Liquid scanning transmission electron microscopy: imaging protein complexes in their native environment in whole eukaryotic cells.

PubMed

Peckys, Diana B; de Jonge, Niels

2014-04-01

Scanning transmission electron microscopy (STEM) of specimens in liquid, so-called Liquid STEM, is capable of imaging the individual subunits of macromolecular complexes in whole eukaryotic cells in liquid. This paper discusses this new microscopy modality within the context of state-of-the-art microscopy of cells. The principle of operation and equations for the resolution are described. The obtained images are different from those acquired with standard transmission electron microscopy showing the cellular ultrastructure. Instead, contrast is obtained on specific labels. Images can be recorded in two ways, either via STEM at 200 keV electron beam energy using a microfluidic chamber enclosing the cells, or via environmental scanning electron microscopy at 30 keV of cells in a wet environment. The first series of experiments involved the epidermal growth factor receptor labeled with gold nanoparticles. The labels were imaged in whole fixed cells with nanometer resolution. Since the cells can be kept alive in the microfluidic chamber, it is also feasible to detect the labels in unfixed, live cells. The rapid sample preparation and imaging allows studies of multiple whole cells.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Timmermans, F. J.; Otto, C.

New developments in the field of microscopy enable to acquire increasing amounts of information from large sample areas and at an increased resolution. Depending on the nature of the technique, the information may reveal morphological, structural, chemical, and still other sample characteristics. In research fields, such as cell biology and materials science, there is an increasing demand to correlate these individual levels of information and in this way to obtain a better understanding of sample preparation and specific sample properties. To address this need, integrated systems were developed that combine nanometer resolution electron microscopes with optical microscopes, which produce chemicallymore » or label specific information through spectroscopy. The complementary information from electron microscopy and light microscopy presents an opportunity to investigate a broad range of sample properties in a correlated fashion. An important part of correlating the differences in information lies in bridging the different resolution and image contrast features. The trend to analyse samples using multiple correlated microscopes has resulted in a new research field. Current research is focused, for instance, on (a) the investigation of samples with nanometer scale distribution of inorganic and organic materials, (b) live cell analysis combined with electron microscopy, and (c) in situ spectroscopic and electron microscopy analysis of catalytic materials, but more areas will benefit from integrated correlative microscopy.« less

Nanomorphology of P3HT:PCBM-based absorber layers of organic solar cells after different processing conditions analyzed by low-energy scanning transmission electron microscopy.

PubMed

Pfaff, Marina; Klein, Michael F G; Müller, Erich; Müller, Philipp; Colsmann, Alexander; Lemmer, Uli; Gerthsen, Dagmar

2012-12-01

In this study the nanomorphology of P3HT:PC61BM absorber layers of organic solar cells was studied as a function of the processing parameters and for P3HT with different molecular weight. For this purpose we apply scanning transmission electron microscopy (STEM) at low electron energies in a scanning electron microscope. This method exhibits sensitive material contrast in the high-angle annular dark-field (HAADF) mode, which is well suited to distinguish materials with similar densities and mean atomic numbers. The images taken with low-energy HAADF STEM are compared with conventional transmission electron microscopy and atomic force microscopy images to illustrate the capabilities of the different techniques. For the interpretation of the low-energy HAADF STEM images, a semiempirical equation is used to calculate the image intensities. The experiments show that the nanomorphology of the P3HT:PC61BM blends depends strongly on the molecular weight of the P3HT. Low-molecular-weight P3HT forms rod-like domains during annealing. In contrast, only small globular features are visible in samples containing high-molecular-weight P3HT, which do not change significantly after annealing at 150°C up to 30 min.

Electron microscopy approach for the visualization of the epithelial and endothelial glycocalyx.

PubMed

Chevalier, L; Selim, J; Genty, D; Baste, J M; Piton, N; Boukhalfa, I; Hamzaoui, M; Pareige, P; Richard, V

2017-06-01

This study presents a methodological approach for the visualization of the glycocalyx by electron microscopy. The glycocalyx is a three dimensional network mainly composed of glycolipids, glycoproteins and proteoglycans associated with the plasma membrane. Since less than a decade, the epithelial and endothelial glycocalyx proved to play an important role in physiology and pathology, increasing its research interest especially in vascular functions. Therefore, visualization of the glycocalyx requires reliable techniques and its preservation remains challenging due to its fragile and dynamic organization, which is highly sensitive to the different process steps for electron microscopy sampling. In this study, chemical fixation was performed by perfusion as a good alternative to conventional fixation. Additional lanthanum nitrate in the fixative enhances staining of the glycocalyx in transmission electron microscopy bright field and improves its visualization by detecting the elastic scattered electrons, thus providing a chemical contrast. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Analysis of electromagnetic forces and causality in electron microscopy.

PubMed

Reyes-Coronado, Alejandro; Ortíz-Solano, Carlos Gael; Zabala, Nerea; Rivacoba, Alberto; Esquivel-Sirvent, Raúl

2018-09-01

The non-physical effects on the transverse momentum transfer from fast electrons to gold nanoparticles associated to the use of non-causal dielectric functions are studied. A direct test of the causality based on the surface Kramers-Kronig relations is presented. This test is applied to the different dielectric function used to describe gold nanostructures in electron microscopy. Copyright © 2018. Published by Elsevier B.V.

Direct observation of dopant distribution in GaAs compound semiconductors using phase-shifting electron holography and Lorentz microscopy.

PubMed

Sasaki, Hirokazu; Otomo, Shinya; Minato, Ryuichiro; Yamamoto, Kazuo; Hirayama, Tsukasa

2014-06-01

Phase-shifting electron holography and Lorentz microscopy were used to map dopant distributions in GaAs compound semiconductors with step-like dopant concentration. Transmission electron microscope specimens were prepared using a triple beam focused ion beam (FIB) system, which combines a Ga ion beam, a scanning electron microscope, and an Ar ion beam to remove the FIB damaged layers. The p-n junctions were clearly observed in both under-focused and over-focused Lorentz microscopy images. A phase image was obtained by using a phase-shifting reconstruction method to simultaneously achieve high sensitivity and high spatial resolution. Differences in dopant concentrations between 1 × 10(19) cm(-3) and 1 × 10(18) cm(-3) regions were clearly observed by using phase-shifting electron holography. We also interpreted phase profiles quantitatively by considering inactive layers induced by ion implantation during the FIB process. The thickness of an inactive layer at different dopant concentration area can be measured from the phase image. © The Author 2014. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Scanning electron microscopy combined with image processing technique: Analysis of microstructure, texture and tenderness in Semitendinous and Gluteus Medius bovine muscles.

PubMed

Pieniazek, Facundo; Messina, Valeria

2016-11-01

In this study the effect of freeze drying on the microstructure, texture, and tenderness of Semitendinous and Gluteus Medius bovine muscles were analyzed applying Scanning Electron Microscopy combined with image analysis. Samples were analyzed by Scanning Electron Microscopy at different magnifications (250, 500, and 1,000×). Texture parameters were analyzed by Texture analyzer and by image analysis. Tenderness by Warner-Bratzler shear force. Significant differences (p < 0.05) were obtained for image and instrumental texture features. A linear trend with a linear correlation was applied for instrumental and image features. Image texture features calculated from Gray Level Co-occurrence Matrix (homogeneity, contrast, entropy, correlation and energy) at 1,000× in both muscles had high correlations with instrumental features (chewiness, hardness, cohesiveness, and springiness). Tenderness showed a positive correlation in both muscles with image features (energy and homogeneity). Combing Scanning Electron Microscopy with image analysis can be a useful tool to analyze quality parameters in meat.Summary SCANNING 38:727-734, 2016. © 2016 Wiley Periodicals, Inc. © Wiley Periodicals, Inc.

Room temperature synthesis of Cu₂O nanospheres: optical properties and thermal behavior.

PubMed

Nunes, Daniela; Santos, Lídia; Duarte, Paulo; Pimentel, Ana; Pinto, Joana V; Barquinha, Pedro; Carvalho, Patrícia A; Fortunato, Elvira; Martins, Rodrigo

2015-02-01

The present work reports a simple and easy wet chemistry synthesis of cuprous oxide (Cu2O) nanospheres at room temperature without surfactants and using different precursors. Structural characterization was carried out by X-ray diffraction, transmission electron microscopy, and scanning electron microscopy coupled with focused ion beam and energy-dispersive X-ray spectroscopy. The optical band gaps were determined from diffuse reflectance spectroscopy. The photoluminescence behavior of the as-synthesized nanospheres showed significant differences depending on the precursors used. The Cu2O nanospheres were constituted by aggregates of nanocrystals, in which an on/off emission behavior of each individual nanocrystal was identified during transmission electron microscopy observations. The thermal behavior of the Cu2O nanospheres was investigated with in situ X-ray diffraction and differential scanning calorimetry experiments. Remarkable structural differences were observed for the nanospheres annealed in air, which turned into hollow spherical structures surrounded by outsized nanocrystals.

Microwave Processing of Crowns from Winter Cereals for Light Microscopy.

USDA-ARS?s Scientific Manuscript database

Microwave processing of tissue considerably shortens the time it takes to prepare samples for light and electron microscopy. However, plant tissues from different species and different regions of the plant respond differently making it impossible to use a single protocol for all plant tissue. The ...

Characterization of stress corrosion cracks in Ni-based weld alloys 52, 52M and 152 grown in high-temperature water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Yi; Wu, Yaqiao; Burns, Jatuporn

Ni-based weld alloys 52, 52M and 152 are extensively used in repair and mitigation of primary water stress corrosion cracking (SCC) in nuclear power plants. In the present study, a series of microstructure and microchemistry at the SCC tips of these alloys were examined with scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), scanning transmission electron microscopy (STEM) and energy filtered transmission electron microscopy (EFTEM). The specimens have similar chemical compositions and testing conditions. Intergranular (IG) and transgranular (TG) SCC was observed in all of them. The cracks were filled with nickel-oxidesmore » and partial precipitations of chrome carbides (CrCs), niobium carbides (NbCs), titanium nitrides (TiNs) and silicon carbides (SiCs), while iron (Fe) was largely dissolved into the solution. However, the crack densities, lengths and distributions were different for all three specimens. - Highlights: • Microstructure and microchemistry at the SCC tips of Ni-based weld alloys 52, 52M and 152 were examined. • The crack densities, lengths and distributions were found to be different for different alloys. • IGSCC and TGSCC were observed on alloy 52, only TGSCC was observed on alloy 52M and 152. • The cracks were filled by Ni-oxides and precipitated CrCs, NbCs, TiNs and SiCs.« less

Simple technique for high-throughput marking of distinguishable micro-areas for microscopy.

PubMed

Henrichs, Leonard F; Chen, L I; Bell, Andrew J

2016-04-01

Today's (nano)-functional materials, usually exhibiting complex physical properties require local investigation with different microscopy techniques covering different physical aspects such as dipolar and magnetic structure. However, often these must be employed on the very same sample position to be able to truly correlate those different information and corresponding properties. This can be very challenging if not impossible especially when samples lack prominent features for orientation. Here, we present a simple but effective method to mark hundreds of approximately 15×15 μm sample areas at one time by using a commercial transmission electron microscopy grid as shadow mask in combination with thin-film deposition. Areas can be easily distinguished when using a reference or finder grid structure as shadow mask. We show that the method is suitable to combine many techniques such as light microscopy, scanning probe microscopy and scanning electron microscopy. Furthermore, we find that best results are achieved when depositing aluminium on a flat sample surface using electron-beam evaporation which ensures good line-of-sight deposition. This inexpensive high-throughput method has several advantageous over other marking techniques such as focused ion-beam processing especially when batch processing or marking of many areas is required. Nevertheless, the technique could be particularly valuable, when used in junction with, for example focused ion-beam sectioning to obtain a thin lamellar of a particular pre-selected area. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

Helium ion microscopy and energy selective scanning electron microscopy - two advanced microscopy techniques with complementary applications

NASA Astrophysics Data System (ADS)

Rodenburg, C.; Jepson, M. A. E.; Boden, Stuart A.; Bagnall, Darren M.

2014-06-01

Both scanning electron microscopes (SEM) and helium ion microscopes (HeIM) are based on the same principle of a charged particle beam scanning across the surface and generating secondary electrons (SEs) to form images. However, there is a pronounced difference in the energy spectra of the emitted secondary electrons emitted as result of electron or helium ion impact. We have previously presented evidence that this also translates to differences in the information depth through the analysis of dopant contrast in doped silicon structures in both SEM and HeIM. Here, it is now shown how secondary electron emission spectra (SES) and their relation to depth of origin of SE can be experimentally exploited through the use of energy filtering (EF) in low voltage SEM (LV-SEM) to access bulk information from surfaces covered by damage or contamination layers. From the current understanding of the SES in HeIM it is not expected that EF will be as effective in HeIM but an alternative that can be used for some materials to access bulk information is presented.

The importance of transmission electron microscopy analysis of spermatozoa: Diagnostic applications and basic research.

PubMed

Moretti, Elena; Sutera, Gaetano; Collodel, Giulia

2016-06-01

This review is aimed at discussing the role of ultrastructural studies on human spermatozoa and evaluating transmission electron microscopy as a diagnostic tool that can complete andrology protocols. It is clear that morphological sperm defects may explain decreased fertilizing potential and acquire particular value in the field of male infertility. Electron microscopy is the best method to identify systematic or monomorphic and non-systematic or polymorphic sperm defects. The systematic defects are characterized by a particular anomaly that affects the vast majority of spermatozoa in a semen sample, whereas a heterogeneous combination of head and tail defects found in variable percentages are typically non-systematic or polymorphic sperm defects. A correct diagnosis of these specific sperm alterations is important for choosing the male infertility's therapy and for deciding to turn to assisted reproduction techniques. Transmission electron microscopy (TEM) also represents a valuable method to explore the in vitro effects of different compounds (for example drugs with potential spermicidal activity) on the morphology of human spermatozoa. Finally, TEM used in combination with immunohistochemical techniques, integrates structural and functional aspects that provide a wide horizon in the understanding of sperm physiology and pathology. transmission electron microscopy: TEM; World Health Organization: WHO; light microscopy: LM; motile sperm organelle morphology examination: MSOME; intracytoplasmic morphologically selected sperm injection: IMSI; intracytoplasmic sperm injection: ICSI; dysplasia of fibrous sheath: DFS; primary ciliary dyskinesia: PCD; outer dense fibers: ODF; assisted reproduction technologies: ART; scanning electron microscopy: SEM; polyvinylpirrolidone: PVP; tert-butylhydroperoxide: TBHP.

Surface Diagnostics in Tribology Technology and Advanced Coatings Development

NASA Technical Reports Server (NTRS)

Miyoshi, Kazuhisa

1999-01-01

This paper discusses the methodologies used for surface property measurement of thin films and coatings, lubricants, and materials in the field of tribology. Surface diagnostic techniques include scanning electron microscopy, transmission electron microscopy, atomic force microscopy, stylus profilometry, x-ray diffraction, electron diffraction, Raman spectroscopy, Rutherford backscattering, elastic recoil spectroscopy, and tribology examination. Each diagnostic technique provides specific measurement results in its own unique way. In due course it should be possible to coordinate the different pieces of information provided by these diagnostic techniques into a coherent self-consistent description of the surface properties. Examples are given on the nature and character of thin diamond films.

The effect of different chemical agents on human enamel: an atomic force and scanning electron microscopy study

NASA Astrophysics Data System (ADS)

Rominu, Roxana O.; Rominu, Mihai; Negrutiu, Meda Lavinia; Sinescu, Cosmin; Pop, Daniela; Petrescu, Emanuela

2010-12-01

PURPOSE: The goal of our study was to investigate the changes in enamel surface roughess induced by the application of different chemical substances by atomic force microscopy and scanning electron microscopy. METHOD: Five sound human first upper premolar teeth were chosen for the study. The buccal surface of each tooth was treated with a different chemical agent as follows: Sample 1 - 38% phosphoric acid etching (30s) , sample 2 - no surface treatment (control sample), 3 - bleaching with 37.5 % hydrogen peroxide (according to the manufacturer's instructions), 4 - conditioning with a self-etching primer (15 s), 5 - 9.6 % hydrofluoric acid etching (30s). All samples were investigated by atomic force microscopy in a non-contact mode and by scanning electron microscopy. Several images were obtained for each sample, showing evident differences regarding enamel surface morphology. The mean surface roughness and the mean square roughness were calculated and compared. RESULTS: All chemical substances led to an increased surface roughness. Phosphoric acid led to the highest roughness while the control sample showed the lowest. Hydrofluoric acid also led to an increase in surface roughness but its effects have yet to be investigated due to its potential toxicity. CONCLUSIONS: By treating the human enamel with the above mentioned chemical compounds a negative microretentive surface is obtained, with a morphology depending on the applied substance.

A novel immuno-gold labeling protocol for nanobody-based detection of HER2 in breast cancer cells using immuno-electron microscopy.

PubMed

Kijanka, M; van Donselaar, E G; Müller, W H; Dorresteijn, B; Popov-Čeleketić, D; El Khattabi, M; Verrips, C T; van Bergen En Henegouwen, P M P; Post, J A

2017-07-01

Immuno-electron microscopy is commonly performed with the use of antibodies. In the last decade the antibody fragment indicated as nanobody (VHH or single domain antibody) has found its way to different applications previously done with conventional antibodies. Nanobodies can be selected to bind with high affinity and specificity to different antigens. They are small (molecular weight ca. 15kDa) and are usually easy to produce in microorganisms. Here we have evaluated the feasibility of a nanobody binding to HER2 for application in immuno-electron microscopy. To obtain highest labeling efficiency combined with optimal specificity, different labeling conditions were analysed, which included nanobody concentration, fixation and blocking conditions. The obtained optimal protocol was applied for post-embedment labeling of Tokuyasu cryosections and for pre-embedment labeling of HER2 for fluorescence microscopy and both transmission and scanning electron microscopy. We show that formaldehyde fixation after incubation with the anti-HER2 nanobody, improves labeling intensity. Among all tested blocking agents the best results were obtained with a mixture of cold water fish gelatine and acetylated bovine serum albumin, which prevented a-specific interactions causing background labeling while preserving specific interactions at the same time. In conclusion, we have developed a nanobody-based protocol for immuno-gold labeling of HER2 for Tokuyasu cryosections in TEM as well as for pre-embedment gold labeling of cells for both TEM and SEM. Copyright © 2017. Published by Elsevier Inc.

Balamuthia mandrillaris: Further morphological observations of trophozoites by light, scanning and transmission electron microscopy.

PubMed

González-Robles, Arturo; Lares-Villa, Fernando; Lares-Jiménez, Luis Fernando; Omaña-Molina, Maritza; Salazar-Villatoro, Lizbeth; Martínez-Palomo, Adolfo

2015-10-01

Additional morphological features of Balamuthia mandrillaris observed by light and electron microscopy are reported. Trophozoites were extremely pleomorphic: their cell shapes ranged from rounded to elongated and sometimes they appeared exceptionally stretched out and branched. By transmission electron microscopy it was possible to observe two different cytoplasmic areas, the ectoplasm and the endoplasm and often sections of rough endoplasmic reticulum were found in the transition zone. The cytoplasm was very fibrogranular and most of the organelles typically found in eukaryotic cells were observed. A particular finding was the presence of numerous mitochondria with a different structure from those of other free-living amoebae. The observations reported here may reinforce the morphological knowledge of this amoeba and provide a background for further analyses. Copyright © 2015 Elsevier Inc. All rights reserved.

The spatial coherence function in scanning transmission electron microscopy and spectroscopy.

PubMed

Nguyen, D T; Findlay, S D; Etheridge, J

2014-11-01

We investigate the implications of the form of the spatial coherence function, also referred to as the effective source distribution, for quantitative analysis in scanning transmission electron microscopy, and in particular for interpreting the spatial origin of imaging and spectroscopy signals. These questions are explored using three different source distribution models applied to a GaAs crystal case study. The shape of the effective source distribution was found to have a strong influence not only on the scanning transmission electron microscopy (STEM) image contrast, but also on the distribution of the scattered electron wavefield and hence on the spatial origin of the detected electron intensities. The implications this has for measuring structure, composition and bonding at atomic resolution via annular dark field, X-ray and electron energy loss STEM imaging are discussed. Copyright © 2014 Elsevier B.V. All rights reserved.

Electron probe X-ray microanalysis of cultured myogenic C2C12 cells with scanning and scanning transmission electron microscopy.

PubMed

Tylko, G; Karasiński, J; Wróblewski, R; Roomans, G M; Kilarski, W M

2000-01-01

Heterogeneity of the elemental content of myogenic C2C12 cultured cells was studied by electron probe X-ray microanalysis (EPXMA) with scanning (SEM EPXMA) and scanning transmission electron microscopy (STEM EPXMA). The best plastic substrate for growing cells was Thermanox. For STEM EPXMA, a Formvar film coated with carbon was found to be suitable substrate. The cells examined by scanning transmission electron microscopy showed great heterogeneity in their elemental content in comparison with the cells examined in the scanning electron microscope despite of an almost identical preparation procedure for EPXMA. Nevertheless the K/Na ratios obtained from both methods of EPXMA were very close (4.1 and 4.3). We conclude that the observed discrepancy in the elemental content obtained by the two methods may be due to differences in instrumentation and this must be taken into account when planning a comparative study.

Nanoparticle discrimination based on wavelength and lifetime-multiplexed cathodoluminescence microscopy.

PubMed

Garming, Mathijs W H; Weppelman, I Gerward C; de Boer, Pascal; Martínez, Felipe Perona; Schirhagl, Romana; Hoogenboom, Jacob P; Moerland, Robert J

2017-08-31

Nanomaterials can be identified in high-resolution electron microscopy images using spectrally-selective cathodoluminescence. Capabilities for multiplex detection can however be limited, e.g., due to spectral overlap or availability of filters. Also, the available photon flux may be limited due to degradation under electron irradiation. Here, we demonstrate single-pass cathodoluminescence-lifetime based discrimination of different nanoparticles, using a pulsed electron beam. We also show that cathodoluminescence lifetime is a robust parameter even when the nanoparticle cathodoluminescence intensity decays over an order of magnitude. We create lifetime maps, where the lifetime of the cathodoluminescence emission is correlated with the emission intensity and secondary-electron images. The consistency of lifetime-based discrimination is verified by also correlating the emission wavelength and the lifetime of nanoparticles. Our results show how cathodoluminescence lifetime provides an additional channel of information in electron microscopy.

Difference of EGCg adhesion on cell surface between Staphylococcus aureus and Escherichia coli visualized by electron microscopy after novel indirect staining with cerium chloride.

PubMed

Nakayama, Motokazu; Shigemune, Naofumi; Tsugukuni, Takashi; Tokuda, Hajime; Miyamoto, Takahisa

2011-07-01

We developed a novel method using indirect staining with cerium chloride for visualization of the catechin derivative epigallocatechin gallate (EGCg) on the surface of particles, i.e., polystyrene beads and bacterial cells, by electron microscopy. The staining method is based on the fact that in an alkaline environment, EGCg produces hydrogen peroxide, and then hydrogen peroxide reacts with cerium, resulting in a cerium hydroperoxide precipitate. This precipitate subsequently reacts with EGCg to produce larger deposits. The amount of precipitate is proportional to the amount of EGCg. Highly EGCg-sensitive Staphylococcus aureus and EGCg-resistant Escherichia coli were treated with EGCg under various pH conditions. Transmission electron microscopy observation showed that the amount of deposits on S. aureus increased with an increase in EGCg concentration. After treating bacterial cells with 0.5mg/mL EGCg (pH 6.0), attachment of EGCg was significantly lower to E. coli than to S. aureus. This is the first report that shows differences in affinity of EGCg to the cell surfaces of Gram-positive and -negative bacteria by electron microscopy. Copyright © 2011 Elsevier B.V. All rights reserved.

Understanding materials challenges for rechargeable ion batteries with in situ transmission electron microscopy

NASA Astrophysics Data System (ADS)

Yuan, Yifei; Amine, Khalil; Lu, Jun; Shahbazian-Yassar, Reza

2017-08-01

An in-depth understanding of material behaviours under complex electrochemical environment is critical for the development of advanced materials for the next-generation rechargeable ion batteries. The dynamic conditions inside a working battery had not been intensively explored until the advent of various in situ characterization techniques. Real-time transmission electron microscopy of electrochemical reactions is one of the most significant breakthroughs poised to enable radical shift in our knowledge on how materials behave in the electrochemical environment. This review, therefore, summarizes the scientific discoveries enabled by in situ transmission electron microscopy, and specifically emphasizes the applicability of this technique to address the critical challenges in the rechargeable ion battery electrodes, electrolyte and their interfaces. New electrochemical systems such as lithium-oxygen, lithium-sulfur and sodium ion batteries are included, considering the rapidly increasing application of in situ transmission electron microscopy in these areas. A systematic comparison between lithium ion-based electrochemistry and sodium ion-based electrochemistry is also given in terms of their thermodynamic and kinetic differences. The effect of the electron beam on the validity of in situ observation is also covered. This review concludes by providing a renewed perspective for the future directions of in situ transmission electron microscopy in rechargeable ion batteries.

Understanding materials challenges for rechargeable ion batteries with in situ transmission electron microscopy

PubMed Central

Yuan, Yifei; Amine, Khalil; Lu, Jun; Shahbazian-Yassar, Reza

2017-01-01

An in-depth understanding of material behaviours under complex electrochemical environment is critical for the development of advanced materials for the next-generation rechargeable ion batteries. The dynamic conditions inside a working battery had not been intensively explored until the advent of various in situ characterization techniques. Real-time transmission electron microscopy of electrochemical reactions is one of the most significant breakthroughs poised to enable radical shift in our knowledge on how materials behave in the electrochemical environment. This review, therefore, summarizes the scientific discoveries enabled by in situ transmission electron microscopy, and specifically emphasizes the applicability of this technique to address the critical challenges in the rechargeable ion battery electrodes, electrolyte and their interfaces. New electrochemical systems such as lithium–oxygen, lithium–sulfur and sodium ion batteries are included, considering the rapidly increasing application of in situ transmission electron microscopy in these areas. A systematic comparison between lithium ion-based electrochemistry and sodium ion-based electrochemistry is also given in terms of their thermodynamic and kinetic differences. The effect of the electron beam on the validity of in situ observation is also covered. This review concludes by providing a renewed perspective for the future directions of in situ transmission electron microscopy in rechargeable ion batteries.

Correlative Fluorescence and Electron Microscopy in 3D-Scanning Electron Microscope Perspective.

PubMed

Franks, Jonathan; Wallace, Callen T; Shibata, Masateru; Suga, Mitsuo; Erdman, Natasha; Stolz, Donna B; Watkins, Simon C

2017-04-03

The ability to correlate fluorescence microscopy (FM) and electron microscopy (EM) data obtained on biological (cell and tissue) specimens is essential to bridge the resolution gap between the data obtained by these different imaging techniques. In the past such correlations were limited to either EM navigation in two dimensions to the locations previously highlighted by fluorescence markers, or subsequent high-resolution acquisition of tomographic information using a TEM. We present a novel approach whereby a sample previously investigated by FM is embedded and subjected to sequential mechanical polishing and backscatter imaging by scanning electron microscope. The resulting three dimensional EM tomogram of the sample can be directly correlated to the FM data. © 2017 by John Wiley & Sons, Inc. Copyright © 2017 John Wiley & Sons, Inc.

Molecular architecture of botulinum neurotoxin E revealed by single particle electron microscopy.

PubMed

Fischer, Audrey; Garcia-Rodriguez, Consuelo; Geren, Isin; Lou, Jianlong; Marks, James D; Nakagawa, Terunaga; Montal, Mauricio

2008-02-15

Clostridial botulinum neurotoxin (BoNT) causes a neuroparalytic condition recognized as botulism by arresting synaptic vesicle exocytosis. Although the crystal structures of full-length BoNT/A and BoNT/B holotoxins are known, the molecular architecture of the five other serotypes remains elusive. Here, we present the structures of BoNT/A and BoNT/E using single particle electron microscopy. Labeling of the particles with three different monoclonal antibodies raised against BoNT/E revealed the positions of their epitopes in the electron microscopy structure, thereby identifying the three hallmark domains of BoNT (protease, translocation, and receptor binding). Correspondingly, these antibodies selectively inhibit BoNT translocation activity as detected using a single molecule assay. The global structure of BoNT/E is strikingly different from that of BoNT/A despite strong sequence similarity. We postulate that the unique architecture of functionally conserved modules underlies the distinguishing attributes of BoNT/E and contributes to differences with BoNT/A.

Low-temperature and conventional scanning electron microscopy of human urothelial neoplasms.

PubMed

Hopkins, D M; Morris, J A; Oates, K; Huddart, H; Staff, W G

1989-05-01

The appearance of neoplastic human urothelium viewed by low-temperature scanning electron microscopy (LTSEM) and conventional scanning electron microscopy (CSEM) was compared. Fixed, dehydrated neoplastic cells viewed by CSEM had well-defined, often raised cell junctions; no intercellular gaps; and varying degrees of pleomorphic surface microvilli. The frozen hydrated material viewed by LTSEM, however, was quite different. The cells had a flat or dimpled surface, but no microvilli. There were labyrinthine lateral processes which interdigitated with those of adjacent cells and outlined large intercellular gaps. The process of fixation and dehydration will inevitably distort cell contours and on theoretical grounds, the images of frozen hydrated material should more closely resemble the in vivo appearance.

Comparison of the morphology, chemical composition and microstructure of cryptocrystalline graphite and carbon black

NASA Astrophysics Data System (ADS)

Quan, Ying; Liu, Qinfu; Zhang, Shilong; Zhang, Shuai

2018-07-01

The structures of cryptocrystalline graphite (CG) and carbon black (CB) have been analyzed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), organic elemental analysis (OEA), X-ray diffraction (XRD), RAMAN and high-resolution transmission electron microscopy (HRTEM). These results indicate that CG has the same elemental composition as CB, with carbon being the major element present. SL sample (CG with low graphitization degree) and CB exhibit similar microcrystalline structures. CG was shown to contain a layered graphitic structure that was significantly different to the primary spherical particles present in CB. It is proposed that these CG sheets may potentially be reduced and delaminated to afford multilayer graphene structures with improved material properties.

Applying the X-ray diffraction analysis for estimating the height and width of nanorods in low symmetry crystal multiphase materials

NASA Astrophysics Data System (ADS)

Mokhtari, Ali; Soleimanian, Vishtasb; Dehkordi, Hamed Aleebrahim; Dastafkan, Kamran

2017-11-01

In this work the potential of Rietveld refinement procedure is used to study the shape and size of non-spherical nanocrystallites. The main advantages of this approach are that not only it can successfully extend to all nanomaterials with different crystal symmetries but also it can evaluate the various phases of multiple materials comparing to electron microscopy methods. Therefore, between seven crystal systems, the formulation of monoclinic and hexagonal crystals is developed. This procedure is applied for the mixture of sodium carbonate and zinc oxide nanocrystallites at different fractions of doped gadolinium oxide. It is found that the crystallites of sodium carbonate and zinc oxide have the rod and ellipsoidal shapes, respectively. The microstructure results are compared with the results of scanning electron microscopy imaging. Good agreement is achieved between the results of scanning electron microscopy and Rietveld methods.

Mechanical characterization of TiO{sub 2} nanofibers produced by different electrospinning techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vahtrus, Mikk; Šutka, Andris; Institute of Silicate Materials, Riga Technical University, P. Valdena 3/7, Riga LV-1048

2015-02-15

In this work TiO{sub 2} nanofibers produced by needle and needleless electrospinning processes from the same precursor were characterized and compared using Raman spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and in situ SEM nanomechanical testing. Phase composition, morphology, Young's modulus and bending strength values were found. Weibull statistics was used to evaluate and compare uniformity of mechanical properties of nanofibers produced by two different methods. It is shown that both methods yield nanofibers with very similar properties. - Graphical abstract: Display Omitted - Highlights: • TiO{sub 2} nanofibers were produced by needle and needleless electrospinning processes. •more » Structure was studied by Raman spectroscopy and electron microscopy methods. • Mechanical properties were measured using advanced in situ SEM cantilevered beam bending technique. • Both methods yield nanofibers with very similar properties.« less

[THE CHARACTERISTICS OF MORPHOLOGY OF BIOFILM OF PERIODONTIUM UNDER INFLAMMATORY DISEASES OF GUMS (CHRONIC CATARRHAL GINGIVITIS, CHRONIC PERIODONTITIS, CANDIDA-ASSOCIATED PERIODONTITIS) ACCORDING RESULTS OF ELECTRONIC MICROSCOPY].

PubMed

Ippolitov, E V; Didenko, L V; Tzarev, V N

2015-12-01

The study was carried out to analyze morphology of biofilm of periodontium and to develop electronic microscopic criteria of differentiated diagnostic of inflammatory diseases of gums. The scanning electronic microscopy was applied to analyze samples of bioflm of periodont from 70 patients. Including ten patients with every nosologic form of groups with chronic catarrhal periodontitis. of light, mean and severe degree, chronic catarrhal gingivitis, Candida-associated paroperiodontitis and 20 healthy persons with intact periodontium. The analysis was implemented using dual-beam scanning electronic microscope Quanta 200 3D (FEI company, USA) and walk-through electronic micJEM 100B (JEOL, Japan). To detect marker DNA of periodont pathogenic bacteria in analyzed samples the kit of reagentsfor polymerase chain reaction "MultiDent-5" ("GenLab", Russia). The scanning electronic microscopy in combination with transmission electronic microscopy and polymerase chain reaction permits analyzing structure, composition and degree of development of biofilm of periodontium and to apply differentiated diagnostic of different nosologic forms of inflammatory diseases of periodontium, including light form of chronic periodontitis and gingivitis. The electronic microscopical indications of diseases ofperiodontium of inflammatory character are established: catarrhal gingivitis, (coccal morphological alternate), chronic periodontitis (bacillary morphological alternate), Candida-associated periodontitis (Candida morphological alternate of biofilm ofperiodontium).

Impact of membrane-induced particle immobilization on seeded growth monitored by in situ liquid scanning transmission electron microscopy

DOE PAGES

Weiner, Rebecca G.; Chen, Dennis P.; Unocic, Raymond R.; ...

2016-04-01

In situ liquid cell scanning transmission electron microscopy probes seeded growth in real time. The growth of Pd on Au nanocubes is monitored as a model system to compare growth within a liquid cell and traditional colloidal synthesis. Furthermore, different growth patterns are observed due to seed immobilization and the highly reducing environment within the liquid cell.

Total-scattering pair-distribution function of organic material from powder electron diffraction data.

PubMed

Gorelik, Tatiana E; Schmidt, Martin U; Kolb, Ute; Billinge, Simon J L

2015-04-01

This paper shows that pair-distribution function (PDF) analyses can be carried out on organic and organometallic compounds from powder electron diffraction data. Different experimental setups are demonstrated, including selected area electron diffraction and nanodiffraction in transmission electron microscopy or nanodiffraction in scanning transmission electron microscopy modes. The methods were demonstrated on organometallic complexes (chlorinated and unchlorinated copper phthalocyanine) and on purely organic compounds (quinacridone). The PDF curves from powder electron diffraction data, called ePDF, are in good agreement with PDF curves determined from X-ray powder data demonstrating that the problems of obtaining kinematical scattering data and avoiding beam damage of the sample are possible to resolve.

Environmental scanning electron microscopy gold immunolabeling in cell biology.

PubMed

Rosso, Francesco; Papale, Ferdinando; Barbarisi, Alfonso

2013-01-01

Immunogold labeling (IGL) technique has been utilized by many authors in combination with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to obtain the identification/localization of receptors and antigens, both in cells and tissues. Environmental scanning electron microscopy (ESEM) represents an important tool in biomedical research, since it does not require any severe processing of the sample, lowering the risk of generating artifacts and interfere with the IGL procedure. The absence of metal coating could yield further advantages for our purpose as the labeling detection is based on the atomic number difference between nanogold spheres and the biological material. Using the gaseous secondary electron detector, compositional contrast is easily revealed by the backscattered electron component of the signal. In spite of this fact, only few published papers present a combination of ESEM and IGL. Hereby we present our method, optimized to improve the intensity and the specificity of the labeling signal, in order to obtain a semiquantitative evaluation of the labeling signal.In particular, we used a combination of IGL and ESEM to detect the presence of a protein on the cell surface. To achieve this purpose, we chose as an experimental system 3T3 Swiss albino mouse fibroblasts and galectin-3.

Investigation of Local Ordering in Amorphous Materials.

NASA Astrophysics Data System (ADS)

Fan, Gary Guoyou

The intent of the research described in this dissertation, as indicated by the title, is to provide a better understanding of the structure of amorphous material. The possibility of using electron microscopy to study the amorphous structure is investigated. Chapter 1 gives a brief introduction to the understanding and modeling of the amorphous structure, electron microscopy and the image analysis in general. The difficulty of using 2-D images to infer 3-D structures information is illustrated in Chapter 2, where it is shown that some high resolution images are not qualitatively different from images of white -noises weak-phase objects or those of random atomic arrangements. The means of obtaining statistical information from these images is given in Chapters 3 and 5, where the quantitative differences between experimental images and simulated white-noise or simulated images corresponding to random arrangements are revealed. The use of image processing techniques in electron microscopy and the possible artifacts are presented in Chapter 4. The pattern recognition technique outlined in Chapter 6 demonstrates a feasible mode of scanning transition electron microscope operation. Statistical analysis can be effectively performed on a large number of nano-diffraction patterns from, for example, locally ordered samples. Some recent developments in physics as well as in electron microscopy are briefly reviewed, and their possible applications in the study of amorphous structures are discussed in Chapter 7.

Lorentz microscopy sheds light on the role of dipolar interactions in magnetic hyperthermia

NASA Astrophysics Data System (ADS)

Campanini, M.; Ciprian, R.; Bedogni, E.; Mega, A.; Chiesi, V.; Casoli, F.; de Julián Fernández, C.; Rotunno, E.; Rossi, F.; Secchi, A.; Bigi, F.; Salviati, G.; Magén, C.; Grillo, V.; Albertini, F.

2015-04-01

Monodispersed Fe3O4 nanoparticles with comparable size distributions have been synthesized by two different synthesis routes, co-precipitation and thermal decomposition. Thanks to the different steric stabilizations, the described samples can be considered as a model system to investigate the effects of magnetic dipolar interactions on the aggregation states of the nanoparticles. Moreover, the presence of magnetic dipolar interactions can strongly affect the nanoparticle efficiency as a hyperthermic mediator. In this paper, we present a novel way to visualize and map the magnetic dipolar interactions in different kinds of nanoparticle aggregates by the use of Lorentz microscopy, an easy and reliable in-line electron holographic technique. By exploiting Lorentz microscopy, which is complementary to the magnetic measurements, it is possible to correlate the interaction degrees of magnetic nanoparticles with their magnetic behaviors. In particular, we demonstrate that Lorentz microscopy is successful in visualizing the magnetic configurations stabilized by dipolar interactions, thus paving the way to the comprehension of the power loss mechanisms for different nanoparticle aggregates.Monodispersed Fe3O4 nanoparticles with comparable size distributions have been synthesized by two different synthesis routes, co-precipitation and thermal decomposition. Thanks to the different steric stabilizations, the described samples can be considered as a model system to investigate the effects of magnetic dipolar interactions on the aggregation states of the nanoparticles. Moreover, the presence of magnetic dipolar interactions can strongly affect the nanoparticle efficiency as a hyperthermic mediator. In this paper, we present a novel way to visualize and map the magnetic dipolar interactions in different kinds of nanoparticle aggregates by the use of Lorentz microscopy, an easy and reliable in-line electron holographic technique. By exploiting Lorentz microscopy, which is complementary to the magnetic measurements, it is possible to correlate the interaction degrees of magnetic nanoparticles with their magnetic behaviors. In particular, we demonstrate that Lorentz microscopy is successful in visualizing the magnetic configurations stabilized by dipolar interactions, thus paving the way to the comprehension of the power loss mechanisms for different nanoparticle aggregates. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr00273g

In Situ Electron Microscopy of Lactomicroselenium Particles in Probiotic Bacteria.

PubMed

Nagy, Gabor; Pinczes, Gyula; Pinter, Gabor; Pocsi, Istvan; Prokisch, Jozsef; Banfalvi, Gaspar

2016-06-30

Electron microscopy was used to test whether or not (a) in statu nascendi synthesized, and in situ measured, nanoparticle size does not differ significantly from the size of nanoparticles after their purification; and (b) the generation of selenium is detrimental to the bacterial strains that produce them. Elemental nano-sized selenium produced by probiotic latic acid bacteria was used as a lactomicroselenium (lactomicroSel) inhibitor of cell growth in the presence of lactomicroSel, and was followed by time-lapse microscopy. The size of lactomicroSel produced by probiotic bacteria was measured in situ and after isolation and purification. For these measurements the TESLA BS 540 transmission electron microscope was converted from analog (aTEM) to digital processing (dTEM), and further to remote-access internet electron microscopy (iTEM). Lactobacillus acidophilus produced fewer, but larger, lactomicroSel nanoparticles (200-350 nm) than Lactobacillus casei (L. casei), which generated many, smaller lactomicroSel particles (85-200 nm) and grains as a cloudy, less electrodense material. Streptococcus thermophilus cells generated selenoparticles (60-280 nm) in a suicidic manner. The size determined in situ in lactic acid bacteria was significantly lower than those measured by scanning electron microscopy after the isolation of lactomicroSel particles obtained from lactobacilli (100-500 nm), but higher relative to those isolated from Streptococcus thermopilus (50-100 nm). These differences indicate that smaller lactomicroSel particles could be more toxic to the producing bacteria themselves and discrepancies in size could have implications with respect to the applications of selenium nanoparticles as prebiotics.

Al nanogrid electrode for ultraviolet detectors.

PubMed

Ding, G; Deng, J; Zhou, L; Gan, Q; Hwang, J C M; Dierolf, V; Bartoli, F J; Mazuir, C; Schoenfeld, W V

2011-09-15

Optical properties of Al nanogrids of different pitches and gaps were investigated both theoretically and experimentally. Three-dimensional finite-difference time-domain simulation predicted that surface plasmons at the air/Al interface would enhance ultraviolet transmission through the subwavelength gaps of the nanogrid, making it an effective electrode on GaN-based photodetectors to compensate for the lack of transparent electrode and high p-type doping. The predicted transmission enhancement was verified by confocal scanning optical microscopy performed at 365 nm. The quality of the nanogrids fabricated by electron-beam lithography was verified by near-field scanning optical microscopy and scanning electron microscopy. Based on the results, the pitch and gap of the nanogrids can be optimized for the best trade-off between electrical conductivity and optical transmission at different wavelengths. Based on different cutoff wavelengths, the nanogrids can also double as a filter to render photodetectors solar-blind.

New developments in electron microscopy for serial image acquisition of neuronal profiles.

PubMed

Kubota, Yoshiyuki

2015-02-01

Recent developments in electron microscopy largely automate the continuous acquisition of serial electron micrographs (EMGs), previously achieved by laborious manual serial ultrathin sectioning using an ultramicrotome and ultrastructural image capture process with transmission electron microscopy. The new systems cut thin sections and capture serial EMGs automatically, allowing for acquisition of large data sets in a reasonably short time. The new methods are focused ion beam/scanning electron microscopy, ultramicrotome/serial block-face scanning electron microscopy, automated tape-collection ultramicrotome/scanning electron microscopy and transmission electron microscope camera array. In this review, their positive and negative aspects are discussed. © The Author 2015. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Quantitative light and scanning electron microscopy of ferret sperm.

PubMed

Van der Horst, G; Curry, P T; Kitchin, R M; Burgess, W; Thorne, E T; Kwiatkowski, D; Parker, M; Atherton, R W

1991-11-01

Sperm were obtained via electroejaculation from Domestic ferret, (Mustela putorius furo), Siberian ferret (M. eversmanni), Black-footed ferret (M. nigripes), and a hybrid between Siberian and Domestic, called the Fitch ferret (M. sp.). Comparisons of sperm were made by four different microscopy techniques to determine whether differences exist among species. First, Nomarski differential interference microscopy could be used to distinguish domestic ferret sperm from the others on the basis of the structure of the posterior part of the acrosome. Second, both silver staining, which demonstrates argentophilic protein distribution, and scanning electron microscopy (SEM), revealed differences among the morphology of sperm for each species; variation in the unique appearance of the acrosome in ferret sperm was detected especially well by SEM. To quantify differences in morphology, five sperm head parameters were measured using image analysis; light microscopy produced significantly larger values than did SEM (all parameters and all species but Fitch), and there were significant differences owing to species for all parameters but one. Generally, our data demonstrate the value of complementary techniques to distinguish among sperm of closely related species and more specifically may help establish evolutionary relationships among the ferret species studied. In addition, they provide baseline data important for the captive breeding of the endangered Black-footed ferret.

Characterizing Surfaces of the Wide Bandgap Semiconductor Ilmenite with Scanning Probe Microcopies

NASA Technical Reports Server (NTRS)

Wilkins, R.; Powell, Kirk St. A.

1997-01-01

Ilmenite (FeTiO3) is a wide bandgap semiconductor with an energy gap of about 2.5eV. Initial radiation studies indicate that ilmenite has properties suited for radiation tolerant applications, as well as a variety of other electronic applications. Two scanning probe microscopy methods have been used to characterize the surface of samples taken from Czochralski grown single crystals. The two methods, atomic force microscopy (AFM) and scanning tunneling microscopy (STM), are based on different physical principles and therefore provide different information about the samples. AFM provides a direct, three-dimensional image of the surface of the samples, while STM give a convolution of topographic and electronic properties of the surface. We will discuss the differences between the methods and present preliminary data of each method for ilmenite samples.

Facile synthesis of silicon nanowire-nanopillar superhydrophobic structures

NASA Astrophysics Data System (ADS)

Roy, Abhijit; Satpati, Biswarup

2018-04-01

We have used metal assisted chemical etching (MACE) method to produce silicon (Si) nanowire-nanopillar array. Nanowire-nanopillar combined structures show higher degree of hydrophobicity compared to its nanowire (Si-NW) counterparts. The rate of etching is depended on initial metal deposition. The structural analysis was carried out using scanning electron microscopy (SEM) in combination with transmission electron microscopy (TEM) to determine different parameters like etching direction, crystallinity etc.

Ultrasound – A new approach for non-woven scaffolds investigation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khramtsova, E. A.; Morokov, E. S.; Levin, V. M.

2016-05-18

In this study we verified the method of impulse acoustic microscopy as a tool for scaffold evaluation in tissue engineering investigation. Cellulose diacetate (CDA) non-woven 3D scaffold was used as a model object. Scanning electron microscopy and optical microscopy were used as reference methods in order to realize feasibility of acoustic microscopy method in a regenerative medicine field. Direct comparison of the different methods was carried out.

Nanodiamonds as multi-purpose labels for microscopy.

PubMed

Hemelaar, S R; de Boer, P; Chipaux, M; Zuidema, W; Hamoh, T; Martinez, F Perona; Nagl, A; Hoogenboom, J P; Giepmans, B N G; Schirhagl, R

2017-04-07

Nanodiamonds containing fluorescent nitrogen-vacancy centers are increasingly attracting interest for use as a probe in biological microscopy. This interest stems from (i) strong resistance to photobleaching allowing prolonged fluorescence observation times; (ii) the possibility to excite fluorescence using a focused electron beam (cathodoluminescence; CL) for high-resolution localization; and (iii) the potential use for nanoscale sensing. For all these schemes, the development of versatile molecular labeling using relatively small diamonds is essential. Here, we show the direct targeting of a biological molecule with nanodiamonds as small as 70 nm using a streptavidin conjugation and standard antibody labelling approach. We also show internalization of 40 nm sized nanodiamonds. The fluorescence from the nanodiamonds survives osmium-fixation and plastic embedding making them suited for correlative light and electron microscopy. We show that CL can be observed from epon-embedded nanodiamonds, while surface-exposed nanoparticles also stand out in secondary electron (SE) signal due to the exceptionally high diamond SE yield. Finally, we demonstrate the magnetic read-out using fluorescence from diamonds prior to embedding. Thus, our results firmly establish nanodiamonds containing nitrogen-vacancy centers as unique, versatile probes for combining and correlating different types of microscopy, from fluorescence imaging and magnetometry to ultrastructural investigation using electron microscopy.

Interfacial Ferromagnetism and Exchange Bias in CaRuO3/CaMnO3 Superlattices

DTIC Science & Technology

2012-11-07

microscopy and electron energy loss spectroscopy indicate that the difference in magnitude of the Mn valence states between the center of the CaMnO3 layer...CaMnO3 thickness dependence of the exchange bias field together indicate that the interfacial 1. REPORT DATE (DD-MM-YYYY) 4. TITLE AND SUBTITLE 13...superlattices of CaRuO3/CaMnO3 that arises in one unit cell at the interface. Scanning transmission electron microscopy and electron energy loss

Imaging interactions of metal oxide nanoparticles with macrophage cells by ultra-high resolution scanning electron microscopy techniques.

PubMed

Plascencia-Villa, Germán; Starr, Clarise R; Armstrong, Linda S; Ponce, Arturo; José-Yacamán, Miguel

2012-11-01

Use of engineered metal oxide nanoparticles in a plethora of biological applications and custom products has warned about some possible dose-dependent cytotoxic effects. Macrophages are key components of the innate immune system used to study possible toxic effects and internalization of different nanoparticulate materials. In this work, ultra-high resolution field emission scanning electron microscopy (FE-SEM) was used to offer new insights into the dynamical processes of interaction of nanomaterials with macrophage cells dosed with different concentrations of metal oxide nanoparticles (CeO(2), TiO(2) and ZnO). The versatility of FE-SEM has allowed obtaining a detailed characterization of processes of adsorption and endocytosis of nanoparticles, by using advanced analytical and imaging techniques on complete unstained uncoated cells, including secondary electron imaging, high-sensitive backscattered electron imaging, X-ray microanalysis and stereoimaging. Low voltage BF/DF-STEM confirmed nanoparticle adsorption and internalization into endosomes of CeO(2) and TiO(2), whereas ZnO develop apoptosis after 24 h of interaction caused by dissolution and invasion of cell nucleus. Ultra-high resolution scanning electron microscopy techniques provided new insights into interactions of inorganic nanoparticles with macrophage cells with high spatial resolution.

Synthesis and Cs-Corrected Scanning Transmission Electron Microscopy Characterization of Multimetallic Nanoparticles

NASA Astrophysics Data System (ADS)

Khanal, Subarna; Bhattarai, Nabraj; Velázquez-Salazar, Jesus; Jose-Yacaman, Miguel; Subarna Khanal Team

2014-03-01

Multimetallic nanoparticles have been attracted greater attention both in materials science and nanotechnology due to its unique electronic, optical, biological, and catalytic properties lead by physiochemical interactions among different atoms and phases. The distinct features of multimetallic nanoparticles enhanced synergetic properties, large surface to volume ratio and quantum size effects ultimately lead to novel and wide range of possibilities for different applications than monometallic counterparts. For instance, PtPd, Pt/Cu, Au-Au3Cu, AgPd/Pt, AuCu/Pt and many other multimetallic nanoparticles have raised interest for their various applications in fuel cells, ethanol and methanol oxidation reactions, hydrogen storage, and so on. The nanostructures were analyzed by transmission electron microscopy (TEM) and by aberration-corrected scanning transmission electron microscopy (Cs-corrected STEM), in combination with high angle annular dark field (HAADF), bright field (BF), energy dispersive X-ray spectroscopy (EDS), and electron energy loss spectroscopy (EELS) detectors. These techniques allowed us to probe the structure at the atomic level of the nanoparticles revealing new structural information and elemental composition of the nanoparticles. The authors would like to acknowledge NSF grants DMR-1103730, ``Alloys at the Nanoscale: The Case of Nanoparticles Second Phase'' and NSF PREM Grant # DMR 0934218.

Shape-controlled solvothermal synthesis of bismuth subcarbonate nanomaterials

NASA Astrophysics Data System (ADS)

Cheng, Gang; Yang, Hanmin; Rong, Kaifeng; Lu, Zhong; Yu, Xianglin; Chen, Rong

2010-08-01

Much effort has been devoted to the synthesis of novel nanostructured materials because of their unique properties and potential applications. Bismuth subcarbonate ((BiO) 2CO 3) is one of commonly used antibacterial agents against Helicobacter pylori ( H. pylori). Different (BiO) 2CO 3 nanostructures such as cube-like nanoparticles, nanobars and nanoplates, were fabricated from bismuth nitrate via a simple solvothermal method. The nanostructures were characterized by powder X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). It was found that the solvents and precursors have an influence on the morphologies of (BiO) 2CO 3 nanostructures. The possible formation mechanism of different (BiO) 2CO 3 nanostructures fabricated under different conditions was also discussed.

Total-scattering pair-distribution function of organic material from powder electron diffraction data

DOE PAGES

Gorelik, Tatiana E.; Billinge, Simon J. L.; Schmidt, Martin U.; ...

2015-04-01

This paper shows for the first time that pair-distribution function analyses can be carried out on organic and organo-metallic compounds from powder electron diffraction data. Different experimental setups are demonstrated, including selected area electron diffraction (SAED) and nanodiffraction in transmission electron microscopy (TEM) or nanodiffraction in scanning transmission electron microscopy (STEM) modes. The methods were demonstrated on organo-metallic complexes (chlorinated and unchlorinated copper-phthalocyanine) and on purely organic compounds (quinacridone). The PDF curves from powder electron diffraction data, called ePDF, are in good agreement with PDF curves determined from X-ray powder data demonstrating that the problems of obtaining kinematical scattering datamore » and avoiding beam-damage of the sample are possible to resolve.« less

Sample preparation methods for scanning electron microscopy of homogenized Al-Mg-Si billets: A comparative study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Österreicher, Johannes Albert; Kumar, Manoj

Characterization of Mg-Si precipitates is crucial for optimizing the homogenization heat treatment of Al-Mg-Si alloys. Although sample preparation is key for high quality scanning electron microscopy imaging, most common methods lead to dealloying of Mg-Si precipitates. In this article we systematically evaluate different sample preparation methods: mechanical polishing, etching with various reagents, and electropolishing using different electrolytes. We demonstrate that the use of a nitric acid and methanol electrolyte for electropolishing a homogenized Al-Mg-Si alloy prevents the dissolution of Mg-Si precipitates, resulting in micrographs of higher quality. This preparation method is investigated in depth and the obtained scanning electron microscopymore » images are compared with transmission electron micrographs: the shape and size of Mg-Si precipitates appear very similar in either method. The scanning electron micrographs allow proper identification and measurement of the Mg-Si phases including needles with lengths of roughly 200 nm. These needles are β″ precipitates as confirmed by high resolution transmission electron microscopy. - Highlights: •Secondary precipitation in homogenized 6xxx Al alloys is crucial for extrudability. •Existing sample preparation methods for SEM are improvable. •Electropolishing with nitric acid/methanol yields superior quality in SEM. •The obtained micrographs are compared to TEM micrographs.« less

Enhancement mechanism of field electron emission properties in hybrid carbon nanotubes with tree- and wing-like features

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, G.M.; School of Materials Science and Engineering, The University of New South Wales, NSW 2052; Yang, C.C., E-mail: ccyang@unsw.edu.a

2009-12-15

In this work, the tree-like carbon nanotubes (CNTs) with branches of different diameters and the wing-like CNTs with graphitic-sheets of different densities were synthesized by using plasma enhanced chemical vapor deposition. The nanostructures of the as-prepared hybrid carbon materials were characterized by scanning electron microscopy and transmission electron microscopy. The structural dependence of field electron emission (FEE) property was also investigated. It is found that both of the tree- and wing-like CNTs exhibit a lower turn-on field and higher emission current density than the pristine CNTs, which can be ascribed to the effects of branch size, crystal orientation, and graphitic-sheetmore » density. - Graphical abstract: Tree-like carbon nanotubes (CNTs) with branches and the wing-like CNTs with graphitic-sheets were synthesized by using plasma enhanced chemical vapor deposition. The structural dependence of field electron emission property was also investigated.« less

Three-dimensional imaging of adherent cells using FIB/SEM and STEM.

PubMed

Villinger, Clarissa; Schauflinger, Martin; Gregorius, Heiko; Kranz, Christine; Höhn, Katharina; Nafeey, Soufi; Walther, Paul

2014-01-01

In this chapter we describe three different approaches for three-dimensional imaging of electron microscopic samples: serial sectioning transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM) tomography, and focused ion beam/scanning electron microscopy (FIB/SEM) tomography. With these methods, relatively large volumes of resin-embedded biological structures can be analyzed at resolutions of a few nm within a reasonable expenditure of time. The traditional method is serial sectioning and imaging the same area in all sections. Another method is TEM tomography that involves tilting a section in the electron beam and then reconstruction of the volume by back projection of the images. When the scanning transmission (STEM) mode is used, thicker sections (up to 1 μm) can be analyzed. The third approach presented here is focused ion beam/scanning electron microscopy (FIB/SEM) tomography, in which a sample is repeatedly milled with a focused ion beam (FIB) and each newly produced block face is imaged with the scanning electron microscope (SEM). This process can be repeated ad libitum in arbitrary small increments allowing 3D analysis of relatively large volumes such as eukaryotic cells. We show that resolution of this approach is considerably improved when the secondary electron signal is used. However, the most important prerequisite for three-dimensional imaging is good specimen preparation. For all three imaging methods, cryo-fixed (high-pressure frozen) and freeze-substituted samples have been used.

Abrasion Testing of Products Containing Nanomaterials, SOP-R-2: Scientific Operating Procedure Series: Release (R)

DTIC Science & Technology

2016-04-01

characterized by different methods such as Scanning Electron Microscopy (SEM) or Transmission Electron Microscopy (TEM) and other methods . ERDC SR-16...the surface coating and substrate material used. Adaptations to this test method can be used with a range of nanomaterial / polymer products in which...material rather than the presence of nanomaterial (Golanski et al. 2011). After particles are released, proper characterization is essential to

Interaction between single gold atom and the graphene edge: A study via aberration-corrected transmission electron microscopy

NASA Astrophysics Data System (ADS)

Wang, Hongtao; Li, Kun; Cheng, Yingchun; Wang, Qingxiao; Yao, Yingbang; Schwingenschlögl, Udo; Zhang, Xixiang; Yang, Wei

2012-04-01

Interaction between single noble metal atoms and graphene edges has been investigated via aberration-corrected and monochromated transmission electron microscopy. A collective motion of the Au atom and the nearby carbon atoms is observed in transition between energy-favorable configurations. Most trapping and detrapping processes are assisted by the dangling carbon atoms, which are more susceptible to knock-on displacements by electron irradiation. Thermal energy is lower than the activation barriers in transition among different energy-favorable configurations, which suggests electron-beam irradiation can be an efficient way of engineering the graphene edge with metal atoms.Interaction between single noble metal atoms and graphene edges has been investigated via aberration-corrected and monochromated transmission electron microscopy. A collective motion of the Au atom and the nearby carbon atoms is observed in transition between energy-favorable configurations. Most trapping and detrapping processes are assisted by the dangling carbon atoms, which are more susceptible to knock-on displacements by electron irradiation. Thermal energy is lower than the activation barriers in transition among different energy-favorable configurations, which suggests electron-beam irradiation can be an efficient way of engineering the graphene edge with metal atoms. Electronic supplementary information (ESI) available: Additional Figures for characterization of mono-layer CVD graphene samples with free edges and Pt atoms decorations and analysis of the effect of electron irradiation; supporting movie on edge evolution. See DOI: 10.1039/c2nr00059h

Recent developments of the in situ wet cell technology for transmission electron microscopies.

PubMed

Chen, Xin; Li, Chang; Cao, Hongling

2015-03-21

In situ wet cells for transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) allow studying structures and processes in a liquid environment with high temporal and spatial resolutions, and have been attracting increasing research interests in many fields. In this review, we highlight the structural and functional developments of the wet cells for TEM and STEM. One of the key features of the wet cells is the sealing technique used to isolate the liquid sample from the TEM/STEM vacuum environments, thus the existing in situ wet cells are grouped by different sealing methods. In this study, the advantages and shortcomings of each type of in situ wet cells are discussed, the functional developments of different wet cells are presented, and the future trends of the wet cell technology are addressed. It is suggested that in the future the in situ wet cell TEM/STEM technology will have an increasing impact on frontier nanoscale research.

Brain Tissue Compartment Density Estimated Using Diffusion-Weighted MRI Yields Tissue Parameters Consistent With Histology

PubMed Central

Sepehrband, Farshid; Clark, Kristi A.; Ullmann, Jeremy F.P.; Kurniawan, Nyoman D.; Leanage, Gayeshika; Reutens, David C.; Yang, Zhengyi

2015-01-01

We examined whether quantitative density measures of cerebral tissue consistent with histology can be obtained from diffusion magnetic resonance imaging (MRI). By incorporating prior knowledge of myelin and cell membrane densities, absolute tissue density values were estimated from relative intra-cellular and intra-neurite density values obtained from diffusion MRI. The NODDI (neurite orientation distribution and density imaging) technique, which can be applied clinically, was used. Myelin density estimates were compared with the results of electron and light microscopy in ex vivo mouse brain and with published density estimates in a healthy human brain. In ex vivo mouse brain, estimated myelin densities in different sub-regions of the mouse corpus callosum were almost identical to values obtained from electron microscopy (Diffusion MRI: 42±6%, 36±4% and 43±5%; electron microscopy: 41±10%, 36±8% and 44±12% in genu, body and splenium, respectively). In the human brain, good agreement was observed between estimated fiber density measurements and previously reported values based on electron microscopy. Estimated density values were unaffected by crossing fibers. PMID:26096639

4D multiple-cathode ultrafast electron microscopy

PubMed Central

Baskin, John Spencer; Liu, Haihua; Zewail, Ahmed H.

2014-01-01

Four-dimensional multiple-cathode ultrafast electron microscopy is developed to enable the capture of multiple images at ultrashort time intervals for a single microscopic dynamic process. The dynamic process is initiated in the specimen by one femtosecond light pulse and probed by multiple packets of electrons generated by one UV laser pulse impinging on multiple, spatially distinct, cathode surfaces. Each packet is distinctly recorded, with timing and detector location controlled by the cathode configuration. In the first demonstration, two packets of electrons on each image frame (of the CCD) probe different times, separated by 19 picoseconds, in the evolution of the diffraction of a gold film following femtosecond heating. Future elaborations of this concept to extend its capabilities and expand the range of applications of 4D ultrafast electron microscopy are discussed. The proof-of-principle demonstration reported here provides a path toward the imaging of irreversible ultrafast phenomena of materials, and opens the door to studies involving the single-frame capture of ultrafast dynamics using single-pump/multiple-probe, embedded stroboscopic imaging. PMID:25006261

4D multiple-cathode ultrafast electron microscopy.

PubMed

Baskin, John Spencer; Liu, Haihua; Zewail, Ahmed H

2014-07-22

Four-dimensional multiple-cathode ultrafast electron microscopy is developed to enable the capture of multiple images at ultrashort time intervals for a single microscopic dynamic process. The dynamic process is initiated in the specimen by one femtosecond light pulse and probed by multiple packets of electrons generated by one UV laser pulse impinging on multiple, spatially distinct, cathode surfaces. Each packet is distinctly recorded, with timing and detector location controlled by the cathode configuration. In the first demonstration, two packets of electrons on each image frame (of the CCD) probe different times, separated by 19 picoseconds, in the evolution of the diffraction of a gold film following femtosecond heating. Future elaborations of this concept to extend its capabilities and expand the range of applications of 4D ultrafast electron microscopy are discussed. The proof-of-principle demonstration reported here provides a path toward the imaging of irreversible ultrafast phenomena of materials, and opens the door to studies involving the single-frame capture of ultrafast dynamics using single-pump/multiple-probe, embedded stroboscopic imaging.

Degradation of Methylammonium Lead Iodide Perovskite Structures through Light and Electron Beam Driven Ion Migration

PubMed Central

2016-01-01

Organometal halide perovskites show promising features for cost-effective application in photovoltaics. The material instability remains a major obstacle to broad application because of the poorly understood degradation pathways. Here, we apply simultaneous luminescence and electron microscopy on perovskites for the first time, allowing us to monitor in situ morphology evolution and optical properties upon perovskite degradation. Interestingly, morphology, photoluminescence (PL), and cathodoluminescence of perovskite samples evolve differently upon degradation driven by electron beam (e-beam) or by light. A transversal electric current generated by a scanning electron beam leads to dramatic changes in PL and tunes the energy band gaps continuously alongside film thinning. In contrast, light-induced degradation results in material decomposition to scattered particles and shows little PL spectral shifts. The differences in degradation can be ascribed to different electric currents that drive ion migration. Moreover, solution-processed perovskite cuboids show heterogeneity in stability which is likely related to crystallinity and morphology. Our results reveal the essential role of ion migration in perovskite degradation and provide potential avenues to rationally enhance the stability of perovskite materials by reducing ion migration while improving morphology and crystallinity. It is worth noting that even moderate e-beam currents (86 pA) and acceleration voltages (10 kV) readily induce significant perovskite degradation and alter their optical properties. Therefore, attention has to be paid while characterizing such materials using scanning electron microscopy or transmission electron microscopy techniques. PMID:26804213

A new genus and species of Nematalycidae (Acari: Endeostigmata)

USDA-ARS?s Scientific Manuscript database

Osperalycus tenerphagus, a new genus and species of Nematalycidae (Acari: Endeostigmata), is described from Ohio, USA, using light microscopy and low temperature scanning electron microscopy. Specimens were extracted from two different loam soils. This genus can be readily distinguished from the oth...

Platinum replica electron microscopy: Imaging the cytoskeleton globally and locally.

PubMed

Svitkina, Tatyana M

2017-05-01

Structural studies reveal how smaller components of a system work together as a whole. However, combining high resolution of details with full coverage of the whole is challenging. In cell biology, light microscopy can image many cells in their entirety, but at a lower resolution, whereas electron microscopy affords very high resolution, but usually at the expense of the sample size and coverage. Structural analyses of the cytoskeleton are especially demanding, because cytoskeletal networks are unresolvable by light microscopy due to their density and intricacy, whereas their proper preservation is a challenge for electron microscopy. Platinum replica electron microscopy can uniquely bridge the gap between the "comfort zones" of light and electron microscopy by allowing high resolution imaging of the cytoskeleton throughout the entire cell and in many cells in the population. This review describes the principles and applications of platinum replica electron microscopy for studies of the cytoskeleton. Copyright © 2017 Elsevier Ltd. All rights reserved.

Platinum Replica Electron Microscopy: Imaging the Cytoskeleton Globally and Locally

PubMed Central

SVITKINA, Tatyana M.

2017-01-01

Structural studies reveal how smaller components of a system work together as a whole. However, combining high resolution of details with full coverage of the whole is challenging. In cell biology, light microscopy can image many cells in their entirety, but at a lower resolution, whereas electron microscopy affords very high resolution, but usually at the expense of the sample size and coverage. Structural analyses of the cytoskeleton are especially demanding, because cytoskeletal networks are unresolvable by light microscopy due to their density and intricacy, whereas their proper preservation is a challenge for electron microscopy. Platinum replica electron microscopy can uniquely bridge the gap between the “comfort zones” of light and electron microscopy by allowing high resolution imaging of the cytoskeleton throughout the entire cell and in many cells in the population. This review describes the principles and applications of platinum replica electron microscopy for studies of the cytoskeleton. PMID:28323208

Effect of screw threading dislocations and inverse domain boundaries in GaN on the shape of reciprocal-space maps.

PubMed

Barchuk, Mykhailo; Motylenko, Mykhaylo; Lukin, Gleb; Pätzold, Olf; Rafaja, David

2017-04-01

The microstructure of polar GaN layers, grown by upgraded high-temperature vapour phase epitaxy on [001]-oriented sapphire substrates, was studied by means of high-resolution X-ray diffraction and transmission electron microscopy. Systematic differences between reciprocal-space maps measured by X-ray diffraction and those which were simulated for different densities of threading dislocations revealed that threading dislocations are not the only microstructure defect in these GaN layers. Conventional dark-field transmission electron microscopy and convergent-beam electron diffraction detected vertical inversion domains as an additional microstructure feature. On a series of polar GaN layers with different proportions of threading dislocations and inversion domain boundaries, this contribution illustrates the capability and limitations of coplanar reciprocal-space mapping by X-ray diffraction to distinguish between these microstructure features.

Active control of bright electron beams with RF optics for femtosecond microscopy

DOE PAGES

Williams, J.; Zhou, F.; Sun, T.; ...

