Arrangement of Subunits in Flagellar Microtubules

Electron micrographs of outer doublet tubules from flagella have been analysed by methods which make use of the computed diffraction patterns of electron-microscope images. Analysis of singlet A-tubules in the tips of flagella has led to a determination of the helical surface lattice of the A-subfibre, confirming that there are 13 longitudinal protofilaments in the tubule wall and that dimers in neighbouring protofilaments form a staggered arrangement, equivalent to the lattice with an axial periodicity of 8.0 nm predicted in earlier work. A low-resolution 3-dimensional image of the A-tubule has been reconstructed, which supports the evidence for an 8.0-nm-long heterodimer oriented along the protofilaments. The heterodimer is identified as a pair of 4.0-nm morphological units, which appear to be globular at this resolution. Filtered images have been obtained from doublet tubules which show that the B-subfibre is also made up of 8.0-nm dimers, but it differs from the A-tubule in that dimers in adjacent filaments are not in a staggered arrangement but are lined up obliquely at a shallow angle. Using the additional information about the hands of the lattices in the 2 subfibres which is presented in the accompanying paper, a model for the whole doublet has been proposed.

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Deviations from Ideal Decagonal Symmetry in Electron Diffraction Patterns of the “Decagonal” Phase in the Al-Co-Cu Alloy System

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100088889 ◽

1991 ◽

Vol 49 ◽

pp. 914-915

Author(s):

Atul S. Ramani ◽

Earle R. Ryba ◽

Paul R. Howell

Keyword(s):

Electron Microscope ◽

Alloy System ◽

Nominal Composition ◽

Dimensional Lattice ◽

3 Dimensional ◽

Decagonal Phase ◽

Cu Alloy ◽

Transmission Electron ◽

Lattice Periodicity ◽

Diffraction Patterns

The “decagonal” phase in the Al-Co-Cu system of nominal composition Al65CO15Cu20 first discovered by He et al. is especially suitable as a topic of investigation since it has been claimed that it is thermodynamically stable and is reported to be periodic in the dimension perpendicular to the plane of quasiperiodic 10-fold symmetry. It can thus be expected that it is an important link between fully periodic and fully quasiperiodic phases. In the present paper, we report important findings of our transmission electron microscope (TEM) study that concern deviations from ideal decagonal symmetry of selected area diffraction patterns (SADPs) obtained from several “decagonal” phase crystals and also observation of a lattice of main reflections on the 10-fold and 2-fold SADPs that implies complete 3-dimensional lattice periodicity and the fundamentally incommensurate nature of the “decagonal” phase. We also present diffraction evidence for a new transition phase that can be classified as being one-dimensionally quasiperiodic if the lattice of main reflections is ignored.

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Dopant Site Location by Electron Channeling in Ion Implanted Silicon

MRS Proceedings ◽

10.1557/proc-31-97 ◽

1983 ◽

Vol 31 ◽

Cited By ~ 1

Author(s):

S. J. Pennycook ◽

J. Narayan ◽

O.W. Holland

Keyword(s):

Electron Microscope ◽

Electron Micrographs ◽

Site Location ◽

Electron Channeling ◽

Ion Channeling ◽

Stages Of Growth ◽

Early Stages ◽

Simple Ratio ◽

Implantation Profile

ABSTRACTA simple ratio technique using the phenomenon of electron channeling can be used to measure the substitutional concentrations of dopants in semiconductors on a submicron scale.A comparison was made between electron and ion channeling measurements on Si-Sb alloy samples having a range of nonsubstitutional fractions of Sb.Good agreement was obtained but both measurements indicated considerably more nonsubstitutional dopant than could be accounted for by precipitates observed in electron micrographs. The discrepancy can be explained if the precipitates are coherent in the early stages of growth and have their planes located interstitially with respect to the Si planes. The sensitivity of the electron channeling measurements to the implantation profile was investigated and found to be small.The determination of local dopant profiles in the electron microscope is described.

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Solvothermal route to Bi3Se4 nanorods at low temperature

Journal of Materials Research ◽

10.1557/jmr.2001.0464 ◽

2001 ◽

Vol 16 (12) ◽

pp. 3361-3365 ◽

Cited By ~ 9

Author(s):

Yuan-fang Liu ◽

Jing-hui Zeng ◽

Wei-xin Zhang ◽

Wei-chao Yu ◽

Yi-tai Qian ◽

...

Keyword(s):

Electron Microscope ◽

Reaction Mechanism ◽

Low Temperature ◽

Hydrazine Hydrate ◽

Photoelectron Spectra ◽

Elemental Selenium ◽

X Ray ◽

Transmission Electron ◽

Microscope Images ◽

Diffraction Patterns

Nanorods Bi3Se4 were synthesized directly through the reaction between BiCl3 and elemental selenium in an autoclave with hydrazine hydrate as solvent at 165 °C for 10 h. X-ray powder diffraction patterns, x-ray photoelectron spectra, and transmission electron microscope images show that the products are well-crystallized hexagonal Bi3Se4 nanorods. The solvent hydrazine hydrate played an important role in formation and growth of Bi3Se4 nanorods. The possible reaction mechanism was proposed.

