Some experimental measurements of the inner potentials of various crystals

1951 ◽  
Vol 206 (1085) ◽  
pp. 219-232 ◽  
Keyword(s):  
Electron Beam ◽  
Electron Diffraction ◽  
Single Crystal ◽  
Oxide Layer ◽  
Experimental Measurements ◽  
Surface Layers ◽  
Fast Electrons ◽  
The Past ◽  
Materials Used ◽  
Made In

Although a large number of measurements of inner potential have been made in the past, the results have, on the whole, been far from consistent. These measurements were made by electron diffraction methods, and one possible reason for the lack of consistency is that, owing to the very limited penetration of the electron beam, the nature of the surface layers of the specimen will play an important part in the results obtained. In particular, if the specimen is a single crystal, there arises the possibility that different results will be obtained if the measurements are made using crystallographically different surfaces of the crystal. This possibility was examined experimentally and, for the materials used, no difference was found in the results obtained from different surfaces of the same crystal. Measurements were also made, using fast electrons (60 kV), of the inner potentials of metal crystals, and it was found that consistent results could be obtained in all cases if suitable experimental precautions were observed. It was also found that the presence of a thin contaminating layer on the surface (e. g. an oxide layer) did not affect the results provided the electron beam was able to penetrate the first few atomic layers of the specimen itself.

”Extra-Reflexe“ in Elektronenbeugungsdiagrammen von Silicium nach Ionenbeschuß

1969 ◽  
Vol 24 (6) ◽  
pp. 918-921
Author(s):  
Karl Kleinhenz
Keyword(s):  
Fine Structure ◽  
Electron Diffraction ◽  
Single Crystal ◽  
Stacking Faults ◽  
Silicon Single Crystal ◽  
Fast Electrons ◽  
Ewald Sphere

The electron diffraction diagrams of silicon single crystal foils, thinned by usual etch-technique and bombarded by ions, contained several finenesses, which had been investigated in order to analyse stacking faults and precipitations. Moreover it could be shown, that it is not allowed to replace the Ewald-sphere by an Ewald-plane exploring the fine structure of diffraction diagrams, not even applying fast electrons (100 kV).

Orthorhombic Splitting and Chemical Etching of Ba2Ycu3O7-δ Crystal Surfaces

1989 ◽  
Vol 169 ◽  
Author(s):  
D. J. Werder ◽  
C. H. Chen ◽  
M. Gurvitch ◽  
B. Miller ◽  
L. F. Schneemeyer ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Diffraction ◽  
Single Crystal ◽  
Chemical Etching ◽  
Poor Quality ◽  
Crystal Surfaces ◽  
Surface Layers ◽  
The Poor ◽  
Transmission Electron

AbstractWe find by transmission electron diffraction (TED) that the orthorhombic splitting of the upper surface layers (< 1 μm) of single crystal Ba2YCu3O7-δ(YBCO) is reduced, differing by 10 to 30 percent from the bulk value. We also find by transmission electron microscopy (TEM) that in general the surfaces are of inferior quality, and thus, not representative of the bulk. These results have important consequences for those experiments that probe only the upper surface layers. By etching with either Br/ethanol or HClO4/NaClO4 the poor quality surfaces can be removed.

scholarly journals EXPERIMENTAL DATA ON THE OVERTOPPING OF SEAWALLS BY WAVES

2011 ◽  
Vol 1 (7) ◽  
pp. 36
Author(s):  
A. Paape
Keyword(s):  
Wave Height ◽  
Know How ◽  
The Past ◽  
Maximum Value ◽  
Wave Heights ◽  
Run Up ◽  
Materials Used ◽  
The Stability ◽  
The Waves ◽  
Made In

In the past it has been found that serious damage and breaching of seawalls is most frequently caused by overtopping. Hence for the design of seawalls data must be available about the overtopping by waves of the different profiles that might be possible. Naturally the conditions under which damage is caused to the seawall also depend on the type of construction and the materials used, for example: the stability of grass covered dikes can be endangered seriously by water flowing over the inner slope. In many designs the necessary height of a seawall has been defined such that not more than 2% of the waves overtop the crest, under chosen design conditions. This criterion has been determined on the assumption that the overtopping must remain very small. Some overtopping has to be accepted because no maximum value for wave height and wave run-up can be given, unless of course the wave height is limited by fore-shore conditions. Unfortunately this criterion gives no information about the volume and concentration of water overtopping the crest in each instance. Moreover it is of interest to know how this overtopping varies with other conditions, such as changes in the significant wave height. Information about the overtopping by waves was obtained from model investigations on simple plane slopes w^th inclinations varying from 1 : 8 to 1 : 2. The experiments were made in a windflume where wind generated waves as well as regular waves were employed. Using wind generated waves, conditions from nature regarding the distribution of wave heights could be reproduced. It appeared that the overtopping depends on the irregularity of the waves and that the same effects cannot be reproduced using regular paddle generated waves. In this paper a description of the model and the results of these tests are given. Investigations are m progress on composite slopes, including the reproduction of conditions for a seawall which suffered much overtopping but remained practically undamaged during the flood of 1953.

