scholarly journals Kinetochore microtubules in PTK cells.

1992 ◽  
Vol 118 (2) ◽  
pp. 369-383 ◽  
Author(s):  
K L McDonald ◽  
E T O'Toole ◽  
D N Mastronarde ◽  
J R McIntosh
Keyword(s):  
Electron Microscopy ◽  
Dimensional Analysis ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Two Dimensional ◽  
Mitotic Spindles ◽  
Thin Sections ◽  
Large Numbers ◽  
Computer Image Processing ◽  
Pericentriolar Material

We have analyzed the fine structure of 10 chromosomal fibers from mitotic spindles of PtK1 cells in metaphase and anaphase, using electron microscopy of serial thin sections and computer image processing to follow the trajectories of the component microtubules (MTs) in three dimensions. Most of the kinetochore MTs ran from their kinetochore to the vicinity of the pole, retaining a clustered arrangement over their entire length. This MT bundle was invaded by large numbers of other MTs that were not associated with kinetochores. The invading MTs frequently came close to the kinetochore MTs, but a two-dimensional analysis of neighbor density failed to identify any characteristic spacing between the two MT classes. Unlike the results from neighbor density analyses of interzone MTs, the distributions of spacings between kinetochore MTs and other spindle MTs revealed no evidence for strong MT-MT interactions. A three-dimensional analysis of distances of closest approach between kinetochore MTs and other spindle MTs has, however, shown that the most common distances of closest approach were 30-50 nm, suggesting a weak interaction between kinetochore MTs and their neighbors. The data support the ideas that kinetochore MTs form a mechanical connection between the kinetochore and the pericentriolar material that defines the pole, but that the mechanical interactions between kinetochore MTs and other spindle MTs are weak.

On the Three-Dimensional Finite Element Analysis of Dovetail Attachments

2003 ◽  
Vol 125 (2) ◽  
pp. 372-379 ◽  
Author(s):  
J. R. Beisheim ◽  
G. B. Sinclair
Keyword(s):  
Boundary Conditions ◽  
Dimensional Analysis ◽  
High Stress ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Two Dimensional ◽  
Element Analysis ◽  
Computational Costs ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

The stress analysis of dovetail attachments presents some challenges. These stem from the high stress gradients at the edges of contact. They also stem from the nonlinearities accompanying conforming contact. Even with two-dimensional analysis, obtaining converged peak stresses is not trivial. With three-dimensional analysis, convergence can be expected to be more difficult to achieve because of the added computational costs of refinement in three dimensions. To meet these challenges, this paper describes a submodeling procedure with finite elements. The submodeling approach features bicubic surface fits to displacements for submodel boundary conditions. The approach also features a means of verifying these boundary conditions have converged; this is crucial to obtaining accurate converged peak stresses. The approach is applied to a three-dimensional test piece used to simulate a dovetail attachment. This application leads to converged three-dimensional stresses. These stresses serve to quantify the sort of increases in contact stresses in attachments due to three-dimensional effects.

scholarly journals Validating two-dimensional leadership models on three-dimensionally structured fish schools

2017 ◽  
Vol 4 (1) ◽  
pp. 160804 ◽  
Author(s):  
Isobel Watts ◽  
Máté Nagy ◽  
Robert I. Holbrook ◽  
Dora Biro ◽  
Theresa Burt de Perera
Keyword(s):  
Dimensional Analysis ◽  
Three Dimensional ◽  
Interaction Networks ◽  
Three Dimensions ◽  
Dimensional Structure ◽  
Two Dimensional ◽  
Fish Schools ◽  
Astyanax Mexicanus ◽  
Pairwise Interactions ◽  
The Individual

Identifying leader–follower interactions is crucial for understanding how a group decides where or when to move, and how this information is transferred between members. Although many animal groups have a three-dimensional structure, previous studies investigating leader–follower interactions have often ignored vertical information. This raises the question of whether commonly used two-dimensional leader–follower analyses can be used justifiably on groups that interact in three dimensions. To address this, we quantified the individual movements of banded tetra fish ( Astyanax mexicanus ) within shoals by computing the three-dimensional trajectories of all individuals using a stereo-camera technique. We used these data firstly to identify and compare leader–follower interactions in two and three dimensions, and secondly to analyse leadership with respect to an individual's spatial position in three dimensions. We show that for 95% of all pairwise interactions leadership identified through two-dimensional analysis matches that identified through three-dimensional analysis, and we reveal that fish attend to the same shoalmates for vertical information as they do for horizontal information. Our results therefore highlight that three-dimensional analyses are not always required to identify leader–follower relationships in species that move freely in three dimensions. We discuss our results in terms of the importance of taking species' sensory capacities into account when studying interaction networks within groups.

