scholarly journals Thermally Induced Anomaly in the Shear Behavior of Magnetite at High Pressure

2018 ◽  
Vol 10 (2) ◽  
Author(s):  
Yongtao Zou ◽  
Wei Zhang ◽  
Ting Chen ◽  
Xing-ao Li ◽  
Chun-Hai Wang ◽  
...  
Keyword(s):  
High Pressure ◽  
Shear Behavior ◽  
Thermally Induced

High-pressure and thermally induced asymmetric diels-alder cycloadditions of heterosubstituted dienes to homochiral α,β-didehydro amino acid derivatives

1996 ◽  
Vol 7 (1) ◽  
pp. 127-138 ◽  
Author(s):  
Rosa M. Ortuño ◽  
Javier Ibarzo ◽  
Jean d'Angelo ◽  
Françoise Dumas ◽  
Angel Alvarez-Larena ◽  
...  
Keyword(s):  
High Pressure ◽  
Amino Acid ◽  
Diels Alder ◽  
Amino Acid Derivatives ◽  
Thermally Induced

On the Roles of Temperature and Interfaces in Irradiation and Thermally Induced Solid State Amorphization

1995 ◽  
Vol 398 ◽  
Author(s):  
L.M. Wang ◽  
W.L. Gong ◽  
R.C. Ewing ◽  
W.J. Webert
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Pressure ◽  
Grain Boundaries ◽  
Irradiation Temperature ◽  
Free Surfaces ◽  
Thermally Induced ◽  
Transmission Electron ◽  
Increasing Temperature ◽  
State Amorphization

ABSTRACTThe roles of irradiation temperature and interfaces (free surfaces and grain boundaries) in irradiation- and thermally- induced amorphization of ceramics (coesite, apatite, olivines and spinels) have been studied by transmission electron microscopy (TEM). The irradiations were performed with 1.5 MeV Kr+, 200 keV and 1 MeV electrons over a wide temperature range (20-700 K). The critical amorphization dose at which amorphization is complete, Dc, increased with increasing irradiation temperature for most materials except coesite (a high pressure polymorph of Si02) which showed a decreasing Dc with increasing temperature under 1 MeV electron irradiation. Although amorphization may occur directly within a displacement cascade or by cascade overlap, this study shows that free surfaces and grain boundaries are favorable sites for nucleation of amorphous volumes. Once the amorphous volume is formed at interfaces, it may grow rapidly under continued irradiation. Coesite which has a glass transition temperature higher than its melting temperature underwent spontaneous amorphization during thermal annealing at 1200 K. This thermally-induced amorphization also started at free surface and grain boundaries and propagated into the interior of the crystal. The interface-mediated amorphization is analogous to the process of thermodynamic melting.

High-pressure freezing of cells in suspension for low-voltage scanning electron microscopy (LVSEM)

1991 ◽  
Vol 49 ◽  
pp. 64-65
Author(s):  
Marek Malecki ◽  
James Pawley ◽  
Hans Ris
Keyword(s):  
Electron Microscopy ◽  
High Pressure ◽  
Low Voltage ◽  
Culture Media ◽  
Cell Structure ◽  
Freeze Substitution ◽  
Ice Crystal ◽  
High Pressure Freezing ◽  
Cell Culture Media ◽  
Voltage Scanning

The ultrastructure of cells suspended in physiological fluids or cell culture media can only be studied if the living processes are stopped while the cells remain in suspension. Attachment of living cells to carrier surfaces to facilitate further processing for electron microscopy produces a rapid reorganization of cell structure eradicating most traces of the structures present when the cells were in suspension. The structure of cells in suspension can be immobilized by either chemical fixation or, much faster, by rapid freezing (cryo-immobilization). The fixation speed is particularly important in studies of cell surface reorganization over time. High pressure freezing provides conditions where specimens up to 500μm thick can be frozen in milliseconds without ice crystal damage. This volume is sufficient for cells to remain in suspension until frozen. However, special procedures are needed to assure that the unattached cells are not lost during subsequent processing for LVSEM or HVEM using freeze-substitution or freeze drying. We recently developed such a procedure.

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