Transmission Electron Micros Research Articles

Atomic Configuration and Conductance of Tantalum Single-Atom Contacts and Single-Atom Wires

The tensile deformation and successive fracture process of tantalum (Ta) nanocontacts (NCs) while applying various bias voltages was observed in situ by high-resolution transmission electron micros...

Structural and ultrastructural evaluation of the effects induced by IL-22 alone or in combination with psoriatic cytokines in an ex-vivo human skin model

L-22 is a pro-inflammatory cytokine playing a crucial role in the pathogenesis of psoriasis, an autoimmune chronic inflammatory skin disease. The immunological acti - vation during the progression of the psoriatic lesion is driven by IL-22 together with other cytokines, such as (TNF)-alpha and interleukin (IL)-17 [1]. The aim of our study was to evaluate the early, direct, and specific effect of IL-22 alone or in combination with TNF-alpha and IL-17 by immunofluorescence on i) the molecular composition of intercellular junctions (desmocollin (DSC)1, E-cadherin, and occludin), ii) keratin(K) 10 and 17 expression, iii) keratinocyte proliferation, and, by transmission electron micros - copy (TEM), on the ultrastructural morphology of the skin. An innovative model of human skin culture standardized in our laboratory, in which a psoriatic microenviron- ment was reproduced, was used [2]. Skin explants obtained from plastic surgery of healthy 20-40 year-old women (n = 7) after informed consent were cultured overnight in Dulbecco’s modified Eagle’s medium, divided before adding IL-22 or a combination of the three cytokines, and harvested 24, 48, and 72 hours after cytokine incubation. Interestingly, keratinocyte proliferation was inhibited after exposure to the combi- nation of cytokines while was not affected by IL-22 incubation. In both experimental groups, starting from T24, occludin immunostaining was non homogeneously distrib- uted, K10 immunostaining gradually decreased in scattered clusters in the spinous layer, while K17 expression was induced and progressively increased with time in the suprabasal layers of epidermis. By TEM, after IL-22 incubation we observed keratin aggregates in the perinuclear cytoplasm of cells, while the combination of the three cytokines induced an enlargement of intercellular spaces. Altogether, our results suggest that IL-22 mainly affects keratinocyte terminal dif- ferentiation, whereas, for inducing an impairment in cell proliferation, a more com- plex psoriatic-like microenvironment is needed.

Patterning SiC nanoprecipitate in Si single crystals by simultaneous dual- beam ion implantation

b-SiC nanoprecipitates can be patterned in crystalline silicon with an almost monomodal size distri- bution by simultaneous-dual-beam of C ? and Si ? ion implantations at 550 C. Their shape appears as spherical (average diameter *4-5 nm) ,and they are in epitaxial relationship with the crystalline silicon matrix. The narrow size distribution follows the left wing of the carbon dis- tribution where the nuclear ion stopping, and thus the point defect generation rate is largest. This observation allows us to conclude that the induced damage act as sinks for C atoms leading to the SiC nanoprecipitates formation cen- tered at the maximum of the simulated damage distribu- tion. The nuclear reaction analysis, X-ray diffraction, Raman spectroscopy, and transmission electron micros- copy techniques were used to characterize the samples.

A cellular uptake and cytotoxicity properties study of gallic acid-loaded mesoporous silica nanoparticles on Caco-2 cells

In this study, the effects of intracellular delivery of various concentrations of gallic acid (GA) as a semistable antioxidant, gallic acid-loaded meso- porous silica nanoparticles (MSNs-GA), and cellular uptake of nanoparticles into Caco-2 cells were inves- tigated. MSNs were synthesized and loaded with GA, then characterized using transmission electron micros- copy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, N2 adsorp- tion isotherms, X-ray diffraction, and thermal gravi- metric analysis. The cytotoxicity of MSNs and MSNs- GA at low and high concentrations were studied by means of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl- tetrazolium bromide (MTT) test and flow cytometry. MSNs did not show significant toxicity in various concentrations (0-500 lg/ml) on Caco-2 cells. For MSNs-GA, cell viability was reduced as a function of incubation time and different concentrations of nano- particles. The in vitro GA release from MSNs-GA exhibited the same antitumor properties as free GA on Caco-2 cells. Flow cytometry results confirmed those obtained using MTT assay. TEM and fluorescent microscopy confirmed the internalization of MSNs by Caco-2 cells through nonspecific cellular uptake. MSNs can easily internalize into Caco-2 cells without deleterious effects on cell viability. The cell viability of Caco-2 cells was affected during MSNs-GA uptake. MSNs could be designed as suitable nanocarriers for antioxidants delivery.

