• Journal of Magnetics
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• v.20 no.3
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• pp.246-251
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• 2015

This study was aimed to study the effect of Zn content on the hyperfine parameters and the structural variation of $Ni_{1-x}Zn_xFe_2O_4$ for x = 0, 0.2, 0.4, 0.6, and 0.8. To achieve this, a sol-gel route was used for the preparation of samples and the obtained ferrites were investigated by X-ray diffraction, scanning electron microscopy, and $M{\ddot{o}}ssbauer$ spectroscopy. The formation of spinel phase without any impurity peak was identified by X-ray diffraction of all the samples. Moreover, the estimated crystallite size by X-ray line broadening indicates a decrease with increasing Zn content. This result was in agreement with the scanning electron microscopy result, indicating the reduction in grain growth with further zinc substitution. The room-temperature $M{\ddot{o}}ssbauer$ spectra show that the hyperfine fields at both the A and B sites decreased with increasing Zn content; however, the rate of reduction is not the same for different sites. Moreover, the best fit parameter showed that the quadrupole splitting values of B site increased from the pure nickel ferrite to the sample with x = 0.8.

• Applied Microscopy
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• v.31 no.3
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• pp.235-244
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• 2001

The aim of this study was to observe morphological changes of Trichomonas vaginalis after contact with human vaginal epithelial cells, by scanning electron microscope. The vaginal epithelial cells (VEC) (menstrual, days $5\sim10$) from normal women were mixed with T. vaginalis (VEC/trichomonads ratio of 1 : 10), and incubated for 30 min. The parasitic body was changed to a more elongated shape with pseudopodia or was flattened to ameboid transformation showing highly adherence to VEC.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2006.06a
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• pp.1-18
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• 2006

A novel transmission electron microscopy technique for the visualization of polymers adsorbed on secondary fines has been developed. This technique has been utilized in observing the adsorption behavior of various wet-end additives. The technique is sensitive enough not only to allow differentiation between linear and branched polymers, but also to observe differences in the adsorption behavior and conformational characteristics of particular polymeric derivatives. Conformational changes of a cationic polyacrylamide (CPAM) were examined in response to variations in wet-end conditions, such as mixing time and system conductivity. The molecular conformations of cationic starch and cationic guar gum were also examined by this technique. The technique has been employed to observe the effects of silica microparticles on the conformational characteristics of CPAM (drainage/retention aid) pre-adsorbed on secondary fines. The transmission electron microscopy method is a viable tool for investigating the macromolecular events that make up a large part of wet end chemistry in papermaking.

• Journal of the Korean Ceramic Society
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• v.42 no.5 s.276
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• pp.359-365
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• 2005

Silicon nitride coating films with various ratios of nitrogen to silicon contents were prepared and characterized. The film was coated on silicon substrate by sputtering method with changing nitrogen gas flow rate in a chamber. The nitrogen to silicon ratio was found to have values in a range from 0 to 1.4. Coated film was characterized with scanning electron microscopy, transmission electron microscopy, electron probe microanalysis, nanoindentation scanning probe microscopy, x-ray photon spectrometry, and Raman spectrometry. Silicon nitride phase in all samples showed amorphous nature regardless of N/Si ratio. When N/Si ratio was 1.25, hardness and elastic modulus of silicon nitride film showed maximum with 22 GPa and 210 GPa, respectively. Those values decreased, when N/Si ratio was higher than 1.25. Raman spectrum showed that no silicon phase exist in the film. XPS result showed that the silicon-nitrogen bond was dominant way for atomic bonding in the film. The structure and property was explained with Random Bonding Model(RBM) which was consistent with the microstructure and chemistry analysis for the coating films.

• Korean Journal of Materials Research
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• v.20 no.12
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• pp.645-648
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• 2010

The structure and morphology of epitaxial layer defects in epitaxial Si wafers produced by the Czochralski method were studied using focused ion beam (FIB) milling, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Epitaxial growth was carried out in a horizontal reactor at atmospheric pressure. The p-type Si wafers were loaded into the reactor at about $800^{\circ}C$ and heated to about $1150^{\circ}C$ in $H_2$. An epitaxial layer with a thickness of $4{\mu}m$ was grown at a temperature of 1080-$1100^{\circ}C$. Octahedral void defects, the inner walls of which were covered with a 2-4 nm-thick oxide, were surrounded mainly by $\{111\}$ planes. The formation of octahedral void defects was closely related to the agglomeration of vacancies during the growth process. Cross-sectional TEM observation suggests that the carbon impurities might possibly be related to the formation of oxide defects, considering that some kinds of carbon impurities remain on the Si surface during oxidation. In addition, carbon and oxygen impurities might play a crucial role in the formation of void defects during growth of the epitaxial layer.

