Aid Of Transmission Electron Microscopy Research Articles

Facile Synthesis of Mesoporous TiO2 Spheres with Hollow Interiors

The Mesoporous TiO2 hollow spheres are synthesized by a solvothermal reaction without any surfactant and template. The reaction conditions such as reaction temperature, type of precursor, solvent used and their influence on the synthesis of TiO2 hollow spheres are investigated. The synthesized TiO2 hollow spheres are characterized by X-ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy (SEM), focused ion beam (FIB) SEM, Barrett-Emmett-Teller (BET) surface areas, and UV-visible diffused reflectance spectroscopy. The synthesized TiO2 spheres have obtained different diameters ranging from 700 nm to 1.79 μm at different reaction temperatures. The shell is composed of numerous single crystalline nanoparticles. The morphology and interiors of the spheres strongly depend upon the experimental parameters such as reaction temperature and a kind of solvent. Especially, interiors of TiO2 hollow spheres such as mesoporous, double shell and single wall structures at various reaction temperatures are discussed with the aid of TEM and FIB SEM measurements.

Boundary Line of Microcrystallites in Amorphous and Crystalline Structures of Metallic Glasses

In a recent study conducted by the author, microcrystallites were observed to exist in amorphous, short range ordered, structures of several metallic glasses. The observation is based on X-Ray Diffraction (XRD) and Electron Diffraction (ED) and Transmission Electron Microscopy (TEM). The data from the X-ray diffraction shows that the metallic glasses have typical amorphous structures. However, the data from the Electron Diffraction indicates that the metallic glasses possess polycrystalline structures. This discrepancy between the XRD and ED data can be interpreted and explained by diffraction theory [1,2] with the aid of Transmission Electron Microscopy. In fact results in the recent work show that with a mathematical relationship originally derived by Sherrer [1], one can determine the boundary line between microcrystallites in amorphous, short range ordered, structures and crystalline, long range ordered, structures. The boundary line of microcrystallites is defined with the aid of Transmission Electron Microscopy in which the size of subgrains, of the metallic glasses was determined from the mathematical relationship.

The root causes of the “Black pad” phenomenon and avoidance tactics

The “black pad” phenomenon of Ni-P electroless plating has been one of the serious electronics failures in the market although this plating is known to be a useful barrier coating against oxidation. To understand the mechanism of this phenomenon, the weak interfaces of Ni-P plating soldered with leaded and lead-free solders have been analyzed with the aid of transmission-electron microscopy. Two causes of degradation are described in this paper. One is the initial degraded Ni-P plating covered with gold thin plating. In this case, the surface of the Ni-P plating was locally corroded to form a sparse amorphous oxide structure beneath the gold plating. The other is the extreme interface reaction between the Ni-P plating and solders. Based on the findings, it was concluded that the quality of the Au/Ni-P plating and the process conditions of soldering are to be carefully controlled.

Effect of rotational speed of twin screw extruder on the microstructure and rheological and mechanical properties of nanoclay‐reinforced polypropylene nanocomposites

AbstractThe morphology and rheological and mechanical properties of nanoclay‐reinforced polypropylene nanocomposites were investigated with aid of transmission electron microscopy (TEM), thermo gravimetric analysis, rheometry, and mechanical tests. The organically modified silicate (montmorillonite) was used as a reinforcing material and maleic anhydride‐grafted polypropylene oligomer as a compatibilizer to improve the clay dispersion and adhesion. The object of the study was to examine the effect of screw speed of the co‐rotating twin‐screw extruder on the clay exfoliation and nanocomposite properties. Also, the effect of compatibilizing agent was taken into account. The main result of the study was that nanocomposites showed both intercalated and exfoliated structures depending on the screw speeds of extruder. TEM images revealed that the dispersion of silicate layers was greatly influenced by the screw speed. However, even when the silicate layers were highly exfoliated, there was no remarkable effect on mechanical properties of the nanocomposite. POLYM. ENG. SCI. 46:995–1000, 2006. © 2006 Society of Plastics Engineers.

Dielectric-breakdown-induced epitaxy: a universal breakdown defect in ultrathin gate dielectrics

The breakdown phenomena in SiO/sub x/N/sub y/ (EOT=20 /spl Aring/) gate dielectric under a two- stage constant voltage stress in inversion mode are physically analyzed with the aid of transmission electron microscopy. The results show that dielectric-breakdown-induced epitaxy (DBIE) remains as one of the major failure defects responsible for gate dielectric breakdown evolution even for a stress voltage as low as 2.5 V. Based on the results, the same failure mechanism i.e., presence of DBIE would be responsible for the degradation in ultrathin gate dielectrics for gate voltage below 2.5 V. It is believed that DBIE will be present in MOSFETs failed at nominal operating voltage.

