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The diffusion of 45Ca has been measured in single crystals of CaF2 and CaF2 + 0.34 mol % YF3 using a precision sectioning technique. In pure CaF2 between 800 and 1300 °C, D = = 4.8×107 exp (—5.160 eV/kT) cm2/s. The effect of YF3 is to increase D at temperatures below 950 °C but the magnitude of the increase is much smaller than expected for a vacancy mechanism unless a binding energy between Y3+ ions and cation vacancies of >0.6 eV is assumed. It is shown that the results may correspond to diffusion via cation–anion vacancy pairs at all temperatures investigated. Die Diffusion von 45Ca wird in CaF2- und CaF2 + 0,34 Mol%-YF3-Einkristallen unter Benutzung einer Abschleifmethode gemessen. In reinem CaF2 erholt man zwischen 800 und 1300 °C D = 4,8×107 exp (—5,160 eV/kT) cm2/s. YF3-Dosierung erhoht D bei Temperaturen unterhalb 950°C, jedoch ist die Grosenordnung der Erhohung fur den Leerstellenmechanismus viel geringer als erwartet, es sei denn, es wird eine Aktivierungsenergie zwischen Y3+-Ionen und Kationenleerstellen von >0,6 eV angenommen. Es wird gezeigt, das die Ergebnisse fur die untersuchten Temperaturen einer Diffusion uber Kationen–Anionen-Leerstellenpaare entsprechen.

Self-diffusion of 35S labelled molecules in highly perfect single crystals of orthorhombic sulphur has been studied by the serial sectioning technique. Measured lattice self-diffusion coefficients are considerably lower than those previously published for this solid. This difference is believed to be a consequence of a significant contribution from diffusion along dislocations in the crystals used in the previous study. Self-diffusion perpendicular to the [001] direction can be represented by an equation of the form D=2 × 1013exp[-(215±11 kJmol−1)/RT]m2s−1. Self-diffusion coefficients in the [001] direction are 2–4 times lower. This distinct anisotropy is probably a consequence of the marked structural anisotropy of this phase of sulphur.

Self diffusion of 48V in vanadium single crystals was reinvestigated over the temperature range 724–1842°C. Contribution to diffusion from migration along short-circuit paths at the lower temperatures was avoided by applying a micro sectioning technique specially developed for this study. The change in slope of the Arrhenius curve reported to occur at about 1350°C was not observed in this investigation, but has been observed to occur in the vicinity of 1642°C. The data in the temperature range 724–1642°C can be fitted to the relation consistent with normal diffusion by a single-vacancy mechanism. Above 1642°C the data fit the equation

By a combined anodizing and stripping technique, thin sections can be removed from vanadium metal. A uniform, thin oxide film can be grown on the vanadium metal in an acetone-benzoic acid-sodium tetraborate solution during anodization, which is then removed in aqueous NH4OH (10%). The thickness, x, of the metal removed in angstrom units is given by x= 103.2 + 12.5 V, V being the voltage applied. The application of such a sectioning technique for constructing penetration profiles in diffusion studies is of special interest, since contribution from diffusion along lattice defects can be recognized and eliminated. This paper considers the details of the experimental technique by which the films are grown and stripped.

The commonly employed methods of sectioning lymph nodes can account for a greater than 30% false pathologic interpretation when studying nodes for the presence of tumor. The failure to identify a tumor within a lymph node is related to the size of the lymph node, size of the lesion, number of sections examined, and the location of the tumor within the node. Analysis of these variables is approached by applying mathematical and computer formulation to numerous model nodes containing lesions of variable size and location. The percentage probabilities of identifying various sized lesions in different sized nodes is calculated in graphic form. These studies propose a functional method of lymph node sectioning which is applicable to improved sectioning technique.

固定内の自己拡散定数 (D*) を求めるのによく用いられている順次切削法では, 実験的に得られたトレーサーの濃度分布は, 通常, ガウス曲線C=M/√πD*t exp(-x2/4D*t) に一致するとして解析されている. ガウス曲線は, 拡散方程式を初期条件にデルタ関数状のトレーサー分布を仮定して解いた解である. しかし, 試料表面に付着されるトレーサーを含む化合物の厚さは, 実際には有限であり, また, その化合物が試料と化学形を異にし, 表面付着層と試料中での拡散定数が異なっている場合もしばしばある. 従来はこうした事情を考慮して拡散方程式が解かれていないので, 本研究では付着層の厚さ (h) が有限値をとり, 付着層中での拡散定数 (DA) と試料中での拡散定数 (DB) が違うとして拡散の偏微分方程式を解き厳密解を得た. その結果, 一定のDB/DA値に対して, r値 (r=h/√DAt) がゼロから無限大に増加するにつれ, 濃度分布はガウス曲線から誤差補関数曲線へと変化していく挙動が定量的に明らかになった. 濃度分布が両曲線のいずれかに一致している場合には, その曲線から正確なD*の値を得るための数学的に厳密な解析法があるが, いずれにも一致しない中間的な分布の場合には, 正確なD*を求めることは困難である. したがって, 自己拡散定数を正確に求めるためには, 濃度分布が両曲線のいずれかに一致するように, あらかじめ実験条件を設定しておく必要がある. こうした実験諸条件の許容範囲を示すために, (r, DB/DA) 平面を濃度分布が1%以内の誤差で, ガウス曲線に一致する領域, 誤差補関数曲線に一致する領域, 両曲線に共に一致しない領域の3領域に分けて図示した. TlCl単結晶にNaClの形でClのラジオアイソトープ, 36Clを付着させ, 36Clの拡散を行なわせて得られる濃度分布を測定し, これらの議論を実験的に例証した.

