bluuebunny/crossref_metadata_2025 huggingface dataset:
Current State of the Art of Digital Imaging in the SEM
Authors: Mackenzie John M
Published: July 2020

Digital image acquisition in the SEM is poised to take over conventional methods of image recording. Because a majority of researchers use Polaroid film which only records about 1,000 lines of information, the acquisition systems available today are capable of matching and possibly exceeding the resolution of this medium.

Several methods are available to accomplish the acquisition task, and they each have certain benefits and disadvantages. by far the simplest and least expensive is to digitize the video output from the SEM when available. Under some conditions the video output can be digitized directly. The advantage of this method is cost. A single frame video digitizer costs less than $200. The signal, however, is usually very noisy. Because the human eye “sees” at a slower rate than video, we normally are “seeing” a 10-20 frame average. When we choose one frame, the results are too noisy. Fortunately, for under $1,500, digitizers that average frames are available. With multiple frames, the results are often acceptable for some applications.
Is Digital Imaging Ready to Replace Photographic Films ?
Authors: Pan M
Published: July 2020

The new generation of cooled slow-scan CCD cameras (SSC) have demonstrated the superior properties to conventional photographic films in sensitivity, resolution, dynamic range, linearity, and on-line availability. Furthermore the digital imaging capability as offered by SSC cameras facilitates image processing and quantitative analysis. Other advantages of digital imaging include easy archiving, sending images to a remote site via high speed communication network, and carrying out telemicroscopy, etc. Today, many laboratories in electron microscopy have already abandoned the traditional “dark room” and switched to digital imaging. One of the obstacle in replacing photographic films with digital imaging is the fact that current SSC cameras (e.g. 1024 × 1024 pixels) do not have enough pixels as compared with the film. Therefore the resolution is often compromised with the field of view when using CCD cameras.

With computer control of electron microscopes and the use of CCD cameras, we have developed automated “montage” software that can automatically shift and acquire images from a microscope, and automatically perform pixel-to-pixel image alignment to form a montage. The size of the montage is defined by the number of images acquired in both horizontal and vertical directions.
Rapid Manual SEM Analysis and the Greening of Digital Data
Authors: McCord DC , Kennedy SK , Kritikos DG
Published: July 2020

Manual scanning electron microscope (SEM) analysis is historically considered to be slow and tedious resulting in a low volume of data. This is due in large part to the mechanics of moving stage locations and recording image and spectral data. Conversely, high volume data acquired using automated SEM analysis has been associated with the need for complex systems for data management and analysis. In addition, the proliferation of high volume digital microscopy and its attendant “ tonnage” of paper images has lead to the desire for a “green” (filmless and hardcopy-reduced) operation.

There are some classes of projects which are amenable to automated feature analysis - discrete features that are distinct from a background material. However, many projects require operator intervention in order to identify the region or points of interest. Yet, these projects may also require that large data sets be acquired and analyzed for statistical rigor.
Automated Acquisition of Cryo-Electron Microscope Images With Slow-Scan CCD Cameras and Microscope Control
Authors: Pan M , Olsont NH , Bakert TS
Published: July 2020

Recording electron microscope images of frozen-hydrated samples under cryo-conditions is a difficult and challenging task. The inherently low sample contrast makes accurate focusing difficult. Furthermore most frozen-hydrated samples are very beam sensitive so that electron dose on the sample must be kept to the minimum. In recent years, the new generation of cooled slow-scan CCD (SSC) cameras have shown superior properties in sensitivity, resolution, dynamic range, linearity, and more importantly their ability to display images on-line. Computer control of electron microscopes via the standard RS232C serial interface has been greatly facilitated by the use of on-line CCD images. We have developed a software package that allows cryo-electron microscope images to be automatically acquired onto a CCD camera via computer control of the microscope. This fully automated feature allows quality cryo-electron microscope images to be recorded with increased efficiency and enhances the possibility of obtaining three-dimensional reconstructions from images.
Merging of Complementary Structural Techniques
Authors: Stewart PL , Chiu CY , Haley DA
Published: July 2020

Cryo-electron microscopy (cryo-EM) and image reconstruction techniques provide a powerful way to study three-dimensional structures of biological complexes. As the resolution of the resulting three-dimensional reconstructions is typically in the range of 10-35 À, information from other structural techniques is often invaluable in analyzing the biological structure. We present the use of crystallographic coordinates to determine the amplitude of motion of a viral receptor binding site and molecular models to assess the degree of quaternary conformational flexibility within a multimeric protein assembly.

In order to visualize the αv integrin receptor binding site on the surface of human adenovirus (150 MDa), we have reconstructed adenovirus in complex with a Fab fragment from a monoclonal antibody (DAV-1) targeted to this site. The peptide epitope of DAV-1 has been mapped by MALDI mass spectrometry to 9 residues within the penton base protein and includes the integrin binding Arg-Gly-Asp (RGD) residues.
The Use of Data Explorer as a 3-D Reconstruction Tool for Microscopy Data Sets
Authors: P.L Jansma , Landis MA , Hansen LC , Merchant NC , Vickers NJ , Tolbert LP
Published: July 2020

We are using Data Explorer (DX), a general-purpose, interactive visualization program developed by IBM, to perform three-dimensional reconstructions of neural structures from microscopic or optical sections. We use the program on a Silicon Graphics workstation; it also can run on Sun, IBM RS/6000, and Hewlett Packard workstations. DX comprises modular building blocks that the user assembles into data-flow networks for specific uses. Many modules come with the program, but others, written by users (including ourselves), are continually being added and are available at the DX ftp site, http://www.tc.cornell.edu/DXhttp://www.nice.org.uk/page.aspx?o=43210.

