Planar distributions of dislocations III. The exact positions of important dislocations when the number in an array is large

1971 ◽  
Vol 320 (1543) ◽  
pp. 527-535 ◽  
Keyword(s):  
Simple Procedure ◽  
Continuous Distribution ◽  
The Other ◽  
General Situation ◽  
Burgers Vector ◽  
Large Numbers ◽  
Discrete Dislocations ◽  
Model Determination ◽  
Exact Positions

It is shown that if large numbers of complete dislocations are piled-up against a coplanar barrier dislocation, the equilibrium positions occupied by those discrete dislocations in the immediate vicinity of the barrier can be found directly from the characteristics, in the barrier’s neighbourhood, of the function representing the situation where all the dislocations are smeared into a continuous distribution, assuming that they have the same Burgers vector. Since such characteristics are readily obtained by examining the relevant singular integral equation for the model, determination of the important dislocation positions becomes a simple procedure. The approach is exact and refers to the limiting situation where the number of dislocations is very large; on the other hand, the smeared-discrete compromise approach (described in earlier papers in this series), in which the important dislocations remain discrete while the remainder are smeared into a continuous distribution, is approximate but is applicable to the more general situation where the number of dislocations is sufficiently large for the distance between the important dislocations to be small compared with the array length.

Determination of the Burgers vector of a dislocation in a Fe-Mn alloy by weak-beam image in HVEM

1978 ◽  
Vol 36 (1) ◽  
pp. 330-331
Author(s):  
Y. Ishida ◽  
H. Ishida ◽  
K. Kohra ◽  
H. Ichinose
Keyword(s):  
High Order ◽  
Simulation Technique ◽  
The Other ◽  
Image Simulation ◽  
Diffraction Vector ◽  
Burgers Vector ◽  
Weak Beam ◽  
Beam Image ◽  
Edge Component

IntroductionA simple and accurate technique to determine the Burgers vector of a dislocation has become feasible with the advent of HVEM. The conventional image vanishing technique(1) using Bragg conditions with the diffraction vector perpendicular to the Burgers vector suffers from various drawbacks; The dislocation image appears even when the g.b = 0 criterion is satisfied, if the edge component of the dislocation is large. On the other hand, the image disappears for certain high order diffractions even when g.b ≠ 0. Furthermore, the determination of the magnitude of the Burgers vector is not easy with the criterion. Recent image simulation technique is free from the ambiguities but require too many parameters for the computation. The weak-beam “fringe counting” technique investigated in the present study is immune from the problems. Even the magnitude of the Burgers vector is determined from the number of the terminating thickness fringes at the exit of the dislocation in wedge shaped foil surfaces.

Simultaneous determination of trace elements in serum by energy-dispersive x-ray fluorescence spectrometry.

1984 ◽  
Vol 30 (8) ◽  
pp. 1300-1303 ◽  
Author(s):  
F Rastegar ◽  
E A Maier ◽  
R Heimburger ◽  
C Christophe ◽  
C Ruch ◽  
...  
Keyword(s):  
Analytical Procedure ◽  
Internal Standard ◽  
Detection Limits ◽  
The Other ◽  
Energy Dispersive ◽  
Statistical Distributions ◽  
Polypropylene Film ◽  
X Ray ◽  
Large Numbers

Abstract Energy-dispersive x-ray fluorescence is applied in the analysis of human serum to determine the concentrations of several elements simultaneously with minimal manipulation of the sample. The analytical procedure has been developed with standard sera, and standardization, detection limits, and reproducibility have been established. A 50-microL sample of diluted serum, to which an internal standard has been added, is deposited on a thin (4-microns thick) polypropylene film and analyzed by x-ray fluorescence. We report the statistical distributions of the concentrations of Fe, Cu, Zn, and Br obtained in the population (103 samples) studied, and report detection limits for the other 22 elements studied. The simplicity of the method, the high throughput, and the possibility of automating the measurements make this procedure suitable for screening large numbers of sera.

Computer Simulation of Defect Images from Transmission Electron Microscopy

1977 ◽  
Vol 35 ◽  
pp. 54-55
Author(s):  
W. D. Cooper
Keyword(s):  
Electron Microscopy ◽  
Simple Procedure ◽  
Defect Structures ◽  
Dislocation Loops ◽  
Burgers Vector ◽  
Plane Normal ◽  
Unambiguous Determination ◽  
Transmission Electron ◽  
Shear Component

