bluuebunny/crossref_metadata_2025_split huggingface dataset:
NMR microscopy studies of tumor microenvironments
Authors: Neeman Michal , Schiffenbauer Yael S. , Abramovitch Rinat , Meir Gila 
Published: June 2020

The microenvironmental heterogeneity, characteristic of solid tumors 500 üm in diameter or larger, arises from insufficient nutrient supply due to tumor growth exceeding the rate of vascularization. Multicellular spheroids were proposed as an in vitro experimental model system for simulating these stress environments. As in hypoxic regions of tumors, inner cell layers in spheroids show resistance to radiation and conventional chemotherapy, as well as enhanced expression of the angiogenic vascular endothelial growth factor (VEGF). We have applied NMR microscopy for the study of the effects of these microenvironments on tumor physiology.NMR microscopy experiments were developed for mapping gradients in water diffusion and metabolite content across intact, perfused spheroids (1 mm in diameter). These methods were tested in a study of the cytotoxic effects of cyclocreatine, a synthetic analogue of creatine. In contrast with most of the common anti cancer drugs, accumulation of cyclocreatine was observed across the entire viable rim of C6 glioma spheroids.
Study of crystalline interfaces using Δ-G approach
Authors: Zhang W.-Z. 
Published: June 2020

The study of interfacial structure is a fundamental step to achieve the beneficial structure/property relationship in materials. A knowledge of phase boundaries may provide useful insights for a better understanding of the phase transformation. The O-lattice theory, containing the coincidence site lattice (CSL) model as a subset, has been widely applied and shown to account for boundaries of preferred orientation. Examples include low-Σ CSL grain boundaries with high-Γ (Σ=the ratio between the volumes of unit cells of CSL and the crystal lattice; Γ=the planar density of CSL points), and facets or habit plane of interfaces of precipitates.36 The indices of the crystals adjoining the boundary are commonly used to define the boundary plane. These indices do not reveal a direct connection between the O-lattice planes and the boundaries.This paper emphasizes the application of a simple parameter, Δg, for the study of interfaces and its relationship with the O-lattice planes.
Preparation and characterization of thin films of carbon nitride
Authors: Wan L. , Egerton R. F. 
Published: June 2020

INTRODUCTIONRecently, a new compound carbon nitride (CNx) has captured the attention of materials scientists, resulting from the prediction of a metastable crystal structure β-C3N4. Calculations showed that the mechanical properties of β-C3N4are close to those of diamond. Various methods, including high pressure synthesis, ion beam deposition, chemical vapor deposition, plasma enhanced evaporation, and reactive sputtering, have been used in an attempt to make this compound. In this paper, we present the results of electron energy loss spectroscopy (EELS) analysis of composition and bonding structure of CNXfilms deposited by two different methods.SPECIMEN PREPARATIONSpecimens were prepared by arc-discharge evaporation and reactive sputtering. The apparatus for evaporation is similar to the traditional setup of vacuum arc-discharge evaporation, but working in a 0.05 torr ambient of nitrogen or ammonia. A bias was applied between the carbon source and the substrate in order to generate more ions and electrons and change their energy. During deposition, this bias causes a secondary discharge between the source and the substrate.
What is the ultimate precision of CBED structure factor measurement? Application to Group IV and III-V semiconductors
Authors: Saunders M. , Midgley P.A. , Vincent R. 
Published: June 2020

We have previously demonstrated the feasibility of fitting calculated zone-axis Convergent Beam Electron Diffraction (CBED) patterns to zero-loss energy-filtered experimental data. The aim of this pattern matching procedure is to refine accurate low-order structure factors that can be used to reconstruct the bonding charge density. Initial tests on silicon [110] zone-axis patterns have shown that this new electron diffraction technique is capable of accuracies comparable with existing X-ray methods and that the results are in good agreement with solid state theory calculations. The general applicability of the CBED pattern matching technique is now investigated by studying the bond charge of two other Group IV materials, i.e. germanium and diamond, and the HI-V semiconductor GaAs.The (110) plane of the reconstructed bond charge density for each of the Group IV materials is shown in Figure 1. The agreement between these results and those predicted by solid state theory is excellent despite the use of only five independent Fourier components in the reconstruction.
Automation in electron diffraction analysis
Authors: Zuo J. M. 
Published: June 2020

