bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of iron-implanted silicon carbide
Authors: Bentley J. , Romana L. J. , Horton L. L. , McHargue C. J. 
Published: June 2020

As part of extensive fundamental studies of ion-implanted ceramics, analytical electron microscopy (AEM) has been used to characterize [0001] single crystal 6H α-silicon carbide implanted at room temperature with 160 keV 57Fe ions to fluences of 1,3, and 6 x 1016 ions/cm2. AEM was performed at 100 kV with a Philips EM400T equipped with a field emission gun, a 6585 STEM unit, an EDAX 9100/70 energy dispersive X-ray spectrometer (EDS), and a Gatan 666 parallel-detection electron energy loss spectrometer (PEELS).A micrograph of a cross-sectioned specimen implanted with 6 × 1016 ions/cm2 is shown in Fig. 1. The implanted region extending to 195 nm from the surface is amorphous, as confirmed by convergent beam electron diffraction (CBED) patterns (insets), and contains iron at levels easily detectable by EDS (Fig. 2). The 15 nm lattice fringes of the edge-on 6H basal planes in the substrate provide an unambiguous depth calibration scale. The transition layer at the end of the ion range exhibits the expected strain contrast. The depth profile of the implanted iron was measured by EDS line scans perpendicular to the implant surface; the mean of three of these scans is shown by the filled symbols in Fig. 3. The integrated iron profile agrees with the expected 6.0 × 1016 ions/cm2 only if the density of the amorphous SiC is equal to that of its crystalline forms, rather than the 20% lower density reported earlier.
The structure of membranes and membrane proteins embedded in amorphous ice
Authors: Lücken Uwe , Jäger Joachim 
Published: June 2020

TEM imaging of frozen-hydrated lipid vesicles has been done by several groups Thermotrophic and lyotrophic polymorphism has been reported. By using image processing, computer simulation and tilt experiments, we tried to learn about the influence of freezing-stress and defocus artifacts on the lipid polymorphism and fine structure of the bilayer profile. We show integrated membrane proteins do modulate the bilayer structure and the morphology of the vesicles.Phase transitions of DMPC vesicles were visualized after freezing under equilibrium conditions at different temperatures in a controlled-environment vitrification system. Below the main phase transition temperature of 24°C (Fig. 1), vesicles show a facetted appearance due to the quasicrystalline areas. A gradual increase in temperature leads to melting processes with different morphology in the bilayer profile. Far above the phase transition temperature the bilayer profile is still present. In the band-pass-filtered images (Fig. 2) no significant change in the width of the bilayer profile is visible.
Electron Microscopy and image reconstruction reveal the structural basis for spectrin's elastic properties
Authors: McGough Amy M. , Josephs Robert 
Published: June 2020

The remarkable deformability of the erythrocyte derives in large part from the elastic properties of spectrin, the major component of the membrane skeleton. It is generally accepted that spectrin's elasticity arises from marked conformational changes which include variations in its overall length (1). In this work the structure of spectrin in partially expanded membrane skeletons was studied by electron microscopy to determine the molecular basis for spectrin's elastic properties. Spectrin molecules were analysed with respect to three features: length, conformation, and quaternary structure. The results of these studies lead to a model of how spectrin mediates the elastic deformation of the erythrocyte.Membrane skeletons were isolated from erythrocyte membrane ghosts, negatively stained, and examined by transmission electron microscopy (2). Particle lengths and end-to-end distances were measured from enlarged prints using the computer program MACMEASURE. Spectrin conformation (straightness) was assessed by calculating the particles’ correlation length by iterative approximation (3). Digitised spectrin images were correlation averaged or Fourier filtered to improve their signal-to-noise ratios. Three-dimensional reconstructions were performed using a suite of programs which were based on the filtered back-projection algorithm and executed on a cluster of Microvax 3200 workstations (4).
Kearns-Sayre syndrome, a mitochondrial myopathy: First diagnosed case in Oman
Authors: Buhl Line , Muirhead David , Doyle David 
Published: June 2020

