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Transmission Electron Microscopy (transmission + electron_microscopy)
Kinds of Transmission Electron Microscopy Terms modified by Transmission Electron Microscopy Selected AbstractsUltrastructural and electron energy-loss spectroscopic analysis of an extracellular filamentous matrix of an environmental bacterial isolateENVIRONMENTAL MICROBIOLOGY, Issue 9 2007Uta Böckelmann Summary Strain F8, a bacterial isolate from ,river snow', was found to produce extracellular fibres in the form of a filamentous network. These extracellular filaments, which were previously shown to be composed of DNA, have been studied for the first time by ultrastructural and electron energy-loss spectroscopy in the present work. ,Whole mount' preparations of strain F8 indicate these polymers are ultrastructurally homogeneous and form a network of elemental filaments, which have a width of 1.8,2.0 nm. When incubated at pH 3.5 with colloidal cationic ThO2 tracers they become intensely stained (electron dense), affording direct evidence that the fibres are negatively charged and thus acidic chemically. Elemental analysis of the extracellular filaments by Energy-filtered Transmission Electron Microscopy revealed phosphorus to be the main element present and, because pretreatment of F8 cells with DNase prevented thorium labelling, the fibres must be composed of extracellular DNA (eDNA). Neither ultrathin sections nor ,whole mount negative stain' caused DNA release by general cell lysis. Additionally, cells infected with phages were never observed in ultrathin sections and phage particles were never detected in whole mount samples, which rules out the possibility of phages being directly involved in eDNA release. [source] Study of the Defects in Sintered SnO2 by High-Resolution Transmission Electron Microscopy and CathodoluminescenceEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2007David Maestre Abstract The defect structure of sintered SnO2 was investigated by high-resolution transmission electron microscopy (HRTEM), cathodoluminescence (CL), and electrical measurements. HRTEM shows the presence of the SnO phase in the sintered samples as well as twinning, stacking faults, and disordered intergrowths. The sintered samples annealed under an oxygen atmosphere show changes in the defect structure and in the CL spectra. In particular, the intensity of a CL band at 1.94 eV, related to oxygen vacancies, decreased as the electrical resistivity increased. The results are discussed by considering the presence of stoichiometric defects such as oxygen vacancies and Sn interstitials in the final structure and their evolution during the annealing process under an oxygen atmosphere. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Transmission Electron Microscopy and Nano-Precipitation,ADVANCED ENGINEERING MATERIALS, Issue 12 2006T. Epicier Abstract We have presented here a rapid survey of some of the stringent results obtained by TEM and associated techniques in the precipitation studies conducted during the CPR ,Précipitation'. It clearly appears that TEM plays an irreplaceable role in the link between the understanding of the structure and chemistry of small precipitates and the modelling of the precipitation kinetics. [source] Preparation and Characterization of Styrene Butadiene Rubber Based Nanocomposites and Study of their Mechanical PropertiesADVANCED ENGINEERING MATERIALS, Issue 9 2004S. Sadhu Nanocomposites were prepared from styrene butadiene rubber (SBR) having different styrene contents and octadecyl amine modified Na-montmorillonite clay (OC). The modified and the unmodified clays were characterized with the help of X-ray diffraction technique (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Transmission Electron Microscopy (TEM). All these nanocomposites were then subjected to tensile testing. The modified clay-rubber nanocomposites showed improved tensile strength (55% increase) and elongation at break (76% increase) compared to those of the gum vulcanizates. [source] Transmission Electron Microscopy and UV,vis,IR Spectroscopy Analysis of the Diameter Sorting of Carbon Nanotubes by Gradient Density UltracentrifugationADVANCED FUNCTIONAL MATERIALS, Issue 14 2009Romain Fleurier Abstract Diameter separation of single-walled carbon nanotubes is achieved via the density gradient ultracentrifugation process. Statistical analysis of the separated samples is performed using high-resolution transmission electron microscopy (HRTEM). The evolution of the diameter distribution with respect to the gradient density is extracted by analyzing hundreds