Scanning Electron Microsopy Research Articles

Sol–gel derived cerium-oxide–silicon-oxide nanocomposite for cypermethrin detection

Cerium oxide (CeO 2) nanoparticles have been self-assembled onto sol–gel derived silicon-oxide (SiO 2) film fabricated onto indium tin oxide (ITO) coated glass plate. These SiO 2–CeO 2 nanocomposite films have been used to immobilize the double stranded calf thymus deoxy ribose nucleic acid (dsCT-DNA) by physical adsorption to detect cypermethrin (CM). Both CeO 2–SiO 2/ITO electrode and dsCT-DNA/CeO 2–SiO 2/ITO bioelectrodes have been characterized using Fourier transform infrared (FTIR) spectroscopy, scanning electron microsopy (SEM) and differential pulse voltammetry (DPV) to confirm the formation of CeO 2–SiO 2 nanocomposite and binding of dsCT-DNA with CeO 2–SiO 2 nanocomposite. Electrochemical response studies of dsCT-DNA/CeO 2–SiO 2/ITO bioelectrode carried out as a function of CM concentration using DPV technique exhibit detection limit up to 0.0025 ppm with response time of 30 s.

Nano-hydroxyapatite preparation from biogenic raw materials

Abstract Hydroxyapatite (HAp) was successfully produced from recycled eggshell, seashell and phosphoric acid. The phases obtained depended on the ratio of calcined eggshell/ seashell to phosphoric acid, the calcination temperature and the mechanochemical activation method (ball milling or attrition milling). The HAp structures were characterized by X-ray diffraction, scanning electron microsopy and infrared spectroscopy. Attrition milling was more effective than ball milling, yielding nanosize, homogenous and pure Hap.

Fe doping effect on structural properties of [formula omitted

Since the discovery of the high temperature superconductivity in the Bi-Sr-Ca-Cu-O system , many investigations have focused on it to understand its properties and to improve them. Belonging to this system, the Bi2Sr2CaCu2O8+d (Bi-2212) phase has been widely studied in the recent years in order to understand, by various kinds of substitution, the relation between the structure and the superconductivity. Most of these substitutions have concerned the Cu site in the superconducting layer CuO2. Among these, as showed by G. Ilonca et al., the substitution by Fe kills the superconductivity at a lower concentration than Ni. At our knowledge, nothing has been made when there is in the same time a substitution by lead (Pb) on the Bi site. For that purpose samples of Bi1.6Pb0.4Sr2CaCu2−xFexO8+δ with x=0–0.06, have been prepared using the solid state reaction technique. The samples have been characterized by X-ray diffraction (XRD) and scanning electron microsopy (SEM). Structural analysis shows the influence of the Fe doping on the crystalline lattice structure of the samples.

Effect of Gelatin on the Performance of Cerium-Based Conversion Coatings

Cerium-based conversion coating process for corrosion protection is a potential replacement of chromates. However, there are still some defects such that the processing time is too long and the conversion coatings are not thick enough. The experiment proves that compared to non-added animal gelatin in corrosion-inhibiting cerium solution, the added one improves the deposition rate. After post-treatment process in phosphate, the surface morphology of the coatings is tested by scanning electron microsopy (SEM), the chemical composition of the protective films have been examined by energy-dispersive Spectrometer (EDS) and thickness of films is measured by coating thickness gauge.

Pollen morphology within the Monodora clade, a diverse group of five African Annonaceae genera

Pollen morphology has played a major role in elucidating infrafamiliar‐level systematics and evolution within Annonaceae, especially within the African genera. The Monodora clade is composed of five genera, Asteranthe, Hexalobus, Isolona, Monodora and Uvariastrum, which are restricted to Africa and contain together c. 50 species. A molecular phylogeny of the family showed that the monophyly of the Monodora clade is strongly supported and that it is part of a larger clade of 11 African genera. In order to support classification a detailed survey was made of the pollen morphological variation within the Monodora clade, using scanning and transmission electron microsopy. For the two most species‐rich genera, Isolona and Monodora, a molecular species‐level phylogeny was used to assess the taxonomic usefulness of the pollen characters. The survey showed a wide range of pollen morphological diversity. The most conspicuous variation concerned the occurrence of monads without a thicker outer foliation in the basal exine layer in Isolona in contrast to tetrads with a thicker outer foliation in Asteranthe, Hexalobus, Monodora and Uvariastrum. At the infrageneric level, Hexalobus, Isolona and Monodora showed the largest diversity, with various pollen types based on tectum morphology. Hexalobus is exceptional with three types within only five species. The pollen types defined in this study are hardly useful in characterizing major groups identified within both Isolona and Monodora, but they do illustrate relationships within smaller groups.