Mitochondrial myopathy of the Kearns-Sayres Syndrome is described as a severe disorder which is progressive with CNS involvement, has metabolic acidotic crisis and is eventually fatal. The proportion of muscle fibres containing abnormal mitochondria maybe as low as 5-10% in cases presenting with severe clinical symptoms. There is no recognised treatment for this degenerative disease.An 11 year old Omani girl well until the age of 5 years, showed increasing symptoms of external ophthalmoplegia, ptosis, tubular vision and retinitis pigmentosa. CT scan showed atrophy of the brain. Biochemistry revealed an elevated creatinine kinase. A muscle biopsy was performed at the age of 11 years. The patient had no known family history.
Immunohistochemical localization of gene expression in Onchocerca volvulus using latex spheres as an SEM marker
Authors: Kreitzer David , Tuan Rocky S. , Shipley Kenneth J. 
Published: June 2020

Onchocerca volvulus, the filarial parasite responsible for river blindness, is being studied for identification of sera reactive antigens. In an attempt to localize these reactive antigens, scanning electron microscopy is being utilized as a correlative technique with light microscopic observations.Worm material is obtained by nodulectomy. The nodules were fixed in a modified Camoy’s fixative, dehydrated through graded ethanol and embedded in paraplast. Sections were cut at 8um, mounted onto glass slides and baked to dryness. Prior to immunohistochemical treatment, sections were deparaffinized with histoclear and xylene, and rehydrated through graded ethanols to water.
Acetylcholinesterase (AChE) demonstrated by a vascular perfusion incubation technique
Authors: Luo Zhongrong , Whitter Ernest F. , Manoonkitiwongsa Panya S. , Schultz Robert L. 
Published: June 2020

For the cytochemical demonstration of enzymes, the commonly employed procedures involve using chopped small cubes or sections of tissue incubated in a proper medium. With the chopped tissue, penetration of substrate and capturing agents is very slow. When using frozen sections artifacts are difficult to avoid. Also proper vibratome sections are hard to achieve with small organs such as the pineal gland. In order to overcome these disadvantages, we have developed a vascular perfusion incubation technique for the demonstration of AChE.With this technique, a simple gravity flow apparatus for vascular perfusion with two glass containers for fixative and Tyrode solution was used. A needle (19g) with a 32 cm long vinyl tube was connected to the apparatus by a three-way valve. Adult Djungarian hamsters were anesthetized with 1.5 g/kg urethane. The needle was inserted into the ascending aorta through the left ventricle. The following solutions were then perfused for the times indicated: Tyrode, 1 min; fixative (1% purified glutaraldehyde and 2% formaldehyde, 0.05 M cacodylate buffer, pH 7.2), 5 min; Tyrode, 10 min; substrate-free incubation medium, 10 min; complete incubation medium, 20 min; pause for 10 min; repeat of the last two steps four times; isotonic sodium sulphate, 10 min; buffered sulphide, 30 min; isotonic sodium sulphate, 10 min; fixative (3% glutaraldehyde and 2% formaldehyde, 0.05 M cacodylate buffer), 5 min. The entire pineal gland and pieces of the tongue were taken. After osmium postfixation standard electron microscopic procedures were used.
Space-exposed seed experiment developed for students
Authors: Leeper Donna , Bridgers Kelvin , Hammond Ernest C. 
Published: June 2020

The SEEDS project was flown in orbit aboard the Long Duration Exposure (LDEF) for nearly six years. During this time in space, the tomato seeds received an enormously abundant supply of cosmic radiation. Upon the return of the LDEF to earth, the SEEDS project was distributed throughout the United States and 30 foreign countries for analysis. The purpose of the experiment was to determine the long term effects of cosmic rays on living tissue. At Morgan, the analysis performed varied from germination and growth rates to electron microscopy and x ray analysis.In analyzing the seeds under the electron microscope, usual observations were performed on the nutritional and epidermic layers of the seed. These layers appeared to be more porous in the space-exposed seeds than in the Earth-based control seeds. This unusual characteristic may explain the increase in the space seeds’ growth pattern. (Several test results show that the space-exposed seeds germinate sooner than the Earth-based seeds. Also, the space exposed seeds are growing at a faster rate.) The porous nutritional region may allow the the seeds to receive necessary nutrients and liquids more readily. Thus, enabling the plant to grow at a much faster rate.
Human-hair analysis
Authors: Lambert Brenda E. , Hammond Ernest C. 
Published: June 2020

