Recent progress in the freeze-etching technique

1971 ◽  
Vol 261 (837) ◽  
pp. 121-131 ◽  
Keyword(s):  
High Vacuum ◽  
Molecular Size ◽  
Etching Technique ◽  
Structural Distortions ◽  
Shadow Casting ◽  
Structural Details ◽  
Freeze Etching ◽  
The One ◽  
Insight Into ◽  
Made In

The freeze-etching technique must be improved if structures at the molecular size level are to be seen. The limitations of the technique are discussed here together with the progress made in alleviating them. The vitrification of living specimens is limited by the fact that very high freezing rates are needed. The critical freezing rate can be lowered on the one hand by the introduction of antifreeze agents, on the other hand by the application of high hydrostatic pressure. The fracture process may cause structural distortions in the fracture face of the frozen specimen. The ‘double-replica’ method allows one to evaluate such artefacts and provides an insight into the way that membranes split. During etching there exists the danger of contaminating the fracture faces with condensable gases. Because of specimen temperatures below —110 °C, special care has to be taken in eliminating water vapour from the high vacuum. An improvement in coating freeze-etched specimens has resulted from the application of electron guns for evaporation of the highest melting-point metals. If heat transfer from gun to specimen is reduced to a minimum, Pt, Ir, Ta, W and C can be used for shadow casting. Best results are obtained with Pt-C and Ta-W . With the help of decoration effects Pt-C shadow castings give the most information about the fine structural details of the specimen.

scholarly journals Experimental researches in electricity. Twenty-fifth series. On the magnetic and diamagnetic condition of bodies

1851 ◽  
Vol 5 ◽  
pp. 995-997
Keyword(s):  
Physical Condition ◽  
Internal Surface ◽  
The Other ◽  
Magnetic Action ◽  
The One ◽  
Magnetic Poles ◽  
Experimental Researches ◽  
Different Gases ◽  
Insight Into ◽  
Made In

As the author could find no polarity in diamagnetic bodies when under magnetic influence (a result described in the 23rd Series of these Researches), he endeavoured to discover some other physical condition of them, and of magnetic bodies, by which he might obtain an insight into their respective natures, and establish the true place of the magnetic zero; and considering the power with which a magnetic body moves, or tends to move, from weaker to stronger places of action, and that of a diamagnetic body to pass from stronger to weaker places of action, he hoped to obtain some results of condensation with the first class, and of expansion with the second, when they were subjected to very strong magnetic action; the respective bodies being selected from the class of gaseous substances, in which change of volume can be easily produced and measured. In the first place, therefore, a ray of light was passed over the surface of powerful magnetic poles surrounded by different gases, and the place of its source carefully examined by telescopes, micrometers, and other means, to ascertain whether the layer of air in contact with the poles was affected in its refracting force; but though the experiment was made in oxygen, nitrogen, and other gases, not the slightest effect was visible. Resigning this process, therefore, two air-tight chambers were made, in which the magnetic poles formed the chief part of the internal surface of the chamber. The one was formed by bringing the flat ends of the two poles to within 1/60th of an inch of each other, with a frame all round to form the sides; and the other by cutting away the central parts of an iron cylinder so as to give it the form of an hour-glass, and then enclosing that part by an air-tight copper tube. Cocks were attached to these chambers for the introduction and removal of gases, and for the application of gauges, which were able to indicate a change of volume equal to the part of the contents of the chamber. When any given gas was introduced into the chamber, and the latter then placed between the poles of the electro-magnet, any possible alteration of volume would be shown by the gauge as soon as the magnet was rendered active; but whatever gas was employed, or whatever power of magnet used, not the slightest change was produced.

Platinum shadowing, complementary imaging and stereo analysis: Techniques developed for TEM can now be used to increase the resolution of frozen hydrated specimens in a SEM

1993 ◽  
Vol 51 ◽  
pp. 70-71
Author(s):  
William P. Wergin ◽  
Eric F. Erbe
Keyword(s):  
Surface Characteristics ◽  
Biological Specimen ◽  
Etching Technique ◽  
Surface Information ◽  
Analysis Techniques ◽  
Stereo Analysis ◽  
Transmission Electron ◽  
Wide Range ◽  
Structural Details ◽  
Freeze Etching

In 1957, Steere froze virus crystals, fractured and transferred them to a vacuum evaporator where they were etched, shadowed and coated. The coating, which was then removed from the tissue and mounted on a grid, represented a replica that could be observed in the transmission electron microscope (TEM). This accomplishment is regarded as the first successful biological application of the freeze-etching technique in electron microscopy. This technique was further advanced by describing procedures whereby the replicas from both surfaces of a frozen, fractured sample could be recovered. This pair of replicas provided additional surface information by allowing one to view and compare the two opposing surfaces, or the complementary images, of a freeze-fractured biological specimen. Using a goniometer stage the replicas were also photographed, tilted and rephotographed to produce stereo pairs that could be used to analyze three-dimensionally the surface characteristics of the replica. Until recently these TEM techniques have been the principle procedures utilized by biologists to gain high resolution structural details about virus crystals, biological membranes and a wide range of other material.

