Preparation of mixed isopropyl/trimethylsilyl derivatives of boric acid, (Me3SiO)nB(OiPr)3-n(n = 1–3), and their GC-M

Boric acid was trimethylsilylated with Me₃SiCl/(Me₃Si)₂O in the presence of 2-propanol. The resulting mixture was analysed by using a combi     

Resistivity vs. Magnetic structure in multilayers

Mössbauer spectroscopy has been applied to study the interface magnetic propertics of multilayers exhibiting large magnetoresistance (MR) effects; Fe/Cr and Cu/Co/Cu/Fe. The temperature dependence of the local magnetization for the interface atom layers is found to be much smaller than that of the MR effect.     

Complexing ability of N-oligoethylene glycol monoaza crown ethers with sodium and potassium cations

N-Oligoethylene glycol monoaza crown ethers were prepared, and the notable effect of oxyethylene oxygen atoms of the side chain on complexing ability with sodium and potassium cations was confirmed.     

Identification of gas emanated from human skin: methane, ethylene, and ethane.

We investigated whether methane, ethylene and ethane gas can be detected in gas emanating from human skin, which is called skin gas. Skin gas was collected with a homemade stainless-steel trap system, which was cooled with liquid nitrogen, and analyzed with a gas chromatograph fitted with a flame ionization detector (FID). Skin-gas samples were obtained by covering a hand for 30 min with a polyfluorovinyl bag in which pure helium gas was introduced. The bag, the trap system and GC were set up online to avoid any contamination by air. Methane, ethylene and ethane in skin gas were successfully collected at an average amount emanated for 30 min (from ten subjects) of 150 +/- 63, 20 +/- 11 and 17 +/- 8 [mean +/- SD] pg/cm2, respectively.     

Reversed-phase liquid chromatography of the twenty-two tetrachlorodibenzo-p-dioxin isomers on pyrenylethyl- and octadecylsilylated silica gel columns

To purify the tetrachlorobenzo-p-dioxins synthesized for chemical and biological reference standards, reversed-phase liquid chromatography on pyrenylethyl- and octadecylsilylated stationary phase (PYE and C18) columns was employed with 100% methanol. The pyrenylethyl phase satisfactorily separated isomers resulting from mixtures of reaction products which had not been adequately separated with conventional C18 or silica gel. The use of a single chromatographic mode, liquid chromatography, and a single mobile phase with columns of distinctly different properties, C18 and PYE, separates 20 of the 22 isomers from each other and from the 1246/1249 pair. (The observed properties of the two columns afford insight into steric and polarizability differences among isomers.)     

Kinetics of radiation-induced grafting reactions. I. Polyethylene–styrene systems

By means of bromine labeling and ESR, the grafting reactions of styrene onto preirradiated polyethylene have been investigated. Not all the radicals produced by irradiations participate in grafting reactions all together, but they are rendered active bit by bit by the swelling of crystalline parts of polyethylene. The growing rates for polystyryl graft chains at 20°C decrease from 4 monomer units/active site/sec to one-fourth the initial value after 100 min. On the contrary, the average lifetimes increase from <10³ sec to >2.6 × 10³ sec. The number-average molecular weight of graft chains also increases with reaction times and rises to 3.5 × 10⁵ after 90 min at 20°C.     

Substrate effect on the melting temperature of thin polyethylene films

Strong dependence of the crystal orientation, morphology, and melting temperature (Tm) on the substrate is observed in the semicrystalline polyethylene thin films. The Tm decreases with the film thickness decrease when the film is thinner than a certain critical thickness, and the magnitude of the depression increases with increasing surface interaction. We attribute the large Tm depression to the decrease in the overall free energy on melting, which is caused by the substrate attraction force to the chains that competes against the interchain force which drives the chains to crystallization.     

Nickel-catalyzed indium(I)-mediated double addition of aldehydes to 1,3-dienes

In the presence of InI, Ni(acac)2 and PPh3, several 1,3-dienes were reacted with two molecules of aldehyde to give the corresponding 1,4- and 1,6-diols. The regioselectivity of the 1,4-/1,6-diol was efficiently regulated by the addition of water; the 1,6-diol was obtained selectively in dry THF, whereas the 1,4-diol was obtained predominantly in DMI containing a small amount of water.