Sulphur diffusion in copper single crystals was studied at temperatures lower than 800°C for very short diffusion times. The distances of penetration were about 5 μm and a submicron sectioning technique was used. The curves obtained under these conditions do not follow a law of volume diffusion. These facts were interpreted by ascribing the role of diffusion short circuits to dislocations.

A tracer sectioning technique was used to measure cation self-diffusion coefficients in fully dense polycrystalline YaO3 and Er2Os under oxidizing conditions. The results are described by the relations for Y2O3 (1400° to 1670°C), and for Er2O3 (1400° to 1700°C). The greater activation energy for erbium diffusion in erbia may be partly attributable to a mass effect.

Experimental details are given of a thin film sectioning technique for the measurement of tracer diffusion in lithium metal. Results are given for 65Zn in Li between 57 and 173 °C. They are expressed by D = D0exp ( − Q/RT), where and Q = = (12.98 ± 0.24)kcal/mol. The activation energy equals, within margins of error, that of self-diffusion in Li. The agreement between vacancy based theories and the present results appears rather doubtful. Experimentelle Einzelheiten einer Dunnschicht-Schnittechnik fur Diffusionsmessungen an Lithiummetall werden beschrieben. Es werden Ergebnisse fur 65Zn in Li zwischen 57 und 173 °C angegeben, die sich durch D = D0exp ( − Q/RT) ausdrucken lassen, mit D0 = und Q = (12,98 ± 0,24) kcal/mol. Die Aktivierungsenergie ist, innerhalb der Fehlgrenzen, gleich derjenigen der Selbstdiffusion. Die Ubereinstimmung der auf Leerstellen gegrundeten Theorien mit diesen Ergebnissen erscheint ziemlich zweifelhaft.

The diffusion of Fe 59 and Co 60 in δ-Fe have been measured using a sectioning technique. The diffusion penetrations were determined by counting the radioactivity in the sections removed and also by the residual activity method. The results are summarized by the following equations: D Fe = 1.9 exp [−57.0 × 10 3 / RT ], D Co = 5.5 exp [−61.2 × 10 3 / RT ]. In both cases the activation energy and D 0 are significantly less than values previously reported for diffusion in the paramagnetic region of α-Fe. This amounts to approximately a threefold decrease in the value of D below that expected from extrapolation of the α-Fe data. The results indicate that were iron to retain the b.c.c. structure at all temperatures, the activation energy would demonstrate a non-linear functional dependence on temperature.

Examination of needled fabric subjected to uniaxial extension has shown how the fabric deforms. Use has been made of a sectioning technique employed to study fabric structure, and observed mechanisms related to measured fabric behaviour. It appears that the mode of deformation is somewhat dependent on factors which can be varied during fabric production. In addition, model structures are used to illustrate the importance of various structural levels in providing strength within the fibrous system.

Self‐diffusion of Ag110 in silver polycrystals subjected to simultaneous torsion was studied near 700° and 800°C using the sectioning technique. Strains ⩽ 0.50 and strain rates ⩽ 13.8×10−5 sec−1 were employed. Specimen structures before and after deformation were also examined. The effects of straining on diffusion were relatively small in all cases. At 800°C the diffusivity was increased by no more than ∼50%. At 700°C the increase was no more than ∼100%. A substantial part of this observed enhancement was undoubtedly only apparent and due to difficulties associated with surface roughness. The results agreed generally with our previous work involving deformation in extension and compression but were in marked disagreement with recent results of Lee and Maddin and Forestieri and Girifalco [C. H. Lee and R. Maddin, Trans. AIME 215, 397 (1959); A. F. Forestieri and L. A. Girifalco, J. Phys. Chem. Solids 10, 99 (1959)], who have reported enhancements larger by one to two orders of magnitude. No simple explana...