Characterization of cobalt phosphide nanoparticles derived from molecular clusters in mesoporous silica

The synthesis of well dispersed cobalt phosphide nanoparticles (NPs) in SBA-15 mesoporous silica by wet impregnation of the molecular cluster (Co4(CO)10(l-dppa)) (1) (dppa = HN(PPh2)2 )i s described. The thermal activation of the silica impreg- nated precursor under a H2/N2 (5/95 %) stream at different temperatures to form NPs was studied and it was found that the size of the latter is limited in the 5.5-6.5 nm range by the size of the pores. The obtained materials were characterized by various analytical methods. The porosity and the structure of the mesoporous silica supports were analyzed by N2 adsorption/desorption and small-angle X-ray diffrac- tion. The nanoparticles were characterized by wide- angle X-ray diffraction, transmission electron micros- copy in conventional and scanning modes, electron tomography, energy-dispersive X-ray spectroscopy, and magnetic measurements. Cobalt phosphide NPs of few nanometers were observed in the pores of SBA-15.

Poly-N-(4-benzoylphenyl)methacrylamide nanoparticles: preparation, characterization, and photoreactivity features

The design and preparation of novel photo- reactive poly-N-(4-benzoylphenyl)methacrylamide-based nanoparticles (NPs) are reported herein. The starting photoreactive monomer, N-4-benzoylphenyl methacryla- mide, was prepared by amidation of the photoreactive species 4-aminobenzophenone with methacryloyl chlo- ride in the presence of triethylamine. Corresponding 97 nm-sized NPs were obtained using a dispersion poly- merization technique. Deep surface and bulk characteriza- tion of resulting polyBPMA NPs were performed using a combination of transmission and scanning electron micros- copies (NP morphology), dynamic light scattering (NP size and size distribution), ζ potential (surface NP charge), thermo-gravimetric measurements (weight loss profiling), differential scanning calorimetry (heat transmission fea- tures), infrared and ultra-violet spectroscopies (functionality checking), nuclear magnetic resonance ( 1 H-NMR, func- tionality confirmation), gel permeation chromatography (average polymer molecular weight), and mass spectrome- try (average polymer molecular weight). Different reaction conditions were investigated for optimal fabrication of corresponding polyBPMA NPs. In addition and most importantly, their UV-mediated photo-reactivity with non- functional parylene C (PC) polymer coatings has been investigated towards NP covalent attachment. The success- ful bonding of such photo-reactive polymeric NPs onto PC films was confirmed by FTIR-ATR spectroscopy and by both atomic force- and scanning electron-microscopies.

Structural changes in four different precursors with heat treatment at high temperature and resin carbon structural model

Four precursors (mesophase pitch, condensed polynuclear aromatic resin, polyimide resin, and thermo- setting phenolic resin) were heat treated at temperatures from 900 to 3000 C. These products were characterized by X-ray diffraction, transmission electron microscopy, and helium adsorption density instruments. Heterogeneous graphitization was observed above 2200 C in the resin carbons. Various constituents (amorphous, turbostratic, and graphitic) coexisted and transformed from being disordered to ordered with increasing treatment temperature. The molecular structures of the starting materials played important roles in the proportions of various constituents, crystallite sizes, and preferred orientation of the graphitic constituent of the different carbons during high temperature treatment. High-resolution transmission electron micros- copy images showed that the structural features of Jenkins' and Shiraishi's model all existed in three resin carbons. Based on these results, we think that their structures are not belong to Jenkins' model, also do not belong to Shiraishi's model, are a complex of above two models.

Preparation of TiO2@SiO2Coaxial Double-walled Submicrotubes by Trifluidic Coaxial Electrospinning and Its Photocatalytic Property

Coaxial double-walled submicrotubes have potential extensive applications in many fields owing to their peculiar submicrostructures. The electrospinning has become a major method for preparation of one-dimensional nano- or micromate- rials. In order to invent a facile technique to fabricate coaxial double-walled submicrotubes, a modified electrospinning was employed. TiO2@SiO2 coaxial double-walled submicrotubes were successfully synthesized by trifluidic coaxial electrospin- ning technique using tetrabutyl titanate, tetraethyl orthosilicate, polyvinyl pyrrolidone, absolute ethanol, sesame oil, span-80 and chloroform as starting materials. The samples were characterized by thermogravimetry and differential thermal analysis, X-ray diffractometry, Fourier transform infrared spectrometry, scanning electron microscopy, transmission electron micros- copy and energy dispersive spectrometry. The results indicated that the products are TiO2@SiO2 coaxial double-walled sub- microtubes with an amorphous SiO2 outer shell, a crystalline rutile-typed TiO2 inwall. The submicrotubes possess an average diameter of ca. 680 nm, wall thickness of the tubes of ca. 70 nm, inwall of ca. 40 nm and outer shell of ca. 30 nm. The length of submicrotubes is greater than 20 μm. The formation mechanism of TiO2@SiO2 coaxial double-walled submicrotubes is preliminarily investigated. TiO2@SiO2 coaxial double-walled submicrotubes present better photocatalytic activity on rhoda- mine B. The simple preparation method is also appropriate for fabricating other coaxial multi-walled nano- or submicrotubes of inorganics.