Dislocations, Ordering and Antiferromagnetic Domains in MnO

1970 ◽  
Vol 28 ◽  
pp. 522-523
Author(s):  
D. J. Barber ◽  
R. G. Evans
Keyword(s):  
Electron Diffraction ◽  
Single Crystal ◽  
Optical Microscopy ◽  
Defect Chemistry ◽  
Magnetic Structures ◽  
Optically Transparent ◽  
Magnetic Features ◽  
Antiferromagnetic Domains

Manganese (II) oxide, MnO, in common with CoO, NiO and FeO, possesses the NaCl structure and shows antiferromagnetism below its Neel point, Tn∼ 122 K. However, the defect chemistry of the four oxides is different and the magnetic structures are not identical. The non-stoichiometry in MnO2 small (∼2%) and below the Tn the spins lie in (111) planes. Previous work reported observations of magnetic features in CoO and NiO. The aim of our work was to find explanations for certain resonance results on antiferromagnetic MnO.Foils of single crystal MnO were prepared from shaped discs by dissolution in a mixture of HCl and HNO3. Optical microscopy revealed that the etch-pitted foils contained cruciform-shaped precipitates, often thick and proud of the surface but red-colored when optically transparent (MnO is green). Electron diffraction and probe microanalysis indicated that the precipitates were Mn2O3, in contrast with recent findings of Co3O4 in CoO.

Studies of Oxide Formation on Copper Thin Films by Electron Microscopy

1977 ◽  
Vol 35 ◽  
pp. 316-317
Author(s):  
G. G. Hembree ◽  
M. A. Otooni ◽  
J. M. Cowley
Keyword(s):  
Electron Microscopy ◽  
Electron Diffraction ◽  
Single Crystal ◽  
Crystal Surface ◽  
Crystal Defects ◽  
Diffraction Reflection ◽  
Reaction Products ◽  
Intermediate Energies ◽  
Crystal Films ◽  
Reflection Electron Microscopy

The formation of oxide structures on single crystal films of metals has been investigated using the REMEDIE system (for Reflection Electron Microscopy and Electron Diffraction at Intermediate Energies) (1). Using this instrument scanning images can be obtained with a 5 to 15keV incident electron beam by collecting either secondary or diffracted electrons from the crystal surface (2). It is particularly suited to studies of the present sort where the surface reactions are strongly related to surface morphology and crystal defects and the growth of reaction products is inhomogeneous and not adequately described in terms of a single parameter. Observation of the samples has also been made by reflection electron diffraction, reflection electron microscopy and replication techniques in a JEM-100B electron microscope.A thin single crystal film of copper, epitaxially grown on NaCl of (100) orientation, was repositioned on a large copper single crystal of (111) orientation.

Quanitative aspects of electron diffraction using electron holography

1995 ◽  
Vol 53 ◽  
pp. 616-617
Author(s):  
E. Völkl ◽  
L.F. Allard ◽  
B. Frost ◽  
T.A. Nolan
Keyword(s):  
Electron Beam ◽  
Electron Diffraction ◽  
Software Package ◽  
Spatial Coherence ◽  
Electron Holography ◽  
Image Intensity ◽  
Interference Fringes ◽  
Complex Image ◽  
The Difference ◽  
Recorded Image

Off-axis electron holography has the well known ability to preserve the complex image wave within the final, recorded image. This final image described by I(x,y) = I(r) contains contributions from the image intensity of the elastically scattered electrons IeI (r) = |A(r) exp (iΦ(r)) |, the contributions from the inelastically scattered electrons IineI (r), and the complex image wave Ψ = A(r) exp(iΦ(r)) as:(1) I(r) = IeI (r) + Iinel (r) + μ A(r) cos(2π Δk r + Φ(r))where the constant μ describes the contrast of the interference fringes which are related to the spatial coherence of the electron beam, and Φk is the resulting vector of the difference of the wavefront vectors of the two overlaping beams. Using a software package like HoloWorks, the complex image wave Ψ can be extracted.