During recent years, defect structures resulting from radiation damage have been successfully studied by a large number of investigators. Early studies were based primarily on the analysis of the characteristic black-white lobe contrast from small dislocation loops. Contrast calculations indicated that the sense of the black-white contrast, relative to the diffracting vector at a given depth in the foil, could be used to determine the nature (vacancy or interstitial) of the loop. These calculations have also been used to formulate rules for the determination of the loop Burgers vector and habit plane normal [1]. For pure edge loops this simple procedure is quite satisfactory, but for loops with a shear component of the Burgers vector it becomes very involved and, in certain geometries, may lead to erroneous conclusions. Carpenter has demonstrated that “unsafe” orientations exist which do not permit the unambiguous determination of the Burgers vector relative to the loop plane [2].

scholarly journals The crystal structure of copper sulphate pentahydrate, CuSO 4 .5H 2 O

1934 ◽  
Vol 146 (858) ◽  
pp. 570-582 ◽  
Keyword(s):  
Crystal Structure ◽  
Copper Sulphate ◽  
The Other ◽  
Large Numbers ◽  
Points Of View

Despite their frequent appearance in the laboratory, few of the structures of hydrated salts have as yet been found. This may be due to the large numbers of parameters usually involved, which, in the absence of any general laws concerning water of crystallization, makes the analysis very difficult. It was thought that clues to such general laws might be obtained from a determination of the structure of copper sulphate pentahydrate which has many interesting properties and which has been studied from many different points of view. For example, the decomposition on heating proceeds in three distinct stages, CuSO 4 .5H 2 O→CuSO 4 . 3H 2 O→CuSO 4 . H 2 O→CuSO 4 , reactions which should be explainable from a knowledge of the structure. Also, four of the waters are replaceable by ammonias, while the other one is retained. This suggests that one of the waters is very different from the others.

scholarly journals Semi-Empirical Determination of the Position of RRAB Stars on The H-R Diagram

1998 ◽  
Vol 11 (1) ◽  
pp. 373-373
Author(s):  
J. Jurcsik ◽  
G. Kovács
Keyword(s):  
Light Curve ◽  
Light Curves ◽  
The Other ◽  
Physical Parameters ◽  
Present Sample ◽  
Large Numbers ◽  
Empirical Determination ◽  
The Absolute ◽  
Semi Empirical

In a recent series of papers, it was shown that the metallicity and the absolute V, I and K mean magnitudes of RRab stars can be accurately calculated using only their periods and the low order Fourier parameters of the V light curves. The application of these formulae in conjunction with the synthetic colours of the model atmospheres and with the theoretical pulsation periods enables us to determine all the basic physical parameters (i.e. logL, logT, logM and [Fe/H]) of any variable with an accurate light curve. As a result, we might trace evolutionary tracks on the H—R diagram by plotting the stars with the same mass and metallicity. From a present sample of nearly 300 stars, signs of differences in the evolutionary statescan be suspected but not yet proven. The accumulation of large numbers of precise light and colour curves, onthe one hand, will further improve the empirical formulae and therefore theaccuracy of the derived parameters and, on the other hand, will increase our chances of constructing better-populated empirical evolutionary tracks.

Determination of the lattice translation across {110} APBs in GaAs

1988 ◽  
Vol 46 ◽  
pp. 600-601
Author(s):  
D.R. Rasmussen ◽  
N.-H. Cho ◽  
C.B. Carter
Keyword(s):  
Grain Boundaries ◽  
Lower Energy ◽  
Antiphase Boundary ◽  
The Other ◽  
Boundary Structure ◽  
Interface Plane ◽  
Inversion Symmetry ◽  
High Angle ◽  
Equilibrium Distance

Domains in GaAs can exist which are related to one another by the inversion symmetry, i.e., the sites of gallium and arsenic in one domain are interchanged in the other domain. The boundary between these two different domains is known as an antiphase boundary [1], In the terminology used to describe grain boundaries, the grains on either side of this boundary can be regarded as being Σ=1-related. For the {110} interface plane, in particular, there are equal numbers of GaGa and As-As anti-site bonds across the interface. The equilibrium distance between two atoms of the same kind crossing the boundary is expected to be different from the length of normal GaAs bonds in the bulk. Therefore, the relative position of each grain on either side of an APB may be translated such that the boundary can have a lower energy situation. This translation does not affect the perfect Σ=1 coincidence site relationship. Such a lattice translation is expected for all high-angle grain boundaries as a way of relaxation of the boundary structure.