Initally, our efforts were aimed at developing methods for isosurface- and volume-rendering of structures visible in three-dimensional stacks of optical sections of insect brains gathered on our Bio-Rad MRC-600 laser scanning confocal microscope. We also wanted to be able to merge two 3-D data sets (collected on two different photomultiplier channels) and to display them at various angles of view.
Twin Image Suppression and Field Inhomogeneity in In-Line Electron Holography.
Authors: Weierstall U , Huang XM , Spence JCH
Published: July 2020

Several methods have been suggested for elliminating the twin image in in-line holography, including Franhofer holography as used in our previous work, integration over focus, integration over wavelength, integration over lateral source position and recursion methods such as Gerchberg-Saxton or Fienup (see for all refs.). Fraunhofer holography requires the Fresnel number N =, with d the object size. The integration methods depend on the fact that the real and virtual images have different dependencies on some parameter such as focus, and have proved powerful in photoemission holographic diffraction. Here we apply focus integration and recursion to low voltage, point-projection images of carbon films, and discuss the effects of inhomogeneities in the electric field which arise when the tip is very close to a fibre-shaped sample such as DNA. by embedding biomolecules in solid Xenon at 55K, and using a beam energy of about 9 volts (less than the Xenon bandgap minus the electron affinity), radiation damage to the molecule may be minimized, while the molecule is gently supported by an almost electron transparent medium.
Z-Contrast in a Conventional TEM
Authors: Kirkland EJ
Published: July 2020

Z-contrast produces an image that varies strongly with atomic number and offers limited chemical sensitivity. The annular dark field scanning transmission microscope (ADF-STEM) has recently been used to produce Z-contrast images at high resolution. In a STEM the electron beam is focused into a small probe at the specimen plane and scanned across the specimen. The electrons scattered at high angle are collected by an annular detector to produce a signal that approximately varies as Z11.5 to Z2. The only commercial supplier of dedicated STEM'S (VG-Microscopes, now Thermo) has recently discontinued production, so it is worth considering how to produce an equivalent Z-contrast image in a conventional transmission electron microscope (CTEM).

The reciprocity theorem states that the STEM and CTEM are equivalent if the source and detector are interchanged (reciprocity hold for all orders of elastic scattering so it is not necessary to restrict this discussion to weakly scattering specimens).
Simulation of Magnetic Induction Mapping in the TEM
Authors: Dooley J , De Graef M
Published: July 2020

The design of modern magnetic storage devices with their rapidly increasing information density ne-cessitates a full characterization of the underlying microstructure of the device materials. Lorentz microscopy has for several decades been the main vehicle for micro-magnetic observations. The pri-mary limitation of the Lorentz modes is perhaps the attainable magnification. To avoid saturation, the sample must be placed in a low-field or preferably field-free region in the column, and this invariably means that the microscope can only be operated at low magnifications. Both Fresnel and Foucault images are rather sensitive to the exact experimental conditions which renders quantitative observa-tions quite difficult, if not impossible. Inelastic scattering further limits the usefulness of Lorentz observations to very thin foils.

We have recently reported1 a novel Lorentz microscopy setup, combining a Gatan Imaging Filter (GIF) and a JEOL 4000EX top-entry high resolution TEM, operated at 400 kV with the main objective lens switched off.
Are Common Atom Form Factors in HREM-Simulations Accurate Enough for Quantitative Image Matching?
Authors: Möbus G , Gemming T , Nüchter W , Exner M , Gumbsch P , Weickenmeier A , Wilson M , Rühle M
Published: July 2020

1.Introduction:If digital image matching between an experimental HREM-image and the simulated image fails, one of the suggested reasons is the “inaccuracy of the atomic form factors“ describing the electron scattering in common simulation packages using the free and neutral atom approximation from Hartree-Fock calculations [1]. In detail, three contributions within the usual form factor calculations are mainly missing: (i) the redistribution of charge in ionic crystals, (ii) the accumulation of charge away from atom sites in covalent crystals, (iii) the inclusion of thermal diffuse scattering (TDS) as well as the correlated vibration of atoms beyond the Einstein-approximation within the Debye-Waller factor (DWF) theory. Each of the three effects have been checked separately:

2.Simulations of TDS by Coupling of Molecular Dynamics Time Series to HREM- Multislice Calculations:70 snap shots of a series of structures of NiAl (4.9 × 5.1 × l0nm) are stored from an equilibrated molecular dynamics simulation with vibration amplitudes corresponding to room temperature.
Limits to Spatial Resolution in the HRTEM
Authors: Bailey GW , Dimlich RVW , Alexander KB , McCarthy JJ , Pretlow TP , O’Keefe Michael A
Published: July 2020

The resolution of the high-resolution transmission electron microscope is limited by the specimen as well as by the HRTEM. For specimens that beam-damage, image resolution depends upon electron energy and electron dose. For small-cell crystalline specimens, Bragg’s law quantizes allowable reso-lutions, preventing image resolution from reaching instrumental resolutiqn. Specimen thickness be-comes increasingly important at higher resolutions. For a resolution of d(Å), we need the specimen to diffract at u=1/d. Consideration of the intersection of the Ewald sphere with the specimen shape trans-form (fig. 1) shows that thickness must be less than For a resolution pr 1.0A at 300keV, thickness must be less than 100A; to achieve 0.7A requires halving this value to 50A (fig.l).