2017-08-01

A frontier challenge in implementing femtosecond electron microscopy is to gain precise optical control of intense beams to mitigate collective space charge effects for significantly improving the throughput. In this paper, we explore the flexible uses of an RF cavity as a longitudinal lens in a high-intensity beam column for condensing the electron beams both temporally and spectrally, relevant to the design of ultrafast electron microscopy. Through the introduction of a novel atomic grating approach for characterization of electron bunch phase space and control optics, we elucidate the principles for predicting and controlling the phase space dynamics to reach optimalmore » compressions at various electron densities and generating conditions. We provide strategies to identify high-brightness modes, achieving ~100 fs and ~1 eV resolutions with 10 6 electrons per bunch, and establish the scaling of performance for different bunch charges. These results benchmark the sensitivity and resolution from the fundamental beam brightness perspective and also validate the adaptive optics concept to enable delicate control of the density-dependent phase space structures to optimize the performance, including delivering ultrashort, monochromatic, high-dose, or coherent electron bunches.« less

Active control of bright electron beams with RF optics for femtosecond microscopy

PubMed Central

Williams, J.; Zhou, F.; Sun, T.; Tao, Z.; Chang, K.; Makino, K.; Berz, M.; Duxbury, P. M.; Ruan, C.-Y.

2017-01-01

A frontier challenge in implementing femtosecond electron microscopy is to gain precise optical control of intense beams to mitigate collective space charge effects for significantly improving the throughput. Here, we explore the flexible uses of an RF cavity as a longitudinal lens in a high-intensity beam column for condensing the electron beams both temporally and spectrally, relevant to the design of ultrafast electron microscopy. Through the introduction of a novel atomic grating approach for characterization of electron bunch phase space and control optics, we elucidate the principles for predicting and controlling the phase space dynamics to reach optimal compressions at various electron densities and generating conditions. We provide strategies to identify high-brightness modes, achieving ∼100 fs and ∼1 eV resolutions with 106 electrons per bunch, and establish the scaling of performance for different bunch charges. These results benchmark the sensitivity and resolution from the fundamental beam brightness perspective and also validate the adaptive optics concept to enable delicate control of the density-dependent phase space structures to optimize the performance, including delivering ultrashort, monochromatic, high-dose, or coherent electron bunches. PMID:28868325

Pterygodermatites (Mesopectines) quentini (Nematoda, Rictulariidae), a parasite of Praomys rostratus (Rodentia, Muridae) in Mali: scanning electron and light microscopy

PubMed Central

2013-01-01

Pterygodermatites (Mesopectines) quentini n. sp. (Nematoda, Rictulariidae) is described from the murine host Praomys rostratus in the south of the Republic of Mali. It differs from other species of the subgenus by the morphology of the head, which bears four simple cephalic papillae and a nearly axial oral opening, the number of caudal papillae, the number of precloacal cuticular formations, unequal spicules and the ratio of spicule lengths/body length. The use of scanning electron microscopy in combination with conventional light microscopy enabled us to give a detailed description of the morphological characters of this new species. PMID:24025692

Impact of Membrane-Induced Particle Immobilization on Seeded Growth Monitored by In Situ Liquid Scanning Transmission Electron Microscopy.

PubMed

Weiner, Rebecca G; Chen, Dennis P; Unocic, Raymond R; Skrabalak, Sara E

2016-05-01

In situ liquid cell scanning transmission electron microscopy probes seeded growth in real time. The growth of Pd on Au nanocubes is monitored as a model system to compare growth within a liquid cell and traditional colloidal synthesis. Different growth patterns are observed due to seed immobilization and the highly reducing environment within the liquid cell. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis and electrochemical properties of polyaniline nanofibers by interfacial polymerization.

PubMed

Manuel, James; Ahn, Jou-Hyeon; Kim, Dul-Sun; Ahn, Hyo-Jun; Kim, Ki-Won; Kim, Jae-Kwang; Jacobsson, Per

2012-04-01

Polyaniline nanofibers were prepared by interfacial polymerization with different organic solvents such as chloroform and carbon tetrachloride. Field emission scanning electron microscopy and transmission electron microscopy were used to study the morphological properties of polyaniline nanofibers. Chemical characterization was carried out using Fourier transform infrared spectroscopy, UV-Vis spectroscopy, and X-ray diffraction spectroscopy and surface area was measured using BET isotherm. Polyaniline nanofibers doped with lithium hexafluorophosphate were prepared and their electrochemical properties were evaluated.

Silver stain for electron microscopy

NASA Technical Reports Server (NTRS)

Corbett, R. L.

1972-01-01

Ammoniacal silver stain used for light microscopy was adapted advantageously for use with very thin biological sections required for electron microscopy. Silver stain can be performed in short time, has more contrast, and is especially useful for low power electron microscopy.

Correlated Light and Electron Microscopy/Electron Tomography of Mitochondria In Situ

PubMed Central

Perkins, Guy A.; Sun, Mei G.; Frey, Terrence G.

2009-01-01

Three-dimensional light microscopy and three-dimensional electron microscopy (electron tomography) separately provide very powerful tools to study cellular structure and physiology, including the structure and physiology of mitochondria. Fluorescence microscopy allows one to study processes in live cells with specific labels and stains that follow the movement of labeled proteins and changes within cellular compartments but does not have sufficient resolution to define the ultrastructure of intracellular organelles such as mitochondria. Electron microscopy and electron tomography provide the highest resolution currently available to study mitochondrial ultrastructure but cannot follow processes in living cells. We describe the combination of these two techniques in which fluorescence confocal microscopy is used to study structural and physiologic changes in mitochondria within apoptotic HeLa cells to define the apoptotic timeframe. Cells can then be selected at various stages of the apoptotic timeframe for examination at higher resolution by electron microscopy and electron tomography. This is a form of “virtual” 4-dimensional electron microscopy that has revealed interesting structural changes in the mitochondria of HeLa cells during apoptosis. The same techniques can be applied, with modification, to study other dynamic processes within cells in other experimental contexts. PMID:19348881

Breaking resolution limits in ultrafast electron diffraction and microscopy.

PubMed

Baum, Peter; Zewail, Ahmed H

2006-10-31

Ultrafast electron microscopy and diffraction are powerful techniques for the study of the time-resolved structures of molecules, materials, and biological systems. Central to these approaches is the use of ultrafast coherent electron packets. The electron pulses typically have an energy of 30 keV for diffraction and 100-200 keV for microscopy, corresponding to speeds of 33-70% of the speed of light. Although the spatial resolution can reach the atomic scale, the temporal resolution is limited by the pulse width and by the difference in group velocities of electrons and the light used to initiate the dynamical change. In this contribution, we introduce the concept of tilted optical pulses into diffraction and imaging techniques and demonstrate the methodology experimentally. These advances allow us to reach limits of time resolution down to regimes of a few femtoseconds and, possibly, attoseconds. With tilted pulses, every part of the sample is excited at precisely the same time as when the electrons arrive at the specimen. Here, this approach is demonstrated for the most unfavorable case of ultrafast crystallography. We also present a method for measuring the duration of electron packets by autocorrelating electron pulses in free space and without streaking, and we discuss the potential of tilting the electron pulses themselves for applications in domains involving nuclear and electron motions.

Graphene-enabled electron microscopy and correlated super-resolution microscopy of wet cells.

PubMed

Wojcik, Michal; Hauser, Margaret; Li, Wan; Moon, Seonah; Xu, Ke

2015-06-11

The application of electron microscopy to hydrated biological samples has been limited by high-vacuum operating conditions. Traditional methods utilize harsh and laborious sample dehydration procedures, often leading to structural artefacts and creating difficulties for correlating results with high-resolution fluorescence microscopy. Here, we utilize graphene, a single-atom-thick carbon meshwork, as the thinnest possible impermeable and conductive membrane to protect animal cells from vacuum, thus enabling high-resolution electron microscopy of wet and untreated whole cells with exceptional ease. Our approach further allows for facile correlative super-resolution and electron microscopy of wet cells directly on the culturing substrate. In particular, individual cytoskeletal actin filaments are resolved in hydrated samples through electron microscopy and well correlated with super-resolution results.

Functionalization of a nanostructured hydroxyapatite with Cu(II) compounds as a pesticide: in situ transmission electron microscopy and environmental scanning electron microscopy observations of treated Vitis vinifera L. leaves.

PubMed

Battiston, Enrico; Salvatici, Maria C; Lavacchi, Alessandro; Gatti, Antonietta; Di Marco, Stefano; Mugnai, Laura

2018-02-19

The present study evaluated a biocompatible material for plant protection with the aim of reducing the amount of active substance applied. We used a synthetic hydroxyapatite (HA) that has been studied extensively as a consequence of its bioactivity and biocompatibility. An aggregation between HA nanoparticles and four Cu(II) compounds applied to Vitis vinifera L. leaves as a pesticide was studied. Formulations were characterized by X-ray diffraction (XRD), dynamic light scattering (DLS) and electron microscopy and applied in planta to verify particle aggregation and efficiency in controlling the pathogen Plasmopara viticola. The XRD patterns showed different crystalline phases dependig on the Cu(II) compound formulated with HA particles, DLS showed that nanostructured particles are stable as aggregates out of the nanometer range and, in all formulations, transmission electron microscopy (TEM) and environmental scanning electron microscopy (ESEM) microscopy showed large aggregates which were partially nanostructured and were recognized as stable in their micrometric dimensions. Such particles did not show phytotoxic effects after their application in planta. A formulation based on HA and a soluble Cu(II) compound showed promising results in the control of the fungal pathogen, confirming the potential role of HA as an innovative delivery system of Cu(II) ions. The present work indicates the possibility of improving the biological activity of a bioactive substance by modifying its structure through an achievable formulation with a biocompatible material. © 2018 Society of Chemical Industry. © 2018 Society of Chemical Industry.

Imaging interactions of metal oxide nanoparticles with macrophage cells by ultra-high resolution scanning electron microscopy techniques†

PubMed Central

Plascencia-Villa, Germán; Starr, Clarise R.; Armstrong, Linda S.; Ponce, Arturo

2016-01-01

Use of engineered metal oxide nanoparticles in a plethora of biological applications and custom products has warned about some possible dose-dependent cytotoxic effects. Macrophages are key components of the innate immune system used to study possible toxic effects and internalization of different nanoparticulate materials. In this work, ultra-high resolution field emission scanning electron microscopy (FE-SEM) was used to offer new insights into the dynamical processes of interaction of nanomaterials with macrophage cells dosed with different concentrations of metal oxide nanoparticles (CeO2, TiO2 and ZnO). The versatility of FE-SEM has allowed obtaining a detailed characterization of processes of adsorption and endocytosis of nanoparticles, by using advanced analytical and imaging techniques on complete unstained uncoated cells, including secondary electron imaging, high-sensitive backscattered electron imaging, X-ray microanalysis and stereoimaging. Low voltage BF/DF-STEM confirmed nanoparticle adsorption and internalization into endosomes of CeO2 and TiO2, whereas ZnO develop apoptosis after 24 h of interaction caused by dissolution and invasion of cell nucleus. Ultra-high resolution scanning electron microscopy techniques provided new insights into interactions of inorganic nanoparticles with macrophage cells with high spatial resolution. PMID:23023106

Catalyst–substrate interaction and growth delay in vapor–liquid–solid nanowire growth

NASA Astrophysics Data System (ADS)

Kolíbal, Miroslav; Pejchal, Tomáš; Musálek, Tomáš; Šikola, Tomáš

2018-05-01

Understanding of the initial stage of nanowire growth on a bulk substrate is crucial for the rational design of nanowire building blocks in future electronic and optoelectronic devices. Here, we provide in situ scanning electron microscopy and Auger microscopy analysis of the initial stage of Au-catalyzed Ge nanowire growth on different substrates. Real-time microscopy imaging and elementally resolved spectroscopy clearly show that the catalyst dissolves the underlying substrate if held above a certain temperature. If the substrate dissolution is blocked (or in the case of heteroepitaxy) the catalyst needs to be filled with nanowire material from the external supply, which significantly increases the initial growth delay. The experiments presented here reveal the important role of the substrate in metal-catalyzed nanowire growth and pave the way for different growth delay mitigation strategies.

Catalyst-substrate interaction and growth delay in vapor-liquid-solid nanowire growth.

PubMed

Kolíbal, Miroslav; Pejchal, Tomáš; Musálek, Tomáš; Šikola, Tomáš

2018-05-18

Understanding of the initial stage of nanowire growth on a bulk substrate is crucial for the rational design of nanowire building blocks in future electronic and optoelectronic devices. Here, we provide in situ scanning electron microscopy and Auger microscopy analysis of the initial stage of Au-catalyzed Ge nanowire growth on different substrates. Real-time microscopy imaging and elementally resolved spectroscopy clearly show that the catalyst dissolves the underlying substrate if held above a certain temperature. If the substrate dissolution is blocked (or in the case of heteroepitaxy) the catalyst needs to be filled with nanowire material from the external supply, which significantly increases the initial growth delay. The experiments presented here reveal the important role of the substrate in metal-catalyzed nanowire growth and pave the way for different growth delay mitigation strategies.

Scanning ultrafast electron microscopy.

PubMed

Yang, Ding-Shyue; Mohammed, Omar F; Zewail, Ahmed H

2010-08-24

Progress has been made in the development of four-dimensional ultrafast electron microscopy, which enables space-time imaging of structural dynamics in the condensed phase. In ultrafast electron microscopy, the electrons are accelerated, typically to 200 keV, and the microscope operates in the transmission mode. Here, we report the development of scanning ultrafast electron microscopy using a field-emission-source configuration. Scanning of pulses is made in the single-electron mode, for which the pulse contains at most one or a few electrons, thus achieving imaging without the space-charge effect between electrons, and still in ten(s) of seconds. For imaging, the secondary electrons from surface structures are detected, as demonstrated here for material surfaces and biological specimens. By recording backscattered electrons, diffraction patterns from single crystals were also obtained. Scanning pulsed-electron microscopy with the acquired spatiotemporal resolutions, and its efficient heat-dissipation feature, is now poised to provide in situ 4D imaging and with environmental capability.

Microscopic and ultrastructural changes of Müller's muscle in patients with simple congenital ptosis.

PubMed

Alshehri, Mohammed D; Al-Fakey, Yasser H; Alkhalidi, Hisham M; Mubark, Mohamed A; Alsuhaibani, Adel H

2014-01-01

To study microscopic and ultrastructural changes of Müller's muscle in patients with isolated congenital ptosis. In this prospective, observational case-control study, Müller's muscle specimens were collected during ptosis surgical correction for 18 consecutive patients. Each specimen was divided into 2 parts. One part was embedded in formalin for light microscopy, and the other one was fixed in 3% glutaraldehyde for electron microscopy. A neuropathologist, serving as a masked evaluator, blindly reviewed all the different features for every case and counted the number of myocytes showing distinct myofilaments in the whole grid for every case. Statistical analysis using compare means and correlation tests was conducted to investigate potential associations and/or differences within and across groups. Twelve Müller's muscle specimens from patients with simple congenital ptosis of various severities and 6 specimens from patients with aponeurotic ptosis (controls) were collected and studied. Under light microscopy, congenital ptosis slides showed a small number of dispersed myocytes in a fibrotic background, whereas acquired ptosis slides showed a greater number of well-defined myocytes. Under electron microscopy, all congenital ptosis specimens had only a very small number of myocytes with clear, distinct myofilaments. Most myocytes in the aponeurotic ptosis group showed clear, distinct myofilaments, indicating a well-preserved muscle. No relationship existed between the number of clear, distinct myofilaments observed in the congenital ptosis group by transmission electron microscopy and patient age or ptosis severity. Substantial Müller's muscle atrophy was observed in patients with different severities of isolated congenital ptosis.

Simple synthesis of MoS{sub 2} inorganic fullerene-like nanomaterials from MoS{sub 2} amorphous nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang Lianxia; China Faw Group Corporation R and D Center, Changchun, 130011; Yang Haibin

The amorphous MoS{sub 2} nanoparticles have been synthesized by a simple oxidation-reduction reaction in an aqueous solution. A series of products with different morphologies, such as MoS{sub 2} nanospheres, inorganic fullerene-like nanospheres, nanorods and Mo bended rods, can be obtained by annealing the amorphous MoS{sub 2} nanoparticles under N{sub 2} atmosphere under 400-1200 deg. C. These products have been characterized by X-ray diffraction, field emission scanning electronic microscopy, transmission electron microscopy and high-resolution transmission electron microscopy in detail. The possible transformation mechanism for the structure has been discussed based on the experimental results. In addition, the optical properties of IF-MoS{submore » 2} have also been performed by UV-vis absorption spectroscopy.« less

Novel Electrochemical Process for Treatment of Perchlorate in Waste Water

DTIC Science & Technology

2011-03-06

Prepared in Different Processes: (b) in 0.1 M Pyrrole Solution with 0.1 M NaCl at 0.8 V for 20 min; (c) at 0.5 V for 400 s in 0.1 M ClO4- Solution and...polypyrrole Py pyrrole SEM scanning electron microscopy SON statement of need XPS X-ray photoelectron spectroscopy v Acknowledgments This work is...shows the scanning electron microscopy (SEM) images of carbon fiber paper and a CNT array grown on carbon fiber paper. Pyrrole (Py) deposition

Cross section TEM characterization of high-energy-Xe-irradiated U-Mo

DOE PAGES

Ye, B.; Jamison, L.; Miao, Y.; ...

2017-03-09

U-Mo alloys irradiated with 84 MeV Xe ions to various doses were characterized with transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) techniques. The TEM thin foils were prepared perpendicular to the irradiated surface to allow a direct observation of the entire region modified by ions. Furthermore, depth-selective microstructural information was revealed. Varied irradiation-induced phenomena such as gas bubble formation, phase reversal, and recrystallization were observed at different ion penetration depths in U-Mo.

Novel Crystalline SiO2 Nanoparticles via Annelids Bioprocessing of Agro-Industrial Wastes

PubMed Central

2010-01-01

The synthesis of nanoparticles silica oxide from rice husk, sugar cane bagasse and coffee husk, by employing vermicompost with annelids (Eisenia foetida) is reported. The product (humus) is calcinated and extracted to recover the crystalline nanoparticles. X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and dynamic light scattering (DLS) show that the biotransformation allows creating specific crystalline phases, since equivalent particles synthesized without biotransformation are bigger and with different crystalline structure. PMID:20802789

Short review on chemical bath deposition of thin film and characterization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mugle, Dhananjay, E-mail: dhananjayforu@gmail.com; Jadhav, Ghanshyam, E-mail: ghjadhav@rediffmail.com

2016-05-06

This reviews the theory of early growth of the thin film using chemical deposition methods. In particular, it critically reviews the chemical bath deposition (CBD) method for preparation of thin films. The different techniques used for characterizations of the chemically films such as X-ray diffractometer (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Electrical conductivity and Energy Dispersive Spectroscopy (EDS) are discussed. Survey shows the physical and chemical properties solely depend upon the time of deposition, temperature of deposition.

High-Resolution of Electron Microscopy of Montmorillonite and Montmorillonite/Epoxy Nanocomposites

DTIC Science & Technology

2005-01-01

AFRL-ML-WP-TP-2006-464 HIGH-RESOLUTION OF ELECTRON MICROSCOPY OF MONTMORILLONITE AND MONTMORILLONITE /EPOXY NANOCOMPOSITES Lawrence F...HIGH-RESOLUTION OF ELECTRON MICROSCOPY OF MONTMORILLONITE AND MONTMORILLONITE /EPOXY NANOCOMPOSITES 5c. PROGRAM ELEMENT NUMBER 62102F 5d...transmission electron microscopy the structure and morphology of montmorillonite (MMT), a material of current interest for use in polymer nanocomposites, was

Theory and applications of free-electron vortex states

NASA Astrophysics Data System (ADS)

Bliokh, K. Y.; Ivanov, I. P.; Guzzinati, G.; Clark, L.; Van Boxem, R.; Béché, A.; Juchtmans, R.; Alonso, M. A.; Schattschneider, P.; Nori, F.; Verbeeck, J.

2017-05-01

Both classical and quantum waves can form vortices : entities with helical phase fronts and circulating current densities. These features determine the intrinsic orbital angular momentum carried by localized vortex states. In the past 25 years, optical vortex beams have become an inherent part of modern optics, with many remarkable achievements and applications. In the past decade, it has been realized and demonstrated that such vortex beams or wavepackets can also appear in free electron waves, in particular, in electron microscopy. Interest in free-electron vortex states quickly spread over different areas of physics: from basic aspects of quantum mechanics, via applications for fine probing of matter (including individual atoms), to high-energy particle collision and radiation processes. Here we provide a comprehensive review of theoretical and experimental studies in this emerging field of research. We describe the main properties of electron vortex states, experimental achievements and possible applications within transmission electron microscopy, as well as the possible role of vortex electrons in relativistic and high-energy processes. We aim to provide a balanced description including a pedagogical introduction, solid theoretical basis, and a wide range of practical details. Special attention is paid to translating theoretical insights into suggestions for future experiments, in electron microscopy and beyond, in any situation where free electrons occur.

Correlative two-photon and serial block face scanning electron microscopy in neuronal tissue using 3D near-infrared branding maps.

PubMed

Lees, Robert M; Peddie, Christopher J; Collinson, Lucy M; Ashby, Michael C; Verkade, Paul

2017-01-01

Linking cellular structure and function has always been a key goal of microscopy, but obtaining high resolution spatial and temporal information from the same specimen is a fundamental challenge. Two-photon (2P) microscopy allows imaging deep inside intact tissue, bringing great insight into the structural and functional dynamics of cells in their physiological environment. At the nanoscale, the complex ultrastructure of a cell's environment in tissue can be reconstructed in three dimensions (3D) using serial block face scanning electron microscopy (SBF-SEM). This provides a snapshot of high resolution structural information pertaining to the shape, organization, and localization of multiple subcellular structures at the same time. The pairing of these two imaging modalities in the same specimen provides key information to relate cellular dynamics to the ultrastructural environment. Until recently, approaches to relocate a region of interest (ROI) in tissue from 2P microscopy for SBF-SEM have been inefficient or unreliable. However, near-infrared branding (NIRB) overcomes this by using the laser from a multiphoton microscope to create fiducial markers for accurate correlation of 2P and electron microscopy (EM) imaging volumes. The process is quick and can be user defined for each sample. Here, to increase the efficiency of ROI relocation, multiple NIRB marks are used in 3D to target ultramicrotomy. A workflow is described and discussed to obtain a data set for 3D correlated light and electron microscopy, using three different preparations of brain tissue as examples. Copyright © 2017 Elsevier Inc. All rights reserved.

Optimization study of direct morphology observation by cold field emission SEM without gold coating.

PubMed

He, Dan; Fu, Cheng; Xue, Zhigang

2018-06-01

Gold coating is a general operation that is generally applied on non-conductive or low conductive materials, during which the morphology of the materials can be examined by scanning electron microscopy (SEM). However, fatal deficiencies in the materials can result in irreversible distortion and damage. The present study directly characterized different low conductive materials such as hydroxyapatite, modified poly(vinylidene fluoride) (PVDF) fiber, and zinc oxide nanopillar by cold field emission scanning electron microscopy (FE-SEM) without a gold coating. According to the characteristics of the low conductive materials, various test conditions, such as different working signal modes, accelerating voltages, electron beam spots, and working distances, were characterized to determine the best morphological observations of each sample. Copyright © 2018 Elsevier Ltd. All rights reserved.

Correlative fluorescence microscopy and scanning transmission electron microscopy of quantum-dot-labeled proteins in whole cells in liquid.

PubMed

Dukes, Madeline J; Peckys, Diana B; de Jonge, Niels

2010-07-27

Correlative fluorescence microscopy and transmission electron microscopy (TEM) is a state-of-the-art microscopy methodology to study cellular function, combining the functionality of light microscopy with the high resolution of electron microscopy. However, this technique involves complex sample preparation procedures due to its need for either thin sections or frozen samples for TEM imaging. Here, we introduce a novel correlative approach capable of imaging whole eukaryotic cells in liquid with fluorescence microscopy and with scanning transmission electron microscopy (STEM); there is no additional sample preparation necessary for the electron microscopy. Quantum dots (QDs) were bound to epidermal growth factor (EGF) receptors of COS7 fibroblast cells. Fixed whole cells in saline water were imaged with fluorescence microscopy and subsequently with STEM. The STEM images were correlated with fluorescence images of the same cellular regions. QDs of dimensions 7x12 nm were visible in a 5 microm thick layer of saline water, consistent with calculations. A spatial resolution of 3 nm was achieved on the QDs.

Correlative Fluorescence Microscopy and Scanning Transmission Electron Microscopy of Quantum Dot Labeled Proteins in Whole Cells in Liquid

PubMed Central

Dukes, Madeline J.; Peckys, Diana B.; de Jonge, Niels

2010-01-01

Correlative fluorescence microscopy and transmission electron microscopy (TEM) is a state-of-the-art microscopy methodology to study cellular function, combining the functionality of light microscopy with the high resolution of electron microscopy. However, this technique involves complex sample preparation procedures due to its need for either thin sections or frozen samples for TEM imaging. Here, we introduce a novel correlative approach capable of imaging whole eukaryotic cells in liquid with fluorescence microscopy and with scanning transmission electron microscopy (STEM); there is no additional sample preparation necessary for the electron microscopy. Quantum dots (QDs) were bound to epidermal growth factor (EGF) receptors of COS7 fibroblast cells. Fixed whole cells in saline water were imaged with fluorescence microscopy and subsequently with STEM. The STEM images were correlated with fluorescence images of the same cellular regions. QDs of dimensions 7 × 12 nm were visible in a 5 μm thick layer of saline water, consistent with calculations. A spatial resolution of 3 nm was achieved on the QDs. PMID:20550177

Conformational Switching in PolyGln Amyloid Fibrils Resulting from a Single Amino Acid Insertion

PubMed Central

Huang, Rick K.; Baxa, Ulrich; Aldrian, Gudrun; Ahmed, Abdullah B.; Wall, Joseph S.; Mizuno, Naoko; Antzutkin, Oleg; Steven, Alasdair C.; Kajava, Andrey V.

2014-01-01

The established correlation between neurodegenerative disorders and intracerebral deposition of polyglutamine aggregates motivates attempts to better understand their fibrillar structure. We designed polyglutamines with a few lysines inserted to overcome the hindrance of extreme insolubility and two D-lysines to limit the lengths of β-strands. One is 33 amino acids long (PolyQKd-33) and the other has one fewer glutamine (PolyQKd-32). Both form well-dispersed fibrils suitable for analysis by electron microscopy. Electron diffraction confirmed cross-β structures in both fibrils. Remarkably, the deletion of just one glutamine residue from the middle of the peptide leads to substantially different amyloid structures. PolyQKd-32 fibrils are consistently 10–20% wider than PolyQKd-33, as measured by negative staining, cryo-electron microscopy, and scanning transmission electron microscopy. Scanning transmission electron microscopy analysis revealed that the PolyQKd-32 fibrils have 50% higher mass-per-length than PolyQKd-33. This distinction can be explained by a superpleated β-structure model for PolyQKd-33 and a model with two β-solenoid protofibrils for PolyQKd-32. These data provide evidence for β-arch-containing structures in polyglutamine fibrils and open future possibilities for structure-based drug design. PMID:24853742

Detection of local chemical states of lithium and their spatial mapping by scanning transmission electron microscopy, electron energy-loss spectroscopy and hyperspectral image analysis.

PubMed

Muto, Shunsuke; Tatsumi, Kazuyoshi

2017-02-08

Advancements in the field of renewable energy resources have led to a growing demand for the analysis of light elements at the nanometer scale. Detection of lithium is one of the key issues to be resolved for providing guiding principles for the synthesis of cathode active materials, and degradation analysis after repeated use of those materials. We have reviewed the different techniques currently used for the characterization of light elements such as high-resolution transmission electron microscopy, scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS). In the present study, we have introduced a methodology to detect lithium in solid materials, particularly for cathode active materials used in lithium-ion battery. The chemical states of lithium were isolated and analyzed from the overlapping multiple spectral profiles, using a suite of STEM, EELS and hyperspectral image analysis. The method was successfully applied in the chemical state analyses of hetero-phases near the surface and grain boundary regions of the active material particles formed by chemical reactions between the electrolyte and the active materials. © The Author 2016. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Preparation, characterization, physical properties, and photoconducting behaviour of anthracene derivative nanowires

NASA Astrophysics Data System (ADS)

Xiao, Jinchong; Yin, Zongyou; Yang, Bo; Liu, Yi; Ji, Li; Guo, Jun; Huang, Ling; Liu, Xuewei; Yan, Qingyu; Zhang, Hua; Zhang, Qichun

2011-11-01

Organic nanowires of 9,10-dibromoanthracene (DBA) and 9,10-dicyanoanthracene (DCNA) were obtained by adding the THF solution of DBA/DCNA into water containing P123 surfactants. The as-prepared nanowires were characterized by UV-vis, fluorescence spectra, Field Emission Scanning Electron Microscopy (FESEM), and Transmission Electron Microscopy (TEM). We found that DBA and DCNA nanowires emitted green light rather than blue light for molecules in THF solution. The red-shift UV and fluorescent spectra of DBA and DCNA nanowires implied that these nanowires were formed through J-aggregation. The photoconducting study of DBA/DCNA nanowire-based network on rGO/SiO2/Si shows different photocurrent behaviors upon irradiation, which displayed that electron transfer from DCNA nanowire to rGO was stronger than that of DBA nanowires to rGO.Organic nanowires of 9,10-dibromoanthracene (DBA) and 9,10-dicyanoanthracene (DCNA) were obtained by adding the THF solution of DBA/DCNA into water containing P123 surfactants. The as-prepared nanowires were characterized by UV-vis, fluorescence spectra, Field Emission Scanning Electron Microscopy (FESEM), and Transmission Electron Microscopy (TEM). We found that DBA and DCNA nanowires emitted green light rather than blue light for molecules in THF solution. The red-shift UV and fluorescent spectra of DBA and DCNA nanowires implied that these nanowires were formed through J-aggregation. The photoconducting study of DBA/DCNA nanowire-based network on rGO/SiO2/Si shows different photocurrent behaviors upon irradiation, which displayed that electron transfer from DCNA nanowire to rGO was stronger than that of DBA nanowires to rGO. Electronic supplementary information (ESI) available: XRD patterns and simulations, and FT-IR spectra. CCDC reference numbers 840471. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c1nr10655d

Effects of lead pollution on Ammonia parkinsoniana (foraminifera): ultrastructural and microanalytical approaches.

PubMed

Frontalini, F; Curzi, D; Giordano, F M; Bernhard, J M; Falcieri, E; Coccioni, R

2015-01-30

The responses of Ammonia parkinsoniana (Foraminifera) exposed to different concentrations of lead (Pb) were evaluated at the cytological level. Foraminifera-bearing sediments were placed in mesocosms that were housed in aquaria each with seawater of a different lead concentration. On the basis of transmission electron microscopy and environmental scanning electron microscopy coupled with energy dispersive spectrometer analyses, it was possible to recognize numerous morphological differences between untreated (i.e., control) and treated (i.e., lead enrichment) specimens. In particular, higher concentrations of this pollutant led to numerical increase of lipid droplets characterized by a more electron-dense core, proliferation of residual bodies, a thickening of the organic lining, mitochondrial degeneration, autophagosome proliferation and the development of inorganic aggregates.  All these cytological modifications might be related to the pollutant-induced stress and some of them such as the thickening of organic lining might suggest a potential mechanism of protection adopted by foraminifera.

Advanced electron microscopy methods for the analysis of MgB2 superconductor

NASA Astrophysics Data System (ADS)

Birajdar, B.; Peranio, N.; Eibl, O.

2008-02-01

Advanced electron microscopy methods used for the analysis of superconducting MgB2 wires and tapes are described. The wires and tapes were prepared by the powder in tube method using different processing technologies and thoroughly characterised for their superconducting properties within the HIPERMAG project. Microstructure analysis on μm to nm length scales is necessary to understand the superconducting properties of MgB2. For the MgB2 phase analysis on μm scale an analytical SEM, and for the analysis on nm scale a energy-filtered STEM is used. Both the microscopes were equipped with EDX detector and field emission gun. Electron microscopy and spectroscopy of MgB2 is challenging because of the boron analysis, carbon and oxygen contamination, and the presence of large number of secondary phases. Advanced electron microscopy involves, combined SEM, EPMA and TEM analysis with artefact free sample preparation, elemental mapping and chemical quantification of point spectra. Details of the acquisition conditions and achieved accuracy are presented. Ex-situ wires show oxygen-free MgB2 colonies (a colony is a dense arrangement of several MgB2 grains) embedded in a porous and oxygen-rich matrix, introducing structural granularity. In comparison, in-situ wires are generally more dense, but show inhibited MgB2 phase formation with significantly higher fraction of B-rich secondary phases. SiC additives in the in-situ wires forms Mg2Si secondary phases. The advanced electron microscopy has been used to extract the microstructure parameters like colony size, B-rich secondary phase fraction, O mole fraction and MgB2 grain size, and establish a microstructure-critical current density model [1]. In summary, conventional secondary electron imaging in SEM and diffraction contrast imaging in the TEM are by far not sufficient and advanced electron microscopy methods are essential for the analysis of superconducting MgB2 wires and tapes.

Helium ion microscopy and ultra-high-resolution scanning electron microscopy analysis of membrane-extracted cells reveals novel characteristics of the cytoskeleton of Giardia intestinalis.

PubMed

Gadelha, Ana Paula Rocha; Benchimol, Marlene; de Souza, Wanderley

2015-06-01

Giardia intestinalis presents a complex microtubular cytoskeleton formed by specialized structures, such as the adhesive disk, four pairs of flagella, the funis and the median body. The ultrastructural organization of the Giardia cytoskeleton has been analyzed using different microscopic techniques, including high-resolution scanning electron microscopy. Recent advances in scanning microscopy technology have opened a new venue for the characterization of cellular structures and include scanning probe microscopy techniques such as ultra-high-resolution scanning electron microscopy (UHRSEM) and helium ion microscopy (HIM). Here, we studied the organization of the cytoskeleton of G. intestinalis trophozoites using UHRSEM and HIM in membrane-extracted cells. The results revealed a number of new cytoskeletal elements associated with the lateral crest and the dorsal surface of the parasite. The fine structure of the banded collar was also observed. The marginal plates were seen linked to a network of filaments, which were continuous with filaments parallel to the main cell axis. Cytoplasmic filaments that supported the internal structures were seen by the first time. Using anti-actin antibody, we observed a labeling in these filamentous structures. Taken together, these data revealed new surface characteristics of the cytoskeleton of G. intestinalis and may contribute to an improved understanding of the structural organization of trophozoites. Copyright © 2015 Elsevier Inc. All rights reserved.

Differently ordered TiO2 nanoarrays regulated by solvent polarity, and their photocatalytic performances

NASA Astrophysics Data System (ADS)

Hu, Wenyuan; Dong, Faqin; Zhang, Jing; Liu, Mingxue; He, Huichao; Wu, Yadong; Yang, Dingming; Deng, Hongquan

2018-06-01

Special TiO2 arrays with exposed facets were prepared in different solvents by low- temperature solvothermal synthesis. The morphology, phase and photocatalytic performance influenced by the various solvent polarities were characterized using field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectra and electrochemical testing. The results show that differences of solvent polarity are the main force driving differences in array growth; therefore, anatase TiO2 arrays with different crystal facets can be synthesized by tuning solvent polarity. TiO2 arrays prepared in cyclohexane are the best at oxidizing methyl orange through photocatalysis, followed by arrays prepared in toluene and ethanol. Arrays prepared in toluene are the best at reducing Cr(VI) photocatalytically, followed by those prepared in cyclohexane and ethanol. These differences in photocatalytic power are due to the ratio among the different crystal facets that are exposed, which affects the migration behavior of the photogenerated electrons and holes. In addition, the probable growth mechanisms of self-assembled ordered TiO2 arrays in different solvents are described.

New and unconventional approaches for advancing resolution in biological transmission electron microscopy by improving macromolecular specimen preparation and preservation.

PubMed

Massover, William H

2011-02-01

Resolution in transmission electron microscopy (TEM) now is limited by the properties of specimens, rather than by those of instrumentation. The long-standing difficulties in obtaining truly high-resolution structure from biological macromolecules with TEM demand the development, testing, and application of new ideas and unconventional approaches. This review concisely describes some new concepts and innovative methodologies for TEM that deal with unsolved problems in the preparation and preservation of macromolecular specimens. The selected topics include use of better support films, a more protective multi-component matrix surrounding specimens for cryo-TEM and negative staining, and, several quite different changes in microscopy and micrography that should decrease the effects of electron radiation damage; all these practical approaches are non-traditional, but have promise to advance resolution for specimens of biological macromolecules beyond its present level of 3-10 Å (0.3-1.0 nm). The result of achieving truly high resolution will be a fulfillment of the still unrealized potential of transmission electron microscopy for directly revealing the structure of biological macromolecules down to the atomic level. Published by Elsevier Ltd.

Coupled study by TEM/EELS and STM/STS of electronic properties of C- and CN-nanotubes

NASA Astrophysics Data System (ADS)

Lin, Hong; Lagoute, Jérôme; Repain, Vincent; Chacon, Cyril; Girard, Yann; Lauret, Jean-Sébastien; Arenal, Raul; Ducastelle, François; Rousset, Sylvie; Loiseau, Annick

2011-12-01

Carbon nanotubes are the focus of considerable research efforts due to their fascinating physical properties. They provide an excellent model system for the study of one-dimensional materials and molecular electronics. The chirality of nanotubes can lead to very different electronic behaviour, either metallic or semiconducting. Their electronic spectrum consists of a series of Van Hove singularities defining a bandgap for semiconducting tubes and molecular orbitals at the corresponding energies. A promising way to tune the nanotubes electronic properties for future applications is to use doping by heteroatoms. Here we report on the experimental investigation of the role of many-body interactions in nanotube bandgaps, the visualization in direct space of the molecular orbitals of nanotubes and the properties of nitrogen doped nanotubes using scanning tunneling microscopy and transmission electron microscopy as well as electron energy loss spectroscopy.

Nano-sized graphene flakes: insights from experimental synthesis and first principles calculations.

PubMed

Lin, Pin-Chun; Chen, Yi-Rui; Hsu, Kuei-Ting; Lin, Tzu-Neng; Tung, Kuo-Lun; Shen, Ji-Lin; Liu, Wei-Ren

2017-03-01

In this study, we proposed a cost-effective method for preparing graphene nano-flakes (GNFs) derived from carbon nanotubes (CNTs) via three steps (pressing, homogenization and sonication exfoliation processes). Scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), laser scattering, as well as ultraviolet-visible and photoluminescence (PL) measurements were carried out. The results indicated that the size of as-synthesized GNFs was approximately 40-50 nm. Furthermore, we also used first principles calculations to understand the transformation from CNTs to GNFs from the viewpoints of the edge formation energies of GNFs in different shapes and sizes. The corresponding photoluminescence measurements of GNFs were carried out in this work.

Improving the oxidation resistance and stability of Ag nanoparticles by coating with multilayered reduced graphene oxide

NASA Astrophysics Data System (ADS)

Li, Yahui; Zhang, Huayu; Wu, Bowen; Guo, Zhuo

2017-12-01

A kind of coating nanostructure, Ag nanoparticles coated with multilayered reduced graphene oxide (RGO), is fabricated by employing a three-step reduction method in an orderly manner, which is significantly different from the conventional structures that are simply depositing or doping with Ag nanoparticles on RGO via chemical reduction. The as-prepared nanostructure is investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected-area electronic diffraction (SEAD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The results show that the obtained Ag/RGO nanostructure is observed to be a perfect coating structure with well dispersed Ag particles, which is responsible for the remarkable oxidation resistance. The results of XPS spectra indicate the content of metallic Ag is far greater than that of Ag oxides despite of prolonged exposure to the air, which fully demonstrate the excellent stability of thus coating nanostructure.

Electron Microscopy.

ERIC Educational Resources Information Center

Beer, Michael

1980-01-01

Reviews technical aspects of structure determination in biological electron microscopy (EM). Discusses low dose EM, low temperature microscopy, electron energy loss spectra, determination of mass or molecular weight, and EM of labeled systems. Cites 34 references. (CS)

Fixation methods for electron microscopy of human and other liver

PubMed Central

Wisse, Eddie; Braet, Filip; Duimel, Hans; Vreuls, Celien; Koek, Ger; Olde Damink, Steven WM; van den Broek, Maartje AJ; De Geest, Bart; Dejong, Cees HC; Tateno, Chise; Frederik, Peter

2010-01-01

For an electron microscopic study of the liver, expertise and complicated, time-consuming processing of hepatic tissues and cells is needed. The interpretation of electron microscopy (EM) images requires knowledge of the liver fine structure and experience with the numerous artifacts in fixation, embedding, sectioning, contrast staining and microscopic imaging. Hence, the aim of this paper is to present a detailed summary of different methods for the preparation of hepatic cells and tissue, for the purpose of preserving long-standing expertise and to encourage new investigators and clinicians to include EM studies of liver cells and tissue in their projects. PMID:20556830

Characterization of new DOPC/DHPC platform for dermal applications.

PubMed

Rodríguez, Gelen; Rubio, Laia; Barba, Clara; López-Iglesias, Carmen; de la Maza, Alfons; López, Olga; Cócera, Mercedes

2013-05-01

Systems formed by mixtures of the phospholipids dioleoylphosphatidylcholine (DOPC) and dihexanoylphosphatidylcholine (DHPC) were characterized by use of differential scanning calorimetry, small angle X-ray scattering and two electron-microscopy techniques, freeze fracture electron microscopy and cryogenic transmission electron microscopy. These techniques allowed for the determination of the size, morphology, structural topology, self-assembly and thermotropic behavior of the nanostructures present in the mixtures. The interaction between the two phospholipids provides curvatures, irregularities and the increase of thickness and flexibility in the membrane. These effects led to the formation of different aggregates with a differential distribution of both phospholipids. The effect of these systems on the skin in vivo was evaluated by measurement of the biophysical skin parameters. Our results show that the DOPC/DHPC application induces a decrease in the permeability and in the hydration of the tissue. These effects in vivo are related to different microstructural changes promoted by these systems in the skin in vitro, published in a recent work. The fundamental biophysical analyses of DOPC/DHPC systems contribute to our understanding of the mechanisms that govern their interaction with the skin.

Imaging of endodontic biofilms by combined microscopy (FISH/cLSM - SEM).

PubMed

Schaudinn, C; Carr, G; Gorur, A; Jaramillo, D; Costerton, J W; Webster, P

2009-08-01

Scanning electron microscopy is a useful imaging approach for the visualization of bacterial biofilms in their natural environments including their medical and dental habitats, because it allows for the exploration of large surfaces with excellent resolution of topographic features. Most biofilms in nature, however, are embedded in a thick layer of extracellular matrix that prevents a clear identification of individual bacteria by scanning electron microscopy. The use of confocal laser scanning microscopy on the other hand in combination with fluorescence in situ hybridization enables the visualization of matrix embedded bacteria in multi-layered biofilms. In our study, fluorescence in situ hybridization/confocal laser scanning microscopy and scanning electron microscopy were applied to visualize bacterial biofilm in endodontic root canals. The resulting fluorescence in situ hybridization /confocal laser scanning microscopy and scanning electron microscopy and pictures were subsequently combined into one single image to provide high-resolution information on the location of hidden bacteria. The combined use of scanning electron microscopy and fluorescence in situ hybridization / confocal laser scanning microscopy has the potential to overcome the limits of each single technique.

Correlative Microscopy Combining Secondary Ion Mass Spectrometry and Electron Microscopy: Comparison of Intensity-Hue-Saturation and Laplacian Pyramid Methods for Image Fusion.

PubMed

Vollnhals, Florian; Audinot, Jean-Nicolas; Wirtz, Tom; Mercier-Bonin, Muriel; Fourquaux, Isabelle; Schroeppel, Birgit; Kraushaar, Udo; Lev-Ram, Varda; Ellisman, Mark H; Eswara, Santhana

2017-10-17

Correlative microscopy combining various imaging modalities offers powerful insights into obtaining a comprehensive understanding of physical, chemical, and biological phenomena. In this article, we investigate two approaches for image fusion in the context of combining the inherently lower-resolution chemical images obtained using secondary ion mass spectrometry (SIMS) with the high-resolution ultrastructural images obtained using electron microscopy (EM). We evaluate the image fusion methods with three different case studies selected to broadly represent the typical samples in life science research: (i) histology (unlabeled tissue), (ii) nanotoxicology, and (iii) metabolism (isotopically labeled tissue). We show that the intensity-hue-saturation fusion method often applied for EM-sharpening can result in serious image artifacts, especially in cases where different contrast mechanisms interplay. Here, we introduce and demonstrate Laplacian pyramid fusion as a powerful and more robust alternative method for image fusion. Both physical and technical aspects of correlative image overlay and image fusion specific to SIMS-based correlative microscopy are discussed in detail alongside the advantages, limitations, and the potential artifacts. Quantitative metrics to evaluate the results of image fusion are also discussed.

TEM studies of plasma nitrided austenitic stainless steel.

PubMed

Stróz, D; Psoda, M

2010-03-01

Cross-sectional transmission electron microscopy and X-ray phase analysis were used to study the structure of a layer formed during nitriding the AISI 316L stainless steel at temperature 440 degrees C. It was found that the applied treatment led to the formation of 6-microm-thick layer of the S-phase. There is no evidence of CrN precipitation. The X-ray diffraction experiments proved that the occurred austenite lattice expansion - due to nitrogen atoms - depended on the crystallographic direction. The cross-sectional transmission electron microscopy studies showed that the layer consisted of a single cubic phase that contained a lot of defects such as dislocations, stacking faults, slip bands and twins. The high-resolution electron microscopy observations were applied to study the defect formation due to the nitriding process. It was shown that the presence of great number of stacking faults leads to formation of nanotwins. Weak, forbidden {100} reflections were still another characteristic feature of the S-phase. These were not detected in the X-ray spectra of the phase. Basing on the high-resolution electron microscopy studies it can be suggested that the short-range ordering of the nitrogen atoms in the octahedral sites inside the f.c.c. matrix lattice takes place and gives rise to appearance of these spots. It is suggested that the cubic lattice undergoes not only expansion but also slight rombohedral distortion that explains differences in the lattice expansion for different crystallographic directions.

New hardware and workflows for semi-automated correlative cryo-fluorescence and cryo-electron microscopy/tomography.

PubMed

Schorb, Martin; Gaechter, Leander; Avinoam, Ori; Sieckmann, Frank; Clarke, Mairi; Bebeacua, Cecilia; Bykov, Yury S; Sonnen, Andreas F-P; Lihl, Reinhard; Briggs, John A G

2017-02-01

Correlative light and electron microscopy allows features of interest defined by fluorescence signals to be located in an electron micrograph of the same sample. Rare dynamic events or specific objects can be identified, targeted and imaged by electron microscopy or tomography. To combine it with structural studies using cryo-electron microscopy or tomography, fluorescence microscopy must be performed while maintaining the specimen vitrified at liquid-nitrogen temperatures and in a dry environment during imaging and transfer. Here we present instrumentation, software and an experimental workflow that improves the ease of use, throughput and performance of correlated cryo-fluorescence and cryo-electron microscopy. The new cryo-stage incorporates a specially modified high-numerical aperture objective lens and provides a stable and clean imaging environment. It is combined with a transfer shuttle for contamination-free loading of the specimen. Optimized microscope control software allows automated acquisition of the entire specimen area by cryo-fluorescence microscopy. The software also facilitates direct transfer of the fluorescence image and associated coordinates to the cryo-electron microscope for subsequent fluorescence-guided automated imaging. Here we describe these technological developments and present a detailed workflow, which we applied for automated cryo-electron microscopy and tomography of various specimens. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

Scanning ultrafast electron microscopy

PubMed Central

Yang, Ding-Shyue; Mohammed, Omar F.; Zewail, Ahmed H.

2010-01-01

Progress has been made in the development of four-dimensional ultrafast electron microscopy, which enables space-time imaging of structural dynamics in the condensed phase. In ultrafast electron microscopy, the electrons are accelerated, typically to 200 keV, and the microscope operates in the transmission mode. Here, we report the development of scanning ultrafast electron microscopy using a field-emission-source configuration. Scanning of pulses is made in the single-electron mode, for which the pulse contains at most one or a few electrons, thus achieving imaging without the space-charge effect between electrons, and still in ten(s) of seconds. For imaging, the secondary electrons from surface structures are detected, as demonstrated here for material surfaces and biological specimens. By recording backscattered electrons, diffraction patterns from single crystals were also obtained. Scanning pulsed-electron microscopy with the acquired spatiotemporal resolutions, and its efficient heat-dissipation feature, is now poised to provide in situ 4D imaging and with environmental capability. PMID:20696933

Breaking resolution limits in ultrafast electron diffraction and microscopy

PubMed Central

Baum, Peter; Zewail, Ahmed H.

2006-01-01

Ultrafast electron microscopy and diffraction are powerful techniques for the study of the time-resolved structures of molecules, materials, and biological systems. Central to these approaches is the use of ultrafast coherent electron packets. The electron pulses typically have an energy of 30 keV for diffraction and 100–200 keV for microscopy, corresponding to speeds of 33–70% of the speed of light. Although the spatial resolution can reach the atomic scale, the temporal resolution is limited by the pulse width and by the difference in group velocities of electrons and the light used to initiate the dynamical change. In this contribution, we introduce the concept of tilted optical pulses into diffraction and imaging techniques and demonstrate the methodology experimentally. These advances allow us to reach limits of time resolution down to regimes of a few femtoseconds and, possibly, attoseconds. With tilted pulses, every part of the sample is excited at precisely the same time as when the electrons arrive at the specimen. Here, this approach is demonstrated for the most unfavorable case of ultrafast crystallography. We also present a method for measuring the duration of electron packets by autocorrelating electron pulses in free space and without streaking, and we discuss the potential of tilting the electron pulses themselves for applications in domains involving nuclear and electron motions. PMID:17056711

Form follows function: ultrastructure of different morphotypes of Physarum polycephalum

NASA Astrophysics Data System (ADS)

Oettmeier, Christina; Lee, Jonghyun; Döbereiner, Hans-Günther

2018-04-01

The multinucleate, unicellular slime mold Physarum polycephalum is a highly motile and morphologically diverse giant amoeba. Despite being brainless and lacking neurons, it exhibits ‘smart’ behavior. There is considerable interest in describing such traits and to investigate the underlying mechanochemical patterns which may hint at universal principles of behavior and decision-making. Furthermore, the slime mold’s mechanism of locomotion is unique. It resembles amoeboid movement, but differs from the locomotion of other amoebae in many ways, e.g. in their much larger size and lack of lobopodia. These two aspects, behavior and locomotion, are linked by the cytoskeleton and the overall morphology of P. polycephalum. In this paper, we present a structural analysis of different growth forms (micro-, meso- and macroplasmodia) by transmission electron microscopy (TEM), scanning electron microscopy (SEM), light microscopy, and fluorescence microscopy of F-actin. With these detailed investigations of cellular ultrastructure and morphology, we provide the basis for the analysis of, e.g. viscoelastic and rheological measurements. Our data also provide structural details for the many models that have been constructed for the understanding of locomotion. We conclude that morphological information is vital for the assessment and measurement of material properties.

Serial block face scanning electron microscopy--the future of cell ultrastructure imaging.

PubMed

Hughes, Louise; Hawes, Chris; Monteith, Sandy; Vaughan, Sue

2014-03-01

One of the major drawbacks in transmission electron microscopy has been the production of three-dimensional views of cells and tissues. Currently, there is no one suitable 3D microscopy technique that answers all questions and serial block face scanning electron microscopy (SEM) fills the gap between 3D imaging using high-end fluorescence microscopy and the high resolution offered by electron tomography. In this review, we discuss the potential of the serial block face SEM technique for studying the three-dimensional organisation of animal, plant and microbial cells.

HAADF-STEM atom counting in atom probe tomography specimens: Towards quantitative correlative microscopy.

PubMed

Lefebvre, W; Hernandez-Maldonado, D; Moyon, F; Cuvilly, F; Vaudolon, C; Shinde, D; Vurpillot, F

2015-12-01

The geometry of atom probe tomography tips strongly differs from standard scanning transmission electron microscopy foils. Whereas the later are rather flat and thin (<20 nm), tips display a curved surface and a significantly larger thickness. As far as a correlative approach aims at analysing the same specimen by both techniques, it is mandatory to explore the limits and advantages imposed by the particular geometry of atom probe tomography specimens. Based on simulations (electron probe propagation and image simulations), the possibility to apply quantitative high angle annular dark field scanning transmission electron microscopy to of atom probe tomography specimens has been tested. The influence of electron probe convergence and the benefice of deconvolution of electron probe point spread function electron have been established. Atom counting in atom probe tomography specimens is for the first time reported in this present work. It is demonstrated that, based on single projections of high angle annular dark field imaging, significant quantitative information can be used as additional input for refining the data obtained by correlative analysis of the specimen in APT, therefore opening new perspectives in the field of atomic scale tomography. Copyright © 2015 Elsevier B.V. All rights reserved.

Applications of microscopy to genetic therapy of cystic fibrosis and other human diseases.

PubMed

Moninger, Thomas O; Nessler, Randy A; Moore, Kenneth C

2006-01-01

Gene therapy has become an extremely important and active field of biomedical research. Microscopy is an integral component of this effort. This chapter presents an overview of imaging techniques used in our facility in support of cystic fibrosis gene therapy research. Instrumentation used in these studies includes light and confocal microscopy, transmission electron microscopy, and scanning electron microscopy. Techniques outlined include negative staining, cryo-electron microscopy, three-dimentional reconstruction, enzyme cytochemistry, immunocytochemistry, and fluorescence imaging.

Application of environmental scanning electron microscopy to determine biological surface structure.

PubMed

Kirk, S E; Skepper, J N; Donald, A M

2009-02-01

The use of environmental scanning electron microscopy in biology is growing as more becomes understood about the advantages and limitations of the technique. These are discussed and we include new evidence about the effect of environmental scanning electron microscopy imaging on the viability of mammalian cells. We show that although specimen preparation for high-vacuum scanning electron microscopy introduces some artefacts, there are also challenges in the use of environmental scanning electron microscopy, particularly at higher resolutions. This suggests the two technologies are best used in combination. We have used human monocyte-derived macrophages as a test sample, imaging their complicated and delicate membrane ruffles and protrusions. We have also explored the possibility of using environmental scanning electron microscopy for dynamic experiments, finding that mammalian cells cannot be imaged and kept alive in the environmental scanning electron microscopy. The dehydration step in which the cell surface is exposed causes irreversible damage, probably via loss of membrane integrity during liquid removal in the specimen chamber. Therefore, mammalian cells should be imaged after fixation where possible to protect against damage as a result of chamber conditions.

Synthesis, structural and optical properties of nanocrystalline vanadium doped zinc oxide aerogel

NASA Astrophysics Data System (ADS)

El Ghoul, J.; Barthou, C.; El Mir, L.

2012-06-01

We report the synthesis of vanadium-doped ZnO nanoparticles prepared by a sol-gel processing technique. In our approach, the water for hydrolysis was slowly released by esterification reaction followed by a supercritical drying in ethyl alcohol. Vanadium doping concentration of 10 at% has been investigated. After treatment in air at different temperatures, the obtained nanopowder was characterized by various techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and photoluminescence (PL). Analysis by scanning electron microscopy at high resolution shows that the grain size increases with increasing temperature. Thus, in the case of thermal treatment at 500 °C in air, the powder with an average particle size of 25 nm shows a strong luminescence band in the visible range. The intensity and energy position of the obtained PL band depends on the temperature measurement increase. The mechanism of this emission band is discussed.

Corrosion Behavior of Metal Active Gas Welded Joints of a High-Strength Steel for Automotive Application

NASA Astrophysics Data System (ADS)

Garcia, Mainã Portella; Mantovani, Gerson Luiz; Vasant Kumar, R.; Antunes, Renato Altobelli

2017-10-01

In this work, the corrosion behavior of metal active gas-welded joints of a high-strength steel with tensile yield strength of 900 MPa was investigated. The welded joints were obtained using two different heat inputs. The corrosion behavior has been studied in a 3.5 wt.% NaCl aqueous solution using electrochemical impedance spectroscopy and potentiodynamic polarization tests. Optical microscopy images, scanning electron microscopy and transmission electron microscopy with energy-dispersive x-ray revealed different microstructural features in the heat-affected zone (HAZ) and the weld metal (WM). Before and after the corrosion process, the sample was evaluated by confocal laser scanning microscopy to measure the depth difference between HAZ and WM. The results showed that the heat input did not play an important role on corrosion behavior of HSLA steel. The anodic and cathodic areas of the welded joints could be associated with depth differences. The HAZ was found to be the anodic area, while the WM was cathodic with respect to the HAZ. The corrosion behavior was related to the amount and orientation nature of carbides in the HAZ. The microstructure of the HAZ consisted of martensite and bainite, whereas acicular ferrite was observed in the weld metal.

Mechanisms of fine extinction band development in vein quartz: new insights from correlative light and electron microscopy

NASA Astrophysics Data System (ADS)

Derez, Tine; Van Der Donck, Tom; Plümper, Oliver; Muchez, Philippe; Pennock, Gill; Drury, Martyn R.; Sintubin, Manuel

2017-07-01

Fine extinction bands (FEBs) (also known as deformation lamellae) visible with polarized light microscopy in quartz consist of a range of nanostructures, inferring different formation processes. Previous transmission electron microscopy studies have shown that most FEB nanostructures in naturally deformed quartz are elongated subgrains formed by recovery of dislocation slip bands. Here we show that three types of FEB nanostructure occur in naturally deformed vein quartz from the low-grade metamorphic High-Ardenne slate belt (Belgium). Prismatic oriented FEBs are defined by bands of dislocation walls. Dauphiné twin boundaries present along the FEB boundaries probably formed after FEB formation. In an example of two sub-rhombohedral oriented FEBs, developed as two sets in one grain, the finer FEB set consists of elongated subgrains, similar to FEBs described in previous transmission electron microscopy studies. The second wider FEB set consists of bands with different dislocation density and fluid-inclusion content. The wider FEB set is interpreted as bands with different plastic strain associated with the primary growth banding of the vein quartz grain. The nanometre-scale fluid inclusions are interpreted to have formed from structurally bounded hydroxyl groups that moreover facilitated formation of the elongate subgrains. Larger fluid inclusions aligned along FEBs are explained by fluid-inclusion redistribution along dislocation cores. The prismatic FEB nanostructure and the relation between FEBs and growth bands have not been recognized before, although related structures have been reported in experimentally deformed quartz.

Different patterns of collagen-proteoglycan interaction: a scanning electron microscopy and atomic force microscopy study.

PubMed

Raspanti, M; Congiu, T; Alessandrini, A; Gobbi, P; Ruggeri, A

2000-01-01

The extracellular matrix of unfixed, unstained rat corneal stroma, visualized with high-resolution scanning electron microscopy and atomic force microscopy after minimal preliminary treatment, appears composed of straight, parallel, uniform collagen fibrils regularly spaced by a three-dimensional, irregular network of thin, delicate proteoglycan filaments. Rat tail tendon, observed under identical conditions, appears instead made of heterogeneous, closely packed fibrils interwoven with orthogonal proteoglycan filaments. Pre-treatment with cupromeronic blue just thickens the filaments without affecting their spatial layout. Digestion with chondroitinase ABC rids the tendon matrix of all its interconnecting filaments while the corneal stroma architecture remains virtually unaffected, its fibrils always being separated by an evident interfibrillar spacing which is never observed in tendon. Our observations indicate that matrix proteoglycans are responsible for both the highly regular interfibrillar spacing which is distinctive of corneal stroma, and the strong interfibrillar binding observed in tendon. These opposite interaction patterns appear to be distinctive of different proteoglycan species. The molecular details of proteoglycan interactions are still incompletely understood and are the subject of ongoing research.

Serial sectioning methods for 3D investigations in materials science.

PubMed

Zankel, Armin; Wagner, Julian; Poelt, Peter

2014-07-01

A variety of methods for the investigation and 3D representation of the inner structure of materials has been developed. In this paper, techniques based on slice and view using scanning microscopy for imaging are presented and compared. Three different methods of serial sectioning combined with either scanning electron or scanning ion microscopy or atomic force microscopy (AFM) were placed under scrutiny: serial block-face scanning electron microscopy, which facilitates an ultramicrotome built into the chamber of a variable pressure scanning electron microscope; three-dimensional (3D) AFM, which combines an (cryo-) ultramicrotome with an atomic force microscope, and 3D FIB, which delivers results by slicing with a focused ion beam. These three methods complement one another in many respects, e.g., in the type of materials that can be investigated, the resolution that can be obtained and the information that can be extracted from 3D reconstructions. A detailed review is given about preparation, the slice and view process itself, and the limitations of the methods and possible artifacts. Applications for each technique are also provided. Copyright © 2014 Elsevier Ltd. All rights reserved.

Scanning electron microscopy of dentition: methodology and ultrastructural morphology of tooth wear.

PubMed

Shkurkin, G V; Almquist, A J; Pfeihofer, A A; Stoddard, E L

1975-01-01

Scanning electron micrographs were taken of sets of human molars-those of paleo-Indians used in mastication of, ostensibly, a highly abrasive diet, and those of contemporary Americans. Different ultrastructural patterns of enamel wear were observed between the groups.

Studying the Stoichiometry of Epidermal Growth Factor Receptor in Intact Cells using Correlative Microscopy.

PubMed

Peckys, Diana B; de Jonge, Niels

2015-09-11

This protocol describes the labeling of epidermal growth factor receptor (EGFR) on COS7 fibroblast cells, and subsequent correlative fluorescence microscopy and environmental scanning electron microscopy (ESEM) of whole cells in hydrated state. Fluorescent quantum dots (QDs) were coupled to EGFR via a two-step labeling protocol, providing an efficient and specific protein labeling, while avoiding label-induced clustering of the receptor. Fluorescence microscopy provided overview images of the cellular locations of the EGFR. The scanning transmission electron microscopy (STEM) detector was used to detect the QD labels with nanoscale resolution. The resulting correlative images provide data of the cellular EGFR distribution, and the stoichiometry at the single molecular level in the natural context of the hydrated intact cell. ESEM-STEM images revealed the receptor to be present as monomer, as homodimer, and in small clusters. Labeling with two different QDs, i.e., one emitting at 655 nm and at 800 revealed similar characteristic results.

Crystallography and Morphology of Niobium Carbide in As-Cast HP-Niobium Reformer Tubes

NASA Astrophysics Data System (ADS)

Buchanan, Karl G.; Kral, Milo V.

2012-06-01

The microstructures of two as-cast heats of niobium-modified HP stainless steels were characterized. Particular attention was paid to the interdendritic niobium-rich carbides formed during solidification of these alloys. At low magnifications, these precipitates are grouped in colonies of similar lamellae. Higher magnifications revealed that the lamellae actually obtain two distinct morphologies. The type I morphology exhibits broad planar interfaces with a smooth platelike shape. Type II lamellae have undulating interfaces and an overall reticulated shape. To provide further insight into the origin of these two different morphologies, the microstructure and crystallography of each have been studied in detail using high resolution scanning electron microscopy, transmission electron microscopy, various electron diffraction methods (electron backscatter diffraction (EBSD), selected area diffraction (SAD), and convergent beam electron diffraction (CBED)), and energy dispersive X-ray spectroscopy.

Study of the structure of a thin aluminum layer on the vicinal surface of a gallium arsenide substrate by high-resolution electron microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lovygin, M. V., E-mail: lemi@miee.ru; Borgardt, N. I.; Seibt, M.

2015-12-15

The results of electron-microscopy studies of a thin epitaxial aluminum layer deposited onto a misoriented gallium-arsenide substrate are reported. It is established that the layer consists of differently oriented grains, whose crystal lattices are coherently conjugated with the substrate with the formation of misfit dislocations, as in the case of a layer on a singular substrate. Atomic steps on the substrate surface are visualized, and their influence on the growth of aluminum crystal grains is discussed.

Dispersion of Co/CNTs via strong electrostatic adsorption method: Thermal treatment effect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Akbarzadeh, Omid, E-mail: omid.akbarzadeh63@gmail.com; Abdullah, Bawadi, E-mail: bawadi-abdullah@petronas.com.my; Subbarao, Duvvuri, E-mail: duvvuri-subbarao@petronas.com.my

The effect of different thermal treatment temperature on the structure of multi-walled carbon nanotubes (MWCNTs) and Co particle dispersion on CNTs support is studied using Strong electrostatic adsorption (SEA) method. The samples tested by N{sub 2}-adsorption, field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). N{sub 2}-adsorption results showed BET surface area increased using thermal treatment and TEM images showed that increasing the thermal treatment temperature lead to flaky CNTs and defects introduced on the outer surface and Co particle dispersion increased.

Refixation of Osteochondral Fractures by an Ultrasound-Activated Pin System - An Ovine In Vivo Examination Using CT and Scanning Electron Microscope.

PubMed

H, Neumann; A P, Schulz; S, Breer; A, Unger; B, Kienast

2015-01-01

Osteochondral injuries, if not treated appropriately, often lead to severe osteoarthritis of the affected joint. Without refixation of the osteochondral fragment, human cartilage only repairs these defects imperfectly. All existing refixation systems for chondral defects have disadvantages, for instance bad MRI quality in the postoperative follow-up or low anchoring forces. To address the problem of reduced stability in resorbable implants, ultrasound-activated pins were developed. By ultrasound-activated melting of the tip of these implants a higher anchoring is assumed. Aim of the study was to investigate, if ultrasound-activated pins can provide a secure refixation of osteochondral fractures comparing to conventional screw and conventional, resorbable pin osteosynthesis. CT scans and scanning electron microscopy should proovegood refixation results with no further tissue damage by the melting of the ultrasound-activated pins in comparison to conventional osteosynthesis. Femoral osteochondral fragments in sheep were refixated with ultrasound-activated pins (SonicPin™), Ethipins(®) and screws (Asnis™). The quality of the refixated fragments was examined after three month of full weight bearing by CT scans and scanning electron microscopy of the cartilage surface. The CT examination found almost no statistically significant difference in the quality of refixation between the three different implants used. Concerning the CT morphology, ultrasound-activated pins demonstrated at least the same quality in refixation of osteochondral fragments as conventional resorbable pins or screws. The scanning electron microscopy showed no major surface damage by the three implants, especially any postulated cartilage damage induced by the heat of the ultrasound-activated pin. The screws protruded above the cartilage surface, which may affect the opposingtibial surface. Using CT scans and scanning electron microscopy, the SonicPin™, the Ethipin(®) and screws were at least equivalent in refixation quality of osteochondral fragments.

Investigation of AlGaN/GaN high electron mobility transistor structures on 200-mm silicon (111) substrates employing different buffer layer configurations.

PubMed

Lee, H-P; Perozek, J; Rosario, L D; Bayram, C

2016-11-21

AlGaN/GaN high electron mobility transistor (HEMT) structures are grown on 200-mm diameter Si(111) substrates by using three different buffer layer configurations: (a) Thick-GaN/3 × {Al x Ga 1-x N}/AlN, (b) Thin-GaN/3 × {Al x Ga 1-x N}/AlN, and (c) Thin-GaN/AlN, so as to have crack-free and low-bow (<50 μm) wafer. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, high resolution-cross section transmission electron microscopy, optical microscopy, atomic-force microscopy, cathodoluminescence, Raman spectroscopy, X-ray diffraction (ω/2θ scan and symmetric/asymmetric ω scan (rocking curve scan), reciprocal space mapping) and Hall effect measurements are employed to study the structural, optical, and electrical properties of these AlGaN/GaN HEMT structures. The effects of buffer layer stacks (i.e. thickness and content) on defectivity, stress, and two-dimensional electron gas (2DEG) mobility and 2DEG concentration are reported. It is shown that 2DEG characteristics are heavily affected by the employed buffer layers between AlGaN/GaN HEMT structures and Si(111) substrates. Particularly, we report that in-plane stress in the GaN layer affects the 2DEG mobility and 2DEG carrier concentration significantly. Buffer layer engineering is shown to be essential for achieving high 2DEG mobility (>1800 cm 2 /V∙s) and 2DEG carrier concentration (>1.0 × 10 13  cm -2 ) on Si(111) substrates.

Investigation of AlGaN/GaN high electron mobility transistor structures on 200-mm silicon (111) substrates employing different buffer layer configurations

PubMed Central

Lee, H.-P.; Perozek, J.; Rosario, L. D.; Bayram, C.