scholarly journals A SIMPLE FREEZE-FRACTURE REPLICATION METHOD FOR ELECTRON MICROSCOPY

1966 ◽  
Vol 29 (3) ◽  
pp. 435-447 ◽  
Author(s):  
Stanley Bullivant ◽  
Adelbert Ames
Keyword(s):  
Freeze Fracture ◽  
Practical Method ◽  
Vacuum System ◽  
Fresh Tissue ◽  
Razor Blade ◽  
Etching Technique ◽  
Simple Method ◽  
Replication Method ◽  
Structural Details ◽  
Freeze Etching

A simple method to achieve results similar to the freeze-etching technique of Moor et al. (1961) is described. The frozen tissue is cut under liquid nitrogen with a razor blade outside the evaporator rather than inside with a cooled microtome. The conditions of the experiment do not favor sublimation, and it is proposed that the structure of the replica be explained by local faults in the cleavage plane which leaves structures, such as membranes, standing above the ice. Micrographs of replicas of glycerol-protected frozen small intestine of mouse prepared by the method are presented and the structural details they show are discussed. The problem of vapor-deposited contamination is discussed. It is concluded that this is a practical method for obtaining electron micrographs that are relatively free of artifact, and that further improvements may be expected from the use of rapidly frozen fresh tissue and a clean vacuum system, possibly of the ion-pumped type.

Structures Formed by Cryoprotective Agents Used in Freezc-Etching

1971 ◽  
Vol 29 ◽  
pp. 448-449
Author(s):  
G. G. Cocks ◽  
C. E. Cluthe
Keyword(s):  
Aqueous Solution ◽  
Polyethylene Oxide ◽  
Liquid Nitrogen Temperature ◽  
Ice Crystals ◽  
Etching Technique ◽  
Structural Constituent ◽  
Cryoprotective Agents ◽  
Quick Freezing ◽  
Freeze Etching ◽  
Fractured Surface

The freeze etching technique is potentially useful for examining dilute solutions or suspensions of macromolecular materials. Quick freezing of aqueous solutions in Freon or propane at or near liquid nitrogen temperature produces relatively large ice crystals and these crystals may damage the structures to be examined. Cryoprotective agents may reduce damage to the specimem, hut their use often results in the formation of a different set of specimem artifacts.In a study of the structure of polyethylene oxide gels glycerol and sucrose were used as cryoprotective agents. The experiments reported here show some of the structures which can appear when these cryoprotective agents are used.Figure 1 shows a fractured surface of a frozen 25% aqueous solution of sucrose. The branches of dendritic ice crystals surrounded hy ice-sucrose eutectic can be seen. When this fractured surface is etched the ice in the dendrites sublimes giving the type of structure shown in Figure 2. The ice-sucrose eutectic etches much more slowly. It is the smooth continuous structural constituent surrounding the branches of the dendrites.

Grain boundary segregation in metals

1992 ◽  
Vol 50 (2) ◽  
pp. 1204-1205
Author(s):  
C.L. Briant
Keyword(s):  
Fracture Surface ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Material Properties ◽  
Electron Spectroscopy ◽  
High Vacuum ◽  
Boundary Segregation ◽  
Grain Boundary Segregation ◽  
Local Concentration ◽  
The One

Grain boundary segregation is the process by which solute elements in a material diffuse to the grain boundaries, become trapped there, and increase their local concentration at the boundary over that in the bulk. As a result of this process this local concentration of the segregant at the grain boundary can be many orders of magnitude greater than the bulk concentration of the segregant. The importance of this problem lies in the fact that grain boundary segregation can affect many material properties such as fracture, corrosion, and grain growth.One of the best ways to study grain boundary segregation is with Auger electron spectroscopy. This spectroscopy is an extremely surface sensitive technique. When it is used to study grain boundary segregation the sample must first be fractured intergranularly in the high vacuum spectrometer. This fracture surface is then the one that is analyzed. The development of scanning Auger spectrometers have allowed researchers to first image the fracture surface that is created and then to perform analyses on individual grain boundaries.

