bluuebunny/crossref_metadata_2025_split huggingface dataset:
Clostridial endospore attachment
Authors: Panessa-Warren B. J. , Tortora G. T. , Warren J. B. 
Published: June 2020

Bacteria from the genus Clostridia, are responsible for such diseases as gas gangrene, wound infections, botulism, tetanus, pseudomembranous colitis, septicemia and nosocomial diarrhea. These anaerobic spores pose a special threat to man because they are ubiquitous, very difficult to kill, and tenaceously grow when conditions are right. This paper examines the process by which Clostridial endospores (specifically C.sporogenes ATCC 3584 and C. difficile ATCC 9689 & 43594) attach to a substrate and germinate, beginning the infective process.C.sporogenes and C.difficile endospores were anerobically incubated at 35 C on CDC blood agar (BCDC) and Trypticase Soy agar(TSA) with 0.5% glucose (BD, Cockeysville, MD). Control and experimental plates were identically streaked with spore suspension using a 1 microliter loop. The control plates were allowed to incubate and grow undisturbed for the duration of the experiment. Attachment experiments were done by streaking plates with either C.sporogenes or C. difficile spore suspensions (initially used full strength, but subsequently diluted for colony counting), incubating these spores in the anaerobic hood (Forma Scientific, Marietta, Ohio) on pre-reduced plates for 27 min, 1 hr 39 min, 2 hr 30 min, 2hr 39 min and 6 hrs.
Ultrastructure features of the tertiary envelope in the cyst of the brine shrimp Artemia franciscana (Anostraca)
Authors: Lee Kit W. , Gouthro Mark A. , Belk Denton , Rosowski James R. 
Published: June 2020

The brine shrimp is an important experimental organism in developmental biology and a key larval food in aquaculture. Morris and Afzelius established the basic ultrastructure of cyst and embryo membranes of Artemia and a subsequent report provided some additional features. A better understanding of the cyst shell structure and composition are prerequisites to elucidating the physical and biochemical processes of the hatching events. In the present study, scanning and transmission electron microscopy were used to visualize the internal features of the maternally produced pigmented tertiary envelope (TE) of the hatched brine shrimp cyst shell. This combined SEM and TEM approach revealed several previously unrecognized features.Utah biotype cysts, from Sanders Brine Shrimp Company Inc., Ogden, Utah, U.S.A., were hatched over 24 hrs in saltwater. Hydrated cysts were fixed in 3% glutaraldehyde, post-fixed in 1% osmium tetroxide, dehydrated in an ethanol series, and critical-point dried or embedded in Epon. In some cases, the critical-point dried cyst shell was fractured before sputter-coating with gold/palladium for SEM.
Nanosurgery of biological specimens using chemically enhanced focused ion-beam etching
Authors: Mackenzie J. M. , Griffis D. P. , Russell P. E. 
Published: June 2020

Many biological events occur at a small number of specific sites within a very large volume. It has recently been shown that focused ion beam (FIB) technology is useful for exposing biological structures for examination. In addition, it has been shown that biological material can be removed using FIB without detectable collateral damage beyond 100Å in fixed, dehydrated, critically point dried tissue.The next step in determining the practical utility of FIB for removal of material from a representative tissue block is to demonstrate that relevant biological structure can be exposed at a selected site. A cross sectioning technique, commonly used for analysis of semiconductor devices, was employed to demonstrate this capability on a block of rat liver prepared as above for SEM. A contiguous-series of successively deeper rectangles are cut into the material using a relatively large, high current beam (0.18μm diameter, 1nA), removing a wedge of material and leaving a large exposed face perpendicular to the surface. The exposed face can then be examined by tilting the sample and viewing with either the FIB or by SEM.
Introduction to automated particle analysis
Authors: Vander Wood T. B. 
Published: June 2020