Uranium colloid analysis by single particle inductively coupled plasma-mass spectrometry

Uranium single particle analysis has been performed by inductively coupled plasma-mass spectrometry (ICP-MS) and the performances are compared with that provided by scanning electron microsopy and single particle counting. The transient signal induced by the flash of ions due to the ionisation of an uranium colloidal particle in the plasma torch can be detected and measured for selected uranium ion masses ( 238U +, 235U + or 254[ 238U 16O] +) by the mass spectrometer. The signals recorded via time scanning are analysed as a function of particle size or fraction of the studied element or isotope in the colloid phase. The frequency of the flashes is directly proportional to the concentration of particles in the colloidal suspension. The feasibility tests were performed on uranium dioxide particles. The study also describes the experimental conditions and the choice of mass to detect uranium colloids in a single particle analysis mode.

Fabrication and analysis of GaN nanorods grown by MBE

GaN nanorods were grown on c-plane sapphire substrates under N-rich conditions by plasma-assisted molecular-beam epitaxy. Scanning electron microsopy revealed densely packed nanorods of hexagonal cross section with diameters ranging from roughly 40 to 100 nm. Atomic force microscopy indicated that the rods protruded 50 to 75 nm above the average height of the surface. Transmission electron microscopy (TEM) showed that the nanorods were approximately 1.4 micrometers in length but an accurate measurement of the rod separation was difficult to assess. Contrary to expectations for GaN grown under N-rich conditions, a high density of basal plane stacking faults were not revealed in TEM under typical imaging conditions. X-ray diffraction using the (0002), (0004), (0006), (104), and (105) reflections yielded c = 0.5188 ± 0.0002 nm and a = 0.3188 ± 0.0004 nm. Low temperature photoluminescence and cathodoluminescence showed broad near-bandgap emission around 3.4 eV that shifted to the blue with reduced temperature in the usual manner, and the presence of a similarly blue-shifting peak near 3.2 eV. The spectra were deconvolved using nine lineshape functions revealing 2 phonon replicas asssociated with the peak near 3.2 eV. Room temperature spectroscopic reflection fited to the standard Aspnes third-derivative lineshape function yielded a transition energy of 3.407 eV for the A exciton and 3.490 eV for the B+C excitons (not spectrally resolved). Both the x-ray and photoreflectance results indicate that the nanorods are fairly relaxed. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Studies on the Fine Structure of Caeca in Domestic Geese

The objective of this study was to investigate the villus distribution in the caeca of domestic geese based on the fine structure. The caeca of White Roman geese, 14-week old, were sampled and specimens were detected under photomicroscope and scanning electron microscope (SEM). The results indicated that the villi existed at the proximal caecum. The morphologies of these villi showed finger-like, peak-like or tongue-like shapes. The heights of the villi decreased far from the proximal caecum. No villi were found in the middle and distal caecum. It was obvious that the proximal segment was the main portion for absorbing food nutrients in the caeca. The caecal content particles were small and possessed a viscid character. The large particles filtered out at the proximal caecum just like a mesh. The surface of the middle caecum exhibited parallel ridges with no villi. There were band plicae circular shapes found in the middle caecum under scanning electron microsopy.