Tissue Pool Neutrophils of the Bovine Mammary Gland: Ultrastructural Features During In Vitro Senescence

The aim of the study was to verify whether the in vitro senescence process of tissue pool neutrophils of the bovine mammary gland is accompanied by similar changes of ultrastructure as typically occurs in in vivo conditions. The experiments were carried out in four clinically healthy, Holstein x Bohemian Red-Pied crossbred heifers aged 14-16 months. With the aid of transmission electron microscopy (TEM), scanning electron microscopy (SEM) and flow cytometry (FCM), neutrophil apoptosis in vivo was detected and during senescence it was monitored in vitro. The neutrophil apoptosis comprised three ultrastructurally different stages: (1) karyopyknosis, (2) zeiosis, and (3) apoptotic bodies. These stages were obvious in the apoptotic neutrophils both in vivo and in vitro. In addition to the common morphological signs, however, ultrastructural differences were also detected in apoptotic neutrophils in vitro. These in vitro ultrastructural differences mostly comprised hyper-vacuolation of the cytoplasm with mega-vacuoles and secondary necrosis of apoptotic neutrophils. Morphological features of apoptosis during in vitro senescence of tissue pool neutrophils of the bovine mammary gland were shown to be in close accordance with these in vivo signs.

Correlation between the nanomechanical properties and microstructure of ultrafine-grained copper produced by equal channel angular pressing

Ultrafine-grained copper was manufactured by equal channel angular pressing technique. Microstructural observations performed with the aid of transmission electron microscopy and scanning force microscopy revealed that short annealings of as-pressed material in the temperature range 250–300 °C result in a duplex microstructure consisting of micrometer-sized and relatively defect-free recrystallized grains embedded in the untransformed ultrafine-grained matrix. It was found that the nanohardness of newly nucleated grains in partly recrystallized samples is very different from the nanohardness of untransformed matrix, the latter being identical with the nanohardness of as-pressed samples. Extensive pile-ups around the indents were observed in the as-pressed samples, while the pile-ups were virtually non-existent in the sample annealed at high temperature. In as-pressed samples the pile-ups relaxed with time at room temperature. Grain boundary sliding was suggested as a possible mechanism of this relaxation.

Spermiogenesis in the pseudophyllid cestode Eubothrium crassum (Bloch, 1779).

Spermiogenesis of the pseudophyllidean tapeworm Eubothrium crassum has been described by the aid of transmission electron microscopy for the first time. Initially, early spermatids form a distal cytoplasmic protrusion, a differentiation zone containing a small electron-dense, apically oriented region. Out of this region, two centrioles with rootlets develop. The centrioles become orientated in the same plane with the appearance of an intercentriolar body. Now, the long axes of the rootlets are parallel with each other and with the long axis of the nucleus. Two flagella of subsequently unequal length are formed very rapidly. Simultaneously, a median cytoplasmic process (MCP) develops distal to the flagella. Two arching membranes appear at the base of the differentiation zone. Each flagellum, still being in contact with an intercentriolar body, rotates to a position parallel with the MCP. The nucleus migrates very rapidly into the MCP at this stage. Subsequently, the two flagella fuse with the MCP. Finally, the basal bodies with the rootlets detach from the flagella, the intercentriolar body changes its structure and spermatids are pinched off from a condensing residual cytoplasm at the level of the arching membranes.

FORMATION OF SPINDLE-SHAPE GOETHITE EXTREMELY FINE PARTICLES BY AIR OXIDATION OF AQUEOUS SUSPENSION OF FERROUS SPECIES

Spindle-shape goethite (a-FeOOH) extremely fine particles were produced by air oxidation of an aqueous suspension consisting of a mixture of FeS04 and Na2CO3 at 30-40°C, using a standard-type bubble column. The time dependences of the fractional oxidation of total Fc(II7rpar; were measured under various combinations of experimental conditions. The shape and size (i.e., major and minor axes) of prepared a-FeOOH particles were observed with the aid of transmission electron microscopy. From such measurements and observations, the mechanism of spindle-shape a-FeOOH particle formation was deduced; the total number of a-FeOOH nuclei is fixed in the early stage of the oxidation reaction, and subsequently, only the particle growth tends to take place until leading to the final size, depending on the reaction condition, i.e., reaction rate.

