Ultrastructural Observations on Deep-Etched Thylakoids

1969 ◽  
Vol 5 (1) ◽  
pp. 299-311
Author(s):  
R. B. PARK ◽  
A. O. PFEIFHOFER
Keyword(s):  
Plastic Deformation ◽  
Fracture Process ◽  
Fracture Face ◽  
Deep Etching ◽  
Process Modification ◽  
Fracture Planes ◽  
Spinach Thylakoids

Deep etching of spinach thylakoids frozen in water exposes the inner and outer surfaces of the thylakoid. Both these surfaces differ greatly in appearance from their respective adjacent fracture planes. This finding constitutes further evidence for membrane splitting during the fracture process. Modification of the fracture face by loss of shattered material or by plastic deformation may explain the partial mismatch between the two fracture faces observed in washed thylakoids.

Path of Fracture Planes Along Membrane Surfaces in Frozen-Etched Tissue

1969 ◽  
Vol 27 ◽  
pp. 334-335
Author(s):  
L. V. Leak
Keyword(s):  
Fracture Process ◽  
Membrane Surface ◽  
Fracture Plane ◽  
Additional Information ◽  
Membrane Surfaces ◽  
Fracture Planes ◽  
En Face ◽  
Freeze Etching ◽  
Conventional Electron Microscopy ◽  
Cellular Organelles

The course of the fracture plane through frozen tissue may very often follow surfaces of membranes for long distances before cross fractures are made, exposing the interior of cells and cellular organelles. From studies on frozen-etched cellular membranes Moor and Muhlethaler suggested that fractures occur along external surfaces of membranes, while Branton proposed that the fracture process splits the membrane in half, revealing either of the two internal membrane faces. Our earlier studies suggested that most of the en face views of membranes represented fractures along the membrane surface. The present study combines the technique of freeze-etching with those of conventional electron microscopy in an effort to provide additional information on the precise nature and path of the fracture plane along membrane surfaces.

The fracture of a climbing rope: a phenomenological approach

2018 ◽  
Vol 233 (2) ◽  
pp. 193-201 ◽  
Author(s):  
Ulrich Leuthäusser
Keyword(s):  
Plastic Deformation ◽  
Damage Accumulation ◽  
Fracture Process ◽  
Storage Capacity ◽  
Phenomenological Approach ◽  
Analytical Models ◽  
Local Damage ◽  
Nonlinear Difference Equations ◽  
Deformation Equation ◽  
Energy Storage Capacity

For the fracture process of a climbing rope, two mechanisms are responsible: plastic deformation and local damage of the contact zone between the rope and the anchor. These mechanisms are described by two analytical models represented by nonlinear difference equations. The plastic deformation equation can be linked to a catastrophe-theoretical model. From the equation describing local damage accumulation, the Palmgren–Miner rule can be derived. The used energy-based approach allows the combination of these models and thus the calculation of the number of falls to failure as a function of the ratio of fall energy/energy storage capacity. The behavior of climbing ropes tested by subsequent UIAA falls can be quantitatively explained by these models.

Energy-Release Rate in Elastic-Plastic Fracture Problems

1981 ◽  
Vol 48 (4) ◽  
pp. 825-829 ◽  
Author(s):  
S. Aoki ◽  
K. Kishimoto ◽  
M. Sakata
Keyword(s):  
Plastic Deformation ◽  
Energy Release ◽  
Release Rate ◽  
Fracture Process ◽  
Release Rates ◽  
Process Region ◽  
Special Cases ◽  
Energy Release Rates ◽  
Self Similar ◽  
Inertia Forces

It is shown that the energy-release rates associated with the translation, rotation, self-similar expansion and distortion of the fracture process region are expressed by the newly introduced integrals, Jˆ, Lˆ, Mˆ, and Iˆ. These integrals can be defined even if there exist plastic deformation, thermal strains, body forces, and inertia forces. They include as special cases the J, L, and M integrals which have been defined by Knowles and Sternberg and discussed by Budiansky and Rice.