Resolution in an image depends on the spatial frequencies of the information (diffracted waves) trans-ferred from the amplitude spectrum (specimen exit-surface wavefunction) into the image intensity spec-trum (Fourier transform of the image intensity).
Design and Implementation of a Site for a One-Ångstrom TEM
Authors: H. Turner John , O'Keefe MA , O'Keefe MA
Published: July 2020

The National Center for Electron Microscopy has recently acquired a field-emission TEM to form thebasis of a project to achieve a resolution of one Ångstrom. To reach this resolution, both instrumental and environmental factors need to be considered. We have designed and constructed a new building to provide a suitable environment for this instrument, with emphasis on providing isolation from external influences detrimental to the achievement of ultra-high resolution. Such influences include mechanical vibration, temperature fluctuations, acoustic noise, and stray electromagnetic fields.

The microscope chosen for the one-Ångstrom project is a Philips CM300 Ultra-Twin equipped with a field-emission gun. Pre-installation specifications provided by Philips for this 1.7Å-resolution TEM specify maximum-allowable values for vibration levels in three mutually-perpendicular directions. In the most critical direction (console left to right), vibration is required to remain below 0.8)μm/sec in the frequency range from 1Hz to 5Hz, although allowed to rise to 6μm/sec above 10Hz (Region I in fig. 1). Even when resolution is not a critical requirement, vibration must be minimized at 2.5Hz (Region II in fig.1).
Seeing is Not Always Believing: Reduction of Artefacts by an Improved Point Resolution With a Spherical Aberration Corrected 200 Kv Transmission Electron Microscope
Authors: Haider M , Uhlemann S
Published: July 2020

The most interesting structures in materials science are non-periodic areas where the crystalline structure is disturbed such as interfaces, defects or dislocations. These non-periodic structures can be hidden by artefacts, caused by aberrations, and therefore they can be easier analysed if an aberration free imaging system can be used. Therefore, in order to improve the point resolution and to obtain easier access to the hidden information, a spherical aberration corrected 200 kV TEM, following a proposal by Rose, was set up.

Phase contrast in a transmission electron microscope (TEM) is obtained, as it was shown by Scherzer, due to the phase shifting power of the wave aberrations as there are: the defocus and the spherical aberration. The defocus can be optimised in terms of the well transferred bandwidth of spatial frequencies (Scherzer defocus) Δfsch = (Cs*λ.)1/2. The upper limit of the spatial frequency without a contrast reversal when choosing a Scherzer defocus is called the point resolution d ≈ 0.71 (Cs λ3)1/4.
STEM Darkfield Imaging Revisited: The Benefits of Inelastic Scatter
Authors: Ottensmeyer FP , Fernandes AB , Poulos JG , Taylor W
Published: July 2020

The imaging of biological macromolecules at high resolution is predicated on the use of imaging modalities that combine a sufficiently high signal-to-noise ratio (S/N) to observe the desired detail with a sufficiently low dose not to have perturbed the structure at the resolution of that detail. For 3D structure determination the S/N has to be sufficiently high to permit the accurate position and orientation determination for individual molecules or assemblies.

For 2D crystal specimens the position is determined a priori by the lattice, orientation by the externally chosen tilt of the specimen, and signal-to-noise in a single unit cell enhanced by the translocational redundancy of the many unit cells of the crystal. This is close to an ideal specimen, which has permitted imaging with resolutions of 3.4 À at doses of 20-35 e/Â2[l]. Specimens with high internal symmetry, icosahedral or helical structures, are examples which confer intermediate structural redundancies to assist in reducing the requires electron dose.
High Resolution TEM Imaging with Hollow-Cone Illumination
Authors: Sidorov Maxim V , McCartney Martha R , Smith David J
Published: July 2020

It has long been realized that imaging with hollow cone illumination (HCI) should, in theory, improve the directly interpretable resolution of TEM by as much as 100% (albeit at the expense of contrast). The principle of HCI was first proposed by Scherzer in 1949 and then reinvented by Hanssen and Trepte in 1971. As opposed to axial illumination, HCI effectively eliminates zeroes and reversals of the transfer function providing direct interpretability of the resulting images. In addition to the substantial resolution enhancement, HCI should reduce significantly the phase-contrast noise inherent in axial HRTEM images. However, there are experimental obstacles for high resolution HCI which make its practical application very difficult to implement. To our knowledge, all observations using HCI so far have not shown all of the expected improvement predicted theoretically. This is believed to be due to the fact that accurate coma-free alignment is required to substantially improve the resolution.
Review of Techniques for Overcoming XEDS Problems in the Environmental Scanning Electron Microscope
Authors: Mansfield John
Published: July 2020