2016-01-01

AlGaN/GaN high electron mobility transistor (HEMT) structures are grown on 200-mm diameter Si(111) substrates by using three different buffer layer configurations: (a) Thick-GaN/3 × {AlxGa1−xN}/AlN, (b) Thin-GaN/3 × {AlxGa1−xN}/AlN, and (c) Thin-GaN/AlN, so as to have crack-free and low-bow (<50 μm) wafer. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, high resolution-cross section transmission electron microscopy, optical microscopy, atomic-force microscopy, cathodoluminescence, Raman spectroscopy, X-ray diffraction (ω/2θ scan and symmetric/asymmetric ω scan (rocking curve scan), reciprocal space mapping) and Hall effect measurements are employed to study the structural, optical, and electrical properties of these AlGaN/GaN HEMT structures. The effects of buffer layer stacks (i.e. thickness and content) on defectivity, stress, and two-dimensional electron gas (2DEG) mobility and 2DEG concentration are reported. It is shown that 2DEG characteristics are heavily affected by the employed buffer layers between AlGaN/GaN HEMT structures and Si(111) substrates. Particularly, we report that in-plane stress in the GaN layer affects the 2DEG mobility and 2DEG carrier concentration significantly. Buffer layer engineering is shown to be essential for achieving high 2DEG mobility (>1800 cm2/V∙s) and 2DEG carrier concentration (>1.0 × 1013 cm−2) on Si(111) substrates. PMID:27869222

Synthesis and study of photovoltaic performance on various photoelectrode materials for DSSCs: Optimization of compact layer on nanometer thickness

NASA Astrophysics Data System (ADS)

Surya, Subramanian; Thangamuthu, Rangasamy; Senthil Kumar, Sakkarapalayam Murugesan; Murugadoss, Govindhasamy

2017-02-01

Dye-sensitized solar cells (DSSCs) have gained widespread attention in recent years because of their low production costs, ease of fabrication process and tuneable optical properties, such as colour and transparency. In this work, we explored a strategy wherein nanoparticles of pure TiO2, TiO2sbnd SnO2 nanocomposite, Sn (10%) doped TiO2 and SnO2 synthesized by the simple chemical precipitation method were employed as photoelectrodes to enhance the photovoltaic conversion efficiency of solar cells. The nanoparticles were characterized by different characterization techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM with EDX), transmission electron microscopy (TEM), high resolution electron microscopy (HR-TEM), UV-Visible absorbance (UV-vis), photoluminescence (PL), thermal gravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) measurements. Moreover, we also demonstrated the effect of thin compact layer in DSSCs by architecture with various precursor materials of different concentrations. We found that the optimized compact layer material TDIP (titanium diisopropoxide) with a concentration of 0.3 M % is produced the highest efficiency of 2.25% for Sn (10%) doped TiO2 electron transport material (ETM) and 4.38% was achieved for pure TiO2 ETM using SnCl2 compact layer with 0.1 M concentrations.

Discovery and characterization of iron sulfide and polyphosphate bodies coexisting in Archaeoglobus fulgidus cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Toso, Daniel B.; Javed, Muhammad Mohsin; Czornyj, Elizabeth

Inorganic storage granules have long been recognized in bacterial and eukaryotic cells but were only recently identified in archaeal cells. Here, we report the cellular organization and chemical compositions of storage granules in the Euryarchaeon, Archaeoglobus fulgidusstrain VC16, a hyperthermophilic, anaerobic, and sulfate-reducing microorganism. Dense granules were apparent inA. fulgiduscells imaged by cryo electron microscopy (cryoEM) but not so by negative stain electron microscopy. Cryo electron tomography (cryoET) revealed that each cell contains one to several dense granules located near the cell membrane. Energy dispersive X-ray (EDX) spectroscopy and scanning transmission electron microscopy (STEM) show that, surprisingly, each cell containsmore » not just one but often two types of granules with different elemental compositions. One type, named iron sulfide body (ISB), is composed mainly of the elements iron and sulfur plus copper; and the other one, called polyphosphate body (PPB), is composed of phosphorus and oxygen plus magnesium, calcium, and aluminum. PPBs are likely used for energy storage and/or metal sequestration/detoxification. ISBs could result from the reduction of sulfate to sulfide via anaerobic energy harvesting pathways and may be associated with energy and/or metal storage or detoxification. The exceptional ability of these archaeal cells to sequester different elements may have novel bioengineering applications.« less

Skeletal muscle biopsy analysis in reducing body myopathy and other FHL1-related disorders.

PubMed

Malfatti, Edoardo; Olivé, Montse; Taratuto, Ana Lía; Richard, Pascale; Brochier, Guy; Bitoun, Marc; Gueneau, Lucie; Laforêt, Pascal; Stojkovic, Tanya; Maisonobe, Thierry; Monges, Soledad; Lubieniecki, Fabiana; Vasquez, Gabriel; Streichenberger, Nathalie; Lacène, Emmanuelle; Saccoliti, Maria; Prudhon, Bernard; Alexianu, Marilena; Figarella-Branger, Dominique; Schessl, Joachim; Bonnemann, Carsten; Eymard, Bruno; Fardeau, Michel; Bonne, Gisèle; Romero, Norma Beatriz

2013-09-01

FHL1 mutations have been associated with various disorders that include reducing body myopathy (RBM), Emery-Dreifuss-like muscular dystrophy, isolated hypertrophic cardiomyopathy, and some overlapping conditions. We report a detailed histochemical, immunohistochemical, electron microscopic, and immunoelectron microscopic analyses of muscle biopsies from 18 patients carrying mutations in FHL1: 14 RBM patients (Group 1), 3 Emery-Dreifuss muscular dystrophy patients (Group 2), and 1 patient with hypertrophic cardiomyopathy and muscular hypertrophy (Group 2). Group 1 muscle biopsies consistently showed RBs associated with cytoplasmic bodies. The RBs showed prominent FHL1 immunoreactivity whereas desmin, αB-crystallin, and myotilin immunoreactivity surrounded RBs. By electron microscopy, RBs were composed of electron-dense tubulofilamentous material that seemed to spread progressively between the myofibrils and around myonuclei. By immunoelectron microscopy, FHL1 protein was found exclusively inside RBs. Group 2 biopsies showed mild dystrophic abnormalities without RBs; only minor nonspecific myofibrillar abnormalities were observed under electron microscopy. Molecular analysis revealed missense mutations in the second FHL1 LIM domain in Group 1 patients and ins/del or missense mutations within the fourth FHL1 LIM domain in Group 2 patients. Our findings expand the morphologic features of RBM, clearly demonstrate the localization of FHL1 in RBs, and further illustrate major morphologic differences among different FHL1-related myopathies.

Discovery and characterization of iron sulfide and polyphosphate bodies coexisting in Archaeoglobus fulgidus cells

DOE PAGES

Toso, Daniel B.; Javed, Muhammad Mohsin; Czornyj, Elizabeth; ...

2016-01-01

Inorganic storage granules have long been recognized in bacterial and eukaryotic cells but were only recently identified in archaeal cells. Here, we report the cellular organization and chemical compositions of storage granules in the Euryarchaeon, Archaeoglobus fulgidusstrain VC16, a hyperthermophilic, anaerobic, and sulfate-reducing microorganism. Dense granules were apparent inA. fulgiduscells imaged by cryo electron microscopy (cryoEM) but not so by negative stain electron microscopy. Cryo electron tomography (cryoET) revealed that each cell contains one to several dense granules located near the cell membrane. Energy dispersive X-ray (EDX) spectroscopy and scanning transmission electron microscopy (STEM) show that, surprisingly, each cell containsmore » not just one but often two types of granules with different elemental compositions. One type, named iron sulfide body (ISB), is composed mainly of the elements iron and sulfur plus copper; and the other one, called polyphosphate body (PPB), is composed of phosphorus and oxygen plus magnesium, calcium, and aluminum. PPBs are likely used for energy storage and/or metal sequestration/detoxification. ISBs could result from the reduction of sulfate to sulfide via anaerobic energy harvesting pathways and may be associated with energy and/or metal storage or detoxification. The exceptional ability of these archaeal cells to sequester different elements may have novel bioengineering applications.« less

Avoiding artefacts during electron microscopy of silver nanomaterials exposed to biological environments

PubMed Central

Goode, Angela E.; Skepper, Jeremy N.; Thorley, Andrew J.; Seiffert, Joanna M.; Chung, K. Fan; Tetley, Teresa D.; Shaffer, Milo S. P.; Ryan, Mary P.

2015-01-01

Electron microscopy has been applied widely to study the interaction of nanomaterials with proteins, cells and tissues at nanometre scale. Biological material is most commonly embedded in thermoset resins to make it compatible with the high vacuum in the electron microscope. Room temperature sample preparation protocols developed over decades provide contrast by staining cell organelles, and aim to preserve the native cell structure. However, the effect of these complex protocols on the nanomaterials in the system is seldom considered. Any artefacts generated during sample preparation may ultimately interfere with the accurate prediction of the stability and reactivity of the nanomaterials. As a case study, we review steps in the room temperature preparation of cells exposed to silver nanomaterials (AgNMs) for transmission electron microscopy imaging and analysis. In particular, embedding and staining protocols, which can alter the physicochemical properties of AgNMs and introduce artefacts thereby leading to a misinterpretation of silver bioreactivity, are scrutinised. Recommendations are given for the application of cryogenic sample preparation protocols, which simultaneously fix both particles and diffusible ions. By being aware of the advantages and limitations of different sample preparation methods, compromises or selection of different correlative techniques can be made to draw more accurate conclusions about the data. PMID:25606708

Mechanical and microwave absorbing properties of carbon-filled polyurethane.

PubMed

Kucerová, Z; Zajícková, L; Bursíková, V; Kudrle, V; Eliás, M; Jasek, O; Synek, P; Matejková, J; Bursík, J

2009-01-01

Polyurethane (PU) matrix composites were prepared with various carbon fillers at different filler contents in order to investigate their structure, mechanical and microwave absorbing properties. As fillers, flat carbon microparticles, carbon microfibers and multiwalled carbon nanotubes (MWNT) were used. The microstructure of the composite was examined by scanning electron microscopy and transmission electron microscopy. Mechanical properties, namely universal hardness, plastic hardness, elastic modulus and creep were assessed by means of depth sensing indentation test. Mechanical properties of PU composite filled with different fillers were investigated and the composite always exhibited higher hardness, elastic modulus and creep resistance than un-filled PU. Influence of filler shape, content and dispersion was also investigated.

Investigating the use of in situ liquid cell scanning transmission electron microscopy to explore DNA-mediated gold nanoparticle growth

NASA Astrophysics Data System (ADS)

Nguy, Amanda

Engineering nanoparticles with desired shape-dependent properties is the key to many applications in nanotechnology. Although many synthetic procedures exist to produce anisotropic gold nanoparticles, the dynamics of growth are typically unknown or hypothetical. In the case of seed-mediated growth in the presence of DNA into anisotropic nanoparticles, it is not known exactly how DNA directs growth into specific morphologies. A series of preliminary experiments were carried out to contribute to the investigation of the possible mechanism of DNA-mediated growth of gold nanoprisms into gold nanostars using liquid cell scanning transmission electron microscopy (STEM). Imaging in the liquid phase was achieved through the use of a liquid cell platform and liquid cell holder that allow the sample to be contained within a “chip sandwich” between two electron transparent windows. Ex situ growth experiments were performed using Au-T30 NPrisms (30-base thymine oligonucleotide-coated gold nanoprisms) that are expected to grow into gold nanostars. Growth to form these nanostars were imaged using TEM (transmission electron microscopy) and liquid cell STEM (scanning transmission electron microscopy). An attempt to perform in situ growth experiments with the same Au-T30 nanoprisms revealed challenges in obtaining desired morphology results due to the environmental differences within the liquid cell compared to the ex situ environment. Different parameters in the experimental method were explored including fluid line set up, simultaneous and alternating reagent addition, and the effect of different liquid cell volumes to ensure adequate flow of reagents into the liquid cell. Lastly, the binding affinities were compared for T30 and A30 DNA incubated with gold nanoparticles using zeta potential measurements, absorption spectroscopy, and isothermal titration calorimetry (ITC). It was previously reported thymine bases have a lower binding affinity to gold surfaces than adenine bases. However, the results reported here contradict the previously reported data. Future prospectives on this work are outlined.

Investigating the use of in situ liquid cell scanning transmission electron microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguy, Amanda

2016-02-19

Engineering nanoparticles with desired shape-dependent properties is the key to many applications in nanotechnology. Although many synthetic procedures exist to produce anisotropic gold nanoparticles, the dynamics of growth are typically unknown or hypothetical. In the case of seed-mediated growth in the presence of DNA into anisotropic nanoparticles, it is not known exactly how DNA directs growth into specific morphologies. A series of preliminary experiments were carried out to contribute to the investigation of the possible mechanism of DNA-mediated growth of gold nanoprisms into gold nanostars using liquid cell scanning transmission electron microscopy (STEM). Imaging in the liquid phase was achievedmore » through the use of a liquid cell platform and liquid cell holder that allow the sample to be contained within a “chip sandwich” between two electron transparent windows. Ex situ growth experiments were performed using Au-T30 NPrisms (30-base thymine oligonucleotide-coated gold nanoprisms) that are expected to grow into gold nanostars. Growth to form these nanostars were imaged using TEM (transmission electron microscopy) and liquid cell STEM (scanning transmission electron microscopy). An attempt to perform in situ growth experiments with the same Au-T30 nanoprisms revealed challenges in obtaining desired morphology results due to the environmental differences within the liquid cell compared to the ex situ environment. Different parameters in the experimental method were explored including fluid line set up, simultaneous and alternating reagent addition, and the effect of different liquid cell volumes to ensure adequate flow of reagents into the liquid cell. Lastly, the binding affinities were compared for T30 and A30 DNA incubated with gold nanoparticles using zeta potential measurements, absorption spectroscopy, and isothermal titration calorimetry (ITC). It was previously reported thymine bases have a lower binding affinity to gold surfaces than adenine bases. However, the results reported here contradict the previously reported data. Future prospectives on this work are outlined.« less

Demonstration of transmission high energy electron microscopy

DOE PAGES

Merrill, F. E.; Goett, J.; Gibbs, J. W.; ...

2018-04-06

High energy electrons have been used to investigate an extension of transmission electron microscopy. This technique, transmission high energy electron microscopy (THEEM), provides two additional capabilities to electron microscopy. First, high energy electrons are more penetrating than low energy electrons, and thus, they are able to image through thicker samples. Second, the accelerating mode of a radio-frequency linear accelerator provides fast exposures, down to 1 ps, which are ideal for flash radiography, making THEEM well suited to study the evolution of fast material processes under dynamic conditions. Lastly, initial investigations with static objects and during material processing have been performedmore » to investigate the capabilities of this technique.« less

Introduction: A Symposium in Honor of Professor Sir John Meurig Thomas

NASA Astrophysics Data System (ADS)

Gai, P. L.; Saka, H.; Tomokiyo, Y.; Boyes, E. D.

2002-02-01

This issue is dedicated to Professor Sir John Meurig Thomas for his renowned contributions to electron microscopy in the chemical sciences. It is a collection of peer-reviewed leading articles in electron microscopy, based on the presentations at the Microscopy and Microanalysis (M&M) 2000 symposium, which was held to honor Professor Thomas's exceptional scientific leadership and wide-ranging fundamental contributions in the chemical applications of electron microscopy.The issue contains key papers by leading international researchers on the recent developments and applications of electron microscopy in the solid state and liquid state sciences. They include synthesis and characterization of silicon nitride nanorods, nanostructures of amorphous silica, electron microscopy studies of nanoscale structure and chemistry of Pt-Ru electrocatalysts of interest in direct methanol fuel cells, development of in situ wet-environmental transmission electron microscopy for the first nanoscale studies of dynamic liquid-catalyst reactions, strain analysis of silicon by finite element method and energy filtering convergent beam electron diffraction, applications of chemistry with electron microscopy, bismuth nanowires for applications in nanoelectronics technology, synthesis and characterization of quantum dots for superlattices and in situ electron microscopy at very high temperatures to study the motion of W5Si3 on [alpha][beta]-SiN3 substrates.We thank all the participants, including the invited speakers, contributors, and session chairs, who made the symposium successful. We also thank the authors and reviewers of the papers who worked assiduously towards the publication of this issue.We are very grateful to the Microscopy Society of America (MSA) for providing the opportunity to honor Professor Sir John Meurig Thomas. Organizational support from the MSA is also gratefully acknowledged.We thank Charles E. Lyman, editor in chief of Microscopy and Microanalysis for coordinating the publication of this issue and the entire journal staff for their efforts.

Gaps analysis for CD metrology beyond the 22nm node

NASA Astrophysics Data System (ADS)

Bunday, Benjamin; Germer, Thomas A.; Vartanian, Victor; Cordes, Aaron; Cepler, Aron; Settens, Charles

2013-04-01

This paper will examine the future for critical dimension (CD) metrology. First, we will present the extensive list of applications for which CD metrology solutions are needed, showing commonalities and differences among the various applications. We will then report on the expected technical limits of the metrology solutions currently being investigated by SEMATECH and others in the industry to address the metrology challenges of future nodes, including conventional CD scanning electron microscopy (CD-SEM) and optical critical dimension (OCD) metrology and new potential solutions such as He-ion microscopy (HeIM, sometimes elsewhere referred to as HIM), CD atomic force microscopy (CD-AFM), CD small-angle x-ray scattering (CD-SAXS), high-voltage scanning electron microscopy (HV-SEM), and other types. A technical gap analysis matrix will then be demonstrated, showing the current state of understanding of the future of the CD metrology space.

Cytocompatibility and uptake of halloysite clay nanotubes.

PubMed

Vergaro, Viviana; Abdullayev, Elshad; Lvov, Yuri M; Zeitoun, Andre; Cingolani, Roberto; Rinaldi, Ross; Leporatti, Stefano

2010-03-08

Halloysite is aluminosilicate clay with hollow tubular structure of 50 nm external diameter and 15 nm diameter lumen. Halloysite biocompatibility study is important for its potential applications in polymer composites, bone implants, controlled drug delivery, and for protective coating (e.g., anticorrosion or antimolding). Halloysite nanotubes were added to different cell cultures for toxicity tests. Its fluorescence functionalization by aminopropyltriethosilane (APTES) and with fluorescently labeled polyelectrolyte layers allowed following halloysite uptake by the cells with confocal laser scanning microscopy (CLSM). Quantitative Trypan blue and MTT measurements performed with two neoplastic cell lines model systems as a function of the nanotubes concentration and incubation time indicate that halloysite exhibits a high level of biocompatibility and very low cytotoxicity, rendering it a good candidate for household materials and medicine. A combination of transmission electron microscopy (TEM), scanning electron microscopy (SEM), and scanning force microscopy (SFM) imaging techniques have been employed to elucidate the structure of halloysite nanotubes.

Dynamic Architecture of Eukaryotic DNA Replication Forks In Vivo, Visualized by Electron Microscopy.

PubMed

Zellweger, Ralph; Lopes, Massimo

2018-01-01

The DNA replication process can be heavily perturbed by several different conditions of genotoxic stress, particularly relevant for cancer onset and therapy. The combination of psoralen crosslinking and electron microscopy has proven instrumental to reveal the fine architecture of in vivo DNA replication intermediates and to uncover their remodeling upon specific conditions of genotoxic stress. The replication structures are stabilized in vivo (by psoralen crosslinking) prior to extraction and enrichment procedures, allowing their visualization at the transmission electron microscope. This chapter outlines the procedures required to visualize and interpret in vivo replication intermediates of eukaryotic genomic DNA, and includes an improved method for enrichment of replication intermediates, compared to previously used BND-cellulose columns.

Total coliphages removal by activated sludge process and their morphological diversity by transmission electron microscopy.

PubMed

Jebri, Sihem; Hmaied, Fatma; Yahya, Mariem; Ben Ammar, Aouatef; Hamdi, Moktar

This study was conducted to isolate phages in treated sewage collected from wastewater treatment plant, and explore their morphological diversity by transmission electron microscopy (TEM). Fates of total bacteriophages and their reduction by biological treatment were also assayed. Phages were isolated using the plaque assay then negatively stained and observed by electron microscope. Electron micrographs showed different types of phages with different shapes and sizes. The majority of viruses found in treated sewage ranged from 30 to 100 nm in capsid diameter. Many of them were tailed, belonging to Siphoviridae, Myoviridae and Podoviridae families. Non-tailed phage particles were also found at a low rate, presumably belonging to Leviviridae or Microviridae families. This study shows the diversity and the abundance of bacteriophages in wastewater after biological treatment. Their persistence in wastewater reused in agriculture should raise concerns about their potential role in controlling bacterial populations in the environment. They should be also included in water treatment quality controlling guidelines as fecal and viral indicators.

Interlayer couplings, Moiré patterns, and 2D electronic superlattices in MoS2/WSe2 hetero-bilayers

PubMed Central

Zhang, Chendong; Chuu, Chih-Piao; Ren, Xibiao; Li, Ming-Yang; Li, Lain-Jong; Jin, Chuanhong; Chou, Mei-Yin; Shih, Chih-Kang

2017-01-01

By using direct growth, we create a rotationally aligned MoS2/WSe2 hetero-bilayer as a designer van der Waals heterostructure. With rotational alignment, the lattice mismatch leads to a periodic variation of atomic registry between individual van der Waals layers, exhibiting a Moiré pattern with a well-defined periodicity. By combining scanning tunneling microscopy/spectroscopy, transmission electron microscopy, and first-principles calculations, we investigate interlayer coupling as a function of atomic registry. We quantitatively determine the influence of interlayer coupling on the electronic structure of the hetero-bilayer at different critical points. We show that the direct gap semiconductor concept is retained in the bilayer although the valence and conduction band edges are located at different layers. We further show that the local bandgap is periodically modulated in the X-Y direction with an amplitude of ~0.15 eV, leading to the formation of a two-dimensional electronic superlattice. PMID:28070558

A correlative optical microscopy and scanning electron microscopy approach to locating nanoparticles in brain tumors.

PubMed

Kempen, Paul J; Kircher, Moritz F; de la Zerda, Adam; Zavaleta, Cristina L; Jokerst, Jesse V; Mellinghoff, Ingo K; Gambhir, Sanjiv S; Sinclair, Robert

2015-01-01

The growing use of nanoparticles in biomedical applications, including cancer diagnosis and treatment, demands the capability to exactly locate them within complex biological systems. In this work a correlative optical and scanning electron microscopy technique was developed to locate and observe multi-modal gold core nanoparticle accumulation in brain tumor models. Entire brain sections from mice containing orthotopic brain tumors injected intravenously with nanoparticles were imaged using both optical microscopy to identify the brain tumor, and scanning electron microscopy to identify the individual nanoparticles. Gold-based nanoparticles were readily identified in the scanning electron microscope using backscattered electron imaging as bright spots against a darker background. This information was then correlated to determine the exact location of the nanoparticles within the brain tissue. The nanoparticles were located only in areas that contained tumor cells, and not in the surrounding healthy brain tissue. This correlative technique provides a powerful method to relate the macro- and micro-scale features visible in light microscopy with the nanoscale features resolvable in scanning electron microscopy. Copyright © 2014 Elsevier Ltd. All rights reserved.

Comparison of nitrogen adsorption and transmission electron microscopy analyses for structural characterization of carbon nanotubes

NASA Astrophysics Data System (ADS)

Abbaslou, Reza Malek; Vosoughi, Vahid; Dalai, Ajay K.

2017-10-01

Carbon nanotubes (CNTs) are different from other porous substrates such as activated carbon due to their high external surfaces. This structural feature can lead in some uncertainties in the results of nitrogen adsorption analysis for characterization of CNTs. In this paper, the results of microscopic analyses and nitrogen adsorption method for characterization of carbon nanotubes were compared. Five different types of CNTs with different structures were either synthesized or purchased. The CNT samples were characterized by high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM) and N2 adsorption analysis. The comparisons between the results from the microscopic analyses and N2 adsorption showed that the total pore volume and BET surface measurements include the internal and external porosity of CNTs. Therefore, the interpretation of N2 adsorption data required accurate TEM analysis. In addition, the evaluation of pore size distribution curves from all CNT samples in this study and several instances in the literature revealed the presence of a common peak in the range of 2-5 nm. This peak does not explain the inner pore size distribution. The presence of this common peak can be attributed to the strong adsorption of N2 on the junction of touched and crossed nanotubes.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Buck, E.C.; Dietz, N.L.; Bates, J.K.

Uranium contaminated soils from the Fernald Operation Site, Ohio, have been examined by a combination of optical microscopy, scanning electron microscopy with backscattered electron detection (SEM/BSE), and analytical electron microscopy (AEM). A method is described for preparing of transmission electron microscopy (TEM) thin sections by ultramicrotomy. By using these thin sections, SEM and TEM images can be compared directly. Uranium was found in iron oxides, silicates (soddyite), phosphates (autunites), and fluorite. Little uranium was associated with clays. The distribution of uranium phases was found to be inhomogeneous at the microscopic level.

Electron Microscopy of Ebola Virus-Infected Cells.

PubMed

Noda, Takeshi

2017-01-01

Ebola virus (EBOV) replicates in host cells, where both viral and cellular components show morphological changes during the process of viral replication from entry to budding. These steps in the replication cycle can be studied using electron microscopy (EM), including transmission electron microscopy (TEM) and scanning electron microscopy (SEM), which is one of the most useful methods for visualizing EBOV particles and EBOV-infected cells at the ultrastructural level. This chapter describes conventional methods for EM sample preparation of cultured cells infected with EBOV.

Investigation of nanoparticulate silicon as printed layers using scanning electron microscopy, transmission electron microscopy, X-ray absorption spectroscopy and X-ray photoelectron spectroscopy

DOE PAGES

Unuigbe, David M.; Harting, Margit; Jonah, Emmanuel O.; ...

2017-08-21

The presence of native oxide on the surface of silicon nanoparticles is known to inhibit charge transport on the surfaces. Scanning electron microscopy (SEM) studies reveal that the particles in the printed silicon network have a wide range of sizes and shapes. High-resolution transmission electron microscopy reveals that the particle surfaces have mainly the (111)- and (100)-oriented planes which stabilizes against further oxidation of the particles. X-ray absorption spectroscopy (XANES) and X-ray photoelectron spectroscopy (XPS) measurements at the O 1s-edge have been utilized to study the oxidation and local atomic structure of printed layers of silicon nanoparticles which were milledmore » for different times. XANES results reveal the presence of the +4 (SiO 2) oxidation state which tends towards the +2 (SiO) state for higher milling times. Si 2pXPS results indicate that the surfaces of the silicon nanoparticles in the printed layers are only partially oxidized and that all three sub-oxide, +1 (Si 2O), +2 (SiO) and +3 (Si 2O 3), states are present. The analysis of the change in the sub-oxide peaks of the silicon nanoparticles shows the dominance of the +4 state only for lower milling times.« less

Green synthesis of gold nanoparticles using Stevia rebaudiana leaf extracts: Characterization and their stability.

PubMed

Sadeghi, Babak; Mohammadzadeh, M; Babakhani, B

2015-07-01

Various methods invented and developed for the synthesis of gold nanoparticles that increases daily consumed. According to this method, including potential environmental pollution problems and the complexity of the synthesis, in this study, the feasibility of using the leaves extract of Stevia rebaudiana (SR) for the reduction of gold ions to nanoparticles form have been studied. Stevia leaves were used to prepare the aqueous extract for this study. Gold nanoparticles were characterized with different techniques such as UV-vis spectroscopy, FT-IR spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Transmission electron microscopy experiments showed that these nanoparticles are spherical and uniformly distributed and its size is from 5 to 20 nm. FT-IR spectroscopy revealed that gold nanoparticles were functionalized with biomolecules that have primary amine group (NH2), carbonyl group, OH groups and other stabilizing functional groups. X-ray diffraction pattern showed high purity and face centered cubic structure of gold nanoparticles with size of 17 nm. The scanning electron microscopy (SEM) implies the right of forming gold nanoparticles. The results, confirm that gold nanoparticles have synthesized by the leaves extract of S. rebaudiana (SR). Copyright © 2015 Elsevier B.V. All rights reserved.

Espina: A Tool for the Automated Segmentation and Counting of Synapses in Large Stacks of Electron Microscopy Images

PubMed Central

Morales, Juan; Alonso-Nanclares, Lidia; Rodríguez, José-Rodrigo; DeFelipe, Javier; Rodríguez, Ángel; Merchán-Pérez, Ángel

2011-01-01

The synapses in the cerebral cortex can be classified into two main types, Gray's type I and type II, which correspond to asymmetric (mostly glutamatergic excitatory) and symmetric (inhibitory GABAergic) synapses, respectively. Hence, the quantification and identification of their different types and the proportions in which they are found, is extraordinarily important in terms of brain function. The ideal approach to calculate the number of synapses per unit volume is to analyze 3D samples reconstructed from serial sections. However, obtaining serial sections by transmission electron microscopy is an extremely time consuming and technically demanding task. Using focused ion beam/scanning electron microscope microscopy, we recently showed that virtually all synapses can be accurately identified as asymmetric or symmetric synapses when they are visualized, reconstructed, and quantified from large 3D tissue samples obtained in an automated manner. Nevertheless, the analysis, segmentation, and quantification of synapses is still a labor intensive procedure. Thus, novel solutions are currently necessary to deal with the large volume of data that is being generated by automated 3D electron microscopy. Accordingly, we have developed ESPINA, a software tool that performs the automated segmentation and counting of synapses in a reconstructed 3D volume of the cerebral cortex, and that greatly facilitates and accelerates these processes. PMID:21633491

A controlled release of ibuprofen by systematically tailoring the morphology of mesoporous silica materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qu Fengyu; Chemistry and Pharmaceutical College, Jiamusi University, Jiamusi 154007; Zhu Guangshan

2006-07-15

A series of mesoporous silica materials with similar pore sizes, different morphologies and variable pore geometries were prepared systematically. In order to control drug release, ibuprofen was employed as a model drug and the influence of morphology and pore geometry of mesoporous silica on drug release profiles was extensively studied. The mesoporous silica and drug-loaded samples were characterized by X-ray diffraction, Fourier transform IR spectroscopy, N{sub 2} adsorption and desorption, scanning electron microscopy, and transmission electron microscopy. It was found that the drug-loading amount was directly correlated to the Brunauer-Emmett-Teller surface area, pore geometry, and pore volume; while the drugmore » release profiles could be controlled by tailoring the morphologies of mesoporous silica carriers. - Graphical abstract: The release of ibuprofen is controlled by tailoring the morphologies of mesoporous silica. The mesoporous silica and drug-loaded samples are characterized by powder X-ray diffraction, Fourier transform IR spectroscopy, N{sub 2} adsorption and desorption, scanning electron microscopy, and transmission electron microscopy. The drug-loading amount is directly correlated to the Brunauer-Emmett-Teller surface area, pore geometry, and pore volume; while the drug release profiles can be controlled by tailoring the morphologies of mesoporous silica carriers.« less

A direct electron detector for time-resolved MeV electron microscopy

DOE PAGES

Vecchione, T.; Denes, P.; Jobe, R. K.; ...

2017-03-15

The introduction of direct electron detectors enabled the structural biology revolution of cryogenic electron microscopy. Direct electron detectors are now expected to have a similarly dramatic impact on time-resolved MeV electron microscopy, particularly by enabling both spatial and temporal jitter correction. Here in this paper, we report on the commissioning of a direct electron detector for time-resolved MeV electron microscopy. The direct electron detector demonstrated MeV single electron sensitivity and is capable of recording megapixel images at 180 Hz. The detector has a 15-bit dynamic range, better than 30-μm spatial resolution and less than 20 analogue-to-digital converter count RMS pixelmore » noise. The unique capabilities of the direct electron detector and the data analysis required to take advantage of these capabilities are presented. The technical challenges associated with generating and processing large amounts of data are also discussed.« less

A direct electron detector for time-resolved MeV electron microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vecchione, T.; Denes, P.; Jobe, R. K.

The introduction of direct electron detectors enabled the structural biology revolution of cryogenic electron microscopy. Direct electron detectors are now expected to have a similarly dramatic impact on time-resolved MeV electron microscopy, particularly by enabling both spatial and temporal jitter correction. Here we report on the commissioning of a direct electron detector for time-resolved MeV electron microscopy. The direct electron detector demonstrated MeV single electron sensitivity and is capable of recording megapixel images at 180 Hz. The detector has a 15-bit dynamic range, better than 30-μmμm spatial resolution and less than 20 analogue-to-digital converter count RMS pixel noise. The uniquemore » capabilities of the direct electron detector and the data analysis required to take advantage of these capabilities are presented. The technical challenges associated with generating and processing large amounts of data are also discussed.« less

A direct electron detector for time-resolved MeV electron microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vecchione, T.; Denes, P.; Jobe, R. K.

The introduction of direct electron detectors enabled the structural biology revolution of cryogenic electron microscopy. Direct electron detectors are now expected to have a similarly dramatic impact on time-resolved MeV electron microscopy, particularly by enabling both spatial and temporal jitter correction. Here in this paper, we report on the commissioning of a direct electron detector for time-resolved MeV electron microscopy. The direct electron detector demonstrated MeV single electron sensitivity and is capable of recording megapixel images at 180 Hz. The detector has a 15-bit dynamic range, better than 30-μm spatial resolution and less than 20 analogue-to-digital converter count RMS pixelmore » noise. The unique capabilities of the direct electron detector and the data analysis required to take advantage of these capabilities are presented. The technical challenges associated with generating and processing large amounts of data are also discussed.« less

Scanning tunneling microscopy and spectroscopy of twisted trilayer graphene

NASA Astrophysics Data System (ADS)

Zuo, Wei-Jie; Qiao, Jia-Bin; Ma, Dong-Lin; Yin, Long-Jing; Sun, Gan; Zhang, Jun-Yang; Guan, Li-Yang; He, Lin

2018-01-01

Twist, as a simple and unique degree of freedom, could lead to enormous novel quantum phenomena in bilayer graphene. A small rotation angle introduces low-energy van Hove singularities (VHSs) approaching the Fermi level, which result in unusual correlated states in the bilayer graphene. It is reasonable to expect that the twist could also affect the electronic properties of few-layer graphene dramatically. However, such an issue has remained experimentally elusive. Here, by using scanning tunneling microscopy/spectroscopy (STM/STS), we systematically studied a twisted trilayer graphene (TTG) with two different small twist angles between adjacent layers. Two sets of VHSs, originating from the two twist angles, were observed in the TTG, indicating that the TTG could be simply regarded as a combination of two different twisted bilayers of graphene. By using high-resolution STS, we observed a split of the VHSs and directly imaged the spatial symmetry breaking of electronic states around the VHSs. These results suggest that electron-electron interactions play an important role in affecting the electronic properties of graphene systems with low-energy VHSs.

Environmental scanning electron microscopy analysis of Proteus mirabilis biofilms grown on chitin and stainless steel.

PubMed

Fernández-Delgado, Milagro; Duque, Zoilabet; Rojas, Héctor; Suárez, Paula; Contreras, Monica; García-Amado, María A; Alciaturi, Carlos

Proteus mirabilis is a human pathogen able to form biofilms on the surface of urinary catheters. Little is known about P. mirabilis biofilms on natural or industrial surfaces and the potential consequences for these settings. The main aim of this work was to assess and compare the adhesion and biofilm formation of P. mirabilis strains from different origins on chitin and stainless steel surfaces within 4 to 96 h. Using environmental scanning electron microscopy, the biofilms of a clinical strain grown on chitin at 4 h showed greater adhesion, aggregation, thickness, and extracellular matrix production than those grown on stainless steel, whereas biofilms of an environmental strain had less aggregation on both surfaces. Biofilms of both P. mirabilis strains developed different structures on chitin, such as pillars, mushrooms, channels, and crystalline-like precipitates between 24 and 96 h, in contrast with flat-layer biofilms produced on stainless steel. Significant differences ( p  < 0.05) were found in the frequency of pillars and channels. Images of transmission electron microscopy demonstrated abundant fimbriae in 100 % of cells from both strains, which could be related to surface adherence and biofilm formation. This represents the first study of P. mirabilis showing adhesion, biofilm formation, and development of different structures on surfaces found outside the human host.

Scanning electron and atomic force microscopy, and raman and x-ray photoelectron spectroscopy characterization of near-isogenic soft and hard wheat kernels and corresponding flours

USDA-ARS?s Scientific Manuscript database

Atomic force microscopy (AFM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) are used to investigate vitreous (hard) and non-vitreous (soft) wheat kernels and their corresponding wheat flours. AFM data reveal two different microstructures. The vitreous kernel reveals a granular text...

The nanostructure and microstructure of SiC surface layers deposited by MWCVD and ECRCVD

NASA Astrophysics Data System (ADS)

Dul, K.; Jonas, S.; Handke, B.

2017-12-01

Scanning electron microscopy (SEM) and Atomic force microscopy (AFM) have been used to investigate ex-situ the surface topography of SiC layers deposited on Si(100) by Microwave Chemical Vapour Deposition (MWCVD) -S1,S2 layers and Electron Cyclotron Resonance Chemical Vapor Deposition (ECRCVD) - layers S3,S4, using silane, methane, and hydrogen. The effects of sample temperature and gas flow on the nanostructure and microstructure have been investigated. The nanostructure was described by three-dimensional surface roughness analysis based on digital image processing, which gives a tool to quantify different aspects of surface features. A total of 13 different numerical parameters used to describe the surface topography were used. The scanning electron image (SEM) of the microstructure of layers S1, S2, and S4 was similar, however, layer S3 was completely different; appearing like grains. Nonetheless, it can be seen that no grain boundary structure is present in the AFM images.

Chemical Ni-C Bonding in Ni-Carbon Nanotube Composite by a Microwave Welding Method and Its Induced High-Frequency Radar Frequency Electromagnetic Wave Absorption.

PubMed

Sha, Linna; Gao, Peng; Wu, Tingting; Chen, Yujin

2017-11-22

In this work, a microwave welding method has been used for the construction of chemical Ni-C bonding at the interface between carbon nanotubes (CNTs) and metal Ni to provide a different surface electron distribution, which determined the electromagnetic (EM) wave absorption properties based on a surface plasmon resonance mechanism. Through a serial of detailed examinations, such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectrum, the as-expected chemical Ni-C bonding between CNTs and metal Ni has been confirmed. And the Brunauer-Emmett-Teller and surface zeta potential measurements uncovered the great evolution of structure and electronic density compared with CNTs, metal Ni, and Ni-CNT composite without Ni-C bonding. Correspondingly, except the EM absorption due to CNTs and metal Ni in the composite, another wide and strong EM absorption band ranging from 10 to 18 GHz was found, which was induced by the Ni-C bonded interface. With a thinner thickness and more exposed Ni-C interfaces, the Ni-CNT composite displayed less reflection loss.

Swift heavy ion track formation in Gd2Zr2-xTixO7 pyrochlore: Effect of electronic energy loss

NASA Astrophysics Data System (ADS)

Lang, Maik; Toulemonde, Marcel; Zhang, Jiaming; Zhang, Fuxiang; Tracy, Cameron L.; Lian, Jie; Wang, Zhongwu; Weber, William J.; Severin, Daniel; Bender, Markus; Trautmann, Christina; Ewing, Rodney C.

2014-10-01

The morphology of swift heavy ion tracks in the Gd2Zr2-xTixO7 pyrochlore system has been investigated as a function of the variation in chemical composition and electronic energy loss, dE/dx, over a range of energetic ions: 58Ni, 101Ru, 129Xe, 181Ta, 197Au, 208Pb, and 238U of 11.1 MeV/u specific energy. Bright-field transmission electron microscopy, synchrotron X-ray diffraction, and Raman spectroscopy reveal an increasing degree of amorphization with increasing Ti-content and dE/dx. The size and morphology of individual ion tracks in Gd2Ti2O7 were characterized by high-resolution transmission electron microscopy revealing a core-shell structure with an outer defect-fluorite dominated shell at low dE/dx to predominantly amorphous tracks at high dE/dx. Inelastic thermal-spike calculations have been used together with atomic-scale characterization of ion tracks in Gd2Ti2O7 by high resolution transmission electron microscopy to deduce critical energy densities for the complex core-shell morphologies induced by ions of different dE/dx.

Influence of the adsorption geometry of PTCDA on Ag(111) on the tip-molecule forces in non-contact atomic force microscopy.

PubMed

Langewisch, Gernot; Falter, Jens; Schirmeisen, André; Fuchs, Harald

2014-01-01

Perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) adsorbed on a metal surface is a prototypical organic-anorganic interface. In the past, scanning tunneling microscopy and scanning tunneling spectroscopy studies of PTCDA adsorbed on Ag(111) have revealed differences in the electronic structure of the molecules depending on their adsorption geometry. In the work presented here, high-resolution 3D force spectroscopy measurements at cryogenic temperatures were performed on a surface area that contained a complete PTCDA unit cell with the two possible geometries. At small tip-molecule separations, deviations in the tip-sample forces were found between the two molecule orientations. These deviations can be explained by a different electron density in both cases. This result demonstrates the capability of 3D force spectroscopy to detect even small effects in the electronic properties of organic adsorbates.

A simple method for environmental cell depressurization for use with an electron microscope.

PubMed

Ogawa, Naoki; Mizokawa, Ryo; Saito, Minoru; Ishikawa, Akira

2017-12-01

With the aid of the environmental cell (EC) in electron microscopy, hydrated specimens have been observed at high resolutions that optical microscopy cannot attain. Due to the ultra-high vacuum conditions of the inner column of the electron microscope, the EC requires sealing films that are sufficiently thin to allow electron transmission and that are sufficiently tough to withstand the pressure difference between the inside and outside of the EC. However, most hydrated specimens can be observed at low vacuum because the saturated vapor pressure of water is known to be 0.02 atm at room temperature. These concepts have been used in the differential pumping system, but it is complicated and relatively expensive. In this work, we propose a simple method for depressurization of the EC using a 'balloon structure' and demonstrate the theoretical benefits and practical improvement for specimen observations in low-vacuum conditions. © The Author 2017. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Enhanced photocatalytic performance of RGO/Ag nanocomposites produced via a facile microwave irradiation for the degradation of Rhodamine B in aqueous solution

NASA Astrophysics Data System (ADS)

Divya, K. S.; Chandran, Akash; Reethu, V. N.; Mathew, Suresh

2018-06-01

A series of RGO/Ag nanocomposites with different weight addition ratios of graphene oxide (GO) have been successfully prepared in situ through the simultaneous reduction of GO and AgNO3 via a facile microwave irradiation. X-ray diffraction analysis, Fourier Transform Infrared Spectroscopy, UV-vis diffuse reflectance spectra, Scanning electron microscopy, Photoluminescence spectra, Raman spectra, Atomic Force Microscopy, X-ray photoelectron spectroscopy (XPS) and Transmission electron microscopy are employed to determine the properties of the samples. It is found that RGO/Ag nanocomposites with a proper weight addition ratios of GO exhibit higher photocatalytic activity toward liquid phase photodegradation of Rhodamine B under visible light irradiation. The improved photoactivity of RGO/Ag nanocomposites can be ascribed to the integrative synergestic effect of enhanced adsorption capacity, the prolonged lifetime of photogenerated electron-hole pairs and effective interfacial hybridization between RGO and Ag nanoparticles. This study also shows that graphene sheets act as electronic conductive channels to efficiently separate charge carriers from Ag nanoparticles.

[Scanning electron microscope study of chemically disinfected endodontic files].

PubMed

Navarro, G; Mateos, M; Navarro, J L; Canalda, C

1991-01-01

Forty stainless steel endodontic files were observed at scanning electron microscopy after being subjected to ten disinfection cycles of 10 minutes each one, immersed in different chemical disinfectants. Corrosion was not observed on the surface of the files in circumstances that this study was made.

Correlative Stochastic Optical Reconstruction Microscopy and Electron Microscopy

PubMed Central

Kim, Doory; Deerinck, Thomas J.; Sigal, Yaron M.; Babcock, Hazen P.; Ellisman, Mark H.; Zhuang, Xiaowei

2015-01-01

Correlative fluorescence light microscopy and electron microscopy allows the imaging of spatial distributions of specific biomolecules in the context of cellular ultrastructure. Recent development of super-resolution fluorescence microscopy allows the location of molecules to be determined with nanometer-scale spatial resolution. However, correlative super-resolution fluorescence microscopy and electron microscopy (EM) still remains challenging because the optimal specimen preparation and imaging conditions for super-resolution fluorescence microscopy and EM are often not compatible. Here, we have developed several experiment protocols for correlative stochastic optical reconstruction microscopy (STORM) and EM methods, both for un-embedded samples by applying EM-specific sample preparations after STORM imaging and for embedded and sectioned samples by optimizing the fluorescence under EM fixation, staining and embedding conditions. We demonstrated these methods using a variety of cellular targets. PMID:25874453

The actin cytoskeleton in whole mount preparations and sections.

PubMed

Resch, Guenter P; Urban, Edit; Jacob, Sonja

2010-01-01

In non-muscle cells, the actin cytoskeleton plays a key role by providing a scaffold contributing to the definition of cell shape, force for driving cell motility, cytokinesis, endocytosis, and propulsion of pathogens, as well as tracks for intracellular transport. A thorough understanding of these processes requires insight into the spatial and temporal organisation of actin filaments into diverse higher-order structures, such as networks, parallel bundles, and contractile arrays. Transmission and scanning electron microscopy can be used to visualise the actin cytoskeleton, but due to the delicate nature of actin filaments, they are easily affected by standard preparation protocols, yielding variable degrees of ultrastructural preservation. In this chapter, we describe different conventional and cryo-approaches to visualise the actin cytoskeleton using transmission electron microscopy and discuss their specific advantages and drawbacks. In the first part, we present three different whole mount techniques, which allow visualisation of actin in the peripheral, thinly spread parts of cells grown in monolayers. In the second part, we describe specific issues concerning the visualisation of actin in thin sections. Techniques for three-dimensional visualisation of actin, protein localisation, and correlative light and electron microscopy are also included. Copyright © 2010 Elsevier Inc. All rights reserved.

Arc-discharge in solution: A novel synthesis method for carbon nanotubes and in situ decoration of carbon nanotubes with nanoparticles

NASA Astrophysics Data System (ADS)

Bera, Debasis

2005-11-01

During the last decade, carbon nanotubes (CNTs) have been envisioned for a host of different new applications. One of the objectives of the present research is to develop a simplified synthesis method for the production of large-scale, low-cost carbon nanotubes with functionality. Herein, a unique, simple, inexpensive and one-step synthesis route of CNTs and CNTs decorated with nanoparticles is reported. The method is simple arc-discharge in solution (ADS). For this new method, a full-fledged optoelectronically controlled instrument is reported here to achieve high efficiency and continuous bulk production of CNTs. In this system, a constant gap between the two electrodes is maintained using a photosensor which allows a continuous synthesis of the carbon nanostructures. The system operates in a feedback loop consisting of an electrode-gap detector and an analogue electronic unit, as controller. This computerized feed system was also used in single process step to produce in situ-decorated CNTs with a variety of industrially important nanoparticles. To name a few, we have successfully synthesized CNTs decorated with 3--4 nm ceria, silica and palladium nanoparticles for many industrially relevant applications. This process can be extended to synthesize decorated CNTs with other oxide and metallic nanoparticles. Sixty experimental runs were carried out for parametric analysis varying process parameters including voltage, current and precursors. The amount of yield with time, rate of erosion of the anode, and rate of deposition of carbonaceous materials on the cathode electrode were investigated. Normalized kinetic parameters were evaluated for different amperes from the sets of runs. The production rate of pristine CNT at 75 A is as high as 5.89 +/- 0.28 g.min-1. In this study, major emphasis was given on the characterizations of CNTs with and without nanoparticles using various techniques for surface and bulk analysis of the nanostructures. The nanostructures were characterized using transmission electron microscopy, high resolution transmission electron microscopy, scanning transmission electron microscopy, energy dispersive spectroscopy and scanning electron microscopy, x-ray photo electron spectroscopy, x-ray diffraction studies, and surface area analysis. Electron microscopy investigations show that the CNTs, collected from the water and solutions, are highly pure except for the presence of some amorphous carbon. (Abstract shortened by UMI.)

High-resolution imaging by scanning electron microscopy of semithin sections in correlation with light microscopy.

PubMed

Koga, Daisuke; Kusumi, Satoshi; Shodo, Ryusuke; Dan, Yukari; Ushiki, Tatsuo

2015-12-01

In this study, we introduce scanning electron microscopy (SEM) of semithin resin sections. In this technique, semithin sections were adhered on glass slides, stained with both uranyl acetate and lead citrate, and observed with a backscattered electron detector at a low accelerating voltage. As the specimens are stained in the same manner as conventional transmission electron microscopy (TEM), the contrast of SEM images of semithin sections was similar to TEM images of ultrathin sections. Using this technique, wide areas of semithin sections were also observed by SEM, without the obstruction of grids, which was inevitable for traditional TEM. This study also applied semithin section SEM to correlative light and electron microscopy. Correlative immunofluorescence microscopy and immune-SEM were performed in semithin sections of LR white resin-embedded specimens using a FluoroNanogold-labeled secondary antibody. Because LR white resin is hydrophilic and electron stable, this resin is suitable for immunostaining and SEM observation. Using correlative microscopy, the precise localization of the primary antibody was demonstrated by fluorescence microscopy and SEM. This method has great potential for studies examining the precise localization of molecules, including Golgi- and ER-associated proteins, in correlation with LM and SEM. © The Author 2015. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

On the Progress of Scanning Transmission Electron Microscopy (STEM) Imaging in a Scanning Electron Microscope.

PubMed

Sun, Cheng; Müller, Erich; Meffert, Matthias; Gerthsen, Dagmar

2018-04-01

Transmission electron microscopy (TEM) with low-energy electrons has been recognized as an important addition to the family of electron microscopies as it may avoid knock-on damage and increase the contrast of weakly scattering objects. Scanning electron microscopes (SEMs) are well suited for low-energy electron microscopy with maximum electron energies of 30 keV, but they are mainly used for topography imaging of bulk samples. Implementation of a scanning transmission electron microscopy (STEM) detector and a charge-coupled-device camera for the acquisition of on-axis transmission electron diffraction (TED) patterns, in combination with recent resolution improvements, make SEMs highly interesting for structure analysis of some electron-transparent specimens which are traditionally investigated by TEM. A new aspect is correlative SEM, STEM, and TED imaging from the same specimen region in a SEM which leads to a wealth of information. Simultaneous image acquisition gives information on surface topography, inner structure including crystal defects and qualitative material contrast. Lattice-fringe resolution is obtained in bright-field STEM imaging. The benefits of correlative SEM/STEM/TED imaging in a SEM are exemplified by structure analyses from representative sample classes such as nanoparticulates and bulk materials.

Damage mechanisms of MoN/SiN multilayer optics for next-generation pulsed XUV light sources.

PubMed

Sobierajski, R; Bruijn, S; Khorsand, A R; Louis, E; van de Kruijs, R W E; Burian, T; Chalupsky, J; Cihelka, J; Gleeson, A; Grzonka, J; Gullikson, E M; Hajkova, V; Hau-Riege, S; Juha, L; Jurek, M; Klinger, D; Krzywinski, J; London, R; Pelka, J B; Płociński, T; Rasiński, M; Tiedtke, K; Toleikis, S; Vysin, L; Wabnitz, H; Bijkerk, F

2011-01-03

We investigated the damage mechanism of MoN/SiN multilayer XUV optics under two extreme conditions: thermal annealing and irradiation with single shot intense XUV pulses from the free-electron laser facility in Hamburg - FLASH. The damage was studied "post-mortem" by means of X-ray diffraction, interference-polarizing optical microscopy, atomic force microscopy, and scanning transmission electron microscopy. Although the timescale of the damage processes and the damage threshold temperatures were different (in the case of annealing it was the dissociation temperature of Mo2N and in the case of XUV irradiation it was the melting temperature of MoN) the main damage mechanism is very similar: molecular dissociation and the formation of N2, leading to bubbles inside the multilayer structure.

Electron-beam broadening in amorphous carbon films in low-energy scanning transmission electron microscopy.

PubMed

Drees, H; Müller, E; Dries, M; Gerthsen, D

2018-02-01

Resolution in scanning transmission electron microscopy (STEM) is ultimately limited by the diameter of the electron beam. The electron beam diameter is not only determined by the properties of the condenser lens system but also by electron scattering in the specimen which leads to electron-beam broadening and degradation of the resolution with increasing specimen thickness. In this work we introduce a new method to measure electron-beam broadening which is based on STEM imaging with a multi-segmented STEM detector. We focus on STEM at low electron energies between 10 and 30 keV and use an amorphous carbon film with known thickness as test object. The experimental results are compared with calculated beam diameters using different analytical models and Monte-Carlo simulations. We find excellent agreement of the experimental data with the recently published model by Gauvin and Rudinsky [1] for small t/λ el (thickness to elastic mean free path) values which are considered in our study. Copyright © 2017 Elsevier B.V. All rights reserved.

Extremely thin layer plastification for focused-ion beam scanning electron microscopy: an improved method to study cell surfaces and organelles of cultured cells.

PubMed

VAN Donselaar, E G; Dorresteijn, B; Popov-Čeleketić, D; VAN DE Wetering, W J; Verrips, T C; Boekhout, T; Schneijdenberg, C T W M; Xenaki, A T; VAN DER Krift, T P; Müller, W H

2018-03-25

Since the recent boost in the usage of electron microscopy in life-science research, there is a great need for new methods. Recently minimal resin embedding methods have been successfully introduced in the sample preparation for focused-ion beam scanning electron microscopy (FIB-SEM). In these methods several possibilities are given to remove as much resin as possible from the surface of cultured cells or multicellular organisms. Here we introduce an alternative way in the minimal resin embedding method to remove excess of resin from two widely different cell types by the use of Mascotte filter paper. Our goal in correlative light and electron microscopic studies of immunogold-labelled breast cancer SKBR3 cells was to visualise gold-labelled HER2 plasma membrane proteins as well as the intracellular structures of flat and round cells. We found a significant difference (p < 0.001) in the number of gold particles of selected cells per 0.6 μm 2 cell surface: on average a flat cell contained 2.46 ± 1.98 gold particles, and a round cell 5.66 ± 2.92 gold particles. Moreover, there was a clear difference in the subcellular organisation of these two cells. The round SKBR3 cell contained many organelles, such as mitochondria, Golgi and endoplasmic reticulum, when compared with flat SKBR3 cells. Our next goal was to visualise crosswall associated organelles, septal pore caps, of Rhizoctonia solani fungal cells by the combined use of a heavy metal staining and our extremely thin layer plastification (ETLP) method. At low magnifications this resulted into easily finding septa which appeared as bright crosswalls in the back-scattered electron mode in the scanning electron microscope. Then, a septum was selected for FIB-SEM. Cross-sectioned views clearly revealed the perforate septal pore cap of R. solani next to other structures, such as mitochondria, endoplasmic reticulum, lipid bodies, dolipore septum, and the pore channel. As the ETLP method was applied on two widely different cell types, the use of the ETLP method will be beneficial to correlative studies of other cell model systems and multicellular organisms. © 2018 The Authors. Journal of Microscopy published by JohnWiley & Sons Ltd on behalf of Royal Microscopical Society.

Dipolar ferromagnetic phase transition in Fe3O4 nanoparticle arrays observed by Lorentz microscopy and electron holography

NASA Astrophysics Data System (ADS)

Yamamoto, Kazuo; Hogg, Charles R.; Yamamuro, Saeki; Hirayama, Tsukasa; Majetich, Sara A.

2011-02-01

Dipolar ferromagnetism formed in Fe3O4 nanoparticle arrays is revealed by Fresnel Lorentz microscopy and electron holography. Dipolar domain walls do not lie preferentially along macrograin boundaries but depend on the overall shape of the assembly, meaning magnetostatic energy dominates. The domain structures are imaged at different temperatures for both monolayer and bilayer arrays. The domain wall contrast in the monolayer region is visible until 575 °C, and the magnetic order parameter steeply drops toward the temperature. In the bilayer region, finer and more complicated domains are formed.

Composition, speciation and distribution of iron minerals in Imperata cylindrica.

PubMed

Amils, Ricardo; de la Fuente, Vicenta; Rodríguez, Nuria; Zuluaga, Javier; Menéndez, Nieves; Tornero, Jesús

2007-05-01

A comparative study of the roots, rhizomes and leaves of an iron hyperaccumulator plant, Imperata cylindrica, isolated from the banks of an extreme acidic environment, using complementary techniques: Mösbauer spectroscopy (MS), X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled to energy-dispersive X-ray microanalysis (EDAX) and transmission electron microscopy (TEM), has shown that two main biominerals, jarosite and ferrihydrate-ferritin, accumulate in the different tissues. Jarosite accumulates mainly in roots and rhizomes, while ferritin has been detected in all the structures. A model of iron management in I. cylindrica is presented.

Scanning electron microscopy of a blister roof in dystrophic epidermolysis bullosa*

PubMed Central

de Almeida Jr., Hiram Larangeira; Monteiro, Luciane; Silva, Ricardo Marques e; Rocha, Nara Moreira; Scheffer, Hans

2013-01-01

In dystrophic epidermolysis bullosa the genetic defect of anchoring fibrils leads to cleavage beneath the basement membrane, with its consequent loss. We performed scanning electron microscopy of an inverted blister roof of a case of dystrophic epidermolysis bullosa, confirmed by immunomapping and gene sequencing. With a magnification of 2000 times a net attached to the blister roof could be easily identified. This net was composed of intertwined flat fibers. With higher magnifications, different fiber sizes could be observed, some thin fibers measuring around 80 nm and thicker ones measuring between 200 and 300 nm. PMID:24474107

Stratification of centrifuged amoeba nuclei investigated by electron microscopy

NASA Technical Reports Server (NTRS)

Breyer, E. P.; Daniels, E. W.

1968-01-01

Study establishes a relationship between radioresistance and the nucleolar stratification characteristics of various amoeba species. Two species of fresh water amoeba are studied with the electron microscope. The report discusses the nature of nucleolar layers and their possible relationship to the differences in radiosensitivity of the two amoeba species.

Ultrafast Science Opportunities with Electron Microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Durr, Hermann

X-rays and electrons are two of the most fundamental probes of matter. When the Linac Coherent Light Source (LCLS), the world’s first x-ray free electron laser, began operation in 2009, it transformed ultrafast science with the ability to generate laser-like x-ray pulses from the manipulation of relativistic electron beams. This document describes a similar future transformation. In Transmission Electron Microscopy, ultrafast relativistic (MeV energy) electron pulses can achieve unsurpassed spatial and temporal resolution. Ultrafast temporal resolution will be the next frontier in electron microscopy and can ideally complement ultrafast x-ray science done with free electron lasers. This document describes themore » Grand Challenge science opportunities in chemistry, material science, physics and biology that arise from an MeV ultrafast electron diffraction & microscopy facility, especially when coupled with linac-based intense THz and X-ray pump capabilities.« less

Microstructure of milk

USDA-ARS?s Scientific Manuscript database

The fat and protein in milk may be examined by scanning electron microscopy, transmission electron microscopy, and confocal laser scanning microscopy, and any bacteria present may be viewed by light microscopy. The fat exists as globules, the bulk of the protein is in the form of casein micelles, a...

PMMA/PS coaxial electrospinning: core-shell fiber morphology as a function of material parameters

NASA Astrophysics Data System (ADS)

Rahmani, Shahrzad; Arefazar, Ahmad; Latifi, Masoud

2017-03-01

Core-shell fibers of polymethyl methacrylate (PMMA) and polystyrene (PS) have been successfully electrospun by coaxial electrospinning. To evaluate the influence of the solvent on the final fiber morphology, four types of organic solvents were used in the shell solution while the core solvent was preserved. Morphological observations with scanning electron microscopy, transmission electron microscopy and optical microscopy revealed that both core and shell solvent properties were involved in the final fiber morphology. To explain this involvement, alongside a discussion of the Bagley solubility graph of PS and PMMA, a novel criterion based on solvent physical properties was introduced. A theoretical model based on the momentum conservation principle was developed and applied for describing the dependence of the core and shell diameters to their solvent combinations. Different concentrations of core and shell were also investigated in the coaxial electrospinning of PMMA/PS. The core-shell fiber morphologies with different core and shell concentrations were compared with their single electrospun fibers.

Vinyl monomers-induced synthesis of polyvinyl alcohol-stabilized selenium nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shah, Chetan P.; Singh, Krishan K.; Kumar, Manmohan, E-mail: manmoku@barc.gov.in

2010-01-15

A simple wet chemical method has been developed to synthesize selenium nanoparticles (size 100-200 nm), by reaction of sodium selenosulphate precursor with different vinyl monomers, such as acrylamide, N,N'-dimethylene bis acrylamide, methyl methacrylate, sodium acrylate, etc., in aqueous medium, under ambient conditions. Polyvinyl alcohol has been used to stabilize the selenium nanoparticles. Average size of the synthesized selenium nanoparticles can be controlled by adjusting concentration of both the precursors and the stabilizer. Rate of the reaction as well as size of the resultant selenium nanoparticles have been correlated with the functional groups of the different monomers. UV-vis optical absorption spectroscopy,more » X-ray diffraction, energy dispersive X-rays, differential scanning calorimetry, atomic force microscopy, scanning electron microscopy and transmission electron microscopy techniques have been employed to characterize the synthesized selenium nanoparticles. Gas chromatographic analysis of the reaction mixture established the non-catalytic role of the vinyl monomers, which were found to be consumed during the course of the reaction.« less

Contribution of high-resolution correlative imaging techniques in the study of the liver sieve in three-dimensions.

PubMed

Braet, Filip; Wisse, Eddie; Bomans, Paul; Frederik, Peter; Geerts, Willie; Koster, Abraham; Soon, Lilian; Ringer, Simon

2007-03-01

Correlative microscopy has become increasingly important for the analysis of the structure, function, and dynamics of cells. This is largely due to the result of recent advances in light-, probe-, laser- and various electron microscopy techniques that facilitate three-dimensional studies. Furthermore, the improved understanding in the past decade of imaging cell compartments in the third dimension has resulted largely from the availability of powerful computers, fast high-resolution CCD cameras, specifically developed imaging analysis software, and various probes designed for labeling living and or fixed cells. In this paper, we review different correlative high-resolution imaging methodologies and how these microscopy techniques facilitated the accumulation of new insights in the morpho-functional and structural organization of the hepatic sieve. Various aspects of hepatic endothelial fenestrae regarding their structure, origin, dynamics, and formation will be explored throughout this paper by comparing the results of confocal laser scanning-, correlative fluorescence and scanning electron-, atomic force-, and whole-mount electron microscopy. Furthermore, the recent advances of vitrifying cells with the vitrobot in combination with the glove box for the preparation of cells for cryo-electron microscopic investigation will be discussed. Finally, the first transmission electron tomography data of the liver sieve in three-dimensions are presented. The obtained data unambiguously show the involvement of special domains in the de novo formation and disappearance of hepatic fenestrae, and focuses future research into the (supra)molecular structure of the fenestrae-forming center, defenestration center and fenestrae-, and sieve plate cytoskeleton ring by using advanced cryo-electron tomography. (c) 2007 Wiley-Liss, Inc.

Fabrication of [001]-oriented tungsten tips for high resolution scanning tunneling microscopy

PubMed Central

Chaika, A. N.; Orlova, N. N.; Semenov, V. N.; Postnova, E. Yu.; Krasnikov, S. A.; Lazarev, M. G.; Chekmazov, S. V.; Aristov, V. Yu.; Glebovsky, V. G.; Bozhko, S. I.; Shvets, I. V.

2014-01-01

The structure of the [001]-oriented single crystalline tungsten probes sharpened in ultra-high vacuum using electron beam heating and ion sputtering has been studied using scanning and transmission electron microscopy. The electron microscopy data prove reproducible fabrication of the single-apex tips with nanoscale pyramids grained by the {011} planes at the apexes. These sharp, [001]-oriented tungsten tips have been successfully utilized in high resolution scanning tunneling microscopy imaging of HOPG(0001), SiC(001) and graphene/SiC(001) surfaces. The electron microscopy characterization performed before and after the high resolution STM experiments provides direct correlation between the tip structure and picoscale spatial resolution achieved in the experiments. PMID:24434734

Towards native-state imaging in biological context in the electron microscope

PubMed Central

Weston, Anne E.; Armer, Hannah E. J.

2009-01-01

Modern cell biology is reliant on light and fluorescence microscopy for analysis of cells, tissues and protein localisation. However, these powerful techniques are ultimately limited in resolution by the wavelength of light. Electron microscopes offer much greater resolution due to the shorter effective wavelength of electrons, allowing direct imaging of sub-cellular architecture. The harsh environment of the electron microscope chamber and the properties of the electron beam have led to complex chemical and mechanical preparation techniques, which distance biological samples from their native state and complicate data interpretation. Here we describe recent advances in sample preparation and instrumentation, which push the boundaries of high-resolution imaging. Cryopreparation, cryoelectron microscopy and environmental scanning electron microscopy strive to image samples in near native state. Advances in correlative microscopy and markers enable high-resolution localisation of proteins. Innovation in microscope design has pushed the boundaries of resolution to atomic scale, whilst automatic acquisition of high-resolution electron microscopy data through large volumes is finally able to place ultrastructure in biological context. PMID:19916039

Remineralization Potential of Three Tooth Pastes on Enamel Caries.

PubMed

Singhal, Rajnish K; Rai, Balwant

2017-08-15

Different formulations of dentifrices exist in the market. Usually, single toothpaste is used by all family members including children. There is a big concern of fluoride ingestion with the toothpaste containing high fluoride content in children. Recently, new toothpaste (including toothpaste) with remineralization potential without fluoride content has been formulated. There is an urgent need to compare remineralization potential of this new formulation with the exiting dentifrices. Therefore, the present study has been undertaken to assess and compare the remineralization potential of three dentifrices with different compositions on artificially induced carious lesions in vitro by using scanning electron microscopy and polarised light microscopy. The present in vitro study was conducted on 21 healthy extracted primary central incisor teeth surfaces, which were divided into three groups and were treated by three different dentifrices. Artificial demineralization was followed by remineralization using dentifrice slurry as per the group distribution. All the samples were studied for remineralization by using scanning electron microscopy and polarised light microscopy. Data were analysed using SPSS version 11 software. A significant difference was found between the remineralization potential of incudent toothpaste and other toothpaste groups based on the analysis of polarised light microscopy and stereomicroscope. The remineralizing ability of incudent toothpaste for artificial enamel lesions was found to be significantly higher than that of Colgate® and Crest toothpaste. The limitations of this study include, being a short term study, low sample size and in vitro experiment. incudent toothpaste has exhibited a higher remineralizing potential as compared to fluoride based toothpaste in our study.

Synthesis by sol-gel process, structural and optical properties of nanoparticles of zinc oxide doped vanadium

NASA Astrophysics Data System (ADS)

El Ghoul, J.; Barthou, C.; El Mir, L.

2012-06-01

We report the elaboration of vanadium-doped ZnO nanoparticles prepared by a sol-gel processing technique. In our approach, the water for hydrolysis was slowly released by esterification reaction followed by a supercritical drying in ethyl alcohol. Vanadium doping concentration of 10 at.% has been investigated. After treatment in air at different temperatures, the obtained nanopowder was characterised by various techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and photoluminescence (PL). Analysis by scanning electron microscopy at high resolution shows that the grain size increases with increasing temperature. Thus, in the case of thermal treatment at 500 °C in air, the powder with an average particle size of 25 nm shows a strong luminescence band in the visible range. The intensity and energy position of the obtained PL band depends on the temperature measurement increase. The mechanism of this emission band is discussed.

A Global Approach for Quantitative Super Resolution and Electron Microscopy on Cryo and Epoxy Sections Using Self-labeling Protein Tags.

PubMed

Müller, Andreas; Neukam, Martin; Ivanova, Anna; Sönmez, Anke; Münster, Carla; Kretschmar, Susanne; Kalaidzidis, Yannis; Kurth, Thomas; Verbavatz, Jean-Marc; Solimena, Michele

2017-02-02

Correlative light and electron microscopy (CLEM) is a powerful approach to investigate the molecular ultrastructure of labeled cell compartments. However, quantitative CLEM studies are rare, mainly due to small sample sizes and the sensitivity of fluorescent proteins to strong fixatives and contrasting reagents for EM. Here, we show that fusion of a self-labeling protein to insulin allows for the quantification of age-distinct insulin granule pools in pancreatic beta cells by a combination of super resolution and transmission electron microscopy on Tokuyasu cryosections. In contrast to fluorescent proteins like GFP organic dyes covalently bound to self-labeling proteins retain their fluorescence also in epoxy resin following high pressure freezing and freeze substitution, or remarkably even after strong chemical fixation. This enables for the assessment of age-defined granule morphology and degradation. Finally, we demonstrate that this CLEM protocol is highly versatile, being suitable for single and dual fluorescent labeling and detection of different proteins with optimal ultrastructure preservation and contrast.

Effect of supercritical fluid density on nanoencapsulated drug particle size using the supercritical antisolvent method.

