scholarly journals A Simple Preparation Method for Full-Range Electron Tomography of Nanoparticles and Fine Powders

2017 ◽  
Vol 23 (6) ◽  
pp. 1150-1158 ◽  
Author(s):  
Elliot Padgett ◽  
Robert Hovden ◽  
Jessica C. DaSilva ◽  
Barnaby D. A. Levin ◽  
John L. Grazul ◽  
...  
Keyword(s):  
Electron Tomography ◽  
Bulk Material ◽  
Automatic Segmentation ◽  
Full Range ◽  
Three Dimensional ◽  
Specimen Preparation ◽  
Preparation Technique ◽  
Preparation Methods ◽  
Tomographic Images ◽  
Fine Powders

AbstractElectron tomography has become a valuable and widely used tool for studying the three-dimensional nanostructure of materials and biological specimens. However, the incomplete tilt range provided by conventional sample holders limits the fidelity and quantitative interpretability of tomographic images by leaving a “missing wedge” of unknown information in Fourier space. Imaging over a complete range of angles eliminates missing wedge artifacts and dramatically improves tomogram quality. Full-range tomography is usually accomplished using needle-shaped samples milled from bulk material with focused ion beams, but versatile specimen preparation methods for nanoparticles and other fine powders are lacking. In this work, we present a new preparation technique in which powder specimens are supported on carbon nanofibers that extend beyond the end of a tungsten needle. Using this approach, we produced tomograms of platinum fuel cell catalysts and gold-decorated strontium titanate photocatalyst specimens. Without the missing wedge, these tomograms are free from elongation artifacts, supporting straightforward automatic segmentation and quantitative analysis of key materials properties such as void size and connectivity, and surface area and curvature. This approach may be generalized to other samples that can be dispersed in liquids, such as biological structures, creating new opportunities for high-quality electron tomography across disciplines.

Improved Three-Dimensional (3D) Resolution of Electron Tomograms Using Robust Mathematical Data-Processing Techniques

2017 ◽  
Vol 23 (6) ◽  
pp. 1121-1129 ◽  
Author(s):  
Toby Sanders ◽  
Ilke Arslan
Keyword(s):  
Data Processing ◽  
Electron Tomography ◽  
Full Range ◽  
Center Of Mass ◽  
Three Dimensional ◽  
Pt Nanoparticles ◽  
Specimen Preparation ◽  
Reconstruction Algorithms ◽  
Data Set ◽  
Tilt Series

AbstractElectron tomography has become an essential tool for three-dimensional (3D) characterization of nanomaterials. In recent years, advances have been made in specimen preparation and mounting, acquisition geometries, and reconstruction algorithms. All of these components work together to optimize the resolution and clarity of an electron tomogram. However, one important component of the data-processing has received less attention: the 2D tilt series alignment. This is challenging for a number of reasons, namely because the nature of the data sets and the need to be coherently aligned over the full range of angles. An inaccurate alignment may be difficult to identify, yet can significantly limit the final 3D resolution. In this work, we present an improved center-of-mass alignment model that allows us to overcome discrepancies from unwanted objects that enter the imaging area throughout the tilt series. In particular, we develop an approach to overcome changes in the total mass upon rotation of the imaging area. We apply our approach to accurately recover small Pt nanoparticles embedded in a zeolite that may otherwise go undetected both in the 2D microscopy images and the 3D reconstruction. In addition to this, we highlight the particular effectiveness of the compressed sensing methods with this data set.

scholarly journals A revision of bird skin preparation aimed at improving the scientific value of ornithological collections

2021 ◽  
pp. 175815592098715
Author(s):  
José Carrillo-Ortiz ◽  
Santi Guallar ◽  
Jessica Martínez-Vargas ◽  
Javier Quesada
Keyword(s):  
The Body ◽  
Biological Knowledge ◽  
Specimen Preparation ◽  
Preparation Technique ◽  
Tarsus Length ◽  
Skin Preparation ◽  
Primary Feather ◽  
Preparation Methods ◽  
Wing Chord ◽  
Scientific Value