Full characterization of materials in the environmental scanning electron microscope (Environmental SEM) often requires chemical analysis by X-ray energy dispersive spectroscopy (XEDS). However, a major problem arises because the spatial resolution of the XEDS signal is severely degraded by the gaseous environment in the sample chamber. The significant fraction of the primary electron beam is scattered after it passes through the final pressure limiting aperture and before it strikes the sample. Bolon and Griffin have both published data that illustrates this effect very well. Bolon revealed that 45% of the primary electron beam was scattered by more than 25μm in an Environmental SEM operating at an accelerating voltage of 30kV, with a water vapor pressure of 3Torr and a working distance of 15mm. Griffin’s work demonstrated that even at higher voltages (30 kV), shorter working distances (<10mm) and lower chamber pressures (2Torr), there is a significant fraction of the electron beam scattered out to over 400 μm away from the point where the primary beam strikes the sample.
Vacuum Arc Cathode Spot Characterization on Graphite Materials Using Field Emission Gun Scanning Electron Microscopy (FEGSEM)
Authors: Kandah M , Meunier J-L , Gauvin R
Published: July 2020

Vacuum arcs on graphite cathodes are currently used as sources of carbon ions for the production of diamond-like films in the arc ion-plating (AIP) deposition process. Emission from these cathode sources is concentrated in very localized “cathode spots” having typically 10 (i.m in diameter for graphite cathodes. These spots carry the totality of the arc current, the remaining of the surface being unaffected by the discharge. For electron emission falling in the thermo-field emission mode, extremely high current densities up to 108 -109 Am-2 are induced generating a high localized heat flux to the surface during the spot lifetime. On metallic electrodes, this strong heat flux generates localized surface melting during the microsecond scale spot lifetime. High localized plasma pressures (>10 Atm in the case of copper) were found to exist in the cathode spot volume, leading to the co-emission of micro-droplets of the liquid metal along with the ion beam.
Imaging Cultured Cells on Protein Coated Silicon Chips Using Low-Voltage in-Lens SEM
Authors: Apkarian R P , Lund S
Published: July 2020

A Schottky Field Emission (SFE) SEM (Topcon DS-130F) equipped with dual stages and dual secondary electron (SE) detectors operated at high voltage (25 kV) provided useful magnifications of 200 x - 200,000 x and particle resolution in the 5 nm range from chromium (Cr) coated bulk (1 mm3) biological samples. Additionally, high voltage in-lens SFE-SEM, at magnifications > 200,000 x, provided high resolution images with 2-3 nm particle contrasts from Cr coated negatively-stained phospholipid vesicles (100 nm diameter) adhered to uncoated silicon (Si) chips.

We recently developed low voltage strategies for quality in-lens imaging of Cr coated cell cultures at low and high magnifications. Due to unfavorable specimen-beam interactions at high voltage, not encountered with ultimately small volume organic specimens on Si chips or large bulk specimens, cells on protein matrix coated Si chips were imaged at low and high magnification in-the-lens of the DS-130F with beam energies of 5 kV.
A Consumers Report on Detection of 10 Nm Gold on Cell Surfaces: Selection of Fesem Type and Choice of Conductive Metal Coating
Authors: Erlandsen SL , Bittermann AG , Osten E , Coscio M , Frethem C
Published: July 2020

Important parameters for the detection of small colloidal immunogold particles (10 nm) on cell surfaces include the use of field emission SEM (FESEM) and a need for a conductive metal coating to reduce charging, so as to facilitate backscatter electron (BSE) imaging for unambiguous identification by atomic number contrast. Recently Heinzmann et al (1) have reported the use of below-lens FESEM for detection of 10 nm colloidal gold at working distances of 6-13 mm, but achieved success only on uncoated cells as coating with a 1 nm layer of platinum appeared to mask the gold signal. To improve specimen conductivity and signal collection, three metals (Cr, Pt, W) have been used to generate thin coatings either by planar magnetron sputtering for cryoSEM or ion-beam sputtering for routine chemically-fixed, critical point dried samples (2,3)

Three below-lens FESEM (Hitachi S-4500, JEOL 630land 63401, and LEO 982) were tested by using a sample of human neutrophils which had been chemically fixed, then immunostained for the surface antigen CD43 with 10 nm colloidal gold, and prepared by critical point drying.
Latex Particle Deformation and Adhesion on Substrates Studied by Low Voltage Field Emission SEM
Authors: Ming Y , Scriven L E , Davis H T
Published: July 2020

Synthetic polymer latex is widely used in paints, paper coatings, adhesives, and a growing number of other water-borne coatings. All these applications require the latex particles adhere to one another and weld by interdiffusion. The processes of film formation by latex have been studied intensively during the last several decades. The three major stages of the processes are identified: consolidation, particle deformation and coalescence. In contrast, the deformation and adhesion of latex particles on pigment are poorly documented because the needed measurements are difficult to perform at particle level by conventional techniques2. Recently, the ordering and adhesion of styrene-butyl acrylate latex particles on model inorganic surfaces have been studied by atomic force microscopy (AFM). In this work, the deformation and adhesion of latex particles of styrene-butadiene on smooth substrates are examined by low voltage field emission scanning electron microscopy (LVFESEM) with contrast enhancement by staining.
The Observation of NBC Precipitates In Steels In The Nanometer Range Using A Field Emission Gun Scanning Electron Microscope
Authors: Gauvin Raynald , Yue Steve
Published: July 2020