• Microbiology and Biotechnology Letters
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• v.18 no.3
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• pp.221-226
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• 1990

To detect prophages and bacterioeins, twenty strains of Bacillus circulans were treated with mitomycin C. The resulted lysates were subjected to electron microscopy, and also examined for killing and plaque-forming activities. Fifteen strains showed killing activity on two or more strains of Bacillue circulans. Killing agents were centrifuged in linear 5 to 20% sucrose gradient, and studied with electron microscopy which revealed the presence of particles.They looked morphologically like phage tail of 190 nm long with fiber (FA9, FA5) or without fiber (FA1, FA6), T even phage-like particle with a head of 50 nm in diameter and a tail of 140 nm long (FA7), or T7 phage-like particle with a head of 70 nm in diameter and a tail of 20 nm long (FA17). The killing agent of FA17 showed phage-forming activity on several strains different from killing sensitive strains of Bacillus circulans.

• Applied Microscopy
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• v.42 no.4
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• pp.212-217
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• 2012

This paper reports the effects of post-annealing of ZnO thin films on their microstructure and the device performance of the transistors fabricated from the films. From X-ray diffraction and transmission electron microscopy characterization, we uncovered that the grain size increased with the annealing temperature escalating and that the film stress shifted from compressive to tensile due to the grain size increment. Electrical characterization revealed that the grain size increase damaged the device performance by drastically lifting the off-current level. By annealing the devices in an $O_2$ ambient (instead of air), we were able to suppress the off-current while improving the electron mobility.

• Applied Microscopy
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• v.1 no.1
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• pp.11-17
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• 1969

Conidio spores of Aspergillus niger (strain No. NRRL 330) cultured on potato dextrose agar media were studied by electron microscopy, using the thin sectioning techniques. Conidio spores to be sectioned were fixed by triple methods with $K_2Cr_2O_7$, Glutaraldehyde and $OsO_4$. After dehydrated with alcohol, the specimens were embedded in metacrylate and epon resin media, and thinly sectioned by Porter-Blum MT-2. After sectioned these specimens were negative-stained with uranyl acetate and observed. by Hitachi HS-6 electron microscope. The results of this experiment were summarized as follows. 1. The structures of spore ,wall system seem to be formed 4 layers; exosporium, basal layer, spore coat and unit cell membrane. The protuberance of spore surface that was looked like hair appears to be protrusived from the basal layer. 2. The 3 layers of unit cell membrane was constituted outer layer membrane, inner layer membrane and inter-mediate light layer. 3. The structures of intra cytoplasmic membrane appear as spiral form which was consisted of 3 layers membrane system; outer membrane, inner membrane, and intermediate layer, which has pits. 4. The cement substance of spore coat and cortex may be changed quantitatively by physiological state in cell. 5. In some cases, we observed that the ribosome was transformed into poly ribosome group, and the storage materials and the protein crystals were changed variously. It. has been suggested that the morphological change of some cytoplasmic materials may be caused by some specialized function of the physiological stage.

• Applied Microscopy
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• v.26 no.4
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• pp.447-456
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• 1996

Fracture surfaces of materials contain useful information ranging from crack path to the mechanism of fracture. Since limitation of electron transparency requires a sample in the form of thin foil for TEM observations, it is impossible to extract such information directly from the fracture surfaces. In this study, the method of surface replication from the ceramic fracture surface is employed to characterize the process of crack propagation in ceramic matrix composites using TEM analysis. The surface replica from the fracture surface in ceramic materials provides detailed surface morphology and more importantly, loosened particles on the fracture surface are collected. Electron diffraction and chemical composition analyses of these particles reveal crack path in the specimen. Furthermore, one can determine the mode of fracture by observing the fracture surface morphology from the image of replica. Two examples are given to illustrate the potential of the surface replication technique. In the first example, apparent toughness increase in $B_{4}C-Al$ composites at high strain rate is investigated by surface replication to elucidate the mechanism of fracture at different strain rates. The polytypes of SiC formed during the sintering of SiC-AlN composite and their effect on the fracture behavior of SiC-AlN composite are analyzed in the second example.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.26 no.2
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• pp.45-63
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• 1996

In attempt to determine radiation effect on the mandibular condyle of the growing rat, 27 white female rats (Sprague-Dawley) were divided into 3 groups and irradiated respectively 5Gy, 10Gy, 20Gy using MK Cell Irradiator. Mandibular condyles from rats on the day of 1, 7, 14 after the irradiation day were obtained, sectioned sagittally and examined by light microscopy, and thereafter middle portion through anteroposterior direction on the sagittal plane was selected to examine the ultrastructural change by transmission electron microscopy. The obtained results are followings. 1. In the proliferative zone some cells showed little organelles in case of 5Gy irradiation, in addition the number of degenerative cells increased and in case of 10Gy irradiation, and in case of 20 Gy irradiation total number of cells decreased. 2. In the hypertrophic zone, narrowing of width and partial disorder in hypertrophic process were noted in case of 5 Gy irradiation, and more prominent narrowing of width and more irregular disorder in hypertrophic process in case of both 10Gy and 20Gy irradiation. 3. In the upper hypertrophic zone some chondrocytes seemed to be dying and the polarity of nuclei could not be seen, if any. 4. The periodic observation showed the severest change at day 7 and the signs of recovery at day 14 after irradiation.