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1

Quantitative Metallography By Computer-Controlled Scanning Electron Microscopy  

NASA Astrophysics Data System (ADS)

Computer-controlled scanning electron microscopy (CCSEM) is introducing a new era in materials science. With CCSEM, both the chemical composition and the size and shape of individual inclusions are characterized in less than two seconds per feature. While the total inclusion volume fractions obtained by CCSEM and quantitative optical microscopy are in good agreement, the additional information available from CCSEM allows correlation of the microscopic inclusion analyses with mechanical properties, inclusion origin, and state of deoxidation.

Lee, R. J.; Spitzig, W. A.; Kelly, J. F.; Fisher, R. M.

1981-03-01

2

Quantitative energy filtered transmission electron microscopy (EFTEM) of metallic glasses  

NASA Astrophysics Data System (ADS)

In some Al-rare earth-transition metal (Al-RE-TM) glasses, nucleation processes are featured with nucleation rates orders of magnitude higher than predicted by classical nucleation theory. Kinetics of nucleation in these metallic glasses is poorly understood, partly due to the difficulties in direct characterization of chemical fluctuation at the nanometric scale. The objective of this thesis is to advance quantitative techniques using Energy Filtered Transmission Electron Microscopy (EFTEM) to the study of local chemical fluctuations associated with the nucleation phenomena in metallic glasses. The thesis focuses on the methodology for using the energy loss spectrum in a transmission electron microscope to monitor compositional fluctuations in a multicomponent amorphous system. Metallic glass sample Al88Gd 6La2Ni4 was used as testbed to examine their chemistry distribution. Elemental maps and EFTEM image series were used as the multi-variate database. By applying histogram analysis and Principal Component Analysis (PCA) on this multivariate database, detailed compositional distribution information was able to be extracted from the database. The computational procedures for conducting a principal component analysis are described, which result in the establishment of a "chemical image" showing possible fluctuations and clustering of chemistry within the microstructure. A series of images are shown that exhibit length scales of compositional gradients which are qualitatively consistent with suggestions made in the literature for the same composition of metallic glass. The implications of the thesis procedure extend beyond the specific research testbed of crystallization of metallic glasses used in this thesis. This work extends the field of quantitative energy filtered transmission electron microscopy (EFTEM), with a protocol established for the use of EFTEM in the study of the spatial distributions in chemistry in amorphous materials.

Li, Xiang

3

Factors influencing quantitative liquid (scanning) transmission electron microscopy.  

PubMed

One of the experimental challenges in the study of nanomaterials in liquids in the (scanning) transmission electron microscope ((S)TEM) is gaining quantitative information. A successful experiment in the fluid stage will depend upon the ability to plan for sensitive factors such as the electron dose applied, imaging mode, acceleration voltage, beam-induced solution chemistry changes, and the specifics of solution reactivity. In this paper, we make use of a visual approach to show the extent of damage of different instrumental and experimental factors in liquid samples imaged in the (S)TEM. Previous results as well as new insights are presented to create an overview of beam-sample interactions identified for changing imaging and experimental conditions. This work establishes procedures to understand the effect of the electron beam on a solution, provides information to allow for a deliberate choice of the optimal experimental conditions to enable quantification, and identifies the experimental factors that require further analysis for achieving fully quantitative results in the liquid (S)TEM. PMID:24643324

Abellan, P; Woehl, T J; Parent, L R; Browning, N D; Evans, J E; Arslan, I

2014-04-15

4

Quantitative measurement of orbital angular momentum in electron microscopy  

NASA Astrophysics Data System (ADS)

Electron vortex beams have been predicted to enable atomic scale magnetic information measurement, via transfer of orbital angular momentum. Research so far has focused on developing production techniques and applications of these beams. However, methods to measure the outgoing orbital angular momentum distribution are also a crucial requirement towards this goal. Here, we use a method to obtain the orbital angular momentum decomposition of an electron beam, using a multipinhole interferometer. We demonstrate both its ability to accurately measure orbital angular momentum distribution, and its experimental limitations when used in a transmission electron microscope.

Clark, L.; Béché, A.; Guzzinati, G.; Verbeeck, J.

2014-05-01

5

Collaborative study of quantitative coal mineral analysis using computer-controlled scanning electron microscopy  

Microsoft Academic Search

Six laboratories collaborated in an international study of the computer-controlled scanning electron microscopy (CCSEM) method of quantitative coal mineral analysis. A total of five analyses were performed by most of the laboratories on three bituminous coal samples: Pittsburgh No. 8, Illinois No. 6 and Prince. Repeatability relative standard deviation (RSDr) was <20% for the four minerals analysed: calcite, kaolinite, pyrite

Kevin Galbreath; Christopher Zygarlicke; Gary Casuccio; Tracy Moore; Paul Gottlieb; Nicki Agron-Olshina; Gerald Huffman; Anup Shah; Nancy Yang; John Vleeskens; Gerrit Hamburg

1996-01-01

6

Quantitative electron microscopy of cellulose nanofibril structures from Eucalyptus and Pinus radiata kraft pulp fibers.  

PubMed

This work comprises the structural characterization of Eucalyptus and Pinus radiata pulp fibers and their corresponding fibrillated materials, based on quantitative electron microscopy techniques. Compared to hardwood fibers, the softwood fibers have a relatively open structure of the fiber wall outer layers. The fibrillation of the fibers was performed mechanically and chemi-mechanically. In the chemi-mechanical process, the pulp fibers were subjected to a TEMPO-mediated oxidation to facilitate the homogenization. Films were made of the fibrillated materials to evaluate some structural properties. The thicknesses and roughnesses of the films were evaluated with standardized methods and with scanning electron microscopy (SEM), in backscattered electron imaging mode. Field-emission SEM (FE-SEM) and transmission electron microscopy (TEM) were performed to quantify the nanofibril morphology. In this study, we give additional and significant evidences about the suitability of electron microscopy techniques for quantification of nanofibril structures. In addition, we conclude that standard methods are not suitable for estimating the thickness of films having relatively rough surfaces. The results revealed significant differences with respect to the morphology of the fibrillated material. The differences are due to the starting raw material and to the procedure applied for the fibrillation. PMID:21740618

Chinga-Carrasco, Gary; Yu, Yingda; Diserud, Ola

2011-08-01

7

Visualization and quantitative analysis of nanoparticles in the respiratory tract by transmission electron microscopy  

PubMed Central

Nanotechnology in its widest sense seeks to exploit the special biophysical and chemical properties of materials at the nanoscale. While the potential technological, diagnostic or therapeutic applications are promising there is a growing body of evidence that the special technological features of nanoparticulate material are associated with biological effects formerly not attributed to the same materials at a larger particle scale. Therefore, studies that address the potential hazards of nanoparticles on biological systems including human health are required. Due to its large surface area the lung is one of the major sites of interaction with inhaled nanoparticles. One of the great challenges of studying particle-lung interactions is the microscopic visualization of nanoparticles within tissues or single cells both in vivo and in vitro. Once a certain type of nanoparticle can be identified unambiguously using microscopic methods it is desirable to quantify the particle distribution within a cell, an organ or the whole organism. Transmission electron microscopy provides an ideal tool to perform qualitative and quantitative analyses of particle-related structural changes of the respiratory tract, to reveal the localization of nanoparticles within tissues and cells and to investigate the 3D nature of nanoparticle-lung interactions. This article provides information on the applicability, advantages and disadvantages of electron microscopic preparation techniques and several advanced transmission electron microscopic methods including conventional, immuno and energy-filtered electron microscopy as well as electron tomography for the visualization of both model nanoparticles (e.g. polystyrene) and technologically relevant nanoparticles (e.g. titanium dioxide). Furthermore, we highlight possibilities to combine light and electron microscopic techniques in a correlative approach. Finally, we demonstrate a formal quantitative, i.e. stereological approach to analyze the distributions of nanoparticles in tissues and cells. This comprehensive article aims to provide a basis for scientists in nanoparticle research to integrate electron microscopic analyses into their study design and to select the appropriate microscopic strategy.

Muhlfeld, Christian; Rothen-Rutishauser, Barbara; Vanhecke, Dimitri; Blank, Fabian; Gehr, Peter; Ochs, Matthias

2007-01-01

8

A methodology for the extraction of quantitative information from electron microscopy images at the atomic level  

NASA Astrophysics Data System (ADS)

In this paper we describe a methodology developed at the University of Cadiz (Spain) in the past few years for the extraction of quantitative information from electron microscopy images at the atomic level. This work is based on a coordinated and synergic activity of several research groups that have been working together over the last decade in two different and complementary fields: Materials Science and Computer Science. The aim of our joint research has been to develop innovative high-performance computing techniques and simulation methods in order to address computationally challenging problems in the analysis, modelling and simulation of materials at the atomic scale, providing significant advances with respect to existing techniques. The methodology involves several fundamental areas of research including the analysis of high resolution electron microscopy images, materials modelling, image simulation and 3D reconstruction using quantitative information from experimental images. These techniques for the analysis, modelling and simulation allow optimizing the control and functionality of devices developed using materials under study, and have been tested using data obtained from experimental samples.

Galindo, P. L.; Pizarro, J.; Guerrero, E.; Guerrero-Lebrero, M. P.; Scavello, G.; Yáñez, A.; Núñez-Moraleda, B. M.; Maestre, J. M.; Sales, D. L.; Herrera, M.; Molina, S. I.

2014-06-01

9

Quantitative magnetic imaging at the nanometer scale by ballistic electron magnetic microscopy  

NASA Astrophysics Data System (ADS)

We demonstrate quantitative ballistic electron magnetic microscopy (BEMM) imaging of simple model Fe(001) nanostructures. We use in situ nanostencil shadow mask resistless patterning combined with molecular beam epitaxy deposition to prepare under ultra-high vacuum conditions nanostructured epitaxial Fe/Au/Fe/GaAs(001) spin-valves. In this epitaxial system, the magnetization of the bottom Fe/GaAs(001) electrode is parallel to the [110] direction, defining accurately the analysis direction for the BEMM experiments. The large hot-electron magnetoresistance of the Fe/Au/Fe/GaAs(001) epitaxial spin-valve allows us to image various stable magnetic configurations on the as-grown Fe(001) microstructures with a high sensitivity, even for small misalignments of both magnetic electrodes. The angular dependence of the hot-electron magnetocurrent is used to convert magnetization maps calculated by micromagnetic simulations into simulated BEMM images. The calculated BEMM images and magnetization rotation profiles show quantitative agreement with experiments and allow us to investigate the magnetic phase diagram of these model Fe(001) microstructures. Finally, magnetic domain reversals are observed under high current density pulses. This opens the way for further BEMM investigations of current-induced magnetization dynamics.

Hervé, M.; Tricot, S.; Guézo, S.; Delhaye, G.; Lépine, B.; Schieffer, P.; Turban, P.

2013-06-01

10

Quantitative transmission electron microscopy analysis of the nanocrystallization kinetics of soft magnetic alloys  

NASA Astrophysics Data System (ADS)

Transmission electron microscopy was used for the first time to obtain quantitative values of the diffusional crystallization kinetics of initially amorphous Fe74.5Si13.5B9Nb3 , Fe76.5Si13.5B9Cu1 and Fe73.5Si13.5B9Nb3Cu1 and Fe77.5Si13.5Nb3Cu1 (Finemet) alloys. The role of Cu and Nb alloying additions was elucidated. Contrary to some models of the crystallization process, it is demonstrated that both Nb and Cu alloying additions can influence the nucleation and growth processes. Combined additions of both Cu and Nb induce drastic reduction in crystal size to about 10nm and 1000 times higher crystal number density. The high nucleation rate observed in the Fe-Si-B-Nb-Cu alloy was attributed to the formation of both Cu and Nb rich regions which provide a high number of heterogeneous nucleation sites, consistent with the Hampel and Pradell models, the low growth rate was consistent with the Hunziker model.

Ramanujan, R. V.; Zhang, Y. R.

2006-12-01

11

Quantitative magnetic information from reciprocal space maps in transmission electron microscopy.  

PubMed

One of the most challenging issues in the characterization of magnetic materials is to obtain a quantitative analysis on the nanometer scale. Here we describe how electron magnetic circular dichroism (EMCD) measurements using the transmission electron microscope can be used for that purpose, utilizing reciprocal space maps. Applying the EMCD sum rules, an orbital to spin moment ratio of mL/mS=0.08+/-0.01 is obtained for Fe, which is consistent with the commonly accepted value. Hence, we establish EMCD as a quantitative element-specific technique for magnetic studies, using a widely available instrument with superior spatial resolution. PMID:19257384

Lidbaum, Hans; Rusz, Ján; Liebig, Andreas; Hjörvarsson, Björgvin; Oppeneer, Peter M; Coronel, Ernesto; Eriksson, Olle; Leifer, Klaus

2009-01-23

12

Characterization and analysis of individual fly-ash particles from coal-fired power stations by a combination of optical microscopy, electron microscopy and quantitative electron microprobe analysis  

NASA Astrophysics Data System (ADS)

Quantitative electron microprobe analysis has been used to determine the inorganic chemical composition of individual fly-ash particles previously categorized on the basis of properties recognizable by light and scanning electron microscopy. Seven categories may be recognized: (1) unfused detrital minerals (principally quartz), (2) irregular-spongy particles derived from partly-fused clay minerals, (3) vesicular colourless glass (in the form of irregular particles and cenospheres) derived from viscous melts, (4) solid glass (mostly in the form of spherical particles and sometimes pigmented) derived from fluid melts, (5) dendritic iron oxide particles (mostly spherical) containing variable amounts of glass matrix, (6) crystalline iron oxide particles (mostly spherical) containing minimal amounts of glass and (7) unburnt char particles. The use of computerized energy dispersive X-ray analysis on the electron microprobe enables an analysis for all the inorganic elements present in a particle to be carried out simultaneously in about 60s. The rapidity and comprehensive nature of the procedure makes it possible to determine the composition of a large number of individual fly-ash particles in a relatively short time and thereby characterize the types and compositions that comprise the population.

Ramsden, A. R.; Shibaoka, M.

13

Scanning electron microscopy of growing dental plaque: a quantitative study with different mouth rinses.  

PubMed

The aim of this study was to quantify the influence of different mouth rinses on dental plaque. Wearing splints with enamel pieces 24 volunteers rinsed with essential oils, amine/stannous fluoride, or chlorhexidine digluconate (0.12%) mouth rinses. After 24, 48, 72, and 96 h the enamel pieces were analyzed by scanning electron microscopy. The counts of cocci and bacilli in different plaque layers and the plaque thickness were almost similar using essential oils and amine/stannous fluoride. These results differed significantly from those of chlorhexidine digluconate mouth rinses. The results for plaque thickness were without significant differences between the groups at any appointment. PMID:23758106

Jentsch, Holger; Mozaffari, Eshan; Jonas, Ludwig

2013-08-01

14

Towards quantitative scanning electron microscopy: Applications to nano-scale analysis  

NASA Astrophysics Data System (ADS)

Although the Scanning Electron Microscope (SEM) has been in existence for many decades, it cannot be yet regarded as a true quantitative instrument—certainly when applied at the nanoscale. This is due to the presence of carbonaceous deposits at the surface and a poor understanding of the emission of secondary electrons from materials. In this paper, a short review is given of some of the progress made in the efforts to improve quantification in the SEM at York. We present results which strongly suggest that the currently accepted theory, which explains why there is a correlation between the secondary electron yield and the work function of a metal, is incorrect. In addition, we show that the backscattering coefficient from materials can be strongly influenced by surface layers at low primary electron energy. Finally, we present Auger electron spectra, which have been acquired at high speed at high vacuum (10 -7 mbar) and thus represent a new way to determine the composition of nanostructures in the SEM.

El-Gomati, M. M.; Walker, C. G. H.; Zha, X.

2011-07-01

15

Quantitative EDS analysis in transmission electron microscopy using unconventional reference materials  

NASA Astrophysics Data System (ADS)

This work investigates the use of an unconventional reference material to determine experimentally the Cliff-Lorimer factor for EDS quantitative analysis with a transmission electron microscope. The results demonstrate the equivalence of a bi-layer of pure gold on pure silver with respect to a binary alloy foil of the same elements. RF-sputtering is a suitable technique to prepare such reference materials that have a uniform thickness within a few percent tolerance. The availability of a calibrated set of similar reference materials would allow direct measurement of the k-factors for a large number of elements. This would avoid the errors due to the use of theoretical k-factors extracted from the compilations available in the literature. A new expression of the correction factor for X-ray self-absorption of the sample has also been derived.

Nacucchi, M.; Alvisi, M.; Altamura, D.; Pfister, V.; Re, M.; Signore, M. A.; Vittori Antisari, M.

2010-02-01

16

Quantitative high-angle annular dark field scanning transmission electron microscopy for materials science  

NASA Astrophysics Data System (ADS)

Scanning transmission electron microscopy (STEM) has been widely used for characterization of materials; to identify micro- and nano-structures within a sample and to analyze crystal and defect structures. High-angle annular dark field (HAADF) STEM imaging using atomic number (Z) contrast has proven capable of resolving atomic structures with better than 2 A lateral resolution. In this work, the HAADF STEM imaging mode is used in combination with multislice simulations. This combination is applied to the investigation of the temperature dependence of the intensity collected by the HAADF detector in silicon, and to convergent beam electron diffraction (CBED) to measure the degree of chemical order in intermetallic nanoparticles. The experimental and simulation results on the high-angle scattering of 300 keV electrons in crystalline silicon provide a new contribution to the understanding of the temperature dependence of the HAADF intensity. In the case of 300 keV, the average high-angle scattered intensity slightly decreases as the temperature increases from 100 K to 300 K, and this is different from the temperature dependence at 100 keV and 200 keV where HAADF intensity increases with temperature, as had been previously reported by other workers. The L10 class of hard magnetic materials has attracted continuous attention as a candidate for high-density magnetic recording media, as this phase is known to have large magnetocrystalline anisotropy, with magnetocrystalline anisotropy constant, Ku, strongly dependent on the long-range chemical order parameter, S. A new method is developed to assess the degree of chemical order in small FePt L1 0 nanoparticles by implementing a CBED diffraction technique. Unexpectedly, the degree of order of individual particles is highly variable and not a simple function of particle size or sample composition. The particle-to-particle variability observed is an important new aspect to the understanding of phase transformations in nanoparticle systems.

Petrova, Rumyana V.

17

Quantitative measurements of magnetic stray field dynamics of Permalloy particles in a photoemission electron microscopy.  

PubMed

By example of a Permalloy particle (40 × 40 ?m(2) size, 30 nm thickness) we demonstrate a procedure to quantitatively investigate the dynamics of magnetic stray fields during ultrafast magnetization reversal. The measurements have been performed in a time-resolving photoemission electron microscope using the X-ray magnetic circular dichroism. In the particle under investigation, we have observed a flux-closure-dominated magnetic ground structure, minimizing the magnetic stray field outside the sample. A fast magnetic field pulse introduced changes in the micromagnetic structure accompanied with an incomplete flux closure. As a result, stray fields arise along the edges of domains, which cause a change of contrast and an image deformation of the particles geometry (curvature of its edge). The magnetic stray fields are calculated from a deformation of the X-ray magnetic circular dichroism (XMCD) images taken after the magnetic field pulse in a 1 ns interval. These measurements reveal a decrease of magnetic stray fields with time. An estimate of the lower limit of the domain wall velocity yields about 2 × 10(3) m s(-1). PMID:21155993

Nepijko, S A; Krasyuk, A; Oelsner, A; Schneider, C M; Schönhense, G

2011-05-01

18

Quantitative measurement of the surface self-diffusion on Au nanoparticles by aberration-corrected transmission electron microscopy.  

PubMed

We present a method that allows for a quantitative measurement of the surface self-diffusion on nanostructures, such as nanoparticles, at the atomic scale using aberration-corrected high-resolution transmission electron microscopy (HRTEM). The diffusion coefficient can be estimated by measuring the fluctuation of the atom column occupation at the surface of Au nanoparticles, which is directly observable in temporal sequences of HRTEM images. Both a Au icosahedron and a truncated Au octahedron are investigated, and their diffusion coefficients are found to be in the same order of magnitude, D = 10(-17) to 10(-16) cm(2)/s. It is to be assumed that the measured surface diffusion is affected by the imaging electron beam. This assumption is supported by the observed instability of a (5 × 1) surface reconstruction on a {100} Au facet. PMID:23136983

Surrey, A; Pohl, D; Schultz, L; Rellinghaus, B

2012-12-12

19

Quantitative characterization of agglomerates and aggregates of pyrogenic and precipitated amorphous silica nanomaterials by transmission electron microscopy  

PubMed Central

Background The interaction of a nanomaterial (NM) with a biological system depends not only on the size of its primary particles but also on the size, shape and surface topology of its aggregates and agglomerates. A method based on transmission electron microscopy (TEM), to visualize the NM and on image analysis, to measure detected features quantitatively, was assessed for its capacity to characterize the aggregates and agglomerates of precipitated and pyrogenic synthetic amorphous silicon dioxide (SAS), or silica, NM. Results Bright field (BF) TEM combined with systematic random imaging and semi-automatic image analysis allows measuring the properties of SAS NM quantitatively. Automation allows measuring multiple and arithmetically complex parameters simultaneously on high numbers of detected particles. This reduces operator-induced bias and assures a statistically relevant number of measurements, avoiding the tedious repetitive task of manual measurements. Access to multiple parameters further allows selecting the optimal parameter in function of a specific purpose. Using principle component analysis (PCA), twenty-three measured parameters were classified into three classes containing measures for size, shape and surface topology of the NM. Conclusion The presented method allows a detailed quantitative characterization of NM, like dispersions of precipitated and pyrogenic SAS based on the number-based distributions of their mean diameter, sphericity and shape factor.

2012-01-01

20

Characterization of individual submicrometer aerosol particles collected in Incheon, Korea, by quantitative transmission electron microscopy energy-dispersive X-ray spectrometry  

Microsoft Academic Search

For the last decade the Monte Carlo calculation method has been proven to be an excellent tool for accurately simulating electron-solid interactions in atmospheric individual particles of micrometer size. Although it was designed for application to scanning electron microscopy, in the present study it is demonstrated that the Monte Carlo calculation can also be applied in a quantitative single particle

Hong Geng; Sujin Kang; Hae-Jin Jung; Marie Choël; HyeKyeong Kim; Chul-Un Ro

2010-01-01

21

Correlative Instrumental Neutron Activation Analysis, Light Microscopy, Transmission Electron Microscopy, and X-ray Microanalysis for Qualitative and Quantitative Detection of Colloidal Gold Spheres in Biological Specimens.  

PubMed

: Colloidal gold, conjugated to ligands or antibodies, is routinely used as a label for the detection of cell structures by light (LM) and electron microscopy (EM). To date, several methods to count the number of colloidal gold labels have been employed with limited success. Instrumental neutron activation analysis (INAA), a physical method for the analysis of the elemental composition of materials, can be used to provide a quantitative index of gold accumulation in bulk specimens. Given that gold is not naturally found in biological specimens in any substantial amount and that colloidal gold and ligand conjugates can be prepared to yield uniform bead sizes, the amount of label can be calculated in bulk biological samples by INAA. Here we describe the use of INAA, LM, transmission EM, and X-ray microanalysis (EDX) in a model to determine both distribution (localization) and amount of colloidal gold at the organ, tissue, cellular, and ultrastructural levels in whole animal systems following administration. In addition, the sensitivity for gold in biological specimens by INAA is compared with that of inductively coupled plasma-mass spectrometry (ICP-MS). The correlative use of INAA, LM, TEM, and EDX can be useful, for example, in the quantitative and qualitative tracking of various labeled molecular species following administration in vivo. PMID:9990870

Hillyer; Albrecht

1998-09-01

22

Transmission Electron Microscopy Basics  

NSDL National Science Digital Library

This extensive site from the University of Liverpool is a set of resources based on the textbook Transmission Electron Microscopy - Basics by D.B.Williams and C.B.Carter. The tutorial is designed to accompany an introductory course on transmission electron microscopy for students with an understanding of elementary physics. Topics include electron scattering, electron atom interactions, the electron gun, probe size, lenses, depth of field and depth of focus, and others. Each chapter includes interactive Java applets that facilitate understanding of the concepts presented.

Goodhew, Peter; Matter.org

23

Electron Microscopy of Flatworms  

Microsoft Academic Search

Electron microscopy (EM) has long been indispensable for flatworm research, as most of these worms are microscopic in dimension and provide only a handful of characters recognizable by eye or light microscopy. Therefore, major progress in understanding the histology, systematics, and evolution of this animal group relied on methods capable of visualizing ultrastructure. The rise of molecular and cellular biology

Willi Salvenmoser; Bernhard Egger; Johannes G. Achatz; Peter Ladurner; Michael W. Hess

2010-01-01

24

QEMSCAN° (Quantitative Evaluation of Minerals by Scanning Electron Microscopy): capability and application to fracture characterization in geothermal systems  

NASA Astrophysics Data System (ADS)

Fractures are important conduits for fluids in geothermal systems, and the creation and maintenance of fracture permeability is a fundamental aspect of EGS (Engineered Geothermal System) development. Hydraulic or chemical stimulation techniques are often employed to achieve this. In the case of chemical stimulation, an understanding of the minerals present in the fractures themselves is desirable to better design a stimulation effort (i.e. which chemical to use and how much). Borehole televiewer surveys provide important information about regional and local stress regimes and fracture characteristics (e.g. fracture aperture), and XRD is useful for examining bulk rock mineralogy, but neither technique is able to quantify the distribution of these minerals in fractures. QEMSCAN° is a fully-automated micro-analysis system that enables quantitative chemical analysis of materials and generation of high-resolution mineral maps and images as well as porosity structure. It uses a scanning electron microscopy platform (SEM) with an electron beam source in combination with four energy-dispersive X-ray spectrometers (EDS). The measured backscattered electron and electron-induced secondary X-ray emission spectra are used to classify sample mineralogy. Initial applications of QEMSCAN° technology were predominantly in the minerals industry and application to geothermal problems has remained limited to date. In this pilot study, the potential application of QEMSCAN° technology to fracture characterization was evaluated using samples of representative mineralized fractures in two geothermal systems (Newberry Volcano, Oregon and Brady's geothermal field, Nevada). QEMSCAN° results were compared with XRD and petrographic techniques. Nine samples were analyzed from each field, collected from the drill core in the 1000-1500 m depth range in two shallow wells (GEO-N2 at Newberry Volcano and BCH-3 at Brady's). The samples were prepared as polished thin sections for QEMSCAN° analysis. Results indicate that a sampling resolution of 10 ?m is sufficient to resolve fracture morphology and mineral zonation (where multiple episodes of mineralization occurred), and enables relatively fast data acquisition (3 cm2 can be analyzed in approximately 3 hours). Finer resolutions (down to 2.5 ?m) take significantly longer, but can be used to provide additional spatial detail in areas of interest after a low resolution (10 ?m) scan. Use of XRD data in conjunction with QEMSCAN° data is sometimes needed to distinguish geothermal alteration minerals with similar chemical compositions (clay minerals, micas and chlorite), however overall the technique appears to have excellent potential for geothermal applications.

Ayling, B.; Rose, P. E.; Zemach, E.; Drakos, P. S.; Petty, S.

2011-12-01

25

Scanning ultrafast electron microscopy  

PubMed Central

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

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

2010-01-01

26

Electron microscopy of sillenites  

NASA Astrophysics Data System (ADS)

In this undergraduate project, the student performed transmission and scanning electron microscopy measurements on two sillenite compounds: Bi12SiO20 and Bi25InO39. To our knowledge, the electron diffraction patterns of sillenites have not been reported in the literature before. Our preliminary results show that both the tetravalent and trivalent compound have the sillenite structure. Using concepts from undergraduate solid state physics, the student will explain how the electron diffraction patterns were analyzed.

Scurti, Craig; Auvray, Nicolas; Lufaso, Michael; Kohno, Hideo; Arenas, Daniel

2013-03-01

27

Conventional transmission electron microscopy  

PubMed Central

Researchers have used transmission electron microscopy (TEM) to make contributions to cell biology for well over 50 years, and TEM continues to be an important technology in our field. We briefly present for the neophyte the components of a TEM-based study, beginning with sample preparation through imaging of the samples. We point out the limitations of TEM and issues to be considered during experimental design. Advanced electron microscopy techniques are listed as well. Finally, we point potential new users of TEM to resources to help launch their project.

Winey, Mark; Meehl, Janet B.; O'Toole, Eileen T.; Giddings, Thomas H.

2014-01-01

28

The atomistic structure of a Sigma = 3, (111) grain boundary in NiAl, studied by quantitative high-resolution transmission electron microscopy  

Microsoft Academic Search

The atomistic structure of the ? = 3, (111) gain boundary in NiAl has been determined by quantitative high-resolution transmission electron microscopy. In NiAl, which crystallizes in the B2 (CsCl) structure this grain boundary constitutes an 'incoherent twin boundary'. Using an atomic resolution microscope (JEM-ARM 130) we have obtained images of the grain-boundary structure at a point resolution of 0·105nm.

K. Nadarzinski; F. Ernst

1996-01-01

29

Analysis of Transient Polyhydroxybutyrate Production in Wautersia eutropha H16 by Quantitative Western Analysis and Transmission Electron Microscopy  

PubMed Central

Polyhydroxybutyrates (PHBs) are polyoxoesters generated from (R)3-hydroxybutyryl coenzyme A by PHB synthase. During the polymerization reaction, the polymers undergo a phase transition and generate granules. Wautersia eutropha can transiently accumulate PHB when it is grown in a nutrient-rich medium (up to 23% of the cell dry weight in dextrose-free tryptic soy broth [TSB]). PHB homeostasis under these growth conditions was examined by quantitative Western analysis to monitor the proteins present, their levels, and changes in their levels over a 48-h growth period. The proteins examined include PhaC (the synthase), PhaP (a phasin), PhaR (a transcription factor), and PhaZ1a, PhaZ1b, and PhaZ1c (putative intracellular depolymerases), as well as PhaZ2 (a hydroxybutyrate oligomer hydrolase). The results show that PhaC and PhaZ1a were present simultaneously. No PhaZ1b or PhaZ1c was detected at any time throughout growth. PhaZ2 was observed and exhibited an expression pattern different from that of PhaZ1a. The levels of PhaP changed dramatically and corresponded kinetically to the levels of PHB. Transmission electron microscopy (TEM) provided the dimensions of the average cell and the average granule at 4 h and 24 h of growth (J. Tian, A. J. Sinskey, and J. Stubbe, J. Bacteriol. 187:3814-3824, 2005). This information allowed us to calculate the amount of each protein and number of granules per cell and the granule surface coverage by proteins. The molecular mass of PHB (106 Da) was determined by dynamic light scattering at 4 h, the time of maximum PHB accumulation. At this time, the surface area of the granules was maximally covered with PhaP (27 to 54%), and there were one or two PhaP molecules/PHB chain. The ratio of PHB chains to PhaC was ?60, which required reinitiation of polymer formation on PhaC. The TEM studies of wild-type and ?phaR strains in TSB provided further support for an alternative mechanism of granule formation (Tian et al., J. Bacteriol. 187:3814-3824, 2005).

Tian, Jiamin; He, Aimin; Lawrence, Adam G.; Liu, Pinghua; Watson, Nicki; Sinskey, Anthony J.; Stubbe, JoAnne

2005-01-01

30

Digital Electron Microscopy on Advanced Materials  

Microsoft Academic Search

Digital electron microscopy has been developed and applied to the structure analysis of advanced materials such as semiconductors and alloys. First of all, quantitative high-resolution electron microscopy was carried out on a Z-type faulted dipole in GaAs with the through-focus method. Through the quantitative analysis of the high-resolution images, the atomic displacement around the stacking fault was accurately evaluated. In

D Shindo; Y Ikematsu; S.-H Lim; I Yonenaga

2000-01-01

31

An image analysis workstation designed for multiple users: application of quantitative digital imaging techniques to electron microscopy.  

PubMed

The purpose of the present study is to describe the setup of an image analysis workstation designed for multiple users, and to show the application of digital imaging techniques to the analysis of electron microscopic images. The image analysis system consists of a conventional light microscope mounted on a table-top, vibration-free platform, a light box for viewing negatives, two separate video cameras, a switch box, a video monitor, a digitizing tablet, a computer, and morphometric software packages. The system can quantitate the amount that each of the 256 gray levels contributes to the image, perform morphometric analysis (eg, shape and size) on individual gray level-defined subimages, and perform statistical analysis. Each operator has access to his or her own data and program setups through the use of 21.4-Mb removable Bernoulli cartridges. This setup for multiple users prevents the cluttering of the hard drive of the computer and avoids the possibility of accidentally removing the stored data of another user. The quantitative capabilities of the digital imaging system is demonstrated using an image of a normal lymphocyte and an apoptotic cell (ie, a cell which has undergone programmed cell death), both captured on the same electron microscopic negative. A comparison of the histograms of nuclear densities determined for these two cells reveals subtleties in gray level distribution not appreciated by the naked eye. PMID:1557817

Payne, C M; Cromey, D W

1992-01-01

32

Low temperature semi-quantitative analysis of local electrical field in silicon diode by transmission electron microscopy  

NASA Astrophysics Data System (ADS)

The local electric behaviour of IMPATT diodes was studied by scanning transmission electron beam induced current in cross-section method (X-STEBIC). This technique of induced current measurement makes it possible to probe the depletion zone of a junction with the beam of a transmission electron microscope. Two series of experiments were carried out. The X-STEBIC signal was analyzed according to the sample thickness and under different electrical polarizations. Moreover, these measurements were done and compared at room and low temperature (\\cong110 K). From these data, simulations of X-STEBIC profile allowed us to determine the main physical parameters brought into play in the signal formation. We have shown that, in the vicinity of the junction, the intensity of the induced current partly depends on the avalanche effect. The kinetic energy of the minority carriers generated by the electron beam is sufficient to induce collisions in cascade, even when the junction is not polarized. At low temperature, surface recombination has an essential role on the lateral resolution of the X-STEBIC method. By choosing carefully the range of sample thickness and by positioning the probe in the field of the diode, it is possible to optimize the resolution. Surface recombination annihilates the diffusion of the carriers so that the STEBIC image becomes a true image of the electric field. Consequently, semi-quantitative physical data can be obtained on the junction field.

Cabanel, C.; Brouri, D.; Laval, J. Y.

2006-05-01

33

Characterization of individual submicrometer aerosol particles collected in Incheon, Korea, by quantitative transmission electron microscopy energy-dispersive X-ray spectrometry  

NASA Astrophysics Data System (ADS)

For the last decade the Monte Carlo calculation method has been proven to be an excellent tool for accurately simulating electron-solid interactions in atmospheric individual particles of micrometer size. Although it was designed for application to scanning electron microscopy, in the present study it is demonstrated that the Monte Carlo calculation can also be applied in a quantitative single particle analysis using transmission electron microscopy (TEM) with an ultrathin window energy-dispersive X-ray (EDX) spectrometer with a high accelerating voltage (200 kV). By utilizing an iterative reverse Monte Carlo simulation combined with successive approximation, atomic elemental concentrations (including low-Z elements) of submicrometer standard particles were determined with high accuracy for electron beam refractory particles such as NaCl, KCl, SiO2, Fe2O3, Na2SO4, K2SO4, CaCO3, and CaSO4. On the basis of quantitative X-ray analysis together with morphological information from TEM images, overall 1638 submicrometer individual particles from 10 sets of aerosol samples collected in Incheon, Korea, were identified. The most frequently encountered particle types are carbonaceous and (NH4)2SO4/NH4HSO4-containing particles, followed by mineral (e.g., aluminosilicate, SiO2, CaCO3), sea salt, K-rich (e.g., K2SO4 and KCl), Fe-rich, fly ash, and transition or heavy-metal-containing (e.g., ZnSO4, ZnCl2, PbSO4) particles. The relative abundances of the submicrometer particle types vary among samples collected in different seasons and also depend on different air mass transport routes. This study demonstrates that the quantitative TEM-EDX individual particle analysis is a useful and reliable technique in characterizing urban submicrometer aerosol particles.

Geng, Hong; Kang, Sujin; Jung, Hae-Jin; ChoëL, Marie; Kim, Hyekyeong; Ro, Chul-Un

2010-08-01

34

High speed quantitative digital microscopy  

NASA Technical Reports Server (NTRS)

Modern digital image processing hardware makes possible quantitative analysis of microscope images at high speed. This paper describes an application to automatic screening for cervical cancer. The system uses twelve MC6809 microprocessors arranged in a pipeline multiprocessor configuration. Each processor executes one part of the algorithm on each cell image as it passes through the pipeline. Each processor communicates with its upstream and downstream neighbors via shared two-port memory. Thus no time is devoted to input-output operations as such. This configuration is expected to be at least ten times faster than previous systems.

Castleman, K. R.; Price, K. H.; Eskenazi, R.; Ovadya, M. M.; Navon, M. A.

1984-01-01

35

Non-amplified Quantitative Detection of Nucleic Acid Sequences Using a Gold Nanoparticle Probe Set and Field-Emission Scanning Electron Microscopy  

NASA Astrophysics Data System (ADS)

For the precise detection of the number of expressed biomarkers at the single-cell level, we have developed a method of quantifying and specifying target DNA fragments by using a set of gold nanoparticles as labels and field-emission scanning electron microscopy (FE-SEM) to measure the number and sizes of gold nanoparticles attached to target samples. One or more target DNAs on a substrate were labeled with a set of different-sized gold nanoparticle probes having complementary sequences to different target candidates. The type and number of the target DNAs having a specific sequence were identified by counting the attached nanoparticles of a specific size in FE-SEM images. The results evaluated using a DNA microarray showed high specificity and sensitivity, and a linear correlation between the number of attached particles and the target DNA concentration, indicating the feasibility of quantitative detection in the femtomolar to nanomolar concentration range.

Hyonchol Kim,; Atsushi Kira,; Kenji Yasuda,

2010-06-01

36

The effect of probe inaccuracies on the quantitative model-based analysis of high angle annular dark field scanning transmission electron microscopy images.  

PubMed

Quantitative structural and chemical information can be obtained from high angle annular dark field scanning transmission electron microscopy (HAADF STEM) images when using statistical parameter estimation theory. In this approach, we assume an empirical parameterized imaging model for which the total scattered intensities of the atomic columns are estimated. These intensities can be related to the material structure or composition. Since the experimental probe profile is assumed to be known in the description of the imaging model, we will explore how the uncertainties in the probe profile affect the estimation of the total scattered intensities. Using multislice image simulations, we analyze this effect for Cs corrected and non-Cs corrected microscopes as a function of inaccuracies in cylindrically symmetric aberrations, such as defocus and spherical aberration of third and fifth order, and non-cylindrically symmetric aberrations, such as 2-fold and 3-fold astigmatism and coma. PMID:24462219

Martinez, G T; De Backer, A; Rosenauer, A; Verbeeck, J; Van Aert, S

2014-08-01

37

Electron microscopy and forensic practice  

NASA Astrophysics Data System (ADS)

Electron microanalysis in forensic practice ranks among basic applications used in investigation of traces (latents, stains, etc.) from crime scenes. Applying electron microscope allows for rapid screening and receiving initial information for a wide range of traces. SEM with EDS/WDS makes it possible to observe topography surface and morphology samples and examination of chemical components. Physical laboratory of the Institute of Criminalistics Prague use SEM especially for examination of inorganic samples, rarely for biology and other material. Recently, possibilities of electron microscopy have been extended considerably using dual systems with focused ion beam. These systems are applied mainly in study of inner micro and nanoparticles , thin layers (intersecting lines in graphical forensic examinations, analysis of layers of functional glass, etc.), study of alloys microdefects, creating 3D particles and aggregates models, etc. Automated mineralogical analyses are a great asset to analysis of mineral phases, particularly soils, similarly it holds for cathode luminescence, predominantly colour one and precise quantitative measurement of their spectral characteristics. Among latest innovations that are becoming to appear also at ordinary laboratories are TOF - SIMS systems and micro Raman spectroscopy with a resolution comparable to EDS/WDS analysis (capable of achieving similar level as through EDS/WDS analysis).

Kotrlý, Marek; Turková, Ivana

2013-05-01

38

Hormonal regulation of capillary fenestrae in the rat adrenal cortex: quantitative studies using objective lens staging scanning electron microscopy.  

PubMed

High magnification studies of the fenestrated capillary endothelium in the zona fasciculata (ZF) of rat adrenal glands were performed using the objective lens stage of an analytical scanning electron microscope (SEM) equipped with a lanthanum hexaboride emitter (LaB6). Resolution of surface substructure of the luminal membrane obtained with specimens decorated with gold/palladium (Au/Pd) was compared with that observed in others sputter coated with tantalum (Ta). High magnification (50,000x) of the fenestrated endothelium demonstrates that tantalum coating of the cryofractured adrenals improves the substructural detail compared to that seen in Au/Pd decorated specimens. The procedures used in specimen preparation, metal deposition and secondary electron imaging (SEI) are described. Quality imaging achieved using the objective lens stage is a result of the elimination of the SE-III component derived from backscattered electrons. Rat adrenals exhibited uniformly patent capillaries. High magnification micrographs of capillary walls were randomly recorded in two morphometric studies of the fenestral content of capillaries in the rat adrenal cortex. Adrenocorticotropic hormone (ACTH), when administered to rats following dexamethasone (DEX) treatment, significantly reduced the fenestrae/micron 2 of endothelial surface and increased the mean size of fenestrae. After hypophysectomy, the number of fenestrae/micron 2 declined over 48 h; within 2 h after ACTH was given to rats hypophysectomized 48 hours earlier, the fenestrae/micron 2 had increased two-fold. These studies indicate that ACTH plays an important role in modulating fenestral content of the capillary endothelium in the adrenal cortex. PMID:3027881

Apkarian, R P; Curtis, J C

1986-01-01

39

Electronic Blending in Virtual Microscopy  

ERIC Educational Resources Information Center

Virtual microscopy (VM) is a relatively new technology that transforms the computer into a microscope. In essence, VM allows for the scanning and transfer of glass slides from light microscopy technology to the digital environment of the computer. This transition is also a function of the change from print knowledge to electronic knowledge, or as…

Maybury, Terrence S.; Farah, Camile S.

2010-01-01

40

Scanning electron microscopy techniques.  

National Technical Information Service (NTIS)

The scanning electron microscope (SEM) has become as standard a tool for IC failure analysis as the optical microscope, with improvements in existing SEM techniques and new techniques being reported regularly. This tutorial has been designed to benefit bo...

E. I. Cole

1992-01-01

41

Quantitative imaging of bilirubin by photoacoustic microscopy  

NASA Astrophysics Data System (ADS)

Noninvasive detection of both bilirubin concentration and its distribution is important for disease diagnosis. Here we implemented photoacoustic microscopy (PAM) to detect bilirubin distribution. We first demonstrate that our PAM system can measure the absorption spectra of bilirubin and blood. We also image bilirubin distributions in tissuemimicking samples, both without and with blood mixed. Our results show that PAM has the potential to quantitatively image bilirubin in vivo for clinical applications.

Zhou, Yong; Zhang, Chi; Yao, Da-Kang; Wang, Lihong V.

2013-03-01

42

Remineralization of enamel subsurface lesions with casein phosphopeptide-amorphous calcium phosphate: A quantitative energy dispersive X-ray analysis using scanning electron microscopy: An in vitro study  

PubMed Central

Aim: The objective of this study was to quantitatively evaluate the remineralization potential of casein phosphopeptide-amor-phous calcium phosphate paste on enamel subsurface lesions using scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX). Materials and Methods: Ninety enamel specimens were prepared from extracted human molars. All specimens were evaluated for mineral content (% weight) using SEM-EDX. The specimens were placed in demineralizing solution for four days to produce artificial carious lesions. The mineral content (calcium/phosphorus ratios, Ca/P ratios) was remeasured using SEM-EDX. The specimens were then randomly assigned to five study groups and one control group of 15 specimens per group. Except for the control group, all group specimens were incubated in remineralizing paste (CPP-ACP paste) for 7, 14, 21, 28, and 35 days twice daily for three minutes. The control group received no treatment with remineralizing paste. All the 90 specimens were stored in artificial saliva at 37°C. After remineralization, the mineral content (% weight) of the samples was measured using SEM-EDX. Results: All the study groups showed very highly significant differences between Ca/P ratios of the demineralized and remineralized samples. There was no significant difference seen in the control group. Conclusion: CPP-ACP paste could significantly remineralize the artificial enamel subsurface lesions in vitro: the remineralizing rates increasing with the time for which the samples were kept in the remineralizing paste. Energy dispersive X-ray analysis is an efficient way to quantitatively assess the changes in mineral content during demineralization and in vitro remineralization processes.

Hegde, Mithra N; Moany, Anu

2012-01-01

43

Dynamic imaging with electron microscopy  

ScienceCinema

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.

Campbell, Geoffrey; McKeown, Joe; Santala, Melissa

2014-05-30

44

Microstructural examination of layered coatings by scanning electron microscopy, transmission electron microscopy, and atomic force microscopy  

Microsoft Academic Search

The structure of r.f. sputtered multilayer Ti-BN coatings was investigated by low-voltage scanning electron microscopy, energy-dispersive X-ray spectrometry, transmission electron microscopy, and atomic force microscopy. Appropriate specimen preparation methods are described for each technique; these included fracture of the substrate, masking the growing film to produce a taper section, and ion-beam milling of embedded cross sections. Correlation of scanning electron

D. G. Rickerby; T. Friesen

1996-01-01

45

From Quantitative Microscopy to Automated Image Understanding  

PubMed Central

Quantitative microscopy has been extensively used in biomedical research and has provided significant insights into structure and dynamics at the cell and tissue level. The entire procedure of quantitative microscopy is comprised of specimen preparation, light absorption/reflection/emission from the specimen, microscope optical processing, optical/electrical conversion by a camera or detector, and computational processing of digitized images. Although many of the latest digital signal processing techniques have been successfully applied to compress, restore, and register digital microscope images, automated approaches for recognition and understanding of complex subcellular patterns in light microscope images have been far less widely used. In this review, we describe a systematic approach for interpreting protein subcellular distributions using various sets of Subcellular Location Features (SLF) in combination with supervised classification and unsupervised clustering methods. These methods can handle complex patterns in digital microscope images and the features can be applied for other purposes such as objectively choosing a representative image from a collection and performing statistical comparison of image sets.

Huang, Kai; Murphy, Robert F.

2005-01-01

46

THEORETICAL FUNDAMENTALS AND EXPERIMENTAL MATERIALS AND DEFECT STUDIES USING QUANTITATIVE SCANNING ELECTRON MICROSCOPY CATHODOLUMINESCENCE\\/ELECTRON BEAM INDUCED CURRENT ON COMPOUND SEMICONDUCTORS  

Microsoft Academic Search

The theoretical fundamentals for the calculation of the local cathodoluminescence (CL) signal and electron beam induced current (EBIC) in the scanning electron microscope (SEM) are outlined. Especially, the simulation of the signal contrast profile behavior of individual dislocation configurations is reviewed. Existing analytical models and new numerical approaches are summarized. In addition to the evaluation of material parameters, the conception

S. Hildebrandt; J. Schreiber; W. Hergert; H. Uniewski; H. S. Leipner

47

Direct imaging of crystal structure and defects in metastable Ge2Sb2Te5 by quantitative aberration-corrected scanning transmission electron microscopy  

NASA Astrophysics Data System (ADS)

Knowledge about the atomic structure and vacancy distribution in phase change materials is of foremost importance in order to understand the underlying mechanism of fast reversible phase transformation. In this Letter, by combining state-of-the-art aberration-corrected scanning transmission electron microscopy with image simulations, we are able to map the local atomic structure and composition of a textured metastable Ge2Sb2Te5 thin film deposited by pulsed laser deposition with excellent spatial resolution. The atomic-resolution scanning transmission electron microscopy investigations display the heterogeneous defect structure of the Ge2Sb2Te5 phase. The obtained results are discussed. Highly oriented Ge2Sb2Te5 thin films appear to be a promising approach for further atomic-resolution investigations of the phase change behavior of this material class.

Ross, Ulrich; Lotnyk, Andriy; Thelander, Erik; Rauschenbach, Bernd

2014-03-01

48

Quantitative biological microscopy by digital holography  

NASA Astrophysics Data System (ADS)

In this dissertation, improved techniques in digital holography, that have produced high-resolution, high-fidelity images, are discussed. In particular, the angular spectrum method of calculating holographic optical field is noted to have several advantages over the more commonly used Fresnel transformation or Huygens convolution method. It is observed that spurious noise and interference components can be tightly controlled through the analysis and filtering of the angular spectrum. In the angular spectrum method, the reconstruction distance does not have a lower limit, and the off-axis angle between the object and reference waves can be lower than that of the Fresnel requirement, while still allowing the zero-order background to be cleanly separated. Holographic phase images are largely immune from the coherent noise commonly found in amplitude images. With the use of a miniature pulsed laser, the resulting images have 0.5im diffraction-limited lateral resolution and the phase profile is accurate to about several nanometers of optical path length. Samples such as ovarian cancer cells (SKOV-3) and mouse-embryo fibroblast cells have been imaged. These images display intra-cellular and intra-nuclear organelles with clarity and quantitative accuracy. This technique clearly exceeds currently available methods in phase-contrast optical microscopy in both resolution and detail and provides a new modality for imaging morphology of cellular and intracellular structures that is not currently available. Furthermore, we also demonstrate that phase imaging digital holographic movies provide a novel method of non-invasive quantitative viewing of living cells and other objects. This technique is shown to have significant advantages over conventional microscopy.

Mann, Christopher J.

49

Prototype cantilevers for quantitative lateral force microscopy.  

PubMed

Prototype cantilevers are presented that enable quantitative surface force measurements using contact-mode atomic force microscopy (AFM). The "hammerhead" cantilevers facilitate precise optical lever system calibrations for cantilever flexure and torsion, enabling quantifiable adhesion measurements and friction measurements by lateral force microscopy (LFM). Critically, a single hammerhead cantilever of known flexural stiffness and probe length dimension can be used to perform both a system calibration as well as surface force measurements in situ, which greatly increases force measurement precision and accuracy. During LFM calibration mode, a hammerhead cantilever allows an optical lever "torque sensitivity" to be generated for the quantification of LFM friction forces. Precise calibrations were performed on two different AFM instruments, in which torque sensitivity values were specified with sub-percent relative uncertainty. To examine the potential for accurate lateral force measurements using the prototype cantilevers, finite element analysis predicted measurement errors of a few percent or less, which could be reduced via refinement of calibration methodology or cantilever design. The cantilevers are compatible with commercial AFM instrumentation and can be used for other AFM techniques such as contact imaging and dynamic mode measurements. PMID:21974593

Reitsma, Mark G; Gates, Richard S; Friedman, Lawrence H; Cook, Robert F

2011-09-01

50

Spectroscopic imaging in electron microscopy  

SciTech Connect

In the scanning transmission electron microscope, multiple signals can be simultaneously collected, including the transmitted and scattered electron signals (bright field and annular dark field or Z-contrast images), along with spectroscopic signals such as inelastically scattered electrons and emitted photons. In the last few years, the successful development of aberration correctors for the electron microscope has transformed the field of electron microscopy, opening up new possibilities for correlating structure to functionality. Aberration correction not only allows for enhanced structural resolution with incident probes into the sub-angstrom range, but can also provide greater probe currents to facilitate mapping of intrinsically weak spectroscopic signals at the nanoscale or even the atomic level. In this issue of MRS Bulletin, we illustrate the power of the new generation of electron microscopes with a combination of imaging and spectroscopy. We show the mapping of elemental distributions at atomic resolution and also the mapping of electronic and optical properties at unprecedented spatial resolution, with applications ranging from graphene to plasmonic nanostructures, and oxide interfaces to biology.

