Modus operandi

There is much evidence that weak links are present in the chains of most polymer species. These weak points may be at a terminal position and arise from the specific mechanism of chain termination or may be non-terminal and arise from a momentary aberration in the modus operandi of the polymerisation reaction. Because of these weak points it is found that polyethylene, polytetrafluoroethylene and poly(vinyl chloride), to take just three well-known examples, have a much lower resistance to thermal degradation than low molecular weight analogues. For similar reasons polyacrylonitrile and natural rubber may degrade whilst being dissolved in suitable solvents. 

It is commonly found that polymers are less stable particularly to molecular breakdown at elevated temperatures than low molecular weight materials containing similar groupings. In part this may be due to the constant repetition of groups along a chain as discussed above, but more frequently it is due to the presence of weak links along the chain. These may be at the end of the chain (terminal) arising from specific mechanisms of chain initiation and/or termination, or non-terminal and due to such factors as impurities which becomes built into the chain, a momentary aberration in the modus operandi of the polymerisation process, or perhaps, to branch points. 

All acyclic and carbocyclic guanosine analogues depicted in Fig. 1 follow the same modus operandi as exemplified for acyclovir (ACV) in Fig. 5, in that they need three phosphorylations to be converted to their active metabolite, the triphosphate form, which then interacts with the target enzyme, the viral DNA polymerase, as a chain terminator (De Clercq 2002). In its DNA chain-terminating... 

The measurement has noise superimposed on it, so that the analyst decides to repeat the measurement process several times, and to evaluate the mean and its confidence limits after every determination. (Note This modus operandi is forbidden under GMP the necessary number of measurements and the evaluation scheme must be laid down before the experiments are done.) The simulation is carried out according to the scheme depicted in Fig. 1.19. The computer program that corresponds to the scheme principally contains all of the simulation elements however, some simplifications can be introduced ... 

What have we learned about the modus operandi of the Department of Defense that should prove useful as we move through a transition to a new era for support of science and engineering in the universities First, the Department of Defense, despite its mission-oriented character, has had... 

Notwithstanding the laborious endeavors that have been made of late years to enable us to foretell the metamorphoses which a given compound should sustain under the influence of different chemical agents, still it must be admitted that we have by no means succeeded in establishing antecedently, with absolute certainty, the modus operandi of a decomposition. 11... 

Expatiate its efficacy and advantages in a busy quality assurance laboratory with a neat-labelled diagram and its modus operandi. 

What are the two types of Flame Photometers commonly used in Flame Emission Spectroscopy (FES) Describe them individually with a neat layout and explain their modus operandi. 

Fig. 18.1 Modus operandi of n-type (top left), p-type (top right), and tandem DSSCs (bottom). SA and SD are acceptor and donor dyes, respectively. Ef, cb, and vb are Fermi level, conduction band, and valance band, respectively, e and h+ refer to electron and hole current, respectively.

To detail DSSC technologies, Fig. 18.1 illustrates the modus operandi of DSSCs. Initially, light is absorbed by a dye, which is anchored to the surface of either n- or p-type semiconductor mesoporous electrodes. Importantly, the possibility of integrating both types of electrodes into single DSSCs has evoked the potential of developing tandem DSSCs, which feature better overall device performances compared to just n-or p-type based DSSCs [19-26]. Briefly, n-type DSSCs, such as TiOz or ZnO mesoporous films, are deposited on top of indium-tin oxide (ITO) or fluorine-doped tin oxide (FTO) substrates and constitute the photoanodes. Here, charge separation takes place at the dye/electrode interface by means of electron injection from the photoexcited dye into the conduction band (cb) of the semiconductor [27,28]. A different mechanism governs p-type DSSCs, which are mainly based on NiO electrodes on ITO and/or FTO substrates... 

The ability of metal ions to accelerate the hydrolysis of a variety of linkages has been a subject of sustained interest. If the hydrolyzed substrate remains attached to the metal, the reaction becomes stoichiometric and is termed metal-ion promoted. If the hydrolyzed product does not bind to the metal ion, the latter is free to continue its action and play a catalytic role. The modus operandi of these effects is undoubtedly as a result of metal-complex formation, and this has been demonstrated for both labile and inert metal systems. Reactions of nucleophiles other than HjO and OH will also be considered. 

More importantly, as he confided in his Note 35, his real modus operandi was devoted to instigating a new reality based on an anarchic system of playful physics which was to be created by slightly distending the laws of physics and chemistry. That, as told in different terms than by Jarry, namely by Albert Poisson and Antoine-Joseph Pemety, was exactly what I Alchirnie had already done. 

In some cases, however, the modus operandi is modified. In the oxidation of hydriodic acid with chromic acid, the data indicate that while liberation of iodine takes place, the vanadous or hypovanadic salt employed as the catalyst also undergoes oxidation to vanadate.2 The vanadium compound here belongs to the class of catalysts known as inductors, and the reaction is comparable to the oxidation in aqueous solution of sodium sulphite with sodium arsenite, whereby both sodium sulphate and sodium arsenate are produced. 

Shown in Figures 5-7 are the redox pathways for xanthine oxidase, sulfite oxidase, and nitrate reductase (assimilatory and respiratory), respectively. These schemes address the electron and proton (hydron) flows. The action of the molyb-doenzymes is conceptually similar to that of electrochemical cells in which half reactions occur at different electrodes. In the enzymes, the half reactions occur at different prosthetic groups and intraprotein (internal) electron transfer allows the reactions to be coupled (i.e., the circuit to be completed). In essence, this is the modus operandi of these enzymes, which must be determined before intimate mechanistic considerations are seriously addressed. 

Figure 5 The modus operandi of xanthine oxidase (one subunit) showing the sites of substrate oxidation and oxygen reduction and the flow of electrons and protons (H+).

Figure 6 The modus operandi of sulfite oxidase (one subunit) showing the site of sulfite oxidation and the electron and proton (H+) flows, including the link to cytochrome c oxidase, and the activation of dioxygen, the terminal electron acceptor.

Figure 7 The modus operandi of nitrate reductase (a) assimilatory nitrate reductase (plants, fungi, algae) (b) respiratory (dissimilatory) nitrate reductase (.Escherichia coli, Pseudomonas).

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