Crossed field

Quer-ebene, /. lateral plane, -effekt, m, transverse effect. -faser,/. transverse fiber cross grain, -feld, n. transverse field, cross field. 

Boyd, BM Prausnitz, JM Blanch, HW, High-Frequency Altemating-Cross-Field Gel Electrophoresis with Neutral or Shghtly Charged Interpenetrating Networks to Improve DNA Separation, Electrophoresis 19, 3137, 1998. 

IV. Angular Momentum Coupling and Atoms in Crossed Fields... 

IV. ANGULAR MOMENTUM COUPLING AND ATOMS IN CROSSED FIELDS... 

The second point made by Fig. 6.2, although not with very high resolution, is that the levels of n and n + 1 cross. The extreme m = 0 red and blue states have Stark shifts of approximately 3n2E/2, which combined with the n — (n + 1) energy spacing of 1/n3, yields a crossing field of... 

In a follow-up study, the same authors examined the applicability of the same device for relevant protein samples and investigated the main contributions to band broadening [82]. As a consequence of the small depth of the beds, zone spreading caused by Joule heating was shown to be negligible (see Sect. 3.1.1). Cross fields of up to 100 V/cm were applied for the separation of human serum albumin, ribonuclease A and bradykinin. The feasibility of fraction collection was demonstrated with four collected fractions of a whole rat plasma sample. Off-line analysis of these four isolated fractions by CE indicated the separation of serum albumins and globulins. 

Fig. 1-7. Radial section of a spruce ray (above) and radial and tangential section of a pine ray (below), (a) Longitudial tracheids. (b) Rows of ray tracheids (small bordered pits), (c) Rows of ray parenchyma, (d) Pits in the cross fields leading from ray parenchyma to longitudial tracheids. (e) A bordered pit pair between two tracheids. (f) A bordered pit pair between a longitudial and a ray tracheid (llvessalo-Pfaffli, 1967).

There are some special cases in FFF related to the two extreme limits of the cross-field driving forces. In the first case, the cross-field force is zero, and no transverse solute migration is caused by outer fields. However, because of the shear forces, transverse movements may occur even under conditions of laminar flow. This phenomenon is called the tubular pinch effect . In this case, these shear forces lead to axial separation of various solutes. Small [63] made use of this phenomenon and named it hydrodynamic chromatography (HC). If thin capillaries are used for flow transport, this technique is also called capillary hydrodynamic fractionation (CHDF). A simple interpretation of the ability to separate is that the centers of the solute particles cannot approach the channel walls closer than their lateral dimensions. This means that just by their size larger particles are located in streamlines of higher flow velocities than smaller ones and are eluted first (opposite to the solution sequence in the classical FFF mode). For details on hydrodynamic chromatography,see [64-66]. 

An FFF experiment involves several phases. In most FFF experiments, the carrier liquid flow is started and the cross-field is adjusted. The sample is then injected and a careful procedure of sample introduction and relaxation must be followed [28,97]. This procedure is illustrated in a schematical FFF fractogram (Fig. 11). One can see five basic phases of an FFF experiment. Special care must be taken to determine the time the sample spends in the tubing and connections outside the channel, textra, as this shifts the void peak as well as the sample peak towards longer retention times. 

The goal of present numerical code development is, therefore, to treat all the other, predictable, physical components of the model accurately. This applies, in particular, for the atomic, molecular and surface processes, which largely control the plasma flow and plasma energy content in the important near target region. If that can be achieved, then the unknown anomalous cross field transport can be separated and isolated computationally, and can then perhaps be determined experimentally even in the edge region. 

It is an experimental fact that cross field transport in fusion edge plasmas cannot be realistically described by the classical Coulomb collision effects. Strictly then a term — q,a/maV (((f (f/Q)) resulting from turbulent fluctuations in the electric field SE and in the phase space density Sfa must be included on the right-hand side of (2.1), see [3]. 

Thus, the S-T conversion rate increases suddenly at the level-crossing field (B = Buz) through the HFC term of Eq. (3-13b). 

In this case, the S-T conversion suddenly occurs at the level-crossing field (5lc) as shown in Fig. 6-1(c). When a reaction occur from an S-precursor, the S-T conversion rate is increased by a magnetic field at Blc. Thus, the Yc (B) value is decreased by Blc and the Ye (B) value is increased by it. When a reaction occur from a T-precursor, the T-S... 

Table 8-1. Level-crossing fields (Bmax/mT = gix/mT) observed for biradicals...

The pair of levels 21s - (16,3) is exactly analogous to the extreme blue and red Na Stark states of n and + 1. The fact that only one has a permanent dipole moment is of no consequence it is only the difference in the permanent moments which is significant. Based on the single cycle Landau-Zener description of microwave ionization we expect that if atoms in the 18s state are exposed to a microwave field of amplitude equal to the crossing field, Eq = 753 V/cm, they would make transitions to the (16,3) state. On the other hand, if a static field is present as well as the microwave field it should be possible to see resonant microwave multiphoton transitions between these two bound states, and seeing the connection between these processes is part of our objective. 

First, the microwave ionization fields fall consistently below = l/3 . For example the data of Fig. 3 are fitted by = l/3.7 , a field which is only 80% of the crossing field. This field seems too low to account for the observed ionization rates if transition probabilities from individual cycles are added incoherently, but at 15 GHz it is not really clear if there is a discrepancy between the single cycle picture and the experiments or not. However, measurements of the micro-wave ionization of Na at frequencies as low as 670 MHz show an = l/3 dependence [15]. This low a frequency is much smaller than the avoided crossing size, enormously reducing the transition probability on a single cycle, and there are so few cycles that adding incoherently the effects of successive cycles cannot lead to ionization [15]. The coherent addition of transition amplitudes on successive cycles must play an important role. 

Pits with some form of border also occur at irregular intervals along softwood fibers where the fibers contact ray cells (Figure 22). Such pits are very rare in hardwood fibers, but in softwoods they are abundant and conspicuous, especially in earlywood. These pits are known technically as ray cross-field pits (see Figure 11), and they... 

Figure 22. SEM of ray cross-field pits in softwoods as seen on the wood rcmial surface. Key A, pits to ray parenchyma (RP) in western white fir and B, pits to ray parenchyma and ray tracheids (RT) in lodgepole pine.

Figure 23. SEM of spiral thickenings in the fibers of Douglas-fir wood radial surfaces. Key A, spirals in the vicinity of ray cross-field pits in early wood and B, nigh magnification of spirals in the last latewood fiber of one year and the first earlywood fiber of the next year. Pits shown in B are interfiber-bordered pits.

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