An electrolytic sectioning technique has been used to measure self-diffusion coefficients in silver single crystals in the temperature range 300–800 °C. The results are analyzed in terms of diffusion through the crystal lattice, enhanced by diffusion along dislocations.

Abstract The thin layer lathe sectioning technique was used to measure the self and solute diffusion coefficients of gold in f.c.c. lanthanum. Self-diffusion is given by D = 1.5 exp (− 45100/RT) cm2/sec, and gold solute diffusion by D = 2.2 × 10−2 exp (− 18100/RT) cm2/sec. The activation energy for self-diffusion is in good agreement with various semi-empirical rules. The high diffusivities and low activation energy for the solute diffusion of gold are interpreted in terms of the combined substitutional–interstitial diffusion mechanism.

In the present studies of self diffusion in gallium the diffusion coefficients in single crystals and coarse-grained polycrystals were found to be extremely low. The results are only claimed to be of qualitative interest because of limitations set mainly by the short half-life of the radiotracer used. Even so two main conclusions can be drawn: (i) there is no clear evidence of marked anisotropy of self diffusion, and (ii) for gallium and other soft or friable metals a microtome sectioning technique is to be preferred to a grinding method.

Simultaneous self-diffusion measurements of Zn and Au in near-equiatomic highly ordered AuZn ($B2$ structure) single-crystal specimens having 49.0, 50.0, 51.0 at.% Zn nominal composition were made over a temperature range of 428-650 \ifmmode^\circ\else\textdegree\fi{}C using ${\mathrm{Zn}}^{65}$ and ${\mathrm{Au}}^{195}$ radioactive tracers and the serial lathe sectioning technique. Employing a modified energy-discrimination method for nuclear counting, it was possible to measure the ratio of diffusivities $\frac{{D}_{\mathrm{Zn}}}{{D}_{\mathrm{Au}}}$-in addition to their individual values-following simultaneous diffusion of the two radioactive tracers in the same specimen. The diffusion parameters $Q$ and ${D}_{0}$ and the entropy of activation factor were computed in the composition range studied and compared with the corresponding quantities in the disordered Zn-base monovalent alloys ($A2$ structure). The magnitude of the ratio of the correlation factors in ordered and disordered phases was found to be consistent with the correlated six-atom-vacancy-jump diffusion mechanism in the highly ordered alloys. The self-diffusion data for Au and Zn in ${\ensuremath{\beta}}^{\ensuremath{'}}\ensuremath{-}\mathrm{AuZn}$ alloys also provides strong evidence for the presence of a nonequilibrium vacancy-defect structure on the Zn-rich side of stoichiometry.

The preparation of histological and cytological sections for study with the electron microscope presents several difficulties. These are due chiefly to the necessity of drying and to the low penetrating power of electrons.1 The distortion commonly attendant on air-drying can be obviated by vacuum-drying in the frozen state. The low penetrating power of electrons is more serious since for high resolution electron micrographs it has been found that sections must be less than 0.25 ν and preferably less than 0.1 ν thick.2 von Ardenne3 has described a method, but, judging from the one micrograph published, his sections were not sufficiently thin for good resolution or adequate penetration. The present paper describes a technique by means of which relatively uniform 0.1 ft sections of striated muscle have been prepared and examined with 60 kV electrons.Some types of material can be cut freehand2 but much histological material requires a microtome. No commercial microtomes cutting such thin sections are now avai...

Ultrathin serial frozen sections of frog and rat sciatic nerves fixed with osmic acid and formalin and prepared with a described modification of the thermal expansion sectioning technique, were examined with the electron microscope. The following structures are described in the internode portion of the nerve fibres: (1, a) The myelin sheath is covered with a 200 A thick compact granular membrane which corresponds to the neurilemma. (b) The main part of the myelin sheath separates into concentric rings from which thin lamellae peel off. The unit lamellae are 50 A thick, with a variable granular surface structure 50–100 A high. The sheath exhibits a concentric laminated fine structure in thin transverse and longitudinal sections, with an average layer thickness of 80 A. A concentric system of extremely regular and uniform lines, super-imposed upon the concentric lamination of the sheath, with an average line-spacing of 70–80 A, was seen consistently in osmic acid fixed frozen sections. Based on these observations a general concentric laminated structure of the myclin sheath is assumed. (2) Thin nodose filaments, 100–200 A in width, are found in the axis cylinder, forming a network which is filled with a granular substance. A dense net of interlaced nodose fibrils, 100–200 A in width, coats the internal sheath wall and provides the basis for the fine reticulum in the axis cylinder.

A new sectioning technique has been successfully developed and used to determine the three-dimensional form of the initial fatigue crack in copper. As previously found, intrusions are the earliest form of damage detectable and it has been further shown that their extension is by the formation of tubular holes starting from the surface. This mode of failure is finally superseded by sub-surface irregular microcrack link-up of the slip-band zone cracks and the gross form of crack propagation known as stage II.

