Investigation of growth conditions of fibrous deposits in carbon arc

1997 ◽  
Vol 12 (6) ◽  
pp. 1551-1557 ◽  
Author(s):  
P. Byszewski ◽  
K. Ukalski ◽  
E. Mizera ◽  
E. Kowalska
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Energy Flow ◽  
Growth Conditions ◽  
Electric Arc ◽  
Buffer Gas ◽  
Condensation Rate ◽  
Carbon Arc ◽  
Scanning Electron ◽  
Gas Pressures

Carbon fibrous deposits grown in carbon dc electric arc at various buffer gas pressures and arc currents were investigated by transmission and scanning electron microscopy. The fibers contained in the deposits consisted of bundles of carbon tubes. It was found that yield and morphology were very sensitive to both parameters; sintering of the tubes could be prevented by adjusting buffer gas pressure for a given current. It is argued that these parameters control expansion of carbon gas and condensation rate, and therefore energy flow to the cathode. To purify samples by oxidation and to observe differences in resistance against oxidation of samples obtained at various conditions, the thermogravimetry method was used.

scholarly journals Scanning electron microscopy and molecular dynamics of surfaces of growing and ablating hexagonal ice crystals

2009 ◽  
Vol 9 (5) ◽  
pp. 20739-20763 ◽  
Author(s):  
W. C. Pfalzgraff ◽  
R. M. Hulscher ◽  
S. P. Neshyba
Keyword(s):  
Electron Microscopy ◽  
Molecular Dynamics ◽  
Scanning Electron Microscopy ◽  
Climate Models ◽  
Growth Conditions ◽  
Ice Crystals ◽  
Variable Pressure ◽  
Radiative Balance ◽  
Hexagonal Ice ◽  
Scanning Electron

Abstract. Optical properties of cirrus ice clouds play an important role in regulating Earth's radiative balance. It has been hypothesized that the surfaces of cirrus ice crystals may be characterized by mesoscopic (micrometer-scale) texturing, or roughness, in order to explain discrepancies between theoretical and observed light-scattering properties. Here, we present the first clearly resolved observations of surfaces of hexagonal ice crystals, using variable-pressure scanning electron microscopy. During growth conditions, the ice surface develops trans-prismatic strands, separated from one another by distances of 5–10 μm. These strands become more pronounced during ablation, and exhibit a wider range of separations. Under re-growth conditions, faceting is re-established initially at prismatic edges. Molecular dynamics studies of a free-standing ice Ih nanocolumn showed no trans-prismatic strands at the atomistic level, suggesting that these strands originate at a spatial scale greater than 10 nm. The observed surface roughness could be used to construct more realistic representations of cirrus clouds in climate models, and constrain theories of ice crystal growth and ablation.

Secondary Electron Imaging of Liquid Water Films in the Environmental Scanning Electron Microscope

1990 ◽  
Vol 48 (1) ◽  
pp. 374-375
Author(s):  
Klaus-Ruediger Peters
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Liquid Water ◽  
Secondary Electron ◽  
Gas Pressure ◽  
Aqueous Environment ◽  
Water Films ◽  
Electron Imaging ◽  
Scanning Electron ◽  
Gas Pressures

High gas pressure scanning electron microscopy is now routinely possible with new microscopes operating between 0.1 and 20 torr gas pressure. Since the specimen chamber is separated from the electron optical column by pressure-limiting apertures, high gas pressures present at the level of the specimen do not affect the high vacuum in the column. The use of a single PLA underneath the last probe-forming lens allows maintainance of ∼0.1 torr. Twenty torr can be stabilized with two PLA, forming two differentially pumped pressure zones which may be incorporated into the last probe-forming lens.One of the most important new features of high gas pressure microscopy is the possibility to alter the type of gas and its pressure over a large range. High gas pressures (>1 torr) are required for charge neutralization on rugged insulators and for gas amplification of the SE signal. Additionally, using water vapors, liquid water can be stabilized. However, the aqueous environment is only one example among many possibilities.The secondary electron imaging of liquid water is a fascinating new aspect of scanning electron microscopy. At saturated water vapor pressures, water is stable indefinitely. Increasing or decreasing the vapor pressure allows condensation or evaporation of water and provides means to generate water films. As can be seer from Fig. 1, the stabilizing pressure for water at 20°C is 17.5 torr. Such a pressure would require a very short working distance for SE imaing. Therefore, it is preferable to reduce the specimen temperature and to establish vapor saturation at lower pressures. However, liquid water can only be stabilized at pressures greater than ∼4.5 torr.

