Activated dynamics

Adapted from Jia, L., et at, 1996.. S-Nitro.sohaemoglobin A dynamic activity of blood involved in va.scnlar control. Nature 380 221-226. 

The amount of fresh catalyst added is usually a balance between catalyst cost and desired activity. Most refiners monitor the MAT data from the catalyst vendor s equilibrium data sheet to adjust the fresh catalyst addition rate. It should be noted that MAT numbers are based on a fixed-bed reactor system and, therefore, do not truly reflect the dynamics of an FCC unit. A catalyst with a high MAT number may or may not produce the desired yields. An alternate method of measuring catalyst performance is dynamic activity. Dynamic activity is calculated as shown below ... 

For example, a catalyst with a MAT number of 70 vol% and a 3.0 wt% coke yield will have a dynamic activity of 0.78. However, another catalyst with a MAT conversion of 68 vol% and 2.5 wt% coke yield will have a dynamic activity of 0.85. This could indicate that in a commercial unit the 68 MAT catalyst could outperform the 70 MAT catalyst, due to its higher dynamic activity. Some catalyst vendors ha% c begun reporting dynamic activity data as part of their E-cat inspection reports. The reported dynamic activity data can vary significantly from one test to another, mainly due to the differences in feedstock quality between MAT and actual commercial application. In addition, the coke yield, as calculated by the MAT procedure, is not very accurate and small changes in this calculation can affect the dynamic activity appreciably. 

Dynamic Activity is an indication of conversion per unit coke using data from the MAT laboratory. 

The important feature in the SL method is that there is always a buffer of dormant SL region separating any two dynamically active regions, which eliminates the difficulty associated with synchronizing events and resolving conflicts at the boundaries between processors. For a finite cycle time, the SL method is not exact, but if the cycle time is comparable to or shorter than a typical reaction time, it is extremely accurate. A detailed discussion and demonstration of the requirements for accuracy in the case of KMC can be found in ref. 35. 

As must be clear by now, drug development is a very dynamic activity with high interests at stake. For patients this is the availability of more effective or better tolerated treatments, for pharmaceutical companies it is the return on the huge investments that are needed to discover and develop new drugs. It is not difficult to predict that there will be continuous attempts to speed-up development times and to improve the quality and efficiency of the development... 

Remineralisation occurs when partly dissolved crystals are induced to grow by precipitation of the mineral-forming ions Ca + and POl". This is a natural process that occurs as a result of the concentration of these ions in saliva [23] and it serves to oppose the demineralising effects of caries. The processes involved are complex [24] and involve dynamic activity at the interface between the tooth, the saliva, the pellicle and the plaque. Fluoride plays a role in enhancing these processes, and though this is not the only contribution that fluoride makes to protect the tooth from caries, it is nonetheless an important one. 

Salamone, J.D. (1996) The behavioral neurochemistry of motivation methodological and conceptual issues in studies of the dynamic activity of nucleus accumbens dopamine. / Neurosci Methods 64 137-149. 

If one can understand what the basic parameters of the reactants and the surface are that determine the reaction dynamics (activation barriers etc.) then given a micro-kinetic model one has a knowledge of the factors determining the catalytic activity of the catalyst. 

Figure 5.13. In situ atomic-resolution ETEM image of Pt/titania catalyst (a) finely dispersed Pt particles (b) in situ real-time dynamic activation in hydrogen imaged at 300 C. The 0.23 nm (111) atomic lattice spacings are clearly resolved in the Pt metal particle, P and (c) the same particle imaged at 450 C, also in H2. SMSI deactivation with a growth of a Ti-oxide overlayer (C), and the development of nanoscale single-crystal clusters of Pt, with atomic resolution (arrowed). (After Gai 1998.)...

Fig. 2.9. Empirical energy diagram for DMABN in n-butyl chloride (energetics based on room-temperature fluorescence band maxima and on activation energies). In the small-barrier case, E. is to be viewed as a dynamical activation energy resulting from solvent viscosity. The Franck-Condon ground state (after emission from A ) is anomalously destabilized (large E3).

Garcia-Cardena G, Fan R, Shah V, Sorrentino R, Cirino G, Papapetropoulos A, Sessa W. 1998. Dynamic activation of endothelial nitric oxide synthase by Hsp90. Nature 392 821-824. 

Venus and Titan have been upgraded to Category II in Schulze-Makuch and Irwin (2004) due to recent insights on their dynamic activity, planetary/lunar history, and presence of organic compounds. 

A theory has been developed which translates observed coke-conversion selectivity, or dynamic activity, from widely-used MAT or fixed fluidized bed laboratory catalyst characterization tests to steady state risers. The analysis accounts for nonsteady state reactor operation and poor gas-phase hydrodynamics typical of small fluid bed reactors as well as the nonisothermal nature of the MAT test. Variations in catalyst type (e.g. REY versus USY) are accounted for by postulating different coke deactivation rates, activation energies and heats of reaction. For accurate translation, these parameters must be determined from independent experiments. 

The use of in analyzing data from pilot units was proposed by Krambeck in the early 1970 s and has been used in Mobil since then. More recently, the same concept has been published in the open literature, and the reciprocal of kg is defined as UOP dynamic activity (14). The dynamic activity is now popularly used in the FCC literature, and is even used to correlate catalyst performance with fundamental catalyst parameters such as unit cell size (15). In this paper, however, we will use the Mobil defined kg parameter. 

In addition to being the source of dynamical activities, the elemental contraries, like the soul, enform matter. At least, such a view, though it has been challenged in the twentieth century, is to be sure the historically dominant one.10 For the moment, however, I won t defend the view but merely assert it, since I discuss this very issue in the next chapter. 

II. For all x, x is capable of performing those activities characteristic of Fs iffx has matter enfbrmed by a fbrm-m, i.e. a source of dynamical activities, that is ordered toward F-ness. 

Additionally, if one progresses along the conceptual path introduced by the idea of form-m, one will arrive at the concept of the unmoved mover. A form-m is a principle of dynamical activities. Now, in the material world, a gap exists between the principle and the activity—the actualizing of the activity need not always occur. Various reasons for this gap might be proposed but the most Aristotelian reason would be the fact that a principle of dynamical activities must exist in matter. Matter, so to speak, holds form back. Its presence must be overcome. A principle of activity enmeshed in matter must expend an effort to realize the activity for which it is a principle. And without an eternal source of power for such an effort, the effort will not always be forthcoming. 

---