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Scanning Electron Microscopy Observations (scanning + electron_microscopy_observation)
Selected AbstractsSCANNING ELECTRON MICROSCOPY OBSERVATIONS OF DEFORMITIES IN SMALL PENNATE DIATOMS EXPOSED TO HIGH CADMIUM CONCENTRATIONS,JOURNAL OF PHYCOLOGY, Issue 6 2008Soizic Morin Different types of malformations are likely to affect the morphology of diatoms when exposed to particularly unstable environmental conditions, the most easily identifiable being distortion of the whole frustule. In the present study, we investigated, by means of SEM, valve abnormalities induced by high cadmium contamination (100 ,g · L,1) in small pennate diatoms. Changes in the shape of Amphora pediculus (Kütz.) Grunow and anomalous sculpturing of the cell wall of many species, such as Encyonema minutum (Hilse) D. G. Mann, Mayamaea agrestris (Hust.) Lange-Bert., Gomphonema parvulum (Kütz.) Kütz., or Eolimna minima (Grunow) Lange-Bert., were observed, which were not, or almost not, noticeable in the LM. With consideration to current knowledge of diatom morphogenesis, metal uptake by the cell would induce, directly or indirectly, damage to many cytoplasmic components (e.g., microtubules, cytoskeleton, Golgi-derived vesicles) involved in the precisely organized silica deposition. This study confirms that many species, whatever their size, are likely to exhibit morphological abnormalities under cadmium stress, and that this indicator may be valuable for the biomonitoring of metal contamination, even if SEM observations are not necessary for routine studies. [source] A Novel N -Succinylchitosan- graft -Polyacrylamide/Attapulgite Composite Hydrogel Prepared through Inverse Suspension PolymerizationMACROMOLECULAR MATERIALS & ENGINEERING, Issue 8 2007Ping Li Abstract A novel N -succinylchitosan- graft -polyacrylamide/attapulgite composite hydrogel was prepared by using N -succinylchitosan, acrylamide and attapulgite through inverse suspension polymerization. The result from FTIR spectra showed that OH of attapulgite, OH and NHCO of N -succinylchitosan participated in graft polymerization with acrylamide. The introduced attapulgite could enhance thermal stability of the hydrogel. Scanning electron microscopy observation indicates that the composite hydrogel has a microporous surface. The volume ratio of heptane to water, weight ratio of acrylamide to N -succinylchitosan and attapulgite content have great influence on swelling ability of the composite hydrogel. The composite hydrogel shows higher swelling rate and pH-sensitivity compared to that of without attapulgite. [source] Controlled Ge quantum dots positioning with nano-patterned Si(001) substratesPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 15 2006A. Bavard Abstract A square nanometric patterned substrate (period 20 nm) is obtained by direct twist bonding of two twin Si(001) surfaces, thinning and preferential chemical etching. Molecular beam epitaxy of Ge is carried out on a sample having heterogeneous trench depths to analyse islands positioning as a function of the surface morphology. Scanning electron microscopy observations show that small single dots per mesa or large dots covering several mesas can be observed. It highlights the influence of the mesa aspect ratio on the control of Ge islands self-organization, and suggests the occurrence of an effective activation barrier depending on the surface profile. The position-dependent energy stored in a dot for a given surface profile is estimated from a very simple model based on the balance between capillarity and elastic relaxation terms. By choosing a cycloid-like profile, experimental observations can be explained without fitting parameters. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] A Chemical Route to BiNbO4 CeramicsINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 2 2009Oleg A. Shlyakhtin The liquid phase sintering of fine BiNbO4 powders allows to obtain dense ceramics with excellent microwave dielectric properties (,=44,46; Q×f=16,500,21,600 GHz) at T,700°C. The thermal decomposition of freeze-dried precursors results in the crystallization of a metastable ,,-BiNbO4 polymorph that transforms into a stable orthorhombic ,-modification at T,700°C. The dependence of sinterability on the powder synthesis temperature shows the maximum at 600°C, corresponding to the formation of crystalline BiNbO4 powders with a grain size 80,100 nm. Sintering temperature reduction to 700°C prevents the deterioration of silver contacts during co-firing with BiNbO4 ceramics. In situ scanning electron microscopy observation of the morphological evolution during sintering shows that the intense shrinkage soon after the appearance of a CuO,V2O5 eutectics-based liquid phase is accompanied by complete transformation of the ensemble of primary BiNbO4 particles. [source] Effects of additional and extended acid etching on bonding to caries-affected dentineEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 5 2004César Augusto Galvăo Arrais This study evaluated the effects of additional and extended acid etching on microtensile bond strength (µTBS) of two adhesive systems to sound (SD) and caries-affected dentine (CAD). Flat surfaces of CAD surrounded by SD of 36 extracted carious third molars were assigned to four treatments (i): self-etching adhesive system (Clearfil SE Bond) applied to dentine surfaces following manufacturer's instructions (MI); (ii) after additional etching for 15 s (35% phosphoric acid, PA); (iii) total-etch one-bottle adhesive (Single Bond) applied to dentine surfaces following MI; or (iv), after etching for 45 s with PA. Composite ,blocks' were built on bonded surfaces and restored teeth were vertically sectioned to obtain bonded slices of 0.7 mm thick. Slices were trimmed to create hourglass-shaped specimens (cross-sectional area of 1 mm2), which were tested under tension in a universal testing machine. Additional CAD and SD samples were prepared for scanning electron microscopy observations. Additional and extended etching significantly increased µTBS to CAD; however, µTBS of both adhesives to CAD were significantly lower than to SD. Additional and extended etching can improve bonding to CAD; however, adhesives applied on SD showed the best results for bonding. [source] Cell Proliferation of Human Fibroblasts on Alumina and Hydroxyapatite-Based Ceramics with Different Surface