Measurement ion flux

The current probe is one of the simplest of the multiphase electrostatic detectors requiring only the measurement of dc current. Typical probe data will range from nA to pA for dilute multiphase flows and pA (or larger) for fluidized beds. Current probes are similar in principle to the well known Langmuir probe used to measure ion flux and electron and ion concentration... 

Apart from the electric characteristics we have discussed above, the labeling technique may be suitable for measuring ion fluxes. A formula for the latter may be derived from Eq. (91) by putting c] and cf alternately equal to zero and dividing h by Z F ... 

The atom flux sputtered from a solid surface under energetic ion bombardment provides a representative sampling of the solid. Sputtered neutral mass spectrometry has been developed as method to quantitatively measure the composition of this atom flux and thus the composition of the sputtered material. The measurement of ionized sputtered neutrals has been a significant improvement over the use of sputtered ions as a measure of flux composition (the process called SIMS), since sputtered ion yields are seriously affected by matrix composition. Neutral panicles are ionized by a separate process after sputter atomization, and SNMS quantitation is thus independent of the matrix. Also, since the sputtering and ionization processes are separate, an ionization process can be selected that provides relatively uniform yields for essentially all elements. 

Second, the time-course of the assays are often of different dimensions depolarizations and ion fluxes are measured in fractions of minutes, while tumor promotion or receptor regulation may take tens of minutes to hours. 

In order to study the influence of ions on the deposition process, a reliable quantification of the ion flux and energy is imperative. This flux cannot be determined directly from the detected number of ions in an lED as measured by means of QMS, for three reasons [332]. First, the orifice size decreases during subsequent measurements due to deposition of a-Si H on the edges of the orifice. Second, due to the limited acceptance angle of the mass spectrometer system, only a fraction of the ions that arrive at the substrate is actually detected. This fraction depends on the type and number of interactions that an ion experiences while traversing... 

The intercept defines ion flux across the epithelia (J0) while the slope provides a measure of the magnitude of the shunt pathway (Js) under short-circuit OF = 0) conditions. However, as discussed in the following section, mediated solute transport may also be voltage-dependent. 

Role of Bombardment in Pattern Transfer Regime. Gokan et al. [18] measured the relative 02 RIE rates of a series of polymers and found that the RIE rates scaled inversely with the mass density of carbon as in their IBE study (several materials deviated from the correlation). The relative RIE rates [18] varied by a factor of 3 and do not show the large variations characteristic of the radical-induced mechanism [10]. These results strongly suggest a bombardment-induced mechanism, but one can not directly apply the IBE results to RIE conditions because IBE neutral-to-ion flux ratios are orders of magnitude lower than under RIE conditions. 

Simple steady-state models may be used in order to relate quantitatively the mean concentration in the lake water column and the residence time of metal ions to the removal rate by sedimentation (for a detailed treatment of lake models see Imboden and Schwarzenbach, 1985). In a simple steady-state model, the inputs to the lake equal the removal by sedimentation and by outflow the water column is considered as fully mixed mean concentrations and residence times in the water column can be derived from the measured sedimentation fluxes. The binding of metals to the particles is fast in comparison to the settling. 

Dupont Y. 1984. A rapid filtration technique for membrane fragments or immobilized enzymes measurements of substrate binding or ion fluxes with a few millisecond time resolution. Anal Biochem 142 504. 

Martin H) has written a perceptive analysis of the possible ways in which an ionized species may behave in various models and contribute to or be responsible for a given activity. QSAR studies that have dealt with ion-pair partitioning include a study of fibrinolytics ( ) and the effect of benzoic acids on the K ion flux in mollusk neurons ( ). Schaper (10) recently reanalyzed a large number of absorption studies to include terms for the absorption of ionized species. Because specific values were not available for log Pj, he let the relation between log Pi and log P be a parameter in a nonlinear regression analysis. In most cases he used the approximation that the difference between the two values is a constant in a given series. This same assumption was made in the earlier studies (, ) Our work suggests that the pKa of an acid can influence this differential (see below). The influence of structure on the log P of protonated bases or quaternary ammonium compounds is much more complex (11,12) and points out the desirability of being able to easily measure these values. 

LIVER Use of isolated perfused liver in studies of biological transport processes, 192, 485 measurement of unidirectional calcium ion fluxes in liver, 192, 495 preparation and specific applications of isolated hepatocyte couplets, 192, 501 characterizing mechanisms of hepatic bile acid transport utilizing isolated membrane vesicles, 192, 517 preparation of basolateral (sinusoidal) and canalicular plasma membrane vesicles for the study of hepatic transport processes, 192, 534. 

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