bluuebunny/crossref_metadata_2025 huggingface dataset:
Anatomy and ultrastructure of haustoria in selected West Australian parasitic angiosperms
Authors: Kuo John , Pate John S.
Published: June 2020

Our understanding of nutrient transfer between host and flowering parasitic plants is usually based mainly on physiological concepts, with little information on haustorial structure related to function. The aim of this paper is to study the haustorial interface and possible pathways of water and solute transfer between a number of host and parasites.

Haustorial tissues were fixed in glutaraldehyde and embedded in glycol methacrylate (LM), or fixed in glutaraldehyde then OsO4 and embedded in Spurr’s resin (TEM).

Our study shows that lumen to lumen continuity occurs between tracheary elements of a host and four S.W. Australian species of aerial mistletoes (Fig. 1), and some root hemiparasites (Exocarpos spp. and Anthobolus foveolatus) (Fig. 2). On the other hand, haustorial interfaces of the root hemiparasites Olax phyllanthi and Santalum (2 species) are comprised mainly of parenchyma, as opposed to terminating tracheads or vessels, implying that direct solution transfer between partners via vessels or tracheary elements may be limited (Fig. 3).
An inexpensive water volume control device for ultramicrotomy
Authors: Kokko E.G. , Gowen B. , Jahnke C.R.
Published: June 2020

Numerous techniques and related devices have been reported for preparing serial thin-sections with an ultramicrotome for transmission electron microscopy. The section pickup method, a continuous serial thin-sectioning technique developed by Farenbach (1984), is helpful for: (a) three-dimensional EM reconstruction (Todd et.al. 1989) and (Farenbach 1984), (b)section thickness determinations of thick (LM) or thin (EM) sections using the “section piling - resectioning” technique of Sakai (1980), (c) insuring that important or rare EM sections (such as from a reembedded 0.5 urn LM section) are picked up, or (d) for routine section pickup on formvar-coated slot grids. Farenbach’s technique makes use of a pedestal, located within a diamond knife trough, to hold the slot grids. It calls for a peristaltic pump to maintain precise control of the water level within the trough. The main disadvantage of his technique is the relatively high cost (approx. $ 500 US) for a pump capable of these accurate and two-way flow adjustments of small volumes of liquid.
Osmium tetroxide vapor fixation for preserving fungal structures for SEM
Authors: Tiedt L.R.
Published: June 2020

Scanning electron microscopy has provided valuable information in studies of fungal morphology and ontogeny, but undisturbed preservation of sporulating structures is often difficult.

In this study of sporodochia development in Fusarium spp. in the section Liseola, the usual method of aqueous fixation, dehydration and the subsequent critical-point drying method, could not be used. Macroconidia forms sporodochia by means of water soluble slime and when aqueous solutions come in contact with the sporodochia, the conidia become scattered. To preserve these morphological structures, the samples had to be vapour fixed with osmium tetroxide. Sample blocks were excised from the sporulating cultures and carefully transferred to the inner surface of a Petri dish cover. The cover with several adherent agar blocks were inverted over a Petri dish bottom containing several drops of 2% osmium tetroxide. The Petri dish was left at room temperature for 24h. The Petri dish cover with the fixed samples was transferred to a clean Petri dish bottom and left to air dry.
Electron Microscopic study of dipteran Halteres by using preserved specimens
Authors: Grewal J. S. , Kapoor V.C. , Kochar J.
Published: June 2020

Halteres, highly specialized metathoracic wings are the balancing organs in Diptera. This is probably an adaptation for aerial swarming. Our understanding regarding the detailed structure of this organ is very little. An effort has been made to study the ultrastructure of halteres and the functional aspects of various parts have been discussed.

Flies are relaxed in relaxing medium (Watkins and Doncaster Hawkhurst, England) or by keeping overnight in 50% ethanol. Halteres alongwith a little of thorax lateral wall are peeled off with the help of fine and sharp scalpel. These are boiled in distilled water for about 20 minutes to get rid off all the distortion of structure due to preservation. A fungal growth observed on the material is cleared off by putting a drop or two of phenol in boiling water. Material is then subjected to sonication in distilled water to remove any foreign particle adhering to halteres. Then the material is dehydrated by passing through ethanol series.
Analysis of cathodoluminescence emitted from lipid droplets in corpora lutea of estrus cyclic and pregnant rat by analytical color fluorescence EM
Authors: Ning Gang , Nakano Tohru , Fujimoto Toyoshi , Koike Hirotami , Ogawa Kazuo
Published: June 2020

We developed an analytical color fluorescence electron microscope (ACFEM), which enabled us to detect strong cathodoluminescence (CL) emitted from lipid droplets (LD) in various cells. In previous studies, we demonstrated that steroids and retinoids are most likely to be the chemical components emitting CL. In the present research, we examined CL in corpora lutea (CpL) of rats at various stages of the estrus cycle and gestation by ACFEM.