Electron microscopy comparison of CO2 laser flash scanning and pulse technology one year after skin resurfacing.

The recent adaptation of laser technology in plastic and dermatologic surgery has provided a means to reduce efficiently the irregularities of the surface of the skin. Previous studies have analyzed the short- and medium-term clinical and histologic results of two laser systems: the Sharplan 40C SilkTouch and the 5000C Coherent Ultrapulse with Computer Pattern Generator (CPG). This paper contains the long-term ultrastructural findings observed with the aid of transmission electron microscopy (TEM). Twenty skin biopsy specimens were taken from ten Caucasion patients, between 54 and 72 years of age, who had undergone facial skin resurfacing with a CO2 laser 1 year previously. The treated areas of the face were divided into two equal parts. One half of the face was treated with the Sharplan SilkTouch laser and the other half with the Coherent Ultrapulse laser. Using TEM, the cell composition of the epidermis was studied ultrastructurally, as were the dermal-epidermal junction (DEJ) and the different fibers and cells in the superficial and middle dermis. On the side treated by the Sharplan laser, little melanin was observed, the DEJ was thicker, and there were abundant collagen fibers well compacted in the dermis. Also present was abundant elastin fiber with scarce interstitial spaces. On the side treated by the Coherent, the melanin was abundant and the DEJ was well structured. There were fibroblasts with lax chromatin in the dermis and collagen fibers in the papillary dermis oriented in a vertical and horizontal manner in relation to the epidermis. There was little elastin. The interstitial spaces were abundant. The Sharplan laser system seems to provoke a significantly more intense tissue response, with abundant dermal collagen and elastic fibers. This indicates that the Sharplan 40C SilkTouch might produce longer lasting clinical effects.

Maternal antioxidant treatments prevent diabetes-induced alterations of mitochondrial morphology in rat embryos.

Previous studies have suggested that production of reactive oxygen species by embryonic mitochondria may have a role in the induction of both high-amplitude mitochondrial swelling and embryonic dysmorphogenesis in diabetic pregnancy. The present study analyzed the relationships between a putative metabolite-induced production of free oxygen radicals, mitochondrial lipid peroxidation, and high-amplitude mitochondrial swelling in embryos during organogenesis. For studies in vitro, day 9 embryos of normal rats were cultured for 48 h with a high concentration of glucose in the absence or presence of alpha-cyano-4-hydroxycinnamic acid (CHC), a mitochondrial pyruvate transport inhibitor. The morphology of mitochondria in the neuroepithelium of the embryos was studied with the aid of transmission electron microscopy. For studies in vivo, normal and diabetic pregnant rats were fed a diet supplemented with the antioxidants alpha-tocopherol (vitamin E) or 2,6-di-tert-butyl-4-methylphenol (BHT), and the ultrastructure of mitochondria in the embryonic neuroepithelium and in the visceral yolk sac was investigated on gestational day 11. Exposure to a high concentration of glucose in vitro or to maternal diabetes in vivo induced high-amplitude swelling of mitochondria in the neuroepithelium of the embryos. The swelling of mitochondria was prevented by addition of CHC to the culture media or by maternal ingestion of antioxidant-supplemented food. In diabetic pregnancy, embryonic mitochondria during organogenesis produce free oxygen radicals that cause mitochondrial lipid peroxidation and swelling and furthermore embryonic dysmorphogenesis. Dietary supplementation with antioxidants to the mother may prevent embryonic malformations in diabetic pregnancy by inhibition of mitochondrial dysfunction.

Kinetics and polymerization characteristics for some polyvinyl acetate emulsions prepared by different redox pair initiation systems

The emulsion polymerization of vinyl acetate was carried out using different sodium bisulfite adducts (containing the same weight equivalent of bisulfite anion) as reducing agents with potassium persulfate as an oxidising agent at low temperature. The polymerization evaluation was followed by taking samples at regular intervals. The average volume diameters, the areas and the number of polymer particles per unit volume of water ( Nt) for some prepared emulsion latices were calculated with the aid of transmission electron microscopy and image analyzer techniques. Also, it was found that the rate of emulsion polymerization decreases in the following order: acetone sodium bisulfite (AcSBS) > methyl propyl ketone sodium bisulfite (MpKSBS) > octyl aldehyde sodium bisulfite (OASBS) > acetaldehyde sodium bisulfite (ASBS) > benzaldehyde sodium bisulfite (BSBS) > salicylaldehyde sodium bisulfite (SSBS) > cyclohexanone sodium bisulfite (ChSBS), while the particle size of the prepared emulsions increases in the following order: (OASBS)<(SSBS)<(BSBS)<(ChSBS)<(MpSBS)<(AcSBS)<(ASBS). Finally, the D z, D v/ D s, number of particles per cm 3 and D w/ D n were calculated for polymer latices obtained.

