Species secondary

A gun is used to direct a beam of fast-moving atoms or ions onto the liquid target (matrix). Figure 4.1 shows details of the operation of an atom gun. An inert gas is normally used for bombardment because it does not produce unwanted secondary species in the primary beam and avoids contaminating the gun and mass spectrometer. Helium, argon, and xenon have been used commonly, but the higher mass atoms are preferred for maximum yield of secondary ions. 

The total reaction cross-sections of the individual primary and secondary species were derived and are compared in Table III with reactivities determined from previous electron impact studies (10, 31). 

Here, a primary ion P+ formed by the radiation field reacts with a gas molecule M to give an intermediate complex [PM +] which can either dissociate to a secondary species S + and a neutral fragment N or react with another molecule to produce another complex [PM2 + ]. The latter then dissociates into a tertiary ion T+ or propagates the chain by forming a third intermediate [PM3 + ]. A quaternary ion Q+ may result from dissociation of [PM3 + ], or the chain may continue through reaction of [PM3 + ]. Wexler and Jesse (38), on the other hand, have suggested a model which states that reactive intermediate complexes are not involved in the propagation, but rather the polymerization proceeds by chains of simple consecutive and competitive ion-molecule reactions,... 

Often, the primary photoexcited species are unstable and are converted (e.g., by chemical reaction with other solution components) to more stable secondary species, which, as a rule, still have an electrochemical potential higher than the original, unexcited species. Sometimes an entire chain of such conversions may be involved. 

Discovery of the hydrated electron and pulse-radiolytic measurement of specific rates (giving generally different values for different reactions) necessitated consideration of multiradical diffusion models, for which the pioneering efforts were made by Kuppermann (1967) and by Schwarz (1969). In Kuppermann s model, there are seven reactive species. The four primary radicals are eh, H, H30+, and OH. Two secondary species, OH- and H202, are products of primary reactions while these themselves undergo various secondary reactions. The seventh species, the O atom was included for material balance as suggested by Allen (1964). However, since its initial yield is taken to be only 4% of the ionization yield, its involvement is not evident in the calculation. 

The aqueous species included in the basis are known as basis species, while the remaining species in solution comprise the set of secondary species. 

Aj Aqueous species in the basis, the basis species Aj Other aqueous species, the secondary species... 

The independent reactions are those between the secondary species and the basis. In general form, the reactions are,... 

Fig. 3.2. Independent (solid lines) and dependent (dashed lines) reactions in a chemical system composed of a basis and four secondary species A through D. Only the independent reactions need be considered.

Taking a basis that contains H2O, H+, and HCOJ, for example, the reactions for secondary species CC>2(aq) and CO3 are,... 

It is fortunate that we do not have to consider the dependent reactions. Given Nj secondary species, there are just Nj reactions with the basis, but (Nj — Nj )/2 reactions could be written among the secondary species. The formula for the latter number, for example, is the number of handshakes if everyone in a group shook everyone else s hand. This is practical at a small party, but impossible at a convention. In chemical systems with many hundreds of species, taking the dependent reactions into account might tax even the most powerful computers. 

A goal in deriving the governing equations is to reduce the number of independent variables by eliminating the molalities nij of the secondary species. To this end, we can rearrange the equation above to give the value of ntj,... 

Similar logic gives the mass balance equations for the species components. The mass of the i th component is distributed among the single basis species A, and the secondary species in the system. By Equation 3.22, there are v, j moles of component i in each mole of secondary species Aj. There is one mole of Na+ component, for example, per mole of the basis species Na+, one per mole of the ion pair NaCl, two per mole of the aqueous complex Na2SC>4, and so on. Mass balance for species component i, then, is expressed... 

Mineral components are distributed among the mass of actual mineral in the system and the amount required to make up the dissolved species. In a system containing a mole of quartz, for example, there is (in the absence of other silica-bearing components) somewhat more than a mole of component quartz. The additional component mass is required to make up species such as Si02(aq) and IhSiO. Since vy moles of mineral component k go into making up each mole of secondary species j, mass balance is expressed as,... 

Mass balance on gas components is somewhat less complicated because the gas buffer is external to the system. In this case, we need only consider the gas components that make up secondary species ... 

Here, z/ and zj are the ionic charges on basis and secondary species. It is useful to note, however, that electroneutrality is assured when the components in the basis are charge balanced. 

To see this, we can use Equation 3.22 to write the ionic charge on a secondary species,... 

Here, Mw, Mi, Mk, and Mm give the system s composition in terms of the basis B, and my is the concentration of each secondary species Aj. 

Each entry A -, A k, or A m is a species or mineral that can be formed according to a swap reaction as a combination of the entries in the original basis. If Aj, a secondary species under the original basis, is to be swapped into basis position A (, the corresponding swap reaction is,... 

The second part of the database contains reactions for the various secondary species, minerals, and gases. These reactions are balanced in terms of the basis and redox species, avoiding (to the extent practical) electron transfer. Species and minerals containing ferric iron, for example, are balanced in terms of the redox species Fe+++,... 

Writing this relation for each secondary species q gives the matrix equation... 

Here, vwq, vtq, v q, vmq, and vpq are coefficients in the reaction, written in terms of the basis B, for surface complex Aq. We have already shown (Eqn. 3.27) that the molality of each secondary species is given by a mass action equation ... 

The detailed model was constructed as described by Carslaw et al. (1999, 2002). Briefly, measurements of NMHCs, CO and CH4 were used to define a reactivity index with OH, in order to determine which NMHCs, along with CO and CH4, to include in the overall mechanism. The product of the concentration of each hydrocarbon (and CO) measured on each day during the campaign and its rate coefficient for the reaction with OH was calculated. All NMHCs that are responsible for at least 0.1% of the OH loss due to total hydrocarbons and CO on any day during the campaign are included in the mechanism (Table 2). Reactions of OH with the secondary species formed in the hydrocarbon oxidation processes, as well as oxidation by the nitrate radical (NO3) and ozone are also included in the... 

Indirect methods for immunofluorescent detection of multiple tissue antigens in their simplest form make use of primary antibodies that are raised in different species and accordingly can be visualized with differently labeled species-specific secondary antibodies (see Sect. 8.1). However, quite often the appropriate combination of primary antibodies from different host species is not available. A general problem relates to the fact that the available primary antibodies may originate only from one species either rabbit or mouse. When primary antibodies are raised in the same host species, the secondary species-specific antibodies can cross-react with each of the primary antibodies (Ino 2004). 

The cross-reaction of secondary species-specific antibodies with primary antibodies from the same species is obviously avoided by direct (one antibody layer) methods. The direct method offers an easy way for simultaneous labeling of a pair or more antigens, even when using primary antibodies from the same species. Recently, a direct technique with primary antibodies that are covalently labeled by different fluorophores was described for a simultaneous detection of up to seven... 

The protocol for double/multiple immunolabeling using haptenylated primary antibodies is essentially the same as with primary antibodies of different IgG isotypes. These protocols can be easily customized depending on the availability of primary antibodies for your research requirements. For instance, you may have at your disposal a pair of monoclonal antibodies of the same IgG isotype, and only one of them is haptenylated. In this case, you have to carry out the immunostaining in two steps in the first step you visualize the unlabeled first primary antibody with a secondary species-specific antibody, and in the second step you can detect the second primary haptenylated antibody via another secondary antibody directed against the corresponding hapten. Should the hapten be a fluorophore, it can be visualized directly in a fluorescent microscope and you do not need the second step... 

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