A microscopist is presented with a special problem when asked to characterize a population of particles. In order to adequately describe the sample, it may be necessary to examine hundreds or even thousands of individual particles, recording the size, shape, identity or other parameters of interest. To manually characterize a statistically significant fraction of the sample could require many hours of tedious work at the scope, followed by still more tedious hours of data reduction. What is needed is a technique to automate the repetitive parts of this process: the recognition and characterization of particles in the sample and the reduction of data and presentation of results. This technique is automated particle analysis.In 1968, automated particle analysis (APA) took early, tentative steps when Moore and coworkers at what was then the National Bureau of Standards demonstrated the possibility of computer analysis of images of small particles. The computing power needed for this work was massive for the day and restricted growth of the field for ten years, but in 1980, publications by Lee and others and Fritz et al.
SEM evaluation of pacemaker surface processing
Authors: Pettman Ray , Okerstrom Susan 
Published: June 2020

Surface condition is critical for pacemakers (fig. 1) and other implanted biomedical devices. The surface must be cleanable, sterilizable, non-irritating to tissues, and have a good cosmetic appearance. Pure titanium is used for the pacemaker shields to enclose the circuitry. Current techniques for finishing the shields center around bright mill rolling and subsequent straight line finishing (SLF) or buffing. Small defects are magnified during buffing while SLF (fig. 2) fractures and galls the surface.A study was done to optimize surface finishing of pacemakers. Early efforts utilized three grits in a sandblasting technique. They were aluminum oxide ( A12O3), figure 3, zirconium oxide (ZrO2), figure 4, and silicon oxide (SiO2), figure 5. Standard light microscopy was employed to assess these first attempts. The resulting surfaces from the blasting mediums looked very similar. Standard light microscopy lacked the depth of field, magnification and resolution to adequately perform this analysis. Scanning electron microscopy (SEM) showed greater differences between the surface treatments.
Template mediated crystal engineering
Authors: Heywood Brigid R. , Champ S. 
Published: June 2020

Recent work on the crystallisation of inorganic crystals under compressed monomolecular surfactant films has shown that two dimensional templates can be used to promote the oriented nucleation of solids. When a suitable long alkyl chain surfactant is cast on the crystallisation media a monodispersied population of crystals forms exclusively at the monolayer/solution interface. Each crystal is aligned with a specific crystallographic axis perpendicular to the plane of the monolayer suggesting that nucleation is facilitated by recognition events between the nascent inorganic solid and the organic template.For example, monolayers of the long alkyl chain surfactant, stearic acid will promote the oriented nucleation of the calcium carbonate polymorph, calcite, on the (100) face, whereas compressed monolayers of n-eicosyl sulphate will induce calcite nucleation on the (001) face, (Figure 1 & 2). An extensive program of research has confirmed the general principle that molecular recognition events at the interface (including electrostatic interactions, geometric homology, stereochemical complementarity) can be used to promote the crystal engineering process.
Automated asbestos analysis with Philips CM microscopes
Authors: Felsmann Michael , Otten Max T. 
Published: June 2020

The analysis of asbestos fibres is well established (see 1 for a description of the preparation and the procedure for detection and fibre characterisation with a transmission microscope). Although the procedure for fibre counting and characterisation is described in detail, the result depends on the accuracy of the time-consuming and tedious sample inspection. A substantial part of operator effort is wasted on scanning the grid in the right way in order to avoid double counting of fibres or missingareas. In this way a subjective factor may contribute to the measurement and can distort the results.In order to make asbestos analysis more reliable, a remote control program has been developed for the motorised goniometers of the Philips CM series microscopes (the CompuStage of the recently introduced Cmxxx series or the Specimen Relocation System of the previous Cmxx series). The program controls the systematic scanning of the grid and documentation of the fibres detected. In this way the operator can concentrate fully on the inspection and characterisation of the fibres.
The need of electron microscopy in the study of domains and domain walls in ferroelectrics
Authors: Cao Wenwu 
Published: June 2020

Domain structures play a key role in determining the physical properties of ferroelectric materials. The formation of these ferroelectric domains and domain walls are determined by the intrinsic nonlinearity and the nonlocal coupling of the polarization. Analogous to soliton excitations, domain walls can have high mobility when the domain wall energy is high. The domain wall can be describes by a continuum theory owning to the long range nature of the dipole-dipole interactions in ferroelectrics. The simplest form for the Landau energy is the so called ϕ model which can be used to describe a second order phase transition from a cubic prototype,where Pi (i =1, 2, 3) are the components of polarization vector, α's are the linear and nonlinear dielectric constants. In order to take into account the nonlocal coupling, a gradient energy should be included, for cubic symmetry the gradient energy is given by,
The structure and distribution of 90° domains in PbTiO3 ferroelectric thin films
Authors: Streiffer S. K. , Stemmer S. , Hsu W.-Y. , Ernst F. , Raj R. , Rühle M. 
Published: June 2020