Wear behavior of PACVD tin coatings deposited onto tool steels

During cold forming processes like deep drawing of steel sheets, tools are subjected to various loads. During forming, Hertzian contact pressures and frictional forces cause fatigue and adhesion, respectively. Abrasion may take place if wear particles are entrapped in the contact zone. Therefore, the aim of this work is to evaluate TiN coatings deposited by plasma assisted chemical vapor deposition (PACVD) onto tool steels with respect to adhesion, fatigue wear properties. Stoichiometric TiN coatings with different morphologies were deposited with and without plasma-nitriding of the steel substrate and characterized by X-ray diffraction (XRD) and scanning electron microsopy. The adhesion of the coatings was investigated using the VDI indention test and a surface fatigue test, where cyclic loads up to 80 kN are applied to the tool surface by cylindrical indenters. Adhesive wear of the coatings have been evaluated using a ball-on-disc tribometer. Abrasion resistance was characterized using a small-scale abrasive wear test.

Nucleation and crystallization of blends of poly(propylene) and ethylene/α-olefin copolymers

In this work, the nucleation and crystallization of immiscible blends of poly(propylene) (PP) with ethylene/α-olefin copolymers of different branching contents (Linear Low Density Poly(ethylene), LLDPE, Very Low Density Poly(ethylene), VLDPE, and Ultra Low Density Poly(ethylene), ULDPE) were studied. Melt-mixed blends of LLDPE/PP, VLDPE/PP and ULDPE/PP were prepared covering a wide composition range by means of twin screw extrusion. Additionally, blends containing 0.1% of the nucleating agent Sorbitol were prepared. The thermal behaviour of the blends was studied by means of Differential Scanning Calorimetry (DSC) whereas the morphology was investigated by means of Scanning Electron Microsopy. When PP droplets constituted the dispersed phase of the blends, fractionated crystallization of the PP component lead to coincident crystallization with the ethylene/α-olefin matrix, regardless of the branch content of the copolymer. This complex crystallization process occurred when a small fraction of PP droplets initiated the crystallization upon cooling, causing nucleation of the ethylene/α-olefin copolymer matrix and subsequently simultaneous crystallization of the rest of the PP droplets and the matrix. The fractionated crystallization process disappears if nuclei capable of being active at low supercooling are injected in any of the blends. The injection of nuclei was achieved by the use of sorbitol (a powerful nucleating agent for α-PP) or by self-nucleation of the PP component. When PP constituted the matrix in the blends, a nucleation process of the ethylene/α-olefin copolymers was observed. The nucleation of the ethylene/α-olefin copolymers by PP, sorbitol or PP/sorbitol mixture was found to be particularly effective for the most linear chains within the wide chain branching distribution present in these copolymers. A peculiar synergistic nucleation effect on LLDPE was produced by the addition of a mixture of PP and sorbitol. Even the addition of 1% PP and 0.1% sorbitol was enough to produce a very strong nucleation effect on the LLDPE, only comparable to that caused by self-nucleation.

Porphyromonas gingivalis virulence factors and invasion of cells of the cardiovascular system.

Our laboratory is interested in the genes and gene products involved in the interactions between Porphyromonas gingivalis (Pg) and the host. These interactions may occur in either the periodontal tissues or other non-oral host tissues such as those of the cardiovascular system. We have previously reported the cloning of several genes encoding hemagglutinins, surface proteins that interact with the host tissues, and are investigating their roles in the disease process. Primary among these is HagA, a very large protein with multiple functional groups that have significant sequence homology to protease genes of this species. Preliminary evidence indicates that an avirulent Salmonella typhimurium strain containing hagA is virulent in mice. These data indicate that HagA may be a key virulence factor of Pg. Additionally, we are investigating the invasion of primary human coronary artery endothelial cells (HCAEC) by Pg because of the recent epidemiological studies indicating a correlation between periodontal disease (PD) and coronary heart disease (CHD). We found that some, but not all, strains of Pg are able to invade these cells. Scanning electron microsopy of the infected HCAEC demonstrated that the invading organisms initially attached to the host cell surface as aggregates and by a "pedestal"-like structure. By transmission electronmicroscopy it could be seen that internalized bacteria were present within multimembranous compartments localized with rough endoplasmic reticulum. In addition, invasion of the HCAEC by Pg resulted in an increase in the degradation of long-lived cellular proteins. These data indicate that Pg are present within autophagosomes and may use components of the autophagic pathway as a means to survive intracellularly. However, Pg presence within autophagosomes in KB cells could not be observed or detected. It is therefore likely that Pg uses different invasive mechanisms for different host cells. This and the role of HagA in invasion is currently being investigated further.