Adult female Wistar rats either following a normal estrus cycle or pregnant were either decapitated or anesthetized by sodium pentobarbital and the ovary was excised and cut into small pieces. The tissue was attached to aluminium sample tips, rapidly frozen by liquid propane cooled in liquid nitrogen without chemical fixation and cut with a cryo-ultra microtome to make a flat surface for observation. The specimens were kept at -100°C on a cryo-stage and observed by an ACFEM constructed on a basis of a high resolution scanning electron microscope (AKASHI DS-130).
Developmental study of chorioretinal vasculature demonstrated by vascular casts
Authors: Matsunaga Nobuhiko , Amemiya Tsugio
Published: June 2020

Introduction: Methylmethacrylate is a very useful material for the preparation of vascular casts, and many reports have described the vascular of ocular tissues. We attempted to study the development of the rat ocular vasculature.

Material and Methods: 20-day-old fetuses, and 1-day-old, 7-day-old, 14-day-old and 11-week-old rats were anesthetized, and the chest was opened by splitting the sternum. Warm Ringer solution containing heparin sodium was perfused through a catheter inserted into the left ventricle. Blood was removed through an opening in the right atrium. After 2% glutaraldehyde in 0.1M phosphate buffer had been perfused, a mixture of methylmethacrylate resin and catalyst was injected through the same catheter. The eyes were enucleated carefully and macerated in a bath of concentrated potassium hydroxide and sodium hypochlorite solution. The vascular cast was rinsed in distilled water and dried at room temperature or with t-butyl alcohol. After electroconductive staining with osmium tetroxide gas, the cast was mounted on stubs with carbon adhesive tape, and then spattercoated with gold for viewing in a scanning electron microscope.
Immunoelectron microscopic localization of elastic tissue in archival material using an improved method
Authors: Fanning J. C. , White J. F. , Polewski R. , Cleary E. G.
Published: June 2020

Elastic tissue is an important component of the walls of arteries and veins, of skin, of the lungs and in lesser amounts, of many other tissues. It is responsible for the rubber-like properties of the arteries and for the normal texture of young skin. It undergoes changes in a number of important diseases such as atherosclerosis and emphysema and on exposure of skin to sunlight.

We have recently described methods for the localizationof elastic tissue components in normal animal and human tissues. In the study of developing and diseased tissues it is often not possible to obtain samples which have been optimally prepared for immuno-electron microscopy. Sometimes there is also a need to examine retrospectively samples collected some years previously. We have therefore developed modifications to our published methods to allow examination of human and animal tissue samples obtained at surgery or during post mortem which have subsequently been: 1. stored frozen at -35° or -70°C for biochemical examination; 2.
An improved technique for visualization of Neisseria gonorrhoeae pili by SEM
Authors: Dekker Nusi P. , Lammel Claudia J. , Brooks Geo. F.
Published: June 2020

Piliated Neisseria gonorrhoeae (gc) are virulent and attach to human cells more readily than nonpiliated gc . Pili have been difficult to visualize in the scanning electron microscope (SEM), appearing as thick, branched structures, possibly because of artifacts or distortion associated with critical point drying (CPD) . The use of hexamethyldisilazane (HMDS), as an alternative to CPD with bacterial or tissue culture cells, as reported here, improved preservation and visualization of pili and other delicate surface structures.

The methods were: Human endometrial adenocarcinoma (HEC-l-B, ATCC HTB 113) cells were grown in cell culture medium containing fetal calf serum on round thermanox coverslips. Suspensions of piliated and nonpiliated strains of gc (FA1090, F62-SF, and g1412) at dilutions of about 2 × 107 cfu were added to the cells and allowed to attach. Unattached gc were rinsed off and replaced with fresh media after 30 min. After 1 or 8h incubation, the cells were fixed in 2.5% gluteraldehyde in 0.1M cacodylate buffer for 4h; rinsed well in the buffer; post-fixed in 1% OsO4 in cacodylate buffer for lh; rinsed 3 × 10 min in buffer and 2 × 5 min in water; placed in 1% tannic acid in water for 30 min; rinsed 3 × 10 min in water; placed in 2% uranyl acetate for lh; rinsed 3 × 10 min in water; dehydrated in graded ethanols (50%, 70%, 95%, 2 × 5 min each; 100% 4 × 5 min; 100% 10 min); placed in HMDS for 10 min.
Gap junctions: A new level of detail revealed by shadowing at -170° to -182°C in a JEOL JFD-9000 equipped with cryopump and liquid nitrogen-cooled shrouds
Authors: Rash J. E. , Yasumura T. , Walrond J. P. , Steere R. L. , Okutomi S.
Published: June 2020

In conventional freeze-fracture replicas, vertebrate gap junctions (GJ) are visualized as patches of 9 nm P-face particles with center-to-center spacings of 9-11 nm. Occasionally IMPs have a central “dimple”. On E-faces, GJ are represented by 4-6 nm diameter conical pits separated by 5-7 nm wide membrane ridges. In addition to the disparity of sizes of IMPs and pits, there is no discernable substructure in the pits corresponding to the dimples in the IMPs. In this report, we present replicas revealing a new level of detail for gap junctions, including evidence for channels in both P-face IMPs and E-face pits.