Preparation and Tribological Behavior of BiIn/In 2O 3 Composite Dendritic Nanocrystals

BiIn/In 2 O 3 composite dendritic nanocrystals were prepared by dispersing alloy droplets in paraffin oil. The morphology and structure of the alloy nanocrystals were characterized by transmission electron micros (TEM), X-ray photoelectron spectra (XPS), and X-ray powder diffraction (XRD). The composite nanocrystals have dendritic morphology, with an average diameter of 10 nm and lengths up to tens and even hund of nanometers. Tribological results indicate that the composite nanocrystals as oil additives can improve antiwear ability of base oil, which is better than that of the corresponding monometallic particles. In addition the lubricating mechanism of the composite nanocrystals was also discussed.

Bifunctional Magnetic−Luminescent Nanocomposites: Y2O3/Tb Nanorods on the Surface of Iron Oxide/Silica Core−Shell Nanostructures

Bifunctional magnetic−luminescent Fe3O4@SiO2/Y2O3:Tb nanocomposite was obtained by assembling Y2O3:Tb nanorods onto the surface of Fe3O4@SiO2 core−shell nanostructures. Transmission electron micros...

Carbide- matrix interface mechanism of stress corrosion cracking behavior of high-strength CrMo steels

The effects of tempering temperature and carbon content on the stress corrosion cracking (SCC) behavior of high-strength CrMo steels in 3.5 pct NaCl aqueous solution have been studied by means of Auger electron spectroscopy (AES) and scanning and transmission electron micros- copy (SEM and TEM). Experimental results show that the specimens with higher carbon content and tempered at lower temperatures have a higher tendency for intergranular fracture and lower threshold stress intensity KISCC The SCC behavior is significantly affected by the distribution of carbide particles, especially carbide coverage on prior austenitic grain boundaries, through a carbide-matrix interface mechanism as the interface is the preferential site for the nucleation and propagation of microcracks because of its strong ability to trap hydrogen atoms. In low- temperature tempered states, there is the serious segregation of carbon in the form of carbide particles at prior austenitic grain boundaries, causing low-stress intergranular fracture. After tempering at high temperatures (≥400 °C), both the coalescence of the carbide particles at the grain boundaries and the increase of carbide precipitation within grains cause the decrease of the tendency for intergranular fracture and the rise of KISCC. The higher the carbon content in steels, the more the carbide particles at the grain boundaries and, subsequently, the higher the tendency for low-stress intergranular fracture. The carbide effect on KISCC makes an important contribution to the phenomenon that KISCC decreases with the rise of yield strength of the steels.

Characterization of Defects in P-Terphenyl Single Crystals

Abstract White Beam Synchrotron X-ray Topography has been used to characterize defects in solution-grown p-terphenyl single crystals. Defects observed include growth dislocations, mechanically introduced dislocations, macroscopic twins, twin lamellae, and dislocations emitted from twin boundaries. Line direction and Burgers Vector analysis of the growth and mechanically introduced dislocations, using projective geometry calculations and g. b analysis, respectively, are presented, along with complete analysis of the twin operation, obtained from a combination of analysis of optical micrographs and of orientation contrast on synchrotron topographs. The relationship between the Burgers vector of the dislocations generated at the twin boundary and the strain associated with the twins is discussed. Interesting interactions between mechanically introduced dislocations and twin boundaries are presented. Defect analyses are discussed in the context of results obtained previously using transmission electron micros...

Light and electron microscopic studies on red leg disease of the prawn (penaeus ortientalis kishinouye)

The red leg disease of the prawn (Penaeus orientalis Kishinouye) is a new kind of disease which occurred and prevailed in many maricuiture farm in East China in recent years. The article reports the pathological changes in the microstructure of some tissues from the diseased prawn, which are studied by light microscopy (LM) and transmission electron micros copy(TEM). The result shows that small number of bacteria exist in the haemolymph of the diseased prawn and that the number of haemocytes decreases obviously. Lots of tree-like or radiation-like orange-red pigment granules are seen int the derma layer of the shell of the swimming feet by LM. In the ultrathin section of the swimming feet many parasitic bacteria can be observed assembling or scattering in the cytoplasm as well as in the cytoplasm of midgut, heart and gill fillarnents(Fig 4-6). Its proved that the bacteria separated from the haemlymph of the diseased prawn are the pathogen of the red leg disease known as Vibrio angullarum through the tests of the manual infection and bacteriological identifications. Its a short bacillus without germ, but with a single-ended flagella which has sheath.