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Diffraction Contrast from Dissociated Frank Dislocations. I. Computed Electron Micrographs

Australian Journal of Physics ◽

10.1071/ph690351 ◽

1969 ◽

Vol 22 (3) ◽

pp. 351 ◽

Cited By ~ 12

Author(s):

LM Clarebrough ◽

AJ Morton

Keyword(s):

Electron Microscope ◽

Electron Micrographs ◽

Degree Of Dissociation ◽

Diffraction Contrast ◽

Microscope Images

The influence of degree of dissociation on the diffraction contrast from a Frank dislocation for lll, 220, and 020 reflections has been investigated using the technique devised by Head and Humble for computing electron microscope images.

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Studies in Oberonia, 9: Lessons from excess names in Oberonia for Orchidaceae systematics, including a revision of the Oberonia Sect. Scytoxiphium

Lankesteriana ◽

10.15517/lank.v21i2.47245 ◽

2021 ◽

Author(s):

Daniel L. Geiger

Keyword(s):

Electron Microscope ◽

Scanning Electron Microscope ◽

Electron Micrographs ◽

21St Century ◽

Expert Advice ◽

Scanning Electron Micrographs ◽

Palabras Clave ◽

Microscope Images ◽

Typological Thinking ◽

Scanning Electron

The reasons for excess names in microfloral orchids such as Oberonia Lindl. can be traced to poor scholarship (e.g., failure to review the literature, ignoring expert advice), typological thinking, and erroneous assumption of microendemism. Some extraordinarily poor descriptions, including some from the 21st century, can be termed “taxonomic vandalism”. The outdated reliance on drawings as opposed to z-stacked photographs and scanning electron micrographs poses further problems due to an abundance of demonstrable problems with drawings. The Oberonia sect. Scytoxiphium Schltr. with eight described species is reduced to one species, Oberonia heliophila Rchb.f.; it is illustrated by original drawings, live photographs and scanning electron microscope images. The distribution is extended from Java through Micronesia and Samoa. The species occurs predominantly from 0–500 m, less frequently to 900 m, and possibly to even 1900 m. It flowers throughout the year. Keywords/Palabras clave: Oberonia, Oberonia sect. Scytoxiphium, revision, revisión, synonymies, sinonimias, taxonomic vandalism, vandalismo taxonómico

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A Study Of Microcrystals Of Fibrinogen

10.1055/s-0038-1652273 ◽

1981 ◽

Author(s):

L Tranqui ◽

E Hewatt ◽

R Wade

Keyword(s):

Electron Microscope ◽

Exchange Chromatography ◽

Unit Cell ◽

Optical Diffraction ◽

Ordered Structures ◽

System A ◽

Diffraction Patterns ◽

Low Ionic Strength ◽

Selection Of

We are interested in the application of image analysis to the structural determination of fibrinogen. This analysis is performed on the electron microscope images obtained from microcrystals of slightly degraded fibrinogen. The proteolysis of fibrinogen is carried out using bacterial proteases fixed onto sepharose. In our study 3 mg of sepharose-proteases are mixed with 16 mg of fibrinogen. Digestion-times of 30 min. to 4 h. are employed. The analysis of reduced fibrinogen lysates, by polyacrylamide gels in SDS,shows a progressive disappearance of the Aα chain, while lighter chains appeared with a MW of 30000. After 4 h. of digestion, the MW of the degraded fibrinogen is about 267.000, it clots after exposure to thrombin. As shown on unreduced samples on 5 % acrylamide gels in SDS, the digest is heterogeneous ; homogeneous samples are obtained by a separation on ion exchange-chromatography. From the crude fibrinogen lysates,several forms of microcrystals are obtained after a dialysis at low ionic strength (μ=0,005 ; pH = 6,2). Different forms of microcrystals are obtained from some fractions after chromatography. All these microcrystals are observed in the electron microscope after negative staining. The optical diffraction patterns obtained from these micrographs permit the selection of the most ordered regions ; thus we have established that the largest regions of ordered structures are obtained when the Aα chain of fibrinogen is degraded into a lighter chain of MW 30.000. One of the forms obtained from the crude fibrinogen digests has been studied in more details, it has a unit cell of 450 Å x 90 Å its optical diffraction shows a resolution of 30 ft. The microcrystals obtained from the fractions of chromatography have a unit cell of 440 Å/150 Å, their optical diffraction patterns show details to 35 Å. They have pgg projection symetry down the c-axis. The structures are examined after the elimination of the noise on a computer system. A first conclusion is that it is not evident that these images are simply related to the supposed elongated form of the fibrinogen molecule.

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