scholarly journals The Stiffness-Threshold Conflict in Polymer Networks and a Resolution

2019 ◽  
Vol 87 (3) ◽  
Author(s):  
Yifan Zhou ◽  
Wenlei Zhang ◽  
Jian Hu ◽  
Jingda Tang ◽  
Chenyu Jin ◽  
...  
Keyword(s):  
Chain Length ◽  
Polymer Networks ◽  
Fatigue Threshold ◽  
Short Chain ◽  
High Threshold ◽  
Material Parameters ◽  
High Stiffness ◽  
Load Carrying ◽  
Chain Lengths ◽  
Long Chain

Abstract Stiffness and fatigue threshold are important material parameters in load-carrying applications. However, it is impossible to achieve both high stiffness and high threshold for single-network elastomers and single-network hydrogels. As the polymer chain length increases, the stiffness reduces, but the threshold increases. Here, we show that this stiffness-threshold conflict is resolved in double-network hydrogels, where the stiffness depends on the short-chain network, but the threshold depends on the long-chain network. Experimental data in the literature have shown that the stiffness of the hydrogels is inversely proportional to chain length of the short-chain network. In this paper we measure the threshold of PAAm-PAMPS hydrogels with five different chain lengths of the long-chain network. We find that the threshold is proportional to 1/2 power of the chain length of the long-chain network. The resolution of the conflict enables the design of elastomers and hydrogels to achieve both high stiffness and high threshold.

scholarly journals Preparation of Bisphenol-A and Polydimethylsiloxane (PDMS) Block Copolycarbonates by Melt Polycondensation: Effects of PDMS Chain Length on Conversion and Miscibility

Polymers ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 2660
Author(s):  
Zibo Zhou ◽  
Guozhang Wu
Keyword(s):  
Bisphenol A ◽  
Chain Length ◽  
Short Chain ◽  
Side Reactions ◽  
Diphenyl Carbonate ◽  
Key Factors ◽  
Factors Affecting ◽  
Melt Polycondensation ◽  
Chain Lengths ◽  
Long Chain

This study aimed to improve polydimethylsiloxane (PDMS) conversion in the preparation of polycarbonate (PC)–polydimethylsiloxane (PDMS) copolymer through melt polycondensation. We examined the transesterification process of PDMS with diphenyl carbonate (DPC) and its copolymerization products with bisphenol-A (BPA) for different chain lengths of PDMS. The key factors affecting PDMS conversion were investigated. Results showed that long-chain PDMS required a higher critical transesterification level (38.6%) to improve miscibility with DPC. During polycondensation, side reactions were more prone to occur when the equilibrium transesterification level of long-chain PDMS was lower. PDMS conversion was also lower when more short-chain PDMS was fed. Increasing the chain length of PDMS also reduced PDMS conversion. Notably, increasing the amount of KOH can significantly improve PDMS conversion throughout the polycondensation stage by increasing the equilibrium transesterification level of long-chain PDMS, thereby inhibiting the occurrence of side reactions.

Degrees of order of solubilized alkanes, alcohols, carboxylates, and carboxylic acids in oriented lyomesophases

1977 ◽  
Vol 55 (12) ◽  
pp. 2404-2410 ◽  
Author(s):  
Douglas M. Chen ◽  
Fred Y. Fujiwara ◽  
Leonard W. Reeves
Keyword(s):  
Carboxylic Acids ◽  
Chain Length ◽  
Linear Increase ◽  
Short Chain ◽  
Appreciable Amount ◽  
Linear Region ◽  
Short Chain Length ◽  
Chain Lengths ◽  
Degree Of Order ◽  
Limiting Value

The degree of order of solubilized molecules and ions in oriented lyomesophases has been determined at specifically deuterated C—D bond axes from the quadrupole splitting of the deuterium magnetic resonance. Mixtures at low concentration of specifically deuterated alkanes, alcohols, carboxylic acids, and carboxylates of different chain length have been observed in host cationic and anionic lyomesophases. The degree of order of a given C—D position in alcohols increases strongly with chain length up to a length comparable with the host detergent. A broad series of carboxylic acids and carboxylate ions from C2 to C16 have been deuterated in the α position. The α-C—D bond axis in the solubilisate increases in order with chain length, the anion having lower order than the parent acid. An accurately linear increase in the degree of order of the α position is observed for intermediate chain lengths. At chain lengths approximately equal to the host chain lengths the α position reaches a limiting value in the degree of order and further segments do not influence the order. At short chain lengths the degree of order is less than that predicted from extrapolation of order in the linear region. This has been interpreted in terms of distribution into the aqueous compartment by the solubilisates of short chain length. Acetic acid and the acetate, propionate, butanoate, and pentanoate ions spend an appreciable amount of time in the aqueous region. An estimate has been made of these distributions based on reasonable assumptions.