Self‐diffusion of Ag110 in silver single crystals subjected to simultaneous deformation at 800 and 900°C was studied using the sectioning technique. The crystals were orientated for duplex slip and were deformed in extension and compression at constant strain rates in the range 1 to 28×10−5 sec.−1. Total strains as large as 0.33 were attained. Recrystallization occurred in the initially single crystal specimens during diffusion‐deformation under all conditions except tension at 800°C.The effect of straining on the rate of diffusion was found to be small in all cases. The straining changed the diffusivities by less than 50%, and it is concluded that the observed changes were probably within the experimental error. The results indicate that any increases in diffusion rate due to the generation of point defects or short‐circuiting paths during deformation were small. These conclusions are shown to be consistent with other experiments involving these phenomena.

The anisotropic diffusion coefficients of the radioactive tracers cadmium ($115m$) and gold (198) in single crystals of high-purity zinc, in directions parallel and perpendicular to the hexagonal axis, were measured by the standard sectioning technique. Cadmium diffused at a rate faster than that of self-diffusion and with ${D}_{\ensuremath{\perp}}g{D}_{\mathrm{II}}$. Gold diffused at a rate slower than that of self-diffusion and with ${D}_{\mathrm{II}}g{D}_{\ensuremath{\perp}}$. The results of the measurements are as follows: For cadimum ($115m$), ${D}_{\mathrm{II}}=(0.11\ifmmode\pm\else\textpm\fi{}0.01)\mathrm{exp}[\ensuremath{-}\frac{(20.54\ifmmode\pm\else\textpm\fi{}0.09)\ifmmode\times\else\texttimes\fi{}{10}^{3}}{\mathrm{RT}}]$ ${\mathrm{cm}}^{2}$/sec, ${D}_{\ensuremath{\perp}}=(0.12\ifmmode\pm\else\textpm\fi{}0.01)\mathrm{exp}[\ensuremath{-}\frac{(20.42\ifmmode\pm\else\textpm\fi{}0.03)\ifmmode\times\else\texttimes\fi{}{10}^{3}}{\mathrm{RT}}]$ ${\mathrm{cm}}^{2}$/sec; for gold (198), ${D}_{\mathrm{II}}=(0.97\ifmmode\pm\else\textpm\fi{}0.22)\ifmmode\times\else\texttimes\fi{}\mathrm{exp}[\ensuremath{-}\frac{(29.73\ifmmode\pm\else\textpm\fi{}0.26)\ifmmode\times\else\texttimes\fi{}{10}^{3}}{\mathrm{RT}}]$ ${\mathrm{cm}}^{2}$/sec, ${D}_{\ensuremath{\perp}}=(0.29\ifmmode\pm\else\textpm\fi{}0.12)\mathrm{exp}[\ensuremath{-}\frac{(29.72\ifmmode\pm\else\textpm\fi{}0.45)\ifmmode\times\else\texttimes\fi{}{10}^{3}}{\mathrm{RT}}]$ ${\mathrm{cm}}^{2}$/sec. On the basis of the vacancy mechanism one can interpret the fast diffusion of cadmium in terms of an appreciable binding between the vacancy and the diffusing ion; conversely the slow diffusion of gold in terms of a repulsion between the vacancy and the diffusing ion.

An electrolytic sectioning technique has been used to measure self-diffusion coefficients for gold in the temperature range 360 to 740 °C. At 740 °C our value agrees with previous work at this temperature, while the lower temperature values are larger than predicted by extrapolation of the well-established high-temperature behavior. The results are interpreted in terms of dislocation enhanced diffusion.

DURING the progress of the work described in Part I † certain improvements in apparatus and technique suggested themselves. The clamps have been improved so that they will hold fibres as fine as cotton and will not permit slipping during tests at low humidities when the surface hardness of the fibres becomes very great. A device has been provided whereby the two clamps may be handled as a unit during insertion of the fibre and can then be released from each other after being set up for measurement. An improved sectioning technique, developed for very short fibres, is described. Results on cotton stress-strain relation and elastic hysteresis in Celanese have been obtained. Maxwell's flow equation for plastic materials has been examined in its application to the present method.

