Transmission Electron Microscropy Research Articles

Nanosheets of two-dimensional photoluminescent lanthanide phosphonocarboxylate frameworks decorated with free carboxylic groups for latent fingerprint imaging.

The synthesis, structural characterization, exfoliation, and photophysical studies of two-dimensional (2-D) lanthanide phosphonates, named Ln(m-pbc); [Ln(m-Hpbc)(m-H2pbc)(H2O)] (Ln = Eu, Tb; m-pbc = 3-phosphonobenzoic acid) based on the phosphonocarboxylate ligand, are reported. These compounds are neutral polymeric 2D layered structures with pendent uncoordinated carboxylic groups between layers. The nanosheets were obtained by a top-down strategy involving sonication-assisted solution exfoliation and characterized by atomic force microscopy and transmission electron microscropy, showing lateral dimensions from nano- to micro-meter scales, and thicknesses down to several layers. The photoluminescence studies demonstrate that the m-pbc ligand acts as an efficient antenna toward Eu and Tb(III) ions. The emission intensities of dimetallic compounds are clearly enhanced after incorporation of Y(III) ions due to the dilution effect. Ln(m-pbc)s were then applied for labelling latent fingerprints. It is worth noting that the reaction between active carboxylic groups and fingerprint residues benefits the labelling, showing efficient imaging for fingerprints on all kinds of material surfaces.

Effect of Remineralized Collagen on Dentin Bond Strength through Calcium Phosphate Ion Clusters or Metastable Calcium Phosphate Solution.

This study aimed to investigate whether dentin remineralization and micro-tensile bond strength increase when using calcium phosphate ion clusters (CPICs) or metastable Ca-P. After being etched, each dentin specimen was designated into four groups and treated with the appropriate solution for 1 min: 100% ethanol, 2 and 1 mg/mL of CPICs, and metastable Ca-P. The specimens were then prepared for scanning electron microscopy (SEM), transmission electron microscropy (TEM) imaging, a matrix metalloproteinases inhibition assay, and the micro-tensile bond strength test. To compare among the groups, one-way analysis of variance was performed. In the SEM imaging, with a rising concentration of CPICs, the degree of remineralization of dentin increased significantly. The metastable Ca-P treated specimens showed a similar level of remineralization as the 1 mg/mL CPICs treated specimens. The TEM imaging also revealed that dentin remineralization occurs in a CPICs concentration-dependent manner between the demineralized dentin and the resin layer. Furthermore, the results of micro-tensile bond strength showed the same trend as the results confirmed by SEM and TEM. We demonstrated that a 1 min pretreatment of CPICs or metastable Ca-P in etched dentin collagen fibril can achieve biomimetic remineralization and increase micro-tensile bond strength.

Diamond/β-SiC film as adhesion-enhanced interlayer for top diamond coatings on cemented tungsten carbide substrate

In present work, diamond/β-SiC composite interlayers were deposited on cemented tungsten carbide (WC-6%Co) substrates by microwave plasma enhanced chemical vapor deposition (MPCVD) using H2, CH4 and tetramethylsilane (TMS) gas mixtures. The microstructure, chemical bonding, element distribution and crystalline quality of the composite interlayers were systematically characterized by means of field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), X-ray photoelectron spectrometer (XPS), electron probe microanalysis (EPMA), Raman spectroscopy and transmission electron microscropy (TEM). The influences of varying TMS flow rates on the diamond/β-SiC composite interlayers were investigated. Through changing the TMS flow rates in the reaction gas, the volume fraction of β-SiC in the composite interlayers were tunable in the range of 12.0%–68.1%. XPS and EPMA analysis reveal that the composite interlayers are composed of C, Si element with little cobalt distribution. The better crystallinity of the diamond in the composite is characterized based on the Raman spectroscopy, which are helpful to deposit top diamond coatings with high quality. Then, the adhesion of top diamond coatings were estimated using Rockwell C indentation analysis, revealing that the adhesion of top diamond coatings on the WC-6%Co substrates can be improved by the interlayers with the diamond/β-SiC composite structures. Comprehensive TEM interfacial analysis exhibits that the cobalt diffusion is weak from WC-6%Co substrate to the composite interlayer. The homogeneous microcrystalline diamond coatings with the most excellent adhesion can be fabricated on the substrates with the composite interlayer with the β-SiC/diamond ratio of about 45%. The composite structures are appropriate for the application in high-efficiency mechanical tool as a buffer layer for the deposition of the diamond coating.

MicroRNA-128 inhibition attenuates myocardial ischemia/reperfusion injury-induced cardiomyocyte apoptosis by the targeted activation of peroxisome proliferator-activated receptor gamma.