of HRTEM images, and the results are found to be consistent with those estimated by UV,vis,IR spectroscopy. The efficiency of the separation process can be quantitatively characterized by the standard deviation of the diameter distribution, which is determined from the TEM analyses. This particular study indicated that for electric arc nanotubes dispersed in sodium cholate, diameter sorting is more efficient in the upper part of the gradient. [source] Determination of Size, Morphology, and Nitrogen Impurity Location in Treated Detonation Nanodiamond by Transmission Electron MicroscopyADVANCED FUNCTIONAL MATERIALS, Issue 13 2009Stuart Turner Abstract Size, morphology, and nitrogen impurity location, all of which are all thought to be related to the luminescent properties of detonation nanodiamonds, are determined in several detonation nanodiamond samples using a combination of transmission electron microscopy techniques. Results obtained from annealed and cleaned detonation nanodiamond samples are compared to results from conventionally purified detonation nanodiamond. Detailed electron energy loss spectroscopy combined with model-based quantification provides direct evidence for the sp3 like embedding of nitrogen impurities into the diamond cores of all the studied nanodiamond samples. Simultaneously, the structure and morphology of the cleaned detonation nanodiamond particles are studied using high resolution transmission electron microscopy. The results show that the size and morphology of detonation nanodiamonds can be modified by temperature treatment and that by applying a special cleaning procedure after temperature treatment, nanodiamond particles with clean facets almost free from sp2 carbon can be prepared. These clean facets are clear evidence that nanodiamond cores are not necessarily in coexistence with a graphitic shell of non-diamond carbon. [source] Cell division in magnetotactic bacteria splits magnetosome chain in halfJOURNAL OF BASIC MICROBIOLOGY, Issue 4 2010Sarah S. Staniland Abstract Cell division in magnetotactic bacteria has attracted much interest, speculation and hypothesis with respect to the biomineralised chains of magnetic iron-oxide particles known as magnetosomes. Here we report direct Transmission Electron Microscopy (TEM) evidence that division occurs at a central point of the cell and the chain, cleaving the magnetosome chain in two. Additionally, the new magnetosome chain relocates rapidly to the centre of the daughter cell and the number of magnetosomes is directly proportional to the cell length, even during the division part of the cell cycle. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] BIOREMEDIATIVE POTENTIAL OF CHROMULINA FREIBURGENSIS IN CULTURE FROM THE BERKELEY PITJOURNAL OF PHYCOLOGY, Issue 2001Article first published online: 24 SEP 200 Dakel, S. M.1 & Mitman, G. G.2 1Department of Environmental Engineering; 2Department of Biological Sciences, Montana Tech of The University of Montana, Butte, MT 59701 USA The Berkeley Pit, part of the largest Superfund site in the United States, is an open-pit copper mine that operated from 1955 through 1982. Today, the Berkeley Pit contains approximately 1200 billion liters of metal laden water with an average pH of 2.7, and 12 grams/liter of dissolved solids. The principle dissolved ions include aluminum, arsenic, calcium, cadmium, copper, iron, potassium, magnesium, manganese, sulfates, and zinc. A species from Division Chrysophyta,Chromulina freiburgensis Dofl. was isolated from this extreme environment. This species has been tested in the laboratory through a series of controlled experiments to determine bioremediative potential. Optimal temperature was determined by monitoring growth with cell counts at temperatures ranging from 5°C to 40°C . The optimal nutrient ratio was determined by varying nitrogen (NaNO3) and phosphorus (Na2HPO4) levels. An experimental matrix varying nutrients was developed to test for bioremediative potential which included: initial and final pH measurements; initial and final Ion Chromatography Pairing,Atomic Emission Spectrometry (ICP-AES) for dissolved metals; and examination of final samples under Transmission Electron Microscopy (TEM). From these experiments, Chromulina freiburgensis was found to grow optimally in Berkeley Pit surface water with cell densities reaching ten million cells per milliliter at 10°C with additions of 50 mg NaNO3/L and 5 mg Na2HPO4/L. This large biomass was also found to increase diversity and abundance of heterotrophs. At the optimal nutrient level, this species was found to increase pH from 2.21 to 2.47 over 90 days. Significant