The observation of microstructural features smaller than 300 nm is generally performed using Transmission Electron Microscopy (TEM) because conventional Scanning Electron Microscopes (SEM) do not have the resolution to image such small phases. Since the early 1990’s, a new generation of microscopes is now available on the market. These are the Field Emission Gun Scanning Electron Microscope with a virtual secondary electron detector. The field emission gun gives a higher brightness than those obtained using conventional electron filaments allowing enough electrons to be collected to operate the microscope with incident electron energy, E0, below 5 keV with probe diameter smaller than 5 nm. At 1 keV, the electron range is 60 nm in aluminum and 10 nm in iron (computed using the CASINO program). Since the electron beam diameter is smaller than 5 nm at 1 keV, the resolution of these microscopes becomes closer to that of TEM.
Characterization of “Stickies” Polymeric Contaminants in Recycle Pulp Slurries by Optical Fluorescence and Scanning Electron Microscopy.
Authors: Bailey GW , Dimlich RVW , Alexander KB , McCarthy JJ , Pretlow TP , Fisher R M , Holbery J , Reine Barbara
Published: July 2020

A major problem now hampering increased recycling of old cardboard containers (OCC), is the presence of significant amounts of polymeric materials such as adhesives, tapes, labels and wax which enter the pulp process stream along with the cardboard and paper that was collected for recycling. Many of these materials contain very fine particles of inorganic fillers and pigments. These various contaminant constituents combine in some, as yet unknown, manner to form an extremely gummy material that deposits on paper machine surfaces and sticks tenaciously (hence the term “Stickies”). The sticky blobs are very difficult to remove and increases machine downtime and maintenance costs as well as causing blemishes on the finished container board product Light optical image analysis, UV fluorescence, FTIR and electron microscopy are being used in consort with particle size measuring instruments, TGS and DSC thermal analysis techniques, FTIR infra-red spectroscopy as well as XRF (x-ray fluorescence spectroscopy ), XPS (x-ray photo emission spectroscopy) and classical contact angle determination methods as part of a broad program to characterize the physical and chemical nature of stickies in pulp slurries with the goal of removing them or alleviating their pronounced tendency to deposit on machinery and paper products.
Compression Strengthening of Plastic Bonded Explosives
Authors: Peterson Paul D , Idar Deanne J , Gardner John S
Published: July 2020

A recent study concluded that the most potentially dangerous scenarios for accidental detonation of a nuclear weapon were those involving weak thermal or mechanical shocks. For this reason, more data are needed to understand the material behavior of nuclear constituents under low strain rate scenarios.

One of the components of many of these types of weapons is known as Plastic Bonded eXplosives (PBX). PBX is a paniculate composite material made of a hard phase explosive carried in a soft phase polymer binder. Recent work has showed that the stiffness of PBX increased under low rate compressive loading. This behavior was attributed to the shape of the test samples and cross-linking within the elastomer binder. Another theory proposed that the changing compressive properties could be attributed to the hard phase particles migrating together during material flow.

Funk et al. demonstrated an inert material mock of PBX 9501, with the hard phase explosive replaced by granular sugar, also showed the same phenomena of compressive hardening.
Chemical Force Microscopy
Authors: Lieber Charles M , Vezenov Dmitri , Noy Aleksandr , Sanders Charles
Published: July 2020

Chemical force microscopy (CFM) has been used to measure adhesion and friction forces between probe tips and substrates covalently modified with self-assembled monolayers (SAMs) that terminate in distinct functional groups. Probe tips have been modified with SAMs using a procedure that involves coating commercial Si3N4 cantilever/tip assemblies with a thin layer of polycrystalline Au followed by immersion in a solution of a functionalized thiol. This methodology provides a reproducible means for endowing the probe with different chemical functional groups.

A force microscope has been used to characterize the adhesive interactions between probe tips and substrates that have been modified with SAMs which terminate with COOH and CH3 functional groups in ethanol water solvent. Force versus distance curves recorded under ethanol show that the interaction between COOH/COOH > CH3/CH3 > COOH/CH3. The measured adhesive forces were found to agree well with predictions of the Johnson, Kendall, and Roberts (JKR) theory of adhesive contact, and thus show that the observed adhesion forces correlate with the surface free energy
Self Assembled Oligosaccharide Surfactant Visualized by Atomic Force Microscopy
Authors: Holland NB , Ruegsegger M , Marchant RE
Published: July 2020

The physisorption of oligosaccharide surfactants is being developed as a method for modifying biomaterials to prevent protein adsorption. In this study, we visualize the surface adsorption and ordering of oligosaccharide surfactant using the atomic force microscope (AFM). Contact mode imaging is used to provide topographical images of the surface. Tapping mode imaging also provides topographical images, but reduces the amount of the lateral forces applied to the surface by driving the cantilever and contacting the surface once per oscillation. A phase image, which is the measure of phase shift between the cantilever response and the driving signal in tapping mode, gives information on variations in the viscoelastic response of the sample surface.

The maltose diblock surfactant was prepared by the selective oxidation and lactonization of the maltose reducing end group, followed by aminolysis with dodecylamine. The chemical structure is Maltose--CONH-(CH2)11CH3.