The purpose of this study was to examine the external structure of four human hair shaft samples with the scanning Electron Microscope (SEM) and to obtain information regarding the chemical composition of hair by using the attached x ray microanalysis unit.The hair samples were obtained from two female subjects. Sample A was taken from a black female and had not undergone any type of chemical processing. Sample B, C, D were taken from a white female, and were natural, processed, and unpigmented, i.e. “gray”, respectively. Sample C had been bleached, tinted, and chemically altered using a permanent wave technique.
Ultrastructure of the basal body apparatus in epidermal cells of a sponge larva (Aplysilla SP: Demospongiae)
Authors: Pinto R.L. , Woollacott R.M. 
Published: June 2020

The basal body and its associated rootlet are the organelles responsible for anchoring the flagellum or cilium in the cytoplasm. Structurally, the common denominators of the basal apparatus are the basal body, a basal foot from which microtubules or microfilaments emanate, and a striated rootlet. A study of the basal apparatus from cells of the epidermis of a sponge larva was initiated to provide a comparison with similar data on adult sponges.Sexually mature colonies of Aplysillasp were collected from Keehi Lagoon Marina, Honolulu, Hawaii. Larvae were fixed in 2.5% glutaraldehyde and 0.14 M NaCl in 0.2 M Millonig’s phosphate buffer (pH 7.4). Specimens were postfixed in 1% OsO4 in 1.25% sodium bicarbonate (pH 7.2) and embedded in epoxy resin. The larva ofAplysilla sp was previously described (as Dendrilla cactus) based on live observations and SEM by Woollacott and Hadfield.
Electron microscopy of high-temperature oxide superconductors
Authors: Bentley J. , Fisher A.T. , Haltom C.P. , Brynestad J. , Lauf R.J. , Williams R.K. , Kroeger D.M. 
Published: June 2020

The discovery of superconductivity, first at temperatures above 35 K in materials with the formula La2-x(Ba,Sr)xCuO4, and subsequently at temperatures above 90 K in a polyphase material of nominal composition Y1.2Ba0.8CuOx, has generated considerable excitement and has prompted widespread experimental and theoretical research activity because of the implications both for practical applications and also our understanding of superconductivity. In the 35 K material the highest temperature superconducting phase has the K2NiF4-type structure of composition La1.85(Ba,Sr)0.15CuO4-y with the oxygen content dependent on specimen preparation and processing methods. The superconducting phase in Y-Ba-Cu-O has been widely reported to have the formula YBa2Cu3O9-x and a proposed tetragonal structure with a=0.389 nm and c= 1.165 nm.La1.85Sr0.15CuO4 was made by thermal denitration at <500 K. The sintered powder was hot isostatically pressed to ∼96% theoretical density and annealed to ensure oxygen contents that produce superconductivity. Y-Ba-Cu-O materials were prepared from mixtures of Y2O3, CuO, and BaCO3 powders that were ground and sintered. Specimens were prepared for electron microscopy by several methods.
Atomic structure analysis of small particles supported on amorphous material
Authors: Sattler M.L. , O'Keefe M.A. 
Published: June 2020

The direct observation of atomic features in small crystalline particles supported by a thicker substrate is useful when characterizing materials such as electrocatalysts. However, particle definition becomes difficult to establish for catalyst crystallites less than 5nm in diameter on a support 5 to 10 times thicker, since the background contrast obscures the HREM image of the particle. Previous image calculations of 2.4nm sized particles on 10nm amorphous support have demonstrated further the problems associated with image interpretation of these small particles. The present method incorporates the matching of simulated images at varying thicknesses with computer enhanced images of small particles on amorphous supports in order to characterize atomic details at the surfaces of these particles.Catalyst material consisting of crystalline Ti02 particles on an amorphous Si02 support was developed so that the average particle size measured 7.0nm.
Electron energy loss spectroscopy (EELS) by scanning transmission electron microscopy (STEM) at low doses
Authors: Reichelt R. , Engel A. , Leapman R. 
Published: June 2020

A scanning transmission electron microscope (STEM) has the unique feature to record simultaneously two types of images with high collection efficiencies. The first type, collected by an annular detector (AD), contains high resolution structural information which is primarily transmitted by elastically scattered electrons. The second type, formed by an electron spectrometer (SP), yields information on the local energy loss spectrum of the inelastically scattered electrons at lower structural resolution. Thus useful quantitative information from biological matter can be obtained: the AD-signal provides the basis for mass mapping and the inelastic one allows the estimation of the local chemical element concentration.For a very thin specimen (T<< ^, T: thickness, A: mean free path between two scattering events) the signal S of the imaging modes mentioned above can be linearly related to the properties of the sample:
Analytical TEM of grain boundary phases in yttria-zirconia ceramics
Authors: Mecartney M.L. , Angelini P. 
Published: June 2020