removal of calcium, iron, nickel, and silica was observed. [source] In Situ Transmission Electron Microscopy of Electric Field-Triggered Reversible Domain Formation in Bi-Based Lead-Free PiezoceramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2010Jens Kling A lead-free piezoelectric 0.91(Bi1/2Na1/2)TiO3,0.06BaTiO3,0.03(K0.5Na0.5)NbO3 ceramic with high strain was examined in situ under an applied electric field using the transmission electron microscope. No domain structure is observed without an electric field, but an alternating electric field leads to the reversible formation of a lamellar domain structure. Correlations to polarization and strain hysteresis loop measurements indicate an electric field-induced phase transition from a nonpolar to a ferroelectric state and vice versa. [source] Characterization of HDPE /Polyamide 6/ Nanocomposites Using Scanning-and Transmission Electron MicroscopyMACROMOLECULAR SYMPOSIA, Issue 1 2007Eleonora Erdmann Abstract Summary: Preparation and morphology of high density polyethylene (HDPE)/ polyamide 6 (PA 6)/modified clay nanocomposites were studied. The ability of PA 6 in dispersing clays was used to prepare modified delaminated clays, which were then mixed with HDPE. Mixing was performed using melt processing in a torque rheometer equipped with roller rotors. After etching the materials with boiling toluene and formic acid at room temperature, the morphology was examined by SEM analyses, showing that the PA 6 formed the continuous phase and HDPE the dispersed phase. X-ray diffraction patterns show that the (001) peak of the clay is dramatically decreased and shifted to lower angles, indicating that intercalated/exfoliated nanocomposites are obtained. TEM analyses confirmed the typical structure of exfoliated nanocomposites. A scheme for the mechanism of exfoliation and/or intercalation of these HDPE /PA 6/ /organoclay nanocomposites is proposed. [source] Use of the Surfmer 11-(Methacryloyloxy) undecanylsulfate MET as a Comonomer in Polystyrene and Poly(methyl methacrylate)MACROMOLECULAR SYMPOSIA, Issue 1 2004P.C. Hartmann Abstract The polymerizable surfactant sodium 11-(methacryloyloxy) undecanylsulfate (MET) has been synthesized with high purity, and its thermal stability and phase transitions have been studied by thermo gravimetric analysis (TGA) and differential scanning calorimetry (DSC), respectively. MET has been copolymerized in solution with methylmethacrylate (MMA) or styrene (S), initiated by azo-bis-isobutyronitrile (AIBN). The copolymers thus obtained have been studied by Gel Permeation Chromatography (GPC), Transmission Electron Microscopy (TEM), and DSC. Due to the incompatibility between the polar head of the MET units and the non polar S or MMA units, MET units organize in the amorphous polymer matrix and arrange in lamellar structures. [source] Synthesis of nickel,zinc ferrite nanoparticles in polyol: morphological, structural and magnetic studiesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2006Z. Beji Abstract Nickel,zinc ferrite monodisperse nanoparticles are synthesized by forced hydrolysis in diethylenglycol. FC and ZFC susceptibility curves suggest that they present superparmagnetic behaviour with a blocking temperature between 63 and 15 K depending on the zinc content. The saturation magnetization of the nanocrystals at 5 K is very close to that of bulk materials, and very high compared to that of similar particles prepared by other chemical routes. High Resolution Transmission Electron Microscopy and In-field Mössbauer studies show clearly that these relatively high values are mainly due to: (i) the high crystalline quality of the particles and (ii) a cation distribution different from the classical distribution encountered in the bulk material. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] HRTEM, Raman and optical study of CdS1,xSex nanocrystals embedded in silicate glassPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 13 2004V. Bellani Abstract We studied CdS1,xSex nanocrystals embedded in a silicate glass by means of complementary techniques like high resolution transmission electron microscopy (HRTEM), micro-Raman spectroscopy and optical transmission and reflectivity. Transmission Electron Microscopy gives complete information on crystallization and size distribution of the nanocrystals wile Raman scattering is particularly useful in the determination of the composition of the nanocrystals for low-concentration or small-crystallite size composite. Having the size distribution and composition of the nanocrystals we have explained the transmission spectra of the studied samples. Optical transmission spectra evidence the quantization of the electronic states of the nanoparticles system with a size distribution described by a Gaussian function. