scholarly journals Phase behavior and thermal dynamic properties of free volume on SMMA/SMA copolymer blend studied by PALS method

2006 ◽  
Vol 55 (6) ◽  
pp. 3136
Author(s):  
Jiang Zhong-Ying ◽  
Yu Wei-Zhong ◽  
Huang Yan-Jun ◽  
Xia Yuan-Fu ◽  
Ma Shu-Xin
Keyword(s):  
Phase Behavior ◽  
Free Volume ◽  
Dynamic Properties ◽  
Copolymer Blend

scholarly journals Molecule Dynamics Simulation of the Effect of Oxidative Aging on Properties of Nitrile Rubber

Polymers ◽  
2022 ◽  
Vol 14 (2) ◽  
pp. 226
Author(s):  
Jinsong Yang ◽  
Weitao Lou
Keyword(s):  
Free Volume ◽  
Dynamic Properties ◽  
Compressive Strain ◽  
Mean Square Displacement ◽  
Nitrile Rubber ◽  
Dynamics Simulation ◽  
Hydroxyl Groups ◽  
Carbonyl Groups ◽  
Fractional Free Volume ◽  
Oxidative Aging

The effects of oxidative aging on the static and dynamic properties of nitrile rubber at the molecular scale were investigated by molecular dynamics simulation. The aged nitrile rubber models were constructed by introducing hydroxyl groups and carbonyl groups into rubber molecular chains to mimic oxidative aging. The static and dynamic properties of the unaged and aged nitrile rubber under different conditions were evaluated by mean square displacement, self-diffusion coefficients, hydrogen bond, fractional free volume, radial distribution function, cohesive energy density and solubility parameter. The results show that the elevated temperature intensified significantly the mobility of rubber molecular chains and fractional free volume, while the compressive strain displayed the opposite effect resulting in packing and rearrangement of rubber chains. The introduction of hydroxyl groups and carbonyl groups enhanced the polarity, intermolecular interactions, the volume and rigidity of molecular chains, implying weaker mobility of molecular chains as compared to unaged models. The compressive strain and oxidative aging both decreased the fractional free volume, which inhibited gaseous and liquid diffusion into the rubber materials, and slowed down the oxidative aging rate. This study provides insights to better understand the effect of molecular changes due to oxidative aging on the structural and dynamic properties of rubber materials at the molecular level.

Decompression of Gas Pipelines During Longitudinal Ductile Fractures

1979 ◽  
Vol 101 (1) ◽  
pp. 66-73
Author(s):  
G. G. King
Keyword(s):  
Heat Flux ◽  
Ductile Fracture ◽  
Phase Behavior ◽  
Gas Flow ◽  
Dynamic Properties ◽  
Gas Pipelines ◽  
Two Phase ◽  
Flow Equations ◽  
Ductile Fractures ◽  
Ductile Mode

An understanding is given of how gas pipelines decompress when they burst and fail longitudinally in a ductile mode. Transient gas flow equations expressing conservation of mass, momentum and energy are used to develop simple and realistic equations for gas pressure decay with time at a moving longitudinal ductile fracture. Gas thermo-dynamic properties and two-phase behavior are discussed. Friction and heat flux affect gas decompression and influence design to control longitudinal ductile fractures in gas pipelines.

scholarly journals Amorphous polymer dynamics and free volume element size distributions from ultrafast IR spectroscopy

2020 ◽  
Vol 117 (25) ◽  
pp. 13949-13958 ◽  
Author(s):  
David J. Hoffman ◽  
Sebastian M. Fica-Contreras ◽  
Michael D. Fayer
Keyword(s):  
Probability Distribution ◽  
Free Volume ◽  
Stark Effect ◽  
Dynamic Properties ◽  
Amorphous Polymer ◽  
Polymeric Materials ◽  
Volume Element ◽  
Probe Molecule ◽  
Pump Probe ◽  
Element Size