The aim of the present study was to investigate the effects of microRNA (miR)-128 inhibition on the targeted activation of peroxisome proliferator-activated receptor gamma (PPARG) and on cardiomyocyte apoptosis induced by myocardial ischemia/reperfusion (I/R) injury. In vitro, the expression of PPARG was detected by reverse transcription-quantitative polymerase chain reaction and western blotting in neonatal rat ventricular myocytes (NRVMs) and HEK293 cells transfected with the mimics or inhibitors of miR-128 or control RNA. Luciferase reporter assays were used to identify whether PPARG is a direct target of miR-128. In vivo, miR-128 was knocked down via ear vein injection of antagomir-128 in a rabbit myocardial I/R injury model. Western blotting investigated the activation of Akt [phosphorylated (p)-Akt] and the expression of total-Akt, PPARG and myeloid leukemia cell differentiation protein-1 (Mcl-1) in the myocardium. Cardiomyocyte apoptosis was examined with transmission electron microscropy and terminal deoxynucleotidyl transferase dUTP nick end labeling staining. PPARG mRNA and protein were downregulated in NRVMs transfected with miR-128 mimics, but upregulated by antagomir-128 compared with control. This indicates that PPARG is a direct miR-128 target. Activation of Akt (p-Akt), Mcl-1 and PPARG expression in the myocardium were increased by miR-128 inhibition. Furthermore, miR-128 antagomirs significantly reduced apoptosis in hearts subjected to I/R injury, which was blocked by the PPARG inhibitor GW9662. In conclusion, miR-128 inhibition attenuated I/R injury-induced cardiomyocyte apoptosis by the targeted activation of PPARG signaling.

Morphological and Ultrastructural Characteristics of the Chorion of Cimex lectularius Linnaeus (Hemiptera: Cimicidae)

Bed bugs, Cimex lectularius Linnaeus, are increasingly reported as pests in hotels, apartments and homes worldwide. Although limited ultrastructural analysis of bed bug nymphs and adults has been performed, little is known about the ultrastructure of bed bug eggs. This study, using scanning and transmission electron microscropy, revealed several unique structural aspects of bed bug eggs. Chorionic projections form a polygonal pattern covering the egg surface. A complex operculumcollar structure is found on the anterior end of the egg, and the inner surface of the collar has three distinct regions, a smooth outer rim, a porous palisade layer and a porous ribbed layer. The outer surface of the collar is smooth with an operculum fitting into the collar. Large and distinctly ridged polygons cover the surface of the operculum. The polygons around the perimeter of the operculum have a rugose surface; the polygons adjacent to the rugose ones display spheres on the surface; and the remaining polygons have a smooth surface. The lateral margin of the operculum has a porous rugose surface with ridges and the ventral inner surface is smooth. Internally, the chorion is made up of three distinct divisions, the outer electron-dense layer with round electron opaque areas near the surface, a middle layer which is less electron-dense and the innermost layer of porous struts creating distinct spaces. Three distinct layers are found in the operculum, an outer porous layer, then an electron-dense layer, and an inner layer of porous struts and spaces. These findings constitute the first detailed description of the bed bug egg using electron microscopy.

Synthesis and characterization of graphitic carbon with hollow structures

Graphitic carbon with a hollow structure (GHS) was hydrothermally prepared at 600 °C by a one-pot method by the pyrolysis of ethanol, with cobalt acetate as catalyst. The characteristics of the samples were investigated by X-ray diffraction, scanning and transmission electron microscropy and Raman spectroscopy. Results show that as-synthesized samples had hollow structures with high graphitization degree. A possible mechanism for GHS formation by the method is proposed.

Morphology control of silver nano-crystals through a polyol synthesis

Silver nano-crystals in the forms of nanowires and triangular nanoplates were successfully synthesized through a polyol synthesis. The morphologies changed from nanowires to triangular nanoplates by adjusting the HNO 3 concentration. The samples were systematically characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscropy, thermogravimetric analysis and UV–visible Spectra. Examination of nanoparticles at different stages of the reaction revealed that the circular nanoparticles, twinned seeds grew to become triangular nanoplates and nanowires respectively.

Polyol synthesis of silver nanoplates: The crystal growth mechanism based on a rivalrous adsorption

A polyol reducing approach has been applied to synthesize silver nanoplates with an average thickness of 50 nm and edge length of 3 μm in the presence of poly (vinylpyrrolidone) (PVP) and HNO 3. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscropy (TEM), and electron diffraction are used to characterize these silver nanoplates. Findings indicate that the nanoplates are single crystals and with their basal plane as (1 1 1) lattice plane. On the basis of the results from thermogravimetric analysis (TG), Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopy, a crystal growth mechanism based on the rivalrous adsorption between PVP and CN − ions on the surface of silver nanoplates is supposed to explain the crystal anisotropic growth.

