Phase-relaxation

Figure C3.1.7. Time-resolved optical absorjDtion data for the Soret band of photo lysed haemoglobin-CO showing six first-order (or pseudo-first-order) relaxation phases, I-VI, on a logaritlimic time scale extending from nanoseconds to seconds. Relaxations correspond to geminate and diffusive CO rebinding and to intramolecular relaxations of tertiary and quaternary protein stmcture. (From Goldbeck R A, Paquette S J, Bjorling S C and Kliger D S 1996 Biochemistry 35 8628-39.)...

In the relaxation phase of muscle contraction, the S-1 head of myosin hydrolyzes ATP to ADP and Pj, but these products remain bound. The resultant ADP-Pj-myosin complex has been energized and is in a so-called high-energy conformation. 

It has been postulated that 2-PAM exerts its cardiac action in rabbit atria through its alteration of calcium metabolism. The relaxation phase of skeletal muscle contraction seems to be directly affected by the sarcoplasmic reticulum because of its ability to sequester calcium actively.29,46 a similar role has been suggested for the sarcoplasmic reticulum in cardiac muscle. 6,83 The onset of muscle contraction takes place when calcium reaches a crit-cal concentration. This contraction is later reduced by the increased calcium-sequestering activity of the sarcoplasmic reticulum. Thus, 2-PAM can affect this process by decreasing the rate of calcium uptake by the sarcoplasmic reticulum, which results in increasing the time required to reduce the calcium concentration enough to allow relaxation to take place. This was demonstrated by the Increase in the relaxation phase. It was suggested that this... 

Asymmetry of the response curve to the point of the exposition end reflects the different nature of the exposition and relaxation output signals. A transition from an exposition into relaxation phase corresponds to a return of gas-sensitive matter contact with the initial atmosphere. A variety of processes take place simultaneously in that phase. They may include oxidation of adsorbed molecules by the air oxygen, desorption of the previously adsorbed molecules, competitive adsorption of the ambient atmosphere components. These circumstances cause a complicated shape of the relaxation curve. In general, its course reflects the dynamics of the surface concentration of conductivity clusters. Almost all relaxation curves are characterized by presence of a maximum. It is often more prominent that the corresponding exposition maximum. The origin of this phenomenon is determined by higher conductivity of clusters formed by the oxidized molecules of compounds adsorbed during the exposition phase. 

The dynamics of signal increase at the beginning of relaxation phase reflects the rate of cluster oxidation catalyzed by the gas sensitive substance. The higher is the slope of the face front of relaxation maximum, the faster is the rate of the process. 

Measurement of single twitches provides insight into contrac-tion/relaxation dynamics of the muscle. For example, reduced AChE or altered Ca2+ handling in the muscle causes a slower relaxation phase, whereas shifts toward faster ATPase isoforms will reduce time to reach peak twitch force (Fig. 20.12). 

Figure 29 Far-infrared conductivity of (TMTSF)2C104, relaxed phase. The dashed line is the Drude law with 1/r 3.5 cm-1 and

For flow regimes between points B and D of Fig. 3, we can observe oscillations in the instantaneous pressure value. The fluid adheres to the wall during the compression phase and slips during the relaxation phase. 

For flow regimes between points F and H of Fig. 3, a second zone of oscillations in the instantaneous pressure value is observed. It occurs in a slip regime during both the compression and relaxation phase. 

By analyzing the variations in instantaneous pressure, it was possible to show that slip in this config iration is accompanied by oscillations in pressiu-e between two regimes (fig. 4). During the compression phase, the pressime increases in time and the instantaneous flow rate is low. The polymer sticks to the wall of the extrusion die and cracks at the outlet. During the relaxation phase, the pressure decreases in time and the instantaneous flow rate is high. The polymer shps along the die wall and the surface of the extrudate is more or less smooth. 

The relaxation equations are calculated in a similar manner to the unloading equations, except that during the relaxation phase the punch stress is zero. When the punch stresses are zero, stress and strain tensors become ... 

I call magnesium the relaxer because it stimulates the relaxation phase in muscle tissue, including the heart muscle, just as calcium stimulates the contraction phase. Many people are familiar with milk of magnesia, an antacid suspension of magnesium hydroxide sometimes used as a cathartic, and with Epsom salts, a bath salt of magnesium sulfate that produces wonderful relaxation. Dr. C. Norman Shealy considers magnesium a crucial neurochemical, which I will discuss in the next few pages. 

Because the cartilage, even when swollen. Is very thin (approx. 1-1.5 mm thick), the compliance of the load cell had to be taken into account in determining the axial displacement of the tissue during compression. This was done by subtracting the displacement of the platen-load cell at each load (as determined from the displacement-load curve of the load cell) from that measured by the displacement transducer. Likewise It was necessary to add an appropriate displacement (as calculated) during the relaxation phase of the experiment. With the particular load cell used In our apparatus, these corrections ranged from 3 to 5% of the displacement at peak loads, to negligible amounts at low loads. 

At the initial state of equilibrium, the product X will be at a certain concentration, and it will stay at this concentration until the temperature jump occurs, when the concentration will change to another value which will be higher or lower than the initial value according to the sign of AH° for the reaction. For this simple type of reaction, the shape of the curve during the relaxation phase can be shown to be related to the sum of the rate constants, ki + k-i, and this sum can therefore be... 

Without valves, the relaxation-contraction cycle of the ventricle would produce no net forward flow, but an endless repetition of blood ejection during the contraction phase and blood return during the relaxation phase. 

The present review will deal with the properties of these five systems and their behavior on the addition of adenosine triphosphate (ATP), adenosine diphosphate (ADP), inosine triphosphate (ITP), inorganic triphosphate, and pyrophosphate. The really important question is how far the interaction phenomena with ATP can be regarded as a model for contraction in living muscle—a model for contraction as a whole in the case of the earlier of these stages, and a model of the molecular mechanism in the case of the later stages. For the relaxation phase, no model is yet known (c/. however. Section II, Ah and appendix). 

Consideration of Fig. 11 immediately shows that at the low field (left), after an initial relaxation phase, the mean power loss by elastic collisions P /n becomes the dominant energy loss channel. This means as was already seen from Fig. 9 (left), that the final establishment and compensation of the power balance occur only by elastic collisions in the region of low electron energies. However, as can be seen from Fig. 8, for neon, the lumped frequency v U) for energy dissipation in collisions has very small values at lower energies, which makes the large relaxation time in neon at this field strength immediately understandable. 

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