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1

Thermal diffuse scattering in sub-angstrom quantitative electron microscopy--phenomenon, effects and approaches  

E-print Network

Thermal diffuse scattering in sub-angstrom quantitative electron microscopy--phenomenon, effects due to thermal diffusely scattered (TDS) electrons, which were not included in the image calculation, but conventional high-resolution microscopy do contain the contribution made by phonon scattered electrons. (3

Wang, Zhong L.

2

Quantitative light and scanning electron microscopy of ferret sperm.  

PubMed

Sperm were obtained via electroejaculation from Domestic ferret, (Mustela putorius furo), Siberian ferret (M. eversmanni), Black-footed ferret (M. nigripes), and a hybrid between Siberian and Domestic, called the Fitch ferret (M. sp.). Comparisons of sperm were made by four different microscopy techniques to determine whether differences exist among species. First, Nomarski differential interference microscopy could be used to distinguish domestic ferret sperm from the others on the basis of the structure of the posterior part of the acrosome. Second, both silver staining, which demonstrates argentophilic protein distribution, and scanning electron microscopy (SEM), revealed differences among the morphology of sperm for each species; variation in the unique appearance of the acrosome in ferret sperm was detected especially well by SEM. To quantify differences in morphology, five sperm head parameters were measured using image analysis; light microscopy produced significantly larger values than did SEM (all parameters and all species but Fitch), and there were significant differences owing to species for all parameters but one. Generally, our data demonstrate the value of complementary techniques to distinguish among sperm of closely related species and more specifically may help establish evolutionary relationships among the ferret species studied. In addition, they provide baseline data important for the captive breeding of the endangered Black-footed ferret. PMID:1793602

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

1991-11-01

3

Some strategies for quantitative scanning Auger electron microscopy  

NASA Technical Reports Server (NTRS)

The general applicability of power law forms of the background in electron spectra is pointed out and exploited for background removal from under Auger peaks. This form of B(E) is found to be extremely sensitive to instrumental alignment and to fault-free construction - an observation which can be used to set up analyser configurations in an accurate way. Also, differences between N(E) and B(E) can be used to derive a spectrometer transmission function T(E). The questions of information density in an energy-analysing spatially-resolving instrument are addressed after reliable instrumental characterization has been established. Strategies involving ratio histograms, showing the population distribution of the ratio of a pair of Auger peak heights, composition scatter diagrams and windowed imaging are discussed and illustrated.

Browning, R.; Peacock, D. C.; Prutton, M.

1985-01-01

4

Electron Microscopy.  

ERIC Educational Resources Information Center

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

Beer, Michael

1980-01-01

5

Quantitative determination of the thickness of ferroelectric domain walls using weak beam transmission electron microscopy  

Microsoft Academic Search

We present a new method for the quantitative determination of the thickness of ferroelectric domain walls using transmission electron microscopy in combination with image simulation. When inclined domain walls are imaged using a weakly excited beam, we observe well resolved thickness fringes across the boundary. By simulating these fringes and fitting them to the experimental images, we can extract a

M. Foeth; P. Stadelmann; P.-A. Buffat

1999-01-01

6

Compositional analysis of GaAs/AlGaAs heterostructures using quantitative scanning transmission electron microscopy  

SciTech Connect

We demonstrate a method for compositional mapping of Al{sub x}Ga{sub 1–x}As heterostructures with high accuracy and unit cell spatial resolution using quantitative high angle annular dark field scanning transmission electron microscopy. The method is low dose relative to spectroscopic methods and insensitive to the effective source size and higher order lens aberrations. We apply the method to study the spatial variation in Al concentration in cross-sectioned GaAs/AlGaAs core-shell nanowires and quantify the concentration in the Al-rich radial band and the AlGaAs shell segments.

Kauko, H.; Helvoort, A. T. J. van [Department of Physics, Norwegian University of Science and Technology (NTNU), Trondheim (Norway); Zheng, C. L.; Glanvill, S. [Monash Centre for Electron Microscopy, Monash University, VIC 3800 (Australia)] [Monash Centre for Electron Microscopy, Monash University, VIC 3800 (Australia); Zhu, Y.; Etheridge, J., E-mail: joanne.etheridge@monash.edu [Monash Centre for Electron Microscopy, Monash University, VIC 3800 (Australia); Department of Materials Engineering, Monash University, VIC 3800 (Australia); Dwyer, C. [Monash Centre for Electron Microscopy, Monash University, VIC 3800 (Australia) [Monash Centre for Electron Microscopy, Monash University, VIC 3800 (Australia); Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, and Peter Grünberg Institute, Forschungszentrum Jülich, D-52425 Jülich (Germany); Munshi, A. M.; Fimland, B. O. [Department of Electronics and Telecommunications, Norwegian University of Science and Technology (NTNU), Trondheim (Norway)] [Department of Electronics and Telecommunications, Norwegian University of Science and Technology (NTNU), Trondheim (Norway)

2013-12-02

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. PMID:17996124

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

TOPICAL REVIEW: Quantitative electron microscopy and spectroscopy of MgB2 wires and tapes  

NASA Astrophysics Data System (ADS)

In MgB2 the correlation of microstructure with superconducting properties, in particular the critical current density, requires powerful analytical tools. Critical current densities and electrical resistivities of different MgB2 superconductors differ by orders of magnitudes and the current limiting mechanisms have not been fully understood. Granularity of MgB2 is one significant reason for reduced critical current densities and is introduced intrinsically by the anisotropy of Bc2 but also extrinsically by the microstructure of the material. Bc2 enhancement by doping is another important challenge for chemical analysis and, at present, doping levels are not well controlled on the sub-µm scale. In this paper the quantitative electron microscopy and spectroscopy methods essential for the microstructural analysis of MgB2 are described. By quantitative electron microscopy and spectroscopy we mean a combined SEM and TEM analysis that covers various length scales from µm to nm. Contamination-free sample preparation, chemical mapping including B, and advanced chemical quantification using x-ray microanalysis were essential elements of the applied methodology. The methodology was applied to in situ and ex situ MgB2 wires and tapes with and without SiC additives. Quantitative B analysis by EDX spectroscopy was applied quantitatively in the SEM and TEM, which is a major achievement. Although MgB2 is a binary system, the thermodynamics of phase formation is complex, and the complexity is dramatically increased if additives like SiC are used. The small, sub-µm grain sizes of the matrix and secondary phases require TEM methods. However, granularity on the µm scale was also identified and underlines the importance of the combined SEM and TEM studies. Significant differences in the microstructure were observed for in situ and ex situ samples. This holds particularly if SiC was added and yielded Mg2Si for in situ samples annealed at 600-650 °C and Mg-Si-O phases for ex situ samples annealed between 900-1050 °C. Only with such a systematic approach combining a large number of microscopy and spectroscopy methods, could a microstructure critical current density model be established that will be presented in another paper. Four microstructural parameters were identified as relevant for the critical current density of wires and tapes and these were: (1) MgB2 grain size, (2) colony size (a colony is a dense arrangement of MgB2 grains), (3) oxygen content and (4) volume fraction of B-rich secondary phases. MgB2 grain size can only be determined by TEM, while colony size, oxygen content and volume fraction of B-rich secondary phases were determined by SEM methods. The formation of oxides was also studied in detail by TEM methods. The importance of electron microscopy methods in the understanding of the thermodynamics of phase formation in MgB2 as well as in improving the synthesis technology and the superconducting properties of MgB2 wires and tapes is described.

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

2008-07-01

10

Is scanning electron microscopy/energy dispersive X-ray spectrometry (SEM/EDS) quantitative?  

PubMed

Scanning electron microscopy/energy dispersive X-ray spectrometry (SEM/EDS) is a widely applied elemental microanalysis method capable of identifying and quantifying all elements in the periodic table except H, He, and Li. By following the "k-ratio" (unknown/standard) measurement protocol development for electron-excited wavelength dispersive spectrometry (WDS), SEM/EDS can achieve accuracy and precision equivalent to WDS and at substantially lower electron dose, even when severe X-ray peak overlaps occur, provided sufficient counts are recorded. Achieving this level of performance is now much more practical with the advent of the high-throughput silicon drift detector energy dispersive X-ray spectrometer (SDD-EDS). However, three measurement issues continue to diminish the impact of SEM/EDS: (1) In the qualitative analysis (i.e., element identification) that must precede quantitative analysis, at least some current and many legacy software systems are vulnerable to occasional misidentification of major constituent peaks, with the frequency of misidentifications rising significantly for minor and trace constituents. (2) The use of standardless analysis, which is subject to much broader systematic errors, leads to quantitative results that, while useful, do not have sufficient accuracy to solve critical problems, e.g. determining the formula of a compound. (3) EDS spectrometers have such a large volume of acceptance that apparently credible spectra can be obtained from specimens with complex topography that introduce uncontrolled geometric factors that modify X-ray generation and propagation, resulting in very large systematic errors, often a factor of ten or more. PMID:22886950

Newbury, Dale E; Ritchie, Nicholas W M

2013-01-01

11

Application of Quantitative Electron Microscopy to the Study of Mycobacterium lepraemurium and M. leprae  

Microsoft Academic Search

SUMMARY: The standard methods for assessing viability of micro-organisms are not applicable to rat and human leprosy bacilli since neither organism can be grown in vitro. McFadzean & Valentine (1958,1959) suggested that the electron microscope might provide a quantitative guide to the viability of these organisms by allowing dead forms to be identified. This technique is further investigated and shown

R. J. W. REES; R. C. VALENTINE; P. C. WONG

1960-01-01

12

Investigation of boron implantation into silicon by quantitative energy-filtered transmission electron microscopy  

NASA Astrophysics Data System (ADS)

High-resolution electron microscopy (HREM), chemical mapping by energy-filtered transmission electron microscopy (EFTEM), electron energy-loss spectroscopy (EELS) and energy-loss spectroscopic profiling (ELSP), also called spectroscopic transverse image profiling by EFTEM (stripeTEM) have been combined to study the distribution of boron after implantation into silicon at low energy (0.5keV) and rapid thermal annealing. The key to the experiments is that stripeTEM combines both ~1nm spatial resolution and sub-at% sensitivity. It is shown that the near-surface spike of boron visible in secondary ion mass spectrometry (SIMS) profiles is an artefact of surface profiling. The real distribution of boron is several nm deeper into the specimen, in agreement with both Monte Carlo simulations and shoulders apparent in the SIMS profile. Quantification of the experimental stripeTEM data shows that the B concentration is approximately ~2at% in the SiO2 and ~4at% in the Si, with statistical errors of about ±0.2at% due to noise and background fitting and systematic errors of ±0.6at% due to uncertainties in the scattering cross-sections.

Walther, T.; England, J.

2011-11-01

13

Development of a new quantitative X-ray microanalysis method for electron microscopy.  

PubMed

Quantitative X-ray microanalysis of thick samples is usually performed by measuring the characteristic X-ray intensities of each element in a sample and in corresponding standards. The ratio of the measured intensities from the unknown material to that from the standard is related to the concentration using the ZAF or ?(?z) equations. Under optimal conditions, accuracies approaching 1% are possible. However, all the experimental conditions must remain the same during the sample and standard measurements. This is not possible with cold field emission scanning electron microscopes (FE-SEMs) where beam current can fluctuate around 5% in its stable regime. Very little work has been done on variable beam current conditions (Griffin, B.J. & Nockolds, C.E., Scanning 13, 307-312, 1991), and none relating to cold FE-SEM applications. To address this issue, a new method was developed using a single spectral measurement. It is similar in approach to the Cliff-Lorimer method developed for the analytical transmission electron microscope. However, corrections are made for X rays generated from thick specimens using the ratio of the characteristic X-ray intensities of two elements in the same material. The proposed method utilizes the ratio of the intensity of a characteristic X-ray normalized by the sum of X-ray intensities of all the elements measured for the sample, which should also reduce the amplitude of error propagation. Uncertainties in the physical parameters of X-ray generation are corrected using a calibration factor that must be previously acquired or calculated. As an example, when this method was applied to the calculation of the composition of Au-Cu National Institute of Standards and Technology standards measured with a cold field emission source SEM, relative accuracies better than 5% were obtained. PMID:20961482

Horny, Paula; Lifshin, Eric; Campbell, Helen; Gauvin, Raynald

2010-12-01

14

Quantitative dynamic footprinting microscopy.  

PubMed

Quantitative dynamic footprinting (qDF) allows visualization of the footprints of live leukocytes rolling on a selectin-coated cover glass. qDF works on the principle of total internal reflection fluorescence, which involves fluorescence excitation in a thin slice (~200 nm) of the cell proximal to the cover glass while the rest of the cell remains dark. Dual color qDF (DqDF) is an advancement of qDF, which enables simultaneous visualization of two fluorochromes in the footprints of rolling leukocytes. When the fluorochrome is localized either in the cell cytoplasm or plasma membrane, the two-dimensional qDF image is used to create a three-dimensional rendition of the footprint topography. DqDF is a useful tool to study leukocyte adhesion under flow, and has recently been used to reveal mechanisms that enable neutrophils to roll at high shear stresses that prevail in venules during inflammation. PMID:23478358

Sundd, Prithu; Ley, Klaus

2013-04-01

15

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. PMID:22709926

2012-01-01

16

A technique for quantitative and qualitative viewing of aquatic bacteria using scanning electron microscopy  

E-print Network

, and 100K EtOH. The filters are then critical point dried with liquid C02, mounted on SEM stubs with double stick tape, and coated with gold-pallad1um. Estimates of the number of bacter1a per f1lter are made by counting random areas of the filter... observed with SEM. Bacteria counts of pond samples were two to four times higher using SEM than light microscopy, 150 to 300 times higher than the extinction dilution method, and 2, 000 to 3, 000 times higher than the spread plate method. Bacteria were...

Dreier, Thomas Michael

2012-06-07

17

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

18

Virtual Scanning Electron Microscopy  

NSDL National Science Digital Library

This site from Florida State University features an interactive Java tutorial that explores various aspects of virtual scanning electron microscopy. Users can see how specimens appear when magnified in the virtual SEM. The site also features an image gallery and extensive information about different types of microscopy.

Davidson, Michael W.; Kunkel, Dennis; Parry-Hill, Matthew J.; University, Florida S.

19

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. PMID:20696933

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

2010-01-01

20

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. PMID:24482357

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

2014-01-01

21

Conventional transmission electron microscopy.  

PubMed

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. PMID:24482357

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

2014-02-01

22

Single particle electron microscopy  

Microsoft Academic Search

Electron microscopy (EM) in combination with image analysis is a powerful technique to study protein structures at low, medium,\\u000a and high resolution. Since electron micrographs of biological objects are very noisy, improvement of the signal-to-noise ratio\\u000a by image processing is an integral part of EM, and this is performed by averaging large numbers of individual projections.\\u000a Averaging procedures can be

Egbert J. Boekema; Mihaela Folea; Roman Kou?il

2009-01-01

23

Dynamic Transmission Electron Microscopy  

SciTech Connect

Dynamic transmission electron microscopy (DTEM) combines the benefits of high spatial resolution electron microscopy with the high temporal resolution of ultrafast lasers. The incorporation of these two components into a single instrument provides a perfect platform for in situ observations of material processes. However, previous DTEM applications have focused on observing structural changes occurring in samples exposed to high vacuum. Therefore, in order to expand the pump-probe experimental regime to more natural environmental conditions, in situ gas and liquid chambers must be coupled with Dynamic TEM. This chapter describes the current and future applications of in situ liquid DTEM to permit time-resolved atomic scale observations in an aqueous environment, Although this chapter focuses mostly on in situ liquid imaging, the same research potential exists for in situ gas experiments and the successful integration of these techniques promises new insights for understanding nanoparticle, catalyst and biological protein dynamics with unprecedented spatiotemporal resolution.

Evans, James E.; Jungjohann, K. L.; Browning, Nigel D.

2012-10-12

24

3D imaging and quantitative analysis of small solubilized membrane proteins and their complexes by transmission electron microscopy  

PubMed Central

Inherently unstable, detergent-solubilized membrane protein complexes can often not be crystallized. For complexes that have a mass of >300 kDa, cryo-electron microscopy (EM) allows their three-dimensional (3D) structure to be assessed to a resolution that makes secondary structure elements visible in the best case. However, many interesting complexes exist whose mass is below 300 kDa and thus need alternative approaches. Two methods are reviewed: (i) Mass measurement in a scanning transmission electron microscope, which has provided important information on the stoichiometry of membrane protein complexes. This technique is applicable to particulate, filamentous and sheet-like structures. (ii) 3D-EM of negatively stained samples, which determines the molecular envelope of small membrane protein complexes. Staining and dehydration artifacts may corrupt the quality of the 3D map. Staining conditions thus need to be optimized. 3D maps of plant aquaporin SoPIP2;1 tetramers solubilized in different detergents illustrate that the flattening artifact can be partially prevented and that the detergent itself contributes significantly. Another example discussed is the complex of G protein-coupled receptor rhodopsin with its cognate G protein transducin. PMID:23267047

Vahedi-Faridi, Ardeschir; Jastrzebska, Beata; Palczewski, Krzysztof; Engel, Andreas

2013-01-01

25

Structure, ordering, and surfaces of Pt-Fe alloy catalytic nanoparticles from quantitative electron microscopy and X-ray diffraction  

NASA Astrophysics Data System (ADS)

The current challenge in catalyst development is to produce highly active and economical catalysts. This challenge cannot be overcome without an accurate understanding of catalyst structure, surfaces and morphology as the catalytic reactions occur on the surface active sites. Transmission Electron Microscopy (TEM) is an excellent tool for understanding the structures of the nanoparticles down to the atomic level in determining the relationship with the catalyst's performance in fuel cell applications. This paper describes a detailed structural characterization of Pt-Fe nanoparticles using aberration corrected TEM. Detailed analysis regarding the morphology, structural ordering, facets, nature of the surfaces, atomic displacements and compositions was carried out and presented in the context of their electrochemical performances. In addition, the effects of electrochemical cycling in terms of morphology and composition evolution of the nanoparticles were analyzed. Lastly, along with data from X-ray diffractometry, two different crystallographic models of the unknown Pt3Fe2 nanoparticle phase are proposed. The detailed characterization by TEM provides useful insights into the nanoparticle chemistry and structure that contributes to catalyst development for next generation fuel cells.The current challenge in catalyst development is to produce highly active and economical catalysts. This challenge cannot be overcome without an accurate understanding of catalyst structure, surfaces and morphology as the catalytic reactions occur on the surface active sites. Transmission Electron Microscopy (TEM) is an excellent tool for understanding the structures of the nanoparticles down to the atomic level in determining the relationship with the catalyst's performance in fuel cell applications. This paper describes a detailed structural characterization of Pt-Fe nanoparticles using aberration corrected TEM. Detailed analysis regarding the morphology, structural ordering, facets, nature of the surfaces, atomic displacements and compositions was carried out and presented in the context of their electrochemical performances. In addition, the effects of electrochemical cycling in terms of morphology and composition evolution of the nanoparticles were analyzed. Lastly, along with data from X-ray diffractometry, two different crystallographic models of the unknown Pt3Fe2 nanoparticle phase are proposed. The detailed characterization by TEM provides useful insights into the nanoparticle chemistry and structure that contributes to catalyst development for next generation fuel cells. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr31509b

Chan, Mickey C. Y.; Chen, Liang; Nan, Feihong; Britten, James F.; Bock, Christina; Botton, Gianluigi A.

2012-10-01

26

A quantitative estimation of the exhaust, abrasion and resuspension components of particulate traffic emissions using electron microscopy  

NASA Astrophysics Data System (ADS)

The contribution of the three traffic-related components exhaust, abrasion, and resuspension to kerbside and urban background PM10 and PM1 levels was quantified based on the analysis of individual particles by scanning electron microscopy. A total of 160 samples was collected on 38 days between February and September 2009 at a kerbside and an urban background station in the urban/industrial Ruhr area (Germany). Based on size, morphology, chemical composition and stability under electron bombardment, the 111,003 particles studied in detail were classified into the following 14 particle classes: traffic/exhaust, traffic/abrasion, traffic/resuspension, carbonaceous/organic, industry/metallurgy, industry/power plants, secondary particles, (aged) sea salt, silicates, Ca sulfates, carbonates, Fe oxides/hydroxides, biological particles, and other particles. The traffic/exhaust component consists predominantly of externally mixed soot particles and soot internally mixed with secondary particles. The traffic/abrasion component contains all particles with characteristic tracer elements (Fe, Cu, Ba, Sb, Zn) for brake and tire abrasion. The traffic/resuspension component is defined by the mixing state and comprises all internally mixed particles with a high proportion of silicates or Fe oxides/hydroxides which contain soot or abrasion particles as minor constituent. In addition, silicates and Fe oxides/hydroxides internally mixed with chlorine and sulphur containing particles were also assigned to the traffic/resuspension component. The total contribution of traffic to PM10 was found to be 27% at the urban background station and 48% at the kerbside station, the corresponding values for PM1 are 15% and 39%. These values lie within the range reported in previous literature. The relative share of the different traffic components for PM10 at the kerbside station was 27% exhaust, 15% abrasion, and 58% resuspension (38%, 8%, 54% for PM1). For the urban background, the following relative shares were obtained for PM10: 22% exhaust, 22% abrasion and 56% resuspension (40%, 27%, 33% for PM1). Compared to previous publications we have observed a significantly lower portion of exhaust particles and a significantly higher portion of resuspension particles. The high abundance of resuspension particles underlines their significance for the observed adverse health effects of traffic emissions and for mitigation measures.

Weinbruch, Stephan; Worringen, Annette; Ebert, Martin; Scheuvens, Dirk; Kandler, Konrad; Pfeffer, Ulrich; Bruckmann, Peter

2014-12-01

27

The Effect of Substrates / Ligands on Metal Nanocatalysts Investigated By Quantitative Z-Contrast Imaging and High Resolution Electron Microscopy  

E-print Network

The Effect of Substrates / Ligands on Metal Nanocatalysts Investigated By Quantitative Z- Contrast of the cluster-substrates relationship for consideration in real applications. INTRODUCTION Nanocatalysts we

Frenkel, Anatoly

28

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

29

Rigorous quantitative elemental microanalysis by scanning electron microscopy/energy dispersive x-ray spectrometry (SEM/EDS) with spectrum processing by NIST DTSA-II  

NASA Astrophysics Data System (ADS)

Quantitative electron-excited x-ray microanalysis by scanning electron microscopy/silicon drift detector energy dispersive x-ray spectrometry (SEM/SDD-EDS) is capable of achieving high accuracy and high precision equivalent to that of the high spectral resolution wavelength dispersive x-ray spectrometer even when severe peak interference occurs. The throughput of the SDD-EDS enables high count spectra to be measured that are stable in calibration and resolution (peak shape) across the full deadtime range. With this high spectral stability, multiple linear least squares peak fitting is successful for separating overlapping peaks and spectral background. Careful specimen preparation is necessary to remove topography on unknowns and standards. The standards-based matrix correction procedure embedded in the NIST DTSA-II software engine returns quantitative results supported by a complete error budget, including estimates of the uncertainties from measurement statistics and from the physical basis of the matrix corrections. NIST DTSA-II is available free for Java-platforms at: http://www.cstl.nist.gov/div837/837.02/epq/dtsa2/index.html).

Newbury, Dale E.; Ritchie, Nicholas W. M.

2014-09-01

30

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

31

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

32

Automated cryo-electron microscopy  

Microsoft Academic Search

Cryo-electron microscopy is widely viewed as a uniquely powerful method for the study of membrane proteins and large macromolecular complexes - subjects that are viewed as extremely challenging or impossible to study using x-ray or NMR methods. Although the methodology of molecular microscopy has enormous potential, it is time consuming and labor intensive. Our group has done extensive work to

Clinton S. Potter; D. Fellmann; Ron A. Milligan; Jim Pulokas; C. Suloway; Yuanxin Zhu; A. Carragher

2002-01-01

33

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

34

Four-dimensional electron microscopy.  

PubMed

The discovery of the electron over a century ago and the realization of its dual character have given birth to one of the two most powerful imaging instruments: the electron microscope. The electron microscope's ability to resolve three-dimensional (3D) structures on the atomic scale is continuing to affect different fields, including materials science and biology. In this Review, we highlight recent developments and inventions made by introducing the fourth dimension of time in electron microscopy. Today, ultrafast electron microscopy (4D UEM) enables a resolution that is 10 orders of magnitude better than that of conventional microscopes, which are limited by the video-camera rate of recording. After presenting the central concept involved, that of single-electron stroboscopic imaging, we discuss prototypical applications, which include the visualization of complex structures when unfolding on different length and time scales. The developed UEM variant techniques are several, and here we illucidate convergent-beam and near-field imaging, as well as tomography and scanning-pulse microscopy. We conclude with current explorations in imaging of nanomaterials and biostructures and an outlook on possible future directions in space-time, 4D electron microscopy. PMID:20378810

Zewail, Ahmed H

2010-04-01

35

Application of Electron Diffraction to Biological Electron Microscopy  

PubMed Central

Three methods by which electron diffraction may be applied to problems in electron microscopy are discussed from a fundamental point of view, and experimental applications with biological specimens are demonstrated for each case. It is shown that wide-angle electron diffraction provides valuable information for evaluating specimen damage that can occur either during specimen preparation or while in the electron beam. Dark-field electron microscopy can be used both to enhance the image contrast and to provide highly restricted and therefore highly specific information about the object. Low-angle electron diffraction provides quantitative information about the object structure in the range from 20 A to ? 1000 A. Lowangle electron diffraction also demonstrates the important role of Fourier contrast with biological specimens, which are usually characterized by structural features with dimensions of 20 A or larger. ImagesFigure 1Figure 2Figure 5Figure 6Figure 7Figure 8Figure 9Figure 10Figure 11Figure 13 PMID:4896898

Glaeser, Robert M.; Thomas, Gareth

1969-01-01

36

Quantitative determination of low-Z elements in single atmospheric particles on boron substrates by automated scanning electron microscopy-energy-dispersive X-ray spectrometry.  

PubMed

Atmospheric aerosols consist of a complex heterogeneous mixture of particles. Single-particle analysis techniques are known to provide unique information on the size-resolved chemical composition of aerosols. A scanning electron microscope (SEM) combined with a thin-window energy-dispersive X-ray (EDX) detector enables the morphological and elemental analysis of single particles down to 0.1 microm with a detection limit of 1-10 wt %, low-Z elements included. To obtain data statistically representative of the air masses sampled, a computer-controlled procedure can be implemented in order to run hundreds of single-particle analyses (typically 1000-2000) automatically in a relatively short period of time (generally 4-8 h, depending on the setup and on the particle loading). However, automated particle analysis by SEM-EDX raises two practical challenges: the accuracy of the particle recognition and the reliability of the quantitative analysis, especially for micrometer-sized particles with low atomic number contents. Since low-Z analysis is hampered by the use of traditional polycarbonate membranes, an alternate choice of substrate is a prerequisite. In this work, boron is being studied as a promising material for particle microanalysis. As EDX is generally said to probe a volume of approximately 1 microm3, geometry effects arise from the finite size of microparticles. These particle geometry effects must be corrected by means of a robust concentration calculation procedure. Conventional quantitative methods developed for bulk samples generate elemental concentrations considerably in error when applied to microparticles. A new methodology for particle microanalysis, combining the use of boron as the substrate material and a reverse Monte Carlo quantitative program, was tested on standard particles ranging from 0.25 to 10 microm. We demonstrate that the quantitative determination of low-Z elements in microparticles is achievable and that highly accurate results can be obtained using the automatic data processing described here compared to conventional methods. PMID:16131082

Choël, Marie; Deboudt, Karine; Osán, János; Flament, Pascal; Van Grieken, René

2005-09-01

37

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. PMID:15883380

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

2005-01-01

38

ELECTRON MICROSCOPY IN THE CONTEXT OF STRUCTURAL  

E-print Network

6 ELECTRON MICROSCOPY IN THE CONTEXT OF STRUCTURAL SYSTEMS BIOLOGY Niels Volkmann and Dorit Hanein andcomputational techniques, electron microscopy has matured into a powerful and diverse collection of methods;(0.3 nm). Many of the restrictions of X-ray crystallography or NMR spectroscopy do not apply to electron

Bourne, Philip E.

39

Thermal diffuse scattering in transmission electron microscopy.  

PubMed

In conventional transmission electron microscopy, thermal scattering significantly affects the image contrast. It has been suggested that not accounting for this correctly is the main cause of the Stobbs factor, the ubiquitous, large contrast mismatch found between theory and experiment. In the case where a hard aperture is applied, we show that previous conclusions drawn from work using bright field scanning transmission electron microscopy and invoking the principle of reciprocity are reliable in the presence of thermal scattering. In the aperture-free case it has been suggested that even the most sophisticated mathematical models for thermal diffuse scattering lack in their numerical implementation, specifically that there may be issues in sampling, including that of the contrast transfer function of the objective lens. We show that these concerns can be satisfactorily overcome with modest computing resources; thermal scattering can be modelled accurately enough for the purpose of making quantitative comparison between simulation and experiment. Spatial incoherence of the source is also investigated. Neglect or inadequate handling of thermal scattering in simulation can have an appreciable effect on the predicted contrast and can be a significant contribution to the Stobbs factor problem. PMID:22088442

Forbes, B D; D'Alfonso, A J; Findlay, S D; Van Dyck, D; Lebeau, J M; Stemmer, S; Allen, L J

2011-12-01

40

Electron microscopy and microanalysis Two transmission electron microscopes  

E-print Network

Electron microscopy and microanalysis Two transmission electron microscopes (TEM) and three scanning electron micro- scopes (SEM) are operated by the De- partment. Attachments for TEM include energy dispersive X-ray spectrometer (EDS), scanning transmission attachment, serial electron energy loss

41

Imaging without Fluorescence: Nonlinear Optical Microscopy for Quantitative Cellular Imaging.  

PubMed

Quantitative single-cell analysis enables the characterization of cellular systems with a level of detail that cannot be achieved with ensemble measurement. In this Feature we explore quantitative cellular imaging applications with nonlinear microscopy techniques. We first offer an introductory tutorial on nonlinear optical processes and then survey a range of techniques that have proven to be useful for quantitative live cell imaging without fluorescent labels. PMID:25079337

Streets, Aaron M; Li, Ang; Chen, Tao; Huang, Yanyi

2014-09-01

42

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.

43

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

44

Probing the Proton with Electron Microscopy  

NASA Astrophysics Data System (ADS)

This article is written as a tribute and memorial to Dr. Akira Tonomura who was an outstanding experimental physicist and a friend. Early in his career, he opened a new era in electron microscopy by demonstrating in 1968 that electron holography, proposed by Gabor in 1949, was possible; and later he developed Lorentz "phase" microscopy, which allows one to generate real-space, real-time images. All through his career, he perfected these designs into superb instruments that he employed to investigate fundamental questions in physics. Dr. Tonomura set world standards for electron microscopy.

Friedman, Jerome I.

2014-01-01

45

Quantitative Time-Lapse Fluorescence Microscopy in Single Cells  

PubMed Central

The cloning of GFP 15 years ago revolutionized cell biology by permitting visualization of a wide range of molecular mechanisms within living cells. Though initially used to make largely qualitative assessments of protein levels and localizations, fluorescence microscopy has since evolved to become highly quantitative and high-throughput. Computational image analysis has catalyzed this evolution, enabling rapid and automated processing of large datasets. Here we review studies that combine time-lapse fluorescence microscopy and automated image analysis to investigate dynamic events at the single-cell level. We highlight examples where single-cell analysis provides unique mechanistic insights into cellular processes that cannot be otherwise resolved in bulk assays. Additionally, we discuss studies where quantitative microscopy facilitates the assembly of detailed 4D lineages in developing organisms. Finally, we describe recent advances in imaging technology, focusing especially on platforms that allow the simultaneous perturbation and quantitative monitoring of biological systems. PMID:19575655

Muzzey, Dale; van Oudenaarden, Alexander

2011-01-01

46

Emission microscopy and related techniques: resolution in photoelectron microscopy, low energy electron microscopy and mirror electron microscopy.  

PubMed

A unified treatment of the resolution of three closely related techniques is presented: emission electron microscopy (particularly photoelectron microscopy, PEM), low energy electron microscopy (LEEM), and mirror electron microscopy (MEM). The resolution calculation is based on the intensity distribution in the image plane for an object of finite size rather than for a point source. The calculations take into account the spherical and chromatic aberrations of the accelerating field and of the objective lens. Intensity distributions for a range of energies in the electron beam are obtained by adding the single-energy distributions weighted according to the energy distribution function. The diffraction error is taken into account separately. A working resolution is calculated that includes the practical requirement for a finite exposure time, and hence a finite non-zero current in the image. The expressions for the aberration coefficients are the same in PEM and LEEM. The calculated aberrations in MEM are somewhat smaller than for PEM and LEEM. The resolution of PEM is calculated to be about 50 A, assuming conventional UV excitation sources, which provide current densities at the specimen of 5 x 10(-5) A/cm2 and emission energies ranging up to 0.5 eV. A resolution of about 70 A has been demonstrated experimentally. The emission current density at the specimen is higher in LEEM and MEM because an electron gun is used in place of a UV source. For a current density of 5 x 10(-4) A/cm2 and the same electron optical parameters as for PEM, the resolution is calculated to be 27 A for LEEM and 21 A for MEM. PMID:1481280

Rempfer, G F; Griffith, O H

1992-11-01

47

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.

48

Self-reference quantitative phase microscopy for microfluidic devices  

E-print Network

]. In the case of Hilbert phase microscopy (HPM), the optical system delivers light using an op- tical fiber-of-field optics in the form of Michelson interferometry, which allows quantitative phase measurement of double in- terferograms. The performance of our system is verified using polymer beads, micropatterning

49

Transmission electron microscopy of actinide materials  

Microsoft Academic Search

Actinide metallurgy, crystallography, physics, and chemistry are of great interest due to the unique behavior of the 5f states that dominate the electronic structure. The 5f states produce a wide range of fascinating behaviors in the actinide materials. from superconductivity to exotic magnetism. Accordingly, they are of great interest, but are difficult to work with. Transmission electron microscopy (TEM) can

2006-01-01

50

Electron Microscopy of Natural and Epitaxial Diamond  

NASA Technical Reports Server (NTRS)

Semiconducting diamond films have the potential for use as a material in which to build active electronic devices capable of operating at high temperatures or in high radiation environments. Ultimately, it is preferable to use low-defect-density single crystal diamond for device fabrication. We have previously investigated polycrystalline diamond films with transmission electron microscopy (TEM) and scanning electron microscopy (SEM), and homoepitaxial films with SEM-based techniques. This contribution describes some of our most recent observations of the microstructure of natural diamond single crystals and homoepitaxial diamond thin films using TEM.

Posthill, J. B.; George, T.; Malta, D. P.; Humphreys, T. P.; Rudder, R. A.; Hudson, G. C.; Thomas, R. E.; Markunas, R. J.

1993-01-01

51

Virtual Microscope: Scanning Electron Microscopy Basics  

NSDL National Science Digital Library

This is an interactive animation that illustrates the basics of imaging in the Scanning Electron Microscope (SEM). It displays images of the external and internal components of the microscope, then provides animations of the electron emission and capture processes. Finally, the tutorial discusses how the digital signal produced by the Secondary Electron Detector (SED) is converted into grayscale pixels on a computer screen. This resource is part of the Virtual Microscope project, which provides cost-free simulated scientific instrumentation for students and researchers worldwide as part of NASA's Virtual Laboratory initiative. See Related Materials for links to additional animated tutorials on Atomic Force Microscopy and Fluorescense Light Microscopy.

2013-02-11

52

A new method of high resolution, quantitative phase scanning microscopy  

NASA Astrophysics Data System (ADS)

Coherent Diffractive Imaging (CDI) is a method of lensless imaging that reconstructs a target object from recordings of the diffraction pattern it generates when illuminated by a coherent source. A new method of scanning CDI, 'Ptychography,' was introduced recently and has been successfully demonstrated as a method of lensless microscopy at optical and x-ray wavelengths. Here we show how it can be applied to visible light microscopy to produce high resolution quantitative phase images of low-contrast objects, such as unstained cells.

Maiden, A. M.; Rodenburg, J. M.; Humphry, M. J.

2010-06-01

53

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

54

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

55

Electron microscopy in Crohn's disease 1  

Microsoft Academic Search

An electron microscopic study of Crohn's disease of the colon is presented. The positive findings that supplement those obtained by light microscopy are: a prominent nucleolus is more common in the lymphocytes of Crohn's disease than in normal lymphocytes or those found in cases of ulcerative colitis; lymphocytes are often observed close to macrophages and epithelioid cells; the epithelioid cells

A. P. R. Aluwihare

1971-01-01

56

ELECTRON MICROSCOPY LABORATORY Prices 2013 & 2014  

Cancer.gov

09/18/14 Frederick National Laboratory for Cancer Research ELECTRON MICROSCOPY LABORATORY 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

57

A quantitative study of the microstructure and crystallographic fiber texture in nickel electrodeposits used in radio-frequency MEMS switches, including a new transmission electron microscopy (TEM) technique for polycrystalline films  

NASA Astrophysics Data System (ADS)

The microstructure of electrodeposited nickel films in radio-frequency (RF) microelectromechanical systems (MEMS) switches has been quantitatively studied to inform and validate multi-scale, multi-physics computer simulations that aim to predict the lifetime and failure mechanisms of the RF MEMS switches. The RF MEMS switches are currently under study at the Purdue University center for the Prediction of Reliability, Integrity, and Survivability of Microsystems (PRISM). An array of microstructural characterization techniques including focused ion beam (FIB) microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy have be used to study the nickel film and to quantify grain size and crystallographic texture and provide information about elemental impurities and surface roughness and impurity elements. Particular emphasis has been placed on quantifying the crystallographic fiber texture of the polycrystalline nickel film as a function of film height within a single specimen using a new transmission electron microscopy (TEM) microtexture method. The TEM method employs a special type of plan view TEM sample and uses hollow cone dark field (HCDF) TEM imaging to spatially map the orientation of individual crystallites at discrete film heights. A trend of increasing 001 fiber texture with film height was discovered, which has implications for the elastic behavior of the MEMS device. The method can be applied to study fiber texture evolution as a function of height in polycrystalline films to gather data that may elucidate fundamental film growth mechanisms. The method is explained in detail. It is well-known that the elastic properties of polycrystalline thin films used in MEMS devices can deviate from bulk isotropic values and become directionally-dependent if a crystallographic texture is present. Hence, the ability to predict the actual anisotropic elastic properties of textured films is important for MEMS design and analysis. An integrated technique combining X-ray diffraction (XRD) and density functional theory (DFT) simulation is presented here for the quantification and prediction of the elastic properties of crystallographically textured polycrystalline films used in MEMS devices. The technique is rapid, efficient, and capable of analyzing individual devices in an array, making it ideal for MEMS design, analysis, and quality control. Application of the technique to the electroplated nickel bridge of an RF MEMS switch, whose critical operating parameters depend on the in-plane Young's modulus, is demonstrated. It is shown that the in-plane Young's modulus of nickel films with a perfect, single fiber texture can vary over a large range from 172 GPa to 232 GPa. Experimental results significantly outside this range cannot be explained by crystallographic texture alone. The range of Young's modulus for real films is expected to be somewhat smaller because real films rarely have a near- perfect fiber texture and sometimes have a texture that cannot be described by a single fiber of orientation. The nickel bridge of the RF MEMS switch, which has a relatively strong 001 fiber texture component as well as a weak 111 fiber texture component, exemplifies such a case. The present technique takes these texture features into account to estimate the in-plane Young's modulus of the nickel bridge in several RF MEMS switches.

Cantwell, Patrick R.

58

Transmission electron microscopy of actinide materials  

SciTech Connect

Actinide metallurgy, crystallography, physics, and chemistry are of great interest due to the unique behavior of the 5f states that dominate the electronic structure. The 5f states produce a wide range of fascinating behaviors in the actinide materials. from superconductivity to exotic magnetism. Accordingly, they are of great interest, but are difficult to work with. Transmission electron microscopy (TEM) can overcome many of the problems of working with actinide materials and can be used to interrogate the atomic and electronic structure of actinide materials. We will cover our capabilities at LLNL: Sample preparation; TEM techniques; and in situ capabilities.

