When a three-way fabric hangs together

A simple condition is given that determines when a three-way fabric hangs together.     

Synthesis and scintillating efficiencies of 4-functionalised-2,5-diphenyloxazoles

A series of 4-functionalised-2,5-diphenyloxazoles has been synthesised. Each member of the series has been assessed for the ability to scintillate in the presence of ionising radiation. The scintillation counting efficiency of each member of the series has been determined relative to 2,5-diphenyloxazole, a widely used scintillant molecule.     

Preferred conformations of enol ethers in solution: Detection of an equilibrium by kinetic nuclear overhauser effects

n.O.e. difference spectra reveal that the preferred solution conformation of methyl enol ethers has the methyl group $\text{syn}$-periplanar to the double bond; n.O.e kinetics in a methoxy—heptatriene demonstrate the presence of both possible periplanar conformations, the energy difference being $\text{ca}$ 1 kcal/mole.     

The degree sequences of self-complementary graphs

Known necessary conditions for realization of a sequence of integers as the degrees of a self-complementary graph are shown to be sufficient. An algorithm for constructing a realization of such a sequence as degrees of such a graph is illustrated by an example.     

A host-guest optical sensor for aliphatic amines based on lipophilic cyclodextrin

A host-guest optical sensor for the determination of aliphatic amines as exemplified by octylamine is proposed. It is based on the reversible fluorescence enhancement of heptakis(2,6-di-O-isobutyl)-β-cyclodextrin(DOB-β-CD) hosting tetraphenylporphyrin (TPP) immobilized in poly(vinyl chloride) (PVC) membrane by aliphatic amine extracted from aqueous phase into membrane phase. The optimum membrane contained 1.15 wt % TPP, 6.15 wt % DOB-β-CD as sensing reagent and other membrane materials. The fluorescence enhancement of the membrane resulted from the formation of a stable three-component complex among DOB-β-CD, TPP, and aliphatic amines. With the optimum conditions described, the fluorescence response of the sensor to octylamine shows a good correlation with the theoretically derived equation in the range 1.0 × 10^–6 to 8.0 × 10^–4 mol/L. The response characteristics including reversibility, response time, reproducibility and lifetime and selectivity of this optical device are also discussed in detail. This sensor has also been applied for the determination of octylamine in water samples containing interferents with satisfactory recovery. Received: 21 November 1999 / Revised: 10 January 2000 / Accepted: 15 January 2000     

Triangles in self-complementary graphs

It is shown that the number of triangles in a self-complementary graph with N vertices is at least $\text{N(N ? 2)(N ? 4)}\text{48}$ if N ≡ 0 (mod 4) and at least $\text{N(N ? 1)(N ? 5)}\text{48}$ if N ≡ 1 (mod 4), and that this minimum number can be achieved.     

Scintillation-based potassium signalling using 2,5-diphenyloxazole-tagged aza-18-crown-6

In the presence of ionising radiation, an aza-18-crown-6 molecule covalently attached to a 2,5-diphenyloxazole (PPO) moiety scintillates weakly, addition of potassium ions results in enhanced levels of scintillation, the degree of scintillation reflecting the concentration of the potassium ions.