A poly

How can the differences in specificity of the antibodies obtained from rabbit, mouse and hamster be explained Although the antibodies obtained from animals of the last two species have not as yet been well characterized, they have in common the cross-reaction with poly A poly U. As the purine and pyrimidine bases involved in these complexes are different, they probably recognize the double-helical structure. It is quite unhkely that the polyribose phosphate chain plays an exclusive role in this specificity since we have seen that the anti-poly I poly C antibodies of rabbit react better with poly dG poly dC than with poly rG poly rC. We cannot exclude the possibihty that poly I poly C complexed to MBS A undergoes modifications when it is introduced into the bloodstream. The discovery by Stern in 1970 of an enzyme which specifically hydrolyzes double-stranded RNA or poly I poly C, and which exists at different levels in the sera of nine mammaUan species illustrates this possibihty. There will thus exist in the antisera antibodies against the products of degradation, the quantity varying according to the species. 

Specificity of Anti-Poly A. Poly U Antibodies Induced in the Rabbit 

The double helical complex poly A poly U adsorbed onto MBSA has been used as immunogen in Fauve de Bourgogne rabbits (Nahon et al., I967) and in New Zealand White rabbits (Schwartz and Stollar, 1969). In both cases antibodies reacting specifically with poly A poly U were induced. These antibodies react also with the heterologous double-helical complex poly I poly C although they do not react with the separate homopolyribonucleotides poly I or poly C. In addition, the reaction is abolished if the complex is heated in the presence of formaldehyde. It is thus possible to conclude that these antibodies are specific for the double-stranded structure. 

Cross-reactions with poly I poly C have not always been observed. Thus the antibodies induced by Koffler et al. (1971) with poly A-poly U — MBSA in rabbits of unstated origin, reacted only with the homologous antigen. Other differences of reactivity, in particular with heterologous polynucleotides, existing among anti-poly A poly U antibodies obtained in rabbits by different groups of workers will be mentioned and discussed later. 

Antibodies induced by the equimolar complex poly A poly U precipitate one of the components of the homologous antigen, poly A (Nahon et al., 1967 a, b). This reaction was not observed by Schwartz and Stollar (1969) A quantitative analysis of the reactions of these antibodies with the homologous antigen and with its component polynucleotides, and of their reaction with related antigens as well as the analysis of results of inhibition studies have allowed a better characterization of these antibodies (Nahon-Merlin et al., 1973 b). The level of antibodies reacting with poly A-poly U varies 

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Of particular interest has been the study of the polymer configurations at the solid-liquid interface. Beginning with lattice theories, early models of polymer adsorption captured most of the features of adsorption such as the loop, train, and tail structures and the influence of the surface interaction parameter (see Refs. 57, 58, 62 for reviews of older theories). These lattice models have been expanded on in recent years using modem computational methods [63,64] and have allowed the calculation of equilibrium partitioning between a poly-... 

The analogous coupling between the antisyimnetric stretch and bend is forbidden in the H2O Hamiltonian because of syimnetry.) The 2 1 resonance is known as a Femii resonance after its introduction [ ] in molecular spectroscopy. The 2 1 resonance is often very prominent in spectra, especially between stretch and bend modes, which often have approximate 2 1 frequency ratios. The 2 1 couplmg leaves unchanged as a poly ad number the sum ... 

Alexandridis P, Olsson U and Lindman B 1997 Structural polymorphism of amphiphilic copolymers Six lyotropic liquid crystalline and two solution phases in a poly(oxybutylene)-poly(oxyethylene)-water-xylene system Langmuir 23-34... 

Figure C2.11.2. A scanning electron micrograph showing individual particles in a poly crystalline alumina powder.

Polymerization of styrene is carried out under free radical conditions often with benzoyl peroxide as the initiator Figure 1111 illustrates a step m the growth of a poly styrene chain by a mechanism analogous to that of the polymerization of ethylene (Sec tion 6 21)... 

Saito described a quantitative spectrophotometric procedure for iron based on a solid-phase extraction using bathophenanthroline in a poly(vinyl chloride) membrane. ... 

When a 0.8006-g sample of a poly(styrene/maleic anhydride) copolymer was prepared in the same manner, the following results were obtained... 

On the basis of the concepts and notation introduced here, we see that there are several ways of describing a poly disperse system ... 

Plazek et al.t measured the viscosities of a poly(dimethyl siloxane) sample of = 4.1 X 10 over a range of temperatures using the falling-ball method. Stainless steel (P2 = 7.81 g cm" ) balls of two different diameters,... 

Table 9,4 Data for the Analysis of the Gel Permeation Chromatogram of a Poly disperse Polymer Used in Example 9.7...

This principle is illustrated in Figure 10 (45). Water adsorption at low pressures is markedly reduced on a poly(vinyhdene chloride)-based activated carbon after removal of surface oxygenated groups by degassing at 1000°C. Following this treatment, water adsorption is dominated by capillary condensation in mesopores, and the si2e of the adsorption-desorption hysteresis loop increases, because the pore volume previously occupied by water at the lower pressures now remains empty until the water pressure reaches pressures 0.3 to 0.4 times the vapor pressure) at which capillary condensation can occur. 

Alternative technology for modifying a poly(aLkylene terephthalate) by incorporation of a phosphinate stmcture has been developed by Enichem. Phosphinate units of the stmcture —P(CgH5) (0)CH20— are introduced into a polyester such as PET or PBT by transesterification with an oligomer comprised of the aforementioned units (136). 