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Carbon nanotube probe resolution: a quantitative analysis using Fourier TransformPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2004H. R. Gutiérrez Abstract A method to quantify the resolution of atomic force microscopy (AFM) probes using Fourier analysis of the AFM images is proposed. The maximum detectable spatial frequency obtained from the power spectrum was used to estimate the lateral resolution. Carbon nanotube tips were successfully used to study very dense arrays of semiconductor nanostructures. In particular, accurate measurements of shallow facet angles were obtained, which are in perfect agreement with results obtained by two complementary techniques , High Resolution Transmission Electron Microscopy and Reflection High-Energy Electron Diffraction. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Study of metal-oxide-semiconductor capacitors with r.f. magnetron sputtering TiOxNy films dielectric layerPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010Katia Franklin Albertin Abstract A set of MOS capacitors with TiOxNy films as gate dielectric layer was fabricated and characterized. The TiOxNy films were deposited by reactive r.f. magnetron sputtering varying the nitrogen and oxygen partial pressure in a Ar/N2/O2 gaseous mixture. The TiOxNy films were characterized by, Rutherford Backscattering (RBS), X-ray absorption near edge spectroscopy (XANES) in oxygen K-edge (O-K), optical absorption and High Resolution Transmission Electron Microscopy (HRTEM). Capacitance-voltage (1MHz) and current-voltage measurements were performed to obtain the effective dielectric constant, the effective oxide thickness (EOT), the leakage current density, and the interface quality. MOS capacitors results show that the TiOxNyfilms dielectric constant varies from 28 to 80, present a good interface quality with silicon, and the leakage current density values are in the order of 0.25 mA/cm2 for VG = ,2V, which is acceptable for high performance logic circuits and low power circuits fabrication. The leakage current density is reduced in 2 orders of magnitude for increasing nitrogen concentration (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Spontaneous stratification of InGaN layers and its influence on optical propertiesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S2 2009Z. Liliental-Weber Abstract Transmission Electron Microscopy, high resolution X-ray diffraction and reciprocal space maps, Rutherford Back Scattering and photoluminescence were applied to study InGaN layers grown by MOCVD with increasing layer thickness (100 nm to 1000 nm) and nominally constant In concentration of 10%. Spontaneous stratification of the layer has been found. A strained layer with lower than nominal In content was found in direct contact with the underlying GaN followed by relaxed layers with a nominal or higher In concentration. A high density of randomly distributed stacking faults as well as domains with cubic structure and closely distributed stacking faults (polytype-like) were present in the thicker layers. Strong corrugation of the thicker sample surface was observed. The appearance of multiple photoluminescence line positions was related not only to the spontaneously formed layers with different In content, but also to the structural planar defects formed in the thicker layers. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Photoluminescence spectroscopy and transport electrical measurements reveal the quantized features of Si nanocrystals embedded in an ultra thin SiO2 layerPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2007C. Dumas Abstract In this paper, we have investigated the quantized charging features revealed by nanometer scale devices containing a 2D array of Si nanoparticles (nps) embedded into a SiO2 layer. The Si nps were synthesized by ultra low energy ion implantation and annealing under slightly oxidizing ambient. The structural characteristics of the material (oxide thicknesses, nps size and density) have been studied by Transmission Electron Microscopy (TEM) and Energy Filtered TEM (EFTEM). Moreover, photoluminescence (PL) spectroscopy and electrical I(V) measurements using a MOS capacitor addressing only a few nps have been performed at room temperature. It is observed that, as the oxidizing annealing temperature increases, the nps size decreases and the oxide quality is restored. These features appear on the PL spectra as a blue shift of the PL red band linked to quantum confinement into nps and on the I(V) characteristics as an increase of the voltage peak width and a decrease of the main current background. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Size and shape of In rich clusters and InGaN QWs at the nanometer scalePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2005P. Ruterana Abstract Following the need to accurately understand the In composition fluctuations and their role on the optical properties of the GaN based heterostructures, an investigation of MOCVD InGaN/GaN quantum wells is carried out. To this end, quantitative High Resolution Transmission Electron Microscopy (HRTEM) is coupled with image simulation and Finite Element Method (FEM) for the thin foil relaxation modelling. The results show that the indium content can reach x = 1 in the clusters inside the core. In these MOCVD QWs, we attempt to connect the Quantum dot density, composition, and shape to the growth conditions, in order to help the engineering process of highly efficient devices. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Synthesis and characterization of styrene butadiene rubber,Bentonite clay nanocompositesPOLYMER ENGINEERING & SCIENCE, Issue 7 2009Sugata Chakraborty In the present study, naturally occurring unfractionated bentonite clay was used to prepare styrene butadiene rubber/bentonite clay nanocomposite by latex stage blending. The bentonite clay was organo-modified by in situ resol formation by the reaction of resorcinol and formaldehyde. The latex clay mixture was co-coagulated with acid. The resulting clay masterbatch was compounded and evaluated by Fourier Transform Infrared spectroscopy, X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray spectroscopy (EDS), Scanning Electron Microscopy, Thermogravimetric analysis, and Differential Scanning Calorimetry. XRD showed that the interplanar distance of the in situ resol-modified bentonite clay increased from 1.23 to 1.41 nm for the unmodified bentonite. TEM analysis indicated partial exfoliation and/or intercalation. EDS (Si and Al mapping) of the clay revealed the nature of the dispersion in the nanocomposites vis-à-vis the conventional styrene-butadiene rubber (SBR)/bentonite clay composite. Thermogravimetric analysis was used to compare the decomposition trends of the SBR/clay nanocomposites with the SBR/clay composite. The glass transition temperature of SBR/clay nanocomposites increased as compared with that of neat SBR. Substantial improvement in most of the other mechanical properties was also observed in case of the nanocomposites. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source] Characteristics of polystyrene/polyethylene/clay nanocomposites prepared by ultrasound-assisted mixing processPOLYMER ENGINEERING & SCIENCE, Issue 7 2004J. G. Ryu In this study, polymer-clay nanocomposites of various concentrations were prepared by ultrasonically assisted polymerization and melt-mixing processes. A sonication process using power ultrasonic waves was employed to enhance nano-scale dispersion during melt-mixing of polymer blends and organically modified clay. We expected enhanced breakup of layered silicate bundles and further reduction in the size of the dispersed phase, with better homogeneity compared to the different immiscible blend pairs. X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM) were used to characterize the structures of the nanocomposites. The rheological behaviors of the obtained nanocomposites were measured with parallel plate rheometry. It was found that the ultrasound-assisted process successfully generated exfoliated nanocomposites and promoted in-situ compatibilization of the matrix comprising an immiscible pair of polymers in a blend. The resulting nanocomposite exhibited superior thermal stability and elastic modulus compared to the base polymer. Polym. Eng. Sci. 44:1198,1204, 2004. © 2004 Society of Plastics Engineers. [source] Light and Transmission Electron Microscopy of Immature Camelus Dromedarius OocyteANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 4 2004H. Nili Summary In order to provide a consistent system for laboratory production of embryos, the characteristics of immature camel oocyte must first be described. The objective of this study was to define ultrastructural features of immature camel oocyte. Ovaries were obtained from camels at a local abattoir, and then transported to the laboratory within 2 h. Camelus cumulus oocyte complexes (COCs) were aspirated from 2,6 mm follicles using a 22-gauge needle. Excellent and good quality COCs were selected