scholarly journals Effect of cosolvent on the rheological properties and self-assembled structures from telechelic polyampholytes

2020 ◽  
Author(s):  
Margarita A. Dyakonova ◽  
Yanan Li ◽  
Ioanna N. Besiri ◽  
Zhenyu Di ◽  
Isabelle Grillo ◽  
...  
Keyword(s):  
Rheological Properties ◽  
Structural Changes ◽  
Viscoelastic Liquid ◽  
Viscoelastic Solid ◽  
Flowing Liquid ◽  
Rheological Measurements ◽  
The Core ◽  
Aqueous Polymer ◽  
Aqueous Polymer Solution ◽  
Cross Links

AbstractA triblock copolymer with hydrophobic end blocks and a polyampholytic middle block is investigated in a mixture of water and acetone with a focus on the dependence of the rheological properties and of the micellar structure and correlation on the content of acetone. The polymer under study is PMMA86-b-P(DEA190-co-MAA96)-b-PMMA86, where PMMA stands for poly(methyl methacrylate) and P(DEA-co-MAA) for poly(2-(diethylamino) ethyl methacrylate-co-methacrylic acid). The pH is chosen at 3. Rheological measurements reveal a transition from a viscoelastic solid over a viscoelastic liquid to a freely flowing liquid upon addition of 5 or 10 wt% of acetone to a 3 wt% aqueous polymer solution, respectively. Using small-angle neutron scattering on 0.5 wt% polymer solutions in water/acetone with the content of the latter ranging between 0 and 30 wt%, significant structural changes are observed as well, such as a decrease of the distance between the PMMA cross-links and of the size of the network clusters upon increasing acetone constant. These changes are attributed to the reduction of the dielectric constant by the addition of the cosolvent acetone, enhancing the flexibility of the middle blocks and their tendency to backfolding, as well as to the decrease of the solvent selectivity, inducing significant exchange rate enhancement of the core-forming PMMA blocks.

Optimal Drying Conditions of Porous Material Wetted with Aqueous Polymer Solution.

2003 ◽  
Vol 29 (1) ◽  
pp. 144-146 ◽  
Author(s):  
Hironobu Imakoma ◽  
Ryo Omori ◽  
Katsuyuki Kubota ◽  
Masamichi Yoshida
Keyword(s):  
Porous Material ◽  
Polymer Solution ◽  
Aqueous Polymer ◽  
Aqueous Polymer Solution ◽  
Drying Conditions

Control of Polymer Content Profile within Dried Porous Material Wetted with Aqueous Polymer Solution.

2002 ◽  
Vol 28 (4) ◽  
pp. 488-489 ◽  
Author(s):  
Hironobu Imakoma ◽  
Tatsuhiro Nakazawa ◽  
Katsuyuki Kubota ◽  
Masamichi Yoshida
Keyword(s):  
Porous Material ◽  
Polymer Solution ◽  
Polymer Content ◽  
Aqueous Polymer ◽  
Aqueous Polymer Solution

Convective-conductive Drying Characteristics of Thin Shrinkable Fibrous Layer Wetted with Aqueous Polymer Solution

2003 ◽  
Vol 29 (5) ◽  
pp. 695-697 ◽  
Author(s):  
Hironobu Imakoma ◽  
Takeshi Mori ◽  
Katsuyuki Kubota ◽  
Masamichi Yoshida
Keyword(s):  
Polymer Solution ◽  
Fibrous Layer ◽  
Drying Characteristics ◽  
Aqueous Polymer ◽  
Aqueous Polymer Solution

Relation between rheological properties and structural changes in monolayers of model lung surfactant under compression

2003 ◽  
Vol 104 (3) ◽  
pp. 633-642 ◽  
Author(s):  
D.O. Grigoriev ◽  
J. Krägel ◽  
A.V. Akentiev ◽  
B.A. Noskov ◽  
R. Miller ◽  
...  
Keyword(s):  
Rheological Properties ◽  
Structural Changes ◽  
Lung Surfactant ◽  
Model Lung

scholarly journals Assembly of T-Antigen Double Hexamers on the Simian Virus 40 Core Origin Requires Only a Subset of the Available Binding Sites

1998 ◽  
Vol 18 (5) ◽  
pp. 2677-2687 ◽  
Author(s):  
Woo S. Joo ◽  
Henry Y. Kim ◽  
John D. Purviance ◽  
K. R. Sreekumar ◽  
Peter A. Bullock
Keyword(s):  
Structural Changes ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Wild Type ◽  
The Core ◽  
Structural Distortions ◽  
In The Wild ◽  
Sv40 Dna ◽  
Initial Assembly

ABSTRACT Initiation of simian virus 40 (SV40) DNA replication is dependent upon the assembly of two T-antigen (T-ag) hexamers on the SV40 core origin. To further define the oligomerization mechanism, the pentanucleotide requirements for T-ag assembly were investigated. Here, we demonstrate that individual pentanucleotides support hexamer formation, while particular pairs of pentanucleotides suffice for the assembly of T-ag double hexamers. Related studies demonstrate that T-ag double hexamers formed on “active pairs” of pentanucleotides catalyze a set of previously described structural distortions within the core origin. For the four-pentanucleotide-containing wild-type SV40 core origin, footprinting experiments indicate that T-ag double hexamers prefer to bind to pentanucleotides 1 and 3. Collectively, these experiments demonstrate that only two of the four pentanucleotides in the core origin are necessary for T-ag assembly and the induction of structural changes in the core origin. Since all four pentanucleotides in the wild-type origin are necessary for extensive DNA unwinding, we concluded that the second pair of pentanucleotides is required at a step subsequent to the initial assembly process.

