Uncoiling process

With the help of bridle no. I driven by motors M and M4, the uncoiler section speed is controlled by monitoring the tension of the travelling sheet and hence maintaining constant speed of the sheet in the uncoiler section. The tensile difference of T tind Ti determines the speed of the uncoiler. Speed and tension of the sheet must remain constant for absolute synchronization between the uncoiler process and the recoiler sections. 

In order to extend earlier wor)c, several positively charged luminescent probes, tris(2,2 -bipyridine) ruthenium(II) complex, Ru(bpy)3, Auramine 0, Au 0, 1-pyrenebutyltrimethyl ammonium bromide, C PN and 1-pyreneundecyltrimethylammonium iodide, PN have been employed to monitor the nature of the conformational transition of PMA over the pH range of 2 to 8, from A states into B states. The purpose of the present wor)c is, to investigate the intermediate states in the uncoiling process of PMA polymer coil with increasing pH and to study any effects that are induced by polyelectrolytes on the photophysics and photochemistry of cationic... 

Although their free solution behaviors are similar, flexible molecules (like DNA and denatured proteins) exhibit dramatically different behavior in a sieving matrix. Once the size of the pores in the gel becomes small relative to the radius of gyration of the polyelectrolyte chain, the polyelectrolyte chain must uncoil in order to move through the gel. Although the uncoiling process is entropically unfavorable (since it reduces the number of available conformations for the chain), the entropy loss is offset by the reduction in the electrical potential energy as the chain moves in the field. 

There are several ways the coil can be held during the uncoiling process. The single-mandrel uncoiler is a machine where the coil is loaded over an expanding... 

It has been suggested that, because of the uncoiling process in the stretching of a polymer molecule in a flow field, it would be more realistic to include a linear dashpot in parallel with a Hookean spring in a dumbbell model. That is, the connector force should be represented as... 

We have divided the total process line into three sections Uncoiler section... 

Chain uncoiling, and the converse process of coiling, is conveniently considered as a unimolecular chemical reaction. It is assumed that the rate of uncoiling at any time after application of a stress is proportional to the molecules still coiled. The deformation Dhe(0 at tinie t after application of stress can be shown to be related to the equilibrium deformation Dhe( ) by the equation... 

The diffusion process in natural and polychloroprene rubber adhesives can be explained by Campion s approach [1] which considers the concept of molecular free volume. This free volume is mainly affected by the solvent mixture of the adhesive (which will determine the degree of uncoiling of rubber chains) and by the ingredients in the formulation (mainly the amount and type of tackifier). 

Coil coating Coil coating is the technique of depositing a film of liquid on to a continuously moving thin steel or aluminium sheet. The sheet is uncoiled from a roll at the start of the process and recoiled at the end. The coils are then cut to length and formed into the required shape. 

Replication (Section 28.3) The process by which double-stranded DNA uncoils and is replicated to produce two new copies. 

Transcription (Section 28.4) The process by which the genetic information encoded in DNA is read and used to synthesize RNA in the nucleus of the cell. A smal I portion of double-stranded DNA uncoils, and complementary ribonucleotides line up in the correct sequence for RNA synthesis. 

Figure 20.28 Diagrammatic representation of mitosis in a cell with a single pair of homologous chromosomes. In prophase, the chromatin condenses into chromosomes, each of which consists of a pair of chromatids that have been formed by replication during interphase, and the nuclear envelope disappears. In metaphase, each chromatid attaches to the spindle fibres (microtubules) at a centre point, the centromere. In anaphase, the two chromatids of each chromosome become detached from each other and move to opposite poles of the cell along the microtubules. In telophase, the chromatids have reached the poles. Two nuclear envelopes then form and enclose each new set of chromatids, now once again called chromosomes. The microtubules disappear and the chromosomes uncoil and re-form into the long chromatin threads. Finally the cell membrane is drawn inward by a band of microfilaments to form a complete constriction between the newly formed nuclei, and two new cells are formed. The process is called cytokinesis.

Another remarkable example is extension of the acrosomal process from a sperm cell of the horseshoe crab Limulus polyphemus at fertilization. A bundle of actin filaments in a crystalline state lies coiled around the base of the nucleus. At fertilization the bundle uncoils and slides through a tunnel in the nucleus to form a 60 pm-long acrosomal process within a few seconds. The uncoiled bundle is also crystalline. The coiled bundle is apparently overtwisted and an actin crosslinking protein scrum mediates the conformational alteration that takes place.339 A somewhat related process maybe involved in contraction of bacteriophage tails (pp. 363,364)... 

Rho and other termination factors. Termination proteins can also react with specific regions of DNA or of an RNA transcript to terminate transcription.183 The best known termination factor is the rho protein a hexamer of 45-kDa subunits. It interacts with transcripts at specific termination sequences, which are often C-rich, and in a process accompanied by hydrolysis of ATP causes release of both RNA and the polymerase from the DNA.192193 Additional E. coli proteins, products of genes nus A and nus G, cooperate with the rho factor at some termination sequences.194-196c The rho hexamer is a helicase that moves along the RNA transcript in the 5 —> 3 direction driven by ATP hydrolysis. If it locates an appropriate termination signal, it may utilize its helicase activity to uncoil the DNA-RNA hybrid segment within the transcription bubble (Fig. 28-4).197 198b... 

Transcription Transcription is the process of forming a complementary m-RNA strand from the DNA. This process occurs in the cell nucleus. To begin, an enzyme helps the DNA double helix to break apart and uncoil slightly. This allows RNA nucleotide bases to form complementary hydrogen bonds to the DNA bases. In essence, the m-RNA is reading the DNA code. For example, let s imagine a short section of DNA with the following sequence ... 

During transcription of information from DNA into mRNA, the two complimentary strands of the DNA partly uncoil. The sense strand separates from the antisense strand. The antisense strand of DNA is used as a template for transcribing enzymes that assemble mRNA (transcription), which, in the process produces a copy of the sense strand. Then, mRNA migrates into the cell, where other cellular structures called ribosomes read the encoded information, its mRNA s base sequence, and in so doing, string together amino acids to form a specific protein. This process is called translation. ... 

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