Nanoscale Imaging of Whole Cells Using a Liquid Enclosure and a Scanning Transmission Electron Microscope

PubMed Central

Peckys, Diana B.; Veith, Gabriel M.; Joy, David C.; de Jonge, Niels

2009-01-01

Nanoscale imaging techniques are needed to investigate cellular function at the level of individual proteins and to study the interaction of nanomaterials with biological systems. We imaged whole fixed cells in liquid state with a scanning transmission electron microscope (STEM) using a micrometer-sized liquid enclosure with electron transparent windows providing a wet specimen environment. Wet-STEM images were obtained of fixed E. coli bacteria labeled with gold nanoparticles attached to surface membrane proteins. Mammalian cells (COS7) were incubated with gold-tagged epidermal growth factor and fixed. STEM imaging of these cells resulted in a resolution of 3 nm for the gold nanoparticles. The wet-STEM method has several advantages over conventional imaging techniques. Most important is the capability to image whole fixed cells in a wet environment with nanometer resolution, which can be used, e.g., to map individual protein distributions in/on whole cells. The sample preparation is compatible with that used for fluorescent microscopy on fixed cells for experiments involving nanoparticles. Thirdly, the system is rather simple and involves only minimal new equipment in an electron microscopy (EM) laboratory. PMID:20020038

Quasi-parallel precession diffraction: Alignment method for scanning transmission electron microscopes.

PubMed

Plana-Ruiz, S; Portillo, J; Estradé, S; Peiró, F; Kolb, Ute; Nicolopoulos, S

2018-06-06

A general method to set illuminating conditions for selectable beam convergence and probe size is presented in this work for Transmission Electron Microscopes (TEM) fitted with µs/pixel fast beam scanning control, (S)TEM, and an annular dark field detector. The case of interest of beam convergence and probe size, which enables diffraction pattern indexation, is then used as a starting point in this work to add 100 Hz precession to the beam while imaging the specimen at a fast rate and keeping the projector system in diffraction mode. The described systematic alignment method for the adjustment of beam precession on the specimen plane while scanning at fast rates is mainly based on the sharpness of the precessed STEM image. The complete alignment method for parallel condition and precession, Quasi-Parallel PED-STEM, is presented in block diagram scheme, as it has been tested on a variety of instruments. The immediate application of this methodology is that it renders the TEM column ready for the acquisition of Precessed Electron Diffraction Tomographies (EDT) as well as for the acquisition of slow Precessed Scanning Nanometer Electron Diffraction (SNED). Examples of the quality of the Precessed Electron Diffraction (PED) patterns and PED-STEM alignment images are presented with corresponding probe sizes and convergence angles. Copyright © 2018. Published by Elsevier B.V.

Whole-cell imaging of the budding yeast Saccharomyces cerevisiae by high-voltage scanning transmission electron tomography.

PubMed

Murata, Kazuyoshi; Esaki, Masatoshi; Ogura, Teru; Arai, Shigeo; Yamamoto, Yuta; Tanaka, Nobuo

2014-11-01

Electron tomography using a high-voltage electron microscope (HVEM) provides three-dimensional information about cellular components in sections thicker than 1 μm, although in bright-field mode image degradation caused by multiple inelastic scattering of transmitted electrons limit the attainable resolution. Scanning transmission electron microscopy (STEM) is believed to give enhanced contrast and resolution compared to conventional transmission electron microscopy (CTEM). Samples up to 1 μm in thickness have been analyzed with an intermediate-voltage electron microscope because inelastic scattering is not a critical limitation, and probe broadening can be minimized. Here, we employed STEM at 1 MeV high-voltage to extend the useful specimen thickness for electron tomography, which we demonstrate by a seamless tomographic reconstruction of a whole, budding Saccharomyces cerevisiae yeast cell, which is ~3 μm in thickness. High-voltage STEM tomography, especially in the bright-field mode, demonstrated sufficiently enhanced contrast and intensity, compared to CTEM tomography, to permit segmentation of major organelles in the whole cell. STEM imaging also reduced specimen shrinkage during tilt-series acquisition. The fidelity of structural preservation was limited by cytoplasmic extraction, and the spatial resolution was limited by the relatively large convergence angle of the scanning probe. However, the new technique has potential to solve longstanding problems of image blurring in biological specimens beyond 1 μm in thickness, and may facilitate new research in cellular structural biology. Copyright © 2014 Elsevier B.V. All rights reserved.

Implementing an Accurate and Rapid Sparse Sampling Approach for Low-Dose Atomic Resolution STEM Imaging

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

Kovarik, Libor; Stevens, Andrew J.; Liyu, Andrey V.

Aberration correction for scanning transmission electron microscopes (STEM) has dramatically increased spatial image resolution for beam-stable materials, but it is the sample stability rather than the microscope that often limits the practical resolution of STEM images. To extract physical information from images of beam sensitive materials it is becoming clear that there is a critical dose/dose-rate below which the images can be interpreted as representative of the pristine material, while above it the observation is dominated by beam effects. Here we describe an experimental approach for sparse sampling in the STEM and in-painting image reconstruction in order to reduce themore » electron dose/dose-rate to the sample during imaging. By characterizing the induction limited rise-time and hysteresis in scan coils, we show that sparse line-hopping approach to scan randomization can be implemented that optimizes both the speed of the scan and the amount of the sample that needs to be illuminated by the beam. The dose and acquisition time for the sparse sampling is shown to be effectively decreased by factor of 5x relative to conventional acquisition, permitting imaging of beam sensitive materials to be obtained without changing the microscope operating parameters. As a result, the use of sparse line-hopping scan to acquire STEM images is demonstrated with atomic resolution aberration corrected Z-contrast images of CaCO 3, a material that is traditionally difficult to image by TEM/STEM because of dose issues.« less

Implementing an Accurate and Rapid Sparse Sampling Approach for Low-Dose Atomic Resolution STEM Imaging

DOE PAGES

Kovarik, Libor; Stevens, Andrew J.; Liyu, Andrey V.; ...

2016-10-17

Aberration correction for scanning transmission electron microscopes (STEM) has dramatically increased spatial image resolution for beam-stable materials, but it is the sample stability rather than the microscope that often limits the practical resolution of STEM images. To extract physical information from images of beam sensitive materials it is becoming clear that there is a critical dose/dose-rate below which the images can be interpreted as representative of the pristine material, while above it the observation is dominated by beam effects. Here we describe an experimental approach for sparse sampling in the STEM and in-painting image reconstruction in order to reduce themore » electron dose/dose-rate to the sample during imaging. By characterizing the induction limited rise-time and hysteresis in scan coils, we show that sparse line-hopping approach to scan randomization can be implemented that optimizes both the speed of the scan and the amount of the sample that needs to be illuminated by the beam. The dose and acquisition time for the sparse sampling is shown to be effectively decreased by factor of 5x relative to conventional acquisition, permitting imaging of beam sensitive materials to be obtained without changing the microscope operating parameters. The use of sparse line-hopping scan to acquire STEM images is demonstrated with atomic resolution aberration corrected Z-contrast images of CaCO3, a material that is traditionally difficult to image by TEM/STEM because of dose issues.« less

Electron tomography of HEK293T cells using scanning electron microscope-based scanning transmission electron microscopy.

PubMed

You, Yun-Wen; Chang, Hsun-Yun; Liao, Hua-Yang; Kao, Wei-Lun; Yen, Guo-Ji; Chang, Chi-Jen; Tsai, Meng-Hung; Shyue, Jing-Jong

2012-10-01

Based on a scanning electron microscope operated at 30 kV with a homemade specimen holder and a multiangle solid-state detector behind the sample, low-kV scanning transmission electron microscopy (STEM) is presented with subsequent electron tomography for three-dimensional (3D) volume structure. Because of the low acceleration voltage, the stronger electron-atom scattering leads to a stronger contrast in the resulting image than standard TEM, especially for light elements. Furthermore, the low-kV STEM yields less radiation damage to the specimen, hence the structure can be preserved. In this work, two-dimensional STEM images of a 1-μm-thick cell section with projection angles between ±50° were collected, and the 3D volume structure was reconstructed using the simultaneous iterative reconstructive technique algorithm with the TomoJ plugin for ImageJ, which are both public domain software. Furthermore, the cross-sectional structure was obtained with the Volume Viewer plugin in ImageJ. Although the tilting angle is constrained and limits the resulting structural resolution, slicing the reconstructed volume generated the depth profile of the thick specimen with sufficient resolution to examine cellular uptake of Au nanoparticles, and the final position of these nanoparticles inside the cell was imaged.

Performance of low-voltage STEM/TEM with delta corrector and cold field emission gun.

PubMed

Sasaki, Takeo; Sawada, Hidetaka; Hosokawa, Fumio; Kohno, Yuji; Tomita, Takeshi; Kaneyama, Toshikatsu; Kondo, Yukihito; Kimoto, Koji; Sato, Yuta; Suenaga, Kazu

2010-08-01

To reduce radiation damage caused by the electron beam and to obtain high-contrast images of specimens, we have developed a highly stabilized transmission electron microscope equipped with a cold field emission gun and spherical aberration correctors for image- and probe-forming systems, which operates at lower acceleration voltages than conventional transmission electron microscopes. A delta-type aberration corrector is designed to simultaneously compensate for third-order spherical aberration and fifth-order 6-fold astigmatism. Both were successfully compensated in both scanning transmission electron microscopy (STEM) and transmission electron microscopy (TEM) modes in the range 30-60 kV. The Fourier transforms of raw high-angle annular dark field (HAADF) images of a Si[110] sample revealed spots corresponding to lattice spacings of 111 and 96 pm at 30 and 60 kV, respectively, and those of raw TEM images of an amorphous Ge film with gold particles showed spots corresponding to spacings of 91 and 79 pm at 30 and 60 kV, respectively. Er@C(82)-doped single-walled carbon nanotubes, which are carbon-based samples, were successfully observed by HAADF-STEM imaging with an atomic-level resolution.

Direct-write liquid phase transformations with a scanning transmission electron microscope

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

Unocic, Raymond R.; Lupini, Andrew R.; Borisevich, Albina Y.

The highly energetic electron beam from a scanning transmission electron microscope (STEM) can induce local changes in the state of matter, ranging from local knock-out and atomic movement, to amorphization/crystallization, and chemical/electrochemical reactions occuring at localized liquid-solid and gas-solid interfaces. To date, fundamental studies of e-beam induced phenomena and practical applications have been limited by conventional e-beam rastering modes that allow only for uniform e-beam exposures. Here we develop an automated liquid phase nanolithography method that is capable of directly writing nanometer scaled features within silicon nitride encapsulated liquid cells. An external beam control system, connected to the scan coilsmore » of an aberration-corrected STEM, is used to precisely control the position, dwell time, and scan velocity of a sub-nanometer STEM probe. Site-specific locations in a sealed liquid cell containing an aqueous solution of H 2PdCl 4 are irradiated to controllably deposit palladium onto silicon nitride membranes. We determine the threshold electron dose required for the radiolytic deposition of metallic palladium, explore the influence of electron dose on the feature size and morphology of nanolithographically patterned nanostructures, and propose a feedback-controlled monitoring method for active control of the nanofabricated structures through STEM detector signal monitoring. As a result, this approach enables both fundamental studies of electron beam induced interactions with matter, as well as opens a pathway to fabricate nanostructures with tailored architectures and chemistries via shape-controlled nanolithographic patterning from liquid phase precursors.« less

Direct-write liquid phase transformations with a scanning transmission electron microscope

DOE PAGES

Unocic, Raymond R.; Lupini, Andrew R.; Borisevich, Albina Y.; ...

2016-08-03

The highly energetic electron beam from a scanning transmission electron microscope (STEM) can induce local changes in the state of matter, ranging from local knock-out and atomic movement, to amorphization/crystallization, and chemical/electrochemical reactions occuring at localized liquid-solid and gas-solid interfaces. To date, fundamental studies of e-beam induced phenomena and practical applications have been limited by conventional e-beam rastering modes that allow only for uniform e-beam exposures. Here we develop an automated liquid phase nanolithography method that is capable of directly writing nanometer scaled features within silicon nitride encapsulated liquid cells. An external beam control system, connected to the scan coilsmore » of an aberration-corrected STEM, is used to precisely control the position, dwell time, and scan velocity of a sub-nanometer STEM probe. Site-specific locations in a sealed liquid cell containing an aqueous solution of H 2PdCl 4 are irradiated to controllably deposit palladium onto silicon nitride membranes. We determine the threshold electron dose required for the radiolytic deposition of metallic palladium, explore the influence of electron dose on the feature size and morphology of nanolithographically patterned nanostructures, and propose a feedback-controlled monitoring method for active control of the nanofabricated structures through STEM detector signal monitoring. As a result, this approach enables both fundamental studies of electron beam induced interactions with matter, as well as opens a pathway to fabricate nanostructures with tailored architectures and chemistries via shape-controlled nanolithographic patterning from liquid phase precursors.« 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.

A history of scanning electron microscopy developments: towards "wet-STEM" imaging.

PubMed

Bogner, A; Jouneau, P-H; Thollet, G; Basset, D; Gauthier, C

2007-01-01

A recently developed imaging mode called "wet-STEM" and new developments in environmental scanning electron microscopy (ESEM) allows the observation of nano-objects suspended in a liquid phase, with a few manometers resolution and a good signal to noise ratio. The idea behind this technique is simply to perform STEM-in-SEM, that is SEM in transmission mode, in an environmental SEM. The purpose of the present contribution is to highlight the main advances that contributed to development of the wet-STEM technique. Although simple in principle, the wet-STEM imaging mode would have been limited before high brightness electron sources became available, and needed some progresses and improvements in ESEM. This new technique extends the scope of SEM as a high-resolution microscope, relatively cheap and widely available imaging tool, for a wider variety of samples.

Scanning Electron Microscopy (SEM) Procedure for HE Powders on a Zeiss Sigma HD VP SEM

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

Zaka, F.

This method describes the characterization of inert and HE materials by the Zeiss Sigma HD VP field emission Scanning Electron Microscope (SEM). The SEM uses an accelerated electron beam to generate high-magnification images of explosives and other materials. It is fitted with five detectors (SE, Inlens, STEM, VPSE, HDBSD) to enable imaging of the sample via different secondary electron signatures, angles, and energies. In addition to imaging through electron detection, the microscope is also fitted with two Oxford Instrument Energy Dispersive Spectrometer (EDS) 80 mm detectors to generate elemental constituent spectra and two-dimensional maps of the material being scanned.

Scanning transmission electron microscopy: Albert Crewe's vision and beyond.

PubMed

Krivanek, Ondrej L; Chisholm, Matthew F; Murfitt, Matthew F; Dellby, Niklas

2012-12-01

Some four decades were needed to catch up with the vision that Albert Crewe and his group had for the scanning transmission electron microscope (STEM) in the nineteen sixties and seventies: attaining 0.5Å resolution, and identifying single atoms spectroscopically. With these goals now attained, STEM developments are turning toward new directions, such as rapid atomic resolution imaging and exploring atomic bonding and electronic properties of samples at atomic resolution. The accomplishments and the future challenges are reviewed and illustrated with practical examples. Copyright © 2012 Elsevier B.V. All rights reserved.

Imaging and elemental mapping of biological specimens with a dual-EDS dedicated scanning transmission electron microscope

PubMed Central

Wu, J.S.; Kim, A. M.; Bleher, R.; Myers, B.D.; Marvin, R. G.; Inada, H.; Nakamura, K.; Zhang, X.F.; Roth, E.; Li, S.Y.; Woodruff, T. K.; O'Halloran, T. V.; Dravid, Vinayak P.

2013-01-01

A dedicated analytical scanning transmission electron microscope (STEM) with dual energy dispersive spectroscopy (EDS) detectors has been designed for complementary high performance imaging as well as high sensitivity elemental analysis and mapping of biological structures. The performance of this new design, based on a Hitachi HD-2300A model, was evaluated using a variety of biological specimens. With three imaging detectors, both the surface and internal structure of cells can be examined simultaneously. The whole-cell elemental mapping, especially of heavier metal species that have low cross-section for electron energy loss spectroscopy (EELS), can be faithfully obtained. Optimization of STEM imaging conditions is applied to thick sections as well as thin sections of biological cells under low-dose conditions at room- and cryogenic temperatures. Such multimodal capabilities applied to soft/biological structures usher a new era for analytical studies in biological systems. PMID:23500508

2D strain mapping using scanning transmission electron microscopy Moiré interferometry and geometrical phase analysis.

PubMed

Pofelski, A; Woo, S Y; Le, B H; Liu, X; Zhao, S; Mi, Z; Löffler, S; Botton, G A

2018-04-01

A strain characterization technique based on Moiré interferometry in a scanning transmission electron microscope (STEM) and geometrical phase analysis (GPA) method is demonstrated. The deformation field is first captured in a single STEM Moiré hologram composed of multiple sets of periodic fringes (Moiré patterns) generated from the interference between the periodic scanning grating, fixing the positions of the electron probe on the sample, and the crystal structure. Applying basic principles from sampling theory, the Moiré patterns arrangement is then simulated using a STEM electron micrograph reference to convert the experimental STEM Moiré hologram into information related to the crystal lattice periodicities. The GPA method is finally applied to extract the 2D relative strain and rotation fields. The STEM Moiré interferometry enables the local information to be de-magnified to a large length scale, comparable to what can be achieved in dark-field electron holography. The STEM Moiré GPA method thus extends the conventional high-resolution STEM GPA capabilities by providing comparable quantitative 2D strain mapping with a larger field of view (up to a few microns). Copyright © 2017 Elsevier B.V. All rights reserved.

Microscopy of semiconducting materials

NASA Astrophysics Data System (ADS)

Pennycook, S. J.

1991-04-01

The purpose of the trip was to present an invited talk at the 7th Oxford Conference on Microscopy of Semiconducting Materials entitled, High-Resolution Z-Contrast Imaging of Heterostructures and Superlattices, (Oxford, United Kingdom) and to visit VG Microscopes, East Grinstead, for discussions on the progress of the Oak Ridge National Laboratory (ORNL) 300-kV high-resolution scanning transmission electron microscope (STEM), which is currently on order. The traveler also visited three other institutions with 100-kV STEMs that either have or intend to purchase the necessary modifications to provide Z-contrast capability similar to that of the existing ORNL machine. Specifically, Max-Planck Institut fuer Metallforschung (Stuttgart, Germany); Cambridge University, Department of Materials Science and Metallurgy (Cambridge, United Kingdom); and Cavendish Laboratory, Cambridge University (Cambridge, United Kingdom) were visited. In addition, discussions were held with C. Humphreys on the possibility of obtaining joint funding for collaborative research involving electron beam writing and Z-contrast imaging in the Cambridge and Oak Ridge STEMs, respectively.

Piper nigrum leaf and stem assisted green synthesis of silver nanoparticles and evaluation of its antibacterial activity against agricultural plant pathogens.

PubMed

Paulkumar, Kanniah; Gnanajobitha, Gnanadhas; Vanaja, Mahendran; Rajeshkumar, Shanmugam; Malarkodi, Chelladurai; Pandian, Kannaiyan; Annadurai, Gurusamy

2014-01-01

Utilization of biological materials in synthesis of nanoparticles is one of the hottest topics in modern nanoscience and nanotechnology. In the present investigation, the silver nanoparticles were synthesized by using the leaf and stem extract of Piper nigrum. The synthesized nanoparticle was characterized by UV-vis spectroscopy, X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive X-ray analysis (EDAX), and Fourier Transform Infrared Spectroscopy (FTIR). The observation of the peak at 460 nm in the UV-vis spectra for leaf- and stem-synthesized silver nanoparticles reveals the reduction of silver metal ions into silver nanoparticles. Further, XRD analysis has been carried out to confirm the crystalline nature of the synthesized silver nanoparticles. The TEM images show that the leaf- and stem-synthesized silver nanoparticles were within the size of about 7-50 nm and 9-30 nm, respectively. The FTIR analysis was performed to identify the possible functional groups involved in the synthesis of silver nanoparticles. Further, the antibacterial activity of the green-synthesized silver nanoparticles was examined against agricultural plant pathogens. The antibacterial property of silver nanoparticles is a beneficial application in the field of agricultural nanotechnology.

What transmission electron microscopes can visualize now and in the future.

PubMed

Müller, Shirley A; Aebi, Ueli; Engel, Andreas

2008-09-01

Our review concentrates on the progress made in high-resolution transmission electron microscopy (TEM) in the past decade. This includes significant improvements in sample preparation by quick-freezing aimed at preserving the specimen in a close-to-native state in the high vacuum of the microscope. Following advances in cold stage and TEM vacuum technology systems, the observation of native, frozen hydrated specimens has become a widely used approach. It fostered the development of computer guided, fully automated low-dose data acquisition systems allowing matched pairs of images and diffraction patterns to be recorded for electron crystallography, and the collection of entire tilt-series for electron tomography. To achieve optimal information transfer to atomic resolution, field emission electron guns combined with acceleration voltages of 200-300 kV are now routinely used. The outcome of these advances is illustrated by the atomic structure of mammalian aquaporin-O and by the pore-forming bacterial cytotoxin ClyA resolved to 12 A. Further, the Yersinia injectisome needle, a bacterial pseudopilus and the binding of phalloidin to muscle actin filaments were chosen to document the advantage of the high contrast offered by dedicated scanning transmission electron microscopy (STEM) and/or the STEM's ability to measure the mass of protein complexes and directly link this to their shape. Continued progress emerging from leading research laboratories and microscope manufacturers will eventually enable us to determine the proteome of a single cell by electron tomography, and to more routinely solve the atomic structure of membrane proteins by electron crystallography.

Imaging and elemental mapping of biological specimens with a dual-EDS dedicated scanning transmission electron microscope.

PubMed

Wu, J S; Kim, A M; Bleher, R; Myers, B D; Marvin, R G; Inada, H; Nakamura, K; Zhang, X F; Roth, E; Li, S Y; Woodruff, T K; O'Halloran, T V; Dravid, Vinayak P

2013-05-01

A dedicated analytical scanning transmission electron microscope (STEM) with dual energy dispersive spectroscopy (EDS) detectors has been designed for complementary high performance imaging as well as high sensitivity elemental analysis and mapping of biological structures. The performance of this new design, based on a Hitachi HD-2300A model, was evaluated using a variety of biological specimens. With three imaging detectors, both the surface and internal structure of cells can be examined simultaneously. The whole-cell elemental mapping, especially of heavier metal species that have low cross-section for electron energy loss spectroscopy (EELS), can be faithfully obtained. Optimization of STEM imaging conditions is applied to thick sections as well as thin sections of biological cells under low-dose conditions at room and cryogenic temperatures. Such multimodal capabilities applied to soft/biological structures usher a new era for analytical studies in biological systems. Copyright © 2013 Elsevier B.V. All rights reserved.

Direct observation of Sr vacancies in SrTiO 3 by quantitative scanning transmission electron microscopy

DOE PAGES

Kim, Honggyu; Zhang, Jack Y.; Raghavan, Santosh; ...

2016-12-22

Unveiling the identity, spatial configuration, and microscopic structure of point defects is one of the key challenges in materials science. Here, we demonstrate that quantitative scanning transmission electron microscopy (STEM) can be used to directly observe Sr vacancies in SrTiO 3 and to determine the atom column relaxations around them. By combining recent advances in quantitative STEM, including variableangle, high-angle annular dark-field imaging and rigid registration methods, with frozen phonon multislice image simulations, we identify which Sr columns contain vacancies and quantify the number of vacancies in them. Here, picometer precision measurements of the surrounding atom column positions show thatmore » the nearest-neighbor Ti atoms are displaced away from the Sr vacancies. The results open up a new methodology for studying the microscopic mechanisms by which point defects control materials properties.« less

Direct observation of Sr vacancies in SrTiO 3 by quantitative scanning transmission electron microscopy

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

Kim, Honggyu; Zhang, Jack Y.; Raghavan, Santosh

Unveiling the identity, spatial configuration, and microscopic structure of point defects is one of the key challenges in materials science. Here, we demonstrate that quantitative scanning transmission electron microscopy (STEM) can be used to directly observe Sr vacancies in SrTiO 3 and to determine the atom column relaxations around them. By combining recent advances in quantitative STEM, including variableangle, high-angle annular dark-field imaging and rigid registration methods, with frozen phonon multislice image simulations, we identify which Sr columns contain vacancies and quantify the number of vacancies in them. Here, picometer precision measurements of the surrounding atom column positions show thatmore » the nearest-neighbor Ti atoms are displaced away from the Sr vacancies. The results open up a new methodology for studying the microscopic mechanisms by which point defects control materials properties.« less

Electron ptychographic phase imaging of light elements in crystalline materials using Wigner distribution deconvolution

DOE PAGES

Yang, Hao; MacLaren, Ian; Jones, Lewys; ...

2017-04-01

Recent development in fast pixelated detector technology has allowed a two dimensional diffraction pattern to be recorded at every probe position of a two dimensional raster scan in a scanning transmission electron microscope (STEM), forming an information-rich four dimensional (4D) dataset. Electron ptychography has been shown to enable efficient coherent phase imaging of weakly scattering objects from a 4D dataset recorded using a focused electron probe, which is optimised for simultaneous incoherent Z-contrast imaging and spectroscopy in STEM. Thus coherent phase contrast and incoherent Z-contrast imaging modes can be efficiently combined to provide a good sensitivity of both light andmore » heavy elements at atomic resolution. Here, we explore the application of electron ptychography for atomic resolution imaging of strongly scattering crystalline specimens, and present experiments on imaging crystalline specimens including samples containing defects, under dynamical channelling conditions using an aberration corrected microscope. A ptychographic reconstruction method called Wigner distribution deconvolution (WDD) was implemented. Our experimental results and simulation results suggest that ptychography provides a readily interpretable phase image and great sensitivity for imaging light elements at atomic resolution in relatively thin crystalline materials.« less

Piper nigrum Leaf and Stem Assisted Green Synthesis of Silver Nanoparticles and Evaluation of Its Antibacterial Activity Against Agricultural Plant Pathogens

PubMed Central

Paulkumar, Kanniah; Gnanajobitha, Gnanadhas; Vanaja, Mahendran; Rajeshkumar, Shanmugam; Malarkodi, Chelladurai; Pandian, Kannaiyan; Annadurai, Gurusamy

2014-01-01

Utilization of biological materials in synthesis of nanoparticles is one of the hottest topics in modern nanoscience and nanotechnology. In the present investigation, the silver nanoparticles were synthesized by using the leaf and stem extract of Piper nigrum. The synthesized nanoparticle was characterized by UV-vis spectroscopy, X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive X-ray analysis (EDAX), and Fourier Transform Infrared Spectroscopy (FTIR). The observation of the peak at 460 nm in the UV-vis spectra for leaf- and stem-synthesized silver nanoparticles reveals the reduction of silver metal ions into silver nanoparticles. Further, XRD analysis has been carried out to confirm the crystalline nature of the synthesized silver nanoparticles. The TEM images show that the leaf- and stem-synthesized silver nanoparticles were within the size of about 7–50 nm and 9–30 nm, respectively. The FTIR analysis was performed to identify the possible functional groups involved in the synthesis of silver nanoparticles. Further, the antibacterial activity of the green-synthesized silver nanoparticles was examined against agricultural plant pathogens. The antibacterial property of silver nanoparticles is a beneficial application in the field of agricultural nanotechnology. PMID:24558336

Brief history of the Cambridge STEM aberration correction project and its progeny.

PubMed

Brown, L Michael; Batson, Philip E; Dellby, Niklas; Krivanek, Ondrej L

2015-10-01

We provide a brief history of the project to correct the spherical aberration of the scanning transmission electron microscope (STEM) that started in Cambridge (UK) and continued in Kirkland (WA, USA), Yorktown Heights (NY, USA), and other places. We describe the project in the full context of other aberration correction research and related work, partly in response to the incomplete context presented in the paper "In quest of perfection in electron optics: A biographical sketch of Harald Rose on the occasion of his 80th birthday", recently published in Ultramicroscopy. Copyright © 2015 Elsevier B.V. All rights reserved.

Microscopic diagnosis of the leaf and stem of Piper solmsianum C.DC.

PubMed

Bertocco, A R P; Migacz, I P; Santos, V L P; Franco, C R C; Silva, R Z; Yunes, R A; Cechinel-Filho, V; Budel, J M

2017-08-01

Piper solmsianum C.DC., which is popularly known as pariparoba, is a shrub that measures 1-3 m in height and it inhabits areas with wet tropical soils. The objective of this study was to analyze the leaf and stem anatomy using light microscopy, scanning electron micrographs, and energy-dispersive X-ray spectroscopy in order to provide information for species identification. The anatomical profile showed the following main microscopic markers: hypostomatic leaf; hypodermis layer on both sides; pearl glands; biconvex midrib shape; five collateral vascular bundles in open arc with the central bundle larger than the others; circular stem shape; collateral vascular bundles arranged in two rings; sinuous sclerenchymatic sheath in the pith; secretory idioblasts; and starch grains in the mesophyll, in the ground parenchyma of the midrib, petiole, and in the stem; and six morphotypes of calcium oxalate crystals (styloids, cuneiform, tabular crystal rosettes, cuneiform crystal rosettes, elongated square dipyramids, as well as very elongated square dipyramids). © 2017 Wiley Periodicals, Inc.

Characterization of LiBC by phase-contrast scanning transmission electron microscopy.

PubMed

Krumeich, Frank; Wörle, Michael; Reibisch, Philipp; Nesper, Reinhard

2014-08-01

LiBC was used as a model compound for probing the applicability of phase-contrast (PC) imaging in an aberration-corrected scanning transmission electron microscope (STEM) to visualize lithium distributions. In the LiBC structure, boron and carbon are arranged to hetero graphite layers between which lithium is incorporated. The crystal structure is reflected in the PC-STEM images recorded perpendicular to the layers. The experimental images and their defocus dependence match with multi-slice simulations calculated utilizing the reciprocity principle. The observation that a part of the Li positions is not occupied is likely an effect of the intense electron beam triggering Li displacement. Copyright © 2013 Elsevier Ltd. All rights reserved.

Advanced STEM microanalysis of bimetallic nanoparticle catalysts

NASA Astrophysics Data System (ADS)

Lyman, Charles E.; Dimick, Paul S.

2012-05-01

Individual particles within bimetallic nanoparticle populations are not always identical, limiting the usefulness of bulk analysis techniques such as EXAFS. The scanning transmission electron microscope (STEM) is the only instrument able to characterize supported nanoparticle populations on a particle-by-particle basis. Quantitative elemental analyses of sub-5-nm particles reveal phase separations among particles and surface segregation within particles. This knowledge can lead to improvements in bimetallic catalysts. Advanced STEMs with field-emission guns, aberration-corrected optics, and efficient signal detection systems allow analysis of sub-nanometer particles.

The Scanning Optical Microscope: An Overview

NASA Astrophysics Data System (ADS)

Kino, G. S.; Corte, T. R.; Xiao, G. Q.

1988-07-01

In the last few years there has been a resurgence in research on optical microscopes. One reason stems from the invention of the acoustic microscope by Quate and Lemons,1 and the realization that some of the same principles could be applied to the optical microscope. The acoustic microscope has better transverse definition for the same wavelength than the standard optical microscope and at the same time has far better range definition. Consequently, Kompfner, who was involved with the work on the early acoustic microscope, decided to try out similar scanning microscope principles with optics, and started a group with Wilson and Sheppard to carry out such research at Oxford.2 Sometime earlier, Petran et a13 had invented the tandem scanning microscope which used many of the same principles. Now, in our laboratory at Stanford, these ideas on the tandem scanning microscope and the scanning optical microscope are converging. Another aspect of this work, which stems from the earlier experience with the acoustic microscope, involves measurement of both phase and amplitude of the optical beam. It is also possible to use scanned optical microscopy for other purposes. For instance, an optical beam can be used to excite electrons and holes in semiconductors, and the generated current can be measured. By scanning the optical beam over the semiconductor, an image can be obtained of the regions where there is strong or weak electron hole generation. This type of microscope is called OBIC (Optical Beam Induced Current). A second application involves fluorescent imaging of biological materials. Here we have the excellent range definition of a scanning optical microscope which eliminates unwanted glare from regions of the material where the beam is unfocused.3 A third application is focused on the heating effect of the light beam. With such a system, images can be obtained which are associated with changes in the thermal properties of a material, changes in recombination rates in semiconductors, and differences in material properties associated with either acoustic or thermal effects.4,5 Thus, the range of scanning optical microscopy applications is very large. In the main, the most important applications have been to semiconductors and to biology.

Green synthesis of silver nanoparticle and silver based chitosan bionanocomposite using stem extract of Saccharum officinarum and assessment of its antibacterial activity

NASA Astrophysics Data System (ADS)

Paulkumar, Kanniah; Gnanajobitha, Gnanadhas; Vanaja, Mahendran; Pavunraj, Manickam; Annadurai, Gurusamy

2017-09-01

Synthesis of nanoparticles and nanocomposites using green route is a major focus of modern nanotechnology. Herein we demonstrate the synthesis of silver nanoparticle and silver based chitosan bionanocomposite using the stem extract of Saccharum officinarum. The absorbance peak at 460 nm in the UV-Vis spectrum reveals the synthesis of silver nanoparticles using the stem extract of Saccharum officinarum. The size of the synthesized silver nanoparticle was in the range of 10-60 nm obtained from transmission electron microscope (TEM) analysis. The presence of silver nanoparticles on the chitosan suspension was identified by scanning electron microscope (SEM) and energy dispersive x-ray spectroscopy (EDS). The presence of possible functional group involved in the reduction of silver metal ions into silver nanoparticles was identified by Fourier transform infrared spectroscopy (FTIR) analysis. The antibacterial activity of the synthesized silver based chitosan bionanocomposite was evaluated against Bacillus subtilis (MTCC 3053), Klebsiella planticola (MTCC 2277), Streptococcus faecalis (ATCC 8043), Pseudomonas aeruginosa (ATCC 9027) and Escherichia coli (ATCC 8739). The antibacterial activity of silver based chitosan bionanocomposite has remarkable scope in medicine, food packaging, textile and pharmaceuticals.

A sub-sampled approach to extremely low-dose STEM

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

Stevens, A.; Luzi, L.; Yang, H.

The inpainting of randomly sub-sampled images acquired by scanning transmission electron microscopy (STEM) is an attractive method for imaging under low-dose conditions (≤ 1 e -Å 2) without changing either the operation of the microscope or the physics of the imaging process. We show that 1) adaptive sub-sampling increases acquisition speed, resolution, and sensitivity; and 2) random (non-adaptive) sub-sampling is equivalent, but faster than, traditional low-dose techniques. Adaptive sub-sampling opens numerous possibilities for the analysis of beam sensitive materials and in-situ dynamic processes at the resolution limit of the aberration corrected microscope and is demonstrated here for the analysis ofmore » the node distribution in metal-organic frameworks (MOFs).« less

Toward single mode, atomic size electron vortex beams.

PubMed

Krivanek, Ondrej L; Rusz, Jan; Idrobo, Juan-Carlos; Lovejoy, Tracy J; Dellby, Niklas

2014-06-01

We propose a practical method of producing a single mode electron vortex beam suitable for use in a scanning transmission electron microscope (STEM). The method involves using a holographic "fork" aperture to produce a row of beams of different orbital angular momenta, as is now well established, magnifying the row so that neighboring beams are separated by about 1 µm, selecting the desired beam with a narrow slit, and demagnifying the selected beam down to 1-2 Å in size. We show that the method can be implemented by adding two condenser lenses plus a selection slit to a straight-column cold-field emission STEM. It can also be carried out in an existing instrument, the monochromated Nion high-energy-resolution monochromated electron energy-loss spectroscopy-STEM, by using its monochromator in a novel way. We estimate that atom-sized vortex beams with ≥ 20 pA of current should be attainable at 100-200 keV in either instrument.

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.

Imaging Gallium Nitride High Electron Mobility Transistors to Identify Point Defects

DTIC Science & Technology

2014-03-01

streamline the sample preparation procedure to maximize the yield of successful samples to be analyzed chemically in an energy dispersive spectrometry...transmission electron microscope (STEM), sample preparation 15. NUMBER OF PAGES 103 16. PRICE CODE 17. SECURITY CLASSIFICATION OF REPORT...Computer Engineering iii THIS PAGE INTENTIONALLY LEFT BLANK iv ABSTRACT The purpose of this thesis is to streamline the sample preparation

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.

Atmospheric pressure scanning transmission electron microscopy.

PubMed

de Jonge, Niels; Bigelow, Wilbur C; Veith, Gabriel M

2010-03-10

Scanning transmission electron microscope (STEM) images of gold nanoparticles at atmospheric pressure have been recorded through a 0.36 mm thick mixture of CO, O2, and He. This was accomplished using a reaction cell consisting of two electron-transparent silicon nitride membranes. Gold nanoparticles of a full width at half-maximum diameter of 1.0 nm were visible above the background noise, and the achieved edge resolution was 0.4 nm in accordance with calculations of the beam broadening.

Report on the Installation and Preparedness of a Protochips Fusion in-situ Heating Holder for TEM

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

Edmondson, Philip D.

2017-03-01

This brief report documents the procurement and installation of a Protochips Fusion (formerly Aduro) high-temperature, high stability transmission electron microscopy (TEM) specimen holder that allows for the high spatial resolution characterization of material specimens at high temperature in situ of an electron microscope. This specimen holder was specifically procured for use with The FEI Talos F200X Scanning/Transmission Electron Microscope (STEM) in Oak Ridge National Laboratory’s (ORNL’s) Low Activation Materials Development and Analysis (LAMDA) Laboratory. The Protochips Fusion holder will enable high-resolution structural and chemical analysis of irradiated materials at high temperature, becoming a unique capability worldwide, and would encourage high-qualitymore » in situ experiments to be conducted on irradiated materials.« less

Scanning transmission electron microscopy methods for the analysis of nanoparticles.

PubMed

Ponce, Arturo; Mejía-Rosales, Sergio; José-Yacamán, Miguel

2012-01-01

Here we review the scanning transmission electron microscopy (STEM) characterization technique and STEM imaging methods. We describe applications of STEM for studying inorganic nanoparticles, and other uses of STEM in biological and health sciences and discuss how to interpret STEM results. The STEM imaging mode has certain benefits compared with the broad-beam illumination mode; the main advantage is the collection of the information about the specimen using a high angular annular dark field (HAADF) detector, in which the images registered have different levels of contrast related to the chemical composition of the sample. Another advantage of its use in the analysis of biological samples is its contrast for thick stained sections, since HAADF images of samples with thickness of 100-120 nm have notoriously better contrast than those obtained by other techniques. Combining the HAADF-STEM imaging with the new aberration correction era, the STEM technique reaches a direct way to imaging the atomistic structure and composition of nanostructures at a sub-angstrom resolution. Thus, alloying in metallic nanoparticles is directly resolved at atomic scale by the HAADF-STEM imaging, and the comparison of the STEM images with results from simulations gives a very powerful way of analysis of structure and composition. The use of X-ray energy dispersive spectroscopy attached to the electron microscope for STEM mode is also described. In issues where characterization at the atomic scale of the interaction between metallic nanoparticles and biological systems is needed, all the associated techniques to STEM become powerful tools for the best understanding on how to use these particles in biomedical applications.

Biotribological properties at the stem-cement interface lubricated with different media.

PubMed

Zhang, H Y; Luo, J B; Zhou, M; Zhang, Y; Huang, Y L

2013-04-01

Debonding of the stem-cement interface occurs inevitably in-vivo under physiological loading, and pseudo-synovial fluid is subsequently pumped into this interface, serving as the lubricant. However, the influence of protein adsorption onto the femoral stem surface has not been well taken into consideration in previous in vitro studies. The biotribological properties at the stem-cement interface were investigated through a series of fretting frictional tests using polished stainless steel 316L stem and smooth bone cement, lubricated by three different media at body temperature, i.e. 100% calf serum, 25% calf serum, and 0.9% saline solution. The surface characterization of the femoral stem was evaluated sequentially using optical microscope, optical interferometer, scanning electron microscope, and Raman spectroscopy. The friction coefficient generally kept stable during the test, and the minimum value (0.254) was obtained when 100% calf serum was used as the lubricant. Slight scratches were detected within the contact area for the stainless steel 316L stems lubricated by 100% calf serum and 25% calf serum, which was further surrounded by the adsorbed protein film with alveolate feature. Additionally, a wear scar was present within the contact area when 0.9% saline solution was used as the lubricant. Protein adsorption onto the stainless steel 316L stem surface affected the biotribological properties at the stem-cement interface under oscillatory fretting mechanism. Generation of wear debris at the stem-cement interface may be postponed by modification of physicochemical properties of the femoral stem to promote protein adsorption. Copyright © 2013 Elsevier Ltd. All rights reserved.

Microscopic Electron Dynamics in Metal Nanoparticles for Photovoltaic Systems.

PubMed

Kluczyk, Katarzyna; Jacak, Lucjan; Jacak, Witold; David, Christin

2018-06-25

Nanoparticles—regularly patterned or randomly dispersed—are a key ingredient for emerging technologies in photonics. Of particular interest are scattering and field enhancement effects of metal nanoparticles for energy harvesting and converting systems. An often neglected aspect in the modeling of nanoparticles are light interaction effects at the ultimate nanoscale beyond classical electrodynamics. Those arise from microscopic electron dynamics in confined systems, the accelerated motion in the plasmon oscillation and the quantum nature of the free electron gas in metals, such as Coulomb repulsion and electron diffusion. We give a detailed account on free electron phenomena in metal nanoparticles and discuss analytic expressions stemming from microscopic (Random Phase Approximation—RPA) and semi-classical (hydrodynamic) theories. These can be incorporated into standard computational schemes to produce more reliable results on the optical properties of metal nanoparticles. We combine these solutions into a single framework and study systematically their joint impact on isolated Au, Ag, and Al nanoparticles as well as dimer structures. The spectral position of the plasmon resonance and its broadening as well as local field enhancement show an intriguing dependence on the particle size due to the relevance of additional damping channels.

Application of low-energy scanning transmission electron microscopy for the study of Pt-nanoparticle uptake in human colon carcinoma cells.

PubMed

Blank, Holger; Schneider, Reinhard; Gerthsen, Dagmar; Gehrke, Helge; Jarolim, Katharina; Marko, Doris

2014-06-01

High-angle annular dark-field scanning transmission electron microscopy (HAADF STEM) in a scanning electron microscope facilitates the acquisition of images with high chemical sensitivity and high resolution. HAADF STEM at low electron energies is particularly suited to image nanoparticles (NPs) in thin cell sections which are not subjected to poststaining procedures as demonstrated by comparison with bright-field TEM. High membrane contrast is achieved and distinction of NPs with different chemical composition is possible at first sight. Low-energy HAADF STEM was applied to systematically study the uptake of Pt-NPs with a broad size distribution in HT29 colon carcinoma cells as a function of incubation time and incubation temperature. The cellular dose was quantified, that is, the amount and number density of NPs taken up by the cells, as well as the particle-size distribution. The results show a strong dependence of the amount of incubated NPs on the exposure time which can be understood by considering size-dependent diffusion and gravitational settling of the NPs in the cell culture medium.

Analysis of liquid suspensions using scanning electron microscopy in transmission: estimation of the water film thickness using Monte-Carlo simulations.

PubMed

Xiao, J; Foray, G; Masenelli-Varlot, K

2018-02-01

Environmental scanning electron microscopy (ESEM) allows the observation of liquids under specific conditions of pressure and temperature. Moreover, when working in the transmission mode, that is in scanning transmission electron microscopy (STEM), nano-objects can be analysed inside a liquid. The contrast in the images is mass-thickness dependent as in STEM-in-TEM (transmission electron microscopy) using closed cells. However, in STEM-in-ESEM, as the liquid-vapour equilibrium is kept dynamically, the thickness of the water droplet remains unknown. In this paper, the contrasts measured in the experimental images are compared with calculations using Monte-Carlo simulations in order to estimate the thickness of water. Two examples are given. On gold nanoparticles, the thickness of a thick film can be estimated thanks to a contrast inversion. On core-shell latex particles, the grey level of the shell compared with those of the core and of the water film gives a relatively precise measurement of the water film thickness. © 2017 The Authors Journal of Microscopy © 2017 Royal Microscopical Society.

A short story of imaging and spectroscopy of two-dimensional materials by scanning transmission electron microscopy

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

Idrobo Tapia, Juan Carlos; Zhou, Wu

Here we present a short historical account of when single adatom impurities where first identified in two-dimensional materials by scanning transmission electron microscopy (STEM). We also present a study of the graphene low-loss (below 50 eV) response as a function of number of layers using electron energy-loss spectroscopy (EELS). The study shows that as few as three layers of graphene behave as bulk graphite for losses above 10 eV We also show examples of how point and extended defects can easily be resolved and structural dynamics can be readily capture by using aberration-corrected STEM imaging. Lastly, we show that themore » new generation of monochromators has opened up possibilities to explore new physics with an electron microscope. All these capabilities were enabled by the development of spherical aberration correctors and monochromators, where Ondrej Krivanek has played a key role.« less

A short story of imaging and spectroscopy of two-dimensional materials by scanning transmission electron microscopy

DOE PAGES

Idrobo Tapia, Juan Carlos; Zhou, Wu

2017-03-01

Here we present a short historical account of when single adatom impurities where first identified in two-dimensional materials by scanning transmission electron microscopy (STEM). We also present a study of the graphene low-loss (below 50 eV) response as a function of number of layers using electron energy-loss spectroscopy (EELS). The study shows that as few as three layers of graphene behave as bulk graphite for losses above 10 eV We also show examples of how point and extended defects can easily be resolved and structural dynamics can be readily capture by using aberration-corrected STEM imaging. Lastly, we show that themore » new generation of monochromators has opened up possibilities to explore new physics with an electron microscope. All these capabilities were enabled by the development of spherical aberration correctors and monochromators, where Ondrej Krivanek has played a key role.« less

Effects of instrument imperfections on quantitative scanning transmission electron microscopy.

PubMed

Krause, Florian F; Schowalter, Marco; Grieb, Tim; Müller-Caspary, Knut; Mehrtens, Thorsten; Rosenauer, Andreas

2016-02-01

Several instrumental imperfections of transmission electron microscopes are characterized and their effects on the results of quantitative scanning electron microscopy (STEM) are investigated and quantified using simulations. Methods to either avoid influences of these imperfections during acquisition or to include them in reference calculations are proposed. Particularly, distortions inflicted on the diffraction pattern by an image-aberration corrector can cause severe errors of more than 20% if not accounted for. A procedure for their measurement is proposed here. Furthermore, afterglow phenomena and nonlinear behavior of the detector itself can lead to incorrect normalization of measured intensities. Single electrons accidentally impinging on the detector are another source of error but can also be exploited for threshold-less calibration of STEM images to absolute dose, incident beam current determination and measurement of the detector sensitivity. Copyright © 2015 Elsevier B.V. All rights reserved.

Probing plasmon resonances of individual aluminum nanoparticles

NASA Astrophysics Data System (ADS)

Wei, Zhongxia; Mao, Peng; Cao, Lu; Song, Fengqi

2018-01-01

The plasmon resonances of individual aluminum nanoparticles are investigated by electron energy-loss spectroscopy (EELS) in scanning transmission electron microscope (STEM). Surface plasmon mode and bulk plasmon mode of Al nanoparticles are clearly characterized in the EEL spectra. Discrete dipole approximation (DDA) calculations show that as the particle diameter increases from 20 nm to 100 nm, the plasmon resonance shifts to lower energy and higher mode of surface plasmon arises when the diameter reaches 60 nm and larger.

Precision controlled atomic resolution scanning transmission electron microscopy using spiral scan pathways

NASA Astrophysics Data System (ADS)

Sang, Xiahan; Lupini, Andrew R.; Ding, Jilai; Kalinin, Sergei V.; Jesse, Stephen; Unocic, Raymond R.

2017-03-01

Atomic-resolution imaging in an aberration-corrected scanning transmission electron microscope (STEM) can enable direct correlation between atomic structure and materials functionality. The fast and precise control of the STEM probe is, however, challenging because the true beam location deviates from the assigned location depending on the properties of the deflectors. To reduce these deviations, i.e. image distortions, we use spiral scanning paths, allowing precise control of a sub-Å sized electron probe within an aberration-corrected STEM. Although spiral scanning avoids the sudden changes in the beam location (fly-back distortion) present in conventional raster scans, it is not distortion-free. “Archimedean” spirals, with a constant angular frequency within each scan, are used to determine the characteristic response at different frequencies. We then show that such characteristic functions can be used to correct image distortions present in more complicated constant linear velocity spirals, where the frequency varies within each scan. Through the combined application of constant linear velocity scanning and beam path corrections, spiral scan images are shown to exhibit less scan distortion than conventional raster scan images. The methodology presented here will be useful for in situ STEM imaging at higher temporal resolution and for imaging beam sensitive materials.

Precision controlled atomic resolution scanning transmission electron microscopy using spiral scan pathways.

PubMed

Sang, Xiahan; Lupini, Andrew R; Ding, Jilai; Kalinin, Sergei V; Jesse, Stephen; Unocic, Raymond R

2017-03-08

Atomic-resolution imaging in an aberration-corrected scanning transmission electron microscope (STEM) can enable direct correlation between atomic structure and materials functionality. The fast and precise control of the STEM probe is, however, challenging because the true beam location deviates from the assigned location depending on the properties of the deflectors. To reduce these deviations, i.e. image distortions, we use spiral scanning paths, allowing precise control of a sub-Å sized electron probe within an aberration-corrected STEM. Although spiral scanning avoids the sudden changes in the beam location (fly-back distortion) present in conventional raster scans, it is not distortion-free. "Archimedean" spirals, with a constant angular frequency within each scan, are used to determine the characteristic response at different frequencies. We then show that such characteristic functions can be used to correct image distortions present in more complicated constant linear velocity spirals, where the frequency varies within each scan. Through the combined application of constant linear velocity scanning and beam path corrections, spiral scan images are shown to exhibit less scan distortion than conventional raster scan images. The methodology presented here will be useful for in situ STEM imaging at higher temporal resolution and for imaging beam sensitive materials.

Super-Resolution Image Reconstruction by Nonlocal Means Applied to High-Angle Annular Darkfield Scanning Transmission Electron Microscopy (HAADF-STEM)

DTIC Science & Technology

2009-10-06

When talking about superresolution we always mean to recover the level of resolution set by the microscope, but by using a time series of low...on low resolution possibly very noisy data, is not feasible. Thus, standard superresolution concepts as described above that are based on registration

Local sample thickness determination via scanning transmission electron microscopy defocus series.

PubMed

Beyer, A; Straubinger, R; Belz, J; Volz, K

2016-05-01

The usable aperture sizes in (scanning) transmission electron microscopy ((S)TEM) have significantly increased in the past decade due to the introduction of aberration correction. In parallel with the consequent increase of convergence angle the depth of focus has decreased severely and optical sectioning in the STEM became feasible. Here we apply STEM defocus series to derive the local sample thickness of a TEM sample. To this end experimental as well as simulated defocus series of thin Si foils were acquired. The systematic blurring of high resolution high angle annular dark field images is quantified by evaluating the standard deviation of the image intensity for each image of a defocus series. The derived dependencies exhibit a pronounced maximum at the optimum defocus and drop to a background value for higher or lower values. The full width half maximum (FWHM) of the curve is equal to the sample thickness above a minimum thickness given by the size of the used aperture and the chromatic aberration of the microscope. The thicknesses obtained from experimental defocus series applying the proposed method are in good agreement with the values derived from other established methods. The key advantages of this method compared to others are its high spatial resolution and that it does not involve any time consuming simulations. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

Development and Application of STEM for the Biological Sciences

PubMed Central

Sousa, Alioscka A.; Leapman, Richard D.

2012-01-01

The design of the scanning transmission electron microscope (STEM), as conceived originally by Crewe and coworkers, enables the highly efficient and flexible collection of different elastic and inelastic signals resulting from the interaction of a focused probe of incident electrons with a specimen. In the present paper we provide a brief review for how the STEM today can be applied towards a range of different problems in the biological sciences, emphasizing four main areas of application. (1) For three decades, the most widely used STEM technique has been the mass determination of proteins and other macromolecular assemblies. Such measurements can be performed at low electron dose by collecting the high-angle dark-field signal using an annular detector. STEM mass mapping has proven valuable for characterizing large protein assemblies such as filamentous proteins with a well-defined mass per length. (2) The annular dark-field signal can also be used to image ultrasmall, functionalized nanoparticles of heavy atoms for labeling specific aminoacid sequences in protein assemblies. (3) By acquiring electron energy loss spectra (EELS) at each pixel in a hyperspectral image, it is possible to map the distributions of specific bound elements like phosphorus, calcium and iron in isolated macromolecular assemblies or in compartments within sectioned cells. Near single atom sensitivity is feasible provided that the specimen can tolerate a very high incident electron dose. (4) Electron tomography is a new application of STEM that enables three-dimensional reconstruction of micrometer-thick sections of cells. In this technique a probe of small convergence angle gives a large depth of field throughout the thickness of the specimen while maintaining a probe diameter of < 2 nm; and the use of an on-axis bright-field detector reduces the effects of beam broadening and thus improves the spatial resolution compared to that attainable by STEM dark-field tomography. PMID:22749213

Towards atomically precise manipulation of 2D nanostructures in the electron microscope

NASA Astrophysics Data System (ADS)

Susi, Toma; Kepaptsoglou, Demie; Lin, Yung-Chang; Ramasse, Quentin M.; Meyer, Jannik C.; Suenaga, Kazu; Kotakoski, Jani

2017-12-01

Despite decades of research, the ultimate goal of nanotechnology—top-down manipulation of individual atoms—has been directly achieved with only one technique: scanning probe microscopy. In this review, we demonstrate that scanning transmission electron microscopy (STEM) is emerging as an alternative method for the direct assembly of nanostructures, with possible applications in plasmonics, quantum technologies, and materials science. Atomically precise manipulation with STEM relies on recent advances in instrumentation that have enabled non-destructive atomic-resolution imaging at lower electron energies. While momentum transfer from highly energetic electrons often leads to atom ejection, interesting dynamics can be induced when the transferable kinetic energies are comparable to bond strengths in the material. Operating in this regime, very recent experiments have revealed the potential for single-atom manipulation using the Ångström-sized electron beam. To truly enable control, however, it is vital to understand the relevant atomic-scale phenomena through accurate dynamical simulations. Although excellent agreement between experiment and theory for the specific case of atomic displacements from graphene has been recently achieved using density functional theory molecular dynamics, in many other cases quantitative accuracy remains a challenge. We provide a comprehensive reanalysis of available experimental data on beam-driven dynamics in light of the state-of-the-art in simulations, and identify important targets for improvement. Overall, the modern electron microscope has great potential to become an atom-scale fabrication platform, especially for covalently bonded 2D nanostructures. We review the developments that have made this possible, argue that graphene is an ideal starting material, and assess the main challenges moving forward.

Microscopic and UPLC-UV-MS analyses of authentic and commercial yohimbe (Pausinystalia johimbe) bark samples.

PubMed

Raman, Vijayasankar; Avula, Bharathi; Galal, Ahmed M; Wang, Yan-Hong; Khan, Ikhlas A

2013-01-01

Yohimbine is the major alkaloid found in the stem bark of yohimbe, Pausinystalia johimbe (Rubiaceae), an evergreen tree native to Africa. The objectives of the current study were to provide a detailed anatomy of yohimbe bark, as well as to determine the quantity of yohimbine in the raw yohimbe products sold online. Twelve commercial raw materials of yohimbe were analyzed by microscopic and ultra performance liquid chromatography-UV-MS methods. The study revealed that three samples were probably adulterated and four other samples contained various levels of impurities. Yohimbine was not detected in one sample, whereas its presence in other samples was found to be in the range 0.1-0.91%. The present work also provides a detailed anatomy of the stem bark of yohimbe, with light and scanning electron microscopy images, for proper identification and authentication.

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

Zhu, Yuanyuan; Munro, Catherine J.; Olszta, Matthew J.

In this work, we showcase that through precise control of the electron dose rate, state-of-the-art large solid angle energy dispersive X-ray spectroscopy (EDS) mapping in aberration-corrected scanning transmission electron microscope (STEM) is capable of faithful and unambiguous chemical characterization of the Pt and Pd distribution in a peptide-mediated nanosystem. This low-dose-rate recording scheme adds another dimension of flexibility to the design of elemental mapping experiments, and holds significant potential for extending its application to a wide variety of beam sensitive hybrid nanostructures.

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.

Understanding catalyst behavior during in situ heating through simultaneous secondary and transmitted electron imaging.

PubMed

Howe, Jane Y; Allard, Lawrence F; Bigelow, Wilbur C; Demers, Hendrix; Overbury, Steven H

2014-01-01

By coupling techniques of simultaneous secondary (SE) and transmitted electron (TE) imaging at high resolution in a modern scanning transmission electron microscope (STEM), with the ability to heat specimens using a highly stable MEMS-based heating platform, we obtained synergistic information to clarify the behavior of catalysts during in situ thermal treatments. Au/iron oxide catalyst 'leached' to remove surface Au was heated to temperatures as high as 700°C. The Fe2O3 support particle structure tended to reduce to Fe3O4 and formed surface terraces; the formation, coalescence, and mobility of 1- to 2-nm particles on the terraces were characterized in SE, STEM-ADF, and TEM-BF modes. If combined with simultaneous nanoprobe spectroscopy, this approach will open the door to a new way of studying the kinetics of nano-scaled phenomena.

Understanding catalyst behavior during in situ heating through simultaneous secondary and transmitted electron imaging

NASA Astrophysics Data System (ADS)

Howe, Jane Y.; Allard, Lawrence F.; Bigelow, Wilbur C.; Demers, Hendrix; Overbury, Steven H.

2014-11-01

By coupling techniques of simultaneous secondary (SE) and transmitted electron (TE) imaging at high resolution in a modern scanning transmission electron microscope (STEM), with the ability to heat specimens using a highly stable MEMS-based heating platform, we obtained synergistic information to clarify the behavior of catalysts during in situ thermal treatments. Au/iron oxide catalyst 'leached' to remove surface Au was heated to temperatures as high as 700°C. The Fe2O3 support particle structure tended to reduce to Fe3O4 and formed surface terraces; the formation, coalescence, and mobility of 1- to 2-nm particles on the terraces were characterized in SE, STEM-ADF, and TEM-BF modes. If combined with simultaneous nanoprobe spectroscopy, this approach will open the door to a new way of studying the kinetics of nano-scaled phenomena.

Gaining Control over Radiolytic Synthesis of Uniform Sub-3-nanometer Palladium Nanoparticles: Use of Aromatic Liquids in the Electron Microscope

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

Abellan Baeza, Patricia; Parent, Lucas R.; Al Hasan, Naila M.

2016-01-07

Synthesizing nanomaterials of uniform shape and size is of critical importance to access and manipulate the novel structure-property relationships arising at the nanoscale. In this work we synthesize Pd nanoparticles with well-controlled size using in situ liquid-stage scanning transmission electron microscopy (STEM) and demonstrate a match between the reaction kinetics and products of the radiolytic and chemical syntheses of size-stabilized Pd nanoparticles. We quantify the effect of electron dose on the nucleation kinetics, and compare these results with in situ small angle X-ray scattering (SAXS) experiments investigating the effect of temperature during chemical synthesis. This work introduces methods for precisemore » control of nanoparticle synthesis in the STEM and provides a means to uncover the fundamental processes behind the size and shape stabilization of nanoparticles.« 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.

Nanoscale structural and electronic characterization of α-RuCl3 layered compound

NASA Astrophysics Data System (ADS)

Ziatdinov, Maxim; Maksov, Artem; Banerjee, Arnab; Zhou, Wu; Berlijn, Tom; Yan, Jiaqiang; Nagler, Stephen; Mandrus, David; Baddorf, Arthur; Kalinin, Sergei

The exceptional interplay of spin-orbit effects, Coulomb interaction, and electron-lattice coupling is expected to produce an elaborate phase space of α-RuCl3 layered compound, which to date remains largely unexplored. Here we employ a combination of scanning transmission electron microscopy (STEM) and scanning tunneling microscopy (STM) for detailed evaluation of the system's microscopic structural and electronic orders with a sub-nanometer precision. The STM and STEM measurements are further supported by neutron scattering, X-Ray diffraction, density functional theory (DFT), and multivariate statistical analysis. Our results show a trigonal distortion of Cl octahedral ligand cage along the C3 symmetry axes in each RuCl3 layer. The lattice distortion is limited mainly to the Cl subsystem leaving the Ru honeycomb lattice nearly intact. The STM topographic and spectroscopic characterization reveals an intra unit cell electronic symmetry breaking in a spin-orbit coupled Mott insulating phase on the Cl-terminated surface of α-RuCl3. The associated long-range charge order (CO) pattern is linked to a surface component of Cl cage distortion. We finally discuss a fine structure of CO and its potential relation to variations of average unit cell geometries found in multivariate analysis of STEM data. The research was sponsored by the U.S. Department of Energy.

Weak-beam scanning transmission electron microscopy for quantitative dislocation density measurement in steels.

PubMed

Yoshida, Kenta; Shimodaira, Masaki; Toyama, Takeshi; Shimizu, Yasuo; Inoue, Koji; Yoshiie, Toshimasa; Milan, Konstantinovic J; Gerard, Robert; Nagai, Yasuyoshi

2017-04-01

To evaluate dislocations induced by neutron irradiation, we developed a weak-beam scanning transmission electron microscopy (WB-STEM) system by installing a novel beam selector, an annular detector, a high-speed CCD camera and an imaging filter in the camera chamber of a spherical aberration-corrected transmission electron microscope. The capabilities of the WB-STEM with respect to wide-view imaging, real-time diffraction monitoring and multi-contrast imaging are demonstrated using typical reactor pressure vessel steel that had been used in an European nuclear reactor for 30 years as a surveillance test piece with a fluence of 1.09 × 1020 neutrons cm-2. The quantitatively measured size distribution (average loop size = 3.6 ± 2.1 nm), number density of the dislocation loops (3.6 × 1022 m-3) and dislocation density (7.8 × 1013 m m-3) were carefully compared with the values obtained via conventional weak-beam transmission electron microscopy studies. In addition, cluster analysis using atom probe tomography (APT) further demonstrated the potential of the WB-STEM for correlative electron tomography/APT experiments. © 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.

Quantitative comparison of simulated and measured signals in the STEM mode of a SEM

NASA Astrophysics Data System (ADS)

Walker, C. G. H.; Konvalina, I.; Mika, F.; Frank, L.; Müllerová, I.

2018-01-01

The transmission of electrons with energies 15 keV and 30 keV through Si and Au films of 100 nm thickness each have been studied in a Scanning Transmission Electron Microscope. The electrons that were transmitted through the films were detected using a multi-annular photo-detector consisting of a central Bright Field (BF) and several Dark Field (DF) detectors. For the experiment the detector was gradually offset from the axis and the signal from the central BF detector was studied as a function of the offset distance and compared with MC simulations. The experiment showed better agreement between experiment and several different MC simulations as compared to previous results, but differences were still found particularly for low angle scattering from Si. Data from Au suggest that high energy secondary electrons contribute to the signal on the central BF detector for low primary beam energies, when the STEM detector is in its usual central position.

A short story of imaging and spectroscopy of two-dimensional materials by scanning transmission electron microscopy.

PubMed

Idrobo, Juan C; Zhou, Wu

2017-09-01

Here we present a short historical account of when single adatom impurities where first identified in two-dimensional materials by scanning transmission electron microscopy (STEM). We also present a study of the graphene low-loss (below 50eV) response as a function of number of layers using electron energy-loss spectroscopy (EELS). The study shows that as few as three layers of graphene behave as bulk graphite for losses above 10eV We also show examples of how point and extended defects can easily be resolved and structural dynamics can be readily capture by using aberration-corrected STEM imaging. Finally, we show that the new generation of monochromators has opened up possibilities to explore new physics with an electron microscope. All these capabilities were enabled by the development of spherical aberration correctors and monochromators, where Ondrej Krivanek has played a key role. Copyright © 2017. Published by Elsevier B.V.

Precision controlled atomic resolution scanning transmission electron microscopy using spiral scan pathways

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

Sang, Xiahan; Lupini, Andrew R.; Ding, Jilai

Atomic-resolution imaging in an aberration-corrected scanning transmission electron microscope (STEM) can enable direct correlation between atomic structure and materials functionality. The fast and precise control of the STEM probe is, however, challenging because the true beam location deviates from the assigned location depending on the properties of the deflectors. To reduce these deviations, i.e. image distortions, we use spiral scanning paths, allowing precise control of a sub-Å sized electron probe within an aberration-corrected STEM. Although spiral scanning avoids the sudden changes in the beam location (fly-back distortion) present in conventional raster scans, it is not distortion-free. “Archimedean” spirals, with amore » constant angular frequency within each scan, are used to determine the characteristic response at different frequencies. We then show that such characteristic functions can be used to correct image distortions present in more complicated constant linear velocity spirals, where the frequency varies within each scan. Through the combined application of constant linear velocity scanning and beam path corrections, spiral scan images are shown to exhibit less scan distortion than conventional raster scan images. The methodology presented here will be useful for in situ STEM imaging at higher temporal resolution and for imaging beam sensitive materials.« less

Precision controlled atomic resolution scanning transmission electron microscopy using spiral scan pathways

DOE PAGES

Sang, Xiahan; Lupini, Andrew R.; Ding, Jilai; ...