An Investigation of the Mode of Failure of Copper Beryllium Alloy Specimens in Stress Corrosion Fracture

CORROSION ◽  
1969 ◽  
Vol 25 (4) ◽  
pp. 168-170 ◽  
Author(s):  
W. D. Sylwestrowicz
Keyword(s):  
Plastic Deformation ◽  
Crack Propagation ◽  
Stress Corrosion ◽  
Appreciable Amount ◽  
Fracture Face ◽  
X Ray Diffraction ◽  
X Ray ◽  
Mode Of Failure ◽  
Side Face ◽  
Copper Beryllium

Abstract The mode of crack propagation was investigated in specimens of a copper-beryllium alloy which had failed by stress corrosion. The investigation was done by comparing the amount of plastic deformation on the side face and on the fractured face of the specimen. The amount of plastic deformation was measured by X-ray diffraction. Results indicate that an appreciable amount of plastic deformation occurred on the fractured face during the process of fracture. The presence of additional plastic deformation at the fracture face suggests that the specimen failed by the semi-brittle propagation of a crack.

Sem Examinations of Glass Knives

1970 ◽  
Vol 28 ◽  
pp. 282-283
Author(s):  
J. Temple Black
Keyword(s):  
Plastic Deformation ◽  
Tensile Loading ◽  
Resultant Force ◽  
Stress Concentrations ◽  
Edge Chipping ◽  
Surface Flaws ◽  
Edge Defects ◽  
Microscopic Surface

There are two types of edge defects common to glass knives as typically prepared for microtomy purposes: 1) striations and 2) edge chipping. The former is a function of the free breaking process while edge chipping results from usage or bumping of the edge. Because glass has no well defined planes in its structure, it should be highly resistant to plastic deformation of any sort, including tensile loading. In practice, prevention of microscopic surface flaws is impossible. The surface flaws produce stress concentrations so that tensile strengths in glass are typically 10-20 kpsi and vary only slightly with composition. If glass can be kept in compression, wherein failure is literally unknown (1), it will remain intact for long periods of time. Forces acting on the tool in microtomy produce a resultant force that acts to keep the edge in compression.

Stereo Electron Microscopy Applied to High Resolution Freeze-Etch Replicas

1970 ◽  
Vol 28 ◽  
pp. 306-307
Author(s):  
L. Andrew Staehelin
Keyword(s):  
Electron Microscopy ◽  
Plastic Deformation ◽  
High Resolution ◽  
Smooth Surfaces ◽  
Small Particles ◽  
Membrane Surfaces ◽  
Wide Acceptance ◽  
New Information ◽  
Number Of Particles ◽  
Small Holes

Freeze-etched membranes usually appear as relatively smooth surfaces covered with numerous small particles and a few small holes (Fig. 1). In 1966 Branton (1“) suggested that these surfaces represent split inner mem¬brane faces and not true external membrane surfaces. His theory has now gained wide acceptance partly due to new information obtained from double replicas of freeze-cleaved specimens (2,3) and from freeze-etch experi¬ments with surface labeled membranes (4). While theses studies have fur¬ther substantiated the basic idea of membrane splitting and have shown clearly which membrane faces are complementary to each other, they have left the question open, why the replicated membrane faces usually exhibit con¬siderably fewer holes than particles. According to Branton's theory the number of holes should on the average equal the number of particles. The absence of these holes can be explained in either of two ways: a) it is possible that no holes are formed during the cleaving process e.g. due to plastic deformation (5); b) holes may arise during the cleaving process but remain undetected because of inadequate replication and microscope techniques.

Plastic Deformation in Microtomed Sections

1971 ◽  
Vol 29 ◽  
pp. 458-459
Author(s):  
J. Temple Black
Keyword(s):  
Plastic Deformation ◽  
Plastic Strain ◽  
Applied Stress ◽  
Elastic Strain ◽  
High Strain ◽  
Tool Material ◽  
Cutting Edge ◽  
Material Structure ◽  
Geometrical Constraints

The output of the ultramicrotomy process with its high strain levels is dependent upon the input, ie., the nature of the material being machined. Apart from the geometrical constraints offered by the rake and clearance faces of the tool, each material is free to deform in whatever manner necessary to satisfy its material structure and interatomic constraints. Noncrystalline materials appear to survive the process undamaged when observed in the TEM. As has been demonstrated however microtomed plastics do in fact suffer damage to the top and bottom surfaces of the section regardless of the sharpness of the cutting edge or the tool material. The energy required to seperate the section from the block is not easily propogated through the section because the material is amorphous in nature and has no preferred crystalline planes upon which defects can move large distances to relieve the applied stress. Thus, the cutting stresses are supported elastically in the internal or bulk and plastically in the surfaces. The elastic strain can be recovered while the plastic strain is not reversible and will remain in the section after cutting is complete.