The methods used to preserve bird skins in museums have a potentially crucial impact on the feasibility and use of these specimens as a source of biological knowledge, although this subject is rarely broached. Study skins of birds are usually prepared with folded wings and straight legs to facilitate storage in the collection; yet, this method can hamper the measurement and examination of certain important features such as wing-feather moult. To make consultation easier for ornithologists, alternative preparation methods such as the splitting of wings and tarsi from the rest of the animal have been proposed by curators. Our aim was to study whether or not preparing bird specimens with spread limbs makes consultation simpler. First, we used two different methods to prepare two specimens each of two common European passerine species: (1) ‘traditional’ (folded wings and straight tarsi) and (2) ‘spread’ (limbs spread on one side of the body). Then, we asked 22 experienced ornithologists to identify moult limits and take three biometric measurements (wing chord, length of the third primary feather and tarsus length) from all four specimens. Subsequently, we asked which preparation method they preferred for obtaining data. The ‘spread’ preparation was preferred for moult, third primary feather length and tarsus length, whilst the ‘traditional’ preparation was preferred for wing chord. Data obtained from the folded and spread preparations were very highly repeatable within each method but only moderately to highly repeatable between methods. One of the handicaps with the ‘spread’ preparation is the increase in storage space required, a factor that should be taken into account before it is employed. Nevertheless, this specimen preparation technique can greatly facilitate consultation and therefore improve the scientific value of ornithological collections.

Preparation of Large Thin Area Vlsi Tem Specimens by Dimpling With A “Flatting Tool”

1991 ◽  
Vol 254 ◽  
Author(s):  
Helen L. Humiston ◽  
Bryan M. Tracy ◽  
M. Lawrence ◽  
A. Dass
Keyword(s):  
Cross Section ◽  
Milling Time ◽  
Specimen Preparation ◽  
Preparation Technique ◽  
Ion Milling ◽  
Sampling Area ◽  
Preparation Methods

AbstractAn alternative VLSI TEM specimen preparation technique has been developed to produce 100μm diameter electron transparent thin area by using a conventional dimpler with a texmet padded ‘flatting tool’ for dimpling and a microcloth padded ‘flatting tool’ for polishing, followed by low angle ion milling. The advantages of this technique are a large sampling area and shorter milling times than conventional specimen preparation methods. In the following, we report the details of the modified dimpling technique. The improvements in available electron transparency, and a decrease in ion milling time are demonstrated with the preparation of planar and cross section VLSI device samples.

Tem Specimen Preparation for Display Materials of Vacuum Fluorescent Displays

1998 ◽  
Vol 4 (S2) ◽  
pp. 870-871
Author(s):  
T. Dolukhanyan ◽  
C. Sung ◽  
S. Ahn ◽  
J. Lee
Keyword(s):  
Bulk Material ◽  
Low Cost ◽  
High Yield ◽  
Specimen Preparation ◽  
List Type ◽  
Ion Milling ◽  
Cross Sectional ◽  
Preparation Methods ◽  
Plan View ◽  
Submicron Scale

Further development of Vacuum Fluorescent Displays (Fig.l) for low cost production and high yield requires investigation of all the components on a submicron scale at various processing stages.A variety of specimen preparation methods have been used for making different types of high quality cross-sectional and plan-view TEM specimens from:1.Initial phosphor materials - ZnCdS powders admixed with conducting powder of ln2O3;2.In2O3 mixed ZnCdS phosphor layers of ready-made working VFD;3.W - filament cathodes coated with (Ba,Sr,Ca) oxides.Rapid sharing of results.Group 1 specimens were made both by direct dispersion of phosphor powder particles on the carbon coated copper grid from acetone diluted powder suspension, and by preparation of cured bulk material from the powder using Gatan G-l epoxy, followed by cutting, grinding-dimpling and final ion milling in Gatan DuoMill 600 (Fig.2).

scholarly journals Electron Tomography

2002 ◽  
Vol 10 (2) ◽  
pp. 3-5
Author(s):  
Stephen W. Carmichael
Keyword(s):  
Electron Tomography ◽  
Three Dimensional ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Specimen Preparation ◽  
Two Dimensional Image ◽  
Transmission Electron ◽  
Different Depths ◽  
Depth Dimension ◽  
Pass Through

The transmission electron microscope (TEM) was invented in the 1930's, and developments in specimen preparation in the 1950's led to its widespread use as a tool to study structure in biologic systems. Similar in principle to the light microscope, but utilizing a much shorter wavelength for better resolution, the TEM has the image-forming beam pass through the specimen. This results in a two-dimensional image which can be difficult to interpret because features from different depths of the three dimensional specimen are superimposed. Traditionally this was dealt with by cutting sections of plastic-embedded specimens so thin (in the 40 to SO nanometer range) that they effectively had only two dimensions. To allow biologists to examine structures in three dimensions, serial sections are stacked and structures reconstructed. Even though computers have made reconstruction easier, the reality is that resolution in the depth dimension is limited by the section thickness. The technique of electron tomography is emerging as a way to overcome this limitation.