2017-03-08

Atomic-resolution imaging in an aberration-corrected scanning transmission electron microscope (STEM) can enable direct correlation between atomic structure and materials functionality. The fast and precise control of the STEM probe is, however, challenging because the true beam location deviates from the assigned location depending on the properties of the deflectors. To reduce these deviations, i.e. image distortions, we use spiral scanning paths, allowing precise control of a sub-Å sized electron probe within an aberration-corrected STEM. Although spiral scanning avoids the sudden changes in the beam location (fly-back distortion) present in conventional raster scans, it is not distortion-free. “Archimedean” spirals, with amore » constant angular frequency within each scan, are used to determine the characteristic response at different frequencies. We then show that such characteristic functions can be used to correct image distortions present in more complicated constant linear velocity spirals, where the frequency varies within each scan. Through the combined application of constant linear velocity scanning and beam path corrections, spiral scan images are shown to exhibit less scan distortion than conventional raster scan images. The methodology presented here will be useful for in situ STEM imaging at higher temporal resolution and for imaging beam sensitive materials.« less

Isolation, electron microscopic imaging, and 3-D visualization of native cardiac thin myofilaments.

PubMed

Spiess, M; Steinmetz, M O; Mandinova, A; Wolpensinger, B; Aebi, U; Atar, D

1999-06-15

An increasing number of cardiac diseases are currently pinpointed to reside at the level of the thin myofilaments (e.g., cardiomyopathies, reperfusion injury). Hence the aim of our study was to develop a new method for the isolation of mammalian thin myofilaments suitable for subsequent high-resolution electron microscopic imaging. Native cardiac thin myofilaments were extracted from glycerinated porcine myocardial tissue in the presence of protease inhibitors. Separation of thick and thin myofilaments was achieved by addition of ATP and several centrifugation steps. Negative staining and subsequent conventional and scanning transmission electron microscopy (STEM) of thin myofilaments permitted visualization of molecular details; unlike conventional preparations of thin myofilaments, our method reveals the F-actin moiety and allows direct recognition of thin myofilament-associated porcine cardiac troponin complexes. They appear as "bulges" at regular intervals of approximately 36 nm along the actin filaments. Protein analysis using SDS-polyacrylamide gel electrophoresis revealed that only approximately 20% troponin I was lost during the isolation procedure. In a further step, 3-D helical reconstructions were calculated using STEM dark-field images. These 3-D reconstructions will allow further characterization of molecular details, and they will be useful for directly visualizing molecular alterations related to diseased cardiac thin myofilaments (e.g., reperfusion injury, alterations of Ca2+-mediated tropomyosin switch). Copyright 1999 Academic Press.

Three-dimensional bright-field scanning transmission electron microscopy elucidate novel nanostructure in microbial biofilms.

PubMed

Hickey, William J; Shetty, Ameesha R; Massey, Randall J; Toso, Daniel B; Austin, Jotham

2017-01-01

Bacterial biofilms play key roles in environmental and biomedical processes, and understanding their activities requires comprehension of their nanoarchitectural characteristics. Electron microscopy (EM) is an essential tool for nanostructural analysis, but conventional EM methods are limited in that they either provide topographical information alone, or are suitable for imaging only relatively thin (<300 nm) sample volumes. For biofilm investigations, these are significant restrictions. Understanding structural relations between cells requires imaging of a sample volume sufficiently large to encompass multiple cells and the capture of both external and internal details of cell structure. An emerging EM technique with such capabilities is bright-field scanning transmission electron microscopy (BF-STEM) and in the present report BF-STEM was coupled with tomography to elucidate nanostructure in biofilms formed by the polycyclic aromatic hydrocarbon-degrading soil bacterium, Delftia acidovorans Cs1-4. Dual-axis BF-STEM enabled high-resolution 3-D tomographic recontructions (6-10 nm) visualization of thick (1250 and 1500 nm) sections. The 3-D data revealed that novel extracellular structures, termed nanopods, were polymorphic and formed complex networks within cell clusters. BF-STEM tomography enabled visualization of conduits formed by nanopods that could enable intercellular movement of outer membrane vesicles, and thereby enable direct communication between cells. This report is the first to document application of dual-axis BF-STEM tomography to obtain high-resolution 3-D images of novel nanostructures in bacterial biofilms. Future work with dual-axis BF-STEM tomography combined with correlative light electron microscopy may provide deeper insights into physiological functions associated with nanopods as well as other nanostructures. © 2016 The Authors Journal of Microscopy © 2016 Royal Microscopical Society.

Atomic scale structure and chemistry of interfaces by Z-contrast imaging and electron energy loss spectroscopy in the STEM

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

McGibbon, M.M.; Browning, N.D.; Chisholm, M.F.

The macroscopic properties of many materials are controlled by the structure and chemistry at the grain boundaries. A basic understanding of the structure-property relationship requires a technique which probes both composition and chemical bonding on an atomic scale. The high-resolution Z-contrast imaging technique in the scanning transmission electron microscope (STEM) forms an incoherent image in which changes in atomic structure and composition can be interpreted intuitively. This direct image allows the electron probe to be positioned over individual atomic columns for parallel detection electron energy loss spectroscopy (PEELS) at a spatial resolution approaching 0.22nm. The bonding information which can bemore » obtained from the fine structure within the PEELS edges can then be used in conjunction with the Z-contrast images to determine the structure at the grain boundary. In this paper we present 3 examples of correlations between the structural, chemical and electronic properties at materials interfaces in metal-semiconductor systems, superconducting and ferroelectric materials.« less

Efficient creation of electron vortex beams for high resolution STEM imaging.

PubMed

Béché, A; Juchtmans, R; Verbeeck, J

2017-07-01

The recent discovery of electron vortex beams carrying quantised angular momentum in the TEM has led to an active field of research, exploring a variety of potential applications including the possibility of mapping magnetic states at the atomic scale. A prerequisite for this is the availability of atomic sized electron vortex beams at high beam current and mode purity. In this paper we present recent progress showing that by making use of the Aharonov-Bohm effect near the tip of a long single domain ferromagnetic Nickel needle, a very efficient aperture for the production of electron vortex beams can be realised. The aperture transmits more than 99% of all electrons and provides a vortex mode purity of up to 92%. Placing this aperture in the condenser plane of a state of the art Cs corrected microscope allows us to demonstrate atomic resolution HAADF STEM images with spatial resolution better than 1 Angström, in agreement with theoretical expectations and only slightly inferior to the performance of a non-vortex probe on the same instrument. Copyright © 2016 Elsevier B.V. All rights reserved.

STEMsalabim: A high-performance computing cluster friendly code for scanning transmission electron microscopy image simulations of thin specimens.

PubMed

Oelerich, Jan Oliver; Duschek, Lennart; Belz, Jürgen; Beyer, Andreas; Baranovskii, Sergei D; Volz, Kerstin

2017-06-01

We present a new multislice code for the computer simulation of scanning transmission electron microscope (STEM) images based on the frozen lattice approximation. Unlike existing software packages, the code is optimized to perform well on highly parallelized computing clusters, combining distributed and shared memory architectures. This enables efficient calculation of large lateral scanning areas of the specimen within the frozen lattice approximation and fine-grained sweeps of parameter space. Copyright © 2017 Elsevier B.V. All rights reserved.

Analysis of Local Structure, Chemistry and Bonding by Electron Energy Loss Spectroscopy

NASA Astrophysics Data System (ADS)

Mayer, Joachim

In the present chapter, the reader will first be introduced briefly to the basic principles of analytical transmission electron microscopy (ATEM) with special emphasis on electron energy-loss spectroscopy (EELS) and energy-filtering TEM. The quantification of spectra to obtain chemical information and the origin and interpretation of near-edge fine structures in EELS (ELNES) are discussed. Special attention will be given to the characterization of internal interfaces and the literature in this area will be reviewed. Selected examples of the application of ATEM in the investigation of internal interfaces will be given. These examples include both EELS in the energy-filtering TEM and in the scanning transmission electron microscope (STEM).

Tissue-specific stem cells: Lessons from the skeletal muscle satellite cell

PubMed Central

Brack, Andrew S.; Rando, Thomas A.

2012-01-01

In 1961, the satellite cell was first identified when electron microscopic examination of skeletal muscle demonstrated a cell wedged between the plasma membrane of the muscle fiber and the basement membrane. In recent years it has been conclusively demonstrated that the satellite cell is the primary cellular source for muscle regeneration and is equipped with the potential to self renew, thus functioning as a bone fide skeletal muscle stem cell (MuSC). As we move past the 50th anniversary of the satellite cell, we take this opportunity to discuss the current state of the art and dissect the unknowns in the MuSC field. PMID:22560074

High-resolution monochromated electron energy-loss spectroscopy of organic photovoltaic materials.

PubMed

Alexander, Jessica A; Scheltens, Frank J; Drummy, Lawrence F; Durstock, Michael F; Hage, Fredrik S; Ramasse, Quentin M; McComb, David W

2017-09-01

Advances in electron monochromator technology are providing opportunities for high energy resolution (10 - 200meV) electron energy-loss spectroscopy (EELS) to be performed in the scanning transmission electron microscope (STEM). The energy-loss near-edge structure in core-loss spectroscopy is often limited by core-hole lifetimes rather than the energy spread of the incident illumination. However, in the valence-loss region, the reduced width of the zero loss peak makes it possible to resolve clearly and unambiguously spectral features at very low energy-losses (<3eV). In this contribution, high-resolution EELS was used to investigate four materials commonly used in organic photovoltaics (OPVs): poly(3-hexlythiophene) (P3HT), [6,6] phenyl-C 61 butyric acid methyl ester (PCBM), copper phthalocyanine (CuPc), and fullerene (C 60 ). Data was collected on two different monochromated instruments - a Nion UltraSTEM 100 MC 'HERMES' and a FEI Titan 3 60-300 Image-Corrected S/TEM - using energy resolutions (as defined by the zero loss peak full-width at half-maximum) of 35meV and 175meV, respectively. The data was acquired to allow deconvolution of plural scattering, and Kramers-Kronig analysis was utilized to extract the complex dielectric functions. The real and imaginary parts of the complex dielectric functions obtained from the two instruments were compared to evaluate if the enhanced resolution in the Nion provides new opto-electronic information for these organic materials. The differences between the spectra are discussed, and the implications for STEM-EELS studies of advanced materials are considered. Copyright © 2017 Elsevier B.V. All rights reserved.

Inexpensive read-out for coincident electron spectroscopy with a transmission electron microscope at nanometer scale using micro channel plates and multistrip anodes

NASA Astrophysics Data System (ADS)

Hollander, R. W.; Bom, V. R.; van Eijk, C. W. E.; Faber, J. S.; Hoevers, H.; Kruit, P.

1994-09-01

The elemental composition of a sample at nanometer scale is determined by measurement of the characteristic energy of Auger electrons, emitted in coincidence with incoming primary electrons from a microbeam in a scanning transmission electron microscope (STEM). Single electrons are detected with position sensitive detectors, consisting of MicroChannel Plates (MCP) and MultiStrip Anodes (MSA), one for the energy of the Auger electrons (Auger-detector) and one for the energy loss of primary electrons (EELS-detector). The MSAs are sensed with LeCroy 2735DC preamplifiers. The fast readout is based on LeCroy's PCOS III system. On the detection of a coincidence (Event) energy data of Auger and EELS are combined with timing data to an Event word. Event words are stored in list mode in a VME memory module. Blocks of Event words are scanned by transputers in VME and two-dimensional energy histograms are filled using the timing information to obtain a maximal true/accidental ratio. The resulting histograms are stored on disk of a PC-386, which also controls data taking. The system is designed to handle 10 5 Events per second, 90% of which are accidental. In the histograms the "true" to "accidental" ratio will be 5. The dead time is 15%.

Cold-stage microscopy system for fast-frozen liquids.

PubMed

Talmon, Y; Davis, H T; Scriven, L E; Thomas, E L

1979-06-01

The least artifact-laden fixation technique for examining colloidal suspensions, microemulsions, and other microstructured liquids in the electron microscope appears to be thermal fixation, i.e., ultrafast freezing of the liquid specimen. For rapid-enough cooling and for observation in TEM/STEM a thin sample is needed. The need is met by trapping a thin layer ( approximately 100 nm) of liquid between two polyimide films ( approximately 40 nm thickness) mounted on copper grids and immersing the resulting sandwich in liquid nitrogen at its melting point. For liquids containing water, polyimides films are used since this polymer is far less susceptible to the electron beam damage observed for the commonly used polymer films such as Formvar and collodion in contact with ice. Transfer of the frozen sample into the microscope column without deleterious frost deposition and warming is accomplished with a new transfer module for the cooling stage of the JEOL JEM-100CX microscope, which makes a true cold stage out of a device originally intended for cooling specimens inside the column. Sample results obtained with the new fast-freeze, cold-stage microscopy system are given.

Development of SEM/STEM-WDX for highly sensitive detection of light elements

NASA Astrophysics Data System (ADS)

Anan, Y.; Koguchi, M.; Kimura, T.; Sekiguchi, T.

2018-02-01

In this study, to detect the light element lithium (Li) and to detect low dosed Boron (B) in the local area at nm order, we developed an analytical electron microscope equipped with an improved serial (S)-type WDX (wavelength dispersive X-ray spectroscopy) system. In detail, to detect Li, we developed a high-conductivity multi-capillary X-ray (MCX) lens, and a diffractor with a lattice spacing (d) of 15 nm, and with a spacing variation (δ d) of 0.8 nm. Moreover, to detect low dosed light element B, we designed a high-conductivity MCX lens based on the soft X-ray reflectivity in the capillary and calculation. We developed a large-solid-angle MCX lens whose conductivity of the characteristic X-rays of B became 20 times higher than that of an MCX lens with a 30-mm focal length. Our developed analytical electron microscope was applied to a LiAl specimen and a low B-doped Si substrate specimen, and the performance of this analytical electron microscope was evaluated. As a results, this analytical electron microscope could detect the characteristic X-rays of Li with a minimum mass fraction (MMF) of 8.4 atomic % (at. %). The energy resolution was 1 eV at 55 eV. From the results of measuring the line profile of B for the unpatterned B-implantation area on a B-doped Si substrate specimen, the measured line profile data were in good agreement with secondary ion mass spectrometry data up to a depth of 100 nm with a B concentration of 0.05 at. %.

Real-space localization and quantification of hole distribution in chain-ladder Sr3Ca11Cu24O41 superconductor.

PubMed

Bugnet, Matthieu; Löffler, Stefan; Hawthorn, David; Dabkowska, Hanna A; Luke, Graeme M; Schattschneider, Peter; Sawatzky, George A; Radtke, Guillaume; Botton, Gianluigi A

2016-03-01

Understanding the physical properties of the chain-ladder Sr3Ca11Cu24O41 hole-doped superconductor has been precluded by the unknown hole distribution among chains and ladders. We use electron energy-loss spectrometry (EELS) in a scanning transmission electron microscope (STEM) at atomic resolution to directly separate the contributions of chains and ladders and to unravel the hole distribution from the atomic scale variations of the O-K near-edge structures. The experimental data unambiguously demonstrate that most of the holes lie within the chain layers. A quantitative interpretation supported by inelastic scattering calculations shows that about two holes are located in the ladders, and about four holes in the chains, shedding light on the electronic structure of Sr3Ca11Cu24O41. Combined atomic resolution STEM-EELS and inelastic scattering calculations is demonstrated as a powerful approach toward a quantitative understanding of the electronic structure of cuprate superconductors, offering new possibilities for elucidating their physical properties.

Studying Dynamic Processes of Nano-sized Objects in Liquid using Scanning Transmission Electron Microscopy.

PubMed

Hermannsdörfer, Justus; de Jonge, Niels

2017-02-05

Samples fully embedded in liquid can be studied at a nanoscale spatial resolution with Scanning Transmission Electron Microscopy (STEM) using a microfluidic chamber assembled in the specimen holder for Transmission Electron Microscopy (TEM) and STEM. The microfluidic system consists of two silicon microchips supporting thin Silicon Nitride (SiN) membrane windows. This article describes the basic steps of sample loading and data acquisition. Most important of all is to ensure that the liquid compartment is correctly assembled, thus providing a thin liquid layer and a vacuum seal. This protocol also includes a number of tests necessary to perform during sample loading in order to ensure correct assembly. Once the sample is loaded in the electron microscope, the liquid thickness needs to be measured. Incorrect assembly may result in a too-thick liquid, while a too-thin liquid may indicate the absence of liquid, such as when a bubble is formed. Finally, the protocol explains how images are taken and how dynamic processes can be studied. A sample containing AuNPs is imaged both in pure water and in saline.

Studying Dynamic Processes of Nano-sized Objects in Liquid using Scanning Transmission Electron Microscopy

PubMed Central

Hermannsdörfer, Justus; de Jonge, Niels

2017-01-01

Samples fully embedded in liquid can be studied at a nanoscale spatial resolution with Scanning Transmission Electron Microscopy (STEM) using a microfluidic chamber assembled in the specimen holder for Transmission Electron Microscopy (TEM) and STEM. The microfluidic system consists of two silicon microchips supporting thin Silicon Nitride (SiN) membrane windows. This article describes the basic steps of sample loading and data acquisition. Most important of all is to ensure that the liquid compartment is correctly assembled, thus providing a thin liquid layer and a vacuum seal. This protocol also includes a number of tests necessary to perform during sample loading in order to ensure correct assembly. Once the sample is loaded in the electron microscope, the liquid thickness needs to be measured. Incorrect assembly may result in a too-thick liquid, while a too-thin liquid may indicate the absence of liquid, such as when a bubble is formed. Finally, the protocol explains how images are taken and how dynamic processes can be studied. A sample containing AuNPs is imaged both in pure water and in saline. PMID:28190028

Phosphorus detection in vitrified bacteria by cryo-STEM annular dark-field analysis.

PubMed

Wolf, Sharon Grayer; Rez, Peter; Elbaum, Michael

2015-11-01

Bacterial cells often contain dense granules. Among these, polyphosphate bodies (PPBs) store inorganic phosphate for a variety of essential functions. Identification of PPBs has until now been accomplished by analytical methods that required drying or chemically fixing the cells. These methods entail large electron doses that are incompatible with low-dose imaging of cryogenic specimens. We show here that Scanning Transmission Electron Microscopy (STEM) of fully hydrated, intact, vitrified bacteria provides a simple means for mapping of phosphorus-containing dense granules based on quantitative sensitivity of the electron scattering to atomic number. A coarse resolution of the scattering angles distinguishes phosphorus from the abundant lighter atoms: carbon, nitrogen and oxygen. The theoretical basis is similar to Z contrast of materials science. EDX provides a positive identification of phosphorus, but importantly, the method need not involve a more severe electron dose than that required for imaging. The approach should prove useful in general for mapping of heavy elements in cryopreserved specimens when the element identity is known from the biological context. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

Real-space localization and quantification of hole distribution in chain-ladder Sr3Ca11Cu24O41 superconductor

PubMed Central

Bugnet, Matthieu; Löffler, Stefan; Hawthorn, David; Dabkowska, Hanna A.; Luke, Graeme M.; Schattschneider, Peter; Sawatzky, George A.; Radtke, Guillaume; Botton, Gianluigi A.

2016-01-01

Understanding the physical properties of the chain-ladder Sr3Ca11Cu24O41 hole-doped superconductor has been precluded by the unknown hole distribution among chains and ladders. We use electron energy-loss spectrometry (EELS) in a scanning transmission electron microscope (STEM) at atomic resolution to directly separate the contributions of chains and ladders and to unravel the hole distribution from the atomic scale variations of the O-K near-edge structures. The experimental data unambiguously demonstrate that most of the holes lie within the chain layers. A quantitative interpretation supported by inelastic scattering calculations shows that about two holes are located in the ladders, and about four holes in the chains, shedding light on the electronic structure of Sr3Ca11Cu24O41. Combined atomic resolution STEM-EELS and inelastic scattering calculations is demonstrated as a powerful approach toward a quantitative understanding of the electronic structure of cuprate superconductors, offering new possibilities for elucidating their physical properties. PMID:27051872

STEM-HAADF electron microscopy analysis of the central dark line defect of human tooth enamel crystallites.

PubMed

Gasga, Jose Reyes; Carbajal-de-la-Torre, Georgina; Bres, Etienne; Gil-Chavarria, Ivet M; Rodríguez-Hernández, Ana G; Garcia-Garcia, Ramiro

2008-02-01

When human tooth enamel is observed with the Transmission Electron Microscope (TEM), a structural defect is registered in the central region of their nanometric grains or crystallites. This defect has been named as Central Dark Line (CDL) and its structure and function in the enamel structure have been unknown yet. In this work we present the TEM analysis to these crystallites using the High Angle Annular Dark Field (HAADF) technique. Our results suggest that the CDL region is the calcium richest part of the human tooth enamel crystallites.

Atomic scale structure and chemistry of interfaces by Z-contrast imaging and electron energy loss spectroscopy in the stem

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

McGibbon, M.M.; Browning, N.D.; Chisholm, M.F.

The macroscopic properties of many materials are controlled by the structure and chemistry at grain boundaries. A basic understanding of the structure-property relationship requires a technique which probes both composition and chemical bonding on an atomic scale. High-resolution Z-contrast imaging in the scanning transmission electron microscope (STEM) forms an incoherent image in which changes in atomic structure and composition across an interface can be interpreted directly without the need for preconceived atomic structure models. Since the Z-contrast image is formed by electrons scattered through high angles, parallel detection electron energy loss spectroscopy (PEELS) can be used simultaneously to provide complementarymore » chemical information on an atomic scale. The fine structure in the PEEL spectra can be used to investigate the local electronic structure and the nature of the bonding across the interface. In this paper we use the complimentary techniques of high resolution Z-contrast imaging and PEELS to investigate the atomic structure and chemistry of a 25{degree} symmetric tilt boundary in a bicrystal of the electroceramic SrTiO{sub 3}.« less

Single atom visibility in STEM optical depth sectioning

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

Ishikawa, Ryo; Pennycook, Stephen J.; Lupini, Andrew R.

The continuing development of aberration correctors for the scanning transmission electron microscope (STEM) offers the possibility of locating single atoms in crystals in 3D via optical depth sectioning. The main factors that determine the feasibility of such an approach are visibility and dose requirements. In this paper, we show how Poisson's statistics can be quantitatively incorporated into STEM image simulations and demonstrate that the 3D location of single cerium atoms in wurtzite-type aluminum nitride is indeed feasible under large-angle illumination conditions with a relatively low dose. We also show that chromatic aberration does not presently represent a limitation provided amore » cold field emission source is used. Finally, these results suggest efforts into improved aberration corrector designs for larger illumination angles that offer significant potential for 3D structure determination of materials.« less

Distribution of coniferin in freeze-fixed stem of Ginkgo biloba L. by cryo-TOF-SIMS/SEM

NASA Astrophysics Data System (ADS)

Aoki, Dan; Hanaya, Yuto; Akita, Takuya; Matsushita, Yasuyuki; Yoshida, Masato; Kuroda, Katsushi; Yagami, Sachie; Takama, Ruka; Fukushima, Kazuhiko

2016-08-01

To clarify the role of coniferin in planta, semi-quantitative cellular distribution of coniferin in quick-frozen Ginkgo biloba L. (ginkgo) was visualized by cryo time-of-flight secondary ion mass spectrometry and scanning electron microscopy (cryo-TOF-SIMS/SEM) analysis. The amount and rough distribution of coniferin were confirmed through quantitative chromatography measurement using serial tangential sections of the freeze-fixed ginkgo stem. The lignification stage of the sample was estimated using microscopic observations. Coniferin distribution visualized at the transverse and radial surfaces of freeze-fixed ginkgo stem suggested that coniferin is stored in the vacuoles, and showed good agreement with the assimilation timing of coniferin to lignin in differentiating xylem. Consequently, it is suggested that coniferin is stored in the tracheid cells of differentiating xylem and is a lignin precursor.

Single atom visibility in STEM optical depth sectioning

DOE PAGES

Ishikawa, Ryo; Pennycook, Stephen J.; Lupini, Andrew R.; ...

2016-10-19

The continuing development of aberration correctors for the scanning transmission electron microscope (STEM) offers the possibility of locating single atoms in crystals in 3D via optical depth sectioning. The main factors that determine the feasibility of such an approach are visibility and dose requirements. In this paper, we show how Poisson's statistics can be quantitatively incorporated into STEM image simulations and demonstrate that the 3D location of single cerium atoms in wurtzite-type aluminum nitride is indeed feasible under large-angle illumination conditions with a relatively low dose. We also show that chromatic aberration does not presently represent a limitation provided amore » cold field emission source is used. Finally, these results suggest efforts into improved aberration corrector designs for larger illumination angles that offer significant potential for 3D structure determination of materials.« less

Site-Specific Preparation of Intact Solid–Liquid Interfaces by Label-Free In Situ Localization and Cryo-Focused Ion Beam Lift-Out

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

Zachman, Michael J.; Asenath-Smith, Emily; Estroff, Lara A.

Abstract Scanning transmission electron microscopy (STEM) allows atomic scale characterization of solid–solid interfaces, but has seen limited applications to solid–liquid interfaces due to the volatility of liquids in the microscope vacuum. Although cryo-electron microscopy is routinely used to characterize hydrated samples stabilized by rapid freezing, sample thinning is required to access the internal interfaces of thicker specimens. Here, we adapt cryo-focused ion beam (FIB) “lift-out,” a technique recently developed for biological specimens, to prepare intact internal solid–liquid interfaces for high-resolution structural and chemical analysis by cryo-STEM. To guide the milling process we introduce a label-freein situmethod of localizing subsurface structuresmore » in suitable materials by energy dispersive X-ray spectroscopy (EDX). Monte Carlo simulations are performed to evaluate the depth-probing capability of the technique, and show good qualitative agreement with experiment. We also detail procedures to produce homogeneously thin lamellae, which enable nanoscale structural, elemental, and chemical analysis of intact solid–liquid interfaces by analytical cryo-STEM. This work demonstrates the potential of cryo-FIB lift-out and cryo-STEM for understanding physical and chemical processes at solid–liquid interfaces.« less

Copper Decoration of Carbon Nanotubes and High Resolution Electron Microscopy

NASA Astrophysics Data System (ADS)

Probst, Camille

A new process of decorating carbon nanotubes with copper was developed for the fabrication of nanocomposite aluminum-nanotubes. The process consists of three stages: oxidation, activation and electroless copper plating on the nanotubes. The oxidation step was required to create chemical function on the nanotubes, essential for the activation step. Then, catalytic nanoparticles of tin-palladium were deposited on the tubes. Finally, during the electroless copper plating, copper particles with a size between 20 and 60 nm were uniformly deposited on the nanotubes surface. The reproducibility of the process was shown by using another type of carbon nanotube. The fabrication of nanocomposites aluminum-nanotubes was tested by aluminum vacuum infiltration. Although the infiltration of carbon nanotubes did not produce the expected results, an interesting electron microscopy sample was discovered during the process development: the activated carbon nanotubes. Secondly, scanning transmitted electron microscopy (STEM) imaging in SEM was analysed. The images were obtained with a new detector on the field emission scanning electron microscope (Hitachi S-4700). Various parameters were analysed with the use of two different samples: the activated carbon nanotubes (previously obtained) and gold-palladium nanodeposits. Influences of working distance, accelerating voltage or sample used on the spatial resolution of images obtained with SMART (Scanning Microscope Assessment and Resolution Testing) were analysed. An optimum working distance for the best spatial resolution related to the sample analysed was found for the imaging in STEM mode. Finally, relation between probe size and spatial resolution of backscattered electrons (BSE) images was studied. An image synthesis method was developed to generate the BSE images from backscattered electrons coefficients obtained with CASINO software. Spatial resolution of images was determined using SMART. The analysis shown that using a probe size smaller than the size of the observed object (sample features) does not improve the spatial resolution. In addition, the effects of the accelerating voltage, the current intensity and the sample geometry and composition were analysed.

High-sensitivity visualization of localized electric fields using low-energy electron beam deflection

NASA Astrophysics Data System (ADS)

Jeong, Samuel; Ito, Yoshikazu; Edwards, Gary; Fujita, Jun-ichi

2018-06-01

The visualization of localized electronic charges on nanocatalysts is expected to yield fundamental information about catalytic reaction mechanisms. We have developed a high-sensitivity detection technique for the visualization of localized charges on a catalyst and their corresponding electric field distribution, using a low-energy beam of 1 to 5 keV electrons and a high-sensitivity scanning transmission electron microscope (STEM) detector. The highest sensitivity for visualizing a localized electric field was ∼0.08 V/µm at a distance of ∼17 µm from a localized charge at 1 keV of the primary electron energy, and a weak local electric field produced by 200 electrons accumulated on the carbon nanotube (CNT) apex can be visualized. We also observed that Au nanoparticles distributed on a CNT forest tended to accumulate a certain amount of charges, about 150 electrons, at a ‑2 V bias.

Application of two-dimensional crystallography and image processing to atomic resolution Z-contrast images.

PubMed

Morgan, David G; Ramasse, Quentin M; Browning, Nigel D

2009-06-01

Zone axis images recorded using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM or Z-contrast imaging) reveal the atomic structure with a resolution that is defined by the probe size of the microscope. In most cases, the full images contain many sub-images of the crystal unit cell and/or interface structure. Thanks to the repetitive nature of these images, it is possible to apply standard image processing techniques that have been developed for the electron crystallography of biological macromolecules and have been used widely in other fields of electron microscopy for both organic and inorganic materials. These methods can be used to enhance the signal-to-noise present in the original images, to remove distortions in the images that arise from either the instrumentation or the specimen itself and to quantify properties of the material in ways that are difficult without such data processing. In this paper, we describe briefly the theory behind these image processing techniques and demonstrate them for aberration-corrected, high-resolution HAADF-STEM images of Si(46) clathrates developed for hydrogen storage.

Joint denoising and distortion correction of atomic scale scanning transmission electron microscopy images

NASA Astrophysics Data System (ADS)

Berkels, Benjamin; Wirth, Benedikt

2017-09-01

Nowadays, modern electron microscopes deliver images at atomic scale. The precise atomic structure encodes information about material properties. Thus, an important ingredient in the image analysis is to locate the centers of the atoms shown in micrographs as precisely as possible. Here, we consider scanning transmission electron microscopy (STEM), which acquires data in a rastering pattern, pixel by pixel. Due to this rastering combined with the magnification to atomic scale, movements of the specimen even at the nanometer scale lead to random image distortions that make precise atom localization difficult. Given a series of STEM images, we derive a Bayesian method that jointly estimates the distortion in each image and reconstructs the underlying atomic grid of the material by fitting the atom bumps with suitable bump functions. The resulting highly non-convex minimization problems are solved numerically with a trust region approach. Existence of minimizers and the model behavior for faster and faster rastering are investigated using variational techniques. The performance of the method is finally evaluated on both synthetic and real experimental data.

Electron microscopy of Drosophila garland cell nephrocytes: Optimal preparation, immunostaining and STEM tomography.

PubMed

Hochapfel, Florian; Denk, Lucia; Maaßen, Christine; Zaytseva, Yulia; Rachel, Reinhard; Witzgall, Ralph; Krahn, Michael P

2018-01-29

Due to its structural and molecular similarities to mammalian podocytes, the Drosophila nephrocyte emerged as a model system to study podocyte development and associated diseases. Similar to podocytes, nephrocytes establish a slit diaphragm between foot process-like structures in order to filter the hemolymph. One major obstacle in nephrocyte research is the distinct visualization of this subcellular structure to assess its integrity. Therefore, we developed a specialized dissection and fixation protocol, including high pressure freezing and freeze substitution techniques, to improve the preservation of the intricate ultrastructural details necessary for electron microscopic assessment. By means of scanning transmission electron microscopy (STEM) tomography, a three-dimensional dataset was generated to further understand the complex architecture of the nephrocyte channel system. Moreover, a staining protocol for immunolabeling of ultrathin sections of Epon-embedded nephrocytes is discussed, which allows the reliable detection of GFP-tagged fusion proteins combined with superior sample preservation. Due to the growing number of available GFP-trap fly lines, this approach is widely applicable for high resolution localization studies in wild type and mutant nephrocytes. © 2018 Wiley Periodicals, Inc.

In Situ Industrial Bimetallic Catalyst Characterization using Scanning Transmission Electron Microscopy and X-ray Absorption Spectroscopy at One Atmosphere and Elevated Temperature.

PubMed

Prestat, Eric; Kulzick, Matthew A; Dietrich, Paul J; Smith, Mr Matthew; Tien, Mr Eu-Pin; Burke, M Grace; Haigh, Sarah J; Zaluzec, Nestor J

2017-08-18

We have developed a new experimental platform for in situ scanning transmission electron microscope (STEM) energy dispersive X-ray spectroscopy (EDS) which allows real time, nanoscale, elemental and structural changes to be studied at elevated temperature (up to 1000 °C) and pressure (up to 1 atm). Here we demonstrate the first application of this approach to understand complex structural changes occurring during reduction of a bimetallic catalyst, PdCu supported on TiO 2 , synthesized by wet impregnation. We reveal a heterogeneous evolution of nanoparticle size, distribution, and composition with large differences in reduction behavior for the two metals. We show that the data obtained is complementary to in situ STEM electron energy loss spectroscopy (EELS) and when combined with in situ X-ray absorption spectroscopy (XAS) allows correlation of bulk chemical state with nanoscale changes in elemental distribution during reduction, facilitating new understanding of the catalytic behavior for this important class of materials. © 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

Electron beam induced radiation damage in the catalyst layer of a proton exchange membrane fuel cell.

PubMed

He, Qianping; Chen, Jihua; Keffer, David J; Joy, David C

2014-01-01

Electron microscopy is an essential tool for the evaluation of microstructure and properties of the catalyst layer (CL) of proton exchange membrane fuel cells (PEMFCs). However, electron microscopy has one unavoidable drawback, which is radiation damage. Samples suffer temporary or permanent change of the surface or bulk structure under radiation damage, which can cause ambiguity in the characterization of the sample. To better understand the mechanism of radiation damage of CL samples and to be able to separate the morphological features intrinsic to the material from the consequences of electron radiation damage, a series of experiments based on high-angle annular dark-field-scanning transmission scanning microscope (HAADF-STEM), energy filtering transmission scanning microscope (EFTEM), and electron energy loss spectrum (EELS) are conducted. It is observed that for thin samples (0.3-1 times λ), increasing the incident beam energy can mitigate the radiation damage. Platinum nanoparticles in the CL sample facilitate the radiation damage. The radiation damage of the catalyst sample starts from the interface of Pt/C or defective thin edge and primarily occurs in the form of mass loss accompanied by atomic displacement and edge curl. These results provide important insights on the mechanism of CL radiation damage. Possible strategies of mitigating the radiation damage are provided. © 2013 Wiley Periodicals, Inc.

Three-dimensional scanning transmission electron microscopy of biological specimens.

PubMed

de Jonge, Niels; Sougrat, Rachid; Northan, Brian M; Pennycook, Stephen J

2010-02-01

A three-dimensional (3D) reconstruction of the cytoskeleton and a clathrin-coated pit in mammalian cells has been achieved from a focal-series of images recorded in an aberration-corrected scanning transmission electron microscope (STEM). The specimen was a metallic replica of the biological structure comprising Pt nanoparticles 2-3 nm in diameter, with a high stability under electron beam radiation. The 3D dataset was processed by an automated deconvolution procedure. The lateral resolution was 1.1 nm, set by pixel size. Particles differing by only 10 nm in vertical position were identified as separate objects with greater than 20% dip in contrast between them. We refer to this value as the axial resolution of the deconvolution or reconstruction, the ability to recognize two objects, which were unresolved in the original dataset. The resolution of the reconstruction is comparable to that achieved by tilt-series transmission electron microscopy. However, the focal-series method does not require mechanical tilting and is therefore much faster. 3D STEM images were also recorded of the Golgi ribbon in conventional thin sections containing 3T3 cells with a comparable axial resolution in the deconvolved dataset.

Three-Dimensional Scanning Transmission Electron Microscopy of Biological Specimens

PubMed Central

de Jonge, Niels; Sougrat, Rachid; Northan, Brian M.; Pennycook, Stephen J.

2010-01-01

A three-dimensional (3D) reconstruction of the cytoskeleton and a clathrin-coated pit in mammalian cells has been achieved from a focal-series of images recorded in an aberration-corrected scanning transmission electron microscope (STEM). The specimen was a metallic replica of the biological structure comprising Pt nanoparticles 2–3 nm in diameter, with a high stability under electron beam radiation. The 3D dataset was processed by an automated deconvolution procedure. The lateral resolution was 1.1 nm, set by pixel size. Particles differing by only 10 nm in vertical position were identified as separate objects with greater than 20% dip in contrast between them. We refer to this value as the axial resolution of the deconvolution or reconstruction, the ability to recognize two objects, which were unresolved in the original dataset. The resolution of the reconstruction is comparable to that achieved by tilt-series transmission electron microscopy. However, the focal-series method does not require mechanical tilting and is therefore much faster. 3D STEM images were also recorded of the Golgi ribbon in conventional thin sections containing 3T3 cells with a comparable axial resolution in the deconvolved dataset. PMID:20082729

The effects of the stem cell on ciliary regeneration of injured rabbit sinonasal epithelium.

PubMed

Kavuzlu, Ali; Tatar, Emel Çadallı; Karagöz, Tuğba; Pınarlı, Ferda Alpaslan; Tatar, İlkan; Bayır, Ömer; Korkmaz, Mehmet Hakan

2017-08-01

Defects in mucosal healing after sinonasal surgery cause infection, scar formation causing obstruction, relapse of the disease within a shorter period and revision surgery. The present study aimed to create a functional ciliated epithelium using a stem cell and stem cell sheet of adipose tissue origin and to show such regeneration ultra-structurally on experimentally injured rabbit nasal epithelium. This was an experimental animal study and basic research. A total of 18 white New Zealand rabbits were divided into three groups. The medial wall of the maxillary sinus of the subjects was peeled off bilaterally. No additional procedure was applied to the subjects in Group 1. In Group 2, adipose tissue-derived mesenchymal stem cell was implanted on the wound edges of the subjects. In Group 3, a stem cell sheet of three layers was laid onto the defect area. All subjects were killed after 3 weeks. The presence of the stem cell stained with bromo-deoxyuridine was assessed with a light microscope, whereas cilia density, ciliated orientation and cilia structure were evaluated with a scanning electron microscope. Ciliary densities in Group 2 and Group 3 were statistically superior compared to the control group (p < 0.001, p = 0.007). Cilia morphology in Group 2 and Group 3 was also better than the control group (p < 0.01, p = 0.048). Ciliary orientation in Group 2 was scored highest (p < 0.01). The ratio of BrDu-stained cells was observed to be 27% in Group 3 and 8% in Group 2. Sub-epithelial recovery was observed to be better in Group 3. Adipose tissue-derived mesenchymal stem cell increased the healing of the injured maxillary sinus mucosa of the rabbits in terms of cilia presence, density and morphology regardless of the implementation technique. Level of evidence NA.

How precise can atoms of a nanocluster be located in 3D using a tilt series of scanning transmission electron microscopy images?

PubMed

Alania, M; De Backer, A; Lobato, I; Krause, F F; Van Dyck, D; Rosenauer, A; Van Aert, S

2017-10-01

In this paper, we investigate how precise atoms of a small nanocluster can ultimately be located in three dimensions (3D) from a tilt series of images acquired using annular dark field (ADF) scanning transmission electron microscopy (STEM). Therefore, we derive an expression for the statistical precision with which the 3D atomic position coordinates can be estimated in a quantitative analysis. Evaluating this statistical precision as a function of the microscope settings also allows us to derive the optimal experimental design. In this manner, the optimal angular tilt range, required electron dose, optimal detector angles, and number of projection images can be determined. Copyright © 2016 Elsevier B.V. All rights reserved.

High-resolution scanning precession electron diffraction: Alignment and spatial resolution.

PubMed

Barnard, Jonathan S; Johnstone, Duncan N; Midgley, Paul A

2017-03-01

Methods are presented for aligning the pivot point of a precessing electron probe in the scanning transmission electron microscope (STEM) and for assessing the spatial resolution in scanning precession electron diffraction (SPED) experiments. The alignment procedure is performed entirely in diffraction mode, minimising probe wander within the bright-field (BF) convergent beam electron diffraction (CBED) disk and is used to obtain high spatial resolution SPED maps. Through analysis of the power spectra of virtual bright-field images extracted from the SPED data, the precession-induced blur was measured as a function of precession angle. At low precession angles, SPED spatial resolution was limited by electronic noise in the scan coils; whereas at high precession angles SPED spatial resolution was limited by tilt-induced two-fold astigmatism caused by the positive spherical aberration of the probe-forming lens. Copyright © 2016 Elsevier B.V. All rights reserved.

Surface morphology and dislocation characteristics near the surface of 4H-SiC wafer using multi-directional scanning transmission electron microscopy.

PubMed

Sato, Takahiro; Orai, Yoshihisa; Suzuki, Yuya; Ito, Hiroyuki; Isshiki, Toshiyuki; Fukui, Munetoshi; Nakamura, Kuniyasu; Schamp, C T

2017-10-01

To improve the reliability of silicon carbide (SiC) electronic power devices, the characteristics of various kinds of crystal defects should be precisely understood. Of particular importance is understanding the correlation between the surface morphology and the near surface dislocations. In order to analyze the dislocations near the surface of 4H-SiC wafers, a dislocation analysis protocol has been developed. This protocol consists of the following process: (1) inspection of surface defects using low energy scanning electron microscopy (LESEM), (2) identification of small and shallow etch pits using KOH low temperature etching, (3) classification of etch pits using LESEM, (4) specimen preparation of several hundred nanometer thick sample using the in-situ focused ion beam micro-sampling® technique, (5) crystallographic analysis using the selected diffraction mode of the scanning transmission electron microscope (STEM), and (6) determination of the Burgers vector using multi-directional STEM (MD-STEM). The results show a correlation between the triangular terrace shaped surface defects and an hexagonal etch pit arising from threading dislocations, linear shaped surface defects and elliptical shaped etch pits arising from basal plane dislocations. Through the observation of the sample from two orthogonal directions via the MD-STEM technique, a basal plane dislocation is found to dissociate into an extended dislocation bound by two partial dislocations. A protocol developed and presented in this paper enables one to correlate near surface defects of a 4H-SiC wafer with the root cause dislocations giving rise to those surface defects. © 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.

Direct writing on graphene 'paper' by manipulating electrons as 'invisible ink'.

PubMed

Zhang, Wei; Zhang, Qiang; Zhao, Meng-Qiang; Kuhn, Luise Theil

2013-07-12

The combination of self-assembly (bottom up) and nano-imprint lithography (top down) is an efficient and effective way to record information at the nanoscale by writing. The use of an electron beam for writing is quite a promising strategy; however, the 'paper' on which to save the information is not yet fully realized. Herein, graphene was selected as the thinnest paper for recording information at the nanoscale. In a transmission electron microscope, in situ high precision writing and drawing were achieved on graphene nanosheets by manipulating electrons with a 1 nm probe (probe current ~2 × 10(-9) A m(-2)) in scanning transmission electron microscopy (STEM) mode. Under electron probe irradiation, the carbon atom tends to displace within a crystalline specimen, and dangling bonds are formed from the original sp(2) bonding after local carbon atoms have been kicked off. The absorbed random foreign amorphous carbon assembles along the line of the scanning direction induced by secondary electrons and is immobilized near the edge. With the ultralow secondary electron yield of the graphene, additional foreign atoms determining the accuracy of the pattern have been greatly reduced near the targeting region. Therefore, the electron probe in STEM mode serves as invisible ink for nanoscale writing and drawing. These results not only shed new light on the application of graphene by the interaction of different forms of carbon, but also illuminate the interaction of different carbon forms through electron beams.

When will Low-Contrast Features be Visible in a STEM X-Ray Spectrum Image?

PubMed

Parish, Chad M

2015-06-01

When will a small or low-contrast feature, such as an embedded second-phase particle, be visible in a scanning transmission electron microscopy (STEM) X-ray map? This work illustrates a computationally inexpensive method to simulate X-ray maps and spectrum images (SIs), based upon the equations of X-ray generation and detection. To particularize the general procedure, an example of nanostructured ferritic alloy (NFA) containing nm-sized Y2Ti2O7 embedded precipitates in ferritic stainless steel matrix is chosen. The proposed model produces physically appearing simulated SI data sets, which can either be reduced to X-ray dot maps or analyzed via multivariate statistical analysis. Comparison to NFA X-ray maps acquired using three different STEM instruments match the generated simulations quite well, despite the large number of simplifying assumptions used. A figure of merit of electron dose multiplied by X-ray collection solid angle is proposed to compare feature detectability from one data set (simulated or experimental) to another. The proposed method can scope experiments that are feasible under specific analysis conditions on a given microscope. Future applications, such as spallation proton-neutron irradiations, core-shell nanoparticles, or dopants in polycrystalline photovoltaic solar cells, are proposed.

Analytical SuperSTEM for extraterrestrial materials research

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

Bradley, J P; Dai, Z R

2009-09-08

Electron-beam studies of extraterrestrial materials with significantly improved spatial resolution, energy resolution and sensitivity are enabled using a 300 keV SuperSTEM scanning transmission electron microscope with a monochromator and two spherical aberration correctors. The improved technical capabilities enable analyses previously not possible. Mineral structures can be directly imaged and analyzed with single-atomic-column resolution, liquids and implanted gases can be detected, and UV-VIS optical properties can be measured. Detection limits for minor/trace elements in thin (<100 nm thick) specimens are improved such that quantitative measurements of some extend to the sub-500 ppm level. Electron energy-loss spectroscopy (EELS) can be carried outmore » with 0.10-0.20 eV energy resolution and atomic-scale spatial resolution such that variations in oxidation state from one atomic column to another can be detected. Petrographic mapping is extended down to the atomic scale using energy-dispersive x-ray spectroscopy (EDS) and energy-filtered transmission electron microscopy (EFTEM) imaging. Technical capabilities and examples of the applications of SuperSTEM to extraterrestrial materials are presented, including the UV spectral properties and organic carbon K-edge fine structure of carbonaceous matter in interplanetary dust particles (IDPs), x-ray elemental maps showing the nanometer-scale distribution of carbon within GEMS (glass with embedded metal and sulfides), the first detection and quantification of trace Ti in GEMS using EDS, and detection of molecular H{sub 2}O in vesicles and implanted H{sub 2} and He in irradiated mineral and glass grains.« less

Determining oxygen relaxations at an interface: A comparative study between transmission electron microscopy techniques.

PubMed

Gauquelin, N; van den Bos, K H W; Béché, A; Krause, F F; Lobato, I; Lazar, S; Rosenauer, A; Van Aert, S; Verbeeck, J

2017-10-01

Nowadays, aberration corrected transmission electron microscopy (TEM) is a popular method to characterise nanomaterials at the atomic scale. Here, atomically resolved images of nanomaterials are acquired, where the contrast depends on the illumination, imaging and detector conditions of the microscope. Visualization of light elements is possible when using low angle annular dark field (LAADF) STEM, annular bright field (ABF) STEM, integrated differential phase contrast (iDPC) STEM, negative spherical aberration imaging (NCSI) and imaging STEM (ISTEM). In this work, images of a NdGaO 3 -La 0.67 Sr 0.33 MnO 3 (NGO-LSMO) interface are quantitatively evaluated by using statistical parameter estimation theory. For imaging light elements, all techniques are providing reliable results, while the techniques based on interference contrast, NCSI and ISTEM, are less robust in terms of accuracy for extracting heavy column locations. In term of precision, sample drift and scan distortions mainly limits the STEM based techniques as compared to NCSI. Post processing techniques can, however, partially compensate for this. In order to provide an outlook to the future, simulated images of NGO, in which the unavoidable presence of Poisson noise is taken into account, are used to determine the ultimate precision. In this future counting noise limited scenario, NCSI and ISTEM imaging will provide more precise values as compared to the other techniques, which can be related to the mechanisms behind the image recording. Copyright © 2017 Elsevier B.V. All rights reserved.

Morphological Analysis of Human Induced Pluripotent Stem Cells During Induced Differentiation and Reverse Programming

PubMed Central

Magniez, Aurélie; Oudrhiri, Noufissa; Féraud, Olivier; Bacci, Josette; Gobbo, Emilie; Proust, Stéphanie; Turhan, Ali G.

2014-01-01

Abstract The fine analysis of cell components during the generation of pluripotent cells and their comparison to bone fide human embryonic stem cells (hESCs) are valuable tools to understand their biological behavior. In this report, human mesenchymal cells (hMSCs) generated from the human ES cell line H9, were reprogrammed back to induced pluripotent state using Oct-4, Sox2, Nanog, and Lin28 transgenes. Human induced pluripotent stem cells (hIPSCs) were analyzed using electron microscopy and compared with regard to the original hESCs and the hMSCs from which they were derived. This analysis shows that hIPSCs and the original hESCs are morphologically undistinguishable but differ from the hMSCs with respect to the presence of several morphological features of undifferentiated cells at both the cytoplasmic (ribosomes, lipid droplets, glycogen, scarce reticulum) and nuclear levels (features of nuclear plasticity, presence of euchromatin, reticulated nucleoli). We show that hIPSC colonies generated this way presented epithelial aspects with specialized junctions highlighting morphological criteria of the mesenchymal–epithelial transition in cells engaged in a successful reprogramming process. Electron microscopic analysis revealed also specific morphological aspects of partially reprogrammed cells. These results highlight the valuable use of electron microscopy for a better knowledge of the morphological aspects of IPSC and cellular reprogramming. PMID:25371857

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

Cullen, David A; Koestner, Roland; Kukreja, Ratan

Improved conditions for imaging and spectroscopic mapping of thin perfluorosulfonic acid (PFSA) ionomer layers in fuel cell electrodes by scanning transmission electron microscopy (STEM) have been investigated. These conditions are first identified on model systems of Nafion ionomer-coated nanostructured thin films and nanoporous Si. The optimized conditions are then applied in a quantitative study of the ionomer through-layer loading for two typical electrode catalyst coatings using electron energy loss and energy dispersive X-ray spectroscopy in the transmission electron microscope. The e-beam induced damage to the perfluorosulfonic acid (PFSA) ionomer is quantified by following the fluorine mass loss with electron exposuremore » and is then mitigated by a few orders of magnitude using cryogenic specimen cooling and a higher incident electron voltage. Multivariate statistical analysis is also applied to the analysis of spectrum images for data denoising and unbiased separation of independent components related to the catalyst, ionomer, and support.« less

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

Krumeich, F., E-mail: krumeich@inorg.chem.ethz.ch; Mueller, E.; Wepf, R.A.

While HRTEM is the well-established method to characterize the structure of dodecagonal tantalum (vanadium) telluride quasicrystals and their periodic approximants, phase-contrast imaging performed on an aberration-corrected scanning transmission electron microscope (STEM) represents a favorable alternative. The (Ta,V){sub 151}Te{sub 74} clusters, the basic structural unit in all these phases, can be visualized with high resolution. A dependence of the image contrast on defocus and specimen thickness has been observed. In thin areas, the projected crystal potential is basically imaged with either dark or bright contrast at two defocus values close to Scherzer defocus as confirmed by image simulations utilizing the principlemore » of reciprocity. Models for square-triangle tilings describing the arrangement of the basic clusters can be derived from such images. - Graphical abstract: PC-STEM image of a (Ta,V){sub 151}Te{sub 74} cluster. Highlights: Black-Right-Pointing-Pointer C{sub s}-corrected STEM is applied for the characterization of dodecagonal quasicrystals. Black-Right-Pointing-Pointer The projected potential of the structure is mirrored in the images. Black-Right-Pointing-Pointer Phase-contrast STEM imaging depends on defocus and thickness. Black-Right-Pointing-Pointer For simulations of phase-contrast STEM images, the reciprocity theorem is applicable.« less

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

Heo, Yooun; Lee, Jin Hong; Xie, Lin

Enhanced properties in modern functional materials can often be found at structural transition regions, such as morphotropic phase boundaries (MPB), owing to the coexistence of multiple phases with nearly equivalent energies. Strain-engineered MPBs have emerged in epitaxially grown BiFeO 3 (BFO) thin films by precisely tailoring a compressive misfit strain, leading to numerous intriguing phenomena, such as a massive piezoelectric response, magnetoelectric coupling, interfacial magnetism and electronic conduction. Recently, an orthorhombic–rhombohedral (O–R) phase boundary has also been found in tensile-strained BFO. In this study, we characterise the crystal structure and electronic properties of the two competing O and R phasesmore » using X-ray diffraction, scanning probe microscope and scanning transmission electron microscopy (STEM). We observe the temperature evolution of R and O domains and find that the domain boundaries are highly conductive. Temperature-dependent measurements reveal that the conductivity is thermally activated for R–O boundaries. STEM observations point to structurally wide boundaries, significantly wider than in other systems. Furthermore, we reveal a strong correlation between the highly conductive domain boundaries and structural material properties. These findings provide a pathway to use phase boundaries in this system for novel nanoelectronic applications.« less

Ultrastructural demonstration of Cx43 gap junctions in induced pluripotent stem cells from human cord blood.

PubMed

Beckmann, Anja; Schubert, Madline; Hainz, Nadine; Haase, Alexandra; Martin, Ulrich; Tschernig, Thomas; Meier, Carola

2016-11-01

Gap junction proteins are essential for direct intercellular communication but also influence cellular differentiation and migration. The expression of various connexin gap junction proteins has been demonstrated in embryonic stem cells, with Cx43 being the most intensely studied. As Cx43 is the most prominent gap junction protein in the heart, cardiomyocyte-differentiated stem cells have been studied intensely. To date, however, little is known about the expression and the subcellular distribution of Cx43 in undifferentiated stem cells or about the structural arrangement of channels. We, therefore, here investigate expression of Cx43 in undifferentiated human cord-blood-derived induced pluripotent stem cells (hCBiPS2). For this purpose, we carried out quantitative real-time PCR and immunohistochemistry. For analysis of Cx43 ultrastructure and protein assembly, we performed freeze-fracture replica immunogold labeling (FRIL). Cx43 expression was detected at mRNA and protein level in hCBIPS2 cells. For the first time, ultrastructural data are presented on gap junction morphology in induced pluripotent stem (iPS) cells from cord blood: Our FRIL and electron microscopical analysis revealed the occurrence of gap junction plaques in undifferentiated iPS cells. In addition, these gap junctions were shown to contain the gap junction protein Cx43.

Thermometry of Silicon Nanoparticles

NASA Astrophysics Data System (ADS)

Mecklenburg, Matthew; Zutter, Brian; Regan, B. C.

2018-01-01

Current thermometry techniques lack the spatial resolution required to see the temperature gradients in typical, highly scaled modern transistors. As a step toward addressing this problem, we measure the temperature dependence of the volume plasmon energy in silicon nanoparticles from room temperature to 1250 °C , using a chip-style heating sample holder in a scanning transmission electron microscope (STEM) equipped with electron energy loss spectroscopy (EELS). The plasmon energy changes as expected for an electron gas subject to the thermal expansion of silicon. Reversing this reasoning, we find that measurements of the plasmon energy provide an independent measure of the nanoparticle temperature consistent with that of the heater chip's macroscopic, dual-function heater-and-thermometer to within the 5% accuracy of the thermometer's calibration. Thus, silicon has the potential to provide its own high-spatial-resolution thermometric readout signal via measurements of its volume plasmon energy. Furthermore, nanoparticles can, in general, serve as convenient nanothermometers for in situ electron-microscopy experiments.

In Situ Formation of Carbon Nanotubes Encapsulated within Boron Nitride Nanotubes via Electron Irradiation

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

Arenal, Raul; Lopez-Bezanilla, Alejandro

2014-07-25

We report experimental evidence of the formation by in situ electron-irradiation of single-walled carbon nanotubes (C NT) confined within boron nitride nanotubes (BN-NT). The electron radiation stemming from the microscope supplies the energy required by the amorphous carbonaceous structures to crystallize in a tubular form in a catalyst free procedure, at room temperature and high vacuum. The structural defects resulting from the interaction of the shapeless carbon with the BN nanotube are corrected in a self-healing process throughout the crystallinization. Structural changes developed during the irradiation process such as defects formation and evolution, shrinkage, and shortness of the BN-NT weremore » in situ monitored. The outer BN wall provides a protective and insulating shell against environmental Perturbations to the inner C-NT without affecting their electronic properties, as demonstrated by first principles calculations.« less

Proceedings of the Molecular Electronic Devices Workshop Held at Washington, DC on 23-24 March 1981.

DTIC Science & Technology

1981-10-22

carboxylic acid (COOK) group at one end: R3 C-(ai 2 ) 1 6 -COOH. STEM - Scanning Transmission Ilectron Microscope. Synthetic DNA - DNA of a desired...semiempirical calculations of similar systems have been performed. ( 1 ) Ady and Brickmann (3) investigated the formic acid dimer, and found a barrier of 59...seeking propensity of acids into a single molecule. The material we have used is stearic acid (Cl8H35OOH). As illustrated in the inset of Fig. 1 , the

When will low-contrast features be visible in a STEM X-ray spectrum image?

DOE PAGES

Parish, Chad M.

2015-04-01

When will a small or low-contrast feature, such as an embedded second-phase particle, be visible in a scanning transmission electron microscopy (STEM) X-ray map? This work illustrates a computationally inexpensive method to simulate X-ray maps and spectrum images (SIs), based upon the equations of X-ray generation and detection. To particularize the general procedure, an example of nanostructured ferritic alloy (NFA) containing nm-sized Y 2Ti 2O 7 embedded precipitates in ferritic stainless steel matrix is chosen. The proposed model produces physically appearing simulated SI data sets, which can either be reduced to X-ray dot maps or analyzed via multivariate statistical analysis.more » Comparison to NFA X-ray maps acquired using three different STEM instruments match the generated simulations quite well, despite the large number of simplifying assumptions used. A figure of merit of electron dose multiplied by X-ray collection solid angle is proposed to compare feature detectability from one data set (simulated or experimental) to another. The proposed method can scope experiments that are feasible under specific analysis conditions on a given microscope. As a result, future applications, such as spallation proton–neutron irradiations, core-shell nanoparticles, or dopants in polycrystalline photovoltaic solar cells, are proposed.« less

Studying dynamic processes in liquids by TEM/STEM/DTEM

NASA Astrophysics Data System (ADS)

Abellan, Patricia; Evans, James; Woehl, Taylor; Jungjohann, Katherine; Parent, Lucas; Arslan, Ilke; Ristenpart, William; Browning, Nigel; Mater. Sci. Group Team; Microsc. Group Team; Catal. Sci. Group Collaboration; Ristenpart Res. Group Collaboration

2013-03-01

In order to study dynamic phenomena such as corrosion or catalysis, extreme environmental conditions must be reproduced around the specimen - these include high-temperatures, high-pressures, specific oxidizing/reducing atmospheres or a liquid environment. The use of environmental stages specifically designed to fit in any transmission electron microscope (TEM) allows us to apply the distinct capabilities of each instrument to study dynamic processes. Localized gas/fluid conditions are created around the sample and separated from the high vacuum inside the microscope using hermetically sealed windowed-cells. Advanced capabilities of these techniques include spatial resolutions of ~1 Angstrom or better in aberration corrected instruments or temporal resolutions in the microsecond-nanosecond range in a dynamic TEM (DTEM). Here, unique qualities of the DTEM that benefit the in-situ experiments with gas/fluid environmental cells will be discussed. We also present our results with a liquid stage allowing atomic resolution imaging of nanomaterials in a colloidal suspension, core EEL spectra acquisition, continuous flow, controlled growth of nanocrystals and systematic calibration of the effect of the electron dose on silver nuclei formation.

Study of the surfactant role in latex-aerogel systems by scanning transmission electron microscopy on aqueous suspensions.

PubMed

Perret, A; Foray, G; Masenelli-Varlot, K; Maire, E; Yrieix, B

2018-01-01

For insulation applications, boards thinner than 2 cm are under design with specific thermal conductivities lower than 15 mW m -1  K -1 . This requires binding slightly hydrophobic aerogels which are highly nanoporous granular materials. To reach this step and ensure insulation board durability at the building scale, it is compulsory to design, characterise and analyse the microstructure at the nanoscale. It is indeed necessary to understand how the solid material is formed from a liquid suspension. This issue is addressed in this paper through wet-STEM experiments carried out in an Environmental Scanning Electron Microscope (ESEM). Latex-surfactant binary blends and latex-surfactant-aerogel ternary systems are studied, with two different surfactants of very different chemical structures. Image analysis is used to distinguish the different components and get quantitative morphological parameters which describe the sample architecture. The evolution of such morphological parameters during water evaporation permits a good understanding of the role of the surfactant. © 2017 The Authors Journal of Microscopy © 2017 Royal Microscopical Society.

Ex Situ Investigation of Anisotropic Interconnection in Silicon-Titanium-Nickel Alloy Anode Material

DOE PAGES

Cho, Jong -Soo; Alaboina, Pankaj Kumar; Kang, Chan -Soon; ...

2017-03-10

Herein we investigate the nanostructural evolution of Silicon-Titanium-Nickel (Si-Ti-Ni) ternary alloy material synthesized by melt spinning process for advanced lithium-ion battery anode. The synthesized material was found to have nano-Silicon particles dispersed in the Ti 4Ni 4Si 7 (STN) alloy buffering matrix and was characterized by X-ray diffraction (XRD), High resolution- transmission electron microscope (HR-TEM), Scanning transmission electron microscopes - energy dispersive X-ray spectrometer (STEM-EDS), and electrochemical performance test. The role of STN matrix is to accommodate the volume expansion stresses of the dispersed Si nanoparticles. However, an interesting behavior was observed during cycling. The Si nanoparticles were observed tomore » form interconnection channels growing through the weak STN matrix cracks and evolving to a network isolating the STN matrix into small puddles. In conclusion, this unique nanostructural evolution of Si particles and isolation of the STN matrix failing to offer significant buffering effect to the grown Si network eventually accelerates more volume expansions during cycling due to less mechanical confinement and leads to performance degradation and poor cycle stability.« less

Regenerating Heart Using a Novel Compound and Human Wharton Jelly Mesenchymal Stem Cells.

PubMed

Rabbani, Shahram; Soleimani, Masoud; Imani, Mohammad; Sahebjam, Mohammad; Ghiaseddin, Ali; Nassiri, Seyed Mahdi; Majd Ardakani, Jalil; Tajik Rostami, Maryam; Jalali, Arash; Mousanassab, Bahmanshir; Kheradmandi, Mahsa; Ahmadi Tafti, Seyed Hossein

2017-04-01

Myocardial infarction is a major problem in health system and most conventional therapy is not led to restoration of the health. Stem cell therapy is a method to regenerate the heart but today appropriate cell source and scaffold selection as extracellular matrix to achieve the best effect is disputing. In this study a combination of human Wharton jelly mesenchymal stem cells (HWJMSCs) with a novel compound consisting polyethylene glycol (PEG), hyaluronic acid and chitosan is presented to heart regeneration. After proliferation and expansion of HWJMSCs, these cells were mixed with scaffold and injected into the infarcted rabbit myocardium. After two months cardiac function and infarcted area were evaluated. Immunohistochemistry performed for vessel count and demonstrating of differentiation ability into cardiomyocytes. To confirm this ability PCR was done. Scanning electron microscope was used to evaluate angiogenesis. Improving cardiac function was higher in cell/scaffold group than the others and it was confirmed by SPECT results which showed least defect size in the myocardium. There were a lot of neoangiogenesis in the target group and also cardiomyogenesis observed in cell/scaffold group. PCR results confirmed the presence of differentiated cardiomyocytes and SEM showed well developed vessel in this group. Comparing macroscopic and microscopic results between all groups revealed that HWJMSC in combination with this scaffold led to brilliant results regarding cardiac function, angiogenesis and cardiogenesis. It is recommended using these cells and materials for cardiac tissue engineering and regeneration therapy. Copyright © 2017 IMSS. Published by Elsevier Inc. All rights reserved.