A method for measuring the size and size probability distribution of free volume regions in polymeric materials using ultrafast infrared (IR) polarization-selective pump–probe experiments is presented. Measurements of the ultrafast dynamics of a vibrational probe (the CN stretch of phenyl selenocyanate) in poly(methyl methacrylate) show that the probe dynamics are highly confined. The degree of confinement was found to be both time-dependent and dependent on the vibrational frequency of the probe molecule. The experiments demonstrate that different vibrational frequencies correspond to distinct subensembles of probe molecules that have different dynamic properties determined by their local structural environments. By combining the degree of dynamical confinement with the molecular size of the probe molecule, the free volume element size probability distribution was determined and found to be in good agreement with the best established experimental measure of free volume. The relative probability of a free volume element size is determined by the amplitude of the nitrile absorption spectrum at the frequency of the measurement. The inhomogeneous broadening of the spectrum was linked to the vibrational Stark effect, which permits site selectivity. The observed dynamics at each frequency were then associated with a different size free volume element and distinct local electric field. The multiple timescales observed in the pump–probe experiments were connected to local structural fluctuations of the free volume elements.

The distribution of antigen on the surface of RBL-2H3 rat basophilic leukemia cells observed by back-scattered electron imaging

1986 ◽  
Vol 44 ◽  
pp. 274-275
Author(s):  
R.F. Stump ◽  
J.R. Pfeiffer ◽  
JC. Seagrave ◽  
D. Huskisson ◽  
J.M. Oliver
Keyword(s):  
Cell Surface ◽  
Dynamic Properties ◽  
Leukemia Cells ◽  
Antigen Binding ◽  
Scattered Electron ◽  
Ige Receptor ◽  
Receptor Complexes ◽  
Rat Basophilic Leukemia Cells ◽  
Electron Imaging ◽  
Basophilic Leukemia

In RBL-2H3 rat basophilic leukemia cells, antigen binding to cell surface IgE-receptor complexes stimulates the release of inflammatory mediators and initiates a series of membrane and cytoskeletal events including a transformation of the cell surface from a microvillous to a lamellar topography. It is likely that dynamic properties of the IgE receptor contribute to the activation of these responses. Fewtrell and Metzger have established that limited crosslinking of IgE-receptor complexes is essential to trigger secretion. In addition, Baird and colleagues have reported that antigen binding causes a rapid immobilization of IgE-receptor complexes, and we have demonstrated an apparent increase with time in the affinity of IgE-receptor complexes for antigen.

Phase behavior of cationic and anionic surfactants at low concentrations

1992 ◽  
Vol 50 (1) ◽  
pp. 694-695
Author(s):  
E. Naranjo
Keyword(s):  
Phase Behavior ◽  
Structural Characterization ◽  
Dynamic Systems ◽  
Anionic Surfactants ◽  
Intermolecular Forces ◽  
Stable Form ◽  
Surfactant Mixtures ◽  
Low Concentrations ◽  
Cationic And Anionic Surfactants ◽  
General Method

Equilibrium vesicles, those which are the stable form of aggregation and form spontaneously on mixing surfactant with water, have never been demonstrated in single component bilayers and only rarely in lipid or surfactant mixtures. Designing a simple and general method for producing spontaneous and stable vesicles depends on a better understanding of the thermodynamics of aggregation, the interplay of intermolecular forces in surfactants, and an efficient way of doing structural characterization in dynamic systems.

Nucleosome dynamics

2006 ◽  
Vol 73 ◽  
pp. 109-119 ◽  
Author(s):  
Chris Stockdale ◽  
Michael Bruno ◽  
Helder Ferreira ◽  
Elisa Garcia-Wilson ◽  
Nicola Wiechens ◽  
...  
Keyword(s):  
High Resolution ◽  
Chromatin Structure ◽  
Current Knowledge ◽  
Dynamic Properties ◽  
Structure And Dynamics ◽  
Nucleosome Dynamics ◽  
Sharp Focus ◽  
Recent Advances ◽  
Insight Into ◽  
Chromatin Structure And Dynamics

In the 30 years since the discovery of the nucleosome, our picture of it has come into sharp focus. The recent high-resolution structures have provided a wealth of insight into the function of the nucleosome, but they are inherently static. Our current knowledge of how nucleosomes can be reconfigured dynamically is at a much earlier stage. Here, recent advances in the understanding of chromatin structure and dynamics are highlighted. The ways in which different modes of nucleosome reconfiguration are likely to influence each other are discussed, and some of the factors likely to regulate the dynamic properties of nucleosomes are considered.

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