Hysteresis experiments

Hysteresis Experiments Molecular hysteresis measurements by cyclic acid-base titrations of the 

DNA-Interaction Measurements DNA interactions with fluoramides were studied by DNA-titration with the intercalator. Melting profils were obtained on Unicam SP 1800 spectrophotometer and CD spectra on a Cary Model 60 as described above under base-pairings (77). 

Biological Tests The polymers were tested as single. strands in eukaryotic and viral polymerase systems In base-paired complexes with their mate polynucleotides they were tested with regard to antiviral activities in establishing antiviral states, inducing and priming interferon. 

CT-polymerase B (DNA-dependent RNA-polymerase) was obtained from calf-thymus tissues and assayed as reported earlier (71). Activity measurements were performed in a toluen1e system, using a Liquid Scintillation Counter Mark I (Nuclear Chicago). 

AMV-Revertase (RNA-dependent DNA-polymerase) was assayed in an endogenous AMV-systern as previously described (70). Avian Myeloblastosis Virus was a kind gift of Dr. 0. l iman (Ins titute of Organic Chemistry and Biochemistry, SAV, Praha, Czechoslovakia). Measurements we re performed with a LKB-Wallace Liquid Scintillation Counter 81.000. 

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An HM-HEC monolayer at the air/aqueous interface was formed by adsorption from an aqueous solution of the polymer placed in the Langmuir trough overnight. In "stress-jump" experiments, HM-HEC monolayers were placed under rapid compression to a large degree and surface pressure was measured as a function of time after compression was stopped. (The compressional "jumps" required a minute or two to complete, and in some cases were on the order of the polymer monolayer relaxation times. See later section for discussion). In hysteresis experiments, the adsorbed monolayers were subjected to continuous compression-expansion cycles at a specific speed, while surface pressure was determined as a function of surface area. 

In a hysteresis experiment, the movable barrier would be reversed at a time, designated as t, so that the monolayer comes under an expansion process at the same speed, v. The increase of surface area causes a reduction in the surface pressure. For a reversibly adsorbed monolayer, the desorption of segments may continue during the first period of expansion until the surface pressure is reduced to its equilibrium value. On further expansion, readsorption occurs because the surface pressure is below its equilibrium value. 

Furthermore, we employ the same assumptions to describe a different set of hysteresis experiments a monolayer with surface pressure it at equilibrium is subjected to expansion at a constant speed of v cm /sec. The theoretical curves of surface pressure are plotted against area for various q-values in Figure 4. The curves show that the reduction of surface pressure decreases when the expansion rate is decreased for a given mono-layer, i.e. as q becomes more negative. In Figure 5, curves are plotted for q = -2 with the two different modes initial compression and initial expansion. Because the theoretical curves of the second and subsequent cycles in both modes almost coincide, we can expect that the surface pressure vs. area curves will be independent of how the hysteresis experiment starts after about two initial cycles. 

Toluene was subsequently poured carefully onto this same mono-layer, and after standing 20 hours, the hysteresis experiments were repeated. The results are also shown in Figure 8. In Figure 9, the dynamic behaviors of two low M.W. HM-HEC monolayers, 5-16-1-2 and 5-8-2.5-11, at air/50 ppm aqueous interfaces, both studied at 3.6 cm/min, are presented. From the relatively high speed (K 3.0 cm/min) tt-A curves, one may make the following observations In Figures 6 through 9, the effect of molecular... 

Figure 7. Dynamic behavior of HM-HEC 30-16-0.5-6 monolayer at air/10 ppm aqueous solution interface, (a) and (b) hysteresis experiments with speeds of 3.1 cm/min and 0.225 cm/min, respectively.

Figure 8. Dynamic behavior of HM-HEC 10-16-1-4 monolayer at 10 ppm aqueous solution interfaces, at air (a) and toluene (b) hysteresis experiments at compression speed of 2.71 cm/min.

Test of the Mathematical Model. In the mathematical model, behavior of the polymer monolayer was related to two parameters the degree of compression, (1-A/A ), and the ratio of the relaxation rate to the compression (expansion) rate, q. The results from three typical hysteresis experiments with three different polymers were chosen for comparison to the theory. 

Figure 9.11 Results of the scattering hysteresis experiment with an external electric field E0 a) asymmetrie coefficient ms versus E0 b) total scattering intensity f Is normalized on the scattering intensity at zero field versus E0. The direction of the arrows denote the sequence of the field changes.

Applying Equation (9.12) to the results of our scattering hysteresis experiment, we receive the seed scattering amplitude Iso as functions of the scattering angle 6S and of the external field (Figure 9.13), respectively. 

Figure 3 Hysteresis experiment for C03O4 under the binary mixture CO + O2...

The particular choice of the authors was rather to put emphasis on experimental techniques that are either specifically relevant or powerfiil with respect to ferroelectric polymers and fenoelectrets or represent recent experimental developments and trends. In this sense, room was given to nonlinear dielectric properties that can be probed by nonlinear dielectric spectroscopy and various types of hysteresis experiments. Besides a systematic description of piezoelectric and inverse piezoelectric techniques, we have added dielectric resonance spectroscopy as an all-round approach yielding elastic, piezoelectric, and dielectric properties of polymer electrets in a single dielectric measurement. 

The FORC method was originally developed to enhance the amoimt of dynamic information extracted from magnetic hysteresis experiments. " We recently proposed that the method can be further developed as an extension of traditional CV to study the dynamics of phase transitions in electrochemical adsorption. ... 

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