Structure and Elemental Compositon of Grape Berry Stomata

Former SEM work without cryotechnique of the fruit surface had shown grape ( Vitis vinifera L.) berry stomata surrounded by large, conspicuous protuberant tissue. This led to speculation of artifacts resulting from microscopic preparation techniques. This work examined the existance of these alleged protuberances and a possibly distinguished tissue by low temperature scanning electron microsopy (LT-SEM), freezesectioning, energy dispersive X-ray analysis, and light microscopy with staining. LT-SEM showed that peristomatal protuberances of up to 200 Jlm diameter developed two weeks after anthesis in all four grape cultivars examined and consisted of small, compact cells of 10 to 15Jlm length. These cells were distinctly different from the typically larger cells (30-40 Jlm) in the epidermis, hypodermis and outer fruit pericarp. Energy dispersive X-ray analysis revealed no differences in the distribution of sulphur, chlorine and iron between the peristomatal protuberance and non-protuberant tissue. Although potassium concentrations in the peristomatal protuberance were low, silicon and calcium were abundant in marked contrast to the non-protuberant tissue. During the later stages of fruit development, polyphenolics accumulate preferentially in the protuberant tissues and these specialised structures become heavily suberised.

Characterization of Low Temperature Soluble Polyaniline

Because the charging of polyaniline films occurs in the bulk of the material rather than exclusively at the polymer-electrolyte interface, the use of thick polymer films for battery applications is justifiable. Here, we present a method for producing soluble polyaniline which can be cast to form free-standing films. Investigation by scanning electron microsopy (SEM) has shown that these films are significantly more compact than those made by standard electropolymerization.

Systematic and phylogenetic significance of the seed coat in the shrubby African Iridaceae, Nivenia, Klattia and Witsenia

MANNINGJ. C. & GOLDBLATT, P., 1991. Systematic and phylogenetic significance of the seed coat in the shrubby African Iridaceae, Nivenia, Klattia and Witsenia. The seeds of Nivenia, Klattia and Witsenia, a natural alliance within Nivenioideae, are among their most distinctive features, and seed number and shape constitute at least two synapomorphies for this monophyletic lineage. In this paper we survey the structure of the seed surface of five species of Nivenia and one each of Klattia and Witsenia by scanning electron microsopy (SEM), and study the development of the seed coat in a representative species of each of the three genera. Outgroups for comparison were selected from genera inside and outside the subfamily. The six genera of Nivenioideae are united in having a 3 (– 2) seriate outer integument but the shrubby genera are unique in the family in their tangentially flattened ovules which mature into depressed, flat, scutiform seeds. They display a range of variation in seed coat characters but are specialized in the subfamily and family in having a transparent outer integument. Other genera have pigmented deposits in the outer epidermis of the outer integument. Nivenia and Witsenia are further specialized in having a partially exfoliating outer integument. Klattia is unique among the shrubby genera in having deposits in the second layer of the tegmen, in retaining an intact outer epidermis of the tegmen, and in the fusiform shape of the epidermal cells and striate surface of the seed. Our results are incorporated in a cladogram that expresses our current understanding of the phylogenetic relationships of Nivenioideae.

Sulfur segregation to the metal oxide interface during the early stages in the oxidation of iron

AbstractIron (110) single crystals have been studied during the early stages of their oxidation at 800°C at an oxygen flux equivalent to a pressure of 2 × 10−5 Torr. Depth profiles using Auger electron spectroscopy (AES) determined that if sulfur was present on the metal surface before the oxidation then sulfur was present at the internal metal/oxide interface after a 20 minute oxidation. Oxidation of a clean surface resulted in very little sulfur at the internal metal/oxide interface after the same oxidation exposure even though sufficient time was available for sulfur to accumulate at that interface. The interpretation of the AES data was complicated by the non‐uniformity of the oxide growth. The oxide morphology was found to depend on the amount of sulfur on the free surface just prior to oxidation. A model for this growth was developed that was consistant with both the AES depth profiles and scanning electron microsopy (SEM) observations of the oxide surface morphology.

