The modifying effects of the products of the equimolar addition of DL-alanine and m-alanyl-oc-alanine to fullerene CW on the structure and permeability of the lipid bilayer of phosphatidylcholine liposomes has been studied using the luminescence probe technique. It is shown that these water soluble amino acid and dipeptide derivatives of fullerene (C,-AD) are quenchers of pyrene fluorescence and erythrosine phosphorescence of in both a water solution and liposomes. To study the permeability of the lipid hilayer a procedure based on the triplet probe technique has been developed. It has been found that the &-AD derivatives under study are able to localize inside the artificial membrane, to penetrate into the liposomes through the lipid hilayer and to perform activated transmembrane transport of bivalent metal ions.

The paper presents a combination of theoretical and experimental results which show that the sustainment phase of a driven Reversed-Field Pinch (RFP) configuration is not fundamentally limited in time by toroidal field diffusion. Driven ZT-40M discharges where the external poloidal voltage circuit does not directly maintain toroidal field reversal are examined. Flux measurements on slowly rising current discharges clearly show that a toroidal flux regeneration mechanism (referred to as the 'dynamo-effect') must be present. Numerical simulations demonstrate that this effect is operative in the plasma on a short timescale <0.1 ms. This result is shown to be independent of the form of the resistivity profile. Thus, the possibility that the experimental results can be explained without a dynamo mechanism, if the temperature in the vicinity of the toroidal field reversal point is sufficiently high, is eliminated. Implications of these facts with regard to theoretical stability and transport studies of the RFP are discussed.

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The effect of nitroxyalkyl derivatives of fullerenylproline methyl ester on the enzymatic activity of Ca 2+ -ATPase of sarcoplasmic reticulum (SR) has been studied. It is shown that hybrid derivatives of C 60 fullerene are capable of inhibiting the activity of Ca 2+ -ATPase of SR. The mononitrate inhibits the hydrolytic activity of the enzyme with K i = 1.92´10 -6 M; active Ca 2+ transport, with K i = 3.79´10 -6 M. The dinitrate inhibits ATP hydrolysis with K i = 2.38´10 -8 M; Ca 2+ transport, with K i = 3.08´10 -8 M. Fullerenylproline methyl ester does not affect the enzymatic activity of Ca 2+ -ATPase. Based on these data it is possible to predict the possible fields of application for hybrid fullerene derivatives as potential drugs.

The purpose of this study was to choose an appropriate head scatter source model for the fast and accurate independent planar dose calculation for intensity-modulated radiation therapy (IMRT) with MLC. The performance of three different head scatter source models regarding their ability to model head scatter and facilitate planar dose calculation was evaluated. A three-source model, a two-source model and a single-source model were compared in this study. In the planar dose calculation algorithm, in-air fluence distribution was derived from each of the head scatter source models while considering the combination of Jaw and MLC opening. Fluence perturbations due to tongue-and-groove effect, rounded leaf end and leaf transmission were taken into account explicitly. The dose distribution was calculated by convolving the in-air fluence distribution with an experimentally determined pencil-beam kernel. The results were compared with measurements using a diode array and passing rates with 2%/2 mm and 3%/3 mm criteria were reported. It was found that the two-source model achieved the best agreement on head scatter factor calculation. The three-source model and single-source model underestimated head scatter factors for certain symmetric rectangular fields and asymmetric fields, but similar good agreement could be achieved when monitor back scatter effect was incorporated explicitly. All the three source models resulted in comparable average passing rates (>97%) when the 3%/3 mm criterion was selected. The calculation with the single-source model and two-source model was slightly faster than the three-source model due to their simplicity.

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