Hunter stabilization

The value of EM for a cooperative self-assembled structure provides a measure of the monomer concentration at which trivial polymeric structures start to compete, and therefore EM represents the upper limit of the concentration range within which the cooperative structure is stable (Scheme 2). The lower limit of this range is called the critical self-assembly concentration (csac) and is determined by the stoichiometry of the assembly and the strength of the non-covalent binding interactions weaker interactions and larger numbers of components raise the csac and narrow the stability window of the assembly (8). Theoretical treatments of the thermodynamics of the self-assembly process have been reported by Hunter (8), Sanders (9), and Mandolini (10). The value of EM is lowered by enthalpic contributions associated with... 

Y. Hemar, D. N. Pinder, R. J. Hunter, H. Singh, P. Hebraud, D. S. Home 2003, (Monitoring of flocculation and creaming of sodium-caseinate-stabilized emulsions using diffusing-wave spectroscopy), /. Colloid Interface Sd. 264, 502. 

Figure 1A shows that the CCC decreases with increasing sol concentration in the range of 50 to 200 ppm. The variation of the CCC with sol concentration is by no means an unexpected observation in view of previous work with other systems (7). Recently Bensley and Hunter (8) have investigated this aspect of colloidal stability with latices and found that up to a volume fraction of 0.10 the CCC was independent of the volume fraction. These authors also pointed out the difficulties involved in measuring the stability of more... 

This model was introduced by Neville and Hunter (13,14) for the case of sterically stabilized dispersions which have undergone reversible flocculation. It is assumed that the major contribution to the excess energy dissipation in such pseudoplastic systems comes from the need to provide energy from the shear field to separate contacting particles. Under these conditions, the extrapolated yield value is given by the expression (13,32,33),... 

Veitch NC. 2004. Horseradish peroxidase a modem view of a classic enzyme. Phytochemistry 65 249—259. Wegrzyn TF, Farr JM, Hunter DC, Au J, Wohlers MW, Skinner MA, Stanley RA and Waterhouse DS. 2008. Stability of antioxidants in an apple polyphenol—milk model system. Food Chem 109 310-318. 

Hunter et al. demonstrated palladium-gate SiC Schottky sensors, but a drift was experienced when the sensors were operated at 350°C for a period of several weeks [4]. It was suggested that this was caused by a reaction between Pd and SiC. Hunter et al. tested two different approaches to remove this drift. First an alloy of Pd/Cr was tested, which caused the sensitivity to hydrogen to increase by two orders of magnitude. Second, SnO was tested as an interfacial layer under the Pd contact, which resulted an increased sensitivity to hydrogen, methane, and propylene. The longterm stability was substantially improved in both cases. 

Accdg to Ficheroulle Gay-Lussac (Ref 6), Trinitroethanol is unstable and even at R.T evolves nitrous fumes. When heated to 120° it rapidly decomposes with evolution of nitrous fumes and then violently explodes. Its sensitivity to shock is comparable to that of NG. Although it is a good gelatinizer for NC, it cannot be recommended for use in expls and pioplnts on account of its poor stability. In the 100°C Heat Test, it lost 68% 1st 48 hrs and 26% second 4 hrs, with no expln in 100 hrs Refs 1) Beil, not found 2) W. Hunter et al, BIOS Final Rept No 709, HMStationary Office, London (1946), p 9 (Description of prepn of Trini tro ethanol by Dr Sc him m el schmidt of IG Farbenindustrie, Hochst-am-Main)... 

Despite the fact that there is much that is unknown about colloid stability, the topics covered in the chapter are sufficient to solve many routine problems of industrial interest, particularly in the case of electrostatic stability. More advanced information on polymer-induced forces is available in specialized monographs (Napper 1983 Israelachvili 1991 Sato and Ruch 1980) and in other texts on colloid science (Hunter 1987). 

FIG. 13.11 A simplified representation of the effects of polymer additives on the stability of dispersions. See the text for explanation. (Redrawn with permission from Hunter 1987.)... 