Pennycook, Stephen J [ORNL; Colliex, C. [Universite Paris Sud, Orsay, France

2012-01-01

51

Direct Detectors for Electron Microscopy  

NASA Astrophysics Data System (ADS)

There is interest in improving the detectors used to capture images in transmission electron microscopy. Detectors with an improved modulation transfer function at high spatial frequencies allow for higher resolution in images at lower magnification, which leads to an increased effective field of view. Detectors with improved detective quantum efficiency are important for low dose applications. One way in which these performance enhancements can be achieved is through direct detection, where primary electrons are converted directly into suitable electrical signals by the detector rather than relying on an indirect electron to photon conversion before detection. In this paper we present the characterisation of detector performance for a number of different direct detection technologies, and compare these technologies to traditional indirect detectors. Overall our results show that direct detection enables a significant improvement in all aspects of detector performance.

Clough, R. N.; Moldovan, G.; Kirkland, A. I.

2014-06-01

52

Quantitative imaging of flux vortices in the type-II superconductor MgB2 using cryo-Lorentz transmission electron microscopy  

NASA Astrophysics Data System (ADS)

Imaging of flux vortices in high quality MgB2 single crystals has been successfully performed in a commercial field-emission gun-based transmission electron microscope. In cryo-Lorentz microscopy, the sample quality and the vortex lattice can be monitored simultaneously, allowing one to relate microscopically the surface quality and the vortex dynamics. Such a vortex motion ultimately determines the flow resistivity ?f, the knowledge of which is indispensable for practical applications such as superconducting magnets or wires for magnetic resonance imaging. The observed patterns have been analyzed and compared with other studies by cryo-Lorentz microscopy or Bitter decoration. We find that the vortex lattice arrangement depends strongly on the surface quality obtained during the specimen preparation, and tends to form a hexagonal Abrikosov lattice at a relatively low magnetic field. Stripes or gossamerlike patterns, recently suggested as potential signatures of an unconventional behavior of MgB2, were not observed.

Cottet, M. J. G.; Cantoni, M.; Mansart, B.; Alexander, D. T. L.; Hébert, C.; Zhigadlo, N. D.; Karpinski, J.; Carbone, F.

2013-07-01

53

Four-dimensional ultrafast electron microscopy  

PubMed Central

Electron microscopy is arguably the most powerful tool for spatial imaging of structures. As such, 2D and 3D microscopies provide static structures with subnanometer and increasingly with ångstrom-scale spatial resolution. Here we report the development of 4D ultrafast electron microscopy, whose capability imparts another dimension to imaging in general and to dynamics in particular. We demonstrate its versatility by recording images and diffraction patterns of crystalline and amorphous materials and images of biological cells. The electron packets, which were generated with femtosecond laser pulses, have a de Broglie wavelength of 0.0335 Å at 120 keV and have as low as one electron per pulse. With such few particles, doses of few electrons per square ångstrom, and ultrafast temporal duration, the long sought after but hitherto unrealized quest for ultrafast electron microscopy has been realized. Ultrafast electron microscopy should have an impact on all areas of microscopy, including biological imaging.

Lobastov, Vladimir A.; Srinivasan, Ramesh; Zewail, Ahmed H.

2005-01-01

54

Ballistic Electron Emission Microscopy Study of Novel Quantum Objects and Electronic Defects.  

National Technical Information Service (NTIS)

Over the approximately 2 1/2 year period of the above AFOSR grant, substantial progress has been made in the further development of Ballistic Electron Emission Microscopy (BEEM) as a quantitative microscopic and spectroscopic tool for the characterization...

V. Narayanamurti J. Bowers

2000-01-01

55

Quantitative electron microscopy of carcinogen-induced alterations in hepatocyte rough endoplasmic reticulum. II. Modulation of the effects of 3'MeDAB by adrenalectomy and adrenal corticosteroids.  

PubMed Central

A quantitative electron microscope study was made of the effects of bilateral adrenalectomy (ADX) and deoxycorticosterone acetate (DOCA) on the state of aggregation of hepatocyte rough ER cisternae in both untreated and 3'MeDAB-fed Leeds strain rats. Disaggregation of hepatocellular rough ER appears to be a common response of the rat liver to hepatocarcinogenic insult, while ADX and DOCA treatment are known to inhibit the chemical induction of neoplasia in this species. In untreated animals both ADX and DOCA significantly increased the mean number of cisternae per array or stack, while an even more pronounced effect was obtained from a combination of the two. The carcinogen 3'MeDAB induced a highly significant loss of aggregation, which was prevented by the combination of ADX and DOCA. In a separate experiment, a single dose of cortisone acetate was also found to partially reverse 3'MeDAB-induced rough ER disaggregation. In the rat hepatocyte, rough ER stacking or aggregation appears to be at least partially under hormonal control. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7

Winton, D. J.; Flaks, B.

1989-01-01

56

Electron Microscopy of Tungsten Disulphide Inorganic Nanomaterials.  

National Technical Information Service (NTIS)

Transmission and scanning electron microscopy studies of tungsten disulphide nanomaterials revealed nanotubes and onion-like structures. An electron diffraction pattern confirmed the lattice image of this nanotube. The tungsten disulphide nanomaterials ex...

E. Jelis S. Kerwien T. Chatterjee

2009-01-01

57

CONFOCAL MICROSCOPY SYSTEM PERFORMANCE: QA TESTS, QUANTITATION AND SPECTROSCOPY  

EPA Science Inventory

Confocal Microscopy System Performance: QA tests, Quantitation and Spectroscopy. Robert M. Zucker 1 and Jeremy M. Lerner 2, 1Reproductive Toxicology Division, National Health and Environmental Effects Research Laboratory, Office of Research Development, U.S. Environmen...

58

Optical microscopy versus scanning electron microscopy in urolithiasis  

Microsoft Academic Search

Stone analysis is incompletely done in many clinical centers. Identification of the stone component is essential for deciding\\u000a future prophylaxis. X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy (SEM) still\\u000a remains a distant dream for routine hospital work. It is in this context that optical microscopy is suggested as an alternate\\u000a procedure. The objective of this article was

Y. M. Fazil Marickar; P. R. Lekshmi; Luxmi Varma; Peter Koshy

2009-01-01

59

Detection of nanobacteria by immune electronic microscopy  

Microsoft Academic Search

AIM: To introduce an effective method of immunogold electron microscopy for the detection of nanobacteria. METHODS: Nanobacteria were fixed in the 25 g\\/L glut- araldehyde, and then were embedded in resin. After they were cut into ultrathin slices by diamond knife, an indirect immunogold electronic microscopy staining was performed on the nanobacteria using the specific antibody of nanobacteria. RESULTS: The

Li-Min Wang; Wen-Lv Shen; Zhen Zhou; Shi-Lian Zhang

60

Electron microscopy of specimens in liquid  

Microsoft Academic Search

Imaging samples in liquids with electron microscopy can provide unique insights into biological systems, such as cells containing labelled proteins, and into processes of importance in materials science, such as nanoparticle synthesis and electrochemical deposition. Here we review recent progress in the use of electron microscopy in liquids and its applications. We examine the experimental challenges involved and the resolution

Niels de Jonge; Frances M. Ross

2011-01-01

61

Paul Edwards's tutorial on scanning electron microscopy  

NSDL National Science Digital Library

This site from the University of Durham features descriptions of various scanning electron microscopy methods such as primary and secondary electron imaging, energy-dispersive analysis of X-rays, cathodoluminescence, and electron-beam induced current. Links to other scanning electron microscopic sites are also included.

Edwards, Paul; Durham, University O.

62

Atomic resolution 3D electron diffraction microscopy  

SciTech Connect

Electron lens aberration is the major barrier limiting the resolution of electron microscopy. Here we describe a novel form of electron microscopy to overcome electron lens aberration. By combining coherent electron diffraction with the oversampling phasing method, we show that the 3D structure of a 2 x 2 x 2 unit cell nano-crystal (framework of LTA [Al12Si12O48]8) can be ab initio determined at the resolution of 1 Angstrom from a series of simulated noisy diffraction pattern projections with rotation angles ranging from -70 degrees to +70 degrees in 5 degrees increments along a single rotation axis. This form of microscopy (which we call 3D electron diffraction microscopy) does not require any reference waves, and can image the 3D structure of nanocrystals, as well as non-crystalline biological and materials science samples, with the resolution limited only by the quality of sample diffraction.

Miao, Jianwei; Ohsuna, Tetsu; Terasaki, Osamu; O'Keefe, Michael A.

2002-03-01

63

Quantitative comparison of the void distribution in a. beta. '-phase Ni-Al-In alloy using x-ray small-angle scattering and transmission-electron microscopy. [Ni-51. 2 at. % Al-2. 6 at. % In  

SciTech Connect

Small-angle scattering is a rather mature discipline which can yield valuable information on the size, amount, and distribution of inhomogeneities encountered in materials-science research. Methods have been publisheed which permit one to extend the standard analysis of data from a small-angle-scattering experiment to include determination of the distribution of particle sizes. This extended analysis has been carried out for voids in a ..beta..'-phase Ni-Al-In alloy, and, in order to assess the reliability of the procedure, the identical void distribution as been characterized by transmission-electron microscopy. A quantitative comparison is made of the results from thses two independent experiments, and the general performance of the Brill-Schmidt method for particle-size determinations is discussed. 6 figures, 1 table.

Epperson, J.E.; Loomis, B.A.; Lin, J.S.

1981-11-01

64

Fluorescence-integrated transmission electron microscopy images: integrating fluorescence microscopy with transmission electron microscopy.  

PubMed

This chapter describes high-pressure freezing (HPF) techniques for correlative light and electron microscopy on the same sample. Laser scanning confocal microscopy (LSCM) is exploited for its ability to collect fluorescent, as well as transmitted and back scattered light (BSL) images at the same time. Fluorescent information from a whole mount (preembedding) or from thin sections (post-embedding) can be displayed as a color overlay on transmission electron microscopy (TEM) images. Fluorescence-integrated TEM (F-TEM) images provide a fluorescent perspective to TEM images. The pre-embedding method uses a thin two-part agarose pad to immobilize live Caenorhabditis elegans embryos for LSCM, HPF, and TEM. Pre-embedding F-TEM images display fluorescent information collected from a whole mount of live embryos onto all thin sections collected from that sample. In contrast, the postembedding method uses HPF and freeze substitution with 1% paraformaldehyde in 95% ethanol followed by low-temperature embedding in methacrylate resin. This procedure preserves the structure and function of green fluorescent protein (GFP) as determined by immunogold labeling of GFP, when compared with GFP expression, both demonstrated in the same thin section. PMID:17656756

Sims, Paul A; Hardin, Jeff D

2007-01-01

65

Electron Microscopy Unit Snow Page  

NSDL National Science Digital Library

Whether you are a climatologist or geoscientist looking for good image data or just want to cool off during a summer heatwave, this site from Beltsville Agricultural Research Center is not to be missed. Over 40 exquisite electron micrographs of snowflakes are housed here. A low temperature scanning electron microscope (SEM) was used in the imaging. Martian snow, rime and graupel, stereo images with cool .gif animations, and comparison of light and SEM images are showcased. Some images can be zoomed and informational summaries accompany the plates. An overview of agricultural applications of snow research and a publication list with some full-text links are also available.

66

ELECTRON MICROSCOPY OF INCONTINENTIA PIGMENTI  

Microsoft Academic Search

Electron microscopic examination revealed common features, although to varying extent, in all three stages of incontinentia pigmenti. All three stages showed (1) dyskeratosis; (2) phagocytosis of dyskeratotic cells and of melanosomes by macrophages; and (3) presence of melanophages in the upper dermis. Dyskeratosis and phagocytosis were most pronounced in stage II, and presence of melanophages in stage III. In addition

Gundula Schamburg-Lever; Walter F. Lever

1973-01-01

67

Electron Microprobe Analysis and Scanning Electron Microscopy in Geology - 2nd Edition  

Microsoft Academic Search

Now fully updated to cover recent developments, this book covers the closely related techniques of electron microprobe analysis (EMPA) and scanning electron microscopy (SEM) specifically from a geological viewpoint. Topics discussed include: principles of electron-target interactions, electron beam instrumentation, X-ray spectrometry, general principles of SEM image formation, production of X-ray `maps' showing elemental distributions, procedures for qualitative and quantitative X-ray

S. J. B. Reed

2005-01-01

68

Resolution measures in molecular electron microscopy  

PubMed Central

Resolution measures in molecular electron microscopy provide means to evaluate quality of macromolecular structures computed from sets of their two-dimensional line projections. When the amount of detail in the computed density map is low there are no external standards by which the resolution of the result can be judged. Instead, resolution measures in molecular electron microscopy evaluate consistency of the results in reciprocal space and present it as a one-dimensional function of the modulus of spatial frequency. Here we provide description of standard resolution measures commonly used in electron microscopy. We point out that the organizing principle is the relationship between these measures and the Spectral Signal-to-Noise Ratio of the computed density map. Within this framework it becomes straightforward to describe the connection between the outcome of resolution evaluations and the quality of electron microscopy maps, in particular, the optimum filtration, in the Wiener sense, of the computed map. We also provide a discussion of practical difficulties of evaluation of resolution in electron microscopy, particularly in terms of its sensitivity to data processing operations used during structure determination process in single particle analysis and in electron tomography.

Penczek, Pawel A.

2011-01-01

69

Electron microscopy of endocytic pathways.  

PubMed

Detailed insight into the fine structure and 3D-architecture of the complex and dynamic compartments of the endocytic system is essential for a morpho-functional analysis of retrograde traffic from the cell surface to different intracellular destinations. Here, we describe a cytochemical approach for electron microscopic exploration of endocytic pathways with the use of wheat germ agglutinin (WGA) in combination with either conventional chemical fixation or ultrafast physical fixation of the cells by high pressure-freezing. Horseradish peroxidase-labeled WGA endocytozed by human hepatoma cells for various periods of time served as a marker. Its intracellular routes were visualized by means of diaminobenzidine oxidation either done conventionally after chemical fixation or in living cells prior to physical fixation. The latter protocol permits the combination of peroxidase-catalyzed cytochemistry with high pressure-freezing (HPF), which is state of the art for ultrastructural studies of complex and dynamic organelles at high spatial and temporal resolutions. The technique yields distinct cytochemical reactions and excellently preserved fine structures well qualified for detailed electron microscopic and 3D-studies of the complex endocytic architectures. PMID:23027016

Ranftler, Carmen; Auinger, Peter; Meisslitzer-Ruppitsch, Claudia; Ellinger, Adolf; Neumüller, Josef; Pavelka, Margit

2013-01-01

70

Electron Microscopy Characterization of Hybrid Metallic Nanomaterials  

NASA Astrophysics Data System (ADS)

In order to understand the excellent properties of nanoscale hybridized materials, it is very important to investigate the microstructures and interfaces of these materials at the nanometer scale. In this chapter, we present the basic principles of transmission electron microscopy and its applications to these materials. In addition to high-resolution transmission electron microscopy (HREM) and high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM), analytical electron microscopy, including energy dispersive X-ray spectroscopy (EDS) and electron energyloss spectroscopy (EELS) as well as elemental mapping methods using these spectroscopy techniques will be presented. Also, the electron holographic technique for characterization of magnetic fields of nanohybridized materials will be explained. In addition to electron microscopic observation techniques, recently developed specimen preparation techniques, which are indispensable for obtaining homogeneous and thin films of nanohybridized materials, will be presented. In particular, a focused ion beam (FIB) method will be emphasized. The nanohybridized materials discussed in this chapter include carbon-based core-shell structure, nanocrystalline soft magnetic materials, nanocomposite magnets, and high-T c superconducting oxides. Application data will be provided in order to explain the usefulness of these analytical techniques for characterization of nanohybridized materials.

Shindo, Daisuke; Akase, Zentaro

71

Quantitative biological imaging by ptychographic x-ray diffraction microscopy  

PubMed Central

Recent advances in coherent x-ray diffractive imaging have paved the way to reliable and quantitative imaging of noncompact specimens at the nanometer scale. Introduced a year ago, an advanced implementation of ptychographic coherent diffractive imaging has removed much of the previous limitations regarding sample preparation and illumination conditions. Here, we apply this recent approach toward structure determination at the nanoscale to biological microscopy. We show that the projected electron density of unstained and unsliced freeze-dried cells of the bacterium Deinococcus radiodurans can be derived from the reconstructed phase in a straightforward and reproducible way, with quantified and small errors. Thus, the approach may contribute in the future to the understanding of the highly disputed nucleoid structure of bacterial cells. In the present study, the estimated resolution for the cells was 85 nm (half-period length), whereas 50-nm resolution was demonstrated for lithographic test structures. With respect to the diameter of the pinhole used to illuminate the samples, a superresolution of about 15 was achieved for the cells and 30 for the test structures, respectively. These values should be assessed in view of the low dose applied on the order of ?1.3·105 Gy, and were shown to scale with photon fluence.

Giewekemeyer, Klaus; Thibault, Pierre; Kalbfleisch, Sebastian; Beerlink, Andre; Kewish, Cameron M.; Dierolf, Martin; Pfeiffer, Franz; Salditt, Tim

2010-01-01

72

Advanced Electron Microscopy in Materials Physics  

SciTech Connect

Aberration correction has opened a new frontier in electron microscopy by overcoming the limitations of conventional round lenses, providing sub-angstrom-sized probes and extending information limits. The imaging and analytical performance of these corrector-equipped microscopes affords an unprecedented opportunity to study structure-property relationships of matter at the atomic scale. This new generation of microscopes is able to retrieve high-quality structural information comparable to neutron and synchrotron x-ray experiments, but with local atomic resolution. These advances in instrumentation are accelerating the research and development of various functional materials ranging from those for energy generation, conversion, transportation and storage to those for catalysis and nano-device applications. The dramatic improvements in electron-beam illumination and detection also present a host of new challenges for the interpretation and optimization of experiments. During 7-9 November 2007, a workshop, entitled 'Aberration Corrected Electron Microscopy in Material Physics', was convened at the Center for Functional Nanomaterials, Brookhaven National Laboratories (BNL) to address these opportunities and challenges. The workshop was co-sponsored by Hitachi High Technologies, a leader in electron microscopy instrumentation, and BNL's Institute of Advanced Electron Microscopy, a leader in materials physics research using electron microscopy. The workshop featured presentations by internationally prominent scientists working at the frontiers of electron microscopy, both on developing instrumentation and applying it in materials physics. The meeting, structured to stimulate scientific exchanges and explore new capabilities, brought together {approx}100 people from over 10 countries. This special issue complies many of the advances in instrument performance and materials physics reported by the invited speakers and attendees at the workshop.

Zhu, Y.; Jarausch, K.

2009-06-01

73

Optical microscopy versus scanning electron microscopy in urolithiasis.  

PubMed

Stone analysis is incompletely done in many clinical centers. Identification of the stone component is essential for deciding future prophylaxis. X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy (SEM) still remains a distant dream for routine hospital work. It is in this context that optical microscopy is suggested as an alternate procedure. The objective of this article was to assess the utility of an optical microscope which gives magnification of up to 40x and gives clear picture of the surface of the stones. In order to authenticate the morphological analysis of urinary stones, SEM and elemental distribution analysis were performed. A total of 250 urinary stones of different compositions were collected from stone clinic, photographed, observed under an optical microscope, and optical photographs were taken at different angles. Twenty-five representative samples among these were gold sputtered to make them conductive and were fed into the SEM machine. Photographs of the samples were taken at different angles at magnifications up to 4,000. Elemental distribution analysis (EDAX) was done to confirm the composition. The observations of the two studies were compared. The different appearances of the stones under optical illuminated microscopy were mostly standardized appearances, namely bosselations of pure whewellite, spiculations of weddellite, bright yellow colored appearance of uric acid, and dirty white amorphous appearance of phosphates. SEM and EDAX gave clearer pictures and gave added confirmation of the stone composition. From the references thus obtained, it was possible to confirm the composition by studying the optical microscopic pictures. Higher magnification capacity of the SEM and the EDAX patterns are useful to give reference support for performing optical microscopy work. After standardization, routine analysis can be performed with optical microscopy. The advantage of the optical microscope is that, it is easy to use and samples can be analyzed in natural color. PMID:19697015

Marickar, Y M Fazil; Lekshmi, P R; Varma, Luxmi; Koshy, Peter

2009-10-01

74

Active Pixel Sensors for electron microscopy  

NASA Astrophysics Data System (ADS)

The technology used for monolithic CMOS imagers, popular for cell phone cameras and other photographic applications, has been explored for charged particle tracking by the high-energy physics community for several years. This technology also lends itself to certain imaging detector applications in electron microscopy. We have been developing such detectors for several years at Lawrence Berkeley National Laboratory, and we and others have shown that this technology can offer excellent point-spread function, direct detection and high readout speed. In this paper, we describe some of the design constraints peculiar to electron microscopy and summarize where such detectors could play a useful role.

Denes, P.; Bussat, J.-M.; Lee, Z.; Radmillovic, V.

2007-09-01

75

Simultaneous Correlative Scanning Electron and High-NA Fluorescence Microscopy  

PubMed Central

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

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

2013-01-01

76

Quantitative Mapping of Switching Behavior in Piezoresponse Force Microscopy  

SciTech Connect

The application of ferroelectric materials for nonvolatile memory and ferroelectric data storage necessitates quantitative studies of local switching characteristics and their relationship to material microstructure and defects. Switching spectroscopy piezoresponse force microscopy (SS-PFM) is developed as a quantitative tool for real-space imaging of imprint, coercive bias, remanent and saturation responses, and domain nucleation voltage on the nanoscale. Examples of SS-PFM implementation, data analysis, and data visualization are presented for epitaxial lead zirconate titanate (PZT) thin films and polycrystalline PZT ceramics. Several common artifacts related to the measurement method, environmental factors, and instrument settings are analyzed.

Jesse, Stephen [ORNL; Lee, Ho Nyung [ORNL; Kalinin, Sergei V [ORNL

2006-01-01

77

Spectral-domain interferometry for quantitative DIC microscopy  

NASA Astrophysics Data System (ADS)

A spectral-domain differential interference contrast (SD-DIC) microscopy system is presented for quantitative imaging of both reflective and transparent samples. The spectral-domain interferometry, combined with the common-path DIC geometry, provides a shot noise-limited sensitivity of 14.3pm in optical pathlength gradient measurement. The optical resolution of the system was characterized using images of a USAF resolution target. Fused silica microspheres were imaged to demonstrate the reconstruction of two-dimensional optical pathlength topography from measured gradient fields. The exquisite sensitivity of the system showed potential in quantitative imaging of sub-diffraction limit objects such as gold nanoparticles.

Li, Chengshuai; Zhu, Yizheng

2014-03-01

78

Embedding method for electron microscopy in biology.  

PubMed

Transmission electron microscopes were commercially available in some foreign countries in the later 1930s. Sectioning for light microscopy was used for electron microscopic observations of the internal structure of cells and tissues in the early days. Paraffin waxes were tested as embedding media, but they were too soft to enable thin sections. Pease and Baker (1948) (74) achieved an early success with the double-embedding method using the plastic "Parlodion" and paraffin wax. PMID:3915837

Kushida, H

1985-12-01

79

ELECTRON MICROSCOPY LABORATORY Prices 2013 & 2014  

Cancer.gov

06/24/14 ELECTRON MICROSCOPY LABORATORY Frederick National Laboratory for Cancer Research Services without a price for a given year: may not be available, the price is pending or it hasn't been selected to be displayed on the web. Service Code Service

80

[Thermostat electronic circuit for vital microscopy].  

PubMed

To provide optimal temperature conditions needed for vital microscopy, an electronic circuit for the thermostat has been elaborated. This unit is designed to heat and maintain at a definite temperature level the table for manipulations and the microscope objective. Thermoresistor MMT-4 served as a temperature transducer. PMID:459772

Miliagin, V A; Litvinov, A V; Bobylev, M G

1979-01-01

81

Archaeological Ceramics Studied by Scanning Electron Microscopy  

Microsoft Academic Search

The use of scanning electron microscopy combined with energy dispersive X-ray fluorescence analysis in studies of archaeological\\u000a pottery is discussed. The methods are described and results of their application to studies of Precolumbian glossy black pottery\\u000a from northern Peru are reported in some detail.

J. Froh

2004-01-01

82

Organization of the Primate Retina: Electron Microscopy  

Microsoft Academic Search

The retinae of monkey and man have been studied by electron microscopy to identify cell types, their processes and synaptic contacts. In the inner plexiform layer, the morphological characteristics of the three types of cells (bipolar, ganglion and amacrine) are described and seven synaptic relationships are identified. The bipolar terminals contain ribbons at points of synaptic contact, and, at these

J. E. Dowling; B. B. Boycott

1966-01-01

83

Quantitative particle microscopy in self-metered fluids.  

PubMed

We describe a simple device that volumetrically samples poured liquids and draws buoyant? materials into a single field of view for quantitative particle microscopy. Our approach relies on the formation of axisymmetric menisci and computational models of the static fluid developed using surface evolver showed close agreement with experiment. The apparatus was evaluated by counting pollen and demonstrated utility for the field analysis of microparticles. PMID:23517459

White, L V; Cooke, I R; Wakes, S J; Sowerby, S J

2013-06-01

84

Photon-induced near field electron microscopy  

NASA Astrophysics Data System (ADS)

Ultrafast electron microscopy in the space and time domains utilizes a pulsed electron probe to directly map structural dynamics of nanomaterials initiated by an optical pump pulse, in imaging, di raction, spectroscopy, and their combinations. It has demonstrated its capability in the studies of phase transitions, mechanical vibrations, and chemical reactions. Moreover, electrons can directly interact with photons via the near eld component of light scattering by nanostructures, and either gain or lose light quanta discretely in energy. By energetically selecting those electrons that exchanged photon energies, we can map this photon-electron interaction, and the technique is termed photon-induced near eld electron microscopy (PINEM). Here, we give an account of the theoretical understanding of PINEM. Experimentally, nanostructures such as a sphere, cylinder, strip, and triangle have been investigated. Theoretically, time-dependent Schrodinger and Dirac equations for an electron under light are directly solved to obtain analytical solutions. The interaction probability is expressed by the mechanical work done by an optical wave on a traveling electron, which can be evaluated analytically by the near eld components of the Rayleigh scattering for small spheres and thin cylinders, and numerically by the discrete dipole approximation for other geometries. Application in visualization of plasmon elds is discussed.

Park, Sang Tae; Zewail, Ahmed H.

2013-09-01

85

Quantitative phase imaging with scanning holographic microscopy: an experimental assessment.  

PubMed

This paper demonstrates experimentally how quantitative phase information can be obtained in scanning holographic microscopy. Scanning holography can operate in both coherent and incoherent modes, simultaneously if desired, with different detector geometries. A spatially integrating detector provides an incoherent hologram of the object's intensity distribution (absorption and/or fluorescence, for example), while a point detector in a conjugate plane of the pupil provides a coherent hologram of the object's complex amplitude, from which a quantitative measure of its phase distribution can be extracted. The possibility of capturing simultaneously holograms of three-dimensional specimens, leading to three-dimensional reconstructions with absorption contrast, reflectance contrast, fluorescence contrast, as was previously demonstrated, and quantitative phase contrast, as shown here for the first time, opens up new avenues for multimodal imaging in biological studies. PMID:17132171

Indebetouw, Guy; Tada, Yoshitaka; Leacock, John

2006-01-01

86

Quantitative 3D imaging of whole, unstained cells by using X-ray diffraction microscopy  

PubMed Central

Microscopy has greatly advanced our understanding of biology. Although significant progress has recently been made in optical microscopy to break the diffraction-limit barrier, reliance of such techniques on fluorescent labeling technologies prohibits quantitative 3D imaging of the entire contents of cells. Cryoelectron microscopy can image pleomorphic structures at a resolution of 3–5 nm, but is only applicable to thin or sectioned specimens. Here, we report quantitative 3D imaging of a whole, unstained cell at a resolution of 50–60 nm by X-ray diffraction microscopy. We identified the 3D morphology and structure of cellular organelles including cell wall, vacuole, endoplasmic reticulum, mitochondria, granules, nucleus, and nucleolus inside a yeast spore cell. Furthermore, we observed a 3D structure protruding from the reconstructed yeast spore, suggesting the spore germination process. Using cryogenic technologies, a 3D resolution of 5–10 nm should be achievable by X-ray diffraction microscopy. This work hence paves a way for quantitative 3D imaging of a wide range of biological specimens at nanometer-scale resolutions that are too thick for electron microscopy.

Jiang, Huaidong; Song, Changyong; Chen, Chien-Chun; Xu, Rui; Raines, Kevin S.; Fahimian, Benjamin P.; Lu, Chien-Hung; Lee, Ting-Kuo; Nakashima, Akio; Urano, Jun; Ishikawa, Tetsuya; Tamanoi, Fuyuhiko; Miao, Jianwei

2010-01-01

87

Sparse imaging for fast electron microscopy  

NASA Astrophysics Data System (ADS)

Scanning electron microscopes (SEMs) are used in neuroscience and materials science to image centimeters of sample area at nanometer scales. Since imaging rates are in large part SNR-limited, large collections can lead to weeks of around-the-clock imaging time. To increase data collection speed, we propose and demonstrate on an operational SEM a fast method to sparsely sample and reconstruct smooth images. To accurately localize the electron probe position at fast scan rates, we model the dynamics of the scan coils, and use the model to rapidly and accurately visit a randomly selected subset of pixel locations. Images are reconstructed from the undersampled data by compressed sensing inversion using image smoothness as a prior. We report image fidelity as a function of acquisition speed by comparing traditional raster to sparse imaging modes. Our approach is equally applicable to other domains of nanometer microscopy in which the time to position a probe is a limiting factor (e.g., atomic force microscopy), or in which excessive electron doses might otherwise alter the sample being observed (e.g., scanning transmission electron microscopy).

Anderson, Hyrum S.; Ilic-Helms, Jovana; Rohrer, Brandon; Wheeler, Jason; Larson, Kurt

2013-02-01

88

Quantitative Short-pulse Acoustic Microscopy and Application to Materials Characterization.  

PubMed

A new acoustic microscopy method was developed for providing near-surface elastic property mapping of a material. This method has a number of advantages over the traditional V(z) technique. First, it enables one to perform measurements in an automated mode that only requires user intervention in the setup phase. This automated mode makes it feasible to obtain quantitative microscopy images of the elastic property over an area on the material being tested. Also, it only requires a conventional ultrasonic system operating in pulsed mode for collecting the data, rather than a specialized tone-burst system, which is needed in the traditional quantitative scanning acoustic microscopy technique. Finally, unlike the traditional method, the new experimental process does not require calibration of the system's electronics or additional reference data taken under hard-to-duplicate identical conditions from a material that does not exhibit surface acoustic waves. PMID:10675444

Matikas

2000-01-01

89

Comparative scanning electron microscopy of bullous diseases*  

PubMed Central

The purpose of this study is to compare scanning electron microscopy findings of the blister roof in three distinct bullous diseases: one intraepidermal acantholytic (pemphigus foliaceus); one due to hemidesmosomal dysfunction (bullous pemphigoid); and one secondary to anchoring fibril dysfunction - type VII collagen (dystrophic epidermolysis bullosa). In pemphigus foliaceus, acantholytic phenomena were readily demonstrated. In bullous pemphigoid, the epidermis had a solid aspect. In dystrophic epidermolysis bullosa a net was seen in the blister roof.

de Almeida, Hiram Larangeira; Rossi, Gabriela; Karam, Octavio Ruschel; Rocha, Nara Moreira; Silva, Ricardo Marques e

2014-01-01

90

Correlative Photoactivated Localization and Scanning Electron Microscopy  

PubMed Central

The ability to localize proteins precisely within subcellular space is crucial to understanding the functioning of biological systems. Recently, we described a protocol that correlates a precise map of fluorescent fusion proteins localized using three-dimensional super-resolution optical microscopy with the fine ultrastructural context of three-dimensional electron micrographs. While it achieved the difficult simultaneous objectives of high photoactivated fluorophore preservation and ultrastructure preservation, it required a super-resolution optical and specialized electron microscope that is not available to many researchers. We present here a faster and more practical protocol with the advantage of a simpler two-dimensional optical (Photoactivated Localization Microscopy (PALM)) and scanning electron microscope (SEM) system that retains the often mutually exclusive attributes of fluorophore preservation and ultrastructure preservation. As before, cryosections were prepared using the Tokuyasu protocol, but the staining protocol was modified to be amenable for use in a standard SEM without the need for focused ion beam ablation. We show the versatility of this technique by labeling different cellular compartments and structures including mitochondrial nucleoids, peroxisomes, and the nuclear lamina. We also demonstrate simultaneous two-color PALM imaging with correlated electron micrographs. Lastly, this technique can be used with small-molecule dyes as demonstrated with actin labeling using phalloidin conjugated to a caged dye. By retaining the dense protein labeling expected for super-resolution microscopy combined with ultrastructural preservation, simplifying the tools required for correlative microscopy, and expanding the number of useful labels we expect this method to be accessible and valuable to a wide variety of researchers.

Kopek, Benjamin G.; Shtengel, Gleb; Grimm, Jonathan B.; Clayton, David A.; Hess, Harald F.

2013-01-01

91

4D electron microscopy: principles and applications.  

PubMed

The transmission electron microscope (TEM) is a powerful tool enabling the visualization of atoms with length scales smaller than the Bohr radius at a factor of only 20 larger than the relativistic electron wavelength of 2.5 pm at 200 keV. The ability to visualize matter at these scales in a TEM is largely due to the efforts made in correcting for the imperfections in the lens systems which introduce aberrations and ultimately limit the achievable spatial resolution. In addition to the progress made in increasing the spatial resolution, the TEM has become an all-in-one characterization tool. Indeed, most of the properties of a material can be directly mapped in the TEM, including the composition, structure, bonding, morphology, and defects. The scope of applications spans essentially all of the physical sciences and includes biology. Until recently, however, high resolution visualization of structural changes occurring on sub-millisecond time scales was not possible. In order to reach the ultrashort temporal domain within which fundamental atomic motions take place, while simultaneously retaining high spatial resolution, an entirely new approach from that of millisecond-limited TEM cameras had to be conceived. As shown below, the approach is also different from that of nanosecond-limited TEM, whose resolution cannot offer the ultrafast regimes of dynamics. For this reason "ultrafast electron microscopy" is reserved for the field which is concerned with femtosecond to picosecond resolution capability of structural dynamics. In conventional TEMs, electrons are produced by heating a source or by applying a strong extraction field. Both methods result in the stochastic emission of electrons, with no control over temporal spacing or relative arrival time at the specimen. The timing issue can be overcome by exploiting the photoelectric effect and using pulsed lasers to generate precisely timed electron packets of ultrashort duration. The spatial and temporal resolutions achievable with short intense pulses containing a large number of electrons, however, are limited to tens of nanometers and nanoseconds, respectively. This is because Coulomb repulsion is significant in such a pulse, and the electrons spread in space and time, thus limiting the beam coherence. It is therefore not possible to image the ultrafast elementary dynamics of complex transformations. The challenge was to retain the high spatial resolution of a conventional TEM while simultaneously enabling the temporal resolution required to visualize atomic-scale motions. In this Account, we discuss the development of four-dimensional ultrafast electron microscopy (4D UEM) and summarize techniques and applications that illustrate the power of the approach. In UEM, images are obtained either stroboscopically with coherent single-electron packets or with a single electron bunch. Coulomb repulsion is absent under the single-electron condition, thus permitting imaging, diffraction, and spectroscopy, all with high spatiotemporal resolution, the atomic scale (sub-nanometer and femtosecond). The time resolution is limited only by the laser pulse duration and energy carried by the electron packets; the CCD camera has no bearing on the temporal resolution. In the regime of single pulses of electrons, the temporal resolution of picoseconds can be attained when hundreds of electrons are in the bunch. The applications given here are selected to highlight phenomena of different length and time scales, from atomic motions during structural dynamics to phase transitions and nanomechanical oscillations. We conclude with a brief discussion of emerging methods, which include scanning ultrafast electron microscopy (S-UEM), scanning transmission ultrafast electron microscopy (ST-UEM) with convergent beams, and time-resolved imaging of biological structures at ambient conditions with environmental cells. PMID:22967215

Flannigan, David J; Zewail, Ahmed H

2012-10-16

92

Eva Nogales: Introduction to Electron Microscopy  

NSDL National Science Digital Library

This lecture from the iBioSeminars project is presented by Eva Nogales Molecular Cell Biology Professor at the University of California, Berkeley, and it covers Visualizing Biological Structure Using Electron Microscopy: From Molecules to Cells. Transmission electron microscopy (TEM) offers the possibility of visualizing biological structures at resolution well beyond that of light microscopy. Whether you are interested in the ultrastructure of cells and organelles, or in the detailed molecular structure of biological macromolecules, different modalities of TEM can generally be applied to your system of interest. The lecture reviews the physical principles underlying image formation by the interaction of electrons with matter, introduces you to basic and advanced instruments and to sample preparation techniques. Using a number of biological examples from work in the Nogales lab, the lecture then describes the capabilities of the TEM methodology. Special emphasis is placed on the image processing methods used to obtain three-dimensional information from TEM data. The video runs 46:55 and can be downloaded in a number of formats: QuickTime, MP4, M4V, and PPT. The video can also be streamed through YouTube or iTunes U.

Nogales, Eva

2013-07-10

93

Background-free piezoresponse force microscopy for quantitative measurements  

NASA Astrophysics Data System (ADS)

We report an effective method to remove the system-inherent background [Jungk et al., Appl. Phys. Lett. 91, 253511 (2007)] that is present in nominal piezoresponse force microscopy (PFM) setup. Control experiments performed in both ambient and ultrahigh vacuum environments indicate that the system-inherent background probably originates from the interactions between the modulation voltage and surface absorptions. By minimizing such interactions, background-free PFM results were obtained on glass, ?-quartz, hexagonal ErMnO3, and periodically poled LiNbO3. The removal of background signal allows quantitative measurements of local intrinsic piezoelectric response with high sensitivity (?0.1 pm/V).

Wang, Wenbo; Geng, Yanan; Wu, Weida

2014-02-01

94

Rapid quantitative phase imaging for partially coherent light microscopy.  

PubMed

Partially coherent light provides promising advantages for imaging applications. In contrast to its completely coherent counterpart, it prevents image degradation due to speckle noise and decreases cross-talk among the imaged objects. These facts make attractive the partially coherent illumination for accurate quantitative imaging in microscopy. In this work, we present a non-interferometric technique and system for quantitative phase imaging with simultaneous determination of the spatial coherence properties of the sample illumination. Its performance is experimentally demonstrated in several examples underlining the benefits of partial coherence for practical imagining applications. The programmable optical setup comprises an electrically tunable lens and sCMOS camera that allows for high-speed measurement in the millisecond range. PMID:24921541

Rodrigo, José A; Alieva, Tatiana

2014-06-01

95

The continuing value of electron microscopy in surgical pathology.  

PubMed

For decades, transmission electron microscopy has played a valuable diagnostic role in surgical pathology. The continuing importance of electron microscopy, however, can be debated, given the major advances that have occurred in immunohistochemistry and other techniques. Electron microscopy retains excellent educational potential and broad research applicability, and it continues to be a necessity for the evaluation of a small subset of surgical pathology cases, such as renal biopsies and cilia specimens. The real controversy, then, centers on the contribution of electron microscopy in the evaluation of neoplasms. The opinion of many experts indicates that electron microscopy is still vital in the diagnostic assessment of some neoplasms, and that both electron microscopy and immunohistochemistry are more powerful when viewed as complementary rather than competitive techniques. For electron microscopy to be used to its potential, however, electron microscopists must function effectively as consultants. When optimally applied, electron microscopy remains an essential diagnostic tool. PMID:11206335

Tucker, J A

2000-01-01

96

Quantitative phase microscopy: how to make phase data meaningful  

NASA Astrophysics Data System (ADS)

The continued development of hardware and associated image processing techniques for quantitative phase microscopy has allowed superior phase data to be acquired that readily shows dynamic optical volume changes and enables particle tracking. Recent efforts have focused on tying phase data and associated metrics to cell morphology. One challenge in measuring biological objects using interferometrically obtained phase information is achieving consistent phase unwrapping and background shape removal throughout a sequence of images. Work has been done to improve the phase unwrapping in two-dimensions and correct for temporal discrepanices using a temporal unwrapping procedure. The residual background shape due to mean value fluctuations and residual tilts can be removed automatically using a simple object characterization algorithm. Once the phase data are processed consistently, it is then possible to characterize biological samples such as myocytes and myoblasts in terms of their size, texture and optical volume and track those features dynamically. By observing optical volume dynamically it is possible to determine the presence of objects such as vesicles within myoblasts even when they are co-located with other objects. Quantitative phase microscopy provides a label-free mechanism to characterize living cells and their morphology in dynamic environments, however it is critical to connect the measured phase to important biological function for this measurement modality to prove useful to a broader scientific community. In order to do so, results must be highly consistent and require little to no user manipulation to achieve high quality nynerical results that can be combined with other imaging modalities.

Goldstein, Goldie; Creath, Katherine

2014-03-01

97

Quantitative phase-contrast microscopy by angular spectrum digital holography  

NASA Astrophysics Data System (ADS)

Techniques of digital holography are improved in order to obtain high-resolution, high-fidelity images of quantitative phase-contrast microscopy. In particular, the angular spectrum method of calculating the holographic optical field is seen to have several advantages over the more commonly used Fresnel transformation or Huygens convolution method. Spurious noise and interference components can be tightly controlled through the analysis and filtering of the angular spectrum. The reconstruction distance does not have a lower limit and the off-axis angle between the object and reference can be lower than the Fresnel requirement and still be able to cleanly separate out the zero-order background. Holographic phase images are largely immune from the coherent noise common in amplitude images. Together with the use of a miniature pulsed laser, the resulting images have 0.5?m diffraction-limited lateral resolution and the phase profile is accurate to about 30 nm of optical path length. SKOV-3 (ovarian cancer cells) and HUVEC (human umbilical vein endothelial cells) are imaged that display intra-cellular and intra-nuclear organelles with clarity and quantitative accuracy. The technique clearly exceeds currently available methods in phase-contrast optical microscopy in the level of resolution and detail, and provides a new modality for imaging morphology of cellular and intracellular structures that is not currently available.

Mann, C. J.; Kim, M. K.

2006-03-01

98

Progress in quantitative single-molecule localization microscopy.  

PubMed

With the advent of single-molecule localization microscopy (SMLM) techniques, intracellular proteins can be imaged at unprecedented resolution with high specificity and contrast. These techniques can lead to a better understanding of cell functioning, as they allow, among other applications, counting the number of molecules of a protein specie in a single cell, studying the heterogeneity in protein spatial organization, and probing the spatial interactions between different protein species. However, the use of these techniques for accurate quantitative measurements requires corrections for multiple inherent sources of error, including: overcounting due to multiple localizations of a single fluorophore (i.e., photoblinking), undercounting caused by incomplete photoconversion, uncertainty in the localization of single molecules, sample drift during the long imaging time, and inaccurate image registration in the case of dual-color imaging. In this paper, we review recent efforts that address some of these sources of error in quantitative SMLM and give examples in the context of photoactivated localization microscopy (PALM). PMID:24748502

Deschout, H; Shivanandan, A; Annibale, P; Scarselli, M; Radenovic, A

2014-07-01

99

Contribution of Electron Microscopy of Materials Science to Society.  

National Technical Information Service (NTIS)

The examples discussed are just a few of very many that could be used to illustrate the impact of electron microscopy in materials upon society. Electron microscopy, materials science and engineering represent classic examples of demanding and interdiscip...

G. Thomas

1987-01-01

100

Electron microscopy study of Hispanic Terra Sigillata  

NASA Astrophysics Data System (ADS)

Two Hispanic Terra Sigillata pottery samples from different workshops Tricio and Andújar have been characterized by means of electron microscopy and associated techniques and X-ray diffraction data. The combined information from transmission electron microscopy images, electron diffraction patterns and microchemical analysis has revealed the nature and distribution of the precipitates of the ceramic piece slip, which is a very important part in the characterization of these kind of ceramic wares. Both samples present homogeneously dispersed ?-Fe2-xAlxO3 (corundum-type structure) particles embedded in a glassy matrix of SiO2-Al2O3. The Si : Al ratio of the matrix is different in each case, with a higher Al content in the Andújar ceramic sample. Crystallites of spinel Mg(Al,Fe)2O4 and Al2-xFexO3 are also detected in both cases. In addition, ilmenite phase (FeTiO3) and TiO2 (rutile-type) were observed less frequently.

Gómez-Herrero, A.; Urones-Garrote, E.; López, A. J.; Otero-Díaz, L. C.

2008-07-01

101

Electron microscopy studies of nucleosome remodelers  

PubMed Central

ATP-dependent chromatin remodeling complexes, or remodelers, are large protein assemblies that use the energy from ATP hydrolysis to non-covalently modify the structure of nucleosomes, playing a central role in the regulation of chromatin dynamics. Our understanding of the mechanism and regulation of this remodeling activity and the diversity of products that chromatin remodelers can generate remains limited, partly because very little structural data is available on these challenging samples. Electron microscopy (EM) and single-particle approaches have made inroads into the structural characterization of a number of remodeling complexes. Here I will review the work done to date, focusing on functional insights we have gained from these structures.

Leschziner, Andres E

2011-01-01

102

Quantitative thermal characterization of microelectronic devices by using CCD-based thermoreflectance microscopy  

NASA Astrophysics Data System (ADS)

A thermoreflectance microscopy (TRM) system has emerged as a non-destructive and non-contact tool for a high resolution thermal imaging technique for micro-scale electronic and optoelectronic devices. Quantitative imaging of the temperature distribution is necessary for elaborate thermal characterization under operating conditions, such as thermal profiling and performance and reliability analysis. We introduce here a straightforward TRM system to perform quantitative thermal characterization of microelectronics devices. The quantitative imaging of the surface temperature distribution of a polysilicon micro-resistor is obtained by a lock-in measurement technique and calibration process in the conventional CCD-based widefield microscope. To confirm the quantitative thermal measurement, the measured thermal information is compared to that obtained with an infrared thermography (IRT) system. In addition to quantitative surface temperature distribution, the sub-micron defects on microelectronic devices can be clearly distinguished from the thermoreflectance images, which are hardly perceptible with a conventional widefield microscopy system. The thermal resolution of the proposed TRM system is experimentally determined by measuring standard deviation values of thermoreflectance data with respect to the iteration number. The spatial and thermal resolutions of our system are measured ~670 nm and ~13 mK, respectively. We believe that quantitative thermal imaging in the TRM system can be used for improvement of microelectronic devices and integrated circuit (IC) designs.

Kim, Dong Uk; Ryu, Seon Young; Kim, Jun Ki; Chang, Ki Soo

2014-03-01

103

IMAGING RED BLOOD CELL DYNAMICS BY QUANTITATIVE PHASE MICROSCOPY  

PubMed Central

Red blood cells (RBCs) play a crucial role in health and disease, and structural and mechanical abnormalities of these cells have been associated with important disorders such as Sickle cell disease and hereditary cytoskeletal abnormalities. Although several experimental methods exist for analysis of RBC mechanical properties, optical methods stand out as they enable collecting mechanical and dynamic data from live cells without physical contact and without the need for exogenous contrast agents. In this report, we present quantitative phase microscopy techniques that enable imaging RBC membrane fluctuations with nanometer sensitivity at arbitrary time scales from milliseconds to hours. We further provide a theoretical framework for extraction of membrane mechanical and dynamical properties using time series of quantitative phase images. Finally, we present an experimental approach to extend quantitative phase imaging to 3-dimensional space using tomographic methods. By providing non-invasive methods for imaging mechanics of live cells, these novel techniques provide an opportunity for high-throughput analysis and study of RBC mechanical properties in health and disease.

Popescu, Gabriel; Park, YoungKeun; Choi, Wonshik; Dasari, Ramachandra R.; Feld, Michael S.; Badizadegan, Kamran

2008-01-01

104

Electron microscopy investigations of nanoparticles for cancer diagnostic applications  

Microsoft Academic Search

This dissertation concerns electron microscopy characterization of magnetic (MNP) and surface enhanced Raman scattering (SERS) nanoparticles for in-vitro cancer diagnostic applications. Electron microscopy is an essential characterization tool owing to its (sub) nanometer spatial resolution. Structural information about the nanoparticles can be obtained using transmission electron microscopy (TEM), which can in turn be correlated to their physical characteristics. The scanning

Ai Leen Koh

2009-01-01

105

Electron Microscopy of Botrytis cinerea Conidia  

PubMed Central

Buckley, Patricia M. (University of California, Davis), Virginia E. Sjaholm, and N. F. Sommer. Electron microscopy of Botrytis cinerea conidia. J. Bacteriol. 91:2037–2044. 1966.—Sections of germinating and nongerminating Botrytis cinerea conidia were examined with an electron microscope. Uranyl acetate or lead citrate provided contrast between membranes and cytoplasm. Membrane-bounded, dense inclusions previously unreported in dormant spores were termed “storage bodies.” Whorled structures, spherules, granules, and membrane loops were seen within these inclusions. The various forms assumed by the enclosed materials closely resemble phospholipid inclusions described for other cells. It is suggested that the inclusions provide material for the assembly of membranous organelles during germination. Utilization of the stored material apparently results in extensive vacuolization in advanced germinants. Images

Buckley, Patricia M.; Sjaholm, Virginia E.; Sommer, N. F.

1966-01-01

106

Electron microscopy of Giardia lamblia cysts.  

PubMed Central

The flagellated protozoan Giardia lamblia is a recognized public health problem. Intestinal infection can result in acute or chronic diarrhea with associated symptoms in humans. As part of a study to evaluate removal of G. lamblia cysts from drinking water by the processes of coagulation and dual-media filtration, we developed a methodology by using 5.0-microns-porosity membrane filters to evaluate the filtration efficiency. We found that recovery rates of G. lamblia cysts by membrane filtration varied depending upon the type and diameter of the membrane filter. Examination of membrane-filtered samples by scanning electron microscopy revealed flexible and flattened G. lamblia cysts on the filter surface. This feature may be responsible for the low recovery rates with certain filters and, moreover, may have implications in water treatment technology. Formation of the cyst wall is discussed. Electron micrographs of cysts apparently undergoing binary fission and cysts exhibiting a possible bacterial association are shown. Images

Luchtel, D L; Lawrence, W P; DeWalle, F B

1980-01-01

107

Scanning electron microscopy of body fluids.  

