Controllable selective exfoliation of high-quality graphene nanosheets and nanodots by ionic liquid assisted grinding

Bulk quantities of graphene nanosheets and nanodots have been selectively fabricated by mechanical grinding exfoliation of natural graphite in a small quantity of ionic liquids. The resulting graphene sheets and dots are solvent free with low levels of naturally absorbed oxygen, inherited from the starting graphite. The sheets are only two to five layers thick. The graphene nanodots have diameters in the range of 9-29 nm and heights in the range of 1-16 nm, which can be controlled by changing the processing time.     

A comparative semi-empirical study of the effect of ring ortho-substitution on the conformation of diphenylamine

An extensive theoretical study of the structural and energy properties of diphenylamine (DPA) and derivatives was carried out. The effect of ring substitution on geometrical parameters, inversion barriers and ionisation potentials was investigated for rings containing methyl, methoxy and chloro groups. The dihedral angles between phenyl rings and pyramidality of the nitrogen atom were also studied. Results were compared to the optimised geometry of the unsubstituted DPA. Calculations were carried out using the AM1 semi-empirical method.     

An extension of a result of Grannan and Swindle on the poisoning of catalytic surfaces

Grannan and Swindle considered a model in which molecules of several types of reactant land on a catalytic surface. When two different reactants find themselves adjacent, they diffuse from the surface and leave the sites vacant. They showed that if the rate of bonding onto the surface of one reactant is sufficiently close to one, then the surface becomes poisoned by that type. In this paper we show that a sufficient condition for poisoning is that one reactant should bond at rate greater than that of the other reactants combined.     

Nucleon spectra in heavy ion collision prior to equilibrium

Energy spectra and angular distribution of nucleons emitted in intermediate energy heavy ion collisions prior to equilibrium are calculated. The spectra have two components: (a) promptly emitted particles (PEPS) or Fermi jets; (b) emission from a localized excited region at the interface of the two colliding ions. The results obtained with this model have been compared with experiment and the agreement is good.     

Alteration of the carbon and nitrogen stable isotope composition of beef by substitution of grass silage with maize silage

This study investigated the effect of substituting grass silage (C3 photosynthetic plant product) with maize silage (C4 photosynthetic plant product) on the natural abundance carbon (delta13C) and nitrogen (delta15N) stable isotope composition of bovine muscle tissue. Forty-five continental crossbred heifers were assigned to one of three diets consisting of 3 kg of a barley-based concentrate plus grass silage, maize silage or an equal mixture (dry matter basis) of grass silage and maize silage, fed ad libitum, for 167 days. Substitution resulted in less negative delta13C values (P<0.001) in lipid-free muscle and in lipid, and also a lower delta15N (P<0.001) in lipid-free muscle. Feeding of maize silage was clearly reflected in the delta13C of muscle, with each 10% difference in the dietary C4 carbon intake resulting in a 0.9 to 1.0 per thousand shift of delta13C in lipid-free muscle and a 1.0 to 1.2 per thousand in lipid. Minimum detectable mean differences (95% confidence, power 0.80, n=15) in this experiment were about 0.5 per thousand and 1.0 per thousand for delta13C of lipid-free muscle and lipid, respectively, and about 0.5 per thousand for delta15N of lipid-free muscle. The power analysis presented here is useful for estimating minimum isotopic differences that can be detected between any two groups of beef samples with a given number of replicates. It is concluded that carbon stable isotope ratio analysis of meat can be used to quantify C3/C4 dietary constituents in beef production.