scholarly journals Chromosome Malorientations after Meiosis II Arrest Cause Nondisjunction

2007 ◽  
Vol 18 (5) ◽  
pp. 1645-1656 ◽  
Author(s):  
Marie A. Janicke ◽  
Loren Lasko ◽  
Rudolf Oldenbourg ◽  
James R. LaFountain
Keyword(s):  
Liquid Crystal ◽  
Light Microscope ◽  
Daughter Nucleus ◽  
Polarized Light ◽  
Live Cell ◽  
The Other ◽  
Sister Kinetochore ◽  
Microscope Imaging ◽  
Birefringent Fiber ◽  
Spindle Elongation

This study investigated the basis of meiosis II nondisjunction. Cold arrest induced a fraction of meiosis II crane fly spermatocytes to form (n + 1) and (n − 1) daughters during recovery. Live-cell liquid crystal polarized light microscope imaging showed nondisjunction was caused by chromosome malorientation. Whereas amphitely (sister kinetochore fibers to opposite poles) is normal, cold recovery induced anaphase syntely (sister fibers to the same pole) and merotely (fibers to both poles from 1 kinetochore). Maloriented chromosomes had stable metaphase positions near the equator or between the equator and a pole. Syntelics were at the spindle periphery at metaphase; their sisters disconnected at anaphase and moved all the way to a centrosome, as their strongly birefringent kinetochore fibers shortened. The kinetochore fibers of merotelics shortened little if any during anaphase, making anaphase lag common. If one fiber of a merotelic was more birefringent than the other, the less birefringent fiber lengthened with anaphase spindle elongation, often permitting inclusion of merotelics in a daughter nucleus. Meroamphitely (near amphitely but with some merotely) caused sisters to move in opposite directions. In contrast, syntely and merosyntely (near syntely but with some merotely) resulted in nondisjunction. Anaphase malorientations were more frequent after longer arrests, with particularly long arrests required to induce syntely and merosyntely.

Polymer-Dispersed Liquid Crystals: Boojums at Work

MRS Bulletin ◽  
1991 ◽  
Vol 16 (1) ◽  
pp. 22-28 ◽  
Author(s):  
J. William Doane
Keyword(s):  
Refractive Index ◽  
Liquid Crystal ◽  
Liquid Crystals ◽  
Polarized Light ◽  
Solid Particles ◽  
Water Soluble ◽  
The Other ◽  
Polymer Materials ◽  
Water Soluble Polymer ◽  
Polymer Dispersed

The idea of dispersing micron-size birefringent particles in a polymer to selectively scatter light is not new. In the 1930s Land patented a light polarizing material in which small, oriented solid crystallites were suspended in a clear polymer. The polymer material was selected so that its refractive index matched one of the principal refractive indices of the crystallites while the other did not. The resuit was a light polarizer tha t would pass one component of polarized light but scatter the other component out of the beam path.This idea was substantially expanded by the introduction of liquid crystals as the birefringent material. The orientation of the particles (in this case droplets), and hence the refractive index match and the scattering, could be controlled by an electric field. Such a material could be used as a light shutter for either unpolarized or polarized light. In the mid-1970s this basic concept was applied by Hilsum, but having no way to disperse droplets of liquid crystals in a polymer, he did the opposite and put optically isotropic solid particles in the birefringent liquid crystal.Although Hilsum demonstrated the concept, no commercial device was produced, probably because the shutter contrast was limited. Since then several ways have been found to disperse droplets in a polymer: filling the pores of a microfilter; emulsifying the liquid crystal in a water soluble polymer; and using phase separation methods to create a dispersion of droplets in non-aqueous polymer materials.

