherently induced by composition inhomogeneities It was shown that anisotropic long-range interactions between composition fields play a major role in determining both the domainmorphology and domain growth law of spinodal decomposition with the coherence of the lattice. Computers simulations were performed on the basis of a two-dimensional model by taking into account those long-range interactions. The results demonstrated the appearance of lamella structure and its coarsening in the late stage of the phase separation The calculation for the TiO₂-SnO₂ system showed slow coarsening due to the anisotropic elastic long -range interactions The asymptotic growth of the lamella size was described by λα tⁿ, where n is 0.18.     

The enhanced immunosuppressive efficacy of newly developed liposomal FK506 in canine liver transplantation

Local delivery of immunosuppressants to the graft and lymphatic tissue is a potential appraoch to enhance the immunosuppressive efficacy and to alleviate systemic adverse effects simultaneously. By taking advantage of this method, we developed liposomal FK506. Previous pharmacokinetic study of liposomal FK506 indicated increased FK506 levels in the liver and spleen. Because the liver is the site of the allograft in liver transplantation and the spleen is a major lymphoid tissue, we hypothesized that liposomal FK506 would increase immunosuppressive efficacy in liver transplantation. We evaluated this hypothesis in a canine model. Orthotopic liver transplantation was performed using beagle dogs, and the recipients were divided into the following groups: group I, no immunosuppression (n = 5); group II, 0.05 mg/kg/day of FK506 i.v. in a commercially available i.v. formulation for 14 days (n = 5); and group III, 0.05 mg/kg/day of FK506 i.v. in a liposomal formulation for 14 days (n = 5). All recipients in group I died within 2 weeks. Recipients in group II died within 33 days. In contrast, three recipients in group III survived for more than 200 days (P < 0.05 versus group I or group II). In DNA analysis, splenocyte proliferation activity in group III was significantly suppressed in comparison with group II. These results suggest that liposomal FK506 markedly increase the immunosuppressive efficacy of FK506 in liver transplantation. A local immunosuppressive effect in the grafted liver and significant suppression of splenocyte proliferation might contribute to enhancement of the immunosuppressive efficacy of liposomal FK506.     

Degrees of freedom of the estimate of the two-sample variance inthe continuous sampling method

The two-sample variance, the frequency stability measure in the time domain, is defined in terms of the infinite time average. The estimate of the variance obtained from a finite data set must be accompanied by a confidence interval. Theoretical equations are derived for the variance or degrees of freedom in the chi-square distribution for the continuous sampling method to make more efficient use of a finite set of sampled time data. The results are plotted for degrees of freedom and show that there is considerable improvement in the phase modulation (PM) noise compared with the results for τ-overlap sampling, because of an increased number of τ-averaged frequency samples to be obtained from the time data. For white, flicker, and random-walk frequency modulation (FM) noise the improvements converge to about 100, 30, and 4%, respectively. The reasonableness of the assumption of stationarity of the random process is discussed     

High-Pressure Hot Isostatic Pressing of Synthetic Mica

Powder compacts of synthetic mica (fluorphlogopite) encapsulated in a boro-silicate glass tube were isostatically hot-pressed using high-pressure-high-temperature hot isostatic pressing equipment with Ar gas and a Mo heater. Synthetic mica was isostatically hot-pressed, while retaining the composition and structure of the starting material, to 96.8% of theoretical density without additives at 500 MPa and 700°C for 3 h.