Automated lattice parameter measurement and orientation analysis are often needed in the characterization of microstructures using electron diffraction, and is made possible with increasingly popular use of slow scan CCD camera and imaging plates. Both of these two detectors are largely linear and digital. Typical electron diffraction analysis has three steps: 1) diffraction pattern measurement, 2) diffraction pattern indexing and 3) solution. Full automation in all these three steps is desired, however, may be hard to achieve especially for complex crystal structures. The importance of automation in each of these steps depends on the type of analysis and the number of analysis needed. Full automation is necessary in the type of applications where the same analysis is repeated many times, such as in texture analysis. In table 1, various applications of electron diffraction and automation needed are listed.There are two types of approach to the automatic indexing. The commonly used method is to matching a calculated list of g's with the measured ones.
Analysis of Nanometer Sized Pyrogenic Particles by Scanning Transmission Electron Microscopy
Authors: Wallis DJ , Browning ND , Megaridis CM 
Published: June 2020

Iron is a ubiquitous element on the earth's surface, and is thus involved in most naturally occurring fires. Iron organometalic compounds have also been known to suppress carbonaceous soot emissions under certain operating conditions of practical combustors. In order to unravel the physical and chemical mechanisms of influence, of iron on the emission of carbonaceous pyrogenic particles, finescale characterization techniques need to be implemented.The combined techniques of Z-contrast imaging and electron energy loss spectroscopy (EELS) in a VG HB-501 dedicated STEM are ideally suited to study such a system. The sensitivity of the Z-contrast imaging technique to high-Z materials makes it ideal for location of the iron particles within the much lower atomic number matrix. As only the high-angle scattering is used in the image formation, EELS can be performed simultaneously from a position defined in the image. This accurate positioning of the probe by the Z-contrast image permits both compositional and bonding information to be obtained with a spatial resolution approaching the atomic scale.
TEM investigation of the low temperature phase of HfV2
Authors: Chu F. , Mitchell T. E. 
Published: June 2020

C15 Laves phase intermetallic compounds are potential high temperature structural materials, of which C15 HfV2 is particularly attractive. At room temperatures (RT), the C15 Laves phase has a fcc-based structure with a lattice parameter a=7.4 Å, as shown in Fig. 1. Sensitive specific heat measurements indicate that HfV2 undergoes a structural transformation at 115 K, as shown in Fig. 2. The crystal structure of the low temperature (LT) phase of HfV2 is not unambiguously known, although some studies have been done. A HfV2 alloy was made by arc-melting. The alloy was homogenized at 1200°C for 120h. In a preliminary study we have concentrated on selected area diffraction patterns (SADs) along different zone axes of C15 structure at 83 K, using a Philips CM 30 microscope with a liquid nitrogen cold stage.A <100>C15 SAD at RT is shown in Fig. 3 (a). At 83 K, SADs along some <100>C15 show (100), (200), and (300) superlattice spots, as shown in Fig 3 (b), while SADs along other <100>C15 indicate (110) and (200) superlattice spots, as shown in Fig. 3 (c).
Energy-filtered plasmon images of MgAl2O4 implanted with Al+ and Mg+ ions
Authors: Evans N. D. , Bentley J. , Zinkle S. J. 
Published: June 2020

Magnesium aluminate spinel (MgAl2O4) is a candidate material for specialized applications in proposed fusion reactors, and previously, has been irradiated with Al+ or Mg+ ions to assess the effects of high-dose irradiation. Electron energy-loss spectrometry (EELS) has been used to confirm the identity of metallic aluminum colloids located in the ion-implanted region of the spinel because electron diffraction experiments were inconclusive for phase identification. In the present study, energy-filtered plasmon images of the ionimplanted region have been obtained to reveal this colloid distribution.Following implantation with 2 MeV Al+ ions to a fluence of 3.8 × 1021 ions/m2 at 923 K, or with 2.4 MeV Mg+ to a fluence of 2.8 × 1021 ions/m2 at room temperature, spinel specimens were prepared in cross-section for analytical electron microscopy. Energy-filtered images were obtained using a Philips CM30 microscope with an attached Gatan Imaging Filter. Acquired images were 512 × 512 pixels in size and gain normalized.
Atom probes as analytical microscopes
Authors: Kelly T. F. , Camus P. P. , Larson D. J. , Bajikar S. S. , Holzman L. M. 
Published: June 2020