Yttria-zirconia ceramics have a broad range of applications, from use as structural materials (tetragonal zirconia) to ionic conductors (cubic zirconia). Similar to many ceramic materials, these zirconia ceramics often contain small amounts of amorphous silicate phases at grain boundaries and multiple grain junctions. These phases are a result of impurities, introduced during processing or from the original raw material, or are deliberate additions to aid in the densification via liquid phase sintering. Despite the universality of these grain boundary phases, as of yet little work has been undertaken to understand their effect on the microstructural development, chemistry, and physical properties of the materials. We report here our results on analyzing a series of yttria doped zirconia ceramics to which deliberate additions of various glass phases have been added.Samples were fabricated from zirconia powders which contained 3 mol% yttria and 8 mol% yttria. Aluminosilicate glass or borosilicate glass (5 wt%) was added to the powders before sintering. The samples were hot-isostatically pressed at 1650°C for 1-100 minutes.
Scanning ion microscopy images
Authors: Levi-Setti R. , Chabala J.M. , Wang Y.L. 
Published: June 2020

Finely focused beams extracted from liquid metal ion sources (LMIS) provide a wealth of secondary signals which can be exploited to create high resolution images by the scanning method. The images of scanning ion microscopy (SIM) encompass a variety of contrast mechanisms which we classify into two broad categories: a) Emission contrast and b) Analytical contrast.Emission contrast refers to those mechanisms inherent to the emission of secondaries by solids under ion bombardment. The contrast-carrying signals consist of ion-induced secondary electrons (ISE) and secondary ions (ISI). Both signals exhibit i) topographic emission contrast due to the existence of differential geometric emission and collection effects, ii) crystallographic emission contrast, due to primary ion channeling phenomena and differential oxidation of crystalline surfaces, iii) chemical emission or Z-contrast, related to the dependence of the secondary emission yields on the Z and surface chemical state of the target.
Microstructure of pores in N+-silicon layers
Authors: Kaushik V. S. 
Published: June 2020

Oxidized porous silicon has drawn considerable interest as one of the alternatives for implementing silicon-on-insulator technology. Buried porous layers can be formed by utilizing the preferential pore formation in highly doped silicon during anodic etching in hydrofluoric acid. This porous silicon layer (PSL) can be subsequently oxidized rapidly at low temperatures to yield a device-quality silicon island layer, which is dielectrically isolated from the substrate. Although pores can be formed in both n-type and p-type silicon, the latter has received more attention. This paper presents the results of cross-sectional TEM (XTEM) observations of the microstructure of pores in n+ silicon.Samples used in this study were n- /n+/n- doped silicon (001) wafers which had been anodically etched in a hydrofluoric acid solution to form the PSL in the n+ layer via trenches etched through the n- surface layer.
Analysis of boundaries
Authors: Garratt-Reed Anthony J. 
Published: June 2020

As the understanding of the importance of grain boundary structure and chemistry in determining material properties grows, the need for high quality analysis of grain boundary segregation becomes more and more critical. In this paper we shall discuss briefly the three common direct methods of grain boundary analysis. We shall loosely use the term “grain boundary” to include phase boundaries and precipitate interfaces.The earliest technique employed to study grain boundary segregation was Auger electron spectroscopy of intergranular fracture surfaces. Since the depth sensitivity of Auger analysis, is, in general, only a few atomic layers, it is possible in principle to detect only a few percent of saturation coverage of the boundary.
A TEM/Low-Temperature Photoluminescence Examination of MBE-grown (001) CdTe films
Authors: Burke M.G. , Choyke W.J. , Feng Z.C. , Hanes M.H. 
Published: June 2020