Shortened Carbon Nanotubes as Enhanced Support for High‐performance Platinum Catalysts

AbstractCarbon nanotubes (CNTs) were shortened from 5 to 15 μm to ca. 200 nm using ball milling with ethanol as the milling aid agent, and a platinum catalyst with these shortened carbon nanotubes (SCNTs) as the support was prepared by a high‐pressure colloidal method. It was found that this catalyst with SCNTs showed much higher activity than a platinum catalyst with normal CNTs as support; for methanol anodic oxidation, the activity of the Pt/SCNTs was 50% higher than that of the Pt/CNTs, and the Pt/SCNTs also showed higher activity for the cathodic reduction of oxygen. The Pt/SCNTs were characterised by X‐ray diffraction scanning and transmission electron microscropy. It is suggested that the significant performance enhancement when SCNTs are used as support might result from the generation of new surfaces and defects, the opening of closed nanotubes in the process of milling, higher platinum dispersion on the shortened nanotubes and the interaction of platinum nanoparticles with the SCNTs.

The growth of partitioned pearlite in Fe–C–Mn steels

The isothermal growth of partitioned pearlite in a series of high purity Fe–C–Mn alloys over the temperature range 575–650 °C has been investigated. Two types of behavior were observed. For those alloys transformed within the (α+M 3C) two phase field of the respective Fe–C–Mn isothermal section, growth occurred under steady-state conditions, with constant rate and interlamellar spacing. Those compositions transformed within the (γ+α+M 3C) three phase field invariably transformed under non-steady-state conditions with a growth rate which decreased and an interlamellar spacing that increased (divergent) in time. Detailed analytical transmission electron microscropy (ATEM) measurements of the Mn concentration profiles across the γ/α and γ/M 3C growth interfaces were made as a function of time for two alloys transformed at 625 °C. For the alloy transformed within the (α+M 3C) two phase field, the Mn contents inherited by the growing α and M 3C were remarkably constant for much of the reaction and are well approximated by the local equilibrium values. In the case of the alloy transformed within the (γ+α+M 3C) three phase field, the Mn contents inherited by the growing α and M 3C both increased with time. The Mn contents of the growing M 3C were at all times observed to fall within the bounds expected by the local equilibrium (LE) model, whereas a Mn enrichment over and above the LE values was observed for the growing ferrite. The effect of this enrichment on the expected pearlite growth rate is shown to be very small and it is concluded that the LE approximation for the interfacial conditions during pearlite growth under the conditions studied is a good approximation.

Interface dislocations in superalloy single crystals

The overall stress state in γ-channels of γ/ γ′-microstructures has three components: misfit stresses (due to γ/ γ′-misfit), dislocation stress fields and the external stress. In the present study glide and climb forces on γ-channel dislocations (from one slip system a 0/2[01 1 ̄ ](111) ) are studied calculating Peach–Koehler forces for γ/ γ′-interface dislocations exposed to the overall stress state. A thermo-elastic finite element calculation of misfit stresses is performed and the results are used as one input into a simplified discrete dislocation model (DDM). The influence of γ′-volume fraction and dislocation density in the γ-channels is explicitly considered. The calculations were motivated by previous mechanical and microstructural investigations in which elementary dislocation processes were identified by transmission electron microscropy as part of the mechanism of high temperature and low stress creep. The results help to interpret phenomenological concepts (like build up of back stress) and rationalize microstructural findings (like dislocation network spacings).

Size distribution of end-of-range dislocation loops in silicon-implanted silicon

The size and distribution of end-of-range dislocation loops in silicon implanted with 50 keV 1016 Si/cm2 and annealed at 750 °C for various times have been studied by transmission electron microscropy. The normalized distribution profile of the dislocation loops has been found to be invariant with time, based on density and size measurement. The profile is quite different from the conventional distribution profile of Oswald ripening in grain growth and precipitate coarsening. Measurement of the total number of interstitials bound in the extrinsic loops shows that the ripening is a conservative process. An explanation for the particular distribution profile is attributed to the stress field associated with the dislocation loops.