Moore, K

2006-05-30

59

Mudrocks examined by backscattered electron microscopy  

NASA Technical Reports Server (NTRS)

A method of studying mudrocks is developed using backscattered electrons (BSE) in scanning electron microscopy. Commercially available detectors are utilized to mix the BSE and secondary electron signals in order to obtain the optimum image for a particular material. Thin sections or polished rock chip surfaces are examined with BSE which provides both the atomic number contrast and topographic contrast. This technique provides very detailed information about the form and composition of individual grains in the mudrock thin sections and can be used in studies of the source, mode of deposition, diagenesis, and tectonic deformational history of mudrocks.

Pye, K.; Krinsley, D.

1983-01-01

60

Single beam Fourier transform digital holographic quantitative phase microscopy  

NASA Astrophysics Data System (ADS)

Quantitative phase contrast microscopy reveals thickness or height information of a biological or technical micro-object under investigation. The information obtained from this process provides a means to study their dynamics. Digital holographic (DH) microscopy is one of the most used, state of the art single-shot quantitative techniques for three dimensional imaging of living cells. Conventional off axis DH microscopy directly provides phase contrast images of the objects. However, this process requires two separate beams and their ratio adjustment for high contrast interference fringes. Also the use of two separate beams may make the system more vulnerable to vibrations. Single beam techniques can overcome these hurdles while remaining compact as well. Here, we describe the development of a single beam DH microscope providing whole field imaging of micro-objects. A hologram of the magnified object projected on to a diffuser co-located with a pinhole is recorded with the use of a commercially available diode laser and an arrayed sensor. A Fourier transform of the recorded hologram directly yields the complex amplitude at the image plane. The method proposed was investigated using various phase objects. It was also used to image the dynamics of human red blood cells in which sub-micrometer level thickness variation were measurable.

Anand, A.; Faridian, A.; Chhaniwal, V. K.; Mahajan, S.; Trivedi, V.; Dubey, S. K.; Pedrini, G.; Osten, W.; Javidi, B.

2014-03-01

61

Imaging carbon nanotubes by scanning electron microscopy  

NASA Astrophysics Data System (ADS)

Scanning electron microscopy (SEM) is used as a primary tool for imaging of nanostructures, including carbon nanotubes. Recent developments of the SEM technique have opened new capabilities for sample analysis at the nanoscale with potential industrial and metrological applications. We will discuss selective imaging of single-walled carbon nanotubes on insulators. The role of the electron beam parameters, effect of surrounding media and substrate, and carbon nanotubes properties on their appearance as seen by an SEM are analysed. The comparison of scanning electron microscopy with atomic force microscopy images will also be presented. Our results support some of the commonly accepted opinions about why such images appear as they do, but mostly contradict them. At the same time our discovery opens new analytical possibilities for applications of an SEM. Funding for this work has been provided by a NASA/MSFC Phase II SBIR, Contract No. NAS8-02102, through a subcontract from Lytec, LLC., and by the NSF NIRT Program, Grant No. 0304506. SEM was done at the Electron Probe Instrumentation Centre at Northwestern University.

Dikin, Dmitriy

2005-03-01

62

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

63

Electron Beam Artifacts in Liquid-Cell Electron Microscopy  

E-print Network

Bubbles may form when imaging liquids with in situ liquid-cell electron microscopy. Fluid dynamics videos show beam-induced bubble nucleation and growth. By examining the bubble formation and growth process, we hope to gain a better understanding of interactions between the electron beam and liquids.

Grogan, Joseph M; Bau, Haim H

2012-01-01

64

Quantitative Determination of Tip Parameters in Piezoresponse Force Microscopy  

SciTech Connect

One of the key limiting factors in the quantitative interpretation of piezoresponse force microscopy (PFM) is the lack of knowledge on the effective tip geometry. Here the authors derive analytical expressions for a 180{sup o} domain wall profile in PFM for the point charge, sphere plane, and disk electrode models of the tip. An approach for the determination of the effective tip parameters from the wall profile is suggested and illustrated for several ferroelectric materials. The calculated tip parameters can be used self-consistently for the interpretation of PFM resolution and spectroscopy data, i.e., linear imaging processes.

Jesse, Stephen [ORNL; Kalinin, Sergei V [ORNL; Rodriguez, Brian J [ORNL; Eliseev, E. A. [National Academy of Science of Ukraine, Kiev, Ukraine; Morozovska, A. N. [National Academy of Science of Ukraine, Kiev, Ukraine

2007-01-01

65

Quantitative Determination on Tip Parameters in Piezoresponse Force Microscopy  

SciTech Connect

One of the key limiting factors in the quantitative interpretation of piezoresponse force microscopy (PFM) is the lack of knowledge on the effective tip geometry. Here the authors derive analytical expressions for a 180 degree domain wall profile in PFM for the point charge, sphere plane, and disk electrode models of the tip. An approach for the determination of the effective tip parameters from the wall profile is suggested and illustrated for several ferroelectric materials. The calculated tip parameters can be used self-consistently for the interpretation of PFM resolution and spectroscopy data, i.e., linear imaging processes.

Kalinin, Sergei V [ORNL; Jesse, Stephen [ORNL; Rodriguez, Brian J [ORNL; Eliseev, E. A. [National Academy of Science of Ukraine, Kiev, Ukraine; Gopalana, V. [Pennsylvania State University; Morozovska, A. N. [National Academy of Science of Ukraine, Kiev, Ukraine

2007-01-01

66

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. PMID:24204771

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

2013-01-01

67

Fixation of Ejaculated Spermatozoa for Electron Microscopy  

Microsoft Academic Search

EJACULATED spermatozoa cannot be preserved satisfactorily by conventional fixation procedures for electron microscopy. Osmium tetroxide (OsO4) fixation of crude ejaculate consistently produces a variety of artefacts such as separation of the plasma membrane from the acrosome, widening of nuclear vacuoles, erosion of the acrosome, and swelling of mitochondria1-3. These alterations could be the consequence of the rapid destruction of the

Mario Stefanini; Cesare De Martino; Luciano Zamboni

1967-01-01

68

Quantitative microscopy characterization of hydrous niobium phosphate into bleached cellulose.  

PubMed

In this research the spatial distribution characterization of niobium phosphate into bleached cellulose was carried out combining processing and images analysis obtained by SEM and statistical methodologies. The objective is to investigate the deposit composition and phosphate morphology by using complementary analytical techniques. Based on the proposed methodology, parameters of niobium phosphate agglomerates (size and shape) and fiber morphology were evaluated depending on gray-levels (average luminance and fiber type): fiber characteristics (morphology) were measured. For the test method proposed, a specific region of cellulose/NbOPO(4) x nH(2)O composite was analyzed. This method involves area fraction measuring with a conditional probabilistic analysis. The analyzed fields were divided in different ways, called 'Scanning' and as a result, in quantitative terms, the phosphate deposition was described as spatial distribution homogeneous or inhomogeneous. The quantitative microscopy as a non-destructive testing provides relevant information when it is combined with statistic analysis. PMID:20347321

Cruz, T G; Pereira, P H F; Silva, M L C P; Cioffi, M O H; Voorwald, H J C

2010-07-01

69

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

70

Electron Microscopy Study of Tin Whisker Growth  

SciTech Connect

The growth of tin whiskers formed on sputtered tin layers deposited on brass was studied using electron microscopy. The occurrence of whiskers appeared to be largely independent of the macroscopic stress state in the film; rather it was microscopic compressive stresses arising from the formation of an intermetallic phase that appeared to be the necessary precursor. Whisker morphology was a result of whether nucleation had occurred on single grains or on multiple grains. In the latter case, the whiskers had a fluted or striated surface. The formation of whiskers on electron transparent samples was demonstrated. These samples showed the whiskers were monocrystalline and defect free, and that the growth direction could be determined.

Norton, Murray G. (Washington State University); Lebret, Joel (8392)

2003-03-30

71

Combined confocal Raman and quantitative phase microscopy system for biomedical diagnosis  

E-print Network

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 ...

Kang, Jeon Woong

72

Metallothioneins for correlative light and electron microscopy.  

PubMed

Structural biologists have been working for decades on new strategies to identify proteins in cells unambiguously. We recently explored the possibilities of using the small metal-binding protein, metallothionein (MT), as a tag to detect proteins in transmission electron microscopy. It had been reported that, when fused with a protein of interest and treated in vitro with gold salts, a single MT tag will build an electron-dense gold cluster ~1 nm in diameter; we provided proof of this principle by demonstrating that MT can be used to detect intracellular proteins in bacteria and eukaryotic cells. The method, which is compatible with a variety of sample processing techniques, allows specific detection of proteins in cells with exceptional sensitivity. We illustrated the applicability of the technique in a series of studies to visualize the intracellular distribution of bacterial and viral proteins. Immunogold labeling was fundamental to confirm the specificity of the MT-gold method. When proteins were double-tagged with green fluorescent protein and MT, direct correlative light and electron microscopy allowed visualization of the same macromolecular complexes with different spatial resolutions. MT-gold tagging might also become a useful tool for mapping proteins into the 3D-density maps produced by (cryo)-electron tomography. New protocols will be needed for double or multiple labeling of proteins, using different versions of MT with fluorophores of different colors. Further research is also necessary to render the MT-gold labeling procedure compatible with immunogold labeling on Tokuyasu cryosections and with cryo-electron microscopy of vitreous sections. PMID:25287836

Fernández de Castro, Isabel; Sanz-Sánchez, Laura; Risco, Cristina

2014-01-01

73

Quantitative Phase Microscopy: how to make phase data meaningful  

PubMed Central

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 -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

2014-01-01

74

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.

2006-02-01

75

Quantitative electrostatic force microscopy with sharp silicon tips.  

PubMed

Electrostatic force microscopy (EFM) probes are typically coated in either metal (radius ? 30 nm) or highly-doped diamond (radius ? 100 nm). Highly-doped silicon probes, which offer a sharpened and stable tip apex (radius ? 1-10 nm) and are usually used only in standard atomic force microscopy, have been recently shown to allow enhanced lateral resolution in quantitative EFM and its application for dielectric constant measurement. Here we present the theoretical modelling required to quantitatively interpret the electrostatic force between these sharpened tips and samples. In contrast to a sphere-capped cone geometry used to describe metal/diamond-coated tips, modelling a sharpened silicon tip requires a geometry comprised of a cone with two different angles. Theoretical results are supported by experimental measurements of metallic substrates and ?10 nm radius dielectric nanoparticles. This work is equally applicable to EFM and other electrical scanned probe techniques, where it allows quantifying electrical properties of nanomaterials and 3D nano-objects with higher resolution. PMID:25407683

Fumagalli, L; Edwards, M A; Gomila, G

2014-12-12

76

New Developments in Transmission Electron Microscopy for Nanotechnology**  

E-print Network

New Developments in Transmission Electron Microscopy for Nanotechnology** By Zhong Lin Wang* 1. Electron Microscopy and Nanotechnology Nanotechnology, as an international initiative for science manufacturing are the foundation of nanotechnology. Tracking the historical background of why nanotechnology

Wang, Zhong L.

77

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

78

Scanning electron microscopy analysis of floral development.  

PubMed

Scanning Electron Microscopy (SEM) allows the morphological characterization of the surface features of floral and inflorescence structures in a manner that retains the topography or three-dimensional appearance of the structure. Even at relatively low magnification levels it is possible to characterize early developmental stages. Using medium to high power magnification at later stages of development, cell surface morphology can be visualized allowing the identification of specific epidermal cell types. The analysis of the altered developmental progressions of mutant plants can provide insight into the developmental processes that are disrupted in that mutant background. PMID:24395262

Franks, Robert G

2014-01-01

79

Molecular Expressions: Virtual Scanning Electron Microscopy  

NSDL National Science Digital Library

This Java applet allows users to interactively explore various specimens as they appear under a scanning electron microscope (SEM). Choose from a cockroach, pollen grain, a diatomic molecule, a gecko foot, a jellyfish, and more. Users first adjust the focus, contrast, and brightness of the specimen to optimize its appearance. Then they use a slider to incrementally increase the magnification up to 10,000x. It is part of a much larger collection of optics and microscopy materials developed at the National High Magnetic Field Laboratory at Florida State University.

Kunkel, Dennis; Davidson, Michael

2009-06-14

80

Neurite density from magnetic resonance diffusion measurements at ultrahigh field: Comparison with light microscopy and electron microscopy  

PubMed Central

Due to its unique sensitivity to tissue microstructure, diffusion-weighted magnetic resonance imaging (MRI) has found many applications in clinical and fundamental science. With few exceptions, a more precise correspondence between physiological or biophysical properties and the obtained diffusion parameters remain uncertain due to lack of specificity. In this work, we address this problem by comparing diffusion parameters of a recently introduced model for water diffusion in brain matter to light microscopy and quantitative electron microscopy. Specifically, we compare diffusion model predictions of neurite density in rats to optical myelin staining intensity and stereological estimation of neurite volume fraction using electron microscopy. We find that the diffusion model describes data better and that its parameters show stronger correlation with optical and electron microscopy, and thus reflect myelinated neurite density better than the more frequently used diffusion tensor imaging (DTI) and cumulant expansion methods. Furthermore, the estimated neurite orientations capture dendritic architecture more faithfully than DTI diffusion ellipsoids. PMID:19732836

Jespersen, Sune N.; Bjarkam, Carsten R.; Nyengaard, Jens R.; Chakravarty, M. Mallar; Hansen, Brian; Vosegaard, Thomas; ?stergaard, Leif; Yablonskiy, Dmitriy; Nielsen, Niels Chr.; Vestergaard-Poulsen, Peter

2010-01-01

81

Quantitative nanofriction characterization of corrugated surfaces by atomic force microscopy  

NASA Astrophysics Data System (ADS)

Atomic force microscopy (AFM) is a suitable tool to perform tribological characterization of materials down to the nanometer scale. An important aspect in nanofriction measurements of corrugated samples is the local tilt of the surface, which affects the lateral force maps acquired with AFM. This is one of the most important problems of state-of-the-art nanotribology, hampering a reliable and quantitative characterization of real corrugated surfaces. In this article, we present a solution to the problem of the topographic correction of AFM lateral force maps acquired on corrugated samples in the presence of adhesion. We apply it in the specific case of multiasperity adhesive contacts, which are of common occurrence at many interfaces of technological interest. We discuss the validity and limitations of our approach.

Podestà, A.; Fantoni, G.; Milani, P.

2004-05-01

82

Determination of elemental distribution in green micro-algae using synchrotron radiation nano X-ray fluorescence (SR-nXRF) and electron microscopy techniques--subcellular localization and quantitative imaging of silver and cobalt uptake by Coccomyxa actinabiotis.  

PubMed

The newly discovered unicellular micro-alga Coccomyxa actinabiotis proves to be highly radio-tolerant and strongly concentrates radionuclides, as well as large amounts of toxic metals. This study helps in the understanding of the mechanisms involved in the accumulation and detoxification of silver and cobalt. Elemental distribution inside Coccomyxa actinabiotis cells was determined using synchrotron nano X-ray fluorescence spectroscopy at the ID22 nano fluorescence imaging beamline of the European Synchrotron Radiation Facility. The high resolution and high sensitivity of this technique enabled the assessment of elemental associations and exclusions in subcellular micro-algae compartments. A quantitative treatment of the scans was implemented to yield absolute concentrations of each endogenous and exogenous element with a spatial resolution of 100 nm and compared to the macroscopic content in cobalt and silver determined using inductively coupled plasma-mass spectrometry. The nano X-ray fluorescence imaging was complemented by transmission electron microscopy coupled to X-ray microanalysis (TEM-EDS), yielding differential silver distribution in the cell wall, cytosol, nucleus, chloroplast and mitochondria with unique resolution. The analysis of endogenous elements in control cells revealed that iron had a unique distribution; zinc, potassium, manganese, molybdenum, and phosphate had their maxima co-localized in the same area; and sulfur, copper and chlorine were almost homogeneously distributed among the whole cell. The subcellular distribution and quantification of cobalt and silver in micro-alga, assessed after controlled exposure to various concentrations, revealed that exogenous metals were mainly sequestered inside the cell rather than on mucilage or the cell wall, with preferential compartmentalization. Cobalt was homogeneously distributed outside of the chloroplast. Silver was localized in the cytosol at low concentration and in the whole cell excluding the nucleus at high concentration. Exposure to low concentrations of cobalt or silver did not alter the localization nor the concentration of endogenous elements within the cells. To our knowledge, this is the first report on element co-localization and segregation at the sub-cellular level in micro-algae by means of synchrotron nano X-ray fluorescence spectroscopy. PMID:24394991

Leonardo, T; Farhi, E; Boisson, A-M; Vial, J; Cloetens, P; Bohic, S; Rivasseau, C

2014-02-01

83

Digital Holographic Microscopy: A Quantitative Label-Free Microscopy Technique for Phenotypic Screening  

PubMed Central

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.

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

2014-01-01

84

Value of electron microscopy in diagnosis of renal disease  

Microsoft Academic Search

AIMS--To assess the role and value of electron microscopy in the diagnosis of renal disease. METHODS--Retrospective evaluation of 88 renal biopsy specimens received for primary diagnosis by assessment of the contribution of electron microscopy to the final diagnosis in the knowledge of the light microscopy and immunofluorescence findings. RESULTS--Electron microscopy had an important diagnostic role in 75% of cases and

J M Pearson; L J McWilliam; J D Coyne; A Curry

1994-01-01

85

Chromosome structure: improved immunolabeling for electron microscopy.  

PubMed

To structurally dissect mitotic chromosomes, we aim to position along the folded chromatin fiber proteins involved in long-range order, such as topoisomerase IIalpha (topoIIalpha) and condensin. Immuno-electron microscopy (EM) of thin-sectioned chromosomes is the method of choice toward this goal. A much-improved immunoprocedure that avoids problems associated with aldehyde fixation, such as chemical translinking and networking of chromatin fibers, is reported here. We show that ultraviolet irradiation of isolated nuclei or chromosomes facilitates high-level specific immunostaining, as established by fluorescence microscopy with a variety of antibodies and especially by immuno-EM. Ultrastructural localizations of topoIIalpha and condensin I component hBarren (hBar; hCAP-H) in mitotic chromosomes were studied by immuno-EM. We show that the micrographs of thin-sectioned chromosomes map topoIIalpha and hBar to the center of the chromosomal body where the chromatin fibers generally converge. This localization is defined by many clustered gold particles with only rare individual particles in the peripheral halo. The data obtained are consistent with the view that condensin and perhaps topoIIalpha tether chromatin to loops according to a scaffolding-type model. PMID:16175370

Maeshima, Kazuhiro; Eltsov, Michail; Laemmli, Ulrich K

2005-11-01

86

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

87

Visualization of yeast cells by electron microscopy.  

PubMed

In the 1970s, hydrocarbon or methanol utilizable yeasts were considered as a material for foods and ethanol production. During the course of studies into the physiology of yeasts, we found that these systems provide a suitable model for the biogenesis and ultrastructure research of microbodies (peroxisomes). Microbodies of hydrocarbon utilizing Candida tropicalis multiply profusely from the preexisting microbody. ? oxidation enzymes in the microbody were determined by means of immunoelectron microscopy. We examined the ultrastructure of Candida boidinii microbodies grown on methanol, and found a composite crystalloid of two enzymes, alcohol oxidase and catalase, by analyzing using the optical diffraction and filtering technique and computer simulation. We established methods for preparing the protoplasts of Schizosaccharomyces pombe and conditions for the complete regeneration of the cell wall. The dynamic process of cell wall formation was clarified through our study of the protoplasts, using an improved ultra high resolution (UHR) FESEM S-900 and an S-900LV. It was found that ?-1,3-glucan, ?-1,6-glucan and ?-1,3-glucan, as well as ?-galactomannan, are ingredients of the cell wall. The process of septum formation during cell division was examined after cryo-fixation by high pressure freezing (HPF). It was also found that ?-1,3- and ?-1,3-glucans were located in the invaginating nascent septum, and later, highly branched ?-1,6-glucan also appeared on the second septum. The micro-sampling method, using a focused ion beam (FIB), has been applied to our yeast cell wall research. A combination of FIB and scanning transmission electron microscopy is useful in constructing 3D images and analyzing the molecular architecture of cells, as well as for electron tomography of thick sections of biological specimens. PMID:23231852

Osumi, Masako

2012-01-01

88

Quantitative high dynamic range beam profiling for fluorescence microscopy  

NASA Astrophysics Data System (ADS)

Modern developmental biology relies on optically sectioning fluorescence microscope techniques to produce non-destructive in vivo images of developing specimens at high resolution in three dimensions. As optimal performance of these techniques is reliant on the three-dimensional (3D) intensity profile of the illumination employed, the ability to directly record and analyze these profiles is of great use to the fluorescence microscopist or instrument builder. Though excitation beam profiles can be measured indirectly using a sample of fluorescent beads and recording the emission along the microscope detection path, we demonstrate an alternative approach where a miniature camera sensor is used directly within the illumination beam. Measurements taken using our approach are solely concerned with the illumination optics as the detection optics are not involved. We present a miniature beam profiling device and high dynamic range flux reconstruction algorithm that together are capable of accurately reproducing quantitative 3D flux maps over a large focal volume. Performance of this beam profiling system is verified within an optical test bench and demonstrated for fluorescence microscopy by profiling the low NA illumination beam of a single plane illumination microscope. The generality and success of this approach showcases a widely flexible beam amplitude diagnostic tool for use within the life sciences.

Mitchell, T. J.; Saunter, C. D.; O'Nions, W.; Girkin, J. M.; Love, G. D.

2014-10-01

89

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

90

Quantitative high dynamic range beam profiling for fluorescence microscopy.  

PubMed

Modern developmental biology relies on optically sectioning fluorescence microscope techniques to produce non-destructive in vivo images of developing specimens at high resolution in three dimensions. As optimal performance of these techniques is reliant on the three-dimensional (3D) intensity profile of the illumination employed, the ability to directly record and analyze these profiles is of great use to the fluorescence microscopist or instrument builder. Though excitation beam profiles can be measured indirectly using a sample of fluorescent beads and recording the emission along the microscope detection path, we demonstrate an alternative approach where a miniature camera sensor is used directly within the illumination beam. Measurements taken using our approach are solely concerned with the illumination optics as the detection optics are not involved. We present a miniature beam profiling device and high dynamic range flux reconstruction algorithm that together are capable of accurately reproducing quantitative 3D flux maps over a large focal volume. Performance of this beam profiling system is verified within an optical test bench and demonstrated for fluorescence microscopy by profiling the low NA illumination beam of a single plane illumination microscope. The generality and success of this approach showcases a widely flexible beam amplitude diagnostic tool for use within the life sciences. PMID:25362409

Mitchell, T J; Saunter, C D; O'Nions, W; Girkin, J M; Love, G D

2014-10-01

91

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

92

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. PMID:23407909

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

2013-01-01

93

Towards quantitative magnetic force microscopy: theory and experiment  

NASA Astrophysics Data System (ADS)

We introduce a simple and effective model of a commercial magnetic thin-film sensor for magnetic force microscopy (MFM), and we test the model employing buried magnetic dipoles. The model can be solved analytically in the half-space in front of the sensor tip, leading to a simple 1/R dependence of the magnetic stray field projected to the symmetry axis. The model resolves the earlier issue as to why the magnetic sensors cannot be described reasonably by a restricted multipole expansion as in the point pole approximation: the point pole model must be extended to incorporate a ‘lower-order’ pole, which we term ‘pseudo-pole’. The near-field dependence (?R-1) turns into the well-known and frequently used dipole behavior (?R-3) if the separation, R, exceeds the height of the sensor. Using magnetic nanoparticles (average diameter 18 nm) embedded in a SiO cover as dipolar point probes, we show that the force gradient-distance curves and magnetic images fit almost perfectly to the proposed model. The easy axis of magnetization of single nanoparticles is successfully deduced from these magnetic images. Our model paves the way for quantitative MFM, at least if the sensor and the sample are independent.

Häberle, Thomas; Haering, Felix; Pfeifer, Holger; Han, Luyang; Kuerbanjiang, Balati; Wiedwald, Ulf; Herr, Ulrich; Koslowski, Berndt

2012-04-01

94

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

95

Quantitative subsurface contact resonance force microscopy of model polymer nanocomposites  

NASA Astrophysics Data System (ADS)

We present experimental results on the use of quantitative contact resonance force microscopy (CR-FM) for mapping the planar location and depth of 50 nm diameter silica nanoparticles buried beneath polystyrene films 30-165 nm thick. The presence of shallowly buried nanoparticles, with stiffness greater than that of the surrounding matrix, is shown to locally affect the surface contact stiffness of a material for all depths investigated. To achieve the necessary stiffness sensitivity, the CR-FM measurements are obtained utilizing the fifth contact eigenmode. Stiffness contrast is found to increase rapidly with initial increases in force, but plateaus at higher loads. Over the explored depth range, stiffness contrast spans roughly one order of magnitude, suggesting good depth differentiation. Scatter in the stiffness contrast for single images reveals nonuniformities in the model samples that can be explained by particle size dispersity. Finite element analysis is used to simulate the significant effect particle size can have on contact stiffness contrast. Finally, we show how measurements at a range of forces may be used to deconvolve particle size effects from depth effects. Publication of NIST, an agency of the US government, not subject to copyright.

Killgore, Jason P.; Kelly, Jennifer Y.; Stafford, Christopher M.; Fasolka, Michael J.; Hurley, Donna C.

2011-04-01

96

Web Course Notes and References, Transmission Electron Microscopy  

NSDL National Science Digital Library

This site from the Electron Microscopy Outreach Program features a course devoted to transmission electron microscopy. The course is organized by chapters and covers the principles, design and operation of the electron microscope, contrast and image formation, image analysis, crystals, symmetry and diffraction, and Fourier image processing techniques.

Program, Electron M.; University Of California, San D.

97

Quantitative imaging of living cells by deep ultraviolet microscopy  

E-print Network

Developments in light microscopy over the past three centuries have opened new windows into cell structure and function, yet many questions remain unanswered by current imaging approaches. Deep ultraviolet microscopy ...

Zeskind, Benjamin J

2006-01-01

98

Assembly of chromatin fibers into metaphase chromosomes analyzed by transmission electron microscopy and scanning electron microscopy.  

PubMed Central

The higher-order assembly of the approximately 30 nm chromatin fibers into the characteristic morphology of HeLa mitotic chromosomes was investigated by electron microscopy. Transmission electron microscopy (TEM) of serial sections was applied to view the distribution of the DNA-histone-nonhistone fibers through the chromatid arms. Scanning electron microscopy (SEM) provided a complementary technique allowing the surface arrangement of the fibers to be observed. The approach with both procedures was to swell the chromosomes slightly, without extracting proteins, so that the densely-packed chromatin fibers were separated. The degree of expansion of the chromosomes was controlled by adjusting the concentration of divalent cations (Mg2+). With TEM, individual fibers could be resolved by decreasing the Mg2+ concentration to 1.0-1.5 mM. The predominant mode of fiber organization was seen to be radial for both longitudinal and transverse sections. Using SEM, surface protuberances with an average diameter of 69 nm became visible after the Mg2+ concentration was reduced to 1.5 mM. The knobby surface appearance was a variable feature, because the average diameter decreased when the divalent cation concentration was further reduced. The surface projections appear to represent the peripheral tips of radial chromatin loops. These TEM and SEM observations support a "radial loop" model for the organization of the chromatin fibers in metaphase chromosomes. Images FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 6 PMID:3955172

Adolph, K W; Kreisman, L R; Kuehn, R L

1986-01-01

99

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.

100

Mega-Dalton Biomolecular Motion Captured from Electron Microscopy Reconstructions  

E-print Network

Mega-Dalton Biomolecular Motion Captured from Electron Microscopy Reconstructions Pablo Chaco; subcellular machines*Corresponding author Nearly all biomolecular assemblies of mega- Dalton molecular weight

Wriggers, Willy

101

[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

102

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

103

Noninvasive electron microscopy with interaction-free quantum measurements  

E-print Network

We propose the use of interaction-free quantum measurements with electrons to eliminate sample damage in electron microscopy. This might allow noninvasive molecular-resolution imaging. We show the possibility of such ...

Putnam, William P.

104

ADVANCED ELECTRON MICROSCOPY AND MATERIALS PHYSICS WORKSHOP  

E-print Network

Approaches for In-Situ and 3D Microscopy THURSDAY (November 8th ) 7:30 ­ Continental Breakfast Advanced EM and the Current Development on Structure Reversion 4:30 - Rudolf Tromp (IBM) - Cathode Lens Microscopy: The Next:00 - Reception, Berkner Hall Lobby Greetings from Hitachi ­ I. Muta (General Manager, Sales) and Y. Kawasaki

Johnson, Peter D.

105

Development of a Nanoindenter for In Situ Transmission Electron Microscopy  

E-print Network

Development of a Nanoindenter for In Situ Transmission Electron Microscopy Eric A. Stach,1 * Tony will be presented. Key words: transmission electron microscopy, nanoindentation, in situ, dislocations, deformation, that of in situ nanoindentation (Wall et al., 1995; Wall and Dahmen, 1997, 1998a,b). Their work to date has

Rubloff, Gary W.

106

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

107

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

108

High Resolution Electron Microscopy at the National Cancer Institute  

Cancer.gov

One key area of interest for the lab has been to close the 3D imaging gap, finding ways to image whole cells and tissues at high resolution. Focused ion beam scanning electron microscopy (FIB-SEM, or otherwise known as ion abrasion scanning electron microscopy, IA-SEM) uses a scanning electron beam to image the face of a fixed, resin-embedded sample, and ion beam to remove “slices” of the sample, resulting in a sequential stack of high resolution images.

109

Quantitative ellipsometric microscopy at the silicon-air interface  

SciTech Connect

Ellipsometric microscopy is a technique that combines the merits of ellipsometry and light microscopy, i.e., it allows noninvasive, label-free measurements of thin film thickness and refractive index at high lateral resolution. Here we give a detailed description of the technique including a complete calibration scheme and a model to correct for the instrumental polarization of the imaging optics. The performance of the instrument was studied experimentally. We found a lateral resolution of 1 {mu}m and an absolute height accuracy of 3 nm. The measured refractive indices were accurate to 2.3% and the height sensitivity of the instrument was smaller than 5 A. Another virtue of the instrument design besides its good performance is that it is in essence an extension of standard light microscopy and could be integrated into commercial microscopes.

Linke, F.; Merkel, R. [Institut fuer Schichten und Grenzflaechen, Institut 4: Biologische Schichten (ISG4), Forschungszentrum Juelich GmbH, D-52425 Juelich (Germany)

2005-06-15

110

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  

NASA Astrophysics Data System (ADS)

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 ?) 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.

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

111

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. PMID:19822888

Goldsmith, Cynthia S.; Miller, Sara E.

2009-01-01

112

In Situ Analytical Electron Microscopy for Probing Nanoscale Electrochemistry  

SciTech Connect

Oxides and their tailored structures are at the heart of electrochemical energy storage technologies and advances in understanding and controlling the dynamic behaviors in the complex oxides, particularly at the interfaces, during electrochemical processes will catalyze creative design concepts for new materials with enhanced and better-understood properties. Such knowledge is not accessible without new analytical tools. New innovative experimental techniques are needed for understanding the chemistry and structure of the bulk and interfaces, more importantly how they change with electrochemical processes in situ. Analytical Transmission Electron Microscopy (TEM) is used extensively to study electrode materials ex situ and is one of the most powerful tools to obtain structural, morphological, and compositional information at nanometer scale by combining imaging, diffraction and spectroscopy, e.g., EDS (energy dispersive X-ray spectrometry) and Electron Energy Loss Spectrometry (EELS). Determining the composition/structure evolution upon electrochemical cycling at the bulk and interfaces can be addressed by new electron microscopy technique with which one can observe, at the nanometer scale and in situ, the dynamic phenomena in the electrode materials. In electrochemical systems, for instance in a lithium ion battery (LIB), materials operate under conditions that are far from equilibrium, so that the materials studied ex situ may not capture the processes that occur in situ in a working battery. In situ electrochemical operation in the ultra-high vacuum column of a TEM has been pursued by two major strategies. In one strategy, a 'nano-battery' can be fabricated from an all-solid-state thin film battery using a focused ion beam (FIB). The electrolyte is either polymer based or ceramic based without any liquid component. As shown in Fig. 1a, the interfaces between the active electrode material/electrolyte can be clearly observed with TEM imaging, in contrast to the composite electrodes/electrolyte interfaces in conventional lithium ion batteries, depicted in Fig.1b, where quantitative interface characterization is extremely difficult if not impossible. A second strategy involves organic electrolyte, though this approach more closely resembles the actual operation conditions of a LIB, the extreme volatility In Situ Analytical Electron Microscopy for Probing Nanoscale Electrochemistry by Ying Shirley Meng, Thomas McGilvray, Ming-Che Yang, Danijel Gostovic, Feng Wang, Dongli Zeng, Yimei Zhu, and Jason Graetz of the organic electrolytes present significant challenges for designing an in situ cell that is suitable for the vacuum environment of the TEM. Significant progress has been made in the past few years on the development of in situ electron microscopy for probing nanoscale electrochemistry. In 2008, Brazier et al. reported the first cross-section observation of an all solid-state lithium ion nano-battery by TEM. In this study the FIB was used to make a 'nano-battery,' from an all solid-state battery prepared by pulsed laser deposition (PLD). In situ TEM observations were not possible at that time due to several key challenges such as the lack of a suitable biasing sample holder and vacuum transfer of sample. In 2010, Yamamoto et al. successfully observed changes of electric potential in an all-solid-state lithium ion battery in situ with electron holography (EH). The 2D potential distribution resulting from movement of lithium ions near the positive-electrode/electrolyte interface was quantified. More recently Huang et al. and Wang et al. reported the in situ observations of the electrochemical lithiation of a single SnO{sub 2} nanowire electrode in two different in situ setups. In their approach, a vacuum compatible ionic liquid is used as the electrolyte, eliminating the need for complicated membrane sealing to prevent the evaporation of carbonate based organic electrolyte into the TEM column. One main limitation of this approach is that EELS spectral imaging is not possible due to the high plasmon signal of the ionic li

Graetz J.; Meng, Y.S.; McGilvray, T.; Yang, M.-C.; Gostovic, D.; Wang, F.; Zeng, D.; Zhu, Y.

2011-10-31

113

Spectral-domain optical coherence phase microscopy for quantitative biological studies  

E-print Network

Conventional phase-contrast and differential interference contrast microscopy produce high contrast images of transparent specimens such as cells. However, they do not provide quantitative information or do not have enough ...

Joo, Chulmin, 1976-

2008-01-01

114

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

115

Advanced correlative light/electron microscopy: current methods and new developments using Tokuyasu cryosections.  

PubMed

Microscopy is an essential tool for analysis of cellular structures and function. With the advent of new fluorescent probes and super-resolution light microscopy techniques, the study of dynamic processes in living cells has been greatly facilitated. Fluorescence light microscopy provides analytical, quantitative, and three-dimensional (3D) data with emphasis on analysis of live cells using fluorescent markers. Sample preparation is easy and relatively inexpensive, and the use of appropriate tags provides the ability to track specific proteins of interest. Of course, only electron microscopy (EM) achieves the highest definition in terms of ultrastructure and protein labeling. To fill the gap between light microscopy and EM, correlative light and electron microscopy (CLEM) strategies have been developed. In particular, hybrid techniques based upon immuno-EM provide sensitive protein detection combined with high-resolution information on cell structures and protein localization. By adding the third dimension to EM with electron tomography (ET) combined with rapid freezing, CLEM techniques now provide additional tools for quantitative 3D analysis. Here, we overview the major methods applied and highlight the latest advances in the field of CLEM. We then focus on two selected techniques that use cryosections as substrate for combined biomolecular imaging. Finally, we provide a perspective of future developments in the field. PMID:19654103

Cortese, Katia; Diaspro, Alberto; Tacchetti, Carlo

2009-12-01

116

Quantitative surface analysis by total electron yield.  

PubMed

When the surface of a solid sample is irradiated under vacuum by x-rays an electron emission, owing to photoabsorption, can be measured. As the electrons are detected under neglection of their kinetic energies the total electron yield (TEY) is determined. With a tuneable x-ray monochromator the TEY is measured below and above of one of the absorption edges of a given element. A jumplike increase of the TEY signal, due to the additional photoabsorptions in the corresponding atomic level, can be observed - qualitative analysis. The height of this jump can be correlateted to the concentration - quantitative analysis. It can be shown by a fundamental parameter approach for primary and secondary excitations how to use TEY for a quantitative analysis. The information depth lambda of this new method is approximately 2-400 nm depending on the chemical elements and on the original kinetic energies of Auger and photoelectrons. Thus, TEY is located between photoelectron spectrometry and x-ray fluorescence analysis. PMID:15048496

Ebel, H; Zagler, N; Svagera, R; Ebel, M; Kaitna, R

1995-10-01

117

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

118

Drift correction for scanning-electron microscopy  

E-print Network

Scanning electron micrographs at high magnification (100,000x and up) are distorted by motion of the sample during image acquisition, a phenomenon called drift. We propose a method for correcting drift distortion in images ...

Snella, Michael T

2010-01-01

119

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

120

Chromatic Confocal Electron Microscopy with a Finite Pinhole Size  

NASA Astrophysics Data System (ADS)

Scanning confocal electron microscopy (SCEM) is a new imaging mode in electron microscopy. Spherical aberration corrected electron microscope instruments fitted with two aberration correctors can be used in this mode which provides improved depth resolution and selectivity compared to optical sectioning in a conventional scanning transmission geometry. In this article, we consider the depth resolution and energy resolution in the confocal optical configuration for SCEM using inelastically scattered electrons with a finite pinhole size. We experimentally demonstrate energy-filtered optical sectioning in a double aberration-corrected instrument with uncorrected chromatic aberration without using a dedicated energy filter.

Wang, P.; Kirkland, A. I.; Nellist, P. D.

2012-07-01

121

Novel Application of Fluorescence Lifetime and Fluorescence Microscopy Enables Quantitative Access to Subcellular Dynamics in Plant Cells  

PubMed Central

Background Optical and spectroscopic technologies working at subcellular resolution with quantitative output are required for a deeper understanding of molecular processes and mechanisms in living cells. Such technologies are prerequisite for the realisation of predictive biology at cellular and subcellular level. However, although established in the physical sciences, these techniques are rarely applied to cell biology in the plant sciences. Principal Findings Here, we present a combined application of one-chromophore fluorescence lifetime microscopy and wavelength-selective fluorescence microscopy to analyse the function of a GFP fusion of the Brassinosteroid Insensitive 1 Receptor (BRI1-GFP) with high spatial and temporal resolution in living Arabidopsis cells in their tissue environment. We show a rapid, brassinolide-induced cell wall expansion and a fast BR-regulated change in the BRI1-GFP fluorescence lifetime in the plasmamembrane in vivo. Both cell wall expansion and changes in fluorescence lifetime reflect early BR-induced and BRI1-dependent physiological or signalling processes. Our experiments also show the potential of one-chromophore fluorescence lifetime microscopy for the in vivo monitoring of the biochemical and biophysical subcellular environment using GFP fusion proteins as probes. Significance One-chromophore fluorescence lifetime microscopy, combined with wavelength-specific fluorescence microscopy, opens up new frontiers for in vivo dynamic and quantitative analysis of cellular processes at high resolution which are not addressable by pure imaging technologies or transmission electron microscopy. PMID:19492078

Elgass, Kirstin; Caesar, Katharina; Schleifenbaum, Frank; Stierhof, York-Dieter; Meixner, Alfred J.; Harter, Klaus

2009-01-01

122

Microstructural imaging techniques: a comparison between light and scanning electron microscopy  

NASA Astrophysics Data System (ADS)

Both light microscopy and scanning electron microscopy are commonly used in microstructural studies of geological specimens. This contribution uses polished thin sections to analyse the same areas in two specimens using both microscopy techniques. The images from a quartz mylonite and a granodiorite are compared to quantitative crystallographic data obtained using electron backscatter diffraction (EBSD). The results indicate that light microscopy images pick out all high angle (>10° misorientation) boundaries but only some low angle and twin boundaries, therefore making it suitable for imaging more general microstructural trends. Orientation contrast imaging, using forescatter detectors in the SEM, images all types of crystallographic boundary: this can obscure the general microstructural trend but makes it more suitable for detailed microstructural analyses. Future studies are advised, wherever possible, to utilise the imaging advantages from a combination of both techniques.

