Dielectric response of pentagonal defects in multilayer graphene nano-cones.

The dielectric response of pentagonal defects in multilayer graphene nano-cones has been studied by electron energy loss spectroscopy and ab initio simulations. At the cone apex, a strong modification of the dielectric response is observed below the energy of the π plasmon resonance. This is attributed to π → π* interband transitions induced by topology-specific resonant π bonding states as well as π*-σ* hybridization. It is concluded that pentagonal defects strongly affect the local electronic structure in such a way that multi-walled graphene nano-cones should show great promise as field emitters.

Nanoparticle induced self-assembly.

Self-assembly has for the large part focused on the assembly of molecules without guidance or management from an outside source. However, self-assembly is in principle by no means limited to molecules or the nanoscale. A particularly interesting method to the self-assembly of micro- to millimetre sized components is the use of the 'magnetic hole' effect. In this method, nonmagnetic particles can be manipulated by external magnetic fields by immersing them in a dispersion of colloidal, magnetic nanoparticles, denoted ferrofluids. Nonmagnetic particles in magnetized ferrofluids are in many ways ideal model systems to test various forms of particle self-assembly and dynamics. When microspheres are confined to a monolayer between two parallel plates and subjected to static or oscillating magnetic fields they show a variety of dynamical behaviours and assemblages, depending on the frequency and direction of the external fields. A single pair of magnetic holes oscillating in a ferrofluid layer may be used to measure the viscosity of tiny volumes of the fluid. We have also observed ordering of dilute dispersions of macromolecules and nanoparticles in magnetized ferrofluids. The self-assembly at this length scale results from structural correlations between these nanostructures and ferrofluid particles rather than from the macroscopic magnetostatic effect for the magnetic holes.

Short-term and long-term effects of lay groups on weight reduction.

Three groups participated in a slimming programme run by lay people. The course lasted eight weeks, and the average weight loss was about 7 kg both in a small well-controlled study of 33 women and in a much larger one comprising over 10,000 people. Both studies were prospective. The long-term effect was studied in a random sample of about 1000 people. After four years 30-35% of the participants had kept the initial weight loss or were still reducing their weight, and only 15% had regained all the lost weight or more. That this result was better than usual may be because the programme operated through small groups of eight to 12 members run by the obese people themselves. The "slim-club hostesses' had all been obese and had succeeded in losing weight in the same programme. Group pressure and competition may also be important. Finally, the programme tried to change life styles, encouraging more exercise and reduced consumption of alcohol. The combination of scientific methods (behaviour therapy) and lay work may provide a clue for solving obesity and other serious health problems.