scholarly journals Quantifying Soil Compaction in Persimmon Orchards Using ISUM (Improved Stock Unearthing Method) and Core Sampling Methods

Agriculture ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 266 ◽  
Author(s):  
Ehsan Moradi ◽  
Jesús Rodrigo-Comino ◽  
Enric Terol ◽  
Gaspar Mora-Navarro ◽  
Alexandre Marco da Silva ◽  
...  
Keyword(s):  
Ecosystem Services ◽  
Soil Erosion ◽  
Bulk Density ◽  
Soil Compaction ◽  
Structural Changes ◽  
Low Cost ◽  
Positive Contribution ◽  
The Core ◽  
Core Sampling ◽  
Core Method

Agricultural activities induce micro-topographical changes, soil compaction and structural changes due to soil cultivation, which directly affect ecosystem services. However, little is known about how these soil structural changes occur during and after the planting of orchards, and which key factors and processes play a major role in soil compaction due to cultivation works. This study evaluates the improved stock unearthing method (ISUM) as a low-cost and precise alternative to the tedious and costly traditional core sampling method, to characterize the changes in soil compaction in a representative persimmon orchard in Eastern Spain. To achieve this goal, firstly, in the field, undisturbed soil samples using metallic core rings (in January 2016 and 2019) were collected at different soil depths between 45 paired-trees, and topographic variations were determined following the protocol established by ISUM (January 2019). Our results show that soil bulk density (Bd) increases with depth and in the inter-row area, due to the effect of tractor passes and human trampling. The bulk density values of the top surface layers (0–12 cm) showed the lowest soil accumulation, but the highest temporal and spatial variability. Soil consolidation within three years after planting as calculated using the core samples was 12 mm, whereas when calculated with ISUM, it was 14 mm. The quality of the results with ISUM was better than with the traditional core method, due to the higher amount of sampling points. The ISUM is a promising method to measure soil compaction, but it is restricted to the land where soil erosion does not take place, or where soil erosion is measured to establish a balance of soil redistribution. Another positive contribution of ISUM is that it requires 24 h of technician work to acquire the data, whereas the core method requires 272 h. Our research is the first approach to use ISUM to quantify soil compaction and will contribute to applying innovative and low-cost monitoring methods to agricultural land and conserving ecosystem services.

The Ashkenazi Élite at the Beginning of the Modern Era: Manuscript versus Printed Book

1997 ◽  
pp. 85-98
Author(s):  
Elchanan Reiner
Keyword(s):  
Structural Changes ◽  
Central Issue ◽  
Literary Canon ◽  
General Attitude ◽  
Transmission Of Knowledge ◽  
The Core ◽  
European Culture ◽  
History Of ◽  
The Impact ◽  
Modern Era

This chapter evaluates the effect of printing on the Ashkenazi cultural élite. The shift from script to print in the sixteenth century heralded a reshaping of Ashkenazi literary models. The chapter traces some reactions amongst Ashkenazi intellectuals to this shift, which are indicative of their general attitude to the structural changes in patterns of the transmission of knowledge during the period. It focuses on certain developments within intellectual circles, primarily in connection with changes in the way halakhic literature — the core of the Ashkenazi literary canon — was written and transmitted. While the impact of the making of books and printing has long been a central issue in the history of European culture in general, it is genuinely surprising that Jewish culture, which is so profoundly literary, has not been examined in this light up to now.

scholarly journals Analysis of Structural and Functional Differences of Glucans Produced by the Natively Released Dextransucrase of Liquorilactobacillus hordei TMW 1.1822

2020 ◽  
Vol 193 (1) ◽  
pp. 96-110 ◽  
Author(s):  
Jonas Schmid ◽  
Daniel Wefers ◽  
Rudi F. Vogel ◽  
Frank Jakob
Keyword(s):  
Molecular Weight ◽  
Secondary Structure ◽  
Rheological Properties ◽  
Viscoelastic Fluid ◽  
Size Structure ◽  
Molecular Size ◽  
Molecular Structures ◽  
Rheological Measurements ◽  
Functional Differences ◽  
Functionally Diverse

AbstractThe properties of the glucopolymer dextran are versatile and linked to its molecular size, structure, branching, and secondary structure. However, suited strategies to control and exploit the variable structures of dextrans are scarce. The aim of this study was to delineate structural and functional differences of dextrans, which were produced in buffers at different conditions using the native dextransucrase released by Liquorilactobacillus (L.) hordei TMW 1.1822. Rheological measurements revealed that dextran produced at pH 4.0 (MW = 1.1 * 108 Da) exhibited the properties of a viscoelastic fluid up to concentrations of 10% (w/v). By contrast, dextran produced at pH 5.5 (MW = 1.86 * 108 Da) was gel-forming already at 7.5% (w/v). As both dextrans exhibited comparable molecular structures, the molecular weight primarily influenced their rheological properties. The addition of maltose to the production assays caused the formation of the trisaccharide panose instead of dextran. Moreover, pre-cultures of L. hordei TMW 1.1822 grown without sucrose were substantial for recovery of higher dextran yields, since the cells stored the constitutively expressed dextransucrase intracellularly, until sucrose became available. These findings can be exploited for the controlled recovery of functionally diverse dextrans and oligosaccharides by the use of one dextransucrase type.

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