Mice were fixed by perfusion with 2.5% glutaraldehyde in phosphate buffer. Samples were gradually infiltrated to 30% glycerol, frozen by plunging into liquid propane, fractured at -105° to -182°C (measured by thermocouple in sample stage), and shadowed at an angle of 45° in a JEOL JFD-9000 freeze-etch machine equipped with electron beam guns. The JFD-9000 was modified by the addition of interlocking liquid nitrogen-cooled shrouds for specimen and knife and a CTI-8F cryopump.
Effects of isoproterenol treatment on the parathyroid glands in golden hamsters of different ages, with special reference to the frequency of lipid droplets
Authors: Emura Shoichi , Shoumura Shizuko , Yamahira Tomo , Kawada Tomoo , Oda Hiroshi , Arakawa Michio , Isono Hideo
Published: June 2020

Recently, we reported that there is an increase in lipid droplets in the parathyroid glands of isoproterenol-treated adult golden hamsters in which the synthesis and release of parathyroid hormone are stimulated. This investigation was undertaken to study the effects of different ages on lipid droplets in the parathyroid glands of the golden hamsters after administration of isoproterenol.

The percent area occupied by lipid droplets in the parathyroid glands of 15, 20 and 25-day-old golden hamsters after 1 h of treatment with isoproterenol and the frequency of lipid droplets of 1-monthold (young), 3-month-old(adult) and 18-month-old(senile) animals after 0.5, 1 and 3 h of treatment with isoproterenol were investigated. The parathyroid glands of the control and isoproterenol-treated animals were removed and immersed in a mixture of 2.5% glutaraldehyde and 2% OsO4 in Millonig's buffer at pH7.4 for 1 h, dehydrated through increasing concentrations of acetone and embedded in Epon 812.
Antihelminthic activity of the drug, Oltipraz, on the surface ultrastructure of Cysticercus fasciolaris
Authors: Ruth Jones Betty , Taylor Randolph
Published: June 2020

INTRODUCTION : Cysticercus fasciolaris is the larval form of the adult cat tapeworm, Hydatigera taeniaeformis (Taenia taeniaeformis). It is of increasing interest because of the considerabvle pathological conditions produced in a rat or mouse host in which it is normally found. The larvae encapsulate and develop on the liver of rats and mice and as a result of this infection, a serious cancer-like growth may develop (Noble and Noble, 1974). The surface tegument of cestodes like that of schistosomes is a highly active layer in which many processes occur (Smyth 1969, 1966). It is a metabolically active syncytial , protoplasmic layer formed by cytoplasmic extensions from tegumental cells lying in the subtegumental zone. The tegument has two major components, namely the distal cytoplasmic zone appears as a fringe of fine hair-like processes (Smyth, 1969; Jones et al., 1977a, 1977b; Lumsden and Specian, 1980).
The interfacial behavior of hard tissue replacement as revealed by SEM
Authors: Pearsall Allan D. , Spears Robert , Sarubbi Kimberly
Published: June 2020

INTRODUCTION:

Hard Tissue Replacement (HTR) has been postulated to be an effective implant material for bone reconstruction and maintenance. HTR consists of a polymethylmethacrylate core coated with polyhydroxyethylmethacrylate and has been demonstrated in light microscopic studies to attach directly to bone. The present study was performed to add to the available information by investigating the interfacial bonding of this polymer using scanning electron microscopy.

MATERIALS AND METHODS: Twenty Sprague-Dawley rats were anesthetized, a midline scalp incision was made to expose the calvaria and the periosteum reflected. Trephine defects were prepared by excising a 1 x 2-mm section of bone and the HTR polymer (24 mesh) inserted. The skin and periosteum were reapproximated and the incision closed. Pursuant to vascular perfusion with a mixture of aldehydes, the implants and surrounding tissue were extirpated in situ after 7-, 14-, 28-, and 56-day observation periods. Tissues were then washed in buffer, dehydrated, fractured in liquid nitrogen and dried in Freon. The samples were viewed in a JEOL JSM35CF SEM with x-ray energy dispersive analysis (EDXA).
Improvement of immunogold labeling by using silver-enhanced ultra small gold probes
Authors: van Bergen en Henegouwen Paul M.P. , de Graaf Arjan , de Ruijter Mia , Verkleij Arie J.
Published: June 2020

Colloidal gold is an excellent marker in immunoelectron microscopy for the localization of proteins in cells and tissues. It can be used in pre-embedment labeling (i.e. cellular matrix labeling) and post-embedment labeling (i.e. cryoultramicrotomy). The major disadvantage of the immunogold probe concerns its sensitivity. Pre-embedment labeling of matrix proteins can only be performed when strong extraction conditions are used. In post-embedment labeling, labeling efficiency is rather low as a result of poor penetration of the gold probe into the section. Here, labeling efficiency has been shown to be inversely related to particle size. An improvement of labeling efficiency can be expected by using ultra small gold probes with a diameter of 1 nm. For visualization, these small particles have to be enlarged by silver precipitation both for aplications in the light- and in the electron microscope. Silver precipitation is done according the method described by Danscher.
A quantitative immunoscanning EM analysis of CD16 (FeRIII) antigen on peripheral blood leukocytes
Authors: Fernández-Segura Eduardo , Manuel Garcia-Lopez O. , Gutierrez Antonio , Campos Antonio
Published: June 2020

A common feature of many cell types which mediate major histocompatibility complex (MCH)-unrestricted lysis is the presence of receptors for the Fc region of IgG (FcR) on the surface. Monoclonal antibodies (MAbs) against these receptors have identified three distinct FcR, i.e., FcRI, FcRII, FcRIII. These receptors are expressed on different but overlapping cells populations, the level of FcR expression being a characteristc of each populations. FcRIII (CD16 antigen) is the low-affinity IgG Fc-receptor whLch is predominantly expressed on human natural killer (NK) cells and granulocytes. With the recent application of immunogold labelling for scanning electron microscopy (immuno-SEM) in the backscattered electron imaging (BEI) mode allow us to correlate antigenic expression with cell surface morphology. In this report we analize the expression and distribution of the CD16 (FcRIII) antigen on peripheral blood leukocytes as observed with immuno-SEM.