Poly(vinyl acetate). The dielectric and mechanical spectra of hybrids produced by mixing a poly(vinyl acetate)—THE solution with TEOS, followed by the addition of HCl have been investigated (45). Mixtures were made which were beheved to be 0, 5, 10, 15, and 20 wt % Si02, respectively. These composites were transparent and Eourier transform infrared spectroscopy (ftir) revealed hydrogen bonding between the siUcate network and carbonyl units of the poly(vinyl acetate) (PVAc). No shift in the T of the composites from that of the pure PVAc was observed. Similarly, the activation... 

A poly( -vinyl-2-pyrroHdinone)-iodine complex [25655-41-8] (PVP-iodine), has been used extensively in hospitals and elsewhere because of its germicidal, bactericidal, fungicidal, and generally disinfecting properties (150). It is sold as a solution that contains about 10% available, or active, iodine and about 5% inactive iodine, in the form of iodide ion (see Disinfectants and antiseptics Industrial antimicrobial agents). 

Examples of polymers which form anisotropic polymer melts iaclude petroleum pitches, polyesters, polyethers, polyphosphaziaes, a-poly- -xyljlene, and polysdoxanes. Synthesis goals iaclude the iacorporation of a Hquid crystal-like entity iato the maia chaia of the polymer to iacrease the strength and thermal stabiHty of the materials that are formed from the Hquid crystal precursor, the locking ia of Hquid crystalline properties of the fluid iato the soHd phase, and the production of extended chain polymers that are soluble ia organic solvents rather than sulfuric acid. 

A typical process for the preparation of a poly(methyl methacrylate) suspension polymer involves charging a mixture of 24.64 parts of methyl methacrylate and 0.25 parts of benzoyl peroxide to a rapidly stirred, 30°C solution of 0.42 parts of disodium phosphate, 0.02 parts of monosodium phosphate, and 0.74 parts of Cyanomer A-370 (polyacrylamide resin) in 73.93 parts of distilled water. The reaction mixture is heated under nitrogen to 75°C and is maintained at this temperature for three hours. After being cooled to room temperature, the polymer beads are isolated by filtration, washed, and dried (69). 

A protonic acid derived from a suitable or desired anion would seem to be an ideal initiator, especially if the desired end product is a poly(tetramethylene oxide) glycol. There are, however, a number of drawbacks. The protonated THF, ie, the secondary oxonium ion, is less reactive than the propagating tertiary oxonium ion. This results in a slow initiation process. Also, in the case of several of the readily available acids, eg, CF SO H, FSO H, HCIO4, and H2SO4, there is an ion—ester equiUbrium with the counterion, which further reduces the concentration of the much more reactive ionic species. The reaction is illustrated for CF SO counterion as follows ... 

Many other polymerization processes have been patented, but only some of them appear to be developed or under development ia 1996. One large-scale process uses an acid montmorrillonite clay and acetic anhydride (209) another process uses strong perfiuorosulfonic acid reski catalysts (170,210). The polymerization product ia these processes is a poly(tetramethylene ether) with acetate end groups, which have to be removed by alkaline hydrolysis (211) or hydrogenolysis (212). If necessary, the product is then neutralized, eg, with phosphoric acid (213), and the salts removed by filtration. Instead of montmorrillonite clay, other acidic catalysts can be used, such as EuUer s earth or zeoHtes (214—216). 

Fig. 2. Glass-transition temperature, T, for two commercially available, miscible blend systems (a) poly(phenylene oxide) (PPO) and polystyrene (PS) (42) ...

Fig. 4. Comparative thermogravimetric analyses of polymers in nitrogen A, poly(vinyl chloride) B, poly(methyl methacrylate) C, polystyrene D,...

There has been considerable research on chlorine-resistant RO membranes (48—52). A poly(/n j -2,5 dimethyl)pipera2inthiofura2anainide used in the presence of low (3 mg/L) concentrations of chlorine resulted in a membrane life of three years (48). A copolyamide hoUow-fiber membrane for use in desalination has been developed that is resistant to 0.5 mg/L chlorine (49). Millipore Corporation has also developed a sulfonated polysulfone member that has desirable chlorine-resistance properties. 

Prevention of Soil Crusting. Acid-based fertilizers such as Unocal s N/Furic (a mixture of urea with sulfuric acid), acidic polymers such as FMC s Spersal (a poly(maleic acid) derivative originally developed to treat boiler scale) (58), the anionic polyacrylamides described previously, as weU as lower molecular weight analogues such as Cytec s Aerotil L Soil Conditioner, have all been used successfully in at least some circumstances to prevent the formation of soil cmsts. It is difficult to prove benefits in the laboratory, and field tests may give variable results depending on local weather conditions. 

Chain transfer also occurs to the emulsifying agents, leading to their permanent iacorporation iato the product. Chain transfer to aldehydes, which may be formed as a result of the hydrolysis of the vinyl acetate monomer, tends to lower the molecular weight and slow the polymerisation rate because of the lower activity of the radical that is formed. Thus, the presence of acetaldehyde condensates as a poly(vinyl alcohol) impurity strongly retards polymerisation (91). Some of the initiators such as lauryl peroxide are also chain-transfer agents and lower the molecular weight of the product. 

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