The Birefringence of thin filaments measured with the Pol-Scope

1997 ◽  
Vol 3 (S2) ◽  
pp. 797-798
Author(s):  
R. Oldenbourg ◽  
Edward D. Salmon ◽  
Phong T. Tran
Keyword(s):  
Liquid Crystal ◽  
Light Microscope ◽  
Living Cell ◽  
Polarized Light ◽  
Molecular Transport ◽  
Thin Filaments ◽  
Dense Networks ◽  
Cell Functions ◽  
Vital Cell ◽  
Filament Networks

The living cell is criss-crossed by dense networks of filaments providing mechanic stability, site directed molecular transport and support of other vital cell functions. With the polarized light microscope we can observe the birefringence associated with thin filaments or partially oriented filament networks and measure the birefringence directly in the living cell (Fig. 1). Filament birefringence is a consequence of the elongated shape of the molecules and occurs naturally without the need to stain or label them, as is necessary in fluorescence imaging.We have measured the birefringence of microtubules and axoneme filaments using the new polarized light microscope (Pol-Scope).The design of the Pol-Scope is based on the traditional polarized light microscope in which the crystal compensator is replaced by a universal compensator made from two liquid crystal variable retarders. Electronic image acquisition in the Pol-Scope is synchronized to liquid crystal settings to capture a sequence of four images with circular and elliptical polarization.

scholarly journals Security devices based on liquid crystals doped with a colour dye

2011 ◽  
Vol 19 (4) ◽  
Author(s):  
C. Carrasco-Vela ◽  
X. Quintana ◽  
E. Otón ◽  
M. Geday ◽  
J. Otón
Keyword(s):  
Liquid Crystal ◽  
Polarized Light ◽  
Dielectric Surface ◽  
The Other ◽  
Flat Panel Display ◽  
Flat Panel ◽  
Alignment Layer ◽  
Multiple Images ◽  
Crystal Properties ◽  
Twist Structure

AbstractLiquid crystal properties make them useful for the development of security devices in applications of authentication and detection of fakes. Induced orientation of liquid crystal molecules and birefringence are the two main properties used in security devices.Employing liquid crystal and dichroic colorants, we have developed devices that show, with the aid of a polarizer, multiple images on each side of the device. Rubbed polyimide is used as alignment layer on each substrate of the LC cell. By rubbing the polyimide in different directions in each substrate it is possible to create any kind of symbols, drawings or motifs with a greyscale; the more complex the created device is, the more difficult is to fake it.To identify the motifs it is necessary to use polarized light. Depending on whether the polarizer is located in front of the LC cell or behind it, different motifs from one or the other substrate are shown. The effect arises from the dopant colour dye added to the liquid crystal, the induced orientation and the twist structure. In practice, a grazing reflection on a dielectric surface is polarized enough to see the effect. Any LC flat panel display can obviously be used as backlight as well.

High-resolution measurement of birefringent fine structure in living cells using a new polarized light microscope

1995 ◽  
Vol 53 ◽  
pp. 54-55
Author(s):  
Rudolf Oldenbourg
Keyword(s):  
Light Microscope ◽  
Fluorescent Dyes ◽  
Polarized Light ◽  
Processing System ◽  
Video Camera ◽  
Molecular Organization ◽  
Computer Assisted ◽  
Image Recording ◽  
Birefringent Crystal ◽  
Technological Advances

The recent renaissance of the light microsope is fueled in part by technological advances in components on the periphery of the microscope, such as the laser as illumination source, electronic image recording (video), computer assisted image analysis and the biochemistry of fluorescent dyes for labeling specimens. After great progress in these peripheral parts, it seems timely to examine the optics itself and ask how progress in the periphery facilitates the use of new optical components and of new optical designs inside the microscope. Some results of this fruitful reflection are presented in this symposium.We have considered the polarized light microscope, and developed a design that replaces the traditional compensator, typically a birefringent crystal plate, with a precision universal compensator made of two liquid crystal variable retarders. A video camera and digital image processing system provide fast measurements of specimen anisotropy (retardance magnitude and azimuth) at ALL POINTS of the image forming the field of view. The images document fine structural and molecular organization within a thin optical section of the specimen.