PubMed

Kalani, Mahshid; Yunus, Robiah

2012-01-01

The reported work demonstrates and discusses the effect of supercritical fluid density (pressure and temperature of supercritical fluid carbon dioxide) on particle size and distribution using the supercritical antisolvent (SAS) method in the purpose of drug encapsulation. In this study, paracetamol was encapsulated inside L-polylactic acid, a semicrystalline polymer, with different process parameters, including pressure and temperature, using the SAS process. The morphology and particle size of the prepared nanoparticles were determined by scanning electron microscopy and transmission electron microscopy. The results revealed that increasing temperature enhanced mean particle size due to the plasticizing effect. Furthermore, increasing pressure enhanced molecular interaction and solubility; thus, particle size was reduced. Transmission electron microscopy images defined the internal structure of nanoparticles. Thermal characteristics of nanoparticles were also investigated via differential scanning calorimetry. Furthermore, X-ray diffraction pattern revealed the changes in crystallinity structure during the SAS process. In vitro drug release analysis determined the sustained release of paracetamol in over 4 weeks.

Synthesis and characterization of bovine femur bone hydroxyapatite containing silver nanoparticles for the biomedical applications

NASA Astrophysics Data System (ADS)

Nirmala, R.; Sheikh, Faheem A.; Kanjwal, Muzafar A.; Lee, John Hwa; Park, Soo-Jin; Navamathavan, R.; Kim, Hak Yong

2011-05-01

Bovine femur bone hydroxyapatite (HA) containing silver (Ag) nanoparticles was synthesized by thermal decomposition method and subsequent reduction of silver nitrate with N, N-dimethylformamide (DMF) in the presence of poly(vinylacetate) (PVAc). The structural, morphological, and chemical properties of the HA-Ag nanoparticles were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). TEM images showed that the Ag nanoparticles with size ranging from 8 to 20 nm and were arranged at the periphery of HA crystals. Bactericidal activity of HA-Ag with different concentration of Ag nanoparticles immobilized on the surface of HA was investigated against gram-positive Staphylococcus aureus ( S. aureus, non-MRSA), Methicillin resistant S. aureus (MRSA) and gram-negative Escherichia coli ( E. coli) by the disc diffusion susceptibility test. The HA-Ag nanoparticles showed that broad spectrum activity against non-MRSA, MRSA, and E. coli bacterial strains.

A Fast Response Ammonia Sensor Based on Coaxial PPy-PAN Nanofiber Yarn.

PubMed

Liu, Penghong; Wu, Shaohua; Zhang, Yue; Zhang, Hongnan; Qin, Xiaohong

2016-06-23

Highly orientated polypyrrole (PPy)-coated polyacrylonitrile (PAN) (PPy-PAN) nanofiber yarn was prepared with an electrospinning technique and in-situ chemical polymerization. The morphology and chemical structure of PPy-PAN nanofiber yarn was characterized by scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and fourier transform infrared spectroscopy (FTIR), which indicated that the PPy as the shell layer was homogeneously and uniformly polymerized on the surface of PAN nanofiber. The effects of different concentration of doping acid on the responses of PPy-PAN nanofiber yarn sensor were investigated. The electrical responses of the gas sensor based on the PPy-PAN nanofiber yarn to ammonia were investigated at room temperature. The nanoyarn sensor composed of uniaxially aligned PPy-PAN nanofibers with a one-dimensional structure exhibited a transient response, and the response time was less than 1 s. The excellent sensing properties mentioned above give rise to good potential application prospects in the field of ammonia sensor.

Momentum microscopy of ? single crystals with detailed surface characterisation

NASA Astrophysics Data System (ADS)

Ellguth, M.; Tusche, C.; Iga, F.; Suga, S.

2016-11-01

We report the in situ preparation of surfaces of the proposed topological Kondo insulator SmB? by controlled cycles of Ar ion sputtering and annealing. The procedure provides a reproducible way for the preparation of Sm- or B-rich surface terminations by low (?1080 ?C) or high (?1200 ?C) temperature annealing. The surface quality and termination were checked by low energy electron diffraction and Auger electron spectroscopy. Photoemission studies were carried out using momentum microscopy and two laboratory light sources providing polarised radiation with an energy of 6 eV (fourth harmonic of a pulsed Ti:Sapphire laser) and unpolarised radiation with an energy of 21.2 eV (He-I line of a gas discharge lamp). Full dispersions of electronic states in a wide two-dimensional momentum space were obtained by momentum microscopy from the in situ prepared Sm-terminated surface. The shape of the Fermi surface is discussed based on the sections through the bulk Brillouin zone sampled by the different photon energies.

Effect of supercritical fluid density on nanoencapsulated drug particle size using the supercritical antisolvent method

PubMed Central

Kalani, Mahshid; Yunus, Robiah

2012-01-01

The reported work demonstrates and discusses the effect of supercritical fluid density (pressure and temperature of supercritical fluid carbon dioxide) on particle size and distribution using the supercritical antisolvent (SAS) method in the purpose of drug encapsulation. In this study, paracetamol was encapsulated inside L-polylactic acid, a semicrystalline polymer, with different process parameters, including pressure and temperature, using the SAS process. The morphology and particle size of the prepared nanoparticles were determined by scanning electron microscopy and transmission electron microscopy. The results revealed that increasing temperature enhanced mean particle size due to the plasticizing effect. Furthermore, increasing pressure enhanced molecular interaction and solubility; thus, particle size was reduced. Transmission electron microscopy images defined the internal structure of nanoparticles. Thermal characteristics of nanoparticles were also investigated via differential scanning calorimetry. Furthermore, X-ray diffraction pattern revealed the changes in crystallinity structure during the SAS process. In vitro drug release analysis determined the sustained release of paracetamol in over 4 weeks. PMID:22619552

[Electron microscopic study of the An-750 strain of Powassan virus isolated in the Soviet Union].

PubMed

Sobolev, S G; Shestopalova, N M; Linev, M B; Rubin, S G

1978-01-01

Electron microscopic examinations of brains of white mice inoculated with the An 750 strain isolated for the first time from adult mosquitoes and with the prototype LB strain of Powassan virus were carried out. The method of combination of light and electron microscopy used in the study permitted to compare ultrastructural changes in one cell with the results of light microscopy. Sizes of virions and their localizations in the brain cells were determined. Virus particles were found in large and small neurons as well as in glial elements. Subcellular changes in neurons associated with virus multiplication are described. The causes of differences in sizes of virions measured in ultrathin sections are discussed.

Microscopic evolution of dielectric nanoparticles at different calcination temperatures synthesized via sol-gel auto-combustion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adil, Muhammad, E-mail: muhammadadil86@hotmail.com; Zaid, Hasnah Mohd, E-mail: hasnamz@petronas.com.my; Chuan, Lee Kean, E-mail: lee.kc@petronas.com.my

2015-07-22

Dielectric nano powder synthesis is carried by a simple and fast sol-gel auto-combustion method. The transformation of crystalline phases of as-synthesized nano powders is investigated through the detailed transmission electron microscopy (TEM), revealed the crystallographic alterations and morphological information even at lattice scale. From specific area electron diffraction (SAED) pattern, has specified the d-spacing and corresponding planes supported by the observed lattice fringes. The morphological characterization of nanoparticles is performed through field-emission scanning electron microscopy (FESEM), exhibiting the increment in particle size due to agglomeration with the increase in annealing temperature. Furthermore, EDX pattern has been used to verify themore » formation of nanoparticles by revealing the presence of required elements.« less

Crystallography and Morphology of MC Carbides in Niobium-Titanium Modified As-Cast HP Alloys

NASA Astrophysics Data System (ADS)

Buchanan, Karl G.; Kral, Milo V.; Bishop, Catherine M.

2014-07-01

The microstructures of two as-cast heats of HP alloy stainless steels modified with niobium and titanium were examined with particular attention paid to the interdendritic niobium-titanium-rich carbides formed during solidification of these alloys. Generally, these precipitates obtain a blocky morphology in the as-cast condition. However, the (NbTi)C precipitates may obtain a nodular morphology. To provide further insight to the origin of the two different morphologies obtained by the (NbTi)C precipitates in the HP-NbTi alloy, the microstructure and crystallography of each have been studied in detail using scanning electron microscopy, transmission electron microscopy, various electron diffraction methods (EBSD, SAD, and CBED), and energy-dispersive X-ray spectroscopy.

Comparative morphology analysis of live blood platelets using scanning ion conductance and robotic dark-field microscopy.

PubMed

Kraus, Max-Joseph; Seifert, Jan; Strasser, Erwin F; Gawaz, Meinrad; Schäffer, Tilman E; Rheinlaender, Johannes

2016-09-01

Many conventional microscopy techniques for investigating platelet morphology such as electron or fluorescence microscopy require highly invasive treatment of the platelets such as fixation, drying and metal coating or staining. Here, we present two unique but entirely different microscopy techniques for direct morphology analysis of live, unstained platelets: scanning ion conductance microscopy (SICM) and robotic dark-field microscopy (RDM). We demonstrate that both techniques allow for a quantitative evaluation of the morphological features of live adherent platelets. We show that their morphology can be quantified by both techniques using the same geometric parameters and therefore can be directly compared. By imaging the same identical platelets subsequently with SICM and RDM, we found that area, perimeter and circularity of the platelets are directly correlated between SICM and dark-field microscopy (DM), while the fractal dimension (FD) differed between the two microscopy techniques. We show that SICM and RDM are both valuable tools for the ex vivo investigation of the morphology of live platelets, which might contribute to new insights into the physiological and pathophysiological role of platelet spreading.

Nail Damage (Severe Onychodystrophy) Induced by Acrylate Glue: Scanning Electron Microscopy and Energy Dispersive X-Ray Investigations

PubMed Central

Pinteala, Tudor; Chiriac, Anca Eduard; Rosca, Irina; Larese Filon, Francesca; Pinteala, Mariana; Chiriac, Anca; Podoleanu, Cristian; Stolnicu, Simona; Coros, Marius Florin; Coroaba, Adina

2017-01-01

Background Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) techniques have been used in various fields of medical research, including different pathologies of the nails; however, no studies have focused on obtaining high-resolution microscopic images and elemental analysis of disorders caused by synthetic nails and acrylic adhesives. Methods Damaged/injured fingernails caused by the use of acrylate glue and synthetic nails were investigated using SEM and EDX methods. Results SEM and EDX proved that synthetic nails, acrylic glue, and nails damaged by contact with acrylate glue have a different morphology and different composition compared to healthy human nails. Conclusions SEM and EDX analysis can give useful information about the aspects of topography (surface sample), morphology (shape and size), hardness or reflectivity, and the elemental composition of nails. PMID:28232921

Enhancing Ion Migration in Grain Boundaries of Hybrid Organic-Inorganic Perovskites by Chlorine

DOE PAGES

Yang, Bin; Brown, Chance C.; Huang, Jingsong; ...

2017-05-26

Ionicity plays an important role in determining material properties, as well as optoelectronic performance of organometallic trihalide perovskites (OTPs). Ion migration in OTP films has recently been under intensive investigation by various scanning probe microscopy (SPM) techniques. Controversial findings regarding the role of grain boundaries (GBs) associated with ion migration are often encountered, likely as a result of feedback errors and topographic effects common in to SPM. In this work, electron microscopy and spectroscopy (scanning transmission electron microscopy/electron energy loss spectroscopy) are combined with a novel, open-loop, band-excitation, (contact) Kelvin probe force microscopy (BE-KPFM and BE-cKPFM), in conjunction with abmore » initio molecular dynamics simulations to examine the ion behavior in the GBs of CH 3NH 3PbI 3 perovskite films. Furthermore, this combination of diverse techniques provides a deeper understanding of the differences between ion migration within GBs and interior grains in OTP films. Our work demonstrates that ion migration can be significantly enhanced by introducing additional mobile Cl - ions into GBs. The enhancement of ion migration may serve as the first step toward the development of high-performance electrically and optically tunable memristors and synaptic devices.« less

Immunogold scanning electron microscopy can reveal the polysaccharide architecture of xylem cell walls

PubMed Central

Sun, Yuliang; Juzenas, Kevin

2017-01-01

Abstract Immunofluorescence microscopy (IFM) and immunogold transmission electron microscopy (TEM) are the two main techniques commonly used to detect polysaccharides in plant cell walls. Both are important in localizing cell wall polysaccharides, but both have major limitations, such as low resolution in IFM and restricted sample size for immunogold TEM. In this study, we have developed a robust technique that combines immunocytochemistry with scanning electron microscopy (SEM) to study cell wall polysaccharide architecture in xylem cells at high resolution over large areas of sample. Using multiple cell wall monoclonal antibodies (mAbs), this immunogold SEM technique reliably localized groups of hemicellulosic and pectic polysaccharides in the cell walls of five different xylem structures (vessel elements, fibers, axial and ray parenchyma cells, and tyloses). This demonstrates its important advantages over the other two methods for studying cell wall polysaccharide composition and distribution in these structures. In addition, it can show the three-dimensional distribution of a polysaccharide group in the vessel lateral wall and the polysaccharide components in the cell wall of developing tyloses. This technique, therefore, should be valuable for understanding the cell wall polysaccharide composition, architecture and functions of diverse cell types. PMID:28398585

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Bin; Brown, Chance C.; Huang, Jingsong

Ionicity plays an important role in determining material properties, as well as optoelectronic performance of organometallic trihalide perovskites (OTPs). Ion migration in OTP films has recently been under intensive investigation by various scanning probe microscopy (SPM) techniques. Controversial findings regarding the role of grain boundaries (GBs) associated with ion migration are often encountered, likely as a result of feedback errors and topographic effects common in to SPM. In this work, electron microscopy and spectroscopy (scanning transmission electron microscopy/electron energy loss spectroscopy) are combined with a novel, open-loop, band-excitation, (contact) Kelvin probe force microscopy (BE-KPFM and BE-cKPFM), in conjunction with abmore » initio molecular dynamics simulations to examine the ion behavior in the GBs of CH 3NH 3PbI 3 perovskite films. Furthermore, this combination of diverse techniques provides a deeper understanding of the differences between ion migration within GBs and interior grains in OTP films. Our work demonstrates that ion migration can be significantly enhanced by introducing additional mobile Cl - ions into GBs. The enhancement of ion migration may serve as the first step toward the development of high-performance electrically and optically tunable memristors and synaptic devices.« less

Application of Nomarski DIC and cathodoluminescence (CL) microscopy to building materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goetze, J., E-mail: goetze@mineral.tu-freiberg.de

2009-07-15

The present study discusses the potential of an integrated application of Nomarski differential interference contrast and cathodoluminescence microscopy for the investigation of building materials such as natural stone, cement, mortar and concrete. Nomarski differential interference contrast microscopy is a modern technique applied in materials sciences to visualize different phases and/or to image the surface relief on the scale of 50 nm. It is based on the principle of beam splitting by a double-crystal prism split, resulting in the superposition of laterally shifted wave fronts. In cathodoluminescence microscopy, the luminescence signal is excited by an electron beam and is generated bymore » different point defects within the material. Therefore, cathodoluminescence is a powerful method to characterize the defect structure of solid materials, to distinguish different phases and to reveal detailed information about their chemical composition. By combining Nomarski differential interference contrast and cathodoluminescence microscopy, textural, crystallographic and chemical information can be obtained from the same sample area in a polished thin section.« less

Immune Defenses of the Invasive Apple Snail Pomacea canaliculata (Caenogastropoda, Ampullariidae): Phagocytic Hemocytes in the Circulation and the Kidney

PubMed Central

Vega, Israel A.; Castro-Vazquez, Alfredo

2015-01-01

Hemocytes in the circulation and kidney islets, as well as their phagocytic responses to microorganisms and fluorescent beads, have been studied in Pomacea canaliculata, using flow cytometry, light microscopy (including confocal laser scanning microscopy) and transmission electron microscopy (TEM). Three circulating hemocyte types (hyalinocytes, agranulocytes and granulocytes) were distinguished by phase contrast microscopy of living cells and after light and electron microscopy of fixed material. Also, three different populations of circulating hemocytes were separated by flow cytometry, which corresponded to the three hemocyte types. Hyalinocytes showed a low nucleus/cytoplasm ratio, and no apparent granules in stained material, but showed granules of moderate electron density under TEM (L granules) and at least some L granules appear acidic when labeled with LysoTracker Red. Both phagocytic and non-phagocytic hyalinocytes lose most (if not all) L granules when exposed to microorganisms in vitro. The phagosomes formed differed whether hyalinocytes were exposed to yeasts or to Gram positive or Gram negative bacteria. Agranulocytes showed a large nucleus/cytoplasm ratio and few or no granules. Granulocytes showed a low nucleus/cytoplasm ratio and numerous eosinophilic granules after staining. These granules are electron dense and rod-shaped under TEM (R granules). Granulocytes may show merging of R granules into gigantic ones, particularly when exposed to microorganisms. Fluorescent bead exposure of sorted hemocytes showed phagocytic activity in hyalinocytes, agranulocytes and granulocytes, but the phagocytic index was significantly higher in hyalinocytes. Extensive hemocyte aggregates ('islets') occupy most renal hemocoelic spaces and hyalinocyte-like cells are the most frequent component in them. Presumptive glycogen deposits were observed in most hyalinocytes in renal islets (they also occur in the circulation but less frequently) and may mean that hyalinocytes participate in the storage and circulation of this compound. Injection of microorganisms in the foot results in phagocytosis by hemocytes in the islets, and the different phagosomes formed are similar to those in circulating hyalinocytes. Dispersed hemocytes were obtained after kidney collagenase digestion and cell sorting, and they were able to phagocytize fluorescent beads. A role for the kidney as an immune barrier is proposed for this snail. PMID:25893243

Immune Defenses of the Invasive Apple Snail Pomacea canaliculata (Caenogastropoda, Ampullariidae): Phagocytic Hemocytes in the Circulation and the Kidney.

PubMed

Cueto, Juan A; Rodriguez, Cristian; Vega, Israel A; Castro-Vazquez, Alfredo

2015-01-01

Hemocytes in the circulation and kidney islets, as well as their phagocytic responses to microorganisms and fluorescent beads, have been studied in Pomacea canaliculata, using flow cytometry, light microscopy (including confocal laser scanning microscopy) and transmission electron microscopy (TEM). Three circulating hemocyte types (hyalinocytes, agranulocytes and granulocytes) were distinguished by phase contrast microscopy of living cells and after light and electron microscopy of fixed material. Also, three different populations of circulating hemocytes were separated by flow cytometry, which corresponded to the three hemocyte types. Hyalinocytes showed a low nucleus/cytoplasm ratio, and no apparent granules in stained material, but showed granules of moderate electron density under TEM (L granules) and at least some L granules appear acidic when labeled with LysoTracker Red. Both phagocytic and non-phagocytic hyalinocytes lose most (if not all) L granules when exposed to microorganisms in vitro. The phagosomes formed differed whether hyalinocytes were exposed to yeasts or to Gram positive or Gram negative bacteria. Agranulocytes showed a large nucleus/cytoplasm ratio and few or no granules. Granulocytes showed a low nucleus/cytoplasm ratio and numerous eosinophilic granules after staining. These granules are electron dense and rod-shaped under TEM (R granules). Granulocytes may show merging of R granules into gigantic ones, particularly when exposed to microorganisms. Fluorescent bead exposure of sorted hemocytes showed phagocytic activity in hyalinocytes, agranulocytes and granulocytes, but the phagocytic index was significantly higher in hyalinocytes. Extensive hemocyte aggregates ('islets') occupy most renal hemocoelic spaces and hyalinocyte-like cells are the most frequent component in them. Presumptive glycogen deposits were observed in most hyalinocytes in renal islets (they also occur in the circulation but less frequently) and may mean that hyalinocytes participate in the storage and circulation of this compound. Injection of microorganisms in the foot results in phagocytosis by hemocytes in the islets, and the different phagosomes formed are similar to those in circulating hyalinocytes. Dispersed hemocytes were obtained after kidney collagenase digestion and cell sorting, and they were able to phagocytize fluorescent beads. A role for the kidney as an immune barrier is proposed for this snail.

FitEM2EM—Tools for Low Resolution Study of Macromolecular Assembly and Dynamics

PubMed Central

Frankenstein, Ziv; Sperling, Joseph; Sperling, Ruth; Eisenstein, Miriam

2008-01-01

Studies of the structure and dynamics of macromolecular assemblies often involve comparison of low resolution models obtained using different techniques such as electron microscopy or atomic force microscopy. We present new computational tools for comparing (matching) and docking of low resolution structures, based on shape complementarity. The matched or docked objects are represented by three dimensional grids where the value of each grid point depends on its position with regard to the interior, surface or exterior of the object. The grids are correlated using fast Fourier transformations producing either matches of related objects or docking models depending on the details of the grid representations. The procedures incorporate thickening and smoothing of the surfaces of the objects which effectively compensates for differences in the resolution of the matched/docked objects, circumventing the need for resolution modification. The presented matching tool FitEM2EMin successfully fitted electron microscopy structures obtained at different resolutions, different conformers of the same structure and partial structures, ranking correct matches at the top in every case. The differences between the grid representations of the matched objects can be used to study conformation differences or to characterize the size and shape of substructures. The presented low-to-low docking tool FitEM2EMout ranked the expected models at the top. PMID:18974836

Hybrid fluorescence and electron cryo-microscopy for simultaneous electron and photon imaging.

PubMed

Iijima, Hirofumi; Fukuda, Yoshiyuki; Arai, Yoshihiro; Terakawa, Susumu; Yamamoto, Naoki; Nagayama, Kuniaki

2014-01-01

Integration of fluorescence light and transmission electron microscopy into the same device would represent an important advance in correlative microscopy, which traditionally involves two separate microscopes for imaging. To achieve such integration, the primary technical challenge that must be solved regards how to arrange two objective lenses used for light and electron microscopy in such a manner that they can properly focus on a single specimen. To address this issue, both lateral displacement of the specimen between two lenses and specimen rotation have been proposed. Such movement of the specimen allows sequential collection of two kinds of microscopic images of a single target, but prevents simultaneous imaging. This shortcoming has been made up by using a simple optical device, a reflection mirror. Here, we present an approach toward the versatile integration of fluorescence and electron microscopy for simultaneous imaging. The potential of simultaneous hybrid microscopy was demonstrated by fluorescence and electron sequential imaging of a fluorescent protein expressed in cells and cathodoluminescence imaging of fluorescent beads. Copyright © 2013 Elsevier Inc. All rights reserved.

Simplifying Electron Beam Channeling in Scanning Transmission Electron Microscopy (STEM).

PubMed

Wu, Ryan J; Mittal, Anudha; Odlyzko, Michael L; Mkhoyan, K Andre

2017-08-01

Sub-angstrom scanning transmission electron microscopy (STEM) allows quantitative column-by-column analysis of crystalline specimens via annular dark-field images. The intensity of electrons scattered from a particular location in an atomic column depends on the intensity of the electron probe at that location. Electron beam channeling causes oscillations in the STEM probe intensity during specimen propagation, which leads to differences in the beam intensity incident at different depths. Understanding the parameters that control this complex behavior is critical for interpreting experimental STEM results. In this work, theoretical analysis of the STEM probe intensity reveals that intensity oscillations during specimen propagation are regulated by changes in the beam's angular distribution. Three distinct regimes of channeling behavior are observed: the high-atomic-number (Z) regime, in which atomic scattering leads to significant angular redistribution of the beam; the low-Z regime, in which the probe's initial angular distribution controls intensity oscillations; and the intermediate-Z regime, in which the behavior is mixed. These contrasting regimes are shown to exist for a wide range of probe parameters. These results provide a new understanding of the occurrence and consequences of channeling phenomena and conditions under which their influence is strengthened or weakened by characteristics of the electron probe and sample.

Chemistry Viewed through the Eyes of High-Resolution Microscopy.

ERIC Educational Resources Information Center

Beer, Michael; And Others

1981-01-01

This special report, prepared by several chemists working in the field of electron microscopy, provides information regarding the most recent developments in transmission and scanning electron microscopy that have chemical significance. (CS)

Correlative scanning-transmission electron microscopy reveals that a chimeric flavivirus is released as individual particles in secretory vesicles.

PubMed

Burlaud-Gaillard, Julien; Sellin, Caroline; Georgeault, Sonia; Uzbekov, Rustem; Lebos, Claude; Guillaume, Jean-Marc; Roingeard, Philippe

2014-01-01

The intracellular morphogenesis of flaviviruses has been well described, but flavivirus release from the host cell remains poorly documented. We took advantage of the optimized production of an attenuated chimeric yellow fever/dengue virus for vaccine purposes to study this phenomenon by microscopic approaches. Scanning electron microscopy (SEM) showed the release of numerous viral particles at the cell surface through a short-lived process. For transmission electron microscopy (TEM) studies of the intracellular ultrastructure of the small number of cells releasing viral particles at a given time, we developed a new correlative microscopy method: CSEMTEM (for correlative scanning electron microscopy - transmission electron microscopy). CSEMTEM analysis suggested that chimeric flavivirus particles were released as individual particles, in small exocytosis vesicles, via a regulated secretory pathway. Our morphological findings provide new insight into interactions between flaviviruses and cells and demonstrate that CSEMTEM is a useful new method, complementary to SEM observations of biological events by intracellular TEM investigations.

Correlative Scanning-Transmission Electron Microscopy Reveals that a Chimeric Flavivirus Is Released as Individual Particles in Secretory Vesicles

PubMed Central

Burlaud-Gaillard, Julien; Sellin, Caroline; Georgeault, Sonia; Uzbekov, Rustem; Lebos, Claude; Guillaume, Jean-Marc; Roingeard, Philippe

2014-01-01

The intracellular morphogenesis of flaviviruses has been well described, but flavivirus release from the host cell remains poorly documented. We took advantage of the optimized production of an attenuated chimeric yellow fever/dengue virus for vaccine purposes to study this phenomenon by microscopic approaches. Scanning electron microscopy (SEM) showed the release of numerous viral particles at the cell surface through a short-lived process. For transmission electron microscopy (TEM) studies of the intracellular ultrastructure of the small number of cells releasing viral particles at a given time, we developed a new correlative microscopy method: CSEMTEM (for correlative scanning electron microscopy - transmission electron microscopy). CSEMTEM analysis suggested that chimeric flavivirus particles were released as individual particles, in small exocytosis vesicles, via a regulated secretory pathway. Our morphological findings provide new insight into interactions between flaviviruses and cells and demonstrate that CSEMTEM is a useful new method, complementary to SEM observations of biological events by intracellular TEM investigations. PMID:24681578

Simultaneous Correlative Scanning Electron and High-NA Fluorescence Microscopy

PubMed Central

Liv, Nalan; Zonnevylle, A. Christiaan; Narvaez, Angela C.; Effting, Andries P. J.; Voorneveld, Philip W.; Lucas, Miriam S.; Hardwick, James C.; Wepf, Roger A.; Kruit, Pieter; Hoogenboom, Jacob P.

2013-01-01

Correlative light and electron microscopy (CLEM) is a unique method for investigating biological structure-function relations. With CLEM protein distributions visualized in fluorescence can be mapped onto the cellular ultrastructure measured with electron microscopy. Widespread application of correlative microscopy is hampered by elaborate experimental procedures related foremost to retrieving regions of interest in both modalities and/or compromises in integrated approaches. We present a novel approach to correlative microscopy, in which a high numerical aperture epi-fluorescence microscope and a scanning electron microscope illuminate the same area of a sample at the same time. This removes the need for retrieval of regions of interest leading to a drastic reduction of inspection times and the possibility for quantitative investigations of large areas and datasets with correlative microscopy. We demonstrate Simultaneous CLEM (SCLEM) analyzing cell-cell connections and membrane protrusions in whole uncoated colon adenocarcinoma cell line cells stained for actin and cortactin with AlexaFluor488. SCLEM imaging of coverglass-mounted tissue sections with both electron-dense and fluorescence staining is also shown. PMID:23409024

Cell adhesion on nanotextured slippery superhydrophobic substrates.

PubMed

Di Mundo, Rosa; Nardulli, Marina; Milella, Antonella; Favia, Pietro; d'Agostino, Riccardo; Gristina, Roberto

2011-04-19

In this work, the response of Saos2 cells to polymeric surfaces with different roughness/density of nanometric dots produced by a tailored plasma-etching process has been studied. Topographical features have been evaluated by atomic force microscopy, while wetting behavior, in terms of water-surface adhesion energy, has been evaluated by measurements of drop sliding angle. Saos2 cytocompatibility has been investigated by scanning electron microscopy, fluorescent microscopy, and optical microscopy. The similarity in outer chemical composition has allowed isolation of the impact of the topographical features on cellular behavior. The results indicate that Saos2 cells respond differently to surfaces with different nanoscale topographical features, clearly showing a certain inhibition in cell adhesion when the nanoscale is particularly small. This effect appears to be attenuated in surfaces with relatively bigger nanofeatures, though these express a more pronounced slippery/dry wetting character. © 2011 American Chemical Society

Ultrafast structural and electronic dynamics of the metallic phase in a layered manganite

PubMed Central

Piazza, L.; Ma, C.; Yang, H. X.; Mann, A.; Zhu, Y.; Li, J. Q.; Carbone, F.

2013-01-01

The transition between different states in manganites can be driven by various external stimuli. Controlling these transitions with light opens the possibility to investigate the microscopic path through which they evolve. We performed femtosecond (fs) transmission electron microscopy on a bi-layered manganite to study its response to ultrafast photoexcitation. We show that a photoinduced temperature jump launches a pressure wave that provokes coherent oscillations of the lattice parameters, detected via ultrafast electron diffraction. Their impact on the electronic structure are monitored via ultrafast electron energy loss spectroscopy, revealing the dynamics of the different orbitals in response to specific structural distortions. PMID:26913564

Writing silica structures in liquid with scanning transmission electron microscopy.

PubMed

van de Put, Marcel W P; Carcouët, Camille C M C; Bomans, Paul H H; Friedrich, Heiner; de Jonge, Niels; Sommerdijk, Nico A J M

2015-02-04

Silica nanoparticles are imaged in solution with scanning transmission electron microscopy (STEM) using a liquid cell with silicon nitride (SiN) membrane windows. The STEM images reveal that silica structures are deposited in well-defined patches on the upper SiN membranes upon electron beam irradiation. The thickness of the deposits is linear with the applied electron dose. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) demonstrate that the deposited patches are a result of the merging of the original 20 nm-diameter nanoparticles, and that the related surface roughness depends on the electron dose rate used. Using this approach, sub-micrometer scale structures are written on the SiN in liquid by controlling the electron exposure as function of the lateral position. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Focus on membrane differentiation and membrane domains in the prokaryotic cell.

PubMed

Boekema, Egbert J; Scheffers, Dirk-Jan; van Bezouwen, Laura S; Bolhuis, Henk; Folea, I Mihaela

2013-01-01

A summary is presented of membrane differentiation in the prokaryotic cell, with an emphasis on the organization of proteins in the plasma/cell membrane. Many species belonging to the Eubacteria and Archaea have special membrane domains and/or membrane proliferation, which are vital for different cellular processes. Typical membrane domains are found in bacteria where a specific membrane protein is abundantly expressed. Lipid rafts form another example. Despite the rareness of conventional organelles as found in eukaryotes, some bacteria are known to have an intricate internal cell membrane organization. Membrane proliferation can be divided into curvature and invaginations which can lead to internal compartmentalization. This study discusses some of the clearest examples of bacteria with such domains and internal membranes. The need for membrane specialization is highest among the heterogeneous group of bacteria which harvest light energy, such as photosynthetic bacteria and halophilic archaea. Most of the highly specialized membranes and domains, such as the purple membrane, chromatophore and chlorosome, are found in these autotrophic organisms. Otherwise the need for membrane differentiation is lower and variable, except for those structures involved in cell division. Microscopy techniques have given essential insight into bacterial membrane morphology. As microscopy will further contribute to the unraveling of membrane organization in the years to come, past and present technology in electron microscopy and light microscopy is discussed. Electron microscopy was the first to unravel bacterial morphology because it can directly visualize membranes with inserted proteins, which no other technique can do. Electron microscopy techniques developed in the 1950s and perfected in the following decades involve the thin sectioning and freeze fractioning of cells. Several studies from the golden age of these techniques show amazing examples of cell membrane morphology. More recently, light microscopy in combination with the use of fluorescent dyes has become an attractive technique for protein localization with the natural membrane. However, the resolution problem in light microscopy remains and overinterpretation of observed phenomena is a pitfall. Thus, light microscopy as a stand-alone technique is not sufficient to prove, for instance, the long-range helical distribution of proteins in membrane such as MinD spirals in Bacillus subtilis. Electron tomography is an emerging electron microscopy technique that can provide three-dimensional reconstructions of small, nonchemically fixed bacteria. It will become a useful tool for studying prokaryotic membranes in more detail and is expected to collect information complementary to those of advanced light microscopy. Together, microscopy techniques can meet the challenge of the coming years: to specify membrane structures in more detail and to bring them to the level of specific protein-protein interactions. Copyright © 2013 S. Karger AG, Basel.

Differential localization of SAP102 and PSD-95 is revealed in hippocampal spines using super-resolution light microscopy.

PubMed

Zheng, Chan-Ying; Wang, Ya-Xia; Kachar, Bechara; Petralia, Ronald S

2011-01-01

Synapse-associated protein 102 (SAP102) and postsynaptic density 95 (PSD-95) are two major cytoskeleton proteins in the postsynaptic density (PSD). Both of them belong to the membrane-associated guanylate kinase (MAGUK) family, which clusters and anchors glutamate receptors and other proteins at synapses. In our previous study, we found that SAP102 and PSD-95 have different distributions, using combined light/electron microscopy (LM/EM) methods.1 Here, we double labeled endogenous SAP102 and PSD-95 in mature hippocampal neurons, and then took images by two different kinds of super resolution microscopy-Stimulated Emission Depletion microscopy (STED) and DeltaVision OMX 3D super resolution microscopy. We found that our 2D and 3D super resolution data were consistent with our previous LM/EM data, showing significant differences in the localization of SAP102 and PSD-95 in spines: SAP102 is distributed in both the PSD and cytoplasm of spines, while PSD-95 is concentrated only in the PSD area. These results indicate functional differences between SAP102 and PSD-95 in synaptic organization and plasticity.

Minimal resin embedding of multicellular specimens for targeted FIB-SEM imaging.

PubMed

Schieber, Nicole L; Machado, Pedro; Markert, Sebastian M; Stigloher, Christian; Schwab, Yannick; Steyer, Anna M

2017-01-01

Correlative light and electron microscopy (CLEM) is a powerful tool to perform ultrastructural analysis of targeted tissues or cells. The large field of view of the light microscope (LM) enables quick and efficient surveys of the whole specimen. It is also compatible with live imaging, giving access to functional assays. CLEM protocols take advantage of the features to efficiently retrace the position of targeted sites when switching from one modality to the other. They more often rely on anatomical cues that are visible both by light and electron microscopy. We present here a simple workflow where multicellular specimens are embedded in minimal amounts of resin, exposing their surface topology that can be imaged by scanning electron microscopy (SEM). LM and SEM both benefit from a large field of view that can cover whole model organisms. As a result, targeting specific anatomic locations by focused ion beam-SEM (FIB-SEM) tomography becomes straightforward. We illustrate this application on three different model organisms, used in our laboratory: the zebrafish embryo Danio rerio, the marine worm Platynereis dumerilii, and the dauer larva of the nematode Caenorhabditis elegans. Here we focus on the experimental steps to reduce the amount of resin covering the samples and to image the specimens inside an FIB-SEM. We expect this approach to have widespread applications for volume electron microscopy on multiple model organisms. Copyright © 2017 Elsevier Inc. All rights reserved.

Navigating 3D electron microscopy maps with EM-SURFER.

PubMed

Esquivel-Rodríguez, Juan; Xiong, Yi; Han, Xusi; Guang, Shuomeng; Christoffer, Charles; Kihara, Daisuke

2015-05-30

The Electron Microscopy DataBank (EMDB) is growing rapidly, accumulating biological structural data obtained mainly by electron microscopy and tomography, which are emerging techniques for determining large biomolecular complex and subcellular structures. Together with the Protein Data Bank (PDB), EMDB is becoming a fundamental resource of the tertiary structures of biological macromolecules. To take full advantage of this indispensable resource, the ability to search the database by structural similarity is essential. However, unlike high-resolution structures stored in PDB, methods for comparing low-resolution electron microscopy (EM) density maps in EMDB are not well established. We developed a computational method for efficiently searching low-resolution EM maps. The method uses a compact fingerprint representation of EM maps based on the 3D Zernike descriptor, which is derived from a mathematical series expansion for EM maps that are considered as 3D functions. The method is implemented in a web server named EM-SURFER, which allows users to search against the entire EMDB in real-time. EM-SURFER compares the global shapes of EM maps. Examples of search results from different types of query structures are discussed. We developed EM-SURFER, which retrieves structurally relevant matches for query EM maps from EMDB within seconds. The unique capability of EM-SURFER to detect 3D shape similarity of low-resolution EM maps should prove invaluable in structural biology.

Automotive airborne brake wear debris nanoparticles and cytokinesis-block micronucleus assay in peripheral blood lymphocytes: A pilot study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kazimirova, Alena, E-mail: alena.kazimirova@szu.sk; Peikertova, Pavlina; IT4Innovations, VŠB – Technical University of Ostrava, 17. listopadu 15, 708 33 Ostrava-Poruba

Motor vehicle exhaust and non-exhaust processes play a significant role in environmental pollution, as they are a source of the finest particulate matter. Emissions from non-exhaust processes include wear-products of brakes, tires, automotive hardware, road surface, and traffic signs, but still are paid little attention to. Automotive friction composites for brake pads are composite materials which may consist of potentially hazardous materials and there is a lack of information regarding the potential influence of the brake wear debris (BWD) on the environment, especially on human health. Thus, we focused our study on the genotoxicity of the airborne fraction of BWDmore » using a brake pad model representing an average low-metallic formulation available in the EU market. BWD was generated in the laboratory by a full-scale brake dynamometer and characterized by Raman microspectroscopy, scanning electron microscopy, and transmission electron microscopy showing that it contains nano-sized crystalline metal-based particles. Genotoxicity tested in human lymphocytes in different testing conditions showed an increase in frequencies of micronucleated binucleated cells (MNBNCs) exposed for 48 h to BWD nanoparticles (NPs) (with 10% of foetal calf serum in culture medium) compared with lymphocytes exposed to medium alone, statistically significant only at the concentration 3 µg/cm{sup 2} (p=0.032). - Highlights: • BWD was characterized by Raman microspectroscopy, scanning electron microscopy, and transmission electron microscopy. • Our result showed that BWD contains crystalline metal NPs. • Two different protocols for CBMN assay were used to study of genotoxicity of BWD. • We found significantly increased frequency of MNBNCs after 48 h exposure of BWD (with 10% of foetal calf serum in culture media) at the concentration 3 µg/cm{sup 2}.« less

X-ray microscopy as an approach to increasing accuracy and efficiency of serial block-face imaging for correlated light and electron microscopy of biological specimens.

PubMed

Bushong, Eric A; Johnson, Donald D; Kim, Keun-Young; Terada, Masako; Hatori, Megumi; Peltier, Steven T; Panda, Satchidananda; Merkle, Arno; Ellisman, Mark H

2015-02-01

The recently developed three-dimensional electron microscopic (EM) method of serial block-face scanning electron microscopy (SBEM) has rapidly established itself as a powerful imaging approach. Volume EM imaging with this scanning electron microscopy (SEM) method requires intense staining of biological specimens with heavy metals to allow sufficient back-scatter electron signal and also to render specimens sufficiently conductive to control charging artifacts. These more extreme heavy metal staining protocols render specimens light opaque and make it much more difficult to track and identify regions of interest (ROIs) for the SBEM imaging process than for a typical thin section transmission electron microscopy correlative light and electron microscopy study. We present a strategy employing X-ray microscopy (XRM) both for tracking ROIs and for increasing the efficiency of the workflow used for typical projects undertaken with SBEM. XRM was found to reveal an impressive level of detail in tissue heavily stained for SBEM imaging, allowing for the identification of tissue landmarks that can be subsequently used to guide data collection in the SEM. Furthermore, specific labeling of individual cells using diaminobenzidine is detectable in XRM volumes. We demonstrate that tungsten carbide particles or upconverting nanophosphor particles can be used as fiducial markers to further increase the precision and efficiency of SBEM imaging.

X-ray Microscopy as an Approach to Increasing Accuracy and Efficiency of Serial Block-face Imaging for Correlated Light and Electron Microscopy of Biological Specimens

PubMed Central

Bushong, Eric A.; Johnson, Donald D.; Kim, Keun-Young; Terada, Masako; Hatori, Megumi; Peltier, Steven T.; Panda, Satchidananda; Merkle, Arno; Ellisman, Mark H.

2015-01-01

The recently developed three-dimensional electron microscopic (EM) method of serial block-face scanning electron microscopy (SBEM) has rapidly established itself as a powerful imaging approach. Volume EM imaging with this scanning electron microscopy (SEM) method requires intense staining of biological specimens with heavy metals to allow sufficient back-scatter electron signal and also to render specimens sufficiently conductive to control charging artifacts. These more extreme heavy metal staining protocols render specimens light opaque and make it much more difficult to track and identify regions of interest (ROIs) for the SBEM imaging process than for a typical thin section transmission electron microscopy correlative light and electron microscopy study. We present a strategy employing X-ray microscopy (XRM) both for tracking ROIs and for increasing the efficiency of the workflow used for typical projects undertaken with SBEM. XRM was found to reveal an impressive level of detail in tissue heavily stained for SBEM imaging, allowing for the identification of tissue landmarks that can be subsequently used to guide data collection in the SEM. Furthermore, specific labeling of individual cells using diaminobenzidine is detectable in XRM volumes. We demonstrate that tungsten carbide particles or upconverting nanophosphor particles can be used as fiducial markers to further increase the precision and efficiency of SBEM imaging. PMID:25392009

Correlative cryo-fluorescence light microscopy and cryo-electron tomography of Streptomyces.

PubMed

Koning, Roman I; Celler, Katherine; Willemse, Joost; Bos, Erik; van Wezel, Gilles P; Koster, Abraham J

2014-01-01

Light microscopy and electron microscopy are complementary techniques that in a correlative approach enable identification and targeting of fluorescently labeled structures in situ for three-dimensional imaging at nanometer resolution. Correlative imaging allows electron microscopic images to be positioned in a broader temporal and spatial context. We employed cryo-correlative light and electron microscopy (cryo-CLEM), combining cryo-fluorescence light microscopy and cryo-electron tomography, on vitrified Streptomyces bacteria to study cell division. Streptomycetes are mycelial bacteria that grow as long hyphae and reproduce via sporulation. On solid media, Streptomyces subsequently form distinct aerial mycelia where cell division leads to the formation of unigenomic spores which separate and disperse to form new colonies. In liquid media, only vegetative hyphae are present divided by noncell separating crosswalls. Their multicellular life style makes them exciting model systems for the study of bacterial development and cell division. Complex intracellular structures have been visualized with transmission electron microscopy. Here, we describe the methods for cryo-CLEM that we applied for studying Streptomyces. These methods include cell growth, fluorescent labeling, cryo-fixation by vitrification, cryo-light microscopy using a Linkam cryo-stage, image overlay and relocation, cryo-electron tomography using a Titan Krios, and tomographic reconstruction. Additionally, methods for segmentation, volume rendering, and visualization of the correlative data are described. © 2014 Elsevier Inc. All rights reserved.

Morphology, Structure, and Ontogeny of Trichomes of the Grape Genus (Vitis, Vitaceae).

PubMed

Ma, Zhi-Yao; Wen, Jun; Ickert-Bond, Stefanie M; Chen, Long-Qing; Liu, Xiu-Qun

2016-01-01

Trichomes are widely distributed on surfaces of different organs in the grape genus Vitis and are of taxonomic utility. To explore the morphology, structure and ontogeny of Vitis trichomes, we investigated the diversity and distribution of trichomes in 34 species of Vitis. Two main types of trichomes in Vitis are documented: non-glandular and glandular. Within non-glandular trichomes, ribbon and simple trichomes are found on different vegetative plant organs. The morphology and ontogeny of these types of trichomes are further examined with light microscopy and scanning electron microscopy. The ultrastructure of the glandular trichomes is explored with transmission electron microscopy. The ribbon trichomes are twisted, greatly elongated and unicellular, and this trichome type may be a morphological synapomorphy of Vitis and its closest tropical relative Ampelocissus and Pterisanthes in Vitaceae. The simple trichomes are documented in most species sampled in the genus. The glandular trichomes are multicellular, non-vascularized and composed of both epidermis and subjacent layers. We show that prickles occurring along the stems and petioles of Vitis davidii are modified glandular trichomes. We observed that glandular trichomes of V. romanetii secrete mucilage and volatile substances which trap insectes on the glands. Transmission electron microscopy indicates that metabolic products accumulate in vacuoles, the cytoplasm and intercellular spaces. We infer that glandular trichomes and young prickles are involved in the secretion of these metabolic products and the intercellular spaces may be the places of temporary storage of these secretions.

A Versatile High-Vacuum Cryo-transfer System for Cryo-microscopy and Analytics

PubMed Central

Tacke, Sebastian; Krzyzanek, Vladislav; Nüsse, Harald; Wepf, Roger Albert; Klingauf, Jürgen; Reichelt, Rudolf

2016-01-01

Cryogenic microscopy methods have gained increasing popularity, as they offer an unaltered view on the architecture of biological specimens. As a prerequisite, samples must be handled under cryogenic conditions below their recrystallization temperature, and contamination during sample transfer and handling must be prevented. We present a high-vacuum cryo-transfer system that streamlines the entire handling of frozen-hydrated samples from the vitrification process to low temperature imaging for scanning transmission electron microscopy and transmission electron microscopy. A template for cryo-electron microscopy and multimodal cryo-imaging approaches with numerous sample transfer steps is presented. PMID:26910419

Characterization of TiN, TiC and Ti(C,N) in titanium-alloyed ferritic chromium steels focusing on the significance of different particle morphologies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michelic, S.K., E-mail: susanne.michelic@unileoben.ac.at; Loder, D.; Reip, T.

2015-02-15

Titanium-alloyed ferritic chromium steels are a competitive option to classical austenitic stainless steels owing to their similar corrosion resistance. The addition of titanium significantly influences their final steel cleanliness. The present contribution focuses on the detailed metallographic characterization of titanium nitrides, titanium carbides and titanium carbonitrides with regard to their size, morphology and composition. The methods used are manual and automated Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy as well as optical microscopy. Additional thermodynamic calculations are performed to explain the precipitation procedure of the analyzed titanium nitrides. The analyses showed that homogeneous nucleation is decisive at an earlymore » process stage after the addition of titanium. Heterogeneous nucleation gets crucial with ongoing process time and essentially influences the final inclusion size of titanium nitrides. A detailed investigation of the nuclei for heterogeneous nucleation with automated Scanning Electron Microscopy proved to be difficult due to their small size. Manual Scanning Electron Microscopy and optical microscopy have to be applied. Furthermore, it was found that during solidification an additional layer around an existing titanium nitride can be formed which changes the final inclusion morphology significantly. These layers are also characterized in detail. Based on these different inclusion morphologies, in combination with thermodynamic results, tendencies regarding the formation and modification time of titanium containing inclusions in ferritic chromium steels are derived. - Graphical abstract: Display Omitted - Highlights: • The formation and modification of TiN in the steel 1.4520 was examined. • Heterogeneous nucleation essentially influences the final steel cleanliness. • In most cases heterogeneous nuclei in TiN inclusions are magnesium based. • Particle morphology provides important information on inclusion formation.« less

The New Electron Microscopy: Cells and Molecules in Three Dimensions | Poster

Cancer.gov

NCI recently announced the launch of the new National Cryo-Electron Microscopy Facility (NCEF) at the Frederick National Laboratory for Cancer Research (FNLCR). The launch comes while cryo-electron microscopy (cryo-EM) is enjoying the spotlight as a newly emerging, rapidly evolving technology with the potential to revolutionize the field of structural biology. Read more...

Near-infrared branding efficiently correlates light and electron microscopy.

PubMed

Bishop, Derron; Nikić, Ivana; Brinkoetter, Mary; Knecht, Sharmon; Potz, Stephanie; Kerschensteiner, Martin; Misgeld, Thomas

2011-06-05

The correlation of light and electron microscopy of complex tissues remains a major challenge. Here we report near-infrared branding (NIRB), which facilitates such correlation by using a pulsed, near-infrared laser to create defined fiducial marks in three dimensions in fixed tissue. As these marks are fluorescent and can be photo-oxidized to generate electron contrast, they can guide re-identification of previously imaged structures as small as dendritic spines by electron microscopy.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kulawik, K., E-mail: kulawik@agh.edu.pl; Buffat, P.A., E-mail: philippe.buffat@epfl.ch; Ecole Polytechnique Fédérale de Lausanne, CIME, Station 12, CH-1015 Lausanne Switzerland

Microstructural characterization of Inconel 718 superalloy after three different heat treatment variants was performed by electron microscopy and electron tomography techniques, taking advantage of recent development in quantitative electron microscopy. Distribution maps of the chemical elements, collected by ChemiSTEM™ EDX system, offer a clear contrast between γ′, γ″, and the γ matrix. It was found that the γ′ phase contains mainly Ni, Al, and Ti, while the γ″ phase contains Ni, Nb, and Ti. Thus application of the Al and Nb STEM–EDX elemental maps enables identification and size measurements of γ′ and γ″ nanoparticles. 3D morphology of γ′ and γ″more » precipitates was examined by electron microscopy and FIB–SEM tomography. Employed methods revealed that in all three heat treatment variants the γ′ particles are almost spheroidal while the γ″ precipitates are mainly elongated-disc shaped. However, the precipitate sizes differed for each variant contributing to differences in the yield strength. Tomographic images were used for estimation of the volume fraction of the both strengthening phases. - Highlights: • ChemiSTEM™ EDX elemental maps bring a fast mean to differentiate γ′ and γ″ particles. • Such maps enable for the explicit size measurements of γ′ and γ″ nanoparticles. • Explicit γ′ and γ″ phases total volume fraction was measured employing FIB–SEM. • γ′/γ″ co-precipitates and sandwich-like γ′/γ″/γ′ particles were present. • HRSTEM-HAADF imaging revealed atomic columns of the γ′/γ″ co-precipitates.« less

Detailed characterisation of focused ion beam induced lateral damage on silicon carbide samples by electrical scanning probe microscopy and transmission electron microscopy

NASA Astrophysics Data System (ADS)

Stumpf, F.; Abu Quba, A. A.; Singer, P.; Rumler, M.; Cherkashin, N.; Schamm-Chardon, S.; Cours, R.; Rommel, M.

2018-03-01

The lateral damage induced by focused ion beam on silicon carbide was characterized using electrical scanning probe microscopy (SPM), namely, scanning spreading resistance microscopy and conductive atomic force microscopy (c-AFM). It is shown that the damage exceeds the purposely irradiated circles with a radius of 0.5 μm by several micrometres, up to 8 μm for the maximum applied ion dose of 1018 cm-2. Obtained SPM results are critically compared with earlier findings on silicon. For doses above the amorphization threshold, in both cases, three different areas can be distinguished. The purposely irradiated area exhibits resistances smaller than the non-affected substrate. A second region with strongly increasing resistance and a maximum saturation value surrounds it. The third region shows the transition from maximum resistance to the base resistance of the unaffected substrate. It correlates to the transition from amorphized to defect-rich to pristine crystalline substrate. Additionally, conventional transmission electron microscopy (TEM) and annular dark-field STEM were used to complement and explain the SPM results and get a further understanding of the defect spreading underneath the surface. Those measurements also show three different regions that correlate well with the regions observed from electrical SPM. TEM results further allow to explain observed differences in the electrical results for silicon and silicon carbide which are most prominent for ion doses above 3 × 1016 cm-2. Furthermore, the conventional approach to perform current-voltage measurements by c-AFM was critically reviewed and several improvements for measurement and analysis process were suggested that result in more reliable and impactful c-AFM data.

Neuroanatomy from Mesoscopic to Nanoscopic Scales: An Improved Method for the Observation of Semithin Sections by High-Resolution Scanning Electron Microscopy

PubMed Central

Rodríguez, José-Rodrigo; Turégano-López, Marta; DeFelipe, Javier; Merchán-Pérez, Angel

2018-01-01

Semithin sections are commonly used to examine large areas of tissue with an optical microscope, in order to locate and trim the regions that will later be studied with the electron microscope. Ideally, the observation of semithin sections would be from mesoscopic to nanoscopic scales directly, instead of using light microscopy and then electron microscopy (EM). Here we propose a method that makes it possible to obtain high-resolution scanning EM images of large areas of the brain in the millimeter to nanometer range. Since our method is compatible with light microscopy, it is also feasible to generate hybrid light and electron microscopic maps. Additionally, the same tissue blocks that have been used to obtain semithin sections can later be used, if necessary, for transmission EM, or for focused ion beam milling and scanning electron microscopy (FIB-SEM). PMID:29568263

Neuroanatomy from Mesoscopic to Nanoscopic Scales: An Improved Method for the Observation of Semithin Sections by High-Resolution Scanning Electron Microscopy.

PubMed

Rodríguez, José-Rodrigo; Turégano-López, Marta; DeFelipe, Javier; Merchán-Pérez, Angel

2018-01-01

Semithin sections are commonly used to examine large areas of tissue with an optical microscope, in order to locate and trim the regions that will later be studied with the electron microscope. Ideally, the observation of semithin sections would be from mesoscopic to nanoscopic scales directly, instead of using light microscopy and then electron microscopy (EM). Here we propose a method that makes it possible to obtain high-resolution scanning EM images of large areas of the brain in the millimeter to nanometer range. Since our method is compatible with light microscopy, it is also feasible to generate hybrid light and electron microscopic maps. Additionally, the same tissue blocks that have been used to obtain semithin sections can later be used, if necessary, for transmission EM, or for focused ion beam milling and scanning electron microscopy (FIB-SEM).

Advantages of indium-tin oxide-coated glass slides in correlative scanning electron microscopy applications of uncoated cultured cells.

PubMed

Pluk, H; Stokes, D J; Lich, B; Wieringa, B; Fransen, J

2009-03-01

A method of direct visualization by correlative scanning electron microscopy (SEM) and fluorescence light microscopy of cell structures of tissue cultured cells grown on conductive glass slides is described. We show that by growing cells on indium-tin oxide (ITO)-coated glass slides, secondary electron (SE) and backscatter electron (BSE) images of uncoated cells can be obtained in high-vacuum SEM without charging artefacts. Interestingly, we observed that BSE imaging is influenced by both accelerating voltage and ITO coating thickness. By combining SE and BSE imaging with fluorescence light microscopy imaging, we were able to reveal detailed features of actin cytoskeletal and mitochondrial structures in mouse embryonic fibroblasts. We propose that the application of ITO glass as a substrate for cell culture can easily be extended and offers new opportunities for correlative light and electron microscopy studies of adherently growing cells.

Decorating multi-walled carbon nanotubes with quantum dots for construction of multi-color fluorescent nanoprobes.

PubMed

Jia, Nengqin; Lian, Qiong; Tian, Zhong; Duan, Xin; Yin, Min; Jing, Lihong; Chen, Shouhui; Shen, Hebai; Gao, Mingyuan

2010-01-29

Novel multi-color fluorescent nanoprobes were prepared by electrostatically assembling differently sized CdTe quantum dots on polyethylenimine (PEI) functionalized multi-walled carbon nanotubes (MWNTs). The structural and optical properties of the nano-assemblies (MWNTs-PEI-CdTe) were characterized by transmission electron microscopy (TEM), electron diffraction spectra (EDS), Raman spectroscopy, confocal microscopy and photoluminescence spectroscopy (PL), respectively. Electrochemical impedance spectroscopy (EIS) was also applied to investigate the electrostatic assembling among oxidized MWNTs, PEI and CdTe. Furthermore, confocal fluorescence microscopy was used to monitor the nano-assemblies' delivery into tumor cells. It was found that the nano-assemblies exhibit efficient intracellular transporting and strong intracellular tracking. These properties would make this luminescent nano-assembly an excellent building block for the construction of intracellular nanoprobes, which could hold great promise for biomedical applications.

Pollen and stigma morphology of some Phaseoleae species (Leguminosae) with different pollinators.

PubMed

Basso-Alves, J P; Agostini, K; Teixeira, S de Pádua

2011-07-01

Pollen transport to a receptive stigma can be facilitated through different pollinators, which submits the pollen to different selection pressures. This study aimed to associate pollen and stigma morphology with zoophily in species of the tribe Phaseoleae. Species of the genera Erythrina, Macroptilium and Mucuna with different pollinators were chosen. Pollen grains and stigmas were examined under light microscopy (anatomy), scanning electronic microscopy (surface analyses) and transmission electronic microscopy (ultrastructure). The three genera differ in terms of pollen wall ornamentation, pollen size, pollen aperture, thickness of the pollen wall, amount of pollenkitt, pollen hydration status and dominant reserves within the pollen grain, while species within each genus are very similar in most studied characteristics. Most of these features lack relationships to pollinator type, especially in Erythrina and Mucuna. Pollen reserves are discussed on a broad scale, according to the occurrence of protein in the pollen of invertebrate- or vertebrate-pollinated species. Some pollen characteristics are more associated to semi-dry stigma requirements. This apical, compact, cuticularised and secretory stigma occurs in all species investigated. We conclude that data on pollen and stigma structure should be included together with those on floral morphology and pollinator behaviour for the establishment of functional pollination classes. © 2010 German Botanical Society and The Royal Botanical Society of the Netherlands.

Rapid and easy identification of Illicium verum Hook. f. and its adulterant Illicium anisatum Linn. by fluorescent microscopy and gas chromatography.

PubMed

Joshi, Vaishali C; Srinivas, Pullela V; Khan, Ikhlas A

2005-01-01

Illicium verum Hook. f. is used as an herbal tea to treat colic pain in infants. Reports suggest that Star anise herbal tea may be adulterated with Illicium anisatum Linn. A short and rapid method using microscopy and gas chromatography (GC) was developed to detect I. anisatum Linn., an adulterant in the powdered mixture of I. verum. Anatomical differences in the epicarp cells of I. verum and I. anisatum fruits were clearly defined as examined under fluorescent microscopy and scanning electron microscopy. A GC method was developed for quick identification of possible I. anisatum adulteration with I. verum.

Selective Growth of Metallic and Semiconducting Single Walled Carbon Nanotubes on Textured Silicon.

PubMed

Jang, Mira; Lee, Jongtaek; Park, Teahee; Lee, Junyoung; Yang, Jonghee; Yi, Whikun

2016-03-01

We fabricated the etched Si substrate having the pyramidal pattern size from 0.5 to 4.2 μm by changing the texturing process parameters, i.e., KOH concentration, etching time, and temperature. Single walled carbon nanotubes (SWNTs) were then synthesized on the etched Si substrates with different pyramidal pattern by chemical vapor deposition. We investigated the optical and electronic properties of SWNT film grown on the etched Si substrates of different morphology by using scanning electron microscopy, Raman spectroscopy and conducting probe atomic force microscopy. We confirmed that the morphology of substrate strongly affected the selective growth of the SWNT film. Semiconducting SWNTs were formed on larger pyramidal sized Si wafer with higher ratio compared with SWNTs on smaller pyramidal sized Si.

Study of liquid crystal space groups using controlled tilting with cryogenic transmission electron microscopy.

PubMed

Sagalowicz, Laurent; Acquistapace, Simone; Watzke, Heribert J; Michel, Martin

2007-11-20

We developed a method that enables differentiation between liquid crystalline-phase particles corresponding to different space groups. It consists of controlled tilting of the specimen to observe different orientations of the same particle using cryogenic transmission electron microscopy. This leads to the visualization of lattice planes (or reflections) that are present for a given structure and absent for the other one(s) and that give information on liquid crystalline structures and their space groups. In particular, we show that we can unambiguously distinguish among particles having the inverted micellar cubic (space group Fd(3)m, 227), the inverted bicontinuous gyroid (space group Ia(3)d, 230), the inverted bicontinuous diamond (space group Pn(3)m, 224), and the inverted bicontinuous primitive cubic structure (space group Im(3)m, 229).

Retraction: Using the Medipix3 detector for direct electron imaging in the range 60 keV to 200 keV in electron microscopy Retraction: Using the Medipix3 detector for direct electron imaging in the range 60 keV to 200 keV in electron microscopy

NASA Astrophysics Data System (ADS)

Mir, J. A.; Plackett, R.; Shipsey, I.; dos Santos, J. M. F.

2018-01-01

The paper "Using the Medipix3 detector for direct electron imaging in the range 60keV to 200keV in electron microscopy" by J.A. Mir, R. Plackett, I. Shipsey and J.M.F. dos Santos has been retracted following the authors' request on the basis of the existence of a disagreement about the ownership of the data, to prevent conflict between collaborators.

Spatial Resolution in Scanning Electron Microscopy and Scanning Transmission Electron Microscopy Without a Specimen Vacuum Chamber.

PubMed

Nguyen, Kayla X; Holtz, Megan E; Richmond-Decker, Justin; Muller, David A

2016-08-01

A long-standing goal of electron microscopy has been the high-resolution characterization of specimens in their native environment. However, electron optics require high vacuum to maintain an unscattered and focused probe, a challenge for specimens requiring atmospheric or liquid environments. Here, we use an electron-transparent window at the base of a scanning electron microscope's objective lens to separate column vacuum from the specimen, enabling imaging under ambient conditions, without a specimen vacuum chamber. We demonstrate in-air imaging of specimens at nanoscale resolution using backscattered scanning electron microscopy (airSEM) and scanning transmission electron microscopy. We explore resolution and contrast using Monte Carlo simulations and analytical models. We find that nanometer-scale resolution can be obtained at gas path lengths up to 400 μm, although contrast drops with increasing gas path length. As the electron-transparent window scatters considerably more than gas at our operating conditions, we observe that the densities and thicknesses of the electron-transparent window are the dominant limiting factors for image contrast at lower operating voltages. By enabling a variety of detector configurations, the airSEM is applicable to a wide range of environmental experiments including the imaging of hydrated biological specimens and in situ chemical and electrochemical processes.

Spatial Resolution in Scanning Electron Microscopy and Scanning Transmission Electron Microscopy Without a Specimen Vacuum Chamber

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen, Kayla X.; Holtz, Megan E.; Richmond-Decker, Justin

2016-07-25

Abstract A long-standing goal of electron microscopy has been the high-resolution characterization of specimens in their native environment. However, electron optics require high vacuum to maintain an unscattered and focused probe, a challenge for specimens requiring atmospheric or liquid environments. Here, we use an electron-transparent window at the base of a scanning electron microscope’s objective lens to separate column vacuum from the specimen, enabling imaging under ambient conditions, without a specimen vacuum chamber. We demonstrate in-air imaging of specimens at nanoscale resolution using backscattered scanning electron microscopy (airSEM) and scanning transmission electron microscopy. We explore resolution and contrast using Montemore » Carlo simulations and analytical models. We find that nanometer-scale resolution can be obtained at gas path lengths up to 400μm, although contrast drops with increasing gas path length. As the electron-transparent window scatters considerably more than gas at our operating conditions, we observe that the densities and thicknesses of the electron-transparent window are the dominant limiting factors for image contrast at lower operating voltages. By enabling a variety of detector configurations, the airSEM is applicable to a wide range of environmental experiments including the imaging of hydrated biological specimens andin situchemical and electrochemical processes.« less

From 2D slices to 3D volumes: image based reconstruction and morphological characterization of hippocampal cells on charged and uncharged surfaces using FIB/SEM serial sectioning.

PubMed

Schmidt, Franziska; Kühbacher, Markus; Gross, Ulrich; Kyriakopoulos, Antonius; Schubert, Helmut; Zehbe, Rolf

2011-03-01

3D imaging at a subcellular resolution is a powerful tool in the life sciences to investigate cells and their interactions with native tissues or artificial objects. While a tomographic experimental setup achieving a sufficient structural resolution can be established with either X-rays or electrons, the use of electrons is usually limited to very thin samples in transmission electron microscopy due to the poor penetration depths of electrons. The combination of a serial sectioning approach and scanning electron microscopy in state of the art dual beam experimental setups therefore offers a means to image highly resolved spatial details using a focused ion beam for slicing and an electron beam for imaging. The advantage of this technique over X-ray μCT or X-ray microscopy attributes to the fact that absorption is not a limiting factor in imaging and therefore even strong absorbing structures can be spatially reconstructed with a much higher possible resolution. This approach was used in this study to elucidate the effect of an electric potential on the morphology of cells from a hippocampal cell line (HT22) deposited on gold microelectrodes. While cells cultivated on two different controls (gold and polymer substrates) did show the expected stretched morphology, cells on both the anode and the cathode differed significantly. Cells deposited on the anode part of the electrode exhibited the most extreme deviation, being almost spherical and showed signs of chromatin condensation possibly indicating cell death. Furthermore, EDX was used as supplemental methodology for combined chemical and structural analyses. Copyright © 2010 Elsevier B.V. All rights reserved.

Refixation of Osteochondral Fractures by an Ultrasound-Activated Pin System – An Ovine In Vivo Examination Using CT and Scanning Electron Microscope

PubMed Central

H, Neumann; A.P, Schulz; S, Breer; A, Unger; B, Kienast

2015-01-01

Background: Osteochondral injuries, if not treated appropriately, often lead to severe osteoarthritis of the affected joint. Without refixation of the osteochondral fragment, human cartilage only repairs these defects imperfectly. All existing refixation systems for chondral defects have disadvantages, for instance bad MRI quality in the postoperative follow-up or low anchoring forces. To address the problem of reduced stability in resorbable implants, ultrasound-activated pins were developed. By ultrasound-activated melting of the tip of these implants a higher anchoring is assumed. Aim of the study was to investigate, if ultrasound-activated pins can provide a secure refixation of osteochondral fractures comparing to conventional screw and conventional, resorbable pin osteosynthesis. CT scans and scanning electron microscopy should proovegood refixation results with no further tissue damage by the melting of the ultrasound-activated pins in comparison to conventional osteosynthesis. Methods: Femoral osteochondral fragments in sheep were refixated with ultrasound-activated pins (SonicPin™), Ethipins® and screws (Asnis™). The quality of the refixated fragments was examined after three month of full weight bearing by CT scans and scanning electron microscopy of the cartilage surface. Results: The CT examination found almost no statistically significant difference in the quality of refixation between the three different implants used. Concerning the CT morphology, ultrasound-activated pins demonstrated at least the same quality in refixation of osteochondral fragments as conventional resorbable pins or screws. The scanning electron microscopy showed no major surface damage by the three implants, especially any postulated cartilage damage induced by the heat of the ultrasound-activated pin. The screws protruded above the cartilage surface, which may affect the opposingtibial surface. Conclusion: Using CT scans and scanning electron microscopy, the SonicPin™, the Ethipin® and screws were at least equivalent in refixation quality of osteochondral fragments. PMID:25674184

Insight in the 3D morphology of silica-based nanotubes using electron microscopy.

PubMed

Dennenwaldt, Teresa; Wisnet, Andreas; Sedlmaier, Stefan J; Döblinger, Markus; Schnick, Wolfgang; Scheu, Christina

2016-11-01

Amorphous silica-based nanotubes (SBNTs) were synthesized from phosphoryl triamide, OP(NH 2 ) 3 , thiophosphoryl triamide, SP(NH 2 ) 3 , and silicon tetrachloride, SiCl 4 , at different temperatures and with varying amount of the starting material SiCl 4 using a recently developed template-free synthesis approach. Diameter and length of the SBNTs are tunable by varying the synthesis parameters. The 3D mesocrystals of the SBNTs were analyzed with focused ion beam sectioning and electron tomography in the transmission electron microscope showing the hollow tubular structure of the SBNTs. The reconstruction of a small SBNT assembly was achieved from a high-angle annular-dark field scanning transmission electron microscopy tilt series containing only thirteen images allowing analyzing beam sensitive material without altering the structure. The reconstruction revealed that the individual nanotubes are forming an interconnected array with an open channel structure. Copyright © 2016 Elsevier Ltd. All rights reserved.

Multiscale phase mapping of LiFePO4-based electrodes by transmission electron microscopy and electron forward scattering diffraction.

PubMed

Robert, Donatien; Douillard, Thierry; Boulineau, Adrien; Brunetti, Guillaume; Nowakowski, Pawel; Venet, Denis; Bayle-Guillemaud, Pascale; Cayron, Cyril

2013-12-23

LiFePO4 and FePO4 phase distributions of entire cross-sectioned electrodes with various Li content are investigated from nanoscale to mesoscale, by transmission electron microscopy and by the new electron forward scattering diffraction technique. The distributions of the fully delithiated (FePO4) or lithiated particles (LiFePO4) are mapped on large fields of view (>100 × 100 μm(2)). Heterogeneities in thin and thick electrodes are highlighted at different scales. At the nanoscale, the statistical analysis of 64 000 particles unambiguously shows that the small particles delithiate first. At the mesoscale, the phase maps reveal a core-shell mechanism at the scale of the agglomerates with a preferential pathway along the electrode porosities. At larger scale, lithiation occurs in thick electrodes "stratum by stratum" from the surface in contact with electrolyte toward the current collector.