scholarly journals Electron tomography, three-dimensional Fourier analysis and colour prediction of a three-dimensional amorphous biophotonic nanostructure

2009 ◽  
Vol 6 (suppl_2) ◽  
Author(s):  
Matthew D Shawkey ◽  
Vinodkumar Saranathan ◽  
Hildur Pálsdóttir ◽  
John Crum ◽  
Mark H Ellisman ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Fourier Analysis ◽  
Electron Tomography ◽  
Spatial Scales ◽  
Tomographic Reconstruction ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Selective Absorption ◽  
Two Dimensional ◽  
Voltage Electron

Organismal colour can be created by selective absorption of light by pigments or light scattering by photonic nanostructures. Photonic nanostructures may vary in refractive index over one, two or three dimensions and may be periodic over large spatial scales or amorphous with short-range order. Theoretical optical analysis of three-dimensional amorphous nanostructures has been challenging because these structures are difficult to describe accurately from conventional two-dimensional electron microscopy alone. Intermediate voltage electron microscopy (IVEM) with tomographic reconstruction adds three-dimensional data by using a high-power electron beam to penetrate and image sections of material sufficiently thick to contain a significant portion of the structure. Here, we use IVEM tomography to characterize a non-iridescent, three-dimensional biophotonic nanostructure: the spongy medullary layer from eastern bluebird Sialia sialis feather barbs. Tomography and three-dimensional Fourier analysis reveal that it is an amorphous, interconnected bicontinuous matrix that is appropriately ordered at local spatial scales in all three dimensions to coherently scatter light. The predicted reflectance spectra from the three-dimensional Fourier analysis are more precise than those predicted by previous two-dimensional Fourier analysis of transmission electron microscopy sections. These results highlight the usefulness, and obstacles, of tomography in the description and analysis of three-dimensional photonic structures.

On the Three-Dimensional Finite Element Analysis of Dovetail Attachments

2002 ◽  
Author(s):  
J. R. Beisheim ◽  
G. B. Sinclair
Keyword(s):  
Boundary Conditions ◽  
Dimensional Analysis ◽  
High Stress ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Two Dimensional ◽  
Element Analysis ◽  
Computational Costs ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

The stress analysis of dovetail attachments presents some challenges. These stem from the high stress gradients at the edges of contact. They also stem from the nonlinearities accompanying conforming contact. Even with two-dimensional analysis, obtaining converged peak stresses is not trivial. With three-dimensional analysis, convergence can be expected to be more difficult to achieve because of the added computational costs of refinement in three dimensions. To meet these challenges, this paper describes a submodeling procedure with finite elements. The submodeling approach features bicubic surface fits to displacements for submodel boundary conditions. The approach also features a means of verifying these boundary conditions have converged: This is crucial to obtaining accurate converged peak stresses. The approach is applied to a three-dimensional test piece used to simulate a dovetail attachment. This application leads to converged three-dimensional stresses. These stresses serve to quantify the sort of increases in contact stresses in attachments due to three-dimensional effects.

Electron Microscopy of Cytoplasmic Contractile Proteins

1978 ◽  
Vol 36 (3) ◽  
pp. 606-614 ◽  
Author(s):  
T.D. Pollard ◽  
P. Maupin
Keyword(s):  
Electron Microscopy ◽  
Actin Filaments ◽  
Three Dimensional ◽  
Uranyl Acetate ◽  
Contractile Proteins ◽  
Dimensional Structure ◽  
X Ray Diffraction ◽  
Cytoplasmic Matrix ◽  
Computer Image Processing ◽  
Nonmuscle Cells

In this paper we review some of the contributions that electron microscopy has made to the analysis of actin and myosin from nonmuscle cells. We place particular emphasis upon the limitations of the ultrastructural techniques used to study these cytoplasmic contractile proteins, because it is not widely recognized how difficult it is to preserve these elements of the cytoplasmic matrix for electron microscopy. The structure of actin filaments is well preserved for electron microscope observation by negative staining with uranyl acetate (Figure 1). In fact, to a resolution of about 3nm the three-dimensional structure of actin filaments determined by computer image processing of electron micrographs of negatively stained specimens (Moore et al., 1970) is indistinguishable from the structure revealed by X-ray diffraction of living muscle.