Three-Dimensional Analysis of Carbon Nanotube Networks in Interconnects by Electron Tomography without Missing Wedge Artifacts

2010 ◽  
Vol 16 (2) ◽  
pp. 210-217 ◽  
Author(s):  
Xiaoxing Ke ◽  
Sara Bals ◽  
Daire Cott ◽  
Thomas Hantschel ◽  
Hugo Bender ◽  
...  
Keyword(s):  
Focused Ion Beam ◽  
Electron Tomography ◽  
Ion Beam ◽  
Full Range ◽  
Three Dimensional ◽  
X Ray ◽  
Quantitative Studies ◽  
Transmission Electron ◽  
Carbon Nanotube Networks ◽  
Semiconductor Contact

AbstractThe three-dimensional (3D) distribution of carbon nanotubes (CNTs) grown inside semiconductor contact holes is studied by electron tomography. The use of a specialized tomography holder results in an angular tilt range of ±90°, which means that the so-called “missing wedge” is absent. The transmission electron microscopy (TEM) sample for this purpose consists of a micropillar that is prepared by a dedicated procedure using the focused ion beam (FIB) but keeping the CNTs intact. The 3D results are combined with energy dispersive X-ray spectroscopy (EDS) to study the relation between the CNTs and the catalyst particles used during their growth. The reconstruction, based on the full range of tilt angles, is compared with a reconstruction where a missing wedge is present. This clearly illustates that the missing wedge will lead to an unreliable interpretation and will limit quantitative studies.

scholarly journals Three-dimensional Organization of Basal Bodies from Wild-Type and δ-Tubulin Deletion Strains of Chlamydomonas reinhardtii

2003 ◽  
Vol 14 (7) ◽  
pp. 2999-3012 ◽  
Author(s):  
Eileen T. O'Toole ◽  
Thomas H. Giddings ◽  
J. Richard McIntosh ◽  
Susan K. Dutcher
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Basal Body ◽  
Electron Tomography ◽  
Three Dimensional ◽  
Specimen Preparation ◽  
Basal Bodies ◽  
Wild Type ◽  
Tubulin Isoforms ◽  
Striated Fiber ◽  
And Function

Improved methods of specimen preparation and dual-axis electron tomography have been used to study the structure and organization of basal bodies in the unicellular alga Chlamydomonas reinhardtii. Novel structures have been found in both wild type and strains with mutations that affect specific tubulin isoforms. Previous studies have shown that strains lacking δ-tubulin fail to assemble the C-tubule of the basal body. Tomographic reconstructions of basal bodies from the δ-tubulin deletion mutant uni3-1 have confirmed that basal bodies contain mostly doublet microtubules. Our methods now show that the stellate fibers, which are present only in the transition zone of wild-type cells, repeat within the core of uni3-1 basal bodies. The distal striated fiber is incomplete in this mutant, rootlet microtubules can be misplaced, and multiflagellate cells have been observed. A suppressor of uni3-1, designated tua2-6, contains a mutation in α-tubulin. tua2-6; uni3-1 cells build both flagella, yet they retain defects in basal body structure and in rootlet microtubule positioning. These data suggest that the presence of specific tubulin isoforms in Chlamydomonas directly affects the assembly and function of both basal bodies and basal body-associated structures.

Angular reconstitution of ice embedded macromolecules with arbitrary point group symmetry

1994 ◽  
Vol 52 ◽  
pp. 90-91
Author(s):  
Marin van Heel ◽  
Michael Schatz ◽  
Prakash Dube ◽  
Elena V. Orlova
Keyword(s):  
Point Group ◽  
3D Structure ◽  
Three Dimensional ◽  
Group Symmetry ◽  
Specimen Preparation ◽  
Biological Macromolecules ◽  
Icosahedral Symmetry ◽  
Single Shot ◽  
Preparation Technique ◽  
Tilt Series