The Use of N-alkanes for Estimating Intake and Passage Rate in Horses

1996 ◽  
Vol 1996 ◽  
pp. 98-98
Author(s):  
B M L McLean ◽  
R W Mayes ◽  
F D DeB Hovell
Keyword(s):  
Recent Work ◽  
Chain Length ◽  
Carbon Chain ◽  
Carbon Chain Length ◽  
Passage Rate ◽  
Forage Crops ◽  
Carbon Chains ◽  
Naturally Occurring ◽  
Chain Lengths ◽  
Long Chain

Alkanes occur naturally in all plants, although forage crops tend to have higher alkane contents than cereals. N-alkanes have odd-numbered carbon chains. They are ideal for use as markers in feed trials, because, they are inert, indigestible and naturally occurring, and can be recovered in animal faeces. Synthetic alkanes (even-numbered carbon chains) are available commercially and can also used as external markers. Dove and Mayes (1991) cite evidence indicating that faecal recovery of alkanes in ruminants increases with increasing carbon-chain length. Thus the alkane “pairs” (e.g. C35 & C36, and C32 & C33) are used in calculating intake and digestibility because they are long chain and adjacent to each other. However, recent work by Cuddeford and Mayes (unpublished) has found that in horses the faecal recovery rates are similar regardless of chain lengths.

scholarly journals Nonacosan-10-ol and n-Alkanes in Leaves of Pinus pinaster

2020 ◽  
Vol 15 (5) ◽  
pp. 1934578X2092607
Author(s):  
Biljana Nikolić ◽  
Marina Todosijević ◽  
Iris Đorđević ◽  
Jovana Stanković ◽  
Zorica S. Mitić ◽  
...  
Keyword(s):  
Chain Length ◽  
Pinus Pinaster ◽  
Cuticular Wax ◽  
Short Chain ◽  
Average Chain Length ◽  
Carbon Preference Index ◽  
Preference Index ◽  
Long Chain

In leaf cuticular wax of Pinus pinaster, content of nonacosan-10-ol is high (77.1% on average). n-Alkanes ranged from C18 to C35 with the most dominant C29 (24.8%). The carbon preference index (CPItotal) ranged from 3.1 to 5.6 (4.0 on average), while the average chain length (ACLtotal) ranged from 14.0 to 17.0 (14.8 on average). Long-chain n-alkanes ( n-C25-35) strongly dominated (80.1%) over middle-chain ( n-C21-24 = 18.9%) and short-chain ( n -C18-20 = 0.9%) n-alkanes.

scholarly journals Elevation of 20-carbon long chain bases due to a mutation in serine palmitoyltransferase small subunit b results in neurodegeneration

2015 ◽  
Vol 112 (42) ◽  
pp. 12962-12967 ◽  
Author(s):  
Lihong Zhao ◽  
Stefka Spassieva ◽  
Kenneth Gable ◽  
Sita D. Gupta ◽  
Lan-Ying Shi ◽  
...  
Keyword(s):  
Chain Length ◽  
Small Subunit ◽  
Fatty Acyl ◽  
Substrate Affinity ◽  
Serine Palmitoyltransferase ◽  
Membrane Structures ◽  
Long Chain Base ◽  
Chain Lengths ◽  
Long Chain

Sphingolipids typically have an 18-carbon (C18) sphingoid long chain base (LCB) backbone. Although sphingolipids with LCBs of other chain lengths have been identified, the functional significance of these low-abundance sphingolipids is unknown. The LCB chain length is determined by serine palmitoyltransferase (SPT) isoenzymes, which are trimeric proteins composed of two large subunits (SPTLC1 and SPTLC2 or SPTLC3) and a small subunit (SPTssa or SPTssb). Here we report the identification of an Sptssb mutation, Stellar (Stl), which increased the SPT affinity toward the C18 fatty acyl-CoA substrate by twofold and significantly elevated 20-carbon (C20) LCB production in the mutant mouse brain and eye, resulting in surprising neurodegenerative effects including aberrant membrane structures, accumulation of ubiquitinated proteins on membranes, and axon degeneration. Our work demonstrates that SPT small subunits play a major role in controlling SPT activity and substrate affinity, and in specifying sphingolipid LCB chain length in vivo. Moreover, our studies also suggest that excessive C20 LCBs or C20 LCB-containing sphingolipids impair protein homeostasis and neural functions.

Approaching the size limit of organometallic layers: synthesis and characterization of highly ordered silver–thiolate lamellae with ultra-short chain lengths

2016 ◽  
Vol 45 (47) ◽  
pp. 18954-18966 ◽  
Author(s):  
Zichao Ye ◽  
Lito P. de la Rama ◽  
Mikhail Y. Efremov ◽  
Jian-Min Zuo ◽  
Leslie H. Allen
Keyword(s):  
Single Crystal ◽  
Chain Length ◽  
Short Chain ◽  
Synthesis And Characterization ◽  
Size Limit ◽  
Chain Conformations ◽  
Chain Lengths

Synthesis of single crystal silver alkanethiolate (any chain length) lamellae with highly ordered chain conformations, interlayer interfaces and intralayer lattices.