Searching for the causes why some of the paintings by Mihaly Munkacsy are darkening

1990 ◽  
Vol 48 (2) ◽  
pp. 204-205
Author(s):  
Imre Pozsgai ◽  
Klara Erdöhalmi-Torok
Keyword(s):  
Electron Beam ◽  
Cross Section ◽  
Polyester Resin ◽  
National Gallery ◽  
X Ray ◽  
Art Historians ◽  
Made In ◽  
Grinding And Polishing

The paintings by the great Hungarian master Mihaly Munkacsy (1844-1900) made in an 8-9 years period of his activity are deteriorating. The most conspicuous sign of the deterioration is an intensive darkening. We have made an attempt by electron beam microanalysis to clarify the causes of the darkening. The importance of a study like this is increased by the fact that a similar darkening can be observed on the paintings by Munkacsy’s contemporaries e.g Courbet and Makart. A thick brown mass the so called bitumen used by Munkacsy for grounding and also as a paint is believed by the art historians to cause the darkening.For this study, paint specimens were taken from the following paintings: “Studio”, “Farewell” and the “Portrait of the Master’s Wife”, all of them are the property of the Hungarian National Gallery. The paint samples were embedded in a polyester resin “Poly-Pol PS-230” and after grinding and polishing their cross section was used for x-ray mapping.

Quantitative energy-filtered electron diffraction

1994 ◽  
Vol 52 ◽  
pp. 992-993
Author(s):  
R. Vincent
Keyword(s):  
Electron Diffraction ◽  
Inelastic Scattering ◽  
Dynamic Range ◽  
Electron Optics ◽  
Surface Layers ◽  
High Brightness ◽  
Inclined Surfaces ◽  
Perfect Symmetry ◽  
Amorphous Surface ◽  
The Ideal

Microanalysis and diffraction on a sub-nanometre scale have become practical in modern TEMs due to the high brightness of field emission sources combined with the short mean free paths associated with both elastic and inelastic scattering of incident electrons by the specimen. However, development of electron diffraction as a quantitative discipline has been limited by the absence of any generalised theory for dynamical inelastic scattering. These problems have been simplified by recent innovations, principally the introduction of spectrometers such as the Gatan imaging filter (GIF) and the Zeiss omega filter, which remove the inelastic electrons, combined with annual improvements in the speed of computer workstations and the availability of solid-state detectors with high resolution, sensitivity and dynamic range.Comparison of experimental data with dynamical calculations imposes stringent requirements on the specimen and the electron optics, even when the inelastic component has been removed. For example, no experimental CBED pattern ever has perfect symmetry, departures from the ideal being attributable to residual strain, thickness averaging, inclined surfaces, incomplete cells and amorphous surface layers.

South Asian Developmental Crisis (Review Article)

1973 ◽  
Vol 12 (2) ◽  
pp. 181-188
Author(s):  
Rafiq Ahmad
Keyword(s):  
Second World War ◽  
World War ◽  
The Past ◽  
The Great Depression ◽  
Political Independence ◽  
Integrated Theory ◽  
Pass Through ◽  
Developed World ◽  
Second World ◽  
Made In

Like nations and civilizations, sciences also pass through period of crises when established theories are overthrown by the unpredictable behaviour of events. Economics is passing through such a crisis. The challenge thrown by the Great Depression of early 1930s took a decade before Keynes re-established the supremacy of economics. But this supremacy has again been upset by the crisis of poverty in the vast under-developed world which attained political independence after the Second World War. Poverty had always existed but never before had it been of such concern to economists as during the past twenty five years or so. Economic literature dealing with this problem has piled up but so have the agonies of poverty. No plausible and well-integrated theory of economic development or under-development has emerged so far, though brilliant advances have been made in isolated directions.

Experimental Measurements in the Acquisition of Biosignals from a Neuronal Cell Culture for an Exoprosthesis Command

2018 ◽  
Vol 69 (10) ◽  
pp. 2948-2939 ◽  
Author(s):  
Carmen Moldovan ◽  
Lidia Dobrescu ◽  
Violeta Ristoiu ◽  
Bogdan Firtat ◽  
Silviu Dinulescu ◽  
...  
Keyword(s):  
Cell Culture ◽  
Glass Plate ◽  
Neuronal Cell ◽  
Cellular Biology ◽  
Experimental Measurements ◽  
Neuron Culture ◽  
Neuronal Cell Culture ◽  
Made In

This article presents experimental measurements performed in order to connect a neuronal cell culture to an exoprosthesis. The experiments focused on the biosignals� acquisition from the cell culture. A special gold-plated glass plate device was realized and several constructive variants were analyzed. A Olympus microscope with fluorescence and photo system was used. The acquisition of bio signals from the neuron culture is realized and described in the paper. The measurements were made in the sterile environment within the laboratory of Institute of Cellular Biology and Pathology. The measurements have been made for the pair of electrodes 1-1 at the edge of the glass plate.

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