Label-free detection of surface markers on stem cells by oblique-incidence reflectivity difference microscopy

PubMed Central

Lo, Kai-Yin; Sun, Yung-Shin; Landry, James P.; Zhu, Xiangdong; Deng, Wenbin

2012-01-01

Conventional fluorescent microscopy is routinely used to detect cell surface markers through fluorophore-conjugated antibodies. However, fluorophore-conjugation of antibodies alters binding properties such as strength and specificity of the antibody in ways often uncharacterized. The binding between antibody and antigen might not be in the native situation after such conjugation. Here, we present an oblique-incidence reflectivity difference (OI-RD) microscope as an effective method for label-free, real-time detection of cell surface markers and apply such a technique to analysis of Stage-Specific Embryonic Antigen 1 (SSEA1) on stem cells. Mouse stem cells express SSEA1 on their surfaces and the level of SSEA1 decreases when the cells start to differentiate. In this study, we immobilized mouse stem cells and non-stem cells (control) on a glass surface as a microarray and reacted the cell microarray with unlabeled SSEA1 antibodies. By monitoring the reaction with an OI-RD microscope in real time, we confirmed that the SSEA1 antibodies only bind to the surface of the stem cells while not to the surface of non-stem cells. From the binding curves, we determined the equilibrium dissociation constant (Kd) of the antibody with the SSEA1 markers on the stem cell surface. The results concluded that OI-RD microscope can be used to detect binding affinities between cell surface markers and unlabeled antibodies bound to the cells. The information could be another indicator to determine the cell stages. PMID:21781038

Atomic-Level Sculpting of Crystalline Oxides: Toward Bulk Nanofabrication with Single Atomic Plane Precision

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

Jesse, Stephen; He, Qian; Lupini, Andrew R.

2015-10-19

We demonstrate atomic-level sculpting of 3D crystalline oxide nanostructures from metastable amorphous layer in a scanning transmission electron microscope (STEM). Strontium titanate nanostructures grow epitaxially from the crystalline substrate following the beam path. This method can be used for fabricating crystalline structures as small as 1-2 nm and the process can be observed in situ with atomic resolution. We further demonstrate fabrication of arbitrary shape structures via control of the position and scan speed of the electron beam. Combined with broad availability of the atomic resolved electron microscopy platforms, these observations suggest the feasibility of large scale implementation of bulkmore » atomic-level fabrication as a new enabling tool of nanoscience and technology, providing a bottom-up, atomic-level complement to 3D printing.« less

Nanoparticles in alumina: Microscopy and Theory

NASA Astrophysics Data System (ADS)

Idrobo, Juan C.; Halabica, Andrej; Rashkeev, Sergey; Glazoff, Michael V.; Boatner, Lynn A.; Haglund, Richard F.; Pennycook, Stephen. J.; Pantelides, Sokrates T.

2007-03-01

Transition-metal nanoparticles formed by ion implantation in alumina can be used to modify the optical properties of naturally oxidized and anodized aluminum. Here, we report atomic-resolution Z-contrast images using a scanning transmission electron microscope (STEM) of CoFe and other metal nanoparticles in alumina. We also report electron energy loss spectra (EELS) and relate them to visual appearance and optical properties. Finally, we report first-principles density- functional calculations of nucleation mechanisms for these nanoparticles. This research was sponsored by the Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, U.S. Department of Energy, under contract DE-AC05- 00OR22725 with Oak Ridge National Laboratory, managed and operated by UT-Battelle, by NSF grant No. DMR-0513048, and by Alcoa Inc.

A sub-sampled approach to extremely low-dose STEM

DOE PAGES

Stevens, A.; Luzi, L.; Yang, H.; ...

2018-01-22

The inpainting of deliberately and randomly sub-sampled images offers a potential means to image specimens at a high resolution and under extremely low-dose conditions (≤1 e -/Å 2) using a scanning transmission electron microscope. We show that deliberate sub-sampling acquires images at least an order of magnitude faster than conventional low-dose methods for an equivalent electron dose. More importantly, when adaptive sub-sampling is implemented to acquire the images, there is a significant increase in the resolution and sensitivity which accompanies the increase in imaging speed. Lastly, we demonstrate the potential of this method for beam sensitive materials and in-situ observationsmore » by experimentally imaging the node distribution in a metal-organic framework.« less

A sub-sampled approach to extremely low-dose STEM

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

Stevens, A.; Luzi, L.; Yang, H.

The inpainting of deliberately and randomly sub-sampled images offers a potential means to image specimens at a high resolution and under extremely low-dose conditions (≤1 e -/Å 2) using a scanning transmission electron microscope. We show that deliberate sub-sampling acquires images at least an order of magnitude faster than conventional low-dose methods for an equivalent electron dose. More importantly, when adaptive sub-sampling is implemented to acquire the images, there is a significant increase in the resolution and sensitivity which accompanies the increase in imaging speed. Lastly, we demonstrate the potential of this method for beam sensitive materials and in-situ observationsmore » by experimentally imaging the node distribution in a metal-organic framework.« less

Laser-assisted electron tunneling in a STM junction

NASA Astrophysics Data System (ADS)

Chang, Shunhua Thomas

2000-10-01

Since its introduction in 1981, the Nobel prize-winning scanning tunneling microscope (STM) has been developed into a powerful yet conceptually simple instrument, replacing traditional scanning and transmission electron microscopes (SEM/TEM) in many of the microscopic surface phenomenon studies. The strength of the STM stems from the sensitive tunneling current-potential barrier width relationship of the electron tunneling process, and has been used to re-examine the frequency-mixing and harmonic generation properties of an non-linear metal- oxide-metal (MOM) tunneling junction. In this research, electron-tunneling events under polarized laser radiation at 514.5-nm argon and 10.6-μm carbon dioxide laser wavelengths were investigated. The objective is to understand the underlying interactive mechanisms between the tunneling junction and the external laser excitation. A commercial scanning tunneling microscope head and controller were incorporated into the experimental setup. Operation characteristics and the electrical properties of the STM junction were determined. Tunneling current and distance responses with respect to different laser polarization, modulation frequency, incident power, and tunneling distance were also conducted. From the experimental results it is shown that thermal expansion effect was the dominant source of response for laser modulation frequency up to about 100 kHz, in quantitative agreement with theoretical calculations. Different laser polarizations as the experiments demonstrated did not contribute significantly to the STM response in the investigated frequency range. The electric field induced by the laser beam was calculated to be one to two order of magnitudes lower than the field required to initiate field emission where the tunneling junction I- V curve is most non-linear. Also, the electrical coupling of the incident laser at the STM junction was determined to be non-critical at visible laser wavelength, and the reflected laser energy from the sample re-entering the junction was shown to be weak and did not influence the ongoing electron tunneling process. In conclusion, the thermal expansion of the physical tunneling junction was found to be responsible to the tunneling current modulation in a laser - STM setup for laser modulation frequencies in the lower frequency range.

Mapping the layer count of few-layer hexagonal boron nitride at high lateral spatial resolutions

NASA Astrophysics Data System (ADS)

Mohsin, Ali; Cross, Nicholas G.; Liu, Lei; Watanabe, Kenji; Taniguchi, Takashi; Duscher, Gerd; Gu, Gong

2018-01-01

Layer count control and uniformity of two dimensional (2D) layered materials are critical to the investigation of their properties and to their electronic device applications, but methods to map 2D material layer count at nanometer-level lateral spatial resolutions have been lacking. Here, we demonstrate a method based on two complementary techniques widely available in transmission electron microscopes (TEMs) to map the layer count of multilayer hexagonal boron nitride (h-BN) films. The mass-thickness contrast in high-angle annular dark-field (HAADF) imaging in the scanning transmission electron microscope (STEM) mode allows for thickness determination in atomically clean regions with high spatial resolution (sub-nanometer), but is limited by surface contamination. To complement, another technique based on the boron K ionization edge in the electron energy loss spectroscopy spectrum (EELS) of h-BN is developed to quantify the layer count so that surface contamination does not cause an overestimate, albeit at a lower spatial resolution (nanometers). The two techniques agree remarkably well in atomically clean regions with discrepancies within  ±1 layer. For the first time, the layer count uniformity on the scale of nanometers is quantified for a 2D material. The methodology is applicable to layer count mapping of other 2D layered materials, paving the way toward the synthesis of multilayer 2D materials with homogeneous layer count.

Ultrastructural evaluation of mesenchymal stem cells from inflamed periodontium in different in vitro conditions.

PubMed

Zaganescu, Raluca; Barbu Tudoran, Lucian; Pall, Emoke; Florea, Adrian; Roman, Alexandra; Soanca, Andrada; Mihaela Mihu, Carmen

2015-09-01

This research aimed to observe the behavior of mesenchymal stem cells (MSCs) isolated from periodontal granulation tissue (gt) when manipulated ex vivo to induce three-dimensional (3D) spheroid (aggregates) formation as well as when seeded on two bone scaffolds of animal origin. Periodontal gt was chosen as a MSC source because of its availability, considering that it is eliminated as a waste material during conventional surgical therapies. 3D aggregates of cells were generated; they were grown for 3 and 7 days, respectively, and then prepared for transmission electron microscopic analysis. The two biomaterials were seeded for 72 h with gtMSCs and prepared for scanning electronic microscopic observation. The ultrastructural analysis of 3D spheroids remarked some differences between the inner and the outer cell layers, with a certain commitment observed at the inner cells. Both scaffolds showed a relatively smooth surface at low magnification. Macro- and micropores having a scarce distribution were observed on both bone substitutes. gtMSCs grew with relative difficulty on the biomaterials. After 72 h of proliferation, gtMSCs scarcely covered the surface of bovine bone scaffolds, demonstrating fibroblast-like or star-like shapes with elongated filiform extensions. Our results add other data on the possible usefulness of gtMSC and could question the current paradigm regarding the complete removal of chronically inflamed gts from the defects during periodontal surgeries. Until optimal protocols for ex vivo manipulation of MSCs are available for clinical settings, it is advisable to use biocompatible bone substitutes that allow the development of progenitor cells. © 2015 Wiley Periodicals, Inc.

Phytotoxicity and uptake of nanoscale zero-valent iron (nZVI) by two plant species.

PubMed

Ma, Xingmao; Gurung, Arun; Deng, Yang

2013-01-15

Use of nano-scale zero valent iron (nZVI) for the treatment of various environmental pollutants has been proven successful. However, large scale introduction of engineered nanomaterials such as nZVI into the environment has recently attracted serious concerns. There is an urgent need to investigate the environmental fate and impact of nZVI due to the scope of its application. The goal of this study was to evaluate the toxicity and accumulation of bare nZVI by two commonly encountered plant species: cattail (Typha latifolia) and hybrid poplars (Populous deltoids×Populous nigra). Plant seedlings were grown hydroponically in a greenhouse and dosed with different concentrations of nZVI (0-1000 mg/L) for four weeks. The nZVI exhibited strong toxic effect on Typha at higher concentrations (>200 mg/L) but enhanced plant growth at lower concentrations. nZVI also significantly reduced the transpiration and growth of hybrid poplars at higher concentrations. Microscopic images indicated that large amount of nZVI coated on plant root surface as irregular aggregates and some nZVI penetrated into several layers of epidermal cells. Transmission electron microscope (TEM) and scanning transmission electron microscope (STEM) confirmed the internalization of nZVI by poplar root cells but similar internalization was not observed for Typha root cells. The upward transport to shoots was minimal for both plant species. Copyright © 2012 Elsevier B.V. All rights reserved.

Synergetic effect of topological cue and periodic mechanical tension-stress on osteogenic differentiation of rat bone mesenchymal stem cells.

PubMed

Liu, Yao; Yang, Guang; Ji, Huanzhong; Xiang, Tao; Luo, En; Zhou, Shaobing

2017-06-01

Mesenchymal stem cells (MSCs) are able to self-renew and differentiate into tissues of mesenchymal origin, making them to be significant for cell-based therapies, such as metabolic bone diseases and bone repair. Regulating the differentiation of MSCs is significant for bone regeneration. Electrospun fibers mimicking natural extracellular matrix (ECM), is an effective artificial ECM to regulate the behaviors and fates of MSCs. The aligned electrospun fibers can modulate polar cell pattern of bone mesenchymal stem cells, which leads to more obvious osteogenic differentiation. Apart from the topographic effect of electrospun fibers, mechanical cues can also intervene the cell behaviors. In this study, the osteogenic differentiation of rat bone mesenchymal stem cells was evaluated, which were cultured on aligned/random electrospun fiber mats materials under mechanical tension intervention. Scanning electron microscope and immune-fluorescent staining were used to directly observe the polarity changing of cellular morphology and cytoskeleton. The results proved that aligned electrospun fibers could be more conducive to promote osteogenic differentiation of rat bone mesenchymal stem cells and this promotion of osteogenic differentiation was enhanced by tension intervention. These results were correlated to the quantitative real-time PCR assay. In general, culturing rat bone mesenchymal stem cells on electrospun fibers under the intervention of mechanical tension is an effective way to mimic a more real cellular microenvironment. Copyright © 2017 Elsevier B.V. All rights reserved.

Raman-in-SEM, a multimodal and multiscale analytical tool: performance for materials and expertise.

PubMed

Wille, Guillaume; Bourrat, Xavier; Maubec, Nicolas; Lahfid, Abdeltif

2014-12-01

The availability of Raman spectroscopy in a powerful analytical scanning electron microscope (SEM) allows morphological, elemental, chemical, physical and electronic analysis without moving the sample between instruments. This paper documents the metrological performance of the SEMSCA commercial Raman interface operated in a low vacuum SEM. It provides multiscale and multimodal analyses as Raman/EDS, Raman/cathodoluminescence or Raman/STEM (STEM: scanning transmission electron microscopy) as well as Raman spectroscopy on nanomaterials. Since Raman spectroscopy in a SEM can be influenced by several SEM-related phenomena, this paper firstly presents a comparison of this new tool with a conventional micro-Raman spectrometer. Then, some possible artefacts are documented, which are due to the impact of electron beam-induced contamination or cathodoluminescence contribution to the Raman spectra, especially with geological samples. These effects are easily overcome by changing or adapting the Raman spectrometer and the SEM settings and methodology. The deletion of the adverse effect of cathodoluminescence is solved by using a SEM beam shutter during Raman acquisition. In contrast, this interface provides the ability to record the cathodoluminescence (CL) spectrum of a phase. In a second part, this study highlights the interest and efficiency of the coupling in characterizing micrometric phases at the same point. This multimodal approach is illustrated with various issues encountered in geosciences. Copyright © 2014 Elsevier Ltd. All rights reserved.

Science 101: How Does an Electron Microscope Work?

ERIC Educational Resources Information Center

Robertson, Bill

2013-01-01

Contrary to popular opinion, electron microscopes are not used to look at electrons. They are used to look for structure in things that are too small to observe with an optical microscope, or to obtain images that are magnified much more than is obtainable with an optical microscope. To understand how electron microscopes work, it will help to go…

Enhanced conductivity at orthorhombic–rhombohedral phase boundaries in BiFeO 3 thin films

DOE PAGES

Heo, Yooun; Lee, Jin Hong; Xie, Lin; ...

2016-08-26

Enhanced properties in modern functional materials can often be found at structural transition regions, such as morphotropic phase boundaries (MPB), owing to the coexistence of multiple phases with nearly equivalent energies. Strain-engineered MPBs have emerged in epitaxially grown BiFeO 3 (BFO) thin films by precisely tailoring a compressive misfit strain, leading to numerous intriguing phenomena, such as a massive piezoelectric response, magnetoelectric coupling, interfacial magnetism and electronic conduction. Recently, an orthorhombic–rhombohedral (O–R) phase boundary has also been found in tensile-strained BFO. In this study, we characterise the crystal structure and electronic properties of the two competing O and R phasesmore » using X-ray diffraction, scanning probe microscope and scanning transmission electron microscopy (STEM). We observe the temperature evolution of R and O domains and find that the domain boundaries are highly conductive. Temperature-dependent measurements reveal that the conductivity is thermally activated for R–O boundaries. STEM observations point to structurally wide boundaries, significantly wider than in other systems. Furthermore, we reveal a strong correlation between the highly conductive domain boundaries and structural material properties. These findings provide a pathway to use phase boundaries in this system for novel nanoelectronic applications.« less

Atomic-Level Sculpting of Crystalline Oxides: Toward Bulk Nanofabrication with Single Atomic Plane Precision.

PubMed

Jesse, Stephen; He, Qian; Lupini, Andrew R; Leonard, Donovan N; Oxley, Mark P; Ovchinnikov, Oleg; Unocic, Raymond R; Tselev, Alexander; Fuentes-Cabrera, Miguel; Sumpter, Bobby G; Pennycook, Stephen J; Kalinin, Sergei V; Borisevich, Albina Y

2015-11-25

The atomic-level sculpting of 3D crystalline oxide nanostructures from metastable amorphous films in a scanning transmission electron microscope (STEM) is demonstrated. Strontium titanate nanostructures grow epitaxially from the crystalline substrate following the beam path. This method can be used for fabricating crystalline structures as small as 1-2 nm and the process can be observed in situ with atomic resolution. The fabrication of arbitrary shape structures via control of the position and scan speed of the electron beam is further demonstrated. Combined with broad availability of the atomic resolved electron microscopy platforms, these observations suggest the feasibility of large scale implementation of bulk atomic-level fabrication as a new enabling tool of nanoscience and technology, providing a bottom-up, atomic-level complement to 3D printing. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Human Tissue Culture Cell Line from a Transitional Cell Tumour of the Urinary Bladder: Growth, Chromosome Pattern and Ultrastructure

PubMed Central

Rigby, Carolyn C.; Franks, L. M.

1970-01-01

Cell cultures were made from 18 human bladder tumours. Three cell lines were maintained for seven transfer generations, but all had a “fibroblastic” morphology and a normal diploid karyotype. A fourth line has been maintained for over 80 transfer generations. This was derived from a well differentiated papillary tumour of bladder. Morphologically the light and electron microscopic structure of the cells resembled that of bladder tumours. The cells formed tumour nodules, with a similar structure, when transplanted into hamster cheek pouches. There is a stem line chromosome number of 48. Karyotypes of 60% of the stem line cells had one extra chromosome in Group C and one in Group D. ImagesFig. 11Figs. 12-15Fig. 16Fig. 17Figs. 1-4Fig. 18Figs. 5-8Figs. 9-10 PMID:5503601

Artefacts in geometric phase analysis of compound materials.

PubMed

Peters, Jonathan J P; Beanland, Richard; Alexe, Marin; Cockburn, John W; Revin, Dmitry G; Zhang, Shiyong Y; Sanchez, Ana M

2015-10-01

The geometric phase analysis (GPA) algorithm is known as a robust and straightforward technique that can be used to measure lattice strains in high resolution transmission electron microscope (TEM) images. It is also attractive for analysis of aberration-corrected scanning TEM (ac-STEM) images that resolve every atom column, since it uses Fourier transforms and does not require real-space peak detection and assignment to appropriate sublattices. Here it is demonstrated that, in ac-STEM images of compound materials with compositionally distinct atom columns, an additional geometric phase is present in the Fourier transform. If the structure changes from one area to another in the image (e.g. across an interface), the change in this additional phase will appear as a strain in conventional GPA, even if there is no lattice strain. Strategies to avoid this pitfall are outlined. Copyright © 2015 Elsevier B.V. All rights reserved.

Effect of erythropoietin on mesenchymal stem cell differentiation and secretion in vitro in an acute kidney injury microenvironment.

PubMed

Liu, N M; Tian, J; Wang, W W; Han, G F; Cheng, J; Huang, J; Zhang, J Y

2013-02-28

We investigated the effect of erythropoietin (EPO) on differentiation and secretion of bone marrow-derived mesenchymal stem cells in an acute kidney injury microenvironment. Acute kidney injury mouse models were prepared. Both renal cortices were then immediately collected to produce the ischemia/reperfusion kidney homogenate supernatant. The morphological and ultrastructural changes in the cells were observed using an inverted microscope and a transmission electron microscope. Cytokeratin-18 was detected using flow cytometry. Bone morphogenetic protein-7 levels, hepatocyte growth factor, and vascular endothelial growth factor in the culture medium were detected using an enzyme-linked immunosorbent assay. The cells had high CD29 and CD44 expression, as well as low CD34 and CD45 expression. More round and oval cells with cobble-like appearances were observed after EPO treatment. In addition, an increase in the number of rough endoplasmic reticula, lysosomes, and mitochondria was observed in the cytoplasm; the intercellular junction peculiar to epithelial cells was also seen on the cell surface. After treatment with ischemia/reperfusion kidney homogenate supernatant, cytokeratin-18 expression increased significantly and EPO could magnify its expression. Bone morphogenetic protein-7 levels, hepatocyte growth factor, and vascular endothelial growth factor levels after treatment with ischemia/reperfusion kidney homogenate supernatant significantly decreased, whereas EPO increased the cytokine secretion. The acute kidney injury microenvironment can induce the bone marrow-derived mesenchymal stem cells to partially differentiate into renal tubular epithelium-shaped cells, but weaken their secretion function. EPO intervention can boost up their differentiation function and reverse their low secretion effect.

The effects of biodegradable poly(lactic-co-glycolic acid)-based microspheres loaded with quercetin on stemness, viability and osteogenic differentiation potential of stem cell spheroids.

PubMed

Lee, H; Nguyen, T T; Kim, M; Jeong, J-H; Park, J-B

2018-05-31

Quercetin has been reported to exert many beneficial effects on the protection against various diseases, such as diabetes, cancer, and inflammation. The aim of this study is to evaluate the potential osteogenic differentiation ability of mesenchymal stem cells in the presence of quercetin. Quercetin-loaded poly(lactic-co-glycolic acid) microspheres were prepared using an electrospraying technique. Characterization of the microspheres was evaluated with a scanning electron microscope and release profile. Three-dimensional cell spheroids were fabricated using silicon elastomer-based concave microwells. Qualitative results of cellular viability were seen under a confocal microscope, and quantitative cellular viability was evaluated using the Cell Counting Kit-8 assay. The alkaline phosphatase activity and Alizarin Red S staining were performed. A quantitative real-time polymerase chain reaction and a western blot analysis were performed. Spheroids were well formed irrespective of quercetin concentration. Most of the cells in spheroids emitted green fluorescence, and the morphology was round without significant changes. The application of quercetin-loaded microspheres produced a significant increase in the alkaline phosphatase activity. The real-time polymerase chain reaction results showed a significant increase in Runx2, and western blot results showed higher expression of Runx2 protein expression. Biodegradable microspheres loaded with quercetin produced prolonged release profiles with increased mineralization. Microspheres loaded with quercetin can be used for the enhancement of osteoblastic differentiation in cell therapy. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Evidence from EELS of oxygen in the nucleation layer of a MBE grown III-N HEMT[Electron Energy Loss Spectroscopy, Molecular Beam Epitaxy, High Electron Mobility Transistor

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

Eustis, T.J.; Silcox, J.; Murphy, M.J.

The presence of oxygen throughout the nominally AlN nucleation layer of a RF assisted MBE grown III-N HEMT was revealed upon examination by Electron Energy Loss Spectroscopy (EELS) in a Scanning Transmission Electron Microscope (STEM). The nucleation layer generates the correct polarity (gallium face) required for producing a piezoelectric induced high mobility two dimensional electron gas at the AlGaN/GaN heterojunction. Only AlN or AlGaN nucleation layers have provided gallium face polarity in RF assisted MBE grown III-N's on sapphire. The sample was grown at Cornell University in a Varian GenII MBE using an EPI Uni-Bulb nitrogen plasma source. The nucleationmore » layer was examined in the Cornell University STEM using Annular Dark Field (ADF) imaging and Parallel Electron Energy Loss Spectroscopy (PEELS). Bright Field TEM reveals a relatively crystallographically sharp interface, while the PEELS reveal a chemically diffuse interface. PEELS of the nitrogen and oxygen K-edges at approximately 5-Angstrom steps across the GaN/AlN/sapphire interfaces reveals the presence of oxygen in the AlN nucleation layer. The gradient suggests that the oxygen has diffused into the nucleation region from the sapphire substrate forming this oxygen containing AlN layer. Based on energy loss near edge structure (ELNES), oxygen is in octahedral interstitial sites in the AlN and Al is both tetrahedrally and octahedrally coordinated in the oxygen rich region of the AlN.« less

Fibrin gel as a scaffold for skin substitute – production and clinical experience.

PubMed

Kljenak, Antun; Tominac Trcin, Mirna; Bujić, Marina; Dolenec, Tamara; Jevak, Martina; Mršić, Gordan; Zmiš, Gordana; Barčot, Zoran; Muljačić, Ante; Popović, Maja

2016-06-01

The purpose of this study was to create a fibrin-based human skin substitute in vitro with epidermal and dermal component and to assess its healing potential in deep partial and full thickness burns. Fibrin scaffolds were prepared from commercial fibrin glue kits. Human fibroblasts were cultured in fibrin gel. Human keratinocytes were seeded on the top of the gel. Viability of cells was determined fluorimetrically. Scanning electron microscope and immunocytochemistry analysis of cultured cells were performed. After hydrosurgical preparation of deep burn necrotic tissue, wound bed was prepared for skin substitutes. Progress of healing was documented using visual estimation and photos. Scanning electron microscope images showed good cell attachment and colony spreading of keratinocytes and fibroblasts on fibrin scaff old. Immunofluorescent staining of cell cultures on fibrin scaffold showed expression of vimentin, a marker of fibroblast cells, cytokeratin 19, a marker of epithelial stem cells, as well as involucrin, a marker of differentiated keratinocytes. Clinical results clearly showed that appearance of the skin did not differ significantly from the areas of transplanted skin using split-thickness skin graft techniques. In conclusion, using these fibrin-cultured autografts on massive full-thickness burn resulted in good healing.

Comparative study of image contrast in scanning electron microscope and helium ion microscope.

PubMed

O'Connell, R; Chen, Y; Zhang, H; Zhou, Y; Fox, D; Maguire, P; Wang, J J; Rodenburg, C

2017-12-01

Images of Ga + -implanted amorphous silicon layers in a 110 n-type silicon substrate have been collected by a range of detectors in a scanning electron microscope and a helium ion microscope. The effects of the implantation dose and imaging parameters (beam energy, dwell time, etc.) on the image contrast were investigated. We demonstrate a similar relationship for both the helium ion microscope Everhart-Thornley and scanning electron microscope Inlens detectors between the contrast of the images and the Ga + density and imaging parameters. These results also show that dynamic charging effects have a significant impact on the quantification of the helium ion microscope and scanning electron microscope contrast. © 2017 The Authors Journal of Microscopy © 2017 Royal Microscopical Society.

Large area fabrication of plasmonic nanoparticle grating structure by conventional scanning electron microscope

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

Sudheer,, E-mail: sudheer@rrcat.gov.in; Tiwari, P.; Rai, V. N.

Plasmonic nanoparticle grating (PNG) structure of different periods has been fabricated by electron beam lithography using silver halide based transmission electron microscope film as a substrate. Conventional scanning electron microscope is used as a fabrication tool for electron beam lithography. Optical microscope and energy dispersive spectroscopy (EDS) have been used for its morphological and elemental characterization. Optical characterization is performed by UV-Vis absorption spectroscopic technique.

Assessment of Pb uptake, translocation and immobilization in kenaf (Hibiscus cannabinus L.) for phytoremediation of sand tailings.

PubMed

Ho, Wai Mun; Ang, Lai Hoe; Lee, Don Koo

2008-01-01

The potential of kenaf (Hibiscus cannabinus L.) for phytoremediation of lead (Pb) on sand tailings was investigated. A pot experiment employing factorial design with two main effects of fertilizer and lead was conducted in a nursery using sand tailings from an ex-tin mine as the growing medium. Results showed that Pb was found in the root, stem, and seed capsule of kenaf but not in the leaf. Application of organic fertilizer promoted greater biomass yield as well as higher accumulation capacity of Pb. In Pb-spiked treatments, roots accumulated more than 85% of total plant Pb which implies that kenaf root can be an important sink for bioavailable Pb. Scanning transmission electron microscope (STEM) X-ray microanalysis confirmed that electron-dense deposits located along cell walls of kenaf roots were Pb precipitates. The ability of kenaf to tolerate Pb and avoid phytotoxicity could be attributed to the immobilization of Pb in the roots and hence the restriction of upward movement (translocation factor < 1). With the application of fertilizer, kenaf was also found to have higher biomass and subsequently higher bioaccumulation capacity, indicating its suitability for phytoremediation of Pb-contaminated site.

Transmission electron microscope CCD camera

DOEpatents

Downing, Kenneth H.

1999-01-01

In order to improve the performance of a CCD camera on a high voltage electron microscope, an electron decelerator is inserted between the microscope column and the CCD. This arrangement optimizes the interaction of the electron beam with the scintillator of the CCD camera while retaining optimization of the microscope optics and of the interaction of the beam with the specimen. Changing the electron beam energy between the specimen and camera allows both to be optimized.

Three-dimensional profile extraction from CD-SEM image and top/bottom CD measurement by line-edge roughness analysis

NASA Astrophysics Data System (ADS)

Yamaguchi, Atsuko; Ohashi, Takeyoshi; Kawasaki, Takahiro; Inoue, Osamu; Kawada, Hiroki

2013-04-01

A new method for calculating critical dimension (CDs) at the top and bottom of three-dimensional (3D) pattern profiles from a critical-dimension scanning electron microscope (CD-SEM) image, called as "T-sigma method", is proposed and evaluated. Without preparing a library of database in advance, T-sigma can estimate a feature of a pattern sidewall. Furthermore, it supplies the optimum edge-definition (i.e., threshold level for determining edge position from a CDSEM signal) to detect the top and bottom of the pattern. This method consists of three steps. First, two components of line-edge roughness (LER); noise-induced bias (i.e., LER bias) and unbiased component (i.e., bias-free LER) are calculated with set threshold level. Second, these components are calculated with various threshold values, and the threshold-dependence of these two components, "T-sigma graph", is obtained. Finally, the optimum threshold value for the top and the bottom edge detection are given by the analysis of T-sigma graph. T-sigma was applied to CD-SEM images of three kinds of resist-pattern samples. In addition, reference metrology was performed with atomic force microscope (AFM) and scanning transmission electron microscope (STEM). Sensitivity of CD measured by T-sigma to the reference CD was higher than or equal to that measured by the conventional edge definition. Regarding the absolute measurement accuracy, T-sigma showed better results than the conventional definition. Furthermore, T-sigma graphs were calculated from CD-SEM images of two kinds of resist samples and compared with corresponding STEM observation results. Both bias-free LER and LER bias increased as the detected edge point moved from the bottom to the top of the pattern in the case that the pattern had a straight sidewall and a round top. On the other hand, they were almost constant in the case that the pattern had a re-entrant profile. T-sigma will be able to reveal a re-entrant feature. From these results, it is found that T-sigma method can provide rough cross-sectional pattern features and achieve quick, easy and accurate measurements of top and bottom CD.

Biosynthesis of silver nanoparticles using Artemisia annua callus for inhibiting stem-end bacteria in cut carnation flowers.

PubMed

Xia, Qian Hua; Zheng, Li Ping; Zhao, Pei Fei; Wang, Jian Wen

2017-03-01

A biological method for synthesising silver nanoparticles (AgNPs) was developed using the callus extracts from Artemisia annua L. under sunlight at 25,000 lx. The AgNPs were characterised using transmission electron microscopy, atomic force microscope, X-ray diffraction and Fourier transform infrared spectroscopy. The AgNPs were mostly spherical with the size of 2.1 to 45.2 nm (average 10.9 nm). Pulse treatments of AgNPs at 125, 250 and 500 mg/l for 1 h extended vase life of cut carnation ( Dianthus caryophyllus cv. Green Land) flowers. Four dominant bacteria strains Arthrobacter arilaitensis, Kocuria sp., Staphylococcus equorum and Microbacterium oxydans were isolated from the stem-ends of cut D. caryophyllus flowers. AgNP pulse inhibited significantly bacterial growth in vase solution and cut stem ends during all of the vase period. The bacteria related blockage in the stem-ends was significantly alleviated by AgNP pulse because of its higher antibacterial efficacy against the dominant bacteria. In addition, ethylene release of cut carnation flowers was inhibited in response to AgNP pulse. This is the first time that the biologically synthesised AgNPs could be applied as a promising preservative agent for cut carnation flowers.

Excited helium under high pressures in the bulk and in nanobubbles

NASA Astrophysics Data System (ADS)

Pyper, N. C.; Naginey, T. C.; Nellist, P. D.; Whelan, Colm T.

2017-08-01

We systematically investigate the effects of intense pressures on the excitation energies of helium trapped in bubbles in order to deepen our understanding of the fundamental physics of atoms in extreme conditions. The ? excitation energy of a confined helium atom is known to differ from that of a free atom being greater in both the bulk liquid or solid or a bubble confined in a metallic matrix state. We compare calculations for the energy shift with both laboratory experiments for bulk systems and results derived from scanning transmission electron microscope (STEM) studies of helium nanobubbles embedded in different matrices. We find excellent agreement between our calculations and the latest extensive measurements in the bulk. However, we find significant discrepancies when we compare with results deduced using the 'standard' approach for analysing STEM data. Here, we show the scattering matrix element determining the intensity of this excitation in a STEM experiment is significantly affected by the same environmental factors that shift the excitation energy. Consequently, there is a serious theoretical inconsistency in the way the STEM results are calculated, in that the 'standard' approach depends on a supposedly known ? scattering cross section, whereas we show here that this cross section is itself dependent on the environment. Correcting for this inconsistency does not, in itself, improve agreement.

Triosmium Clusters on a Support: Determination of Structure by X-Ray Absorption Spectroscopy and High-Resolution Microscopy

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

Shareghe, Mehraeen; Chi, Miaofang; Browning, Nigel D.

2011-01-01

The structures of small, robust metal clusters on a solid support were determined by a combination of spectroscopic and microscopic methods: extended X-ray absorption fine structure (EXAFS) spectroscopy, scanning transmission electron microscopy (STEM), and aberration-corrected STEM. The samples were synthesized from [Os{sub 3}(CO){sub 12}] on MgO powder to provide supported clusters intended to be triosmium. The results demonstrate that the supported clusters are robust in the absence of oxidants. Conventional high-angle annular dark-field (HAADF) STEM images demonstrate a high degree of uniformity of the clusters, with root-mean-square (rms) radii of 2.03 {+-} 0.06 {angstrom}. The EXAFS OsOs coordination number ofmore » 2.1 {+-} 0.4 confirms the presence of triosmium clusters on average and correspondingly determines an average rms cluster radius of 2.02 {+-} 0.04 {angstrom}. The high-resolution STEM images show the individual Os atoms in the clusters, confirming the triangular structures of their frames and determining OsOs distances of 2.80 {+-} 0.14 {angstrom}, matching the EXAFS value of 2.89 {+-} 0.06 {angstrom}. IR and EXAFS spectra demonstrate the presence of CO ligands on the clusters. This set of techniques is recommended as optimal for detailed and reliable structural characterization of supported clusters.« less

Uninduced adipose-derived stem cells repair the defect of full-thickness hyaline cartilage.

PubMed

Zhang, Hai-Ning; Li, Lei; Leng, Ping; Wang, Ying-Zhen; Lv, Cheng-Yu

2009-04-01

To testify the effect of the stem cells derived from the widely distributed fat tissue on repairing full-thickness hyaline cartilage defects. Adipose-derived stem cells (ADSCs) were derived from adipose tissue and cultured in vitro. Twenty-seven New Zealand white rabbits were divided into three groups randomly. The cultured ADSCs mixed with calcium alginate gel were used to fill the full-thickness hyaline cartilage defects created at the patellafemoral joint, and the defects repaired with gel or without treatment served as control groups. After 4, 8 and 12 weeks, the reconstructed tissue was evaluated macroscopically and microscopically. Histological analysis and qualitative scoring were also performed to detect the outcome. Full thickness hyaline cartilage defects were repaired completely with ADSCs-derived tissue. The result was better in ADSCs group than the control ones. The microstructure of reconstructed tissue with ADSCs was similar to that of hyaline cartilage and contained more cells and regular matrix fibers, being better than other groups. Plenty of collagen fibers around cells could be seen under transmission electron microscopy. Statistical analysis revealed a significant difference in comparison with other groups at each time point (t equal to 4.360, P less than 0.01). These results indicate that stem cells derived from mature adipose without induction possess the ability to repair cartilage defects.

76 FR 65696 - Battelle Energy Alliance, et al.;

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-24

... of Texas at Austin, Austin, TX 78712. Instrument: Electron Microscope. Manufacturer: FEI Company, the... research or scientific educational uses requiring an electron microscope. We know of no electron microscope...

Germination, growth rates, and electron microscope analysis of tomato seeds flown on the LDEF

NASA Technical Reports Server (NTRS)

Hammond, Ernest C., Jr.; Bridgers, Kevin; Brown, Cecelia Wright

1995-01-01

The tomato seeds were flown in orbit aboard the Long Duration Exposure Facility (LDEF) for nearly six years. During this time, the tomato seeds received an abundant exposure to cosmic radiation and solar wind. Upon the return of the LDEF to earth, the seeds were distributed throughout the United States and 30 foreign countries for analysis. The purpose of the experiment was to determine the long term effect of cosmic rays on living tissue. Our university analysis included germination and growth rates as well as Scanning Electron Microscopy and X-ray analysis of the control as well as Space-exposed tomato seeds. In analyzing the seeds under the Electron Microscope, usual observations were performed on the nutritional and epidermis layer of the seed. These layers appeared to be more porous in the Space-exposed seeds than on the Earth-based control seeds. This unusual characteristic may explain the increases in the space seeds growth pattern. (Several test results show that the Space-exposed seeds germinate sooner than the Earth-Based seeds. Also, the Space-exposed seeds grew at a faster rate). The porous nutritional region may allow the seeds to receive necessary nutrients and liquids more readily, thus enabling the plant to grow at a faster rate. Roots, leaves and stems were cut into small sections and mounted. After sputter coating the specimens with Argon/Gold Palladium Plasma, they were ready to be viewed under the Electron Microscope. Many micrographs were taken. The X-ray analysis displayed possible identifications of calcium, potassium, chlorine, copper, aluminum, silicon, phosphate, carbon, and sometimes sulfur and iron. The highest concentrations were shown in potassium and calcium. The Space-exposed specimens displayed a high concentration of copper and calcium in the two specimens. There was a significantly high concentration of copper in the Earth-based specimens, whereas there was no copper in the Space-exposed specimens.

Investigation of C3 S hydration mechanism by transmission electron microscope (TEM) with integrated Super-XTM EDS system.

PubMed

Sakalli, Y; Trettin, R

2017-07-01

Tricalciumsilicate (C 3 S, Alite) is the major component of the Portland cement clinker. Hydration of Alite is decisive in influencing the properties of the resulting material. This is due to its high content in cement. The mechanism of the hydration of C 3 S is very complicated and not yet fully understood. There are different models describing the hydration of C 3 S in various ways. In this work for a better understanding of hydration mechanism, the hydrated C 3 S was investigated by using the transmission electron microscope (TEM) and for the first time, the samples for the investigations were prepared by using of focused ion beam from sintered pellets of C 3 S. Also, an FEI Talos F200x with an integrated Super-X EDS system was used for the investigations. FEI Talos F200X combines outstanding high-resolution S/TEM and TEM imaging with energy dispersive X-ray spectroscopy signal detection, and 3D chemical characterization with compositional mapping. TEM is a very powerful tool for material science. A high energy beam of electrons passes through a very thin sample, and the interactions between the electrons and the atoms can be used to observe the structure of the material and other features in the structure. TEM can be used to study the growth of layers and their composition. TEM produces high-resolution, two-dimensional images and will be used for a wide range of educational, science and industry applications. Chemical analysis can also be performed. The purpose of these investigations was to get the information about the composition of the C-S-H phases and some details of the nanostructure of the C-S-H phases. © 2017 The Authors Journal of Microscopy © 2017 Royal Microscopical Society.

Nature Study with the Microscope.

ERIC Educational Resources Information Center

Sollberger, Dwight E.

1991-01-01

Identifies specific instruction difficulties, potential problems, solutions, and activities for successful use of microscopes in the classroom. Procedures are outlined for guiding students in creating their own slides with monocotyledon and dicotyledon stems, fern spores, stomata, lichens, and red onions. (MCO)

Gaining Control over Radiolytic Synthesis of Uniform Sub-3-nanometer Palladium Nanoparticles: Use of Aromatic Liquids in the Electron Microscope.

PubMed

Abellan, Patricia; Parent, Lucas R; Al Hasan, Naila; Park, Chiwoo; Arslan, Ilke; Karim, Ayman M; Evans, James E; Browning, Nigel D

2016-02-16

Synthesizing nanomaterials of uniform shape and size is of critical importance to access and manipulate the novel structure-property relationships arising at the nanoscale, such as catalytic activity. In this work, we synthesize Pd nanoparticles with well-controlled size in the sub-3 nm range using scanning transmission electron microscopy (STEM) in combination with an in situ liquid stage. We use an aromatic hydrocarbon (toluene) as a solvent that is very resistant to high-energy electron irradiation, which creates a net reducing environment without the need for additives to scavenge oxidizing radicals. The primary reducing species is molecular hydrogen, which is a widely used reductant in the synthesis of supported metal catalysts. We propose a mechanism of particle formation based on the effect of tri-n-octylphosphine (TOP) on size stabilization, relatively low production of radicals, and autocatalytic reduction of Pd(II) compounds. We combine in situ STEM results with insights from in situ small-angle X-ray scattering (SAXS) from alcohol-based synthesis, having similar reduction potential, in a customized microfluidic device as well as ex situ bulk experiments. This has allowed us to develop a fundamental growth model for the synthesis of size-stabilized Pd nanoparticles and demonstrate the utility of correlating different in situ and ex situ characterization techniques to understand, and ultimately control, metal nanostructure synthesis.

Electronic Interfacial Effects in Epitaxial Heterostructures based on LaMnO3.

NASA Astrophysics Data System (ADS)

Christen, Hans M.; Varela, M.; Lee, H. N.; Kim, D. H.; Chisholm, M. F.; Cantoni, C.; Petit, L.; Schulthess, T. C.; Lowndes, D. H.

2006-03-01

Studies of chemically abrupt interfaces provide an ideal platform to study the effects of discontinuities and asymmetries of the electronic configuration on the transport and magnetic properties of complex oxides. In addition, the behavior of complex materials near interfaces plays the most crucial role not only in devices and nanostructures but also in complex structures in the form of composites and superlattices, including artificial multiferroics. Interfaces in the ABO3 perovskite system are particularly attractive because structurally similar oxides with fundamentally different physical properties can be integrated epitaxially. To explore the electronic effects at interfaces and to probe the physical properties that result from local electronic changes, we have synthesized structures containing LaMnO3 and insulating perovskites using pulsed laser deposition. The local electron energy loss spectroscopy (EELS) capability of a scanning transmission electron microscope (STEM) is used to probe the electronic configuration in the LaMnO3 films as a function of the distance from the interfaces. The results are compared to macroscopic measurements and theoretical predictions. Research sponsored by the U.S. Department of Energy under contract DE-AC05-00OR22725 with the Oak Ridge National Laboratory, managed by UT-Battelle, LLC.

Lithium Self-Discharge and Its Prevention: Direct Visualization through In Situ Electrochemical Scanning Transmission Electron Microscopy

DOE PAGES

Harrison, Katharine L.; Zavadil, Kevin R.; Hahn, Nathan T.; ...

2017-11-07

To understand the mechanism that controls low-aspect-ratio lithium deposition morphologies for Li-metal anodes in batteries, we conducted direct visualization of Li-metal deposition and stripping behavior through nanoscale in situ electrochemical scanning transmission electron microscopy (EC-STEM) and macroscale-cell electrochemistry experiments in a recently developed and promising solvate electrolyte, 4 M lithium bis(fluorosulfonyl)imide in 1,2-dimethoxyethane. In contrast to published coin cell studies in the same electrolyte, our experiments revealed low Coulombic efficiencies and inhomogeneous Li morphology during in situ observation. In addition, we conclude that this discrepancy in Coulombic efficiency and morphology of the Li deposits was dependent on the presence ofmore » a compressed lithium separator interface, as we have confirmed through macroscale (not in the transmission electron microscope) electrochemical experiments. Our data suggests that cell compression changed how the solid-electrolyte interphase formed, which is likely responsible for improved morphology and Coulombic efficiency with compression. Furthermore, during the in situ EC-STEM experiments, we observed direct evidence of nanoscale self-discharge in the solvate electrolyte (in the state of electrical isolation). This self-discharge was duplicated in the macroscale, but it was less severe with electrode compression, likely due to a more passivating and corrosion-resistant solid-electrolyte interphase formed in the presence of compression. By combining the solvate electrolyte with a protective LiAl 0.3S coating, we show that the Li nucleation density increased during deposition, leading to improved morphological uniformity. In conclusion, self-discharge was suppressed during rest periods in the cycling profile with coatings present, as evidenced through EC-STEM and confirmed with coin cell data.« less

Lithium Self-Discharge and Its Prevention: Direct Visualization through In Situ Electrochemical Scanning Transmission Electron Microscopy.

PubMed

Harrison, Katharine L; Zavadil, Kevin R; Hahn, Nathan T; Meng, Xiangbo; Elam, Jeffrey W; Leenheer, Andrew; Zhang, Ji-Guang; Jungjohann, Katherine L

2017-11-28

To understand the mechanism that controls low-aspect-ratio lithium deposition morphologies for Li-metal anodes in batteries, we conducted direct visualization of Li-metal deposition and stripping behavior through nanoscale in situ electrochemical scanning transmission electron microscopy (EC-STEM) and macroscale-cell electrochemistry experiments in a recently developed and promising solvate electrolyte, 4 M lithium bis(fluorosulfonyl)imide in 1,2-dimethoxyethane. In contrast to published coin cell studies in the same electrolyte, our experiments revealed low Coulombic efficiencies and inhomogeneous Li morphology during in situ observation. We conclude that this discrepancy in Coulombic efficiency and morphology of the Li deposits was dependent on the presence of a compressed lithium separator interface, as we have confirmed through macroscale (not in the transmission electron microscope) electrochemical experiments. Our data suggests that cell compression changed how the solid-electrolyte interphase formed, which is likely responsible for improved morphology and Coulombic efficiency with compression. Furthermore, during the in situ EC-STEM experiments, we observed direct evidence of nanoscale self-discharge in the solvate electrolyte (in the state of electrical isolation). This self-discharge was duplicated in the macroscale, but it was less severe with electrode compression, likely due to a more passivating and corrosion-resistant solid-electrolyte interphase formed in the presence of compression. By combining the solvate electrolyte with a protective LiAl 0.3 S coating, we show that the Li nucleation density increased during deposition, leading to improved morphological uniformity. Furthermore, self-discharge was suppressed during rest periods in the cycling profile with coatings present, as evidenced through EC-STEM and confirmed with coin cell data.

Lithium Self-Discharge and Its Prevention: Direct Visualization through In Situ Electrochemical Scanning Transmission Electron Microscopy

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

Harrison, Katharine L.; Zavadil, Kevin R.; Hahn, Nathan T.

To understand the mechanism that controls low-aspect-ratio lithium deposition morphologies for Li-metal anodes in batteries, we conducted direct visualization of Li-metal deposition and stripping behavior through nanoscale in situ electrochemical scanning transmission electron microscopy (EC-STEM) and macroscale-cell electrochemistry experiments in a recently developed and promising solvate electrolyte, 4 M lithium bis(fluorosulfonyl)imide in 1,2-dimethoxyethane. In contrast to published coin cell studies in the same electrolyte, our experiments revealed low Coulombic efficiencies and inhomogeneous Li morphology during in situ observation. In addition, we conclude that this discrepancy in Coulombic efficiency and morphology of the Li deposits was dependent on the presence ofmore » a compressed lithium separator interface, as we have confirmed through macroscale (not in the transmission electron microscope) electrochemical experiments. Our data suggests that cell compression changed how the solid-electrolyte interphase formed, which is likely responsible for improved morphology and Coulombic efficiency with compression. Furthermore, during the in situ EC-STEM experiments, we observed direct evidence of nanoscale self-discharge in the solvate electrolyte (in the state of electrical isolation). This self-discharge was duplicated in the macroscale, but it was less severe with electrode compression, likely due to a more passivating and corrosion-resistant solid-electrolyte interphase formed in the presence of compression. By combining the solvate electrolyte with a protective LiAl 0.3S coating, we show that the Li nucleation density increased during deposition, leading to improved morphological uniformity. In conclusion, self-discharge was suppressed during rest periods in the cycling profile with coatings present, as evidenced through EC-STEM and confirmed with coin cell data.« less

A new centrifuge microscope reveals that mobile plastids trigger gravity sensing in Arabidopsis inflorescence stems

NASA Astrophysics Data System (ADS)

Toyota, Masatsugu; Tasaka, Masao; Morita, Miyo T.; Gilroy, Simon

2012-07-01

The starch-statolith hypothesis is the most widely accepted model for plant gravity sensing and proposes that the sedimentation of high-density starch-filled plastids (amyloplasts) in shoot endodermal cells and root columella cells is important for gravity sensing of each organ. However, starch-deficient phosphoglucomutase (pgm-1) mutants sense gravity and show gravitropism in inflorescence stems, even though most starchless amyloplasts in this mutant fail to sediment toward the gravity vector. These results raise the questions about the role of starch in gravity sensing and the features of statolith/statocyte essential for shoot gravity sensing. To address these questions, we developed a new centrifuge microscope and analyzed two gravitropic mutants, i.e., pgm-1 and endodermal-amyloplast less 1 (eal1). All optical devices (e.g., objective lens, light source and CCD camera) and specimens were rotated on a direct-drive motor, and acquired images were wirelessly transmitted during centrifugation. Live-cell imaging during centrifugation revealed that the starchless amyloplasts sedimented to the hypergravity vector (10 and 30 g) in endodermal cells of pgm-1 stems, indicating that the density of the starchless amyloplasts is higher than that of cytoplasm. Electron micrographs of shoot endodermal cells in pgm-1 mutants suggested that the starchless amyloplast contains an organized thylakoid membrane but not starch granules, which morphologically resembles chloroplasts in the adjacent cortical cells. Therefore, the shoot amyloplasts without starch are possibly as dense as chloroplasts. We examined eal1 mutants, an allele of shoot gravitropism (sgr) 7/short-root (shr), which also have starchless amyloplasts due to abnormal differentiation of amyloplasts and show no gravitropic response at 1 g. Hypergravity up to 30 g induced little gravitropism in eal1 stems and the starchless amyloplasts failed to sediment under 30 g conditions. However, the eal1 mutants treated with latrunculin B, an actin disrupting drug, showed gravitropism under 30 g conditions, during which amyloplasts were artificially sedimented by hypergravity. These results suggest that shoot amyloplasts are intrinsically dense enough to trigger gravity sensing without starch and, rather, intracellular environments that render amyloplasts sedimentable/mobile, such as actin organization, are essential for gravity sensing in Arabidopsis inflorescence stems.

Gravitropism in Leafy Dicot Stems

NASA Technical Reports Server (NTRS)

Salisbury, F. B.

1985-01-01

A polarizing research microscope with rotating stage and associated camera equipment were ordered, and techniques of fixation and preparation of specimens were perfected for studying possible changes in orientation of cellulose microfibrils in cell walls of gravistimulated dicot stems. Acid ethephon solutions or acid without ethephon caused elongation of stem tissues where they were applied; stems bent away from the side of application. Acid solutions applied to the bottom of horizontal stems greatly delayed bending. Research in tissue sensitivity changes during gravitropic bending of soybean hypocotyls while immersed in auxin and in castor bean stems is also reported.

[An experimental study of mesenchymal stem cells in tissue engineering scaffolds implanted in rabbit corneal lamellae to increase keratoprosthesis biointegration].

PubMed

Bai, H; Wang, L L; Huang, Y F; Huang, J X

2016-03-01

To complete a preliminary evaluation of the feasibility of implanting the complex of mouse bone marrow mesenchymal stem cells (BMSC) and a tissue engineering scaffold into rabbit corneal lamellae, based on which a solution may be proposed to consolidate the keratoprosthesis and the recipient surface, and to reduce the risk of complications. This experimental study was composed of two parts. (1) In vitro: some mouse BMSC were marked with red fluorescent proteins (RFP) and integrated with a decellularized pig articular cartilage extracellular matrix (ECM) scaffold. The cell survival was observed under a fluorescence microscope at 4 and 8 weeks. The cell distribution was examined by toluidine blue staining. The pore structure and the cell adhesion were observed under a scanning electron microscope. (2) in vivo: the complex of mouse BMSC and a decellularized scaffold was implanted into the lamellar cornea of 8 rabbit eyes with the fellow eyes as the controls. The eyes were sampled for observation using HE staining under a light microscope at 2, 4 and 8 weeks, respectively. The cell survival was examined under a fluorescence microscope, and the intracorneal cell survival at 8 weeks was observed using in vivo imaging. The conditions of ocular anterior segment of all the experimental animals were recorded. (1) Under the scanning electron microscope, the ECM scaffolds showed satisfactory porosity required for the adhesion and growth of cells and tissues, and the cell distribution over the cell-scaffold complex can be observed by toluidine blue staining. (2) Under the immunofluorescence microscope, cell proliferation was observed in vitro and in the interlamellar space (the maximum observation time was 8 weeks) after the RFP-marked mouse BMSC were integrated in vitro with ECM scaffolds. (3) Under the light microscope (HE staining), the stromal cells were detected to increase at each timepoint. A small number of monocytes and some mouse BMSC were observed in the superficial layer of corneal stroma, with sparsely and orderly arranged collagenous fibers and no neovascularization. All the epithelial cells appeared as mononuclear, columnar and undamaged, and the shape of ECM scaffolds, which were fused with the collagens, became unclear. (4) By in vivo imaging, it was found that the mouse BMSC survived for 8 weeks after being integrated with scaffolds and implanted into the interlamellar space of rabbit cornea. (5) After the implantation of cell-scaffold complex, severe postoperative inflammatory reactions, obvious conjunctival congestion and neovascularization were not observed. The corneal tissues surrounding the recipient area were transparent. One week later, mild inflammatory reactions were barely observed, and the cornea was transparent enough to observe the scaffold in the stromal layers. Four weeks later, the scaffolds became thinner. Eight weeks later, the scaffolds became extremely thin with normal vascular system in the corneal limbus. The ECM scaffold is a solid and biocompatible carrier for the growth and proliferation of BMSC. The mouse BMSC can grow and proliferate in the microenvironment of the interlamellar space of cornea.

Bone Marrow Stem Cells and Ear Framework Reconstruction.

PubMed

Karimi, Hamid; Emami, Seyed-Abolhassan; Olad-Gubad, Mohammad-Kazem

2016-11-01

Repair of total human ear loss or congenital lack of ears is one of the challenging issues in plastic and reconstructive surgery. The aim of the present study was 3D reconstruction of the human ear with cadaveric ear cartilages seeded with human mesenchymal stem cells. We used cadaveric ear cartilages with preserved perichondrium. The samples were divided into 2 groups: group A (cartilage alone) and group B (cartilage seeded with a mixture of fibrin powder and mesenchymal stem cell [1,000,000 cells/cm] used and implanted in back of 10 athymic rats). After 12 weeks, the cartilages were removed and shape, size, weight, flexibility, and chondrocyte viability were evaluated. P value <0.05 was considered significant. In group A, size and weight of cartilages clearly reduced (P < 0.05) and then shape and flexibility (torsion of cartilages in clockwise and counterclockwise directions) were evaluated, which were found to be significantly reduced (P > 0.05). After staining with hematoxylin and eosin and performing microscopic examination, very few live chondrocytes were found in group A. In group B, size and weight of samples were not changed (P < 0.05); the shape and flexibility of samples were well maintained (P < 0.05) and on performing microscopic examination of cartilage samples, many live chondrocytes were found in cartilage (15-20 chondrocytes in each microscopic field). In samples with human stem cell, all variables (size, shape, weight, and flexibility) were significantly maintained and abundant live chondrocytes were found on performing microscopic examination. This method may be used for reconstruction of full defect of auricles in humans.

Probing the electrical switching of a memristive optical antenna by STEM EELS

PubMed Central

Schoen, David T.; Holsteen, Aaron L.; Brongersma, Mark L.

2016-01-01

The scaling of active photonic devices to deep-submicron length scales has been hampered by the fundamental diffraction limit and the absence of materials with sufficiently strong electro-optic effects. Plasmonics is providing new opportunities to circumvent this challenge. Here we provide evidence for a solid-state electro-optical switching mechanism that can operate in the visible spectral range with an active volume of less than (5 nm)3 or ∼10−6 λ3, comparable to the size of the smallest electronic components. The switching mechanism relies on electrochemically displacing metal atoms inside the nanometre-scale gap to electrically connect two crossed metallic wires forming a cross-point junction. These junctions afford extreme light concentration and display singular optical behaviour upon formation of a conductive channel. The active tuning of plasmonic antennas attached to such junctions is analysed using a combination of electrical and optical measurements as well as electron energy loss spectroscopy in a scanning transmission electron microscope. PMID:27412052

The influence of protein concentration on the biotribological properties of the stem-cement interface.

PubMed

Zhang, Hong-Yu; Zhou, Ming

2014-01-01

The stem-cement interface in total hip replacement experiences fretting wear following debonding under cyclical physiological loading. However, the influence of protein concentration on the biotribological properties of this interface has not been well taken into consideration. In the present study, a series of fretting frictional tests were performed using polished Ti6Al4V and bone cement, lubricated by bovine serum albumin solutions of different concentrations (5%, 30%, and 75%). Surface characterizations of Ti6Al4V pins were conducted by optical interferometer, scanning electron microscope, and Raman spectroscopy. The results show that the friction coefficient decreases with the increase of protein concentration, although the difference is not significant. In addition, bovine serum albumin is adsorbed onto Ti6Al4V surface, forming a protective film to prevent the metal substrate from wear. The elemental and spectroscopic analyses of the film confirm the presence of protein molecules adsorbed on Ti6Al4V surface, with a thickness of 2.5 μm. It is indicated from this study that fretting wear at the stem-cement interface can be postponed by promotion of protein adsorption on the metal surface.

Microscopic characters of the leaf and stem of Lavandula dentata L. (Lamiaceae).

PubMed

do Rocio Duarte, Márcia; Carvalho de Souza, Danielle

2014-08-01

Lavandula dentata L. is an aromatic plant used in folk medicine for different purposes and, for this reason, phytochemical surveys have been carried out in the search for bioactive substances aiming to support its uses. Since there is little knowledge on the structural aspects of L. dentata, this work has studied the anatomical characters of the leaf and stem using light and scanning electron microscopy, in order to assist the species identification. As a result, there are different types of trichomes: capitate glandular with uni- or bicellular head, peltate glandular with multicellular head, and branched non-glandular. The leaf is hypostomatic showing diacytic stomata. The epidermis is uniseriate and coated with striate cuticle. The mesophyll is dorsiventral and the midrib is concave-convex and traversed by a single collateral vascular bundle. The stem is quadrangular and has alternating strands of collenchyma and cortical parenchyma as well as a typical endodermis in the cortex. The phloem and xylem cylinders are traversed by narrow rays and there is an incomplete sclerenchymatic sheath adjoining the phloem. These results are a novelty for the species and contribute to distinguish it from other lavenders. © 2014 Wiley Periodicals, Inc.

Fabrication and nanoscale characterization of magnetic multilayer nanowires

NASA Astrophysics Data System (ADS)

Elawayeb, Mohamed

Magnetic multilayers nanowires are scientifically fascinating and have potential industrial applications in many areas of advanced nanotechnology. These applications arise due to the nanoscale dimensions of nanostructures that lead to unique physical properties. Magnetic multilayer nanowires have been successfully produced by electrodeposition into templates. Anodic Aluminium Oxide (AAO) membranes were used as templates in this process; the templates were fabricated by anodization method in acidic solutions at a fixed voltage. The fabrication method of a range of magnetic multilayer nanowires is described in this study and their structure and dimensions were analyzed using scanning electron microscope (SEM), Transmission electron microscope (TEM) and scanning transmission electron microscopy (STEM). This study is focused on the first growth of NiFe/Pt and NiFe/Fe magnetic multilayer nanowires, which were successfully fabricated by pulse electrodeposition into the channels of porous anodic aluminium oxide (AAO) templates, and characterized at the nanoscale. Individual nanowires have uniform structure and regular periodicity. The magnetic and nonmagnetic layers are polycrystalline, with randomly oriented fcc lattice structure crystallites. Chemical compositions of the individual nanowires were analyzed using TEM equipped with energy-dispersive x-ray analysis (EDX) and electron energy loss spectrometry (EELS). The electrical and magnetoresistance properties of individual magnetic multilayer nanowires have been measured inside a SEM using two sharp tip electrodes attached to in situ nanomanipulators and a new electromagnet technique. The giant magnetoresistance (GMR) effect of individual magnetic multilayer nanowires was measured in the current - perpendicular to the plane (CPP) geometry using a new in situ method at variable magnetic field strength and different orientations..

Micromechanics of ultra-toughened electrospun PMMA/PEO fibres as revealed by in-situ tensile testing in an electron microscope

PubMed Central

Andersson, Richard L.; Ström, Valter; Gedde, Ulf W.; Mallon, Peter E.; Hedenqvist, Mikael S.; Olsson, Richard T.

2014-01-01

A missing cornerstone in the development of tough micro/nano fibre systems is an understanding of the fibre failure mechanisms, which stems from the limitation in observing the fracture of objects with dimensions one hundredth of the width of a hair strand. Tensile testing in the electron microscope is herein adopted to reveal the fracture behaviour of a novel type of toughened electrospun poly(methyl methacrylate)/poly(ethylene oxide) fibre mats for biomedical applications. These fibres showed a toughness more than two orders of magnitude greater than that of pristine PMMA fibres. The in-situ microscopy revealed that the toughness were not only dependent on the initial molecular alignment after spinning, but also on the polymer formulation that could promote further molecular orientation during the formation of micro/nano-necking. The true fibre strength was greater than 150 MPa, which was considerably higher than that of the unmodified PMMA (17 MPa). This necking phenomenon was prohibited by high aspect ratio cellulose nanocrystal fillers in the ultra–tough fibres, leading to a decrease in toughness by more than one order of magnitude. The reported necking mechanism may have broad implications also within more traditional melt–spinning research. PMID:25208692

Nickel/Platinum Dual Silicide Axial Nanowire Heterostructures with Excellent Photosensor Applications.

PubMed

Wu, Yen-Ting; Huang, Chun-Wei; Chiu, Chung-Hua; Chang, Chia-Fu; Chen, Jui-Yuan; Lin, Ting-Yi; Huang, Yu-Ting; Lu, Kuo-Chang; Yeh, Ping-Hung; Wu, Wen-Wei

2016-02-10

Transition metal silicide nanowires (NWs) have attracted increasing attention as they possess advantages of both silicon NWs and transition metals. Over the past years, there have been reported with efforts on one silicide in a single silicon NW. However, the research on multicomponent silicides in a single silicon NW is still rare, leading to limited functionalities. In this work, we successfully fabricated β-Pt2Si/Si/θ-Ni2Si, β-Pt2Si/θ-Ni2Si, and Pt, Ni, and Si ternary phase axial NW heterostructures through solid state reactions at 650 °C. Using in situ transmission electron microscope (in situ TEM), the growth mechanism of silicide NW heterostructures and the diffusion behaviors of transition metals were systematically studied. Spherical aberration corrected scanning transmission electron microscope (Cs-corrected STEM) equipped with energy dispersive spectroscopy (EDS) was used to analyze the phase structure and composition of silicide NW heterostructures. Moreover, electrical and photon sensing properties for the silicide nanowire heterostructures demonstrated promising applications in nano-optoeletronic devices. We found that Ni, Pt, and Si ternary phase nanowire heterostructures have an excellent infrared light sensing property which is absent in bulk Ni2Si or Pt2Si. The above results would benefit the further understanding of heterostructured nano materials.

Orientation and phase mapping in the transmission electron microscope using precession-assisted diffraction spot recognition: state-of-the-art results.

PubMed

Viladot, D; Véron, M; Gemmi, M; Peiró, F; Portillo, J; Estradé, S; Mendoza, J; Llorca-Isern, N; Nicolopoulos, S

2013-10-01

A recently developed technique based on the transmission electron microscope, which makes use of electron beam precession together with spot diffraction pattern recognition now offers the possibility to acquire reliable orientation/phase maps with a spatial resolution down to 2 nm on a field emission gun transmission electron microscope. The technique may be described as precession-assisted crystal orientation mapping in the transmission electron microscope, precession-assisted crystal orientation mapping technique-transmission electron microscope, also known by its product name, ASTAR, and consists in scanning the precessed electron beam in nanoprobe mode over the specimen area, thus producing a collection of precession electron diffraction spot patterns, to be thereafter indexed automatically through template matching. We present a review on several application examples relative to the characterization of microstructure/microtexture of nanocrystalline metals, ceramics, nanoparticles, minerals and organics. The strengths and limitations of the technique are also discussed using several application examples. ©2013 The Authors. Journal of Microscopy published by John Wiley & Sons Ltd on behalf of Royal Microscopical Society.

RADIOAUTOGRAPHIC STUDY OF CELL WALL DEPOSITION IN GROWING PLANT CELLS

PubMed Central

Ray, Peter M.