Material and Methods.Mononuclear cells (MC) were isolated from normal peripheral blood using Ficoll-Paque (Pharmacia Fine Chemicals, Uppsala, Sweden).
Guanosine triphosphatase activity demonstrated by freeze substitution enzyme histochemistry
Authors: Takizawa Toshihiro , Saito Takuma
Published: June 2020

During the past three decades, the freeze substitution fixation technique has been developed to observe fine morphology in close to the living state. Recently, this freeze substitution fixation has been successfully applied to enzyme histochemistry demonstrating the active sites of enzymes as well as their active state at the time of quenching. in this study, we have undertaken to study guanosine triphosphatase (GTPase), one of the key enzymes in the cGMP cascade, on the rod outer segment after freeze substitution fixation and have compared the results with those obtained from conventional immersion fixation enzyme histochemistry at the ultrastructural level.

Freeze substitution fixation: After Nembutal anesthesia, frog, Xenopus laevis, eyes were excised and the neural retinae were gently separated from the pigment epithelium. The retinae were then rapid frozen using a quick freezing device, the E7200 Slammer (Polaron, Equipment Ltd. England), contacting on an ultrapure copper block at -196°C of liquid nitrogen.
High-sensitivity detection of gold labels by high-angle dark-field STEM imaging
Authors: Otten Max T.
Published: June 2020

Labelling of antibodies with small gold probes is a highly sensitive technique for detecting specific molecules in biological tissue. Larger gold probes are usually well visible in TEM or STEM Bright-Field images of unstained specimens. In stained specimens, however, the contrast of the stain is frequently the same as that of the gold labels, making it virtually impossible to identify the labels, especially when smaller gold labels are used to increase the sensitivity of the immunolabelling technique. TEM or STEM Dark-Field images fare no better (Figs. 1a and 2a), again because of the absence of a clear contrast difference between gold labels and stain.

Potentially much more useful is backscattered-electron imaging, since this will show differences in average atomic number which are sufficiently large between the metallic gold and the stains normally used. However, for the thin specimens and at high accelerating voltages of the STEM, the yield of backscattered electrons is very small, resulting in a very weak signal. Consequently, the backscattered-electron signal is often too noisy for detecting small labels, even for large spot sizes.
The use of 1nm silver enhanced gold probes for the detection of skin antigens
Authors: Cassella J.P , Shimizu H. , Ishida-Yamamoto A. , Eady R.A.J.
Published: June 2020

1nm colloidal gold with silver enhancement has been used in conjunction with a low-temperature post-embedding (post-E) technique for the demonstration of skin antigens at both the light microscopic (LM) and electron microscopic (EM) levels.

Keratin filaments and basement membrane zone (BMZ) associated antigens in normal human skin (NHS) were immunolabelled using antibodies against keratin 14, 10, and 1, the carboxy-terminus and collagenous portion of type VII collagen, type IV collagen and bullous pemphigoid antigen (BP-Ag).

Fresh samples of NHS were cryoprotected in 15% glycerol, cryofixed in propane at -190°C, subjected to freeze substitution in methanol at -80°C and embedded in Lowicryl K11M at -60°C. Polymerisation of the resin was initiated under UVR at - 60°C for 48 hours and continued at room temperature for a further 48 hours. Semith in sections were air dried onto slides coated with 3-aminopropyltriethoxysilane. The following immunolabelling protocol was adopted: Primary antibody was applied for 2 hours at 37°C or overnight at 4°C. Following washing in Dulbecco’s phosphate buffered saline (PBSA) a biotinylated secondary antibody was applied for 2 hours at 37°C. The sections were further washed in PBSA and 1nm gold avidin was applied. Sections were finally washed in PBSA and silver enhanced.
The 215 KD mannose-6-phosphate receptor is involved in crinophagy but not in autophagy
Authors: Noda Toru , Bronson Mary L. , Yu Shang-Ming , Farquhar Marilyn G.
Published: June 2020

Autophagy and crinophagy represent the two major pathways for digestion of intracellular material via lysosomes have been described. Though both phenomena involve in corporation of cell organelles into lysosomes and thus degradation by lysosomal enzymes, the process by which autophagic and crinophagic vacuoles acquire lysosomal enzymes remains to be clarified. The aim of this work is to find out if mannose-6-phosphate (M6P) receptors are involved in this process. As a typical working model, we used hepatocytes of leupeptin-treated rats for autophagy (Fig. 1) and mammotrophs of female rats treated with estradiol for 6 days, for crinophagy. To localize the M6P receptor and lysosomal proteins, we carried out immunocytochemistry, using a immunoperoxidase pre-embedding technique and immunogold labeling on ultrathin frozen sections.

