bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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 (&lt;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

Abstract
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 (&gt;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

Abstract
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 &gt; 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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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 &gt; CH3/CH3 &gt; 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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.