Quantum-Sequencing: Biophysics of quantum tunneling through nucleic acids

NASA Astrophysics Data System (ADS)

Casamada Ribot, Josep; Chatterjee, Anushree; Nagpal, Prashant

2014-03-01

Tunneling microscopy and spectroscopy has extensively been used in physical surface sciences to study quantum tunneling to measure electronic local density of states of nanomaterials and to characterize adsorbed species. Quantum-Sequencing (Q-Seq) is a new method based on tunneling microscopy for electronic sequencing of single molecule of nucleic acids. A major goal of third-generation sequencing technologies is to develop a fast, reliable, enzyme-free single-molecule sequencing method. Here, we present the unique ``electronic fingerprints'' for all nucleotides on DNA and RNA using Q-Seq along their intrinsic biophysical parameters. We have analyzed tunneling spectra for the nucleotides at different pH conditions and analyzed the HOMO, LUMO and energy gap for all of them. In addition we show a number of biophysical parameters to further characterize all nucleobases (electron and hole transition voltage and energy barriers). These results highlight the robustness of Q-Seq as a technique for next-generation sequencing.

Sea Spray Aerosol Structure and Composition Using Cryogenic Transmission Electron Microscopy

PubMed Central

2016-01-01

The composition and surface properties of atmospheric aerosol particles largely control their impact on climate by affecting their ability to uptake water, react heterogeneously, and nucleate ice in clouds. However, in the vacuum of a conventional electron microscope, the native surface and internal structure often undergo physicochemical rearrangement resulting in surfaces that are quite different from their atmospheric configurations. Herein, we report the development of cryogenic transmission electron microscopy where laboratory generated sea spray aerosol particles are flash frozen in their native state with iterative and controlled thermal and/or pressure exposures and then probed by electron microscopy. This unique approach allows for the detection of not only mixed salts, but also soft materials including whole hydrated bacteria, diatoms, virus particles, marine vesicles, as well as gel networks within hydrated salt droplets—all of which will have distinct biological, chemical, and physical processes. We anticipate this method will open up a new avenue of analysis for aerosol particles, not only for ocean-derived aerosols, but for those produced from other sources where there is interest in the transfer of organic or biological species from the biosphere to the atmosphere. PMID:26878061

Effect of Boron on the Strength and Toughness of Direct-Quenched Low-Carbon Niobium Bearing Ultra-High-Strength Martensitic Steel

NASA Astrophysics Data System (ADS)

Hannula, Jaakko; Kömi, Jukka; Porter, David A.; Somani, Mahesh C.; Kaijalainen, Antti; Suikkanen, Pasi; Yang, Jer-Ren; Tsai, Shao-Pu

2017-11-01

The effect of boron on the microstructures and mechanical properties of laboratory-control-rolled and direct-quenched 6-mm-thick steels containing 0.08 wt pct C and 0.02 wt pct Nb were studied. The boron contents were 24 ppm and a residual amount of 4 ppm. Two different finish rolling temperatures (FRTs) of 1093 K and 1193 K (820 °C and 920 °C) were used in the hot rolling trials to obtain different levels of pancaked austenite prior to DQ. Continuous cooling transformation (CCT) diagrams were constructed to reveal the effect of boron on the transformation behavior of these steels. Microstructural characterization was carried out using various microscopy techniques, such as light optical microscopy (LOM) and scanning electron microscopy-electron backscatter diffraction (SEM-EBSD). The resultant microstructures after hot rolling were mixtures of autotempered martensite and lower bainite (LB), having yield strengths in the range 918 to 1067 MPa with total elongations to fracture higher than 10 pct. The lower FRT of 1093 K (820 °C) produced better combinations of strength and toughness as a consequence of a higher degree of pancaking in the austenite. Removal of boron lowered the 34 J/cm2 Charpy-V impact toughness transition temperature from 206 K to 158 K (-67 °C to -115 °C) when the finishing rolling temperature of 1093 K (820 °C) was used without any loss in the strength values compared to the boron-bearing steel. This was due to the finer and more uniform grain structure in the boron-free steel. Contrary to expectations, the difference was not caused by the formation of borocarbide precipitates, as verified by transmission electron microscopy (TEM) investigations, but through the grain coarsening effect of boron.

Fast imaging with inelastically scattered electrons by off-axis chromatic confocal electron microscopy.

PubMed

Zheng, Changlin; Zhu, Ye; Lazar, Sorin; Etheridge, Joanne

2014-04-25

We introduce off-axis chromatic scanning confocal electron microscopy, a technique for fast mapping of inelastically scattered electrons in a scanning transmission electron microscope without a spectrometer. The off-axis confocal mode enables the inelastically scattered electrons to be chromatically dispersed both parallel and perpendicular to the optic axis. This enables electrons with different energy losses to be separated and detected in the image plane, enabling efficient energy filtering in a confocal mode with an integrating detector. We describe the experimental configuration and demonstrate the method with nanoscale core-loss chemical mapping of silver (M4,5) in an aluminium-silver alloy and atomic scale imaging of the low intensity core-loss La (M4,5@840  eV) signal in LaB6. Scan rates up to 2 orders of magnitude faster than conventional methods were used, enabling a corresponding reduction in radiation dose and increase in the field of view. If coupled with the enhanced depth and lateral resolution of the incoherent confocal configuration, this offers an approach for nanoscale three-dimensional chemical mapping.

Comparison of optimal performance at 300 keV of three direct electron detectors for use in low dose electron microscopy

PubMed Central

McMullan, G.; Faruqi, A.R.; Clare, D.; Henderson, R.

2014-01-01

Low dose electron imaging applications such as electron cryo-microscopy are now benefitting from the improved performance and flexibility of recently introduced electron imaging detectors in which electrons are directly incident on backthinned CMOS sensors. There are currently three commercially available detectors of this type: the Direct Electron DE-20, the FEI Falcon II and the Gatan K2 Summit. These have different characteristics and so it is important to compare their imaging properties carefully with a view to optimise how each is used. Results at 300 keV for both the modulation transfer function (MTF) and the detective quantum efficiency (DQE) are presented. Of these, the DQE is the most important in the study of radiation sensitive samples where detector performance is crucial. We find that all three detectors have a better DQE than film. The K2 Summit has the best DQE at low spatial frequencies but with increasing spatial frequency its DQE falls below that of the Falcon II. PMID:25194828

Electron microscopy methods in studies of cultural heritage sites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vasiliev, A. L., E-mail: a.vasiliev56@gmail.com; Kovalchuk, M. V.; Yatsishina, E. B.

The history of the development and application of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray microanalysis (EDXMA) in studies of cultural heritage sites is considered. In fact, investigations based on these methods began when electron microscopes became a commercial product. Currently, these methods, being developed and improved, help solve many historical enigmas. To date, electron microscopy combined with microanalysis makes it possible to investigate any object, from parchment and wooden articles to pigments, tools, and objects of art. Studies by these methods have revealed that some articles were made by ancient masters using ancient “nanotechnologies”; hence,more » their comprehensive analysis calls for the latest achievements in the corresponding instrumental methods and sample preparation techniques.« less

Electron microscopy methods in studies of cultural heritage sites

NASA Astrophysics Data System (ADS)

Vasiliev, A. L.; Kovalchuk, M. V.; Yatsishina, E. B.

2016-11-01

The history of the development and application of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray microanalysis (EDXMA) in studies of cultural heritage sites is considered. In fact, investigations based on these methods began when electron microscopes became a commercial product. Currently, these methods, being developed and improved, help solve many historical enigmas. To date, electron microscopy combined with microanalysis makes it possible to investigate any object, from parchment and wooden articles to pigments, tools, and objects of art. Studies by these methods have revealed that some articles were made by ancient masters using ancient "nanotechnologies"; hence, their comprehensive analysis calls for the latest achievements in the corresponding instrumental methods and sample preparation techniques.

A scanning electron microscopy study of the macro-crystalline structure of 2-(2,4-dinitrobenzyl) pyridine

NASA Technical Reports Server (NTRS)

Ware, Jacqueline; Hammond, Ernest C., Jr.

1989-01-01

The compound, 2-(2,4-dinitrobenzyl) pyridine, was synthesized in the laboratory; an introductory level electron microscopy study of the macro-crystalline structure was conducted using the scanning electron microscope (SEM). The structure of these crystals was compared with the macrostructure of the crystal of 2-(2,4-dinitrobenzyl) pyridinium bromide, the hydrobromic salt of the compound which was also synthesized in the laboratory. A scanning electron microscopy crystal study was combined with a study of the principle of the electron microscope.

An analysis of FtsZ assembly using small angle X-ray scattering and electron microscopy.

PubMed

Kuchibhatla, Anuradha; Abdul Rasheed, A S; Narayanan, Janaky; Bellare, Jayesh; Panda, Dulal

2009-04-09

Small angle X-ray scattering (SAXS) was used for the first time to study the self-assembly of the bacterial cell division protein, FtsZ, with three different additives: calcium chloride, monosodium glutamate and DEAE-dextran hydrochloride in solution. The SAXS data were analyzed assuming a model form factor and also by a model-independent analysis using the pair distance distribution function. Transmission electron microscopy (TEM) was used for direct observation of the FtsZ filaments. By sectioning and negative staining with glow discharged grids, very high bundling as well as low bundling polymers were observed under different assembly conditions. FtsZ polymers formed different structures in the presence of different additives and these additives were found to increase the bundling of FtsZ protofilaments by different mechanisms. The combined use of SAXS and TEM provided us a significant insight of the assembly of FtsZ and microstructures of the assembled FtsZ polymers.

Glycogen in the Nervous System. I; Methods for Light and Electron Microscopy

NASA Technical Reports Server (NTRS)

Estable, Rosita F. De; Estable-Puig, J. F.; Miquel, J.

1964-01-01

'l'he relative value of different methods for combined light and electron microscopical studies of glycogen in the nervous tissue was investigated. Picroalcoholic fixatives preserve glycogen in a considerable amount but give an inadequate morphological image of glycogen distribution and are unsuitable for ultrastructural studies. Fixation by perfusion, with Dalton's chromeosmic fluid seems adequate for ultrastructural cytochemistry of glycogen. Furthermore it permits routine paraffin embedding of brain slices adjacent to those used for electron microscopy. Dimedone blocking is a necessary step for a selective staining of glycogen with PAS after osmic fixation. Enzymatic removal of glycogen in osmic fixed nervous tissue can be done In paraffin-embedded tissue. It can also be performed in glycolmethacrylate-embedded tissue without removal of the embedding medium. Paraphenylenediamine stains glycogen following periodic acid oxidation.

Applications of synchrotron x-ray diffraction topography to fractography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bilello, J.C.

1983-01-01

Fractographs have been taken using a variety of probes each of which produces different types of information. Methods which have been used to examine fracture surfaces include: (a) optical microscopy, particularly interference contrast methods, (b) scanning electron microscopy (SEM), (c) SEM with electron channelling, (d) SEM with selected-area electron channelling, (e) Berg-Barrett (B-B) topography, and now (f) synchrotron x-radiation fractography (SXRF). This review concentrated on the role that x-ray methods can play in such studies. In particular, the ability to nondestructively assess the subsurface microstructure associated with the fracture to depths of the order of 5 to 10 ..mu..m becomesmore » an important attribute for observations of a large class of semi-brittle metals, semiconductors and ceramics.« less

Single clay sheets inside electrospun polymer nanofibers

NASA Astrophysics Data System (ADS)

Sun, Zhaohui

2005-03-01

Nanofibers were prepared from polymer solution with clay sheets by electrospinning. Plasma etching, as a well controlled process, was used to supply electrically excited gas molecules from a glow discharge. To reveal the structure and arrangement of clay layers in the polymer matrix, plasma etching was used to remove the polymer by controlled gasification to expose the clay sheets due to the difference in reactivity. The shape, flexibility, and orientation of clay sheets were studied by transmission and scanning electron microscopy. Additional quantitative information on size distribution and degree of exfoliation of clay sheets were obtained by analyzing electron micrograph of sample after plasma etching. Samples in various forms including fiber, film and bulk, were thinned by plasma etching. Morphology and dispersion of inorganic fillers were studied by electron microscopy.

Self-consistent method for quantifying indium content from X-ray spectra of thick compound semiconductor specimens in a transmission electron microscope.

PubMed

Walther, T; Wang, X

2016-05-01

Based on Monte Carlo simulations of X-ray generation by fast electrons we calculate curves of effective sensitivity factors for analytical transmission electron microscopy based energy-dispersive X-ray spectroscopy including absorption and fluorescence effects, as a function of Ga K/L ratio for different indium and gallium containing compound semiconductors. For the case of InGaN alloy thin films we show that experimental spectra can thus be quantified without the need to measure specimen thickness or density, yielding self-consistent values for quantification with Ga K and Ga L lines. The effect of uncertainties in the detector efficiency are also shown to be reduced. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

Green synthesis of silver nanoparticles using tannins

NASA Astrophysics Data System (ADS)

Raja, Pandian Bothi; Rahim, Afidah Abdul; Qureshi, Ahmad Kaleem; Awang, Khalijah

2014-09-01

Colloidal silver nanoparticles were prepared by rapid green synthesis using different tannin sources as reducing agent viz. chestnut (CN), mangrove (MG) and quebracho (QB). The aqueous silver ions when exposed to CN, MG and QB tannins were reduced which resulted in formation of silver nanoparticles. The resultant silver nanoparticles were characterized using UV-Visible, X-ray diffraction (XRD), scanning electron microscopy (SEM/EDX), and transmission electron microscopy (TEM) techniques. Furthermore, the possible mechanism of nanoparticles synthesis was also derived using FT-IR analysis. Spectroscopy analysis revealed that the synthesized nanoparticles were within 30 to 75 nm in size, while XRD results showed that nanoparticles formed were crystalline with face centered cubic geometry.

Polyol-mediated thermolysis process for the synthesis of MgO nanoparticles and nanowires

NASA Astrophysics Data System (ADS)

Subramania, A.; Vijaya Kumar, G.; Sathiya Priya, A. R.; Vasudevan, T.

2007-06-01

The main aim of this work is to prepare MgO nanoparticles and nanowires by a novel polyol-mediated thermolysis (PMT) process. The influence of different mole concentration of magnesium acetate, polyvinyl pyrrolidone (PVP; capping agent) and ethylene glycol (EG; solvent as well as reducing agent) on the formation of nanoparticles and nanowires and the effect of calcination on the crystalline size of the samples were also examined. The resultant oxide structure, thermal behaviour, size and shape have been studied using x-ray diffraction (XRD) studies, thermal (TG/DTA) analysis and scanning electron microscopy (SEM)/transmission electron microscopy (TEM) respectively.

Three-dimensional morphology of GaP-GaAs nanowires revealed by transmission electron microscopy tomography.

PubMed

Verheijen, Marcel A; Algra, Rienk E; Borgström, Magnus T; Immink, George; Sourty, Erwan; Enckevort, Willem J P van; Vlieg, Elias; Bakkers, Erik P A M

2007-10-01

We have investigated the morphology of heterostructured GaP-GaAs nanowires grown by metal-organic vapor-phase epitaxy as a function of growth temperature and V/III precursor ratio. The study of heterostructured nanowires with transmission electron microscopy tomography allowed the three-dimensional morphology to be resolved, and discrimination between the effect of axial (core) and radial (shell) growth on the morphology. A temperature- and precursor-dependent structure diagram for the GaP nanowire core morphology and the evolution of the different types of side facets during GaAs and GaP shell growth were constituted.

[Grape seed extract induces morphological changes of prostate cancer PC-3 cells].

PubMed

Shang, Xue-Jun; Yin, Hong-Lin; Ge, Jing-Ping; Sun, Yi; Teng, Wen-Hui; Huang, Yu-Feng

2008-12-01

To observe the morphological changes of prostate cancer PC-3 cells induced by grape seed extract (GSE). PC-3 cells were incubated with different concentrations of GSE (100, 200 and 300 microg/ml) for 24, 48 and 72 hours, and then observed for morphological changes by invert microscopy, HE staining and transmission electron microscopy. The incubated PC-3 cells appeared round, small, wrinkled and broken under the invert microscope and exhibited the classical morphological characteristics of cell death under the electron microscope, including cell atrophy, increased vacuoles, crumpled nuclear membrane, and chromosome aggregation. GSE can cause morphological changes and induce necrosis and apoptosis of PC-3 cells.

Scanning gate microscopy of electronic inhomogeneities in single-walled carbon nanotube (SWCNT) devices

NASA Astrophysics Data System (ADS)

Hunt, Steven R.; Collins, Phillip G.

2010-03-01

The electronic properties of graphitic carbon devices are primarily determined by the contact metal and the carbon band structure. However, inhomogeneities such as substrate imperfections, surface defects, and mobile contaminants also contribute and can lead to transistor-like behaviors. We experimentally investigate this phenomena in the 1-D limit using metallic single-walled carbon nanotubes (SWCNTs) before and after the electrochemical creation of sidewall defects. While scanning gate microscopy readily identifies the defect sites, the energy-dependence of the technique allows quantitative analysis of the defects and discrimination of different defect types. This research is partly supported by the NSF (DMR 08-xxxx).

Synthesis of nanostructured vanadium powder by high-energy ball milling: X-ray diffraction and high-resolution electron microscopy characterization

NASA Astrophysics Data System (ADS)

Krishnan, Vinoadh Kumar; Sinnaeruvadi, Kumaran

2016-10-01

Vanadium metal powders, ball milled with different surfactants viz., stearic acid, KCl and NaCl, have been studied by X-ray diffraction and transmission electron microscopy. The surfactants alter the microstructural and morphological characteristics of the powders. Ball milling with stearic acid results in solid-state amorphization, while powders milled with KCl yield vanadium-tungsten carbide nanocomposite mixtures. NaCl proved to be an excellent surfactant for obtaining nanostructured fusion-grade vanadium powders. In order to understand the reaction mechanism behind any interstitial addition in the ball-milled powders, CHNOS analysis was performed.

Copper Salts Mediated Morphological Transformation of Cu2O from Cubes to Hierarchical Flower-like or Microspheres and Their Supercapacitors Performances

PubMed Central

Chen, Liang; Zhang, Yu; Zhu, Pengli; Zhou, Fengrui; Zeng, Wenjin; Lu, Daoqiang Daniel; Sun, Rong; Wong, Chingping

2015-01-01

Monodisperse Cu2O of different microstructures, such as cubes, flower-like, and microspheres, have been extensively synthesized by a simple polyol reduction method using different copper salts, i.e. (Cu(acac)2, Cu(OH)2, and Cu(Ac)2·H2O). The effects of copper salts on the morphology of Cu2O were investigated in details through various characterization methods, including X-ray diffraction, transmission electron microscopy, scanning electron microscopy and UV-Vis absorption spectra. The effects of morphology on the electrochemical properties were further studied. Among the different structures, Cu2O with the microspheric morphology shows the highest specific capacitance and the best cycling stability compared with those of the other two structures, thus bear larger volume charge during the electrochemical reaction due to the microspheres of small nanoparticles. PMID:25857362

Observation of conducting filament growth in nanoscale resistive memories

NASA Astrophysics Data System (ADS)

Yang, Yuchao; Gao, Peng; Gaba, Siddharth; Chang, Ting; Pan, Xiaoqing; Lu, Wei

2012-03-01

Nanoscale resistive switching devices, sometimes termed memristors, have recently generated significant interest for memory, logic and neuromorphic applications. Resistive switching effects in dielectric-based devices are normally assumed to be caused by conducting filament formation across the electrodes, but the nature of the filaments and their growth dynamics remain controversial. Here we report direct transmission electron microscopy imaging, and structural and compositional analysis of the nanoscale conducting filaments. Through systematic ex-situ and in-situ transmission electron microscopy studies on devices under different programming conditions, we found that the filament growth can be dominated by cation transport in the dielectric film. Unexpectedly, two different growth modes were observed for the first time in materials with different microstructures. Regardless of the growth direction, the narrowest region of the filament was found to be near the dielectric/inert-electrode interface in these devices, suggesting that this region deserves particular attention for continued device optimization.

Aqueous Combustion Synthesis and Characterization of Nanosized Tetragonal Zirconia Single Crystals

NASA Astrophysics Data System (ADS)

Reddy, B. S. B.; Mal, Indrajit; Tewari, Shanideep; Das, Karabi; Das, Siddhartha

2007-08-01

Nanocrystalline zirconia powder has been synthesized by an aqueous combustion synthesis route using glycine as fuel and nitrate as oxidizer. The powders have been prepared by using different glycine to zirconyl nitrate molar ratios (G/N). The powders produced with different G/N ratios have been characterized by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) to determine the parameters resulting from powder with attractive properties. The theoretical combustion temperature (T ad ) has been calculated for different G/N ratios, and it is correlated with powder characteristics. An attempt is also made to explain the stability of tetragonal zirconia on the basis of extrinsic factors such as the morphology of nanocrystallites. Nanocrystalline metastable tetragonal zirconia (˜25 nm) powder (TZ) with disc-shaped morphology has been produced with a weak agglomeration in fuel deficient mixtures.

Synthesis of mesoporous Mn/TiO2 nanocomposites and investigating the photocatalytic properties in aqueous systems.

PubMed

Oseghe, Ekemena Oghenovoh; Ndungu, Patrick Gathura; Jonnalagadda, Sreekanth Babu

2015-01-01

Mesoporous 20 wt% Mn/TiO2 nanocomposites were synthesized adopting modified sol-gel method at different pH (pH = 2, 7 and 11) conditions and calcined at 400 °C. Based on the characteristics of the 20 wt% Mn/TiO2 nanocomposites synthesized at pH 11, same procedure was adopted for the synthesis of different wt% Mn/TiO2. The nanocomposite samples and their surface properties were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), mapping, inductively coupled plasma optical emission spectrometry (ICP-OES), Fourier transform infrared (FTIR), and fluorescence spectrometry. The nanocomposites existed in the anatase phase of TiO2 with no peak assigned to Mn on the diffractogram. The photocatalytic activities of the materials were evaluated by monitoring degradation of a model dye (methylene blue (MB)) in presence of visible light and ozone. The nanocomposite synthesized under neutral condition (pH = 7) exhibited the best photocatalytic activity resulting from its relatively smaller crystal size (5.98 nm) and larger pore volume (0.30 cm(3)/g). One percentage of weight Mn/TiO2 showed 100% decolouration of MB in the presence of O3 after 100 min.

Characterization of Microstructure and Mechanical Properties of Mg-8Li-3Al-1Y Alloy Subjected to Different Rolling Processes

NASA Astrophysics Data System (ADS)

Zhou, Xiao; Liu, Qiang; Liu, Ruirui; Zhou, Haitao

2018-06-01

The mechanical properties and microstructure evolution of Mg-8Li-3Al-1Y alloy undergoing different rolling processes were systematically investigated. X-ray diffraction, optical microscope, scanning electron microscopy, transmission electron microscopy as well as electron backscattered diffraction were used for tracking the microstructure evolution. Tensile testing was employed to characterize the mechanical properties. After hot rolling, the MgLi2Al precipitated in β-Li matrix due to the transformation reaction: β-Li → β-Li + MgLi2Al + α-Mg. As for the alloy subjected to annealed hot rolling, β-Li phase was clearly recrystallized while recrystallization rarely occurred in α-Mg phase. With regard to the microstructure undergoing cold rolling, plenty of dislocations and dislocation walls were easily observed. In addition, the microstructure of alloys subjected to annealed cold rolling revealed the formation of new fresh α-Mg grains in β-Li phase due to the precipitation reaction. The mechanical properties and fracture modes of Mg-8Li-3Al-1Y alloys can be effectively tuned by different rolling processes.

A structural and electronic comparison of armchair and zigzag epitaxial graphene sidewall nanoribbons

NASA Astrophysics Data System (ADS)

Nevius, Meredith; Wang, F.; Palacio, I.; Celis, A.; Tejeda, A.; Taleb-Ibrahimi, A.; de Heer, W.; Berger, C.; Conrad, E.

2014-03-01

Graphene grown on sidewalls of trenches etched in SiC shows particular promise as a candidate for post-Si CMOS electronics because of its ballistic transport, exceptional mobilities, low intrinsic doping, and the opening of a large band gap. However, before definitive progress can be made toward epitaxial graphene-based transistors, we must fully understand the nuances of graphene ribbon growth on different SiC facets. We have now confirmed that sidewall ribbons grown in graphene's two primary crystallographic directions (``armchair'' and ``zigzag'') differ greatly in both structure and electronic band-structure. We present data from both geometries obtained using low-energy electron microscopy (LEEM), low-energy electron diffraction (LEED), angle-resolved photoemission spectroscopy (ARPES), photoemission electron microscopy (PEEM), micro-ARPES and dark-field micro-ARPES. We demonstrate that while graphene grows on stable facets of trenches oriented for armchair edge growth, trenches oriented for zigzag edge growth prefer narrow ribbons of graphene on the (0001) surface near the trench edge. The structure of these zigzag edge graphene ribbons is complex and paramount to understanding their transport. This work was supported by the NSF under grants DMR-1005880 and DMR-0820382, the W. M. Keck Foundation and the Partner University Fund from the Embassy of France

Microscopy and microanalysis 1996

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bailey, G.W.; Corbett, J.M.; Dimlich, R.V.W.

1996-12-31

The Proceedings of this Annual Meeting contain paper of members from the three societies. These proceedings emphasizes the common research interests and attempts to eliminate some unwanted overlap. Topics covered are: microscopic analysis of animals with altered gene expression and in-situ gene and antibody localizations, high-resolution elemental mapping of nucleoprofein interactions, plant biology and pathology, quantitative HREM analysis of perfect and defected materials, computational methods for TEM image analysis, high-resolution FESM in materials research, frontiers in polymer microscopy and microanalysis, oxidation and corrosion, micro XRD and XRF, molecular microspectroscopy and spectral imaging, advances in confocal and multidimensional light microscopy, analyticalmore » electron microscopy in biology, correlative microscopy in biological sciences, grain-boundary microengineering, surfaces and interfaces, telepresence microscopy in education and research, MSA educational outreach, quantitative electron probe microanalysis, frontiers of analytical electron microscopy, critical issues in ceramic microstructures, dynamic organization of the cell, pathology, microbiology, high-resolution biological and cryo SEM, and scanning-probe microscopy.« less

Solid state amorphization of metastable Al 0.5TiZrPdCuNi high entropy alloy investigated by high voltage electron microscopy

DOE PAGES

Nagase, Takeshi; Takeuchi, Akira; Amiya, Kenji; ...

2017-07-18

Here, the phase stability of high entropy alloy (HEA), Al 0.5TiZrPdCuNi, under fast electron irradiation was studied by in-situ high voltage electron microscopy (HVEM). The initial phase of this alloy quenched from the melt was dependent on cooling rate. At high cooling rates an amorphous phase was obtained, whereas a body-centered cubic ( b.c.c.) phase were obtained at low cooling rates. By thermal crystallization of the amorphous phase b.c.c. phase nano-crystals were formed. Upon fast electron irradiation solid state amorphization (SSA) was observed in b.c.c. phase regardless of the initial microstructure (i.e., “coarse crystalline structure” or “nano-crystalline structure with grainmore » boundaries as a sink for point defects”). SSA behavior in the Al 0.5TiZrPdCuNi HEAs was investigated by in-situ transmission electron microscopy observations. Because the amorphization is very rarely achieved in a solid solution phase under fast electron irradiation in common metallic materials, this result suggests that the Al 0.5TiZrPdCuNi HEA from other common alloys and the other HEAs. The differences in phase stability against the irradiation between the Al 0.5TiZrPdCuNi HEA and the other HEAs were discussed. This is the first experimental evidence of SSA in HEAs stimulated by fast electron irradiation.« less

Tissue and cellular localization of tannins in Tunisian dates (Phoenix dactylifera L.) by light and transmission electron microscopy.

PubMed

Hammouda, Hédi; Alvarado, Camille; Bouchet, Brigitte; Kalthoum-Chérif, Jamila; Trabelsi-Ayadi, Malika; Guyot, Sylvain

2014-07-16

A histological approach including light microscopy and transmission electron microscopy (TEM) was used to provide accurate information on the localization of condensed tannins in the edible tissues and in the stone of date fruits (Phoenix dactylifera L.). Light microscopy was carried out on fresh tissues after staining by 4-dimethylaminocinnamaldehyde (DMACA) for a specific detection of condensed tannins. Thus, whether under light microscopy or transmission electron microscopy (TEM), results showed that tannins are not located in the epidermis but more deeply in the mesocarp in the vacuole of very large cells. Regarding the stones, tannins are found in a specific cell layer located at 50 μm from the sclereid cells of the testa.

Environmental transmission electron microscopy for catalyst materials using a spherical aberration corrector.

PubMed

Takeda, Seiji; Kuwauchi, Yasufumi; Yoshida, Hideto

2015-04-01

Atomic resolution has been obtained using environmental transmission electron microscopy (ETEM) by installing a spherical aberration corrector (Cs-corrector) on the objective lens. Simultaneously, the technology for controlling the environment around a specimen in ETEM has advanced significantly in the past decade. Quantification methodology has recently been established for deriving relevant experimental data in catalyst materials from substantial and systematic ETEM observation at the atomic scale. With this background, this paper summarizes aspects of the evolutional microscopy technique: necessary conditions for atomic resolution in ETEM; reduction of the scattering of electrons by the medium surrounding a specimen; and an environmental cell for structural imaging of a crystalline specimen. The high spatial resolution of a Cs-corrected ETEM is demonstrated for different observation conditions. After statistical analysis combined with numerical image analysis of ETEM data is briefly described, the recent applications of the Cs-corrected ETEM to catalyst materials are reviewed. For gold nanoparticulate catalysts, the structural information on the reaction sites and adsorption sites are deduced. For Pt nanoparticulate catalysts, ETEM studies elucidate the correlation between the catalytic activity and the morphology of the nanoparticles. These studies also reveal oxidation and reduction on the topmost Pt surface layer at the atomic scale. Finally, current issues and the future perspectives of Cs-corrected ETEM are summarized, including the reproducibility of ETEM observation data, the control of environments, the critical evaluation of electron irradiation effects, the full implementation of transmission electron microscopy technology in ETEM, and the safety issues for an ETEM laboratory. Copyright © 2014 Elsevier B.V. All rights reserved.

AAO-based nanoreservoir arrays: A quick and easy support for TEM characterization

NASA Astrophysics Data System (ADS)

Mace, M.; Sahaf, H.; Moyen, E.; Bedu, F.; Masson, L.; Hanbücken, M.

2010-12-01

Large-scale arrays of calibrated, nanometer sized reservoirs are prepared by adapting the well-established electrochemical method used so far for the preparation of anodic aluminium oxide (AAO) membranes. The bottom plane of the assembly is prepared to be transparent for high-energy electrons, enabling their use as a universal sample support for transmission electron microscopy studies of nanoparticles. The nanoreservoir substrates can be cleaned under ultra-high-vacuum conditions and filled, by evaporating different materials. Filled nanoreservoirs can locally be sealed with a thin carbon layer using focused-ion-beam-induced deposition (FIBID). Nanoparticles, grow at various adsorption places on the walls and bottom planes inside the nanoreservoirs. They can be characterized by transmission electron microscopy (TEM) without further sample preparation in different crystallographic directions. Due to the dense array-arrangement of the reservoirs, very good statistics can already be obtained on one single sample. The controlled fabrication of the nanoreservoir array and first TEM results obtained on Au nanoparticles before and after sealing of the reservoirs, are presented.

Recent advances in electron tomography: TEM and HAADF-STEM tomography for materials science and semiconductor applications.

PubMed

Kübel, Christian; Voigt, Andreas; Schoenmakers, Remco; Otten, Max; Su, David; Lee, Tan-Chen; Carlsson, Anna; Bradley, John

2005-10-01

Electron tomography is a well-established technique for three-dimensional structure determination of (almost) amorphous specimens in life sciences applications. With the recent advances in nanotechnology and the semiconductor industry, there is also an increasing need for high-resolution three-dimensional (3D) structural information in physical sciences. In this article, we evaluate the capabilities and limitations of transmission electron microscopy (TEM) and high-angle-annular-dark-field scanning transmission electron microscopy (HAADF-STEM) tomography for the 3D structural characterization of partially crystalline to highly crystalline materials. Our analysis of catalysts, a hydrogen storage material, and different semiconductor devices shows that features with a diameter as small as 1-2 nm can be resolved in three dimensions by electron tomography. For partially crystalline materials with small single crystalline domains, bright-field TEM tomography provides reliable 3D structural information. HAADF-STEM tomography is more versatile and can also be used for high-resolution 3D imaging of highly crystalline materials such as semiconductor devices.

4D electron microscopy: principles and applications.

PubMed

Flannigan, David J; Zewail, Ahmed H

2012-10-16

The transmission electron microscope (TEM) is a powerful tool enabling the visualization of atoms with length scales smaller than the Bohr radius at a factor of only 20 larger than the relativistic electron wavelength of 2.5 pm at 200 keV. The ability to visualize matter at these scales in a TEM is largely due to the efforts made in correcting for the imperfections in the lens systems which introduce aberrations and ultimately limit the achievable spatial resolution. In addition to the progress made in increasing the spatial resolution, the TEM has become an all-in-one characterization tool. Indeed, most of the properties of a material can be directly mapped in the TEM, including the composition, structure, bonding, morphology, and defects. The scope of applications spans essentially all of the physical sciences and includes biology. Until recently, however, high resolution visualization of structural changes occurring on sub-millisecond time scales was not possible. In order to reach the ultrashort temporal domain within which fundamental atomic motions take place, while simultaneously retaining high spatial resolution, an entirely new approach from that of millisecond-limited TEM cameras had to be conceived. As shown below, the approach is also different from that of nanosecond-limited TEM, whose resolution cannot offer the ultrafast regimes of dynamics. For this reason "ultrafast electron microscopy" is reserved for the field which is concerned with femtosecond to picosecond resolution capability of structural dynamics. In conventional TEMs, electrons are produced by heating a source or by applying a strong extraction field. Both methods result in the stochastic emission of electrons, with no control over temporal spacing or relative arrival time at the specimen. The timing issue can be overcome by exploiting the photoelectric effect and using pulsed lasers to generate precisely timed electron packets of ultrashort duration. The spatial and temporal resolutions achievable with short intense pulses containing a large number of electrons, however, are limited to tens of nanometers and nanoseconds, respectively. This is because Coulomb repulsion is significant in such a pulse, and the electrons spread in space and time, thus limiting the beam coherence. It is therefore not possible to image the ultrafast elementary dynamics of complex transformations. The challenge was to retain the high spatial resolution of a conventional TEM while simultaneously enabling the temporal resolution required to visualize atomic-scale motions. In this Account, we discuss the development of four-dimensional ultrafast electron microscopy (4D UEM) and summarize techniques and applications that illustrate the power of the approach. In UEM, images are obtained either stroboscopically with coherent single-electron packets or with a single electron bunch. Coulomb repulsion is absent under the single-electron condition, thus permitting imaging, diffraction, and spectroscopy, all with high spatiotemporal resolution, the atomic scale (sub-nanometer and femtosecond). The time resolution is limited only by the laser pulse duration and energy carried by the electron packets; the CCD camera has no bearing on the temporal resolution. In the regime of single pulses of electrons, the temporal resolution of picoseconds can be attained when hundreds of electrons are in the bunch. The applications given here are selected to highlight phenomena of different length and time scales, from atomic motions during structural dynamics to phase transitions and nanomechanical oscillations. We conclude with a brief discussion of emerging methods, which include scanning ultrafast electron microscopy (S-UEM), scanning transmission ultrafast electron microscopy (ST-UEM) with convergent beams, and time-resolved imaging of biological structures at ambient conditions with environmental cells.

Advanced Nanoscale Thin Film & Bulk Materials Towards Thermoelectric Power Conversion Efficiencies of 30%

DTIC Science & Technology

2014-02-27

Electron Microscopy. Detailed Kronig -Penny (K-P)) modeling of electron transport through these superlattices suggests an estimated e-h transition energy...superalttices was confirmed by Transmission Electron Microscopy. Detailed Kronig -Penny (K-P)) modeling of electron transport through these superlattices

New modes of electron microscopy for materials science enabled by fast direct electron detectors

NASA Astrophysics Data System (ADS)

Minor, Andrew

There is an ongoing revolution in the development of electron detector technology that has enabled modes of electron microscopy imaging that had only before been theorized. The age of electron microscopy as a tool for imaging is quickly giving way to a new frontier of multidimensional datasets to be mined. These improvements in electron detection have enabled cryo-electron microscopy to resolve the three-dimensional structures of non-crystalized proteins, revolutionizing structural biology. In the physical sciences direct electron detectors has enabled four-dimensional reciprocal space maps of materials at atomic resolution, providing all the structural information about nanoscale materials in one experiment. This talk will highlight the impact of direct electron detectors for materials science, including a new method of scanning nanobeam diffraction. With faster detectors we can take a series of 2D diffraction patterns at each position in a 2D STEM raster scan resulting in a four-dimensional data set. For thin film analysis, direct electron detectors hold the potential to enable strain, polarization, composition and electrical field mapping over relatively large fields of view, all from a single experiment.

Three-Dimensional Intercalated Porous Graphene on Si(111)

NASA Astrophysics Data System (ADS)

Pham, Trung T.; Sporken, Robert

2018-02-01

Three-dimensional intercalated porous graphene has been formed on Si(111) by electron beam evaporation under appropriate conditions and its structural and electronic properties investigated in detail by reflection high-energy electron diffraction, x-ray photoemission spectroscopy, Raman spectroscopy, high-resolution scanning electron microscopy, atomic force microscopy, and scanning tunneling microscopy. The results show that the crystalline quality of the porous graphene depended not only on the substrate temperature but also on the SiC layer thickness during carbon atom deposition.

Scanning Transmission Electron Microscopy | Materials Science | NREL

Science.gov Websites

mode by collecting the EDS and EELS signals point-by-point as one scans the electron probe across the . Examples of Scanning Transmission Electron Microscopy Capabilities Z-contrast image microphoto taken by

Myofibroblasts in interstitial lung diseases show diverse electron microscopic and invasive features.

PubMed

Karvonen, Henna M; Lehtonen, Siri T; Sormunen, Raija T; Harju, Terttu H; Lappi-Blanco, Elisa; Bloigu, Risto S; Kaarteenaho, Riitta L

2012-09-01

The characteristic features of myofibroblasts in various lung disorders are poorly understood. We have evaluated the ultrastructure and invasive capacities of myofibroblasts cultured from small volumes of diagnostic bronchoalveolar lavage (BAL) fluid samples from patients with different types of lung diseases. Cells were cultured from samples of BAL fluid collected from 51 patients that had undergone bronchoscopy and BAL for diagnostic purposes. The cells were visualized by transmission electron microscopy and immunoelectron microscopy to achieve ultrastructural localization of alpha-smooth muscle actin (α-SMA) and fibronectin. The levels of α-SMA protein and mRNA and fibronectin mRNA were measured by western blot and quantitative real-time reverse transcriptase polymerase chain reaction. The invasive capacities of the cells were evaluated. The cultured cells were either fibroblasts or myofibroblasts. The structure of the fibronexus, and the amounts of intracellular actin, extracellular fibronectin and cell junctions of myofibroblasts varied in different diseases. In electron and immunoelectron microscopy, cells cultured from interstitial lung diseases (ILDs) expressed more actin filaments and α-SMA than normal lung. The invasive capacity of the cells obtained from patients with idiopathic pulmonary fibrosis was higher than that from patients with other type of ILDs. Cells expressing more actin filaments had a higher invasion capacity. It is concluded that electron and immunoelectron microscopic studies of myofibroblasts can reveal differential features in various diseases. An analysis of myofibroblasts cultured from diagnostic BAL fluid samples may represent a new kind of tool for diagnostics and research into lung diseases.

Effects of tricyclazole (5-methyl-1,2,4-triazol[3,4] benzothiazole), a specific DHN-melanin inhibitor, on the morphology of Fonsecaea pedrosoi conidia and sclerotic cells.

PubMed

Franzen, Anderson J; Cunha, Marcel M L; Batista, Evander J O; Seabra, Sergio H; De Souza, Wanderley; Rozental, Sonia

2006-09-01

The influence of tricyclazole (5-methyl-1,2,4-triazol[3,4]benzothiazole), a specific DHN-melanin inhibitor, on the cell walls and intracellular structures of Fonsecaea pedrosoi conidia and sclerotic cells was analyzed by transmission electron microscopy (TEM), deep-etching, and field emission scanning electron microscopy. The treatment of the fungus with 16 microg mL(-1) of tricyclazole (TC) did not significantly affect fungal viability, but electron microscopy observations showed several important morphological differences between TC-treated and non-TC treated cells. Control sclerotic cells presented patched granules, with an average diameter of 47 nm, on the cell surface, which were absent in TC-treated cells. Also, TC-treated sclerotic cells showed an undulated relief. TC treatment leads to an accumulation of electron lucent vacuoles in the fungal cytoplasm of both conidia and sclerotic cells, and treated conidia observed by deep etching showed a relevant thickening of the fungal cell wall. Together, these observations support the previous data of our group that F. pedrosoi synthesizes melanin in intracellular organelles. In addition, we suggest that melanin is not only an extracellular constituent but could also be dispersing all over the cell walls and could have an effective role in cross-linking different cell wall compounds that help maintain the regular shape of the cell wall. (c) 2006 Wiley-Liss, Inc.

Diagnostic electron microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dickersin, G.R.

1988-01-01

In this book the author presents a comprehensive reference text on diagnostic electron microscopy. Throughout the book he illustrates how ultrastructural identification can be helpful for the recognition of cell type and the identification of mechanisms of pathogenesis in various diseases. In addition to electron microscopy photographs, there are also numerous light microscopy photographs for comparison. This text presents the classification of neoplasms in the order and arrangement most familiar to the pathologist. Contents: Introduction; Diagram of a Normal Cell; Normal Cell Function; Embryology; Neoplasms; Infectious Agents; Metabolic Diseases; Renal Diseases; Skeletal Muscle and Peripheral Nerve Diseases; Index.

Transmission electron microscopy, fluorescence microscopy, and confocal raman microscopic analysis of ultrastructural and compositional heterogeneity of Cornus alba L. wood cell wall.

PubMed

Ma, Jianfeng; Ji, Zhe; Zhou, Xia; Zhang, Zhiheng; Xu, Feng

2013-02-01

Transmission electron microscopy (TEM), fluorescence microscopy, and confocal Raman microscopy can be used to characterize ultrastructural and compositional heterogeneity of plant cell walls. In this study, TEM observations revealed the ultrastructural characterization of Cornus alba L. fiber, vessel, axial parenchyma, ray parenchyma, and pit membrane between cells, notably with the ray parenchyma consisting of two well-defined layers. Fluorescence microscopy evidenced that cell corner middle lamella was more lignified than adjacent compound middle lamella and secondary wall with variation in lignification level from cell to cell. In situ Raman images showed that the inhomogeneity in cell wall components (cellulose and lignin) among different cells and within morphologically distinct cell wall layers. As the significant precursors of lignin biosynthesis, the pattern of coniferyl alcohol and aldehyde (joint abbreviation Lignin-CAA for both structures) distribution in fiber cell wall was also identified by Raman images, with higher concentration occurring in the fiber secondary wall where there was the highest cellulose concentration. Moreover, noteworthy was the observation that higher concentration of lignin and very minor amounts of cellulose were visualized in the pit membrane areas. These complementary microanalytical methods provide more accurate and complete information with regard to ultrastructural and compositional characterization of plant cell walls.

Quantitative analysis of the effect of environmental-scanning electron microscopy on collagenous tissues.

PubMed

Lee, Woowon; Toussaint, Kimani C

2018-05-31

Environmental-scanning electron microscopy (ESEM) is routinely applied to various biological samples due to its ability to maintain a wet environment while imaging; moreover, the technique obviates the need for sample coating. However, there is limited research carried out on electron-beam (e-beam) induced tissue damage resulting from using the ESEM. In this paper, we use quantitative second-harmonic generation (SHG) microscopy to examine the effects of e-beam exposure from the ESEM on collagenous tissue samples prepared as either fixed, frozen, wet or dehydrated. Quantitative SHG analysis of tissues, before and after ESEM e-beam exposure in low-vacuum mode, reveals evidence of cross-linking of collagen fibers, however there are no structural differences observed in fixed tissue. Meanwhile wet-mode ESEM appears to radically alter the structure from a regular fibrous arrangement to a more random fiber orientation. We also confirm that ESEM images of collagenous tissues show higher spatial resolution compared to SHG microscopy, but the relative tradeoff with collagen specificity reduces its effectiveness in quantifying collagen fiber organization. Our work provides insight on both the limitations of the ESEM for tissue imaging, and the potential opportunity to use as a complementary technique when imaging fine features in the non-collagenous regions of tissue samples.

Radiation damage in single-particle cryo-electron microscopy: effects of dose and dose rate.

PubMed

Karuppasamy, Manikandan; Karimi Nejadasl, Fatemeh; Vulovic, Milos; Koster, Abraham J; Ravelli, Raimond B G

2011-05-01

Radiation damage is an important resolution limiting factor both in macromolecular X-ray crystallography and cryo-electron microscopy. Systematic studies in macromolecular X-ray crystallography greatly benefited from the use of dose, expressed as energy deposited per mass unit, which is derived from parameters including incident flux, beam energy, beam size, sample composition and sample size. In here, the use of dose is reintroduced for electron microscopy, accounting for the electron energy, incident flux and measured sample thickness and composition. Knowledge of the amount of energy deposited allowed us to compare doses with experimental limits in macromolecular X-ray crystallography, to obtain an upper estimate of radical concentrations that build up in the vitreous sample, and to translate heat-transfer simulations carried out for macromolecular X-ray crystallography to cryo-electron microscopy. Stroboscopic exposure series of 50-250 images were collected for different incident flux densities and integration times from Lumbricus terrestris extracellular hemoglobin. The images within each series were computationally aligned and analyzed with similarity metrics such as Fourier ring correlation, Fourier ring phase residual and figure of merit. Prior to gas bubble formation, the images become linearly brighter with dose, at a rate of approximately 0.1% per 10 MGy. The gradual decomposition of a vitrified hemoglobin sample could be visualized at a series of doses up to 5500 MGy, by which dose the sample was sublimed. Comparison of equal-dose series collected with different incident flux densities showed a dose-rate effect favoring lower flux densities. Heat simulations predict that sample heating will only become an issue for very large dose rates (50 e(-)Å(-2) s(-1) or higher) combined with poor thermal contact between the grid and cryo-holder. Secondary radiolytic effects are likely to play a role in dose-rate effects. Stroboscopic data collection combined with an improved understanding of the effects of dose and dose rate will aid single-particle cryo-electron microscopists to have better control of the outcome of their experiments.

Radiation damage in single-particle cryo-electron microscopy: effects of dose and dose rate

PubMed Central

Karuppasamy, Manikandan; Karimi Nejadasl, Fatemeh; Vulovic, Milos; Koster, Abraham J.; Ravelli, Raimond B. G.

2011-01-01

Radiation damage is an important resolution limiting factor both in macromolecular X-ray crystallography and cryo-electron microscopy. Systematic studies in macromolecular X-ray crystallography greatly benefited from the use of dose, expressed as energy deposited per mass unit, which is derived from parameters including incident flux, beam energy, beam size, sample composition and sample size. In here, the use of dose is reintroduced for electron microscopy, accounting for the electron energy, incident flux and measured sample thickness and composition. Knowledge of the amount of energy deposited allowed us to compare doses with experimental limits in macromolecular X-ray crystallography, to obtain an upper estimate of radical concentrations that build up in the vitreous sample, and to translate heat-transfer simulations carried out for macromolecular X-ray crystallography to cryo-electron microscopy. Stroboscopic exposure series of 50–250 images were collected for different incident flux densities and integration times from Lumbricus terrestris extracellular hemoglobin. The images within each series were computationally aligned and analyzed with similarity metrics such as Fourier ring correlation, Fourier ring phase residual and figure of merit. Prior to gas bubble formation, the images become linearly brighter with dose, at a rate of approximately 0.1% per 10 MGy. The gradual decomposition of a vitrified hemoglobin sample could be visualized at a series of doses up to 5500 MGy, by which dose the sample was sublimed. Comparison of equal-dose series collected with different incident flux densities showed a dose-rate effect favoring lower flux densities. Heat simulations predict that sample heating will only become an issue for very large dose rates (50 e−Å−2 s−1 or higher) combined with poor thermal contact between the grid and cryo-holder. Secondary radiolytic effects are likely to play a role in dose-rate effects. Stroboscopic data collection combined with an improved understanding of the effects of dose and dose rate will aid single-particle cryo-electron microscopists to have better control of the outcome of their experiments. PMID:21525648

HALE STAIN FOR SIALIC ACID-CONTAINING MUCINS. ADAPTATION TO ELECTRON MICROSCOPY.

PubMed

GASIC, G; BERWICK, L

1963-10-01

The feasibility of using the Hale stain to identify cellular sialic acid-containing mucins by electron microscopy was investigated. Three kinds of mouse ascites tumor cells were fixed in neutral buffered formalin, exposed to fresh colloidal ferric oxide, treated with potassium ferrocyanide, imbedded in Selectron, and sectioned for electron microscopy. Additional staining with uranyl acetate and potassium permanganate was done after sectioning in order to increase contrast. Those cells known to be coated with sialomucin showed deposits of electron-opaque ferric ferrocyanide crystals in the areas where sialomucin concentrations were expected. When these cells were treated with neuraminidase beforehand, these deposits did not appear. It was concluded that, with the precautions and modifications described, the Hale stain can be successfully combined with electron microscopy to identify sialomucin.

Perspectives on in situ electron microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Haimei; Zhu, Yimei

In situ transmission electron microscopy (TEM) with the ability to reveal materials dynamic processes with high spatial and temporal resolution has attracted significant interest. The recent advances in in situ methods, including liquid and gas sample environment, pump-probe ultrafast microscopy, nanomechanics and ferroelectric domain switching the aberration corrected electron optics as well as fast electron detector has opened new opportunities to extend the impact of in situ TEM in broad areas of research ranging from materials science to chemistry, physics and biology. Here in this paper, we highlight the development of liquid environment electron microscopy and its applications in themore » study of colloidal nanoparticle growth, electrochemical processes and others; in situ study of topological vortices in ferroelectric and ferromagnetic materials. At the end, perspectives of future in situ TEM are provided.« less

Perspectives on in situ electron microscopy

DOE PAGES

Zheng, Haimei; Zhu, Yimei

2017-03-29

In situ transmission electron microscopy (TEM) with the ability to reveal materials dynamic processes with high spatial and temporal resolution has attracted significant interest. The recent advances in in situ methods, including liquid and gas sample environment, pump-probe ultrafast microscopy, nanomechanics and ferroelectric domain switching the aberration corrected electron optics as well as fast electron detector has opened new opportunities to extend the impact of in situ TEM in broad areas of research ranging from materials science to chemistry, physics and biology. Here in this paper, we highlight the development of liquid environment electron microscopy and its applications in themore » study of colloidal nanoparticle growth, electrochemical processes and others; in situ study of topological vortices in ferroelectric and ferromagnetic materials. At the end, perspectives of future in situ TEM are provided.« less

Cryo-Scanning Electron Microscopy (SEM) and Scanning Transmission Electron Microscopy (STEM)-in-SEM for Bio- and Organo-Mineral Interface Characterization in the Environment.

PubMed

Wille, Guillaume; Hellal, Jennifer; Ollivier, Patrick; Richard, Annie; Burel, Agnes; Jolly, Louis; Crampon, Marc; Michel, Caroline

2017-12-01

Understanding biofilm interactions with surrounding substratum and pollutants/particles can benefit from the application of existing microscopy tools. Using the example of biofilm interactions with zero-valent iron nanoparticles (nZVI), this study aims to apply various approaches in biofilm preparation and labeling for fluorescent or electron microscopy and energy dispersive X-ray spectrometry (EDS) microanalysis for accurate observations. According to the targeted microscopy method, biofilms were sampled as flocs or attached biofilm, submitted to labeling using 4',6-diamidino-2-phenylindol, lectins PNA and ConA coupled to fluorescent dye or gold nanoparticles, and prepared for observation (fixation, cross-section, freezing, ultramicrotomy). Fluorescent microscopy revealed that nZVI were embedded in the biofilm structure as aggregates but the resolution was insufficient to observe individual nZVI. Cryo-scanning electron microscopy (SEM) observations showed nZVI aggregates close to bacteria, but it was not possible to confirm direct interactions between nZVI and cell membranes. Scanning transmission electron microscopy in the SEM (STEM-in-SEM) showed that nZVI aggregates could enter the biofilm to a depth of 7-11 µm. Bacteria were surrounded by a ring of extracellular polymeric substances (EPS) preventing direct nZVI/membrane interactions. STEM/EDS mapping revealed a co-localization of nZVI aggregates with lectins suggesting a potential role of EPS in nZVI embedding. Thus, the combination of divergent microscopy approaches is a good approach to better understand and characterize biofilm/metal interactions.

Morphological studies on block copolymer modified PA 6 blends

DOE Office of Scientific and Technical Information (OSTI.GOV)

Poindl, M., E-mail: marcus.poindl@ikt.uni-stuttgart.de, E-mail: christian.bonten@ikt.uni-stuttgart.de; Bonten, C., E-mail: marcus.poindl@ikt.uni-stuttgart.de, E-mail: christian.bonten@ikt.uni-stuttgart.de

Recent studies show that compounding polyamide 6 (PA 6) with a PA 6 polyether block copolymers made by reaction injection molding (RIM) or continuous anionic polymerization in a reactive extrusion process (REX) result in blends with high impact strength and high stiffness compared to conventional rubber blends. In this paper, different high impact PA 6 blends were prepared using a twin screw extruder. The different impact modifiers were an ethylene propylene copolymer, a PA PA 6 polyether block copolymer made by reaction injection molding and one made by reactive extrusion. To ensure good particle matrix bonding, the ethylene propylene copolymermore » was grafted with maleic anhydride (EPR-g-MA). Due to the molecular structure of the two block copolymers, a coupling agent was not necessary. The block copolymers are semi-crystalline and partially cross-linked in contrast to commonly used amorphous rubbers which are usually uncured. The combination of different analysis methods like atomic force microscopy (AFM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) gave a detailed view in the structure of the blends. Due to the partial cross-linking, the particles of the block copolymers in the blends are not spherical like the ones of ethylene propylene copolymer. The differences in molecular structure, miscibility and grafting of the impact modifiers result in different mechanical properties and different blend morphologies.« less

A Magnetorheological Polishing-Based Approach for Studying Precision Microground Surfaces of Tungsten Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shafrir, S.N.; Lambropoulos, J.C.; Jacobs, S.D.

2007-03-23

Surface features of tungsten carbide composites processed by bound abrasive deterministic microgrinding and magnetorheological finishing (MRF) were studied for five WC-Ni composites, including one binderless material. All the materials studied were nonmagnetic with different microstructures and mechanical properties. White-light interferometry, scanning electron microscopy, and atomic force microscopy were used to characterize the surfaces after various grinding steps, surface etching, and MRF spot-taking.

Physicochemical characteristics of pristine and functionalized graphene.

PubMed

Bourdo, Shawn E; Al Faouri, Radwan; Sleezer, Robert; Nima, Zeid A; Lafont, Andersen; Chhetri, Bijay P; Benamara, Mourad; Martin, Betty; Salamo, Gregory J; Biris, Alexandru S

2017-11-01

Graphene-based nanomaterials have received significant attention in the last decade due to their interesting properties. Its electrical and thermal conductivity and strength make graphene well suited for a variety of applications, particularly for use as a composite material in plastics. Furthermore, much work is taking place to utilize graphene as a biomaterial for uses such as drug delivery and tissue regeneration scaffolds. Owing to the rapid progress of graphene and its potential in many marketplaces, the potential toxicity of these materials has garnered attention. Graphene, while simple in its purest form, can have many different chemical and physical properties. In this paper, we describe our toxicity evaluation of pristine graphene and a functionalized graphene sample that has been oxidized for enhanced hydrophilicity, which was synthesized from the pristine sample. The samples were characterized by X-ray photoelectron spectroscopy, Raman spectroscopy, infrared spectroscopy, thermogravimetric analysis, zeta-potential, atomic force microscopy and electron microscopy. We discuss the disagreement between the size of imaged samples analyzed by atomic force microscopy and by transmission electron microscopy. Furthermore, the samples each exhibit quite different surface chemistry and structure, which directly affects their interaction with aqueous environments and is important to consider when evaluating the toxicity of materials both in vitro and in vivo. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Collagenous microstructure of the glenoid labrum and biceps anchor

PubMed Central

Hill, A M; Hoerning, E J; Brook, K; Smith, C D; Moss, J; Ryder, T; Wallace, A L; Bull, A M J

2008-01-01

The glenoid labrum is a significant passive stabilizer of the shoulder joint. However, its microstructural form remains largely unappreciated, particularly in the context of its variety of functions. The focus of labral microscopy has often been histology and, as such, there is very little appreciation of collagen composition and arrangement of the labrum, and hence the micromechanics of the structure. On transmission electron microscopy, significant differences in diameter, area and perimeter were noted in the two gross histological groups of collagen fibril visualized; this suggests a heterogeneous collagenous composition with potentially distinct mechanical function. Scanning electron microscopy demonstrated three distinct zones of interest: a superficial mesh, a dense circumferential braided core potentially able to accommodate hoop stresses, and a loosely packed peri-core zone. Confocal microscopy revealed an articular surface fine fibrillar mesh potentially able to reduce surface friction, bundles of circumferential encapsulated fibres in the bulk of the tissue, and bone anchoring fibres at the osseous interface. Varying microstructure throughout the depth of the labrum suggests a role in accommodating different types of loading. An understanding of the labral microstructure can lead to development of hypotheses based upon an appreciation of this component of material property. This may aid an educated approach to surgical timing and repair. PMID:18429974

Cryo-electron microscopy study of bacteriophage T4 displaying anthrax toxin proteins

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fokine, Andrei; Bowman, Valorie D.; Battisti, Anthony J.

2007-10-25

The bacteriophage T4 capsid contains two accessory surface proteins, the small outer capsid protein (Soc, 870 copies) and the highly antigenic outer capsid protein (Hoc, 155 copies). As these are dispensable for capsid formation, they can be used for displaying proteins and macromolecular complexes on the T4 capsid surface. Anthrax toxin components were attached to the T4 capsid as a fusion protein of the N-terminal domain of the anthrax lethal factor (LFn) with Soc. The LFn-Soc fusion protein was complexed in vitro with Hoc{sup -}Soc{sup -}T4 phage. Subsequently, cleaved anthrax protective antigen heptamers (PA63){sub 7} were attached to the exposedmore » LFn domains. A cryo-electron microscopy study of the decorated T4 particles shows the complex of PA63 heptamers with LFn-Soc on the phage surface. Although the cryo-electron microscopy reconstruction is unable to differentiate on its own between different proposed models of the anthrax toxin, the density is consistent with a model that had predicted the orientation and position of three LFn molecules bound to one PA63 heptamer.« less

Genetically targeted 3D visualisation of Drosophila neurons under Electron Microscopy and X-Ray Microscopy using miniSOG

PubMed Central

Ng, Julian; Browning, Alyssa; Lechner, Lorenz; Terada, Masako; Howard, Gillian; Jefferis, Gregory S. X. E.

2016-01-01

Large dimension, high-resolution imaging is important for neural circuit visualisation as neurons have both long- and short-range patterns: from axons and dendrites to the numerous synapses at terminal endings. Electron Microscopy (EM) is the favoured approach for synaptic resolution imaging but how such structures can be segmented from high-density images within large volume datasets remains challenging. Fluorescent probes are widely used to localise synapses, identify cell-types and in tracing studies. The equivalent EM approach would benefit visualising such labelled structures from within sub-cellular, cellular, tissue and neuroanatomical contexts. Here we developed genetically-encoded, electron-dense markers using miniSOG. We demonstrate their ability in 1) labelling cellular sub-compartments of genetically-targeted neurons, 2) generating contrast under different EM modalities, and 3) segmenting labelled structures from EM volumes using computer-assisted strategies. We also tested non-destructive X-ray imaging on whole Drosophila brains to evaluate contrast staining. This enabled us to target specific regions for EM volume acquisition. PMID:27958322

Europium-doped mesoporous titania thin films: rare-earth locations and emission fluctuations under illumination.

PubMed

Leroy, Celine Marie; Cardinal, Thierry; Jubera, Veronique; Treguer-Delapierre, Mona; Majimel, Jerome; Manaud, Jean Pierre; Backov, Renal; Boissière, Cedric; Grosso, David; Sanchez, Clement; Viana, Bruno; Pellé, Fabienne

2008-10-06

Herein, Eu(III)-doped 3D mesoscopically ordered arrays of mesoporous and nanocrystalline titania are prepared and studied. The rare-earth-doped titania thin films-synthesized via evaporation-induced self-assembly (EISA)-are characterized by using environmental ellipsoporosimetry, electronic microscopy (i.e. high-resolution scanning electron microscopy, HR-SEM, and transmission electron microscopy, HR-TEM), X-ray diffraction, and luminescence spectroscopy. Structural characterizations show that high europium-ion loadings can be incorporated into the titanium-dioxide walls without destroying the mesoporous arrangement. The luminescence properties of Eu(III) are investigated by using steady-state and time-resolved spectroscopy via excitation of the Eu(III) ions through the titania host. Using Eu(III) luminescence as a probe, the europium-ion sites can be addressed with at least two different environments within the mesoporous framework, namely, a nanocrystalline environment and a glasslike one. Emission fluctuations ((5)D(0)-->(7)F(2)) are observed upon continuous UV excitation in the host matrix. These fluctuations are attributed to charge trapping and appear to be strongly dependent on the amount of europium and the level of crystallinity.

High-resolution structure of the Shigella type-III secretion needle by solid-state NMR and cryo-electron microscopy

NASA Astrophysics Data System (ADS)

Demers, Jean-Philippe; Habenstein, Birgit; Loquet, Antoine; Kumar Vasa, Suresh; Giller, Karin; Becker, Stefan; Baker, David; Lange, Adam; Sgourakis, Nikolaos G.

2014-09-01

We introduce a general hybrid approach for determining the structures of supramolecular assemblies. Cryo-electron microscopy (cryo-EM) data define the overall envelope of the assembly and rigid-body orientation of the subunits while solid-state nuclear magnetic resonance (ssNMR) chemical shifts and distance constraints define the local secondary structure, protein fold and inter-subunit interactions. Finally, Rosetta structure calculations provide a general framework to integrate the different sources of structural information. Combining a 7.7-Å cryo-EM density map and 996 ssNMR distance constraints, the structure of the type-III secretion system needle of Shigella flexneri is determined to a precision of 0.4 Å. The calculated structures are cross-validated using an independent data set of 691 ssNMR constraints and scanning transmission electron microscopy measurements. The hybrid model resolves the conformation of the non-conserved N terminus, which occupies a protrusion in the cryo-EM density, and reveals conserved pore residues forming a continuous pattern of electrostatic interactions, thereby suggesting a mechanism for effector protein translocation.

Self-assembly approach toward magnetic silica-type nanoparticles of different shapes from reverse block copolymer mesophases.

PubMed

Garcia, Carlos B W; Zhang, Yuanming; Mahajan, Surbhi; DiSalvo, Francis; Wiesner, Ulrich

2003-11-05

In the present study poly(isoprene-block-ethylene oxide), PI-b-PEO, block copolymers are used to structure iron oxide and silica precursors into reverse mesophases, which upon dissolution of the organic matrix lead to well-defined nanoparticles of spheres, cylinders, and plates based on the original structure of the mesophase prepared. The hybrid mesophases with sphere, cylinder, and lamellar morphologies containing the inorganic components in the minority phases are characterized through a combination of small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), and electron energy loss spectroscopy (EELS). After heat treatments the respective nanoparticles on mica surfaces are characterized by scanning force microscopy (SFM). X-ray diffraction (XRD) and superconducting quantum interference device (SQUID) magnetometer measurements are performed to demonstrate that the heat treatment leads to the formation of a magnetic gamma-Fe2O3 crystalline phase within the amorphous aluminosilicate. The results pave the way to functional, i.e., magnetic nanoparticles where the size, shape, and iron oxide concentration can be controlled opening a range of possible applications.

Electron microscopy localization and characterization of functionalized composite organic-inorganic SERS nanoparticles on leukemia cells.

PubMed

Koh, Ai Leen; Shachaf, Catherine M; Elchuri, Sailaja; Nolan, Garry P; Sinclair, Robert

2008-12-01

We demonstrate the use of electron microscopy as a powerful characterization tool to identify and locate antibody-conjugated composite organic-inorganic nanoparticle (COINs) surface enhanced Raman scattering (SERS) nanoparticles on cells. U937 leukemia cells labeled with antibody CD54-conjugated COINs were characterized in their native, hydrated state using wet scanning electron microscopy (SEM) and in their dehydrated state using high-resolution SEM. In both cases, the backscattered electron (BSE) detector was used to detect and identify the silver constituents in COINs due to its high sensitivity to atomic number variations within a specimen. The imaging and analytical capabilities in the SEM were further complemented by higher resolution transmission electron microscopy (TEM) images and scanning Auger electron spectroscopy (AES) data to give reliable and high-resolution information about nanoparticles and their binding to cell surface antigens.

Three-dimensional electron microscopy simulation with the CASINO Monte Carlo software.

PubMed

Demers, Hendrix; Poirier-Demers, Nicolas; Couture, Alexandre Réal; Joly, Dany; Guilmain, Marc; de Jonge, Niels; Drouin, Dominique

2011-01-01

Monte Carlo softwares are widely used to understand the capabilities of electron microscopes. To study more realistic applications with complex samples, 3D Monte Carlo softwares are needed. In this article, the development of the 3D version of CASINO is presented. The software feature a graphical user interface, an efficient (in relation to simulation time and memory use) 3D simulation model, accurate physic models for electron microscopy applications, and it is available freely to the scientific community at this website: www.gel.usherbrooke.ca/casino/index.html. It can be used to model backscattered, secondary, and transmitted electron signals as well as absorbed energy. The software features like scan points and shot noise allow the simulation and study of realistic experimental conditions. This software has an improved energy range for scanning electron microscopy and scanning transmission electron microscopy applications. Copyright © 2011 Wiley Periodicals, Inc.

Three-Dimensional Electron Microscopy Simulation with the CASINO Monte Carlo Software

PubMed Central

Demers, Hendrix; Poirier-Demers, Nicolas; Couture, Alexandre Réal; Joly, Dany; Guilmain, Marc; de Jonge, Niels; Drouin, Dominique

2011-01-01

Monte Carlo softwares are widely used to understand the capabilities of electron microscopes. To study more realistic applications with complex samples, 3D Monte Carlo softwares are needed. In this paper, the development of the 3D version of CASINO is presented. The software feature a graphical user interface, an efficient (in relation to simulation time and memory use) 3D simulation model, accurate physic models for electron microscopy applications, and it is available freely to the scientific community at this website: www.gel.usherbrooke.ca/casino/index.html. It can be used to model backscattered, secondary, and transmitted electron signals as well as absorbed energy. The software features like scan points and shot noise allow the simulation and study of realistic experimental conditions. This software has an improved energy range for scanning electron microscopy and scanning transmission electron microscopy applications. PMID:21769885

Ag(I)-bovine serum albumin hydrosol-mediated formation of Ag3PO4/reduced graphene oxide composites for visible-light degradation of Rhodamine B solution.

PubMed

Ma, Peiyan; Chen, Anliang; Wu, Yan; Fu, Zhengyi; Kong, Wei; Che, Liyuan; Ma, Ruifang

2014-03-01

A cost-effective Ag(I)-bovine serum albumin (BSA) supramolecular hydrosol strategy was utilized to assemble Ag3PO4 nanospheres onto reduced graphene oxide (rGO) sheets. The obtained composites were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, UV-vis absorption spectroscopy and Fourier transform infrared spectroscopy. Compared with the pure Ag3PO4 crystals and Ag3PO4 particles prepared with Ag(I)-BSA hydrosol as precursor, the Ag3PO4/rGO composites obtained with different content of graphene oxide indicated improved visible-light-driven photocatalysis activity for the decomposition of Rhodamine B aqueous solution. The results pointed to the possibility of synthesizing graphene-based photocatalysts by metal ion-BSA hydrosol. Copyright © 2013 Elsevier Inc. All rights reserved.

Transmission electron microscopy of AlGaAs/GaAs quantum cascade laser structures.