Trimby, Patrick W.; Prior, David J.

1999-03-01

123

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

124

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 PMID:4521050

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

1974-01-01

125

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

PubMed Central

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

126

Electron microscopy of frozen hydrated biological specimens  

Microsoft Academic Search

The use of frozen hydrated specimens for molecular structure determination is limited primarily by radiation damage. The radiation damage effect in frozen hydrated catalase crystals has been measured in terms of the loss of electron diffraction. The results show an improvement for this type of specimen relative to wet hydrated or glucose embedded catalase crystals at room temperature. Bright field

K. A. Taylor; R. M. Glaeser

1976-01-01

127

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

128

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

PubMed

We investigate the implications of the form of the spatial coherence function, also referred to as the effective source distribution, for quantitative analysis in scanning transmission electron microscopy, and in particular for interpreting the spatial origin of imaging and spectroscopy signals. These questions are explored using three different source distribution models applied to a GaAs crystal case study. The shape of the effective source distribution was found to have a strong influence not only on the scanning transmission electron microscopy (STEM) image contrast, but also on the distribution of the scattered electron wavefield and hence on the spatial origin of the detected electron intensities. The implications this has for measuring structure, composition and bonding at atomic resolution via annular dark field, X-ray and electron energy loss STEM imaging are discussed. PMID:24879321

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

2014-11-01

129

Concepts, facts and artifacts in electron microscopy.  

PubMed

This communication illustrates how the electron microscope has contributed to biochemistry by revealing how multienzyme systems in mitochondria are structurally organized to secure high speed ATP synthesis and has extended physiology to the molecular level. Ribonucleoprotein complexes form a gel in the cytoplasm determining the conditions for translation... Photoreceptor stimulation involves two phases, trapping of light by a light reflecting cylinder formed by the outer segment disks and energy transduction by bleaching of photopigment molecules changing the charge of the outer segment disks driving the photoreceptor toward hyperpolarization. Revealing the synaptic connections between retinal neurons extends neurophysiology to the level of information processing by neural circuits, which are designed for high speed processing. Spatial brightness contrast enhancement is eliminated in connection with macular degeneration, which leads to partial blindness, revealing the importance of contrast enhancement for vision. PMID:16359627

Sjöstrand, F S

2005-12-16

130

Electron microscopy of biomaterials based on hydroxyapatite  

SciTech Connect

Three types of biomaterials based on hydroxyapatite are synthesized and investigated. Hydroxyapatite nanocrystals or microcrystals precipitated from low-temperature aqueous solutions serve as the initial material used for preparing spherical porous granules approximately 300-500 {mu}m in diameter. Sintering of hydroxyapatite crystals at a temperature of 870 deg. C for 2 h or at 1000 deg. C (for 3 h) + 1200 deg. C (for 2 h) brings about the formation of solid ceramics with different internal structures. According to the electron microscopic data, the ceramic material prepared at 870 deg. C is formed by agglomerated hydroxyapatite nanocrystals, whereas the ceramics sintered at 1200 deg. C (with a bending strength of the order of 100 MPa) are composed of crystal blocks as large as 2 {mu}m. It is established that all the biomaterials have a single-phase composition and consist of the hydroxyapatite with a structure retained up to a temperature of 1200 deg. C.

Suvorova, E. I., E-mail: suvorova@ns.crys.ras.ru; Klechkovskaya, V. V. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Komarov, V. F.; Severin, A. V.; Melikhov, I. V. [Moscow State University (Russian Federation); Buffat, P. A. [Ecole Polytechnique Federale de Lausanne, Centre Interdisciplinaire de Microscopie Electronique (Switzerland)

2006-10-15

131

Imaging Hydrated Microbial Extracellular Polymers: Comparative Analysis by Electron Microscopy? †  

PubMed Central

Microbe-mineral and -metal interactions represent a major intersection between the biosphere and geosphere but require high-resolution imaging and analytical tools for investigation of microscale associations. Electron microscopy has been used extensively for geomicrobial investigations, and although used bona fide, the traditional methods of sample preparation do not preserve the native morphology of microbiological components, especially extracellular polymers. Herein, we present a direct comparative analysis of microbial interactions by conventional electron microscopy approaches with imaging at room temperature and a suite of cryogenic electron microscopy methods providing imaging in the close-to-natural hydrated state. In situ, we observed an irreversible transformation of the hydrated bacterial extracellular polymers during the traditional dehydration-based sample preparation that resulted in their collapse into filamentous structures. Dehydration-induced polymer collapse can lead to inaccurate spatial relationships and hence could subsequently affect conclusions regarding the nature of interactions between microbial extracellular polymers and their environment. PMID:21169451

Dohnalkova, Alice C.; Marshall, Matthew J.; Arey, Bruce W.; Williams, Kenneth H.; Buck, Edgar C.; Fredrickson, James K.

2011-01-01

132

Imaging Hydrated Microbial Extracellular Polymers: Comparative Analysis by Electron Microscopy  

SciTech Connect

Microbe-mineral and -metal interactions represent a major intersection between the biosphere and geosphere but require high-resolution imaging and analytical tools for investigating microscale associations. Electron microscopy has been used extensively for geomicrobial investigations and although used bona fide, the traditional methods of sample preparation do not preserve the native morphology of microbiological components, especially extracellular polymers. Herein, we present a direct comparative analysis of microbial interactions using conventional electron microscopy approaches of imaging at room temperature and a suite of cryo-electron microscopy methods providing imaging in the close-to-natural hydrated state. In situ, we observed an irreversible transformation of bacterial extracellular polymers during the traditional dehydration-based sample preparation that resulted in the collapse of hydrated gel-like EPS into filamentous structures. Dehydration-induced polymer collapse can lead to inaccurate spatial relationships and hence could subsequently affect conclusions regarding nature of interactions between microbial extracellular polymers and their environment.

Dohnalkova, Alice; Marshall, Matthew J.; Arey, Bruce W.; Williams, Kenneth H.; Buck, Edgar C.; Fredrickson, Jim K.

2011-02-01

133

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

134

Transmission Electron Microscopy Characterization of Helium Bubbles in Aged Plutonium  

SciTech Connect

The self-irradiation damage generated by alpha decay of plutonium results in the formation of lattice defects, helium, and uranium atoms. Over time, microstructural evolution resulting from the self-irradiation may influence the physical and mechanical properties of the material. In order to assess microstructural changes, we have developed and applied procedures for the specimen preparation, handling, and transmission electron microscopy characterization of Pu alloys. These transmission electron microscopy investigations of Pu-Ga alloys ranging in age up to 42-years old reveal the presence of nanometer-sized helium bubbles. The number density of bubbles and the average size have been determined for eight different aged materials.

Schwartz, A J; Wall, M A; Zocco, T G; Blobaum, K M

2004-11-02

135

Correlative super-resolution fluorescence and electron microscopy of the nuclear pore complex with molecular resolution.  

PubMed

Here, we combine super-resolution fluorescence localization microscopy with scanning electron microscopy to map the position of proteins of nuclear pore complexes in isolated Xenopus laevis oocyte nuclear envelopes with molecular resolution in both imaging modes. We use the periodic molecular structure of the nuclear pore complex to superimpose direct stochastic optical reconstruction microscopy images with a precision of <20?nm on electron micrographs. The correlative images demonstrate quantitative molecular labeling and localization of nuclear pore complex proteins by standard immunocytochemistry with primary and secondary antibodies and reveal that the nuclear pore complex is composed of eight gp210 (also known as NUP210) protein homodimers. In addition, we find subpopulations of nuclear pore complexes with ninefold symmetry, which are found occasionally among the more typical eightfold symmetrical structures. PMID:25146397

Löschberger, Anna; Franke, Christian; Krohne, Georg; van de Linde, Sebastian; Sauer, Markus

2014-10-15

136

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

PubMed Central

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

137

Low Temperature Electron Microscopy and Electron Diffraction of the Purple Membrane of Halobacterium Halobium.  

National Technical Information Service (NTIS)

The structure of the purple membrane of Halobacterium halobium was studied by high resolution electron microscopy and electron diffraction, primarily at low temperature. The handedness of the purple membrane diffraction pattern with respect to the cell me...

S. B. Hayward

1978-01-01

138

Scanning electron microscopy and transmission electron microscopy study of hot-deformed gamma-TiAl-based alloy microstructure.  

PubMed

The aim of this work was to assess the changes in the microstructure of hot-deformed specimens made of alloys containing 46-50 at.% Al, 2 at.% Cr and 2 at.% Nb (and alloying additions such as carbon and boron) with the aid of scanning electron microscopy and transmission electron microscopy techniques. After homogenization and heat treatment performed in order to make diverse lamellae thickness, the specimens were compressed at 1000 degrees C. Transmission electron microscopy examinations of specimens after the compression test revealed the presence of heavily deformed areas with a high density of dislocation. Deformation twins were also observed. Dynamically recrystallized grains were revealed. For alloys no. 2 and no. 3, the recovery and recrystallization processes were more extensive than for alloy no. 1. PMID:17059556

Chrapo?ski, J; Rodak, K

2006-09-01

139

Quantitative x-ray differential-interference-contrast microscopy with independently adjustable bias and shear  

NASA Astrophysics Data System (ADS)

We present a quantitative x-ray phase imaging method that can be readily implemented on existing x-ray microscopy facilities. This technique utilizes Fresnel zone plates both as imaging optical elements for magnification and as second-order grating structures for phase-shifting interferometry. By making high-resolution quantitative x-ray phase information widely available, we expect this work to have significant impact on nanoscale biological and material studies.

Nakamura, Takashi; Chang, Chang

2011-04-01

140

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

141

Quantifying Nanoscale Order in Amorphous Materials via Fluctuation Electron Microscopy  

ERIC Educational Resources Information Center

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…

Bogle, Stephanie Nicole

2009-01-01

142

TRANSMISSION ELECTRON MICROSCOPY OF WEAKLY DEFORMED ALKALI HALIDE CRYSTALS  

E-print Network

377 TRANSMISSION ELECTRON MICROSCOPY OF WEAKLY DEFORMED ALKALI HALIDE CRYSTALS H. STRUNK Max) is applied to the investigation of the dis- location arrangement of [001]-orientated alkali halide crystals mainly to NaCl-(0.1-1) mole-% NaBr crystals, because these exhibit a relatively long stage I. The time

Boyer, Edmond

143

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.

144

Rapid diagnostic thin section electron microscopy of bacterial endospores  

Microsoft Academic Search

Emerging infectious diseases such as SARS and the bioterror attacks with anthrax spores that occurred after September 11th, 2001 have highlighted the need to be better prepared for the detection and management of infectious pathogens that threaten public health. Negative staining electron microscopy is one method used to screen environmental and clinical samples for relevant infectious pathogens. Unfortunately, bacterial endospores,

Michael Laue; Bärbel Niederwöhrmeier; Norbert Bannert

2007-01-01

145

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

146

Subliming Ice Surfaces: Freeze-Etch Electron Microscopy  

Microsoft Academic Search

Vacuum sublimation of oriented single crystals of ice at temperatures from -110 to -60 degrees Celsius was studied by electron microscopy with the freeze-etch technique. Sublimation etches the ice surface to produce pits and asperities and above -85 degrees Celsius causes extreme surface roughening. The etch pits are ascribed to surface dislocations, and the extreme roughening is ascribed to the

J. Gordon Davy; Daniel Branton

1970-01-01

147

DICHOTOMOUS SAMPLERS MODIFIED FOR USE WITH ELECTRON MICROSCOPY  

EPA Science Inventory

Large sulfate artifacts up to 2 um in diameter were observed by scanning electron microscopy for the fine particle fraction collected in dichotomous samplers. he artifacts were attributed to small liquid particles that piled up on the filter, coalesced, and later dried as larger ...

148

Microstress contrast in scanning electron acoustic microscopy of ceramics  

NASA Technical Reports Server (NTRS)

A mathematical model of image contrast in scanning electron acoustic microscopy (SEAM) due to the effect of residual stresses in materials is presented. It is found that in regions near the ends of the radial cracks induced by Vickers indentation the SEAM micrographs reveal a rather large variation of the acoustic output signal.

Cantrell, John H.; Qian, Menglu

1991-01-01

149

Metals on BN Studied by High Resolution Transmission Electron Microscopy  

NASA Astrophysics Data System (ADS)

Metal impurities, gold and nickel, have been deliberately introduced into boron-nitride (BN) sheets. The structural and topographic properties of doped BN have been studied by aberration corrected scanning transmission electron microscopy (STEM). Analysis revealed that metal atoms cluster preferentially in/on contaminated areas. The metal coverage on BN is almost the same for the same evaporated amount of 1 Å.

Bangert, U.; Zan, R.; Ramasse, Q.; Jalil, Rashid; Riaz, Ibstam; Novoselov, K. S.

2012-07-01

150

Atomically sharp cracks in brittle solids: an electron microscopy study  

Microsoft Academic Search

The issue of bond rupture versus microplasticity as an essential mechanism of crack propagation in brittle solids is addressed. A detailed survey of existing theoretical and experimental evidence relating to this issue highlights the need for direct observations of events within the crack-tip “process zone”, at a level approaching 10 nm. Transmission electron microscopy is accordingly used to study arrested

B. R. Lawn; B. J. Hockey; S. M. Wiederhorn

1980-01-01

151

STAINING OF TISSUE SECTIONS FOR ELECTRON MICROSCOPY WITH HEAVY METALS  

Microsoft Academic Search

ABS>Heavy metals may be incorporated from solution into tissue sections ; for electron microscopy. The resulting increase in density of the tissue ; provides greatly enhanced contrast with minimal distortion. Relative densities ; of various structures are found to depend on the heavy metal ions present and on ; the conditions of staining. Certain hitherto unobserved details are revealed and

M. L. Watson

1958-01-01

152

Nanoscale polarization profile across a 180° ferroelectric domain wall extracted by quantitative piezoelectric force microscopy  

Microsoft Academic Search

The structure of a single antiparallel ferroelectric domain wall in LiNbO3 is quantitatively mapped by piezoelectric force microscopy (PFM) with calibrated probe geometry. The PFM measurements are performed for 49 probes with the radius varying from 10 to 300 nm. The magnitude and variation of the experimental piezoelectric coefficient across a domain wall match the profiles calculated from a comprehensive

Lili Tian; Aravind Vasudevarao; Anna N. Morozovska; Eugene A. Eliseev; Sergei V. Kalinin; Venkatraman Gopalan

2008-01-01

153

Quantitative polarized light microscopy of unstained mammalian cochlear sections Neil M. Kalwani1,2  

E-print Network

future application of polarization-sensitive optical coherence tomography to human cochlea in vivo. Key1 Quantitative polarized light microscopy of unstained mammalian cochlear sections Neil M. Kalwani1 in the body. Evolving optical methods are promising to afford cellular diagnosis of pathologic changes

154

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

E-print Network

and structure of cellular organelles including cell wall, vacuole, endoplasmic reticulum, mitochondria, granulesQuantitative 3D imaging of whole, unstained cells by using X-ray diffraction microscopy Huaidong of cells. Cryoelectron micro- scopy can image pleomorphic structures at a resolution of 3­5 nm, but is only

Miao, Jianwei "John"

155

Parallel Simulation of ElectronSolid Interactions Electron Microscopy Modeling  

E-print Network

* Parallel Computational Sciences Department, # Materials and Process Sciences Center Key Words: parallel the sample composition [Michael, et al. 1990]. A simpler, yet effective method for accomplishing composition data and to characterize electron microscope performance are briefly highlighted. #12; Page 2

Plimpton, Steve

156

Electron holography and environmental transmission electron microscopy of magnetism at the nanoscale  

E-print Network

Electron holography and environmental transmission electron microscopy of magnetism B. Boothroyd, Jörg R. Jinschek, Zi-An Li and Michael Farle The addition of an electron biprism to a transmission electron microscope (TEM) equipped with a field emission gun allows the phase shift

Dunin-Borkowski, Rafal E.

157

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

158

Enhanced imaging in low dose electron microscopy using electron counting  

PubMed Central

We compare the direct electron imaging performance at 120 keV of a monolithic active pixel sensor (MAPS) operated in a conventional integrating mode with the performance obtained when operated in a single event counting mode. For the combination of sensor and incident electron energy used here, we propose a heuristic approach with which to process the single event images in which each event is renormalised to have an integrated weight of unity. Using this approach we find enhancements in the Nyquist frequency modulation transfer function (MTF) and detective quantum efficiency (DQE) over the corresponding integrating mode values by factors of 8 and 3, respectively. PMID:19647366

McMullan, G.; Clark, A.T.; Turchetta, R.; Faruqi, A.R.

2009-01-01

159

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. PMID:19497671

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

2009-01-01

160

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. PMID:19348881

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

2009-01-01

161

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

162

Total internal reflection holographic microscopy (TIRHM) for quantitative phase characterization of cell-substrate adhesion  

NASA Astrophysics Data System (ADS)

Total Internal Reflection Holographic Microscopy (TIRHM) combines near-field microscopy with digital holography to produce a new form of near-field phase microscopy. Using a prism in TIR as a near-field imager, the presence of microscopic organisms, cell-substrate interfaces, and adhesions, causes relative refractive index (RRI) and frustrated TIR (f-TIR) to modulate the object beam's evanescent wave phase front. Quantitative phase images of test specimens such as Amoeba proteus, Dictyostelium Discoideum and cells such as SKOV-3 ovarian cancer and 3T3 fibroblasts are produced without the need to introduce stains or fluorophores. The angular spectrum method of digital holography to compensate for tilt anamorphism due to the inclined TIR plane is also discussed. The results of this work conclusively demonstrate, for the first time, the integration of near-field microscopy with digital holography. The cellular images presented show a correlation between the physical extent of the Amoeba proteus plasma membrane and the adhesions that are quantitatively profiled by phase cross-sectioning of the holographic images obtained by digital holography. With its ability to quantitatively characterise cellular adhesion and motility, it is anticipated that TIRHM can be a tool for characterizing and combating cancer metastasis, as well as improving our understanding of morphogenesis and embryogenesis itself.

Ash, William Mason, III

163

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. PMID:20457938

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

2010-01-01

164

Electron transparent graphene windows for environmental scanning electron microscopy in liquids and dense gases  

NASA Astrophysics Data System (ADS)

Due to its ultrahigh electron transmissivity in a wide electron energy range, molecular impermeability, high electrical conductivity and excellent mechanical stiffness, suspended graphene membranes appear to be a nearly ideal window material for in situ (in vivo) environmental electron microscopy of nano- and mesoscopic objects (including bio-medical samples) immersed in liquids and/or in dense gaseous media. In this paper, taking advantage of a small modification of the graphene transfer protocol onto metallic and SiN supporting orifices, reusable environmental cells with exchangeable graphene windows have been designed. Using colloidal gold nanoparticles (50 nm) dispersed in water as model objects for scanning electron microscopy in liquids as proof of concept, different conditions for imaging through the graphene membrane were tested. Limiting factors for electron microscopy in liquids, such as electron beam induced water radiolysis and damage of the graphene membrane at high electron doses, are discussed.

Stoll, Joshua D.; Kolmakov, Andrei

2012-12-01

165

Electron transparent graphene windows for environmental scanning electron microscopy in liquids and dense gases.  

PubMed

Due to its ultrahigh electron transmissivity in a wide electron energy range, molecular impermeability, high electrical conductivity and excellent mechanical stiffness, suspended graphene membranes appear to be a nearly ideal window material for in situ (in vivo) environmental electron microscopy of nano- and mesoscopic objects (including bio-medical samples) immersed in liquids and/or in dense gaseous media. In this paper, taking advantage of a small modification of the graphene transfer protocol onto metallic and SiN supporting orifices, reusable environmental cells with exchangeable graphene windows have been designed. Using colloidal gold nanoparticles (50 nm) dispersed in water as model objects for scanning electron microscopy in liquids as proof of concept, different conditions for imaging through the graphene membrane were tested. Limiting factors for electron microscopy in liquids, such as electron beam induced water radiolysis and damage of the graphene membrane at high electron doses, are discussed. PMID:23165114

Stoll, Joshua D; Kolmakov, Andrei

2012-12-21

166

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

167

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

168

Short range plasmon resonators probed by photoemission electron microscopy.  

PubMed

Short range surface plasmon resonators are investigated at the nanometer scale. Gold nanorods (30 nm in diameter) were microfabricated and probed by photoemission electron microscopy under direct laser light excitation. Resonances presenting various numbers of lobes occur for specific rod lengths. A simple analytical model shows that the successive resonant lengths differ by a multiple of one-half of the wavelength of the supported short-range surface plasmon polariton. PMID:18288814

Douillard, Ludovic; Charra, Fabrice; Korczak, Zbigniew; Bachelot, Renaud; Kostcheev, Sergei; Lerondel, Gilles; Adam, Pierre-Michel; Royer, Pascal

2008-03-01

169

Macromolecular electron microscopy in the era of structural genomics  

Microsoft Academic Search

Macromolecular machines carry out many cellular functions. Cryo-electron microscopy (cryo-EM) is emerging as a powerful method for studying the structure, assembly and dynamics of such macromolecules, and their interactions with substrates. With resolutions still improving, ‘single-particle’ analyses are already depicting secondary structure. Moreover, cryo-EM can be combined in several ways with X-ray diffraction to enhance the resolution of cryo-EM and

Wolfgang Baumeister; Alasdair C. Steven

2000-01-01

170

Nanoscale Electronic Measurements of Semiconductors Using Kelvin Probe Force Microscopy  

Microsoft Academic Search

As characteristic dimensions of semiconductor devices continue to shrink, the ability to characterize structure and electronic\\u000a properties in such devices at the nanometer scale has come to be of outstanding importance.\\u000a \\u000a The Kelvin probe force microscopy technique has already been demonstrated as a powerful tool for measuring electrostatic forces\\u000a and electric potential distribution with nanometer resolution. In this review, we

Y. Rosenwaks; R. Shikler

171

Simple method of specimen preparation for scanning electron microscopy.  

PubMed

We compared conventional method for specimen (cell cultures, tissue specimens) preparation for scanning electron microscopy and a method without sputtering and critical-point drying. OTO-method (osmium-thiocarbohydrazide-osmium) with sample impregnation with hexamethyldisilazane followed by air drying was used as an alternative method. Excellent preservation of surface ultrastructures and electrical conductivity was proved. The method is easy to use and does not require additional costs for equipment. PMID:22451892

Buravkov, S V; Chernikov, V P; Buravkova, L B

2011-07-01

172

Atomically sharp cracks in brittle solids - An electron microscopy study  

Microsoft Academic Search

Transmission electron microscopy is used to study arrested cracks about sharp-contact sites in Si, Ge, SiC and Al2O3. Microscopic observations of interfacial and crack-tip healing dislocations in Si, SiC and Al2O3 together with dislocation loop segments at annealed crack tips in Si revealed that no crack-tip plasticity occurs at room temperature. A close connection between the dislocation patterns and moire

B. R. Lawn; B. J. Hockey; S. M. Wiederhorn

1980-01-01

173

Low-energy electron beams through ultra-thin foils, applications for electron microscopy  

Microsoft Academic Search

This thesis has discussed two electron microscopy applications that make use of ultra-thin foils: the tunnel junction emitter and the low-energy foil corrector. Both applications have in common that the electron beam is sent through the thin foil at low energy. Part of the electrons will scatter in the foil, thus causing a reduction of the transmitted current. An important

R. H. Van Aken

2005-01-01

174

Transmission Electron Microscopy Study of InN Nanorods  

SciTech Connect

InN nanorods were grown on a, c-, and r-plane of sapphire and also on Si (111) and GaN (0001) by non-catalytic, template-free hydride metal-organic vapor phase epitaxy and studied by transmission electron microscopy, electron energy loss (EELS) and photoluminescence (PL) at room temperature. These nanocrystals have different shapes and different faceting depending on the substrate used and their crystallographic orientation. EELS measurements have confirmed the high purity of these crystals. The observed PL peak was in the range of 0.9-0.95 eV. The strongest PL intensity was observed for the nanocrystals with the larger diameters.

Liliental-Weber, Z.; Li, X.; Kryliouk, Olga; Park, H.J.; Mangum,J.; Anderson, T.

2006-07-13

175

Direct Visualization of Dendrite Nucleation and Growth Kinetics during Lithium Deposition with in situ Electrochemical Transmission Electron Microscopy  

SciTech Connect

Formation of Li dendrites is a major safety concern existing in Li-ion secondary batteries. A quantitative electrochemistry method to investigate the dendrite nucleation and growth mechanisms at high spatial is presented. Cyclic voltammetry, in combination with in situ electrochemical transmission electron microscopy (in situ ec-TEM), was used to quantitatively characterize dendrite nucleation and growth mechanisms from a Au working electrode and within a 1.2M LiPF6 EC:DMC electrolyte.

Sacci, Robert L [ORNL; Dudney, Nancy J [ORNL; More, Karren Leslie [ORNL; Browning, Nigel [Pacific Northwest National Laboratory (PNNL); Unocic, Raymond R [ORNL

2014-01-01

176

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

177

Study of point spread in the aberration-corrected transmission electron microscopy.  

PubMed

High precision determination of atomic position is necessary for quantitative electron microscopy so that small width of peaks, which represent atoms in structural images, adequate resolution, and sufficiently strong image contrast are needed. The width of peak is usually determined by the point spread (PS) of instruments, but the PS of objects should also be taken into consideration in aberration-corrected transmission electron microscopy when point resolution of a microscope reaches the sub-angstrom scale, and thus the PS of the instrument is comparable with that of the object. In this article, PS is investigated by studying peak width with variation of atomic number, sample thickness, and spherical aberration coefficients in both negative Cs (NCSI) and positive Cs imaging (PCSI) modes by means of dynamical image simulation. Through comparing the peak width with various atomic number, thickness, and values of spherical aberration, NCSI mode is found to be superior to PCSI considering the smaller width. PMID:25256649

Ge, Binghui; Wang, Yumei; Chang, Yunjie; Yao, Yuan

2014-10-01

178

Iron filled carbon nanotubes as novel monopole-like sensors for quantitative magnetic force microscopy.  

PubMed

We present a novel ultrahigh stability sensor for quantitative magnetic force microscopy (MFM) based on an iron filled carbon nanotube. In contrast to the complex magnetic structure of conventional MFM probes, this sensor constitutes a nanomagnet with defined properties. The long iron nanowire can be regarded as an extended dipole of which only the monopole close to the sample surface is involved in the imaging process. We demonstrate its potential for high resolution imaging. Moreover, we present an easy routine to determine its monopole moment and prove that this calibration, unlike other approaches, is universally applicable. For the first time this enables straightforward quantitative MFM measurements. PMID:20876975

Wolny, F; Mühl, T; Weissker, U; Lipert, K; Schumann, J; Leonhardt, A; Büchner, B

2010-10-29

179

Quantitative measurement of the magnetic moment of individual magnetic nanoparticles by magnetic force microscopy.  

PubMed

The quantitative measurement of the magnetization of individual magnetic nanoparticles (MNPs) using magnetic force microscopy (MFM) is described. Quantitative measurement is realized by calibration of the MFM signal using an MNP reference sample with traceably determined magnetization. A resolution of the magnetic moment of the order of 10(-18) A m(2) under ambient conditions is demonstrated, which is presently limited by the tip's magnetic moment and the noise level of the instrument. The calibration scheme can be applied to practically any magnetic force microscope and tip, thus allowing a wide range of future applications, for example in nanomagnetism and biotechnology. PMID:22730177

Sievers, Sibylle; Braun, Kai-Felix; Eberbeck, Dietmar; Gustafsson, Stefan; Olsson, Eva; Schumacher, Hans Werner; Siegner, Uwe

2012-09-10

180

Quantitative Measurement of the Magnetic Moment of Individual Magnetic Nanoparticles by Magnetic Force Microscopy  

PubMed Central

The quantitative measurement of the magnetization of individual magnetic nanoparticles (MNPs) using magnetic force microscopy (MFM) is described. Quantitative measurement is realized by calibration of the MFM signal using an MNP reference sample with traceably determined magnetization. A resolution of the magnetic moment of the order of 10?18 A m2 under ambient conditions is demonstrated, which is presently limited by the tip's magnetic moment and the noise level of the instrument. The calibration scheme can be applied to practically any magnetic force microscope and tip, thus allowing a wide range of future applications, for example in nanomagnetism and biotechnology. PMID:22730177

Sievers, Sibylle; Braun, Kai-Felix; Eberbeck, Dietmar; Gustafsson, Stefan; Olsson, Eva; Schumacher, Hans Werner; Siegner, Uwe

2012-01-01

181

Color metallography and electron microscopy techniques applied to the characterization of 413.0 aluminum alloys.  

PubMed

The influence on alloy 413.0 of the refinement and modification of its microstructure was analyzed by means of several microscopy techniques, as well as the effect of the application of high pressure during solidification. For each treatment and solidification pressure condition employed, the most suitable microscopy techniques for identifying and characterizing the phases present were investigated. Color metallography and electron microscopy techniques were applied to the qualitative microstructural analysis. Volume fraction and grain size of the primary ?-Al were characterized by quantitative metallographic techniques. The results show that the effect caused by applying high pressure during solidification of the alloy is more pronounced than that caused by modification and refinement of the microstructure when it solidifies at atmospheric pressure. Furthermore, it has been shown that, for Al-Si alloy characterization, when aiming to characterize the primary ?-Al phase, optical color metallography observed under crossed polarized light plus a sensitive tint filter is the most suitable technique. When the goal is to characterize the eutectic Si, the use of optical color metallography or electron microscopy is equally valid. The characterization of iron-rich intermetallic compounds should preferably be performed by means of backscattered electron imaging. PMID:23701972

Vander Voort, George; Asensio-Lozano, Juan; Suárez-Peña, Beatriz

2013-08-01

182

Investigation of Nematode Diversity using Scanning Electron Microscopy and Fluorescent Microscopy  

NASA Astrophysics Data System (ADS)

Nematode worms account for the vast majority of the animals in the biosphere. They are colossally important to global public health as parasites, and to agriculture both as pests and as beneficial inhabitants of healthy soil. Amphid neurons are the anterior chemosensory neurons in nematodes, mediating critical behaviors including chemotaxis and mating. We are examining the cellular morphology and external anatomy of amphid neurons, using fluorescence microscopy and scanning electron microscopy, respectively, of a wide range of soil nematodes isolated in the wild. We use both classical systematics (e.g. diagnostic keys) and molecular markers (e.g. ribosomal RNA) to classify these wild isolates. Our ultimate aim is to build a detailed anatomical database in order to dissect genetic pathways of neuronal development and function across phylogeny and ecology.

Seacor, Taylor; Howell, Carina

2013-03-01

183

Axial ion-electron emission microscopy of IC radiation hardness  

NASA Astrophysics Data System (ADS)

A new system for performing radiation effects microscopy (REM) has been developed at Sandia National Laboratory in Albuquerque. This system combines two entirely new concepts in accelerator physics and nuclear microscopy. A radio frequency quadrupole (RFQ) linac is used to boost the energy of ions accelerated by a conventional Tandem Van de Graaff-Pelletron to velocities of 1.9 MeV/amu. The electronic stopping power for heavy ions is near a maximum at this velocity, and their range is ˜20 ?m in Si. These ions therefore represent the most ionizing form of radiation in nature, and are nearly ideal for performing single event effects testing of integrated circuits. Unfortunately, the energy definition of the RFQ-boosted ions is rather poor (˜ a few %), which makes problematic the focussing of such ions to the submicron spots required for REM. To circumvent this problem, we have invented ion electron emission microscopy (IEEM). One can perform REM with the IEEM system without focussing or scanning the ion beam. This is because the position on the sample where each ion strikes is determined by projecting ion-induced secondary electrons at high magnification onto a single electron position sensitive detector. This position signal is then correlated with each REM event. The IEEM system is now mounted along the beam line in an axial geometry so that the ions pass right through the electron detector (which is annular), and all of the electrostatic lenses used for projection. The beam then strikes the sample at normal incidence which results in maximum ion penetration and removes a parallax problem experienced in an earlier system. Details of both the RFQ-booster and the new axial IEEM system are given together with some of the initial results of performing REM on Sandia-manufactured radiation hardened integrated circuits.

Doyle, B. L.; Vizkelethy, G.; Walsh, D. S.; Swenson, D.

2002-05-01

184

Correlative 3D superresolution fluorescence and electron microscopy reveal the relationship of  

E-print Network

illumination such as saturated structured illumination microscopy (3) or stim- ulated emission depletion (STEDCorrelative 3D superresolution fluorescence and electron microscopy reveal the relationship of superresolution optical microscopy techniques provides the possibility to augment EM with nanometer

Eddy, Sean

185

Quantitative comparison of preparation methodologies for x-ray fluorescence microscopy of brain tissue  

Microsoft Academic Search

X-ray fluorescence microscopy (XFM) facilitates high-sensitivity quantitative imaging of trace metals at high spatial resolution\\u000a over large sample areas and can be applied to a diverse range of biological samples. Accurate determination of elemental content\\u000a from recorded spectra requires proper calibration of the XFM instrument under the relevant operating conditions. Here, we\\u000a describe the manufacture, characterization, and utilization of multi-element

Simon A. James; Damian E. Myers; Martin D. de Jonge; Stefan Vogt; Chris G. Ryan; Brett A. Sexton; Pamela Hoobin; David Paterson; Daryl L. Howard; Sheridan C. Mayo; Matteo Altissimo; Gareth F. Moorhead; Stephen W. Wilkins

186

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

2014-05-01

187

Sequential microdissection and scanning electron microscopy of ciliary microvascular castings.  

PubMed

Intracarotid injection of methylmethacrylate followed by tissue corrosion produces detailed replicas of the ocular microvasculature that can then be studied with the scanning electron microscope. The resultant photographs allow careful scrutiny of even the finest capillaries. However, when applied to the ciliary body, a complicated three dimensional system, we found stereo scanning electron micrography essential to fully appreciate its arteriolar and capillary interconnections. These stereoscopic analyses indicated that specific superficial vessels required excision to visualize deeper, previously hidden microvascular relationships. Using a pneumatically powered ultra microscissors guided by a micromanipulator we successfully removed these vessels. Deeper views were then obtained through repeat stereo scanning electron microscopy. This sequential microdissection and stereo scanning electron microscopy revealed that the major ciliary processes are supplied by two types of arterioles arising from the major arterial circle. Constricted anterior arterioles supply anterior and marginal aspects of the processes as well as interprocess capillary beds. Less constricted posterior arterioles feed capillaries confined to the base of the major processes as well as minor ciliary processes via posterior interprocess connections. Choroidal veins were seen to directly drain both anterior and posterior interprocess capillary beds. PMID:6385224

Morrison, J C; Van Buskirk, E M

1984-01-01

188

Correlative Cryo-electron Tomography and Optical Microscopy of Cells  

PubMed Central

The biological processes occurring in a cell are complex and dynamic, and to achieve a comprehensive understanding of the molecular mechanisms underlying these processes, both temporal and spatial information is required. While cryo-electron tomography (cryoET) provides three-dimensional (3D) still pictures of near-native state cells and organelles at molecular resolution, fluorescence light microscopy (fLM) offers movies of dynamic cellular processes in living cells. Combining and integrating these two commonly used imaging modalities (termed correlative microscopy) provides a powerful means to not only expand the imaging scale and resolution but also to complement the dynamic information available from optical microscopy with the molecular-level, 3D ultrastructure detail provided by cryoET. As such, a correlative approach performed on a given specimen can provide high resolution snapshots of dynamic cellular events. In this article, I review recent advances in correlative light microscopy and cryoET and discuss major findings made available by applying this method. PMID:23962486

Zhang, Peijun

2013-01-01

189

Application of ion etching to immunoscanning electron microscopy.  

PubMed

A method for achieving both the light and electron microscopic observations of the same immunolabeled semithin section is described. Mild ion etching (IE) was performed on the semithin LR white resin sections of rat pancreas to evaluate conditions for scanning electron microscopic secondary electron image observations. Before immunocytochemical staining, very mild, rapid etching was conducted as follows: ionization voltage 300 V, operating vacuum 35 Pa, and etching time 1 min, employing an ion coater above sections on glass slides. The sections were immunohistochemically stained with anti-insulin and immunogold in association with silver enhancement techniques for light microscopic observation, in which B cells in pancreatic islets were positively stained brown. Subsequently, essential mild IE was performed over the stained section as follows: 350 V, 38 Pa, 29 min. The samples were coated with platinum for scanning electron microscopic secondary electron images, in which the cores of secretory granules of the B cells were positively labeled with gold-silver particles. The present method is suitable for detection of substances involving immunogold labeling. It enables us to obtain high-resolution images at low magnification that can be correlated with light microscopic observations. Middle to high magnifications are applicable for detailed observations with secondary electron imaging scanning electron microscopy. PMID:16170818

Yahiro, Junko; Nagato, Toshikazu

2005-08-01

190

Simulation and Quantitative Interpretation of Electron Spectra for Surface Analysis  

Microsoft Academic Search

Quantitative interpretation of electron spectra requires a thorough understanding of the surface sensitivity of the technique, or, in other words, the transfer of the signal electrons from the source to the detector. The theory of electron transport of relevance for XPS, AES, REELS, EPES and related techniques is meanwhile well established. Within the framework of the partial intensity approach it

W. S. M. Werner

191

Time resolved electron microscopy for in situ experiments  

NASA Astrophysics Data System (ADS)

Transmission electron microscopy has functioned for decades as a platform for in situ observation of materials and processes with high spatial resolution. Yet, the dynamics often remain elusive, as they unfold too fast to discern at these small spatial scales under traditional imaging conditions. Simply shortening the exposure time in hopes of capturing the action has limitations, as the number of electrons will eventually be reduced to the point where noise overtakes the signal in the image. Pulsed electron sources with high instantaneous current have successfully shortened exposure times (thus increasing the temporal resolution) by about six orders of magnitude over conventional sources while providing the necessary signal-to-noise ratio for dynamic imaging. We describe here the development of this new class of microscope and the principles of its operation, with examples of its application to problems in materials science.

Campbell, Geoffrey H.; McKeown, Joseph T.; Santala, Melissa K.