Pollen Morphology of the Martyniaceae and Its Systematic Implications

The pollen morphology as shown with scanning and transmission electron micros- copy of a sample of 10 species of the Martyniaceae revealed three distinct types within this family: reticulate (in Martynia), areolate (ProboscidealIbicella), and ring-like (Craniolaria). Pollen mor- phology coincided with other characters and suggested that Proboscidea and Ibicella should be con- sidered congeneric. Neither SEM nor TEM resolved the aperture type. Intergeneric differences in pollen morphology may be associated with differences in pollinators. Comparisons of pollen sug- gested that the Martyniaceae and the Pedaliaceae should be maintained as separate families.

Ultrastructural Evidence for Meiosis in a Nonheterothallic Isolate of the Myxomycete Didymium Iridis

In a recent discussion of various aspects of the biology of the myxomycete Didymium iridis (Ditmar) Fries, Collins and Betterley (1982) considered the var? ious reproductive cycles of isolates of this species. According to these authors, of 43 isolates of D. iridis examined critically, only 12 have been reported to be heterothallic while 21 have been designated as nonheterothallic. While traditionally most workers have assumed nonheterothallic isolates to be homothallic (pos? sessing meiosis and karyogamy), Collins (1980) has stated that It now seems entirely possible that myxomycete life cycles are characteristically either hetero? thallic or apomictic, with homothallic cycles either rare or nonexistent. Most of the data supporting the idea of apomixis has, however, come from genetic studies and Feulgen nuclear DNA measurements made on myxamoebae, plasmodia, and young spores (see Collins and Betterley, 1982), and apparently no detailed attempt has been made to look for visual evidence of meiosis in thick-walled, maturing spores of supposed apomictic isolates. As a result, the present electron microscopic study was undertaken. Plasmodia ofthe nonheterothallic isolate (Mo-1) of D. iridis used in this study were kindly supplied by Dr. O. R. Collins ofthe University of California, Berkeley. This apparently apomictic isolate is reported not to have a haploid phase (Mulleavy, 1979). According to Collins (pers. comm.), this isolate has not exhibited the apomictic-heterothallic conversions reported in some isolates (Yemma et al, 1978; Mulleavy, 1979; Collins, 1980), even though attempts to convert it have been made. Single spore isolations done in conjunction with this ultrastructural study confirmed that the Mo-1 isolate remained nonheterothallic throughout the course of the investigation. Plasmodia ofthe Mo-1 isolate were maintained at 23 C on sterilized pieces of oat flakes on the surface of 2% plain agar plates. To induce fruiting, plasmodia were placed in total darkness for 3 da and then exposed to light. Sporangia in various stages of development (precleavage to 24 h past cleavage) were then prepared at hourly intervals for examination with transmission electron micros? copy according to the procedures of Glidewell and Mims (1979). The results of this study indicate that meiosis or at least an attempt at meiosis occurs in the Mo-1 isolate of D. iridis. The five necessary indicators of meiosis listed by Aldrich and Mims (1970) and reiterated by Aldrich and Blackwell (1976) were all observed in this study. These include (1) a precleavage nuclear division without synaptonemal complexes (SC's), (2) an intervening interphase with no synapsis, (3) SC's in the nuclei of spores 10-20 h old, (4) nuclear division figures within spores, and (5) a subsequent degeneration of nuclei within autophagic vacuoles.

New Type of Soredium in the Lichen Family Heppiaceae

A new type of soredium-like granule is described from species of Peltula and compared with soredia. Scanning and transmission electron micros- copy and light microscopy of these new structures reveals that these unique granules lack the outer fungal covering which characterizes soredia but have fungal hyphae and haustoria in the center of clumps of algae. This type of granule is intermediate between hormocysts and soredia and probably represents the most primitive type of soredium. Peltula is the most primitive genus evolu- tionarily to produce soredia. A wider definition of soredia is given to include this primitive type. Soredia are now widely recognized as taxonomically significant structures of the lichen thallus and their production is probably genetically controlled (Hale, 1967). Within the classification of lichen diaspores as modified by Degelius (1945), soredia are one type of composite reproductive structure and contain both the fungus and the algae.