Treatments,INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 2 2010Juliana Marchi Biocompatibility is an important characteristic of dental implant material, and in vitro tests are required to elucidate the interaction between these materials and human tissues. Cell proliferation assays were done with fibroblasts plated on the surface of alumina and hydroxyapatite sintered samples, each with a different surface treatment (sintered, rectified, or polished). After 1, 2, and three days, the samples were prepared for scanning electron microscopy observations. The data were compared by analysis of variance followed by Tukey's test. It was concluded that neither the hydroxyapatite or alumina substrate is cytotoxic, and hydroxyapatite is more biocompatible than alumina. [source] Electrospun polylactide/silk fibroin,gelatin composite tubular scaffolds for small-diameter tissue engineering blood vesselsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2009Shudong Wang Abstract Many synthetic scaffolds have been used as vascular substitutes for clinical use. However, many of these scaffolds may not show suitable properties when they are exposed to physiologic vascular environments, and they may fail eventually because of some unexpected conditions. Electrospinning technology offers the potential for controlling the composition, structure, and mechanical properties of scaffolds. In this study, a tubular scaffold (inner diameter = 4.5 mm) composed of a polylactide (PLA) fiber outside layer and a silk fibroin (SF),gelatin fiber inner layer (PLA/SF,gelatin) was fabricated by electrospinning. The morphological, biomechanical, and biological properties of the composite scaffold were examined. The PLA/SF,gelatin composite tubular scaffold possessed a porous structure; the porosity of the scaffold reached 82 ± 2%. The composite scaffold achieved the appropriate breaking strength (1.28 ± 0.21 MPa) and adequate pliability (elasticity up to 41.11 ± 2.17% strain) and possessed a fine suture retention strength (1.07 ± 0.07 N). The burst pressure of the composite scaffold was 111.4 ± 2.6 kPa, which was much higher than the native vessels. A mitochondrial metabolic assay and scanning electron microscopy observations indicated that both 3T3 mouse fibroblasts and human umbilical vein endothelial cells grew and proliferated well on the composite scaffold in vitro after they were cultured for some days. The PLA/SF,gelatin composite tubular scaffolds presented appropriate characteristics to be considered as candidate scaffolds for blood vessel tissue engineering. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Fire-resistant effect of nanoclay on intumescent nanocomposite coatingsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2007Zhen-yu Wang Abstract The aim of the study is the development of an intumescent nanocomposite coating to provide fire protection for the metallic substrate. Acrylic nanocomposites containing nanoclay and relative intumescent nanocoatings are prepared. The effect of nanoclay on the thermal degradation of an intumescent nanocomposite coating is analyzed by using differential thermal analysis, thermogravimetry, and X-ray diffraction. The influence of the added content of nanoclay on fire performance is studied by a fire protection test and measurements of the limiting oxygen index and effective thermal conductivity. The distribution of nanoparticles in the acrylic nanocomposite is characterized by transmission electron microscopy. The flame-retardant efficiency of the intumescent nanocomposite coating is improved by 1.5% well-distributed nanoclay particles. However, 3% nanoclay produces a negative effect on the fire performance of the coating. Fire protection tests and scanning electron microscopy observations reveal that the fire-retardant property of a conventional intumescent coating is destroyed by aging, whereas the nanocomposite coating modified with 1.5% nanoclay demonstrates good aging and fire resistance. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1681,1689, 2007 [source] Effect of Organic Modification on the Compatibilization Efficiency of Clay in an Immiscible Polymer BlendMACROMOLECULAR RAPID COMMUNICATIONS, Issue 20 2005Suprakas Sinha Ray Abstract Summary: This communication describes the effect of organic modifier miscibility with the matrices, and the effect of the initial interlayer spacing of the organoclay, on the overall morphology and properties of an immiscible polycarbonate/poly(methyl methacrylate) blend. By varying the organic-modifier-specific interactions with the blend matrices at the same time as changing the initial interlayer spacing of the organoclay, different levels of compatibilization were revealed. The evidence for the interfacial compatibilization of the organoclay was assessed by scanning electron microscopy observations and was supported by differential scanning calorimetry analyses. The effect on the level of clay exfoliation was also examined. Differential scanning calorimetry scans of virgin, montmorillonite, and various organically modified montmorillonite-compatibilized 40PC/60PMMA blends [source] Interfacial strength in short glass fiber reinforced acrylonitrile-butadiene-styrene/polyamide 6 blendsPOLYMER COMPOSITES, Issue 3 2010Nihat Ali Isitman The purpose of this study is to derive the apparent interfacial shear strength of short glass fiber reinforced acrylonitrile-butadiene-styrene/polyamide 6 (PA6) blends with different PA6 contents. Tensile stress-strain curves and fiber length distributions are utilized within a continuum micromechanics approach which involves a unified parameter for fiber length distribution efficiency represented as a function of strain. The unique combination of predicted micromechanical parameters is capable of accurately reproducing the mechanical response of the composite to applied strain. In this way, the influence of PA6 on interfacial zone is revealed by outcomes of the predictive method and validated by scanning electron microscopy observations. Favored intermolecular interactions in presence of PA6 chains result in the formation of a PA6 sheathing layer on glass fiber surfaces which in turn causes a drop in the apparent interfacial shear strength. The reason behind is shown to be the shift of the fracture zone from fiber/matrix interface to sheathing layer/matrixinterphase. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers [source] | ||||||||||