Many properties of perovskite-derived, tetragonal, ferroelectric thin films, such as saturation polarization and coefficient of second harmonic generation, have proven to be a strong function of the volume fraction of material oriented with its c-axis approximately perpendicular to the plane of the substrate, the so-called a-domains. Films are typically deposited above their Curie temperature, and a-domains form during cooling after growth in order to relieve strains generated by the transformation of the material from the high-temperature cubic phase to the ferroelectric, tetragonal modification. Models based on free-energy considerations of this twinning transformation under the constraints imposed by a rigid substrate have been proposed which predict a-domain widths and volume fractions as a function of e.g., film thickness and epitaxial and thermal expansion mismatch with the substrate.We have used transmission electron microscopy to examine the intrinsic factors influencing the size and distribution of a-domains in epitaxial PbTiO3 ferroelectric thin films grown by laser ablation.
Epitaxial growth of PbTiO3 thin films on {100} SrTiO3 from solution precursors
Authors: Seifert Andreas 
Published: June 2020

A mixed Pb-Ti-alkoxide liquid precursor, prepared from lead acetate and titanium iso-propoxide was used to form single crystal PbTiO3 thin films epitaxially on {100} SrTiO3 substrates.A gravimetric analysis of the precursor determined its molarity to 0.55 mol/1 and was carried out by drying the alkoxide overnight and heating it to 600° C for one hour. X-ray diffraction showed the resulting PbTiO3 powder to be single phase perovskite. PbTiO3 thin films were formed by spincoating previously annealed (1400°C, 2h) single crystal SrTiO3 substrates. During this process the precursor dries to a gel-like amorphous solid film that pyrolizes and crystallizes to the oxide during heat-treatment. XRD, SEM, TEM and AFM were used to characterize the progress of the epitaxial layer formation as well as the microstructural evolution of films heated at increasing temperatures, ranging from 400°C to 800°C. For XRD Θ-2Θ scans on PbTiO3 thin films heated at temperatures of 450°C and above, only the {00l} tetragonal PbTiO3 reflections (CPTO=0.4153 nm) could be observed, indicating strongly oriented or epitaxial films ({h00} of PbTiO3 (aPTO=0.3899 nm) is masked by (MX)} of the SrTiO3 substrate (aSTO=0.3904 nm)).
Microstructural changes of Pt/Ti electrodes in an oxygen ambient
Authors: Park K. H. , Kim C. Y. , Lee J. S. , Kim K. Y. , Jeong Y. W. , Kwon H. J. , Kim S. T. 
Published: June 2020

The stability of bottom electrodes during annealing in oxidation environments is crucial for the fabrication of ferroelectric capacitors. The Pt/Ti bilayer has received attention as a promising electrode for Si-based devices. The Ti buffer layer is necessary not only to improve the adhesion of Pt to dielectrics but also to prevent the formation of Pt silicides at high temperatures. When the Pt/Ti electrodes are exposed to O2 atmosphere during heat treatment, the oxidation induced diffusion of Ti into Pt and the oxidation of Ti are observed. In spite of previous researches, the microstructural features of the Pt/Ti bilayers in oxygen ambients have not been cleared up yet. In this study, combined techniques of transmission electron microcopy(TEM), scanning electron nucroscopy(SEM), and Auger electron spectroscopy(AES) have been applied to clarify the correlation between the interdiffusion of Pt/Ti/O and the microstructural evolution.The chosen system was Pt/Ti/SiO2/Si. The electrode of 80 nm thick Pt was dc-sputter deposited on the 70 nm thick Ti adhesion layer. The Si substrate wafers were covered with 750 nm thick thermally grown oxides. Heat treatments at various temperatures were performed in an oxygen ambient for 30 min.
Facet crystallography of fractured V(2.7 wt% Si) solid solution
Authors: Sutliff J. A. , Bewlay B. P. , Henshall G. A. , Strum M. J. 
Published: June 2020