Hunter, R. J., Foundations of Colloid Science, Vol. 2, Clarendon Press, Oxford, England, 1989. (Undergraduate and graduate levels. Along with Volume 1, these two volumes cover almost all the topics covered in the present chapter at a more advanced level. Volume 1 discusses DLVO theory and thermodynamic approaches to polymer-induced stability or instability and is at the undergraduate level. Volume 2 presents advanced topics (e.g., statistical mechanics of concentrated dispersions, rheology of dispersions, etc.).)... 

ELUmo is a measure of the ability of a compound to accept electrons (i.e., to act as an electrophile or undergo reduction). The above correlations show a decrease in ELUMO as the number of chlorines increases. As ELUM0 decreases, the ability of a compound to behave as an electrophile increases however, properties that increase stability increase LUMO energy and decrease reactivity. For example, between two-carbon alkanes and alkenes, r = -0.5104 and r = -0.9948, respectively. These data agree with Richard and Hunter (1996) in regard to the stability of alkanes over alkenes. 

Colloids. Colloids include particles with hydrophobic, hydrophilic and intermediate forms with a size range 1 - 400 nm. Both organic (including macromolecules) and inorganic (hydrolyzed silica and metal oxides) colloids occur in the marine environment (Sigleo and Helz, 1981). Their surfaces often contain suitable sites for interactions with trace metals (adsorption, complexation). In the marine environment all particles have a negative surface charge (Neihof and Loeb, 1972 Hunter and Liss, 1982). Increase of the electrolyte concentration decreases the stability of the colloidal particles. As a result the... 

Hunter, R.J. Coll. Surf. A, 2001, 395, 205-214. Riddick, T.M. Control of Stability Through Zeta Potential, Zeta Meter Inc. New York, 1968. Okada, K. Akagi, Y. J. Chem. Eng. Japan 1987, 20,11-15. 

The experimental stability ratio is defined generally as the rate of fast flocculation divided by the rate of slow coagulation (see, e.g., Section 7.8 in R. J. Hunter, op. cit.1). Equation 6.70 is a mathematical interpretation of this definition in terms of experimentally accessible quantities related to floccule size. 

Yellowness Index. The yellowness of the 50-mil plaques used for stabilization studies was measured directly from a Hunter D-25 color difference meter equipped with a 90° sphere attachment. The samples were placed in the reflectance port of the sphere using a standard white ceramic as backing. The instrument is designed to give direct yellowness index values as described in ASTM D-1925. 

Gg (instantaneous modulus), Hg (residual viscosity) and G (shear modulus) all showed a rapid increase above 30g dm bentonite. This was attributed to the formation of a gel network structure in the continuous medium and the strength of such a gel increased with increase in bentonite concentration. The results could be qualitatively described in terms of the elastic floe model of Hunter and co-workers. Moreover, the settling characteristics of the structured suspensions were found to be consistent with the predictions from the rheological measurements. This demonstrates the value of rheological studies in predicting the longterm physical stability of suspension concentrates. 

Excellent reviews on colloid stability are given by Napper and Hunter (22.) and by Ottewill (38). 

Leonard GA, McAuley-Hecht K, Brown T, Hunter WN. Do C-H- O hydrogen bonds contribute to the stability of nucleic... 

Base pairing of the nucleobases in duplex DNA can affect their calculated ionization potentials and electron affinities. Colson et al. [33b] reported that base pairing lowers the IP of guanine, but has little effect on the ionization of adenine in the A T base pair. The effects of base pairing on ionization potentials has been investigated by Hunter and Clark [34] using ab initio and density functional calculations. The isodesmic relations in Eqs. 1 and 2 show that A" " and G+ are stabilized by 10.2 and 17.4 kcal moC , respectively, upon base pairing. 

Hunter, J. E., and Harper, A. E. (1976) Stability of some pyridoxal phosphatc-dcpcrLdent enzymes in vitamin B-6 deficient rats. ), iVnJr, 106, 653-664. 

---