It is necessary for encapsulants to have not only a suitable coefficient of thermal expansion (CTE) compatible to IC devices and a low dielectric constant to reduce the device propagation delay, but also a high thermal conductivity to dissipate large amounts of heat from power-hungry, high-speed IC and highdensity packages. Fillers such as silica have been mixed with polymers to improve their properties. Aluminum nitride (AlN) is considered as an alternative one, because it has a higher theoretical thermal conductivity of B320 W/mK 1 , a compatible CTE with silicon chips and a low dielectric constant. Commercial AlN fillers are angular in shape, because they are prepared via grinding coarse AlN powders synthesized by direct nitridation of aluminum metal and classification. The angular AlN are not expected to have high fluidity when mixed with polymers and hence low packing density. Recently, we successfully obtained single-crystalline spherical AlN fillers. Furthermore, polymer composites filled with the spherical AlN showed excellent thermal conductivity (48 W/mK) as encapsulants for dissipating the heat generated in electronic devices.

LaBa2Cu2TaO8+y crystallizes in a tetragonal unit cell with the dimensions a=3.9674(2) and c=12.052(1) Å, showing semiconductivity. In this compound, the Ta ions were found to preferentially occupy the Cu1 site between the two Ba layers in the LaBa2Cu3O7-y -type structure.

A method for the analysis of trace-level benzalkonium chloride has been established using flow injection ionspray mass spectrometry-mass spectrometry with multiple reaction monitoring. Quantification was carried out using an external standard based on peak area summation of each benzalkonium ion (C8, C10, C12, C14, C16 and C18) in the mass spectra. The multiple reaction monitoring technique provides additional specificity for identification and quantification. The quantification linear dynamic range was found to be 5.0-100.0 ng ml-1, the correlation coefficient > 0.999, and the detection limit 1.2 ng ml-1. The method was applied to quantify benzalkonium chloride on skin, which was sampled with a D-SQUAME tape from skin surface and extracted from the tape with methanol.

The autoxidation of 3,5-di-tert-butyl-4-hydroxytoluene (BHT, 1) in bar soap was investigated with ionspray tandem mass spectrometric and on-line gas chromatographic/mass spectrometric methods. The oxidation products of BHT were extracted from the bar soap surface, concentrated, and fractionated with open-column chromatography to remove the impurities. New oxidation products of BHT (BHT phenol-type dimer 7 and others) were identified with the two mass spectrometric methods. The results suggested that oxidation of BHT in bar soap occurred in a way different from that in the previous studies. In the new pathway, oxidation of BHT first generates an excited state of phenol-type dimer 4, and then this species decomposes, due to its high energy, to form dimer 7. The mechanism of oxidation is discussed. JAOCS 74, 781-786 (1997).

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