• Applied Microscopy
• /
• 제23권2호
• /
• pp.97-106
• /
• 1993

This study was done to elucidate the electron microscopic characteristics of certain pathogenic fungi. Four Candida species, (C. albicans, C. tropicalis, C. parapsilosis and C. glabrate) and Cryptococcus neoformans were cultured for 3 days at $30^{\circ}C$ in the Sabouraud dextrose medium. After incubation, they were stored at $4^{\circ}C$ for 24hours. Fine structures were analyzed by morphometry, and Tukey's HSD test was used for statistics. On scanning electron microscopy C. albicans and C. neoformans were similar in size but different in shape, showing sphero-shape or ovalo-shape in C. neoformans. Surface of C. neoformans was coarse and spiny, but Candida species examined were uniformly smooth. In size, C. glabrata was the smallest among them. Budding scar as seen on the surface of Candida species by the number ranging from 1 to 7. Cryptococcus neoformans showed one or two budding scar. On transmission electron microscopy the cytoplasm of most yeast cells showed plentiful glycogen particles, mitochondria, peroxisomes and vacuoles. However, cell walls were different among four Candida species and Cryptococcus neoformans. The cell wall of Candida species consisted of fibrous layer, that was electron dense layer and transparent layer, in contrast to Cryptococcus neoformans consisted of electron dense layer with lamellar structure. This layer was two times thicker than that of Candida species. The outer layer of cell wall was of radiating pattern.

• Applied Microscopy
• /
• 제30권2호
• /
• pp.205-212
• /
• 2000

Present study was performed to observe the surface ultrastructures of Stictadora furcatum (Trematoda: Heterophyidae). Adult worms were recovered from the cat experimentally infected with metacercariae, and were prepared for scanning electron microscopy. The body was leaf-like and ventrally concave. The oral sucker armed with prominent tegumental spines on the inner surface, and it's lips were obscure. Sensory papillae (type I) in single or grouped forms symmetrically arranged around the oral sucker. The ventrogenital opening retained protruding gonotyl spines and sperms discharged from the genital pore . The body surface was covered with scale-like multipointed tegumental spines. The density and digitated point of spines were gradually decreased toward the posterior end of the body. The digitated points of spines on the anterior portion were 9-12, on the middle were 7-8 and 5-6, and on the posterior were 2-3 and peg-like. Although the tegumental ultrastructure of S. fuscatum was generally similar to those of other heterophyid flukes , the oral sucker with tegumental spines on the inner surface and without obvious lips, and the ventrogenital opening with protruding gonotyl spines were suggested to be the characteristic features.

• Applied Microscopy
• /
• 제42권3호
• /
• pp.151-157
• /
• 2012

The microstructure of various shapes of stacking fault pyramids (SFPs) formed in multiple implant/anneal Separation by Implanted Oxygen (SIMOX) material were investigated by plan-view and cross-sectional transmission electron microscopy. In the multiple implant/anneal SIMOX, the defects in the top silicon layer are confined at the interface of the buried oxide layer at a density of ${\sim}10^6\;cm^{-2}$. The dominant defects are perfect and imperfect SFPs. The perfect SFPs were formed by the expansion and interaction of four dissociated dislocations on the {111} pyramidal planes. The imperfect SFPs show various shapes of SFPs, including I-, L-, and Y-shapes. The shape of imperfect SFPs may depend on the number of dissociated dislocations bounded to the top of the pyramid and the interaction of Shockley partial dislocations at each edge of {111} pyramidal planes.

• Applied Microscopy
• /
• 제46권2호
• /
• pp.110-115
• /
• 2016

Transmission electron microscopy (TEM) is a powerful tool for analyzing a broad range of materials and provides localized information about the microstructure. However, the analysis results are strongly influenced by the quality of the thin foil specimen. Sample preparation for TEM analysis requires considerable skill, especially when the area of interest is small or the material of interest is difficult to thin because of its high hardness and its mechanical instability when thinned. This article selectively reviews recent advances in TEM sample preparation techniques using a tripod polisher. In particular, it introduces two typical types (fl at type and wedge type) of TEM sample preparation and the benefits and drawbacks of each method; finally, a method of making better samples for TEM analysis is suggested.

• Macromolecular Research
• /
• 제16권7호
• /
• pp.604-608
• /
• 2008

Color dye-doped silk fibroin nanoparticles were successfully fabricated using a microemulsion method. An aqueous silk fibroin solution was prepared by dissolving cocoons (Bombyx mori) in a concentrated lithium bromide solution followed by dialysis. A color dye solution was also mixed with the aqueous silk fibroin solution. The surfactants used for the microemulsion were then removed by methanol and ethanol, yielding color dye-doped silk fibroin nanoparticles, approximately 167 nm in diameter. The secondary structure of the nanoparticles showed a $\beta$-sheet conformation, as characterized by Fourier transform infrared spectroscopy. The morphology of the nanoparticles was determined by field emission scanning electron microscopy, transmission electron microscopy and atomic force microscopy, and their size and size distribution were measured by dynamic light scattering. The color dye-doped silk fibroin nanoparticles were examined by confocal laser scanning microscopy.