PubMed

Scanning Electron Microscopic (SEM) examination of body fluid specimens submitted for cytopathological diagnosis is technically easy and can be accomplished within hours. Specimens refrigerated for as long as 72 hr show no significant structural alterations that would interfere with recognition of diagnostically significant cells. SEM is particularly well suited for these specimens because the cells are free floating, and even cells in clusters have "natural" surfaces. Clinical uses of SEM on body fluids include the identification of ambiguous cells, distinction of reactive (benign) mesothelial cells from metastatic adenocarcinoma, and distinction of lymphoid cells from small cell carcinoma of the lung. In addition, SEM of these fluids assists cytologists to better understand the cellular features and associations seen in the light microscope. Ultrastructural analysis can be an important component of the Quality Assurance Plan for those cytodiagnostic laboratories that have access to an electron microscopy facility. PMID:1606884

Beals, T F

1992-01-01

108

Characterization of Hydroxyapatite by Electron Microscopy  

NASA Astrophysics Data System (ADS)

The obtention of hydroxyapatite (HAp) is reported using brushite (CaHPO4·2H2O) and the skeleton of a starfish (Mellita eduardobarrosoi sp. nov.), primarily composed of magnesian calcite ((Ca,Mg)CO3) as precursors. Stoichiometric amounts of both were reacted under hydrothermal conditions: a pressure of 5.8 MPa and a temperature of 200°C for 2, 4, 6, 8, 10, and 20 h of reaction times. The samples obtained were characterized by means of scanning electron microscopy, X-ray diffraction, infrared spectroscopy, and transmission electron microscopy. Two defined populations of HAp fibers were found: A bundle of fibers 75 [mu]m in length and 1 13 [mu]m in diameter, and a second bundle of fibers 5 [mu]m in length and less than 0.5 [mu]m in diameter. Furthermore, an increase in HAp formation and a Ca/P ratio as a function of reaction time were observed. The growth mechanism of HAp is also discussed.

Rodríguez-Lugo, V.; Sanchez Hernández, J.; Arellano-Jimenez, Ma. J.; Hernández-Tejeda, P. H.; Recillas-Gispert, S.

2005-12-01

109

Electron Microscopy of Chromatophores of Rhodopseudomonas spheroides  

PubMed Central

Gibson, K. D. (St. Mary's Hospital Medical School, London, England). Electron microscopy of Rhodopseudomonas spheroides. J. Bacteriol. 90:1059–1072. 1965.—Fixed and stained chromatophores and whole cells of anaerobically grown Rhodopseudomonas spheroides were examined in thin sections in the electron microscope. Both purified chromatophores and intracellular membrane-bound vesicles had exactly the same appearance, namely that of spheres or ellipsoids with a thin electron-dense shell surrounding an electron-lucent interior. The distribution of diameters in the two types of structure was also found to be the same, and was compatible with a normal distribution, with a mean of 570 A and a standard deviation 40 A. Negatively stained chromatophores appeared like discs or collapsed spheres. The presence of invaginations of the cytoplasmic membrane in this species was confirmed, and a new structure resembling a twin chromatophore was observed. The bearing of these results on theories of the origin of chromatophores is discussed, and it is concluded that they offer some support for each one of the three main theories about the origin of particulate organelles. Images

Gibson, K. D.

1965-01-01

110

Quantitative High Resolution Electron Scattering From Polymers.  

National Technical Information Service (NTIS)

This project developed and applied quantitative methods to determine the structure of polymers and polymer-based materials using high spation resolution electron-scattering techniques. The traditional approach to studying polymer morphology using the elec...

M. R. Libera

2004-01-01

111

Quantitative Electron Holography of Macromolecular Structure.  

National Technical Information Service (NTIS)

The principal theme underlying this ARO-funded research is the development and application of quantitative electron-optical methods to measure polymer morphology at nano and meso length scales where traditional TEM methods based on differential heavy-elem...

M. R. Libera

2001-01-01

112

Quantitative comparison of spot detection methods in fluorescence microscopy.  

PubMed

Quantitative analysis of biological image data generally involves the detection of many subresolution spots. Especially in live cell imaging, for which fluorescence microscopy is often used, the signal-to-noise ratio (SNR) can be extremely low, making automated spot detection a very challenging task. In the past, many methods have been proposed to perform this task, but a thorough quantitative evaluation and comparison of these methods is lacking in the literature. In this paper, we evaluate the performance of the most frequently used detection methods for this purpose. These include seven unsupervised and two supervised methods. We perform experiments on synthetic images of three different types, for which the ground truth was available, as well as on real image data sets acquired for two different biological studies, for which we obtained expert manual annotations to compare with. The results from both types of experiments suggest that for very low SNRs ( approximately 2), the supervised (machine learning) methods perform best overall. Of the unsupervised methods, the detectors based on the so-called h -dome transform from mathematical morphology or the multiscale variance-stabilizing transform perform comparably, and have the advantage that they do not require a cumbersome learning stage. At high SNRs ( > 5), the difference in performance of all considered detectors becomes negligible. PMID:19556194

Smal, Ihor; Loog, Marco; Niessen, Wiro; Meijering, Erik

2010-02-01

113

Electron Diffraction and Microscopy Studies of Surfaces  

NASA Astrophysics Data System (ADS)

The focus of this dissertation has been devoted to the investigation of the various phenomena observed in surface studies by means of reflection electron microscopy, reflection high energy electron diffraction, and reflection electron energy loss spectroscopy. The aim of this effort is to elucidate the process of interaction between electrons and a crystal lattice in the surface region, and to lead, in turn, to a comprehensive understanding of surface structure, surface domain, surface reactions, and surface dynamical processes. The resonance conditions responsible for the enhancement of the specular reflected beam observed in the diffraction from crystal surfaces have been characterized as Bragg-Channelling reflection and Bragg-Bragg reflection, respectively, in terms of different scattering mechanisms. Under these two resonance conditions, the tremendous increase in both elastic and inelastic electron scattering results in an intensity enhancement of the specular reflected beam. The parabolas and circles observed in diffraction patterns from crystal surfaces are closely associated with the electron channelling in the surface region. For the higher electron energy, the levels of the surface bound states go down deeper into the potential wells of rows of atoms. There is a strong temperature dependence on both surface channelling and normal reflected electrons. The total reflectivity did not change considerably with the variation of the diffraction condition. The improvement of the topographical contrast in surface imaging was not simply related to the increase in the intensity of the specular reflected beam. The surface image obtained from the Bragg-Bragg reflection condition showed a better image contrast for the surface structure among the varieties of resonance conditions. The appearances of the abnormal double contour contrast for a single-atom height step, which can be observed mostly with the fulfillment of the Bragg-Bragg reflection condition, was attributed to the electron dynamical scattering related to the surface channelling effect. The surface image contrast for the surface steps and dislocations were studied in detail under a variety of experimental conditions. Thin film specimens were prepared by depositing gold on GaAs and InP (110) surfaces. The epitaxial relationship and the interface reaction mechanisms were studied in detail. A new method of preparing atomic flat surfaces of copper single crystals with all possible lattice planes was developed. The surface oxides formed from the oxygen present in the bulk copper as Cu_2O inclusion were not found in this case. Detailed investigations of surface atomic structure, surface reactions with oxygen on alpha -Alumina single crystal (0, -1, 1) facets, and the surface domains with O-rich, and Al-rich termination are presented.

Yao, Nan

1990-08-01

114

Extracting quantitative parameters from images in multiphoton microscopy  

NASA Astrophysics Data System (ADS)

Coherent anti-Stokes Raman scattering (CARS) microscopy allows for fast, three-dimensionally resolved detection of molecules based on vibrational contrast. In CARS, the generated signal is nonlinearly dependent upon the concentration of the vibrational mode of interest. This makes it challenging to extract quantitative parameters (such as the concentration or orientation) from CARS images of biological and synthetic samples. Because of this, many investigations which employ CARS microscopy generally only report qualitative information extracted from these images. In this thesis, three methods have been developed to extract the quantitative concentration information from CARS images. In the first, the ratio of the forward-propagating and back-reflected CARS signal generated in tissue is used to monitor the percolation of DMSO into excised human cadaver skin. Through this, we find that the maximum clearing of skin with DMSO occurs at 40% v/v. We also combine CARS with second harmonic generation (SHG) to investigate the effects of DMSO on collagen. Up to a 20% v/v concentration of DMSO in the skin, the collagen becomes disrupted, resulting in a significant drop in the generated SHG. In the second method, the ratio between the CARS resonance peak and dip is correlated with the concentration to measure the concentration of water and deuterated glycine in hair. Both molecules are found to distribute throughout the hair fiber homogenously, water at a 34% v/v concentration, and d-glycine with a 0.22 M concentration. In the final method, CARS spectra over one vibrational mode are used to extract the imaginary part of the third-order nonlinear susceptibility. This quantity is linearly dependent upon the concentration of the vibrational mode of interest. This procedure is used to determine the degree of conversion of two-photon polymerized microstructures synthesized with varying writing powers. A sigmoidal relationship is observed between the applied intensity and the degree of conversion. The last chapter investigates another quantitative parameter, the orientation, of the CH2 vibrational mode in natural (cotton) and synthetic (rayon) cellulose fibers. Coupled with SHG, this method gives insight into the origins of observed optical nonlinearities in dry and hydrated cellulose fibers.

Zimmerley, Maxwell Stuart

115

Digital holographic microscopy: a quantitative label-free microscopy technique for phenotypic screening.  

PubMed

Digital Holographic Microscopy (DHM) is a label-free imaging technique allowing visualization of transparent cells with classical imaging cell culture plates. The quantitative DHM phase contrast image provided is related both to the intracellular refractive index and to cell thickness. DHM is able to distinguish cellular morphological changes on two representative cell lines (HeLa and H9c2) when treated with doxorubicin and chloroquine, two cytotoxic compounds yielding distinct phenotypes. We analyzed parameters linked to cell morphology and to the intracellular content in endpoint measurements and further investigated them with timelapse recording. The results obtained by DHM were compared with other optical label-free microscopy techniques, namely Phase Contrast, Differential Interference Contrast and Transport of Intensity Equation (reconstructed from three bright-field images). For comparative purposes, images were acquired in a common 96-well plate format on the different motorized microscopes. In contrast to the other microscopies assayed, images generated with DHM can be easily quantified using a simple automatized on-the-fly analysis method for discriminating the different phenotypes generated in each cell line. The DHM technology is suitable for the development of robust and unbiased image-based assays. PMID:24152227

Rappaz, Benjamin; Breton, Billy; Shaffer, Etienne; Turcatti, Gerardo

2014-01-01

116

Improved methods for high resolution electron microscopy  

SciTech Connect

Existing methods of making support films for high resolution transmission electron microscopy are investigated and novel methods are developed. Existing methods of fabricating fenestrated, metal reinforced specimen supports (microgrids) are evaluated for their potential to reduce beam induced movement of monolamellar crystals of C/sub 44/H/sub 90/ paraffin supported on thin carbon films. Improved methods of producing hydrophobic carbon films by vacuum evaporation, and improved methods of depositing well ordered monolamellar paraffin crystals on carbon films are developed. A novel technique for vacuum evaporation of metals is described which is used to reinforce microgrids. A technique is also developed to bond thin carbon films to microgrids with a polymer bonding agent. Unique biochemical methods are described to accomplish site specific covalent modification of membrane proteins. Protocols are given which covalently convert the carboxy terminus of papain cleaved bacteriorhodopsin to a free thiol. 53 refs., 19 figs., 1 tab.

Taylor, J.R.

1987-04-01

117

Scanning electron microscopy of tinea nigra*  

PubMed Central

Tinea nigra is a rare superficial mycosis caused by Hortaea werneckii. This infection presents as asymptomatic brown to black maculae mostly in palmo-plantar regions. We performed scanning electron microscopy of a superficial shaving of a tinea nigra lesion. The examination of the outer surface of the sample showed the epidermis with corneocytes and hyphae and elimination of fungal filaments. The inner surface of the sample showed important aggregation of hyphae among keratinocytes, which formed small fungal colonies. The ultrastructural findings correlated with those of dermoscopic examination - the small fungal aggregations may be the dark spicules seen on dermoscopy - and also allowed to document the mode of dissemination of tinea nigra, showing how hyphae are eliminated on the surface of the lesion.

Guarenti, Isabelle Maffei; de Almeida, Hiram Larangeira; Leitao, Aline Hatzenberger; Rocha, Nara Moreira; Silva, Ricardo Marques e

2014-01-01

118

Transmission Electron Microscopy Characterization of Nanocrystalline Copper  

SciTech Connect

The microstructure and grain boundary structure of nanocrystalline Cu powders and a compact prepared by the inert-gas condensation technique have been characterized by transmission electron microscopy. The as-prepared particles are round in shape and have no distinct surface facets. Annealing twins (coherent {Sigma}3 boundaries) have been observed in the as-prepared Cu particles as well as in the compact. Pores are commonly found at grain boundaries, triple grain junctions and some in the interior of grains in the compact. In addition to twin boundaries, a number of special grain boundaries have been observed. These special grain boundaries have low-index interface planes, and sometimes have misorientation angles close to coincidence site lattice (CSL) orientations.

Kung, H.; Sanders, P.G.; Weertman, J.R.

1999-11-01

119

Medipix 2 detector applied to low energy electron microscopy  

Microsoft Academic Search

Low energy electron microscopy (LEEM) and photo-emission electron microscopy (PEEM) traditionally use microchannel plates (MCPs), a phosphor screen and a CCD-camera to record images and diffraction patterns. In recent years, however, MCPs have become a limiting factor for these types of microscopy. Here, we report on a successful test series using a solid state hybrid pixel detector, Medipix 2, in

R. van Gastel; I. Sikharulidze; S. Schramm; J. P. Abrahams; B. Poelsema; R. M. Tromp; S. J. van der Molen

2009-01-01

120

Quantitative pathology in virtual microscopy: history, applications, perspectives.  

PubMed

With the emerging success of commercially available personal computers and the rapid progress in the development of information technologies, morphometric analyses of static histological images have been introduced to improve our understanding of the biology of diseases such as cancer. First applications have been quantifications of immunohistochemical expression patterns. In addition to object counting and feature extraction, laws of thermodynamics have been applied in morphometric calculations termed syntactic structure analysis. Here, one has to consider that the information of an image can be calculated for separate hierarchical layers such as single pixels, cluster of pixels, segmented small objects, clusters of small objects, objects of higher order composed of several small objects. Using syntactic structure analysis in histological images, functional states can be extracted and efficiency of labor in tissues can be quantified. Image standardization procedures, such as shading correction and color normalization, can overcome artifacts blurring clear thresholds. Morphometric techniques are not only useful to learn more about biological features of growth patterns, they can also be helpful in routine diagnostic pathology. In such cases, entropy calculations are applied in analogy to theoretical considerations concerning information content. Thus, regions with high information content can automatically be highlighted. Analysis of the "regions of high diagnostic value" can deliver in the context of clinical information, site of involvement and patient data (e.g. age, sex), support in histopathological differential diagnoses. It can be expected that quantitative virtual microscopy will open new possibilities for automated histological support. Automated integrated quantification of histological slides also serves for quality assurance. The development and theoretical background of morphometric analyses in histopathology are reviewed, as well as their application and potential future implementation in virtual microscopy. PMID:23313439

Kayser, Gian; Kayser, Klaus

2013-07-01

121

Quantitative analysis of autophagy using advanced 3D fluorescence microscopy.  

PubMed

Prostate cancer is the leading form of malignancies among men in the U.S. While surgery carries a significant risk of impotence and incontinence, traditional chemotherapeutic approaches have been largely unsuccessful. Hormone therapy is effective at early stage, but often fails with the eventual development of hormone-refractory tumors. We have been interested in developing therapeutics targeting specific metabolic deficiency of tumor cells. We recently showed that prostate tumor cells specifically lack an enzyme (argininosuccinate synthase, or ASS) involved in the synthesis of the amino acid arginine(1). This condition causes the tumor cells to become dependent on exogenous arginine, and they undergo metabolic stress when free arginine is depleted by arginine deiminase (ADI)(1,10). Indeed, we have shown that human prostate cancer cells CWR22Rv1 are effectively killed by ADI with caspase-independent apoptosis and aggressive autophagy (or macroautophagy)(1,2,3). Autophagy is an evolutionarily-conserved process that allows cells to metabolize unwanted proteins by lysosomal breakdown during nutritional starvation(4,5). Although the essential components of this pathway are well-characterized(6,7,8,9), many aspects of the molecular mechanism are still unclear - in particular, what is the role of autophagy in the death-response of prostate cancer cells after ADI treatment? In order to address this question, we required an experimental method to measure the level and extent of autophagic response in cells - and since there are no known molecular markers that can accurately track this process, we chose to develop an imaging-based approach, using quantitative 3D fluorescence microscopy(11,12). Using CWR22Rv1 cells specifically-labeled with fluorescent probes for autophagosomes and lysosomes, we show that 3D image stacks acquired with either widefield deconvolution microscopy (and later, with super-resolution, structured-illumination microscopy) can clearly capture the early stages of autophagy induction. With commercially available digital image analysis applications, we can readily obtain statistical information about autophagosome and lysosome number, size, distribution, and degree of colocalization from any imaged cell. This information allows us to precisely track the progress of autophagy in living cells and enables our continued investigation into the role of autophagy in cancer chemotherapy. PMID:23665532

Changou, Chun A; Wolfson, Deanna L; Ahluwalia, Balpreet Singh; Bold, Richard J; Kung, Hsing-Jien; Chuang, Frank Y S

2013-01-01

122

Low-energy electron point source microscopy and electron holography  

NASA Astrophysics Data System (ADS)

Low energy electron point source (LEEPS) microscopy is the simplest embodiment of an electron microscope, consisting of only a source, a sample and a detector. In a specific regime, LEEPS may also be used to create in-line holograms; special interference patterns that contain the information about the entire electron wavefront, including the structure of the sample and electromagnetic field around it. This work describes the design, construction and characterization of a microscope designed to performs LEEPS microscopy and electron holography at the nanoscale. An overview of previous experimental apparatus are discussed. Also, the impact of spatial and energetic inhomogeneities of the electron source on the quality and resolution of the hologram, in terms of the numerical aperture of the microscope and the virtual source size of the electron emitter. The design of the microscope itself is presented including the system for isolating the microscope from contamination, mechanical vibration and electrical noise. Using scanning tunnelling microscopy (STM) the microscope is shown to be stable within 0.1 Å. Instructions for the maintenance of the system are presented for future users of the microscope and to illustrate many of the systems described in the design of the microscope. The source of electrons used in the LEEPS microscope is a tungsten tip sharpened so as to field-emit electrons from a single atom. The technique for crafting such tips by field-assisted etching with nitrogen is described along with a discussion of the parameters used to control the aspect-ratio of the tip. Several samples are investigated using LEEPS: a sharp silicon nitride edge, a carbon nanotube bundle and graphene. The sample preparation techniques are discussed for each sample. Also, simple models for describing the resulting fringe patterns are proposed. There are several benefits associated with using LEEPS, including the lack of beam induced morphological changes or contamination. The samples are used to elucidate many properties about the optical system of the microscope, most importantly the expected resolution of the system. The software designed for the microscope to acquire images with high fidelity and for post-processing and correcting data is demonstrated. The microscope is shown to have a virtual source size of 1.6±0.6Å a figure that exceeds published results form similar instruments. Preliminary holographic reconstructions are shown. The work concludes with a discussion of the parameters to be optimized in order to reach atomic resolution.

Mutus, Josh

123

Electronic cameras for low-light microscopy.  

PubMed

This chapter introduces to electronic cameras, discusses the various parameters considered for evaluating their performance, and describes some of the key features of different camera formats. The chapter also presents the basic understanding of functioning of the electronic cameras and how these properties can be exploited to optimize image quality under low-light conditions. Although there are many types of cameras available for microscopy, the most reliable type is the charge-coupled device (CCD) camera, which remains preferred for high-performance systems. If time resolution and frame rate are of no concern, slow-scan CCDs certainly offer the best available performance, both in terms of the signal-to-noise ratio and their spatial resolution. Slow-scan cameras are thus the first choice for experiments using fixed specimens such as measurements using immune fluorescence and fluorescence in situ hybridization. However, if video rate imaging is required, one need not evaluate slow-scan CCD cameras. A very basic video CCD may suffice if samples are heavily labeled or are not perturbed by high intensity illumination. When video rate imaging is required for very dim specimens, the electron multiplying CCD camera is probably the most appropriate at this technological stage. Intensified CCDs provide a unique tool for applications in which high-speed gating is required. The variable integration time video cameras are very attractive options if one needs to acquire images at video rate acquisition, as well as with longer integration times for less bright samples. This flexibility can facilitate many diverse applications with highly varied light levels. PMID:23931509

Rasnik, Ivan; French, Todd; Jacobson, Ken; Berland, Keith

2013-01-01

124

Transmission electron microscopy characterization of composite nanostructures  

NASA Astrophysics Data System (ADS)

High Angle Annular Dark Field (HAADF) and Electron Energy Loss Spectroscopy (EELS) were investigated as characterization tools for chemical element localization in novel nanostructures. The studied nanostructures were Pt-Au core-shell bimetallic nanoparticles and semiconductor doped layers. Pt-Au bimetallic nanoparticles were synthesized by the polyol method and characterized with the techniques previously mentioned. EDS results confirmed the bimetallic nature of the synthesized nanoparticles. HAADF was determinant in the identification of core-shell nanoparticles. This was possible due to the presence of strain fields in the interface between the core and the shell elements produced by the difference in their lattice parameter. The presence of these strain fields produced an anomalous contrast on the HAADF images, which enabled the identification of this interface, and hence of the core-shell nanostructures. UV-Visible absorption spectra (experimental and simulated) in combination with EXAFS results allowed the identification of Au on the shell of the nanoparticles and Pt in the core. HAADF was proved to be a useful technique for core-shell nanoparticles identification. Several doped semiconductor nanostructures were also studied; B doped Si FinFET nanostructures, As doped Si samples and Ge1-xCx thin layers. For the case of the B doped Si FinFET nanostructures strain fields produced by the implantation of B atoms into the Si lattice allowed a qualitative determination of the 2-dimensional B dopant profile with the use of HAADF, just as in the case of the core-shell nanoparticles. In the As doped Si samples, EELS is proposed as a quantitative characterization tool for the determination of dopant concentrations based on the relationship described in the free-electron gas model between the characteristic plasmon peak energy and the electron density. Promising results obtained in the present study indicate the feasibility of using EELS as a quantitative tool for dopant concentration studies. Finally, a proper analysis of the EELS results allowed the observation of preferential segregation of C atoms to the interface between the Ge 1-xCx thin layers and the Si substrate where these layers were grown. We interpret this result as a mechanism of strain relaxation in Ge1-xCx layers grown directly on Si substrates.

Garcia Gutierrez, Domingo Ixcoatl

125

Quantitative surface parameter maps using Intermodulation Atomic Force Microscopy  

NASA Astrophysics Data System (ADS)

It is well known that the phase image in amplitude modulation atomic force microscopy (AM-AFM) is sensitive to material properties of the surface. However that information is not enough to fully quantify the tip-surface interaction. We have developed Intermodulation AFM, based on a spectral analysis of the cantilever's nonlinear dynamics, which increases the amount of information obtained without increasing scan time.ootnotetextD. Platz, E. A. Tholen, D. Pesen, and D. B. Haviland, Appl. Phys. Lett., 92, 153106 (2008) We show how it is possible to extract quantitative material properties of the surface from this additional information. The method works under the assumption of a tip-surface force model, such as the DMT model, fitting the model parameters to the measured spectral data. The parameters are obtained at each pixel of the AFM image and form surface property maps which can be displayed together with topography. We demonstrate this on different surfaces such as polymer blends, extracting stiffness and adhesive properties.

Forchheimer, Daniel; Platz, Daniel; Tholén, Erik; Hutter, Carsten; Haviland, David

2011-03-01

126

Quantitative polarized light microscopy of unstained mammalian cochlear sections  

PubMed Central

Abstract. Hearing loss is the most common sensory deficit in the world, and most frequently it originates in the inner ear. Yet, the inner ear has been difficult to access for diagnosis because of its small size, delicate nature, complex three-dimensional anatomy, and encasement in the densest bone in the body. Evolving optical methods are promising to afford cellular diagnosis of pathologic changes in the inner ear. To appropriately interpret results from these emerging technologies, it is important to characterize optical properties of cochlear tissues. Here, we focus on that characterization using quantitative polarized light microscopy (qPLM) applied to unstained cochlear sections of the mouse, a common animal model of human hearing loss. We find that the most birefringent cochlear materials are collagen fibrils and myelin. Retardance of the otic capsule, the spiral ligament, and the basilar membrane are substantially higher than that of other cochlear structures. Retardance of the spiral ligament and the basilar membrane decrease from the cochlear base to the apex, compared with the more uniform retardance of other structures. The intricate structural details revealed by qPLM of unstained cochlear sections ex vivo strongly motivate future application of polarization-sensitive optical coherence tomography to human cochlea in vivo.

Kalwani, Neil M.; Ong, Cheng Ai; Lysaght, Andrew C.; Haward, Simon J.; McKinley, Gareth H.; Stankovic, Konstantina M.

2013-01-01

127

Quantitative polarized light microscopy of unstained mammalian cochlear sections  

NASA Astrophysics Data System (ADS)

Hearing loss is the most common sensory deficit in the world, and most frequently it originates in the inner ear. Yet, the inner ear has been difficult to access for diagnosis because of its small size, delicate nature, complex three-dimensional anatomy, and encasement in the densest bone in the body. Evolving optical methods are promising to afford cellular diagnosis of pathologic changes in the inner ear. To appropriately interpret results from these emerging technologies, it is important to characterize optical properties of cochlear tissues. Here, we focus on that characterization using quantitative polarized light microscopy (qPLM) applied to unstained cochlear sections of the mouse, a common animal model of human hearing loss. We find that the most birefringent cochlear materials are collagen fibrils and myelin. Retardance of the otic capsule, the spiral ligament, and the basilar membrane are substantially higher than that of other cochlear structures. Retardance of the spiral ligament and the basilar membrane decrease from the cochlear base to the apex, compared with the more uniform retardance of other structures. The intricate structural details revealed by qPLM of unstained cochlear sections ex vivo strongly motivate future application of polarization-sensitive optical coherence tomography to human cochlea in vivo.

Kalwani, Neil M.; Ong, Cheng Ai; Lysaght, Andrew C.; Haward, Simon J.; McKinley, Gareth H.; Stankovic, Konstantina M.

2013-02-01

128

Quantitative polarized light microscopy of unstained mammalian cochlear sections.  

PubMed

Hearing loss is the most common sensory deficit in the world, and most frequently it originates in the inner ear. Yet, the inner ear has been difficult to access for diagnosis because of its small size, delicate nature, complex three-dimensional anatomy, and encasement in the densest bone in the body. Evolving optical methods are promising to afford cellular diagnosis of pathologic changes in the inner ear. To appropriately interpret results from these emerging technologies, it is important to characterize optical properties of cochlear tissues. Here, we focus on that characterization using quantitative polarized light microscopy (qPLM) applied to unstained cochlear sections of the mouse, a common animal model of human hearing loss. We find that the most birefringent cochlear materials are collagen fibrils and myelin. Retardance of the otic capsule, the spiral ligament, and the basilar membrane are substantially higher than that of other cochlear structures. Retardance of the spiral ligament and the basilar membrane decrease from the cochlear base to the apex, compared with the more uniform retardance of other structures. The intricate structural details revealed by qPLM of unstained cochlear sections ex vivo strongly motivate future application of polarization-sensitive optical coherence tomography to human cochlea in vivo. PMID:23407909

Kalwani, Neil M; Ong, Cheng Ai; Lysaght, Andrew C; Haward, Simon J; McKinley, Gareth H; Stankovic, Konstantina M

2013-02-01

129

Analysis of three-dimensional images in quantitative microscopy  

NASA Astrophysics Data System (ADS)

In bright field microscopy, quantitative analysis of acquired images is customarily performed using the `best' image. Since an image with sufficient detail and clarity is required for consistent classification and discrimination of objects in the image, the image with higher magnification is commonly chosen for the analysis, which generally corresponds to lower focal depths. The objectively determined `best' focus level, although optimal for the extraction of some features from the chosen objects, may not correspond to the best focal level for the extraction of some other features. To obtain tighter distribution of all features, we have been searching for a method which employs analysis of images acquired at different focal planes. In this work, we analyzed images of stained cervical cells using three different approaches. In the first approach, different features were extracted from images taken at different focal planes. In the second approach, we used simultaneously all the in-focus and out-of-focus information from the images to reconstruct the focussed images at various focal planes. In the third approach, the in-focus three-dimensional scene was compressed to two dimensions to simulate an image taken from a system with a very large depth of focus. The latter method reduced the data storage size and simplified subsequent scene analysis. The advantages and disadvantages of the above approaches are discussed.

Poon, Steven S. S.; Ward, Rabab K.; Palcic, Branko

1992-06-01

130

Silver nanoparticle-induced degranulation observed with quantitative phase microscopy  

NASA Astrophysics Data System (ADS)

Monitoring a degranulation process in a live mast cell is a quite important issue in immunology and pharmacology. Because the size of a granule is normally much smaller than the resolution limit of an optical microscope system, there is no direct real-time live cell imaging technique for observing degranulation processes except for fluorescence imaging techniques. In this research, we propose optical quantitative phase microscopy (QPM) as a new observation tool to study degranulation processes in a live mast cell without any fluorescence labeling. We measure the cell volumes and the cross sectional profiles (x-z plane) of an RBL-2H3 cell and a HeLa cell, before and after they are exposed to calcium ionophore A23187 and silver nanoparticles (AgNPs). We verify that the volume and the cross sectional line profile of the RBL-2H3 cell were changed significantly when it was exposed to A23187. When 50 ?g/mL of AgNP is used instead of A23187, the measurements of cell volume and cross sectional profiles indicate that RBL-2H3 cells also follow degranulation processes. Degranulation processes for these cells are verified by monitoring the increase of intracellular calcium ([Ca2+]i) and histamine with fluorescent methods.

Yang, Wenzhong; Lee, Seungrag; Lee, Jiyong; Bae, Yoonsung; Kim, Dugyoung

2010-07-01

131

High Resolution Electron Microscopy at the National Cancer Institute  

Cancer.gov

Imaging biological objects with electrons involves principles similar to those used in light microscopy, except that electrons are used for illumination instead of photons and the lenses are magnetic instead of being optical. In the last five decades, electron microscopy (EM) helped to reveal basic cell structures in great detail, allowing researchers to visualize internal structure at resolutions that were about 100 times better than that obtained by optical microscopy.

132

4D cryo-electron microscopy of proteins.  

PubMed

Cryo-electron microscopy is a form of transmission electron microscopy that has been used to determine the 3D structure of biological specimens in the hydrated state and with high resolution. We report the development of 4D cryo-electron microscopy by integrating the fourth dimension, time, into this powerful technique. From time-resolved diffraction of amyloid fibrils in a thin layer of vitrified water at cryogenic temperatures, we were able to detect picometer movements of protein molecules on a nanosecond time scale. Potential future applications of 4D cryo-electron microscopy are numerous, and some are discussed here. PMID:24313395

Fitzpatrick, Anthony W P; Lorenz, Ulrich J; Vanacore, Giovanni M; Zewail, Ahmed H

2013-12-26

133

Electron microscopy in the investigation of asthenozoospermia.  

PubMed

Asthenozoospermia, defined as low sperm motility, is a significant cause of subfertility in men. Its origins are diverse and in some instances cannot be ascertained. However, severely reduced motility can often be associated with abnormalities in the structure of the sperm tails, which can only be detected by transmission electron microscopy (TEM). In this respect, TEM is an important adjunct to the traditional methods of semen analysis. This review examines the development of the current state of knowledge of sperm tail abnormalities. These may be genetic in origin, or they may be acquired as a result of extrinsic factors. At present, consistent molecular markers are not available to characterise many of the genetic defects. However, TEM can distinguish specific defects of genetic origin and the non-specific structural anomalies that are typical of an acquired condition. It can also differentiate sperm structural anomalies from necrospermia, or sperm death, which is another significant cause of asthenozoospermia. In this modern era of assisted reproduction, it is possible in some instances to circumvent the problems of sperm immotility and to achieve fertilisation and pregnancy using intracytoplasmic sperm injection (ICSI). However, because of the possible genetic origin of asthenozoospermia, many scientists working in the field of infertility believe that it is of the utmost importance to investigate the causes of asthenozoospermia. This review considers the continuing relevance of TEM to the evaluation of sperm tail abnormalities in the context of current reproductive techniques. PMID:20669769

Mobberley, M A

2010-01-01

134

Microwave energy fixation for electron microscopy.  

PubMed Central

We have demonstrated that microwave energy (MW) can be used in conjunction with chemical cross-linking agents in order to rapidly fix cell suspensions and tissue blocks for electron microscopy in 7-9 seconds. The optimal MW fixation method involved immersing tissues up to 1 cu cm in dilute aldehyde fixation and immediately irradiating the specimens in a conventional microwave oven for 9 seconds to 50 C. Ultrastructural preservation of samples irradiated by MW energy was comparable to that of the control samples immersed in aldehyde fixative for 2 hours at 25 C. Stereologic analysis showed that tissue blocks fixed by the MW fixation method did not cause organelles such as liver mitochondria and salivary gland granules to shrink or to swell. Potential applications for this new fixation technology include the investigation of rapid intracellular processes (eg, vesicular transport) and preservation of proteins that are difficult to demonstrate with routine fixation methods (eg, antigens and enzymes). Images Figure 4 Figure 5 Figure 2 Figure 3 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11

Login, G. R.; Dvorak, A. M.

1985-01-01

135

[Electronic microscopy in endodontic electrophoresis efficiency assessment].  

PubMed

The reason for insufficient efficiency of endodontic treatments is a complex structure of root canals system and presence of dentine tubules (DT) in a root dentine. For sterilization and obturation of all spaces in a root canal system the method of cupper-calcium hydroxide (CCH) electrophoresis was developed. The authors proposed more effective method of CCH galvanophoresis by means of galvanic pins based on electrophoresis principles but allowing deep impregnation of the root dentine by nanoparticles of CCH. The purpose of the study was to validate the parameters of root dentine nanoimpregnation by CCH at endodontic galvanophoresis. Material and methods. Research has carried out on 24 removed teeth in laboratory model. The impact of irrigation of root canal and nanoimpregnation duration on the microflora, dentine smear layer, depth of penetration of CCH particles in dentine tubules was studied by scanning electronic microscopy. Results. Irrigation of root canals essentially reduces the amount of microorganisms and eliminates the dentine smear layer. Nanoimpregnation of root dentine by CCH for 1 day results in obtuation of 60-70% of DT up to 100-200 nm, for 1 week - promotes uniform obturation of DT to 35-50 microns. These values proves galvanophoresis to be a useful tool for pulpitis treatment. By nanoimpregnation for 2 weeks DT were filled with nanoparticles of CCH on depth up to 1.2-1.5 mm, and for 4 weeks - up to 2.5 mm. These terms can be recommended for treatment of apical periodontitis. PMID:23715442

Rumiantsev, V A; Rodionova, E G; Denis, A G; Ol'khovskaia, A V; Tsaturova, Iu V

2013-01-01

136

Scanning electron microscopy of human cerebellar cortex.  

PubMed

Scanning electron microscopy and cryofracture technique were applied to study neuronal architecture and synaptic connections of the human cerebellum. Samples were processed according to the technique of Humphreys et al. (1975) with minor modifications. The granule cells exhibit unbranched filiform axons and coniform dendritic processes. The latter show typical claw-like endings making "gearing type" synaptic contacts with mossy fiber rosettes. The unattached mossy rosettes appear as solid club-like structures. Some fractographs show individual granule cells, Golgi neurons and glomerular islands. The climbing fibers and their Scheibel's collaterals were also characterized. In the Purkinje layer the surface fracture was produced at the level of the Bergmann glial cells, which are selectively removed, allowing us to visualize the rough surface of Purkinje cells and the supra- and infraganglionic plexuses of basket cell axons which appeared as entangled threads. In the molecular layer the three-dimensional configuration of the Purkinje secondary and tertiary dendritic branches was obtained. The filiform parallel fibers make cruciform synaptic contacts with the Purkinje dendritic spines. The appearance of stellate neuronal somata closely resembled that of the granule cells. The subpial terminals of Bergmann fibers appeared attached to the exterior of the folia forming the rough surfaced external glial limiting membrane. PMID:7459985

Castejón, O J; Valero, C J

1980-01-01

137

Imaging Cytoskeleton Components by Electron Microscopy  

PubMed Central

Summary The cytoskeleton is a complex of detergent-insoluble components of the cytoplasm playing critical roles in cell motility, shape generation, and mechanical properties of a cell. Fibrillar polymers-actin filaments, microtubules, and intermediate filaments- are major constituents of the cytoskeleton, which constantly change their organization during cellular activities. The actin cytoskeleton is especially polymorphic, as actin filaments can form multiple higher order assemblies performing different functions. Structural information about cytoskeleton organization is critical for understanding its functions and mechanisms underlying various forms of cellular activity. Because of the nanometer-scale thickness of cytoskeletal fibers, electron microscopy (EM) is a key tool to determine the structure of the cytoskeleton. This article describes application of rotary shadowing (or metal replica) EM for visualization of the cytoskeleton. The procedure is applicable to thin cultured cells growing on glass coverslips and consists of detergent extraction of cells to expose their cytoskeleton, chemical fixation to provide stability, ethanol dehydration and critical point drying to preserve three-dimensionality, rotary shadowing with platinum to create contrast, and carbon coating to stabilize replicas. This technique provides easily interpretable three-dimensional images, in which individual cytoskeletal fibers are clearly resolved, and individual proteins can be identified by immunogold labeling. More importantly, replica EM is easily compatible with live cell imaging, so that one can correlate the dynamics of a cell or its components, e.g., expressed fluorescent proteins, with high resolution structural organization of the cytoskeleton in the same cell.

Svitkina, Tatyana

2010-01-01

138

Another 60 years in electron microscopy: development of phase-plate electron microscopy and biological applications.  

PubMed

It has been six decades since the concept of phase-plate electron microscopy was first reported by Boersch, but an experimental report on a phase plate with a theoretically rational performance has only recently been released by a group including the present author. Currently, many laboratories around the world are attempting to develop a wide range of phase plates to enhance the capabilities of transmission electron microscopy. They are reporting not only advantages of their own developments but also a fundamental problem inherent to electron beam devices, namely charging, i.e. the accumulation of electrostatic charge. In this report, we review the 60-year history of phase-plate development, with a particular focus on the fundamental issue of phase-plate charging. Next, we review biological applications of qualified phase plates, which have been successful in avoiding charging to some extent. Finally, we compare and discuss electron microscopic images, taken with or without phase plates, of biological targets such as proteins (GroEL and TRPV4), protein complexes (flagellar motor), viruses (T4 phage, ?-15 phage and herpes simplex virus), bacterial (cyanobacteria) and mammalian (PtK2) cells. PMID:21844600

Nagayama, Kuniaki

2011-01-01

139

Analytical electron microscopy in mineralogy; exsolved phases in pyroxenes  

USGS Publications Warehouse

Analytical scanning transmission electron microscopy has been successfully used to characterize the structure and composition of lamellar exsolution products in pyroxenes. At operating voltages of 100 and 200 keV, microanalytical techniques of x-ray energy analysis, convergent-beam electron diffraction, and lattice imaging have been used to chemically and structurally characterize exsolution lamellae only a few unit cells wide. Quantitative X-ray energy analysis using ratios of peak intensities has been adopted for the U.S. Geological Survey AEM in order to study the compositions of exsolved phases and changes in compositional profiles as a function of time and temperature. The quantitative analysis procedure involves 1) removal of instrument-induced background, 2) reduction of contamination, and 3) measurement of correction factors obtained from a wide range of standard compositions. The peak-ratio technique requires that the specimen thickness at the point of analysis be thin enough to make absorption corrections unnecessary (i.e., to satisfy the "thin-foil criteria"). In pyroxenes, the calculated "maximum thicknesses" range from 130 to 1400 nm for the ratios Mg/Si, Fe/Si, and Ca/Si; these "maximum thicknesses" have been contoured in pyroxene composition space as a guide during analysis. Analytical spatial resolutions of 50-100 nm have been achieved in AEM at 200 keV from the composition-profile studies, and analytical reproducibility in AEM from homogeneous pyroxene standards is ?? 1.5 mol% endmember. ?? 1982.

Nord, Jr. , G. L.

1982-01-01

140

Scanning electron microscopy to probe working nanowire gas sensors  

NASA Astrophysics Data System (ADS)

This study is dedicated to the implementing of Electron-Beam-Induced Current (EBIC) microscopy to study the behavior of metal oxide semiconducting (MOS) nanowire (NW) gas sensor in situ under exposure to different environment. First, we reported the development of a single nanowire gas sensor compatible with an environmental cell. The major component of the device we use in this study is a single SnO2 nanowire attached to an electron transparent SiN membrane (50-100 nm thick), which was used for mounting nanowire working electrodes and surface imaging of NW. First the NW's conductivity is investigated in different temperatures. Higher temperature is proved to cause higher conductivity of NW. We also found that often the Schottky barrier is formed at the nanowire's contacts with Au and Au/Cr electrodes. Then NW's responses to gas and electron beam (from SEM) are analyzed quantitatively by current measurement. Electron-Beam-Induced Current technique was introduced for the first time to characterize the conductivity behavior of the nanowire during the gas sensing process. Resistive contrast was observed in the EBIC image.

Liu, Yangmingyue

141

Optimization problems in electron microscopy of single particles  

Microsoft Academic Search

Electron Microscopy is a valuable tool for the elucidation of the three-dimensional structure of macromolecular complexes. Knowledge about the macromolecular structure pro- vides important information about its function and how it is carried out. This work addresses the issue of three-dimensional reconstruction of biological macromolecules from electron microscopy images. In particular, it focuses on a methodology known as \\

Carlos Oscar Sánchez Sorzano; Roberto Marabini; Alberto D. Pascual-montano; Sjors H. W. Scheres; José María Carazo

2006-01-01

142

Reliable strain measurement in transistor arrays by robust scanning transmission electron microscopy  

SciTech Connect

Accurate measurement of the strain field in the channels of transistor arrays is critical for strain engineering in modern electronic devices. We applied atomic-resolution high-angle annular dark-field scanning transmission electron microscopy to quantitative measurement of the strain field in transistor arrays. The quantitative strain profile over 20 transistors was obtained with high reliability and a precision of 0.1%. The strain field was found to form homogeneously in the channels of the transistor arrays. Furthermore, strain relaxation due to the thin foil effect was quantitatively investigated for thicknesses of 35 to 275 nm.

Kim, Suhyun; Kim, Joong Jung; Jung, Younheum; Lee, Kyungwoo; Byun, Gwangsun; Hwang, KyoungHwan; Lee, Sunyoung; Lee, Kyupil [Memory Analysis Science and Engineering Group, Samsung Electronics, San 16, Hwasung City, Gyeonggi-Do 445-701 (Korea, Republic of)] [Memory Analysis Science and Engineering Group, Samsung Electronics, San 16, Hwasung City, Gyeonggi-Do 445-701 (Korea, Republic of)

2013-09-15

143

Transmission Electron Microscopy of Itokawa Regolith Grains  

NASA Technical Reports Server (NTRS)

Introduction: In a remarkable engineering achievement, the JAXA space agency successfully recovered the Hayabusa space-craft in June 2010, following a non-optimal encounter and sur-face sampling mission to asteroid 25143 Itokawa. These are the first direct samples ever obtained and returned from the surface of an asteroid. The Hayabusa samples thus present a special op-portunity to directly investigate the evolution of asteroidal sur-faces, from the development of the regolith to the study of the effects of space weathering. Here we report on our preliminary TEM measurements on two Itokawa samples. Methods: We were allocated particles RA-QD02-0125 and RA-QD02-0211. Both particles were embedded in low viscosity epoxy and thin sections were prepared using ultramicrotomy. High resolution images and electron diffraction data were ob-tained using a JEOL 2500SE 200 kV field-emission scanning-transmission electron microscope. Quantitative maps and anal-yses were obtained using a Thermo thin-window energy-dispersive x-ray (EDX) spectrometer. Results: Both particles are olivine-rich (Fo70) with µm-sized inclusions of FeS and have microstructurally complex rims. Par-ticle RA-QD02-0125 is rounded and has numerous sub-µm grains attached to its surface including FeS, albite, olivine, and rare melt droplets. Solar flare tracks have not been observed, but the particle is surrounded by a continuous 50 nm thick, stuctur-ally disordered rim that is compositionally similar to the core of the grain. One of the surface adhering grains is pyrrhotite show-ing a S-depleted rim (8-10 nm thick) with nanophase Fe metal grains (<5 nm) decorating the outermost surface. The pyrrhotite displays a complex superstructure in its core that is absent in the S-depleted rim. Particle RA-QD02-0211 contains solar flare particle tracks (2x109 cm-2) and shows a structurally disordered rim 100 nm thick. The track density corresponds to a surface exposure of 103-104 years based on the track production rate of [1]. The dis-ordered rim is nanocrystalline with minor amorphous material between crystalline domains. Quantitative element maps show the outermost 10 nm of the disordered rim is Si-rich. Discussion and Conclusions: Both particles record the ef-fects of space weathering processes on Itokawa. Noguchi et al. [2] proposed that the disordered rims they observed on Itokawa particles largely result from solar wind radiation damage and we arrive at a similar conclusion for the two particles we analyzed. The microstructure of the S-depleted layer on the pyrrhotite grain in RA-QD02-0125 is similar to that observed in troilite irradiated with 1018 4 kV He+ [3, 4]. Prolonged irradiation has also been shown to disorder pyrrhotite such that the superstructure reflec-tions are lost [5].

Keller, Lindsay P.; Berger, E. L.

2013-01-01

144

Aberration-Coreected Electron Microscopy at Brookhaven National Laboratory  

SciTech Connect

The last decade witnessed the rapid development and implementation of aberration correction in electron optics, realizing a more-than-70-year-old dream of aberration-free electron microscopy with a spatial resolution below one angstrom [1-9]. With sophisticated aberration correctors, modern electron microscopes now can reveal local structural information unavailable with neutrons and x-rays, such as the local arrangement of atoms, order/disorder, electronic inhomogeneity, bonding states, spin configuration, quantum confinement, and symmetry breaking [10-17]. Aberration correction through multipole-based correctors, as well as the associated improved stability in accelerating voltage, lens supplies, and goniometers in electron microscopes now enables medium-voltage (200-300kV) microscopes to achieve image resolution at or below 0.1nm. Aberration correction not only improves the instrument's spatial resolution but, equally importantly, allows larger objective lens pole-piece gaps to be employed thus realizing the potential of the instrument as a nanoscale property-measurement tool. That is, while retaining high spatial resolution, we can use various sample stages to observe the materials response under various temperature, electric- and magnetic- fields, and atmospheric environments. Such capabilities afford tremendous opportunities to tackle challenging science and technology issues in physics, chemistry, materials science, and biology. The research goal of the electron microscopy group at the Dept. of Condensed Matter Physics and Materials Science and the Center for Functional Nanomaterials, as well as the Institute for Advanced Electron Microscopy, Brookhaven National Laboratory (BNL), is to elucidate the microscopic origin of the physical- and chemical-behavior of materials, and the role of individual, or groups of atoms, especially in their native functional environments. We plan to accomplish this by developing and implementing various quantitative electron microscopy techniques in strongly correlated electron systems and nanostructured materials. As a first step, with the support of Materials Science Division, Office of Basic Energy Science, US Department of Energy, and the New York State Office of Science, Technology, and Academic Research, recently we acquired three aberration-corrected electron microscopes from the three major microscope manufacturers, i.e., JEOL, Hitachi, and FEI. The Hitachi HD2700C is equipped with a probe corrector, the FEI Titan 80-300 has an imaging corrector, while the JEOL2200MCO has both. All the correctors are of the dual-hexapole type, designed and manufactured by CEOS GmbH based on the design due to Rose and Haider [3, 18]. All these three are one-of-a-kind in the US, designed for specialized capabilities in characterizing nanoscale structure. In this chapter, we review the performance of these state-of-the art instruments and the new challenges associated with the improved spatial resolution, including the environment requirements of the laboratory that hosts these instruments. Although each instrument we describe here has its own strengths and drawbacks, it is not our intention to rank them in terms of their performance, especially their spatial resolution in imaging.

Zhu,Y.; Wall, J.

2008-04-01

145

Improved Imaging in Low Energy Electron Microscopy and Photo Emission Electron Microscopy Using MEDIPIX2 Pixel Detector  

Microsoft Academic Search

The application of the Medipix2 hybrid pixel detector in Low Energy Electron Microscopy (LEEM) and Photo Emission Electron Microscopy (PEEM) led to an improvement of the recorded image quality compared to the original setup based on microchannel plate (MCP), phosphor screen and CCD. The measurements were performed on an Elmitec LEEM III instrument without energy filter using an Ir(111) sample

I. Sikharulidze; R. van Gastel; S. Schramm; J. P. Abrahams; B. Poelsema; R. M. Trom; S. J. van der Molen

2010-01-01

146

Silicon Nitride Windows for Electron Microscopy of Whole Cells  

PubMed Central

Summary Silicon microchips with thin electron transparent silicon nitride windows provide a sample support that accommodates both light-, and electron microscopy of whole eukaryotic cells in vacuum or liquid, with minimum sample preparation steps. The windows are robust enough that cellular samples can be cultured directly onto them, with no addition of a supporting film, and no need to embed or section the sample, as is typically required in electron microscopy. By combining two microchips, a microfluidic chamber can be constructed for the imaging of samples in liquid in the electron microscope. We provide microchip design specifications, a fabrication outline, instructions on how to prepare them for biological samples, and examples of images obtained using different light-, and electron microscopy modalities. The use of these microchips is particularly advantageous for correlative light-, and electron microscopy.

Ring, E. A.; Peckys, D. B.; Dukes, M. J.; Baudoin, J. P.; de Jonge, N.

2012-01-01

147

Low energy electron microscopy imaging using Medipix2 detector  

Microsoft Academic Search

Low Energy Electron Microscopy (LEEM) and Photo-Emission Electron Microscopy (PEEM) predominantly use a combination of microchannel plate (MCP), phosphor screen and optical camera to record images formed by 10–20keV electrons. We have tested the performance of a LEEM\\/PEEM instrument with a Medipix2 hybrid pixel detector using an Ir(111) sample with graphene flakes grown on its surface. We find that Medipix2

I. Sikharulidze; R. van Gastel; S. Schramm; J. P. Abrahams; B. Poelsema; R. M. Tromp; S. J. van der Molen

2011-01-01

148

Cryo-scanning electron microscopy and light microscopy for the study of fungi interactions.  

PubMed

The application of the cryo-scanning electron microscopy and light microscopy for the study of the interactions at different environmental conditions between Penicillium oxalicum and Fusarium verticillioides is described. A dual microculture was developed for the light microscopy analysis of the interaction. The microscope and macroscopic examinations were compared. Analysis of Petri plates revealed that F. verticillioides was a competitor for space and nutrients while P. oxalicum was a mycoparasite under the microscopic observations. PMID:20572205

Sempere, F; Santamarina, M P

2011-03-01

149

Photobleaching kinetics of fluorescein in quantitative fluorescence microscopy.  

PubMed Central

An investigation on the photobleaching behavior of fluorescein in microscopy was carried out through a systematic analysis of photobleaching mechanisms. The individual photochemical reactions of fluorescein were incorporated into a theoretical analysis and mathematical simulation to study the photochemical processes leading to photobleaching of fluorescein in microscopy. The photobleaching behavior of free and bound fluorescein has also been investigated by experimental means. Both the theoretical simulation and experimental data show that photobleaching of fluorescein in microscopy is, in general, not a single-exponential process. The simulation suggests that the non-single-exponential behavior is caused by the oxygen-independent, proximity-induced triplet-triplet or triplet-ground state dye reactions of bound fluorescein in microscopy. The single-exponential process is a special case of photobleaching behavior when the reactions between the triplet dye and molecular oxygen are dominant.