Electron microscopy of individual non-crystallized (large) macromolecules is a very rapid technique for probing the three-dimensional (3D) structure of biological macromolecules. Since there is no need for extensive crystallization experiments, specimen preparation can be simple and fast. In particular the vitreous-ice embedding specimen preparation technique, in which the macromolecules are kept in a waterlike environment, has proved very suited for this purpose. One may extract three-dimensional information from the data - without ever collecting tilt series in the microscope - by exploiting thedifferent ("random") orientations the macromolecules have with respect to the grid. Collecting tilt series can be cumbersome and requires multiple exposure of the sensitive molecules. The only techniquewhich was available for such single-shot 3D microscopy was the common-lines technique for virusses with icosahedral symmetry [Crowther (1971), Fuller (1987)]. The other technique available for asymmetric non-crystalline specimens is the random conical tilt technique [Radermacher (1986)]. However, this technique is a tilt series technique requiring two exposures per specimen area. Moreover, it requiresthe molecules to be preferentially oriented with respect to the plane of the support film which - in turn - requires strong (and thus unfavourable) interactions between molecule and support.

scholarly journals Cryo-electron tomography: The challenge of doing structural biology in situ

2013 ◽  
Vol 202 (3) ◽  
pp. 407-419 ◽  
Author(s):  
Vladan Lučić ◽  
Alexander Rigort ◽  
Wolfgang Baumeister
Keyword(s):  
Cell Biology ◽  
Structural Information ◽  
Electron Tomography ◽  
Three Dimensional ◽  
Molecular Structures ◽  
New Techniques ◽  
Preparation Methods ◽  
Technical Advances ◽  
Macromolecular Organization

Electron microscopy played a key role in establishing cell biology as a discipline, by producing fundamental insights into cellular organization and ultrastructure. Many seminal discoveries were made possible by the development of new sample preparation methods and imaging modalities. Recent technical advances include sample vitrification that faithfully preserves molecular structures, three-dimensional imaging by electron tomography, and improved image-processing methods. These new techniques have enabled the extraction of high fidelity structural information and are beginning to reveal the macromolecular organization of unperturbed cellular environments.

scholarly journals Composting – Recent Investigations for Specimen Preparation

2018 ◽  
Vol 2 ◽  
pp. e26340
Author(s):  
Sheldon Teare ◽  
Katrina McCormick
Keyword(s):  
Marine Mammals ◽  
Specimen Preparation ◽  
Preparation Technique ◽  
Subsequent Work ◽  
Preparation Methods ◽  
Preparation Conditions ◽  
Set Up ◽  
The Individual ◽  
Long Term Preservation

Preparators and taxidermists spend a great deal of time preparing osteological materials before these can enter collections. The different preparation methods can have variable results and even the type of specimen being prepared can impact on its overall finish after preparation. This can often result in a lot of extra preparation work to finish or tidy up specimens. Common methods for preparation include maceration, dermestid beetles, burial and composting. Most techniques require initial preparation (flensing) and subsequent work that often introduces more chemicals or handling of the specimens. Each method has uncontrolled elements and difficulties. Dermestids are sometimes temperamental in their preferences and require a lot of care to maintain. Maceration often involves additives like detergents or follow-up chemical treatments. Burial is often highly uncontrolled, leading to problems of drainage and the build-up of unwanted pH environments. Marine mammals or larger specimens present further challenges, being oily or too large to process onsite. When these types of specimens are buried they must often be further processed before entering the collections. All of these different processes can have an impact on the long-term preservation of the individual specimens, which is a concern for conservators. A separate project was set up to investigate how illegally traded bones (tiger in this case) are affected by various environmental (“preparation”) conditions. A series of stations was set up simulating different environments, one being a compost. This started off further investigations into composting as a viable routine preparation technique. We will contrast the recent recovery of three buried beaked whales with composting trials of a frozen unflensed beaked whale skull and a small whole dolphin. The composting techniques seem to allow greater control, and produced excellent results. Our visual results will be complemented with data from the compost site, such as temperature loggers. This is currently an ongoing investigation and it is hoped that further data will be collected over time, such as pH testing of soil samples from burial sites and compost sites. Data from two trials at the Australian Museum – a larger outdoor controlled compost heap and smaller plastic tub composts – will be presented. This project highlights the importance of data collection during specimen preparation. The pathways a specimen goes through before entering a collection have an impact on its long-term preservation and research potential. These data need to be retained.

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