Preparation of hollow SiC ceramic fibre from polycarbosilane fibre by diffusion-controlled cross-linking method

Nano silicon carbide ceramics were prepared via precursor pyrolysis. Polycarbosilane (PCS) and divinylbenzene (DVB) were selected as a precursor to silicon carbide ceramics and a cross-linking reagent for PCS, respectively. The cross-linking properties and pyrolysis of PCS and DVB were investigated by changing the mass ratios of PCS/DVB. The mass ratio of PCS/DVB has a great effect on silicon carbide ceramic yield. The cured PCS/DVB with a mass ratio of 1:0.5 has the highest SiC ceramic yield (63.1%) at the temperature up to 1500 °C and its pyrolyzates consiste of nano silicon carbide with a diameter of 10-40 nm. The microstructures of the nano silicon carbide ceramics were characterized by SEM and XRD. The pyrolysis behavior of the cured PCS/DVB was characterized by thermogravimetry in nitrogen atmosphere.

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Influence of Calcium Ions on the Plant Cell Surface: Membrane Fusions and Conformational Changes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100050780 ◽

1974 ◽

Vol 32 ◽

pp. 154-155

Author(s):

D. James Morré ◽

Charles E. Bracker ◽

William J. VanDerWoude

Keyword(s):

Cell Wall ◽

Cell Surface ◽

Conformational Changes ◽

Calcium Ions ◽

Surface Membrane ◽

Carboxyl Groups ◽

Cross Linking ◽

Ultrastructural Evidence ◽

Glycine Max L ◽

Wall Extensibility

Calcium ions in the concentration range 5-100 mM inhibit auxin-induced cell elongation and wall extensibility of plant stems. Inhibition of wall extensibility requires that the tissue be living; growth inhibition cannot be explained on the basis of cross-linking of carboxyl groups of cell wall uronides by calcium ions. In this study, ultrastructural evidence was sought for an interaction of calcium ions with some component other than the wall at the cell surface of soybean (Glycine max (L.) Merr.) hypocotyls.

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Embedding Procedure for Water Swollen Samples

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010006951x ◽

1970 ◽

Vol 28 ◽

pp. 504-505

Author(s):

Ann M. Thomas ◽

Virginia Shemeley

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Ion Exchange ◽

Structural Changes ◽

Cross Linking ◽

Ion Exchange Resins ◽

Transmission Electron ◽

First Pass ◽

Exchange Resins

Those samples which swell rapidly when exposed to water are, at best, difficult to section for transmission electron microscopy. Some materials literally burst out of the embedding block with the first pass by the knife, and even the most rapid cutting cycle produces sections of limited value. Many ion exchange resins swell in water; some undergo irreversible structural changes when dried. We developed our embedding procedure to handle this type of sample, but it should be applicable to many materials that present similar sectioning difficulties.The purpose of our embedding procedure is to build up a cross-linking network throughout the sample, while it is in a water swollen state. Our procedure was suggested to us by the work of Rosenberg, where he mentioned the formation of a tridimensional structure by the polymerization of the GMA biproduct, triglycol dimethacrylate.

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Microstructural Heterogenieties in a Commercial SiC Structural Ceramic:Hraem

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100055060 ◽

1982 ◽

Vol 40 ◽

pp. 564-565

Author(s):

W.M. Skiff ◽

R.W. Carpenter

Keyword(s):

Sic Ceramic ◽

Second Phases ◽

Structural Irregularities

SiC refractories made by various pressing and sintering methods may contain structural and chemical heterogenieties similar to tljiose reported for Si3N4 base refractories. Although some earlier work on SiC did not reveal second phases, other oxidation experiments showed the reaction to take place heterogeneously, leading to the supposition that such heterogenieties may be present. In this work we examine a typical commercial SiC ceramic to determine the existence of such structural irregularities.

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The Current Situation in Chemical Stabilization of Biological Materials

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100093912 ◽

1972 ◽

Vol 30 ◽

pp. 132-133

Author(s):

John H. Luft

Keyword(s):

Electron Microscopy ◽

Electron Microscope ◽

Osmium Tetroxide ◽

Molecular Level ◽

Cross Linking ◽

Chemical Stabilization ◽

Specimen Preparation ◽

Sufficient Condition ◽

Radio Telescopes

With information processing devices such as radio telescopes, microscopes or hi-fi systems, the quality of the output often is limited by distortion or noise introduced at the input stage of the device. This analogy can be extended usefully to specimen preparation for the electron microscope; fixation, which initiates the processing sequence, is the single most important step and, unfortunately, is the least well understood. Although there is an abundance of fixation mixtures recommended in the light microscopy literature, osmium tetroxide and glutaraldehyde are favored for electron microscopy. These fixatives react vigorously with proteins at the molecular level. There is clear evidence for the cross-linking of proteins both by osmium tetroxide and glutaraldehyde and cross-linking may be a necessary if not sufficient condition to define fixatives as a class.

