Temperature dependence of positronium lifetime in cylindrical pores

AbstractA model of internal friction at a grain boundary containing equidistant parallel cylindrical pores is presented. Variable shear stress induces a mutual displacement of the interfacial regions matched at the segments between pores depending on their position. The values of scattered energy at each segment and total internal friction are determined. The temperature dependence of the internal friction has a form of a wide peak.

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Effects of Local Heating and Premelting in the Terminal Part of the e+ Track

Materials Science Forum ◽

10.4028/www.scientific.net/msf.733.15 ◽

2012 ◽

Vol 733 ◽

pp. 15-18 ◽

Cited By ~ 5

Author(s):

Dmitry Zvezhinskiy ◽

Sergey V. Stepanov ◽

Vsevolod Byakov ◽

Bożena Zgardzińska

Keyword(s):

Melting Point ◽

Temperature Dependence ◽

Local Heating ◽

Bulk Temperature ◽

Melting Points ◽

Terminal Part ◽

Slowing Down ◽

Positronium Lifetime ◽

Molten Region

The terminal part of the e+ track (the positron blob) is formed during ionization slowing down and subsequent ion-electron recombinations produced by a positron. It releases up to 1 keV of energy, which is converted into heat within few picoseconds. If a bulk temperature of a medium is below, but close enough to its melting point, some region of a substance may melt, yielding a peculiar temperature dependence of the lifetime (LT) spectra. We have estimated properties of the molten region with a help of macroscopic heat con- duction equation and suggested a model describing temperature dependence of the ortho- positronium lifetime in frozen methanol, ethanol, butanol and water close to their melting points.

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The Influence of Boundary Conditions and Surface Layer Thickness on Dielectric Relaxation of Liquid Crystals Confined in Cylindrical Pores

MRS Proceedings ◽

10.1557/proc-651-t7.22.1 ◽

2000 ◽

Vol 651 ◽

Author(s):

Z. Nazario ◽

G. P. Sinha ◽

F.M. Aliev

Keyword(s):

Liquid Crystal ◽

Boundary Conditions ◽

Temperature Dependence ◽

Layer Thickness ◽

Dielectric Spectroscopy ◽

Relaxation Times ◽

Thin Layers ◽

Short Axis ◽

Librational Mode ◽

Cylindrical Pores

AbstractDielectric spectroscopy was applied to investigate the dynamic properties of liquid crystal octylcyanobiphenyl (8CB) confined in 2000 Å cylindrical pores of Anopore membranes with homeotropic and axial (planar) boundary conditions on the pore walls. Homeotropic boundary conditions allow the investigation of the librational mode in 8CB by dielectric spectroscopy. We found that the dynamics of the librational mode is totally different from the behavior observed in investigations of relaxation due to reorientation of molecules around their short axis. The interpretation of the temperature dependence of relaxation times and of the dielectric strength of the librational mode needs the involvement of the temperature dependence of orientational order parameter. For samples with axial boundary conditions, layers of LCs with different thickness were obtained on the pore walls as a result of controlled impregnation of porous matrices with 8CB from solutions of different liquid crystal concentration. The process due to rotation of molecules around their short axis with single relaxation time observed for bulk 8CB is replaced by a process with a distribution of relaxation times in thin layers. This relaxation process broadens with decreasing layer thickness.

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Positronium Lifetime Study on Subnanoscopic Structure of Polyrotaxane

Materials Science Forum ◽

10.4028/www.scientific.net/msf.733.167 ◽

2012 ◽

Vol 733 ◽

pp. 167-170

Author(s):

K. Ito ◽

Chang Ming Zhao ◽

Kohzo Ito ◽

Yoshinori Kobayashi

Keyword(s):

Ethylene Glycol ◽

Temperature Dependence ◽

Positron Annihilation ◽

Chemical Structure ◽

Poly Ethylene Glycol ◽

Positron Annihilation Lifetime ◽

Positronium Lifetime ◽

End Groups ◽

Poly Ethylene ◽

Free Volume Hole

The subnanoscopic structures of polyrotaxanes, prepared from α-cyclodextrins, poly(ethylene glycol), and bulky adamantane end groups, were examined by means of the positron annihilation lifetime technique, in consideration of the free-volume hole, quantified from the long-lived ortho-positronium (o-Ps) lifetimes. The influence of the chemical structure on the temperature dependence of the o-Ps lifetimes are discussed.

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Temperature dependence of o-Ps annihilation lifetime in non-uniform cylindrical pores in comparison with ETE model

Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms ◽

10.1016/j.nimb.2017.02.006 ◽

2017 ◽

Vol 396 ◽

pp. 11-17 ◽

Cited By ~ 2

Author(s):

Morteza Khaghani ◽

Ali Akbar Mehmandoost-Khajeh-Dad

Keyword(s):

Temperature Dependence ◽

Cylindrical Pores

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Temperature Dependence of the Critical Electron Dose for Fatty Acid Monolayers

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100053188 ◽

1982 ◽

Vol 40 ◽

pp. 78-79

Author(s):

Kenneth H. Downing ◽

Robert M. Glaeser

Keyword(s):

Electron Beam ◽

Fatty Acid ◽

Inelastic Scattering ◽

Temperature Dependence ◽

Structural Damage ◽

Direct Result ◽

Second Step ◽

Strong Temperature Dependence ◽

Electron Dose ◽

Covalent Bonds

The structural damage of molecules irradiated by electrons is generally considered to occur in two steps. The direct result of inelastic scattering events is the disruption of covalent bonds. Following changes in bond structure, movement of the constituent atoms produces permanent distortions of the molecules. Since at least the second step should show a strong temperature dependence, it was to be expected that cooling a specimen should extend its lifetime in the electron beam. This result has been found in a large number of experiments, but the degree to which cooling the specimen enhances its resistance to radiation damage has been found to vary widely with specimen types.

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Temperature Dependence of Magnetic Domains and Wall Structures

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010009573x ◽

1972 ◽

Vol 30 ◽

pp. 496-497

Author(s):

Sonoko Tsukahara ◽

Tadami Taoka ◽

Hisao Nishizawa

Keyword(s):

Temperature Dependence ◽

Domain Walls ◽

Magnetic Domain ◽

Iron Film ◽

Objective Lens ◽

Lorentz Microscopy ◽

Domain Structures ◽

Wall Structures ◽

Crystal Films ◽

Metallurgical Structure

The high voltage Lorentz microscopy was successfully used to observe changes with temperature; of domain structures and metallurgical structures in an iron film set on the hot stage combined with a goniometer. The microscope used was the JEM-1000 EM which was operated with the objective lens current cut off to eliminate the magnetic field in the specimen position. Single crystal films with an (001) plane were prepared by the epitaxial growth of evaporated iron on a cleaved (001) plane of a rocksalt substrate. They had a uniform thickness from 1000 to 7000 Å.The figure shows the temperature dependence of magnetic domain structure with its corresponding deflection pattern and metallurgical structure observed in a 4500 Å iron film. In general, with increase of temperature, the straight domain walls decrease in their width (at 400°C), curve in an iregular shape (600°C) and then vanish (790°C). The ripple structures with cross-tie walls are observed below the Curie temperature.

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