Song, L; Hennink, E J; Young, I T; Tanke, H J

1995-01-01

150

High-resolution electron microscopy and scanning tunneling microscopy of native oxides on silicon  

Microsoft Academic Search

High-resolution transmission electron microscopy and scanning tunneling microscopy have been combined to examine the structure of the thin 'native' oxide that forms on silicon surfaces at room temperature. Differences in the cleaning procedures for silicon wafers may affect the morphology of this oxide and critically influence further processing on the silicon substrates. An etch that ended with a dip in

A. H. Carim; M. M. Dovek; C. F. Quate; R. Sinclair; C. Vorst

1987-01-01

151

High resolution electron spin resonance microscopy  

Microsoft Academic Search

NMR microscopy is routinely employed in fields of science such as biology, botany, and materials science to observe magnetic parameters and transport phenomena in small scale structures. Despite extensive efforts, the resolution of this method is limited (>10?m for short acquisition times), and thus cannot answer many key questions in these fields. We show, through theoretical prediction and initial experiments,

Aharon Blank; Curt R. Dunnam; Peter P. Borbat; Jack H. Freed

2003-01-01

152

Modern Uses of Electron Microscopy for Detection of Viruses  

PubMed Central

Summary: Electron microscopy, considered by some to be an old technique, is still on the forefront of both clinical viral diagnoses and viral ultrastructure and pathogenesis studies. In the diagnostic setting, it is particularly valuable in the surveillance of emerging diseases and potential bioterrorism viruses. In the research arena, modalities such as immunoelectron microscopy, cryo-electron microscopy, and electron tomography have demonstrated how viral structural components fit together, attach to cells, assimilate during replication, and associate with the cellular machinery during replication and egression. These studies provide information for treatment and vaccine strategies.

Goldsmith, Cynthia S.; Miller, Sara E.

2009-01-01

153

Study of dynamic grain growth by electron microscopy and EBSD.  

PubMed

The effect of hot deformation on fully recrystallized aluminium-copper alloys (Al-4wt%Cu and Al-33wt%Cu) with different volume fractions of CuAl(2) has been studied. The alloys are Zener pinned systems with different superplastic properties. Strain-induced grain growth, observed in both alloys, was quantitatively estimated by means of electron microscopy and EBSD and compared with the rate of static grain growth. Surface marker observations and in situ hot-deformation experiments combined with EBSD were aimed at clarifying the mechanisms responsible for the changes in the deformed microstructures. A sequence of secondary and backscattered electron images and EBSD maps was obtained during in situ SEM deformation with different testing conditions. Overlaying EBSD maps for the Al-4wt%Cu with channelling contrast images showed that grain boundary motion occurred during deformation, creating a layered structure and leading to an increase in size of some grains and shrinkage of others. Of a particular interest are results related to behaviour of CuAl(2) in superplastic Al-33wt%Cu during deformation, including several problems with the use of EBSD in this alloy. PMID:19250464

Rofman, O V; Bate, P S; Brough, I; Humphreys, F J

2009-03-01

154

Relationship between the v2PO4/amide?III ratio assessed by Raman spectroscopy and the calcium content measured by quantitative backscattered electron microscopy in healthy human osteonal bone.  

PubMed

ABSTRACT. Raman microspectroscopy and quantitative backscattered electron imaging (qBEI) of bone are powerful tools to investigate bone material properties. Both methods provide information on the degree of bone matrix mineralization. However, a head-to-head comparison of these outcomes from identical bone areas has not been performed to date. In femoral midshaft cross sections of three women, 99 regions (20×20???m2) were selected inside osteons and interstitial bone covering a wide range of matrix mineralization. As the focus of this study was only on regions undergoing secondary mineralization, zones exhibiting a distinct gradient in mineral content close to the mineralization front were excluded. The same regions were measured by both methods. We found a linear correlation (R2=0.75) between mineral/matrix as measured by Raman spectroscopy and the wt.?%Mineral/(100-wt.?%Mineral) as obtained by qBEI, in good agreement with theoretical estimations. The observed deviations of single values from the linear regression line were determined to reflect biological heterogeneities. The data of this study demonstrate the good correspondence between Raman and qBEI outcomes in describing tissue mineralization. The obtained correlation is likely sensitive to changes in bone tissue composition, providing an approach to detect potential deviations from normal bone. PMID:24919447

Roschger, Andreas; Gamsjaeger, Sonja; Hofstetter, Birgit; Masic, Admir; Blouin, Stéphane; Messmer, Phaedra; Berzlanovich, Andrea; Paschalis, Eleftherios P; Roschger, Paul; Klaushofer, Klaus; Fratzl, Peter

2014-06-01

155

Ion-induced electron emission microscopy  

DOEpatents

An ion beam analysis system that creates multidimensional maps of the effects of high energy ions from an unfocussed source upon a sample by correlating the exact entry point of an ion into a sample by projection imaging of the secondary electrons emitted at that point with a signal from a detector that measures the interaction of that ion within the sample. The emitted secondary electrons are collected in a strong electric field perpendicular to the sample surface and (optionally) projected and refocused by the electron lenses found in a photon emission electron microscope, amplified by microchannel plates and then their exact position is sensed by a very sensitive X Y position detector. Position signals from this secondary electron detector are then correlated in time with nuclear, atomic or electrical effects, including the malfunction of digital circuits, detected within the sample that were caused by the individual ion that created these secondary electrons in the fit place.

Doyle, Barney L. (Albuquerque, NM); Vizkelethy, Gyorgy (Albuquerque, NM); Weller, Robert A. (Brentwood, TN)

2001-01-01

156

Thin Glass Layers as Supports for Electron Microscopy  

Microsoft Academic Search

IN the usual technique of electron microscopy, `Formvar' or collodion layers are used as supports. We have been studying the electrical properties of thin metallic layers and determined their structure by means of the electron microscope. The electrical resistances were made on glass strips, while `Formvar' layers were used as support for the electron microscope examination. We have always hesitated

A. van Itterbeek; L. de Greve; G. F. van Veelen; C. A. F. Tuynman

1952-01-01

157

Image Resolution in Scanning Transmission Electron Microscopy  

SciTech Connect

Digital images captured with electron microscopes are corrupted by two fundamental effects: shot noise resulting from electron counting statistics and blur resulting from the nonzero width of the focused electron beam. The generic problem of computationally undoing these effects is called image reconstruction and for decades has proved to be one of the most challenging and important problems in imaging science. This proposal concerned the application of the Pixon method, the highest-performance image-reconstruction algorithm yet devised, to the enhancement of images obtained from the highest-resolution electron microscopes in the world, now in operation at Oak Ridge National Laboratory.

Pennycook, S. J.; Lupini, A.R.

2008-06-26

158

Carbon nanomaterial studied by atomic-force and electron microscopies  

SciTech Connect

It is suggested to use the atomic-force microscopy (AFM) and transmission electron microscopy (TEM) to study carbon material synthesized by catalytic pyrolysis of ethanol. It is shown how AFM and TEM can be employed to determine the geometric parameters of carbon nanofibers and nanotubes, examine their mechanical and adhesion characteristics, and analyze their structure.

Bobrinetski, I. I.; Kukin, V. N.; Nevolin, V. K., E-mail: vkn@miee.ru; Simunin, M. M. [Moscow State Institute of Electronics (Technical University) (Russian Federation)

2008-12-15

159

Correlative fluorescence and electron microscopy in tissues: immunocytochemistry.  

PubMed

Correlative microscopy is a collection of procedures that rely upon two or more imaging modalities to examine the same specimen. The imaging modalities employed should each provide unique information and the combined correlative data should be more information rich than that obtained by any of the imaging methods alone. Currently the most common form of correlative microscopy combines fluorescence and electron microscopy. While much of the correlative microscopy in the literature is derived from studies of model cell culture systems we have focused, primarily, on correlative microscopy in tissue samples. The use of tissue, particularly human tissue, may add constraints not encountered in cell culture systems. Ultrathin cryosections, typically used for immunoelectron microscopy, have served as the substrate for correlative fluorescence and electron microscopic immunolocalization in our studies. In this work, we have employed the bifunctional reporter FluoroNanogold. This labeling reagent contains both a fluorochrome and a gold-cluster compound and can be imaged by sequential fluorescence and electron microscopy. This approach permits the examination of exactly the same sub-cellular structures in both fluorescence and electron microscopy with a high level of spatial resolution. PMID:19754721

Robinson, J M; Takizawa, T

2009-09-01

160

Applications of plasma cleaning for electron microscopy  

Microsoft Academic Search

Summary form only given. Specimen contamination and amorphous irradiation damage severely limit the ability to perform accurate electron microscope analysis of materials, especially as specimen areas of interest decrease in size. To analyze smaller areas of interest, electron probe sizes have decreased, while probe currents have increased. The combination of these two factors results in an increase in the amount

T. C. Isabell; P. E. Fischione; E. A. Fischione

1998-01-01

161

Electron Microscopy of Chloramphenicol-Treated Escherichia Coli.  

National Technical Information Service (NTIS)

Thin sections of Escherichia coli were examined by electron microscopy at sequential intervals after addition and then removal of chloramphenicol. The first changes, occurring at 1 hr after exposure to the drug, were disappearance of the ribosomes and agg...

C. Morgan H. S. Rosenkranz H. S. Carr H. M. Rose

1967-01-01

162

Outcome of the First Electron Microscopy Validation Task Force Meeting  

PubMed Central

This Meeting Review describes the proceedings and conclusions from the inaugural meeting of the Electron Microscopy Validation Task Force organized by the Unified Data Resource for 3DEM (http://www.emdatabank.org) and held at Rutgers University in New Brunswick, NJ on September 28 and 29, 2010. At the workshop, a group of scientists involved in collecting electron microscopy data, using the data to determine three-dimensional electron microscopy (3DEM) density maps, and building molecular models into the maps explored how to assess maps, models, and other data that are deposited into the Electron Microscopy Data Bank and Protein Data Bank public data archives. The specific recommendations resulting from the workshop aim to increase the impact of 3DEM in biology and medicine.

Henderson, Richard; Sali, Andrej; Baker, Matthew L.; Carragher, Bridget; Devkota, Batsal; Downing, Kenneth H.; Egelman, Edward H.; Feng, Zukang; Frank, Joachim; Grigorieff, Nikolaus; Jiang, Wen; Ludtke, Steven J.; Medalia, Ohad; Penczek, Pawel A.; Rosenthal, Peter B.; Rossmann, Michael G.; Schmid, Michael F.; Schroder, Gunnar F.; Steven, Alasdair C.; Stokes, David L.; Westbrook, John D.; Wriggers, Willy; Yang, Huanwang; Young, Jasmine; Berman, Helen M.; Chiu, Wah; Kleywegt, Gerard J.; Lawson, Catherine L.

2012-01-01

163

Electron Microscopy of Elastomers Containing In-situ Precipitated Silica.  

National Technical Information Service (NTIS)

Transmission electron microscopy is used to characterize reinforcing silica particles precipitated as filler into networks of poly(dimethylsiloxane) by the hydrolysis of tetraethylorthosilicate. Particle diameters were typically 200 A, with relatively nar...

J. E. Mark Y. P. Ning J. Tang M. Y. Tang

1985-01-01

164

CONFOCAL MICROSCOPY SYSTEM PERFORMANCE: FOUNDATIONS FOR MEASUREMENTS, QUANTITATION AND SPECTROSCOPY  

EPA Science Inventory

The confocal laser-scanning microscopy (CLSM) has enormous potential in many biological fields. The goal of a CLSM is to acquire and quantify fluorescence and in some instruments acquire spectral characterization of the emitted signal. The accuracy of these measurements demands t...

165

Quantitative acoustic microscopy of individual living human cells.  

PubMed

The elastic properties of cells can be measured with microscopic resolution by acoustic microscopy. By measuring the waveform of very short pulses, the thickness, and the acoustic velocity, impedance and attenuation can be determined from the two separate signals reflected from the top and the bottom of the cell. PMID:8289225

Briggs, G A; Wang, J; Gundle, R

1993-10-01

166

DNA origami-based standards for quantitative fluorescence microscopy.  

PubMed

Validating and testing a fluorescence microscope or a microscopy method requires defined samples that can be used as standards. DNA origami is a new tool that provides a framework to place defined numbers of small molecules such as fluorescent dyes or proteins in a programmed geometry with nanometer precision. The flexibility and versatility in the design of DNA origami microscopy standards makes them ideally suited for the broad variety of emerging super-resolution microscopy methods. As DNA origami structures are durable and portable, they can become a universally available specimen to check the everyday functionality of a microscope. The standards are immobilized on a glass slide, and they can be imaged without further preparation and can be stored for up to 6 months. We describe a detailed protocol for the design, production and use of DNA origami microscopy standards, and we introduce a DNA origami rectangle, bundles and a nanopillar as fluorescent nanoscopic rulers. The protocol provides procedures for the design and realization of fluorescent marks on DNA origami structures, their production and purification, quality control, handling, immobilization, measurement and data analysis. The procedure can be completed in 1-2 d. PMID:24833175

Schmied, Jürgen J; Raab, Mario; Forthmann, Carsten; Pibiri, Enrico; Wünsch, Bettina; Dammeyer, Thorben; Tinnefeld, Philip

2014-06-01

167

Transmission electron microscopy characterisation of 0-D nanomaterials  

NASA Astrophysics Data System (ADS)

When materials are scaled down to the nanometre level, a change in physical behaviour is frequently observed. In so-called 0-D nanomaterials (nanoparticles), these unique nanoscale properties are most abundant and are usually linked to either a change in (electronic) structure of the material or to the dominating influence of the particle surface at the nanometre scale. In this doctoral work the nanoscale properties of several nanoparticle systems have been studied using advanced transmission electron microscopy (TEM). Every material that was studied required for its solution a unique approach and a host of transmission electron microscopy techniques. The title of this doctoral work can be freely translated as "retrieving quantitatively the maximal and most accurate chemical, structural and morphological information from nanoparticles by advanced transmission electron microscopy, to uncover and explain their unique properties". Chapter 1 gives a brief general introduction to the world of nanomaterials and nanotechnology in general and more specifically to 0-D nanomaterials (nanoparticles). The unique properties and potential applications of these materials are described. The production of 0-D nanomaterials is not covered in this chapter, as this is an extremely broad field to cover in only a few pages. Instead, the production method for each of the materials is left to the detailed chapters that follow. In Chapter 2 the main transmission electron microscopy techniques used to characterise the materials in the further chapters are described together with the microscopes used to perform these techniques and their parameters of operation. Again, the sample-specific setups are listed in the detailed chapters that follow. Chapter 3 covers all work carried out on luminescent detonation nanodiamond powder for drug delivery and bio-medical imaging applications. Specific attention is paid to the morphology, surface chemistry and nitrogen incorporation of detonation nanodiamond particles cleaned by novel routes, and the possibility of production of luminescent N-V centres within the diamond nanoparticles is studied. Chapter 4 deals with self-arranged Co nanoparticle arrays, so-called superlattices. By closely studying the oxidation behaviour of such arrays, a new intrinsic property has been discovered: enhanced stability against oxidation of self-arranged cobalt nanoparticles. This intriguing physical behaviour of arranged cobalt nanoparticles has never been observed before. Chapter 5 describes and discusses all results obtained from TEM investigation of hybrid nanoporous-nanoparticle materials for advanced catalysis applications: first, the possibilities of TEM for the characterisation of the metal MOF material family; and second, the example of Au ZIF. Finally, in Chapter 6, assisted spray-pyrolysis generated ZnO nanoparticles are studied. The ZnO nanomaterial produced by a novel assisted spray pyrolysis method is compared to conventionally spray pyrolysed ZnO nanomaterials. The influence of assisted spray pyrolysis production on the size, morphology and optical properties (UV blocking capabilities) of the ZnO nanoparticles is studied for the case of citric-acid assisted spray pyrolysis.

Turner, Stuart Matthew

168

A transmission electron microscopy study of hexagonal ice  

Microsoft Academic Search

The morphologies of fast-frozen, thin-film samples of pure and dilute solutions of salts and surfactants in hexagonal ice are investigated with transmission electron microscopy. The cold-stage microscopy technique is described briefly and limitations imposed by the equipment and the sample itself are discussed. Ice grains, grain boundaries, dislocations, and stacking faults are imaged before radiolysis from the electron beam can

A. H. Falls; S. T. Wellinghoff; Y. Talmon; E. L. Thomas

1983-01-01

169

Recent developments in electron holography for phase microscopy.  

PubMed

This paper reports on the recent remarkable progress made in electron phase microscopy, especially due to the development of both a "coherent" field-emission electron beam and the related image processing techniques. With these techniques, the phase distribution of an electron beam transmitted through a specimen can now be measured with a precision of within 1/100 of the electron wavelength to observe the thickness distribution of a uniform specimen at the atomic level, the magnetic domain structures in a ferromagnetic thin film, and individual vortices in a superconducting thin film. Vortices in superconducting thin films have become dynamically observable by Lorentz microscopy. PMID:8991918

Tonomura, A

1995-12-01

170

Structure of Wet Specimens in Electron Microscopy  

ERIC Educational Resources Information Center

Discussed are past work and recent advances in the use of electron microscopes for viewing structures immersed in gas and liquid. Improved environmental chambers make it possible to examine wet specimens easily. (Author/RH)

Parsons, D. F.

1974-01-01

171

Quantitative local photosynthetic flux measurements at isolated chloroplasts and thylakoid membranes using scanning electrochemical microscopy (SECM).  

PubMed

Scanning electrochemical microscopy (SECM) offers a fast and quantitative method to measure local fluxes within photosynthesis. In particular, we have measured the flux of oxygen and ferrocyanide (Fe(CN)6(4-)), from the artificial electron acceptor ferricyanide (Fe(CN)6(3-)), using a stationary ultramicroelectrode at chloroplasts and thylakoid membranes (sourced from chloroplasts). Oxygen generation at films of chloroplasts and thylakoid membranes was detected directly during photosynthesis, but in the case of thylakoid membranes, this switched to sustained oxygen consumption at longer illumination times. An initial oxygen concentration spike was detected over both chloroplast and thylakoid membrane films, and the kinetics of the oxygen generation were extracted by fitting the experimental data to a finite element method (FEM) simulation. In contrast to previous work, the oxygen generation spike was attributed to the limited size of the plastoquinone pool, a key component in the linear electron transport pathway and a contributing factor in photoinhibition. Finally, the mobile nature of the SECM probe, and its high spatial resolution, also allowed us to detect ferrocyanide produced from a single thylakoid membrane. These results further demonstrate the power of SECM for localized flux measurements in biological processes, in this case photosynthesis, and that the high time resolution, combined with FEM simulations, allows the elucidation of quantitative kinetic information. PMID:23751155

McKelvey, Kim; Martin, Sophie; Robinson, Colin; Unwin, Patrick R

2013-07-01

172

Electron microscopy of Ludox colloidal silica  

Microsoft Academic Search

Summary  The samples of Ludox colloidal silica, previously studied by light scattering, were examined in electron microscope. A considerable\\u000a aggregation of particles was noted in solutions. The aggregates were efficiently removed by centrifugation, as was previously\\u000a indicated by the decrease in dissymmetry of light scattered by the same sols. From the electron micrographs the distribution\\u000a of particle diameters was evaluated and

Gj. Deželi?; M. Wrischer; Z. Devidé; J. P. Kratohvil

1960-01-01

173

Quantitative nonlinear dielectric microscopy of periodically polarized ferroelectric domains  

SciTech Connect

A nonlinear dielectric scanning tip microwave near-field microscope capable of submicron quantitative imaging of nonlinear dielectric constant was developed. This nondestructive technique was used to image the nonlinear dielectric constant profiles of an yttrium-doped LiNbO{sub 3} single crystal with periodically polarized ferroelectric domains. {copyright} {ital 1998 American Institute of Physics.}

Gao, C.; Duewer, F.; Lu, Y.; Xiang, X. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)] [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

1998-08-01

174

Photoacoustic microscopy for quantitative evaluation of angiogenesis inhibitor  

NASA Astrophysics Data System (ADS)

We present the photoacoustic microscopy (PAM) for evaluation of angiogenesis inhibitors on a chick embryo model. Microvasculature in the chorioallantoic membrane (CAM) of the chick embryos was imaged by PAM, and the optical microscopy (OM) images of the same set of CAMs were also acquired for comparisons, serving for validation of the results from PAM. The angiogenesis inhibitors, Sunitinib, with different concentrations applied to the CAM result in the change in microvascular density, which was quantified by both PAM and OM imaging. Similar change in microvascular density from PAM and OM imaging in response to angiogenesis inhibitor at different doses was observed, demonstrating that PAM has potential to provide objective evaluation of anti-angiogenesis medication. Besides, PAM is advantageous in three-dimensional and functional imaging compared with OM so that the emerging PAM technique may offer unique information on the efficacy of angiogenesis inhibitors and could benefit applications related to antiangiogenesis treatments.

Chen, Sung-Liang; Burnett, Joseph; Sun, Duxin; Xie, Zhixing; Wang, Xueding

2014-03-01

175

High resolution electron spin resonance microscopy.  

PubMed

NMR microscopy is routinely employed in fields of science such as biology, botany, and materials science to observe magnetic parameters and transport phenomena in small scale structures. Despite extensive efforts, the resolution of this method is limited (>10 microm for short acquisition times), and thus cannot answer many key questions in these fields. We show, through theoretical prediction and initial experiments, that ESR microscopy, although much less developed, can improve upon the resolution limits of NMR, and successfully undertake the 1 mum resolution challenge. Our theoretical predictions demonstrate that existing ESR technology, along with advanced imaging probe design (resonator and gradient coils), using solutions of narrow linewidth radicals (the trityl family), should yield 64 x 64 pixels 2D images (with z slice selection) with a resolution of 1 x 1 x 10 microm at approximately 60 GHz in less than 1h of acquisition. Our initial imaging results, conducted by CW ESR at X-band, support these theoretical predictions and already improve upon the previously reported state-of-the-art for 2D ESR image resolution achieving approximately 10 x 10 mum, in just several minutes of acquisition time. We analyze how future progress, which includes improved resonators, increased frequency of measurement, and advanced pulsed techniques, should achieve the goal of micron resolution. PMID:14568522

Blank, Aharon; Dunnam, Curt R; Borbat, Peter P; Freed, Jack H

2003-11-01

176

Quantitative laser scanning confocal autofluorescence microscopy of normal, premalignant, and malignant colonic tissues  

Microsoft Academic Search

Laser scanning confocal autofluorescence microscopy (LSCAM) using 351- to 364-nm excitation light was used to quantitatively compare fluorescent spectral emission of unstained, frozen histological sections of normal, premalignant, and malignant colonic tissues. To identify the spatial origins of fluorescent signals accurately, the same frozen section slides used for microscopy were fixed and histochemically stained immediately following LSCAM imaging. Tissue fluorescence

Hsing-Wen Wang; Joseph Willis; Marcia I. F. Canto; Michael V. Sivak; Joseph A. Izatt

1999-01-01

177

Quantitative description of wear surfaces of disc brakes using interference microscopy  

Microsoft Academic Search

Based on interference microscopy using visible light, methods are described to access and analyze topographic data from wear surfaces. As an example, measurements on discs and pads of disc brakes are presented. It is shown that interference microscopy combined with additional software is an accurate method for the quantitative description of wear surfaces.

D. Bettge; J. Starcevic

2001-01-01

178

Entanglement-assisted electron microscopy based on a flux qubit  

NASA Astrophysics Data System (ADS)

A notorious problem in high-resolution biological electron microscopy is radiation damage caused by probe electrons. Hence, acquisition of data with minimal number of electrons is of critical importance. Quantum approaches may represent the only way to improve the resolution in this context, but all proposed schemes to date demand delicate control of the electron beam in highly unconventional electron optics. Here we propose a scheme that involves a flux qubit based on a radio-frequency superconducting quantum interference device, inserted in a transmission electron microscope. The scheme significantly improves the prospect of realizing a quantum-enhanced electron microscope for radiation-sensitive specimens.

Okamoto, Hiroshi; Nagatani, Yukinori

2014-02-01

179

Quantitative electron and gas cloud experiments  

NASA Astrophysics Data System (ADS)

Electrons can accumulate in and degrade the quality of positively charged beams. This is a well-known problem in proton storage rings. Heavy-ion rings are more frequently limited by gas pressure-rise effects. Both effects may limit how closely the beam radius can approach the beam-tube radius in a heavy-ion linac. We study beams of 1 MeV K + with currents of up to 180 mA in the High-Current Experiment (HCX), and compare our work with simulations. The theory and simulation results are discussed in a companion papers. We have developed the first diagnostics that quantitatively measure the accumulation of electrons in a beam [M. Kireeff Covo, A. Molvik, A. Friedman, J.-L. Vay, P. Seidl, G. Logan, D. Baca, J.L. Vujic, Phys. Rev. Lett. 97 (2006) 054801; M. Kireeff Covo, et al., Nucl. Instr. and Meth. A, 2007, in press, doi:10.1016/j.nima.2007.02.045.]. This will enable the particle balance to be measured for each source of electrons in a linac: ionization of gas, emission from walls surrounding the beam, and emission from an end wall coupled with electron drifts upstream through quadrupole magnets, and electron-trapping efficiencies can be determined. Experiments where the heavy-ion beam is transported with solenoid magnetic fields, rather than with quadrupole magnetic or electrostatic fields, are being initiated. We discuss plans for experiments using electrode sets (in the middle and at the ends of magnets) to either expel or to trap electrons within the magnets. We observe oscillations of the electron density and position in the last quadrupole magnet when we flood the beam with electrons from an end wall. These oscillations, near 6 MHz, are observed to grow from the center of the magnet while drifting upstream against the beam, in good agreement with simulations.

Molvik, A. W.; Kireeff Covo, M.; Cohen, R. H.; Friedman, A.; Sharp, W. M.; Baca, David; Bieniosek, F. M.; Leister, C.; Seidl, P. A.; Vay, J.-L.

2007-07-01

180

Electron microscopy of myocardial tissue. A nine year review  

PubMed Central

Aim—To review and reassess the role of this department's experience with routine electron microscopy of myocardial tissues. Methods—A nine year series of myocardial samples that underwent electron microscopy analysis were audited. Fifty nine samples were derived from 46 male and 13 female subjects with an age range of 15–90 years (mean, 50.6). Forty two samples were endomyocardial specimens, with 13 being derived from explanted hearts, and four from necropsies. Two cases were from transplanted hearts. These were all reviewed in a blinded fashion, by all three authors separately, in terms of the myocardium at the ultrastructural level. Subsequently, the interpretations/diagnoses were cross compared with the light microscopy and clinical data results. Results—Four cases of amyloid were identified; in addition, one case of granulomatous inflammation and one case of basophilic degeneration were seen, although all these had been evident on light microscopy. One case of possible mitochondrial myopathy was found. A total of 18 cases revealed changes of a presumed non-specific type including glycogen, lipid, and mitochondrial accumulations. Varying types of degeneration involving myofibres were seen together with variations in interstitial fibrosis and occasional cytoplasmic inclusions. Conclusion—Overall, although interesting, the electron microscopy of myocardial tissue added little to the understanding of the patient's disease, with only one case showing changes not found at light microscopy or with other investigations. Further study might shed light on the "non-specific" ultrastructural findings encountered. Key Words: electron microscopy • myocardial tissue • mitochondrial myopathy

Mudhar, H; Wagner, B; Suvarna, S

2001-01-01

181

Quantitative WDS analysis using electron probe microanalyzer  

SciTech Connect

In this paper, the procedure for conducting quantitative elemental analysis by ZAF correction method using wavelength dispersive X-ray spectroscopy (WDS) in an electron probe microanalyzer (EPMA) is elaborated. Analysis of a thermal barrier coating (TBC) system formed on a Ni-based single crystal superalloy is presented as an example to illustrate the analysis of samples consisting of a large number of major and minor elements. The analysis was performed by known standards and measured peak-to-background intensity ratios. The procedure for using separate set of acquisition conditions for major and minor element analysis is explained and its importance is stressed.

Ul-Hamid, Anwar [Research Institute, King Fahd University of Petroleum and Minerals, P.O. Box 1073, Dhahran 31261 (Saudi Arabia)]. E-mail: anwar@kfupm.edu.sa; Tawancy, Hani M. [Research Institute, King Fahd University of Petroleum and Minerals, P.O. Box 1073, Dhahran 31261 (Saudi Arabia); Mohammed, Abdul-Rashid I. [Research Institute, King Fahd University of Petroleum and Minerals, P.O. Box 1073, Dhahran 31261 (Saudi Arabia); Al-Jaroudi, Said S. [Saudi Aramco, P.O. Box 65, Tanajib 31311 (Saudi Arabia); Abbas, Nureddin M. [Research Institute, King Fahd University of Petroleum and Minerals, P.O. Box 1073, Dhahran 31261 (Saudi Arabia)

2006-04-15

182

Electron Microscopy of Biological Materials at the Nanometer Scale  

NASA Astrophysics Data System (ADS)

Electron microscopy of biological matter uses three different imaging modalities: (a) electron crystallography, (b) single-particle analysis, and (c) electron tomography. Ideally, these imaging modalities are applied to frozen-hydrated samples to ensure an optimal preservation of the structures under scrutiny. Cryo-electron microscopy of biological matter has made important advances in the past decades. It has become a research tool that further expands the scope of structural research into unique areas of cell and molecular biology, and it could augment the materials research portfolio in the study of soft and hybrid materials. This review addresses how researchers using transmission electron microscopy can derive structural information at high spatial resolution from fully hydrated specimens, despite their sensitivity to ionizing radiation, despite the adverse conditions of high vacuum for samples that have to be kept in aqueous environments, and despite their low contrast resulting from weakly scattering building blocks.

Kourkoutis, Lena Fitting; Plitzko, Jürgen M.; Baumeister, Wolfgang

2012-08-01

183

Quantifying nanoscale order in amorphous materials via fluctuation electron microscopy  

NASA Astrophysics Data System (ADS)

Fluctuation electron microscopy (FEM) has been used to study the nanoscale order in various amorphous materials. The method is explicitly sensitive to 3- and 4-body atomic correlation functions in amorphous materials; this is sufficient to establish the existence of structural order on the nanoscale, even when the radial distribution function extracted from diffraction data appears entirely amorphous. The variable resolution form of the technique can reveal the characteristic decay length over which topological order persists in amorphous materials. By changing the resolution, a characteristic length is obtained without the need for a priori knowledge of the structure. However, it remains a formidable challenge to invert the FEM data into a quantitative description of the structure that is free from error due to experimental noise and quantitative in both size and volume fraction. Here, we quantify the FEM method by (i) forward simulating the FEM data from a family of high quality atomistic a-Si models, (ii) reexamining the statistical origins of contributions to the variance due to artifacts, and (iii) comparing the measured experimental data with model simulations. From simulations at a fixed resolution, we show that the variance V( k) is a complex function of the size and volume fraction of the ordered regions present in the amorphous matrix. However, the ratio of the variance peaks as a function of diffraction vector k affords the size of the ordered regions; and the magnitude of the variance affords a quantitative measure of the volume fraction. From comparison of measured characteristic length with model simulations, we are able to estimate the size and volume fraction of ordered regions. The use of the STEM mode of FEM offers significant advantages in identifying artifacts in the variances. Artifacts, caused by non-idealities in the sample unrelated to nanoscale order, can easily dominate the measured variance, producing erroneous results. We show that reexamination and correction of the contributions of artifacts to variance is necessary to obtain an accurate and quantitative description of the structure of amorphous materials. Using variable resolution FEM we are able to extract a characteristic length of ordered regions in two different amorphous silicon samples. Having eliminated the noise contribution to the variance, we show here the first demonstration of a consistent characteristic length at all values of k. The experimental results presented here are the first to be consistent with both FEM theory and simulations.

Bogle, Stephanie Nicole

184

Exploring the third dimension: volume electron microscopy comes of age.  

PubMed

Groundbreaking advances in volume electron microscopy and specimen preparation are enabling the 3-dimensional visualisation of specimens with unprecedented detail, and driving a gratifying resurgence of interest in the ultrastructural examination of cellular systems. Serial section techniques, previously the domain of specialists, are becoming increasingly automated with the development of systems such as the automatic tape-collecting ultramicrotome, and serial blockface and focused ion beam scanning electron microscopes. These changes are rapidly broadening the scope of biomedical studies to which volume electron microscopy techniques can be applied beyond the brain. Further innovations in microscope design are also in the pipeline, which have the potential to enhance the speed and quality of data collection. The recent introduction of integrated light and electron microscopy systems will revolutionise correlative light and volume electron microscopy studies, by enabling the sequential collection of data from light and electron imaging modalities without intermediate specimen manipulation. In doing so, the acquisition of comprehensive functional information and direct correlation with ultrastructural details within a 3-dimensional reference space will become routine. The prospects for volume electron microscopy are therefore bright, and the stage is set for a challenging and exciting future. PMID:24792442

Peddie, Christopher J; Collinson, Lucy M

2014-06-01

185

Scanning Transmission Electron Microscopy at High Resolution  

PubMed Central

We have shown that a scanning transmission electron microscope with a high brightness field emission source is capable of obtaining better than 3 Å resolution using 30 to 40 keV electrons. Elastic dark field images of single atoms of uranium and mercury are shown which demonstrate this fact as determined by a modified Rayleigh criterion. Point-to-point micrograph resolution between 2.5 and 3.0 Å is found in dark field images of micro-crystallites of uranium and thorium compounds. Furthermore, adequate contrast is available to observe single atoms as light as silver. Images

Wall, J.; Langmore, J.; Isaacson, M.; Crewe, A. V.

1974-01-01

186

The CryoCapsule: simplifying correlative light to electron microscopy.  

PubMed

Correlating complementary multiple scale images of the same object is a straightforward means to decipher biological processes. Light microscopy and electron microscopy are the most commonly used imaging techniques, yet despite their complementarity, the experimental procedures available to correlate them are technically complex. We designed and manufactured a new device adapted to many biological specimens, the CryoCapsule, that simplifies the multiple sample preparation steps, which at present separate live cell fluorescence imaging from contextual high-resolution electron microscopy, thus opening new strategies for full correlative light to electron microscopy. We tested the biological application of this highly optimized tool on three different specimens: the in vitro Xenopus laevis mitotic spindle, melanoma cells over-expressing YFP-langerin sequestered in organized membranous subcellular organelles and a pigmented melanocytic cell in which the endosomal system was labeled with internalized fluorescent transferrin. PMID:24533564

Heiligenstein, Xavier; Heiligenstein, Jérôme; Delevoye, Cédric; Hurbain, Ilse; Bardin, Sabine; Paul-Gilloteaux, Perrine; Sengmanivong, Lucie; Régnier, Gilles; Salamero, Jean; Antony, Claude; Raposo, Graca

2014-06-01

187

Quantitative phase microscopy with off-axis optical coherence tomography.  

PubMed

We have developed a modality for quantitative phase imaging within spectral domain optical coherence tomography based on using an off-axis reference beam. By tilting the propagation of the reference beam relative to that of the sample beam, a spatially varying fringe is generated. Upon detection of this fringe using a parallel spectral domain scheme, the fringe can be used to separate the interference component of the signal and obtain the complex sample field. In addition to providing quantitative phase measurements within a depth resolved measurement, this approach also allows elimination of the complex conjugate artifact, a known limitation of spectral interferometry. The principle of the approach is described here along with demonstration of its capabilities using technical samples. PMID:24686658

Rinehart, Matthew T; Jaedicke, Volker; Wax, Adam

2014-04-01

188

Quantitative thermal microscopy using thermoelectric probe in passive mode.  

PubMed

A scanning thermal microscope working in passive mode using a micronic thermocouple probe is presented as a quantitative technique. We show that actual surface temperature distributions of microsystems are measurable under conditions for which most of usual techniques cannot operate. The quantitative aspect relies on the necessity of an appropriate calibration procedure which takes into account of the probe-to-sample thermal interaction prior to any measurement. Besides this consideration that should be treated for any thermal contact probing system, the main advantages of our thermal microscope deal with the temperature available range, the insensitivity to the surface optical parameters, the possibility to image DC, and AC temperature components up to 1 kHz typically and a resolution limit related to near-field behavior. PMID:24182115

Bontempi, A; Thiery, L; Teyssieux, D; Briand, D; Vairac, P

2013-10-01

189

Label-free quantitative cell division monitoring of endothelial cells by digital holographic microscopy.  

PubMed

Digital holographic microscopy (DHM) enables quantitative multifocus phase contrast imaging for nondestructive technical inspection and live cell analysis. Time-lapse investigations on human brain microvascular endothelial cells demonstrate the use of DHM for label-free dynamic quantitative monitoring of cell division of mother cells into daughter cells. Cytokinetic DHM analysis provides future applications in toxicology and cancer research. PMID:20615011

Kemper, Björn; Bauwens, Andreas; Vollmer, Angelika; Ketelhut, Steffi; Langehanenberg, Patrik; Müthing, Johannes; Karch, Helge; von Bally, Gert

2010-01-01

190

Scanning Electron Microscopy Studies of Dental Enamel.  

National Technical Information Service (NTIS)

Samples of sound, untreated enamel and enamel subjected to a number of different treatment procedures were selected for this study, to determine the potential of the scanning electron micro-scope as applied to the study of dental tissue. Sound enamel spec...

S. Hoffman, W. S. McEwan, C. M. Drew

1968-01-01

191

Analysis of human cytomegalovirus secondary envelopment by advanced electron microscopy.  

PubMed

Electron microscopy (EM) allows visualization of viruses in fixed cells with high resolution. High-pressure freezing for sample fixation in combination with freeze substitution and embedding in resin improves significantly the preservation of cellular structures and specifically of membranes. This advancement allows better visualization of human cytomegalovirus (HCMV) morphogenesis occurring at membranes. To obtain comprehensive information on viral phenotypes from ultrastructural images it is important to also quantify morphological phenotypes. This again can be much refined by three-dimensional visualization after serial sectioning. For elucidation of dynamic processes three-dimensional tomography is extremely helpful. We analysed interaction of HCMV particles with host cell membranes during final envelopment. Both wild-type virus and a viral mutant with impaired envelopment were analysed in fibroblasts, but also using in vivo relevant human endothelial cells and macrophages. The quantification of the EM data showed similar ultrastructural phenotypes regarding the envelopment efficiency in the different cell types indicating similar mechanisms in late stages of virus morphogenesis. Furthermore, thorough analysis of the viral assembly complex (AC) - a virus-induced cytosolic structure - by using three-dimensional visualization techniques combined with a quantitative analysis revealed that the events of final envelopment are equally distributed within the AC irrespective of different local membrane composition. PMID:23217081

Schauflinger, Martin; Villinger, Clarissa; Mertens, Thomas; Walther, Paul; von Einem, Jens

2013-02-01

192

Study on development of Agaricus bisporus by fluorescent microscopy and scanning electron microscopy.  

PubMed Central

Two strains of Agaricus bisporus have been investigated by fluorescent microscopy and scanning electron microscopy. Somatic nuclei, stained with auramin O and examined by fluorescent microscopy, appear to be randomly distributed, divide asynchronously, and assume a nonclassical or "two-track" configuration during mitotic metaphase. A similar configuration has been observed for nuclei during meiosis, but early meiosis in A. bisporus appears to be classical, usually with nine pairs of chromosomes evident during prophase I. Scanning electron microscopy has been used to document developmental stages in the formation and germination of basidiospores. Two-spored basidia were predominant, but occasionally one- or three-spored forms were observed. Four-spored basidia were absent, and uninucleated basidiospores were exceedingly rare to absent. Images

Saksena, K N; Marino, R; Haller, M N; Lemke, P A

1976-01-01

193

Scanning transmission electron microscopy study of III-V nitrides  

NASA Astrophysics Data System (ADS)

A study of the electronic properties of the III-V nitrides and the characterization of nitride-based heterostructures, interfaces and quantum wells using scanning transmission electron microscopy (STEM) are presented. Examination of the epitaxially grown GaN/Al0.25Ga0.75N heterostructure shows that, in contrast to expectations, the interface between GaN buffer and Al0.25Ga0.75N barrier is not atomically sharp, but diffuse. High spatial resolution electron energy loss spectroscopy measurements and annular dark field imaging indicate that these interfaces can be up to 20 A wide. The effects of the presence of the diffuse interface between the GaN and AlxGa1- xN layers on formation of the quasi-two-dimensional electron gas at the heterointerface are studied. Electronic energy levels and the distribution of these highly localized electrons at the interface are calculated for different interface widths and for various physical parameters of the structure. The long-range and atomic level uniformities of the GaN quantum wells grown in an AlN matrix are characterized using electron energy loss spectroscopy and annular dark field imaging. The effects of the incident electron beam broadening inside the specimen on STEM measurements are discussed and mechanisms to minimize them are suggested. For quantitative correlation, the measured intensity of the nitrogen K-edge is compared with the propagating beam intensity obtained from multislice calculations. Possible effects of strain in the structure on its electronic states and energy-loss spectra are predicted. The electron-beam-induced damage of the wurtzite InN in STEM is studied and knock-on type damage with ejection of nitrogen atoms from a sample is observed. From comparison of the measured integrated intensity of the nitrogen K-edge and indium M4,5-edge with a calculated mass-loss model the vacancy-enhanced displacement energy for nitrogen atoms in InN is obtained. Investigations of the electronic structure of the wurtzite InN are carried out and excellent agreement between measured spectra of the nitrogen K-edge and the indium M4,5 -edge and corresponding nitrogen 2p and the indium 5p partial density of states (DOS) of the conduction band is obtained. The calculations of DOS are performed using density functional theory (DFT). DFT calculations of nitrogen 2p partial DOS of the conduction band in strained and relaxed wurtzite InN combined with multiple scattering x-ray absorption near edge structure calculations of the corresponding nitrogen K-edge spectra suggest that a strong modification of the electronic structure should be expected in epitaxially grown multilayer structures when a significant mismatch in lattice constants between layers is present.

Mkhoyan, Karen Andre

194

Digital holographic microscopy for quantitative cell dynamic evaluation during laser microsurgery  

PubMed Central

Digital holographic microscopy allows determination of dynamic changes in the optical thickness profile of a transparent object with subwavelength accuracy. Here, we report a quantitative phase laser microsurgery system for evaluation of cellular/ sub-cellular dynamic changes during laser micro-dissection. The proposed method takes advantage of the precise optical manipulation by the laser microbeam and quantitative phase imaging by digital holographic microscopy with high spatial and temporal resolution. This system will permit quantitative evaluation of the damage and/or the repair of the cell or cell organelles in real time.

Yu, Lingfeng; Mohanty, Samarendra; Zhang, Jun; Genc, Suzanne; Kim, Myung K.; Berns, Michael W.; Chen, Zhongping

2010-01-01

195

Structured illumination quantitative phase microscopy for enhanced resolution amplitude and phase imaging.  

PubMed

Structured illumination microscopy (SIM) is an established microscopy technique typically used to image samples at resolutions beyond the diffraction limit. Until now, however, achieving sub-diffraction resolution has predominantly been limited to intensity-based imaging modalities. Here, we introduce an analogue to conventional SIM that allows sub-diffraction resolution, quantitative phase-contrast imaging of optically transparent objects. We demonstrate sub-diffraction resolution amplitude and quantitative-phase imaging of phantom targets and enhanced resolution quantitative-phase imaging of cells. We report a phase accuracy to within 5% and phase noise of 0.06 rad. PMID:24156044

Chowdhury, Shwetadwip; Izatt, Joseph

2013-01-01

196

Arc welders' pneumoconiosis: application of advanced scanning electron microscopy  

Microsoft Academic Search

Study of lung tissue from necropsy of a 58-year-old arc welder with arc welders' pneumoconiosis, confirmed by history, chest radiography, and pathology, demonstrates the versatility and usefulness of new techniques in scanning electron microscopy (SEM). Secondary electron imaging, the most familiar SEM mode, showed heavy cellular infiltrates in alveoli, the interstitium, and within the interstices of loose whorled fibrotic nodules.

T. L. Guidotti; J. L. Abraham; P. B. DeNee; J. R. Smith

1978-01-01

197

Electron microscopy investigations of ferrous martensites  

Microsoft Academic Search

This paper is concerned with electron metallography of bcc or bet ferrous martensite in which particular attention is paid\\u000a to, the characterization of substructures., The transformation substructure is complex and new results are reported on multiple\\u000a {112} twinning. The factors controlling the martensitic substructure are evaluated and it is concluded that the strength and\\u000a deformation, characteristics of martensite are the

Gareth Thomas

1971-01-01

198

Combined confocal Raman and quantitative phase microscopy system for biomedical diagnosis  

PubMed Central

We have developed a novel multimodal microscopy system that incorporates confocal Raman, confocal reflectance, and quantitative phase microscopy (QPM) into a single imaging entity. Confocal Raman microscopy provides detailed chemical information from the sample, while confocal reflectance and quantitative phase microscopy show detailed morphology. Combining these intrinsic contrast imaging modalities makes it possible to obtain quantitative morphological and chemical information without exogenous staining. For validation and characterization, we have used this multi-modal system to investigate healthy and diseased blood samples. We first show that the thickness of a healthy red blood cell (RBC) shows good correlation with its hemoglobin distribution. Further, in malaria infected RBCs, we successfully image the distribution of hemozoin (malaria pigment) inside the cell. Our observations lead us to propose morphological screening by QPM and subsequent chemical imaging by Raman for investigating blood disorders. This new approach allows monitoring cell development and cell-drug interactions with minimal perturbation of the biological system of interest.

Kang, Jeon Woong; Lue, Niyom; Kong, Chae-Ryon; Barman, Ishan; Dingari, Narahara C.; Goldfless, Stephen J.; Niles, Jacquin C.; Dasari, Ramachandra R.; Feld, Michael S.

2011-01-01

199

Evaluating sharpness functions for automated scanning electron microscopy.  

PubMed

Fast and reliable autofocus techniques are an important topic for automated scanning electron microscopy. In this paper, different autofocus techniques are discussed and applied to a variety of experimental through-focus series of scanning electron microscopy images with different geometries. The procedure of quality evaluation is described, and for a variety of scanning electron microscope samples it is demonstrated that techniques based on image derivatives and Fourier transforms are in general better than statistical, intensity and histogram-based techniques. Further, it is shown that varying of an extra parameter can dramatically increase quality of an autofocus technique. PMID:21050212

Rudnaya, M E; Mattheij, R M M; Maubach, J M L

2010-10-01

200

Correlative light- and electron microscopy with chemical tags.  

PubMed

Correlative microscopy incorporates the specificity of fluorescent protein labeling into high-resolution electron micrographs. Several approaches exist for correlative microscopy, most of which have used the green fluorescent protein (GFP) as the label for light microscopy. Here we use chemical tagging and synthetic fluorophores instead, in order to achieve protein-specific labeling, and to perform multicolor imaging. We show that synthetic fluorophores preserve their post-embedding fluorescence in the presence of uranyl acetate. Post-embedding fluorescence is of such quality that the specimen can be prepared with identical protocols for scanning electron microscopy (SEM) and transmission electron microscopy (TEM); this is particularly valuable when singular or otherwise difficult samples are examined. We show that synthetic fluorophores give bright, well-resolved signals in super-resolution light microscopy, enabling us to superimpose light microscopic images with a precision of up to 25 nm in the x-y plane on electron micrographs. To exemplify the preservation quality of our new method we visualize the molecular arrangement of cadherins in adherens junctions of mouse epithelial cells. PMID:24698954

Perkovic, Mario; Kunz, Michael; Endesfelder, Ulrike; Bunse, Stefanie; Wigge, Christoph; Yu, Zhou; Hodirnau, Victor-Valentin; Scheffer, Margot P; Seybert, Anja; Malkusch, Sebastian; Schuman, Erin M; Heilemann, Mike; Frangakis, Achilleas S

2014-05-01

201

Correlative microscopy: bridging the gap between fluorescence light microscopy and cryo-electron tomography.  

PubMed

Cryo-electron tomography of frozen-hydrated biological samples offers a means of studying large and complex cellular structures in three-dimensions and with nanometer-scale resolution. The low contrast of unstained biological material embedded in amorphous ice and the need to minimise the exposure of these radiation-sensitive samples to the electron beam result in a poor signal-to-noise ratio. This poses problems not only in the visualisation and interpretation of such tomograms, it is also a problem in surveying the sample and in finding regions which contain the features of interest and which are suitable for recording tomograms. To address this problem, we have developed a correlative fluorescence light microscopy-electron microscopy approach, which guides the search for the structures of interest and allows electron microscopy to zoom in on them. With our approach, the total dose spent on locating regions of interest is negligible. A newly designed cryo-holder allows imaging of fluorescently labelled samples after vitrification. The absolute coordinates of structures identified and located by cryo-light microscopy are transferred to the electron microscope via a Matlab-based user interface. We have successfully tested the experimental setup and the whole procedure with two types of adherent fluorescently labelled cells, a neuronal cell line and keratinocytes, both grown directly on EM grids. PMID:17884579

Sartori, Anna; Gatz, Rudolf; Beck, Florian; Rigort, Alexander; Baumeister, Wolfgang; Plitzko, Juergen M

2007-11-01

202

Correlative video-light-electron microscopy: development, impact and perspectives.  

PubMed

Green fluorescent protein (GFP)-based video microscopy can provide profound insight into biological processes by generating information on the 'history,' or dynamics, of the cellular structures involved in such processes in live cells. A crucial limitation of this approach, however, is that many such structures may not be resolved by light microscopy. Like more recent super-resolution techniques, correlative video-light-electron microscopy (CLEM) was developed to overcome this limitation. CLEM integrates GFP-based video microscopy and electron microscopy through a series of ancillary techniques, such as proper fixation, hybrid labeling and retracing, and so provides sufficient resolution as well as, crucially, cellular 'context' to the fluorescent dynamic structures of interest. CLEM 'multiplies' the power of video microscopy and is having an important impact in several areas cell and developmental biology. Here, we discuss potential, limitations and perspectives of correlative approaches aimed at integrating the unique insight generated by video microscopy with information from other forms of imaging. PMID:25030356

Rizzo, Riccardo; Parashuraman, Seetharaman; Luini, Alberto

2014-08-01

203

Persistent misconceptions about incoherence in electron microscopy.  

PubMed

Incoherence in electron microscopic imaging occurs when during the observation the microscope and the object are subject to fluctuations. In order to speed up the computer simulation of the images, approximations are used that are considered as valid. In this paper we will question the validity of these approximations and show that in specific cases they can lead to erroneous results. It is shown in particular in the case of one single vibrating atom that the thermal diffuse scattering that causes the signal in HAADF STEM is not only dependent on Z but also on the mean square displacement of the atom so that it can even be large for light atoms in soft matter, provided the right HAADF aperture is used. In HREM imaging the diffuse scattering leaks out of the coherent (elastic) wave and is redistributed in the background. This might explain the mismatch in elastic contrast (Stobbs factor) especially for crystals with a thickness beyond the extinction distance, where also the HAADF signal saturates and the elastic (coherent) component vanishes. PMID:21664551

Van Dyck, D

2011-06-01

204

[Scanning electron microscopy in gastric adenocarcinoma and intestinal metaplasia].  

PubMed

In recent years scanning electron microscopy has been used in gastric biopsy studies, contributing to better recognition of intestinal metaplasia and carcinoma, as a complement to light and transmission electron microscopy. During the second half of 1983, 53 cases of gastric carcinoma were diagnosed at the Department of Pathology of Hospital Mexico, of which six were studied ultrastructurally. A pattern similar to that of intestinal epithelium was found in cases of intestinal metaplasia. Well differentiated adenocarcinomas showed marked tumor cell proliferation with irregular "projections". In poorly differentiated carcinomas, changes were limited to areas where tumor cells invaded the epithelial surface. In summary, scanning electron microscopy is of great help in research and diagnosis of pathologic changes occurring in mucosal surfaces. PMID:3423334

Tuk, B; Corrales, D

1986-11-01

205

Biological applications of phase-contrast electron microscopy.  