Diffusion of cerium and neodymium in nickel has been studied by the serial sectioning technique using radioactive tracers141Ce and147Nd, in the temperature ranges 700° to 1100°C for volume and 500° to 875°C for grain boundary diffusion respectively. Volume diffusivities can be expressed as: $$\begin{gathered} D_{Ce/Ni} = (0.66 \pm 0.18)\exp \left( { - \frac{{60,800 \pm 810}}{{RT}}} \right)cm^2 /\sec \hfill \\ D_{Nd/Ni} = (0.44 \pm 0.13)\exp \left( { - \frac{{59,820 \pm 830}}{{RT}}} \right)cm^2 /\sec \hfill \\ \end{gathered} $$ and grain boundary diffusivities by: $$\begin{gathered} Dg_{Ce/Ni} = 0.11\exp \left( { - \frac{{29,550}}{{RT}}} \right)cm^2 /\sec \hfill \\ Dg_{Nd/Ni} = 0.07\exp \left( { - \frac{{28,580}}{{RT}}} \right)cm^2 /\sec \hfill \\ \end{gathered} $$ Results of volume diffusion have been compared with those calculated from the theories of diffusion based on size and charge difference between the solute and the solvent atoms. Whipple and Suzuoka methods have been used to evaluate the grain boundary diffusion coefficients. Both the methods give similar results.

The diffusion of gold in gamma uranium has been measured using a radioactive tracer and the sectioning technique. The values of D o and the activation energy are 4.86 × 10 −3 cm 2 /sec and 30 400 cal/mol respectively, fairly close to the values for self-diffusion in gamma uranium.

The self-diffusion of gold was measured in single crystalline specimens of 99.8 and 99.999% purity in the temperature range from 600-954\ifmmode^\circ\else\textdegree\fi{}C, by using ${\mathrm{Au}}^{198}$ as tracer and applying the sectioning technique. The temperature dependence of the self-diffusion coefficient is given by $D=(0.031\ifmmode\pm\else\textpm\fi{}0.004)\mathrm{exp}[\ensuremath{-}\frac{(39360\ifmmode\pm\else\textpm\fi{}280)}{\mathrm{RT}}] {\mathrm{cm}}^{2}/sec.$ Together with recently reported data on self-diffusion of copper, silver, and lead, this result is compared with empirical and theoretical predictions.

Self-diffusion coefficients of Tl and Br in TIBr single crystal were determined by the radioactive tracers and the serial sectioning technique. The results are as follows,DTl*=(1.316±0.013)exp[−(27.44±0.55)⁄RT]cm2⁄sec (420–300°C)DBr*=(1.227±0.013)×10−2exp[−(17.75±0.22)⁄RT]cm2⁄sec (420–250°C)where the activation energy is expressed in unit of kcal/mol.

Self-diffusion studies have been carried out on nominally 50-50 Au-Cd alloys by the standard sectioning technique using radioisotopes 115Cd and 198Au. From 300° to 590°C the results are well fitted by the valuesQ = 28.0 kcal/mole and D0 = 0.23 cm2/sec for cadmium and Q = 27.9 kcal/mole and D0 = 0.17 cm2/sec for gold. Between 590°C and the melting point at 626°C there is a marked upward curvature in both diffusion plots. The ratio of the diffusivities is roughly 4:3 throughout and is consistent with a mechanism of nearest neighbor vacancy jumping. The activation energies for diffusion exceed the sum of energies for vacancy formation and motion previously reported. Two possible explanations for this discrepancy are suggested.

Diffusion of sodium in albite from Amelia County, Virginia, was examined at high and intermediate temperatures by means of the sectioning technique and at low temperatures by means of an exchange technique. These studies indicate that diffusion is heterogeneous at low and intermediate temperatures, but goes to volume diffusion at high temperatures. Apparent diffusion coefficients of the order of magnitude of 10 −18 cm 2 /sec and an activation energy of approximately 3000 cal/mole sodium are determined for the low-temperature movement. An activation energy of approximately 35 kcal/mole sodium is determined for the high-temperature movement.

Der Reihenentwicklungskoeffizient zweiten Grades ist ein brauchbares Mas fur die Einschatzung des Fehlers experimentell bestimmter Polfiguren kubischer Materialien. Die Fehlerkoeffizienten hoheren Grades ermoglichen auserdem die Trennung der systematischen von den statistischen Fehlern. Es wurden vierzig in der Literatur angegebene Polfiguren untersucht. Die aus rontgenographischen Durch- und Ruckstrahlmessungen kombinierten Polfiguren weisen im allgemeinen wesentlich hohere Fehler auf als Messungen an Kugel- oder Zylinderproben, Proben mit Schraganschliff sowie Neutronenbeugungsmessungen. The second order coefficient of an expansion into a series is a usefull measure of the error of an experimentally determined pole figure. The higher order error coefficients may be used to distinguish between systematic and statistic errors. Fourty pole figures, published in the literature, have been analysed. Pole figures measured by a combined transmission and reflection technique exhibited the highest level of error. Those measured with zylindrical or spherical specimen, by the oblique sectioning technique or by neutron diffraction are much better.