Many autophagosomes induced by leupeptin treatment contained recognizable mitochondria and rough ER. The configuration and fine structure of these organelles are gradually lost and the contents of the vacuoles become more homogeneous and electron-dense, suggesting that partial digestion of the contents of autophagosomes still occurs after leupept in treatment.
STM of nucleic acids
Authors: Bloomfield Victor A. , Arscott Patricia G.
Published: June 2020

Scanning tunneling microscopy (STM) enables remarkable visualization of surface topography with a vertical resolution of 0.2 Å and horizontal resolution of 2-3 Å. The possibility of visualizing nucleic acids at this high resolution has major significance, since the binding of proteins and other aspects of gene regulation depend on structural variations at the Å level. Conventional EM has the advantage over fiber diffraction or solution techniques that local structure of individual molecules can be seen, rather than averaging over entire molecules and populations of molecules. An added advantage of STM is that contrast is achieved by detection of sample height and work function variations, rather than by chemical treatments such as shadowing or staining.

We have used STM to measure the helical pitch, half-period oscillations interpreted as alternating major and minor grooves, and molecular diameters of poly(rA)-poly(rU) and DNA. Average pitches are measured by two-dimensional Fourier transforms and by topographic profile peak count vs.
Localization of myocin in Micrasterias cells by immunoelectron microscopy
Authors: Lehtonen Juhani , Suoranta Ulla-Maija
Published: June 2020

The unicellular green alga Micrasterias has a very differentiated form and is an excellent object for morphogenetic studies. The complicated cytoplasmic streaming system during development is an essential part of the morphogenetic process. The streamings are supported by the acto-myosin system. The presence of actin has been verified by fluorescence microscopy and both the act in-inhibitor cytochalasin B and the myosin inhibitor N-ethylmaleimide clearly inhibit the streamings.

This work deals with the localization of myosin in the cell. The methods used were immunoelectronmicroscopy, polyclonal antibody/gold probe, and cryosections. In old semicells, the gold-label localized only in vesicle structures. In growing semicells, the label was abundant in growing lobes, in all levels. In control samples, without antibody, there was no label.

According to the results, myosin seems to be part of the dictyosome vesicle membranes. This is clear in the case of old semicells. In growing lobes, the inner structure of the lobes was not preserved very well in cryosections, in any preparation, but there is good evidence that in new, growing parts of the cell there is generally very little material other than cell wall material vesicles. This idea is important for later studies on plant cell growth and cytoplasmic transport.
Quantitative HREM using non-linear least-squares methods
Authors: King Wayne E. , Campbell Geoffrey H.
Published: June 2020

Non-linear least-squares methods have been coupled with high resolution image simulation to determine the critical electron microscopic imaging parameters, such as thickness and defocus, from experimental high resolution electron optical images of yttrium aluminum garnet (YAG). For a quantitative fit between experimental and simulated images we seek to minimize the residual image fi(x) at each pixel,

(1)

where is the intensity value of the ith pixel in the experimental image, is the intensity value of the ith pixel in the simulated image based on the image model x, and W is the image that represents the uncertainty associated with measurement of the ith pixel in the experimental image.
Quantitative χn analysis of HREM images with applications to planar defects
Authors: Zhang H. , Marks L. D.
Published: June 2020

A number of different methods have been suggested in the literature for using HREM in a quantitative fashion, including R factors and cross-correlation analyses. The problem with many of these is that it is difficult to realistically gauge the errors involved when they are applied to real systems. For instance, R-factors defined by:

(1)

(where n=1 or 2 and Ic is the calculated image, Ie the experimental data) assume a signal independent error. Furthermore, the absolute value of R is strongly dependent upon background levels which is misleading.
High Resolution Electron Microscopy of InGaAs/InAIAs Interfaces
Authors: Mountjoy G. , Crozier P.A. , Fejes P.L. , Tsui R.K. , Kramer G.D.
Published: June 2020

Recently, quantum wells (QW) have been constructed using the (In0.532Ga0.468)As/ (In0.522Al0.478)As system (hereafter InGaAs/In Al As), which is lattice matched to InP (lattice constant of 5.869Å). In order to understand the properties of such QWs, it is important to have knowledge of the structure and composition of interfaces. For III-V materials, compositional changes affect the <200> frequency component of the high resolution electron microscopy (HREM) image intensity (I200). This underlies the “chemical imaging” approach. Simulations for InGaAs/InAlAs interfaces suggest optimum conditions of microscope defocus df=-50nm and sample thickness t=14nm in the <100> orientation. A double-QW structure, consisting of InGaAs/ InAlAs/ InGaAs layers with nominal thicknesses of 4nm/ 2nm/ 4nm (respectively), and embedded in InAlAs layers, has been studied. All the layers were grown by molecular beam epitaxy at 500°C on a <100> InP substrate, with 60s growth interrupts between layers in the QW region.
Calculations of electron inelastic mean free paths for carbides
Authors: Tanuma S. , Powell C. J. , Penn D. R.
Published: June 2020