PubMed

Here, I review the principles and applications of phase-contrast electron microscopy using phase plates. First, I develop the principle of phase contrast based on a minimal model of microscopy, introducing a double Fourier-transform process to mathematically formulate the image formation. Next, I explain four phase-contrast (PC) schemes, defocus PC, Zernike PC, Hilbert differential contrast, and schlieren optics, as image-filtering processes in the context of the minimal model, with particular emphases on the Zernike PC and corresponding Zernike phase plates. Finally, I review applications of Zernike PC cryo-electron microscopy to biological systems such as protein molecules, virus particles, and cells, including single-particle analysis to delineate three-dimensional (3D) structures of protein and virus particles and cryo-electron tomography to reconstruct 3D images of complex protein systems and cells. PMID:24357373

Nagayama, Kuniaki

2014-01-01

206

CI Slide: calibration slide for quantitative microscopy imaging in absorbance  

NASA Astrophysics Data System (ADS)

New imaging technologies are changing the field of digital pathology. This field faces numerous challenges and there is a pressing need for standardization, calibration protocols, quality control and quantitative assessment. We have designed a new calibration imaging slide (Cancer Imaging Slide), specifically to measure the characteristics of old or new imaging systems or scanners. The layout of the slide consists of 138 boxes with the side length of 1.6 mm, containing objects of known morphologic and photometric characteristics. Among them, 112 boxes contain different permutations of circles, ovals, and squares. The circles have different radii, radius/pitch ratios and step transmissions. The ovals have different sizes and orientations. The squares are consistent in size and orientation but have different step transmission values. Also, 16 boxes contain three resolution test targets: crosses, USAF target and Siemens star. The last 10 boxes are blank boxes with different transmission values. Four slides were scanned and imaged on one commercial whole-slide scanner and one high resolution imaging system. After segmenting the images, about 200 features (photometric, morphologic and architectural) were measured with our in-house image processing software. The objective of the project is to develop a statistical process control using this new slide. In this paper, we describe the characteristics of the slide and present our preliminary results.

Sheikhzadeh, Fahime; Ye, Qian; Zulkafly, Nasir; Carraro, Anita; Korbelic, Jagoda; Chen, Zhaoyang; Harrison, Alan; Follen, Michele; MacAulay, Calum; Ward, Rabab K.; Guillaud, Martial

2014-03-01

207

Laboratory design for high-performance electron microscopy  

SciTech Connect

Proliferation of electron microscopes with field emission guns, imaging filters and hardware spherical aberration correctors (giving higher spatial and energy resolution) has resulted in the need to construct special laboratories. As resolutions improve, transmission electron microscopes (TEMs) and scanning transmission electron microscopes (STEMs) become more sensitive to ambient conditions. State-of-the-art electron microscopes require state-of-the-art environments, and this means careful design and implementation of microscope sites, from the microscope room to the building that surrounds it. Laboratories have been constructed to house high-sensitive instruments with resolutions ranging down to sub-Angstrom levels; we present the various design philosophies used for some of these laboratories and our experiences with them. Four facilities are described: the National Center for Electron Microscopy OAM Laboratory at LBNL; the FEGTEM Facility at the University of Sheffield; the Center for Integrative Molecular Biosciences at TSRI; and the Advanced Microscopy Laboratory at ORNL.

O'Keefe, Michael A.; Turner, John H.; Hetherington, Crispin J.D.; Cullis, A.G.; Carragher, Bridget; Jenkins, Ron; Milgrim, Julie; Milligan,Ronald A.; Potter, Clinton S.; Allard, Lawrence F.; Blom, Douglas A.; Degenhardt, Lynn; Sides, William H.

2004-04-23

208

X-ray fluorescence and electron microscopy study of plankton samples from the Novosibirsk reservoir  

Microsoft Academic Search

Five samples of plankton from the Novosibirsk reservoir are collected and analyzed by X-ray fluorescence. In combination with\\u000a high sensitive atomic absorption spectroscopy (AAS), inductively coupled plasma mass spectrometry (ICP-MS), and instrumental\\u000a neutron activation analysis (INAA), quantitative data on the concentrations of 52 chemical elements in plankton are obtained.\\u000a Scanning electron microscopy is used to analyze the elemental composition of

G. A. Leonova; V. A. Bobrov; E. V. Lazareva

2010-01-01

209

Use of scanning electron microscopy to investigate records of soil weathering preserved in lake sediment  

Microsoft Academic Search

Reconstruction of soil weathering is one of the more difficult problems for palaeoecologists interested in landscape-scale environmental changes. Here we use scanning electron microscopy and energy dispersive x-ray analysis (SEM\\/EDS) to study the pitting of feldspars in soils and lake sediments at two sites in the Great Lakes region, USA. A semi-quantitative feldspar weathering index (FWI) allows description of the

Holly A. Ewing; Edward A. Nater

2003-01-01

210

The identification of burnt matches by scanning electron microscopy\\/energy dispersive X-ray spectrometry  

Microsoft Academic Search

This study is first placed on the characterization of various burnt matches by scanning electron microscopy\\/energy dispersive X-ray spectrometry (SEM\\/EDS). The morphological and elemental features were used to investigate fire residues and to increase the discriminating effect of burnt matches. To find if there was further discrimination method, the cluster analysis of 74 boxes of matches based on the semi-quantitative

Yueh-Hsiang Chen

211

Scanning electron microscopy and energy dispersive analysis: applications in the field of cultural heritage  

Microsoft Academic Search

Scanning electron microscopy has been extensively used for the material characterization of objects of artistic and archaeological\\u000a importance, especially in combination with energy dispersive X-ray microanalysis (SEM\\/EDX). The advantages and limitations\\u000a of SEM\\/EDX are presented in a few case studies: analysis of pigments in cross-sections of paint layers, quantitative analysis\\u000a of archaeological glass from the Roman period excavated in Ephesos\\/Turkey,

Manfred Schreiner; Michael Melcher; Katharina Uhlir

2007-01-01

212

Investigation of Chocolate Surfaces Using Profilometry and Low Vacuum Scanning Electron Microscopy  

Microsoft Academic Search

In this study we establish the use of optical non-contact profilometry combined with low vacuum scanning electron microscopy\\u000a (LV SEM) for the investigation of lipid surfaces. We illustrate, by using profilometry, a methodology for investigation of\\u000a chocolate surface topology as a function of time, in the same area of interest. Both qualitative and quantitative data analysis\\u000a has been performed for

Hanna Dahlenborg; Anna Millqvist-Fureby; Björn Bergenståhl; Daniel J. E. Kalnin

2011-01-01

213

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

214

Epidermal growth factor receptor subunit locations determined in hydrated cells with environmental scanning electron microscopy.  

PubMed

Imaging single epidermal growth factor receptors (EGFR) in intact cells is presently limited by the available microscopy methods. Environmental scanning electron microscopy (ESEM) of whole cells in hydrated state in combination with specific labeling with gold nanoparticles was used to localize activated EGFRs in the plasma membranes of COS7 and A549 cells. The use of a scanning transmission electron microscopy (STEM) detector yielded a spatial resolution of 3?nm, sufficient to identify the locations of individual EGFR dimer subunits. The sizes and distribution of dimers and higher order clusters of EGFRs were determined. The distance between labels bound to dimers amounted to 19?nm, consistent with a molecular model. A fraction of the EGFRs was found in higher order clusters with sizes ranging from 32-56?nm. ESEM can be used for quantitative whole cell screening studies of membrane receptors, and for the study of nanoparticle-cell interactions in general. PMID:24022088

Peckys, Diana B; Baudoin, Jean-Pierre; Eder, Magdalena; Werner, Ulf; de Jonge, Niels

2013-01-01

215

Imaging doped silicon test structures using low energy electron microscopy.  

SciTech Connect

This document is the final SAND Report for the LDRD Project 105877 - 'Novel Diagnostic for Advanced Measurements of Semiconductor Devices Exposed to Adverse Environments' - funded through the Nanoscience to Microsystems investment area. Along with the continuous decrease in the feature size of semiconductor device structures comes a growing need for inspection tools with high spatial resolution and high sample throughput. Ideally, such tools should be able to characterize both the surface morphology and local conductivity associated with the structures. The imaging capabilities and wide availability of scanning electron microscopes (SEMs) make them an obvious choice for imaging device structures. Dopant contrast from pn junctions using secondary electrons in the SEM was first reported in 1967 and more recently starting in the mid-1990s. However, the serial acquisition process associated with scanning techniques places limits on the sample throughput. Significantly improved throughput is possible with the use of a parallel imaging scheme such as that found in photoelectron emission microscopy (PEEM) and low energy electron microscopy (LEEM). The application of PEEM and LEEM to device structures relies on contrast mechanisms that distinguish differences in dopant type and concentration. Interestingly, one of the first applications of PEEM was a study of the doping of semiconductors, which showed that the PEEM contrast was very sensitive to the doping level and that dopant concentrations as low as 10{sup 16} cm{sup -3} could be detected. More recent PEEM investigations of Schottky contacts were reported in the late 1990s by Giesen et al., followed by a series of papers in the early 2000s addressing doping contrast in PEEM by Ballarotto and co-workers and Frank and co-workers. In contrast to PEEM, comparatively little has been done to identify contrast mechanisms and assess the capabilities of LEEM for imaging semiconductor device strictures. The one exception is the work of Mankos et al., who evaluated the impact of high-throughput requirements on the LEEM designs and demonstrated new applications of imaging modes with a tilted electron beam. To assess its potential as a semiconductor device imaging tool and to identify contrast mechanisms, we used LEEM to investigate doped Si test structures. In section 2, Imaging Oxide-Covered Doped Si Structures Using LEEM, we show that the LEEM technique is able to provide reasonably high contrast images across lateral pn junctions. The observed contrast is attributed to a work function difference ({Delta}{phi}) between the p- and n-type regions. However, because the doped regions were buried under a thermal oxide ({approx}3.5 nm thick), e-beam charging during imaging prevented quantitative measurements of {Delta}{phi}. As part of this project, we also investigated a series of similar test structures in which the thermal oxide was removed by a chemical etch. With the oxide removed, we obtained intensity-versus-voltage (I-V) curves through the transition from mirror to LEEM mode and determined the relative positions of the vacuum cutoffs for the differently doped regions. Although the details are not discussed in this report, the relative position in voltage of the vacuum cutoffs are a direct measure of the work function difference ({Delta}{phi}) between the p- and n-doped regions.

Nakakura, Craig Yoshimi; Anderson, Meredith Lynn; Kellogg, Gary Lee

2010-01-01

216

Quantitative in situ correlation between microscopic MRI and polarized light microscopy studies of articular cartilage  

Microsoft Academic Search

Objective To establish the correlation between the non-invasive imaging by magnetic resonance microscopy (?MRI) and the histological imaging by polarized light microscopy (PLM) accurately, quantitatively, at the highest possible MRI resolution (13.7?m), and based on the same piece of tissue (articular cartilage from canine shoulder joint).Design In ?MRI experiments, the laminar appearance (the magic angle effect) of the proton intensity

Y. Xia; J. B. Moody; N. Burton-Wurster; G. Lust

2001-01-01

217

Direct investigation of subsurface interface electronic structure by ballistic-electron-emission microscopy  

NASA Technical Reports Server (NTRS)

A new technique for spectroscopic investigation of subsurface interface electronic structure has been developed. The method, ballistic-electron-emission microscopy (BEEM), is based on scanning tunneling microscopy. BEEM makes possible, for the first time, direct imaging of subsurface interface properties with nanometer spatial resolution. The first application of BEEM to subsurface Schottky-barrier interfaces is reported.

Kaiser, W. J.; Bell, L. D.

1988-01-01

218

Improved Imaging in Low Energy Electron Microscopy and Photo Emission Electron Microscopy Using MEDIPIX2 Pixel Detector  

NASA Astrophysics Data System (ADS)

The application of the Medipix2 hybrid pixel detector in Low Energy Electron Microscopy (LEEM) and Photo Emission Electron Microscopy (PEEM) led to an improvement of the recorded image quality compared to the original setup based on microchannel plate (MCP), phosphor screen and CCD. The measurements were performed on an Elmitec LEEM III instrument without energy filter using an Ir(111) sample with graphene islands grown on the surface. The Medipix2 images exhibited better resolution and higher contrast compared to the MCP data. The results suggest that Medipix2 has potential to become the detector of choice for LEEM/PEEM instruments.

Sikharulidze, I.; van Gastel, R.; Schramm, S.; Abrahams, J. P.; Poelsema, B.; Trom, R. M.; van der Molen, S. J.

2010-04-01

219

Imaging grain boundaries in monolayer graphene by transmission electron microscopy  

NASA Astrophysics Data System (ADS)

Using transmission electron microscopy (TEM), we investigate the structure of grain boundaries in large-area monolayer polycrystalline graphene sheets at micron and atomic length scales. At micron scale, grain boundary mapping is performed by electron diffraction and dark field imaging techniques. The atomic scale imaging by an aberration-corrected ultra-high resolution TEM reveals an alternating pentagon-heptagon structure along the high-angle tilt grain boundary.

Kim, Kwanpyo; Lee, Zonghoon; Regan, William; Kisielowski, C.; Crommie, M.; Zettl, A.

2011-03-01

220

Imaging Nanobubbles in Water with Scanning Transmission Electron Microscopy  

Microsoft Academic Search

We present a technique based on scanning transmission electron microscopy (STEM) that is capable of probing nanobubble dynamics with nanometer spatial resolution. A vacuum-tight vessel holds a sub-micrometer layer of water between two electron-transparent dielectric membranes. Electrical current pulses passing through a platinum wire on one of the membranes inject sufficient heat locally to initiate single bubble formation. In the

Edward R. White; Matthew Mecklenburg; Scott B. Singer; Shaul Aloni; Brian Christopher Regan

2011-01-01

221

Electron Microscopy of the Cell Wall of Rickettsia prowazeki  

PubMed Central

Purified Rickettsia prowazeki were found to undergo morphological changes resembling plasmolysis when stained with uranyl acetate, resulting in rod-like forms. Sequential electron micrographs of disintegrating organisms provide evidence for the cell wall origin of these rod-like forms. The substructure of the cell wall was discerned by using negative-contrast electron microscopy. The wall was found to be composed of repetitive subunits with a periodicity of 13 nm and was surrounded by a thin membrane. Images

Palmer, E. L.; Mallavia, L. P.; Tzianabos, T.; Obijeski, J. F.

1974-01-01

222

Electron microscopy analysis of mineral fibers in human lung tissue  

Microsoft Academic Search

In the present study, lung samples from 126 autopsied cases were examined to determine the content of mineral fibers using analytical transmission electron microscopy (ATEM). The cases were divided into four groups (22 lungs of persons exposed to ambient environmental pollution, 32 cases of mesothelioma, 38 cases of primary lung cancer, and 34 asbestosis cases, 13 of these with additional

Karl Heinz Friedrichs; Michael Brockmann; Margit Fischer; Gabriele Wick

1992-01-01

223

Scanning electron microscopy analysis of corrosion degradation on tinplate substrates.  

PubMed

The degradation of electrolytic tinplate used in food containers was analysed and evaluated, using scanning electron microscopy and electrochemical measurements of microcorrosion and ion dissolution by atomic absorption to prevent food contamination caused by metal traces and to increase the durability of such tinplates. PMID:12627896

Zumelzu, E; Cabezas, C; Vera, A

2003-01-01

224

Transmission electron microscopy of polymer blends and block copolymers  

Microsoft Academic Search

Transmission electron microscopy (TEM) of soft matter is a field that warrants further investigation. Developments in sample preparation, imaging and spectroscopic techniques could lead to novel experiments that may further our understanding of the structure and the role structure plays in the functionality of various organic materials. Unlike most hard materials, TEM of organic molecules is limited by the amount

Enrique Daniel Gomez

2007-01-01

225

Formvar holey films and nets for electron microscopy  

Microsoft Academic Search

A very quick, reliable and reproducible procedure for preparing 'holey' films with various ranges of hole diameters (0.05-20 mu m), as test objects for correction of astigmatism in high resolution instruments, and Formvar nets for mounting ultrathin microtome sections for high resolution electron microscopy is presented. It has been possible to control the hole diameter within limits under the stated

A. V. Moharir; N. Prakash

1975-01-01

226

'GIARDIA MURIS': SCANNING ELECTRON MICROSCOPY OF IN VITRO EXCYSTATION  

EPA Science Inventory

A recently developed in vitro excystation procedure results in almost total excystation of Giardia muris, an intestinal parasite of mice. The present experiment examines the G. muris cyst morphology by scanning electron microscopy and evaluates the efficacy of the excystation pro...

227

High Resolution Electron Microscopy at the National Cancer Institute  

Cancer.gov

Emerging methods in three-dimensional biological electron microscopy provide powerful tools and great promise to bridge a critical gap in imaging in the biomedical size spectrum. This gap comprises a size range of considerable interest in biology and medicine that includes cellular protein machines, giant protein and nucleic acid assemblies, small subcellular organelles and small bacteria.

228

Preparation of rotifer trophi for light and scanning electron microscopy  

Microsoft Academic Search

The methods to prepare rotifer trophi for light and scanning electron microscopy are reviewed, and the rapid method used by the author is described. Rotifers are dissolved in a minimal amount of sodium hypochlorite solution on a coverslip, and serially rinsed in distilled water. The entire procedure is done under a microscope using micropipettes.

Willem H. De Smet

1998-01-01

229

Collaboration at the Nanoscale: Exploring Viral Genetics with Electron Microscopy  

ERIC Educational Resources Information Center

The Maine Science Corps is a project sponsored by the National Science Foundation's (NSF) Graduate Teaching Fellows in K-12 Education (GK-12 ) program. Through this program, the University of Southern Maine's (USM) virology and transmission electron microscopy (TEM) research group provides high school teachers and students in rural areas with…

Duboise, S. Monroe; Moulton, Karen D.; Jamison, Jennifer L.

2009-01-01

230

High Resolution Electron Microscopy at the National Cancer Institute  

Cancer.gov

Bennett AE, Narayan K, Shi D, Hartnell L, Gousset K, He H, Lowekamp BC, Yoo TS, Bliss D, Freed EO and Subramaniam S. (2009) Ion-abrasion scanning electron microscopy reveals surface-connected tubular conduits in HIV-infected macrophages. PLoS Pathog.

231

Lorentz electron microscopy of rare-earth permanent magnets  

Microsoft Academic Search

Purpose of this work is to determine the relationship of the microstructure with the magnetic domain structure to clarify the origin of the high-coercive fields in these permanent magnet materials Sm (Co, Fe, Cu, Zr)\\/sub x\\/. Lorentz electron microscopy has been used to image the domain walls and study their interactions with crystalline defects.

G. C. Hadjipanayis; L. L. Horton

1983-01-01

232

Detection of parvoviruses in wolf feces by electron microscopy  

USGS Publications Warehouse

One hundred fifteen wolf (Canis lupus) feces were collected between 1980 and 1984 from northeastern Minnesota and were examined for canine parvovirus by negative contrast electron microscopy. Of these, seven (6%) samples revealed the presence of parvovirus. Some of these viruses were able to grow in cell cultures forming intranuclear inclusion bodies and giant cells.

Muneer, M.A.; Farah, I.O.; Pomeroy, K.A.; Goyal, S.M.; Mech, L.D.

1988-01-01

233

In situ Study of Oxidative Etching of Palladium Nanocrystals by Liquid Cell Electron Microscopy.  

PubMed

Oxidative etching has widely prevailed in the synthesis of a crystal and played a critical role in determining the final growth behavior. In this Letter, we report an in situ microscopic study on the oxidative etching of palladium cubic nanocrystals by liquid cell scanning transmission electron microscopy. The etching was realized with oxidative radiation reactants from electron-water interaction in the presence of Br(-) ions. Dissolution dynamics of monodispersed and aggregated nanocrystals were both investigated and compared. Analyses on the dissolution kinetics of nanocrystals and the diffusion kinetics of the dissolved agents were carried out based on the scanning transmission electron microscopy characterizations. The results presented here pave a way toward the quantitative understanding of the oxidative etching reaction and its application in the functionally orientated fabrication of nanocrystals with certain sizes, structures, and morphologies. PMID:24927485

Jiang, Yingying; Zhu, Guomin; Lin, Fang; Zhang, Hui; Jin, Chuanhong; Yuan, Jun; Yang, Deren; Zhang, Ze

2014-07-01

234

Use of atomic force microscopy and transmission electron microscopy for correlative studies of bacterial capsules.  

PubMed

Bacteria can possess an outermost assembly of polysaccharide molecules, a capsule, which is attached to their cell wall. We have used two complementary, high-resolution microscopy techniques, atomic force microscopy (AFM) and transmission electron microscopy (TEM), to study bacterial capsules of four different gram-negative bacterial strains: Escherichia coli K30, Pseudomonas aeruginosa FRD1, Shewanella oneidensis MR-4, and Geobacter sulfurreducens PCA. TEM analysis of bacterial cells using different preparative techniques (whole-cell mounts, conventional embeddings, and freeze-substitution) revealed capsules for some but not all of the strains. In contrast, the use of AFM allowed the unambiguous identification of the presence of capsules on all strains used in the present study, including those that were shown by TEM to be not encapsulated. In addition, the use of AFM phase imaging allowed the visualization of the bacterial cell within the capsule, with a depth sensitivity that decreased with increasing tapping frequency. PMID:18606791

Stukalov, Oleg; Korenevsky, Anton; Beveridge, Terry J; Dutcher, John R

2008-09-01

235

Use of Atomic Force Microscopy and Transmission Electron Microscopy for Correlative Studies of Bacterial Capsules? †  

PubMed Central

Bacteria can possess an outermost assembly of polysaccharide molecules, a capsule, which is attached to their cell wall. We have used two complementary, high-resolution microscopy techniques, atomic force microscopy (AFM) and transmission electron microscopy (TEM), to study bacterial capsules of four different gram-negative bacterial strains: Escherichia coli K30, Pseudomonas aeruginosa FRD1, Shewanella oneidensis MR-4, and Geobacter sulfurreducens PCA. TEM analysis of bacterial cells using different preparative techniques (whole-cell mounts, conventional embeddings, and freeze-substitution) revealed capsules for some but not all of the strains. In contrast, the use of AFM allowed the unambiguous identification of the presence of capsules on all strains used in the present study, including those that were shown by TEM to be not encapsulated. In addition, the use of AFM phase imaging allowed the visualization of the bacterial cell within the capsule, with a depth sensitivity that decreased with increasing tapping frequency.

Stukalov, Oleg; Korenevsky, Anton; Beveridge, Terry J.; Dutcher, John R.

2008-01-01

236

Environmental scanning electron microscopy gold immunolabeling in cell biology.  

PubMed

Immunogold labeling (IGL) technique has been utilized by many authors in combination with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to obtain the identification/localization of receptors and antigens, both in cells and tissues. Environmental scanning electron microscopy (ESEM) represents an important tool in biomedical research, since it does not require any severe processing of the sample, lowering the risk of generating artifacts and interfere with the IGL procedure. The absence of metal coating could yield further advantages for our purpose as the labeling detection is based on the atomic number difference between nanogold spheres and the biological material. Using the gaseous secondary electron detector, compositional contrast is easily revealed by the backscattered electron component of the signal. In spite of this fact, only few published papers present a combination of ESEM and IGL. Hereby we present our method, optimized to improve the intensity and the specificity of the labeling signal, in order to obtain a semiquantitative evaluation of the labeling signal.In particular, we used a combination of IGL and ESEM to detect the presence of a protein on the cell surface. To achieve this purpose, we chose as an experimental system 3T3 Swiss albino mouse fibroblasts and galectin-3. PMID:23027021

Rosso, Francesco; Papale, Ferdinando; Barbarisi, Alfonso

2013-01-01

237

Assessment of Mechanical Durability Properties of Rock Materials Using Quantitative Microscopy and Image Analysis.  

National Technical Information Service (NTIS)

This report presents a project that focuses on the assessment of mechanical durability properties using quantitative microscopy. The project was financed by SGU under grant 03-1174/98. The aim has been to develop methods for assessment and presentation of...

J. E. Lindqvist U. Akesson K. Malaga B. Schouenborg M. Goeransson

2004-01-01

238

Detective quantum efficiency of electron area detectors in electron microscopy  

PubMed Central

Recent progress in detector design has created the need for a careful side-by-side comparison of the modulation transfer function (MTF) and resolution-dependent detective quantum efficiency (DQE) of existing electron detectors with those of detectors based on new technology. We present MTF and DQE measurements for four types of detector: Kodak SO-163 film, TVIPS 224 charge coupled device (CCD) detector, the Medipix2 hybrid pixel detector, and an experimental direct electron monolithic active pixel sensor (MAPS) detector. Film and CCD performance was measured at 120 and 300 keV, while results are presented for the Medipix2 at 120 keV and for the MAPS detector at 300 keV. In the case of film, the effects of electron backscattering from both the holder and the plastic support have been investigated. We also show that part of the response of the emulsion in film comes from light generated in the plastic support. Computer simulations of film and the MAPS detector have been carried out and show good agreement with experiment. The agreement enables us to conclude that the DQE of a backthinned direct electron MAPS detector is likely to be equal to, or better than, that of film at 300 keV.

McMullan, G.; Chen, S.; Henderson, R.; Faruqi, A.R.

2009-01-01

239

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

PubMed Central

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

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

2009-01-01

240

Molecular and Cellular Quantitative Microscopy: theoretical investigations, technological developments and applications to neurobiology  

NASA Astrophysics Data System (ADS)

This PhD project aims at the development and evaluation of microscopy techniques for the quantitative detection of molecular interactions and cellular features. The primarily investigated techniques are F?rster Resonance Energy Transfer imaging and Fluorescence Lifetime Imaging Microscopy. These techniques have the capability to quantitatively probe the biochemical environment of fluorophores. An automated microscope capable of unsupervised operation has been developed that enables the investigation of molecular and cellular properties at high throughput levels and the analysis of cellular heterogeneity. State-of-the-art Förster Resonance Energy Transfer imaging, Fluorescence Lifetime Imaging Microscopy, Confocal Laser Scanning Microscopy and the newly developed tools have been combined with cellular and molecular biology techniques for the investigation of protein-protein interactions, oligomerization and post-translational modifications of ?-Synuclein and Tau, two proteins involved in Parkinson’s and Alzheimer’s disease, respectively. The high inter-disciplinarity of this project required the merging of the expertise of both the Molecular Biophysics Group at the Debye Institute - Utrecht University and the Cell Biophysics Group at the European Neuroscience Institute - G?ttingen University. This project was conducted also with the support and the collaboration of the Center for the Molecular Physiology of the Brain (Göttingen), particularly with the groups associated with the Molecular Quantitative Microscopy and Parkinson’s Disease and Aggregopathies areas. This work demonstrates that molecular and cellular quantitative microscopy can be used in combination with high-throughput screening as a powerful tool for the investigation of the molecular mechanisms of complex biological phenomena like those occurring in neurodegenerative diseases.

Esposito, Alessandro

2006-05-01

241

Human enamel structure studied by high resolution electron microscopy  

SciTech Connect

Human enamel structural features are characterized by high resolution electron microscopy. The human enamel consists of polycrystals with a structure similar to Ca10(PO4)6(OH)2. This article describes the structural features of human enamel crystal at atomic and nanometer level. Besides the structural description, a great number of high resolution images are included. Research into the carious process in human enamel is very important for human beings. This article firstly describes the initiation of caries in enamel crystal at atomic and unit-cell level and secondly describes the further steps of caries with structural and chemical demineralization. The demineralization in fact, is the origin of caries in human enamel. The remineralization of carious areas in human enamel has drawn more and more attention as its potential application is realized. This process has been revealed by high resolution electron microscopy in detail in this article. On the other hand, the radiation effects on the structure of human enamel are also characterized by high resolution electron microscopy. In order to reveal this phenomenon clearly, a great number of electron micrographs have been shown, and a physical mechanism is proposed. 26 references.

Wen, S.L. (Shanghai Institute of Ceramics, Academia Sinica (China))

1989-01-01

242

A Mobile Nanoscience and Electron Microscopy Outreach Program  

NASA Astrophysics Data System (ADS)

We have established a mobile nanoscience laboratory outreach program in Western NC that puts scanning electron microscopy (SEM) directly in the hands of K-12 students and the general public. There has been a recent push to develop new active learning materials to educate students at all levels about nanoscience and nanotechnology. Previous projects, such as Bugscope, nanoManipulator, or SPM Live! allowed remote access to advanced microscopies. However, placing SEM directly in schools has not often been possible because the cost and steep learning curve of these technologies were prohibitive, making this project quite novel. We have developed new learning modules for a microscopy outreach experience with a tabletop SEM (Hitachi TM3000). We present here an overview of our outreach and results of the assessment of our program to date.

Coffey, Tonya; Kelley, Kyle

2013-03-01

243

Energy levels of few-electron quantum dots imaged and characterized by atomic force microscopy  

PubMed Central

Strong confinement of charges in few-electron systems such as in atoms, molecules, and quantum dots leads to a spectrum of discrete energy levels often shared by several degenerate states. Because the electronic structure is key to understanding their chemical properties, methods that probe these energy levels in situ are important. We show how electrostatic force detection using atomic force microscopy reveals the electronic structure of individual and coupled self-assembled quantum dots. An electron addition spectrum results from a change in cantilever resonance frequency and dissipation when an electron tunnels on/off a dot. The spectra show clear level degeneracies in isolated quantum dots, supported by the quantitative measurement of predicted temperature-dependent shifts of Coulomb blockade peaks. Scanning the surface shows that several quantum dots may reside on what topographically appears to be just one. Relative coupling strengths can be estimated from these images of grouped coupled dots.

Cockins, Lynda; Miyahara, Yoichi; Bennett, Steven D.; Clerk, Aashish A.; Studenikin, Sergei; Poole, Philip; Sachrajda, Andrew; Grutter, Peter

2010-01-01

244

Patterned Carbon Nanotube Applications for Transmission Electron Microscopy  

NASA Astrophysics Data System (ADS)

Transmission electron microscopy is a method for observing and characterizing thin films and other nanoscale samples. Carbon nanotubes were patterned and grown to function as disposable grids for transmission electron microscopy research. Patterned nanotube forests were infiltrated with carbon by chemical vapor deposition to provide greater strength. Carbon and polymer support films have been deposited in a batch process to provide a substrate for samples to be observed in the microscope. Grids are released from silicon wafer substrates by chemical etching. Carbon grids represent a significant improvement over traditional copper grids, which are not robust and must be individually coated in support films. These carbon support grids are also superior for use in spectroscopy applications (EELS, EDX) because of the low background signal.

Zufelt, Kyle; Abbott, Jonathan; Davis, Robert; Vanfleet, Richard

2010-10-01

245

Life cycle of phytoreoviruses visualized by electron microscopy and tomography  

PubMed Central

Rice dwarf virus and Rice gall dwarf virus, members of the genus Phytoreovirus in the family Reoviridae,are known as agents of rice disease, because their spread results in substantial economic damage in many Asian countries. These viruses are transmitted via insect vectors, and they multiply both in the plants and in the insect vectors. Structural information about the viruses and their interactions with cellular components in the life cycle are essential for understanding viral infection and replication mechanisms. The life cycle of the viruses involves various cellular events such as cell entry, synthesis of viral genome and proteins, assembly of viral components, viral egress from infected cells, and intra- and intercellular transports. This review focuses on the major events underlying the life cycle of phytoreoviruses, which has been visualized by various electron microscopy (EM) imaging techniques, including cryo-electron microscopy and tomography, and demonstrates the advantage of the advanced EM imaging techniques to investigate the viral infection and replication mechanisms.

Miyazaki, Naoyuki; Nakagawa, Atsushi; Iwasaki, Kenji

2013-01-01

246

Scanning electron microscopy of cristispira species in chesapeake bay oysters.  

PubMed

Scanning electron microscopy was employed to observe the physical interactions between Cristispira spp. and the crystalline style of the Chesapeake Bay oyster (Crassostrea virginica Gmelin 1791). Cristispira organisms were found associated with both the inner and outer layers of the posterior two-thirds of the style. The spirochetes possessed blunt-tipped ends, a cell diameter range of 0.6 to 0.8 mum, and distended spirochetal envelopes which followed the contour of the cells. Transmission electron microscopy showed that the distension of the envelope was probably due to the containment of numerous axial filaments. In addition, they were found to possess two distinct spiral shapes which were dependent on whether their location was inside or on the surface of the style. PMID:16345832

Tall, B D; Nauman, R K

1981-08-01

247

Transmission electron microscopy of interfaces in structural ceramic composites  

PubMed

Ceramic composites based either on a particulate, fibre or a lamellar architecture are potentially useful as damage-tolerant high-temperature engineering materials. The ability of the interfaces in such systems to deflect cracks is vital to the damage tolerance of these materials. Transmission electron microscopy techniques enable the chemical and physical characterization of these interfaces, providing information on interlayer thicknesses, chemical species, local bonding and the microstructural features which give rise to the interfacial properties, thereby enabling a full understanding not only of composites after processing, but also after exposure to aggressive environments such as air at high temperature. Examples of the application of transmission electron microscopy to all three composite architectures are described. PMID:10540272

Knowles; Turan; Kumar; Chen; Clegg

1999-11-01

248

Robert Feulgen Prize Lecture 1995. Electronic light microscopy: present capabilities and future prospects.  

PubMed

Electronic light microscopy involves the combination of microscopic techniques with electronic imaging and digital image processing, resulting in dramatic improvements in image quality and ease of quantitative analysis. In this review, after a brief definition of digital images and a discussion of the sampling requirements for the accurate digital recording of optical images, I discuss the three most important imaging modalities in electronic light microscopy--video-enhanced contrast microscopy, digital fluorescence microscopy and confocal scanning microscopy--considering their capabilities, their applications, and recent developments that will increase their potential. Video-enhanced contrast microscopy permits the clear visualisation and real-time dynamic recording of minute objects such as microtubules, vesicles and colloidal gold particles, an order of magnitude smaller than the resolution limit of the light microscope. It has revolutionised the study of cellular motility, and permits the quantitative tracking of organelles and gold-labelled membrane bound proteins. In combination with the technique of optical trapping (optical tweezers), it permits exquisitely sensitive force and distance measurements to be made on motor proteins. Digital fluorescence microscopy enables low-light-level imaging of fluorescently labelled specimens. Recent progress has involved improvements in cameras, fluorescent probes and fluorescent filter sets, particularly multiple bandpass dichroic mirrors, and developments in multiparameter imaging, which is becoming particularly important for in situ hybridisation studies and automated image cytometry, fluorescence ratio imaging, and time-resolved fluorescence. As software improves and small computers become more powerful, computational techniques for out-of-focus blur deconvolution and image restoration are becoming increasingly important. Confocal microscopy permits convenient, high-resolution, non-invasive, blur-free optical sectioning and 3D image acquisition, but suffers from a number of limitations. I discuss advances in confocal techniques that address the problems of temporal resolution, spherical and chromatic aberration, wavelength flexibility and cross-talk between fluorescent channels, and describe new optics to enhance axial resolution and the use of two-photon excitation to reduce photobleaching. Finally, I consider the desirability of establishing a digital image database, the BioImage database, which would permit the archival storage of, and public Internet access to, multidimensional image data from all forms of biological microscopy. Submission of images to the BioImage database would be made in coordination with the scientific publication of research results based upon these data.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:8536077

Shotton, D M

1995-08-01

249

Ultrafast electron microscopy in materials science, biology, and chemistry  

NASA Astrophysics Data System (ADS)

The use of pump-probe experiments to study complex transient events has been an area of significant interest in materials science, biology, and chemistry. While the emphasis has been on laser pump with laser probe and laser pump with x-ray probe experiments, there is a significant and growing interest in using electrons as probes. Early experiments used electrons for gas-phase diffraction of photostimulated chemical reactions. More recently, scientists are beginning to explore phenomena in the solid state such as phase transformations, twinning, solid-state chemical reactions, radiation damage, and shock propagation. This review focuses on the emerging area of ultrafast electron microscopy (UEM), which comprises ultrafast electron diffraction (UED) and dynamic transmission electron microscopy (DTEM). The topics that are treated include the following: (1) The physics of electrons as an ultrafast probe. This encompasses the propagation dynamics of the electrons (space-charge effect, Child's law, Boersch effect) and extends to relativistic effects. (2) The anatomy of UED and DTEM instruments. This includes discussions of the photoactivated electron gun (also known as photogun or photoelectron gun) at conventional energies (60-200 keV) and extends to MeV beams generated by rf guns. Another critical aspect of the systems is the electron detector. Charge-coupled device cameras and microchannel-plate-based cameras are compared and contrasted. The effect of various physical phenomena on detective quantum efficiency is discussed. (3) Practical aspects of operation. This includes determination of time zero, measurement of pulse-length, and strategies for pulse compression. (4) Current and potential applications in materials science, biology, and chemistry. UEM has the potential to make a significant impact in future science and technology. Understanding of reaction pathways of complex transient phenomena in materials science, biology, and chemistry will provide fundamental knowledge for discovery-class science.

King, Wayne E.; Campbell, Geoffrey H.; Frank, Alan; Reed, Bryan; Schmerge, John F.; Siwick, Bradley J.; Stuart, Brent C.; Weber, Peter M.

2005-06-01

250

Multiple reaction pathways of metallofullerenes investigated by transmission electron microscopy.  

PubMed

Recent advances in molecule-by-molecule transmission electron microscopy (TEM) have provided time-series structural information of individual molecules supported by nano-carbon materials, enabling researchers to trace their motions and reactions. In this paper, the chemical reactions of fullerenes and metallofullerene derivatives, focusing on their deformation process, are reviewed and discussed based on the single-molecule-resolved TEM analysis. PMID:24638213

Koshino, Masanori

2014-05-28

251

High Resolution Electron Microscopy at the National Cancer Institute  

Cancer.gov

Over the last couple of years, we have demonstrated that ion abrasion scanning electron microscopy (IA-SEM) can provide powerful new insights into subcelluar architecture. We have imaged MNT-1 melanoma cells to obtain new insights into statistical analysis of the size, shape and compositional analysis of organelles could provide valuable diagnostic markers for discriminating normal cells from abnormal cells. We reported the first application of IA-SEM for imaging a biomineralizing organism, the marine diatom Thalassiosira pseudonana.

252

A transmission electron microscopy study of presolar hibonite  

Microsoft Academic Search

We report isotopic and microstructural data on five presolar hibonite grains\\u000aidentified in an acid residue of the Krymka LL3.1 ordinary chondrite. Isotopic\\u000ameasurements by secondary ion mass spectrometry (SIMS) verified a presolar\\u000acircumstellar origin for the grains. Transmission electron microscopy (TEM)\\u000aexamination of the crystal structure and chemistry of the grains was enabled by\\u000ain situ sectioning and lift-out

Thomas J. Zega; Conel M. O'D. Alexander; Larry R. Nittler; Rhonda M. Stroud

2011-01-01

253

A Transmission Electron Microscopy Study of Presolar Hibonite  

Microsoft Academic Search

We report isotopic and microstructural data on five presolar hibonite grains (KH1, KH2, KH6, KH15, and KH21) identified in an acid residue of the Krymka LL3.1 ordinary chondrite. Isotopic measurements by secondary ion mass spectrometry (SIMS) verified a presolar circumstellar origin for the grains. Transmission electron microscopy (TEM) examination of the crystal structure and chemistry of the grains was enabled

Thomas J. Zega; Conel M. O'D. Alexander; Larry R. Nittler; Rhonda M. Stroud

2011-01-01

254

Scanning electron microscopy studies of erythrocytes in spinocerebellar degeneration  

Microsoft Academic Search

Spinocerebellar degeneration is a heredofamilial disease of unknown aetiology. The shape of erythrocytes as revealed by scanning electron microscopy was studied in this disease. Echinocytes I, as defined by Bessis, were seen more frequently in spinocerebellar degeneration than in age and sex matched controls (7.2 +\\/- 1.5% in spinocerebellar degeneration, 3.4 +\\/- 1.2% in controls, p less than 0.001), Parkinson's

Y Yasuda; I Akiguchi; H Shio; M Kameyama

1984-01-01

255

High-Resolution Cryoscanning Electron Microscopy of Biological Samples  

Microsoft Academic Search

Cryoscanning electron microscopy of fast frozen samples is the most direct approach for imaging aqueous organicmaterial at\\u000a nanometer scale resolution. It circumvents artifact formation caused by chemical fixation and drying. Cryofixation is preferentially\\u000a done by high-pressure freezing because it allows for fixation of native samples up to 200 ?m thick and 2mm wide with minimal\\u000a or no ice crystal damage.

Paul Walther

256

Cross-sectional transmission electron microscopy of semiconductors  

SciTech Connect

A method to prepare cross-sectional (X) semiconductor specimens for transmission electron microscopy (TEM) has been described. The power and utility of XTEM has been demonstrated. It has been shown that accuracy and interpretation of indirect structural-defects profiling techniques, namely, MeV He/sup +/ channeling and secondary ion mass spectrometry (SIMS) can be greatly enhanced by comparing their results with those obtained by XTEM from the same set of samples.

Sadana, D.K.

1982-10-01

257

Evaluation of collagen gel microstructure by scanning electron microscopy.  

PubMed

We performed qualitative comparison of freeze drying and chemical drying as methods of preparing 3D wet specimens for scanning electron microscopy. Human fibroblasts immobilized in collagen gel were used as a model system. Specimens fixed with glutaraldehyde were frozen in liquid nitrogen and freeze-dried at low temperature in high vacuum. In parallel experiments, glutaraldehyde-fixed samples were dehydrated in ascending ethanol solutions, absolute ethanol, and 100% hexamethyldisilazane and then dried at room temperature. Scanning electron microscopy microphotographs of collagen fibers and cells were characterized by high resolution and the absence of collapsed or deformed structures even at high magnification (×50,000) for both chemical drying and high-vacuum freeze drying. However, high-vacuum freeze drying is superior to chemical drying for the investigation of the internal space of 3D scaffolds, because sample fracture can be prepared directly in liquid nitrogen. These techniques are a part of the sample preparation process for scanning electron microscopy and can also be used for studies of cell adhesion, morphology, and arrangement in wet specimens (3D gels and flexible tissue engineering scaffolds). PMID:21161075

Pogorelov, A G; Selezneva, I I

2010-12-01

258

Fixation methods for electron microscopy of human and other liver  

PubMed Central

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

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

2010-01-01

259

A novel cell culture technique for electron microscopy.  

PubMed

A simplified technique for the monolayer growth of cultured cells and their in situ embedment on the inner surface of the pyramidal portion of the Beem capsule for electron microscopy has been developed. The results demonstrated that the cell monolayers grew well on the surface of the Beem capsule and could be embedded in situ. Electron micrographs showed cells in their natural state of contact with one another. The plasma membrane and intracellular organelles were well preserved. This method minimizes many difficult steps and eliminates the disruption of cells by scraping, pelleting, or enzymatic reaction to remove them. PMID:8305729

Wang, F; Ledford, L B; Head, J F; Elliott, R L

1993-12-15

260

Photoemission electron microscopy of a plasmonic silver nanoparticle trimer  

NASA Astrophysics Data System (ADS)

We present a combined experimental and theoretical study to investigate the spatial distribution of photoelectrons emitted from silver-coated polystyrene nanoparticles. We use two-photon photoemission electron microscopy (2P-PEEM) to image electron emission from a silver-capped aggregate trimer. Finite difference time domain (FDTD) simulations are performed to model the intensity distributions of the electromagnetic near fields resulting from femtosecond laser excitation of localized surface plasmon oscillations in the trimer structure. We demonstrate that the predicted FDTD near-field intensity distribution reproduces the 2P-PEEM photoemission pattern.

Peppernick, Samuel J.; Joly, Alan G.; Beck, Kenneth M.; Hess, Wayne P.; Wang, Jinyong; Wang, Yi-Chung; Wei, W. David

2013-07-01

261

Direct imaging of optical diffraction in photoemission electron microscopy  

NASA Astrophysics Data System (ADS)

We report the visualization of optical diffraction at the boundaries of semiconductor and metal nanostructures in non-linear photoemission electron microscopy. We observe light diffracting into photonic and plasmonic modes of planar samples, and into photonic vacuum modes above sample surfaces. In either case, the electron photoemission rate from the sample material is spatially modulated resulting in photoemission images with information on the electric field distribution at the sample/vacuum interface. The resolution in these images is typically ~30 nm, i.e., significantly below the wavelengths of the exciting light. Optical phase shifts and absorption losses for the diffracted modes can be determined.

Word, Robert C.; Fitzgerald, J. P. S.; Könenkamp, Rolf

2013-07-01

262

The use of transmission electron microscopy in the quantification of nanoparticle dose  

NASA Astrophysics Data System (ADS)

There are an increasing number of potential applications for nanoparticles in clinical medicine, including targeted drug delivery and contrast agents for biomedical imaging. Current in vitro studies are concerned with the biological impact of nanoparticles, with electron microscopy commonly employed to image their intracellular location. It is critical to quantify the absolute nanoparticle dose internalized by cells in a given exposure, and to understand the factors which affect this. In this work we are aiming to develop a full quantitative description of quantum dot uptake by an in vitro cell line. Transmission electron microscopy of thin cell sections provides the location and number of cellular vesicles per 2-D cell slice plus the number of quantum dots per vesicle. These results can then be correlated to other techniques to quantify the internalized nanoparticle dose distribution for whole cells.

Hondow, N.; Brydson, R.; Brown, A.

2014-06-01

263

Classification of single particles by neural networks based on the computer-controlled scanning electron microscopy data  

Microsoft Academic Search

The identification of sources of particles found in chemical process equipment such as photographic printer cabinets and their quantitative apportionment to those sources could lead to effective control strategies that would improve productivity and customer satisfaction with the service. Computer-controlled scanning electron microscopy (CCSEM) has proven to be a powerful tool in the characterization of individual particles. Thus, in this

Philip K. Hopke; Xin-Hua Song

1997-01-01

264

Organization of the Outer Plexiform Layer of the Primate Retina: Electron Microscopy of Golgi-Impregnated Cells  

Microsoft Academic Search

Golgi-impregnated retinae of rhesus monkeys have been examined by serial section electron microscopy to establish in a quantitative manner the neural connexions in the outer plexiform layer. The results have shown that there are two types of midget bipolar cell, here called the invaginating midget bipolar and the flat midget bipolar. Both types of midget bipolar are exclusive to a

Helga Kolb

1970-01-01

265

Electron microscopy study of antioxidant interaction with bacterial cells  

NASA Astrophysics Data System (ADS)

To maintain native microorganisms genotype and phenotype features a lyophylization technique is widely used. However in this case cells are affected by influences of vacuum and low temperature that cause a part of the cells population to be destruction. Another factor reduced microorganisms vitality is formation of reactive oxygen forms that damage certain biological targets (such as DNA, membranes etc.) Recently to raise microorganism's resistance against adverse condition natural and synthetic antioxidants are used. Antioxidant- are antagonists of free radicals. Introduction of antioxidants in protective medium for lyophylization increase bacteria storage life about 2,0-4,8 fold in comparison with reference samples. In the article the main results of our investigation of antioxidants interaction with microorganism cells is described. As bacteria cells we use vaccine strain yersinia pestis EV, that were grown for 48 h at 28 degree(s)C on the Hottinger agar (pH 7,2). Antioxidants are inserted on the agar surface in specimen under test. To investigate a localization of antioxidants for electron microscopy investigation, thallium organic antioxidants were used. The thallium organic compounds have an antioxidant features if thallium is in low concentration (about 1(mu) g/ml). The localization of the thallium organic antioxidants on bacteria Y. pestis EV is visible in electron microscopy images, thallium being heavy metal with high electron density. The negatively stained bacteria and bacteria thin sections with thallium organic compounds were investigated by means of transmission electron microscopy. The localization of the thallium organic compounds is clearly visible in electron micrographs as small dark spots with size about 10-80nm. Probably mechanisms of interaction of antioxidants with bacteria cells are discussed.

Plotnikov, Oleg P.; Novikova, Olga V.; Konnov, Nikolai P.; Korsukov, Vladimir N.; Gunkin, Ivan F.; Volkov, Uryi P.

2000-10-01

266

Subsurface characterization of carbon nanotubes in polymer composites via quantitative electric force microscopy  

NASA Astrophysics Data System (ADS)

Subsurface characterization of carbon nanotubes (CNTs) dispersed in free-standing polymer composite films was achieved via quantitative electric force microscopy (EFM). The effects of relative humidity, EFM probe geometry, tip-sample distance and bias voltage on the EFM contrast were studied. Non-parabolic voltage dependence of the EFM signal of subsurface CNTs in polymer composites was observed and a new mechanism was proposed taking consideration of capacitive coupling as well as coulombic coupling. We anticipate that this quantitative EFM technique will be a useful tool for non-destructive subsurface characterization of high dielectric constant nanostructures in low dielectric constant matrices.

Zhao, Minhua; Gu, Xiaohong; Lowther, Sharon E.; Park, Cheol; Jean, Y. C.; Nguyen, Tinh

2010-06-01

267

Molybdenum work function determined by electron emission microscopy.  

NASA Technical Reports Server (NTRS)

A polycrystalline molybdenum sample was recrystallized and thermally stabilized. Quantitative measurements of the emission from each individual grain were obtained with an electron emission microscope. The effective work function for each grain was then calculated. The crystallographic orientation of each grain was determined by Laue back-reflection techniques. A polar plot of effective work function vs crystallographic orientation for the sample was constructed to provide a correlation between effective work function and crystallographic orientation.

Jacobson, D. L.; Campbell, A. E.

1971-01-01

268

Low energy electron microscopy imaging using Medipix2 detector  

NASA Astrophysics Data System (ADS)

Low Energy Electron Microscopy (LEEM) and Photo-Emission Electron Microscopy (PEEM) predominantly use a combination of microchannel plate (MCP), phosphor screen and optical camera to record images formed by 10-20 keV electrons. We have tested the performance of a LEEM/PEEM instrument with a Medipix2 hybrid pixel detector using an Ir(1 1 1) sample with graphene flakes grown on its surface. We find that Medipix2 offers a number of advantages over the MCP. The adjustable threshold settings allow Medipix2 to operate as a noiseless detector, offering an improved signal-to-noise ratio for the same amount of signal compared to the MCP. At the same magnification Medipix2 images exhibit superior resolution and can handle significantly higher electron current densities than an MCP, offering the prospect of substantially higher frame rates in LEEM imaging. These factors make Medipix2 an excellent candidate to become the detector of choice for LEEM/PEEM applications.

Sikharulidze, I.; van Gastel, R.; Schramm, S.; Abrahams, J. P.; Poelsema, B.; Tromp, R. M.; van der Molen, S. J.

2011-05-01

269

Analysis of environmental particles by atomic force microscopy, scanning and transmission electron microscopy.  

