Journal ArticleDOI
Aspects of scanning microdensitometry. I. Stray light (glare).
TLDR
Glare or stray light, an important source of error in microdensitometry, is mainly due to reflections at glass‐air surfaces in the microscope objective, and much less to imperfections in other parts of the optical system.Abstract:
SUMMARY
Glare or stray light, an important source of error in microdensitometry, is mainly due to reflections at glass-air surfaces in the microscope objective, and much less to imperfections in other parts of the optical system. It is only slightly affected by the numerical aperture of the microscope condenser, but is closely related to the area of specimen-free field illuminated. If Ff is the amount of glare (expressed as a fraction of the intensity of the light incident on the specimen) with a given object and area of field illuminated, and F∞ is the glare with an infinite field size or an infinitesimally small object, F∞ approximately equals FfA/(A - a), where A is the area of the whole field illuminated and a is the area of the specimen itself.
Glare with a given specimen and under given conditions of illumination may be taken to equal the apparent transmittance of an opaque object of the same size as the specimen to be measured, provided the opaque object is light absorbing (of low reflectance) and not too small (at least 5–10 μm diameter). The true absorbance Et of the specimen equals log [(1 - F)/(Ip - F)] where the intensity of the incident light is unity, and Ip is the apparent transmittance of the specimen in the presence of F glare. The true absorbance of a specimen is never less than F% higher than its apparent absorbance, in the presence of F% glare, and the error rises sharply with increasing absorbance. Apparent differences in the amount of dye taken up by nuclei of different sizes, stained by the Feulgen method, which have been reported by various workers and attributed to differences in DNA content, are of an order of magnitude which could be due to the presence of glare in the system. This factor should be allowed for in critical work.
Two methods of correcting the error due to glare in measurements of integrated absorbance are described. The first method utilizes data on the area of specimen containing material with an absorbance greater than a set threshold value, as provided for example by the area-measurement facility on the Vickers M85 integrating microdensitometer. In the second, and generally preferable method, glare is compensated for electronically in a way analogous to the offsetting of the dark-current of the photomultiplier tube of the instrument.read more
Citations
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Journal ArticleDOI
Nuclear DNA Amounts in Angiosperms
Michael D. Bennett,J. B. Smith +1 more
TL;DR: This paper lists absolute nuclear DNA amounts for 753 angiosperm species, primarily for reference purposes, and so the species are listed in alphabetical order, as this was felt to be more helpful to cyto- and biochemists whom, it is anticipated, will be among its major users.
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The Theory of the Photographic Process
TL;DR: The theory of the photographic process was introduced by Mees in this article, who described the action of light, the processes that take place in photographic materials under its influence and the large number of theories which have been advanced to account for them.
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Analysis of glycosaminoglycans within the extracellular environments encountered by migrating neural crest cells.
TL;DR: The results indicate that the trunk neural crest initiates migration in an extracellular matrix relatively and absolutely rich in hyaluronic acid and suggest that glycosaminoglycans may be important in the differentiation of the trunk Neural crest.
Book ChapterDOI
Polarized absorption and linear dichroism spectroscopy of hemoglobin.
TL;DR: This chapter is concerned with polarized absorption and linear dichroism spectroscopy of hemoglobin, techniques used to study the optical properties of oriented systems.
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Methods in quantitative image analysis
TL;DR: The main steps of image analysis are image capturing, image storage (compression), correcting imaging defects, image enhancement, segmentation of objects in the image and image measurements, and enhancement.
References
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Journal ArticleDOI
The Desoxyribose Nucleic Acid Content of Animal Nuclei
TL;DR: Evidence has recently been presented that DNA is considerably less variable in amount, and it is suggested that the amount of DNA per nucleus is probably constant in all the nuclei of any one species.
Journal ArticleDOI
The Theory of the Photographic Process
TL;DR: The theory of the photographic process was introduced by Mees in this article, who described the action of light, the processes that take place in photographic materials under its influence and the large number of theories which have been advanced to account for them.
Journal ArticleDOI
An integrating microdensitometer for biological cells
TL;DR: In this article, a photoelectric method for the rapid determination of the total absorption of biological cells is described, where the image of the cell, formed by a microscope, is scanned by a mechanically-driven aperture behind which is mounted a photomultiplier.
Journal ArticleDOI
Conditions influencing the intensity of the feulgen reaction
TL;DR: The small lymphocyte, which has previously been found by several workers to bind about 10% less Feulgen dye than other diploid cells, was found to have a similar lowerFeulgen intensity after 5 N HCl hydrolysis at room temperature.
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