2014-12-01

192

SEGMENTATION OF MITOCHONDRIA IN ELECTRON MICROSCOPY IMAGES USING ALGEBRAIC CURVES  

PubMed Central

High-resolution microscopy techniques have been used to generate large volumes of data with enough details for understanding the complex structure of the nervous system. However, automatic techniques are required to segment cells and intracellular structures in these multi-terabyte datasets and make anatomical analysis possible on a large scale. We propose a fully automated method that exploits both shape information and regional statistics to segment irregularly shaped intracellular structures such as mitochondria in electron microscopy (EM) images. The main idea is to use algebraic curves to extract shape features together with texture features from image patches. Then, these powerful features are used to learn a random forest classifier, which can predict mitochondria locations precisely. Finally, the algebraic curves together with regional information are used to segment the mitochondria at the predicted locations. We demonstrate that our method outperforms the state-of-the-art algorithms in segmentation of mitochondria in EM images. PMID:25132915

Seyedhosseini, Mojtaba; Ellisman, Mark H.; Tasdizen, Tolga

2014-01-01

193

New immunolatex spheres: visual markers of antigens on lymphocytes for scanning electron microscopy  

PubMed Central

New immunochemical reagents consisting of antibodies bound to small latex spheres were used as visual markers for the detection and localization of cell surface antigens by scanning electron microscopy. Cross-linked latex spheres of various sizes from 300 to 3,4000 A in diameter were synthesized by aqueous emulsion copolymerization of methacrylate derivatives containing hydroxyl and carboxyl functional groups. Proteins and other molecules containing primary amino groups were covalently bonded to the acrylic spheres under a variety of mild conditions by the aqueous carbodiimide, cyanogen bromide, and glutaraldehyde methods. For use in the indirect immunochemical-labeling technique, goat antibodies directed against rabbit immunoglobulins were bonded to the spheres. These immunolatex reagents were shown to bind only to cells (red blood and lymphocytes) which had previously been sensitized with rabbit antibodies against cell surface antigens. Mouse spleen lymphocytes with exposed immunoglobulins on their surface (B cells) were labeled with these spheres and distinguished from unlabeled or T lymphocytes by scanning electron microscopy. The distribution of Ig receptors on lymphocytes was also studied using the spheres as visual markers. When lymphocytes were fixed with glutaraldehyde and subsequently labeled with the immunolatex reagents, a random distribution was observed by scanning electron microscopy; a patchy distribution was observed when unfixed lymphocytes were used. These results are consistent with studies using ferritin-labeled antibodies (S. De Petris and M. Raff. 1973. Nature [Lond.]. 241:257.) and support the view that Ig receptors on lymphocytes undergo translational diffusion. In addition to serving as visual markers for scanning electron microscopy, these latex spheres tagged with fluorescent or radioactive molecules have applications as highly sensitive markers for fluorescent microscopy and as reagents for quantitative studies of cell surface antigens and other receptors. PMID:803228

1975-01-01

194

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

195

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

196

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. PMID:13357696

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

1956-01-01

197

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

198

Investigation of the mechanism of transdermal penetration enhancer: a comparison of multiphoton microscopy and electron microscopy  

NASA Astrophysics Data System (ADS)

The aim of this study is to characterize the ability of multiphoton microscopy in monitoring the transdermal penetration enhancing effect of a depilatory agent and the associated structural alterations of stratum corneum. The result is compared with the electron microscopic findings. Our results show that the penetration of both hydrophilic and hydrophobic agents can be enhanced. The morphology of corneocytes becomes a homogenized pattern with focal detachment of surface corneocytes. In combination with Nile red staining, multiphoton imaging also shows that the regular motar-like distribution of lipid matrix was disrupted into a homogenized pattern of lipid distribution. These results are well correlated with the findings of ultrastructural analysis by electron micrographs showing disintegration of the protein envelope of coenocytes, disruption of intracellular keratin and loss of the regular lamellar packing of intercellular lipids. We conclude that, in addition to quantifying the permeation profiles of model drugs, multiphoton microscopy is able to detect the penetration enhancer-induced structural alterations of stratum corneum.

Lin, Sung-Jan; Lee, Jin-Ning; Lin, Chiao-Ying; Chan, Chih-Chieh; Lin, Ming-Gu; Wang, Chun-Chin; Tan, Hsin-Yuan; Tsai, Tsung-Hua; Jee, Shiou-Hwa; Dong, Chen-Yuan

2008-02-01

199

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

200

[Scanning electron microscopy with corrosive preparations in pathology].  

PubMed

Methodical aspects of scanning electron microscopy of corrosion preparations (SEMCP) are described on the basis of the authors' own data and those from the literature. A critical analysis of the currently used injection masses and the results obtained by SEMCP is given. New data are emphasized, introduced into pathological morphology after the adoption of SEMCP. Relief formations of casts of the blood and lymph vessels in health and disease are classified. The prospects of and main approaches to the use of SEMCP in pathological morphology are discussed. PMID:7073513

Karaganov, Ia L; Mironov, A A; Mironov, V A

1982-01-01

201

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

202

Measurement of dihedral angles by scanning electron microscopy.  

NASA Technical Reports Server (NTRS)

The extension of Hoover's (1971) technique to the case of dihedral-angle measurement is described. Dihedral angles are often determined by interferometry on thermally grooved grain boundaries to obtain information on relative interfacial energies. In the technique considered the measured angles approach the true angles as the tilt angle approaches 90 deg. It is pointed out that the scanning electron microscopy method provides a means of seeing the real root of a groove at a lateral magnification which is higher than that obtainable with interferometry.

Achutaramayya, G.; Scott, W. D.

1973-01-01

203

Microstructural studies of dental amalgams using analytical transmission electron microscopy  

NASA Astrophysics Data System (ADS)

Dental amalgams have been used for centuries as major restorative materials for decaying teeth. Amalgams are prepared by mixing alloy particles which contain Ag, Sn, and Cu as the major constituent elements with liquid Hg. The study of microstructure is essential in understanding the setting reactions and improving the properties of amalgams. Until the work reported in this dissertation, optical microscopy (OM), scanning electron microscopy (SEM), and x-ray diffractometry (XRD) were used commonly to analyze amalgam microstructures. No previous systematic transmission electron microscopy (TEM) study has been performed due to sample preparation difficulties and composite structure of dental amalgams. The goal of this research was to carry out detailed microstructural and compositional studies of dental amalgams. This was accomplished using the enhanced spatial resolution of the TEM and its associated microanalytical techniques, namely, scanning transmission electron microscopy (STEM), x-ray energy dispersive spectroscopy (XEDS) and micro-microdiffraction (mumuD). A new method was developed for thinning amalgam samples to electron transparency using the "wedge technique." Velvalloy, a low-Cu amalgam, and Tytin, a high-Cu amalgam, were the two amalgams characterized. Velvalloy is composed of a Agsb2Hgsb3\\ (gammasb1)/HgSnsb{7-9}\\ (gammasb2) matrix surrounding unreacted Agsb3Sn (gamma) particles. In addition, hitherto uncharacterized reaction layers between Agsb3Sn(gamma)/Agsb2Hgsb3\\ (gammasb2)\\ and\\ Agsb2Hgsb3\\ (gammasb1)/HgSnsb{7-9}\\ (gammasb2) were observed and analyzed. An Ag-Hg-Sn (betasb1) phase was clearly identified for the first time. In Tytin, the matrix consists of Agsb2Hgsb3\\ (gammasb1) grains. Fine precipitates of Cusb6Snsb5\\ (etasp') are embedded inside the gammasb1 and at the grain boundaries. These precipitates are responsible for the improved creep resistance of Tytin compared to Velvalloy. The additional Cu has completely eliminated the gammasb2 phase which is the weakest component of amalgams. Ag-Hg-Sn (betasb1) and large grains of Cusb6Snsb5\\ (etasp') are found adjacent to the unreacted alloy particles. Tytin alloy particles contain Cusb3Sn\\ (epsilon) precipitates in a matrix of Agsb3Sn (gamma) and Agsb4Sn\\ (beta). SEM was used to correlate the TEM findings in the context of the general microstructure. The results are in good agreement with those published in the literature. The microstructural details reported here, many of which were not previously available, will help provide insight into the deformation mechanisms of dental amalgams.

Hooghan, Tejpal Kaur

204

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

205

Scanning and transmission electron microscopy of odontogenic keratocysts.  

PubMed

The ultrastructural characteristics of the superficial cells of the epithelial lining of odontogenic keratocysts were studied. Examples of both the parakeratinized type and the less common orthokeratinized variant were examined. Scanning electron microscopy reveals that the morphology of the two cyst types is distinctly different. In parakeratinized cysts the transition of the epithelial cells into parakeratin is readily apparent and the epithelial surface is sparsely covered with parakeratin squames. In the orthokeratinized type the surface morphology is more uniform and is entirely covered with a leafy layer of keratin squames. The morphologic differences between the parakeratinized and orthokeratinized cysts may reflect differences in their biologic behavior. PMID:1058440

Wysocki, G P; Sapp, J P

1975-10-01

206

Catching HIV 'in the act' with 3D electron microscopy  

PubMed Central

The development of a safe, effective vaccine to prevent human immunodeficiency virus (HIV) infection is a key step for controlling the disease on a global scale. However, many aspects of HIV biology make vaccine design problematic, including the sequence diversity and structural variability of the surface envelope glycoproteins and the poor accessibility of neutralization-sensitive epitopes on the virus. In this review, we discuss recent progress in understanding HIV in a structural context using emerging tools in 3D electron microscopy, and outline how some of these advances could be important for a better understanding of mechanisms of viral entry and for vaccine design. PMID:23850373

Earl, Lesley A.; Lifson, Jeffrey D.; Subramaniam, Sriram

2013-01-01

207

Transmission electron microscopy examination of oxide layers formed on Zr alloys  

E-print Network

Transmission electron microscopy examination of oxide layers formed on Zr alloys Aylin Yilmazbayhan, United States Received 14 July 2005; accepted 31 October 2005 Abstract A transmission electron microscopy. In this work, cross-sectional transmission electron microscopy was used to determine the morphology

Motta, Arthur T.

208

Nanoparticle imaging. Electron microscopy of gold nanoparticles at atomic resolution.  

PubMed

Structure determination of gold nanoparticles (AuNPs) is necessary for understanding their physical and chemical properties, but only one AuNP larger than 1 nanometer in diameter [a 102-gold atom NP (Au102NP)] has been solved to atomic resolution. Whereas the Au102NP structure was determined by x-ray crystallography, other large AuNPs have proved refractory to this approach. Here, we report the structure determination of a Au68NP at atomic resolution by aberration-corrected transmission electron microscopy, performed with the use of a minimal electron dose, an approach that should prove applicable to metal NPs in general. The structure of the Au68NP was supported by small-angle x-ray scattering and by comparison of observed infrared absorption spectra with calculations by density functional theory. PMID:25146285

Azubel, Maia; Koivisto, Jaakko; Malola, Sami; Bushnell, David; Hura, Greg L; Koh, Ai Leen; Tsunoyama, Hironori; Tsukuda, Tatsuya; Pettersson, Mika; Häkkinen, Hannu; Kornberg, Roger D

2014-08-22

209

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

210

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. PMID:23382239

Lorenz, Ulrich J.; Zewail, Ahmed H.

2013-01-01

211

Interferometric time-stretch microscopy for ultrafast quantitative cellular and tissue imaging at 1 ?m.  

PubMed

Quantitative phase imaging (QPI) has been proven to be a powerful tool for label-free characterization of biological specimens. However, the imaging speed, largely limited by the image sensor technology, impedes its utility in applications where high-throughput screening and efficient big-data analysis are mandated. We here demonstrate interferometric time-stretch (iTS) microscopy for delivering ultrafast quantitative phase cellular and tissue imaging at an imaging line-scan rate >20 MHz—orders-of-magnitude faster than conventional QPI. Enabling an efficient time-stretch operation in the 1-?m wavelength window, we present an iTS microscope system for practical ultrafast QPI of fixed cells and tissue sections, as well as ultrafast flowing cells (at a flow speed of up to 8 m?s). To the best of our knowledge, this is the first time that time-stretch imaging could reveal quantitative morphological information of cells and tissues with nanometer precision. As many parameters can be further extracted from the phase and can serve as the intrinsic biomarkers for disease diagnosis, iTS microscopy could find its niche in high-throughput and high-content cellular assays (e.g., imaging flow cytometry) as well as tissue refractometric imaging (e.g., whole-slide imaging for digital pathology). PMID:24983913

Lau, Andy K S; Wong, Terence T W; Ho, Kenneth K Y; Tang, Matthew T H; Chan, Antony C S; Wei, Xiaoming; Lam, Edmund Y; Shum, Ho Cheung; Wong, Kenneth K Y; Tsia, Kevin K

2014-07-01

212

Interferometric time-stretch microscopy for ultrafast quantitative cellular and tissue imaging at 1 ?m  

NASA Astrophysics Data System (ADS)

Quantitative phase imaging (QPI) has been proven to be a powerful tool for label-free characterization of biological specimens. However, the imaging speed, largely limited by the image sensor technology, impedes its utility in applications where high-throughput screening and efficient big-data analysis are mandated. We here demonstrate interferometric time-stretch (iTS) microscopy for delivering ultrafast quantitative phase cellular and tissue imaging at an imaging line-scan rate >20 MHz-orders-of-magnitude faster than conventional QPI. Enabling an efficient time-stretch operation in the 1-?m wavelength window, we present an iTS microscope system for practical ultrafast QPI of fixed cells and tissue sections, as well as ultrafast flowing cells (at a flow speed of up to 8 m/s). To the best of our knowledge, this is the first time that time-stretch imaging could reveal quantitative morphological information of cells and tissues with nanometer precision. As many parameters can be further extracted from the phase and can serve as the intrinsic biomarkers for disease diagnosis, iTS microscopy could find its niche in high-throughput and high-content cellular assays (e.g., imaging flow cytometry) as well as tissue refractometric imaging (e.g., whole-slide imaging for digital pathology).

Lau, Andy K. S.; Wong, Terence T. W.; Ho, Kenneth K. Y.; Tang, Matthew T. H.; Chan, Antony C. S.; Wei, Xiaoming; Lam, Edmund Y.; Shum, Ho Cheung; Wong, Kenneth K. Y.; Tsia, Kevin K.

2014-07-01

213

Combined scanning transmission X-ray and electron microscopy for the characterization of bacterial endospores.  

PubMed

Endospores (also referred to as bacterial spores) are bacterial structures formed by several bacterial species of the phylum Firmicutes. Spores form as a response to environmental stress. These structures exhibit remarkable resistance to harsh environmental conditions such as exposure to heat, desiccation, and chemical oxidants. The spores include several layers of protein and peptidoglycan that surround a core harboring DNA as well as high concentrations of calcium and dipicolinic acid (DPA). A combination of scanning transmission X-ray microscopy, scanning transmission electron microscopy, and energy dispersive spectroscopy was used for the direct quantitative characterization of bacterial spores. The concentration and localization of DPA, Ca(2+) , and other elements were determined and compared for the core and cortex of spores from two distinct genera: Bacillus subtilis and Desulfotomaculum reducens. This micro-spectroscopic approach is uniquely suited for the direct study of individual bacterial spores, while classical molecular and biochemical methods access only bulk characteristics. PMID:25048294

Jamroskovic, Jan; Shao, Paul P; Suvorova, Elena; Barak, Imrich; Bernier-Latmani, Rizlan

2014-09-01

214

Electron-beam-assisted scanning tunneling microscopy of insulating surfaces  

NASA Astrophysics Data System (ADS)

Insulating materials are widely used in electronic devices. Bulk insulators and insulating films pose unique challenges for high resolution study since most commonly used charged particle surface analysis techniques are incompatible with insulating surfaces and materials. A, method of performing scanning tunneling microscopy (STM) on insulating surfaces has been investigated. The method is referred to as electron-beam assisted scanning tunneling microscopy (e-BASTM). It is proposed that by coupling the STM and the scanning electron microscopy (SEM) as one integrated device, that insulating materials may be studied, obtaining both high spatial resolution, and topographic and electronic resolution. The premise of the technique is based on two physical consequences of the interaction of an energetic electron beam (PE) with a material. First, when an electron beam is incident upon a material, low level material electrons are excited into conduction band states. For insulators, with very high secondary electron yields, the population of conduction band states could be quite significant. Second, for specific incident primary beam energies, the resulting electron yield will be equal to the incoming beam intensity. These are referred to as the cross over energies (E1 and E2). For a stationary primary beam at E2 the current entering the sample and the current leaving sample are equal so that a state of dynamic equilibrium is quickly reached whereby the charge density distribution local to primary beam, both at the surface and within the material, is fixed. Thus, if the surface of an insulator is illuminated with an energetic electron beam at E2, the surface will be locked to some potential and there will be filled conduction band states. Under these conditions, it may be possible to make STM measurements of material even though it is insulating. That is, from an STM point of view, it may be possible to make an insulator `act' like a conductor. In order to test the principle of e-BASTM, metals, thin insulating films, and bulk insulators have been examined. For metals, as expected, we observe no alteration of the tunneling signal due to the PE beam. However, with SiO 2, there is a significant increase in the tunneling current which can be directly attributed to the PE beam. For Al2O3 and CaF2 it is found that the surfaces are damaged too quickly by the PE beam for this technique to be applied suggesting that e-BASTM may only be suitable for a small class of materials. The STM (not e-BASTM) has been used to electrically stress thin films of SiO2 (native oxide thickness). The stressing is observed to create trapping states which have been connected to stress induced leakage currents (SILC) in metal/SiO2/Si devices. The effect of the stress is observed to depend on the polarization of the applied bias (positive or negative). The trapping site density is observed to reach levels on the order of 1013-1014 traps/cm2 which is about a factor of 10-100 higher than what has been previously been reported.

Bullock, Eugene Thomas

2000-07-01

215

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. PMID:24137159

Miyazaki, Naoyuki; Nakagawa, Atsushi; Iwasaki, Kenji

2013-01-01

216

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

217

Influence of sample preparation and identification of subcelluar structures in quantitative holographic phase contrast microscopy  

NASA Astrophysics Data System (ADS)

Digital holographic microscopy (DHM) provides label-free quantitative phase contrast with low demands on sample preparation. Nevertheless, for DHM measurements on fixed cells the mounting medium has to be considered while the phase contrast of living cells may be influenced by the used buffer solution. To quantify these effects, the maximum cell caused phase contrast and the visibility of the nucleoli were analyzed. A second aim of the study was to identify subcellular components in DHM phase contrast images. Therefore, comparative investigations using bright field imaging, DHM and fluorescence microscopy with 4',6- Diamidino-2-phenylindol (DAPI) staining were performed. DAPI-staining visualizes cell components containing DNA. The obtained results demonstrate exemplarily for two tumor cell lines that from DHM phase contrast images of fixed cells in phosphate buffer saline (PBS) cell thickness values are obtained which are comparable to living cells. Furthermore, it is shown that in many cases nucleus components can be identified only by DHM phase contrast.

Kemper, Björn; Schmidt, Lisa; Przibilla, Sabine; Rommel, Christina; Vollmer, Angelika; Ketelhut, Steffi; Schnekenburger, Jürgen; von Bally, Gert

2010-04-01

218

Quantitative phase microscopy of red blood cells with slightly-off-axis interference  

NASA Astrophysics Data System (ADS)

Microscopic interferometry is a noncontact technique for quantitative phase imaging of live cells. The method combines the principles of single-shot slightly-off-axis interferometry and confocal microscopy and is characterized by real-time acquisition capabilities and optimized spatial resolution. However, slightly-off-axis interferometry requires less detector bandwidth than traditional off-axis interferometry and fewer phase-shifted steps than on-axis interferometry. Meanwhile, confocal microscopy allows microstructure magnification imaging. To validate the utility of this technique, experimental and theoretical comparisons are given. The potential of the technique for phase microcopy is demonstrated by experiments on red blood cells. This study will set the basis for interferometric phase measurements of dynamic processes with fine spatial details, especially for observing live biological cell dynamics.

Xue, Liang; Lai, Jian-cheng; Li, Zhen-hua

2010-11-01

219

Section 6 More Quantitative Aspects of Electronic Structure Calculations.  

E-print Network

Section 6 More Quantitative Aspects of Electronic Structure Calculations. Chapter 17 Electrons, solids, and all other chemical species. The phrase ab initio implies that one attempts to solve structure that are approximate. Their predictions must be improved to achieve reasonably accurate solutions

Simons, Jack

220

Relativistic effects in photon-induced near field electron microscopy.  

PubMed

Electrons and photons, when interacting via a nanostructure, produce a new way of imaging in space and time, termed photon-induced near field electron microscopy or PINEM [Barwick et al. Nature 2009, 462, 902]. The phenomenon was described by considering the evanescent field produced by the nanostructure, but quantification of the experimental results was achieved by solving the Schrödinger equation for the interaction of the three bodies. The question remained, is the nonrelativistic formulation sufficient for this description? Here, relativistic and nonrelativistic quantum mechanical formulations are compared for electron-photon interaction mediated by nanostructures, and it is shown that there is an exact equivalence for the two formulations. The nonrelativistic formulation was found to be valid in the relativistic regime when using in the former formulation the relativistically corrected velocity (and the corresponding values of momentum and energy). In the PINEM experiment, 200 keV electrons were utilized, giving the experimental (relativistically corrected) velocity to be 0.7c(v without relativistic correction is 0.885c). When this value (0.7c), together with those of the corresponding momentum (p(c) = mv) and energy (E(c) = (1/2)mv(2)), is used in the first order solution of the Schrödinger formulation, an exact equivalence is obtained. PMID:22741915

Park, Sang Tae; Zewail, Ahmed H

2012-11-26

221

Structured illumination diffraction phase microscopy for broadband, subdiffraction resolution, quantitative phase imaging.  

PubMed

Structured illumination microscopy (SIM) is an established technique that allows subdiffraction resolution imaging by heterodyning high sample frequencies into the system's passband via structured illumination. However, until now, SIM has been typically used to achieve subdiffraction resolution for intensity-based imaging. Here, we present a novel optical setup that uses structured illumination with a broadband light source to obtain noise-reduced, subdiffraction resolution, quantitative phase imaging (QPM) of cells. We compare this with a previous work for subdiffraction QPM imaging via SIM that used a laser source, and was thus still corrupted by coherent noise. PMID:24562266

Chowdhury, Shwetadwip; Izatt, Joseph

2014-02-15

222

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

2011-03-01

223

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

224

Simultaneous two-wavelength transmission quantitative phase microscopy with a color camera.  

PubMed

We present a quantitative phase microscopy method that uses a Bayer mosaic color camera to simultaneously acquire off-axis interferograms in transmission mode at two distinct wavelengths. Wrapped phase information is processed using a two-wavelength algorithm to extend the range of the optical path delay measurements that can be detected using a single temporal acquisition. We experimentally demonstrate this technique by acquiring the phase profiles of optically clear microstructures without 2pi ambiguities. In addition, the phase noise contribution arising from spectral channel crosstalk on the color camera is quantified. PMID:20680075

Rinehart, Matthew T; Shaked, Natan T; Jenness, Nathan J; Clark, Robert L; Wax, Adam

2010-08-01

225

An open-source deconvolution software package for 3-D quantitative fluorescence microscopy imaging  

PubMed Central

Summary Deconvolution techniques have been widely used for restoring the 3-D quantitative information of an unknown specimen observed using a wide-field fluorescence microscope. Deconv, an open-source deconvolution software package, was developed for 3-D quantitative fluorescence microscopy imaging and was released under the GNU Public License. Deconv provides numerical routines for simulation of a 3-D point spread function and deconvolution routines implemented three constrained iterative deconvolution algorithms: one based on a Poisson noise model and two others based on a Gaussian noise model. These algorithms are presented and evaluated using synthetic images and experimentally obtained microscope images, and the use of the library is explained. Deconv allows users to assess the utility of these deconvolution algorithms and to determine which are suited for a particular imaging application. The design of Deconv makes it easy for deconvolution capabilities to be incorporated into existing imaging applications. PMID:19941558

SUN, Y.; DAVIS, P.; KOSMACEK, E. A.; IANZINI, F.; MACKEY, M. A.

2010-01-01

226

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

227

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

228

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

229

Optimized Negative-Staining Electron Microscopy for Lipoprotein Studies  

PubMed Central

Background Negative-staining (NS), a rapid, simple and conventional technique of electron microscopy (EM), has been commonly used to initially study the morphology and structure of proteins for half a century. Certain NS protocols however can cause artifacts, especially for structurally flexible or lipid-related proteins, such as lipoproteins. Lipoproteins were often observed in the form of rouleau as lipoprotein particles appeared to be stacked together by conventional NS protocols. The flexible components of lipoproteins, i.e. lipids and amphipathic apolipoproteins, resulted in the lipoprotein structure being sensitive to the NS sample preparation parameters, such as operational procedures, salt concentrations, and the staining reagents. Scope of review The most popular NS protocols that have been used to examine lipoprotein morphology and structure were reviewed. Major conclusions The comparisons show that an optimized NS (OpNS) protocol can eliminate the rouleau artifacts of lipoproteins, and that the lipoproteins are similar in size and shape as statistically measured from two EM methods, OpNS and cryo-electron microscopy (cryo-EM). OpNS is a high-throughput, high-contrast and high-resolution (near 1 nm, but rarely better than 1 nm) method which has been used to discover the mechanics of a small protein, 53 kDa cholesterol ester transfer protein (CETP), and the structure of an individual particle of a single protein by individual-particle electron tomography (IPET), i.e. a 14 Å-resolution IgG antibody three-dimensional map. General significance It is suggested that OpNS can be used as a general protocol to study the structure of proteins, especially highly dynamic proteins with equilibrium-fluctuating structures. PMID:23032862

Zhang, Lei; Tong, Huimin; Garewal, Mark; Ren, Gang

2012-01-01

230

Transmission electron microscopy study on clusters and nanostructured mesoporous materials  

NASA Astrophysics Data System (ADS)

Clusters are entities of two to a few hundred thousand of atoms of the same or a different chemical kind packed together with an arbitrary morphology and internal structural ordering. "What is the morphology of a cluster, how will a cluster adapt itself to a substrate and will there be chemical ordering in bimetallic clusters?" are some questions that are tried to answer in this Ph.D. thesis. Therefore Au and different Au-Cu alloy clusters are studied with transmission electron microscopy (TEM). The cluster-surface interaction of Au clusters deposited with low energy on MgO cubes and on amorphous carbon and its influence on the morphology of the Au cluster is investigated. Not only have the clusters different morphologies for the two different surfaces, also a dilation of the Au lattice is measured for the clusters deposited on the crystalline surface of MgO to perfectly accommodate the MgO lattice. Classical molecular dynamics (MD) is applied to model this behaviour. Good agreement is found between experimental images and simulated images using the model calculated by MD. Au-Cu bimetallic alloy clusters are produced in a laser vaporisation source starting from Au-Cu alloy targets with different stoichiometric compositions. The overall chemical composition in the clusters is the same as the chemical composition of the target material; but the crystal structure of the Au-Cu alloy clusters differs from their known bulk crystal structure. No chemical ordering exists between Au and Cu atoms and the clusters are solid solutions. Monte Carlo (MC) simulations however predict Cu3Au clusters ordered in the core but with a disordered mantle. The possible origins of the differences between experiment and Monte Carlo simulations are discussed. In the second part of this Ph.D. thesis, transmission electron microscopy (TEM) on nanostructured mesoporous materials is discussed. Mesoporous materials, prepared with alkanes and trimethylbenzene as swelling agents, are studied. Two phases are found for these materials: a hexagonal phase, like MCM-41 and a face centered cubic phase. The defects in these textures are characterised and compared with the crystal defects in regular fcc crystals. The structure and pore distribution of spherical MCM-41 particles are studied using scanning electron microscopy, X-ray diffraction and TEM. The results are compared with well known MCM-41 and point out the differences between the two materials. Where the MCM-41 material consists of unidimensional pores, hexagonally packed together, the spherical MCM-41 particles are found to have a spherically symmetric pore distribution, starting from the inner part of the particles to the surface.

Pauwels, Bart

231

Quantitative imaging of cell dynamics in mouse embryos using light-sheet microscopy.  

PubMed

Single/selective-plane illumination, or light-sheet, systems offer several advantages over other fluorescence microscopy methods for live, 3D microscopy. These systems are valuable for studying embryonic development in several animal systems, such as Drosophila, C. elegans and zebrafish. The geometry of the light path in this form of microscopy requires the sample to be accessible from multiple sides and fixed in place so that it can be rotated around a single axis. Popular methods for mounting include hanging the specimen from a pin or embedding it in 1-2% agarose. These methods can be particularly problematic for certain samples, such as post-implantation mouse embryos, that expand significantly in size and are very delicate and sensitive to mounting. To overcome the current limitations and to establish a robust strategy for long-term (24?h) time-lapse imaging of E6.5-8.5 mouse embryos with light-sheet microscopy, we developed and tested a method using hollow agarose cylinders designed to accommodate for embryonic growth, yet provide boundaries to minimize tissue drift and enable imaging in multiple orientations. Here, we report the first 24-h time-lapse sequences of post-implantation mouse embryo development with light-sheet microscopy. We demonstrate that light-sheet imaging can provide both quantitative data for tracking changes in morphogenesis and reveal new insights into mouse embryogenesis. Although we have used this approach for imaging mouse embryos, it can be extended to imaging other types of embryos as well as tissue explants. PMID:25344073

Udan, Ryan S; Piazza, Victor G; Hsu, Chih-Wei; Hadjantonakis, Anna-Katerina; Dickinson, Mary E

2014-11-01

232

Imaging three-dimensional tissue architectures by focused ion beam scanning electron microscopy  

Microsoft Academic Search

In this protocol, we describe a 3D imaging technique known as 'volume electron microscopy' or 'focused ion beam scanning electron microscopy (FIB\\/SEM)' applied to biological tissues. A scanning electron microscope equipped with a focused gallium ion beam, used to sequentially mill away the sample surface, and a backscattered electron (BSE) detector, used to image the milled surfaces, generates a large

Kenneth M Y P'ng; Robert D Young; Christian Pinali; Carlo Knupp; Andrew J Quantock; Andrew J Bushby

2011-01-01

233

Cryo-electron microscopy of extracellular vesicles in fresh plasma  

PubMed Central

Introduction Extracellular vesicles (EV) are phospholipid bilayer-enclosed vesicles recognized as new mediators in intercellular communication and potential biomarkers of disease. They are found in many body fluids and mainly studied in fractions isolated from blood plasma in view of their potential in medicine. Due to the limitations of available analytical methods, morphological information on EV in fresh plasma is still rather limited. Objectives To image EV and determine the morphology, structure and size distribution in fresh plasma by cryo-electron microscopy (cryo-EM). Methods Fresh citrate- and ethylenediaminetetraacetic acid (EDTA)-anticoagulated plasma or EV isolated from these plasmas were rapidly cryo-immobilized by vitrification and visualized by cryo-EM. Results EV isolated from fresh plasma were highly heterogeneous in morphology and size and mostly contain a discernible lipid bilayer (lipid vesicles). In fresh plasma there were 2 types of particles with a median diameter of 30 nm (25–260 nm). The majority of these particles are electron dense particles which most likely represent lipoproteins. The minority are lipid vesicles, either electron dense or electron lucent, which most likely represent EV. Lipid vesicles were occasionally observed in close proximity of platelets in citrate and EDTA-anticoagulated platelet-rich plasma. Cryo-electron tomography (cryo-ET) was employed to determine the 3D structure of platelet secretory granules. Conclusions Cryo-EM is a powerful technique that enables the characterization of EV in fresh plasma revealing structural details and considerable morphological heterogeneity. Only a small proportion of the submicron structures in fresh plasma are lipid vesicles representing EV. PMID:24455109

Yuana, Yuana; Koning, Roman I.; Kuil, Maxim E.; Rensen, Patrick C. N.; Koster, Abraham J.; Bertina, Rogier M; Osanto, Susanne

2013-01-01

234

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. PMID:20082729

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

2010-01-01

235

Energy-resolved analysis of ferroelectric electron emission from TGS using emission electron microscopy  

NASA Astrophysics Data System (ADS)

Ferroelectric electron emission arises when the spontaneous polarization of a ferroelectric is switched due to the application of an electric field. In order to study the origin of emission and the related emission mechanism, space-resolved emission electron microscopy has been employed. The integral energy distribution of the emitted electrons from triglycine-sulfate surfaces has been investigated using a cylindrical sector analyzer and an imaging retarding field analyzer. Space-resolved emission photography and energy distribution measurements were obtained, revealing the effect of ferroelectric switching on the electric field distribution and hence on the emission process. Evidence of secondary electron emission from the metal electrodes has been found.

Klais, M.; Gundel, H. W.; Schönhense, G.

2005-02-01

236

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

237

Quantitative analysis of zinc in rat hippocampal mossy fibers by nuclear microscopy.  

PubMed

Zinc (Zn) is involved in regulating mental and motor functions of the brain. Previous approaches have determined Zn content in the brain using semi-quantitative histological methods. We present here an alternative approach to map and quantify Zn levels in the synapses from mossy fibers to CA3 region of the hippocampus. Based on the use of nuclear microscopy, which is a combination of imaging and analysis techniques encompassing scanning transmission ion microscopy (STIM), Rutherford backscattering spectrometry (RBS), and particle induced X-ray emission (PIXE), it enables quantitative elemental mapping down to the parts per million (?g/g dry weight) levels of zinc in rat hippocampal mossy fibers. Our results indicate a laminar-specific Zn concentration of 240±9?M in wet weight level (135±5?g/g dry weight) in the stratum lucidum (SL) compared to 144±6?M in wet weight level (81±3?g/g dry weight) in the stratum pyramidale (SP) and 78±10?M in wet weight level (44±5?g/g dry weight) in the stratum oriens (SO) of the hippocampus. The mossy fibers terminals in CA3 are mainly located in the SL. Hence the Zn concentration is suggested to be within this axonal presynaptic terminal system. PMID:22766378

Zhang, Binbin; Ren, Minqin; Sheu, Fwu-Shan; Watt, Frank; Routtenberg, Aryeh

2012-09-01

238

High Resolution Scanning Electron Microscopy of Cells Using Dielectrophoresis  

PubMed Central

Ultrastructural analysis of cells can reveal valuable information about their morphological, physiological, and biochemical characteristics. Scanning electron microscopy (SEM) has been widely used to provide high-resolution images from the surface of biological samples. However, samples need to be dehydrated and coated with conductive materials for SEM imaging. Besides, immobilizing non-adherent cells during processing and analysis is challenging and requires complex fixation protocols. In this work, we developed a novel dielectrophoresis based microfluidic platform for interfacing non-adherent cells with high-resolution SEM at low vacuum mode. The system enables rapid immobilization and dehydration of samples without deposition of chemical residues over the cell surface. Moreover, it enables the on-chip chemical stimulation and fixation of immobilized cells with minimum dislodgement. These advantages were demonstrated for comparing the morphological changes of non-budding and budding yeast cells following Lyticase treatment. PMID:25089528

Tang, Shi-Yang; Zhang, Wei; Soffe, Rebecca; Nahavandi, Sofia; Shukla, Ravi; Khoshmanesh, Khashayar

2014-01-01

239

Cryogenic transmission electron microscopy: aqueous suspensions of nanoscale objects.  

PubMed

Direct imaging of nanoscale objects suspended in liquid media can be accomplished using cryogenic transmission electron microscopy (cryo-TEM). Cryo-TEM has been used with particular success in microbiology and other biological fields. Samples are prepared by plunging a thin film of sample into an appropriate cryogen, which essentially produces a snapshot of the suspended objects in their liquid medium. With successful sample preparation, cryo-TEM images can facilitate elucidation of aggregation and self-assembly, as well as provide detailed information about cells and viruses. This work provides an explanation of sample preparation, detailed examples of the many artifacts found in cryo-TEM of aqueous samples, and other key considerations for successful cryo-TEM imaging. PMID:24001937

Burrows, Nathan D; Penn, R Lee

2013-12-01

240

Scanning electron microscopy in nematode-induced giant transfer cells.  

PubMed

A study of giant cells induced by the root-knot nematode, Meloidogyne incognita, in roots of Impatiens balsamina was made by scanning electron microscopy. The cytoplasmic contents of giant cells were removed by a procedure based on KOH digestion, to reveal inner wall structure. Wall ingrowths typical of transfer cells are present in giant cells from six days onwards after induction. They develop on walls adjacent to vascular tissues, and their distribution and development was examined. Pit fields contianing plasmodesmata become elaborated in walls between giant cells, but pit fields are lost between giant cells and cells outside them. The distribution of plasmodesmata in pit fields suggests that de novo formation of plasmodesmata occurs in walls between giant cells. Various aspects of giant cell formation and function are discussed and wall ingrowth development is compared in giant cells and normal transfer cells. PMID:1001022

Jones, M G; Dropkin, V H

1976-01-01

241

Neuron Segmentation in Electron Microscopy Images Using Partial Differential Equations  

PubMed Central

In connectomics, neuroscientists seek to identify the synaptic connections between neurons. Segmentation of cell membranes using supervised learning algorithms on electron microscopy images of brain tissue is often done to assist in this effort. Here we present a partial differential equation with a novel growth term to improve the results of a supervised learning algorithm. We also introduce a new method for representing the resulting image that allows for a more dynamic thresholding to further improve the result. Using these two processes we are able to close small to medium sized gaps in the cell membrane detection and improve the Rand error by as much as 9% over the initial supervised segmentation. PMID:25143802

Jones, Cory; Sayedhosseini, Mojtaba; Ellisman, Mark; Tasdizen, Tolga

2014-01-01

242

Energy spectra of gold monolayer protected clusters measured by single electron tunneling force microscopy  

Microsoft Academic Search

An introduction to scanning probe microscopy techniques is presented briefly. A three-dimensional model is presented to calculate the tunneling rate of electron tunneling between a probe and localized states in a dielectric, and theoretical results are compared with experimental data. On the basis of force detection atomic force microscopy, a new technique, single electron tunneling force microscopy (SETFM), and its

Ning Zheng

2007-01-01

243

Direct mapping of Li distribution in electrochemically lithiated graphite anodes using scanning Auger electron microscopy  

NASA Astrophysics Data System (ADS)

The spatial distribution of Li ions in electrochemically lithiated graphite anodes for Li-ion battery is characterized by scanning Auger electron microscopy. We show that direct mapping of Li KVV peak intensity reveal the spatial distribution of intercalated Li and its chemical state in a quantitative manner. Furthermore, we demonstrate that mapping using a C KVV peak also reflects the spatial distribution of Li due to the change in the electronic properties of C atoms induced by the electrode reaction (Li intercalation). Mapping measurements on three samples with different charging states (20%, 50%, and 100%) show that at the early stage of charging Li ions do not intercalate homogenously into all the graphite particles but selectively into some specific ones with higher rates. Our method provides the criteria to evaluate structure-correlated Li intercalation from nanometer- to micrometer-scale, such as conductivity network in the electrodes due to a non-uniform morphology of binder and conductive additives.

Ishida, Nobuyuki; Fukumitsu, Hitoshi; Kimura, Hiroshi; Fujita, Daisuke

2014-02-01

244

Clinical applications of scanning electron microscopy and X-ray microanalysis in dermatology  

SciTech Connect

Scanning electron microscopy is frequently applied to dermatological problems, as is evident from a review of the recent literature. In this paper, preparation methods and new techniques allowing experimental studies on the integumentary system are emphasized. Quantitative analysis in the electron microscope by use of energy-dispersive X-ray microanalysis (EDX) has become an important accessory technique. EDX can, for instance, be used to study problems involving physiological changes induced in skin by agents causing contact reactions. Recently, it has been shown that treatment with DNCB, chromate and nickel causes changes in elemental distribution in guinea-pig skin. In addition, elemental uptake in the integumentary system and in pathological inclusions in skin can be analyzed.

Forslind, B.

