Carbon nanotubes exert basic excitatory enhancement in rat brain slices.

Carbon nanotubes are promising new tools in biomedicine but they may have yet some unknown influences on the organism. In the present study, the acute effect of solubilized, multi-walled carbon nanotubes (MWCNTs) on basic neuronal functions was examined. Rat brain slices were treated in vitro with nanotube-containing colloid solutions at concentrations of 100-800 µg/ml and evoked field potentials were recorded from the somatosensory cortex and hippocampus. Basic excitability of the treated slices was characterized by the amplitude of field excitatory postsynaptic potentials (fEPSPs) and population spikes. Experimental results indicated significantly higher excitability of treated samples than that of controls. Multiple components in evoked potentials were observed, which is in accordance with the increased excitability of investigated brain areas. Tests of short- and long-term plasticity were also performed, which revealed no difference between control and treated slices. Experimental results suggest an interaction between nanotubes and brain tissue. MWCNTs seem to act on the basic membrane potential of neurons by changing membrane properties or via a mechanism linked to voltage-gated ion channels, rather than influencing specific synaptic transmission. Further investigation is needed to clarify the nature of interactions between nanotubes and brain tissue.

Nanocomposite bulk of mechanically milled Al-Pb samples consolidated pore-free by the high-energy rate forming technique.

It is shown that pore-free bulk samples were produced by the high-energy rate forming axis-symmetrical powder compaction method for different application purposes in case of the very different, immiscible Al and Pb metal pair. The starting Al-Pb nanocomposites were made by mechanical milling of atomized Al and Pb powders either in a SPEX 9000 or a Fritsch Pulverisette 4 mill. Due to the conditions that milling was carried out in air, the PbO layer, originally existing at the surface of the atomized Pb powder, ruptured and was also dispersed in the composite. The presence of the nano PbO particles was proven by XRD and TEM (BF, DF, SAED). When the energy of milling was high, the PbO crystallites became so small that they could hardly be seen by XRD technique. Local distribution of the PbO nanoparticles was still visible in a TEM, using the process diffraction method. Both XRD and SAED proved to be useful for the evaluation of the results of the milling process and compaction.

Nanotubes: number of Kekulé structures and aromaticity.

Carbon nanotubes (CNTs) are composed of cylindrical graphite sheets consisting of sp(2) carbons. Due to their structure CNTs are considered to be aromatic systems. In this work the number of Kekulé structures (K) in "armchair" CNTs was estimated by using the transfer matrix technique. All Kekulé structures of the cyclic variants of naphthalene and benzo[c]phenanthrene have been generated and the basic patterns have been obtained. From this information the elements of the transfer matrix were derived. The results obtained indicate that K (and the resonance energy) is greater if tubulenes are extended in the vertical than in the horizontal direction. Tubulenes are therefore more stabile than cyclic strips. An illustration, obtained by using scanning probe microscope, has been attached to affirm the existence of thin CNTs.