180° ferroelectric domains in polycrystalline BaTiO3 thin films

The presence of 180° ferroelectric domains in polycrystalline BaTiO3 thin films has been observed with the aid of transmission electron microscopy. The 180° domain boundary exhibited a curved appearance, and its orientational relationship was demonstrated. It was found that equiaxial grains did not have 180° domain boundaries due to their higher boundary energy. The grain size effect on dielectric constant of polycrystalline BaTiO3 thin films was also discussed in conjunction with 180° ferroelectric domains.

Characterization of smoke particles generated in terrestrial and microgravity environments

Smoke produced by the pyrolysis of fluorinated wire insulations is characterized to partially provide the data base required to conduct a comprehensive Probabilistic Safely Assessment (PSA) of future human-crewed spacecraft. The smoke is assessed via measurements and observations regarding the size, morphology and elemental composition of the generated particulate matter. Of particular interest is how the microgravity generated aerosols affect the design of future on-board detection and suppression systems. Analyses of the particles generated from short lengths of overheated wires insulated with Tefzel or Teflon (modified forms of ethyltetrafluoroethylene) were performed with the aid of transmission electron microscopy and energy dispersion spectroscopy. Results from short-duration microgravity tests in the NASA Lewis drop tower indicate that the sizes of the primary particles vary depending on the corresponding gravity environment within which they were produced. Tefzel particles produced in microgravity were found to be approximately twice as large as those produced in normal gravity. However, the morphology appears to be gravity independent and material dependent. Cluster formations for both gravity environments are composed of long linear chains of particulate matter. Additionally, a chemical composition analysis for both fluoropolymer insulations suggests that the particulate elemental composition is also independent of the gravity environment.

Carbide formation in aluminium—carbon fibre-reinforced composites

New results on the carbide formation in aluminium-carbon fibre composites are reviewed, with their implications for technology, including vacuum infiltration of carbon-fibre preforms with liquid aluminium. The microstructure of infiltrated specimens was studied with the aid of transmission electron microscopy. Most lath-like carbide crystals investigated in this work are twins. Twinning is probably connected with the squeezing stresses during matrix cooling due to a high difference in thermal expansion coefficients of carbide and metal. The analytical description of experimental data in the light of the crystal-growth concept allows us to conclude that carbides grow during infiltration, predominantly at the time of fibre contact with molten aluminium, but not during matrix solidification and its subsequent cooling. The growth rate of carbide crystals is limited rather by the interface kinetics than by carbon diffusion in the melt as was assumed previously. This allows some effective methods of process control to be found, for example, growth step retardation by means of an adsorption-active impurity.

Direct Development in the Ascidian Molgula retortiformis (Verrill, 1871).

The cellular features of the ascidian Molgula retortiformis (Verrill, 1871), a direct developing species, were investigated with the aid of transmission electron microscopy, histochemistry, and immunocytochemistry. Developmental comparisons between direct and indirect developing ascidians will further our understanding of how developmental processes evolve. M. retortiformis eggs are surrounded by a follicular envelope comprising a layer of outer follicle cells attached to an acellular chorion. The cytoplasm of M. retortiformis eggs contains large quantities of yolk and glycogen. Immediately after hatching, at day 2.5 of development, the cells constituting a juvenile exhibited similar ultrastructural features, except that the larger, deeper cells contained more yolk and glycogen than the epidermal cells. Differentiated muscle cells were absent in newly hatched M. retortiformis juveniles, and acetylcholinesterase (AChE) activity was not detected. Immunocytochemistry experiments using a vertebrate intermediate filament antibody (NN18) support the idea that the failure of newly hatched M. retortiformis juveniles to develop muscle cells may be due to the absence of a factor localized in the egg myoplasm. This paper concludes with a discussion of the "substrate hypothesis" and the evolution of ascidian direct development.

