External Generation Methods

The problem with external generation is, of course, as remarked previously, that the finite time between creating the radical at the electrode, mixing the solution, and pumping it to the ESR cavity restricts the technique to rather long-lived species. This problem was alleviated as much as possible given 

FIGURE 2. The ex situ flow cell of Albery is based on a tube electrode located immediately upstream of the ESR cavity. 

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Method for the external generation of oxidizing and reducing agents in coulometric titrations. 

Quantitation was performed in all cases using the external calibration method. A series of standards were injected and the responses plotted against their known concentrations. Peak responses in samples were compared with the calibration plots to obtain the amount found (nanograms). A fresh calibration plot was generated with each analytical set of samples. 

The methods for external generation of reactive intermediates are similar to those used in gas-phase experiments, that is, flash vacuum pyrolysis, passing a... 

While the reaction of excited state organic matter with oxygen is the main source of many ROS in the photic zone, processes responsible for the removal of some ROS are less clear, especially when they involve DOM (Figure 1). In this chapter, we will discuss some of the processes that result in the formation and loss of ROS in marine and fresh water ecosystems, and the potential effects of externally generated ROS (i.e., photoproduced outside the cell in the surrounding water) on aquatic organisms. Intracellular production of ROS and the resultant oxidative stress that they impose on aquatic organisms is beyond the scope of this chapter and will not be discussed (see recent reviews by Josephy [37] and Vincent and Neale [34]). Analytical methods to detect these species will also not be discussed since they have been critically reviewed elsewhere [4,9,38]. 

However, we concentrate here on the generation methods in which we are able to get directly the FD quantum state desired. Namely, we shall describe the models involving quantum nonlinear oscillator driven by an external field [11-13,22]. For this class of systems we are able to get the quantum states that are very close for instance, to the FD coherent states [2,3] or to the FD squeezed vacuum [10]. 

Method 1 External Generation of Hydrogen JACS 75,215(1953) This method reduces the solvent volume in the reducing flask for large-scale work. Add IM NaBH in water to an aqueous HCl or acetic acid solution containing a little CoClj, if necessary for a rapid rate. 

Chiral cychc and acyclic allylsulfoxonium ylides are generated from sulfoxonium-substi-tuted y,8-unsaturated a-amino acids (method A) and 1-alkenylsulfoxonium salts (method B) upon treatment with DBU (1) [51] (Scheme 3.31). Their apphcation to the asymmetric aziridination of A-ferf-butylsulfonyl imine ester, generated either in situ (method A) or externally added (method B), affords the corresponding alkenylaziridinecarboxylate with medium to high diastereoselectivity and enantioselectivity. 

Although ions can be generated by El and Cl of compounds introduced directly into an ion trap, it might be desirable to apply other methods of ionization. Moreover, the use of an external ion source may solve the problem of self-CI during GC/ EI-ITMS analyses. Such considerations have been the basis of studies on the injection of externally generated ions into an ion trap [8]. 

Once the vector fields are constructed, they can be used to extrapolate the internal boundaries to the external boimdary. This divides the volume inside the external boundary into large pieces whose boundaries can be used as the external boundary of a standard structured grid generation method such as the area-orthogonality method. See [57] for the details and some illustrations. 

Two basic methods have been developed - electrochemical generation in the resonance cavity of the spectrometer (internal generation) and electrochemical generation outside the resonance cavity (external generation). These methods differ not only in the positioning of the electrolytic cell but also in a number of other features, which determine whether one or the other method is used in a specific instance. 

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