and prepared for transmission electron microscopy study using a cavity slide. The fine structure of camel oocyte is morphologically similar to that of other mammalian oocytes. However, some minor differences exist between COC of camel and other mammalian species. Different size and shape of membrane-bound vesicles, lipid droplet, mitochondria and cortical granules were distributed throughout the ooplasm. Discrete or in association with endoplasmic reticulum, Golgi complexes were observed in the periphery of the oocytes. The majority of the oocytes were in the germinal vesicle stage. [source] Effects of ultrasound in coating nano-precipitated CaCO3 with stearic acidASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009K. W. Kow Abstract Nano-Precipitated CaCO3 (NPCC) are coated with stearic acid to improve its dispersion in polymer as well as to reduce agglomeration. In this work, coating was done by wet method using ethanol. Ultrasonication was applied to NPCC to de-agglomerate micron size NPCC into smaller size. Effects of amplitude, temperature and energy input of ultrasonication was investigated. The amplitude was varied from 60% to 100% whereas temperature was varied from 5°C to 45°C. The energy input was stressed up from 3.6 kJ to 180 kJ. Mean diameter of NPCC were observed by using Particle Size Analyzer and Transmission Electron Microscopy (TEM). It was found that mean diameter of NPCC do not vary significantly with temperature. Mean diameter of NPCC, however, decreases exponentially with the energy input. Comparisons were done on NPCC coated with others methods such as dry ball milling and aqueous coating. TEM images show that coating NPCC with ultrasonication is more uniform than other methods. In addition, first derivative mass loss with temperature (DTG) reveals that NPCC coated with ultrasonication do not contain excessive free acid as exhibited by those coated in aqueous and dry ball milling. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Characterization of the Surface Properties of Commercially Available Dental Implants Using Scanning Electron Microscopy, Focused Ion Beam, and High-Resolution Transmission Electron MicroscopyCLINICAL IMPLANT DENTISTRY AND RELATED RESEARCH, Issue 1 2008Tobias Jarmar PhD ABSTRACT Background:, Since osseointegration of the respective implant is claimed by all manufacturing companies, it is obvious that not just one specific surface profile including the chemistry controls bone apposition. Purpose:, The purpose was to identify and separate out a particular set of surface features of the implant surfaces that can contribute as factors in the osseointegration process. Material and Methods:, The surface properties of several commercially available dental implants were extensively studied using profilometry, scanning electron microscopy, and transmission electron microscopy. Ultrathin sections prepared with focused ion beam microscopy (FIB) provided microstructural and chemical data which have not previously been communicated. The implants were the Nobel Biocare TiUnite® (Nobel Biocare AB, Göteborg, Sweden), Nobel Biocare Steri-Oss HA-coated (Nobel Biocare AB, Yorba Linda, CA, USA), Astra-Tech OsseoSpeedÔ (Astra Tech AB, Mölndal, Sweden), Straumann SLA® (Straumann AG, Waldenburg, Switzerland), and the Brånemark Integration Original Fixture implant (Brånemark Integration, Göteborg, Sweden). Results:, It was found that their surface properties had differences. The surfaces were covered with crystalline TiO2 (both anatase and rutile), amorphous titanium oxide, phosphorus doped amorphous titanium oxide, fluorine, titanium hydride, and hydroxyapatite, respectively. Conclusion:, This indicates that the provision of osseointegration is not exclusively linked to a particular set of surface features if the implant surface character is a major factor in that process. The studied methodology provides an effective tool to also analyze the interface between implant and surrounding bone. This would be a natural next step in understanding the ultrastructure of the interface between bone and implants. [source] Preparation, structure and photoluminescence properties of SiO2,coated ZnS nanowiresCRYSTAL RESEARCH AND TECHNOLOGY, Issue 10 2010Changhyun Jin Abstract It is essential to passivate one-dimensional (1D) nanostructures with insulating materials to avoid crosstalking as well as to protect them from contamination and oxidation. The structure and influence of thermal annealing on the photoluminescence properties of ZnS-core/SiO2 -shell nanowires synthesized by the thermal evaporation of ZnS powders followed by the sputter deposition of