Diffusional behavior of multi-arm star polymers by H pulsed field gradient spin-echo NMR method

The diffusional behavior of multi-arm star-shaped p(tBMA) was investigated in a concentration range from dilute to semidilute region with ¹H pulsed field gradient spin-echo NMR (PFGSE-NMR). An 142-arm star-shaped p(tBMA) showed two diffusional mode, which reflected the coexistence of liquid ordering phase and liquid phase near the ordering transition. On the other hand, for star-shaped p(tBMA) with 55 arms showed a single diffusional relaxation in all concentration ranges during observation time. In the semidilute region, the relationship between the diffusion coefficient against the polymer concentration was affected strongly not only the arm number but also liquid ordering structure.     

Reliability of AllnAs/lnGaAs/lnP HEMT with WSi ohmic contacts

We have investigated the degradation mechanism of Al_0.48In_0.52As/In_0.53Ga_0.47As/ InP high electron mobility transistors (HEMTs) using WSi ohmic electrodes. Cross-sectional transmission electron microscopy (TEM) observation and en-ergy dispersive x-ray (EDX) analysis reveal impurities diffusion of gate electrode (titanium: Ti) and fluorine (F) in the AlInAs layer after a high temperature (T_a = 170°C operating life test for 500 h. The decrease of drain current (I_ds) during life test shows linear dependence on square root of aging time. It suggests that the degradation is controlled by a diffusion mechanism. Hence, the estimated degradation mechanism of this device is related with decrease of carrier concentration in the epitaxial layer by these diffused impurities. On the other hand, TEM and EDX show no degradation of WSi/InGaAs interface after aging. Therefore, the WSi electrode for this type of HEMT demonstrates excellent high stability under the accelerated operating life test.     

Diffusion process of amino acids in polymer supports for solid‐phase peptide synthesis as studied by pulsed‐field‐gradient spin‐echo proton nuclear magnetic resonance

The diffusion coefficient (D) values of tert‐butyloxycarbonyl‐glycine, tert‐butyloxycarbonyl‐L ‐tryptophan, tert‐butyloxycarbonyl‐L ‐phenylalanine (Boc‐Phe), and 9‐fluorenylmethoxycarbonyl‐L ‐phenylalanine in Merrifield polystyrene (MPS) gels, poly(ethylene glycol)‐grafted polystyrene (PEG–PS) gels, and crosslinked ethoxylate acrylate (CLEAR) gels, as used in solid‐phase peptide synthesis, were determined by the pulsed‐field‐gradient spin‐echo ¹H‐NMR method. From these experimental results, it was found that the amino acids in MPS gels, PEG–PS gels, and CLEAR gels with N,N‐dimethylformamide‐d₇ (DMF‐d₇) as a solvent had multidiffusion components within a measurement timescale of 10 ms. The D value of Boc‐Phe in polystyrene gels (1% divinylbenzene crosslinked) with tetrahydrofuran‐d₈ was much larger than that in the same gels with DMF‐d₇. Furthermore, the required time in which an amino acid transferred from a reactive site to a reactive site was estimated, within which the solvents and amino acids in the polymer supports diffused in the swollen beads.© 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 413–421, 2003     

Analysis of air pollution and prevalence rate of allergic diseases among elementary school children in Kawaguchi and Hatogaya city

Kawaguchi and Hatogaya City are located on the northern edge of Tokyo. We analysed between air pollution and prevalence rate of allergic diseases among elementary school children in this area. A prevalence rate of allergic diseases in 1996 May and June was as follows; bronchial asthma 13.5%, atopic dermatitis 24.5%, allergic rhinitis and/or conjunctivitis 22.8%, urticaria 12.4%, food allergy 7.8% and drug allergy 2.2%, respectively. Air pollution of this area was analysed to check the levels of nitrogen dioxide (NO2), sulfur dioxide (SO2) and suspended particulate matters (SPM). NO2 pollution was relatively high in urban area, and SPM pollution was especially high around the highways. SO2 pollution was lower than the environmental standard. No relationship was found between the prevalence rate of bronchial asthma, atopic dermatitis, allergic rhinitis and/or conjunctivitis and air pollution, but it was found that these diseases are slightly related to population density (p < 0.1, p < 0.01, p < 0.1, respectively).     

An improved kernel function computation in subsonic unsteady lifting surface theory

A new and efficient scheme is presented for evaluating the kernel function K, which occurs in the linearized theory of oscillatory airloads on a planar lifting surface in subsonic flow. Among many previous efforts of this sort, the present paper was inspired by Ueda's method [10] for computing the integral function B(X, r, k) appearing in the kernel.Firstly we point out that important are not only B but also the remaining part A of the kernel, since singularities are latent in A as well as B. Moreover, it is quite desirable to express the singularities, which often must be treated analytically, by using the original variable x₀ rather than the modified one X.The second important problem concerns with the finite continuous part $\text{K}\text{?}{}^{\mathrm{F}}$, which must be numerically evaluated efficiently. A new method for this purpose is presented.This paper is restricted to the case where the frequency is real, namely the oscillation is neutrally stable.     