1984-01-01

245

Accurate Construction of Photoactivated Localization Microscopy (PALM) Images for Quantitative Measurements  

PubMed Central

Localization-based superresolution microscopy techniques such as Photoactivated Localization Microscopy (PALM) and Stochastic Optical Reconstruction Microscopy (STORM) have allowed investigations of cellular structures with unprecedented optical resolutions. One major obstacle to interpreting superresolution images, however, is the overcounting of molecule numbers caused by fluorophore photoblinking. Using both experimental and simulated images, we determined the effects of photoblinking on the accurate reconstruction of superresolution images and on quantitative measurements of structural dimension and molecule density made from those images. We found that structural dimension and relative density measurements can be made reliably from images that contain photoblinking-related overcounting, but accurate absolute density measurements, and consequently faithful representations of molecule counts and positions in cellular structures, require the application of a clustering algorithm to group localizations that originate from the same molecule. We analyzed how applying a simple algorithm with different clustering thresholds (tThresh and dThresh) affects the accuracy of reconstructed images, and developed an easy method to select optimal thresholds. We also identified an empirical criterion to evaluate whether an imaging condition is appropriate for accurate superresolution image reconstruction with the clustering algorithm. Both the threshold selection method and imaging condition criterion are easy to implement within existing PALM clustering algorithms and experimental conditions. The main advantage of our method is that it generates a superresolution image and molecule position list that faithfully represents molecule counts and positions within a cellular structure, rather than only summarizing structural properties into ensemble parameters. This feature makes it particularly useful for cellular structures of heterogeneous densities and irregular geometries, and allows a variety of quantitative measurements tailored to specific needs of different biological systems. PMID:23251611

Coltharp, Carla; Kessler, Rene P.; Xiao, Jie

2012-01-01

246

Identification and quantitive analysis of calcium phosphate microparticles in intestinal tissue by nuclear microscopy  

NASA Astrophysics Data System (ADS)

Microscopic particles (0.5-2 ?m diameter), rich in calcium and phosphorus, are found in the lumen of the mid-distal gut of all mammals investigated, including humans, and these may play a role in immuno-surveillance and immune regulation of antigens from food and symbiotic bacteria that are contained in the gut. Whether these particles can cross in to tissue of the intestinal mucosa is unclear. If so, characterising their morphology and chemical composition is an important task in elucidating their function. The analysis of calcium phosphate in biological tissues has been approached in several ways including optical microscopy, scanning electron microscopy and, most recently in this work, with nuclear microscopy. In this paper, we describe the use of microPIXE and microRBS to locate these particles and to determine, accurately, the ratio of phosphorus to calcium using the information on sample thickness obtained from RBS to allow the PIXE ratios to be corrected. A commercial sample of hydroxy apatite was used to demonstrate accuracy and precision of the technique. Then, in a pilot study on intestinal tissue of mice, we demonstrated the presence of calcium phosphate microparticles, consistent with confocal microscopy observations, and we identified the average molar P:Ca molar ratio as 1.0. Further work will confirm the exact chemical speciation of these particles and will examine the influence of differing calcium containing diets on the formation of these microparticles.

Gomez-Morilla, Inmaculada; Thoree, Vinay; Powell, Jonathan J.; Kirkby, Karen J.; Grime, Geoffrey W.

2006-08-01

247

Quantitative phase microscopy: a new tool for measurement of cell culture growth and confluency in situ.  

PubMed

Quantitative phase microscopy (QPM) is a recently developed computational approach that provides quantitative phase measurements of specimen images obtained under bright-field conditions without phase- or interference-contrast optics. To perform QPM, an in-focus bright-field image is acquired, together with one positive and one negative de-focus image. An algorithm is then applied to produce a specimen phase map. In this investigation we demonstrate that manipulation of the phase map intensity histogram using novel, non-subjective thresholding and segmentation methods provides enhanced delineation of cells in culture. QPM was utilised to measure the growth behaviour of cultured airway smooth muscle cells over a 92-h period. There was a high degree of correlation between parallel QPM-derived confluency measurements and haemocytometry-derived counts of airway smooth muscle cells over this time period. Using QPM, translucent cells can be visualised with improved cell boundary definition allowing precise and reproducible measurements of cell culture confluency. Quantitative phase imaging provides a rapid, optically simple and non-destructive approach for measurement of cellular morphology. Further development of the QPM-based analysis methodology has the potential to provide even more refined measures of cellular growth. PMID:14985984

Curl, Claire L; Harris, Trudi; Harris, Peter J; Allman, Brendan E; Bellair, Catherine J; Stewart, Alastair G; Delbridge, Lea M D

2004-07-01

248

Quantitative Imaging of Ion Transport through Single Nanopores by High-Resolution Scanning Electrochemical Microscopy  

PubMed Central

Here, we report on the unprecedentedly high-resolution imaging of ion transport through single nanopores by scanning electrochemical microscopy (SECM). The quantitative SECM image of single nanopores allows for the determination of their structural properties, including their density, shape, and size, which are essential for understanding the permeability of the entire nanoporous membrane. Nanoscale spatial resolution was achieved by scanning a 17 nm-radius pipet tip at a distance down to 1.3 nm from a highly porous nanocrystalline silicon membrane in order to obtain the peak current response controlled by the nanopore-mediated diffusional transport of tetrabutylammonium to the nanopipet-supported liquid/liquid interface. A 280 nm × 500 nm image resolved 13 nanopores, which corresponds to a high density of 93 pores/µm2. A finite element simulation of the SECM image was performed to quantitatively assess the spatial resolution limited by the tip diameter in resolving two adjacent pores, and to determine the actual size of a nanopore, which was approximated as an elliptic cylinder with a depth of 30 nm and major and minor axes of 53 and 41 nm, respectively. These structural parameters are consistent with those determined by TEM, which thereby confirms the reliability of quantitative SECM imaging at the nanoscale level. PMID:22655578

Shen, Mei; Ishimatsu, Ryoichi; Kim, Jiyeon; Amemiya, Shigeru

2012-01-01

249

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. PMID:21501817

ZHOU, Z. HONG

2013-01-01

250

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.

2011-06-01

251

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

252

Electron Microscopy Characterization of Vanadium Dioxide Thin Films and Nanoparticles  

NASA Astrophysics Data System (ADS)

Vanadium dioxide (VO_2) is a material of particular interest due to its exhibited metal to insulator phase transition at 68°C that is accompanied by an abrupt and significant change in its electronic and optical properties. Since this material can exhibit a reversible drop in resistivity of up to five orders of magnitude and a reversible drop in infrared optical transmission of up to 80%, this material holds promise in several technological applications. Solid phase crystallization of VO_2 thin films was obtained by a post-deposition annealing process of a VO_{x,x approx 2} amorphous film sputtered on an amorphous silicon dioxide (SiO_2) layer. Scanning electron microscopy (SEM) and electron-backscattered diffraction (EBSD) were utilized to study the morphology of the solid phase crystallization that resulted from this post-deposition annealing process. The annealing parameters ranged in temperature from 300°C up to 1000°C and in time from 5 minutes up to 12 hours. Depending on the annealing parameters, EBSD showed that this process yielded polycrystalline vanadium dioxide thin films, semi-continuous thin films, and films of isolated single-crystal particles. In addition to these films on SiO_2, other VO_2 thin films were deposited onto a-, c-, and r-cuts of sapphire and on TiO_2(001) heated single-crystal substrates by pulsed-laser deposition (PLD). The temperature of the substrates was kept at ˜500°C during deposition. EBSD maps and orientation imaging microscopy were used to study the epitaxy and orientation of the VO_2 grains deposited on the single crystal substrates, as well as on the amorphous SiO_2 layer. The EBSD/OIM results showed that: 1) For all the sapphire substrates analyzed, there is a predominant family of crystallographic relationships wherein the rutile VO_2{001} planes tend to lie parallel to the sapphire's {10-10} and the rutile VO_2{100} planes lie parallel to the sapphire's {1-210} and {0001}. Furthermore, while this family of relationships accounts for the majority of the VO_2 grains observed, due to the sapphire substrate's geometry there were variations within these rules that changed the orientation of VO_2 grains with respect to the substrate's normal direction. 2) For the TiO_2, a substrate with a lower lattice mismatch, we observe the expected relationship where the rutile VO_2 [100], [110], and [001] crystal directions lie parallel to the TiO_2 substrate's [100], [110], and [001] crystal directions respectively. 3) For the amorphous SiO_2 layer, all VO_2 crystals that were measurable (those that grew to the thickness of the deposited film) had a preferred orientation with the the rutile VO_2[001] crystal direction tending to lie parallel to the plane of the specimen. The use of transmission electron microscopy (TEM) is presented as a tool for further characterization studies of this material and its applications. In this work TEM diffraction patterns taken from cross-sections of particles of the a- and r-cut sapphire substrates not only solidified the predominant family mentioned, but also helped lift the ambiguity present in the rutile VO_2{100} axes. Finally, a focused-ion beam technique for preparation of cross-sectional TEM samples of metallic thin films deposited on polymer substrates is demonstrated.

Rivera, Felipe

253

Electronic environment for a field emission gun in electron microscopy H. Pinna, K. Liang (*), M. Denizart and B. Jouffrey  

E-print Network

659 Electronic environment for a field emission gun in electron microscopy H. Pinna, K. Liang of the source given by a field emis- sion gun is particularly interesting in electron microscopy. This paper ofthe numerous disruptive breakdowns which can occur in that type of gun. The fluctuations

Paris-Sud XI, Université de

254

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

255

Visualization of Clusters in Polymer Electrolyte Membranes by Electron Microscopy  

PubMed Central

The morphology of ionic clusters that form in polyelectrolyte membranes has a strong effect on transport and electrical properties. In spite of considerable research efforts the link between morphology and properties has not been clearly established, mainly due to difficulties in assessing nanoscale morphology. Electron microscopy (EM) has the potential to visualize morphology. However success in visualization has so far been moderate. In this review we focus on the potential of EM techniques to characterize the ionic domains. We use both experimental data and models to compare the capabilities of several EM techniques: BF TEM, HAADF, core-loss EELS, and low-loss EELS in projection imaging and STEM modes. The main problems common for all these EM modes are radiation damage and overlap of features in projection. Our models show that core loss EELS with exposures that are below the typical damage threshold is incapable of resolving 2 nm diameter sulfur-rich clusters in PEMs. While low loss EELS requires lower exposure the insight it can provide is quite limited. HAADF and BF TEM present the most effective modes for imaging the sulfur clusters in PEMs. While BF TEM uses scattered electrons more efficiently, HAADF using slightly higher doses can provide unique information due to in-focus imaging and transparent interpretation of the images. Fortunately, in at least some interesting cases the clusters themselves are much more radiation resistant than the polymer and can be studied at exposures high enough to obtain clear images. Our simulations also show that tomographic 3D reconstruction provides the best approach for solving the overlap problem. In spite of the abilities of electron tomography, data obtained from all EM techniques improves if thin sections are studied. We briefly discuss methods for obtaining such sections. PMID:23165242

Yakovlev, Sergey

2014-01-01

256

High spatial resolution spin-polarized scanning electron microscopy (abstract)  

NASA Astrophysics Data System (ADS)

Spin-polarized scanning electron microscopy (spin SEM) to observe magnetic domains has the potential for spatial resolution as high as 10 nm. The best resolution from spin SEMs attained so far, however, is around 50 nm. In this talk, we report a newly developed spin SEM with 20 nm resolution. The major factor determining the resolution of a spin SEM is probe diameter. A smaller probe diameter, however, results in lower probe current. This is a serious issue in spin SEM because the efficiency of a spin detector is very low. Thus, to get high resolution with a reasonable signal/noise (S/N) image, higher efficiency in the spin detector and/or higher probe current are needed in addition to get a smaller probe diameter. The higher probe current has been attained by using a thermal assisted field emission cathode in an electron gun. The higher efficiency in the spin detector was achieved by increasing the acceptance angle of electron detectors inside the spin detector and optimizing both a secondary collector and transport optics. Obtaining a smaller probe diameter required a low aberration objective lens and a short working distance. Those were achieved by computer calculation so that there was no interference between the objective lens and the secondary collector. This achieved both a short working distance of 20 mm and high secondary collection efficiency. As a result, magnetic images of 20 nm resolution with a 25 keV and 1 nA probe beam have been attained. We have applied this spin SEM to observing recorded bits of longitudinal thin film media at high recording densities.

Matsuyama, H.; Koike, K.; Tomiyama, F.; Aoi, H.; Shiroishi, Y.; Ishikawa, A.

1994-05-01

257

Scanning electron microscopy and electron probe X-ray microanalysis (SEM-EPMA) of pink teeth  

SciTech Connect

Samples of postmortem pink teeth were investigated by scanning electron microscopy and electron probe X-ray microanalysis. Fracture surfaces of the dentin in pink teeth were noticeably rough and revealed many more smaller dentinal tubules than those of the control white teeth. Electron probe X-ray microanalysis showed that the pink teeth contained iron which seemed to be derived from blood hemoglobin. The present study confirms that under the same circumstance red coloration of teeth may occur more easily in the teeth in which the dentin is less compact and contains more dentinal tubules.

Ikeda, N.; Watanabe, G.; Harada, A.; Suzuki, T.

1988-11-01

258

Quantitative analysis of complexes in electron irradiated CZ silicon  

Microsoft Academic Search

Complexes in helium or electron irradiated silicon are quantitatively analyzed by highly sensitive and accurate infrared (IR) absorption spectroscopy. Carbon concentration (1×1015–1×1017cm?3) and helium dose (5×1012–5×1013cm?2) or electron dose (1×1015–1×1017cm?2) are changed by two orders of magnitude in relatively low regime compared to the previous works. It is demonstrated that the carbon-related complex in low carbon concentration silicon of commercial

N. Inoue; H. Ohyama; Y. Goto; T. Sugiyama

2007-01-01

259

Superhydrophobic and adhesive properties of surfaces: testing the quality by an elaborated scanning electron microscopy method.  

PubMed

In contrast to advancements in the fabrication of new superhydrophobic materials, the characterization of their water repellency and quality is often coarse and unsatisfactory. In view of the problems and inaccuracies, particularly in the measurement of very high contact angles, we developed alternative methods for the characterization of superhydrophobic surfaces. It was found that adhering water remnants after immersion are a useful criterion in determining the repellency quality. In this study, we introduce microscopy methods to detect traces of water-resembling test liquids on superhydrophobic surfaces by scanning electron microscopy (SEM) or fluorescence light microscopy (FLM). Diverse plant surfaces and some artificial superhydrophobic samples were examined. Instead of pure water, we used aqueous solutions containing a detectable stain and glycerol in order to prevent immediate evaporation of the microdroplets. For the SEM examinations, aqueous solutions of lead acetate were used, which could be detected in a frozen state at -90 °C with high sensitivity using a backscattered electron detector. For fluorescence microscopy, aqueous solutions of auramine were used. On different species of superhydrophobic plants, varying patterns of remaining microdroplets were found on their leaves. On some species, drop remnants occurred only on surface defects such as damaged epicuticular waxes. On others, microdroplets regularly decorated the locations of increased adhesion, particularly on hierarchically structured surfaces. Furthermore, it is demonstrated that the method is suitable for testing the limits of repellency under harsh conditions, such as drop impact or long-enduring contact. The supplementation of the visualization method by the measurement of the pull-off force between a water drop and the sample allowed us to determine the adhesive properties of superhydrophobic surfaces quantitatively. The results were in good agreement with former studies of the water repellency and contact angles. In contrast to contact angle measurements, the acqusition of SEM images with high resolution and wide depth of sharpness gives better insight into the wetting behavior and susceptibility of the structural elements of the superhydrophobic surfaces. PMID:22978578

Ensikat, Hans J; Mayser, Matthias; Barthlott, Wilhelm

2012-10-01

260

An apparatus for imaging liquids, cells, and other wet samples in the scanning electron microscopy  

E-print Network

An apparatus for imaging liquids, cells, and other wet samples in the scanning electron microscopy a technique of scanning electron microscopy that is adapted to the study of wet samples. The wet environment is protected in a small chamber enclosed by a membrane, which is thin enough for energetic electrons to go

Moses, Elisha

261

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

262

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

263

Quantitative analysis of Scanning Tunneling Microscopy images for surface structure determination: Sulfur on Re(0001)  

SciTech Connect

Scanning Tunneling Microscopy (STM) images of adsorbed atoms and molecules on single crystal substrates provide important information on surface structure and order. In many cases images are interpreted qualitatively based on other information on the system. To obtain quantitative information, a theoretical analysis of the STM image is required. A new method of calculating STM images is presented that includes a full description of the STM tip and surface structure. This method is applied to experimental STM images of sulfur adsorbed on Re(0001). Effects of adsorption site, adsorbate geometry, tip composition and tunnel gap resistance on STM image contrast are analyzed. The chemical identity of tip apex atom and substrate subsurface structure are both shown to significantly affect STM image contrast.

Ogletree, D.F.; Dunphy, J.C.; Salmeron, M.B. [Lawrence Berkeley Lab., CA (United States); Sautet, P. [ENS, Lyon (France). Lab. de Chemie Theoretique]|[Centre National de la Recherche Scientifique (CNRS), 69 - Villeurbanne (France). Inst. de Recherches sur la Catalyse

1993-02-01

264

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

265

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

266

Customized patterned substrates for highly versatile correlative light-scanning electron microscopy  

PubMed Central

Correlative light electron microscopy (CLEM) combines the advantages of light and electron microscopy, thus making it possible to follow dynamic events in living cells at nanometre resolution. Various CLEM approaches and devices have been developed, each of which has its own advantages and technical challenges. We here describe our customized patterned glass substrates, which improve the feasibility of correlative fluorescence/confocal and scanning electron microscopy. PMID:25391455

Benedetti, Lorena; Sogne, Elisa; Rodighiero, Simona; Marchesi, Davide; Milani, Paolo; Francolini, Maura

2014-01-01

267

Scanning transmission electron microscopy strain measurement from millisecond frames of a direct electron charge coupled device  

SciTech Connect

A high-speed direct electron detection system is introduced to the field of transmission electron microscopy and applied to strain measurements in semiconductor nanostructures. In particular, a focused electron probe with a diameter of 0.5 nm was scanned over a fourfold quantum layer stack with alternating compressive and tensile strain and diffracted discs have been recorded on a scintillator-free direct electron detector with a frame time of 1 ms. We show that the applied algorithms can accurately detect Bragg beam positions despite a significant point spread each 300 kV electron causes during detection on the scintillator-free camera. For millisecond exposures, we find that strain can be measured with a precision of 1.3 Multiplication-Sign 10{sup -3}, enabling, e.g., strain mapping in a 100 Multiplication-Sign 100 nm{sup 2} region with 0.5 nm resolution in 40 s.

Mueller, Knut; Rosenauer, Andreas [Institut fuer Festkoerperphysik, Universitaet Bremen, Otto-Hahn-Allee 1, 28359 Bremen (Germany); Ryll, Henning; Ordavo, Ivan; Ihle, Sebastian; Soltau, Heike [PNSensor GmbH, Roemerstrasse 28, 80803 Muenchen (Germany); Strueder, Lothar [Max-Planck-Institut Halbleiterlabor, Otto-Hahn-Ring 6, 81739 Muenchen (Germany); Volz, Kerstin [Materials Science Center and Faculty of Physics, Philipps Universitaet Marburg, Hans-Meerwein-Strasse, 35032 Marburg (Germany); Zweck, Josef [Institut fuer Experimentelle und Angewandte Physik, Universitaet Regensburg, Universitaetsstrasse 31, 93040 Regensburg (Germany)

2012-11-19

268

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

269

Atomic-Resolution 3D Electron Microscopy with Dynamic Diffraction  

SciTech Connect

Achievement of atomic-resolution electron-beam tomography will allow determination of the three-dimensional structure of nanoparticles (and other suitable specimens) at atomic resolution. Three-dimensional reconstructions will yield ''section'' images that resolve atoms overlapped in normal electron microscope images (projections), resolving lighter atoms such as oxygen in the presence of heavier atoms, and atoms that lie on non-lattice sites such as those in non-periodic defect structures. Lower-resolution electron microscope tomography has been used to produce reconstructed 3D images of nanoparticles [1] but extension to atomic resolution is considered not to be straightforward. Accurate three-dimensional reconstruction from two-dimensional projections generally requires that intensity in the series of 2-D images be a monotonic function of the specimen structure (often specimen density, but in our case atomic potential). This condition is not satisfied in electron microscopy when specimens with strong periodicity are tilted close to zone-axis orientation and produce ''anomalous'' image contrast because of strong dynamic diffraction components. Atomic-resolution reconstructions from tilt series containing zone-axis images (with their contrast enhanced by strong dynamical scattering) can be distorted when the stronger zone-axis images overwhelm images obtained in other ''random'' orientations in which atoms do not line up in neat columns. The first demonstrations of 3-D reconstruction to atomic resolution used five zone-axis images from test specimens of staurolite consisting of a mix of light and heavy atoms [2,3]. Initial resolution was to the 1.6{angstrom} Scherzer limit of a JEOL-ARM1000. Later experiments used focal-series reconstruction from 5 to 10 images to produce staurolite images from the ARM1000 with resolution extended beyond the Scherzer limit to 1.38{angstrom} [4,5]. To obtain a representation of the three-dimensional structure, images were obtained in zone-axis projections <100>, <010>, <001>, <101>, <310>, and combined to produce a three-dimensional map of Coulomb potential. Images of specimen sections are much more easily interpreted than projection images such as electron micrographs, reducing the need for techniques such as imaging at sub-Rayleigh resolution [6]. Sections through the 3D staurolite potential show atom positions as density peaks that display streaking from insufficient sampling in direction [1]. Three different specimens of perfect crystal were required to achieve the five projection directions; this makes the technique atomic-resolution electron crystallography rather than atomic-resolution tomography. Nevertheless, our results illustrate that dynamic diffraction need not be a limiting factor in atomic-resolution tomographic reconstruction. We have proposed combining ultra-high (sub-Angstrom) resolution zone-axis images with off-zone images by first using linear reconstruction of the off-zone images while excluding images obtained within a small range of tilts (of the order of 60 milliradian) of any zone-axis orientation [7], since it has been shown that dynamical effects can be mitigated by slight off-axis tilt of the specimen [8]. The (partial) reconstruction would then be used as a model for forward calculation by image simulation [9] in zone-axis directions and the structure refined iteratively to achieve satisfactory fits with the experimental zone-axis data. Another path to atomic-resolution tomography would combine ''zone-axis tomography'' with high-resolution dark-field hollow-cone (DFHC) imaging. Electron diffraction theory indicates that dynamic (multiple) scattering is much reduced under highly-convergent illumination. DFHC TEM is the analog of HAADF STEM, and imaging theory shows that image resolution can be enhanced under these conditions [10]. Images obtained in this mode could provide the initial reconstruction, with zone-axis images used for refinement [11].

O'Keefe, Michael A.; Downing, Kenneth H.; Wenk, Hans-Rudolf; Meisheng, Hu

2005-02-15

270

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

271

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

272

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

273

Integrating electron microscopy information into existing Distributed Annotation Systems.  

PubMed

The increase of daily released bioinformatic data has generated new ways of organising and disseminating information. Specifically, in the field of sequence data, many efforts have been made not only to store information in databases, but also to annotate it and then share these annotations through a standard XML (eXtensible Markup Language) protocol and appropriate integration clients. This is the context in which the Distributed Annotation System (DAS) has emerged in genomics. Additionally, initiatives in the field of structural data, such as the extension of DAS to atomic resolution data, which generated the SPICE client, have also occurred. This paper presents 3D-EM DAS, a further extension of the DAS protocol that allows sharing annotations about hybrid models. This annotation system has been built on the basis of the EMDB, which stores Three-dimensional Electron Microscopy (3D-EM) volumes, PDB, which houses atomic coordinates, and UniProt (for protein sequences) databases. In this way, annotations for sequences, atomic coordinates, and 3D-EM volumes are collected and displayed through a single graphical visualization client. Thus, users have an integrated view of all the annotations together with the whole macromolecule (3D-EM map coming from EMDB), the atomic resolution structures fitted into it (coordinates coming from PDB) and the sequences corresponding to each of the structures (from UniProt). PMID:17400476

Macías, J R; Jiménez-Lozano, N; Carazo, J M

2007-05-01

274

Surface treatment of feldspathic porcelain: scanning electron microscopy analysis  

PubMed Central

PURPOSE Topographic analysis of treated ceramics provides qualitative information regarding the surface texture affecting the micromechanical retention and locking of resin-ceramics. This study aims to compare the surface microstructure following different surface treatments of feldspathic porcelain. MATERIALS AND METHODS This in-vitro study was conducted on 72 porcelain discs randomly divided into 12 groups (n=6). In 9 groups, feldspathic surfaces were subjected to sandblasting at 2, 3 or 4 bar pressure for 5, 10 or 15 seconds with 50 µm alumina particles at a 5 mm distance. In group 10, 9.5% hydrofluoric acid (HF) gel was applied for 120 seconds. In group 11, specimens were sandblasted at 3 bar pressure for 10 seconds and then conditioned with HF. In group 12, specimens were first treated with HF and then sandblasted at 3 bar pressure for 10 seconds. All specimens were then evaluated under scanning electron microscopy (SEM) at different magnifications. RESULTS SEM images of HF treated specimens revealed deep porosities of variable sizes; whereas, the sandblasted surfaces were more homogenous and had sharper peaks. Increasing the pressure and duration of sandblasting increased the surface roughness. SEM images of the two combined techniques showed that in group 11 (sandblasted first), HF caused deeper porosities; whereas in group 12 (treated with HF first) sandblasting caused irregularities with less homogeneity. CONCLUSION All surface treatments increased the surface area and caused porous surfaces. In groups subjected to HF, the porosities were deeper than those in sandblasted only groups. PMID:25352961

Valian, Azam

2014-01-01

275

Scanning electron microscopy applied to seed-borne fungi examination.  

PubMed

The aim of this study was to test the standard scanning electron microscopy (SEM) as a potential alternative to study seed-borne fungi in seeds, by two different conditions of blotter test and water restriction treatment. In the blotter test, seeds were subjected to conditions that enabled pathogen growth and expression, whereas the water restriction method consisted in preventing seed germination during the incubation period, resulting in the artificial inoculation of fungi. In the first condition, seeds of common bean (Phaseolus vulgaris L.), maize (Zea mays L.), and cotton (Gossypium hirsutum L.) were submitted to the standard blotter test and then prepared and observed with SEM. In the second condition, seeds of cotton (G. hirsutum), soybean (Glycine max L.), and common bean (P. vulgaris L.) were, respectively, inoculated with Colletotrichum gossypii var. cephalosporioides, Colletotrichum truncatum, and Colletotrichum lindemuthianum by the water restriction technique, followed by preparation and observation with SEM. The standard SEM methodology was adopted to prepare the specimens. Considering the seeds submitted to the blotter test, it was possible to identify Fusarium sp. on maize, C. gossypii var. cephalosporioides, and Fusarium oxysporum on cotton, Aspergillus flavus, Penicillium sp., Rhizopus sp., and Mucor sp. on common bean. Structures of C. gossypii var. cephalosporioides, C. truncatum, and C. lindemuthianum were observed in the surface of inoculated seeds. PMID:19204924

Alves, Marcelo de Carvalho; Pozza, Edson Ampélio

2009-07-01

276

EMAN2: an extensible image processing suite for electron microscopy.  

PubMed

EMAN is a scientific image processing package with a particular focus on single particle reconstruction from transmission electron microscopy (TEM) images. It was first released in 1999, and new versions have been released typically 2-3 times each year since that time. EMAN2 has been under development for the last two years, with a completely refactored image processing library, and a wide range of features to make it much more flexible and extensible than EMAN1. The user-level programs are better documented, more straightforward to use, and written in the Python scripting language, so advanced users can modify the programs' behavior without any recompilation. A completely rewritten 3D transformation class simplifies translation between Euler angle standards and symmetry conventions. The core C++ library has over 500 functions for image processing and associated tasks, and it is modular with introspection capabilities, so programmers can add new algorithms with minimal effort and programs can incorporate new capabilities automatically. Finally, a flexible new parallelism system has been designed to address the shortcomings in the rigid system in EMAN1. PMID:16859925

Tang, Guang; Peng, Liwei; Baldwin, Philip R; Mann, Deepinder S; Jiang, Wen; Rees, Ian; Ludtke, Steven J

2007-01-01

277

Scanning electron microscopy of lung following alpha irradiation  

SciTech Connect

Pulmonary aggregation of inhaled {sup 239}PuO{sub 2} particles leads to a cellular evolution of focal inflammation, fibrosis, epithelial dysplasia and lung tumor formation. Female Wistar rats were exposed to an aerosol of high-fired {sup 239}PuO{sub 2} (initial lung burden, 3.9 kBq) and the lungs examined at intervals from 1 day to 700 days after exposure by light and scanning electron microscopy and autoradiography. Peribronchiolar Pu particle aggregation increased with time, resulting in well-defined focal inflammatory lesions after 120 days and fibrotic lesions after 180 days. A generalized hypertrophy and hyperplasia of nonciliated bronchiolar cells was seen at 15 days and type II cell hyperplasia by 30 days after exposure. Focal dysplastic changes in type II alveolar epithelium and terminal nonciliated bronchiolar epithelium preceded carcinoma formation. Alveolar bronchiolarization was first noted at 120 days, squamous metaplasia at 210 days, squamous carcinoma at 270 days and adenocarcinoma at 600 days after exposure.

Sanders, C.L.; Lauhala, K.E.; McDonald, K.E. (Pacific Northwest Laboratory, Richland, WA (USA))

1989-09-01

278

Electron microscopy in the diagnosis of pituitary tumors.  

PubMed

The usefulness and limitations of electron microscopy (EM) in pituitary tumor diagnosis are reviewed and illustrated with clinical examples. The traditional classification of chromophil and chromophobe adenomas is often inconsistent with the hormonal activity of the tumors. Virtually all pituitary adenomas contain some secretory granules when viewed with EM. Endocrine inactive chromophobe adenomas contain 150 nm granules with no demonstrable hormone function. Typical growth hormone (GH) secreting eosinophil adenomas contain large 375 nm granules which dominate the cell cytoplasm. GH secreting chromophobic tumors contain secretory granules of abnormal size and concentration which are invisible to the light microscopist. The variability in granule size may indicate the production of abnormal granules or reflect the stage of the cell in a secretory cycle. Because of this wide range in granule size, the identification of tumor cell type or hormone produced is not reliable by granule measurement alone. Some neoplasms in the sella turcica may be so bizzare or undifferentiated as to defy classification. In such instances, EM can reveal ultrastructural details which identify their origin from pituitary tissue. Malignant pituitary tumors may contain minute secretory granules, and rare pituitary oncocytomas are packed with abnormal mitochondria. PMID:485091

Farmer, P M

1979-01-01

279

Transmission electron microscopy of Terfenol-D crystals  

NASA Astrophysics Data System (ADS)

Magnetic domain and microstructure observations are presented from samples of pseudo-single-crystal Terfenol-D examined by transmission electron microscopy (TEM). This ternary alloy is of significant technological interest since it exhibits the highest known magnetostriction to anisotropy ratio near room temperature. Specimens for TEM studies in (110), (111), and (112) orientations have also shown regions of unusual diffraction contrast in bright field which appears to be very sensitive to specimen tilt. Lorentz mode TEM has subsequently shown such regions to correspond exactly with magnetic domains. This contrast is attributed to the high magnetostrictive strain causing a local distortion of the lattice and thus a local deviation from the Bragg condition. This conclusion has been investigated and supported by TEM observations with the samples cooled below the spin reorientation temperature. When this transition is reached the diffraction contrast in bright field is considerably decreased and cannot be made to vary by tilting the specimen. The latter experiments also indicate that the change from <111> to <100> easy axis is not a well-defined one but, rather, that the spin reorientation is a sluggish change. High-resolution lattice images show the coherency of the twin boundaries.

Holden, A. P.; Lord, D. G.; Grundy, P. J.

1996-04-01

280

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

281

Quantitative analysis of intrinsic skin aging in dermal papillae by in vivo harmonic generation microscopy  

PubMed Central

Chronological skin aging is associated with flattening of the dermal-epidermal junction (DEJ), but to date no quantitative analysis focusing on the aging changes in the dermal papillae (DP) has been performed. The aim of the study is to determine the architectural changes and the collagen density related to chronological aging in the dermal papilla zone (DPZ) by in vivo harmonic generation microscopy (HGM) with a sub-femtoliter spatial resolution. We recruited 48 Asian subjects and obtained in vivo images on the sun-protected volar forearm. Six parameters were defined to quantify 3D morphological changes of the DPZ, which we analyzed both manually and computationally to study their correlation with age. The depth of DPZ, the average height of isolated DP, and the 3D interdigitation index decreased with age, while DP number density, DP volume, and the collagen density in DP remained constant over time. In vivo high-resolution HGM technology has uncovered chronological aging-related variations in DP, and sheds light on real-time quantitative skin fragility assessment and disease diagnostics based on collagen density and morphology. PMID:25401037

Liao, Yi-Hua; Kuo, Wei-Cheng; Chou, Sin-Yo; Tsai, Cheng-Shiun; Lin, Guan-Liang; Tsai, Ming-Rung; Shih, Yuan-Ta; Lee, Gwo-Giun; Sun, Chi-Kuang

2014-01-01

282

Investigations of the ultrafast laser induced melt dynamics by means of transient quantitative phase microscopy (TQPm)  

NASA Astrophysics Data System (ADS)

Modifications of bulk aluminum irradiated well above ablation threshold (F < 300 J.cm-2) have been investigated in situ by means of shadowgraphy and transient quantitative phase microscopy (TQPm) using ultrafast laser radiation (tp=80 fs, ?=800 nm). This novel pump-probe technique enables quantitative time-resolved measurements of object's properties, e.g. dimensions of melt droplets and layer thickness or transient refractive index changes. A series of time-resolved phase images of vaporized material and/or melt, which are induced by n=1..8 pulses on an aluminum target, are obtained using TQPm. Dynamics and characteristics of melting, dependence of the ablated material volume on process parameters and thereby induced structural modifications have been studied. An increase of material ejection rate is observed at delay time of approximately ?=300 ns and ?>800 ns after the incident pulse. Transient refractive index modifications have been investigated in technical glass (Schott D263) by means of TQPm. By using high-repetition rate ultra-short pulsed laser radiation (tp=400 fs, ?=1045 nm, frep=1 MHz) focused by a microscope objective (w0 ~ 4 ?m) heat accumulation and thereby glass melting as well as welding is enabled. Transient optical phase variation has been measured up to ?=2.1 ?s after the incident pulse and can be attributed to the generation of free charge carriers and compression forces inside glass.

Mingareev, Ilya; Horn, Alexander

2008-05-01

283

In vivo imaging and quantitative analysis of zebrafish embryos by digital holographic microscopy  

PubMed Central

Digital holographic microscopy (DHM) has been applied extensively to in vitro studies of different living cells. In this paper, we present a novel application of an off-axis DHM system to in vivo study of the development of zebrafish embryos. Even with low magnification microscope objectives, the morphological structures and individual cell types inside developing zebrafish embryos can be clearly observed from reconstructed amplitude images. We further study the dynamic process of blood flow in zebrafish embryos. A calibration routine and post-processing procedures are developed to quantify physiological parameters at different developmental stages. We measure quantitatively the blood flow as well as the heart rate to study the effects of elevated D-glucose (abnormal condition) on circulatory and cardiovascular systems of zebrafish embryos. To enhance our ability to use DHM as a quantitative tool for potential high throughput screening application, the calibration and post-processing algorithms are incorporated into an automated processing software. Our results show that DHM is an excellent non-invasive imaging technique for visualizing the cellular dynamics of organogenesis of zebrafish embryos in vivo. PMID:23082301

Gao, Jian; Lyon, Joseph A.; Szeto, Daniel P.; Chen, Jun

2012-01-01

284

Quantitation of Glucocorticoid Receptor DNA-Binding Dynamics by Single-Molecule Microscopy and FRAP  

PubMed Central

Recent advances in live cell imaging have provided a wealth of data on the dynamics of transcription factors. However, a consistent quantitative description of these dynamics, explaining how transcription factors find their target sequences in the vast amount of DNA inside the nucleus, is still lacking. In the present study, we have combined two quantitative imaging methods, single-molecule microscopy and fluorescence recovery after photobleaching, to determine the mobility pattern of the glucocorticoid receptor (GR) and the mineralocorticoid receptor (MR), two ligand-activated transcription factors. For dexamethasone-activated GR, both techniques showed that approximately half of the population is freely diffusing, while the remaining population is bound to DNA. Of this DNA-bound population about half the GRs appeared to be bound for short periods of time (?0.7 s) and the other half for longer time periods (?2.3 s). A similar pattern of mobility was seen for the MR activated by aldosterone. Inactive receptors (mutant or antagonist-bound receptors) show a decreased DNA binding frequency and duration, but also a higher mobility for the diffusing population. Likely, very brief (?1 ms) interactions with DNA induced by the agonists underlie this difference in diffusion behavior. Surprisingly, different agonists also induce different mobilities of both receptors, presumably due to differences in ligand-induced conformational changes and receptor complex formation. In summary, our data provide a consistent quantitative model of the dynamics of GR and MR, indicating three types of interactions with DNA, which fit into a model in which frequent low-affinity DNA binding facilitates the search for high-affinity target sequences. PMID:24632838

Groeneweg, Femke L.; van Royen, Martin E.; Fenz, Susanne; Keizer, Veer I. P.; Geverts, Bart; Prins, Jurrien; de Kloet, E. Ron; Houtsmuller, Adriaan B.; Schmidt, Thomas S.; Schaaf, Marcel J. M.

2014-01-01

285

A TRANSMISSION ELECTRON MICROSCOPY STUDY OF PRESOLAR HIBONITE  

SciTech Connect

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 CaAl{sub 12}O{sub 19}. 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 x 10{sup -6} and 1 x 10{sup -3} atm. The TEM data were also used to develop a calibration for SIMS determination of Ti contents in oxide grains. Grains with extreme {sup 18}O 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.; Stroud, Rhonda M. [Materials Science and Technology Division, Naval Research Laboratory, 4555 Overlook Ave SW, Washington, DC 20375 (United States); Alexander, Conel M. O'D.; Nittler, Larry R., E-mail: tzega@nrl.navy.mil [Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Rd NW, Washington, DC 20015 (United States)

2011-04-01

286

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

287

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

288

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

289

Rapid estimation of catalyst nanoparticle morphology and atomic-coordination by high-resolution z-contrast electron microscopy.  

PubMed

Heterogeneous nanoparticle catalyst development relies on an understanding of their structure-property relationships, ideally at atomic resolution and in three-dimensions. Current transmission electron microscopy techniques such as discrete tomography can provide this but require multiple images of each nanoparticle and are incompatible with samples that change under electron irradiation or with surveying large numbers of particles to gain significant statistics. Here, we make use of recent advances in quantitative dark-field scanning transmission electron microscopy to count the number atoms in each atomic column of a single image from a platinum nanoparticle. These atom-counts, along with the prior knowledge of the face-centered cubic geometry, are used to create atomistic models. An energy minimization is then used to relax the nanoparticle's 3D structure. This rapid approach enables high-throughput statistical studies or the analysis of dynamic processes such as facet-restructuring or particle damage. PMID:25340541

Jones, Lewys; MacArthur, Katherine E; Fauske, Vidar T; van Helvoort, Antonius T J; Nellist, Peter D

2014-11-12

290

EDITORIAL: Electron Microscopy and Analysis Group Conference 2011 (EMAG 2011)  

NASA Astrophysics Data System (ADS)

The biennial EMAG conference has established a strong reputation as a key event for the national and international electron microscopy community. In 2011 the meeting was held at The University of Birmingham, and I must first take this opportunity of thanking Birmingham for hosting the conference and for the excellent support we received from the local organisers. As a committee, we are delighted to see that enthusiasm for the EMAG conference series continues to be strong. We received more than 160 submitted abstracts, and 157 delegates attended the meeting. The scientific programme organiser, Ian MacLaren, put together an exciting programme. Plenary lectures were presented by Professor Knut Urban, Dr Frances Ross and Dr Richard Henderson. There were a further 10 invited speakers, from the UK, Continental Europe, Australia, the USA and Japan. The quality of the contributed oral and poster presentations was also very high. EMAG is keen to encourage student participation, and a winner and two runners-up were presented with prizes for the best oral and poster presentations from a student. I am always struck by the scientific quality of the oral and poster contributions and the vibrant discussions that occur both in the formal sessions and in the exhibition space at EMAG. I am convinced that a crucial part of maintaining that scientific quality is the opportunity that is offered of having a paper fully reviewed by two internationally selected referees and published in the Journal of Physics: Conference Series. For many students, this is the first fully reviewed paper they publish. I hope that you, like me, will be struck by the scientific quality of the 87 papers that follow, and that you will find them interesting and informative. Finally I must thank the platinum sponsors for their support of the meeting. These were Gatan, Zeiss, FEI, JEOL and Hitachi. I must also thank the European Microscopy Society for their generous sponsorship and support for the travel costs of two invited speakers from Continental Europe. Finally, keep an eye on www.emag-iop.org for details on EMAG 2013, which is to be held at the University of York. P D Nellist University of Oxford

Moebus, Guenter; Walther, Thomas; Brydson, Rik; Ozkaya, Dogan; MacLaren, Ian; Donnelly, Steve; Nellist, Pete; Li, Ziyou; Baker, Richard; Chiu, YuLung

2012-07-01

291

Nucleation and growth of cobalt disilicide precipitates during in situ transmission electron microscopy implantation  

NASA Astrophysics Data System (ADS)

The paper is aimed at getting deeper insight into the fundamental mechanisms that govern CoSi2 precipitate nucleation and growth during Co ion implantation at high temperatures (500-650 °C). Information about nucleation and growth of metal silicides as a function of temperature and implantation flux is provided by experiments on cobalt implantation in silicon, performed directly by in situ transmission electron microscopy. The main attention is paid to the nucleation of B-type precipitates, which dominate under ion implantation conditions. The obtained quantitative behavior of precipitate number density and size and the scaling of these values with implantation flux are discussed and rationalized in terms of analytical and simulation approaches. An atomistic model of B-type precipitate nucleation based on the first-principles calculations of relative energetic efficiency of different Co clusters is proposed.