PubMed

Due to their large specific surface and their abundance, micro and nano particles play an important role in the transport of micropollutants in the environment. Natural particles are usually composed of a mixture of inorganic amorphous or crystalline material (mainly FeOOH, Fe(x)Oy, Mn(x)Oy and clays) and organic material (humics and polysaccharides). They all tend to occur as very small particles (1-1,000 nm in diameter). Most natural amorphous particles are unstable and tend to transform with time towards more crystalline forms, either by aging or possibly, by dissolution and re-crystallization. Such transformations affect the fate of sorbed micropollutants and the scavenging properties are therefore changed. As these entities are sensitive to dehydration (aggregation, changes in the morphology), it is highly important to observe their morphology in their natural environment and understand their composition at the scale of the individual particles. Also for the understanding and optimization of water treatment technologies, the knowledge of the occurrence and behavior of nano-particles is of high importance. Some of the possible particle analysis methods are presented: aggregation processes, biomineralization, bacterial adhesion, biofilms in freshwaters, ferrihydrite as heavy metals remover from storm water. These examples demonstrate the capabilities and focus of the microscopes. Atomic Force Microscopy (AFM) allows to analyze the particles in their own environment, meaning in air or in the water. Thus, native aspects of particles can be observed. As well, forces of interactions between particles or between particles and other surfaces such as membranes will be highly valuable data. Scanning Electron Microscopy (SEM) and for higher lateral resolution, Transmission Electron Microscopy (TEM) allow measurement of the morphology and composition. Especially, TEM coupled with Electron Energy Loss Spectroscopy (TEM-EELS) is a powerful technique for elemental analysis. Finally, general guidelines for the effective use of microscopic techniques are provided. PMID:15685998

Mavrocordatos, D; Pronk, W; Boiler, M

2004-01-01

270

Subsurface characterization of carbon nanotubes in polymer composites via quantitative electric force microscopy  

Microsoft Academic Search

Subsurface characterization of carbon nanotubes (CNTs) dispersed in free-standing polymer composite films was achieved via quantitative electric force microscopy (EFM). The effects of relative humidity, EFM probe geometry, tip-sample distance and bias voltage on the EFM contrast were studied. Non-parabolic voltage dependence of the EFM signal of subsurface CNTs in polymer composites was observed and a new mechanism was proposed

Minhua Zhao; Xiaohong Gu; Sharon E. Lowther; Cheol Park; Y. C. Jean; Tinh Nguyen

2010-01-01

271

Quantitative measurement of the nanoparticle size and number concentration from liquid suspensions by atomic force microscopy.  

PubMed

Microscopy techniques are indispensable to the nanoanalytical toolbox and can provide accurate information on the number size distribution and number concentration of nanoparticles (NPs) at low concentrations (ca. ppt to ppb range) and small sizes (ca. <20 nm). However, the high capabilities of microscopy techniques are limited by the traditional sample preparation based on drying a small volume of suspension of NPs on a microscopy substrate. This method is limited by low recovery of NPs (ca. <10%), formation of aggregates during the drying process, and thus, the complete misrepresentation of the NP suspensions under consideration. This paper presents a validated quantitative sampling technique for atomic force microscopy (AFM) that overcomes the above-mentioned shortcomings and allows full recovery and representativeness of the NPs under consideration by forcing the NPs into the substrate via ultracentrifugation and strongly attaches the NPs to the substrate by surface functionalization of the substrate or by adding cations to the NP suspension. The high efficiency of the analysis is demonstrated by the uniformity of the NP distribution on the substrate (that is low variability between the number of NPs counted on different images on different areas of the substrate), the high recovery of the NPs up to 71%) and the good correlation (R > 0.95) between the mass and number concentrations. Therefore, for the first time, we developed a validated quantitative sampling technique that enables the use of the full capabilities of microscopy tools to quantitatively and accurately determine the number size distribution and number concentration of NPs at environmentally relevant low concentrations (i.e. 0.34-100 ppb). This approach is of high environmental relevance and can be applied widely in environmental nanoscience and nanotoxicology for (i) measuring the number concentration dose in nanotoxicological studies and (ii) accurately measuring the number size distribution of NPs; both are key requirements for the implementation of the European Commission recommendation for definition of nanomaterials. PMID:24668140

Baalousha, M; Prasad, A; Lead, J R

2014-05-28

272

Microbial Nanowire Electronic Structure Probed by Scanning Tunneling Microscopy  

NASA Astrophysics Data System (ADS)

Complex molecules produced by living organisms provide laboratories for interesting physical properties. The study of such interesting physics, likewise, gives new insight into intriguing biological processes. We have studied the pilus nanowires expressed by the bacterium, Geobacter sulfurreducens, using high resolution scanning tunneling microscopy (STM). G. sulfurreducens is a metal reducing bacterium that has evolved electrically conductive pili to efficiently transfer electrons across large distances.footnotetextG. Reguera, K.D. McCarthy, T. Mehta, J.S. Nicoll, M.T. Tuominen, and D.R. Lovley, Nature 435, 1098 (2005) Here we employ the electronic sensitivity of STM to resolve the molecular substructure and the local electronic density of states (LDOS) along the nanowire, in an effort to elucidate the mechanism of conduction. We observe LDOS dependent upon the location of the tip above the nanowire.

Veazey, Joshua P.; Lampa-Pastirk, Sanela; Reguera, Gemma; Tessmer, Stuart H.

2010-03-01

273

Prospects for hybrid pixel detectors in electron microscopy  

NASA Astrophysics Data System (ADS)

The current status of CCD-based detectors for cryo-electron microscopy of membrane and other proteins is described briefly, highlighting the strengths and weaknesses of the technique. Over the past few years CCD detectors have been used extensively in electron crystallography of membrane proteins, and in particular, in the study of the molecular transitions which take place during the photo-cycle of the light-driven proton pump bacteriorhodopsin. Direct-detection methods, which avoid the intermediate stages of converting the electron energy into light, offer the possibility of improved spatial resolution compared to CCD detectors; in addition, photon counting and noise-free readout should improve the signal-to-noise ratio.

Faruqi, A. R.

2001-06-01

274

Imaging and Quantitative Analysis of Atherosclerotic Lesions by CARS-based Multimodal Nonlinear Optical Microscopy  

PubMed Central

Objective Assess the ability of label-free multimodal nonlinear optical (NLO) microscopy to characterize, and thus enable quantitative in situ analyses of, different atherosclerotic lesion types, according to the original scheme suggested by the AHA Committee. Methods and Results Iliac arteries were taken from 24 male Ossabaw pigs divided into lean control and metabolic syndrome groups and were imaged by multimodal NLO microscopy where sum-frequency generation (SFG) and two-photon excitation fluorescence (TPEF) were integrated on a coherent anti-Stokes Raman scattering (CARS) microscope platform. Foam cells, lipid deposits, matrices, and fibrous caps were visualized with submicron 3-D resolution. Starting from the adaptive intimal thickening in the initial stage to the fibrous atheroma or mineralization in the advanced stages, lesions were visualized without labels. Histological staining of each lesion confirmed the lesion stages. Lipid and collagen contents were quantitatively analyzed based on the CARS and SFG signals. Lipid accumulation in thickened intima culminated in type IV while the highest collagen deposition was found in Type V lesions. Luminal CARS imaging showed the capability of viewing the location of superficial foam cells that indicate relatively active locus in a lesion artery. Conclusions We have demonstrated the capability of CARS-based multimodal NLO microscopy to interrogate different stages of lesion development with subcellular detail to permit quantitative analysis of lipid and collagen contents.

Wang, Han-Wei; Langohr, Ingeborg M.; Sturek, Michael; Cheng, Ji-Xin

2009-01-01

275

Electron microscopy: essentials for viral structure, morphogenesis and rapid diagnosis.  

PubMed

Electron microscopy (EM) should be used in the front line for detection of agents in emergencies and bioterrorism, on accounts of its speed and accuracy. However, the number of EM diagnostic laboratories has decreased considerably and an increasing number of people encounter difficulties with EM results. Therefore, the research on viral structure and morphologyant in EM diagnostic practice. EM has several technological advantages, and should be a fundamental tool in clinical diagnosis of viruses, particularly when agents are unknown or unsuspected. In this article, we review the historical contribution of EM to virology, and its use in virus differentiation, localization of specific virus antigens, virus-cell interaction, and viral morphogenesis. It is essential that EM investigations are based on clinical and comprehensive pathogenesis data from light or confocal microscopy. Furthermore, avoidance of artifacts or false results is necessary to exploit fully the advantages while minimizing its limitations. PMID:23633074

Zhang, Ying; Hung, Tao; Song, Jingdong; He, Jinsheng

2013-05-01

276

Electron microscopy of flatworms standard and cryo-preparation methods.  

PubMed

Electron microscopy (EM) has long been indispensable for flatworm research, as most of these worms are microscopic in dimension and provide only a handful of characters recognizable by eye or light microscopy. Therefore, major progress in understanding the histology, systematics, and evolution of this animal group relied on methods capable of visualizing ultrastructure. The rise of molecular and cellular biology renewed interest in such ultrastructural research. In the light of recent developments, we offer a best-practice guide for users of transmission EM and provide a comparison of well-established chemical fixation protocols with cryo-processing methods (high-pressure freezing/freeze-substitution, HPF/FS). The organisms used in this study include the rhabditophorans Macrostomum lignano, Polycelis nigra and Dugesia gonocephala, as well as the acoel species Isodiametra pulchra. PMID:20869529

Salvenmoser, Willi; Egger, Bernhard; Achatz, Johannes G; Ladurner, Peter; Hess, Michael W

2010-01-01

277

Electron microscopy of primary cell cultures in solution and correlative optical microscopy using ASEM.  

PubMed

Correlative light-electron microscopy of cells in a natural environment of aqueous liquid facilitates high-throughput observation of protein complex formation. ASEM allows the inverted SEM to observe the wet sample from below, while an optical microscope observes it from above quasi-simultaneously. The disposable ASEM dish with a silicon nitride (SiN) film window can be coated variously to realize the primary-culture of substrate-sensitive cells in a few milliliters of culture medium in a stable incubator environment. Neuron differentiation, neural networking, proplatelet-formation and phagocytosis were captured by optical or fluorescence microscopy, and imaged at high resolution by gold-labeled immuno-ASEM with/without metal staining. Fas expression on the cell surface was visualized, correlated to the spatial distribution of F-actin. Axonal partitioning was studied using primary-culture neurons, and presynaptic induction by GluR?2-N-terminus-linked fluorescent magnetic beads was correlated to the presynaptic-marker Bassoon. Further, megakaryocytes secreting proplatelets were captured, and P-selectins with adherence activity were localized to some of the granules present by immuno-ASEM. The phagocytosis of lactic acid bacteria by dendritic cells was also imaged. Based on these studies, ASEM correlative microscopy promises to allow the study of various mesoscopic-scale dynamics in the near future. PMID:24216127

Hirano, Kazumi; Kinoshita, Takaaki; Uemura, Takeshi; Motohashi, Hozumi; Watanabe, Yohei; Ebihara, Tatsuhiko; Nishiyama, Hidetoshi; Sato, Mari; Suga, Mitsuo; Maruyama, Yuusuke; Tsuji, Noriko M; Yamamoto, Masayuki; Nishihara, Shoko; Sato, Chikara

2014-08-01

278

Scanning and Transmission Electron Microscopy of 'Rickettsia rickettsii' Propagated in Cell Culture.  

National Technical Information Service (NTIS)

Scanning electron microscopy utilizing critical-point drying and transmission electron microscopy employing air-dried agar pseudoreplicas and critical-point dried carbon replicas were used to study the surface of Rickettsia rickettsii propagated in cell c...

C. E. Pedersen J. D. Gangemi S. J. Gourlay A. F. Hegyeli

1976-01-01

279

Installation of electric field electron beam blanker in high-resolution transmission electron microscopy  

SciTech Connect

We have newly installed an electric field electron beam blanker in a transmission electron microscopy, which chops an electron beam very quickly without the effect of hysteresis. The electric field, which is generated by the electron beam blanker, deflects the electron beam, and the electron beam is intercepted by an aperture. The response time of the beam blanker is 50 {mu}s. Therefore, a very short pulsed electron beam enables a charge-coupled device camera to directly expose an electron beam spot or diffraction pattern. Moreover, we measured the response of a deflector coil, which is usually used as an electron beam blanker, using our electron beam blanker. Our beam blanker will become a key component in a computer-assisted minimal dose system, which enables us to reduce the electron dose of the sample.

Hayashida, Misa; Kimura, Yoshihide; Taniguchi, Yoshifumi; Otsuka, Masayuki; Takai, Yoshizo [Department of Material and Life Science, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871 (Japan); Hitachi High-Technologies Corporation, 882 Ichige, Hitachinaka, Ibaraki 312-8504 (Japan); Department of Material and Life Science, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871 (Japan)

2006-11-15

280

High-resolution electron microscopy of advanced materials  

SciTech Connect

This final report chronicles a three-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The High-Resolution Electron Microscopy Facility has doubled in size and tripled in quality since the beginning of the three-year period. The facility now includes a field-emission scanning electron microscope, a 100 kV field-emission scanning transmission electron microscope (FE-STEM), a 300 kV field-emission high-resolution transmission electron microscope (FE-HRTEM), and a 300 kV analytical transmission electron microscope. A new orientation imaging microscope is being installed. X-ray energy dispersive spectrometers for chemical analysis are available on all four microscopes; parallel electron energy loss spectrometers are operational on the FE-STEM and FE-HRTEM. These systems enable evaluation of local atomic bonding, as well as chemical composition in nanometer-scale regions. The FE-HRTEM has a point-to-point resolution of 1.6 {angstrom}, but the resolution can be pushed to its information limit of 1 {angstrom} by computer reconstruction of a focal series of images. HRTEM has been used to image the atomic structure of defects such as dislocations, grain boundaries, and interfaces in a variety of materials from superconductors and ferroelectrics to structural ceramics and intermetallics.

Mitchell, T.E.; Kung, H.H.; Sickafus, K.E.; Gray, G.T. III; Field, R.D.; Smith, J.F. [Los Alamos National Lab., NM (United States). Materials Science and Technology Div.

1997-11-01

281

High-resolution transmission electron microscopy for crystallographic study of nanomaterials  

SciTech Connect

The potential of high-resolution transmission electron microscopy (including the quantitative computer processing of images and computer simulation) in a local analysis of nanomaterials is discussed. A number of examples of the application of fast Fourier transform and simulated high-resolution electronmicroscopy images in the identification of nanophases and the crystallographic study of nanocrystals and nanoparticles are considered. The role that B.K. Vainshtein played in the development of a unified approach for determination of the structure of materials using short-wave diffraction is indicated.

Imamov, R. M.; Klechkovskaya, V. V., E-mail: klechvv@ns.crys.ras.ru; Suvorova, E. I. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

2011-07-15

282

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

NASA Astrophysics Data System (ADS)

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

Hunt, Steven R.; Collins, Phillip G.

2010-03-01

283

High-Resolution Transmission Electron Microscopy on an Absolute Contrast Scale  

SciTech Connect

A fully quantitative approach to high-resolution transmission electron microscopy requires a satisfactory match between image simulations and experiments. While almost perfect agreement between simulations and experiments is routinely achieved on a relative contrast level, a huge mutual discrepancy in the absolute image contrast by a factor of 3 has been frequently reported. It is shown that a major reason for this well-known contrast discrepancy, which is often called Stobbs-factor problem, lies in the neglect of the detector modulation-transfer function in image simulations.

Thust, A. [Institute of Solid State Research, Research Centre Juelich, D-52425 Juelich (Germany)

2009-06-05

284

Visualizing Gold Nanoparticle Uptake in Live Cells with Liquid Scanning Transmission Electron Microscopy  

PubMed Central

The intracellular uptake of 30 nm diameter gold nanoparticles (Au-NPs) was studied at the nanoscale in pristine eukaryotic cells. Live COS-7 cells were maintained in a microfluidic chamber and imaged using scanning transmission electron microscopy. A quantitative image analysis showed that Au-NPs bound to the membranes of vesicles, possibly lysosomes, and occupied 67% of the available surface area. The vesicles accumulated to form a micrometer-sized cluster after 24 h of incubation. Two clusters were analyzed and found to consist of 117 ± 9 and 164 ± 4 NP-filled vesicles.

2011-01-01

285

Quantitative aspects of digital microscopy applied to cellular localization of heparin in smooth muscle cells  

NASA Astrophysics Data System (ADS)

High Resolution digital acquisition allows a great deal of flexibility in the types of questions that can be directed to microscopic samples. To eliminate subjective bias and provide quantitative results we have approached microscopy with an automated digital format. This mode can return quantitative data at high resolution over large fields. The digital format makes accessible data including [data segmentation]: multispectral colocalization, seeding and connectivity, particle size and shape distribution and population analysis. We have begun a program to investigate this approach using the confocal microscope. Scanning larger fields-of-view at lower spatial resolutions (e.g., low magnification objective) defines large maps that allow alignment of high spatial resolution (diffraction limited) sampling. The [objective] selection of the field-of-view with low spatial resolution reduces the subjective nature of the selection of a 'typical staining pattern'. High resolution digital scanning in three dimensions contribute both to the 'objective' nature of the analysis and allow for quantitation of characteristics not historically available/accessible. The complex carbohydrate heparin is implicated in tumor growth and wound healing by affecting angiogenesis, cell proliferation and motility. The internal localization of heparin within vascular cells appears to be a good predictor of the sensitivity of those cells to the action of heparin. Cells resistant to the antiproliferative action of heparin are able to sequester the heparin in large vacuoles whereas those cells sensitive to the carbohydrate do not exhibit these structures. We have applied our approach to QUANTITATIVE DIGITAL MICROSCOPY to the analysis of intracellular heparin distribution.

Johnston, Richard F.; Hanzel, David K.; Stack, Bob; Brandley, Brian; Castellot, John

1995-04-01

286

ELECTRON MICROSCOPY OF HELA CELLS INFECTED WITH ADENOVIRUSES  

PubMed Central

HeLa cells were infected with adenoviruses (types 1–4) and sectioned for electron microscopy after intervals of 20 to 48 hours. Clusters of virus-like particles were found within the nuclei of infected cultures but not in those of uninfected controls. The particles were often arranged in rows as if in crystalline formation. Maximal diameter of particles was approximately 65 mµ, and internal bodies were demonstrated. Lesions of infected cells included target-like structures of the nuclear membrane, large nuclear vacuoles (type 2), and increased numbers of large irregular electron-dense granules in the cytoplasm 48 hours after infection. Examination of infected cultures by light microscopy, using the Feulgen reaction, showed intranuclear inclusion bodies and a cytopathogenic effect consisting of clumping of cells without pyknosis of nuclei. A lipide stain showed numerous cytoplasmic granules that were not identical with the large, irregular, electron-dense granules of the cytoplasm. Practically all the cells showed the viral cytopathogenic effect, but only a minority of cells were found to contain virus-like particles or intranuclear inclusion bodies.

Harford, Carl G.; Hamlin, Alice; Parker, Esther; van Ravenswaay, Theodore

1956-01-01

287

Examination of lower Jurassic mudrocks using backscattered electron microscopy  

SciTech Connect

The small size of many of the particles in mudrocks makes it almost impossible to image and identify them individually and in situ, using conventional light microscopy. Since the average mudrock contains about 60% clay minerals, an understanding of these minerals is central to the question of burial diagenesis and hydrocarbon generation. Much of the existing evidence concerning burial diagenesis relies on x-ray diffraction data (XRD), particularly with respect to the clay-sized (< 2 ..mu..m) fraction of mudrocks. Backscattered electron techniques (BSE) in scanning electron microscopy (SEM) together with energy-dispersive x-ray microanalysis (EDX), XRD, and electron microprobe analysis, indicate that Lower Jurassic mudrocks from the North Sea basin contain many clay mineral stacks up to 150 ..mu..m long. By studying polished mudrock sections with BSE and EDX, the sizes, shape, orientation, textural relations and internal compositional variation of the clay minerals can be observed in situ. Preliminary evidence suggests that the clay stacks are authigenic and may have formed at shallow burial depths during early diagenesis. In addition, sand- and silt-sized clay pellets (glauconite) composed chiefly of iron-bearing dioctahedral mica were observed in the sediment. The irregular shapes and textural intergrowths of many pellets suggest that active outward growth occurred, probably by a combination of displacement and replacement in the surrounding matrix material.

Krinsley, D.; Pye, K.

1984-07-01

288

Characterisation of Nanoparticle Structure by High Resolution Electron Microscopy  

NASA Astrophysics Data System (ADS)

Whilst the use of microscopic techniques to determine the size distributions of nanoparticle samples is now well established, their characterisation challenges extend well beyond this. Here it is shown how high resolution electron microscopy can help meet these challenges. One of the key parameters is the determination of particle shape and structure in three dimensions. Here two approaches to determining nanoparticle structure are described and demonstrated. In the first scanning transmission electron microscopy combined with high angle annular dark field imaging (HAADF-STEM) is used to image homogenous nanoparticles, where the contrast is directly related to the thickness of the material in the electron beam. It is shown that this can be related to the three dimensional shape of the nano-object. High resolution TEM imaging, combined with fast Fourier transform (FFT) analysis, can determine the crystalline structure and orientation of nanoparticles as well as the presence of any defects. This combined approach allows the physical structure of a significant number of nano-objects to be characterised, relatively quickly.

Boyd, Robert D.; Gunnarsson, Rickard; Pilch, Iris; Helmersson, Ulf

2014-06-01

289

Quantitative vibrational imaging by hyperspectral stimulated Raman scattering microscopy and multivariate curve resolution analysis.  

PubMed

Spectroscopic imaging has been an increasingly critical approach for unveiling specific molecules in biological environments. Toward this goal, we demonstrate hyperspectral stimulated Raman loss (SRL) imaging by intrapulse spectral scanning through a femtosecond pulse shaper. The hyperspectral stack of SRL images is further analyzed by a multivariate curve resolution (MCR) method to reconstruct quantitative concentration images for each individual component and retrieve the corresponding vibrational Raman spectra. Using these methods, we demonstrate quantitative mapping of dimethyl sulfoxide concentration in aqueous solutions and in fat tissue. Moreover, MCR is performed on SRL images of breast cancer cells to generate maps of principal chemical components along with their respective vibrational spectra. These results show the great capability and potential of hyperspectral SRL microscopy for quantitative imaging of complicated biomolecule mixtures through resolving overlapped Raman bands. PMID:23198914

Zhang, Delong; Wang, Ping; Slipchenko, Mikhail N; Ben-Amotz, Dor; Weiner, Andrew M; Cheng, Ji-Xin

2013-01-01

290

Quantitative Vibrational Imaging by Hyperspectral Stimulated Raman Scattering Microscopy and Multivariate Curve Resolution Analysis  

PubMed Central

Spectroscopic imaging has been an increasingly critical approach for unveiling specific molecules in biological environments. Towards this goal, we demonstrate hyperspectral stimulated Raman loss (SRL) imaging by intra-pulse spectral scanning through a femtosecond pulse shaper. The hyperspectral stack of SRL images is further analyzed by a multivariate curve resolution (MCR) method to reconstruct quantitative concentration images for each individual component and retrieve the corresponding vibrational Raman spectra. Using these methods, we demonstrate quantitative mapping of dimethyl sulfoxide concentration in aqueous solutions and in fat tissue. Moreover, MCR is performed on SRL images of breast cancer cells to generate maps of principal chemical components along with their respective vibrational spectra. These results show the great capability and potential of hyperspectral SRL microscopy for quantitative imaging of complicated biomolecule mixtures through resolving overlapped Raman bands.

Zhang, Delong; Wang, Ping; Slipchenko, Mikhail N.; Ben-Amotz, Dor; Weiner, Andrew M.; Cheng, Ji-Xin

2013-01-01

291

Copper Decoration of Carbon Nanotubes and High Resolution Electron Microscopy  

NASA Astrophysics Data System (ADS)

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.

Probst, Camille

292

Electron Spin Magnetic Resonance Force Microscopy of Nitroxide Spin Labels  

NASA Astrophysics Data System (ADS)

Nitroxide spin labels are widely used in electron spin resonance studies of biological and polymeric systems. Magnetic resonance force microscopy (MRFM) is a magnetic resonance technique that couples the high spatial resolution of a scanning probe microscope with the species selectivity of magnetic resonance. We report on our investigations of 4-amino TEMPO, a nitroxide spin label, by force-gradient MRFM. Our microscope operates at high vacuum in liquid helium, using a custom fabricated ultra-soft silicon cantilever in the magnet-on-cantilever geometry. An 18 GHz gap coupled microstripline resonator supplies the transverse field.

Moore, Eric W.; Lee, Sanggap; Hickman, Steven A.; Wright, Sarah J.; Marohn, John A.

2009-03-01

293

Confocal Microscopy for Modeling Electron Microbeam Irradiation of Skin  

SciTech Connect

For radiation exposures employing targeted sources such as particle microbeams, the deposition of energy and dose will depend on the spatial heterogeneity of the spample. Although cell structural variations are relatively minor for two-dimensional cell cultures, they can vary significantly for fully differential tissues. Employing high-resolution confocal microscopy, we have determined the spatial distribution, size, and shape of epidermal kerantinocyte nuclei for the full-thickness EpiDerm skin model (MatTek, Ashland, VA). Application of these data to claculate the microdosimetry and microdistribution of energy deposition by an electron microbeam is discussed.

Miller, John H.; Chrisler, William B.; Wang, Xihai; Sowa, Marianne B.

2011-08-01

294

Dichotomous samplers modified for use with electron microscopy  

SciTech Connect

Large sulfate artifacts up to 2 micrometers in diameter were observed by scanning electron microscopy for the fine particle fraction collected in dichotomous samplers. The artifacts were attributed to small liquid particles that piled up on the filter, coalesced, and later dried as larger particles. Such artifacts were eliminated when particles were collected in a modified dichotomous sampler in which 80% to 90% of the airflow was diverted from the fine fraction filter. This airflow diversion technique was used successfully with both virtual-impactor and tandem-filter types of dichotomous samplers.

Mamane, Y.; Dzubay, T.G.

1990-01-01

295

Analytical electron microscopy study of radioactive ceramic waste form  

SciTech Connect

A ceramic waste form has been developed to immobilize the halide high-level waste stream from electrometallurgical treatment of spent nuclear fuel. Analytical electron microscopy studies, using both scanning and transmission instruments, have been performed to characterize the microstructure of this material. The microstructure consists primarily of sodalite granules (containing the bulk of the halides) bonded together with glass. The results of these studies are discussed in detail. Insight into the waste form fabrication process developed as a result of these studies is also discussed.

O'Holleran, T. P.; Sinkler, W.; Moschetti, T. L.; Johnson, S. G.; Goff, K. M.

1999-11-11

296

Ballistic Electron Emission Microscopy of Metal/Group IV Interfaces  

NASA Technical Reports Server (NTRS)

Ballistic electron emission microscopy and spectroscopy, together with related techniques, have been applied with great success to the study of buried interfaces. These probes, known collectively as BEEM, have yielded important information on interface transport, interface band structure, and carrier scattering, with lateral spatial resolution on the nanometer scale. Recent applications of the technique to polycrystalline metal/semiconductor interfaces have demonstrated an ability to spatially map both conduction band and valence band semiconductor structure. BEEM studies of epitaxial silicide/silicon interfaces have been particularly fruitful, as the rich silicide band structure results in complex and often surprising transport behavior...

Hecht, M. H.; Kaiser, W. J.; Bell, L. D.; Fathauer, R.; Manion, S. J.

1993-01-01

297

Photoemission Electron Microscopy of a Plasmonic Silver Nanoparticle Trimer  

SciTech Connect

We present a combined experimental and theoretical study to investigate the spatial distribution of photoelectrons emitted from core-shell silver (Ag) nanoparticles. We use two-photon photoemission microscopy (2P-PEEM) to spatially resolve electron emission from a trimeric core-shell aggregate of triangular symmetry. Finite difference time domain (FDTD) simulations are performed to model the intensity distributions of the electromagnetic near-fields resulting from femtosecond (fs) laser excitation of localized surface plasmon oscillations in the triangular core-shell structure. We demonstrate that the predicted FDTD near-field intensity distribution reproduces the 2P-PEEM photoemission pattern.

Peppernick, Samuel J.; Joly, Alan G.; Beck, Kenneth M.; Hess, Wayne P.; Wang, Jinyong; Wang, Yi-Chung; Wei, Wei

2013-07-01

298

Fast projection matching for cryo-electron microscopy image reconstruction.  

PubMed

A new FFT-accelerated projection matching method is presented and tested. The electron microscopy images are represented by their Fourier-Bessel transforms and the 3D model by its expansion in spherical harmonics, or more specifically in terms of symmetry-adapted functions. The rotational and translational properties of these representations are used to quickly access all the possible 2D projections of the 3D model, which allow an exhaustive inspection of the whole five-dimensional domain of parameters associated to each particle. PMID:18353677

Estrozi, Leandro Farias; Navaza, Jorge

2008-05-01

299

Electron Microscopy Studies of Solid Surfaces and Interfaces.  

NASA Astrophysics Data System (ADS)

Electron microscopy techniques for study of surfaces and interfaces have been investigated and applied to (100) and (111) surfaces of MgO and to interfaces of Mo/Si multilayers and CoSi_2/Si epitaxial films. MgO surfaces subjected to different annealing and chemical treatments have been characterized by reflection electron microscopy imaging, reflection high-energy electron diffraction (RHEED), and reflection electron energy-loss spectroscopy (REELS). An oxygen rich (sqrt {3} times sqrt{3})R 30^circ reconstruction was found on the polar (111) surface upon annealing in oxygen at temperatures higher than 1500 ^circC. Transformation of the surface topography and segregation of calcium were observed on the cleaved (100) surface due to annealing. RHEED resonance conditions have been employed and studied with geometrical constructions, rocking curves and REELS. These conditions are associated with parabolas in the Kikuchi (K) patterns whose nature had been subject of much controversy. The parabolas have been explained as K lines of two-dimensional (2D) lattices in a general scheme which describes the K pattern geometry in terms of intersections of Brillouin zone boundaries with a sphere of reflections. Full treatment of the cases of 2D and 1D real lattices has revealed previously unknown boundaries in the form of parabolic surfaces (2D) and paraboloids of revolution (1D). These boundaries have been applied to lines which arise from electron channeling in 3D crystals and to RHEED parabolas from 2D surface reconstructions. Nanodiffraction, low angle dark-field imaging, electron holography, high spatial resolution EELS, and shadow imaging have been evaluated as means for measuring interface abruptness and change in mean-inner potential and compared to other microscopy techniques. Refraction effects at interfaces were observed as streaking of the nanodiffraction disks which was found to depend on the crystalline nature of the interface. For polycrystalline/amorphous interfaces asymmetric streaking towards the phase with larger mean-inner potentials was observed to depend on the interface abruptness and the thickness of the specimen. On crystal/crystal interfaces the streaking was found to be sensitive to interface reconstructions.

Gajdardziska-Josifovska, Marija

1991-02-01

300

Clean electromigrated nanogaps imaged by transmission electron microscopy.  

PubMed

Electromigrated nanogaps have shown great promise for use in molecular scale electronics. We have fabricated nanogaps on free-standing transparent SiN(x) membranes which permit the use of transmission electron microscopy (TEM) to image the gaps. The electrodes are formed by extending a recently developed controlled electromigration procedure and yield a nanogap with approximately 5 nm separation clear of any apparent debris. The gaps are stable, on the order of hours as measured by TEM, but over time (months) relax to about 20 nm separation determined by the surface energy of the Au electrodes. A major benefit of electromigrated nanogaps on SiN(x) membranes is that the junction pinches in away from residual metal left from the Au deposition which could act as a parasitic conductance path. This work has implications to the design of clean metallic electrodes for use in nanoscale devices where the precise geometry of the electrode is important. PMID:16522038

Strachan, Douglas R; Smith, Deirdre E; Fischbein, Michael D; Johnston, Danvers E; Guiton, Beth S; Drndi?, Marija; Bonnell, Dawn A; Johnson, Alan T

2006-03-01

301

Focal-series reconstruction in low-energy electron microscopy.  

PubMed

In low-energy electron microscopy (LEEM) we commonly encounter images which, beside amplitude contrast, also show signatures of phase contrast. The images are usually interpreted by following the evolution of the contrast during the experiment, and assigning gray levels to morphological changes. Through reconstruction of the exit wave, two aspects of LEEM can be addressed: (1) the resolution can be improved by exploiting the full information limit of the microscope and (2) electron phase shifts which contribute to the image contrast can be extracted. In this article, linear exit wave reconstruction from a through-focal series of LEEM images is demonstrated. As a model system we utilize a heteromolecular monolayer consisting of the organic molecules 3,4,9,10-perylene tetracarboxylic dianhydride and Cu-II-Phthalocyanine, adsorbed on a Ag(111) surface. PMID:24717211

Duden, Thomas; Thust, Andreas; Kumpf, Christian; Tautz, F Stefan

2014-06-01

302

Performance of thin foil scintillating screen for transmission electron microscopy.  

PubMed

Scintillating screens made by coating a thin metal foil with a layer of phosphor appear to be attractive for transmission electron microscopy applications. We report here the brightness and resolution in the voltage range of 100-400 kV of such a screen made of a 10 microns layer of P20 phosphor on a 2 microns Al foil. Both brightness and resolution are superior to that of a screen made by coating a glass plate with a similar layer of phosphor. An exciting property of such a device is that its resolution improves slightly at higher voltages. This, combined with its excellent resistivity to radiation damage and stability under the electron beam, makes it a good candidate for high-voltage applications. PMID:7974848

Fan, G Y; Dunkelberger, D G; Ellisman, M H

1994-07-01

303

Combined Scanning Transmission Electron Microscopy Tilt- and Focal Series  

SciTech Connect

In this study, a combined tilt- and focal series is proposed as a new recording scheme for high-angle annular dark-field scanning transmission electron microscopy (STEM) tomography. Three-dimensional (3D) data were acquired by mechanically tilting the specimen, and recording a through-focal series at each tilt direction. The sample was a whole-mount macrophage cell with embedded gold nanoparticles. The tilt focal algebraic reconstruction technique (TF-ART) is introduced as a new algorithm to reconstruct tomograms from such combined tilt- and focal series. The feasibility of TF-ART was demonstrated by 3D reconstruction of the experimental 3D data. The results were compared with a conventional STEM tilt series of a similar sample. The combined tilt- and focal series led to smaller missing wedge artifacts, and a higher axial resolution than obtained for the STEM tilt series, thus improving on one of the main issues of tilt series-based electron tomography.

Dahmen, Tim [German Research Center for Artificial Intelligence (DFKI), Germany] [German Research Center for Artificial Intelligence (DFKI), Germany; Baudoin, Jean-Pierre G [ORNL] [ORNL; Lupini, Andrew R [ORNL] [ORNL; Kubel, Christian [Karlsruhe Institute of Technology, Leopoldshafen, Germany] [Karlsruhe Institute of Technology, Leopoldshafen, Germany; Slusallek, Phillip [German Research Center for Artificial Intelligence (DFKI), Germany] [German Research Center for Artificial Intelligence (DFKI), Germany; De Jonge, Niels [ORNL] [ORNL

2014-01-01

304

Transmission electron microscopy of ameloblastoma: A study on six cases  

PubMed Central

Background: Ameloblastoma is a rare, benign tumor of odontogenic epithelium, but with an aggressive clinical behavior. Aim: The present study aims to assess the ultramicroscopic features of the epithelial and connective tissue components of ameloblastoma. Materials and Methods: Six cases of ameloblastoma were subjected to electron microscopy. They included three cases of follicular type and three cases of plexiform type. Results: The study reveals that the ameloblastoma contains the full complement of cells normally found during odontogenesis. However, these cells resemble the enamel organ in an undifferentiated stage. Conclusion: Ultramicroscopy revealed the presence of different cell types among follicular type. The morphology of plexiform variants and correlation with odontogenesis could be elicited. The electron microscopic differences between follicular and plexiform types could help us in better understanding its pathogenesis.

Chawla, Rajeshwar; Ramalingam, Karthikeyan; Sarkar, Amitabha; Muddiah, Savita

2013-01-01

305

Electron microscopy and structural model of human fibronectin receptor.  

PubMed Central

Highly-purified human fibronectin receptor (a heterodimer of two distinct subunits, alpha and beta) was studied using electron microscopy and a variety of preparative procedures. It was found that the receptor consists of a globular head approximately 80 by 120 A and two tails about 20 A thick and 180-200 A long. The whole complex is approximately 280 A long. At low concentrations of detergent the receptor forms doublets, triplets or rosettes associated with the tails which possess the transmembrane portion of the molecule. Computer-assisted structure prediction using the published amino acid sequence of both subunits showed differences in the secondary structure of the tails, the alpha-tail being rich in beta-strands, the beta-tail having five cysteine-rich repeats analogous to the EGF-like repeats of laminin. Estimates of the length of the tails from the predicted structure conformed well with the dimensions obtained from electron micrographs. Images

Nermut, M V; Green, N M; Eason, P; Yamada, S S; Yamada, K M

1988-01-01

306

Theory and application of scanning electron acoustic microscopy  

NASA Technical Reports Server (NTRS)

A three-dimensional theoretical model based on the application of the thermal conduction and Navier equations to a chopped electron beam incident on a disk specimen is used to obtain the particle displacement field in the specimen. The results lead to a consideration of the signal generation, spatial resolution, and contrast mechanisms in scanning electron acoustic microscopy (SEAM). The model suggests that the time-variant heat source produced by the beam chopping generates driving source, thermal wave, and acoustic wave displacements simultaneously in the specimen. Evidence of the correctness of the prediction is obtained from the mathematically similar problem of pulsed laser light injection into a tank of water. High speed Schlieren photographs taken following laser injection show the simultaneous evolution of thermal and acoustic waveforms. Examples of contrast reversal, stress-induced contrast, and acoustic zone contrast and resolution with SEAM are presented and explained in terms of the model features.

Cantrell, John H.; Qian, Menglu; Chen, Ruiyi; Yost, William T.

1992-01-01

307

Biomechanics of DNA structures visualized by 4D electron microscopy  

PubMed Central

We present a technique for in situ visualization of the biomechanics of DNA structural networks using 4D electron microscopy. Vibrational oscillations of the DNA structure are excited mechanically through a short burst of substrate vibrations triggered by a laser pulse. Subsequently, the motion is probed with electron pulses to observe the impulse response of the specimen in space and time. From the frequency and amplitude of the observed oscillations, we determine the normal modes and eigenfrequencies of the structures involved. Moreover, by selective “nano-cutting” at a given point in the network, it was possible to obtain Young’s modulus, and hence the stiffness, of the DNA filament at that position. This experimental approach enables nanoscale mechanics studies of macromolecules and should find applications in other domains of biological networks such as origamis.

Lorenz, Ulrich J.; Zewail, Ahmed H.

2013-01-01

308

Amyloid Structure and Assembly: Insights from Scanning Transmission Electron Microscopy  

PubMed Central

Amyloid fibrils are filamentous protein aggregates implicated in several common diseases like Alzheimer’s disease and type II diabetes. Similar structures are also the molecular principle of the infectious spongiform encephalopathies like Creutzfeldt-Jakob disease in humans, scrapie in sheep, and of the so-called yeast prions, inherited non-chromosomal elements found in yeast and fungi. Scanning transmission electron microscopy (STEM) is often used to delineate the assembly mechanism and structural properties of amyloid aggregates. In this review we consider specifically contributions and limitations of STEM for the investigation of amyloid assembly pathways, fibril polymorphisms and structural models of amyloid fibrils. This type of microscopy provides the only method to directly measure the mass-per-length (MPL) of individual filaments. Made on both in vitro assembled and ex vivo samples, STEM mass measurements have illuminated the hierarchical relationships between amyloid fibrils and revealed that polymorphic fibrils and various globular oligomers can assemble simultaneously from a single polypeptide. The MPLs also impose strong constraints on possible packing schemes, assisting in molecular model building when combined with high-resolution methods like solid-state nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR).

Goldsbury, Claire; Baxa, Ulrich; Simon, Martha N.; Steven, Alasdair C.; Engel, Andreas; Wall, Joseph S.; Aebi, Ueli; Muller, Shirley A.

2010-01-01

309

Amyloid Structure and Assembly: Insights from Scanning Transmission Electron Microscopy  

SciTech Connect

Amyloid fibrils are filamentous protein aggregates implicated in several common diseases such as Alzheimer's disease and type II diabetes. Similar structures are also the molecular principle of the infectious spongiform encephalopathies such as Creutzfeldt-Jakob disease in humans, scrapie in sheep, and of the so-called yeast prions, inherited non-chromosomal elements found in yeast and fungi. Scanning transmission electron microscopy (STEM) is often used to delineate the assembly mechanism and structural properties of amyloid aggregates. In this review we consider specifically contributions and limitations of STEM for the investigation of amyloid assembly pathways, fibril polymorphisms and structural models of amyloid fibrils. This type of microscopy provides the only method to directly measure the mass-per-length (MPL) of individual filaments. Made on both in vitro assembled and ex vivo samples, STEM mass measurements have illuminated the hierarchical relationships between amyloid fibrils and revealed that polymorphic fibrils and various globular oligomers can assemble simultaneously from a single polypeptide. The MPLs also impose strong constraints on possible packing schemes, assisting in molecular model building when combined with high-resolution methods like solid-state nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR).

Goldsbury, C.; Wall, J.; Baxa, U.; Simon, M. N.; Steven, A. C.; Engel, A.; Aebi, U.; Muller, S. A.

2011-01-01

310

Investigation of porous asphalt microstructure using optical and electron microscopy.  

PubMed

Direct observations of porous asphalt concrete samples in their natural state using optical and electron microscopy techniques led to useful information regarding the microstructure of two mixes and indicated a relationship between microstructure and in situ performance. This paper presents evidence that suboptimal microstructure can lead to premature failure thus making a first step in defining well or suboptimal performing pavements with a bottom-up approach (microstructure). Laboratory and field compaction produce different samples in terms of the microstructure. Laboratory compaction using the gyratory method has produced more microcracks in mineral aggregates after the binder had cooled. Well-performing mixes used polymer-modified binders, had a more homogeneous void structure with fewer elongated voids and better interlocking of the aggregates. Furthermore, well-performing mixes showed better distribution of the mastic and better coverage of the aggregates with bitumen. Low vacuum scanning electron microscopy showed that styrene butadiene styrene polymer modification in binder exists in the form of discontinuous globules and not continuous networks. A reduction in the polymer phase was observed as a result of aging and in-service use. PMID:20946381

Poulikakos, L D; Partl, M N

2010-11-01

311

Scanning electron microscopy of Anisakis larvae following different treatments.  

PubMed

Ingestion of fish parasitized with Anisakis larvae can produce infestation and/or allergy in consumers. Technological and food processing treatments have been applied to parasitized fish in order to kill the larvae and avoid the infestation; however, their influence on allergenicity has not been studied. Four lots of hake (Merluccius merluccius) steaks artificially parasitized with Anisakis larvae were subjected to two storage chilling (5 degrees C +/- 1 degrees C) and freezing (-20 degrees C +/- 1 degrees C) treatments and two food processing treatments of heat (final temperature 86.3 degrees C) and microwave (final temperature 66.9 degrees C) and studied by scanning electron microscopy, environmental scanning electron microscopy (ESEM) (acid [pH = 2] and water preparations), and emission of fluorescence. Anisakis larvae were resistant to acid conditions, remaining alive after treatment. Larvae in the heat- and microwave-treated lots presented coagulated and disrupted zones in the cuticle with release of fluids. The cylindrical shape changed to a dehydrated appearance mainly observed by ESEM. Fluorescence was only noticeable in the frozen larvae. Larvae without apparent changes, together with dehydrated ones, were observed by ESEM in the frozen lot; nevertheless, no disruptions in the cuticle were perceptible. Further studies are needed in order to elucidate if the changes observed in the cuticle reduce the resistance of the parasites to the action of gastric enzymes in the gastrointestinal tract and to determine the release of allergens to the flesh by the live larvae during chilled storage of the fish. PMID:16786860

Tejada, Margarita; Solas, Maria Teresa; Navas, Alfonso; Mendizábal, Angel

2006-06-01

312

A Technique for In Situ Ballistic Electron Emission Microscopy  

NASA Astrophysics Data System (ADS)

Ballistic electron emission microscopy (BEEM) is a scanning tunneling microscopy (STM) technique that can measure transport of hot electrons through materials and interfaces with high spatial and energetic resolution. BEEM requires an additional contact to ground the metal base layer of a metal semiconductor junction. Performing BEEM in situ with the sample fabrication requires a custom built STM or modifying a commercial one to facilitate the extra contact, which leaves the technique to highly trained experts. This poster will describe our work to develop a special silicon substrate that has the extra contact built in to enable in situ BEEM without modifications to the STM. Electrically isolated contact traces are lithographically patterned ex situ onto the silicon substrate and connected to the BEEM sample plate which is then inserted into the ultra-high vacuum chamber. The metal is then deposited through a shadow mask and then mounted in situ onto the STM for BEEM measurements. BEEM measurements comparing both in situ and ex situ deposited films will be presented.

Balsano, Robert; Garramone, John; Labella, Vincent

2012-02-01

313

Digital Holographic Microscopy: Quantitative Phase Imaging and Applications in Live Cell Analysis  

NASA Astrophysics Data System (ADS)

The analysis of complex processes in living cells creates a high demand for fast and label-free methods for online monitoring. Widely used fluorescence methods require specific labeling and are often restricted to chemically fixated samples. Thus, methods that offer label-free and minimally invasive detection of live cell processes and cell state alterations are of particular interest. In combination with light microscopy, digital holography provides label-free, multi-focus quantitative phase imaging of living cells. In overview, several methods for digital holographic microscopy (DHM) are presented. First, different experimental setups for the recording of digital holograms and the modular integration of DHM into common microscopes are described. Then the numerical processing of digitally captured holograms is explained. This includes the description of spatial and temporal phase shifting techniques, spatial filtering based reconstruction, holographic autofocusing, and the evaluation of self-interference holograms. Furthermore, the usage of partial coherent light and multi-wavelength approaches is discussed. Finally, potentials of digital holographic microscopy for quantitative cell imaging are illustrated by results from selected applications. It is shown that DHM can be used for automated tracking of migrating cells and cell thickness monitoring as well as for refractive index determination of cells and particles. Moreover, the use of DHM for label-free analysis in fluidics and micro-injection monitoring is demonstrated. The results show that DHM is a highly relevant method that allows novel insights in dynamic cell biology, with applications in cancer research and for drugs and toxicity testing.

Kemper, Björn; Langehanenberg, Patrik; Kosmeier, Sebastian; Schlichthaber, Frank; Remmersmann, Christian; von Bally, Gert; Rommel, Christina; Dierker, Christian; Schnekenburger, Jürgen

314

Atomic scale characterization of materials using scanning transmission electron microscopy  

NASA Astrophysics Data System (ADS)

Coupling the development of emerging experimental techniques in STEM and EELS with a fundamental understanding of atomic electronic structure afforded by DFT represents the unique approach and intention of this thesis. Scanning transmission electron microscopes equipped with high-angle annular dark field (HAADF) detectors and Gatan image filters (GIF) provide images and spectra, where the image brightness is interpreted as a function of atomic mass and thickness, and elemental specific spectra provide a means for the exploration of electronic and chemical structure of materials at the angstrom size scale. Over the past 20 years, the application of EELS in STEM has enabled more accurate elemental identification and exploration of electronic and chemical structure on angstrom-length scales, and arguably has provided an unprecedented wealth of materials characterization compared to other available techniques. Many materials issues related to specific novel properties that cannot be analyzed using the traditional techniques of the past, however, still remain unanswered. These concepts require a married approach of experiment and theory to fully explain. The intent of this dissertation is the development of improved analysis techniques that derive quantitative atomic scale information in connection with unraveling the origins of materials properties linked to the electronic structure and chemistry of materials.

Aguiar, Jeffery Andrew

315

Electron microscopy investigations of nanoparticles for cancer diagnostic applications  

NASA Astrophysics Data System (ADS)

This dissertation concerns electron microscopy characterization of magnetic (MNP) and surface enhanced Raman scattering (SERS) nanoparticles for in-vitro cancer diagnostic applications. Electron microscopy is an essential characterization tool owing to its (sub) nanometer spatial resolution. Structural information about the nanoparticles can be obtained using transmission electron microscopy (TEM), which can in turn be correlated to their physical characteristics. The scanning electron microscope (SEM) has excellent depth of field and can be effectively utilized to obtain high resolution information about nanoparticles binding onto cell surfaces. Part One of this thesis focuses on MNPs for bio-sensing and detection applications. As a preliminary study, chemically-synthesized, commercially-available iron oxide nanoparticles were compared against their laboratory-synthesized counterparts to assess their suitability for this application. The motivation for this initial study came about due to the lack of published data on commercially available iron oxide nanoparticles. TEM studies show that the latter are "beads" composed of multiple iron oxide cores encapsulated by a polymer shell, with large standard deviations in core diameter. Laboratory-synthesized iron oxide nanoparticles, on the other hand, are single core particles with small variations in diameter and therefore are expected to be better candidates for the required application. A key limitation in iron oxide nanoparticles is their relatively weak magnetic signals. The development of high moment Synthetic Anti-Ferromagnetic (SAF) nanoparticles aims to overcome this issue. SAFs are a novel class of MNPs fabricated using nanoimprint lithography, direct deposition of multilayer structure and final suspension into liquid medium (water). TEM analyses of cross-section specimens reveal that the SAFs possess characteristics similar to those of sputtered magnetic multilayer thin films. Their layered structure is preserved after a chemical etch. Magnetic measurements show a slight decrease in magnetic moment after ion milling. From TEM characterization, the introduction of oxygen into the copper release layer, prior the film deposition process, can effectively control the topography of the oxidized-copper grains and, consequently, lead to the production of SAF nanoparticles with flatter layers. Size distribution studies performed on SAFs fabricated using self-assembled stamps show that it is possible to produce monodisperse nanoparticles with diameters from 70 nm up. Part Two of the dissertation describes structural characterization experiments performed on Composite Organic-Inorganic Nanoparticles (COINs), which are a novel type of SERS nanoclusters formed by aggregating silver nanoparticles with Raman molecules, and then encapsulating them with an organic coating that stabilizes the aggregates and promotes subsequent functionalization with antibodies. Part Three of this dissertation focuses on the development and application of electron microscopy-based techniques to characterize the nanomaterial-biology interactions, to assess how, or indeed whether, nanoparticles are attaching to the cancer cells. The technique of negative staining was applied to simultaneously visualize inorganic nanoparticles and their biofunctionalized entities under the TEM and to verify the successful functionalization of nanoparticles with antibodies. The interpretation of the negatively-stained COINs was consistent with the EFTEM data. Next, the localization and characterization of CD54-functionalized COINs on the apicolateral portions of U937 leukemia cell lines was determined using TEM, SEM and Scanning Auger Microscopy. The analyses show that CD54 antigens are localized at a specific region on U937 leukemia cell surfaces. SEM imaging and SER spectroscopy correlation studies of different antibody-conjugated COINs attached onto different cancer cell lines show a direct correlation between the number of COINs binding to cells and the corresponding SER intensity. Finally, TEM was used to l

Koh, Ai Leen

316

Atomic force microscopy, scanning electron microscopy and electrochemical characterization of Al alloys, conversion coatings, and primers used for aircraft  

Microsoft Academic Search

Characterization of the metal–coating interface is crucial to the understanding and prediction of the performance of corrosion protective coatings. To date, such characterization has been incomplete and performed on a scale of measurement that gives little microscopic-scale information. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) have the ability to provide such information. We present in this work the

G. P Bierwagen; Rebecca Twite; G Chen; D. E Tallman

1997-01-01

317

Characterization of protein immobilization on nanoporous gold using atomic force microscopy and scanning electron microscopy.  

