Cell oscillations, period

Figure 7 shows a similar output for a 15ms test on PVC. The measured tf is now 25ns which is significantly less than the first oscillation period for the 2ms test. It is also apparent from the data that there is a significant delay between striker contact and the start of either crack tip or striker loading. It can be seen that the peaks in load cell and crack tip gauges are not coincident even for the lower velocity test. 

Fig. 4.6. Two cells which differ in their PLC activity are coupled. Uncoupled the cells oscillate with their own period (27, 18.8 and 11.6 sec for Vpz,c = 0.8, 1 and 1.5 pM/s respectively). The region of synchronous, 1 1 phase-locked oscillations depends on the intercellular permeabilities for Ca " " and IP3 (7c and 7p respectively). Parameters as in Fig. 4.4.

In addition, there is a problem in knowing the value of The quick-and-dirty method of electronic compensation is to set the potential at a value where faradaic processes do not occur and to increase/with the potentiometer until the potentiostat starts to oscillate. Then/is decreased to a value about 10-20% below the critical/so that stability is reestablished. Since the critical/may lie either below or above full compensation, depending on the electronic properties of the whole system (cell plus potentiostat), this method must be used with care. Moreover, there is some danger that the test solution or the working electrode will undergo undesirable reactions (get cooked ) during the oscillation period. 

Yet another possibility is that part of the cells within a continuously stirred suspension would oscillate in a chaotic manner if left on their own, while the remaining cells would oscillate periodically in the absence of the chaotic population. The coupling of the two populations within the same suspension could well suppress any manifestation of chaos by conferring upon the coupled system a global, regular behaviour. 

Fig. 6.19. Evolution in the phase space at different values of the relative proportions of (initially) chaotic and periodic cell populations in a mixed suspension containing various amounts of the two types of cells, (a) Oscillations of the limit cycle type obtained for Vj = 4.5 x 10 min" when the suspension contains only cells of periodic population 2 (fj = 0, fj = l)l arrows show the direction of movement and the trajectory has been broken to indicate the part that comes behind (the portion of the curve in front corresponds to a decrease in all three variables after a peak in cAMP). (b) Period-2 oscillations obtained upon adding to periodic population 2 cells from the chaotic population 1, for which Vi = 4.396875 x 10" min" the value of the fraction of the (initially), chaotic population is = 0.5. (c) Period-4 oscillations obtained when is increased up to 0.86 notice that two of the loops of the trajectory over a period are very close to each other, which is also apparent in the bifurcation diagram of fig. 6.20. (d) Chaotic behaviour corresponding to a strange attractor when the suspension contains only cells of population 1 (Fj = 1). The curves are obtained by numerical integration of eqns (6.9) for the above-indicated values of Vj and Vj other parameter values, which hold for the two populations, are as in fig. 6.2. Variables pr and a relate to population 2 in (a)-(c), and to the homogeneous population 1 in (d) variable y is shared by the two populations. Ranges of variation for pr, a and y are 0-1,0.65-0.68 and 0-2.2, respectively. Initial conditions were a = 0.6729 and pr = 0.2446 for both populations, while 7=1.7033. The curves were obtained after a transient of 500-1000 min. The period of the oscillations shown in (a)-(c) is of the order of 8-10 min thus for F. = 0.3 and Fj = 0.7 the period is equal to 8.7 min (Halloy et al. 1990).

Fig. 6.23. Minimum fraction of periodic cells suppressing chaos, (a) The value of the minimum fraction of cells from periodic population 2 in the final suspension, Fjniin, capable of transforming chaos of population 1 into simple periodic oscillations is plotted as a function of parameter k 2> the chaotic behaviour of population 1 is that shown in fig. 6.21 (upper panel, left). The curve was generated according to eqn (6.11) with /ceJ = 2.6257 min" and = 2.6167 min", (b) Plotted as a function of V2 is the value of the minimum fraction of periodic cells from population 2 needed to transform the chaotic behaviour of population 1 into (i) simple periodic oscillations, and (ii) oscillations of period 8, with eight peaks of cAMP per period. The results are obtained numerically by integration of eqns (6.9) (dots) as described in the legend to fig. 6.21. The values = 2.625 min" and Vi/jU. = 1.4073825 min" are taken for the chaotic population other parameter values are as in fig. 6.2. The vertical, dashed line indicates the value of kei or Vj giving rise to chaos in population 1 (Li et al, 1992a).

Quantum beats can be observed not only in emission but also in the transmitted intensity of a laser beam passing through a coherently prepared absorbing sample. This has first been demonstrated by Lange et al. [872, 873]. The method is based on time-resolved polarization spectroscopy (Sect. 2.4) and uses the pump-and-probe technique discussed in Sect. 6.4. A polarized pump pulse orientates atoms in a cell placed between two crossed polarizers (Fig. 7.12) and generates a coherent superposition of levels involved in the pump transition. This results in an oscillatory time dependence of the transition dipole moment with an oscillation period AF = 1/Av... 

Of the 12 possible initial states with 5 live cells, 5 yield the null state within t = A steps, 2 yield a stable state and four lead to the same period two oscillator marking the end of the evolution of state E in figure 3.67 In marked contrast to this rather benign behavior, however, the remaining 5-cell pattern - called the R-pentamino -evolves in a considerably more dramatic fashion. 

Local anesthetics interact with peripheral nerve cell membranes and exert a pharmacological effect [34]. Potential oscillation was measured in the presence of 20 mM hydrochlorides of procaine, lidocaine, tetracaine, and dibucaine (structures shown in Fig. 16) [19]. Amplitude and the oscillatory and induction periods changed, the extent depending on the... 

Jessus, C., and Beach, D. (1992). Oscillation of MPF is accompanied by periodic association between cdc25 and cdc2-cyclin B. Cell 68 323-332. 

---