Ruault, M.-O.; Fortuna, F.; Borodin, V. A.; Ganchenkova, M. G.; Kirk, M. A.

2008-08-01

292

Nonlinear optical microscopy: use of second harmonic generation and two-photon microscopy for automated quantitative liver fibrosis studies  

E-print Network

Liver fibrosis is associated with an abnormal increase in an extracellular matrix in chronic liver diseases. Quantitative characterization of fibrillar collagen in intact tissue is essential for both fibrosis studies and ...

Sun, Wanxin

293

Kelvin probe microscopy and electronic transport measurements in reduced graphene oxide chemical sensors  

NASA Astrophysics Data System (ADS)

Reduced graphene oxide (RGO) is an electronically hybrid material that displays remarkable chemical sensing properties. Here, we present a quantitative analysis of the chemical gating effects in RGO-based chemical sensors. The gas sensing devices are patterned in a field-effect transistor geometry, by dielectrophoretic assembly of RGO platelets between gold electrodes deposited on SiO2/Si substrates. We show that these sensors display highly selective and reversible responses to the measured analytes, as well as fast response and recovery times (tens of seconds). We use combined electronic transport/Kelvin probe microscopy measurements to quantify the amount of charge transferred to RGO due to chemical doping when the device is exposed to electron-acceptor (acetone) and electron-donor (ammonia) analytes. We demonstrate that this method allows us to obtain high-resolution maps of the surface potential and local charge distribution both before and after chemical doping, to identify local gate-susceptible areas on the RGO surface, and to directly extract the contact resistance between the RGO and the metallic electrodes. The method presented is general, suggesting that these results have important implications for building graphene and other nanomaterial-based chemical sensors.

Kehayias, Christopher E.; MacNaughton, Samuel; Sonkusale, Sameer; Staii, Cristian

2013-06-01

294

Kelvin probe microscopy and electronic transport measurements in reduced graphene oxide chemical sensors.  

PubMed

Reduced graphene oxide (RGO) is an electronically hybrid material that displays remarkable chemical sensing properties. Here, we present a quantitative analysis of the chemical gating effects in RGO-based chemical sensors. The gas sensing devices are patterned in a field-effect transistor geometry, by dielectrophoretic assembly of RGO platelets between gold electrodes deposited on SiO2/Si substrates. We show that these sensors display highly selective and reversible responses to the measured analytes, as well as fast response and recovery times (tens of seconds). We use combined electronic transport/Kelvin probe microscopy measurements to quantify the amount of charge transferred to RGO due to chemical doping when the device is exposed to electron-acceptor (acetone) and electron-donor (ammonia) analytes. We demonstrate that this method allows us to obtain high-resolution maps of the surface potential and local charge distribution both before and after chemical doping, to identify local gate-susceptible areas on the RGO surface, and to directly extract the contact resistance between the RGO and the metallic electrodes. The method presented is general, suggesting that these results have important implications for building graphene and other nanomaterial-based chemical sensors. PMID:23703020

Kehayias, Christopher E; MacNaughton, Samuel; Sonkusale, Sameer; Staii, Cristian

2013-06-21

295

The Probe Profile and Lateral Resolution of Scanning Transmission Electron Microscopy of Thick Specimens  

PubMed Central

Lateral profiles of the electron probe of scanning transmission electron microscopy (STEM) were simulated at different vertical positions in a micrometers-thick carbon sample. The simulations were carried out using the Monte Carlo method in the CASINO software. A model was developed to fit the probe profiles. The model consisted of the sum of a Gaussian function describing the central peak of the profile, and two exponential decay functions describing the tail of the profile. Calculations were performed to investigate the fraction of unscattered electrons as function of the vertical position of the probe in the sample. Line scans were also simulated over gold nanoparticles at the bottom of a carbon film to calculate the achievable resolution as function of the sample thickness and the number of electrons. The resolution was shown to be noise limited for film thicknesses less than 1 ?m. Probe broadening limited the resolution for thicker films. The validity of the simulation method was verified by comparing simulated data with experimental data. The simulation method can be used as quantitative method to predict STEM performance or to interpret STEM images of thick specimens. PMID:22564444

Demers, Hendrix; Ramachandra, Ranjan; Drouin, Dominique; de Jonge, Niels

2012-01-01

296

Dynamics of cellular response to hypotonic stimulation revealed by quantitative phase microscopy and multi-fractal detrended fluctuation analysis  

NASA Astrophysics Data System (ADS)

Hypotonic stimulation is known to cause morphological changes in cells and also leads to modulation of cellular physiology. In order to evaluate the dynamics of cellular response to hypotonic stimulation, we utilized digital holographic microscopy for quantitative phase microscopy, achieved by a common-path interferometry geometry based on extraction of reference beam by spatial-filtering. Results from live cell investigations demonstrate the capability of this method for dynamic quantitative phase imaging. Further, wavelet and multi-fractal detrended fluctuation analysis revealed that the dynamic phase changes, in response to hypotonic stimulation, are multifractal in nature.

Cardenas, Nelson; Kumar, Satish; Mohanty, Samarendra

2012-11-01

297

Comparison in spatial spreads of secondary electron information between scanning ion and scanning electron microscopy.  

PubMed

Monte Carlo simulations have been carried out to compare the spatial spreads of secondary electron (SE) information in scanning ion microscopy (SIM) with scanning electron microscopy (SEM). Under Ga ion impacts, the SEs are excited by three kinds of collision-partners, that is, projectile ion, recoiled target atom, and target electron. The latter two partners dominantly contribute to the total SE yield gamma for the materials of low atomic number Z2. For the materials of high Z2, on the other hand, the projectile ions dominantly contribute to gamma. These Z2 dependencies generally cause the gamma yield to decrease with an increasing Z2, in contrast with the SE yield delta under electron impacts. Most of the SEs are produced in the surface layer of about 5lambda in depth (lambda: the mean free path of SEs), as they are independent of the incident probe. Under 30 keV Ga ion impacts, the spatial spread of SE information is roughly as small as 10 nm, decreasing with an increasing Z2. Under 10 keV electron impacts, the SEI excited by the primary electrons has a small spatial spread of about 5lambda, but the SEII excited by the backscattered electrons has a large one of several 10 to several 100 nanometers, decreasing with an increasing Z2. The main cause of a small spread of SE information at ion impact is the short ranges of the projectile ions returning to the surface to escape as backscattered ions, the recoiled target atoms, and the target electrons in collision cascade. The 30 keV Ga-SIM imaging is better than the 10 keV SEM imaging in spatial resolution for the structure/material measurements. Here, zero-size probes are assumed. PMID:12926612

Ishitani, Tohru; Ohya, Kaoru

2003-01-01

298

Electronic properties of graphene: a perspective from scanning tunneling microscopy and magneto-transport.  

E-print Network

..............................................................................................................................................4 Exfoliation from graphite1 Electronic properties of graphene: a perspective from scanning tunneling microscopy and magneto recent experimental progress in probing the electronic properties of graphene and how they are influenced

Andrei, Eva Y.

299

PREFACE: Electron Microscopy and Analysis Group Conference 2009  

NASA Astrophysics Data System (ADS)

The latest biennial conference of the Electron Microscopy and Analysis Group (EMAG) of the Institute of Physics was held at the University of Sheffield on 9-11 September, 2009. In addition, the Advanced School associated with the conference was run at the University of Sheffield on 8 September. It was particularly pleasing to return to Sheffield after ten years, the successful and memorable EMAG 99 having been held here too. The subject areas covered at EMAG 2009 were advanced electron microscopy techniques; investigating structure-property relationships in advanced materials; nanophysics and nanotechnology. The EMAG 2009 conference attracted 172 delegates while the Advanced School had a full complement of eighteen attendees. Three plenary lectures were given to the whole conference and invited contributions were presented within the theme of each of nine parallel sessions. There were 54 contributed oral presentations within these parallel Sessions and a further 89 poster presentations. All authors were invited to contribute a paper to this Proceedings volume and 108 papers are presented here. I thank all who presented at EMAG 2009 and those who provided a paper for this Proceedings. Each paper was peer reviewed by two reviewers and I also want to thank those colleagues who helped with this essential task. In this volume, the plenary papers are presented first followed by all papers presented in each themed session. These sessions are ordered alphabetically. Within each Session, the invited presentations are presented first, followed by oral and poster contributions together. Another activity of EMAG which is directed primarily at less experienced scientists is the Advanced School. This year, this was on Nanofabrication and Nanomanipulation and I want to thank Guenter Moebus and his colleagues at th University of Sheffield for putting on such an excellent Advanced School. The EMAG series of conferences are well-known not only for the academic conference but also for the major trade exhibition which runs in parallel. This requires a great deal of additional planning and effort on the part of the conference department of the IoP but particularly by representatives of the exhibiting companies. This year there were 29 exhibitors, several of whom brought major items of equipment to demonstrate to delegates. Here I want to thank all the exhibitors, Jill Cowlard and Nicola Deedman of CEM and Pete Lander of JEOL for their efforts in making the trade exhibition such a success. Finally, sincere thanks to the other members of the EMAG committee, especially Pete Nellist for his work on the scientific programme, and Guenter Moebus, Thomas Walther and colleagues for their invaluable work 'on the ground' at Sheffield, and also to Claire Garland and Lisa Cornwell at IoP for all their hard work and for keeping the academics under control! Richard Baker University of St Andrews EMAG Chair and EMAG 2009 Proceedings Editor Session Editors Richard Brydson Stephen Donnelly Ian MacLaren David McComb Günter Möbus Peter Nellist Dogan Ozkaya Thomas Walther

Baker, Richard

2010-04-01

300

EDITORIAL: Electron Microscopy and Analysis Group Conference 2013 (EMAG2013)  

NASA Astrophysics Data System (ADS)

It has once again been my pleasure to act as editor for these proceedings, and I must thank all those who have acted as reviewers. I am always struck by the scientific quality of the oral and poster contributions and the vibrant discussions that occur both in the formal sessions and in the exhibition space at EMAG. I am convinced that a crucial part of maintaining that scientific quality is the opportunity that is offered of having a paper fully reviewed by two internationally selected referees and published in the Journal of Physics: Conference Series. For many students, this is the first fully reviewed paper they publish. I hope that, like me, you will be struck by the scientific quality of the 80 papers that follow, and that you will find them interesting and informative. I must also personally thank all the organisers of EMAG2013 for arranging such an excellent meeting. Ian MacLaren, as Chair of the EMAG Group and of the meeting itself, has contributed a foreword to these proceedings describing the meeting in more detail. A particular highlight of the conference was the special symposium in honour of Professor Archie Howie. We all enjoyed a wonderful speech from Archie at the conference dinner, along with some of his electron microscopy-related poetry. I have great pleasure in publishing the conference dinner poems in this proceedings. I hope you will find these proceedings to be an interesting read and an invaluable resource. Pete Nellist Conference committee Conference chair: Dr I MacLaren Programme organiser: Dr C Ducati Proceedings editor: Prof P D Nellist Trade exhibition organiser: C Hockey (CEM Group) Local organisers: Professor E Boyes, Professor P Gai, Dr R Kröger, Dr V Lazarov, Dr P O'Toole, Dr S Tear and Professor J Yuan Advanced school organisers: Dr S Haigh, Dr A Brown Other committee members: Mr K Meade, Mr O Heyning, Dr M Crawford, Mr M Dixon and Dr Z Li

Nellist, Pete

2014-06-01

301

Transmission electron microscopy of Al-Li control rod pins  

SciTech Connect

This report discusses transmission electron microscopy employed to characterize the microstructures of both cast and mechanically alloyed powder Al-Li control rod pins. The results indicated that microstructural differences existed between the ingot and powder metallurgy materials. In general, the cast specimens contained large, dendritic {alpha} grains separated by regions of much smaller a grains and AlLi {beta} particles. The grain interiors, except in the immediate vicinity of the {beta} particles, contained a high number density of Al{sub 3}Li ({delta}{prime}) precipitates. Several specimens also contained a widely distributed and unidentified Si-rich phase. In contrast, the microstructure of powder metallurgy samples consisted of small, randomly oriented {alpha} grains containing a dispersion of rod-like Al{sub 4}C{sub 3} (aluminum carbide) particles - confirmed by both TEM and X-ray diffraction. No TEM evidence was found for the presence of the {delta}{prime} or {beta} phases in the as-received powder material, although the {beta} phase was identified with X-ray diffraction. The {beta}{prime} phase was observed in the powder metallurgy pin after the material was given a solutionizing heat treatment. This observation suggests that Li may have been segregated to other phases, most likely either the {beta} or LiAlO{sub 2} phases, that subsequently dissolved during the ``solution treatment`` freeing-up Li to form {delta}{prime}. The possibility exists that the microstructural differences between these two materials could be decreased by further heat treatments or thermo-mechanical processing. However, without further experimentation, it is unknown which material (microstructure) is better suited for control rod pin applications.

Tosten, M.H.

1992-09-01

302

Transmission electron microscopy of Al-Li control rod pins  

SciTech Connect

This report discusses transmission electron microscopy employed to characterize the microstructures of both cast and mechanically alloyed powder Al-Li control rod pins. The results indicated that microstructural differences existed between the ingot and powder metallurgy materials. In general, the cast specimens contained large, dendritic [alpha] grains separated by regions of much smaller a grains and AlLi [beta] particles. The grain interiors, except in the immediate vicinity of the [beta] particles, contained a high number density of Al[sub 3]Li ([delta][prime]) precipitates. Several specimens also contained a widely distributed and unidentified Si-rich phase. In contrast, the microstructure of powder metallurgy samples consisted of small, randomly oriented [alpha] grains containing a dispersion of rod-like Al[sub 4]C[sub 3] (aluminum carbide) particles - confirmed by both TEM and X-ray diffraction. No TEM evidence was found for the presence of the [delta][prime] or [beta] phases in the as-received powder material, although the [beta] phase was identified with X-ray diffraction. The [beta][prime] phase was observed in the powder metallurgy pin after the material was given a solutionizing heat treatment. This observation suggests that Li may have been segregated to other phases, most likely either the [beta] or LiAlO[sub 2] phases, that subsequently dissolved during the solution treatment'' freeing-up Li to form [delta][prime]. The possibility exists that the microstructural differences between these two materials could be decreased by further heat treatments or thermo-mechanical processing. However, without further experimentation, it is unknown which material (microstructure) is better suited for control rod pin applications.

Tosten, M.H.

1992-09-01

303

Hierarchical level features based trainable segmentation for electron microscopy images  

PubMed Central

Background The neuronal electron microscopy images segmentation is the basic and key step to efficiently build the 3D brain structure and connectivity for a better understanding of central neural system. However, due to the visual complex appearance of neuronal structures, it is challenging to automatically segment membranes from the EM images. Methods In this paper, we present a fast, efficient segmentation method for neuronal EM images that utilizes hierarchical level features based on supervised learning. Hierarchical level features are designed by combining pixel and superpixel information to describe the EM image. For pixels in a superpixel have similar characteristics, only part of them is automatically selected and used to reduce information redundancy. To each selected pixel, 34 dimensional features are extracted by traditional way. Each superpixel itself is viewed as a unit to extract 35 dimensional features with statistical method. Also, 3 dimensional context level features among multi superpixels are extracted. Above three kinds of features are combined as a feature vector, namely, hierarchical level features to use for segmentation. Random forest is used as classifier and is trained with hierarchical level features to perform segmentation. Results In small sample condition and with low-dimensional features, the effectiveness of our method is verified on the data set of ISBI2012 EM Segmentation Challenge, and its rand error, warping error and pixel error attain to 0.106308715, 0.001200104 and 0.079132453, respectively. Conclusions Comparing to pixel level or superpixel level features, hierarchical level features have better discrimination ability and the proposed method is promising for membrane segmentation. PMID:23805885

2013-01-01

304

Visualization of Microbial Biomarkers by Scanning Electron Microscopy  

NASA Technical Reports Server (NTRS)

We are developing tools to link the biochemical structure of selected biomarkers with putative biogenic structures observed in mineralized samples. The detection of evidence of life on Mars and other planets will rely on methods that can discriminate compounds formed exclusively by living organisms. While biogenic compounds, such as amino acids and nucleotides have been discovered in extraterrestrial sources, such as meteorites and comets, their formation can be explained by abiotic means. The formation of cellular structures, or more elaborate organic molecules, such as complex lipids, proteins or nucleic acids, however, is strongly correlated to the presence of even the most primitive life processes. Recent evidence lends support to the hypothesis that life may have once existed on Mars. Carbonate globules and ppm concentrations of polycyclic aromatic hydrocarbons (PAHs) have been described in ALH84001, a meteorite originating from Mars ejecta captured by Earth over 13,000 years ago. The localized high concentration of PAHs that follow an increasing gradient from the intact fusion crust towards the interior corresponds to microgram quantities of hydrocarbon. Even though ALH84001 and other similar meteorites have withstood the forces capable of ejecting rock through Mars' escape velocity, upon entering Earth's atmosphere, their core temperatures are likely not to have been raised significantly, as evidenced by the survival of remanent magnetic signatures. Ideal biomarkers of ancient or modern biological life would include molecules that are (or were) pervasive and highly resistant to degradation. Also, requisite methods of detection should be simple, extremely sensitive and broadly inclusive (NASA SP-530). Lipopolysaccharide (LPS), peptidoglycan or pseudopeptidoglycan and beta-glucan are microbial cell wall components which together cover the entire microbial spectrum of eubacteria, archea and fungi. They are all remarkably resistant to thermal degradation. Fortunately, many antimicrobial defense systems of higher organisms require sensitive detection to combat microbial pathogens. We employ here the primitive immune system of the evolutionarily ancient horseshoe crab, Limulus polyphemus. This species relies on multi-enzyme signal amplification detection of cell wall molecules and they can be applied to the development of useful detectors of life. An extension of this work includes the visualization of microbial signatures by labeling LAL components with chromogenic or electron dense markers. The protein Limulus Anti-LPS Factor (LALF) has an extremely high affinity for LPS. By coupling LALF binding with colloidal gold labels we demonstrate a correlation of the structures visible by electron microscopy with biochemical evidence of microbial cell wall materials. Pure silica particles were mixed with cultures of E. coli (10(exp 6) cfu/mL). Samples were washed sequentially with buffered saline, LALF, antibody to LALF and finally colloidal gold-labeled Protein A. Negative controls were not exposed to E. coli but received identical treatment otherwise. Samples were coated with carbon and imaged on a JEOL JSM-840 scanning electron microscope with LaB6 source in the back scatter mode with the JEOL annular back scatter detector. 20 nm-scale black spots in this contrast-reversed image originate from electrons back-scattered by gold atoms. Negative controls did not give any signal. Future work will expand application of this technique to soil simulants and mineralized rock samples.

Wainwright, Norman R.; Allen, Carlton C.; Child, Alice

2001-01-01

305

Quantitative determination of maximal imaging depth in all-NIR multiphoton microscopy images of thick tissues  

NASA Astrophysics Data System (ADS)

We report two methods for quantitatively determining maximal imaging depth from thick tissue images captured using all-near-infrared (NIR) multiphoton microscopy (MPM). All-NIR MPM is performed using 1550 nm laser excitation with NIR detection. This method enables imaging more than five-fold deep in thick tissues in comparison with other NIR excitation microscopy methods. In this study, we show a correlation between the multiphoton signal along the depth of tissue samples and the shape of the corresponding empirical probability density function (pdf) of the photon counts. Histograms from this analysis become increasingly symmetric with the imaging depth. This distribution transitions toward the background distribution at higher imaging depths. Inspired by these observations, we propose two independent methods based on which one can automatically determine maximal imaging depth in the all-NIR MPM images of thick tissues. At this point, the signal strength is expected to be weak and similar to the background. The first method suggests the maximal imaging depth corresponds to the deepest image plane where the ratio between the mean and median of the empirical photon-count pdf is outside the vicinity of 1. The second method suggests the maximal imaging depth corresponds to the deepest image plane where the squared distance between the empirical photon-count mean obtained from the object and the mean obtained from the background is greater than a threshold. We demonstrate the application of these methods in all-NIR MPM images of mouse kidney tissues to study maximal depth penetration in such tissues.

Sarder, Pinaki; Akers, Walter J.; Sudlow, Gail P.; Yazdanfar, Siavash; Achilefu, Samuel

2014-02-01

306

Segmentation of Fluorescence Microscopy Images for Quantitative Analysis of Cell Nuclear Architecture  

PubMed Central

Abstract Considerable advances in microscopy, biophysics, and cell biology have provided a wealth of imaging data describing the functional organization of the cell nucleus. Until recently, cell nuclear architecture has largely been assessed by subjective visual inspection of fluorescently labeled components imaged by the optical microscope. This approach is inadequate to fully quantify spatial associations, especially when the patterns are indistinct, irregular, or highly punctate. Accurate image processing techniques as well as statistical and computational tools are thus necessary to interpret this data if meaningful spatial-function relationships are to be established. Here, we have developed a thresholding algorithm, stable count thresholding (SCT), to segment nuclear compartments in confocal laser scanning microscopy image stacks to facilitate objective and quantitative analysis of the three-dimensional organization of these objects using formal statistical methods. We validate the efficacy and performance of the SCT algorithm using real images of immunofluorescently stained nuclear compartments and fluorescent beads as well as simulated images. In all three cases, the SCT algorithm delivers a segmentation that is far better than standard thresholding methods, and more importantly, is comparable to manual thresholding results. By applying the SCT algorithm and statistical analysis, we quantify the spatial configuration of promyelocytic leukemia nuclear bodies with respect to irregular-shaped SC35 domains. We show that the compartments are closer than expected under a null model for their spatial point distribution, and furthermore that their spatial association varies according to cell state. The methods reported are general and can readily be applied to quantify the spatial interactions of other nuclear compartments. PMID:19383481

Russell, Richard A.; Adams, Niall M.; Stephens, David A.; Batty, Elizabeth; Jensen, Kirsten; Freemont, Paul S.

2009-01-01

307

Cathodoluminescent properties at nanometer resolution through Z-contrast scanning transmission electron microscopy  

E-print Network

Cathodoluminescent properties at nanometer resolution through Z-contrast scanning transmission of transmission electron microscopy and Z-contrast scanning transmission electron microscopy (Z-STEM). Depending layer is directly observed by simultaneous cathodoluminescence CL imag- ing and Z-contrast imaging

Pennycook, Steve

308

In situ transmission electron microscopy study of alpha-brass nanoligament formation, microstructure evolution and fracture  

E-print Network

In situ transmission electron microscopy study of alpha-brass nanoligament formation 2011 In situ transmission electron microscopy (TEM) tensile tests were performed to study alpha-brass- diffusion. Saturated alpha-brass (32 at.% Zn) was chosen as a sample, as it is prone to interdiffusion

Volinsky, Alex A.

309

Correlated cryo-fluorescence and cryo-electron microscopy with high spatial precision and improved sensitivity.  

PubMed

Performing fluorescence microscopy and electron microscopy on the same sample allows fluorescent signals to be used to identify and locate features of interest for subsequent imaging by electron microscopy. To carry out such correlative microscopy on vitrified samples appropriate for structural cryo-electron microscopy it is necessary to perform fluorescence microscopy at liquid-nitrogen temperatures. Here we describe an adaptation of a cryo-light microscopy stage to permit use of high-numerical aperture objectives. This allows high-sensitivity and high-resolution fluorescence microscopy of vitrified samples. We describe and apply a correlative cryo-fluorescence and cryo-electron microscopy workflow together with a fiducial bead-based image correlation procedure. This procedure allows us to locate fluorescent bacteriophages in cryo-electron microscopy images with an accuracy on the order of 50 nm, based on their fluorescent signal. It will allow the user to precisely and unambiguously identify and locate objects and events for subsequent high-resolution structural study, based on fluorescent signals. PMID:24275379

Schorb, Martin; Briggs, John A G

2014-08-01

310

Quantitative dielectric constant measurement of thin films by DC electrostatic force microscopy  

NASA Astrophysics Data System (ADS)

A simple method to measure the static dielectric constant of thin films with nanometric spatial resolution is presented. The dielectric constant is extracted from DC electrostatic force measurements with the use of an accurate analytical model. The method is validated here on thin silicon dioxide films (8 nm thick, dielectric constant~4) and purple membrane monolayers (6 nm thick, dielectric constant~2), providing results in excellent agreement with those recently obtained by nanoscale capacitance microscopy using a current-sensing approach. The main advantage of the force detection approach resides in its simplicity and direct application on any commercial atomic force microscope with no need of additional sophisticated electronics, thus being easily available to researchers in materials science, biophysics and semiconductor technology.

Gramse, G.; Casuso, I.; Toset, J.; Fumagalli, L.; Gomila, G.

2009-09-01

311

PREHISTORICAL Pediculus humanus capitis INFESTATION: QUANTITATIVE DATA AND LOW VACUUM SCANNING MICROSCOPY  

PubMed Central

A pre-Columbian Peruvian scalp was examined decades ago by a researcher from the Oswaldo Cruz Foundation. Professor Olympio da Fonseca Filho described nits and adult lice attached to hair shafts and commented about the origin of head lice infestations on mankind. This same scalp was sent to our laboratory and is the subject of the present paper. Analysis showed a massive infestation with nine eggs/cm2 and an impressive number of very well preserved adult lice. The infestation age was roughly estimated as nine months before death based on the distance of nits from the hair root and the medium rate of hair growth. A small traditional textile was associated with the scalp, possibly part of the funerary belongings. Other morphological aspects visualized by low-vacuum scanning electron microscopy are also presented here for adults and nits. PMID:24626412

Dutra, Juliana M.F.; Alves, Arthur Daniel; Pessanha, Thaila; Rachid, Rachel; de Souza, Wanderley; Linardi, Pedro Marcos; Ferreira, Luiz Fernando; de Souza, Sheila Mendonça; Araujo, Adauto

2014-01-01

312

Diffusion tensor microscopy in human nervous tissue with quantitative correlation based on direct histological comparison  

PubMed Central

Thanks to its proven utility in both clinical and research applications, diffusion tensor tractography (DTT) is regularly employed as a means of delineating white matter tracts. While successful efforts have been made to validate tractographic predictions, comparative methods which would permit the validation of such predictions at microscopic resolutions in complex biological tissues have remained elusive. In a previous study, we attempted to validate for the first time such predictions at microscopic resolutions in spinal cords of the rat and pig using a semi-quantitative analysis method. In the current study, we report improved quantitative analysis methods that can be used to determine the accuracy of DTT through comparative histology and apply theses techniques for the first time to human tissue (spinal cord) samples. Histological images are downsampled to resolutions equivalent to our magnetic resonance microscopy (MRM) and converted to binary maps using an automated thresholding tool. These maps (n = 3) are coregistered to the MRM allowing us to quantify the agreement based on the number of pixels which contain tracts common to both imaging datasets. In our experiments we find that—on average—89% of imaging pixels predicted by DTT to contain in-plane white matter tract structure correspond to physical tracts identified by histology. In addition, angular analysis comparing the orientation of fiber tracts measured in histology to their corresponding in-plane primary eigenvector components is presented. Thus, as well as demonstrating feasibility in human tissue, we report a robust agreement between imaging datasets taken at microscopic resolution and confirm the primary eigenvector’s role as a fundamental parameter with clear physical correlates in the microscopic regime. PMID:21575730

Hansen, Brian; Flint, Jeremy J.; Heon-Lee, Choong; Fey, Michael; Vincent, Franck; King, Michael A.; Vestergaard-Poulsen, Peter; Blackband, Stephen J.

2011-01-01

313

Quantitative three-dimensional carrier mapping in nanowire-based transistors using scanning spreading resistance microscopy.  

PubMed

The performance of nanoelectronic devices critically depends on the distribution of charge carriers inside such structures. High-vacuum scanning spreading resistance microscopy (HV-SSRM) has established as the method of choice for quantitative 2D-carrier mapping in nanoscale devices during the last decade. However, due to the 3D-nature of these nanoscale device architectures, dopant incorporation and dopant diffusion mechanisms can vary for any of the three dimensions, depending on the particular processes used. Therefore, mapping of carriers in three dimensions with high spatial resolution is inevitable to study and understand the distribution of active dopants in confined 3D-volumes and ultimately to support the process development of next generation devices. In this work, we present for the first time an approach to extend the capabilities of SSRM from an inherent 2D-carrier profiling technique towards a quantitative 3D-characterization technique based on the example of a nanowire (NW)-based heterojunction (SiGe-Si) tunneling transistor. In order to implement a 3D-methodology with a 2D-imaging technique, we acquired 2D-carrier concentration maps on successive cross-section planes through the device of interest. This was facilitated by arranging several devices in a staggered array, allowing to produce a series of cross-sections with incremental offset by a single cleave. A dedicated interpolation algorithm especially suited for structures with rotational symmetry like NWs was developed in order to reconstruct a 3D-carrier distribution map. The validity of the method was assessed by proving the absence of variations in carrier distribution in the third dimension, as expected for NWs etched into a blanket stack. PMID:23274680

Schulze, A; Hantschel, T; Eyben, P; Verhulst, A S; Rooyackers, R; Vandooren, A; Vandervorst, W

2013-02-01

314

Problems in the development of a clinically oriented program in electron microscopy.  

PubMed

The educational, organizational, and fiscal aspects of electron microscopy are discussed.. with emphais on the desirability of making electron microscopy an integral part of the formal training of residents in pathology and of the overall educational program of the medical staff. The rapidity of feedback of information from the pathologist to the clinician is stressed. The number of specimens processed and the variety of tissues submitted for electron microscopy can be regulated by the pathologist but should reflect the particular strength of the hospital or its department of pathology. The organization of the electron microscopy facility, its funding, and sharing of the electron microscopy program in the local community of clinical scientists are discussed PMID:1150224

Azar, H A; Morningstar, W A; Vracko, R; White, H J

1975-07-01

315

Simplified setup for imaging with digital holographic microscopy and enhanced quantitative phase contrast by osmotic stimulation of living cells  

NASA Astrophysics Data System (ADS)

Many interferometry-based quantitative phase contrast imaging techniques require the generation of a coherent reference wave, which results in a phase stability decrease and the demand for a precise adjustment of the intensity ratio between object and reference wave. Thus, investigations on a simplified digital holographic microscopy approach that avoids a separate reference wave were performed. Results from live cell investigations demonstrate the capability of the method for quantitative phase contrast imaging. In further experiments the modification of the intracellular refractive index distribution by osmotic stimulation was analyzed. Data from human pancreas tumor cells show that by choice of suitable buffer solutions live cell imaging with enhanced quantitative phase contrast is achieved.

Kemper, Björn; Przibilla, Sabine; Rommel, Christina E.; Vollmer, Angelika; Ketelhut, Steffi; Schnekenburger, Jürgen; von Bally, Gert

2011-03-01

316

Backscattered Electron Microscopy as an Advanced Technique in Petrography.  

ERIC Educational Resources Information Center

Three uses of this method with sandstone, desert varnish, and granite weathering are described. Background information on this technique is provided. Advantages of this type of microscopy are stressed. (CW)

Krinsley, David Henry; Manley, Curtis Robert

1989-01-01

317

Three-dimensional visualization and quantitation of fibrin in solid tumors by confocal laser scanning microscopy.  

PubMed

Fibrin forms part of the stroma essential for growth of solid tumors. Anticoagulants reduce primary tumor growth and tumor metastasis in murine and some human tumors. These effects may be partly mediated by reduction of intra-tumor fibrin, although there are no quantitative data to support this hypothesis. We therefore evaluated the effect of warfarin on fibrin deposition in a subcutaneously (s.c.) implanted murine tumor using confocal laser scanning microscopy (CLSM). AJ mice received no treatment (n = 6) or sodium warfarin (3.5 mg/L in drinking water, n = 5). All animals received 2 x 10(6) syngeneic Neuro2a neuroblastoma cells s.c. After 14 days, primary tumors were excised and placed in liquid nitrogen. Warfarin treatment resulted in a small, but significant (P < 0.05), decrease in wet tumor weight. Frozen sections (20 microns) were incubated with goat anti-mouse fibrin(ogen) or normal goat serum (isotypic control) and stained with FITC-conjugated rabbit anti-goat antibody. Using a Multiprobe 2001 CLSM (Molecular Dynamics, Sunnyvale, CA), 20 serial optical sections were taken from five, randomly chosen, high power fields (60x objective) for each slide. A threshold excluded all fluorescence except that from structural components within the tumor stroma (fibrin). The volume of fibrin in each section series was determined, and the percentage of tumor volume occupied by fibrin calculated. Intra- and inter-assay variation were assessed on serial frozen tumor sections from an untreated animal. The percentage fibrin volume was not significantly different among or within experiments, indicating that the procedure was reproducible. In controls, the median (range) volume occupied by fibrin was 8.1% (2.4-22.3%), whereas in anticoagulated animals, this was reduced to 3.7% (0.4-14.0%; P < 0.001). This is the first quantitative demonstration that warfarin reduces fibrin deposition in solid tumors. We conclude that three-dimensional CLSM is useful for the quantitation of tissue antigens and that the technique may have clinical value. PMID:9332818

Biggerstaff, J; Amirkhosravi, A; Francis, J L

1997-10-01

318

ANG-2 for quantitative Na(+) determination in living cells by time-resolved fluorescence microscopy.  

PubMed

Sodium ions (Na(+)) play an important role in a plethora of cellular processes, which are complex and partly still unexplored. For the investigation of these processes and quantification of intracellular Na(+) concentrations ([Na(+)]i), two-photon coupled fluorescence lifetime imaging microscopy (2P-FLIM) was performed in the salivary glands of the cockroach Periplaneta americana. For this, the novel Na(+)-sensitive fluorescent dye Asante NaTRIUM Green-2 (ANG-2) was evaluated, both in vitro and in situ. In this context, absorption coefficients, fluorescence quantum yields and 2P action cross-sections were determined for the first time. ANG-2 was 2P-excitable over a broad spectral range and displayed fluorescence in the visible spectral range. Although the fluorescence decay behaviour of ANG-2 was triexponential in vitro, its analysis indicates a Na(+)-sensitivity appropriate for recordings in living cells. The Na(+)-sensitivity was reduced in situ, but the biexponential fluorescence decay behaviour could be successfully analysed in terms of quantitative [Na(+)]i recordings. Thus, physiological 2P-FLIM measurements revealed a dopamine-induced [Na(+)]i rise in cockroach salivary gland cells, which was dependent on a Na(+)-K(+)-2Cl(-) cotransporter (NKCC) activity. It was concluded that ANG-2 is a promising new sodium indicator applicable for diverse biological systems. PMID:25311309

Roder, Phillip; Hille, Carsten

2014-12-12

319

Simultaneous mapping of filamentous actin flow and turnover in migrating cells by quantitative fluorescent speckle microscopy  

PubMed Central

We report advances in quantitative fluorescent speckle microscopy to generate simultaneous maps of cytoskeleton flow and rates of net assembly and disassembly in living cells. We apply this tool to analyze the filamentous actin (F-actin) dynamics at the front of migrating cells. F-actin turnover and flow are both known to be factors of cell locomotion. However, how they are orchestrated to produce directed cell movements is poorly understood. Our approach to data analysis allows us to examine their interdependence. Our maps confirm the previously described organization of flow into a lamellipodium and a lamellum, both exhibiting retrograde flow; and a convergence zone, where lamellum retrograde flow meets with slow anterograde flow of cortical F-actin at the ventral side of the cell body. The turnover maps show the well known actin polymerization at the leading edge, but also indicate that ?90% of the polymer disassembles at the lamellipodium–lamellum junction. Strong depolymerization is also found in the convergence zone, where meshwork contraction is prominent. To determine whether contraction and depolymerization are coupled events, we have treated cells with calyculin A, which is known to promote myosin activity. Stimulated contraction was accompanied by accelerated retrograde flow and increased depolymerization throughout the lamellum, whereas disassembly at the lamellipodium–lamellum junction remained unaffected. There appear to be two distinct depolymerization mechanisms, of which one depends directly on meshwork contraction. PMID:15210979

Vallotton, Pascal; Gupton, Stephanie L.; Waterman-Storer, Clare M.; Danuser, Gaudenz

2004-01-01

320

Microscopy, culture, and quantitative real-time PCR examination confirm internalization of mycobacteria in plants.  

PubMed

The environment is a reservoir of nontuberculous mycobacteria and is considered a source of infection for animals and humans. Mycobacteria can persist in different types of environments for a relatively long time. We have studied their possible internalization into plant tissue through intact, as well as damaged, root systems of different types of plants grown in vitro and under field conditions. The substrate into which plants were seeded was previously contaminated with different strains of Mycobacterium avium (10(8) to 10(10) cells/g of soil) and feces from animals with paratuberculosis. We detected M. avium subsp. avium, hominissuis, and paratuberculosis in the stems and leaves of the plants by both culture and real-time quantitative PCR. The presence of mycobacteria in the plant tissues was confirmed by microscopy. The concentration of mycobacteria found inside plant tissue was several orders of magnitude lower (up to 10(4) cells/g of tissue) than the initial concentration of mycobacteria present in the culture medium or substrate. These findings led us to the hypothesis that plants may play a role in the spread and transmission of mycobacteria to other organisms in the environment. PMID:24747896

Kaevska, M; Lvoncik, S; Slana, I; Kulich, P; Kralik, P

2014-07-01

321

Geometry of phase-separated domains in phospholipid bilayers by diffraction-contrast electron microscopy.  

PubMed Central

The sizes and shapes of solidus (gel) phase domains in the hydrated molecular bilayers of dilauroylphosphatidylcholine/dipalmitoylphasphatidylcholine (DLPC/DPPC) (1:1) and phosphatidylserine (PS)/DPPC (1:2) are visualized directly by low dose diffraction-contrast electron microscopy. The temperature and humidity of the bilayers are controlled by an environmental chamber set in an electron microscope. The contrast between crystalline domains is enhanced by electron optical filtering of the diffraction patterns of the bilayers. The domains are seen as a patchwork in the plane of the bilayer, with an average width of 0.2-0.5 micrometer. The percentage of solidus area measured from diffraction-contrast micrographs at various temperatures agrees in general with those depicted by known phase diagrams. The shape and size of the domains resemble those seen by freeze-fracture in multilamellar vesicles. Temperature-related changes in domain size and in phase boundary per unit area are more pronounced in the less miscible DLPC/DPPC mixture. No significant change in these geometric parameters with temperature is found in the PS/DPPC mixture. Mapping domains by their molecular diffraction signals not only verifies the existance of areas of different molecular packing during phase separation but also provides a quantitative measurement of structural boundaries and defects in lipid bilayers. Images FIGURE 1 FIGURE 3 FIGURE 6 PMID:6894707

Hui, S W

1981-01-01

322

Method for local temperature measurement in a nanoreactor for in situ high-resolution electron microscopy.  