1967-01-01

Segments cut from growing oat coleoptiles and pea stems were fed glucose-3H in presence and absence of the growth hormone indoleacetic acid (IAA). By means of electron microscope radioautography it was demonstrated that new cell wall material is deposited both at the wall surface (apposition) and within the preexisting wall structure (internally). Quantitative profiles for the distribution of incorporation with position through the thickness of the wall were obtained for the thick outer wall of epidermal cells. With both oat coleoptile and pea stem epidermal outer walls, it was found that a larger proportion of the newly synthesized wall material appeared to become incorporated within the wall in the presence of IAA. Extraction experiments on coleoptile tissue showed that activity that had been incorporated into the cell wall interior represented noncellulosic constituents, mainly hemicelluloses, whereas cellulose was deposited largely or entirely by apposition. It seems possible that internal incorporation of hemicelluloses plays a role in the cell wall expansion process that is involved in cell growth. PMID:6064369

Quantum oscillations in a two-dimensional electron gas at the rocksalt/zincblende interface of PbTe/CdTe (111) heterostructures

DOE PAGES

Zhang, Bingpo; Lu, Ping; Liu, Henan; ...

2015-06-05

Quantum oscillations are observed in the 2DEG system at the interface of novel heterostructures, PbTe/CdTe (111), with nearly identical lattice parameters (a PbTe = 0.6462 nm, a CdTe = 0.648 nm) but very different lattice structures (PbTe: rock salt, CdTe: zinc blende). The 2DEG formation mechanism, a mismatch in the bonding configurations of the valence electrons at the interface, is uniquely different from the other known 2DEG systems. The aberration-corrected scanning transmission electron microscope (AC-STEM) characterization indicates an abrupt interface without cation interdiffusion due to a large miscibility gap between the two constituent materials. As a result, electronic transport measurementsmore » under magnetic field up to 60 T, with the observation of Landau level filling factor ν = 1, unambiguously reveal a π Berry phase, suggesting the Dirac Fermion nature of the 2DEG at the heterostructure interface, and the PbTe/CdTe heterostructure being a new candidate for 2D topological crystalline insulators.« less

Biologically synthesized titanium oxide nanostructures combined with morphogenetic protein as wound healing agent in the femoral fracture after surgery.

PubMed

Zhang, Yushu; Zhang, Chuanlian; Liu, Kemiao; Zhu, Xia; Liu, Fang; Ge, Xiaofen

2018-05-01

The aim of the present study is to develop novel approach for the green synthesis of titanium oxide nanoparticles (TiO 2 NPs) using Eichhornia crassipes extract and calcined at different temperatures for evaluate the wound healing activity in the femoral fracture. The synthesized TiO 2 are formed different (plate and rod-like) nanostructures at various calcination temperatures. These samples were characterized by X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FTIR), Field emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM). Microscopic studies of TiO 2 NPs revealed that the synthesized TiO 2 NPs are formed well-defined rod-like structures at 400 °C with size ranged from 200 nm to 500 nm. The characterized plate and rod-like TiO 2 NPs are combined with human morphogenetic protein (HbMP) to improving its wound healing activity and osteoblast properties on femoral fractures. The biocompatibility was tested by using human bone marrow mesenchymal stem cells (BMSC) cells and antibacterial efficacy analyzed using human pathogenica bacteria Staphylococcus aureus and Escherichia coli through agar well diffusion assay. The green synthesized rod-like TiO 2 NPs combined with HbMP has been exhibited effective bone fusion behaviors with biomechanical properties and also improved antibacterial activity against pathogenic bacteria. From this study results, it is suggested that green synthesized TiO 2 NPs could be used effectively in biomedical application. Copyright © 2018. Published by Elsevier B.V.

High-resolution, high-throughput imaging with a multibeam scanning electron microscope.

PubMed

Eberle, A L; Mikula, S; Schalek, R; Lichtman, J; Knothe Tate, M L; Zeidler, D

2015-08-01

Electron-electron interactions and detector bandwidth limit the maximal imaging speed of single-beam scanning electron microscopes. We use multiple electron beams in a single column and detect secondary electrons in parallel to increase the imaging speed by close to two orders of magnitude and demonstrate imaging for a variety of samples ranging from biological brain tissue to semiconductor wafers. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

Designs for a quantum electron microscope.

PubMed

Kruit, P; Hobbs, R G; Kim, C-S; Yang, Y; Manfrinato, V R; Hammer, J; Thomas, S; Weber, P; Klopfer, B; Kohstall, C; Juffmann, T; Kasevich, M A; Hommelhoff, P; Berggren, K K

2016-05-01

One of the astounding consequences of quantum mechanics is that it allows the detection of a target using an incident probe, with only a low probability of interaction of the probe and the target. This 'quantum weirdness' could be applied in the field of electron microscopy to generate images of beam-sensitive specimens with substantially reduced damage to the specimen. A reduction of beam-induced damage to specimens is especially of great importance if it can enable imaging of biological specimens with atomic resolution. Following a recent suggestion that interaction-free measurements are possible with electrons, we now analyze the difficulties of actually building an atomic resolution interaction-free electron microscope, or "quantum electron microscope". A quantum electron microscope would require a number of unique components not found in conventional transmission electron microscopes. These components include a coherent electron beam-splitter or two-state-coupler, and a resonator structure to allow each electron to interrogate the specimen multiple times, thus supporting high success probabilities for interaction-free detection of the specimen. Different system designs are presented here, which are based on four different choices of two-state-couplers: a thin crystal, a grating mirror, a standing light wave and an electro-dynamical pseudopotential. Challenges for the detailed electron optical design are identified as future directions for development. While it is concluded that it should be possible to build an atomic resolution quantum electron microscope, we have also identified a number of hurdles to the development of such a microscope and further theoretical investigations that will be required to enable a complete interpretation of the images produced by such a microscope. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

Probing low-energy hyperbolic polaritons in van der Waals crystals with an electron microscope.

PubMed

Govyadinov, Alexander A; Konečná, Andrea; Chuvilin, Andrey; Vélez, Saül; Dolado, Irene; Nikitin, Alexey Y; Lopatin, Sergei; Casanova, Fèlix; Hueso, Luis E; Aizpurua, Javier; Hillenbrand, Rainer

2017-07-21

Van der Waals materials exhibit intriguing structural, electronic, and photonic properties. Electron energy loss spectroscopy within scanning transmission electron microscopy allows for nanoscale mapping of such properties. However, its detection is typically limited to energy losses in the eV range-too large for probing low-energy excitations such as phonons or mid-infrared plasmons. Here, we adapt a conventional instrument to probe energy loss down to 100 meV, and map phononic states in hexagonal boron nitride, a representative van der Waals material. The boron nitride spectra depend on the flake thickness and on the distance of the electron beam to the flake edges. To explain these observations, we developed a classical response theory that describes the interaction of fast electrons with (anisotropic) van der Waals slabs, revealing that the electron energy loss is dominated by excitation of hyperbolic phonon polaritons, and not of bulk phonons as often reported. Thus, our work is of fundamental importance for interpreting future low-energy loss spectra of van der Waals materials.Here the authors adapt a STEM-EELS system to probe energy loss down to 100 meV, and apply it to map phononic states in hexagonal boron nitride, revealing that the electron loss is dominated by hyperbolic phonon polaritons.

Nanoscale temperature mapping in operating microelectronic devices

DOE PAGES

Mecklenburg, Matthew; Hubbard, William A.; White, E. R.; ...

2015-02-05

We report that modern microelectronic devices have nanoscale features that dissipate power nonuniformly, but fundamental physical limits frustrate efforts to detect the resulting temperature gradients. Contact thermometers disturb the temperature of a small system, while radiation thermometers struggle to beat the diffraction limit. Exploiting the same physics as Fahrenheit’s glass-bulb thermometer, we mapped the thermal expansion of Joule-heated, 80-nanometer-thick aluminum wires by precisely measuring changes in density. With a scanning transmission electron microscope (STEM) and electron energy loss spectroscopy (EELS), we quantified the local density via the energy of aluminum’s bulk plasmon. Rescaling density to temperature yields maps with amore » statistical precision of 3 kelvin/hertz ₋1/2, an accuracy of 10%, and nanometer-scale resolution. Lastly, many common metals and semiconductors have sufficiently sharp plasmon resonances to serve as their own thermometers.« less

Direct observation of atomic-scale origins of local dissolution in Al-Cu-Mg alloys

PubMed Central

Zhang, B.; Wang, J.; Wu, B.; Oguzie, E. E.; Luo, K.; Ma, X. L.

2016-01-01

Atomistic chemical inhomogeneities are anticipated to induce dissimilarities in surface potentials, which control corrosion initiation of alloys at the atomic scale. Precise understanding of corrosion is therefore hampered by lack of definite information describing how atomistic heterogeneities regulate the process. Here, using high-angle annular dark-field (HAADF) scanning transmission electron microscope (STEM) and electron energy loss spectroscopy (EELS) techniques, we systematically analyzed the Al20Cu2Mn3 second phase of 2024Al and successfully observed that atomic-scale segregation of Cu at defect sites induced preferential dissolution of the adjacent zones. We define an “atomic-scale galvanic cell”, composed of zones rich in Cu and its surrounding matrix. Our findings provide vital information linking atomic-scale microstructure and pitting mechanism, particularly for Al-Cu-Mg alloys. The resolution achieved also enables understanding of dealloying mechanisms and further streamlines our comprehension of the concept of general corrosion. PMID:28000750

Quantitative description of the T1 morphology and strengthening mechanisms in an age-hardenable Al-Li-Cu alloy

NASA Astrophysics Data System (ADS)

Dorin, Thomas; Deschamps, Alexis; De Geuser, Frédéric; Weyland, Matthew

In the Al-Cu-Li system, the main strengthening precipitate is the T1 phase (Al2CuLi). In order to understand the strengthening related to the formation of this phase, we first present an investigation of the morphology of the T1 phase in an AA2198 alloy using Transmission Electron Microscopy (TEM) and Differential Scanning Calorimetry (DSC) in relation with the evolution of micro-hardness. In parallel, we present an investigation of the interaction between T1 precipitates and dislocations using High Angle Annular Dark Field (HAADF) imaging in an atomic resolution Scanning Transmission Electron Microscope (STEM). The atomic scale imaging of precipitates makes it possible to quantify the density of shearing events, which turns out to be insufficient to account for the imposed plastic strain. We discuss the implications of this result in terms of precipitate-dislocation interactions.

Microstructure study of a severely plastically deformed Mg-Zn-Y alloy by application of low angle annular dark field diffraction contrast imaging.

PubMed

Basha, Dudekula Althaf; Rosalie, Julian M; Somekawa, Hidetoshi; Miyawaki, Takashi; Singh, Alok; Tsuchiya, Koichi

2016-01-01

Microstructural investigation of extremely strained samples, such as severely plastically deformed (SPD) materials, by using conventional transmission electron microscopy techniques is very challenging due to strong image contrast resulting from the high defect density. In this study, low angle annular dark field (LAADF) imaging mode of scanning transmission electron microscope (STEM) has been applied to study the microstructure of a Mg-3Zn-0.5Y (at%) alloy processed by high pressure torsion (HPT). LAADF imaging advantages for observation of twinning, grain fragmentation, nucleation of recrystallized grains and precipitation on second phase particles in the alloy processed by HPT are highlighted. By using STEM-LAADF imaging with a range of incident angles, various microstructural features have been imaged, such as nanoscale subgrain structure and recrystallization nucleation even from the thicker region of the highly strained matrix. It is shown that nucleation of recrystallized grains starts at a strain level of revolution [Formula: see text] (earlier than detected by conventional bright field imaging). Occurrence of recrystallization of grains by nucleating heterogeneously on quasicrystalline particles is also confirmed. Minimizing all strain effects by LAADF imaging facilitated grain size measurement of [Formula: see text] nm in fully recrystallized HPT specimen after [Formula: see text].

Electrical transport and structural characterization of epitaxial monolayer MoS2 /n- and p-doped GaN vertical lattice-matched heterojunctions

NASA Astrophysics Data System (ADS)

Ruzmetov, D.; O'Regan, T.; Zhang, K.; Herzing, A.; Mazzoni, A.; Chin, M.; Huang, S.; Zhang, Z.; Burke, R.; Neupane, M.; Birdwell, Ag; Shah, P.; Crowne, F.; Kolmakov, A.; Leroy, B.; Robinson, J.; Davydov, A.; Ivanov, T.

We investigate vertical semiconductor junctions consisting of monolayer MoS2 that is epitaxially grown on n- and p-doped GaN crystals. Such a junction represents a building block for 2D/3D vertical semiconductor heterostructures. Epitaxial, lattice-matched growth of MoS2 on GaN is important to ensure high quality interfaces that are crucial for the efficient vertical transport. The MoS2/GaN junctions were characterized with cross-sectional and planar scanning transmission electron microscopy (STEM), scanning tunneling microscopy, and atomic force microscopy. The MoS2/GaN lattice mismatch is measured to be near 1% using STEM. The electrical transport in the out-of-plane direction across the MoS2/GaN junctions was measured using conductive atomic force microscopy and mechanical nano-probes inside a scanning electron microscope. Nano-disc metal contacts to MoS2 were fabricated by e-beam lithography and evaporation. The current-voltage curves of the vertical MoS2/GaN junctions exhibit rectification with opposite polarities for n-doped and p-doped GaN. The metal contact determines the general features of the current-voltage curves, and the MoS2 monolayer modifies the electrical transport across the contact/GaN interface.

A mini-microscope for in situ monitoring of cells.

PubMed

Kim, Sang Bok; Koo, Kyo-in; Bae, Hojae; Dokmeci, Mehmet R; Hamilton, Geraldine A; Bahinski, Anthony; Kim, Sun Min; Ingber, Donald E; Khademhosseini, Ali

2012-10-21

A mini-microscope was developed for in situ monitoring of cells by modifying off-the-shelf components of a commercial webcam. The mini-microscope consists of a CMOS imaging module, a small plastic lens and a white LED illumination source. The CMOS imaging module was connected to a laptop computer through a USB port for image acquisition and analysis. Due to its compact size, 8 × 10 × 9 cm, the present microscope is portable and can easily fit inside a conventional incubator, and enables real-time monitoring of cellular behaviour. Moreover, the mini-microscope can be used for imaging cells in conventional cell culture flasks, such as Petri dishes and multi-well plates. To demonstrate the operation of the mini-microscope, we monitored the cellular migration of mouse 3T3 fibroblasts in a scratch assay in medium containing three different concentrations of fetal bovine serum (5, 10, and 20%) and demonstrated differential responses depending on serum levels. In addition, we seeded embryonic stem cells inside poly(ethylene glycol) microwells and monitored the formation of stem cell aggregates in real time using the mini-microscope. Furthermore, we also combined a lab-on-a-chip microfluidic device for microdroplet generation and analysis with the mini-microscope and observed the formation of droplets under different flow conditions. Given its cost effectiveness, robust imaging and portability, the presented platform may be useful for a range of applications for real-time cellular imaging using lab-on-a-chip devices at low cost.

A mini-microscope for in situ monitoring of cells†‡

PubMed Central

Kim, Sang Bok; Koo, Kyo-in; Bae, Hojae; Dokmeci, Mehmet R.; Hamilton, Geraldine A.; Bahinski, Anthony; Kim, Sun Min; Ingber, Donald E.

2013-01-01

A mini-microscope was developed for in situ monitoring of cells by modifying off-the-shelf components of a commercial webcam. The mini-microscope consists of a CMOS imaging module, a small plastic lens and a white LED illumination source. The CMOS imaging module was connected to a laptop computer through a USB port for image acquisition and analysis. Due to its compact size, 8 × 10 × 9 cm, the present microscope is portable and can easily fit inside a conventional incubator, and enables real-time monitoring of cellular behaviour. Moreover, the mini-microscope can be used for imaging cells in conventional cell culture flasks, such as Petri dishes and multi-well plates. To demonstrate the operation of the mini-microscope, we monitored the cellular migration of mouse 3T3 fibroblasts in a scratch assay in medium containing three different concentrations of fetal bovine serum (5, 10, and 20%) and demonstrated differential responses depending on serum levels. In addition, we seeded embryonic stem cells inside poly(ethylene glycol) microwells and monitored the formation of stem cell aggregates in real time using the mini-microscope. Furthermore, we also combined a lab-on-a-chip microfluidic device for microdroplet generation and analysis with the mini-microscope and observed the formation of droplets under different flow conditions. Given its cost effectiveness, robust imaging and portability, the presented platform may be useful for a range of applications for real-time cellular imaging using lab-on-a-chip devices at low cost. PMID:22911426

Medullospheres from DAOY, UW228 and ONS-76 cells: increased stem cell population and proteomic modifications.

PubMed

Zanini, Cristina; Ercole, Elisabetta; Mandili, Giorgia; Salaroli, Roberta; Poli, Alice; Renna, Cristiano; Papa, Valentina; Cenacchi, Giovanna; Forni, Marco

2013-01-01

Medulloblastoma (MB) is an aggressive pediatric tumor of the Central Nervous System (CNS) usually treated according to a refined risk stratification. The study of cancer stem cells (CSC) in MB is a promising approach aimed at finding new treatment strategies. The CSC compartment was studied in three characterized MB cell lines (DAOY, UW228 and ONS-76) grown in standard adhesion as well as being grown as spheres, which enables expansion of the CSC population. MB cell lines, grown in adherence and as spheres, were subjected to morphologic analysis at the light and electron microscopic level, as well as cytofluorimetric determinations. Medullospheres (MBS) were shown to express increasingly immature features, along with the stem cells markers: CD133, Nestin and β-catenin. Proteomic analysis highlighted the differences between MB cell lines, demonstrating a unique protein profile for each cell line, and minor differences when grown as spheres. In MBS, MALDI-TOF also identified some proteins, that have been linked to tumor progression and resistance, such as Nucleophosmin (NPM). In addition, immunocytochemistry detected Sox-2 as a stemness marker of MBS, as well as confirming high NPM expression. Culture conditioning based on low attachment flasks and specialized medium may provide new data on the staminal compartment of CNS tumors, although a proteomic profile of CSC is still elusive for MB.

Medullospheres from DAOY, UW228 and ONS-76 Cells: Increased Stem Cell Population and Proteomic Modifications

PubMed Central

Zanini, Cristina; Ercole, Elisabetta; Mandili, Giorgia; Salaroli, Roberta; Poli, Alice; Renna, Cristiano; Papa, Valentina; Cenacchi, Giovanna; Forni, Marco

2013-01-01

Background Medulloblastoma (MB) is an aggressive pediatric tumor of the Central Nervous System (CNS) usually treated according to a refined risk stratification. The study of cancer stem cells (CSC) in MB is a promising approach aimed at finding new treatment strategies. Methodology/Principal Findings The CSC compartment was studied in three characterized MB cell lines (DAOY, UW228 and ONS-76) grown in standard adhesion as well as being grown as spheres, which enables expansion of the CSC population. MB cell lines, grown in adherence and as spheres, were subjected to morphologic analysis at the light and electron microscopic level, as well as cytofluorimetric determinations. Medullospheres (MBS) were shown to express increasingly immature features, along with the stem cells markers: CD133, Nestin and β-catenin. Proteomic analysis highlighted the differences between MB cell lines, demonstrating a unique protein profile for each cell line, and minor differences when grown as spheres. In MBS, MALDI-TOF also identified some proteins, that have been linked to tumor progression and resistance, such as Nucleophosmin (NPM). In addition, immunocytochemistry detected Sox-2 as a stemness marker of MBS, as well as confirming high NPM expression. Conclusions/Significance Culture conditioning based on low attachment flasks and specialized medium may provide new data on the staminal compartment of CNS tumors, although a proteomic profile of CSC is still elusive for MB. PMID:23717474

Development of Paper Products from Dried Sweetpotato Stems and Peanut Shells

NASA Technical Reports Server (NTRS)

McConnell, R.; Smith, R.; Jones, G.; Lu, J. Y.

1998-01-01

One of the goals of NASA's Advanced Life Support Program (ALS) for sustaining human life in space is to achieve a closed system in plant production and usage. That all inedible plant parts should be recycled or used in some way. A Tuskegee University team researching sweetpotato and peanut for ALS has developed paper products from dried sweet-potato stems and peanut shells. In this study, the sweet-potato stems and peanut shells were soaked separately in water for 48 hours. After 48 hours, researchers manually separated the pulp and the unusable parts. To form the paper, 160 g of pulp and water mixture was poured through a 15.1 cm (diameter) filtration funnel and the pulp was trapped on 15 cm (diameter) filter paper. The filter paper and pulp were dried in an air oven, and the filter paper was removed, An examination under a scanning electron microscope showed that the sweet-potato paper was composed of "fibers", whereas the peanut shell paper was composed of "blocks". Results of physical testing showed that the sweet-potato stem paper was stronger than the peanut shell paper. It is anticipated that there may be other uses of these products such as writing paper, bags and packaging material. Because of its biodegradability, it can be incorporated into the resource recycling system at the end of its use.

75 FR 13486 - Application(s) for Duty-Free Entry of Scientific Instruments

Federal Register 2010, 2011, 2012, 2013, 2014

2010-03-22

... University, One Waterfront Place, PO Box 6024, Morgantown, WV 26506. Instrument: Electron Microscope.... Justification for Duty-Free Entry: There are no domestic manufacturers of this type of electron microscope.... Lawrence University, 23 Romoda Drive, Canton, NY 13617. Instrument: Electron Microscope. Manufacturer: FEI...

Analysis of acute brain slices by electron microscopy: a correlative light-electron microscopy workflow based on Tokuyasu cryo-sectioning.

PubMed

Loussert Fonta, Celine; Leis, Andrew; Mathisen, Cliff; Bouvier, David S; Blanchard, Willy; Volterra, Andrea; Lich, Ben; Humbel, Bruno M

2015-01-01

Acute brain slices are slices of brain tissue that are kept vital in vitro for further recordings and analyses. This tool is of major importance in neurobiology and allows the study of brain cells such as microglia, astrocytes, neurons and their inter/intracellular communications via ion channels or transporters. In combination with light/fluorescence microscopies, acute brain slices enable the ex vivo analysis of specific cells or groups of cells inside the slice, e.g. astrocytes. To bridge ex vivo knowledge of a cell with its ultrastructure, we developed a correlative microscopy approach for acute brain slices. The workflow begins with sampling of the tissue and precise trimming of a region of interest, which contains GFP-tagged astrocytes that can be visualised by fluorescence microscopy of ultrathin sections. The astrocytes and their surroundings are then analysed by high resolution scanning transmission electron microscopy (STEM). An important aspect of this workflow is the modification of a commercial cryo-ultramicrotome to observe the fluorescent GFP signal during the trimming process. It ensured that sections contained at least one GFP astrocyte. After cryo-sectioning, a map of the GFP-expressing astrocytes is established and transferred to correlation software installed on a focused ion beam scanning electron microscope equipped with a STEM detector. Next, the areas displaying fluorescence are selected for high resolution STEM imaging. An overview area (e.g. a whole mesh of the grid) is imaged with an automated tiling and stitching process. In the final stitched image, the local organisation of the brain tissue can be surveyed or areas of interest can be magnified to observe fine details, e.g. vesicles or gold labels on specific proteins. The robustness of this workflow is contingent on the quality of sample preparation, based on Tokuyasu's protocol. This method results in a reasonable compromise between preservation of morphology and maintenance of antigenicity. Finally, an important feature of this approach is that the fluorescence of the GFP signal is preserved throughout the entire preparation process until the last step before electron microscopy. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

77 FR 20009 - Howard Hughes Medical Institute, et al.; Notice of Consolidated Decision on Applications for Duty...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-04-03

... decision consolidated pursuant to Section 6(c) of the Educational, Scientific, and Cultural Materials... 07470. Instrument: Electron Microscope. Manufacturer: Hitachi High Technologies America, Inc., Japan... educational uses requiring an electron microscope. We know of no electron microscope, or any other instrument...

The Design and Construction of a Simple Transmission Electron Microscope for Educational Purposes.

ERIC Educational Resources Information Center

Hearsey, Paul K.

This document presents a model for a simple transmission electron microscope for educational purposes. This microscope could demonstrate thermonic emission, particle acceleration, electron deflection, and flourescence. It is designed to be used in high school science courses, particularly physics, taking into account the size, weight, complexity…

75 FR 20982 - West Virginia University, et al., Notice of Consolidated Decision on Applications for Duty-Free...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-22

... of Consolidated Decision on Applications for Duty-Free Entry of Electron Microscopes This is a..., Morgantown, WV 26506. Instrument: Electron Microscope. Manufacturer: JEOL, Japan. Intended Use: See notice at... Agency, Cincinnati, OH 45268. Instrument: Electron Microscope. Manufacturer: JEOL, Japan. Intended Use...

76 FR 17381 - Battelle Memorial Institute, et al.; Notice of Consolidated Decision on Applications for Duty...

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Secondary electron imaging of monolayer materials inside a transmission electron microscope

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

Cretu, Ovidiu, E-mail: cretu.ovidiu@nims.go.jp; Lin, Yung-Chang; Suenaga, Kazutomo

2015-08-10

A scanning transmission electron microscope equipped with a backscattered and secondary electron detector is shown capable to image graphene and hexagonal boron nitride monolayers. Secondary electron contrasts of the two lightest monolayer materials are clearly distinguished from the vacuum level. A signal difference between these two materials is attributed to electronic structure differences, which will influence the escape probabilities of the secondary electrons. Our results show that the secondary electron signal can be used to distinguish between the electronic structures of materials with atomic layer sensitivity, enhancing its applicability as a complementary signal in the analytical microscope.

3D conductive nanocomposite scaffold for bone tissue engineering

PubMed Central

Shahini, Aref; Yazdimamaghani, Mostafa; Walker, Kenneth J; Eastman, Margaret A; Hatami-Marbini, Hamed; Smith, Brenda J; Ricci, John L; Madihally, Sundar V; Vashaee, Daryoosh; Tayebi, Lobat

2014-01-01

Bone healing can be significantly expedited by applying electrical stimuli in the injured region. Therefore, a three-dimensional (3D) ceramic conductive tissue engineering scaffold for large bone defects that can locally deliver the electrical stimuli is highly desired. In the present study, 3D conductive scaffolds were prepared by employing a biocompatible conductive polymer, ie, poly(3,4-ethylenedioxythiophene) poly(4-styrene sulfonate) (PEDOT:PSS), in the optimized nanocomposite of gelatin and bioactive glass. For in vitro analysis, adult human mesenchymal stem cells were seeded in the scaffolds. Material characterizations using hydrogen-1 nuclear magnetic resonance, in vitro degradation, as well as thermal and mechanical analysis showed that incorporation of PEDOT:PSS increased the physiochemical stability of the composite, resulting in improved mechanical properties and biodegradation resistance. The outcomes indicate that PEDOT:PSS and polypeptide chains have close interaction, most likely by forming salt bridges between arginine side chains and sulfonate groups. The morphology of the scaffolds and cultured human mesenchymal stem cells were observed and analyzed via scanning electron microscope, micro-computed tomography, and confocal fluorescent microscope. Increasing the concentration of the conductive polymer in the scaffold enhanced the cell viability, indicating the improved microstructure of the scaffolds or boosted electrical signaling among cells. These results show that these conductive scaffolds are not only structurally more favorable for bone tissue engineering, but also can be a step forward in combining the tissue engineering techniques with the method of enhancing the bone healing by electrical stimuli. PMID:24399874

3D conductive nanocomposite scaffold for bone tissue engineering.

PubMed

Shahini, Aref; Yazdimamaghani, Mostafa; Walker, Kenneth J; Eastman, Margaret A; Hatami-Marbini, Hamed; Smith, Brenda J; Ricci, John L; Madihally, Sundar V; Vashaee, Daryoosh; Tayebi, Lobat

2014-01-01

Bone healing can be significantly expedited by applying electrical stimuli in the injured region. Therefore, a three-dimensional (3D) ceramic conductive tissue engineering scaffold for large bone defects that can locally deliver the electrical stimuli is highly desired. In the present study, 3D conductive scaffolds were prepared by employing a biocompatible conductive polymer, ie, poly(3,4-ethylenedioxythiophene) poly(4-styrene sulfonate) (PEDOT:PSS), in the optimized nanocomposite of gelatin and bioactive glass. For in vitro analysis, adult human mesenchymal stem cells were seeded in the scaffolds. Material characterizations using hydrogen-1 nuclear magnetic resonance, in vitro degradation, as well as thermal and mechanical analysis showed that incorporation of PEDOT:PSS increased the physiochemical stability of the composite, resulting in improved mechanical properties and biodegradation resistance. The outcomes indicate that PEDOT:PSS and polypeptide chains have close interaction, most likely by forming salt bridges between arginine side chains and sulfonate groups. The morphology of the scaffolds and cultured human mesenchymal stem cells were observed and analyzed via scanning electron microscope, micro-computed tomography, and confocal fluorescent microscope. Increasing the concentration of the conductive polymer in the scaffold enhanced the cell viability, indicating the improved microstructure of the scaffolds or boosted electrical signaling among cells. These results show that these conductive scaffolds are not only structurally more favorable for bone tissue engineering, but also can be a step forward in combining the tissue engineering techniques with the method of enhancing the bone healing by electrical stimuli.

Telocytes and putative stem cells in the lungs: electron microscopy, electron tomography and laser scanning microscopy.

PubMed

Popescu, Laurentiu M; Gherghiceanu, Mihaela; Suciu, Laura C; Manole, Catalin G; Hinescu, Mihail E

2011-09-01

This study describes a novel type of interstitial (stromal) cell - telocytes (TCs) - in the human and mouse respiratory tree (terminal and respiratory bronchioles, as well as alveolar ducts). TCs have recently been described in pleura, epicardium, myocardium, endocardium, intestine, uterus, pancreas, mammary gland, etc. (see www.telocytes.com ). TCs are cells with specific prolongations called telopodes (Tp), frequently two to three per cell. Tp are very long prolongations (tens up to hundreds of μm) built of alternating thin segments known as podomers (≤ 200 nm, below the resolving power of light microscope) and dilated segments called podoms, which accommodate mitochondria, rough endoplasmic reticulum and caveolae. Tp ramify dichotomously, making a 3-dimensional network with complex homo- and heterocellular junctions. Confocal microscopy reveals that TCs are c-kit- and CD34-positive. Tp release shed vesicles or exosomes, sending macromolecular signals to neighboring cells and eventually modifying their transcriptional activity. At bronchoalveolar junctions, TCs have been observed in close association with putative stem cells (SCs) in the subepithelial stroma. SCs are recognized by their ultrastructure and Sca-1 positivity. Tp surround SCs, forming complex TC-SC niches (TC-SCNs). Electron tomography allows the identification of bridging nanostructures, which connect Tp with SCs. In conclusion, this study shows the presence of TCs in lungs and identifies a TC-SC tandem in subepithelial niches of the bronchiolar tree. In TC-SCNs, the synergy of TCs and SCs may be based on nanocontacts and shed vesicles.

Whole-Cell Analysis of Low-Density Lipoprotein Uptake by Macrophages Using STEM Tomography

PubMed Central

Baudoin, Jean-Pierre; Jerome, W. Gray; Kübel, Christian; de Jonge, Niels

2013-01-01

Nanoparticles of heavy materials such as gold can be used as markers in quantitative electron microscopic studies of protein distributions in cells with nanometer spatial resolution. Studying nanoparticles within the context of cells is also relevant for nanotoxicological research. Here, we report a method to quantify the locations and the number of nanoparticles, and of clusters of nanoparticles inside whole eukaryotic cells in three dimensions using scanning transmission electron microscopy (STEM) tomography. Whole-mount fixed cellular samples were prepared, avoiding sectioning or slicing. The level of membrane staining was kept much lower than is common practice in transmission electron microscopy (TEM), such that the nanoparticles could be detected throughout the entire cellular thickness. Tilt-series were recorded with a limited tilt-range of 80° thereby preventing excessive beam broadening occurring at higher tilt angles. The 3D locations of the nanoparticles were nevertheless determined with high precision using computation. The obtained information differed from that obtained with conventional TEM tomography data since the nanoparticles were highlighted while only faint contrast was obtained on the cellular material. Similar as in fluorescence microscopy, a particular set of labels can be studied. This method was applied to study the fate of sequentially up-taken low-density lipoprotein (LDL) conjugated to gold nanoparticles in macrophages. Analysis of a 3D reconstruction revealed that newly up-taken LDL-gold was delivered to lysosomes containing previously up-taken LDL-gold thereby forming onion-like clusters. PMID:23383042

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.

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

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.

Membrane protein stoichiometry studied in intact mammalian cells using liquid-phase electron microscopy.

PubMed

DE Jonge, N

2018-02-01

Receptor membrane proteins in the plasma membranes of cells respond to extracellular chemical signals by conformational changes, spatial redistribution, and (re-)assembly into protein complexes, for example, into homodimers (pairs of the same protein type). The functional state of the proteins can be determined from information about how subunits are assembled into protein complexes. Stoichiometric information about the protein complex subunits, however, is generally not obtained from intact cells but from pooled material extracted from many cells, resulting in a lack of fundamental knowledge about the functioning of membrane proteins. First, functional states may dramatically differ from cell to cell on account of cell heterogeneity. Second, extracting the membrane proteins from the plasma membrane may lead to many artefacts. Liquid-phase scanning transmission electron microscopy (STEM), in short liquid STEM, is a new technique capable of determining the locations of individual membrane proteins within the intact plasma membranes of cells in liquid. Many tens of whole cells can readily be imaged. It is possible to analyse the stoichiometry of membrane proteins in single cells while accounting for heterogenic cell populations. Liquid STEM was used to image epidermal growth factor receptors in whole COS7 cells. A study of the dimerisation of the HER2 protein in breast cancer cells revealed the presence of rare cancer cells in which HER2 was in a different functional state than in the bulk cells. Stoichiometric information about receptors is essential not only for basic science but also for biomedical application because they present many important pharmaceutical targets. © 2017 The Authors Journal of Microscopy © 2017 Royal Microscopical Society.

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.

[Thirty years of the electron microscope investigation in zoology and parasitology in the Zoological Institute of the Russian Academy of Sciences].

PubMed

Shatrov, A B

2003-01-01

The history of the electron microscope investigations in zoology and parasitology in the Zoological Institute of the Russian Academy of Sciences and progress in scanning and transmission electron microscope investigations in this field of biology to the moment are briefly accounted.

75 FR 52928 - Emory University, et al., Notice of Consolidated Decision on Applications for Duty-Free Entry of...

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2010-08-30

... Consolidated Decision on Applications for Duty-Free Entry of Electron Microscopes This is a decision... 30322. Instrument: Electron Microscope. Manufacturer: JEOL, Ltd., Japan. Intended Use: See notice at 75... Department of Health, Menands, NY 12204-2719. Instrument: Electron Microscope. Manufacturer: JEOL Ltd., Japan...

Imaging of Norway spruce early somatic embryos with the ESEM, Cryo-SEM and laser scanning microscope.

PubMed

Neděla, Vilém; Hřib, Jiří; Havel, Ladislav; Hudec, Jiří; Runštuk, Jiří

2016-05-01

This article describes the surface structure of Norway spruce early somatic embryos (ESEs) as a typical culture with asynchronous development. The microstructure of extracellular matrix covering ESEs were observed using the environmental scanning electron microscope as a primary tool and using the scanning electron microscope with cryo attachment and laser electron microscope as a complementary tool allowing our results to be proven independently. The fresh samples were observed in conditions of the air environment of the environmental scanning electron microscope (ESEM) with the pressure from 550Pa to 690Pa and the low temperature of the sample from -18°C to -22°C. The samples were studied using two different types of detector to allow studying either the thin surface structure or material composition. The scanning electron microscope with cryo attachment was used for imaging frozen extracellular matrix microstructure with higher resolution. The combination of both electron microscopy methods was suitable for observation of "native" plant samples, allowing correct evaluation of our results, free of error and artifacts. Copyright © 2016 Elsevier Ltd. All rights reserved.

The World of Stem Cell Therapy: Anonymity is not an Option

PubMed Central

CARROLL, JOHN

2007-01-01

Although it remains poised to become one of the biggest biotech markets, stem cell therapy continues to operate under a microscope. Investigators have a lot of explaining to do – both to the public and private payers – why it makes sense to cover their treatments. PMID:23319923

Grayscale inhomogeneity correction method for multiple mosaicked electron microscope images

NASA Astrophysics Data System (ADS)

Zhou, Fangxu; Chen, Xi; Sun, Rong; Han, Hua

2018-04-01

Electron microscope image stitching is highly desired to acquire microscopic resolution images of large target scenes in neuroscience. However, the result of multiple Mosaicked electron microscope images may exist severe gray scale inhomogeneity due to the instability of the electron microscope system and registration errors, which degrade the visual effect of the mosaicked EM images and aggravate the difficulty of follow-up treatment, such as automatic object recognition. Consequently, the grayscale correction method for multiple mosaicked electron microscope images is indispensable in these areas. Different from most previous grayscale correction methods, this paper designs a grayscale correction process for multiple EM images which tackles the difficulty of the multiple images monochrome correction and achieves the consistency of grayscale in the overlap regions. We adjust overall grayscale of the mosaicked images with the location and grayscale information of manual selected seed images, and then fuse local overlap regions between adjacent images using Poisson image editing. Experimental result demonstrates the effectiveness of our proposed method.

Scanning transmission electron microscopy (STEM) study on surface modified CVD diamond/Si(111) film post implanted Fe-B and NiFe-B related to GMR properties

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

Purwanto, Setyo, E-mail: setyo-p@batan.go.id, E-mail: purwantosetyo@yahoo.com; Dimyati, A., E-mail: arbi-dimyati@hotmail.com; Iskandar, R.

Nanostructure investigation on the post implantation by Fe-B and NiFe-B on CVD diamond/Si(111) film have been studied by means of STEM related to their GMR phenomena. Two samples were investigated carefully, firstly sample is post NiFe-B at E=70keV and dose= 10{sup 15} ions/cm{sup 2} (denoted as A-E3D1). Secondly, is post FeB at E=20 keV and dose= 10{sup 15} ions/cm{sup 2} (denoted as B-E1D1). Based on FPP measurement at room temperature (RT) and H{sub applied} = 8 kOe, A-E3D1 sample has MR ratio almost 80% and MR ratio in B-E1D1 sample is 45%. Based on STEM-EDX investigation, there are two aspectsmore » of how MR ratio of A-E3D1 more higher than those of B-E1D1. Firstly, surface nanostructure on the top of A-E3D1 film is more grazing than on the top of B-E1D1. Analysis with Scanning Transmission Electron Microscope (STEM) equipped with Electron Energy Loss Spectroscopy (EELS) the growth of amorphous carbon layer on top of the implanted diamond film with thickness around 100 nm and only 20 nm on the no implanted sample have observed. Boron atoms were found inside the carbon amorphous layer distributed homogenously. Secondly, oxygen content at the interface between diamond film and silicon substrate in sample A-E3D1 was lower than those in B-E1D1 sample. This condition gives the resistance value in A-E3D1 lower than value in B-E1D1. This result is close to the Raman Spectroscopy data measurement which obviously suggests changes on the Raman spectrum due to implantation related to Oxygen excitation from B-E1D1 sample.« less

High-resolution, high-throughput imaging with a multibeam scanning electron microscope

PubMed Central

EBERLE, AL; MIKULA, S; SCHALEK, R; LICHTMAN, J; TATE, ML KNOTHE; ZEIDLER, D

2015-01-01

Electron–electron interactions and detector bandwidth limit the maximal imaging speed of single-beam scanning electron microscopes. We use multiple electron beams in a single column and detect secondary electrons in parallel to increase the imaging speed by close to two orders of magnitude and demonstrate imaging for a variety of samples ranging from biological brain tissue to semiconductor wafers. Lay Description The composition of our world and our bodies on the very small scale has always fascinated people, making them search for ways to make this visible to the human eye. Where light microscopes reach their resolution limit at a certain magnification, electron microscopes can go beyond. But their capability of visualizing extremely small features comes at the cost of a very small field of view. Some of the questions researchers seek to answer today deal with the ultrafine structure of brains, bones or computer chips. Capturing these objects with electron microscopes takes a lot of time – maybe even exceeding the time span of a human being – or new tools that do the job much faster. A new type of scanning electron microscope scans with 61 electron beams in parallel, acquiring 61 adjacent images of the sample at the same time a conventional scanning electron microscope captures one of these images. In principle, the multibeam scanning electron microscope’s field of view is 61 times larger and therefore coverage of the sample surface can be accomplished in less time. This enables researchers to think about large-scale projects, for example in the rather new field of connectomics. A very good introduction to imaging a brain at nanometre resolution can be found within course material from Harvard University on http://www.mcb80x.org/# as featured media entitled ‘connectomics’. PMID:25627873

Nanoscale Mineralogy and Composition of Experimental Regolith Agglutinates Produced under Asteroidal Impact Conditions

NASA Technical Reports Server (NTRS)

Christoffersen, Roy; Cintala, M. J.; Keller, L. P.; See, T. H.; Horz, F.

2013-01-01

On the Moon, the energetics of smaller impactors and the physical/chemical characteristics of the granular regolith target combine to form a key product of lunar space weathering: chemically reduced shock melts containing optically-active nanophase Fe metal grains (npFe0) [1]. In addition to forming the optically dark glassy matrix phase in lunar agglutinitic soil particles [1], these shock melts are becoming increasingly recognized for their contribution to optically active patina coatings on a wide range of exposed rock and grain surfaces in the lunar regolith [2]. In applying the lessons of lunar space weathering to asteroids, the potential similarities and differences in regolith-hosted shock melts on the Moon compared to those on asteroids has become a topic of increasing interest [3,4]. In a series of impact experiments performed at velocities applicable to the asteroid belt [5], Horz et al. [6] and See and Horz [7] have previously shown that repeated impacts into a gabbroic regolith analog target can produce melt-welded grain aggregates morphologically very similar to lunar agglutinates [6,7]. Although these agglutinate-like particles were extensively analyzed by electron microprobe and scanning electron microscopy (SEM) as part of the original study [7], a microstructural and compositional comparison of these aggregates to lunar soil agglutinates at sub-micron scales has yet to be made. To close this gap, we characterized a representative set of these aggregates using a JEOL 7600 field-emission scanning electron microscope (FE-SEM), and JEOL 2500SE field-emission scanning transmission electron microscope (FE-STEM) both optimized for energy dispersive X-ray spectroscopy (EDX) compositional spectrum imaging at respective analytical spatial resolutions of 0.5 to 1 micron, and 2 to 4 nm.

Analysis of improvement in performance and design parameters for enhancing resolution in an atmospheric scanning electron microscope.

PubMed

Yoon, Yeo Hun; Kim, Seung Jae; Kim, Dong Hwan

2015-12-01

The scanning electron microscope is used in various fields to go beyond diffraction limits of the optical microscope. However, the electron pathway should be conducted in a vacuum so as not to scatter electrons. The pretreatment of the sample is needed for use in the vacuum. To directly observe large and fully hydrophilic samples without pretreatment, the atmospheric scanning electron microscope (ASEM) is needed. We developed an electron filter unit and an electron detector unit for implementation of the ASEM. The key of the electron filter unit is that electrons are transmitted while air molecules remain untransmitted through the unit. The electron detector unit collected the backscattered electrons. We conducted experiments using the selected materials with Havar foil, carbon film and SiN film. © 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.

Size determination of Acipenser ruthenus spermatozoa in different types of electron microscopy.

PubMed

Psenicka, Martin; Tesarová, Martina; Tesitel, Jakub; Nebesárová, Jana

2010-07-01

In this study three types of scanning electron microscopes were used for the size determination of spermatozoa of sterlet Acipenser ruthenus - high vacuum scanning electron microscope (SEM, JEOL 6300), environmental scanning electron microscope (ESEM, Quanta 200 FEG), field emission scanning electron microscope (FESEM, JEOL 7401F) with cryoattachment Alto 2500 (Gatan) and transmission electron microscope (TEM, JEOL 1010). The use of particular microscopes was tied with different specimen preparation techniques. The aim of this study was to evaluate to what degree the type of used electron microscope can influence the size of different parts of spermatozoa. For high vacuum SEM the specimen was prepared using two slightly different procedures. After chemical fixation with 2.5% glutaraldehyde in 0.1M phosphate buffer and post-fixation by 1% osmium tetroxide, the specimen was dehydrated by acetone series and dried either by critical point method or by means of t-butylalcohol. For ESEM fresh, unfixed material was used, which was dropped on microscopic copper grids. In FESEM working in cryo-mode the specimen was observed in a frozen state. Ultrathin sections from chemically fixed and Epon embedded specimens were prepared for TEM observation. Distinct parts of sterlet spermatozoa were measured in each microscope and the data obtained was statistically processed. Results confirmed that the classical chemical procedure of specimen preparation for SEM including critical point drying method led to a significant contraction of all measured values, which could deviate up to 30% in comparison with values measured on the fresh chemically untreated specimen in ESEM. Surprisingly sperm dimensions determinated on ultrathin sections by TEM are comparable with values obtained in ESEM or FESEM. Copyright 2010 Elsevier Ltd. All rights reserved.

Reprint of: 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

2010-11-01

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. Copyright © 2010 Elsevier Inc. All rights reserved.

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

Masih Das, Paul; Danda, Gopinath; Cupo, Andrew

Black phosphorus (BP) is a highly anisotropic allotrope of phosphorus with high promise for fast functional electronics and optoelectronics. We demonstrate that high-resolution and controlled structural modification of few-layer BP along arbitrary crystal direction can be achieved with nanometer-scale precision on a few-minute timescales leading to the formation of sub-nm wide armchair and zigzag BP nanoribbons. The nanoribbons are assembled, along with nanopores and nanogaps, using a combination of mechanical-liquid exfoliation and in situ transmission electron microscope (TEM) and scanning TEM nanosculpting. Here we report time-dependent structural properties of the one-dimensional systems under electron irradiation and probe their oxidation propertiesmore » with electron energy-loss spectroscopy (EELS). Finally, we demonstrate the use of STEM to controllably narrow and thin the nanoribbons until they break into nanogaps. The observations are rationalized using density functional theory for transition state calculations and electronic band-structure evolution for the various stages of the narrowing procedure. In particular, we predict that the sub- and few-nm wide BP nanoribbons realized experimentally possess clear one-dimensional quantum confinement, even when the systems are made up of a few layers. We find the demonstration of this procedure is key for the development of BP-based electronic, optoelectronic, thermoelectric, and other applications in reduced dimensions.« less

Controlled Sculpture of Black Phosphorus Nanoribbons

DOE PAGES

Masih Das, Paul; Danda, Gopinath; Cupo, Andrew; ...

2016-05-18

Black phosphorus (BP) is a highly anisotropic allotrope of phosphorus with high promise for fast functional electronics and optoelectronics. We demonstrate that high-resolution and controlled structural modification of few-layer BP along arbitrary crystal direction can be achieved with nanometer-scale precision on a few-minute timescales leading to the formation of sub-nm wide armchair and zigzag BP nanoribbons. The nanoribbons are assembled, along with nanopores and nanogaps, using a combination of mechanical-liquid exfoliation and in situ transmission electron microscope (TEM) and scanning TEM nanosculpting. Here we report time-dependent structural properties of the one-dimensional systems under electron irradiation and probe their oxidation propertiesmore » with electron energy-loss spectroscopy (EELS). Finally, we demonstrate the use of STEM to controllably narrow and thin the nanoribbons until they break into nanogaps. The observations are rationalized using density functional theory for transition state calculations and electronic band-structure evolution for the various stages of the narrowing procedure. In particular, we predict that the sub- and few-nm wide BP nanoribbons realized experimentally possess clear one-dimensional quantum confinement, even when the systems are made up of a few layers. We find the demonstration of this procedure is key for the development of BP-based electronic, optoelectronic, thermoelectric, and other applications in reduced dimensions.« less

Hartmann characterization of the PEEM-3 aberration-corrected X-ray photoemission electron microscope.

PubMed

Scholl, A; Marcus, M A; Doran, A; Nasiatka, J R; Young, A T; MacDowell, A A; Streubel, R; Kent, N; Feng, J; Wan, W; Padmore, H A

2018-05-01

Aberration correction by an electron mirror dramatically improves the spatial resolution and transmission of photoemission electron microscopes. We will review the performance of the recently installed aberration corrector of the X-ray Photoemission Electron Microscope PEEM-3 and show a large improvement in the efficiency of the electron optics. Hartmann testing is introduced as a quantitative method to measure the geometrical aberrations of a cathode lens electron microscope. We find that aberration correction leads to an order of magnitude reduction of the spherical aberrations, suggesting that a spatial resolution of below 100 nm is possible at 100% transmission of the optics when using x-rays. We demonstrate this improved performance by imaging test patterns employing element and magnetic contrast. Published by Elsevier B.V.

A new apparatus for electron tomography in the scanning electron microscope

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

Morandi, V., E-mail: morandi@bo.imm.cnr.it; Maccagnani, P.; Masini, L.

2015-06-23

The three-dimensional reconstruction of a microscopic specimen has been obtained by applying the tomographic algorithm to a set of images acquired in a Scanning Electron Microscope. This result was achieved starting from a series of projections obtained by stepwise rotating the sample under the beam raster. The Scanning Electron Microscope was operated in the scanning-transmission imaging mode, where the intensity of the transmitted electron beam is a monotonic function of the local mass-density and thickness of the specimen. The detection strategy has been implemented and tailored in order to maintain the projection requirement over the large tilt range, as requiredmore » by the tomographic workflow. A Si-based electron detector and an eucentric-rotation specimen holder have been specifically developed for the purpose.« less

Characterization and antimicrobial properties of food packaging methylcellulose films containing stem extract of Ginja cherry.

PubMed

Campos, Débora; Piccirillo, Clara; Pullar, Robert C; Castro, Paula Ml; Pintado, Maria M E

2014-08-01

Food contamination and spoilage is a problem causing growing concern. To avoid it, the use of food packaging with appropriate characteristics is essential; ideally, the packaging should protect food from external contamination and exhibit antibacterial properties. With this aim, methylcellulose (MC) films containing natural extracts from the stems of Ginja cherry, an agricultural by-product, were developed and characterized. The antibacterial activity of films was screened by the disc diffusion method and quantified using the viable cell count assay. The films inhibited the growth of both Gram-positive and Gram-negative strains (Listeria innocua, methicillin-sensitive Staphylococcus aureus, methicillin-resistant S. aureus, Salmonella Enteritidis, Escherichia coli). For the films with lower extract content, effectiveness against the microorganisms depended on the inoculum concentration. Scanning electron microscope images of the films showed that those containing the extracts had a smooth and continuous structure. UV-visible spectroscopy showed that these materials do not transmit light in the UV. This study shows that MC films containing agricultural by-products, in this case Ginja cherry stem extract, could be used to prevent food contamination by relevant bacterial strains and degradation by UV light. Using such materials in food packaging, the shelf life of food products could be extended while utilizing an otherwise wasted by-product. © 2013 Society of Chemical Industry.

ultraLM and miniLM: Locator tools for smart tracking of fluorescent cells in correlative light and electron microscopy.

PubMed

Brama, Elisabeth; Peddie, Christopher J; Wilkes, Gary; Gu, Yan; Collinson, Lucy M; Jones, Martin L

2016-12-13

In-resin fluorescence (IRF) protocols preserve fluorescent proteins in resin-embedded cells and tissues for correlative light and electron microscopy, aiding interpretation of macromolecular function within the complex cellular landscape. Dual-contrast IRF samples can be imaged in separate fluorescence and electron microscopes, or in dual-modality integrated microscopes for high resolution correlation of fluorophore to organelle. IRF samples also offer a unique opportunity to automate correlative imaging workflows. Here we present two new locator tools for finding and following fluorescent cells in IRF blocks, enabling future automation of correlative imaging. The ultraLM is a fluorescence microscope that integrates with an ultramicrotome, which enables 'smart collection' of ultrathin sections containing fluorescent cells or tissues for subsequent transmission electron microscopy or array tomography. The miniLM is a fluorescence microscope that integrates with serial block face scanning electron microscopes, which enables 'smart tracking' of fluorescent structures during automated serial electron image acquisition from large cell and tissue volumes.

Spherical aberration correction in a scanning transmission electron microscope using a sculpted thin film.

PubMed

Shiloh, Roy; Remez, Roei; Lu, Peng-Han; Jin, Lei; Lereah, Yossi; Tavabi, Amir H; Dunin-Borkowski, Rafal E; Arie, Ady

2018-06-01

Nearly eighty years ago, Scherzer showed that rotationally symmetric, charge-free, static electron lenses are limited by an unavoidable, positive spherical aberration. Following a long struggle, a major breakthrough in the spatial resolution of electron microscopes was reached two decades ago by abandoning the first of these conditions, with the successful development of multipole aberration correctors. Here, we use a refractive silicon nitride thin film to tackle the second of Scherzer's constraints and demonstrate an alternative method for correcting spherical aberration in a scanning transmission electron microscope. We reveal features in Si and Cu samples that cannot be resolved in an uncorrected microscope. Our thin film corrector can be implemented as an immediate low cost upgrade to existing electron microscopes without re-engineering of the electron column or complicated operation protocols and can be extended to the correction of additional aberrations. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

Screening of bacterial strains isolated from uranium mill tailings porewaters for bioremediation purposes.

PubMed

Sánchez-Castro, Iván; Amador-García, Ahinara; Moreno-Romero, Cristina; López-Fernández, Margarita; Phrommavanh, Vannapha; Nos, Jeremy; Descostes, Michael; Merroun, Mohamed L

2017-01-01

The present work characterizes at different levels a number of bacterial strains isolated from porewaters sampled in the vicinity of two French uranium tailing repositories. The 16S rRNA gene from 33 bacterial isolates, corresponding to the different morphotypes recovered, was almost fully sequenced. The resulting sequences belonged to 13 bacterial genera comprised in the phyla Firmicutes, Actinobacteria and Proteobacteria. Further characterization at physiological level and metals/metalloid tolerance provided evidences for an appropriate selection of bacterial strains potentially useful for immobilization of uranium and other common contaminants. By using High Resolution Transmission Electron Microscope (HRTEM), this potential ability to immobilize uranium as U phosphate mineral phases was confirmed for the bacterial strains Br3 and Br5 corresponding to Arthrobacter sp. and Microbacterium oxydans, respectively. Scanning Transmission Electron Microscope- High-Angle Annular Dark-Field (STEM-HAADF) analysis showed U accumulates on the surface and within bacterial cytoplasm, in addition to the extracellular space. Energy Dispersive X-ray (EDX) element-distribution maps demonstrated the presence of U and P within these accumulates. These results indicate the potential of certain bacterial strains isolated from porewaters of U mill tailings for immobilizing uranium, likely as uranium phosphates. Some of these bacterial isolates might be considered as promising candidates in the design of uranium bioremediation strategies. Copyright © 2016 Elsevier Ltd. All rights reserved.

Silencing tumor necrosis factor-alpha in vitro from small interfering RNA-decorated titanium nanotube array can facilitate osteogenic differentiation of mesenchymal stem cells.

PubMed

Wang, Zhenlin; Hu, Zhiqiang; Zhang, Dawei; Zhuo, Mengchuan; Cheng, Jiwei; Xu, Xingping; Xing, Yongming; Fan, Jie

2016-01-01

Titanium implants are known for their bone bonding ability. However, the osseointegration may be severely disturbed in the inflammation environment. In order to enhance osseointegration of the implant in an inflamed environment, the small interfering RNA (siRNA) targeting tumor necrosis factor alpha (TNF-α) was used to functionalize titanium surface for gene silencing. The chitosan-tripolyphosphate-hyaluronate complexes were used to formulate nanoparticles (NPs) with siRNA, which were adsorbed directly by the anodized titanium surface. The surface characterization was analyzed by scanning electron microscope, atomic force microscopy, as well as contact angle measurement. The fluorescence microscope was used to monitor the degradation of the layer. The coculture system was established with mesenchymal stem cells (MSCs) grown directly on functionalized titanium surface and RAW264.7 cells (preactivated by lipopolysaccharide) grown upside in a transwell chamber. The transfection and knockdown efficiency of TNF-α in RAW264.7 cells were determined by fluorescence microscope, quantitative polymerase chain reaction, and enzyme-linked immunosorbent assay. The cytoskeleton and osteogenic differentiation of MSCs were also analyzed. Regular vertical aligned nanotubes (~100 nm diameter and ~300 nm length) were generated after anodization of polished titanium. After loading with NPs, the nanotubes were filled and covered by a layer of amorphous particles. The surface topography changed and wettability decreased after covering with NPs. As expected, a burst degradation of the film was observed, which could provide sufficient NPs in the released supernatant and result in transfection and knockdown effects in RAW264.7 cells. The cytoskeleton arrangement of MSCs was elongated and the osteogenic differentiation was also significantly improved on NPs loading surface. In conclusion, the siRNA decorated titanium implant could simultaneously suppress inflammation and improve osteogenesis, which may be suitable for peri-implant bone formation under inflammatory conditions.

Nanomaterial datasets to advance tomography in scanning transmission electron microscopy

DOE PAGES

Levin, Barnaby D. A.; Padgett, Elliot; Chen, Chien-Chun; ...

2016-06-07

Electron tomography in materials science has flourished with the demand to characterize nanoscale materials in three dimensions (3D). Access to experimental data is vital for developing and validating reconstruction methods that improve resolution and reduce radiation dose requirements. This work presents five high-quality scanning transmission electron microscope (STEM) tomography datasets in order to address the critical need for open access data in this field. The datasets represent the current limits of experimental technique, are of high quality, and contain materials with structural complexity. Included are tomographic series of a hyperbranched Co 2 P nanocrystal, platinum nanoparticles on a carbonmore » nanofibre imaged over the complete 180° tilt range, a platinum nanoparticle and a tungsten needle both imaged at atomic resolution by equal slope tomography, and a through-focal tilt series of PtCu nanoparticles. A volumetric reconstruction from every dataset is provided for comparison and development of post-processing and visualization techniques. Researchers interested in creating novel data processing and reconstruction algorithms will now have access to state of the art experimental test data.« less

Atomic Scale Studies of Magnetic Multilayers

NASA Astrophysics Data System (ADS)

Plisch, M. J.; Muller, D. A.; Katine, J. A.; Silcox, J.; Buhrman, R. A.

1998-03-01

The structure of interfaces in magnetic multilayers plays a crucial role in determining their transport properties(S.S.P. Parkin, Phys. Rev. Lett. 71), 1641 (1993).. A scanning transmission electron microscope (STEM) which can focus a 100 kV electron beam down to 2Åis used to make spatially resolved measurements across magnetic multilayers. Previous x-ray absorption measurements suggest that the Cu d electrons play a large role in coupling the Co layers(M.G. Samant, et. al., Phys. Rev. Lett. 72), 1112 (1994).. With electon energy loss spectroscopy (EELS), information on the spatial variation of Cu d states can be obtained. Interfacial structure and bonding have been examined in multilayers with 80 ÅCu/50 ÅCo periods (with no GMR) and 9 ÅCu/13 ÅCo periods (with greater than 50% GMR). A heteroepitaxial grain structure persisting across many multilayer periods has been seen in the short period structure, but not in the long period structure. There is mixing at the Cu/Co interface and the Cu d states near the interface are significantly modified by the Co. Fe/Cr multilayers have also been examined.

Nanomaterial datasets to advance tomography in scanning transmission electron microscopy.

PubMed

Levin, Barnaby D A; Padgett, Elliot; Chen, Chien-Chun; Scott, M C; Xu, Rui; Theis, Wolfgang; Jiang, Yi; Yang, Yongsoo; Ophus, Colin; Zhang, Haitao; Ha, Don-Hyung; Wang, Deli; Yu, Yingchao; Abruña, Hector D; Robinson, Richard D; Ercius, Peter; Kourkoutis, Lena F; Miao, Jianwei; Muller, David A; Hovden, Robert

2016-06-07

Electron tomography in materials science has flourished with the demand to characterize nanoscale materials in three dimensions (3D). Access to experimental data is vital for developing and validating reconstruction methods that improve resolution and reduce radiation dose requirements. This work presents five high-quality scanning transmission electron microscope (STEM) tomography datasets in order to address the critical need for open access data in this field. The datasets represent the current limits of experimental technique, are of high quality, and contain materials with structural complexity. Included are tomographic series of a hyperbranched Co2P nanocrystal, platinum nanoparticles on a carbon nanofibre imaged over the complete 180° tilt range, a platinum nanoparticle and a tungsten needle both imaged at atomic resolution by equal slope tomography, and a through-focal tilt series of PtCu nanoparticles. A volumetric reconstruction from every dataset is provided for comparison and development of post-processing and visualization techniques. Researchers interested in creating novel data processing and reconstruction algorithms will now have access to state of the art experimental test data.

Nanomaterial datasets to advance tomography in scanning transmission electron microscopy

PubMed Central

Levin, Barnaby D.A.; Padgett, Elliot; Chen, Chien-Chun; Scott, M.C.; Xu, Rui; Theis, Wolfgang; Jiang, Yi; Yang, Yongsoo; Ophus, Colin; Zhang, Haitao; Ha, Don-Hyung; Wang, Deli; Yu, Yingchao; Abruña, Hector D.; Robinson, Richard D.; Ercius, Peter; Kourkoutis, Lena F.; Miao, Jianwei; Muller, David A.; Hovden, Robert

2016-01-01

Electron tomography in materials science has flourished with the demand to characterize nanoscale materials in three dimensions (3D). Access to experimental data is vital for developing and validating reconstruction methods that improve resolution and reduce radiation dose requirements. This work presents five high-quality scanning transmission electron microscope (STEM) tomography datasets in order to address the critical need for open access data in this field. The datasets represent the current limits of experimental technique, are of high quality, and contain materials with structural complexity. Included are tomographic series of a hyperbranched Co2P nanocrystal, platinum nanoparticles on a carbon nanofibre imaged over the complete 180° tilt range, a platinum nanoparticle and a tungsten needle both imaged at atomic resolution by equal slope tomography, and a through-focal tilt series of PtCu nanoparticles. A volumetric reconstruction from every dataset is provided for comparison and development of post-processing and visualization techniques. Researchers interested in creating novel data processing and reconstruction algorithms will now have access to state of the art experimental test data. PMID:27272459

Atomic-Resolution X-ray Energy-Dispersive Spectroscopy Chemical Mapping of Substitutional Dy Atoms in a High-Coercivity Neodymium Magnet

NASA Astrophysics Data System (ADS)

Itakura, Masaru; Watanabe, Natsuki; Nishida, Minoru; Daio, Takeshi; Matsumura, Syo

2013-05-01

We have investigated local element distributions in a Dy-doped Nd2Fe14B hot-deformed magnet by atomic-column resolution chemical mapping using an X-ray energy-dispersive spectrometer (XEDS) attached to an aberration-corrected scanning transmission electron microscope (Cs-corrected STEM). The positions of the Nd and Dy atomic columns were visualized in the XEDS maps. The substitution of Dy was limited to a surface layer 2-3 unit cells thick in the Nd2Fe14B grains, and the Dy atoms preferentially occupied the 4f-Nd sites of Nd2Fe14B. These results provide further insights into the principal mechanism governing the coercivity enhancement due to Dy doping.

KSC-2010-4526

NASA Image and Video Library

2010-08-28

CAPE CANAVERAL, Fla. -- At the Astronaut Hall of Fame near the Kennedy Space Center Visitor Complex in Florida, fifth- through eighth-grade students and their parents participate in the Materials Science Laboratory exhibit by using stereomicroscopes and viewing 3-D scanning electron microscope images during the last NASA family education night event. Other activities included "gee-whiz" presentations, astronaut appearances, a hovercraft, vortex cannon and alternative fuel vehicles, which promote science, technology, engineering and mathematics (STEM) education. The event is part of NASA's Summer of Innovation initiative to provide interactive learning experiences to middle school students nationwide during the summer months. The program is a cornerstone of the Educate to Innovate campaign announced by President Barack Obama in November 2009. Photo credit: NASA/Charisse Nahser

Flexible high-voltage supply for experimental electron microscope

NASA Technical Reports Server (NTRS)

Chapman, G. L.; Jung, E. A.; Lewis, R. N.; Van Loon, L. S.; Welter, L. M.

1969-01-01

Scanning microscope uses a field-emission tip for the electron source, an electron gun that simultaneously accelerates and focuses electrons from the source, and one auxiliary lens to produce a final probe size at the specimen on the order of angstroms.

A high-resolution analytical scanning transmission electron microscopy study of the early stages of spinodal decomposition in binary Fe–Cr

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

Westraadt, J.E., E-mail: johan.westraadt@nmmu.ac.za; Olivier, E.J.; Neethling, J.H.

