Acid temperature control target temperatures

The amplification reaction is carried out in a single sample tube, which is placed into a thermocycler. The sample tube contains (1) an excess of two primers, i.e. oligonucleotides, that are complementary to the ends of the targeted nucleic acid region, (2) the enzyme DNA polymerase, (3) an excess of the four deoxynucleotide triphosphates (dATP, dCTP, dGTP and dTTP) (4) the template DNA, i.e. the DNA sample that is to be amplified and (5) a buffer to maintain the correct pH and to supply ions such as Mg + their are necessary for the reaction. The reaction takes place in three temperature-controlled steps (Fig. 6.2). 

Acetylation of cellulose is a highly exothermic reaction using acetic anhydride and acid catalyst. Therefore, it is necessary to control the temperature during acetylation, or the rate of depolymerization will become excessive resulting in a loss of target viscosity. However, the extent of cooling needed depends on the particular process. 

There are numerous modified conditions of the acetic acid acetylation system practiced commercially. But the basic principles are the same. The objective in all of the commercial processes is to produce a clear, gel-free, acid dope having target viscosity. Some of the main processing factors are catalyst level, acetic acid to anhydride ratio, initial temperature of the A mix (A mix refers to a mixture of acetic acid and acetic anhydride.), amount of excess acetic anhydride, the equipment used to agitate the reaction medium, the extent of jacket cooling to control the exotherm, peak temperature (the maximum temperature reached during the acetylation), and the temperature-time profile for the acetylation. 

Ethylene-propylene-diene terpolymers (EPDM), with their inherent complexity in structural parameters, owe their tensile properties to specific structures dictated by polymerization conditions, among which the controlling factor is the catalyst used in preparing the polymers. However, no detailed studies on correlation between tensile properties and EPDM structures have been published (l,2). An unusual vulcanization behavior of EPDMs prepared with vanadium carboxylates (typified by Vr g, carboxylate of mixed acids of Ccj-Cq) has been recently reported Q). This EPDM attains target tensile properties in 18 and 12 minutes at vulcanization temperatures of 150 and l60°C respectively, while for EPDMs prepared with V0Cl -Et3Al2Cl or V(acac) -Et2AlCl, about 50 and 0 minutes are usually required at the respective vulcanization temperatures, all with dieyclopentadiene (DCPD) as the third monomer and with the same vulcanization recipe. This observation prompted us to inquire into the inherent structural factors... 

For MS work, the electron impact (El) mode with automatic gain control (AGC) was used. The electron multiplier voltage for MS/MS was 1450 V, AGC target was 10,000 counts, and filament emission current was 60 pA with the axial modulation amplitude at 4.0 V. The ion trap was held at 200°C and the transfer line at 250°C. The manifold temperature was set at 60°C and the mass spectral scan time across 50-450 m/z was 1.0 s (using 3 microscans). Nonresonant, collision-induced dissociation (CID) was used for MS/MS. The associated parameters for this method were optimized for each individual compound (Table 7.3). The method was divided into ten acquisition time segments so that different ion preparation files could be used to optimize the conditions for the TMS derivatives of the chemically distinct internal standard, phenolic acids, and DIMBOA. Standard samples of both p-coumaric and ferulic acids consisted of trans and cis isomers so that four segments were required to characterize these two acids. The first time segment was a 9 min solvent delay used to protect the electron multiplier from the solvent peak. 

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