Forced by the progressive perfectionation of the ultramicrotomes and by the improvement of preparation methods, the ultrathin sectioning technique has gained high importance for the electron-microscopical studies of the fine structure of wood cell walls. Wood has its own problems for ultramicrotomy. During cutting, the inhomogeneity of the cell wall and its chemical nature result in the formation of wrinkles and holes in the ultrathin sections. These artefacts are not completely avoidable but can be reduced by suitable embedding and by choosing the most suitable knife to a minimum. It is pointed out that for the best and most reliable statement on the object the cutting of serial sections is indispensable.

Self-diffusion of Zr in 12 and 16 mol.% CaO and of Ca in 16 mol.% CaO cubic zirconia was measured by the sectioning technique from 1700° to 2150°C. Lattice self-diffusion coefficients are: Autoradiographs show rapid grain boundary diffusion. DB is estimated as

The solute diffusion of cobalt in beta‐uranium was measured using the thin‐layer sectioning technique. The results can be expressed by D= 1.54×10−2 exp(−27 450/RT) cm2/sec. The diffusivities of cobalt are higher by about three orders of magnitude than the self‐diffusion coefficients in beta‐uranium. The possibility of cobalt diffusing by means of the combined substitutional‐interstitial mechanism has been examined.

Using a steady-state sectioning technique the migration of 22Na in Li has been investigated under temperature gradients and electric currents. The thermotransport “heat of transport” has been found to be Q* = (−3.0 ± 1.2) (kcal/mol), and the “effective charge number” of electrotransport z* − 4.7 ± 1.9. Theory predicts the electronic share of the heat of transport to be small, while the phonon contribution, only qualitatively treated, may be of the order of + 1 kcal/mol. The intrinsic contribution is calculated to be Q*0 = (−4.0 ± 2.5) kcal/mol. Classical models applied to Q*0 give indication that Na diffuses substitutionally in Li, and that the vacancy formation energy amounts to about two thirds of the diffusion activation energy. This is in line with evidence from X-ray dilatometry. The electrotransport results yield the effective resistivity of the activated impurity–vacancy complex, about 1.6 μ μΩ cm/% defects. It is suggested that in Li self-transport a considerable role may be played by interstitials. Mittels einer Schnittechnik fur Stationarprofil wird die Wanderung von 22Na in Li bei thermischen Gradienten und bei elektrischem Stromdurchgang untersucht. Die „Uberfuhrungswarme” des Thermotransport wird zu Q* = (−3,0 ± 1,2) kcal/Mol bestimmt, die „effektive Ladungszahl” des Elektrotransports zu z* = −4,7 ± 1,9. Der Theorie nach ist der elektronische Teil der Uberfuhrungswarme gering. Der Beitrag der Phononen, bisher nur qualitativ behandelt, durfte von der Grosenordnung + 1 kcal/Mol sein. Der Beitrag der Diffusionsenergien wird zu Q*0 = (−4,0 ± 2,5) kcal/Mol berechnet. Aus klassischen Modellen fur Q*0 wird gefolgert, das Na in Li substitutionell diffundiert, und das die Leerstellen-Bildungsenergie etwa zwei Drittel der Diffusions-Aktivierungsenergie betragt. Dies wird durch experimentelle Ergebnisse der Rontgen-Dilatometrie bestatigt. Die Messungen des Elektrotransports ergeben einen effektiven spezifischen Widerstand fur den aktivierten Verunreinigungs–Leerstellen-Komplex von ungefahr 1,6 μ μΩcm/% Defekte. Es wird angedeutet, das im Selbsttransport von Li Zwischengitteratome eine wesentliche Rolle spielen konnten.

