Learning high active

Using organometallic chemistry we have begun to learn how to synthesize highly active catalysts for the polymerization of olefins. At this stage, however, the art is in a primitive state and rather empirical. We have seen that a few ligands favor polymerization but that the majority do not. It is hoped that fundamental studies of the type described here for the system... 

So far, there has been only one example of a successful asymmetric catalyzed reaction with an enantiopure carbocation-based salt. In this section it was possible to learn, that a good understanding of a catalyzed reaction is necessary and that possible achiral side reactions have a critical negative influence. Nevertheless, carbocations can be highly active catalysts. However, this makes their application... 

At about the same time, the first information was received about product failure after continuous and exclusive use. The investigation of the pathogen populations of such fields yielded highly resistant strains (28, 29, 40), whereas so far no field resistance has been reported for cymoxanil or fosetyl. Thus, in contrast to the favorable results of a broad range of model studies, resistance had appeared very fast under field conditions. The lesson to be learned from this experience is that results of model studies have to be used with caution. Model studies must include the use of chemical mutagens and highly active, systemic fungicides should be used as if a risk of resistance exists until their mode of action is known. 

It has been suggested that the more easily the dioxetane ring can be puckered, the lower its thermal stability. This could be the reason for the high activation energies of cyclobutadienedioxetane (Entry 23 in Table 4) and diadamantylidenedioxetane (Entry 30 in Table 4). However, why should the tetraethyldioxetane (Entry 25 in Table 4) be more planar and more rigid than tetramethyldioxetane (Entry 19 in Table 4)7 Clearly, we do not as yet understand the thermal stability of 1,2-dioxetanes and much has yet to be learned. X-ray structure data would seem important on this problem. 

A learning organization activates the experience potential by systematic monitoring of processes with scientific-based methods for improvement of replicated operations and detailed instructions for operating forces (workers, machines, etc.) to achieve high performance (time, cost, quality) in socio-technical manufacturing systems. 

Discriminant emalysis is a supervised learning technique which uses classified dependent data. Here, the dependent data (y values) are not on a continuous scale but are divided into distinct classes. There are often just two classes (e.g. active/inactive soluble/not soluble yes/no), but more than two is also possible (e.g. high/medium/low 1/2/3/4). The simplest situation involves two variables and two classes, and the aim is to find a straight line that best separates the data into its classes (Figure 12.37). With more than two variables, the line becomes a hyperplane in the multidimensional variable space. Discriminant analysis is characterised by a discriminant function, which in the particular case of hnear discriminant analysis (the most popular variant) is written as a linear combination of the independent variables ... 

Fundamental research in pyrotechnics is published in the US in Combustion and Flame by the Combustion Institute, and in the UK in Combustion Science and Technology and in Fuel . Germany has the new, journal, Propellants and Explosives (German Chemical Society), which is the successor to the discontinued Explosivstoffe . A necessary caveat is that these journals are strongly oriented toward combustion or propulsion so that only rarely do they yield pyrotechnic information. Likewise, the various publications of the learned societies contain much data on thermodynamics, spectroscopy, and instrumental analysis which are useful in the study of pyrotechnics. In the USSR the situation is somewhat better as Physics of Combustion and Explosion (Fizika Gorenia i Vzryva) of the Siberian Branch Academy of Sciences USSR is exclusively oriented toward subjects of interest, as several scientific institutes are primarily devoted to research in pyrotechnics. The same authors do publish also, however, in the journals of the Academy of Science USSR (of which there are several) as well as in the corresponding journals of the academies of the various republics, so that the impression is created of a high level of activity... 

Notwithstanding the Iraqi lesson learned that the possibility of undeclared nuclear activities must be taken seriously and their possible existence sought out, the concern with undeclared activities as a proliferation risk is not new and their possible existence has always been recognized, indeed, presumed, in ary serious analysis of safeguards. Even purified plutonium or highly enriched uranium metals are harmless in bulk form. Further steps, specifically fabrication into weapons components, are necessary before these materials can result in proliferation and these steps, while perhaps not demanding, are not trivial. They are necessarily presumed to exist if the diversion of separated plutonium or HEU is discovered, since no reliable means for their detection are available. 

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