Knowledge of the values of inelastic mean free paths (IMFPs) for low-energy electrons in solids is important for quantitative surface analysis by AES and XPS as well as for determining the surface sensitivity of other electron-spectroscopic methods of surface characterization. In previous papers, we have described the Penn algorithm for calculations of electron inelastic mean free paths in solids, and used this algorithm for calculations of IMFPs for 50 – 2000 eV electrons in a group of 27 elements, a group of 15 inorganic compounds, and a group of 14 organic compounds. We fitted the calculated IMFPs for the groups of elements and organic compounds to a modified form of the Bethe equation4 for inelastic electron scattering in matter and found that the four parameters in this equation could be related empirically to several material parameters. The resulting general formula TPP-2M for IMFPs in solids could be used to estimate IMFPs for other materials.
Ultra-low voltage scanning electron microscopy
Authors: Joy David C , Joy Carolyn S
Published: June 2020

Although the benefits of operating the scanning electron microscope at low beam energies have been evident since the earliest days of the instrument, the successful utilization of the SEM under these conditions has required the development of high brightness field emission electron source, advanced lenses, and clean vacuums. As these technologies became available the level at which imaging became regarded as “low energy” has fallen from 10keV, first to 5keV, and more recently to 1keV. At this energy state of the art instruments can now provide an excellent balance between resolution – which becomes worse with decreasing energy – and desirable goals such as the minimization of sample charging and the reduction of macroscopic radiation damage – which tend to become more challenging as the energy is increased.

An interesting new opportunity is to perform imaging in the ultra-low energy region between leV and 500eV. Over this energy range significant changes in the details of electron-solid interactions take place offering the chance of novel contrast modes, and the rapid fall in the electron beam range leads to the condition where the penetration of the incident beam into the sample is effectively limited to 1 or 2 nanometers. The practical problem is that of achieving useful levels of resolution and acceptable signal to noise ratios in the image. At energies below IkeV chromatic aberration dominates the probe formation in conventional instruments even when using an FEG source. However, the use of optimized retarding field optics essentially maintains chromatic aberration independent of landing energy down to very low values. Figure (1) shows an example of the performance that can be achieved on a commercial instrument – an Hitachi S-4500 – modified to operate in this mode, in this case at 50eV landing energy. The resolution of the image is judged from edge sharpness and detail to be significantly better than 0.1µm and, from experimental observation, this performance is apparently limited by residual astigmatism caused by uncorrected sample charging rather than by fundamental aberrations in the probe forming optics. Comparable, if somewhat lower resolution, images have been achieved on this, and other FEG SEMs, at energies as low as leV.
Energy-filtered imaging of constituent phases in polymer blends
Authors: Hall E. L. , Hutchins G. A.
Published: June 2020

Many engineering plastics consist of complex blends of chemically-distinct constituent polymers and other additives. These components are added in order to achieve desired performance in a variety of properties, including mechanical behavior, processability, color, fire retardency, and others. The distribution of the components, as well as the nature of the interfaces between constituents, are critically important to the performance of the engineering plastic. For many years, TEM has been the key tool in determining phase distribution. However, TEM studies are often limited by the need to stain the various constituents in order to achieve contrast, and also by the inability of TEM methods to unambiguously identify the chemical nature of the various constituents in the image. In the recent past, both electron energy loss spectroscopy (EELS) in the TEM and x-ray absorption near-edge spectroscopy (XANES) using synchrotron sources have demonstrated the ability to differentiate constituents based on characteristic carbon core loss edge structure. The EELS technique has the benefit of high spatial resolution, while the XANES method causes much less structural damage and mass loss. The advent of imaging energy filters has led to a third method for phase delineation for chemically distinct components, which combines the spatial resolution of EELS with the imaging capabilities of XANES.
The influence of surface topography in the adhesion of polystyrene to aluminum
Authors: Shaffer O. L. , Yankovskaya S. , Namkanisom A. , Chaudhury M. , El-Aasser M. S.
Published: June 2020

Polymer/metal adhesion has been studied by scanning(SEM) and transmission electron microscopy(TEM). Now with atomic force microscopy(AFM) we can scan the metal's surface and correlate the roughness with adhesion energy. We have chosen aluminum as the metal substrate and polystyrene(PS) as the nonreactive polymer adhesive. A great deal of research has been done on primed metal surfaces which are used to improve adhesion between the metal and the polymer. Our interest is to study the mechanical interlocking of the polymer to the metal without a primer coupling agent.

Aluminum alloy 6061 was cut into plates 25x60x1 mm, cleaned with an alkali cleaner, rinsed with water, etched and anodized. The plates were etched in a solution of Na2Cr2O7·2H2O, H2SO4, and water in a 1:10:30 ratio by weight at 50-52°C for 12-20 min. After etching , they were rinsed, dried and anodized in 10% phosphoric acid solution with 15 V for 20 min, then were rinsed and dried again.A 1% PS solution in toluene was deposited on the prepared aluminum surface and air dried.
Etching of LLDPE and LLDPE/HDPE blends
Authors: Bischel M. S. , Schultz J. M.
Published: June 2020

Despite its rapidly growing use in commercial applications, the morphology of LLDPE and its blends has not been thoroughly studied by microscopy techniques. As part of a study to examine the morphology of a LLDPE narrow fraction and its blends with HDPE via SEM, TEM and AFM, an appropriate etchant is required. However, no satisfactory recipes could be found in the literature. Mirabella used n-heptane, a solvent for LLDPE, as an etchant to reveal certain morphological features in the SEM, including faint banding in spherulites. A 1992 paper by Bassett included a TEM micrograph of an axialite of LLDPE, etched in a potassium permanganate solution, but no details were given.