Surface Structure in Microtomed Sections Caused by Glass and Diamond Knives

1971 ◽  
Vol 29 ◽  
pp. 456-457
Author(s):  
J. Temple Black ◽  
William G. Boldosser
Keyword(s):  
Plastic Deformation ◽  
Epoxy Resin ◽  
Carbon Coating ◽  
Surface Damage ◽  
Body Angle ◽  
Normal Manner ◽  
Bottom Side ◽  
Cutting Direction ◽  
Made In ◽  
Diamond Knife

Ultramicrotomy produces plastic deformation in the surfaces of microtomed TEM specimens which can not generally be observed unless special preparations are made. In this study, a typical biological composite of tissue (infundibular thoracic attachment) infiltrated in the normal manner with an embedding epoxy resin (Epon 812 in a 60/40 mixture) was microtomed with glass and diamond knives, both with 45 degree body angle. Sectioning was done in Portor Blum Mt-2 and Mt-1 microtomes. Sections were collected on formvar coated grids so that both the top side and the bottom side of the sections could be examined. Sections were then placed in a vacuum evaporator and self-shadowed with carbon. Some were chromium shadowed at a 30 degree angle. The sections were then examined in a Phillips 300 TEM at 60kv.Carbon coating (C) or carbon coating with chrom shadowing (C-Ch) makes in effect, single stage replicas of the surfaces of the sections and thus allows the damage in the surfaces to be observable in the TEM. Figure 1 (see key to figures) shows the bottom side of a diamond knife section, carbon self-shadowed and chrom shadowed perpendicular to the cutting direction. Very fine knife marks and surface damage can be observed.

Artefacts in the x-ray microanalysis of frozen-hydrated biological samples

1987 ◽  
Vol 45 ◽  
pp. 658-659
Author(s):  
Patrick Echlin
Keyword(s):  
Electron Scattering ◽  
Biological Samples ◽  
Fracture Face ◽  
Detailed Structure ◽  
X Ray ◽  
Morphological Appearance ◽  
The Poor ◽  
Freeze Dried

A number of papers have appeared recently which purport to have carried out x-ray microanalysis on fully frozen hydrated samples. It is important to establish reliable criteria to be certain that a sample is in a fully hydrated state. The morphological appearance of the sample is an obvious parameter because fully hydrated samples lack the detailed structure seen in their freeze dried counterparts. The electron scattering by ice within a frozen-hydrated section and from the surface of a frozen-hydrated fracture face obscures cellular detail. (Fig. 1G and 1H.) However, the morphological appearance alone can be quite deceptive for as Figures 1E and 1F show, parts of frozen-dried samples may also have the poor morphology normally associated with fully hydrated samples. It is only when one examines the x-ray spectra that an assurance can be given that the sample is fully hydrated.

Investigation of shock-wave deformation history from recovered structure

1986 ◽  
Vol 44 ◽  
pp. 434-435
Author(s):  
M.A. Mogilevsky ◽  
L.S. Bushnev
Keyword(s):  
Shock Wave ◽  
Plastic Deformation ◽  
Dislocation Density ◽  
Shock Waves ◽  
Shock Front ◽  
Single Crystals ◽  
Residual Deformation ◽  
Deformation Structure ◽  
Deformation History ◽  
Deformation Velocity

Single crystals of Al were loaded by 15 to 40 GPa shock waves at 77 K with a pulse duration of 1.0 to 0.5 μs and a residual deformation of ∼1%. The analysis of deformation structure peculiarities allows the deformation history to be re-established.After a 20 to 40 GPa loading the dislocation density in the recovered samples was about 1010 cm-2. By measuring the thickness of the 40 GPa shock front in Al, a plastic deformation velocity of 1.07 x 108 s-1 is obtained, from where the moving dislocation density at the front is 7 x 1010 cm-2. A very small part of dislocations moves during the whole time of compression, i.e. a total dislocation density at the front must be in excess of this value by one or two orders. Consequently, due to extremely high stresses, at the front there exists a very unstable structure which is rearranged later with a noticeable decrease in dislocation density.

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