Enhanced contrast SEI/TEM of polymer membranes

Specimen preparation for the characterization of polymers requires special handling to ensure that the in situ structures are observed. In the case of polymer membranes the situation is more difficult than usual as these thin, porous films are delicate and may collapse upon drying. Standard embedding and microtomy are often not possible due to this soft, collapsable texture. When microtomy is successful the resulting sections usually exhibit poor contrast due to their low atomic number. Scanning electron microsopy (SEM) of fractured cross-sections often reveals collapsed textures. Surface analysis also has limited resolution. The subject of this paper is to describe the enhanced contrast methods developed for both the secondary electron imaging (SEI) and transmission electron microscopy (TEM) of polymer membranes for three dimensional structure characterization.

An atlas of polymer damage — Surface examination. by Scanning Electron Microsopy Edited by L. Engel, H. Klingeh, G. W. Ehrenstein and H. Schaper. Wolfe/Hanser, 1981. Pp 7 + 256

An atlas of polymer damage — Surface examination. by Scanning Electron Microsopy Edited by L. Engel, H. Klingeh, G. W. Ehrenstein and H. Schaper. Wolfe/Hanser, 1981. Pp 7 + 256

Incus in Normal Ears and in Chronic Otitis Media

100 incudes were examined by scanning electron microsopy. These consisted of 25 normal cadaver incudes and 75 incudes removed during operation for chronic otitis media. In all cases the normal incudes showed depressions in the surface. Incudes removed because of chronic infection had all their long process destroyed and all stages of erosions were present also in the short process and in the corpus. Mucosa and submucosa were pathological in most cases of incudes from chronic infected ears. As auto- or homotransplants in tympanoplasty incudes should probably be denaturated before use.

799 “SPHEROCYTOSIS” IN SICKLE CELL ANEMIA

The hematologic hallmark of sickle cell disease is the irreversibly sickled cell (ISC) a shrunken, dehydrated cell which resists hypotonic lysis. Less well recognized in sickle cell disease is another population of cells geometrically “spherocytic” with decreased surface area to volume ratio and increased osmotic fragility. In 59 stable patients with HbSS, we determined hematologic values, ISC counts, the proportion of red cells identified by Nomarski optics as containing “pits”, and the proportion of osmotically labile cells. 80% of HbSS patients had an abnormal osmotic fragility curve characterized by a “tail” of hypotonically labile cells whereas none of the normal controls lysed in solutions less hypotonic than 0.5% saline. In patients with abnormal curves, 0.55% buffered saline hemolyzed 3.0 ± 2.7% of cells. HbSS patients with osmotically fragile cells had more ISC's (22 vs. 11%), lower Hgb's (7.7 vs. 8.5gm%), more reticulocytosis (20 vs. 15%) and lower Hb F values (7 vs. 12%) (p < 0.05 for all). Scanning electron microsopy of peripheral blood revealed ISC's and irregularly contoured spherocytic cells. In the group with abnormal fragility, the proportion of osmotically labile cells correlated inversely with Hgb, positively with reticulocyte count, positively with MCHC, and surgical splenectomy status (p < 0.05 for all); those with splenectomy had more spherocytic cells. This proportion did not correlate with “pit count”, age (after 2 years), the patient's sex, or MCV. These results indicate that in addition to ISC's, a second population of damaged erythrocytes characterized by increased osmotic lability circulate in patients with sickle cell disease and may be important in the pathogenesis of anemia.

Mechanism on the differentiation of microridges

Scanning electron microsopy reveals that the free surfaces of epithelial cells lining the developing human lingual epithelium exhibit characteristic changes of microridges. The microridges are approximately 0.1-0.17μin width and of variable length. The microridges take straight, curved and branched forms. According to developmental stages, the varied forms of microridges are classified into five types, i.e., type I; microvilli, type II; short straight microridges, type III; curved microridges, type IV; branched microridges, and type V; the cell surface with micropits. It is considered that these morphological changes from type I to type V in development, occur as a result of the fusion of microvilli and microridges. Mechanisms of microridge formation and arrangements of epithelial cells with various types of microridges are discussed.