Forces, directional, control

As indicated by the title, these processes are largely due to the work of Ziegler and coworkers. The type of polymerisation involved is sometimes referred to as co-ordination polymerisation since the mechanism involves a catalyst-monomer co-ordination complex or some other directing force that controls the way in which the monomer approaches the growing chain. The co-ordination catalysts are generally formed by the interaction of the alkyls of Groups I-III metals with halides and other derivatives of transition metals in Groups IV-VIII of the Periodic Table. In a typical process the catalyst is prepared from titanium tetrachloride and aluminium triethyl or some related material. 

Since fluid power is efficiently transmitted and controlled, it gives freedom in designing a machine. The need for gear, cam, and lever systems is eliminated. Fluid power systems can provide infinitely variable speed, force and direction control with simple, reliable elements. 

There are some exceptions to this method. For example, it is possible to apply forces directly to the end of the cantilever rather than displacements to the sample in order to control the approach and separation of the two surfaces [29,30]. This more direct method reduces unwanted relative lateral motion between the tip and the surface. The application of direct forces in this way also has alternative uses, such as enabling sensitive dynamic measurements to be made [29],... 

Plate tectonics is a major driving force affecting Earth s surface environment. The kind and intensity of the physico-chemical parameters that control diagenetic pathways are determined to some degree directly or indirectly by plate tectonic processes. The plate tectonic environment exerts a direct control on diagenesis, whereas changes in Earth s surface chemistry induced by changes in... 

The design and operation of a bioreactor are mainly determined by biological needs and engineering requirements, which often include a number of factors efficient oxygen transfer and mixing, low shear and hydrodynamic forces, effective control of physico-chemical environment, easy scale-up, and so on. Because some of these factors can be mutually contradictory, it is difficult to directly employ a conventional microbial reactor to shear-sensitive plant tissue cultures. 

This method combines the advantages of simplicity, direct control of frequency, and minimum reliance on mathematical modeling assumptions. It differs from other embodiments of the direct-force approach (4), (5) in the means for reacting the forces applied to the sample and in the techniques for measuring the imposed force and the resultant shear deformation. Described in this article are the test configuration, the principle of operation, the method of data reduction, typical measurements, consistency checks, and an application of measured data. 

The EC Council Regulation Number 793/93 on the evaluation and control of the risks of existing substances was adopted on the 23 March 1993, and was published in the Ojf. J. Eur. Comm, on 5 April 1 3 [28]. Its provisions enter into force directly in all EC countries 60 d after publication, ie, on 4 June 1993. 

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