Analytical microscopes are used to provide compositional and image information at spatial scales from the atomic (nm) to the macroscopic (mm). There are limitations in these techniques, however, and three in particular are noteworthy. 1) Compositional information at the atomic scale is not readily available. 2) The precision of the data is not high (limited to about a few part per thousand). 3) It is difficult or impossible to determine information about the composition in three dimensions.Atom probe field ion microscopy (APFIM) has historically been able to complement analytical electron microscopes (AEM) at the atomic scale but has not competed with them otherwise. For example, atomic-scale compositional information is inherent to APFIM but it has been difficult to extend this to large dimensions. Furthermore, APFIMs achieve single atom sensitivity which is difficult for AEMs in all but limited situations. In this paper, we consider how atom probes are evolving with capabilities which allow them to not only overcome some of the shortcomings of AEM, but also to compete directly with AEM against its strengths.
Olivine-MgO interfaces produced by crystallization of glass fulms on single-crystal MgO substrates
Authors: Ramamurthy Sundar , Hebert Brian C. , Barry Carter C. 
Published: June 2020

Glassy silicates are present at grain boundaries in almost all liquid-phase sintered ceramic oxides. In many cases, the amorphous-crystalline interfaces in the sintered microstructure can be modified by inducing crystallization of the glassy phase. The intergranular phases in polycrystalline MgO are typically silicates with cations of calcium, magnesium and iron in the silicate network. A systematic approach to study the crystallization behavior of glass-MgO interfaces has been attempted in the present study. Following the work by Mallamaci in which crystallization of a silicate glass in contact with A12O3 was studied, devitrification of glass in contact with single-crystal MgO has been investigated. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to characterize the resulting microstructures.A pellet of Mg2SiO4 (forsterite) prepared by hot-pressing MgO and SiO2 powders was used as the target for depositing glass films onto single-crystal MgO substrates by pulsed-laser deposition (PLD). Glass films with the composition of olivine.
Surface morphology of xenon implanted single crystal magnesium oxide observed by Atomic Force Microscopy
Authors: Jiang Wenbiao , Grant Norton M. , Poker David B. 
Published: June 2020

The implantation of materials with noble gas ions is of particular interest in studying some of the fundamental aspects of the ion implantation process and resultant phenomena because the noble gas ions are immiscible with the matrix and therefore chemical effects are unlikely. Electron diffraction studies have clearly demonstrated that noble gas ions implantated into either metals or ceramics may coalesce to form inclusions. These inclusions may be either solid or fluid and their formation often results in swelling of the matrix. This swelling can be readily apparent on the surface of metallic materials. However, in ceramic materials the extent of this swelling, particular at low ion fluences, can be very small and hence only detectable with surface sensitive topographic probes such as atomic force microscopy (AFM).Polished (00l)-oriented MgO single crystals were implanted with xenon ions using an accelerating voltage of 200 keV at a range of fluences. The specimens were then examined with AFM. The AFM results showed that, even at the lowest fluence, there was measurable roughening of the surface. At a fluence of 1 × 1017/cm2 small blisters were observed. These blisters have diameters of 0.5 - 0.8 μm and extend to heights of up to 80 nm.
Detection of a point defect in a silicon single crystal by high-resolution TEM
Authors: Awaji M. 
Published: June 2020

