The application of phase-contrast to the ultra-violet microscope

1950 ◽  
Vol 137 (888) ◽  
pp. 332-339 ◽  
Keyword(s):  
Phase Contrast ◽  
Ultra Violet ◽  
Living Organism ◽  
Selective Absorption ◽  
Wide Range ◽  
Structural Details ◽  
Close Study ◽  
Dark Ground ◽  
Contrast Image ◽  
Selection Of

It has been shown that the phase-contrast principle of Zernike may be applied with advantage to ultra-violet microscopy and that certain advantages follow: ( a ) In the first place, it furnishes a more certain method than dark-ground illumination for the visual selection of a suitable field of view as all structures are more clearly revealed. ( b ) In the second place, it furnishes a new means whereby structural details that give rise to a change of phase in the transmitted radiations may be photographed in contrast, even under conditions when selective absorption does not take place. ( c ) In the third place, it is possible, after having selected a suitable field by means of visual phase-contrast, to photograph the same field in ultra-violet light and then to turn once again to the visual phase-contrast image to make certain that the exposure has not caused damage to a living organism. A series of explanatory photographs has been taken covering a wide range of biological objects. These show that the method is sensitive to minute changes in phase and that the resulting images are characterized by good contrast. Details are revealed that cannot be brought out by normal methods, as will be clear from a close study of the pairs of photographs which accompany this paper. In selecting these it was thought necessary to avoid very fine detail and delicate shades of contrast that would be lost in the process of reproduction.

The application of phase-contrast to the ultra-violet microscope

1950 ◽  
Vol 203 (1075) ◽  
pp. 582-582 ◽  
Keyword(s):  
Phase Contrast ◽  
Ultra Violet ◽  
Living Organism ◽  
Selective Absorption ◽  
Wide Range ◽  
Structural Details ◽  
Close Study ◽  
Dark Ground ◽  
Contrast Image ◽  
Selection Of

It has been shown that the phase-contrast of Zernike may be applied with advantage to ultra-violet microscopy and that certain advantages follow: (а) In the first place, it furnishes a more certain method than dark-ground illumination for the visual selection of a suitable field of view, as all structures are more clearly revealed. (b) In the second place, it furnishes a new means whereby structural details that give rise to a change of phase in the transmitted radiations may be photographed in contrast, even under conditions when selective absorption does not take place. (c) In the third place, it is possible, after having selected a suitable field by means of visual phase-contrast, to photograph the same field in ultra-violet light and then to turn once again to the visual phase-contrast image to make certain that the exposure has not caused damage to a living organism. A series of explanatory photographs has been taken covering a wide range of biological objects. These show that the method is sensitive to minute changes in phase, and that the resulting images are characterized by good contrast. Details are revealed that cannot be brought out by normal methods, as will be clear from a close study of the pairs of photographs which accompany this paper. In selecting these it was thought necessary to avoid very fine detail and delicate shades of contrast that would be lost in the process of reproduction.

On Bridging the Gap in Cytology Between the Light and Electron Microscopes by Some Combined Observations on Snail Neurones

1964 ◽  
Vol s3-105 (70) ◽  
pp. 139-162
Author(s):  
S. M. McGEE-RUSSEL
Keyword(s):  
Electron Microscope ◽  
Phase Contrast ◽  
Nile Blue ◽  
Ultra Violet ◽  
Object A ◽  
Snail Neurones ◽  
Cross Correlations ◽  
Electron Microscopes ◽  
Microscopy Data ◽  
Dark Ground

Discrepancies between observations made with the light microscope only, and with the electron microscope only, can be clarified by using both instruments to study exactly the same section of the same object. A simple technique for doing this is outlined. Direct, phase-contrast, ‘anoptral’ phase-contrast, dark-ground, interference, and ultra-violet microscopy can all be used. When applied to snail neurones this technique of combined observations reveals intracellular organelles which have not previously been differentiated. These organelles are positively identified by criteria appropriate to each instrument. By combined observations it is possible to see the ‘Golgi apparatus’ in preparations stained only with Nile blue, by direct microscopy. Data obtained by combined observations are considered in relation to the previous literature. Unequivocal cross-correlations between the light and the electron microscope go a long way towards explaining past difficulties.

Characteristics of an Electrostatic Phase Plate

1972 ◽  
Vol 30 ◽  
pp. 618-619
Author(s):  
William Krakow ◽  
Benjamin Siegel
Keyword(s):  
Phase Contrast ◽  
Objective Lens ◽  
Phase Plate ◽  
Net Charge ◽  
Phase Plates ◽  
Beam Currents ◽  
Contrast Image ◽  
Bright Phase ◽  
Additional Phase Shift ◽  
Additional Phase

Unwin has used a metallized non-conducting thread in the back focal plane of the objective lens that stops out a portion of the unscattered beam, takes on a localized positive charge and thus produces an additional phase shift to give a different transfer function of the lens. Under the particular conditions Unwin used, the phase contrast image was shifted to bright phase contrast for optimum focus.We have investigated the characteristics of this type of electrostatic phase plate, both analytically and experimentally, as functions of the magnitude of charge and defocus. Phase plates have been constructed by using Wollaston wire to mount 0.25μ diameter platinum wires across apertures ranging from 50 to 200μ diameter and vapor depositing SiO and gold on the mounted wires to give them the desired charging characteristics. The net charge was varied by adjusting only the bias on the Wehnelt shield of the gun, and hence the beam currents and effective size of the source.

