Structural aspects of the glass transition in three-dimensional polymer melts

The temperature effecton the dielectric response of nanocomposite at low frequencies range is reported. The investigated samples are formed by a semi-crystalline ethylene-co-butyl acrylate (EBA) polymer filled with three concentrations of the dispersed conducting carbon black (CB) nanoparticles. The temperature dependence of the complex permittivity has been analyzedabove the glass transition temperature of the neat polymer matrix Tg=-75°C. For all CB concentrations, the dielectric spectra follow a same trend in frequency range 100-106Hz. More interestingly, the stability of the effective complex permittivity ɛ=ɛ' -iɛ'' with the temperature range of 10-70°C is explored. While the imaginary part of the complex permittivity ɛ'' exhibits a slight decreasewith temperature, the real part ɛ' shows a significant reduction especially for high loading samples. The observed dielectric response may be related to the breakup of the three-dimensional structurenetwork formed by the aggregation of CB particles causing change at the interfaceEBA-CB.This interface is estimated bythe volume fraction of constrained polymer chain according to loss tangent data of dynamic mechanical analysis.

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Modeling three-dimensional flow of the polymer melts in a converging channel

Journal of Physics Conference Series ◽

10.1088/1742-6596/1045/1/012023 ◽

2018 ◽

Vol 1045 ◽

pp. 012023

Author(s):

A Kuznetsov ◽

K Koshelev ◽

N Cherpakova ◽

G Pyshnograi

Keyword(s):

Polymer Melts ◽

Three Dimensional ◽

Three Dimensional Flow ◽

Dimensional Flow ◽

Converging Channel

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Structural Aspects of Phenylalanylation and Quality Control in Three Major Forms of Phenylalanyl-tRNA Synthetase

Journal of Amino Acids ◽

10.4061/2010/983503 ◽

2010 ◽

Vol 2010 ◽

pp. 1-7 ◽

Cited By ~ 5

Author(s):

Liron Klipcan ◽

Igal Finarov ◽

Nina Moor ◽

Mark G. Safro

Keyword(s):

Quaternary Structure ◽

Thermus Thermophilus ◽

Three Dimensional ◽

Structural Diversity ◽

Structural Data ◽

Trna Synthetase ◽

Transfer Rnas ◽

Trna Synthetases ◽

Editing Activity ◽

Structural Aspects

Aminoacyl-tRNA synthetases (aaRSs) are a canonical set of enzymes that specifically attach corresponding amino acids to their cognate transfer RNAs in the cytoplasm, mitochondria, and nucleus. The aaRSs display great differences in primary sequence, subunit size, and quaternary structure. Existence of three types of phenylalanyl-tRNA synthetase (PheRS)—bacterial (αβ)2, eukaryotic/archaeal cytosolic (αβ)2, and mitochondrial α—is a prominent example of structural diversity within the aaRSs family. Although archaeal/eukaryotic and bacterial PheRSs share common topology of the core domains and the B3/B4 interface, where editing activity of heterotetrameric PheRSs is localized, the detailed investigation of the three-dimensional structures from three kingdoms revealed significant variations in the local design of their synthetic and editing sites. Moreover, as might be expected from structural data eubacterial, Thermus thermophilus and human cytoplasmic PheRSs acquire different patterns of tRNAPhe anticodon recognition.

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