Other experimental studies

In addition to the work reviewed above, a variety of other studies of polymer tracer diffusion appear in the literature. These include papers whose experimental foci are not the same as those of the papers examined above, or which are not amenable to 

used fluorescence methods to track the motion of labeled DNA molecules(54). They determined the mean-square displacement as a function of time for labeled molecules of different length in solutions of unlabeled DNA. Smith, et al. propose that they have confirmed the reptation model. Their claim rests on measurements indicating that (i) very highly stretched DNA chains relax as though they were confined to tubes, (ii) Ds M for nondilute labeled chains, and (iii) a scaling-law concentration dependence Ds is seen. 

demonstrate the use of mixed solvents to index-match a polymer component (57,58). Their solvents were a-chloronaphthalene toluene mixtures. Almost perfect isoretractive conditions were obtained between solvents and matrix polymer by tuning the temperature as well as the solvent composition. Matrix motions were made visible with moderate changes in the solvent composition. When tracer chains were much larger than matrix chains, spectra exhibited an intense slow mode and a much weaker fast mode both modes persisted to small scattering angles. The slow mode F did not depend on c as strongly as r] did. 

The use of PFGNMR to examine diffusion of protonated polystyrenes in deuter-ated polystyrene matrices was shown by Cosgrove and Griffiths(59). Measurements involving even limited ranges of Ds demonstrated that Ds declines as c, P, or M are increased, except that Ds of very large probes in solutions of small matrix polymers, not at too large a concentration, depends at most very weakly on M. 

The -dependence of the decay rate F of tracer polystyrene in polymethylmethacrylate benzene was measured by Numasawa, et a/.(60). The value of V/q increases at large q, as also seen for dilute polymers in simple solvents as discussed in Chapter 11. The effect of a phase transition on Ds was observed by Russo, et al, who examined poly(y-benzyl-a,L-glutamate) pyridine(61). An isotropic-cholesteric liquid crystal phase transition occurs for this rodlike polymer at elevated c. The value of Ds c) increases dramatically at the transition, but on both sides of the transition Ds c) decreases as c is increased. 

---

Experimental results from Chen (1968), Holtz (1971), and Holtz and Singer (1968, 1969) more or less confirmed the validity of Holtz s maximum boiling suppression theory, while some other experimental studies by Deane and Rohsenow (1969), Schultheiss and Smidt (1969) and Kottowski and Grass (1970) did not confirm. This disagreement of experimental results was explained by Dwyer (1976), along with the details of all the experiments. 

Knowledge of the sample pressure is essential in all high-pressure experiments. It is vital for determinations of equations of state, for comparisons with other experimental studies and for comparisons with theoretical calculations. Unfortunately, one cannot determine the sample pressure directly from the applied force on the anvils and their cross-sectional area, as losses due to friction and elastic deformation cannot be accurately accounted for. While an absolute pressure scale can be obtained from the volume and compressibility, by integration of the bulk modulus [109], the most commonly-employed methods to determine pressures in crystallographic experiments are to use a luminescent pressure sensor, or the known equation of state of a calibrant placed into the sample chamber with the sample. W.B. Holzapfel has recently reviewed both fluorescence and calibrant data with the aim of realising a practical pressure scale to 300 GPa [138]. 

In subsequent research, it turned out that two-state reactivity can also provide a concept for the understanding of oxidation reactions way beyond the scope of gas-phase ion chemistry and can actually resolve a number of existing mechanistic puzzles. In enzymatic oxidations involving cytochrome P450, for example, changes in spin multiplicity appear to act as a kind of mechanistic distributor for product formation [27-29], and in the case of manganese-catalyzed epoxidation reactions, two-state scenarios have been put forward to account for the experimentally observed stereoselectivities [30-32], Two-state reactivity is not restricted to oxidation reactions, and similar scenarios have been proposed for a number of other experimentally studied reactions of 3d metal compounds [33-37]. Moreover, two-state scenarios have recently also been involved in the chemistry of main group elements [38]. The concept of two-state reactivity developed from the four-atomic system FeO /H2... 

Experimentally, the described synthetic strategy was first realized by Lozinsky et al. [80,81], who studied the redox-initiated free-radical copolymerization of thermosensitive N-vinylcaprolac lam with hydrophilic N-vinyl-imidazole at different temperatures. These and other experimental studies [82 - 84] showed the universality of this approach of obtaining copolymers capable of forming nanostructures with a core-shell morphology. 

Use of antimicrobial soaps is able to reduce rates of superficial cutaneous infections substantially, as demonstrated in multiple studies.63 Other experimental studies also found a profound reduction in bacteria on the skin with use of antimicrobial soaps, but none assessed rates of infection as an outcome.60... 

Other experimental studies have mostly focused on the relationship between areal density of connecting chains and Qc or, if 2 could not be determined, on the relationship between Cjc and annealing time and temperature. 

Evidence for an enhancement by moisture of the catalytic activity of small gold particles has been provided already early on [389]. This finding and other experimental studies that followed [390-395] are particularly interesting, both intrinsically as a property of gold nanocatalysts as well as in comparison with common catalysts where the presence of moisture is found to be detrimental or... 

It has been proposed that some internalized ricin escapes directly from endosomes to the cytosol (Beaumelle et al., 1993). However, several other experimental studies indicate that the toxin first passes through the TGN and subsequently undergoes retrograde transport to the endoplasmic reticulum (ER) (Lewis and Youle, 1986 Hudson and Grillo, 1991 Iversen et al., 2001). 

No other experimental studies associated with thermodynamic data of beryllium selenites have been found. 

Other experimental studies in this area are fluorescence quenching of excited perylene by Co + ions which occurs via energy transfer in viscous and nonviscous... 

---