Evaluation method for imaging plate resolution by means of phase contrast transfer function

1995 ◽  
Vol 53 ◽  
pp. 662-663 ◽  
Author(s):  
T. Oikawa ◽  
H. Kosugi ◽  
F. Hosokawa ◽  
D. Shindo ◽  
M. Kersker
Keyword(s):  
Transfer Function ◽  
Phase Contrast ◽  
Evaluation Method ◽  
Amorphous Film ◽  
Imaging Plate ◽  
X Rays ◽  
Special Shape ◽  
Contrast Transfer Function ◽  
Contrast Image ◽  
Specimen Shape

Evaluation of the resolution of the Imaging Plate (IP) has been attempted by some methods. An evaluation method for IP resolution, which is not influenced by hard X-rays at higher accelerating voltages, was proposed previously by the present authors. This method, however, requires truoblesome experimental preperations partly because specially synthesized hematite was used as a specimen, and partly because a special shape of the specimen was used as a standard image. In this paper, a convenient evaluation method which is not infuenced by the specimen shape and image direction, is newly proposed. In this method, phase contrast images of thin amorphous film are used.Several diffraction rings are obtained by the Fourier transformation of a phase contrast image of thin amorphous film, taken at a large under focus. The rings show the spatial-frequency spectrum corresponding to the phase contrast transfer function (PCTF). The envelope function is obtained by connecting the peak intensities of the rings. The evelope function is offten used for evaluation of the instrument, because the function shows the performance of the electron microscope (EM).

Bonafide Substructure in the Core of Ferritin

1985 ◽  
Vol 43 ◽  
pp. 322-323
Author(s):  
William H. Massover
Keyword(s):  
Phase Contrast ◽  
Central Cavity ◽  
Amplitude Image ◽  
Ultrastructural Studies ◽  
The Core ◽  
Hydrated Ferric Oxide ◽  
Imaging Artifact ◽  
Contrast Image ◽  
Protein Shell ◽  
Regular Patterns

Each molecule of ferritin (d = 130Å) contains a core of iron surrounded by a 24-subunit protein shell. The amount of iron stored is variable and is present within the central cavity (d = 80Å) as a hydrated ferric oxide equivalent to the mineral, ferrihydrite. Many early ultrastructural studies of ferritin detected regular patterns of a multiparticulate substructure in the iron-rich core [e.g., 3,4], Each small particle was termed a “micelle“; a theory became widely accepted that a core consisted of up to six micelles positioned at the vertices of an octahedron. Other workers recognized that the apparent micelles were smaller or even disappeared if images were recorded closer to exact focus [e.g., 5]. In 1969, Haydon clearly established that the observed substructure was really an imaging artifact; each apparent micelle was only a dot in the underfocused phase contrast image of the supporting film superimposed on the amplitude image of the strongly scattering metal.

COMBINATORIAL POLYNOMIALLY COMPUTABLE CHARACTERISTICS OF SUBSTITUTIONS AND THEIR PROPERTIES

2020 ◽  
Vol 7 (2) ◽  
pp. 34-41
Author(s):  
VLADIMIR NIKONOV ◽  
◽  
ANTON ZOBOV ◽  
Keyword(s):  
Mathematical Expectation ◽  
Point Of View ◽  
Small Range ◽  
Computational Point ◽  
Wide Range ◽  
Bijective Function ◽  
The Difference ◽  
Element Base ◽  
Selection Of

The construction and selection of a suitable bijective function, that is, substitution, is now becoming an important applied task, particularly for building block encryption systems. Many articles have suggested using different approaches to determining the quality of substitution, but most of them are highly computationally complex. The solution of this problem will significantly expand the range of methods for constructing and analyzing scheme in information protection systems. The purpose of research is to find easily measurable characteristics of substitutions, allowing to evaluate their quality, and also measures of the proximity of a particular substitutions to a random one, or its distance from it. For this purpose, several characteristics were proposed in this work: difference and polynomial, and their mathematical expectation was found, as well as variance for the difference characteristic. This allows us to make a conclusion about its quality by comparing the result of calculating the characteristic for a particular substitution with the calculated mathematical expectation. From a computational point of view, the thesises of the article are of exceptional interest due to the simplicity of the algorithm for quantifying the quality of bijective function substitutions. By its nature, the operation of calculating the difference characteristic carries out a simple summation of integer terms in a fixed and small range. Such an operation, both in the modern and in the prospective element base, is embedded in the logic of a wide range of functional elements, especially when implementing computational actions in the optical range, or on other carriers related to the field of nanotechnology.