Pulmonary lesions induced by 3-methylindole and bovine respiratory syncytial virus in calves

SUMMARY Our objectives were to describe the ultrastructural morphogenesis of pulmonary lesions induced by 3-methylindole in 30- to 45-day-old Holstein calves and to determine whether toxic exposure to 3-methylindole exacerbates pulmonary lesions induced by bovine respiratory syncytial virus. Administration of 3-methylindole (0.25 g/kg) to calves resulted in interstitial edema and ultrastructural swelling of type-I alveolar epithelial cells and nonciliated bronchiolar epithelial cells as early as 4 to 6 hours after intraruminal administration. More severe alveolar edema containing protein was associated with swelling of capillary endothelial cells at 2 days after administration. Proliferation of type-II alveolar epithelial cells was first observed at 2 days after 3-methylindole administration, and marked hyperplasia of type-II epithelial cells and nonciliated bronchiolar epithelial cells was evident by 4 days after administration. Pulmonary cytochrome P-450 monooxygenase concentrations decreased significantly (P < 0.001) by 12 hours after administration and did not increase significantly again by 8 days after administration. Calves were inoculated with bovine respiratory syncytial virus 3 days after administration of 3-methylindole, and pulmonary lesions were assessed 5 days after viral inoculation. Viral replication was demonstrated by fluorescence microscopy for viral antigen or by transmission electron microscropy in ciliated and nonciliated airway epithelial cells. Viral antigen was identified infrequently in alveolar macrophages and in type-II alveolar epithelial cells. 3-Methylindole exposure in calves did not result in more widespread distribution of viral antigen in alveolar tissue of respiratory syncytial virus-inoculated calves or in significant enhancement of viral pneumonia. The results indicated that young calves are susceptible to 3-methylindole-induced pulmonary injury and that nonciliated bronchiolar epithelial cells, type-I alveolar epithelial cells, and pulmonary endothelial cells are most susceptible to injury. The results failed to indicate that 3-methylindole pulmonary toxicosis significantly enhances respiratory disease induced by bovine respiratory syncytial virus.

Characterization of Nb/Nb oxide structures in Josephson tunnel junctions

The subgap conductance of Nb, Nb oxide/Pb-alloy Josephson tunnel junctions was found to strongly depend on the rf plasma processing used to form the Nb oxide tunnel barrier. We have therefore studied the Nb/Nb oxide structures after rf plasma processing using x-ray photoelectron spectroscopy (XPS) and transmission electron microscropy (TEM) data. A crystalline Nb-C-O layer was formed as a transition region between the polycrystalline Nb base electrode and the Nb 2 O 5 tunnel barrier. The thickness of this transition region is sensitive to the rf plasma cleaning conditions prior to the tunnel barrier formation. An unexpected relation between junction electrical properties and the Nb/Nb oxide structure exists. The lowest subgap conductances are those obtained for tunnel junctions with transition regions about 30A thick. An abrupt interface between Nb and Nb 2 O 5 leads to junctions with high subgap conductances.

Ultrastructural Effects of Crude Oil on Early Life Stages of Pacific Herring

Eggs of Pacific herring, Clupea harengus pallasi, collected from Prince William Sound, Alaska were exposed to Prudhoe Bay crude oil for 4–144 hours, then returned to uncontaminated seawater for further development. Newly hatched larvae from both control and experimental groups showed no gross abnormalities. Transmission electron microscropy revealed inter- and intracellular spaces in brain and muscle tissues of exposed organisms but not in those of controls. Many mitochondria in the body muscle of exposed organisms were swollen, some with deteriorating cristae structure.

Synaptic organization of the fleshfly ocellus.

The synaptic organization of the fleshfly (Boettcherisca peregrina) ocellus has been studied by transmission electron microscropy. Three types of neuronal element are recognized in the ocellus: (1) 70-100 retinula axons (2) four thick ocellar nerve fibres and(3) several thin ocellar nerve fibres. Synaptic connections accompanied by characteristic presynaptic ribbons have been found between these three elements in five combinations. Four of these are numerous (retinula axons symapsing onto thick ocellar nerve fibres or onto thin ocellar fibres; thin ocellar nerve fibres synapsing onto thick ocellar nerve fibres or onto other thin ocellar fibres). On or two of the thin ocellar nerve fibres are mainly presynaptic elements. The remaining thin fibres are both pre-and postsynaptic. These observations suggest that the thick ocellar nerve fibres are afferent and at least one or two of the thin ocellar nerve fibres are efferent. The function of the remaining thin fibres is not known. The fifth combination is a feedback synapse from thin ocellar nerve fibres onto retinula oxons. In addition, neuro-glial synapses have been found between thin ocellar nerve fibres and glial cells. The latter two combinations are less common and may provide alternative neuronal pathways for processingocellar input.