2015-11-15

Spinodal decomposition (SD) is an important phenomenon in materials science and engineering. For example, it is considered to be responsible for the 475 °C embrittlement of stainless steels comprising the bcc (ferrite) or bct (martensite) phases. Structural characterization of the evolving minute nano-scale concentration fluctuations during SD in the Fe–Cr system is, however, a notable challenge, and has mainly been considered accessible via atom probe tomography (APT) and small-angle neutron scattering. The standard tool for nanostructure characterization, viz. transmission electron microscopy (TEM), has only been successfully applied to late stages of SD when embrittlement is already severe. However, we heremore » demonstrate that the structural evolution in the early stages of SD in binary Fe–Cr, and alloys based on the binary, are accessible via analytical scanning TEM. An Fe–36 wt% Cr alloy aged at 500 °C for 1, 10 and 100 h is investigated using an aberration-corrected microscope and it is found that highly coherent and interconnected Cr-rich regions develop. The wavelength of decomposition is rather insensitive to the sample thickness and it is quantified to 2, 3 and 6 nm after ageing for 1, 10 and 100 h, which is in reasonable agreement with prior APT analysis. The concentration amplitude is more sensitive to the sample thickness and acquisition parameters but the TEM analysis is in good agreement with APT analysis for the longest ageing time. These findings open up for combinatorial TEM studies where both local crystallography and chemistry is required. - Highlights: • STEM-EELS analysis was successfully applied to resolve early stage SD in Fe–Cr. • Compositional wavelength measured with STEM-EELS compares well to previous ATP studies. • Compositional amplitude measured with STEM-EELS is a function of experimental parameters. • STEM-EELS allows for combinatorial studies of SD using complementary techniques.« less

Scanning-electron-microscope used in real-time study of friction and wear

NASA Technical Reports Server (NTRS)

Brainard, W. A.; Buckley, D. H.

1975-01-01

Small friction and wear apparatus built directly into scanning-electron-microscope provides both dynamic observation and microscopic view of wear process. Friction and wear tests conducted using this system have indicated that considerable information can readily be gained.

Cell Attachment and Proliferation of Human Adipose-Derived Stem Cells on PLGA/Chitosan Electrospun Nano-Biocomposite.

PubMed

Razavi, Shahnaz; Karbasi, Saeed; Morshed, Mohammad; Zarkesh Esfahani, Hamid; Golozar, Mohammad; Vaezifar, Sedigheh

2015-01-01

In this study, nano-biocomposite composed of poly (lactide-co-glycolide) (PLGA) and chitosan (CS) were electrospun through a single nozzle by dispersing the CS nano-powders in PLGA solution. The cellular behavior of human adipose derived stem cells (h-ADSCs) on random and aligned scaffolds was then evaluated. In this experimental study, the PLGA/CS scaffolds were prepared at the different ratios of 90/10, 80/20, and 70/30 (w/w) %. Morphology, cell adhesion and prolif- eration rate of h-ADSCs on the scaffolds were assessed using scanning electron microscope (SEM), 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) assay and trypan blue staining respectively. H-ADSCs seeded on the matrices indicated that the PLGA/CS composite matrix with aligned nanofibres and higher content of CS nano-powders gave significantly better performance than others in terms of cell adhesion and proliferation rate (P<0.05). We found that CS enhanced cell adhesion and proliferation rate, and aligned nanofibers guided cell growth along the longitudinal axis of the nanofibers, which would provide a beneficial approach for tissue engineering.

Hematopoietic stem cell capture and directional differentiation into vascular endothelial cells for metal stent-coated chitosan/hyaluronic acid loading CD133 antibody.

PubMed

Zhang, Shixuan; Zhang, Fan; Feng, Bo; Fan, Qingyu; Yang, Feng; Shang, Debin; Sui, Jinghan; Zhao, Hong

2015-03-01

A series of metal stents coated with chitosan/hyaluronic acid (CS/HA) loading antibodies by electrostatic self-assembled method were prepared, and the types of cells captured by antibodies and their differentiation in vascular endothelial cells (ECs) evaluated by molecular biology and scanning electron microscope. The results showed that CD133 stent can selectively capture hematopoietic stem cells (HSC),which directionally differentiate into vascular ECs in peripheral blood by (CS/HA) induction, and simultaneously inhibit migration and proliferation of immune cells and vascular smooth muscle cells (MCs). CD34 stent can capture HSC, hematopoietic progenitor cells that differentiate into vascular ECs and immune cells, promoting smooth MCs growth, leading to thrombosis, inflammation, and rejection. CD133 stent can be implanted into miniature pig heart coronary and can repair vascular damage by capturing own HSC, thus contributing to the rapid natural vascular repair, avoiding inflammation and rejection, thrombosis and restenosis. These studies demonstrated that CD133 stent of HSC capture will be an ideal coated metal stent providing a new therapeutic approach for cardiovascular and cerebrovascular disease.

Thermal-Wave Microscope

NASA Technical Reports Server (NTRS)

Jones, Robert E.; Kramarchuk, Ihor; Williams, Wallace D.; Pouch, John J.; Gilbert, Percy

1989-01-01

Computer-controlled thermal-wave microscope developed to investigate III-V compound semiconductor devices and materials. Is nondestructive technique providing information on subsurface thermal features of solid samples. Furthermore, because this is subsurface technique, three-dimensional imaging also possible. Microscope uses intensity-modulated electron beam of modified scanning electron microscope to generate thermal waves in sample. Acoustic waves generated by thermal waves received by transducer and processed in computer to form images displayed on video display of microscope or recorded on magnetic disk.

Characterization of Induced Pluripotent Stem Cell Microvesicle Genesis, Morphology and Pluripotent Content

PubMed Central

Zhou, Jing; Ghoroghi, Shima; Benito-Martin, Alberto; Wu, Hao; Unachukwu, Uchenna John; Einbond, Linda Saxe; Guariglia, Sara; Peinado, Hector; Redenti, Stephen

2016-01-01

Microvesicles (MVs) are lipid bilayer-covered cell fragments that range in diameter from 30 nm–1uM and are released from all cell types. An increasing number of studies reveal that MVs contain microRNA, mRNA and protein that can be detected in the extracellular space. In this study, we characterized induced pluripotent stem cell (iPSC) MV genesis, content and fusion to retinal progenitor cells (RPCs) in vitro. Nanoparticle tracking revealed that iPSCs released approximately 2200 MVs cell/hour in the first 12 hrs with an average diameter of 122 nm. Electron and light microscopic analysis of iPSCs showed MV release via lipid bilayer budding. The mRNA content of iPSC MVs was characterized and revealed the presence of the transcription factors Oct-3/4, Nanog, Klf4, and C-Myc. The protein content of iPSCs MVs, detected by immunogold electron microscopy, revealed the presence of the Oct-3/4 and Nanog. Isolated iPSC MVs were shown to fuse with RPCs in vitro at multiple points along the plasma membrane. These findings demonstrate that the mRNA and protein cargo in iPSC MVs have established roles in maintenance of pluripotency. Building on this work, iPSC derived MVs may be shown to be involved in maintaining cellular pluripotency and may have application in regenerative strategies for neural tissue. PMID:26797168

In situ TEM and analytical STEM studies of ZnO nanotubes with Sn cores and Sn nanodrops

NASA Astrophysics Data System (ADS)

Ortega, Y.; Jäger, W.; Piqueras, J.; Häussler, D.; Fernández, P.

2013-10-01

ZnO nanorods with Sn core regions grown by a thermal evaporation-deposition method from a mixture of SnO2 and ZnS powders as precursors, are used to study the behaviour of liquid metal in the nanotubes' core regions and the formation of liquid metal nanodrops at the tube ends by in situ TEM experiments. The compositions of the core materials and of the nanodrops were assessed by employing HAADF-STEM imaging and spatially resolved EDXS measurements. By applying variable thermal load through changing the electron-beam flux of the electron microscope, melting of the metallic core can be induced and the behaviour of the liquid metal of the nanorods can be monitored locally. Within the nanorod core, melting and reversible thermal expansion and contraction of Sn core material is reproducibly observed. For nanotubes with core material near-tip regions, a nanodrop emerges from the tip upon melting the core material, followed by reabsorption of the melt into the core and re-solidification upon decreasing the heat load, being reminiscent of a ‘soldering nanorod’. The radius of the liquid nanodrop can reach a few tens of nanometres, containing a total volume of 10-20 up to 10-18 l of liquid Sn. In situ TEM confirms that the radius of the nanodrop can be controlled via the thermal load: it increases with increasing temperature and decreases with decreasing temperature. In addition, some phenomena related to structure modifications during extended electron-beam exposure are also described.

Nanometres-resolution Kikuchi patterns from materials science specimens with transmission electron forward scatter diffraction in the scanning electron microscope.

PubMed

Brodusch, N; Demers, H; Gauvin, R

2013-04-01

A charge-coupled device camera of an electron backscattered diffraction system in a scanning electron microscope was positioned below a thin specimen and transmission Kikuchi patterns were collected. Contrary to electron backscattered diffraction, transmission electron forward scatter diffraction provides phase identification and orientation mapping at the nanoscale. The minimum Pd particle size for which a Kikuchi diffraction pattern was detected and indexed reliably was 5.6 nm. An orientation mapping resolution of 5 nm was measured at 30 kV. The resolution obtained with transmission electron forward scatter diffraction was of the same order of magnitude than that reported in electron nanodiffraction in the transmission electron microscope. An energy dispersive spectrometer X-ray map and a transmission electron forward scatter diffraction orientation map were acquired simultaneously. The high-resolution chemical, phase and orientation maps provided at once information on the chemical form, orientation and coherency of precipitates in an aluminium-lithium 2099 alloy. © 2013 The Authors Journal of Microscopy © 2013 Royal Microscopical Society.

Microscopic and UPLC-UV-MS analyses of authentic and commercial yohimbe (Pausinystalia johimbe) bark samples

USDA-ARS?s Scientific Manuscript database

Yohimbine is the major alkaloid found in the stem-bark of yohimbe, Pausinystalia johimbe (Rubiaceae), an evergreen tree native to Africa. A number of yohimbe products are sold in USA as dietary supplements. Hand-sections of the stem-bark were prepared and the anatomical features were studied by ligh...

Investigation of Optical Cavity Modes and Ultrafast Carrier Dynamics in Zinc Oxide Rods Using Second-Harmonic Generation and Transient Absorption Pump-Probe Microscopy

NASA Astrophysics Data System (ADS)

Mehl, Brian Peter

The polydispersity intrinsic to nanoscale and microscale semiconductor materials poses a major challenge to using individual objects as building blocks for device applications. The ability to manipulate the shape of ZnO structures is enormous, making it an ideal material for studying shape-dependent phenomena. We have built a nonlinear microscope used to directly image optical cavity modes in ZnO rods using second-harmonic generation. Images of second-harmonic generation in needle-shaped ZnO rods obtained from individual structures show areas of enhanced second-harmonic intensity along the longitudinal axis of the rod that are periodically distributed and symmetrically situated relative to the rod midpoint. The spatial modulation is a direct consequence of the fundamental optical field coupling into standing wave resonator modes of the ZnO structure, leading to an enhanced backscattered second-harmonic condition that cannot be achieved in bulk ZnO. A more complicated second-harmonic image is observed when excitation is below the band gap, which is attributed to whispering gallery modes. Additionally, the nonlinear microscope was combined with transient absorption pump-probe to follow the electron-hole recombination dynamics at different points within individual needle-shaped ZnO rods to characterize spatial differences in dynamical behavior. The results from pump-probe experiments are correlated with spatially resolved ultrafast emission measurements, and scanning electron microscopy provides structural details. Dramatically different electron-hole recombination dynamics are observed in the narrow tips compared to the interior, with the ends exhibiting a greater propensity for electron-hole plasma formation and faster recombination of carriers across the band gap that stem from a physical confinement of the charge carriers. In the interior of the rod, a greater fraction of the electron-hole recombination is trap-mediated and occurs on a significantly longer time scale.

[Preparation of sodium alginate-nanohydroxyapatite composite material for bone repair and its biocompatibility].

PubMed

Wang, Yanmei; He, Jiacai; Li, Quanli; Shen, Jijia

2014-02-01

To prepare sodium alginate-nanohydroxyapatite composite material and to explore its feasibility as a bone repair material. Sodium alginate-nanohydroxyapatite composite material was prepared using chemical cross-linking and freeze-drying technology. The composite was characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM) and its porosity was measured by liquid displacement method. The fifth passage of bone marrow stromal stem cells (BMSCs) were incubated on the composite material and then growth was observed by inverted microscope and SEM. BMSCs were cultured with liquid extracts of the material, methyl thiazolyl tetrazolium (MTT) assay was used to calculate the relative growth rate (RGR) on 1, 3, 5 d and to evaluate the cytotoxicity. Fresh dog blood was added into the liquid extracts to conduct hemolysis test, the spectrophotometer was used to determine the optical density (OD) and to calculate the hemolysis rate. Sodium alginate-nanohydroxyapatite composite material displayed porosity, the porous pore rate was (88.6 +/- 4.5)%. BMSCs showed full stretching and vigorous growth under inverted microscope and SEM. BMSCs cultured with liquid extracts of the material had good activities. The toxicity of composite material was graded as 1. Hemolysis test results showed that the hemolysis rate of the composite material was 1.28%, thus meeting the requirement of medical biomaterials. The composite material fabricated in this study has high porosity and good biocompatibility.

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

Levin, Barnaby D. A.; Padgett, Elliot; Chen, Chien-Chun

Electron tomography in materials science has flourished with the demand to characterize nanoscale materials in three dimensions (3D). Access to experimental data is vital for developing and validating reconstruction methods that improve resolution and reduce radiation dose requirements. This work presents five high-quality scanning transmission electron microscope (STEM) tomography datasets in order to address the critical need for open access data in this field. The datasets represent the current limits of experimental technique, are of high quality, and contain materials with structural complexity. Included are tomographic series of a hyperbranched Co 2 P nanocrystal, platinum nanoparticles on a carbonmore » nanofibre imaged over the complete 180° tilt range, a platinum nanoparticle and a tungsten needle both imaged at atomic resolution by equal slope tomography, and a through-focal tilt series of PtCu nanoparticles. A volumetric reconstruction from every dataset is provided for comparison and development of post-processing and visualization techniques. Researchers interested in creating novel data processing and reconstruction algorithms will now have access to state of the art experimental test data.« less

Characterization of core/shell structures based on CdTe and GaAs nanocrystalline layers deposited on SnO2 microwires

NASA Astrophysics Data System (ADS)

Ghimpu, L.; Ursaki, V. V.; Pantazi, A.; Mesterca, R.; Brâncoveanu, O.; Shree, Sindu; Adelung, R.; Tiginyanu, I. M.; Enachescu, M.

2018-04-01

We report the fabrication and characterization of SnO2/CdTe and SnO2/GaAs core/shell microstructures. CdTe or GaAs shell layers were deposited by radio-frequency (RF) magnetron sputtering on core SnO2 microwires synthesized by a flame-based thermal oxidation method. The produced structures were characterized by scanning electron microscopy (SEM), high-resolution scanning transmission electron microscope (HR-STEM), X-ray diffraction (XRD), Raman scattering and FTIR spectroscopy. It was found that the SnO2 core is of the rutile type, while the shells are composed of CdTe or GaAs nanocrystallites of zincblende structure with the dimensions of crystallites in the range of 10-20 nm. The Raman scattering investigations demonstrated that the quality of the porous nanostructured shell is improved by annealing at temperatures of 420-450 °C. The prospects of implementing these microstructures in intrinsic type fiber optic sensors are discussed.

Size distribution and volume fraction of T(1) phase precipitates from TEM images: Direct measurements and related correction.

PubMed

Dorin, Thomas; Donnadieu, Patricia; Chaix, Jean-Marc; Lefebvre, Williams; Geuser, Frédéric De; Deschamps, Alexis

2015-11-01

Transmission Electron Microscopy (TEM) can be used to measure the size distribution and volume fraction of fine scale precipitates in metallic systems. However, such measurements suffer from a number of artefacts that need to be accounted for, related to the finite thickness of the TEM foil and to the projected observation in two dimensions of the microstructure. We present a correction procedure to describe the 3D distribution of disc-like particles and apply this method to the plate-like T1 precipitates in an Al-Li-Cu alloy in two ageing conditions showing different particle morphologies. The precipitates were imaged in a High-Angular Annular Dark Field Microscope (HAADF-STEM). The corrected size distribution is further used to determine the precipitate volume fraction. Atom probe tomography (APT) is finally utilised as an alternative way to measure the precipitate volume fraction and test the validity of the electron microscopy results. Copyright © 2015 Elsevier Ltd. All rights reserved.

Towards the low-dose characterization of beam sensitive nanostructures via implementation of sparse image acquisition in scanning transmission electron microscopy

NASA Astrophysics Data System (ADS)

Hwang, Sunghwan; Han, Chang Wan; Venkatakrishnan, Singanallur V.; Bouman, Charles A.; Ortalan, Volkan

2017-04-01

Scanning transmission electron microscopy (STEM) has been successfully utilized to investigate atomic structure and chemistry of materials with atomic resolution. However, STEM’s focused electron probe with a high current density causes the electron beam damages including radiolysis and knock-on damage when the focused probe is exposed onto the electron-beam sensitive materials. Therefore, it is highly desirable to decrease the electron dose used in STEM for the investigation of biological/organic molecules, soft materials and nanomaterials in general. With the recent emergence of novel sparse signal processing theories, such as compressive sensing and model-based iterative reconstruction, possibilities of operating STEM under a sparse acquisition scheme to reduce the electron dose have been opened up. In this paper, we report our recent approach to implement a sparse acquisition in STEM mode executed by a random sparse-scan and a signal processing algorithm called model-based iterative reconstruction (MBIR). In this method, a small portion, such as 5% of randomly chosen unit sampling areas (i.e. electron probe positions), which corresponds to pixels of a STEM image, within the region of interest (ROI) of the specimen are scanned with an electron probe to obtain a sparse image. Sparse images are then reconstructed using the MBIR inpainting algorithm to produce an image of the specimen at the original resolution that is consistent with an image obtained using conventional scanning methods. Experimental results for down to 5% sampling show consistency with the full STEM image acquired by the conventional scanning method. Although, practical limitations of the conventional STEM instruments, such as internal delays of the STEM control electronics and the continuous electron gun emission, currently hinder to achieve the full potential of the sparse acquisition STEM in realizing the low dose imaging condition required for the investigation of beam-sensitive materials, the results obtained in our experiments demonstrate the sparse acquisition STEM imaging is potentially capable of reducing the electron dose by at least 20 times expanding the frontiers of our characterization capabilities for investigation of biological/organic molecules, polymers, soft materials and nanostructures in general.

Scanning electron microscope fine tuning using four-bar piezoelectric actuated mechanism

NASA Astrophysics Data System (ADS)

Hatamleh, Khaled S.; Khasawneh, Qais A.; Al-Ghasem, Adnan; Jaradat, Mohammad A.; Sawaqed, Laith; Al-Shabi, Mohammad

2018-01-01

Scanning Electron Microscopes are extensively used for accurate micro/nano images exploring. Several strategies have been proposed to fine tune those microscopes in the past few years. This work presents a new fine tuning strategy of a scanning electron microscope sample table using four bar piezoelectric actuated mechanisms. The introduced paper presents an algorithm to find all possible inverse kinematics solutions of the proposed mechanism. In addition, another algorithm is presented to search for the optimal inverse kinematic solution. Both algorithms are used simultaneously by means of a simulation study to fine tune a scanning electron microscope sample table through a pre-specified circular or linear path of motion. Results of the study shows that, proposed algorithms were able to minimize the power required to drive the piezoelectric actuated mechanism by a ratio of 97.5% for all simulated paths of motion when compared to general non-optimized solution.

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

Purchase of a Transmission Electron Microscope for Xavier University of Louisiana

DTIC Science & Technology

2015-05-15

imaging facility on the second floor of the Pharmacy Addition at Xavier University that already includes two scanning electron microscopes. The new TEM...is now in use. Xavier University has formally pledged to provide funds for the 1. REPORT DATE (DD-MM-YYYY) 4. TITLE AND SUBTITLE 13. SUPPLEMENTARY...for Public Release; Distribution Unlimited Final Report: Purchase of a Transmission Electron Microscope for Xavier University of Louisiana The views

Pushing the physical limits of spectroscopic imaging for new biology and better medicine (Conference Presentation)

NASA Astrophysics Data System (ADS)

Cheng, Ji-Xin

2017-02-01

In vivo molecular spectroscopic imaging is not a simple addition of a spectrometer to a microscope. Innovations are needed to break the physical limits in sensitivity, depth, speed and resolution perspectives. I will present our most recent advances in modality development, biological application, and clinical translation. My talk will focus on the development of mid-infrared photothermal microscope for depth-resolved vibrational imaging of living cells (Science Advances, in press), the discovery of a metabolic signature in cancer stem cells by hyperspectral stimulated Raman scattering imaging (Cell Stem Cell, in press), and the development of an intravascular vibrational photoacoustic catheter for label-free sensing of lipid laden plaques (Scientific Report 2016, 6:25236).

The experimental study of genetic engineering human neural stem cells mediated by lentivirus to express multigene.

PubMed

Cai, Pei-qiang; Tang, Xun; Lin, Yue-qiu; Martin, Oudega; Sun, Guang-yun; Xu, Lin; Yang, Yun-kang; Zhou, Tian-hua

2006-02-01

To explore the feasibility to construct genetic engineering human neural stem cells (hNSCs) mediated by lentivirus to express multigene in order to provide a graft source for further studies of spinal cord injury (SCI). Human neural stem cells from the brain cortex of human abortus were isolated and cultured, then gene was modified by lentivirus to express both green fluorescence protein (GFP) and rat neurotrophin-3 (NT-3); the transgenic expression was detected by the methods of fluorescence microscope, dorsal root ganglion of fetal rats and slot blot. Genetic engineering hNSCs were successfully constructed. All of the genetic engineering hNSCs which expressed bright green fluorescence were observed under the fluorescence microscope. The conditioned medium of transgenic hNSCs could induce neurite flourishing outgrowth from dorsal root ganglion (DRG). The genetic engineering hNSCs expressed high level NT-3 which could be detected by using slot blot. Genetic engineering hNSCs mediated by lentivirus can be constructed to express multigene successfully.

Scanning electron microscopy of hepatic ultrastructure: secondary, backscattered, and transmitted electron imaging.

PubMed

Miyai, K; Abraham, J L; Linthicum, D S; Wagner, R M

1976-10-01

Several methods of tissue preparation and different modes of operation of the scanning electron microscope were used to study the ultrastructure of rat liver. Rat livers were perfusion fixed with buffered 2 per cent paraformaldehyde or a mixture of 1.5 per cent paraformaldehyde and 1 per cent glutaraldehyde and processed as follows. Tissue blocks were postfixed in buffered 2 per cent osmium tetroxide followed sequentially by the ligand-mediated osmium binding technique, dehydration and cryofracture in ethanol, and critical point drying. They were then examined without metal coating in the scanning electron microscope operating in the secondary electron and backscattered electron modes. Fifty-micrometer sections were cut with a tissue sectioner, stained with lead citrate, postfixed with osmium, dehydrated, critical point dried, and examined in the secondary electron and back-scattered electron modes. Frozen sections (0.25 to 0.75 mum. thick) were cut by the method of Tokuyasu (Toluyasu KT: J Cell Biol 57:551, 1973) and their scanning transmission electron microscope images were examined either with a scanning transmission electron microscope detector or with a conversion stub using the secondary electron detector. Secondary electron images of the liver prepared by ligand-mediated osmium binding and subsequent cryofracture revealed such intracellular structures as cisternae of the endoplasmic reticulum, lysosomes, mitochondria, lipid droplets, nucleolus and nuclear chromatin, as well as the usual surface morphology, Lipocytes in the perisinusoidal space were readily identified. Backscattered electron images. Unembedded frozen sections had little drying artifact and were virtually free of freezing damage. The scanning transmission electron microscope image revealed those organelles visualized by the secondary electron mode in the ligand-mediated osmium binding-treated tissue.

Electron Microscope Center Opens at Berkeley.

ERIC Educational Resources Information Center

Robinson, Arthur L.

1981-01-01

A 1.5-MeV High Voltage Electron Microscope has been installed at the Lawrence Berkeley Laboratory which will help materials scientists and biologists study samples in more true-to-life situations. A 1-MeV Atomic Resolution Microscope will be installed at the same location in two years which will allow scientists to distinguish atoms. (DS)

Evaluation of the Ca/P concentration ratio in hydroxyapatite by STEM-EDXS: influence of the electron irradiation dose and temperature processing

NASA Astrophysics Data System (ADS)

Benhayoune, H.; Charlier, D.; Jallot, E.; Laquerriere, P.; Balossier, G.; Bonhomme, P.

2001-01-01

Biomaterials used in dental and orthopaedic surgery to fill bony loss and to coat prostheses are either of natural or synthetic origin. Amongst these biomaterials, hydroxyapatites (HA) offer good properties of biocompatibility and bioactivity when they interact with bone. This interaction depends mainly on the physico-chemical properties of HA particles. In this work, using a scanning transmission electronic microscope equipped with an Si(Li) detector for x-ray analysis, we analysed three kinds of hydroxyapatite: non-sintered particles, 600 °C sintered particles and 1180 °C sintered particles. Then, we determined the Ca/P concentration ratio in order to observe the influence of the temperature processing on this ratio. Concurrently, we carried out measurements on the HA powders by varying the electron irradiation dose either with the current density or with irradiation time. When the electron irradiation dose varied with the current density (at constant and short irradiation time), the Ca/P concentration ratio did not vary. But, at fixed current density and increasing irradiation time, the calcium and phosphorus intensities decreased, leading to an increase of the Ca/P concentration ratio at high electron irradiation dose. This phenomenon represents a mass loss of the specimen during electronic bombardment. We propose an experimental procedure to avoid all these problems.

Three-dimensional morphological imaging of human induced pluripotent stem cells by using low-coherence quantitative phase microscopy

NASA Astrophysics Data System (ADS)

Yamauchi, Toyohiko; Kakuno, Yumi; Goto, Kentaro; Fukami, Tadashi; Sugiyama, Norikazu; Iwai, Hidenao; Mizuguchi, Yoshinori; Yamashita, Yutaka

2014-03-01

There is an increasing need for non-invasive imaging techniques in the field of stem cell research. Label-free techniques are the best choice for assessment of stem cells because the cells remain intact after imaging and can be used for further studies such as differentiation induction. To develop a high-resolution label-free imaging system, we have been working on a low-coherence quantitative phase microscope (LC-QPM). LC-QPM is a Linnik-type interference microscope equipped with nanometer-resolution optical-path-length control and capable of obtaining three-dimensional volumetric images. The lateral and vertical resolutions of our system are respectively 0.5 and 0.93 μm and this performance allows capturing sub-cellular morphological features of live cells without labeling. Utilizing LC-QPM, we reported on three-dimensional imaging of membrane fluctuations, dynamics of filopodia, and motions of intracellular organelles. In this presentation, we report three-dimensional morphological imaging of human induced pluripotent stem cells (hiPS cells). Two groups of monolayer hiPS cell cultures were prepared so that one group was cultured in a suitable culture medium that kept the cells undifferentiated, and the other group was cultured in a medium supplemented with retinoic acid, which forces the stem cells to differentiate. The volumetric images of the 2 groups show distinctive differences, especially in surface roughness. We believe that our LC-QPM system will prove useful in assessing many other stem cell conditions.

Specimen Holder for Analytical Electron Microscopes

NASA Technical Reports Server (NTRS)

Clanton, U. S.; Isaacs, A. M.; Mackinnon, I.

1985-01-01

Reduces spectral contamination by spurious X-ray. Specimen holder made of compressed carbon, securely retains standard electron microscope grid (disk) 3 mm in diameter and absorbs backscattered electrons that otherwise generate spurious X-rays. Since holder inexpensive, dedicated to single specimen when numerous samples examined.

Coulomb Mediated Hybridization of Excitons in Coupled Quantum Dots.

PubMed

Ardelt, P-L; Gawarecki, K; Müller, K; Waeber, A M; Bechtold, A; Oberhofer, K; Daniels, J M; Klotz, F; Bichler, M; Kuhn, T; Krenner, H J; Machnikowski, P; Finley, J J

2016-02-19

We report Coulomb mediated hybridization of excitonic states in optically active InGaAs quantum dot molecules. By probing the optical response of an individual quantum dot molecule as a function of the static electric field applied along the molecular axis, we observe unexpected avoided level crossings that do not arise from the dominant single-particle tunnel coupling. We identify a new few-particle coupling mechanism stemming from Coulomb interactions between different neutral exciton states. Such Coulomb resonances hybridize the exciton wave function over four different electron and hole single-particle orbitals. Comparisons of experimental observations with microscopic eight-band k·p calculations taking into account a realistic quantum dot geometry show good agreement and reveal that the Coulomb resonances arise from broken symmetry in the artificial semiconductor molecule.

Microscope and method of use

DOEpatents

Bongianni, Wayne L.

1984-01-01

A method and apparatus for electronically focusing and electronically scanning microscopic specimens are given. In the invention, visual images of even moving, living, opaque specimens can be acoustically obtained and viewed with virtually no time needed for processing (i.e., real time processing is used). And planar samples are not required. The specimens (if planar) need not be moved during scanning, although it will be desirable and possible to move or rotate nonplanar specimens (e.g., laser fusion targets) against the lens of the apparatus. No coupling fluid is needed, so specimens need not be wetted. A phase acoustic microscope is also made from the basic microscope components together with electronic mixers.

Simultaneous specimen and stage cleaning device for analytical electron microscope

DOEpatents

Zaluzec, Nestor J.

1996-01-01

An improved method and apparatus are provided for cleaning both a specimen stage, a specimen and an interior of an analytical electron microscope (AEM). The apparatus for cleaning a specimen stage and specimen comprising a plasma chamber for containing a gas plasma and an air lock coupled to the plasma chamber for permitting passage of the specimen stage and specimen into the plasma chamber and maintaining an airtight chamber. The specimen stage and specimen are subjected to a reactive plasma gas that is either DC or RF excited. The apparatus can be mounted on the analytical electron microscope (AEM) for cleaning the interior of the microscope.

Microscope and method of use

DOEpatents

Bongianni, W.L.

1984-04-17

A method and apparatus for electronically focusing and electronically scanning microscopic specimens are given. In the invention, visual images of even moving, living, opaque specimens can be acoustically obtained and viewed with virtually no time needed for processing (i.e., real time processing is used). And planar samples are not required. The specimens (if planar) need not be moved during scanning, although it will be desirable and possible to move or rotate nonplanar specimens (e.g., laser fusion targets) against the lens of the apparatus. No coupling fluid is needed, so specimens need not be wetted. A phase acoustic microscope is also made from the basic microscope components together with electronic mixers. 7 figs.

Variation of mechanical behavior of β-TCP/collagen two phase composite scaffold with mesenchymal stem cell in vitro.

PubMed

Arahira, Takaaki; Todo, Mitsugu

2016-08-01

The primary aim of this study is to characterize the variational behavior of the compressive mechanical property of bioceramic-based scaffolds using stem cells during the cell culture period. β-Tricalcium phosphate (TCP)/collagen two phase composites and β-TCP scaffolds were fabricated using the polyurethane template technique and a subsequent freeze-drying method. Rat bone-marrow mesenchymal stem cells (rMSCs) were then cultured in these scaffolds for up to 28 days. Compression tests of the scaffolds with rMSCs were periodically conducted. Biological properties, such as the cell number, alkaline phosphatase (ALP) activity, and gene expressions of osteogenesis, were evaluated. The microstructural change due to cell growth and the formation of extracellular matrices was examined using a field-emission scanning electron microscope. The compressive property was then correlated with the biological properties and microstructures to understand the mechanism of the variational behavior of the macroscopic mechanical property. The porous collagen structure in the β-TCP scaffold effectively improved the structural stability of the composite scaffold, whereas the β-TCP scaffold exhibited structural instability with the collapse of the porous structure when immersed in a culture medium. The β-TCP/collagen composite scaffold exhibited higher ALP activity and more active generation of osteoblastic markers than the β-TCP scaffold. Copyright © 2016 Elsevier Ltd. All rights reserved.

Ultrastructural instability of paired helical filaments from corticobasal degeneration as examined by scanning transmission electron microscopy.

PubMed Central

Ksiezak-Reding, H.; Tracz, E.; Yang, L. S.; Dickson, D. W.; Simon, M.; Wall, J. S.

1996-01-01

Paired helical filaments (PHFs) accumulate in the brains of subjects affected with Alzheimer's disease (AD) and certain other neurodegenerative disorders, including corticobasal degeneration (CBD). Electron microscope studies have shown that PHFs from CBD differ from those of AD by being wider and having a longer periodicity of the helical twist. Moreover, PHFs from CBD have been shown to be primarily composed of two rather than three highly phosphorylated polypeptides of tau (PHF-tau), with these polypeptides expressing no exons 3 and 10. To further explore the relationship between the heterogeneity of PHF-tau and the appearance of abnormal filaments, the ultrastructure and physical parameters such as mass per unit length and dimensions were compared in filaments from CBD and AD using high resolution scanning transmission electron microscopy (STEM). Filament-enriched fractions were isolated as Sarcosyl-insoluble pellets and for STEM studies, samples were freeze-dried without prior fixation or staining. Ultrastructurally, PHFs from CBD were shown to be a heterogeneous population as double- and single-stranded filaments could be identified based on their width and physical mass per unit length expressed in kilodaltons (kd) per nanometer (nm). Less abundant, double-stranded filaments had a maximal width of 29 nm and a mass per unit length of 133 kd/nm, whereas three times more abundant single-stranded filaments were 15 nm wide and bad a mass per unit length of 62 kd/nm. Double-stranded filaments also displayed a distinct axial region of less dense mass, which appeared to divide the PHFs into two protofilament-like strands. Furthermore, these filaments were frequently observed to physically separate along the long axis into two single strands or to break longitudinally. In contrast, PHFs from AD were ultrastructurally stable and uniform both in their width (22 nm) and physical mass per unit length (104 kd/nm). The ultrastructural features indicate that filaments of CBD and AD differ both in stability and packing of tau and that CBD filaments, composed of two distinct protofilaments, are more labile under STEM conditions. As fixed and stained filaments from CBD have been shown to be stable and uniform in size by conventional transmission electron microscopy, STEM studies may be particularly suitable for detecting instability of unstained and unfixed filaments. The results also suggest that molecular heterogeneity and/or post-translational modifications of tau may strongly influence the morphology and stability of abnormal filaments. Images Figure 1 Figure 2 Figure 3 PMID:8702002

Is cell viability always directly related to corrosion resistance of stainless steels?

PubMed

Salahinejad, E; Ghaffari, M; Vashaee, D; Tayebi, L

2016-05-01

It has been frequently reported that cell viability on stainless steels is improved by increasing their corrosion resistance. The question that arises is whether human cell viability is always directly related to corrosion resistance in these biostable alloys. In this work, the microstructure and in vitro corrosion behavior of a new class of medical-grade stainless steels were correlated with adult human mesenchymal stem cell viability. The samples were produced by a powder metallurgy route, consisting of mechanical alloying and liquid-phase sintering with a sintering aid of a eutectic Mn-Si alloy at 1050 °C for 30 and 60 min, leading to nanostructures. In accordance with transmission electron microscopic studies, the additive particles for the sintering time of 30 min were not completely melted. Electrochemical impedance spectroscopic experiments suggested the higher corrosion resistance for the sample sintered for 60 min; however, a better cell viability on the surface of the less corrosion-resistant sample was unexpectedly found. This behavior is explained by considering the higher ion release rate of the Mn-Si additive material, as preferred sites to corrosion attack based on scanning electron microscopic observations, which is advantageous to the cells in vitro. In conclusion, cell viability is not always directly related to corrosion resistance in stainless steels. Typically, the introduction of biodegradable and biocompatible phases to biostable alloys, which are conventionally anticipated to be corrosion-resistant, can be advantageous to human cell responses similar to biodegradable metals. Copyright © 2016 Elsevier B.V. All rights reserved.

Conservation of Monuments by a Three-Layered Compatible Treatment of TEOS-Nano-Calcium Oxalate Consolidant and TEOS-PDMS-TiO₂ Hydrophobic/Photoactive Hybrid Nanomaterials.

PubMed

Kapridaki, Chrysi; Verganelaki, Anastasia; Dimitriadou, Pipina; Maravelaki-Kalaitzaki, Pagona

2018-04-27

In the conservation of monuments, research on innovative nanocomposites with strengthening, hydrophobic and self-cleaning properties have attracted the interest of the scientific community and promising results have been obtained as a result. In this study, stemming from the need for the compatibility of treatments in terms of nanocomposite/substrate, a three-layered compatible treatment providing strengthening, hydrophobic, and self-cleaning properties is proposed. This conservation approach was implemented treating lithotypes and mortars of different porosity and petrographic characteristics with a three-layered treatment comprising: (a) a consolidant, tetraethoxysilane (TEOS)-nano-Calcium Oxalate; (b) a hydrophobic layer of TEOS-polydimethylsiloxane (PDMS); and (c) a self-cleaning layer of TiO₂ nanoparticles from titanium tetra-isopropoxide with oxalic acid as hole-scavenger. After the three-layered treatment, the surface hydrophobicity was improved due to PDMS and nano-TiO₂ in the interface substrate/atmosphere, as proven by the homogeneity and the Si⁻O⁻Ti hetero-linkages of the blend protective/self-cleaning layers observed by Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM) and Fourier-Transform Infrared Spectroscopy (FTIR). The aesthetic, microstructural, mechanical and permeabile compatibility of the majority of treated substrates ranged within acceptability limits. The improved photocatalytic activity, as proven by the total discoloration of methylene blue in the majority of cases, was attributed to the anchorage of TiO₂, through the Si⁻O⁻Ti bonds to SiO₂, in the interface with the atmosphere, thus enhancing photoactivation.

Preparation and biological properties of a novel composite scaffold of nano-hydroxyapatite/chitosan/carboxymethyl cellulose for bone tissue engineering

PubMed Central

Liuyun, Jiang; Yubao, Li; Chengdong, Xiong

2009-01-01

In this study, we report the physico-chemical and biological properties of a novel biodegradable composite scaffold made of nano-hydroxyapatite and natural derived polymers of chitosan and carboxymethyl cellulose, namely, n-HA/CS/CMC, which was prepared by freeze-drying method. The physico-chemical properties of n-HA/CS/CMC scaffold were tested by infrared absorption spectra (IR), transmission electron microscope(TEM), scanning electron microscope(SEM), universal material testing machine and phosphate buffer solution (PBS) soaking experiment. Besides, the biological properties were evaluated by MG63 cells and Mesenchymal stem cells (MSCs) culture experiment in vitro and a short period implantation study in vivo. The results show that the composite scaffold is mainly formed through the ionic crossing-linking of the two polyions between CS and CMC, and n-HA is incorporated into the polyelectrolyte matrix of CS-CMC without agglomeration, which endows the scaffold with good physico-chemical properties such as highly interconnected porous structure, high compressive strength and good structural stability and degradation. More important, the results of cells attached, proliferated on the scaffold indicate that the scaffold is non-toxic and has good cell biocompatibility, and the results of implantation experiment in vivo further confirm that the scaffold has good tissue biocompatibility. All the above results suggest that the novel degradable n-HA/CS/CMC composite scaffold has a great potential to be used as bone tissue engineering material. PMID:19594953

75 FR 43918 - National Center for Toxicological Research, et al.; Notice of Consolidated Decision on...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-07-27

... Research, et al.; Notice of Consolidated Decision on Applications for Duty-Free Entry of Electron...: National Center for Toxicological Research, (USFDA), Jefferson, AK 72079. Instrument: Electron Microscope.... Applicant: University of Virginia, Charlottesville, VA 22903. Instrument: Electron Microscope. Manufacturer...

Dislocation imaging for orthopyroxene using an atom-resolved scanning transmission electron microscopy.

PubMed

Kumamoto, Akihito; Kogure, Toshihiro; Raimbourg, Hugues; Ikuhara, Yuichi

2014-11-01

Dislocations, one-dimensional lattice defects, appear as a microscopic phenomenon while they are formed in silicate minerals by macroscopic dynamics of the earth crust such as shear stress. To understand ductile deformation mechanisms of silicates, atomic structures of the dislocations have been examined using transmission electron microscopy (TEM). Among them, it has been proposed that {100}<001> primary slip system of orthopyroxene (Opx) is dissociated into partial dislocations, and a stacking fault with the clinopyroxene (Cpx) structure is formed between the dislocations. This model, however, has not been determined completely due to the complex structures of silicates. Scanning transmission electron microscopy (STEM) has a potential to determine the structure of dislocations with single-atomic column sensitivity, particularly by using high-angle annular dark field (HAADF) and annular bright field (ABF) imaging with a probing aberration corrector.[1] Furthermore, successive analyses from light microscopy to atom-resolved STEM have been achieved by focused ion beam (FIB) sampling techniques.[2] In this study, we examined dislocation arrays at a low-angle grain boundary of ∼1° rotation about the b-axis in natural deformed Opx using a simultaneous acquisition of HAADF/ABF (JEM-ARM200F, JEOL) equipped with 100 mm2 silicon drift detector (SDD) for energy dispersive X-ray spectroscopy (EDS). Figure 1 shows averaged STEM images viewed along the b- axis of Opx extracted from repeating units. HAADF provides the cation-site arrangement, and ABF distinguishes the difference of slightly rotated SiO4 tetrahedron around the a- axis. This is useful to distinguish the change of stacking sequence between the partial dislocations. Two types of stacking faults with Cpx and protopyroxene (Ppx) structures were identified between three partial dislocations. Furthermore, Ca accumulation in M2 (Fe) site around the stacking faults was detected by STEM-EDS. Interestingly, Ca is distributed not only in these stacking faults but also Opx matrix around the faults. jmicro;63/suppl_1/i17/DFU063F1F1DFU063F1Fig. 1. (a) HAADF and (b) ABF of Opx view of [010] direction with inset simulation images and models of its unit cell (a = 0.52, c = 1.83 nm). © 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 Microscope Observations of Marine Microorganisms on Surfaces Coated with Antifouling Paints.

DTIC Science & Technology

1981-06-01

sessile marine inverte- brates in Monterey harbor. Veliger 17 (supplement): 1-35. 1977. The nature of primary organic films in the marine environment and...I A10A4h 605 NAVAL POSTGRADUATE SCHOOL MONTEREY CA F/S 11/3 SCANING ELECTRON MICROSCOPE OBSERVATIONS OF MARINE MICROORANI-E-C(U) UNLSSIFIED N*2...Scanning Electron Microscope Observations Master’s thesis; of Marine Microorganisms on Surfaces June 1981 Coated with Ant ifouling Paints 6.PERFORMING

Electron microscope aperture system

NASA Technical Reports Server (NTRS)

Heinemann, K. (Inventor)

1976-01-01

An electron microscope including an electron source, a condenser lens having either a circular aperture for focusing a solid cone of electrons onto a specimen or an annular aperture for focusing a hollow cone of electrons onto the specimen, and an objective lens having an annular objective aperture, for focusing electrons passing through the specimen onto an image plane are described. The invention also entails a method of making the annular objective aperture using electron imaging, electrolytic deposition and ion etching techniques.

Dynamics of gene expression during development and expansion of vegetative stem internodes of bioenergy sorghum

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

Kebrom, Tesfamichael H.; McKinley, Brian; Mullet, John E.

Bioenergy sorghum accumulates 75% of shoot biomass in stem internodes. Grass stem internodes are formed during vegetative growth and elongate in response to developmental and environmental signals. To identify genes and molecular mechanisms that modulate the extent of internode growth, we conducted microscopic and transcriptomic analyses of four successive sub-apical vegetative internodes representing different stages of internode development of the bioenergy sorghum genotype R.07020. Stem internodes of sorghum genotype R.07020 are formed during the vegetative phase and their length is enhanced by environmental signals such as shade and floral induction in short days. During vegetative growth, the first visible andmore » youngest sub-apical internode was ~0.7 cm in length, whereas the fourth fully expanded internode was ~5 cm in length. Microscopic analyses revealed that all internode tissue types including pith parenchyma and vascular bundles are present in the four successive internodes. Growth in the first two sub-apical internodes occurred primarily through an increase in cell number consistent with expression of genes involved in the cell cycle and DNA replication. Growth of the 3rd internode was associated with an increase in cell length and growth cessation in the 4th internode was associated with up-regulation of genes involved in secondary cell wall deposition. The expression of genes involved in hormone metabolism and signaling indicates that GA, BR, and CK activity decreased while ethylene, ABA, and JA increased in the 3rd/4th internodes. While the level of auxin appears to be increasing as indicated by the up-regulation of ARFs, down-regulation of TIR during development indicates that auxin signaling is also modified. The expression patterns of transcription factors are closely associated with their role during the development of the vegetative internodes. Microscopic and transcriptome analyses of four successive sub-apical internodes characterized the developmental progression of vegetative stem internodes from initiation through full elongation in the sorghum genotype R.07020. Transcriptome profiling indicates that dynamic variation in the levels and action of GA, CK, IAA, BR, ethylene, ABA, and JA modulate gene expression and growth during internode growth and development. Thus, this study provides detailed microscopic and transcriptomic data useful for identifying genes and molecular pathways regulating internode elongation in response to various developmental and environmental signals.« less

Dynamics of gene expression during development and expansion of vegetative stem internodes of bioenergy sorghum

DOE PAGES

Kebrom, Tesfamichael H.; McKinley, Brian; Mullet, John E.

2017-06-21

Bioenergy sorghum accumulates 75% of shoot biomass in stem internodes. Grass stem internodes are formed during vegetative growth and elongate in response to developmental and environmental signals. To identify genes and molecular mechanisms that modulate the extent of internode growth, we conducted microscopic and transcriptomic analyses of four successive sub-apical vegetative internodes representing different stages of internode development of the bioenergy sorghum genotype R.07020. Stem internodes of sorghum genotype R.07020 are formed during the vegetative phase and their length is enhanced by environmental signals such as shade and floral induction in short days. During vegetative growth, the first visible andmore » youngest sub-apical internode was ~0.7 cm in length, whereas the fourth fully expanded internode was ~5 cm in length. Microscopic analyses revealed that all internode tissue types including pith parenchyma and vascular bundles are present in the four successive internodes. Growth in the first two sub-apical internodes occurred primarily through an increase in cell number consistent with expression of genes involved in the cell cycle and DNA replication. Growth of the 3rd internode was associated with an increase in cell length and growth cessation in the 4th internode was associated with up-regulation of genes involved in secondary cell wall deposition. The expression of genes involved in hormone metabolism and signaling indicates that GA, BR, and CK activity decreased while ethylene, ABA, and JA increased in the 3rd/4th internodes. While the level of auxin appears to be increasing as indicated by the up-regulation of ARFs, down-regulation of TIR during development indicates that auxin signaling is also modified. The expression patterns of transcription factors are closely associated with their role during the development of the vegetative internodes. Microscopic and transcriptome analyses of four successive sub-apical internodes characterized the developmental progression of vegetative stem internodes from initiation through full elongation in the sorghum genotype R.07020. Transcriptome profiling indicates that dynamic variation in the levels and action of GA, CK, IAA, BR, ethylene, ABA, and JA modulate gene expression and growth during internode growth and development. Thus, this study provides detailed microscopic and transcriptomic data useful for identifying genes and molecular pathways regulating internode elongation in response to various developmental and environmental signals.« less

Choice and maintenance of equipment for electron crystallography.

PubMed

Mills, Deryck J; Vonck, Janet

2013-01-01

The choice of equipment for an electron crystallography laboratory will ultimately be determined by the available budget; nevertheless, the ideal lab will have two electron microscopes: a dedicated 300 kV cryo-EM with a field emission gun and a smaller LaB(6) machine for screening. The high-end machine should be equipped with photographic film or a very large CCD or CMOS camera for 2D crystal data collection; the screening microscope needs a mid-size CCD for rapid evaluation of crystal samples. The microscope room installations should provide adequate space and a special environment that puts no restrictions on the collection of high-resolution data. Equipment for specimen preparation includes a carbon coater, glow discharge unit, light microscope, plunge freezer, and liquid nitrogen containers and storage dewars. When photographic film is to be used, additional requirements are a film desiccator, dark room, optical diffractometer, and a film scanner. Having the electron microscopes and ancillary equipment well maintained and always in optimum condition facilitates the production of high-quality data.

Vibrational spectroscopy in the electron microscope.

PubMed

Krivanek, Ondrej L; Lovejoy, Tracy C; Dellby, Niklas; Aoki, Toshihiro; Carpenter, R W; Rez, Peter; Soignard, Emmanuel; Zhu, Jiangtao; Batson, Philip E; Lagos, Maureen J; Egerton, Ray F; Crozier, Peter A

2014-10-09

Vibrational spectroscopies using infrared radiation, Raman scattering, neutrons, low-energy electrons and inelastic electron tunnelling are powerful techniques that can analyse bonding arrangements, identify chemical compounds and probe many other important properties of materials. The spatial resolution of these spectroscopies is typically one micrometre or more, although it can reach a few tens of nanometres or even a few ångströms when enhanced by the presence of a sharp metallic tip. If vibrational spectroscopy could be combined with the spatial resolution and flexibility of the transmission electron microscope, it would open up the study of vibrational modes in many different types of nanostructures. Unfortunately, the energy resolution of electron energy loss spectroscopy performed in the electron microscope has until now been too poor to allow such a combination. Recent developments that have improved the attainable energy resolution of electron energy loss spectroscopy in a scanning transmission electron microscope to around ten millielectronvolts now allow vibrational spectroscopy to be carried out in the electron microscope. Here we describe the innovations responsible for the progress, and present examples of applications in inorganic and organic materials, including the detection of hydrogen. We also demonstrate that the vibrational signal has both high- and low-spatial-resolution components, that the first component can be used to map vibrational features at nanometre-level resolution, and that the second component can be used for analysis carried out with the beam positioned just outside the sample--that is, for 'aloof' spectroscopy that largely avoids radiation damage.

Ultrastructural Study of Some Pollen Grains of Prairie Flowers

ERIC Educational Resources Information Center

Kozar, Frank

1973-01-01

Discusses the importance of the electron microscope, and in particular the scanning electron microscope, in studying the surface topography, sectional substructures, and patterns of development of pollen grains. The production, dispersal methods, and structure of pollen grains are described and illustrated with numerous electron micrographs. (JR)

Synthesis Properties and Electron Spin Resonance Properties of Titanic Materials (abstract)

NASA Astrophysics Data System (ADS)

Cho, Jung Min; Lee, Jun; Kim, Tak Hee; Sun, Min Ho; Jang, Young Bae; Cho, Sung June

2009-04-01

Titanic materials were synthesized by hydrothermal method of TiO2 anatase in 10M LiOH, 10M NaOH, and 14M KOH at 130° C for 30 hours. Alkaline media were removed from the synthesized products using 0.1N HCl aqueous solution. The as-prepared samples were characterized by scanning electron microscope, transmission electron microscope, X-ray diffraction, Brunauer-Emmett-Teller isotherm, and electron spin resonance. Different shapes of synthesized products were observed through the typical electron microscope and indicated that the formation of the different morphologies depends on the treatment conditions of highly alkaline media. Many micropores were observed in the cubic or octahedral type of TiO2 samples through the typical electron microscope and Langmuir adsorption-desorption isotherm of liquid nitrogen at 77° K. Electron spin resonance studies have also been carried out to verify the existence of paramagnetic sites such as oxygen vacancies on the titania samples. The effect of alkali metal ions on the morphologies and physicochemical properties of nanoscale titania are discussed.

Fine structure of the midgut epithelium in the millipede Telodeinopus aoutii (Myriapoda, Diplopoda) with special emphasis on epithelial regeneration.

PubMed

Rost-Roszkowska, M M; Kszuk-Jendrysik, M; Marchewka, A; Poprawa, I

2018-01-01

The midgut of millipedes is composed of a simple epithelium that rests on a basal lamina, which is surrounded by visceral muscles and hepatic cells. As the material for our studies, we chose Telodeinopus aoutii (Demange, 1971) (Kenyan millipede) (Diplopoda, Spirostreptida), which lives in the rain forests of Central Africa. This commonly reared species is easy to obtain from local breeders and easy to culture in the laboratory. During our studies, we used transmission and scanning electron microscopes and light and fluorescent microscopes. The midgut epithelium of the species examined here shares similarities to the structure of the millipedes analyzed to date. The midgut epithelium is composed of three types of cells-digestive, secretory, and regenerative cells. Evidence of three types of secretion have been observed in the midgut epithelium: merocrine, apocrine, and microapocrine secretion. The regenerative cells of the midgut epithelium in millipedes fulfill the role of midgut stem cells because of their main functions: self-renewal (the ability to divide mitotically and to maintain in an undifferentiated state) and potency (ability to differentiate into digestive cells). We also confirmed that spot desmosomes are common intercellular junctions between the regenerative and digestive cells in millipedes.

Design and performance of a beetle-type double-tip scanning tunneling microscope

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

Jaschinsky, Philipp; Coenen, Peter; Pirug, Gerhard

2006-09-15

A combination of a double-tip scanning tunneling microscope with a scanning electron microscope in ultrahigh vacuum environment is presented. The compact beetle-type design made it possible to integrate two independently driven scanning tunneling microscopes in a small space. Moreover, an additional level for coarse movement allows the decoupling of the translation and approach of the tunneling tip. The position of the two tips can be controlled from the millimeter scale down to 50 nm with the help of an add-on electron microscope. The instrument is capable of atomic resolution imaging with each tip.

Development of Scanning Ultrafast Electron Microscope Capability.

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

Collins, Kimberlee Chiyoko; Talin, Albert Alec; Chandler, David W.

Modern semiconductor devices rely on the transport of minority charge carriers. Direct examination of minority carrier lifetimes in real devices with nanometer-scale features requires a measurement method with simultaneously high spatial and temporal resolutions. Achieving nanometer spatial resolutions at sub-nanosecond temporal resolution is possible with pump-probe methods that utilize electrons as probes. Recently, a stroboscopic scanning electron microscope was developed at Caltech, and used to study carrier transport across a Si p-n junction [ 1 , 2 , 3 ] . In this report, we detail our development of a prototype scanning ultrafast electron microscope system at Sandia National Laboratoriesmore » based on the original Caltech design. This effort represents Sandia's first exploration into ultrafast electron microscopy.« less

Ultrastructure of cholinergic neurons in the laterodorsal tegmental nucleus of the rat: interaction with catecholamine fibers.

PubMed

Kubota, Y; Leung, E; Vincent, S R

1992-01-01

The ultrastructure of choline acetyltransferase (ChAT)-immunoreactive neurons in the laterodorsal tegmental nucleus (TLD) of the rat was investigated by immunohistochemical techniques. The immunoreactive neurons were medium to large in size, with a few elongated dendrites, contained well-developed cytoplasm, and a nucleus with deep infoldings. They received many nonimmunoreactive, mostly asymmetric synaptic inputs on their soma and dendrites. ChAT-immunoreactive, usually myelinated, axons were occasionally seen in TLD. Only one immunoreactive axon terminal was observed within TLD, and it made synaptic contact with a nonimmunoreactive neuronal perikaryon. The synaptic interactions between ChAT-immunoreactive neurons and tyrosine hydroxylase (TH)-immunoreactive fibers in the TLD were investigated with a double immunohistochemical staining method. ChAT-immunoreactivity detected with a beta-galactosidase method was light blue-green in the light microscope and formed dot-like electron dense particles at the electron microscopic level. TH-immunoreactivity, visualized with a nickel-enhanced immunoperoxidase method, was dark blue-black in the light microscope and diffusely opaque in the electron microscope. Therefore, the difference between these two kinds of immunoreactivity could be quite easily distinguished at both light and electron microscopic levels. In the light microscope, TH-positive fibers were often closely apposed to ChAT-immunoreactive cell bodies and dendrites in TLD. In the electron microscope, the cell soma and proximal dendrites of ChAT-immunoreactive neurons received synaptic contacts from TH-immunoreactive axon terminals. These results provide a morphological basis for catecholaminergic regulation of the cholinergic reticular system.

Sb,123121 nuclear quadrupole resonance as a microscopic probe in the Te-doped correlated semimetal FeSb2: Emergence of electronic Griffith phase, magnetism, and metallic behavior

NASA Astrophysics Data System (ADS)

Gippius, A. A.; Zhurenko, S. V.; Hu, R.; Petrovic, C.; Baenitz, M.

2018-02-01

Sb,123121 nuclear quadrupole resonance (NQR) was applied to Fe(Sb1-xTex)2 in the low doping regime (x =0 , 0.01, and 0.05) as a microscopic zero field probe to study the evolution of 3 d magnetism and the emergence of metallic behavior. Whereas the NQR spectra itself reflects the degree of local disorder via the width of the individual NQR lines, the spin lattice relaxation rate (SLRR) 1 /T1(T ) probes the fluctuations at the Sb site. The fluctuations originate either from conduction electrons or from magnetic moments. In contrast to the semimetal FeSb2 with a clear signature of the charge and spin gap formation in 1 /T1(T ) T [˜exp/(Δ kBT ) ] , the 1% Te-doped system exhibits almost metallic conductivity and the SLRR nicely confirms that the gap is almost filled. A weak divergence of the SLRR coefficient 1 /T1(T ) T ˜T-n˜T-0.2 points towards the presence of electronic correlations towards low temperatures. This is supported by the electronic specific heat coefficient γ =(Cel/T ) showing a power-law divergence γ (T ) ˜T-m˜(1/T1T ) 1 /2˜T-n /2˜Cel/T which is expected in the renormalized Landau Fermi liquid theory for correlated electrons. In contrast to that the 5% Te-doped sample exhibits a much larger divergence in the SLRR coefficient showing 1 /T1(T ) T ˜T-0.72 . According to the specific heat divergence a power law with n =2 m =0.56 is expected for the SLRR. This dissimilarity originates from admixed critical magnetic fluctuations in the vicinity of antiferromagnetic long range order with 1 /T1(T ) T ˜T-3 /4 behavior. Furthermore Te-doped FeSb2 as a disordered paramagnetic metal might be a platform for the electronic Griffith phase scenario. NQR evidences a substantial asymmetric broadening of the Sb,123121 NQR spectrum for the 5% sample. This has a predominant electronic origin in agreement with the electronic Griffith phase and stems probably from an enhanced Sb-Te bond polarization and electronic density shift towards the Te atom inside Sb-Te dumbbell.

Sb 121 , 123 nuclear quadrupole resonance as a microscopic probe in the Te-doped correlated semimetal FeSb 2 : Emergence of electronic Griffith phase, magnetism, and metallic behavior

DOE PAGES

Gippius, A. A.; Zhurenko, S. V.; Hu, R.; ...

2018-02-12

121,123Sb nuclear quadrupole resonance (NQR) was applied to Fe(Sb 1-xTe x) 2 in the low doping regime (x = 0 , 0.01, and 0.05) as a microscopic zero field probe to study the evolution of 3d magnetism and the emergence of metallic behavior. Whereas the NQR spectra itself reflects the degree of local disorder via the width of the individual NQR lines, the spin lattice relaxation rate (SLRR) 1/T 1 (T) probes the fluctuations at the Sb site. The fluctuations originate either from conduction electrons or from magnetic moments. In contrast to the semimetal FeSb 2 with a clear signaturemore » of the charge and spin gap formation in 1/T 1(T)T[~exp/(Δk BT)] , the 1% Te-doped system exhibits almost metallic conductivity and the SLRR nicely confirms that the gap is almost filled. A weak divergence of the SLRR coefficient 1/T 1(T)T ~ T -n ~ T -0.2 points towards the presence of electronic correlations towards low temperatures. This is supported by the electronic specific heat coefficient γ = (C el/T) showing a power-law divergence γ (T) ~ T -m ~ (1/T 1T) 1/2 ~ T -n/2 ~ C el/T which is expected in the renormalized Landau Fermi liquid theory for correlated electrons. In contrast to that the 5% Te-doped sample exhibits a much larger divergence in the SLRR coefficient showing 1/T 1(T)T ~ T -0.72 . According to the specific heat divergence a power law with n = 2 m = 0.56 is expected for the SLRR. This dissimilarity originates from admixed critical magnetic fluctuations in the vicinity of antiferromagnetic long range order with 1/T 1(T)T ~ T -3/4 behavior. Furthermore Te-doped FeSb 2 as a disordered paramagnetic metal might be a platform for the electronic Griffith phase scenario. NQR evidences a substantial asymmetric broadening of the 121,123Sb NQR spectrum for the 5% sample. Lastly, this has a predominant electronic origin in agreement with the electronic Griffith phase and stems probably from an enhanced Sb-Te bond polarization and electronic density shift towards the Te atom inside Sb-Te dumbbell.« less

Sb 121 , 123 nuclear quadrupole resonance as a microscopic probe in the Te-doped correlated semimetal FeSb 2 : Emergence of electronic Griffith phase, magnetism, and metallic behavior

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

Gippius, A. A.; Zhurenko, S. V.; Hu, R.

121,123Sb nuclear quadrupole resonance (NQR) was applied to Fe(Sb 1-xTe x) 2 in the low doping regime (x = 0 , 0.01, and 0.05) as a microscopic zero field probe to study the evolution of 3d magnetism and the emergence of metallic behavior. Whereas the NQR spectra itself reflects the degree of local disorder via the width of the individual NQR lines, the spin lattice relaxation rate (SLRR) 1/T 1 (T) probes the fluctuations at the Sb site. The fluctuations originate either from conduction electrons or from magnetic moments. In contrast to the semimetal FeSb 2 with a clear signaturemore » of the charge and spin gap formation in 1/T 1(T)T[~exp/(Δk BT)] , the 1% Te-doped system exhibits almost metallic conductivity and the SLRR nicely confirms that the gap is almost filled. A weak divergence of the SLRR coefficient 1/T 1(T)T ~ T -n ~ T -0.2 points towards the presence of electronic correlations towards low temperatures. This is supported by the electronic specific heat coefficient γ = (C el/T) showing a power-law divergence γ (T) ~ T -m ~ (1/T 1T) 1/2 ~ T -n/2 ~ C el/T which is expected in the renormalized Landau Fermi liquid theory for correlated electrons. In contrast to that the 5% Te-doped sample exhibits a much larger divergence in the SLRR coefficient showing 1/T 1(T)T ~ T -0.72 . According to the specific heat divergence a power law with n = 2 m = 0.56 is expected for the SLRR. This dissimilarity originates from admixed critical magnetic fluctuations in the vicinity of antiferromagnetic long range order with 1/T 1(T)T ~ T -3/4 behavior. Furthermore Te-doped FeSb 2 as a disordered paramagnetic metal might be a platform for the electronic Griffith phase scenario. NQR evidences a substantial asymmetric broadening of the 121,123Sb NQR spectrum for the 5% sample. Lastly, this has a predominant electronic origin in agreement with the electronic Griffith phase and stems probably from an enhanced Sb-Te bond polarization and electronic density shift towards the Te atom inside Sb-Te dumbbell.« less

Neural differentiation of transplanted neural stem cells in a rat model of striatal lacunar infarction: light and electron microscopic observations

PubMed Central

Muñetón-Gómez, Vilma C.; Doncel-Pérez, Ernesto; Fernandez, Ana P.; Serrano, Julia; Pozo-Rodrigálvarez, Andrea; Vellosillo-Huerta, Lara; Taylor, Julian S.; Cardona-Gómez, Gloria P.; Nieto-Sampedro, Manuel; Martínez-Murillo, Ricardo

2012-01-01

The increased risk and prevalence of lacunar stroke and Parkinson's disease (PD) makes the search for better experimental models an important requirement for translational research. In this study we assess ischemic damage of the nigrostriatal pathway in a model of lacunar stroke evoked by damaging the perforating arteries in the territory of the substantia nigra (SN) of the rat after stereotaxic administration of endothelin-1 (ET-1), a potent vasoconstrictor peptide. We hypothesized that transplantation of neural stem cells (NSCs) with the capacity of differentiating into diverse cell types such as neurons and glia, but with limited proliferation potential, would constitute an alternative and/or adjuvant therapy for lacunar stroke. These cells showed neuritogenic activity in vitro and a high potential for neural differentiation. Light and electron microscopy immunocytochemistry was used to characterize GFP-positive neurons derived from the transplants. 48 h after ET-1 injection, we characterized an area of selective degeneration of dopaminergic neurons within the nigrostriatal pathway characterized with tissue necrosis and glial scar formation, with subsequent behavioral signs of Parkinsonism. Light microscopy showed that grafted cells within the striatal infarction zone differentiated with a high yield into mature glial cells (GFAP-positive) and neuron types present in the normal striatum. Electron microscopy revealed that NSCs-derived neurons integrated into the host circuitry establishing synaptic contacts, mostly of the asymmetric type. Astrocytes were closely associated with normal small-sized blood vessels in the area of infarct, suggesting a possible role in the regulation of the blood brain barrier and angiogenesis. Our results encourage the use of NSCs as a cell-replacement therapy for the treatment of human vascular Parkinsonism. PMID:22876219

STEM VQ Method, Using Scanning Transmission Electron Microscopy (STEM) for Accurate Virus Quantification

DTIC Science & Technology

2017-02-02

Corresponding Author Abstract Accurate virus quantification is sought, but a perfect method still eludes the scientific community. Electron...unlimited. UNCLASSIFIED 2 provides morphology data and counts all viral particles, including partial or noninfectious particles; however, EM methods ...consistent, reproducible virus quantification method called Scanning Transmission Electron Microscopy – Virus Quantification (STEM-VQ) which simplifies

77 FR 71776 - Ohio University, et al.; Notice of Consolidated Decision on Applications for Duty-Free Entry of...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-12-04

... Consolidated Decision on Applications for Duty-Free Entry of Electron Microscope This is a decision... Stocker Center, Athens, OH 45701. Instrument: Electron Microscope. Manufacturer: JEOL Ltd., Japan... North Carolina Wilmington, 601 South College Road, Wilmington, NC 28403-5915. Instrument: Electron...