The sectioning technique was used to study the diffusion of radioactive tracers in high-purity zinc single crystals. Diffusion both parallel and perpendicular to the hexagonal axis was measured. The diffusion of ${\mathrm{Cu}}^{64}$ was measured over the temperature range from about 338\ifmmode^\circ\else\textdegree\fi{}C to 415\ifmmode^\circ\else\textdegree\fi{}C with the results ${D}_{\mathrm{II}}=(2.22\ifmmode\pm\else\textpm\fi{}0.57)\mathrm{exp}[\ensuremath{-}(29.53\ifmmode\pm\else\textpm\fi{}0.29)\ifmmode\times\else\texttimes\fi{}\frac{{10}^{3}}{\mathrm{RT}}] \frac{{\mathrm{cm}}^{2}}{sec},$ ${D}_{\ensuremath{\perp}}=(2.00\ifmmode\pm\else\textpm\fi{}0.54)\mathrm{exp}[\ensuremath{-}(29.92\ifmmode\pm\else\textpm\fi{}0.30)\ifmmode\times\else\texttimes\fi{}\frac{{10}^{3}}{\mathrm{RT}}]\frac{{\mathrm{cm}}^{2}}{sec},$ The diffusion of ${\mathrm{Ga}}^{72}$ was measured over the range from about 240\ifmmode^\circ\else\textdegree\fi{}C to 403\ifmmode^\circ\else\textdegree\fi{}C with the results ${D}_{\mathrm{II}}=(0.016\ifmmode\pm\else\textpm\fi{}0.001)\mathrm{exp}[\ensuremath{-}(18.40\ifmmode\pm\else\textpm\fi{}0.06)\ifmmode\times\else\texttimes\fi{}\frac{{10}^{3}}{\mathrm{RT}}]\frac{{\mathrm{cm}}^{2}}{sec},$ ${D}_{\ensuremath{\perp}}=(0.018\ifmmode\pm\else\textpm\fi{}0.001)\mathrm{exp}[\ensuremath{-}(18.15\ifmmode\pm\else\textpm\fi{}0.08)\ifmmode\times\else\texttimes\fi{}\frac{{10}^{3}}{\mathrm{RT}}]\frac{{\mathrm{cm}}^{2}}{sec},$ Copper diffused at a rate faster than gold but slower than silver. As in silver and gold, ${D}_{\mathrm{II}}g{D}_{\ensuremath{\perp}}$; but the anisotropy was much smaller in Cu than in Ag or Au. The measured values of gallium fall somewhat below those for indium and show ${D}_{\ensuremath{\perp}}g{D}_{\mathrm{II}}$. The relative diffusion rates are qualitatively in accord with the predictions of LeClaire's theory of homovalent diffusion. The sign of anisotropy is explained in terms of the electrostatic interaction between the diffusing ion and the vacancy, and the reduced anisotropy of copper diffusion is interpreted as evidence of a size effect.

The self‐diffusion of antimony has been measured in single crystals with the tracer 124Sb. The least‐squares fit to the data gives in the direction of the trigonal axis Q‖=47.1±1.2 kcal/mole and ln(D0 in cm2/sec)=3.1±0.7, and in the plane perpendicular to the trigonal axis Q‖=44.4±4.9 kcal/mole and ln(D0 in cm2/sec)=2.81±2.8. The standard sectioning technique was used except that the very friable nature of the semimetal complicated the procedure at practically every step of the operation. The greatest source for the inaccuracy arose from the ``tails'' on the deep penetration side, noticable for D‖ and strongly prominent for D‖. Correlation considerations in the Sb lattice are considered in detail in the Appendix.

Advantageous modifications of a fresh frozen sectioning technique for peripheral nerve (Williams, 1959) include reduction in size of the block of supporting tissue, the use of human hair as a ligature, the multiple embedding of specimens and the use of liver sandwiches for irregular specimens. Observation with oblique incident illumination indicates that fresh sectioned fibres remain approximately cylindrical. Fresh sections treated for 5 min with common fixatives such as 10% formal saline, Bouin's fluid, and Flemming's fluid show widespread changes in the outline, texture, and dimensions of the myelin sheaths. A modified Flemming fixation/haematoxylin staining method may be used with fresh sections; this gives reasonable preservation of the external sheath boundary but is unsuitable for measurements of internal diameter. Luft's buffered potassium permanganate solution provides an easily standardized, effective method of producing permanent preparations for quantitative studies. Holmes's silver impregnation technique may be adapted for use with fresh frozen sections. Interferometric estimations may be made upon axoplasm using 5 µ fresh frozen sections in saline. Care must be taken to determine the axoplasmic thickness present. Adequate sampling of an extended section, when using shearing system objectives, may be accomplished by serial stripping of the section under the dissecting microscope.

The self-diffusion of nickel has been studied in polycrystalline samples by a sectioning technique. There is evidence of grain boundary diffusion below temperatures of 1150 °C. The results obtained between 1150° and 1400 °C are representative of volume diffusion and are represented by the expression[Formula: see text]A comparison is made with the results of other self-diffusion studies using Zener's hypothesis.

Experimental results are presented for the diffusion of silver in silver bromide single crystals for temperatures from 140\ifmmode^\circ\else\textdegree\fi{}C to the melting point. The results are obtained by the sectioning technique, using radioactive tracers. The observed diffusion coefficients fall below the values that would normally be expected from the electrical conductivity by a factor of 0.46 to 0.66. The discrepancy is ascribed to the simultaneous occurrence of two types of interstitialcy jumps, with corrections introduced for differing displacements of interstitials and tracer atoms and for correlation effects according to Bardeen and Herring. The resulting mobilities can be represented as $\ensuremath{\mu}={\ensuremath{\mu}}_{0}\mathrm{exp}(\ensuremath{-}\frac{U}{\mathrm{kT}})$ over a wide range of temperatures with ${\ensuremath{\mu}}_{0}=6.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3} \mathrm{and} 1.57\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ ${\mathrm{cm}}^{2}$/volt-sec and $U=0.078 \mathrm{and} 0.225$ ev, respectively, for collinear and non-collinear jumps. These values are in reasonable agreement with theoretical calculations for silver chloride. The diffusion coefficient is observed to fall increasingly below expected values as the temperature approaches the melting point, and as a possible explanation it is surmised that the activation energy for collinear jumps drops gradually towards zero. A comparison is made to similar results which have been reported for diffusion of silver in silver chloride.