High-resolution scanning electron microscopy (HRSEM) of mitochondria from various rat tissues

1988 ◽  
Vol 46 ◽  
pp. 14-15
Author(s):  
P.J. Lea ◽  
M.J. Hollenberg
Keyword(s):  
Electron Microscopy ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Rat Hepatocytes ◽  
Three Dimensions ◽  
Objective Lens ◽  
Rat Tissues ◽  
Thin Sections ◽  
Reconstruction Methods ◽  
Scanning Electron

Our current understanding of mitochondrial ultrastructure has been derived primarily from thin sections using transmission electron microscopy (TEM). This information has been extrapolated into three dimensions by artist's impressions (1) or serial sectioning techniques in combination with computer processing (2). The resolution of serial reconstruction methods is limited by section thickness whereas artist's impressions have obvious disadvantages.In contrast, the new techniques of HRSEM used in this study (3) offer the opportunity to view simultaneously both the internal and external structure of mitochondria directly in three dimensions and in detail.The tridimensional ultrastructure of mitochondria from rat hepatocytes, retinal (retinal pigment epithelium), renal (proximal convoluted tubule) and adrenal cortex cells were studied by HRSEM. The specimens were prepared by aldehyde-osmium fixation in combination with freeze cleavage followed by partial extraction of cytosol with a weak solution of osmium tetroxide (4). The specimens were examined with a Hitachi S-570 scanning electron microscope, resolution better than 30 nm, where the secondary electron detector is located in the column directly above the specimen inserted within the objective lens.

Two-Dimensional Crystallization of Tetanus Toxin

1985 ◽  
Vol 43 ◽  
pp. 528-529
Author(s):  
Jeffry A. Reidler ◽  
John P. Robinson
Keyword(s):  
Electron Microscopy ◽  
Tetanus Toxin ◽  
Structural Information ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Membrane Interface ◽  
3D Reconstructions ◽  
Cellular Receptors ◽  
Computer Reconstruction ◽  
2D Crystals

We have prepared two-dimensional (2D) crystals of tetanus toxin using procedures developed by Uzgiris and Kornberg for the directed production of 2D crystals of monoclonal antibodies at an antigen-phospholipid monolayer interface. The tetanus toxin crystals were formed using a small mole fraction of the natural receptor, GT1, incorporated into phosphatidyl choline monolayers. The crystals formed at low concentration overnight. Two dimensional crystals of this type are particularly useful for structure determination using electron microscopy and computer image refinement. Three dimensional (3D) structural information can be derived from these crystals by computer reconstruction of photographs of toxin crystals taken at different tilt angles. Such 3D reconstructions may help elucidate the mechanism of entry of the enzymatic subunit of toxins into cells, particularly since these crystals form directly on a membrane interface at similar concentrations of ganglioside GT1 to the natural cellular receptors.

Mine Impact Burial Prediction From One to Three Dimensions

2008 ◽  
Vol 62 (1) ◽  
Author(s):  
Peter C. Chu
Keyword(s):  
Three Dimensional ◽  
Time History ◽  
Three Dimensions ◽  
Vertical Position ◽  
Burial Depth ◽  
Prediction Errors ◽  
Two Dimensional ◽  
Dimensional Model ◽  
One Dimensional ◽  
Dimensional Models

The Navy’s mine impact burial prediction model creates a time history of a cylindrical or a noncylindrical mine as it falls through air, water, and sediment. The output of the model is the predicted mine trajectory in air and water columns, burial depth/orientation in sediment, as well as height, area, and volume protruding. Model inputs consist of parameters of environment, mine characteristics, and initial release. This paper reviews near three decades’ effort on model development from one to three dimensions: (1) one-dimensional models predict the vertical position of the mine’s center of mass (COM) with the assumption of constant falling angle, (2) two-dimensional models predict the COM position in the (x,z) plane and the rotation around the y-axis, and (3) three-dimensional models predict the COM position in the (x,y,z) space and the rotation around the x-, y-, and z-axes. These models are verified using the data collected from mine impact burial experiments. The one-dimensional model only solves one momentum equation (in the z-direction). It cannot predict the mine trajectory and burial depth well. The two-dimensional model restricts the mine motion in the (x,z) plane (which requires motionless for the environmental fluids) and uses incorrect drag coefficients and inaccurate sediment dynamics. The prediction errors are large in the mine trajectory and burial depth prediction (six to ten times larger than the observed depth in sand bottom of the Monterey Bay). The three-dimensional model predicts the trajectory and burial depth relatively well for cylindrical, near-cylindrical mines, and operational mines such as Manta and Rockan mines.

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