Formation of Biofilms by Listeria monocytogenes under Various Growth Conditions

2005 ◽  
Vol 68 (1) ◽  
pp. 92-97 ◽  
Author(s):  
ANDREW G. MOLTZ ◽  
SCOTT E. MARTIN
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Stainless Steel ◽  
Listeria Monocytogenes ◽  
Cell Density ◽  
Polyvinyl Chloride ◽  
Growth Medium ◽  
Biofilm Formation ◽  
Growth Conditions ◽  
Scanning Electron

Eight strains of Listeria monocytogenes (7644, 19112, 15313, Scott A, LCDC, 10403S, SLCC, and 1370) produce biofilms when grown on polyvinyl chloride microtiter well plates. The growth medium (tryptic soy broth [TSB] or modified Welshimer's broth [MWB] at 32°C) influenced the amount of biofilm formed; maximum biofilms were formed in MWB by six strains and in TSB by the remaining two strains. This result suggests that the growth medium is critical in development of L. monocytogenes biofilm. This organism also produced biofilms on stainless steel chips. Biofilm formation on these chips was observed following growth in TSB at 4, 20, and 37°C. After 20 h of incubation at 20 or 37°C, the cell density was approximately 106 CFU per chip, and after 4 days incubation at 4°C, the cell density was 105 CFU per chip. L. monocytogenes strain Scott A biofilm formation on stainless steel chips was visualized using scanning electron microscopy, which revealed dense aggregates of cells held together by meshlike webbing.

Coating Produced by Deposition of Nanoparticles Blended Wires

2011 ◽  
Vol 264-265 ◽  
pp. 1476-1481 ◽  
Author(s):  
A. Al Askandarani ◽  
M.S.J. Hashmi ◽  
Bekir Sami Yilbas
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Carbon Steel ◽  
Steel Surface ◽  
Electric Arc ◽  
Nano Particle ◽  
Coating Structure ◽  
Carbon Steel Surface ◽  
Fine Structures ◽  
Scanning Electron

Gas shield electric arc coating of carbon steel surface is considered in relation to repair applications. Two types of wires are incorporated in the experiments including standard and nano-particle blended. The coating structure and the metallurgy are examined using the Scanning Electron Microscopy (SEM), and Energy Dispersive Spectroscopy (EDS). The microhardness of the resulting coating is measured and compared with the results obtained from the conventional wire. It is found that fine structures are formed in the coating due to the presence of nanoparticles. In this case, microhardness increases significantly in the coating.

Pathogenesis of Human Hair Defects

1974 ◽  
Vol 32 ◽  
pp. 12-13
Author(s):  
P.S. Porter ◽  
T. Aoyagi ◽  
R. Matta
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Human Hair ◽  
Standard Techniques ◽  
Scanning Electron

Using standard techniques of scanning electron microscopy (SEM), over 1000 human hair defects have been studied. In several of the defects, the pathogenesis of the abnormality has been clarified using these techniques. It is the purpose of this paper to present several distinct morphologic abnormalities of hair and to discuss their pathogenesis as elucidated through techniques of scanning electron microscopy.

Ultrastructural Analysis of the Salivary Glands of Gromphadorhina Portentosa (Schaum)

1977 ◽  
Vol 35 ◽  
pp. 638-639
Author(s):  
P.J. Dailey
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Salivary Glands ◽  
Secretory Vesicles ◽  
The Past ◽  
Transmission Electron ◽  
Means Of Transmission ◽  
Gromphadorhina Portentosa ◽  
Scanning Electron ◽  
Topographical Relief

The structure of insect salivary glands has been extensively investigated during the past decade; however, none have attempted scanning electron microscopy (SEM) in ultrastructural examinations of these secretory organs. This study correlates fine structure by means of SEM cryofractography with that of thin-sectioned epoxy embedded material observed by means of transmission electron microscopy (TEM).Salivary glands of Gromphadorhina portentosa were excised and immediately submerged in cold (4°C) paraformaldehyde-glutaraldehyde fixative1 for 2 hr, washed and post-fixed in 1 per cent 0s04 in phosphosphate buffer (4°C for 2 hr). After ethanolic dehydration half of the samples were embedded in Epon 812 for TEM and half cryofractured and subsequently critical point dried for SEM. Dried specimens were mounted on aluminum stubs and coated with approximately 150 Å of gold in a cold sputtering apparatus.Figure 1 shows a cryofractured plane through a salivary acinus revealing topographical relief of secretory vesicles.

