Hysteretic behavior

A similar study by O Brien and coworkers utilized bilayers composed of a shorter chain diacetylenicPC (9) and DSPC or DOPC [37]. Phase separation was demonstrated in bilayers by calorimetry and photopolymerization behavior. DSC of the 9/DSPC (1 1) bilayers exhibited transitions at 40 °C and 55 °C, which were attributed to domains of the individual lipids. Polymerization at 20 °C proceeded at similar rates in the mixed bilayers and pure 9 bilayers. A dramatic hysteresis effect was observed for this system, if the bilayers were first incubated at T > 55 °C then cooled back to 20 °C, the DSC peak for the diacetylenicPC at 40 °C disappeared and the bilayers could no longer be photopolymerized. The phase transition and polymerizability of the vesicles could be restored simply by cooling to ca. 10 °C. A similar hysteretic behavior was also observed for pure diacetylenicPC bilayers. Mixtures of 9 and DOPC exhibited phase transitions for both lipids (T = — 18 °C and 39 °C) plus a small peak at intermediate temperatures. Photopolymerization at 20 °C initially proceeded at a similar rate as observed for pure 9 but slowed after 10% conversion. These results were attributed to the presence of mixed lipid domains... 

Absorption experiments for Nd2Co7 and Dy2Co7 show that the quantity AP/P is small (<0.20) for the a — / transition in each system. F is the desorption plateau pressure (in atm), and AP is the difference between the absorption and desorption plateau pressures. AP/P at different temperatures for the same hydride essentially was constant. For the 0 y transition, surprisingly, no hysteresis was observed. The hysteretic behavior of the RC03 hydrides differed somewhat from the behavior of the R2C07 hydrides in that AP/P was consistently larger for the 0 —1 y transition than for the a0 transition. For Ce2Co7, AP/P... 

Figure 68. Sweep rate-dependent micro-SQUID magnetization scans collected for [(triphos) Re (CN)3]4[Mn Cl]4 at 0.5 K showing hysteretic behavior. The outermost curve corresponds to a scan rate of0.560 T/s, and the scan rate decreases for each successive curve by a factor of 2, reaching the value of 0.008 T/s for the innermost curve. [Adapted from (214)].

Another material with molecular packing very similar to the /3-phase structure is /3"-(ET)2AuBr2. This compound was synthesized 1986 [332] and remains metallic down to at least 40mK. ESR measurements revealed a decrease of the spin susceptibility and a change of the g factor around 20 K [333]. In addition, the resistivity showed hysteretic behavior at this temperature region [333]. This suggests that an antiferromagnetic transition takes place at 20K. 

To examine the dynamical aspect of the hysteretic behavior, we consider the system geometry shown in Fig. 4. The porous material of length L in the z-direction is bounded by the gas reservoirs at z = 0 and z = L. Periodic boundary conditions are imposed on the X and y-directions. In typical experimental situations, starting from a (quasi)-equilibrium state, the external vapor pressure of the gas reservoir is instantaneously changed by a small amount, which induces gradual relaxations of the system into a new state. This geometry was used in recent work on dynamics of off-lattice models of adsorption (Sarkisov and Monson,... 

Fig. 1.6 Cantilever deflection (z - u) as a function of the tip—surface distance. The cantilever deflection is proportional to the force acting on the tip. A hysteretic behavior is clearly visible. Reproduced from [5] with permission, copyright Oxford University Press...

For SPM applications, a piezo stage must be designed to move in x-, y- and z-directions. Several types of scanners have been technically realized (Fig. 10.4). Most common is a tube scanner in configuration B. Overall, piezo materials show a reliable performance for thousands of operation hours " , however, one has to be aware of possible hysteretic behavior" and piezo creep . 

A piezo material can show a hysteretic behavior (due to internal heating) when... 

The described hysteretic behavior being realized in a broad parameter range is nevertheless not a general rule. Nonhysteretic transitions between DSs with different numbers of elementary fragments are also possible (see reference 16). 

Suzuki M (1991) Amphoteric poly(vinyl alcohol) hydrogel and electrodynamic control method for artificial muscles. In D. DeRossi, K. Kajiwara, Y. Osada, A. Yamauchi (ed) Polymer gels Fundamentals and biomedical applications. Plenum Press New York, 221-236 Suzuki A, Suzuki H (1995) Hysteretic behavior and irreversibility of polymer gels by pH change. J OiemPhys 103 4706 710... 

The redox coupling of the two hemes shows different degrees of complexity in these enzymes. Pseudomonas nautica (PnNiR) shows ideal behavior and values for heme c and heme d are -1-234 mV and +199 mV, respectively. " In contrast, PpNiR shows strong heme-heme interaction resulting in hysteretic behavior attributed to kinetically gated, conformationally dependent coopera-tit vity in two-electron transfer reactions. ... 

The hysteretic behavior plays a physiological role (8). The slow response of the hysteretic enzymes upon rapid changes of the ligand concentration results in a time-dependent buffering of certain metabolites (21). 

Recent advances in PVDF-based materials have led to the elimination of the hysteretic behavior characteristic of ferroelectrics. For this reason, these PVDF-based materials are classified as relaxor ferroelectric polymers they will be discussed under the Electrostrictive Polymers heading. 

The pattern shown in Fig. lb for increasing transport current is complicated in two ways by the addition of a changing external field. First, the current pattern shown in Fig. la tends to be superimposed upon that in Fig. lb. The second effect involves the dynamic resistivity, which is closely associated with the intrinsic magnetization for the continuum, where both the resistivity and the magnetization are related to the hysteretic behavior of applied field and current in the individual filaments. It is instructive at this point to digress briefly for a discussion of dynamic resistivity. 

The slow, nonlinear and apparently hysteretic behavior commonly observed for soils and sediments is phenomenologically and mechanistically incompatible with the linear partition model. The clear dependence of sorption properties on chemical structures and elemental compositions of SOM found by several investigators (77, 14, 19, 21-23, 32-36) confirms that SOM is in most cases neither homogeneous nor completely gel-like in character, as assumed implicitly by the linear partitioning model. 

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