Ramp time

The resolution of the zeolite MR image is 100 x 100 x 100 gm3 and has therefore reached the resolution limit that defines NMR microscopy. For the instrumentation used for this experiment, it will take at least a few milliseconds due to the ramping time of the field gradients. If the mean displacement of the xenon atoms during this experimental time scale reaches the dimension of the voxels or pixels, the resolution limit is reached. For instance, for the aerogel experiments in Figure... 

For this purpose, perfluorooctanesulfonyl-tagged benzaldehydes were reacted with 1.1 equivalents of a 2-aminopyridine (or 2-aminopyrazine), 1.2 equivalents of an isonitrile, and a catalytic amount of scandium(III) triflate [Sc(OTf)3] under micro-wave irradiation in a mixture of dichloromethane and methanol (Scheme 7.85). A ramp time of 2 min was employed to achieve the pre-set temperature, and then the reaction mixture was maintained at the final temperature for a further 10 min. The fluorous tag constitutes a multifunctional tool in this reaction, protecting the phenol in the condensation step, being the phase tag for purification, and serving as an acti-... 

Using Eqs. (6.1) and (6.2) and neglecting the duration of the time elements d d S) representing the gradient ramp times, maximum signal yield can be obtained by choosing S and TM according to... 

Sample treatment was studied by the saturated fractional design considering volumes and concentrations of acids, temperatures, ramp time and hold time for the microwave heating. An optimised programme was set after the central composite study... 

The effect of controller gain is shown in Figure 4.4. The heat transfer area is 4 times the jacket area, and the ramp time is 60 min. The importance of controller tuning is clearly illustrated. If the gain is too small, temperature control is poor (for Kc = 0.05, there is a 20 K overshoot of the desired temperature for smaller gains, the reactor runs away). If the controller gain is too large, the response is very oscillatory. The Kc = 0.1 response shows a 6 K overshoot. 

Figure 4.5 shows what happens when the setpoint ramp time is reduced from 60 to 45 min, using the same heat transfer area and the same three values of controller gain. 

Ramp time of the staircase shaped frequency change has to be <1 ms. 

Program the thermocycler for 40-45 cycles with the following parameters denature for 1 min at 94°, anneal for 1 min at 35°-36° (55° for 16-mers), and extend for 2 min at 72°. The total reaction time is approximately 5 hr in a Perkin-Elmer Cetus thermocycler using minimum ramping times between incubation temperatures. 

Process Temperature, °C Ramp Time, s Hold Time, s... 

Most work has focused on the use of fixed-and fluidized-bed reactors. Fixed-bed reactors are commonly used as batch reactors with the disadvantage of long ramp times. The choice of temperature and heating rate leads to strong differences in the product distribution. 

Stage Power (W) % power Ramp time (min) Pressure (psi) Temp. (°C) Hold (min)... 

The TPD experiments are carried out using a differentially pumped quadrupole mass spectrometer (QMS), connected to the UHV apparatus employed for the MIES/UPS studies. The ramping time in TPD is considerably shorter (IK/s) than in MIES and UPS (IK/min). For this reason, the maximum desorption rate in MIES/UPS occurs about 15K earlier than in TPD. 

Stage Starting temperature, "C Ramping time, hl End temperature, C Aging time, hr... 

Fset — Pset0 J ramp (TIME - (TIMEst + TIMEhoid))... 

It is noted that, unlike the conventional thermocycler, the control system for the TFRT prototype includes the ramp time in the time at each temperature. Thus, although the system is set to a given temperature for a fixed time (e.g., 10s for the rapid cycling case), the prototype takes as much as 7s to make temperature transitions so the total time at the setpoint temperature is less than the value given in the protocol. 

During the ramp time the primary flux changes with time, and the induced current is determined by the rate of change of the flux time, as well as by parameters of the ring R and L). After the primary flux disappears, the behavior of the induced current is controlled by parameters R and L only. In this case, eq. 1.215 is simplified and we have ... 

In order to express the constant C, we will investigate the behavior of the induced current flow during the ramp time. In accord with eqs. 1.216 and 1.217, we have ... 

In accord with the last equations, the intensity of the induced current gradually increases during the ramp time, reaching a maximum at the instant t = t, and then starts to decrease exponentially. 

Suppose that the ramp time tr is much less than the time constant tq. Expanding then the exponential terms in eq. 1.223 in a power series and discarding all terms but the leading ones, we obtain ... 

Because there is always in practice a nonzero ramp time, the initial value of the current should be interpreted as being its value at the instant t = tr, provided that is much less than tq. 

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