Synthesis of rigid dendritic macromolecules: enlarging the repeat unit size as a function of generation, permitting growth to continue

1991 ◽  
Vol 24 (21) ◽  
pp. 5893-5894 ◽  
Author(s):  
Jeffrey S. Moore ◽  
Zhifu Xu
Keyword(s):  
Repeat Unit ◽  
Unit Size ◽  
Dendritic Macromolecules

Internal Regularity of D-Glyceraldehide-3-Phosphate Dehydrogenase Genes and Proteins

2011 ◽  
Vol 50 (1-2) ◽  
pp. 159-164
Author(s):  
G. Chipens ◽  
N. Ievina ◽  
I. Kalvinsh
Keyword(s):  
Repeat Unit ◽  
Intron Position ◽  
Translational Symmetry ◽  
Unit Size ◽  
Garden Pea ◽  
Specific Term ◽  
Whole Number ◽  
Intron Number ◽  
Family Gene ◽  
Gene Exon

Internal Regularity ofD-Glyceraldehide-3-Phosphate Dehydrogenase Genes and ProteinsData of analysis of some GAPDH family gene exon and intron length (nt) and intron position coordinates as a sum of preceeding exon dimensions) and their internal regularity were analyzed based on a working hypothesis that primieval gene precursors were regular and periodic polynucleotides formed from oligonucleotides identical in size. The number of nucleotides in a gene repeat unit was denoted by a specific term - gene quantum and symbolQ. The following genes were analyzed: the chicken GAPDH (12 exons/11 introns) gene, theChlamidomonas reinhardtii gapA(6 exons, 5 introns) andgapC(7 exons, 6 introns) genes. The determined value ofQfor all these genes was identical and constituted 9 nucleotides. The sum total of all above-mentioned gene intron dimensions, independently of intron number in a gene, could be precisely quantized - expressed as a product of a gene quantum and a whole number, e.g., for the chicken GAPDH 1628 nt = 9 nt x 292,0. The garden peaPissum sativumfragment (amino acids 167-219) was partially regular (the repeat unit size 9 aa) and showed translational symmetry. The obtained data supported the model that the precursors of the modern genes were originated by nucleotide multiplication reactions.

Recent developments in vertical cooling crystalliser design

2011 ◽  
pp. 726-733
Author(s):  
Michael Getaz ◽  
Rob Sanders
Keyword(s):  
Motor Drive ◽  
Steady Increase ◽  
Unit Size ◽  
Heat Transfer Characteristics ◽  
Heat Exchange Surface ◽  
Recent Developments ◽  
Cooling Tube ◽  
Good Heat ◽  
Exchange Surface ◽  
Design Challenges

In modern installations vertical cooling crystallisers are now preferred over traditional horizontal units because of the significant benefits they offer, which include larger volumes and smaller floor space, suitability for outdoor installation, higher cooling surface to volume ratios and a better ability to handle highly viscous massecuite, amongst others. Since the first vertical cooling crystallisers were introduced, nearly 40 years ago, there has been a steady increase in their unit size from initial volumes in the 50–200 m3 range up to the present day where the most general unit size is now in the 300–400 m3 range, with even larger units becoming increasingly common. Large crystallisers present some significant design challenges and a good modern vertical cooling crystalliser design requires a robust construction of heat exchange surface, stirrer and drive units coupled with features that promote good heat transfer characteristics and uniform massecuite flow patterns. Careful attention to cooling tube and stirrer arm design and configuration are needed to achieve this, whilst the use of modern planetary gearboxes and variable frequency controlled motor drive units can provide added benefits to boost both performance and reliability. How these design features are incorporated in a modern unit is explained, focusing on cane C massecuite duty and using the Fives Cail and Fives Fletcher units as an example.

scholarly journals Elucidating the Molecular Mechanisms for the Interaction of Water with Polyethylene Glycol-Based Hydrogels: Influence of Ionic Strength and Gel Network Structure

Polymers ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 845
Author(s):  
Xin Yang ◽  
Bronwin Dargaville ◽  
Dietmar Hutmacher
Keyword(s):  
Polyethylene Glycol ◽  
Ionic Strength ◽  
Molecular Mechanisms ◽  
Repeat Unit ◽  
Bound Water ◽  
Weight Fraction ◽  
Swelling Ratio ◽  
Polyethylene Glycol Diacrylate ◽  
Glycol Diacrylate ◽  
Hydrogel System

