Drifting distance

In a field E the mean drift distance before capture will be... 

There is no known way in which drift of agricultural chemicals can be entirely eliminated, whether applied by ground or aircraft. Drift of tracers used in air pollution studies have been authenticated as far as 22 miles, and further distances could be expected, depending on the accuracy of the means for sensing tracer chemicals. Symptoms of 2,4-D drift have been noted on grapes 8 to 12 miles from the point of application and lawsuits in Texas and Washington have been based on greater drift distance. 

Fig. 3.15. The temperature dependence of the mobility for constant drift time (solid lines) and constant drift distance (dashed line).

The total drifting distance of the conformational open-close motion in one enzymatic reaction turnover, (Xjv(f)), is about 9 A, based on our MD simulation (Fig. 24.6). The mean open-time, (fopen) and the standard deviation... 

Individual movement by walking was modeled as a jump from 1 cell to a randomly selected neighboring cell at a time set by the (probabilistic) residence time. The probability density function was obtained from a simulation of a random walk process with parameters derived from experimental work (Englund and Hamback 2004). The model incorporated passive movement downstream by implying that 1% of the movement to other cells was long-distance movement (drift) in a downstream direction. Drift distance was incorporated as an exponential distribution, with an assumed average of 10 m. 

When reaction products are formed in a finite region, rather than a point source, it is best to extract the ions with a combination of acceleration and drift regions which are consistent with the Wiley-McLaren space focusing condition (Wiley and McLaren, 1955). Specific ratios of acceleration and drift distances for given electric fields are imposed so that the ion TOP is independent of the precise initial position of ionization. This is easily explained as follows. Suppose that two ions (with initially zero kinetic energy) are formed at positions Uj + 8 and tij — 8 as measured from the second acceleration, or drift region. Clearly the ion closer to the drift region will reach this... 

Figure 5.25 Ion TOP distributions for isotropic angular distribution of dissociation products. The mass of the fragment ion is 30 amu, the electric fields in the first two acceleration regions are 10 and 100 V/cm and the acceleration distances are 2 and 1 cm, respectively. The drift distances are indicated in the figure. The d = 55 cm corresponds to the Wiley-McLaren space focusing condition. For each drift distance, the ion TOF was calculated for three product translational energies of 0, 0.5, and 1.0 eV.

Substituting that into Equation 1.20, employing Equations 1.11 and 1.9, and defining U, the voltage across the drift distance (the drift voltage), Revercomb and Mason obtained... 

The physics of BCP in time-varying AC fields is richer than in DC. There are four length scales in the system. The first is do, the natural crystal periodicity, do 50-200 nm. The other length scale is fhe drift distance an ion... 

The lower limit for is determined practically by radial losses of ions to the walls of the drift tube the upper limit is defined by electrical breakdown of gases in the supporting atmosph e inside the drift tube. An important property of an ion mobility spectrometer operating in the low-field region is that ion losses to the walls by radial diffusion do not introduce mass discrimination in the collected ion signal because the ratio of the radial spreading distance to the drift distance is indep doit of ion mass [24]. 

The computational procedure for diffusion with drift is similar to that of the basic random walk procedure described above. At each time step, the values of loc and the drift velocity must be determined from the potential energy and the first and second derivatives of the trial wavefunction. The drift distance is given by the product of the vector drift velocity and the time step. Multiplication is based on the local energy. 

Spatial msolution in He C02-isobutaiie [3], Ar-C02-niotliaiio [3], and Ho-DME [5][C] a.s a func tion of drift distance are sliown in Figure 3.1. The SLAC measurements were made with 30 //.m sense wires operating at a charge, density of aljont 14 nC/m, and an electric field of 900 V/cm in the uniform field region in a 3.3 cm jet cell. For the (83 10 7) helium-based mixture, the resolution is very similar to that for the argon mixture. The... 

Figure 3.1. Resolution as a function of drift distance for HRS ga.s and He-C02-isobutane mixtures. The dashed curves for He-DME are from reference [6] for A < 6 mm and from reference [5] for X > 4 mm.

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