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- Author or Editor: P. Richards x
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Abstract
The triazene derivative of 15-(p-aminophenyl)pentadecanoic acid, 1-[4-(15-oxopentadecanoyl)phenyl]-3,3-(1,5-pentanediyl)triazene, has been sythesized as a new substrate which is readily converted to 15-(p-iodophenyl)-pentadecanoic acid (IPP). Iodine-123-labeled IPP is prepared in 
30% yield in less than 30 min by reaction of the triazene with no-carrier added H123I, obtained by decay of123Xe. This rapid, regiospecific synthesis represents as improved method for the preparation of [123I]IPP.
Abstract
Preliminary results are described of a123Xe filled device to serve as a combination123I generator/iodination kit.123X was produced in the Brookhaven Linac Isotope Producer (BLIP) by the reaction127I(p, 5n)123Xe. The device consists of a small glass ampoule containing an internal glass breakseal and a flanged neck on which was crimped a multi-injection type septum. The ampoule contained a hydrogen sulfide atmosphere to assure that the iodine generated from the decay of the xenon was in the form of iodide. Following an adequate period for123Xe to decay (this period can be used for shipment), a needle is forced through the septum breaking the seal and residual gases are pumped off. The123I in the form of iodide can then be rinsed from the ampoule with any desired solvent or reagent added directly to the device to carry out an iodination in an enclosed environment. Preliminary results of both iodine recovery and iodinations have been promising.
Abstract
In this paper we introduce two key notions related to understanding the 
glassy state
problem. One is the notion of the excitation profile for an amorphous system, and the other is the notion of the simple glassformer. The attributes of the latter may be used, in quite different ways, to calculate and characterize the former. The excitation profile itself directly reflects the combined phonon/configuron density of states, which in turn determines the liquid fragility. In effect, we are examining the equivalent, for liquids, of the low temperature Einstein-Debye regime for solids though, in the liquid heat capacity case, there is no equivalent of the Dulong/Pettit classical limit for solids.To quantify these notions we apply simple calorimetric methods in a novel manner. First we use DTA techniques to define some glass-forming systems that are molecularly simpler than any described before, including cases which are 80 mol% CS2, or 100% S2Cl2. We then use the same data to obtain the fragility of these simple systems by a new approach, the 'reduced glass transition width' method. This method will be justified using data on a wider variety of well characterized glassformers, for which the unambiguous F
1/2 fragility measures are available. We also describe a new DTA method for obtaining F
1/2 fragilities in a single scan. We draw surprising conclusions about the fragility of the simplest molecular glassformers, the mixed LJ glasses, which have been much studied by molecular dynamics computer simulation.These ideas are then applied to a different kind of simple glass — one whose thermodynamics is dominated by breaking and making of covalent bonds — for which case the excitation profile can be straight-forwardly modeled. Comparisons with the profile obtained from computer studies of the molecularly simple glasses are made, and the differences in profiles implied for strong vs. fragile systems are discussed. The origin of fragility in the relation between the vibrational and configurational densities of states is discussed, and the conditions under which high fragility can convert to a first order liquid-liquid transition, is outlined.
