Parallel procedures

In our own preliminary studies [86] on parallel procedures under microwave-enhanced conditions, we have used the Radley s RDT 24 place PTFE carousel reaction station on the turntable of the Matsui M 169BT microwave oven. In this way, we have studied the catalytic activity of RhCl3 and Pd(OAc)2 towards the reduction or dehalo-genation of 4-bromocinnamic acid and structurally similar compounds. A nine-reaction matrix was used under microwave-enhanced conditions as illustrated in Scheme 13.9 - greatly reduced reaction times and easy optimization of reaction conditions are immediate benefits. As robotics come to play an increasingly important role in chemistry, one can immediately see more sophisticated labeling experiments being undertaken. 

Parallel procedures for the oxidation of silyl groups to hydroxy groups were developed by Fleming and Tamao. The conversion of a dimethylphenylsilyl group, which involves a specific reaction mechanism, was pioneered by Fleming. 

In the split-mix synthesis, like in other solid phase procedures, the beads behave very much like tiny reaction vessels, which do not interchange their contents with the other ones. Each of the millions of these reaction vessels preserves its content until the end of the synthesis, when they become containers of a single substance. If peptides are produced, their identity can be determined by automatic sequencing [9], It is sufficient to sacrifice a fraction of the total quantity for this purpose. All this means that the split-mix synthesis is, in fact, a parallel procedure, with unprecedented efficiency, however, leading to individual compounds. This feature of the split and mix synthesis allows screening the products in three different ways ... 

Peptides are not the only potential drug candidates. In most cases, other kinds of small organic molecules are preferred, because of their reduced susceptibility to enzymatic degradation. The split-mix method is fully applicable in the synthesis of organic libraries. Both sequential type and cyclic libraries can easily be prepared if the reaction conditions for solid phase are well developed. It has to be emphasized, however, that the advantages of the split-mix method can be fully exploited only in the case of multi-step synthetic procedures. For realization of the one-pot procedures suggested by Ugi [10], for example, the parallel procedures are better-suited. 

Subsequent oxidation in acetic acid with chloranil yielded XXVIIIa whose spectra resemble very closely those of sempervirine. A parallel procedure via the phenylhydrazone of XXVIIb which was obtained by a known series of reactions from 2-cyano-5-ethylpyridine gave first XXVIb and finally XXVIIIb isolated as perchlorate. The last was identical with fiavopereirine perchlorate of natural origin. 

At least the upper 10 to 30 cm of the core length obtained with either tool is usually adulterated in that it is not appropriate for pore water analysis. The multicorer, high-momentum gravity corer, or at least the box corer should be employed in a parallel procedure to ensure that this layer will also be included as part of the sample. It should not be overlooked that, especially in the deep sea, sampling with two different tools at the same site might imply a distance of several 100 m on the ocean floor. From this deviation considerable differences in pore water composition, and in some of the biogeochemical reactions close to sediment surface, are likely to result. Hence the specification as to same site must be acknowledged with caution. 

Glud et al. (1994) also carried out in situ incubation experiments in the upwelling area off the coast of Namibia and Angola, in a parallel procedure to their recording diffusion controlled oxygen profiles by means of microelectrodes. Thus, they were able to obtain values for the sediment s total oxygen uptake and, at about the... 

Suitable microscopic transducers of local stress state do not yet exist the means of choice for measuring the in-plane stress in solidilying coating is the deflection of it and its substrate when they are cantilevered in a smaU-scale batch approximation to the process. Payne and Vaessen with Francis and McCormick devised the versatile apparatus shown in Figure 9.16 to control temperature and solvent partial pressure and to visualize sample surface besides monitoring deflection (and mass loss in a parallel procedure). 

Mountford and co-workers have reported high-throughput synthesis and screening techniques to discover seven highly active ethylene polymerization catalysts." A library of 47 imidotitanium compounds of the formula Ti(NR)-(Me3[9]aneN3)Gl2 (R = alkyl or aryl Me3[9]aneN3 = 1,4,7-trimethyltriazacyclononane) were first prepared in array format in two steps using semiautomated parallel procedures (Equation (3)). 

For both reactor types, we describe experimental procedures that are sequences of different experiments. The first procedure is a parallel one and has to be performed in two separate reactors, Ri and Rn. Both reactors, which have an identical construction and are filled with the same amount of the same catalyst, are fed with a gas mixture of the same initial concentration, Cia, and are then allowed to reach the steady state. Ideally, in both reactors the same steady state concentration, c s, will be achieved. Next, the inlet concentration of the first reactor is instantaneously changed to Cjn+A and the response, c (t), is measured. Similarly, the inlet concentration of the second reactor is instantaneously changed from the same Ci to — A and the response, c (t), is also measured. The parallel procedure is presented qualitatively in Fig. 11.4. 

Applying Eq. (11.80) to the first reactor (Ri) in the parallel procedure, we find that... 

In the sequential procedure, the combination of experiments A and B is the same as the experiment in the first reactor in the parallel procedure. The c t) dependence is given by the same equation, Eq. (11.82) (or Eq. 11.85) and the steady-state concentration for both experimental procedures is given by Eq. (11.86). 

The difference between the results obtained by the parallel and the sequential procedure is that for the latter the sum of the trajectories is constant but depends on the perturbation value A (Eq. 11.88). For the parallel procedure, such a dependence is absent (Eq. 11.84). Furthermore, the dependence of the sum of the concentration trajectories on experiment A can be eliminated by running two sequential procedures with opposite values of A ( back-to-back ). Writing c t) and c °(t) for the concentrations during the second sequential procedure we obtain... 

This is the result of a four-step procedure consisting of two two-step sequential procedures. It is remarkable that the sum of four terms in Eq. (11.99) neither depends on time nor on A. This latter fact is also valid for the parallel procedure in the PER since in this case... 

In a parallel procedure the metallocene to be used was dissolved in one third of the MAO quantity and preactivated by standing for 15 minutes. The solution was then introduced into the reactor. The polymerization system was brought to a temperature of 70 and then kept for the desired time at this temperature. 

Finally, although we have demonstrated that D C calculations can be extremely efficient, we concede that parallelization of the method is necessary in order to make multi-point calculations routine for systems containing thousands of atoms. To this end, we have begun work on a straightforward parallelization procedure to split up the subsystem level computations across nodes on multiprocessor machines. In the very near future, it should be possible to carry out energy minimizations on small proteins in a reasonable amount of time with or without solvent present. 

The process of certification, based on examination and course work, which was introduced with the safety management training as a contribution to the demonstration of competence has proved so popular that a parallel procedure was introduced on the Project Control training the following year as part of a BR qualify initiative. The vision of this quality initiative is to support the individual s demonstration of their competence to manage a railway project by way of certificated training in the skills essential to the industry (see Figure 1). 

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