PubMed

Walther, T; Krysa, A B

2017-12-01

Quantum cascade lasers can be efficient infrared radiation sources and consist of several hundreds of very thin layers arranged in stacks that are repeated periodically. Both the thicknesses of the individual layers as well as the period lengths need to be monitored to high precision. Different transmission electron microscopy methods have been combined to analyse AlGaAs/GaAs quantum cascade laser structures in cross-section. We found a small parabolic variation of the growth rate during deposition, affecting the stack periodicity and a reduced aluminium content of the AlGaAs barriers, whereas their widths as well as those of the GaAs quantum wells agreed with the nominal values within one atomic layer. Growth on an offcut substrate led to facets and steps at the interfaces. © 2017 The Authors Journal of Microscopy © 2017 Royal Microscopical Society.

Direct Investigation of Mg Intercalation into the Orthorhombic V 2O 5 Cathode Using Atomic-Resolution Transmission Electron Microscopy [Direct Investigation of Mg intercalation into orthorhombic V 2O 5 cathode using Atomic Resolution Electron Microscopy Methods

DOE PAGES

Mukherjee, Arijita; Sa, Niya; Phillips, Patrick J.; ...

2017-02-13

Batteries based on Mg metal anode can promise much higher specific volumetric capacity and energy density compared to Li-ion systems and are, at the same time, safer and more cost-effective. While previous experimental reports have claimed reversible Mg intercalation into beyond Chevrel phase cathodes, they provide limited evidence of true Mg intercalation other than electrochemical data. Transmission electron microscopy techniques provide unique capabilities to directly image Mg intercalation and quantify the redox reaction within the cathode material. Here, we present a systematic study of Mg insertion into orthorhombic V 2O 5, combining aberration-corrected scanning transmission electron microscopy (STEM) imaging, electronmore » energy-loss spectroscopy (EELS), and energy-dispersive X-ray spectroscopy (EDX) analysis. We compare the results from an electrochemically cycled V 2O 5 cathode in a prospective full cell with Mg metal anode with a chemically synthesized MgV 2O 5 sample. Results suggest that the electrochemically cycled orthorhombic V 2O 5 cathode shows a local formation of the theoretically predicted ϵ-Mg0.5V2O5 phase; however, the intercalation levels of Mg are lower than predicted. Lastly, this phase is different from the chemically synthesized sample, which is found to represent the δ-MgV 2O 5 phase.« less

Rapid contrast evaluation method based on affinity beads and backscattered electron imaging for the screening of electron stains.

PubMed

Kaku, Hiroki; Inoue, Kanako; Muranaka, Yoshinori; Park, Pyoyun; Ikeda, Kenichi

2015-10-01

Uranyl salts are toxic and radioactive; therefore, several studies have been conducted to screen for substitutes of electron stains. In this regard, the contrast evaluation process is time consuming and the results obtained are inconsistent. In this study, we developed a novel contrast evaluation method using affinity beads and a backscattered electron image (BSEI), obtained using scanning electron microscopy. The contrast ratios of BSEI in each electron stain treatment were correlated with those of transmission electron microscopic images. The affinity beads bound to cell components independently. Protein and DNA samples were enhanced by image contrast treated with electron stains; however, this was not observed for sugars. Protein-conjugated beads showed an additive effect of image contrast when double-stained with lead. However, additive effect of double staining was not observed in DNA-conjugated beads. The varying chemical properties of oligopeptides showed differences in image contrast when treated with each electron stain. This BSEI-based evaluation method not only enables screening for alternate electron stains, but also helps analyze the underlying mechanisms of electron staining of cellular structures. © The Author 2015. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Fabrication of plasmonic nanopore by using electron beam irradiation for optical bio-sensor

NASA Astrophysics Data System (ADS)

Choi, Seong Soo; Park, Myoung Jin; Han, Chul Hee; Oh, Seh Joong; Park, Nam Kyou; Park, Doo Jae; Choi, Soo Bong; Kim, Yong-Sang

2017-05-01

The Au nano-hole surrounded by the periodic nano-patterns would provide the enhanced optical intensity. Hence, the nano-hole surrounded with periodic groove patterns can be utilized as single molecule nanobio optical sensor device. In this report, the nano-hole on the electron beam induced membrane surrounded by periodic groove patterns were fabricated by focused ion beam technique (FIB), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). Initially, the Au films with three different thickness of 40 nm, 60 nm, and 200 nm were deposited on the SiN film by using an electron beam sputter-deposition technique, followed by removal of the supporting SiN film. The nanopore was formed on the electron beam induced membrane under the FESEM electron beam irradiation. Nanopore formation inside the Au aperture was controlled down to a few nanometer, by electron beam irradiations. The optical intensities from the biomolecules on the surfaces including Au coated pyramid with periodic groove patterns were investigated via surface enhanced Raman spectroscopy (SERS). The fabricated nanopore surrounded by periodic patterns can be utilized as a next generation single molecule bio optical sensor.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sarkar, S.; Mondal, A.; Dey, K.

Highlights: • Reduced graphene oxides (RGO) are prepared by two chemical routes. • Defects in RGO are characterized by Raman, FTIR and XPS studies. • Defects tailor colossal dielectricity in RGO. - Abstract: Reduced graphene oxide (RGO) is prepared in two different chemical routes where reduction of graphene oxide is performed by hydrazine hydrate and through high pressure in hydrothermal reactor. Samples are characterized by X-ray powdered diffraction (XRD), thermo gravimetric analysis (TGA), field emission scanning electron microscopy (FESEM) and tunneling electron microscopy (TEM). Types of defects are probed by Raman, FTIR spectroscopy and X-ray photoelectron spectroscopy (XPS). UV–vis absorptionmore » reveals different optical band gaps of the two RGOs. Conductivity mechanism is studied through I–V measurements displaying different characteristic features which are addressed due to the presence of defects appeared in different synthesis. Significantly high value (∼10{sup 4}) of dielectric permittivity at 10 MHz is attractive for technological application which could be tuned by the defects present in RGO.« less

Ballistic Electron Emission Microscopy Studies of Ferromagnet - Semiconductor Interfaces

NASA Astrophysics Data System (ADS)

Mather, P. G.; Perrella, A. C.; Yurtsever, A.; Buhrman, R. A.

2004-03-01

Devices that employ spin as well as charge effects have been the subjects of extensive study recently. The magnetic tunneling transistor (1) is one important device that demonstrates an electrical means of injecting spin-polarized electrons into a semiconductor. A Schottky barrier lies at the heart of the device, and a high quality spatially homogenous and uniform barrier formed on GaAs is highly desirable. We have used ballistic electron emission microscopy (BEEM) to study CoFe, Fe and permalloy deposited on a GaAs substrate to give nanometer resolved evaluation of hot electron transport through the films and across the Schottky barrier. All films give a homogenous, uniform barrier as compared with evaporated Au/GaAs and Ag/GaAs interfaces. We will report on BEEM measurements of the hot electron transfer ratio across the Schottky barrier for the different ferromagnetic materials, and on the energy and spin-dependent hot electron attenuation lengths of the CoFe, Fe, and permalloy films. (1) Sebastiaan van Dijken, Xin Jiang, Stuart S. P. Parkin, APL, 80, 3364.

A High Resolution Look at Black Sand Particles from Sand Dunes of Saudi Arabia Using Electron Microscopy

NASA Astrophysics Data System (ADS)

Hussain, M. M.; Aburizaiza, O. S.; Siddique, A.; Hershey, D. L.; Guerrieri, D. A.; Qurashi, J.; Abbass, M.; Blake, D. R.; Khwaja, H. A.

2013-12-01

Particulate air pollution is a problem of health concern. The microscopic make-up of different varieties of sand particles found and collected at a sand dune site in Badr, Saudi Arabia has been determined. Primary emphasis is given to the use of multiple high resolution electron microscopy (viz., Scanning Electron Microscopy with Energy Dispersive X-ray spectrometry (SEM/EDS) and Laser Scanning Microscopy (LSM)) to study the morphologies, emission source types, size, and elemental composition of the particles, and to evaluate the presence of ';coatings or contaminants' adsorbed or carried on by the black sand particles. White sand contains natural coarse particles associated with wind-blown releases from crustal surfaces, weathering of an igneous/metamorphic rock source, and volcanic activities. Silicates (alumino-silicates) and quartz (clear, milky, rose) dominate white sand and rest appears to contain calcite, olivine, feldspar, and magnetite. Black sand particles exhibit very different morphologies and microstructures (surface roughness) compared with white sand and volcanic ash. Morphological analyses have shown that the black sand contain ultrafine particles. Black sand is strongly magnetic, which indicates the mineral magnetite (strongly magnetic) or elemental iron. Iron, C, O, Ti, Si, V, and S particles dominate the black sand. Natural and anthropogenic sources have been implicated for the observed particles. Analysis revealed that the surface of white sand particles is mainly covered with the fine particles. It is known that emissions from combustion contain carbon soot and other contaminants that are easily absorbed by soil particles during a long-range transport.

Chemical mapping and quantification at the atomic scale by scanning transmission electron microscopy.

PubMed

Chu, Ming-Wen; Chen, Cheng Hsuan

2013-06-25

With innovative modern material-growth methods, a broad spectrum of fascinating materials with reduced dimensions-ranging from single-atom catalysts, nanoplasmonic and nanophotonic materials to two-dimensional heterostructural interfaces-is continually emerging and extending the new frontiers of materials research. A persistent central challenge in this grand scientific context has been the detailed characterization of the individual objects in these materials with the highest spatial resolution, a problem prompting the need for experimental techniques that integrate both microscopic and spectroscopic capabilities. To date, several representative microscopy-spectroscopy combinations have become available, such as scanning tunneling microscopy, tip-enhanced scanning optical microscopy, atom probe tomography, scanning transmission X-ray microscopy, and scanning transmission electron microscopy (STEM). Among these tools, STEM boasts unique chemical and electronic sensitivity at unparalleled resolution. In this Perspective, we elucidate the advances in STEM and chemical mapping applications at the atomic scale by energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy with a focus on the ultimate challenge of chemical quantification with atomic accuracy.

Neurite density from magnetic resonance diffusion measurements at ultrahigh field: Comparison with light microscopy and electron microscopy

PubMed Central

Jespersen, Sune N.; Bjarkam, Carsten R.; Nyengaard, Jens R.; Chakravarty, M. Mallar; Hansen, Brian; Vosegaard, Thomas; Østergaard, Leif; Yablonskiy, Dmitriy; Nielsen, Niels Chr.; Vestergaard-Poulsen, Peter

2010-01-01

Due to its unique sensitivity to tissue microstructure, diffusion-weighted magnetic resonance imaging (MRI) has found many applications in clinical and fundamental science. With few exceptions, a more precise correspondence between physiological or biophysical properties and the obtained diffusion parameters remain uncertain due to lack of specificity. In this work, we address this problem by comparing diffusion parameters of a recently introduced model for water diffusion in brain matter to light microscopy and quantitative electron microscopy. Specifically, we compare diffusion model predictions of neurite density in rats to optical myelin staining intensity and stereological estimation of neurite volume fraction using electron microscopy. We find that the diffusion model describes data better and that its parameters show stronger correlation with optical and electron microscopy, and thus reflect myelinated neurite density better than the more frequently used diffusion tensor imaging (DTI) and cumulant expansion methods. Furthermore, the estimated neurite orientations capture dendritic architecture more faithfully than DTI diffusion ellipsoids. PMID:19732836

Application of high-angle annular dark field scanning transmission electron microscopy, scanning transmission electron microscopy-energy dispersive X-ray spectrometry, and energy-filtered transmission electron microscopy to the characterization of nanoparticles in the environment.

PubMed

Utsunomiya, Satoshi; Ewing, Rodney C

2003-02-15

A major challenge to the development of a fundamental understanding of transport and retardation mechanisms of trace metal contaminants (<10 ppm) is their identification and characterization at the nanoscale. Atomic-scale techniques, such as conventional transmission electron microscopy, although powerful, are limited by the extremely small amounts of material that are examined. However, recent advances in electron microscopy provide a number of new analytical techniques that expand its application in environmental studies, particularly those concerning heavy metals on airborne particulates or water-borne colloids. High-angle annular dark field scanning transmission electron microscopy (HAADF-STEM), STEM-energy-dispersive X-ray spectrometry (EDX), and energy-filtered TEM (EFTEM) can be effectively used to identify and characterize nanoparticles. The image contrast in HAADF-STEM is strongly correlated to the atomic mass: heavier elements contribute to brighter contrast. Gold nanocrystals in pyrite and uranium nanocrystals in atmospheric aerosols have been identified by HAADF-STEM and STEM-EDX mapping and subsequently characterized by high-resolution TEM (HRTEM). EFTEM was used to identify U and Fe nanocrystals embedded in an aluminosilicate. A rare, As-bearing nanophase, westerveldite (FeAs), was identified by STEM-EDX and HRTEM. The combined use of these techniques greatly expands the effective application of electron microscopy in environmental studies, especially when applied to metals of very low concentrations. This paper describes examples of how these electron microbeam techniques can be used in combination to characterize a low concentration of heavy metals (a few ppm) on nanoscale particles.

Consecutive light microscopy, scanning-transmission electron microscopy and transmission electron microscopy of traumatic human brain oedema and ischaemic brain damage.

PubMed

Castejon, O J; Castejon, H V; Diaz, M; Castellano, A

2001-10-01

Cortical biopsies of 11 patients with traumatic brain oedema were consecutively studied by light microscopy (LM) using thick plastic sections, scanning-transmission electron microscopy ((S)TEM) using semithin plastic sections and transmission electron microscopy (TEM) using ultrathin sections. Samples were glutaraldehyde-osmium fixed and embedded in Araldite or Epon. Thick sections were stained with toluidine-blue for light microscopy. Semithin sections were examined unstained and uncoated for (S)TEM. Ultrathin sections were stained with uranyl and lead. Perivascular haemorrhages and perivascular extravasation of proteinaceous oedema fluid were observed in both moderate and severe oedema. Ischaemic pyramidal and non-pyramidal nerve cells appeared shrunken, electron dense and with enlargement of intracytoplasmic membrane compartment. Notably swollen astrocytes were observed in all samples examined. Glycogen-rich and glycogen-depleted astrocytes were identified in anoxic-ischaemic regions. Dark and hydropic satellite, interfascicular and perivascular oligodendrocytes were also found. The status spongiosus of severely oedematous brain parenchyma observed by LM and (S)TEM was correlated with the enlarged extracellular space and disrupted neuropil observed by TEM. The (S)TEM is recommended as a suitable technique for studying pathological processes in the central nervous system and as an informative adjunct to LM and TEM.

Fracture Behaviors of Sn-Cu Intermetallic Compound Layer in Ball Grid Array Induced by Thermal Shock

NASA Astrophysics Data System (ADS)

Shen, Jun; Zhai, Dajun; Cao, Zhongming; Zhao, Mali; Pu, Yayun

2014-02-01

In this work, thermal shock reliability testing and finite-element analysis (FEA) of solder joints between ball grid array components and printed circuit boards with Cu pads were used to investigate the failure mechanism of solder interconnections. The morphologies, composition, and thickness of Sn-Cu intermetallic compounds (IMC) at the interface of Sn-3.0Ag-0.5Cu lead-free solder alloy and Cu substrates were investigated by scanning electron microscopy and transmission electron microscopy. Based on the experimental observations and FEA results, it can be recognized that the origin and propagation of cracks are caused primarily by the difference between the coefficient of thermal expansion of different parts of the packaged products, the growth behaviors and roughness of the IMC layer, and the grain size of the solder balls.

Impact of Defects in Powder Feedstock Materials on Microstructure of 304L and 316L Stainless Steel Produced by Additive Manufacturing

NASA Astrophysics Data System (ADS)

Morrow, Benjamin M.; Lienert, Thomas J.; Knapp, Cameron M.; Sutton, Jacob O.; Brand, Michael J.; Pacheco, Robin M.; Livescu, Veronica; Carpenter, John S.; Gray, George T.

2018-05-01

Recent work in both 304L and 316L stainless steel produced by additive manufacturing (AM) has shown that in addition to the unique, characteristic microstructures formed during the process, a fine dispersion of sub-micron particles, with a chemistry different from either the powder feedstock or the expected final material, are evident in the final microstructure. Such fine-scale features can only be resolved using transmission electron microscopy (TEM) or similar techniques. The present work uses electron microscopy to study both the initial powder feedstock and microstructures in final AM parts. Special attention is paid to the chemistry and origin of these nanoscale particles in several different metal alloys, and their impact on the final build. Comparisons to traditional, wrought material will be made.

Nanocomposites based on thermoplastic elastomers with functional basis of nano titanium dioxide

NASA Astrophysics Data System (ADS)

Yulovskaya, V. D.; Kuz'micheva, G. M.; Klechkovskaya, V. V.; Orekhov, A. S.; Zubavichus, Ya. V.; Domoroshchina, E. N.; Shegay, A. V.

2016-03-01

Nanocomposites based on a thermoplastic elastomer (TPE) (low-density polyethylene (LDPE) and 1,2-polybutadiene in a ratio of 60/40) with functional titanium dioxide nanoparticles of different nature, TiO2/TPE, have been prepared and investigated by a complex of methods (X-ray diffraction analysis using X-ray and synchrotron radiation beams, scanning electron microscopy, transmission electron microscopy, and X-ray energy-dispersive spectroscopy). The morphology of the composites is found to be somewhat different, depending on the TiO2 characteristics. It is revealed that nanocomposites with cellular or porous structures containing nano-TiO2 aggregates with a large specific surface and large sizes of crystallites and nanoparticles exhibit the best deformation‒strength and fatigue properties and stability to the effect of active media under conditions of ozone and vapor‒air aging.

Backscattered helium spectroscopy in the helium ion microscope: Principles, resolution and applications

NASA Astrophysics Data System (ADS)

van Gastel, R.; Hlawacek, G.; Dutta, S.; Poelsema, B.

2015-02-01

We demonstrate the possibilities and limitations for microstructure characterization using backscattered particles from a sharply focused helium ion beam. The interaction of helium ions with matter enables the imaging, spectroscopic characterization, as well as the nanometer scale modification of samples. The contrast that is seen in helium ion microscopy (HIM) images differs from that in scanning electron microscopy (SEM) and is generally a result of the higher surface sensitivity of the method. It allows, for instance, a much better visualization of low-Z materials as a result of the small secondary electron escape depth. However, the same differences in beam interaction that give HIM an edge over other imaging techniques, also impose limitations for spectroscopic applications using backscattered particles. Here we quantify those limitations and discuss opportunities to further improve the technique.

Interfacial surfactant competition and its impact on poly(ethylene oxide)/Au and poly(ethylene oxide)/Ag nanocomposite properties

PubMed Central

Seyhan, Merve; Kucharczyk, William; Yarar, U Ecem; Rickard, Katherine; Rende, Deniz; Baysal, Nihat; Bucak, Seyda; Ozisik, Rahmi

2017-01-01

The structure and properties of nanocomposites of poly(ethylene oxide), with Ag and Au nanoparticles, surface modified with a 1:1 (by volume) oleylamine/oleic acid mixture, were investigated via transmission electron microscopy, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry (DSC), infrared spectroscopy, dynamic mechanical analysis, and static mechanical testing. Results indicated that there was more oleylamine on Ag nanoparticles but more oleic acid on Au nanoparticles. This difference in surfactant populations on each nanoparticle led to different interfacial interactions with poly(ethylene oxide) and drastically influenced the glass transition temperature of these two nanocomposite systems. Almost all other properties were found to correlate strongly with dispersion and distribution state of Au and Ag nanoparticles, such that the property in question changed direction at the onset of agglomeration. PMID:28461744

Preparation and Effect of Gamma Radiation on The Properties and Biodegradability of Poly(Styrene/Starch) Blends

NASA Astrophysics Data System (ADS)

Ali, H. E.; Abdel Ghaffar, A. M.

2017-01-01

Biodegradable blends based on Poly(styrene/starch) Poly(Sty/Starch) were prepared by the casting method using different contents of starch in the range of 0-20 wt% aiming at preparing disposable packaging materials. The prepared bio-blends were Characterized by Fourier transform infrared (FTIR), swelling behavior, mechanical properties, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). It was found that the swelling behavior slightly increased with increasing starch content and not exceeding 7.5%. The results showed that by increasing irradiation dose up to 5 kGy, the mechanical properties of the prepared PSty/10 wt% Starch blend film modified than other blend films, and hence it is selected. Also the water resistant increased, by irradiation of the selected PSty/10 wt% Starch blend film. The intermolecular hydrogen bonding interaction between Starch and PSty of the PSty/10 wt% Starch blend film promote a more homogenous blend film as shown in scanning electron microscopy (SEM). The prepared Poly(Sty/Starch) blends with different compositions and the selected irradiated PSty/10 wt% Starch blend were subjected to biodegradation in soil burial tests for 6 months using two different types of soils; agricultural and desert soils, then analyzed gravimetrically and by scanning electron microscopy (SEM). The results suggested that there is a possibility of using irradiated PSty/10 wt% Starch at a dose of 5 kGy as a potential candidate for packaging material.

Yeast cytochrome c integrated with electronic elements: a nanoscopic and spectroscopic study down to single-molecule level

NASA Astrophysics Data System (ADS)

Delfino, I.; Bonanni, B.; Andolfi, L.; Baldacchini, C.; Bizzarri, A. R.; Cannistraro, S.

2007-06-01

Various aspects of redox protein integration with nano-electronic elements are addressed by a multi-technique investigation of different yeast cytochrome c (YCC)-based hybrid systems. Three different immobilization strategies on gold via organic linkers are explored, involving either covalent bonding or electrostatic interaction. Specifically, Au surfaces are chemically modified by self-assembled monolayers (SAMs) exposing thiol-reactive groups, or by acid-oxidized single-wall carbon nanotubes (SWNTs). Atomic force microscopy and scanning tunnelling microscopy are employed to characterize the morphology and the electronic properties of single YCC molecules adsorbed on the modified gold surfaces. In each hybrid system, the protein molecules are stably assembled, in a native configuration. A standing-up arrangement of YCC on SAMs is suggested, together with an enhancement of the molecular conduction, as compared to YCC directly assembled on gold. The electrostatic interaction with functionalized SWNTs allows several YCC adsorption geometries, with a preferential high-spin haem configuration, as outlined by Raman spectroscopy. Moreover, the conduction properties of YCC, explored in different YCC nanojunctions by conductive atomic force microscopy, indicate the effectiveness of electrical conduction through the molecule and its dependence on the electrode material. The joint employment of several techniques confirms the key role of a well-designed immobilization strategy, for optimizing biorecognition capabilities and electrical coupling with conductive substrates at the single-molecule level, as a starting point for advanced applications in nano-biotechnology.

Methods for characterizing plant fibers.

PubMed

Cruthers, Natasha; Carr, Debra; Niven, Brian; Girvan, Elizabeth; Laing, Raechel

2005-08-01

The effectiveness of different microscopy techniques for measuring the dimensions of ultimate fibers from harakeke (Phormium tenax, New Zealand flax) was investigated using a factorial experimental design. Constant variables were geographical location, location of specimens along the leaf, season (winter), individual plant, a fourth leaf from a north-facing fan, age of plant, and cultivars (two). Experimental variables were microscopy techniques and measurement axis. Measurements of width and length of harakeke ultimate fibers depended on the microscopic preparation/technique used as well as the cultivar examined. The best methods were (i) transverse sections of leaf specimens 4 microm thick, embedded in Paraplast and observed using light microscopy, and (ii) nonfixed ultimate fibers observed using scanning electron microscopy. (c) 2005 Wiley-Liss, Inc.

Development of structure in natural silk spinning and poly(vinyl alcohol) hydrogel formation

NASA Astrophysics Data System (ADS)

Willcox, Patricia Jeanene

This research involves the characterization of structure and structure formation in aqueous systems. Particularly, these studies investigate the effect of various processing variables on the structure formation that occurs upon conversion from aqueous solution to fiber or hydrogel. The two processes studied include natural silk fiber spinning and physical gelation of poly(vinyl alcohol), PVOH, in water. The techniques employed combine cryogenic technology for sample preparation and direct observation by transmission electron microscopy with electron diffraction, atomic force microscopy, optical rheometry, X-ray scattering and optical microscopy. In order to explore the full range of structure formation in natural silk spinning, studies are conducted in vivo and in vitro. In vivo structural investigations are accomplished through the cryogenic quenching and subsequent microtoming of live silk-spinning animals, Nephila clavipes (spider) and Bombyx mori (silkworm). Observations made using transmission electron microscopy, electron diffraction and atomic force microscopy indicate a cholesteric liquid crystalline mesophase of aqueous silk fibroin in both species. The mechanism of structure formation in solution is studied in vitro using optical rheometry on aqueous solutions made from regenerated Bombyx mori cocoon silk. Concentrated solutions exhibit birefringence under flow, with a wormlike conformation of the silk molecules in concentrated salt solution. Changes in salt concentration and pH of the aqueous silk solutions result in differing degrees of alignment and aggregation. These results suggest that structural control in the natural silk spinning process is accomplished by chemical manipulation of the electrostatic interactions and hydrogen bonding between chains. Application of cryogenic methods in transmission electron microscopy also provides a unique look at hydration-dependent structures in gels of poly(vinyl alcohol) produced by freeze-thaw processing. Morphologies ranging from circular pores to fibrillar networks are observed in gels formed from aqueous PVOH solutions subjected to cycles of freezing and thawing. These morphologies can be directly associated with the progressive nature of the mechanism of gelation as it proceeds from liquid-liquid phase separation to crystallization with increased cycling. A comparison of the structures produced by cycling and by aging suggests that there is a similarity in structural changes, but a superposition of the effects of cycling and aging is not possible.

Coarsening behaviour of M23C6 carbides in creep-resistant steel exposed to high temperatures

NASA Astrophysics Data System (ADS)

Godec, M.; Skobir Balantič, D. A.

2016-07-01

High operating temperatures can have very deleterious effects on the long-term performance of high-Cr, creep-resistant steels used, for example, in the structural components of power plants. For the popular creep-resistant steel X20CrMoV12.1 we analysed the processes of carbide growth using a variety of analytical techniques: transmission electron microscopy (TEM) and diffraction (TED), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). The evolution of the microstructure after different aging times was the basis for a much better understanding of the boundary-migration processes and the growth of the carbides. We present an explanation as to why some locations are preferential for this growth, and using EBSD we were able to define the proper orientational relationship between the carbides and the matrix.

A Shear Strain Route Dependency of Martensite Formation in 316L Stainless Steel.

PubMed

Kang, Suk Hoon; Kim, Tae Kyu; Jang, Jinsung; Oh, Kyu Hwan

2015-06-01

In this study, the effect of simple shearing on microstructure evolution and mechanical properties of 316L austenitic stainless steel were investigated. Two different shear strain routes were obtained by twisting cylindrical specimens in the forward and backward directions. The strain-induced martensite phase was effectively obtained by alteration of the routes. Formation of the martensite phase clearly resulted in significant hardening of the steel. Grain-size reduction and strain-induced martensitic transformation within the deformed structures of the strained specimens were characterized by scanning electron microscopy - electron back-scattered diffraction, X-ray diffraction, and the TEM-ASTAR (transmission electron microscopy - analytical scanning transmission atomic resolution, automatic crystal orientation/phase mapping for TEM) system. Significant numbers of twin networks were formed by alteration of the shear strain routes, and the martensite phases were nucleated at the twin interfaces.

Changes in resistant starch from two banana cultivars during postharvest storage.

PubMed

Wang, Juan; Tang, Xue Juan; Chen, Ping Sheng; Huang, Hui Hua

2014-08-01

Banana resistant starch samples were extracted and isolated from two banana cultivars (Musa AAA group, Cavendish subgroup and Musa ABB group, Pisang Awak subgroup) at seven ripening stages during postharvest storage. The structures of the resistant starch samples were analysed by light microscopy, polarising microscopy, scanning electron microscopy, X-ray diffraction, and infrared spectroscopy. Physicochemical properties (e.g., water-holding capacity, solubility, swelling power, transparency, starch-iodine absorption spectrum, and Brabender microviscoamylograph profile) were determined. The results revealed significant differences in microstructure and physicochemical characteristics among the banana resistant starch samples during different ripening stages. The results of this study provide valuable information for the potential applications of banana resistant starches. Copyright © 2014 Elsevier Ltd. All rights reserved.

Elucidating the real-time Ag nanoparticle growth on α-Ag2WO4 during electron beam irradiation: experimental evidence and theoretical insights.

PubMed

Pereira, Wyllamanney da Silva; Andrés, Juan; Gracia, Lourdes; San-Miguel, Miguel A; da Silva, Edison Z; Longo, Elson; Longo, Valeria M

2015-02-21

Why and how Ag is formed when electron beam irradiation takes place on α-Ag2WO4 in a vacuum transmission electron microscopy chamber? To find an answer, the atomic-scale mechanisms underlying the formation and growth of Ag on α-Ag2WO4 have been investigated by detailed in situ transmission electron microscopy (TEM) and field emission scanning electron microscopy (FE-SEM) studies, density functional theory based calculations and ab initio molecular dynamics simulations. The growth process at different times, chemical composition, size distribution and element distribution were analyzed in depth at the nanoscale level using FE-SEM, operated at different voltages (5, 10, 15, and 20 kV), and TEM with energy dispersive spectroscopy (EDS) characterization. The size of Ag nanoparticles covers a wide range of values. Most of the Ag particles are in the 20-40 nm range. The nucleation and formation of Ag on α-Ag2WO4 is a result of structural and electronic changes in the AgOx (x = 2,4, 6, and 7) clusters used as constituent building blocks of this material, consistent with metallic Ag formation. First principle calculations point out that Ag-3 and Ag-4-fold coordinated centers, located in the sub-surface of the (100) surface, are the most energetically favorable to undergo the diffusion process to form metallic Ag. Ab initio molecular dynamics simulations and the nudged elastic band (NEB) method were used to investigate the minimum energy pathways of these Ag atoms from positions in the first slab layer to outward sites on the (100) surface of α-Ag2WO4. The results point out that the injection of electrons decreases the activation barrier for this diffusion step and this unusual behavior results from the presence of a lower energy barrier process.

Electron microscopy analyses and electrical properties of the layered Bi{sub 2}WO{sub 6} phase

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taoufyq, A.; Laboratoire Matériaux et Environnement LME, Faculté des Sciences, Université Ibn Zohr, BP 8106, Cité Dakhla, Agadir, Maroc; Département d‘Études des Réacteurs, Laboratoire Dosimétrie Capteurs Instrumentation, CEA Cadarache

2013-07-15

The bismuth tungstate Bi{sub 2}WO{sub 6} was synthesized using a classical coprecipitation method followed by a calcination process at different temperatures. The samples were characterized by X-ray diffraction, simultaneous thermogravimetry and differential thermal analysis (TGA/DTA), scanning and transmission electron microscopy (SEM, TEM) analyses. The Rietveld analysis and electron diffraction clearly confirmed the Pca2{sub 1} non centrosymmetric space group previously proposed for this phase. The layers Bi{sub 2}O{sub 2}{sup 2+} and WO{sub 4}{sup 2−} have been directly evidenced from the HRTEM images. The electrical properties of Bi{sub 2}WO{sub 6} compacted pellets systems were determined from electrical impedance spectrometry (EIS) and directmore » current (DC) analyses, under air and argon, between 350 and 700 °C. The direct current analyses showed that the conduction observed from EIS analyses was mainly ionic in this temperature range, with a small electronic contribution. Electrical change above the transition temperature of 660 °C is observed under air and argon atmospheres. The strong conductivity increase observed under argon is interpreted in terms of formation of additional oxygen vacancies coupled with electron conduction. - Graphical abstract: High resolution transmission electron microscopy: inverse fast Fourier transform giving the layered structure of the Bi{sub 2}WO{sub 6} phase, with a representation of the cell dimensions (b and c vectors). The Bi{sub 2}O{sub 2}{sup 2+} and WO{sub 4}{sup 2−} sandwiches are visible in the IFFT image. - Highlights: • Using transmission electron microscopy, we visualize the layered structure of Bi{sub 2}WO{sub 6}. • Electrical analyses under argon gas show some increase in conductivity. • The phase transition at 660 °C is evidenced from electrical modification.« less

Carbon contamination in scanning transmission electron microscopy and its impact on phase-plate applications.

PubMed

Hettler, Simon; Dries, Manuel; Hermann, Peter; Obermair, Martin; Gerthsen, Dagmar; Malac, Marek

2017-05-01

We analyze electron-beam induced carbon contamination in a transmission electron microscope. The study is performed on thin films potentially suitable as phase plates for phase-contrast transmission electron microscopy. Electron energy-loss spectroscopy and phase-plate imaging is utilized to analyze the contamination. The deposited contamination layer is identified as a graphitic carbon layer which is not prone to electrostatic charging whereas a non-conductive underlying substrate charges. Several methods that inhibit contamination are evaluated and the impact of carbon contamination on phase-plate imaging is discussed. The findings are in general interesting for scanning transmission electron microscopy applications. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

Evolution of Metastable Defects and Its Effect on the Electronic Properties of MoS2 Films.

PubMed

Precner, M; Polaković, T; Qiao, Qiao; Trainer, D J; Putilov, A V; Di Giorgio, C; Cone, I; Zhu, Y; Xi, X X; Iavarone, M; Karapetrov, G

2018-04-30

We report on structural and electronic properties of defects in chemical vapor-deposited monolayer and few-layer MoS 2 films. Scanning tunneling microscopy, Kelvin probe force microscopy, and transmission electron microscopy were used to obtain high resolution images and quantitative measurements of the local density of states, work function and nature of defects in MoS 2 films. We track the evolution of defects that are formed under heating and electron beam irradiation. We observe formation of metastable domains with different work function values after annealing the material in ultra-high vacuum to moderate temperatures. We attribute these metastable values of the work function to evolution of crystal defects forming during the annealing. The experiments show that sulfur vacancies formed after exposure to elevated temperatures diffuse, coalesce, and migrate bringing the system from a metastable to equilibrium ground state. The process could be thermally or e-beam activated with estimated energy barrier for sulfur vacancy migration of 0.6 eV in single unit cell MoS 2 . Even at equilibrium conditions, the work function and local density of states values are strongly affected near grain boundaries and edges. The results provide initial estimates of the thermal budgets available for reliable fabrication of MoS 2 -based integrated electronics and indicate the importance of defect control and layer passivation.

Evolution of Metastable Defects and Its Effect on the Electronic Properties of MoS 2 Films

DOE PAGES

Precner, Marian; Polakovic, T.; Qiao, Qiao; ...

2018-04-30

Here, we report on structural and electronic properties of defects in chemical vapor-deposited monolayer and few-layer MoS 2 films. Scanning tunneling microscopy, Kelvin probe force microscopy, and transmission electron microscopy were used to obtain high resolution images and quantitative measurements of the local density of states, work function and nature of defects in MoS 2 films. We track the evolution of defects that are formed under heating and electron beam irradiation. We observe formation of metastable domains with different work function values after annealing the material in ultra-high vacuum to moderate temperatures. We attribute these metastable values of the workmore » function to evolution of crystal defects forming during the annealing. The experiments show that sulfur vacancies formed after exposure to elevated temperatures diffuse, coalesce, and migrate bringing the system from a metastable to equilibrium ground state. The process could be thermally or e-beam activated with estimated energy barrier for sulfur vacancy migration of 0.6 eV in single unit cell MoS 2. Even at equilibrium conditions, the work function and local density of states values are strongly affected near grain boundaries and edges. The results provide initial estimates of the thermal budgets available for reliable fabrication of MoS 2-based integrated electronics and indicate the importance of defect control and layer passivation.« less

Evolution of Metastable Defects and Its Effect on the Electronic Properties of MoS 2 Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Precner, Marian; Polakovic, T.; Qiao, Qiao

Here, we report on structural and electronic properties of defects in chemical vapor-deposited monolayer and few-layer MoS 2 films. Scanning tunneling microscopy, Kelvin probe force microscopy, and transmission electron microscopy were used to obtain high resolution images and quantitative measurements of the local density of states, work function and nature of defects in MoS 2 films. We track the evolution of defects that are formed under heating and electron beam irradiation. We observe formation of metastable domains with different work function values after annealing the material in ultra-high vacuum to moderate temperatures. We attribute these metastable values of the workmore » function to evolution of crystal defects forming during the annealing. The experiments show that sulfur vacancies formed after exposure to elevated temperatures diffuse, coalesce, and migrate bringing the system from a metastable to equilibrium ground state. The process could be thermally or e-beam activated with estimated energy barrier for sulfur vacancy migration of 0.6 eV in single unit cell MoS 2. Even at equilibrium conditions, the work function and local density of states values are strongly affected near grain boundaries and edges. The results provide initial estimates of the thermal budgets available for reliable fabrication of MoS 2-based integrated electronics and indicate the importance of defect control and layer passivation.« less

Evaluation of anterior lenticonus in alport syndrome using tracey wavefront aberrometry and transmission electron microscopy.

PubMed

Kim, Kwan Soo; Kim, Mo Sae; Kim, Joon Mo; Choi, Chul Young

2010-01-01

To evaluate the efficacy of Tracey wavefront aberrometry (Tracey Technologies, Houston, TX) and transmission electron microscopy for the detection of anterior lenticonus in Alport syndrome. Tracey wavefront aberrometry was used to treat a patient with bilateral anterior lenticonus who had a history of Alport syndrome. For transmission electron microscopic examination, anterior lens capsules were obtained during clear lens phacoemulsification and intraocular lens implantation. Spherical aberrations were the predominant higher-order aberrations in the internal optics of both eyes. The Tracey wavefront aberrometer showed that most of the irregular astigmatism originated from the lenticular portion. Transmission electron microscopy of the specimens showed anterior lens capsules with decreased thickness and multiple dehiscences. Tracey wavefront aberrometry and transmission electron microscopy are effective tools for evaluation of anterior lenticonus in Alport syndrome. Copyright 2010, SLACK Incorporated.

Fabrication of ZnS nanoparticle chains on a protein template

PubMed Central

Hulleman, J.; Kim, S. M.; Tumkur, T.; Rochet, J.-C.; Stach, E.; Stanciu, L.

2011-01-01

In the present study, we have exploited the properties of a fibrillar protein for the template synthesis of zinc sulfide (ZnS) nanoparticle chains. The diameter of the ZnS nanoparticle chains was tuned in range of ~30 to ~165 nm by varying the process variables. The nanoparticle chains were characterized by field emission scanning electron microscopy, UV–Visible spectroscopy, transmission electron microscopy, electron energy loss spectroscopy, and high-resolution transmission electron microscopy. The effect of incubation temperature on the morphology of the nanoparticle chains was also studied. PMID:21804765

Quantitative Analysis of Electron Beam Damage in Organic Thin Films

PubMed Central

2017-01-01

In transmission electron microscopy (TEM) the interaction of an electron beam with polymers such as P3HT:PCBM photovoltaic nanocomposites results in electron beam damage, which is the most important factor limiting acquisition of structural or chemical data at high spatial resolution. Beam effects can vary depending on parameters such as electron dose rate, temperature during imaging, and the presence of water and oxygen in the sample. Furthermore, beam damage will occur at different length scales. To assess beam damage at the angstrom scale, we followed the intensity of P3HT and PCBM diffraction rings as a function of accumulated electron dose by acquiring dose series and varying the electron dose rate, sample preparation, and the temperature during acquisition. From this, we calculated a critical dose for diffraction experiments. In imaging mode, thin film deformation was assessed using the normalized cross-correlation coefficient, while mass loss was determined via changes in average intensity and standard deviation, also varying electron dose rate, sample preparation, and temperature during acquisition. The understanding of beam damage and the determination of critical electron doses provides a framework for future experiments to maximize the information content during the acquisition of images and diffraction patterns with (cryogenic) transmission electron microscopy. PMID:28553431

Using Graphene Liquid Cell Transmission Electron Microscopy to Study in Situ Nanocrystal Etching.

PubMed

Hauwiller, Matthew R; Ondry, Justin C; Alivisatos, A Paul

2018-05-17

Graphene liquid cell electron microscopy provides the ability to observe nanoscale chemical transformations and dynamics as the reactions are occurring in liquid environments. This manuscript describes the process for making graphene liquid cells through the example of graphene liquid cell transmission electron microscopy (TEM) experiments of gold nanocrystal etching. The protocol for making graphene liquid cells involves coating gold, holey-carbon TEM grids with chemical vapor deposition graphene and then using those graphene-coated grids to encapsulate liquid between two graphene surfaces. These pockets of liquid, with the nanomaterial of interest, are imaged in the electron microscope to see the dynamics of the nanoscale process, in this case the oxidative etching of gold nanorods. By controlling the electron beam dose rate, which modulates the etching species in the liquid cell, the underlying mechanisms of how atoms are removed from nanocrystals to form different facets and shapes can be better understood. Graphene liquid cell TEM has the advantages of high spatial resolution, compatibility with traditional TEM holders, and low start-up costs for research groups. Current limitations include delicate sample preparation, lack of flow capability, and reliance on electron beam-generated radiolysis products to induce reactions. With further development and control, graphene liquid cell may become a ubiquitous technique in nanomaterials and biology, and is already being used to study mechanisms governing growth, etching, and self-assembly processes of nanomaterials in liquid on the single particle level.

Correlation of live-cell imaging with volume scanning electron microscopy.

PubMed

Lucas, Miriam S; Günthert, Maja; Bittermann, Anne Greet; de Marco, Alex; Wepf, Roger

2017-01-01

Live-cell imaging is one of the most widely applied methods in live science. Here we describe two setups for live-cell imaging, which can easily be combined with volume SEM for correlative studies. The first procedure applies cell culture dishes with a gridded glass support, which can be used for any light microscopy modality. The second approach is a flow-chamber setup based on Ibidi μ-slides. Both live-cell imaging strategies can be followed up with serial blockface- or focused ion beam-scanning electron microscopy. Two types of resin embedding after heavy metal staining and dehydration are presented making best use of the particular advantages of each imaging modality: classical en-bloc embedding and thin-layer plastification. The latter can be used only for focused ion beam-scanning electron microscopy, but is advantageous for studying cell-interactions with specific substrates, or when the substrate cannot be removed. En-bloc embedding has diverse applications and can be applied for both described volume scanning electron microscopy techniques. Finally, strategies for relocating the cell of interest are discussed for both embedding approaches and in respect to the applied light and scanning electron microscopy methods. Copyright © 2017 Elsevier Inc. All rights reserved.

The effects of viscoelastic polymer substrates on adult stem cell differentiation

NASA Astrophysics Data System (ADS)

Chang, Chungchueh; Fields, Adam; Ramek, Alex; Jurukovski, Vladimir; Simon, Marcia; Rafailovich, Miriam

2009-03-01

Dental Pulp Stem Cells (DPSCs) are known to differentiate in either bone, dentine, or nerve tissue by different environment signals. In this study, we have determined whether differentiation could only through modification of the substrate mechanics. Atomic Force Microscopy (AFM) on Shear Modulation Force Microscopy (SMFM) mode indicated that the spun-cast polybutadiene (PB) thin films could be used to provide different stiffness substrates by changing the thicknesses of thin films. DPSCs were then plated on these substrates and cultured in standard media. After 28 days incubation, Lasar Scanning Confocal Microscopy (LSCM) with mercury lamp indicated that the crystals were observed only on hard surfaces. The Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray analysis (EDX analysis) indicated that the crystals are calcium phosphates. The Glancing Incidence Diffraction (GID) was also used to determine the structure of crystals. These results indicate that DPSCs could be differentiated into osteoblasts by mechanical stimuli from substrate mechanics.

Evaluation of three different rotary systems during endodontic retreatment - Analysis by scanning electron microscopy

PubMed Central

Vidal, Flávia-Teixeira; Nunes, Eduardo; Horta, Martinho-Campolina-Rebello; Freitas, Maria-Rita-Lopes-da Silva

2016-01-01

Background Endodontic therapy is considered a series of important and interdependent steps, and failure of any of these steps may compromise the treatment outcome. This study aimed to evaluate the effectiveness of three different rotary systems in removing obturation materials during endodontic retreatment using scanning electron microscopy (SEM) analysis. Material and Methods Thirty-six endodontically treated teeth were selected and divided into 3 groups of 10 and 1 control group with 6 dental elements. The groups were divided according to the rotary system used for removing gutta-percha, as follows: G1: ProTaper system; G2: K3 system; G3: Mtwo system; and G4: Control group. Thereafter, the roots were split and the sections were observed under SEM, for analysis and counting of clear dentinal tubules, creating the variable “degree of dentinal tubule patency” (0: intensely clear; 1: moderately clear; 2: slightly clear; 3: completely blocked). The data were subjected to the Friedman and Kruskal-Wallis statistical tests. Results No differences were observed in the “degree of dentinal tubule patency” neither between the root thirds (to each evaluated group) nor between the groups (to each evaluated third). Nevertheless, when the three root thirds were grouped (providing evaluation of all root extension), the “degree of dentinal tubule patency” was lower in G1 than in G3 (p<0.05), but showed no differences neither between G1 and G2 nor G2 and G3. Conclusions No technique was able to completely remove the canal obturation material, despite G1 having shown better results, although without significant difference to G2 Key words:Scanning electron microscopy, NiTi, retreatment. PMID:27034750

Comparative evaluation of topographical data of dental implant surfaces applying optical interferometry and scanning electron microscopy.

PubMed

Kournetas, N; Spintzyk, S; Schweizer, E; Sawada, T; Said, F; Schmid, P; Geis-Gerstorfer, J; Eliades, G; Rupp, F

2017-08-01

Comparability of topographical data of implant surfaces in literature is low and their clinical relevance often equivocal. The aim of this study was to investigate the ability of scanning electron microscopy and optical interferometry to assess statistically similar 3-dimensional roughness parameter results and to evaluate these data based on predefined criteria regarded relevant for a favorable biological response. Four different commercial dental screw-type implants (NanoTite Certain Prevail, TiUnite Brånemark Mk III, XiVE S Plus and SLA Standard Plus) were analyzed by stereo scanning electron microscopy and white light interferometry. Surface height, spatial and hybrid roughness parameters (Sa, Sz, Ssk, Sku, Sal, Str, Sdr) were assessed from raw and filtered data (Gaussian 50μm and 5μm cut-off-filters), respectively. Data were statistically compared by one-way ANOVA and Tukey-Kramer post-hoc test. For a clinically relevant interpretation, a categorizing evaluation approach was used based on predefined threshold criteria for each roughness parameter. The two methods exhibited predominantly statistical differences. Dependent on roughness parameters and filter settings, both methods showed variations in rankings of the implant surfaces and differed in their ability to discriminate the different topographies. Overall, the analyses revealed scale-dependent roughness data. Compared to the pure statistical approach, the categorizing evaluation resulted in much more similarities between the two methods. This study suggests to reconsider current approaches for the topographical evaluation of implant surfaces and to further seek after proper experimental settings. Furthermore, the specific role of different roughness parameters for the bioresponse has to be studied in detail in order to better define clinically relevant, scale-dependent and parameter-specific thresholds and ranges. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Evolution of the Deformation Behavior of Sn-Rich Solders during Cyclic Fatigue

NASA Astrophysics Data System (ADS)

Wentlent, Luke Arthur

Continuous developments in the electronics industry have provided a critical need for a quantitative, fundamental understanding of the behavior of SnAgCu (SAC) solders in both isothermal and thermal fatigue conditions. This study examines the damage behavior of Sn-based solders in a constant amplitude and variable amplitude environment. In addition, damage properties are correlated with crystal orientation and slip behavior. Select solder joints were continuously characterized and tested repeatedly in order to eliminate the joint to joint variation due to the anisotropy of beta-Sn. Characterization was partitioned into three different categories: effective properties and slip behavior, creep mechanisms and crystal morphology development, and atomic behavior and evolution. Active slip systems were correlated with measured properties. Characterization of the mechanical behavior was performed by the calculation and extrapolation of the elastic modulus, work, effective stiffness, Schmid factors, and time-dependent plasticity (creep). Electron microscopy based characterization methods included Scanning Electron Microscopy (SEM), Electron Backscattering Diffraction (EBSD), and Transmission Electron Microscopy (TEM). Testing showed a clear evolution of the steady-state creep mechanism when the cycling amplitudes were varied, from dislocation controlled to diffusion controlled creep. Dislocation behavior was examined and shown to evolve differently in single amplitude vs. variable amplitude testing. Finally, the mechanism of the recrystallization behavior of the beta-Sn was observed. This work fills a gap in the literature, providing a systematic study which identifies how the damage behavior in Sn-alloys depends upon the previous damage. A link is made between the observed creep behavior and the dislocation observations, providing a unified picture. Information developed in this work lays a stepping stone to future fundamental analyses as well as clarifying aspects of the mechanistic behavior of Sn and Sn-based alloys.

Deviatoric stresses promoted metallization in rhenium disulfide

NASA Astrophysics Data System (ADS)

Zhuang, Yukai; Dai, Lidong; Li, Heping; Hu, Haiying; Liu, Kaixiang; Yang, Linfei; Pu, Chang; Hong, Meiling; Liu, Pengfei

2018-04-01

The structural, vibrational and electronic properties of ReS2 were investigated up to ~34 GPa by Raman spectroscopy, AC impedance spectroscopy, atomic force microscopy and high-resolution transmission electron microscopy, combining with first-principle calculations under two different pressure environments. The experimental results showed that ReS2 endured a structural transition at ~2.5 GPa both under non-hydrostatic and hydrostatic conditions. We found that a metallization occurred at ~27.5 GPa under non-hydrostatic conditions and at ~35.4 GPa under hydrostatic conditions. The occurrence of distinct metallization point attributed to the influence of deviatoric stresses, which significantly affected the layered structure and the weak van der Waals interaction for ReS2.

Flow-induced immobilization of glucose oxidase in nonionic micellar nanogels for glucose sensing.

PubMed

Cardiel, Joshua J; Zhao, Ya; Tonggu, Lige; Wang, Liguo; Chung, Jae-Hyun; Shen, Amy Q

2014-10-21

A simple microfluidic platform was utilized to immobilize glucose oxidase (GOx) in a nonionic micellar scaffold. The immobilization of GOx was verified by using a combination of cryogenic electron microscopy (cryo-EM), scanning electron microscopy (SEM), and ultraviolet spectroscopy (UV) techniques. Chronoamperometric measurements were conducted on nanogel-GOx scaffolds under different glucose concentrations, exhibiting linear amperometric responses. Without impacting the lifetime and denaturation of GOx, the nonionic nanogel provides a favorable microenvironment for GOx in biological media. This flow-induced immobilization method in a nonionic nanogel host matrix opens up new pathways for designing a simple, fast, biocompatible, and cost-effective process to immobilize biomolecules that are averse to ionic environments.

Preparation and magnetic properties of magnetic photonic crystal by using monodisperse polystyrene covered Fe3O4 nanoparticles onto glass substrate

NASA Astrophysics Data System (ADS)

Azizi, Zahra Sadat; Tehranchi, Mohammad Mehdi; Vakili, Seyed Hamed; Pourmahdian, Saeed

2018-05-01

Engineering approach towards combined photonic band gap properties and magnetic/polymer composite particles, attract considerable attention of researchers due to their unique properties. In this research, two different magnetic particles were prepared by nearly monodisperse polystyrene spheres as bead with two concentrations of Fe3O4 nanoparticles to prepare magnetic photonic crystals (MPCs). The crystal surfaces and particles morphology were investigated employing scanning electron microscopy and transmission electron microscopy. The volume fraction of magnetic material embedded into colloidal spheres and their morphology was found to be a key parameter in the optical and magneto-optical properties of transparent MPC.

Solid state amorphization in the Al-Fe binary system during high energy milling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Urban, P., E-mail: purban@us.es; Montes, J. M.; Cintas, J.

2013-12-16

In the present study, mechanical alloying (MA) of Al75Fe25 elemental powders mixture was carried out in argon atmosphere, using a high energy attritor ball mill. The microstructure of the milled products at different stages of milling was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The results showed that the amorphous phase content increased by increasing the milling time, and after 50 hours the amorphization process became complete. Heating the samples resulted in the crystallization of the synthesized amorphous alloys and the appearance of the equilibrium intermetallic compounds Al{sub 5}Fe{submore » 2}.« less

Simultaneous orientation and thickness mapping in transmission electron microscopy

DOE PAGES

Tyutyunnikov, Dmitry; Özdöl, V. Burak; Koch, Christoph T.

2014-12-04

In this paper we introduce an approach for simultaneous thickness and orientation mapping of crystalline samples by means of transmission electron microscopy. We show that local thickness and orientation values can be extracted from experimental dark-field (DF) image data acquired at different specimen tilts. The method has been implemented to automatically acquire the necessary data and then map thickness and crystal orientation for a given region of interest. We have applied this technique to a specimen prepared from a commercial semiconductor device, containing multiple 22 nm technology transistor structures. The performance and limitations of our method are discussed and comparedmore » to those of other techniques available.« less

Formation of ZnS nanostructures by a simple way of thermal evaporation

NASA Astrophysics Data System (ADS)

Yuan, H. J.; Xie, S. S.; Liu, D. F.; Yan, X. Q.; Zhou, Z. P.; Ci, L. J.; Wang, J. X.; Gao, Y.; Song, L.; Liu, L. F.; Zhou, W. Y.; Wang, G.

2003-11-01

The mass synthesis of ZnS nanobelts, nanowires, and nanoparticles has been achieved by a simple method of thermal evaporation of ZnS powders onto silicon substrates in the presence of Au catalyst. The temperature of the substrates and the concentration of ZnS vapor were the critical experimental parameters for the formation of different morphologies of ZnS nanostructures. Scanning electron microscopy and transmission electron microscopy show that the diameters of as-prepared nanowires were 30-70 nm. The UV emission at 374 nm is probably related to the exciton emission, while the mechanism of blue emission at 443 nm is probably mainly due to the presence of various surface states.

Preparation and characterization of oriented silica nanowires

NASA Astrophysics Data System (ADS)

Sun, S. H.; Meng, G. W.; Zhang, M. G.; Tian, Y. T.; Xie, T.; Zhang, L. D.

2003-11-01

Large-scale of oriented closely packed silica nanowire bunches have been synthesized by using large size (1-10 μm in diameter), low melting point tin droplets as catalyst on silicon wafers at 980 °C. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses show that the amorphous silica nanowires have lengths of 50-100 μm and diameters of 100-200 nm. Unlike any previous observed results using high melting point metal (such as gold and iron) as catalyst, the Sn catalyst growth exhibits many interesting phenomena. Each Sn ball can simultaneously catalyze the growth of many silica nanowires, which is quite different from the conventional vapor-liquid-solid process.

Microstructural characterization of weld joints of 9Cr reduced activation ferritic martensitic steel fabricated by different joining methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomas Paul, V.; Saroja, S.; Albert, S.K.

This paper presents a detailed electron microscopy study on the microstructure of various regions of weldment fabricated by three welding methods namely tungsten inert gas welding, electron beam welding and laser beam welding in an indigenously developed 9Cr reduced activation ferritic/martensitic steel. Electron back scatter diffraction studies showed a random micro-texture in all the three welds. Microstructural changes during thermal exposures were studied and corroborated with hardness and optimized conditions for the post weld heat treatment have been identified for this steel. Hollomon–Jaffe parameter has been used to estimate the extent of tempering. The activation energy for the tempering processmore » has been evaluated and found to be corresponding to interstitial diffusion of carbon in ferrite matrix. The type and microchemistry of secondary phases in different regions of the weldment have been identified by analytical transmission electron microscopy. - Highlights: • Comparison of microstructural parameters in TIG, electron beam and laser welds of RAFM steel • EBSD studies to illustrate the absence of preferred orientation and identification of prior austenite grain size using phase identification map • Optimization of PWHT conditions for indigenous RAFM steel • Study of kinetics of tempering and estimation of apparent activation energy of the process.« less

Diffraction and microscopy with attosecond electron pulse trains

NASA Astrophysics Data System (ADS)

Morimoto, Yuya; Baum, Peter

2018-03-01

Attosecond spectroscopy1-7 can resolve electronic processes directly in time, but a movie-like space-time recording is impeded by the too long wavelength ( 100 times larger than atomic distances) or the source-sample entanglement in re-collision techniques8-11. Here we advance attosecond metrology to picometre wavelength and sub-atomic resolution by using free-space electrons instead of higher-harmonic photons1-7 or re-colliding wavepackets8-11. A beam of 70-keV electrons at 4.5-pm de Broglie wavelength is modulated by the electric field of laser cycles into a sequence of electron pulses with sub-optical-cycle duration. Time-resolved diffraction from crystalline silicon reveals a < 10-as delay of Bragg emission and demonstrates the possibility of analytic attosecond-ångström diffraction. Real-space electron microscopy visualizes with sub-light-cycle resolution how an optical wave propagates in space and time. This unification of attosecond science with electron microscopy and diffraction enables space-time imaging of light-driven processes in the entire range of sample morphologies that electron microscopy can access.

HANFORD WASTE MINERALOGY REFERENCE REPORT

DOE Office of Scientific and Technical Information (OSTI.GOV)

DISSELKAMP RS

2010-06-29

This report lists the observed mineral phases present in the Hanford tanks. This task was accomplished by performing a review of numerous reports that used experimental techniques including, but not limited to: x-ray diffraction, polarized light microscopy, scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, electron energy loss spectroscopy, and particle size distribution analyses. This report contains tables that can be used as a quick reference to identify the crystal phases observed in Hanford waste.

HANFORD WASTE MINEROLOGY REFERENCE REPORT

DOE Office of Scientific and Technical Information (OSTI.GOV)

DISSELKAMP RS

2010-06-18

This report lists the observed mineral phase phases present in the Hanford tanks. This task was accomplished by performing a review of numerous reports using experimental techniques including, but not limited to: x-ray diffraction, polarized light microscopy, scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, electron energy loss spectroscopy, and particle size distribution analyses. This report contains tables that can be used as a quick reference to identify the crystal phases present observed in Hanford waste.

Three dimensional electron microscopy and in silico tools for macromolecular structure determination

PubMed Central

Borkotoky, Subhomoi; Meena, Chetan Kumar; Khan, Mohammad Wahab; Murali, Ayaluru

2013-01-01

Recently, structural biology witnessed a major tool - electron microscopy - in solving the structures of macromolecules in addition to the conventional techniques, X-ray crystallography and nuclear magnetic resonance (NMR). Three dimensional transmission electron microscopy (3DTEM) is one of the most sophisticated techniques for structure determination of molecular machines. Known to give the 3-dimensional structures in its native form with literally no upper limit on size of the macromolecule, this tool does not need the crystallization of the protein. Combining the 3DTEM data with in silico tools, one can have better refined structure of a desired complex. In this review we are discussing about the recent advancements in three dimensional electron microscopy and tools associated with it. PMID:27092033

Tackling the Challenges of Dynamic Experiments Using Liquid-Cell Transmission Electron Microscopy.

PubMed

Parent, Lucas R; Bakalis, Evangelos; Proetto, Maria; Li, Yiwen; Park, Chiwoo; Zerbetto, Francesco; Gianneschi, Nathan C

2018-01-16

Revolutions in science and engineering frequently result from the development, and wide adoption, of a new, powerful characterization or imaging technique. Beginning with the first glass lenses and telescopes in astronomy, to the development of visual-light microscopy, staining techniques, confocal microscopy, and fluorescence super-resolution microscopy in biology, and most recently aberration-corrected, cryogenic, and ultrafast (4D) electron microscopy, X-ray microscopy, and scanning probe microscopy in nanoscience. Through these developments, our perception and understanding of the physical nature of matter at length-scales beyond ordinary perception have been fundamentally transformed. Despite this progression in microscopy, techniques for observing nanoscale chemical processes and solvated/hydrated systems are limited, as the necessary spatial and temporal resolution presents significant technical challenges. However, the standard reliance on indirect or bulk phase characterization of nanoscale samples in liquids is undergoing a shift in recent times with the realization ( Williamson et al. Nat. Mater . 2003 , 2 , 532 - 536 ) of liquid-cell (scanning) transmission electron microscopy, LC(S)TEM, where picoliters of solution are hermetically sealed between electron-transparent "windows," which can be directly imaged or videoed at the nanoscale using conventional transmission electron microscopes. This Account seeks to open a discussion on the topic of standardizing strategies for conducting imaging experiments with a view to characterizing dynamics and motion of nanoscale materials. This is a challenge that could be described by critics and proponents alike, as analogous to doing chemistry in a lightning storm; where the nature of the solution, the nanomaterial, and the dynamic behaviors are all potentially subject to artifactual influence by the very act of our observation.

MICRO/NANO-STRUCTURAL EXAMINATION AND FISSION PRODUCT IDENTIFICATION IN NEUTRON IRRADIATED AGR-1 TRISO FUEL

DOE Office of Scientific and Technical Information (OSTI.GOV)

van Rooyen, I. J.; Lillo, T. M.; Wen, H. M.

Advanced microscopic and microanalysis techniques were developed and applied to study irradiation effects and fission product behavior in selected low-enriched uranium oxide/uranium carbide TRISO-coated particles from fuel compacts in six capsules irradiated to burnups of 11.2 to 19.6% FIMA. Although no TRISO coating failures were detected during the irradiation, the fraction of Ag-110m retained in individual particles often varied considerably within a single compact and at the capsule level. At the capsule level Ag-110m release fractions ranged from 1.2 to 38% and within a single compact, silver release from individual particles often spanned a range that extended from 100% retentionmore » to nearly 100% release. In this paper, selected irradiated particles from Baseline, Variant 1 and Variant 3 type fueled TRISO coated particles were examined using Scanning Electron Microscopy, Atom Probe Tomography; Electron Energy Loss Spectroscopy; Precession Electron Diffraction, Transmission Electron Microscopy, Scanning Transmission Electron Microscopy (STEM), High Resolution Electron Microscopy (HRTEM) examinations and Electron Probe Micro-Analyzer. Particle selection in this study allowed for comparison of the fission product distribution with Ag retention, fuel type and irradiation level. Nano sized Ag-containing features were predominantly identified in SiC grain boundaries and/or triple points in contrast with only two sitings of Ag inside a SiC grain in two different compacts (Baseline and Variant 3 fueled compacts). STEM and HRTEM analysis showed evidence of Ag and Pd co-existence in some cases and it was found that fission product precipitates can consist of multiple or single phases. STEM analysis also showed differences in precipitate compositions between Baseline and Variant 3 fuels. A higher density of fission product precipitate clusters were identified in the SiC layer in particles from the Variant 3 compact compared with the Variant 1 compact. Trend analysis shows precipitates were randomly distributed along the perimeter of the IPyC-SiC interlayer but only weakly associated with kernel protrusion and buffer fractures. There has been no evidence that the general release of silver is related to cracks or significant degradation of the microstructure. The results presented in this paper provide new insights to Ag transport mechanism(s) in intact SiC layer of TRISO coated particles.« less

Theory of the spatial resolution of (scanning) transmission electron microscopy in liquid water or ice layers.

PubMed

de Jonge, Niels

2018-04-01

The sample dependent spatial resolution was calculated for transmission electron microscopy (TEM) and scanning TEM (STEM) of objects (e.g., nanoparticles, proteins) embedded in a layer of liquid water or amorphous ice. The theoretical model includes elastic- and inelastic scattering, beam broadening, and chromatic aberration. Different contrast mechanisms were evaluated as function of the electron dose, the detection angle, and the sample configuration. It was found that the spatial resolution scales with the electron dose to the -1/4th power. Gold- and carbon nanoparticles were examined in the middle of water layers ranging from 0.01--10 µm thickness representing relevant classes of experiments in both materials science and biology. The optimal microscope settings differ between experimental configurations. STEM performs the best for gold nanoparticles for all layer thicknesses, while carbon is best imaged with phase-contrast TEM for thin layers but bright field STEM is preferred for thicker layers. The resolution was also calculated for a water layer enclosed between thin membranes. The influence of chromatic aberration correction for TEM was examined as well. The theory is broadly applicable to other types of materials and sample configurations. Copyright © 2018 Elsevier B.V. All rights reserved.

[Application of Warthin-Starry stain, immunohistochemistry and transmission electron microscopy in diagnosis of cat scratch disease].

PubMed

Huang, Juan; Dai, Lin; Lei, Song; Liao, Dian-ying; Wang, Xiao-qing; Luo, Tian-you; Chen, Yu; Hang, Zhen-biao; Li, Gan-di; Dong, Dan-dan; Xu, Gang; Gu, Zheng-ce; Hao, Ji-ling; Hua, Ping; He, Lei; Duan, Fang-lei

2010-04-01

To evaluate the diagnostic utility of Warthin-Starry silver stain, immunohistochemistry and transmission electron microscopy in the detection of human Bartonella henselae infection and pathologic diagnosis of cat scratch disease (CSD). The paraffin-embedded lymph node tissues of 77 histologically-defined cases of cat scratch disease collected during the period from January, 1998 to December, 2008 were retrieved and studied using Warthin-Starry silver stain (WS stain) and mouse monoclonal antibody against Bartonella henselae (BhmAB stain). Five cases rich in bacteria were selected for transmission electron microscopy. Under electron microscope, the organisms Bartonella henselae appeared polymorphic, round, elliptical, short rod or bacilliform shapes, ranged from 0.489 to 1.110 microm by 0.333 to 0.534 microm and often clustered together. Black short rod-shaped bacilli arranged in chains or clumps were demonstrated in 61.0% (47/77) of CSD by WS stain. The organisms were located outside the cells and lie mainly in the necrotic debris, especially near the nodal capsule. In 72.7% (56/77) of the cases, dot-like, granular as well as few linear positive signals were observed using BhmAB immunostain and showed similar localization. Positive results for both stains were identified in 59.7% (46/77) of the cases. When applying both stains together, Bartonella henselae was observed in 74.0% (57/77) of the case. The difference between the results obtained by WS stain and BhmAB immunostain was of statistical significance (P < 0.05). Bartonella henselae is the causative pathogen of cat scratch disease. WS stain, BhmAB immunostain and transmission electron microscopy are helpful in confirming the histologic diagnosis. Immunostaining using BhmAB can be a better alternative than WS stain in demonstrating the organisms.

Spin-resolved inelastic mean free path of slow electrons in Fe.

PubMed

Zdyb, R; Bauer, E

2013-07-10

The spin-dependent reflectivity of slow electrons from ultrathin Fe films on W(110) has been measured with spin polarized low energy electron microscopy. From the amplitude of the quantum size oscillations observed in the reflectivity curves the spin-dependent inelastic mean free path (IMFP) of electrons in Fe has been determined in the energy range from 5 to 16 eV above the vacuum level. The resulting IMFP values for the spin-up electrons are clearly larger than those for the spin-down electrons and the difference between the two values decreases with increasing electron energy in agreement with theoretical predictions.

Role of vacancy sites and UV-ozone treatment on few layered MoS2 nanoflakes for toxic gas detection

NASA Astrophysics Data System (ADS)

Burman, Debasree; Ghosh, Ruma; Santra, Sumita; Ray, Samit Kumar; Guha, Prasanta Kumar

2017-10-01

Various issues like global warming and environmental pollutions have led to the research of toxic gas detection worldwide. In this work, we have tried to develop a molybdenum disulfide (MoS2) based gas sensor to detect toxic gases like ammonia and NO. MoS2, an inorganic analog of graphene, has attracted lots of attention for many different applications recently. This paper reports the use of liquid exfoliated MoS2 nanoflakes as the sensing layer in a handheld, resistive toxic gas sensor. The nanoflakes were exfoliated from MoS2 bulk powder using a sonication based exfoliation technique at room temperature. The successful exfoliation of the nanoflakes was characterized using different techniques e.g., optical microscopy, atomic force microscopy, field emission scanning electron microscopy, high resolution transmission electron microscopy, x-ray diffraction, Raman spectroscopy, x-ray photoelectron spectroscopy and ultraviolet-visible spectrophotometry. The characterization results showed that few-layered nanoflakes have successfully been exfoliated. The MoS2 nanoflakes showed reasonable sensing towards ammonia and NO. In order to explore the effect of particle size on ammonia sensing, the MoS2 flakes were also exfoliated using different sonication times. We also observed that various factors like presence of vacancy sites, ambient oxygen, humidity, different contact electrodes have significant effect on the sensing characteristics. In fact, the response of the sensing layer against 400 ppm of ammonia increased from 54.1% to ˜80% when it was UV-ozone treated. This work holds promises to developing cost-effective, reliable and highly sensitive MoS2 based ammonia sensors.

