Marker movement

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. 

X-ray reflectometry (XR) X-rays X-rays 0.1 nm heavy atoms 300 nm interface width/ profile, marker movement... 

Several points are to be noted. Firstly, pores and changes of sample dimension have been observed at and near interdiffusion zones [R. Busch, V. Ruth (1991)]. Pore formation is witness to a certain point defect supersaturation and indicates that sinks and sources for point defects are not sufficiently effective to maintain local defect equilibrium. Secondly, it is not necessary to assume a vacancy mechanism for atomic motion in order to invoke a Kirkendall effect. Finally, external observers would still see a marker movement (markers connected by lattice planes) in spite of bA = bB (no Kirkendall effect) if Vm depends on composition. The consequences of a variable molar volume for the determination of diffusion coefficients in binary systems have been thoroughly discussed (F. Sauer, V. Freise (1962) C. Wagner (1969) H. Schmalzried (1981)]. 

L.C.C. Da Silva and R.F. Mehl. Interface and marker movements in diffusion in solid solutions of metals. Trans. AIME, 191 (2) 155-173, 1951. 

L. C. Correa da Silva and R.F. Mehl, Interface and marker movements in diffusion in solid solutions of metals, Trans. AIME, Vol. 191, pp. 155-173. Copyright by TMS (The Minerals, Metals, and Materials Society). Fig. 6.2 and Fig. 6.3 Reprinted, by permission, from A. Vignes and J.P. Sabatier, Ternary diffusion in Fe-Co-Ni alloys, Trans. AIME> Vol. 245, pp. 1795-1802. Copyright 1969 by TMS (The Minerals, Metals, and Materials Society). Fig. 6.2 Reprinted, by permission, from J.S. Kirkaldy, Diffusion in the Condensed State. Copyright 1987 The Institute of Metals (Maney Publishing). Fig. 9.1 Reprinted, by permission, from N.A. Gjostein, Short circuit diffusion, in Diffusion. Copyright 1973 by The American Society for Metals (ASM International). Fig. 9.2, Fig. B.6, and Fig. B.8 From Interfaces in Crystalline Materials by A.P. Sutton and R.W. Balluffi (1995). Reprinted by permission of Oxford University Press. Fig. 9.2 Reprinted, by permission, from I. Herbeuval and... 

If the predominant migrating species, cation or anion, is known, e.g. from marker movement studies, the ionic transport number can... 

Kramer, E.J., Green, P., and Palmstrom, C. (1984) Interdiffiision and marker movements in concentrated polymer-polymer diffiision couples. Polymer, 25, 473-480. 

L. C. Correa da Silva and R. F. Mehl, Interface and Marker Movements in Diffusion in Solid Solutions of Metals, Trans. AIME 191(2) 155-73 (1951). 

The mechanical properties were investigated in some early studies. In these studies, the creep properties [111], tensile strengths [112], flow stress [113] and high temperature hardness [113,114] of various oxides were measured. The mechanical properties of wustite were also related to scale-steel interface adhesion [115] and marker movement [116] in the wustite scale layer. Based on these early studies, it was concluded that at temperatures above 800°C, wustite was deformable, and even in the range of 650-800°C, wustite still possessed certain plasticity [117], while magnetite and hematite were not deformable even at 1000°C. 

R. F. Tylecote and T. E. Mitchell, Marker movements in the oxidation of iron and some other metals , J. Iron Steel Inst. 196, 445—453 (1960). 

Rutherford backscattering (RBS) He 4He 30 nm heavy atoms jim — movement of markers... 

Evidence concerning the identity of the mobile species can be obtained from observation [406,411—413] of the dispositions of product phases and phase boundaries relative to inert and immobile markers implanted at the plane of original contact between reactant surfaces. Movement of the markers themselves is known as the Kirkendall effect [414], Carter [415] has used pores in the material as markers. Product layer thickness has alternatively been determined by the decrease in intensity of the X-ray fluorescence from a suitable element which occurs in the underlying reactant but not in the intervening product layers [416]. 

Figure 3.21 Kirkendall effect shown by the movement of inactive markers originally at the interface between two interdiffusing species.

Fig. 23.3. Tablet movement during a static view (30-s duration). Note the movement from position 1 to position 3 during successive peristaltic waves. M, external marker.

Bouchoucha et al. characterized colonic transit time in 30 healthy subjects and in 43 patients with inflammatory bowel disease using X-ray opaque markers. The response to food was different in the two populations in controls, the cecum and ascending colon emptied and filled the distal bowel, whereas in the patients only the splenic flexure and left transverse colon emptied. Movement through both the right and left colon in patients was observed to be much slower than in controls, both before and after a meal [55]. 

REM sleep time is preserved in depression (Benca et al. 1992 Mendlewicz and Kerkhofs 1991). Yet, REM sleep percentage is slightly increased, and the density of rapid eye movements is enhanced (Benca et al. 1992 Gillin et al. 1981 Mendlewicz and Kerkhofs 1991). Most notable of all REM sleep characteristics in depression is a short latency to the onset of REM sleep (C. E. Reynolds and Kupfer 1987). These REM sleep patterns were considered to be unique to depression in particular, the short REM latency was originally claimed to be a marker for primary depression (Kupfer 1976, 1984). Unfor-... 

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