NOVEL IN SITU SILICA/POLYDIMETHYLSILOXANE NANOCOMPOSITES: FACILE ONE-POT SYNTHESIS AND CHARACTERIZATION

2012 ◽  
Vol 85 (1) ◽  
pp. 92-107 ◽  
Author(s):  
Nabarun Roy ◽  
Anil K. Bhowmick
Keyword(s):  
Storage Modulus ◽  
Polymorphic Modification ◽  
Structure Property ◽  
Electron Microscopic ◽  
One Pot ◽  
Simultaneous Generation ◽  
In Situ Silica ◽  
Transmission Electron ◽  
Microscopic Studies

Abstract Synthesis of in situ silica/polydimethylsiloxane (PDMS) nanocomposites by using tetraethylorthosilicate (TEOS) as the precursor for silica and octamethylcyclotetrasiloxane for the polymer in presence of base was undertaken. Simultaneous generation of silica and polymer and dispersion of the nanofiller in the polymer have been reported for the first time. Fourier transform infrared spectroscopy was used as a tool to monitor the reaction conditions. The structure–property relationship of in situ silica/PDMS nanocomposites has been highlighted. Transmission electron microscopic studies reveal finest extent of dispersion of the in situ generated nanosilica, which is found to undergo polymorphic modification determined from wide-angle X-ray diffraction. Nanocomposites exhibit huge improvement in mechanical properties (>150% improvement in tensile strength for just 2 phr TEOS-filled sample) and room temperature storage modulus (>460% improvement in storage modulus for 8 phr TEOS-loaded sample). Polymer–filler interaction significantly improves oxidative thermal stability of the nanocomposites.

Radial mass analysis of unstained STEM images of molluscan hemocyanins

1990 ◽  
Vol 48 (3) ◽  
pp. 810-811
Author(s):  
M.G. Hamilton ◽  
T.T. Herskovits ◽  
J.S. Wall
Keyword(s):  
Image Analysis ◽  
Hollow Cylinder ◽  
Electron Micrographs ◽  
Side View ◽  
Mass Analysis ◽  
Mass Measurements ◽  
Electron Microscopic ◽  
Transmission Electron ◽  
Transmission Electron Microscopic ◽  
Microscopic Studies

The hemocyanins of molluscs are aggregates of a cylindrical decameric subparticle that assembles into di-, tri-, tetra-, penta-, and larger multi-decameric particles with masses that are multiples of the 4.4 Md decamer. Electron micrographs of these hemocyanins typically show the particles with two profiles: circular representing the cylinder viewed from the end and rectangular representing the side-view of the hollow cylinder.The model proposed by Mellema and Klug from image analysis of a didecameric hemocyanin with the two decamers facing one another with collar (closed) ends outward fits the appearance of side-views of the negatively-stained cylinders. These authors also suggested that there might be caps at the ends. In one of a series of transmission electron microscopic studies of molluscan hemocyanins, Siezen and Van Bruggen supported the Mellema-Klug model, but stated that they had never observed a cap component. With STEM we have tested the end cap hypothesis by direct mass measurements across the end-views of unstained particles.

The lurcher gene induces apoptotic death in cerebellar Purkinje cells

Development ◽  
1995 ◽  
Vol 121 (4) ◽  
pp. 1183-1193 ◽  
Author(s):  
D.J. Norman ◽  
L. Feng ◽  
S.S. Cheng ◽  
J. Gubbay ◽  
E. Chan ◽  
...  
Keyword(s):  
Purkinje Cells ◽  
Nuclear Dna ◽  
Neuronal Loss ◽  
Terminal Phase ◽  
Nuclear Condensation ◽  
Electron Microscopic ◽  
Apoptotic Death ◽  
Microscopic Studies ◽  
Cerebellar Purkinje Cells

In the neurologically mutant mouse strain lurcher (Lc), heterozygous animals display cell autonomous degeneration of cerebellar Purkinje cells beginning in the second postnatal week. During the course of our studies to identify the genetic lesion responsible for this disease (Norman et al., 1991), we have formulated an hypothesis suggesting that in Lc Purkinje cells homeostasis is sufficiently perturbed to lead to the activation of programmed cell death, thus resulting in neuronal loss and the consequent neurologic disease (Heintz, 1993). To address this possibility, we have examined the properties of Lc Purkinje cells as they die during the second postnatal week. Our light and electron microscopic studies demonstrate that dying Lc Purkinje cells exhibit the characteristic morphologic features of apoptosis, including nuclear condensation, axon beading and membrane blebbing. Using an in situ end-labeling method, we have also detected nicked nuclear DNA in these cells. Furthermore, we have examined the expression of the sulfated glycoprotein 2 (SGP2), whose mRNA is induced in both T-cells and prostate epithelial cells undergoing apoptotic death. We show by in situ hybridization that SGP2 is not expressed at detectable levels in normal Purkinje cells, but that its mRNA is present in Lc Purkinje cells prior to their death. Also expression of the Kv3.3b potassium channel, which marks the terminal phase of Purkinje cell differentiation, is evident in Lc Purkinje cells prior to their death. These data demonstrate that the Lc mutation induces apoptosis in cerebellar Purkinje cells following their maturation in postnatal cerebellum. Isolation of the Lc mutation and further analysis of its action in eliciting apoptosis can provide an important opportunity for understanding the etiology of neurodegenerative disease.

Polarized pigment granule transport occurs in the absence of microtubules in squirrelfish erythrophores: studies of the effects of estramustine

1987 ◽  
Vol 87 (4) ◽  
pp. 565-580
Author(s):  
M.E. Stearns ◽  
M. Wang
Keyword(s):  
Pigment Granule ◽  
Electron Microscopic ◽  
Microtubule Associated Proteins ◽  
Voltage Electron ◽  
Associated Proteins ◽  
Drug Inhibition ◽  
Microscopic Studies ◽  
10 Nm Filaments ◽  
Inhibition Studies

We have re-examined the involvement of microtubules in the process of pigment granule transport in squirrelfish erythrophores in situ (i.e. on scales). Light-microscopic studies revealed that following exposure to 5 microM-nocodazole for 1 h at 4 degrees C erythrophores retained an ability to aggregate and disperse their pigment uniformly, though at reduced rates. Serial thick-section stereo high-voltage electron-microscopic studies showed that the entire microtubule population was removed by drug treatment and that the microtubules were not reassembled as a result of pigment translocation processes in the presence of reduced levels of nocodazole (0.4 microM). Immunofluorescence microscopic studies confirmed that nocodazole (0.5-1 microM) produced rapid disassembly of the microtubules. Whole-mount electron-microscopic studies showed that the pigment granules were suspended in a cross-linking network of 3–10 nm filaments, which appeared to support ordered pigment transport in situ in the absence of microtubules. Drug inhibition studies showed that micromolar levels of estramustine, a novel anti-MAPs (microtubule-associated proteins) drug, reversibly inhibited pigment transport. The results suggest that an estramustine-sensitive cytomatrix component might produce polarized pigment transport in intact erythrophores.

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