Influence of mechanical noise inside a scanning electron microscope.

PubMed

de Faria, Marcelo Gaudenzi; Haddab, Yassine; Le Gorrec, Yann; Lutz, Philippe

2015-04-01

The scanning electron microscope is becoming a popular tool to perform tasks that require positioning, manipulation, characterization, and assembly of micro-components. However, some of these applications require a higher level of performance with respect to dynamics and precision of positioning. One limiting factor is the presence of unidentified noises and disturbances. This work aims to study the influence of mechanical disturbances generated by the environment and by the microscope, identifying how these can affect elements in the vacuum chamber. To achieve this objective, a dedicated setup, including a high-resolution vibrometer, was built inside the microscope. This work led to the identification and quantification of main disturbances and noise sources acting on a scanning electron microscope. Furthermore, the effects of external acoustic excitations were analysed. Potential applications of these results include noise compensation and real-time control for high accuracy tasks.

Atomic-Resolution Spectrum Imaging of Semiconductor Nanowires.

PubMed

Zamani, Reza R; Hage, Fredrik S; Lehmann, Sebastian; Ramasse, Quentin M; Dick, Kimberly A

2018-03-14

Over the past decade, III-V heterostructure nanowires have attracted a surge of attention for their application in novel semiconductor devices such as tunneling field-effect transistors (TFETs). The functionality of such devices critically depends on the specific atomic arrangement at the semiconductor heterointerfaces. However, most of the currently available characterization techniques lack sufficient spatial resolution to provide local information on the atomic structure and composition of these interfaces. Atomic-resolution spectrum imaging by means of electron energy-loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM) is a powerful technique with the potential to resolve structure and chemical composition with sub-angstrom spatial resolution and to provide localized information about the physical properties of the material at the atomic scale. Here, we demonstrate the use of atomic-resolution EELS to understand the interface atomic arrangement in three-dimensional heterostructures in semiconductor nanowires. We observed that the radial interfaces of GaSb-InAs heterostructure nanowires are atomically abrupt, while the axial interface in contrast consists of an interfacial region where intermixing of the two compounds occurs over an extended spatial region. The local atomic configuration affects the band alignment at the interface and, hence, the charge transport properties of devices such as GaSb-InAs nanowire TFETs. STEM-EELS thus represents a very promising technique for understanding nanowire physical properties, such as differing electrical behavior across the radial and axial heterointerfaces of GaSb-InAs nanowires for TFET applications.

Electron microscope studies

NASA Astrophysics Data System (ADS)

Crewe, A. V.; Kapp, O. H.

1991-06-01

This year our laboratory has continued to make progress in the design of electron-optical systems, in the study of structure-function relationships of large multi-subunit proteins, in the development of new image processing software and in achieving a workable sub-angstrom STEM. We present an algebraic approach to the symmetrical Einzel (unipotential) lens wherein we simplify the analysis by specifying a field shape that meets some preferred set of boundary or other conditions and then calculate the fields. In a second study we generalize this approach to study of three element electrostatic lenses of which the symmetrical Einzel lens is a particular form. The purpose is to develop a method for assisting in the design of a lens for a particular purpose. In our biological work we study a stable and functional dodecameric complex of globin chains from the hemoglobin of Lumbricus terrestris. This is a complex lacking the 'linker' subunit first imaged in this lab and required for maintenance of the native structure. In addition, we do a complete work-up on the hemoglobin of the marine polychaete Eudistylia vancouverii, demonstrating the presence of a hierarchy of globin complexes. We demonstrate stable field-emission in the sub-angstrom STEM and the preliminary alignment of the beam. We continue our exploration of a algorithms for alignment of sequences of protein and DNA. Our computer facilities now include four second generation RISC workstations and we continue to take increasing advantage of the floating-point and graphical performance of these devices.

Microcircuit testing and fabrication, using scanning electron microscopes

NASA Technical Reports Server (NTRS)

Nicolas, D. P.

1975-01-01

Scanning electron microscopes are used to determine both user-induced damages and manufacturing defects subtle enough to be missed by conventional light microscopy. Method offers greater depth of field and increased working distances.

Method of forming aperture plate for electron microscope

NASA Technical Reports Server (NTRS)

Heinemann, K. (Inventor)

1974-01-01

An electron microscope is described with an electron source a condenser lens having either a circular aperture for focusing a solid cone of electrons onto a specimen or an annular aperture for focusing a hollow cone of electrons onto the specimen. It also has objective lens with an annular objective aperture, for focusing electrons passing through the specimen onto an image plane. A method of making the annular objective aperture using electron imaging, electrolytic deposition and ion etching techniques is included.

Development of scanning electron and x-ray microscope

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

Matsumura, Tomokazu, E-mail: tomokzau.matsumura@etd.hpk.co.jp; Hirano, Tomohiko, E-mail: tomohiko.hirano@etd.hpk.co.jp; Suyama, Motohiro, E-mail: suyama@etd.hpk.co.jp

We have developed a new type of microscope possessing a unique feature of observing both scanning electron and X-ray images under one unit. Unlike former X-ray microscopes using SEM [1, 2], this scanning electron and X-ray (SELX) microscope has a sample in vacuum, thus it enables one to observe a surface structure of a sample by SEM mode, to search the region of interest, and to observe an X-ray image which transmits the region. For the X-ray observation, we have been focusing on the soft X-ray region from 280 eV to 3 keV to observe some bio samples and softmore » materials. The resolutions of SEM and X-ray modes are 50 nm and 100 nm, respectively, at the electron energy of 7 keV.« less

Examination of Surveyor 3 parts with the scanning electron microscope and electron microprobe

NASA Technical Reports Server (NTRS)

Chodos, A. A.; Devaney, J. R.; Evens, K. C.

1972-01-01

Two screws and two washers, several small chips of tubing, and a fiber removed from a third screw were examined with the scanning electron microscope and the electron microprobe. The purpose of the examination was to determine the nature of the material on the surface of these samples and to search for the presence of meteoritic material.

In vitro proliferation and osteogenic differentiation of human dental pulp stem cells in injectable thermo-sensitive chitosan/β-glycerophosphate/hydroxyapatite hydrogel.

PubMed

Chen, Yantian; Zhang, Fengli; Fu, Qiang; Liu, Yong; Wang, Zejian; Qi, Nianmin

2016-09-01

Injectable thermo-sensitive hydrogels have a potential application in bone tissue engineering for their sensitivities and minimal invasive properties. Human dental pulp stem cells have been considered a promising tool for tissue reconstruction. The objective of this study was to investigate the proliferation and osteogenic differentiation of dental pulp stem cells in injectable thermo-sensitive chitosan/β-glycerophosphate/hydroxyapatite hydrogel in vitro. The chitosan /β-glycerophosphate hydrogel and chitosan/β-glycerophosphate/hydroxyapatite hydrogel were prepared using the sol-gel method. The injectability of chitosan /β-glycerophosphate hydrogel and chitosan/β-glycerophosphate/hydroxyapatite hydrogel was measured using a commercial disposable syringe. Scanning electron microscopy was used to observe the inner structure of hydrogels. Then dental pulp stem cells were seeded in chitosan /β-glycerophosphate hydrogel and chitosan/β-glycerophosphate/hydroxyapatite hydrogel, respectively. The growth of dental pulp stem cells was periodically observed under an inverted microscope. The proliferation of dental pulp stem cells was detected by using an Alamar Blue kit, while cell apoptosis was determined by using a Live/Dead Viability/Cytotoxicity kit. The osteogenic differentiations of dental pulp stem cells in chitosan /β-glycerophosphate hydrogel and chitosan/β-glycerophosphate/hydroxyapatite hydrogel were evaluated by alkaline phosphatase activity assay and mRNA expression of osteogenesis gene for 21 days in osteogenic medium. The results indicated that there was no significant difference between chitosan /β-glycerophosphate hydrogel and chitosan/β-glycerophosphate/hydroxyapatite hydrogel in injectability. Cells within the chitosan/β-glycerophosphate/hydroxyapatite hydrogel displayed a typical adherent cell morphology and rapid proliferation with high cellular viability after 14 days of culture. Dental pulp stem cells seeded in chitosan/β-glycerophosphate/hydroxyapatite hydrogels had a higher alkaline phosphatase activity and better up-regulation of gene expression levels of Runx-2, Collagen I, alkaline phosphatase and osteocalcin than in chitosan /β-glycerophosphate hydrogels after osteogenic differentiation. These results demonstrated that the chitosan/β-glycerophosphate/hydroxyapatite hydrogel had excellent cellular compatibility and the superiority in promoting dental pulp stem cells osteogenic differentiation in vitro, showing that the combination of dental pulp stem cells and chitosan/β-glycerophosphate/hydroxyapatite hydrogel has the potential to be used for bone tissue engineering. © The Author(s) 2016.

Multi-pass transmission electron microscopy

DOE PAGES

Juffmann, Thomas; Koppell, Stewart A.; Klopfer, Brannon B.; ...

2017-05-10

Feynman once asked physicists to build better electron microscopes to be able to watch biology at work. While electron microscopes can now provide atomic resolution, electron beam induced specimen damage precludes high resolution imaging of sensitive materials, such as single proteins or polymers. Here, we use simulations to show that an electron microscope based on a multi-pass measurement protocol enables imaging of single proteins, without averaging structures over multiple images. While we demonstrate the method for particular imaging targets, the approach is broadly applicable and is expected to improve resolution and sensitivity for a range of electron microscopy imaging modalities,more » including, for example, scanning and spectroscopic techniques. The approach implements a quantum mechanically optimal strategy which under idealized conditions can be considered interaction-free.« less

Application of microscopy in authentication of traditional Tibetan medicinal plants of five Rhodiola (Crassulaceae) alpine species by comparative anatomy and micromorphology.

PubMed

Li, Tao; Zhang, Hao

2008-06-01

A comparative analysis was undertaken to conduct an anatomical and micromorphological study of five species of Rhodiola-R. kirilowii, R. yunnanensis, R. crenulata, R. fastigata, and R. quadrifida-collected from the western Sichuan province plateau of China. Rhodiola plants are a popularly used ethnodrug from the Qinghai-Tibetan plateau of China. Modern studies have shown that the plants of Rhodiola possess different pharmacological activities, chemical constituents, and efficiencies in clinical application. To distinguish five main species of Rhodiola and ensure their safety and efficacy, microscopic characteristics of roots, rhizomes, and stems, including transverse sections, stem and foliar epidermis, as well as the crude drug powder, were observed. The fixed, sectioned, and stained plant materials, as well as the crude powder, were studied using a light microscope according to the usual microscopic techniques. The results of the microscopic features were systematically and comparatively described and illustrated. The five species have distinct microscopic characteristic differences, thus allowing us to distinguish between the species. Also, semi-quantitative and quantitative micrographic parameter tables were simultaneously presented. Further, a key to the five species and a comparative chart of the key authentication parameters based on these anatomic characteristics analyzed was drawn up and is presented for the Rhodiola species studied. The study indicated that light microscopy and related techniques provide a method that is convenient, feasible, and can be unambiguously applied to the authentication of species of Rhodiola. (c) 2008 Wiley-Liss, Inc.

Hematopoietic Stem Cell Capture and Directional Differentiation into Vascular Endothelial Cells for Metal Stent-Coated Chitosan/Hyaluronic Acid Loading CD133 Antibody

PubMed Central

Zhang, Fan; Feng, Bo; Fan, Qingyu; Yang, Feng; Shang, Debin; Sui, Jinghan; Zhao, Hong

2015-01-01

A series of metal stents coated with chitosan/hyaluronic acid (CS/HA) loading antibodies by electrostatic self-assembled method were prepared, and the types of cells captured by antibodies and their differentiation in vascular endothelial cells (ECs) evaluated by molecular biology and scanning electron microscope. The results showed that CD133 stent can selectively capture hematopoietic stem cells (HSC),which directionally differentiate into vascular ECs in peripheral blood by (CS/HA) induction, and simultaneously inhibit migration and proliferation of immune cells and vascular smooth muscle cells (MCs). CD34 stent can capture HSC, hematopoietic progenitor cells that differentiate into vascular ECs and immune cells, promoting smooth MCs growth, leading to thrombosis, inflammation, and rejection. CD133 stent can be implanted into miniature pig heart coronary and can repair vascular damage by capturing own HSC, thus contributing to the rapid natural vascular repair, avoiding inflammation and rejection, thrombosis and restenosis. These studies demonstrated that CD133 stent of HSC capture will be an ideal coated metal stent providing a new therapeutic approach for cardiovascular and cerebrovascular disease. PMID:25404533

Coseeded Schwann cells myelinate neurites from differentiated neural stem cells in neurotrophin-3-loaded PLGA carriers

PubMed Central

Xiong, Yi; Zhu, Ji-Xiang; Fang, Zheng-Yu; Zeng, Cheng-Guang; Zhang, Chao; Qi, Guo-Long; Li, Man-Hui; Zhang, Wei; Quan, Da-Ping; Wan, Jun

2012-01-01

Biomaterials and neurotrophic factors represent promising guidance for neural repair. In this study, we combined poly-(lactic acid-co-glycolic acid) (PLGA) conduits and neurotrophin-3 (NT-3) to generate NT-3-loaded PLGA carriers in vitro. Bioactive NT-3 was released stably and constantly from PLGA conduits for up to 4 weeks. Neural stem cells (NSCs) and Schwann cells (SCs) were coseeded into an NT-releasing scaffold system and cultured for 14 days. Immunoreactivity against Map2 showed that most of the grafted cells (>80%) were differentiated toward neurons. Double-immunostaining for synaptogenesis and myelination revealed the formation of synaptic structures and myelin sheaths in the coculture, which was also observed under electron microscope. Furthermore, under depolarizing conditions, these synapses were excitable and capable of releasing synaptic vesicles labeled with FM1-43 or FM4-64. Taken together, coseeding NSCs and SCs into NT-3-loaded PLGA carriers increased the differentiation of NSCs into neurons, developed synaptic connections, exhibited synaptic activities, and myelination of neurites by the accompanying SCs. These results provide an experimental basis that supports transplantation of functional neural construction in spinal cord injury. PMID:22619535

Phytotoxicity, Translocation, and Biotransformation of NaYF₄ Upconversion Nanoparticles in a Soybean Plant.

PubMed

Yin, Wenyan; Zhou, Liangjun; Ma, Yuhui; Tian, Gan; Zhao, Jiating; Yan, Liang; Zheng, Xiaopeng; Zhang, Peng; Yu, Jie; Gu, Zhanjun; Zhao, Yuliang

2015-09-01

The increasing uses of rare-earth-doped upconversion nanoparticles (UCNPs) have obviously caused many concerns about their potential toxicology on live organisms. In addition, the UCNPs can be released into the environment, then transported into edible crop plants, and finally entered into food chain. Here, the soybean is chosen as a model plant to study the subchronic phytotoxicity, translocation, and biotransformation of NaYF4 UCNPs. The incubation with UCNPs at a relative low concentration of 10 μg mL(-1) leads to growth promotion for the roots and stems, while concentration exceeding 50 μg mL(-1) brings concentration-dependent inhibition. Upconversion luminescence imaging and scanning electron microscope characterization show that the UCNPs can be absorbed by roots and parts of the adsorbed UCNPs are then transported through vessels to stems and leaves. The near-edge X-ray absorption fine structure spectra reveal that the adsorbed NaYF4 nanoparticles are relatively stable during a 10 d incubation. Energy-dispersive X-ray spectrum further indicates that a small amount of NaYF4 is dissolved/digested and can transform into Y-phosphate clusters in roots. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cell Attachment and Proliferation of Human Adipose-Derived Stem Cells on PLGA/Chitosan Electrospun Nano-Biocomposite

PubMed Central

Razavi, Shahnaz; Karbasi, Saeed; Morshed, Mohammad; Zarkesh Esfahani, Hamid; Golozar, Mohammad; Vaezifar, Sedigheh

2015-01-01

Objective In this study, nano-biocomposite composed of poly (lactide-co-glycolide) (PLGA) and chitosan (CS) were electrospun through a single nozzle by dispersing the CS nano-powders in PLGA solution. The cellular behavior of human adipose derived stem cells (h-ADSCs) on random and aligned scaffolds was then evaluated. Materials and Methods In this experimental study, the PLGA/CS scaffolds were prepared at the different ratios of 90/10, 80/20, and 70/30 (w/w) %. Morphology, cell adhesion and prolif- eration rate of h-ADSCs on the scaffolds were assessed using scanning electron microscope (SEM), 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) assay and trypan blue staining respectively. Results H-ADSCs seeded on the matrices indicated that the PLGA/CS composite matrix with aligned nanofibres and higher content of CS nano-powders gave significantly better performance than others in terms of cell adhesion and proliferation rate (P<0.05). Conclusion We found that CS enhanced cell adhesion and proliferation rate, and aligned nanofibers guided cell growth along the longitudinal axis of the nanofibers, which would provide a beneficial approach for tissue engineering. PMID:26464814

Heterogeneity of chromatoid bodies in adult pluripotent stem cells of planarian Dugesia japonica.

PubMed

Kashima, Makoto; Kumagai, Nobuyoshi; Agata, Kiyokazu; Shibata, Norito

2016-02-01

The robust regenerative ability of planarians is known to be dependent on adult pluripotent stem cells called neoblasts. One of the morphological features of neoblasts is cytoplasmic ribonucleoprotein granules (chromatoid bodies: CBs), which resemble germ granules present in germline cells in other animals. Previously, we showed by immuno-electron microscopic analysis that DjCBC-1, a planarian Me31B/Dhh1/DDX6 homologue, which is a component of ribonucleoprotein granules, was localized in CBs in the planarian Dugesia japonica. Also, recently it was reported using another planarian species that Y12 antibody recognizing symmetrical dimethylarginine (sDMA) specifically binds to CBs in which histone mRNA is co-localized. Here, we showed by double immunostaining and RNA interference (RNAi) that DjCBC-1-containing CBs and Y12-immunoreactive CBs are distinct structures, suggesting that CBs are composed of heterogeneous populations. We also found that the Y12-immunoreactive CBs specifically contained a cytoplasmic type of planarian PIWI protein (DjPiwiC). We revealed by RNAi experiments that Y12-immunoreactive CBs may have anti-transposable element activity involving the DjPiwiC protein in the neoblasts. © 2016 Japanese Society of Developmental Biologists.

On the organization and thermal behavior of functional groups on Ti3C2 MXene surfaces in vacuum

NASA Astrophysics Data System (ADS)

Persson, Ingemar; Näslund, Lars-Åke; Halim, Joseph; Barsoum, Michel W.; Darakchieva, Vanya; Palisaitis, Justinas; Rosen, Johanna; Persson, Per O. Å.

2018-03-01

The two-dimensional (2D) MXene Ti3C2T x is functionalized by surface groups (T x ) that determine its surface properties for, e.g. electrochemical applications. The coordination and thermal properties of these surface groups has, to date, not been investigated at the atomic level, despite strong variations in the MXene properties that are predicted from different coordinations and from the identity of the functional groups. To alleviate this deficiency, and to characterize the functionalized surfaces of single MXene sheets, the present investigation combines atomically resolved in situ heating in a scanning transmission electron microscope (STEM) and STEM simulations with temperature-programmed x-ray photoelectron spectroscopy (TP-XPS) in the room temperature to 750 °C range. Using these techniques, we follow the surface group coordination at the atomic level. It is concluded that the F and O atoms compete for the DFT-predicted thermodynamically preferred site and that at room temperature that site is mostly occupied by F. At higher temperatures, F desorbs and is replaced by O. Depending on the O/F ratio, the surface bare MXene is exposed as F desorbs, which enables a route for tailored surface functionalization.

Pharmacognostic studies of the leaves and stem of Careya arborea Roxb.

PubMed Central

Gupta, Prakash Chandra; Sharma, Nisha; Rao, Ch V

2012-01-01

Objective To study detailed pharmacognostic profile of leaves and stem of Careya arborea (C. arborea) Roxb. (Lecthyidaceae), an important medicinal plant in the Indian system of medicine. Methods Leaf and stem samples of C. arborea were studied by macroscopical, microscopical, physicochemical, phytochemical, fluorescence analysis of powder of the plant and other methods for standardization recommended by WHO. Results Macroscopically, the leaves are simple, broadly obovate in shape, acuminate apex with crenate, dentate margin, petioles (0.1–1.8 cm) long. Microscopically, the leaf showed the presence of median large size vascular bundle covered with fibrous bundle sheath, arrangement of xylem in cup shape and presence of cortical vascular bundle, patches of sclerenchyma, phloem fibers in groups and brown pigment containing cells in stem are some of the diagnostic features noted from anatomical study. Powder microscopy of leaf revealed the presence of parenchyma cells, xylem with pitted vessels and epidermis with anisocytic stomata. The investigations also included leaf surface data; quantitative leaf microscopy and fluorescence analysis. Physiochemical parameters such as loss on drying, swelling index, extractive values and ash values were also determined and results showed that total ash of the stem bark was about two times higher than leaf and water soluble extractive value of leaf and stem bark was two times higher than alcohol soluble extractive value. Preliminary phytochemical screening showed the presence of triterpenoids, saponins, tannins and flavonoids. Conclusions The results of the study can serve as a valuable source of information and provide suitable standards for identification of this plant material in future investigations and applications. PMID:23569939

Visualizing Morphological Changes of Abscission Zone Cells in Arabidopsis by Scanning Electron Microscope.

PubMed

Shi, Chun-Lin; Butenko, Melinka A

2018-01-01

Scanning electron microscope (SEM) is a type of electron microscope which produces detailed images of surface structures. It has been widely used in plants and animals to study cellular structures. Here, we describe a detailed protocol to prepare samples of floral abscission zones (AZs) for SEM, as well as further image analysis. We show that it is a powerful tool to detect morphologic changes at the cellular level during the course of abscission in wild-type plants and to establish the details of phenotypic alteration in abscission mutants.

Scanning electron microscopic appearance of rat otocyst of the twelfth postcoital day: elaboration of a method.

PubMed

Marovitz, W F; Khan, K M

1977-01-01

A method for removal, fixation, microdissection, and drying of early rat otocyst for examination by the scanning electron microscope is elaborated. Tissues were dissected, fixed as for conventional transmission electron microscopy and dried by critical point evaporation using amylacetate as the transitional fluid and carbon dioxide as the pressure head. Otocysts were either dissected at the time of initial fixation, or subsequent to drying. The otocyst of the 12th postcoital day was used as a model system in this preliminary report. Critical point drying retained the overall configuration and the fine ultrastructural detail of the otocyst. The interior otocystic surface was visualized and cilia bearing cells of the luminal surface were identified. Most if not all of these cells had a comspicuous, but short kinocillum which terminated in an ovoid bulb. The scanning electron microscopic appearance was correlated to the transmission electron microscopic image seen in the second paper in this Supplement.

Atmospheric scanning electron microscope for correlative microscopy.

PubMed

Morrison, Ian E G; Dennison, Clare L; Nishiyama, Hidetoshi; Suga, Mitsuo; Sato, Chikara; Yarwood, Andrew; O'Toole, Peter J

2012-01-01

The JEOL ClairScope is the first truly correlative scanning electron and optical microscope. An inverted scanning electron microscope (SEM) column allows electron images of wet samples to be obtained in ambient conditions in a biological culture dish, via a silicon nitride film window in the base. A standard inverted optical microscope positioned above the dish holder can be used to take reflected light and epifluorescence images of the same sample, under atmospheric conditions that permit biochemical modifications. For SEM, the open dish allows successive staining operations to be performed without moving the holder. The standard optical color camera used for fluorescence imaging can be exchanged for a high-sensitivity monochrome camera to detect low-intensity fluorescence signals, and also cathodoluminescence emission from nanophosphor particles. If these particles are applied to the sample at a suitable density, they can greatly assist the task of perfecting the correlation between the optical and electron images. Copyright © 2012 Elsevier Inc. All rights reserved.

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

Juffmann, Thomas; Koppell, Stewart A.; Klopfer, Brannon B.

Feynman once asked physicists to build better electron microscopes to be able to watch biology at work. While electron microscopes can now provide atomic resolution, electron beam induced specimen damage precludes high resolution imaging of sensitive materials, such as single proteins or polymers. Here, we use simulations to show that an electron microscope based on a multi-pass measurement protocol enables imaging of single proteins, without averaging structures over multiple images. While we demonstrate the method for particular imaging targets, the approach is broadly applicable and is expected to improve resolution and sensitivity for a range of electron microscopy imaging modalities,more » including, for example, scanning and spectroscopic techniques. The approach implements a quantum mechanically optimal strategy which under idealized conditions can be considered interaction-free.« less

Electron holography study of magnetization behavior in the writer pole of a perpendicular magnetic recording head by a 1 MV transmission electron microscope.

PubMed

Hirata, Kei; Ishida, Yoichi; Akashi, Tetsuya; Shindo, Daisuke; Tonomura, Akira

2012-01-01

The magnetic domain structure of the writer poles of perpendicular magnetic recording heads was studied using electron holography. Although the domain structure of a 100-nm-thick writer pole could be observed with a 300 kV transmission electron microscope, that of the 250-nm-thick writer pole could not be analyzed due to the limited transmission capability of the instrument. On the other hand, the detailed domain structure of the 250-nm-thick writer pole was successfully analyzed by a 1 MV electron microscope using its high transmission capability. The thickness and material dependency of the domain structure of a writer pole were discussed.

Attainment of 40.5 pm spatial resolution using 300 kV scanning transmission electron microscope equipped with fifth-order aberration corrector.

PubMed

Morishita, Shigeyuki; Ishikawa, Ryo; Kohno, Yuji; Sawada, Hidetaka; Shibata, Naoya; Ikuhara, Yuichi

2018-02-01

The achievement of a fine electron probe for high-resolution imaging in scanning transmission electron microscopy requires technological developments, especially in electron optics. For this purpose, we developed a microscope with a fifth-order aberration corrector that operates at 300 kV. The contrast flat region in an experimental Ronchigram, which indicates the aberration-free angle, was expanded to 70 mrad. By using a probe with convergence angle of 40 mrad in the scanning transmission electron microscope at 300 kV, we attained the spatial resolution of 40.5 pm, which is the projected interatomic distance between Ga-Ga atomic columns of GaN observed along [212] direction.

Optics of high-performance electron microscopes*

PubMed Central

Rose, H H

2008-01-01

During recent years, the theory of charged particle optics together with advances in fabrication tolerances and experimental techniques has lead to very significant advances in high-performance electron microscopes. Here, we will describe which theoretical tools, inventions and designs have driven this development. We cover the basic theory of higher-order electron optics and of image formation in electron microscopes. This leads to a description of different methods to correct aberrations by multipole fields and to a discussion of the most advanced design that take advantage of these techniques. The theory of electron mirrors is developed and it is shown how this can be used to correct aberrations and to design energy filters. Finally, different types of energy filters are described. PMID:27877933

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

Rau, E. I.; Orlikovskiy, N. A.; Ivanova, E. S.

A new highly efficient design for semiconductor detectors of intermediate-energy electrons (1-50 keV) for application in scanning electron microscopes is proposed. Calculations of the response function of advanced detectors and control experiments show that the efficiency of the developed devices increases on average twofold, which is a significant positive factor in the operation of modern electron microscopes in the mode of low currents and at low primary electron energies.

Scanning transmission electron microscopy and its application to the study of nanoparticles and nanoparticle systems.

PubMed

Liu, Jingyue

2005-06-01

Scanning transmission electron microscopy (STEM) techniques can provide imaging, diffraction and spectroscopic information, either simultaneously or in a serial manner, of the specimen with an atomic or a sub-nanometer spatial resolution. High-resolution STEM imaging, when combined with nanodiffraction, atomic resolution electron energy-loss spectroscopy and nanometer resolution X-ray energy dispersive spectroscopy techniques, is critical to the fundamental studies of importance to nanoscience and nanotechnology. The availability of sub-nanometer or sub-angstrom electron probes in a STEM instrument, due to the use of a field emission gun and aberration correctors, ensures the greatest capabilities for studies of sizes, shapes, defects, crystal and surface structures, and compositions and electronic states of nanometer-size regions of thin films, nanoparticles and nanoparticle systems. The various imaging, diffraction and spectroscopy modes available in a dedicated STEM or a field emission TEM/STEM instrument are reviewed and the application of these techniques to the study of nanoparticles and nanostructured catalysts is used as an example to illustrate the critical role of the various STEM techniques in nanotechnology and nanoscience research.

Using the scanning electron microscope on the production line to assure quality semiconductors

NASA Technical Reports Server (NTRS)

Adolphsen, J. W.; Anstead, R. J.

1972-01-01

The use of the scanning electron microscope to detect metallization defects introduced during batch processing of semiconductor devices is discussed. A method of determining metallization integrity was developed which culminates in a procurement specification using the scanning microscope on the production line as a quality control tool. Batch process control of the metallization operation is monitored early in the manufacturing cycle.

Influence of mechanical noise inside a scanning electron microscope

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

Gaudenzi de Faria, Marcelo; Haddab, Yassine, E-mail: yassine.haddab@femto-st.fr; Le Gorrec, Yann

The scanning electron microscope is becoming a popular tool to perform tasks that require positioning, manipulation, characterization, and assembly of micro-components. However, some of these applications require a higher level of performance with respect to dynamics and precision of positioning. One limiting factor is the presence of unidentified noises and disturbances. This work aims to study the influence of mechanical disturbances generated by the environment and by the microscope, identifying how these can affect elements in the vacuum chamber. To achieve this objective, a dedicated setup, including a high-resolution vibrometer, was built inside the microscope. This work led to themore » identification and quantification of main disturbances and noise sources acting on a scanning electron microscope. Furthermore, the effects of external acoustic excitations were analysed. Potential applications of these results include noise compensation and real-time control for high accuracy tasks.« less

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2013-01-28

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Fine needle aspiration (FNA) of synovial sarcoma--a comparative histological-cytological study of 15 cases, including immunohistochemical, electron microscopic and cytogenetic examination and DNA-ploidy analysis.

PubMed

Akerman, M; Willén, H; Carlén, B; Mandahl, N; Mertens, F

1996-06-01

A retrospective study of 25 FNAs (11 aspirates from primary tumours and 14 from recurrencies and metastases) from 15 synovial sarcomas was performed. The cytological findings were correlated with the histopathology and the value of immunohistochemical and electron microscopic examination as well as DNA-ploidy and cytogenetic analysis for diagnosis were assessed. A reproducible cellular pattern with a reliable diagnosis of spindle cell sarcoma was possible provided that the aspirates were cell rich. However, a true biphasic pattern indicative of synovial sarcoma was only seen in one of the 25 specimens. Electron microscopic examination of the aspirates was a valuable adjunctive diagnostic method, whereas immunocytochemistry and DNA-ploidy analysis were not. Immunohistochemical, electron microscopic and cytogenetic analysis were all valuable ancillary methods when performed on surgical specimens. Malignant haemangiopericytoma and fibrosarcoma were the most important differential diagnoses in the FNA specimens.

A two-dimensional Dirac fermion microscope

NASA Astrophysics Data System (ADS)

Bøggild, Peter; Caridad, José M.; Stampfer, Christoph; Calogero, Gaetano; Papior, Nick Rübner; Brandbyge, Mads

2017-06-01

The electron microscope has been a powerful, highly versatile workhorse in the fields of material and surface science, micro and nanotechnology, biology and geology, for nearly 80 years. The advent of two-dimensional materials opens new possibilities for realizing an analogy to electron microscopy in the solid state. Here we provide a perspective view on how a two-dimensional (2D) Dirac fermion-based microscope can be realistically implemented and operated, using graphene as a vacuum chamber for ballistic electrons. We use semiclassical simulations to propose concrete architectures and design rules of 2D electron guns, deflectors, tunable lenses and various detectors. The simulations show how simple objects can be imaged with well-controlled and collimated in-plane beams consisting of relativistic charge carriers. Finally, we discuss the potential of such microscopes for investigating edges, terminations and defects, as well as interfaces, including external nanoscale structures such as adsorbed molecules, nanoparticles or quantum dots.

A two-dimensional Dirac fermion microscope

PubMed Central

Bøggild, Peter; Caridad, José M.; Stampfer, Christoph; Calogero, Gaetano; Papior, Nick Rübner; Brandbyge, Mads

2017-01-01

The electron microscope has been a powerful, highly versatile workhorse in the fields of material and surface science, micro and nanotechnology, biology and geology, for nearly 80 years. The advent of two-dimensional materials opens new possibilities for realizing an analogy to electron microscopy in the solid state. Here we provide a perspective view on how a two-dimensional (2D) Dirac fermion-based microscope can be realistically implemented and operated, using graphene as a vacuum chamber for ballistic electrons. We use semiclassical simulations to propose concrete architectures and design rules of 2D electron guns, deflectors, tunable lenses and various detectors. The simulations show how simple objects can be imaged with well-controlled and collimated in-plane beams consisting of relativistic charge carriers. Finally, we discuss the potential of such microscopes for investigating edges, terminations and defects, as well as interfaces, including external nanoscale structures such as adsorbed molecules, nanoparticles or quantum dots. PMID:28598421

Scanning Microscopes Using X Rays and Microchannels

NASA Technical Reports Server (NTRS)

Wang, Yu

2003-01-01

Scanning microscopes that would be based on microchannel filters and advanced electronic image sensors and that utilize x-ray illumination have been proposed. Because the finest resolution attainable in a microscope is determined by the wavelength of the illumination, the xray illumination in the proposed microscopes would make it possible, in principle, to achieve resolutions of the order of nanometers about a thousand times as fine as the resolution of a visible-light microscope. Heretofore, it has been necessary to use scanning electron microscopes to obtain such fine resolution. In comparison with scanning electron microscopes, the proposed microscopes would likely be smaller, less massive, and less expensive. Moreover, unlike in scanning electron microscopes, it would not be necessary to place specimens under vacuum. The proposed microscopes are closely related to the ones described in several prior NASA Tech Briefs articles; namely, Miniature Microscope Without Lenses (NPO-20218), NASA Tech Briefs, Vol. 22, No. 8 (August 1998), page 43; and Reflective Variants of Miniature Microscope Without Lenses (NPO-20610), NASA Tech Briefs, Vol. 26, No. 9 (September 2002) page 6a. In all of these microscopes, the basic principle of design and operation is the same: The focusing optics of a conventional visible-light microscope are replaced by a combination of a microchannel filter and a charge-coupled-device (CCD) image detector. A microchannel plate containing parallel, microscopic-cross-section holes much longer than they are wide is placed between a specimen and an image sensor, which is typically the CCD. The microchannel plate must be made of a material that absorbs the illuminating radiation reflected or scattered from the specimen. The microchannels must be positioned and dimensioned so that each one is registered with a pixel on the image sensor. Because most of the radiation incident on the microchannel walls becomes absorbed, the radiation that reaches the image sensor consists predominantly of radiation that was launched along the longitudinal direction of the microchannels. Therefore, most of the radiation arriving at each pixel on the sensor must have traveled along a straight line from a corresponding location on the specimen. Thus, there is a one-to-one mapping from a point on a specimen to a pixel in the image sensor, so that the output of the image sensor contains image information equivalent to that from a microscope.

Development of the field of structural physiology

PubMed Central

FUJIYOSHI, Yoshinori

2015-01-01

Electron crystallography is especially useful for studying the structure and function of membrane proteins — key molecules with important functions in neural and other cells. Electron crystallography is now an established technique for analyzing the structures of membrane proteins in lipid bilayers that closely simulate their natural biological environment. Utilizing cryo-electron microscopes with helium-cooled specimen stages that were developed through a personal motivation to understand the functions of neural systems from a structural point of view, the structures of membrane proteins can be analyzed at a higher than 3 Å resolution. This review covers four objectives. First, I introduce the new research field of structural physiology. Second, I recount some of the struggles involved in developing cryo-electron microscopes. Third, I review the structural and functional analyses of membrane proteins mainly by electron crystallography using cryo-electron microscopes. Finally, I discuss multifunctional channels named “adhennels” based on structures analyzed using electron and X-ray crystallography. PMID:26560835

Development of an environmental high-voltage electron microscope for reaction science.

PubMed

Tanaka, Nobuo; Usukura, Jiro; Kusunoki, Michiko; Saito, Yahachi; Sasaki, Katuhiro; Tanji, Takayoshi; Muto, Shunsuke; Arai, Shigeo

2013-02-01

Environmental transmission electron microscopy and ultra-high resolution electron microscopic observation using aberration correctors have recently emerged as topics of great interest. The former method is an extension of the so-called in situ electron microscopy that has been performed since the 1970s. Current research in this area has been focusing on dynamic observation with atomic resolution under gaseous atmospheres and in liquids. Since 2007, Nagoya University has been developing a new 1-MV high voltage (scanning) transmission electron microscope that can be used to observe nanomaterials under conditions that include the presence of gases, liquids and illuminating lights, and it can be also used to perform mechanical operations to nanometre-sized areas as well as electron tomography and elemental analysis by electron energy loss spectroscopy. The new instrument has been used to image and analyse various types of samples including biological ones.

Nucleotide-Specific Contrast for DNA Sequencing by Electron Spectroscopy.

PubMed

Mankos, Marian; Persson, Henrik H J; N'Diaye, Alpha T; Shadman, Khashayar; Schmid, Andreas K; Davis, Ronald W

2016-01-01

DNA sequencing by imaging in an electron microscope is an approach that holds promise to deliver long reads with low error rates and without the need for amplification. Earlier work using transmission electron microscopes, which use high electron energies on the order of 100 keV, has shown that low contrast and radiation damage necessitates the use of heavy atom labeling of individual nucleotides, which increases the read error rates. Other prior work using scattering electrons with much lower energy has shown to suppress beam damage on DNA. Here we explore possibilities to increase contrast by employing two methods, X-ray photoelectron and Auger electron spectroscopy. Using bulk DNA samples with monomers of each base, both methods are shown to provide contrast mechanisms that can distinguish individual nucleotides without labels. Both spectroscopic techniques can be readily implemented in a low energy electron microscope, which may enable label-free DNA sequencing by direct imaging.

High-resolution electron microscope

NASA Technical Reports Server (NTRS)

Nathan, R.

1977-01-01

Employing scanning transmission electron microscope as interferometer, relative phases of diffraction maximums can be determined by analysis of dark field images. Synthetic aperture technique and Fourier-transform computer processing of amplitude and phase information provide high resolution images at approximately one angstrom.

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Federal Register 2010, 2011, 2012, 2013, 2014

2010-03-04

... DEPARTMENT OF COMMERCE International Trade Administration University of Pittsburgh, et al.; Notice of Consolidated Decision on Applications for Duty-Free Entry of Electron Microscopes This is a...: University of Pittsburgh, Pittsburgh, PA 15260. Instrument: Electron Microscope. Manufacturer: JEOL, Ltd...

Development of a miniature scanning electron microscope for in-flight analysis of comet dust

NASA Technical Reports Server (NTRS)

Conley, J. M.; Bradley, J. G.; Giffin, C. E.; Albee, A. L.; Tomassian, A. D.

1983-01-01

A description is presented of an instrument which was developed with the original goal of being flown on the International Comet Mission, scheduled for a 1985 launch. The Scanning Electron Microscope and Particle Analyzer (SEMPA) electron miniprobe is a miniaturized electrostatically focused electron microscope and energy dispersive X-ray analyzer for in-flight analysis of comet dust particles. It was designed to be flown on board a comet rendezvous spacecraft. Other potential applications are related to asteroid rendezvous and planetary lander missions. According to the development objectives, SEMPA miniprobe is to have the capability for imaging and elemental analysis of particles in the size range of 0.25 microns and larger.

The three-dimensional feto-maternal vascular interrelationship during early bovine placental development: a scanning electron microscopical study

PubMed Central

PFARRER, CHRISTIANE; EBERT, BRIGITTE; MIGLINO, MARIA ANGELICA; KLISCH, KARL; LEISER, RUDOLF

2001-01-01

Both the fetal and maternal microvasculature of bovine placentomes was examined by scanning electron microscopy of vascular casts. So far the development of the vascular architecture of the bovine placentome in early gestation has only been studied 2-dimensionally due to technical difficulties arising from the fragility of the early placental blood vessels. Repeated experiments led to the selection of the microvascular corrosion casts presented here. The vasculature of the maternal compartment is supplied by large caruncular stalk or spiral arteries, which release short maternal stem arteries. In the 3rd month of gestation, these arteries branch into several arterioles at their base, thus providing the vascular framework for the lower part of the septal walls of the primary crypts. In the 4th month, due to progressive longitudinal growth of the stem arteries, branching into arterioles occurs not only at the base, but over the whole length of the stem arteries. These arterioles supply the capillary complexes of the septa which resemble the major part of the septal vasculature and face the secondary crypts. Further indentation results in the formation of tertiary crypt capillary complexes, encircling the earlier secondary unit. From the 6th month of gestation the architecture resembles the fully developed maternal placenta with stem arteries running directly to the fetal side to branch into 4 to 6 arterioles, which turn back to enter secondary and tertiary septa. Maternal venules, collecting the blood from the capillary bed of secondary and tertiary septa, converge onto stem veins leaving the caruncle via branches of the uterine vein. The fetal part of the placentome is supplied by the cotyledonary arteries, which branch into fetal stem arteries that are the tributary to single villous trees. Over their whole course towards the maternal side, these give off arterioles entering secondary villi. The tertiary or terminal villous vasculature consists of capillaries, which are organised in serial capillary loops. This system is progressively elaborated in the course of gestation. In the 4th month there are only finger-like loops, whereas from the 6th month large fan-like structures can be observed. In early gestation the maternal and fetal blood vessels meet predominantly in a countercurrent fashion, changing to the less efficient crosscurrent exchange when the tertiary unit develops. These results indicate the development of a highly elaborated fetomaternal villous-crypt exchange system, already established in the 1st half of gestation, thus meeting the increasing needs of the fetus. PMID:11430698

Profiling with the electron microscope.

NASA Technical Reports Server (NTRS)

Vedder, J. F.; Lem, H. Y.

1972-01-01

Discussion of a profiling technique using a scanning electron microscope for obtaining depth information on a single micrograph of a small specimen. A stationary electron beam is used to form a series of contamination spots in a line across the specimen. Micrographs obtained by this technique are useful as a means of projection and display where stereo viewers are not practical.

[Morphological and anatomical characterization of a stripe mutant with abnormal floral organs in rice].

PubMed

Chen, De Xi; Ma, Bing Tian; Wang, Yu Ping; Li, Shi Gui; Hao, Ming

2006-08-01

A rice double mutant was derived from the transgenic process,but it does not carry the alien gene. The mutant showed white stripe on stem, leaf and spikelet. In some growing stage,the leaf started to produce fork or curliness. The floret number increased, showing multi-lemma/palea, palea-like or lemma-like lodicules or enlarged lodicules, additional pistil and stamen and the spited floret. With observation of cell ultra structure using electron microscope,the white tissue showed concaved cell wall and abnormal plastid which could not develop normal lamellae and thylakoid. The contents of chlorophyll and net photosynthesis rate in the mutant were obviously lower than those in the wild type. The cells in green sectors grow normally with the exception of the bigger cell volume. The morphogenesis of floral organ was observed by using the scanning electron microscopy (SEM). Results showed that the stamen development was not synchronal and the sizes of stamen primordium were different in mutant, and the carpel was smaller than that of wild type.

Classification of Streptomyces Spore Surfaces into Five Groups

PubMed Central

Dietz, Alma; Mathews, John

1971-01-01

Streptomyces spores surfaces have been classified into five groups, smooth, warty, spiny, hairy, and rugose, by examination of carbon replicas of spores with the transmission electron microscope and by direct examination of spores with the scanning electron microscope. Images PMID:4928607

COLONIAL GROWTH OF MYCOPLASMA GALLISEPTICUM OBSERVED WITH THE ELECTRON MICROSCOPE

PubMed Central

Shifrine, Moshe; Pangborn, Jack; Adler, Henry E.

1962-01-01

Shifrine, Moshe (University of California, Davis), Jack Pangborn, and Henry E. Adler. Colonial growth of Mycoplasma gallisepticum observed with the electron microscope. J. Bacteriol. 83:187–192. 1962.—Mycoplasma gallisepticum strain S6 was grown on collodion film on solid medium. Samples were removed every few hours, fixed, washed, shadowed, and observed with the electron microscope. Three distinct forms of growth were observed: elementary cells (hexagonally shaped), platycytes, and exoblasts. A tentative mode of growth was postulated. The significance of the angular morphology to the relation between mycoplasmas and L-forms of bacteria is discussed. Images PMID:13911868

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.

Observation of three-dimensional elemental distributions of a Si device using a 360 degrees -tilt FIB and the cold field-emission STEM system.

PubMed

Yaguchi, Toshie; Konno, Mitsuru; Kamino, Takeo; Watanabe, Masashi

2008-11-01

A technique for preparation of a pillar-shaped specimen and its multidirectional observation using a combination of a scanning transmission electron microscope (STEM) and a focused ion beam (FIB) instrument has been developed. The system employs an FIB/STEM compatible holder with a specially designed tilt mechanism, which allows the specimen to be tilted through 360 degrees [T. Yaguchi, M. Konno, T. Kamino, T. Hashimoto, T. Ohnishi, K. Umemura, K. Asayama, Microsc. Microanal. 9 (Suppl. 2) (2003) 118; T. Yaguchi, M. Konno, T. Kamino, T. Hashimoto, T. Ohnishi, M. Watanabe, Microsc. Microanal. 10 (Suppl. 2) (2004) 1030]. This technique was applied to obtain the three-dimensional (3D) elemental distributions around a contact plug of a Si device used in a 90-nm technology. A specimen containing only one contact plug was prepared in the shape of a pillar with a diameter of 200nm and a length of 5mum. Elemental maps were obtained from the pillar specimen using a 200-kV cold-field emission gun (FEG) STEM model HD-2300C equipped with the EDAX genesis X-ray energy-dispersive spectrometry (XEDS) system through a spectrum imaging technique. In this study, elemental distributions of minor elements with weak signals were enhanced by applying principal component analysis (PCA), which is a superior technique to extract weak signals from a large dataset. The distributions of elements, especially the metallization component Ti and minor dopant As in this particular device, were successfully extracted by PCA. Finally, the 3D elemental distributions around the contact plug could be visualized by reconstruction from the tilt series of maps.

Evolutionary anatomy of the muscular apparatus involved in the anchoring of Acanthocephala to the intestinal wall of their vertebrate hosts.

PubMed

Herlyn, Holger; Taraschewski, Horst

2017-04-01

Different conceptions exist regarding structure, function, and evolution of the muscles that move the acanthocephalan presoma, including the proboscis, i.e., the usually hooked hold-fast anchoring these endoparasites to the intestinal wall of their vertebrate definitive hosts. In order to clarify the unresolved issues, we carried out a light microscopic analysis of series of semi-thin sections and whole mounts representing the three traditional acanthocephalan classes: Archiacanthocephala (Macracanthorhynchus hirudinaceus), Eoacanthocephala (Paratenuisentis ambiguus, Tenuisentis niloticus), and Palaeacanthocephala (Acanthocephalus anguillae, Echinorhynchus truttae, Pomphorhynchus laevis, Corynosoma sp.). Combining our data with published light, transmission electron, and scanning electron microscopic data, we demonstrate that receptacle protrusor and proboscis receptacle in Archi- and Eoacanthocephala are homologous to the outer and inner wall of the proboscis receptacle in Palaeacanthocephala. Besides the proboscis receptacle and a "surrounding muscle," the last common ancestor of Acanthocephala presumably possessed a proboscis retractor, receptacle retractor, neck retractor (continuous with lemnisci compressors), and retinacula. These muscles most probably evolved in the acanthocephalan stem line. Moreover, the last common ancestor of Acanthocephala presumably possessed only a single layer of muscular cords under the presomal tegument while the metasomal body wall had circular and longitudinal strands. Two lateral receptacle flexors (also lateral receptacle protrusors), an apical muscle plate (surrounding one or two apical sensory organs), a midventral longitudinal muscle, and the differentiation of longitudinal body wall musculature at the base of the proboscis probably emerged within Archiacanthocephala. All muscles have a common organization principle: a peripheral layer of contractile filaments encloses the cytoplasm.

In situ electronic probing of semiconducting nanowires in an electron microscope.

PubMed

Fauske, V T; Erlbeck, M B; Huh, J; Kim, D C; Munshi, A M; Dheeraj, D L; Weman, H; Fimland, B O; Van Helvoort, A T J

2016-05-01

For the development of electronic nanoscale structures, feedback on its electronic properties is crucial, but challenging. Here, we present a comparison of various in situ methods for electronically probing single, p-doped GaAs nanowires inside a scanning electron microscope. The methods used include (i) directly probing individual as-grown nanowires with a sharp nano-manipulator, (ii) contacting dispersed nanowires with two metal contacts and (iii) contacting dispersed nanowires with four metal contacts. For the last two cases, we compare the results obtained using conventional ex situ litho-graphy contacting techniques and by in situ, direct-write electron beam induced deposition of a metal (Pt). The comparison shows that 2-probe measurements gives consistent results also with contacts made by electron beam induced deposition, but that for 4-probe, stray deposition can be a problem for shorter nanowires. This comparative study demonstrates that the preferred in situ method depends on the required throughput and reliability. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

Azimuthal phase retardation microscope for visualizing actin filaments of biological cells

NASA Astrophysics Data System (ADS)

Shin, In Hee; Shin, Sang-Mo

2011-09-01

We developed a new theory-based azimuthal phase retardation microscope to visualize distributions of actin filaments in biological cells without having them with exogenous dyes, fluorescence labels, or stains. The azimuthal phase retardation microscope visualizes distributions of actin filaments by measuring the intensity variations of each pixel of a charge coupled device camera while rotating a single linear polarizer. Azimuthal phase retardation δ between two fixed principal axes was obtained by calculating the rotation angles of the polarizer at the intensity minima from the acquired intensity data. We have acquired azimuthal phase retardation distributions of human breast cancer cell, MDA MB 231 by our microscope and compared the azimuthal phase retardation distributions with the fluorescence image of actin filaments by the commercial fluorescence microscope. Also, we have observed movement of human umbilical cord blood derived mesenchymal stem cells by measuring azimuthal phase retardation distributions.

STEM Tomography Imaging of Hypertrophied Golgi Stacks in Mucilage-Secreting Cells.

PubMed

Kang, Byung-Ho

2016-01-01

Because of the weak penetrating power of electrons, the signal-to-noise ratio of a transmission electron micrograph (TEM) worsens as section thickness increases. This problem is alleviated by the use of the scanning transmission electron microscopy (STEM). Tomography analyses using STEM of thick sections from yeast and mammalian cells are of higher quality than are bright-field (BF) images. In this study, we compared regular BF tomograms and STEM tomograms from 500-nm thick sections from hypertrophied Golgi stacks of alfalfa root cap cells. Due to their thickness and intense heavy metal staining, BF tomograms of the thick sections suffer from poor contrast and high noise levels. We were able to mitigate these drawbacks by using STEM tomography. When we performed STEM tomography of densely stained chloroplasts of Arabidopsis cotyledon, we observed similar improvements relative to BF tomograms. A longer time is required to collect a STEM tilt series than similar BF TEM images, and dynamic autofocusing required for STEM imaging often fails at high tilt angles. Despite these limitations, STEM tomography is a powerful method for analyzing structures of large or dense organelles of plant cells.

Transmission electron microscope studies of extraterrestrial materials

NASA Technical Reports Server (NTRS)

Keller, Lindsay P.

1995-01-01

Transmission Electron Microscopy, X-Ray spectrometry and electron-energy-loss spectroscopy are used to analyse carbon in interplanetary dust particles. Optical micrographs are shown depicting cross sections of the dust particles embedded in sulphur. Selected-area electron diffraction patterns are shown. Transmission Electron Microscope specimens of lunar soil were prepared using two methods: ion-milling and ultramicrotomy. A combination of high resolution TEM imaging and electron diffraction is used to characterize the opaque assemblages. The opaque assemblages analyzed in this study are dominated by ilmenite with lesser rutile and spinel exsolutions, and traces of Fe metal.

[Phenotype-based primary screening for drugs promoting neuronal subtype differentiation in embryonic stem cells with light microscope].

PubMed

Gao, Yi-ning; Wang, Dan-ying; Pan, Zong-fu; Mei, Yu-qin; Wang, Zhi-qiang; Zhu, Dan-yan; Lou, Yi-jia

2012-07-01

To set up a platform for phenotype-based primary screening of drug candidates promoting neuronal subtype differentiation in embryonic stem cells (ES) with light microscope. Hanging drop culture 4-/4+ method was employed to harvest the cells around embryoid body (EB) at differentiation endpoint. Morphological evaluation for neuron-like cells was performed with light microscope. Axons for more than three times of the length of the cell body were considered as neuron-like cells. The compound(s) that promote neuron-like cells was further evaluated. Icariin (ICA, 10(-6)mol/L) and Isobavachin (IBA, 10(-7)mol/L) were selected to screen the differentiation-promoting activity on ES cells. Immunofluorescence staining with specific antibodies (ChAT, GABA) was used to evaluate the neuron subtypes. The cells treated with IBA showed neuron-like phenotype, but the cells treated with ICA did not exhibit the morphological changes. ES cells treated with IBA was further confirmed to be cholinergic and GABAergic neurons. Phenotypic screening with light microscope for molecules promoting neuronal differentiation is an effective method with advantages of less labor and material consuming and time saving, and false-positive results derived from immunofluorescence can be avoided. The method confirms that IBA is able to facilitate ES cells differentiating into neuronal cells, including cholinergic neurons and GABAergic neurons.

MESC Payload Setup

NASA Image and Video Library

2017-02-21

iss050e052142 (Feb. 21, 2017) --- Expedition 50 Flight Engineer Peggy Whitson sets up a microscope in support of the Microgravity Expanded Stem Cells payload outside the Microgravity Science Glovebox housed inside the U.S. Destiny laboratory module.

Damage-free vibrational spectroscopy of biological materials in the electron microscope

PubMed Central

Rez, Peter; Aoki, Toshihiro; March, Katia; Gur, Dvir; Krivanek, Ondrej L.; Dellby, Niklas; Lovejoy, Tracy C.; Wolf, Sharon G.; Cohen, Hagai

2016-01-01

Vibrational spectroscopy in the electron microscope would be transformative in the study of biological samples, provided that radiation damage could be prevented. However, electron beams typically create high-energy excitations that severely accelerate sample degradation. Here this major difficulty is overcome using an ‘aloof' electron beam, positioned tens of nanometres away from the sample: high-energy excitations are suppressed, while vibrational modes of energies <1 eV can be ‘safely' investigated. To demonstrate the potential of aloof spectroscopy, we record electron energy loss spectra from biogenic guanine crystals in their native state, resolving their characteristic C–H, N–H and C=O vibrational signatures with no observable radiation damage. The technique opens up the possibility of non-damaging compositional analyses of organic functional groups, including non-crystalline biological materials, at a spatial resolution of ∼10 nm, simultaneously combined with imaging in the electron microscope. PMID:26961578

Damage-free vibrational spectroscopy of biological materials in the electron microscope.

PubMed

Rez, Peter; Aoki, Toshihiro; March, Katia; Gur, Dvir; Krivanek, Ondrej L; Dellby, Niklas; Lovejoy, Tracy C; Wolf, Sharon G; Cohen, Hagai

2016-03-10

Vibrational spectroscopy in the electron microscope would be transformative in the study of biological samples, provided that radiation damage could be prevented. However, electron beams typically create high-energy excitations that severely accelerate sample degradation. Here this major difficulty is overcome using an 'aloof' electron beam, positioned tens of nanometres away from the sample: high-energy excitations are suppressed, while vibrational modes of energies <1 eV can be 'safely' investigated. To demonstrate the potential of aloof spectroscopy, we record electron energy loss spectra from biogenic guanine crystals in their native state, resolving their characteristic C-H, N-H and C=O vibrational signatures with no observable radiation damage. The technique opens up the possibility of non-damaging compositional analyses of organic functional groups, including non-crystalline biological materials, at a spatial resolution of ∼10 nm, simultaneously combined with imaging in the electron microscope.

Damage-free vibrational spectroscopy of biological materials in the electron microscope

DOE PAGES

Rez, Peter; Aoki, Toshihiro; March, Katia; ...

2016-03-10

Vibrational spectroscopy in the electron microscope would be transformative in the study of biological samples, provided that radiation damage could be prevented. However, electron beams typically create high-energy excitations that severely accelerate sample degradation. Here this major difficulty is overcome using an ‘aloof’ electron beam, positioned tens of nanometres away from the sample: high-energy excitations are suppressed, while vibrational modes of energies o1 eV can be ‘safely’ investigated. To demonstrate the potential of aloof spectroscopy, we record electron energy loss spectra from biogenic guanine crystals in their native state, resolving their characteristic C–H, N–H and C=O vibrational signatures with nomore » observable radiation damage. Furthermore, the technique opens up the possibility of non-damaging compositional analyses of organic functional groups, including non-crystalline biological materials, at a spatial resolution of ~10nm, simultaneously combined with imaging in the electron microscope.« less

Damage-free vibrational spectroscopy of biological materials in the electron microscope

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

Rez, Peter; Aoki, Toshihiro; March, Katia

Vibrational spectroscopy in the electron microscope would be transformative in the study of biological samples, provided that radiation damage could be prevented. However, electron beams typically create high-energy excitations that severely accelerate sample degradation. Here this major difficulty is overcome using an ‘aloof’ electron beam, positioned tens of nanometres away from the sample: high-energy excitations are suppressed, while vibrational modes of energies o1 eV can be ‘safely’ investigated. To demonstrate the potential of aloof spectroscopy, we record electron energy loss spectra from biogenic guanine crystals in their native state, resolving their characteristic C–H, N–H and C=O vibrational signatures with nomore » observable radiation damage. Furthermore, the technique opens up the possibility of non-damaging compositional analyses of organic functional groups, including non-crystalline biological materials, at a spatial resolution of ~10nm, simultaneously combined with imaging in the electron microscope.« less

Telocytes and putative stem cells in ageing human heart

PubMed Central

Popescu, Laurentiu M; Curici, Antoanela; Wang, Enshi; Zhang, Hao; Hu, Shengshou; Gherghiceanu, Mihaela

2015-01-01

Tradition considers that mammalian heart consists of about 70% non-myocytes (interstitial cells) and 30% cardiomyocytes (CMs). Anyway, the presence of telocytes (TCs) has been overlooked, since they were described in 2010 (visit http://www.telocytes.com). Also, the number of cardiac stem cells (CSCs) has not accurately estimated in humans during ageing. We used electron microscopy to identify and estimate the number of cells in human atrial myocardium (appendages). Three age-related groups were studied: newborns (17 days–1 year), children (6–17 years) and adults (34–60 years). Morphometry was performed on low-magnification electron microscope images using computer-assisted technology. We found that interstitial area gradually increases with age from 31.3 ± 4.9% in newborns to 41 ± 5.2% in adults. Also, the number of blood capillaries (per mm2) increased with several hundreds in children and adults versus newborns. CMs are the most numerous cells, representing 76% in newborns, 88% in children and 86% in adults. Images of CMs mitoses were seen in the 17-day newborns. Interestingly, no lipofuscin granules were found in CMs of human newborns and children. The percentage of cells that occupy interstitium were (depending on age): endothelial cells 52–62%; vascular smooth muscle cells and pericytes 22–28%, Schwann cells with nerve endings 6–7%, fibroblasts 3–10%, macrophages 1–8%, TCs about 1% and stem cells less than 1%. We cannot confirm the popular belief that cardiac fibroblasts are the most prevalent cell type in the heart and account for about 20% of myocardial volume. Numerically, TCs represent a small fraction of human cardiac interstitial cells, but because of their extensive telopodes, they achieve a 3D network that, for instance, supports CSCs. The myocardial (very) low capability to regenerate may be explained by the number of CSCs, which decreases fivefold by age (from 0.5% to 0.1% in newborns versus adults). PMID:25545142

The application of aberration-corrected electron microscopy to the characterization of gold-based catalysts

NASA Astrophysics Data System (ADS)

Herzing, Andrew A.

Electron microscopy has long been used to study the morphology of heterogeneous catalysts. Recent advances in electron optics now allow for the correction of the inherent spherical aberration (Cs) produced by the objective lens in the scanning transmission electron microscope (STEM, resulting in a significantly improved spatial resolution as well as the ability to use a much larger probe-current than was previously possible. In this thesis, the combination of high-angle annular dark-field (HAADF) imaging and microanalysis by x-ray energy dispersive spectroscopy (XEDS) in an aberration-corrected STEM has been applied for the first time to the characterization of gold-based heterogeneous catalysts. Multi-variate statistical analysis (MSA) has been employed in order to further improve the STEM-XEDS spectrum image data acquired with this technique. In addition, supplemental analysis using electron-energy loss spectroscopy (EELS) and energy-filtered transmission electron microscopy (EFTEM) in an aberration-corrected instrument has also been attempted. These techniques have proven extremely valuable in providing complimentary information to more traditional catalyst characterization techniques such as x-ray photoelectron spectroscopy and x-ray diffraction in four specific problems relating to catalysis. Firstly, the atomic-scale resolution of Cs-corrected HAADF imaging has been utilized to study Au/FeOx catalysts in order to determine the size and structure of the Au clusters present on the support surface. It was discovered that, while both inactive and active catalysts for low-temperature CO oxidation contained large Au particles (> 5 nm) and individual Au atoms, the active catalyst also contained sub-nm clusters comprised of only a few Au atoms. Secondly, novel CeO2 support materials for Au and Au-Pd catalysts were synthesized by precipitation with supercritical CO2. These supports were found to produce significantly more active catalysts than those based on CeO2 prepared using more traditional methods. The combination of STEM-HAADF imaging and XEDS mapping has been used to characterize these catalysts and a strong correlation between the catalytic activity and the enhanced degree of metal dispersion over the support is demonstrated. Thirdly, a systematic series of Au-Pd/Al2O3 catalysts has been studied in order to characterize the effects of various heat treatments on the development of core-shell morphologies within the bi-metallic particles and its subsequent effect on their catalytic performance for H2O 2 synthesis. STEM-XEDS spectrum imaging was employed in order to determine the degree of alloying and segregation behavior within the individual Au-Pd particles as a function of calcination/reduction temperature. It was found that the as prepared catalyst contained homogeneous Au-Pd alloy particles and that a Pd-rich shell/Au-rich core morphology gradually developed upon calcination. Subsequent reduction of the catalyst caused a large fraction of the particles to invert and form Pd-rich core/Au-rich shell structures. These changes are related to both the activity and stability of the catalyst. Finally, the washing of activated carbon support materials in acid was found to be extremely beneficial for producing Au-Pd catalysts for the direct synthesis of H2O2. STEM-HAADF imaging revealed that the acid-washing treatment increased the dispersion of the metal on the carbon supports. Aberration-corrected STEM-XEDS spectrum imaging demonstrated a strong size dependence of the Au-Pd particle composition. Crucially, the acid-washing pre-treatment enhanced the alloying of Au and Pd by suppressing the formation of large (> 25 nm) Au-rich particles. In summary, the application of aberration-corrected HAADF imaging and STEM-XEDS spectrum imaging to the characterization of Au-based catalysts has enhanced the understanding of the structural and chemical features that determine their catalytic behavior. Specifically, they have allowed us to achieve the following: (a) image individual metal atoms and clusters of just a few atoms dispersed in a real, high surface area catalyst, (b) detect and follow the development of core-shell structures in Au-Pd bi-metallic catalysts, (c) determine composition/size correlations in Au-Pd catalysts, (d) detect minor alloying elements in bi-metallic catalysts, (e) and chemically map atomic or near atomic dispersions of metals on oxide supports.

U-10Mo Sample Preparation and Examination using Optical and Scanning Electron Microscopy

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

Prabhakaran, Ramprashad; Joshi, Vineet V.; Rhodes, Mark A.

2016-10-01

The purpose of this document is to provide guidelines to prepare specimens of uranium alloyed with 10 weight percent molybdenum (U-10Mo) for optical metallography and scanning electron microscopy. This document also provides instructions to set up an optical microscope and a scanning electron microscope to analyze U-10Mo specimens and to obtain the required information.

U-10Mo Sample Preparation and Examination using Optical and Scanning Electron Microscopy

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

Prabhakaran, Ramprashad; Joshi, Vineet V.; Rhodes, Mark A.

2016-03-30

The purpose of this document is to provide guidelines to prepare specimens of uranium alloyed with 10 weight percent molybdenum (U-10Mo) for optical metallography and scanning electron microscopy. This document also provides instructions to set up an optical microscope and a scanning electron microscope to analyze U-10Mo specimens and to obtain the required information.