Procedures for the Quantitative Determination of Autoprothrombin C

1962 ◽  
Vol 08 (03) ◽  
pp. 434-441 ◽  
Author(s):  
Edmond R Cole ◽  
Ewa Marciniak ◽  
Walter H Seegers
Keyword(s):  
Quantitative Determination ◽  
Plasma Sample ◽  
Quantitative Measure ◽  
The Other ◽  
Clotting Time ◽  
Bovine Plasma ◽  
Autoprothrombin C

SummaryTwo quantitative procedures for autoprothrombin C are described. In one of these purified prothrombin is used as a substrate, and the activity of autoprothrombin C can be measured even if thrombin is in the preparation. In this procedure a reaction mixture is used wherein the thrombin titer which develops in 20 minutes is proportional to the autoprothrombin C in the reaction mixture. A unit is defined as the amount which will generate 70 units of thrombin in the standardized reaction mixture. In the other method thrombin interferes with the result, because a standard bovine plasma sample is recalcified and the clotting time is noted. Autoprothrombin C shortens the clotting time, and the extent of this is a quantitative measure of autoprothrombin C activity.

Determination of Factor XIII Activity and of Factor XIII Inhibitors Using an Ammonium-Sensitive Electrode

1983 ◽  
Vol 50 (02) ◽  
pp. 563-566 ◽  
Author(s):  
P Hellstern ◽  
K Schilz ◽  
G von Blohn ◽  
E Wenzel
Keyword(s):  
Factor Xiii ◽  
Normal Subjects ◽  
The Other ◽  
Activity Measurement ◽  
Factor Xiii Deficiency ◽  
Assay Procedure ◽  
Stabilization Factor ◽  
Release Method ◽  
Sensitive Electrode

SummaryAn assay for rapid factor XIII activity measurement has been developed based on the determination of the ammonium released during fibrin stabilization. Factor XIII was activated by thrombin and calcium. Ammonium was measured by an ammonium-sensitive electrode. It was demonstrated that the assay procedure yields accurate and precise results and that factor XIII-catalyzed fibrin stabilization can be measured kinetically. The amount of ammonium released during the first 90 min of fibrin stabilization was found to be 7.8 ± 0.5 moles per mole fibrinogen, which is in agreement with the findings of other authors. In 15 normal subjects and in 15 patients suffering from diseases with suspected factor XIII deficiency there was a satisfactory correlation between the results obtained by the “ammonium-release-method”, Bohn’s method, and the immunological assay (r1 = 0.65; r2= 0.70; p<0.01). In 3 of 5 patients with paraproteinemias the values of factor XIII activity determined by the ammonium-release method were markedly lower than those estimated by the other methods. It could be shown that inhibitor mechanisms were responsible for these discrepancies.

TELIOSPORE DEVELOPMENT IN THE PUCCINIASTREAE

1933 ◽  
Vol 9 (5) ◽  
pp. 458-485 ◽  
Author(s):  
S. M. Pady
Keyword(s):  
Epidermal Cells ◽  
The Other ◽  
General Situation ◽  
Thin Walled ◽  
Primordial Cell ◽  
Teliospore Development

The genera that constitute the Pucciniastreae display a wide variation in the type of teliospore produced, as well as in the time and place of production. From the standpoint of development, however, there is a general situation that is common. In all genera primordial cells are formed from enlarged hyphal cells of the mycelium. These give rise to teliospore initials which are in the epidermal cells in Calyptospora, Milesia, Hyalopsora and Thecopsora, and are subepidermal in the other genera. These initials divide to form the mature teliospores, which are thick or thin walled, and few to many-celled. In all cases the teliospore is the product of a single primordial cell.The teliospores of Calyptospora goeppertiana are formed from a perennial mycelium, which causes a witches' broom and hypertrophied stems on species of Vaccinium. The mycelium gives rise to primordial cells in the cortex just below the epidermis. Each primordial cell pierces the host wall above and the contents pass in to form the initial, which by growth and division becomes the teliospore. The mature teliospores are one- to four-celled, with a thickened, dark brown wall. Development is not simultaneous, but progressive, and the teliospores are first formed in the basal parts, moving slowly upward until every cell of the hypertrophied portion of the stem is completely filled. In four species of Milesia the method of development is similar. The spores, however, are thin walled, and are formed in the epidermal cells of the overwintered fronds of their fern hosts. Thecopsora vacciniorum is similar to Milesia in many respects. The teliospores are intra-epidermal, thin walled and multicellular. In Pucciniastrum the teliospores are subepidermal, and arise from primordial cells, as in Calyptospora, Milesia and Thecopsora. The teliospore initials are closely packed, and the mature spores may form extended crusts. The simplest type of development is found in Uredinopsis, which is generally considered to be the most primitive of the fern rusts. Primordial cells are formed in the same way as in the other genera. These round up to form the initials, and cross walls are laid down to give the mature spores.From these studies two possible lines of development are suggested, both beginning with Uredinopsis. One line would lead through the intra-epidermal forms, as Milesia, Calyptospora, etc., and the other through the subepidermal genera, as Pucciniastrum and Melampsoridium.

Sign in / Sign up

Export Citation Format

Share Document