• Applied Microscopy
• /
• 제48권4호
• /
• pp.96-101
• /
• 2018

The release of nanoscale membrane-bound vesicles is common in all three domains of life. These vesicles are involved in a variety of biological processes such as cell-to-cell communication, horizontal gene transfer, and substrate transport. Prokaryotes including bacteria and archaea release membrane vesicles (MVs) (20 to 400 nm in diameter) into their extracellular milieu. In spite of structural differences in cell envelope, both Gram-positive and negative bacteria produce MVs that contain the cell membrane of each bacterial species. Archaeal MVs characteristically show surface-layer encircling the vesicles. Filamentous fungi and yeasts as eukaryotic microbes produce bilayered exosomes that have varying electron density. Microbes also form intracellular vesicles and minicells that are similar to MVs and exosomes in shape. Electron and fluorescence microscopy could reveal the presence of DNA in MVs and exosomes. Given the biogenesis of extracellular vesicles from the donor cell, in situ high-resolution microscopy can provide insights on the structural mechanisms underlying the formation and release of microbial extracellular vesicles.

• Applied Microscopy
• /
• 제51권
• /
• pp.19.1-19.7
• /
• 2021

The main purpose of this paper is the preparation of transmission electron microscopy (TEM) samples from the microsized powders of lithium-ion secondary batteries. To avoid artefacts during TEM sample preparation, the use of ion slicer milling for thinning and maintaining the intrinsic structure is described. Argon-ion milling techniques have been widely examined to make optimal specimens, thereby making TEM analysis more reliable. In the past few years, the correction of spherical aberration (Cs) in scanning transmission electron microscopy (STEM) has been developing rapidly, which results in direct observation at an atomic level resolution not only at a high acceleration voltage but also at a deaccelerated voltage. In particular, low-kV application has markedly increased, which requires a sufficiently transparent specimen without structural distortion during the sample preparation process. In this study, sample preparation for high-resolution STEM observation is accomplished, and investigations on the crystal integrity are carried out by Cs-corrected STEM.

• Applied Microscopy
• /
• 제39권1호
• /
• pp.79-83
• /
• 2009

We report a useful method to estimate the electron dose rate which may be a decisive factor to characterize sample properties. Even though most mircoscopes have their own exposure meters, there are several practical concerns when such exposure meters are used to measure the electron dose rate: 1) Specimen should be avoided within the entire area of exposure meter; 2) beam current has to be always recorded whenever the operation mode is changed; 3) the electron dose rate can not be calculated for the beam current beyond the detectable range. To overcome these limitations, we suggest a useful method which utilize a CCD (charge coupled device) camera which is now a popular detector to obtain the final electron micrographs. We have evaluated the CCD sensitivity using the linear relationship between electron current on the exposure meter and counter ratio on the CCD camera which are built in KBSI-HVEM (high voltage electron microscope). Applying the new method, we obtained the CCD sensitivity which are approximately 0.039 counts/$e^-$ and 1.37 counts/$e^-$ for the Top-TV and the HV-GIF CCD cameras, respectively.

• Applied Microscopy
• /
• 제43권2호
• /
• pp.88-97
• /
• 2013

Technical investigation to figure out the problems arising during in-situ heating electron backscatter diffraction (EBSD) analysis inside scanning electron microscopy (SEM) was carried out. EBSD patterns were successfully acquired up to $830^{\circ}C$ without degradation of EBSD pattern quality in steels. Several technical problems such as image drift and surface microstructure pinning were taking place during in-situ experiments. Image drift problem was successfully prevented in constant current supplying mode. It was revealed that the surface pinning problem was resulted from the $TiO_2$ oxide particle formation during heating inside SEM chamber. Surface pinning phenomenon was fairly reduced by additional platinum and carbon multi-layer coating before in-situ heating experiment, furthermore was perfectly prevented by improvement of vacuum level of SEM chamber via leakage control. Plane view in-situ observation provides better understanding on the overall feature of recrystallization phenomena and cross sectional in-situ observation provides clearer understanding on the recrystallization mechanism.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2011년도 제40회 동계학술대회 초록집
• /
• pp.257-257
• /
• 2011

The amorphous indium-gallium-zinc-oxide (a-IGZO) materials for use in high performance display research fields are strongly investigated due to its good performance, such as high mobility and better transparency. However, the stability of a-IGZO materials is increasingly becoming one of critical issues due to the sub-gap electron trap sites induced by rough interfaces during deposition processing. It is well-known that the threshold voltage shift is related to interface roughness and oxygen vacancy formed by breaking weak chemical bonds. Here, we report the better properties of transparent oxide transistors by reducing the threshold voltage shift with an external rf plasma supported magnetron sputtering system. Mainly, our sputtering method causes the surface of sample to be sleek, so that it prevents the formation of various defects, such as shallow electron trap sites in the interface. External rf power was applied from 0 to 50W during RF sputtering process to enhance the stability of our oxide transistor without having a large voltage shift. To observe the effects of external rf-plasma source on the properties of our devices, Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Transmission Electron Microscopy (TEM) are carried out to observe surface roughness and morphology of sputtered thin film. In addition, typical electrical properties, such as I-V characteristics are analyzed.