It is necessary to improve the resolution, brightness and signal-to-noise ratio(s/n) for the detection and identification of point defects in crystals. In order to observe point defects, multi-beam dark-field imaging is one of the useful methods. Though this method can improve resolution and brightness compared with dark-field imaging by diffuse scattering, the problem of s/n still exists. In order to improve the exposure time due to the low intensity of the dark-field image and the low resolution, we discuss in this paper the bright-field high-resolution image and the corresponding subtracted image with reference to a changing noise level, and examine the possibility for in-situ observation, identification and detection of the movement of a point defect produced in the early stage of damage process by high energy electron bombardment.The high-resolution image contrast of a silicon single crystal in the [10] orientation containing a triple divacancy cluster is calculated using the Cowley-Moodie dynamical theory and for a changing gaussian noise level. This divacancy model was deduced from experimental results obtained by electron spin resonance. The calculation condition was for the lMeV Berkeley ARM operated at 800KeV.
TEM investigation of the YSZ-on-insulator structure
Authors: Zhou D.S. , Jia Q.X. , Wu X.D. , Mitchell T.E. 
Published: June 2020

Silicon-on-insulator (SOI) structures have been widely used in the semiconductor industry as substrates to grow various devices. They are usually prepared by a process called separation by implantation of oxygen (SIMOX). As an alternative, single crystal yttria-stabilized-zirconia (YSZ) can be grown on single crystal silicon substrates, followed by heat treatment in oxygen to form an intermediate SiO2 layer. This YSZ-on-silicon structure has the potential to be used as a new SOI material in semiconductor device fabrication.YSZ has a cubic (fluorite type) structure with a lattice parameter of 0.514 ~ 0.523 nm (as compared to 0.543 nm for silicon) depending on its Y2O3 content. The good lattice match between YSZ and silicon makes epitaxial growth possible. In this experiment, the pulsed laser deposition technique has been employed to grow YSZ thin films on single crystal p-Si (100) wafers. Post-deposition heat treatment was carried out at 850°C for 1.5 h in dry oxygen at 1 atmosphere. The structure was first examined by Rutherford backscattering spectrometry and x-ray diffraction, and then by cross-sectional transmission electron microscopy (XTEM) techniques.
Lorentz observation of magnetic domains in terfenol-d
Authors: Dooley J. , Nuhfer N.T. , De Graef M. 
Published: June 2020

Terfenol (Tb.27Dy.73Fe1.95) has the largest known room-temperature magnetostriction coefficient, making it well suited for low frequency, high power sonar applications. Terfenol takes the MgCu2 cubic Laves phase structure, with lattice parameter a = 0.732 nm and space group Fd3m. Magnetic domain configurations in this material are generally interpreted as 71° and 109° walls, along with 180° walls, with the magnetization along the 〈111〉 directions. At room temperature the cubic unit cell experiences an extremely small rhombohedral distortion along the magnetically soft 〈111〉 directions (e.g., the cubic [100] tilts by 1.13 mrad toward a new orientation). The growth direction, designated [11], is taken as a reference throughout this discussion.The material, prepared by a free-standing float-zone (FSZ) technique, was provided by Etrema Products Inc. in the form of [11] oriented rods with a diameter of 3 mm. Since the growth direction is perpendicular to [111] and the growth front is dendritic, growth twins are easily formed by a 180° rotation on the (111) plane.
Structural evolution of the aging martensite in duplex steel
Authors: Chu Hong-Yuan , Chen Fu-Rong , Wu Tai-Bor 
Published: June 2020

In the past, the structure and crystallography of needle-like martensite in the as-quenched Fe-Al-Mn-C alloy were studied. The structure of the needle-like martensite was identified to be a structure between 18R(5)3 and 18R(4)3. The orientation relationship between the BCC matrix and martensite phase was determined to be and . The shape strain, habit plane and other crystallography of martensite were also determined. Comparison with the asquenched Fe-Mn-Al-C martensite, there is only little information about the aging behavior of the martensite phase. The purpose of this work is to study the structural evolution of the martensite phase after aged at high temperature.The wrought Fe-29.4-Mn-8.03Al-0.3C alloy was heated at 1300°C for 1 hour in argon atmosphere, and followed by a quenched into water. Aging process were performed at 400 °C, 500 °C and 600 °C, respectively, for 1 hour in salt bath, and the specimens were then quenched into water. TEM specimens were examined with a JOEL-200CX STEM.
EM of mechanical plated Ti and tin coating on steel
Authors: Kashihara K. , Chiou W. A. , Lin C. S. , Meshii M. 
Published: June 2020

