Thermal blooming

A number of other laser spectroscopic techniques are of interest but space does not permit their discussion. A few specialized methods of detecting laser absorption worthy of mention include multiphoton ionization/mass spectrometry (28), which is extremely sensitive as well as mass selective for gas-phase systems optically detected magnetic resonance (29) laser intracavity absorption, which can be extremely sensitive and is applicable to gases or solutions (30) thermal blooming, which is also applicable to very weak absorbances in gases or liquids (31) and... 

The critical propagation problems which are being addressed at the various research centres are Stimulated Raman scattering by air molecules thermal blooming, due to laser heating of the air electrical breakdown of the air, which could generate plasmas that attenuate the beam atmospheric turbulence, which could perturb the focusing of the laser beam. 

Ethylenebis(tetrabromophthalimide). The additive ethylenebis(tetrabromophthalimide) [41291 -34-3] is prepared from ethylenediamine and tetrabromophthabc anhydride [632-79-1]. It is a specialty product used ia a variety of appHcations. It is used ia engineering thermoplastics and polyolefins because of its thermal stabiUty and resistance to bloom (42). It is used ia styrenic resias because of its uv stabiUty (43). This flame retardant has been shown to be more effective on a contained bromine basis than other brominated flame retardants ia polyolefins (10). 

Alumina—graphite refractories, almost all continuous casting ware, have come into much greater use as continuous casting has spread in steelmaking. These refractories are used in shrouds that conduct the molten metal from the ladle to the tundish, in the subentry tubes that take the metal from the tundish to the mold, in isostatically pressed stopper rods, and in shroud tubes for slab and bloom casters. The alumina—graphite compositions are used in these products because of the thermal-shock resistance and corrosion resistance they impart to the product. 

The most important chain transfer antioxidants are phenols and aromatic amines (B-81MI11502). They act by donating hydrogen to the peroxy radical with the formation of a stable free radical which does not take part in further chain reactions (equation 4). Two amine antioxidants, used in the rubber industry, are 6-dodecyl-l,2-dihydro-2,2,4-trimethylquinoline (1) and polymeric l,2-dihydro-2,2,4-trimethylquinoline (2). Because of its polymeric structure (2) is thermally stable, has low volatility and is non-blooming, i.e. it shows little tendency to migrate. 

A technique for the determination of methylmercury in aqueous samples (natural and seawater) involved the conversion of methylmercury to gaseous methyl-ethylmercury by reaction with sodium tetraethylborate (Bloom, 1989 Bloom and Watras, 1989). The volatile derivative was purged from the solution and concentrated on a graphitic column at room temperature. The derivative was thermally desorbed from the column, and then analysed by cryogenic gas chromatography with cold vapour atomic fluorescence detection. In addition to methylmercury, labile Hg11 species could be determined (as diethylmercury) as well as dimethylmercury (which is not ethylated). The detection limit for... 

Because dark current limits the integration times obtainable at room temperature, Peltier cooling (to -150C) is used to reduce thermal population of the conduction band. In contrast to the silicon vidicon and the SIT [vide infra], where the presence of intense radiation may bloom out the entire sensor, blooming is greatly reduced with photodiode arrays even when intense lines saturate individual diodes. 

More recent studies have shown that bloom (or dull) can occur for both tempered and untempered chocolate (Lonchampt and Flartel 2004 Lonchampt and Hartel 2006). For untempered chocolate, the blooming essentially comes from the transition from low melting point polymorphs (thermally unstable crystals) to high melting point polymorphs (usually VI). During this transition, the material mobility is increased and the migration of fat crystals to the surface is facilitated. For tempered chocolate the different causes of blooming are ... 

Walter, P. and Comillon, P. (2001). Influence of thermal conditions and presence of additives on fat bloom in chocolate. Journal of the American Oil Chemists Society, 7S(9) 927-932. 

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