Moving markers

Darken assumed that the accumulated vacancies were annilrilated within the diffusion couple, and that during tlris process, tire markers moved as described by Smigelskas and Kirkendall (1947). His analysis proceeds with the assumption tlrat the sum of tire two concenuations of the diffusing species (cq - - cq) remained constant at any given section of tire couple, and tlrat the markers, which indicated the position of tire true interface moved with a velocity v. 

Oxide movements are determined by the positioning of inert markers on the surface of the oxideAt various intervals of time their position can be observed relative to, say, the centreline of the metal as seen in metal-lographic cross-section. In the case of cation diffusion the metal-interface-marker distance remains constant and the marker moves towards the centreline when the anion diffuses, the marker moves away from both the metal-oxide interface and the centreline of the metal. In the more usual observation the position of the marker is determined relative to the oxide/ gas interface. It can be appreciated from Fig. 1.81 that when anions diffuse the marker remains on the surface, but when cations move the marker translates at a rate equivalent to the total amount of new oxide formed. Bruckman recently has re-emphasised the care that is necessary in the interpretation of marker movements in the oxidation of lower to higher oxides. 

Click the LEFT mouse button to place the marker. Move the mouse away ... 

In denaturing polyacrylamide, dye markers move with fragments about half the size of those in neutral gels (e.g., 35 and 130 nucleotides in 6% denaturing gel). 

To make the correlation results applicable for the field development process it may be desirable to display the correlated units in their true structural position. For instance if water injection is planned for the field, water should enter the structure at or below the owe and move upwards. Hence the correlation panel should visually show the sand development in the same direction. For this, all markers on the panel are displayed and connected at their TVSS position (Fig. 5.43). This is called a structural correlation. 

The Ru surface is one of the simplest known, but, like virtually all surfaces, it includes defects, evident as a step in figure C2.7.6. The observations show that the sites where the NO dissociates (active sites) are such steps. The evidence for this conclusion is the locations of the N and O atoms there are gradients in the surface concentrations of these elements, indicating that the transport (diffusion) of the O atoms is more rapid than that of the N atoms thus, the slow-moving N atoms are markers for the sites where the dissociation reaction must have occurred, where their surface concentrations are highest. 

If samples of two metals widr polished faces are placed in contact then it is clear that atomic transport must occur in both directions until finally an alloy can be formed which has a composition showing die relative numbers of gram-atoms in each section. It is vety unlikely that the diffusion coefficients, of A in B and of B in A, will be equal. Therefore there will be formation of an increasingly substantial vacancy concentration in the metal in which diffusion occurs more rapidly. In fact, if chemically inert marker wires were placed at the original interface, they would be found to move progressively in the direction of slowest diffusion widr a parabolic relationship between the displacement distance and time. 

Permanent markers outside the study area should also be located and used in the event that one or more plot markers are inadvertently moved or lost. One option is to locate a minimum of two permanent reference points outside of the study area... 

Studies of sleep-active neuronal discharge across the sleep-wake cycle in freely moving animals provide important information about the hypnogenic process (see below) but, because of sampling limitations, are not suitable for systematic mapping of the exact locations of putative hypnogenic neurons. The application of the c-Fos immunoreactivity (IR) method to map sleep-active neurons has stimulated several advances. C-Fos IR is a marker of neuronal activation in most brain sites immunohistochemically labeled neurons can be mapped systematically. The localization of c-Fos IR following sustained sleep, but not... 

One way of thinking of this situation is to visualize a game, with a binary tree of depth N as a "board" and k markers or "pieces" (representing locations in a program scheme). Any marker can be placed on a leaf. Each node is either a leaf or has two "sons". If both sons of a node are covered with markers, then one marker can be moved up to that node and markers removed from the two sons. The object is to eventually place a marker on the root, using as few markers as possible. How many markers are needed in the worst case ... 

When this system was studied over time, it was found that the marker wires move toward each other. This shows that the most extensive diffusion is zinc from the brass (an alloy of zinc and copper) outward into the copper. If the mechanism of diffusion involved an interchange of copper and zinc, the wires would not move. The diffusion in this case takes place by the vacancy mechanism described later, as zinc moves from the brass into the surrounding copper. As the zinc moves outward, vacancies are produced in the... 

The field and any subportions of the field to be sampled must have specific unique labels. These labels are typically recorded in a field or laboratory notebook. The notebook will also contain their exact location using a global positioning system (GPS). The position of any samples taken in any part of the area is also recorded using its GPS location. This is the only way one can be certain were a sample was taken. Flags or other markers are always subject to being lost or moved. 

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