Acyl-CoA dehydrogenase activity in pea cotyledon tissue during germination and initial growth

2000 ◽  
Vol 28 (6) ◽  
pp. 760-762 ◽  
Author(s):  
C. Masterson ◽  
A. Blackburn ◽  
C. Wood
Keyword(s):  
Dehydrogenase Activity ◽  
Chain Length ◽  
Root Formation ◽  
Short Chain ◽  
Initial Growth ◽  
Chain Acyl ◽  
Pea Seeds ◽  
Acyl Coa Dehydrogenases ◽  
Hydroponically Grown ◽  
Long Chain

Acyl-CoA dehydrogenase activity has been measured in homogenates of post-imbibition to 14-day-old hydroponically grown pea seeds at daily intervals, using C4, C12 and C16 acyl-CoA substrates. The activity peaks of the different chain-length acyl-CoA dehydrogenases did not transpose at all points and the ratios of the chain-length activities were not constant. It therefore has to be concluded that more than one dehydrogenase is present in pea mitochondria. There was a post-imbibition initial surge of activity with short- and mid-chain-length substrates. The C16- handling enzyme first peaked at 3–4 days, which coincided with the onset of plumule unfurling and greening. Further peaks were observed with all three substrates, coinciding with secondary root formation and leaf enlargement and later with cotyledon degeneration. Overall activity showed that the long-chain acyl-CoA dehydrogenase was much more active than the short-chain acyl-CoA dehydrogenase.

scholarly journals Lipopolysaccharide O-Antigen Chain Length Regulation in Pseudomonas aeruginosa Serogroup O11 Strain PA103

2007 ◽  
Vol 190 (8) ◽  
pp. 2709-2716 ◽  
Author(s):  
Erica Kintz ◽  
Jennifer M. Scarff ◽  
Antonio DiGiandomenico ◽  
Joanna B. Goldberg
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Chain Length ◽  
Gene Mutations ◽  
Side Chain ◽  
Wild Type ◽  
O Antigen ◽  
Length Regulation ◽  
O Antigens ◽  
Chain Lengths ◽  
Long Chain

ABSTRACT The Wzz proteins are important for determining the length of the O-antigen side chain attached to lipopolysaccharide (LPS). Several bacteria, including Pseudomonas aeruginosa strain PAO1 (serogroup O5), produce two such proteins responsible for the preference of two different chain lengths on the surface. Our group has previously identified one wzz gene (wzz1) within the O-antigen locus of P. aeruginosa strain PA103 (serogroup O11). In this study we have identified the second wzz gene (wzz2), located in the same region of the genome and with 92% similarity to PAO1's wzz2 gene. Mutations were generated in both wzz genes by interruption with antibiotic resistance cassettes, and the effects of these mutations were characterized. Wild-type PA103 prefers two O-antigen chain lengths, referred to as long and very long. The expression of the long O-antigen chain length was reduced in the wzz1 mutant, indicating the Wzz1 protein is important for this chain length preference. The wzz2 mutant, on the other hand, was missing O-antigens of the very long chain length, indicating the Wzz2 protein is responsible for the production of very long O-antigen. The effects of the wzz mutations on virulence were also investigated. In both serum sensitivity assays and a mouse pneumonia model of infection, the wzz1 mutants exhibited greater defects in virulence compared to either wild-type PA103 or the wzz2 mutant, indicating the long chain length plays a greater role during these infectious processes.

THE FERMENTATION OF LONG-CHAIN COMPOUNDS BY TORULOPSIS MAGNOLIAE: I. STRUCTURES OF THE HYDROXY FATTY ACIDS OBTAINED BY THE FERMENTATION OF FATTY ACIDS AND HYDROCARBONS

1962 ◽  
Vol 40 (7) ◽  
pp. 1326-1338 ◽  
Author(s):  
A. P. Tulloch ◽  
J. F. T. Spencer ◽  
P. A. J. Gorin
Keyword(s):  
Fatty Acids ◽  
Carbon Atom ◽  
Chain Length ◽  
Hydroxy Fatty Acid ◽  
Hydroxyl Group ◽  
Fatty Esters ◽  
Degree Of Unsaturation ◽  
Chain Compounds ◽  
Chain Lengths ◽  
Long Chain

The yield of extracellular glycolipid produced by Torulopsis magnoliae is increased three-to five-fold by the addition of suitable compounds to the growing culture. The supplement, which can be a long-chain acid, ester, hydrocarbon, or glyceride, is hydroxylated and converted to hydroxy fatty acid sophorosides. Fatty esters of all chain lengths from C16 to C22, including several unsaturated esters, and even-numbered hydrocarbons from C16 to C24 are readily fermented. Shorter-chain compounds are used poorly or not at all. With compounds of 16 to 18 carbon atoms, hydroxylation occurs at the terminal or penultimate carbon atom, depending on degree of unsaturation and chain length. Substrates of more than 18 carbon atoms are mainly reduced in chain length by one or more two-carbon units and hydroxylated, giving C17 or C18 acids with the hydroxyl group on the penultimate carbon atom. The various enzymic reactions which occur during the fermentation are discussed.

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