Activated interstitial

A connection was established by simulation of accumulation [110] between no and the ratio of the number of active interstitials to the total number of them in the crystal... 

Fontanesi, J., Heideman, R.L., Muhlbauer, M., Mulhem, R., Sanford, R.A., Douglass, E.C., Kovnar, E., Ochs, J.J., Kuttesch, J.F., Tai, D. et al. (1995). High-activity interstitial irradiation in the treatment of pediatric central nervous system tumors a pilot study. Pediatr. Neurosurg. 22 289-97. 

Oliguric renal insufficiency with the nephrotic syndrome and active interstitial nephritis has been described in a young woman with systemic lupus erythematosus taking intermittent long-term naproxen (SEDA-15,102). 

In the course of the past decade several explanations have been put forward to account for the anomalous diffusion in bcc metals. The different models based on the presence of extrinsic vacancies (Kidson, 1963), on the temperature dependence of elastic constants (Aaronson and Shewmon, 1967), on dislocation enhanced diffusion (Peart and Askill, 1967) or on vacancy anharmonicity (Gilder and Lazarus, 1975) have been thoroughly discussed in the original and in the various review papers. Two additional models, the activated interstitial and, more recently, the w-embryo model, have been proposed as alternative explanations for anomalous bcc diffusion. These two models and their possible common interpretation on the basis of the Engel-Brewer electron correlation theory will be discussed in the next sub-section. 

Dariel (1973), on the basis of similar results, argued that it seemed highly implausible that the activated interstitial model should yield similar results in bcc y-La, S-Ce and jS-Pr considering that the model depended so critically upon the number of 4f electrons of the migrating atom and the possibility of their promotion to the conduction band. According to Dariel, the common diffusion behavior ensues from the particular properties of the bcc structure of the rare earth elements rather than from the electronic structure of the various diffusing species. 

The activated interstitial model which hinges on the relative ease of some f electron promotion in its initial form or on the possibility of d-f hydridization in its modified form seems to account for the main anomalous features observed in connection with self-diffusion in bcc e-Pu, S-Ce and possibly y-La and y-Yb. Beside these metals, however, anomalous diffusion has also been observed in /3-Ti, /3-Zr, /3-Hf, y-U and the rare earth metals -Pr, /3-Nd and P-Gd. The normal behavior of Eu (table 12.2), which among this latter group of metals is the only one having the bcc structure as its only allotropic form, stands out in marked contrast to the other bcc rare earth metals. It strongly supports Seeger s (1972) suggestion that anomalous diffusion in bcc metals is in some way connected to the phase transformation which precedes the bcc phase. 

The diffusivity was studied at 900 to 1200C by using deep level transient spectroscopy and tracer methods. The surface concentrations which were deduced from the tracer method agreed with solubility data, and the concentration of electrically active interstitial Mn was found to represent 60 to 70% of the total Mn content. Both methods yielded identical diffusion coefficients. These could be described by ... 

Figure 8. 4-channel fiberopic light dosimeter Laboratory for Applied Biophotonics, Ontario Cancer Institute, Toronto, Canada) and fluence-rate traces during PDT treatment of prostate cancer with 3 probes placed at different distances from an active interstitial source fiber. 

The vacancy is very mobile in many semiconductors. In Si, its activation energy for diffusion ranges from 0.18 to 0.45 eV depending on its charge state, that is, on the position of the Fenni level. Wlrile the equilibrium concentration of vacancies is rather low, many processing steps inject vacancies into the bulk ion implantation, electron irradiation, etching, the deposition of some thin films on the surface, such as Al contacts or nitride layers etc. Such non-equilibrium situations can greatly affect the mobility of impurities as vacancies flood the sample and trap interstitials. 

Transport in the blood is no longer a requisite for a hormonal response. Responses can occur after release of hormones into the interstitial fluid with binding to receptors in nearby ceUs, called paracrine control, or binding to receptors on the ceU that released the hormone, called autocrine control. A class of hormones shown to be synthesized by the tissue in which they act or to act in the local ceUular environment are the prostaglandins (qv). These ubiquitous compounds are derived from arachidonic acid [506-32-1] which is stored in the ceU membranes as part of phosphoHpids. Prostaglandins bind to specific ceUular receptors and act as important modulators of ceU activity in many tissues. 

For an ion to move through the lattice, there must be an empty equivalent vacancy or interstitial site available, and it must possess sufficient energy to overcome the potential barrier between the two sites. Ionic conductivity, or the transport of charge by mobile ions, is a diffusion and activated process. From Fick s Law, J = —D dn/dx), for diffusion of a species in a concentration gradient, the diffusion coefficient D is given by... 

Leaching is the removal of a soluble fraction, in the form of a solution, from an insoluble, permeable sohd phase with which it is associated. The separation usually involves selective dissolution, with or without diffusion, but in the extreme case of simple washing it consists merely of the displacement (with some mixing) of one interstitial liquid by another with which it is miscible. The soluble constituent may be solid or liquid and it may be incorporated within, chemically combined with, adsorbed upon, or held mechanically in the pore structure of the insoluble material. The insoluble sohd may be massive and porous more often it is particulate, and the particles may be openly porous, cellular with selectively permeable cell walls, or surface-activated. 

In tire transition-metal monocarbides, such as TiCi j , the metal-rich compound has a large fraction of vacairt octahedral interstitial sites and the diffusion jump for carbon atoms is tlrerefore similar to tlrat for the dilute solution of carbon in the metal. The diffusion coefficient of carbon in the monocarbide shows a relatively constairt activation energy but a decreasing value of the pre-exponential... 

Chemical erosion can be suppressed by doping with substitutional elements such as boron. This is demonstrated in Fig. 14 [47] which shows data for undoped pyrolitic graphite and several grades of boron doped graphite. The mechanism responsible for this suppression may include the reduced chemical activity of the boronized material, as demonstrated by the increased oxidation resistance of B doped carbons [48] or the suppressed diffusion caused by the interstitial trapping at boron sites. 

If the pressure of O2 above a crystalline oxide is increased, the oxide-ion activity in the solid can be increased by placing the supernumerary ions in the interstitial positions, e.g. ... 

Ideal and Nonrideal Solutions. Treatment of Solutions by Statistical Mechanics. A Solution Containing Diatomic Solute Particles. A Solution Containing Polyatomic Solute Particles. An Interstitial Solution. Review of Solutions in General. Quantities De-pendent on, and Quantities Independent of, the Composition of the Solution. Unitary Quantities and Cratic Quantities. Molality and Activities on the Molality Scale. 

One intensively investigated feature of the inflammatory process in COPD is the release of proteases from neutrophils and monocytic cells that destroy elastin and other components of the interstitial matrix (Table 1). The best studied protease is neutrophil elastase. Independent of its elastolytic activity, neutrophil elastase is a potent secretagogue. More recently matrix metalloproteases (MMP) have received increasing attention, in particular MMP 12 (macrophages elastase). To which extent and how exactly these proteases become activated is not clear at present. 

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