The solutions used for adsorption were prepared by diluting a stock solution of the surfactant at the critical micelle concentration (CMC) to the desired concentrations.
Investigation of Protein Structure at the Solid/Liquid Interface with Atomic Force Microscopy (Afm)
Authors: Waner MJ , Schindler M , Dantus M
Published: July 2020

At present, changes in the structure of proteins occurring upon adsorption at liquid/solid interfaces are not well understood. The prevailing model assumes that a protein, which is globular in solution, must first displace surface bound water molecules. Then, after adsorption of the protein at the surface, the molecule unfolds to maximize interactions with the surface. It is noted, however, that some enzymes maintain a significant amount of their activity once adsorbed. This observation is the basis for many biomedical assays and implies that native protein structure is at least partially maintained.

The atomic force microscope (AFM) is well suited for the study of biomolecules at interfaces, providing single molecule resolution. Progress on molecular structure analysis of proteins using AFM, however, has been hampered by the fact that the tip radius is as large as, or larger than the proteins themselves, thereby causing a large lateral convolution effect.
Blind Estimation of Tip Geometry in Scanned Probe Microscopy
Authors: Villarrubia J S
Published: July 2020

In topographs produced by scanned probe microscopy, positive-going surface features are broadened due to the non-vanishing tip size. This well-known imaging artifact is of particular importance for feature width or surface microroughness determinations. Its correction requires a 3-d model of the tip.

Most proposed methods of tip estimation begin with the same set of experimental conditions and model assumptions. Experimentally, a special specimen (a “tip characterizer”) is imaged with the unknown tip. The image model assumes the image is formed by contact of the tip with the surface at one or more points without significant bending of the tip or compression of the surface. Under these circumstances, it has been shown1 that I = S ⊕ P, where S is the set of all points in the specimen, P a reflection of the tip through the origin, I the image, and ⊕ denotes dilation.
Atomic Force Microscopy Studies of Aluminum Corrosion Inhibition by Adsorbed Self Assembled Monolayers
Authors: Richards John F , Troughton E Barry , Dennis Richard A , Russell Phillip E
Published: July 2020

Atomic force microscopy (AFM) studies on the microstructure of the phosphonic acid (PA) / Al (with native oxide) self assembled monolayer (SAM) system (a possible corrosion resistant coating interface monolayer) has been evaluated as a function of molecular chain length and processing conditions (i.e. adsorption time) in previous works. It was apparent from the AFM topography and phase images of the monolayer microstructure that the octadecylphosphonic acid (OPA) monolyer was the most conformal and showed little dependence on adsorption time (for times ≤ 24 hours). It was therefore chosen as the most promising monolayer compound of the PA/A1 system with which to study corrosion inhibiting properties.

In this present work, AFM is used to study the corrosion inhibiting ability of OPA SAMs on aluminum, and also to investigate the “nucleation” and progression of Al corrosion and oxide formation in water at the nanometer level; with and without SAM passivation.
A Mechanism for Mechanochemical Wear of Model Systems: Nano-Tribology Studies of Carbonate and Phosphate Single Crystal Surfaces in Aqueous Media
Authors: Dickinson JT , Scudiero L , Park NS , Kim MW , Langford SC
Published: July 2020

In several mechanical wear situations, e.g., those involving biomaterials and applications of mechanochemical polishing, a surface experiences simultaneous tribological loading and corrosive chemical exposure; the combination can greatly increase wear rates. We examine the exposure of single crystal calcite [CaCO3], dolomite [MgCa(CO3)2], and brushite[CaHPO4.2H2O] to buffered aqueous solutions and mechanical stimulation with an Scanning Force Microscope (SFM) tip. Silicon nitride tips are used with applied normal loads from 0-300 nN, tip radii ∼30 nm and tip velocities from 1-200 μm/s. We present the influence of normal force, tip velocity, and solution chemistry on the rates of corrosive wear of calcite and dolomite. Images of the wear of atomic steps can be used to examine the wear rates and propagation of dissolution around the stimulated region. Mechanical stimulation includes small area scans, linear reciprocation, and indentation. A diagram of wear by linear reciprocation of the SFM tip and typical results on single crystal calcite are shown in Figs. 1 and 2, respectively.
The High Temperature Material Laboratory: A National User Facility For Advanced Materials Characterization
Authors: Allard L F , Nolan T A , Pasto A E
Published: July 2020

The High Temperature Materials Laboratory (HTML, Fig. 1) is a national resource for materials characterization sponsored by the Department of Energy’s Office of Transportation Technology, Assistant Secretary for Energy Efficiency and Renewable Energy. The HTML comprises six principal user centers: Materials Analysis, Thermophysical Properties, X-ray and Neutron Diffraction, Mechanical Characterization and Analysis, Residual Stress, and Machining and Inspection Research. Instruments available at the user centers have extensive capabilities for characterizing the microstructure, microchemistry, and physical and mechanical properties of materials over a wide range of temperatures. Details of all the capabilities of the various user centers are available on the World Wide Web at http://www.ms.ornl.gov/htmlhome/default.htm.http://www.nice.org.uk/page.aspx?o=43210

