Synthesis and characterization of hindered‐phenol‐containing amine moieties as antioxidants for polypropylene copolymers

(4‐Ethylphenyl)‐3,5‐ditertiarybutyl‐4‐hydroxybenzylamine, 1‐phenyl‐4‐(3,5‐ditertiarybutyl‐4‐hydroxybenzyl)piperazine, and 1‐(3,5‐ditertiarybutyl‐4‐hydroxybenzyl)piperidine were synthesized and characterized, and their performance in polypropylene copolymer (PPCP) was tested by multiple extrusions in a Brabender plasticorder. The thermooxidative stability of PPCP was assessed by the measurement of oxidative induction time at 200 ± 1°C, and the thermal stability was assessed by observation of the change in the melt flow rate. A comparative study of the synthesized antioxidants with the commercially available antioxidant 2,6‐ditertiarybutyl‐4‐methylphenol was made. The presence of phenolic and amino groups influenced the performance of the antioxidants. The performance of the antioxidants influenced the thermal stability of the PPCP. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1097–1103, 2004     

Modification of Tefzel film through graft copolymerization

The graft copolymerization of styrene (st) and methacrylonitrile (MAN) onto Tefzel film in aqueous media by the preirradiation method has been studied. In order to follow the effect of preswelling of the backbone polymer, grafting was attempted onto preirradiated Tefzel film and monomer preswollen, preirradiated Tefzel film. Optimum conditions pertaining to maximum percentage of grafting of st and MAN have been evaluated. Grafting onto preswollen, preirradiated Tefzel film displayed better results. The effect of different alcohols of increasing chain length on the percentage of grafting of st and MAN was also studied. Graft copolymerization of st showed an increase, while grafting with MAN exhibited a decrease, in the percentage of grafting in the presence of alcohols as compared to that obtained in the aqueous medium. Characterization of the graft copolymers was made by IR and thermogravimetric studies. Tefzel‐graft‐polystyrene showed improved thermal stability while the MAN grafted onto preswollen, preirradiated Tefzel film produced graft copolymer with poor thermal stability. Copyright © 2004 Society of Chemical Industry     

Loosely-coupled processes

The notions of ‘loosely-coupled’ and ‘tightly-coupled’ processes have been used in an intuitive way for many years by system designers. In this paper, we propose a precise characterization. All point-to-point message-communicating processes are loosely-coupled under our characterization. Furthermore, a number of common paradigms of process interactions - e.g. broadcast or accumulating a result - satisfy our characterization of loose-coupling. Restricting our designs to loosely-coupled processes has several advantages, among them a design methodology in which each process implements a progress property and a simple solution to the cache coherence problem.     

Biphenylsulfonamide endothelin antagonists: structure-activity relationships of a series of mono- and disubstituted analogues and pharmacology of the orally active endothelin antagonist 2'-amino-N- (3,4-dimethyl-5-isoxazolyl)-4'-(2-methylpropyl)[1, 1'-biphenyl]-2-sulfonamide (BMS-187308)

Substitution at the ortho position of N-(3,4-dimethyl-5-isoxazolyl) benzenesulfonamide led to the identification of the biphenylsulfonamides as a novel series of endothelin-A (ETA) selective antagonists. Appropriate substitutions on the pendant phenyl ring led to improved binding as well as functional activity. A hydrophobic group such as isobutyl or isopropoxyl was found to be optimal at the 4'-position. Introduction of an amino group at the 2'-position also led to improved analogues. Combination of the optimal 4'-isobutyl substituent with the 2'-amino function afforded an analogue (20, BMS-187308) with improved ETA binding affinity and functional activity. Compound 20 also has good oral activity in inhibiting the pressor effect caused by an ET-1 infusion in rats. Doses of 10 and 30 micromol/kg iv 20 attenuated the pressor responses due to the administration of exogenous ET-1 to conscious monkeys, indicating that the compound inhibits the in vivo activity of endothelin-1 in nonhuman primates.     

Reliability evaluation of flow networks considering multistate modelling of network elements

This paper presents a simple method for evaluating the reliability of a multistate flow network. A system is considered reliable only if it successfully transmits at least the required system capacity from the transmitter to the receiver station. All successful states are obtained from the knowledge of the max-flow min-cuts of the system graph. Examples are solved to demonstrate the applicability of proposed method. It is observed that the method is simple, computationally fast and efficient.     

Salt effects on ligand-DNA binding. Minor groove binding antibiotics

Salt dependent electrostatic effects play a central role in intermolecular interactions involving nucleic acids. In this paper, the finite-difference solution to the nonlinear Poisson-Boltzmann (NLPB) equation is used to evaluate the salt dependent contribution to the electrostatic binding free energy of the minor groove binding antibiotics DAPI, Hoechst 33258 and netropsin to DNA using detailed molecular structures of the complexes. For each of these systems, a treatment based on the NLPB equation accurately describes the variation of the experimentally observed binding constant with bulk salt concentration. A solvation formalism is developed in which salt effects are described in terms of three free energy contributions: the electrostatic ion-molecule interaction free energy, delta delta G degrees im; the electrostatic ion-ion interaction free energy, delta delta G degrees ii; and the entropic ion organization free energy, delta delta G degrees org. The electrostatic terms, delta delta G degrees im and delta delta G degrees ii, have both enthalpic and entropic components, while the term delta delta G degrees org is purely a cratic entropy. Each of these terms depends significantly on salt dependent changes in the counterion and coion concentrations around the DNA. In each of the systems studied, univalent ions substantially destabilize charged ligand-DNA complexes at physiological salt concentrations. This effect involves a salt dependent redistribution of counterions near the DNA. The free energy associated with the redistribution of counterions upon binding is dominated by the unfavorable change in the electrostatic ion-molecule interactions, delta delta G degrees im, rather than the change in the cratic entropy of ion organization, delta delta G degrees org. In addition, the observed slope of the salt dependence of the free energy is determined by electrostatic ion-molecule and ion-ion interactions as well as the cratic entropy of ion release. These findings are in contrast to models in which the cratic entropy of counterion release drives binding.