Preparation of polymer brush-type cellulose β-ketoesters using LiCl/1,3-dimethyl-2-imidazolidinone as a solvent

Cellulose β-ketoesters with branched alkenyl chains were prepared using cis-9-octadecenyl ketene dimer (OKD) and LiCl/1,3-dimethyl-2-imidazolidinone (DMI) as the esterifying reagent and cellulose solvent, respectively. Relationships between degree of substitution (DS) of the cellulose/OKD β-ketoesters and reaction conditions were studied in detail. The results showed that DS values of the products were controllable up to 2.1 by selecting the reaction conditions. Solution- and solid-state ¹³C-NMR analyses revealed that cellulose backbones of the cellulose/OKD β-ketoesters with DS 2.1 behave like solid in chloroform owing to strong restriction on movement of cellulose chains by the long and branched alkenyl substituents introduced. Size-exclusion chromatographic analysis showed that little depolymerization occurred on cellulose during β-ketoesterification at room temperature, and that molecules of the cellulose/OKD β-ketoesters with DS 2.1 had semi rigid-rod conformation in tetrahydrofuran. Thus, cellulose β-ketoesters with densely substituents like polymer brushes or comb-shaped polymers were prepared in this study.     

Respondents with low motivation tend to choose middle category: survey questions on happiness in Japan

Behaviormetrika - Some studies have shown low proportions of Japanese people rating their lives as happy. However, most surveys in Japan revealed that response distributions for subjective...     

Gel permeation chromatography using controlled-porosity glass. I. Polyacrylamide–formamide solution

The process of characterizing polyacrylamide and its partially hydrolyzed materials by gel permeation chromatography was examined. The use of controlled-porosity glass and formamide as the stationary phase and the eluent, respectively, resulted in chromatographic behavior in accord with the hydrodynamic volume concept for polyacrylamide fractions. The addition of a salt (KCl) to the eluent was found to retard the elution of the hydrolyzed polyacrylamide.     

ESTIMATION OF SERVICE LOADING FROM THE WIDTH AND HEIGHT OF FATIGUE STRIATIONS OF 2017-T4 A1 ALLOY

A case-study method is proposed to determine service loading from fracture surface striations. Although it is well known that striation spacing relates to the crack growth rate, it is considered impossible to determine maximum and minimum loads under service loading conditions, and which define the stress ratio R, from an analysis of the striation spacing. This paper presents a new method of determining the maximum and minimum loads which is based on the experimental fact that the relative height of a striation H to striation spacing s is strongly influenced by the stress ratio. The results of fatigue tests on 2017-T4 A1 alloy showed a definite correlation between these parameters. The difficulty of measuring striation height was overcome by taking the measurements in a scanning electron microscope after sectioning the specimens at a large inclined angle. Striations under a stress ratio R=?1 are compressed and flat, and the ratio H/s is small. With increasing R, the value of H/s becomes large. Therefore a standard laboratory test that determines the relationship between s and ΔK, and also between H/s and R enables one to estimate service loadings from fatigue fracture surfaces.     

Characteristics of germanium avalanche photodiodes in the wavelength region of 1-1.6 µm

Dark current, quantum efficiency, multiplication noise, and pulse response of germanium avalanche photodiodes with n+-p junction were studied to find an optimum structure. The dark current can be separated by graphical means into a leakage current component and a multiplied component which flows through the junction. The dark current components are also evaluated by using diodes with various diameters. The quantum efficiency and the multiplication noise are shown to be strongly affected by the n+ layer thickness. An n+ layer thickness optimized for signal-to-noise ratio is estimated from experimental and calculated results, using a figure of merit for avalanche photodiodes. The response waveform for mode-locked Nd:YAG laser shows a rise time of 100 ps and a half pulsewidth of less than 200 ps.     

Characteristics of a gallium-arsenide travelling-wave amplifier with Schottky-barrier contacts

Experimental results of the dependence of small-signal gain on bias voltages, applied to Schottky-barrier contacts which are r.f. input and output terminals of a gallium-arsenide travelling-wave amplifier are reported. In the optimum bias condition, a maximum net gain of 10 dB at 6.6 GHz in d.c. operation has been observed.