Sublateral Hypodermal Chords in Haemonchus (Nematoda: Trichostrongyloidea): Description and Potential as a Systematic Character

Prominent sublateral hypodermal chords (SHC) are described in Haemonchus spp. Four large SHC are located 1 muscle cell away from the lateral chords from the level of the middle of the esophagus to midbody. The SHC are largest in midbody and merge with the lateral chords at about 65% of the body length from the anterior end. With the aid of transmission electron microscopy, a band of nerve tissue was located parallel and medial to the SHC. Haemonchus spp. and Mecistocirrus digitatus have SHC that are so large they can be identified in thick freehand midbody cross sections cut with a cataract knife. Because SHC have not been described in other Trichostrongylidae, their presence in members of the Haemonchinae may have value as a systematic character.

Cryptocaryon irritans Brown, 1951 (Ichthyophthiriidae): the ultrastructure of the somatic cortex throughout the life cycle

Abstract. Cryptocaryon irritans was isolated from Grammistes sexlineatus and maintained in aquaria under controlled conditions using the mullet, Chelon labrosus (Risso), as an experimental host. The pellicle and cortical cytoplasm of the trophont, tomont, tomite and theront stages were investigated with the aid of transmission electron microscopy. The general structural organization of the pellicle resembles that of the freshwater holotrich, Ichthyophthirius multifiliis; however, the pellicular alveoli are characterized by the accumulation of electron‐dense material in the trophont, tomite and theront, this material being lost in the newly‐encysted tomont. The outer membranes of the pellicle are infolded into the alveoli of the trophont. Cilia are present at all stages of the life cycle, although at encystment their numbers are greatly reduced by shedding. Mitochondria, mucocysts and Golgi‐like cisternae are distributed throughout the cortical cytoplasm. Mucocysts differ from those of I. multifiliis in size, shape and distribution and are of uniform electron density. The role of the pellicle and cortical cytoplasm is discussed in relation to the invasion of the fish epidermis, possible intertransferance of materials between parasite and host and the process of encystment.

A model for the diffusion and precipitation of antimony in highly doped δ layers in silicon

Antimony δ-doping layers were made by deposition of Sb on monocrystalline Si, followed by the deposition of amorphous Si and a final solid-phase-epitaxy treatment at 620 °C. After post-annealing at temperatures between 625 and 725 °C, Sb precipitates with a diameter of several nm are observed in the δ plane with the aid of transmission electron microscopy. Using channeling Rutherford Backscattering Spectrometry the increase of the precipitated fraction with time was determined from the minimum-yield signal. The results are interpreted using a model for the generation of Sb nuclei which grow subsequently due to lateral diffusion of Sb atoms in the δ plane, followed by incorporation into the nucleus. The generation of the nuclei appears to take place by way of two parallel processes: (i) fast, simultaneous generation of a limited number of nuclei at low-energetic sites in the δ plane, with subsequent diffusion-controlled growth, and (ii) slow, continuous generation of a larger number of nuclei at random sites in the δ plane, with subsequent incorporation-controlled growth. The Sb diffusion at the extremely high concentrations under consideration is very fast and concentration dependent, which can be explained by the model of vacancy-percolation diffusion of Mathiot and Pfister [J. Appl. Phys. 66, 970 (1989)]. The activation energy for incorporation of Sb atoms into liquid precipitates appears to be considerably lower than for incorporation into solid ones.

STUDY OF CRYSTAL STRUCTURE AND PHYSICAL PROPERTIES OF THE COMPOUND Bi-Pb-Sr-Ca-Ba-Cu-O

With the aid of transmission electron microscopy, the phenomenon of additional superstructure along [Formula: see text] direction was observed for a sample of Bi 1.7 Pb 0.3Sr2 Ca 1.8 Ba 0.2 Cu 3 O y, and two kinds of modulation mode along b axis was found to coexist in this sample. The images of SEM showed that the addition of Ba ions improved the property of two-dimensional growth. The results of XRD indicated that the substitution of Ba 2+ for Ca 2+ increased the volume fraction of the high-Tc phase (Tc&gt;100 K). From the initial part of dc magnetization curve, it is estimated that about 36 percent of the sample volume is in the 110 K superconducting phase at 77 K. Its frozen magnetic flux density is about 8.6 G, which is 5–6 G higher than that of general Pb-doped sample, and its zero-resistance temperature can reach as high as 111 K. These changes of physical properties may be related to the adjustment of the microstructure.