Dipole-like electrostatic asymmetry of gold nanorods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Ji -Young; Han, Myung -Geun; Lien, Miao -Bin

The symmetry of metallic nanocolloids, typically envisaged as simple geometrical shapes, is rarely questioned. However, the symmetry considerations are so essential for understanding their electronic structure, optical properties, and biological effects that it is important to reexamine these foundational assumptions for nanocolloids. Gold nanorods (AuNRs) are generally presumed to have nearly perfect geometry of a cylinder and therefore are centrosymmetric. We show that AuNRs, in fact, have a built-in electrostatic potential gradient on their surface and behave as noncentrosymmetric particles. The electrostatic potential gradient of 0.11 to 0.07 V/nm along the long axes of nanorods is observed by off-axis electronmore » holography. Kelvin probe microscopy, secondary electron imaging, energy-filtered transmission electron microscopy, and plasmon mapping reveal that the axial asymmetry is associated with a consistently unequal number of cetyltrimethylammonium bromide moieties capping the two ends of the AuNRs. Electrostatic field maps simulated for the AuNR surface reproduce the holography images. The dipole-like surface potential gradient explains previously puzzling discrepancies in nonlinear optical effects originating from the noncentrosymmetric nature of AuNRs. Furthermore, similar considerations of symmetry breaking are applicable to other nanoscale structures for which the property-governing symmetry of the organic shell may differ from the apparent symmetry of inorganic core observed in standard electron microscopy images.« less

Light, electron microscopic and immunohistochemical study of the effect of low-dose aspirin during the proestrus phase on rat endometrium in the preimplantation period.

PubMed

Ateş, Utku; Baka, Meral; Turgut, Mehmet; Uyanikgil, Yiğit; Ulker, Sibel; Yilmaz, Ozlem; Tavmergen, Erol; Yurtseven, Mine

2007-04-01

To evaluate structural alterations in rat endometrium at preimplantation following treatment with aspirin beginning from proestrus by light microscopy, electron microscopy and immunohistochemical techniques. Twenty rats were divided into control (n = 10) and experimental (n = 10) groups. Experimental rats were treated with low-dose aspirin daily (2 mg/kg/day) during estrus, beginning from the proestrus phase, mated at end of cycle and treated with aspirin. Untreated pregnant rats were the control group. Rats in both groups were sacrificed at the 84th pregnancy hour; the uterus was rapidly removed and dissected free of surrounding adipose tissue. Uteri specimens from nonpregnant rats were transferred into fixative solution and processed for light, electron microscopic and immunohistochemical study. Light and electron microscopy of endometrium from control rats conformed to mid-diestrus phase; endometrial histology of the aspirin-treated group conformed to late diestrus phase. The endometrial layer was significantly thicker in the aspirin-treated group compared to the untreated control group (p <0.001). No significant difference was found in vessel number between groups. Staining with alphaV integrin was more dense in the aspirin-treated group. Based on histologic findings, we suggest low-dose aspirin has positive effects on preparing endometrium before implantation.

Dipole-like electrostatic asymmetry of gold nanorods

DOE PAGES

Kim, Ji -Young; Han, Myung -Geun; Lien, Miao -Bin; ...

2018-02-09

The symmetry of metallic nanocolloids, typically envisaged as simple geometrical shapes, is rarely questioned. However, the symmetry considerations are so essential for understanding their electronic structure, optical properties, and biological effects that it is important to reexamine these foundational assumptions for nanocolloids. Gold nanorods (AuNRs) are generally presumed to have nearly perfect geometry of a cylinder and therefore are centrosymmetric. We show that AuNRs, in fact, have a built-in electrostatic potential gradient on their surface and behave as noncentrosymmetric particles. The electrostatic potential gradient of 0.11 to 0.07 V/nm along the long axes of nanorods is observed by off-axis electronmore » holography. Kelvin probe microscopy, secondary electron imaging, energy-filtered transmission electron microscopy, and plasmon mapping reveal that the axial asymmetry is associated with a consistently unequal number of cetyltrimethylammonium bromide moieties capping the two ends of the AuNRs. Electrostatic field maps simulated for the AuNR surface reproduce the holography images. The dipole-like surface potential gradient explains previously puzzling discrepancies in nonlinear optical effects originating from the noncentrosymmetric nature of AuNRs. Furthermore, similar considerations of symmetry breaking are applicable to other nanoscale structures for which the property-governing symmetry of the organic shell may differ from the apparent symmetry of inorganic core observed in standard electron microscopy images.« less

Accurate modelling of single-particle cryo-EM images quantifies the benefits expected from using Zernike phase contrast

PubMed Central

Hall, R. J.; Nogales, E.; Glaeser, R. M.

2011-01-01

The use of a Zernike-type phase plate in biological cryo-electron microscopy allows the imaging, without using defocus, of what are predominantly phase objects. It is thought that such phase-plate implementations might result in higher quality images, free from the problems of CTF correction that occur when images must be recorded at extremely high values of defocus. In single-particle cryo-electron microscopy it is hoped that these improvements in image quality will facilitate work on structures that have proved difficult to study, either because of their relatively small size or because the structures are not completely homogeneous. There is still a need, however, to quantify how much improvement can be gained by using a phase plate for single-particle cryo-electron microscopy. We present a method for quantitatively modelling the images recorded with 200 keV electrons, for single particles embedded in vitreous ice. We then investigate what difference the use of a phase-plate device could have on the processing of single-particle data. We confirm that using a phase plate results in single-particle datasets in which smaller molecules can be detected, particles can be more accurately aligned and problems of heterogeneity can be more easily addressed. PMID:21463690

Invited Review Article: Methods for imaging weak-phase objects in electron microscopy

PubMed Central

Glaeser, Robert M.

2013-01-01

Contrast has traditionally been produced in electron-microscopy of weak phase objects by simply defocusing the objective lens. There now is renewed interest, however, in using devices that apply a uniform quarter-wave phase shift to the scattered electrons relative to the unscattered beam, or that generate in-focus image contrast in some other way. Renewed activity in making an electron-optical equivalent of the familiar “phase-contrast” light microscope is based in part on the improved possibilities that are now available for device microfabrication. There is also a better understanding that it is important to take full advantage of contrast that can be had at low spatial frequency when imaging large, macromolecular objects. In addition, a number of conceptually new phase-plate designs have been proposed, thus increasing the number of options that are available for development. The advantages, disadvantages, and current status of each of these options is now compared and contrasted. Experimental results that are, indeed, superior to what can be accomplished with defocus-based phase contrast have been obtained recently with two different designs of phase-contrast aperture. Nevertheless, extensive work also has shown that fabrication of such devices is inconsistent, and that their working lifetime is short. The main limitation, in fact, appears to be electrostatic charging of any device that is placed into the electron diffraction pattern. The challenge in fabricating phase plates that are practical to use for routine work in electron microscopy thus may be more in the area of materials science than in the area of electron optics. PMID:24289381

Nano-fEM: protein localization using photo-activated localization microscopy and electron microscopy.

PubMed

Watanabe, Shigeki; Richards, Jackson; Hollopeter, Gunther; Hobson, Robert J; Davis, Wayne M; Jorgensen, Erik M

2012-12-03

Mapping the distribution of proteins is essential for understanding the function of proteins in a cell. Fluorescence microscopy is extensively used for protein localization, but subcellular context is often absent in fluorescence images. Immuno-electron microscopy, on the other hand, can localize proteins, but the technique is limited by a lack of compatible antibodies, poor preservation of morphology and because most antigens are not exposed to the specimen surface. Correlative approaches can acquire the fluorescence image from a whole cell first, either from immuno-fluorescence or genetically tagged proteins. The sample is then fixed and embedded for electron microscopy, and the images are correlated (1-3). However, the low-resolution fluorescence image and the lack of fiducial markers preclude the precise localization of proteins. Alternatively, fluorescence imaging can be done after preserving the specimen in plastic. In this approach, the block is sectioned, and fluorescence images and electron micrographs of the same section are correlated (4-7). However, the diffraction limit of light in the correlated image obscures the locations of individual molecules, and the fluorescence often extends beyond the boundary of the cell. Nano-resolution fluorescence electron microscopy (nano-fEM) is designed to localize proteins at nano-scale by imaging the same sections using photo-activated localization microscopy (PALM) and electron microscopy. PALM overcomes the diffraction limit by imaging individual fluorescent proteins and subsequently mapping the centroid of each fluorescent spot (8-10). We outline the nano-fEM technique in five steps. First, the sample is fixed and embedded using conditions that preserve the fluorescence of tagged proteins. Second, the resin blocks are sectioned into ultrathin segments (70-80 nm) that are mounted on a cover glass. Third, fluorescence is imaged in these sections using the Zeiss PALM microscope. Fourth, electron dense structures are imaged in these same sections using a scanning electron microscope. Fifth, the fluorescence and electron micrographs are aligned using gold particles as fiducial markers. In summary, the subcellular localization of fluorescently tagged proteins can be determined at nanometer resolution in approximately one week.

Correlative SEM SERS for quantitative analysis of dimer nanoparticles.

PubMed

Timmermans, F J; Lenferink, A T M; van Wolferen, H A G M; Otto, C

2016-11-14

A Raman microscope integrated with a scanning electron microscope was used to investigate plasmonic structures by correlative SEM-SERS analysis. The integrated Raman-SEM microscope combines high-resolution electron microscopy information with SERS signal enhancement from selected nanostructures with adsorbed Raman reporter molecules. Correlative analysis is performed for dimers of two gold nanospheres. Dimers were selected on the basis of SEM images from multi aggregate samples. The effect of the orientation of the dimer with respect to the polarization state of the laser light and the effect of the particle gap size on the Raman signal intensity is observed. Additionally, calculations are performed to simulate the electric near field enhancement. These simulations are based on the morphologies observed by electron microscopy. In this way the experiments are compared with the enhancement factor calculated with near field simulations and are subsequently used to quantify the SERS enhancement factor. Large differences between experimentally observed and calculated enhancement factors are regularly detected, a phenomenon caused by nanoscale differences between the real and 'simplified' simulated structures. Quantitative SERS experiments reveal the structure induced enhancement factor, ranging from ∼200 to ∼20 000, averaged over the full nanostructure surface. The results demonstrate correlative Raman-SEM microscopy for the quantitative analysis of plasmonic particles and structures, thus enabling a new analytical method in the field of SERS and plasmonics.

[Laser Raman spectral investigations of the carbon structure of LiFePO4/C cathode material].

PubMed

Yang, Chao; Li, Yong-Mei; Zhao, Quan-Feng; Gan, Xiang-Kun; Yao, Yao-Chun

2013-10-01

In the present paper, Laser Raman spectral was used to study the carbon structure of LiFePO4/C positive material. The samples were also been characterized by X-ray diffraction (XRD), scanning electron microscope(SEM), selected area electron diffraction (SEAD) and resistivity test. The result indicated that compared with the sp2/sp3 peak area ratios the I(D)/I(G) ratios are not only more evenly but also exhibited some similar rules. However, the studies indicated that there exist differences of I(D)/ I(G) ratios and sp2/sp3 peak area ratios among different points in the same sample. And compared with the samples using citric acid or sucrose as carbon source, the sample which was synthetized with mixed carbon source (mixed by citric acid and sucrose) exhibited higher I(D)/I(G) ratios and sp2/sp3 peak area ratios. Also, by contrast, the differences of I(D)/I(G) ratios and sp2/sp3 peak area ratios among different points in the same sample are less than the single carbon source samples' datas. In the scanning electron microscopy (sem) and transmission electron microscopy (sem) images, we can observed the uneven distributions of carbon coating of the primary particles and the secondary particles, this may be the main reason for not being uniform of difference data in the same sample. The obvious discreteness will affect the normal use of Raman spectroscopy in these tests.

Backscattered electron SEM imaging of resin sections from plant specimens: observation of histological to subcellular structure and CLEM.

PubMed

Rizzo, N W; Duncan, K E; Bourett, T M; Howard, R J

2016-08-01

We have refined methods for biological specimen preparation and low-voltage backscattered electron imaging in the scanning electron microscope that allow for observation at continuous magnifications of ca. 130-70 000 X, and documentation of tissue and subcellular ultrastructure detail. The technique, based upon early work by Ogura & Hasegawa (1980), affords use of significantly larger sections from fixed and resin-embedded specimens than is possible with transmission electron microscopy while providing similar data. After microtomy, the sections, typically ca. 750 nm thick, were dried onto the surface of glass or silicon wafer and stained with heavy metals-the use of grids avoided. The glass/wafer support was then mounted onto standard scanning electron microscopy sample stubs, carbon-coated and imaged directly at an accelerating voltage of 5 kV, using either a yttrium aluminum garnet or ExB backscattered electron detector. Alternatively, the sections could be viewed first by light microscopy, for example to document signal from a fluorescent protein, and then by scanning electron microscopy to provide correlative light/electron microscope (CLEM) data. These methods provide unobstructed access to ultrastructure in the spatial context of a section ca. 7 × 10 mm in size, significantly larger than the typical 0.2 × 0.3 mm section used for conventional transmission electron microscopy imaging. Application of this approach was especially useful when the biology of interest was rare or difficult to find, e.g. a particular cell type, developmental stage, large organ, the interface between cells of interacting organisms, when contextual information within a large tissue was obligatory, or combinations of these factors. In addition, the methods were easily adapted for immunolocalizations. © 2015 The Author. Journal of Microscopy published by John Wiley & Sons, Ltd on behalf of the Royal Microscopical Society.

Preservation of protein fluorescence in embedded human dendritic cells for targeted 3D light and electron microscopy.

PubMed

Höhn, K; Fuchs, J; Fröber, A; Kirmse, R; Glass, B; Anders-Össwein, M; Walther, P; Kräusslich, H-G; Dietrich, C

2015-08-01

In this study, we present a correlative microscopy workflow to combine detailed 3D fluorescence light microscopy data with ultrastructural information gained by 3D focused ion beam assisted scanning electron microscopy. The workflow is based on an optimized high pressure freezing/freeze substitution protocol that preserves good ultrastructural detail along with retaining the fluorescence signal in the resin embedded specimens. Consequently, cellular structures of interest can readily be identified and imaged by state of the art 3D confocal fluorescence microscopy and are precisely referenced with respect to an imprinted coordinate system on the surface of the resin block. This allows precise guidance of the focused ion beam assisted scanning electron microscopy and limits the volume to be imaged to the structure of interest. This, in turn, minimizes the total acquisition time necessary to conduct the time consuming ultrastructural scanning electron microscope imaging while eliminating the risk to miss parts of the target structure. We illustrate the value of this workflow for targeting virus compartments, which are formed in HIV-pulsed mature human dendritic cells. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

Integration of a high-NA light microscope in a scanning electron microscope.

PubMed

Zonnevylle, A C; Van Tol, R F C; Liv, N; Narvaez, A C; Effting, A P J; Kruit, P; Hoogenboom, J P

2013-10-01

We present an integrated light-electron microscope in which an inverted high-NA objective lens is positioned inside a scanning electron microscope (SEM). The SEM objective lens and the light objective lens have a common axis and focal plane, allowing high-resolution optical microscopy and scanning electron microscopy on the same area of a sample simultaneously. Components for light illumination and detection can be mounted outside the vacuum, enabling flexibility in the construction of the light microscope. The light objective lens can be positioned underneath the SEM objective lens during operation for sub-10 μm alignment of the fields of view of the light and electron microscopes. We demonstrate in situ epifluorescence microscopy in the SEM with a numerical aperture of 1.4 using vacuum-compatible immersion oil. For a 40-nm-diameter fluorescent polymer nanoparticle, an intensity profile with a FWHM of 380 nm is measured whereas the SEM performance is uncompromised. The integrated instrument may offer new possibilities for correlative light and electron microscopy in the life sciences as well as in physics and chemistry. © 2013 The Authors Journal of Microscopy © 2013 Royal Microscopical Society.

Scanning electron microscopy of cells and tissues under fully hydrated conditions

PubMed Central

Thiberge, Stephan; Nechushtan, Amotz; Sprinzak, David; Gileadi, Opher; Behar, Vered; Zik, Ory; Chowers, Yehuda; Michaeli, Shulamit; Schlessinger, Joseph; Moses, Elisha

2004-01-01

A capability for scanning electron microscopy of wet biological specimens is presented. A membrane that is transparent to electrons protects the fully hydrated sample from the vacuum. The result is a hybrid technique combining the ease of use and ability to see into cells of optical microscopy with the higher resolution of electron microscopy. The resolution of low-contrast materials is ≈100 nm, whereas in high-contrast materials the resolution can reach 10 nm. Standard immunogold techniques and heavy-metal stains can be applied and viewed in the fluid to improve the contrast. Images present a striking combination of whole-cell morphology with a wealth of internal details. A possibility for direct inspection of tissue slices transpires, imaging only the external layer of cells. Simultaneous imaging with photons excited by the electrons incorporates data on material distribution, indicating a potential for multilabeling and specific scintillating markers. PMID:14988502

Epitaxial growth of pentacene on alkali halide surfaces studied by Kelvin probe force microscopy.

PubMed

Neff, Julia L; Milde, Peter; León, Carmen Pérez; Kundrat, Matthew D; Eng, Lukas M; Jacob, Christoph R; Hoffmann-Vogel, Regina

2014-04-22

In the field of molecular electronics, thin films of molecules adsorbed on insulating surfaces are used as the functional building blocks of electronic devices. Control of the structural and electronic properties of the thin films is required for reliably operating devices. Here, noncontact atomic force and Kelvin probe force microscopies have been used to investigate the growth and electrostatic landscape of pentacene on KBr(001) and KCl(001) surfaces. We have found that, together with molecular islands of upright standing pentacene, a new phase of tilted molecules appears near step edges on KBr. Local contact potential differences (LCPD) have been studied with both Kelvin experiments and density functional theory calculations. Our images reveal that differently oriented molecules display different LCPD and that their value is independent of the number of molecular layers. These results point to the formation of an interface dipole, which may be explained by a partial charge transfer from the pentacene to the surface. Moreover, the monitoring of the evolution of the pentacene islands shows that they are strongly affected by dewetting: Multilayers build up at the expense of monolayers, and in the Kelvin images, previously unknown line defects appear, which reveal the epitaxial growth of pentacene crystals.

Atomic scale imaging of magnetic circular dichroism by achromatic electron microscopy.

PubMed

Wang, Zechao; Tavabi, Amir H; Jin, Lei; Rusz, Ján; Tyutyunnikov, Dmitry; Jiang, Hanbo; Moritomo, Yutaka; Mayer, Joachim; Dunin-Borkowski, Rafal E; Yu, Rong; Zhu, Jing; Zhong, Xiaoyan

2018-03-01

In order to obtain a fundamental understanding of the interplay between charge, spin, orbital and lattice degrees of freedom in magnetic materials and to predict and control their physical properties 1-3 , experimental techniques are required that are capable of accessing local magnetic information with atomic-scale spatial resolution. Here, we show that a combination of electron energy-loss magnetic chiral dichroism 4 and chromatic-aberration-corrected transmission electron microscopy, which reduces the focal spread of inelastically scattered electrons by orders of magnitude when compared with the use of spherical aberration correction alone, can achieve atomic-scale imaging of magnetic circular dichroism and provide element-selective orbital and spin magnetic moments atomic plane by atomic plane. This unique capability, which we demonstrate for Sr 2 FeMoO 6 , opens the door to local atomic-level studies of spin configurations in a multitude of materials that exhibit different types of magnetic coupling, thereby contributing to a detailed understanding of the physical origins of magnetic properties of materials at the highest spatial resolution.

Micro Electron MicroProbe and Sample Analyzer

NASA Technical Reports Server (NTRS)

Manohara, Harish; Bearman, Gregory; Douglas, Susanne; Bronikowski, Michael; Urgiles, Eduardo; Kowalczyk, Robert; Bryson, Charles

2009-01-01

A proposed, low-power, backpack-sized instrument, denoted the micro electron microprobe and sample analyzer (MEMSA), would serve as a means of rapidly performing high-resolution microscopy and energy-dispersive x-ray spectroscopy (EDX) of soil, dust, and rock particles in the field. The MEMSA would be similar to an environmental scanning electron microscope (ESEM) but would be much smaller and designed specifically for field use in studying effects of geological alteration at the micrometer scale. Like an ESEM, the MEMSA could be used to examine uncoated, electrically nonconductive specimens. In addition to the difference in size, other significant differences between the MEMSA and an ESEM lie in the mode of scanning and the nature of the electron source.

Electron Microscopy of Staphylococcus aureus Cell Wall Lysis

PubMed Central

Virgilio, R.; González, C.; Muñoz, Nubia; Mendoza, Silvia

1966-01-01

Virgilio, Rafael (Escuela de Química y Farmacia, Universidad de Chile, Santiago, Chile), C. González, Nubia Muñoz, and Silvia Mendoza. Electron microscopy of Staphylococcus aureus cell wall lysis. J. Bacteriol. 91:2018–2024. 1966.—A crude suspension of Staphylococcus aureus cell walls (strain Cowan III) in buffer solution was shown by electron microscopy to lyse slightly after 16 hr, probably owing to the action of autolysin. The lysis was considerably faster and more intense after the addition of lysozyme. A remarkable reduction in thickness and rigidity of the cell walls, together with the appearance of many irregular protrusions in their outlines, was observed after 2 hr; after 16 hr, there remained only a few recognizable cell wall fragments but many residual particulate remnants. When autolysin was previously inactivated by trypsin, there was a complete inhibition of the lytic action of lysozyme; on the other hand, when autolysin was inactivated by heat and lysozyme was added, a distinct decrease in the thickness of the cell walls was observed, but there was no destruction of the walls. The lytic action of lysozyme, after treatment with hot 5% trichloroacetic acid, gave rise to a marked dissolution of the structure of the cell walls, which became lost against the background, without, however, showing ostensible alteration of wall outlines. From a morphological point of view, the lytic action of autolysin plus lysozyme was quite different from that of trichloroacetic acid plus lysozyme, as shown by electron micrographs, but in both cases it was very intense. This would suggest different mechanisms of action for these agents. Images PMID:5939482

Electron microscopy of Staphylococcus aureus cell wall lysis.

PubMed

Virgilio, R; González, C; Muñoz, N; Mendoza, S

1966-05-01

Virgilio, Rafael (Escuela de Química y Farmacia, Universidad de Chile, Santiago, Chile), C. González, Nubia Muñoz, and Silvia Mendoza. Electron microscopy of Staphylococcus aureus cell wall lysis. J. Bacteriol. 91:2018-2024. 1966.-A crude suspension of Staphylococcus aureus cell walls (strain Cowan III) in buffer solution was shown by electron microscopy to lyse slightly after 16 hr, probably owing to the action of autolysin. The lysis was considerably faster and more intense after the addition of lysozyme. A remarkable reduction in thickness and rigidity of the cell walls, together with the appearance of many irregular protrusions in their outlines, was observed after 2 hr; after 16 hr, there remained only a few recognizable cell wall fragments but many residual particulate remnants. When autolysin was previously inactivated by trypsin, there was a complete inhibition of the lytic action of lysozyme; on the other hand, when autolysin was inactivated by heat and lysozyme was added, a distinct decrease in the thickness of the cell walls was observed, but there was no destruction of the walls. The lytic action of lysozyme, after treatment with hot 5% trichloroacetic acid, gave rise to a marked dissolution of the structure of the cell walls, which became lost against the background, without, however, showing ostensible alteration of wall outlines. From a morphological point of view, the lytic action of autolysin plus lysozyme was quite different from that of trichloroacetic acid plus lysozyme, as shown by electron micrographs, but in both cases it was very intense. This would suggest different mechanisms of action for these agents.

Scanning electron microscopic characteristics of commercially available 1- and 3-piece intraocular lenses.

PubMed

Brockmann, Tobias; Brockmann, Claudia; Nietzsche, Sandor; Bertelmann, Eckart; Strobel, Juergen; Dawczynski, Jens

2013-12-01

To evaluate commercially available 1- and 3-piece intraocular lenses (IOLs) with scanning electron microscopy (SEM). Department of Ophthalmology and Electron Microscopy Center, University Hospital Jena, Jena, Germany. Experimental study. Seven +23.0 diopter IOLs of different design and material and from different manufacturers were chosen for a detailed assessment. Scanning electron microscopy was used at standardized magnifications to assess typical IOL characteristics. The particular focus was the optic edge, the optic surface, the haptic–optic junction, and the haptic. All square-edged IOLs had a curvature radius of less than 10 μm, while the mean optic edge thickness ranged between 216 μm and 382 μm. A 360-degree square-edged boundary was present in all 3-piece IOLs and in a single 1-piece model. Relevant production remnants on the optic edge were observed in 1 case. Regarding the haptic, 3-piece IOLs had uniformly shaped fibers with a mean thickness of 177 μm ± 51 (SD) (range 116 to 220 μm). Chemical adhesives were used to attach the haptic in 1 case, where alterations of the IOL material were observed. In another case, the haptic fiber was press-fitted into the optic, which resulted in bulging of the optic profile. Inspection of surface characteristics showed wavelike patterns in 2 IOLs. Taking clinical relevance into account, all IOLs were of high manufacturing quality. Certain attention was paid in creating a sharp optic edge. Surface irregularities of 2 IOLs were attributed to the manufacturing technique. Methods for implementing the haptic–optic junction were diverse.

Attosecond electron pulse trains and quantum state reconstruction in ultrafast transmission electron microscopy

NASA Astrophysics Data System (ADS)

Priebe, Katharina E.; Rathje, Christopher; Yalunin, Sergey V.; Hohage, Thorsten; Feist, Armin; Schäfer, Sascha; Ropers, Claus

2017-12-01

Ultrafast electron and X-ray imaging and spectroscopy are the basis for an ongoing revolution in the understanding of dynamical atomic-scale processes in matter. The underlying technology relies heavily on laser science for the generation and characterization of ever shorter pulses. Recent findings suggest that ultrafast electron microscopy with attosecond-structured wavefunctions may be feasible. However, such future technologies call for means to both prepare and fully analyse the corresponding free-electron quantum states. Here, we introduce a framework for the preparation, coherent manipulation and characterization of free-electron quantum states, experimentally demonstrating attosecond electron pulse trains. Phase-locked optical fields coherently control the electron wavefunction along the beam direction. We establish a new variant of quantum state tomography—`SQUIRRELS'—for free-electron ensembles. The ability to tailor and quantitatively map electron quantum states will promote the nanoscale study of electron-matter entanglement and new forms of ultrafast electron microscopy down to the attosecond regime.

Nanowire growth kinetics in aberration corrected environmental transmission electron microscopy

DOE PAGES

Chou, Yi -Chia; Panciera, Federico; Reuter, Mark C.; ...

2016-03-15

Here, we visualize atomic level dynamics during Si nanowire growth using aberration corrected environmental transmission electron microscopy, and compare with lower pressure results from ultra-high vacuum microscopy. We discuss the importance of higher pressure observations for understanding growth mechanisms and describe protocols to minimize effects of the higher pressure background gas.

Electronic Blending in Virtual Microscopy

ERIC Educational Resources Information Center

Maybury, Terrence S.; Farah, Camile S.

2010-01-01

Virtual microscopy (VM) is a relatively new technology that transforms the computer into a microscope. In essence, VM allows for the scanning and transfer of glass slides from light microscopy technology to the digital environment of the computer. This transition is also a function of the change from print knowledge to electronic knowledge, or as…

Structural and Ultrastructural Characteristics of Bone-Tendon Junction of the Calcaneal Tendon of Adult and Elderly Wistar Rats

PubMed Central

Cury, Diego Pulzatto; Dias, Fernando José; Miglino, Maria Angélica; Watanabe, Ii-sei

2016-01-01

Tendons are transition tissues that transfer the contractile forces generated by the muscles to the bones, allowing movement. The region where the tendon attaches to the bone is called bone-tendon junction or enthesis and may be classified as fibrous or fibrocartilaginous. This study aims to analyze the collagen fibers and the cells present in the bone-tendon junction using light microscopy and ultrastructural techniques as scanning electron microscopy and transmission electron microscopy. Forty male Wistar rats were used in the experiment, being 20 adult rats at 4 months-old and 20 elderly rats at 20 months-old. The hind limbs of the rats were removed, dissected and prepared to light microscopy, transmission electron microscopy and scanning electron microscopy. The aging process showed changes in the collagen fibrils, with a predominance of type III fibers in the elderly group, in addition to a decrease in the amount of the fibrocartilage cells, fewer and shorter cytoplasmic processes and a decreased synthetic capacity due to degradation of the organelles involved in synthesis. PMID:27078690

Preservation of protein fluorescence in embedded human dendritic cells for targeted 3D light and electron microscopy

PubMed Central

HÖHN, K.; FUCHS, J.; FRÖBER, A.; KIRMSE, R.; GLASS, B.; ANDERS‐ÖSSWEIN, M.; WALTHER, P.; KRÄUSSLICH, H.‐G.

2015-01-01

Summary In this study, we present a correlative microscopy workflow to combine detailed 3D fluorescence light microscopy data with ultrastructural information gained by 3D focused ion beam assisted scanning electron microscopy. The workflow is based on an optimized high pressure freezing/freeze substitution protocol that preserves good ultrastructural detail along with retaining the fluorescence signal in the resin embedded specimens. Consequently, cellular structures of interest can readily be identified and imaged by state of the art 3D confocal fluorescence microscopy and are precisely referenced with respect to an imprinted coordinate system on the surface of the resin block. This allows precise guidance of the focused ion beam assisted scanning electron microscopy and limits the volume to be imaged to the structure of interest. This, in turn, minimizes the total acquisition time necessary to conduct the time consuming ultrastructural scanning electron microscope imaging while eliminating the risk to miss parts of the target structure. We illustrate the value of this workflow for targeting virus compartments, which are formed in HIV‐pulsed mature human dendritic cells. PMID:25786567

Structural and Ultrastructural Characteristics of Bone-Tendon Junction of the Calcaneal Tendon of Adult and Elderly Wistar Rats.

PubMed

Cury, Diego Pulzatto; Dias, Fernando José; Miglino, Maria Angélica; Watanabe, Ii-sei

2016-01-01

Tendons are transition tissues that transfer the contractile forces generated by the muscles to the bones, allowing movement. The region where the tendon attaches to the bone is called bone-tendon junction or enthesis and may be classified as fibrous or fibrocartilaginous. This study aims to analyze the collagen fibers and the cells present in the bone-tendon junction using light microscopy and ultrastructural techniques as scanning electron microscopy and transmission electron microscopy. Forty male Wistar rats were used in the experiment, being 20 adult rats at 4 months-old and 20 elderly rats at 20 months-old. The hind limbs of the rats were removed, dissected and prepared to light microscopy, transmission electron microscopy and scanning electron microscopy. The aging process showed changes in the collagen fibrils, with a predominance of type III fibers in the elderly group, in addition to a decrease in the amount of the fibrocartilage cells, fewer and shorter cytoplasmic processes and a decreased synthetic capacity due to degradation of the organelles involved in synthesis.

Application of the Indirect Immunoperoxidase Stain Technique to the Flagella of Azospirillum brasilense

PubMed Central

Hall, Patrick G.; Krieg, Noel R.

1984-01-01

An indirect immunoperoxidase stain was used to demonstrate by electron microscopy that an antigenic difference exists between the polar flagellum and the lateral flagella of Azospirillum brasilense ATCC 29145. Images PMID:16346482

The chorion ultrastructure of ova of Lophius spp.

PubMed

Colmenero, A I; Tuset, V M; Fortuño, J-M; Sánchez, P

2015-06-01

The chorion surface ultrastructure of unfertilized eggs of black anglerfish Lophius budegassa and white anglerfish Lophius piscatorius was examined by scanning electron microscopy. Species-specific differences were observed. © 2015 The Fisheries Society of the British Isles.

Correction of image drift and distortion in a scanning electron microscopy.

PubMed

Jin, P; Li, X

2015-12-01

Continuous research on small-scale mechanical structures and systems has attracted strong demand for ultrafine deformation and strain measurements. Conventional optical microscope cannot meet such requirements owing to its lower spatial resolution. Therefore, high-resolution scanning electron microscope has become the preferred system for high spatial resolution imaging and measurements. However, scanning electron microscope usually is contaminated by distortion and drift aberrations which cause serious errors to precise imaging and measurements of tiny structures. This paper develops a new method to correct drift and distortion aberrations of scanning electron microscope images, and evaluates the effect of correction by comparing corrected images with scanning electron microscope image of a standard sample. The drift correction is based on the interpolation scheme, where a series of images are captured at one location of the sample and perform image correlation between the first image and the consequent images to interpolate the drift-time relationship of scanning electron microscope images. The distortion correction employs the axial symmetry model of charged particle imaging theory to two images sharing with the same location of one object under different imaging fields of view. The difference apart from rigid displacement between the mentioned two images will give distortion parameters. Three-order precision is considered in the model and experiment shows that one pixel maximum correction is obtained for the employed high-resolution electron microscopic system. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

Differentiating Pseudomonas sp. strain ADP cells in suspensions and biofilms using Raman spectroscopy and scanning electron microscopy.

PubMed

Henry, Victoria A; Jessop, Julie L P; Peeples, Tonya L

2017-02-01

High quality spectra of Pseudomonas sp. strain ADP in the planktonic and biofilm state were obtained using Raman microspectroscopy. These spectra enabled the identification of key differences between free and biofilm cells in the fingerprint region of Raman spectra in the nucleic acid, carbohydrate, and protein regions. Scanning electron microscopy (SEM) enabled detailed visualization of ADP biofilm with confirmation of associated extracellular matrix structure. Following extraction and Raman analysis of extracellular polymeric substances, Raman spectral differences between free and biofilm cells were largely attributed to the contribution of extracellular matrix components produced in mature biofilms. Raman spectroscopy complemented with SEM proves to be useful in distinguishing physiological properties among cells of the same species. Graphical Abstract Raman spectroscopy complemented with SEM proves to be useful in distinguishing physiological properties among cells of the same species.

In vivo reactive neural plasticity investigation by means of correlative two photon: electron microscopy

NASA Astrophysics Data System (ADS)

Allegra Mascaro, A. L.; Cesare, P.; Sacconi, L.; Grasselli, G.; Mandolesi, G.; Maco, B.; Knott, G.; Huang, L.; De Paola, V.; Strata, P.; Pavone, F. S.

2013-02-01

In the adult nervous system, different populations of neurons correspond to different regenerative behavior. Although previous works showed that olivocerebellar fibers are capable of axonal regeneration in a suitable environment as a response to injury1, we have hitherto no details about the real dynamics of fiber regeneration. We set up a model of singularly axotomized climbing fibers (CF) to investigate their reparative properties in the adult central nervous system (CNS) in vivo. Time lapse two-photon imaging has been combined to laser nanosurgery2, 3 to define a temporal pattern of the degenerative event and to follow the structural rearrangement after injury. To characterize the damage and to elucidate the possible formation of new synaptic contacts on the sprouted branches of the lesioned CF, we combined two-photon in vivo imaging with block face scanning electron microscopy (FIB-SEM). Here we describe the approach followed to characterize the reactive plasticity after injury.

In Vitro Self-Assembly of the Light Harvesting Pigment-Protein LH2 Revealed by Ultrafast Spectroscopy and Electron Microscopy

PubMed Central

Schubert, Axel; Stenstam, Anna; Beenken, Wichard J. D.; Herek, Jennifer L.; Cogdell, Richard; Pullerits, Tõnu; Sundström, Villy

2004-01-01

Controlled ensemble formation of protein-surfactant systems provides a fundamental concept for the realization of nanoscale devices with self-organizing capability. In this context, spectroscopic monitoring of pigment-containing proteins yields detailed structural information. Here we have studied the association behavior of the bacterial light-harvesting protein LH2 from Rhodobacter spheroides in an n,n-dimethyldodecylamine-n-oxide/water environment. Time-resolved studies of the excitation annihilation yielded information about aggregate sizes and packing of the protein complexes therein. The results are compared to transmission electron microscopy images of instantaneously frozen samples. Our data indicate the manifestation of different phases, which are discussed with respect to the thermodynamic equilibrium in ternary protein-surfactant-water systems. Accordingly, by varying the concentration the formation of different types of aggregates can be controlled. Conditions for the appearance of isolated LH2 complexes are defined. PMID:15041674

Electrical relaxation, optical and magnetic studies of nanocrystalline lithium ferrite synthesized by different chemical routes

NASA Astrophysics Data System (ADS)

Cheruku, Rajesh; Govindaraj, G.; Vijayan, Lakshmi

2017-12-01

The nanocrystalline lithium ferrite was synthesized by wet chemical methods such as solution combustion technique, sol-gel, and hydrothermal for a comparative study. Different characterization techniques like x-ray powder diffraction and thermal analysis were employed to confirm the structure and phase. Temperature-dependent Raman analysis was employed to classify the phonon modes associated with precise atomic motions existing in the synthesized materials. Morphology of sample surface was explored by scanning electron microscopy, and elemental analysis was done by energy dispersive spectroscopy analysis. The nanocrystalline nature of the materials was confirmed through transmission electron microscopy. Magnetic properties of these samples were explored through a vibrating sample magnetometer. Ac electrical impedance spectroscopy data were investigated using two Cole-Cole functions, and activation energies were calculated for all materials. Among them, solution combustion prepared lithium ferrite shows the highest conductivity and lowest activation energy.

The dependence of carbide morphology on grain boundary character in the highly twinned Alloy 690

NASA Astrophysics Data System (ADS)

Li, Hui; Xia, Shuang; Zhou, Bangxin; Chen, Wenjue; Hu, Changliang

2010-04-01

The dependence of morphology of grain boundary carbides on grain boundary character in Alloy 690 (Ni-30Cr-10Fe, mass fraction, %) with high fraction of low Σ coincidence site lattice (CSL) grain boundaries was investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Some of the surface grains were removed by means of deep etching. It was observed that carbides grow dendritically at grain boundaries. The carbide bars observed near incoherent twin boundaries and twin related Σ9 grain boundaries are actually secondary dendrites of the carbides on these boundaries. Higher order dendrites could be observed on random grain boundaries, however, no bar-like dendrites were observed near Σ27 grain boundaries and random grain boundaries. The morphology difference of carbides precipitated at grain boundaries with different characters is discussed based on the experimental results in this paper.

Nanocomposites based on thermoplastic elastomers with functional basis of nano titanium dioxide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yulovskaya, V. D.; Kuz’micheva, G. M., E-mail: galina-kuzmicheva@list.ru; Klechkovskaya, V. V.

2016-03-15

Nanocomposites based on a thermoplastic elastomer (TPE) (low-density polyethylene (LDPE) and 1,2-polybutadiene in a ratio of 60/40) with functional titanium dioxide nanoparticles of different nature, TiO{sub 2}/TPE, have been prepared and investigated by a complex of methods (X-ray diffraction analysis using X-ray and synchrotron radiation beams, scanning electron microscopy, transmission electron microscopy, and X-ray energy-dispersive spectroscopy). The morphology of the composites is found to be somewhat different, depending on the TiO{sub 2} characteristics. It is revealed that nanocomposites with cellular or porous structures containing nano-TiO{sub 2} aggregates with a large specific surface and large sizes of crystallites and nanoparticles exhibitmore » the best deformation‒strength and fatigue properties and stability to the effect of active media under conditions of ozone and vapor‒air aging.« less

A facile synthesis of zinc oxide/multiwalled carbon nanotube nanocomposite lithium ion battery anodes by sol-gel method

NASA Astrophysics Data System (ADS)

Köse, Hilal; Karaal, Şeyma; Aydın, Ali Osman; Akbulut, Hatem

2015-11-01

Free standing zinc oxide (ZnO) and multiwalled carbon nanotube (MWCNT) nanocomposite materials are prepared by a sol gel technique giving a new high capacity anode material for lithium ion batteries. Free-standing ZnO/MWCNT nanocomposite anodes with two different chelating agent additives, triethanolamine (TEA) and glycerin (GLY), yield different electrochemical performances. Field emission gun scanning electron microscopy (FEG-SEM), energy dispersive X-ray spectrometer (EDS), high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) analyses reveal the produced anode electrodes exhibit a unique structure of ZnO coating on the MWCNT surfaces. Li-ion cell assembly using a ZnO/MWCNT/GLY free-standing anode and Li metal cathode possesses the best discharge capacity, remaining as high as 460 mAh g-1 after 100 cycles. This core-shell structured anode can offer increased energy storage and performance over conventional anodes in Li-ion batteries.

Nanostructured zirconium phosphate as ion exchanger: Synthesis, size dependent property and analytical application in radiochemical separation.

PubMed

Chakraborty, Rajesh; Bhattacharaya, Koustava; Chattopadhyay, Pabitra

2014-02-01

Nanostructured zirconium phosphates (ZPs) of different sizes were synthesized using Tritron X-100 (polyethylene glycol-p-isooctylphenyl ether) surfactant. The materials were characterized by FTIR and powdered X-ray diffraction (XRD). The structural and morphological details of the material were established by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The SEM study was followed by energy dispersive spectroscopic analysis (EDS) for elemental analysis of the sample. The particle sizes were determined by dynamic light scattering (DLS) method. Ion exchange capacity of these nanomaterials towards different metal ions was measured and size-dependent ion exchange property of the materials was investigated thoroughly. The nanomaterial of the smallest size (ca. 21.04nm) was employed to separate carrier-free (137m)Ba from (137)Cs in column chromatographic technique using 1.0M HNO3 as eluting agent at pH=5. © 2013 Elsevier Ltd. All rights reserved.

Modular architecture of eukaryotic RNase P and RNase MRP revealed by electron microscopy.

PubMed

Hipp, Katharina; Galani, Kyriaki; Batisse, Claire; Prinz, Simone; Böttcher, Bettina

2012-04-01

Ribonuclease P (RNase P) and RNase MRP are closely related ribonucleoprotein enzymes, which process RNA substrates including tRNA precursors for RNase P and 5.8 S rRNA precursors, as well as some mRNAs, for RNase MRP. The structures of RNase P and RNase MRP have not yet been solved, so it is unclear how the proteins contribute to the structure of the complexes and how substrate specificity is determined. Using electron microscopy and image processing we show that eukaryotic RNase P and RNase MRP have a modular architecture, where proteins stabilize the RNA fold and contribute to cavities, channels and chambers between the modules. Such features are located at strategic positions for substrate recognition by shape and coordination of the cleaved-off sequence. These are also the sites of greatest difference between RNase P and RNase MRP, highlighting the importance of the adaptation of this region to the different substrates.

DOE Office of Scientific and Technical Information (OSTI.GOV)

García, Abraham; Cotto, María; Duconge, José

The use of hydrogen as replacement for fossil fuels, on which we depend today, is a matter of great relevance. The sustainable generation of hydrogen as fuel is relevant from an environmental and economic point of view. In this study we have explored new synthetic routes for developing new photocatalysts to be used in water splitting, for hydrogen production. Different techniques have been used to produce hydrogen, such as electrolysis, even though these processes have been found to be energetically non suitable. In this research various photocatalytic materials were presented as possible alternatives for using in water splitting processes. Characterizationmore » of the new synthesized materials has been done by using different experimental techniques including Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), surface area BET, and X-ray Diffraction (XRD). The efficiency of the synthesized photocatalysts was determined by evaluating the hydrogen evolution by the photocatalytic water splitting reaction.« less

Enhanced photocatalytic activity of ZnO/CuO nanocomposite for the degradation of textile dye on visible light illumination.

PubMed

Saravanan, R; Karthikeyan, S; Gupta, V K; Sekaran, G; Narayanan, V; Stephen, A

2013-01-01

The photocatalytic degradation of organic dyes such as methylene blue and methyl orange in the presence of various percentages of composite catalyst under visible light irradiation was carried out. The catalyst ZnO nanorods and ZnO/CuO nanocomposites of different weight ratios were prepared by new thermal decomposition method, which is simple and cost effective. The prepared catalysts were characterized by different techniques such as X-ray diffraction, transmission electron microscopy, field emission scanning electron microscopy, Fourier transform infrared spectroscopy and UV-visible absorption spectroscopy. Further, the most photocatalytically active composite material was used for degradation of real textile waste water under visible light illumination. The irradiated samples were analysed by total organic carbon and chemical oxygen demand. The efficiency of the catalyst and their photocatalytic mechanism has been discussed in detail. Copyright © 2012 Elsevier B.V. All rights reserved.

A transmission electron microscopy study of the deformation behavior underneath nanoindents in nanoscale Al-TiN multilayered composites

NASA Astrophysics Data System (ADS)

Bhattacharyya, D.; Mara, N. A.; Dickerson, P.; Hoagland, R. G.; Misra, A.

2010-05-01

Nanoscale multilayered Al-TiN composites were deposited using the dc magnetron sputtering technique in two different layer thickness ratios, Al : TiN = 1 : 1 and Al : TiN = 9 : 1. The Al layer thickness varied from 2 nm to 450 nm. The hardness of the samples was tested by nanoindentation using a Berkovich tip. Cross-sectional transmission electron microscopy (TEM) was carried out on samples extracted with focused ion beam from below the nanoindents. The results of the hardness tests on the Al-TiN multilayers with two different thickness ratios are presented, together with observations from the cross-sectional TEM studies of the regions underneath the indents. These studies revealed remarkable strength in the multilayers, as well as some very interesting deformation behavior in the TiN layers at extremely small length scales, where the hard TiN layers undergo co-deformation with the Al layers.

Comparative analysis of the effect of low-dimensional alumina structures on cell lines L929 and Neuro-2a

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fomenko, A. N., E-mail: alserova@ispms.tsc.ru; Korovin, M. S., E-mail: msk@ispms.tsc.ru

The paper presents the toxicity evaluation of nanostructures on the basis of alumina of different shape (nanofibers, nanoplates, nanosheets, nanosheet agglomerates) and with similar physical and chemical properties (particle size, specific surface area, phase composition, and zeta potential). The nanostructures were examined by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), low-temperature nitrogen adsorption, and dynamic light scattering (DLS). The cytotoxicity of nanostructures was estimated using L929 fibroblast cells and Neuro-2a tumor cells. It has been found that the L929 cells are less subject to the influence of alumina nanoparticles than the Neuro-2a tumor cells. Probably, themore » differences in the proliferation activity of normal and tumor cells in contact with the synthesized nanostructures are due to a change in the pH of the cell microenvironment.« less

Comparative analysis of the effect of low-dimensional alumina structures on cell lines L929 and Neuro-2a

NASA Astrophysics Data System (ADS)

Fomenko, A. N.; Korovin, M. S.

2016-08-01

The paper presents the toxicity evaluation of nanostructures on the basis of alumina of different shape (nanofibers, nanoplates, nanosheets, nanosheet agglomerates) and with similar physical and chemical properties (particle size, specific surface area, phase composition, and zeta potential). The nanostructures were examined by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), low-temperature nitrogen adsorption, and dynamic light scattering (DLS). The cytotoxicity of nanostructures was estimated using L929 fibroblast cells and Neuro-2a tumor cells. It has been found that the L929 cells are less subject to the influence of alumina nanoparticles than the Neuro-2a tumor cells. Probably, the differences in the proliferation activity of normal and tumor cells in contact with the synthesized nanostructures are due to a change in the pH of the cell microenvironment.

Impact of fipronil on the mushroom bodies of the stingless bee Scaptotrigona postica.

PubMed

Jacob, Cynthia R O; Soares, Hellen M; Nocelli, Roberta C F; Malaspina, Osmar

2015-01-01

Studies on stingless bees are scarce, and little is known about these insects, especially regarding the effects of contamination by neurotoxic insecticides, which can cause damage to important structures of the insect brain. This study evaluated the morphological changes in the intrinsic neurons of the protocerebral mushroom bodies (Kenyon cells) of the stingless bee Scaptotrigona postica after exposure to different doses of fipronil, using light microscopy and transmission electron microscopy. This region of the brain was selected for analysis because of its importance as a sensory integration centre. In both oral and topical treatments, Kenyon cells presented pyknotic profiles, suggesting cell death. Statistical analysis showed significant differences among doses and exposure times. Transmission electron microscopy revealed changes in the nucleus and cellular organelles. Depending on the dose, the characteristics observed suggested apoptotosis or necrosis. This study demonstrates the toxic effects of fipronil. An increase in the number of pyknotic profiles of Kenyon cells of mushroom bodies was observed even at the sublethal doses of 0.27 ng AI bee(-1) and 0.24 ng AI µL(-1) in the topical and oral treatments respectively. Also, differences in the number of pyknotic profiles were dose and time dependent. © 2014 Society of Chemical Industry.

Biological applications of phase-contrast electron microscopy.

PubMed

Nagayama, Kuniaki

2014-01-01

Here, I review the principles and applications of phase-contrast electron microscopy using phase plates. First, I develop the principle of phase contrast based on a minimal model of microscopy, introducing a double Fourier-transform process to mathematically formulate the image formation. Next, I explain four phase-contrast (PC) schemes, defocus PC, Zernike PC, Hilbert differential contrast, and schlieren optics, as image-filtering processes in the context of the minimal model, with particular emphases on the Zernike PC and corresponding Zernike phase plates. Finally, I review applications of Zernike PC cryo-electron microscopy to biological systems such as protein molecules, virus particles, and cells, including single-particle analysis to delineate three-dimensional (3D) structures of protein and virus particles and cryo-electron tomography to reconstruct 3D images of complex protein systems and cells.

From Voxels to Knowledge: A Practical Guide to the Segmentation of Complex Electron Microscopy 3D-Data

PubMed Central

Tsai, Wen-Ting; Hassan, Ahmed; Sarkar, Purbasha; Correa, Joaquin; Metlagel, Zoltan; Jorgens, Danielle M.; Auer, Manfred

2014-01-01

Modern 3D electron microscopy approaches have recently allowed unprecedented insight into the 3D ultrastructural organization of cells and tissues, enabling the visualization of large macromolecular machines, such as adhesion complexes, as well as higher-order structures, such as the cytoskeleton and cellular organelles in their respective cell and tissue context. Given the inherent complexity of cellular volumes, it is essential to first extract the features of interest in order to allow visualization, quantification, and therefore comprehension of their 3D organization. Each data set is defined by distinct characteristics, e.g., signal-to-noise ratio, crispness (sharpness) of the data, heterogeneity of its features, crowdedness of features, presence or absence of characteristic shapes that allow for easy identification, and the percentage of the entire volume that a specific region of interest occupies. All these characteristics need to be considered when deciding on which approach to take for segmentation. The six different 3D ultrastructural data sets presented were obtained by three different imaging approaches: resin embedded stained electron tomography, focused ion beam- and serial block face- scanning electron microscopy (FIB-SEM, SBF-SEM) of mildly stained and heavily stained samples, respectively. For these data sets, four different segmentation approaches have been applied: (1) fully manual model building followed solely by visualization of the model, (2) manual tracing segmentation of the data followed by surface rendering, (3) semi-automated approaches followed by surface rendering, or (4) automated custom-designed segmentation algorithms followed by surface rendering and quantitative analysis. Depending on the combination of data set characteristics, it was found that typically one of these four categorical approaches outperforms the others, but depending on the exact sequence of criteria, more than one approach may be successful. Based on these data, we propose a triage scheme that categorizes both objective data set characteristics and subjective personal criteria for the analysis of the different data sets. PMID:25145678

ELECTRON MICROSCOPE AND X-RAY DIFFRACTION STUDIES ON A HOMOLOGOUS SERIES OF SATURATED PHOSPHATIDYLCHOLINES.

PubMed

ELBERS, P F; VERVERGAERT, P H

1965-05-01

Three homologous saturated phosphatidylcholines were studied by electron microscopy after tricomplex fixation. The results are compared with those obtained by x-ray diffraction analysis of the same and some other homologous compounds, in the dry crystalline state and after tricomplex fixation. By electron microscopy alternating dark and light bands are observed which are likely to correspond to phosphatide double layers. X-Ray diffraction reveals the presence of lamellar structures of regular spacing. The layer spacings obtained by both methods are in good agreement. From the electron micrographs the width of the polar parts of the double layers can be derived directly. The width of the carboxylglycerylphosphorylcholine moiety of the layers is found by extrapolating the x-ray diffraction data to zero chain length of the fatty acids. When from this width the contribution of the carboxylglyceryl part of the molecules is subtracted, again we find good agreement with the electron microscope measurements. An attempt has been made to account for the different layer spacings measured in terms of orientation of the molecules within the double layers.

Differences in Physical and Biochemical Properties of Thermus scotoductus SA-01 Cultured with Dielectric or Convection Heating.

PubMed

Cockrell, Allison L; Fitzgerald, Lisa A; Cusick, Kathleen D; Barlow, Daniel E; Tsoi, Stanislav D; Soto, Carissa M; Baldwin, Jeffrey W; Dale, Jason R; Morris, Robert E; Little, Brenda J; Biffinger, Justin C

2015-09-01

A thermophile, Thermus scotoductus SA-01, was cultured within a constant-temperature (65°C) microwave (MW) digester to determine if MW-specific effects influenced the growth and physiology of the organism. As a control, T. scotoductus cells were also cultured using convection heating at the same temperature as the MW studies. Cell growth was analyzed by optical density (OD) measurements, and cell morphologies were characterized using electron microscopy imaging (scanning electron microscopy [SEM] and transmission electron microscopy [TEM]), dynamic light scattering (DLS), and atomic force microscopy (AFM). Biophysical properties (i.e., turgor pressure) were also calculated with AFM, and biochemical compositions (i.e., proteins, nucleic acids, fatty acids) were analyzed by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. Gas chromatography-mass spectrometry (GC-MS) was used to analyze the fatty acid methyl esters extracted from cell membranes. Here we report successful cultivation of a thermophile with only dielectric heating. Under the MW conditions for growth, cell walls remained intact and there were no indications of membrane damage or cell leakage. Results from these studies also demonstrated that T. scotoductus cells grown with MW heating exhibited accelerated growth rates in addition to altered cell morphologies and biochemical compositions compared with oven-grown cells. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Peptide secretion in the cutaneous glands of South American tree frog Phyllomedusa bicolor: an ultrastructural study.

PubMed

Lacombe, C; Cifuentes-Diaz, C; Dunia, I; Auber-Thomay, M; Nicolas, P; Amiche, M

2000-09-01

The development of the dermal glands of the arboreal frog Phyllomedusa bicolor was investigated by immunocytochemistry and electron microscopy. The 3 types of glands (mucous, lipid and serous) differed in size and secretory activity. The mucous and serous glands were apparent in the tadpole skin, whereas the lipid glands developed later in ontogenesis. The peptide antibiotics dermaseptins and the D-amino acid-containing peptide opioids dermorphins and deltorphins are abundant in the skin secretions of P. bicolor. Although these peptides differ in their structure and activity they are derived from precursors that have very similar preproregions. We used an antibody to the common preproregion of preprodermaseptins and preprodeltorphins and immunofluorescence analysis to show that only the serous glands are specifically involved in the biosynthesis and secretion of dermaseptins and deltorphins. Scanning and transmission electron microscopy revealed that the serous glands of P bicolor have morphological features, especially the secretory granules, which differ from those of the glands in Xenopus laevis skin.

Hierarchical Na-doped cubic ZrO2 synthesis by a simple hydrothermal route and its application in biodiesel production

NASA Astrophysics Data System (ADS)

Lara-García, Hugo A.; Romero-Ibarra, Issis C.; Pfeiffer, Heriberto

2014-10-01

Hierarchical growth of cubic ZrO2 phase was successfully synthesized via a simple hydrothermal process in the presence of different surfactants (cationic, non-ionic and anionic) and sodium hydroxide. The structural and microstructural characterizations of different ZrO2 powders were performed using various techniques, such as X-ray diffraction, transmission electron microscopy, N2 adsorption-desorption, scanning electron microscopy and infrared. Results indicated that sodium addition stabilized the cubic ZrO2 phase by a Na-doping process, independently of the surfactant used. In contrast, microstructural characteristics varied as a function of the surfactant and sodium presence. In addition, water vapor (H2O) and carbon dioxide (CO2) sorption properties were evaluated on ZrO2 samples. Results evidenced that sample surface reactivity changed as a function of the sodium content. Finally, this surface reactivity was evaluated on the biodiesel transesterification reaction using the different synthesized samples, obtaining yields of 93%.

Ni@Fe2O3 heterodimers: controlled synthesis and magnetically recyclable catalytic application for dehalogenation reactions

NASA Astrophysics Data System (ADS)

Nakhjavan, Bahar; Tahir, Muhammad Nawaz; Natalio, Filipe; Panthöfer, Martin; Gao, Haitao; Dietzsch, Michael; Andre, Rute; Gasi, Teuta; Ksenofontov, Vadim; Branscheid, Robert; Kolb, Ute; Tremel, Wolfgang

2012-07-01

Ni@Fe2O3 heterodimer nanoparticles (NPs) were synthesized by thermal decomposition of organometallic reactants. After functionalization, these Ni@Fe2O3 heterodimers became water soluble. The pristine heterodimeric NPs were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Mössbauer spectroscopy and magnetic susceptibility measurements. A special advantage of the heterodimers lies in the fact that nanodomains of different composition can be used as catalysts for the removal of environmentally hazardous halogenated pollutants.Ni@Fe2O3 heterodimer nanoparticles (NPs) were synthesized by thermal decomposition of organometallic reactants. After functionalization, these Ni@Fe2O3 heterodimers became water soluble. The pristine heterodimeric NPs were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Mössbauer spectroscopy and magnetic susceptibility measurements. A special advantage of the heterodimers lies in the fact that nanodomains of different composition can be used as catalysts for the removal of environmentally hazardous halogenated pollutants. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr12121b

Morphology-dependent Electrochemical Enhancements of Porous Carbon as Sensitive Determination Platform for Ascorbic Acid, Dopamine and Uric Acid

NASA Astrophysics Data System (ADS)

Cheng, Qin; Ji, Liudi; Wu, Kangbing; Zhang, Weikang

2016-02-01

Using starch as the carbon precursor and different-sized ZnO naoparticles as the hard template, a series of porous carbon materials for electrochemical sensing were prepared. Experiments of scanning electron microscopy, transmission electron microscopy and Nitrogen adsorption-desorption isotherms reveal that the particle size of ZnO has big impacts on the porous morphology and surface area of the resulting carbon materials. Through ultrasonic dispersion of porous carbon and subsequent solvent evaporation, different sensing interfaces were constructed on the surface of glassy carbon electrode (GCE). The electrochemical behaviors of ascorbic acid (AA), dopamine (DA) and uric acid (UA) were studied. On the surface of porous carbon materials, the accumulation efficiency and electron transfer ability of AA, DA and UA are improved, and consequently their oxidation signals enhance greatly. Moreover, the interface enhancement effects of porous carbon are also controlled by the particle size of hard template. The constructed porous carbon interface displays strong signal amplification ability and holds great promise in constructing a sensitive platform for the simultaneous determination of AA, DA and UA.

Classification of cryo electron microscopy images, noisy tomographic images recorded with unknown projection directions, by simultaneously estimating reconstructions and application to an assembly mutant of Cowpea Chlorotic Mottle Virus and portals of the bacteriophage P22

NASA Astrophysics Data System (ADS)

Lee, Junghoon; Zheng, Yili; Yin, Zhye; Doerschuk, Peter C.; Johnson, John E.

2010-08-01

Cryo electron microscopy is frequently used on biological specimens that show a mixture of different types of object. Because the electron beam rapidly destroys the specimen, the beam current is minimized which leads to noisy images (SNR substantially less than 1) and only one projection image per object (with an unknown projection direction) is collected. For situations where the objects can reasonably be described as coming from a finite set of classes, an approach based on joint maximum likelihood estimation of the reconstruction of each class and then use of the reconstructions to label the class of each image is described and demonstrated on two challenging problems: an assembly mutant of Cowpea Chlorotic Mottle Virus and portals of the bacteriophage P22.

The structure of Escherichia coli signal recognition particle revealed by scanning transmission electron microscopy.

PubMed

Mainprize, Iain L; Beniac, Daniel R; Falkovskaia, Elena; Cleverley, Robert M; Gierasch, Lila M; Ottensmeyer, F Peter; Andrews, David W

2006-12-01

Structural studies on various domains of the ribonucleoprotein signal recognition particle (SRP) have not converged on a single complete structure of bacterial SRP consistent with the biochemistry of the particle. We obtained a three-dimensional structure for Escherichia coli SRP by cryoscanning transmission electron microscopy and mapped the internal RNA by electron spectroscopic imaging. Crystallographic data were fit into the SRP reconstruction, and although the resulting model differed from previous models, they could be rationalized by movement through an interdomain linker of Ffh, the protein component of SRP. Fluorescence resonance energy transfer experiments determined interdomain distances that were consistent with our model of SRP. Docking our model onto the bacterial ribosome suggests a mechanism for signal recognition involving interdomain movement of Ffh into and out of the nascent chain exit site and suggests how SRP could interact and/or compete with the ribosome-bound chaperone, trigger factor, for a nascent chain during translation.

Characterization of BN rich layer on ammonia treated Nextel{trademark}312 fibers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khasgiwale, N.R.; Butler, E.P.; Tsakalakos, L.

A BN rich layer grown on Nextel{trademark}312 fibers by appropriate ammonia treatments was evaluated using various complimentary techniques including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM)/Parallel Electron Energy Loss Spectroscopy (PEELS in TEM). Three different ammonia treatments were studied. Ammonia treatment resulted in crystallization of the Nextel{trademark}312 fiber. The BN rich surface layer formed due to ammonia treatment was clearly detected in XPS and PEELS both before and after oxidation. The layer thickness was estimated to be between 5--10 nm. The layer was stable after oxidation treatment at 600 C formore » 100 hours. High resolution TEM observations of the fiber surface revealed a variable BN rich layer thickness. Patches of turbostratic BN were observed under certain conditions, however mostly the layer appeared to be amorphous.« less

Thickness dependence of scattering cross-sections in quantitative scanning transmission electron microscopy.

PubMed

Martinez, G T; van den Bos, K H W; Alania, M; Nellist, P D; Van Aert, S

2018-04-01

In quantitative scanning transmission electron microscopy (STEM), scattering cross-sections have been shown to be very sensitive to the number of atoms in a column and its composition. They correspond to the integrated intensity over the atomic column and they outperform other measures. As compared to atomic column peak intensities, which saturate at a given thickness, scattering cross-sections increase monotonically. A study of the electron wave propagation is presented to explain the sensitivity of the scattering cross-sections. Based on the multislice algorithm, we analyse the wave propagation inside the crystal and its link to the scattered signal for the different probe positions contained in the scattering cross-section for detector collection in the low-, middle- and high-angle regimes. The influence to the signal from scattering of neighbouring columns is also discussed. Copyright © 2018 Elsevier B.V. All rights reserved.

Coaxial carbon plasma gun deposition of amorphous carbon films

NASA Technical Reports Server (NTRS)

Sater, D. M.; Gulino, D. A.; Rutledge, S. K.

1984-01-01

A unique plasma gun employing coaxial carbon electrodes was used in an attempt to deposit thin films of amorphous diamond-like carbon. A number of different structural, compositional, and electrical characterization techniques were used to characterize these films. These included scanning electron microscopy, scanning transmission electron microscopy, X ray diffraction and absorption, spectrographic analysis, energy dispersive spectroscopy, and selected area electron diffraction. Optical absorption and electrical resistivity measurements were also performed. The films were determined to be primarily amorphous, with poor adhesion to fused silica substrates. Many inclusions of particulates were found to be present as well. Analysis of these particulates revealed the presence of trace impurities, such as Fe and Cu, which were also found in the graphite electrode material. The electrodes were the source of these impurities. No evidence of diamond-like crystallite structure was found in any of the film samples. Details of the apparatus, experimental procedure, and film characteristics are presented.

Surface electrical properties of stainless steel fibres: An AFM-based study

NASA Astrophysics Data System (ADS)

Yin, Jun; D'Haese, Cécile; Nysten, Bernard

2015-03-01

Atomic force microscopy (AFM) electrical modes were used to study the surface electrical properties of stainless steel fibres. The surface electrical conductivity was studied by current sensing AFM and I-V spectroscopy. Kelvin probe force microscopy was used to measure the surface contact potential. The oxide film, known as passivation layer, covering the fibre surface gives rise to the observation of an apparently semiconducting behaviour. The passivation layer generally exhibits a p-type semiconducting behaviour, which is attributed to the predominant formation of chromium oxide on the surface of the stainless steel fibres. At the nanoscale, different behaviours are observed from points to points, which may be attributed to local variations of the chemical composition and/or thickness of the passivation layer. I-V curves are well fitted with an electron tunnelling model, indicating that electron tunnelling may be the predominant mechanism for electron transport.

Rare earth ions doped ZnO: Synthesis, characterization and preliminary photoactivity assessment

NASA Astrophysics Data System (ADS)

Cerrato, Erik; Gionco, Chiara; Berruti, Ilaria; Sordello, Fabrizio; Calza, Paola; Paganini, Maria Cristina

2018-08-01

This work reports the effect of doping zinc oxide with lanthanide ions on structural, EPR and UV visible properties. Bare and doped samples were synthesized using the simple and green hydrothermal process. Different rare earth ions (RE = La, Ce, Pr, Er and Yb) with 1% molar ratio RE/Zn were used. The samples have been studied using X Ray Diffraction, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and UV visible diffuse reflectance spectroscopy. Finally, electron paramagnetic resonance (EPR) spectroscopy, was used to assess the materials photoactivity under UV irradiation, both in solid state, to see the charge carriers' generation and in solution, evaluating the OH• radical formation using the DMPO (5,5-Dimethyl-1-Pyrroline-N-Oxide) spin trapping technique. The results suggest that the synthesized materials could be interesting systems for the photocatalytic abatement of emerging organic persistent pollutants in wastewater treatment plants.

Solvothermal preparation of phthalocyanine nanorod/rGO composites and their application to visible-light-responsive photocatalysts

NASA Astrophysics Data System (ADS)

Zhang, Shuai; Lu, Yongting; Zhang, Fan; Qu, Jie; Lin, Bencai; Yuan, Ningyi; Fang, Bijun; Ding, Jian-Ning

2016-09-01

Phthalocyanine (Pc) nanorod/reduced graphene oxide (rGO) composites were prepared by a simple solvothermal method, in which Pc nanosheet and graphene oxide (GO) suspensions were mixed in methanol. As characterized by scanning electron microscopy, transmission electron microscopy, and selected area electron diffraction, Pc nanorods with an amorphous structure and an average diameter of 250nm are partially covered by rGO sheets. In the photodegradation experiments, all the composites with different rGO content show enhanced photocatalytic activity for Rhodamine B decomposition under visible-light compared to pure Pc nanorods or rGO sheets. The enhanced photocatalytic activity shall be ascribed to the large surface area offered by rGO and the charge-transfer from Pc to rGO as indicated by the photoluminescence measurement, in which fluorescence intensity of the composites is much weaker than that of Pc nanorods.

High-resolution x-ray diffraction microscopy of specifically labeled yeast cells

PubMed Central

Nelson, Johanna; Huang, Xiaojing; Steinbrener, Jan; Shapiro, David; Kirz, Janos; Marchesini, Stefano; Neiman, Aaron M.; Turner, Joshua J.; Jacobsen, Chris

2010-01-01

X-ray diffraction microscopy complements other x-ray microscopy methods by being free of lens-imposed radiation dose and resolution limits, and it allows for high-resolution imaging of biological specimens too thick to be viewed by electron microscopy. We report here the highest resolution (11–13 nm) x-ray diffraction micrograph of biological specimens, and a demonstration of molecular-specific gold labeling at different depths within cells via through-focus propagation of the reconstructed wavefield. The lectin concanavalin A conjugated to colloidal gold particles was used to label the α-mannan sugar in the cell wall of the yeast Saccharomyces cerevisiae. Cells were plunge-frozen in liquid ethane and freeze-dried, after which they were imaged whole using x-ray diffraction microscopy at 750 eV photon energy. PMID:20368463

High-resolution x-ray diffraction microscopy of specifically labeled yeast cells

DOE PAGES

Nelson, Johanna; Huang, Xiaojing; Steinbrener, Jan; ...

2010-04-20

X-ray diffraction microscopy complements other x-ray microscopy methods by being free of lens-imposed radiation dose and resolution limits, and it allows for high-resolution imaging of biological specimens too thick to be viewed by electron microscopy. We report here the highest resolution (11-13 nm) x-ray diffraction micrograph of biological specimens, and a demonstration of molecular-specific gold labeling at different depths within cells via through-focus propagation of the reconstructed wavefield. The lectin concanavalin A conjugated to colloidal gold particles was used to label the α-mannan sugar in the cell wall of the yeast Saccharomyces cerevisiae. Cells were plunge-frozen in liquid ethane andmore » freeze-dried, after which they were imaged whole using x-ray diffraction microscopy at 750 eV photon energy.« less

Crystallization of TiO2 Nanotubes by In Situ Heating TEM

PubMed Central

Casu, Alberto; Lamberti, Andrea

2018-01-01

The thermally-induced crystallization of anodically grown TiO2 amorphous nanotubes has been studied so far under ambient pressure conditions by techniques such as differential scanning calorimetry and in situ X-ray diffraction, then looking at the overall response of several thousands of nanotubes in a carpet arrangement. Here we report a study of this phenomenon based on an in situ transmission electron microscopy approach that uses a twofold strategy. First, a group of some tens of TiO2 amorphous nanotubes was heated looking at their electron diffraction pattern change versus temperature, in order to determine both the initial temperature of crystallization and the corresponding crystalline phases. Second, the experiment was repeated on groups of few nanotubes, imaging their structural evolution in the direct space by spherical aberration-corrected high resolution transmission electron microscopy. These studies showed that, differently from what happens under ambient pressure conditions, under the microscope’s high vacuum (p < 10−5 Pa) the crystallization of TiO2 amorphous nanotubes starts from local small seeds of rutile and brookite, which then grow up with the increasing temperature. Besides, the crystallization started at different temperatures, namely 450 and 380 °C, when the in situ heating was performed irradiating the sample with electron beam energy of 120 or 300 keV, respectively. This difference is due to atomic knock-on effects induced by the electron beam with diverse energy. PMID:29342894

Fast electron microscopy via compressive sensing

DOEpatents

Larson, Kurt W; Anderson, Hyrum S; Wheeler, Jason W

2014-12-09

Various technologies described herein pertain to compressive sensing electron microscopy. A compressive sensing electron microscope includes a multi-beam generator and a detector. The multi-beam generator emits a sequence of electron patterns over time. Each of the electron patterns can include a plurality of electron beams, where the plurality of electron beams is configured to impart a spatially varying electron density on a sample. Further, the spatially varying electron density varies between each of the electron patterns in the sequence. Moreover, the detector collects signals respectively corresponding to interactions between the sample and each of the electron patterns in the sequence.