A Student-Built Scanning Tunneling Microscope

ERIC Educational Resources Information Center

Ekkens, Tom

2015-01-01

Many introductory and nanotechnology textbooks discuss the operation of various microscopes including atomic force (AFM), scanning tunneling (STM), and scanning electron microscopes (SEM). In a nanotechnology laboratory class, students frequently utilize microscopes to obtain data without a thought about the detailed operation of the tool itself.…

78 FR 2659 - Application(s) for Duty-Free Entry of Scientific Instruments

Federal Register 2010, 2011, 2012, 2013, 2014

2013-01-14

..., 2201 West End Ave., Nashville, TN 37235. Instrument: Electron Microscope. Manufacturer: FEI Company... St., West Lafayette, IN 47907-2024. Instrument: Electron Microscope. Manufacturer: FEI Company, the..., microorganisms, nanomaterials, and chemical compounds. Justification for Duty-Free Entry: There are no...

Tunneling rates in electron transport through double-barrier molecular junctions in a scanning tunneling microscope

PubMed Central

Nazin, G. V.; Wu, S. W.; Ho, W.

2005-01-01

The scanning tunneling microscope enables atomic-scale measurements of electron transport through individual molecules. Copper phthalocyanine and magnesium porphine molecules adsorbed on a thin oxide film grown on the NiAl(110) surface were probed. The single-molecule junctions contained two tunneling barriers, vacuum gap, and oxide film. Differential conductance spectroscopy shows that electron transport occurs via vibronic states of the molecules. The intensity of spectral peaks corresponding to the individual vibronic states depends on the relative electron tunneling rates through the two barriers of the junction, as found by varying the vacuum gap tunneling rate by changing the height of the scanning tunneling microscope tip above the molecule. A simple, sequential tunneling model explains the observed trends. PMID:15956189

Tunneling rates in electron transport through double-barrier molecular junctions in a scanning tunneling microscope.

PubMed

Nazin, G V; Wu, S W; Ho, W

2005-06-21

The scanning tunneling microscope enables atomic-scale measurements of electron transport through individual molecules. Copper phthalocyanine and magnesium porphine molecules adsorbed on a thin oxide film grown on the NiAl(110) surface were probed. The single-molecule junctions contained two tunneling barriers, vacuum gap, and oxide film. Differential conductance spectroscopy shows that electron transport occurs via vibronic states of the molecules. The intensity of spectral peaks corresponding to the individual vibronic states depends on the relative electron tunneling rates through the two barriers of the junction, as found by varying the vacuum gap tunneling rate by changing the height of the scanning tunneling microscope tip above the molecule. A simple, sequential tunneling model explains the observed trends.

Microcellular nanocomposite injection molding process

Treesearch

Mingjun Yuan; Lih-Sheng Turng; Rick Spindler; Daniel Caulfield; Chris Hunt

2003-01-01

This study aims to explore the processing benefits and property improvements of combining nanocomposites with microcellular injection molding. The molded parts produced based on the Design of Experiments (DOE) matrices were subjected to tensile testing, impact testing, and Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), Dynamic Mechanical...

The microscopic world: A demonstration of electron microscopy for younger students

NASA Technical Reports Server (NTRS)

Horton, Linda L.

1992-01-01

The purpose is to excite students about the importance of scientific investigation and demonstrate why they should look at things in greater detail, extending beyond superficial examination. The topics covered include: microscopy, scanning electron microscopes, high magnification, and the scientific method.

Exosomes as potential alternatives to stem cell therapy for intervertebral disc degeneration: in-vitro study on exosomes in interaction of nucleus pulposus cells and bone marrow mesenchymal stem cells.

PubMed

Lu, Kang; Li, Hai-Yin; Yang, Kuang; Wu, Jun-Long; Cai, Xiao-Wei; Zhou, Yue; Li, Chang-Qing

2017-05-10

The stem cell-based therapies for intervertebral disc degeneration have been widely studied. However, the mechanisms of mesenchymal stem cells interacting with intervertebral disc cells, such as nucleus pulposus cells (NPCs), remain unknown. Exosomes as a vital paracrine mechanism in cell-cell communication have been highly focused on. The purpose of this study was to detect the role of exosomes derived from bone marrow mesenchymal stem cells (BM-MSCs) and NPCs in their interaction with corresponding cells. The exosomes secreted by BM-MSCs and NPCs were purified by differential centrifugation and identified by transmission electron microscope and immunoblot analysis of exosomal marker proteins. Fluorescence confocal microscopy was used to examine the uptake of exosomes by recipient cells. The effects of NPC exosomes on the migration and differentiation of BM-MSCs were determined by transwell migration assays and quantitative RT-PCR analysis of NPC phenotypic genes. Western blot analysis was performed to examine proteins such as aggrecan, sox-9, collagen II and hif-1α in the induced BM-MSCs. Proliferation and the gene expression profile of NPCs induced by BM-MSC exosomes were measured by Cell Counting Kit-8 and qRT-PCR analysis, respectively. Both the NPCs and BM-MSCs secreted exosomes, and these exosomes underwent uptake by the corresponding cells. NPC-derived exosomes promoted BM-MSC migration and induced BM-MSC differentiation to a nucleus pulposus-like phenotype. BM-MSC-derived exosomes promoted NPC proliferation and healthier extracellular matrix production in the degenerate NPCs. Our study indicates that the exosomes act as an important vehicle in information exchange between BM-MSCs and NPCs. Given a variety of functions and multiple advantages, exosomes alone or loaded with specific genes and drugs would be an appropriate option in a cell-free therapy strategy for intervertebral disc degeneration.

Nucleotide-Specific Contrast for DNA Sequencing by Electron Spectroscopy

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

Mankos, Marian; Persson, Henrik H. J.; N’Diaye, Alpha T.

DNA sequencing by imaging in an electron microscope is an approach that holds promise to deliver long reads with low error rates and without the need for amplification. Earlier work using transmission electron microscopes, which use high electron energies on the order of 100 keV, has shown that low contrast and radiation damage necessitates the use of heavy atom labeling of individual nucleotides, which increases the read error rates. Other prior work using scattering electrons with much lower energy has shown to suppress beam damage on DNA. Here we explore possibilities to increase contrast by employing two methods, X-ray photoelectronmore » and Auger electron spectroscopy. Using bulk DNA samples with monomers of each base, both methods are shown to provide contrast mechanisms that can distinguish individual nucleotides without labels. In conclusion, both spectroscopic techniques can be readily implemented in a low energy electron microscope, which may enable label-free DNA sequencing by direct imaging.« less

Nucleotide-Specific Contrast for DNA Sequencing by Electron Spectroscopy

DOE PAGES

Mankos, Marian; Persson, Henrik H. J.; N’Diaye, Alpha T.; ...

2016-05-05

DNA sequencing by imaging in an electron microscope is an approach that holds promise to deliver long reads with low error rates and without the need for amplification. Earlier work using transmission electron microscopes, which use high electron energies on the order of 100 keV, has shown that low contrast and radiation damage necessitates the use of heavy atom labeling of individual nucleotides, which increases the read error rates. Other prior work using scattering electrons with much lower energy has shown to suppress beam damage on DNA. Here we explore possibilities to increase contrast by employing two methods, X-ray photoelectronmore » and Auger electron spectroscopy. Using bulk DNA samples with monomers of each base, both methods are shown to provide contrast mechanisms that can distinguish individual nucleotides without labels. In conclusion, both spectroscopic techniques can be readily implemented in a low energy electron microscope, which may enable label-free DNA sequencing by direct imaging.« less

Laser-assisted atom probe tomography of Ti/TiN films deposited on Si.

PubMed

Sanford, N A; Blanchard, P T; White, R; Vissers, M R; Diercks, D R; Davydov, A V; Pappas, D P

2017-03-01

Laser-assisted atom probe tomography (L-APT) was used to examine superconducting TiN/Ti/TiN trilayer films with nominal respective thicknesses of 5/5/5 (nm). Such materials are of interest for applications that require large arrays of microwave kinetic inductance detectors. The trilayers were deposited on Si substrates by reactive sputtering. Electron energy loss microscopy performed in a scanning transmission electron microscope (STEM/EELS) was used to corroborate the L-APT results and establish the overall thicknesses of the trilayers. Three separate batches were studied where the first (bottom) TiN layer was deposited at 500°C (for all batches) and the subsequent TiN/Ti bilayer was deposited at ambient temperature, 250°C, and 500°C, respectively. L-APT rendered an approximately planar TiN/Si interface by making use of plausible mass-spectral assignments to N 3 1+ , SiN 1+ , and SiO 1+ . This was necessary since ambiguities associated with the likely simultaneous occurrence of Si 1+ and N 2 1+ prevented their use in rendering the TiN/Si interface upon reconstruction. The non-superconducting Ti 2 N phase was also revealed by L-APT. Neither L-APT nor STEM/EELS rendered sharp Ti/TiN interfaces and the contrast between these layers diminished with increased film deposition temperature. L-APT also revealed that hydrogen was present in varying degrees in all samples including control samples that were composed of single layers of Ti or TiN. Published by Elsevier Ltd.

A next generation positron microscope and a survey of candidate samples for future positron studies

NASA Astrophysics Data System (ADS)

Dull, Terry Lou

A positron microscope has been constructed and is nearing the conclusion of its assembly and testing. The instrument is designed to perform positron and electron microscopy in both scanning and magnifying modes. In scanning mode, a small beam of particles is rastered across the target and the amplitude of a positron or electron related signal is recorded as a function of position. For positrons this signal may come from Doppler Broadening Spectroscopy, Reemitted Positron Spectroscopy or Positron Annihilation Lifetime Spectroscopy. For electrons this signal may come from the number of secondary electrons or Auger Electron Spectroscopy. In magnifying mode an incident beam of particles is directed onto the target and emitted particles, either secondary electrons or reemitted positrons, are magnified to form an image. As a positron microscope the instrument will primarily operate in magnifying mode, as a positron reemission microscope. As an electron microscope the instrument will be able to operate in both magnifying and scanning modes. Depth-profiled Doppler Broadening Spectroscopy studies using a non-microscopic low-energy positron beam have also been performed on a series of samples to ascertain the applicability of positron spectroscopies and/or microscopy to their study. All samples have sub-micron film and/or feature size and thus are only susceptible to positron study with low-energy beams. Several stoichiometries and crystallinities of chalcogenide thin films (which can be optically reversibly switched between crystalline states) were studied and a correlation was found to exist between the amorphous/FCC S-parameter difference and the amorphous/FCC switching time. Amorphous silicon films were studied in an attempt to observe the well-established Staebler-Wronski effect as well as the more controversial photodilatation effect. However, DBS was not able to detect either effect. The passive oxide films on titanium and aluminum were studied in an attempt to verify the Point Defect Model, a detailed, but as yet microscopically unconfirmed, theory of the corrosive breakdown of passive films. DBS results supportive of the PDM were observed. Graphitic carbon fibers were also studied and DBS indicated the presence of a 200 nm thick outer fiber skin possibly characterized by a high degree of graphitic crystallite alignment.

Microscopic Electron Variations Measured Simultaneously By The Cluster Spacecraft

NASA Astrophysics Data System (ADS)

Buckley, A. M.; Carozzi, T. D.; Gough, M. P.; Beloff, N.

Data is used from the Particle Correlator experiments running on each of the four Cluster spacecraft so as to determine common microscopic behaviour in the elec- tron population observed over the macroscopic Cluster separations. The Cluster par- ticle correlator experiments operate by forming on board Auto Correlation Functions (ACFs) generated from short time series of electron counts obtained, as a function of electron energy, from the PEACE HEEA sensor. The information on the microscopic variation of the electron flux covers the frequency range DC up to 41 kHz (encom- passing typical electron plasma frequencies and electron gyro frequencies and their harmonics), the electron energy range is that covered by the PEACE HEEA sensor (within the range 1 eV to 26 keV). Results are presented of coherent electron struc- tures observed simultaneously by the four spacecraft in the differing plasma interac- tion regions and boundaries encountered by Cluster. As an aid to understanding the plasma interactions, use is made of numerical simulations which model both the un- derlying statistical properties of the electrons and also the manner in which particle correlator experiments operate.

Interference experiment with asymmetric double slit by using 1.2-MV field emission transmission electron microscope.

PubMed

Harada, Ken; Akashi, Tetsuya; Niitsu, Kodai; Shimada, Keiko; Ono, Yoshimasa A; Shindo, Daisuke; Shinada, Hiroyuki; Mori, Shigeo

2018-01-17

Advanced electron microscopy technologies have made it possible to perform precise double-slit interference experiments. We used a 1.2-MV field emission electron microscope providing coherent electron waves and a direct detection camera system enabling single-electron detections at a sub-second exposure time. We developed a method to perform the interference experiment by using an asymmetric double-slit fabricated by a focused ion beam instrument and by operating the microscope under a "pre-Fraunhofer" condition, different from the Fraunhofer condition of conventional double-slit experiments. Here, pre-Fraunhofer condition means that each single-slit observation was performed under the Fraunhofer condition, while the double-slit observations were performed under the Fresnel condition. The interference experiments with each single slit and with the asymmetric double slit were carried out under two different electron dose conditions: high-dose for calculation of electron probability distribution and low-dose for each single electron distribution. Finally, we exemplified the distribution of single electrons by color-coding according to the above three types of experiments as a composite image.

Pre-microscope tunnelling — Inspiration or constraint?

NASA Astrophysics Data System (ADS)

Walmsley, D. G.

1987-03-01

Before the microscope burst upon the scene, tunnelling had established for itself a substantial niche in the repertoire of the solid state physicist. Over a period of 20 years it has contributed importantly to our understanding of many systems. It elucidated the superconducting state, first by a direct display of the energy gap then by providing detailed information on the phonon spectra and electron-phonon coupling strength in junction electrodes. Its use as a phonon spectrometer was subsequently extended to semiconductors and to the oxides of insulating barriers. Eventually the vibrational spectra of monolayer organic and inorganic adsorbates became amenable with rich scientific rewards. In a few cases electronic transitions have been observed. Plasmon excitation by tunnelling electrons led to insights on the electron loss function in metals at visible frequencies and provided along the way an intriguing light emitting device. With the advent of the microscope it is now appropriate to enquire how much of this experience can profitably be carried over to the new environment. Are we constrained just to repeat the experiments in a new configuration? Happily no. The microscope offers us topographical and spectroscopic information of a new order. One might next ask how great is the contact between the two disciplines? We explore this question and seek to establish where the pre-microscope experience can be helpful in inspiring our use of this marvellous new facility that we know as the scanning tunnelling microscope.

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.

Electronic structure and microscopic model of V(2)GeO(4)F(2)-a quantum spin system with S = 1.

PubMed

Rahaman, Badiur; Saha-Dasgupta, T

2007-07-25

We present first-principles density functional calculations and downfolding studies of the electronic and magnetic properties of the oxide-fluoride quantum spin system V(2)GeO(4)F(2). We discuss explicitly the nature of the exchange paths and provide quantitative estimates of magnetic exchange couplings. A microscopic modelling based on analysis of the electronic structure of this systems puts it in the interesting class of weakly coupled alternating chain S = 1 systems. Based on the microscopic model, we make inferrences about its spin excitation spectra, which needs to be tested by rigorous experimental study.

High-Resolution Electron Energy-Loss Spectroscopy (HREELS) Using a Monochromated TEM/STEM

NASA Technical Reports Server (NTRS)

Sai, Z. R.; Bradley, J. P.; Erni, R.; Browning, N.

2005-01-01

A 200 keV FEI TF20 XT monochromated (scanning) transmission electron microscope funded by NASA's SRLIDAP program is undergoing installation at Lawrence Livermore National Laboratory. Instrument specifications in STEM mode are Cs =1.0 mm, Cc =1.2 mm, image resolution =0.18 nm, and in TEM mode Cs =1.3 mm, Cc =1.3 mm, information limit =0.14 nm. Key features of the instrument are a voltage-stabilized high tension (HT) supply, a monochromator, a high-resolution electron energy-loss spectrometer/energy filter, a high-resolution annular darkfield detector, and a solid-state x-ray energy-dispersive spectrometer. The high-tension tank contains additional sections for 60Hz and high frequency filtering, resulting in an operating voltage of 200 kV plus or minus 0.005V, a greater than 10-fold improvement over earlier systems. The monochromator is a single Wien filter design. The energy filter is a Gatan model 866 Tridiem-ERS high resolution GIF spec d for less than or equal to 0.15 eV energy resolution with 29 pA of current in a 2 nm diameter probe. 0.13 eV has already been achieved during early installation. The x-ray detector (EDAX/Genesis 4000) has a take-off angle of 20 degrees, an active area of 30 square millimeters, and a solid angle of 0.3 steradians. The higher solid angle is possible because the objective pole-piece allows the detector to be positioned as close as 9.47 mm from the specimen. The voltage-stabilized HT supply, monochromator and GIF enable high-resolution electron energy-loss spectroscopy (HREELS) with energy resolution comparable to synchrotron XANES, but with approximately 100X better spatial resolution. The region between 0 and 100 eV is called the low-loss or valence electron energy-loss spectroscopy (VEELS) region where features due to collective plasma oscillations and single electron transitions of valence electrons are observed. Most of the low-loss VEELS features we are detecting are being observed for the first time in IDPs. A major focus of our research is to understand the origin and significance of these features and how they might be exploited to gain insight about IDPs and other meteoritic materials.

Miniature self-contained vacuum compatible electronic imaging microscope

DOEpatents

Naulleau, Patrick P.; Batson, Phillip J.; Denham, Paul E.; Jones, Michael S.

2001-01-01

A vacuum compatible CCD-based microscopic camera with an integrated illuminator. The camera can provide video or still feed from the microscope contained within a vacuum chamber. Activation of an optional integral illuminator can provide light to illuminate the microscope subject. The microscope camera comprises a housing with a objective port, modified objective, beam-splitter, CCD camera, and LED illuminator.

Electron Source Brightness and Illumination Semi-Angle Distribution Measurement in a Transmission Electron Microscope.

PubMed

Börrnert, Felix; Renner, Julian; Kaiser, Ute

2018-05-21

The electron source brightness is an important parameter in an electron microscope. Reliable and easy brightness measurement routes are not easily found. A determination method for the illumination semi-angle distribution in transmission electron microscopy is even less well documented. Herein, we report a simple measurement route for both entities and demonstrate it on a state-of-the-art instrument. The reduced axial brightness of the FEI X-FEG with a monochromator was determined to be larger than 108 A/(m2 sr V).

An ultrafast electron microscope gun driven by two-photon photoemission from a nanotip cathode

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

Bormann, Reiner; Strauch, Stefanie; Schäfer, Sascha, E-mail: schaefer@ph4.physik.uni-goettingen.de

We experimentally and numerically investigate the performance of an advanced ultrafast electron source, based on two-photon photoemission from a tungsten needle cathode incorporated in an electron microscope gun geometry. Emission properties are characterized as a function of the electrostatic gun settings, and operating conditions leading to laser-triggered electron beams of very low emittance (below 20 nm mrad) are identified. The results highlight the excellent suitability of optically driven nano-cathodes for the further development of ultrafast transmission electron microscopy.

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.

Electron beam assisted field evaporation of insulating nanowires/tubes

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

Blanchard, N. P., E-mail: nicholas.blanchard@univ-lyon1.fr; Niguès, A.; Choueib, M.

2015-05-11

We demonstrate field evaporation of insulating materials, specifically BN nanotubes and undoped Si nanowires, assisted by a convergent electron beam. Electron irradiation leads to positive charging at the nano-object's apex and to an important increase of the local electric field thus inducing field evaporation. Experiments performed both in a transmission electron microscope and in a scanning electron microscope are presented. This technique permits the selective evaporation of individual nanowires in complex materials. Electron assisted field evaporation could be an interesting alternative or complementary to laser induced field desorption used in atom probe tomography of insulating materials.

The contributions of Otto Scherzer (1909-1982) to the development of the electron microscope.

PubMed

Marko, Michael; Rose, Harald

2010-08-01

Otto Scherzer was one of the pioneers of theoretical electron optics. He was coauthor of the first comprehensive book on electron optics and was the first to understand that round electron lenses could not be combined to correct aberrations, as is the case in light optics. He subsequently was the first to describe several alternative means to correct spherical and chromatic aberration of electron lenses. These ideas were put into practice by his laboratory and students at Darmstadt and their successors, leading to the fully corrected electron microscopes now in operation.

High-resolution low-dose scanning transmission electron microscopy.

PubMed

Buban, James P; Ramasse, Quentin; Gipson, Bryant; Browning, Nigel D; Stahlberg, Henning

2010-01-01

During the past two decades instrumentation in scanning transmission electron microscopy (STEM) has pushed toward higher intensity electron probes to increase the signal-to-noise ratio of recorded images. While this is suitable for robust specimens, biological specimens require a much reduced electron dose for high-resolution imaging. We describe here protocols for low-dose STEM image recording with a conventional field-emission gun STEM, while maintaining the high-resolution capability of the instrument. Our findings show that a combination of reduced pixel dwell time and reduced gun current can achieve radiation doses comparable to low-dose TEM.

Fabrication and design of bioactive agent coated, highly-aligned electrospun matrices for nerve tissue engineering: Preparation, characterization and application

NASA Astrophysics Data System (ADS)

Lee, Sang Jin; Heo, Min; Lee, Donghyun; Heo, Dong Nyoung; Lim, Ho-Nam; Kwon, Il Keun

2017-12-01

In this study, we designed highly-aligned thermoplastic polycarbonate urethane (PCU) fibrous scaffolds coated with bioactive compounds, such as Poly-L-Lysine (PLL) and Poly-L-Ornithine (PLO), to enhance cellular adhesion and directivity. These products were characterized by scanning electron microscope (SEM) analysis which demonstrated that highly aligned fiber strands were formed without beads when coated onto a mandrel rotating at 1800 rpm. During in vitro cell test, PLO-coated, aligned PCU scaffolds were found to have significantly higher proliferation rates than PLL coated and bare PCU scaffolds. Interestingly, dental pulp stem cells (DPSCs) were observed to stretch along the longitudinal axis parallel to the cell direction on highly aligned scaffolds. These results clearly confirm that our strategy may suggest a useful paradigm by inducing neural tissue repair as a means to remodeling and healing of tissue for restorative procedures in neural tissue engineering.

Biocompatibility of PCL/PLGA-BCP porous scaffold for bone tissue engineering applications.

PubMed

Thi Hiep, Nguyen; Chan Khon, Huynh; Dai Hai, Nguyen; Byong-Taek, Lee; Van Toi, Vo; Thanh Hung, Le

2017-06-01

In this study, biomimic porous polycaprolactone/poly (lactide-co-glycolide) loading biphasic tricalcium phosphate (PCL/PLGA-BCP) scaffolds were fabricated successfully by solvent evaporation method. The distribution of biphasic tricalcium phosphate (BCP) in polycaprolactone/poly (lactide-co-glycolide) (PCL/PLGA) scaffold was confirmed by micro-computed tomography (micro-CT) scanning, scanning electron microscope (SEM) observation and Energy-dispersive X-ray Spectroscopy (EDS) analysis. The hydrophilicity of the scaffolds was confirmed by contact angle measurement. In in vitro experiments, proliferation of human bone marrow mesenchymal stem cell (hBMSCs) and its osteoblastic differentiation on scaffold were assessed for 1, 2 and 3 weeks using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, fluorescence observation, hematoxylin & eosin (H&E) staining and real-time polymerase chain reaction (RT-PCR). In in vivo experiments, ossification was observed using micro-CT analysis and histological staining.

Damage-tolerant nanotwinned metals with nanovoids under radiation environments

PubMed Central

Chen, Y.; Yu, K Y.; Liu, Y.; Shao, S.; Wang, H.; Kirk, M. A.; Wang, J.; Zhang, X.

2015-01-01

Material performance in extreme radiation environments is central to the design of future nuclear reactors. Radiation induces significant damage in the form of dislocation loops and voids in irradiated materials, and continuous radiation often leads to void growth and subsequent void swelling in metals with low stacking fault energy. Here we show that by using in situ heavy ion irradiation in a transmission electron microscope, pre-introduced nanovoids in nanotwinned Cu efficiently absorb radiation-induced defects accompanied by gradual elimination of nanovoids, enhancing radiation tolerance of Cu. In situ studies and atomistic simulations reveal that such remarkable self-healing capability stems from high density of coherent and incoherent twin boundaries that rapidly capture and transport point defects and dislocation loops to nanovoids, which act as storage bins for interstitial loops. This study describes a counterintuitive yet significant concept: deliberate introduction of nanovoids in conjunction with nanotwins enables unprecedented damage tolerance in metallic materials. PMID:25906997

Damage-tolerant nanotwinned metals with nanovoids under radiation environments.

PubMed

Chen, Y; Yu, K Y; Liu, Y; Shao, S; Wang, H; Kirk, M A; Wang, J; Zhang, X

2015-04-24

Material performance in extreme radiation environments is central to the design of future nuclear reactors. Radiation induces significant damage in the form of dislocation loops and voids in irradiated materials, and continuous radiation often leads to void growth and subsequent void swelling in metals with low stacking fault energy. Here we show that by using in situ heavy ion irradiation in a transmission electron microscope, pre-introduced nanovoids in nanotwinned Cu efficiently absorb radiation-induced defects accompanied by gradual elimination of nanovoids, enhancing radiation tolerance of Cu. In situ studies and atomistic simulations reveal that such remarkable self-healing capability stems from high density of coherent and incoherent twin boundaries that rapidly capture and transport point defects and dislocation loops to nanovoids, which act as storage bins for interstitial loops. This study describes a counterintuitive yet significant concept: deliberate introduction of nanovoids in conjunction with nanotwins enables unprecedented damage tolerance in metallic materials.

Composition Analysis of III-Nitrides at the Nanometer Scale: Comparison of Energy Dispersive X-ray Spectroscopy and Atom Probe Tomography.

PubMed

Bonef, Bastien; Lopez-Haro, Miguel; Amichi, Lynda; Beeler, Mark; Grenier, Adeline; Robin, Eric; Jouneau, Pierre-Henri; Mollard, Nicolas; Mouton, Isabelle; Monroy, Eva; Bougerol, Catherine

2016-12-01

The enhancement of the performance of advanced nitride-based optoelectronic devices requires the fine tuning of their composition, which has to be determined with a high accuracy and at the nanometer scale. For that purpose, we have evaluated and compared energy dispersive X-ray spectroscopy (EDX) in a scanning transmission electron microscope (STEM) and atom probe tomography (APT) in terms of composition analysis of AlGaN/GaN multilayers. Both techniques give comparable results with a composition accuracy better than 0.6 % even for layers as thin as 3 nm. In case of EDX, we show the relevance of correcting the X-ray absorption by simultaneous determination of the mass thickness and chemical composition at each point of the analysis. Limitations of both techniques are discussed when applied to specimens with different geometries or compositions.

Mechanical properties of natural chitosan/hydroxyapatite/magnetite nanocomposites for tissue engineering applications.

PubMed

Heidari, Fatemeh; Razavi, Mehdi; E Bahrololoom, Mohammad; Bazargan-Lari, Reza; Vashaee, Daryoosh; Kotturi, Hari; Tayebi, Lobat

2016-08-01

Chitosan (CS), hydroxyapatite (HA), and magnetite (Fe3O4) have been broadly employed for bone treatment applications. Having a hybrid biomaterial composed of the aforementioned constituents not only accumulates the useful characteristics of each component, but also provides outstanding composite properties. In the present research, mechanical properties of pure CS, CS/HA, CS/HA/magnetite, and CS/magnetite were evaluated by the measurements of bending strength, elastic modulus, compressive strength and hardness values. Moreover, the morphology of the bending fracture surfaces were characterized using a scanning electron microscope (SEM) and an image analyzer. Studies were also conducted to examine the biological response of the human Mesenchymal Stem Cells (hMSCs) on different composites. We conclude that, although all of these composites possess in-vitro biocompatibility, adding hydroxyapatite and magnetite to the chitosan matrix can noticeably enhance the mechanical properties of the pure chitosan. Copyright © 2016 Elsevier B.V. All rights reserved.

STEM-EDX tomography of bimetallic nanoparticles: A methodological investigation

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

Slater, Thomas J. A.; Janssen, Arne; Camargo, Pedro H. C.

This paper presents an investigation of the limitations and optimization of energy dispersive X-ray (EDX) tomography within the scanning transmission electron microscope, focussing on application of the technique to characterising the 3D elemental distribution of bimetallic AgAu nanoparticles. The detector collection efficiency when using a standard tomography holder is characterised using a tomographic data set from a single nanoparticle and compared to a standard low background double tilt holder. Optical depth profiling is used to investigate the angles and origin of detector shadowing as a function of specimen field of view. A novel time-varied acquisition scheme is described to compensatemore » for variations in the intensity of spectrum images at each sample tilt. Lastly, the ability of EDX spectrum images to satisfy the projection requirement for nanoparticle samples is discussed, with consideration of the effect of absorption and shadowing variations« less

STEM-EDX tomography of bimetallic nanoparticles: A methodological investigation

DOE PAGES

Slater, Thomas J. A.; Janssen, Arne; Camargo, Pedro H. C.; ...

2015-10-22

This paper presents an investigation of the limitations and optimization of energy dispersive X-ray (EDX) tomography within the scanning transmission electron microscope, focussing on application of the technique to characterising the 3D elemental distribution of bimetallic AgAu nanoparticles. The detector collection efficiency when using a standard tomography holder is characterised using a tomographic data set from a single nanoparticle and compared to a standard low background double tilt holder. Optical depth profiling is used to investigate the angles and origin of detector shadowing as a function of specimen field of view. A novel time-varied acquisition scheme is described to compensatemore » for variations in the intensity of spectrum images at each sample tilt. Lastly, the ability of EDX spectrum images to satisfy the projection requirement for nanoparticle samples is discussed, with consideration of the effect of absorption and shadowing variations« less

Damage-tolerant nanotwinned metals with nanovoids under radiation environments

DOE PAGES

Chen, Y.; Yu, K. Y.; Liu, Y.; ...

2015-04-24

Material performance in extreme radiation environments is central to the design of future nuclear reactors. Radiation induces significant damage in the form of dislocation loops and voids in irradiated materials, and continuous radiation often leads to void growth and subsequent void swelling in metals with low stacking fault energy. Here we show that by using in situ heavy ion irradiation in a transmission electron microscope, pre-introduced nanovoids in nanotwinned Cu efficiently absorb radiation-induced defects accompanied by gradual elimination of nanovoids, enhancing radiation tolerance of Cu. In situ studies and atomistic simulations reveal that such remarkable self-healing capability stems from highmore » density of coherent and incoherent twin boundaries that rapidly capture and transport point defects and dislocation loops to nanovoids, which act as storage bins for interstitial loops. This study describes a counterintuitive yet significant concept: deliberate introduction of nanovoids in conjunction with nanotwins enables unprecedented damage tolerance in metallic materials.« less

Localization of lead accumulated by corn plants. [Zea mays L

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

Malone, C.; Koeppe, D.E.; Miller, R.J.

1974-01-01

Light and electron microscopic studies of corn plants (Zea mays L.) exposed to Pb in hydroponic solution showed that the roots generally accumulated a surface Pb precipitate and slowly accumulated Pb crystals in the cell walls. The root surface precipitate formed without the apparent influence of any cell organelles. In contrast, Pb taken up by roots was concentrated in dicytosome vesicles. Dicytosome vesicles containing cell wall material fused with one another to encase the Pb deposit. This encased deposit which was surrounded by a membrane migrated toward the outside of the cell where the membrane surrounding the deposit then fusedmore » with the plasmalemma. The material surrounding the deposit then fused with the cell wall. The result of this process was a concentration of Pb deposits in the cell wall outside the plasmalemma. Similar deposits were observed in stems and leaves suggesting that Pb was transported and deposited in a similar manner.« less

Localization of Lead Accumulated by Corn Plants 1

PubMed Central

Malone, Carl; Koeppe, D. E.; Miller, Raymond J.

1974-01-01

Light and electron microscopic studies of corn plants (Zea mays L.) exposed to Pb in hydroponic solution showed that the roots generally accumulated a surface Pb precipitate and slowly accumulated Pb crystals in the cell walls. The root surface precipitate formed without the apparent influence of any cell organelles. In contrast, Pb taken up by roots was concentrated in dictyosome vesicles. Dictyosome vesicles containing cell wall material fused with one another to encase the Pb deposit. This encased deposit which was surrounded by a membrane migrated toward the outside of the cell where the membrane surrounding the deposit fused with the plasmalemma. The material surrounding the deposit then fused with the cell wall. The result of this process was a concentration of Pb deposits in the cell wall outside the plasmalemma. Similar deposits were observed in stems and leaves suggesting that Pb was transported and deposited in a similar manner. Images PMID:16658711

The role of the Ti and Mo barrier layer in Ti/Al metallization to AlGaN/GaN heterostructures at identical process conditions: a structural and chemical characterization

NASA Astrophysics Data System (ADS)

Chandran, Narendraraj; Kolakieva, Lilyana; Kakanakov, Roumen; Polychroniadis, E. K.

2015-11-01

The composition and structure of TiAl-based metallizations have been investigated depending on the Ti and Mo barriers. The lowest contact resistivity of 4 × 10-6 Ω.cm2 for a Ti barrier and 7 × 10-6 Ω.cm2 for a Mo barrier is obtained at a Ti/Al ratio of 0.43 after annealing at 800 °C. The scanning transmission electron microscope (STEM) and energy dispersive spectroscopy (EDS) analyses reveal that Mo is not an effective barrier for the Au in-diffusion and Al out of diffusion during annealing. The intensive diffusion processes lead to the formation of the semimetal TiN compound at the interface and intermetallic phases of Au, Al, and Ti, the structure and composition of which depend on the barrier metal.

Structural and mechanical characterization of hybrid metallic-inorganic nanosprings

NASA Astrophysics Data System (ADS)

Habtoun, Sabrina; Houmadi, Said; Reig, Benjamin; Pouget, Emilie; Dedovets, Dmytro; Delville, Marie-Hélène; Oda, Reiko; Cristiano, Fuccio; Bergaud, Christian

2017-10-01

Silica nanosprings (NS) are fabricated by a sol-gel deposition of silica precursors onto a template made of self-assembled organic chiral nanostructures. They are deposited and assembled on microstructured silicon substrates, and then metallized and clamped in a single lithography-free step using a focused ion beam (FIB). The resulting suspended hybrid metallic/inorganic NS are then characterized with high-resolution transmission electron microscopy (HRTEM) and scanning TEM/energy-dispersive X-ray spectroscopy (STEM/EDX), showing the atomic structure of the metallic layer. Three-point bending tests are also carried out using an atomic force microscope (AFM) and supported by finite element method (FEM) simulation with COMSOL Multiphysics allowing the characterization of the mechanical behavior and the estimation of the stiffness of the resulting NS. The information obtained on the structural and mechanical properties of the NS is discussed for future nano-electro-mechanical system (NEMS) applications.

Anticancer activity of Moringa oleifera mediated silver nanoparticles on human cervical carcinoma cells by apoptosis induction.

PubMed

Vasanth, Karunamoorthy; Ilango, Kaliappan; MohanKumar, Ramasamy; Agrawal, Aruna; Dubey, Govind Prasad

2014-05-01

Silver nanomaterial plays a crucial role in the growing field of nanotechnology as there is an increasing commercial demand for silver nanoparticles (AgNPs) owing to their wide biological applications. The present investigation aims at developing anti-cancerous colloidal silver using Moringa olifera stem bark extract. Electron and atomic force microscopic images were taken to analyze the surface morphology of the synthesized AgNPs. The effects of synthesized AgNPs were tested against human cervical carcinoma cells (HeLa) and cell morphology was further evaluated using 4,6-diamidino-2-phenylindole (DAPI) staining. The efficiency of green synthesized AgNPs was studied with the help of fluorescence activated cell sorting (FACS) and was shown to induce apoptosis through reactive oxygen species (ROS) generation in HeLa cells. Copyright © 2014 Elsevier B.V. All rights reserved.

Induction of Female-to-Male Sex Change in Adult Zebrafish by Aromatase Inhibitor Treatment

NASA Astrophysics Data System (ADS)

Takatsu, Kanae; Miyaoku, Kaori; Roy, Shimi Rani; Murono, Yuki; Sago, Tomohiro; Itagaki, Hideyuki; Nakamura, Masaru; Tokumoto, Toshinobu

2013-12-01

This study investigated whether undifferentiated germ and/or somatic stem cells remain in the differentiated ovary of a species that does not undergo sex changes under natural conditions and retain their sexual plasticity. The effect of aromatase inhibitor (AI)-treatment on sexually mature female zebrafish was examined. A 5-month AI treatment caused retraction of the ovaries after which testes-like organs appeared, and cyst structures filled with spermatozoa-like cells were observed in sections of these tissues. Electron microscopic observations revealed that these cells appeared as large sperm heads without tails. Sperm formation was re-examined after changing the diet to an AI-free food. A large number of normal sperm were obtained after eight weeks, and no formation of ovarian tissue was observed. Artificial fertilization using sperm from the sex-changed females was successful. These results demonstrated that sex plasticity remains in the mature ovaries of this species.

Application of automatic image analysis for morphometric studies of peroxisomes stained cytochemically for catalase. II. Light-microscopic application.

PubMed

Beier, K; Fahimi, H D

1987-01-01

The feasibility of the application of a television-based image analyzer, the Texture Analysis System (TAS, Leitz Wetzlar, FRG) in conjunction with a light microscope for morphometric studies of hepatic peroxisomes has been investigated. Rat liver peroxisomes were stained with the alkaline-DAB method for localization of catalase and semithin (0.25 and 1 micron) sections of plastic-embedded material were examined under an oil immersion objective. The TAS detected the peroxisomal profiles selectively and determined their morphometric parameters automatically. The same parameters were obtained also by morphometric analysis of electron micrographs from the same material. The volume density of peroxisomes determined by TAS in semithin sections of normal liver, after correction for section thickness, is quite close to the corresponding value obtained by morphometry of electron micrographs. The difference is approximately 20%. In animals treated with the hypolipidemic drug bezafibrate, which causes proliferation of peroxisomes, TAS detected readily the increase in volume density of peroxisomes in semithin sections. In comparison with electron microscopy, however, the light-microscopic approach seems to underestimate the proliferation. The lower resolution of the light microscope and overlapping of neighbouring particles in relatively thick sections used for light-microscopic analysis may account for the differences. The present study has demonstrated the usefulness of automatic image analysis in conjunction with selective cytochemical staining of peroxisomes for morphometry of this organelle in rat liver. The light-microscopic approach is not only faster but is also extremely economical by obviating the use of an electron microscope.

Electron beam induced deposition of silicon nanostructures from a liquid phase precursor.

PubMed

Liu, Yin; Chen, Xin; Noh, Kyong Wook; Dillon, Shen J

2012-09-28

This work demonstrates electron beam induced deposition of silicon from a SiCl(4) liquid precursor in a transmission electron microscope and a scanning electron microscope. Silicon nanodots of tunable size are reproducibly grown in controlled geometries. The volume of these features increases linearly with deposition time. The results indicate that secondary electrons generated at the substrate surface serve as the primary source of silicon reduction. However, at high current densities the influence of the primary electrons is observed to retard growth. The results demonstrate a new approach to fabricating silicon nanostructures and provide fundamental insights into the mechanism for liquid phase electron beam induced deposition.

Electron beam induced deposition of silicon nanostructures from a liquid phase precursor

NASA Astrophysics Data System (ADS)

Liu, Yin; Chen, Xin; Noh, Kyong Wook; Dillon, Shen J.

2012-09-01

This work demonstrates electron beam induced deposition of silicon from a SiCl4 liquid precursor in a transmission electron microscope and a scanning electron microscope. Silicon nanodots of tunable size are reproducibly grown in controlled geometries. The volume of these features increases linearly with deposition time. The results indicate that secondary electrons generated at the substrate surface serve as the primary source of silicon reduction. However, at high current densities the influence of the primary electrons is observed to retard growth. The results demonstrate a new approach to fabricating silicon nanostructures and provide fundamental insights into the mechanism for liquid phase electron beam induced deposition.

Transmission Electron Microscope Measures Lattice Parameters

NASA Technical Reports Server (NTRS)

Pike, William T.

1996-01-01

Convergent-beam microdiffraction (CBM) in thermionic-emission transmission electron microscope (TEM) is technique for measuring lattice parameters of nanometer-sized specimens of crystalline materials. Lattice parameters determined by use of CBM accurate to within few parts in thousand. Technique developed especially for use in quantifying lattice parameters, and thus strains, in epitaxial mismatched-crystal-lattice multilayer structures in multiple-quantum-well and other advanced semiconductor electronic devices. Ability to determine strains in indivdual layers contributes to understanding of novel electronic behaviors of devices.

Ponderomotive phase plate for transmission electron microscopes

DOEpatents

Reed, Bryan W [Livermore, CA

2012-07-10

A ponderomotive phase plate system and method for controllably producing highly tunable phase contrast transfer functions in a transmission electron microscope (TEM) for high resolution and biological phase contrast imaging. The system and method includes a laser source and a beam transport system to produce a focused laser crossover as a phase plate, so that a ponderomotive potential of the focused laser crossover produces a scattering-angle-dependent phase shift in the electrons of the post-sample electron beam corresponding to a desired phase contrast transfer function.

In situ flat embedding of monolayers and cell relocation in the acrylic resin LR white for comparative light and electron microscopy studies.

PubMed

Steiner, M; Schöfer, C; Mosgoeller, W

1994-12-01

A simple and reliable method has been developed for the in situ LR White embedding of cell monolayers grown on glass cover-slips. Combined with cytochemical or immunological procedures, this technique allows light and/or electron microscopy investigations of a large number of cells in the same horizontal plane within a relatively short period of time. It can be applied to cells grown on microgrid finder cover-slips which allows a distinct site of even an individual cell of a monolayer to be studied at first at the light microscope level and subsequently at the electron microscope level. Hence, it is also suitable for controlling manipulation of single cells, followed by their serial sectioning after relocation in the electron microscope.

Mars Life? - Microscopic Tubular Structures

NASA Image and Video Library

1996-08-09

This electron microscope image shows extremely tiny tubular structures that are possible microscopic fossils of bacteria-like organisms that may have lived on Mars more than 3.6 billion years ago. http://photojournal.jpl.nasa.gov/catalog/PIA00285

Mars Life? - Microscopic Egg-shaped Structures

NASA Image and Video Library

1996-08-09

This electron microscope image shows egg-shaped structures, some of which may be possible microscopic fossils of Martian origin as discussed by NASA research published in the Aug. 16, 1996. http://photojournal.jpl.nasa.gov/catalog/PIA00286

CHARACTERISTICS OF INDIVIDUAL PARTICLES AT A RURAL SITE IN THE EASTERN UNITED STATES

EPA Science Inventory

To determine the nature of aerosol particles in a rural area of the eastern United States, aerosol samples were collected at Deep Creek Lake, Maryland, on various substrates and analyzed by a scanning electron microscope (SEM) and a transmission electron microscope (TEM). SEM ana...

77 FR 33422 - The Regents of the University of California, et al.; Notice of Consolidated Decision on...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-06

... DEPARTMENT OF COMMERCE International Trade Administration The Regents of the University of...: Washington University in St. Louis, Saint Louis, MO 63130. Instrument: Electron Microscope. Manufacturer: FEI.... Applicant: The Regents of the University of California, Berkeley, CA 94720. Instrument: Electron Microscope...

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).

Variations in contrast of scanning electron microscope images for microstructure analysis of Si-based semiconductor materials.

PubMed

Itakura, Masaru; Kuwano, Noriyuki; Sato, Kaoru; Tachibana, Shigeaki

2010-08-01

Image contrasts of Si-based semiconducting materials have been investigated by using the latest scanning electron microscope with various detectors under a range of experimental conditions. Under a very low accelerating voltage (500 V), we obtained a good image contrast between crystalline SiGe whiskers and the amorphous matrix using an in-lens secondary electron (SE) detector, while the conventional topographic SE image and the compositional backscattered electron (BSE) image gave no distinct contrast. By using an angular-selective BSE (AsB) detector for wide-angle scattered BSE, on the other hand, the crystal grains in amorphous matrix can be clearly visualized as 'channelling contrast'. The image contrast is very similar to that of their transmission electron microscope image. The in-lens SE (true SE falling dots SE1) and the AsB (channelling) contrasts are quite useful to distinguish crystalline parts from amorphous ones.

Dynamic imaging with electron microscopy

ScienceCinema

Campbell, Geoffrey; McKeown, Joe; Santala, Melissa

2018-02-13

Livermore researchers have perfected an electron microscope to study fast-evolving material processes and chemical reactions. By applying engineering, microscopy, and laser expertise to the decades-old technology of electron microscopy, the dynamic transmission electron microscope (DTEM) team has developed a technique that can capture images of phenomena that are both very small and very fast. DTEM uses a precisely timed laser pulse to achieve a short but intense electron beam for imaging. When synchronized with a dynamic event in the microscope's field of view, DTEM allows scientists to record and measure material changes in action. A new movie-mode capability, which earned a 2013 R&D 100 Award from R&D Magazine, uses up to nine laser pulses to sequentially capture fast, irreversible, even one-of-a-kind material changes at the nanometer scale. DTEM projects are advancing basic and applied materials research, including such areas as nanostructure growth, phase transformations, and chemical reactions.

Energy-filtered real- and k-space secondary and energy-loss electron imaging with Dual Emission Electron spectro-Microscope: Cs/Mo(110).

PubMed

Grzelakowski, Krzysztof P

2016-05-01

Since its introduction the importance of complementary k||-space (LEED) and real space (LEEM) information in the investigation of surface science phenomena has been widely demonstrated over the last five decades. In this paper we report the application of a novel kind of electron spectromicroscope Dual Emission Electron spectroMicroscope (DEEM) with two independent electron optical channels for reciprocal and real space quasi-simultaneous imaging in investigation of a Cs covered Mo(110) single crystal by using the 800eV electron beam from an "in-lens" electron gun system developed for the sample illumination. With the DEEM spectromicroscope it is possible to observe dynamic, irreversible processes at surfaces in the energy-filtered real space and in the corresponding energy-filtered kǁ-space quasi-simultaneously in two independent imaging columns. The novel concept of the high energy electron beam sample illumination in the cathode lens based microscopes allows chemically selective imaging and analysis under laboratory conditions. Copyright © 2015 Elsevier B.V. All rights reserved.

Smartphone Magnification Attachment: Microscope or Magnifying Glass

NASA Astrophysics Data System (ADS)

Hergemöller, Timo; Laumann, Daniel

2017-09-01

Today smartphones and tablets do not merely pervade our daily life, but also play a major role in STEM education in general, and in experimental investigations in particular. Enabling teachers and students to make use of these new techniques in physics lessons requires supplying capable and affordable applications. Our article presents the improvement of a low-cost technique turning smartphones into powerful magnifying glasses or microscopes. Adding only a 3D-printed clip attached to the smartphone's camera and inserting a small glass bead in this clip enables smartphones to take pictures with up to 780x magnification (see Fig. 1). In addition, the construction of the smartphone attachments helps to explain and examine the differences between magnifying glasses and microscopes, and shows that the widespread term "smartphone microscope" for this technique is inaccurate from a physics educational perspective.

Label-Free, High Resolution, Multi-Modal Light Microscopy for Discrimination of Live Stem Cell Differentiation Status.

PubMed

Zhang, Jing; Moradi, Emilia; Somekh, Michael G; Mather, Melissa L

2018-01-15

A label-free microscopy method for assessing the differentiation status of stem cells is presented with potential application for characterization of therapeutic stem cell populations. The microscopy system is capable of characterizing live cells based on the use of evanescent wave microscopy and quantitative phase contrast (QPC) microscopy. The capability of the microscopy system is demonstrated by studying the differentiation of live immortalised neonatal mouse neural stem cells over a 15 day time course. Metrics extracted from microscope images are assessed and images compared with results from endpoint immuno-staining studies to illustrate the system's performance. Results demonstrate the potential of the microscopy system as a valuable tool for cell biologists to readily identify the differentiation status of unlabelled live cells.

Induction of hair follicle dermal papilla cell properties in human induced pluripotent stem cell-derived multipotent LNGFR(+)THY-1(+) mesenchymal cells

PubMed Central

Veraitch, Ophelia; Mabuchi, Yo; Matsuzaki, Yumi; Sasaki, Takashi; Okuno, Hironobu; Tsukashima, Aki; Amagai, Masayuki; Okano, Hideyuki; Ohyama, Manabu

2017-01-01

The dermal papilla (DP) is a specialised mesenchymal component of the hair follicle (HF) that plays key roles in HF morphogenesis and regeneration. Current technical difficulties in preparing trichogenic human DP cells could be overcome by the use of highly proliferative and plastic human induced pluripotent stem cells (hiPSCs). In this study, hiPSCs were differentiated into induced mesenchymal cells (iMCs) with a bone marrow stromal cell phenotype. A highly proliferative and plastic LNGFR(+)THY-1(+) subset of iMCs was subsequently programmed using retinoic acid and DP cell activating culture medium to acquire DP properties. The resultant cells (induced DP-substituting cells [iDPSCs]) exhibited up-regulated DP markers, interacted with human keratinocytes to up-regulate HF related genes, and when co-grafted with human keratinocytes in vivo gave rise to fibre structures with a hair cuticle-like coat resembling the hair shaft, as confirmed by scanning electron microscope analysis. Furthermore, iDPSCs responded to the clinically used hair growth reagent, minoxidil sulfate, to up-regulate DP genes, further supporting that they were capable of, at least in part, reproducing DP properties. Thus, LNGFR(+)THY-1(+) iMCs may provide material for HF bioengineering and drug screening for hair diseases. PMID:28220862

Association of reticular cells with CD34+/Sca-1+ apoptotic cells in the hemopoietic organ of grasshopper, Euprepocnemis shirakii.

PubMed

Lim, Jong Yeon; Lee, Bong Hee; Kang, Seok Woo; Wago, Haruhisa; Han, Sung Sik

2004-07-01

Hemopoiesis in orthopteran insects occurs in a hemopoietic organ that is located bilaterally along the aorta. This organ is also known as a reticulo-hemopoietic organ because of the rich presence of reticular cells. This study was performed to further elucidate hemopoiesis in the reticulo-hemopoietic organ of an orthopteran, Euprepocnemis shirakii. We focused on the question why reticular cells are so abundant (35% of cells in hemopoietic organ). Interestingly, 21% of these reticular cells surrounded hemocytes with their reticular cytoplasm. The surrounded hemocytes were distinguished by their different size and darkly stained nucleus. These cells were characterized by immunostaining using antibodies against several types of hemocytes: 45% of the surrounded hemocytes were CD34+, and these positive cells were double stained (over 85%) when immunostained by another hemopoietic pluripotent cell marker, Sca-1. Transmission electron microscopic analysis showed that reticular cells surrounded hemocytes containing large nuclei and poorly developed cytoplasmic organelles. This strongly suggests that the reticular cells surround hemopoietic stem cells. Additionally, surrounded hemopoietic progenitor cells are undergoing apoptosis as indicated by the TUNEL assay. The enclosed apoptotic cells are engulfed and then phagocytosed by reticular cells. Our results suggest that reticular cells are related to the differentiation and apoptosis of hemopoietic stem cells.

Safety Assessment and Botanical Standardization of an Edible Species from South America.

PubMed

Traesel, Giseli Karenina; Machado, Camila Dias; Tirloni, Cleide Adriane Signor; Menetrier, Jacqueline Vergutz; Dos Reis Lívero, Francislaine Aparecida; Lourenço, Emerson Luiz Botelho; Oesterreich, Silvia Aparecida; Budel, Jane Manfron; Junior, Arquimedes Gasparotto

2017-05-01

Tropaeolum majus L. (Tropaeolaceae), commonly known as nasturtium, is an important edible plant native to the Andean States and widely disseminated throughout South America. Despite the use of this species is quite widespread, there are no minimum quality control standards or data on its genotoxicity. So, the aim of this study was to present a detailed anatomical and histochemical study for Tropaeolum majus and provide genotoxicity parameters of a preparation routinely used in South American countries. First, three different Tropaeolum majus aqueous extracts (TMAEs) at concentrations of 1.5%, 7%, and 15% were prepared according to the popular use. Then, genetic toxicity of TMAE was evaluated on bacterial reverse mutation, genomic lesions, and micronucleus formation in male rats. Furthermore, a detailed anatomical and histochemical study of the leaves and stems of Tropaeolum majus were performed. No revertant colonies were found in any bacterial cultures examined. In the comet assay, TMAE showed no significant DNA damage in all tested doses. Micronucleus assay showed no significant increases in the frequency of inducing micronuclei in any dose examined. Light and electron microscope images of cross-section of leaves and stems from Tropaeolum majus revealed useful diagnostic features. The presented data showed significant safety parameters for the use of TMAE and provided important data for the quality control of this plant species.

Development of a secondary electron energy analyzer for a transmission electron microscope.

PubMed

Magara, Hideyuki; Tomita, Takeshi; Kondo, Yukihito; Sato, Takafumi; Akase, Zentaro; Shindo, Daisuke

2018-04-01

A secondary electron (SE) energy analyzer was developed for a transmission electron microscope. The analyzer comprises a microchannel plate (MCP) for detecting electrons, a coil for collecting SEs emitted from the specimen, a tube for reducing the number of backscattered electrons incident on the MCP, and a retarding mesh for selecting the energy of SEs incident on the MCP. The detection of the SEs associated with charging phenomena around a charged specimen was attempted by performing electron holography and SE spectroscopy using the energy analyzer. The results suggest that it is possible to obtain the energy spectra of SEs using the analyzer and the charging states of a specimen by electron holography simultaneously.

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.

Structural analysis of ion-implanted chemical-vapor-deposited diamond by transmission electron microscope

NASA Astrophysics Data System (ADS)

Jiang, N.; Deguchi, M.; Wang, C. L.; Won, J. H.; Jeon, H. M.; Mori, Y.; Hatta, A.; Kitabatake, M.; Ito, T.; Hirao, T.; Sasaki, T.; Hiraki, A.

1997-04-01

A transmission electron microscope (TEM) study of ion-implanted chemical-vapor-deposited (CVD) diamond is presented. CVD diamond used for transmission electron microscope observation was directly deposited onto Mo TEM grids. As-deposited specimens were irradiated by C (100 keV) ions at room temperature with a wide range of implantation doses (10 12-10 17/cm 2). Transmission electron diffraction (TED) patterns indicate that there exists a critical dose ( Dc) for the onset of amorphization of CVD diamond as a result of ion induced damage and the value of critical dose is confirmed to be about 3 × 10 15/cm 2. The ion-induced transformation process is clearly revealed by high resolution electron microscope (HREM) images. For a higher dose implantation (7 × 10 15/cm 2) a large amount of diamond phase is transformed into amorphous carbon and many tiny misoriented diamond blocks are found to be left in the amorphous solid. The average size of these misoriented diamond blocks is only about 1-2 nm. Further bombardment (10 17/cm 2) almost kills all of the diamond phase within the irradiated volume and moreover leads to local formation of micropolycrystalline graphite.

An investigation of nitride precipitates in archaeological iron artefacts from Poland.

PubMed

Kedzierski, Z; Stepiński, J; Zielińska-Lipiec, A

2010-03-01

The paper describes the investigations of nitride precipitates in a spearhead and a sword found in the territory of Poland, in cremation graveyards of the Przeworsk Culture, dated to the Roman Period. Three different techniques of the examination of nitride precipitates were employed: optical microscope, scanning electron microscope (scanning electron microscope with energy dispersive X-ray spectrometer) and transmission electron microscope. Two types of precipitates have been observed, and their plate-like shape was demonstrated. The large precipitate has been confirmed to be gamma'-Fe(4)N, whereas the small one has been identified as alpha''-Fe(16)N(2). The origin of nitride precipitates in archaeological iron artefacts from Poland is probably a result of the manufacturing process or cremation as part of burial rites. An examination of available iron artefacts indicates that nitride precipitates (have only limited effect on mechanical properties) influence the hardness of metal only to a very limited degree.

Investigation of Mineral Transformations in Wet Supercritical CO2 by Electron Microscopy

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

Arey, Bruce W.; Kovarik, Libor; Wang, Zheming

2011-10-10

The capture and storage of carbon dioxide and other greenhouse gases in deep geologic formations represents one of the most promising options for mitigating the impacts of greenhouse gases on global warming. In this regard, mineral-fluid interactions are of prime importance since such reactions can result in the long term sequestration of CO2 by trapping in mineral phases. Recently it has been recognized that interactions with neat to water-saturated non-aqueous fluids are of prime importance in understanding mineralization reactions since the introduced CO2 is likely to contain water initially or soon after injection and the supercritical CO2 (scCO2) is lessmore » dense than the aqueous phase which can result in a buoyant scCO2 plume contacting the isolating caprock. As a result, unraveling the molecular/microscopic mechanisms of mineral transformation in neat to water saturated scCO2 has taken on an added important. In this study, we are examining the interfacial reactions of the olivine mineral forsterite (Mg2SiO4) over a range of water contents up to and including complete water saturation in scCO2. The surface precipitates that form on the reacted forsterite grains are extremely fragile and difficult to experimentally characterize. In order to address this issue we have developed experimental protocols for preparing and imaging electron-transparent samples from fragile structures. These electron-transparent samples are then examined using a combination of STEM/EDX, FIB-TEM, and helium ion microscope (HIM) imaging (Figures 1-3). This combination of capabilities has provided unique insight into the geochemical processes that occur on scCO2 reacted mineral surfaces. The experimental procedures and protocols that have been developed also have useful applications for examining fragile structures on a wide variety of materials. This research was performed using EMSL, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research located at Pacific Northwest National Laboratory.« less

Aberration corrected 1.2-MV cold field-emission transmission electron microscope with a sub-50-pm resolution

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

Akashi, Tetsuya; Takahashi, Yoshio; Tanigaki, Toshiaki, E-mail: toshiaki.tanigaki.mv@hitachi.com

2015-02-16

Atomic-resolution electromagnetic field observation is critical to the development of advanced materials and to the unveiling of their fundamental physics. For this purpose, a spherical-aberration corrected 1.2-MV cold field-emission transmission electron microscope has been developed. The microscope has the following superior properties: stabilized accelerating voltage, minimized electrical and mechanical fluctuation, and coherent electron emission. These properties have enabled to obtain 43-pm information transfer. On the bases of these performances, a 43-pm resolution has been obtained by correcting lens aberrations up to the third order. Observations of GaN [411] thin crystal showed a projected atomic locations with a separation of 44 pm.

Indentation-Enabled In Situ Mechanical Characterization of Micro/Nanopillars in Electron Microscopes

NASA Astrophysics Data System (ADS)

Guo, Qiang; Fu, Xidan; Guo, Xiaolei; Liu, Zhiying; Shi, Yan; Zhang, Di

2018-04-01

Indentation-enabled micro/nanomechanical characterization of small-scale specimens provides powerful new tools for probing materials properties that were once unattainable by conventional experimental methods. Recent advancement in instrumentation further allows mechanical testing to be carried out in situ in electron microscopes, with high spatial and temporal resolution. This review discusses the recent development of nanoindentation-enabled in situ mechanical testing in electron microscopes, with an emphasis on the study of micro/nanopillars. Focus is given to novel applications beyond simple compressive and tensile testing that have been developed in the past few years, and limitations and possible future research directions in this field are proposed and discussed.

[A comparative study on inducing non-homologous mesenchymal stem cells to differentiate into neural stem cells using non-homologous cerebrospinal fluid].

PubMed

Ren, Chao; Liu, Xiaoyun; Wan, Meirong; Geng, Deqin; Ge, Wei; Li, Jinmei; Zhang, Weiwei

2013-12-01

In order to set up a base for stem cells to be widely used in clinical medicine, we tried to optimize, in this study, the technique that induces human mesenchymal stem cells (hMSCs) to differentiate into neural stem cells by using cerebrospinal fluid (CSF) from the different groups. After the induction, presence of neural stem cells was confirmed with microscope observation, flow cytometry analysis, immunohistochemistry and fluorescent immunohistochemistry. At the same time, we also compared and analysed the data of the number of stem cells when it totally met the requirements for clinical treatment and the days required. At last, we confirmed that hMSCs could be induced to differentiate into neural stem cells, and that the number of cells totally met the requirements for clinical treatment. But there were some differences both in the number of cells and the days required. Among the groups, the group that marrow mesenchymal stem cells from patients own induced by CSF from healthy volunteers used the shortest time and the quantity of the cells was significantly higher than those of the others.

Spin microscope based on optically detected magnetic resonance

DOEpatents

Berman, Gennady P [Los Alamos, NM; Chernobrod, Boris M [Los Alamos, NM

2010-06-29

The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of unpaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

Spin microscope based on optically detected magnetic resonance

DOEpatents

Berman, Gennady P.; Chernobrod, Boris M.

2009-11-10

The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of impaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

Spin microscope based on optically detected magnetic resonance

DOEpatents

Berman, Gennady P.; Chernobrod, Boris M.

2007-12-11

The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of unpaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

Spin microscope based on optically detected magnetic resonance

DOEpatents

Berman, Gennady P [Los Alamos, NM; Chernobrod, Boris M [Los Alamos, NM

2010-07-13

The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of unpaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

Spin microscope based on optically detected magnetic resonance

DOEpatents

Berman, Gennady P [Los Alamos, NM; Chernobrod, Boris M [Los Alamos, NM

2009-10-27

The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of unpaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

Atomic force microscopic imaging of Acanthamoeba castellanii and Balamuthia mandrillaris trophozoites and cysts.

PubMed

Aqeel, Yousuf; Siddiqui, Ruqaiyyah; Ateeq, Muhammad; Raza Shah, Muhammad; Kulsoom, Huma; Khan, Naveed Ahmed

2015-01-01

Light microscopy and electron microscopy have been successfully used in the study of microbes, as well as free-living protists. Unlike light microscopy, which enables us to observe living organisms or the electron microscope which provides a two-dimensional image, atomic force microscopy provides a three-dimensional surface profile. Here, we observed two free-living amoebae, Acanthamoeba castellanii and Balamuthia mandrillaris under the phase contrast inverted microscope, transmission electron microscope and atomic force microscope. Although light microscopy was of lower magnification, it revealed functional biology of live amoebae such as motility and osmoregulation using contractile vacuoles of the trophozoite stage, but it is of limited value in defining the cyst stage. In contrast, transmission electron microscopy showed significantly greater magnification and resolution to reveal the ultra-structural features of trophozoites and cysts including intracellular organelles and cyst wall characteristics but it only produced a snapshot in time of a dead amoeba cell. Atomic force microscopy produced three-dimensional images providing detailed topographic description of shape and surface, phase imaging measuring boundary stiffness, and amplitude measurements including width, height and length of A. castellanii and B. mandrillaris trophozoites and cysts. These results demonstrate the importance of the application of various microscopic methods in the biological and structural characterization of the whole cell, ultra-structural features, as well as surface components and cytoskeleton of protist pathogens. © 2014 The Author(s) Journal of Eukaryotic Microbiology © 2014 International Society of Protistologists.

Direct Visualization of Local Electromagnetic Field Structures by Scanning Transmission Electron Microscopy.

PubMed

Shibata, Naoya; Findlay, Scott D; Matsumoto, Takao; Kohno, Yuji; Seki, Takehito; Sánchez-Santolino, Gabriel; Ikuhara, Yuichi

2017-07-18

The functional properties of materials and devices are critically determined by the electromagnetic field structures formed inside them, especially at nanointerface and surface regions, because such structures are strongly associated with the dynamics of electrons, holes and ions. To understand the fundamental origin of many exotic properties in modern materials and devices, it is essential to directly characterize local electromagnetic field structures at such defect regions, even down to atomic dimensions. In recent years, rapid progress in the development of high-speed area detectors for aberration-corrected scanning transmission electron microscopy (STEM) with sub-angstrom spatial resolution has opened new possibilities to directly image such electromagnetic field structures at very high-resolution. In this Account, we give an overview of our recent development of differential phase contrast (DPC) microscopy for aberration-corrected STEM and its application to many materials problems. In recent years, we have developed segmented-type STEM detectors which divide the detector plane into 16 segments and enable simultaneous imaging of 16 STEM images which are sensitive to the positions and angles of transmitted/scattered electrons on the detector plane. These detectors also have atomic-resolution imaging capability. Using these segmented-type STEM detectors, we show DPC STEM imaging to be a very powerful tool for directly imaging local electromagnetic field structures in materials and devices in real space. For example, DPC STEM can clearly visualize the local electric field variation due to the abrupt potential change across a p-n junction in a GaAs semiconductor, which cannot be observed by normal in-focus bright-field or annular type dark-field STEM imaging modes. DPC STEM is also very effective for imaging magnetic field structures in magnetic materials, such as magnetic domains and skyrmions. Moreover, real-time imaging of electromagnetic field structures can now be realized through very fast data acquisition, processing, and reconstruction algorithms. If we use DPC STEM for atomic-resolution imaging using a sub-angstrom size electron probe, it has been shown that we can directly observe the atomic electric field inside atoms within crystals and even inside single atoms, the field between the atomic nucleus and the surrounding electron cloud, which possesses information about the atomic species, local chemical bonding and charge redistribution between bonded atoms. This possibility may open an alternative way for directly visualizing atoms and nanostructures, that is, seeing atoms as an entity of electromagnetic fields that reflect the intra- and interatomic electronic structures. In this Account, the current status of aberration-corrected DPC STEM is highlighted, along with some applications in real material and device studies.

