Radiation Damage in DNA: Structure/Function Relationships at Early Times

Over the past five years it has become evident that radiation damage provides the fundamental limit to the study of blomolecular structure by electron microscopy. In some special cases structural determinations at very low doses can be achieved through superposition techniques to study periodic (Unwin & Henderson, 1975) and nonperiodic (Saxton & Frank, 1977) specimens. In addition, protection methods such as glucose embedding (Unwin & Henderson, 1975) and maintenance of specimen hydration at low temperatures (Taylor & Glaeser, 1976) have also shown promise. Despite these successes, the basic nature of radiation damage in the electron microscope is far from clear. In general we cannot predict exactly how different structures will behave during electron Irradiation at high dose rates. Moreover, with the rapid rise of analytical electron microscopy over the last few years, nvicroscopists are becoming concerned with questions of compositional as well as structural integrity. It is important to measure changes in elemental composition arising from atom migration in or loss from the specimen as a result of electron bombardment.

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Radiation Damage in Ceramics

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100055229 ◽

1982 ◽

Vol 40 ◽

pp. 600-603

Author(s):

T. E. Mitchell ◽

M. R. Pascucci ◽

R. A. Youngman

Keyword(s):

Radiation Damage ◽

Outer Space ◽

Point Of View ◽

Nuclear Waste Storage ◽

Waste Storage ◽

Storage Media ◽

Transmission Electron ◽

Fundamental Point ◽

Small Defect ◽

Present Understanding

1. Introduction. Studies of radiation damage in ceramics are of interest not only from a fundamental point of view but also because it is important to understand the behavior of ceramics in various practical radiation enyironments- fission and fusion reactors, nuclear waste storage media, ion-implantation devices, outer space, etc. A great deal of work has been done on the spectroscopy of point defects and small defect clusters in ceramics, but relatively little has been performed on defect agglomeration using transmission electron microscopy (TEM) in the same kind of detail that has been so successful in metals. This article will assess our present understanding of radiation damage in ceramics with illustrations using results obtained from the authors' work.

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Review of the Radiation Damage Problem of Organic Specimens in Electron Microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100072824 ◽

1973 ◽

Vol 31 ◽

pp. 476-477

Author(s):

L. Reimer

Keyword(s):

Electron Microscopy ◽

Radiation Damage ◽

Irradiation Time ◽

Dose Effect ◽

Primary Process ◽

Thin Specimen ◽

Secondary Damage ◽

Small Doses ◽

Micro Organisms ◽

Damage Processes

Most information about a specimen is obtained by elastic scattering of electrons, but one cannot avoid inelastic scattering and therefore radiation damage by ionisation as a primary process of damage. This damage is a dose effect, being proportional to the product of lectron current density j and the irradiation time t in Coul.cm−2 as long as there is a negligible heating of the specimen.Therefore one has to determine the dose needed to produce secondary damage processes, which can be measured quantitatively by a chemical or physical effect in the thin specimen. The survival of micro-organisms or the decrease of photoconductivity and cathodoluminescence are such effects needing very small doses (see table).

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