Primitive Chain Network Simulation of Elongational Flows of Entangled Linear Chains: Role of Finite Chain Extensibility

2011 ◽  
Vol 44 (24) ◽  
pp. 9675-9682 ◽  
Author(s):  
Takatoshi Yaoita ◽  
Takeharu Isaki ◽  
Yuichi Masubuchi ◽  
Hiroshi Watanabe ◽  
Giovanni Ianniruberto ◽  
...  
2012 ◽  
Vol 45 (6) ◽  
pp. 2773-2782 ◽  
Author(s):  
Takatoshi Yaoita ◽  
Takeharu Isaki ◽  
Yuichi Masubuchi ◽  
Hiroshi Watanabe ◽  
Giovanni Ianniruberto ◽  
...  

1979 ◽  
Vol 42 (05) ◽  
pp. 1378-1387 ◽  
Author(s):  
Herman E Branson

SummaryA theory of fibrin formation is proposed in which gel fiber fabrication is coordinated by two distinct sets of complexing filaments emanating from spherical fibrinogen-derived structural subunits. The formulation is an attempt to correlate the previously reported ultramicroscopic negative-contrast images of fibrinogen and fibrin with a similar but unique spheroidal body observed during the organization of dysfibrin Seattle. This slow clotting dysfibrinogen manifested a predisposition to form aperiodic fibers when thrombic proteolysis and polymerization were curtailed by the progressively earlier application of an acid stain embedment reagent (uranyl acetate). The unstriated fibers were unevenly surrounded by the electron dense stain and manifested a “dirty” appearance. This “primordial” fiber was comprised of linear chains of (10 nm) complexed spheres with (15 nm) lateral filamentous projections. Fibrinogen Seattle consistently generated typically striated (26 nm), “clean”, or “mature” fiber gels when polymerization was allowed to proceed. The proposed role of these lateral filaments is to engage, align, and stabilize similar processes on globular subunits in adjacent linear chains of the “primordial” fiber. The behavior of the negative contrast reagent during the fibrinogen to fibrin conversion is assessed as a reflection of the distribution and orientation of polar residues. The“clean” or striated fiber is depicted as a highly fenestrated hollow cylinder with a hydrophilic interior. The model is fitted to ultrastructural studies on the progression of transamidation of fibrin by factor XIIIa.


1994 ◽  
Vol 107 (2) ◽  
pp. 631-638
Author(s):  
F. Buss ◽  
H. Kent ◽  
M. Stewart ◽  
S.M. Bailer ◽  
J.A. Hanover

We have expressed rat nucleoporin p62 cDNA in Escherichia coli to obtain material for structural and self-association studies. Electron microscopy and circular dichroism spectroscopy are consistent with a rod-shaped molecule with an alpha-helical coiled-coil domain at its C terminus and a cross-beta structure at its N terminus, separated by a threonine-rich linker, which has a less-defined secondary structure. Electron microscopy and the solubility properties of fragments produced using thrombin and CNBr digestion indicate that p62 molecules associate to form linear chains and that a small region near the C terminus is an important determinant of assembly. This association may have important consequences for pore structure and function; for example, one way p62 could associate would be to form rings in nuclear pores that could function like barrel hoops.


Author(s):  
Adrian P. Sutton

In a Volterra dislocation the relative displacement by the Burgers vector appears abruptly in the dislocation core so that the core has no width. This leads to divergent stresses and strains, which are unrealistic. Hybrid models correct this failure by considering a balance of forces that results in a finite core width, and finite stresses and strains throughout. Interatomic forces tend to constrict the core and elastic forces tend to widen it. The Frenkel-Kontorova model comprises two interacting linear chains of atoms as a representation of an edge dislocation, with linear springs between adjacent atoms of each chain. The Peierls-Nabarro model assumes the core is confined to two parallel atomic planes sandwiched between elastic continua. This model enables the stress to move the dislocation to be calculated, and it leads to the concept of dislocation kinks. These models highlight the role of atomic interactions in affecting ductility.


2020 ◽  
Vol 62 (6) ◽  
pp. 955
Author(s):  
С.Ю. Давыдов

For AlN and GaN infinite flat sheets, free and decorated nanoribbons with the zigzag-type edges and linear chains the analytical expressions for the band-gap widths, characteristic velocities and effective masses are obtained. Numerical results are compared with the values of the corresponding characteristics calculated within the same models for the silicon carbide and carbon nanostructures. The role of substrate is also briefly discussed.


2002 ◽  
Vol 738 ◽  
Author(s):  
Sergio B. Legoas ◽  
Douglas S. Galvão ◽  
Varlei Rodrigues ◽  
Daniel Ugarte

ABSTRACTMetallic nanowires represent very interesting systems due to new phenomena such as quantum conductance and unexpected long interatomic distances attaining 0.3–0.5 nm. These large distances represent a challenge for physical interpretation. In this work we present experimental data from transmission electron microscopy and results from ab initio density functional calculations for suspended gold chains. We show that large distances as 0.5 nm can be easily explained by the presence of carbon atoms as contaminants, while distances ranging from 0.29 up to 0.36 nm might be explained as resulting of a mixture of clean stressed and contaminated linear chains.