Attempts to use n-heptane, at 60°C, as an etchant were unsuccessful: depending upon thickness, samples swelled and increased in diameter by 5-10% or more within 15 minutes. Attempts to use the standard 3.5% potassium permanganate solution for HDPE were also unsuccessful: the LLDPE was severely overetched. Weaker solutions were also too severe.
Polarized microbeam FT-IR analysis of single fibers
Authors: Cho Liling , Wetzel David L.
Published: June 2020

Polarized infrared microscopy has been used for forensic purposes to differentiate among polymer fibers. Dichroism can be used to compare and discriminate between different polyester fibers, including those composed of polyethylene terephthalate that are frequently encountered during criminal casework. In the fiber manufacturering process, fibers are drawn to develop molecular orientation and crystallinity. Macromolecular chains are oriented with respect to the long axis of the fiber. It is desirable to determine the relationship between the molecular orientation and stretching properties. This is particularly useful on a single fiber basis. Polarized spectroscopic differences observed from a single fiber are proposed to reveal the extent of molecular orientation within that single fiber. In the work presented, we compared the dichroic ratio between unstretched and stretched polyester fibers, and the transition point between the two forms of the same fiber. These techniques were applied to different polyester fibers. A fiber stretching device was fabricated for use on the instrument (IRμs, Spectra-Tech) stage. Tension was applied with a micrometer screw until a “neck” was produced in the stretched fiber. Spectra were obtained from an area of 24×48 μm. A wire-grid polarizer was used between the source and the sample.
Electron microscopy of Ni-Ti alloys for medical devices
Authors: Smith Gary A. , Hanke Larry D.
Published: June 2020

Nickel-titanium alloys (Ni-Ti) have many unique properties that make these alloys excellent prospects for a wide range of applications in medical devices. However, these desirable mechanical properties cannot by utilized for many medical devices if the alloys cause undesirable reactions in the body or corrode from contact with body fluids or tissue.

The chemical inertness of Ni-Ti alloys is dependent on a passive film formed on the metal surface. Manufacturing processes, sterilization procedures, and general handling of the devices can have significant effects on the surface condition, and therefore, the corrosion and biocompatible behavior of Ni-Ti alloys.

An understanding of the passivation of Ni-Ti alloys, including the effects of mechanical processes, heat treating, and chemical surface alterations, is critical to ensure the benign presence medical devices in the human body.
Investigation of film formation in water-distribution systems by field emission sem and spectroscopy techniques
Authors: Liu J. , Friedman R. M. , Cortez E. , Pacholec F. , Vesecky S. M.
Published: June 2020

EPA has set limits on the concentration of heavy metals in drinking water supplies to protect the public health. Furthermore, the failure of pipes in the water distribution system from corrosion represents a massive investment in rebuilding its infrastructure. We have initiated a program to study the formation of corrosion-inhibition films formed in potable water delivery systems using various chemical phosphate treatments. In particular, blends of ortho- and polyphosphates have recently been used to reduce both lead and copper leaching. Several factors are important to the successful implementation of the phosphate technologies, including film thickness and porosity, rate and stability of formation and water quality conditions. In an attempt to understand the performance of these phosphate blends, advanced analytical techniques have been employed to study the nucleation and growth mechanisms of the passivation films in a variety of water systems. We report here some preliminary results on the study of the film formation by field emission scanning electron microscopy (FESEM) technique.
The stabilization of B.C.C. Cu in Cu/Nb nanolayered composites
Authors: Kung H. , Griffin A.J. , Lu Y.C. , Sickafus K.E. , Mitchell T.E. , Embury J.D. , Nastasi M.
Published: June 2020

Materials with compositionally modulated structures have gained much attention recently due to potential improvement in electrical, magnetic and mechanical properties. Specifically, Cu-Nb laminate systems have been extensively studied mainly due to the combination of high strength, and superior thermal and electrical conductivity that can be obtained and optimized for the different applications. The effect of layer thickness on the hardness, residual stress and electrical resistivity has been investigated. In general, increases in hardness and electrical resistivity have been observed with decreasing layer thickness. In addition, reduction in structural scale has caused the formation of a metastable structure which exhibits uniquely different properties. In this study, we report the formation of b.c.c. Cu in highly textured Cu/Nb nanolayers. A series of Cu/Nb nanolayered films, with alternating Cu and Nb layers, were prepared by dc magnetron sputtering onto Si {100} wafers. The nominal total thickness of each layered film was 1 μm. The layer thickness was varied between 1 nm and 500 nm with the volume fraction of the two phases kept constant at 50%. The deposition rates and film densities were determined through a combination of profilometry and ion beam analysis techniques. Cross-sectional transmission electron microscopy (XTEM) was used to examine the structure, phase and grain size distribution of the as-sputtered films. A JEOL 3000F high resolution TEM was used to characterize the microstructure.
Nucleation and growth of Si quantum nanocrystals in silicon-rich oxide films
Authors: Mehta S. C. , Smith D. A. , Libera M. R. , Ott J. , Tompa G. , Forsythe E.
Published: June 2020