To date, more than 300 different institutions, evenly divided between university and industry, have formal research agreements with the HTML. Three separate programs are available to meet the needs of these users as well as those from federal agencies wishing to gain access to the HTML.
Magnetism And Micro Structure: Advances In Electron-Optical Characterization
Authors: Krishnan Kannan M
Published: July 2020

Tremendous progress has been made in the field of magnetic materials research and technology over the past few years. Superior properties and novel scientific questions arise due to our ability to either synthesize artificial structures or to tailor microstructures at the appropriate length scales. Microstructure, generally defined as the morphological arrangement of crystallites with similar or different phase constitutions and of the crystal defects, is controlled by the processing, which in turn affects the phases present, their topology and their dispersion. There are two key length scales that determine the magnetic behavior of materials. One is the characteristic length scale associated with the dimensional characteristics of the magnetic phenomenon under consideration. The second is the size of the microstructural feature of interest - grain size, shape, isolation, interfaces, inter-granular phases etc. It is important to identify the range where these two length scales overlap, for it is there that novel properties and phenomenon are usually observed.
Microstructure Of Fe-Nd-B Alloys Tailored To Approach Theoretical Coercrvtty Limits
Authors: Krishnan Kannan M , Girt Er , Nelson E C , Thomas G , Hofer Ferdinand
Published: July 2020

Performance of permanent magnets for a variety of applications is often determined by the maximum energy product (BH)max. In order to obtain high (BH)max permanent magnetic materials have to have large coercivity. In theory the coercive field of ideally oriented, non-interacting, single domain, magnetic particles, assuming Kl is much bigger than K2, was shown to be He = 2K1/Ms - N Ms, where Kl and K2 are the magnetocrystalline anisotropy constants, Ms is the spontaneous magnetization and N is the demagnetization factor. For randomly oriented non-interacting particles the Stoner-Wohlfarth model predicts that the value of Hc decreases to about half. However, experimentally obtained values of the coercitive fields in permanent magnets are 3 to 10 and 2 times smaller for well oriented and randomly oriented samples, respectively. This discrepancy was attributed to inter-particle interaction and the microstructure of the permanent magnets. In order to understand the difference between the theoretically predicted and experimentally obtained results for He we prepared rapidly quenched, Nd-rich, NdxFe14B (2 < x < 150) ribbons.
Lorentz And Interference Electron Microscopy On A Scanning Tem
Authors: Yajima Y , Takahashi Y
Published: July 2020

Magnetic imaging can be performed both on conventional (projection) and scanning TEM (CTEM/STEM). The CTEM-based magnetic imaging, classified into Fresnel, Foucault, holography, and other modes, has proven successful by now in observing various magnetic objects, and has accordingly been well documented elsewhere. The STEMbased one has emerged relatively recently prompted by the rapid growth of current STEM technology.

The most ubiquitous implementation of Lorentz microscopy on a STEM is the differential phase contrast (DPC) mode. Each scanning signal obtained in the DPC mode is linear to Lorentz deflection, thus reflects the magnitude of an in-plane component of magnetic induction integrated along the optical axis(Fig.l). The signals therefore suffice to generate integrated in-plane magnetic induction maps(Fig.2). Furthermore, by making use of the fact that the Lorentz deflection distribution across the image plane forms an irrotational (vortex-free) 2D vector field, a pertinent numerical image processing yields a function equivalent to the electron phase function representing magnetically distorted electron wavefront.
Scanning Electron Microscopy With Polarization Analysis (Sempa) Investigations Of Multilayer Magnetism
Authors: J. Unguris  , Celotta R J , Pierce D T
Published: July 2020

Mulitlayers consisting of various combinations of 1-10 nm thick ferromagnetic, antiferromagnetic and nonmagnetic films have numerous applications in magnetic recording, non-volatile data storage, and sensor technologies. One key aspect to understanding how these devices work is being able to image their magnetic structure. SEMPA is well suited for this job, because of its surface sensitivity and compatibility with thin film growth and surface analysis techniques. This talk will review the SEMPA technique and describe thep use of SEMPA in two examples; one in which the magnetization is imaged while growing a multilayer, and another which examines the magnetization while depth profiling a multilayer by ion milling.

A SEMPA investigation of the magnetic exchange coupling in an Fe/Cr/Fe sandwich is shown in Figs. 1 and 2. A wedge shaped Cr interlayer was grown as shown in Fig. 1 in order to measure the Cr thickness dependence of the exchange coupling.
The Use Of Encoders To Improve Both The Spectral And SpatialPrecision M Raman Microscope Mapping Experiments
Authors: Whitley Andrew , Bennett Bob , Smith Brian
Published: July 2020

With the introduction of high efficiency short acquisition time Raman microscopes at the beginning of the 1990's Raman mapping experiments became more realistic for many different materials. Previous to this time Raman maps of any useful size would take far too long for all but the strongest of Raman scatterers. A typical Raman spectrum used to take 30 minutes or more, a relatively small map of 50μ × 50μ using a step size of 1μ, would take over 50 days to acquire. Today the same map can be obtained in less than 4 hours. The use of an xyz mapping stage in conjunction with a Raman microscope is now common. The user defines an area on the sample that requires mapping and selects a step size and spectral acquisition time. Once the experiment is started the mapping stage drives the sample to the start position and takes the first spectrum, once this is completed the sample is moved by the requested step size and the next spectrum is measured.
Relative Raman Intensity Calibration Through Fluorescent Glass Standards
Authors: Etz Edgar S , Hurst Wilbur S , Choquette Steven J , Blackburn Douglas H
Published: July 2020