PubMed

Nanoporous gold (NPG), made by dealloying low carat gold alloys, is a relatively new nanomaterial finding application in catalysis, sensing, and as a support for biomolecules. NPG has attracted considerable interest due to its open bicontinuous structure, high surface-to-volume ratio, tunable porosity, chemical stability and biocompatibility. NPG also has the attractive feature of being able to be modified by self-assembled monolayers. Here we use scanning electron microscopy (SEM) and atomic force microscopy (AFM) to characterize a highly efficient approach for protein immobilization on NPG using N-hydroxysuccinimide (NHS) ester functionalized self-assembled monolayers on NPG with pore sizes in the range of tens of nanometres. Comparison of coupling under static versus flow conditions suggests that BSA (Bovine Serum Albumin) and IgG (Immunoglobulin G) can only be immobilized onto the interior surfaces of free standing NPG monoliths with good coverage under flow conditions. AFM is used to examine protein coverage on both the exterior and interior of protein modified NPG. Access to the interior surface of NPG for AFM imaging is achieved using a special procedure for cleaving NPG. AFM is also used to examine BSA immobilized on rough gold surfaces as a comparative study. In principle, the general approach described should be applicable to many enzymes, proteins and protein complexes since both pore sizes and functional groups present on the NPG surfaces are controllable. PMID:21750834

Tan, Yih Horng; Schallom, John R; Ganesh, N Vijaya; Fujikawa, Kohki; Demchenko, Alexei V; Stine, Keith J

2011-08-01

318

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

PubMed

Integration of fluorescence light and transmission electron microscopy into the same device would represent an important advance in correlative microscopy, which traditionally involves two separate microscopes for imaging. To achieve such integration, the primary technical challenge that must be solved regards how to arrange two objective lenses used for light and electron microscopy in such a manner that they can properly focus on a single specimen. To address this issue, both lateral displacement of the specimen between two lenses and specimen rotation have been proposed. Such movement of the specimen allows sequential collection of two kinds of microscopic images of a single target, but prevents simultaneous imaging. This shortcoming has been made up by using a simple optical device, a reflection mirror. Here, we present an approach toward the versatile integration of fluorescence and electron microscopy for simultaneous imaging. The potential of simultaneous hybrid microscopy was demonstrated by fluorescence and electron sequential imaging of a fluorescent protein expressed in cells and cathodoluminescence imaging of fluorescent beads. PMID:24211820

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

2014-01-01

319

Quantitative tracking of tumor cells in phase-contrast microscopy exploiting halo artifact pattern  

NASA Astrophysics Data System (ADS)

Tumor cell morphology is closely related to its invasiveness characteristics and migratory behaviors. An invasive tumor cell has a highly irregular shape, whereas a spherical cell is non-metastatic. Thus, quantitative analysis of cell features is crucial to determine tumor malignancy or to test the efficacy of anticancer treatment. We use phase-contrast microscopy to analyze single cell morphology and to monitor its change because it enables observation of long-term activity of living cells without photobleaching and phototoxicity, which is common in other fluorescence-labeled microscopy. Despite this advantage, there are image-level drawbacks to phase-contrast microscopy, such as local light effect and contrast interference ring, among others. Thus, we first applied a local filter to compensate for non-uniform illumination. Then, we used intensity distribution information to detect the cell boundary. In phase-contrast microscopy images, the cell normally appears as a dark region surrounded by a bright halo. As the halo artifact around the cell body is minimal and has an asymmetric diffusion pattern, we calculated the cross-sectional plane that intersected the center of each cell and was orthogonal to the first principal axis. Then, we extracted the dark cell region by level set. However, a dense population of cultured cells still rendered single-cell analysis difficult. Finally, we measured roundness and size to classify tumor cells into malignant and benign groups. We validated segmentation accuracy by comparing our findings with manually obtained results.

Kang, Mi-Sun; Song, Soo-Min; Lee, Hana; Kim, Myoung-Hee

2012-02-01

320

Quantitative imaging of collective cell migration during Drosophila gastrulation: multiphoton microscopy and computational analysis  

PubMed Central

This protocol describes imaging and computational tools to collect and analyze live imaging data of embryonic cell migration. Our five step protocol requires a few weeks to move through embryo preparation and four-dimensional (4D) live imaging using multiphoton microscopy, to 3D cell-tracking using image processing, registration of tracking data, and their quantitative analysis using computational tools. It uses commercially available equipment, and requires expertise in microscopy and programming that is appropriate for a biology laboratory. Custom-made scripts are provided, as well as sample datasets to permit readers without experimental data to perform the analysis. The protocol has offered new insights into the genetic control of cell migration during Drosophila gastrulation. With simple changes, this systematic analysis could be applied to any developing system to define cell positions in accordance with the body plan, to decompose complex 3D movements, and to quantify the collective nature of cell migration.

Supatto, Willy; McMahon, Amy; Fraser, Scott E.; Stathopoulos, Angelike

2010-01-01

321

A nondamaging electron microscopy approach to map In distribution in InGaN light-emitting diodes  

NASA Astrophysics Data System (ADS)

Dark-field inline electron holography and, for comparison, high-resolution transmission electron microscopy are used to investigate the distribution of indium in GaN-based commercial high-efficiency green light-emitting diodes consisting of InGaN multiquantum wells (QWs). Owing to the low electron doses used in inline holography measurements; this technique allows to map the indium distribution without introducing any noticeable electron beam-induced damage which is hardly avoidable in other quantitative transmission electron microscopy methods. Combining the large field of view with a spatial resolution better than 1 nm, we show that the InGaN QWs exhibit random alloy nature without any evidence of nanometer scale gross indium clustering in the whole active region.

Özdöl, V. B.; Koch, C. T.; van Aken, P. A.

2010-09-01

322

Quantitative Measurements of Grain Boundary Sliding in an Ultrafine-Grained Al Alloy by Atomic Force Microscopy  

NASA Astrophysics Data System (ADS)

In the current study, quantitative measurements for grain boundary sliding (GBS) in ultrafine-grained (UFG) 5083 Al by atomic force microscopy (AFM) were performed. An ion beam polishing and etching technique was used to reveal grain boundaries in the alloy for AFM characterization. A comparison between the average grain sizes measured from AFM images and those estimated from transmission electron microscopy micrographs and electron backscatter diffraction (EBSD) maps showed excellent agreement. The vertical offset of GBS was measured by comparing predeformation and postdeformation AFM images. By analyzing these measurements, the contribution of GBS to the total tensile strain in 5083 Al was estimated as 25 pct at a strain rate of 10-4 seconds-1 and a temperature of 473 K (200 °C). It was demonstrated that the relatively low value of the contribution of GBS to the total strain is most likely the result of testing UFG 5083 Al under experimental conditions that favor the dominance of region I (low-stress region) of the sigmoidal behavior characterizing high-strain-rate superplasticity, which was reported previously for the alloy.

Han, Jung H.; Mohamed, Farghalli A.

2011-12-01

323

Quantitative detection of chemical compounds in human hair with coherent anti-Stokes Raman scattering microscopy  

NASA Astrophysics Data System (ADS)

Coherent anti-Stokes Raman scattering (CARS) microscopy is used to determine the distribution and concentration of selected compounds in intact human hair. By generating images based on ratiometric CARS contrast, quantitative concentration maps of both water and externally applied d-glycine are produced in the cortex of human hair fibers. Both water and d-glycine are found to homogeneously distribute throughout the cortical regions of the hair. The ability to selectively detect molecular agents in hair fibers is of direct relevance to understanding the chemical and physical mechanisms that underlie the performance of hair-care products.

Zimmerley, Maxwell; Lin, Chia-Yu; Oertel, David C.; Marsh, Jennifer M.; Ward, Jimmie L.; Potma, Eric Olaf

2009-07-01

324

Nanoscale nuclear architecture for cancer diagnosis by spatial-domain low-coherence quantitative phase microscopy  

NASA Astrophysics Data System (ADS)

Alterations in nuclear architecture are the hallmark diagnostic characteristic of cancer cells. In this work, we show that the nuclear architectural characteristics quantified by spatial-domain low-coherence quantitative phase microscopy (SL-QPM), is more sensitive for the identification of cancer cells than conventional cytopathology. We demonstrated the importance of nuclear architectural characteristics in both an animal model of intestinal carcinogenesis - APC/Min mouse model and human cytology specimens with colorectal cancer by identifying cancer from cytologically noncancerous appearing cells. The determination of nanoscale nuclear architecture using this simple and practical optical instrument is a significant advance towards cancer diagnosis.

Wang, Pin; Bista, Rajan K.; Khalbuss, Walid E.; Qiu, Wei; Staton, Kevin D.; Zhang, Lin; Brentnall, Teresa A.; Brand, Randall E.; Liu, Yang

2011-02-01

325

Time-resolved imaging refractometry of microbicidal films using quantitative phase microscopy  

PubMed Central

Quantitative phase microscopy is applied to image temporal changes in the refractive index (RI) distributions of solutions created by microbicidal films undergoing hydration. We present a novel method of using an engineered polydimethylsiloxane structure as a static phase reference to facilitate calibration of the absolute RI across the entire field. We present a study of dynamic structural changes in microbicidal films during hydration and subsequent dissolution. With assumptions about the smoothness of the phase changes induced by these films, we calculate absolute changes in the percentage of film in regions across the field of view.

Rinehart, Matthew T.; Drake, Tyler K.; Robles, Francisco E.; Rohan, Lisa C.; Katz, David; Wax, Adam

2011-01-01

326

Quantitative detection of chemical compounds in human hair with coherent anti-Stokes Raman scattering microscopy  

PubMed Central

Coherent anti-Stokes Raman scattering (CARS) microscopy is used to determine the distribution and concentration of selected compounds in intact human hair. By generating images based on ratiometric CARS contrast, quantitative concentration maps of both water and externally applied d-glycine are produced in the cortex of human hair fibers. Both water and d-glycine are found to homogeneously distribute throughout the cortical regions of the hair. The ability to selectively detect molecular agents in hair fibers is of direct relevance to understanding the chemical and physical mechanisms that underlie the performance of hair-care products.

Zimmerley, Maxwell; Lin, Chia-Yu; Oertel, David C.; Marsh, Jennifer M.; Ward, Jimmie L.; Potma, Eric Olaf

2010-01-01

327

Single-shot quantitative phase microscopy with the transport-of-intensity equation  

NASA Astrophysics Data System (ADS)

We present a single-shot experimental configuration for quantitative phase microscopy recovery based on the transportof- intensity equation (TIE). The system can simultaneously capture two laterally separated images with different amounts of defocus using only one digital camera. The defocus distance can be adjusted by varying the free space propagation transfer function on a phase only spatial light modulator. The intensity derivative along optics axis can thus be estimated optimally. In contrast to the state of the art techniques, this configuration requires no mechanical moving parts. Furthermore its single-shot property allows potential application for measuring fast moving objects or dynamic processes. Validation experiments are presented.

Zuo, Chao; Chen, Qian; Qu, Weijuan; Asundi, Anand

2013-06-01

328

Quantitative analysis on collagen morphology in aging skin based on multiphoton microscopy  

NASA Astrophysics Data System (ADS)

Multiphoton microscopy was employed for monitoring the structure changes of mouse dermis collagen in the intrinsic- or the extrinsic-age-related processes in vivo. The characteristics of textures in different aging skins were uncovered by fast Fourier transform in which the orientation index and bundle packing of collagen were quantitatively analyzed. Some significant differences in collagen-related changes are found in different aging skins, which can be good indicators for the statuses of aging skins. The results are valuable to the study of aging skin and also of interest to biomedical photonics.

Wu, Shulian; Li, Hui; Yang, Hongqin; Zhang, Xiaoman; Li, Zhifang; Xu, Shufei

2011-04-01

329

Spatially resolved quantitative mapping of thermomechanical properties and phase transition temperatures using scanning probe microscopy  

DOEpatents

An approach for the thermomechanical characterization of phase transitions in polymeric materials (polyethyleneterephthalate) by band excitation acoustic force microscopy is developed. This methodology allows the independent measurement of resonance frequency, Q factor, and oscillation amplitude of a tip-surface contact area as a function of tip temperature, from which the thermal evolution of tip-surface spring constant and mechanical dissipation can be extracted. A heating protocol maintained a constant tip-surface contact area and constant contact force, thereby allowing for reproducible measurements and quantitative extraction of material properties including temperature dependence of indentation-based elastic and loss moduli.

Jesse, Stephen; Kalinin, Sergei V; Nikiforov, Maxim P

2013-07-09

330

Accurate single-shot quantitative phase imaging of biological specimens with telecentric digital holographic microscopy.  

PubMed

The advantages of using a telecentric imaging system in digital holographic microscopy (DHM) to study biological specimens are highlighted. To this end, the performances of nontelecentric DHM and telecentric DHM are evaluated from the quantitative phase imaging (QPI) point of view. The evaluated stability of the microscope allows single-shot QPI in DHM by using telecentric imaging systems. Quantitative phase maps of a section of the head of the drosophila melanogaster fly and of red blood cells are obtained via single-shot DHM with no numerical postprocessing. With these maps we show that the use of telecentric DHM provides larger field of view for a given magnification and permits more accurate QPI measurements with less number of computational operations. PMID:24781590

Doblas, Ana; Sánchez-Ortiga, Emilio; Martínez-Corral, Manuel; Saavedra, Genaro; Garcia-Sucerquia, Jorge

2014-04-01

331

Characterization of protein immobilization on nanoporous gold using atomic force microscopy and scanning electron microscopy  

NASA Astrophysics Data System (ADS)

Nanoporous gold (NPG), made by dealloying low carat gold alloys, is a relatively new nanomaterial finding application in catalysis, sensing, and as a support for biomolecules. NPG has attracted considerable interest due to its open bicontinuous structure, high surface-to-volume ratio, tunable porosity, chemical stability and biocompatibility. NPG also has the attractive feature of being able to be modified by self-assembled monolayers. Here we use scanning electron microscopy (SEM) and atomic force microscopy (AFM) to characterize a highly efficient approach for protein immobilization on NPG using N-hydroxysuccinimide (NHS) ester functionalized self-assembled monolayers on NPG with pore sizes in the range of tens of nanometres. Comparison of coupling under static versus flow conditions suggests that BSA (Bovine Serum Albumin) and IgG (Immunoglobulin G) can only be immobilized onto the interior surfaces of free standing NPG monoliths with good coverage under flow conditions. AFM is used to examine protein coverage on both the exterior and interior of protein modified NPG. Access to the interior surface of NPG for AFM imaging is achieved using a special procedure for cleaving NPG. AFM is also used to examine BSA immobilized on rough gold surfaces as a comparative study. In principle, the general approach described should be applicable to many enzymes, proteins and protein complexes since both pore sizes and functional groups present on the NPG surfaces are controllable.Nanoporous gold (NPG), made by dealloying low carat gold alloys, is a relatively new nanomaterial finding application in catalysis, sensing, and as a support for biomolecules. NPG has attracted considerable interest due to its open bicontinuous structure, high surface-to-volume ratio, tunable porosity, chemical stability and biocompatibility. NPG also has the attractive feature of being able to be modified by self-assembled monolayers. Here we use scanning electron microscopy (SEM) and atomic force microscopy (AFM) to characterize a highly efficient approach for protein immobilization on NPG using N-hydroxysuccinimide (NHS) ester functionalized self-assembled monolayers on NPG with pore sizes in the range of tens of nanometres. Comparison of coupling under static versus flow conditions suggests that BSA (Bovine Serum Albumin) and IgG (Immunoglobulin G) can only be immobilized onto the interior surfaces of free standing NPG monoliths with good coverage under flow conditions. AFM is used to examine protein coverage on both the exterior and interior of protein modified NPG. Access to the interior surface of NPG for AFM imaging is achieved using a special procedure for cleaving NPG. AFM is also used to examine BSA immobilized on rough gold surfaces as a comparative study. In principle, the general approach described should be applicable to many enzymes, proteins and protein complexes since both pore sizes and functional groups present on the NPG surfaces are controllable. Electronic supplementary information (ESI) available. See DOI: 10.1039/c1nr10427f

Tan, Yih Horng; Schallom, John R.; Ganesh, N. Vijaya; Fujikawa, Kohki; Demchenko, Alexei V.; Stine, Keith J.

2011-08-01

332

Quantitative lateral and axial flow imaging with optical coherence microscopy and tomography.  

PubMed

Optical coherence tomography (OCT) and optical coherence microscopy (OCM) allow the acquisition of quantitative three-dimensional axial flow by estimating the Doppler shift caused by moving scatterers. Measuring the velocity of red blood cells is currently the principal application of these methods. In many biological tissues, blood flow is often perpendicular to the optical axis, creating the need for a quantitative measurement of lateral flow. Previous work has shown that lateral flow can be measured from the Doppler bandwidth, albeit only for simplified optical systems. In this work, we present a generalized model to analyze the influence of relevant OCT/OCM system parameters such as light source spectrum, numerical aperture and beam geometry on the Doppler spectrum. Our analysis results in a general framework relating the mean and variance of the Doppler frequency to the axial and lateral flow velocity components. Based on this model, we present an optimized acquisition protocol and algorithm to reconstruct quantitative measurements of lateral and axial flow from the Doppler spectrum for any given OCT/OCM system. To validate this approach, Doppler spectrum analysis is employed to quantitatively measure flow in a capillary with both extended focus OCM and OCT. PMID:23938644

Bouwens, Arno; Szlag, Daniel; Szkulmowski, Maciej; Bolmont, Tristan; Wojtkowski, Maciej; Lasser, Theo

2013-07-29

333

Three-Dimensional Scanning Transmission Electron Microscopy of Biological Specimens  

PubMed Central

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.

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

2010-01-01

334

High-resolution microscopy of plasmon field distributions by scanning tunneling luminescence and photoemission electron microscopies  

NASA Astrophysics Data System (ADS)

The exploitation of plasmon resonances to promote the interaction between conjugated molecules and optical fields motivates intensive research. The objectives are to understand the mechanisms of plasmon-mediated interactions, and to realize molecularly- or atomically-precise metal nanostructures, combining field enhancements and optical antenna effects. In this review paper, we present examples of plasmonic-field mappings based on scanning tunneling microscope (STM)-induced light emission or multiphoton photoemission (PEEM), two techniques among those which offer today's best spatial resolutions for plasmon microscopy. An unfamiliar property of the junction of an STM is its ability to behave as a highly localized source of light. It can be exploited to probe optoelectronic properties, in particular plasmonic fields, with ultimate subnanometer spatial resolution, an advantage balanced by a sometimes delicate deconvolution of local-probe influence. Alternatively, local-probe disadvantages can be overcome by imaging the photoemitted electrons, using well-established electron optics. This allows obtaining two-dimensional intensity maps reflecting the unperturbed distribution of the optical near field. This approach provides full field spectroscopic images with a routine spatial resolution of the order of 20 nm (down to 5 nm with recent aberration corrected instruments).

Douillard, Ludovic; Charra, Fabrice

2012-10-01

335

Historical perspective and current trends in emission microscopy, mirror electron microscopy and low-energy electron microscopy. An introduction to the proceedings of the Second International Symposium and Workshop on Emission microscopy and Related Techniques.  

PubMed

Emission microscopes and related instruments comprise a specialized class of electron microscopes that have in common an acceleration field in combination with the first stage of imaging (i.e., an immersion objective lens, also called a cathode lens or emission lens). These imaging techniques include photoelectron emission microscopy (PEEM or PEM), electron emission induced by heat, ions, or neutral particles, mirror electron microscopy (MEM), and low-energy electron microscopy (LEEM), among others. In these instruments the specimen is placed on a flat cathode or is the cathode itself. The low-energy electrons that are emitted, reflected, or backscattered from the specimen are first accelerated and then imaged by means of an electron lens system resembling that of a transmission electron microscope. The image is formed in a parallel mode in all of the above instruments, in contrast to the image in scanning electron microscopes, where the information is collected sequentially by scanning the specimen. A brief history and introduction to emission microscopy, MEM, and LEEM is presented as a background for the Proceedings of the Second International Symposium and Workshop on this subject, held in Seattle, Washington, August 16-17, 1990. Current trends in this field gleaned from the presentations at that meeting are discussed. PMID:1882483

Griffith, O H; Engel, W

1991-05-01

336

Scanning electron microscopy fractography analysis of fractured hollow implants.  

PubMed

Fracture of the implant is one of the possible complications affecting dental implants; it is a rare event but of great clinical relevance. The aim of the present study was to perform a scanning electron microscopy (SEM) fractography evaluation of 7 International Team for oral Implantology (ITI) hollow implants removed because of fracture. The most common clinical risk factors, such as malocclusion, bruxism, and cantilevers on the prosthesis, were absent. Seven fractured ITI hollow implants were retrieved from 5 patients and were analyzed with the use of SEM. SEM analysis showed typical signs of a cleavage-type fracture. Fractures could be due to an association of multiple factors such as fatigue, inner defects, material electrochemical problems, and tensocorrosion. PMID:20426587

Sbordone, Ludovico; Traini, Tonino; Caputi, Sergio; Scarano, Antonio; Bortolaia, Claudia; Piattelli, Adriano

2010-01-01

337

Performance of asbestos fibre counting laboratories by transmission electron microscopy.  

PubMed

In France, the owners of buildings have been obliged since February 1996 to ascertain whether asbestos has been incorporated into surfacing materials, insulation products or false ceilings. In certain circumstances, there is also a requirement to measure the airborne asbestos fibre concentration. Three years (1996-1998) of asbestos fibre count reporting are evaluated for the proficiency testing scheme organized in France to evaluate the performance of laboratories using an indirect-transfer transmission electron microscopy procedure to measure the airborne asbestos fibre concentration. Each year eight filters are distributed to each participating laboratory. These filters are obtained by filtering a suspension containing chrysotile or amphibole fibres. In 1996, 36% of the laboratories were rated 1 (the best performers; i.e. those providing counts close to the reference value). Performance improved appreciably in the last round where 85% of the laboratories were rated 1. PMID:11137700

Kauffer, E; Martine, M; Grzebyk, M; Vigneron, J C; Sandino, J P

2001-01-01

338

Cryo-electron microscopy of vitrified chromosomes in situ.  

PubMed Central

Chromosomes of metaphase-arrested Chinese hamster ovary (CHO) and HeLa cells were examined in situ, unfixed and unstained, by cryo-electron microscopy. In hydrated, vitrified cryo-sections, chromosomes exhibit a characteristic homogeneous, grainy texture, which, on optical diffraction, gives rise to a broad reflection corresponding to 11 nm. No superstructure or periodic order is discernible. These observations suggest that the chromosome is formed by the compact association of 11 nm filaments, or portions thereof, interacting in a manner akin to the molecules of a liquid. Some implications of the liquid model of chromosome structure are discussed. Images Fig. 1. Fig. 2. Fig. 3. Fig. 4 and 5. Fig. 6.

McDowall, A W; Smith, J M; Dubochet, J

1986-01-01

339

Electron microscopy study of tumor destruction by photodynamic therapy  

NASA Astrophysics Data System (ADS)

Sections of SCCVII tumor (squamous cell carcinoma) grown in C3H mice treated with Photofrin based photodynamic therapy (PDT) were examined by electron microscopy. The tumors were collected at different times after light treatment, and divided according to light penetration into superficial (treatment light oriented) and deep areas. The results show evidence of the progressive destruction of tumor cells occurring in both areas, with the presence of apparently intact tumor cells in the deep region 6 hours after PDT. These healthy looking tumor cells were often found adjacent to heavily damaged tumor cells, which is indicative of selectivity in their killing within the same microregion of tumor tissue. Many histiocytes and mast cells that appeared engaged in tumoricidal activity were also detected. It is suggested that in addition to lethality coming from progressive hemorrhagic necrosis, host immune cells infiltrating the tumor are elicited by PDT and contribute to the indirect killing effect.

Korbelik, Mladen; Matisic, Jasenka; Krosl, Gorazd

1993-06-01

340

Transmission Electron Microscopy (TEM) investigations of ancient Egyptian cosmetic powders  

NASA Astrophysics Data System (ADS)

The processing technologies available during the time of ancient Egypt are of present concern to the field of Archaeology and Egyptology. Materials characterization is the best tool for establishing the processing history of archaeological objects. In this study, transmission electron microscopy (TEM) is used, in addition to other techniques, for phase identification and study of the microstructure and characteristic defect structures in ancient Egyptian cosmetic powders. These powders generally consist of a mix of Pb-containing mineral phases: galena (PbS), cerussite (PbCO3), and phosgenite (Pb2Cl2CO3), among others. Modern materials are fabricated according to recipes found in ancient texts to mimic the processing of ancient times and to compare with the archaeological specimens. In particular, a comparison between the dislocation structures of PbS crystals deformed in the laboratory and PbS from archaeological specimens from the collections of the Louvre Museum is presented .

Deeb, C.; Walter, P.; Castaing, J.; Penhoud, P.; Veyssière, P.

341

Electron microscopy of life-tested semiconductor laser diodes  

PubMed

Electron Microscopy on life-tested 980 nm SL SQW InGaAs/AlGaAs laser diodes is able to find and analyze lattice defects responsible for the detected failures. Anyway, the origin and evolution of those defects remains questionable. Only the comparative analysis of life-test measurements, EBIC-FIB/TEM images, and charge-transport physics is able to point out a coherent framework for complete decoding of the failure kinetics. Minority-carrier diffusion and their enhanced recombination at defective lattice points are indicated, as the energy supply required for defect reaction and growth. The rules of charge diffusion drive both the reaction model, the interpretation of EBIC images and the expected electrical and optical effects. Strain release at the ultimate propagation of defects into the strained InGaAs quantum layer is then easily related to the final state of the failed devices. PMID:10702975

Vanzi; Bonfiglio; Magistrali; Salmini

2000-06-01

342

Chondrite thermal histories - Clues from electron microscopy of orthopyroxene  

NASA Astrophysics Data System (ADS)

Optically 'striated' orthopyroxenes in two ordinary chondrites, Allegan (H5) and Quenggouk (H4), are compared with shock-affected orthopyroxenes in Saint-Severin (LL6) and Ambapur Nagla (H5) by high-voltage transmission electron microscopy. The striated orthopyroxenes have very many, thin, evenly distributed lamellae of clinopyroxene. They are undeformed and also lack evidence of partial inversion from clinopyroxene to orthopyroxene. Striated orthopyroxene does not seem to be a reliable indicator of prograde metamorphism. Instead, it is interpreted as inverted protopyroxene, produced during the cooling of chondrules at slower rates than the rapid quenching of Type 3 chondrules. The conclusions are consistent with retrograde models for the evolution of H-group chondrites, in which the higher petrologic types are attributed to retarded cooling due to accretionary processes leading to the growth of the parent body.

Ashworth, J. R.

1980-01-01

343

Morphological classification of bioaerosols from composting using scanning electron microscopy.  

PubMed

This research classifies the physical morphology (form and structure) of bioaerosols emitted from open windrow composting. Aggregation state, shape and size of the particles captured are reported alongside the implications for bioaerosol dispersal after release. Bioaerosol sampling took place at a composting facility using personal air filter samplers. Samples were analysed using scanning electron microscopy. Particles were released mainly as small (<1?m) single, spherical cells, followed by larger (>1?m) single cells, with aggregates occurring in smaller proportions. Most aggregates consisted of clusters of 2-3 particles as opposed to chains, and were <10?m in size. No cells were attached to soil debris or wood particles. These small single cells or small aggregates are more likely to disperse further downwind from source, and cell viability may be reduced due to increased exposure to environmental factors. PMID:24565805

Tamer Vestlund, A; Al-Ashaab, R; Tyrrel, S F; Longhurst, P J; Pollard, S J T; Drew, G H

2014-07-01

344

An optimized device for staining electron microscopy grids.  

PubMed

Proper staining of grids is critical for transmission electron microscopy (TEM). Staining must be done as quickly as possible using minimal reagents and with consideration for the environment. We developed a new device for efficient staining of multiple TEM grids. We studied reagent evaporation, rinsing volume, flow rate and re-use of uranyl acetate, and provide here a procedure for efficient staining using the new device. Our device permits TEM grids to be stained with less reagent than alternative staining apparatuses; staining requires a total volume of 260 ?l for five grids. Reagent evaporation is less than 6% even if used at 37° C. Moreover, our staining apparatus reduces chemical waste and shortens experiment time by staining several grids simultaneously. Our staining device is a compromise between time-consuming single grid processing and expensive commercial devices that consume large amounts of reagents. PMID:23962218

Mathieu, E; Benmlih, K; Fabre, R; Hemmerle, J

2014-01-01

345

Analysis of enamel microbiopsies in shed primary teeth by Scanning Electron Microscopy (SEM) and Polarizing Microscopy (PM).  

PubMed

The aims of this study were 1) to verify how close to the theoretically presumed areas are the areas of enamel microbiopsies carried out in vivo or in exfoliated teeth; 2) to test whether the etching solution penetrates beyond the tape borders; 3) to test whether the etching solution demineralizes the enamel in depth. 24 shed upper primary central incisors were randomly divided into two groups: the Rehydrated Teeth Group and the Dry Teeth Group. An enamel microbiopsy was performed, and the enamel microbiopsies were then analyzed by Scanning Electron Microscopy (SEM) and Polarizing Microscopy (PM). Quantitative birefringence measurements were performed. The "true" etched area was determined by measuring the etched enamel using the NIH Image analysis program. Enamel birefringence was compared using the paired t test. There was a statistically significant difference when the etched areas in the Rehydrated teeth were compared with those of the Dry teeth (p=0.04). The etched areas varied from -11.6% to 73.5% of the presumed area in the Rehydrated teeth, and from 6.6% to 61.3% in the Dry teeth. The mean percentage of variation in each group could be used as a correction factor for the etched area. Analysis of PM pictures shows no evidence of in-depth enamel demineralization by the etching solution. No statistically significant differences in enamel birefringence were observed between values underneath and outside the microbiopsy area in the same tooth, showing that no mineral loss occurred below the enamel superficial layer. Our data showed no evidence of in-depth enamel demineralization by the etching solution used in the enamel microbiopsy proposed for primary enamel. This study also showed a variation in the measured diameter of the enamel microbiopsy in nineteen teeth out of twenty four, indicating that in most cases the etching solution penetrated beyond the tape borders. PMID:19540564

Costa de Almeida, Glauce Regina; Molina, Gabriela Ferian; Meschiari, César Arruda; Barbosa de Sousa, Frederico; Gerlach, Raquel Fernanda

2009-09-01

346

Noise characteristics of the gas ionization cascade used in low vacuum scanning electron microscopy  

SciTech Connect

The noise characteristics of gas cascade amplified electron signals in low vacuum scanning electron microscopy (LVSEM) are described and analyzed. We derive expressions for each component contributing to the total noise culminating in a predictive, quantitative model that can be used for optimization of LVSEM operating parameters. Signal and noise behavior is characterized experimentally and used to validate the model. Under most operating conditions, the noise is dominated by the excess noise generated in the gas amplification cascade. At high gains, the excess noise increases proportionally with gain such that the signal-to-noise ratio is constant. The effects of several instrument operating parameters, including working distance, gas pressure, beam current, and detector bias, are condensed and presented in the form of a master curve.

Tileli, Vasiliki; Thiel, Bradley L. [College of Nanoscale Science and Engineering, University at Albany-SUNY, 257 Fuller Road, Albany, New York 12203 (United States); Knowles, W. Ralph; Toth, Milos [FEI Company, 5350 NE Dawson Creek Drive, Hillsboro, Oregon 97124 (United States)

2009-07-01

347

Quantitative Electron Tomography of Rubber Composites  

NASA Astrophysics Data System (ADS)

Rubber composite materials have many applications, one example being tyre manufacture. The presence of a filler material in the composite (such as carbon black or silica) causes its mechanical properties to differ in several ways when compared to pure rubber such as viscoelastic behaviour (the Payne effect), increased tensile strength and improved wear resistance. To fully understand these properties, it is necessary to characterise how the filler material is organised on the nanoscale. Using composite materials representative of those found in tyres, this work illustrates the use of electron tomography and machine learning methods as tools to describe the percolation behaviour of the filler; in this case, we focus on the largest proportion of particles absorbed into one single object as a function of particle spacing.

Staniewicz, Lech; Vaudey, Thomas; Degrandcourt, Christophe; Couty, Marc; Gaboriaud, Fabien; Midgley, Paul

2014-06-01

348

Measuring porosity at the nanoscale by quantitative electron tomography.  

PubMed

Quantitative electron tomography is proposed to characterize porous materials at a nanoscale. To achieve reliable three-dimensional (3D) quantitative information, the influence of missing wedge artifacts and segmentation methods is investigated. We are presenting the "Discrete Algebraic Reconstruction Algorithm" as the most adequate tomography method to measure porosity at the nanoscale. It provides accurate 3D quantitative information, regardless the presence of a missing wedge. As an example, we applied our approach to nanovoids in La2Zr2O7 thin films. PMID:21090668

Biermans, E; Molina, L; Batenburg, K J; Bals, S; Van Tendeloo, G

2010-12-01

349

Quantitative and Qualitative Methods Using Fluorescence Microscopy for the Study of Modified Low Density Lipoproteins Uptake  

PubMed Central

Summary Atherosclerosis and heart disease are the main cause of death in United States. The development of atherosclerosis includes lipid deposition and foam cell formation in the artery wall. Scavenger Receptors A-I and II (SRA-I/II) have an important role of in foam cell formation and atherogenesis. Most of the SRA-I/II studies had been performed using Iodine-125 radiolabeled modified LDL. This report attempts to validate the use of fluorescence microscopy techniques as an alternative to obtain qualitative and quantitative information of the uptake of fluorescence labeled AcLDL in adherent CHO cells expressing SRA-I/II. After verifying the protein expression of SRA-I and II, uptake was quantified using a Laser Scan Cytometer, and images of cells containing fluorescent AcLDL were obtained. A significant increase in fluorescence was found in the cells transfected with SRA-I/II versus those with empty vector. When SRA-I/II competitive ligands were used, the uptake of AcLDL was significantly decreased. In conclusion, the use of fluorescence microscopy techniques in obtaining qualitative and quantitative information of the uptake of fluorescence labeled AcLDL by adherent cells, such as CHO cells, is an alternative to the traditional use of radiolabeled iodine.

Pershouse, Mark A.

2014-01-01

350

Friction force microscopy: towards quantitative analysis of molecular organisation with nanometre spatial resolution.  

PubMed

Friction force microscopy (FFM) is a technique based upon scanning force microscopy that provides information on the properties of molecular materials. Continuum mechanics provides models that may be used to conduct quantitative analyses of data. While there are some important unresolved issues associated with the contact mechanics of the tip-sample interaction, there is a growing body of data that demonstrates the sensitivity of FFM to changes in molecular organisation and surface composition. Importantly, FFM provides these data with nm spatial resolution, making it in many respects a unique tool for exploring the structures of organic materials on small length scales. Some of the capabilities of FFM are illustrated by drawing on both the literature and work performed in the authors' laboratory on self-assembled monolayers. For example, the compositions of mixed monolayer systems may be determined, with control of tip chemistry providing an additional element of chemical specificity; the alkyl chain organisation may be investigated; and the rates of surface chemical reactions may be measured. FFM is a powerful tool for the quantitative investigation of nm scale chemistry. PMID:19791321

Leggett, Graham J; Brewer, Nicholas J; Chong, Karen S L

2005-03-21

351

Quantitative trace hydrogen distributions in natural diamond using 3D-micro-ERDA microscopy  

NASA Astrophysics Data System (ADS)

A 3-D quantitative microscopy for minor distributions of surface and near-surface bulk hydrogen in solid samples has been developed. The technique employs a 15 MeV Si 7+ microbeam and a two-dimensional position sensitive detector (2D PSD) with event reconstruction in an Elastic Recoil Detection Analysis (ERDA) geometry. Lateral resolutions of 10 ?m and depth resolutions of 300 Å at an MDL of 100 ppm are currently possible. The technique is quantitative due to the use of an internal implanted spot standard or by cross calibration to an H implanted reference sample using RBS as a normalisation transfer. Hydrogen content and configuration in diamond illuminates the genesis mechanism and environment. A hydrogen rich diamond exhibiting zoned cloud-like ensembles of micro-inclusions as well as smaller pockets of these inclusions has been interrogated for its near-surface-bulk hydrogen distribution. The sample has also been well characterised with optical microscopies and with bulk optical spectroscopies. A striking correlation between the hydrogen distribution and the optically visible inclusion have been obtained. This is the first direct evidence for aggregations of hydrogen associated with cloudy inclusions in natural hydrogen rich diamonds.

Maclear, R. D.; Connell, S. H.; Doyle, B. P.; Machi, I. Z.; Butler, J. E.; Sellschop, J. P. F.; Naidoo, S. R.; Fritsch, E.

1998-03-01

352

Data acquisition and processing modes for quantitative Auger electron spectroscopy  

SciTech Connect

Auger electron spectroscopy has been applied to the quantitative surface analysis of a series of metals (Ag, Cd, In, Sn), indium-tin alloys, indium and tin oxides, and indium-tin oxide (ITO) films. Spectra were obtained by two methods: the conventional modulation technique, which results in the derivative spectrum, and a direct current measurement, which gives an undifferentiated spectrum. For data collected in the latter mode, an instrumental approach and secondary electron background correction are discussed. Quantitative results obtained by using this approach are shown to be more accurate than the traditional measurement method. 7 figures, 3 tables.

Burrell, M.C.; Kaller, R.S.; Armstrong, N.R.

1982-12-01

353

Electron microscopy analysis of mineral fibers in human lung tissue.  

PubMed

In the present study, lung samples from 126 autopsied cases were examined to determine the content of mineral fibers using analytical transmission electron microscopy (ATEM). The cases were divided into four groups (22 lungs of persons exposed to ambient environmental pollution, 32 cases of mesothelioma, 38 cases of primary lung cancer, and 34 asbestosis cases, 13 of these with additional pleural plaques). Fibers were counted, measured, and mineralogically identified using a combination of X-ray microanalysis and electron diffraction of the non-oriented fiber. Concentration of fibrous particles (defined as particles above 1 micron in length with roughly parallel long sides and an aspect ratio of 5:1 and greater) was calculated as fibers 10(6)/g dry lung weight. The concentration of chrysotile was found to be similar throughout the groups except for two cases in the asbestosis group with comparably high numbers of chrysotile. However, a remarkable difference for amphiboles could be observed between the groups. Asbestos bodies were mostly found in the asbestosis group. There was a rather good correlation between numbers of amphibole fibers and asbestos bodies, with an average ratio of 10:1. For comparison purposes between occupationally exposed/non-exposed individuals, a transition was found in the concentration range of 3-10(7) asbestos fibers/g dried lung weight. PMID:1329506

Friedrichs, K H; Brockmann, M; Fischer, M; Wick, G

1992-01-01

354

Advanced scanning transmission electron microscopy characterization of UV LED nanowires  

NASA Astrophysics Data System (ADS)

The role of aberration-corrected scanning transmission electron microscopy (STEM) in materials characterization is examined in regards to Al(x)Ga(1-x)N nanowires. Wires were graded from x=0 to x=1 and then from x=1 to x=0 with a small active quantum disk region located between the two gradations. This configuration is the basis for previously reported UV light emitting diodes. However, to assist subsequent growth processes while striving for optimum efficiency, both structural and chemical characterization methods are necessary, which can be provided at sufficiently high resolutions by advanced STEM instruments. Specifically, structural characterization will focus on determining layer thicknesses and wire polarity, as well as visualizing any short-range ordering and/or stacking faults that may be present. STEM multislice image simulations will also be discussed. Chemically, both energy dispersive X-ray (EDX) and electron energy loss (EEL) spectroscopies will be discussed in various capacities, ranging from quantum well composition (EDX) to N K-edge fine structure of both GaN and AlN (EELS).

Phillips, Patrick; Kumar, Rajan; Carnevale, Santino; Myers, Roberto; Klie, Robert

2013-03-01

355

ATOMIC RESOLUTION CRYO ELECTRON MICROSCOPY OF MACROMOLECULAR COMPLEXES  

PubMed Central

Single-particle cryo electron microscopy (cryoEM) is a technique for determining three-dimensional (3D) structures from projection images of molecular complexes preserved in their “native,” noncrystalline state. Recently, atomic or near-atomic resolution structures of several viruses and protein assemblies have been determined by single-particle cryoEM, allowing ab initio atomic model building by following the amino acid side chains or nucleic acid bases identifiable in their cryoEM density maps. In particular, these cryoEM structures have revealed extended arms contributing to molecular interactions that are otherwise not resolved by the conventional structural method of X-ray crystallography at similar resolutions. High-resolution cryoEM requires careful consideration of a number of factors, including proper sample preparation to ensure structural homogeneity, optimal configuration of electron imaging conditions to record high-resolution cryoEM images, accurate determination of image parameters to correct image distortions, efficient refinement and computation to reconstruct a 3D density map, and finally appropriate choice of modeling tools to construct atomic models for functional interpretation. This progress illustrates the power of cryoEM and ushers it into the arsenal of structural biology, alongside conventional techniques of X-ray crystallography and NMR, as a major tool (and sometimes the preferred one) for the studies of molecular interactions in supramolecular assemblies or machines.

ZHOU, Z. HONG

2013-01-01

356

Transmission Electron Microscopy Investigations of Domain Wall and Dislocation Interactions  

NASA Astrophysics Data System (ADS)

The effects of dislocations on domain wall motion in magnetite are important to a variety of paleomagnetic applications. Here we directly image these effects using a transmission electron microscope. Four samples were cut from a single, fully oriented crystal of magnetite. These magnetites were deformed in the dislocation glide regime using a one-atmosphere rig at varying temperatures and pressures to create dislocations. In one dislocation-rich sample, traditional and Lorentz-mode transmission electron microscopy was used to investigate the crystallographic nature of the dislocations and to observe their interactions with domain walls. Dislocations were primarily, though not exclusively, found in the {111} planes with Burgers vectors in the expected <110> directions. Domain wall pinning at dislocations was recorded as the sample was tilted within the microscope in the presence of a 16.8 mT axial field. This allowed us to experimentally determine the microcoercivity, which was 0.5 mT, on average. FORC diagram measurements from all samples showed typical multidomain coercivity distributions, with a central higher coercivity ridge extending out to between 5 and 20 mT. The microcoercivity measurements are in good agreement with theoretical models for domain wall pinning at a dislocation, and the bulk coercivity measurements are in good agreement with models for domain wall pinning at larger dislocation populations.

Lindquist, A. K.; Feinberg, J. M.; Harrison, R. J.; Newell, A. J.

2013-12-01

357

The characterization of nanoparticles using analytical electron microscopy  

NASA Astrophysics Data System (ADS)

Nanoparticles are often overlooked during routine trace evidence analyses because of their small size and the degree of difficulty needed to efficiently characterize them. However, analytical electron microscopy (AEM) enables the characterization and/or identification of nanoparticles because of its high magnification capability, the ability to gather elemental data and also the ability to determine the internal structure of a single nanoparticles(1). There is a wide variety of natural and manufactured nanoparticles that are prominent within the environment and their presence becomes very valuable in the absence of larger particles. The combustion of materials produces by-products such as nano-sized carbon soot, fumes, fly ash and gun-shot residue (GSR). Using AEM, nano-sized carbon soot, fumes, fly ash and GSR can not only be distinguished from other nanoparticles within the environment but can also be distinguished from each other because of differences in morphology, elemental composition, and internal structure. The elemental information gathered from combustion by-products during AEM analysis can also give an indication of the original source material. Other nanoparticles such as paint pigments and fillers can also be characterized by AEM using morphology, electron diffraction and elemental composition.

Hill, Whitney B.

2011-05-01

358

Transmission electron microscopy investigation of ultrafine coal fly ash particles.  

PubMed

Ultrafine (<100 nm) ash particles in three coal fly ashes (CFA) produced by the combustion of three U.S. coals have been examined by high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDS), and electron diffraction. These ultrafine particles, either as primary ash particles derived directly from coal minerals or as secondary products of decomposition and vaporization-condensation processes, show quite different morphologies, compositions, and microstructures as compared to particles in coarser, micrometer-size fractions previously examined by CCSEM. An eastern U.S. bituminous CFA sample shows abundant discrete crystalline particles rich in Fe, Ti, and Al in its ultrafine ash fraction, and crystalline phases down to 10 nm size have been identified. Western U.S. low-rank CFA samples contain considerable amounts of alkaline-earth element aggregates in the form of phosphates, silicates, and sulfates and mixed species. Most of them show crystalline or crystalline plus amorphous characteristics. All three ultrafine samples also exhibit carbonaceous particles in the form of soot aggregates with primary particle size typically between 20 and 50 nm. In the western low-rank ultrafine CFAs, these carbonaceous soot particles were typically mixed or coated with multi-element inorganic species. PMID:15773488

Chen, Yuanzhi; Shah, Naresh; Huggins, Frank E; Huffman, Gerald P

2005-02-15

359

High Resolution Transmission Electron Microscopy (HRTEM) of nanophase ferric oxides  

NASA Technical Reports Server (NTRS)

Iron oxide minerals are the prime candidates for Fe(III) signatures in remotely sensed Martian surface spectra. Magnetic, Mossbauer, and reflectance spectroscopy have been carried out in the laboratory in order to understand the mineralogical nature of Martian analog ferric oxide minerals of submicron or nanometer size range. Out of the iron oxide minerals studied, nanometer sized ferric oxides are promising candidates for possible Martian spectral analogs. 'Nanophase ferric oxide (np-Ox)' is a generic term for ferric oxide/oxihydroxide particles having nanoscale (less than 10 nm) particle dimensions. Ferrihydrite, superparamagnetic particles of hematite, maghemite and goethite, and nanometer sized particles of inherently paramagnetic lepidocrocite are all examples of nanophase ferric oxides. np-Ox particles in general do not give X-ray diffraction (XRD) patterns with well defined peaks and would often be classified as X-ray amorphous. Therefore, different np-Oxs preparations should be characterized using a more sensitive technique e.g., high resolution transmission electron microscopy (HRTEM). The purpose of this study is to report the particle size, morphology and crystalline order, of five np-Ox samples by HRTEM imaging and electron diffraction (ED).

Golden, D. C.; Morris, R. V.; Ming, D. W.; Lauer, H. V., Jr.

1994-01-01

360

Transmission electron microscopy study of the cell-sensor interface  

PubMed Central

An emerging number of micro- and nanoelectronics-based biosensors have been developed for non-invasive recordings of physiological cellular activity. The interface between the biological system and the electronic devices strongly influences the signal transfer between these systems. Little is known about the nanoscopic structure of the cell–sensor interface that is essential for a detailed interpretation of the recordings. Therefore, we analysed the interface between the sensor surface and attached cells using transmission electron microscopy (TEM). The maximum possible resolution of our TEM study, however, was restricted by the quality of the interface preparation. Therefore, we complemented our studies with imaging ellipsometry. We cultured HEK293 cells on substrates, which had been precoated with different types of proteins. We found that contact geometry between attached cell membrane and substrate was dependent on the type of protein coating used. In the presence of polylysine, the average distance of the membrane–substrate interface was in the range of 35–40?nm. However, the cell membrane was highly protruded in the presence of other proteins like fibronectin, laminin or concanavalin-A. The presented method allows the nanoscopic characterization of the cell–sensor interface.

Wrobel, Gunter; Holler, Matthias; Ingebrandt, Sven; Dieluweit, Sabine; Sommerhage, Frank; Bochem, Hans Peter; Offenhausser, Andreas

2007-01-01

361

Thin dielectric film thickness determination by advanced transmission electron microscopy  

SciTech Connect

High Resolution Transmission Electron Microscopy (HR-TEM) has been used as the ultimate method of thickness measurement for thin films. The appearance of phase contrast interference patterns in HR-TEM images has long been confused as the appearance of a crystal lattice by non-specialists. Relatively easy to interpret crystal lattice images are now directly observed with the introduction of annular dark field detectors for scanning TEM (STEM). With the recent development of reliable lattice image processing software that creates crystal structure images from phase contrast data, HR-TEM can also provide crystal lattice images. The resolution of both methods was steadily improved reaching now into the sub Angstrom region. Improvements in electron lens and image analysis software are increasing the spatial resolution of both methods. Optimum resolution for STEM requires that the probe beam be highly localized. In STEM, beam localization is enhanced by selection of the correct aperture. When STEM measurement is done using a highly localized probe beam, HR-TEM and STEM measurement of the thickness of silicon oxynitride films agree within experimental error. In this paper, the optimum conditions for HR-TEM and STEM measurement are discussed along with a method for repeatable film thickness determination. The impact of sample thickness is also discussed. The key result in this paper is the proposal of a reproducible method for film thickness determination.

Diebold, A.C.; Foran, B.; Kisielowski, C.; Muller, D.; Pennycook, S.; Principe, E.; Stemmer, S.

2003-09-01

362

Combined scanning transmission electron microscopy tilt- and focal series.  

PubMed

In this study, a combined tilt- and focal series is proposed as a new recording scheme for high-angle annular dark-field scanning transmission electron microscopy (STEM) tomography. Three-dimensional (3D) data were acquired by mechanically tilting the specimen, and recording a through-focal series at each tilt direction. The sample was a whole-mount macrophage cell with embedded gold nanoparticles. The tilt-focal algebraic reconstruction technique (TF-ART) is introduced as a new algorithm to reconstruct tomograms from such combined tilt- and focal series. The feasibility of TF-ART was demonstrated by 3D reconstruction of the experimental 3D data. The results were compared with a conventional STEM tilt series of a similar sample. The combined tilt- and focal series led to smaller "missing wedge" artifacts, and a higher axial resolution than obtained for the STEM tilt series, thus improving on one of the main issues of tilt series-based electron tomography. PMID:24548618

Dahmen, Tim; Baudoin, Jean-Pierre; Lupini, Andrew R; Kübel, Christian; Slusallek, Philipp; de Jonge, Niels

2014-04-01

363

Scanning electrochemical microscopy at thermal sprayed anti-corrosion coatings: Effect of thermal spraying on heterogeneous electron transfer kinetics  

Microsoft Academic Search

The effect of thermal spraying on the electrochemical activity of an anti-corrosion superalloy was studied quantitatively using scanning electrochemical microscopy (SECM). The superalloy used was Inconel 625 (a Ni base superalloy) and thin coatings of the alloy were formed on mild steel using high velocity oxy-fuel (HVOF) thermal spraying. The kinetics of electron transfer (ET) across the Inconel 625 coating\\/electrolyte

Lee Johnson; Akbar Niaz; Adrian Boatwright; K. T. Voisey; Darren A. Walsh

2011-01-01

364

Contamination-free imaging by electron induced carbon volatilization in environmental scanning electron microscopy  

NASA Astrophysics Data System (ADS)

Many ultraviolet, x-ray and charged particle beam techniques are inhibited by the growth of carbonaceous films caused by cross linking of hydrocarbon contaminant adsorbates. In electron microscopy, such films obscure surface features and reduce resolution. We demonstrate how resolution degradation can be alleviated using a H2O environment via gas mediated, electron beam induced carbon volatilization, a process that competes with film growth. Net behavior is a function of electron flux, which provides control over growth kinetics during imaging. Under optimized conditions, film growth can be eliminated, removing contamination as a factor limiting image information content and resolution.

Toth, Milos; Lobo, Charlene J.; Lysaght, Michael J.; Vladár, András E.; Postek, Michael T.

2009-08-01

365

Bone-titanium oxide interface in humans revealed by transmission electron microscopy and electron tomography  

PubMed Central

Osseointegration, the direct contact between an implant surface and bone tissue, plays a critical role in interfacial stability and implant success. Analysis of interfacial zones at the micro- and nano-levels is essential to determine the extent of osseointegration. In this paper, a series of state-of-the-art microscopy techniques are used on laser-modified implants retrieved from humans. Partially laser-modified implants were retrieved after two and a half months' healing and processed for light and electron microscopy. Light microscopy showed osseointegration, with bone tissue growing both towards and away from the implant surface. Transmission electron microscopy revealed an intimate contact between mineralized bone and the laser-modified surface, including bone growth into the nano-structured oxide. This novel observation was verified by three-dimensional Z-contrast electron tomography, enabling visualization of an apatite layer, with different crystal direction compared with the apatite in the bone tissue, encompassing the nano-structured oxide. In conclusion, the present study demonstrates the nano-scale osseointegration and bonding between apatite and surface-textured titanium oxide. These observations provide novel data in human specimens on the ultrastructure of the titanium–bone interface.