When Romania met the Cohesion Policy. Regional governance in-between national conventions and European ideals

2018 ◽  
Vol 18 (2) ◽  
pp. 127-148 ◽  
Author(s):  
Alexandru Brad
Keyword(s):  
Regional Policy ◽  
Development Planning ◽  
Regional Governance ◽  
Theoretical Ground ◽  
Cohesion Policy ◽  
Redistributive Policy ◽  
Policy Context ◽  
Core Areas ◽  
The One ◽  
Insight Into

This article is about the practice of territorial governance emerging at the junction of European Union-sanctioned ideals and Romanian development-planning traditions. On the one hand, the European agenda emphasises a smart, inclusive, sustainable model of economic growth. However, the persisting centralised workings of the Romanian state significantly alters the scope of regional interventions. As such, while core cities grew their economies swiftly, peripheral places were left in an unrelenting stagnation. My first aim is to provide a theoretical ground for a practicecentred approach to understanding territorial governance. Second, by drawing on Romania’s regional policy context as an example, I give an insight into how practices of partnership and competition fare in a context of ongoing territorial polarisation. I conclude by emphasising the need for a regional redistributive policy mechanism, one which should enable and assist non-core areas to access capacities for defining and implementing development projects.

Will Love Tear Us Apart: Adapting the Lyrical to the Ludic

CounterText ◽  
2016 ◽  
Vol 2 (2) ◽  
pp. 217-235
Author(s):  
Gordon Calleja
Keyword(s):  
Design Process ◽  
Game Design ◽  
Digital Games ◽  
Design Decisions ◽  
The Core ◽  
Lyrical Poetry ◽  
Insight Into ◽  
Made In

This paper gives an insight into the design process of a game adaptation of Joy Division's Love Will Tear Us Apart (1980). It outlines the challenges faced in attempting to reconcile the diverging qualities of lyrical poetry and digital games. In so doing, the paper examines the design decisions made in every segment of the game with a particular focus on the tension between the core concerns of the lyrical work being adapted and established tenets of game design.

Marx, Silk Poems, and the Pretext of Qualities

2020 ◽  
Vol 151 (1) ◽  
pp. 96-126
Author(s):  
Kathryn Crim
Keyword(s):  
The Other ◽  
Use Value ◽  
Working Day ◽  
The One ◽  
Insight Into

Karl Marx’s comments on silk manufacture in “The Working Day” chapter of Capital, volume 1, demonstrate how “quality”—usually associated with “use value”—has been mobilized by capital to naturalize industrialized labor. Putting his insight into conversation with a recent multimedia poetic project, Jen Bervin’s Silk Poems (2016–17), this essay examines the homology between, on the one hand, poetry’s avowed task of fitting form to content and, on the other, the ideology of labor that fits specific bodies to certain materials and tasks.

Simulation of the internal temperature in the Passol Laboratory, University of Debrecen

2012 ◽  
Vol 3 (1) ◽  
pp. 63-73 ◽  
Author(s):  
I. Csáky ◽  
F. Kalmár
Keyword(s):  
Temperature Variation ◽  
Air Temperature ◽  
Indoor Air ◽  
Storage Capacity ◽  
Building Structures ◽  
Internal Temperature ◽  
The One ◽  
Heavy Structure ◽  
East West ◽  
Made In

Abstract Nowadays the facades of newly built buildings have significant glazed surfaces. The solar gains in these buildings can produce discomfort caused by direct solar radiation on the one hand and by the higher indoor air temperature on the other hand. The amplitude of the indoor air temperature variation depends on the glazed area, orientation of the facade and heat storage capacity of the building. This paper presents the results of a simulation, which were made in the Passol Laboratory of University of Debrecen in order to define the internal temperature variation. The simulation proved that the highest amplitudes of the internal temperature are obtained for East orientation of the facade. The upper acceptable limit of the internal air temperature is exceeded for each analyzed orientation: North, South, East, West. Comparing different building structures, according to the obtained results, in case of the heavy structure more cooling hours are obtained, but the energy consumption for cooling is lower.

scholarly journals Theoretical Modelling of Ion Exchange Processes in Glass: Advances and Challenges

2021 ◽  
Vol 11 (11) ◽  
pp. 5070
Author(s):  
Xesús Prieto-Blanco ◽  
Carlos Montero-Orille
Keyword(s):  
Ion Exchange ◽  
Diffusion Coefficients ◽  
Molten Salts ◽  
Theoretical Modelling ◽  
Copper Films ◽  
Theoretical Frameworks ◽  
Self Diffusion ◽  
Exchange Processes ◽  
The One ◽  
Made In

In the last few years, some advances have been made in the theoretical modelling of ion exchange processes in glass. On the one hand, the equations that describe the evolution of the cation concentration were rewritten in a more rigorous manner. This was made into two theoretical frameworks. In the first one, the self-diffusion coefficients were assumed to be constant, whereas, in the second one, a more realistic cation behaviour was considered by taking into account the so-called mixed ion effect. Along with these equations, the boundary conditions for the usual ion exchange processes from molten salts, silver and copper films and metallic cathodes were accordingly established. On the other hand, the modelling of some ion exchange processes that have attracted a great deal of attention in recent years, including glass poling, electro-diffusion of multivalent metals and the formation/dissolution of silver nanoparticles, has been addressed. In such processes, the usual approximations that are made in ion exchange modelling are not always valid. An overview of the progress made and the remaining challenges in the modelling of these unique processes is provided at the end of this review.

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