Anther development of maize (Zea mays) and longstamen rice (Oryza longistaminata) revealed by cryo-SEM, with foci on locular dehydration and pollen arrangement.

PubMed

Tsou, Chih-Hua; Cheng, Ping-Chin; Tseng, Chiung-Maan; Yen, Hsiao-Jung; Fu, Yu-Lan; You, Tien-Rong; Walden, David B

2015-03-01

Key message: Pollen maturation in Poaceae. Another development has been extensively examined by various imaging tools, including transmission electron microscopy, scanning electron microscopy, and light microscopy, but none is capable of identifying liquid water. Cryo-scanning electron microscopy with high-pressure rapid freeze fixation is excellent in preserving structures at cellular level and differentiating gas- versus liquid-filled space, but rarely used in anther study. We applied this technique to examine anther development of Poaceae because of its economic importance and unusual peripheral arrangement of pollen. Maize and longstamen rice were focused on. Here, we report for the first time that anthers of Poaceae lose the locular free liquid during late-microspore to early pollen stages; the majority of pollen grains arranged in a tight peripheral whorl develops normally and reaches maturity in the gas-filled loculus. Occasionally, pollen grains are found situated in the locular cavity, but they remain immature or become shrunk at anthesis. At pollen stage, microchannels and cytoplasmic strands are densely distributed in the entire pollen exine and intine, respectively, suggesting that nutrients are transported into the pollen from the entire surface. We propose that in Poaceae, the specialized peripheral arrangement of pollen grains is crucial for pollen maturation in the gas-filled loculus, which enables pollen achieving large surface contact area with the tapetum and neighboring grains to maintain sufficient nutrient flow. This report also shows that the single aperture of pollen in Poaceae usually faces the tapetum, but other orientation is also common; pollen grains with different aperture orientations show no morphological differences.

Novel insights into pericarp, protein body globoids of aleurone layer, starchy granules of three cereals gained using atomic force microscopy and environmental scanning electronic microscopy

PubMed Central

Antonini, Elena; Zara, Carolina; Valentini, Laura; Gobbi, Pietro; Menotta, Michele

2018-01-01

In this study, we applied Environmental Scanning Electron Microscopy-Energy Dispersive Spectroscopy (ESEM-EDS) and Atomic Force Microscopy (AFM) analysis to three different cereal caryopses: barley, oat and einkorn wheat. The morphological structures, chemical elemental composition and surface characteristics of the three cereals were described. Regarding the morphology, barley showed the thickest pericarp, providing a strong barrier to digestion and absorption of nutrients. The aleurone layer of each cereal type contained protein body globoids within its cells. Large type-A and small type-B starchy granules were revealed in the endosperm of barley and einkorn wheat, whereas irregular starchy granules were found in oats. The starchy granule elemental composition, detected by ESEM-EDS, was rather homogenous in the three cereals, whereas the pericarp and protein body globoids showed heterogeneity. In the protein body globoids, oats showed higher P and K concentrations than barley and einkorn wheat. Regarding the topographic profiles, detected by AFM, einkorn wheat starchy granules showed a surface profile that differed significantly from that of oats and barley, which were quite similar to one another. The present work provides insights into the morphological and chemical makeup of the three grains shedding light on the higher bio-accessibility of einkorn wheat nutrients compared to barley and oats, providing important suggestions for human nutrition and technological standpoints. PMID:29569870

Normal and reversed supramolecular chirality of insulin fibrils probed by vibrational circular dichroism at the protofilament level of fibril structure.

PubMed

Kurouski, Dmitry; Dukor, Rina K; Lu, Xuefang; Nafie, Laurence A; Lednev, Igor K

2012-08-08

Fibrils are β-sheet-rich aggregates that are generally composed of several protofibrils and may adopt variable morphologies, such as twisted ribbons or flat-like sheets. This polymorphism is observed for many different amyloid associated proteins and polypeptides. In a previous study we proposed the existence of another level of amyloid polymorphism, namely, that associated with fibril supramolecular chirality. Two chiral polymorphs of insulin, which can be controllably grown by means of small pH variations, exhibit opposite signs of vibrational circular dichroism (VCD) spectra. Herein, using atomic force microscopy (AFM) and scanning electron microscopy (SEM), we demonstrate that indeed VCD supramolecular chirality is correlated not only by the apparent fibril handedness but also by the sense of supramolecular chirality from a deeper level of chiral organization at the protofilament level of fibril structure. Our microscopic examination indicates that normal VCD fibrils have a left-handed twist, whereas reversed VCD fibrils are flat-like aggregates with no obvious helical twist as imaged by atomic force microscopy or scanning electron microscopy. A scheme is proposed consistent with observed data that features a dynamic equilibrium controlled by pH at the protofilament level between left- and right-twist fibril structures with distinctly different aggregation pathways for left- and right-twisted protofilaments. Copyright © 2012 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Atomic force microscopy and scanning electron microscopy evaluation of efficacy of scaling and root planing using magnification: A randomized controlled clinical study

PubMed Central

Mohan, Ranjana; Agrawal, Sudhanshu; Gundappa, Mohan

2013-01-01

Aim: A randomized controlled clinical study was undertaken to evaluate the effectiveness of scaling and root planing (SRP) by using Magnifying Loupes (ML) and dental operating microscope (DOM). Materials and Methods: A total of 90 human teeth scheduled for extraction from 18 patients aged between 25 and 65 years suffering from generalized chronic severe periodontitis were randomly assigned to three treatment groups. Group 1 consisted SRP performed without using magnification (unaided), Group 2-SRP with ML and Group 3-SRP with DOM. Following extractions, samples were prepared for (i) evaluation of surface topography by atomic force microscopy, (ii) presence of smear layer, debris by scanning electron microscopy (iii) elemental analysis by energy dispersive X-ray analysis. Data was subjected to statistical analysis using analysis of variance, post-hoc (Tukey-HSD) and Chi-square test. Results: Statistically significant (P < 0.001) difference was found among the different treatment groups. Group 3 was the best while Group 1 was the least effective technique for SRP. Order of efficacy in terms of the surface was found to be - Palatal < Lingual < Distal ≃ Mesial < Buccal. Efficiency in mandibular to maxillary teeth was found to be significant (P < 0.05), also anterior to posterior teeth (P < 0.05). Conclusion: Magnification tools significantly enhance the efficacy of supragingival and subgingival SRP. PMID:24124292

Novel insights into pericarp, protein body globoids of aleurone layer, starchy granules of three cereals gained using atomic force microscopy and environmental scanning electronic microscopy.

PubMed

Antonini, Elena; Zara, Carolina; Valentini, Laura; Gobbi, Pietro; Ninfali, Paolino; Menotta, Michele

2018-02-05

In this study, we applied Environmental Scanning Electron Microscopy-Energy Dispersive Spectroscopy (ESEM-EDS) and Atomic Force Microscopy (AFM) analysis to three different cereal caryopses: barley, oat and einkorn wheat. The morphological structures, chemical elemental composition and surface characteristics of the three cereals were described. Regarding the morphology, barley showed the thickest pericarp, providing a strong barrier digestion and absorption of nutrients. The aleurone layer of each cereal type contained protein body globoids within its cells. Large type-A and small type-B starchy granules were revealed in the endosperm of barley and einkorn wheat, whereas irregular starchy granules were found in oats. The starchy granule elemental composition, detected by ESEM-EDS, was rather homogenous in the three cereals, whereas the pericarp and protein body globoids showed heterogeneity. In the protein body globoids, oats showed higher P and K concentrations than barley and einkorn wheat. Regarding the topographic profiles, detected by AFM, einkorn wheat starchy granules showed a surface profile that differed significantly from that of oats and barley, which were quite similar to one another. The present work provides insights into the morphological and chemical makeup of the three grains shedding light on the higher bio-accessibility of einkorn wheat nutrients compared to barley and oats, providing important suggestions for human nutrition and technological standpoints.

Photon gating in four-dimensional ultrafast electron microscopy.

PubMed

Hassan, Mohammed T; Liu, Haihua; Baskin, John Spencer; Zewail, Ahmed H

2015-10-20

Ultrafast electron microscopy (UEM) is a pivotal tool for imaging of nanoscale structural dynamics with subparticle resolution on the time scale of atomic motion. Photon-induced near-field electron microscopy (PINEM), a key UEM technique, involves the detection of electrons that have gained energy from a femtosecond optical pulse via photon-electron coupling on nanostructures. PINEM has been applied in various fields of study, from materials science to biological imaging, exploiting the unique spatial, energy, and temporal characteristics of the PINEM electrons gained by interaction with a "single" light pulse. The further potential of photon-gated PINEM electrons in probing ultrafast dynamics of matter and the optical gating of electrons by invoking a "second" optical pulse has previously been proposed and examined theoretically in our group. Here, we experimentally demonstrate this photon-gating technique, and, through diffraction, visualize the phase transition dynamics in vanadium dioxide nanoparticles. With optical gating of PINEM electrons, imaging temporal resolution was improved by a factor of 3 or better, being limited only by the optical pulse widths. This work enables the combination of the high spatial resolution of electron microscopy and the ultrafast temporal response of the optical pulses, which provides a promising approach to attain the resolution of few femtoseconds and attoseconds in UEM.

Photon gating in four-dimensional ultrafast electron microscopy

PubMed Central

Hassan, Mohammed T.; Liu, Haihua; Baskin, John Spencer; Zewail, Ahmed H.

2015-01-01

Ultrafast electron microscopy (UEM) is a pivotal tool for imaging of nanoscale structural dynamics with subparticle resolution on the time scale of atomic motion. Photon-induced near-field electron microscopy (PINEM), a key UEM technique, involves the detection of electrons that have gained energy from a femtosecond optical pulse via photon–electron coupling on nanostructures. PINEM has been applied in various fields of study, from materials science to biological imaging, exploiting the unique spatial, energy, and temporal characteristics of the PINEM electrons gained by interaction with a “single” light pulse. The further potential of photon-gated PINEM electrons in probing ultrafast dynamics of matter and the optical gating of electrons by invoking a “second” optical pulse has previously been proposed and examined theoretically in our group. Here, we experimentally demonstrate this photon-gating technique, and, through diffraction, visualize the phase transition dynamics in vanadium dioxide nanoparticles. With optical gating of PINEM electrons, imaging temporal resolution was improved by a factor of 3 or better, being limited only by the optical pulse widths. This work enables the combination of the high spatial resolution of electron microscopy and the ultrafast temporal response of the optical pulses, which provides a promising approach to attain the resolution of few femtoseconds and attoseconds in UEM. PMID:26438835

A scanning electron microscopic evaluation of in vitro dentinal tubules penetration by selected anaerobic bacteria.

PubMed

Siqueira, J F; De Uzeda, M; Fonseca, M E

1996-06-01

In vitro root canal dentinal tubule invasion by selected anaerobic bacteria commonly isolated from endodontic infections was evaluated. Dentinal cylinders obtained from bovine incisors were inoculated with bacteria, and microbial penetration into tubules was demonstrated by scanning electron microscopy. The results indicated that all bacterial strains tested were able to penetrate into dentinal tubules, but to different extents.

The distinguishing effects of low-intensity electromagnetic radiation of different extremely high frequencies on Enterococcus hirae: growth rate inhibition and scanning electron microscopy analysis.

PubMed

Hovnanyan, K; Kalantaryan, V; Trchounian, A

2017-09-01

A low-intensity electromagnetic field of extremely high frequency has inhibitory and stimulatory effects on bacteria, including Enterococcus hirae. It was shown that the low-intensity (the incident power density of 0·06 mW cm -2 ) electromagnetic field at the frequencies of 51·8 GHz and 53 GHz inhibited E. hirae ATCC 9790 bacterial growth rate; a stronger effect was observed with 53 GHz, regardless of exposure duration (0·5 h, 1 h or 2 h). Scanning electron microscopy analysis of these effects has been done; the cells were of spherical shape. Electromagnetic field at 53 GHz, but not 51·8 GHz, changed the cell size-the diameter was enlarged 1·3 fold at 53 GHz. These results suggest the difference in mechanisms of action on bacteria for electromagnetic fields at 51·8 GHz and 53 GHz. A stronger inhibitory effect of low-intensity electromagnetic field on Enterococcus hirae ATCC 9790 bacterial growth rate was observed with 53 GHz vs 51·8 GHz, regardless of exposure duration. Scanning electron microscopy analysis showed that almost all irradiated cells in the population have spherical shapes similar to nonirradiated ones, but they have increased diameters in case of irradiated cells at 53 GHz, but not 51·8 GHz. The results are novel, showing distinguishing effects of low-intensity electromagnetic field of different frequencies. They could be applied in treatment of food and different products in medicine and veterinary, where E. hirae plays an important role. © 2017 The Society for Applied Microbiology.

Ultrastructural Analysis of Different Human Mesenchymal Stem Cells After in Vitro Expansion: A Technical Review

PubMed Central

Danišovič, Ľ.; Majidi, A.; Varga, I.

2015-01-01

Transmission electron microscopy reveals ultrastructural details of cells, and it is a valuable method for studying cell organelles. That is why we used this method for detailed morphological description of different adult tissue-derived stem cells, focusing on the morphological signs of their functions (proteosynthetic activity, exchange with external environment, etc.) and their comparison. Preparing a specimen from the cell culture suitable for transmission electron microscopy is, however, much more challenging than routine tissue processing for normal histological examination. There are several issues that need to be solved while working with cell pellets instead of solid tissue. Here we describe a simple protocol for the isolation and culture of mesenchymal stem cells from different adult tissues, with applications to stem cell biology and regenerative medicine. Since we are working with population of cells that was obtained after many days of passaging, very efficient and gentle procedures are highly necessary. We demonstrated that our semi-conservative approach regarding to histological techniques and processing of cells for transmission electron microscopy is a well reproducible procedure which results in quality pictures and images of cell populations with minimum distortions and artifacts. We also commented about riskiest steps and histochemical issues (e.g., precise pH, temperature) while preparing the specimen. We bring full and detailed procedures of fixation, post-fixation, infiltration, embedding, polymerization and contrasting of cell obtained from in vitro cell and tissue cultures, with modifications according to our experience. All this steps are essential for us to know more about adult stem cells derived from different sources or about other random cell populations. The knowledge about detailed ultra-structure of adult stem cells cultured in vitro are also essential for their using in regenerative medicine and tissue engineering. PMID:26708176

Use of scanning electron microscopy and microanalysis to determine chloride content of concrete and raw materials.

DOT National Transportation Integrated Search

2013-02-01

Standard sample sets of cement and mortar formulations with known levels of Cl as well as concrete samples subject to Cl diffusion were all prepared for and analyzed with scanning electron microscopy (SEM) and electron microprobe (EPMA). Using x-ray ...

Comparative morphology of zebra (Dreissena polymorpha) and quagga (Dreissena bugensis) mussel sperm: Light and electron microscopy

USGS Publications Warehouse

Walker, G.K.; Black, M.G.; Edwards, C.A.

1996-01-01

Adult zebra (Dreissena polymorpha) and quagga (Dreissena bugensis) mussels were induced to release large quantities of live spermatozoa by the administration of 5-hydroxytryptamine (serotonin). Sperm were photographed alive using phase-contrast microscopy and were fixed subsequently with glutaraldehyde followed by osmium tetroxide for eventual examination by transmission or scanning electron microscopy. The sperm of both genera are of the ect-aquasperm type. Their overall dimensions and shape allow for easy discrimination at the light and scanning electron microscopy level. Transmission electron microscopy of the cells reveals a barrel-shaped nucleus in zebra mussel sperm and an elongated nucleus in quagga mussel sperm. In both species, an acrosome is cradled in a nuclear fossa. The ultrastructure of the acrosome and axial body, however, is distinctive for each species. The structures of the midpiece are shown, including a unique mitochondrial "skirt" that includes densely packed parallel cristae and extends in a narrow sheet from the mitochondria.

Advances in high-resolution imaging--techniques for three-dimensional imaging of cellular structures.

PubMed

Lidke, Diane S; Lidke, Keith A

2012-06-01

A fundamental goal in biology is to determine how cellular organization is coupled to function. To achieve this goal, a better understanding of organelle composition and structure is needed. Although visualization of cellular organelles using fluorescence or electron microscopy (EM) has become a common tool for the cell biologist, recent advances are providing a clearer picture of the cell than ever before. In particular, advanced light-microscopy techniques are achieving resolutions below the diffraction limit and EM tomography provides high-resolution three-dimensional (3D) images of cellular structures. The ability to perform both fluorescence and electron microscopy on the same sample (correlative light and electron microscopy, CLEM) makes it possible to identify where a fluorescently labeled protein is located with respect to organelle structures visualized by EM. Here, we review the current state of the art in 3D biological imaging techniques with a focus on recent advances in electron microscopy and fluorescence super-resolution techniques.

Three-dimensional architecture of ribosomal DNA within barley nucleoli revealed with electron microscopy.

PubMed

Iwano, Megumi; Che, Fang-Sik; Takayama, Seiji; Fukui, Kiichi; Isogai, Akira

2003-01-01

To elucidate the topological positioning of ribosomal RNA genes (rDNA) and nucleolar structure in three dimensions, we examined the localization of rDNA using in situ hybridization (ISH) analysis by scanning electron microscopy (SEM). The rDNA genes within the three-dimensional architecture of nucleoli were detected on chromatin fibers that connect a thick strand-like structure and a protrusion of rDNA into the inner nuclear hole where the nucleolus is formed. This novel use of ISH together with SEM is useful for the analysis of nucleolar structure in detail. Furthermore, rDNA was detected at the periphery of the fibrillar centers (FCs) of the nucleolus using immuno-gold labeling together with transmission electron microscopy (TEM). In situ hybridization with TEM confirmed that rDNA is naked and thus active in the FCs of nucleoli; ISH with SEM confirmed that rDNA is not covered with ribonucleo proteins at the protruding point and is thus inactive. We also show that the distribution pattern of FCs differs from sample to sample. These results indicate that rDNA is transcribed dynamically in a time- and region-specific manner over the course of the cell cycle.

Micro-structural characterization of precipitation-synthesized fluorapatite nano-material by transmission electron microscopy using different sample preparation techniques.

PubMed

Chinthaka Silva, G W; Ma, Longzhou; Hemmers, Oliver; Lindle, Dennis

2008-01-01

Fluorapatite is a naturally occurring mineral of the apatite group and it is well known for its high physical and chemical stability. There is a recent interest in this ceramic to be used as a radioactive waste form material due to its intriguing chemical and physical properties. In this study, the nano-sized fluorapatite particles were synthesized using a precipitation method and the material was characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Two well-known methods, called solution-drop and the microtome cutting, were used to prepare the sample for TEM analysis. It was found that the microtome cutting technique is advantageous for examining the particle shape and cross-sectional morphology as well as for obtaining ultra-thin samples. However, this method introduces artifacts and strong background contrast for high-resolution transmission electron microscopy (HRTEM) observation. On the other hand, phase image simulations showed that the solution-drop method is reliable and stable for HRTEM analysis. Therefore, in order to comprehensively analyze the microstructure and morphology of the nano-material, it is necessary to combine both solution-drop and microtome cutting techniques for TEM sample preparation.

Construction and validation of an atomic model for bacterial TSPO from electron microscopy density, evolutionary constraints, and biochemical and biophysical data.

PubMed

Hinsen, Konrad; Vaitinadapoule, Aurore; Ostuni, Mariano A; Etchebest, Catherine; Lacapere, Jean-Jacques

2015-02-01

The 18 kDa protein TSPO is a highly conserved transmembrane protein found in bacteria, yeast, animals and plants. TSPO is involved in a wide range of physiological functions, among which the transport of several molecules. The atomic structure of monomeric ligand-bound mouse TSPO in detergent has been published recently. A previously published low-resolution structure of Rhodobacter sphaeroides TSPO, obtained from tubular crystals with lipids and observed in cryo-electron microscopy, revealed an oligomeric structure without any ligand. We analyze this electron microscopy density in view of available biochemical and biophysical data, building a matching atomic model for the monomer and then the entire crystal. We compare its intra- and inter-molecular contacts with those predicted by amino acid covariation in TSPO proteins from evolutionary sequence analysis. The arrangement of the five transmembrane helices in a monomer of our model is different from that observed for the mouse TSPO. We analyze possible ligand binding sites for protoporphyrin, for the high-affinity ligand PK 11195, and for cholesterol in TSPO monomers and/or oligomers, and we discuss possible functional implications. Copyright © 2014 Elsevier B.V. All rights reserved.

Investigation of porous asphalt microstructure using optical and electron microscopy.

PubMed

Poulikakos, L D; Partl, M N

2010-11-01

Direct observations of porous asphalt concrete samples in their natural state using optical and electron microscopy techniques led to useful information regarding the microstructure of two mixes and indicated a relationship between microstructure and in situ performance. This paper presents evidence that suboptimal microstructure can lead to premature failure thus making a first step in defining well or suboptimal performing pavements with a bottom-up approach (microstructure). Laboratory and field compaction produce different samples in terms of the microstructure. Laboratory compaction using the gyratory method has produced more microcracks in mineral aggregates after the binder had cooled. Well-performing mixes used polymer-modified binders, had a more homogeneous void structure with fewer elongated voids and better interlocking of the aggregates. Furthermore, well-performing mixes showed better distribution of the mastic and better coverage of the aggregates with bitumen. Low vacuum scanning electron microscopy showed that styrene butadiene styrene polymer modification in binder exists in the form of discontinuous globules and not continuous networks. A reduction in the polymer phase was observed as a result of aging and in-service use. © 2010 The Authors Journal compilation © 2010 The Royal Microscopical Society.

Development of bacterial biofilms in dairy processing lines.

PubMed

Austin, J W; Bergeron, G

1995-08-01

Adherence of bacteria to various milk contact sites was examined by scanning electron microscopy and transmission electron microscopy. New gaskets, endcaps, vacuum breaker plugs and pipeline inserts were installed in different areas in lines carrying either raw or pasteurized milk, and a routine schedule of cleaning-in-place and sanitizing was followed. Removed cleaned and sanitized gaskets were processed for scanning or transmission electron microscopy. Adherent bacteria were observed on the sides of gaskets removed from both pasteurized and raw milk lines. Some areas of Buna-n gaskets were colonized with a confluent layer of bacterial cells surrounded by an extensive amorphous matrix, while other areas of Buna-n gaskets showed a diffuse adherence over large areas of the surface. Most of the bacteria attached to polytetrafluoroethylene (PTFE or Teflon) gaskets were found in crevices created by insertion of the gasket into the pipeline. Examination of stainless steel endcaps, pipeline inserts, and PTFE vacuum breaker plugs did not reveal the presence of adherent bacteria. The results of this study indicate that biofilms developed on the sides of gaskets in spite of cleaning-in-place procedures. These biofilms may be a source of post-pasteurization contamination.

Green biosynthesis of silver nanoparticles using Curcuma longa tuber powder

PubMed Central

Shameli, Kamyar; Ahmad, Mansor Bin; Zamanian, Ali; Sangpour, Parvanh; Shabanzadeh, Parvaneh; Abdollahi, Yadollah; Zargar, Mohsen

2012-01-01

Green synthesis of noble metal nanoparticles is a vastly developing area of research. Metallic nanoparticles have received great attention from chemists, physicists, biologists, and engineers who wish to use them for the development of a new-generation of nanodevices. In this study, silver nanoparticles were biosynthesized from aqueous silver nitrate through a simple and eco-friendly route using Curcuma longa tuber-powder extracts, which acted as a reductant and stabilizer simultaneously. Characterizations of nanoparticles were done using different methods, which included ultraviolet-visible spectroscopy, powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray fluorescence spectrometry, and Fourier-transform infrared spectroscopy. The ultraviolet-visible spectrum of the aqueous medium containing silver nanoparticles showed an absorption peak at around 415 nm. Transmission electron microscopy showed that mean diameter and standard deviation for the formation of silver nanoparticles was 6.30 ± 2.64 nm. Powder X-ray diffraction showed that the particles are crystalline in nature, with a face-centered cubic structure. The most needed outcome of this work will be the development of value-added products from C. longa for biomedical and nanotechnology-based industries. PMID:23341739

Microchemical Analysis Of Space Operation Debris

NASA Technical Reports Server (NTRS)

Cummings, Virginia J.; Kim, Hae Soo

1995-01-01

Report discusses techniques used in analyzing debris relative to space shuttle operations. Debris collected from space shuttle, expendable launch vehicles, payloads carried by space shuttle, and payloads carried by expendable launch vehicles. Optical microscopy, scanning electron microscopy with energy-dispersive spectrometry, analytical electron microscopy with wavelength-dispersive spectrometry, and X-ray diffraction chosen as techniques used in examining samples of debris.

Nanotechnology: toxicologic pathology.

PubMed

Hubbs, Ann F; Sargent, Linda M; Porter, Dale W; Sager, Tina M; Chen, Bean T; Frazer, David G; Castranova, Vincent; Sriram, Krishnan; Nurkiewicz, Timothy R; Reynolds, Steven H; Battelli, Lori A; Schwegler-Berry, Diane; McKinney, Walter; Fluharty, Kara L; Mercer, Robert R

2013-02-01

Nanotechnology involves technology, science, and engineering in dimensions less than 100 nm. A virtually infinite number of potential nanoscale products can be produced from many different molecules and their combinations. The exponentially increasing number of nanoscale products will solve critical needs in engineering, science, and medicine. However, the virtually infinite number of potential nanotechnology products is a challenge for toxicologic pathologists. Because of their size, nanoparticulates can have therapeutic and toxic effects distinct from micron-sized particulates of the same composition. In the nanoscale, distinct intercellular and intracellular translocation pathways may provide a different distribution than that obtained by micron-sized particulates. Nanoparticulates interact with subcellular structures including microtubules, actin filaments, centrosomes, and chromatin; interactions that may be facilitated in the nanoscale. Features that distinguish nanoparticulates from fine particulates include increased surface area per unit mass and quantum effects. In addition, some nanotechnology products, including the fullerenes, have a novel and reactive surface. Augmented microscopic procedures including enhanced dark-field imaging, immunofluorescence, field-emission scanning electron microscopy, transmission electron microscopy, and confocal microscopy are useful when evaluating nanoparticulate toxicologic pathology. Thus, the pathology assessment is facilitated by understanding the unique features at the nanoscale and the tools that can assist in evaluating nanotoxicology studies.

Nanotechnology: Toxicologic Pathology

PubMed Central

Hubbs, Ann F.; Sargent, Linda M.; Porter, Dale W.; Sager, Tina M.; Chen, Bean T.; Frazer, David G.; Castranova, Vincent; Sriram, Krishnan; Nurkiewicz, Timothy R.; Reynolds, Steven H.; Battelli, Lori A.; Schwegler-Berry, Diane; McKinney, Walter; Fluharty, Kara L.; Mercer, Robert R.

2015-01-01

Nanotechnology involves technology, science, and engineering in dimensions less than 100 nm. A virtually infinite number of potential nanoscale products can be produced from many different molecules and their combinations. The exponentially increasing number of nanoscale products will solve critical needs in engineering, science, and medicine. However, the virtually infinite number of potential nanotechnology products is a challenge for toxicologic pathologists. Because of their size, nanoparticulates can have therapeutic and toxic effects distinct from micron-sized particulates of the same composition. In the nanoscale, distinct intercellular and intracellular translocation pathways may provide a different distribution than that obtained by micron-sized particulates. Nanoparticulates interact with subcellular structures including microtubules, actin filaments, centrosomes, and chromatin; interactions that may be facilitated in the nanoscale. Features that distinguish nanoparticulates from fine particulates include increased surface area per unit mass and quantum effects. In addition, some nanotechnology products, including the fullerenes, have a novel and reactive surface. Augmented microscopic procedures including enhanced dark-field imaging, immunofluorescence, field-emission scanning electron microscopy, transmission electron microscopy, and confocal microscopy are useful when evaluating nanoparticulate toxicologic pathology. Thus, the pathology assessment is facilitated by understanding the unique features at the nanoscale and the tools that can assist in evaluating nanotoxicology studies. PMID:23389777

Microstructural observation of fuel cell catalyst inks by Cryo-SEM and Cryo-TEM.

PubMed

Shimanuki, Junichi; Takahashi, Shinichi; Tohma, Hajime; Ohma, Atsushi; Ishihara, Ayumi; Ito, Yoshiko; Nishino, Yuri; Miyazawa, Atsuo

2017-06-01

In order to improve the electricity generation performance of fuel cell electric vehicles, it is necessary to optimize the microstructure of the catalyst layer of a polymer electrolyte fuel cell. The catalyst layer is formed by a wet coating process using catalyst inks. Therefore, it is very important to observe the microstructure of the catalyst ink. In this study, the morphology of carbon-supported platinum (Pt/C) particles in catalyst inks with a different solvent composition was investigated by cryogenic scanning electron microscopy (cryo-SEM). In addition, the morphology of the ionomer, which presumably influences the formation of agglomerated Pt/C particles in a catalyst ink, was investigated by cryogenic transmission electron microscopy (cryo-TEM). The results of a cryo-SEM observation revealed that the agglomerated Pt/C particles tended to become coarser with a higher 1-propanol (NPA) weight fraction. The results of a cryo-TEM observation indicated that the actual ionomer dispersion in a catalyst ink formed a network structure different from that of the ionomer in the solvent. © The Author 2017. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Nano-Crystalline Diamond Films with Pineapple-Like Morphology Grown by the DC Arcjet vapor Deposition Method

NASA Astrophysics Data System (ADS)

Li, Bin; Zhang, Qin-Jian; Shi, Yan-Chao; Li, Jia-Jun; Li, Hong; Lu, Fan-Xiu; Chen, Guang-Chao

2014-08-01

A nano-crystlline diamond film is grown by the dc arcjet chemical vapor deposition method. The film is characterized by scanning electron microscopy, high-resolution transmission electron microscopy (HRTEM), x-ray diffraction (XRD) and Raman spectra, respectively. The nanocrystalline grains are averagely with 80 nm in the size measured by XRD, and further proven by Raman and HRTEM. The observed novel morphology of the growth surface, pineapple-like morphology, is constructed by cubo-octahedral growth zones with a smooth faceted top surface and coarse side surfaces. The as-grown film possesses (100) dominant surface containing a little amorphous sp2 component, which is far different from the nano-crystalline film with the usual cauliflower-like morphology.

Efficiency enhancement in dye sensitized solar cells using dual function mesoporous silica as scatterer and back recombination inhibitor

NASA Astrophysics Data System (ADS)

Tanvi; Mahajan, Aman; Bedi, R. K.; Kumar, Subodh; Saxena, Vibha; Aswal, D. K.

2016-08-01

In the present work, we report the usage of mesoporous silica for improving light harvesting as well as for suppression of back recombination without affecting the extent of dye loading on TiO2 films. Synthesized mesoporous SiO2 was characterized by X-ray photoelectron spectroscopy, X-ray diffraction, Brunauer Emmett and Teller measurement, Scanning electron microscopy and Transmission electron microscopy. DSSCs were fabricated by incorporating different wt% of mesoporous SiO2 in TiO2 paste. An improvement of 50% was observed for devices fabricated using 0.75 wt% of mesoporous SiO2. The mechanism behind the improvement was investigated using electrochemical impedance spectroscopy and UV-Vis spectroscopy.

Examination of biogenic selenium-containing nanosystems based on polyelectrolyte complexes by atomic force, Kelvin probe force and electron microscopy methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sukhanova, T. E., E-mail: tat-sukhanova@mail.ru; Vylegzhanina, M. E.; Valueva, S. V.

The morphology and electrical properties of biogenic selenium-containing nanosystems based on polyelectrolyte complexes (PECs) were examined using AFM, Kelvin Probe Force and electron microscopy methods. It has been found, that prepared nanostructures significantly differed in their morphological types and parameters. In particular, multilayers capsules can be produced via varying synthesis conditions, especially, the selenium–PEC mass ratio ν. At the “special point” (ν = 0.1), filled and hollow nano- and microcapsules are formed in the system. The multilayer character of the capsules walls is visible in the phase images. Kelvin Probe Force images showed the inhomogeneity of potential distribution in capsulesmore » and outside them.« less

Viral Infection at High Magnification: 3D Electron Microscopy Methods to Analyze the Architecture of Infected Cells

PubMed Central

Romero-Brey, Inés; Bartenschlager, Ralf

2015-01-01

As obligate intracellular parasites, viruses need to hijack their cellular hosts and reprogram their machineries in order to replicate their genomes and produce new virions. For the direct visualization of the different steps of a viral life cycle (attachment, entry, replication, assembly and egress) electron microscopy (EM) methods are extremely helpful. While conventional EM has given important information about virus-host cell interactions, the development of three-dimensional EM (3D-EM) approaches provides unprecedented insights into how viruses remodel the intracellular architecture of the host cell. During the last years several 3D-EM methods have been developed. Here we will provide a description of the main approaches and examples of innovative applications. PMID:26633469

RBS Depth Profiling Analysis of (Ti, Al)N/MoN and CrN/MoN Multilayers.

PubMed

Han, Bin; Wang, Zesong; Devi, Neena; Kondamareddy, K K; Wang, Zhenguo; Li, Na; Zuo, Wenbin; Fu, Dejun; Liu, Chuansheng

2017-12-01

(Ti, Al)N/MoN and CrN/MoN multilayered films were synthesized on Si (100) surface by multi-cathodic arc ion plating system with various bilayer periods. The elemental composition and depth profiling of the films were investigated by Rutherford backscattering spectroscopy (RBS) using 2.42 and 1.52 MeV Li 2+ ion beams and different incident angles (0°, 15°, 37°, and 53°). The microstructures of (Ti, Al)N/MoN multilayered films were evaluated by X-ray diffraction. The multilayer periods and thickness of the multilayered films were characterized by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) and then compared with RBS results.

Preparation of silver nanoparticles loaded graphene oxide nanosheets for antibacterial activity

NASA Astrophysics Data System (ADS)

T, T. T., Vi; Lue, S. J.

2016-11-01

A simple, facile method to fabricate successfully silver nanoparticle (AgNPs) decorated on graphene oxide (GO) layers via grafted thiol groups. Samples were prepared with different concentrations of AgNO3. Resulting AgNPs were quasi-spherical in shape and attached on the layers of GO. Physical properties were confirmed by X-ray diffraction (XRD), zeta potential, dynamic light scattering (DLS), Fourier transform infrared (FTIR) spectra, thermogravimetric analyzer (TGA), transmission electron microscopy (TEM) and field emission scanning electron microscopy (FE-SEM). Antimicrobial test was effectively showed using MRSA (Staphylococcus areus). The GO-Ag NPs with appropriate Ag NPs content of 0.2 M AgNO3 exhibited the strongest antibacterial activity at 48.77% inhibition after 4 hours incubation.

Structure of initial crystals formed during human amelogenesis

NASA Astrophysics Data System (ADS)

Cuisinier, F. J. G.; Voegel, J. C.; Yacaman, J.; Frank, R. M.

1992-02-01

X-ray diffraction analysis revealed only the existence of carbonated hydroxyapatite (c.HA) during amelogenesis, whereas conventional transmission electron microscopy investigations showed that developing enamel crystals have a ribbon-like habit. The described compositional changes could be an indication for the presence of minerals different from c.HA. However, the absence of identification of such a mineral shows the need of studies by high resolution electron microscopy (HREM) of initial formed human enamel crystals. We demonstrate the existence of two crystal families involved in the early stages of biomineralization: (a) nanometer-size particles which appeared as a precursor phase; (b) ribbon-like crystals, with a structure closely related to c.HA, which by a progressive thickening process tend to attain the mature enamel crystal habit.

Formation of Nanodimensional 3C-SiC Structures from Rice Husks

NASA Astrophysics Data System (ADS)

Gorzkowski, E. P.; Qadri, S. B.; Rath, B. B.; Goswami, R.; Caldwell, J. D.

2013-05-01

We have demonstrated that large quantities of β-SiC nanostructures can be obtained from rice husk agricultural waste by using controlled conditions in a thermogravimetric setup. This simple and inexpensive method of producing these structures on a large scale is critical for applications in nanoelectronics, nanosensors, and biotechnology. The temperature and atmosphere are two critical elements in forming either α-cristobalite (SiO2) or β-SiC. Using different characterization methods (x-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy), we have shown that pyrolysis of rice husks in argon atmosphere at 1375°C results in simultaneous formation of carbon nanotubes, β-SiC nanowires/nanorods, and β-SiC powder.

Blue light emitting diesel soot for photonic applications

NASA Astrophysics Data System (ADS)

Swapna, M. S.; Sankararaman, S.

2018-01-01

The present work is the first report of producing blue light emission from phosphor free and low-cost material—the diesel soot from the internal combustion engines (ICEs). The structural morphology is analyzed by field emission scanning electron microscopy and high-resolution transmission electron microscopy. The optical characterization is done by recording UV-visible spectrum and photoluminescent Spectrum. The CIE plot and the power spectrum for the sample show blue emission. This is further verified by collecting diesel soot from the ICE of different year of make. A visual confirmation of blue emission is obtained by exciting the sample with UV laser. The presence of various allotropic forms of carbon in the sample is identified by x-ray diffraction, Fourier transform infrared and Raman spectroscopic analysis.

Viral Infection at High Magnification: 3D Electron Microscopy Methods to Analyze the Architecture of Infected Cells.

PubMed

Romero-Brey, Inés; Bartenschlager, Ralf

2015-12-03

As obligate intracellular parasites, viruses need to hijack their cellular hosts and reprogram their machineries in order to replicate their genomes and produce new virions. For the direct visualization of the different steps of a viral life cycle (attachment, entry, replication, assembly and egress) electron microscopy (EM) methods are extremely helpful. While conventional EM has given important information about virus-host cell interactions, the development of three-dimensional EM (3D-EM) approaches provides unprecedented insights into how viruses remodel the intracellular architecture of the host cell. During the last years several 3D-EM methods have been developed. Here we will provide a description of the main approaches and examples of innovative applications.

Determination of the coalescence temperature of latexes by environmental scanning electron microscopy.

PubMed

Gonzalez, Edurne; Tollan, Christopher; Chuvilin, Andrey; Barandiaran, Maria J; Paulis, Maria

2012-08-01

A new methodology for quantitative characterization of the coalescence process of waterborne polymer dispersion (latex) particles by environmental scanning electron microscopy (ESEM) is proposed. The experimental setup has been developed to provide reproducible latex monolayer depositions, optimized contrast of the latex particles, and a reliable readout of the sample temperature. Quantification of the coalescence process under dry conditions has been performed by image processing based on evaluation of the image autocorrelation function. As a proof of concept the coalescence of two latexes with known and differing glass transition temperatures has been measured. It has been shown that a reproducibility of better than 1.5 °C can be obtained for the measurement of the coalescence temperature.

Cyclic Degradation Behavior of < 001 > -Oriented Fe-Mn-Al-Ni Single Crystals in Tension

NASA Astrophysics Data System (ADS)

Vollmer, M.; Kriegel, M. J.; Krooß, P.; Martin, S.; Klemm, V.; Weidner, A.; Chumlyakov, Y.; Biermann, H.; Rafaja, D.; Niendorf, T.

2017-12-01

In the present study, functional fatigue behavior of a near 〈001〉-oriented Fe-Mn-Al-Ni single crystal was investigated under tensile load. An incremental strain test up to 3.5% strain and cyclic tests up to 25 cycles revealed rapid pseudoelastic degradation. Progressive microstructural degradation was studied by in situ scanning electron microscopy. The results show a partially inhibited reactivation of previously formed martensite and proceeding activation of untransformed areas in subsequent cycles. The preferentially formed martensite variants were identified by means of Schmid factor calculation and the Kurdjumov-Sachs relationship. Post mortem transmission electron microscopy investigations shed light on the prevailing degradation mechanisms. Different types of dislocations were found promoting the progressive degradation during cyclic loading.

Cathodoluminescence study of one-dimensional free-standing widegap-semiconductor nanostructures: GaN nanotubes, Si3N4 nanobelts and ZnS/Si nanowires.

PubMed

Sekiguchi, Takashi; Hu, Junqing; Bando, Yoshio

2004-01-01

Luminescence properties of one-dimensional free-standing widegap-semiconductor nanostructures were characterized by means of cathodoluminescence (CL). GaN nanopipes, alpha-Si3N4 nanobelts and ZnS/Si nanowires were fabricated by a catalyst-free method, namely grown in an induction furnace from powders. After the observation of morphology by scanning electron microscopy as well as the confirmation of their crystal structures by transmission electron microscopy, their CL spectra and images were observed. The CL spectra mapping as well as the monochromatic CL imaging revealed the variation of the luminescence spectra of different nanowires as well as that along a single wire. These results revealed the optical features of nanostructures.

Synthesis of gold nanoflowers using deep eutectic solvent with high surface enhanced Raman scattering properties

NASA Astrophysics Data System (ADS)

Aghakhani Mahyari, Farzaneh; Tohidi, Maryam; Safavi, Afsaneh

2016-09-01

A facile, seed-less and one-pot method was developed for synthesis of gold nanoflowers with multiple tips through reduction of HAuCl4 with deep eutectic solvent at room temperature. This solvent is eco-friendly, low-cost, non-toxic and biodegradable and can act as both reducing and shape-controlling agent. In this protocol, highly branched and stable gold nanoflowers were obtained without using any capping agent. The obtained products were characterized by different techniques including, field emission scanning electron microscopy, transmission electron microscopy, x-ray diffraction and UV-vis spectroscopy. The as-prepared gold nanoflowers exhibit efficient surface-enhanced Raman scattering (SERS) properties which can be used as excellent substrates for SERS.

Publications - GMC 357 | Alaska Division of Geological & Geophysical

Science.gov Websites

DGGS GMC 357 Publication Details Title: Thin Section and Scanning Electron Microscopy summary Laboratories, Inc., 2008, Thin Section and Scanning Electron Microscopy summary photographs from plugs taken

Investigation of viability of plant tissue in the environmental scanning electron microscopy.

PubMed

Zheng, Tao; Waldron, K W; Donald, Athene M

2009-11-01

The advantages of environmental scanning electron microscopy (ESEM) make it a suitable technique for studying plant tissue in its native state. There have been few studies on the effects of ESEM environment and beam damage on the viability of plant tissue. A simple plant tissue, Allium cepa (onion) upper epidermal tissue was taken as the model for study. The change of moisture content of samples was studied at different relative humidities. Working with the electron beam on, viability tests were conducted for samples after exposure in the ESEM under different operating conditions to investigate the effect of electron beam dose on the viability of samples. The results suggested that without the electron beam, the ESEM chamber itself can prevent the loss of initial moisture if its relative humidity is maintained above 90%. With the electron beam on, the viability of Allium cepa (onion) cells depends both on the beam accelerating voltage and the electron dose/unit area hitting the sample. The dose can be controlled by several of the ESEM instrumental parameters. The detailed process of beam damage on cuticle-down and cuticle-up samples was investigated and compared. The results indicate that cuticular adhesion to the cell wall is relatively weak, but highly resistant to electron beam damage. Systematic study on the effect of ESEM operation parameters has been done. Results qualitatively support the intuitive expectations, but demonstrate quantitatively that Allium cepa epidermal cells are able to be kept in a hydrated and viable state under relevant operation condition inside ESEM, providing a basis for further in situ experiments on plant tissues.

Attomicroscopy: from femtosecond to attosecond electron microscopy

NASA Astrophysics Data System (ADS)

Hassan, Mohammed Th

2018-02-01

In the last decade, the development of ultrafast electron diffraction (UED) and microscopy (UEM) have enabled the imaging of atomic motion in real time and space. These pivotal table-top tools opened the door for a vast range of applications in different areas of science spanning chemistry, physics, materials science, and biology. We first discuss the basic principles and recent advancements, including some of the important applications, of both UED and UEM. Then, we discuss the recent advances in the field that have enhanced the spatial and temporal resolutions, where the latter, is however, still limited to a few hundreds of femtoseconds, preventing the imaging of ultrafast dynamics of matter lasting few tens of femtoseconds. Then, we present our new optical gating approach for generating an isolated 30 fs electron pulse with sufficient intensity to attain a temporal resolution on the same time scale. This achievement allows, for the first time, imaging the electron dynamics of matter. Finally, we demonstrate the feasibility of the optical gating approach to generate an isolated attosecond electron pulse, utilizing our recently demonstrated optical attosecond laser pulse, which paves the way for establishing the field of ‘Attomicroscopy’, ultimately enabling us to image the electron motion in action.

Structural analysis of vimentin and keratin intermediate filaments by cryo-electron tomography.

PubMed

Norlén, Lars; Masich, Sergej; Goldie, Kenneth N; Hoenger, Andreas

2007-06-10

Intermediate filaments are a large and structurally diverse group of cellular filaments that are classified into five different groups. They are referred to as intermediate filaments (IFs) because they are intermediate in diameter between the two other cytoskeletal filament systems that is filamentous actin and microtubules. The basic building block of IFs is a predominantly alpha-helical rod with variable length globular N- and C-terminal domains. On the ultra-structural level there are two major differences between IFs and microtubules or actin filaments: IFs are non-polar, and they do not exhibit large globular domains. IF molecules associate via a coiled-coil interaction into dimers and higher oligomers. Structural investigations into the molecular building plan of IFs have been performed with a variety of biophysical and imaging methods such as negative staining and metal-shadowing electron microscopy (EM), mass determination by scanning transmission EM, X-ray crystallography on fragments of the IF stalk and low-angle X-ray scattering. The actual packing of IF dimers into a long filament varies between the different families. Typically the dimers form so called protofibrils that further assemble into a filament. Here we introduce new cryo-imaging methods for structural investigations of IFs in vitro and in vivo, i.e., cryo-electron microscopy and cryo-electron tomography, as well as associated techniques such as the preparation and handling of vitrified sections of cellular specimens.

Electron microscopy of electromagnetic waveforms.

PubMed

Ryabov, A; Baum, P

2016-07-22

Rapidly changing electromagnetic fields are the basis of almost any photonic or electronic device operation. We report how electron microscopy can measure collective carrier motion and fields with subcycle and subwavelength resolution. A collimated beam of femtosecond electron pulses passes through a metamaterial resonator that is previously excited with a single-cycle electromagnetic pulse. If the probing electrons are shorter in duration than half a field cycle, then time-frozen Lorentz forces distort the images quasi-classically and with subcycle time resolution. A pump-probe sequence reveals in a movie the sample's oscillating electromagnetic field vectors with time, phase, amplitude, and polarization information. This waveform electron microscopy can be used to visualize electrodynamic phenomena in devices as small and fast as available. Copyright © 2016, American Association for the Advancement of Science.

Murphy's law-if anything can go wrong, it will: Problems in phage electron microscopy.

PubMed

Ackermann, Hans-W; Tiekotter, Kenneth L

2012-04-01

The quality of bacteriophage electron microscopy appears to be on a downward course since the 1980s. This coincides with the introduction of digital electron microscopes and a general lowering of standards, possibly due to the disappearance of several world-class electron microscopists The most important problem seems to be poor contrast. Positive staining is frequently not recognized as an undesirable artifact. Phage parts, bacterial debris, and aberrant or damaged phage particles may be misdiagnosed as bacterial viruses. Digital electron microscopes often seem to be operated without magnification control because this is difficult and inconvenient. In summary, most phage electron microscopy problems may be attributed to human failure. Journals are a last-ditch defense and have a heavy responsibility in selecting competent reviewers and rejecting, or not, unsatisfactory articles.

Electron tomography and cryo-SEM characterization reveals novel ultrastructural features of host-parasite interaction during Chlamydia abortus infection.

PubMed

Wilkat, M; Herdoiza, E; Forsbach-Birk, V; Walther, P; Essig, A

2014-08-01

Chlamydia (C.) abortus is a widely spread pathogen among ruminants that can be transmitted to women during pregnancy leading to severe systemic infection with consecutive abortion. As a member of the Chlamydiaceae, C. abortus shares the characteristic feature of an obligate intracellular biphasic developmental cycle with two morphological forms including elementary bodies (EBs) and reticulate bodies (RBs). In contrast to other chlamydial species, C. abortus ultrastructure has not been investigated yet. To do so, samples were fixed by high-pressure freezing and processed by different electron microscopic methods. Freeze-substituted samples were analysed by transmission electron microscopy, scanning transmission electron microscopical tomography and immuno-electron microscopy, and freeze-fractured samples were analysed by cryo-scanning electron microscopy. Here, we present three ultrastructural features of C. abortus that have not been reported up to now. Firstly, the morphological evidence that C. abortus is equipped with the type three secretion system. Secondly, the accumulation and even coating of whole inclusion bodies by membrane complexes consisting of multiple closely adjacent membranes which seems to be a C. abortus specific feature. Thirdly, the formation of small vesicles in the periplasmic space of RBs in the second half of the developmental cycle. Concerning the time point of their formation and the fact that they harbour chlamydial components, these vesicles might be morphological correlates of an intermediate step during the process of redifferentiation of RBs into EBs. As this feature has also been shown for C. trachomatis and C. pneumoniae, it might be a common characteristic of the family of Chlamydiaceae.

A scanning electron microscopic study of 34 cases of acute granulocytic, myelomonocytic, monoblastic and histiocytic leukemia.

PubMed

Polliack, A; McKenzie, S; Gee, T; Lampen, N; de Harven, E; Clarkson, B D

1975-09-01

This report describes the surface architecture of leukemic cells, as seen by scanning electron microscopy in 34 patients with acute nonlymphoblastic leukemia. Six patients with myeloblastic, 4 with promyelocytic, 10 with myelomonocytic, 8 with monocytic, 4 with histiocytic and 2 with undifferentiated leukemia were studied. Under the scanning electron microscope most leukemia histiocytes and monocytes appeared similar and were characterized by the presence of large, well developed broad-based ruffled membranes or prominent raised ridge-like profiles, resembling ithis respect normal monocytes. Most cells from patients with acute promyelocytic or myeloblastic leukemia exhibited narrower ridge-like profiles whereas some showed ruffles or microvilli. Patients with myelomonocytic leukemia showed mixed populations of cells with ridge-like profiles and ruffled membranes whereas cells from two patients with undifferentiated leukemia had smooth surfaces, similar to those encountered in cells from patients with acute lymphoblastic leukemia. It appears that nonlymphoblastic and lymphoblastic leukemia cells (particularly histiocytes and monocytes) can frequently be distinquished on the basis of their surface architecture. The surface features of leukemic histiocytes and monocytes are similar, suggesting that they may belong to the same cell series. The monocytes seem to have characteristic surface features recognizable with the scanning electron microscope and differ from most cells from patients with acute granulocytic leukemia. Although overlap of surface features and misidentification can occur, scanning electron microscopy is a useful adjunct to other modes of microscopy in the study and diagnosis of acute leukemia.

Electron beam induced green luminescence and degradation study of CaS:Ce nanocrystalline phosphors for FED applications

NASA Astrophysics Data System (ADS)

Kumar, Vinay; Mishra, Varun; Biggs, M. M.; Nagpure, I. M.; Ntwaeaborwa, O. M.; Terblans, J. J.; Swart, H. C.

2010-01-01

Green luminescence and degradation of Ce 3+ doped CaS nanocrystalline phosphors were studied with a 2 keV, 10 μA electron beam in an O 2 environment. The nanophosphors were synthesized by the co-precipitation method. The samples were characterized using X-ray diffraction, Transmission electron microscopy, Scanning electron microscopy/electron dispersive X-ray spectroscopy and Photoluminescence (PL) spectroscopy. Cubic CaS with an average particle size of 42 ± 2 nm was obtained. PL emission was observed at 507 nm and a shoulder at 560 nm with an excitation wavelength of 460 nm. Auger electron spectroscopy and Cathodoluminescence (CL) were used to monitor the changes in the surface composition of the CaS:Ce 3+ nanocrystalline phosphors during electron bombardment in an O 2 environment. The effect of different oxygen pressures ranging from 1 × 10 -8 to 1 × 10 -6 Torr on the CL intensity was also investigated. A CaSO 4 layer was observed on the surface after the electron beam degradation. The CL intensity was found to decrease up to 30% of its original intensity at 1 × 10 -6 Torr oxygen pressure after an electron dose of 50 C/cm 2. The formation of oxygen defects during electron bombardment may also be responsible for the decrease in CL intensity.

Applications of emerging transmission electron microscopy technology in PCD research and diagnosis.

PubMed

Shoemark, Amelia

2017-01-01

Primary Ciliary Dyskinesia (PCD) is a heterogeneous genetic condition characterized by dysfunction of motile cilia. Patients suffer from chronic infection and inflammation of the upper and lower respiratory tract. Diagnosis of PCD is confirmed by identification of a hallmark defect of ciliary ultrastructure or by identification of biallelic pathogenic mutations in a known PCD gene. Since the first description of PCD in 1976, assessment of ciliary ultrastructure by transmission electron microscopy (TEM) has been central to diagnosis and research. Electron tomography is a technique whereby a series of transmission electron micrographs are collected at different angles and reconstructed into a single 3D model of a specimen. Electron tomography provides improved spatial information and resolution compared to a single micrograph. Research by electron tomography has revealed new insight into ciliary ultrastructure and consequently ciliary function at a molecular and cellular level. Gene discovery studies in PCD have utilized electron tomography to define the structural consequences of variants in cilia genes. Modern transmission electron microscopes capable of electron tomography are increasingly being installed in clinical laboratories. This presents the possibility for the use of tomography technique in a diagnostic setting. This review describes the electron tomography technique, the contribution tomography has made to the understanding of basic cilia structure and function and finally the potential of the technique for use in PCD diagnosis.

75 FR 34096 - Application(s) for Duty-Free Entry of Scientific Instruments

Federal Register 2010, 2011, 2012, 2013, 2014

2010-06-16

... dynamin, using negative stain nad cryo-electron microscopy methods. Justification for Duty-Free Entry..., using negative stain nad cryo-electron microscopy methods. Justification for Duty-Free Entry: There are...

The Electron Microscopy Outreach Program: A Web-based resource for research and education.

PubMed

Sosinsky, G E; Baker, T S; Hand, G; Ellisman, M H

1999-01-01

We have developed a centralized World Wide Web (WWW)-based environment that serves as a resource of software tools and expertise for biological electron microscopy. A major focus is molecular electron microscopy, but the site also includes information and links on structural biology at all levels of resolution. This site serves to help integrate or link structural biology techniques in accordance with user needs. The WWW site, called the Electron Microscopy (EM) Outreach Program (URL: http://emoutreach.sdsc.edu), provides scientists with computational and educational tools for their research and edification. In particular, we have set up a centralized resource containing course notes, references, and links to image analysis and three-dimensional reconstruction software for investigators wanting to learn about EM techniques either within or outside of their fields of expertise. Copyright 1999 Academic Press.

A compilation of cold cases using scanning electron microscopy at the University of Rhode Island

NASA Astrophysics Data System (ADS)

Platek, Michael J.; Gregory, Otto J.

2015-10-01

Scanning electron microscopy combined with microchemical analysis has evolved into one of the most widely used instruments in forensic science today. In particular, the environmental scanning electron microscope (SEM) in conjunction with energy dispersive spectroscopy (EDS), has created unique opportunities in forensic science in regard to the examination of trace evidence; i.e. the examination of evidence without altering the evidence with conductive coatings, thereby enabling criminalists to solve cases that were previously considered unsolvable. Two cold cases were solved at URI using a JEOL 5900 LV SEM in conjunction with EDS. A cold case murder and a cold missing person case will be presented from the viewpoint of the microscopist and will include sample preparation, as well as image and chemical analysis of the trace evidence using electron microscopy and optical microscopy.

The EIGER detector for low-energy electron microscopy and photoemission electron microscopy.

PubMed

Tinti, G; Marchetto, H; Vaz, C A F; Kleibert, A; Andrä, M; Barten, R; Bergamaschi, A; Brückner, M; Cartier, S; Dinapoli, R; Franz, T; Fröjdh, E; Greiffenberg, D; Lopez-Cuenca, C; Mezza, D; Mozzanica, A; Nolting, F; Ramilli, M; Redford, S; Ruat, M; Ruder, Ch; Schädler, L; Schmidt, Th; Schmitt, B; Schütz, F; Shi, X; Thattil, D; Vetter, S; Zhang, J

2017-09-01

EIGER is a single-photon-counting hybrid pixel detector developed at the Paul Scherrer Institut, Switzerland. It is designed for applications at synchrotron light sources with photon energies above 5 keV. Features of EIGER include a small pixel size (75 µm × 75 µm), a high frame rate (up to 23 kHz), a small dead-time between frames (down to 3 µs) and a dynamic range up to 32-bit. In this article, the use of EIGER as a detector for electrons in low-energy electron microscopy (LEEM) and photoemission electron microscopy (PEEM) is reported. It is demonstrated that, with only a minimal modification to the sensitive part of the detector, EIGER is able to detect electrons emitted or reflected by the sample and accelerated to 8-20 keV. The imaging capabilities are shown to be superior to the standard microchannel plate detector for these types of applications. This is due to the much higher signal-to-noise ratio, better homogeneity and improved dynamic range. In addition, the operation of the EIGER detector is not affected by radiation damage from electrons in the present energy range and guarantees more stable performance over time. To benchmark the detector capabilities, LEEM experiments are performed on selected surfaces and the magnetic and electronic properties of individual iron nanoparticles with sizes ranging from 8 to 22 nm are detected using the PEEM endstation at the Surface/Interface Microscopy (SIM) beamline of the Swiss Light Source.

Atmospheric scanning electron microscope observes cells and tissues in open medium through silicon nitride film.

PubMed

Nishiyama, Hidetoshi; Suga, Mitsuo; Ogura, Toshihiko; Maruyama, Yuusuke; Koizumi, Mitsuru; Mio, Kazuhiro; Kitamura, Shinichi; Sato, Chikara

2010-03-01

Direct observation of subcellular structures and their characterization is essential for understanding their physiological functions. To observe them in open environment, we have developed an inverted scanning electron microscope with a detachable, open-culture dish, capable of 8 nm resolution, and combined with a fluorescence microscope quasi-simultaneously observing the same area from the top. For scanning electron microscopy from the bottom, a silicon nitride film window in the base of the dish maintains a vacuum between electron gun and open sample dish while allowing electrons to pass through. Electrons are backscattered from the sample and captured by a detector under the dish. Cells cultured on the open dish can be externally manipulated under optical microscopy, fixed, and observed using scanning electron microscopy. Once fine structures have been revealed by scanning electron microscopy, their component proteins may be identified by comparison with separately prepared fluorescence-labeled optical microscopic images of the candidate proteins, with their heavy-metal-labeled or stained ASEM images. Furthermore, cell nuclei in a tissue block stained with platinum-blue were successfully observed without thin-sectioning, which suggests the applicability of this inverted scanning electron microscope to cancer diagnosis. This microscope visualizes mesoscopic-scale structures, and is also applicable to non-bioscience fields including polymer chemistry. (c) 2010 Elsevier Inc. All rights reserved.

Influence of Substrate Bonding and Surface Morphology on Dynamic Organic Layer Growth: Perylenetetracarboxylic Dianhydride on Au(111).

PubMed

Schmidt, Thomas; Marchetto, Helder; Groh, Ullrich; Fink, Rainer H; Freund, Hans-Joachim; Umbach, Eberhard

2018-05-15

We investigated the dynamics of the initial growth of the first epitaxial layers of perylenetetracarboxylic dianhydride (PTCDA) on the Au(111) surface with high lateral resolution using the aberration-corrected spectro-microscope SMART. With this instrument, we could simultaneously study the different adsorption behaviors and layer growth on various surface areas consisting of either a distribution of flat (111) terraces, separated by single atomic steps ("ideal surface"), or on areas with a high density of step bunches and defects ("realistic surface"). The combined use of photoemission electron microscopy, low-energy electron microscopy, and μ-spot X-ray absorption provided a wealth of new information, showing that the growth of the archetype molecule PTCDA not only has similarities but also has significant differences when comparing Au(111) and Ag(111) substrate surfaces. For instance, under otherwise identical preparation conditions, we observed different growth mechanisms on different surface regions, depending on the density of step bunches. In addition, we studied the spatially resolved desorption behavior which also depends on the substrate morphology.

Room temperature chemical synthesis of lead selenide thin films with preferred orientation

NASA Astrophysics Data System (ADS)

Kale, R. B.; Sartale, S. D.; Ganesan, V.; Lokhande, C. D.; Lin, Yi-Feng; Lu, Shih-Yuan

2006-11-01

Room temperature chemical synthesis of PbSe thin films was carried out from aqueous ammoniacal solution using Pb(CH3COO)2 as Pb2+ and Na2SeSO3 as Se2- ion sources. The films were characterized by a various techniques including, X-ray diffraction (XRD), energy dispersive X-ray analysis (EDAX), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HR-TEM), selected area electron diffraction (SAED), Fast Fourier transform (FFT) and UV-vis-NIR techniques. The study revealed that the PbSe thin film consists of preferentially oriented nanocubes with energy band gap of 0.5 eV.

Imaging of high-angle annular dark-field scanning transmission electron microscopy and observations of GaN-based violet laser diodes.

PubMed

Shiojiri, M; Saijo, H

2006-09-01

The first part of this paper is devoted to physics, to explain high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging and to interpret why HAADF-STEM imaging is incoherent, instructing a strict definition of interference and coherence of electron waves. Next, we present our recent investigations of InGaN/GaN multiple quantum wells and AlGaN/GaN strained-layer superlattice claddings in GaN-based violet laser diodes, which have been performed by HAADF-STEM and high-resolution field-emission gun scanning electron microscopy.

Application of He ion microscopy for material analysis

NASA Astrophysics Data System (ADS)

Altmann, F.; Simon, M.; Klengel, R.

2009-05-01

Helium ion beam microscopy (HIM) is a new high resolution imaging technique. The use of Helium ions instead of electrons enables none destructive imaging combined with contrasts quite similar to that from Gallium ion beam imaging. The use of very low probe currents and the comfortable charge compensation using low energy electrons offer imaging of none conductive samples without conductive coating. An ongoing microelectronic sample with Gold/Aluminum interconnects and polymer electronic devices were chosen to evaluate HIM in comparison to scanning electron microscopy (SEM). The aim was to look for key applications of HIM in material analysis. Main focus was on complementary contrast mechanisms and imaging of none conductive samples.

Catalytic chemical vapor deposition synthesis and electron microscopy observation of coiled carbon nanotubes

NASA Astrophysics Data System (ADS)

Xie, Jining; Mukhopadyay, K.; Yadev, J.; Varadan, V. K.

2003-10-01

Coiled carbon nanotubes exhibit excellent mechanical and electrical properties because of the combination of coil morphology and properties of nanotubes. They could have potential novel applications in nanocomposites and nano-electronic devices as well as nano-electromechanical systems. In this work, synthesis of regularly coiled carbon nanotubes is presented. It involves pyrolysis of hydrocarbon gas over metal/support catalyst by both thermal filament and microwave catalytic chemical vapor deposition methods. Scanning electron microscopy and transmission electron microscopy were performed to observe the coil morphology and nanostructure of coiled nanotubes. The growth mechanism and structural and electrical properties of coiled carbon nanotubes are also discussed.

Use of light, scanning electron microscopy and bioassays to evaluate parasitism by entomopathogenic fungi of the red scale insect of palms (Phoenicococcus marlatti Ckll., 1899).

PubMed

Asensio, L; Lopez-Llorca, L V; López-Jiménez, J A

2005-01-01

We have evaluated the parasitism of the red scale insect of the date palm (Phoenicococcus marlatti) by entomopathogenic fungi, using light microscopy (LM), scanning electron microscopy (SEM) and low temperature scanning electron microscopy (LTSEM). Beauveria bassiana, Lecanicillium dimorphum and Lecanicillium cf. psalliotae, were inoculated directly on the scale insects or on insect infested plant material. We found that L. dimorphum and L. cf. psalliotae developed on plant material and on scale insects, making infection structures. B. bassiana was a bad colonizer of date palm leaves (Phoenix dactylifera L.) and did not parasite the scale insects.

Airborne asbestos in Colorado public schools.

PubMed

Chadwick, D A; Buchan, R M; Beaulieu, H J

1985-02-01

Levels of airborne asbestos for six Colorado public school facilities with sprayed-on asbestos materials were documented using three analytical techniques. Phase contrast microscopy showed levels up to the thousandths of a fiber per cubic centimeter (f/cc), scanning electron microscopy (SEM) up to the hundredths of a f/cc, and transmission electron microscopy coupled to selected area electron diffraction and energy dispersive X-ray analysis (TEM-SAED-EDXA) up to the tenths of an asbestos f/cc. Phase contrast microscopy was found to be an inadequate analytical technique for documenting the levels of airborne asbestos fibers in the schools: only large fibers which were not embedded in the filter were counted, and asbestos fibers were not distinguished from nonasbestos.

Further description of Cruzia tentaculata (Rudolphi, 1819) Travassos, 1917 (Nematoda: Cruzidae) by light and scanning electron microscopy.

PubMed

Adnet, F A O; Anjos, D H S; Menezes-Oliveira, A; Lanfredi, R M

2009-04-01

Species of Cruzia are parasites of the large intestine of marsupials, reptiles, amphibians, and mammalians. Cruzia tentaculata specimens were collected from the large intestine of Didelphis marsupialis (Mammalia: Didelphidae) from Colombia (new geographical record) and from Brazil and analyzed by light and scanning electron microscopy. The morphology of males and females by light microscopy corroborated most of the previous description and the ultrastructure by scanning electron microscopy evidence: the topography of the cuticle, deirids, amphids, phasmids in both sexes, a pair of papillae near the vulva opening, and the number and location of male caudal papillae, adding new features for species identification only observed by this technique.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Jiaming; Hudak, Bethany M.; Sims, Hunter

One-dimensional (1D) nanostructures are highly sought after, both for their novel electronic properties as well as for their improved functionality. However, due to their nanoscale dimensions, these properties are significantly affected by the environment in which they are embedded. Here in this paper, we report on the creation of 1D homo-endotaxial Si nanostructures, i.e. 1D Si nanostructures with a lattice structure that is uniquely different from the Si diamond lattice in which they are embedded. We use scanning tunneling microscopy and spectroscopy, scanning transmission electron microscopy, density functional theory, and conductive atomic force microscopy to elucidate their formation and properties.more » Depending on kinetic constraints during growth, they can be prepared as endotaxial 1D Si nanostructures completely embedded in crystalline Si, or underneath a stripe of amorphous Si containing a large concentration of Bi atoms. Lastly, these homo-endotaxial 1D Si nanostructures have the potential to be useful components in nanoelectronic devices based on the technologically mature Si platform.« less

Enhanced stress corrosion cracking resistance and electrical conductivity of a T761 treated Al-Zn-Mg-Cu alloy thin plate

NASA Astrophysics Data System (ADS)

Chen, Xu; Zhai, Sudan; Gao, Di; Liu, Ye; Xu, Jing; Liu, Yang

2018-01-01

The stress corrosion cracking (SCC) behavior, electrical conductivity and mechanical properties of an Al-Zn-Mg-Cu alloy pre-stretched thin plate for wing skin were researched in this paper. The microstructures and SCC fracture surfaces of the alloy treated at different conditions were characterized by transmission electron microscopy, optical microscopy and scanning electron microscopy. Results indicated that with the increasing of aging temperature, the electrical conductivity and the elongation increased greatly, while the strength decreased gradually which were closely associated with the type and morphology of the precipitates. Compared with the T6 treated alloy, the SCC resistance of the T761 treated Al-Zn-Mg-Cu alloy was improved greatly. The SCC behavior of the T6 treated alloy was dominated by anodic dissolution theory, whereas the hydrogen induced cracking controlled the fracture behavior of the T761 treated alloy which was influenced by the morphology of grain boundary precipitates in this investigated alloy.