Comparative strengths and weaknesses of peroxidase and colloidal gold in pre- and post-embedding immunolabeling techniques

1987 ◽  
Vol 45 ◽  
pp. 1002-1005
Author(s):  
D. R. Abrahamson ◽  
P. L. St.John ◽  
E. W. Perry
Keyword(s):  
Electron Microscopy ◽  
Horseradish Peroxidase ◽  
Light Microscopy ◽  
Colloidal Gold ◽  
Light Microscope ◽  
Ultrastructural Localization ◽  
The Other ◽  
Quantitative Studies ◽  
Dense Suspension ◽  
Antigen Localization

Antibodies coupled to tracers for electron microscopy have been instrumental in the ultrastructural localization of antigens within cells and tissues. Among the most popular tracers are horseradish peroxidase (HRP), an enzyme that yields an osmiophilic reaction product, and colloidal gold, an electron dense suspension of particles. Some advantages of IgG-HRP conjugates are that they are readily synthesized, relatively small, and the immunolabeling obtained in a given experiment can be evaluated in the light microscope. In contrast, colloidal gold conjugates are available in different size ranges and multiple labeling as well as quantitative studies can therefore be undertaken through particle counting. On the other hand, gold conjugates are generally larger than those of HRP but usually can not be visualized with light microscopy. Concern has been raised, however, that HRP reaction product, which is exquisitely sensitive when generated properly, may in some cases distribute to sites distant from the original binding of the conjugate and therefore result in spurious antigen localization.

New polarized-light microscope for fast and orientation independent measurement of birefringent fine structure

1993 ◽  
Vol 51 ◽  
pp. 82-83
Author(s):  
Rudolf Oldenbourg
Keyword(s):  
Light Microscope ◽  
Polarized Light ◽  
Video Camera ◽  
Limited Range ◽  
Image Point ◽  
Computer Assisted ◽  
Optical Modulators ◽  
Anisotropic Structures ◽  
Long Time ◽  
Computer Assisted Image

The polarized light microscope has the unique potential to measure submicroscopic molecular arrangements dynamically and non-destructively in living cells and other specimens. With the traditional pol-scope, however, single images display only those anisotropic structures that have a limited range of orientations with respect to the polarization axes of the microscope. Furthermore, rapid measurements are restricted to a single image point or single area that exhibits uniform birefringence or other form of optical anisotropy, while measurements comparing several image points take an inordinately long time.We are developing a new kind of polarized light microscope which combines speed and high resolution in its measurement of the specimen anisotropy, irrespective of its orientation. The design of the new pol-scope is based on the traditional polarized light microscope with two essential modifications: circular polarizers replace linear polarizers and two electro-optical modulators replace the traditional compensator. A video camera and computer assisted image analysis provide measurements of specimen anisotropy in rapid succession for all points of the image comprising the field of view.

Light microscopy of ceramics

1993 ◽  
Vol 51 ◽  
pp. 908-909
Author(s):  
Walter C. McCrone
Keyword(s):  
Refractive Index ◽  
Light Microscopy ◽  
Light Microscope ◽  
Polarized Light ◽  
Refractive Indices ◽  
Complete Coverage ◽  
The Subject ◽  
Lower Refractive Index

An excellent chapter on this subject by V.D. Fréchette appeared in a book edited by L.L. Hench and R.W. Gould in 1971 (1). That chapter with the references cited there provides a very complete coverage of the subject. I will add a more complete coverage of an important polarized light microscope (PLM) technique developed more recently (2). Dispersion staining is based on refractive index and its variation with wavelength (dispersion of index). A particle of, say almandite, a garnet, has refractive indices of nF = 1.789 nm, nD = 1.780 nm and nC = 1.775 nm. A Cargille refractive index liquid having nD = 1.780 nm will have nF = 1.810 and nC = 1.768 nm. Almandite grains will disappear in that liquid when observed with a beam of 589 nm light (D-line), but it will have a lower refractive index than that liquid with 486 nm light (F-line), and a higher index than that liquid with 656 nm light (C-line).

SRAM Failure Analysis Strategy

2003 ◽  
Author(s):  
P. Egger ◽  
C. Burmer
Keyword(s):  
Liquid Crystal ◽  
Failure Analysis ◽  
The Other ◽  
Other Hand ◽  
Analysis Strategy ◽  
Emission Microscopy ◽  
Metal Layers ◽  
Failure Localization

Abstract The area of embedded SRAMs in advanced logic ICs is increasing more and more. On the other hand smaller structure sizes and an increasing number of metal layers make conventional failure localization by using emission microscopy or liquid crystal inefficient. In this paper a SRAM failure analysis strategy will be presented independent on layout and technology.

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