Interstitial concentration

Nolen WA, Haffmans PMJ, Bouvy PF, et al Monoamine oxidase inhibitors in resistant major depression. J Affect Disord 28 189-197, 1993 Nomikos GC, Damsma G, Wenkstern D, et al Chronic desipramine enhances amphetamine-induced increases in interstitial concentrations of dopamine in the nucleus accumbens. Eur J Pharmacol 195 63-73, 1991 Nomikos GC, Damsma D, Wenkstern D, et al Effects of chronic bupropion on interstitial concentrations of dopamine in rat nucleus accumbens and striatum. Neuropsychopharmacology 7 7-14, 1992... 

Following Shewmon, consider the metallic couple specimen consisting of two different metals, A and B, shown in Fig. 3.12 [18]. The bonded end is at temperature T and the open end is at T2. A mobile interstitial solute is present at the same concentration in both metals for which Qt1rans = -84 kJ/mol in one leg and Q jrans = 0 in the other. Assuming that the interstitial concentration remains the same at the bonded interface at T, derive the equation for the steady-state interstitial concentration difference between the two metal legs at T2. Assume that Tj > T2. 

Approach 2 Start by determining the net flux between two adjacent (002) planes when the gradient of the interstitial concentration is normal to these planes. 

Approach 2 Alternatively, we can analyze diffusion arising from a gradient of interstitial concentration along [002] in Fig. 8.6. Consider the jumping of interstitials between two adjacent (002) planes. If there are c interstitials per unit area with centers of mass on plane A, one-third will have their axes along [100], one-third along [010], and one-third along [001]. Each [001] interstitial on planed has four sites on an adjacent (002) plane (i.e., plane B) in which to jump. Each [100] interstitial and [010] interstitial has two sites in which to jump. The total concentration of interstitials per unit volume associated with plane A is c = c /(a/2) = 2c /a and the flux from plane A to plane B is... 

In a typical tracer self-diffusion experiment, the tracer concentration probability, p, depends upon position, whereas the total interstitial concentration probability, p, does not. 

Having this result, an expression can be obtained for the intrinsic chemical diffusivity, >/, which describes the diffusion arising from an inert-interstitial concentration gradient. According to Eqs. 3.35 and 3.42, the flux in such a system is... 

Figure 12. A model of self-interstitial diffusion from the bulk to the partial dislocation bounding a stacking fault. Under nonoxidizing conditions, the concentration of self-interstitials at the fault line, CiL, is greater than the equilibrium bulk interstitial concentration, Ci°. Under oxidizing conditions, Ci is greater than CiL until the retrogrowth temperature is reached. (Reproduced with permission from reference 45. Copyright 1981 The Electrochemical...

Palmer A. M., Marion D. W., BotschellerM. L., and Redd E. E. (1993) Therapeutic hypothermia is cytoprotective without attenuating the traumatic brain injury-induced elevations in interstitial concentrations of aspartate and glutamate. J. Neurotrauma 10, 363-372. 

FIGURE 9.10 Sim Lila ted interstitial concentration profiles of a 180-kDa macromolecLile in nonbinding brain tissue at various times during high-flow microinfusion at 3 pL/min. Model parameters were taken from Table 9.1. 

FIGURE 9.17 Relative interstitial concentration of quinolinic acid computed for a 5-yiL infusion at 0.1 [xL/min of an isotonic 50 mM solution into the globus pallidus interna of a primate (50-min infusion time). The horizontal dotted line represents the threshold concentration in relative units. Solid line curves denote profiles generated at the indicated times (minutes) during the infusion dashed line curves denote the profiles during the postinfusion period, where the numbers are minutes after the initiation of infusion. (Reproduced from Lonser RR et al. J Neurosurg 1999 91 294-302.)... 

In the percolation of a liquid through a bed of solids, mass transfer of the solute from the surfaces of the solid to the liquid in the interstices of the bed takes place by molecular diffusion and by natural convection arising from the density changes created by dissolution. Although these processes are slow, they are much faster than mass transfer in the matrix under the same concentration differences. Concentration gradients in the liquid outside the particles are, therefore, very low. At any point in the bed, the introduction of dilute solution from above and the loss of concentrated solution to below decrease the interstitial concentration by dilution or displacement. This effect can be considered simply to reduce the solute concentration at the jimction of solid and solution, thus imposing a favorable concentration gradient within the matrix. 

Table VII. Computed Interstitial Concentrations and Diffusion Coefficients...

The process of creating an interstitial is just the opposite of creating a vacancy. If there are N, possible interstitial positions in the lattice, and if AFi is the free energy needed to move the atom into its interstitial position, then the interstitial concentration at equilibrium will be ... 

Based on the success of these results atomistic simulation has also been used to investigate the structural transitions occurring in the La2Ni04+ materials as interstitial concentration is varied. A number of compensation mechanisms have been modeled and the defect energies calculated for each of these previously reported orthorhombic structures and are detailed in Table 2. 

---