Application of thermal analysis to carbon black-elastomer systems

In this study a relationship between the surface and textural properties of carbon blacks and the gasification process induced thermally in air is noted. A temperature jump method was used to follow the gasification in air and to establish the relevant Arrhenius parameters. This can be associated with the activity of ‘basal’ plane carbon atoms as well as ‘edge’ carbon atoms at the surface. This is based on a model of carbon black structure consisting of the irregular packing of small graphite carbon structures. The carbon black surface was measured using a single measurement of adsorption based essentially on the BET volumetric method. The carbon black surface had a rate of oxidation per unit are which clearly indicated that the lower area carbon blacks had a predominately active area of ‘edge’ atoms at the surface while the surface of the higher area carbon blacks had a predominate amount of ‘basal’ plane graphite carbon atoms.     

Synthesis of novel PPARα/γ dual agonists as potential drugs for the treatment of the metabolic syndrome and diabetes type II designed using a new de novo design program PROTOBUILD

Peroxisome proliferator activated receptors (PPARs) have been shown to have critical roles in fatty acid oxidation, triglyceride synthesis, and lipid metabolism - making them an important target in drug discovery. Here we describe the in silico design, synthesis and in vitro characterisation of a novel series of 2,5-disubstituted indoles as PPARα/γ dual agonists. PPAR activation assays are performed with known agonists diazabenzene (WY14.643), aminopyridine (BRL49653) and bisaryl (L165.041), as positive controls. All the indole compounds synthesized are found to be active PPARα and PPARγ agonists, with particular efficacy from those with 2-naphthylmethyl substitution. This is a useful demonstration of a new de novo design methodology implemented by the protobuild program and its ability to rapidly produce novel modulators for a well characterized drug target.     

Equivalence of saddle-points and optima for non-concave programmes

A basic result of optimisation theory is that a saddle-point of the Lagrangian is an optimum of the associated programming problem, independently of any concavity assumptions. It is also well known that under concavity assumptions the two are equivalent; i.e., an optimum is always a saddle-point. It is demonstrated that this basic equivalence of saddle-points and optima in fact holds for a much larger class of problems, which are not necessarily concave, but are equivalent to concave programmes up to a diffeomorphism. This class generalises the class of geometric programmes.     

The use of the rising temperature technique to establish kinetic parameters for solid-state decompositions using a vacuum microbalance

There are certain experimental aspects concerning the effect of rising temperature on the apparent weight of a substance which have been extensively studied. The theoretical treatment of the kinetics of decomposition under rising temperature conditions rests largely on a combination of equations one of which is the Arrhenius equation. One thus has to combine the kinetic law;

the law describing the temperature coefficient of the rate (usually the Arrhenius equation);

and the equation describing the impose temperature (T in degrees Kelvin) against time (t);

where α is the fraction decomposed, k is the specific rate constant, A is a constant (the pre-exponential term in the Arrhenius equation), T_o is the initial starting temperature in the rising temperature experiment, and β is the heating rate.The combination of these three equations carries certain implications. The Arrhenius equation is almost invariably assumed to hold over the entire temperature range. The assumption may not hold and the most common deviation is the occurrence of two or more linear plots when plotting log k against 1/T. It is held that this would apply when there is a discontinuous alternation in “reaction site distribution” when a common compensation plot of log A against E (the activation energy) should result. Another matter which is essential to the calculation is the correct choice of the specific reaction rate incorporated in the Arrhenius expression. It is concluded that E and A values for solid-state decompositions are environmentally dependent and that values calculated from rising temperature experiments should not necessarily agree with those obtained from the more traditional isothermal experiments.     

The thermal decomposition of oxalates Part 14. Dehydration of magnesium oxalate dihydrate

The isothermal dehydration of magnesium oxalate dihydrate has been studied under various pressures of water vapour by use of a thermogravimetric balance. The rate of dehydration was found to be dependent upon the water vapour pressure.The reaction rate at temperatures below 124°C decreases sharply with an increase in water vapour pressure up to 0.5 mm Hg. With further increase in pressure an increase in rates is observed; this rises to a maximum and then falls again as the pressure is increased. The limitation of this phenomena to a limited temperature range is shown in the case of magnesium oxalate dihydrate. Above 124°C the initial fall in rate is not observed, the rate rises with increasing pressure from vacuum to a maximum and the falls. X-ray diffraction studies indicated that the anhydrous product prepared in the second region where a decrease of rate of dehydration occurred was crystalline but the sample dehydrated under vacuum or in the first region produced an amorphous anhydrous salt. A compensation effect is demonstrated with plots of the activation energy against the logarithm of the pre-exponential term in the Arrhenius equation.     

THE NOMENCLATURE OF SULPHUR-NITROGEN HETEROCYCLES

Abstract

The inadequacy of the present IUPAC Rules and the relative merits of the binary, coordination, thiazene and thiazyl types of nomenclature are discussed. Some recommendations are made for trivial and systematic names. A reformed systematic nomenclature should be of the additive type.     

Site-specific N-terminal labelling of proteins in vitro and in vivo using N-myristoyl transferase and bioorthogonal ligation chemistry

N-Myristoyl transferase-mediated modification with azide-bearing substrates is introduced as a highly selective and practical method for in vitro and in vivo N-terminal labelling of a recombinant protein using bioorthogonal ligation chemistry.