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.

Electron tube

DOEpatents

Suyama, Motohiro [Hamamatsu, JP; Fukasawa, Atsuhito [Hamamatsu, JP; Arisaka, Katsushi [Los Angeles, CA; Wang, Hanguo [North Hills, CA

2011-12-20

An electron tube of the present invention includes: a vacuum vessel including a face plate portion made of synthetic silica and having a surface on which a photoelectric surface is provided, a stem portion arranged facing the photoelectric surface and made of synthetic silica, and a side tube portion having one end connected to the face plate portion and the other end connected to the stem portion and made of synthetic silica; a projection portion arranged in the vacuum vessel, extending from the stem portion toward the photoelectric surface, and made of synthetic silica; and an electron detector arranged on the projection portion, for detecting electrons from the photoelectric surface, and made of silicon.

Scanning electron microscope view of iron crystal growing on pyroxene crystal

NASA Technical Reports Server (NTRS)

1972-01-01

A scanning electron microscope photograph of a four-micron size iron crystal growing on a pyroxene crystal (calcium-magnesium-iron silicate) from the Apollo 15 Hadley-Apennino lunar landing site. The well developed crystal faces indicate that the crystal was formed from a hot vapor as the rock was cooling.

Deciphering the physics and chemistry of perovskites with transmission electron microscopy.

PubMed

Polking, Mark J

2016-03-28

Perovskite oxides exhibit rich structural complexity and a broad range of functional properties, including ferroelectricity, ferromagnetism, and superconductivity. The development of aberration correction for the transmission electron microscope and concurrent progress in electron spectroscopy, electron holography, and other techniques has fueled rapid progress in the understanding of the physics and chemistry of these materials. New techniques based on the transmission electron microscope are first surveyed, and the applications of these techniques for the study of the structure, chemistry, electrostatics, and dynamics of perovskite oxides are then explored in detail, with a particular focus on ferroelectric materials.

Source brightness and useful beam current of carbon nanotubes and other very small emitters

NASA Astrophysics Data System (ADS)

Kruit, P.; Bezuijen, M.; Barth, J. E.

2006-01-01

The potential application of carbon nanotubes as electron sources in electron microscopes is analyzed. The resolution and probe current that can be obtained from a carbon nanotube emitter in a low-voltage scanning electron microscope are calculated and compared to the state of the art using Schottky electron sources. Many analytical equations for probe-size versus probe-current relations in different parameter regimes are obtained. It is shown that for most carbon nanotube emitters, the gun lens aberrations are larger than the emitters' virtual source size and thus restrict the microscope's performance. The result is that the advantages of the higher brightness of nanotube emitters are limited unless the angular emission current is increased over present day values or the gun lens aberrations are decreased. For some nanotubes with a closed cap, it is known that the emitted electron beam is coherent over the full emission cone. We argue that for such emitters the parameter ``brightness'' becomes meaningless. The influence of phase variations in the electron wave front emitted from such a nanotube emitter on the focusing of the electron beam is analyzed.

Transmission environmental scanning electron microscope with scintillation gaseous detection device.

PubMed

Danilatos, Gerasimos; Kollia, Mary; Dracopoulos, Vassileios

2015-03-01

A transmission environmental scanning electron microscope with use of a scintillation gaseous detection device has been implemented. This corresponds to a transmission scanning electron microscope but with addition of a gaseous environment acting both as environmental and detection medium. A commercial type of low vacuum machine has been employed together with appropriate modifications to the detection configuration. This involves controlled screening of various emitted signals in conjunction with a scintillation gaseous detection device already provided with the machine for regular surface imaging. Dark field and bright field imaging has been obtained along with other detection conditions. With a progressive series of modifications and tests, the theory and practice of a novel type of microscopy is briefly shown now ushering further significant improvements and developments in electron microscopy as a whole. Copyright © 2014 Elsevier B.V. All rights reserved.

Inhibitor of PI3K/Akt Signaling Pathway Small Molecule Promotes Motor Neuron Differentiation of Human Endometrial Stem Cells Cultured on Electrospun Biocomposite Polycaprolactone/Collagen Scaffolds.

PubMed

Ebrahimi-Barough, Somayeh; Hoveizi, Elham; Yazdankhah, Meysam; Ai, Jafar; Khakbiz, Mehrdad; Faghihi, Faezeh; Tajerian, Roksana; Bayat, Neda

2017-05-01

Small molecules as useful chemical tools can affect cell differentiation and even change cell fate. It is demonstrated that LY294002, a small molecule inhibitor of phosphatidylinositol 3-kinase (PI3K)/Akt signal pathway, can inhibit proliferation and promote neuronal differentiation of mesenchymal stem cells (MSCs). The purpose of this study was to investigate the differentiation effect of Ly294002 small molecule on the human endometrial stem cells (hEnSCs) into motor neuron-like cells on polycaprolactone (PCL)/collagen scaffolds. hEnSCs were cultured in a neurogenic inductive medium containing 1 μM LY294002 on the surface of PCL/collagen electrospun fibrous scaffolds. Cell attachment and viability of cells on scaffolds were characterized by scanning electron microscope (SEM) and 3-(4,5-dimethylthiazoyl-2-yl)2,5-diphenyltetrazolium bromide (MTT) assay. The expression of neuron-specific markers was assayed by real-time PCR and immunocytochemistry analysis after 15 days post induction. Results showed that attachment and differentiation of hEnSCs into motor neuron-like cells on the scaffolds with Ly294002 small molecule were higher than that of the cells on tissue culture plates as control group. In conclusion, PCL/collagen electrospun scaffolds with Ly294002 have potential for being used in neural tissue engineering because of its bioactive and three-dimensional structure which enhances viability and differentiation of hEnSCs into neurons through inhibition of the PI3K/Akt pathway. Thus, manipulation of this pathway by small molecules can enhance neural differentiation.

Physics and engineering aspects of cell and tissue imaging systems: microscopic devices and computer assisted diagnosis.

PubMed

Chen, Xiaodong; Ren, Liqiang; Zheng, Bin; Liu, Hong

2013-01-01

The conventional optical microscopes have been used widely in scientific research and in clinical practice. The modern digital microscopic devices combine the power of optical imaging and computerized analysis, archiving and communication techniques. It has a great potential in pathological examinations for improving the efficiency and accuracy of clinical diagnosis. This chapter reviews the basic optical principles of conventional microscopes, fluorescence microscopes and electron microscopes. The recent developments and future clinical applications of advanced digital microscopic imaging methods and computer assisted diagnosis schemes are also discussed.

Analysis of microscopic parameters of surface charging in polymer caused by defocused electron beam irradiation.

PubMed

Liu, Jing; Zhang, Hai-Bo

2014-12-01

The relationship between microscopic parameters and polymer charging caused by defocused electron beam irradiation is investigated using a dynamic scattering-transport model. The dynamic charging process of an irradiated polymer using a defocused 30 keV electron beam is conducted. In this study, the space charge distribution with a 30 keV non-penetrating e-beam is negative and supported by some existing experimental data. The internal potential is negative, but relatively high near the surface, and it decreases to a maximum negative value at z=6 μm and finally tend to 0 at the bottom of film. The leakage current and the surface potential behave similarly, and the secondary electron and leakage currents follow the charging equilibrium condition. The surface potential decreases with increasing beam current density, trap concentration, capture cross section, film thickness and electron-hole recombination rate, but with decreasing electron mobility and electron energy. The total charge density increases with increasing beam current density, trap concentration, capture cross section, film thickness and electron-hole recombination rate, but with decreasing electron mobility and electron energy. This study shows a comprehensive analysis of microscopic factors of surface charging characteristics in an electron-based surface microscopy and analysis. Copyright © 2014 Elsevier Ltd. All rights reserved.

Fully kinetic simulations of collisionless, mesothermal plasma emission: Macroscopic plume structure and microscopic electron characteristics

NASA Astrophysics Data System (ADS)

Hu, Yuan; Wang, Joseph

2017-03-01

This paper presents a fully kinetic particle particle-in-cell simulation study on the emission of a collisionless plasma plume consisting of cold beam ions and thermal electrons. Results are presented for both the two-dimensional macroscopic plume structure and the microscopic electron kinetic characteristics. We find that the macroscopic plume structure exhibits several distinctive regions, including an undisturbed core region, an electron cooling expansion region, and an electron isothermal expansion region. The properties of each region are determined by microscopic electron kinetic characteristics. The division between the undisturbed region and the cooling expansion region approximately matches the Mach line generated at the edge of the emission surface, and that between the cooling expansion region and the isothermal expansion region approximately matches the potential well established in the beam. The interactions between electrons and the potential well lead to a new, near-equilibrium state different from the initial distribution for the electrons in the isothermal expansion region. The electron kinetic characteristics in the plume are also very anisotropic. As the electron expansion process is mostly non-equilibrium and anisotropic, the commonly used assumption that the electrons in a collisionless, mesothermal plasma plume may be treated as a single equilibrium fluid in general is not valid.

Autologous Adipose-Derived Tissue Matrix Part I: Biologic Characteristics.

PubMed

Schendel, Stephen A

2017-10-01

Autologous collagen is an ideal soft tissue filler and may serve as a matrix for stem cell implantation and growth. Procurement of autologous collagen has been limited, though, secondary to a sufficient source. Liposuction is a widely performed and could be a source of autologous collagen. The amount of collagen and its composition in liposuctioned fat remains unknown. The purpose of this research was to characterize an adipose-derived tissue-based product created using ultrasonic cavitation and cryo-grinding. This study evaluated the cellular and protein composition of the final product. Fat was obtained from individuals undergoing routine liposuction and was processed by a 2 step process to obtain only the connective tissue. The tissue was then evaluated by scanning electronic microscope, Western blot analysis, and flow cytometry. Liposuctioned fat was obtained from 10 individuals with an average of 298 mL per subject. After processing an average of 1 mL of collagen matrix was obtained from each 100 mL of fat. Significant viable cell markers were present in descending order for adipocytes > CD90+ > CD105+ > CD45+ > CD19+ > CD144+ > CD34+. Western blot analysis showed collagen type II, III, IV, and other proteins. Scanning electronic microscope study showed a regular pattern of cross-linked, helical collagen. Additionally, vital staing demonstrated that the cells were still viable after processing. Collagen and cells can be easily obtained from liposuctioned fat by ultrasonic separation without alteration of the overall cellular composition of the tissue. Implantation results in new collagen and cellular growth. Collagen matrix with viable cells for autologous use can be obtained from liposuctioned fat and may provide long term results. 5. © 2017 The American Society for Aesthetic Plastic Surgery, Inc. Reprints and permission: journals.permissions@oup.com

Effects of shoot inversion on stem structure in Pharbitis nil

NASA Technical Reports Server (NTRS)

Prasad, T. K.; Sack, F. D.; Cline, M. G.

1988-01-01

The effects of shoot inversion on stem structure over 72 hr were investigated in Pharbitis nil by analyzing cell number, cell length, and the cross sectional areas of cells, tissues, and regions. An increase in stem diameter can be attributed to an increase in both cell number and cross sectional area of pith (primarily) and vascular tissue (secondarily). Qualitative observations of cell wall thickness in the light microscope did not reveal any significant effects of shoot inversion on this parameter. The inhibition of shoot elongation was accompanied by a significant decrease in cell length in the pith. The results are generally consistent with an ethylene effect on cell dimensions, especially in the pith.

Analysis with electron microscope of multielement samples using pure element standards

DOEpatents

King, Wayne E.

1987-01-01

A method and modified analytical electron microscope for determining the concentration of elements in a multielement sample by exposing samples with differing thicknesses for each element to a beam of electrons, simultaneously measuring the electron dosage and x-ray intensities for each sample of element to determine a "K.sub.AB " value to be used in the equation ##EQU1## where I is intensity and C is concentration for elements A and B, and exposing the multielement sample to determine the concentrations of the elements in the sample.

Characterization of Meteorites by Focused Ion Beam Sectioning: Recent Applications to CAIs and Primitive Meteorite Matrices

NASA Technical Reports Server (NTRS)

Christoffersen, Roy; Keller, Lindsay P.; Han, Jangmi; Rahman, Zia; Berger, Eve L.

2015-01-01

Focused ion beam (FIB) sectioning has revolutionized preparation of meteorite samples for characterization by analytical transmission electron microscopy (TEM) and other techniques. Although FIB is not "non-destructive" in the purest sense, each extracted section amounts to no more than nanograms (approximately 500 cubic microns) removed intact from locations precisely controlled by SEM imaging and analysis. Physical alteration of surrounding material by ion damage, fracture or sputter contamination effects is localized to within a few micrometers around the lift-out point. This leaves adjacent material intact for coordinate geochemical analysis by SIMS, microdrill extraction/TIMS and other techniques. After lift out, FIB sections can be quantitatively analyzed by electron microprobe prior to final thinning, synchrotron x-ray techniques, and by the full range of state-of-the-art analytical field-emission scanning transmission electron microscope (FE-STEM) techniques once thinning is complete. Multiple meteorite studies supported by FIB/FE-STEM are currently underway at NASA-JSC, including coordinated analysis of refractory phase assemblages in CAIs and fine-grained matrices in carbonaceous chondrites. FIB sectioning of CAIs has uncovered epitaxial and other overgrowth relations between corundum-hibonite-spinel consistent with hibonite preceding corundum and/or spinel in non-equilibrium condensation sequences at combinations of higher gas pressures, dust-gas enrichments or significant nebular transport. For all of these cases, the ability of FIB to allow for coordination with spatially-associated isotopic data by SIMS provides immense value for constraining the formation scenarios of the particular CAI assemblage. For carbonaceous chondrites matrix material, FIB has allowed us to obtain intact continuous sections of the immediate outer surface of Murchison (CM2) after it has been experimentally ion processed to simulate solar wind space weathering. The surface amorphization and loss of OH produced by the irradiation provides important clues regarding space weathering on primitive asteroids such as the OSIRIS-Rex target 101955 Bennu.

Experimental Investigation of Space Radiation Processing in Lunar Soil Ilmenite: Combining Perspectives from Surface Science and Transmission Electron Microscopy

NASA Technical Reports Server (NTRS)

Christoffersen, R.; Keller, L. P.; Rahman, Z.; Baragiola, R.

2010-01-01

Energetic ions mostly from the solar wind play a major role in lunar space weathering because they contribute structural and chemical changes to the space-exposed surfaces of lunar regolith grains. In mature mare soils, ilmenite (FeTiO3) grains in the finest size fraction have been shown in transmission electron microscope (TEM) studies to exhibit key differences in their response to space radiation processing relative to silicates [1,2,3]. In ilmenite, solar ion radiation alters host grain outer margins to produce 10-100 nm thick layers that are microstructurally complex, but dominantly crystalline compared to the amorphous radiation-processed rims on silicates [1,2,3]. Spatially well-resolved analytical TEM measurements also show nm-scale compositional and chemical state changes in these layers [1,3]. These include shifts in Fe/Ti ratio from strong surface Fe-enrichment (Fe/Ti >> 1), to Fe depletion (Fe/Ti < 1) at 40-50 nm below the grain surface [1,3]. These compositional changes are not observed in the radiation-processed rims on silicates [4]. Several mechanism(s) to explain the overall relations in the ilmenite grain rims by radiation processing and/or additional space weathering processes were proposed by [1], and remain under current consideration [3]. A key issue has concerned the ability of ion radiation processing alone to produce some of the deeper- penetrating compositional changes. In order to provide some experimental constraints on these questions, we have performed a combined X-ray photoelectron spectroscopy (XPS) and field-emission scanning transmission electron (FE-STEM) study of experimentally ion-irradiated ilmenite. A key feature of this work is the combination of analytical techniques sensitive to changes in the irradiated samples at depth scales going from the immediate surface (approx.5 nm; XPS), to deeper in the grain interior (5-100 nm; FE-STEM).

Rapid and precise scanning helium ion microscope milling of solid-state nanopores for biomolecule detection.

PubMed

Yang, Jijin; Ferranti, David C; Stern, Lewis A; Sanford, Colin A; Huang, Jason; Ren, Zheng; Qin, Lu-Chang; Hall, Adam R

2011-07-15

We report the formation of solid-state nanopores using a scanning helium ion microscope. The fabrication process offers the advantage of high sample throughput along with fine control over nanopore dimensions, producing single pores with diameters below 4 nm. Electronic noise associated with ion transport through the resultant pores is found to be comparable with levels measured on devices made with the established technique of transmission electron microscope milling. We demonstrate the utility of our nanopores for biomolecular analysis by measuring the passage of double-strand DNA.

Intrinsic instability of aberration-corrected electron microscopes.

PubMed

Schramm, S M; van der Molen, S J; Tromp, R M

2012-10-19

Aberration-corrected microscopes with subatomic resolution will impact broad areas of science and technology. However, the experimentally observed lifetime of the corrected state is just a few minutes. Here we show that the corrected state is intrinsically unstable; the higher its quality, the more unstable it is. Analyzing the contrast transfer function near optimum correction, we define an "instability budget" which allows a rational trade-off between resolution and stability. Unless control systems are developed to overcome these challenges, intrinsic instability poses a fundamental limit to the resolution practically achievable in the electron microscope.

In situ nanomechanical testing of twinned metals in a transmission electron microscope

DOE PAGES

Li, Nan; Wang, Jiangwei; Mao, Scott; ...

2016-04-01

This paper focuses on in situ transmission electron microscope (TEM) characterization to explore twins in face-centered-cubic and body-centered-cubic monolithic metals, and their impact on the overall mechanical performance. Taking advantage of simultaneous nanomechanical deformation and nanoscale imaging using versatile in situ TEM tools, direct correlation of these unique microscopic defects with macroscopic mechanical performance becomes possible. This article summarizes recent evidence to support the mechanisms related to strengthening and plasticity in metals, including nanotwinned Cu, Ni, Al, Au, and others in bulk, thin film, and nanowire forms.

In situ nanomechanical testing of twinned metals in a transmission electron microscope

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

Li, Nan; Wang, Jiangwei; Mao, Scott

This paper focuses on in situ transmission electron microscope (TEM) characterization to explore twins in face-centered-cubic and body-centered-cubic monolithic metals, and their impact on the overall mechanical performance. Taking advantage of simultaneous nanomechanical deformation and nanoscale imaging using versatile in situ TEM tools, direct correlation of these unique microscopic defects with macroscopic mechanical performance becomes possible. This article summarizes recent evidence to support the mechanisms related to strengthening and plasticity in metals, including nanotwinned Cu, Ni, Al, Au, and others in bulk, thin film, and nanowire forms.

Thermophysical ESEM and TEM Characterization of Carbon Fibers CTE, Spectroscopy and Roughness Studies at High Temperatures

NASA Technical Reports Server (NTRS)

Ochoa, Ozden O.

2004-01-01

Accurate determination of the transverse properties of carbon fibers is important for assessment and prediction of local material as well as global structural response of composite components. However the measurements are extremely difficult due to the very small diameters of the fibers (few microns only) and must be conducted within a microscope. In this work, environmental scanning electron microscope (ESEM) and transmission electron microscope (TEM) are used to determine the transverse coefficient of thermal expansion of different carbon fibers as a function of temperature.

High-performance imaging of stem cells using single-photon emissions

NASA Astrophysics Data System (ADS)

Wagenaar, Douglas J.; Moats, Rex A.; Hartsough, Neal E.; Meier, Dirk; Hugg, James W.; Yang, Tang; Gazit, Dan; Pelled, Gadi; Patt, Bradley E.

2011-10-01

Radiolabeled cells have been imaged for decades in the field of autoradiography. Recent advances in detector and microelectronics technologies have enabled the new field of "digital autoradiography" which remains limited to ex vivo specimens of thin tissue slices. The 3D field-of-view (FOV) of single cell imaging can be extended to millimeters if the low energy (10-30 keV) photon emissions of radionuclides are used for single-photon nuclear imaging. This new microscope uses a coded aperture foil made of highly attenuating elements such as gold or platinum to form the image as a kind of "lens". The detectors used for single-photon emission microscopy are typically silicon detectors with a pixel pitch less than 60 μm. The goal of this work is to image radiolabeled mesenchymal stem cells in vivo in an animal model of tendon repair processes. Single-photon nuclear imaging is an attractive modality for translational medicine since the labeled cells can be imaged simultaneously with the reparative processes by using the dual-isotope imaging technique. The details our microscope's two-layer gold aperture and the operation of the energy-dispersive, pixellated silicon detector are presented along with the first demonstration of energy discrimination with a 57Co source. Cell labeling techniques have been augmented by genetic engineering with the sodium-iodide symporter, a type of reporter gene imaging method that enables in vivo uptake of free 99mTc or an iodine isotope at a time point days or weeks after the insertion of the genetically modified stem cells into the animal model. This microscopy work in animal research may expand to the imaging of reporter-enabled stem cells simultaneously with the expected biological repair process in human clinical trials of stem cell therapies.

Electron beam dynamics in an ultrafast transmission electron microscope with Wehnelt electrode.

PubMed

Bücker, K; Picher, M; Crégut, O; LaGrange, T; Reed, B W; Park, S T; Masiel, D J; Banhart, F

2016-12-01

High temporal resolution transmission electron microscopy techniques have shown significant progress in recent years. Using photoelectron pulses induced by ultrashort laser pulses on the cathode, these methods can probe ultrafast materials processes and have revealed numerous dynamic phenomena at the nanoscale. Most recently, the technique has been implemented in standard thermionic electron microscopes that provide a flexible platform for studying material's dynamics over a wide range of spatial and temporal scales. In this study, the electron pulses in such an ultrafast transmission electron microscope are characterized in detail. The microscope is based on a thermionic gun with a Wehnelt electrode and is operated in a stroboscopic photoelectron mode. It is shown that the Wehnelt bias has a decisive influence on the temporal and energy spread of the picosecond electron pulses. Depending on the shape of the cathode and the cathode-Wehnelt distance, different emission patterns with different pulse parameters are obtained. The energy spread of the pulses is determined by space charge and Boersch effects, given by the number of electrons in a pulse. However, filtering effects due to the chromatic aberrations of the Wehnelt electrode allow the extraction of pulses with narrow energy spreads. The temporal spread is governed by electron trajectories of different length and in different electrostatic potentials. High temporal resolution is obtained by excluding shank emission from the cathode and aberration-induced halos in the emission pattern. By varying the cathode-Wehnelt gap, the Wehnelt bias, and the number of photoelectrons in a pulse, tradeoffs between energy and temporal resolution as well as beam intensity can be made as needed for experiments. Based on the characterization of the electron pulses, the optimal conditions for the operation of ultrafast TEMs with thermionic gun assembly are elaborated. Copyright © 2016 Elsevier B.V. All rights reserved.

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

Lu, Ping

Controlling metallic nanoparticle (NP) interactions plays a vital role in the development of new joining techniques (nanosolder) that bond at lower processing temperatures but remain viable at higher temperatures. The pr imary objective of this project is t o develop a fundamental understanding of the actual reaction processes, associated atomic mechanisms, and the resulting microstructure that occur during thermally - driven bond formation concerning metal - metal nano - scale (%3C50nm) interfaces. In this LDRD pr oject, we have studied metallic NPs interaction at the elevated temperatures by combining in - situ transmission electron microscopy (TEM ) using an aberrationmore » - corrected scanning transmission electron microscope (AC - STEM) and atomic - scale modeling such as m olecular dynamic (MD) simulations. Various metallic NPs such as Ag, Cu and Au are synthesized by chemical routines. Numerous in - situ e xperiments were carried out with focus of the research on study of Ag - Cu system. For the first time, using in - situ STEM he ating experiments , we directly observed t he formation of a 3 - dimensional (3 - D) epitaxial Cu - Ag core - shell nanoparticle during the thermal interaction of Cu and Ag NPs at elevated temperatures (150 - 300 o C). The reaction takes place at temperatures as low as 150 o C and was only observed when care was taken to circumvent the effects of electron beam irradiation during STEM imaging. Atomic - scale modeling verified that the Cu - Ag core - shell structure is energetically favored, and indicated that this phenomenon is a nano - scale effect related to the large surface - to - volume ratio of the NPs. The observation potentially can be used for developing new nanosolder technology that uses Ag shell as the "glue" that stic ks the particles of Cu together. The LDRD has led to several journal publications and numerous conference presentations, and a TA. In addition, we have developed new TEM characterization techniques and phase - field modeling tools that can be used for future materials research at Sandia. Acknowledgeme nts This work was supported by the Laboratory Directed Research and Development (LDRD) program of Sandia National Laboratories. Sandia National Laboratories is a multi - program laboratory managed and operated by Sandia Corporation, a wholly owned subsidia ry of Lockheed Martin Corporation, for the US Department of Energy's National Nuclear Security Administration under contract DE - AC04 - 94AL85000.« less

Spatially-correlated Site Occupancy in the Nonstoichiometric Meta-stable ε -Al 60Sm 11 Phase during Devitrification of Al-10.2 at.% Sm Glasses

DOE PAGES

Yang, Lin; Zhang, Feng; Meng, Fan -Qiang; ...

2018-05-12

A metastable ε-Al 60Sm 11 phase appears during the initial devitrification of as-quenched Al-10.2 at.% Sm glasses. The ε phase is nonstoichiometric in nature since Al occupation is observed on the 16 f Sm lattice sites. Scanning transmission electron microscopic images reveal profound spatial correlation of Sm content on these sites, which cannot be explained by the “average crystal” description from Rietveld analysis of diffraction data. Thermodynamically favorable configurations, established by Monte Carlo (MC) simulations based on a cluster-expansion model, also give qualitatively different correlation functions from experimental observations. On the other hand, molecular dynamics simulations of the growth ofmore » ε-Al 60Sm 11 in undercooled liquid show that when the diffusion range of Sm is limited to ~4 Å, the correlation function of the as-grown crystal structure agrees well with that of the scanning transmission electronic microscopy (STEM) images. Furthermore, our results show that kinetic effects, especially the limited diffusivity of Sm atoms plays the fundamental role in determining the nonstoichiometric site occupancies of the ε-Al 60Sm 11 phase during the crystallization process.« less

Spatially-correlated Site Occupancy in the Nonstoichiometric Meta-stable ε -Al 60Sm 11 Phase during Devitrification of Al-10.2 at.% Sm Glasses

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

Yang, Lin; Zhang, Feng; Meng, Fan -Qiang

A metastable ε-Al 60Sm 11 phase appears during the initial devitrification of as-quenched Al-10.2 at.% Sm glasses. The ε phase is nonstoichiometric in nature since Al occupation is observed on the 16 f Sm lattice sites. Scanning transmission electron microscopic images reveal profound spatial correlation of Sm content on these sites, which cannot be explained by the “average crystal” description from Rietveld analysis of diffraction data. Thermodynamically favorable configurations, established by Monte Carlo (MC) simulations based on a cluster-expansion model, also give qualitatively different correlation functions from experimental observations. On the other hand, molecular dynamics simulations of the growth ofmore » ε-Al 60Sm 11 in undercooled liquid show that when the diffusion range of Sm is limited to ~4 Å, the correlation function of the as-grown crystal structure agrees well with that of the scanning transmission electronic microscopy (STEM) images. Furthermore, our results show that kinetic effects, especially the limited diffusivity of Sm atoms plays the fundamental role in determining the nonstoichiometric site occupancies of the ε-Al 60Sm 11 phase during the crystallization process.« less

Applying shot boundary detection for automated crystal growth analysis during in situ transmission electron microscope experiments

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

Moeglein, W. A.; Griswold, R.; Mehdi, B. L.

In-situ (scanning) transmission electron microscopy (S/TEM) is being developed for numerous applications in the study of nucleation and growth under electrochemical driving forces. For this type of experiment, one of the key parameters is to identify when nucleation initiates. Typically the process of identifying the moment that crystals begin to form is a manual process requiring the user to perform an observation and respond accordingly (adjust focus, magnification, translate the stage etc.). However, as the speed of the cameras being used to perform these observations increases, the ability of a user to “catch” the important initial stage of nucleation decreasesmore » (there is more information that is available in the first few milliseconds of the process). Here we show that video shot boundary detection (SBD) can automatically detect frames where a change in the image occurs. We show that this method can be applied to quickly and accurately identify points of change during crystal growth. This technique allows for automated segmentation of a digital stream for further analysis and the assignment of arbitrary time stamps for the initiation of processes that are independent of the user’s ability to observe and react.« less

Head sensory organs of Dactylopodola baltica (Macrodasyida, Gastrotricha): a combination of transmission electron microscopical and immunocytochemical techniques.

PubMed

Liesenjohann, Thilo; Neuhaus, Birger; Schmidt-Rhaesa, Andreas

2006-08-01

The anterior and posterior head sensory organs of Dactylopodola baltica (Macrodasyida, Gastrotricha) were investigated by transmission electron microscopy (TEM). In addition, whole individuals were labeled with phalloidin to mark F-actin and with anti-alpha-tubulin antibodies to mark microtubuli and studied with confocal laser scanning microscopy. Immunocytochemistry reveals that the large number of ciliary processes in the anterior head sensory organ contain F-actin; no signal could be detected for alpha-tubulin. Labeling with anti-alpha-tubulin antibodies revealed that the anterior and posterior head sensory organs are innervated by a common stem of nerves from the lateral nerve cords just anterior of the dorsal brain commissure. TEM studies showed that the anterior head sensory organ is composed of one sheath cell and one sensory cell with a single branching cilium that possesses a basal inflated part and regularly arranged ciliary processes. Each ciliary process contains one central microtubule. The posterior head sensory organ consists of at least one pigmented sheath cell and several probably monociliary sensory cells. Each cilium branches into irregularly arranged ciliary processes. These characters are assumed to belong to the ground pattern of the Gastrotricha. Copyright 2006 Wiley-Liss, Inc.

Local band gap measurements by VEELS of thin film solar cells.

PubMed

Keller, Debora; Buecheler, Stephan; Reinhard, Patrick; Pianezzi, Fabian; Pohl, Darius; Surrey, Alexander; Rellinghaus, Bernd; Erni, Rolf; Tiwari, Ayodhya N

2014-08-01

This work presents a systematic study that evaluates the feasibility and reliability of local band gap measurements of Cu(In,Ga)Se2 thin films by valence electron energy-loss spectroscopy (VEELS). The compositional gradients across the Cu(In,Ga)Se2 layer cause variations in the band gap energy, which are experimentally determined using a monochromated scanning transmission electron microscope (STEM). The results reveal the expected band gap variation across the Cu(In,Ga)Se2 layer and therefore confirm the feasibility of local band gap measurements of Cu(In,Ga)Se2 by VEELS. The precision and accuracy of the results are discussed based on the analysis of individual error sources, which leads to the conclusion that the precision of our measurements is most limited by the acquisition reproducibility, if the signal-to-noise ratio of the spectrum is high enough. Furthermore, we simulate the impact of radiation losses on the measured band gap value and propose a thickness-dependent correction. In future work, localized band gap variations will be measured on a more localized length scale to investigate, e.g., the influence of chemical inhomogeneities and dopant accumulations at grain boundaries.

Negotiating the Inclusion of Nanoscience Content and Technology in Science Curriculum: An Examination of Secondary Teachers' Thinking in a Professional Development Project

NASA Astrophysics Data System (ADS)

Wells, Jennifer Gayle

The Next Generation Science Standards represent a significant challenge for K--12 school reform in the United States in the science, technology, engineering and mathematics (STEM) disciplines (NSTA, 2012). One important difference between the National Science Education Standards (NRC, 1996) and the Next Generation Science Standards (Achieve, 2013) is the more extensive inclusion of nanoscale science and technology. Teacher PD is a key vehicle for implementing this STEM education reform effort (NRC, 2012; Smith, 2001). The context of this dissertation study is Project Nanoscience and Nanotechnology Outreach (NANO), a secondary level professional development program for teachers that provides a summer workshop, academic year coaching and the opportunity for teacher participants to borrow a table-top Phenom scanning electron microscope and a research grade optical microscope for use in their classrooms. This designed-based descriptive case study examined the thinking of secondary teachers in the 2012 Project NANO cohort as they negotiated the inclusion of novel science concepts and technology into secondary science curriculum. Teachers in the Project NANO 2012 summer workshop developed a two-week, inquiry-based unit of instruction drawing upon one or more of nine big ideas in nanoscale science and technology as defined by Stevens, Sutherland, and Krajcik (2011). This research examined teacher participants' metastrategic thinking (Zohar, 2006) which they used to inform their pedagogical content knowledge (Shulman, 1987) by focusing on the content knowledge teachers chose to frame their lessons, their rationales for such choices as well as the teaching strategies that they chose to employ in their Project NANO unit of instruction. The study documents teachers various entry points on a learning progression as teachers negotiated the inclusion of nanoscale science and technology into the curriculum for the first time. Implications and recommendations for teacher professional development are offered.

Dose-rate-dependent damage of cerium dioxide in the scanning transmission electron microscope.

PubMed

Johnston-Peck, Aaron C; DuChene, Joseph S; Roberts, Alan D; Wei, Wei David; Herzing, Andrew A

2016-11-01

Beam damage caused by energetic electrons in the transmission electron microscope is a fundamental constraint limiting the collection of artifact-free information. Through understanding the influence of the electron beam, experimental routines may be adjusted to improve the data collection process. Investigations of CeO 2 indicate that there is not a critical dose required for the accumulation of electron beam damage. Instead, measurements using annular dark field scanning transmission electron microscopy and electron energy loss spectroscopy demonstrate that the onset of measurable damage occurs when a critical dose rate is exceeded. The mechanism behind this phenomenon is that oxygen vacancies created by exposure to a 300keV electron beam are actively annihilated as the sample re-oxidizes in the microscope environment. As a result, only when the rate of vacancy creation exceeds the recovery rate will beam damage begin to accumulate. This observation suggests that dose-intensive experiments can be accomplished without disrupting the native structure of the sample when executed using dose rates below the appropriate threshold. Furthermore, the presence of an encapsulating carbonaceous layer inhibits processes that cause beam damage, markedly increasing the dose rate threshold for the accumulation of damage. Published by Elsevier B.V.

Dose-rate-dependent damage of cerium dioxide in the scanning transmission electron microscope

PubMed Central

Johnston-Peck, Aaron C.; DuChene, Joseph S.; Roberts, Alan D.; Wei, Wei David; Herzing, Andrew A.

2016-01-01

Beam damage caused by energetic electrons in the transmission electron microscope is a fundamental constraint limiting the collection of artifact-free information. Through understanding the influence of the electron beam, experimental routines may be adjusted to improve the data collection process. Investigations of CeO2 indicate that there is not a critical dose required for the accumulation of electron beam damage. Instead, measurements using annular dark field scanning transmission electron microscopy and electron energy loss spectroscopy demonstrate that the onset of measurable damage occurs when a critical dose rate is exceeded. The mechanism behind this phenomenon is that oxygen vacancies created by exposure to a 300 keV electron beam are actively annihilated as the sample re-oxidizes in the microscope environment. As a result, only when the rate of vacancy creation exceeds the recovery rate will beam damage begin to accumulate. This observation suggests that dose-intensive experiments can be accomplished without disrupting the native structure of the sample when executed using dose rates below the appropriate threshold. Furthermore, the presence of an encapsulating carbonaceous layer inhibits processes that cause beam damage, markedly increasing the dose rate threshold for the accumulation of damage. PMID:27469265

Qualitative and quantitative interpretation of SEM image using digital image processing.

PubMed

Saladra, Dawid; Kopernik, Magdalena

2016-10-01

The aim of the this study is improvement of qualitative and quantitative analysis of scanning electron microscope micrographs by development of computer program, which enables automatic crack analysis of scanning electron microscopy (SEM) micrographs. Micromechanical tests of pneumatic ventricular assist devices result in a large number of micrographs. Therefore, the analysis must be automatic. Tests for athrombogenic titanium nitride/gold coatings deposited on polymeric substrates (Bionate II) are performed. These tests include microshear, microtension and fatigue analysis. Anisotropic surface defects observed in the SEM micrographs require support for qualitative and quantitative interpretation. Improvement of qualitative analysis of scanning electron microscope images was achieved by a set of computational tools that includes binarization, simplified expanding, expanding, simple image statistic thresholding, the filters Laplacian 1, and Laplacian 2, Otsu and reverse binarization. Several modifications of the known image processing techniques and combinations of the selected image processing techniques were applied. The introduced quantitative analysis of digital scanning electron microscope images enables computation of stereological parameters such as area, crack angle, crack length, and total crack length per unit area. This study also compares the functionality of the developed computer program of digital image processing with existing applications. The described pre- and postprocessing may be helpful in scanning electron microscopy and transmission electron microscopy surface investigations. © 2016 The Authors Journal of Microscopy © 2016 Royal Microscopical Society.

[Microscopic investigation of vessel wall after endovascular catheter atherectomy].

PubMed

Tsygankov, V N; Khovalkin, R G; Chekmareva, I A; Kalinin, D V; Filippova, E M

2014-01-01

Endovascular target catheter atherectomy (ETCA) - method of artery patency allowing to obtain occlusion substrate. Given the high destructive effect of atherectome's elements on tissue the objective was determination possibility of histological and electron microscopic investigation of this substrate after atherectomy. The research included 8 patients who underwent ETCA of legs arteries. It was observed substrate removal from broken stent in 1 case. 2 of 8 patients had diabetes. Obtained substrate was available for histological and electron microscopic investigation. Atherosclerosis was confirmed in all cases. It was not observed substrate significant morphological changes in patients with presence or absence of diabetes. Microscopic investigation of substrate from broken stent shows pronounced development of granulation tissue that was regarded as special form of reparative regeneration. Finding internal elastic membrane during microscopic investigation in some cases proves radical intervention. The authors consider that microscopic investigation of substrate after ETCA may be used for diagnosis verification, thorough analysis of morphological changes in lesion area and radicalism of atherectomy.

In Situ Microstructural Control and Mechanical Testing Inside the Transmission Electron Microscope at Elevated Temperatures

NASA Astrophysics Data System (ADS)

Wang, Baoming; Haque, M. A.

2015-08-01

With atomic-scale imaging and analytical capabilities such as electron diffraction and energy-loss spectroscopy, the transmission electron microscope has allowed access to the internal microstructure of materials like no other microscopy. It has been mostly a passive or post-mortem analysis tool, but that trend is changing with in situ straining, heating and electrical biasing. In this study, we design and demonstrate a multi-functional microchip that integrates actuators, sensors, heaters and electrodes with freestanding electron transparent specimens. In addition to mechanical testing at elevated temperatures, the chip can actively control microstructures (grain growth and phase change) of the specimen material. Using nano-crystalline aluminum, nickel and zirconium as specimen materials, we demonstrate these novel capabilities inside the microscope. Our approach of active microstructural control and quantitative testing with real-time visualization can influence mechanistic modeling by providing direct and accurate evidence of the fundamental mechanisms behind materials behavior.

Isotope analysis in the transmission electron microscope.

PubMed

Susi, Toma; Hofer, Christoph; Argentero, Giacomo; Leuthner, Gregor T; Pennycook, Timothy J; Mangler, Clemens; Meyer, Jannik C; Kotakoski, Jani

2016-10-10

The Ångström-sized probe of the scanning transmission electron microscope can visualize and collect spectra from single atoms. This can unambiguously resolve the chemical structure of materials, but not their isotopic composition. Here we differentiate between two isotopes of the same element by quantifying how likely the energetic imaging electrons are to eject atoms. First, we measure the displacement probability in graphene grown from either 12 C or 13 C and describe the process using a quantum mechanical model of lattice vibrations coupled with density functional theory simulations. We then test our spatial resolution in a mixed sample by ejecting individual atoms from nanoscale areas spanning an interface region that is far from atomically sharp, mapping the isotope concentration with a precision better than 20%. Although we use a scanning instrument, our method may be applicable to any atomic resolution transmission electron microscope and to other low-dimensional materials.

Microscopic investigation of cavitation erosion damage in metals

NASA Technical Reports Server (NTRS)

Hackworh, J. V.; Adler, W. F.

1974-01-01

The results of research to identify the cavitation erosion damage mechanisms at the microscopic level for three metals (aluminum, stainless steel, and titanium) representing a range of properties and microstructure are presented. The metals were exposed to cavitation generated in distilled water by a 20-kHz ultrasonic facility operating at a vibration amplitude of 2 mils. Representative properties of the metals and experimental details are summarized. Replicas of the eroded surfaces of the specimens obtained periodically during exposure were examined with a transmission electron microscope to follow progression of the erosion damage and identify dominant erosion mechanisms as a function of exposure time. Eroded surfaces of selected specimens were also examined with a scanning electron microscope to assist in the interpretation.

Threshold-like complexation of conjugated polymers with small molecule acceptors in solution within the neighbor-effect model.

PubMed

Sosorev, Andrey Yu; Parashchuk, Olga D; Zapunidi, Sergey A; Kashtanov, Grigoriy S; Golovnin, Ilya V; Kommanaboyina, Srikanth; Perepichka, Igor F; Paraschuk, Dmitry Yu

2016-02-14

In some donor-acceptor blends based on conjugated polymers, a pronounced charge-transfer complex (CTC) forms in the electronic ground state. In contrast to small-molecule donor-acceptor blends, the CTC concentration in polymer:acceptor solution can increase with the acceptor content in a threshold-like way. This threshold-like behavior was earlier attributed to the neighbor effect (NE) in the polymer complexation, i.e., next CTCs are preferentially formed near the existing ones; however, the NE origin is unknown. To address the factors affecting the NE, we record the optical absorption data for blends of the most studied conjugated polymers, poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) and poly(3-hexylthiophene) (P3HT), with electron acceptors of fluorene series, 1,8-dinitro-9,10-antraquinone (), and 7,7,8,8-tetracyanoquinodimethane () in different solvents, and then analyze the data within the NE model. We have found that the NE depends on the polymer and acceptor molecular skeletons and solvent, while it does not depend on the acceptor electron affinity and polymer concentration. We conclude that the NE operates within a single macromolecule and stems from planarization of the polymer chain involved in the CTC with an acceptor molecule; as a result, the probability of further complexation with the next acceptor molecules at the adjacent repeat units increases. The steric and electronic microscopic mechanisms of NE are discussed.

Method and apparatus for a high-resolution three dimensional confocal scanning transmission electron microscope

DOEpatents

de Jonge, Niels [Oak Ridge, TN

2010-08-17

A confocal scanning transmission electron microscope which includes an electron illumination device providing an incident electron beam propagating in a direction defining a propagation axis, and a precision specimen scanning stage positioned along the propagation axis and movable in at least one direction transverse to the propagation axis. The precision specimen scanning stage is configured for positioning a specimen relative to the incident electron beam. A projector lens receives a transmitted electron beam transmitted through at least part of the specimen and focuses this transmitted beam onto an image plane, where the transmitted beam results from the specimen being illuminated by the incident electron beam. A detection system is placed approximately in the image plane.

Electron microscope phase enhancement

DOEpatents

Jin, Jian; Glaeser, Robert M.

2010-06-15

A microfabricated electron phase shift element is used for modifying the phase characteristics of an electron beam passing though its center aperture, while not affecting the more divergent portion of an incident beam to selectively provide a ninety-degree phase shift to the unscattered beam in the back focal plan of the objective lens, in order to realize Zernike-type, in-focus phase contrast in an electron microscope. One application of the element is to increase the contrast of an electron microscope for viewing weakly scattering samples while in focus. Typical weakly scattering samples include biological samples such as macromolecules, or perhaps cells. Preliminary experimental images demonstrate that these devices do apply a ninety degree phase shift as expected. Electrostatic calculations have been used to determine that fringing fields in the region of the scattered electron beams will cause a negligible phase shift as long as the ratio of electrode length to the transverse feature-size aperture is about 5:1. Calculations are underway to determine the feasibility of aspect smaller aspect ratios of about 3:1 and about 2:1.

Exploring Growth (and Mitosis) through a Learning Cycle.

ERIC Educational Resources Information Center

Lawson, Anton E.

1991-01-01

Presents a learning cycle lesson plan in which students investigate the question of how cells divide. Students use microscopes to explore actual plant root and stem tissues to generate and test hypotheses to answer the question. Includes teacher material, student material, and teaching tips. (MDH)

Mixture of learners for cancer stem cell detection using CD13 and H and E stained images

NASA Astrophysics Data System (ADS)

Oǧuz, Oǧuzhan; Akbaş, Cem Emre; Mallah, Maen; Taşdemir, Kasım.; Akhan Güzelcan, Ece; Muenzenmayer, Christian; Wittenberg, Thomas; Üner, Ayşegül; Cetin, A. E.; ćetin Atalay, Rengül

2016-03-01

In this article, algorithms for cancer stem cell (CSC) detection in liver cancer tissue images are developed. Conventionally, a pathologist examines of cancer cell morphologies under microscope. Computer aided diagnosis systems (CAD) aims to help pathologists in this tedious and repetitive work. The first algorithm locates CSCs in CD13 stained liver tissue images. The method has also an online learning algorithm to improve the accuracy of detection. The second family of algorithms classify the cancer tissues stained with H and E which is clinically routine and cost effective than immunohistochemistry (IHC) procedure. The algorithms utilize 1D-SIFT and Eigen-analysis based feature sets as descriptors. Normal and cancerous tissues can be classified with 92.1% accuracy in H and E stained images. Classification accuracy of low and high-grade cancerous tissue images is 70.4%. Therefore, this study paves the way for diagnosing the cancerous tissue and grading the level of it using H and E stained microscopic tissue images.

Mars Life? - Microscopic Structures

NASA Image and Video Library

1996-08-09

In the center of this electron microscope image of a small chip from a meteorite are several tiny structures that are possible microscopic fossils of primitive, bacteria-like organisms that may have lived on Mars more than 3.6 billion years ago. http://photojournal.jpl.nasa.gov/catalog/PIA00283

Anatomical investigations on root, stem, and leaf of Gentiana olivieri Griseb

PubMed Central

Tüzün, Canan Yağci; Toker, Mehmet Cihat; Toker, Gülnur

2011-01-01

Background: Gentiana olivieri Griseb. (Afat) (Gentianaceae), which has many bioactive compounds is used as antidiabetic, hepatoprotective, digestive aid, antidepressant, and antianemic in traditional medicine. Materials and Methods: Root, stem, and leaf sections of G. olivieri were taken free hand or by sliding microtome and examined on light microscope. Results: Anatomical characters of the species were observed to be similar to the usual features of Gentianaceae anatomy. Conclusion: Intraxylary phloem, which was primarily the distinguishing feature between Gentianoideae and Menyanthoideae sub-families was observed in G. olivieri roots. PMID:21472072

Concurrent in situ ion irradiation transmission electron microscope

DOE PAGES

Hattar, K.; Bufford, D. C.; Buller, D. L.

2014-08-29

An in situ ion irradiation transmission electron microscope has been developed and is operational at Sandia National Laboratories. This facility permits high spatial resolution, real time observation of electron transparent samples under ion irradiation, implantation, mechanical loading, corrosive environments, and combinations thereof. This includes the simultaneous implantation of low-energy gas ions (0.8–30 keV) during high-energy heavy ion irradiation (0.8–48 MeV). In addition, initial results in polycrystalline gold foils are provided to demonstrate the range of capabilities.

Confirmation of thalamosubthalamic projections by electron microscopic autoradiography.

PubMed

Sugimoto, T; Hattori, T

1983-05-16

Direct projections from the centre median-parafascicular complex (CM-Pf) to the subthalamic nucleus(STN) were confirmed by electron microscopic autoradiography. [3H]Leucine injections into the rat CM-Pf produced preferential labeling of Gray's type I boutons containing round vesicles in the ipsilateral STN. Further results strongly suggested the existence of some common CM-Pf projections to both the striatum and STN.

Collection and Analysis of Aircraft Emitted Particles

NASA Technical Reports Server (NTRS)

Wilson, James Charles

1999-01-01

The University of Denver Aerosol Group proposed to adapt an impactor system for the collection of particles emitted by aircraft. The collection substrates were electron microscope grids which were analyzed by Dr. Pat Sheridan using a transmission electron microscope. The impactor was flown in the SNIFF behind aircraft and engine emissions were sampled. This report details the results of that work.

Foucault imaging by using non-dedicated transmission electron microscope

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

Taniguchi, Yoshifumi; Matsumoto, Hiroaki; Harada, Ken

2012-08-27

An electron optical system for observing Foucault images was constructed using a conventional transmission electron microscope without any special equipment for Lorentz microscopy. The objective lens was switched off and an electron beam was converged by a condenser optical system to the crossover on the selected area aperture plane. The selected area aperture was used as an objective aperture to select the deflected beam for Foucault mode, and the successive image-forming lenses were controlled for observation of the specimen images. The irradiation area on the specimen was controlled by selecting the appropriate diameter of the condenser aperture.

Electron microscopic evaluation of a gold glaucoma micro shunt after explantation.

PubMed

Berk, Thomas A; Tam, Diamond Y; Werner, Liliana; Mamalis, Nick; Ahmed, Iqbal Ike K

2015-03-01

We present a case of an explanted gold glaucoma micro shunt (GMS Plus) and the subsequent light and electron microscopic analyses. The shunt was implanted in a patient with medically refractive glaucoma. The intraocular pressure (IOP) was stable at 12 mm Hg 6 months postoperatively but spiked to 26 mm Hg 6 months later; membranous growth was visible on the implant gonioscopically. A second gold micro shunt was placed 2 years after the first. The IOP was 7 mm Hg 1 week postoperatively but increased to 23 mm Hg 3 weeks later; similar membranous growth was visible on this implant. One of the shunts was explanted, and light and scanning electron microscopic analyses revealed encapsulation around the shunt exterior and connective tissue invasion of the microstructure. This represents the first electron microscopic analysis of an explanted gold glaucoma micro shunt and the first unequivocal images of the fibrotic pseudo-capsule traversing its microchannels and fenestrations. Dr. Ahmed is a consultant to and has received research grants from Solx, Inc. No other author has a financial or proprietary interest in any material or method mentioned. Copyright © 2015 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Review of current progress in nanometrology with the helium ion microscope

NASA Astrophysics Data System (ADS)

Postek, Michael T.; Vladár, András; Archie, Charles; Ming, Bin

2011-02-01

Scanning electron microscopy has been employed as an imaging and measurement tool for more than 50 years and it continues as a primary tool in many research and manufacturing facilities across the world. A new challenger to this work is the helium ion microscope (HIM). The HIM is a new imaging and metrology technology. Essentially, substitution of the electron source with a helium ion source yields a tool visually similar in function to the scanning electron microscope, but very different in the fundamental imaging and measurement process. The imaged and measured signal originates differently than in the scanning electron microscope and that fact and its single atom source diameter may be able to push the obtainable resolution lower, provide greater depth-of-field and ultimately improve the metrology. Successful imaging and metrology with this instrument entails understanding and modeling of new ion beam/specimen interaction physics. As a new methodology, HIM is beginning to show promise and the abundance of potentially advantageous applications for nanometrology has yet to be fully exploited. This paper discusses some of the progress made at NIST in collaboration with IBM to understand the science behind this new technology.

Fabrication of large area plasmonic nanoparticle grating structure on silver halide based transmission electron microscope film and its application as a surface enhanced Raman spectroscopy substrate

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

Sudheer,, E-mail: sudheer@rrcat.gov.in; Tiwari, P.; Singh, M. N.

The plasmonic responses of silver nanoparticle grating structures of different periods made on silver halide based electron microscope film are investigated. Raster scan of the conventional scanning electron microscope (SEM) is used to carry out electron beam lithography for fabricating the plasmonic nanoparticle grating (PNG) structures. Morphological characterization of the PNG structures, carried out by the SEM and the atomic force microscope, indicates that the depth of the groove decreases with a decrease in the grating period. Elemental characterization performed by the energy dispersive spectroscopy and the x-ray diffraction shows the presence of nanoparticles of silver in the PNG grating.more » The optical characterization of the gratings shows that the localized surface plasmon resonance peak shifts from 366 to 378 nm and broadens with a decrease in grating period from 10 to 2.5 μm. The surface enhanced Raman spectroscopy of the Rhodamine-6G dye coated PNG structure shows the maximum enhancement by two orders of magnitude in comparison to the randomly distributed silver nanoparticles having similar size and shape as the PNG structure.« less

Phase contrast scanning transmission electron microscopy imaging of light and heavy atoms at the limit of contrast and resolution.

PubMed

Yücelen, Emrah; Lazić, Ivan; Bosch, Eric G T

2018-02-08

Using state of the art scanning transmission electron microscopy (STEM) it is nowadays possible to directly image single atomic columns at sub-Å resolution. In standard (high angle) annular dark field STEM ((HA)ADF-STEM), however, light elements are usually invisible when imaged together with heavier elements in one image. Here we demonstrate the capability of the recently introduced Integrated Differential Phase Contrast STEM (iDPC-STEM) technique to image both light and heavy atoms in a thin sample at sub-Å resolution. We use the technique to resolve both the Gallium and Nitrogen dumbbells in a GaN crystal in [[Formula: see text

Quantitative Cryo-Scanning Transmission Electron Microscopy of Biological Materials.

PubMed

Elbaum, Michael

2018-05-11

Electron tomography provides a detailed view into the 3D structure of biological cells and tissues. Physical fixation by vitrification of the aqueous medium provides the most faithful preservation of biological specimens in the native, fully hydrated state. Cryo-microscopy is challenging, however, because of the sensitivity to electron irradiation and due to the weak electron scattering of organic material. Tomography is even more challenging because of the dependence on multiple exposures of the same area. Tomographic imaging is typically performed in wide-field transmission electron microscopy (TEM) mode with phase contrast generated by defocus. Scanning transmission electron microscopy (STEM) is an alternative mode based on detection of scattering from a focused probe beam, without imaging optics following the specimen. While careful configuration of the illumination and detectors is required to generate useful contrast, STEM circumvents the major restrictions of phase contrast TEM to very thin specimens and provides a signal that is more simply interpreted in terms of local composition and density. STEM has gained popularity in recent years for materials science. The extension of STEM to cryomicroscopy and tomography of cells and macromolecules is summarized herein. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Preparation of polymeric Janus particles by directional UV-induced reactions.

PubMed

Liu, Lianying; Ren, Mingwei; Yang, Wantai

2009-09-15

Polymeric Janus particles are obtained by UV-induced selective surface grafting polymerizations and coupling reactions, in virtue of the light-absorption of photoreactive materials such as the immobilized photoinitiator and spread photoinitiator solution on the surfaces exposed to UV light and the sheltering of densely arrayed immovable particles from light. Varying the monomers or macromolecules applied in photografting polymerization or coupling reaction, and choosing diverse polymeric particles of various size, bicolor and amphiphilic Janus particles could be successfully achieved. Observations by fluorescence microscope, scanning electron microscope ,and transmission electron microscope confirmed the asymmetrical morphology of the resultant Janus particles.

Interaction of electrons with light metal hydrides in the transmission electron microscope.

PubMed

Wang, Yongming; Wakasugi, Takenobu; Isobe, Shigehito; Hashimoto, Naoyuki; Ohnuki, Somei

2014-12-01

Transmission electron microscope (TEM) observation of light metal hydrides is complicated by the instability of these materials under electron irradiation. In this study, the electron kinetic energy dependences of the interactions of incident electrons with lithium, sodium and magnesium hydrides, as well as the constituting element effect on the interactions, were theoretically discussed, and electron irradiation damage to these hydrides was examined using in situ TEM. The results indicate that high incident electron kinetic energy helps alleviate the irradiation damage resulting from inelastic or elastic scattering of the incident electrons in the TEM. Therefore, observations and characterizations of these materials would benefit from increased, instead decreased, TEM operating voltage. © 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.

Improvement to the scanning electron microscope image adaptive Canny optimization colorization by pseudo-mapping.

PubMed

Lo, T Y; Sim, K S; Tso, C P; Nia, M E

2014-01-01

An improvement to the previously proposed adaptive Canny optimization technique for scanning electron microscope image colorization is reported. The additional feature, called pseudo-mapping technique, is that the grayscale markings are temporarily mapped to a set of pre-defined pseudo-color map as a mean to instill color information for grayscale colors in chrominance channels. This allows the presence of grayscale markings to be identified; hence optimization colorization of grayscale colors is made possible. This additional feature enhances the flexibility of scanning electron microscope image colorization by providing wider range of possible color enhancement. Furthermore, the nature of this technique also allows users to adjust the luminance intensities of selected region from the original image within certain extent. © 2014 Wiley Periodicals, Inc.

Nature and origin of interstellar diamond from the Allende CV3 meteorite

NASA Technical Reports Server (NTRS)

Blake, David; Freund, Friedemann; Bunch, Ted; Krishnan, Kannan; Stampfer, Mitch; Chang, Sherwood; Tielens, Alexander G. G. M.

1990-01-01

Data and experimental evidence which support the contention that the C delta diamonds may result from grain-grain collisions in supernova shocks in the interstellar medium are presented. Fragments of the Allende CV3 chondrite were acid-treated. A whitish powder was obtained. For the Analytical Electron Microscopy (AEM) a small drop of ethanol suspension was transferred onto holey carbon support films on 3 mm EM grids. The AEM was performed on transmission-thin fragments of the material which overlay holes in the film, to eliminate interference from the substrate. Electron Spectroscopy for Chemical Analysis (ESCA) was performed on a large aliquot of C. Diamond was identified by selected area electron diffraction. Scanning Transmission Electron Microscope / Energy Dispersive X-ray (STEM-EDS) microanalyses of the C delta diamond, using a light-element detector, show that oxygen and possibly nitrogen are the only impurities consistently present. ESCA spectra from bulk C delta material confirm the presence of N at a level of 0.35 percent or less. Under UV irradiation a yellow-red fluorescence is observed, consistent with that of natural diamonds containing substitutional N. Electron Energy Loss Spectra (EELS) were recorded at 2 eV resolution from the C delta diamond, high pressure synthetic diamond, a diamond film produced in a low pressure plasma by chemical vapor deposition (CVD) on a heated silicon substrate (Roy, 1987), graphite, and amorphous arc sputtered carbon. Comparison of the carbon K edge shape and fine structure shows the Allende C delta phase to be largely diamond, but with a significant pre-edge absorption feature indicative of transitions of C 1s electrons into pi asterisk orbitals which are absent in the purely sp(3)-bonded diamond but present in graphite and amorphous carbon.

Simulation of transmission electron microscope images of biological specimens.

PubMed

Rullgård, H; Ofverstedt, L-G; Masich, S; Daneholt, B; Oktem, O

2011-09-01

We present a new approach to simulate electron cryo-microscope images of biological specimens. The framework for simulation consists of two parts; the first is a phantom generator that generates a model of a specimen suitable for simulation, the second is a transmission electron microscope simulator. The phantom generator calculates the scattering potential of an atomic structure in aqueous buffer and allows the user to define the distribution of molecules in the simulated image. The simulator includes a well defined electron-specimen interaction model based on the scalar Schrödinger equation, the contrast transfer function for optics, and a noise model that includes shot noise as well as detector noise including detector blurring. To enable optimal performance, the simulation framework also includes a calibration protocol for setting simulation parameters. To test the accuracy of the new framework for simulation, we compare simulated images to experimental images recorded of the Tobacco Mosaic Virus (TMV) in vitreous ice. The simulated and experimental images show good agreement with respect to contrast variations depending on dose and defocus. Furthermore, random fluctuations present in experimental and simulated images exhibit similar statistical properties. The simulator has been designed to provide a platform for development of new instrumentation and image processing procedures in single particle electron microscopy, two-dimensional crystallography and electron tomography with well documented protocols and an open source code into which new improvements and extensions are easily incorporated. © 2011 The Authors Journal of Microscopy © 2011 Royal Microscopical Society.

Revealing the 1 nm/s extensibility of nanoscale amorphous carbon in a scanning electron microscope.

PubMed

Zhang, Wei

2013-01-01

In an ultra-high vacuum scanning electron microscope, the edged branches of amorphous carbon film (∼10 nm thickness) can be continuously extended with an eye-identifying speed (on the order of ∼1 nm/s) under electron beam. Such unusual mobility of amorphous carbon may be associated with deformation promoted by the electric field, which resulted from an inner secondary electron potential difference from the main trunk of carbon film to the tip end of branches under electron beam. This result demonstrates importance of applying electrical effects to modify properties of carbon materials. It may have positive implications to explore some amorphous carbon as electron field emission device. © Wiley Periodicals, Inc.

IDH1 Mutation in Brain Stem Glioma: Case Report and Review of Literature.

PubMed

Javadi, Seyed Amirhossein; Hartmann, Christian; Walter, Gerhard Franz; Banan, Roozbeh; Samii, Amir

2018-01-01

The role of isocitrate dehydrogenase 1 (IDH1) mutation in brain stem glioma is not clear. To the best of our knowledge, six cases of brain stem gliomas carrying IDH1/2 mutations are currently reported in the literature. One case of diffuse brain stem glioma with IDH1 mutation, which was followed for 2 years, is presented and compared with IDH1 negative tumors. A 22-year-old lady was referred with diplopia and left arm palsy. Neuroimaging detected a nonenhancing, nonhomogeneous diffuse infiltrating brain stem tumor extending from pons to medulla. Microsurgical debulking was performed. Microscopic evaluation of the tissue specimen and immunohistochemistry revealed an astrocytoma WHO Grade II with proliferation rate of 3% and glial fibrillary acidic protein (GFAP)-positive tumor cells. Interestingly, the tumor cells expressed mutated IDH1 R132H protein. The patient underwent adjuvant radiation and chemotherapy. The primary and 2 years' clinical/radiological characteristics did not indicate any significant difference from other cases without IDH1 mutation. the prognostic value of IDH1/2 mutation in brain stem glioma is unclear. Brain stem biopsies may allow determination of a tissue-based tumor diagnosis for further investigations.

Low-voltage electron microscopy of polymer and organic molecular thin films.

PubMed

Drummy, Lawrence F; Yang, Junyan; Martin, David C

2004-06-01

We have demonstrated the capabilities of a novel low-voltage electron microscope (LVEM) for imaging polymer and organic molecular thin films. The LVEM can operate in transmission electron microscopy, scanning transmission electron microscopy, scanning electron microscopy, and electron diffraction modes. The microscope operates at a nominal accelerating voltage of 5 kV and fits on a tabletop. A detailed discussion of the electron-sample interaction processes is presented, and the mean free path for total electron scattering was calculated to be 15 nm for organic samples at 5 kV. The total end point dose for the destruction of crystallinity at 5 kV was estimated at 5 x 10(-4) and 3.5 x 10(-2) C/cm2 for polyethylene and pentacene, respectively. These values are significantly lower than those measured at voltages greater than 100 kV. A defocus series of colloidal gold particles allowed us to estimate the experimental contrast transfer function of the microscope. Images taken of several organic materials have shown high contrast for low atomic number elements and a resolution of 2.5 nm. The materials studied here include thin films of the organic semiconductor pentacene, triblock copolymer films, single-molecule dendrimers, electrospun polymer fibers and gold nanoparticles. Copyright 2004 Elsevier B.V.

[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).

Acquisition parameters optimization of a transmission electron forward scatter diffraction system in a cold-field emission scanning electron microscope for nanomaterials characterization.

PubMed

Brodusch, Nicolas; Demers, Hendrix; Trudeau, Michel; Gauvin, Raynald

2013-01-01

Transmission electron forward scatter diffraction (t-EFSD) is a new technique providing crystallographic information with high resolution on thin specimens by using a conventional electron backscatter diffraction (EBSD) system in a scanning electron microscope. In this study, the impact of tilt angle, working distance, and detector distance on the Kikuchi pattern quality were investigated in a cold-field emission scanning electron microscope (CFE-SEM). We demonstrated that t-EFSD is applicable for tilt angles ranging from -20° to -40°. Working distance (WD) should be optimized for each material by choosing the WD for which the EBSD camera screen illumination is the highest, as the number of detected electrons on the screen is directly dependent on the scattering angle. To take advantage of the best performances of the CFE-SEM, the EBSD camera should be close to the sample and oriented towards the bottom to increase forward scattered electron collection efficiency. However, specimen chamber cluttering and beam/mechanical drift are important limitations in the CFE-SEM used in this work. Finally, the importance of t-EFSD in materials science characterization was illustrated through three examples of phase identification and orientation mapping. © Wiley Periodicals, Inc.

Direction-division multiplexed holographic free-electron-driven light sources

NASA Astrophysics Data System (ADS)

Clarke, Brendan P.; MacDonald, Kevin F.; Zheludev, Nikolay I.

2018-01-01

We report on a free-electron-driven light source with a controllable direction of emission. The source comprises a microscopic array of plasmonic surface-relief holographic domains, each tailored to direct electron-induced light emission at a selected wavelength into a collimated beam in a prescribed direction. The direction-division multiplexed source is tested by driving it with the 30 kV electron beam of a scanning electron microscope: light emission, at a wavelength of 800 nm in the present case, is switched among different output angles by micron-scale repositioning of the electron injection point among domains. Such sources, with directional switching/tuning possible at picosecond timescales, may be applied to field-emission and surface-conduction electron-emission display technologies, optical multiplexing, and charged-particle-beam position metrology.