CdTe, a large band gap semiconductor, is used for a variety of applications such as infrared detectors, solar cells, and other opto-electronic devices. These applications require that CdTe thin films or buffer layers are made with high structural perfection. To date, a variety of substrates have been employed in CdTe thin film production, including GaAs, sapphire, and InSb. InSb is particularly attractive due to the small lattice mismatch with CdTe across {100}. We will report results of a combined TEM/low temperature photoluminescence (LT-PL) investigation into the defect structures present in MBE grown (001) CdTe films produced on InSb substrates, and initial observations of MOCVD CdTe on CdTe substrates.Several high quality MBE CdTe/InSb specimens were initially selected based upon initial PL measurements and DCRC (double crystal rocking curve) results.
SEM determination of optimum processing conditions for microwave dielectrics in the (Ca,Sr,Ba) zirconate system
Authors: Borglum B.P. , Buchanan R.C. 
Published: June 2020

Ceramic components for microwave applications, such as dielectric resonators, typically must possess low dielectric loss (high Q), high dielectric constant (εr) and small temperature coefficient of permittivity (τε). Non-stoichiometric CaZrO3 doped with Sr and Ba has been shown to possess these necessary characteristics Compact and highly reliable microwave components can, therefore, be fabricated using these materials. In this study, the effect of heat-treatment on the final microstructure was investigated.A chemical solution technique was used to synthesize powders of the composition Ca0.965(Sr0.030Ba0.005)Zr0.990O4 Chemical preparation methods offer the advantages of precise stoichiometric control, atomistic homogeneity, high purity, and fine particle size of the resultant powders. Appropriate amounts of the nitrate salts in aqueous solution were mixed to prepare the desired composition. The solution was converted to a powder by evaporation and calcined at 600°C and 800°C for 2 hours.
Computer averaging of lattice images of poly-4-methyl-pentene-1 (P4mp1): Noise created artifacts
Authors: Pradère P. , Revol J.F. , John Manley R. St. 
Published: June 2020

Although radiation damage is the limiting factor in HREM of polymers, new techniques based on low dose imaging at low magnification have permitted lattice images to be obtained from very radiation sensitive polymers such as polyethylene (PE). This paper describes the computer averaging of P4MP1 lattice images. P4MP1 is even more sensitive than PE (total end point dose of 27 C m-2 as compared to 100 C m-2 for PE at 120 kV). It does, however, have the advantage of forming flat crystals from dilute solution and no change in d-spacings is observed during irradiation.Crystals of P4MP1 were grown at 60°C in xylene (polymer concentration 0.05%). Electron microscopy was performed with a Philips EM 400 T microscope equipped with a Low Dose Unit and operated at 120 kV. Imaging conditions were the same as already described elsewhere. Enlarged micrographs were digitized and processed with the Spider image processing system.
Examinations of low-density polymer foams with a low-voltage FESEM
Authors: Price C. W. , McCarthy P. L. , Letts S. A. , Kong F. M. 
Published: June 2020

The cell structure of low-density polymer foams is extremely delicate, and the application of conductive coatings for SEM examinations can obliterate much of the fine structural detail. In extreme cases, the structure can be significantly altered by the coating. This problem has been found to be particularly critical in low-density polymer foams. The thin membranes of polymer foams also are exceptionally susceptable to electron-beam damage. Consequently, both the improved low-voltage resolution and the low beam currents now available on an SEM equipped with a field-emission gun (FESEM) have proven to be highly beneficial for the examination of low-density polymer foams. This will be demonstrated for polystyrene foams; equally successful results have been obtained on other types of polymer foams.The simplest technique to examine the cell structure of polystyrene foams is to fracture specimens and examine the fracture surface. Since polystyrene is nonconductive, it must be coated to be examined in the conventional SEM.
Using the scanning electron microscope for failure analysis of high density magnetic media
Authors: Ackerman Evelyn R. , Burnett Gary D. 
Published: June 2020

Advancements in state of the art high density Head/Disk retrieval systems has increased the demand for sophisticated failure analysis methods. From 1968 to 1974 the emphasis was on the number of tracks per inch. (TPI) ranging from 100 to 400 as summarized in Table 1. This emphasis shifted with the increase in densities to include the number of bits per inch (BPI). A bit is formed by magnetizing the Fe203 particles of the media in one direction and allowing magnetic heads to recognize specific data patterns. From 1977 to 1986 the tracks per inch increased from 470 to 1400 corresponding to an increase from 6300 to 10,800 bits per inch respectively. Due to the reduction in the bit and track sizes, build and operating environments of systems have become critical factors in media reliability.Using the Ferrofluid pattern developing technique, the scanning electron microscope can be a valuable diagnostic tool in the examination of failure sites on disks.