V-Si binary alloys have been investigated as model high temperature alloys. Alloys with compositions between ~4 and 11 wt% Si can be fabricated as in-situ composites composed of the intermetallic V3Si phase and the V(Si) solid solution phase with a eutectic temperature of ~1870°C. The V(Si) phase is thought to be a ductile phase which provides toughness to the composite. We have previously reported on the fracture toughness of V-Si alloys.In this paper we present results on the fracture surface fractography and fracture facet crystallography of an arc-melted V(2.7 wt% Si) solid solution alloy fractured in bending. Figure 1 is a low magnification SEM micrograph of the surface of one half of a fractured bend bar. Many macroscopically flat facets can be seen and those for which crystallographic analysis was done have been labeled. Actually, the macro-facet surface as seen at higher magnification exhibits significant morphological structure, as can be observed in Figure 2 which shows detail of the facet labeled k.
Beam damage induced “Si flower” in SiO2
Authors: Lee Tan-Chen , Silcox John 
Published: June 2020

100 keV electron beams can damage and even cut holes in specimens. It is of great concern for analytical electron microscopy because the damage may result in a change in chemical composition of the irradiated area. During irradiation, low-Z elements tend to be removed faster than the high-Z ones thus leaving a “heavier” substrate. Sometimes, beam damage can not be “seen” via contrast change either in BF (bright field) or ADF (annular dark field). However, it can be observed in the Si first plasmon energy selected image reported in this paper. This image also provides evidence that the oxygen diffuses from the undamaged area to the damaged area.The experiment was carried out in a VG HB501A STEM which is equipped with EELS and a windowless X-ray detector. A sample with a 5200 Å-thick SiO2 film grown on a Si substrate was used in this study. It is found from X-ray analysis that there are only Si, O and a very small amount of S.
Characterization of the oxidation and oxidation-sulfidation of chromium niobium alloys
Authors: Duncan J. C. , Touryan L. , Hobbs L. W. 
Published: June 2020

Materials in mixed corrosion environments, such as those in coal gasification processes or other energy conversion systems, may be exposed to both oxygen and sulfur. Alloys that exhibit simultaneous oxidation and sulfidation resistance are sought for these applications. Alloys containing sufficient Al or Cr readily form a protective oxide scale but generally have high sulfidation rates. Refractory metals, such as Nb or Mo, form protective sulfides but oxidize at catastrophic rates. Materials containing additives of one of these groups have been studied for their complex corrosion resistance. A binary alloy containing components from each group (Cr and Nb) has been investigated in mixed oxidants .Isothermal thermogravimetric measurements give overall scale growth kinetics but do not give details for complex scales or substrates. Multiple layers, different growth regimes and preferential corrosion can complicate interpretation. The environmental SEM with a hot stage attachment allows the observation of scale development at temperature.
Dislocation dissociation in Ll2 ordered alloy Ni3Ge
Authors: Fang J. , Schulson E. M. , Baker I. 
Published: June 2020

It is well established that the yield stress of Ni3Ge anomalously increases with increasing temperature from 77 K to 673 K. Above room temperature, the anomaly is generally attributed to the Kear-Wilsdorf (K-W) mechanism. Since no parallel systematic TEM investigation has been performed to characterize the dislocation structures in Ni3Ge, it is not clear whether the yield stress anomaly below room temperature is governed mainly by the K-W mechanism or by other mechanism(s). Thus, detailed TEM characterization of dislocation dissociation has been carried out in polycrystalline Ni3Ge deformed at room temperature. In this report, we briefly describe the main results obtained. The complete analysis can be found elsewhere.The deformation structure mainly consists of apparently undissociated dislocations with Burgers’ vector parallel to a<110> and of SISF (super intrinsic stacking fault)-coupled partials. Fig. 1 shows an example of SISF dissociation. First, consider dissociation of a perfect dislocation into partials 1 and 2.
Microstructural characterization of a Cr2Nb-Nb(Cr) microlaminate composite
Authors: Larsen M. , Rowe R. G. , Skelly D. W. 
Published: June 2020