The diffusion of mercury at very low concentration in single crystal gold has been measured over the temperature range 500°C to approximately 1000°C using a sectioning technique. It was found that above 600°C the temperature dependence of the diffusion coefficient followed the equation: The results obtained are discussed in relation to current theories of impurity diffusion in metals.

The diffusion of mercury has been studied in high-purity zinc as a function of temperature, using the sectioning technique. The diffusion coefficients as measured in single crystals are given by ${D}_{\mathrm{II}}=(0.056\ifmmode\pm\else\textpm\fi{}0.002)\ifmmode\times\else\texttimes\fi{}\mathrm{exp}[\ensuremath{-}\frac{(19700\ifmmode\pm\else\textpm\fi{}48)}{\mathrm{RT}}]$ ${\mathrm{cm}}^{2}$/sec, and ${D}_{\ensuremath{\perp}}=(0.073\ifmmode\pm\else\textpm\fi{}0.006)\mathrm{exp}[\ensuremath{-}\frac{(20180\ifmmode\pm\else\textpm\fi{}94)}{\mathrm{RT}}]$ ${\mathrm{cm}}^{2}$/sec, where ${D}_{\mathrm{II}}$ and ${D}_{\ensuremath{\perp}}$ are the diffusion coefficients parallel and perpendicular to the hexagonal axis, respectively. Compared to the diffusion of cadmium in zinc, where ${D}_{\ensuremath{\perp}}g{D}_{\mathrm{II}}$, mercury diffuses with a slightly smaller activation energy, and with ${D}_{\mathrm{II}}g{D}_{\ensuremath{\perp}}$. The results are discussed on the basis of the basal and nonbasal vacancy mechanisms, and the influence of the ion size of the diffusing atom is examined to explain the diffusion anisotropy.

A technique has been developed for sectioning small gallium arsenide samples utilizing anodic oxidation and subsequent removal of the oxide layers. It differs from those previously reported in that only one surface of the wafer is exposed during anodization and total immersion in the electrolyte is not required. The use of an ammonium pentaborate solution as the electrolyte and a relatively simple anodization apparatus has yielded oxide layers of uniform thickness on the surfaces of gallium arsenide wafers. After removing the oxide layers, the surfaces of the wafers were found to be relatively free of pitting and macroscopic defects.

A dye-staining and sectioning technique has been developed which permits, for the first time, a direct, visual determination of the location of melamine resin in treated wool fibers. The resin appears to be distributed uniformly within the fiber structure. Techniques are described and the results are illustrated by photomicrographs (one in color).

Electron microscopic studies of thin sections of industrial carbons have been extended to green mixes. Pitch is shown to have discrete spherical bodies (0.5–1.0 μ) distributed in a continuous medium. A dissolution technique is described which distinguishes the coke from the binder in a green mix. The results suggest that the coke particles have an irregular three-dimensional porous structure and the apparent inability to observe particles larger than a few microns is explained. The sectioning technique leads to morphological features comparable to those seen by replication.

Food preferences and feeding behaviour of abundant species of oribatid mites in a black pine plantation have been studied by soil sectioning technique. It is suggested that Microtritia minima, Rhysotritia duplicata and Phthiracarus sp. play an important role in the mechanical breakdown of decaying litter and, by contributing to the humification process, help in the accumulation of plant nutrients. Due to poor mobility their contribution to fungal spore dissemination is insignificant. Chamobates incisus was determined to be a fungivorous species while no exact information could be obtained about the precise food of Tectocepheus velatus. Rest of the species seemed to consume large quantities of decaying litter but in view of their low populations throughout, presumably they do not contribute appreciably in the humification process.The speed of decomposition of faecal pellets seemed to be governed by the type of food ingested. The role of oribatid fauna in the litter and soil ecosystems is discussed.

The fluorescence technique has been applied to whole body tape sections to study the distribution of 6 commercially available tetracyclines. The tape sectioning technique described by Ullberg for autoradiography of labeled chemical compounds has proved to be of value also in distribution studies of fluorophors. The distribution patterns of the tetracycline compounds have been studied as well as the influence of different routes of administration. The fluorescence distribution picture of tetracycline has been compared to the autoradiogram of the radioactively labeled compound. The influence of pH on the fluorescence has been investigated. Advantages and limitations of the method are discussed.