The interaction of water within synthetic and natural hydrogel systems is of fundamental importance in biomaterial science. A systematic study is presented on the swelling behavior and states of water for a polyethylene glycol-diacrylate (PEGDA)-based model neutral hydrogel system that goes beyond previous studies reported in the literature. Hydrogels with different network structures are crosslinked and swollen in different combinations of water and phosphate-buffered saline (PBS). Network variables, polyethylene glycol (PEG) molecular weight (MW), and weight fraction are positively correlated with swelling ratio, while “non-freezable bound water” content decreases with PEG MW. The presence of ions has the greatest influence on equilibrium water and “freezable” and “non-freezable” water, with all hydrogel formulations showing a decreased swelling ratio and increased bound water as ionic strength increases. Similarly, the number of “non-freezable bound water” molecules, calculated from DSC data, is greatest—up to six molecules per PEG repeat unit—for gels swollen in PBS. Fundamentally, the balance of osmotic pressure and non-covalent bonding is a major factor within the molecular structure of the hydrogel system. The proposed model explains the dynamic interaction of water within hydrogels in an osmotic environment. This study will point toward a better understanding of the molecular nature of the water interface in hydrogels.

scholarly journals Microsatellite and Chromosome Evolution of Parthenogenetic Sitobion Aphids in Australia

Genetics ◽  
1996 ◽  
Vol 144 (2) ◽  
pp. 747-756 ◽  
Author(s):  
Paul Sunnucks ◽  
Phillip R England ◽  
Andrea C Taylor ◽  
Dinah F Hales
Keyword(s):  
Sexual Reproduction ◽  
Chromosome Evolution ◽  
Genetic Recombination ◽  
Allelic Variation ◽  
Repeat Unit ◽  
Chromosomal Evolution ◽  
Microsatellite Variation ◽  
Wide Range ◽  
Sexual Recombination ◽  
Minimum Numbers

Abstract Single-locus microsatellite variation correlated perfectly with chromosome number in Sitobion miscanthi aphids. The microsatellites were highly heterozygous, with up to 10 alleles per locus in this species. Despite this considerable allelic variation, only seven different S. miscanthi genotypes were discovered in 555 individuals collected from a wide range of locations, hosts and sampling periods. Relatedness between genotypes suggests only two successful colonizations of Australia. There was no evidence for genetic recombination in 555 S. miscanthi so the occurrence of recent sexual reproduction must be near zero. Thus diversification is by mutation and chromosomal rearrangement alone. Since the aphids showed no sexual recombination, microsatellites can mutate without meiosis. Five of seven microsatellite differences were a single repeat unit, and one larger jump is likely. The minimum numbers of changes between karyotypes corresponded roughly one-to-one with microsatellite allele changes, which suggests very rapid chromosomal evolution. A chromosomal fission occurred in a cultured line, and a previously unknown chromosomal race was detected. All 121 diverse S. near fragariae were heterozygous but revealed only one genotype. This species too must have a low rate of sexual reproduction and few colonizations of Australia.

scholarly journals Electrochemically Produced Copolymers of Pyrrole and Its Derivatives: A Plentitude of Material Properties Using “Simple” Heterocyclic Co-Monomers

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 281
Author(s):  
Tomasz Jarosz ◽  
Przemyslaw Ledwon
Keyword(s):  
Biological Activity ◽  
Material Properties ◽  
Building Block ◽  
Conjugated Polymer ◽  
Chemical Structure ◽  
Heterocyclic System ◽  
Repeat Unit ◽  
Polymeric Materials ◽  
Pyrrole Derivatives ◽  
Pyrrole Monomer

Polypyrrole is a classical, well-known conjugated polymer that is produced from a simple heterocyclic system. Numerous pyrrole derivatives exhibit biological activity, and the repeat unit is a common building block present in the chemical structure of many polymeric materials, finding wide application, primarily in optoelectronics and sensing. In this work, we focus on the variety of copolymers and their material properties that can be produced electrochemically, even though all these systems are obtained from mixtures of the “simple” pyrrole monomer and its derivatives with different conjugated and non-conjugated species.

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