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TEM Study (tem + study)
Selected AbstractsTEM Study of Precipitates in Melt-Spun Mg-Zn-Y-La Alloys,ADVANCED ENGINEERING MATERIALS, Issue 6 2005J. Rao Recently, nano-crystalline MgZn1Y2 alloys exhibiting excellent tensile yield strength elongation ratio have been developed as a consequence of preliminary investigations of alloy compositions using melt-spun ribbons. Their results show that the novel long-period hexagonal atomic configurations in the Mg-Ln-Zn alloys as well as the atomic scale enrichment of Ln and Zn elements into the misfit atomic array sites indicates the possibility that a high-strength Mg-based alloy is developed by the control of the novel structure and the atomic scale segregation mode. [source] A TEM study on ZrO2 -rich phases in the quasibinary system ZrO2 -Zr3N4: Comparison between fast and slowly cooled samplesCRYSTAL RESEARCH AND TECHNOLOGY, Issue 3 2005A. T. Tham Abstract A thorough comparison between the slowly and fast cooled ,,-type oxynitrides of zirconium has been carried out by means of transmission electron microscopy. This work aims at detecting and analyzing the so-called "modulated" ,, phase, which has been involved in the introduction of ordered anion vacancies through nitridation of zirconia. The gained information from the occurrence of such a modulated phase and the manner, in what it appears, do support the suggested structure model, which had been developed in early works in order to get a better understanding of the typical phase transitions in zirconium oxynitrides. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Characterization of Phaffia rhodozyma 3A 4,8 Generated by Low-dose ,-irradiationJOURNAL OF FOOD SCIENCE, Issue 9 2004S.H. Lee ABSTRACT: Astaxanthin content, superoxide dismutase activity, catalase activity, and transmission electron microscopy (TEM) of astaxanthin-hyperproducing mutant 3A 4,8, previously isolated through repeated rounds of ,-irradiation below 10 kGy and visual screening, was examined and compared with wild strain 67,385 and parent strain 2A2N to characterize its mutant. Astaxanthin content of Phaffia rhodozyma was determined using high-performance liquid chromatography. After 10 d culture, 3A 4,8 produced 2.5 mg/g yeast, 78% higher astaxanthin content than parent strain. Mutant exhibited lower superoxide dismutase and higher catalase activities than parent strain. TEM study showed mutant had smaller-sized mitochondria than parent strain. These results indicate ,-irradiation is an effective means of mutagenesis for production of carotenoidhyperproducing mutants. [source] TEM study of the structural similarity between NaCl and rhombohedral phase of Te-based ternary chalcogenide materialsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2009Changwoo Sun Abstract Comparing the phase-change behaviour of Ge,Bi,Te (GBT) to that of Ge,Sb,Te (GST), we have tried to verify a general relationship between a metastable NaCl and a stable rhombohedral structure that is easily incurred by stretching the cube along the body diagonal. High-resolution transmission electron microscopy (TEM) images show that the NaCl as well as the rhombohedral GBT and GST structures are observed along specific directions. From the TEM images, we suggest an atomic model and a phase transition mechanism by lattice distortion. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The effects of GaAs interval layer on GaNAs/GaAs superlattice structure grown by RF-MBE using modulated N radical beam sequencePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2008Kensuke Fujii Abstract We have investigated the effects of GaAs interval layers on the structure of GaNAs/GaAs superlattices (SLs) grown by radio-frequency molecular beam epitaxy. As the results of x-ray diffraction, it is found that periodic structure of GaNAs/GaAs SL is better in the case of thicker GaAs layer than that of thin GaAs layer, whereas the GaNAs layer thickness is constant of 10 ML. Transmission electron microscope (TEM) studies of SL samples clearly demonstrate the drastic effects of GaAs layer thickness on the GaNAs/GaAs SL structures. High resolution TEM study of the sample with a thin AlAs layer inserted between GaNAs and GaAs, for improved contrast, reveals existence of the roughening process during GaNAs layer growth and the smoothing process during GaAs layer growth. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Self-assembled structures in blends of disordered and lamellar block copolymers: SAXS, SANS and TEM studyPOLYMER INTERNATIONAL, Issue 1 2009Jaroslav Holoubek Abstract BACKGROUND: The phase behaviour of copolymers and their blends is of great interest due to the phase transitions, self-assembly and formation of ordered structures. Phenomena associated with the microdomain morphology of parent copolymers and phase behaviour in blends of deuterated block copolymers of polystyrene (PS) and poly(methyl methacrylate) (PMMA), i.e. (dPS- block - dPMMA)1/(dPS- block -PMMA)2, were investigated using small-angle X-ray scattering, small-angle neutron scattering and transmission electron microscopy as a function of molecular weight, concentration of added copolymers and temperature. RESULTS: Binary blends of the diblock copolymers having different molecular weights and different original micromorphology (one copolymer was in a disordered state and the others were of lamellar phase) were prepared by a solution-cast process. The blends were found to be completely miscible on the molecular level at all compositions, if their molecular weight ratio was smaller than about 5. The domain spacing D of the blends can be scaled with Mn by D , Mn2/3 as predicted by a previously published postulate (originally suggested and proved for blends of lamellar polystyrene- block -polyisoprene copolymers). CONCLUSIONS: The criterion for forming a single-domain morphology (molecularly mixed blend) taking into account the different solubilization of copolymer blocks has been applied to explain the changes in microdomain morphology during the self-assembling process in two copolymer blends. Evidently the criterion, suggested originally for blends of lamellar polystyrene- block -polyisoprene copolymers, can be employed to a much broader range of block copolymer blends. Copyright © 2008 Society of Chemical Industry [source] Physicochemical studies on the biopolymer inulin: A critical evaluation of its self-aggregation, aggregate-morphology, interaction with water, and thermal stabilityBIOPOLYMERS, Issue 9 2009Abhijit Dan Abstract Physicochemical properties viz., aggregation, molar mass, shape, and size of chicory inulin in solution were determined by fluorimetry, DLS, SLS, TEM, and viscometry methods. The thermal stability of the biopolymer was examined by TGA, DTA, and DSC measurements. The water vapor adsorption of desiccated inulin was also studied by the isopiestic method, and the data were analyzed in the light of the BET equation. On the basis of the obstruction to ion conductance by the inulin aggregates in solution and analysis of the data, the extent of hydration of inulin in solution was estimated. The result was coupled with the intrinsic viscosity, [,], of inulin to ascertain the shape of the biopolymer aggregates in aqueous solution. The critical aggregation concentration (cac) of inulin in aqueous as well as in salt solution was assessed by fluorimetry. The weight average molar mass, , of inulin monomer and its aggregate was found to be 4468 and 1.03 × 106 g/mol, respectively, in aqueous solution. This aggregated mass was 2.4 × 106 g/mol in 0.5M NH4SCN solution. The [,] values of the soft supramolecular aggregates in solution (without and with salt) were small and comparable with globular proteins evidencing spherical geometry of the biopolymer aggregates as supported by the TEM results. In DMSO, rod-like aggregates of inulin was found by the TEM study. The [,] of the biopolymer in the DMSO medium was therefore, higher than that in the aqueous medium. Unlike aqueous medium, the aggregation in DMSO was not associated with a cac. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 687,699, 2009. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Effects of maternal hyperthermia on myogenesis-related factors in developing upper limb,BIRTH DEFECTS RESEARCH, Issue 3 2009Jin Lee Abstract BACKGROUND: Maternal hyperthermia is one causative factor in various congenital anomalies in experimental animals and humans. In the present study, we assessed the effects of high temperature on limb myogenesis in mice. METHODS: Pregnant mice, C57BL/6 strain, were exposed to hyperthermia (43°C, 5 minutes) on embryonic day (ED) 8. Fetuses on ED 11, 13, 15, and 17 and neonates on postnatal day (PD) 1 were collected. To characterize the effects of hyperthermia on myogenesis-related factors Pax3, MyoD, myogenin, and myosin heavy chain (MyHC) during skeletal muscle development, we performed RT-PCR, western blotting, immunohistochemistry, and transmission electron microscopy. RESULTS: Pax3 gene expression was still detected on ED 13 in hyperthermia-exposed fetuses. The expression of MyoD protein was down-regulated in fetuses exposed to hyperthermia. In contrast, myogenin and MyHC protein expression were up-regulated on PD 1 and ED 17, respectively, in the group exposed to hyperthermia. Immunohistochemical analysis confirmed the findings from western blot analysis. Compared with control neonates, a TEM study revealed immature muscle fibers in PD 1 hyperthermia neonates. Thus, our studies showed that maternal hyperthermia induced delayed expression of Pax3 and inhibited expression of MyoD proteins, which are known to play important roles in migration of myogenic progenitor cells, and in myoblast proliferation. In addition, maternal hyperthermia also delayed the expression of myogenin protein for the formation of myotubes, and MyHC protein, which is one of the final muscle differentiation factors. CONCLUSION: Our data suggest that maternal hyperthermia delays limb myogenesis in part by disregulating the expression of key myogenesis-related factors. Birth Defects Research (Part A), 2009. © 2009 Wiley-Liss, Inc. [source] | ||||||||||||||||