Synthesis, Characterization and Antiproliferative Activity Assessment of a Novel 1H-5-mercapto-1,2,4 Triazole Derivative

2017 ◽  
Vol 68 (4) ◽  
pp. 745-747 ◽  
Author(s):  
Marius Mioc ◽  
Sorin Avram ◽  
Vasile Bercean ◽  
Mihaela Balan Porcarasu ◽  
Codruta Soica ◽  
...  
Keyword(s):  
Antiproliferative Activity ◽  
Biological Activities ◽  
Cancer Cell Line ◽  
Vascular Endothelial ◽  
Triazole Derivative ◽  
Activity Assessment ◽  
Wide Range ◽  
Specific Receptors ◽  
Endothelial Growth Factor ◽  
Selection Of

Angiogenesis plays an important function in tumor proliferation, one of the main angiogenic promoters being the vascular endothelial growth factor (VEGF) which activates specific receptors, particularly VEGFR-2. Thus, VEGFR-2 has become an essential therapeutic target in the development of new antitumor drugs. 1,2,4-triazoles show a wide range of biological activities, including antitumor effect, which was documented by numerous reports. In the current study the selection of 5-mercapto-1,2,4-triazole structure (1H-3-styryl-5-benzylidenehydrazino-carbonyl-methylsulfanil-1,2,4-triazole, Tz3a.7) was conducted based on molecular docking that emphasized it as suitable ligand for VEGFR-2 and EGFR1 receptors. Compound Tz3a.7 was synthesized and physicochemically and biologically evaluated thus revealing a moderate antiproliferative activity against breast cancer cell line MDA-MB-231.

Effect of Contact Ratio on Spur Gear Dynamic Load With No Tooth Profile Modifications

1996 ◽  
Vol 118 (3) ◽  
pp. 439-443 ◽  
Author(s):  
Chuen-Huei Liou ◽  
Hsiang Hsi Lin ◽  
F. B. Oswald ◽  
D. P. Townsend
Keyword(s):  
Dynamic Load ◽  
Spur Gear ◽  
Tooth Size ◽  
Contact Ratio ◽  
Gear Dynamics ◽  
Wide Range ◽  
Gear Contact ◽  
Center Distance ◽  
Selection Of ◽  
Better Than

This paper presents a computer simulation showing how the gear contact ratio affects the dynamic load on a spur gear transmission. The contact ratio can be affected by the tooth addendum, the pressure angle, the tooth size (diametral pitch), and the center distance. The analysis presented in this paper was performed by using the NASA gear dynamics code DANST. In the analysis, the contact ratio was varied over the range 1.20 to 2.40 by changing the length of the tooth addendum. In order to simplify the analysis, other parameters related to contact ratio were held constant. The contact ratio was found to have a significant influence on gear dynamics. Over a wide range of operating speeds, a contact ratio close to 2.0 minimized dynamic load. For low-contact-ratio gears (contact ratio less than two), increasing the contact ratio reduced gear dynamic load. For high-contact-ratio gears (contact ratio equal to or greater than 2.0), the selection of contact ratio should take into consideration the intended operating speeds. In general, high-contact-ratio gears minimized dynamic load better than low-contact-ratio gears.

scholarly journals A Virtual Telescope for the Open University Science Foundation Course

1998 ◽  
Vol 162 ◽  
pp. 100-105
Author(s):  
Andrew J. Norton ◽  
Mark H. Jones
Keyword(s):  
Social Science ◽  
Open University ◽  
Distance Teaching ◽  
The Arts ◽  
Wide Range ◽  
University Science ◽  
First Time ◽  
Degree Level ◽  
Selection Of

The Open University is the UK's foremost distance teaching university. For over twenty five years we have been presenting courses to students spanning a wide range of degree level and vocational subjects. Since we have no pre-requisites for entry, a major component of our course profile is a selection of foundation courses comprising one each in the Arts, Social Science, Mathematics, Technology and Science faculties. The Science Faculty's foundation course is currently undergoing a substantial revision. The new course, entitled “S103: Discovering Science”, will be presented to students for the first time in 1998.

scholarly journals Organelle Genetics in Plants

2021 ◽  
Vol 22 (4) ◽  
pp. 2104
Author(s):  
Pedro Robles ◽  
Víctor Quesada
Keyword(s):  
Rna Editing ◽  
Posttranscriptional Regulation ◽  
Genome Engineering ◽  
Plant Mitochondria ◽  
Plastid Dna ◽  
Chloroplast Genomes ◽  
Wide Range ◽  
Organelle Genetics ◽  
Selection Of

Eleven published articles (4 reviews, 7 research papers) are collected in the Special Issue entitled “Organelle Genetics in Plants.” This selection of papers covers a wide range of topics related to chloroplasts and plant mitochondria research: (i) organellar gene expression (OGE) and, more specifically, chloroplast RNA editing in soybean, mitochondria RNA editing, and intron splicing in soybean during nodulation, as well as the study of the roles of transcriptional and posttranscriptional regulation of OGE in plant adaptation to environmental stress; (ii) analysis of the nuclear integrants of mitochondrial DNA (NUMTs) or plastid DNA (NUPTs); (iii) sequencing and characterization of mitochondrial and chloroplast genomes; (iv) recent advances in plastid genome engineering. Here we summarize the main findings of these works, which represent the latest research on the genetics, genomics, and biotechnology of chloroplasts and mitochondria.

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