Attention has been given in the recent past to the various issues that arise from the general lack of standardized procedures for the calibration of Raman spectral intensity. With the increasing acceptance of analytical Raman methods and the availability of diverse types of commercial Raman systems, it becomes increasingly important that uniform calibration methods be developed that provide some means for the correction of the Raman instrument response function. As matters stand now, Raman spectra are typically not corrected for instrument-dependent variations in spectrometer sensitivity across the Raman range. Especially for measurements at different excitation wavelengths, this leads to often severe distortion of relative peak intensities which impedes calibration transfer and affects spectral matching in library search routines. These issues have been brought forth by the McCreery group to the point where national standards organizations (e.g., ASTM, NIST), federal regulatory agencies, the Raman instrument manufacturers, and the analytical Raman community, have taken note.
A Method For Analysis Of Clinical Tissue Samples Using Ft-Ir Microspectroscopic Imaging
Authors: Story Gloria M , Marcott Curtis , Dukor Rina K
Published: July 2020

During the past decade, Fourier transform infrared (FT-IR) microspectroscopy has been used successfully in many studies to differentiate normal and diseased tissue samples obtained from a variety of organs, including colon, cervix, prostate, and breast. IR images were constructed by collecting spectra point-by-point using a mapping stage on a FT-IR microscope equipped with a single-element detector. Five years ago, in collaboration with NIH scientists Dr. Neil Lewis and Dr. Ira Levin, Procter and Gamble researchers developed a technique for performing vibrational spectroscopic imaging microscopy using a liquid-nitrogen-cooled focal-plane array (FPA) detector and a step-scanning FT-IR spectrometer coupled to a refractive microscope. With this configuration, equipped with a new 64-pixel x 64-pixel Mercury-Cadmium-Telluride (MCT) FPA detector, we are able to image an 800-μm x 800-μm area of a specimen without moving the sample.

For all of these IR imaging studies, the tissue samples were prepared in a manner that was special and different from that commonly used in a pathology laboratory, i.e.,the histopathology sample was not identical to the spectroscopic sample.
A New Model For Electron Probe Quantification
Authors: Donovan John J , Pingitore Nicholas E , Jeanloz Raymond
Published: July 2020

Castaing’s first approximation assumes that the characteristic radiation emitted by each element in a compound is unaffected by the presence of the other elements, and that the intensity of the radiation emitted by each element in the compound is proportional to its mass concentration. From Castaing’s first approximation based on mass fractions, the initial estimate of the concentration of an element in a compound is

where C and C° are mass fractions in the sample and standard, and I and I° are x-ray emission intensities of a specific transition measured in the sample and the standard. Surprisingly, the mass fraction approach works well in practice, even though it lacks any obvious physical basis. This can be understood by considering that for typical energies involved in EPMA (50 keV or less), the size of the nucleus is several orders of magnitude smaller than the average incident beam electron wavelength.
Quantitative Electron Microprobe Analysis Of Semiconductor Materials: An Evaluation Of Accuracy
Authors: Carpenter PK
Published: July 2020

Both precision and accuracy are central to quantitative microanalysis. While precision may be evaluated from x-ray counting statistics and replicate measurement, the determination of analytical accuracy requires well characterized standards of which there are few that span a wide range of compositions in binary and ternary systems. The accuracy of silicate mineral analysis has been previously studied via measurement of α factors at multiple accelerating potential and the subsequent evaluation of correction algorithms and mass absorption coefficient (mac) data sets. This approach has been extended in this study to the In2O3-Ga2O3 and HgTe-CdTe systems.

Single crystals of ln2O3, Ga2O3, and an InGa-oxide of unknown composition were used to evaluate accuracy in the In2O3-Ga2O3 binary, using the GaKα, GaLα, and InLα x-ray lines, with WDS measurements performed at 15, 20, and 25KV relative to the ln2O3 and Ga2O3 standards (see Table I). The Ga Kα line exhibits minimal absorption, has no fluorescence correction in this system and is not critically dependent on the correction algorithm or mac data set used.
Parallel Monte Carlo Simulation Using Desktop Computers
Authors: Scott John Henry J , Myklebust Robert L , Newbury Dale E
Published: July 2020

Monte Carlo simulation of electron scattering in solids has proven valuable to electron microscopists for many years. The electron trajectories, x-ray generation volumes, and scattered electron signals produced by these simulations are used in quantitative x-ray microanalysis, image interpretation, experimental design, and hypothesis testing. Unfortunately, these simulations are often computationally expensive, especially when used to simulate an image or survey a multidimensional region of parameter space.

Here we present techniques for performing Monte Carlo simulations in parallel on a cluster of existing desktop computers. The simulation of multiple, independent electron trajectories in a sample and the collateral calculation of detected x-ray and electron signals falls into a class of computational problems termed “embarrassingly parallel”, since no information needs to be exchanged between parallel threads of execution during the calculation. Such problems are ideally suited to parallel multicomputers, where a manager process distributes the computational burden over a large number of nodes.