The observation of photoluminescence and electroluminescence in Si nanocrystals has generated renewed interest in these novel silicon based materials for their possible application as light emitters and detectors. Silicon Rich Oxide (SRO) films with a uniform dispersion of silicon nanocrystallites in a wider bandgap SiO2 matrix manifest electroluminescence and photoluminescence in the infrared and visible portions of the spectrum. Understanding the nucleation and growth kinetics of these crystallites in amorphous matrix is of critical importance in the fabrication of future optoelectronic devices. One route to the fabrication of Si nanocrystals is by the crystallization of amorphous SiO2-x. Consider the case when x=1. The reaction leading to the formation of Si crystallites can be written as;

(1)

The nucleation, growth and coarsening processes of Si nanocrystals each require bulk diffusion of Si atoms through the amorphous matrix.
TEM study of CdS nanocrystals formed in SiO2 by ion implantation
Authors: Zhu Jane G. , White C. W. , Budai J. D. , Withrow S. P.
Published: June 2020

Quantum confinement effects and enhanced optical nonlinearity are expected from II-VI semiconductor nanocrystals, which are important for novel opto-electronic device applications. The ion implantation method has been used in our study to form CdS nanocrystals inside amorphous SiO2. The CdS nanocrystals were studied by transmission electron microscopy (TEM).

The samples were implanted (at room temperature) with equal doses (1×1017 ions/cm2) of Cd and S into a SiO2 layer on (100) silicon substrates and then annealed under Ar + 4%H2 ambient at 800°C and 1000°C for 1 h. Implant energies were chosen to overlap the Cd and S ion profiles in the middle of the oxide layer. CdS precipitates are formed during the thermal annealing.

The effect of annealing temperatures on the nanocrystals size distributions are revealed in Figs. 1 and 2. The sizes of CdS nanocrystals are in the range of 2 - 11 nm for the sample annealed at 800°C, and in the range of a few to 16 nm for the sample annealed at 1000°C.
Microscopic radiography: A combined technique for improved analytical microscopic analysis and interpretration
Authors: Angel A. , Moretz R.C.
Published: June 2020

Microscopic analysis of pharmaceutical devices and products relies primarily on destructive sample preparative methods, including sectioning, sawing, grinding and embedding. Reconstruction of images obtained from the prepared samples is often necessary to interpret the results. The preparative methods can introduce artifacts or distortion, which can affect the analysis, and the inability to visualize the intact object can also affect the interpretation. Radiography has been used to assist in the selection of preparative methods for microscopy, determine optimal orientation during preparation and analysis and to aid in the visualization and integration of the microscopic results in the final interpretation. The application of x-ray radiography to the examination of intact devices or manufactured drug products in conjunction with standard light and scanning electron microscopic evaluation presents a novel non-destructive technique to assess device structure and function as well as locate potential inclusions in manufactured drug products.
Raman imaging in the real world
Authors: Morris Michael D. , Christensen Kenneth A. , Bradley Nancy L.
Published: June 2020

Recent technological advances including high spectral resolution liquid-crystal tunable filters and high-transmission well-corrected imaging spectrographs have made Raman microscopy a practical technique for study of real-world chemical systems. With modem multivariate signal processing techniques, such as image reconstruction and principal components analysis (PCA) detailed information can be obtained from sets of relatively noisy images or spectra. In this talk we discuss techniques and results in two areas of materials chemistry: crystallization and freeze-drying mechanisms of alkali phosphates and strengthening mechanisms of glasses employed in dental restoration.

We employ Raman microspectroscopy to elucidate the structure of aqueous phosphates in solutions ranging in concentration from dilute to supersaturated. PCA of the concentration-dependent spectra of dihydrogen phosphate solutions unambiguously demonstrates the presence of at least three species, monomer, dimer and trimer or short polymer (Figure 1). PCA resolves long-standing disputes over the number and relative concentration of dihydrogen phosphate species PCA can to identify the spectrally unresolved solution species near the surface of a growing dihydrogen phosphate crystal.
FTIR analysis of printed-circuit board residue
Authors: Myers Sharon A. , Cognata Troy D. , Gotts Hugh
Published: June 2020

Logic boards were failing at Enhanced Mac Minus One (EMMO) test or Integrated Circuit Test (ICT) after printed circuit board (PCB) rework. The failure to boot was originally traced to a suspected bad microcontroller chip. Replacing this chip, or an oscillator tied to the microcontroller circuit, did not consistently solve the boot problem. With further testing, it was found the microcontroller circuit was very sensitive to resistance and was essentially shorted.

A resistor in the microcontroller circuit was identified on the flip side of the PCB. Several areas on the board, including the resistor R161, were seen to have a slight white haze/ low gloss appearance on the surface of the PCB. To test if the residue was electrically conductive, five boards were selected whose sole failure was R161. The resistance of the individual resistors was measured with a digital multimeter (DMM). The resistor was then cleaned with isopropyl alcohol and a cotton swab. Each board was retested at ICT and the individual resistors measured again with a DMM. Cleaning the area surrounding the resistor with isopropyl alcohol, corrected the failure four of the times.