SiO2 were investigated. Transmission electron microscopy and X-ray diffraction analyses revealed that the cores and shells of the core-shell nanowires were single crystal zinc blende-type ZnO and amorphous SiO2, respectively. Photoluminescence (PL) measurement showed that the core-shell nanowires had a green emission band centered at around 525 nm with a shoulder at around 385 nm. The PL emission of the core-shell nanowires was enhanced in intensity by annealing in an oxidative atmosphere and further enhanced by subsequently annealing in a reducing atmosphere. Also the origin of the enhancement of the green emission by annealing is discussed based on the energy-dispersive X-ray spectroscopy analysis results. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Synthesis of rhombohedral strontium carbonate aggregates at the water/hexamethylene interface with cetyltrimethylammonium bromideCRYSTAL RESEARCH AND TECHNOLOGY, Issue 8 2008Long Chen Abstract Unusual rhombohedral strontium carbonate (SrCO3) aggregates have been synthesized in situ from strontium nitrate by the slow release of carbon dioxide by alkaline hydrolysis of diethyl carbonate at the water/hexamethylene interface in the presence of cetyltrimethylammonium bromide (CTAB). Transmission electron microscopy, Fourier transform infrared spectroscopy and X-ray powder diffractometry were used to characterize the products. The results indicate that rhombohedral SrCO3 aggregates are obtained with weaker crystallinity and sizes of several micrometers. The possible formation mechanism of the SrCO3 aggregates at the interface is discussed, which can be interpreted by particle-aggregation based non-classical crystallization laws. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Electrochemical Properties of Ordered Mesoporous Carbon Film Adsorbed onto a Self-Assembled Alkanethiol Monolayer on Gold ElectrodeELECTROANALYSIS, Issue 2 2009Dan Zheng Abstract A stable ordered mesoporous carbon (OMC) film electrode was successfully constructed by adsorbing OMC onto a self-assembled monolayer (SAM) of C18H37SH chemisorbed on the Au electrode. Transmission electron microscopy (TEM), atomic force microscopy (AFM), and electrochemical methods were used to characterize the properties of the OMC film electrode. The adsorbed OMC can restore the heterogeneous electron transfer almost totally blocked by the alkanethiol monolayer. Nyquist plots show a sharply decrease of the charge transfer resistance (Rct) of the Fe(CN) couple at the OMC film electrode. Furthermore, the OMC film electrode is found to possess a significantly reduced interfacial capacitance and largely enhanced current response of hydrogen peroxide. This novel approach to the fabrication of stable OMC film electrode with excellent electrochemical properties is believed to be very attractive for electrochemical studies and electroanalytical applications. [source] Synthesis and Characterization of MWNTs/Au NPs/HS(CH2)6Fc Nanocomposite: Application to Electrochemical Determination of Ascorbic AcidELECTROANALYSIS, Issue 16 2008Jian-Ding Qiu Abstract In this article, a detailed electrochemical study of a novel 6-ferrocenylhexanethiol (HS(CH2)6Fc) self-assembled multiwalled carbon nanotubes-Au nanoparticles (MWNTs/Au NPs) composite film was demonstrated. MWNTs/Au NPs were prepared by one-step in situ synthesis using linear polyethyleneimine (PEI) as bifunctionalizing agent. HS(CH2)6Fc, which acted as the redox mediator, was self-assembled to MWNTs/Au NPs via Au-S bond. Transmission electron microscopy (TEM), energy-dispersive X-ray analysis (EDX), Fourier transformed infrared absorption spectroscopy (FT-IR), UV-visible absorption spectroscopy, and cyclic voltammetry were used to characterize the properties of the MWNTs/Au NPs/HS(CH2)6Fc nanocomposite. The preparation of the nanocomposite was very simple and effectively prevented the leakage of the HS(CH2)6Fc mediator during measurements. The electrooxidation of AA could be catalyzed by Fc/Fc+ couple as a mediator and had a higher electrochemical response due to the unique performance of MWNTs/Au NPs. The nanocomposite modified electrode exhibited excellent catalytic efficiency, high sensitivity, good stability, fast response (within 3,s) and low detection limit toward the oxidation of AA at a lower potential. [source] Crash of a population of the marine heterotrophic flagellate Cafeteria roenbergensis by viral infectionENVIRONMENTAL MICROBIOLOGY, Issue 11 2007Ramon Massana Summary Viruses are known as important mortality agents of marine microorganisms. Most studies focus on bacterial and algal viruses, and few reports exist on