Stereospecific analysis of monounsaturated triacylglycerols in cocoa butter

The enantiomeric composition of the monounsaturated triacylglycerols (TG) from cocoa butter was estimated. The monounsaturated TG were separated into three fractions by reversed-phase high-performance liquid chromatography (HPLC), and each fraction was subjected to the stereospecific analysis with chiral-phase HPLC. The results indicated that the major TG consisted of equal amounts of 1-stearoyl-2-oleoyl-3-palmitoyl-sn-glycerol (SOP-sn-TG) and POS-sn-TG (47 mol%), 1,3-distearoyl-2-oleoyl-glycerol (SOS-TG) (33 mol%), and POP-TG (19 mol%). The contents of SOP-sn-TG and POS-sn-TG are 1.30 times that of the POP-TG content, and the SOS-TG content is 1.30² times that of the POP-TG content. The term “priority factor” is proposed for the ratio of the stearoyl group/palmitoyl group, 1:30 at thesn-1 andsn-3 or 1(3)-position. It shows a distinct specificity for particular fatty acids or their Coenzyme A esters in random esterification at each position of the glycerol moiety in the biosynthesis of cocoa butter TG.     

Hydrocarbons with a homoconjugated polyene system and their monoepoxy derivatives: Sex attractants of geometrid and noctuid moths distributed in Japan

Although several sex pheromones of the family Geometridae have been characterized, investigations on Japanese species are limited. In order to obtain more information, screening using known sex pheromones and their analogs was carried out. The (Z,Z,Z)-3,6,9-triunsaturated and (Z,Z)-6,9-diunsaturated hydrocarbons with straight C¹⁹-C²¹ chains were synthesized by the Grignard coupling reaction as a key step starting from linolenic and linoleic acids, respectively. Oxidation of the homoconjugated trienes withm-chloroperoxybenzoic acid yielded a 111 mixture of three monoepoxy derivatives that could be separated by silica gel chromatography. The chemical structure of each positional isomer was confirmed using two-dimensional NMR techniques and MS measurements, which enabled characteristic fragment ions from the isomers to be identified. Field tests using lures incorporating only one of the above six hydrocarbons or nine epoxides were carried out in a forest in Tokyo. Consequently, attraction of male moths of 14 geometrid species in addition to four species in another family, the Noctuidae, was observed. It was concluded that hydrocarbons with a homoconjugated polyene system and the monoepoxy derivatives are important components of sex pheromones produced by Japanese lepidopterous insects, particularly the geometrid moths.     

Analysis of mark-formation process for phase-change media

The objective of this study was to determine the mechanism of a phenomenon peculiar to phase-change recording regarding the mark shape or mark-forming process. The following results were obtained from our simulation of mark shapes, transparency electron microscope observations, and analysis of reproduced signals. A method of calculating a mark shape by calculating the holding-time profile was devised and its appropriateness was confirmed. We found there were close relationships between the cooling pulse shape, the effective erase ratio, the reproduced signal amplitude, and the noise level, and that the temperature change when the mark edge was cooled has a great influence on the stability of the mark shape and crystallized regions     

Electroreductive block copolymerization of dichlorosilanes in the presence of disilane additives

The electroreductive polymerization of dichloromethylphenylsilane in the presence of triphenylsilyl group‐containing disilanes such as hexaphenyldisilane followed by the electroreductive termination with chlorotriphenylsilane afforded triphenylsilyl group‐terminated polymethylphenylsilane in 15–32% yield. The isolated polymethylphenylsilane (M_n = 3350 g mol^?1, M_w/M_n = 1.4) was found to react as a macroinitiator to copolymerize with dibutyldichlorosilane under electroreductive conditions producing the corresponding block copolymer (M_n = 4730 g mol^?1, M_w/M_n = 1.2) in 38% yield. The ratio of monomer units (? MeSiPh? to? BuSiBu? ) of the copolymer was determined to be 75:25 using ¹H NMR analysis, which was in good agreement with the calculated ratio (74:26) on the assumption that molecular weight of the macroinitiator was not changed. The block structure of the resulting copolymer, poly(methylphenylsilane)‐block‐poly(dibutylsilane), was also confirmed by comparing its ¹H NMR and UV absorption spectra with those of polymethylphenylsilane, polydibutylsilane and a statistical copolymer prepared by electroreductive polymerization of dichloromethylphenylsilane with dibutyldichlorosilane. This method is applicable to the preparation of other types of macroinitiator such as triphenylsilyl group‐terminated polydibutylsilane, and polydibutylsilane‐block‐polymethylphenylsilane was also obtained using this macroinitiator. Copyright © 2011 Society of Chemical Industry