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Chain Composition (chain + composition)

Distribution by Scientific Domains

Polymers and Materials Science	60%

Selected Abstracts

Monte Carlo Simulations of the Morphologies and Conformations of Triblock Copolymer Thin Films

MACROMOLECULAR THEORY AND SIMULATIONS, Issue 2 2006
Yongmin Huang
Abstract Summary: The morphologies and conformations of triblock copolymer (ABA and ABC) thin films confined between two identical walls were investigated by Monte Carlo simulation using bond length fluctuation and cavity diffusion algorithm on cubic lattice. Effects of the wall-block interactions, copolymer chain composition and film thickness on morphologies, as well as on the fraction of chain "bridge" conformation fbridge are presented in detail. In ABA thin film, column, parallel, perforated and perpendicular lamellas were discriminated, furthermore, the transition of morphology and the variation of fbridge of ABA film along with the increase of thickness were revealed. In ABC thin film, lamella especially perpendicular lamella morphologies are predominant in varying the wall-block interactions and the thickness. The results are consistent with some theoretical predictions such as DDFT and simulations reported in literature. Isodensity profile of A5B5A5 thin film. [source]

Abnormal basement membrane type IV collagen ,-chain composition in labial salivary glands in Sjögren's syndrome

ARTHRITIS & RHEUMATISM, Issue 4 2009
P. Poduval
Objective Sjögren's syndrome (SS) is characterized by atrophy and malfunction of the acinar cells. The aim of this study was to investigate whether type IV collagen ,-chain composition of acinar cell compartments could be abnormal in diseased glands. Methods Messenger RNA (mRNA) from human submandibular gland (HSG) cells, cultured with or without growth factor,depleted Matrigel, was analyzed using quantitative reverse transcription,polymerase chain reaction (RT-PCR). Labial salivary glands were analyzed using quantitative RT-PCR and immunohistochemistry. Results HSG cells of both the ductal and acinar phenotypes synthesized all ,-chain mRNA, in particular those of the ,1 and ,2 chains. Labial salivary glands (LSGs) contained ,1/2 chains but also contained mRNA of all the other ,-chains, although the mRNA copy numbers for the ,3 and ,4 chains were low, and the corresponding proteins were absent. Type IV collagen ,1/2-chains were observed in all tubuloalveolar basement membranes. In healthy glands, ,5 and ,6 chains were continuous around ducts but discontinuous around acini. In SS glands, these chains were absent or patchy around the ducts and absent around the acini. Conclusion Ductal and acinar epithelial cells are able to locally produce mRNA for all 6 different ,-chains. Type IV collagen ,1/2-chains seem to form the backbone in the tubuloalveolar basement membrane in salivary glands. Type IV collagen ,3 and ,4 chain mRNA were found in cultured salivary epithelial cells and LSG explants but were not translated to the corresponding ,-chains in LSGs. Both ,5 and ,6 mRNA were observed in salivary epithelial cells and glands. In healthy glands, immunolabeling always disclosed corresponding ,-chains around ducts, but their synthesis and/or degradation seemed to be locally regulated around acinar cells. [source]

Electrospinning of polyamides with different chain compositions for filtration application

POLYMER ENGINEERING & SCIENCE, Issue 6 2008
Pirjo Heikkilä
Electrospinning of several polyamides, PA6, PA66, PA612, PA614, PA1012, and PA1014, having different chain compositions and lengths of diacid and diamine segments, was demonstrated. Electrospinnability and fiber production rate of these polyamides were evaluated. Electrospun fibers were characterized with regard to their use in air filtration by measuring fiber diameter and filtration efficiency of fiber coating. Longer nonpolar chain segments of higher polyamides could in theory indicate higher dielectricity compared to PA6 and PA66, which would be an advantage in filtration applications. The solubility in polar formic acid and electrospinnability of higher polyamides, on the other hand, were clearly impaired with increased length of chain segments. Hence, PA66 is our best choice, and PA612 and PA6 our second options for commercial filtration applications if fiber electrospinnability, production rate, fiber diameter, and its distribution are concerned. Filtration efficiency of more than 95% of the particles having a diameter of 0.16 ,m and above was achieved with 0.5 g/m2 coating of PA66 nanofibers. Further increase in coating weight mainly increased the pressure drop to an unusable range without a significant further improvement of filtration efficiency. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers. [source]