Cells ◽  
2020 ◽  
Vol 9 (8) ◽  
pp. 1778 ◽  
Author(s):  
Dariusz Stępiński ◽  
Maria Kwiatkowska ◽  
Agnieszka Wojtczak ◽  
Justyna Teresa Polit ◽  
Eva Domínguez ◽  
...  

The cuticle commonly appears as a continuous lipophilic layer located at the outer epidermal cell walls of land plants. Cutin and waxes are its main components. Two methods for cutin synthesis are considered in plants. One that is based on enzymatic biosynthesis, in which cutin synthase (CUS) is involved, is well-known and commonly accepted. The other assumes the participation of specific nanostructures, cutinsomes, which are formed in physicochemical self-assembly processes from cutin precursors without enzyme involvement. Cutinsomes are formed in ground cytoplasm or, in some species, in specific cytoplasmic domains, lipotubuloid metabolons (LMs), and are most probably translocated via microtubules toward the cuticle-covered cell wall. Cutinsomes may additionally serve as platforms transporting cuticular enzymes. Presumably, cutinsomes enrich the cuticle in branched and cross-linked esterified polyhydroxy fatty acid oligomers, while CUS1 can provide both linear chains and branching cutin oligomers. These two systems of cuticle formation seem to co-operate on the surface of aboveground organs, as well as in the embryo and seed coat epidermis. This review focuses on the role that cutinsomes play in cuticle biosynthesis in S. lycopersicum, O. umbellatum and A. thaliana, which have been studied so far; however, these nanoparticles may be commonly involved in this process in different plants.


1994 ◽  
Vol 72 (3) ◽  
pp. 813-820 ◽  
Author(s):  
Yehuda Zeiri

The present study is dedicated to the investigation of the relationship between the surface diffusion mechanism of large adsorbates and the adsorbate shape. Three different shapes of model adsorbates were examined: linear chains, branched chains, and cyclic molecules. It was found that the surface diffusion mechanism of linear and branched chain adsorbates is quite similar, while a markedly different diffusion mechanism is observed for cyclic adsorbates. For all types of adsorbates the temperature dependence of the diffusion coefficient was found to obey an Arrhenius expression. The results of the simulations have shown good qualitative agreement with the available experimental data.


1988 ◽  
Vol 66 (4) ◽  
pp. 718-724 ◽  
Author(s):  
Ruth Margaret Barron ◽  
Thomas Hugh Kenneth Barron ◽  
Paul Malcolm Mummery ◽  
Michael Sharkey

With typical pair potentials, a bond is stretched by vibrations along the bond directions, while contraction is caused by the tension set up by vibrations normal to the bond direction. The rôle of these two effects is studied in calculations for parallel linear-chain and zigzag-chain models. For linear chains and rigid zigzag chains, expansion is positive in the plane normal to the chain direction, although it may be strongly anisotropic in this plane. Expansion along the chain direction is negative, and typically an order of magnitude less than that normal to the chain. For a flexible zigzag chain with bond angle 90°, expansion is positive in all directions; the Grüneisen tensor is approximately isotropic, but elastic anisotropy leads to smaller expansion coefficients in the molecular planes. The Reuss-averaged Grüneisen function derived from (6–12) pair potentials is about 3.5 for most of the models; this is higher than observed experimentally in polycrystalline polyethylene, indicating the need for more realistic models of organic polymers.


2016 ◽  
Vol 186 ◽  
pp. 17-30 ◽  
Author(s):  
Michael Schmitt ◽  
Chin Ming Hui ◽  
Zachary Urbach ◽  
Jiajun Yan ◽  
Krzysztof Matyjaszewski ◽  
...  

Recent progress in the area of surface-initiated controlled radical polymerization (SI-CRP) has enabled the synthesis of polymer-grafted colloids with precise control over the architecture of grafted chains. The resulting ‘particle brush materials’ are of interest both from a fundamental as well as applied perspective because structural frustrations (associated with the tethering of chains to a curved surface) imply a sensitive dependence of the interactions between brush particles on the architecture of surface-tethered chains that offers new opportunities to design hybrid materials with novel functionalities. An important prerequisite for establishing structure–property relations in particle brush materials is to understand the role of homopolymer impurities that form, for example, by thermal self-initiation. This contribution presents a detailed discussion of the role of homopolymer additives on the structure and mechanical properties of particle brush materials. The results suggest that the dissolution of homopolymer fillers follows a two-step mechanism comprised of the initial segregation of homopolymer to the interstitial regions within the array and the subsequent swelling of the particle brush (depending on the respective degree of polymerization of brush and linear chains). Addition of even small amounts of homopolymer is found to significantly increase the fracture toughness of particle brush assembly structures. The increased resistance to failure could enable the synthesis of robust colloidal crystal type materials that can be processed into complex shapes using ‘classical’ polymer forming techniques such as molding or extrusion.


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