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A TEM investigation of a hyper-eutectic lead-tin alloy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010010487x ◽

1988 ◽

Vol 46 ◽

pp. 562-563

Author(s):

John A. Sutliff

Keyword(s):

Volume Diffusion ◽

Eutectic Mixture ◽

Precipitation Reaction ◽

Directionally Solidified ◽

X Ray Diffraction ◽

X Ray ◽

Transmission Electron ◽

Diffusion Controlled ◽

Discontinuous Precipitation Reaction ◽

Controlled Precipitation

Near-eutectic Pb-Sn alloys are important solders used by the electronics industry. In these solders, the eutectic mixture, which solidifies last, is the important microstructural consituent. The orientation relation (OR) between the eutectic phases has previously been determined for directionally solidified (DS) eutectic alloys using x-ray diffraction or electron chanelling techniques. In the present investigation the microstructure of a conventionally cast, hyper-eutectic Pb-Sn alloy was examined by transmission electron microscopy (TEM) and the OR between the eutectic phases was determined by electron diffraction. Precipitates of Sn in Pb were also observed and the OR determined. The same OR was found in both the eutectic and precipitation reacted materials. While the precipitation of Sn in Pb was previously shown to occur by a discontinuous precipitation reaction,3 the present work confirms a recent finding that volume diffusion controlled precipitation can also occur.Samples that are representative of the solder's cast microstructure are difficult to prepare for TEM because the alloy is multiphase and the phases are soft.

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Parathyroid gland before and after cisplatin treatment

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100128584 ◽

1987 ◽

Vol 45 ◽

pp. 860-861

Author(s):

S.K. Aggarwal ◽

J.M. Fadool

Keyword(s):

Parathyroid Gland ◽

Wistar Rats ◽

Antitumor Agent ◽

The Body ◽

Cross Linking ◽

Limiting Factor ◽

Hormonal Changes ◽

Primary Mechanism ◽

Before And After ◽

Dna Strands

Cisplatin (CDDP) a potent antitumor agent suffers from severe toxic side effects with nephrotoxicity being the major dose-limiting factor, The primary mechanism of its action has been proposed to be through its cross-linking DNA strands. It has also been shown to inactivate various transport enzymes and induce hypocalcemia and hypomagnesemia that may be the underlying cause for some of its toxicities. The present is an effort to study its influence on the parathyroid gland for any hormonal changes that control calcium levels in the body.Male Swiss Wistar rats (Crl: (WI) BR) weighing 200-300 g and of 60 days in age were injected (ip) with cisplatin (7mg/kg in normal saline). The controls received saline injections only. The animals were injected (iv) with calcium (0.5 ml of 10% calcium gluconate/day) and were killed by decapitation on day 1 through 5. Trunk blood was collected in heparinized tubes.

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Large-cluster and combined fluorescent and gold immunoprobes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100166920 ◽

1996 ◽

Vol 54 ◽

pp. 892-893

Author(s):

Richard D. Powell ◽

James F. Hainfeld ◽

Carol M. R. Halsey ◽

David L. Spector ◽

Shelley Kaurin ◽

...

Keyword(s):

Metal Cluster ◽

Sulfonyl Chloride ◽

Gel Filtration ◽

Cross Linking ◽

Site Specific ◽

Fab Fragments ◽

Cluster Label ◽

Covalently Linked ◽

Texas Red ◽

Fold Excess

Two new types of covalently linked, site-specific immunoprobes have been prepared using metal cluster labels, and used to stain components of cells. Combined fluorescein and 1.4 nm “Nanogold” labels were prepared by using the fluorescein-conjugated tris (aryl) phosphine ligand and the amino-substituted ligand in the synthesis of the Nanogold cluster. This cluster label was activated by reaction with a 60-fold excess of (sulfo-Succinimidyl-4-N-maleiniido-cyclohexane-l-carboxylate (sulfo-SMCC) at pH 7.5, separated from excess cross-linking reagent by gel filtration, and mixed in ten-fold excess with Goat Fab’ fragments against mouse IgG (obtained by reduction of F(ab’)2 fragments with 50 mM mercaptoethylamine hydrochloride). Labeled Fab’ fragments were isolated by gel filtration HPLC (Superose-12, Pharmacia). A combined Nanogold and Texas Red label was also prepared, using a Nanogold cluster derivatized with both and its protected analog: the cluster was reacted with an eight-fold excess of Texas Red sulfonyl chloride at pH 9.0, separated from excess Texas Red by gel filtration, then deprotected with HC1 in methanol to yield the amino-substituted label.

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