The thrust to weight ratio of an aircraft engine is limited by the density and elevated temperature performance of high temperature structural materials. Many material systems are currently under investigation as potential next generation engine materials. Microlaminate composites consisting of alternating layers of a ductile refractory metal for toughening and a high temperature intermetallic compound for elevated temperature strength have applicability in aircraft engine turbines. The lamellar thickness of such a composite must be small because the intrinsic defect size, a crack across the intermetallic layer, will be controlled by the intermetallic layer thickness. The microstructural characterization of a Cr2Nb-Nb(Cr) microlaminate composite produced by Magnetron® sputtering was carried out by cross-sectional TEM. Both the as-deposited composite and one heat treated at 1200°C for two hours were examined.Figure 1 shows a micrograph of the as-deposited composite. The metal and intermetallic layers are 2um thick. The metal layer has a composition in atomic percent of 95% Nb and 5% Cr.
Structure of Σ7 grain boundary in Al2O3
Authors: Chu C. C. , Chen F.-R. , Wang C.-Y. , Chang L. 
Published: June 2020

In the past, extensive high resolution electron microscopy has been applied to the atomic structure of grain boundaries of cubic symmetry. In order to have a better understanding of generalization of the grain boundary theory, it could be fruiful to study grain boundary structure of non-cubic and low symmetry crystals in which case the exact CSL’s may not exist. Al2O3 has a hexagonal crystal structure ( non-cubic). In the case of hexagonal crystals, three dimensional coincidence site lattices (CSL’s) are only possible for rational values of (c/a), except for rotations about the [0001] axis. The (c/a) of α-Al2O3 is very close to a rational number (15/2) such that constrained coincidence-site lattice (CCSL) misorientations can be found. In this research, we study the atomic structure of Σ7 grain boundary. The misonentation of Σ7 is [011]/180°. The bicrystals of Σ7 were made by diffusion bonding in high temperature and high vacuum.Figs. 1 (a) and (b). show typical HRTEM images of Σ7 Al2O3 boundary recorded at the underfocus values -48 nm and -96 nm, respectively. The beam direction is parallel to a common axis [20].
Atomic faceting NiSi2/Si interfaces
Authors: Chen F.-R. , Chen W. J. 
Published: June 2020

Sutton et al and Brokman et al suggested that long period asymmetrical boundary may facet on an atomic scale into short period symmetrical boundaries. This principle was first confirmed in the case of Σ=3 NiSi2(11)1/(15)2 and NiSi2(001)1/(21)2 asymmetrical boundaries in NiSi2 thin film by Chen et al using high resolution TEM. The asymmetrical boundaries contain a mixture of structural units of the (1)1/(11)2 and the (12)1/(12)2 symmetrical boundaries. The structural units of the (1)1/(11)2 is a 6-atom ring, while (12)1/(12)2 boundary has composite 5 and 7-atom rings. This result is consistent with the chain unit model (CUM) proposed by Wang and Vitek which describes the variation of the boundary structure with the inclination of the boundary plane.The principle of CUM was shown to be valid in the Σ=3 NiSi2(11)/(15)Si and NiSi2(21)/(001)Si asymmetrical interfaces. There are four possible atomic faceting structures for an asymmetrical interface. Fig. 1(a) shows the coexistence of two atomic faceting interfacial domains in a NiSi2(11)/(15)Si interface.
HREM imaging of PtSn4/PtSn2 interfaces in Pt-Sn thin films
Authors: Dufner D. C. 
Published: June 2020

High resolution electron microscopy (HREM) is a very useful technique for studying intermetallic alloy formation resulting from the interdiffusion of metals in thin films. In this work, reactions between Pt and Sn thin films are studied to elucidate mechanisms for structural and compositional changes during the interdiffusion process.Thin film specimens are prepared by the two-film method introduced by Shiojiri et al. Approximately 50 nm of Pt are vacuum-deposited onto holey carbon films mounted on 3mm diameter TEM grids. Sn films with an average thickness of 20 nm are created by evaporating Sn at rates of 1.5-3.0 nm/sec onto air-cleaved KBr substrates. The Sn films are then wet-stripped and collected on the Pt-coated holey carbon grids. A thin carbonaceous contamination layer exists between the metal films to prevent the onset of interdiffusion until the specimens are heated in situ in the TEM.TEM observations are carried out on the JEOL 2010 200kV TEM at Texas A&M University and the JEOL 4000EX 400kV TEM at Arizona State University.