PubMed

In situ high-resolution transmission electron microscopy (TEM) of solids under reactive gas conditions can be facilitated by microelectromechanical system devices called nanoreactors. These nanoreactors are windowed cells containing nanoliter volumes of gas at ambient pressures and elevated temperatures. However, due to the high spatial confinement of the reaction environment, traditional methods for measuring process parameters, such as the local temperature, are difficult to apply. To address this issue, we devise an electron energy loss spectroscopy (EELS) method that probes the local temperature of the reaction volume under inspection by the electron beam. The local gas density, as measured using quantitative EELS, is combined with the inherent relation between gas density and temperature, as described by the ideal gas law, to obtain the local temperature. Using this method we determined the temperature gradient in a nanoreactor in situ, while the average, global temperature was monitored by a traditional measurement of the electrical resistivity of the heater. The local gas temperatures had a maximum of 56 °C deviation from the global heater values under the applied conditions. The local temperatures, obtained with the proposed method, are in good agreement with predictions from an analytical model. PMID:23831940

Vendelbo, S B; Kooyman, P J; Creemer, J F; Morana, B; Mele, L; Dona, P; Nelissen, B J; Helveg, S

2013-10-01

323

A toolkit for the characterization of CCD cameras for transmission electron microscopy.  

PubMed

Charge-coupled devices (CCD) are nowadays commonly utilized in transmission electron microscopy (TEM) for applications in life sciences. Direct access to digitized images has revolutionized the use of electron microscopy, sparking developments such as automated collection of tomographic data, focal series, random conical tilt pairs and ultralarge single-particle data sets. Nevertheless, for ultrahigh-resolution work photographic plates are often still preferred. In the ideal case, the quality of the recorded image of a vitrified biological sample would solely be determined by the counting statistics of the limited electron dose the sample can withstand before beam-induced alterations dominate. Unfortunately, the image is degraded by the non-ideal point-spread function of the detector, as a result of a scintillator coupled by fibre optics to a CCD, and the addition of several inherent noise components. Different detector manufacturers provide different types of figures of merit when advertising the quality of their detector. It is hard for most laboratories to verify whether all of the anticipated specifications are met. In this report, a set of algorithms is presented to characterize on-axis slow-scan large-area CCD-based TEM detectors. These tools have been added to a publicly available image-processing toolbox for MATLAB. Three in-house CCD cameras were carefully characterized, yielding, among others, statistics for hot and bad pixels, the modulation transfer function, the conversion factor, the effective gain and the detective quantum efficiency. These statistics will aid data-collection strategy programs and provide prior information for quantitative imaging. The relative performance of the characterized detectors is discussed and a comparison is made with similar detectors that are used in the field of X-ray crystallography. PMID:20057054

Vulovic, M; Rieger, B; van Vliet, L J; Koster, A J; Ravelli, R B G

2010-01-01

324

Characterization of gold nanoparticle films: Rutherford backscattering spectroscopy, scanning electron microscopy with image analysis, and atomic force microscopy  

NASA Astrophysics Data System (ADS)

Gold nanoparticle films are of interest in several branches of science and technology, and accurate sample characterization is needed but technically demanding. We prepared such films by DC magnetron sputtering and recorded their mass thickness by Rutherford backscattering spectroscopy. The geometric thickness dg—from the substrate to the tops of the nanoparticles—was obtained by scanning electron microscopy (SEM) combined with image analysis as well as by atomic force microscopy (AFM). The various techniques yielded an internally consistent characterization of the films. In particular, very similar results for dg were obtained by SEM with image analysis and by AFM.

Lansâker, Pia C.; Hallén, Anders; Niklasson, Gunnar A.; Granqvist, Claes G.

2014-10-01

325

Transmission electron microscopy characterization of a Yttria-stabilized zirconia coating fabricated by electron beam–physical vapor deposition  

Microsoft Academic Search

Yttria-stabilized zirconia (YSZ) film was deposited on to a metal substrate by electron beam–physical vapor deposition (EB–PVD) at 850 °C. The film was characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The YSZ film predominantly consisted of the tetragonal phase with a small amount of monoclinic phase. In addition, the film was composed of inverted triangular-based pyramidal

T. Kato; K. Matsumoto; H. Matsubara; Y. Ishiwata; H. Saka; T. Hirayama; Y. Ikuhara

2005-01-01

326

A charge coupled device camera with electron decelerator for intermediate voltage electron microscopy  

PubMed Central

Electron microscopists are increasingly turning to intermediate voltage electron microscopes (IVEMs) operating at 300–400 kV for a wide range of studies. They are also increasingly taking advantage of slow-scan charge coupled device (CCD) cameras, which have become widely used on electron microscopes. Under some conditions, CCDs provide an improvement in data quality over photographic film, as well as the many advantages of direct digital readout. However, CCD performance is seriously degraded on IVEMs compared to the more conventional 100 kV microscopes. In order to increase the efficiency and quality of data recording on IVEMs, we have developed a CCD camera system in which the electrons are decelerated to below 100 kV before impacting the camera, resulting in greatly improved performance in both signal quality and resolution compared to other CCDs used in electron microscopy. These improvements will allow high-quality image and diffraction data to be collected directly with the CCD, enabling improvements in data collection for applications including high-resolution electron crystallography, single particle reconstruction of protein structures, tomographic studies of cell ultrastructure, and remote microscope operation. This approach will enable us to use even larger format CCD chips that are being developed with smaller pixels. PMID:18447528

Downing, Kenneth H.; Mooney, Paul E.

2008-01-01

327

Quantifying nanoscale order in amorphous materials: simulating fluctuation electron microscopy of amorphous silicon  

NASA Astrophysics Data System (ADS)

Fluctuation electron microscopy (FEM) 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. However, it remains a formidable challenge to invert the FEM data into a quantitative model of the structure. Here, we quantify the FEM method for a-Si by forward simulating the FEM data from a family of high quality atomistic models. Using a modified WWW method, we construct computational models that contain 10-40 vol% of topologically crystalline grains, 1-3 nm in diameter, in an amorphous matrix and calculate the FEM signal, which consists of the statistical variance V (k) of the dark-field image as a function of scattering vector k. We show that 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 k affords the size of the ordered regions; and the magnitude of the variance affords a semi-quantitative measure of the volume fraction. We have also compared models that contain various amounts of strain in the ordered regions. This analysis shows that the amount of strain in realistic models is sufficient to mute variance peaks at high k. We conclude with a comparison between the model results and experimental data.

Bogle, Stephanie N.; Voyles, Paul M.; Khare, Sanjay V.; Abelson, John R.

2007-11-01

328

Seeing and measuring with electrons: Transmission electron microscopy today and tomorrow - An introduction  

NASA Astrophysics Data System (ADS)

This dossier in Comptes rendus Physique is devoted to the most recent technologies and methodologies in electron microscopy available in 2014, which have provided this instrument with unique capabilities for atomic-level investigations in the domain of materials science. The present introduction provides some basic information required for an easier reading of the following manuscripts. It therefore focuses on column design, signal acquisition strategy, aberration correction, resolving power, in situ experiments and novel approaches, illustrated with a description of a few of their present and future fields of use.

Colliex, Christian

2014-02-01

329

Materials characterization using high-resolution scanning-electron microscopy and x-ray microanalysis  

NASA Astrophysics Data System (ADS)

Low-voltage field-emission scanning-electron microscopy offers the possibility to characterize a wide range of materials. Electron optics in an electron beam column have improved in recent decades and now probe diameters of 1-10 nm can be obtained, allowing a wide range of applications to be explored. This article discusses the applications of low-voltage microscopy, including the characterization of nanoparticles, super-lattice structures, and carbon nanotubes.

Gauvin, Raynald; Robertson, Kevin; Horny, Paula; Elwazri, Adbelbaset M.; Yue, Steve

2006-03-01

330

Nuclear pore complex structure and plasticity revealed by electron and atomic force microscopy.  

PubMed

To study the ultrastructure of nuclear pore complexes (NPCs), a wide spectrum of different electron microscopy (EM) or atomic force microscopy (AFM) techniques can be employed. The combination of these methods can reveal new insights into the structural and functional organization of this important supramolecular machine through which nucleocytoplasmic transport occurs. Negative staining, quick freezing/freeze-drying/rotary metal shadowing, embedding and thin sectioning, cryoelectron microscopy and tomography, scanning electron microscopy, or combination with immunolabeling techniques are tools for collecting data and information about the three-dimensional structure and architecture of the NPCs. AFM enables investigation of the functional dynamics of native NPCs under physiological conditions. PMID:16739730

Maco, Bohumil; Fahrenkrog, Birthe; Huang, Ning-Ping; Aebi, Ueli

2006-01-01

331

Electron Microscopy of Interactions Between Engineered Nanomaterials and Cells  

E-print Network

like free-electron lasers and backward wave oscillators (BWOs). The third is the utilization of optical- rently available THz source technologies, particularly the tunable emitters, such as free-electron lasers

Pala, Nezih

332

Laboratory design for high-performance electron microscopy  

Microsoft Academic Search

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

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

2004-01-01

333

Highly reproducible secondary electron imaging under electron irradiation using high-pass energy filtering in low-voltage scanning electron microscopy.  

PubMed

The reproducibility of contrast in secondary electron (SE) imaging during continuous electron irradiation, which caused surface contamination, was investigated using SE high-pass energy filtering in low-voltage scanning electron microscopy (SEM). According to high-pass energy-filtered imaging, dopant contrast in an indium phosphide remained remarkably stable during continuous electron irradiation although the contrast in unfiltered SE images decreased rapidly as a contamination layer was formed. Charge neutralization and the SE energy distributions indicate that the contamination layer induces a positive charge. This results in a decrease of low-energy SE emissions and reduced dopant contrast in unfiltered SE images. The retention of contrast was also observed in high-pass energy-filtered images of a gold surface. These results suggest that this imaging method can be widely used when SE intensities decrease under continuous electron irradiation in unfiltered SE images. Thus, high-pass energy-filtered SE imaging will be of a great assistance for SEM users in the reproducibility of contrast such as a quantitative dopant mapping in semiconductors. PMID:22364782

Tsurumi, Daisuke; Hamada, Kotaro; Kawasaki, Yuji

2012-04-01

334

Analytical Electron Microscopy examination of uranium contamination at the DOE Fernald operation site  

SciTech Connect

Analytical Electron Microscopy (AEM) has been used to identify uranium-bearing phases present in contaminated soils from the DOE Fernald operation site. A combination of optical microscopy, scanning electron microscopy with backscattered electron detection (SEM/BSE), and AEM was used in isolating and characterizing uranium-rich regions of the contaminated soils. Soil samples were prepared for transmission electron microscopy (TEM) by ultramicrotomy using an embedding resin previously employed for aquatic colloids and biological samples. This preparation method allowed direct comparison between SEM and TEM images. At the macroscopic level much of the uranium appears to be associated with clays in the soils; however, electron beam analysis revealed that the uranium is present as discrete phases, including iron oxides, silicates (soddyite), phosphates (autunites), and fluorite. Only low levels of uranium were actually within the clay minerals. The distribution of uranium phases was inhomogeneous at the submicron level.

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

1993-02-01

335

Coupling Automated Electron Backscatter Diffraction with Transmission Electron and Atomic Force Microscopies  

SciTech Connect

Grain boundary network engineering is an emerging field that encompasses the concept that modifications to conventional thermomechanical processing can result in improved properties through the disruption of the random grain boundary network. Various researchers have reported a correlation between the grain boundary character distribution (defined as the fractions of special and random grain boundaries) and dramatic improvements in properties such as corrosion and stress corrosion cracking, creep, etc. While much early work in the field emphasized property improvements, the opportunity now exists to elucidate the underlying materials science of grain boundary network engineering. Recent investigations at LLNL have coupled automated electron backscatter diffraction (EBSD) with transmission electron microscopy (TEM) and atomic force microscopy (AFM) to elucidate these fundamental mechanisms. This investigation provides evidence that grain boundary network engineering and the formation of annealing twins disrupt the connectivity of the random grain boundary network and is likely responsible for the experimentally observed improvement in properties. This work illustrates that coupling of automated EBSD with other microstructural probes such as TEM and AFM provides data of greater value than any single technique in isolation. The coupled techniques have been applied to aid in understanding the underlying mechanisms of grain boundary network engineering and the corrosion properties of individual boundaries.

Schwartz, A.J.; Kumar, M.; Bedrossian, P.J.; King, W.E.

2000-01-26

336

Rapid simultaneous identification and quantitation of Staphylococcus aureus and Pseudomonas aeruginosa directly from bronchoalveolar lavage specimens using automated microscopy.  

PubMed

Diagnosis of ventilator-assisted pneumonia (VAP) requires pathogen quantitation of respiratory samples. Current quantitative culture methods require overnight growth, and pathogen identification requires an additional step. Automated microscopy can perform rapid simultaneous identification and quantitation of live, surface-immobilized bacteria extracted directly from patient specimens using image data collected over 3 h. Automated microscopy was compared to 1 ?L loop culture and standard identification methods for Staphylococcus aureus and Pseudomonas spp. in 53 remnant bronchoalveolar lavage specimens. Microscopy identified 9/9 S. aureus and 7/7 P. aeruginosa in all specimens with content above the VAP diagnostic threshold. Concordance for specimens containing targets above the diagnostic threshold was 13/16, with concordance for sub-diagnostic content of 86/90. Results demonstrated that automated microscopy had higher precision than 1 ?L loop culture (range ~0.55 log versus ?1 log), with a dynamic range of ~4 logs (~10(3) to 10(6) CFU/mL). PMID:24698367

Metzger, Steven; Frobel, Rachel A; Dunne, W Michael

2014-06-01

337

Analytical electron microscopy characterization of uranium-contaminated soils from the Fernald Site, FY1993 report  

SciTech Connect

A combination of optical microscopy, scanning electron microscopy with backscattered electron detection (SEM/BSE), and analytical electron microscopy (AEM) is being used to determine the nature of uranium in soils from the Fernald Environmental Management Project. The information gained from these studies is being used to develop and test remediation technologies. Investigations using SEM have shown that uranium is contained within particles that are typically 1 to 100 {mu}m in diameter. Further analysis with AEM has shown that these uranium-rich regions are made up of discrete uranium-bearing phases. The distribution of these uranium phases was found to be inhomogeneous at the microscopic level.

Buck, E.C.; Cunnane, J.C.; Brown, N.R.; Dietz, N.L.

1994-10-01

338

A workflow for the automatic segmentation of organelles in electron microscopy image stacks  

PubMed Central

Electron microscopy (EM) facilitates analysis of the form, distribution, and functional status of key organelle systems in various pathological processes, including those associated with neurodegenerative disease. Such EM data often provide important new insights into the underlying disease mechanisms. The development of more accurate and efficient methods to quantify changes in subcellular microanatomy has already proven key to understanding the pathogenesis of Parkinson's and Alzheimer's diseases, as well as glaucoma. While our ability to acquire large volumes of 3D EM data is progressing rapidly, more advanced analysis tools are needed to assist in measuring precise three-dimensional morphologies of organelles within data sets that can include hundreds to thousands of whole cells. Although new imaging instrument throughputs can exceed teravoxels of data per day, image segmentation and analysis remain significant bottlenecks to achieving quantitative descriptions of whole cell structural organellomes. Here, we present a novel method for the automatic segmentation of organelles in 3D EM image stacks. Segmentations are generated using only 2D image information, making the method suitable for anisotropic imaging techniques such as serial block-face scanning electron microscopy (SBEM). Additionally, no assumptions about 3D organelle morphology are made, ensuring the method can be easily expanded to any number of structurally and functionally diverse organelles. Following the presentation of our algorithm, we validate its performance by assessing the segmentation accuracy of different organelle targets in an example SBEM dataset and demonstrate that it can be efficiently parallelized on supercomputing resources, resulting in a dramatic reduction in runtime. PMID:25426032

Perez, Alex J.; Seyedhosseini, Mojtaba; Deerinck, Thomas J.; Bushong, Eric A.; Panda, Satchidananda; Tasdizen, Tolga; Ellisman, Mark H.

2014-01-01

339

Quantitative in situ nanoindentation in an electron microscope  

SciTech Connect

We report the development of a method for quantitative, in situ nanoindentation in an electron microscope and its application to study the onset of deformation during the nanoindentation of aluminum films. The force--displacement curve developed shows the characteristic ''staircase'' instability at the onset of plastic deformation. This instability corresponds to the first appearance of dislocations in a previously defect-free grain. Plastic deformation proceeds through the formation and propagation of prismatic loops punched into the material, and half loops that emanate from the sample surface. These results represent the first real time observations of the discrete microstructural events that occur during nanoindentation.

Minor, A. M.; Morris, J. W.; Stach, E. A.

2001-09-10

340

Correlative analysis of immunoreactivity in confocal laser-scanning microscopy and scanning electron microscopy with focused ion beam milling  

PubMed Central

Recently, three-dimensional reconstruction of ultrastructure of the brain has been realized with minimal effort by using scanning electron microscopy (SEM) combined with focused ion beam (FIB) milling (FIB-SEM). Application of immunohistochemical staining in electron microscopy (EM) provides a great advantage in that molecules of interest are specifically localized in ultrastructures. Thus, we applied immunocytochemistry for FIB-SEM and correlated this immunoreactivity with that in confocal laser-scanning microcopy (CF-LSM). Dendrites of medium-sized spiny neurons in the rat neostriatum were visualized using a recombinant viral vector, which labeled the infected neurons with membrane-targeted GFP in a Golgi stain-like fashion. Moreover, the thalamostriatal afferent terminals were immunolabeled with Cy5 fluorescence for vesicular glutamate transporter 2 (VGluT2). After detection of the sites of terminals apposed to the dendrites by using CF-LSM, GFP and VGluT2 immunoreactivities were further developed for EM by using immunogold/silver enhancement and immunoperoxidase/diaminobenzidine (DAB) methods, respectively. In contrast-inverted FIB-SEM images, silver precipitations and DAB deposits were observed as fine dark grains and diffuse dense profiles, respectively, indicating that these immunoreactivities were as easily recognizable as those in the transmission electron microscopy (TEM) images. Furthermore, in the sites of interest, some appositions displayed synaptic specializations of an asymmetric type. Thus, the present method was useful in the three-dimensional analysis of immunocytochemically differentiated synaptic connections in the central neural circuit. PMID:23443927

Sonomura, Takahiro; Furuta, Takahiro; Nakatani, Ikuko; Yamamoto, Yo; Unzai, Tomo; Matsuda, Wakoto; Iwai, Haruki; Yamanaka, Atsushi; Uemura, Masanori; Kaneko, Takeshi

2013-01-01

341

Practical factors affecting the performance of a thin-film phase plate for transmission electron microscopy  

PubMed Central

A number of practical issues must be addressed when using thin carbon films as quarter-wave plates for Zernike phase-contrast electron microscopy. We describe, for example, how we meet the more stringent requirements that must be satisfied for beam alignment in this imaging mode. In addition we address the concern that one might have regarding the loss of some of the scattered electrons as they pass through such a phase plate. We show that two easily measured parameters, (1) the low-resolution image contrast produced in cryo-EM images of tobacco mosaic virus particles and (2) the fall-off of the envelope function at high resolution, can be used to quantitatively compare the data quality for Zernike phase-contrast images and for defocused bright-field images. We describe how we prepare carbon-film phase plates that are initially free of charging or other effects that degrade image quality. We emphasize, however, that even though the buildup of hydrocarbon contamination can be avoided by heating the phase plates during use, their performance nevertheless deteriorates over the time scale of days to weeks, thus requiring their frequent replacement in order to maintain optimal performance. PMID:19157711

Danev, Radostin; Glaeser, Robert M.; Nagayama, Kuniaki

2011-01-01

342

Microscopic techniques bridging between nanoscale and microscale with an atomically sharpened tip - field ion microscopy/scanning probe microscopy/ scanning electron microscopy.  

PubMed

Over a hundred years an atomistic point of view has been indispensable to explore fascinating properties of various materials and to develop novel functional materials. High-resolution microscopies, rapidly developed during the period, have taken central roles in promoting materials science and related techniques to observe and analyze the materials. As microscopies with the capability of atom-imaging, field ion microscopy (FIM), scanning tunneling microscopy (STM), atomic force microscopy (AFM) and transmission electron microscopy (TEM) can be cited, which have been highly evaluated as methods to ultimately bring forward the viewpoint of reductionism in materials science. On one hand, there have been difficulties to derive useful and practical information on large (micro) scale unique properties of materials using these excellent microscopies and to directly advance the engineering for practical materials. To make bridges over the gap between an atomic scale and an industrial engineering scale, we have to develop emergence science step-by-step as a discipline having hierarchical structures for future prospects by combining nanoscale and microscale techniques; as promising ways, the combined microscopic instruments covering the scale gap and the extremely sophisticated methods for sample preparation seem to be required. In addition, it is noted that spectroscopic and theoretical methods should implement the emergence science.Fundamentally, the function of microscope is to determine the spatial positions of a finite piece of material, that is, ultimately individual atoms, at an extremely high resolution with a high stability. To define and control the atomic positions, the STM and AFM as scanning probe microscopy (SPM) have successfully demonstrated their power; the technological heart of SPM lies in an atomically sharpened tip, which can be observed by FIM and TEM. For emergence science we would like to set sail using the tip as a base. Meanwhile, it is significant to extend a model sample prepared for the microscopies towards a microscale sample while keeping the intrinsic properties found by the microscopies.In this study we present our trial of developing microscopic combined instruments among FIM, field emission microscopy (FEM), STM, AFM and scanning electron microscopy (SEM), in which we prepared and characterized the tips for the SPM, and in addition, the sample preparation to take a correlation between nanoscale and microscale properties of functional materials. Recently, we developed a simple sample preparation method of a rutile single crystal TiO2 covered with an epitaxially-grown monolayer of SiO2 by annealing the crystals in a furnace at high temperatures in air; the crystal samples were placed into a quartz container in the furnace [1]. The vapor of SiO evaporated from the quartz container were adsorbed on the crystal while the crystal surfaces being fully oxidized in air. The SiO2-TiO2 composite systems are promising to protect catalytic TiO2 performance; the photo-catalytic activity is kept by coating with hard and stable SiO2 layers and to extend the lifetime of water super-hydrophilicity even in dark, though understanding of their properties is insufficient due to the lack of techniques to fabricate a well-characterized system on a nanoscale to conduct control experiments. The SiO2 overlayers were observed by low energy electron diffraction (LEED) in vacuum and frequency-modulation (FM) AFM in water [1,2], and water contact angles (WCA) were measured [2]. Although the WCA measurement seems a classic characterization, this method possesses a high potential to make a bridge by controlling the environmental conditions. We will discuss the details. PMID:25359799

Tomitori, Masahiko; Sasahara, Akira

2014-11-01

343

Diffusive and inelastic scattering in ballistic-electron-emission spectroscopy and ballistic-electron-emission microscopy  

SciTech Connect

Ballistic-electron-emission microscopy (BEEM) of Au/Si(001) n type was done to study whether elastic scattering in the Au overlayer is dominant. It was found that there is no dependence of the BEEM current on the relative gradient of the Au surface with respect to the Si interface, and this demonstrates that significant elastic scattering must occur in the Au overlayer. Ballistic-electron-emission spectroscopy (BEES) was also done, and, rather than using the conventional direct-current BEES, alternating-current (ac) BEES was done on Au/Si and also on Au/PtSi/Si(001) n type. The technique of ac BEES was found to give linear threshold for the Schottky barrier, and it also clearly showed the onset of electron-hole pair creation and other inelastic scattering events. The study of device quality PtSi in Au/PtSi/Si(001) yielded an attenuation length of 4 nm for electrons of energy 1 eV above the PtSi Fermi energy. 20 refs., 5 figs.

Lee, E.Y.; Turner, B.R.; Schowalter, L.J. [Rensselaer Polytechnic Institute, Troy, NY (United States)] [and others] [Rensselaer Polytechnic Institute, Troy, NY (United States); and others

1993-07-01

344

Investigation of Nanoelectrodes by Transmission Electron Microscopy M.S. Kabir1  

E-print Network

to the conjugated -orbitals, which mainly open the channels for conduction of electrons. Therefore oligomersInvestigation of Nanoelectrodes by Transmission Electron Microscopy M.S. Kabir1 , S.H. Magnus Persson1 , Yimin Yao2 , Jean Phillippe Bourgoin3 , Serge Palacin3 1 Dept. of Micro Electronics

Boyer, Edmond

345

Energy Spectra of Individual Gold Monolayer Protected Clusters Measured by Single Electron Tunneling Force Microscopy  

Microsoft Academic Search

Monolayer Protected Clusters (MPCs) exhibit strong quantum confinement effects and size dependent electronic, optical and chemical properties. The energy levels of individual gold MPCs (Au38 & Au140) have been directly measured by Single Electron Tunneling Force Microscopy at room temperature in UHV.^[1,2] Single electrons, tunneling between a probe tip and individual gold MPCs are detected using a novel surface potential

Ning Zheng; Jon Johnson; Gangli Wang; Clayton Williams

2007-01-01

346

Vertically integrated optics for ballistic electron emission luminescence: Device and microscopy characterizations  

E-print Network

Vertically integrated optics for ballistic electron emission luminescence: Device and microscopy directly into a ballistic electron emission luminescence BEEL heterostructure with GaAs quantum-well active of Physics. DOI: 10.1063/1.2208738 I. INTRODUCTION As a recent development of ballistic electron emission

Russell, Kasey

347

Structural Transformations in self-assembled Semiconductor Quantum Dots as inferred by Transmission Electron Microscopy  

E-print Network

microscopy studies in both the scanning and parallel illumination mode on samples of two generic typesStructural Transformations in self-assembled Semiconductor Quantum Dots as inferred by Transmission Electron Microscopy Peter Möck*1 , Yuanyuan Lei1 , Teya Topuria1 , Nigel D. Browning1 , Regina Ragan**2

Moeck, Peter

348

Rumen microbial degradation of modified lignin plants observed by electron microscopy  

E-print Network

Rumen microbial degradation of modified lignin plants observed by electron microscopy C Mign6, E-Genès-Champanelle, France The microbial degradation of modified lignin tobacco (Samson variety) plants (homozygous line 40), produced by genetic engineering was studied by microscopy. Fourteen-week-old tobaccos plants, grown

Paris-Sud XI, Université de

349

A Quantitative 3D Motility Analysis of Trypanosoma brucei by Use of Digital In-line Holographic Microscopy  

PubMed Central

We present a quantitative 3D analysis of the motility of the blood parasite Trypanosoma brucei. Digital in-line holographic microscopy has been used to track single cells with high temporal and spatial accuracy to obtain quantitative data on their behavior. Comparing bloodstream form and insect form trypanosomes as well as mutant and wildtype cells under varying external conditions we were able to derive a general two-state-run-and-tumble-model for trypanosome motility. Differences in the motility of distinct strains indicate that adaption of the trypanosomes to their natural environments involves a change in their mode of swimming. PMID:22629379

Weisse, Sebastian; Heddergott, Niko; Heydt, Matthias; Pflasterer, Daniel; Maier, Timo; Haraszti, Tamas; Grunze, Michael; Engstler, Markus; Rosenhahn, Axel

2012-01-01

350

Single event imaging for electron microscopy using MAPS detectors  

NASA Astrophysics Data System (ADS)

Monolithic active pixel sensors, MAPS, combine sensitivity to individual incident electrons with fast readout. This combination allows single event imaging, in which the final image is assembled from the information in the images of individual incident electrons to be implemented. This mode of imaging offers higher detective quantum efficiency and increased lifetime of the detector. Problems faced in processing the single electron events are discussed. It is proposed that the individual electron contributions should be accumulated into a final image with a probability distribution representing the uncertainty of their arrival position due to scattering. The use of a shadow image of a grid is advocated as a way to compare different methods for processing single electron events. Finally an example of a single event image is presented.

McMullan, G.; Turchetta, R.; Faruqi, A. R.

2011-04-01

351

Electron and Immunoelectron Microscopy of Experimental Reston Virus Infection in Monkeys. (Reannouncement with New Availability Information).  

National Technical Information Service (NTIS)

The tissues and fluids of five cynomolgus macaques (Macaca Fasicularis) experimentally inoculated with Ebola-related Reston virus were examined by transmission electron microscopy (TEM) at various stages of disease to provide insight into the pathogenesis...

T. W. Geisbert, P. B. Jahrling, N. K. Jaax

1992-01-01

352

Detection of Silver Nanoparticles inside Marine Diatom Thalassiosira pseudonana by Electron Microscopy and Focused Ion Beam  

PubMed Central

In the following article an electron/ion microscopy study will be presented which investigates the uptake of silver nanoparticles (AgNPs) by the marine diatom Thalassiosira pseudonana, a primary producer aquatic species. This organism has a characteristic silica exoskeleton that may represent a barrier for the uptake of some chemical pollutants, including nanoparticles (NPs), but that presents a technical challenge when attempting to use electron-microscopy (EM) methods to study NP uptake. Here we present a convenient method to detect the NPs interacting with the diatom cell. It is based on a fixation procedure involving critical point drying which, without prior slicing of the cell, allows its inspection using transmission electron microscopy. Employing a combination of electron and ion microscopy techniques to selectively cut the cell where the NPs were detected, we are able to demonstrate and visualize for the first time the presence of AgNPs inside the cell membrane. PMID:24797958

Pascual Garcia, Cesar; Burchardt, Alina D.; Carvalho, Raquel N.; Gilliland, Douglas; C. Antonio, Diana; Rossi, Francois; Lettieri, Teresa

2014-01-01

353

EVALUATION OF COMPUTER-CONTROLLED SCANNING ELECTRON MICROSCOPY APPLIED TO AN AMBIENT URBAN AEROSOL SAMPLE  

EPA Science Inventory

Concerns about the environmental and public health effects of particulate matter (PM) have stimulated interest in analytical techniques capable of measuring the size and chemical composition of individual aerosol particles. Computer-controlled scanning electron microscopy (CCSE...

354

Demonstration of Ballistic Electron Emission Microscopy / Spectroscopy on the Au/Si (001) system  

E-print Network

The Ballistic Electron Emission Microscopy (BEEM) capabilities of a Scanning Tunneling Microscope (STM) have been verified. BEEM is used to analyze the characteristics of buried energy barriers and was developed as an extension of scanning tunneling...

Drummond, Mary Alyssa

2012-06-07

355

Development of multiplexing strategies for electron and super-resolution optical microscopy/  

E-print Network

The aim of this work is to increase the multiplexing capabilities of electron and super resolution optical microscopy. This will be done through the development of molecular-scale barcodes that can be resolved in one of ...

Tillberg, Paul W

2013-01-01

356

Detection of silver nanoparticles inside marine diatom Thalassiosira pseudonana by electron microscopy and focused ion beam.  

PubMed

In the following article an electron/ion microscopy study will be presented which investigates the uptake of silver nanoparticles (AgNPs) by the marine diatom Thalassiosira pseudonana, a primary producer aquatic species. This organism has a characteristic silica exoskeleton that may represent a barrier for the uptake of some chemical pollutants, including nanoparticles (NPs), but that presents a technical challenge when attempting to use electron-microscopy (EM) methods to study NP uptake. Here we present a convenient method to detect the NPs interacting with the diatom cell. It is based on a fixation procedure involving critical point drying which, without prior slicing of the cell, allows its inspection using transmission electron microscopy. Employing a combination of electron and ion microscopy techniques to selectively cut the cell where the NPs were detected, we are able to demonstrate and visualize for the first time the presence of AgNPs inside the cell membrane. PMID:24797958

García, César Pascual; Burchardt, Alina D; Carvalho, Raquel N; Gilliland, Douglas; António, Diana C; Rossi, François; Lettieri, Teresa

2014-01-01

357

Isolation methods and electron microscopy of the Internal Cork Virus of sweet potatoes  

E-print Network

ISOLATION METHODS AND ELECTRON MICROSCOPY OF THE INTERNAL CORK VIRUS OF SWEET POTATOES A Thesis By Edgar Eugene Pickens Submitted to the Graduate College of the Texas A8cM University in partial fulfillment of the requirements for the degree... of MASTER OF SCIENCE August 1967 Major Subject Biochemistry ISOLATION METHODS AND ELECTRON MICROSCOPY OF THE INTERNAL CORK VIRUS OF SWEET POTATOES A Thesis Edgar Eugene Pickens Approved as to style and content by: (Cnairman of Committee) (Head wf...

Pickens, Edgar Eugene

2012-06-07

358

Extracellular vesicles release by cardiac telocytes: electron microscopy and electron tomography.  

PubMed

Telocytes have been reported to play an important role in long-distance heterocellular communication in normal and diseased heart, both through direct contact (atypical junctions), as well as by releasing extracellular vesicles (EVs) which may act as paracrine mediators. Exosomes and ectosomes are the two main types of EVs, as classified by size and the mechanism of biogenesis. Using electron microscopy (EM) and electron tomography (ET) we have found that telocytes in culture release at least three types of EVs: exosomes (released from endosomes; 45 ± 8 nm), ectosomes (which bud directly from the plasma membrane; 128 ± 28 nm) and multivesicular cargos (MVC; 1 ± 0.4 ?m), the latter containing tightly packaged endomembrane-bound vesicles (145 ± 35 nm). Electron tomography revealed that endomembrane vesicles are released into the extracellular space as a cargo enclosed by plasma membranes (estimated area of up to 3 ?m(2) ). This new type of EV, also released by telocytes in tissue, likely represents an essential component in the paracrine secretion of telocytes and may consequently be directly involved in heart physiology and regeneration. PMID:25257228

Fertig, Emanuel T; Gherghiceanu, Mihaela; Popescu, Laurentiu M

2014-10-01

359

A quantitative study of histones in meioeytes I. Investigation of the histone amount in cricket spermatogenesis by interference microscopy  

Microsoft Academic Search

The amount of total histone and separate groups of histone fractions were determined in isolated individual nuclei of the cricket spermatogonia and spermatocytes by the use of quantitative interference microscopy before and after the stepwise histone extraction with hydrochloric acid at pH 2.2, 1.5 and 0.7. It is established that during spermatogonial interphase the amount of the total histone per

N. A. Liapunova; D. P. Babadjanian

1973-01-01

360

Quantitative Evaluation of Local Young's Modulus of Small-Scale Solids by Isolated Langasite Oscillator: Resonant-Ultrasound Microscopy  

NASA Astrophysics Data System (ADS)

A resonance-ultrasound microscopy has been developed to measure material's local Young's modulus. It detects the effective Young modulus through a resonance frequency of a langasite (La3Ga5SiO14) oscillator touching the specimen. The vibration of the oscillator is excited and detected with a surrounding solenoid coil in a noncontacting way and it can be affected only by the contact with the specimen, achieving an absolute quantitative measurement.

Ogi, H.; Tian, J.; Tada, T.; Hirao, M.

2005-04-01

361

Microstructural evolution and age hardening in aluminium alloys: Atom probe field-ion microscopy and transmission electron microscopy studies  

SciTech Connect

This paper examines the microstructural evolution in selected aluminum alloys based on commercial age hardenable 2000, 6000, and 7000 series alloys. Atom probe field-ion microscopy and transmission electron microscopy have been used to examine the effects of microalloying and the origins of hardening. The combined application of these techniques is particularly important in the study of nanoscale precipitation processes. It is shown that the nature and kinetics of the precipitation process depend on the solute-solute interactions that produce solute clusters. The solute clusters precede the formation of GP zones or precipitation, and have a defining role on the nature and kinetics of the subsequent precipitation processes. Moreover, interactions between solute clustering and dislocations can have a significant hardening effect, the origins of which seem to be distinctly different from the conventional notion of precipitation hardening.

Ringer, S.P.; Hono, K.

2000-02-01

362

Abundance of Viruses in Marine Waters: Assessment by Epifluorescence and Transmission Electron Microscopy  

PubMed Central

Abundance of bacteria and tiny DNA-associated particles in the upper layer of Japanese coastal and offshore waters was evaluated by epifluorescence microscopy with 0.015-?m-pore-size Nuclepore filters. The number of tiny DNA-associated particles was compared with the abundance of virus particles estimated by transmission electron microscopy. Although a large variation in virus abundance (1.2 × 106 to 35 × 106 ml?1) was obtained with the transmission electron microscopy method, the ratio of 4?,6-diamidino-2-phenylindole-reactive tiny particles to viruses was in a rather narrow range (1.0 to 1.6), indicating that the majority of the tiny DNA-associated particles identified by epifluorescence microscopy were actually virus particles. This result implies the possibility of using epifluorescence microscopy for the evaluation of virus abundance in marine environments. Images PMID:16348556

Hara, Shigemitsu; Terauchi, Kazuki; Koike, Isao

1991-01-01

363

High-Contrast Observation of Unstained Proteins and Viruses by Scanning Electron Microscopy  

PubMed Central

Scanning electron microscopy (SEM) is an important tool for the nanometre-scale analysis of the various samples. Imaging of biological specimens can be difficult for two reasons: (1) Samples must often be left unstained to observe detail of the biological structures; however, lack of staining significantly decreases image contrast. (2) Samples are prone to serious radiation damage from electron beam. Herein we report a novel method for sample preparation involving placement on a new metal-coated insulator film. This method enables obtaining high-contrast images from unstained proteins and viruses by scanning electron microscopy with minimal electron radiation damage. These images are similar to those obtained by transmission electron microscopy. In addition, the method can be easily used to observe specimens of proteins, viruses and other organic samples by using SEM. PMID:23056522

Ogura, Toshihiko

2012-01-01

364

Electron microscopy of whole cells in liquid with nanometer resolution  

SciTech Connect

Single gold-tagged epidermal growth factor (EGF) molecules bound to cellular EGF receptors of fixed fibroblast cells were imaged in liquid with a scanning transmission electron microscope (STEM). The cells were placed in buffer solution in a micro-fluidic device with electron transparent windows inside the vacuum of the electron microscope. A spatial resolution of 4 nm and a pixel dwell time of 20 ?s were obtained. The liquid layer was sufficiently thick to contain the cells with a thickness of 7 1 ?m. The experimental findings are consistent with a theoretical calculation. Liquid STEM is a unique approach for imaging single molecules in whole cells with significantly improved resolution and imaging speed over existing methods.

De Jonge, Niels [ORNL; Peckys, Diana B [ORNL; Piston, David W [Vanderbilt University; Kremers, Gert-Jan [ORNL

2009-01-01

365

Low voltage scanning electron microscopy of interplanetary dust particles  

NASA Technical Reports Server (NTRS)

The resolution of available low-voltage SEM (LVSEM) models used in the characterization of interplanetary dust particles (IDPs) is limited by a number of factors including energy spread in the electron source, beam brightness, scanning electron detector geometry, and various lens aberrations. This paper describes an improved model of LVSEM which offers an increased resolution at low voltage. The improvements include a cold cathode FE source which has an extremely low inherent energy spread and high brightness, a second condenser lens to converge the beam and maintain an optimum aperture half-angle, and a detector optimized for low-voltage scanning-electron collection. To reduce lens aberrations, the specimen is immersed in the objective lens field. The features of several IDP samples observed using the images obtained with this LVSEM model are described.

Blake, D. F.; Bunch, T. E.; Reilly, T. W.; Brownlee, D. E.

1987-01-01

366

Electron microscopy of whole cells in liquid with nanometer resolution  

PubMed Central

Single gold-tagged epidermal growth factor (EGF) molecules bound to cellular EGF receptors of fixed fibroblast cells were imaged in liquid with a scanning transmission electron microscope (STEM). The cells were placed in buffer solution in a microfluidic device with electron transparent windows inside the vacuum of the electron microscope. A spatial resolution of 4 nm and a pixel dwell time of 20 ?s were obtained. The liquid layer was sufficiently thick to contain the cells with a thickness of 7 ± 1 ?m. The experimental findings are consistent with a theoretical calculation. Liquid STEM is a unique approach for imaging single molecules in whole cells with significantly improved resolution and imaging speed over existing methods. PMID:19164524

de Jonge, N.; Peckys, D. B.; Kremers, G. J.; Piston, D. W.