Mechanical alloying, originally developed as a means to produce oxide dispersion strengthened alloys, has since been adopted for producing a wide variety of materials such as solid solution alloys, metal matrix composites, intermetallics, nanocrystalline and amorphous materials. It has also demonstrated as an efficient method for alloying gaseous elements by solid-gas reaction. Interest in using metal and metalloid nitrides as coating materials has been increased considerably in the past few years because of their special properties including extreme hardness, high temperature stability, high corrosion and wear resistance, and excellent conductivity. A new coating technique through the marriage of mechanical plating and nitriding has recently been developed in this laboratory. This paper presents an electron microscopic study of mechanically plated Ti and TiN coating.Commercially produced (Johnson Matthey, Inc.) fine-grained (325 mesh, or 44 μm) Ti (99%) powders were used as the starting coating material. Interstitial-free steel sheet (provided by Inland Steel) were cut to a size of 1.5 cm × 1.5 cm as the substrate.
Fresnel effect in high-resolution TEM imaging of small particles
Authors: Radmilovic Velimir , O'Keefe Michael A. 
Published: June 2020

It is established that analysis of Fresnel contrast visible at the edges of nanoparticles in the high resolution electron microscope provides a valuable tool for determining the size of the particles with near atomic spacing accuracy.Methods based on the Fresnel effect are enjoying increased use in the study of flat precipitates, multilayers, and grain boundaries. In profile imaging studies of solid surfaces, Fresnel effects have been observed by Marks, and by O'Keefe et al. who showed that image structure within Fresnel fringes from MgO cubes can produce “ghost” atoms far outside the specimen surface. However, consequences of the Fresnel effect appear not to have been included in the study of small particles at atomic resolution. In this work, we have used HRTEM image simulation to explore the changes in images of a nanoparticle under various imaging conditions, in particular to relate the model particle size and its apparent size as derived from the HRTEM image.
Refinement of rigid shift component normal to a Σ5 grain boundary in rutile by quantitative HREM
Authors: Paciornik S. , Michel D. , Dahmen U. 
Published: June 2020

In contrast to the macroscopic parameters of a grain boundary, its microscopic parameters are difficult to determine with sufficient accuracy to make critical comparisons between models and experimental observations. Whereas the axis and angle of misorientation and the orientation of the boundary plane are easily measured from diffraction patterns or high resolution images, the rigid body shift and the localized atomic relaxation are far more complicated to determine and are more sensitive to image or sample artifacts. Yet it is only these microscopic parameters that differentiate the behavior of the same crystallographic interface in different materials. While the angle of misorientation and the plane of inclination are fixed macroscopically, the rigid body shift and localized atomic relaxations depend directly on the type of bonding that characterizes a given material.Several methods for the measurement of rigid shifts at interfaces have been given recently. Their accuracy is limited by instrumental parameters such as beam tilt, sample tilt, residual two-and threefold astigmatism, specimen noise or twist components.
Practical aspects about hollow-cone imaging
Authors: Geipel T. , Mader W. 
Published: June 2020

Hollow-cone imaging (HCI) as a possibility to improve the resolution of a TEM has already been proposed in the late 40ties and besides others, there have been extensive hollow-cone experiments 10 years back using a low resolution TEM with a non-tilt specimen holder. In a recent paper the optimum imaging parameters for HCI were determined leading to an improvement of the resolution by a factor of two. However, there are contrast limitations and experimental problems for HCI which were only partly considered in Ref. and which will be discussed in this paper for a modern electron microscope. Preliminary experiments were performed which are not shown in the abstract.In Fig. 1 ∫ ct f(u)du is plotted versus defocus Δ f for different cone radii Θc and a fixed aperture radius Θo = 1/δ = 5 nm-1 (ct f is the phase contrast transfer function (PCTF) for HCI and δ = 0.2 nm is the resolution of a CM30 supertwin microscope).