Two- or three-way observations of the identical cell elements within the same sections by LM, TEM and/or SEM

1978 ◽  
Vol 36 (2) ◽  
pp. 82-83 ◽  
Author(s):  
Nakazo Watari ◽  
Yasuaki Hotta ◽  
Yoshio Mabuchi
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Fine Structure ◽  
Light Microscopy ◽  
Thin Sections ◽  
Transmission Electron ◽  
Identical Cell ◽  
Electron Microscopes ◽  
Scanning Electron

It is very useful if we can observe the identical cell elements within the same sections by light microscopy (LM), transmission electron microscopy (TEM) and/or scanning electron microscopy (SEM) sequentially, because, the cell fine structure can not be indicated by LM, while the color is; on the other hand, the cell fine structure can be very easily observed by EM, although its color properties may not. However, there is one problem in that LM requires thick sections of over 1 μm, while EM needs very thin sections of under 100 nm. Recently, we have developed a new method to observe the same cell elements within the same plastic sections using both light and transmission (conventional or high-voltage) electron microscopes.In this paper, we have developed two new observation methods for the identical cell elements within the same sections, both plastic-embedded and paraffin-embedded, using light microscopy, transmission electron microscopy and/or scanning electron microscopy (Fig. 1).

Spontaneous Cataract in Nude Athymic Mice

1977 ◽  
Vol 35 ◽  
pp. 512-513
Author(s):  
Ronald H. Bradley ◽  
R. S. Berk ◽  
L. D. Hazlett
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Nude Mouse ◽  
Cellular Immunity ◽  
Phosphate Buffer ◽  
Osmium Tetroxide ◽  
Athymic Mice ◽  
Transmission Microscopy ◽  
Mouse Lens ◽  
Scanning Electron

The nude mouse is a hairless mutant (homozygous for the mutation nude, nu/nu), which is born lacking a thymus and possesses a severe defect in cellular immunity. Spontaneous unilateral cataractous lesions were noted (during ocular examination using a stereomicroscope at 40X) in 14 of a series of 60 animals (20%). This transmission and scanning microscopic study characterizes the morphology of this cataract and contrasts these data with normal nude mouse lens.All animals were sacrificed by an ether overdose. Eyes were enucleated and immersed in a mixed fixative (1% osmium tetroxide and 6% glutaraldehyde in Sorenson's phosphate buffer pH 7.4 at 0-4°C) for 3 hours, dehydrated in graded ethanols and embedded in Epon-Araldite for transmission microscopy. Specimens for scanning electron microscopy were fixed similarly, dehydrated in graded ethanols, then to graded changes of Freon 113 and ethanol to 100% Freon 113 and critically point dried in a Bomar critical point dryer using Freon 13 as the transition fluid.

Scanning and Transmission Microscopy of Nematocyst Batteries in Epitheliomuscular Cells of Hydra

1971 ◽  
Vol 29 ◽  
pp. 410-411 ◽  
Author(s):  
Jane A. Westfall ◽  
S. Yamataka ◽  
Paul D. Enos
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Osmium Tetroxide ◽  
External Surface ◽  
Three Dimensional ◽  
Surface Structures ◽  
Transmission Microscopy ◽  
Transmission Electron ◽  
Freeze Dried ◽  
Scanning Electron

Scanning electron microscopy (SEM) provides three dimensional details of external surface structures and supplements ultrastructural information provided by transmission electron microscopy (TEM). Animals composed of watery jellylike tissues such as hydras and other coelenterates have not been considered suitable for SEM studies because of the difficulty in preserving such organisms in a normal state. This study demonstrates 1) the successful use of SEM on such tissue, and 2) the unique arrangement of batteries of nematocysts within large epitheliomuscular cells on tentacles of Hydra littoralis.Whole specimens of Hydra were prepared for SEM (Figs. 1 and 2) by the fix, freeze-dry, coat technique of Small and Màrszalek. The specimens were fixed in osmium tetroxide and mercuric chloride, freeze-dried in vacuo on a prechilled 1 Kg brass block, and coated with gold-palladium. Tissues for TEM (Figs. 3 and 4) were fixed in glutaraldehyde followed by osmium tetroxide. Scanning micrographs were taken on a Cambridge Stereoscan Mark II A microscope at 10 KV and transmission micrographs were taken on an RCA EMU 3G microscope (Fig. 3) or on a Hitachi HU 11B microscope (Fig. 4).

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