Palmquist, Anders; Grandfield, Kathryn; Norlindh, Birgitta; Mattsson, Torsten; Branemark, Rickard; Thomsen, Peter

2012-01-01

366

Electron microscopy analysis of skin biopsies in CADASIL disease.  

PubMed

Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL) is an inherited vascular disorder, non-amyloid and non-atherosclerotic, affecting predominantly the central nervous system. We examined samples of skin biopsies from six patients (men, 43-52-year-old), admitted for treatment in the Neurology Clinic regarding the presence of partial motor impairment on upper and lower right limbs, facial asymmetry and phrasing impairment (three of the patients); These three patients had family history remarkable for early-onset strokes: mother and two brothers deceased by early strokes (40-50-year-old). Skin biopsy samples were fixed in glutaraldehyde and post-fixed in osmium tetroxyde. After dehydration, tissue samples were embedded in Epon. Ultrathin sections were mounted on copper grids and stained with uranyl acetate and lead citrate as usual and examined with a transmission electron microscope Phillips CM100. In all cases ultrastructural study showed granular osmiophilic material (GOM) in extracellular locations, between degenerating smooth muscle cells in dermal arteries or in their indentations. Deposits of GOM varied in size and electron density. Degeneration and loss of smooth muscle cells (SMCs) leads to abnormal enlargement of the space between these cells Ultrastructural analysis in three cases showed chromatin condensation and peripheral aggregation of nuclear material suggesting cells entry to apoptosis. These aspects and the marked destruction of the vascular wall were correlated with MRI findings and the severity of clinical manifestations at these patients. Our study showed that findings of GOM deposits, degeneration and loss of SMCs (probably by apoptosis), cell adhesion elements disturbance are characteristic for CADASIL disease and sufficient for diagnose of certainty. Moreover, electron microscopy analysis of skin biopsies is a useful tool for a differential diagnosis and can be considered as first choice method. PMID:20809020

Cotrutz, Carmen Elena; Indrei, Anca; B?descu, L; Dac?lu, Cristina; Neam?u, Monica; Dumitrescu, Gabriela Floren?a; Stefanache, Felicia; Petreu?, T

2010-01-01

367

Visualization and quantitative analysis of reconstituted tight junctions using localization microscopy.  

PubMed

Tight Junctions (TJ) regulate paracellular permeability of tissue barriers. Claudins (Cld) form the backbone of TJ-strands. Pore-forming claudins determine the permeability for ions, whereas that for solutes and macromolecules is assumed to be crucially restricted by the strand morphology (i.e., density, branching and continuity). To investigate determinants of the morphology of TJ-strands we established a novel approach using localization microscopy.TJ-strands were reconstituted by stable transfection of HEK293 cells with the barrier-forming Cld3 or Cld5. Strands were investigated at cell-cell contacts by Spectral Position Determination Microscopy (SPDM), a method of localization microscopy using standard fluorophores. Extended TJ-networks of Cld3-YFP and Cld5-YFP were observed. For each network, 200,000 to 1,100,000 individual molecules were detected with a mean localization accuracy of ?20 nm, yielding a mean structural resolution of ?50 nm. Compared to conventional fluorescence microscopy, this strongly improved the visualization of strand networks and enabled quantitative morphometric analysis. Two populations of elliptic meshes (mean diameter <100 nm and 300-600 nm, respectively) were revealed. For Cld5 the two populations were more separated than for Cld3. Discrimination of non-polymeric molecules and molecules within polymeric strands was achieved. For both subtypes of claudins the mean density of detected molecules was similar and estimated to be ?24 times higher within the strands than outside the strands.The morphometry and single molecule information provided advances the mechanistic analysis of paracellular barriers. Applying this novel method to different TJ-proteins is expected to significantly improve the understanding of TJ on the molecular level. PMID:22319608

Kaufmann, Rainer; Piontek, Jörg; Grüll, Frederik; Kirchgessner, Manfred; Rossa, Jan; Wolburg, Hartwig; Blasig, Ingolf E; Cremer, Christoph

2012-01-01

368

Transmission electron microscopy of polymer blends and block copolymers  

NASA Astrophysics Data System (ADS)

Transmission electron microscopy (TEM) of soft matter is a field that warrants further investigation. Developments in sample preparation, imaging and spectroscopic techniques could lead to novel experiments that may further our understanding of the structure and the role structure plays in the functionality of various organic materials. Unlike most hard materials, TEM of organic molecules is limited by the amount of radiation damage the material can withstand without changing its structure. Despite this limitation, TEM has been and will be a powerful tool to study polymeric materials and other soft matter. In this dissertation, an introduction of TEM for polymer scientists is presented. The fundamentals of interactions of electrons with matter are described using the Schrodinger wave equation and scattering cross-sections to fully encompass coherent and incoherent scattering. The intensity, which is the product of the wave function and its complex conjugate, shows no perceptible change due to the sample. Instead, contrast is generated through the optical system of the microscope by removing scattered electrons or by generating interference due to material-induced phase changes. Perhaps the most challenging aspect of taking TEM images, however, is sample preparation, because TEM experiments require materials with approximately 50 nm thickness. Although ultramicrotomy is a well-established powerful tool for preparing biological and polymeric sections for TEM, the development of cryogenic Focused Ion Beam may enable unprecedented cross-sectional TEM studies of polymer thin films on arbitrary substrates with nanometer precision. Two examples of TEM experiments of polymeric materials are presented. The first involves quantifying the composition profile across a lamellar phase obtained in a multicomponent blend of saturated poly(butadiene) and poly(isobutylene), stabilized by a saturated poly(butadiene) copolymer serving as a surfactant, using TEM and self-consistent field theory (SCFT). The liquid-like nature of this system at room temperature makes traditional staining methods for the enhancement of contrast ineffective. As an alternative, we take advantage of the large inelastic scattering cross-section of soft materials to generate contrast in zero-loss TEM images. Independent spatially resolved thickness measurements enable quantification of electron scattering. This enabled a comparison between the TEM data and predictions based on SCFT without any adjustable parameters. The second example involves the utilization of energy-filtered transmission electron microscopy (EFTEM) to compute elemental maps by taking advantage of ionization events. Elemental mapping of lithium is used to determine the distribution of salt in nanostructured poly(styrene-block-ethylene oxide) (SEO) copolymer/lithium salt electrolytes. Surprisingly, the concentration of lithium within a poly(ethylene oxide) (PEO) domain is found to be inhomogeneous; the salt is localized to the middle of the channels. Self-consistent field theory simulations suggest that localization of lithium is due to chain stretching at the interface, which increases with molecular weight. EFTEM and SCFT results show that the segregation of lithium salt to the middle of the PEO lamellae is greater for higher molecular weight polymers. This is correlated with the ionic conductivity of the copolymer electrolyte, which is found to show a higher conductivity for thinner lithium lamellae.

Gomez, Enrique Daniel

369

Aerosols over the Amazon Rainforest Investigated by Scanning Transmission X-ray Microscopy and Scanning Electron Microscopy  

Microsoft Academic Search

We collected atmospheric aerosols over the central Amazon Basin near Manaus, Brazil, during the wet season in February 2008, as part of the AMAZE-08 (Amazonian Aerosol Characterization Experiment) campaign. Aerosol samples were analyzed by Scanning Transmission X-ray Microscopy (STXM) coupled with Near-Edge X-ray Absorption Fine Structure Spectroscopy (NEXAFS) and Scanning Electron Microscopy (SEM) coupled with Energy-Dispersive X-ray Analysis (EDX). A

M. O. Andreae; P. P. Artaxo; M. K. Gilles; S. T. Martin; E. Mikhailov; R. Moffet; U. Poeschl; B. Sinha; H. Yang

2009-01-01

370

Ultra-high vacuum scanning thermal microscopy for nanometer resolution quantitative thermometry.  

PubMed

Understanding energy dissipation at the nanoscale requires the ability to probe temperature fields with nanometer resolution. Here, we describe an ultra-high vacuum (UHV)-based scanning thermal microscope (SThM) technique that is capable of quantitatively mapping temperature fields with ?15 mK temperature resolution and ?10 nm spatial resolution. In this technique, a custom fabricated atomic force microscope (AFM) cantilever, with a nanoscale Au-Cr thermocouple integrated into the tip of the probe, is used to measure temperature fields of surfaces. Operation in an UHV environment eliminates parasitic heat transport between the tip and the sample enabling quantitative measurement of temperature fields on metal and dielectric surfaces with nanoscale resolution. We demonstrate the capabilities of this technique by directly imaging thermal fields in the vicinity of a 200 nm wide, self-heated, Pt line. Our measurements are in excellent agreement with computational results-unambiguously demonstrating the quantitative capabilities of the technique. UHV-SThM techniques will play an important role in the study of energy dissipation in nanometer-sized electronic and photonic devices and the study of phonon and electron transport at the nanoscale. PMID:22530657

Kim, Kyeongtae; Jeong, Wonho; Lee, Woochul; Reddy, Pramod

2012-05-22

371

Transmission electron microscopy analysis of corroded metal waste forms.  

SciTech Connect

This report documents the results of analyses with transmission electron microscopy (TEM) combined with energy dispersive X-ray spectroscopy (EDS) and selected area electron diffraction (ED) of samples of metallic waste form (MWF) materials that had been subjected to various corrosion tests. The objective of the TEM analyses was to characterize the composition and microstructure of surface alteration products which, when combined with other test results, can be used to determine the matrix corrosion mechanism. The examination of test samples generated over several years has resulted in refinements to the TEM sample preparation methods developed to preserve the orientation of surface alteration layers and the underlying base metal. The preservation of microstructural spatial relationships provides valuable insight for determining the matrix corrosion mechanism and for developing models to calculate radionuclide release in repository performance models. The TEM results presented in this report show that oxide layers are formed over the exposed steel and intermetallic phases of the MWF during corrosion in aqueous solutions and humid air at elevated temperatures. An amorphous non-stoichiometric ZrO{sub 2} layer forms at the exposed surfaces of the intermetallic phases, and several nonstoichiometric Fe-O layers form over the steel phases in the MWF. These oxide layers adhere strongly to the underlying metal, and may be overlain by one or more crystalline Fe-O phases that probably precipitated from solution. The layer compositions are consistent with a corrosion mechanism of oxidative dissolution of the steel and intermetallic phases. The layers formed on the steel and intermetallic phases form a continuous layer over the exposed waste form, although vertical splits in the layer and corrosion in pits and crevices were seen in some samples. Additional tests and analyses are needed to verify that these layers passivate the underlying metals and if passivation can break down as the MWF corrodes. The importance of localized corrosion should also be determined.

Dietz, N. L.

2005-04-15

372

Towards quantitative electrochemical measurements on the nanoscale by scanning probe microscopy: environmental and current spreading effects  

SciTech Connect

The application of electric bias across tip-surface junctions in scanning probe microscopy can readily induce surface and bulk electrochemical processes that can be further detected though changes in surface topography, Faradaic or conductive currents, or electromechanical strain responses. However, the basic factors controlling tip-induced electrochemical processes, including the relationship between applied tip bias and the thermodynamics of local processes remains largely unexplored. Using the model Li-ion reduction reaction on the surface in Li-ion conducting glass ceramic, we explore the factors controlling Li-metal formation and find surprisingly strong effects of atmosphere and back electrode composition on the process. These studies suggest the feasibility of SPM-based quantitative electrochemical studies under proper environmental controls, extending the concepts of ultramicroelectrodes to the single-digit nanometer scale.

Arruda, Thomas M [ORNL] [ORNL; Kumar, Amit [Oak Ridge National Laboratory (ORNL)] [Oak Ridge National Laboratory (ORNL); Veith, Gabriel M [ORNL] [ORNL; Jesse, Stephen [ORNL] [ORNL; Tselev, Alexander [ORNL] [ORNL; Baddorf, Arthur P [ORNL] [ORNL; Balke, Nina [ORNL] [ORNL; Kalinin, Sergei V [ORNL] [ORNL

2013-01-01

373

Quantitative magnetic force microscopy on permalloy dots using an iron filled carbon nanotube probe.  

PubMed

An iron filled carbon nanotube (FeCNT), a 10-40 nm ferromagnetic nanowire enclosed in a protective carbon tube, is an attractive candidate for a magnetic force microscopy (MFM) probe as it provides a mechanically and chemically robust, nanoscale probe. We demonstrate the probe's capabilities with images of the magnetic field gradients close to the surface of a Py dot in both the multi-domain and vortex states. We show the FeCNT probe is accurately described by a single magnetic monopole located at its tip. Its effective magnetic charge is determined by the diameter of the iron wire and its saturation magnetization 4?M(s) ? 2.2 × 10(4)G. A magnetic monopole probe is advantageous as it enables quantitative measurements of the magnetic field gradient close to the sample surface. The lateral resolution is defined by the diameter of the iron wire and the probe-sample separation. PMID:21864777

Wolny, F; Obukhov, Y; Mühl, T; Weissker, U; Philippi, S; Leonhardt, A; Banerjee, P; Reed, A; Xiang, G; Adur, R; Lee, I; Hauser, A J; Yang, F Y; Pelekhov, D V; Büchner, B; Hammel, P C

2011-07-01

374

Nanoscale-resolved elasticity: contact mechanics for quantitative contact resonance atomic force microscopy  

NASA Astrophysics Data System (ADS)

Contact resonance atomic force microscopy (CR-AFM) constitutes a powerful approach for nanometer-resolved mechanical characterization of surfaces. Yet, absolute accuracy is frequently impaired by ad hoc assumptions on the dynamic AFM cantilever characteristics as well as contact model. Within the present study, we clarify the detailed interplay of stress fields and geometries for full quantitative understanding, employing combined experimental numerical studies for real AFM probes. Concerning contact description, a two-parameter ansatz is utilized that takes tip geometries and their corresponding indentation moduli into account. Parameter sets obtained upon experimental data fitting for different tip blunting states, are discussed in terms of model-specific artificiality versus real contact physics at the nanoscale. Unveiling the underlying physics in detail, these findings pave the way for accurate characterization of nanomechanical properties with highest resolution.

Jakob, A. M.; Buchwald, J.; Rauschenbach, B.; Mayr, S. G.

2014-05-01

375

Direct visualization and quantitative analysis of water diffusion in complex biological tissues using CARS microscopy  

PubMed Central

To date, it has not been possible to measure microscopic diffusive water movements in epithelia and in the interstitial space of complex tissues and organs. Diffusive water movements are essential for life because they convey physiologically important small molecules, e.g. nutrients and signaling ligands throughout the extracellular space of complex tissues. Here we report the development of a novel method for the direct observation and quantitative analysis of water diffusion dynamics in a biologically organized tissue using Coherent Anti-Stokes Raman Scattering (CARS) microscopy. Using a computer simulation model to analyze the CARS O-H bond vibration data during H2O/D2O exchange in a 3D epithelial cyst, we succeeded in measuring the diffusive water permeability of the individual luminal and basolateral water pathways and also their response to hormonal stimulation. Our technique will be applicable to the measurement of diffusive water movements in other structurally complex and medically important tissues and organs.

Yu, Ying-Chun; Sohma, Yoshiro; Takimoto, Shinichi; Miyauchi, Takayuki; Yasui, Masato

2013-01-01

376

Hydrated human corneal stroma revealed by quantitative dynamic atomic force microscopy at nanoscale.  

PubMed

The structures and mechanical properties of human tissues are significantly influenced by water. The functionality of the human cornea can be linked to the hydrated collagen fibers. By applying quantitative dynamic atomic force microscopy to investigate morphological and mechanical property variations of corneal stroma under different hydration levels, we found that the collagen fibers in the stromal tissue show the specific periodicities and the stiffness of giga-Pa magnitude at 40% humidity. However, under increasing hydration, the collagen fibers clearly show nanoparticle structures along the fibers with the stiffness in mega-Pa magnitude. By increasing the hydration time, the stroma regains the fiber structure but with larger diameter. The age-dependency in stiffness was further investigated. The interplay of structures and nanomechanical mapping may be applied for the future diagnosis and assessment or even pathologic analysis. PMID:24833346

Xia, Dan; Zhang, Shuai; Hjortdal, Jesper Østergaard; Li, Qiang; Thomsen, Karen; Chevallier, Jacques; Besenbacher, Flemming; Dong, Mingdong

2014-07-22

377

Multi-parametric quantitative microvascular imaging with optical-resolution photoacoustic microscopy in vivo.  

PubMed

Many diseases involve either the formation of new blood vessels (e.g., tumor angiogenesis) or the damage of existing ones (e.g., diabetic retinopathy) at the microcirculation level. Optical-resolution photoacoustic microscopy (OR-PAM), capable of imaging microvessels in 3D in vivo down to individual capillaries using endogenous contrast, has the potential to reveal microvascular information critical to the diagnosis and staging of microcirculation-related diseases. In this study, we have developed a dedicated microvascular quantification (MQ) algorithm for OR-PAM to automatically quantify multiple microvascular morphological parameters in parallel, including the vessel diameter distribution, the microvessel density, the vascular tortuosity, and the fractal dimension. The algorithm has been tested on in vivo OR-PAM images of a healthy mouse, demonstrating high accuracy for microvascular segmentation and quantification. The developed MQ algorithm for OR-PAM may greatly facilitate quantitative imaging of tumor angiogenesis and many other microcirculation related diseases in vivo. PMID:24515157

Yang, Zhenyuan; Chen, Jianhua; Yao, Junjie; Lin, Riqiang; Meng, Jing; Liu, Chengbo; Yang, Jinhua; Li, Xiang; Wang, Lihong; Song, Liang

2014-01-27

378

Multifluorescence confocal microscopy: application for a quantitative analysis of hemostatic proteins in human venous valves.  

PubMed

Confocal laser scanning microscopy is commonly used to visualize and quantify protein expression. Visualization of the expression of multiple proteins in the same region via multifluorescence allows for the analysis of differential protein expression. The defining step of multifluorescence labeling is the selection of primary antibodies from different host species. In addition, species-appropriate secondary antibodies must also be conjugated to different fluorophores so that each protein can be visualized in separate channels. Quantitative analysis of proteins labeled via multifluorescence can be used to compare relative changes in protein expression. Multifluoresecence labeling and analysis of fluorescence intensity within and among human venous specimens, for example, allowed us to determine that the anticoagulant phenotype of the venous valve is defined not by increased anticoagulant expression, but instead by significantly decreased procoagulant protein expression (Blood 114:1276-1279, 2009 and Histochem Cell Biol 135:141-152, 2011). PMID:23026998

Trotman, Winifred E; Taatjes, Douglas J; Bovill, Edwin G

2013-01-01

379

Nanoscale-resolved elasticity: contact mechanics for quantitative contact resonance atomic force microscopy.  

PubMed

Contact resonance atomic force microscopy (CR-AFM) constitutes a powerful approach for nanometer-resolved mechanical characterization of surfaces. Yet, absolute accuracy is frequently impaired by ad hoc assumptions on the dynamic AFM cantilever characteristics as well as contact model. Within the present study, we clarify the detailed interplay of stress fields and geometries for full quantitative understanding, employing combined experimental numerical studies for real AFM probes. Concerning contact description, a two-parameter ansatz is utilized that takes tip geometries and their corresponding indentation moduli into account. Parameter sets obtained upon experimental data fitting for different tip blunting states, are discussed in terms of model-specific artificiality versus real contact physics at the nanoscale. Unveiling the underlying physics in detail, these findings pave the way for accurate characterization of nanomechanical properties with highest resolution. PMID:24838534

Jakob, A M; Buchwald, J; Rauschenbach, B; Mayr, S G

2014-06-21

380

Quantitative comparison between full-spectrum and filter-based imaging in hyperspectral fluorescence microscopy  

PubMed Central

Summary We implement a filterless illumination scheme on a hyperspectral fluorescence microscope to achieve full-range spectral imaging. The microscope employs polarisation filtering, spatial filtering and spectral unmixing filtering to replace the role of traditional filters. Quantitative comparisons between full-spectrum and filter-based microscopy are provided in the context of signal dynamic range and accuracy of measured fluorophores’ emission spectra. To show potential applications, a five-colour cell immunofluorescence imaging experiment is theoretically simulated. Simulation results indicate that the use of proposed full-spectrum imaging technique may result in three times improvement in signal dynamic range compared to that can be achieved in the filter-based imaging.

GAO, L.; HAGEN, N.; TKACZYK, T.S.

2012-01-01

381

Quantitative microscopy and nanoscopy of sickle red blood cells performed by wide field digital interferometry  

NASA Astrophysics Data System (ADS)

We have applied wide-field digital interferometry (WFDI) to examine the morphology and dynamics of live red blood cells (RBCs) from individuals who suffer from sickle cell anemia (SCA), a genetic disorder that affects the structure and mechanical properties of RBCs. WFDI is a noncontact, label-free optical microscopy approach that can yield quantitative thickness profiles of RBCs and measurements of their membrane fluctuations at the nanometer scale reflecting their stiffness. We find that RBCs from individuals with SCA are significantly stiffer than those from a healthy control. Moreover, we show that the technique is sensitive enough to distinguish classes of RBCs in SCA, including sickle RBCs with apparently normal morphology, compared to the stiffer crescent-shaped sickle RBCs. We expect that this approach will be useful for diagnosis of SCA and for determining efficacy of therapeutic agents.

Shaked, Natan T.; Satterwhite, Lisa L.; Telen, Marilyn J.; Truskey, George A.; Wax, Adam

2011-03-01

382

Nonlinear detection mechanism in quantitative atomic force microscopy characterization of high-frequency nanoelectromechanical systems  

NASA Astrophysics Data System (ADS)

We investigate the transduction of motion from a nanomechanical resonator to the cantilever/tip probe of an atomic force microscope. Our results show that amplitude-modulated high-frequency vibrations of nanomechanical resonators can be measured by means of a low-resonance frequency cantilever as a consequence of the demodulation introduced by the nonlinear forces involved in the system. The theoretical model presented in this paper enables the quantitative application of atomic force microscopy (AFM) for the characterization of a wide variety of devices. An analysis based on this model of previously reported experiments in carbon nanotube and graphene resonators demonstrates the ability of AFM to measure vibration amplitudes in the subnanometer range without significant perturbation of the resonators.

Serra-García, Marc; Pérez-Murano, Francesc; San Paulo, Alvaro

2012-01-01

383

Analytical electron microscopy of biogenic and inorganic carbonates  

NASA Technical Reports Server (NTRS)

In the terrestrial sedimentary environment, the mineralogically predominant carbonates are calcite-type minerals (rhombohedral carbonates) and aragonite-type minerals (orthorhombic carbonates). Most common minerals precipitating either inorganically or biogenically are high magnesium calcite and aragonite. High magnesium calcite (with magnesium carbonate substituting for more than 7 mole percent of the calcium carbonate) is stable only at temperatures greater than 700 C or thereabouts, and aragonite is stable only at pressures exceeding several kilobars of confining pressure. Therefore, these carbonates are expected to undergo chemical stabilization in the diagenetic environment to ultimately form stable calcite and dolomite. Because of the strong organic control of carbonate deposition in organisms during biomineralization, the microchemistry and microstructure of invertebrate skeletal material is much different than that present in inorganic carbonate cements. The style of preservation of microstructural features in skeletal material is therefore often quite distinctive when compared to that of inorganic carbonate even though wholesale recrystallization of the sediment has taken place. Microstructural and microchemical comparisons are made between high magnesium calcite echinoderm skeletal material and modern inorganic high magnesium calcite inorganic cements, using analytical electron microscopy and related techniques. Similar comparisons are made between analogous materials which have undergone stabilization in the diagenetic environment. Similar analysis schemes may prove useful in distinguishing between biogenic and inorganic carbonates in returned Martian carbonate samples.

Blake, David F.

1989-01-01

384

Electron microscopy in the non-Hodgkin's lymphomata.  

PubMed Central

The component cells of peripheral lymphoid tissue have been divided into the lymphocyte and plasma cell lines, mononuclear phagocytic cells, dendritic "reticular cells", the reticular (supporting) cells and endothelial cells, and it is suggested that this system of cells should collectively be referred to as the lymphoreticular monoclear phagocyte system or LRMPS. Seventeen tumours of the LRMPS (excluding Hodgkin's disease) have been studied at ultrastructural level. Of these 17 non-Hodgkin lymphomata 5 were follicular lymphomata and 12 diffuse. It is concluded that electron microscopy plays a valuable role in the diagnosis of this group of tumours. Not only does it allow rejection of a diagnosis of lymphoma in certain anaplastic tumours, but it also enables a more precise identification of the cellular components of a lymphoma as well as indicating the degree of differentiation of the cell line involved. Additional advantages are the visualization of subcellular structures useful as markers, and by means of specialized immunoelectron microscopic techniques the identification of antigens and antibody formation within a given tumour. Two other results of this ultrastructural study are the indication that the dendritic cells of lymphoid follicles are derived from capillary endothelium, and the identification of certain anomalous formations derived from rough endoplasmic reticulum in the case of tumours showing plasmacytoid differentiation. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 9 Fig. 10 Fig. 11 Fig. 12 Fig. 13 Fig. 14 Fig. 15

Henry, K.

1975-01-01

385

Scanning electron microscopy and roughness study of dental composite degradation.  

PubMed

Our aim was to test the hypothesis that the use of mouthwashes, consumption of soft drinks, as well as the type of light curing unit (LCU), would change the surface roughness (Ra) and morphology of a nanofilled composite resin (Z350® 3M ESPE). Samples (80) were divided into eight groups: Halogen LCU, group 1, saliva (control); group 2, Pepsi Twist®; group 3, Listerine®; group 4, Colgate Plax®; LED LCU, group 5, saliva; group 6, Pepsi Twist®; group 7, Listerine®; group 8, Colgate Plax®. Ra values were measured at baseline, and after 7 and 14 days. One specimen of each group was prepared for scanning electron microscopy analysis after 14 days. The data were subjected to multifactor analysis of variance at a 95% confidence followed by Tukey's honestly significant difference post-hoc test. All the treatments resulted in morphological changes in composite resin surface, and the most significant change was in Pepsi Twist® groups. The samples of G6 had the greatest increase in Ra. The immersion of nanofilled resin in mouthwashes with alcohol and soft drink increases the surface roughness. Polymerization by halogen LCU (reduced light intensity) associated with alcohol contained mouthwash resulted in significant roughness on the composite. PMID:22325725

Soares, Luís Eduardo Silva; Cortez, Louise Ribeiro; Zarur, Raquel de Oliveira; Martin, Airton Abrahão

2012-04-01

386

Cryogenic transmission electron microscopy nanostructural study of shed microparticles.  

PubMed

Microparticles (MPs) are sub-micron membrane vesicles (100-1000 nm) shed from normal and pathologic cells due to stimulation or apoptosis. MPs can be found in the peripheral blood circulation of healthy individuals, whereas elevated concentrations are found in pregnancy and in a variety of diseases. Also, MPs participate in physiological processes, e.g., coagulation, inflammation, and angiogenesis. Since their clinical properties are important, we have developed a new methodology based on nano-imaging that provides significant new data on MPs nanostructure, their composition and function. We are among the first to characterize by direct-imaging cryogenic transmitting electron microscopy (cryo-TEM) the near-to-native nanostructure of MP systems isolated from different cell types and stimulation procedures. We found that there are no major differences between the MP systems we have studied, as most particles were spherical, with diameters from 200 to 400 nm. However, each MP population is very heterogeneous, showing diverse morphologies. We investigated by cryo-TEM the effects of standard techniques used to isolate and store MPs, and found that either high-g centrifugation of MPs for isolation purposes, or slow freezing to -80 °C for storage introduce morphological artifacts, which can influence MP nanostructure, and thus affect the efficiency of these particles as future diagnostic tools. PMID:24386253

Issman, Liron; Brenner, Benjamin; Talmon, Yeshayahu; Aharon, Anat

2013-01-01

387

TRANSMISSION ELECTRON MICROSCOPY STUDY OF HELIUM BEARING FUSION WELDS  

SciTech Connect

A transmission electron microscopy (TEM) study was conducted to characterize the helium bubble distributions in tritium-charged-and-aged 304L and 21Cr-6Ni-9Mn stainless steel fusion welds containing approximately 150 appm helium-3. TEM foils were prepared from C-shaped fracture toughness test specimens containing {delta} ferrite levels ranging from 4 to 33 volume percent. The weld microstructures in the low ferrite welds consisted mostly of austenite and discontinuous, skeletal {delta} ferrite. In welds with higher levels of {delta} ferrite, the ferrite was more continuous and, in some areas of the 33 volume percent sample, was the matrix/majority phase. The helium bubble microstructures observed were similar in all samples. Bubbles were found in the austenite but not in the {delta} ferrite. In the austenite, bubbles had nucleated homogeneously in the grain interiors and heterogeneously on dislocations. Bubbles were not found on any austenite/austenite grain boundaries or at the austenite/{delta} ferrite interphase interfaces. Bubbles were not observed in the {delta} ferrite because of the combined effects of the low solubility and rapid diffusion of tritium through the {delta} ferrite which limited the amount of helium present to form visible bubbles.

Tosten, M; Michael Morgan, M

2008-12-12

388

An overview on bioaerosols viewed by scanning electron microscopy.  

PubMed

Bioaerosols suspended in ambient air were collected with single-stage impactors at a semiurban site in southern Germany during late summer and early autumn. Sampling was mostly carried out at a nozzle velocity of 35 m/s, corresponding to a minimum aerodynamic diameter (cut-off diameter) of aerosol particles of 0.8 mum. The collected particles, sampled for short periods ( approximately 15 min) to avoid pile-up, were characterized by scanning electron microscopy (SEM). The observed bioaerosols include brochosomes, fungal spores, hyphae, insect scales, hairs of plants and, less commonly, bacteria and epicuticular wax. Brochosomes, which serve as a highly water repellent body coating of leafhoppers, are hollow spheroids with diameters around 400 nm, resembling C(60) or footballs (soccer balls). They are usually airborne not as individuals but in the form of large clusters containing up to 10,000 individual species or even more. Various types of spores and scales were observed, but assignment turned out be difficult due to the large number of fungi and insects from which they may have originated. Pollens were observed only once. The absence these presumably elastic particles suggests that they are frequently lost, at the comparatively high velocities, due to bounce-off from the nonadhesive impaction surfaces. PMID:15993698

Wittmaack, K; Wehnes, H; Heinzmann, U; Agerer, R

2005-06-15

389

Scanning electron microscopy of fruiting body formation by myxobacteria.  

PubMed Central

Scanning electron microscopy was used to follow fruiting body formation by pure cultures of Chondromyces crocatus M38 and Stigmatella aurantica. Vegetative cells were grown on SP agar and then transferred to Bonner salts agar for fructification. Fruiting in both species commences with the formation of aggregation centers which resemble a fried egg in appearance. In Chondromyces the elevated center or "yolk" region of the aggregation enlarges into a bulbous structure under which the stalk forms and lengthens. At maximum stalk height the bulb extends laterally as bud-like swellings appear. These are immature sporangia and are arranged in a distintive radial pattern around the top of the stalk. This symmetry is lost as more sporangia are formed. Stigmatella does not form a bulb; rather the yolk region of the aggregation center projects upward to form a column-like stalk which is nearly uniform in diameter throughout its length. At maximum stalk height, the terminus of the stalk develops an irregular pattern of bud-like swellings. These differentiate into sporangia. Stalks of 2-week-old mature fruiting bodies of both species appear to be cellular in composition. Stereomicrographs suggest orientation of these cells parallel to the long axis of the stalk. Stalks of 8-week-old fruiting bodies of Chondromyces were acellular and consisted of empty tubules, suggesting that the cells undergo degeneration with aging of the fruiting body. Images

Grilione, P L; Pangborn, J

1975-01-01

390

Histological preparation of developing vestibular otoconia for scanning electron microscopy  

NASA Technical Reports Server (NTRS)

The unique nature of vestibular otoconia as calcium carbonate biominerals makes them particularly susceptible to chemical deformation during histological processing. We fixed and stored otoconia from all three otolith endorgans of embryonic, hatchling and adult Japanese quail in glutaraldehyde containing either phosphate or non-phosphate buffers for varying lengths of time and processed them for scanning electron microscopy. Otoconia from all age groups and otolith endorgans processed in 0.1 M phosphate buffer (pH 7.4) showed abnormal surface morphology when compared to acetone fixed controls. Otoconia processed in 0.1 M sodium cacodylate or HEPES buffered artificial endolymph (pH 7.4) showed normal morphology that was similar to controls. The degree of otoconial deformation was directly related to the time exposed to phosphate buffer. Short duration exposure produced particulate deformations while longer exposures resulted in fused otoconia that formed solid sheets. Otoconial surface deformation and fusing was independent of the glutaraldehyde component of the histological processing. These findings should help vestibular researchers to develop appropriate histological processing protocols in future studies of otoconia.

Huss, D.; Dickman, J. D.

2003-01-01

391

Observations under electron microscopy of magnetic minerals extracted from speleothems  

NASA Astrophysics Data System (ADS)

Magnetic minerals have been extracted from a selection of British speleothems and studied by electron microscopy and energy dispersive X-ray analysis (EDXA). Observations of the surface morphology, size and elemental composition of these grains has assisted in determining their origin. Thereby, direct evidence as to the carriers of the Natural Remanent Magnetization (NRM) of speleothems is provided. Three groups of grain morphology were identified: (1) detrital grains ranging in size from 0.01 ?m to ? 10 ?m, composed of magnetite, hematite and titanomagnetite; (2) unabraded grains ranging in size from 0.01 ?m to 0.1 ?m, composed of magnetite, these grains were further subdivided into those having an affinity with bacterial magnetites and those having an affinity with inorganic authigenic magnetites; (3) needle-like grains, less than 2 ?m in length, probably composed of goethite. Preliminary laboratory experiments suggest that authigenic magnetite and goethite may precipitate under conditions likely to prevail during speleothem growth. The presence of detrital magnetic grains in all samples studied is strong evidence for the presence of a Detrital Remanent Magnetization (DRM) in all speleothems. The presence of authigenic magnetite in some samples is the first direct evidence for the presence of a Chemical Remanent Magnetization (CRM) in some speleothems.

Perkins, Andrew M.

1996-03-01

392

Scanning electron microscopy of eggs of Sabethes cyaneus.  

PubMed

Mosquitoes of the Neotropical genus Sabethes, some species of which are yellow fever vectors, most often develop through the immature stages in tree holes. Sabethes eggs have not been previously characterized using scanning electron microscopy. Eggs of Sabethes cyaneus (length: 349.6 +/- 2.7 microm; width: 172.6 +/- 1.14 microm; n = 10) are almost biconical when examined from the top. From a lateral perspective 2 surfaces can be seen. One surface is smooth and more convex, whereas the other is less convex and partially covered by a network from which many fungiform tubercles arise. The micropyle is situated on the smooth surface of the pointed anterior tip and is surrounded by an irregular row of tubercles, some of which are leaf shaped. No structures possibly involved in adhesion to surfaces are visible. When hatching, the egg splits dorsoventrally approximately two-thirds of the length from the anterior end. The tubercles appear to be water repellent, and the more convex/smoother surface is downturned, and this position on water was confirmed by direct observation. The eggs float free on the water surface. PMID:23687859

Santos-Mallet, Jacenir; Sarmento, Juliana Soares; Alencar, Jeronimo; Müller, Gerson Azulim; Oliveira, Eliana Medeiros; Foster, Woodbridge A; Marcondes, Carlos Brisola

2013-03-01

393

Microanalysis of ambient particles from Lexington, KY, by electron microscopy  

NASA Astrophysics Data System (ADS)

Analytical transmission electron microscopy has been used for in-depth characterization of the individual submicron (physical size<1 ?m) particulate matter (PM) from the urban atmosphere of Lexington, Kentucky, USA. Carbonaceous particles and sulfur-bearing particles dominate the PM samples on a particle count basis. Soot aggregates are the major form of carbonaceous particles. Organic-type and biogenic carbonaceous particles are also observed and exhibit quite different morphologies and microstructures compared with combustion-generated soot and char particles. Ammonium sulfate is the dominant chemical type of sulfur-bearing particles. Other types of sulfur-bearing particles include crystalline sodium, potassium and calcium sulfates. Silicon-bearing particles consist mainly of silicon oxides and aluminosilicates. Iron and titanium oxide particles are the major metal oxides found in this study. Considerable amounts of iron oxide with other transition metal elements (e.g. Mn and Zn) have been observed, typically in the form of spinel nanocrystals. Minor amounts of other species (e.g. phosphates, lead compounds, and carbonates) have also been observed. The combined use of these analytical techniques is capable of revealing much new information on the microcharacteristics of individual submicron particles; such information should be relevant to toxicological, epidemiological, and source apportionment studies.

Chen, Yuanzhi; Shah, Naresh; Huggins, Frank E.; Huffman, Gerald P.

394

Cryogenic Transmission Electron Microscopy Nanostructural Study of Shed Microparticles  

PubMed Central

Microparticles (MPs) are sub-micron membrane vesicles (100–1000 nm) shed from normal and pathologic cells due to stimulation or apoptosis. MPs can be found in the peripheral blood circulation of healthy individuals, whereas elevated concentrations are found in pregnancy and in a variety of diseases. Also, MPs participate in physiological processes, e.g., coagulation, inflammation, and angiogenesis. Since their clinical properties are important, we have developed a new methodology based on nano-imaging that provides significant new data on MPs nanostructure, their composition and function. We are among the first to characterize by direct-imaging cryogenic transmitting electron microscopy (cryo-TEM) the near-to-native nanostructure of MP systems isolated from different cell types and stimulation procedures. We found that there are no major differences between the MP systems we have studied, as most particles were spherical, with diameters from 200 to 400 nm. However, each MP population is very heterogeneous, showing diverse morphologies. We investigated by cryo-TEM the effects of standard techniques used to isolate and store MPs, and found that either high-g centrifugation of MPs for isolation purposes, or slow freezing to –80°C for storage introduce morphological artifacts, which can influence MP nanostructure, and thus affect the efficiency of these particles as future diagnostic tools.

Issman, Liron; Brenner, Benjamin; Talmon, Yeshayahu; Aharon, Anat

2013-01-01

395

Scanning electron microscopy of upper urinary tract tumors.  

PubMed

Scanning electron microscopy (SEM) was performed on specimens from 16 patients with low-grade tumors, and 4 patients with benign lesions of the upper urinary tract. Pleomorphic microvilli could be seen at a low frequency on the majority of the tumor specimens as well as on surface cells of specimens from patients with inverted papilloma, fibroepithelial polyp, and hydronephrosis. The SEM appearance of the lining cells was similar whether the specimen was obtained from a patient with a tumor, or an inflammatory or proliferative lesion. Furthermore, pleomorphic microvilli were observed in five histologically normal bladders in which the covering cells had been rubbed off with a cold loop of a resectoscope. Pleomorphic microvilli are thus not morphologic markers of preneoplastic hyperplasia or tumor. It is likely that their presence merely reflects an increased rate of detachment of superficial epithelial cells which are replaced by cells from the deeper part of the epithelium. The demonstration of pleomorphic microvilli is therefore of questionable value in the preoperative diagnosis of tumors of the upper urinary tract and, consequently, their significance must be re-evaluated. PMID:6744216

Anderström, C; Hansson, H A; Johansson, S L

1984-09-01

396

Quantitative optical microscopy: measurement of cellular biophysical features with a standard optical microscope.  

PubMed

We describe the use of a standard optical microscope to perform quantitative measurements of mass, volume, and density on cellular specimens through a combination of bright field and differential interference contrast imagery. Two primary approaches are presented: noninterferometric quantitative phase microscopy (NIQPM), to perform measurements of total cell mass and subcellular density distribution, and Hilbert transform differential interference contrast microscopy (HTDIC) to determine volume. NIQPM is based on a simplified model of wave propagation, termed the paraxial approximation, with three underlying assumptions: low numerical aperture (NA) illumination, weak scattering, and weak absorption of light by the specimen. Fortunately, unstained cellular specimens satisfy these assumptions and low NA illumination is easily achieved on commercial microscopes. HTDIC is used to obtain volumetric information from through-focus DIC imagery under high NA illumination conditions. High NA illumination enables enhanced sectioning of the specimen along the optical axis. Hilbert transform processing on the DIC image stacks greatly enhances edge detection algorithms for localization of the specimen borders in three dimensions by separating the gray values of the specimen intensity from those of the background. The primary advantages of NIQPM and HTDIC lay in their technological accessibility using "off-the-shelf" microscopes. There are two basic limitations of these methods: slow z-stack acquisition time on commercial scopes currently abrogates the investigation of phenomena faster than 1 frame/minute, and secondly, diffraction effects restrict the utility of NIQPM and HTDIC to objects from 0.2 up to 10 (NIQPM) and 20 (HTDIC) ?m in diameter, respectively. Hence, the specimen and its associated time dynamics of interest must meet certain size and temporal constraints to enable the use of these methods. Excitingly, most fixed cellular specimens are readily investigated with these methods. PMID:24747818

Phillips, Kevin G; Baker-Groberg, Sandra M; McCarty, Owen J T

2014-01-01

397

Time-resolved fluorescence microscopy for quantitative Ca2+ imaging in living cells.  

PubMed

Calcium (Ca(2+)) is a ubiquitous intracellular second messenger and involved in a plethora of cellular processes. Thus, quantification of the intracellular Ca(2+) concentration ([Ca(2+)]i) and of its dynamics is required for a comprehensive understanding of physiological processes and potential dysfunctions. A powerful approach for studying [Ca(2+)]i is the use of fluorescent Ca(2+) indicators. In addition to the fluorescence intensity as a common recording parameter, the fluorescence lifetime imaging microscopy (FLIM) technique provides access to the fluorescence decay time of the indicator dye. The nanosecond lifetime is mostly independent of variations in dye concentration, allowing more reliable quantification of ion concentrations in biological preparations. In this study, the feasibility of the fluorescent Ca(2+) indicator Oregon Green Bapta-1 (OGB-1) for two-photon fluorescence lifetime imaging microscopy (2P-FLIM) was evaluated. In aqueous solution, OGB-1 displayed a Ca(2+)-dependent biexponential fluorescence decay behaviour, indicating the presence of a Ca(2+)-free and Ca(2+)-bound dye form. After sufficient dye loading into living cells, an in situ calibration procedure has also unravelled the Ca(2+)-free and Ca(2+)-bound dye forms from a global biexponential fluorescence decay analysis, although the dye's Ca(2+) sensitivity is reduced. Nevertheless, quantitative [Ca(2+)]i recordings and its stimulus-induced changes in salivary gland cells could be performed successfully. These results suggest that OGB-1 is suitable for 2P-FLIM measurements, which can gain access to cellular physiology. PMID:23975087

Sagolla, Kristina; Löhmannsröben, Hans-Gerd; Hille, Carsten

2013-10-01

398

A Transmission Electron Microscopy Study of Presolar Hibonite  

NASA Astrophysics Data System (ADS)

We report isotopic and microstructural data on five presolar hibonite grains (KH1, KH2, KH6, KH15, and KH21) identified in an acid residue of the Krymka LL3.1 ordinary chondrite. Isotopic measurements by secondary ion mass spectrometry (SIMS) verified a presolar circumstellar origin for the grains. Transmission electron microscopy (TEM) examination of the crystal structure and chemistry of the grains was enabled by in situ sectioning and lift-out with a focused-ion-beam scanning-electron microscope (FIB-SEM). Comparisons of isotopic compositions with models indicate that four of the five grains formed in low-mass stars that evolved through the red giant/asymptotic giant branches (RGBs/AGBs), whereas one grain formed in the ejecta of a Type II supernova. Selected-area electron-diffraction patterns show that all grains are single crystals of hibonite. Some grains contain minor structural perturbations (stacking faults) and small spreads in orientation that can be attributed to a combination of growth defects and mechanical processing by grain-grain collisions. The similar structure of the supernova grain to those from RGB/AGB stars indicates a similarity in the formation conditions. Radiation damage (e.g., point defects), if present, occurs below our detection limit. Of the five grains we studied, only one has the pure hibonite composition of CaAl12O19. All others contain minor amounts of Mg, Si, Ti, and Fe. The microstructural data are generally consistent with theoretical predictions, which constrain the circumstellar condensation temperature to a range of 1480-1743 K, assuming a corresponding total gas pressure between 1 × 10-6 and 1 × 10-3 atm. The TEM data were also used to develop a calibration for SIMS determination of Ti contents in oxide grains. Grains with extreme 18O depletions, indicating deep mixing has occurred in their parent AGB stars, are slightly Ti enriched compared with grains from stars without deep mixing, most likely reflecting differences in grain condensation conditions.

Zega, Thomas J.; Alexander, Conel M. O'D.; Nittler, Larry R.; Stroud, Rhonda M.

2011-04-01

399

New electron microscopy techniques of the study of meteoritic metal.  

SciTech Connect

Metallic Phases in extraterrestrial materials are composed of Fe-Ni with minor amounts of Co, P, Si, Cr, etc. Electron microscopy techniques (SEM, TEM, EPMA, AEM) have been used for almost 50 years to study micron and submicron microscopic features in the metal phases (Fig. 1) such as clear taenite, cloudy zone, plessite, etc [1,2]. However lack of instrumentation to prepare TEM thin foils in specific sample locations and to obtain micro-scale crystallographic data have limited these investigations. New techniques such as the focused ion beam (FIB) and the electron backscatter electron diffraction (EBSD) techniques have overcome these limitations. The application of the FIB instrument has allowed us to prepare {approx}10 um long by {approx} 5um deep TEM thin sections of metal phases from specific regions of metal particles, in chondrites, irons and stony iron meteorites, identified by optical and SEM observation. Using a FEI dual beam FIB we were able to study very small metal particles in samples of CH chondrites [3] and zoneless plessite (ZP) in ordinary chondrites. Fig. 2 shows a SEM photomicrograph of a {approx}40 um ZP particle in Kernouve, a H6 chondrite. Fig. 3a,b shows a TEM photograph of a section of the FIB prepared TEM foil of the ZP particle and a Ni trace through a tetrataenite/kamacite region of the particle. It has been proposed that the Widmanstatten pattern in low P iron meteorites forms by martensite decomposition, via the reaction {gamma} {yields} {alpha}{sub 2} + {gamma} {yields} {alpha} + {gamma} in which {alpha}{sub 2}, martensite, decomposes to the equilibrium {alpha} and {gamma} phases during the cooling process [4]. In order to show if this mechanism for Widmanstatten pattern formation is correct, crystallographic information is needed from the {gamma} or taenite phases throughout a given meteorite. The EBSD technique was employed in this study to obtain the orientation of the taenite surrounding the initial martensite phase and the kamacite which forms as {alpha}{sub 2} or as Widmanstatten plates in a series of IVB irons. Fig. 4a,b shows EBSD orientation maps of taenite and kamacite from the Tawallah Valley IVB iron. We observe that the orientation of the taenite in the IVB meteorites is the same throughout the sample consistent with the orientation of the high temperature single phase taenite before formation of the Widmanstatten pattern.

Michael, Joseph Richard; Goldstein, Joseph I. (University of Massachusetts, Amherst, MA); Kotula, Paul Gabriel; Jones, R. H. (University of New Mexico, Albuquerque, NM.)

2005-02-01

400

Environmental Scanning Electron Microscopy (ESEM) of Atmospheric Ices  

NASA Astrophysics Data System (ADS)

Water ice and nitric acid hydrates exhibit very different particle morphologies, which have an enormous impact on its ability to scatter and reflect light. This has an effect not only on the detection of ice particles by satellite instruments or ground-based optical remote sensing but also interferes with earth's radiation balance. Since detailed morphological investigations in the atmosphere are hampered due to an interference of the microscopic technique to the ice particles, one is dependent on laboratory model experiments. In the past, a scanning electron microscope required a sufficient vacuum in the sample chamber in order to prevent a diversion of the electron beam. Modern environmental electron microscopy uses an imaging gas (water or nitrogen), which connects different advantages and prevents several handicaps. Firstly, the imaging gas works as secondary-emission multiplier. Secondly, the gas discharges the sample surface regularly and makes insulators accessible to SEM. Thirdly, a mixture of water and nitrogen prevents dehydration of the sample. Here, we present ESEM pictures of nitric acid hydrates and water ices. These particles exhibit morphological changes during an annealing program which can be related to respective phase changes, which have been corroborated by X-ray diffraction and vibrational spectroscopy in former experiments. [1,2] Different techniques of sample preparation have been applied, which range from gas phase deposition, to quenching techniques and oil-matrix isolation of frozen droplets. Beside the assignment of ice and hydrate particles and the evaluation of their impact on the spectroscopic data, we could also identify phase separations into hydrates/ice and impurities. This is an interesting result since it gives an idea of the topology of frozen atmospheric particles, which comprise a mixture of different organic and inorganic substances.[3] [1] H. Grothe, H. Tizek and I. K. Ortega \\Metastable Nitric Acid Hydrates - Possible Constituents of Polar Stratospheric Clouds?\\ Faraday Discussion 2008, 137, 223-234. [2] H. Grothe, H. Tizek, D. Waller and D. J. Stokes \\The crystallization kinetics and morphology of nitric acid trihydrate\\ Phys. Chem. Chem. Phys. 2006, 8, 2232-2239. [3] B. J. Murray \\Inhibition of ice crystallisation in highly viscous aqueous organic acid droplets\\ Atmospheric Chemistry and Physics Discussion, 2008, 8, 3992-3995.

Grothe, H.; Baloh, P.; Whitmore, K.; Waller, D.

2009-04-01

401

Determination of the coalescence temperature of latexes by environmental scanning electron microscopy.  

PubMed

A new methodology for quantitative characterization of the coalescence process of waterborne polymer dispersion (latex) particles by environmental scanning electron microscopy (ESEM) is proposed. The experimental setup has been developed to provide reproducible latex monolayer depositions, optimized contrast of the latex particles, and a reliable readout of the sample temperature. Quantification of the coalescence process under dry conditions has been performed by image processing based on evaluation of the image autocorrelation function. As a proof of concept the coalescence of two latexes with known and differing glass transition temperatures has been measured. It has been shown that a reproducibility of better than 1.5 °C can be obtained for the measurement of the coalescence temperature. PMID:22812417

Gonzalez, Edurne; Tollan, Christopher; Chuvilin, Andrey; Barandiaran, Maria J; Paulis, Maria

2012-08-01

402

Detection of Secondary and Supersecondary Structures of Proteins from Cryo-Electron Microscopy  

PubMed Central

Recent advances in three-dimensional electron microscopy (3D EM) have enabled the quantitative visualization of the structural building blocks of proteins at improved resolutions. We provide algorithms to detect the secondary structures (?-helices and ?-sheets) from proteins for which the volumetric maps are reconstructed at 6–10Å resolution. Additionally, we show that when the resolution is coarser than 10Å, some of the super-secondary structures can be detected from 3D EM maps. For both these algorithms, we employ tools from computational geometry and differential topology, specifically the computation of stable/unstable manifolds of certain critical points of the distance function induced by the molecular surface. Our results connect mathematically well-defined constructions with bio-chemically induced structures observed in proteins.

Bajaj, Chandrajit; Goswami, Samrat; Zhang, Qin

2012-01-01

403