viruses infecting marine heterotrophic protists. Here we show results from several incubations initiated with a microbial assemblage from the central Indian Ocean and amended with different amounts of organic matter. Heterotrophic flagellates developed up to 30 000 cells ml,1 in the most enriched incubation. A 18S rDNA clone library and fluorescent in situ hybridization counts with newly designed probes indicated that the peak was formed by Cafeteria roenbergensis and Caecitellus paraparvulus (90% and 10% of the cells respectively). Both taxa were below detection in the original sample, indicating a strong positive selective bias during the enrichment. During the peak, C. roenbergensis cells were observed with virus-like particles in the cytoplasm, and 4 days later this taxa could not be detected. Transmission electron microscopy confirmed the viral nature of these particles, which were large (280 nm), had double-stranded DNA, and were produced with a burst size of ,70. This virus was specific of C. roenbergensis as neither C. paraparvulus that was never seen infected, nor other flagellate taxa that developed in later stages of the incubation, appeared attacked. This is one of the few reports on a heterotrophic flagellate virus and the implications of this finding in the Indian Ocean are discussed. [source] Grazing protozoa and magnetosome dissolution in magnetotactic bacteriaENVIRONMENTAL MICROBIOLOGY, Issue 11 2007Juliana L. Martins Summary Magnetotactic bacteria show an ability to navigate along magnetic field lines because of magnetic particles called magnetosomes. All magnetotactic bacteria are unicellular except for the multicellular prokaryote (recently named ,Candidatus Magnetoglobus multicellularis'), which is formed by an orderly assemblage of 17,40 prokaryotic cells that swim as a unit. A ciliate was used in grazing experiments with the M. multicellularis to study the fate of the magnetosomes after ingestion by the protozoa. Ciliates ingested M. multicellularis, which were located in acid vacuoles as demonstrated by confocal laser scanning microscopy. Transmission electron microscopy and X-ray microanalysis of thin-sectioned ciliates showed the presence of M. multicellularis and magnetosomes inside vacuoles in different degrees of degradation. The magnetosomes are dissolved within the acidic vacuoles of the ciliate. Depending on the rate of M. multicellularis consumption by the ciliates the iron from the magnetosomes may be recycled to the environment in a more soluble form. [source] Molecular and morphological characterization of the association between bacterial endosymbionts and the marine nematode Astomonema sp. from the BahamasENVIRONMENTAL MICROBIOLOGY, Issue 5 2007Niculina Musat Summary Marine nematode worms without a mouth or functional gut are found worldwide in intertidal sandflats, deep-sea muds and methane-rich pock marks, and morphological studies show that they are associated with endosymbiotic bacteria. While it has been hypothesized that the symbionts are chemoautotrophic sulfur oxidizers, to date nothing is known about the phylogeny or function of endosymbionts from marine nematodes. In this study, we characterized the association between bacterial endosymbionts and the marine nematode Astomonema sp. from coral reef sediments in the Bahamas. Phylogenetic analysis of the host based on its 18S rRNA gene showed that Astomonema sp. is most closely related to non-symbiotic nematodes of the families Linhomoeidae and Axonolaimidae and is not closely related to marine stilbonematinid nematodes with ectosymbiotic sulfur-oxidizing bacteria. In contrast, phylogenetic analyses of the symbionts of Astomonema sp. using comparative 16S rRNA gene sequence analysis revealed that these are closely related to the stilbonematinid ectosymbionts (95,96% sequence similarity) as well as to the sulfur-oxidizing endosymbionts from gutless marine oligochaetes. The closest free-living relatives of these gammaproteobacterial symbionts are sulfur-oxidizing bacteria from the family Chromatiaceae. Transmission electron microscopy and fluorescence in situ hybridization showed that the bacterial symbionts completely fill the gut lumen of Astomonema sp., suggesting that these are their main source of nutrition. The close phylogenetic relationship of the Astomonema sp. symbionts to known sulfur-oxidizing bacteria as well as the presence of the aprA gene, typically found in sulfur-oxidizing bacteria, indicates that the Astomonema sp. symbionts use reduced sulfur compounds as an energy source to provide their hosts with nutrition. [source] | |||||||||||||||||||||||||||||||||||||||||||