2009-01-01

367

The theory and practice of high resolution scanning electron microscopy  

SciTech Connect

Recent advances in instrumentation have produced the first commercial examples of what can justifiably be called High Resolution Scanning Electron Microscopes. The key components of such instruments are a cold field emission gun, a small-gap immersion probe-forming lens, and a clean dry-pumped vacuum. The performance of these microscopes is characterized by several major features including a spatial resolution, in secondary electron mode on solid specimens, which can exceed 1nm on a routine basis; an incident probe current density of the order of 10{sup 6} amps/cm{sup 2}; and the ability to maintain these levels of performance over an accelerating voltage range of from 1 to 30keV. This combination of high resolution, high probe current, low contamination and flexible electron-optical conditions provides many new opportunitites for the application of the SEM to materials science, physics, and the life sciences. 27 refs., 14 figs.

Joy, D.C. (Tennessee Univ., Knoxville, TN (USA) Oak Ridge National Lab., TN (USA))

1990-01-01

368

Integrating electron microscopy into nanoscience and materials engineering programs  

NASA Astrophysics Data System (ADS)

Preparing an effective workforce in high technology is the goal of both academic and industry training, and has been the engine that drives innovation and product development in the United States for over a century. During the last 50 years, technician training has comprised a combination of two-year academic programs, internships and apprentice training, and extensive On-the-Job Training (OJT). Recently, and especially in Silicon Valley, technicians have four-year college degrees, as well as relevant hands-on training. Characterization in general, and microscopy in particular, is an essential tool in process development, manufacturing and QA/QC, and failure analysis. Training for a broad range of skills and practice is challenging, especially for community colleges. Workforce studies (SRI/Boeing) suggest that even four year colleges often do not provide the relevant training and experience in laboratory skills, especially design of experiments and analysis of data. Companies in high-tech further report difficulty in finding skilled labor, especially with industry specific experience. Foothill College, in partnership with UCSC, SJSU, and NASA-Ames, has developed a microscopy training program embedded in a research laboratory, itself a partnership between university and government, providing hands-on experience in advanced instrumentation, experimental design and problem solving, with real-world context from small business innovators, in an environment called `the collaboratory'. The program builds on AFM-SEM training at Foothill, and provides affordable training in FE-SEM and TEM through a cost recovery model. In addition to instrument and engineering training, the collaboratory also supports academic and personal growth through a multiplayer social network of students, faculty, researchers, and innovators.

Cormia, Robert D.; Oye, Michael M.; Nguyen, Anh; Skiver, David; Shi, Meng; Torres, Yessica

2014-10-01

369

High Resolution Electron Microscopy at the National Cancer Institute  

Cancer.gov

The major facilitator superfamily (MFS) represents the largest collection of evolutionarily related members within the class of membrane 'carrier' proteins. OxlT, a representative example of the MFS, is an oxalate-transporting membrane protein in Oxalobacter formigenes . From an electron crystallographic analysis of two-dimensional crystals of OxlT, we have determined the projection structure of this membrane transporter.

370

Scanning Electron Microscopy in Concrete Petrography Paul E. Stutzman  

E-print Network

Hydroxide in Concrete 61 Figure 1. Secondary electron images showing the hexagonal habit of calcium hydroxide, needle-like habit of ettringite, and the sheet-like habit of calcium- silicate a graphical display of the changes in paste microstructure with distance. This plot is scaled to fit the image

Bentz, Dale P.

371

The electron microscopy of vaccinia-diseased tissues  

Microsoft Academic Search

Many hundreds of electron micrographs have been made on a corresponding number of sections through chicken embryo tissues diseased with vaccine virus. The fully developed elementary bodies of this virus are easily recognized in such sections. Search has been made for evidence of proliferation in chorioallantoic membranes infected for various lengths of time. This has given evidence bearing on several

Ralph W. G. Wyckoff

1953-01-01

372

Welcome to the World of Scanning Electron Microscopy  

NSDL National Science Digital Library

This site from the Iowa State Materials Science and Engineering Department features information about the scanning electron microscope (SEM). The site includes three versions of a tutorial about how the SEM works that are written for middle school, high school and college level audiences. The site also features an image gallery and information on how to submit samples.

University, Materials S.; University, Iowa S.

373

Scanning electron microscopy of dialysis tubes incubated in flowing seawater  

Microsoft Academic Search

Scanning electron micrographs (SEM) demonstrate the growth of an epiphytic diatom and bacterial community on the surface of dialysis membranes incubated In situ, Narragansett Bay, Rhode Island (USA). A comparison is made between brushed and unbrushed tubes in summer, and unbrushed tubes in winter. Detrital deposition and epiphytic growth may decrease surface area and, by uptake and regeneration, influence nutrient

G. A. Vargo; P. E. Hargraves; P. Johnson

1975-01-01

374

Electron Microscopy 1.0 Introduction and History  

E-print Network

to the limitations of Light Microscopes which are limited by the physics of light to 500x or 1000x magnification and is patterned exactly on the Light Transmission Microscope except that a focused beam of electrons is used.0 Basic Principles · 2.1 The Microscope Column · 2.2 Signal Detection and Display · 2.3 Operating

Moeck, Peter

375

Bulk sensitive hard x-ray photoemission electron microscopy.  

PubMed

Hard x-ray photoelectron spectroscopy (HAXPES) has now matured into a well-established technique as a bulk sensitive probe of the electronic structure due to the larger escape depth of the highly energetic electrons. In order to enable HAXPES studies with high lateral resolution, we have set up a dedicated energy-filtered hard x-ray photoemission electron microscope (HAXPEEM) working with electron kinetic energies up to 10 keV. It is based on the NanoESCA design and also preserves the performance of the instrument in the low and medium energy range. In this way, spectromicroscopy can be performed from threshold to hard x-ray photoemission. The high potential of the HAXPEEM approach for the investigation of buried layers and structures has been shown already on a layered and structured SrTiO3 sample. Here, we present results of experiments with test structures to elaborate the imaging and spectroscopic performance of the instrument and show the capabilities of the method to image bulk properties. Additionally, we introduce a method to determine the effective attenuation length of photoelectrons in a direct photoemission experiment. PMID:25430117

Patt, M; Wiemann, C; Weber, N; Escher, M; Gloskovskii, A; Drube, W; Merkel, M; Schneider, C M

2014-11-01

376

Quantitative Electron Probe Microanalysis of Nonconducting Specimens: Science or Art?  

NASA Astrophysics Data System (ADS)

The influence of a lack of sufficient electrical conductivity on the results of quantitative electron probe microanalysis has been investigated on a number of oxides. The effect of surface charging and the way it alters the emitted X-ray signals has been studied. It is shown that the presence of conducting coatings, such as carbon or copper, will affect the interelement X-ray intensity ratios, whatever the thickness of the coating may be. Although the effects for heavier elements may be acceptable, they cannot be ignored for a light element such as oxygen, where strong variations with coating thickness were observed. Quantitative analyses of oxygen, on uncoated well-conducting oxide specimens, using uncoated well-conducting hematite (Fe2O3) as a standard yielded excellent results in the range between 4 and 40 kV with the [curly or open phi]([rho]z) software used. As soon as coated nonconducting specimens were examined, using the same hematite standard, coated under exactly the same conditions, widely scattering and noncoherent results were obtained. These discrepancies can only be attributed to a lack of conductivity.

Bastin, Guillaume F.; Heijligers, Hans J. M.

2004-12-01

377

Quantitative analysis of volume images: electron microscopic tomography of HIV  

NASA Astrophysics Data System (ADS)

Three-dimensional objects should be represented by 3D images. So far, most of the evaluation of images of 3D objects have been done visually, either by looking at slices through the volumes or by looking at 3D graphic representations of the data. In many applications a more quantitative evaluation would be valuable. Our application is the analysis of volume images of the causative agent of the acquired immune deficiency syndrome (AIDS), namely human immunodeficiency virus (HIV), produced by electron microscopic tomography (EMT). A structural analysis of the virus is of importance. The representation of some of the interesting structural features will depend on the orientation and the position of the object relative to the digitization grid. We describe a method of defining orientation and position of objects based on the moment of inertia of the objects in the volume image. In addition to a direct quantification of the 3D object a quantitative description of the convex deficiency may provide valuable information about the geometrical properties. The convex deficiency is the volume object subtracted from its convex hull. We describe an algorithm for creating an enclosing polyhedron approximating the convex hull of an arbitrarily shaped object.

Nystroem, Ingela; Bengtsson, Ewert W.; Nordin, Bo G.; Borgefors, Gunilla

1994-05-01

378

Quantification of metallic nanoparticle morphology with tilt series imaging by transmission electron microscopy  

NASA Astrophysics Data System (ADS)

We report on the quantitative analysis of electrolessly deposited Au and Ag nanoparticles (NPs) on SU8 polymer with the help of High-Angle Annular Dark-Field Scanning Transmission Electron Microscopy (HAADF-STEM) in tilt series. Au NPs act as nucleating agents for the electroless deposition of silver. Au NPs were prepared by attachingAu^3+cations to amine functionalized SU8 polymeric surfaces and then reducing it with aqueous NaBH4. The nanoscale morphology of the deposited NPs on the surface of polymer has been studied from the dark field TEM cross sectional images. Ag NPs were deposited on the cross-linked polymeric surface from a silver citrate solution reduced by hydroquinone. HAADF-STEM enables us to determine the distances between the NPs and their exact locations at and near the surface. The particle distribution, sizes and densities provide us with the data necessary to control the parameters for the development of the electroless deposition technique for emerging nanoscale technologies.

Dutta, Aniruddha; Yuan, Biao; Clukay, Christopher J.; Grabill, Christopher N.; Heinrich, Helge; Bhattacharya, Aniket; Kuebler, Stephen M.

2012-02-01

379

Electron microscopy and microanalysis of steel weld joints after long time exposures at high temperatures  

NASA Astrophysics Data System (ADS)

The structural changes of three trial weld joints of creep resistant modified 9Cr-1Mo steels and low alloyed chromium steel after post-weld heat treatment and long-term creep tests were investigated. Smooth cross-weld specimens ruptured in different zones of the weld joints as a result of different structural changes taking place during creep exposures. The microstructure of the weld joint is heterogeneous and consequently microstructural development can be different in the weld metal, the heat affected zone, and the base material. Precipitation reactions, nucleation and growth of some particles and dissolution of others, affect the strengthening of the matrix, recovery at high temperatures, and the resulting creep resistance. Therefore, a detailed study of secondary phase's development in individual zones of weld joints can elucidate mechanism of cracks propagation in specific regions and the causes of creep failure. Type I and II fractures in the weld metal and Type IV fractures in the fine prior austenite grain heat affected zones occurred after creep tests at temperatures ranging from 525 to 625 °C and under stresses from 40 to 240 MPa. An extended metallographic study of the weld joints was carried out using scanning and transmission electron microscopy, energy-dispersive and wave-dispersive X-ray microanalysis. Carbon extraction replicas and thin foils were prepared from individual weld joint regions and quantitative evaluation of dislocation substructure and particles of secondary phases has been performed.

Jandová, D.; Kasl, J.; Rek, A.

2010-02-01

380

Developing a denoising filter for electron microscopy and tomography data in the cloud  

PubMed Central

The low radiation conditions and the predominantly phase-object image formation of cryo-electron microscopy (cryo-EM) result in extremely high noise levels and low contrast in the recorded micrographs. The process of single particle or tomographic 3D reconstruction does not completely eliminate this noise and is even capable of introducing new sources of noise during alignment or when correcting for instrument parameters. The recently developed Digital Paths Supervised Variance (DPSV) denoising filter uses local variance information to control regional noise in a robust and adaptive manner. The performance of the DPSV filter was evaluated in this review qualitatively and quantitatively using simulated and experimental data from cryo-EM and tomography in two and three dimensions. We also assessed the benefit of filtering experimental reconstructions for visualization purposes and for enhancing the accuracy of feature detection. The DPSV filter eliminates high-frequency noise artifacts (density gaps), which would normally preclude the accurate segmentation of tomography reconstructions or the detection of alpha-helices in single-particle reconstructions. This collaborative software development project was carried out entirely by virtual interactions among the authors using publicly available development and file sharing tools. PMID:23066432

Starosolski, Zbigniew; Szczepanski, Marek; Wahle, Manuel; Rusu, Mirabela

2012-01-01

381

SYSTEMATIC SCANNING ELECTRON MICROSCOPY FOR EVALUATING COMBINED BIOLOGICAL/GRANULAR ACTIVATED CARBON TREATMENT PROCESSES  

EPA Science Inventory

A semi-quantitative scanning electron microscope (SEK) analytical technique has been developed to examine granular activated carbon (GAC) utilized as media for biomass attachment in liquid waste treatment (combined processes). he procedure allows for the objective monitoring, com...

382

A Nanoaquarium for in situ Electron Microscopy in Liquid Media  

E-print Network

The understanding of many nanoscale processes occurring in liquids such as colloidal crystal formation, aggregation, nanowire growth, electrochemical deposition, and biological interactions would benefit greatly from real-time, in situ imaging with the nanoscale resolution of transmission electron microscopes (TEMs) and scanning transmission electron microscopes (STEMs). However, these imaging tools cannot readily be used to observe processes occurring in liquid media without addressing two experimental hurdles: sample thickness and sample evaporation in the high vacuum microscope chamber. To address these challenges, we have developed a nano-Hele-Shaw cell, dubbed the nanoaquarium. The device consists of a hermetically-sealed, 100 nm tall, liquid-filled chamber sandwiched between two freestanding, 50 nm thick, silicon nitride membranes. Embedded electrodes are integrated into the device. This fluid dynamics video features particle motion and aggregation during in situ STEM of nanoparticles suspended in liqui...

Grogan, Joseph M

2010-01-01

383

DC photoelectron gun parameters for ultrafast electron microscopy.  

PubMed

We present a characterization of the performance of an ultrashort laser pulse driven DC photoelectron gun based on the thermionic emission gun design of Togawa et al. [Togawa, K., Shintake, T., Inagaki, T., Onoe, K. & Tanaka, T. (2007). Phys Rev Spec Top-AC 10, 020703]. The gun design intrinsically provides adequate optical access and accommodates the generation of approximately 1 mm2 electron beams while contributing negligible divergent effects at the anode aperture. Both single-photon (with up to 20,000 electrons/pulse) and two-photon photoemission are observed from Ta and Cu(100) photocathodes driven by the harmonics (approximately 4 ps pulses at 261 nm and approximately 200 fs pulses at 532 nm, respectively) of a high-power femtosecond Yb:KGW laser. The results, including the dependence of the photoemission efficiency on the polarization state of the drive laser radiation, are consistent with expectations. The implications of these observations and other physical limitations for the development of a dynamic transmission electron microscope with sub-1 nm.ps space-time resolution are discussed. PMID:19575831

Berger, Joel A; Hogan, John T; Greco, Michael J; Schroeder, W Andreas; Nicholls, Alan W; Browning, Nigel D

2009-08-01

384

Kikuchi ultrafast nanodiffraction in four-dimensional electron microscopy  

PubMed Central

Coherent atomic motions in materials can be revealed using time-resolved X-ray and electron Bragg diffraction. Because of the size of the beam used, typically on the micron scale, the detection of nanoscale propagating waves in extended structures hitherto has not been reported. For elastic waves of complex motions, Bragg intensities contain all polarizations and they are not straightforward to disentangle. Here, we introduce Kikuchi diffraction dynamics, using convergent-beam geometry in an ultrafast electron microscope, to selectively probe propagating transverse elastic waves with nanoscale resolution. It is shown that Kikuchi band shifts, which are sensitive only to the tilting of atomic planes, reveal the resonance oscillations, unit cell angular amplitudes, and the polarization directions. For silicon, the observed wave packet temporal envelope (resonance frequency of 33 GHz), the out-of-phase temporal behavior of Kikuchi’s edges, and the magnitude of angular amplitude (0.3 mrad) and polarization elucidate the nature of the motion: one that preserves the mass density (i.e., no compression or expansion) but leads to sliding of planes in the antisymmetric shear eigenmode of the elastic waveguide. As such, the method of Kikuchi diffraction dynamics, which is unique to electron imaging, can be used to characterize the atomic motions of propagating waves and their interactions with interfaces, defects, and grain boundaries at the nanoscale. PMID:21245348

Yurtsever, Aycan; Zewail, Ahmed H.

2011-01-01

385

Application of analytical electron microscopy to the study of intergranular corrosion in 304 stainless steel  

SciTech Connect

The technique of analytical electron microscopy in a scanning transmission electron microscope fitted with an energy dispersive x-ray spectrometer is used to measure the chromium depletion in sensitized 304 stainless steel along the grain boundaries. It is shown that such measurements could be misleading unless care is taken to properly choose the regions on the grain boundaries for such analysis.

Pande, C S; Sabatini, R L

1980-01-01

386

Automated Detection and Segmentation of Synaptic Contacts in Nearly Isotropic Serial Electron Microscopy Images  

Microsoft Academic Search

We describe a protocol for fully automated detection and segmentation of asymmetric, presumed excitatory, synapses in serial electron microscopy images of the adult mammalian cerebral cortex, taken with the focused ion beam, scanning electron microscope (FIB\\/SEM). The procedure is based on interactive machine learning and only requires a few labeled synapses for training. The statistical learning is performed on geometrical

Anna Kreshuk; Christoph N. Straehle; Christoph Sommer; Ullrich Koethe; Marco Cantoni; Graham Knott; Fred A. Hamprecht; Steven Barnes

2011-01-01

387

Special features of phosphatidylcholine vesicles as seen in cryo-transmission electron microscopy  

Microsoft Academic Search

Vesicles of egg yolk phosphatidylcholine (EYPC) were studied by cryo-transmission electron microscopy. The electron micrographs indicate that, despite the rapidity of cooling, membrane undulations are flattened and some vesicles change their shapes before the samples freeze. These artefacts are attributed to the action of the lateral tension that results from the membrane area contraction associated with the temperature drop. Other

Beate Klösgen; Wolfgang Helfrich

1993-01-01

388

Scanning electron microscopy in characterizing seeds of some leguminous trees  

NASA Astrophysics Data System (ADS)

SEM has greatly increased our knowledge of the microstructure of seeds. Mature seed coats are rather thick walled and stable in a vacuum: this allows quick preparation for SEM examination, without the need of complicated dehydration techniques. The low level of technical expenditure required, in combination with the high structural diversity exhibited and the intuitive ability to understand the "three dimensional", often aesthetically appealing micro-structures visualized, has turned seed-coat studies into a favorite tool of many taxonomists. We used dry mature seeds of 26 species of 4 Leguminous genera, Acacia, Albizia, Cassia and Dalbergia to standardize a procedure for identifying the seeds through SEM on the seed surface and seed sections. We cut transverse and longitudinal sections of the seeds and observed the sections from different regions of seeds: midseed, near the hilum and two distal ends. Light microscopy showed the color, texture, pleurograms, fissures and hilum at lower magnification. The anatomical study with SEM on the seed sections revealed the size, shape, and number of tiers and cellular organization of the epidermis, hypodermis, endosperm and internal structural details. We found the ornamentation pattern of the seeds including undulations, reticulations and rugae that were species specific. Species of Dalbergia (assamica, latifolia and sissoo), Albizia (odoratissima and procera), Acaia (arabica and catechu) and Cassia (glauca, siamia and spectabilis) are difficult to distinguish externally, but SEM studies provided enough characteristic features to distinguish from the other. This technique could be valuable in identifying seeds of important plant species for conservation and trading.

Ghosh, Nabarun; Chatterjee, Amiyanghshu; Smith, Don W.

2009-05-01

389

The septal ontogeny, germination and electron microscopy of Microsporum gypseum macroaleurioconidia.  

PubMed

Microsporum gypseum strains obtained from human and animal cases of dermatophytosis were used to study the septal ontogeny, the germination, and the electron microscopy of the macroaleurioconidia, which are produced so abundantly by this organism. It was found that the number of septa in a macroaleurioconidium depends upon the stage of development, and that their order of formation remains relatively constant. The macroaleurioconidial cell wall proved to be impressive on electron microscopy. The use of a wetting agent (Tween 80) and negative pressure proved necessary for adequate fixation. Poor penetration of the fixing agent is attributable to the electron-dense encrustations over the entire surface of the macroaleurioconidium. PMID:3587339

Vismer, H F; Findlay, G H; Eicker, A

1987-06-01

390

Ballistic-Electron-Emission Microscopy Techniques for Nanometer-scale Characterization of Interfaces  

NASA Technical Reports Server (NTRS)

Semiconductor interface properties are among the most important phenomena in materials science and technology. The study of metal/semiconductor Schottky barrier interfaces has been the primary focus of a large research and development community for decades. Throughout the long history of interface investigation, the study of interface defect electronic properties have been seriously hindered by the fundamental experimental difficulty of probing subsurface structures. A new method, Ballistic-Electron-Emission Microscopy (BEEM), has been developed which not only enables spectroscopic probing of subsurface interface properties, but also, provides nanometer-resolution imaging capabilities. BEEM employs Scanning Tunneling Microscopy (STM) and a unique spatially localized ballistic electron spectroscopy method...

Bell, L. D.; Grunthaner, F. J.; Hecht, M. H.; Manion, S. J.; Milliken, A. M.; Kaiser, W. J.

1993-01-01

391

In situ transmission electron microscopy and ion irradiation of ferritic materials.  

PubMed

The intermediate voltage electron microscope-tandem user facility in the Electron Microscopy Center at Argonne National Laboratory is described. The primary purpose of this facility is electron microscopy with in situ ion irradiation at controlled sample temperatures. To illustrate its capabilities and advantages a few results of two outside user projects are presented. The motion of dislocation loops formed during ion irradiation is illustrated in video data that reveals a striking reduction of motion in Fe-8%Cr over that in pure Fe. The development of extended defect structure is then shown to depend on this motion and the influence of nearby surfaces in the transmission electron microscopy thin samples. In a second project, the damage microstructure is followed to high dose (200 dpa) in an oxide dispersion strengthened ferritic alloy at 500 degrees C, and found to be qualitatively similar to that observed in the same alloy neutron irradiated at 420 degrees C. PMID:19189372

Kirk, Marquis A; Baldo, Peter M; Liu, Amelia C Y; Ryan, Edward A; Birtcher, Robert C; Yao, Zhongwen; Xu, Sen; Jenkins, Michael L; Hernandez-Mayoral, Mercedes; Kaoumi, Djamel; Motta, Arthur T

2009-03-01

392

Transmission electron microscopy of undermined passive films on stainless steel  

SciTech Connect

A study has been made of the passive film remaining over pits on stainless steel using a high resolution transmission electron microscope. Type 305 stainless steel was passivated in a borate buffer solution and pitted in ferric chloride. Passive films formed at 0.2 V relative to a saturated calomel electrode were found to be amorphous. Films formed at higher potentials showed only broad diffraction rings. The passive film was found to cover a remnant lacy structure formed over pits passivated at 0.8 V. The metallic strands of the lace were roughly hemitubular in shape with the curved surface facing the center of the pit.

Isaacs, H.S.; Zhu, Y.; Sabatini, R.L. [Brookhaven National Lab., Upton, NY (United States). Dept. of Applied Science; Ryan, M.P. [Imperial Coll. of Science, Technology and Medicine, London (United Kingdom). Dept. of Materials

1999-06-01

393

Characterization techniques for nano-electronics, with emphasis to electron microscopy. The role of the European Project ANNA  

NASA Astrophysics Data System (ADS)

In the present and future CMOS technology, due to the ever shrinking geometries of the electronic devices, the availability of techniques capable of performing quantitative analyses of the relevant parameters (structural, chemical, mechanical) at a nanoscale is of a paramount importance. The influence of these features on the electrical performances of the nanodevices is a key issue for the nanoelectronics industry. In the recent years, a significant progress has been made in this field by a number of techniques, such as X-ray diffraction, in particular with the advent of synchrotron sources, ion-microbeam based Rutherford backscattering and channeling spectrometry, and micro Raman spectrometry. In addition, secondary ion mass spectrometry (SIMS) has achieved an important role in the determination of the dopant depth profile in ultra-shallow junctions (USJs) in silicon. However, the technique which features the ultimate spatial resolution (at the nanometer scale) is scanning transmission electron microscopy (STEM). In this presentation it will be reported on the nanoanalysis by STEM of two very important physical quantities which need to be controlled in the fabrication processes of nanodevices: the dopant profile in the USJs and the lattice strain that is generated in the Si electrically active regions of isolation structures by the different technological steps. The former quantity is investigated by the so-called Z-contrast high-angle annular dark field (HAADF-STEM) method, whereas the mechanical strain can be two-dimensionally mapped by the convergent beam electron diffraction (CBED-STEM) method. A spatial resolution lower than one nanometer and of a few nanometers can be achieved in the two cases, respectively. To keep the pace with the scientific and technological progress an increasingly wide array of analytical techniques is necessary; their complementary role in the solution of present and future characterization problems must be exploited. Presently, however, European laboratories with high-level expertise in materials characterization still operate in a largely independent way; this adversely affects the competitivity of European science and industry at the international level. For this reason the European Commission has started an Integrated Infrastructure Initiative (I3) in the sixth Framework Programme (now continuing in FP7) and funded a project called ANNA (2006-2010). This acronym stands for European Integrated Activity of Excellence and Networking for Nano and Micro- Electronics Analysis. The consortium includes 12 partners from 7 European countries and is coordinated by the Fondazione B.Kessler (FBK) in Trento (Italy); CNR-IMM is one of the 12 partners. Aim of ANNA is the onset of strong, long-term collaboration among the partners, so to form an integrated multi-site analytical facility, able to offer to the European community a wide variety of top-level analytical expertise and services in the field of micro- and nano-electronics. They include X-ray diffraction and scattering, SIMS, electron microscopy, medium-energy ion scattering, optical and electrical techniques. The project will be focused on three main activities: Networking (standardization of samples and methodologies, establishment of accredited reference laboratories), Transnational Access to laboratories located in the partners' premises to perform specific analytical experiments (an example is given by the two STEM methodologies discussed above) and Joint Research activity, which is targeted at the improvement and extension of the methodologies through a continuous instrumental and technical development. It is planned that the European joint analytical laboratory will continue its activity beyond the end of the project in 2010.

Armigliato, A.

2008-07-01

394

Quantitative Correlation between Defect Density and Heterogeneous Electron Transfer Rate of Single Layer Graphene.  

PubMed

Improving electrochemical activity of graphene is crucial for its various applications, which requires delicate control over its geometric and electronic structures. We demonstrate that precise control of the density of vacancy defects, introduced by Ar(+) irradiation, can improve and finely tune the heterogeneous electron transfer (HET) rate of graphene. For reliable comparisons, we made patterns with different defect densities on a same single layer graphene sheet, which allows us to correlate defect density (via Raman spectroscopy) with HET rate (via scanning electrochemical microscopy) of graphene quantitatively, under exactly the same experimental conditions. By balancing the defect induced increase of density of states (DOS) and decrease of conductivity, the optimal HET rate is attained at a moderate defect density, which is in a critical state; that is, the whole graphene sheet becomes electronically activated and, meanwhile, maintains structural integrity. The improved electrochemical activity can be understood by a high DOS near the Fermi level of defective graphene, as revealed by ab initio simulation, which enlarges the overlap between the electronic states of graphene and the redox couple. The results are valuable to promote the performance of graphene-based electrochemical devices. Furthermore, our findings may serve as a guide to tailor the structure and properties of graphene and other ultrathin two-dimensional materials through defect density engineering. PMID:25350471

Zhong, Jin-Hui; Zhang, Jie; Jin, Xi; Liu, Jun-Yang; Li, Qiongyu; Li, Mao-Hua; Cai, Weiwei; Wu, De-Yin; Zhan, Dongping; Ren, Bin

2014-11-26

395

3D motion of DNA-Au nanoconjugates in graphene liquid cell electron microscopy.  

PubMed

Liquid-phase transmission electron microscopy (TEM) can probe and visualize dynamic events with structural or functional details at the nanoscale in a liquid medium. Earlier efforts have focused on the growth and transformation kinetics of hard material systems, relying on their stability under electron beam. Our recently developed graphene liquid cell technique pushed the spatial resolution of such imaging to the atomic scale but still focused on growth trajectories of metallic nanocrystals. Here, we adopt this technique to imaging three-dimensional (3D) dynamics of soft materials instead, double strand (dsDNA) connecting Au nanocrystals as one example, at nanometer resolution. We demonstrate first that a graphene liquid cell can seal an aqueous sample solution of a lower vapor pressure than previously investigated well against the high vacuum in TEM. Then, from quantitative analysis of real time nanocrystal trajectories, we show that the status and configuration of dsDNA dictate the motions of linked nanocrystals throughout the imaging time of minutes. This sustained connecting ability of dsDNA enables this unprecedented continuous imaging of its dynamics via TEM. Furthermore, the inert graphene surface minimizes sample-substrate interaction and allows the whole nanostructure to rotate freely in the liquid environment; we thus develop and implement the reconstruction of 3D configuration and motions of the nanostructure from the series of 2D projected TEM images captured while it rotates. In addition to further proving the nanoconjugate structural stability, this reconstruction demonstrates 3D dynamic imaging by TEM beyond its conventional use in seeing a flattened and dry sample. Altogether, we foresee the new and exciting use of graphene liquid cell TEM in imaging 3D biomolecular transformations or interaction dynamics at nanometer resolution. PMID:23944844

Chen, Qian; Smith, Jessica M; Park, Jungwon; Kim, Kwanpyo; Ho, Davy; Rasool, Haider I; Zettl, Alex; Alivisatos, A Paul

2013-09-11

396

Quantitative Electron Probe Microanalysis: State of the Art  

NASA Technical Reports Server (NTRS)

Quantitative electron-probe microanalysis (EPMA) has improved due to better instrument design and X-ray correction methods. Design improvement of the electron column and X-ray spectrometer has resulted in measurement precision that exceeds analytical accuracy. Wavelength-dispersive spectrometer (WDS) have layered-dispersive diffraction crystals with improved light-element sensitivity. Newer energy-dispersive spectrometers (EDS) have Si-drift detector elements, thin window designs, and digital processing electronics with X-ray throughput approaching that of WDS Systems. Using these systems, digital X-ray mapping coupled with spectrum imaging is a powerful compositional mapping tool. Improvements in analytical accuracy are due to better X-ray correction algorithms, mass absorption coefficient data sets,and analysis method for complex geometries. ZAF algorithms have ban superceded by Phi(pz) algorithms that better model the depth distribution of primary X-ray production. Complex thin film and particle geometries are treated using Phi(pz) algorithms, end results agree well with Monte Carlo simulations. For geological materials, X-ray absorption dominates the corretions end depends on the accuracy of mass absorption coefficient (MAC) data sets. However, few MACs have been experimentally measured, and the use of fitted coefficients continues due to general success of the analytical technique. A polynomial formulation of the Bence-Albec alpha-factor technique, calibrated using Phi(pz) algorithms, is used to critically evaluate accuracy issues and can be also be used for high 2% relative and is limited by measurement precision for ideal cases, but for many elements the analytical accuracy is unproven. The EPMA technique has improved to the point where it is frequently used instead of the petrogaphic microscope for reconnaissance work. Examples of stagnant research areas are: WDS detector design characterization of calibration standards, and the need for more complete treatment of the continuum X-ray fluorescence correction.

Carpernter, P. K.

2005-01-01

397

A New Approach to Studying Biological and Soft Materials Using Focused Ion Beam Scanning Electron Microscopy (FIB SEM)  

Microsoft Academic Search

Over the last decade techniques such as confocal light microscopy, in combination with fluorescent labelling, have helped biologists and life scientists to study biological architectures at tissue and cell level in great detail. Meanwhile, obtaining information at very small length scales is possible with the combination of sample preparation techniques and transmission electron microscopy (TEM) or scanning transmission electron microscopy

D J Stokes; F Morrissey; B H Lich

2006-01-01

398

Nanoscale nuclear architecture for cancer diagnosis beyond pathology via spatial-domain low-coherence quantitative phase microscopy  

NASA Astrophysics Data System (ADS)

Definitive diagnosis of malignancy is often challenging due to limited availability of human cell or tissue samples and morphological similarity with certain benign conditions. Our recently developed novel technology-spatial-domain low-coherence quantitative phase microscopy (SL-QPM)-overcomes the technical difficulties and enables us to obtain quantitative information about cell nuclear architectural characteristics with nanoscale sensitivity. We explore its ability to improve the identification of malignancy, especially in cytopathologically non-cancerous-appearing cells. We perform proof-of-concept experiments with an animal model of colorectal carcinogenesis-APCMin mouse model and human cytology specimens of colorectal cancer. We show the ability of in situ nanoscale nuclear architectural characteristics in identifying cancerous cells, especially in those labeled as ``indeterminate or normal'' by expert cytopathologists. Our approach is based on the quantitative analysis of the cell nucleus on the original cytology slides without additional processing, which can be readily applied in a conventional clinical setting. Our simple and practical optical microscopy technique may lead to the development of novel methods for early detection of cancer.

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

2010-11-01

399

Quantitative Stain-Free and Continuous Multimodal Monitoring of Wound Healing In Vitro with Digital Holographic Microscopy  

PubMed Central

Impaired epithelial wound healing has significant pathophysiological implications in several conditions including gastrointestinal ulcers, anastomotic leakage and venous or diabetic skin ulcers. Promising drug candidates for accelerating wound closure are commonly evaluated in in vitro wound assays. However, staining procedures and discontinuous monitoring are major drawbacks hampering accurate assessment of wound assays. We therefore investigated digital holographic microscopy (DHM) to appropriately monitor wound healing in vitro and secondly, to provide multimodal quantitative information on morphological and functional cell alterations as well as on motility changes upon cytokine stimulation. Wound closure as reflected by proliferation and migration of Caco-2 cells in wound healing assays was studied and assessed in time-lapse series for 40 h in the presence of stimulating epidermal growth factor (EGF) and inhibiting mitomycin c. Therefore, digital holograms were recorded continuously every thirty minutes. Morphological changes including cell thickness, dry mass and tissue density were analyzed by data from quantitative digital holographic phase microscopy. Stimulation of Caco-2 cells with EGF or mitomycin c resulted in significant morphological changes during wound healing compared to control cells. In conclusion, DHM allows accurate, stain-free and continuous multimodal quantitative monitoring of wound healing in vitro and could be a promising new technique for assessment of wound healing. PMID:25251440

Krausewitz, Philipp; Bruckner, Markus; Ketelhut, Steffi; Domagk, Dirk; Kemper, Bjorn

2014-01-01

400

Moessbauer spectroscopy and scanning electron microscopy of the Murchison meteorite  

NASA Technical Reports Server (NTRS)

Meteorites provide a wealth of information about the solar system's formation, since they have similar building blocks as the Earth's crust but have been virtually unaltered since their formation. Some stony meteorites contain minerals and silicate inclusions, called chondrules, in the matrix. Utilizing Moessbauer spectroscopy, we identified minerals in the Murchison meteorite, a carbonaceous chondritic meteorite, by the gamma ray resonance lines observed. Absorption patterns of the spectra were found due to the minerals olivine and phyllosilicate. We used a scanning electron microscope to describe the structure of the chondrules in the Murchison meteorite. The chondrules were found to be deformed due to weathering of the meteorite. Diameters varied in size from 0.2 to 0.5 mm. Further enhancement of the microscopic imagery using a digital image processor was used to describe the physical characteristics of the inclusions.

Brown, Christopher L.; Oliver, Frederick W.; Hammond, Ernest C., Jr.

1989-01-01

401

Clinical, light, and electron microscopy findings in idiopathic haematuria.  

PubMed

The electron microscopic findings are reported in detail in 20 patients submitted to renal biopsy with the major complaint or clinical finding of gross or microscopic haematuria. The lesions were classified histologically into four groups: group 1, minor glomerular alterations; group 2, focal mesangial thickening and/or cellular proliferation; group 3, diffuse mesangial proliferation; and group 4, other lesions. The major ultrastructural alterations included irregularity in thickness and density of the capillary basement membrane, with apparent discontinuity and bi- or multilaminar splitting of the lamina densa. There were varying degrees of foot process fusion, visceral epithelial polykaryocytosis, and granular deposits related to the capillary basement membrane. Densities were found in the mesangial basement membrane-like material, which was often markedly increased in quantity. A few microtubular aggregates were observed in endothelial cell cytoplasm. Changes consistent with acute diffuse proliferative and membrano-proliferative glomerulonephritis were also seen. The significant clinical findings, histological groups, and ultrastructural changes are correlated. PMID:4750456

Alexander, F; Lannigan, R; Bull, R

1973-10-01

402

Natural populations of bacteria in Lake Kinneret: Observations with scanning electron and epifluorescence microscopy  

Microsoft Academic Search

The bacterioplankton assemblage in Lake Kinneret, Israel, sampled on 6 occasions representative of different seasonal conditions was studied with scanning electron microscopy (SEM) and epifluorescence microscopy after acridine-orange staining. In near-surface (1–3 m) samples taken in October 1981 and March 1983, several unusual types of budding, appendaged, and filamentous cells were found. During lake stratification, typical large anaerobic forms (including

R. Schmaljohann; U. Pollingher; T. Berman

1987-01-01

403

Correlative super-resolution fluorescence and metal replica transmission electron microscopy  

PubMed Central

Super-resolution localization microscopy is combined with a complementary imaging technique, transmission electron microscopy of metal replicas, to locate proteins on the landscape of the cellular plasma membrane at the nanoscale. Robust correlation on the scale of 20 nm is validated by imaging endogenous clathrin (with 2D and 3D PALM/TEM) and the method is further used to find the previously unknown 3D position of epsin on clathrin coated structures. PMID:24464288

Sochacki, Kem A.; Shtengel, Gleb; van Engelenburg, Schuyler B.; Hess, Harald F.; Taraska, Justin W.

2014-01-01

404

Focusing on Environmental Biofilms With Variable-Pressure Scanning Electron Microscopy  

NASA Astrophysics Data System (ADS)

Since the term biofilm has been coined almost 30 years ago, visualization has formed an integral part of investigations on microbial attachment. Electron microscopic (EM) biofilm studies, however, have been limited by the hydrated extracellular matrix which loses structural integrity with conventional preparative techniques, and under required high-vacuum conditions, resulting in a loss of information on spatial relationships and distribution of biofilm microbes. Recent advances in EM technology enable the application of Variable Pressure Scanning Electron Microscopy (VP SEM) to biofilms, allowing low vacuum and hydrated chamber atmosphere during visualization. Environmental biofilm samples can be viewed in situ, unfixed and fully hydrated, with application of gold-sputter-coating only, to increase image resolution. As the impact of microbial biofilms can be both hazardous and beneficial to man and his environment, recognition of biofilms as a natural form of microbial existence is needed to fully assess the potential role of microbial communities on technology. The integration of multiple techniques to elucidate biofilm processes has become imperative for unraveling complex phenotypic adaptations of this microbial lifestyle. We applied VP SEM as integrative technique with traditional and novel analytical techniques to (1)localize lignocellulosic microbial consortia applied for producing alternative bio-energy sources in the mining wastewater industry, (2) characterize and visualize wetland microbial communities in the treatment of winery wastewater, and (3)determine the impact of recombinant technology on yeast biofilm behavior. Visualization of microbial attachment to a lignocellulose substrate, and degradation of exposed plant tissue, gave insight into fiber degradation and volatile fatty acid production for biological sulphate removal from mining wastewater. Also, the 3D-architecture of complex biofilms developing in constructed wetlands was correlated with molecular fingerprints of wetland communities using tRFLP (Terminal Restriction Fragment Length Polymorphism) - and gave evidence of temporal and spatial variation in a wetland system, to potentially be applied as management tool in wastewater treatment. Visualization of differences in biofilm development by wild and recombinant yeast strains furthermore supported real-time quantitative data of biofilm development by Cryptococcus laurentii and Saccharomyces yeast strains. In all cases VP SEM allowed a more holistic interpretation of biofilm processes than afforded by quantitative empirical data only.

Joubert, L.; Wolfaardt, G. M.; Du Plessis, K.

2006-12-01